Periodic-Review Inventory Model with Three Consecutive Delivery Modes and Forecast Updates

This paper is concerned with a periodic-review inventory system with three consecutive delivery modes (fast, medium, and slow) and demand forecast updates. At the beginning of each period, the inventory level and demand information are updated and decisions on how much to order using each of the three delivery modes are made. It is shown that there is a base-stock policy for fast and medium modes which is optimal. Furthermore, the optimal policy for the slow mode may not be a base-stock policy in general.This research was supported in part by a Faculty Research Grant from the University of Texas at Dallas, a RGC (Hong Kong) Competitive Earmarked Research Grant, a Distinguished Young Investigator Grant from the National Natural Sciences Foundation of China, and a Grant from the Hundred Talents Program of the Chinese Academy of Sciences.     

在预报更新的环境下具有两种配送方式的供应链模型

本文研究在预报更新环境下具有快、慢两种配送方式和需求预报更新的库存系统，为了得到更多关于费用参数和预报改进对最优定货量以及最优的平均费用的影响，我们考虑两个周期的情形．以动态规划为工具我们得到了系统的最优策略．对于需求预报服从均匀分布情形，本文得到了最优定货量和最优的平均总费用的精确表达式．我们通过一些数值例子来说明库存费用、罚金、需求的预报改进和预报误差对最优定货量和最优的     

随机需求条件下的延迟发运策略模型及性质

本针对随机需求条件下物流配送中心的库存和运输联合决策问题，在基本库存和自身运输能力不足的情况下，提出对剩余客户订货需求采取部分延迟到下一期与部分利用第三方物流立即发运两相结合的策略，并在具有一般惩罚(损失)费延迟发运量限制的条件下，建立运输和库存相关总成本数学期望最小的优化模型，论证了该模型的主要性质，在此基础上很容易构造求解该类问题的优化方法。     

季节调整的PSO-SVR模型及其在旅游客流量预测中的应用——以海南省三亚市为例

准确的旅游客流量预测对旅游目的地做好事前准备工作至关重要.然而旅游客流量具有明显的非线性和季节性特征,采取季节调整方法对样本数据进行预处理,消除季节性的影响,可以提高客流量预测的准确性.同时SVR(支持向量回归机)是一种良好的机器学习方法,非常适合预测研究,辅以PSO(粒子群算法)选取合适的回归参数可以获得更加精确的预测结果.提出了一种考虑季节影响并通过PSO优化SVR模型的旅游客流量预测模型,并以海南省三亚市为例进行了实证研究.研究结果表明,季节调整的PSO-SVR模型预测精度明显高于SVR、季节调整的SVR和PSO-SVR模型,是进行旅游客流量预测的有效工具.     

Control theory and the management of ecosystems: A threshold policy with hysteresis is robust

Control theory is much used in engineering to stabilize a given dynamical system at a desired equilibrium point or to confine its trajectories to a region. Extinction of species is one of the most serious problems facing fishery and, to avoid it, different policies are applied. The threshold policy (TP) is a harvesting strategy commonly used in fisheries all over the world, and also is a special and simple case of the variable structure control (VSC). In this paper, the concept of virtual equilibrium point is used to design three different kinds of threshold policies; the standard one (TP), one with delay (TPD) and finally with hysteresis and delay (TPHD), for logistic models subject to Euler as well as two different nonstandard discretization schemes. Uncertainties in the intrinsic growth rate, in the carrying capacity, in the population density, and in the effort policy as well as an overexploitation situation are considered. A time lag in the control policies is also introduced. The important novel characteristic of the TPD and TPHD is that both ensure that, even though the system is subjected to uncertainties and a period of overexploitation, the system eventually stabilizes in bounded oscillations in a desired safe region of the state space. In addition, the sustainable yield under the proposed policies is compared with that of the proportional policy proposed in [1], in order to discuss economic aspects of the proposed threshold policies.     

Spectrum of the Operator Corresponding to the M/M/1 Queueing Model with Vacations and Multiple Phases of Operation and Application

We describe the point spectrum of the operator which corresponds to the M/M/1 queueing model with vacations and multiple phases of operation. Then by using this result we prove that the essential growth bound of the C₀-semigroup generated by the operator is 0, the C₀-semigroup is not compact, not eventually compact, even not quasi-compact. Moreover, we verify that it is impossible that the time-dependent solution of the M/M/1 queueing model with vacations and multiple phases of operation exponentially converges to its steady-state solution. In addition, we obtain the spectral radius and essential spectral radius of the C₀-semigroup. Lastly, we discuss other spectrum of the operator and obtain a set which belongs to the union of its continuous spectrum and residual spectrum.     

具有带临界和非临界故障的可修k/N:G冗余表决系统研究中出现的投影算子的表达式及其应用(英文)

当修复率为常数时通过研究具有带临界和非临界故障的可修k/N:G冗余表决系统研究中出现的投影算子的表达式得到该系统的时间依赖解指数收敛于该系统的稳态解.