There are provided an optical measurement probe capable of obtaining a more stable measurement result, and an optical measurement device provided with the same. An incidence surface of an optical window to be used in a high temperature environment is covered by a deposited film. The optical window is formed of sapphire, and the deposited film is formed from SiO2. Adhesion of dirt to the incidence surface, and an influence, on a measurement result, of the adhesion of dirt on the incidence surface can thereby be prevented, and a more stable measurement result can be obtained.

1. Field of the Invention
The present invention relates to an optical measurement probe for guiding light generated in a high temperature environment to an appliance, and an optical measurement device provided with the same.
2. Description of the Related Art
For example, at the time of evaluating the combustion state in a combustion chamber of an internal combustion engine of a car, measurement is performed using an optical measurement probe for guiding light generated at the time of combustion to an appliance (for example, see JP-A-2012-118080, and JP-A-2011-241753). Such an optical measurement probe to be used in a high temperature environment has to be designed by giving enough consideration to heat resistance.
The optical measurement probe is provided with an optical window, and a light guide, for example. Light generated in a high temperature environment enters from an incidence surface of a transparent optical window, and light transmitted through the optical window is guided to an appliance by a light guide formed of an optical fiber, for example. Heat resistance of the optical window is particularly important in the case of such a structure.

Optical measurement probe, and optical measurement device provided with the same


Provided is a test apparatus that tests a device under test, comprising an upper sequencer that sequentially designates packets transmitted to and from the device under test, by executing a test program for testing the device under test; a packet data sequence storing section that stores a data sequence included in each of a plurality of types of packets; and a lower sequencer that reads, from the packet data sequence storing section, a data sequence of a packet designated by the upper sequencer and generates a test data sequence used for testing the device under test.

1. Technical Field
The present invention relates to a test apparatus and a test method.
2. Related Art
A device for transmitting packets is known. A test apparatus that tests a device for transmitting packets is also known.
Each packet involved in the packet transmission between devices includes, in addition to the actual data, redundant data such as a start code, an end code, and a check code. Therefore, when testing the device for transmitting packets, the test apparatus must generate a complicated test pattern that includes such redundant data.
The device transmitting the packets performs a handshake with its communication partner. The device transmitting packets may exchange transmission requests and denials, transmission initiation and completion responses, transmission successes and failures, and the like, with the communication partner.
Furthermore, when testing the device transmitting the packets, the test apparatus must perform a handshake with the device under test. While waiting for a response from the device under test during the handshake, the test apparatus must also send idle packets and prepare the next transmission in order to respond quickly. Accordingly, when testing such a device, the test apparatus must generate a complicated test pattern.


To prevent an inflow of resin at the time of integral molding and prevent the outer shape from upsizing, there is provided a cable connector including a connector body formed of an insulating material and formed with a plurality of terminal through holes; connecting terminals fitted into the terminal through holes; a cable including a plurality of leads having end portions that are crimped to base portions of the connecting terminals respectively; and a synthetic resin bushing configured to couple the connector body, a tip end portion of the cable including the leads exposed and diverged therefrom integrally by molding. Stoppers are disposed between end portions of the leads and the connecting terminals and inside the connector body and prevent intrusion of synthetic resin as the bushing material so as not to flow from ends of the leads toward ends of the connecting terminals when coupling by molding.

1. Field of the Invention
The present invention relates to a cable connector and, more specifically, to a cable connector of structure which prevents inflow of molding resin when integrally molding a cable connected to a terminal with a bushing in order to enhance a tensile strength of a cable and to secure fluid-tight properties.
2. Prior Art
In the prior art, as disclosed in JP-UM-A-62-57390, a cable connector including a bushing passed through and mounted to a pass-through slot of an equipment member in a fluid-tight manner, and a waterproof connector connected to the pass-through bushing and having a terminal connected to a conductor of a cable is known. The fluid-tight properties (water-proof properties) of the cable connector configured in this manner can hardly be secured and maintained due to its age deterioration, for example. Therefore, as shown in FIGS. 9A to 10C, a cable connector 20 is coupled by integrally molding an outer insulating matrix 21 and an inner insulator 21a with a tip end portion of a cable 26 including a plurality of leads 22 exposed and diverged therefrom using a bushing 25 formed of synthetic resin.
In other words, as shown in FIGS. 9A and 9B, the cable connector 20 includes the outer insulating matrix 21 and the inner insulator 21a, and the inner insulator 21a is formed with a plurality of assembly holes 21b for terminals which are formed into a grid shape and pass through in the fore-and-aft (fitting) direction. Metallic connecting terminals 23 connected to the respective ends of the leads 22 by crimped portions 23b are fitted into the assembly holes 21b. The connecting terminals 23 connected to the leads 22 are press-fitted into the inner insulator 21a. Then, the inner insulator 21a is covered with the insulating matrix 21, and is accommodated in a metal mold. Subsequently, the outer insulating matrix 21, the leads 22, the tip end portion of the cable 26 including a plurality of leads 22 exposed and diverged therefrom and the bushing 25 which envelopes the outer insulating matrix 21, the leads 22, and the tip end portion of the cable 26, are integrally molded. Reference numeral 25a designates a mounting hole, and reference numeral 26a designates an outer sheath of the cable 26, respectively.
However, in the case of the cable connector 20 as described above, as shown in FIG. 9B, resin may flow from the terminal assembly holes 21b in the direction indicated by arrows 24 at the time of integral molding, and reach electrical contact portions, thereby hindering the electrical communication. Also, there is a case where components such as the connecting terminals 23 are pressed and hence deformed by being pressed by a molding pressure at the time of the integral molding (G in the figure), thereby hindering the fitting of the connector.
Therefore, as shown in FIGS. 11A to 11C, there is a case where a lid member (spacer) 27 that dogs the terminal assembly holes 21b is provided for preventing the resin from flowing into the terminal assembly holes 21b of the insulator. The lid member 27 is formed of an elastic rubber plate. The lid member 27 is assembled in a procedure shown in FIG. 11C. As shown in FIG. 12A, there is a case where a sealing material 28 is applied before molding to prevent intrusion of the resin.
However, according to a countermeasure for preventing the intrusion of the resin at the time of integral molding, for example, as shown in FIG. 11B, the shape of the connector product is upsized by an amount corresponding to an a portion in the longitudinal direction of the cable or by an amount corresponding to a 13 portion as shown in FIG. 12B. In addition, as shown in FIG. 13, water or air propagates in the leads 22 and hence enters the inside of the connector product as shown by arrows 24a, thereby resulting in a product inferior in air-tight properties or fluid-tight properties.


SDRAM 1000 outputs data, in a 2-bit prefetch operation, by simultaneously selecting two columns in memory cell array banks A0 and A1 in accordance with column select signals YE0-YEk and YO0-YOk issued from Y-address operation circuit 68. In a full page mode, data are output from all columns crossing rows alternately selected in memory cell array banks A0 and A1 in accordance with an internal address signal issued from a Y-address counter circuit 82.

1. Field of the Invention
The present invention relates to a semiconductor memory device, and in particular to a synchronous semiconductor memory device for taking in an external signal in synchronization with an externally and periodically applied clock signal. More particularly, the invention relates to a synchronous dynamic random access memory (which will be referred to as a "SDRAM" hereinafter) allowing random access.
2. Description of the Background Art
Dynamic random access memories (which will be referred to as "DRAMs") which are used as main storage units have been improved for faster operation, but the operation speeds thereof are still lower than operation speeds of microprocessors (which will be referred to as "MPUs" hereinafter). Therefore, it is often said that the access time and cycle time of the DRAM form a bottleneck in performance of a whole system. In recent years, SDRAMs which operate in synchronization with clock signals have been available as main storage units for fast MPUs.
For fast access, the SDRAM may employ such a specification that continuous bits (e.g., eight bits) per one data I/O terminal are accessed fast in synchronization with a system clock signal. FIG. 25 shows a standard timing chart satisfying this specification for continuous access. More specifically, FIG. 25 shows an operation of reading data of continuous eight bits in a SDRAM which can input and output data of 8 bits (1 byte) through data I/O terminals DQ0-DQ7. Thus, data of 64 bits (=8 bits.times.8) can be continuously read out.
The number of bits of data which are continuously read or written is called a burst length. In the SDRAM, the burst length can be changed by a mode register set.
As shown in FIG. 25, the SDRAM takes in externally supplied control signals such as a row address strobe signal /RAS, a column address strobe signal /CAS and an address signal Add, for example, at a rising edge of an externally supplied clock signal CLK which is a system clock.
Address signal Add contains a row address signal Xa and a column address signal Yb which are multiplexed together in a time sharing manner.
At the rising edge of clock signal CLK in a cycle 1, external row address strobe signal ext./RAS is active and therefore at "L" level, and external column address strobe signal ext./CAS and external write enable signal ext./WE are at "H" level. In this case, address signal Add at this point of time is taken in as a bank designating signal BA or BB and a row address signal Xa, and one row in one bank of the SDRAM memory cell array is selected in accordance with row address signal Xa.
At the falling edge of clock signal CLK in a cycle 4, external column address strobe signal ext./CAS is active and therefore at "L" level, and external row address strobe signal ext./RAS and external write enable signal ext./WE are at "H" level. When this state is attained, the operation enters a read mode, and address signal Add supplied at this point of time is taken in as bank designating signal BA or BB and a column address signal Yb. One column in the memory cell array is selected in accordance with this column address signal Yb. When a predetermined clock period (3 clock cycles in FIG. 25) elapses from the cycle in which this read mode is set, first data b0 among data of 8 bits to be output from data I/O terminal DQ is output. Thereafter, data b1-b7 are successively output in response to rising of clock signal CLK.
FIG. 26 is a timing chart showing change in external signal over time during an operation of continuously writing data of 8 bits per one data I/O terminal DQ in the SDRAM.
In the write operation, bank designating signal BA or BB and row address signal Xa are taken in similarly to the data read operation. More specifically, when such a state is achieved at the rising edge of clock signal CLK in cycle 1 that signal ext./RAS is active and therefore at "L" level, and signals ext./CAS and ext./WE are at "H" level, address signal Add at this time is taken in as bank designating signal BA or BB and row address signal Xa, and one row in one bank of the SDRAM memory cell array is selected in accordance with row address signal Xa.
When such a state is attained at the rising edge of clock signal CLK in cycle 4 that external row address strobe signal ext./RAS is at "H" level, and both signals ext./CAS and ext./WE are active and therefore at "L" level, the operation enters the write mode, and address signal Add at this time is taken in as bank designating signal BA or BB and column address signal Yb. In accordance with column address signal Yb thus taken, one column in the memory cell array is selected. At the same time, data b0 applied to data I/O terminal DQ is taken in as first write data among data of 8 bits to be continuously written, and is written into the selected memory cell.
After the cycle in which this write mode is set, input data b1-b7 are successively taken into the same row of the same bank in synchronization with clock signal CLK, and the input data is written into the memory cells designated by the column addresses which are internally and successively issued.
As described above, the SDRAM does not operate in a manner similar to that of a conventional DRAM in which the operation is performed by taking in an address signal, input data and others in synchronization with external control signals, i.e., row address strobe signal ext./RAS and column address strobe signal ext./CAS, but operates in such a manner that the external signals such as address strobe signals ext./RAS and ext./CAS, address signal and input data are taken in at the rising edge of clock signal CLK which is an externally supplied system clock.
As described above, the SDRAM performs the operation of taking in the control signals and data signals in synchronization with the externally supplied clock signal. Therefore, it is not necessary to keep a margin for a data input/output time which may be required due to a skew (shift in timing) of the address signal. This achieves an advantage that the cycle time can be reduced. Since writing and reading of continuous data can be executed in synchronization with the clock signal as described above, it is possible to reduce an access time in the operation of continuously accessing the continuous addresses.
As an architecture achieving the SDRAM, Choi et. al. has announced a SDRAM of 2-bit prefetch for writing data two bits a time (1993 Symposium on VLSI Circuit). The 2-bit prefetch operation will now be described below with reference to the drawings.
FIG. 27 shows a functional structure of a major portion of a SDRAM 300 performing the 2-bit prefetch operation in the prior art.
More specifically, FIG. 27 shows a structure of a functional portion related to input/output data of 1 bit in the SDRAM of a x16-bit structure.
The memory cell array portion related to data I/O terminal DQi includes memory cell arrays 71a and 71a' forming a bank A, and memory cell arrays 71b and 71b' forming a bank B.
Bank A is divided into memory cell array banks A0 and A1 to be selected in accordance with the address signal, and memory cell array bank B is likewise divided into memory cell array banks B0 and B1.
For memory cell array banks A0 and Al, there are provided X-decoder groups 52a and 52a' each including a plurality of row decoders for decoding address signals ext.A0-ext.Ai and selecting corresponding rows in memory cell array 71a, 71a', Y-decoder groups 53a and 53a' each including a plurality of column decoders which decode column address signals Y1-Yk and issue column select signals for selecting the corresponding columns in memory cell array 71a or 71a', and sense amplifier groups 54a and 54a' for sensing and amplifying data of the memory cells connected to the selected rows in memory cell arrays 71a and 71a', respectively.
X-decoder groups 52a and 52a' include row decoders provided correspondingly to the word lines in the memory cell arrays 71a and 71a', respectively. In accordance with internal address signals X0-Xi which are issued in response to external address signals ext.A0-ext.Ai, respectively, the corresponding row decoders selects the word lines provided correspondingly to the row decoders, respectively, and sense amplifier groups 54a and 54a' each sense the data of the selected one row.
Y-decoder groups 53a and 53a' each include column decoders provided correspondingly to column select lines in memory cell arrays 71a or 71a', respectively. The column select line selects intended data from data of one row sensed by the sense amplifier group 54a or 54a'.
X-decoder group 52a and Y-decoder group 53a select the memory cell of 1 bit in memory cell array bank A0, and X-decoder group 52a' and Y-decoder group 53a' select the memory cell of 1 bit in memory cell array bank A1. X-decoder groups 52a and 52a' as well as Y-decoder groups 53a and 53a' are activated by bank designating signal BA. For memory cell array banks B0 and B1, there are provided X-decoder groups 52b and 52b' and Y-decoder groups 53b and 53b', respectively, which are activated by bank designating signal BB.
For the bank A, there are further provided internal data transmission lines (global I/O lines) for transmitting data sensed and amplified by sense amplifier groups 54a and 54a' and for transmitting write data to the memory cells selected in memory cell arrays 71a and 71a'. More specifically, global I/O line bus GIO0 is provided for memory cell array bank A0, and global I/O line bus GIO1 is provided for memory cell array bank A1.
A write register 59a and a write buffer group 60a are provided correspondingly to global I/O line pair GIO0 for memory cell array bank A0. A write register 59a' and a write buffer group 60a' are provided correspondingly to global I/O line pair GIO1 for memory cell array bank A1.
An input buffer 58a having a width of 1 bit produces internal write data from input data sent to data I/O terminal DQi. A selector 69a is controlled by a selector control signal .phi.SEA issued from a second control signal generating circuit 63, and selectively applies an output of input buffer 58a to write registers 59a or 59a'.
Thus, input buffer 58a is activated in accordance with an input buffer activating signal .phi.WDBA, and thereby produces the internal write data from the input data applied to data I/O terminal DQi. Selector 69a is controlled in accordance with a selector control signal .phi.SEA which is issued from a second control signal generating circuit 63 in accordance with the address signal, as will be described later, and thereby sends the internal write data to one of write registers 59a and 59a'.
Write registers 59a and 59a' are activated in response to register activating signals .phi.RWA0 and .phi.RwA1, respectively, and successively store the write data sent from selector 69a. Write buffer groups 60a and 60a' are activated in response to write buffer activating signals .phi.WBA0 and .phi.WBA1, and thereby operate to amplify and transmit the data stored in corresponding write registers 59a and 59a' onto corresponding global I/O line pair buses GIO0 and GIO1, respectively.
An equalize circuit (not shown) is provided commonly for two global I/O line pairs GIO0 and GIO1. This equalize circuit is activated in response to an equalize circuit activating signal .phi.WEQA (not shown), and equalizes global I/O line pair buses GIO0 and GIO1.
Likewise, memory cell array bank B includes memory cell array banks B0 and B1. Memory cell array banks B0 and B1 include X-decoder groups 52b and 52b', Y-decoder groups 53b and 53b', sense amplifier groups 54b and 54b' which are activated in response to sense amplifier activating signal .phi.SAB, equalize circuit groups (not shown) which are activated in response to equalize circuit activating signals .phi.WEQB, write buffer groups 60b and 60b' which are activated in response to buffer activating signals .phi.WBB0 and .phi.WBB1, respectively, write registers 59b and 59b' which are activated in response to register activating signals .phi.RwB0 and .phi.RwB1, respectively, and selectors 69b and 70b which are controlled by selector control signal .phi.SEB, respectively, and also include an input buffer 58b which is activated in response to buffer activating signal .phi.WDBB.
The banks A and B have the same structures. Provision of write registers 59a and 59a' as well as 59b and 59b' allows input/output of data to and from one data I/O terminal DQ1 in synchronization with a fast clock signal.
The control signals for banks A and B are issued in accordance with bank designating signals BA and BB in such a manner that the control signals for only one of banks A and B are issued.
In the functional block for data reading, data sensed and amplified by sense amplifiers 54a and 54a' are transmitted onto buses GIO of the internal data transmitting lines (global I/O lines) provided for bank A.
For data reading, there are provided a read preamplifier 55a, which is activated in response to a preamplifier activating signal .phi.RBA0 and thereby amplifies data on global I/O line bus GIO0 in bank A0, and a read register 56a, which is activated in response to a register activating signal .phi.RrA0 and thereby stores the data amplified by read preamplifier 55a.
There are also provided a read preamplifier 55a', which is activated in response to a preamplifier activating signal .phi.RBA1 and thereby amplifies data on global I/O line bus GIO1 provided correspondingly to bank A1, and a read register 56a', which is activated in response to a register activating signal .phi.RrA1 and thereby stores the data amplified by read preamplifier 55a'.
A functional block 100 shown in FIG. 27 further includes a selector 70a which receives data from read registers 56a and 56a', and successively issues data sent from read register 56a or data sent from read register 56a' in accordance with selector signal .phi.SEA, and an output buffer 67a which receives the output of selector 70a for successively outputting the data.
Read preamplifier 55a and read register 56a each has a structure of a width of 4 bits corresponding to the four global I/O line pairs. Read register 56a is responsive to register activating signal .phi.RrA1 to latch and successively output the data sent from read preamplifier 55a.
Read preamplifier 55a' and read register 56a' operate in manners similar to those described above.
The output buffer 57a is responsive to an output enable signal .phi.OUTA to transmit the data, which is successively sent from read selector 70a, to data I/O terminal DQi. In the structure shown in FIG. 27, input and output of data are performed through data I/O terminal DQi. However, input and output of data may be performed through different terminals, respectively.
The completely same structure is employed for memory cell array bank B. Thus, the structure for memory cell array bank B includes read amplifiers B0 and B1 which are activated by read amplifier activating signals .phi.RBB0 and RBB1, respectively, read registers B0 and B1 which are activated by register activating signals .phi.RrB0 and .phi.RrB1, respectively, a selector 70b which is responsive to a signal .phi.SEB to selectively output the output of read register B0 or B1, and an output buffer 57b which is responsive to a signal .phi.OUTB to output the output data coming from selector 70b to data I/O terminal DQi.
The functional block 100 shown in FIG. 27 is arranged correspondingly to each data I/O terminal. If the SDRAM has a x16-bit structure, the SDRAM includes sixteen functional blocks 100 which correspond to the data I/O terminals, respectively.
Banks A and B have the substantially same structures and only one of them is selected in accordance with bank designating signals BA and BB, whereby the banks A and B can operate substantially independently of each other.
As a control system for independently controlling the banks A and B, there are arranged a first control signal generating circuit 62, a second control signal generating circuit 63 and a clock counter 64.
First control signal generating circuit 62 takes in the externally supplied control signals, i.e., external row address strobe signal ext./RAS, external column address strobe signal ext./CAS, chip select signal ext./CS and external write enable signal ext./WE in synchronization with external clock signal CLK, and issues internal control signals .phi.xa, .phi.ya, .phi.W, .phi.O, .phi.R and .phi.C.
Second control signal generating circuit 63 is responsive to bank designating signals BA and BB, a lowest bit Y0 of the externally applied address signal, internal control signals .phi.W, .phi.O, .phi.R and .phi.C, and the output of clock counter 64, and thereby issues control signals for independently driving banks A and B, i.e., equalize circuit activating signals .phi.WEQA and .phi.WEQB, sense amplifier activating signals .phi.SAA and .phi.SAB, write buffer activating signals .phi.WBA0, .phi.WBA1, .phi.WBB0 and .phi.WBB1, write register activating signals .phi.RwA0, .phi.RwA1, .phi.RwB0 and .phi.RwB1, selector control signals .phi.SEA and .phi.SEB, input buffer activating signals .phi.DBA and .phi.DBB, read preamplifier activating signals .phi.RBB0, .phi.RBB1, .phi.RBA0 and .phi.RBA1, read register activating signals .phi.RrB0, .phi.RrB1, .phi.RrA0 and .phi.RrA1, and output buffer activating signals .phi.OUTA and .phi.OUTB.
SDRAM 3000 further includes, as peripheral circuits, an X-address buffer 65 which is responsive to internal control signal .phi.xa and thereby operates to take in external address signals ext./A0-ext./Ai and issue internal address signals X0-Xj as well as bank select signals BA and BB, and a Y-address buffer 66 which is activated in response to internal control signal .phi.ya, and thereby issues column select signals Y0-Yk for designating the column select lines.
SDRAM 3000 further includes, as peripheral circuits, a Y-address operation circuit 68 which is controlled by clock signal CLK, and issues signals YE0-YEk and YO0-YOk which correspond to the column addresses to be selected.
Signals YE0-YEk described above represent internal column address signals corresponding to the column addresses in memory cell array bank A0 or B0, and signals YO0-YOk are internal column address signals representing the column addresses in memory cell array bank A1 or B1.
The above description has been given on the structure including only two banks. However, the banks may be generally increased in number, and the registers, buffers and I/O lines of the numbers corresponding to the number of banks may be employed. Even in this case, the banks can be accessed independently from each other.
The data is selectively written into memory cell array bank A0 or A1 in accordance with the lowest one bit of the address which is applied at the time of input of a write command.
This operation will be briefly described below. When the write command is input, the Y-decoder is activated in accordance with the applied address. The first data is stored in register A0, and then the data stored in register A0 is written into memory cell array bank A0 through I/O line GIO0 in response to activation of signal .phi.WBA0.
The data applied at the next rising edge of the clock signal is stored in register A1, and thereafter is written into memory cell array bank A1 through I/O line GIO1 in response to activation of signal .phi.WBA1. When writing of the data of 2 bits is completed, signals .phi.WBA0 and .phi.WBA1 are deactivated, and the potential levels on I/O lines GIO0 and GIO1 connecting the memory cell arrays to the buffers are equalized for next writing of data.
The 2-bit prefetch operation described above has such a disadvantage that an area penalty is large because the registers, buffers and I/O lines are required for each bank independently of the other banks. This disadvantage becomes more remarkable with increase in number of the banks and increase in number of bits of input and output.
Thus, due to a large area penalty, the 2-bit prefetch manner cannot be actually used for data reading, for example, in a so-called page mode, i.e., an operation mode that data is read from all the memory cells arranged at crossings between the selected row and all the columns crossing the selected row.
The above problem generally arises not only in the case where the stored data is read from all the memory cells present at the crossing between the selected row and all the columns crossing the selected row, but also in the case where the stored data is simultaneously read from a large number of memory cells among those present at the crossing between the selected row and the columns crossing the selected row.
For the above problem, Takai et. al. has announced a SDRAM of a pipeline type (1993 Symposium on VLSI Circuit). FIG. 28 shows a structure of this SDRAM 4000. FIG. 28 schematically shows a structure of a functional portion 300 of SDRAM 4000.
A difference with respect to SDRAM 3000 in FIG. 27 is as follows. In SDRAM 3000, each of memory cell array banks A and B is further divided into banks A0 and A1 or banks B0 and B1. However, SDRAM 4000 does not employ this structure. Therefore, the numbers of required registers, buffers and I/O lines are equal to those of a standard DRAM, and a difference with respect to the standard DRAM is that a latch circuit is arranged on a critical path of data transmission.
In contrast to SDRAM 3000, the registers, buffers and I/O lines are not distinguished for banks A0 and A1, and are commonly used for both the banks.
The data to be continuously written can be processed in such a manner that input data is written into the register while preceding data latched by the register is being written into the corresponding memory cell array bank. However, this data writing is performed bit by bit in contrast to the 2-bit prefetch type. Therefore, an operation frequency cannot be increased compared with the 2-bit prefetch type allowing simultaneous writing of data of two bits.

Synchronous semiconductor memory device allowing fast operation in either of prefetch operation and full page mode operation


A semiconductor element includes a semiconductor part, first to third electrodes and a control electrode. The first electrode is provided at a front side of the semiconductor part. The second and third electrodes are provided at a back side of the semiconductor part. The control electrode is provided between the semiconductor part and the first electrode. The semiconductor part includes first and third layers of a first conductivity type and second and fourth layers of a second conductivity type. The first layer is provided between the first and second electrodes and between the first and third electrodes. The first layer is connected to the third electrode at the back side. The second layer is provided between the first layer and the first electrode. The third layer is provided between the second layer and the first electrode. The fourth layer is provided between the second electrode and the first layer.

In recent years, IGBTs (Insulated Gate Bipolar Transistors) are being widely used as semiconductor elements having breakdown voltages not less than 600 V. For example, an IGBT is used as a switch in a power converter. Hence, it is desirable for the IGBT to have a low on-resistance and a fast switching speed. The power loss of the power converter can be reduced thereby.

Semiconductor element and semiconductor device

TOSHIBA ELECTRONIC DEVICES & STORAGE CORPORATION


The invention provides a method of simulating behavior of a flow interacting with an object. The invention improves the accuracy of the approximation of the spatial pth derivative Dp, p≧1, and therefore reduces the cost of the simulation. It includes in the approximation values of the parameter at points which do not lay on grid lines passing through the point of computation P, and by using these values to optimize the approximation. The use of these additional points depends on a preferential direction, such as determined by the advection direction of the flow. The points used in the approximation extend beyond a unit cube on the computational grid. The simulation is in three or more dimensions. The numerical simulation produces output which can be used in the design or optimization of the object which interacts with the flow. In certain cases, it is the output by itself which is important.

The numerical simulation of physical phenomena is well known, and numerical solutions obtained from computer codes are used in many domains of industry. In the following example, we will recapitulate the steps which enter into the daily routine of the application of numerical simulations. The domain of application of the example is Computational Fluid Dynamics (CFD), but the methodology applies equally to other domains and applications. Consider a company which makes aircraft, and who wishes to design or to optimize a wing for the lift to drag ratio. The design department decides to use the tool of numerical simulations since wind tunnel tests are expensive. Their CFD department responds to this request in the following way.
1. A decision is made on which part of physics is important to describe in enough detail the phenomena in a meaningful simulation. In many fluid dynamics cases, the basic fluid dynamics equations like the Navier-Stokes equations are adequate. Perhaps a more simple description can be used. If viscous effects are less important, the Euler equations can be used. At low Mach number, an incompressible approximation can be used. Maybe the potential flow approximation is sufficient. On the other hand, a turbulence model may be needed, together with acoustic models, and a description of the deflection of the wing under aerodynamic forces.
The physical description is expressed in a mathematical model comprising of one or more equations which describe the relations between the physically relevant parameters (mass, density, energy, forces, impulse, pressure, volume, temperature, species concentration, charge density, magnetic field, . . . ). In general, the mathematical model uses spatial derivatives of one or more of the parameters, as well as time derivatives. Together with the number of space dimensions, the physical model determines the number of variables which are needed in the solution. In the case of the Navier-Stokes equations in three dimensions, five variables which depend on space and time describe the physical solution. These five variables can be e.g. the density, the momentum in the three directions and the energy. This set of variables is commonly known as conservative variables. Other combinations are possible, such as the density, the three velocity components and the pressure, which is known as the set of primitive variables. Yet another set of variables is known as entropy variables, since one of the variables is chosen to be proportional to the entropy. A transformation is always possible between different sets of independent variables.
2. The next step is to choose a computer program which can compute a solution to the problem which is compatible with the physical description of the problem. The simulation code will be run on a computer. While the physics and the mathematical model describe a continuum, the computer can only work with discrete values in a limited number of points. The solution of the mathematical model with a computer program therefore involves the procedure of discretization, which consists of two steps.
First, the continuous variable is replaced by a discrete variable in space. A grid defines points in space where the values of the parameters are stored.
The second step is to rewrite the relations between the continuous variables of the mathematical model in relations between discrete variables. In particular, the derivatives which appear in the mathematical model are replaced by their discrete equivalent, which are differences which are locally calculated using the values of the discrete variables of the surrounding grid points. This step involves an approximation and is not exact.
In general, a big enough company has the means and experience to develop and maintain an in-house computer code. Such a code is tuned to the specific needs of the company. It may compute solutions to only a very restricted number of physical problems, but it is likely to be up to date. The developments in the domain are followed, and e.g. new space discretizations, faster solution techniques such as accelerators and so on are coded. After testing, the code is ready for production runs. Smaller enterprises often can afford only a small CFD group, which uses programs from a specialized provider. This is normally a more general code, since it will have to accommodate a larger spectrum of clients with different applications.
3. The computation of the numerical solution is preceded by a pre-processing step. A geometrical description of the wing is used to generate a computational grid. This grid defines the points in space where the solution is calculated. Together with this grid an initial solution is generated. In the case of the Navier-Stokes equations, the five independent variables are given a certain value for each of the grid points, corresponding to e.g. uniform flow at the design Mach number. The grid and the initial solution are written to one or more files.
4. The next step is to run the simulation code. The program performs the following actions:                a) The program reads the grid, and stores for each point the coordinates in the memory of the computer.        b) It reads the initial solution and stores for each grid point the value of the physical parameters in memory.        c) Additional files are read which specify computational parameters such as the number of iterations or a convergence criterion, which physical model to use, which of the coded space discretizations to use, and additional information if necessary. Boundary conditions are specified which are used at the extremities of the part of space under consideration. They represent inflow and outflow from the domain, the way the wing influences the flow, and any other interaction of the flow with its surroundings.        d) Using the grid, the initial solution and the boundary conditions, it solves iteratively and approximately the discrete mathematical equations which describe the physical problem.        e) The code stops after a specified number of iterations, or when a solution is obtained which is accurate enough.        f) The code writes the solution to a file. This output solution consists of the value of physical variables in each of the grid points, where the number of physical variables corresponds to the problem. Another output file may be written which contains the grid.
5. A post-processing program is used to read the grid file and the output file of step 4f. Normally this very general program permits to extract any desired physical parameter which can be computed from the solution. If the solution is written in the form of conservative variables, this program can compute the pressure, which is needed for the lift and drag. It can also compute variables like the Mach number, the temperature and so on.
6. The results are used to modify or improve the geometry.
Steps 3-6 are repeated until the design is optimal. In the case of insufficiency of the physical model, a more elaborate one is chosen, and coded if necessary. If there is insufficient resolution of the simulated physical phenomena on parts of the grid, a finer grid is generated.
The above describes the typical computation of a numerical solution and its use in an industrial environment. A similar procedure is followed when the purpose is to design or to optimize part of a car, a ship, a vehicle in general, a turbo machine, a ventilation system, a wind mill, a pump, a combustion engine, a channel, the mixture of steam and oil or water and oil in porous media for oil recovery, and so on, or to describe the evolution of flow such as in weather prediction, climate modeling or in a forest fire. In step 1, the physical model depends on the problem under consideration. In a magneto-hydrodynamics application, the description of the electromagnetic field enters. This entails the use of additional variables in the solution. In an application with different chemical species, the concentration of each of the species enters, together with a description of the transformation between the different chemical compounds. In multi-phase flow, such as e.g. oil and steam, or water and air, all fluids require equations and variables for a proper description.
The pre-processing and post-processing, steps 3 and 5 respectively, are normally separate programs. Occasionally, they can be incorporated in the numerical solver.
In step 3 the grid is generated once for a given geometry. In current practice a grid can contain many millions of points. Very large computational grids are normally composed of different blocks. Such a multi-block grid can then be distributed to multiple processors or even to different computers for a parallel computation. Some numerical simulation programs are able to refine or derefine automatically the grid locally using an error estimation based on the computed solution. Some programs use such a capability to compute a time-accurate simulation where a concentration of grid points follows a physical phenomena like e.g. a vortex or a shock. In the case of a time-accurate simulation, step 4f is repeated for each intermediate solution of interest. This is e.g. the case for the instationary behavior of a turbo machine where the radiated sound is computed. Another example is combustion.
The practical use of numerical simulations is illustrated in step 5, where the output of the program is transformed into a useful result. The output of the numerical simulation can serve many purposes, depending on the application. Quite often, this involves the pressure, since this relates to forces on the object under design. For a wing, this can be the Mach number for restricting the shock strength. For turbo machines, this can be the pressure on the blades, or the thermal load. For a heart valve, this can be the velocity field which needs to be smooth to avoid cluttering. For a forest fire simulation, this is again the velocity field to predict the likely progress of the fire.
Normally, the person who runs the program makes use of the output as illustrated in step 6. The output can also be fed back without human interference into the program. This is e.g. the case for inverse methods, where the desired pressure distribution is prescribed in the form of a goal. The geometry of the object and the related grid possess degrees of freedom which allow optimization to reach the goal. Remark that the purpose in the example above is the optimal geometry of the wing. The numerical solution is a convenient tool to achieve this goal.
At the core of the numerical simulation is the approximation of space derivatives as used in step 4d. The discrete mathematical equations which are used in that step are the subject of the invention.
For the computation of each value of a space derivative at a grid point, also called node, one of the methods, known under the name of Finite Differences, consists of the computation of an approximate value of each space derivative as a linear combination of values of the parameter(s) taken at each of the points of a set of grid points, called stencil, which are in general points surrounding the point of computation, and with weighting coefficients chosen in such a way that the best possible approximation results.
Another method is the Finite Volume method, which is very closely related to Finite Differences, and is based on an integral formulation using fluxes through a control volume. These fluxes are in turn a function of a number of the nodal unknowns, defining again a stencil. The number and relative importance of nodes involved in the fluxes allows for optimizing the approximation according to predefined criteria.
Yet another method is the Finite Element method, where the space is subdivided into elements, containing nodes at which the approximation of the physical parameter(s) u is stored. Basis functions 0, also called interpolation functions, are defined on the elements, which are used to approximate the physical value u on the element. The integral of the derivative is computed on the element, using a test function V, also called weighting function. The combination of X and V is then chosen in such a way that the approximation of the derivative is optimal.
Then, there are Distribution Methods. They share with Finite Elements the representation of the unknown(s) is on the element. One variant, the Residual Distribution method shares with the Finite Volume method a volume over which the integral of the derivative is computed. The integral of the derivative is split into parts which are distributed over the nodes. Another variant, the Flux Vector Distribution method uses like the Finite Volume method fluxes through a control volume. These fluxes are distributed over the nodes. In both cases, the characteristics and the optimization of the discretization follow from the choice of the distribution coefficients.
All these methods have in common that the approximation is ultimately dependent on the values of the parameter(s) at the nodes of the stencil, and that certain discretization parameters, which are inherent to the particular numerical framework under consideration, influence the accuracy of the approximation and the numerical properties of the numerical simulation of the physical phenomena.
The choice of the stencil, the values of the discretization parameters and the associated numerical method are commonly called the numerical scheme of the numerical simulation of physical phenomena.
Stencils are commonly classified according to the relative position of the points with respect to the advection direction in velocity fields. In an upwind discretization, the stencil has nodes which are upstream of the point where the derivative is computed. Another type of discretization is central, where the stencil is symmetric with respect to the advection speed for the point where the derivative is computed. Finally, there are many discretizations which are a combination of the two.
Concerning the grid, one can use a regular or structured mesh, formed by N families of rectilinear or curved lines, where the mesh points are located at the intersections. The number of families of lines corresponds to the number of space dimensions. Another type of grid, called unstructured grid, uses a connection table to identify the points of a stencil, and the points are in general less regularly positioned in space. However, unstructured grids can be locally perfectly regular, allowing to discern locally families of lines.
The accuracy of the simulation depends directly on the grid spacing. If the error in each space derivative reduces linearly with the mesh size, the scheme is said to be of first order. If the error reduces quadratically with the mesh size, the scheme is said to be of second order. In general, when the error reduces with the power M of the mesh size, the scheme is said to be of order M.
For a given application, the choice of the scheme is linked with practical constraints of the computation, called numerical constraints, which correspond to certain priorities imposed by the user on resulting errors of the simulation. Among the numerical constraints, one may refer to consistency, convergence and stability of the simulation, the desired order of the scheme (industrial applications require an order of at least 2), the diffusion and dispersion properties of the numerical scheme, and computational cost (which may impose a maximum size of the stencil, generally indicated by compactness).
The order of the approximation and the extent of the stencil are related. On a stencil of given extent, the order of accuracy of an approximation is limited. In other words, for an approximation of a given order, the stencil has to have a certain minimum extent. It depends on the numerical constraints of the application if the size of the stencil or the order of the approximation is predominant. When the appropriate combination of the size of the stencil and the desired accuracy is chosen, remaining degrees of freedom can be used for optimizing other numerical constraints.
An extended description of the above, and of numerical methods in general can be found in (D1), "Numerical computation of internal and external flow", C. Hirsch, J. Wiley & Sons, New York, Vol. 1, Fundamentals of numerical discretization, 1988 and Vol. 2, Computational methods for inviscid and viscous flows, 1990.
There are various methods to obtain the discretization parameters appearing in the specific numerical framework. In general, a truncated Taylor series expansion with respect to the computational point is used for the value of the physical parameter(s). Given that only the first terms of the Taylor series are used, the value obtained is accompanied with an error, called truncation error, which depends in particular on the degree of the last retained term in the series. The discretization parameters are then chosen such that they optimize the error in the discretization of the derivative, which is a function of the values resulting from the truncated Taylor series. Other criteria follow from considering the Fourier transform of the discretization, thereby choosing the discretization parameters in such a way that the behavior of certain Fourier components is optimized. This means tuning the dissipation and dispersion of the numerical scheme, optimizing for the stability of the numerical scheme, or for the damping of certain components resulting in accelerated convergence. Other optimizations related to the choice of the discretization involve computational cost, ease of use in multi-block codes, ease of coding and others.
As pointed out, for each application, the most appropriate choice has to be made on:                the numerical formulation with associated discretization parameters which is used for the simulation,        the stencil itself, and notably the number of points and their relative position with respect to the point of computation,        the optimization of the discretization, e.g. based on the truncation error in the truncated Taylor series expansion used in the computation of the discretization parameters, or based on the behavior of certain Fourier components, or other.
Many methods for numerical simulation have been proposed and are used in industry with more or less satisfactory performances. The above mentioned books D1 give an overview of the mathematical models, discretization techniques, numerical schemes and solution methods for the numerical simulation of space derivatives in flow phenomena. In particular, in D1 Volume 1, part 2, chapter IV, pages 167-180, the fundamentals are described of the method of Finite Differences, on a regular grid in one dimension. As explained, the weighting coefficients used in the linear combination can be determined if the number of points of the stencil is coherent with the order of the desired discretization. In particular, the book mentions the general method of Hildebrand for determining Finite Difference formulas.
An example is a general one-dimensional discretization for a derivative at node i which uses the stencil between the nodes i−m and i+n, where m and n are given positive integers. On the stencil S=(i−m,i−m+1, . . . , i−1,i,i+1, . . . , i+n−1,i+n), the approximation of the first derivative can be written as
                                                                        u                x                            =                                                                            1                                      Δ                                                                                x                                                                                (                                                                                a                                                  -                          m                                                                                u                                                  i                          -                          m                                                                                +                                                                  a                                                                              -                            m                                                    +                          1                                                                                u                                                  i                          -                          m                          +                          1                                                                                +                    …                    +                                                                                a                                          -                      1                                                                                u                                          i                      -                      1                                                                      +                                                      a                    0                                                                          u                    i                                                  +                                                      a                    1                                                                          u                                          i                      +                      1                                                                      +                …                +                                                                                a                                              n                        -                        1                                                                                u                                              i                        +                        n                        -                        1                                                                              +                                                            a                      n                                                                                u                                              i                        +                        n                                                                                )                            .                                                          (        1        )
The coefficients aj, j∈S determine the numerical properties of the discretization. A general description of the above discretization can be found in D1 which discusses the method for obtaining the coefficients aj. Expression (1) also generalizes to higher derivatives.
The conjunction in two or more dimensions of the above one-dimensional discretization has a small error if the preferential direction points from one grid point to another, following a grid line. In between, the error becomes quite large. The reason is that a derivative which is related to a preferential direction has to be approximated with grid-based derivatives. Grid-based derivatives are using values of the physical unknown(s) which are stored at predefined positions of the grid. A conjunction of one-dimensional discretizations uses only points on the grid lines, and not in between.
This is illustrated in FIG. 1, where a part of a two-dimensional structured grid is shown. The indices are for the x-direction 0,1, . . . , i−1, i, i+1, . . . , imax and for the y-direction 0,1, . . . , j−1, j, j+1, . . . , jmax, and the nodal unknowns are indicated by ui,j for node i, j. Indicated are two directions, {right arrow over (a)}1 and {right arrow over (a)}2. Both point from one grid point to another, but only {right arrow over (a)}1 follows a grid line, and the discretization has a small error. For the direction of {right arrow over (a)}2, the error is maximal when using a conjunction of one-dimensional discretizations.
The report (D2), "Progress in multidimensional upwind differencing", B. van Leer, NASA Contractor Report 189708, ICASE report #92-43, September 1992, NASA Langley Research Center, Hampton, Va., describes different known approaches for the simulation of convection phenomena in two dimensions which go beyond one-dimensional methods. In this framework, different state of the art approaches have been proposed to optimize the methods of numerical simulation in two dimensions, with more or less satisfactory performances. Only the methods using an unstructured grid have been exploited in practice using a low order upwind scheme.
In the majority of practical applications, the physical phenomena take place in three dimensional space, which makes it indispensable to realize a numerical simulation of at least three dimensions. In practice, it may be necessary to use more than three dimensions, e.g. to incorporate time as additional dimension, taking into account the fact that an unsteady physical process in N dimensions can be modeled by a N+1 dimensional steady process.
However, actually all the industrial methods of numerical simulation in three dimensions (cf. e.g. the documents D1 and D2) are limited to a conjunction of one-dimensional methods.
Besides these one-dimensional methods, certain attempts of truly multi-dimensional numerical simulations in three dimensions have been reported. Nevertheless, taking into account the complexity of the problem presented, and the difficulties encountered in two dimensions, the use of a truly multi-dimensional method in three or more dimensions is considered to be extremely complex.
The paper (D3) "Optimum positive linear schemes for advection in two and three dimensions", P. L. Roe and D. Sidilkover, SIAM J. Num. Anal., December 1992, #6, vol. 29, pages 1542-1568, constitutes one of the rare publications which treat until now a scheme for the simulation of advection phenomena, considering a class of first order upwind schemes. In the case of three dimensions, the authors of the paper, like all authors until now, consider it suitable to choose on a structured grid a minimal upwind stencil formed by a cube of eight points.
Having chosen and predefined this stencil, the different weighting coefficients are computed to obtain the best simulation possible, which is the case of the scheme called "N scheme". Denote the components of the vector {right arrow over (a)} of the preferential direction in N dimensions by a, b, c, . . . , that is {right arrow over (a)}=(a, b, c, . . . )T. One-dimensional upwind schemes take the discretization stencil based on a≧0 or a≦0. Applying a conjunction of one-dimensional discretization in N dimensions means choosing the stencil depending on the sign of a, b, c, . . . separately. The N scheme uses instead the combination a≧b≧c≧ . . . ≧0 and points of the stencil which do not lie on a grid line through the point of computation P. Nevertheless, the results obtained with the scheme given in the paper are largely insufficient in practice. Indeed, one cannot obtain a high order scheme with this method on such a small stencil. Furthermore, the simulation in three dimensions generates specific problems which are not encountered in two dimensions.
Moreover, since the date of this paper, no author has effectively imagined that it is possible to obtain higher order accurate discretizations using a larger stencil which includes points beyond the grid lines on a structured grid in three dimensions.
However, as indicated by the publication (D4) "Numerical Aerodynamics: Past Successes and Future Challenges from an Industrial Point of View", David Paul Hills, Computational Methods in Applied Sciences, 1996, ECCOMAS, pages 166-173, one-dimensional methods as used in industry have reached their limits, and real gains should be sought in multi-dimensional methods. In spite of continued research since 1992, no such method has been found yet.
Furthermore, the majority of the publications on this subject since 1990 indicate, like the previous, that the true multi-dimensional methods imply upwind discretizations on unstructured grids. Neither multi-dimensional efforts on structured grids nor attempts to find central space discretizations with a reduced error have resulted in numerical simulations which can be applied in an industrial environment.
The invention aims to dispose of these shortcomings by proposing a simulation method which provides a simulated numerical representation in N dimensions, with N≧3, of spatial pth derivatives Dp, p≧1, of at least one physical parameter u of a phenomenon to which is associated a velocity field d which determines a preferential direction in every point of at least a part of space, and which permits                to reduce significantly the error in the numerical simulation,        a consistent, stable and convergent simulation,        a locally monotone simulation,        the simulation of spatial pth derivatives, with p>1, with an error of a desired order, incorporating numerical constraints as desired.
The invention aims also to propose a method which                is compatible with current technologies, notably computation time and memory requirements,        is compatible with the simulation of nonlinear phenomena,        can be used for systems of equations,        can be used with acceleration techniques like e.g. multi-grid, GMRES and preconditioning,        and which allows simulations in Finite Element formulations, Finite Volume formulations, Finite Difference formulations, Residual Distribution formulations, Flux Vector Distribution formulation, or others.
The invention also aims at providing a global simulation method of a physical phenomenon and a data processing system, a software, in particular in the form of a digital storage medium, to implement such methods.

Method for the numerical simulation of a physical phenomenon with a preferential direction


A method, system, and program for efficient parallel bitwise sweeps of larger objects during garbage collection are provided. During a bitwise sweep, a helper thread scans a mark vector looking for a consecutive sequence of unmarked bits of a sufficient length following a marked bit. Once a consecutive sequence of unmarked bits of a sufficient length following a marked bit is detected, the helper thread fetches the size of a marked object corresponding to the marked bit. If the size of the marked object exceeds a size represented by the consecutive sequence of unmarked bits, the remainder of the bits representing the marked object are skipped, such that once a marked object is identified as potentially exceeding an object fetch threshold the helper thread efficiently skips the remainder of the bits represents the marked object and continues scanning for a number of consecutive zeroes indicating free space.

1. Technical Field
The present invention relates in general to improved garbage collection and in particular to improved efficiency in handling large objects during garbage collection. Still more particularly, the present invention relates to improved efficiency in handling a parallel bitwise sweep of larger objects during garbage collection.
2. Description of the Related Art
Software systems, such as the Java Virtual Machine (JVM), that employ garbage collection typically provide an explicit call for allocating objects, but no explicit call for freeing objects. Instead, in a system that employs garbage collection, when available storage on a heap is exhausted, all operations are suspended and garbage collection is invoked to replenish the free storage.
A common garbage collection algorithm is called "mark and sweep". During the mark phase, all Java objects that are still accessible to a program are identified and marked. Next, during the sweep phase, unmarked objects of the heap are identified as free space. In particular, free space is typically identified as the space bounded by marked objects or by the beginning or end of the heap.
In particular, during the sweep phase, the free spaces that are of a sufficiently large size are considered free items that may be arranged into lists or structures that facilitate subsequent object allocation. Any free memory fragments that are not of sufficient large size are deemed unnecessary and are not included in the list.
In sweep phrase implementation, it is common for a garbage collection algorithm to require that the size of objects currently within the heap be derivable from an examination of the object. Additionally, some garbage collection algorithms may require that free memory fragments have a derivable size.
One approach for facilitating object and fragment size derivation is to include a prefix to every object and fragment, where the prefix indicates a size field. Another approach for facilitating object and fragment size derivation is by implementing a bitwise sweep algorithm. To implement a bitwise sweep algorithm, a dedicated bit array that is independent of the heap identifies marked objects where each bit represents a fixed storage size (e.g. 8 bytes) and each object is aligned to this size. At the onset of the mark phase, the dedicated bit array is cleared. Then, referenced objects are marked by setting the bit that represents the starting location of the object. Next, during the sweep phase, the bitwise sweep algorithm is implemented by scanning the dedicated bit array, searching for runs of zero bits bound on each side by marked bits. When a sufficiently large run of zeroes bound by marked bits is located, the object at the beginning of the run is examined and its size fetched. The size of the initial marked object is then subtracted from the size represented by the run of zeroes and if the resulting size is sufficiently large, the storage bound by the marked objects is considered a free item and is saved in a way to allow it to be used for subsequent object allocation.
Garbage collection becomes more complex in a multiprocessor system. In particular, a parallel garbage collector may be implemented to handle garbage collection in a multiprocessor system. A parallel garbage collector may implement sufficient helper threads to use all the available processors during garbage collection. In one example of an implementation of a parallel sweep phase, the heap may be divided among multiple sections so that each helper thread can work on unique sections and not impede the other helper threads.
When all sections have been processed by helper threads, the helper threads are suspended and the garbage collector enters single thread mode. In single thread mode, a single thread examines all the section data and may identify free items that span sections. The single thread arranges all the identified free items into appropriate structures for subsequent allocations. In particular, during single thread mode, all other threads of the Java process are suspended and only one process is used by the Java process.
When a Java application is run on a multiprocessors system, it is important that parallel garbage collectors are as efficient as possible. First, it is important to make helper threads function as efficiently as possible because when the helper threads are executing on the multiple processors, the Java application threads are suspended. In particular, it is important to have helper threads finish sweeping all sections close to the same time to reduce the amount of time that processors remain idle waiting for other helper threads to finish. Second, it is important to make the single thread mode runtime as short as possible because when the single thread executes during single thread mode, all other Java threads are suspended.
The bitwise sweep algorithm is one efficient method of facilitating sweeps when objects are small, but the current bitwise sweep algorithm is inefficient when used to facilitate object size derivation for large objects, and in particular large objects that are significantly larger than the size requirement for addition to a free list. For example, large database applications and applications that display images may instantiate objects that are several megabytes in size, while the typical free list may only require unmarked objects to be several hundred bytes to be eligible for storage in a free list. Under the current bitwise sweep, each bit representing the length of the initial marked object must be scanned and a marked bit reached before the size of the object is fetched. Thus, the current bitwise sweep algorithm is inefficient because if the size of the fetched object is large, many bits are unnecessarily scanned.
In allocating sections, multiple small sections maybe allocated to promote sweep efficiency. In particular, when there are multiple small sections, the time that helper threads sweep each section is reduced, allowing the helper threads to complete sweeping all the sections more closely to each other. However, as the number of small sections increases, the amount of time required for single thread mode increases, which may effectively decrease the efficiency gained from allocating multiple small sections. In addition, while allocating multiple small sections may promote efficient sweeps of small objects, sweeping multiple small sections for larger objects is inefficient. In particular, when a larger marked object extends across multiple small sections, in a bitwise sweep, each bit of each portion of the larger object is inefficiently scanned within each section.
Therefore, in view of the foregoing, there is a need for a method, system, and program for improving the efficiency of bitwise sweeps in a parallel garbage collector and the efficiency of section dispersal to improve the efficiency of handling larger objects, and in particular for handling objects that are substantially larger than the size required for addition of the object to the free list.

Efficient parallel bitwise sweep during garbage collection

International Business Machines Corporation


An ordinary-temperature purifying catalyst includes an oxide having an oxygen defect introduced by a reduction treatment, and a noble metal loaded on the oxide. For example, the oxide can be at least one oxide selected from the group consisting of cerium oxides and zirconium oxides, at least a part of which has an oxygen defect. The catalyst can purify an environmental loading material, such as carbon monoxide, a nitrogen oxide, ethylene, formaldehyde, trimethylamine, methyl mercaptan and acetaldehyde, in air at an ordinary temperature. A method for how to use the catalyst is also disclosed.

1. Field of the Invention
The present invention relates to an ordinary-temperature purifying catalyst, which can purify and remove an environmental loading material, such as carbon monoxide (CO), odorants, nitrogen oxides (NOx) and hydrocarbons (IC), formaldehyde which often generates in houses, and an ethylene gas which causes to deteriorate the freshness of foods, at an ordinary temperature (e.g., room temperature).
2. Description of the Related Art
Conventionally, in order to remove odorants and harmful gases, adsorbents, such as activated carbon and zeolite, have been used so far. However, the adsorbents require means for processing the adsorbed components.
Further, in order to purify carbon monoxide, one of harmful gases, the performance is required which purifies and removes carbon monoxide in a lower temperature range and in a shorter period of time. However, conventional catalysts have been still insufficient in the purifying ability at an ordinary temperature. Accordingly, a further improvement is required in the purifying performance.
The influences of formaldehyde to human bodies are irritating actions to the eyes, nose and throat. For example, the influences accompany syndromes, such as discomfort feelings, tearing, sneezing, coughing, vomiting and difficult breathing. The sources of the generation in the housing spaces are believed to be cigarette smoking, usages of heating apparatuses, home appliances, pieces of furniture and building materials. The formaldehyde is used as urea-formaldehyde adhesives in a large amount, is a raw material for adhesives for plywoods and particle boards, and is used as antiseptics for adhesives for wall papers. Accordingly, the Japanese Health and Welfare Ministry presents that the reference value of the formaldehyde concentration be 0.1 mg/Nm 3 (=80 ppb) or less in a room.
Recently, the formaldehyde has been regarded as one of the materials which cause the sick-house syndromes. Accordingly, the material makers and the housing makers try to construct houses with materials, which do not generate the formaldehyde, and to age houses so as to reduce the formaldehyde concentration before they hand over the houses to the customers. However, it cannot be said that the aforementioned treatments necessarily satisfy the reference values of the Japanese Health and Welfare Ministry.
Whilst, in order to remove the volatile formaldehyde, adsorbents, such as activated carbon and zeolite, have been used. However, the adsorbents have limited longevity. Accordingly, it is necessary to regularly replace the adsorbents, and to spend economical expenses. Further, it is necessary to provide means for processing the components adsorbed on the adsorbents anew.
As means for removing thee indoor odorants, etc., at an ordinary temperature, air purifiers have been known generally into which activated carbon is incorporated. Further, air purifiers have been commercially available which utilize photocatalysts.
In addition, the following have been put in markets: namely; methods for removing the odorants, etc., with ozone; methods by using photocatalysts therefor; apparatuses therefor; and filters therefor. However, regarding ozone, it is necessary to exceed the regulatory value of the ozone concentration in order to exhibit the advantages. Further, it is necessary to provide a catalyst for removing the ozone. Concerning the photocatalytic system, it is necessary to provide an artificial light source which excites the photocatalysts. Further, it is necessary to spend expenses for electricity when the light source always irradiates the photocatalysts. Hence, the costs go up.
In Japanese Unexamined Patent Publication (KOKAI) No. 6-219,721, a catalyst is disclosed. The catalyst includes metallic oxide particles, in which noble metal particles are mixed uniformly, and which are composed of CeO2. The metallic oxide can be at least one member selected from the group consisting of CeO2, ZrO2, TiO2 and SnO2 This catalyst is made by coprecipitating the metallic oxide, which is composed of the noble metal particles for purifying carbon monoxide to carbon dioxide. The catalyst has anionic holes in the surface so that it exhibits a high reactivity without a hydrogen reduction treatment. However, the publication discloses that the purifying performance was evaluated under the temperature condition of 150xc2x0 C. or more, and does not refer to the purifying activity in a room temperature range.
Whilst, a specific catalyst is proposed as a method for oxidizing and decomposing odorants or harmful gases in air. For instance, Japanese Unexamined Patent Publication (KOKAI) No. 10-296,087 discloses that a catalyst,, which requires zirconia or ceria as an indispensable component and at least one member selected from the group consisting of Ag, Pd, Pt, Mn and Rh is loaded thereon, can be used to oxidize and decompose trimethylamine. However, in this case as well, the disclosed catalyst was simply examined for the purifying activity under the temperature condition of 200xc2x0 C. in the examples. Further, the publication does not set forth the oxygen defect of the oxide used in the catalyst. Therefore, it is not believed that the catalyst keeps a sufficient ability of decomposing trimethylamine at a room temperature.
In a publication of the PCT applications, e.g., No. WO-91/01,175, a catalyst is disclosed which oxidizes oxydants in a low temperature range. The catalyst includes at least one reducing metallic oxide selected from the group consisting of iron oxide, ceria, zirconia, copper oxide, rare-earth element oxide, manganese oxide, vanadium oxide and chromium oxide, and a noble metal loaded on the metallic oxide. According to the publication, the catalyst oxidizes oxydants whose molecular weight is 50 or less at a temperature of up to 30xc2x0 C. When paying attention to the reduction temperature as one of the production conditions of this catalyst, the publication sets forth that the reduction treatment was carried out at room temperature. However, it is impossible to introduce an oxygen defect, which exhibits a function of the present invention, into the aforementioned metallic oxides at room temperature.
In Japanese Unexamined Patent Publication (KOKAI) No. 7-51,567, a catalyst is disclosed. The catalyst is made by suspending activated carbon in an aqueous solution, in which molybdenum or cerium and platinum are solved, and by loading the molybdenum or cerium and the platinum on the activated carbon with heat or a reducing agent. However, the publication does not refer to subjecting the catalyst to a certain treatment after the loading.
Generally speaking, air cleaner filters using activated carbon effect the deodoring ability by physically adsorbing the odorants on the activated carbon. However, the activated carbon exhibits an upper limit of the adsorption, and does not effect the deodoring performance more than the saturated adsorption. Accordingly, the filters have short lives. Hence, it is essential to regenerate the filters for a long period of usage. When the regenerating is not carried out, it is indispensable to replace the filters.
In the filters using photocatalysts, it is indispensable to irradiate a light to actuate the photocatalysts in order to purify harmful substances. In order to carry out this, it is necessary to use a light source, such as a mercury lamp. Therefore, there arises a drawback in that the air cleaners, which employ the filters using the photocatalysts, are remarkably expensive in terms of the equipment costs and the running costs.
An ethylene gas contained in air is believed to degrade the freshness of fruit and vegetables by facilitating the physiological actions of fruit and vegetables and by developing the additional aging thereof. Accordingly, in order to preserve the freshness of perishables, the following methods are proposed: namely; decomposing the ethylene with ozone or hydrogen peroxide; and adsorbing the ethylene.
However, in the aforementioned methods, the adsorbing method exhibits the shortened duration of the good effects. Accordingly, when the ozone decomposition or the photocatalyst is used together with the adsorbing method in order to compensate for the disadvantage, there arises a problem in that an apparatus taking part in the removing means is large-sized so that it is too costly or it requires a large equipment space. Thus, the adsorbing method has a drawback in terms of the practical application.
The present invention has been developed in view of the aforementioned circumstances. It is therefore an object of the present invention to provide an ordinary-temperature catalyst which can decompose or purify the environmental loading material, such as formaldehyde and ethylene, contained in air at an ordinary temperature, and which is less likely to degrade chronologically. The xe2x80x9cordinary temperaturexe2x80x9d hereinafter means a temperature range including a room temperature which does not require special heating and cooling or less.
An ordinary-temperature purifying catalyst according to the present invention comprises: an oxide having an oxygen defect introduced by a reduction treatment; and a noble metal loaded on the oxide. By loading the noble metal on the oxide having an oxygen defect, the present catalyst has an ability of purifying an environmental loading material in air at an ordinary temperature. As for the environmental loading material, it is possible to list odorants, carbon monoxide, hydrocarbons, such as ethylene, and nitrogen oxides.
The oxide constituting the present ordinary-temperature purifying catalyst can preferably be at least one oxide selected from the group consisting of an oxide of transition metal elements and an oxide of rare-earth elements. As for the oxide of transition metal elements, it is possible to use at least one oxide selected from the group consisting of oxides of zirconium, iron, manganese, cobalt, nickel, copper, chromium, molybdenum and niobium. As for the oxide of rare-earth elements, it is possible to use at least one oxide selected from the group consisting of oxides of cerium, yttrium, neodymium, praseodymium and samarium.
The oxide constituting the present ordinary-temperature purifying catalyst can be composed of a cerium oxide, and at least a part of the cerium oxide can have an oxygen defect by a reduction treatment. The cerium oxide can preferably be represented by a formula of CeOn wherein 1.5xe2x89xa6n less than 2. The cerium oxide can further preferably be represented by a formula of CeOn wherein 1.5xe2x89xa6nxe2x89xa61.8. The present catalyst including the cerium oxide is capable of purifying at least one member selected from the group consisting of aldehyde, amine, mercaptan, fatty acids, aromatic hydrocarbon, and odorants.
In the present ordinary-temperature purifying catalyst, the oxide can preferably include a cerium oxide and a zirconium oxide, at least a part of the cerium oxide having the oxygen defect. Further, the cerium oxide and the zirconium oxide can preferably form a solid solution, a composite oxide, or a mixture thereof.
The oxide can preferably have a specific surface area of 50 m2/g or more by being subjected to a reduction treatment at 500xc2x0 C. for 1 hour. Under different conditions, the oxide can preferably have a specific surface area of 15 m2/g or more by being subjected to a reduction treatment at 800xc2x0 C. for 1 hour.
The temperature of the reduction treatment can preferably fall in a range of from 100 to 800xc2x0 C., further preferably in a range of from 200 to 600xc2x0 C.
The present ordinary-temperature purifying catalyst can be loaded on at least one support selected from the group consisting of titanium oxide, alumina, silica, zeolite, cordierite, sepiolite and activated carbon.
After a purifying reaction of the odorant is carried out at 25xc2x0 C. at a space velocity of 600,000 hrxe2x88x921, the present ordinary-temperature purifying catalyst can have a conversion ratio of 50% or more at 20 minutes after starting the purifying reaction. Further, the present ordinary-temperature purifying catalyst can have a conversion ratio of 40% or more at 30 minutes after the initiation of the purifying reaction provided that the carbon monoxide is supplied at 25xc2x0 C. at a space velocity of 120,000 hrxe2x88x921.
A method for using an ordinary-temperature purifying catalyst according to the present invention comprises a step of contacting the above-described ordinary-temperature purifying catalyst with air including at least one environmental loading material selected from the group consisting of carbon monoxide, a nitrogen oxide, ethylene, aldehyde, amine, mercaptan, fatty acids, aromatic hydrocarbon, and odorants, thereby purifying the environmental loading material at an ordinary temperature.
Since the present ordinary-temperature purifying catalyst comprises the noble metal loaded on the oxide at least a part of which has an oxygen defect by a reduction treatment, the harmful materials. can be removed and purified by the actions of the both of the oxide and the noble metal. Particularly, it is possible to purify even the harmful materials which exist in a trace amount in air. Especially, when the present ordinary-temperature catalyst includes the cerium oxide and the noble metal, it is possible to efficiently remove the formaldehyde in air at room temperature. Thus, the present ordinary-temperature catalyst can reduce the loads to human bodies in the housing environment, and contribute to improving the housing environment.
Further, since the present ordinary-temperature catalyst can decompose and remove the ethylene in an ordinary temperature range, it is possible to suppress the physiological actions of fruit and vegetables so as to inhibit them from chronologically aging additionally. Thus, it is possible to easily keep the freshness of fruit and vegetables.
Furthermore, since the present ordinary-temperature catalyst carries out an oxidation reaction, it yields carbon dioxide and consumes oxygen while it decomposes the ethylene. Accordingly, it is possible to form an optimum gas composition for keeping the freshness of fruit and vegetables whose oxygen concentration is low, carbon dioxide concentration is high and ethylene concentration is low.
Moreover, when the present ordinary-temperature catalyst comprises the activated carbon on which the cerium oxide with an oxygen defect and the noble metal are loaded, the adsorbing ability of the activated carbon can be utilized. Accordingly, it is possible to reduce the amount of the harmful materials which contact with the noble metal and the cerium oxide in a unit period of time. Thus, the catalytically active portions can be inhibited from being poisoned by the adsorbed harmful materials. As a result, it is possible to maintain the purifying performance for a long period of time.


A heat-resistant inorganic pigment of the present invention comprises a composite metal oxide containing Ti and two divalent metals selected from the group consisting of Mg, Fe, Ni and Co, the content of said two divalent metals in said composite metal oxide being 0.95 to 1.05, in an atomic ratio, based on Ti, and the composition ratio of said two divalent metals being 95/5 to 5/95 in an atomic ratio. The pigment of the present invention is useful as a pigment for a heat-resistant coating material and is a novel heat-resistant inorganic pigment which does not pollute the environment.

The present invention relates to a heat-resistant inorganic pigment and a process for producing the same, and more particularly, it relates to a heat-resistant inorganic pigment assuming various hues and a process for producing the same. The pigment of the present invention is useful as a pigment for a heat-resistant coating material and is a novel heat-resistant inorganic pigment which does not pollute the environment.
As a representative of composite metal oxides containing one divalent metal M and Ti, ilmenite (titanic iron) will be cited in which the divalent metal M is Fe. Composite metal oxides which contain one selected from the group consisting of Mn, Mg, Ni and Co as the divalent metal M and Ti are also reported in J. Phys. Soc. Jpn. Vol. 11, No. 5, published in May, 1956 and ibiden Vol. 13, No. 10, published in October 1958 as a composite metal oxide which contains other than Fe as the divalent metal M.
Any of these composite metal oxides such as ilmenite, etc., which contain one divalent metal M and Ti is obtained by heating and calcining at a temperature of not lower than 1350.degree. C., as described in the above literature.
Japanese Patent Application Laid-Open (KOKAI) Nos. 1-298028 (1989), 4-325419 (1992) and 4-55324 (1992) disclose methods of synthesizing FeTiO.sub.3 particles, MnTiO.sub.3 particles and CoTiO.sub.3 particles, respectively, in an autoclave.
The ilmenite particles disclosed in Japanese Patent Application Laid-Open (KOKAI) No. 1-298028 (1989) are individual FeTiO.sub.3 particles which have an average particle diameter of 0.05 to 2.0 .mu.m and which have a uniform particle size; the pigment particles disclosed in Japanese Patent Application Laid-Open (KOKAI) No. 4-325419 (1992) are individual MnTiO.sub.3 particles which have an average particle diameter of 0.5 to 2.0 .mu.m and which have a uniform particle size; and the pigment particles disclosed in Japanese Patent Application Laid-Open (KOKAI) No. 4-55324 (1992) are individual CoTiO.sub.3 particles which have an average particle diameter of 0.5 to 2.0 .mu.m and which have a uniform particle size.
It is widely known that each composite metal oxide MTiO.sub.3 (M represents a divalent metal) represented by ilmenite, MnTiO.sub.3 or COTiO.sub.3 has a good heat resistance, but each has a monotonous hue and lacks in variety. For example, the hues of the composite metal oxides of FeTiO.sub.3, MnTiO.sub.3 or CoTiO.sub.3 particles obtained by the methods of synthesis described in Japanese Patent Application Laid-Open (KOKAI) Nos. 1-298028 (1989), 4-325419 (1992) and 4-55324 (1992), are black, yellow and green.
Although it is described in the afore-mentioned Japanese KOKAIs that the heat resistance of each composite metal oxide is not lower than 150.degree. C., since it is obtained by synthesizing at a temperature of not higher than 300.degree. C. as described therein, the upper limit of the heat resistance is about 300.degree. C. (refer to Comparative Example described later). These composite metal oxides are, therefore, used in the field of general coating materials and toners, and use thereof in the field which requires a heat resistance exceeding 300.degree. C. is not disclosed nor taught.
Accordingly, a technical problem of the present invention is to provide at the production of a novel heat-resistant inorganic pigment which assumes various sharpness hues and is rich in variety, which is usable in the field requiring a heat resistance of not lower than 300.degree. C., and which does not pollute the environment.
As a result of earnest studies undertaken by the present inventor to solve the afore-mentioned problem, it has been found that by mixing compounds of two divalent metals selected from the group consisting of Mg, Fe, Ni and Co with TiO.sub.2, heating and calcining the obtained mixture at a temperature of not more than 1350.degree. C., and pulverizing the calcined material, the obtained particles containing a specified ratio of two divalent metals selected from the group consisting of Mg, Fe, Ni and Co, and Ti, assume various sharpness hues and are usable as a pigment in the field which requires a heat resistance of not lower than 300.degree. C. On the basis of this finding, the present invention has been achieved.

Heat-resistant inorganic pigment and process for producing the same


A post-processing apparatus includes a conveyance unit, a discharge port, a tray, an elevation unit, a detection unit, and a control unit. The conveyance unit conveys a print medium supplied from an image forming apparatus. The discharge port discharges the print medium conveyed by the conveyance unit. The tray is stacked with the print medium discharged from the discharge port and can be raised and lowered in a vertical direction. The elevation unit raises and lower the tray in the vertical direction. The detection unit detects a top surface of an uppermost print medium of one or more sheets of print media stacked on the tray. The control unit controls the conveyance unit and the elevation unit and hold a relative position of the top surface with respect to the discharge port if the print medium is discharged from the discharge port at a first position. The control unit causes the conveyance unit to convey the print medium at a first speed if a discharge time from a first timing indicating the timing relating to discharge of the print medium from the discharge port to a second timing indicating the timing when the print medium is detected by the detection unit is a first time and causes the conveyance unit to convey the print medium at a second speed different from the first speed if the discharge time is a second time.

In the related art, in a post-processing apparatus connected to an image forming apparatus, a print medium on which an image was already formed by the image forming apparatus is discharged from a discharge port provided in the post-processing apparatus onto a tray on which the print medium is stacked. In this case, in the post-processing apparatus of the related art, a speed at which the print medium is discharged from the discharge port is changed depending on a type of the print medium, the number of bundles of the print medium, a height of the print medium stacked on the tray, and the like. However, the post-processing apparatus of the related art does not detect a stacking state of the print medium stacked on the tray. For that reason, in the post-processing apparatus of the related art, excessive projection of the print medium due to a downward curl of the print medium and rising of a rear end of the print medium due to an upward curl of the print medium stacked on the tray may occur. Occurrence of these events is not preferable because the events cause defective alignment of the print medium on the tray, a paper jam of the print medium discharged from the discharge port, and the like.


Maintenance requirements for hydraulic cylinders used to actuate heavy equipment may be predicted by measuring actual use of the cylinders. Sensors measuring piston position within each cylinder are integrated and the results stored in histograms bins to provide a permanent record of motion. Hydraulic pressure and temperature are also recorded. Data are downloaded periodically and compared with data from laboratory tests and/or from other units in the field.

There are numerous advantages to recording operational data for mechanical and electrical systems and components thereof. The availability of electronic devices, more particularly microprocessors or "black boxes" has facilitated the obtention and recordation of such information. Particularly in the area of heavy equipment such as wheel loaders, back hoes, dozers and other moving equipment having implements which are operated through the use of hydraulic cylinders, the accumulation of data on use is very valuable for the prediction of failures, and for the determination of need for routine maintenance and for other out-of-service events.
U.S. Pat. No. 5,987,394 to Takakura et al., granted Nov. 16, 1999, is directed to a system for downloading electronic control units on motor vehicles which is adaptable to different vehicles having different specifications and different numbers of modules.
U.S. Pat. No. 5,748,496 to Takahashi et al., granted May 5, 1998, is directed to a diagnosis system for monitoring the operation of a manufacturing facility in which the system predicts future changes and potential production defects on the basis of sensed information. This information is depicted in a simplified form to expedited a proper response from line employees.
U.S. Pat. No. 5,506,773 to Takaba et al, granted 9 Apr. 1996, is directed to a self-diagnosis system for a motor vehicle and particularly to the storage of data indicating malfunctions and relating them to error codes.
U.S. Pat. No. 5,852,793 to Board et al., granted December 22, 1998, is directed to life cycle measurements of rotating or reciprocating machinery using transducers detecting vibration, friction and shock waves and provides necessary filters to eliminate extraneous data.
The prior art discloses either real time expert systems, event flags which have been "collected" during operation of a vehicle or other device or revert to the time-honored process of simply measuring engine hours. There remains a need for data collection in the field from hydraulic devices which can be related to parameters established in laboratory on a test stand and/or to recorded histories of equivalent hydraulic devices in the field. The present invention is directed to overcoming the problems and disadvantages associated with the prior art as set forth above.