Simulation optimization approach for hybrid flow shop scheduling problem in semiconductor back-end manufacturing

This study presents a simulation optimization approach for a hybrid flow shop scheduling problem in a real-world semiconductor back-end assembly facility. The complexity of the problem is determined based on demand and supply characteristics. Demand varies with orders characterized by different quantities, product types, and release times. Supply varies with the number of flexible manufacturing routes but is constrained in a multi-line/multi-stage production system that contains certain types and numbers of identical and unrelated parallel machines. An order is typically split into separate jobs for parallel processing and subsequently merged for completion to reduce flow time. Split jobs that apply the same qualified machine type per order are compiled for quality and traceability. The objective is to achieve the feasible minimal flow time by determining the optimal assignment of the production line and machine type at each stage for each order. A simulation optimization approach is adopted due to the complex and stochastic nature of the problem. The approach includes a simulation model for performance evaluation, an optimization strategy with application of a genetic algorithm, and an acceleration technique via an optimal computing budget allocation. Furthermore, scenario analyses of the different levels of demand, product mix, and lot sizing are performed to reveal the advantage of simulation. This study demonstrates the value of the simulation optimization approach for practical applications and provides directions for future research on the stochastic hybrid flow shop scheduling problem.     

A resilient buffer allocation scheme in active queue management: a stochastic cooperative game theoretic approach

During the last decade, a plentiful number of active queue management schemes have been proposed, but their main objectives are simply allocating the buffer resource to all flows evenly, or protecting responsive flows from being degraded by unresponsive flows. However, the sending rates of the responsive flows can be determined diversely, and not all unresponsive flows have aggressively high sending rates. Furthermore, it is rational to reserve a portion of the buffer resource for certain privileged traffic. Grounded by these evidences, in this paper, we present a resilient active queue management algorithm, named Prior‐Core‐based Buffer Allocation considering diverse congestion control algorithms, fair‐unresponsive flows, and some privileged traffic. Our approach is based on stochastic cooperative game theory, where the payoffs yielded by cooperation are described by random variables, and the core is defined only over the distribution of these random payoffs; the core in this situation is called the prior‐core. As a result, it is shown that our buffer allocation, yielded by the prior‐core, achieves completely fair allocation for those flows whose requirement does not exceed the fair‐share regardless of the responsiveness, whereas aggressive flows are restricted according to availability of the buffer; all these are verified through ns‐2 simulation experiments. Copyright © 2014 John Wiley & Sons, Ltd.     

增效过磷酸钙的增效机制及其对玉米生长的影响

利用猪毛、风化煤和腐植酸钠的水解液为增效剂制备了一种增效过磷酸钙,探讨了增效过磷酸钙的增效机制及其对玉米生长的影响。结果表明,蒸馏水浸提条件下,增效过磷酸钙能减缓水溶磷的释放,具备较高的pH值缓冲性。与普通过磷酸钙相比,增效过磷酸钙处理的玉米生物量平均增加了41.9%,吸磷量和吸钙量分别增加了61.7%和27.8%,根系活力增加了24.3%。该研究结果对过磷酸钙生产的技术改进具有指导意义。     

Receding horizon time-optimal control for a class of differentially flat systems

A closed-loop, time-optimal path-following control scheme is proposed for a class of constrained differentially flat systems. Within a receding horizon framework, a finite horizon optimisation problem is solved at each sample, using available state feedback and feedforward path information. Irrespective of horizon length, the proposed formulation guarantees exact path-following. Moreover, the requirements under which the proposed algorithm achieves minimum-time path-following are established. Simulations conducted with a rigid X–Y table model confirm the theoretical results.     

Hydrogen storage and electrochemical properties of annealed low-Co AB5 type intermetallic compounds

The structure, hydrogen storage and electrochemical properties of annealed low-Co AB₅-type intermetallic compounds have been investigated. La-alloy, Nd-alloy and Cr-alloy are used to represent La_0.8Ce_0.2Ni₄Co_0.4Mn_0.3Al_0.3, La_0.6Ce_0.2Nd_0.2Ni₄Co_0.4Mn_0.3Al_0.3 and La_0.6Ce_0.2Nd_0.2Ni_3.8Co_0.4Mn_0.3Al_0.3Cr_0.2, respectively. The XRD results indicated that annealed samples are all single-phase alloys with CaCu₅ type structure. The maximum of both hydrogen content and discharge capacity is obtained for La-alloy 1.23 wt%H₂ and 321.1 mA h/g, respectively. All the investigated alloys are quiet stable with ΔH of hydrogen desorption about 36–38 kJ/mol H₂. Cycle life of alloy electrode has been improved by partial substitution of La for Nd and Ni for Cr. The highest capacity retention of 92.2% after 100 charge/discharge cycles at 1C has been observed for Nd-alloy. The hydrogen diffusion coefficient measured by PITT is higher at the start of charging process and dramatically reduces by 2–3 order of magnitude with saturation of β-hydride. The highest value 6.9 × 10^?13 cm²/s is observed for La alloy at 100% SOC. Partial substitution La for Nd and Cr for Ni in low-Co AB₅ metal hydride alloys slightly reduces maximum discharge capacity, HRD performance and hydrogen diffusion kinetics. Low-Co alloys show good overall electrochemical properties compared to high-Co alloys and might be perspective materials for various electrochemical applications.     

社区居家养老服务设施的规划配置研究

社区和居家养老是我国当前和未来的主要养老模式，然而，与机构养老设施相比较而言，我国社区居家养老服务设施的发展明显滞后，具体表现为设施的建成基础薄弱、空间资源的配置要素模糊、规范和管控手段缺位等。在概述现状与问题的基础上，系统地探讨了我国社区层面养老服务资源的配置主体、配置对象和配置思路。针对养老服务需求和供给主体日益多元化的挑战，提出结合社区实际情况灵活配置服务模块的建议，采用总量控制和复合设置的规划手段落实配建，从而实现服务设施综合效益最大化的建设目标。     

Designing amino-based ionic liquids for improved carbon capture: One amine binds two CO2

Generally, amine group captures CO₂ according to 2:1 or 1:1 stoichiometry. Here, we report a kind of improved carbon capture using amino-functionalized ionic liquids (ILs) through 1:2 stoichiometry. A serial of amino-functionalized ILs various with basicity and steric hindrance of anion were designed, prepared, and applied in CO₂ capture. Through a combination of absorption experiment, quantum chemical calculation, spectroscopic investigation and calorimetric method, the results indicated that one amine group could bind two CO₂ through proton transfer (PT) process and intramolecular hydrogen bond formation, which leading to enhanced capacity that breaks through equimolar. The basicity and steric hindrance of anion play a significant role in promoting amine group to capture two CO₂. [P₆₆₆₁₄]₂[Asp] with dual anion was further designed and synthesized to promote PT process, which showed high capacity of 1.96 mol/mol IL at 30°C and 1 atm as well as excellent reversibility. © 2018 American Institute of Chemical Engineers AIChE J, 65: 230–238, 2019     

Optimal operation of cogeneration system coordinated by aggregator for providing the demand and supply regulation capacity

Recent growth of renewable energy generations with natural variability, such as photovoltaic generation and wind turbine generation, would make the demand and supply control in a whole power system more difficult, and therefore, alternatives for demand and supply regulation resources would be required. The authors focus on cogeneration system (CGS) as one of regulation resources. In order to procure adequate volume of regulation capability, an aggregator coordinates a number of CGSs efficiently and flexibly considering the wide variety of electricity/thermal demands of CGS owners. This paper proposes a novel optimal operation strategy of CGS coordinated by the aggregator considering the energy balance and operation cost of individual CGS owner. This paper also demonstrates the availability of CGSs for regulation capability by numerical case studies in which the actual consumption profile is employed.     

随机森林算法在温度分布重建中的应用

为提高温度分布重建精度,提出了使用随机森林算法对温度测点进行优化布置的新方法。 将测点位置作为样本特征, 以不同的测点布置方式及其对应的重建误差作为样本数据集。 使用样本数据集构建随机森林模型,评估样本特征重要性,根据 特征重要性排序实现温度测点的优化布置。 设定仿真实验与燃烧实验验证优化布置算法的可行性与有效性。 分析实验数据, 所提出的优化布置算法相对于原有算法,重建精度提升了 20%以上。 研究结果表明,随机森林算法在温度分布重建中具有良好 的应用价值,并为解决工业实际问题提供了新思路。     

A case study of socio-cultural and technical factors in automobile design: Discourses between designers and potential users on a new electric vehicle in Africa

Technological artifacts emerge and develop within social contexts, inextricably interconnecting technology and society. This article addresses this interconnection empirically, analyzing the implementation of an electric vehicle designed and built by students of automotive engineering at the Technical University of Munich (TUM) in Germany. The students created this vehicle to address problems of mobility for rural populations in Africa, aiming to provide local residents with better access to necessities of life such as healthcare, education, and transportation. The article examines African perceptions of and responses to the vehicle, as well as specific suggestions for future improvement. It discusses not only African reactions to the vehicle and its potential social impact on African societies, but also the concepts and ideas of the designers behind this automotive construction. It also acknowledges the ways in which the engineers based their work on assumptions about African needs rather than on substantial ethnographic research, which diminished their ability to succeed.