A virtual scanning electron microscope. 4. Simulator-based implementation

A virtual scanning electron microscope (VSEM), which is based on a simulator of information, obtained on a real scanning electron microscope (SEM), is described. A semiempirical generation model of images in a SEM, operating in the low-voltage mode and high-voltage mode during recording backscattered and secondary slow electrons, forms the basis of a virtual SEM. A method of comparing real and virtual images is proposed. Examples of operation of the virtual SEM are given for elements of structures which are located both far from the edges of the structure and near these edges.     

一种基于H.264的视频转码方案

本文提出了一种基于H.264降低图像尺寸转码中的宏块类型快速选择方案.文中以原始图像中对应四个宏块的非零系数总个数为准则选择宏块类型,首次提出以指数模型来描述阈值和重新量化参数的关系(Th-Q_r模型),并将其线性化为一元线性回归模型,进一步使用最小二乘法来估计模型中的参数.帧内模式选择中,Th-Q_r模型是用来区分I4×4和I16×16宏块;帧间模式选择中,Th-Q_r模型区分出当前宏块所处区域的运动性质,进而简化候选宏块类型个数.实验结果表明,与全搜索法相比,在保证压缩性能损失不大的情况下,本文提出的帧内模式选择方法的速度能提高4到5倍,帧间模式选择方法的速度能提高约35倍.     

A multiscale expectation-maximization semisupervised classifier suitable for badly posed image classification.

This paper deals with the problem of badly posed image classification. Although underestimated in practice, bad-posedness is likely to affect many real-world image classification tasks, where reference samples are difficult to collect (e.g., in remote sensing (RS) image mapping) and/or spatial autocorrelation is relevant. In an image classification context affected by a lack of reference samples, an original inductive learning multiscale image classifier, termed multiscale semisupervised expectation maximization (MSEM), is proposed. The rationale behind MSEM is to combine useful complementary properties of two alternative data mapping procedures recently published outside of image processing literature, namely, the multiscale modified Pappas adaptive clustering (MPAC) algorithm and the sample-based semisupervised expectation maximization (SEM) classifier. To demonstrate its potential utility, MSEM is compared against nonstandard classifiers, such as MPAC, SEM and the single-scale contextual SEM (CSEM) classifier, besides against well-known standard classifiers in two RS image classification problems featuring few reference samples and modestly useful texture information. These experiments yield weak (subjective) but numerous quantitative map quality indexes that are consistent with both theoretical considerations and qualitative evaluations by expert photointerpreters. According to these quantitative results, MSEM is competitive in terms of overall image mapping performance at the cost of a computational overhead three to six times superior to that of its most interesting rival, SEM. More in general, our experiments confirm that, even if they rely on heavy class-conditional normal distribution assumptions that may not be true in many real-world problems (e.g., in highly textured images), semisupervised classifiers based on the iterative expectation maximization Gaussian mixture model solution can be very powerful in practice when: 1) there is a lack of reference samples with respect to the problem/model complexity and 2) texture information is considered negligible (i.e., a piecewise constant image model holds).     

A study of diffused bipolar transistors by electron microscopy

Shallow junction bipolar transistors have been fabricated on bulk (001) silicon starting material using a diffusion processing technology. The resultant junction depths were about 0.5 and 0.8 μ m respectively for the emitter-base and base-collector junctions. The crystallographic defects present have been detected and characterized using a combination of electrical measurements, the electron beam induced current (EBIC) mode of the scanning electron microscope (SEM) and both conventional and high voltage transmission electron microscopy (TEM).Two types of dislocations were identified in the TEM. The first consisted of an orthogonal array of sessile, diffusion-induced edge dislocations located about halfway down in the heavily doped emitter. The second type consisted of 60° glissile dislocations that looped down from the orthogonal array and in some cases penetrated the emitter-base junction.Observations of a number of 60° dislocations yielded a good correlation between their depth and their contrast when imaged in the EBIC mode of the SEM. The 60° dislocations locally retard the emitter diffusion when they lie near to the emitter-base junction. Local breakdown effects under reverse bias were observed at the sites of these dislocations.     

Microelectronic test structures for rapid automated contactlessinline defect inspection

Simple but unique and space-saving microelectronic test structures were designed to afford automated inline contactless defect inspection in a Scanning Electron Microscope (SEM)-voltage contrast (VC) mode for rapid electrical defect-monitoring, along with in situ defect-isolation and characterization capabilities. Such an automated inspection can support accelerated yield learning through increased defect-learning cycles, particularly on the sub-0.25-μm-rule designs, as defects below optical resolution become significant. The system is also capable of the traditional visual inspection in the high-energy secondary-electron emission mode, affording the accurate determination of the “transfer coefficients” between the optical inspection results and the electrical faults from the SEM-VC inspection, needed for any foreign-material or contamination-to-yield model with high correlation or at a high confidence level     

Resistive contrast imaging: A new SEM mode for failure analysis

Semiconductor device path resistance is obtained from scanning electron microscope (SEM) images using a modified electron-beam-induced current (EBIC) mode. We call this new method resistance contrast imaging (RCI). The intensity of these images is proportional to internal device resistance ratios. Applications of the RCI method to device failure analysis are presented. This method is non-destructive and applicable to passivated devices.     

A dynamical polarization mode dispersion emulator

A polarization mode dispersion (PMD) emulator is presented which accurately follows the dynamics of PMD in field optical fiber. A modification on a dynamic mode coupling wave-plate model is presented to model the emulator. It is found that the emulator and model can accurately describe the dynamical behavior of the state of polarization and thus PMD in a field fiber. The emulator is shown to be repeatable. Generally, the dynamical PMD emulator is shown to cause more realistic bit-error-rate degradation than a classical PMD emulator.     

基于重核衰变原理的单电子存储器寿命模型

单电子存储器是依据库仑阻塞原理操纵单个电子进行信息存储的一种量子器件。它具有低功耗、高速度、极小尺寸的优点,是现有存储器极有希望的替代品。信息的记忆性能是衡量存储器的一个重要参数,因而对单电子存储器的记忆性能研究有重要的意义。存储器的结构以及温度、电磁辐射等环境因素都对单电子存储器记忆时间产生影响,因而有必要寻求一种模型来综合各种因素对储存器存储寿命的影响。借鉴Gamow、Gurney和Condon处理某些重核α粒子自然衰变的方法对单电子存储器的记忆能力进行研究,考虑到了环境参数和结构参数对记忆性能的影响,给出了一种新的单电子存储器记忆时间模型,并对该模型进行详细的理论分析。     

服务网格的用户3A使用模式

用户如何方便有效地使用网格是网格界面和使用模式研究的一个关键问题,用户3A使用网格,即Any time,Any place,and on Any device,体现了用户对网格使用的基本需求.本文给出了用户3A使用模式的形式定义,并利用ASM(Abstract State Machine)对用户和服务网格(USG)进行了形式化建模,最后证明了用户和服务网格系统在满足用户合法性、session连通性和服务连续性的情况下,用户可以3A使用服务网格.     

Pt/YSZ电极结构形貌的表征

根据YSZ型氧传感器中O在电极表面的吸附、扩散以及Pt/YSZ界面O(Pt电极中)/O2(YSZ中)的传递的机理,提出了一种对Pt /YSZ电极界面进行定量表征的模型。用此模型对不同烧结温度下的电极形貌Pt/空气/ YSZ三相界面长度进行了定量表征,同时,采用复阻抗测试技术和氧传感器响应测试技术对表征结果的合理性进行了验证。理论推算和试验结果都表明:采用1 000℃,1 h烧结的电极形貌具有最佳的电化学性能。     

提高H.26L压缩视频抗误码性能的全局率失真优化方法

该文从较新的H.26L视频压缩编码标准出发,并结合Internet信道的Bernoulli和Gilbert 的包丢失模型,提出了一种全局率失真优化的编码模式判决方法,使编码的视频流具有更强的错误恢复能力。实验证明,在实际的Internet信道误码环境下,此方法具有更强的抗错误和实用性,得到了较好的效果。     

A calculus for network delay. I. Network elements in isolation

A calculus is developed for obtaining bounds on delay and buffering requirements in a communication network operating in a packet switched mode under a fixed routing strategy. The theory developed is different from traditional approaches to analyzing delay because the model used to describe the entry of data into the network is nonprobabilistic. It is supposed that the data stream entered into the network by any given user satisfies burstiness constraints. A data stream is said to satisfy a burstiness constraint if the quantity of data from the stream contained in any interval of time is less than a value that depends on the length of the interval. Several network elements are defined that can be used as building blocks to model a wide variety of communication networks. Each type of network element is analyzed by assuming that the traffic entering it satisfies bursting constraints. Under this assumption, bounds are obtained on delay and buffering requirements for the network element; burstiness constraints satisfied by the traffic that exits the element are derived     

基于H.264具有抗分组丢失能力的帧内刷新算法

 本文提出一种基于H.264的具有抗分组丢失能力的帧内刷新算法.该算法首先建立帧内刷新尺度矩阵,来记录每个宏块被后继帧参考的重要程度;然后,基于帧内刷新尺度矩阵提出了丢包环境下的端到端率失真模型(ME2ERD);接下来,利用H.264中补充增强信息域进行信息交互,结合ME2ERD模型自适应进行帧内刷新,从而降低分组丢失对恢复图像质量的影响.实验结果表明在高丢包率环境下,使用本文提出的帧内刷新算法,与使用随机帧内刷新算法相比,恢复图像的平均PSNR(峰值信噪比)提高5dB以上.算法与H.264标准兼容,且运算复杂度低,具有实用价值.     

Time-domain techniques in the singularity expansion method

New methods of determining the natural frequencies and natural modes of a structure as characterized in the singularity expansion method (SEM) are presented. The method is based on the time-domain scattering equation which can be east in the form of a matrix difference equation. The homogeneous solution of the difference equation is a series of exponentials as found in the SEM representation. The natural frequency and mode solutions may be obtained either from the determinant of a matrix sum, which is similar to the current frequency-domain search method, or by an eigenvalue approach as in systems theory. The latter has shown promise for efficient SEM computations. An example of each approach is presented.     

A Transmission-Line Model for Full-Wave Analysis of Mixed-Mode Propagation

The paper presents a generalized transmission line model able to describe the high-frequency mixed-mode propagation along electrical interconnects. The model is derived from a full-wave formulation and extends the validity of the standard transmission line (TL) model to frequency ranges where the propagation is no longer of transmission electron microscopy (TEM)-type. This generalized TL model describes the high-frequency differential and common mode propagation and the mode conversion. Within its validity limits, the proposed model provides solutions in good agreement with those obtained through full-wave models. Case studies are carried out to evaluate the high-frequency mode conversion in asymmetric interconnects.     

A model of write-inhibition in dynamic injection MNOS

Dynamic Injection MNOS (DIMNOS) memory devices feature high-speed writing, 5-V drain voltage, and MNOS backup one-transistor-type dynamic RAM's. They are written on MNOS, like conventional one-transistor-type dynamic RAM's, when high writing voltage is applied to the MNOS gate. In experiments with DIMNOS, the threshold-voltage shift (Delta V_{th}) of MNOS in the writing mode does not depend very much on temperature;Delta V_{th}in the write-inhibited mode depends hardly at all on temperature; andDelta V_{th}in the write-inhibited mode decreases under the condition that the product of the number of attempts and pulsewidth is constant when he pulsewidth is longer than 10^-4s. The proposed model in the write-inhibited mode means that weak avalanche occurs due to field concentration between the control transistor and MNOS memory region. As a result, hot electrons are injected between the ultrathin SiO2and Si3N4films of MNOS. This model is supported by the above mentioned experimental results in the write-inhibited mode.     

A refined nonlinear averaged model for constant frequency currentmode controlled PWM converters

A refined, duo-mode model for current programmed buck power converters is presented. The refined model uses a form of the current mode control law which is truly invariant with respect to operating conditions. That is, it is valid for both transient and steady-state operating conditions regardless of the converter operating mode, which could be either continuous conduction mode (CCM) or discontinuous conduction mode (DCM). The large-signal transient response predicted using the refined average model is shown to be virtually indistinguishable, in an average sense, from that predicted using a pulse-by-pulse simulation. The refined model is shown to exhibit improved high-frequency accuracy in both time and frequency domains. The model has been implemented in SPICE 2G6 and runs with default analysis options     

A unified analysis of PWM converters in discontinuous modes

Three discontinuous operating modes of PWM (pulsewidth modulated) converters are considered: the discontinuous inductor current mode (DICM), the discontinuous capacitor voltage mode (DCVM), and a previously unidentified mode called the discontinuous quasi-resonant mode (DQRM). DC and small-signal AC analyses are applicable to all basic PWM converter topologies. Any particular topology is taken into account via its DC conversion ratio in the continuous conduction mode. The small-signal model is of the same order as the state-space averaged model for the continuous mode, and it offers improved predictions of the low-frequency dynamics of PWM converters in the discontinuous modes. It is shown that converters in discontinuous modes exhibit lossless damping similar to the effect of the current-mode programming     

Heating characteristics of thin helical antennas with conductingcores in a lossy medium. I. Noninsulated antennas

We report a combined theoretical and experimental study of the heating characteristics of helical antennas in lossy dielectric media. Proposed biomedical application of such antennas include angioplasty, hyperthermia, and catheter ablation of tissue. The study focuses on helical antennas, operated in the normal mode (wavelength greater than antenna diameter but comparable to antenna length), that are terminated at one end by a short circuit and at the other by a coaxial feedpoint. The analytical model is based on the helical sheath approximation, extended to the case of lossy media. In addition, experimental studies were performed on helical antennas immersed in aqueous electrolyte of various conductivity. The antennas show two distinct modes of propagation: a slow mode similar to that observed in helical antennas in loss-free media, and a faster mode. The analytical/numerical results are in good agreement with experimental data, thus demonstrating the validity of the model