一类变量为梯形模糊数的线性规划

针对变量为梯形模糊数的模糊线性规划问题,利用结构元方法定义了一种模糊数的排序准则,讨论了如何将变量是梯形模糊数的线性规划去模糊化,即将含有变量为梯形模糊数的模糊线性规划转化为经典模糊线性规划.同时,证明了该模型的最优解等价于经典的线性规划的最优解,再利用单纯形法求出最优解.并设计了求解该类模型的算法.通过算例验证了该方法的可行性和算法的有效性,从而为变量模糊的广义模糊线性规划问题的研究提供了新的方法.     

不定二次规划全局求解的一个新算法

针对工程设计、设施布局等领域出现的不定二次规划问题的求解,本文给出了一个新的全局优化算法.首先根据二次函数的特点,利用线性松弛化技巧,建立不定二次规划问题的松弛线性规划问题;然后通过一系列松弛线性规划问题的解逐步逼近原问题的最优解.理论上证明了算法的收敛性,数值算例表明算法是有效可行的.     

基于最优潮流的可用输电能力计算分析

本文通过建立计及晶闸管控制的移相器的ATC计算模型和基于最优潮流（OPF）方法,将可用输电能力的计算转化为求解多约束的非线性规划问题,在算法上采用半光滑牛顿算法,通过对IEEE30节点系统的计算结果,证明了所提出的模型及算法的正确性。     

一种变量是梯形模糊数的两层多随从线性规划模型及其算法

针对具有递阶特征的多层管理系统,本文建立了一种变量为梯形模糊数的两层多随处线性规划模型.利用模糊结构元理论,通过模糊数的结构元加权序,将梯形模糊数的排序转化为单调有界函数的排序,从而证明了该模型的最优解等价于两层多随处线性规划模型的最优解;进而提出了求解该模型的有效算法.最后,通过两个数值算例验证了该方法的可行性.     

求解不定二次约束二次规划问题的全局优化算法

不定二次约束二次规划问题广泛应用于芯片设计、无线通信网络、财政金融和众多工程实际问题．目前尚没有通用的全局收敛准则,这使得求解该问题的全局最优解面临着极大挑战．本文使用矩阵的初等变换技巧将原问题转化为等价双线性规划问题,基于等价问题的特征和线性化松弛技巧构造了等价问题的松弛线性规划,通过求解一系列松弛规划问题的最优解逐步逼近原问题的全局最优解．证明了算法的全局收敛性,并进行数值对比和随机实验,实验结果表明算法高效可行．     

求解模糊线性规划问题的一种解法

本文首先建立一类模糊线性规划问题的对偶问题,利用求解对偶问题,得到原规划问题的最优解。由于将模糊向量转移到目标函数中去,因而初始可行基只计算一次,从而可压缩计算量,文中给出了一般计算步骤和数值例子,并对两种算法进行了比较,结果表明新算法计算量小。 文中还证明了原规划与对偶规划的最优判决相等。     

对公务员招聘问题的思考

本文利用层次分析法和0-1型整数规划建立了一个公务员招聘的数学模型,并结合实际提出了通用可行的算法.首先利用层次分析法确定了招聘人员面试成绩对用人部门的权重,再把笔试成绩转化为相应的权重,然后将笔试成绩和面试成绩对用人部门的权重结合起来,建立了权重计算模型.再把应聘人员的志愿转化为用人单位对应聘人员的权重,建立了双向选择的权重计算模型.然后确定最优方案模型,被选人员对用人单位的权重之和最大时的人员选取即为所求,从而建立了应聘人员最优选取的0-1整数规划模型,制定出最优的分配方案,并对一股情况即N个应聘人员M个用人单位时,对模型做了推广.最后利用Matlab和Lingo编程对上述模型和算法进行了实践求解.针对实际本文还充分考虑了多种情况下各种因素对人员招聘的影响,较完满地解决了公务员招聘问题,并检验了模型的合理性,文章分析了模型的优缺点和改进方向,同时提出了一些实用性建议.     

基于离散事件优化的流水线集成优化设计研究

流水线集成优化问题包含三个子问题:工作站分配问题,工作量切分问题与缓存分配问题。同时解决上述三个子问题,研究满足目标生产率要求的成本最低的流水线设计。为了解决上述问题,基于离散事件优化方法,建立描述仿真优化的混合整数规划模型;由于精确模型的求解复杂度高,精确的混合整数规划模型被近似为线性规划模型;这一近似模型的精度不足,为了进一步完善模型,调整了近似模型的构造,并以此为基础开发了数学启发式算法。数值实验表明,与现有的仿真优化软件相比,该数学启发式算法可以在较短的时间内求得满足约束条件且更接近全局最优的解。还研究了集成优化问题中的工作量切分与缓存分配图样。     

加工时间存在双重约束的批调度模型及算法

为了提高热处理的加工效率并实现准时交货,本文根据热处理各批次加工时间受装炉量和批中最大工件尺寸双重约束的特点,分别以最小化最大完成时间和最小化最大拖期量为调度目标,构建混合整数线性规划模型Model C和Model L。根据分批数量上界设定值与Model C运算结果的关系特性,构建启发式算法HC提高Model C的运算效率。通过反例说明Model C所具有的特性并不适用于求解Model L。提出启发式算法HL求解最小化最大拖期量问题,并证明算法HL的计算复杂度。通过大量实验数据验证,结果显示两个数学模型都分别能够求得最优解,但调度规模不超过18个工件;算法HC能得到调度规模为60个工件的最优解;算法HL与最优解相比平均偏差不超过15%,调度性能明显优于其他2种典型算法。     

校园停车政策的数学模型

佐治亚理工学院校园停车问题错综复杂。本文建立了一个变系数的线性规划模型解决这一问题，即考虑给定多组不同的价格表，对每一组价格分别求线性规划的最优解，再根据收支应有一定盈余的要求确定一组最佳的停车价格及相应的停车位分配方案。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Friction Stir Processing Strategies for Uniform Distribution of Reinforcement in a Surface Composite

Friction stir processing (FSP) is an important technique for preparing surface composites. Fabricating defect-free surface composites with uniform particle distribution by FSP is a challenging task. In this study, silicon carbide particles reinforced AA5083 alloy surface composites was fabricated using different FSP strategies including variation in process parameters, dual-tool processing and tool offset overlapping. Material flow of the processed material with reinforcement particles demonstrated that the distribution of particles was influenced by the stirring action of the probe as well as the extrusion of the plasticized material due to the movement of the tool. Process parameters, particularly rotational speed, showed a dominant influence on the distribution of silicon carbide particles.