Abstract: The present invention provides a wireless transmission system capable of exerting a maximum path diversity effect by using combinations formed by a plurality of symbol waveforms even when a maximum number of effective branches is limited to a small number. A transmission timing controlling section (23) determines a timing delayed from a reference timing by a predetermined delay amount as a transmission start timing. A modulating section (21) modulates a signal, by using one symbol waveform among a plurality of symbol waveform candidates, utilizing a modulation scheme in which a phase transition of a symbol waveform, which exerts an anti-multipath property by demodulating the signal on the receiving side, represents a waveform being changed, and then transmits the modulated signal at a transmission start timing.

Abstract: A wireless station according to the present invention is a wireless station used as one of a plurality of relay stations forming transmission paths, respectively, different from each other, in a wireless transmission system for transmitting a packet from a transmitting station to a receiving station through the plurality of relay stations, and the wireless station comprises: a reception section for receiving a packet transmitted from the transmitting station, and receiving a packet which is transmitted, based on the packet transmitted from the transmitting station, from a relay station other than the one of the plurality of relay stations, and is transmitted before the one of the plurality of relay stations performs transmission, by using a transmission parameter for obtaining a path diversity effect in the wireless transmission system; a transmission parameter estimation section for estimating the transmission parameter used by the relay station other than the one of the plurality of relay stations, based on

Abstract: At a time T131, a wireless communication apparatus 11A determines to transmit a data packet, and then performs interference signal detection for a period TA. At a time T132 preceding a time T133 at which the period TA has elapsed since the time T131, the wireless communication apparatus 11A detects a data packet d21 (an interference signal). At a time T134 at which a period TB has elapsed since the time T132 at which the interference signal has been detected, the wireless communication apparatus 11A starts transmitting a data packet d11 to a wireless communication apparatus 12A. At a time T136, the wireless communication apparatus 11A completes the transmission of the data packet d11.

Abstract: A process for forming a tubular member is provided which includes a pre-forming process for tube-expanding (bulge) forming and bending forming a tubular material using first and second molds and a final forming process for crush forming a preformed tube using a third mold so as to give its cross section a desired shape, the pre-forming step being carried out using the first and second molds heated at temperatures equal to or higher than the recrystallization temperature of the tubular material and the final forming step being carried out using the third mold heated at temperatures equal to or lower than the recrystallization temperature of the tubular material. The process enables a tubular material of aluminum alloy to be formed into a tubular member of high precision and high quality which has expanded portions as well as bent portions and whose cross section varies across its length.

Abstract: A delay section delays a detected signal by less than one bit time in the NRZ data. A subtraction section performs subtraction between a delayed signal and the detected signal, and outputs a resultant signal. A clock extraction section extracts, from crossing points of a subtracted signal, crossing points whose time interval is more than or equal to (Tb??) and less than or equal to (Tb+?) (wherein 0<??Tb/8, 0<??Tb: Tb is one bit time in the NRZ data), and outputs a synchronous signal synchronized with the extracted crossing point. A clock recovery section synchronizes a clock signal with the phase of the synchronous signal, and outputs a data clock signal. A determination section determines the polarity of the subtracted signal outputted from the subtraction section in accordance with the data clock signal, and outputs the determination result as the NRZ data.

Abstract: The present invention provides a wireless station capable of increasing the probability that a path diversity effect can be obtained in a case where a plurality of wireless stations transmit packets using a modulation/demodulation scheme with an anti-multipath property. A delay amount determining section (48) randomly selects a delay amount from among a plurality of candidate values. A transmission timing control section (47) determines a transmission start timing, at which to start the packet transmission, to be a timing obtained by delaying a reference timing by the delay amount selected by the delay amount determining section. At the transmission start timing, a modulation section (49) transmits the packet via an RF section (42) and an antenna (41). The difference between the candidate values is greater than or equal to a predetermined delay resolution, and the difference between a maximum candidate value and a minimum candidate value is less than or equal to a predetermined maximum delay.

Abstract: In a wireless communication system using the contention method, collisions between transmission signals sent from terminals to a base station are avoided, and a communication area is flexibly formed while suppressing unnecessary radiation of the communication area.

Abstract: The present invention provides a wireless transmission system in which it is possible to exert a maximum path diversity effect even if the maximum number of effective branches is limited to a small number. A transmission timing control section (23) determines a transmission start timing to be a timing obtained by delaying a reference timing by a predetermined delay amount. A modulation section (21) modulates a signal by a modulation scheme such that an anti-multipath property is exerted when the signal is demodulated on a receiver side, and transmits the modulated signal at the transmission start timing. In a receiving station (12), a demodulation section (33) demodulates the receive signal to obtain receive data.

Abstract: A wireless transmission system capable of performing a multi-station simultaneous transmission of data, that is, simultaneously transmitting data by wireless to a plurality of stations. The wireless transmission system includes a plurality of wireless stations for transmitting/receiving data and it constitutes a system for path diversity by use of a wireless station at the transmitting end, a multipath transmission path, and a wireless station at the receiving end. At least one of the plurality of wireless stations decides, in accordance with a response packet responsive to a multi-station simultaneous transmission request packet transmitted by the wireless station or other stations, a plurality of delay amounts relative to a reference timing during the multi-station simultaneous transmission in the wireless transmission system.

Abstract: A light emitting section outputs an optical signal having an intensity corresponding to a transmission timing signal, the optical signal modulated based on a radio transmission signal. A received photocurrent detection section detects an intensity of an optical signal received by a light receiving section. In accordance with the detected intensity, a high frequency amplification section amplifies the output signal of the light receiving section, and a transmission timing signal reconstruction section reconstructs the transmission timing signal.

Abstract: A process is provided for producing a hollow member having a wall thickness, in a cross section orthogonal to the longitudinal direction, that varies in the longitudinal direction, the process including a heating step of heating a tubular material (Pa) so that the tubular material (Pa) is given a temperature variation in the longitudinal direction, and a stretching step of axially stretching the tubular material (Pa) that has been heated in the preceding step. In this way, a hollow member having a cross-sectional wall thickness that is variable in the longitudinal direction can be easily produced.

Abstract: A diversity receiver carries out error detection, error correction, and data detection on each detected data string 21. An output switching unit 17 outputs a decoded data string 24 of a branch selected by a branch selector 16. The branch selector 16 selects a branch of highest priority in priority information 29 from branches of which a data detection signal 25 indicates that the data is valid and of which the number of error symbols 22 coincides with a minimum value. In the priority information 29, higher priority is assigned to a branch that includes an antenna of which the coverage is closer to that of an antenna included in a branch selected at the immediately-previous time. Thus, selected from the plurality of branches having the minimum number of error symbols 22 is the one that includes the antenna of which the coverage is closest to the coverage of the antenna included in the branch selected at the immediately-previous time.

Abstract: A delay section delays a detected signal by less than one bit time in NRZ data. A subtraction section performs subtraction between a delayed signal and the detected signal, and outputs a resultant signal. A clock extraction section extracts, from crossing points of a subtracted signal, crossing points whose time interval is more than or equal to Tb-? and less than or equal to Tb+? (0<??Tb/8, 0<??Tb: Tb is one bit time in the NRZ data), and outputs a synchronous signal synchronized with the extracted crossing point. A clock recovery section synchronizes a clock signal with the phase of the synchronous signal, and outputs a data clock signal. A determination section determines the polarity of the subtracted signal outputted from the subtraction section in accordance with the data clock signal, and outputs the determination result as NRZ data.

Abstract: A process is provided for producing a hollow member having a wall thickness, in a cross section orthogonal to the longitudinal direction, that varies in the longitudinal direction, the process including a heating step of heating a tubular material (Pa) so that the tubular material (Pa) is given a temperature variation in the longitudinal direction, and a stretching step of axially stretching the tubular material (Pa) that has been heated in the preceding step. In this way, a hollow member having a cross-sectional wall thickness that is variable in the longitudinal direction can be easily produced.

Abstract: A process for forming a tubular member is provided which includes a preforming process for tube-expanding (bulge) forming and bending forming a tubular material (Pa) using first and second molds (M1, M2) and a final forming process for crush forming a preformed tube (Pc) using a third mold (M3) so as to give its cross section a desired shape, the preforming being carried out using the first and second molds (M1, M2) heated at temperatures equal to or higher than the recrystallization temperature of the tubular material and the final forming being carried out using the third mold (M3) heated at temperatures equal to or lower than the recrystallization temperature of the tubular material. The process enables a tubular material of aluminium alloy to be formed into a tubular member of high precision and high quality which has expanded portions as well as bent portions and whose cross section varies across its length. The process also enables drastic increase in productivity.

Abstract: A light emitting section 12 outputs an optical signal having an intensity corresponding to a transmission timing signal 81, the optical signal modulated based on a radio transmission signal 82. A received photocurrent detection section 22 detects an intensity of an optical signal received by a light receiving section 21. In accordance with the detected intensity, a high frequency amplification section 23 amplifies the output signal of the light receiving section 21, and a transmission timing signal reconstruction section 24 reconstructs the transmission timing signal. The use of the light emitting section 12 outputting no optical signal in a non-transmission state and the use of the high frequency amplification section 23 outputting no signal in the non-transmission state allow noise caused in an antenna side base station 20 in the non-transmission state to be reduced.

Abstract: A diversity receiver carries out error detection, error correction, and data detection on each detected data string 21. An output switching unit 17 outputs a decoded data string 24 of a branch selected by a branch selector 16. The branch selector 16 selects a branch of highest priority in priority information 29 from branches of which a data detection signal 25 indicates that the data is valid and of which the number of error symbols 22 coincides with a minimum value. In the priority information 29, higher priority is assigned to a branch that includes an antenna of which the coverage is closer to that of an antenna included in a branch selected at the immediately-previous time. Thus, selected from the plurality of branches having the minimum number of error symbols 22 is the one that includes the antenna of which the coverage is closest to the coverage of the antenna included in the branch selected at the immediately-previous time.

Abstract: Before a deterioration of a secondary current sensor is detected, a controller effects a feedback control process based on a secondary current from the secondary winding of a welding transformer which is energized by an inverter, for thereby controlling a welding current with a high degree of accuracy, e.g., an accuracy level of .+-.1%. At the same time, it is monitored whether a detected value of a primary current from the primary winding of the welding transformer, which is detected by a primary current sensor, exceeds a predetermined allowable range with respect to a reference value of the primary current. If the detected value of the primary current exceeds the predetermined allowable range, then it is decided that the secondary current sensor is deteriorated.

Abstract: A direct current resistance welding machine and a method of controlling the direct current resistance welding machine wherein primary current of a welding transformer is detected when a plurality of switching devices of an inverter are controlled based on corresponding pulses having a predetermined frequency and each having a time width corresponding to the value of a required secondary current. Rise and fall times of the detected primary current are detected. An upper limit frequency Of the primary current is computed based on the time width of each pulse and on the rise and fall times. Thus, the primary current of the welding transformer is controlled by controlling the switching devices based on pulses having a frequency falling within the computed upper limit frequency.

Abstract: A direct-current resistance welding apparatus includes pneumatic actuators for pressurizing welding guns, respectively, to grip respective workpieces, an inverter composed of a plurality of parallel-connected switching device units each comprising a pair of series-connected switching devices, and a plurality of welding transformers connected to the welding guns, respectively, and also connected between the switching device units. A timer circuit applies an energization signal to energize the switching device units. The pneumatic actuators are actuated by a control circuit to pressurize the welding guns and successively energize the switching device units according to s sequence read from a sequence memory circuit.