Impact of Asset Utilization on Replacement Decisions

这笔拨款为优化工具的开发提供资金，以确定随机操作环境下一组资产的替换决策。传统模型提供离散（年度）间隔的更换决策，基于预期的运营、维护和回收成本，这些成本取决于运营（每日）决策确定的资产利用率水平。然而，由于与业务有关的不确定性，例如需求或预算水平的波动，这些预期的利用水平在实践中可能无法实现，从而使更换计划失效。该研究将把战略（替换）和操作（利用）决策联系起来，使替换时间表成为资产利用的功能。这个问题将在运输业的背景下加以审查，发起人包括一家铁路公司和一家卡车租赁公司。研究了一种双端排队模型，用以逼近运输系统的运行情况，确定运输系统的利用水平。将该模型构建为确定最小成本购销决策的非线性优化模型。大型非线性程序的研究求解过程是基于增广拉格朗日技术的。这项研究在工业和军事领域有许多潜在的应用，因为这些组织通常依赖于在不确定的环境中受到不同程度利用的资产组或舰队。分析将合并两个传统上独立的决策，即静态替换问题和动态操作问题，这样战略资本预算决策就基于对实际操作的衡量。由于收购决策依赖于资产利用率，该模型将改进传统上依赖于静态数据的资产置换决策过程。该研究还将有助于改进大规模非线性优化模型的求解技术，并为双端队列提供更多的研究，尽管双端队列的应用在研究中并不突出。

Hartman 9713690 This grant provides funding for the development of an optimization tool to determine replacement decisions for a group of assets subject to a random operational environment. Traditional models, which provide replacement decisions over discrete (annual) intervals, are based on expected operating, maintenance and salvage costs which are dependent on asset utilization levels determined by operational (daily) decisions. However, due to uncertainty associated with operations, such as fluctuating demand or budget levels, these expected utilization levels may not be realized in practice, thus invalidating the replacement schedule. The research will link strategic (replacement) and operational (utilization) decisions such that replacement schedules are functions of asset utilization. This problem will be examined in the context of the transportation industry, with sponsors including a railroad and a truck leasing firm. A double-ended queueing model is researched to approximate the operations of the transportation system and determine utilization levels. This model is built into a non-linear optimization model which determines minimum cost purchase and sale decisions. The research solution procedure for the large scale non-linear program is based on augmented Lagrangian techniques. There are numerous potential applications of this research in industry and the military as these organizations generally rely on groups or fleets of assets which are subject to varying levels of utilization in an uncertain environment. The analysis will merge two traditionally separate decisions, the static replacement problem and the dynamic operational problem, such that strategic capital budgeting decisions are based on a measurement of actual operations. As acquisition decisions are dependent on asset utilization, the model will improve the asset replacement decision process which traditionally relies on static data. This research will also contribute to improved solution techniques for large scale non-linear optimization models and provide more investigation into double-ended queues which despite their numerous applications are not prominent in research.