A joint replenishment problem considering multiple trucks with shipment and resource constraints

A joint replenishment problem (JRP) is presented to determine the optimal reordering policy for multi-items with a percentage of defective items. This JRP also has several constraints, such as shipment constraint, budget constraint, and transportation capacity constraint. At the meantime, multiple trucks, each with a fixed transportation cost, are considered and also order quantities of restricted items are not shared among the trucks during the shipment. The objective is to minimize the total expected cost per unit time. A two-dimensional genetic algorithm (GA) is provided to determine an optimal family cycle length and the reorder frequencies. A numerical example is presented and the results are discussed. Extensive computational experiments are performed to test the performance of the GA. The JRP is also solved by using an evolutionary algorithm (EA) and the results obtained from GA and EA are compared.     

高排放标准下道路燃油车处境分析

针对国六排放标准实施后道路燃油车竞争和生存压力加大的问题,调查统计近5 a汽车及新能源汽车的保有量,汽车保有量以年均12%的比例增长,新能源汽车保有量以每年约50%的比例增长;研究和对比近年来机动车排放标准,分析道路燃油车节能减排存在的问题,从政策引导制约、供油企业升级改造、燃油车本身的改进优化等几方面提出时效性方案与建议。     

Significance of AE crack monitoring in fracture toughness evaluation and non-linear rock fracture mechanics

This paper describes results of experimental research in which the fracture toughness of a granite is determined by means of the J-integral approach and an acoustic-emission (AE) technique. Compact tension specimens and three-point bend specimens of various sizes were tested, and the effects of specimen size and loading condition on the fracture toughness were examined. Concurrently with the fracture toughness tests. AE monitoring was conducted, and the relation between the AE characteristics and fracture behavior was examined. Energy measurements of AE signals and frequency spectral analyses were made to characterize the AE signals. The AE measurements were used to determine a fracture toughness evaluation point and to obtain the critical J-integral value, denoted by J_iAE. It is demonstrated that the J_iAE value is reasinably constant for a wide range of specimen sizes and specimen types. Based on the result, the fracture toughness of the granite K_Ic was then computed from the J_iAE value using the conversion equation under the assumption of linear elastic response. A comparison of linear elastic fracture toughness values with K_Ic showed that the J-integral approach combined with the AE technique can be applied to determine a valid fracture toughness of the granite. Finally, a reason for the specimen size dependency observed in the linear elastic toughness value is discussed on the basis of the experimental results.     

核桃无损检测技术研究进展

核桃品种多样、食味香纯、口感细腻、出油率高,能够健脑益智、补气养血、润燥化痰、防癌抗癌,是我国栽培历史悠久、营养价值丰富的农产品,有着“万岁子”“长寿果”的美誉。但核桃在生长和处理过程中,受产地、品种、气候、储存环境、处理设备等因素的影响,容易造成核桃品质不一,甚至出现霉烂、虫害和变质等现象,影响核桃品质和后续深加工。为保证核桃产品质量,需对核桃进行检测和分级,而无损检测技术可以在不破坏核桃本身的情况下对其进行高效快速的检测,避免检测过程中样品成分和营养损失,因此被广泛应用在核桃检测中。本文总结了3种无损检测技术,对比分析了3种无损检测技术的优劣,并从产地品种检测、内部品质检测、外部缺陷检测、异物分类检测4个方面总结了无损检测在核桃相关检测中的应用研究进展,提出了核桃相关检测中存在的问题,并对核桃无损检测研究的发展前景进行了展望,为无损检测技术在核桃相关领域应用提供了参考。     

基于IGBT的固态高压脉冲电源的研究与设计

由于脉冲电源有断续供电的特性,在很多领域都获得了广泛的应用,其中高压脉冲电源是系统的核心组成部分。为了获取高重复频率、陡前沿高压脉冲电源,文中提出了一种基于IGBT的高压脉冲电源,系统主要由高压直流充电电源和脉冲形成电路两部分组成,由DSP作为主控制芯片,控制IGBT的触发和实现软开关技术,并用仿真软件PSIM对高压脉冲电源进行仿真分析。验证了设计思想的正确性。     

激光织构形状间距对单晶硅摩擦磨损特性的影响

目的 提高单晶硅的减摩耐磨性能。方法 利用紫外激光在单晶硅试样表面刻蚀不同形状,间距为0.1、0.2、0.3 mm,宽度为0.2 mm的织构。基于MRTR-1摩擦磨损实验机,研究干摩擦条件下织构参数对单晶硅摩擦学性能的影响。利用光学显微镜和扫描电子显微镜(SEM)观察单晶硅表面织构的微观形貌和磨痕形貌,用电子天平称量实验前后试样的质量,并计算磨损率,通过Ansys有限元软件模拟仿真试样表面应力和摩擦生热的温度分布。结果 与无织构相比,刻蚀表面织构均能不同程度地降低试样的磨损率,磨损率从0.012 mm³/(N.m)降至0.008 mm³/(N.m);部分表面织构试样的摩擦因数下降,低于0.14;单晶硅试样的磨损机制主要为磨粒磨损和黏着磨损。仿真结果表明,织构试样的平均等效应力均大于无织构试样,在单晶硅试样表面加工织构会影响其表面整体性,容易出现应力集中现象;织构试样表面高于环境温度的区域面积小于无织构试样,且试样表面的最高温度与摩擦因数呈正相关。结论 在单晶硅表面加工织构,可以有效提高试样的耐磨性能,合适的织构参数还能够降低摩擦因数。通过加工表面织构,一方面可以影响试样的整体性,另一方面能够改善试样的散热性能。     

Heat transfer analysis of H-type finned tube embedded in packed bed for gasification to produce hydrogen

Gasification for hydrogen production by the H-type finned tube embedded in the packed bed is considered to be more economical. Based on the thermal flow reversal reactor, the heat transfer characteristics of H-type finned tube embedded on the both sides of high-temperature zone of the packed bed under the quasi-steady were researched. The contribution of radiation heat transfer rate on the H-type finned tube is about 60.5% at most and radiation mainly occurs on the central tube. Within the range of inlet temperature and Re, the fin-assisted degree is both decreased gradually and the maximum is 48.9%. When the temperature is above 906 K or within the range of Re, the heat transfer rate of the fin is mainly from the radiation heat transfer rate. Under the condition of high inlet temperature and high Re, the fin-assisted degree is minimum, which indicates the operation stability of the H-type finned tube is better.     

柴油机燃用生物柴油的多环芳香烃排放试验研究

在一台直喷式增压柴油机上进行了生物柴油、柴油及其掺混油B20的排放特性试验,分别用玻璃纤维滤膜和“聚氨基甲酸乙酯泡沫（PUF）＋XAD．2”采集了尾气排放物中的颗粒相和气相多环芳香烃（PAHs）,并用色谱．质谱联用仪对PAHs进行了分析。结果表明：生物柴油的颗粒相、气相以及总PAHs的排放在大多数工况下低于柴油,其平均排放浓度均低于柴油。3种燃料的二环PAHs排放均在50％,生物柴油的三环以上PAHs所占比例均低于柴油。生物柴油PAHs排放的毒性当量与柴油相比有较大程度地下降。燃用生物柴油可以降低柴油机PAHs排放物对人体的危害。