The invention relates to a method for performing a handover of a mobile node (MN) from a source to a target network, wherein a handover proxy node (HPN) is used to relay the handover of the MN to one of previously measured cells. The MN discovers an appropriate HPN and triggers the handover to the HPN by reporting the measurements together with the HPN ID as destination of the handover. When receiving the Handover Initiation message for handing over the MN to the HPN, the HPN will not proceed with the handover but adapts said handover to indicate a handover of the MN from the HPN to the target base station. Upon receiving the Handover Initiation message in the target network, system resources are configured for data forwarding between the source and target network, and for the data path used by the MN when attaching to the target base station.

Communications systems evolve more and more towards an Internet Protocol (IP)-based network. They typically consist of many interconnected networks, in which speech and data is transmitted from one terminal to another terminal in pieces, so-called packets. IP packets are routed to the destination by routers in a connection-less manner. Therefore, packets comprise IP header and payload information, and the header comprises, amongst other things, a source and destination IP address.
For scalability reasons, an IP network uses a hierarchical addressing scheme. Hence, an IP address does not only identify the corresponding terminal, but additionally contains location information about this terminal. With additional information provided by routing protocols, routers in the network are able to identify the next router towards a specific destination.
LTE—Long Term Evolution
UMTS (Universal Mobile Telecommunications System) is the 3G (3rd Generation) mobile communication system standardized by 3GPP (3rd Generation Partnership Project).
The 3GPP (3rd Generation Partnership Project) launched a study item "Evolved UTRA and UTRAN" better known as "Long Term Evolution (LTE)". The study will investigate means of achieving major leaps in performance in order to improve service provisioning, and to reduce user and operator costs. Out of that and because interworking with other radio access technologies should be possible, the need arose for a new evolved Packet Core Network.
An exemplary representation of the E-UTRAN architecture is given in FIG. 1. The E-UTRAN consists of evolved Node Bs (eNB or eNodeB), providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the mobile node (also referred to in the following as UEs, MS or MNs).
The eNB hosts the Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Control Protocol (PDCP) layers that include the functionality of user-plane header-compression and encryption. It also offers Radio Resource Control (RRC) functionality corresponding to the control plane. Further, it performs many functions including radio resource management, admission control, scheduling, enforcement of negotiated UL-QoS (Quality of Service), cell information broadcast, ciphering/deciphering of user and control plane data, and compression/decompression of DL/UL user plane packet headers. The eNBs are connected by means of the S1 interface to the EPC (Evolved Packet Core), more specifically to the MME (Mobility Management Entity) via the S1-MME, and to the Serving Gateway (S-GW) by means of the S1-U interface.
The S-GW routes and forwards user data packets, while also acting as the mobility anchor for the user plane during inter-eNB handovers and as the anchor for mobility between LTE and other 3GPP technologies (terminating S4 interface and relaying the traffic between 2G/3G systems and Packet Data Network Gateway). For idle state UEs, the S-GW terminates the DL data path and triggers paging when DL data arrives for the UE. It manages and stores UE contexts, e.g. parameters of the IP bearer service, network internal routing information. It also performs replication of the user traffic in case of lawful interception.
The MME is the key control-node for the LTE access-network. It is responsible for idle mode UE tracking and paging procedure including retransmissions. It is involved in the bearer activation/deactivation process and is also responsible for choosing the S-GW for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation. It is responsible for authenticating the user (by interacting with the Home Subscriber Server, HSS). It checks the authorization of the UE to camp on the service provider's Public Land Mobile Network (PLMN) and enforces UE roaming restrictions. The MME is the termination point in the network for ciphering/integrity protection for NAS signaling and handles the security key management. The MME also provides the control plane function for mobility between LTE and 2G/3G access networks with the S3 interface terminating at the MME from the SGSN (Serving GPRS Support Node). The MME also terminates the S6a interface towards the home HSS for roaming UEs.
The Packet Data Network Gateway (PDN-GW) provides connectivity for the UE to external packet data networks by being the point of exit and entry of traffic for the UE. A UE may have simultaneous connectivity with more than one PDN-GW for accessing multiple PDNs. The PDN-GW performs MN IP address allocation, policy enforcement, packet filtering (e.g. deep packet inspection, packet screening) for each user in order to map the MN's traffic to an appropriate QoS level, charging support, lawful interception and packet screening. The PGW performs the function management of a HA in case of MIPv6 and of LMA in case PMIPv6 protocols are used for mobility. Another key role of the PDN-GW is to act as the anchor for mobility between 3GPP and non-3GPP technologies.
To summarize the above, in order to support the new E-UTRAN access, the new 3GPP Core Network is mainly separated into three logical entities. At first, in the user plane the PDN-GW is the gateway to the external networks and the global mobility anchor for mobility between 3GPP and non-3GPP access technologies (like CDMA2000, WiMAX or WIFI). Second, another user plane entity, the Serving Gateway, is the mobility anchor for mobility between 3GPP accesses (E-UTRAN, UTRAN, GERAN). Third, a Mobility Management Entity is the control plane entity responsible for the mobility management of mobile terminals moving between different EUTRAN base stations (eNodeBs) and also responsible for the session management.
As described above, the MME is responsible for mobility management and session management. For each mobile terminal attached to an MME, specific mobility management and evolved packet system context information is stored in the MME. These contexts comprise, e.g. the mobility state, the temporary identity, the current Tracking Area List, last known cell, authentication vectors, access restrictions, subscribed QoS profile, subscribed charging characteristics, and for each active PDN connection the APN (Access Point Name) in use, IPv4/IPv6 addresses, PDN-GW address for control plane, and also information for each EPS (Evolved Packet System) bearer within the PDN connection, as for example EPS bearer QoS profile, EPS bearer charging characteristics.
Public Land Mobile Networks & Roaming Agreements
A public land mobile network (PLMN) is a network that is established and operated by an administration or by a recognized operating agency for providing land mobile telecommunications services. PLMNs interconnect with other PLMNs and Public switched telephone networks (PSTN) for telephone communications or with internet service providers for data and internet access. A PLMN may be considered as an extension of a fixed network, e.g. the Public Switched Telephone Network (PSTN) or as an integral part of the PSTN. This is just one view-point on PLMN. PLMN mostly refers to the whole system of hardware and software which enables wireless communication, irrespective of the service area or service provider. A separate PLMN may be defined for each country or for each service provider.
Every PLMN organisation has its own management infrastructure, which performs different functions depending on the role played and the equipment used by that entity. However, the core management architecture of the PLMN organisation is similar, such as: providing services to its customers; infrastructure to fulfil the services (advertise, ordering, creation, provisioning, . . . ); assuring the services (Operation, Quality of Service, Trouble Reporting & Fixing . . . ); billing the services (Rating, Discounting, . . . ).
Not every PLMN organisation will implement the complete Management Architecture and related processes. Some processes may be missing depending on the role a particular organisation is embodying. Processes not implemented by a particular organisation are accessed via interconnections to other organisations, which have implemented these processes. The Management architecture itself does not distinguish between external and internal interfaces.
A MN subscribed to 3GPP services has a home PLMN (HPLMN) that maintains the subscription data, allowed services and QoS levels. When the MN is attached to a network different from the HPLMN, the MN is indicated as roaming node and the visited network is denoted as visited PLMN (VPLMN).
In general, "roaming" can be defined as the ability for a cellular customer to automatically make and receive voice calls, send and receive data, or access other services, including home data services, when travelling outside the geographical coverage area of the home network, by means of using a visited network.
The differentiation between HPLMN and VPLMN is technically given by the type of subscriber entry in a specific network. When a mobile device enters a new visited network and has no entry in the home subscriber register of the network (e.g. Home Location Register, HLR, in GSM networks or local customer database in WLANs), the required subscriber data must first be requested by the visited network e.g. from the subscriber's home network in order that the subscriber can be authenticated and any authorization for using the network services can be checked. The "visiting" subscriber acquires an entry in a user database of the visited network (e.g. Visited Location Register, VLR) and the authorized network services are enabled. If there is no roaming agreement between the two networks, i.e. HPLMN and VPLMN, maintenance of service is impossible, and service is denied by the visited network.
A roaming user is connected to the E-UTRAN, MME and S-GW of the visited network. However, by using the home network's PDN-GW, the user has access to the home operator's services even while in the visited network.
Generic Access Network (GAN)
Another system specified by 3GPP and independent from LTE/SAE is the Generic Access Network (GAN) also known as Unlicensed Mobile Access (UMA). GAN provides access to mobile operator services and to the 3GPP core network using a generic IP connection (e.g. WLAN+DSL). With GAN certain 3GPP protocols are tunnelled from the terminal over the IP connection to the 3GPP Core Network (see FIG. 2). Furthermore, GAN supports seamless handover between wireless LANs and the 3GPP access for dual-mode terminals. On the cellular network, the mobile terminal communicates over the air with a NodeB, through a base station controller, to nodes in the core network. Under the GAN system, when the terminal detects a wireless LAN, it establishes a secure IP connection through a gateway to a server called a GAN Controller (GANC) on the 3GPP network. The GANC presents itself to the mobile core network as a standard cellular base station. The terminal communicates with the GANC over the secure connection using existing GSM/UMTS protocols. Thus, when the terminal moves from a 3GPP to an 802.11 network, it appears to the core network as if it is simply on a different base station.
In the following, some of the standard GAN procedures will be described with reference to FIG. 5-9. Some of the embodiments of the invention partly reuse messages of the GAN protocol to perform an improved handover.
Discovery Procedure
When a MS supporting GAN first attempts to connect to a GAN, the MS needs to identify the Default GANC. Each GAN capable MS can be configured with the FQDN (or IP address) of the Provisioning GANG. The MS first connects to a GANC in the HPLMN of the MS, by establishing a secure IPsec tunnel and a TCP connection using the provisioned or derived addresses. The MS obtains the FQDN or IP address of the Default GANC in the HPLMN through the Discovery procedure. The following steps of the discovery procedure are illustrated in FIG. 5.                1. If the MS has a provisioned or derived FQDN of the Provisioning GANC, it performs a DNS (Domain Name Service) query to resolve the FQDN to an IP address.        2. The DNS Server returns a response including the IP Address of the Provisioning GANC.        3. The MS establishes a secure tunnel to the Provisioning GANC.        4. The MS sets up a TCP connection to a well-defined port on the Provisioning GANC. It then queries the Provisioning GANG for the Default GANC, using GA-RC DISCOVERY REQUEST. The message contains:                    Cell Info: Either current camping GERAN/UTRAN cell ID, or last LAI where the MS successfully registered, along with an indicator stating which one it is.            Generic IP access network attachment point information: AP-ID            MS Identity: IMSI.                        5. The Provisioning GANG returns the GA-RC DISCOVERY ACCEPT message, using the information provided by the MS (e.g. the CGI, Cell Global Identifier), to provide the FQDN or IP address of the Default GANC. This is done so the MS is directed to a "local" Default GANC in the HPLMN to optimize network performance.        6. If the Provisioning GANC cannot accept the GA-RC DISCOVERY REQUEST message, it returns a GA-RC DISCOVERY REJECT message indicating the reject cause.        7. The secure IPsec tunnel to the Provisioning GANC is released. It shall also be possible to reuse the same IPsec tunnel for GAN Registration procedures. In this case the IPsec tunnel is not released.Registration Procedure
Following the Discovery procedure the MS establishes a secure tunnel with the secure gateway of the Default GANC, provided by the Provisioning GANG in the Discovery procedure, and attempts to register with the Default GANG. The Default GANG may become the Serving GANG for that connection by accepting the registration, or the Default GANG may redirect a MS performing registration to a different Serving GANG.
GANC redirection may be based on information provided by the MS during the Registration procedure, operator chosen policy or network load balancing. The following steps for the registration procedure are illustrated in FIG. 6.                1. If the MS was provided the FQDN of the Default or Serving GANG, the MS shall perform a DNS query to resolve the FQDN to an IP address.        2. The DNS Server returns a response.        3. The MS shall then set up a secure IPsec tunnel to the GANG. This step may be omitted if an IPsec tunnel is being reused from an earlier Discovery or Registration.        4. The MS then sets up a TCP connection to a TCP port on the GANG. The TCP port can either be a well-known port or one that has been earlier received from the network during Discovery or Registration. The MS shall attempt to register on the GANG by transmitting the GA-RC REGISTER REQUEST. The message includes:                    Cell Info: Either current camping GERAN/UTRAN cell ID, or last LAI where the MS successfully registered, along with an indicator stating which one it is. In addition, the MS includes the UARFCN of the current serving cell (if that cell is a UTRAN cell). Generic IP access network attachment point information: AP-ID.            MS Identity: IMSI.                        5. If the GANG accepts the registration attempt it shall respond with a GA-RC REGISTER ACCEPT. The message contains:                    GAN specific system information (e.g.):            GAN Mode Indicator: GAN A/Gb mode or GAN Iu mode.            Cell description of the GAN cell:                            a. If GAN Iu mode selected: The UTRA ARFCN (UARFCN) and Primary Scrambling Code (PSC) corresponding to the GAN cell.                                    Location-area identification comprising the mobile country code, mobile network code, and location area code corresponding to the GANC cell.            Cell identity identifying the cell within the location area corresponding to the GAN cell.                        In this case the TCP connection and the secure IPsec tunnel are not released and are maintained as long as the MS is registered to this GANC.        6. Alternatively, the GANC may reject the request. In this case, it shall respond with a GA-RC REGISTER REJECT indicating the reject cause. The TCP connection and the secure IPsec tunnel are released        7. Alternatively, if the GANC wishes to redirect the MS to (another) Serving GANC, it shall respond with a GA-RC REGISTER REDIRECT providing the FQDN or IP address of the target Serving GANC. In this case the TCP connection is released and the secure IPsec tunnel is optionally released depending on if the network indicates that the same IPsec tunnel can be reused for the next registration.PS (packet switched) Handover from UTRAN to GAN (Preparation Phase) FIG. 7a         1. Based on measurement results and knowledge of the RAN topology, the source SRNC decides to initiate a combined hard handover and SRNS relocation.        2. The source SRNC sends a Relocation Required message (Relocation Type, Cause, Source ID, Target ID, Source RNC To Target RNC Transparent Container) to the SGSN.        3. The SGSN determines the target cell is the GANC, based on the contents of Relocation Required. It then sends the Relocation Request message (Permanent NAS UE Identity, Cause, CN Domain Indicator, Source RNC To Target RNC Transparent Container, RAB To Be Setup) to the GANG.        4. One or more GAN PTCs are established between the GANG and MS. Upon the GA-RRC PTC establishment, the PS domain GA-RRC sublayer entity in the MS enters the PTC-ACTIVE substate.        5. The GANG sends the Relocation Request Acknowledge message (Target RNC To Source RNC Transparent Container, RABs Setup, RABs Failed To Setup) to the SGSN.PS Handover from UTRAN to GAN (Execution Phase) FIG. 7b         1. Upon receiving the positive acknowledgement from the GANG to serve the MS, the SGSN initiates the Execution Phase by sending the Relocation Command to the source SRNC.        2. a) The RNC may start forwarding GTP PDUs to the GANG while still transmitting them in the downlink to the MS. This forwarding is routed via the Iu-PS interface. The GANG may buffer, start a blind transmission of downlink user data towards the MS over the allocated PTC(s), or discard these forwarded GTP PDUs, depending on the QoS profile, network conditions, and whether it supports data forwarding.                    b) The RNC instructs the MS to initiate the switch to GAN via the Physical Channel Reconfiguration message.            c) The RNC sends the Forward SRNS Context message to the GANG via the SGSN.                        3. Immediately after receiving the Physical Channel Reconfiguration message, the MS sends GA-RRC RELOCATION COMPLETE message to the GANG. Upon receiving this message and the Forward SRNS Context message, the GANG becomes the Serving RNC.        4. Immediately upon receiving the GA-RRC HANDOVER COMPLETE message from the MS, the GANG sends the Relocation Detect message to the SGSN.        5. The GANG sends the Relocation Complete message to the SGSN.        6. The MS, GANC and CN exchange user data via the established PTC.        7. The SGSN releases the Iu-PS connection with the old RNC.        8. If the Routing Area of the GANC cell (as indicated by the GANC to the MS in GAN registration) is different from that under the old RNC, then the MS performs the Routing Area Update procedure.PS Handover from GAN to UTRAN (Preparation Phase) FIG. 8a         1. The MS is in active packet flow exchange with active PDP Context(s) and PTC(s) in the GAN.        2. The GANC may send a GA-RRC UPLINK QUALITY INDICATION if there is a problem with the uplink quality for the ongoing session. Uplink Quality Indication is information sent by the GANC to the MS indicating the crossing of an uplink quality threshold in the uplink direction. Whenever the MS receives an indication of bad quality, it should start the relocation procedure, as described in the next step. Alternatively, MS can use its local measurements to decide to initiate the handover procedure.        3. The MS decides to initiate a PS handover from GAN to UTRAN by sending GA-RRC RELOCATION INFORMATION message to the GANC. The GA-RRC RELOCATION INFORMATION message indicates a list of target cells, identified by cell ID, in order of preference for PS handover, and includes the received signal strength for each identified cell.        4. The GANC selects a target RNC based on the contents of the GA-RRC RELOCATION INFORMATION message. It sends a Relocation Required message to the SGSN containing the selected RNC information.        5. The SGSN sends a Relocation Request message to the target RNC.        6. The RNC performs the necessary allocation of radio and Iu transport resources.        7. The RNC returns a Relocation Request Acknowledge message to the SGSN. This message contains a transparent container that contains channelization information needed by MS to access UTRAN.PS Handover from GAN to UTRAN (Execution Phase) FIG. 8b         1. The SGSN begins the Execution Phase by issuing the Relocation Command message to the GANC. The message contains the channel access information in the target UTRAN cell.        2. a) The GANC sends the GA-RRC RELOCATION COMMAND to the MS. This message contains the information from the Relocation Command received in Step 1 earlier.                    b) The GANC also sends the Forward SRNS Context message to the target RNC via the SGSN.                        3. The SGSN relays the Forward SRNS Context message to the target RNC.        4. Upon receiving the GA-RRC RELOCATION COMMAND, the MS immediately suspends uplink GTP PDU transfer. It immediately begins accessing the UTRAN using the indicated channelization parameters in the message. The MS's access attempt is detected by the Node B and RNC, and is reported to the SGSN via the Relocation Detect message.        5. The MS completes the lower layer setup and configuration, and sends the RRC Physical Channel Reconfiguration Complete to the target RNC. This triggers the target RNC to send the Relocation Complete message to SGSN. At this stage, the target RNC assumes the role of SRNC for the MS.        6. The packet data flow is now active via the UTRAN.        7. The SGSN releases the Iu-PS connection by sending the Iu Release Command message to the GANC, to which GANG responds with Iu Release Complete message.        8. If the Routing Area of the UTRAN cell is different from that of the GAN cell, then the MS performs the Routing Area Update procedure.PTC Activation when Gang Receives Relocation Request
The following FIG. 9 depicts the Packet Transport Channel activation procedure when the GANG receives the Relocation Request message from the SGSN.                1. The MS has successfully registered with the GANG. The MS, GANG and SGSN perform signalling procedures related to PS handover.        2. The SGSN sends the Relocation Request message to the GANG and includes the RAB ID, the CN Transport Layer Address (IP address) and the CN Iu Transport Association (GTP-U Tunnel Endpoint Identifier, TEID) for user data.        3. The GANG sends the GA-RRC RELOCATION REQUEST message to the MS to request activation of the Packet Transport Channel(s) for PS handover purposes. The message includes the RAB ID, a TEID that the GANG assigns to the MS for downlink data transfer, the GANG PTC IP Address (i.e., the destination address for PTC GA-RRC PDU messages from the MS) and the GANG TEID assigned by the GANG for uplink data transfer, for each of the RABs.        3. The MS acknowledges the activation of the PTC(s) in the GA-RRC RELOCATION REQUEST ACK message. The PS domain GA-RRC sublayer entity in the MS transitions to the GA-RRC-CONNECTED state and the PTC-ACTIVE substate for each PTC and starts the PTC Timer for each PTC.        4. The GANG sends the Relocation Request Ack message to the SGSN to complete the handover preparation procedure. The GANG includes the RAB ID, the RAN Transport Layer Address (i.e., the GANC's Iu-PS IP address) and the RAN Iu Transport Association (i.e., the TEID that the GANG assigned to the MS) for each RAB.        5. PS handover is performed.        6. The MS transfers uplink user data by sending a GA-RRC PDU message to the GANG PTC IP address received in step 3. The message includes the GANG TEID received in step 3, which allows the GANG to relay the GA-RRC PDU message payload using the correct GTP-U tunnel on the Iu-PS interface. The GANG relays the message payload to the SGSN in the Iu-PS G-PDU message.        7. The SGSN transfers downlink user data by sending a Iu-PS G-PDU message to the GANG Iu-PS IP address received in step 5. The message includes the MS TEID received in step 5, which allows the GANG to relay the Iu-PS G-PDU message payload using the correct PTC on the Up interface. The GANG relays the message payload to the MS in the GA-RRC PDU message.
The specific scenario explained in the following applies to the above described 3GPP system environment. The starting point of the scenario is that a roaming UE, i.e. the UE is connected to a cell of a base station (eNB) of a visited network operator (e.g. VPLMN1), is moving out of coverage of VPLMN1's cells. One exemplary use case for this scenario is that the VPLMN1 cell is a macro cell and the user is entering a subway station or underground shopping mall and the power of the signal of the VPLMN1 cells is too low to reach the UE in the underground. Furthermore, there is no other base station of VPLMN1 deployed in the underground, however, cells of other operators (e.g. VPLMN2) are in the coverage of the UE in the underground, for example because the VPLMN2 operator has deployed eNBs covering smaller cells in the underground.
In order to support seamless mobility in the scenario described above, it should be possible for an active UE to handover from cells of VPLMN1 to cells of VPLMN2 (see FIGS. 3 and 4).
The capability of performing seamless handover may depend on the relationship between the different operators of the VPLMNs. For example, if there is a special kind of mutual roaming relationship/agreement between all the involved operators, i.e. the home operator of the UE (HPLMN), the visited operator VPLMN1 and the visited operator VPLMN2, the networks may be configured to support active handover, i.e. the source access eNBs are aware of the target access eNBs, and context transfer and data forwarding between the two visited PLMNs is possible. However, if there is a roaming agreement between the home operator of the UE (HPLMN) and VPLMN1 and also an agreement between HPLMN and VPLMN2, but no specific roaming agreement between VPLMN1 and VPLMN2, an active handover with context transfer etc. is not possible.
Even if the UE is able to measure the VPLMN2 cell and report information to the source eNB to which the UE is still connected, the source eNB is not aware of the target eNB, i.e. does not know the target eNB to which the UE shall perform the handover. And even if the source eNB would be aware of the Enhanced Global Cell Identity (ECGI) of the target cell and would request handover, the source MME in the VPLMN1 network may not find the target MME or is not allowed to trigger active handover to the target network, and thus, the UE will not be triggered to do handover. In addition, the UE will not be informed about an unsuccessful handover attempt to VPLMN2.
Thus, if there is no special roaming agreement between VPLMN1 and VPLMN2, after loosing coverage, the UE has to search for a new cell in VPLMN2 and do an attach, thereby disrupting the service.
In the following two possibilities are presented to perform a handover between two VPLMNs that do not have a roaming agreement for allowing an active/seamless handover of a MN.
One possible solution is that the UE, prior to loosing coverage completely, goes to IDLE mode and starts to scan cells of other PLMNs in the vicinity. Then, when a cell of another VPLMN is found, the UE can connect to the new cell and perform a Tracking Area Update (TAU) with the "active flag" set. Because of the active flag, the MME triggers activation of all radio and S1 bearers, thus the user plane is setup and the session continuity is guaranteed.
However, this mechanism would still require at least some kind of roaming relationship between VPLMN1 and VPLMN2, because during the TAU procedure the new MME contacts the old MME to retrieve context information for the UE. Further, the handover performance is not optimal in this case. Downlink data sent from the HPLMN to the old VPLMN can get lost, and delivery is delayed during the scanning phase of the VPLMN2 cells and during the handover execution, because bearers in the target access are setup in a re-active manner.
A first sub-issue of the IDLE mode solution above is when the UE starts with the handover procedure. As already mentioned, there is no special roaming agreement between VPLMN1 and VPLMN2, and therefore, VPLMN1 eNBs are not aware of VPLMN2 eNBs. Even if the UE reports VPLMN2 cells to the VPLMN1 eNB, the VPLMN1 eNB is not able to trigger the handover.
One possibility to overcome this issue is that the UE measures and compares the signal strength of the eNB in VPLMN1 and of the eNB in VPLMN2. If the source eNB signal strength is below a threshold and the target eNB signal strength is above a threshold, the UE does not wait for the Handover Command from the source eNB any longer, but starts with the handover to the new eNB in VPLMN2.
This UE behaviour may cause a UE-initiated handover although network-initiated is also possible. The problem is that the UE does not know that there is no special roaming relationship between the two PLMNs and that the source eNB can not trigger the handover. Thus, one way to avoid that the UE falsely initiates the handover is that in case the source MME can not send a handover (forward relocation) request to the target MME, the UE is informed by the source MME/eNB that network-initiated handover is not possible. Only then, the UE starts with handover attach to the new eNB in VPLMN2.
As already mentioned, the second sub-issue of the IDLE mode solution explained above is that even this solution requires some kind of roaming relationship between VPLMN1 and VPLMN2. This can be avoided by the UE indicating the HPLMN as source network during the TAU procedure. Then, the target MME will ask the HPLMN about the context, and the HPLMN can retrieve the context from the source MME. Another problem is that there is still a handover delay, because the UE is already attached to the target eNB before context is retrieved from the source access.

Inter-VPLMN handover via a handover proxy node

PANASONIC INTELLECTUAL PROPERTY CORPORATION OF AMERICA


A server computing device and related method for providing recommendations to a user computing device are disclosed. In one example, user activity of the user of a user computing device and friend activity of a friend using a friend computing device are received. A request for a recommendation is received from the user device. Based on the user and friend activities, it is estimated that the user and friend will approach an intersecting location within a window of time, and the user and friend are available to meet in that window. A recommendation of a service offered within a distance of the location is sent, with the recommendation displayed on the user computing device.

Prior to the advent of wireless navigation devices, drivers on the freeway often relied upon signs that notified them of services that could be accessed at the next freeway exit. This situation could lead to inadequate planning, including multiple intense conversations in vehicles during the short interval between the notification by sign and opportunities to exit the highway efficiently, regarding whether the passengers desired to exit the freeway to access the services. With the advent of wireless navigation devices, a vehicle passenger may now input a desired service (e.g., gas station, restaurant) while traveling in the vehicle along a route, and view a list of such service locations and a distance to each along the route.
As helpful as such wireless navigational devices may be, vehicle passengers are tasked with requesting a list of services from these devices prior to receiving a list of results. To accomplish this task, a passenger has to be cognizant of the desire to utilize a service ahead of time, and has to take the time to input the service request into the navigational device. This can result in many missed opportunities to utilize services that the user would otherwise have desired to use. As one example, this realization may arise after driving by a freeway exit, and hearing a young child plaintively announce from the back seat that "I have to go to the bathroom," only to see a sign indicating "Next Exit 43 miles". This is but one example of many in which systems that necessitate that users be cognizant of their own needs in order to request information on nearby services, fail to deliver satisfactory results for the user.

This patent is subject to a terminal disclaimer.

Server computing device for recommending meeting a friend at a service location based on current location, travel direction, and calendar activity


A mop is disclosed. The mop comprises a mop head (1), a mop shank (2) and a joint (3) connecting the mop head (1) and the mop shank (2), wherein the mop head (1) comprises a cleaning face which is disposed to enable at least one part of the cleaning face to be dynamically switched relative to the other parts thereof, for forming a coplanar state or a non-coplanar state with the other parts.

1. Field of Invention
The present invention relates to household cleaning apparatus, more particularly, to a mop for house cleaning.
2. Description of the Related Arts
As shown in FIG. 1, floor cleaning tools currently available for household are known as flat plate mops or flat mops. The flat mop generally has a mop shank 200 to be hold by the user, a mop head 100 installed thereon with a mop cloth 110 made of disposable cleaning material as well as a hinging joint (not shown) connecting the mop shank 200 and the mop head 100. Usually, the user holds the mop shank 200 and drives the mop head 100 carrying the mop cloth 110, so that the mop cloth 110 is brought to directly contact with the floor and to rub against the floor back and forth so as to achieve cleaning of the floor.
Currently, the mop head of the common flat mop available in the market generally has a flat bottom surface. Due to this, when the mop head 100 is moved over the floor (along the directions as shown by the left and right arrows in FIG. 1) to clean dust, the dust on the floor is only heaped at an edge of a cleaning face at bottom of the mop head 100, while the middle portion of the cleaning face of the mop head 100 can not be utilized, i.e., being so called "snow plowing effect". Therefore, on one hand, the use efficiency of the cleaning material is poor and thus the cleaning effect is not satisfactory; on the other hand, it is nearly possible for the large pieces of dust over the floor to be brought into contact with the cleaning material. Consequently, dust can only be moved from one position to another position, and can not be taken away. In this case, the user has to make secondary cleaning by other known means.


A DC bias feedback circuit stabilizes the I.sub.ds of an active MESFET with respect to process-dependent I.sub.dss variations to improve yield and reduce the effect of process variations.

The saturation current with no applied gate voltage, I.sub.dss, between the source and drain of a field effect transistor (FET) is an important parameter of an FET. The value of I.sub.dss for a particular FET is process dependent. The value of source drain current when a gate voltage is applied, I.sub.ds is dependent on the characteristic I.sub.dss of the device; as I.sub.dss increases so does I.sub.dss.
Various techniques, such as carefully controlling process variables or using large source resistors for biasing, have been proposed to limit the variation or effect of variation of I.sub.dss. However, controlling I.sub.dss in process lowers yield and using large resistors increases power dissipation.
Accordingly, techniques to increase the I.sub.dss window are needed to increase yield.

DC bias feedback circuit for MESFET bias stability


A self-aligned multiple crown storage cell structure 10 for use in a semiconductor memory device and method of formation that provide a storage capacitor with increased capacitance. A double crown storage cell structure embodiment 10 can be formed by patterning a contact via 18 into a planarized base layer that can include an insulating layer 12, an etch stop layer 14, and a hard mask layer 16, depositing a first conductive layer 20, etching the first conductive layer 20, etching the hard mask layer 16, depositing a second conductive layer 24 onto the conductive material-coated patterned via 18 and the etch stop layer 14, depositing a sacrificial (oxide) layer 26 onto the second conductive layer 24, etching the sacrificial layer 26, depositing a third conductive layer 28, and etching conductive material and the remaining sacrificial layer 26. The last several steps can be repeated to form a storage cell structure 10 with three or more crowns.

It is a generally desirable goal in semiconductor fabrication to reduce the size of semiconductor devices. This holds true for semiconductor memory devices such as Dynamic Random Access Memory (DRAM) devices. As semiconductor memory device dimensions continue to shrink, and the corresponding density continues to increase by a 4.times. rule, the storage cell gets increasingly smaller while the required storage charge remains about the same. Conventional oxynitride (N/O or O/N/O) dielectrics have a relatively low capacitance per unit area (.about.7.7 fF/um2, for an effective oxide thickness of 4.5 nm) that limits the storage capacity because of potential high tunneling leakage. To combat this problem, various area enhancement technique have been proposed, including hemispherical grain (HSG) rugged poly, disks, fins, and corrugated cylindrical cell (CCC). However, these area enhancement techniques have inherent limitations.
The HSG technique requires complicated deposition processes within a narrow temperature window. Storage cells that incorporate fins, disks, and CCC formations are primarily composed of multiple horizontal fins. As the storage cell size is further decreased, the fins add less surface area than vertical sidewalls. Furthermore, the typical fin-type structure fabrication is not a robust manufacturing process, and results in a storage cell that is less mechanically stable, especially during oxide removal between horizontal fins and particle removal.
In another attempt to overcome the limitations of conventional oxynitride dielectrics, high dielectric constant materials, including Ta.sub.2 O.sub.5, Ba.sub.1-x Sr.sub.X TiO.sub.3 (BST), SrTiO.sub.3, and Pb.sub.1-x Zr.sub.x TiO.sub.3 (PZT), have been proposed as storage dielectrics due to their high capacitance per unit area. The high capacitance per unit area could theoretically allow use of a simple stacked cell storage cell structure. However, high dielectric constant materials are new to semiconductor fabrication and several obstacles exist to implementation in semiconductor fabrication, including contamination to transistors, robust deposition process development, etching of the new materials, integration experience, and reliability.

Self-aligned multiple crown storage capacitor and method of formation


A method and apparatus for disinfection or sterilizing an article which is a food or foodstuff, or a surface of an article for contacting a food or foodstuff. According to the invention, the article is grounded and is treated with an electrically charged mist of a liquid having a redox potential and a predetermined pH. The mist is subsequently evaporated from the article.

This present invention is concerned with a method for disinfection and sterilization of foods and vegetable products and produce, feeding stuffs or machinery and equipment for food and/or feeding stuff production.
A similar method is known for U.S. Pat. No. 4,849,237.
This mentioned patent specification concerns a method for desinfection of chicken bodies kept immersed in cooling water with ozone added, which water is made to move or flow in the opposite direction of the chicken's movement. The disadvantage of that known method is that the cooling water acts as contaminator from one chicken to another, and further the process may cause mean and fat to deteriorate and go rancid.
This present invention is concerned with a method for desinfection and/or sterilization of foods of all kinds for use in any part of the food or foodstuff or feeding stuff industry, by organisations, corporations, companies and institutions in the food sector, and the method described has the purpose of preventing the risk of humans or animals being exposed to infection from micro organisms or their byproducts resulting in subsequent pathological diseases or reactions, poisonings and other illnesses. Authorities and health care organisations today often report the increasing need for methods to transport, treat, process, manufacture, pack, deliver and distribute food and feeding stuffs without dangerous, poisonous, infectuous, pathological and disease-causing effects.
Most infections of the nature described in the above start or are caused by growth of micro organisms on the surfaces of food products or produce or on the surfaces of other materials or equipment able to hold and carry micro organisms.
For many years it has been a common and acknowledged practice in the industries and companies mentioned in the above text to control raw materials and production with help from authority representatives and own experts by having samples taken at intervals and in quantities stipulated for each separate production, which samples are taken checked and analysed in official, recognised and/or own laboratories. Frequently controls concentrate on checks for salmonella bacteria, which occur in some 2,000 different known types, some of which cause severe cases of illness or poisonings in humans or animals after consumption.
The consequential effects of bacteria infection and the occurrence of pathological cases have increased considerably over the past few years, presumably because of shorter production times, large quantity manufacturing and mass production, automation and mechanised control and processing, at the same time as the craftsman's job and his control during the manufacturing process has been taken over by technical installations and sporadic or statistically determined controls.
One common procedure is to take out small sample items of the processed food or feeding stuff and submit these to a laboratory for testing. Here, microorganisms are cultivated on various substrates (nutritious media) and after 3 or 4 days growths of bacteria or micro organisms may be found. Next the decision has to be taken whether the growths have to be subjected to further special analysis, which can only be dealt with by large, specialised laboratories with adequate equipment, and the bacteria samples are therefore sent to such special laboratories causing added cost and time delays.
Food articles or feeding stuffs are sampled from manufacturing plants immediately after processing, or they are sent away for freezing, and therefore results of such testing is often only available several days later than dispatch due to industry requirements for quick processing and short warehouse periods.
A few types of Salmonella and other bacteria provoke serious cases of disease. Acute gastroeneritis would be caused by e.g. Salmonella Typhi Murium or Enteriditis. More serious cases are caused by bacteria such as Salmonella Paratyphi type A, B or C and also by Salmonella Dublini, which infections may be mortal. Salmonella Typhi especially is the cause of the infectuous typhoid disease which may cause death from poisoning or mass epidemics in humans under certain conditions.
It is a known fact that many such cases of infection are not reported to public authorities so that they do not appear in statistics, but in medical circles the assumption is that the number of diseases, poisonings or other cases may be counted in hundreds of thousands per year globally, and mortal cases are reported to be several thousands every year.
One recently registered patent, EP No: 0 299 601 (Al) indicates that the invention described may certify the occurrence of Salmonella infection within 24 hours, thus reducing the time needed for analysis and testing, but the method of the invention does not prevent or preclude any such infection.
The existence of micro organisms or bacteria in or on foods or feeding stuffs is dangerous to consumers since neither cooling nor freezing result in bactericidal processes, sterilization or desinfection. During transportation, delivery, commercial distribution and warehousing in cooled, refrigerated or frozen conditions the bacteria growth comes to a standstill, but subsequent use or application will enable the bacteria to cause renewed growth under favourable temperatures and conditions.
Salmonella bacteria are surface bacteria which will, if subjected to favourable temperatures in the surroundings and to nutrient substrates in the form of foods or feeding stuffs, multiply through duplication every 20 minutes, which means that the Salmonella bacteria count should be multiplied by a factor larger than 10.sup.21 for every 24 hours, enabling the the huge number of infectuous matter to spread easily in the processing environment through human hand, transportation, cutting, manufacture, processing and storage.
Traditionally, people in the profession have over time taken care to this risk in all concerned industries and services, and bacteria growth and the spreading of micro organisms have been prevented by cleaning and sanitation, but the precautions taken have not been sufficient to prevent infection and the occurrence of pathological events, especially gastroenteritis or stomach poisonings, and authorities, companies engaged in food processing or feeding stuff production, corporations, distributors and other manufacturing or servicing units have not been able to offer the public and the consumers sterilised products free of the risk of the infections indicated in the above.

Method and apparatus for disinfecting or sterilizing foodstuffs and other articles


A phase-shifted full-bridge converter and a control method thereof are disclosed. The proposed control method of a phase-shifted full-bridge converter, wherein the phase-shifted full-bridge converter includes a full-bridge switching circuit having a first and a second output terminals, a main transformer having a primary winding and coupled to the switching circuit, and an autotransformer having a primary winding and coupled to the main transformer, includes providing an induced common current flowing through the primary winding of the autotransformer; and causing the induced common current being reflected to the primary winding of the main transformer to cause a primary side current flowing through the primary winding of the main transformer to increase both slopes of a valid duty cycle and a dead-zone period such that the primary side current has a relatively lower transition level and a relatively shorter transition time.

The well-known PS-FB converter with a one-inductor filter is still a suitable and reliable source of power supply, which attains high-efficiency power output by reducing switching loss via the use of phase-shifted zero-voltage switching (ZVS). In order to improve the power handling capability of PS-FB converter, many different studies have been proposed, and one improvement direction is to decrease the transition time and to increase the valid duty period. FIG. 1 shows a circuit diagram of a PS-FB converter having a current-doubler rectifier (CDR) filter. In FIG. 1, the PS-FB converter having the CDR filter 1 includes a full-bridge switching circuit 11, a transformer (T1) 12, a CDR filter 13, a resonant inductor Lr and a coupling capacitor Cc, wherein the coupling capacitor Cc and the resonant inductor Lr are electrically connected between a first output terminal of the full-bridge switching circuit 11 and a first terminal of a primary winding of the transformer T1 in series, and the PS-FB converter 1 can increase an output current thereof to two times of that of the above-mentioned PS-FB converter having a one-inductor filter. But the PS-FB converter 1 is not for help in shortening transition time. As shown in FIG. 1, the full-bridge switching circuit 11 has four power switches Q1-Q4 (wherein each power switch includes a body diode (D1-D4) and a body capacitor (C01-C04)), a first and a second input terminals receiving a DC input voltage Vdc, the first output terminal A and the second output terminal B. There is a voltage difference VAB between these two output terminals. The transformer T1 has the primary winding and a secondary winding (its turn ratio is n=Np/Ns). A cross voltage of the primary winding is vp, a cross voltage of the secondary winding is vs, a current flows through the primary winding is ip, a current flows through the secondary winding at Phase-I is is1, a current flows through the secondary winding at Phase-II is is2, and a current flows through the load is io. The CDR filter 13 includes a first diode Ds1, a second diode Ds2, a first inductor L1, a second inductor L2, and a load, wherein the load is a battery pack, and has a cross voltage or an output voltage VB.
A time period of the above-mentioned voltage difference VAB is a sum of a transition period and a valid duty period, and the sum is a fixed value. Thus, when a transition time is decreased to result in a decrease of the transition period, a valid duty period is increased. Shortening the transition time to enhance the efficiency of PS-FB converter's power capability is still the most efficient and feasible method, and thus how to decrease the transition time of the PS-FB converter to enhance the efficiency of PS-FB converter's power capability are important aspects for development in the field.
Keeping the drawbacks of the prior art in mind, and through the use of robust and persistent experiments and research, the applicant has finally conceived of a PS-FB converter with a half-current multiplier output and a control method thereof.

Phase-shifted full-bridge converter with half-current multiplier output and control method thereof


A method for passive aerial cord release mechanisms and an aerial cord release mechanism for an aerial vehicle (AV). A method includes determining a retracting force to be applied to a winch of an aerial vehicle (AV), wherein the determined retracting force is a force required to retract a cord to be coiled around the winch within the AV, and the cord is temporarily coupled to the winch, such that an external force exceeding a predetermined threshold causes decoupling between the cord and the winch.

As aerial parcel delivery becomes more popular, so do solutions for securing various aspects of aerial parcel delivery. For example, unmanned aerial vehicles, such as drones, have become more popular for delivering parcels to customers, and techniques for protecting drones and the parcels that they deliver are needed.
One such technique for securing drones and the parcels they deliver, e.g., from theft or damage, is to limit the landing of a drone to an area in close proximity to an intended recipient so that only an authorized person can remove the parcel from the drone. However, this technique requires landing a drone, which may be a somewhat large, close to civilians who may not strictly adhere to safety precautions and regulations, thereby risking injury along with increased liability concerns.
Another technique for securing drones or parcels includes lowering parcels from a drone via a cable using a mechanism such as a drone-mounted winch. However, this technique also presents challenges due to the complexity of such cable mechanisms, as it will often require the capacity to detach the cable from the parcel automatically without human intervention. The mechanisms used for existing solutions are expensive and prone to failure. In particular, the greater the number of moving parts included in such a mechanism, the higher the likelihood that the mechanism will malfunction due to the failure of one or more of its components.
An additional concern during package delivery is that an unexpected force exerted on a cord used for parcel delivery, before the cord's retraction, may cause damage to the drone itself. Something or someone, e.g., a child or an animal, could grasp onto the low-hanging cord and become entangled as it is being retracted into the air, which would not only be dangerous, but could additionally cause damage to the drone. Further, there is potential for vandalism or theft of the drone itself, whereby someone may purposefully pull on the cord in an attempt to pull the drone to the ground. Employing sensors to detect an applied force and determine the best response is costly and difficult to efficiently implement.
It would therefore be advantageous to provide a solution that would overcome the challenges noted above.

System and method for aerial cord release mechanisms


The invention is directed to a method for adjusting a supplemental quantity of fuel which is supplied to an internal combustion engine during warm-up operation in addition to a basic quantity measured for an operationally warm engine. The method includes the step of basing the adaptation of the supplemental quantity of fuel on an evaluation of the control actuating variable of an idle speed control.

Known methods adjust a supplemental quantity of fuel during warm-up which is comparatively large at the start and is reduced in accordance with a predetermined function with increasing duration of the warm-up and therefore with increasing warming of the engine. At the latest, no supplemental quantity of fuel is supplied any more when the operating temperature of the engine is reached. U.S. Pat. No. 4,205,635 discloses an example of this known method.
The necessity of a warm-up enrichment by increasing the quantity of fuel is caused by the so-called wall-film losses. These losses occur because a portion of the fuel injected into the intake pipe of the engine condenses on the inner wall surfaces of the intake pipe and forms a fuel wall film. This portion of the injected fuel is not available for combustion in the cylinder. Its magnitude is also determined by the condensation behavior and boiling behavior of the fuel used. The fuel quantity injected during warm-up is increased in order to obtain a desired fuel/air ratio .lambda. notwithstanding the wall-film effect.
In accordance with the known method, the warm-up enrichment takes place in a controlled manner such that a specific fuel quality leads to a desired .lambda. in the cylinder. A comparatively lean warm-up adaptation is advantageous for present day exhaust-gas strategies. For the comparatively lean warm-up adaptation, driving problems can occur because of a mixture which is too lean because of seasonal and regionally fluctuating qualities of fuel or even because of changes of the through-flow characteristic of the injection valve caused by deterioration. A conventional lambda control cannot eliminate these problems because it is not active during warm-up for various reasons.

Method for adjusting a supplemental quantity of fuel in the warm-up phase of an internal combustion engine


The present invention is directed to a method for alignment of nucleic acid data traces. The method involves selecting reference alignment points from among internal peaks representing highly conserved bases, preferably consisting of heterogeneous multiplets. The alignment points may also optionally include the primer peak and/or the full-length peak. Reference position numbers are assigned to these alignment points reflecting the known relative position of the alignment point, a sequence position number is assigned to peaks in the data traces so as to maximize assigning the sequence position number and the reference position number to the same base. Optionally, the method may include the step of determining the average peak spacing interval between alignment points and assigning a sequence position number to peaks occurring at the intervals. The data traces are then aligned based on the assigned sequence position numbers.

This application relates to a method for alignment of data traces obtained from a DNA sequencing apparatus, and to apparatus adapted for practicing of this method.
DNA sequencing is becoming an increasingly important diagnostic tool, and also forms an important component of research efforts such as the Human Genome Project. The most common sequencing procedures used today are based on the primer extension or "Sanger" methodology. In the "dye primer" version of Sanger DNA sequencing, a 5′-end-labelled oligodeoxynucleotide primer is bound sequence-specifically to a target DNA template which is to be sequenced. The primer is extended by a DNA polymerase enzyme, via incorporation of dNTPs. A chain-terminating dideoxy-NTP of one particular base type (A, C, G, T) is added to the reaction, to effect a termination of DNA chains at random positions along the sequence. The nested series of DNA fragments produced in this reaction is loaded on one lane of a thin denaturing polyacrylamide gel, and the bands are electrophoretically resolved, to produce a series of 5′ end labeled bands in the profile of that lane. A set of four reactions (with chain termination occurring via ddA, ddC, ddG, ddT incorporation) is required for explicit determination of the positions of all four bases in the sequence, and typically is run on four adjacent lanes of a sequencing gel.
Data traces are collected indicating the peak positions in each of the four lanes of a gel. In an ideal system, these four data traces could simply be placed one over another and the sequence could be read. This reading process is called "base-calling." In practice, however, the data traces are not ideal because of a variety of factors including mobility differences between lanes and changes in resolution which occur as the size the fragments increases. Prior to the development of automated sequencing apparatus, the data traces were generally aligned by eye prior to base-calling, that is by a skilled technician looking at the traces and shifting the relative positions of the traces based on accumulated experience. One of the challenges of automated DNA sequencing is the proper alignment of the data traces using computer processing rather than human analysis.
Various approaches have been taken to the need for accurate trace alignment which is an essential prerequisite to accurate base-calling. One approach is the use of a multi-dye sequencer, in which the traces from all four bases are obtained from a single lane of a gel. (See, for example, U.S. Pat. Nos. 5,751,534 and 5,821,058.) This reduces many of the sources of variability, but requires the utilization of four different label types, and may involve an increase in the complexity of the detection apparatus. Another approach is described in commonly assigned U.S. Pat. No. 5,916,747. The present application provides yet another approach to the solution of this problem.

Method and apparatus for alignment of DNA sequencing data traces


At least one intermetallic compound A.sub.m1 B.sub.n1 (n1/m1>n0/m0) having a constitutional ratio of a metal B higher than that of an intermetallic compound A.sub.m0 B.sub.n0 is melted two or more times in a high vacuum atmosphere by using an electron beam. The metal B is gradually evaporated in accordance with passage of melting time. Thus, the composition of the intermetallic compound can be adjusted to be A.sub.m0 B.sub.n0. NbAl.sub.3 and Nb.sub.2 Al are used as starting materials, which are heated to an approximately intermediate temperature between melting points of them to obtain a single-phase of Nb.sub.2 Al. Alternatively, Nb.sub.3 Al and Nb.sub.2 Al are used as starting materials, which are heated to an approximately intermediate temperature between melting points of them to obtain a single-phase of Nb.sub.3 Al. It is possible to perform purification for removing impurities, and it is easy to adjust the stoichiometric ratio of the intermetallic compound.

1. Field of the Invention
The present invention relates to a method for producing an intermetallic compound. In particular, the present invention relates to a method for producing an intermetallic compound having a desired composition by melting an intermetallic compound by means of an electron beam.
2. Description of the Related Art
Those hitherto known as methods for producing intermetallic compounds such as those based on a Nb--Al system include a powder metallurgy method and a pressurized atmosphere melting method for melting a material while adjusting a pressurized condition of a rare gas such as Ar. These methods are designed to obtain an intermetallic compound containing components in a desired stoichiometric ratio by controlling the amount of evaporation of a readily volatile metal which is relatively easy to evaporate, such as Al.
Japanese Patent Publication No. 7-17970 discloses a plasma electron beam melting and casting method for Al-containing intermetallic compounds, in which a compressed preparation of a material of an intermetallic compound is melted in a water-cooled horizontal copper mold to obtain a rod-shaped ingot, and the ingot is melted by irradiating it with a plasma electron beam to perform solidification while dripping the melted metal. In this method, evaporation of Al is controlled by finely adjusting the flow amount of an inert gas to be introduced when the ingot is irradiated with the plasma electron beam.
However, in the case of the powder metallurgy method, the grain boundary tends to become brittle due to intergranular oxidation, and an obtained intermetallic compound is insufficient in processability. If a third component is added in order to improve the processability, characteristics originally possessed by the intermetallic compound may be deteriorated. On the other hand, the pressurized atmosphere melting method is excellent in adjustment of the stoichiometric ratio, however, it is impossible to expect any purification effect for removing impurity gas elements by means of volatilization. In the conventional methods as described above, mechanical and physical characteristics inherent in a material itself are not embodied due to the occurrence of fracture in the grain boundary itself and the influence exerted by contained impurities, in addition to the characteristic fracture mechanism based on the cleavage property inherent in the intermetallic compound.

Method for producing intermetallic compound


The present invention provides a method for measuring the self-consistency of inference algorithms. The present invention provides a method for measuring the accuracy of an inference algorithm that does not require comparison to ground truth. Rather, the present invention pertains to a method for measuring the accuracy of an inference algorithm by comparing the outputs of the inference algorithm against each other. Essentially, the present invention looks at how well the algorithm applied to many of the different observations gives the same answer. In particular, the present invention provides a method that is not time and labor intensive and is cost effective.

An inference algorithm is any algorithm that takes input observations from the world and makes inferences about the causes of those observations. Different types of inference algorithms are stereo algorithms and computer vision algorithms. Inference algorithms are used in several areas including three-dimensional imaging and voice recognition and natural language understanding. As technology utilizing inference algorithms advances, methods for determining the accuracy of these algorithms is essential. Accuracy determinations are based on statistical characterizations of the performance of the algorithm.
One possible statistical characterization of the performance of an inference algorithm is in terms of the error of the matches compared to "ground truth." Comparison with ground truth requires the build up a corpus of ground truth observations and training the algorithm based on the corpus. If sufficient quantities of ground truth are available estimating the distribution of errors over many image pairs of many scenes is relatively straight forward. This distribution could then be used as a prediction of the accuracy of matches in new images.
The comparison to ground truth, however, has several drawbacks. Acquiring ground truth for any scene is an expensive and problematic proposition, as several observations must be recorded. Also, aquiring ground truth for any scene is extremely time and labor intensive. Furthermore, any ground truth measurements are subject to discrepancies in the measurements, therefore reducing the accuracy of the performance.
Accordingly, a need exists for a method for measuring the accuracy of an inference algorithm that does not require comparison to ground truth. A need exists for a method that can satisfy the above need and that is not time and labor intensive. Furthermore, a need exists for a method that can satisfy the above needs and that is cost effective and not overly expensive.

Method and system for estimating the accuracy of inference algorithms using the self-consistency methodology


An intravascular guidewire with integrated imaging and pressure measurement capabilities is disclosed. The guidewire can comprise an integrated CMUT-on-CMOS ultrasound transducer array to provide 3D imaging of vasculature and other tissue. The guidewire can also comprise a conventional FFR pressure sensor or Doppler flow sensor. Due to the low power consumption of the chip, power can be provided via a single pair of wire pair proximate the core wire of the guidewire to provide power and ground to the chip. The system can also include a power wire, a ground wire, and a data wire, the data wire using similar data transmission techniques. Data from the sensor array can be transmitted over the power wire using, for example, RF or impedance modulation. Data can also be transmitted through the body using an ultra wideband wireless transmitter and flexible patch antenna on the skin.

1. Field of the Invention
Embodiments of the present invention relate to ultrasound imaging probes, and particularly, to flexible, capacitive micromachined ultrasonic transducer (CMUT) based guidewire ultrasound imaging probes using CMUT arrays integrated with Complementary metal-oxide-semiconductor (CMOS) electronics, and integration of pressure (e.g. fractional flow reserve (FFR)) sensors with the same imaging probe.
2. Background of Related Art
Side-looking intravascular ultrasound ("IVUS") imaging probes exist that provide relatively high resolution images of tissue and fluid. This can be useful, for example, when inspecting the inside surfaces of vessels or tissues immediately surrounding the vessel.
In order to navigate tortuous arteries and coronary structures, for example, an important aspect of IVUS probes is the size and flexibility of the probes. As a result, the rigid section of the probe close to the imaging tip should be as short as small in diameter as possible. Current ultrasound array probes used for these purposes are rigid over several mm, limiting their maneuverability.
During cardiac or other vascular procedures, the surgeon first inserts a guidewire in to the desired artery, sometimes anchoring it in place. The surgeon then uses a series of catheters that are "threaded" over the guidewire. In order to change catheters, e.g., from a balloon catheter to an imaging catheter, the first catheter must be completely removed and the second catheter inserted. This must be done carefully to avoid injuring the vessels walls and thus, can take a significant amount of time—generally 15-20 minutes. Both the extra time involved and the increased risk of incidental injury increase the risks associated with the procedure. As a result, while IVUS greatly improves the outcome of intravascular procedures, for example, it is only used in approximately 20% of intravascular procedures.
In contrast, guidewires are used in nearly 100% of intravascular procedures. Thus, an imaging array integrated into a standard guidewire would eliminate the need to change catheters during the procedure. The surgeon could simply image the vessel as the guidewire is being inserted, during the interventional procedure or after the procedure without a need to exchange catheters. This would improve the outcome of intravascular procedures with no increase in the time or risks associated with removing and inserting multiple catheters.
To maintain the flexibility and mechanical properties of the guidewire, however, the number of electrical connections connecting the probe electronics to the back end imaging system should be limited. In other words, a larger number of cables would make the guidewire thicker and less flexible. The number of external connections is also important, for example, because it adversely affects the mechanical performance of the guidewire if the core of the guidewire is thinned down to make space for the electrical connection wires without increasing the diameter of the guidewire.
In addition to size constraints, ultrasound probes typically must limit their power consumption. When the probe is activated, the temperature of the probe must be limited to prevent damage to surrounding tissue, or simply to prevent the probe from overheating when in open air. In some instances, for example, the probe may remain active outside the body. In this instance, power consumption should be limited to prevent the probe electronics from overheating and damaging the mechanical structure of the probe such as the adhesion layers or coatings.
Measurement of pressure in the blood vessels to obtain FFR information has proven to be useful in evaluating the treatment options in cardiovascular interventions. Therefore, integrating this functionality to the IVUS imaging guidewire is desirable because it enables the use of a single guidewire to better evaluate the condition of the blood vessels.
What is needed, therefore, is a CMUT-CMOS integrated ultrasonic probe on a standard guidewire-sized package. The probe should include reduced power consumption through custom electronics design and intelligent power management. The probe should comprise improved resolution with minimal cross-sectional area and interconnects along the catheter. The probe may also include an integrated FFR sensor to or Doppler sensor to measure blood pressure and/or flow while providing ultrasound imaging. It is to such an ultrasonic probe that embodiments of the present invention are primarily directed.

CMUT-on-CMOS based guidewire intravascular imaging


A MAC (Medium Access Control) control block for controlling transmission of data between a plurality of MAC clients and a plurality of MACs in an Ethernet passive optical network (EPON) is provided. The MAC control block includes the plurality of MAC clients and the plurality of MACs associated with the MAC clients for forming a frame for data transmission; a plurality of optical multipoint (OMP) blocks connected between the MAC clients and the MACs for implementing a multipoint control protocol (MPCP); and a multipoint gating control block for controlling the OMP blocks so that when any one of the OMP blocks is transmitting the data, the other OMP blocks are prevented from transmitting data.

1. Field of the Invention
The present invention relates generally to an Ethernet passive optical network (EPON), and in particular, to an effective multipoint gating control method between an optical line termination (OLT) and a plurality of optical network units (ONUs) of an EPON.
2. Description of the Related Art
Standardization of medium access control (MAC) technology for Gigabit Ethernet and asynchronous transfer mode-passive optical network (ATM-PON) has been completed recently, and the contents thereof are disclosed in IEEE 802.3z and ITU-T G.983.1. In an ATM-PON, upstream and downstream transmissions are performed using a frame, which consist of a group of ATM cells having a predetermined size. In a tree-type PON, an OLT selectively inserts downstream cells to a frame to be distributed to the respective ONUs.
FIG. 1 is a block diagram illustrating a physical network structure of a general passive optical network. FIG. 1 shows an example in which three ONUs 110-1 to 110-3 are connected to one OLT 100. At least one end user (or network device) 120-1 to 120-3 is connected to each of the ONUs 110-1 to 110-3. Data 131-1 to 133-1 transmitted by the end users 120-1 to 120-3 is delivered to the OLT 100 via the ONUs 110-1 to 110-3.
In operation, ONU's data is accessed by time division multiplexing (TDM) for upstream transmission. An optical distribution network (ODN), which is a passive element, prevents data collision through a so-called ranging method. In other words, during upstream transmission, data from the ONUs 110-1 to 110-3 is multiplexed before being transmitted to the OLT 100. During downstream transmission, the ONUs 110-1 to 110-3 receiving data broadcasted by the OLT 100 select only its own data from the received data. To this end, upstream and downstream frames include a field capable of exchanging messages at the specified periods, which assigned in a private ATM cell or a general ATM cell. With the development of Internet technology, a subscriber side now requires more bandwidth, so an end-to-end transmission is typically achieved with Gigabit Ethernet technology, which provides relatively cheaper equipments and higher bandwidth over the ATM technology, which requires segmentation of IP packet and has a limited bandwidth. Therefore, Ethernet technology is ideal for the PON structure instead of ATM technology. Standardization of such an EPON is now under way in IEEE 802.3ah in the name of EFM (Ethernet in the First Mile).
Such an EPON, unlike the conventional Ethernet-based network, is characterized by having a point-to-multipoint structure instead of a point-to-point (PTP) structure. Therefore, Draft v1.0 of IEEE 802.3ah has introduced a virtual MAC (vMAC) structure so that an OLT which is a master can efficiently manage respective ONUs.
FIG. 2 is a diagram illustrating a vMAC structure for an OLT in the EPON standard. As shown in FIG. 2, unlike the existing MAC, the illustrated MAC is divided into several virtual MACs, and the virtual MACs are mapped to respective ONUs. That is, upon receiving a frame, a reconcile sublayer (RS) analyzes a logical link identifier (LLID), splits the received frame to a vMAC associated with the LLID, and delivers the split frame to an upper layer. In actual implementation, vMACs can be optionally implemented with one MAC.
In this case, an optical multipoint (OMP) function block for implementing a multipoint control protocol (MPCP) of an EPON as well as a function of managing and controlling a plurality of MACs is achieved in the MAC control layer. Therefore, this is called "multipoint MAC control" in IEEE 802.3ah. The OMP function block includes a Flow control function performed in the existing MAC control, and such MPCH functions as Gate processing, Report processing, and Discovery processing functions.
Meanwhile, in EPON standardization which is now under way in IEEE 802.3ah, a control block is required which informs the respective logical or physical MACs for the transmission of the frames in order for several MAC clients to send frames to one PHY, or physical port, via their logical of physical MACs. If several logical or physical MACs simultaneously transmit frames, collision may occur in the PHY, or physical port, shared by the MACs.
In order to prevent such collision between MACs, the ongoing IEEE 802.3ah EPON standardization has proposed Muxing Control for controlling the collision. Its fundamental operational principle is to provide a transmission enable signal (transmitEnable) to respective logical or physical MACs, to control when and how long the MACs can transmit fames.
FIG. 3 is a diagram illustrating a case in which several MAC clients transmit frames to one physical port. As shown in FIG. 3, a multiplexing control block 230 can control (or inform) several logical or physical MACs when and how long they can transmit frames. However, while a logical or physical MAC 204 is transmitting a frame in response to its transmission enable signal (transmitEnable) being turned On, if the transmission enable signal transmitEnable to the MAC 204 is turned Off and a transmission enable signal (transmitEnable) to a logical or physical MAC 214 is turned On, collision occurs between the frame being transmitted by the MAC 204 and a frame newly transmitted by the MAC 214. In order to prevent the collision, frame transmission by the MAC 204 must be immediately suspended. As a result, in the conventional standard technology, frame collision or frame loss may occur during the frame transmission.
In this structure, since MAC clients as well as MACs are separated, there is a demand for a mechanism capable of transmitting only one frame at a time during frame transmission from a MAC client to a MAC. However, the current Draft provides no definition on it.

Multipoint gating control block in an Ethernet passive optical network and method therefor

Maetan-Dong, Yeong Tong-Gu, Suwon-Si, Gyeonggi-Do


A linear motor and a linear compressor including said motor. The linear motor comprises a set of inner laminations (90), forming the stator, mounted around the outer circumference of a fixed member (60), and a set of outer laminations (30) mounted spaced from the inner laminations (90). An actuator (85) is connected to a movable member (80) and carries a magnet member (86) in the space defined between the inner laminations (90) and the outer laminations (30). The upper ends of the inner laminations (90) and outer laminations (30) are connected by a connecting element (100) made of a non-magnetic material, in order to stabilize the laminations and serve as a suspension mounting for the set of outer laminations (30). Application of electric current to a coil (95) causes the actuator (85) to move and carry the movable member (80) with it. The fixed member (60) is defined by the cylinder of the compressor and the movable member (80) by the piston, which is reciprocated inside the cylinder to compress a refrigerant gas, and the connecting element (100) does not contact the cylinder. This arrangement does not require any special configuration of the cylinder or use of an additional plate to provide the connection to the outer laminations.

Electric linear motors are well known devices, in which one of a coil or magnet element is mounted to a fixed member, and the other element is mounted to a member to be moved. Electric current is applied to the coil, which generates magnetic lines of force to interact with the magnet to produce linear motion of the movable member. Such electric linear motors are generally used in refrigeration compressors in which the movable member is defined by the piston of the compressor and the magnet is mounted to said piston. The coil is fixedly mounted to an external portion of the compressor structure that forms the cylinder, inside which the piston is reciprocated.
FIG. 1 of the appended drawings illustrates a prior art linear compressor of the type disclosed in U.S. Pat. No. 5,945,748. In this known prior art construction, there is provided a hermetic shell 10, within which is mounted a cylindrical inner cup 20 that defines a predetermined inner space. A set of outer laminations 30 for a linear motor is affixed to the inner face of the inner cup 20. A disk shaped cover plate 40 has a hole in a center portion thereof and is connected to a flange 61 that is incorporated to the upper end of a cylinder 60 and to upper end portions of both the inner cup 20 and outer laminations 30. A lower cover 50, which is also disk shaped, is connected to the lower end portion of the inner cup 20. An upper portion of the cylinder 60 extends through the open center portion of the cover plate 40, and a valve system 70 is mounted to the center of the upper portion of the cylinder 60 to tightly cover the hole through which the upper portion of the cylinder 60 extends. A conventional valve plate having suction and discharge valves can also be used. Inside the cylinder 60 is mounted a piston 80 which, upon being reciprocated by the linear motor, compresses a refrigerant gas in a known manner. A set of inner laminations 90 of the linear motor is mounted around a portion of an outer circumferential surface of the cylinder 60, said internal laminations 90 maintaining a predetermined spacing from the set of outer laminations 30.
A coil 95, of toroidal shape, is located in a cut-out portion of an outer circumferential surface of the inner laminations 90, and the ends of the coil 95 are connected to lead wires (not shown) that supply electric current to the coil 95. If desired, the coil 95 can also be located on the set of outer laminations 30. A connecting member in the form of a disk connects the lower end of the piston 80 to a cylindrical actuator 85, to the upper end of which is attached a magnet member 86 usually formed by a plurality of permanent magnets (not shown). The magnet member 86 moves in the space between the sets of outer laminations 30 and inner laminations 90.
As seen from FIG. 1, the linear motor includes the set of outer laminations 30, the set of inner laminations 90 carrying the coil 95, and also the actuator 85, to which the magnet member 86 is attached.
Inner helical springs 66 are provided between the connecting member 65 and a support 68 that is affixed to the bottom of the set of inner laminations 90 to elastically support the reciprocation of the piston 80. Outer helical springs 67 are disposed between the connecting member 65 and the lower cover 50 to support the compressor as the piston 80 reciprocates. At least one refrigerant gas path 80a is provided along an upper portion of the cylinder 60 for admitting refrigerant gas into the latter at a determined position of the piston 80.
In the operation of the compressor illustrated in FIG. 1, when electric current is supplied to the coil 95, the magnet member 86, mounted to the actuator 85, reacts with the magnetic lines of force and reciprocates the actuator 85 in a straight line between the inner laminations 90 and the outer laminations 30, whereby the piston 80 is reciprocated in the cylinder 60 as a function of the corresponding displacement of the actuator 85. The refrigerant gas flows into the cylinder 60 through the refrigerant gas paths 80a provided in the cylinder 60. The refrigerant gas compressed in the cylinder 60 is discharged through the valve system 70, and the above described operation is repeatedly performed.
The inner laminations 90 may be mounted to the cylinder by using any one of the constructions presently known, such as the one illustrated in FIG. 1. For example, there can be provided a molded bracket member mounted to the cylinder and carrying the inner laminations 90, these laminations having a cut-out in the outer surfaces thereof for lodging the coil 95.
FIG. 1A illustrates a type of mounting that can be used for mounting the outer laminations 30. This figure illustrates a modification of an arrangement shown in said US patent. The outer laminations 30, made of a magnetic metal, such as iron or steel, are radially disposed relative to the center of the compressor. A tubular frame 25 is mounted internal of the wall of the inner cup 20 and carries a shelf 26 onto which is mounted the lower end of each outer lamination 30, and the tubular frame 25 is further provided with an upper bracket 27 to connect the upper end of the outer laminations 30. Nevertheless, it should be understood that any suitable mounting arrangement might be used for adequately securing the outer laminations 30 to the wall of the inner cup 20.
As seen in the compressor of FIG. 1, the cylinder 60 is formed with a flange 61 extending radially outwardly from the top of the cylinder 60, and the cover plate 40 provides a connection between the flange 61 of the cylinder 60 and the outer laminations 30. As described below, this known construction gives rise to various problems.
FIG. 2 shows a part of another type of prior art compressor formed by a cylinder 60, to whose outer face is affixed, by glue or any other fixing means, a linear motor, whose stator comprises inner laminations 90 having an external cut-out for housing a toroidal coil 95, as already described in relation to FIG. 1. The upper ends of a set of outer laminations 30 are directly affixed, by glue, welding or any other fixing means, to the inner surface of an external portion of a flange 61 incorporated to the cylinder 60 and extending radially outwardly therefrom, in order to provide a suspension mounting to the outer laminations 30. The lower surface of the flanges 61 also contacts the tops of the inner laminations 90. Thus, there is provided a direct connection between the flange 61 of the cylinder 60 and the outer laminations 30 and the inner laminations 90.
Heretofore the linear motor has been described as used in a linear compressor. However, such linear motors also find use in other devices. For example, a stationary bushing can replace the cylinder 60 of the compressor and the piston of the latter can be replaced by a shaft that can be reciprocated to perform a determined work as the linear motor operates. Such other devices may require arrangements for mounting the inner and outer laminations, and may present variations in the structural configurations thereof in relation to those illustrated in FIGS. 1, 1A and 2. However, all these known variations use a direct connection between the three components that are, (or correspond to, in other devices) the cylinder 60 with its flange 61, the inner laminations 90, and the outer laminations 30 of the linear motor.
Such constructions, which are described particularly for the linear compressor, but have equivalent components in other useful devices, have the following disadvantages:                a large amount of material is required for constructing the cylinder, since the cylinder must incorporate its radially outwardly projecting flange 61. Moreover, in the embodiment illustrated in FIG. 1, it is further required the provision of the cover plate 40.        the cylinder must be made of a non-magnetic material, in order to avoid the flow of magnetic lines of force through the structure. This would generate Foucault currents producing heat and energy loss.        the non-magnetic materials for producing the cylinder are usually of the austenitic type, or of various types of stainless steel or aluminum, among others, and all such materials being relatively expensive.        the construction of the cover plate 40 and the flange 61 of the cylinder 60 present a large surface, causing undesired irradiation of noise.        a large number of machining operations is needed to form the cylinders illustrated in FIGS. 1 and 2, as well as a large amount of investment in equipment to produce the cylinders.        some non-magnetic materials used to produce the cylinder are inadequate for the components to be subjected to friction, as it occurs, for example, between the reciprocating piston and the cylinder, or between the reciprocating shaft and the stationary bushing, making necessary, in certain cases, to use a sleeve of a harder material for the cylinder or bushing. This makes the mounting operation more difficult, increasing the cost of the final product.

Linear motor and linear compressor including said motor

Empresa Brasileira de Compressores S.A. -Embraco


An analog-digital converter with successive approximation includes a capacitor array for being loaded by applying a given input signal potential and for providing a sampling potential, wherein capacitors of the capacitor array are serially coupled with switches. A decision latch is included for evaluating the sampling potential in a number of consecutive decision steps. The analog-digital converter also includes a logic unit for selectively changing the sampling potential by selectively switching switches associated to the capacitors of the capacitor array for each decision step based on an evaluation result of a previous decision step, wherein the switches are respectively coupled with a calibration switch.

1. Technical Field
The present invention relates to analog-digital converters, in particular to successive approximation register (SAR) analog-digital converters (ADCs) and measures to increase the accuracy thereof while maintaining conversion speed and power consumption.
2. Description of the Related Art
SAR converters for analog-digital conversion are well known in the art. In particular, SAR converters are frequently used in integrated CMOS devices since they provide a reasonable resolution and conversion time and can be implemented by optimally utilizing the advantages of the CMOS technology, which are small-sized switches and capacitors having relatively well-defined relative capacitances.
Although SAR ADCs can be implemented in different topologies, they generally include at least one capacitor array. The capacitor array may include a unit capacitor array with stages of identical capacitances and one stage with a doubled capacitance, or a capacitance ladder network comprising stages with capacitance values in a mutual relation of a factor of 2n (n=number of stages).
The capacitors, of the capacitor, array may be charged by connecting to a signal line carrying an input signal potential to be converted. The capacitor array is connected to a latch/comparator which serves for comparing a potential, stored in the capacitor array, to a reference potential in a sampling phase. The comparison result is stored in a shift register. Based on the comparison result of the previous comparing phase, a switching of a capacitance of the capacitor array is performed to increase or decrease the potential stored in the capacitor array before a next comparison is performed. This is repeated until all stages of the capacitor array have been processed.
SAR ADCs generally rely on a capacitor array, including integrated capacitors having well-defined relative capacitances. However, the capacitances of the integrated capacitor array are prone to have a remaining relative mismatch due to the commonly used CMOS technology, e.g., due to lithography, which might result in a higher integral and differential nonlinearity. The matching accuracy of the capacitors strongly depends on their size, such that the higher the areas of the matched capacitors the lower the matching error. In general, the matching error of the capacitors is determined to be no less than an ADC resolution error. Implementing the capacitor array with an intrinsic matching of the capacitors (determined by the area use of the capacitors) beyond the required resolution is, therefore, inefficient with respect to area and power consumption.
Document U.S. Pat. No. 8,223,044 B2 discloses an SAR ADC in which correction capacitors are provided to correct an integral nonlinearity error. The correction capacitors are coupled with a certain comparator depending on stored integral nonlinearity error information, wherein the correction capacitors are selectively coupled to either a ground voltage or a reference voltage.
Document U.S. Pat. No. 7,944,379 B2 discloses an apparatus for analog-to-digital conversion using successive approximation, wherein an integral nonlinearity compensator is configured to provide an integral nonlinearity compensation signal for reducing the integral nonlinearity of the analog-to-digital conversion in response to the digital code representing a conversion result.
Document U.S. Pat. No. 7,280,063 B2 discloses an SAR digital-to-analog converter with an operational amplifier and a plurality of ladder elements of a ladder network. Each ladder element includes a tunable voltage source for providing a voltage, a capacitor, and a switch for selecting a first voltage or a reference voltage and for providing the first selected voltage to the first capacitor. The output of the ladder elements is coupled to the inverting input of the operational amplifier. The reference voltages can be programmed to minimize a mismatch between the capacitors.
Document V. Kerzérho et al., "Fast Digital Post-Processing Technique for Integral Nonlinearity Correction of Analog-to-Digital Converters: Validation on a 12-Bit Folding-and-Interpolating Analog-to-Digital Converter", IEEE Transactions on Instrumentation and Measurement, Vol. 60, Issue 3, March 2011, discloses an SAR ADC converter using a look-up table for the online correction of integral nonlinearity.
Furthermore, document U. Moon et al., "A Switched Capacitor DAC with Analog Mismatch Correction", Electronics Letters, Vol. 35, Issue 22, Oct. 28, 1999, discloses a calibration method for enhancing the accuracy and linearity of a switched-capacitor digital-to-analog converter.

INTERNATIONAL BUSINESS MACHINES CORPORATION


A furnace having improved heat exchanger, which is particularly suitable for use in a positive pressure, direct-vented hot air furnace. The heat exchanger has a split housing construction allowing the heat exchanger to be partible into halves. Parting the heat exchanger housing of the present invention permits access to the ceramic combustion chamber disposed therein, facilitating periodic repair and replacement. The partible portions of the present heat exchanger housing are connectable using one of several available connection means, including bolted mating flanges, encircling clamps, and twisting quick-locking means. The connection between the partible portions is gasketed to provide a positive pressure seal of the connection, impeding leakage of pressurized combustion gases from within the heat exchanger to the occupied air.

Heating appliances, such as oil-fired furnaces, boilers and water heaters, often have "drum-style" heat exchangers which house a combustion chamber or fire pot. Drum-style heat exchangers are usually cylindrical, however heat exchangers having rectangular or polygonal-prismatic shapes are also known. The combustion chamber is typically composed of a ceramic material and is configured to surround the burner flame to evenly distribute heat within the heat exchanger and to increase the temperature in the combustion zone. A fluid, such as air, is circulated around the heat exchanger for heating and subsequently distributed or stored elsewhere. Cool fluid is returned to the device for heating.
In operation, the combustion chamber is subjected to extreme heat, sometimes in excess of 1500.degree. C., which inevitably causes degradation of the chamber. Therefore it is necessary to provide access to, and permit removal of, the combustion chamber for periodic maintenance, repair and replacement, as required.
Conventional hot-air furnaces having drum-style heat exchangers typically include a rectangular cross-sectioned horizontal duct, extending from a lower housing portion of the heat exchanger to the outside casing of the furnace, through which the combustion chamber may be removed for servicing. Such a design is disclosed in U.S. Pat. No. 2,389,264 to Livar. This design, however, blocks the flow of air around a portion of the heat exchanger, thereby reducing the efficiency of the heat exchanger. As the market prices for fossil fuels continually increase, there is an ever-increasing need for improved efficiency heaters.
The rectangular cross-sectioned horizontal duct of the prior art has further disadvantages. With the advent of side wall-vented furnaces, also known as direct-vented furnaces, the combustion gases within the heat exchanger are pressurized in relation to the air outside the heat exchanger. The presence of a positive pressure inside the heat exchanger necessitates a heat exchanger having a complete pressure seal to prevent combustion gases from leaking into the circulation air and endangering the health and safety of building occupants. There is no similar concern in chimney-vented furnaces, since combustion gases in the heat exchanger are maintained at a negative pressure in relation to the circulation air, and any leaks in the heat exchanger simply result in circulation air being drawn into the heat exchanger. When used in a direct-vented furnace, however, the large opening of the rectangularly-ducted heat exchanger of the prior art is disadvantageous because the rectangular access to the duct is difficult to completely pressure seal. Pressure sealing this prior art heat exchanger design requires careful placement of many fasteners, as well as gasketing, around the perimeter of the opening, which results in increased material and labour costs in manufacture. Accordingly, there is also a need for a heat exchanger facilitating easier means for providing a pressure seal therefor.

1036684 Ontario Inc. c.o.b. as Clare Brothers