同步VLSI设计环境下AES模块的异步流水线结构实现

本文提出了一种可在同步VLSI设计环境下,由已有的流水线结构同步集成电路的算法或者RTL代码直接得到其异步集成电路网表的方法。并使用此方法,实现了128位异步AES加、解密模块。解密模块为多功能流水线,既可以进行生成子密钥运算,也可以进行解密输入数据。对加、解密模块均通过10级、5级、3级、2级流水四种结构分别实现并加以比较。     

Short period superlattices under hydrostatic pressure

Hydrostatic pressure (0–13 kbar) has been used to probe the Bloch transport in GaAs/AlAs and Ga_0.47In_0.53As/Al_0.48In_0.52As short-period superlattices between 77 K and room temperature. We show that for both types of superlattices, the width of the lowest Γ conduction miniband decreases with increasing pressure due to the increase of the effective mass. Moreover, in GaAs/AlAs short period superlattices, an additional effect of the increasing pressure is the change of the relative energy separation between the lowest Γ miniband and the lowest X states and the resulting transfer of carriers from Γ to X.     

Radiation defects in semiconductors under hydrostatic pressure

The effect of hydrostatic pressure on the sensitivity of the electrical properties of irradiated semiconductors as functions of the position of the Fermi level in the band gap of the crystal has been investigated. A numerical analysis of the experimental data has been performed. This analysis is based on a model of the crystal as having an isotropic band gap 〈E _G〉, where 〈E _G〉 is the average energy interval between the conduction band and the valence band. It is shown that varying the pressure results in hardly any change in the position of the radiation defect levels relative to the energy corresponding to the center of the isotropic gap 〈E _G〉/2, which is identical to the value of the “limiting” position of the Fermi level (F _lim) in an irradiated semiconductor. Fiz. Tekh. Poluprovodn. 33, 1290–1294 (November 1999)     

Spectroscopic study of Ga-doped Ge under uniaxial pressure

To identify the optical transitions responsible for the excitation of long-wavelength stimulated emission in uniaxially compressed Ga-doped Ge, the optical absorption and photoconductivity spectra of the material were investigated at a wide range of pressures in directions [111] and [001]. The dependence of the valence band splitting between the light-and heavy-hole subbands in Ge as a function of the applied pressure was found. As determined from this dependence, the deformation potential constants for the valence band appeared to be less than the presently accepted values. It is shown that, as pressure increases, some of the excited states of the Ga impurity levels reach the light-hole band, enter it, and remain close to its edge (the resonant states). It is possible that a population inversion of these resonant states gives rise to the excitation of stimulated emission at a photon energy of about 10 meV. No specific features confirming the existence of resonant impurity states near the edge of the heavy-hole band were found in the spectra.     

Behavior of ZnO acoustoelectric devices under uniaxial pressure

The effects of uniaxial pressure along the c axis of zinc oxide acoustoelectric single crystals while biased below and above the threshold field are discussed.     

Reliability of spring pressure contacts under environmental stress

Spring contacts are an excellent solution for connecting a power module with a printed circuit board (PCB). They can be applied in a wide current range from sensor currents of a few milliamps to load currents of several amps. They offer many advantages like easy assembly without soldering and also easy disassembly for maintenance purposes. The reliability of spring contacts under environmental stress by mechanical wear, rapid temperature change and corrosive atmosphere is significant for the application. The experimental results presented in this paper certify that spring contacts are reliable even under harsh environmental conditions.     

Diffusion of chromium in GaAs under equilibrium arsenic-vapor pressure

The diffusion of chromium in GaAs is studied under equilibrium arsenic-vapor pressure. The temperature dependences of chromium diffusivity and solubility in GaAs are determined. These dependences are described by the Arrhenius equation with the parameters D ₀ = 3.1 × 10⁵ cm²/s and E = 3.2 ± 0.4 eV for the diffusivity and N _S = 2.1 × 10²¹ cm^?3 and E _S = 1.0 ± 0.3 eV for the solubility. The obtained experimental results are compared with our previously published data on the diffusion of chromium under high arsenic-vapor pressure and analyzed in terms of the dissociative mechanism of migration of chromium in GaAs.     

High-field properties of n-InP under high pressure

The high electric field properties of n-InP at 300 K have been studied as a function of pressure. Hydrostatic measurements are made in a piston and cylinder apparatus, using a liquid pressure-transmitting medium. The threshold fields (E_T) for transferred electron instabilities range from 7.5 to 8.5 kV/cm at atmospheric pressure. The resistivity of the samples increases with increasing pressure. The most reliable results show that E_T increases slightly with pressure below 40 kbar. This behavior can be explained qualitatively in terms of possible band structure changes. By using known variations of parameters such as effective mass and sub-band energy gaps, detailed theoretical calculations are carried out to fit the data and to determine the correct mode of operation (two- or three-level operation). The results are also compared with analogous experiments on GaAs.     

Optical properties of wurtzite and rock-salt ZnO under pressure

This paper reports on the pressure dependence of the optical absorption edge of ZnO in the wurtzite and rock-salt phase, up to 14 GPa. Both vapor-phase monocrystals and pulsed-laser-deposition thin films have been investigated. In both types of samples the wurtzite to rock-salt transition is observed at 9.7±0.2 GPa. The absorption tail of the fundamental gap, as measured in monocrystals, exhibits a pressure coefficient of 24.5±2 meV/GPa. The evolution under pressure of the full absorption edge of the wurtzite phase is studied with thin film samples, yielding a slightly lower pressure coefficient (23.0±0.5 meV/GPa for the A-B exciton). Rock-salt ZnO is shown to be an indirect semiconductor with a bandgap of 2.7±0.2 eV. At higher photon energy a direct transition (E_gd-4.5 eV) can be also identified in thin films transited to the rock-salt phase. Results on the high-pressure phase are interpreted on the basis of density-functional-theory (DFT) electronic structure calculations.     

Structural analysis of jacketed optical fiber under lateral pressure

A theory is presented on the deformation of jacketed fibers due to lateral pressure, and its influence on microbending losses is assessed. This analysis, which is based on the theory Of elasticity, helps to clarify how lateral pressure and the structure of the fiber jacket conspire to cause excess fiber losses. Periodic pressure distributions with certain unfavorable period lengths are shown to lead to a pronounced enhancement of excess losses.     

聚合物封装FBG侧向压力敏感机理的研究

目前大多数关于FBG压力敏感的研究都基于轴向压力,而关于FBG侧向压力敏感的研究却很少,加强侧向压力传感器的研究很有必要.     

卷取夹送辊单侧压力模式下阻力补偿方式的研究

本文从解决卷形尾部错层入手,分析出卷取夹送辊阻力大是导致夹送辊辊缝偏差难以控制、卷形错层的根本原因,详细描述了以超调的形式对阻力进行提前补偿,和以辊缝偏差为依据对阻力进行滞后补偿的方法,取得一定的效果.     

高孔隙水压力下裸光纤光栅应变测试

裸光纤光栅与电阻应变计相比具有体积小、防水、抗电磁干扰等优点,利用其在高压孔隙水环境下进行应变测试理论上是可行的.以相关课题试验研究为背景,进行了高孔隙水压下裸光纤光栅应变测试的研究.首先通过试验研究,根据裸光纤光栅应变灵敏度系数与长期稳定性选择合适的胶黏剂,在此基础上利用裸光纤光栅对高孔隙水压力下的模型井壁外缘切向应变进行测量,通过与井壁内缘的电阻应变计测值对比发现,二者测值非常接近,试验表明高水压下裸光纤光栅应变测试是可行的,具有足够的灵敏度与精度,同时发现粘贴工艺的标准化、胶黏剂的选择以及裸光纤光栅的存活率是影响测试成败的重要因素.     

Crystal growth of aluminum nitride under high pressure of nitrogen

We report on the results of AlN crystal growth at high nitrogen pressure of the order of 1 GPa and temperatures up to 2000 K. Both, needle-like and bulk form of AlN single crystals up to 1 cm and 1 mm, respectively, have been obtained. We discuss the influence of temperature and supersaturation on the habit and morphology of AlN crystals. The crystals were characterized by X-ray diffraction method, scanning electron microscopy (SEM) and energy dispersive X-ray analyser attached to SEM.     

Charge neutrality level and electronic properties of GaSe under pressure

Calculations of lattice parameters and electron band spectra of GaSe have been carried out from the first principles. The dependence of these parameters on hydrostatic compression as high as 5 GPa and on homogeneous biaxial tensile and compressive stresses (from −3 to 3 GPa) in the basal plane of the unit cell is considered. The calculations adequately reproduce the experimental features of the major interband transitions in GaSe under a hydrostatic pressure and, in the absence of experimental data, predict the dependence of structural and electronic properties of GaSe under the effect of a biaxial stress. On the basis of calculated band spectra, the energy position of the local charge neutrality level CNL, E _v + 0.8 eV, has been determined and electronic properties of the as-grown material and energy diagrams for interphase boundaries in GaSe have been analyzed.     

Transferred electron effects in n-GaAs and n-InP under hydrostatic pressure

Experimental results are presented showing the variation of the peak velocity, electric field at peak velocity and saturated velocity of the velocity-field curve for bulk n-GaAs under hydrostatic pressure. Similar data are presented for the field at peak velocity for bulk n-InP. The extraction of the data from the current-voltage characteristics is based on an exploitation of the influence of boundary conditions on the manifestation of transferred-electron induced (Gunn) current instabilities. Our results, which differ from those of other investigations, are compared with our Monte Carlo calculations of the velocity-field curves for these materials. We find that ionized impurity scattering plays an important role in the understanding of our data.     

Designing a robust adaptive dynamic controller for nonholonomic mobile robots under modeling uncertainty and disturbances

The main stream of researches on the mobile robot is planning motions of the mobile robot under nonholonomic constraints. Much has been written about the problem of motion planning under nonholonomic constraints using only a kinematic model of a mobile robot. Those methods, however, assume that there is some kind of a dynamic controller that can produce perfectly the same velocity that is necessary for the kinematic controller. Also there is little literature on the robustness of the controller when there are uncertainties or external disturbances in the dynamical model of a mobile robot. In this paper, we proposed a robust adaptive controller that can achieve perfect velocity tracking while considering not only a kinematic model but also a dynamic model of the mobile robot. The proposed controller can overcome uncertainties and external disturbances by robust adaptive technique. The stability of the dynamic system will be shown through the Lyapunov method.     

Designing for health

System readiness is vital to supporting the war fighter's needs. A robust health management system (HMS) enables the war fighter and maintainer to quickly access the health of a system through diagnostics and the probable failure impact of a mission through prognostics increasing probability of mission success. This systems engineering approach to integrated diagnostics and prognostics provides the foundation to supporting the total test environment with traceability of requirements through analysis and implementation while reducing false alarms and could-not duplicates (CNDs).