A liquid crystal display element includes two substrates each covered with a transparent conducting layer and having a liquid crystal layer therebetween, in which the liquid crystal layer is a pure nematic electrooptical matrix or sensitized electrooptical mixture with nanoobjects and in which the conducting layers have been treated with a surface electromagnetic wave. The present invention increases a response speed of the liquid crystal display element due to a decrease of the switching time of electrooptical liquid crystal layer up to 1 ms or less; decreases the number of layers in the liquid crystal display element because an alignment layer is absent, and thus increases the transparency of element; decreases a supply voltage amplitude; and increases a possibility to develop different configurations of the liquid crystal display element.

1. Field of the Invention
The present invention relates generally to liquid crystal display elements, and more particularly, to liquid crystal display elements with high speed electrooptical response and conducting layers specially treated with a surface electromagnetic wave.
2. Description of the Related Art
It is well known that properties of registered media, in the development of modern displays, for example, are important for information processing. These properties are responsible for reversible processes, for example, in such materials as liquid crystal that stimulate the development of optical memory devices, real-time laser amplitude-phase correctors and new display elements. In these media, writing, reading, modulation and switching of the information are realized, in particular, with variations of refractive index. The basic unit of these processes is an interface condition between liquid crystal mesophase and orientation of conducting layers. The influence of operating and interface conditions on dynamic characteristics of the liquid crystal registered media has been shown in the following references [1-6]:
[1] R. S. McEwen, "Liquid crystals, displays and devices for optical processing", J. Phys. B: Sci. Instrum., Vol. 20, pp. 364-377 (1987).
[2] M. Schadt, "Linear and non-linear liquid crystal materials, electro-optical effects and surface interactions. Their application in present and future devices", Liq. Cryst., 14, pp. 73-104 (1993).
[3] N. V. Kamanina and N. A. Vasilenko, "High-speed SLM with a photosensitive polymer layer," Electron. Lett., Vol. 31, pp. 394-395 (1995).
[4] N. V. Kamanina and N. A. Vasilenko, "Influence of operating conditions and of interface properties on dynamic characteristics of liquid-crystal spatial light modulators", Opt. Quantum Electron., Vol. 29, No. 1, pp. 1-9 (1997).
[5] N. V. Kamanina, "Fullerene-dispersed liquid crystal structure: dynamic characteristics and self-organization processes", Physics-Uspekhi, Vol. 48,No. 4, pp. 419-427 (2005).
[6] V. V. Belyaev, <<Using substrate with different surface microrelief in the optoelectronics and information processing>>, Optich. Zhurn., Vol. 72, No. 9, c. 79-85 (2005). The authors of the above references have clearly demonstrated the possibilities to improve the dynamic parameters of the devices by changing geometric dimensions of the structure, characteristics of the supply voltage, changing the delay between applied supply voltage and laser pulse, optimizing the dynamic and spectral range of light irradiation, modifying the physical-chemical properties of nematic liquid crystal ("nematic LC"), applying the substrate with different surface microrelief, etc. A weak point of the references mentioned above, however, is the presence of an additional alignment layer in a complicated sandwich structure of the liquid crystal display element. The additional alignment layer decreases the transparency of the device and thus requires a sufficiently increased applied voltage.
Up to now, the question of improving the dynamic relaxation processes has been an open question. It is well known that the relaxation processes are responsible for the speed (e.g., high-speed switching) of the liquid crystal systems such as an electrooptical response of display elements. This problem is investigated in the present disclosure.
It should be noticed, that when different technology improvements have been used, the switching parameters of current display elements of different industry companies are in a range of about 4 milliseconds to about 16 milliseconds (ms). For example, see the following references [7-10]:
[7] http://www.astera.ru/displaynews/?id=37795 ("ΠpO 3BOTe -CeeB IyT"3OOTyIO cepeHy").
[8] http://www.astera.ru/displaynews/?id=37228 ("LC-monitor with TV-tuner from Samsung").
[9] http://www.astera.ru/displaynews/?id=38080 ("Two new LCD-monitors from IIYAMA company".
[10] htpp://www.meadowlark.com ("Custom liquid crystal capabilities").
For example, in reference [8] the switching parameters of a typical nematic LC have been indicated, which have been placed in a range of about 4 ms to about 8 ms and used by the assignee of the present application. It should be mentioned, that a thickness of electrooptical layers used in references [8 and 11] (e.g., [11] V. V. Belyaev, "Universal market of large dimension display", Electronic components, No. 10, c. 18-30 (2004)) has been placed in a range of about 3 micrometers to about 4 micrometers. To decrease the switching times of electrooptical response, unique electric schemes and synchronizing process between electrical voltage and laser pulse, as well as the smectic LC, have been applied. However, alignment of smectic LC layers has been observed to be problematic. Moreover, the smectic LC structures are very expensive because they contain many components. The problems mentioned above retard the development and industrial application of ferroelectric liquid crystal displays ("LCDs").
The method proposed in a reference [12] (e.g., [12] P. Ya. Vasilyev, N. V. Kamanina, "Fullerene-containing liquid crystal spatial light modulator with conducting layers treated by surface electromagnetic wave", ZhTF Lett., T. 33, No. 1, c. 17-22 (2007)) can be considered as a new step to improve the switching parameters of a liquid crystal display element via decreasing the relaxation time of LC mesophase. In this reference [12], the experimental realization of a thin nematic layer (e.g., thickness of about 10 micrometers to about 12 micrometers) has been shown, which provide a complete cycle switch-on/switch-off duration time of 1 ms. The authors of the reference [12] have used the traditional nematic LC from cyanobiphenyl group, as well as having applied the optimized twisted nematic ("TN") LC with low conductivity. The reference [12] can be considered as a prototype of the present invention. However, a weak point of this prototype includes connection using only a planar configuration of the display element. Nevertheless, it should be mentioned that these switching characteristics of the nematic LC display element have not been found in the prior art up to now.

Liquid crystal display element with conducting layers treated with surface electromagnetic wave


A modulus counter counts first clock pulses to modulus M and outputs the count value as an m-bit reference signal, M being an integer. A latch circuit samples and holds the reference signal in response to a trigger signal generated by a trigger signal generator in synchronism with an input signal. A high-speed counter is supplied with second clock pulses of a frequency higher than that of the first clock pulses and starts counting the second clock pulses in response to the trigger signal and stops the counting in response to a first one of the first clock pulses immediately thereafter. A data processor converts the n-bit count value of the high-speed counter to n-bit data corresponding to a phase fraction of a phase quantization step in the latch, combines the n-bit data as low-order bits with m-bit data from the latch and outputs the combined data as phase difference data.

The present invention relates to a phase comparator for detecting the difference in phase between two signals with high precision and, more particularly, to a sample-and-hold-type digital phase comparator.
A digital mobile communication system is now being developed as a next generation mobile communication system which will take the place of conventional analogue mobile communication systems. A frequency synthesizer for use in radio equipment for digital mobile communication is adapted to be capable of switching its oscillation frequency, for example, at intervals of 25 kHz around 800 MHz for switching the channel. The frequency switching time needs to be reduced far shorter than in the case of the analogue system. This calls for the development of a frequency synthesizer capable of high-speed switching of frequency and necessitates further reduction of its size and power dissipation as well.
The frequency synthesizer for mobile communications is an oscillator utilizing phase locked loop (PLL) technology. The frequency switching time of such a frequency synthesizer could be effectively reduced by increasing the sensitivity of a phase comparator that is used in the phase locked loop. On the other hand, it is effective in the miniaturization of the synthesizer to form the phase comparator by a digital circuit.
In FIG. 1 there is shown, as a prior art example of the comparator formed by a digital circuit, the principal part of a sample-and-hold-type phase comparator disclosed in Utsui et al, "DIFFERENTIAL DETECTOR USING DIGITAL IC's," IEICE Japan Technical Report CS82-122. This phase comparator outputs, as an m-bit binary number, a phase difference .DELTA..phi. between a reference signal S.sub.R generated by a reference signal generator 13 and an input signal under measurement, Sx, provided to an input terminal 10. The reference signal generator 13 is made up of a pulse generator 13A and a modulus counter 13B. The modulus counter 13B counts clock pulses PCK (FIG. 2, Row B) from the pulse generator 13A to modulus M which is an integer, and repeatedly outputs a series of count values Cm incremented one by one from O to M. The reference signal level Cm, which is the count value of the counter 13B, takes a staircase-like saw-tooth waveform as shown in FIG. 2, Row A which shows the case of M=3. Thus, the count value Cm corresponds to the phase of the reference signal S.sub.R.
The M+1 count values of the modulus counter 13B from O to M are each assigned or allotted to one of M+1 equally-displaced phase values 0 to 2.pi. rad of the phase .phi..sub.R of the reference signal S.sub.R (which phase .phi..sub.R will hereinafter be referred to as a reference phase). The count value Cm of the counter 13B corresponding to the reference phase .phi..sub.R is sampled by a latch circuit 14 through use of a trigger signal Tr synchronized with the input signal Sx and the sampled value is held as a value corresponding to the phase difference .DELTA..phi. between the input signal Sx and the reference signal S.sub.R. In the example of FIG. 2, a trigger generator 17 generates the trigger signal Tr of Row C (a negative pulse in this example) by the positive edge of the input signal Sx of Row D. By the positive edge of the trigger signal Tr the latch circuit 14 is driven to fetch thereinto the count value Cm of the counter 13B at that time point. The output value Cm of the latch circuit 14 is a binary m-bit digital signal corresponding to the phase difference .DELTA..phi.between the reference signal S.sub.R and the input signal Sx, and the binary m-bit digital signal will hereinafter be identified by the same symbol .DELTA..phi. as that of the above-said phase difference.
In such a sample-and-hold-type digital phase comparator as described above, the magnitude of a minimum unit phase or phase accuracy (i.e. a quantization error of phase or quantization step of phase) .phi..sub.Q of the reference phase .phi..sub.R depends on the modulus M which is the maximum count value of the counter 13B, and it can be expressed as follows: EQU .phi..sub.Q =2.pi./(M+1) (1)
Here, the reference phase .phi..sub.R varies with the count value Cm of the modulus counter 13B as expressed as follows: EQU .phi..sub.R =.phi..sub.Q Cm EQU Cm=0, 1, 2, . . . , M, 0, 1, 2, . . . , M, 0, 1, 2, . . . (2)
To increase the sensitivity of such a digital phase comparator, the reduction of the quantization step .phi..sub.Q is needed, which is, however, difficult for the reasons given below. As indicated by Eq. (1), the quantization step .phi..sub.Q is dependent on the maximum count value or modulus M of the modulus counter 13B. For instance, a counter of m=2 bits counts from "0" to "3," and in this instance, the quantization step .phi..sub.Q is 2.pi./4 rad. Since the relationship between the number of bits, m, and modulus M of the counter 13B is M=2.sup.m -1, Eq. (1) becomes as follows: EQU .phi..sub.Q =2.pi./2.sup.m ( 3)
Hence, the quantization step .phi..sub.Q could be reduced by increasing the number of bits, m, of the modulus counter 13B. On the other hand, the frequency f.sub.CK of the clock pulse PCK from the pulse generator 13A can be expressed as follows: EQU f.sub.CK =f.sub.R 2.sup.m ( 4)
where f.sub.R is the repetition frequency of the count value Cm of the counter 13B from "0" to "M" (i.e. the frequency of the reference signal S.sub.R). As will be seen from Eq. (4), the clock frequency f.sub.CK drastically increases with an increase in the number of bits m. To realize such a very small quantization step .phi..sub.Q, it is necessary that the clock frequency f.sub.CK be remarkably higher than the frequency f.sub.R of the reference signal S.sub.R. For example, in the case of obtaining a quantization step .phi..sub.Q of 2.pi./2.sup.16 (=96 .mu.rad) when the reference frequency f.sub.R is 25 kHz, the pulse generator 13A needs to generate the clock pulse PCK at a frequency of about 1.6 GHz.
Thus, the conventional phase comparator requires a very high clock frequency f.sub.CK to obtain a very small quantization step. It is necessary, therefore, to employ, as the modulus counter 13B, a high-speed counter which operates at high frequencies. Since power dissipation of counters designed for high-speed operation is usually large, the reduction of the quantization step in the conventional phase comparator to improve its sensitivity is accompanied by the defect of its increased power dissipation.

High precision phase comparator and phase locked loop

Nippon Telegraph and Telephone Corporation


A frame with a mounting ear, a display device using the frame and a method of manufacture thereof are provided. The frame includes a frame body and a mounting ear. The frame body has a top frame and a sidewall extending from an edge of the frame top frame. A tap hole is formed on the frame body, and the ear passes through the tap hole to connect with an inner surface of the sidewall. Besides the frame, the display device further includes a display panel module. The display panel module is disposed inside the frame and outwardly displays images via a transparent area enclosed by the frame.

1. Field of the Invention
This invention relates to a frame having a mounting ear, a display device using the frame and a manufacturing method thereof.
2. Description of the Prior Art
Display panels including liquid crystal display panels and organic light emitting diode display panels, as well as the panel display devices using the display panels have become the mainstream of all kinds of display devices. For example, all kinds of panel display boards, home flat television, the flat panel monitors of personal computer and laptop computers, and the display screens of mobile phones and digital cameras are all the products which largely use display panels.
Conventionally, when the display panels are connected to the housings of flat monitors, laptop computers, mobile phones or other products, it is necessary to dispose tap holes in the front frame to be secured. As illustrated by FIG. 1a, in the conventional design, the top of the front frame 30 of the display panel 10 is disposed with the connecting pieces 50 having tap holes 51. The connecting pieces 50 are secured to the front frame 30 to support the weight of the display panel 10. By disposing the connecting piece 50, screws should go through the tap holes 51 during assembly, in order to secure the display panel 10 to the system housing 70. However, in such design, because the connecting pieces 50 are disposed on the outside of the front frame 30 as an add-on, the part where the connecting piece 50 and front frame 30 are connected will cause unevenness on the outer side of the front frame. The system housing 70 needs to be adjusted during manufacturing process in order to accommodate the connection between the connecting piece 50 and the front frame 30.
FIG. 1b illustrates another design of the conventional display device. In this design, the connecting pieces 50 are formed by partly stamping the front frame 30 of the display panel 10; in other words, part of the front frame 30 is cut and bent upwards to form the connecting piece 50. The connecting piece 50 is disposed with tap holes 51, which are used to secure the display panel 10 to the system housing 70. Although this design does not have the problem of unevenness on the outer side of the front frame 30, the strength of the front frame 30 is influenced. The connecting piece 50 is formed by cutting part of the front frame 30 and bending the cut part of the front frame 30 upwards, thus there will be a discontinuous part on the front frame 30. This discontinuous part will decrease the overall mechanical strength and rigidity.

Frame with a mounting ear, display device using the frame and a method of manufacturing the same


A touch screen assembly includes a first outer layer (102) and a second outer layer (110) separated by a separator layer (118). The first and second outer layers are transparent, and the separator layer has openings (120) at button locations where buttons will be defined. On each of the outer layers is a layer of transparent conductor (104, 112). On the first outer layer the transparent conductor is in the form of a contiguous trace or path. The touch screen assembly is placed on a display element (203) and images displayed on the display element can be seen through the touch screen assembly. Images such as characters are displayed at button locations, and when a user presses on one of the images the conductive layers on the first and second outer layers of the touch screen assembly come into contact.

Portable electronic devices have been designed to perform a large variety of functions, including personal digital assistants (PDAs), pagers and two-way pagers, cellular and radiotelephones to name some of the most popular devices. All of these devices store information and perform tasks under direction of the user of the device, and therefore have a user interface. A typical user interface includes a means for displaying information, a means for inputting information and operation control, and often a means for playing sounds and audio signals.
One of the most common means for allowing a user to control the device or input, information is a keypad or buttons. A keypad is a collection of buttons that are typically arranged in a conventional format, depending on the type of device. For example, two-way pagers typically have a so called "QWERTY" keypad, similar to that of a keyboard for a computer. Cellular phones typically have a conventional pushbutton telephone keypad layout, with the addition of specialized keys for operating the cellular phone. In both of these devices, perhaps the most widely used button mechanism is a popple switch button. A small dome may be fabricated from various grades of sheet-metal, typically 0.005″ stainless steel, rendering the entire popple as a conductive element for switching functionality; or in an alternative embodiment, a dome is formed from a non-conductive polymer sheet (such as Mylar™) but with the addition of a conductive element (such as Carbon based Ink). In either method of popple construction, (metal or polymer) the popple is adhered into place using a separate tape with adhesive, and positioned on a printed circuit board. When the popple is depressed, it creates a connection between the conductor layer disposed on the PCB and the conductor pad under the popple dome, completing an electrical circuit which is detected by a controller of the device. To press the popple, a mechanical actuator is disposed over the popple. Typically an image or character is printed on the actuator indicating when that particular button is pushed, that particular character will be entered, or an action associated with the image will be taken by the device. A very similar button mechanism is a membrane button. A membrane button may use a popple dome and have the character or image printed on the dome, or it may simply be two insulator layers separated by a spacer. Each of the insulator layers has a conductor disposed on them which make contact when pushed or pressed together. By printing images or characters on the button, however, limits the button to a fixed function or character or number. Sometimes one of several alternative characters may be selected by repeatedly pressing the button until the desired character appears on a display of the device, as is common on cellular phones.
The limitation of fixed buttons is somewhat alleviated by the use of so called "soft" keys. Soft keys are buttons located near a display of the device, and in the course of operating the device, various characters, images, or words will be displayed on the display at a location corresponding to the button. Typically at least two soft keys are used so as to permit the user to select one of two alternative actions. In addition to popple and membrane buttons, numerous other button mechanisms are known. Other than soft keys or repeated pressing to select alternative characters, however, these buttons are essentially fixed in meaning.
An alternative to fixed buttons is the touch screen display. A touch screen display comprises a conventional display with a touch detection overlay. Information can be displayed on the display and the user touches the display at a desired location corresponding to the desired information, image, or icon. When the user touches the touch detection overlay, the electrical parameters are changed, and by sensing the change from various positions at the edge of the overlay the position where the user touched the overlay can be inferred. Although it allows a user to touch anywhere in the two dimensional plane of the display, the algorithm that performs this inference is fairly complicated. In fact, very few portable electronic devices use this type of input mechanism partly because of the complexity involved, and also because of the lack of applications that require being able to detect a touch anywhere on the screen.

Touch screen assembly and display for an electronic device


An aerated recirculated aquaculture system including a culture tank and an aeration and circulation system. The culture tank houses live aquaculture. The culture tank defines a first flow path. The aeration and circulation system includes an aeration device configured to aerate water. The aeration device defines a second flow path. The first flow path and second flow path at least partially defining a substantially closed flow path sequentially passing through the culture tank and the aeration device. The aeration and circulation system is configured to circulate the water around the substantially closed flow path.

The present invention relates to an aquaculture system and, in particular, it concerns a system for increasing aquaculture biomass density by aeration using atmospheric air only.
By way of introduction, modem aquaculture is trying to reduce cost of operation and investment in intensive aquaculture facilities by reducing the size of the farm facilities. This is being achieved by creating a relatively small culture volume in which the reared species is cultured at high densities. Such high densities are not common in the natural environment and special means are needed to support the need for dissolved oxygen, degassing of carbon dioxide and removal of solids from the culture water.
The most wide spread solution is to use oxygen enrichment from a liquid oxygen source or from an oxygen generator. The high concentration of the source allows super saturation of oxygen and thus allows a low rate of water recirculation. In this method, high-energy input is needed to dissolve-in the oxygen, as well as to strip off the carbon dioxide created by respiration.
Other methods relying on aeration apparatus such as paddle wheels, surface agitators, and air diffusers, limit maximum bio-density. Bio-density is limited due to the narrow band available for oxygen introduction between saturation and the minimal concentration required for the well being of the reared species. Typically the minimum concentration needed is not far from saturation (1-3 parts per million difference). Bio-density is also limited due to the maximum velocity and turbulence created by such apparatus, limiting its use and creating a maximum density barrier derived from the rate of oxygen consumption and the maximum allowable speed and turbulence.
Therefore, there is a need for a system to surpass the density limitation for an aerated recirculated aquaculture system


The present invention provides methods and apparatus for reducing power consumption. One method includes detecting the presence of an object, identifying whether the object is a valid device and restricting power if it is not a valid device. Another method includes temporarily applying a low amount of power to the primary unit to detect a load, supplying more power to determine if it is a valid secondary device, and restricting power if it is not. An apparatus for reducing power consumption includes two power inputs, where the lower power input powers a sense circuit. A switch selectively decouples the higher power input from the primary subcircuit during detection mode and couples the higher power input to the primary subcircuit during power supply mode.

It is more convenient to be able to power portable devices without the need to plug in a traditional power cable into the device. For example some wireless power systems include a portable device that when placed near a wireless power supply unit can receive power without the need for a direct electrical contact. However, when there is no device on the unit (or when the only devices on the unit are fully charged) it is possible to keep the power consumption at a minimum.
Some wireless power units have a standby mode, whereby it periodically transmits power for a short period to look for devices. If the unit detects a valid device that is requesting power and determines that there are no foreign objects that would get hot or hinder power transfer in the vicinity then the unit may come out of standby. The power level of the pulses in standby mode are sufficiently high to transfer enough power to the portable device so that it can communicate back, because it is possible that the device's batteries may be fully depleted. The length of the pulses are long enough to determine that the device is a valid device and that there are no foreign objects present that may get hot or otherwise interfere with the system. The time between the pulses is short enough that the user gets quick feedback that the unit is operational. There is therefore a limit to how low the power consumption can be during standby.
In addition to the power for determining the presence of devices to be powered, there are practical limitations that increase the power consumption. For instance, in some inductive power supplies a DC power source is used even between the transmitted pulses. This means that mains rectification losses are always present and can be considerable. In some scenarios, multiple DC voltages are used and it would not be practical to start these up within the pulse duration, so DC conversion losses might always be present. The microprocessor in the unit that drives the pulse width modulation for the inverter typically is relatively high performance and consumes a certain amount of power continuously.
These and other factors make it challenging for a wireless power system to have low standby power. One attempted solution is to have a switch, so that the user switches the unit on before placing a device on it. However, this considerably detracts from the main benefit the system provides—the convenience of just putting the device on the wireless power supply. With careful design it is possible to achieve standby powers as low as 0.5 W. However, there is a desire for these figures to be reduced further. A typical mobile phone charger may only be used for 3 hours a week and spend the rest of the time in standby. Assuming an average of 4 W consumption during charging and 0.5 W during standby, the annual energy consumption would be 0.624 kWH to charge the phone and 4.38 kWH whilst in standby. This means that seven times as much energy is wasted in standby compared to the energy used. The impact of shipping 100 M units (10% of annual cell phone sales in 2007) would mean approximately 50 MW of power generation capacity just to service the standby. There is increasing awareness that energy wastage through electronic devices left on standby may contribute to climate change. As a result there are initiatives to reduce the power consumption of electronic devices whilst in standby.
There have been several devices aimed at reducing the standby power of televisions and other appliances using remote controls (U.S. Pat. No. 6,330,175, WO2006106310). However, these are not applicable to wireless power systems.
In addition to wireless power systems, other systems for example contactless card systems also suffer from power wastage in standby.


There is disclosed a system for controlling creeping movements of a motor vehicle having a power train with an automated clutch between the engine and the transmission, an electronic control unit for the clutch, and sensors which transmit to the control unit signals denoting the condition of one or more brakes, the positions of an operator-actuatable load lever for the engine, and others. Signals from the control unit are utilized to operate the clutch and, to this end, the control unit includes an arrangement for effecting a creeping movement of the vehicle when the transmission is in gear, the brake or brakes is or are idle, and the load lever is actuated. Such arrangement can effect the transmission of torque in accordance with at least one first predeterminable function to thus induce a creeping movement of the vehicle. The control unit further includes a device for effecting a starting movement of the vehicle in response to actuation of the load lever while the brake is or are idle and the transmission is in gear; such device includes an assembly for selecting the transmission of torque by the clutch in accordance with at least one second predeterminable factor.

The invention relates to an apparatus for controlling a torque transmitting system in the power train of a motor vehicle with an engine, a torque transmitting system and a transmission, with an actuating unit, such as an actuator, which is controllable by a control unit to actuate, such as engage and/or disengage, the torque transmitting system or for the selection of the torque which can be transmitted by the torque transmitting system, and with a control unit which is in signal transmitting communication with sensors and, if necessary, other electronic units.
Such apparatus became known from DE-OS 40 11 850, DE-OS 44 26 260 and DE-OS 195 04 847. Motor vehicles which are equipped with such apparatus normally comprise a combustion engine or another driving unit; for example, one can provide a hybrid system with a combustion engine and an energy storing device and/or an electric motor. The torque transmitting system which is disposed in the power train to establish a driving connection can be controlled in an automated manner by means of an actuator, such as an actuating unit in order to be engaged and/or disengaged. The transmission can be a manually operable gear shift transmission or an automated transmission with automatically controlled gear shift. The transmission can operate with or without interruption of pulling force.

Device for driving a torque transmission system


A dental implant structure includes a fixture fixed to an alveolar bone, an abutment coupled to the fixture and configured to attach an artificial tooth thereto, and a coupling element configured to couple the fixture and the abutment to each other. In the dental implant structure, the fixture includes a lower fixture portion fixed to the alveolar bone and an upper fixture portion coupled to the abutment, a first thread is formed on a part or all of a surface of the lower fixture portion so as to be fixed to the alveolar bone, the lower fixture portion has a shape extending along a rotation axis of the first thread, a second thread is formed on a part or all of a surface of the upper fixture portion, and the upper fixture portion has a shape extending along a rotation axis of the second thread.

A tooth implant structure is implanted to an alveolar bone so as to form an artificial dental root when a tooth is lost such that an artificial dental tooth is attached thereto. When the tooth implant structure is inserted into an alveolar bone tissue and coalesces into the surrounding alveolar bone tissue, an artificial tooth is attached onto the tooth implant structure.
The dental implant structure includes a fixture that is inserted into the alveolar bone and fixedly coalesces into the alveolar bone tissue, and an element called an abutment coupled to the upper side of the fixture such that the artificial tooth is attached thereto.
In a conventional dental implant structure, the fixture has a threaded hole formed in the center of the fixture in the longitudinal direction and the abutment has a hole formed through the abutment from the upper end to the lower end thereof and a step formed in the middle of the hole. A screw is inserted into the hole from the upper end of the abutment such that the head of the screw is supported on the step, and the threads of the screw are engaged with the threads of the hole formed in the fixture, whereby the abutment is fixed to the fixture.
A typical form of such a prior art tooth implant structure is illustrated in FIG. 1.
A dental implant structure 100 illustrated in FIG. 1 is called a submerged-type structure. A cylindrical fixture 110 having threads 111 formed on the surface thereof is implanted in the alveolar bone 10. An inclined mounting surface 112, the diameter of which decreases from the upper end of the fixture 110 toward the lower end, is formed radially inwardly and a fastening hole 113 having threads 114 to which a fastening screw 130 is fastened is formed at the center of the mounting surface 112.
The abutment 120 includes a columnar lower portion 122, the diameter of which decreases toward the lower end thereof so as to abut with the mounting surface 112 of the fixture and a columnar upper portion 121, the diameter of which decreases toward the upper end thereof. The lower portion 122 is inserted into the mounting surface 122 of the fixture 110 from the lower end thereof so that a part thereof is placed and supported on the mounting surface 112.
A fastening hole 123 is formed in the center of the abutment 120 to penetrate the abutment 120 from the upper end to the lower end of the abutment 120, and the lower portion of the fastening hole 123 from the middle point in the longitudinal direction to the lower end thereof has a diameter smaller than that of the upper portion thereof so that a step 124 is formed between the upper portion and the lower portion of the fastening hole 123.
After the fixture 110 is implanted in the alveolar bone 10, the lower portion 122 of the abutment 120 is placed on the mounting surface 112 of the fixture 110 to abut on the mounting surface 112 so as to be supported, the fastening screw 130 is inserted into the fastening hole 123 from the upper end of the abutment 120 such that the threads 131 formed in the lower portion of the fastening screw 130 are engaged with the threads 114 formed in the fastening hole 113 of the fixture 110, and the head 132 of the screw 130 is supported on the step 124 formed in the fastening hole 123 of the abutment 120.
In this state, a crown 140, which is an artificial tooth, bonded to the upper portion 121 of the abutment 120 with cement, so that the implantation of the crown is completed. In this structure, the remaining portion of the upper portion 121 of the abutment 120, which is not inserted into the mounting surface 112 of the fixture 110 is in contact with a gum 20.
However, the prior art tooth implant structure having such a configuration has some serious problems.
The crown placed at the uppermost position in the tooth implant structure receives occlusal load acting in the process of masticating food or the like. The occlusal load is applied, through the abutment on which the crown is fixed, to the screw-coupled portion between the fixture and the fastening screw and to the portion where the abutment abuts on the fixture so as to be supported.
The occlusal load acting on the crown also acts on the center of crown not only in the vertical direction but also in an inclined direction with respect to the vertical direction. Further, the occlusal load is also applied to a position deviating from the center of the crown. The horizontal component of the occlusal load acts on the screw-coupled portion between the fixture and the fastening screw as load in the horizontal direction.
Here, the "vertical direction" means a direction in which a dental implant structure is implanted, that is, the axial direction of the substantially columnar fixture and the abutment, and the "horizontal direction" means a direction parallel to a plane perpendicular to the vertical direction. Herein, the terms "vertical direction" and "horizontal direction" are used in the meaning of the above-mentioned definition.
Due to the occlusal load acting on the crown, the stress acting on the screw-coupled portion between the fixture and the abutment causes the screw-coupled portion to be loosened, and in particular, the horizontal stress applied due to the occlusal load further facilitates the loosening of the screw-coupled portion. This is because the screw joint exhibits a strong supporting force for the load in the direction substantially perpendicular to the thread surfaces, but it is weak against the load in the horizontal direction on the thread surfaces.
The occlusal load generated by using of the teeth continuously acts on the fastening screw, thereby causing the fastening screw to be loosened and, in the worst case, causing the fastening screw to be broken.
Therefore, even after implantation and coalescence of the fixture to alveolar bone tissue have been successfully performed and thus an implant procedure has been successfully performed, it is necessary to continuously receive a procedure of re-tightening the fastening screw after removing the crown due to the loosening phenomenon of the fastening screw that fixes the abutment to the fixture.
When the loosening phenomenon is left untreated without such a procedure, a clearance is formed between the abutment and the fixture due to the loosening of the fastening screw, resulting in gingivitis and oral odor, which lead to inflammation of alveolar bone, resulting in absorption of alveolar bone tissue.
Particularly, when a strong occlusal load is applied due to a mastication habit or the fastening screw is subjected to a strong load or is continuously shaken by leaving the loosened state of the fastening screw for a long time, a case in which the fastening screw is broken and thus it is necessary to receive the implant procedure including re-implantation also occurs frequently.
In the prior art tooth implant structure 100 illustrated in FIG. 1, since the mounting surface 112 is formed in the upper portion of the fixture 110 from the upper end to the lower side of the fixture 110, the thickness of the outer wall of the upper portion of the fixture 110 is very thin.
Therefore, there is a problem in that the occlusal load acting on the crown acts on the outer wall of the fixture or the outer wall of the abutment, whereby the outer wall of the fixture or the outer wall of the abutment is broken.
An invention conceived by the inventor of the present application, which solves the problems of the prior art tooth implant structure, is disclosed in Korean Patent No. 1559823 (Document 1).
FIG. 2 illustrates one embodiment of the dental implant structure disclosed in Document 1.
In the dental implant structure 200 of Document 1, a fixture 210 is implanted in an alveolar bone 10, in which the fixture 210 is divided into an upper portion 211 and a lower portion 212. In the lower fixture portion, threads 216 are formed on the columnar surface thereof and is implanted to the alveolar bone 10, and the threads allow the fixture to be implanted to the alveolar bone such that the fixture coalesces into the alveolar bone tissue.
Threads 217 are formed on a part or all of the surface of the upper portion 211 of the fixture.
The abutment 220 includes an upper portion 221 having an outer surface to which the crown 230 is attached and a lower portion 222 which functions as a connection portion between the upper portion 221 of the abutment and the fixture while abutting on the gum 20.
A cavity 223 is formed from the upper portion of the abutment to the lower end of the lower portion, and threads 224 are formed in the cavity so as to be engaged with the threads 217 on the upper portion of the fixture. After the fixture is implanted to the alveolar bone, the threads 217 of the fixture and the threads of the abutment 224 are engaged with each other while the upper fixture portion is inserted into the cavity in the abutment, whereby the abutment is coupled to the fixture 210.
The dental implant structure of the document 1 has a great advantage over the conventional submerged-type dental implant structure illustrated in FIG. 1.
In the dental implant structure of Document 1, when the same occlusal load acts on the upper end surface of the crown compared with the submerged-type dental implant structure of FIG. 1, horizontal stress acting on the threads in the coupled portion between the fixture and abutment becomes small.
The influence of the abutment and fixture structure on the stress acting on the threads fastening the abutment and fixture to each other by the occlusal load acting on the crown will be described with reference to FIG. 4.
In FIG. 4, the symbols indicate the following items.
F1: occlusal load acting on the upper end of a crown in an oblique direction
Fx: horizontal component of the occlusal load applied to the upper end of the crown
Fz: vertical component of the occlusal load applied to the upper end of the crown
F2: occlusal load acting on a side portion of the upper end of the crown
fx: horizontal stress applied to the middle portion of a screw in the longitudinal direction of the screw
fz: vertical stress applied to the middle portion of the screw in the longitudinal direction of the screw
L1: vertical distance from the upper end of the crown to the middle portion of the screw in the longitudinal direction of the screw
L2: horizontal distance from the axis of the screw or the center of the fixture to the center of the screw
T: torque applied by occlusal load to a position corresponding to the center of the screw in the longitudinal direction on the axis of the fixture
The left side of FIG. 4 illustrates a cross section of the prior art submerged-type implant structure illustrated in FIG. 1, and the right side illustrates a cross section of the dental implant structure according to the invention of Document 1. Although the two implant structures are illustrated with the same dimensions for ease of understanding and comparison of differences in structures, the lengths of the distances L1 and L2 are considerably different from each other due to the differences in the two structures.
First, the occlusal load F1 acting on the upper end of the crown may be divided into a horizontal component Fx and a vertical component Fz.
The vertical component Fz of the occlusal load acts as the substantially vertical stress fz on the surface of the threads of the screw-coupled portion between the fixture and the abutment, but the horizontal component Fx acts as the horizontal stress fx on the threads of the screw-coupled portion. The horizontal component Fx of the occlusal load and the horizontal stress fx have the following relationship.Fx*L1=T=fx*L2
Therefore, fx=Fx*L1/L2
That is, with respect to the same occlusal load, the horizontal stress acting on the screw-coupled portion between the fixture and the abutment increases as L1 becomes larger and decreases as L2 becomes larger.
In other words, the horizontal stress acting on the screw-coupled portion between the fixture and the abutment increases as the vertical distance from the upper end of the crown to the screw-coupled portion increases, and decreases as the horizontal distance from the center of the fixture to the screw, that is, the diameter of the screw increases.
In addition, the horizontal stress acting on screw-coupled portion between the fixture and the abutment due to the occlusal load acting on the side portion of the upper end of the crown has the following relationship.F2*L3=T=fx*L2fx=F2*L3/L2
According to the above equation, under the condition in which L3 and F2 are constant, the horizontal stress fx acting on the screw-coupled portion between the fixture and abutment due to the occlusal load F2 becomes smaller as the diameter of the screw L2 becomes larger.
In other words, the horizontal stress acting on the screw-coupled portion between the fixture and the abutment due to the occlusal load acting on the side portion of the upper end of the crown becomes smaller as the horizontal distance from the center of the fixture to the screw, that is, the diameter of the screw, becomes larger.
When comparing the prior art submerged-type dental implant structure 100 and the dental implant structure 200 of Document 1 based on the above-described relationship, in the dental implant structure 200, since the threads 217 and 224 that couples the fixture 210 and the abutment to each other are disposed above the upper end of the alveolar bone, the vertical distance L1 from the upper end of the crown to the screw-coupled portion is short, and the threads 217 are formed on the outer surface of the upper fixture portion 211 and the threads 224 are directly formed on the abutment itself without using a separate coupling screw so as to couple the fixture and the abutment, it is possible to set the radius of the threads, that is, the distance L2 to be long.
Therefore, in the dental implant structure according to the invention of Document 1, since L1 is set to be small and L2 is set to be large, the stress acting on the threads coupling the fixture and the abutment to each other due to the occlusal loads F1 and F2 is minimized.
On the contrary, in the prior art submerged-type dental implant structure 100, since the fastening screw 130 that couples the fixture 110 to the abutment 120 is fastened at the lower portion in the entire implant structure, the vertical distance L1 from the upper end of the crown 140 to the screw-coupled portion is long. Further, since the fastening screw 130 is coupled to the fastening hole 113 formed inside the fixture 110, it is impossible to increase the diameter of the screw.
Accordingly, in the prior art submerged-type dental implant structure 100, since L1 is large and L2 is small, the stress acting on the threads coupling the fixture and the abutment due to the occlusal loads F1 and F2 is large.
As described above, due to the structural differences between the prior art submerged-type dental implant structure, in the dental implant structure of Document 1, the stress acting in the horizontal direction on the threads coupling the abutment and the fixture due to the occlusal load acting on the crown is minimized, and thus the occurrence of the problem of loosening or breaking the threads by the stress acting in the horizontal direction is minimized.
Meanwhile, the Korean Patent Document No. 0938991 (Document 2) discloses another prior art dental implant structure in which a screw-coupled portion that connects and fixes a fixture and an abutment are disposed above the upper end of an alveolar bone as in the dental implant structure of Document 1.
The configuration of the dental implant structure disclosed in Document 2 is described with reference to FIG. 3.
A fixture 251 illustrated in FIG. 3 includes an implantation portion 261 formed on the lower side thereof to be implanted into the alveolar bone, a tapered portion 262 formed above the implantation portion, a post portion 263 formed above the tapered portion, and threads 63a formed around the post portion. A post groove 271 is formed in the lower portion of the abutment 252 and the abutment 252 is fixed to the fixture 251 by the coupling between the threads formed in the post groove 271 and the threads 263a of the post portion 263.
A plurality of flat portions 263 formed by removing the threads 263a of the post portion 263 are distributed around the post portion 263 while intersecting the curved portions of the threads, and the flat portions 263 are engaged with a tool for rotating the abutment 252.
The dental implant structure having this structure is also referred to as a mini-implant, and is typically used for restoration of a front tooth, where the occlusal load is weakly applied, or for supporting a short-term temporary prosthesis.
The mini-implant used for such a purpose usually employs a cement bonding method or a frictional bonding method in which a mallet or the like is pressed against the abutment in order to connect the abutment to the fixture. However, the mini-implant structure of document 2 uses a screw-connecting method in order to achieve simple, easy, and stable fixation.
Meanwhile, in the implant structure of Document 2, the distance from the upper end of the abutment 2 to the screw-connected portion is shorter than the distance from the prior art submerged-type dental implant structure 100. Therefore, it is possible to obtain an additional effect of suppressing the screw-loosening phenomenon as in the implant structure of Document 1.
However, since a substantial portion of the threads is damaged by the plurality of flat portions 131, the screw-coupling force is remarkably reduced, and the above-mentioned effect is canceled. As a result, there arises a problem that the screw-coupling is easily loosened as in the prior art submerged-type dental implant structure.
As described above, the dental implant structure having the configuration according to the invention of Document 1 solves the problem of loosening or breaking of the screw that couples the fixture and the abutment in the prior art submerged-type dental implant structure or the dental implant structure according to the invention of Document 2. However, these dental implant structures also have the same problems as the existing implants.
It is desirable that an abutment in a dental implant structure be formed in various shapes according to the shape of a natural tooth to be replaced. A front tooth serves to cut food, and has an asymmetrical shape in which the distal center of the crown is considerably eccentric and inclined with respect to the longitudinal axis extending in the up-and-down direction of the tooth. Thus, basically, occlusal load greatly acts on the lateral side thereof. In addition, the front tooth also has a shape in which in terms of a crown size, the length from the longitudinal axis of the tooth to the crown surface varies. Therefore, the abutment to which an artificial tooth is attached should also have an asymmetric inclined shape such that an aesthetically formed artificial tooth can be attached thereto.
A molar tooth acts to grind food like a millstone, and thus the occlusal load acts thereon strongly, and in particular, food is easily caught between the teeth or attached to the gums. In addition, although there is no incline, the deviation of the length from the longitudinal axis of the tooth to the surface of the crown is more severe than that of the front teeth. Thus, the abutment should also have a shape corresponding thereto, so that the original function thereof can be performed well and the food is not caught or attached.
However, in order to adopt this type of abutment, the implant structures according to the inventions of Document 1 or Document 2 has a limitation in adopting this type of abutment. The implant structure according to the invention of Document 1 adopts a method of forming threads in the fixture and the abutment and screw-coupling the abutment to the fixture by rotating the abutment. Thus, in order to prevent interference between the teeth around the portion in which the fixture is implanted and the abutment, the abutment should have a shape in which the distance from the rotational axis to the circumferential surface is equivalent, that is, in a circular shape, Consequently, despite the advantages of the screw being much hardly loosened than the existing implant structure, there is problems in that it is impossible to form the abutment to have a sufficiently large size and it is difficult to form the abutment in various asymmetric shapes matched to the shapes of natural teeth.
As a problem caused by this, when the existing circular abutment is coupled at the time of applying the implant structure according to the invention of Document 1 to a front tooth, there is a troublesome combined with the conventional abutment for the reason described above, and it is troublesome to grind the abutment directly in the oral cavity in order to make an inclination.
In the case of applying such an implant structure according to the related art to a molar in which a large occlusal load is applied, when the artificial tooth is bonded to a small circular abutment, the holding force against the artificial tooth is lowered, and thus the artificial tooth may be detached prematurely even after the final bonding.
In addition, as described above, in order to assure that the food is not caught nor attached to the teeth or gums in the molar region, it is essential that a proper void between the teeth and a proper proximal contact between teeth be formed such that the artificial tooth has a harmonious relationship with the adjacent teeth and gums. However, it is impossible to accomplish this using a small circular abutment.
If a proper void between teeth and a proximal contact between teeth are not ensured, oral hygiene is difficult to manage and the long-term prognosis of the implant may deteriorate.
Meanwhile, even in the case of the implant according to the prior art illustrated in FIG. 1, it is theoretically possible to adopt an asymmetric large abutment having various shapes, but it is impossible to actually use it.
The reason for this is that when an asymmetric large abutment corresponding to the crown shape in a natural tooth is used, the physical stress acting on the fixture itself and the screw-connected portion rather than the circular small abutment increases. Therefore, the screw loosening phenomenon and breaking of the fixture, abutment, or the threads according to the screw loosening phenomenon occur more easily. Particularly, in such a dental implant structure having the above-described configuration, screw loosening and breaking phenomena become serious because it is impossible to implant a fixture having a large diameter capable of exerting a strong coalescence force with respect to the alveolar bone.


According to one implementation, a rotating device includes at least one ring, at least one motor and a power transmission mechanism. The least one ring rotates in a circumference direction. The at least one ring includes no hub for housing a motor inside the at least one ring. The at least one motor generates power for rotating the at least one ring. The power transmission mechanism transmits the power to the at least one ring.

Conventionally, a fan is used as a rotating device having the power for air blow or obtaining thrust (for example, refer to Japanese Patent Application Publication JP2015-501751 A). A typical fan has a structure in which a casing called a hub is disposed at a center and blades are coupled to the circumference of the hub. The hub houses a motor, such as an electric motor, inside.
However, a hub is always exposed to a flow of fluid induced by rotation of blades. Moreover, a path of the fluid is narrowed due to arrangement of a hub. Therefore, a hub causes the increase in a fluid resistance and a pressure loss. As a result, a hub is a deterioration factor in transfer efficiency of fluid. For example, when a fan is intended for air blow, a hub is a deterioration factor in the generation efficiency of a wind. Meanwhile, when a fan is a ducted fan of an aircraft for obtaining thrust, a hub is a deterioration factor in the generation efficiency of the thrust.
On the other hand, a rotor for an aircraft having a structure in which a hub is not disposed has been also proposed. As an example, a floating mechanism, composed of two rotating rings disposed one above the other and blades radially attached to the outer surfaces of the rotating rings, which generates lift by rotating the two rotating rings reversely to each other, has been proposed for a V/STOL (vertical and/or short take-off and landing) aircraft (for example, refer to Japanese Patent Application Publication JP2015-501751 A). This floating mechanism can rotate the two rotating rings by three motors disposed on spokes fixed to the inside of the rotating rings.
As for a rotating device having the power, such as a fan, it is preferable not to dispose any structural object, which may obstruct a flow of fluid, as well as a hub around a rotation center in order to achieve the purpose of the rotating device more efficiently. For example, when a fan is intended for air blow, it leads to improvement in air blow efficiency to dispose no structural objects other than blades around a rotation center. Meanwhile, when a fan is a ducted fan of an aircraft, it leads to improvement in thrust to dispose no structural objects other than blades around a rotation center.
Accordingly, an object of the present invention is to reduce parts which should be disposed near a rotation center of a rotating device, such as a fan, which rotates by power, as much as possible.


For controlling a traction motor of a vehicle, a current command value is determined based on a torque command and a load value representative of running load of the vehicle. A voltage command value is calculated in such a manner that a difference between the current command value and the actual current of the motor is converged to zero. An allowable range is determined for the voltage command value based on the load value and physical quantity associated with an operating condition of the motor. The voltage command value is compared with the lower and upper limits of the allowable range. A safeguard is set on the voltage command value when the latter is becoming smaller than the lower limit or greater than the upper limit. Preferably, the current command value is scaled down or scaled up depending on the voltage command value relative to the allowable range.

1. Field of the Invention
The present invention relates to a control system for regulating a traction motor that generates at least part of the torque of a motor vehicle or a hybrid vehicle.
2. Description of the Related Art
As described in Japanese Patent Publication No. 2003-009573, part or whole torque of a vehicle generated by a traction motor is controlled by regulating its voltage in response to a command signal supplied from a motor ECU (electronic control unit), which provides calculation to generate a current command value and a voltage command value. The current command value is determined based on a torque value supplied from an external ECU and a load value represented by the number of revolutions of the traction motor. The voltage command value is determined by using a feedback control algorithm that reduces the difference between the determined current command value and the actual current of the motor to zero. The voltage command value is supplied to an inverter, where the voltage command value is converted to AC power that drives the traction motor corresponding to the torque command value.
However, if a sudden change occurs in the running load of the vehicle, it can cause excessive slip or lock of the driven wheels, which could result in a loss of vehicle stability.
In a hybrid vehicle, the HV-ECU calculates the necessary torque from accelerator pedal opening, vehicle speed or the number of revolutions (RPM) of the traction motor. The motor ECU receives this calculated torque as a command value and performs a feedback control on the motor current so that it approaches its command value, whereby the traction motor generates a torque corresponding to its torque command value supplied from the HV-ECU. If a sudden change occurs in the running load, the HV-ECU will alter its torque command value in order to compensate for the sudden load change. However, this requires communication between the HV-ECU and the motor ECU and computations, which results in a delay time (typically, 20 milliseconds) and hence a sudden change in the speed of revolutions of the traction motor.
In response to the sudden change in motor speed, the output voltage of the motor and hence the output of the inverter varies rapidly. Eventually, the sudden variation affects the usable lifetime of the battery.
Therefore, a need exists to provide a traction motor control system that assures vehicle stability and avoids sudden change in battery power consumption for extending its lifetime.


In a heat shield (10), in particular for the stator of gas turbines, which heat shield (10) is composed of a plurality of individual segments (10a, b; 20a, b), whose end surfaces (15a, b) respectively abut one another so as to form a gap (12), and which have cooling holes (13a, b) for cooling purposes in the region of the end surfaces (15a, b), through which cooling holes (13a, b) a cooling fluid is blown out into the gap (12), cooling is ensured, even when the gap is closed, by a chamber (11), which is widened relative to the gap (12) and into which the cooling holes (13a, b) open, being arranged in the region of the gap (12).

The present invention refers to the field of thermal machines. The present invention relates to a heat shield, in particular for gas turbines.
Heat shields for gas turbines are known, for examples, from the publication U.S. Pat. No. 4,573,866 or EP-A1-0 516 322.
In thermal machines such as gas turbines, there are certain contours (for example the annular, stator-side heat shields which surround the rotor blades of the rotor), which are composed of individual segments whose end surfaces abut one another so as to form gaps. Such segmented contours require cooling of the flanks by blowing out a cooling fluid, as a rule cooling air. For this purpose, special cooling holes are provided (88 in FIG. 2 of EP-A1-0 516 322 or C in FIG. 3 of U.S. Pat. No. 4,573,866), through which the cooling fluid is blown out into the gaps.
Under certain operational conditions, however, the gaps between the segments can become practically closed. The openings of the cooling holes emerging into the gaps are then covered by the side walls of the adjacent segments, which leads to a failure of the cooling in this region.
One of the objectives of the invention is, therefore, to create a heat shield which avoids the quoted disadvantages of known heat shields and, in particular, ensures sufficient cooling of the segment edges near the gaps even when the gaps are closed.
The core of the invention consists in providing, in the region of the outlet flow openings of the cooling holes, a widened space which ensures unhindered emergence of the cooling fluid even when the gap is completely closed.
The invention can be effected in a particularly simple manner if, in accordance with a preferred embodiment, the chamber is configured as a recess, which, starting from the thermally loaded side of the heat shield, extends into the gap. The depth of the chamber is then preferably a specified percentage, in particular between 10% and 90%, of the thickness of the heat shield in the region of the gap.
The length of the chamber is, preferably, a specified percentage of the width of the heat shield, in particular between 10% and 80%.


A semiconductor chip includes a core region having a plurality of first memory cells and a first edge adjacent to a first side of the core region. The first edge includes a first region and a second region. The first region includes a plurality of second memory cells, and the second region includes a first pad portion through which at least one of an address signal, a command signal, a clock signal, a data signal and a control signal is inputted or outputted.

1. Technical Field
Embodiments of the present disclosure generally relate to semiconductor chips.
2. Related Art
In the electronics industry, high performance semiconductor devices are increasingly in demand with the development of smaller electronic systems. In response to such a demand, various technologies have been developed to provide large capacity of semiconductor modules. The large capacity of semiconductor modules may be achieved by increasing the number of memory cells which are integrated in a limited area. Recently, techniques for stacking two or more semiconductor chips are widely used to provide the large capacity of semiconductor modules which are suitable for increasing the memory capacity.
In the event that semiconductor chips having pads on their edges are stacked, spacers may be required to provide a uniform space between the semiconductor chips. The spaces between the semiconductor chips may be necessary to connect the pads to bonding wires. However, the spacers disposed between the semiconductor chips may increase a total height of each semiconductor module. Thus, there may be some limitations in realizing the large capacity of semiconductor modules.
When each of the semiconductor chips has a rectangular shape including a width and a length greater than the width, pads may be disposed on both edges of each semiconductor chip in the length direction and the rectangular semiconductor chips may be stacked to cross each other to expose the pads. In such a case, spaces may be provided on the pads even without disposing the spacers between semiconductor chips. Thus, bonding wires may be connected to the pads even without the use of the spacers. However, if the rectangular semiconductor chips are stacked to cross each other, both edges of each semiconductor chip may act as overhangs which are not physically supported by the underlying semiconductor chip. Accordingly, the bonding wires bonded to the pads may be more readily lifted to cause bonding failures. If the length of the semiconductor chips increases, the length of the overhangs may also become increased to cause more bonding failures.


A fluorine coating agent having enhanced dental tubule permeability and coating endurance, and a method for preparing the same. The fluorine coating agent applied on the surface of a tooth is enhanced in abrasion resistance to increase a period of time during which a coating membrane lasts, thereby preventing dental caries. Further, the curing time of the fluorine coating agent can be controlled to allow the agent to permeate and thus block the dental tubule.

Dental caries develops when teeth are damaged due to chemical destruction caused by an acid, which is produced by the bacterial decomposition of nutrients (especially, monosaccharides) that the host ingests in dental plaque which is a mass of bacteria present in the oral cavity, dissolving a calcium salt among inorganic constituents of teeth.
Among various types of acids made by the bacteria of dental plaque, especially, lactic acid is so small in size that it can penetrate into the structure of the enamel of a tooth and thus cause severe damage to the internal enamel containing a relatively low amount of fluoride. This damage leads to the demineralization of calcium salts right under the tooth surface and the formation of larger and finer cavities under a tooth surface than those on the tooth surface, and the cavities are called white spots.
When the mechanism of development of dental caries is demineralization, the preventive mechanism thereof is remineralization. By inhibiting the development mechanism or restoring the initially formed caries to change the structure of the tooth surface through remineralization, it is possible to suppress the development or progression of the caries development mechanism.
A representative method used for the purpose of preventing dental caries is the use of fluoride-containing agents or materials. Since the application of the fluoride compound in an oral cavity promotes the remineralization of demineralized enamel, it can greatly help to treat tooth sensitivity to cold (dentin hypersensitivity) and prevent tooth decay (dental caries). In addition, since a coating film containing the fluoride compound is formed on teeth so as to strengthen enamel, it is possible to prevent tooth decay and promote a process of binding minerals such as calcium and the like to the teeth.
The mechanism of action of fluoride whereby dental caries is prevented or inhibited is effective, especially, for deciduous teeth containing a trace amount of fluoride. This is because the inclusion of fluoride in a crystal structure of enamel during the development of deciduous teeth results in the formation of a substance called fluoroapatite which is not dissolved well in an acid, and a large amount of fluoride is accumulated on a surface of enamel surrounded by body fluids, especially, immediately before deciduous teeth are developed in the oral cavity so as to rapidly increase the fluoride concentration, thereby apatite which is a crystal structure of the tooth surface has more chemical and physical stability.
According to the data of the oral health project of the Ministry of Health and Welfare, the representative oral care products using fluoride are divided into four categories: a fluoride dentifrice (fluoride-containing toothpaste-like product); a fluoride mouth rinse solution (fluoride-containing mouthwash-like product); a fluoride gel (product used by introducing the fluoride gel into a tray and keeping the tray in the mouth); and a fluoride coating agent (product applied together with pine resin which is natural rosin to keep fluoride adhered to the tooth surface for a long time).
Among these four categories, the fluoride coating agent is found to be most effective for preventing tooth decay, and the tooth decay prevention effect thereof is twice as high as that of the fluoride gel that was previously used. In addition, when the fluoride coating agent and the fluoride dentifrice are used together, it has been reported that the effect is improved by about 10%.
Since the conventional fluoride coating agent includes pine resin which is natural rosin tinged with red, the fluoride coating agent is not easily decomposed in a wet environment such as the oral cavity, easily adhered to the teeth due to having high adhesion to the teeth, and has high penetrability into dentinal tubules. However, the conventional fluoride coating agent imparts a high level of aesthetic rejection to patients due to the color change of the teeth after treatment with the fluoride coating agent and is maintained only for a short period of about 3 to 7 days after being applied on the teeth due to non-curing properties thereof, thereby the conventional fluoride coating agent could not be expected to have an effect of sustainedly preventing dental caries and suppressing dentin hypersensitivity.
In order to compensate for the disadvantages, photocurable fluoride coating agents having enhanced coating durability, high strength, and high hardness were developed. The photocurable fluoride coating agents can be expected to have the effect of preventing dental caries for a long period of time because a coating film is maintained for 1 month or more such that fluoride ions are sustainedly released but cannot be expected to have the effect of suppressing dentin hypersensitivity because a coating film is formed quickly as the photocurable fluoride coating agent is cured as soon as it is exposed to light such that the agent does not penetrate into dentinal tubules of the tooth and it is difficult to occlude dentinal tubules.
Therefore, the need for a fluoride coating agent, which is capable of sustainedly preventing dental caries by maintaining a coating film on the tooth surface for a long period of time and suppressing tooth sensitivity to cold caused by dentin hypersensitivity by occluding dentinal tubules while satisfying the aesthetic needs of patients and imparting procedure convenience and efficiency to operators, is increasing.

Fluorine coating agent having enhanced dental tubule permeability and coating endurance and method for preparing same


A method for extracting hydrocarbons from a vessel by displacement. The method including the displacement of a hydrocarbon source with a material of different density and recovery of the hydrocarbons from the vessel. Additionally, a method for extracting hydrocarbons from a vessel by gas displacement through chemical introduction. The method including introduction of hydrochloric acid and sodium bicarbonate into a vessel, production of carbon dioxide from the reaction of the hydrochloric acid and the sodium bicarbonate, displacement of a hydrocarbon source inside the vessel, and recovery of the hydrocarbon source from the vessel.

Offshore drilling and production platforms used for recovering oil from subterranean formations disposed beneath ocean water include a number of structural support legs for supporting a plurality of work areas. Generally, below the work areas, a plurality of hollow concrete multi-cell structures may sit on the seabed floor. The hollow concrete multi-cell structures may be large, in some cases including over eighty cells, each cell reaching volumes of thousands of cubic meters.
Previously, the hollow concrete multi-cell structures may have been used to separate hydrocarbons from water, store hydrocarbons, or otherwise collect a hydrocarbon source. As a function of operation, hydrocarbons may become trapped in the hollow concrete multi-cell structures. The hydrocarbons trapped in the hollow multi-cell structures are often referred to in the industry as "attic oil."
At one time abandoned storage vessels could remain partially filled with residual hydrocarbons. One such source of abandoned hydrocarbons occurs in storage vessels awaiting decommission. Prior to decommissioning, the remaining hydrocarbons in the storage vessels must be removed. Additionally, to prevent contamination of the ecology around the hollow multi-cell structures, the decommissioning of storage vessels must occur in an environmentally clean manner.
While methods for removing oil from subterranean reservoirs are known to those skilled in the art, the methods are directed to the removal of oil from subsurface formations, and do not consider the constraints of removing oil from storage vessels, for example, above ground or on the seabed floor. One such method is disclosed by U.S. Pat. No. 4,676,314 ("the '314 patent"), hereby incorporated by reference herein. The '314 patent describes injecting air into the top of a subterranean formation that is filled with both oil and water. As the air displaces the water, the water flows out of the formation, the oil settles towards the bottom of the formation, and a well is dug to extract the oil which has settled to the bottom of the formation.
Another method is disclosed in U.S. Pat. No. 4,679,627 ("the '627 patent"), hereby incorporated by reference herein. The '627 patent describes injecting gas into a subterranean reservoir, forcing the oil to the bottom of the formation, and then generating pressure waves to release additional oil retained by the reservoir. The oil is then removed by drilling a well into the formation, and extracting the displaced oil from the bottom of the formation.
While the '314 patent and the '627 patent describe methods of injecting gas into a subterranean formation to recover oil trapped therein, the methods both involve drilling a well into the formation, an option that is not available when removing oil from a storage vessel on the seabed floor. Further, the prior disclosures remove the oil through an export location drilled through the top of a formation. On oil platforms, rather than being located on the top of the storage vessels, the export location is generally located below the hydrocarbon layer, thereby preventing removal though the simple pumping described in prior disclosures.
Accordingly, there exists a need for a method to extract hydrocarbons from storage vessels in an efficient, environmentally clean, and profitable manner.


An antenna device of the present invention includes a dielectric block having top and bottom surfaces and side surfaces, a ground conductor disposed on the bottom surface of the dielectric block, and a radiation element which is provided on the top surface and the side surfaces of the dielectric block.

The present invention relates to an antenna device, in particular, to a compact antenna device suitable for receiving radio waves from an artificial satellite as well as ground waves.
Antenna devices using a GPS (global positioning system) have been well known as antenna devices for receiving radio waves from an artificial satellite (hereinafter referred to as satellite waves). This type of GPS antenna devices for vehicle-mounted communication terminals or mobile communication terminals are required to be miniaturized.
An example of the GPS antenna devices will be described with reference to FIG. 1. FIG. 1 shows an example of a compact flat patch antenna device. An antenna device 30 includes a dielectric block 31 comprising resin or a ceramic material and a radiation element 32 disposed on the top surface of the dielectric block 31. A ground conductor 33 is disposed on the bottom surface of the dielectric block 31. Further, a grounding substrate 34 is disposed under the bottom surface of the dielectric block 31 and is electrically connected to the ground conductor 33. This type of antenna device is disclosed in Japanese Patent Application Publication (JP-A) No. 2002-198725, for example.
Although not shown in the figure, a feeding point is usually set in the radiation element 32 in this type of antenna device. Further, a feeding conductor (not shown) is connected to the feeding point through a through-hole (not shown) provided in the dielectric block 31, the ground conductor 33, and the grounding substrate 34. The feeding conductor is derived from the bottom side of the grounding substrate 34.
FIGS. 2A and 2B show the matching frequency and vertical radiation pattern characteristics of the antenna device shown in FIG. 1. The matching frequency is 1.927 (GHz) and the gain is 2.372 (dBi).
Herein, the frequency of a satellite wave transmitted from a GPS satellite is about 1.575 (GHz). Therefore, by shifting the matching frequency of the antenna device having the characteristics shown in FIGS. 2A and 2B to the vicinity of 1.57 (GHz), a receiving characteristic for the satellite wave can be enhanced. In the conventional antenna devices, a dielectric material of high permittivity is used for a dielectric block or the size of dielectric block is set large in order to obtain a lower matching frequency.
However, the cost increases by using a high-permittivity material. On the other hand, by setting the size of dielectric block large, the entire antenna device also becomes large. This is against the requirement for miniaturization.


A spatial image type display includes a front display device and a rear display device having display surfaces for displaying images in the same direction. The display devices are arranged with a predetermined spacing between their respective display surfaces. The display surfaces are provided with sub pixels formed at almost the same pixel pitches, and aligned with each other. Transparent regions are formed next to the respective sub pixels of the front display device. The light emitted from the sub pixels of the rear display device is transmitted through the transparent regions, and emitted toward the viewer along with the light emitted from the sub pixels of the front display device. A stereoscopic image is thus displayed in accordance with the brightnesses of the images displayed on the front display device and the rear display device. These display devices are made of an organic EL display or a liquid crystal display. Thus, there is provided a spatial image type display which is small in thickness, light in weight, and new in structure.

With the recent trend of information toward multimedia and the like, spatial image type displays for enabling realistic image display have been put under research and development.
Among the spatial image type displays under research are ones of a two-dimensional display system and ones of a three-dimensional display system.
A head mounted display (HMD) is known as a representative example of the spatial image type displays of the two-dimensional display system. The unitized apparatus, a combination of display devices and optical systems, is mounted on the head of a user, i.e., a viewer. When images displayed on the display devices are viewed through the optical systems, a virtual image formed in the front space appears as if an image is floating.
The spatial image type displays of the three-dimensional display system are typically referred to as stereoscopic displays, 3D displays, or the like, being broadly divided into eyeglass types and glassless types.
Among the known representative examples of the 3D displays of eyeglass type are ones of polarized glass type, shutter glass type, and head mounted display type (HMD type).
In the 3D display of polarized glass type, the display surface of the display shows right and left parallax images independently with light having polarized planes orthogonal to each other. A parallax is given to between the eyes of the viewer by using a pair of glasses having right and left orthogonal polarizers, so that a stereoscopic image can be displayed.
In the 3D display of shutter glass type, the display device switches to show right and left images alternately at predetermined cycles. A parallax is given to between the eyes of the viewer by using a pair of glasses which are alternately switched on/off in light transmittance in synchronization with the switching cycles, so that a stereoscopic image can be displayed.
In the 3D display of HMD type, the unitized apparatus, or a combination of display devices, optical systems, and a pair of glasses, is mounted on the head of the viewer. As with the polarized glass type and the shutter glass type, parallax images are given to the eyes of the viewer so that a stereoscopic image can be displayed.
Among the known representative examples of the 3D displays of glassless type are ones of parallax barrier type, lenticular lens type, and electronic holography type.
In the 3D display of parallax barrier type, the display surface of the display shows right and left images in strips alternately. The right and left images are viewed by the right and left eyes through a slit plate which is arranged in front of the display surface. Parallax images are thus given to the eyes of the viewer so that a stereoscopic image can be displayed.
In the 3D display of lenticular lens type, a screen plate, or an integration of small semi-cylindrical lenticular lenses, is arranged in front of the display surface of the display device instead of the slit plate which is arranged in the parallax barrier type. Right and left images are shown to the right and left eyes through the lenticular lenses, so that parallax images can be given to the eyes of the viewer to show a stereoscopic image.
The 3D display of electronic holography type uses a hologram, the three-dimensional shape of a subject to be recorded as interference fringes. This hologram is irradiated with illumination light so that it is reproduced as a real image or virtual image by the resulting diffraction light, thereby showing a stereoscopic image.
For the case of the head mounted display, i.e., the spatial image type display of the two-dimensional display system described above, the viewer must wear the heavy, large apparatus on the head and cover the eyes with the optical systems of the apparatus. Thus, there have been pointed out such drawbacks that wearing the apparatus is troublesome and inconvenient, and can cause eyestrain.
The 3D displays of eyeglass type are also known to have such drawbacks that the glasses must be worn troublesomely and inconveniently, and that eyestrain can occur since the right and left eyes view the parallax images alternately.
Among the 3D displays of glassless type, those of parallax barrier type and lenticular lens type are known to have a problem of extremely difficult application to general uses since the viewing angle at which the viewer can see precise binocular parallax images is extremely narrow and the stereoscopic image may disappear even with a slight head movement.
For the 3D display of electronic holography type, it is found difficult to develop a simple, small-sized holography device for realizing holography. A technical breakthrough has been expected, leaving an extreme difficulty in application to general uses.
In this research-and-development stage of spatial image type displays, an epoch-making research has been published. The following provides the display principle underlying the research.
FIG. 17 shows the display principle schematically. A front display surface PL1 and a rear display surface PL2 for displaying images toward the viewer are arranged opposite to each other. Two images displayed on the respective display surfaces PL1 and PL2 are shown to the viewer to produce such an illusion that a stereoscopic image appears in the space between the front display surface PL1 and the rear display surface PL2.
That is, the front display surface PL1 and the rear display surface PL2 both make display surfaces for emitting light toward the viewer by themselves. Besides, the image of the rear display surface PL2 is transmitted through the front display surface PL1 so that the viewer can see both the images of the front display surface PL1 and the rear display surface PL2.
The front display surface PL1 and the rear display surface PL2 show the same image along the direction of the optical axis (the direction of emission of light) though in different brightnesses. When the viewer views the overlaid images, the foregoing illusion shows a stereoscopic image as if lying in the space between the front display surface PL1 and the rear display surface PL2, thereby achieving stereoscopic display.
Here, when the front display surface PL1 shows an image F11 of certain brightness and the rear display surface PL2 shows an image F21 of the same shape, having brightness higher than that of the image F11, an image appears closer to the rear display surface PL2. When the front display surface PL1 and the rear display surface PL2 show images F12 and F22 of the same brightness and the same shape, an image appears at an intermediate position between the front display surface PL1 and the rear display surface PL2. When the front display surface PL1 shows an image F13 of higher brightness and the rear display surface PL2 shows an image F23 of lower brightness, an image appears closer to the front display surface PL1.
Thus, the display images on the front display surface PL1 and the rear display surface PL2 can be adjusted in brightness to achieve stereoscopic display.
To realize a spatial image type display based on the display principle of FIG. 17 requires, however, such components as a complicated optical system for displaying images on the front display surface PL1 and the rear display surface PL2. It has therefore been difficult to reduce the apparatus in weight, thickness, size, etc., with a problem of extremely difficult application to general uses.
For more details of the problem, FIG. 18 schematically shows possible configuration of a spatial image type display to which the display principle of FIG. 17 is applied.
This spatial image type display includes a liquid crystal display LCD1, a liquid crystal display LCD2, and a half mirror BS. The liquid crystal display LCD1 corresponds to the front display surface PL1. The liquid crystal display LCD2 corresponds to the rear display surface PL2. The half mirror BS reflects and transmits the images displayed on the display surfaces of the liquid crystal displays LCD1 and LCD2, respectively, and emits the resultant toward the viewer.
For the sake of self luminescence of the respective images, the liquid crystal displays LCD1 and LCD2 are provided with backlights BL1 and BL2, respectively.
According to this configuration, the images F11, F12, F13, etc. formed by the liquid crystal display LCD1 are reflected at the half mirror BS and emitted toward the viewer, realizing the front display surface PL1 shown in FIG. 17. The images F21, F22, F23, etc. formed by the liquid crystal display LCD2 are transmitted through the half mirror BS and emitted toward the viewer, realizing the rear display surface PL2.
Nevertheless, since the display surfaces of the liquid crystal displays LCD1 and LCD2 must be directed toward the half mirror BS, the liquid crystal display LCD1 is necessarily laid down along the depth direction. This increases the thickness d in the depth direction as shown in the diagram, causing a problem of yet greater size of the entire apparatus.
Note that FIG. 18 shows the basic configuration of the apparatus alone for convenience of explanation. In fact, the complicated optical system including the half mirror BS inevitably increases the overall weight of the apparatus. Consequently, there have been such problems that an increase occurs not only in the aforementioned thickness d in the depth direction but in width and height as well, and that the optical system is susceptible to vibrations etc. and is difficult to adjust for improved optical precision.


A method of forming a semiconductor device is disclosed. A sacrificial oxide layer is formed on a substrate having first and second areas. Using a photoresist mask exposing the first area and covering the second area as a mask layer, by a wet etching process, the sacrificial oxide layer in the first area and an edge portion of the sacrificial oxide layer in the second area are simultaneously removed, wherein the sacrificial oxide layer remained in the second area has a sidewall with a slope smaller than 40 degrees. An oxide-nitride-oxide (ONO) layer is formed over the first and second areas. The sacrificial oxide layer and the ONO layer formed thereon in the second area are removed, so that the ONO layer remained in the first area forms a first gate insulating layer in the first area. A second gate insulating layer is formed in the second area.

Field of the Invention
The invention relates to an integrated circuit fabrication, and particularly relates to a method of forming a semiconductor device.
Description of Related Art
Generally, a memory device includes a select gate and a control gate, and an oxide-nitride-oxide (ONO) layer serves as a control gate insulating layer and also serves as a charge storage layer for memory and an oxide layer serves as a select gate insulating layer. In the conventional method of forming the control gate insulating layer, a sacrificial oxide layer is formed over a substrate including a select gate area and a control gate area, and then by using a hard mask layer exposing the control gate area and covering the select gate area, the sacrificial oxide layer in the control gate area is removed. Thereafter, an ONO layer is formed in the select gate area and the control gate area, and the ONO layer and the hard mask layer therebeneath in the select gate area are removed. Accordingly, the remained ONO layer in the control gate area forms the gate insulating layer for the control gate to be formed.
However, when using a silicon nitride layer as the hard mask layer, the ONO layer and the hard mask layer therebeneath at the boundary of the select gate area and the control gate area are difficult to remove completely since the ONO layer has a steep sidewall. As a result, as shown in FIG. 1, the ONO residue R is remained between the select gate SG and the control gate CG. Furthermore, when performing an implantation process on the substrate by using the select gate and the control gate as a mask, a good implant profile is hard to achieve due to the masking defect of the ONO residue, and the electronic performance of the device may be effected.


A spread spectrum communication system has a plurality of transmit ends capable of simultaneous communications and at least one receive end. Each of the transmit ends modulates digital information by a PN code to provide a spread signal, modulates a carrier by the spread signal to provide modulated signal, and then transmits the modulated signal to the receive end. These transmit ends use the same PN code for spreading the respective digital information and use carriers having different frequencies from each other so that spectrums of at least two of the modulated signals overlap each other. The receive end receives signals transmitted from the transmit ends to provide a received signal, frequency-converts the received signal to provide a converted signal, and calculates a correlation between the converted signal and the PN code to recover the digital information transmitted from the desired transmit end. This receive end extracts a signal having a center frequency which corresponds to the carrier frequency of the desired transmit end to provide the converted signal.

1. Field of the Invention
The present invention relates to a direct sequence spread spectrum (DS-SS) communication system used for multiple access communications, such as satellite communications, cellular mobile communications, indoor wireless communications for computer remote terminal, and wireless local area network (LAN) communications.
2. Description of the Related Art
One application of DS-SS is code division multiple access (CDMA) technique, which is considered to be a candidate multiple access method for future telecommunication systems. In CDMA system, different kinds of pseudo-random noise (PN) codes and the same carrier frequency are assigned to each communication station. Since all stations use the same frequency band, each station shall be distinguished with the assigned PN code by using the property that the cross correlation among PN codes is very low.
In practice, according to the conventional CDMA communication system, information signals are spectrum spread by different PN codes first, and then the spectrum spread signals modulate carriers having the same frequency f.sub.a at respective transmit stations. Thus modulated signals are transmitted from respective transmit stations to receive stations after filtered by respective band pass filters. At one of the receive stations, the transmitted signals are frequency-converted by a local oscillator, and then despread by the same PN code used for spectrum spreading of desired information. Since PN code indicates strong correlation only with the signal spread by the same PN code, the desired information signal can be selectively obtained among the various received signals.
As shown in FIG. 1, according to the conventional CDMA communication system, spectrums of received signal from the transmit stations 1 to k (k is the number of transmit stations communicating simultaneously) are completely overlapped which each other because their center (carrier) frequencies coincide at the frequency f.sub.a.
Generally, as for PN codes for signal spectrums spreading in the DS-SS communication system, maximum length sequences are utilized. The number of existing maximum length sequences is small when the code length thereof is short, for example, the number is only 18 when the code length thereof is 127 bits, 16 when 255 bits, and 48 when 511 bits. Therefore, in order to accommodate more stations simultaneously in the CDMA communication system in which each of the transmit stations is distinguished only with the assigned PN code, maximum length sequences with extremely longer code length, in other words maximum length sequences having greater number of independent sequences would be required. The longer code length of the PN code sequences, the more complicating PN code generation process, construction of correlators, and also demodulation process.
In the CDMA system, the same PN code cannot be used at the same carrier frequency. Thus, according to the conventional CDMA system, in case that more transmit stations than the number of the existing PN codes are required in the system, a plurality of frequency bands should be employed to reuse the PN code as shown in FIG. 1. In this figure, one set of 1 to k stations with the carrier frequency f.sub.a and the other set of 1 to k stations with the carrier frequency f.sub.b are illustrated. However, this configuration requires m times of frequency band width in order to accommodate m times of the transmit stations simultaneously, namely to reuse the same PN code for m times.
Furthermore, in case that PN codes are not assigned permanently to the respective stations but assigned corresponding to the demands for communication, it is necessary that each station has a correlator device which can recognize all the PN code sequences used therein. This results in too many matched filters whose code patterns are physically fixed such as surface acoustic wave (SAW) filters, or the device which has the programmable functions. A digital logic LSI which can respond to various PN code sequences may be used. However, in case of using the PN codes with very long code length, information bit rate or operation speed thereof will be limited due to the heating or power consumption problems.