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《数学的实践与认识》2020,(9)
石化类企业备件管理的难度较大,主要原因在于其备件需求往往是间断、离散、随机产生.针对石化类企业备件的间断需求特点,提出Markov过程的bootstrap方法取得备件需求的分布规律,在此基础上构建了备件库存优化模型,利用某大型石化企业实际管理运行数据进行了算例及仿真计算,结果验证了备件需求规律统计方法和库存优化模型的优越性,对于该类企业的备件库存管理实践提供了一定的借鉴意义. 相似文献
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为了合理储备战时航材备件,通过分析战时故障备件的需求特点,改进了传统的单机故障备件需求模型.根据多机种协同作战任务的不同,引入备件工作运行比的概念,建立了基于作战任务的多机种故障备件需求模型.为解决多机种协同作战时的保障资源配置问题提供了思路和方法. 相似文献
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高原驻训航材保障中,有寿件重要度较高,部队必须携带足够的备件数量来满足任务需要.根据高原驻训条件下航材有寿件需求特点,将有寿件的需求分为到寿更换需求和随机故障消耗产生的需求两部分,分别用数学公式和仿真计算方法进行预测,再将两者结果相加为总需求量.通过实例分析验证,采用工程测算方法可以避免逐一分析器材寿命的繁杂,而单独考虑随机故障消耗可以进一步保证有寿件备件不短缺率在90%以上.该预测,该模型可以为航材有寿件到寿情况分析以及有寿件的携行方案制定提供参考. 相似文献
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航材备件是保障航空装备日常训练和作战正常使用的重要影响因素,针对部分航材备件样本数据量少,影响因素多且复杂多变,预测结果与装备系统完好性要求偏差较大等问题.建立基于灰色关联分析(GRA)与偏最小二乘(PLS)及最小二乘向量机(LSSVM)相结合的航材备件预测模型,采集某无人机航材备件数据,通过对统计数据进行灰色关联分析,提取航材备件需求的相关因素作为模型训练样本,确定关键因素,利用偏最小二乘对关键因素特征提取,然后将偏最小二乘特征提取后的数据作为最小二乘向量机输入,进行模型构建及分析.通过实验验证了该方法的可行性与适用性,能够满足无人机航材备件预测的实际需要. 相似文献
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针对备件需求数量与备件库存数量的随机特性,应用序列运算理论对其供需随机过程进行动态描述.通过概率性序列的期望值理论定义了备件需求满足率,并建立了一定的备件满足率要求条件下的备件存储决策模型. 相似文献
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概述了干扰管理理论的内涵、意义以及目标,依据未来不确定因素引起飞机备件需求量变化以及备件供应时限性增强的实际情况,创建了时限一致度算子,优化了备件需求泊松分布模型,提高了备件供应的精确度,并选取了优化后的模型中的多个参量,进行了多因素的扰动性分析,最后构造了算例,验证了本方法的科学性和有效性. 相似文献
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通过分析原始数据和“千车故障数”计算的不合理性,提出了改进的千车故障数的计算方法,并对原始数据进行变换得到了合理的数据表.通过假设检验得出瞬时故障率是服从Weibull分布,在此基础上提出了单批次预测的概率模型.进一步,利用数据横向和纵向的相关性,在单批次概率模型的基础上,提出了基于样条拟合的多批次双向联合预测模型,这个模型保证了横向和纵向的有机结合,通过拟合汽车的质量参数,来进行联合预测,维护了数据的统一性. 相似文献
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用模糊理论描述备件需求是一种科学适用的方法,针对现有模糊变量隶属度函数构建方法的不足, 设计了基于贝塞尔曲线理论的备件需求模糊隶属度函数构建方法,给出了隶属度求解算法,分析了使拟合误差最小的控制点选择方法.同时通过实例验证以及与最小二乘法的对比分析,验证了贝塞尔曲线方法在构建备件需求模糊隶属度函数方面的有效性.此方法无需事先假设隶属度函数的形态,简单易用、使用灵活并且精度较高. 相似文献
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Accurate demand forecasting is of vital importance in inventory management of spare parts in process industries, while the intermittent nature makes demand forecasting for spare parts especially difficult. With the wide application of information technology in enterprise management, more information and data are now available to improve forecasting accuracy. In this paper, we develop a new approach for forecasting the intermittent demand of spare parts. The described approach provides a mechanism to integrate the demand autocorrelated process and the relationship between explanatory variables and the nonzero demand of spare parts during forecasting occurrences of nonzero demands over lead times. Two types of performance measures for assessing forecast methods are also described. Using data sets of 40 kinds of spare parts from a petrochemical enterprise in China, we show that our method produces more accurate forecasts of lead time demands than do exponential smoothing, Croston's method and Markov bootstrapping method. 相似文献
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Summary A computational framework for estimation of multivariate conditional distributions is presented. It allows the forecast of
the joint distribution of target variables in dependence on explaining variables. The concept can be applied to general distribution
families such as stable or hyperbolic distributions. The estimation is based on the numerical minimization of the cross entropy,
using the Multi-Level Single-Linkage global optimization method. Nonlinear dependencies of conditional parameters can be modeled
with help of general functional approximators such as multi-layer perceptrons. In applications, the information about a complete
distribution of forecasts can be used to quantify the reliability of the forecast or for decision support. This is illustrated
on a case study concerning the spare parts demand forecast. The improvement of the forecast error due to using non-Gaussian
distributions is presented in another case study concerning the truck sales forecast. 相似文献
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L W G Strijbosch R M J Heuts E H M van der Schoot 《The Journal of the Operational Research Society》2000,51(10):1184-1192
This paper examines the performance of two different (s, Q) inventory models, namely a simple and an advanced model, for spare parts in a production plant of a confectionery producer in the Netherlands. The simple approach is more or less standard: the undershoot of the reorder level is not taken into account and the normal distribution is used as the distribution of demand during lead-time. The advanced model takes undershoots into account, differentiates between zero and nonzero demands during lead-time, and utilises the gamma distribution for the demand distribution. Both models are fed with parameters estimated by a procedure that forecasts demand sizes and time between demand occurrences separately (intermittent demand). The results show that the advanced approach yields a service level close to the desired one under many circumstances, while the simple approach is not consistent, in that it leads to much larger inventories in meeting the desired service level for all spare parts. 相似文献
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Wenbin Wang 《European Journal of Operational Research》2012,216(1):127-139
Spare parts demands are usually generated by the need of maintenance either preventively or at failures. These demands are difficult to predict based on historical data of past spare parts usages, and therefore, the optimal inventory control policy may be also difficult to obtain. However, it is well known that maintenance costs are related to the availability of spare parts and the penalty cost of unavailable spare parts consists of usually the cost of, for example, extended downtime for waiting the spare parts and the emergency expedition cost for acquiring the spare parts. On the other hand, proper planned maintenance intervention can reduce the number of failures and associated costs but its performance also depends on the availability of spare parts. This paper presents the joint optimisation for both the inventory control of the spare parts and the Preventive Maintenance (PM) inspection interval. The decision variables are the order interval, PM interval and order quantity. Because of the random nature of plant failures, stochastic cost models for spare parts inventory and maintenance are derived and an enumeration algorithm with stochastic dynamic programming is employed for finding the joint optimal solutions over a finite time horizon. The delay-time concept developed for inspection modelling is used to construct the probabilities of the number of failures and the number of the defective items identified at a PM epoch, which has not been used in this type of problems before. The inventory model follows a periodic review policy but with the demand governed by the need for spare parts due to maintenance. We demonstrate the developed model using a numerical example. 相似文献
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Forecasting spare parts demand is notoriously difficult, as demand is typically intermittent and lumpy. Specialized methods such as that by Croston are available, but these are not based on the repair operations that cause the intermittency and lumpiness of demand. In this paper, we do propose a method that, in addition to the demand for spare parts, considers the type of component repaired. This two-step forecasting method separately updates the average number of parts needed per repair and the number of repairs for each type of component. The method is tested in an empirical, comparative study for a service provider in the aviation industry. Our results show that the two-step method is one of the most accurate methods, and that it performs considerably better than Croston’s method. Moreover, contrary to other methods, the two-step method can use information on planned maintenance and repair operations to reduce forecasts errors by up to 20%. We derive further analytical and simulation results that help explain the empirical findings. 相似文献
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《European Journal of Operational Research》2005,161(1):183-190
This paper addresses inventory policy for spare parts, when demand for the spare parts arises due to regularly scheduled preventive maintenance, as well as random failure of units in service. A stochastic dynamic programming model is used to characterize an ordering policy which addresses both sources of demand in a unified manner. The optimal policy has the form (s(k),S(k)), where k is the number of periods until the next scheduled preventive maintenance operation. The nature of the (s(k),S(k)) policy is characterized through numeric evaluation. The efficiency of the optimal policy is evaluated, relative to a simpler policy which addresses the failure replacement and preventive maintenance demands with separate ordering policies. 相似文献