陶瓷材料冲击性能研究进展

陶瓷材料由于其多种优良特性得到了越来越广泛的应用。有关陶瓷材料的冲击力学性能研究是最近几十年才开始的。本文从陶瓷材料的应变率效应、冲击下的高压行为、冲击损伤、层裂现象和失效波响应，以及相关的理论研究和数值分析等方面，介绍了国内外对陶瓷材料冲击性能研究的现状，并对进一步的工作提出了建议和展望。     

Sensor technologies for monitoring metabolic activity in single cells-part I: optical methods

A review of optical, chemical, and biological sensors to detect metabolic activity at the single-cell level is presented in the context of the development of lab-on-a-chip research instrumentation. The sensors reviewed include optical sensors, at both research and commercial levels, that can optically detect intracellular metabolites including adenosine triphosphate, nicotinamide-adenine dinucleotide, reduced flavin adenine dinucleotide, and other metabolites, including oxygen, carbon dioxide, and glucose. Methods to optically detect pH changes which are a general indicator of activity in extracellular space are also briefly reviewed. Performance metrics such as sensitivity, sensor size, drift, time response, and sensing range are included when available. Highly suitable optical sensor technologies for monitoring cellular metabolic activity include luminescent (fluorescent, phosphorescent, and chemiluminescent) and colorimetric optical probes. Different approaches to extracting luminescent and colorimetric information are reviewed, including benchtop techniques, fiber-optic approaches, and the use of probes encapsulated by biologically localized embedding. A brief discussion of alternate optical sensor technologies, such as surface plasmon resonance and infrared absorption spectroscopy, is also presented.     

Experimental realization of a new transistor

The authors report on the fabrication and characteristics of a unipolar, three-terminal, resonant-tunneling transistor. The operating principle of this new transistor is based on the fact that the quantum mechanical resonant-tunneling probability of hot electrons between the emitter and the collector is switched almost completely on and off, when either the base or the collector bias is swept. The emitter injects hot electrons to the second lowest subband of a thin (100 Å in this work) GaAs quantum well. Subsequently, the hot electrons will either resonantly tunnel to the collector, or relax to the lowest subband and contribute to the base current. As a result of resonant transmission, at 77 K the current-voltage characteristics of the transistor display negative differential resistance with extremely large (4691) peak-to-valley ratio. Furthermore, when biased near resonance, a maximum DC current gain of ~1.2 and a maximum AC current gain of ~11.9 were observed. The first use of a new `tunneling-in and tunneling-out' scheme in contacting a thin quantum well is also demonstrated     

Geometric model for nuclear absorption from microscopic theory

A parameter-free geometric model for nuclear absorption is derived from microscopic theory. The expression for the absorption cross section in the eikonal approximation taken in integral form is separated into a geometric contribution, described by an energy-dependent effective radius, and two surface terms which are shown to cancel in an asymptotic series expansion. For collisions of light nuclei, an expression for the effective radius is derived using harmonic-oscillator nuclear density functions. A direct extension to heavy nuclei with Woods-Saxon densities is made by identifying the equivalent half density radius for the harmonic-oscillator functions. Coulomb corrections are incorporated and a simplified geometric form of the Bradt-Peters type obtained. Results spanning the energy range of 1 MeV/nucleon to 1 GeV/nucleon are presented. Good agreement with experimental results are obtained.     

A comparison of various measured and calculated shieldingeffectiveness data for a wire cage

Considers the shielding effectiveness (SE) of a wire cage structure (2 m cube). The SE is predicted using various analytical approximations and measured using a number of different methods. Both near-field and far-field coupling through the mesh are considered. The results show that calculated and measured SE data can cover a large range of values depending on the configuration used. Upper and lower SE bounds for the near and far-field cases are discussed     

Effect of ion energy on hydrogen diffusion in n- and p-GaAs

The ion energy during electron cyclotron resonance (ECR) plasma hydrogenation is found to have a strong effect on both the effective diffusivity and solubility of hydrogen in n⁺ and p⁺ GaAs. For fixed plasma exposure conditions (30 min, 250°C) the diffusion depths for -150 V acceleration voltage are ~50 and ~100% larger, respectively, in p⁺- and n⁺-GaAs compared to 0 V acceleration voltage. The smaller incorporation depths at lower ion energy coincide with much larger peak hydrogen concentrations and higher apparent thermal stability of passivated dopants     

Resurgence of derived stimulus relations

Resurgence has been shown in human and nonhuman operant behavior, but not in derived relational responses. The present study examined this issue. Twenty-three undergraduates were trained to make conditional discriminations in a three-choice matching-to-sample paradigm. The training resulted in three equivalence classes, each consisting of four arbitrarily configured visual stimuli. The same 12 stimuli were then reorganized, and the conditional discrimination training was repeated such that three new classes were possible. In a subsequent test of derived relations, most subjects showed response patterns that were consistent with the altered conditional discriminations. Subjects were then exposed to conditional discrimination trials under extinction. Most subjects continued to respond consistently with the most recently reinforced conditional discrimination trials. During the next phase, subjects were exposed to symmetry and equivalence trials. Responses consistent with the most recent training produced feedback saying that the responses were incorrect, whereas other responses produced no feedback. Most subjects showed a resurgence of responding that was consistent with their earlier training. Finally, subjects were exposed to conditional discrimination trials carried out in extinction. Most subjects continued to show a resurgence of responding that was consistent with their early training.     

三维定量储层地质模型与参数动态预测方法

提出了三维定量储层地质模型及其参数动态预测方法，用该方法可预测储层开采状态，水淹区及剩余油区分布和各剩余油区的可采储量，三维定量储层地质模型的预测图件可为合理开采提供依据。     

The future of behavior therapy.

Predicts the future of behavior therapy, focusing on theoretical development, therapeutic techniques, and empirical research. The importance of cognitive and affective processes in behavior change will attract increasing attention. Already one of the most widely adopted approaches, behavior therapy will be used to treat an expanded range of psychiatric disorders and health problems. Research will focus on comparative outcome studies and provide probes for investigating the nature of specific disorders and the mechanisms of therapeutic change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An investigation into the performance and cost effectiveness of thermosyphon solar water heaters

In this paper, the TRNSYS Simulation Program is used to investigate the monthly and annual solar fraction of a Thermosyphon Solar Water Heater and to evaluate its economic viability in terms of its life cycle savings over a conventional water heating system. The results of the simulation indicate that the yearly solar contribution of the system ranges from 63% for a high hot water consumption profile to 89% for a low consumption pattern. The payback period of the system is as low as 3 years when compared to electric water heating systems. As long as the competitor is diesel oil, the payback period increases to 7–9 years, depending on the hot water consumption profile used.