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961.
962.
This paper extends the build–operate–transfer (BOT) concession model (BOTCcM) to establishing a risk concession model for BOT contract projects. The decision for a concession period is one of the most important decisions in determining a BOT contract. BOTCcM presents an alternative method to assist in determining a concession period that can protect the basic interests of both the investor and the government concerned. However, there is a major limitation in using the model, namely it gives no consideration to the impacts of risks on the estimation of various economic variables in the model. This study considers the risk impacts to the BOTCcM model and presents an additional risk concession model. This model provides an approach for formulating a concession period to consider the impacts of risks and, at the same time, protect the basic interests of both the investor and the government concerned. A hypothetical case is used to show the procedures of formulating the risk concession period through the assistance of the Monte Carlo simulation method. 相似文献
963.
Project delays due to late availabilities of resource and information (RI) prerequisites are one of the major threats to construction management. It is desirable to avoid such delays through better means of constraint management. With most contemporary planning methodologies and tools, it is generally difficult to represent many hidden flow constraints in a construction work plan. However, evaluating the impact of flow constraints is crucial in determining their criticalities, based on which the flow constraints may be prioritized and consequently resolved to minimize project delays. Due to the fact that limited resources are often shared among various trades, it may not be practical to resolve all the constraints simultaneously so that a tradeoff is inevitable, which suggests that management should focus on the most important ones termed as key constraints (i.e., those directly contributing to project delays). This paper presents a methodology that augments the traditional critical path method with RI availability constraints to analyze the causes of delays and locate the key constraints binding on project completion without ambiguity based on the principles of the theory of constraints. The methodology of key constraint analysis has been implemented with the integrated production scheduler, a constraint-based scheduling tool which facilitates the modeling, analysis, and management of constraints at the production planning level. An illustrative example is depicted to demonstrate how the proposed methodology works. 相似文献
964.
Bo Liu Chaoshu Shi Jianming Chen Dingzhong Shen 《IEEE transactions on nuclear science》2005,52(2):527-529
The temperature dependent luminescence and thermoluminescence (TL) from PbFCl single crystal scintillator as well as its annealing effect were investigated. The experimental results show that under the X-ray excitation the luminescent intensity decreases rapidly above 170 K. The temperature dependence of luminescence meets the thermal quenching principle and the luminescence intensity at room temperature is about one fortieth of 100 K. The TL curve of PbFCl consists of a dominant band peaking at 167 K with a shoulder at about 152 K and four relatively weak bands peaking at 113, 125, 198, and 233 K. The isothermal decay curve indicates that the TL band peaking at 167 K obeys the first-order kinetic process. The trap parameters are obtained using fitting method. The annealing experiment in air shows that the oxygen contamination can quench the luminescence and increase the traps responsible for the TL bands in the range of 113-152 K. 相似文献
965.
建立毛细管模型并通过实验数据验证了模型,给出制冷剂的干度x、温度t、速度W、压力P沿毛细管长度的变化关系,研究了毛细管的内直径、长度、冷凝温度、过冷度等因素对毛细管内R134a、R600a两种制冷剂的质量流量的影响. 相似文献
966.
移动荷载作用下的桥梁振动及其TMD控制 总被引:6,自引:3,他引:6
为了全面地了解移动荷载作用下桥梁的振动机理及其调质阻尼器(TMD)控制,将列车简化成移动简谐力模型,对列车过桥时桥梁的振动形态幅频特性作了详细的探讨。然后论述了移动荷载作用下的TMD控制。给出了桥梁在不同速度下的幅频特性曲线以及TMD控制的质量比影响曲线,揭示了移动荷载作用下的桥梁振动及其控制的特点,同时为进一步的桥梁振动控制提供详尽的参考数据。 相似文献
967.
968.
969.
通过论述海绵钛反应机理,分析了镁法制取海绵钛生产液镁利用率低的形成原因,探索了提高镁利用率的途径,试验表明:提升后期反应液面,可以提高镁利用率,提高海绵钛单炉产能。 相似文献
970.