Email alert
1986 Vol. 8, No. 6
Display Method:
1986, 8(6): 401-407.
Abstract:
Three generalized threshold Chase algorithms called GTC Ⅰ, GTC Ⅱ and STC are proposed in this paper. The computing speeds of these algorithms are faster than that of the ordinary Chase algorithm, and the probabilities of the decoding error of these algorithms are the same as that of the ordinary Chase algolithm. Finally, the performances of these algorithms and the ordinary Chase algorithm for (15, 7, 5) binary BCH codes are compared by using computer simulations
Three generalized threshold Chase algorithms called GTC Ⅰ, GTC Ⅱ and STC are proposed in this paper. The computing speeds of these algorithms are faster than that of the ordinary Chase algorithm, and the probabilities of the decoding error of these algorithms are the same as that of the ordinary Chase algolithm. Finally, the performances of these algorithms and the ordinary Chase algorithm for (15, 7, 5) binary BCH codes are compared by using computer simulations
1986, 8(6): 408-415.
Abstract:
The work functions of transition metals vary drastically wirh the coverage of adsorbed alkali or alkaline earth metal atoms. This phenomenon is studied theoretically by a refined model, i.e., the transition-metal substrate is treated whh high accuracy by the film LAPW method, while the simple metal overlayer is simulated by the jellium model. Computation of the electronic structure of the adsorbed system with a coverage of lower than monolayer will become possible by using this model. The variations of work function () with the converage () of Cs on the W-substrate are presemted. the calculated min=1.441.48eV is in goood agreement with the experimental value (1.351.55eV). The close dependance of the results on the choice of parameter, Ev, is also discussed.
The work functions of transition metals vary drastically wirh the coverage of adsorbed alkali or alkaline earth metal atoms. This phenomenon is studied theoretically by a refined model, i.e., the transition-metal substrate is treated whh high accuracy by the film LAPW method, while the simple metal overlayer is simulated by the jellium model. Computation of the electronic structure of the adsorbed system with a coverage of lower than monolayer will become possible by using this model. The variations of work function () with the converage () of Cs on the W-substrate are presemted. the calculated min=1.441.48eV is in goood agreement with the experimental value (1.351.55eV). The close dependance of the results on the choice of parameter, Ev, is also discussed.
1986, 8(6): 416-422.
Abstract:
The results calculated by computer for the double-drift-region IMPATT diode on 3 mm waveband are reported. A comparison between single-drift and double-drift diodes is presented. The advantage of double-drift devices in respect to power output and efficiency is given. At the same time, effects of doping profile, current density and RF voltage on the performences of these devices are investigated. The theoretical data for design of double-drift IMPATT oscillator and amplifier on 8 mm waveband is also given.
The results calculated by computer for the double-drift-region IMPATT diode on 3 mm waveband are reported. A comparison between single-drift and double-drift diodes is presented. The advantage of double-drift devices in respect to power output and efficiency is given. At the same time, effects of doping profile, current density and RF voltage on the performences of these devices are investigated. The theoretical data for design of double-drift IMPATT oscillator and amplifier on 8 mm waveband is also given.
1986, 8(6): 423-432.
Abstract:
The method used for measuring the near-field light intensity profiles, radiative intensity line width and equi-amplitude contour areas in the radiative region, is introduced. For devices with different stripe geometries, the change of light emitting width and area, far-field light intensity patterns and light intensity topograph, as a function of the injection current is analysed.
The method used for measuring the near-field light intensity profiles, radiative intensity line width and equi-amplitude contour areas in the radiative region, is introduced. For devices with different stripe geometries, the change of light emitting width and area, far-field light intensity patterns and light intensity topograph, as a function of the injection current is analysed.
1986, 8(6): 433-441.
Abstract:
Luminous spectra and electrical characteristics of gas mixtures: Ar + He, Kr + He, He + Ne, He + Xe, Kr + Ar and Ar + Hg are studied to find a gas mixture which gives blue-green colour for the AC plasma display panel. It has been found That the gas mixture Ar + Hg is the best, because it does have blue-green luminous eolour, but with higher brightness and lower firing voltage.
Luminous spectra and electrical characteristics of gas mixtures: Ar + He, Kr + He, He + Ne, He + Xe, Kr + Ar and Ar + Hg are studied to find a gas mixture which gives blue-green colour for the AC plasma display panel. It has been found That the gas mixture Ar + Hg is the best, because it does have blue-green luminous eolour, but with higher brightness and lower firing voltage.
1986, 8(6): 442-448.
Abstract:
Some data of emission and evaporation properties referring to the tungsten matrix structure of the impregnated cathode are analyzed. The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total inside surface area of all pores, the diffusion length of barium over the tungsten grain surface, and the diameter and length of path for the barium to transport through. These factors all relate to the properties and operation mechanism of an impregnated cathode; therefore, it would not be strictly right to employ only the matrix porosity for characterizing the cathode properties. Finally, the preferred structure of porous tungsten matrix depending on different applications of impregnated cathode is proposed.
Some data of emission and evaporation properties referring to the tungsten matrix structure of the impregnated cathode are analyzed. The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total inside surface area of all pores, the diffusion length of barium over the tungsten grain surface, and the diameter and length of path for the barium to transport through. These factors all relate to the properties and operation mechanism of an impregnated cathode; therefore, it would not be strictly right to employ only the matrix porosity for characterizing the cathode properties. Finally, the preferred structure of porous tungsten matrix depending on different applications of impregnated cathode is proposed.
1986, 8(6): 449-456.
Abstract:
Test-card for colour TV is a signal widely used to evaluate visually the quality of a TV set. Based on the microprocessor Z-80 a test-card generator for colour TV with synchronizing is realized. By taking advantage of microprocessor programming, the techniques of computer, digital and IC are combined to simplify greatly the system circuits which originally need a large quantity of logical gates. Now, the functions of control and the generation of signal, such as compound synchronous signal, compoud blanking signal, etc, are realized with the help of CPU programming to get the advantages of low cost, high reliability and small size. All system programs are stored in EPROMs and thus any wanted changes in the pattern of test card can be conveniently realized by changing programs, and it is not necessary to change the whole configuration of the hardware circuits. The system can also be transferred into different types of non-standard TV synchronizers and test-card generators by only changing the programs.
Test-card for colour TV is a signal widely used to evaluate visually the quality of a TV set. Based on the microprocessor Z-80 a test-card generator for colour TV with synchronizing is realized. By taking advantage of microprocessor programming, the techniques of computer, digital and IC are combined to simplify greatly the system circuits which originally need a large quantity of logical gates. Now, the functions of control and the generation of signal, such as compound synchronous signal, compoud blanking signal, etc, are realized with the help of CPU programming to get the advantages of low cost, high reliability and small size. All system programs are stored in EPROMs and thus any wanted changes in the pattern of test card can be conveniently realized by changing programs, and it is not necessary to change the whole configuration of the hardware circuits. The system can also be transferred into different types of non-standard TV synchronizers and test-card generators by only changing the programs.
1986, 8(6): 457-461.
Abstract:
In this paper, the high-order AR estimator of ARMA power spectrum and the criterion of determing the order by whitening the noise of AR order are given. Due to the fact that the high-order AR estimator relates to problems of the ill-condition and the algorithmic robustness in numerical computation, the recursive algorithm of Householder transform is used to solve the high-order AR parameter estimation. The results obtained are satisfactory.
In this paper, the high-order AR estimator of ARMA power spectrum and the criterion of determing the order by whitening the noise of AR order are given. Due to the fact that the high-order AR estimator relates to problems of the ill-condition and the algorithmic robustness in numerical computation, the recursive algorithm of Householder transform is used to solve the high-order AR parameter estimation. The results obtained are satisfactory.
1986, 8(6): 462-468.
Abstract:
An approach for finding the transfer characteristic of wave digital filter is presented and a general computer program is developed. The program can be used to analyse the quantification effect of different coefficient word-lengths to the transfer characteristic of wave digital filter, thus it is possible to make a reasoriable choice of coefficient Word-length jn order to take account of the economics as well as the technical specification in the hardware implementation of wave digital filter.
An approach for finding the transfer characteristic of wave digital filter is presented and a general computer program is developed. The program can be used to analyse the quantification effect of different coefficient word-lengths to the transfer characteristic of wave digital filter, thus it is possible to make a reasoriable choice of coefficient Word-length jn order to take account of the economics as well as the technical specification in the hardware implementation of wave digital filter.
1986, 8(6): 469-476.
Abstract:
The charge-density method is investigated mainly on the errors which arise from the finite segments and their distribution. It is proved that the higher accuracy will reach if more segments are chosen. at where the charge density is high and at the region nearby the area where the field is to be ealculated. A program is set up. The differencc between the ealeulated data. and the published ones given by E. Harting and F. H. Eead (1976) is less than 1%.
The charge-density method is investigated mainly on the errors which arise from the finite segments and their distribution. It is proved that the higher accuracy will reach if more segments are chosen. at where the charge density is high and at the region nearby the area where the field is to be ealculated. A program is set up. The differencc between the ealeulated data. and the published ones given by E. Harting and F. H. Eead (1976) is less than 1%.
