An unified numerical approach for computing the outage probabilityfor mobile radio systems

A general finite-range integral for the probability of outage in mobile radio systems is derived. The method handles noninteger Nakagami-fading indices, unequal Rice factors, unequal shadowing spreads, and unequal transmitted powers as well as all the common fading distributions (Rayleigh, Rice, Nakagami-m, Nakagami-q, lognormal-Rice, Suzuki, and lognormal-Nakagami-m). The integral expression can also be approximated by a Gauss-Chebychev quadrature (GCQ) formula requiring knowledge of the moment generating function at only a small number of points. An estimate of the remainder term is also derived. This numerical technique allows computing the outage with arbitrary precision and it is extremely easy to program     

An Eulerian PDE approach for computing tissue thickness

We outline an Eulerian framework for computing the thickness of tissues between two simply connected boundaries that does not require landmark points or parameterizations of either boundary. Thickness is defined as the length of correspondence trajectories, which run from one tissue boundary to the other, and which follow a smooth vector field constructed in the region between the boundaries. A pair of partial differential equations (PDEs) that are guided by this vector field are then solved over this region, and the sum of their solutions yields the thickness of the tissue region. Unlike other approaches, this approach does not require explicit construction of any correspondence trajectories. An efficient, stable, and computationally fast solution to these PDEs is found by careful selection of finite differences according to an upwinding condition. The behavior and performance of our method is demonstrated on two simulations and two magnetic resonance imaging data sets in two and three dimensions. These experiments reveal very good performance and show strong potential for application in tissue thickness visualization and quantification.     

An efficient numerical approach for modeling microstrip-typeantennas

An efficient numerical approach to model antennas that include a microstrip element radiating in the presence of material layers is developed. The class of antennas considered is fed through the ground plane by a coaxial transmission line. The reaction integral equation is formulated by treating the coaxial aperture as part of the antenna. The substrate thickness can be arbitrary, making this numerical technique suitable for high-frequency applications. The effects of the substrate are also included in the analysis. Numerical results are obtained for the current distribution and input impedance. The algorithm is validated with experimental results     

New tight bounds on the pairwise error probability for unitary space-time modulations

We present two upper bounds and one lower bound on the pairwise error probability (PEP) of unitary space-time modulation (USTM) over the Rayleigh fading channel. The two new upper bounds are the tightest so far, and the new lower bound is the tightest at low signal-to-noise ratio. Some implications for USTM constellation design are also pointed out.     

A recursive algorithm for computing Cramer-Rao-type bounds onestimator covariance

We give a recursive algorithm to calculate submatrices of the Cramer-Rao (CR) matrix bound on the covariance of any unbiased estimator of a vector parameter &thetas;_. Our algorithm computes a sequence of lower bounds that converges monotonically to the CR bound with exponential speed of convergence. The recursive algorithm uses an invertible “splitting matrix” to successively approximate the inverse Fisher information matrix. We present a statistical approach to selecting the splitting matrix based on a “complete-data-incomplete-data” formulation similar to that of the well-known EM parameter estimation algorithm. As a concrete illustration we consider image reconstruction from projections for emission computed tomography     

An effective approach for the optimal focusing of array fieldssubject to arbitrary upper bounds

A new approach to the optimal focusing of array fields subject to arbitrary upper bounds is presented. The approach formulates the problem as the minimization of a linear function in a convex set. Unlike other approaches, this one guarantees the achievement of the global optimum by using local optimization techniques and can, moreover, deal with any convex constraint on the unknowns, such as near field constraints. Optimization is performed by two ad hoc developed solution algorithms, which exploit the geometrical characteristics of the problem at hand, thus leading to extremely effective and computationally efficient numerical codes. An extensive numerical analysis has been performed in all cases of linear, planar, and circular arc arrays. The enhanced performance of the proposed technique with respect to the solution algorithms available in the literature fully confirms the effectiveness of the approach     

A simulation approach for computing systems reliability

The basis of the concept of reliability is that a given component has a certain stress-resisting capacity; if the stress induced by the operating conditions exceeds this capacity, failure results. Most of the published results in this area are based upon analytical modelling of stress and strength, using various probability distributions, and then trying to find an exact expression for system reliability, which can be very difficult to obtain sometimes. The approach used in this paper is very simple and uses simulation techniques to repeatedly generate stress and strength of a system by the computer, using a random number generator and methods such as the inverse transformation technique. The advantage of this approach is that it can be used for any stress-strength distribution functions. Finally, numerical results obtained from using this approach are compared with results obtained using the analytical methods for various strength-stress distribution functions, such as exponential, normal, log normal, gamma and Weibull. Results show the viability of the simulation approach.     

An approach of numerical multi-objective optimization in stacked packaging

The main aim for the development of small electronic packages is supported by an ongoing development of portable communication devices. Thin silicon dies are believed to improve the device performance as well as its reliability. Additionally, novel packaging techniques such as stacked packaging reduce packaging cost and size, and improve the functionality and reliability. In the case of the stacked packages, wafers are stacked to form a 3D multi-chip package. On the other hand, the electronic market requires novel and efficient numerical designing tools to deal properly with the optimization. The goal of the current work was to design a reliable numerical model of the stacked package and afterwards perform numerical multi-objective optimization in reference to a number of variables, which influence the stacked package reliability.     

An adaptive approach to the numerical solution of Fresnel's waveequation

An adaptive approach to the numerical solution of the wave propagation in integrated optics devices with 1-D cross sections is described. Fresnel's approximation of the exact wave equation resulting from Maxwell's equations is considered. A criterion to estimate the validity of this approximation is derived. Discretization in longitudinal direction with step-size control leads to a stationary subproblem for the transversal field distribution, which is then handled by an adaptive finite-element method. Thus, full adaptivity of the algorithm is realized. The numerical examples focus on waveguide tapers     

An efficient numerical approach, for determining the dispersioncharacteristics of dual-mode elliptical-core optical fibers

Based on vectorial formulations which combine the surface integral equation method and the finite-element method, a novel numerical approach is proposed for calculating the dispersion coefficients of dual-mode elliptical-core fibers with arbitrary refractive index profiles. By differentiating the original formulations involving the propagation constant β and the guided mode fields H_x and H_y once and twice with respect to the normalized frequency V, the new formulations for {dβ/dV, dH_x/dV, dH_y/dV} and for {d²β/dV², d² H_x/dV², d²H_y/dV² } are obtained respectively. Once {β, H_x, H_y } is solved through the eigenvalue procedure which dominates the computing time, only a few matrix manipulations are required to obtain {dβ/dV, dH_x/dV, dH_y/dV} and {d²β/dV², d²H_x/dV² , d²H_y/dV²}. Some numerical examples are examined to see the influence of different refractive index distributions with dips on the dispersions of the four nondegenerate LP ₁₁ modes for elliptical-core fibers     

SAPA-based approach for defending DoS attacks in cloud computing

Denial of service (DoS) attack was one of the major threats to cloud computing.Security access path algorithm (SAPA) used node route table (NRT) to compose security access path.It simplified role nodes of traditional secure overlay services (SOS),and periodically updated role nodes,and cached security access paths.Therefore,SAPA was more appropriate for cloud computing to defend DoS attacks.Based on the turn routing architecture of cloud computing,the mathematical model of SAPA was built and its performance was analyzed in theory.The performance of SAPA was tested in OMNeT++ experimental platform.Also,the Test-bed experiments were performed to evaluate the effectiveness of SAPA for defending DoS attack.Experimental results show that comparing with SOS,SAPA can degrade the impact of communication success rate caused by DoS attack effectively,and guarantees the access delay small enough.     

An integrated testbed for wireless multimedia computing

A testbed has been constructed to evaluate node architectures that support multimedia applications and services across a wireless network. Using this testbed, a low bitrate subband video compression algorithm has been prototyped in a field programmable gate array (FPGA) and evaluated for video networking across bandwidth-limited RF channels. A radio interface has been prototyped in an FPGA and a common applications programming interface (API) has been developed to allow experimentation with multiple radios. This testbed has been used to evaluate node performance under two different wireless applications: 1) simultaneous video and data networking (VTALK) and 2) TCP/IP utilities such as FTP and telnet. Based on this evaluation, the design of a battery-operated high throughput wireless multimedia node is presented.     

面向云计算平台的层次化性能问题诊断方法

提出一种层次式在线性能问题诊断方法——Magnifier,将用户请求执行路径划分为构件层、模块层和方法层3个层次,自顶向下逐层定位问题根源。基于阿里巴巴云计算平台的实验结果表明,Magnifier能够在调用方法种类多、执行路径复杂的条件下,快速定位出性能降级的主要原因。     

异构网格环境下任务分配的自主计算方法

首先对网格环境的异构性进行描述，定义了关键计算域并给出其划分算法。刻画了基于多agent系统进行任务分配的机制，分析了在自主agent不同移动策略下网格各区域任务分布的不同。采用控制理论的方法加速agent的合理分布，从而可以充分利用关键计算域的异构特征。实例研究表明，提出的任务分配机制具有自配置和自优化特征，能够动态适应异构网格环境的要求。     

Improved wavelength decomposition approach for computing blocking probabilities in WRONs

Wavelength decomposition approach has been proposed to compute blocking probability (BP) of fixed routing in wavelength-routed optical networks (WRONs) without wavelength conversions.By means of wavele...     

A rule-based computing approach for the segmentation of semiconductor defects

This paper presents a rule-based approach to detect defect patterns and to classify the defect patterns that appear on the semiconductor wafer surfaces. To obtain a general and modular defect pattern detection technique, the proposed approach adopts a hierarchical perspective. A formal analogy has been drawn between the structure of defect patterns and the symptom of disease in clinical practice. The defect patterns to be recognized are viewed as decision made to a particular disease. Design goals include detection of flaws and correlation of defect features based on co-occurrence matrix. The system is capable of identifying the defects on the wafers after die sawing. Each unique defect structure is defined as an object. Objects are grouped into user-defined categories such as chipping, metallization peel off, silicon dust contamination, etc. after die sawing and micro-crack, scratch, ink dot being washed off, bridging, etc. from the wafer.     

A path decomposition approach for computing blocking probabilitiesin wavelength-routing networks

We study a class of circuit-switched wavelength-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wavelength converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed in isolation, and the individual results are appropriately combined to obtain a solution for the overall network. To analyze individual subsystems, we first construct an exact Markov process that captures the behavior of a path in terms of wavelength use. We also obtain an approximate Markov process which has a closed-form solution that can be computed efficiently for short paths. We then develop an iterative algorithm to analyze approximately arbitrarily long paths. The path decomposition approach naturally captures the correlation of both link loads and link blocking events. Our algorithm represents a simple and computationally efficient solution to the difficult problem of computing call-blocking probabilities in wavelength-routing networks. We also demonstrate how our analytical techniques can be applied to gain insight into the problem of converter placement in wavelength-routing networks     

A new approach for computing the bandwidth statistics of avalanchephotodiodes

A new approach for characterizing the avalanche-buildup-time-limited bandwidth of avalanche photodiodes (APD's) is introduced which relies on the direct knowledge of the statistics of the random response time. The random response time is the actual duration of the APD's finite buildup limited random impulse response function. A theory is developed characterizing the probability distribution function (PDF) of the random response time. Recurrence equations are derived and numerically solved to yield the PDF of the random response time. The PDF is then used to compute the mean and the standard deviation of the bandwidth. The dependence of the mean and the standard deviation of the bandwidth on the APD mean gain and the ionization coefficient ratio is investigated. Exact asymptotics of the tail of the PDF of the response time are also developed to aid the computation efficiency. The technique can be readily applied to multiplication models which incorporate dead space and can be extended to cases for which the carrier ionization coefficient is position dependent     

面向近邻泄露的数值型敏感属性隐私保护方法

提出一种面向近邻泄露的数值型敏感属性隐私保护方法,该方法首先在保护准标识符属性和数值型敏感属性内在关系的前提下,将数值型敏感属性进行离散化划分;然后,提出一种面向近邻泄露的隐私保护原则——(k, ε)- proximity;最后,设计了最大邻域优先算法MNF(maximal neighborhood first)来实现该原则。实验结果表明,提出的方法能在有效保护数值型敏感信息不泄露的同时保持较高的数据效用,并且保护了数据间的关系。