Performance bounds on optimal fixed prices

We consider the problem of selling a fixed stock of items over a finite horizon when the buyers arrive following a Poisson process. We obtain a general lower bound on the performance of using a fixed price rather than dynamically adjusting the price. The bound is 63.21% for one unit of inventory, and it improves as the inventory increases. For the one-unit case, we also obtain tight bounds: 89.85% for the constant-elasticity and 96.93% for the linear price-response functions.     

浅谈实验室自动测试软件的管理

自动测试软件已经成为各检测/校准实验室开展测试工作的重要手段之一,因此如何进一步加强实验室自动测试软件的管理,提高自动测试软件的可靠性,成为各检测/校准实验室急需解决的问题。针对目前各检测/校准实验室自动测试软件开发、使用过程中普遍存在的问题,提出了具体的解决措施。     

Optimal cash management under uncertainty

We solve an agent’s optimization problem of meeting demands for cash over time with cash deposited in bank or invested in stock. The stock pays dividends and uncertain capital gains, and a commission is incurred in buying and selling of stock. We use a stochastic maximum principle to obtain explicitly the optimal transaction policy.     

Fully polynomial-time approximation schemes for time–cost tradeoff problems in series–parallel project networks

We consider the deadline problem and budget problem of the nonlinear time–cost tradeoff project scheduling model in a series–parallel activity network. We develop fully polynomial-time approximation schemes for both problems using K-approximation sets and functions, together with series and parallel reductions.     

ARMA(1,1)需求条件下供应链需求提前承诺的影响效果分析

为了分析供应链需求提前承诺的影响效果,考虑供应链所面临的顾客需求满足ARMA（1,1）过程。首先从理论上建立正常顾客需求与顾客需求提前承诺时零售商订单量波动程度和平均库存的定量描述模型,通过两种情形下的比较分析,得出在顾客需求自回归系数大于零时,顾客需求提前承诺将减小牛鞭效应和平均库存水平;同时得出在顾客需求提前承诺时,如果顾客需求自回归系数大于零,顾客提前承诺的需求比例越高,则牛鞭效应和平均库存水平越低;顾客需求提前承诺的时间跨度越长,则牛鞭效应和平均库存水平也越低。反之亦然。其次运用仿真方法分析了顾客需求提前承诺对零售商平均库存成本的影响,得出在顾客需求自回归系数大于零时,顾客需求提前承诺将有效降低零售商的平均库存成本。     

Exact methods for large-scale multi-period financial planning problems

A relevant financial planning problem is the periodical rebalance of a portfolio of assets such that the portfolio’s total value exhibits certain characteristics. This problem can be modelled using a transition graph G to represent the future state space evolution of the corresponding economy and mathematically formulated as a linear programming problem. We present two different mathematical formulations of the problem. The first considers explicitly the set of the possible scenarios (scenario-based approach), while the second considers implicitly the whole set of scenarios provided by the graph G (graph-based approach). Unfortunately, for both the formulations the size of the corresponding linear programs can be huge even for simple financial problems. However, the graph-based approach seems to be a more powerful model, since it allows to consider a huge number of scenarios in a very compact formulation. The purpose of this paper is to present both heuristic and exact methods for the solution of large-scale multi-period financial planning problems using the graph-based model. In particular, in this paper we propose lower and upper bounds and three exact methods based on column, row and column/row generation, respectively. Since the methods based on column/row generation exploits simultaneously both the primal and the dual structure of the problem we call it Criss-Cross generation method. Computational results are given to prove the effectiveness of the proposed methods.      

零售业连锁网点选址与布局演化模型

蚁群算法是近年来出现的一种新型仿生优化算法,是求解复杂优化问题有效方法.本文建立了基于蚁群算法的零售业连锁网点选址与布局演化模型,并利用Matlab进行仿真研究.通过对模拟结果的分析,验证了零售业连锁网点的选址与布局规律.     

Impulsive control in a stage structure population model with birth pulses

The dynamical behavior of a stage structure population model with birth pulses and impulsive pest management strategy is discussed analytically and numerically. It is assumed that birth pulse and impulsive pest management strategy act with the same period, but not simultaneously. The existence and stability of the positive 2T-period solution are investigated. By using center manifold theorem and bifurcation theorem, the conditions of existence for flip bifurcation are derived. Moreover, some detailed numerical results for phase portraits, periodic solutions, bifurcation diagram, and chaotic attractors, which are illustrated with two examples, are in good agreement with the theoretical analysis.     

On the supplier diversification under binomial yield

In a recent article, Fadiloglu et al. study an EOQ inventory model with multiple suppliers and binomial yields and conclude that sole sourcing is always optimal. This finding is contrary to the literature advocating diversification of the supply base in the presence of uncertainty. In this note, we present an alternative and more elegant proof of the optimality of sole sourcing in the EOQ model with binomial yield. Our approach extends this result to a general structure for the fixed order cost and provides more insights into the problem.     

Better than optimal mean–variance portfolio policy in multi-period asset–liability management problem

When the wealth is larger than some threshold in multi-period mean–variance asset–liability management, the pre-committed policy is no longer mean–variance efficient policy for the remaining investment horizon. To revise the policy, by relaxing self-financing constraint and allowing to withdraw some wealth, we derive a new dominating policy, which is better than the pre-committed policy. The revised policy can achieve the same mean–variance pairs attained by the pre-committed policy, and yields a nonnegative free cash flow stream over the investment horizon.