Self-adaptive space and time grids in device simulation

For the solution of the three basic semiconductor equations in two space dimensions fully self-adaptive grids are a powerful tool to optimize the ratio between the number of unknowns and the accuracy of the solution. For the method of finite differences hardly any mathematically founded criterion for automatic grid control can be given which can be implemented in a computer program with acceptable effort. Therefore most of the strategies for self-adaptive grid control are totally heuristic or derived from physical properties. In this paper we present criteria for the design of an initial space grid. We discuss some conventional strategies for the automatic control of space grids (e.g. equidistribution of the local discretization error) and present new criteria (e.g. degree of coupling of the equations, physical properties like net generation rate). For the time grid an automatic step length control algorithm is presented and the interaction between space and time grid is analysed. Throughout the paper the results are illustrated by realistic examples.     

Sampling from discrete Gaussians for lattice-based cryptography on a constrained device

Modern lattice-based public-key cryptosystems require sampling from discrete Gaussian (normal) distributions. The paper surveys algorithms to implement such sampling efficiently, with particular focus on the case of constrained devices with small on-board storage and without access to large numbers of external random bits. We review lattice encryption schemes and signature schemes and their requirements for sampling from discrete Gaussians. Finally, we make some remarks on challenges and potential solutions for practical lattice-based cryptography.     

航空电子模块储热器工作时间预测

航空电子模块储热器是一类广泛应用于航空电子设备的热管理装置.为了给航空电子模块储热器的工程设计提供理论支撑,对其工作时间与功耗、设定温度之间的关系进行研究.首先,综合考虑自然对流和热辐射的影响,运用传热学理论构建了储热器在实际工作环境下的热模型.然后,运用焓-多孔介质法对储热器的瞬态储热过程进行了数值模拟,并通过求解相...     

Sampling and electrophoretic analysis of segmented flow streams using virtual walls in a microfluidic device

A method for sampling and electrophoretic analysis of aqueous plugs segmented in a stream of immiscible oil is described. In the method, an aqueous buffer and oil stream flow parallel to each other to form a stable virtual wall in a microfabricated K-shaped fluidic element. As aqueous sample plugs in the oil stream make contact with the virtual wall, coalescence occurs and sample is electrokinetically transferred to the aqueous stream. Using this virtual wall, two methods of injection for channel electrophoresis were developed. In the first, discrete sample zones flow past the inlet of an electrophoresis channel and a portion is injected by electroosmotic flow, termed the "discrete injector". With this approach at least 800 plugs could be injected without interruption from a continuous segmented stream with 5.1% RSD in peak area. This method generated up to 1,050 theoretical plates, although analysis of the injector suggested that improvements may be possible. In a second method, aqueous plugs are sampled in a way that allows them to form a continuous stream that is directed to a microfluidic cross-style injector, termed the "desegmenting injector". This method does not analyze each individual plug but instead allows periodic sampling of a high-frequency stream of plugs. Using this system at least 1000 injections could be performed sequentially with 5.8% RSD in peak area and 53,500 theoretical plates. This method was demonstrated to be useful for monitoring concentration changes from a sampling device with 10 s temporal resolution. Aqueous plugs in segmented flows have been applied to many different chemical manipulations including synthesis, assays, sampling processing and sampling. Nearly all such studies have used optical methods to analyze plug contents. This method offers a new way to analyze such samples and should enable new applications of segmented flow systems.     

Polarization effects in nitride semiconductors and device structures

Wide bandgap nitride semiconductors have recently attracted a great level of attention owing to their direct bandgaps in the visible to ultraviolet regions of the spectrum as emitters and detectors. Moreover, this material system with its favorable hetero-junctions and transport properties began to produce very respectable power levels in microwave amplifiers. If and when the breakdown fields achieved experimentally approach the predicted values, this material system would also be very attractive for power switching devices. In addition to the premature breakdown, high concentration of defects, and inhomogeneities, a number of scientific challenges remain including a clear experimental investigation of polarization effects. In this paper, following a succinct review of the progress that has been made, spontaneous and piezoelectric polarization effects and their impact on sample device-like hetero-structures will be treated. Received: 5 April 1999 / Reviewed and accepted: 19 April 1999     

A new device for the recording and summation of periods of time

Summary The described device makes it possible to determine the sum of a considerable number of arbitrary periods of time and to record the number of these periods. The instrument makes it considerably easier to determine the second and its hundredths by reducing the time needed for calculations. In addition, the computing chronoscope, whose output is binary, can form a basis for the automation of the calculation processes which are carried out in determining time.     

Real time neutron radiography using a Lixi neutron imaging device

A real time neutron radiography system has been developed at the University of Michigan Phoenix Memorial Laboratory (PML) and has recently been used to test the imaging capabilities of a neutron imaging device developed by Lixi, Inc. of Downers Grove, Ill. This device uses an input phosphor that is high in gadolinium to generate a light image which is then sent through an intensifier stage to provide images that can be viewed by eye, video camera, or standard 35 mm camera. It was determined that this device provides images of much higher resolution and sensitivity than those obtained with the imaging system currently being used at PML. Using computerized image enhancement techniques, the images obtained with the Lixi neutron imaging device can then be futher enhanced or processed to obtain quantitative information on the object being imaged.     

On the evaluation of the time of periodical dissolution of a dispersed material in a rotor-pulse device

Results are presented of experimental and numerical investigations of the kinetics of periodical dissolution of benzoic and salicylic acids in water using the rotor-pulse device. It is found that the process obeys the firstorder kinetics. A determining influence of the rotation frequency of the device rotor and the size of the radial gap between the rotor and the stator on the dissolution time is shown. Favorable agreement between the experimental and calculated time dependences for the concentration of the dissolved substance are obtained.     

Mechanical effects in a vortex device with a rotating core

The process of the appearance of forced rotation of an axial core mounted in a modified vortex tube in the direction opposite to the rotation of the air vortex and the precession of its axis have been studied. It has been established that dynamical bending of a metal axial core arises in the process of rotation which causes mechanical wear of its end part and fracture in the fastening area of the bearing without residual curvature of the core axis. The excitation of rotation and observed force effects are not related to the mechanical action of rotating air flow on the axial core.     

Local density of states effects at the metal-molecule interfaces in a molecular device

Clarifying the nature of interactions between metal electrodes and organic molecules still represent one of the challenging problems in molecular electronics that needs to be solved in order to optimize electron transport through a molecular device. For this purpose, electronic properties at metal-molecule interfaces were studied by combining experimental and theoretical methods. Applying a novel electrochemical approach, strictly two-dimensional Pd islands were prepared on top of 4-mercaptopyridine self-assembled monolayers (4MP-SAMs) which, in turn, were deposited on (111)-oriented Au single crystals. Electron spectroscopy together with density functional theory calculations revealed strong interactions between the molecules and the islands due to Pd-N bonds, resulting in a drastically reduced density of states (DOS) at the Fermi level EF for a nearly closed Pd monolayer, and even non-metallic properties for nanometre-sized islands. Similarly, a significantly reduced DOS at EF was observed for the topmost Au layer at the Au-SAM interface due to Au-S interactions, suggesting that these effects are rather general.     

Fluorescence-based blood coagulation assay device for measuring activated partial thromboplastin time

The measurement of blood clotting time is important in a range of clinical applications such as assessing coagulation disorders and controlling the effect of various anticoagulant drug therapies. Clotting time tests essentially measure the onset of clot formation which results from the formation of fibrin fibers in the blood sample. However, such assays are inherently imprecise due to the highly variable nature of the clot formation process and the sample matrix. This work describes a clotting time measurement assay which uses a fluorescent probe to very precisely detect the onset of fibrin clot formation. It uses a microstructured surface which enhances the formation of multiple localized clot loci and which results in the abrupt redistribution of the fluorescent label at the onset of clot formation in both whole blood and plasma. This methodology was applied to the development of an activated partial thromboplastin time (aPTT) test in a lateral flow microfluidic platform and used to monitor the effect of heparin dosage where it showed linearity from 0 to 2 U/mL in spiked plasma samples (R(2)=0.996, n = 3), correlation against gold standard coagulometry of 0.9986, and correlation against standard hospital aPTT in 32 patient samples of 0.78.     

Censored Sampling in Curtailed Sampling Plans by Attributes

In this paper we have considered four different ways of reporting the results of sampling inspection associated with the curtailed sampling plans of [2]. These cases take into consideration that some information of the inspection results is suppressed and hence these cases turn to be particular cases of censored sampling. Maximum likelihood estimate of the fraction defective and its asymptotic variance are obtained and comparison is made between the cases considered here and cases in [2].     

A Double Sampling Procedure to Control the Variance in Net Weight Acceptance Sampling

This paper describes a double sampling scheme to estimate with at least a given precision the mean of a variate whose variance has two components one of which is unknown. Although the procedure is described almost entirely in terms of a particular problem (quality control of net weight), it may be applied in a more general situation (section 5). The consequences of using either the mean square error or the range to estimate variance are investigated.     

The effects of time delays in adaptive phase measurements

Abstract

It is not possible to make measurements of the phase of an optical mode using linear optics without introducing an extra phase uncertainty. This extra phase variance is quite large for heterodyne measurements, however it is possible to reduce it to the theoretical limit of log [nbar]/(4[nbar]2) using adaptive measurements. These measurements are quite sensitive to experimental inaccuracies, especially time delays and inefficient detectors. Here it is shown that the minimum introduced phase variance when there is a time delay of log τ is τ/(8[nbar]). This result is verified numerically, showing that the phase variance introduced approaches this limit for most of the adaptive schemes using the best final phase estimate. The main exception is the adaptive mark II scheme with simplified feedback, which is extremely sensitive to time delays. The extra phase variance due to time delays is considered for the mark I case with simplified feedback, verifying the τ/2 result obtained by Wiseman and Killip both by a more rigorous analytic technique and numerically.     

Interdisciplinarity and impact: the effects of the citation time window

Scientometrics - The relationship between interdisciplinarity and citation impact is affected by many factors, and the citation time window is a crucial factor. Our study examines the effect of the...     

Estimating the effects over time of alcohol on injury severity

Estimates of the effect of blood alcohol on injury severity obtained through studies of patients at clinical facilities have been found to be quite different from those estimated through the analysis of highway accident data. Several factors have been suggested to account for these differences, including consideration of the relative frequencies of alcohol-involved and alcohol free drivers who were killed at the scene or who died before reaching a treatment facility. More generally, the nature of the way that the effect of alcohol varies as a function of time from injury may play a important role. In this paper information from highway accident data was combined with time of death information from state medical examiner files to yield estimates of the function P(T), the probability that an injured driver dies at the time T or later from an injury occurring at T = 0, for classes of crash-involved drivers with differing blood alcohol concentrations. Other factors also considered in the analyses included measures of crash severity, driver age, and restraint use. Elevated blood alcohol was consistently found to be associated with shorter survival times.     

The effects of element shape on the critical time step in explicit time integrators for elasto‐dynamics

In this paper, the effects of element shape on the critical time step are investigated. The common rule‐of‐thumb, used in practice, is that the critical time step is set by the shortest distance within an element divided by the dilatational (compressive) wave speed, with a modest safety factor. For regularly shaped elements, many analytical solutions for the critical time step are available, but this paper focusses on distorted element shapes. The main purpose is to verify whether element distortion adversely affects the critical time step or not. Two types of element distortion will be considered, namely aspect ratio distortion and angular distortion, and two particular elements will be studied: four‐noded bilinear quadrilaterals and three‐noded linear triangles. The maximum eigenfrequencies of the distorted elements are determined and compared to those of the corresponding undistorted elements. The critical time steps obtained from single element calculations are also compared to those from calculations based on finite element patches with multiple elements. Copyright © 2014 John Wiley & Sons, Ltd.