Quantitative assessments of performance and robustness of maintenance policies for stochastically deteriorating production systems

Over the last few decades, many efforts have been invested in improving the economic performances of maintenance policies for stochastically deteriorating production systems. However, with the development of complex production systems, maintenance managers are interested not only in cost saving, but also in how to trustworthily plan and allocate the required maintenance budget. In this context, the robustness of maintenance policies which is related to the maintenance cost variability from a renewal cycle to another plays a pivotal role. This research deals with a quantitative approach to jointly assess the economic performance and robustness of some representatives of two most well-known classes of maintenance policies: time-based and condition-based maintenance. To this end, we first propose a new cost criterion which combines the long-run expected cost rate and standard deviation of maintenance cost per renewal cycle. Then, we develop and compare the associated mathematical cost models of the considered maintenance policies on the basis of the Gamma degradation process and the theory of stochastic renewal processes. The comparison results under different situations of maintenance costs and system characteristics show that the optimal configuration of maintenance policies gives the best compromise between the performance and robustness, and is mostly affected by the system downtime. Under this aspect, the condition-based maintenance remains more profitable than the time-based maintenance. Still, maintenance managers could implement condition-based maintenance policies that efficiently control the downtime to maximise the maintenance effectiveness of production systems from both performance and robustness viewpoints.     

Multicriterion optimal electric drive vehicle selection based on lifecycle emission and lifecycle cost

This research paper examines the optimal choice among conventional gasoline vehicles, hybrid electric vehicles (HEVs), plug‐in HEVs (PHEV), and full‐battery EVs taking into account the different characteristics of these vehicles, such as cost, emissions per mile, and vehicle miles to be traveled between refueling and acceleration time. The existing challenges for wide‐spread deployment of EVs are availability of charging infrastructure, higher cost, long time for charging, and lower travel millage compared with conventional vehicles. Statistical data are considered for determining the spatially varying average daily vehicle miles traveled (VMT) across the United States, which, together with charging behavior, can influence the optimal choice among EV with different travel ranges. Two alternative cases for charging are examined: (1) home‐only charging and (2) home plus work charging. The motivation of this work is to select the optimal EV among their types when lifecycle cost and lifecycle emission are considered. The optimization model seeks to minimize total lifecycle cost and emissions for each level of VMT per day. It is found that when lifecycle cost is the sole objective, HEV is usually the best choice, especially for higher VMT levels. When lifecycle greenhouse gas emission is the sole objective, PHEV1 (PHEV with 1 charging station) is the optimal solution over a wide range of VMTs. The outcome of this provides a roadmap for the selection of EVs based on their annual VMT to reduce both lifecycle emission and lifecycle cost.     

Reactive power pricing structure for hydroelectric power station in condenser mode operation

Reactive power support is critical for system security and pricing of reactive power is a vital issue in restructured environment. Peaking units at hydroelectric power plant in condenser mode operation can provide major reactive power support. Therefore costing structure for hydroelectric power plant incorporating various cost components in condenser mode operation is presented in this paper. Major cost components include capital cost component, changeover cost component and a cost component related to number of service hours in condenser mode operation. A methodology is proposed based on these components. A case study of Koyna Hydro Electric Power Plant (KHEPP) is elaborated.     

建筑施工成本控制分析

主要阐述了如何在整个建筑工程管理过程中分阶段进行成本分析，以及对各阶段目标成本完成情况进行成本控制，并提出相应的改进性建议，以保证成本目标的顺利实现。     

日钢集装箱板生产的关键技术

介绍了日照钢铁控股集团有限公司通过将C含量控制在0.07％～0.11％,并尽可能降低Ni含量,以降低成本,连铸中采用集装箱板专用保护渣,加热炉控制为弱氧化性气氛或还原性气氛,通过控制轧制控制冷却和平整处理,实现了SPA-H热轧集装箱板的优质、低成本生产.     

Extension of dynamic programming models for management optimisation from single structure to multi-structures level

The aim of this article is the management optimisation (inspection, maintenance and rehabilitation (IM&R)) of a group of structures. It is supposed that the optimisation is constrained by limited available budget at the beginning of each time period during the entire time horizon thus creating an economical dependence between the decisions related to each of the structures. A Lagrangian relaxation technique is used for the extension of existing dynamic programming methods from single structure to multi-structures level. The methodology is illustrated by using a Generalised Partially Observable Markov Decision Process having a decision tree composed of a sequence of two decisions at the beginning of each time period, namely an inspection decision followed by a maintenance action decision. A numerical example concerning the optimisation of IM&R of 16 different bridges is presented.     

Optimization models for operative planning in drinking water networks

The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms, which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component models for the network elements. In combination with further nonlinear programming techniques (Burgschweiger et al. in ZIB Report ZR-05-31, Zuse Institute Berlin, 2005), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe.     

公路工程项目成本控制

本文介绍了笔者所在企业进行成本管理和控制的经验,阐述了如何有效地进行公路成本控制,以实现成本管理的目的,使企业取得最大的经济效益。     

浅议建设项目工程造价实施阶段的控制

针对工程造价中存在的概算超估算、预算超概算、决算超预算等问题及现状，着重对工程实施阶段如何严格掌控预算造价问题进行了有益的探讨。     

不平衡报价对工程造价控制的影响

不平衡报价在工程招投标活动中被投标人作为一种投标策略应用得越来越广泛,给工程项目的顺利完成带来了极大的消极影响.本文就不平衡报价的主要形式、影响和防范措施进行了论述.