零等待混合流水车间问题优化研究

研究了带零等待的混合流水车间调度问题,考虑工件动态到达的实际生产特征,以最小化总加权完成时间为目标,建立整数规划模型,然后设计一种基于代理次梯度法的改进拉格朗日松弛算法.基于工件分解策略将拉格朗日松弛问题分解为多个工件级子问题,不同于每次迭代要求最优求解所有子问题的次梯度法,所设计的代理次梯度法通过每次迭代最优求解几个子问题得到松弛问题的近似解,进而获得搜索拉格朗日乘子的代理次梯度方向,最后设计启发式构造可行时间表.通过仿真实验,证明了所设计的算法在解的质量和收敛性方面均优于传统的使用次梯度法的拉格朗日松弛算法.     

钢铁一体化生产调度模型与优化算法北大核心CSSCI

为达到降低在制品库存及保证生产连续性等目标,将炼钢-连铸-热轧一体化生产过程归结为中间阶段为批处理机的多阶段柔性流水车间调度问题,建立了一体化生产模型。该模型以总加权完成时间和总加权滞留时间之和为优化目标,综合考虑了机器加工能力、浇次处理要求、炉次释放时间等约束条件。将拉格朗日松弛算法应用于模型中,利用该算法的批分解方式和子问题的双向动态规划求解策略,提高了算法的收敛速度和下界。不同规模问题的测试结果表明了模型和算法的有效性。     

钢铁一体化生产调度模型与优化算法

为达到降低在制品库存及保证生产连续性等目标,将炼钢-连铸-热轧一体化生产过程归结为中间阶段为批处理机的多阶段柔性流水车间调度问题,建立了一体化生产模型。该模型以总加权完成时间和总加权滞留时间之和为优化目标,综合考虑了机器加工能力、浇次处理要求、炉次释放时间等约束条件。将拉格朗日松弛算法应用于模型中,利用该算法的批分解方式和子问题的双向动态规划求解策略,提高了算法的收敛速度和下界。不同规模问题的测试结果表明了模型和算法的有效性。     

考虑平行机环境下紧急任务最大等待时间的优化调度

以快速响应无预知到达的紧急任务为研究背景，考虑两台平行机环境下紧急任务等待时间的优化调度问题。给定机器最大完工时间上界，考虑机器在加工过程中可空闲情形，在不中断常规任务的条件下，以最小化紧急任务的最大等待时间为研究目标，构建了混合整数规划模型，并对问题的某一类最优方案进行分析，证明了该类最优解满足两台机器无同时空闲以及最大完工时间达到上界的性质。基于该性质，设计了一种启发式算法以及随机键编码的遗传算法对该问题进行求解。仿真实验结果表明：遗传算法在小规模工件求解时略优，但计算时间较长；启发式算法在大规模工件求解时其求解质量与求解时间均有明显优势。本研究可为实际中对限定机器工作负荷的场景如何安排机器的空闲时间以快速响应紧急任务提供决策建议。     

库存与运输整合问题的多种算法比较

通过循序渐进地应用拉格朗日乘数法、基于样本的DSSP(Dynamic Slope Scaling Procedure)启发法和基于拉格朗日松弛模型的DSSP启发法等几种算法,分别求解多对多配送系统中的库存与运输整合优化问题,逐渐找到了解决问题的更加有效的方法———基于拉格朗日松弛模型的DSSP启发法。通过比较实验证明了此法在解决库存与运输整合优化问题时能在更少的计算时间里获得更优化的解。     

有限等待流水车间调度邻域搜索算法

针对工序间等待时间受限,目标函数为最大完工时间最短的流水车间调度问题,提出了一种动态变邻域搜索算法。算法采用工件对比较算法和贪婪插入规则,构建了初始调度;通过嵌入3-opt,2-opt实现动态变邻域搜索;并在迭代过程中加入动态禁忌策略。     

考虑降低碳排放的废钢铁再制造等待时间受限生产调度研究

针对工件等待时间受限的废钢铁再制造生产调度问题,在碳排放约束下构建了等待时间受限的废钢铁再制造生产调度模型,并设计遗传算法进行了求解.最后结合算例,比较分析了碳排放对生产调度的影响,并得出:废钢铁再制造过程产生的碳排放量与设备空转时间呈显著的正相关关系;工件等待时间受限作为约束其主要作用在于避免重调度,对于减少makespan和碳排放量影响不大.     

空箱资源约束调度的列生成算法研究

研究了可重用空箱资源约束下的入厂物流车辆运输调度问题。首先对该问题进行数学描述,建立混合整数线性规划模型。鉴于问题的NP难解性,研究求解该问题的列生成方法,提出虚工件等技巧,建立适合序列依赖的可重用资源约束调度的列生成主问题模型以及基于检验数求解的子问题模型,并研究求解子问题的动态规划算法。进一步采用分支定界技巧,最终提出适合本问题求解的列生成算法。数值实验表明方法的有效性与高效性。     

基于后悔值准则的个性化产品鲁棒调度

个性化产品的生产过程具有非重复性,致使工序的加工时间不确定且难以估计其概率信息。因此,传统的确定调度和随机调度方法不再适用。采用最小化最大后悔值的鲁棒优化方法,研究变速平行机加工环境下个性化产品的生产调度问题。首先,采用区间情景描述不确定的加工时间,构建基于后悔值准则的个性化产品鲁棒调度模型;其次,证明任意调度方案带来的最大后悔值可通过求解一个指派问题得到;然后,提出基于混合整数规划和迭代松弛过程的两种精确算法获取最优解;最后,通过仿真实验评估两种精确算法的有效性,结果表明基于混合整数规划的精确算法明显优于迭代松弛算法,并且可以快速求解中小规模的调度问题。     

供应链中生产和运输协调调度问题初探

提出了解决供应链中生产和航空运输协调调度问题的理论框架.基于对生产调度和航空运输调度彼此制约关系的分析,协调调度问题被分解为两个子调度问题.建立了航空运输子调度问题的整数规划模型,并证明了该问题为NP完全问题.提出了基于倒排调度方法(backward scheduling method)的调度算法解单机生产调度子问题.     

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...     

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.     

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.……     

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.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.