A hook device for bungee cords comprising a pair of opposing hooks whose bends substantially overlap when the device is in a closed configuration. The hooks may rotate away from each other into an opened configuration to enclose an object, and the hooks may rotate towards each other into a crossed configuration to provide a pull tab. The hooks are resistively held in each configuration by retaining elements. One hook may have a shallow throat to enable insertion into narrow openings.

The present invention relates to straps and cords for tying, bundling, or securing objects. Examples include bungee cords, tie-downs, tarp straps, cargo cords, and stretch cords (hereafter simply referred to as bungee cords, collectively). A bungee cord is generally a segment of elastic cord with a rigid hook on one or both ends. The elastic cord may be shock cord, elastic webbing, natural or synthetic rubber such as EPDM, or any suitable elastomeric material. The hook may be metal and/or plastic, and may have practically any shape, size, and strength.
The shank, gape, and throat of a hook determine the size and type of objects that can be hooked. For example, a hook having a shallow throat (short bend) may not attach securely around an object but it may be inserted into a small-diameter hole. On the other hand, a hook having a deep throat may attach securely around an object but it may not be inserted into a small-diameter hole. Most standard "S" and "C" hooks have deep throats, and are therefore not suited for all applications. Consequently, manufacturers produce bungee cords with hooks specially shaped for certain applications. For example, U.S. Pat. No. 4,995,329 discloses a hook with a restricted opening that permits a cord of a certain diameter to pass in and out of the hook when stretched but not when contracted. However, a user may want to limit the number of special-purpose bungee cords he buys or carries. U.S. Pat. No. 8,069,539 partially addresses this issue by disclosing a universal fitting that allows a user to attach differently sized and shaped hooks to the cord segment. Although this system may reduce the number of cords, it still requires the user to manage a collection of hooks.
Bungee cords having "S" or "C" hooks may frustrate a user when he attempts to remove a single bungee cord from a bin of bungee cords. Such hooks may tangle with cords and other hooks. To provide more user-friendly storage, U.S. Pat. No. 9,249,825 discloses a bungee cord with interlocking hooks to prevent tangling. Additionally, tangle-free racks and carriers for storing bungee cords have been disclosed, e.g., U.S. Pat. Nos. 5,845,787, 6,099,060, and 9,345,346.
Many "S" and "C" hooks, as well as carabiners, do not provide an adequate grip to hold on to when stretching a bungee cord. If a bungee cord recoils when a user loses his grip, it may cause injury or property damage. Additionally, if a user curls a finger around the bend of the hook, his finger may get pinched. To address these issues, U.S. Pat. Nos. 4,380,101 and 5,317,788 and US Pat. App. 2013/0232733 disclose various embodiments of disposing a pull tab on the shank of a hook for gripping with a finger.
Finally, a notable limitation of standard "S" and "C" hooks is that they may detach from an object due to slack in the cord, shifting of an object, or vibrations. Hooks such as carabiners and snap hooks address this limitation by providing a pivoting or sliding gate that creates an enclosed loop. The gate of a carabiner hook usually pivots inward, and may be biased by a spring, e.g., U.S. Pat. No. 6,606,769; a magnet, e.g., U.S. Pat. No. 8,448,307; or a flexible member, e.g., U.S. Pat. Nos. 805,646, 3,748,703, and 4,380,101. The gate may be shaped as a hook as disclosed in U.S. Pat. No. 1,686,424. That device comprises a stationary C-shaped jaw and an opposing coplanar rotatable C-shaped jaw acting as a gate. Instead of a bias means to hold the gate in the closed position, that device has a notch on the bend of the stationary jaw and a complementary rib on the bend of the rotatable jaw. However, a small amount of play in the pivot joint may cause a large planar separation between the adjacent surfaces of the bends and therefore cause the retainer to fail. That device it does not provide a means to retain the rotatable jaw in an opened position, nor does it provide a means to rotate or retain the rotatable jaw past the stationary jaw to implement a pull tab.
Four issues of hook devices have been described above: (1) a hook having either too deep too shallow of a throat; (2) a hook tangling with cords and other hooks; (3) a hook lacking an adequate grip; and (4) a hook detaching from an object. The prior art has addressed several of these issues, but with tradeoffs in functionality, cost, and/or easy or use. This disclosure teaches a hook assembly that addresses all four issues simultaneously without significant tradeoffs.


An example operation may include one or more of capturing a current version of sensitive data by a data processor node, hashing, by the data processor node, the current version of the sensitive data, storing, by the data processor node, a hash of the current version of the sensitive data on a first blockchain, encrypting, by the data processor node, the current version of the sensitive data using a secret key, and storing the encrypted current version of the sensitive data on a second blockchain.

This application generally relates to a storage system, and more particularly, to protecting sensitive data.
A centralized database stores and maintains data in a single database (e.g., a database server) at one location. This location is often a central computer, for example, a desktop central processing unit (CPU), a server CPU, or a mainframe computer. Information stored on a centralized database is typically accessible from different points. Multiple users or client workstations can work simultaneously on the centralized database, for example, based on a client/server configuration. A centralized database is easy to manage, maintain, and control, especially for purposes of security because of its single location. Within a centralized database, data redundancy is minimized as a single storing place of all data also implies that a given set of data only has one primary record.
A centralized database has a single point of failure. In particular, if a failure occurs (for example, a hardware, firmware, and/or a software failure), all data within the database may be lost and work of all users may be interrupted. In addition, centralized databases are highly dependent on network connectivity. As a result, the slower the connection, the amount of time needed for each database access is increased. An occurrence of bottlenecks is possible when a centralized database experiences high traffic due to a single location. Additionally, a centralized database maintains only one copy of the data. As a result, multiple devices cannot access the same piece of data at the same time without creating significant problems or risk overwriting stored data. Furthermore, because a database storage system has minimal to no data redundancy, if data is unexpectedly lost, it is very difficult to retrieve the data other than through manual operation from back-up storage. As such, what is needed is a blockchain-based solution that may be used for efficient data storage. Reliable protection and restoration of sensitive data is often difficult and error-prone.
Accordingly, a solution for efficient protection of sensitive data in blockchain network is desired.


A method for synchronism acquisition between a spread code sequence at a transmission side and a despread code sequence at a reception side in spread spectrum (SS) communication such as a direct sequence (DS). The method includes steps of (a) calculating correlation values for the despread code at different chip phases with successively displacing the chip phases of the despread code at intervals of 1/N chip over a full search range for the synchronism acquisition, N being an integer equal to or larger than 2, (b) selecting, as candidates, a plurality of chip phases which correspond to comparatively high values from among the correlation values, (c) adding, for each of the candidates, correlation values of chip phases adjacent the candidate to the correlation value of the candidate, and (d) determining one of the candidates which exhibits a highest result of addition as a chip phase having acquired synchronism.

1. Field of the Invention
This invention relates to a synchronism acquisition method and apparatus for use to correlation demodulate a spread code modulated by spread spectrum modulation.
2. Description of the Prior Arts
In spread spectrum (SS) communication based on a direct sequence (DS), an information code is spread modulated, on the transmission side, using a PN code sequence (pseudo-random noise code sequence, PN; pseudo-random noise) to produce a spread code and the spread code is transmitted. Then, on the reception side, the received signal is correlation demodulated (despread) using the same PN code sequence as that used on the transmission side to obtain an information code. The PN code sequence on the reception side is also called despread code. When a spread spectrum is used for communication, synchronism must be established between the PN code sequences of the transmission side and the reception side. However, since generally the generation timings of the PN code sequences on the transmission side and the reception side do not coincide with each other when communication is to be started, synchronism acquisition processing for synchronizing the PN code sequence on the reception side with the PN code sequence on the transmission side must be performed by the reception side upon starting of the communication. Here, the synchronism acquisition processing is processing which is performed at the reception side to estimate a generation timing of the PN code sequence on the transmission side with a predetermined degree of accuracy within one chip.
Also in a frequency hopping (FH) which is one of spread spectrum communication methods together with the direct sequence, synchronism acquisition processing must be performed upon starting of communication to establish synchronism between a frequency hopping sequence on the transmission side and a frequency hoping sequence on the reception side.
It is to be noted that processing for establishing synchronism between PN code sequences or frequency hopping sequences includes a synchronism acquisition process for establishing coarse synchronism which is described herein and a synchronism tracking process for establishing fine synchronism after the coarse synchronism is established and for finely adjusting the generation timing of a despread code sequence so that the established synchronism may not be lost.
A basic method of the synchronism acquisition process is a method of receiving a PN code sequence from the transmission side while successively varying the generation timing of a PN code sequence on the reception side little by little to effect correlation demodulation to find out a generation timing at which a high correlation value is obtained, that is, a sequence search method. With this method, however, a rather long time is required to acquire synchronism where the S/N (signal-to-noise ratio) of a transmission line is not high or a like case, and therefore, several techniques for performing synchronism acquisition processing at a high speed have been proposed. For example, Japanese Patent Laid-Open Application No. Hei 3-3530 (JP, A, 3-3530) by Y. Komatsu discloses a correlation demodulation apparatus wherein a primary search is performed for a full search range to find, as candidates, a plurality of chip phases which have relatively high correlation values and then a secondary search is performed to integrate the candidate chip phases by a plurality of times so that a chip phase synchronized with that of the transmission side can be found out in a comparatively short time.
FIG. 1 is a block diagram showing a construction of the correlation demodulation apparatus disclosed in above JP, A, 3-3530. The correlation demodulation apparatus shown in FIG. 1 includes three correlation detectors 2 to 4 to which a received signal 1 is inputted. The correlation demodulation apparatus further includes a clock generator 13 for generating a clock signal, a PN code generator 5 for generating a PN code sequence in response to the clock signal, and a shift register 6 for shifting the phase of the generated PN code sequence by +1/2 chip and -1/2 chip. The PN code sequence from the shift register 6 which has no displacement in phase is supplied to the correlation detector 2 while PN code sequences which are shifted by +1/2 chip and -1/2 chip in phase are supplied to the correlation detectors 3 and 4, respectively. The correlation detectors 3 and 4 are provided to effect synchronism tracking processing (fine synchronization). The correlation demodulation apparatus further includes reset integrators 7 to 9 provided on the output sides of the correlation detectors 2 to 4, respectively, registers 10 to 12 for holding the outputs of the reset integrators 7 to 9, respectively, and a controller 14 for controlling the entire apparatus.
In the conventional correlation demodulation apparatus shown in FIG. 1, synchronism acquisition processing is performed in the following manner. A PN code sequence is generated successively delaying it by one chip until a phase delay corresponding to one repetition period of a code sequence is produced, and the PN code sequence is inputted to the correlation detector 2 and correlation values (i.e., reception levels) then are calculated by the reset integrator 7 and successively stored into the register 10. In this manner, correlation values for one repetition period of the code sequence which individually correspond to the chip phases of the PN code sequence are stored into the register 10. Then, as the primary search, chip phases corresponding to the correlation values which have comparatively high values and are stored in the register 10 are selected as candidates. Next, as the secondary search, the correlation values are integrated with the phases corresponding to the candidates and it is determined that synchronism is acquired when the integrated value exceeds a predetermined determination level.
After the above synchronism acquisition processing, the correlation demodulation apparatus subsequently performs synchronism tracking processing.
With the conventional synchronism acquisition method which involves a primary search and a secondary search, since a primary search is first performed for a full synchronism acquisition range and then correlation detection and correlation integration are performed again, in order to raise the S/N ratio, for all candidates selected by the primary search to calculate correlation values to find out an optimum chip phase, there is a problem in that much time is required to establish chip synchronism. Further, since correlation values are calculated at the intervals of one chip for the full synchronism acquisition range, where a peak is present, for example, at a position spaced by 1/2 chip, this peak cannot be detected. Therefore, the conventional synchronism acquisition method has another problem in that a peak of a correlation value cannot be detected accurately for the full synchronism acquisition range.

Synchronism acquisition method and apparatus for correlation demodulation


A replay attack from an unauthorized user is easily avoided by wireless communication authentication. A mobile node acquires an inherent identification number owned by a base station connected to the mobile node, and sends authentication packet data including the identification number and information providing transfer route information for packet data sent to the mobile node through a wireless link. A router holds an inherent identification number owned by a base station connected to the router, and, if the identification number held by the router agrees with the identification number included in the authentication packet data sent from the mobile node, registers the transfer route information in a route table based on the authentication packet data.

1. Field of the Invention
The present invention relates to a wireless communication authentication system and a wireless communication authentication method for excluding an unauthorized user from a network that is connected to a wireless communication area.
2. Description of the Related Art
Generally, wireless communication systems need to authenticate legitimate users who are going to use the network in order to exclude an unauthorized user who would attempt to intercept data sent from a mobile node owned by a legitimate user to a wireless link and abuse the network based on the intercepted data.
FIG. 1 of the accompanying drawings shows a conventional host routing hierarchical network comprising external network 100, a plurality of routers 101, 102-1, 102-2, 103-1 through 103-4, a plurality of base stations 104-1 through 104-8, mobile node 105, and authentication server 106. Router 101 is connected to external network 100. Routers 102-1, 102-2 are connected to and operate under router 101. Routers 103-1, 103-2 are connected to and operate under router 102-1. Routers 103-3, 103-4 are connected to and operate under router 102-2. Base stations 104-1, 104-2 are connected to and operate under router 103-1. Base stations 104-3, 104-4 are connected to and operate under router 103-2. Base stations 104-5, 104-6 are connected to and operate under router 103-3. Base stations 104-7, 104-8 are connected to and operate under router 103-4. Mobile node 105 is a node that is movable while being connected to the network. Authentication server 106 serves to authenticate data in routers 103-1 through 103-4.
A wireless communication authentication process which is carried out in the conventional host routing hierarchical network shown in FIG. 1 will be described below with reference to FIG. 2 of the accompanying drawings.
It is assumed that mobile node 105 is currently present in an area covered by base station 104-2 and is connected to base station 104-2 through a wireless link. Therefore, data sent from mobile node 105 travels through a communication route extending from mobile node 105 through base station 104-2, router 103-1, router 102-1 to router 101. The communication route is held in route tables that are owned respectively by routers 101, 102-1, 103-1.
Thereafter, mobile node 105 moves from the area covered by base station 104-2 into an area covered by base station 104-3.
When mobile node 105 moves, it sends route update data to base station 104-3 (step 301). The route update data includes the identifier of a destination router, the identifier of mobile node 105, a time stamp or a sequence number.
When the route update data sent from mobile node 105 is received by base station 104-3 (step 302), the received route update data is sent from base station 104-3 to router 103-2 (step 303).
When the route update data sent from base station 104-3 is received by router 103-2 (step 304), the received route update data is sent from router 103-2 to authentication server 106 (step 305).
When the route update data sent from router 103-2 is received by authentication server 106 (step 306), the received route update data is authenticated by authentication server 106 (step 307).
The route update data includes an authentication code in addition to the items described above. The authentication code is calculated by a hash function from a secret key and the above items, other than the authentication code, of the route update data. The secret key can be recognized by only authentication server 106 and mobile node 105. In step 307, the route update data is authenticated by recalculating the authentication code and determining whether the received authentication code is correct or not.
Even if the route update data is intercepted and used by an unauthorized user in the wireless zone between mobile node 105 and base stations 104-1 through 104-8, the route update data thus intercepted and used is rejected as incorrect data. Specifically, since the route update data includes the time stamp or the sequence number, authentication server 106 detects a duplication of the time stamp or the sequence number and judges that the duplicated route update data is used by an unauthorized user.
When authentication server 106 authenticates the route update data, authentication server 106 sends an authentication result to router 103-2 (step 308).
When the authentication result sent from authentication server 106 is received by router 103-2 (step 309), if the authentication result is GOOD, then the route table in router 103-2 is updated based on the route update data which has been authenticated and information indicating that the base station to which the route update data has been sent is base station 104-3 (step 310). At this time, the route table in router 103-2 is updated such that data to be sent to mobile node 105 will be routed through base station 104-3. If the authentication result is NOT GOOD, then the route table is not updated, and the authentication process is put to an end.
After the route table in router 103-2 is updated, the route update data is sent from router 103-2 to router 102-1 (step 312). Based on the received route update data and information indicating that the route update data is sent from router 103-2, the route table in router 102-1 is updated (step 313). At this time, the route table in router 102-1 is updated such that data to be sent to mobile node 105 will be routed through router 103-2.
Router 101 which is higher in level than router 102-1 already has route information with respect to mobile node 105 and the route information does not need to be changed. Therefore, the route update data is not sent from router 102-1 to router 101.
However, because one common authentication server is used to authenticate the route update data in routers 103-1 through 103-4, problems arise as follows:
When a mobile node switches base stations which the mobile node connected to according to a technique known as handover for wireless communication systems, the authentication server authenticates the connected user for the base station which is newly connected to the mobile node. If the authentication server is widely spaced from the newly connected base station, then an authentication packet transmitted between the authentication server and the base station suffers a transmission delay, possibly resulting in a communication failure time upon handover.
It has been considered to reduce the transmission delay time by placing a plurality of authentication servers in respective positions close to the base stations or designing the base stations such that they also serve as authentication servers.
However, the above solutions make it possible for an unauthorized user to use the network based on a replay attack. The replay attack is one of hacking attempts to eavesdrop on the password or the encryption key of a user and use it to masquerade the user.
FIG. 3 of the accompanying drawings shows a wireless communication authentication system employing routers which also serve as authentication servers. The wireless communication authentication system shown in FIG. 3 comprises external network 200, a plurality of authentication-capable routers 201, 202-1, 202-2, a plurality of base stations 204-1 through 204-8, and mobile nodes 205, 207. Router 201 is connected to external network 200. Routers 202-1, 202-2 are connected to and operate under router 201. Authentication-capable routers 203-1, 203-2 are edge routers with an authenticating function which are connected to and operate under router 202-1. Authentication-capable routers 203-3, 203-4 are edge routers with an authenticating function which are connected to and operate under router 202-2. Base stations 204-1, 204-2 are connected to and operate under authentication-capable router 203-1. Base stations 204-3, 204-4 are connected to and operate under authentication-capable router 203-2. Base stations 204-5, 204-6 are connected to and operate under authentication-capable router 203-3. Base stations 204-7, 204-8 are connected to and operate under router 203-4. Mobile nodes 205, 207 are nodes that are movable while being connected to the network. Mobile node 207 is the mobile node of an unauthorized user who intercepts route update data in a wireless zone between mobile node 205 and base station 204-2 and attempts to masquerade mobile node 205 to use the network.
A wireless communication authentication process which is carried out in the wireless communication authentication system shown in FIG. 3 will be described below with reference to FIG. 4 of the accompanying drawings.
It is assumed that mobile node 205 is currently present in an area covered by base station 204-2 and is going to be connected to base station 204-2 through a wireless link. Mobile node 205 sends route update data to base station 204-2 (step 401). The route update data includes the identifier of a destination router, the identifier of mobile node 205, a time stamp or a sequence number.
When the route update data sent from mobile node 205 is received by base station 204-2 (step 402), the received route update data is sent from base station 204-2 to authentication-capable router 203-1 (step 403).
When the route update data sent from base station 204-2 is received by authentication-capable router 203-1 (step 404), the received route update data is authenticated by authentication-capable router 203-1 (step 405).
The route update data includes an authentication code in addition to the items described above. The authentication code is calculated by a hash function from a secret key and the above items, other than the authentication code, of the route update data. The secret key is recognized by only authentication-capable routers 203-1 through 203-4 and mobile node 205. In step 405, the route update data is authenticated by recalculating the authentication code and determining whether the received authentication code is correct or not.
If the authentication result produced by authentication-capable router 203-1 is GOOD, then the route table in authentication-capable router 203-1 is updated based on the route update data which has been authenticated and information indicating that the base station to which the route update data has been sent is base station 204-2 (step 406). At this time, the route table in authentication-capable router 203-1 is updated such that data to be sent to mobile node 205 will be routed through base station 204-2. If the authentication result is NOT GOOD, then the route table is not updated, and the authentication process is put to an end.
After the route table in authentication-capable router 203-1 is updated, the route update data is sent from authentication-capable router 203-1 to router 202-1 (step 407).
When the route update data sent from authentication-capable router 203-1 is received by router 202-1 (step 408), the route table in router 202-1 is updated based on the received route update data and information indicating that authentication-capable router from which the route update data has been sent is authentication-capable router 203-1 (step 409). At this time, the route table in router 202-1 is updated such that data to be sent to mobile node 205 will be routed through authentication-capable router 203-1. Thereafter, the route update data is sent from router 202-1 to router 201 (step 410).
The route update data sent from mobile node 205 to base station 204-2 in step 401 is intercepted by mobile node 207 owned by an unauthorized user who is present in the area covered by base station 204-3 (step 411). Mobile node 207 masquerades mobile node 205 and sends the intercepted route update data to base station 204-3 (step 412). The route update data sent from mobile node 207 is received by base station 204-3 (step 413). The received route update data is sent from base station 204-3 to authentication-capable router 203-2 (step 414).
When the route update data sent from base station 204-3 is received by authentication-capable router 203-2 (step 415), the received route update data is authenticated by authentication-capable router 203-2 (step 416).
Unlike authentication server 106 shown in FIG. 1 which is common to all the routers, the individual routers shown in FIG. 3 have respective authenticating functions. Therefore, even though the route update data includes a sequence number or a time stamp, the route update data that includes the same sequence number or the same time stamp is received by the different authentication-capable routers. Each of the authentication-capable routers is thus unable to determine whether the route update data is incorrect or not from its authentication records, but recognizes all successfully authenticated route update data as legitimate route update data. Accordingly, the data used by the unauthorized user is not excluded, but is normally processed.
If the authentication result produced by authentication-capable router 203-2 is GOOD, then the route table in authentication-capable router 203-2 is updated based on the route update data which has been authenticated and information indicating that the base station to which the route update data has been sent is base station 204-3 (step 417). At this time, the route table in authentication-capable router 203-2 is updated such that data to be sent to mobile node 205 will be routed through base station 204-3. If the authentication result is NOT GOOD, then the route table is not updated, and the authentication process is put to an end.
After the route table in authentication-capable router 203-2 is updated, the route update data is sent from authentication-capable router 203-2 to router 202-1 (step 418).
When the route update data sent from authentication-capable router 203-2 is received by router 202-1 (step 419), the route table in router 202-1 is updated based on the received route update data and information indicating that authentication-capable router from which the route update data has been sent is authentication-capable router 203-2 (step 420). At this time, the route table in router 202-1 is updated such that data to be sent to mobile node 205 will be routed through authentication-capable router 203-2.
As described above, the communication route to legitimate mobile node 205, which has been updated in step 409, is changed by mobile node 207 that has impersonated mobile node 205. Consequently, legitimate mobile node 205 is no longer able to use the wireless communication authentication system.
In view of the above problems, a process of excluding an unauthorized user is disclosed in JP-1995-203540A. According to the disclosed process, the base stations of a wireless communication network have respective authenticating functions. When a mobile node sends a connection request to a base station, the base station sends an inherent identification number of its own to the mobile node. The mobile node generates an authentication code as well as other route information based on the identification number, adds the authentication code to route update data, and sends the route update data to the base station. The base station determines, based on its authenticating function, whether the identification number included in the received route update data is the same as the identification number of the base station or not. An unauthorized user who has sent route update data including a different identification number is thus excluded.
The process disclosed in the above patent document is problematic in that many base stations installed in a wireless communication area need to have respective authenticating functions, and an edge router has to recognize whether all base stations connected to and operable under the edge router have respective authenticating functions or not. In addition, if there is a base station having no authenticating function, then the edge router is required to perform some authenticating process on its own.


An inlet guide vane device having a central axis comprises a first base, a guide sleeve, a blade, a second base, a transmission disk, and an actuator. The first base has at least one first support groove and at least one guide groove. The first support groove extends along a radial direction of the central axis, and the at least one guide groove is located in the first support groove. The guide sleeve is disposed on the first support groove in a manner that the guide sleeve is capable of moving along the radial direction. The guide sleeve has a sliding sleeve, an upper guide post and a lower guide post, the sliding sleeve has a through hole extending along the radial direction. The upper guide post and the lower guide post pass through the sliding groove, and the lower guide post is movably disposed on the guide groove.

A centrifugal compressor is used for compressing fluid, and it mainly comprises an impeller, a shaft, a cylinder, a diffuser, corners, a reflux, an intake manifold and an exhaust pipe. An inlet guide vane device is employed on the impeller.
When the centrifugal compressor operates, the impeller rotates in a high speed so that the airflow inside thereof rotates accordingly. By the impact of the centrifugal force generated by the rotation of the impeller, the fluid is driven to the diffuser behind. Thus, a vacuum space is formed in the impeller so that the air is sucked in and thrown out thereafter. Since the impeller keeps rotating, the air is continuously sucked in and thrown out and this ensures the continuous flow of the air. Compared to the reciprocating compressor, the advantages of the centrifugal compressor include its compact structure, small size, light weight and continuous and uniform exhaust. Besides, the centrifugal compressor does not require an intermediate tank. As a result, the centrifugal compressor generates less vibration and requires fewer consumables.
The blades of the inlet guide vane device near the impeller and the air let can rotate for modifying the flow of the fluid, or even for closing the channel. However, today's structure for the rotation of the blades is too complicated, thereby resulting in poor efficiency. Consequently, it is important to improve the rotation structure of the blades, in order to control the flow of the fluid effectively.

INDUSTRIAL TECHNOLOGY RESEARCH INSTITUTE


A method and apparatus for quenching steel plates after they come from an austenitizing furnace. The plates are rotated to a vertical orientation and rapidly submerged into a water bath while being held flat between reciprocating rolls. The superior uniformity and severity of the quench produces plates of commercial flatness and uniform mechanical properties throughout in an apparatus of simple construction and low energy consumption.

1. Field of Invention
This invention relates to an improved method and apparatus for quenching steel plates.
2. Description of the Related Art
Since the introduction to the construction industry by the steel producers of low carbon, heat treated, weldable, constructional alloy steel plates of high mechanical yield strengths and superior notch toughness, the most critical phase of the manufacturing process has been the water quenching of the plates during heat treatment.
Commercial steel quenched and tempered heat treated plates generally range in size from 20 to 50 feet long, 72 to 156 inches wide and 3/16 to 4 inches thick and in weight form ¼ to 50 tons.
The purpose of the quench is to cool a plate uniformly and sufficiently rapid, from a high temperature, usually 1650 degrees F., to obtain the optimum microstructure throughout the full thickness of the plate and to retain or improve the plate flatness as produced by the rolling mill. This operation is best explained by describing both the heat treating equipment originally used along with the modern day prior art equipment in terms of steel microstructures that are dependent upon the steel analysis, temperature and cooling rate in the quench.
The fundamental property of steel from which its response to heat treatment derives is the ability of steel to exist with its atoms arranged in two distinctly different crystallographic forms; one that is characteristic of steel at high temperature (above 1500 degrees F. for a 0.20% carbon steel); and one that is characteristic of steel at lower temperatures. The high temperature form is called austenite, and depending on its rate of cooling, will transform into either of two general categories of low temperature forms-lamellar or acicular. The acicular structure called martensite is a much stronger form of steel than the lamellar pearlite and is the microstructure desired when water quenching. The martensitic microstructure, after a tempering heat treatment, usually between 750 degrees F. and 1300 degrees F., results in a more optimum combination of strength, ductility and notch toughness than any of the known steel microstructures. Every analysis of steel has a minimum rate of cooling from the austenitic form that will result in a transformation to martensite. This rate is referred to as "Critical Cooling Rate." Alloy additions to steel lower this rate. During the quenching operation any portion of a plate that cools slower than its critical cooling rate will transform to the lower strength lamellar microstructure. Keeping in mind that the internal portions of a plate cool slower than the plate surface and in the case of a non-uniform quench the steel analysis must be designed with enough alloy content to compensate for the slowest cooling location. Such characteristics of the quenching apparatus as cooling severity and uniformity have dictated the alloy content for any plate thickness, and the maximum thickness of plate of any specific alloy that will result in complete transformation to martensite.
The original method of heat treating quench and temper plates was to heat the plate in a car bottom furnace, lift the hot plate from the car bottom by an overhead crane equipped with plate hooks attached to a spreader bar and submerge the plate held horizontally into a water bath. The plate hooks held only a small portion of the plate edges. Steam pockets formed on the bottom plate surface, creating uneven cooling between the top and bottom surfaces causing a high degree of plate distortion. Since all these plates required mechanical leveling their strength level, width and thickness were restricted to the flattening machines capabilities. A further restriction depended on the end use of the plate, as sheared or gas cut sections from a leveled plate distorted them to a degree proportional to the amount of cold work applied to the parent plate during leveling. The first efforts to improve upon this method employed for the plate supports was a series of C shaped hooks attached to a spreader bar that lifted a plate from the furnace car bottom and submerged it into a water dip tank. This device supported a plate across its entire width and allowed for the quenching of wider plates that would otherwise buckle when lifted by plate hooks. This method also created steam pockets on the bottom plate surface and resulted in the same degree of distortion as the plate hook method.
Plates quenched and tempered by this dip quench, primarily Protective Deck Plate and Special Treatment Steel for the U.S. Navy during the World War II period were highly alloyed with nickel and chromium and presented no metallurgical problems.
Shortly after the World War II period the United States Steel Corp. developed a low alloy, high strength, quench and temper steel characterized by good weldability and toughness for the construction industry. See Hodge et al U.S. Pat. No. 2,586,042. This steel was successfully dip quenched out of car bottom furnaces but also required extensive leveling. Other plate manufacturers followed suit and there was a strong need for a quenching process that produced a flat plate. These steels were and still are produced under the specification ASTM, A514, and A517.
The maintaining of plate flatness during the quenching operation had had a far greater influence upon the design of plate heat treating facilities than the quest for microstructure. In 1942, the Drever Co. of Bethayres, Pa., a furnace manufacturer, in concert with Dofasco, engineered the first plate pressure quench to create and manufacture the continuous plate heat treating concept. In operation, a plate would exit the furnace and move into the quench on conveyor rolls. Once the plate was in position the conveyor rolls would be hydraulically lowered, the plate coming to rest on the fingers (feet, jaws) of the lower platen, while at the same time, the upper platen would be lowered onto the plate. The platens are so designed to allow space for the spray pipes that extend across the width of the plate. Water sprays from the pipes then sprayed on the plate from above and below. Typical water flows for roller pressure spray quenches range from 14 to 25 GPM/sq. ft. on each side of the plate while pressures are about 15 psi. The restraining force provided by the platens was as high as 8500 lbs/sq. ft. and as low as 350 lbs/sq.ft. on others.
In the early 1950's the Drever Co. installed the roller pressure spray quenches, as part of continuous plate heat treating facilities in plate mills world wide. The continuous plate heat treating facility consisted of a roller hearth high heat furnace for austenitizing plates, usually at 1650 degrees F., a roller pressure spray quench, roller transfer cars, roller tables for air cooling normalized plates, a roller hearth tempering furnace, for temperatures between 750 degrees F. and 1300 degrees F., and a roller leveler all in line.
To support the spray quench was a 250,000 gallon reservoir, two pumps rated at 11,000 GPM, two 24″ reverse flush Kinney type strainers, six on/off and six throttle valves, and an operating pulpit to control the system. At a later date a 200 ft. high, 1,000,000 gallon capacity water tower and additional pumps was added to ensure a more uniform water pressure to the quench. This water pumping capacity limited the length of the roller spray quench to 50 ft. To maintain the equivalent water volume and pressure for a longer quench would require additional pumping and elevated tank capacities.
The plate product quenched and tempered was the highly alloyed HY-80 and HY-100 armor plate for the U.S. Navy and the high strength commercial steel described in Hodge et al U.S. Pat. No. 2,586,042. The quenched and tempered tonnage heat treated amounted to 20% of the product, the balance being normalized carbon plate up to 3″ thick, the weight capacity of the furnace rolls.
For some twenty plus years this facility was the state of the art operating profitably at plate manufacturing mills.
During this entire time period the most serious operating problem of the facility was the choking and blocking of the spray pipe orifices with foreign material. It caused plates to be quenched out-of-flat and failures to meet required mechanical properties.
The choking was gradual at different rates at random locations and not detectable. It created a constant changing non-uniform quench pattern. Total orifice blocking appeared spontaneously and generally favored the mid-width of the quench as the spray pipes were fed from both ends. The detrimental affect increased as the hardenability (alloy) decreased and the plate thickness increased.
A quality assurance problem exists with the tendency of the pipes producing a lower quench severity to the plate mid-width and official specified mechanical tests are taken from the plate one quarter width. This created the condition that the official physical test results did not always represent the mechanical strength of the entire plate.
Analysis of the foreign material showed it to be a combination of mill scale and algae from the make-up water.
To alleviate the choking and blocking problem the plate manufacturers resorted to replacing the carbon steel spray pipes with stainless steel, installing flush valves on each pipe, reaming the pipes with rotating wire brushes and removing the pipes for redrilling. These procedures gave only temporary relief. Water treatment was also tried unsuccessfully.
In the early 1960's, the high strength heat treat plate market had become highly competitive. Plate customers were demanding the less expensive high strength steels of leaner alloys and carbon steel grades. The roller spray quenches were unable to satisfy these demands.
This brought about efforts within the steel industry to improve the quenching effectiveness of the spray quenches. It was the general opinion that the platen fingers by contacting the plate prior to the water application created a non-uniform temperature within the plate and also shielded the plate from the sprays. It was also thought that increasing the water volume and pressure would solve the problem.
The two major plate manufacturers-U.S. Steel and Bethlehem, the quench manufacturer-Drever Co. and a large plate fabricator-Caterpillar Tractor Co. initiated research programs to improve the efficiency of the plate quenches.
In the early 1960's, the Bethlehem Steel Corp. identified several of the problems and enumerated them in a paper presented at a technical meeting of the American Iron and Steel Institute. This paper described the specific disadvantages of the platens and further claimed it was also impossible to uniformly quench a stationary plate in the roller spray quench.
The Bethlehem Steel Corp. solution was to eliminate the platens and quench plates moving continuously, or progressively, between top and bottom high pressure spray curtains and then thru a lower pressure spray section similar to the roller quench. Plates were held flat between top and bottom rolls. See Malloy et al U.S. Pat. No. 3,756,869.
The Drever Co. solution was to maintain flatness between top and bottom rolls and reciprocate the plate back and forth between the top and bottom sprays. See Safford et al U.S. Pat. No. 3,423,254.
An additional solution of the Drever Co. was to quench plates moving continuously first thru top and bottom high pressure sprays and then thru the top and bottom low pressure sprays similar to the roller quench. The top and bottom rolls were tired, or ribbed, to allow better water flow on the surfaces. See Safford et al U.S. Pat. No. 3,420,083.
Caterpillar Tractor Co. also adopted the tired top and bottom rolls and higher water volumes and reciprocating the plate during the quench. See Lenz U.S. Pat. No. 3,546,911.
The aforementioned patents eliminated the platen hold down system in favor of top and bottom rolls to maintain plate flatness but retained the top and bottom sprays.
The United States Steel Corp. conducted a much more extensive in depth study to evaluate the effectiveness of their roller spray quenches. They introduced the use of the "Quench Severity Test" capable of measuring severities as close as ⅛ inch apart on the plate. The test required a Jominy Test from each plate as tested, a Rockwell C hardness test from the plate mid-gauge per test, the thermal diffusivity of the steel and the use of "Russell's Heat Flow Tables for Plates and Slabs." The quench severities values are given in H values. H=1.00 being the value arbitrarily assigned to still water at 65 degrees F. and the historically established acceptable value for industrial plate heat treating.
Plates from the same heat were quenched on the three U.S. Steel Homestead Works plate roller spray quenches and on the Duquesne Works bar dip quench for comparison.
After being quenched the plates were tested for quench severity over the entire plate in areas under the platen fingers and in areas between the platen fingers as well as areas remote form the fingers. Brinell hardness tests were also taken in the same areas.
The results did show the platen fingers adversely affected the plate areas under the fingers. Of more metallurgical significance the results revealed the spray pattern responsible for the nonuniformity of the spray quench and the dip quench was superior to the spray quench in both quench severity and uniformity.
With the knowledge gained from their quench investigations, U.S. Steel adopted the practice of conducting periodic quench severity tests and adjusting the alloy content of their steels to compensate for low quench severity values. Low quench severity tests on their oldest No. 1 quench, installed in 1957, necessitated a complete overhaul in 1962 to remove foreign material build-up in spray pipes, operating valves, strainer screens, pipe headers and manifolds.
The Bethlehem Steel Corp. and the Drever Co. in a joint effort in 1966 designed and built at the Bethlehem Steel Burns Harbor plant, a roller quench that quenched plates moving continuously between upper and lower sprays. It consisted of a short high intensity curtain quench followed by a lower pressure quench section similar to the platen quench. Flatness was maintained between upper and lower rolls. The initial high intensity quench consisted of top and bottom water spray curtains rated at 100 psi and 260 GPM volume on each surface developed by high pressure pumps. This was followed by two high pressure spray pipes and a low pressure section, 50 ft. long, applying sprays at 25 GPM/sq ft. volume and 15 psi. on each surface supplied by the 200 ft. high water tank.
During the development phase of the continuous plate quenching process the U.S. Steel Corp. supplied different steel grades to be quenched experimentally on the Drever Co. pilot continuous quenching apparatus. U.S. Steel Corp. personnel observed the trials and evaluated the plates for flatness and quenching efficiency at their Homestead Works. The report of these trials, dated Feb. 12, 1965, shows the continuous plate heat treating process unsatisfactory in obtaining the desired quenching severity, quenching uniformity and plate flatness.
The Bethlehem/Drever quench, due to the addition of high pressure pumps, is a higher cost apparatus than the platen quenches. By 1971, the Drever Co. had installed 25 continuous quenches world wide, two of which were installed in U.S. Steel Corp. plants; one at the 160/210 inch plate mill at the Gary, Ind. Works and one at the 160 inch plate mill at Baytown, Tex. Works.
During the start up phase of these continuous quenches at both the U.S. Steel plants they failed to obtain any measure of plate flatness on any grade or thickness. Plate surface hardness readings showed unsatisfactory uniformity and hardness levels. After extensive trials under the direction of the Drever Co. personnel no improvement was made. The lighter gauge plates were severely buckled and the heavier plates were crowned across the plate width at one end dished at the other end.
U.S. Steel modified these two quenches by eliminating the high pressure sections and the top and bottom curtains and quenched plates when totally within the low pressure section. They also added time delay devices that delayed the application of water slightly to one of the surfaces with respect to the other to achieve plate flatness. See Lacy U.S. Pat. No. 4,148,673.
This U.S. Steel Corp. modification in 1972 became the state of the art. It differed from the original roller quench in that the plates were confined between the directly opposed rolls of top and bottom roller tables instead of top and bottom platen fingers and the addition of timing devices that delayed the application of water from either top or bottom sprays. Plate flatness was improved over that of the continuous quenches, but, it retained all of the disadvantages of the spray system. These quenches produced large tonnages profitably by the addition of sufficient alloy to the plate analysis to compensate for the nonuniformity and low severity of the spray quench.
An investigation was conducted on the Texas quench, on Aug. 25, 1981, to compare the water pressure on each individual spray pipe. The low pressure quench section contains 53 top and 53 bottom pipes. The pipes are fed from 3 top and 3 bottom manifolds on each side. All spray pipes were reamed by rotating wire brushes prior to the test. Readings were taken on every pipe during 3 quenches. The results showed a favorable pressure consistency for each pipe but a significant difference from pipe to pipe.
A review of the background information, as heretofore presented, and an analysis of the available technical information, reveals the specific causes of the roller spray quench limitations and shortcomings. The nonuniformity and poor quench severity values, plate flatness problems, spray pipe orifice choking and blocking, inordinate apparatus structure and high energy consumption are all directly related to the spray system. The nonuniformity of the spray system results from the spray pattern wherein the areas of the plate surface impinged by the rod like jet sprays cool faster than the plate surfaces in the gaps between the sprays. This is amplified when the gap areas of the top and bottom plate surfaces are directly opposite. The plate flatness problem results from the difficulties equating the cooling effect of the top and bottom sprays. The plate is cooled by two separate sprays diversely affected by gravity in which the top surface floods and the bottom sprays impinge the plate and fall away. This action creates unequal quenching uniformity and severity between the top and bottom plate surfaces. This is further complicated by the quench being divided lengthwise into three sections controlled by separate flow valves, by the random choking and blocking of the spray pipe orifices and the changes of water pressure with different water levels in the elevated water tank.
In retrospect, the reasons the plate and quench manufacturers never considered abandoning the spray quench system were primarily financial. The plate industry committed to the roller spray quench in the 1950's and the continuous plate heat treating lines operated at a profit for years. When the plate manufacturers encountered difficulties treating the leaner alloy plates in the 1960's all their efforts were made to improve the existing spray equipment. The U.S. Steel Corp. research study, showing the dip quench superior to the spray quench, was never published.
The continuous plate heat treating lines remained profitable because 80% of the plates heat treated were the air cooled normalized grades, by adding alloys to the quench and temper grades and the plate manufacturers tolerating the production delays caused by the blocking and choking of the spray pipe orifices.
The roller spray quench had no serious competitors but other plate quenches were developed for quenching plates on the rolling mill tables immediately after being controlled rolled. This came about after the development of the controlled rolling process which achieves a fine austenitic grain suitable for quenching.
A French company, USINOR in Dunkirk, developed the Rapid Accelerated Cooling, RAC, process in which the austenitic plate immediately after rolling is held flat between upper and lower rolls while traveling through a water tunnel. This process attempts total transformation and requires further tempering.
A Japanese company, Fukayame Works of Nippon Kokan, developed the On Line Accelerated Cooling, OLAC, process in which the plates immediately after rolling are cooled by laminar water flow on the top surface and water sprays on the bottom. The O.L.A.C. process does not attempt to produce the high strength steel grades which require a tempering heat treatment after quenching. The O.L.A.C. process partially quenches the carbon steel grades after controlled rolling to produce a bainite microstructure leaving the plate with sufficient retained heat to temper the bainite and aid in the plate leveling process. The purpose is to achieve the required physical properties in carbon steels with lower carbon content to improve the welding.
The overriding disadvantage of quenching plates on the rolling mill tables is the addition of a cumbersome operation with special requirements to the rolling mill which decreases rolling mill production.


A magnetoresistive element includes a pair of shield portions, and an MR stack and a bias magnetic field applying layer that are disposed between the pair of shield portions. The shield portions respectively include single magnetic domain portions. The MR stack includes a pair of ferromagnetic layers magnetically coupled to the pair of single magnetic domain portions, and a spacer layer disposed between the pair of ferromagnetic layers. The MR stack has a front end face, a rear end face and two side surfaces. The magnetoresistive element further includes two flux guide layers disposed between the pair of single magnetic domain portions and respectively adjacent to the two side surfaces of the MR stack. Each of the two flux guide layers has a front end face and a rear end face. The bias magnetic field applying layer has a front end face that faces the rear end face of the MR stack and the respective rear end faces of the two flux guide layers.

1. Field of the Invention
The present invention relates to a magnetoresistive element, and to a thin-film magnetic head, a head assembly and a magnetic disk drive each including the magnetoresistive element.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of magnetic disk drives has increased. A widely used type of thin-film magnetic head is a composite thin-film magnetic head that has a structure in which a write head and a read head are stacked on a substrate, the write head incorporating an induction-type electromagnetic transducer for writing, the read head incorporating a magnetoresistive element (hereinafter, also referred to as MR element) for reading.
Examples of the MR element include a GMR (giant magnetoresistive) element utilizing a giant magnetoresistive effect, and a TMR (tunneling magnetoresistive) element utilizing a tunneling magnetoresistive effect.
Read heads are required to have characteristics of high sensitivity and high output. As the read heads that satisfy such requirements, those incorporating spin-valve GMR elements or TMR elements have been mass-produced.
A spin-valve GMR element and a TMR element each typically include a free layer, a pinned layer, a spacer layer disposed between the free layer and the pinned layer, and an antiferromagnetic layer disposed on a side of the pinned layer farther from the spacer layer. The free layer is a ferromagnetic layer having a magnetization that changes its direction in response to a signal magnetic field. The pinned layer is a ferromagnetic layer having a magnetization in a fixed direction. The antiferromagnetic layer is a layer that fixes the direction of the magnetization of the pinned layer by means of exchange coupling with the pinned layer. The spacer layer is a nonmagnetic conductive layer in a spin-valve GMR element, and is a tunnel barrier layer in a TMR element.
Examples of a read head incorporating a GMR element include one having a CIP (current-in-plane) structure in which a current used for detecting a signal magnetic field (hereinafter referred to as a sense current) is fed in the direction parallel to the planes of the layers constituting the GMR element, and one having a CPP (current-perpendicular-to-plane) structure in which the sense current is fed in a direction intersecting the planes of the layers constituting the GMR element, such as the direction perpendicular to the planes of the layers constituting the GMR element.
Read heads each incorporate a pair of shields sandwiching the MR element. The distance between the two shields is called a read gap length. Recently, with an increase in recording density, there have been increasing demands for a reduction in track width and a reduction in read gap length in read heads.
As an MR element capable of reducing the read gap length, there has been proposed an MR element including a pair of ferromagnetic layers each functioning as a free layer, and a spacer layer disposed between the pair of ferromagnetic layers (such an MR element is hereinafter referred to as an MR element of the three-layer structure), as disclosed in U.S. Pat. No. 7,035,062 B1, for example. In the MR element of the three-layer structure, the pair of ferromagnetic layers have magnetizations that are in directions antiparallel to each other and parallel to the track width direction when no external magnetic field is applied to those ferromagnetic layers, and that change their directions in response to an external magnetic field.
In a read head incorporating an MR element of the three-layer structure, a bias magnetic field is applied to the pair of ferromagnetic layers. The bias magnetic field changes the directions of the magnetizations of the pair of ferromagnetic layers so that each of the directions forms an angle of approximately 45 degrees with respect to the track width direction. As a result, the relative angle between the directions of the magnetizations of the pair of ferromagnetic layers becomes approximately 90 degrees. When a signal magnetic field sent from the recording medium is applied to the read head, the relative angle between the directions of the magnetizations of the pair of ferromagnetic layers changes, and the resistance of the MR element thereby changes. For this read head, it is possible to detect the signal magnetic field by detecting the resistance of the MR element. The read head incorporating an MR element of the three-layer structure allows a much greater reduction in read gap length, compared with a read head incorporating a conventional GMR element.
For an MR element of the three-layer structure, one of methods for directing the magnetizations of the pair of ferromagnetic layers antiparallel to each other when no external magnetic field is applied thereto is to antiferromagnetically couple the pair of ferromagnetic layers to each other by the RKKY interaction through the spacer layer.
Disadvantageously, however, this method imposes limitation on the material and thickness of the spacer layer to allow antiferromagnetic coupling between the pair of ferromagnetic layers. In addition, since this method limits the material of the spacer layer to a nonmagnetic conductive material, it is not applicable to a TMR element that is expected to have a high output, or a GMR element of a current-confined-path type CPP structure, which is an MR element also expected to have a high output and having a spacer layer that includes a portion allowing the passage of currents and a portion intercepting the passage of currents. The above-described method further has a disadvantage that, even if it could be possible to direct the magnetizations of the pair of ferromagnetic layers antiparallel to each other, it is difficult to direct those magnetizations parallel to the track width direction with reliability.
Under the circumstances, the inventors of the present application have contemplated providing a pair of shields to sandwich the MR element and controlling the directions of the magnetizations of the pair of ferromagnetic layers of the MR element by using the pair of shields. The pair of shields each include a fixed-magnetization portion in which the direction of the magnetization is fixed. The MR element is disposed between the respective fixed-magnetization portions of the pair of shields. The pair of ferromagnetic layers of the MR element are coupled to the fixed-magnetization portions of the pair of shields, whereby the directions of the magnetizations of the pair of ferromagnetic layers are controlled. An example of a shield including the fixed-magnetization portion may be one that is loop-shaped as a whole and that includes a portion formed of a hard magnetic layer, the remainder being formed of a soft magnetic layer.
The inventors of the present application have prototyped a read head in which the directions of the magnetizations of the pair of ferromagnetic layers of the MR element are controlled by the pair of shields as described above, and investigated the characteristic of this read head by performing a quasi static test on the read head. As a result, a phenomenon has been found to occur with high frequency in which the output of the read head abruptly changes to greatly deviate from its ideal value. This phenomenon is undesirable because it becomes a cause of noise in the output of the read head.

Magnetoresistive element including a pair of ferromagnetic layers coupled to a pair of shield layers


A control apparatus calculates a exhaust gas air-fuel ratio of a plurality of cylinders, in which the operation angle of an intake valve is set to a predetermined operation angle, e.g., a maximum operation angle, based on a value output from an air-fuel ratio sensor so as to minimize a variation in an fuel injection quantity between the plurality of cylinders by that exhaust gas air-fuel ratio. That is, the exhaust gas air-fuel ratio of the plurality of cylinders, in which the valve opening characteristics of the intake valve and an exhaust valve are set such that the intake air amount to be introduced into the plurality of cylinders is limited by the opening amount of a throttle valve, for example, and not limited by the valve opening characteristics of the intake valve or the exhaust valve is calculated, and the variation in the fuel injection quantity among the plurality of cylinders is then reduced by that exhaust gas air-fuel ratio. Then, the variation in valve opening characteristics among the cylinders is reduced.

1. Field of Invention
The invention relates generally to control apparatus and methods for a multi-cylinder internal combustion engine.
2. Description of Related Art
Conventionally, a control apparatus for a multi-cylinder internal combustion engine, which reduces variation in the air-fuel ratio between cylinders is known. An example of this type of control apparatus is disclosed in Japanese Patent Application Laid-Open Publication No. 6-213044. The control apparatus disclosed in this publication calculates the air-fuel ratio of each of a plurality of cylinders based on a value output from an air-fuel sensor. Any variation in the air-fuel ratios between the cylinders is then minimized by controlling the valve lift amount of each of the cylinders.
Variation in the fuel injection quantity between cylinders, however, may lead to a variation in torque between the cylinders, which may result in pulsation. With the control apparatus disclosed in the above-mentioned publication, it is possible that, even if a variation in air-fuel ratio between the cylinders is minimized, a variation in torque may still occur between the cylinders.
Further in the control apparatus disclosed in the foregoing publication, although variation in the air-fuel ratio between the cylinders is minimized by controlling the valve lift amount, the publication discloses nothing about how to control the variation in air-fuel ratio between the cylinders in the event that the amount of valve overlap of the intake valve and the exhaust valve can be changed. Moreover, the publication discloses nothing about how to control the variation in the air-fuel ratio between the cylinders in the event that the operation angle of the intake valve can be changed. Therefore, variation in the air-fuel ratio between the cylinders with this control apparatus is not able to be appropriately controlled both in the case where the amount of the valve overlap of the intake valve and the exhaust valve is able to be changed, and in the case where the operation angle of the intake valve is able to be changed.

Control apparatus for multi-cylinder internal combustion engine and control method


This current invention is about a switching implement enabled to perform the remote-controlled switching of electric consumers, consisting of multiple electro-mechanical bistable switches, plus at least one actuating element allocated to the bistable switches such that it can selectively change the state of any of the bistable switches from one of its two states to the other and vice versa.

1. Field of the Invention
The invention presented herein is about a switching implement suitable for the remote-controlled switching of electrical components.
2. Related Art
The invention presented herein is about a switching implement suitable for the remote-controlled switching of electrical consumers. Standard vehicle configurations feature one or two fuse and relay boxes for frequently switching or small to medium loads. Many of these fuse and relay boxes are so-called smart junction boxes with an extra circuitry and sometimes included semiconductor switches.
A switching implement of this kind is described in EP 0 181 534 131 and other publications. This type of switching implement with its many relays and blow-out fuses for protection requires a fairly elaborate design and is of limited reliability due to its many fuses, relays and plug connections. It also leads to comparatively much power being lost during operation because every fuse, every relay coil, every relay contact, and every contact dissipates some of the power. Since the plug-in fuses need to be replaced every time a situation occurs that their job is to protect the vehicle against (e.g. overload or short circuit), the entire switching implement needs to be installed at a place in the vehicle where it can be accessed for maintenance.
The state of the art has revealed maintenance-free switching implements using semiconductor switches for actuating the electrical consumers, However, the highcurrent switching transistors deployed in these switching implements are very expensive. Thermal bimetal switching devices failed to become the standard means of overload and short-circuit protection because their design-specific disadvantages disallow their general use in motor vehicles.
EP 1 033 288 A1 describes a fusing system featuring a motor-driven actuator which can be remote controlled to reversibly break the contact of multiples lines. However, this fusing system allows but a single set sequence of on or off switching actions regarding the consumer lines. The fusing system with its single actuator fails to independently switch the different consumers on or off. Another fact is that having a motor break the contacts slows down the process of breaking the contacts whose long arc durations as specifically generated by short circuit currents will wear down the contacts faster, thereby shortening the life of the contacts.
Hence, the task of the current invention is to provide a switching implement for the remote-controlled switching of electrical components or groups of components, where the continuous power loss of the implement rates significantly lower than that of conventional fuse and relay boxes, where the design of the implement is of a small footprint, robust and cost-effective, and where the means of protection against overload and short circuit can be re-actuated which allows the switching implement to be installed in less accessible places in the vehicle.

Ganged power circuit switches for on-board electrical system in motor vehicles


A method of forming a semiconductor structure includes forming a gate structure having a first conductive material above a semiconductor substrate, gate spacers on opposing sides of the first conductive material, and a first interlevel dielectric (ILD) layer surrounding the gate spacers and the first conductive material. An upper portion of the first conductive material is recessed. The gate spacers are recessed until a height of the gate spacers is less than a height of the gate structure. An isolation liner is deposited above the gate spacers and the first conductive material. A portion of the isolation liner is removed so that a top surface of the first conductive material is exposed. A second conductive material is deposited in a contact hole created above the first conductive material and the gate spacers to form a gate contact.

The present invention generally relates to integrated circuits, and more particularly to fabricating semiconductor structures having gate contacts electrically isolated from source-drain regions.
Contacts may be formed in order to make electrical connections to a semiconductor device. Contacts to source-drain regions of the semiconductor device may be referred to as CA contacts. CA contacts may be distinguished from CB contacts which may form an electrical connection to the gate of a semiconductor structure. The source-drain regions may remain electrically insulated from the gate terminal in order to improve functionality of the semiconductor device. Additionally, a short circuit between the source-drain regions and the gate may damage the semiconductor device. CA and CB contacts may be formed in a contact hole etched in an interlevel dielectric (ILD) layer deposited over the semiconductor device, and therefore may be surrounded by the ILD layer. As a result of device scaling, CB contacts may be placed in increasingly close proximity to the source-drain regions, thus raising the possibilities of having a short circuit between the CB contact and an adjacent source-drain region.

Gate contact with vertical isolation from source-drain

International Business Machines Corporation


A protective circuit and a signal processor for a three-CRT projection TV for preventing CRT burnout, deterioration of luminous characteristics, and damage to lenses by heat. Each CRT beam current detection circuit detects the beam current of each CRT. A state of the video image is predicted based on the detected beam current values and their duration. A microcomputer determines a control voltage for controlling the contrast based on the state of the video image, detected values, and their duration. The contrast is thus controlled by a control signal output to a video control circuit which controls the beam current.

When excessive beam current flows through projection TVs consisting of three CRTs for projecting red, blue, and green video images and a lens system, damage such as CRT burnout due to beam current, deterioration of luminous characteristics, and deterioration of lenses and lens coating due to heat generation may occur. (Hereafter referred to as deterioration of the CRT and lens).
To prevent this deterioration, conventional 3-CRT projection TVs detect the beam current of each CRT and measure the duration when the detected value exceeds a certain value. The duration is measured based on a circuit time constant using a resistance and capacitor. Then, in response to measurement results, a control circuit is employed to reduce the level of beam current. However, this type of control circuit suffers from too large a control error.
Conventional 3-CRT projection TVs which can project still pictures employ, for example, a circuit configured with a field discriminating circuit, an A/D converter, a D/A converter, and a field memory, which is same as that used for 1-CRT direct view TVs, as is disclosed in Japanese Laid-open Patent No. H5-344371 for preventing deterioration of the CRT and lens. Intervals with a smaller difference in fields are counted and a control voltage is output in response to the results.
This circuit also detects the beam current of each CRT and measures the duration when the detected value exceeds a certain value. The duration is measured based on a circuit time constant using a resistance and capacitor. The level of beam current is then reduced in response to the measurement results.
This method reduces the video contrast at a fixed rate due to the use of the circuit time constant. Therefore, in some cases, the time taken to detect the beam current for preventing deterioration of the CRT and lens before the beam current is reduced to a safe level for preventing CRT phosphor burnout may not be appropriate, resulting in the deterioration of the CRT and lens in some video patterns.
In addition, as 2-picture wide screen TVs and teletext broadcasting are becoming more popular, usage where the beam current is concentrated on either the left or right side of CRTs is increasing. A conventional circuit configuration is incapable of protecting CRTs under these usage conditions.
Furthermore, the circuit disclosed in the Japanese Laid-open Patent No. H5-344371 is expensive.

Matsushita Electric Industrial Co., Ltd.


A work machine includes an internal combustion (IC) engine having an output, and an infinitely variable transmission (IVT) coupled with the IC engine output. The IVT includes a hydraulic module and a mechanical drivetrain module. A pressure transducer is associated with and provides an output signal representing a hydraulic pressure within the hydraulic module. At least one electrical processing circuit is configured for controlling the IC engine output, dependent upon the output signal from the pressure transducer.

A work machine, such as a construction work machine, an agricultural work machine or a forestry work machine, typically includes a prime mover in the form of an internal combustion (IC) engine. The IC engine may either be in the form of a compression ignition engine (i.e., diesel engine) or a spark ignition engine (i.e., gasoline engine). For most heavy work machines, the prime mover is in the form of a diesel engine having better lugging, pull-down and torque characteristics for associated work operations.
The step load response of an IC engine in transient after a load impact is a feature mostly influenced by the engine displacement, the hardware of the engine (e.g., whether it has a standard turbocharger, a turbocharger with waste gate or variable geometry, etc.), and by the software strategy for driving the air and fuel actuators (e.g., exhaust gas recirculation, turbocharger with variable geometry turbine (VGT), fuel injector configuration, etc.) with respect to the requirements of emissions legislation (e.g., visible smoke, nitrous oxides (NOx), etc.), noise or vibrations. The load impact may be the result of a drivetrain load (e.g., an implement towed behind the work machine) or an external load (e.g., an auxiliary hydraulic load such as a front end loader, backhoe attachment, etc.)
Engine systems as a whole react in a linear manner during the application of a transient load. Initially, the load is applied to the drive shaft of the IC engine. The IC engine speed decreases when the load increases. The engine speed drop is influenced by whether the governor is isochronous or has a speed droop. The air flow is increased to provide additional air to the IC engine by modifying the air actuators. A time delay is necessary to achieve the new air flow set point. The fuel injection quantity, which is nearly immediate, is increased with respect to both the smoke limit and maximum allowable fuel quantity. The engine then recovers to the engine speed set point. The parameters associated with an engine step load response in transient after a load impact are the speed drop and the time to recover to the engine set point.
An IC engine may be coupled with an IVT which provides continuous variable output speed from 0 to maximum in a stepless fashion. An IVT typically includes hydrostatic and mechanical gearing components. The hydrostatic components convert rotating shaft power to hydraulic flow and vice versa. The power flow through an IVT can be through the hydrostatic components only, through the mechanical components only, or through a combination of both depending on the design and output speed.
One example of an IVT for use in a work machine is a hydromechanical transmission which includes a hydraulic module coupled with a planetary gear set. Another example of an IVT for a work machine is a hydrostatic transmission which includes a hydraulic module coupled with a gear set.
A work machine including an IVT may be prone to loss of traction control and wheel slip when the IVT ratio changes to match load conditions. The IVT controller senses engine speed and deepens the IVT ratio as engine speed decreases under load. When at low ground speeds, the amount of power required for the work machine is a low percentage of what the engine can generate, so the engine may not lug down when the output torque from the engine increases. The operator will then not be aware that the torque at the wheels is increasing. In this case, the drive wheels can lose traction and spin out without notice. This is undesirable for certain operations.
What is needed in the art is a work machine configured with an IVT which is not prone to losing traction in low ground speed conditions.

Work machine with torque limiting control for an infinitely variable transmission


Esterification reactions conducted in the presence of Lewis acids, including the reactions between aromatic carboxylic acids and alcohols and between epoxides and carboxylic acids, may be conducted with the use as the catalyst of a hexaalkylguanidinium or .alpha.,.omega.-bis(pentaalkylguanidinium)alkane salt such as hexaethyiguanidinium chloride or bromide.

This invention relates to chemical reactions performed in the presence of Lewis acids as catalysts. More particularly, it relates to a genus of compounds useful as such catalysts.
Numerous types of chemical reactions proceed best when catalyzed by Lewis acids. By "Lewis acid" is meant a compound that can accept an electron pair. Numerous types of Lewis acids are known, and many of them are transition metal compounds, especially the halides. Illustrative compounds are ferric chloride, aluminum chloride, zinc chloride and stannous chloride.
Lewis acid-catalyzed reactions include many forms of esterification. For example, the reaction of an aromatic carboxylic acid with an alcohol is best conducted in the presence of a Lewis acid. The same is true of the reactions of carboxyiic acids with epoxides. In each case, the product is an ester of the carboxylic acid.
It is of interest to develop new kinds of Lewis acids, particularly in the form of organic compounds. Since many esterification reactions take place at relatively high temperatures, Lewis acid-active organic compounds which are stable under high temperature conditions are especially desirable.
Hexaaikylguanidinium salts are known, as is their use as phase transfer catalysts is known. As disclosed, for example, is U.S. Pat. Nos. 5,116,975 and 5,229,482, they may be employed in various reactions ultimately yielding polyimides as products. They are also known for their high thermal stability when so used.

Method for conducting Lewis acid-catalyzed reactions


The present invention comprises spumavirus isolated from humans. More specifically, the spumavirus of the present invention was isolated from humans who had exposure to nonhuman primates. Importantly, the spumavirus of the present invention or antibodies to the spumavirus can be used to detect the presence of spumavirus or antibodies in body fluids, for pathogenicity studies of related viruses, and as a vector for gene therapies.

Spumavirus, also known as foamy virus for the characteristics of vacuolization the virus induces in cell culture, belongs to a distinct group of retroviruses. The simian foamy viruses (SFVs) include isolates from Old World and New World monkeys and are classified into 10 different serotypes based on serological cross-reactivities. Virus appears to persist in the host for a long period of time in a latent form and can exist in the presence of neutralizing antibody.
Currently the most studied retrovirus, Human Immunodeficiency Virus, is believed to be derived from nonhuman primate transmission into humans at some past time. Concerns about the risk of transmission of retroviruses from non-human primates to humans working in research laboratories were heightened in the early 1990's when two persons developed antibodies to SIV (Simian Immunodeficiency Virus) following work- related exposures, one of whom had clear evidence of persistent viral infection. (See CDC. Anonymous survey for simian immunodeficiency virus (SIV) seropositivity in SIV laboratory researchers--United States, 1992. MMWR Morb Mort Wkly Rep 1992; 41: 814-5; Khabbaz R. F., et al. Brief report: infection of a laboratory worker with simian immunodeficiency virus. New Eng J. Med. 1994; 330: 172-7; Khabbaz R. F., et al. Simian immunodeficiency virus needlestick accident in a laboratory worker. Lancet 1992; 340: 271-3; and CDC. Guideline to prevent simian immunodeficiency virus infection in laboratory workers and animal handlers. MMWR 1988; 37: 693-704.) In addition to SIV, nonhuman primate species used in biomedical research are commonly infected with SFV (simian foamy virus), STLV (simian t-cell lymphotrophic virus), and/or type D retroviruses. All of these retroviruses cause lifelong infections in nonhuman primates, and some are known to be transmissible through sexual contact, blood, or breast feeding. Natural SFV infections in non-human primates have not been definitively associated with disease. In non-human primates, infection with the other retroviruses may result in a clinical spectrum ranging from asymptomatic infection to life threatening immunodeficiency syndromes or lymphoproliferative disorders. The transmission routes of SFVs among non-human primates remain undefined, but the prevalence of seroreactivity is high among captive adult non-human primates.
Studies of the prevalence of spumavirus infection of humans are limited and the findings are not definitive. Though there is some evidence of human infection with SFV (antibodies and positive PCR results), such occurrence has been reported in only two persons, both of whom had occupational risks for infection. Associated disease was not reported in either. (See Schweizer M., et al. Absence of foamy virus DNA in Graves' disease. AIDS Res & Human Retrov 1994; 10: 601-5; Neumann-Haefelin D., et al., Foamy viruses. Intervirology 1993; 35: 196-207; and Schweizer M., et al., Markers of foamy virus infections in monkeys, apes, and accidentally infected humans: appropriate testing fails to confirm suspected foamy virus prevalence in humans. AIDS Res & Human Retrov 1995; 11: 161-70.) There have been no published reports that virus was ever isolated from these infected individuals.
Other inconclusive evidence was seen in early studies which described a relatively high rate of seroreactivity to antibodies to spumaviruses among human populations not known to be exposed to non-human primates. In some instances seroreactivity was suggestively linked to human disease, including disorders of the central nervous system, thyroid disease, and Chronic Fatigue Syndrome. In most instances these studies lacked definitive evidence of human infection and were not subsequently confirmed. (See Heneine W., et al., Absence of evidence for human spumaretrovirus sequences in patients with Graves' disease letter!. J Acq Immune Defic Synd & Human Retrov. 1995; 9: 99-101; Simonsen L., et al.,. Absence of evidence for infection with the human spuma retrovirus in an outbreak of Meniere-like vertiginous illness in Wyoming, USA letter!. Acta Oto-Laryngologica 1994; 114: 223-4; and Heneine W., et al., Lack of evidence for infection with known human and animal retroviruses in patients with chronic fatigue syndrome. Clin Infect Dis 1994; 18: S121-5).
To the knowledge of the inventors, there has not been a documented, definitive isolation of a nonhuman primate origin spumavirus from humans. Previous reports of human spumavirus isolates are now widely regarded as laboratory contaminants.
Recent publications indicate that earlier serological tests showing human spumavirus antibodies in the human population were incorrect. Immunological investigation of a previously reported human spumavirus revealed that it shared common antigens in complement fixation, immunofluorescence and neutralization assays with the chimpanzee foamy virus, SFV-6. Furthermore, failure to detect serological evidence of HFV infection in people from a wide geographical area suggested that this virus isolate was a variant of SFV-6, particularly since sera from chimpanzees naturally infected with SFV-6 neutralized both viruses. In a survey for prevalence of human foamy virus in more than 5000 human sera, collected from geographically diverse populations, none of the serum samples were confirmed as positive. Taken together with sequence analysis endorsing the phylogenetic closeness of the purported human spumavirus to SFV-6/7, these data strongly suggest that human foamy virus is not naturally found in the human population. (See Ali, M. et al., "No Evidence of Antibody to Human Foamy Virus in Widespread Human Populations," AIDS Research and Human Retroviruses, Vol. 12, No. 15, 1996.)
Recent concern that xenotransplantation, the use of living tissues from nonhuman species in humans for medical purposes, may introduce new infections into the human community has increased the importance of defining the ability of simian retroviruses to infect and/or cause disease in humans (See Chapman L. E., et al. Xenotransplantation and xenogeneic infections. New Engl J Med 1995; 333: 1498-1501; DHHS. Docket No. 96M-0311. Draft Public Health Service (PHS) Guideline on Infectious Disease Issues in Xenotransplantation. Federal Register Vol.61, No. 185. Sep. 23, 1996.). The primary animal species considered as donors for xenografts are baboons and pigs. Thus, what is needed are compositions and methods for detecting viruses that may be transmitted from the nonhuman organ donors to the recipient human. Additionally, information regarding these transmissible agents may provide valuable information about the organ donors' cellular receptors that may be important for transplantation success.
Gene therapies have long looked for a good vector that can transport the foreign gene of choice into human cells. The lack of any known disease associated with the virus of the present invention makes the present invention an ideal candidate for gene therapy regimens. Thus, compositions and methods for gene therapy are needed that use a vector capable of carrying a significant amount of foreign DNA that will enter the host organism and not cause disease.

Center For Disease Control And Prevention


A myo-inositol derivative:

The majority of phosphorous (P) in farm animal feed grains is present as a mixed salt of myo-inositol hexakisphosphate, shown below, and more commonly referred to as phytic acid ("myo-IP6").

Because grain-consuming animals such as swine and poultry do not produce the enzyme phytase, myo-IP6 is largely unavailable as a phosphorus-containing nutrient source and is thus excreted in high concentrations in the waste of these animals. Such waste is, however, applied to croplands as a means of enhancing soil fertility, though little information exists regarding the process of how myo-IP6 is transformed into a crop-available nutrient. At least in part, this lack of information respecting the fate of myo-IP6 in soil and water-sediment environments is attributable to the absence of artificial substrates that can be used for the convenient measurement of phytase activity. Still, recent experimental evidence suggests that bacterial phytase plays an important role in the (bio)chemical transformation.
Phytases catalyze the sequential hydrolysis of myo-IP6, forming orthophosphate (ortho-P) and a series of partially dephosphorylated phosphoric esters of myo-inositol. In some cases, hydrolysis may go to completion yielding the parent compound myo-inositol. Based on biochemical properties of the amino acid sequence alignment, others have characterized phytases into two major classes, the histidine acid phytases (comprising the PhyA, PhyB, and PhyC groups), to which most of the bacterial and fungal phytases belong, and the alkaline phytases (PhyD). The phytate-degrading enzyme, 3-phytase (myo-inositol hexakisphosphate 3-phosphohydrolase, EC 22.214.171.124; PhyA and PhyB groups) hydrolyzes myo-IP6 preferentially at the C-3 position, while 6-phytase (myo-inositol hexakisphsophate 6-phosphohydrolase, EC 184.108.40.206; PhyC) hydrolyzes myo-IP6 preferentially at the C-6 position.
Conventional phytase assays conducted on bacterial cell wall-free lysate or whole cell lysate routinely call for the addition of myo-IP6 to buffered cell lysate and subsequent measurement of the released ortho-P by colorimetric analysis. However, experiments by the inventor hereof demonstrates substantial ortho-P release from bacterial cell lysate resulting from "cell free" phosphate-mediated hydrolysis of cell-associated phosphate compounds, including accumulated intracellular polyphosphate. Notably, bacteria, archaea and fungi are all capable of producing polyphosphate. Thus, it would seem that the conventional ortho-P release assay is not a specific measure of phytase activity in lysed cell preparations, and its use under such conditions may result in an exaggerated estimate of phytase activity or, possibly, even a false positive test result.
In light of the foregoing, it would be desirable to provide a specific and sensitive quantitative enzyme assay capable of measuring phytase activity in cell culture filtrates, cell-lysate preparations, soils, etc.

Abstract: A myo-inositol derivative:

Abstract: R1, R2, R3 and R4 are identical, being selected from PO3H2, PO3Na2, PO3K2, PO3Li2, PO3Ca, PO3Mg, PO3(NH4)2, PO3(RNH3)2, PO3(R2NH2)2, PO3(R4N)2, PO(OR)2, H, COZ and BHPP, where R is benzyl or alkyl of 1 to 6 carbon atoms and Z is an alkyl or arylalky group providing a cleavable protecting group; R5 is one of H, benzyl, 4-methoxybenzyl, COZ, PO3H2, PO3Na2, PO3K2, PO3Li2, PO3Ca, PO3Mg, PO3(NH4)2, PO3(RNH3)2, PO3(R2NH2)2, PO3(R4N)2, PO(OR)2, and BHPP, where R is benzyl or alkyl of 1 to 6 carbon atoms and Z is an alkyl or arylalky group providing a cleavable protecting group; X is one of CH2, CH2CH2O, and CH2CH2CH2O; n is an integer from 1 to 8; L1 is a single bond or CH2; L2 is one of a single bond, CONH, CH2CONH, CH2CH2CONH, CH2CH2NHCO, CH2CH2NHCONH, CH2CH2NHCSNH, CH2CH2NHSO2, CH2CH2CH2NHCO, CH2CH2CH2NHCONH, CH2CH2CH2NHCSNH, CH2CH2CH2NHSO2, NHCO, NHCONH, NHCSNH, OCONH, CH2, CH2CH2, CH2CH2O, CH2CH2S, CH2CH2NH, CH2CH2CH2, CH2CH2CH2O, CH2CH2CH2S, CH2CH2CH2NH, and NH—SO2; and R6 is a UV-visible chromophore, a UV-chromophore, a fluorescent moiety, or a radiolabeled moiety.


Methods, systems, and apparatus, including computer programs encoded on computer storage media, for scheduling operations represented on a computation graph. One of the methods receiving, by a computation graph system, a request to generate a schedule for processing a computation graph, obtaining data representing the computation graph generating a separator of the computation graph; and generating the schedule to perform the operations represented in the computation graph, wherein generating the schedule comprises: initializing the schedule with zero nodes; for each node in the separator: determining whether the node has any predecessor nodes in the computation graph, when the node has any predecessor nodes, adding the predecessor nodes to the schedule, and adding the node in the schedule, and adding to the schedule each node in each subgraph that is not a predecessor to any node in the separator on the computation graph.

Neural networks are machine learning models that employ one or more layers of nonlinear units to predict an output for a received input. Some neural networks include one or more hidden layers in addition to an output layer. The output of each hidden layer is used as input to the next layer in the network, i.e., the next hidden layer or the output layer. Each layer of the network generates an output from a received input in accordance with current values of a respective set of parameters.
To allow neural networks perform better on a variety of tasks, e.g., speech, language, and vision processing tasks, neural networks are designed with larger sizes layers, larger numbers of layers, and/or increasingly complex and intricate data dependence. However, large and complex neural networks are difficult to train as the computation costs and the required memory capacity are high. To facilitate computation speed, specialized hardware such as GPUs and AI accelerators have been commonly adopted when training complex neural network models. In more and more recent neural networks, the peak memory capacity of the hardware falls short of the peak demands on the memory when training these large models, turning memory capacity into a bottleneck for the training.

Scheduling operations on a computation graph