Storage allocation in transshipment hubs under uncertainties

The state-of-the-art methods for yard storage allocation seldom consider uncertain factors, e.g. unexpected changes of loading/unloading time of vessels, workloads in each time shift, etc. All of these unforeseen events may reduce the efficiency of the initial plan and even render it infeasible. This paper firstly investigates the recovery strategy in yard storage allocation, which is the traditional way for handling uncertainties, whereas it could not be effective for universal situations and may fail in some complex circumstances. Thus, this paper proposes a real-time decision support system (DSS) which can act as an ultimate solution for coping with uncertainties in yard storage allocation process. This DSS is oriented to the planning for one time shift under the dynamic yard template, hence enables port operators to cope with flexible volume of arriving containers and uncertainties in the realistic circumstances. Some numerical experiments are performed to validate that the proposed real-time DSS has better performances than traditional methods in flexible and dynamic environments.     

Pricing and capacity planning for product-line expansion and reduction

We investigate optimal pricing and capacity planning decisions for product-line settings such as introducing a new product or dropping an existing one. We consider a two-product, two-period model with stochastic demands, where price and capacity decisions are made at the outset. Investment in capacity must be traded-off against the possibility of buying at higher spot market prices due to shortage in capacity or charging a higher price to manage the demand. Prior studies argue that introducing an additional product to the product-line strains capacity, resulting in an increase in the price of an existing product. In contrast, we find that introducing a new product can also result in a drop in price of an existing product, enabling strategic pricing by firms. The necessary condition for this to occur is that the demand uncertainties for the products are of similar magnitude and negatively correlated. Similar insights are obtained for the setting where an existing product is dropped from the product-line. Hence, product-market decisions and contextual factors play a role in capacity planning, capacity cost allocation and pricing.     

An interval-parameter two-stage stochastic integer programming model for environmental systems planning under uncertainty

An interval-parameter two-stage stochastic mixed integer programming (ITMILP) technique is developed for waste management under uncertainty. It is a hybrid of inexact two-stage stochastic programming and mixed integer linear programming methods. The ITMILP method can directly handle uncertainties expressed not only as probability density functions but also as discrete intervals. It can be used to analyse various policy scenarios that are associated with different levels of economic penalties when the promised policy targets are violated. More importantly, it can facilitate dynamic analysis of decisions on capacity expansion planning within a multi-region, multi-facility, multi-period, and multi-option context. The results will help to generate a range of decision alternatives under various system conditions, and thus offer insight into the trade-offs between environmental and economic objectives. The ITMILP method is applied to planning facility expansion and waste flow allocation within a waste management system. The results indicate that reasonable solutions have been generated for both binary and continuous variables. The binary-variable solutions represent the decisions of facility expansion, while the continuous-variable solutions are related to decisions on waste flow allocation.     

随机环境下班轮公司之间合作调箱研究

目的研究随机因素对2种调箱方式的影响,以体现合作调箱方式在随机环境下的优越性。方法综合考虑港口空箱需求和空箱运力限额的随机性,以决策周期内调箱总成本最小为目标,构建随机环境下班轮公司之间合作调箱模型,然后通过算例,研究不同港口服务水平和运力限制水平对2种调箱方式的影响,以及对调箱系统中随机因素进行灵敏度分析。结果当班轮公司采用保守-成本型决策、保守-服务型决策、冒险-成本型决策、冒险-服务型决策时,2种调箱方式的总成本差值分别为9638,22862,10710,19284美元。结论降低运力限制水平可以压缩调箱总成本,但是提高港口服务水平会增加调箱总成本,且当港口服务水平和运力限制水平均处于高值时,合作调箱方式的优势更加显著;与单独调箱方式相比,合作调箱方式可以降低调箱系统中随机因素波动对调箱总成本的影响。     

Storage Decisions in Information Systems

The problem is to dynamically store different data records in different storage devices in each period so as to minimize the total expected discounted cost over a planning horizon. Each device has a fixed total capacity, each record has a given storage space requirement, while the number of requests for each record per period is changing stochastically through time. Given an allocation, the total cost per period consists of the storage cost (depending on the storage requirements and device), the access cost including update and retrieval costs (depending on the number of requests) and the transfer cost (depending upon the change of allocation from the previous period). A dynamic programming model is presented to yield optimal strategies. The special case of independent identically distributed demands is completely solved, using a generalized transportation algorithm while a heuristic procedure is indicated for the general problem using parametric analysis.     

Synchronization of yard truck scheduling and storage allocation in container terminals

Yard truck scheduling and storage allocation, as two separate subproblems in port operations, have been extensively studied in the past decades. However, from the operational point of view, they are highly interdependent. This article proposes an integer programming model in which yard truck scheduling and storage allocation problems are formulated as a whole for heterogeneous import containers. Different stacking times at yard blocks is modelled as well. The objective of the proposed model is to reduce the congestion and waiting time of yard trucks in the terminal so as to decrease the makespan of discharging containers. Owing to the inherent computational complexity, a genetic algorithm and a greedy heuristic algorithm have been designed. Computational experiments show that the proposed genetic algorithm and greedy algorithm are both effective in solving the studied problem.     

水冷压缩式CO2水合物蓄冷系统的蓄冷特性实验研究

本文实验研究了初始充注压力为3.5~4.0 MPa时水冷压缩式CO2水合物蓄冷系统的蓄冷特性,通过实验数据计算蓄冷量和蓄冷速率。结果表明：高充注压力具有更好的蓄冷特性,原因在于充注压力越高,反应釜入口干度越小,单位质量CO2携带的冷量越大。在初始充注压力为4.0 MPa时,蓄冷特性最好：蓄冷时间最短（11.33 min）,平均蓄冷速率最高（5.19 kW）,水合物生成质量最多（3.96 kg）,水合物蓄冷量占总蓄冷量比例最高（57%）;在初始充注压力为3.5 MPa时,蓄冷特性最差：蓄冷时间最长（37.50 min）,平均蓄冷速率最低（1.07kW）,水合物生成质量最少（1.58 kg）,水合物蓄冷量占总蓄冷量比例最低（34%）。与风冷压缩式蓄冷系统相比,水冷压缩式蓄冷系统水合物生成质量增长率最高为38.6%,总蓄冷量增长率最高为13.24%。     

太阳能空调相变蓄冷理论及实验研究

针对一种自制的能够与太阳能空调系统匹配的相变蓄冷材料,建立了蓄冷球蓄\释冷过程数学模型,得到稳态及非稳态工况下蓄冷球内温度分布、蓄\释冷量、蓄\释冷速率的变化规律及影响因素。同时,在相应工况下对单个蓄冷球进行蓄\释冷循环实验,验证理论结果。研究表明,自制蓄冷球能够在170min完成相变。缩小球径、降低冷冻水温度、增大球壁热导率及减小球壁厚度均可缩短蓄冷时间。稳态运行工况下,蓄冷球的蓄\释冷量分别为17.30kJ和16.46kJ;太阳能空调非稳态运行工况下,蓄冷球在165min完成相变,蓄冷量为16.34kJ。     

Analytic Cognitive Task Allocation: a decision model for cognitive task allocation

This paper introduces Analytic Cognitive Task Allocation (Analytic CTA) as a decision model for cognitive task allocation. Analytic CTA can support system designers systematically analyse alternative allocation choices, evaluate them through criterion-based quantitative judgements and integrate partial judgements towards a final allocation decision. Analytic CTA was applied in the design of cognitive task allocation by testing three hypotheses. The hypotheses postulated that Analytic CTA can effectively support system designers in three ways: (a) in the identification of task requirements; (b) in the definition of design trade-offs between human allocation and automation; and (c) in the derivation of the allocation decision. Two groups of system designers allocated cognitive functions from three task scenarios in production planning and control. The experimental group, which was supported by the decision model, made allocation decisions which expressed weak preference for either human allocation or automation, consistent with the experimental tasks which had been selected as to elicit weak preferences. The control group relied on the early selection of an automation technology as the means of structuring the design problem. This involved reducing the task to a version suitable for automation, introduced a pro-automation bias and resulted in allocation decisions expressing strong preference for automation. These results were found in support of the experimental hypotheses.     

NH3在中小型冷库中的应用前景

基于对我国目前氨制冷系统在中小型冷库的应用情况,结合当前氨制冷设备和技术的发展状况和趋势,探讨氨制冷剂在我国中小型冷库中的应用前景。笔者认为：氨是一种综合性能优良的天然制冷剂,我国应结合国情,高度重视其相关技术发展,研究其安全保障措施,并在中小型冷库中进行推广应用试验,以积累相关实验数据;需进一步加强氨蒸气压缩式制冷系统及其部件、自动控制设备相关技术的研究,以推进氨制冷技术的发展。     

An improved robust buffer allocation method for the project scheduling problem

Unpredictable uncertainties cause delays and additional costs for projects. Often, when using traditional approaches, the optimizing procedure of the baseline project plan fails and leads to delays. In this study, a two-stage multi-objective buffer allocation approach is applied for robust project scheduling. In the first stage, some decisions are made on buffer sizes and allocation to the project activities. A set of Pareto-optimal robust schedules is designed using the meta-heuristic non-dominated sorting genetic algorithm (NSGA-II) based on the decisions made in the buffer allocation step. In the second stage, the Pareto solutions are evaluated in terms of the deviation from the initial start time and due dates. The proposed approach was implemented on a real dam construction project. The outcomes indicated that the obtained buffered schedule reduces the cost of disruptions by 17.7% compared with the baseline plan, with an increase of about 0.3% in the project completion time.     

Shelf life assessment of MalaysianPangasius sutchi during cold storage

The findings of the present work yield useful information about the MalaysianPangasius sutchi concerning the marketing sector from the point of view of shelf life and storage temperature in the range of 0 to 10‡C. A fresh batch of typical samples, were stored similarly in four chillers of different temperatures for a period of 28 days. During the course of storage, the samples were periodically subjected to pH and sensory tests performed by trained panelists. Experimental observations were analysed and regressed to develop three correlations. The first one was between the sensory tests and the storage time and temperatures, while the second one related pH values to storage time and temperatures. Finally, a correlation between sensorial and pH values was developed as well. The first correlation is presented in tabular form to yield a simple guide to fish retailers, by which quality and shelf life of the displayed fish commodity may be estimated.     

几种添加剂对冷冻水产品持水性的影响

在冷冻前将新鲜鱼片和虾仁用不同浓度的持水剂浸渍处理,再进行冻藏,测定解冻后二者的持水情况.结果表明磷酸盐对于提高水产品的持水力效果优于NaCl.在确定的混和盐配比下,鱼片和虾仁的最佳浸渍浓度分别为1.6%和1.2%,浸渍时间为20min,持水性分别提高2.28%和3.08%.     

Short-term space allocation for storage yard management in a transshipment hub port

In transshipment ports, the containers to the same destination vessel are usually stored together to facilitate the loading process, which is called the “consignment”. During operation, the actual containers that will come in are only known for a short period in advance. Thus, short-term space allocation is needed to assign incoming containers taking into account the transporting vehicles, yard cranes and storage space. Currently, the space is allocated based on the experience of port operators. To balance the current and future impacts of short-term planning, we develop a systematic method called “space allocation given long-term plan (SALP)”. The corresponding MIP model is formulated to utilize not only the short-term information, which includes the existing containers and the actual incoming containers, but also the given long-term plan, which provides a forecast of future requirements. The SALP method is evaluated under two storage strategies to achieve consignment, namely, the “non-sharing strategy” and the “flexible space-sharing strategy”. The numerical experiments show that the SALP method improves operational efficiency, but its performance is affected by the portion of long-term plan under consideration. The SALP method performs well under both storage strategies when space is sufficient. However, the performance under the “flexible space-sharing strategy” is better than the “non-sharing strategy” when space is tight.     

ECONOMIC DESIGN OF REFRIGERATED AUTOMATED STORAGE AND RETRIEVAL SYSTEMS

The objective of this paper is the development of a design model for refrigerated automated storage and retrieval systems (R-AS/RS). Compared with ordinary unit-load AS/RS, the R-AS/RS under this study has several different design and operating characteristics: (I) greater emphasis is placed on the storage function and so it has a double-depth lane in the storage rack; (2) cooling units are required to maintain a cold temperature environment in the system; (3) the maximum number of storage orders handled per unit time is limited by the system capacity. Considering the above characteristics, the design problem is formulated as a non-linear mixed integer programming problem in which the cost of the system is minimized. The decision variables are the storage volume, the number of storage and retrieval (S/R) machines, the type and number of cooling units, and the physical configuration of the building. A case problem is solved to illustrate the model.     

蓄冷箱在疫苗冷链中的研究进展

每年疫苗产品损耗的主要因素之一是冷链运输的失效,在运输过程中使用最为普遍的设备是蓄冷箱。影响蓄冷箱保温性能的因素主要包括保温箱体的绝热性能、蓄冷材料的蓄冷能力及保温包装方式的设计。本文综述了蓄冷箱在疫苗冷链中的研究进展,分析了疫苗蓄冷箱常用保温材料及相变蓄冷材料的选择和应用,并讨论了箱体热阻的计算及蓄冷箱温度的监控。在此基础上指出整体包装和开发相变蓄冷材料的研究方向。     

A strategic decision framework for a value added supply chain

Supply chains are becoming increasingly complex. The structure of the supply chain and the suppliers who participate in it are critical decisions for managers. The supply chain is no longer simply a source of inputs or services but an integral source of value added. It is clear that in some cases strategic supply chain objectives may require trade-offs, for example, between cost and innovation capability or between managing risk and maximising flexibility. These decisions balancing trade-offs between desirable partner characteristics are critical and can make a significant contribution to business performance. A framework is outlined, based on the foundation of extant literature, within which firms can make strategic decisions on supply chain structure by categorising the characteristics they prioritise in their supply chain strategy. There is also a strong foundation in the literature on developing mathematical models that provide insight into the decision-making process. A mixed integer programming model is specified that incorporates the opportunity for diversification and provides a demand allocation decision. The model is robust enough to allow for single or diversified supplier strategies based not only on capacity constraints but also on risk pooling and minimum performance requirements for key characteristics that form the basis of the strategy. A Lagrangian relaxation is proposed and satisfactory performance results are provided.     

Uncertainty Analysis and Resource Allocation in Construction Project Management

Abstract

The premise of dealing with uncertainty in this article is to figure out the impact of uncertainties on project performance. This article proposes a framework for quantitative analysis that combines a fuzzy mathematics approach with system dynamics theory. Simulations generated using a model based on the framework show that uncertainties affect project performance by changing project parameters, and the mechanisms involved depend on the sources of the uncertainties. Furthermore, while technical and financial uncertainties mainly influence project costs, uncertainties related to markets, regulations, and organizational structures affect both project duration and cost. Finally, strategies for coping with uncertainties in a resource allocation perspective are presented.     

Strategic network planning for an international automotive manufacturer

This article addresses the strategic network planning for international automotive manufacturers, in particular of premium cars. The focus is on the product to plant allocation and capacity expansion decisions for a given network design with fixed plant locations. A mixed integer program minimizing the net present value (NPV) of all capital expenditures and operational cost while incorporating flexibility of a network by a specific allocation structure (“chain”) is formulated. Computational illustrations on the influence of flexible allocation structures on the NPV are demonstrated considering changes in demand, exchange rates and total available capacity.     

前置仓装配式冷库动态能耗研究与影响因素分析

为研究前置仓装配式冷库实际运行状态下的动态负荷,本文以上海市某前置仓装配式冷库为研究对象,测试其在冷藏温区下运行的实际负荷.考虑货物进库因素后,装配式冷库动态负荷模型的相对误差由17.8％降至5.26％,提高了冷库动态负荷的计算精度,证明该模型具有一定的准确性,并通过MATLAB建立冷库负荷相关因素的数学模型.结果表明...