A Comparison Between Machine Flexibility and Routing Flexibility

In this paper, we evaluate two types of flexibility, machine flexibility and routing flexibility, in terms of manufacturing performance in various shop environments. A simulation-based investigation was conducted to analyze the impact of these types of flexibility on the average flow time of parts under various job flow pattern conditions, which characterize the shop nature from a random job shop to a flow shop, operation time variance, setup time, and shop load. The experimental results show how these types of flexibility affect the average flow time of parts and which type is superior under what conditions. Management can obtain better insight and guidelines for determining priorities or the scale, or scope, of various decision items relating to design standardization, process and operations improvement, investment in new equipment and tools, and the like.     

东川坝塘水库土工膜联接段SR防渗体系止水技术与应用

重点介绍了SR防渗体系止水技术在东川坝塘水库土工膜防渗方面的应用,并对其中应用的新材料和新技术作了简介。     

Model for flexibility evaluation in manufacturing network strategic planning

In response to market pressures, manufacturers have adopted different approaches to provide flexibility regarding several aspects. In this paper, we suggest a model for the evaluation of the flexibility of the manufacturing supply chain, based on graph theory techniques. This model defines maximum excess demand that may be met using flexibility. Recourse to flexibility enablers is determined based on cost minimisation. Such enablers are volume flexibility, mix flexibility and safety stocks. The proposed model is solved using a two-step Mix Integer Linear Programme; the first step consists in defining maximum demand that may be met while the second step concerns minimising cost. The main benefit of our model is to deal with realistic problems in a rather short time. Therefore, it can be used in a wide ‘what-if’ design process. It means evaluating various contemplated flexibility configurations in multiple demand scenarios in order to choose the best option. It can be also used during operational supply chain planning in order to face to an unbalanced situation. This paper ends with a numerical example illustrating our model’s efficiency.     

A genetic algorithm-based approach to machine assignment problem

Over the last few decades, production scheduling problems have received much attention. Due to global competition, it is important to have a vigorous control on production costs while keeping a reasonable level of production capability and customer satisfaction. One of the most important factors that continuously impacts on production performance is machining flexibility, which can reduce the overall production lead-time, work-in-progress inventories, overall job lateness, etc. It is also vital to balance various quantitative aspects of this flexibility which is commonly regarded as a major strategic objective of many firms. However, this aspect has not been studied in a practical way related to the present manufacturing environment.

In this paper, an assignment and scheduling model is developed to study the impact of machining flexibility on production issues such as job lateness and machine utilisation. A genetic algorithm-based approach is developed to solve a generic machine assignment problem using standard benchmark problems and real industrial problems in China. Computational results suggest that machining flexibility can improve the overall production performance if the equilibrium state can be quantified between scheduling performance and capital investment. Then production planners can determine the investment plan in order to achieve a desired level of scheduling performance.     

A Method for Flexible Heat Exchanger Network Design under Severe Operation Uncertainty

Most investigations on heat exchanger network (HEN) synthesis which plays an important role in improving the efficiency of industrial plants, focus on deterministic conditions whereas operational flexibility and feasibility are less concerned. In the real industrial world, each system experiences various disturbances due to changes in stream temperature, flow rate, and other uncertain factors. An approach for flexible HEN synthesis under severe operation uncertainty is proposed, which is represented by the Probability bounds analysis (PBA) theory and is sampled by a double‐loop sampling method. A case study, which generates a better solution with less total annual cost and good flexibility under severe uncertainty, demonstrates the capability of this simplified approach.     

A mathematical programming formulation for temporal flexibility analysis

Realistic chemical processes are often operated in the presence of complex and uncertain dynamics. While an ill designed system may become inoperable due to variations in some process parameters at certain instances, the cumulative effects of temporary disturbances in finite time intervals can also result in serious consequences. The latter issue is studied in the present study on the basis of a novel concept – temporal flexibility. Specifically, the mathematical program used for evaluating the corresponding performance measure is built with a dynamic system model, which usually consists of a set of differential-algebraic equations (DAEs). The numerical technique of differential quadrature (DQ) is adopted to approximate these DAEs with equality constraints. As a result, any solution strategy for the conventional steady-state flexibility analysis is applicable. Two examples, a simple liquid storage tank and a solar thermal driven membrane distillation desalination process, are adopted to demonstrate the usefulness of temporal flexibility analysis. All results obtained in case studies show that the proposed approach is convenient and effective for assessing realistic issues in operating complex dynamic chemical processes.     

重塑边界：总体规划改革与地方实践

现阶段总体规划实践面临众多困境,包括编制内容过多、编制时间过长、不适应实际管理需求等,大部分学者提出“减负”是当前总体规划的改革核心。在综合研究相关案例的基础上,提出当前总体规划面临的核心问题是“边界模糊”,这些模糊的边界包括中央与地方的事权边界、政府与市场的作用边界、城市人口规模预测的边界、规划区与中心城区的范围边界、部门之间的规划权利边界,以及大城市与小城市的内容边界。针对这些问题,地方政府通过编制其它规划来替代总体规划,包括战略规划、都市区规划、县域总体规划、三规合一规划等等。这些“规划替代”其实就是地方总体规划改革的一种创新,结合这些创新实践,认为未来总体规划改革的方向是要“重塑边界”,包括放权中央与地方的事权边界,明晰政府的刚性边界与市场弹性边界,模糊城市人口规模边界,扩大规划区与中心城区范围边界,统一部门之间规划边界、区分大城市与小城市的内容边界。     

Strength reduction factor for MDOF soil–structure systems

In most of the seismic design provision, the concept of strength reduction factor has been developed to account for inelastic behavior of structures under seismic excitations. Most recent studies considered soil–structure interaction (SSI) in inelastic response analysis are mainly based on idealized structural models of single degree‐of‐freedom (SDOF) systems. However, an SDOF system might not be able to well capture the SSI and structural response characteristics of real multiple degrees‐of‐freedom (MDOF) systems. In this paper, through a comprehensive parametric study of 21600 MDOF and its equivalent SDOF (E‐SDOF) systems subjected to an ensemble of 30 earthquake ground motions recorded on alluvium and soft soils, effects of SSI on strength reduction factor of MDOF systems have been intensively investigated. It is concluded that generally, SSI reduces the strength reduction factor of both MDOF and more intensively SDOF systems. However, depending on the number of stories, soil flexibility, aspect ratio and inelastic range of vibration, the strength reduction factor of MDOF systems could be significantly different from that of E‐SDOF systems. A new simplified equation, which is a function of fixed‐base fundamental period, ductility ratio, the number of stories, structure slenderness ratio and dimensionless frequency, is proposed to estimate strength reduction factors for MDOF soil–structure systems. Copyright © 2012 John Wiley & Sons, Ltd.     

土地利用规划编制和实施管理中原则性与灵活性研究

从土地利用总体规划中原则性与灵活性的辩证关系入手，指出新一轮土地利用总体规划应坚持以原则性为基础、灵活性为补充。明确了规划原则性内容，并从规划模式、时隔、体系、指标、地类认定、用途分区、图文互认等方面讨论了原则性基础上的灵活性方法，以期为本轮土地利用总体规划提供参考。     

认知弹性理论对网络环境下专题教学的启示

文章简要回顾认知弹性理论,重点对其给网络专题教学带来的启示进行探讨,并试图建构用于网络环境专题教学中的随机进入教学模式.