逆（反）对策问题与“奇门遁甲”预测理论（术）

本文首先提出逆（反）对策这一新问题，给出了数学模型；探讨了“奇门遁甲”预测理论（术）中的数学问题；通过系统分析“专门遁甲”预测过程，可知它的预测过程隐含着一个特殊的逆（反）对策问题；最后指出逆（反）对策问题的广泛存在并给出案例分析．     

Enhanced electron emission from phosphorus-doped diamond-cladsilicon field emitter arrays

Undoped and phosphorus (P)-doped diamond-clad Si field emitter arrays have been successfully fabricated using microwave plasma chemical vapor deposition (MPCVD) technology. The electron emission from the blunt diamond-clad microtips are much higher than those for the pure Si tips with sharp curvature due to a lower work function. Furthermore, the characteristics of emission current against applied voltage for the P-doped diamond-clad tips show superior emission at lower field to the undoped ones. After the examination of Auger electron spectroscopy (AES) and electrical characteristics of as-grown diamond, such a significant enhancement of the electron emission from the P-doped diamond-clad tips is attributed to a higher electron conductivity and defect densities     

A BiCMOS dynamic carry lookahead adder circuit for VLSIimplementation of high-speed arithmetic unit

A BiCMOS dynamic carry lookahead circuit that is free from race problems is presented. A 16 b full-adder test circuit, which has been designed based on a 2 μm BiCMOS technology, shows a more than five times improvement in speed as compared to the CMOS Manchester carry lookahead (MCLA) circuit. The speed advantage of the BiCMOS dynamic carry lookahead circuit is even greater in a 32- or 64-b adder     

Multiple negative-differential-resistance (MNDR) phenomena of ametal-insulator-semiconductor-insulator-metal (MISIM)-like structurewith step-compositioned InxGa1-xAs quantum wells

In this paper, a new multiple negative-differential-resistance (MNDR) device based on a metal-insulator-semiconductor-insulator-metal (MISIM)-like structure with step-compositional In_xGa_1-x As quantum wells has been fabricated and demonstrated. The interesting MNDR phenomena are found in the current-voltage (I-V) characteristics of this device. At room temperature, the triple switching behaviours and quadruple stable operation states are obtained. In addition, the sixfold switching behaviors and a staircase-shaped I-V characteristic are observed at -105°C. A sequential carrier accumulation at InGaAs subwells and the potential lowering process are used to qualitatively explain the interesting MNDR phenomena. From the experimental results, it is shown that the studied device has good potential in multiple-valued logic applications     

Implementation of media processors

Conventional standard processors do not correspond well to the characteristics of multimedia signal processor algorithms. Therefore, special architectural approaches are necessary for multimedia processors to deliver the required high processing power with efficient use of hardware resources. Programmable approaches offer a high degree of flexibility. In order to attain multimedia signal processor performance, architectural strategies for programmable processors are based on parallelization and adaptation principles. The future multimedia signal processor implementation hinges upon an optimal trade-off between the two design spaces, which can be effectively addressed by a codesign approach     

Design of finite-length metal-clad optical waveguide polarizer

The performance of optical metal-clad waveguide polarizers is analyzed in this paper with a view to optimizing the extinction ratio, a condition for which power of the TM mode is completely attenuated is identified here. In general, such a condition corresponding to an infinitely high extinction ratio can be met for a wide range of buffer layer thicknesses by selection of metal film thickness and polarizer length. When a very thick (e.g., semi-infinitely thick) metal film is used, the aforementioned condition can be met with a properly chosen buffer layer thickness and polarizer length. The numerical results show that all the polarizers designed here for realization of infinitely high extinction ratios have either quite low or reasonably acceptable attenuations for the TE mode     

Superconducting control for surge currents

Systems designed to use superconductors to limit fault currents in power grids are undergoing testing. The authors describe superconducting fault current limiters (SCFCL) which may be categorised into resistive or shielded core types. The features and operation of each type of device are outlined. Both the shielded-core and resistive types of SCFCL use the same amount of superconductor material to achieve a given limitation behavior. This is because the rated power per volume of conductor is determined by the product of fault-induced field and critical current, which is the same for both devices, assuming the same type of superconducting material is employed. The shielded-core limiter works only with AC currents and is much larger and heavier than the resistive SCFCL. While there is only one large program left in the low-temperature type of SCFCL, more than 10 major projects are under way worldwide on the high-temperature type of device. The main reason is the lower HTS cooling cost     

A new space-vector-modulated control for a unidirectionalthree-phase switch-mode rectifier

A unidirectional three-phase switch-mode rectifier that delivers sinusoidal input currents in phase with the corresponding input phase voltages is proposed and analyzed in this paper. In the proposed topology, three AC switches are placed before the bridge rectifier and, respectively, across two power lines. A simple control scheme combing space-vector modulation and hysteresis current control is presented. Sinusoidal input line currents are observed in experimental results     

Double-diffusive convection for a heated cylinder submerged in a salt-stratified fluid layer

Double-diffusive convection due to a cylindrical source submerged in a salt-stratified solution is numerically investigated in this study. For proper simulation of the vortex generated around the cylinder, a computational domain with irregular shape is employed. Flow conditions depend strongly on the thermal Rayleigh number, Ra _T , and the buoyancy ratio, R _ρ. There are two types of onset of instability existing in the flow field. Both types are due to either the interaction of the upward temperature gradient and downward salinity gradient or the interaction of the lateral temperature gradient and downward salinity gradient. The onset of layer instability due to plume convection is due to the former, whereas, the onset of layer instability of layers around the cylinder is due to the latter. Both types can be found in the flow field. The transport mechanism of layers at the top of the basic plume belongs to former while that due to basic plume and layer around the cylinder are the latter. The increase in Ra _T reinforces the plume convection and reduces the layer numbers generated around the cylinder for the same buoyancy ratio. For the same Ra _T , the increase of R _ρ suppresses the plume convection but reinforces the layers generated around the cylinder. The profiles of local Nusselt number reflects the heat transfer characteristics of plume convection and layered structure. The profiles of averaged Nusselt number are between the pure conduction and natural convection modes and the variation is due to the evolution of layers. Received on 13 September 1996     

在柔性变焦系统中的压力变焦镜

从理论上和实验上对水冷镜的镜面曲率半径随压力变化的规律作了研究。对压力变形后镜面相对于球面作了波像差分析，分析表明压力变焦镜用于中红外激光系统是合适的