Simple model for the hysteretic behavior of thin-filmelectroluminescent devices

The hysteretic behaviour of TFEL (thin-film electroluminescent) devices can be simulated relatively well with the numerical model introduced by W.E. Howard et al. (1982). An approximate model is developed by introducing a time-independent space-charge distribution. With this method, steady-state solutions can be calculated very efficiently. Hysteretic curves obtained with this method are given for different frequencies, and the results are discussed     

Dealing with hysteretic sensors: investigation on quasi-static behavior

Piezoelectrics, ferroelectrics, and ferromagnetics show hysteretic (intrinsically nonlinear) input-output characteristics. The interest in understanding the behavior of hysteretic devices is due to their useful characteristics, especially when used as detectors. This article studies the quasi-static behavior of hysteretic devices.     

Space-charge effect on large-signal behavior of transit-time-effect devices

A unified view of the latge-signal behavior of transit-time-effect diodes under cartier injection in-phase with the cathode field is given by modeling the injection characteristic as an exponential dependence on cathode field. The concept consists of an extension of a unified view of small-signal behavior by introducing another parameter which expresses the nonlinearity of injection in addition to small-signal injection conductance, and by assuming velocity saturation. Phase advance and suppression of injection current due to space-charge effect are influential factors which dominate the large-signal behavior and which impose a limitation on output power. The present treatment gives a way for optimizing the device and circuit as well as for estimation of the ultimate available power for a given carrier-injection characteristic.     

Negative dynamic resistance in MOS devices

An electro thermal model is presented to explain negative dynamic resistance phenomena observed in the saturation region of MOS transistors operating at moderate and elevated power levels (P/SUB d//spl ges/300 mW).     

Quasi-static behavior of MOS devices in the freeze-out regime

The quasi-static CV curves (low-frequency C-V curves) measured in the freeze-out regime of MOS transistors result in peaks near the accumulation or inversion regions depending on the direction of the voltage sweep. In this paper, we report a study of these peaks in n- and p-channel CMOS transistors within and outside compensating wells. The peaks in the quasi-static CV curves are attributed to the capture of minority carriers near inversion by the interface states and the capture of majority carriers by the interface states near accumulation     

基于触屏行为的智能移动设备身份认证

在移动设备的身份认证方面,传统密码认证方式易受到窥肩攻击和屏幕解锁痕迹攻击,不足以保证移动设备隐私安全.本文提出一种基于触屏行为的身份认证方案,获取手指与屏幕交互数据,经预处理后提取触屏行为特征向量,用机器学习算法训练后生成认证模型,对用户进行身份认证.与传统密码身份认证不同,该方案以用户触屏行为信息作为认证密钥,持续检测移动设备用户真实性,即使攻击者看到用户操作行为也很难再现,提高了身份认证安全性.经实验验证,基于触屏行为的身份认证实现了94.42％的认证准确率.     

The characterization of the static behavior of p-n junction devices

This paper examines the static behavior of certain p-n junction devices that are governed by Van Roosbroeck's differential equations. It is found that this set of first-order differential equations accurately predicts semiconductor static behavior in both the bulk and the transition regions. The purpose of this model is to find the hole and electron concentrations, hole and electron currents, and electric field as functions of position and external excitation. For part of the paper, use is made of the quasi-neutrality approximation in the bulk regions and the quasi-equilibrium Boltzmann relations (QEBR) which relate the hole and electron concentrations at transition region edges to the applied voltage across the transition region. The unijunction transistor with intrinsic base, p-i and p-in diodes, and a new current gain device are examined using these concepts, and the results are compared with experiment. By applying boundary conditions only at the ohmic contacts, a p-i diode problem is solved on a computer. One especially important point in this problem is that quasi-neutrality of the base and the QEBR are not imposed upon the problem. However, the final results indicate that these concepts are good approximations, except for extremely short devices.     

Theoretical analysis of transient behavior of optoelectronicintegrated devices

Transient behavior of an optoelectronic integrated device composed of a heterojunction phototransistor and a light-emitting diode is studied theoretically. The transient behavior of the integrated device is investigated by considering: 1) the frequency response of a phototransistor and a light-emitting diode, and 2) the optical feedback inside the devices. The analytical expressions describing the transient response of the integrated device are derived, and the rise times in both the amplification and the switching modes also are calculated. By increasing the optical feedback, the rise time in the amplification mode is increased along with an increasing output, while that in the switching mode can be reduced effectively with a saturated output     

Influence of silicon crystal defects and contamination on the electrical behavior of power devices

Since power devices require a thick electrically active n-type silicon layer with high resistivity and a large area, their electrical characteristics are extremely sensitive to contamination. If heavy metals diffuse into the silicon wafers during the high-temperature steps, an uncontrolled increase in the leakage current and the on-state voltage can be observed. Furthermore, current filamentation and instabilities of the electrical data can occur. It turned out that the optimization of the cleaning processes, high-temperature steps and gettering treatments alone is not sufficient to avoid such effects. It is also important to avoid silicon crystal defects by proper processing. A dramatic increase in the leakage current was correlated with the appearance of silicon defects decorated with heavy metals. As a consequence of the low doping level of the n-base, the blocking voltage and the failure rate due to cosmic radiation are sensitive to contaminating atoms acting as donors.     

Optimal dynamic transport selection for wireless portable devices

Recent technological advances in mobile computing and wireless communication have made portable devices, such as PDA, laptops, and wireless modems to be very compact and affordable. On the other hand, wireless networks have gained such wide popularity that new network infrastructure is continually introduced. It is thus likely that many of the future portable devices will be equipped with multiple wireless modems such as Bluetooth and 802.11 WLAN, in order to increase device inter‐operability. The availability of multiple modems can leverage the performance of the communication traffic generated by the applications, for example Internet access. We envision a tool for managing the device connection through these modems. At the core of this tool is an optimization engine that splits packet traffic across a subset of the available transports so that user's performance metrics are maximized. This paper describes a mathematical model for such an optimization problem considering its applicability to small portable devices. Relevant quality of service (QoS) parameters such as bandwidth, average delay, and energy consumption are covered in the model. The mathematical formulation is validated using a simulated environment. The experimental results have demonstrated the effectiveness of our model and captured the inter‐relationship among the quality parameters. Copyright © 2006 John Wiley & Sons, Ltd.     

U型动力救生装置的仿真优化分析

针对落水者的安全快速营救问题,提出了对U型动力救生装置优化设计方案.该方案从减阻外形、动力优化、安全性优化分析三个角度出发,采用基于UGNX11.0软件创建U型动力救生装置的三维模型,获得符合人体工学的结构设计;基于Solidworks flow simulation进行计算流体力学(CFD)仿真分析,获得优化的减阻外...     

Notes on the asymptotic behavior of the information rate of block codes (Corresp.)

The behavior of the signaling rate of error-correcting codes of lengthnand minimum distanced_{n}is studied in the limit for largenwhen the sequenced_{n}/napproaches a prescribed limitdelta. A functionR(delta)representating the asymptotic signaling rate is defined and is shown to be continuous.     

Optimisation of dynamic interface selection mechanisms on multi-radio devices in ad hoc networks

Selecting the most appropriate output interface on multi-radioequipped terminals leads to an optimised system. The results from both experimental and simulated analyses of two different strategies on dynamic selection of the outbound interface on multi-radio devices in wireless ad hoc networks are presented and compared. Findings from the studies are twofold. First, they show that intelligent selection of a communication interface in heterogeneous ad hoc networks leads to enhanced performance in terms of throughput and packet loss. Secondly, different strategies result in optimisation of different parameters. This latter aspect is particularly interesting since a cognitive user-centric use of the different strategies could be leveraged in order to best serve the specific service and user originated requirements.     

Modeling the static and dynamic behavior of quarter-wave-shiftedDFB lasers

High-coupling (grating coupling constant=3.0) phase-shifted distributed-feedback (DFB) lasers are studied using a transmission-line laser model (TTLM) which includes spatial hole burning (SHB), the material gain spectrum, refractive index dependence on carrier concentration, and random spontaneous emission. Good agreement for CW spectra is shown with other models and experimental results. Dynamic simulation of laser transients shows SHB-induced deterministic mode hopping and chirping at moderate output powers. The effects of mode hopping and chirping on system performance are studied using a laser model combined with a fiber model     

脉冲方波驱动强化热电制冷的瞬态特性

采用有限差分法对脉冲电压驱动下的瞬态热电效应及其动态特性过程进行了理论分析,探索了非稳态工况下帕尔帖效应、焦耳热效应与傅里叶导热效应之间的耦合关系及其关键制约因素对制冷性能的影响规律,进而探讨了脉冲驱动强化热电制冷性能的作用机理。分析结果得到,在合理电压域值内采用主动控制方法,对热电模块周期性施加数倍于稳态工况理想电压的脉冲突变电压,有益于充分利用帕尔贴制冷效应而推迟出现以焦耳热和傅里叶热耗散形式为主的内部热积聚对热电模块冷端引起的负效应,并能瞬态实现冷端面的制冷强化作用和最大程度实现输入电能的有效转换。该结论不仅为进一步提出脉冲驱动模式的优化控制策略提供了理论依据,也为瞬态热电制冷效应的应用开辟了一条新思路。     

Controlling the dynamic behavior of light emitting electrochemical cells

Light emitting electrochemical cells (LECs) present an attractive route towards cost efficient lighting applications. By utilizing ionic phosphorescent transition metal complexes, efficient electroluminescence can be realized from a single layer device using air stable electrodes. These devices achieve efficient charge carrier injection due to ion accumulation at the interface upon driving, resulting in a dynamic response upon device operation. Here we investigate the device operation by using fast current and luminance versus voltage sweeps during normal fixed bias operating. A universal set of JL–V curves can be identified in which different regimes are observable. The speed and extent in which a LEC evolves through this set of curves can be controlled by varying the driving voltage, enabling the device to operate in it maximum efficacy state.     

Numerical method for the solution of the transient behavior of bipolar semiconductor devices

A numerical technique is presented which permits a computer solution of the complete set of time dependent partial differential equations governing bipolar semiconductor behavior. The scheme does not require any of the often made assumptions and approximations such as abrupt junctions, quasi-neutrality or restricted injection levels. The resulting solution describes device terminal properties and gives a detailed account of internal parameters as a function of time and distance.The present method is distinguished from others by the use of the technique of quasilinearization which converts the nonlinear boundary value problem into a linear form. The latter is solved iteratively, yielding highly stable and convergent solutions. The method uses the complete form of Poisson's equation and an implicit time advancement formulation to generate a stable time trajectory of the solution. The Scharfetter-Gummel spatial discretization scheme is used for greater accuracy.Computer and experimental results are given and compared for the transient behavior of a p⁺nn⁺ diode structure. Both forward and reverse transients are described.     

Compact modeling of vertical hall-effect devices: electrical behavior

This paper presents the development of a design-oriented compact model of vertical Hall-effect sensors integrated in CMOS technologies. Such a model makes easier the design of integrated Hall systems, permitting designers to co-simulate the Hall sensing element with the biasing and processing electronics thanks to a single electrical simulator. Here focus is put on the electrical behavior, i.e. the resistive behavior of a 5-contact vertical Hall device. The model is based both on theoretical considerations and on FEM numerical simulations performed with COMSOL^®. The result is a new predictive compact model, written in Verilog-A, with 7 input terminals and 14 parameters, mainly sensor geometrical and technological parameters. These parameters can be easily extracted from measurements carried out on a single sensor. The compact model has been validated by FEM simulations, as well as by comparing its response with experimental results obtained from a vertical Hall device fabricated in a CMOS 0.35 μm technology. The root mean square error of the model with respect to experimental results obtained on a wide range of typical sensor biasing conditions is below 2 %. Such a resistive model opens the way to an efficient, complete compact model of the vertical Hall device, i.e. including the Hall-effect as well as all the second-order galvanomagnetic effects.     

Effect of dynamic aging of dislocations on the deformation behavior of extrinsic semiconductors

The Alexander-Haasen theory of deformation in semiconductor crystals with low dislocation density was generalized by taking into account the effect of dynamic aging of dislocation caused by the impurity drag. The generalized theory explains some qualitative distinctions of the elastic-plastic transition in Czochralski-grown Si crystals from that in crystals of higher purity. Particularly, this concerns the dependence of the height of the yield-point peak on the initial dislocation density and the weakening of the strain-rate sensitivity of the yield stress.     

Influence of post-stress effects on the dynamic hot-carrierdegradation behavior of passivated n-channel MOSFET's

An apparently non-quasi-static degradation behavior is found for nMOS transistors that are dynamically stressed with conditions which favor hot-hole injection. This effect can be ascribed to a post-stress effect occurring during the waiting time between the different pulses. It is shown that this effect is of importance only when a net positive charge is built up during the stress. The deviating behavior under dynamic stress conditions can be predicted based on the measurement of the post-stress effect after a static degradation