Scheduling a production–distribution system to optimize the tradeoff between delivery tardiness and distribution cost

We consider a make‐to‐order production–distribution system with one supplier and one or more customers. A set of orders with due dates needs to be processed by the supplier and delivered to the customers upon completion. The supplier can process one order at a time without preemption. Each customer is at a distinct location and only orders from the same customer can be batched together for delivery. Each delivery shipment has a capacity limit and incurs a distribution cost. The problem is to find a joint schedule of order processing at the supplier and order delivery from the supplier to the customers that optimizes an objective function involving the maximum delivery tardiness and the total distribution cost. We first study the solvability of various cases of the problem by either providing an efficient algorithm or proving the intractability of the problem. We then develop a fast heuristic for the general problem. We show that the heuristic is asymptotically optimal as the number of orders goes to infinity. We also evaluate the performance of the heuristic computationally by using lower bounds obtained by a column generation approach. Our results indicate that the heuristic is capable of generating near optimal solutions quickly. Finally, we study the value of production–distribution integration by comparing our integrated approach with two sequential approaches where scheduling decisions for order processing are made first, followed by order delivery decisions, with no or only partial integration of the two decisions. We show that in many cases, the integrated approach performs significantly better than the sequential approaches. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005     

混沌序列相关特性研究及在扩频通信中的应用

分别用Logistic映射和Chebyshev映射产生出混沌序列,在Matlab下进行相关性分析,再以Chebyshev映射产生的混沌序列代替传统的伪随机序列作为扩频通信系统的扩频码,在Simulink下进行扩频通信系统的仿真,综合分析了基于混沌序列的扩频系统的抗噪性能,仿真结果验证了基于混沌序列的扩频系统的抗干扰性能和混沌序列作为码的应用价值.     

Nitro-tetrazole based high performing explosives: Recent overview of synthesis and energetic properties

Heterocyclic skeleton (Azoles) and different energetic groups containing high performing explosives are highly emerged in recent years to meet the challenging requirements of energetic materials in both military and civilian applications with improved performance. For this purpose tetrazole (Azole) is identified as an attractive heterocyclic backbone with energetic functional groups nitro (-NO₂), nitrato (-ONO₂), nitrimino (-NNO₂), and nitramino (–NH–NO₂) to replace the traditionally used high performing explosives. The tetrazole based compounds having these energetic functional groups demonstrated advanced energetic performance (detonation velocity and pressure), densities, and heat of formation (HOF) and became a potential replacement of traditional energetic compounds such as RDX. This review presents a summary of the recently reported nitro-tetrazole energetic compounds containing poly-nitro, di/mono-nitro, nitrato/nitramino/nitrimino, bridged/bis/di tetrazole and nitro functional groups, describing their preparation methods, advance energetic properties, and further applications as high-performing explosives, especially those reported in the last decade. This review aims to provide a fresh concept for designing nitro-tetrazole based high performing explosives together with major challenges and perspectives.     

Prediction of three-dimensional elastic behavior of filament-wound composites based on the bridging model

This work provides a method to predict the three-dimensional equivalent elastic properties of the filament-wound composites based on the multi-scale homogenization principle.In the meso-scale,a representative volume element(RVE)is defined and the bridging model is adopted to establish a theoretical predictive model for its three-dimensional equivalent elastic constants.The results obtained through this method for the previous experimental model are compared with the ones gained respec-tively by experiments and classical laminate theory to verify the reliability of this model.In addition,the effects of some winding parameters,such as winding angle,on the equivalent elastic behavior of the filament-wound composites are analyzed.The rules gained can provide a theoretical reference for the optimum design of filament-wound composites.     

Approximation algorithms for minimizing total weighted completion time of orders on identical machines in parallel

We consider the problem of scheduling orders on identical machines in parallel. Each order consists of one or more individual jobs. A job that belongs to an order can be processed by any one of the machines. Multiple machines can process the jobs of an order concurrently. No setup is required if a machine switches over from one job to another. Each order is released at time zero and has a positive weight. Preemptions are not allowed. The completion time of an order is the time at which all jobs of that order have been completed. The objective is to minimize the total weighted completion time of the orders. The problem is NP‐hard for any fixed number (≥2) of machines. Because of this, we focus our attention on two classes of heuristics, which we refer to as sequential two‐phase heuristics and dynamic two‐phase heuristics. We perform a worst case analysis as well as an empirical analysis of nine heuristics. Our analyses enable us to rank these heuristics according to their effectiveness, taking solution quality as well as running time into account. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

AN ENDOGENOUS GROWTH MODEL OF CAPITAL AND ARMS ACCUMULATION

This paper attempts to examine the effect of an anticipated foreign military threat on the steady‐state growth rate and the transitional behavior of the economy. The modeling strategy follows the Sandler and Hartley (1995 Sandler, T. and Hartley, K. 1995. The Economics of Defense, Cambridge: Cambridge University Press.  [Google Scholar]) and Dunne et al. (2005 Dunne, J.P., Smith, R.P. and Willenbockel, D. 2005. Models of military expenditure and growth: a critical review. Defence and Peace Economics, 16: 449–461. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) viewpoints to emphasize the role of national defense in affecting growth from the perspective of both the demand and the supply sides. We thus combine the public capital version of endogenous growth with a framework of competitive arms accumulation. It is found that the key factor determining the steady state and the transitional effects of a rise in the foreign military threat on the home weapon–capital ratio, the consumption–capital ratio, and the rate of economic growth, is the degree of relative risk aversion.     

TERRORIST THREATS AND TRANSITIONAL DYNAMICS IN AN OVERLAPPING GENERATIONS MODEL

Previous research has shown that the duration of a civil war is in part a function of how it ends: in government victory, rebel victory, or negotiated settlement. We present a model of how protagonists in a civil war choose to stop fighting. Hypotheses derived from this theory relate the duration of a civil war to its outcome as well as characteristics of the civil war and the civil war nation. Findings from a competing risk model reveal that the effects of predictors on duration vary according to whether the conflict ended in government victory, rebel victory, or negotiated settlement.     

Country survey IX: Spain

From the early 1980s Spain embarked on a wide‐ranging process of military reform, from organisational changes to defence industrial policies. Investment in military equipment was set to grow, policies were drawn up to foster the domestic defence industrial base, defence R&D rocketed, and Spain joined a myriad of international arms development programmes. Yet, by 1991 the process of reform had run out of steam. Expenditure planning proved unreliable, and firms suffered from sharp cutbacks in procurement expenditure. The model of defence industrial growth sketched in the mid‐1980s had floundered. The Spanish case provides an example of how the quest to maximise defence procurement from domestic sources can fall victim to industrial and budgetary constraints. Spanish defence producers are now becoming increasingly intertwined with foreign defence companies.     

THE DEFENCE SPENDING–EXTERNAL DEBT NEXUS IN ETHIOPIA

The aim of this paper is to examine the impact of defence spending and income on the evolution of Ethiopia’s external debt over the period 1970–2005. Using the bounds test approach to cointegration and Granger causality tests, we find a long run and a causal relationship between external debt, defence spending and income. Defence spending had a positive and a significant impact on the stock of external debt while income had a negative and a statistically significant impact on external debt. Our findings suggest that an increase in defence spending contributes to the accumulation of Ethiopia’s external debt, while an increase in economic growth helps Ethiopia to reduce its external debt.