Spectral estimation with rational modeling of the log spectrum

A new type of methods for spectral estimation is presented starting from the Burg's variational formulation. These methods assume as data an accurate set of autocorrelation values and estimate the spectrum by modeling its logarithm with a rational function. They are compared with the Blackman-Tukey and the maximum entropy methods both theoretically and experimentally. Iterative algorithms of descent type making use of Levinson recursions are employed in the experimental investigation. Two kinds of results are reported: (1) when the data are exact and (2) when the data arise from the periodogram. In this latter case, the comparison is based on the mean and the variance of the spectrum estimates.     

Error log analysis: statistical modeling and heuristic trendanalysis

Most error-log analysis studies perform a statistical fit to the data assuming a single underlying error process. The authors present the results of an analysis that demonstrates that the log is composed of at least two error processes: transient and intermittent. The mixing of data from multiple processes requires many more events to verify a hypotheses using traditional statistical analysis. Based on the shape of the interarrival time function of the intermittent errors observed from actual error logs, a failure-prediction heuristic, the dispersion frame technique (DFT), is developed. The DFT was implemented in a distributed system for the campus-wide Andrew file system at Carnegie Mellon University. Data collected from 13 file servers over a 22-month period were analyzed using both the DFT and conventional statistical methods. It is shown that the DFT can extract intermittent errors from the error log and uses only one fifth of the error-log entry points required by statistical methods for failure prediction. The DFT achieved a 93.7% success rate in predicting failures in both electromechanical and electronic devices     

Systematic features of the formation of semiconductor nanostructures using a focused ion beam

The systematic features of three-dimensional nanostructure fabrication using a focused ion beam are studied. The dependence of the depth of ion-beam-modified structures on the number of etching passes for the same ion dose is revealed with the aim of achieving accurate and predictable nanostructure formation. At the qualitative level, the effect of the thermodynamic parameters of Si, GaAs, and GaN semiconductors on the results of etching is analyzed.     

Modification of: error log analysis: statistical modeling andheuristic trend analysis

The above-titled paper by T.-T.Y. Lin and D.P. Siewiorek (see ibid., vol.39, p.419-32, Oct. 1990) used traditional statistical analysis to demonstrate the superiority of the proposed dispersion frame technique. The purpose was to distinguish between transient and intermittent errors and predict the occurrence of intermittent errors. It is shown here that those traditional statistical methods were too traditional, since they involved fitting a distribution to data which were not identically distributed. Appropriate statistical techniques for fitting models to such nonstationary data are briefly discussed, and reasons are proffered for the persistence of too-traditional statistical methods in the reliability literature     

Fast algorithms for measurement-based traffic modeling

This paper develops fast algorithms for the construction of a circulant modulated rate process to match with the two primary traffic statistical functions: rate distribution f(x) and autocorrelation R(τ). Using existing modeling techniques, f(x) has to be limited to certain forms such as Gaussian or binomial; R(τ) can only consist of one or two exponential terms which are often real exponentials rather than complex. In reality, these two functions are collected from real traffic traces and generally expressed in a very complicated form. We only consider the traffic whose correlation function can be approximated by the sum of complex exponentials. Our emphasis is placed on the algorithm design for matching complicated R(τ) in traffic modeling. The typical CPU time for traffic modeling with R(τ) consisting of five or six complex exponential terms is found to be in the range of a few minutes by the proposed algorithms. Our study further shows an excellent agreement between the original traffic traces and the sequences generated by the matched analytical model. The selection of the measurement-window in traffic statistics collection for queueing performance analysis is also discussed     

聚焦离子束(FIB)快速制备透射电镜样品

高性能聚焦离子束系统(简称FIB)具有许多独特且重要的功能，已广泛地应用于半导体工业中。近年来，FIB在材料科学研究领域也有了广泛的应用。本文主要介绍利用FIB快速制备TEM样品的方法。实验设备为日本精工公司生产的型号为Seiko SM12200的聚焦离子束系统。     

Fast multiscale modeling of cardiac electrophysiology including Purkinje system

In this paper, we present a modeling methodology to couple the cardiac conduction system to cardiac myocytes through a model of Purkinje-ventricular junctions to yield fast and realistic electrical activation of the ventricles. A patient-specific biventricular geometry is obtained from processing computed tomography scan data. A one-manifold implementation of the fast marching method based on Eikonal-type equations is used for modeling heart electrophysiology, which facilitates the multiscale 1-D-3-D coupling at very low computational costs. The method is illustrated in in-silico experiments where we analyze and compare alternative pacing strategies on the same patient-specific anatomy. We also show very good agreement between the results from the proposed approach and more detailed and comprehensive biophysical models for modeling cardiac electrophysiology. The effect of atrioventricular delay on the distribution of activation time in myocardium is studied with two experiments. Given the reasonable computational times and realistic activation sequences provided by our method, it can have an important clinical impact on the selection of optimal implantation sites of pacing leads or placement of ablation catheter's tip in the context of cardiac rhythm management therapies.     

Fast two-dimensional diffraction modeling for site-specificpropagation prediction in urban microcellular environments

This paper presents fast two-dimensional (2-D) diffraction modeling in the horizontal plane for site-specific propagation prediction in urban microcellular environments. The modeling makes three contributions which are: (1) the introduction and use of an extended formulation for multiple building forward diffraction; (2) a novel equivalent source simplification for parallel street multiple diffraction; and (3) the inclusion of reflections from curved surfaces of street building corners. Comparison with measurements and simulation of published results validate the 2-D modeling that significantly reduces the computation time and overcomes the limitation and difficulty of existing techniques for multiple diffraction     

Intensity of a focused beam in a turbulent medium

The effect of the strength of turbulence on the intensity distribution in the focal plane of a focused laser beam is studied. The intensity in the focal region is found to be unaffected by the turbulence provided Cn²< 0.45 k0^-2S^-5/6F^-1, where Cnis the index of the refraction structure constant, k0is the signal wavenumber, S is the initial cross section of the beam, and F is the focal length.     

Defocusing loss for a log periodic-fed reflector

Log periodic designs are a well established wide-band antenna technology, but one in which the phase center travels along the structure as the frequency varies. When a log periodic antenna is used as a feed for a reflector antenna, the phase center location cannot be maintained at the reflector focus over the frequency range and defocusing results. The purpose of this analysis is to quantify the defocusing loss for a log periodicfed reflector. The analysis presented compares favorably with measured results.     

Fast numerical modeling of multitransmitter electromagnetic data using multigrid quasi-linear approximation

Multitransmitter electromagnetic (EM) surveys are widely used in remote-sensing and geophysical exploration. The interpretation of the multitransmitter geophysical data requires numerous three-dimensional (3-D) modelings of the responses of the receivers for different geoelectrical models of complex geological formations. In this paper, we introduce a fast method for 3-D modeling of EM data, based on a modified version of quasilinear approximation, which uses a multigrid approach. This method significantly speeds up the modeling of multitransmitter-multireceiver surveys. The developed algorithm has been applied for the interpretation of marine controlled-source electromagnetic (MCSEM) data. We have tested our new method using synthetic problems and for the simulation of MCSEM data for a geoelectrical model of a Gemini salt body.     

Fast color correction for multi-view video by modeling spatio-temporal variation

In multi-view video, a number of cameras capture the same scene from different viewpoints. Color variations between the camera views may deteriorate the performance of multi-view video coding or virtual view rendering. In this paper, a fast color correction method for multi-view video is proposed by modeling spatio-temporal variation. In the proposed method, multi-view keyframes are defined to establish the spatio-temporal relationships for accurate and fast implementation. For keyframes, accurate color correction is performed based on spatial color discrepancy model that disparity estimation is used to find correspondence points between views, and linear regression is performed on these sets of points to find the optimal correction coefficients. For non-keyframes, fast color correction is performed based on temporal variations model that time-invariant regions are detected to reflect the change trends of correction coefficients. Experimental results show that compared with other methods, the proposed method can promote the correction speed greatly without noticeable quality degradation, and obtain higher coding performance.     

Study and formation of 2D microstructures of sapphire by focused ion beam milling

Dry etching of C-plane sapphire wafer has been studied using Ga⁺ focused ion beam milling (FIBM). Due to a much lower milling rate of sapphire compared to GaN, it has been proven that gas-assisted FIBM (GAFIBM) is a necessity. Furthermore, it needs to be determined whether XeF₂- or I₂-GAFIBM can improve the technique. We found that XeF₂-GAFIBM gave the highest milling rate. The obtained enhancement factor of the XeF₂-GAFIBM milling rate compared to FIBM rate varied from 2.3 to 1.2 for the ion beam current in the range 20 pA-1 nA. A favorable milling rate selectivity of sapphire to nickel film of about 1.5 was obtained by XeF₂-GAFIBM at 350 pA. We have successfully fabricated a variety of 2D sapphire-based submicron pillar or hole arrays in regular crystals, quasicrystals and aperiodic symmetries. The nearest neighbor distance was down to 230 nm. The depth achieved was deeper than 400 nm. The air filling factor ranged from 12% to 60%. These sapphire-based 2D microstructures were applied on flip-chip GaN-based light emitting diodes (LEDs) and more than 40% improvement in light extraction was obtained.     

Sequential modeling of via formation in photosensitive dielectricmaterials for MCM-D applications

Multichip module (MCM) technology is considered a strategic solution in electronics packaging because this approach offers significant advantages in electrical and thermal performance and reliability. However, manufacturing cost is a critical issue for mass production of high-performance MCM packages. To realize low-cost manufacturing technology, process modeling, optimization, and control techniques are required. In this paper, a modeling approach for via formation in MCM dielectric layers composed of photosensitive benzocyclobutene (BCB) is presented. A series of designed experiments are used to characterize the via formation workcell (which consists of the spin coat, soft bake, expose, develop, cure, and plasma descum unit process steps). The output characteristics considered are film thickness, refractive index, uniformity, film retention, and via yield. Sequential neural network process models are constructed to characterize the entire process. In the sequential scheme, each workcell subprocess is modeled individually, and each subprocess model is linked to previous subprocess outputs and subsequent subprocess inputs. This modeling scheme is compared with both the global and unit process modeling approaches to evaluate model prediction capability. The sequential method shows superior capability, with an average rms prediction error of 6.40% over all responses, compared to a 11.61% rmse for the global model and a 12.05% error for the unit process models     

某型计程仪检测装置中精密信号源的设计

根据某型计程仪检测装置的设计要求,设计实现了一种基于单片集成电路芯片ICL8038的精密信号源电路.在介绍ICL8038的基础上对其整个结构进行了详细的设计,给出了具体测试电路图,并根据实际应用进行了测试电路验证.实践证明该信号源电路具有频率漂移小、失真度低、频率占空比可调、工作性能稳定等特点,能够满足计程仪性能检测对信号源的要求.     

An integrated modeling approach to solder joint formation

The attachment of electronic components to printed circuit boards using solder material is a complex process. This paper presents a novel modeling methodology, which integrates the governing physics taking place. Multiphysics modeling technology, imbedded into the simulation tool-PHYSICA is used to simulate fluid flow, heat transfer, solidification and stress evolution in an integrated manner. Results using this code are presented, detailing the mechanical response of two solder materials as they cool, solidify and then deform. The shape that a solder joint takes upon melting is predicted using the SURFACE EVOLVER code. Details are given on how these predictions can be used in the PHYSICA code to provide a modeling route by which the shape, solidification history, and resulting stress profiles can be predicted     

基于模型化DSP快速设计的音频信号采集系统

数字信号控制器具有数字信号处理器和微控制器的优点,在现代自动控制、数据采集系统中占据着重要的地位,TMS320F28335作为目前最主流的数字信号控制器,在实际工程中被广泛的使用。目前该处理器存在着程序设计周期长,程序设计过程复杂等问题。采用模型化设计的DSP嵌入式系统程序开发方法能很好地解决这个问题。以设计一个基于DSP的音频数据采集系统为例,通过将CCS软件和Matlab/Simulink进行有机的结合,对模型进行图形化界面配置,最终实现目标处理器程序代码的自动生成、下载、调试和运行,从而快速地实现音频信号数据采集系统的设计。     

Fast and accurate thermal modeling and simulation of manycore processors and workloads

Today's microprocessors require careful analysis of their thermal behavior both at design time as well as at runtime. However, accurate prediction of thermal behavior is possible only through simulations due to the complexity and the high dynamicity of their operation. Unfortunately, accurate simulations of such complex systems are computationally intensive, therefore time consuming, while on the other hand, simplified models often cause mispredictions leading to overdesign and lowered performance. In our work, we propose a new discrete-time method of assessment of the run-time temperature of a processor based on an approximation of its instructions-per-cycle (IPC) by a finite Fourier series expansion. Our method is AC-based, and shows significant increase of accuracy in comparison to well-known DC (average)-based models. Furthermore, we provide a new Dynamic Voltage and Frequency Scaling (DVFS) model based on our estimations.     

Fast, quasi-3D modeling of base resistance for circuit simulation

Modifications are made to a finite-difference device simulator (PISCES) to model distributed base resistance. The simulator is modified to run in a quasi-3-D mode in which two numerically simulated dimensions model the lateral flow of the base current, and the third dimension is modeled with the modified Gummel-Poon (MGP) equations. The modulation of the intrinsic base sheet resistivity and the base current injection at each node are determined by the MGP model. Basewidth modulation, high injection, emitter debiasing, bias dependence of current paths, and interactions among these effects are studied for a variety of drawn geometries, sheet resistances, and temperatures. It is found that the standard models used in circuit simulation (SPICE) do not adequately model some of these effects. A model that adds an extra term into the function of base resistance is introduced to model these effects. Performing curve fits to the simulation results allows the base resistance parameters to be expressed as a polynomial sum in terms of geometry, the intrinsic and extrinsic sheet resistivities, and temperature     

Chukwa在日志数据监控方面的运用

Chukwa是Hadoop软件家族成员的一员,是一个分布式系统,应用于大规模集群的数据收集上,构建在Hadoop的HDFS和MapReduce框架之上。文章通过对数据日志的采集、存储、分析和展示,为用户提供全面、灵活、可视化的服务,弥补了MapReduce对大量日志文件处理能力不足的弱点。