Chromosome Reconstruction from Physical Maps Using a Cluster of Workstations

Ordering clones from a genomic library into physical maps of whole chromosomes presents a central computational problem in genetics. Chromosome reconstruction via clone ordering is shown to be isomorphic to the classical NP-complete Optimal Linear Arrangement problem. Parallel algorithms for simulated annealing and microcanonical annealing based on Markov chain decomposition are proposed and applied to the problem of chromosome reconstruction via clone ordering. These algorithms are implemented on a cluster of UNIX workstations using the Parallel Virtual Machine (PVM) system. PVM is a software system that permits a heterogeneous collection of networked computers to be viewed by a user's program as a single monolithic parallel computing resource. The parallel algorithms are implemented and tested on clonal data derived from Chromosome IV of the fungus Asperigillus nidulans Perturbation methods and problem-specific annealing heuristics for the parallel simulated annealing and parallel microcanonical annealing algorithms are proposed and described. Convergence, speedup and scalability characteristics of the various parallel algorithms are analyzed and discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

钛酸锶粉体的制备及超声降解性能的研究

以硝酸锶和钛酸四丁酯为前驱物,采用溶胶-凝胶法制备了钛酸锶粉体.采用傅里叶红外光谱、X射线粉末衍射和扫描电镜等测试手段,对钛酸锶粉体进行了表征,并对其超声降解甲基橙性能进行了研究.结果表明:在锻烧温度为700℃,锻烧时间为2.0 h时生成的钛酸锶超声降解甲基橙效率最高;掺杂五氧化二钒可显著提高钛酸锶催化活性,掺杂三氧化...     

Determination of tangential momentum accommodation coefficient and slip coefficients for rarefied gas flow in a microchannel

This paper presents an experimental study of rarefied gas flow in a trapezoidal microchannel with a constant depth of 103 µm, top width of 1143 µm, bottom width of 998 µm and length of 2 cm. The aim of the study is to verify the upper limit of the validity of the second-order slip boundary condition to model rarefied gas flows. The slip coefficients and the tangential momentum accommodation coefficient (TMAC) are determined for three different gases, viz. argon, nitrogen and oxygen, and it is observed that they compare well to the literature values. The range of mean Knudsen number (Kn_m) investigated is 0.007–1.2. The non-dimensional mass flow rate exhibits the well-known Knudsen minimum in the transition regime (Kn_m?~?1). It is seen that the Navier–Stokes equation with a second-order boundary condition fits the data satisfactorily with a high value of correlation coefficient (r²?>?99.95%) in the entire range of Kn_m investigated. This work contributes by extending the range of Knudsen number studied in the context of validity of the second-order slip boundary condition.     

基于EKF的低速永磁电机控制系统建模与分析

为了实现大转矩、低转速永磁电机的变频控制,提出了一种基于卡尔曼滤波原理的调速系统。在系统中,采用卡尔曼滤波算法对电机位置、转速和d—q轴电流进行了估计。在广义卡尔曼滤波（EKF）的基础上,系统的电流环和速度环采用PI控制,电机采用空间矢量脉宽调制（SVPWM）矢量控制方法。利用Matlab／Simulink对整个系统进行了仿真建模,并对仿真结果进行了分析。通过对误差的分析以及参数鲁棒性的分析,可以证明卡尔曼滤波算法适用于低速的永磁电机调速系统。     

PRO/E在翻罐卷扬机设计中的应用

叙述了在翻罐卷扬机的设计中用PRO/E进行铁水罐的三维实体造型工作,并模拟了铁水罐的倾翻过程,进而精确地计算出了在这一进程中铁水罐地倾翻特性,为翻罐卷扬机地设计提供了准确地数据。     

Testing the controllability of linear time-invariant systems

A method for studying the controllability of a linear time-invariant system by considering the controllability of a smaller subsystem is proposed. The method is most effective when the system under study has a large number of inputs and states.     

Creep and fracture of a Laves phase strengthened ferritic alloy

The microstructural changes which occurred during creep were examined in a carbon-free ferritic alloy containing 1 at. pct Ta and 7 at. pct Cr. The alloy derived its creep resistance from a uniform dispersion of almost spherical particles of the Laves phase Fe₂Ta in a bcc matrix. There was a lath-like substructure in this alloy, with dislocation tangles and subgrains within the laths. Partial recovery during creep led to the formation of a regular subgrain structure. The Laves phase particles prevented total recovery by pinning individual dislocations and subgrain boundaries. The apparent activation energy for creep, the estimated stress sensitivity of minimum creep rate, and the substructural features observed in crept specimens suggested that creep deformation of the alloy occurred by two or more independent processes. Fracture under creep conditions was initiated by void formation at precipitate-matrix interfaces. Intergranular void formation played an important role in the fracture of creep specimens tested at 1200°F (649°C), but not at lower temperatures.     

A novel feature-based tracking approach to the detection, localization, and 3-D reconstruction of internal defects in hardwood logs using computer tomography

A novel feature-based tracking approach based on the Kalman filter is proposed for the detection, localization, and 3-D reconstruction of internal defects in hardwood logs from cross-sectional computer tomography (CT) images. The defects are simultaneously detected, classified, localized, and reconstructed in 3-D space, making the proposed scheme computationally much more efficient than existing methods where the defects are detected and localized independently in individual CT image slices and the 3-D reconstruction of the defects accomplished via correspondence analysis across the various CT image slices. Robust techniques for defect detection and classification are proposed. Defect class-specific tracking schemes based on the Kalman filter, B-spline contour approximation, and Snakes contour fitting are designed which use the geometric parameters of the defect contours as the tracking variables. Experimental results on cross-sectional CT images of hardwood logs from select species such as white ash, hard maple, and red oak are presented.