一种新的电源定序方法

目前,大部分为通信和数据处理应用而设计的电路板需要多种集成电路供电电压.长期以来,在上电和断电过程中正确的给这类电源定序一直是个设计问题,这个问题由于最新集成电路的苛刻要求而日益严重.本文考察了各类定序方法,重点阐述了具有内置定序特性的新一代模块式负载点(POL)转换器,它提供了一种特别有成本效益的解决方案.     

提高便携式超声波系统的图像质量

便携式超声波系统是紧急护理点使用的强大诊断工具之一。这种无创成像工具让许多自然灾害如地震、飓风和路侧事故等中的受害者能够快速地得到的诊断和治疗。这种便携式设备大小不一,从膝上型到手持式,重量为10磅甚至更轻,并且可以使用电池供电。由于得到新兴超声波市场的广泛认可,在最近几年发展势头迅猛。     

SN65LVDS32B的有源故障保护电路特性

差分式数据线路接收器在没有输入信号的情况下,会受噪声影响.这种情况发生在总线驱动器被关闭或连接电缆损坏和断开的时候.通常,这个问题用外部电阻网络在未被信号驱动的输入引脚上施加固定值偏压来解决.除了外部元件的成本之外,这种办法会降低输入信号的幅度并减小差分噪声容限.     

The Performance of the Adaptive Aggregation Mechanism (AAM) Under Mixed Traffic Loads

The adaptive packet aggregation algorithm (AAM) has been shown to have a superior performance over the first-in first-out (FIFO) algorithm in terms of the throughput and delay (Deng and Davis in International conference on wireless communications and signal processing 2013 (WCSP2013), Hangzhou, China, pp 449–504, 2013; 20th IEEE symposium on communications and vehicular technology in the Benelux 2013 (IEEE SCVT 2013), Namur, 2013). In this paper, we will show that when compared with the FIFO and smallest-size first-served algorithms, the AAM algorithm has the best performances in terms of the trade-off between the overhead saving and the average delay under mixed traffic loads in wireless LANs. The simulation results show that the AAM algorithm produces the largest average aggregate packet size.     

In Situ Study of Nanostructure and Electrical Resistance of Nanocluster Films Irradiated with Ion Beams

An in situ study is reported on the structural evolution in nanocluster films under He⁺ ion irradiation using an advanced helium ion microscope. The films consist of loosely interconnected nanoclusters of magnetite or iron‐magnetite (Fe‐Fe₃O₄) core‐shells. The nanostructure is observed to undergo dramatic changes under ion‐beam irradiation, featuring grain growth, phase transition, particle aggregation, and formation of nanowire‐like network and nanopores. Studies based on ion irradiation, thermal annealing and electron irradiation have indicated that the major structural evolution is activated by elastic nuclear collisions, while both electronic and thermal processes can play a significant role once the evolution starts. The electrical resistance of the Fe‐Fe₃O₄ films measured in situ exhibits a super‐exponential decay with dose. The behavior suggests that the nanocluster films possess an intrinsic merit for development of an advanced online monitor for fast neutron radiation with both high detection sensitivity and long‐term applicability, which can enhance safety measures in many nuclear operations.     

Simulation of Terahertz Generation from Lateral Diffusion Currents in Semiconductor Devices

In this paper we model the carrier dynamics and resulting THz emission from lateral diffusion currents within a semiconductor device which has been partially masked by a metallic mask. We present a numerical 1D model and a 1D Monte Carlo simulation which both demonstrate that regardless of the excitation laser spot shape we do not expect to see measurable THz emission in the direction of the optical pump propagation from lateral diffusion currents. Experimentally such devices do produce strong THz emission. We analytically investigate the role of the metal mask and we found that it suppresses the emission of dipoles that are in a region that is less than a wavelength away from the interface. The results from the numerical model are also included in a finite element analysis model of the geometry which predicts THz emission if and only if the metal mask is present.     

Analogue electronic circuit diagnosis based on ANNs

Feed-forward artificial neural networks (ANNs) have been applied to the diagnosis of nonlinear dynamic analogue electronic circuits. Using the simulation-before-test (SBT) approach, a fault dictionary was first created containing responses observed at all inputs and outputs of the circuit. The ANN was considered as an approximation algorithm to capture mapping enclosed within the fault dictionary and, in addition, as an algorithm for searching the fault dictionary in the diagnostic phase. In the example given DC and small signal frequency domain measurements were taken as these data are usually given in device’s data-sheets. A reduced set of data per fault (DC output values, the nominal gain and the 3 dB cut-off frequency, measured at one output terminal) was recorded. Soft (parametric) and catastrophic (shorts and opens) defects were introduced and diagnosed simultaneously and successfully. Large representative set of faults was considered, i.e., all possible catastrophic transistor faults and qualified representatives of soft transistor faults were diagnosed in an integrated circuit. The generalization property of the ANNs was exploited to handle noisy measurement signals.     

Vector-adaptive vector quantization with application to speechcoding

A vector-adaptive vector quantization (VAVQ) scheme, which may be viewed as a generalization of gain-adaptive vector quantization, is described. The proposed scheme adjusts each component of the encoding signal vector according to a statistical estimate of the signal characteristics. The VAVQ scheme can cope with large input dynamic ranges. It can be used in either the time domain or the transform domain, and exhibits approximately 4 dB improvement in segmental signal-to-noise ratio (SNR) over the fixed VQ