Effects of viscosities on the transient current in homeotropic nematic liquid crystal cells

Effects of the Leslie viscosity coefficients α_i (i = 1, 2, …, 5) of nematic liquid crystals (NLCs) with negative dielectric anisotropy (Δε < 0) on the electric-field-induced director reorientation in homeotropic NLC cells have been studied from the analysis of the transient current induced by step voltage application. The transient current in a homeotropic NLC cell with Δε < 0 was well reproduced by computer simulation, based on the theory of NLCs in which the flow effects and the free-slip boundary condition are taken into account. It is found that the response time of vertical alignment NLC displays is dominantly governed by α₂ and α₄ + α₅ of NLCs with Δε < 0.     

"Facilitative and disruptive effects of prior exposure to shock on subsequent avoidance performance": Erratum.

Reports an error in "Facilitative and disruptive effects of prior exposure to shock on subsequent avoidance performance" by H. Anisman and T. Waller (Journal of Comparative and Physiological Psychology, 1972[Jan], Vol 78[1], 113-122). On page 114, the sentence beginning on Line 56, Column 2, should read: "Thirty seconds after placement in the compartment one half of the rats were given 10 CS (light and tone) presentations in which the CS was 9 sec. in duration, while the remaining rats received 10 CS-US presentations in which the US was a 1-ma. shock (constant current, ac) 2 sec. in duration." (The following abstract of this article originally appeared in record 1972-22565-001.) Subjected 40 male rats from each of 5 strains to 10 signaled inescapable 1-ma shock presentations. Shock facilitated subsequent 1-way and shuttle-avoidance performance (1-ma shock) in Charles River hooded, Wistar, Holtzman, and Sasco Ss, but did not significantly affect avoidance learning in Sprague-Dawley Ss. A 2nd experiment employing 120 male Holtzman rats indicated that inescapable shock of 1 ma. facilitated subsequent 1-way and shuttle-avoidance performance, while exposure to shock of 2 ma. facilitated 1-way and interfered with shuttle-avoidance performance. Movement ratings recorded during both CS and intershock intervals in pretraining were found to be good predictors of subsequent avoidance performance in preshocked Ss. Results are interpreted in terms of response repertoire changes produced by shock in conjunction with the defense reaction necessary in acquiring the avoidance response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Office communications: reshaping our society?

A revolution in office communications technology is about to overtake organizational administrators. This revolution has two sides: one concerned with the production of organizational intelligence and the other with its distribution. The paper suggests that new technology in the office will have a greater impact on society than is currently expected. The older computer technology (large mainframe-based systems) tended to promote ‘centralization’, whereas the new communications technology (videotex, fibre optics) promotes ‘distributed intelligence’. A study of the effect of new technology in one company is examined. Its use influenced organizational structures within the company and altered human interaction patterns. The paper suggests that society needs to rethink the very notion of an organizational system as communications technology advances.     

MODEL DEVELOPMENT AND EXPERIMENTAL STUDIES OF VERTICAL PNEUMATIC CONVEYING DRYERS

A theoretical model is presented for particle motion, heat and mass transfer and drying rates in vertical tubular pneumatic conveying dryers. The model is one-dimensional and takes time increments along the tube; a computer program is required for its implementation. It is similar to previous models but incorporates several refinements, notably in wall friction, agglomeration and heat transfer. The predictions are compared with experimental results; agreement is good and clearly superior to that obtained by earlier models. The method may be used either for initial design or for scale-up from pilot plant data.     

温粘效应下椭圆瓦轴承动特性系数一维模型算法分析

该文建立了轴向解析、周向有限元压力分布的一维变粘度场有限宽椭圆瓦轴承动特性系数模型.忽略泊肃叶流项对速度的影响,不考虑轴向温度变化并沿径向方向积分,三维能量方程可降阶为平均温度场只沿周向分布的一维形式,与雷诺方程解耦.采用一维直接解法求解雷诺方程和轴承在平衡点的挠动和速度方程.既考虑了温粘效应对轴承动力学性能的影响,又提供了无需迭代确定油膜破裂边界和求解油膜力和动特性系数快速算法.作为应用,对进油槽位于水平两侧的椭圆瓦轴承进行了动力润滑热效应分析,与工程数据比较,计算结果稳合,证明该模型合理,适用于工程上多瓦轴承的分析计算.     

Chemomechanical effects in optical coating systems

The major in-service failure mechanisms of modern optical coatings for architectural glass can be mechanical (e.g. scratch damage). Many of these coatings are multilayer structures of less than 100 nm thickness and different coating architectures are possible (i.e. different layer materials, thickness and stacking order). These coatings are exposed to different types of climatic conditions. In such circumstances it has been shown that chemomechanical effects can lead to changes in the hardness as well as the fracture resistance of bulk oxides. High performance glass is coated with anti-reflection coatings (e.g. ZnO, SnO₂) and barrier layers (e.g. TiO_xN_y) which are also expected to suffer from such chemomechanical effects. In this study we have demonstrated the chemomechanical behaviour of a range of optical coatings exposed to water. Water exposure tends to reduce the hardness and increase the fracture resistance of the coating making it more vulnerable to plastic deformation during scratching. The susceptibility of different coatings to chemomechanical effects is discussed.     

Compensation and doping effects in heavily helium-radiated silicon for power device applications

The formation of defects modifying the effective doping concentration of helium-radiated p⁺-n⁻-n⁺ and p⁺-p⁻-n⁺ silicon diodes is analyzed as a function of the annealing temperature. After irradiation with helium at high energy levels and annealing at 220 °C, the probable formation of divacancy clusters increases the number of charged-acceptor states in a space-charge region. Capacitance-Voltage and Spreading-Resistance Profile measurements show that annealing at 350 °C results in the formation of an acceptor-like defect that deep level transient spectroscopy measurements suggest can be tentatively attributed to the V₂O or V₄/V₅ centre. Annealing at 430 °C results in the disappearance of the acceptor-like defect. Instead, pronounced donor formation in a range close to the penetration depth of the helium ions is observed. The influence of these effects on device characteristics is discussed.     

红外源强度对激光干扰效应的影响

分析了红外目标源辐射强度随距离和时间的变化。在不同红外源强度的 条件下，进行了红外源强度对红外系统输出信号的响应定标。同时，在激光辐照功率67W和辐照时间460ms条件下，用1.06μm连续ND：AYG激光对不同红外源强度下红外系统输出信号的干扰效果进行了对比实验。结果表明：激光对红外系统的干扰效果与红外目标源的强度成正比。当红外源强度在红外系统工作的线性范围时，激光对红外系统的干扰效果最明显。     

DIRECTION REVERSALS IN THE MECHANICAL SIGNATURE OF CELLULAR SNACKS: A MEASURE OF BRITTLENESS?

The “mechanical signatures” of brittle cellular foods are known to be irregular and irreproducible. Nevertheless, their degree of jaggedness is remarkably similar and can be a measure of such foods' brittleness and perceived crunchiness/crispiness. An irregular curve's “jaggedness” is manifested by frequent direction reversals. Hence, their number can serve as a jaggedness's index. Counting the number of direction reversals in a digitized force‐displacement curve can be done with a simple algorithm, implemented in any general‐purpose software. The number of direction reversals is strongly correlated with the signature's apparent fractal dimension. It is also a reproducible enough parameter to monitor the loss of brittleness in snacks as a result of moisture sorption. This measure of jaggedness, however, is inapplicable to smooth force‐displacement curves because in such records, the small random force fluctuations produced by the digitizing process can create a false impression of “jaggedness.” Although a correction for this artifact can be introduced into the program, its utility is doubtful.     

AlGaN/GaN HEMT二维静态模型与模拟

考虑AlGaN/GaN材料的自发、压电极化效应和量子效应,通过泊松方程、薛定谔方程和流体力学方程组的数值自洽求解方法,对AlGaN/GaN HEMT的二维静态模型与模拟问题进行了研究,得到了器件区域的导带图、二维电子气分布、电子温度特性、直流输出和转移特性,并对模拟结果进行了分析与讨论.