Approximation methods for the analysis of a multicomponent,multiproduct assemble‐to‐order system

In this article, we consider the performance evaluation of a multicomponent, multiproduct assemble‐to‐order (ATO) system. Each component is managed independently using a base‐stock policy at a supply facility with limited production capacity and an infinite buffer. The arrivals of demands follow a multivariate Poisson process and unfilled demands are backlogged. Because exact analysis of the proposed system is not feasible, we propose two approximation methods which provide upper and lower bounds for various performance measures such as fill rate, average waiting time, and average number of backorders of the proposed system. Our computational experiments demonstrate the effectiveness of the two approximation methods under various system settings. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

锆酸铅PbZrO3序参量的量子饱和

在503 K反铁电体PbZrO3发生立方-正交相变,序参量是反平行离子位移引起的超晶格;在低温相时,PbZrO3的反铁电超晶格反射强度随温度的变化成正比,可以由考虑量子效应的Landau唯象理论加以描述;高于室温时,Γ25超晶格反射强度显示了不同的温度依赖性。     

Dynamic order acceptance and capacity planning on a single bottleneck resource

We present a tactical decision model for order acceptance and capacity planning that maximizes the expected profits from accepted orders, allowing for aggregate regular as well as nonregular capacity. The stream of incoming order arrivals is the main source of uncertainty in dynamic order acceptance and the company only has forecasts of the main properties of the future incoming projects. Project proposals arrive sequentially with deterministic interarrival times and a decision on order acceptance and capacity planning needs to be made each time a proposal arrives and its project characteristics are revealed. We apply stochastic dynamic programming to determine a profit threshold for the accept/reject decision as well as to deterministically allocate a single bottleneck resource to the accepted projects, both with an eye on maximizing the expected revenues within the problem horizon. We derive a number of managerial insights based on an analysis of the influence of project and environmental characteristics on optimal project selection and aggregate capacity usage. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

The impact of component commonality on composite assembly policies

Assemble in Advance (AIA) policy reduces assembly cost due to advance planning, while Assemble to Order (ATO) policy eliminates assembly of excessive (more than demanded) units. The tradeoffs between the two policies have been studied in the past for single product environments. Moreover, it was shown that it is beneficial to employ AIA and ATO simultaneously. In this article, we study the employment of such a composite assembly policy in a multiproduct environment with component commonality. When common components are used, ATO may also enable us to benefit from the risk pooling effect. We provide important managerial insights such as: the multiperiod problem is myopic and changes in inventory levels due to the use of common components, and demonstrate the potential profit increase compared to other policies.© 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

一类多维双重时序 AR(1)-MA(q) 模型的平稳性

讨论了一类多维双重时序ＡＲ（１）－ＭＡ（ｑ）模型的二阶平稳性问题。通过导出一组线性方程组，给出了这类模型二阶平稳的显式充分条件和必要条件，为验证模型的二阶平稳性提供了一个可行的途径。     

环形区域极点/协方差约束下的模型简化设计

提出离散随机系统模型简化的一种新方法,即环形区域极点／协方差约束下的模型简化方法。这种设计方法的基本思路是构造指定维数的降阶模型,使其匹配给定的环形区域极点和稳态协方差参数,在系统的动态特性和稳态特性方面逼近给定的满阶模型。文中导出了期望的简化模型的存在条件及解析表达式,并提供了一个数值算例。     

四阶Fibonacci数列的通项及性质

著名的二阶Fibonacci数列有许多通项表达式和性质.文中运用矩阵方法,对四阶Fibonacci数列进行了比较深入的研究,求得了四阶Fibonacci数列的3个通项表达式,并得到了一些与Fibonacci数列相似的性质.     

Analysis and optimal design of discrete order picking technologies along a line

Order picking accounts for most of the operating expense of a typical distribution center, and thus is often considered the most critical function of a supply chain. In discrete order picking a single worker walks to pick all the items necessary to fulfill a single customer order. Discrete order picking is common not only because of its simplicity and reliability, but also because of its ability to pick orders quickly upon receipt, and thus is commonly used by e‐commerce operations. There are two primary ways to reduce the cost (walking distance required) of the order picking system. First is through the use of technology—conveyor systems and/or the ability to transmit order information to pickers via mobile units. Second is through the design—where best to locate depots (where workers receive pick lists and deposit completed orders) and how best to lay out the product. We build a stochastic model to compare three configurations of different technology requirements: single‐depot, dual‐depot, and no‐depot. For each configuration we explore the optimal design. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Understanding China’s goals and strategy in the South China Sea: bringing context to a revisionist systemic challenge – intentions and impact

ABSTRACT

The slow moving conflict in the South China Sea has been characterized by some as “not worth the candle.” China claims the entirety of the South China Sea pursuant to a nine-dash line, the legal impact of which has been limited by international courts. At the same time, China has changed the reality of control over the South China Sea by building a number of fortified islands in the Spratly Islands and elsewhere. The US has either refused to stand up to China's behavior (Obama) or responded unevenly (Trump). This paper examines the impact of China's behaviour on local parties, US interests, and the liberal international system.     

消防法中责令停止执业的法律依据

《消防法》规定的责令停止执业是对有法定消防行政违法行为的单位予以暂停相应资质、资格的一种处罚措施。其处罚主体为国家认证认可监督管理委员会以及地方质检部门;其处罚过程应适用听证程序,并确认、核实情节是否严重;其处罚实施应附有合理期限,同时需要采取相应保障措施。