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西安交通大学学报

西安交通大学学报

北大核心

CSCD

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Journal of Xi'an Jiaotong University
本刊是由国家教育部主管、西安交通大学主办的综合性自然科学学术理论刊物，国际标准开本，国内外公开发行，具有明显的机电特色。主要刊登机械、电气、能源、动力、材料、电子、信息与控制、计算机、物理、力学、化学工程、生物工程、建筑工程以及有关新兴、交叉学科方面的最新研究成果。
  • 发文量：6581
  • 被引量：3543
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  • 国内刊号/CN：61-1069/T
    国际刊号/ISSN：0253-987X
  • 发行周期：月刊
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  • 主管单位：中华人民共和国教育部
    主办单位：西安交通大学
西安交通大学学报-联系信息
  • 主编：陶文铨
  • 电话：029-82668337 82667978
  • 邮箱：xuebao@mail.xjtu.edu.cn
  • 地址：西安市咸宁西路28号
  • 邮编：710049
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西安交通大学学报 >2024年第6期
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  • 摘要：针对超临界直流锅炉水冷壁结构特点及炉内热负荷分布特点,将水冷壁划分为由流量回路、压力节点和连接管组成的流动网络系统.根据质量守恒、动量守恒和能量守恒方程,建立了超临界直流锅炉水冷壁压降和出口汽温的数学计算模型.在此基础上,对利港发电厂600 MW超临界螺旋管圈直流锅炉在不同负荷时上升系统总压降及上、下炉膛水冷壁出口汽温进行了计算,并与实炉数据进行了比较,表明100%负荷(锅炉最大连续蒸发量)、75%负荷及50%负荷时,上、下炉膛水冷壁出口汽温误差均不超过2%;75%负荷时上升系统总压降相差0.058 MPa,误差为2.87%.由此表明所建立的600 MW超临界螺旋管圈直流锅炉水动力计算模型和所开发的程序是正确可靠的,完全可用于实际工程计算,为超临界锅炉设计提供了参考.%The water wall system can be equivalent to a network consisting of circuits, pressure grids, and connecting pipes. A mathematical model for calculating pressure drop and outlet steam temperature of a supercritical once-through boiler was established on the basis of the mass conservation, momentum conservation and energy conservation equations. Moreover,the pressure drop in the up-system and the outlet steam temperature of a 600 MW supercritical once-through boiler with spiral tube coils at Ligang Power Plant were calculated under different loads, and compared with field test data. The results show that the errors of outlet steam temperature of the water wall pipes for the upper-furnace and lower-furnace were all less than 2％ under 100％ load (boiler maximum continuous rating, BMCR), 75％ load and 50％ load; the error of the pressure drop under 75 ％ load for the up-system was 2. 87 ％. It shows that the present hydrodynamic calculation model and the program developed for the 600 MW supercritical once-through boiler are accurate and reliable.
  • 摘要：为了开发对材料裂纹产生前的早期损伤程度进行定量无损检测的新方法,探讨自然磁化机理,以核能设备中常用的常磁性材料--奥氏体不锈钢SUS304为研究对象,通过实验对不同形状和厚度的材料试样进行多次拉伸,测量相应的自然磁化漏磁场磁感应强度和残余应变分布,从而建立了基于自然磁化现象的机械损伤与其磁化漏磁场的定量关系,进而证明了可以通过检测自然磁化漏磁场强度实现对奥氏体不锈钢材料损伤程度的定量检测和评估.基于实验所建立的机械损伤与自然磁化漏磁场的定量关系,结合磁记忆检测方法的优点,提出了一种较为简单但更为全面的对局部缺陷损伤程度进行定量检测的方法.奥氏体不锈钢的自然磁化机理可以初步认为是机械损伤引起的位错堆积导致了奥氏体不锈钢中马氏体含量和位错能的增加,由于材料的各向异性致使在铁磁属性的马氏体组织内产生了自然磁化,从而使材料整体呈现自然磁化特性.%To develop a new nondestructive testing (NDT) method for nondestructive evaluation of mechanical damage before the initiation of macro cracks and reveal the mechanism of natural magnetization, the quantitative correlation between the natural magnetization and the mechanical damage was experimentally investigated for a typical austenitic stainless steel SUS304, which is extensively used in nuclear power plants. In the experiments, simple tensile loading was performed to initialize plastic damages in specimens under different states. The corresponding leakage magnetic field due to natural magnetization and the residual strain distribution were measured after each loading cycle. The quantitative relation between mechanical damage and leakage magnetic field was established based on the phenomenon of natural magnetization, which shows the possibility to quantitatively detect mechanical damages in the austenitic stainless steel by measuring the natural magnetic field. Following the above results and combining with the advantages of metal memory measurement, a new mechanical damage detection method via NDT is presented.
  • 摘要：针对现有CAD领域的检索算法对模型的局部细节特征描述不足的现状,提出了一种基于最大公共子图的三维CAD模型检索算法,通过提取CAD模型的B-Rep信息,将模型用属性邻接图来表示.根据如果2个CAD模型存在相似的特征或局部结构,CAD模型所对应的属性邻接图应存在公共子图的原理,通过检测属性邻接图中的公共子图,得到了2个与CAD相似的局部细节特征,并利用这2个相似的局部细节特征对CAD模型进行了相似性评价.实验表明,该方法能够实现三维CAD模型检索,且检索的效率能够满足工程检索的要求,因此可以实现CAD模型设计和制造知识的重用.%Since the current retrieval algorithms cannot describe local features of CAD models detailed in the CAD field, a new one of 3D CAD model retrieval based on maximum common subgraph is proposed. Extracting B-Rep information of CAD models, the models are represented by the attribute adjacent graph (AAG). If two CAD models contain similar sub-parts, the corresponding AAGs ought to have common subgraph. According to this principle, the similar subparts are obtained by detecting the common subgraph of AAG. The similarity of the CAD models is evaluated by comparing the similar sub-parts. The experimental results show the efficiency of 3D CAD model retrieval to meet the requirements of engineering retrieval and reuse of design and manufacture.
  • 摘要：通过分析、研究气动充放气系统外部结露的发生机理,提出了一种快捷的结露判别方法.当元件表面的平衡温度达到或低于环境露点,系统将发生外部结露,反之则不会发生结露.据此机理的判别方法是:假设系统元件的初始温度为环境露点温度,在考虑系统内部气体、元件及外部空气之间的耦合传热的同时来比较若干个充放气周期结束时元件表面周期温度的变化趋势,如果元件表面周期温度逐渐升高,则系统不会发生外部结露,反之系统将发生外部结露.在气动充放气系统的二维轴对称模型中进行了数值模拟,结果表明所提方法可快速准确地判断出系统的结露情况.%The mechanism of external condensation on a pneumatic charging and discharging system was analyzed, and then a convenient judgement method for external condensation on a pneumatic system was proposed. In the judgement method, the initial temperature of components is assumed to equal the dew point of the ambient air, and then the tendency of surface period-temperature of components for several charging and discharging periods is compared considering the coupling heat transfer of the pneumatic components, the inside air and the ambient air. If the period-temperature of components rises, the external condensation will not occur, otherwise the external condensation will occur. The numerical simulation with the two-dimensional axisymmetric model of pneumatic charging and discharging system shows that the proposed judgement method can predict external condensation quickly and accurately.
  • 摘要：A method to predict the operating back pressure for an air-cooled unit was proposed by adding the program for condensation heat transfer between the cold air and steam turbine exhaust in the finned tube exchangers.The performance of the air-cooled unit under windy conditions was simulated, and operating back pressures under different windy speeds and temperatures were predicted with the present method.The result shows that the fan flow rate of the air-cooled unit drops from 476.9 ma/s to 328.6 m3/s when the wind speed increases from 0 m/s to 12 m/s.The heat transfer rate also drops from 15.86 MW to 12.45 MW, and the corresponding operating back pressure rises from 21.5 kPa to 62.5 kPa.In addition, the heat transfer rate drops from 16.36 MW to 15.43 MW and the operating back pressure rises from 12 kPa to 25 kPa when the wind temperature increases from 290 K to 306 K.%通过加栽冷空气与翅片管换热器内汽轮机排汽凝结换热程序,提出了一种直接空冷单元运行背压的预测方法,并用该方法模拟了环境风影响下空冷单元的运行性能,得到了不同风速和风温下空冷单元的运行背压.计算结果表明:空冷单元风机风量随着环境风速的上升而下降,当环境风速由0 m/s上升至12 m/s时,风机风量由476.9 m<'3>/s下降至328.6m<'3>/s,下降幅度达到20.5%,计算换热量由15.86 Mw下降至12.45 Mw,相应的运行背压由21.5 kPa上升至62.5 kPa;环境风温的变化将改变换热的冷端进口温度,当环境风温由290 K上升至306 K时,换热量由16.36MW下降至15.43 MW,相应的空冷单元运行背压由12 kPa上升至25 kPa.所提方法为空冷电厂空冷凝汽器运行背压的预测提供了理论基础,对直接空冷电厂的设计具有指导意义.
  • 摘要：Statistical quantity in turbulence and turbulence structure were investigated by direct numerical simulation on turbulent flow triggered by different mechanisms in a vertical channel. The statistical results for forced convection, combined convection and natural convection include mean streamwise velocity, mean temperature, intensity of fluctuating velocity and temperature, Reynolds stress, and turbulent structure. The results show that: Compared with forced convection, for combined convection, buoyancy leads to the higher mean velocity and lower intensity of velocity fluctuation near hot wall, but the lower mean velocity and higher intensity of velocity fluctuation near the cold wall; buoyancy results in the stronger temperature fluctuation near the wall regions and the weaker temperature fluctuation in the central part of the channel. Compared with forced convection and combined convection, for the natural convection, the profile of the mean velocity is antisymmetric to the center line, and both the largest velocity fluctuation and the smallest temperature fluctuation occur in the central part of the channel; the maximum value of Reynolds stress also locates in the central part of the channel, and negative Reynolds stresses are near the walls.%采用直接数值模拟方法研究了在不同湍流引发机制作用下竖直槽道湍流中统计量的变化以及湍流结构的变化,分别给出了强迫对流、混合对流和自然对流湍流时平均速度、平均温度、湍流脉动强度、雷诺切应力的统计结果以及湍流结构.结果表明:与强迫对流时相比,混合对流时浮升力作用使高温侧的平均速度升高,速度脉动强度降低,而低温侧的平均速度降低,速度脉动强度升高;浮升力使温度脉动强度在壁面附近区域显著增强,而在通道中心区域变弱.与强迫对流和混合对流的情况相比,自然对流的平均速度分布关于通道中心线反对称,通道中间区域的速度脉动强度最大,温度脉动强度则最小;雷诺应力最大值出现在通道中心区域,而负的雷诺应力产生在壁面附近.
  • 摘要：Three kinds of classical growth morphologies appearing in the physical vapor transport (PVT) growth process of silicon carbide bulk crystal are analyzed with regard to thermal stress by finite elements method. The results indicate that the maximum of thermal stress is located in the adjacent region of the silicon carbide and the graphite crucible lid. The distributions of the temperature field, and the corresponding thermal strain field and equivalent stress field get more homogenous in the flat growth morphology than that in the concave and convex growth morphology. And stress concentration appears at the center of the concave growth morphology and at the margin of the convex growth morphology. For improving the crystal quality, transition layer of silicon carbide formed by deposition or reaction on the graphite crucible lid is suggested to reduce the thermal stress, and the growth system of SiC crystal should be modified to maintain crystal growth in the flat morphology.%利用有限元方法对物理气相传输(PVT)法生长碳化硅晶体过程中出现的3种典型生长形态进行了热应力分析.结果表明:在3种晶体生长形态中,热应力最大值都出现在晶体与石墨坩埚盖接触区域;平面型生长形态中温度场及相应的热应变场和等效应力场分布均比较均匀;凸面型和凹面型生长形态的温度场及相应的热应变场和等效应力场分布均变化较大,而且在凸面型的中间区域和凹面型的边缘区域也存在较大的应力值.因此,为提高晶体质量,提出在石墨坩埚盖上沉积或反应生成碳化硅过渡层来减小热应力的改良方法,同时调整碳化硅晶体生长系统,尽量保证碳化硅晶体的平面型生长形态.
  • 摘要：以导电性的石墨和绝缘性的氧化铝为测试对象,对等离子活化烧结过程中试样和模具所组成体系的温度分布进行了理论分析和实验研究.结果表明,在200～800℃的测量范围内,石墨-模具体系和氧化铝-模具体系内均存在径向温度梯度,试样的温度均高于模具外壁的温度,2种体系的径向温差随温度的升高成抛物线趋势增大.在同一温度下,石墨-模具体系的径向温度梯度大于氧化铝-模具体系的径向温度梯度,2种体系内测温点与试样中心点之间的温差均随两点之间距离的增大而成抛物线趋势增大,这与理论分析结果是相一致的.%The temperature distribution of the sample-die system during plasma activated sintering (PAS) process was investigated theoretically and experimentally. For the experimental measurements, the electrical conductive graphite and non-conductive alumina samples were used.The results show that a radial temperature gradient exists in both the graphite-die and aluminadie systems, and that the temperature in the sample gets higher than that in the die in the temperature range of 200-800 ℃. Moreover, at the same temperature, the temperature gradient in the graphite-die system is larger than that in the alumina-die system. With increasing distance between measuring point and sample center, the radial temperature differences in both the systems increase following a parabolic trend, which agrees with the theoretical analysis. And the radial temperature difference exhibits a parabolic increase tendency with increasing temperature.
  • 摘要：采用注射成型制备氧化铝陶瓷,分析了热塑性黏结剂含量、混料工艺对氧化铝陶瓷粉末注射成型浆料的流变性、成型性及注射生坯性能的影响.用TGDSC分析了蜡基黏结剂体系的热特性,用SEM分析了注射成型生坯的显微结构.试验结果表明:选取聚丙烯、石蜡、硬脂酸3种黏结剂的质量比为20:70:10,氧化铝质量分数为80%,采用加热搅拌方式进行混料并结合一定的注射成型工艺,可得到成分均匀、无变形、无缺陷的氧化铝陶瓷生坯试样,烧结后试样的密度和抗弯强度较高.%The effect of thermoplastic binder and the corresponding mixing technology for alumina ceramic injection molding on the rheology behavior, formability and mechanical properties are discussed. The thermal behavior of the binders is analyzed by TG-DSC, the microstructure of the green bodies is characterized by SEM. The results show that the adequate thermoplastic binders are made up by polypropylene, paraffin and stearic acid in the mass ratio of 20 : 70: 10, and the mass fraction of alumina gets 80％. The density and three-bending strength of the sintered samples are improved by increasing the alumina and paraffin contents. The green alumina ceramics with fewer structural defects and excellent performances can be obtained when the rotational stirring heating-mixed technology is adopted.
  • 摘要：《西安交通大学学报》是西安交通大学主办的自然科学综合性学术理论刊物，它以马克思列宁主义、毛泽东思想和邓小平理论为指导，以促进科学技术发展、培育科技人才、为社会主义现代化建设服务为宗旨，坚持以“出精品、创名牌、办一流学报，争时效、促交流、举科技人才”为目标，主要登载机械、能源、动力、工程力学、电气、材料、电子、信息与控制、计算机等主学科．以及化学工程、生物医学工程、建筑、管理工程、数学、物理等学科方向的最新研究成果，重点突出机电特色．本刊为月刊，国际标准开本，国内外公开发行．为了保证刊物的质量，根据国家的有关标准和本刊的实际，特制定本简则．
  • 摘要：针对多目标跟踪算法对多目标状态提取的需求,提出了一种基于Dirichlet分布的概率假设密度滤波器多目标状态提取方法.该算法利用负指数Dirichlet分布的不稳定性来极大似然估计多目标状态;利用期望极大化算法搜寻极大似然解,同时利用Dirichlet分布驱使不相关分量消亡;为了平衡成功初始化与减少算法时间开销的要求,利用k-d树初始化Dirichlet分布.仿真结果表明,基于Dirichlet分布的概率假设密度滤波器多目标状态提取算法在多目标跟踪中优于已有算法.%A multiple target state extraction algorithm of probability hypothesis density filter based on Dirichlet distribution is proposed. The instability of Dirichlet distribution with negative exponent parameters is applied in estimating multiple target state by maximum likelihood criterion. Dirichlet distribution drives irrelevant components to extinction while the maximum likelihood solution is being searched by expectation maximum algorithm. In order to balance the successful initialization and the reduction of time cost of algorithm, a k-dimensional tree is applied to initialize Dirichlet distribution. Simulation results show that the multiple target state extraction algorithm based on Dirichlet distribution is superior to the existing algorithms for the probability hypothesis density filter in multiple target tracking.
  • 摘要：提出一种新的基于图上半监督学习的彩色图像前景/背景分割模型与算法.该算法的目的是利用人工标定的部分像素点分割信息以实现对整幅图像的分割.通过结合像素点颜色特征和像素点颜色与前景/背景颜色的相似性特征,构造了新的图节点之间的双高斯权重函数,并对此提出自适应的参数选择策略与彩色图像半监督分割的能量模型,通过优化该能量模型将已知像素点的标号信息扩散到未知像素点.实验结果表明,所提出的新算法较已有算法具有更高的分割精度,因此具有重要的应用价值.%A novel color image foreground/background segmentation model by semi-supervised learning is proposed. The essence is how to use the labeled pixels to achieve the whole image segmentation. Combining the color similarity between neighboring pixels and the color similarity between the unknown pixel and the known foreground/background pixels, a double-Gaussian function for the weight of graph nodes is constructed. And an adaptive parameter selection strategy and an energy model of semi-supervised segmentation are presented. The energy model is used to predict the labels of the unlabeled points by an optimization process. The experiments demonstrate the better segmentation accuracy than the competing algorithms.
  • 摘要：为使分级身份签名方案能够获得高安全性并同时缩短签名长度、降低计算量,提出一种标准模型下可证明安全的分级身份签名方案.现有的方案通常在签名过程中将消息作为一个整体进行运算,而文中方案则时消息进行分段处理,使得方案不仅具有效率上的优势,同时在相同的效率级别上,安全性明显优于其他现有方案.方案的安全性优势体现在:安全性证明基于完全身份的标准模型,安全性规约于计算Diffie-Hellman(CDH)假设,并且CDH假设的安全性明显优于其他的困难假设而仅次于离散对数问题,因此方案具有较强的安全性.方案的效率优势体现在:签名长度为常数,验证过程只需要进行3次双线性对运算,用户私钥长度随着级数的增加而减少.性能分析和安全性分析表明,文中方案的安全性和效率均优于现有方案.%Aiming at the intrinsic problems in hierarchical identity based signature (HIBS) schemes, such as enhancing the security, shortening the signature length, and reducing the computational costs, a novel hierarchical identity based signature scheme is proposed. The available schemes always handle the message as an entirety in the signature process; while our scheme processes the message as segments so that the scheme is not only efficient but also achieves higher security level. The suggested scheme is more secure than the existing schemes since it is proved secure in the standard model over full identity adaptive chosen message attack, and its security is reduced to computational Diffie-Hellman (CDH) assumption. The hardness of CDH assumption is superior to the other assumptions except the discrete logarithm problem. The new scheme has some efficiency advantages over the available schemes: the size of the signature is a constant, verification requires only three bilinear pairing operations, and the private keys size shrinks as the identity depth increases. The efficiency and security analysis shows that the proposed scheme is more secure and efficient compared with the existing HIBS schemes.
  • 摘要：鉴于基本概率指派生成对证据理论的研究具有重要的意义,文中针对辨识框架不完整情况提出了一种强约束广义基本概率指派赋值方法,新方法可以生成空集不为零的广义基本概率指派赋值,该数值的大小反映了系统是开放世界的可能性,针对辨识框架完整情况提出了一种弱约束基本概率指派赋值方法,该方法在样本与表示模型之间不相交时,也可以给出样本与模型相似性度量的数值,根据所提出的策略生成弱约束的基本概率指派.算例表明了所提出方法的有效性.%Determination of the basic probability assignment (BPA) is the first step to use evidence theory.How to determine BPA is still an open issue.Two methods, namely strong constrain method and weak constrain method, are proposed to deal with open world and close world respectively.In the framework of the proposed generalized evidence theory, a strong constrain method for determination of generalized basic probability assignment (GBPA) is developed.Compared with the existing methods, the new method can generate GBPA without the constrain that the empty set should be set zero.In addition, the value of the empty illustrates the possibility degree that the frame of discernment is not complete.A weak constrain method is also presented to generate BPA in the close world.The weak constrain can determine the BPA even the sample does not cross with the representation model.Some numerical examples are used to illustrate the efficiency of the proposed methods.
  • 摘要：提出一种基于独立分量分析(ICA)和局部线性嵌入流形学习算法(LLE)的新型高压直流输电(VSC-HVDC)系统故障诊断方法.由于随机噪声的干扰,单个传感器测得的系统故障信号无法直接用于故障检测,故使用快速ICA对多通道传感器测得的直流电压和电流信号进行盲源分离处理以恢复去噪的系统故障源信号;然后利用LLE挖掘潜藏于恢复信号中的子流形,提取故障敏感特征;最后将LLE提取的故障特征量作为支持向量机(SVM)的输入,建立系统故障诊断模型.通过对系统交流相对相故障、交流相对地故障以及复合故障等仿真信号进行分析,表明所提出的ICA-LLE方法能够有效地提取故障关键特征,并在3维空间将故障特征隔离,从而得到满意的SVM故障识别效果,且SVM分类精度比只使用LLE提高了近20%.%A fault diagnosis scheme for voltage source converter-high voltage direct current transmission (VSC-HVDC) system is proposed based on the independent component analysis (ICA) and the locally linear embedding (LLE) in the present work. The measured signals in the VSCHVDC can not be used directly to detect system fault due to the heavy inference noise. The FastlCA is hence employed to eliminate the disturbed noise and recover the fault sources from the measured DC line voltage and current observation signals. Then the LLE algorithm is applied to extract distinct characteristics hiding in the recovered fault signals. To enhance the fault pattern recognition, the support vector machine (SVM) is adopted to learn the relationship between the fault features and the system operation conditions. The ability of the proposed ICA-LLE method to detect VSC-HVDC system fault is evaluated with the simulated data. The analysis results demonstrate the feasibility and effectiveness. The distinguished features of the fault signals, such as AC line-to-line fault and AC line-to-ground fault, and the compound faults, can be extracted efficiently and then isolated in the 3-D feature space correctly. The classification rate of the SVM with the proposed scheme is increased by 20％ compared with LLE.
  • 摘要：An algorithm for orthogonal 4-tap integer multiwavelet transforms is proposed. By the singular value decomposition (SVD), the transform matrix can be rewritten in a product of two block diagonal matrices and a permutation matrix, and the block matrix in block diagonal matrices is factorized into triangular elementary reversible matrices (TERMs), which map integers to integers by rounding arithmetic. The cost of factorizing block matrix into TERMs does not increase with the increasing dimension of transform matrix, and the proposed algorithm is in-place calculation without allocating auxiliary memory. The examples of integer multiwavelet transform for CL, DGHM, SA4, SA4-1, SA4-2, SA4-3 and OPTFR verify that the proposed algorithm outperforms the existing algorithm for orthogonal 4-tap integer multiwavelet transform. Compared with the Van Fleet algorithm, the weighted entropy of the proposed method is decreased by 1.9-2. 8 bits.%针对4抽头多小波整数变换算法在图像无损压缩中加权熵较大的问题,提出了一种利用矩阵奇异值分解和三角分解的4抽头正交多小波整数变换算法.首先把多小波系数矩阵组成的右循环变换矩阵分解为两个块对角阵与一个置换阵之积,并对块对角阵中的块矩阵进行基本三角分解,其次对输入图像中的每一列依次与基本三角阵相乘,并对每一次相乘的结果进行取整运算,最后在输入图像列变换结果的基础上对每一行再重复上述对图像的列运算.因为在整个变换过程中该算法实现了原位计算,所以减少了运算的存储空间和运算时间.对CL、DGHM、SA4、SA4-1、SA4-2、SA4-3、OPTFR多小波的实验结果表明:相对于4抽头多小波Van Fleet算法,该算法对图像压缩的加权熵减少了1.9～2.8 b.
  • 摘要：为了提高无线网络中数据包的传输效率,提出了一种利用机会式网络编码的无线广播重传方法(WBR方法).该方法在基站先以最小重传次数下限为约束条件选择编码数据包,再传输采用机会式网络编码方法生成的组合重传包,在终端从收到的单个或多个组合重传包中恢复丢包.由于选择了更多的丢包编码生成组合重传包,使终端能从更少的组合重传包中恢复其丢包,从而有效地减少了广播重传次数.相比传统自动重传请求方法和基于网络编码的重传方法,WBR方法具有传输效率更高的特点.仿真结果表明,与自动重传请求方法和已有的基于网络编码方法相比,WBR方法的平均广播重传次数最少,而且相比自动重传请求方法的平均重传次数减少了55%.%A novel wireless broadcast retransmission method (WBR) is proposed to improve transmission efficiency over wireless networks. The lost packets from multiple terminals are selected subject to the lower-bounds on the minimum number of retransmissions at base stations.Then the selected packets are combined to generate retransmission packets by employing the opportunistic network coding. Finally, the lost packets are retrieved at terminals from the transmitted retransmission packets. Because the number of retransmission packets is less than that of lost packets, the proposed method can improve network transmission efficiency significantly. Comparisons with the automatic repeat request(ARQ) method and the existing network coding (NC)based methods show that the improvement obtained from the WBR method is clear. The simulation results show that the average number of retransmissions of WBR method is 55％ less than that of ARQ method, and the WBR method also outperforms the existing NC based methods.
  • 摘要：A two-dimensional model for fully depleted cylindrical/surrounding gate MOSFET is proposed to address the issues that the short channel effects (SCEs) of deep submicron MOSFET are more obvious with the decrease of channel length, and that mobile charge has a significant impact on surface potential when the device is working in strong-inversion regions. Taking account of the effects of both depletion charge and free charge, an one-dimensional potential model is obtained by solving one-dimensional Poisson's equation with the boundary conditions at the interface of the channel and the oxide layer. Then the Laplace equation is solved by using the boundary conditions at the source and drain regions to construct the accurate two-dimensional surface potential model. Then analytical models for both the threshold voltage and the subthreshold slope are derived. These models are verified by device simulation software Sentaurus. The results show that the proposed model is applicable from the sub-threshold region to the strong-inversion region in different channel doping conditions, and overcomes the shortcomings that the intrinsic model is not valid under the heavy doping conditions and the model based on only depletion charge fails in the strong-inversion region. Comparisons with existing models show that the error of threshold voltage reduces by 45.5 ％.%针对深亚微米围栅金属氧化物半导体场效应管(MOSFET)的短沟道效应随沟道长度减小而愈加明显,以及移动电荷在器件强反型区对表面势影响显著的问题,提出了一种全耗尽围栅MOSFET二维模型.同时考虑耗尽电荷和自由电荷的影响,结合沟道与氧化层界面处的边界条件,求解一维泊松方程,得到一维电势分布模型,然后结合器件源漏处的边界条件求解拉普拉斯方程,最终得到全耗尽围栅MOSFET精确的二维表面势模型,并在此基础上得到了阈值电压、亚阈值斜率等电学参数的解析模型.利用Sentaurus软件对解析模型进行了验证,结果表明:该模型克服了本征模型在重掺杂情况下失效和仅考虑耗尽电荷的模型在强反型区失效的缺点,在不同沟道掺杂情况下从亚阈值区到强反型区都适用;与原有模型相比,该阈值电压模型的误差减小了45.5%.
  • 摘要：针对软件开发过程中安全性分析与设计不足的问题,在研究现有软件安全性建模及形式化验证技术的基础上,提出了一种适用于面向对象的软件安全性建模与验证方法.建立软件安全属性的非形式化UML模型,采用安全扩展有限自动机创建其形式化模型,并使用线性时序逻辑描述安全属性,将形式化模型与安全属性共同作为模型检测器的输入,得到模型是否满足性质的验证结果,从而实现了软件安全设计与验证技术的有机结合.实验结果表明,该方法能够在软件设计初期对所涉及的安全性进行有效分析与验证.%In order to improve the analysis and design of software safety, on the basis of current researches on safety model and verification technology, a modeling and checking method is proposed for object-oriented software safety.Establishing non-formal UML models of software safety, safety extended deterministic finite automata and linear temporal logic are used to create the formal models and describe the safety properties separately.Through a model checker, we get the verification result.This approach realizes the combination of software safety model and verification technology.Experimental results show that the method can analyze and verify the safety properties effectively in the early stage of software design.
  • 摘要：A Steiner tree movement control algorithm (SMC) is proposed to improve low success rate and large movement cost in wireless ad hoc network topology recovery.The SMC computes a Steiner tree by calling 3STP-MSP algorithm, where the vertices contain all the nodes in the network and the introduced Steiner points.Then the Steiner points are regarded as movement destinations, and some nodes are selected and scheduled to move to these Steiner points.SMC runs iteratively until the network is connected.Simulation results show that the SMC not only reconnects the network with a success rate 100％, but also decreases the movement cost significantly,compared with the MST-based PMST-UV algorithm, and that the total movement distance is reduced by 37％ to 45％ and the number of total movement nodes is reduced by 9％ to 29％.%针对无线Ad HOC网络中拓扑修复成功率低、节点移动开销大的问题.提出了一种Steiner树移动控制算法(SMC).采用三近似最少Steiner点算法建立一棵包含网络节点和Steiner点的Steiner树.然后将引入的Steiner点作为节点移动的目的点,选择并调度一些节点移动到这些Stei-ner点上,最后更新网络拓扑,迭代执行算法直到建立一个连通的网络拓扑.仿真结果表明,与基于分区最小生成树的移动控制算法相比,SMC算法不仅修复网络拓扑的成功率可达到100%,而且还显著降低了节点移动开销,其中节点移动总距离减小了37%～45%,节点移动总数减少了9%～29%.
  • 摘要：在具有加工和安装误差的情况下,为了研究各蜗杆参数对无侧隙双滚子包络环面蜗杆的齿廓及蜗杆齿面接触线的影响规律,建立了包含加工误差和安装误差的蜗杆传动啮合函数,建立了蜗杆齿面接触线及蜗杆齿廓方程,利用三维建模技术分析了蜗杆、蜗轮轴交角误差,中心距误差,蜗杆轴向窜动误差,蜗轮滚子齿距角误差,砂轮滚子偏距误差,转角误差等对蜗杆齿廓的影响,同时分析了在误差作用下蜗杆齿面接触线发生的变化,并进行了运动学仿真.研究结果表明:转角误差、砂轮滚子齿距角误差达0.5°时对蜗杆齿廓影响较为明显,即容易产生卡死现象;当蜗杆轴交角误差达0.5°时,整个蜗杆齿廓产生了严重变形,且蜗杆轴断面变为椭圆形,极易发生蜗轮轮齿折断现象;其他误差在1 mm以内时对齿廓及齿接触线的影响较小.%For a new non-backlash double-roller enveloping hourglass worm, the tooth profile and contact curve equation, which involves several errors of worm parameters, was established to investigate the effects of the errors on the worm tooth profile. Technology of three-dimensional modeling was chosen to analyze the influence law of the errors. The influences of the setover error of roller, the error of axial float of worm, the centre distance error, the error of axial movement, the angular pitch error and the error of shaft angle on the tooth profile were discussed, the contact curve was analyzed, and the kinematic simulation was carried out. The results show that the axial movement error, the angular pitch error and the error of shaft angle reaching 0.5° exert clear influence on the tooth profile of worm; especially, when the error of shaft angle gets 0. 5°the tooth profile of worm is heavily deformed and the axis cross-section becomes ellipse; however, the other errors have lighter influence on the tooth profile of worm as the values are limited within 1.0 mm.
  • 摘要：Since artificial intelligence(Al) planners have different application domains and precondition, while the method of Web service composition using single AI planner has restricted the development of AI planner in Web service composition, we propose a novel approach to translates Web service to planning domain definition language(PDDL) in consideration of the similarity between Web ontology language for services(OWL-S) and PDDL.In this method, the problem of Web service composition is translated to the problem of plan by the corresponding elements translation between OWL-S and PDDL.After the translation, we can choose the most suitable AI planner to compose Web service.The composition method is verified by the experiment of weather finder.The result of experiment shows that the proposed method can be used in the problem of Web service composition, and it increases the AI planner's universality in resolving the Web service composition problem.%针对单个智能(AI)规划器在解决Web服务组合问题时通用性不高以及性能受问题搜索空间影响较大的情况,基于本体描述语言(OWL-S)和规划描述语言(PDDL)结构上有极大的相似性,提出了一种将Web服务转化为PDDL描述的算法.该算法通过对OWL-S和PDDL中相应元素的转换,将Web服务组合问题成功地转换为规划问题.完成该转换后,就可自由选择AI规划器对Web服务进行组合.以查询天气信息作为组合案例,对本文提出的组合方法进行了验证,结果表明,文中所提的组合方法可用于解决Web服务组合问题,提高了AI规划器在Web服务组合问题上的普适性.
  • 摘要：针对Ad Hoc网络节点具有的可移动的特点,提出了一种基于接收信号功率的移动控制算法.该算法是在无法获取节点位置信息的情况下,对网络拓扑进行优化配置.文中定义了基于接收信号强度的性能函数,当节点位于该函数的最小值点时,传输数据所需的能量消耗最小.可将该函数取得最优解的位置作为节点移动的目标位置,并根据检测到的接收信号强度逐步搜索到该位置.实验结果表明,在位置信息未知的情况下,可通过该算法找到节点移动的目标位置从而减少传输能量的消耗.%According to the mobility of the nodes in Ad Hoc network, this paper gives an algorithm of the movement control based on the strength of the receiving signal.It proposes a way to optimize the network configuration in the situation that the position information of nodes is unavailable.And furthermore, in this paper, the performance function is also defined.That is,when a node moves to the point where the function is minimized, the transmission cost is also minimized.On the basis of this concept, we can fix the node's target point at the optimum solution of the function.And this solution can be found through the receiving signal strength.Simulation results show that the algorithm can be used to find a node's target point and minimize the transmission cost by moving the node to this target point.
  • 摘要：Zirconium oxide microfiltration membrane was modified by nano zinc oxide by coprecipitation.The variations of permeation flux and oil rejection of the unmodified and zinc oxide modified membranes in the oil/water separation process were discussed.The results show that the modified membrane has good microstructure, the permeation flux of zinc oxide modified membranes is higher than that of the unmodified membrane in the oil/water separation process; especially, the permeation flux of nano zinc oxide once modified microfiltration membrane increases by more 26.2％ compared with that of the unmodified membrane.The oil content in the permeation of unmodified membrane does not reach the national standards after 120 min, but that of the modified membranes comes up to the national standards.And the oil rejection of the modified membranes gets higher than that of the unmodified membrane.%采用均相沉淀法.对ZrO2微滤膜进行纳米ZnO改性,考察了未改性和ZnO改性微滤膜在油水分离过程中的渗透通量和油截留率的变化规律.实验结果表明,改性微滤膜具有良好的显微结构,同时在油水分离过程中,改性膜的渗透通量明显高于未改性膜,其中ZnO一次改性微滤膜的渗透通量比未改性膜提高了26.2%.在进行了120 min的油水分离后,未改性膜渗透液中的油浓度仍未达标,而改性膜的渗透液已经达标,且其油截留率均高于未改性膜.
  • 摘要：It is not efficient for the approach of constraining outdegree to enhance delay and loss rate synthetically for an application-level multicast tree. This paper proposes an application-level multicast tree which achieves minimum cost in terms of delay and loss rate. A cost function which consists of delay and loss rate is given to compute transmission cost of the multicast tree, and the problem model about how to construct the minimum multiplex-cost multicast tree is also given.Unlike existing problem models, this model abandons the approach of constraining outdegree.Furthermore, a variation of the maximal delay path greed algorithm is proposed to address the problem model. This variation algorithm optimizes total cost of a multicast tree. Finally, our extensive experimental results help to give the concrete suggestion about the parameters which the cost function involves, and demonstrate that the proposed application-level multicast tree construction algorithm has higher efficiency in total cost of the multicast tree than another related algorithm has.%针对度约束方式难以减少应用层组播树的延迟和丢包率的问题,提出了一种延迟和丢包率综合代价最小的应用层组播树构树算法.为避免度约束的局限性,给出一个包含延迟和丢包率的复合代价函数,以此来计算传输代价,进而构建了一种最小复合代价组播树的问题模型.为了求解该问题模型,提出了一种基于最大延迟路径贪婪算法的变异算法,同时在构树时对总传输代价进行优化.通过实验,给出复合代价函数的具体参数建议.对比相关算法,文中的构树算法在总传输代价方面有更好的性能.
  • 摘要：A novel testing system for stability of organic light emitting devices (OLED) is proposed to improve the circuital complexity and high cost of existing systems.The proposed system employs the high precision IC operational amplifiers to achieve driving power supply, and uses silicon photocells to capture brightness of OLED.Then an acquisition board based on PCI bus is used to obtain the data concerning the variation of brightness and voltage of OLED.The testing system can provide two different power sources, i.e., a constant current source and a hybrid current-voltage source (a constant current source for direct bias and a constant voltage source for reverse bias).Silicon photocells are used to replace traditional brightness photometers so that costs are substantially reduced, while the use of the acquisition board based on PCI bus decreases development difficulty and shortens the development time.Testing results show that the system is competent to measure luminance delay and voltage raising, and is stable and reliable.%针对目前有机电致发光器件的稳定性测试系统电路复杂和成本较高等问题,设计了一种有机电致发光器件稳定性测试系统.该系统采用集成运放组建器件的驱动电源,用硅光电池俘获亮度值.并选用基于PCI总线的采集卡来采集亮度数据和电压数据.该稳定性测试系统不仅能够提供常用的恒流驱动方式.而且可以提供一种电流一电压混合源(正向恒流反向恒压)驱动.由于采用硅光电池代替传统的辉度计,因此大幅度节约了成本;基于PCI总线的采集卡的选择,降低了开发设计的难杂程度,缩短了开发周期.测试结果表明,该系统能够测试不同样品的亮度衰减和电压上升情况,性能稳定,数据可靠.
  • 摘要：针对目前雨衰预测模型在Ka频段雨衰估计中复杂度高、计算量大的问题,提出了一种结构相对简单、计算量较小的自相关雨衰预测模型.该模型首先利用前导雨衰数据之间的自相关性,采用平均误差功率最小的原则计算出模型的参数,然后结合前导数据迭代推算出Ka频段各个频率点的雨衰值.仿真结果表明,不同的前导数据量和预测间隔具有不同的预测精度,在前导数据量为20、预测间隔为0.05 GHZ时,新模型的雨衰量预测误差在整个Ka频段均达到10-5 dB以下.%In order to reduce the complexity of current rain attenuation prediction models, a new auto-correlation rain attenuation prediction model is proposed. The model has the advantages of relatively simple structure and less computational consumption. The new model takes the advantage of the auto-correlation character of preamble dates, and computes the model parameters by minimizing the average error power. Then, the preamble data and model parameters are used to compute the rain attenuation at each frequency point in Ka band. Simulation results show that prediction precision varies with different prediction intervals and different amount of preamble data. The prediction error of the new model is less than 10-5 dB in Ka band when the number of preamble data is 20 and the prediction interval is 0. 05 GHz.
  • 摘要：A synthesis constitution (SC) method of metamaterials which have an electric response and a magnetic response is proposed.The metallic triangular open loop resonators etched on the dielectric board have the magnetic response, i.e., the negative permeability; and the metallic wire arrays etched on the dielectric board have the electric response, i.e., the negative permittivity.Through locating the wire in the middle part of the loop and combining the two structures mentioned above, the SC method constitutes the triangular electromagnetic resonator (TER) which simultaneously has the magnetic and the electric responses and composes the novel metamaterials in the TER array form.Both theoretical simulation and experiment measurement prove that compared with the conventional split ring resonator (SRR) and wire structure, TER have the dual stopbands property which corresponds to the electric and magnetic responses.Moreover,the left-handed passband of the double negative metamaterial composed of TER-wire is 217％ wider than that of the conventional SRR-wire design.%提出了一种同时具有电磁模式响应的人工电磁媒质的综合构成(SC)方法.在介质基板上单面刻蚀的三角形金属开口对环只具有磁响应,即只具有负的磁导率,在介质基板上单面刻蚀的金属线阵列只具有电响应,即只具有负的介电常数,SC方法通过将金属线设计在开口环的中部,将以上两种结构连接起来,从而构成同时具有电磁响应的三角形电磁谐振(TER)单元结构,并通过将TER排成阵列构成新型人工电磁媒质.理论仿真与实验测量结果表明,与传统的金属环加线结构相比,TER单元具有电响应与磁响应的双阻带特性,并且由其构成的双负媒质的左手传输通带带宽比环加线结构的带宽扩展了217%.
  • 摘要：《西安交通大学学报》是西安交通大学主办的自然科学综合性学术理论刊物，它以马克思列宁主义、毛泽东思想和邓小平理论为指导，以促进科学技术发展、培育科技人才、为社会主义现代化建设服务为宗旨，坚持以“出精品、创名牌、办一流学报，争时效、促交流、举科技人才”为目标，主要登载机械、能源、动力、工程力学、电气、材料、电子、信息与控制、计算机等主学科，以及化学工程、生物医学工程、建筑、管理工程、数学、物理等学科方向的最新研究成果，重点突出机电特色．
  • 摘要：针对工程复杂性、时变性、非线性的特点,提出了基于混沌免疫粒子群算法(CIPSO)与El-man神经网络的耦合算法(CIPSD-ENN),用于非线性动态模型参数辨识.CIPSO优化算法将人工免疫系统中的克隆选择和混沌优化机制引入粒子群算法,在粒子群种群进化过程中.该算法对粒子进行克隆选择,提高其收敛速度,对克隆后的粒子混沌变异以增强种群局部搜索能力,最后,CIPSO与动态反馈型Elman神经网络融合,对其权值、阈值寻优,建立了基于CIPSO和ENN的耦合算法系统辨识模型.实验结果表明,算法具有收敛速度快、收敛精度高、鲁棒性强的特点,与单纯Elman网络辨识相比,模型收敛速度提高了10倍,拟合精度提高了2个数量级.%Aiming at the complexity, time varying and nonlinearity of the projects, a CIPSO-ENN coupling algorithm for identifying the parameters of nonlinear dynamic models is proposed, where the clonal selection of artificial immune system and chaotic mutation mechanism are embedded into standard particle swarm optimization.In the evolution of the particle swarm optimization population, this algorithm accelerates convergence of particle clonal selection and enhances the particle swarm local search capability after cloned particle chaotic mutation.Then CIPSO algorithm is merged with dynamic feedback Elman neural network to construct system identification model based on the CIPSO-ENN.The experiment results show that the identification model convergence rate is increased by 10 times and fitting accuracy is increased by 2 orders of magnitude compared with the pure Elman network identification method.

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