LEVEL SET输运方程的求解方法及其对气-液两相流运动界面数值模拟的影响

用数值模拟方法来研究气-液两相流动与传热现象是当今多相流领域的一个热门课题.由于两相流固有的复杂性,气-液两相流界面迁移现象的数值模拟一直是两相流研究中的一大难点.本文介绍了捕捉气-液两相流相界面运动的水平集方法(Level Set)及其研究进展,介绍了求解Level Set输运方程的3种方法,即一般差分格式、Superbee-TVD格式和Runge-Kutta法-5阶WENO组合格式.结合主流场的求解,分别用这3种方法对4种典型相界面在5种流场中的迁移特性进行了模拟计算,并对计算结果进行了比较和分析.结果表明,Runge-Kutta法-5阶WENO组合格式求解Level Set输运方程的效果最好,在以后的计算中将主要采用这种组合格式来进行气-液相界面输运方程的求解.

Influence of stochastic mesoscopic structure on macroscopic mechanical behavior of brittle material

A newly developed numerical code, MFPA(2D) (Material Failure Process Analysis), is applied to study the influence of stochastic mesoscopic structure on macroscopic mechanical behavior of rock-like materials. A set of uniaxial compression tests has been numerically studied with numerical specimens containing pre-existing crack-like flaw. The numerical results reveal the influence of random mesoscopic structure on failure process of brittle material, which indicates that the variation of failure mode is strongly sensitive to the local disorder feature of the specimen. And the patterns of the crack evolution in the specimens are very different from each other due to the random mesoscopic structure in material. The results give a good explanation for various kinds of fracture modes and peak strength variation observed in laboratory studies with specimens made from the same rock block being statistically homogenous in macro scale. In addition, the evolution of crack is more complicated in heterogeneous cases than in homogeneous cases.

The Relationship between Decision Trees and the Scale of Train Data Set

Decision Trees need train samples in the train data set to get classification rules. If the number of train data was too small, the important information might be missed and thus the model could not explain the classification rules of data. While it is not affirmative that large scale of train data set can get well model. This Paper analysis the relationship between decision trees and the train data scale. We use nine decision tree algorithms to experiment the accuracy, complexity and robustness of decision tree algorithms. Some results are demonstrated.

Two-step digit-set-restricted modified signed-digit addition-subtraction algorithm and its optoelectronic implementation

A novel, to our knowledge, two-step digit-set-restricted modified signed-digit (MSD) addition-subtraction algorithm is proposed. With the introduction of the reference digits, the operand words are mapped into an intermediate carry word with all digits restricted to the set {(1) over bar, 0} and an intermediate sum word with all digits restricted to the set {0, 1}, which can be summed to form the final result without carry generation. The operation can be performed in parallel by use of binary logic. An optical system that utilizes an electron-trapping device is suggested for accomplishing the required binary logic operations. By programming of the illumination of data arrays, any complex logic operations of multiple variables can be realized without additional temporal latency of the intermediate results. This technique has a high space-bandwidth product and signal-to-noise ratio. The main structure can be stacked to construct a compact optoelectronic MSD adder-subtracter. (C) 1999 Optical Society of America.

Code conversion from signed-digit to complement representation based on look-ahead optical logic operations

We present, for the first time to our knowledge, a generalized lookahead logic algorithm for number conversion from signed-digit to complement representation. By properly encoding the signed-digits, all the operations are performed by binary logic, and unified logical expressions can be obtained for conversion from modified-signed-digit (MSD) to 2's complement, trinary signed-digit (TSD) to 3's complement, and quarternary signed-digit (QSD) to 4's complement. For optical implementation, a parallel logical array module using an electron-trapping device is employed and experimental results are shown. This optical module is suitable for implementing complex logic functions in the form of the sum of the product. The algorithm and architecture are compatible with a general-purpose optoelectronic computing system. (C) 2001 Society of Photo-Optical Instrumentation Engineers.

One-step digit-set-restricted modified signed-digit adder using an incoherent correlator based on a shared content-addressable memory

An efficient one-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In this technique, carry propagation is avoided by introducing reference digits to restrict the intermediate carry and sum digits to {1,0} and {0,1}, respectively. The proposed technique requires significantly fewer minterms and simplifies system complexity compared to the reported one-step MSD addition techniques. An incoherent correlator based on an optoelectronic shared content-addressable memory processor is suggested to perform the addition operation. In this technique, only one set of minterms needs to be stored, independent of the operand length. (C) 2002 society or Photo-Optical Instrumentation Engineers.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

蔷薇类的分子系统学研究—兼论系统发育基因组学的原理和方法(以SET基因超家族为例)

分子系统发育分析的主要任务包括：（1）帮助建立生命之树（tree of life）;（2）追踪基因和基因家族（gene family）的起源和进化, 以获知基因在进化过程中的功能分化和伴随发生的重要分子事件（key molecular events）和形态性状的关键创新（key innovation）。这两个方面在本研究中都有所涉及。对于前者，选用植物线粒体matR基因重建被子植物蔷薇类群的系统发育关系;对于后者，则以SET基因超家族为例，探讨其在真核生物中的进化分类以及与功能多样性的关系。 I 蔷薇类的分子系统学 蔷薇类（rosids）是基于分子数据建立的被子植物的主要分支之一，包含13个目，大约三分之一的被子植物物种。两个主要蔷薇类内部分支是豆类fabids（包含7个目）和锦葵类malvids（包含3个目）。然而，这两个分支内部，以及这两个分支与蔷薇类基部类群，包括牻牛儿苗目（Geraniales）、桃金娘目（Myrtales）和流苏子目（Crossosomatales）之间的关系大多是不清楚的。本研究中，我们选取174个物种来代表72个蔷薇类（rosids）的科，利用两个数据集，即线粒体matR单基因数据集和包括线粒体matR基因、两个质体基因(rbcL、 atpB)和一个核基因(18S rDNA) 的4基因数据集，重建蔷薇类在科以上分类阶元水平的系统发育关系。同时，还对线粒体matR基因的进化特征和用于大尺度系统发育分析的适合度和潜力进行了评价。 线粒体matR单基因数据支持malvids和大多数蔷薇类目的单系性质，然而，豆类（fabids）成员没有形成一个分支，其COM亚支，包括卫矛目（Celastrales）、酢浆草目（Oxalidales）、金虎尾目（Malpighiales）和蒜树科（Huaceae），分辨为锦葵类（malvids）的姐妹群。这个关系在最近根据花结构特征曾被提出过，但从未在之前的分子系统发育分析中得到分辨。4基因数据集支持首先是牻牛儿苗目（Geraniales），接着是桃金娘目（Myrtales）作为蔷薇类（rosids）的最基部的分支;流苏子目（Crossosomatales）是锦葵类（malvids）姐妹群，以及蔷薇类（rosids）的核心部分包括豆类（fabids），锦葵类（malvids）和流苏子目（Crossosomatales）。线粒体matR基因的进化特征分析显示，与两个叶绿体基因(rbcL 和atpB)比较，同义替代速率约是它们的1/4，而非同义替代速率接近于自身的同义替代速率，表明matR 基因具有松弛的选择压力。线粒体matR基因相对慢速的进化使非同源相似（homoplasious）突变减少，提高了系统发育信息的质量，同时，松弛的选择压力使非同义替代数量增加，弥补了慢速进化导致的系统发育信息数量不足的缺陷，这两个方面的结合使线粒体matR基因非常适用于被子植物在科以上水平的系统发育研究。 II SET基因超家族的系统发育基因组学分析 SET基因超家族基因编码含有SET结构域的蛋白，在真核生物中，SET-domain蛋白一般是多结构域（multi-domain）的。SET-domain蛋白具有对组蛋白H3和H4的N末端尾部进行赖氨酸残基甲基化修饰的酶活性;从异染色质形成到基因转录，甲基化的组蛋白广泛影响染色质水平的基因调控。依据SET结构域一级序列的相似性和结构域组织（domain architecture）特征，目前，SET-domain基因超家族被划分为4-7个家族。由于这些划分或者使用动物或者使用植物SET基因，只有少数其它类群的物种加入分析，因此这样的划分可能是不完整的。本研究采用系统发育基 因组学方法（phylogenomic approach），在真核生物范围内广泛取样，期望获得相对完整的SET-domain基因家族的 进化分类方案，在此基础上加深理解SET-domain基因的进化机制和功能多样性。 在提取了17个物种，代表5个真核超群的SET蛋白序列基础上，系统发育分析结合“结构域组织特征”鉴别了9个SET基因家族，其中一个是新的SET基因家族。以前的SET8和Class VI家族,及SMYD和SUV4-20家族分别合并为一个家族。大部分家族在进化过程中发生了2次以上的基因重复事件，通过获得不同的结构域产生具有不同功能的新基因。一个SET基因家族在进化过程中推测发生了从脊椎动物祖先向盘基网柄菌（Dictyostelium discoideum）的水平基因转移。

Study on Closed-set Speaker Identification Based on Biomimetic Pattern Recognition

In this paper, a new classifier of speaker identification has been proposed, which is based on Biomimetic pattern recognition (BPR). Distinguished from traditional speaker recognition methods, such as DWT, HMM, GMM, SVM and so on, the proposed classifier is constructed by some finite sub-space which is reasonable covering of the points in high dimensional space according to distributing characteristic of speech feature points. It has been used in the system of speaker identification. Experiment results show that better effect could be obtained especially with lesser samples. Furthermore, the proposed classifier employs a much simpler modeling structure as compared to the GMM. In addition, the basic idea "cognition" of Biomimetic pattern recognition (BPR) results in no requirement of retraining the old system for enrolling new speakers.

Quantum Confinement and Electronic Properties of Rutile TiO2 Nanowires

The quantum confinement effect, electronic properties, and optical properties of TiO2 nanowires in rutile structure are investigated via first-principles calculations. We calculate the size- and shape-dependent band gap of the nanowires and fit the results with the function E-g = E-g(bulk) + beta/d(alpha). We find that the quantum confinement effect becomes significant for d < 25 angstrom, and a notable anisotropy exists that arises from the anisotropy of the effective masses. We also evaluate the imaginary part of the frequency-dependent dielectric function [epsilon(2)(omega)] within the electric-dipole approximation, for both the polarization parallel [epsilon(parallel to)(2)(omega)] and the perpendicular [epsilon 1/2(omega)] to the axial (c) direction. The band structure of the nanowires is calculated, with which the fine structure of epsilon(parallel to)(2)(omega) has been analyzed.

Analog-digital and digital-analog converters using single-electron and MOS transistors

This paper proposes two kinds of novel single-electron analog-digital conversion (ADC) and digital-analog conversion (DAC) circuits that consist of single-electron transistors (SETs) and metal-oxide-semiconductor (MOS) transistors. The SET/MOS hybrid ADC and DAC circuits possess the merits of the SET circuit and the MOS circuit. We obtain the SPICE macro-modeling code of the SET transistor by studying and fitting the characteristics of the SET with SPICE simulation and Monte Carlo simulation methods. The SPICE macro-modeling code is used for the simulation of the SET/MOS hybrid ADC and DAC circuits. We simulate the performances of the SET/MOS hybrid 3-b ADC and 2-b DAC circuits by using the H-SPICE simulator. The simulation results demonstrate that the hybrid circuits can perform analog-digital and digital-analog data conversion well at room temperature. The hybrid ADC and DAC circuits have advantages as-follows: 1) compared with conventional circuits, the architectures of the circuits are simpler; 2) compared with single electron transistor circuits, the circuits have much larger load capability; 3) the power dissipation of the circuits are lower than uW; 4) the data conversion rate of the circuits can exceed 100 MHz; and 5) the resolution of the ADC and DAC circuits can be increased by the pipeline architectures.

Detecting a set of entanglement measures in an unknown tripartite quantum state by local operations and classical communication

We propose a more general method for detecting a set of entanglement measures, i.e., negativities, in an arbitrary tripartite quantum state by local operations and classical communication. To accomplish the detection task using this method, three observers do not need to perform partial transposition maps by the structural physical approximation; instead, they only need to collectively measure some functions via three local networks supplemented by a classical communication. With these functions, they are able to determine the set of negativities related to the tripartite quantum state.