The present invention is a low noise blockdown converter (LNB) capable of ensuring sharing of specific information between or among a plurality of microcomputers. In the event that receiver 15 is connected to I/O port 14c assigned to slave microcomputer 13, slave microcomputer 13 may receive inquiry or inquiries from receiver 15 for information specific to LNB 11. Upon receiving such inquiry or inquiries, slave microcomputer 13 may, by way of bus 16, request that master microcomputer 12 provide specific information. Upon receiving such request or requests, master microcomputer 12 may, by way of bus 16, provide slave microcomputer 13 with specific information stored in advance at master microcomputer 12. Slave microcomputer 13 may send this specific information from I/O port 14c to receiver 15.

1. Field of Invention
The present invention pertains to a low noise blockdown converter capable of accepting input of one or more signals received by means of one or more substantially parabolic antennas, capable of carrying out frequency conversion on at least one of the received signal or signals, and capable of sending at least one signal produced as a result of this frequency conversion to one or more receivers.
2. Conventional Art
A low noise blockdown converter (hereinafter also referred to as "LNB") of this type, being attached to a feeder horn of a parabolic antenna for use in receiving satellite broadcasts, accepts input of a received signal gathered by the parabolic antenna and guided thereto by the feeder horn. Moreover, this received signal is subjected to frequency conversion, and the signal produced as a result of frequency conversion is sent to a receiver by way of coaxial cable. If, for example, a received signal of several GHz is input thereto, this received signal might be converted to a signal of several MHz which is then sent therefrom.
Furthermore, a high-performance LNB might have microcomputer(s) installed therein. LNB 101 shown in FIG. 9 may have a single microcomputer 104 installed therein, connection of microcomputer 104 to respective receiver(s) 103 being permitted by way of I/O port(s) 102.
Here, the maximum number of I/O ports 102 which microcomputer 104 is capable of accommodating might for example be defined in advance to be two. Accordingly, an LNB 111 having a single I/O port 102 such as that shown in FIG. 10 would have a single microcomputer 104 installed therein. Furthermore, an LNB 121 having four I/O ports 102 such as that shown in FIG. 11 would require that two microcomputers 104 be installed therein. Moreover, if the number of I/O ports 102 is increased, it will be necessary to increase the number of microcomputers 104.
Responsive, for example, to inquiry or inquiries from receiver(s), such LNB microcomputer(s) might return, from I/O port(s) to receiver(s), information specific to the LNB. LNB-specific information might include the serial number of the LNB in question, which might be used for customer support purposes.
Furthermore, where a plurality of microcomputers are installed in the same LNB, it will be necessary for the microcomputers to share information specific to the LNB. Specific information which is identical in content has therefore conventionally been stored in each of a number of microcomputers which have then been installed in the same LNB.
However, where a plurality of microcomputers in which specific information that is identical in content has been stored are to be installed in the same LNB in accordance with the conventional art as described above, it has been necessary to manage the microcomputers as a single set, which has complicated parts control. Alternatively it is sometimes the case that a plurality of microcomputers storing sets of specific information that are respectively different in content are accidentally installed in the same LNB, which fact has resulted in a defective LNB.
Furthermore, separate special-purpose microcomputers might be developed to accommodate each of the several possible numbers of LNB I/O ports, making it possible for a single microcomputer to be installed in a single LNB no matter how many LNB I/O ports there are and eliminating the possibility that any one LNB could receive a plurality of sets of specific information that are mutually different in content. However, in such a case, the increase in the number of types of microcomputers would complicate parts control and would lead to increased microcomputer cost.


A starter device (1) for an internal combustion engine has a starter drum (4) which acts upon a spring housing (11) when starting. An intermediate spring (10) is arranged in the spring housing (11). One end of the intermediate spring (10) is fixed to the spring housing (11) and the other end of the intermediate spring (10) can be coupled to the crankshaft (3) of the engine via a first catch (23). The spring housing (11) and the starter drum (4) are journalled on a shaft (7) held at one end. The center of gravity (S) of the spring housing (11) lies in the region of the support of the spring housing (11) in order to reduce the acting bearing forces and to increase the service life of the starter device.

U.S. Pat. No. 6,508,220 discloses a starter device for an internal combustion engine wherein the starter drum acts on the spring housing of an intermediate spring. The spring housing and the starter drum are journalled on a shaft supported on one side. The support is arranged in the region of the starter drum. A collar of the spring housing projects through the starter drum. The spring housing is journalled on the collar. During operation of the engine, the starter drum is at standstill in the housing. The housing of the intermediate spring is decoupled from the crankshaft via the catch; however, the spring housing rotates with the crankshaft because of the high rpm thereof. In this way, comparatively high rpms can be reached. This leads to high bearing forces which must be taken up by the shaft clamped at one end. The forces developing during operation lead to a malfunction of the spring starter which thereby has only a short service life.

Starter device for an internal combustion engine


A group poll mechanism (GPM) that schedules upstream bandwidth for cable modems by pointing a request opportunity normally reserved for a single service flow to more than one service flow. Essentially, instead of using the seldom-used poll requests one per service flow, this same request opportunity is pointed to multiple service flows. In such kind of a scheme the GPM gives the same mini-slot to multiple service flows. The GPM implements the use of place-holder SIDs and novel mapping of information elements in MAP messages.

Recently, there has been an explosive demand for services, such as data, voice, and video, to be delivered over broadband communications systems. So-called cable modem technology is one of the most popular methods of providing such broadband services to subscribers. Cable modem technology competes with technologies such as Asymmetric Digital Subscriber Lines (ADSL) and ISDN (Integrated Services Digital Network). Many in the industry forecast that cable modem systems will be the prevailing technology for providing broadband services since cable television is already widely in use.
FIG. 1 illustrates a simplified diagram of a conventional cable modem system. The DOCSIS (Data Over Cable Service Interface Specifications) Radio Frequency Interface Specification specifies the transfer of IP traffic, between the cable headend system and customer locations, over an all-coaxial or a hybrid-fiber/coax (HFC) cable network 52. The transmission path over the cable system is realized at the headend by a Cable Modem Termination System (CMTS) 50, and at each customer location by a Cable Modem (CM) 56. The DOCSIS standard defines a single transmitter for each downstream channel—the CMTS 50. All CMs 56 listen to all frames transmitted on the downstream channel upon which they are registered and accept those where the destinations match the CM 56 itself or CPEs (Customer Premises Equipment) 58 connected. CMs 56 can communicate with other CMs 56 only through the CMTS 50.
The upstream channel is characterized by many transmitters (i.e. CMs 56) and one receiver (i.e. the CMTS 50). Time in the upstream channel is slotted, providing for TDMA at regulated time ticks. The CMTS 50 provides the time reference and controls the allowed usage for each interval. Intervals may be granted for transmissions by particular CMs 56, or for contention by all CMs 56. CMs 56 may contend to request transmission time. To a limited extent, CMs 56 may also contend to transmit actual data. In both cases, collisions can occur and retries are used.
The upstream Physical Media Dependent (PMD) sublayer uses a Frequency Division Multiple Access (FDMA)/TDMA burst modulation format, which provides five symbol rates and two modulation formats (Quadrature Phase Shift Keying (QPSK) and 16-QAM (Quadrature Amplitude Modulation)). The modulation format includes pulse shaping for spectral efficiency, is carrier-frequency agile, and has selectable output power level. The PMD sublayer format includes a variable-length modulated burst with precise timing beginning at boundaries spaced at integer multiples of 6.25 microseconds apart (which is 16 symbols at the highest data rate). Each burst supports a flexible modulation, symbol rate, preamble, randomization of the payload, and programmable FEC (Forward Error Correction) encoding. All of the upstream transmission parameters associated with burst transmission outputs from the CM 56 are configurable by the CMTS 50 via MAC (Media Access Controller) messaging.
The concept of Service Flows is central to the operation of the DOCSIS upstream transmission. Service Flows provide a mechanism for upstream Quality of Service management. In particular, they are integral to bandwidth allocation. A Service Flow ID defines a particular unidirectional mapping between a cable modem and the CMTS. Active upstream Service Flow IDs also have associated Service IDs or SIDs. Upstream bandwidth is allocated to SIDs, and hence to cable modems, by the CMTS upstream scheduler. SIDs provide the mechanism by which upstream Quality of Service is implemented.
In a basic cable modem implementation, two Service Flows (one upstream, one downstream) could be used, for example, to offer best-efforts IP (Internet Protocol) service. However, the Service Flow concept allows for more complex cable modems to be developed which support for multiple service classes while supporting interoperability with more basic modems. With these more complex cable modems, it is possible that certain Service Flows will be configured in such a way that they cannot carry all types of traffic. That is, they may have a maximum packet size limitation or be restricted to small fixed size unsolicited grants. Furthermore it might not be appropriate to send other kinds of data on Service Flows that are being used for Constant Bit Rate (CBR)-type applications.
Even in these complex modems, it is necessary to be able to send certain upstream packets needed for MAC management, SNMP management, key management, etc. For the network to function properly, all cable modems should support at least one upstream and one downstream Service Flow. All Service Flow IDs are unique within the upstream. The mapping of a unicast Service Identifier to an active/admitted Service Flow is unique within a single upstream. The length of the Service Flow ID is 32 bits. The length of the Service ID is 14 bits.
As shown in FIG. 2, the upstream transmission time-line is divided into intervals by the upstream bandwidth allocation mechanism. Each interval is an integral number of mini-slots. A "mini-slot" is the unit of granularity for upstream transmission opportunities. There is no implication that any PDU can actually be transmitted in a single mini-slot. Each interval is labeled with a usage code, which defines both the type of traffic that can be transmitted during that interval and the physical-layer modulation encoding. A mini-slot is a power-of-two multiple of 6.25 microseconds increments, i.e., 2, 4, 8, 16, 32, 64, or 128 times 6.25 microseconds. Since the upstream channel is modeled as a stream of mini-slots, the CMTS generates the time reference for identifying these slots. The CMTS also controls access to these slots by the cable modems. For example, it may grant some number of contiguous slots to a cable modem for it to transmit a data PDU. The cable modem times its transmission such that the CMTS receives it in the time reference specified. The basic mechanism for assigning bandwidth management is the bandwidth allocation MAP.
The bandwidth allocation MAP is a MAC Management message transmitted by the CMTS on the downstream channel which describes, for some interval of time, the uses to which the upstream frequency will be used by a given CM. A given MAP may describe some time slots as grants for particular stations to transmit data in, other time slots as available for contention transmission, and other slots as an opportunity for new stations to join the link. FIG. 3 illustrates a MAC Header and MAC Management Message Header Fields.
The upstream bandwidth allocation MAP includes a fixed-length header followed by a variable number of information elements (IEs) as shown in FIG. 4. The upstream bandwidth allocation MAP message header contains the following information:                Upstream Channel ID: The identifier of the upstream channel to which this message refers.        UCD Count: Matches the value of the Configuration Change Count of the UCD which describes the burst parameters which apply to this map.        Number Elements: Number of information elements in the map.        Alloc Start Time: Effective start time from CMTS initialization (in mini-slots) for assignments within this map.        Ack Time: Latest time, from CMTS initialization, (mini-slots) processed in upstream. This time is used by the CMs for collision detection purposes.        Ranging Backoff Start: Initial back-off window for initial ranging contention, expressed as a power of two. Values range 0–15 (the highest order bits must be unused and set to 0).        Ranging Backoff End: Final back-off window for initial ranging contention, expressed as a power of two. Values range 0–15 (the highest order bits must be unused and set to 0).
The number of Transmit Opportunities associated with a particular Information Element (IE) in a MAP is dependent on the total size of the region as well as the allowable size of an individual transmission. As an example, assume a REQ IE defines a region of 12 mini-slots. If the UCD defines a REQ Burst Size that fits into a single mini-slot then there are 12 Transmit Opportunities associated with this REQ IE, i.e., one for each mini-slot. If the UCD defines a REQ that fits in two mini-slots, then there are six Transmit Opportunities and a REQ can start on every other mini-slot.
TABLE 1The Interval Usage CodesInterval Usage CodeInformation Element Name 1Request 2REQ/Data 3Initial Maintenance 4Station Maintenance 5Short Data Grant 6Long Data Grant 7Null IE 8Data Acknowledge 9–14Reserved15Expanded IUC
As another example, assume a REQ/Data IE that defines a 24 mini-slot region. If it is sent with an SID of 0×3FF4, then a CM can potentially start a transmit on every fourth mini-slot; so this IE contains a total of six Transmit Opportunities (TX OP). Similarly, a SID of 0×3FF6 implies four TX OPs; 0×3FF8 implies three TX OPs; and 0 ×3FFC implies two TX OPs.
For an Initial Maintenance IE, a CM starts its transmission in the first mini-slot of the region; therefore it has a single Transmit Opportunity. The remainder of the region is used to compensate for the round trip delays since the CM has not yet been ranged. Station Maintenance IEs, Short/Long Data Grant IEs and unicast Request IEs are unicast and thus are not typically associated with contention Transmit Opportunities. They represent a single dedicated, or reservation based, Transmit Opportunity.
Each IE consists of a 14-bit Service ID, a 4-bit type code, and a 14-bit starting. FIG. 5 illustrates the structure of a MAP IE. Since all stations will scan all IEs, it is critical that IEs be short and relatively fixed format. IEs within the MAP are strictly ordered by starting offset. For most purposes, the duration described by the IE is inferred by the difference between the IE's starting offset and that of the following IE. For this reason, a Null IE terminates the list.
Types of Information Elements (IEs)
Four types of Service IDs are defined:
1. 0×3FFF—broadcast, intended for all stations.
2. 0×2000–0×3FFE—multicast, purpose is defined administratively.
3. 0×0001–0×1FFF—unicast, intended for a particular CM or a particular service within that cable modem.
4. 0×0000—null address, addressed to no station.
All of the Information Elements defined are supported by cable modems. A CMTS uses any of these Information Elements when creating Bandwidth Allocation Maps.
The Request (REQ) IE
The Request IE provides an upstream interval in which requests can be made for bandwidth for upstream data transmission. The character of this IE changes depending on the class of Service ID. If broadcast, this is an invitation for all cable modems to contend for requests. If unicast, this is an invitation for a particular CM to request bandwidth.
A small number of Priority Request SIDs are defined in DOCSIS. These allow contention for Request IEs to be limited to service flows of a given Traffic Priority. The Request/Data IE provides an upstream interval in which requests for bandwidth or short data packets may be transmitted. This IE is distinguished from the Request IE in that it provides a means by which allocation algorithms may provide for "immediate" data contention under light loads, and a means by which this opportunity can be withdrawn as network loading increases.
Multicast Service IDs are used to specify maximum data length, as well as allowed random starting points within the interval. For example, a particular multicast ID may specify a maximum of 64-byte data packets, with transmit opportunities every fourth slot.
Short and Long Data Grant IEs
The Short and Long Data Grant IEs provide an opportunity for a cable modem to transmit one or more upstream PDUs. These IEs are issued either in response to a request from a station, or because of an administrative policy providing some amount of bandwidth to a particular station (see class-of-service discussion below). These IEs can also be used with an inferred length of zero mini slots (a zero length grant), to indicate that a request has been received and is pending (a Data Grant pending).
Short Data Grants are used with intervals less than or equal to the maximum burst size for this usage specified in the Upstream Channel Descriptor. If Short Data burst profiles are defined in the UCD, then all Long Data Grants are for a larger number of mini-slots than the maximum for Short Data. The distinction between Long and Short Data Grants may be exploited in physical-layer forward-error-correction coding; otherwise, it is not meaningful to the bandwidth allocation process.
If this IE is a Data Grant Pending (a zero length grant), it will follow the NULL IE. This allows cable modems to process all actual allocations first, before scanning the MAP for data grants pending and data acknowledgments.
Data Acknowledge IE
The Data Acknowledge IE acknowledges that a data PDU was received. The cable modem will have requested this acknowledgment within the data PDU (normally this would be done for PDUs transmitted within a contention interval in order to detect collisions). This IE will follow the NULL IE. This allows cable modems to process all actual interval allocations first, before scanning the Map for data grants pending and data acknowledgments.
Requests
Requests refer to the mechanism that cable modems use to indicate to the CMTS that it needs upstream bandwidth allocation. A transmission request may come as a stand-alone Request Frame transmission or it may come as a piggyback request in the EHDR of another Frame transmission.
The Request Frame may be transmitted during any of the following intervals:                Request IE        Request/Data IE        Short Data Grant IE        Long Data Grant IE
A piggyback request may be contained in the following Extended Headers (EHs):                Request EH element        Upstream Privacy EH element        Upstream Privacy EH element with Fragmentation
The request will include:                The Service ID making the request        The number of mini-slots requested
The number of mini-slots requested will be the total number that are desired by the cable modem at the time of the request (including any physical layer overhead), subject to UCD 2 and administrative limits. The cable modem will request a number of mini-slots corresponding to one complete frame, except in the case of fragmentation in Piggyback Mode.
The cable modem will have only one request outstanding at a time per Service ID. If the CMTS does not immediately respond with a Data Grant, the cable modem is able to unambiguously determine that its request is still pending because the CMTS will continue to issue a Data Grant Pending in every MAP for as long as a request is unsatisfied. In MAPs, the CMTS cannot make a data grant greater than 255 mini-slots to any assigned Service ID. This puts an upper bound on the grant size the cable modem has to support.
The allocation MAP transmitted in time to propagate across the physical cable and be received and handled by the receiving cable modems. As such, it may be transmitted considerably earlier than its effective time. The components of the delay are:                Worst-case round-trip propagation delay—may be network-specific, but on the order of hundreds of microseconds;        Queuing delays within the CMTS—implementation-specific;        Processing delays within the CMs will allow a minimum processing time by each cable modem; and        PMD-layer FEC interleaving.
Within these constraints, vendors may wish to minimize this delay so as to minimize latency of access to the upstream channel. The number of mini-slots described vary from MAP to MAP. At a minimum, a MAP describes a single mini-slot. This would be wasteful in both downstream bandwidth and in processing time within the cable modems. At maximum, a MAP may stretch to tens of milliseconds. Such a MAP would provide poor upstream latency.
Allocation algorithms vary the size of the MAPs over time to provide a balance of network utilization and latency under varying traffic loads. A MAP would contain at least two Information Elements: one to describe an interval and a null IE to terminate the list. At the most, a MAP is bounded by a limit of 240 information elements. Maps are also bounded in that they will not describe more than 4096 mini-slots into the future. The latter limit is intended to bound the number of future mini-slots that each cable modem is required to track. A cable modem is able to support multiple outstanding MAPs. Even though multiple MAPs may be outstanding, the sum of the number of mini-slots they describe will not exceed 4096. The set of all maps, taken together, describes every mini-slot in the upstream channel. If a cable modem fails to receive a MAP describing a particular interval, it will not transmit during that interval.
FIG. 6 illustrates a protocol exchange between a cable modem and CMTS. This example illustrates the interchange between the cable modem and the CMTS when the cable modem has data to transmit. If a cable modem has a data PDU available for transmission, then the following steps occur:.
1. At time t1, the CMTS transmits a MAP whose effective starting time is t3. Within this MAP is a Request IE which will start at t5. The difference between t1 and t3 is needed to allow for:                Downstream propagation delay (including FEC interleaving) to allow all CMs to receive the MAP;        Processing time at the cable modem (allows the cable modems to parse the MAP and translate it into transmission opportunities);        Upstream propagation delay (to allow the cable modem's transmission of the first upstream data to begin in time to arrive at the CMTS at time t3).
2. At t2, the cable modem receives this MAP and scans it for request opportunities. In order to minimize request collisions, it calculates t6 as a random offset based on the Data Backoff Start value in the most recent MAP.
3. At t4, the cable modem transmits a request for as many mini-slots as needed to accommodate the PDU. Time t4 is chosen based on the ranging offset so that the request will arrive at the CMTS at t6.
4. At t6, the CMTS receives the request and schedules it for service in the next MAP. (The choice of which requests to grant will vary with the class of service requested, any competing requests, and the algorithm used by the CMTS.)
5. At t7, the CMTS transmits a MAP whose effective starting time is t9. Within this MAP, a data grant for the CM will start at t11.
6. At t8, the cable modem receives the MAP and scans for its data grant.
7. At t10, the CM transmits its data PDU so that it will arrive at the CMTS at t11. Time t10 is calculated from the ranging offset as in step 3 above.
Steps 1 and 2 need not contribute to access latency if cable modems routinely maintain a list of request opportunities. At step 3, the request may collide with requests from other cable modems and be lost. The CMTS does not directly detect the collision. The cable modem determines that a collision (or other reception failure) occurred when the next MAP fails to include acknowledgment of the request. The cable modem will then perform a back-off algorithm and retry.
At step 4, the CMTS scheduler fail to accommodate the request within the next MAP. If so, it will reply with a zero-length grant in that MAP or discard the request by giving no grant at all. It will continue to report this zero-length grant in all succeeding maps until the request can be granted or is discarded. This will signal to the cable modem that the request is still pending. So long as the cable modem is receiving a zero-length grant, it will not issue new requests for that service queue.
Since many different scheduling algorithms can be implemented in the CMTS, the DOCSIS specification does not mandate a particular scheduling algorithm. Instead, DOCSIS describes the protocol elements by which bandwidth is requested and granted. Cable modems may issue requests to the CMTS for upstream bandwidth. The CMTS transmit allocation MAP PDUs on the downstream channel define the allowed usage of each mini-slot.
Contention Resolution
The DOCSIS specification mandates the method of contention resolution as the truncated binary exponential back-off, with the initial back-off window and the maximum back-off window controlled by the CMTS. The values are specified as part of the Bandwidth Allocation Map (MAP) MAC message and represent a power-of-two value. For example, a value of 4 indicates a window between 0 and 15; a value of 10 indicates a window between 0 and 1023.
When a cable modem has information to send and wants to enter the contention resolution process, it sets its internal back-off window equal to the Data Backoff Start defined in the MAP currently in effect. The cable modem will randomly select a number within its back-off window. This random value indicates the number of contention transmit opportunities which the cable modem will defer before transmitting. A cable modem will only consider contention transmit opportunities for which this transmission would have been eligible. These are defined by either Request IEs or Request/Data IEs in the MAP. Note: Each IE can represent multiple transmission opportunities.
As an example, consider a cable modem whose initial back-off window is 0 to 15 and it randomly selects the number 11. The cable modem must defer a total of 11 contention transmission opportunities. If the first available Request IE is for 6 requests, the cable modem does not use this and has 5 more opportunities to defer. If the next Request IE is for 2 requests, the cable modem has 3 more to defer. If the third Request IE is for 8 requests, the cable modem transmits on the fourth request, after deferring for 3 more opportunities.
After a contention transmission, the cable modem waits for a Data Grant (Data Grant Pending) or Data Acknowledge in a subsequent MAP. Once either is received, the contention resolution is complete. The cable modem determines that the contention transmission was lost when it finds a MAP without a Data Grant (Data Grant Pending) or Data Acknowledge for it and with an Ack time more recent than the time of transmission. The cable modem will now increase its back-off window by a factor of two, as long as it is less than the maximum back-off window. The cable modem will randomly select a number within its new back-off window and repeat the deferring process described above.
This re-try process continues until the maximum number of retries (16) has been reached, at which time the PDU will be discarded. The maximum number of retries is independent of the initial and maximum back-off windows that are defined by the CMTS. If the cable modem receives a unicast Request or Data Grant at any time while deferring for this SID, it will stop the contention resolution process and use the explicit transmit opportunity.
The CMTS has much flexibility in controlling the contention resolution. At one extreme, the CMTS may choose to set up the Data Backoff Start and End to emulate an Ethernet-style back-off with its associated simplicity and distributed nature, but also its fairness and efficiency issues. This would be done by setting Data Backoff Start=0 and End=10 in the MAP. At the other end, the CMTS may make the Data Backoff Start and End identical and frequently update these values in the MAP so all cable modems are using the same, and hopefully optimal, back-off window.
CM Bandwidth Utilization
The following rules govern the response a CM makes when processing maps. These standard behaviors can be overridden by the CM's Request/Transmission Policy:
1. A cable modem will first use any Grants assigned to it. Next, the CM will use any unicast REQ for it. Finally, the cable modem will use the next available broadcast/multicast REQ or REQ/Data IEs for which it is eligible.
2. A cable modem will not have more than one Request outstanding at a time for a particular Service ID.
3. If a cable modem has a Request pending, it will not use intervening contention intervals for that Service ID.
DOCSIS CMTS Scheduling
DOCSIS scheduling services are designed to improve the efficiency of the poll/grant process. By specifying a scheduling service and its associated quality-of-service (QoS) parameters, the DOCSIS CMTS can anticipate the throughput and latency needs of the upstream traffic and provide polls and/or grants at the appropriate times.
Each service is tailored to a specific type of data flow as described below. The basic services comprise:                Unsolicited Grant Service (UGS)        Real-Time Polling Service (rtPS)        Unsolicited Grant Service with Activity Detection (UGS-AD)        Non-Real-Time Polling Service (nrtPS)        Best Effort (BE) service.
FIG. 7 illustrates the relationship between the scheduling services and the related QoS parameters. Each of these is discussed in more detail below:
Unsolicited Grant Service
The Unsolicited Grant Service (UGS) is designed to support real-time service flows that generate fixed size data packets on a periodic basis, such as Voice over IP. The UGS service offers fixed size grants on a real-time periodic basis, which eliminate the overhead and latency of cable modem requests and assure that grants will be available to meet the flow's real-time needs.
The CMTS provides fixed size data grants at periodic intervals to the Service Flow. In order for this service to work correctly, the Request/Transmission Policy setting will be such that the cable modem is prohibited from using any contention request or request/data opportunities and the CMTS does not provides any unicast request opportunities. The Request/Transmission Policy also prohibits piggyback requests. This will result in the cable modem only using unsolicited data grants for upstream transmission. The key service parameters are the Unsolicited Grant Size, the Nominal Grant interval, the Tolerated Grant Jitter and the Request/Transmission Policy.
ATM CBR (Constant Bit Rate) Services
The Constant Bit Rate (CBR) service class is intended for real-time applications, i.e. those requiring tightly constrained delay and delay variation, as would be appropriate for voice and video applications. The consistent availability of a fixed quantity of bandwidth is considered appropriate for CBR service. Cells which are delayed beyond the value specified by CTD (cell transfer delay) are assumed to be significantly less value to the application.
For CBR, the following ATM attributes are specified:                PCR/CDVT(peak cell rate/cell delay variation tolerance)        Cell Loss Rate        CTD/CDV        CLR may be unspecified for CLP=1.Real-Time Polling Service
The Real-Time Polling Service (rtPS) is designed to support real-time service flows that generate variable size data packets on a periodic basis, such as MPEG video. The service offers real-time, periodic, unicast request opportunities, which meet the flow's real-time needs and allow the CM to specify the size of the desired grant. This service requires more request overhead than UGS, but supports variable grant sizes for optimum data transport efficiency.
The CMTS will provide periodic unicast request opportunities. In order for this service to work correctly, the Request/Transmission Policy setting will be such that the cable modem is prohibited from using any contention request or request/data opportunities. The Request/Transmission Policy will also prohibit piggyback requests. The CMTS may issue unicast request opportunities as prescribed by this service even if a grant is pending. This will result in the cable modem using only unicast request opportunities in order to obtain upstream transmission opportunities (the cable modem could still use unsolicited data grants for upstream transmission as well). All other bits of the Request/Transmission Policy are not relevant to the fundamental operation of this scheduling service and should be set according to network policy. The key service parameters are the Nominal Polling Interval, the Tolerated Poll Jitter and the Request/Transmission Policy.
ATM Real Time VBR
The real time VBR service class is intended for real-time applications, i.e., those requiring tightly constrained delay and delay variation, as would be appropriate for voice and video applications. Sources are expected to transmit at a rate which varies with time. Equivalently the source can be described "bursty". Cells which are delayed beyond the value specified by CTD are assumed to be of significantly less value to the application. Real-time VBR service may support statistical multiplexing of real-time sources, or may provide a consistently guaranteed QoS.
For real time VBR, the following ATM attributes are specified:                PCR/CDVT        CLR        CTD/CDV        SCR and BT (sustainable cell rate and burst tolerance)Unsolicited Grant Service with Activity Detection
The Unsolicited Grant Service with Activity Detection (UGS/AD) is designed to support UGS flows that may become inactive for substantial portions of time (i.e. tens of milliseconds or more), such as Voice over IP with silence suppression. The service provides Unsolicited Grants when the flow is active and unicast polls when the flow is inactive. This combines the low overhead and low latency of UGS with the efficiency of rtPS. Though USG/AD combines UGS and rtPS, only one scheduling service is active at a time.
The CMTS will provide periodic unicast grants, when the flow is active, but will revert to providing periodic unicast request opportunities when the flow is inactive. The CMTS can detect flow inactivity by detecting unused grants. However, the algorithm for detecting a flow changing from an active to an inactive state is dependent on the CMTS implementation. In order for this service to work correctly, the Request/Transmission Policy setting will be such that the cable modem is prohibited from using any contention request or request/data opportunities. The Request/Transmission Policy will also prohibit piggyback requests. This results in the cable modem using only unicast request opportunities in order to obtain upstream transmission opportunities. However, the cable modem will use unsolicited data grants for upstream transmission as well.
All other bits of the Request/Transmission Policy are not relevant to the fundamental operation of this scheduling service and should be set according to network policy. The key service parameters are the Nominal Polling Interval, the Tolerated Poll Jitter, the Nominal Grant Interval, the Tolerated Grant Jitter, the Unsolicited Grant Size and the Request/Transmission Policy.
In UGS-AD service, when restarting UGS after an interval of rtPS, the CMTS will provide additional grants in the first (and/or second) grant interval such that the cable modem receives a total of one grant for each grant interval from the time the cable modem requested restart of UGS, plus one additional grant.
Because the Service Flow-is provisioned as a UGS flow with a specific grant interval and grant size, when restarting UGS, the cable modem will not request a different sized grant than the already provisioned UGS flow. As with any Service Flow, changes can only be requested with a DSC command. If the restarted activity requires more than one grant per interval, the CM MUST indicate this in the Active Grants field of the UGSH beginning with the first packet sent.
The Service Flow Extended Header Element allows for the cable modem to dynamically state how many grants per interval are required to support the number of flows with activity present. In UGS/AD, the cable modem may use the Queue Indicator Bit in the UGSH. The remaining seven bits of the UGSH define the Active Grants field. This field defines the number of grants within a Nominal Grant Interval that this Service Flow currently requires.
When using UGS/AD, the cable modem will indicate the number of requested grants per Nominal Grant Interval in this field. The Active Grants field of the UGSH is ignored with UGS without Activity Detection. This field allows the cable modem to signal to the CMTS to dynamically adjust the number of grants per interval that this UGS Service Flow is actually using. The cable modem will not request more than the number of Grants per Interval in the ActiveQoSParameterSet.
If the CMTS allocates additional bandwidth in response to the QI bit, it will use the same rate limiting formula as UGS, but the formula only applies to steady state periods where the CMTS has adjusted the grants_per_interval to match the active_grants requested by the cable modem.
When the cable modem is receiving unsolicited grants and it detects no activity on the Service Flow, it may send one packet with the Active Grants field set to zero grants and then cease transmission. Because this packet may not be received by the CMTS, when the Service Flow goes from inactive to active the cable modem will be able to restart transmission with either polled requests or unsolicited grants.
Non-Real-Time Polling Service
The Non-Real-Time Polling Service (nrtPS) is designed to support non real-time service flows that require variable size data grants on a regular basis, such as high bandwidth FTP. The service offers unicast polls on a regular basis which assures that the flow receives request opportunities even during network congestion. The CMTS typically polls nrtPS SIDs on an (periodic or non-periodic) interval on the order of one second or less.
The CMTS provide timely unicast request opportunities. In order for this service to work correctly, the Request/Transmission Policy setting will be such that the cable modem is allowed to use contention request opportunities. This will result in the cable modem using contention request opportunities as well as unicast request opportunities and unsolicited data grants. All other bits of the Request/Transmission Policy are not relevant to the fundamental operation of this scheduling service and should be set according to network policy. The key service parameters are Nominal Polling Interval, Minimum Reserved Traffic Rate, Maximum Sustained Traffic Rate, Request/Transmission Policy and Traffic Priority.
ATM Non-Real Time VBR
The non-real time VBR service class is intended for non-real time applications which have 'bursty' traffic characteristics and which can be characterized in terms of a GCRA. For those cells which are transferred, it expects a bound on the cell transfer delay. Non-real time VBR service supports statistical multiplexing of connections.
For real time VBR, the following ATM attributes are specified:                PCR/CDVT        CLR        CTD        SCR and BTBest Effort Service
The intent of the Best Effort (BE) service is to provide efficient service to best effort traffic. In order for this service to work correctly, the Request/Transmission Policy setting will be such that the cable modem is allowed to use contention request opportunities. This will result in the cable modem using contention request opportunities as well as unicast request opportunities and unsolicited data grants. All other bits of the Request/Transmission Policy are not relevant to the fundamental operation of this scheduling service and should be set according to network policy. The key service parameters are the Minimum Reserved Traffic Rate, the Maximum Sustained Traffic Rate, and the Traffic Priority.
ATM UBR (Unspecified Bit Rate)
The UBR service class is intended for delay-tolerant or non-real-time applications, i.e., those which do not require tightly constrained delay and delay variation, such as traditional computer communications applications. Sources are expected to transmit non-continuous bursts of cells. UBR service supports a high degree of statistical multiplexing among sources. UBR service includes no notion of a per-VC allocated bandwidth resource. Transport of cells in UBR service is not necessarily guaranteed by mechanisms operating at the cell level. However it is expected that resources will be provisioned for UBR service in such a way as to make it usable for some set of applications. UBR service may be considered as interpretation of the common term "best effort service".
For UBR, the following ATM attributes are specified:                PCR/CDVTATM ABR (Available Bit Rate)
Many applications have the ability to reduce their information transfer rate if the network requires them to do so. Likewise, they may wish to increase their information transfer rate if there is extra bandwidth available within the network. There may not be deterministic parameters because the users are willing to live with unreserved bandwidth. To support traffic from such sources in an ATM network will require facilities different from those for Peak Cell Rate of Sustainable Cell Rate traffic. The ABR service is designed to fill this need.
Relevant Encodings for the Upstream Scheduling
Service Flow Scheduling Type
The value of this parameter specifies which upstream scheduling service is used for upstream transmission requests and packet transmissions. If this parameter is omitted, then the Best Effort service will be assumed. This parameter is only applicable at the CMTS. If defined, this parameter MUST be enforced by the CMTS.
TypeLengthValue24.1510 Reserved1 for Undefined (CMTS implementation-dependent 1)2 for Best Effort3 for Non-Real-Time Polling Service4 for Real-Time Polling Service5 for Unsolicited Grant Service withActivity Detection6 for Unsolicited Grant Service7 through 255 are reserved for futureuseRequest/Transmission Policy
The value of this parameter specifies 1) which IUC opportunities the cable modem uses for upstream transmission requests and packet transmissions for this Service Flow, 2) whether requests for this Service Flow may be piggybacked with data and 3) whether data packets transmitted on this Service Flow can be concatenated, fragmented, or have their payload headers suppressed. For UGS, it also specifies how to treat packets that do not fit into the UGS grant. The data grants referred to include both short and long data grants.                Bit #0—The Service Flow will not use "all cable modems" broadcast request opportunities.        Bit #1—The Service Flow will not use Priority Request multicast request opportunities.        Bit #2—The Service Flow will not use Request/Data opportunities for Requests.        Bit #3—The Service Flow will not use Request/Data opportunities for Data.        Bit #4—The Service Flow will not piggyback requests with data.        Bit #5—The Service Flow will not concatenate data.        Bit #6—The Service Flow will not fragment data.        Bit #7—The Service Flow will not suppress payload headers.        Bit #8—The Service Flow will drop packets that do not fit in the Unsolicited Grant Size.Priority Request Service IDs
These Service IDs (0×3Exx) are reserved for Request IEs:
If 0×01 bit is set, priority zero can request.
If 0×02 bit is set, priority one can request.
If 0×04 bit is set, priority two can request.
If 0×08 bit is set, priority three can request.
If 0×10 bit is set, priority four can request.
If 0×20 bit is set, priority five can request.
If 0×40 bit is set, priority six can request.
If 0×80 bit is set, priority seven can request.
Bits can be combined as desired by the CMTS upstream scheduler for any Request IUCs.
Traffic Priority
The value of this parameter specifies the priority assigned to a Service Flow. Given two Service Flows identical in all QoS parameters besides priority, the higher priority Service Flow should be given lower delay and higher buffering preference. For otherwise non-identical Service Flows, the priority parameter will not take precedence over any conflicting Service Flow QoS parameter. The specific algorithm for enforcing this parameter is not mandated here.
For upstream service flows, the CMTS should use this parameter when determining precedence in request service and grant generation, and the cable modem will preferentially select contention Request opportunities for Priority Request Service IDs based on this priority and its Request/Transmission Policy.
To illustrate the problem current CMTS scheduling under DOCSIS presents an example application known commonly in the industry as "PacketCable" is discussed below. PacketCable is a project conducted by Cable Television Laboratories, Inc. and its member companies. The PacketCable project is aimed at defining interface specifications that can be used to develop interoperable equipment capable of providing packet-based voice, video and other high-speed multimedia services over hybrid fiber coax (HFC) cable systems utilizing the DOCSIS protocol. PacketCable utilizes a network superstructure that overlays the two-way data-ready broadband cable access network. While the initial PacketCable offering will be packet-based voice communications for existing and new cable subscribers, the long-term project vision encompasses a large suite of packet-based capabilities.
The application of NCS PacketCable call setup will be used throughout when discussing the various embodiments of the invention. The example uses the PacketCable NCS call protocol along with the DQoS setup procedure. The PacketCable NCS protocol requires a big number of messages passed between the eMTA (embedded MTA: a device which includes both the VoIP functionality and the cable modem functionality). The messages passed in their protocol flow are shown in FIG. 8, FIG. 9 and FIG. 10.
There are three alternatives to the PacketCable NCS call setup using strict DOCSIS mechanisms. The first one is the simplest one and put the call signaling messaging in the request/contention area, the second is to use the polled requests for the NCS call signaling and the last, is to use the priority requests. These are discussed in turn:
Using Broadcast Request Opportunities
In the method that uses broadcast request opportunities the NCS call signaling uses the best effort scheduling type. There are two problems with such kind of a use: the first one is that the time it takes the eMTA to send a packet, and the problem of using a contention are that is shared with the data packets.
The first issue is that assuming there is no contention on the Cable Modem requests, the time it takes the packet to be transmitted. FIG. 11, FIG. 12 and FIG. 13 show all the messages that are exchanged between the eMTA and the CMTS for transmission of the call signaling packets when using broadcast request opportunities. Referring to FIGS. 11–13, it can be shown that there are 4 packets that have to be sent upstream before the phone rings on the originator and 3 packets that has to be send out on the far-end. This is assuming that the dial map is designed in such a way that the first time the eMTA contacts the CMTS is the time that all the digits are completed.
To further analyze, certain designs of a CMTS issue MAP messages every 4 milliseconds. Thus using that metric, on average, packets have to be waiting in the queue of the CMTS for 2 milliseconds to make the request. Further, it takes 1 millisecond for the message to propagate to the CMTS. Also assume that the request can be granted in the first MAP message and on average the packet would be scheduled from the arrival of MAP within 2 milliseconds. It takes 2 milliseconds for the MAP packet to be received from the CMTS to CM.
The result is shown in Table 3 below:
TABLE 3ExplanationDelayTotal DelayThe request is send in the2 ms2mscontention areaInterleaving delay3 ms5msUpstream Propagation delay1 ms6msThe CMTS processes the request and1 ms7msschedulesDownstream propagation delay1 ms8msThe data area is used2 ms10msInterleaving delay3 ms13msThe data is received by the CMTS1 ms14ms
It has to be noted that these numbers assume that the CMTS processing is in such a way that the data grant is issued with the next MAP message. A more realistic number is 15 millisecond average delay between the call signaling packet interception at the Cable Modem to the packet to be arriving at the CMTS for further processing.
If the contribution of cable transmission delay to post dial delay is to be calculated for originating side:                4 upstream messages *15 ms per message delay=60 ms delay.
For the far-end the number is:                3 upstream messages *15 ms per message delay=45 ms delay.
Therefore, 10% of end-to-end delay budget of under one second of post dial delay is consumed by the cable segment transmission.
For the second issue it has been shown that the sharing of request/contention areas with data transmission introduces a very big delay to the system that during congestion intervals it may not be acceptable. It is possible that such is not applicable to a modern scheduler in which engineers the number of contention/requests to the traffic usage pattern. But the issue still remains and since the use of request/contention area cannot be prioritized between SIDs that are on different cable modems, meaning that it is not possible for CMTS to give call signaling packets a preferential treatment. Since the cable transmission delay cannot be guaranteed, this would be reason enough for the request/contention area not to be used. The second alternative is the use of the non-real time polling.
Using Polled Request Opportunities
The polled request opportunity method assumes that all of the NCS call signaling packets are send through the service flows that are using the non-real-time polled scheduling type as defined by DOCSIS. In the non-real time polling the cable modem can use the request/contention grants but the CMTS is responsible for providing timely unicast request opportunities. The problem with this kind of scheduling is that since the CMTS cannot guess which cable modems are in contention in a contention/request opportunity, when a contention is detected, the cable modem should revert to the Unicast Polling Opportunities, which makes the use of the request/contention opportunities during high traffic.
Due to the reasons whether the non-real-time polling or the real-time polling is to be used in such kind of a situation the service flow should not be using the broadcast request opportunities. For the real-time polling the CMTS should be generating a request opportunity for each of the service flow individually. If we use the AT&T numbers the CMTS should be giving unicast request opportunity to each one of the 1000 cable modems. Assuming that a unicast request takes 12 bytes which for the best case of transmission takes 12.5 microseconds of upstream time. For all cable modems, this yields an upstream time of (12.5 microseconds *1000=) 12.5 milliseconds.
Assuming that the maintenance overhead and others the minimum interval for the cable modem polling cannot be higher than 7 millisecond intervals. It is important to note that in such a case the whole upstream bandwidth is being used for polling and the upstream bandwidth cannot be used for other data transmission. It is important to consider that the main idea is to be able to use the upstream for the transport of VoIP and other data transmission as well.
Using Priority Request Opportunities
The last method is to use the priority request service IDs for the NCS call signaling packets. In this method all of the NCS call signaling packets use the service flows that has the request transmission policy set as the Cable Modem will not use the broadcast request opportunities and the cable modem will use the priority request multicast opportunities.
Even though the DOCSIS specification defines these fields as strict ordering for lower delay and higher buffering it is possible to use the priority for grouping the service flows for NCS call signaling. Now if it is assumed that all the remaining flows with best effort scheduling type are using the priority zero and the NCS call signaling is using priority 5 then if the CMTS schedules with every MAP cycle a priority 5 request opportunity (using SID x3E20).
In such a case the Internet data using the priority 0 will be using the broadcast request opportunities and the priority 5 request opportunity will be used by the NCS call signaling. The benefit of such a scheme is that there is no waste of bandwidth due to individual poll and at the same time the NCS call signaling packets will not be contending with the NCS data packets.
The only issue with such a method is that the cable modem will use the truncated binary exponential backoff algorithm to pick which opportunity it will utilize, and there are only one global data backoff start and data backoff end settings. If one uses the same values that is being used for the broadcast data opportunities or any of the other contention request opportunities then this would cause an unnecessary bandwidth waste. One solution may be to use the segmented backoff setting bandwidth allocation MAP messages generation in the CMTS scheduler.
The problem with using Priority Requests is as follows. Lets assume that the priority 5 is being used for the NCS call signaling and the data backoff setting of a start value of 0 and an end value of 3 is sufficient for the expected contention probability. We can assume that the broadcast request opportunities use the start value of 2 and an end value of 7. Table 4 below contains the number of mini-slots in one 4 millisecond interval for various symbol rates/modulations:
TABLE 4mini-slot size (ticks)248163264128mini-slot size (us)12.52550100200400800number ofsymbol ratemini-slots in 4 ms interval160000N/AN/AN/AN/A20105320000N/AN/AN/A4020105640000N/AN/A8040201051280000N/A16080402010525600000320160804020105160000N/AN/AN/AN/A20105320000N/AN/AN/A4020105640000N/AN/A8040201051280000N/A16080402010525600000320160804020105
Assuming that a request takes 2 mini-slots we get the number of request opportunities on a 4 millisecond interval to be as shown in Table 5:
TABLE 5mini-slot size (ticks)248163264128mini-slot size (us)12.52550100200400800number ofsymbol raterequests in 4 ms interval16000N/AN/AN/AN/A1052.532000N/AN/AN/A201052.564000N/AN/A40201052.5128000N/A8040201052.525600001608040201052.516000N/AN/AN/AN/A1052.532000N/AN/AN/A201052.564000N/AN/A40201052.5128000N/A8040201052.525600001608040201052.5
If we assume that all the priority request type are being used then we have 8 requests per MAP at least. The difference between using the broadcast request data backoff settings and a specific value for the priority request is: 8 priority values *3 unnecessary requests per MAP interval =24 unnecessary requests.
Due to the fact that the main reason for the use of priority requests is the timely transport of packets it is assumed that at least the initial data backoff setting of priority request opportunities has to be given in each interval. If we take into account that there are at least 4 requests per MAP interval we calculate the wasted interval as shown in Table 6:
TABLE 6mini-slot size (ticks)248mini-slot size (us)12.52550symbol ratenumber of requests in 4 ms interval160000N/AN/AN/A320000N/AN/AN/A640000N/AN/A0.6666671280000N/A0.3157890.666667256000000.1538460.3157890.666667160000N/AN/AN/A320000N/AN/AN/A640000N/AN/A0.6666671280000N/A0.3157890.666667256000000.1538460.3157890.666667
This implies that a minimum of 15% of the upstream mini-slots will be wasted due to inability of the scheduler to send bandwidth allocation MAP messages with different data backoff settings.
A challenging aspect of DOCSIS CMTS design are problems with scheduling channels and service flows generated therein based upon applications that use the bandwidth provided to them by the cable modem system. Today, the general analysis of the DOCSIS upstream scheduling is carried out in the domain of scheduling the data transmission opportunities. The request for upstream transmission is assumed to be arrived at the CMTS timely, and a uniform delay distribution is generally assumed for request arrival. For instance, the typical cable modem will have no idea if the application requesting a service flow is an HTTP application or a Voice over IP The main challenge for the CMTS is to meet the delay, bandwidth and other requirements of service flow quality of service encodings by scheduling the data transmission opportunities.

Use of group poll scheduling for broadband communication systems


A battery unit includes a positive relay switch, a negative relay switch, a first resistor disposed in a third wiring portion extending between a positive external terminal and a negative external terminal, a second resistor serially connected to a portion on more negative side than the first resistor, a third resistor disposed in a second wiring portion and connected in parallel with the negative relay switch, a potential difference detection section capable of detecting a first potential difference which is a potential difference between the portion of the third wiring portion on more negative side than the first resistor and a negative terminal and a failure determination section for determining a failure of the positive relay switch and the negative relay switch respectively, based on the first potential difference.

As disclosed in the publications of Japanese Patent No. 3536716 and Japanese Patent No. 4572168, the technique of detecting welding adhesion of a relay switch to a load subject is known conventionally. In the publications of Japanese Patent No. 3536716, a current value at time of discharging is determined and a welding adhesion state is determined if this current value exceeds a predetermined value. And, in the publications of Japanese Patent No. 4572168, the technique determines a voltage drop at the time of switching of relay switches ("main relays" in the document) on the positive side and the negative side respectively to their shutoff states, and a welding adhesion state is determined if there is found no such voltage drop.
In the case of the conventional techniques, the techniques generally detect welding adhesion of a relay switch in a battery unit, with the battery unit and the load subject being formed integral with each other; thus, the techniques do not allow detection of welding adhesion without connection to the load subject. Further, since the voltage of the battery unit may be vulnerable to influence from a circuit of the load subject at the time of determination of the voltage of the battery unit, it was necessary to compare values of a plurality of voltage sensors, in order to detect the welding adhesion of this relay switch. In view of the above-described state of the art, the object of the present invention is to provide a battery unit capable of detecting a welding adhesion of a relay switch incorporated therein with a simple arrangement.


A mass transfer system for decontaminating a contaminated liquid or gas stream. The system includes a container with a liquid inlet, a liquid outlet, a gas inlet and a gas outlet. The container is adapted to channel a liquid stream from the liquid inlet to the liquid outlet. The vessel is also adapted to channel a gas stream from the gas inlet to the gas outlet. At least one grid is mounted within the container and is positioned within the gas and liquid streams. The grid has a plurality of apertures formed therein which are adapted to disperse the gas flow as it passes through the grid. The dispersion of the gas flow generates a fluidized bed within the container. The grid is preferably parabolic in shape. A light assembly is mounted on the container and has a light emitting unit positioned so as to emit light into the container. The light irradiates at least one of the streams flowing therein. The configuration of the system is designed to cause the mixture of the gas stream and liquid streams to become turbulent, thereby increasing the liquid surface area. The light emitting unit is positioned so as to irradiate the two turbulent fluid flows so as to catalyze a chemical reaction. In one embodiment, an oxidant is added to one of the streams which, when irradiated by the ultraviolet light, produces hydroxyl radicals which chemically react with the contaminants in the stream.

A heightened awareness of the effects that chemical by-products have on the environment has led to more stringent governmental regulations on virtually all chemical processes. Many of these regulations are directed to limiting levels of toxics and related chemicals which can be discharged into the environment. For example, the process gases in pulp and paper manufacture include trace levels of methanol and AOX (absorbable organic halogens). These contaminants travel with the process gases and may escape into the atmosphere or into the end product if not removed prior to discharge.
There are many methods for removing gaseous contaminates and particulate matter from gas or liquid streams. One method which is finding increased interest is known as scrubbing. Scrubbing involves the mixing of a process gas or vapor with a scrubbing liquid in a vessel. The mixing of the two constituents is designed to dislodge entrained particulate matter or to remove soluble gases from the gas or vapor stream. One method for scrubbing utilizes a tray or grid through which the gas or vapor stream and the liquid stream are passed. The grid consists of a plurality of apertures. As the gas/vapor stream passes through the grid and meets with the liquid stream, ebullition or bubbling of the liquid occurs on one side of the grid. The bubbling of the two streams forms as a fluidized bed. As the process gas bubbles pass through the fluidized bed the bubbles burst creating small droplets that impact into the contaminate particles and create a large surface area for gas absorption. Alternately, if the liquid and/or gas stream is mixed with a chemical scrubbing agent, reaction and neutralization of entrained contaminate gases may occur.
Conventional scrubbing processes are designed to provide a continuous flow of gas and liquid streams. That is, the liquid and gas feed stock streams are continuously introduced into a contact vessel, and the resulting gas and liquid product streams are continuously withdrawn. Countercurrent flow of the gas and liquid streams is the most common flow pattern used in conventional scrubbers. The liquid stream is introduced at or near the top of the vessel and withdrawn at the bottom. The gas stream is fed in at or near the bottom of the vessel and withdrawn at the top. Concurrent flow type scrubbers channel both streams through the vessel in the same direction.
The grids or trays are mounted at one or more locations within the vessel so as to insure that the desired degree of contact between the gas and liquid occurs. The desired degree and duration of contact between the streams is dependent on many considerations, such as the desired quality (purity) and quantity (yield) needed. It may also be desirable to minimize the pressure drop of the gas stream through the contact or scrubbing vessel. The configuration of the apparatus is also an important feature inasmuch as the preferred vessel is small, simple and relatively easy to maintain.
U.S. Pat. No. 4,432,914, incorporated herein by reference, discloses a catenary grid scrubber which is effective in removing particulate matter and soluble gases from a process gas stream. The scrubber includes a parabolic or contoured grid designed to effectively and efficiently control the rate of gas and liquid interaction so as to maximize the capture or solubility of the entrained contaminates.
To date, scrubber effectiveness has been limited to removing particulate matter or inducing solubility of entrained gases. Alternate systems have been developed to remove insoluble contaminate gases or microscopic particulate (e.g., bacteria). One such system uses ultraviolet light to destroy or chemically convert the contaminate. Ultraviolet (UV) light systems operate by directing a high intensity UV light at a liquid steam that includes a process chemical (usually an oxidant) containing the contaminant. The properties of the UV light produce a catalytic reaction within the stream which eliminates the contaminant or converts it to a more favorable chemical composition which may be subsequently removed.
The primary deficiency with UV light systems is that they are surface area dependent. That is, the UV light cannot deeply penetrate into a liquid stream for irradiating the contaminants. UV light systems, therefore, must channel the liquid stream through thin tubes during UV light irradiation. This severely limits the quantity of irradiated product that can be produced using a UV light system. In order to increase the amount of surface area of liquid irradiated, conventional systems utilize a plurality of thin tubes, each with a suitable UV light source. UV light systems are also not effective in removing large particulate matter from gas streams.
However, as stricter government regulations are imposed on the pulp and paper, electronics and chemical processing industry, these conventional methods for cleaning gas and/or liquid streams are becoming less and less effective. For example, the government has recently proposed stricter rules on the amount and type of emissions allowed in a pulp bleaching operation. These rules propose the elimination of methanol from the pulp bleach plant scrubber exhaust. Conventional scrubbers cannot effectively remove methanol from a process stream. Conventional UV light systems are capable of removing the methanol from a liquid stream but only on a small scale.
Criticism has also developed over the use of chlorine based biocides in cooling tower water disinfection and algae control. In order to effectively disinfect water, conventional scrubbing devices would require the use of non-chlorine additives. UV light systems can be utilized but, due to the small surface area required for effectively catalyzing the contaminates, the amount of product stream cleansed is limited.
A need therefore exists for an improved system that effectively and efficiently removes particulate matter and/or soluble gaseous matter from a process stream, while producing a large liquid surface area that can be irradiated with UV light for the destruction of the absorbed organic compounds.

Ultraviolet light irradiated ebullating mass transfer system


An image acquisition system determines first and second sets of points defining an iris-pupil boundary and an iris-sclera boundary in an acquired image; determines respective ellipses fitting the first and second sets of points; determines a transformation to transform one of the ellipses into a circle on a corresponding plane; using the determined transformation, transforms the selected ellipse into a circle on the plane; using the determined transformation, transforms the other ellipse into a transformed ellipse on the plane; determines a plurality of ellipses on the plane for defining an iris grid, by interpolating a plurality of ellipses between the circle and the transformed ellipse; moves the determined grid ellipses onto the iris in the image using an inverse transformation of the determined transformation; and extracts an iris texture by unwrapping the iris and interpolating image pixel values at each grid point defined along each of the grid ellipses.

The iris surrounds the dark, inner pupil region of an eye and extends concentrically to the white sclera of the eye. A. K. Jain, A. Ross, and S. Prabhakar, "An introduction to biometric recognition," IEEE Trans. Circuits Syst. Video Technol., vol. 14, 2004 discloses that the iris of the eye is a near-ideal biometric.
For the purposes of iris-based recognition/authentication, during an acquisition phase an image of a subject comprising an iris region is acquired with an imaging system, typically using infra-red (IR) illumination to bring out the main features of an underlying iris pattern. Then, eye/iris detection is applied over the acquired image to identify a region of the image containing the iris pattern. Iris segmentation is performed on the detected region of the image in order to define an iris segment. The extracted iris code can be used in conjunction with iris code(s) acquired and stored in an enrolment phase to recognise or authenticate the subject of the image.
Conventional iris biometrics algorithms operate under the assumption that the subject cooperates during the enrolment and acquisition phases by looking directly into the camera, in such a way as the subject's gaze is close to, or actually parallel to the optical axis of the camera of the image acquisition system.
These scenarios are referred to as on-axis gaze imagery, where acquired images include an almost circular iris whose texture is isotropic. Thus, a best possible iris template can be generated from the intermediate region between the iris-pupil and iris-sclera boundary, which identifies the subject.
However, in virtual, augmented or mixed reality (VR, AR, MR) applications, fewer restrictions may be imposed on a user's direction of gaze (eye pose) when they are being recognized/authenticated. Furthermore, the imaging system can be embedded in apparatus such as a helmet or glasses that are worn by a user where the system camera is offset rather than disposed directly in front of the user such as when a user authenticates to a typical smartphone.
As such, in these applications the user's gaze is rarely, if not ever, aligned to the optical axis of the camera and a significant offset angle, even of an average 45°, along with a significant fluctuation in that angle as the user's gaze changes, can be present between the direction of user's gaze and the optical axis of the camera when an image of the user's eye region is to be acquired as part of recognition/authentication.
These scenarios, where the eye pose is not collinear with the principle point of the camera, are referred to as off-axis gaze imagery. In these scenarios, the offset between the user's gaze and the optical axis of the imaging system causes a distortion of the circular shape of the iris, resulting in an elliptical shape having an eccentricity that varies with the offset. An exemplary off-axis iris image having an elliptical shape is illustrated in FIG. 1 where the discrepancy in area between an inner circular approximation 1 and an outer circular approximation 2 of an imaged off-axis iris are evident.
It will be appreciated that accurate detection of the iris boundaries is important in iris recognition. Inaccurate boundary detection can result in areas of the sclera and/or periocular region being wrongly included or regions of the iris being wrongly excluded in the extracted iris templates.
In ISO standard images and other images typically used for iris recognition, the iris-sclera boundary is conventionally modelled as a circle, and detecting one point on each side of the circular boundary is considered sufficient. However, as can be seen from FIG. 1, a circular segmentation may not be sufficient for achieving an accurate segmentation in case that the eccentricity of an off-axis imaged iris is quite high. Thus, if the radius of the segmentation circle is set to correspond to the minor axis of the elliptic iris shape (circle 1 in FIG. 1), parts of the iris will be excluded from the segmentation and resulting iris template. Alternatively, parts of the sclera and/or the periocular region (e.g. of the eyelid) will be wrongly included in the iris template if the circle radius is set to the major axis of the ellipse (circle 2 in FIG. 1).
Similarly, dissimilarities between iris images acquired during the acquisition phase and the enrolment phase, that are due to different user's direction of gaze, can cause errors in the recognition/authentication of the user, thus negatively affecting the False Acceptance Rate (FAR) and False Rejection Rate (FRR) of the system.
"An Investigation of Iris Recognition in Unconstrained Environments", by Richard Bonner, Doctor of Philosophy (PhD) thesis, University of Kent, discloses the use of multiple gaze angles for images acquired at the enrolment phase to reduce errors in recognition systems operating on off-axis eye images. The principle underlying this solution is that comparing an authentication template acquired when the user is looking in a similar direction to that used for an enrolment template will provide a more reliable result than comparing two templates acquired when the user is looking in different directions. The use of several enrolment templates acquired from different gaze angles is also known in biometric modes other than iris recognition, such as face recognition.
Nevertheless, a comparison between an authentication template and each of several enrolment templates associated with any potential users of the system can be computationally demanding.
Another effect that can cause errors in the recognition/authentication of a user in off-axis eye images is cornea refraction, occurring when light rays extending from the pupil's boundary are refracted at the cornea surface. This refraction causes non-linear distortions of the imaged iris captured by the camera and, therefore, in the extracted iris texture. The distortions can negatively impact the comparison between the extracted iris texture and iris textures stored in the enrolment templates. The degree of the distortion increases as the angle between the eye gaze and the optical axis of the camera increases.
Solutions for correcting angular distortions in iris templates extracted from off-axis eye images are disclosed in Stephanie Schuckers, Natalia Schmid, Aditya Abhyankar, Vivekanand Dorairaj, Christopher Boyce and Lawrence Hornak "On Techniques for Angle Compensation in Nonideal Iris Recognition" IEEE Transactions on Systems, Man, and Cybernetics, Part B (Cybernetics) volume 37(5) (Oct.) 2007. According to these solutions, methods adapted from camera calibration are used to train a network with known angular distortions (eye gaze angles), and with estimated angular distortions. Once the gaze angle is found, the image is corrected using an orthographic rotation in the image plane and the corrected iris image is treated as it were a frontal view image.
Joseph Thompson, Hector Santos-Villalobos, Mahmut Karakaya, Del Barstow, David Bolme and Chris Boehnen "Off-angle iris correction using a biological model" IEEE Sixth International Conference on Bio-metrics: Theory, Applications and Systems (BTAS) (October) 2013, discloses the use of a 3D biological model of the eye and cornea to infer the correction for cornea refraction. The 3D model is an approximation, i.e. a generalized model for all eyes, which does not use knowledge of individual subjects' physiological characteristics.
Advancements in information technology, especially related to augmented, mixed or virtual reality applications, have generated an increasing demand for iris biometrics which can perform in a reliable and efficient way, without relying on cooperation of the user in keeping their gaze aligned to the optical axis of the camera—a requirement that would result in a poor user experience in augmented, mixed or virtual reality.

Image acquisition system for off-axis eye images


A process for efficiently producing 2,6-dimethylnaphthalene which comprises subjecting 2-methyl-1-(p-tolyl)butene and/or 2-methyl-1-(p-tolyl)butane as the starting raw material to a cyclization dehydrogenation reaction in the presence of a catalyst comprising (a) a palladium component, (b) an alkali or alkaline earth metal compound and (c) aluminum oxide. The process enables the production of highly pure 2,6-dimethylnaphthalene in a high yield at a low cost. The catalyst used in the process affords high safety and stability.

1. Field of the Invention
The present invention relates to a process for producing 2,6-dimethylnaphthalene. More particularly, it pertains to a catalyst for producing 2,6-dimethylnaphthalene which is useful as a starting raw material for 2,6-naphthalene dicarboxylic acid.
2,6-Napthalene dicarboxylic acid has an industrially important use as a starting raw material for high-performance polyester, polyethylene naphthalate fibers and films having excellent tensile strength and heat resistance.
2. Description of Related Art
2,6-Dimethylnaphthalene has heretofore been obtained by isolating it from a coal tar fraction or a fraction of heavy oil subjected to fluid catalytic cracking (FCC). However, the aforementioned isolation process affords the fraction in the form of a mixture containing almost all the types of methyl group-position isomers such as 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3- and 2,7-dimethylnaphthalene in addition to the objective 2,6-dimethylnaphthalene. Thus, the process for isolating and purifying 2,6-dimethylnaphthalene from such fraction mixture suffers from the disadvantage of a number of steps and a high cost required in the production thereof, making itself unsuitable for inexpensive mass-production of 2,6-dimethylnaphthalene.
There have recently been proposed several processes for producing 2,6-dimethylnaphthalene from a variety of starting raw materials, but there has not yet been established an industrial production process capable of efficiently and selectively synthesizing 2,6-dimethylnaphthalene by the use of inexpensive starting raw material available in a large quantity.
Examples of the above-mentioned process include the process disclosed in Japanese Patent Application Laid-Open Nos. 172937/1985, 29536/1987 and 8344/1988 in which naphthalene or monomethylnaphthalene is methylated into dimethylnaphthalene and the process disclosed in Japanese Patent Application Laid-Open Nos. 45536/1985 and 14737/1988 in which naphthalene or monomethylnaphthalene is transmethylated into dimethylnaphthalene by using polymethylbenzene.
Nevertheless, the process disclosed in any of the aforesaid laid-open patent applications suffers from the defects that the conversion of naphthalene and monomethylnaphthalene to 2,6-dimethylnaphthalene is low and selective production of 2,6-dimethylnaphthalene is difficult. Consequently, the process necessitates complicated isolating purification steps and intricate isomerization steps, thus causing disadvantageous problems from the industrial point of view.
In addition, Japanese Patent Application Laid-Open Nos. 61647/1973 and 48647/1974 disclose a process for production of 2,6-dimethylnaphthalene by cyclization, dehydrogenation and isomerization of 5-(o-tolyl)pentene-2 to be used as a starting material. Moreover, Japanese Patent Publication Nos. 17983/1975, 17985/1975 and 22550/1975 disclose a process for producing dimethylnaphthalene by the cyclization dehydrogenation of 5-(o-tolyl)pentene-2.
In the above-mentioned processes, however, 5-(o-tolyl)pentene-2 to be used as a starting material is usually produced from o-xylene and 1,3-butadiene by the use of an alkali metal such as potassium or sodium as a catalyst, and many problems remain unsolved with, regard to the catalyst handling, especially with respect of safety. Likewise, as the resultant dimethylnaphthalene is obtained as the mixture of isomers such as 1,5-dimethylnaphthalene, 1,6-dimethylnaphthalene, 2,6-dimethylnaphthalene and the like, the production of 2,6-dimethylnaphthalene therefrom suffers a lot of disadvantages that the steps of isomerization, separation and purification are necessary.
On the other hand, attempts have been made to selectively produce 2,6-dimethylnaphthalene by cyclization and dehydrogenation of 2-methyl-1-(p-tolyl)butene or 2-methyl-1-(p-tolyl)butane as disclosed, for example, in Japanese Patent Publication No. 5292/1978 wherein a catalyst comprising rhenium oxide, an alkali metal oxide or alkaline earth metal oxide and alumina is used, and in Japanese Patent Publication No. 1701/1976 wherein a catalyst of chromia/alumina series containing an alkali metal oxide is employed.
However, the above-disclosed catalysts are unfavorable, since the use thereof results in a low yield and an insufficient purity of the objective 2,6-dimethylnaphthalene; besides the highly toxic chrominum compound contained therein will bring about environmental pollution problems.
It has been disclosed by the present inventors, in Japanese Patent Application Laid-Open Nos. 173834/1991 and 251545/1991, that in the production of 2,6-dimethylnaphthalene by cyclization dehydrogenation of 2-methyl-1-(p-tolyl)butene or 2-methyl-1-(p-tolyl)butane, 2,6-dimethylnaphthalene with high purity is obtained at a relatively high yield by the application of a catalyst comprising lead and alumina incorporated with a third component and a catalyst comprising indium and alumina incorporated with a third component. Nevertheless, the above-developed catalysts still involve some problems such that the catalyst containing a lead component is industrially unfavorable due to its toxicity and the catalyst containing an indium component sometimes evaporates away during its use owing to the high volatility of a monovalent indium compound formed during the reaction and the like. Under such circumstances, it has been sought for a long time to develop a catalyst capable of producing highly pure 2,6-dimethylnaphthalene at a high yield with a stabilized operation without causing any problem relating to sanitation.
In the case where 2-methyl-1-(p-tolyl)butene or 2-methyl-1-(p-tolyl)-butane as a raw material is reacted by the use of a catalyst consisting of aluminum oxide alone, dimethylnaphthalene is generally produced but the yield thereof is too low and unfavorable side reaction such as isomerization, decomposition and polymerization of a raw material are too excessive to make the catalyst industrially usable.
The application of a catalyst consisting of aluminum oxide incorporated with a palladium component to the above reaction improves the selectivity to cyclization dehydrogenation and increases the yield of dimethylnaphthalene, but remarkable side reactions such as isomerization and demethylation of the resultant dimethylnaphthalene takes place together with decomposition and polymerization of a raw material, thus unfavorably lowering the selectivity to the objective 2,6-dimethylnaphthalene.
On the other hand, the application of a catalyst consisting of an alkali metal component or an alkaline earth metal component each supported on aluminum oxide can suppress decomposition and polymerization of 2-methyl-1-(p-tolyl)butene or 2-methyl-1-(p-tolyl)butane as a raw material, but the catalyst scarcely exhibits cyclization dehydrogenation activity or even if it exhibits the activity, the yield of dimethylnaphthalene is too low to make the catalyst industrially usable.
Specifically, the use of a catalyst consisting only of aluminum oxide unfavorably causes a variety of side reactions due to acid points on the surface of the catalyst including isomerization, decomposition and polymerization of a raw material to take place in the reaction process.
In view of the above, intensive research and investigation were concentrated by the present inventors in order to solve and overcome the above-mentioned problems. As a result, it has been discovered by the present inventors that highly pure 2,6-dimethylnaphthalene is obtained at a high yield by the use of a catalyst comprising a palladium component, at least one compound selected from alkali metal compounds and alkaline earth metal compounds and aluminum oxide. The present invention has been accomplished on the basis of the above-mentioned finding and information.

Process for producing 2,6-dimethylnaphthalene


A radar highway motor vehicle guidance apparatus for guiding a land vehicle along a roadway using a backward looking and a forward looking, lateral position sensing, monopulse tracking radar guidance apparatus which transmits radar pulses backward and forward of the vehicle. The pulses are reflected back to the vehicle by a stripe distributed along the roadway. The stripe is a frequency selective surface which generates retro-reflective grating lobes at an operating frequency of the tracking radar. Operating the radar at two frequencies allows the radar to look at regions spaced at two different distances from the front of the vehicle. Highway related information may be encoded in the frequency selective surface by variations in the shape or dimensions of the frequency selective stripe morphology in order to modulate the reflected signal with highway information which is then also detected at the radar receiver. Target discrimination is enhanced by using pseudo random codes and matching antenna polarization with stripe polarization.

Automated highway systems utilize sensing and computing equipment to assist operators of motor vehicles in safely and comfortably travelling along a suitably equipped highway. A future automated highway system minimally provides supplemental information to the operator and optimally permits entirely autonomous machine control of each individual truck or automobile without requiring substantial operator intervention. Such an automated system must be capable of detecting roadway obstructions and other traffic, steering the vehicle and controlling its speed, maintaining a safe spacing between vehicles and detecting information such as roadway weather conditions, location for navigational purposes and upcoming highway structures, such as exits.
An extensive variety of automated highway system architectures have been proposed. Several use radar systems which sense obstructions in the forward or side directions, such as other vehicles and guide rails. Radar has the advantage that it is an active system giving all-weather and day or night performance, and has the inherent capability of sensing distance and direction to reflective targets. Radar has also been used for the guidance of airborne ordnance delivery vehicles, such as guided missiles and airplanes. Modern radar scattering technology also allows echo signatures from objects to be interpreted and used for providing additional information. However, within the knowledge of the inventors, a forward-looking radar system has not been developed for highway motor vehicle guidance, i.e. steering.
It is an object and feature of the present invention to provide a highway vehicle guidance system utilizing radar which looks backwards or looks both backwards and ahead of the vehicle to detect information both for guiding the vehicle along the highway and for detecting prerecorded information about upcoming highway structures and conditions.


An roller assembly for attachment to a lawnmower. The roller assembly generally includes a tow arm having first and second links. The first link is configured to be supported at least indirectly on the lawnmower frame. The second link is connected to a shaft mounted with one or more rollers. A spring is disposed between the first and second links and configured to bias the second link downwardly relative to the first link, thereby biasing the rollers against a ground surface. The roller assembly further includes a quick connect assembly for rapid attachment and detachment of the roller assembly to the lawnmower. The roller assembly yet further includes latch assembly configured to hold the second link and shaft of rollers in a raised position relative to the ground surface.

1. Field of the Invention
The invention relates to a roller assembly and, more particularly, relates to a roller assembly towed by a lawnmower for striping a grass lawn.
2. Discussion of the Related Art
Roller assemblies are generally known in the grooming of lawns. In particular, roller assemblies are typically used in areas such as golf courses and baseball stadiums to create the aesthetic striped appearance on the grass. The roller assemblies generally tow behind lawnmowers and bend the freshly cut grass to create the desired striped appearance across the lawn.
However, known roller assemblies have several drawbacks. For instance, typical roller assemblies are directly attached to the cutting deck of lawnmowers. Consequently, the roller assembly is unable to float independently with respect to the cutting deck. In addition, known roller assemblies require significant effort and additional tools to attach/detach from the lawnmowers. As yet another example, known roller assemblies either are not raisable to a stowed, inoperative position or require cumbersome ropes, chains, or other attachments linked to the lawnmower to stow the roller assembly. In yet another example, known roller assemblies include spring assemblies attached between a removable part of the roller assemblies and a permanent fixture on the frame of the mowers.
In light of the foregoing, a roller assembly is desired that improves the state of the art by overcoming one or more of the aforesaid problems of the prior art.


A yarn supply apparatus is equipped with a clutch arrangement in order to couple a drive wheel to rotate with a yarn supply wheel as necessary. The clutch arrangement is constructed in an open design, in which any development of narrowing spaces is avoided. For this purpose one clutch half is provided with axial fingers, which engage in radially open longitudinal slots, formed by a toothing, of the other clutch half. The slots of the toothing are longer than the engagement length between fingers and toothing. The intermediate space formed between the ends of the fingers and the nearest wall in axial direction is open in radial direction or is in communication with a larger inner space. Thereby the compression or compaction of deposited fluff is prevented.

Textile machinery or accessory apparatus therefor often needs clutch arrangements with which rotatable machine parts can as necessary be affixed to rotate with each other or separated from each other to disengage a driving relationship. Such clutch arrangements usually operate interengagingly. A problem in such clutch arrangements is the relatively large dirt load. Dust in the form of detaching filaments breaks away from the processed yarn and settles on stationary and moving machine parts. Particles of impregnating material also become detached from the yarn, which is often moving at relatively high speed, and then settle as a thin paraffin coating, for example, on the machine parts. The filaments and possibly the particles of impregnating material then form a fluff deposit, which frequently is troublesome and can impair the function of the clutch arrangement.
Clutch arrangements in particular can suffer from fluff deposits. For example, if an engageable teeth clutch is disengaged for some time, fluff (disordered deposits of filaments, dust and other dirt particles such as paraffin, oil and others) can be deposited on the exposed teeth and then be compressed when the teeth clutch is engaged. If this process is repeated several times, in that the clutch is disengaged and then reengaged with fluff deposited on the teeth, so much compacted fluff gradually accumulates on the teeth clutch that it can no longer be adequately engaged.
The inventors have tried to overcome this problem using the yarn supply apparatus known from practice illustrated in FIG. 1. The yarn supply apparatus is provided with a support member 1, which can be fixed with one end 2 to a mating ring of a knitting machine. At the opposite end the base member is provided with an attachment 3 containing a through-hole, in which a shaft 6, which during use is usually vertically oriented, is rotatably mounted by means of two deep-groove ball bearings 4, 5 disposed some distance apart. At its lower end according to FIG. 1, the shaft 6 carries a cage-type yarn supply wheel 7. At its upper end the shaft 6 carries two drive wheels 11, 12, mounted rotatably and disposed some distance apart on the shaft via deep-groove ball bearings 8, 9. Between the drive wheels 11, 12 a clutch piece 15 is seated on and for rotation with a hexagonal segment 14, which in turn is affixed to rotate with the shaft 6. At its two opposite flat sides (top and bottom sides), this clutch piece 15 is provided with externally toothed hubs 16, 17. The external toothings mesh respectively with internal toothings 18, 19 provided on the drive wheels 11, 12, so that the respective drive wheel 11 or 12 is coupled for rotation with the shaft 6 when the clutch piece 15 is engaged with the corresponding drive wheel 11 or 12.
To prevent ingress of dust, fluff or other deposits to the toothings 16, 17, 18 and 19, the clutch piece 15 is provided on both flat sides with tubular attachments 21, 22, which engage in matching annular spaces 23, 24 of the drive wheels 11, 12 and thus close off the clutch arrangement to the outside.
A certain amount of clearance must be available between the respective attachment 21, 22 and the walls of the respective annular space 23, 24, to prevent engagement or frictional coupling of the clutch arrangement in disengaged position. Thus naturally the seal can only be imperfect. Moreover, fluff can collect in the annular spaces 23, 24 and ultimately prevent the clutch piece 15 from being moved axially. While it is indisputable that fluff can therefore penetrate though the annular spaces 23, 24 in the course of time, it is trapped therein during the engagement process, or in other words during constriction of the annular spaces 23, 24. Although the annular spaces 23, 24 are not hermetically sealed, they do not allow the fluff to escape during the engagement process, and to this extent are tight.
Another problem results from a latching arrangement 26 provided on the clutch piece 15. This consists of a ball mounted in a radial bore or of a pin that presses radially inward under spring action and engages in corresponding notches in the hexagonal segment 14. If fretting corrosion develops or fluff penetrates here, proper function can no longer be assured. For example, the coupling piece 15 can be blocked, such that it can no longer be moved axially, or the latching action can fail, so that the clutch piece 15 is no longer retained in its intended positions.
Fretting corrosion can also develop between the clutch piece and the hexagonal segment, whereby the clutch piece can become jammed.
From DE 30 42 989 A1 (Federal Republic of Germany) there is known a yarn supply apparatus for textile machinery which is provided with a rotatably mounted, driven yarn supply wheel. The yarn supply wheel is coupled with a drive wheel via a clutch arrangement. The clutch arrangement is a shiftable interengageable clutch, one clutch half of which is provided with studs extending in axial direction and the other clutch half of which is provided with corresponding holes to receive the studs.
Fluff can be deposited on the clutch halves and then be compacted when the clutch halves are closed together. Deposited and compacted fluff layers can ultimately become so thick that the clutch can no longer be reliably engaged.
This problem is seen analogously in the yarn supply apparatus known from TW 108049 (Taiwan). The yarn supply apparatus is provided with a teeth clutch, the clutch halves of which are provided on the face side with toothed bushings or attachments bearing on mating faces. Deposits in this region can prevent proper engagement.

Yarn supply apparatus and clutch arrangement therefor


An image sensor includes a light source that emits modulated light such as visible light, white light, or white light-emitting diode (LED) light to a target object, a plurality of pixels, and an image processing unit. The pixels include at least one pixel for outputting pixel signals according to light reflected by the target object. The image processing unit simultaneously generates a color image and a depth image from the pixel signals of the at least one pixel.

1. Technical Field
The inventive concept relates to an image sensor, and more particularly, to an image sensor for simultaneously obtaining a color image and a depth image, a method of operating the image sensor, and an image processing system including the image sensor.
2. Discussion of Related Art
Since digital cameras, digital camcorders, and mobile phones having a camera or camcorder function are widely used, there is a growing demand for high quality image sensors. An image sensor is a semiconductor device for converting an optical image into an electric signal. Stereoscopy refers to a technique for creating or enhancing the illusion of depth in an image by presenting two offset images separately to the left and right eye of the viewer. Since the demand for stereoscopic images have increased, there is a growing demand for image sensors that can capture image data including both color information and depth information.

Image sensor for simultaneously obtaining color image and depth image, method of operating the image sensor, and image processing system including the image sensor