An adaptive forecasting algorithm and inventory policy for products with short life cycles

Products with short life cycles are becoming increasingly common in many industries, such as the personal computer (PC) and mobile phone industries. Traditional forecasting methods and inventory policies can be inappropriate for forecasting demand and managing inventory for a product with a short life cycle because they usually do not take into account the characteristics of the product life cycle. This can result in inaccurate forecasts, high inventory cost, and low service levels. Besides, many forecasting methods require a significant demand history, which is available only after the product has been sold for some time. In this paper, we present an adaptive forecasting algorithm with two characteristics. First, it uses structural knowledge on the product life cycle to model the demand. Second, it combines knowledge on the demand that is available prior to the launch of the product with actual demand data that become available after the introduction of the product to generate and update demand forecasts. Based on the forecasting algorithm, we develop an optimal inventory policy. Since the optimal inventory policy is computationally expensive, we propose three heuristics and show in a numerical study that one of the heuristics generates near‐optimal solutions. The evaluation of our approach is based on demand data from a leading PC manufacturer in the United States, where the forecasting algorithm has been implemented. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

Optimal pricing for a short life‐cycle product when customer price‐sensitivity varies over time

Technology products often experience a life‐cycle demand pattern that resembles a diffusion process, with weak demand in the beginning and the end of the life cycle and high demand intensity in between. The customer price‐sensitivity also changes over the life cycle of the product. We study the prespecified pricing decision for a product that exhibits such demand characteristics. In particular, we determine the optimal set of discrete prices and the times to switch from one price to another, when a limited number of price changes are allowed. Our study shows that the optimal prices and switching times show interesting patterns that depend on the product's demand pattern and the change in the customers' price sensitivity over the life cycle of the product. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

对高重频PD雷达的舍脉冲干扰

高重频PD雷达是为解决测速模糊而在机载雷达中广泛采用的一种PD雷达工作模式,从PD雷达的特性来讲,由于带宽比较窄使得噪声干扰能量利用效率不是很高。采用DRFM精确获取雷达信号实施干扰是当前干扰的发展方向,但是对占空比接近50%的高重频PD雷达,采用对低重频PD及中重频PD可行的距离拖引,速度拖引等一系列在雷达信号脉冲串间隔内产生复杂调制的干扰方法是不合适的。主要针对高重频PD雷达重频高、占空比大的特点,提出了一种舍脉冲干扰方法,对DRFM截获的雷达信号进行快速部分转发,间隔一定脉冲数舍弃一个脉冲,改变原雷达信号的脉冲重复周期,使得在频域上产生多个速度欺骗性干扰信号,并通过仿真验证了干扰的有效性。     

一类二次微分系统在三次多项式扰动下的极限环估计

计算了一类二次Hamilton微分系统的一阶Mel’nikov函数,通过此方法对该系统在三次多项式扰动下分岔的极限环个数进行了估计。     

质漏对联合循环化学发动机性能的影响

分析存在有限速率传质和质漏损失的联合循环化学发动机性能,导出功率、效率最佳关系,最大功率及其相应效率,以及最大效率及其相应功率     

压剪加载下炸药装药中剪切带形成与发展模型

研究了在压剪加载下炸药这类粘塑性介质中剪切带的形成与发展。提出了一种反映炸药装药中剪切带形成和发展的计算方法,并分析了剪切带发展变化特性与炸药起爆的关系     

闭式循环柴油机技术综述

基于采用海水吸收的闭式循环柴油机系统,综合分析了系统实现的一般原则和目前的技术状况,并提出了系统实现中存在的问题及其解决的思路．     

System availability in a gamma alternating renewal process

We measure the effectiveness of a repairable system by the proportion of time the system is on, where on-time and off-times are assumed independent and both gamma-distributed. This measure is helpful for system planning and control in the short term, before the steady-state is reached, and its mean value is intermediary between instantaneous and steady-state availabilities. We also present other significant results concerning the Gamma Alternating Renewal Process. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 822–844, 1999     

Determining a threshold control policy for an imperfect production system with rework jobs

Consider a threshold control policy for an imperfect production system with only a work center handling both regular and rework jobs. An imperfect production system studied here, generates defect jobs by factors other than machine failures. A threshold control or (ω, s) policy sets the guideline for a work center to switch between regular and rework jobs. A production cycle begins with loading and processing of several batches of regular jobs with a lot size equal to s. The outcome of each completed regular job is an independent Bernoulli trial with three possibilities: good, rework, or scrap. Once the work center accumulates more than a threshold ω of rework jobs, it finishes the last batch of regular jobs and switches to rework jobs. The objective of this research is to find a threshold ω and a lot size s that maximize the average long‐term profit. The ultimate goal is to construct a simple algorithm to search for ω and s that can be implemented directly in production management systems, as a result of this work. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 273–301, 1999     

工质变比热和传热损失对Diesel循环性能的影响

用有限时间热力学的方法分析空气标准Diesel循环,由数值计算给出了存在传热损失和工质变比热时循环功与压缩比、效率与压缩比以及功和效率的特性关系,并分析了传热损失和工质变比热对循环性能的影响特点,通过分析可知传热和变比热特性对Diesel循环性能有较大影响,所以在实际循环分析中应该予以考虑.