The generalized bin packing problem

In the Generalized Bin Packing Problem (GBPP), given two sets of compulsory and non-compulsory items characterized by volume and profit and a set of bins with given volume and cost, we want to select the subset of profitable non-compulsory items to be loaded together with the compulsory ones into the appropriate bins in order to minimize the total net cost. Lower and upper bounds to the GBPP are given. The results of extensive computational experiments show that the proposed procedures are efficient and the bounds are tight.     

A Generalized Nash Equilibrium network model for post-disaster humanitarian relief

We develop a Generalized Nash Equilibrium network model for post-disaster humanitarian relief by nongovernmental organizations (NGOs). NGOs derive utility from providing relief supplies to victims of the disaster at demand points in a supply chain context while competing with each other for financial funds provided by donations. The shared constraints consist of lower and upper bounds for demand for relief items at the demand points to reduce materiel convergence or congestion. This game theory problem is reformulated as an optimization problem and numerical examples and a theoretical case study on Hurricane Katrina given.     

Efficiency of the plate-number-based traffic rationing in general networks

Road space rationing based on vehicle plate numbers restricts vehicle access to a network based upon the license number on pre-established days. It has been used in some large cities especially when there are some major events. This paper analyzes the efficiency of road space rationing schemes by establishing the bounds of the reduction in the system cost associated with the restricted flow pattern at user equilibrium in comparison with the system cost at the original user equilibrium. The bounds are established under the general traffic equilibrium model formulated as variational inequalities and illustrated with a simple example.     

The fixed charge facility location problem with coverage restrictions

This paper develops a fixed charge facility location model with coverage restrictions, minimizing cost while maintaining an appropriate level of service, in identifying facility locations. Further, it discusses the insights that can be gained using the model. Two Lagrangian relaxation based heuristics are presented and tested. Both heuristics use a greedy adding algorithm to calculate upper bounds and subgradient optimization to calculate lower bounds. While both procedures are capable of generating good solutions, one is computationally superior.     

The multi-class, multi-criterion traffic equilibrium and the efficiency of congestion pricing

We consider the effect of the so-called second-best tolls on the price of anarchy of the traffic equilibrium problem where there are multiple classes of users with a discrete set of values of time. We derive several bounds of the price of anarchy for this problem when the tolls are considered and not considered as part of the system cost, with the time-based criterion and the cost-based criterion, respectively. All the bounds give us useful information on the effect of the tolls, which can be used to design network toll schemes.     

铁路短期变动成本的特征及计算方法探讨

根据铁路短期变动成本的变化频繁性、非连续性、与运量关系复杂性和不可归依性4个特征,提出铁路短期变动成本的计算方法和步骤。首先将企业总成本划分为固定成本和变动成本,然后分别计算直接变动成本的支出率、间接变动成本的附加率、联合产品的总变动成本和个别产品的变动成本等。     

云南省物流需求预测

基于价值量和实物量对云南省物流需求进行预测,根据云南省2010年和2020年GDP预测总量,对物流成本占GDP比重进行粗略估计,得到云南省社会物流总成本的估算。选用一元线性回归分析方法对云南省综合货运量的预测,说明云南省社会物流总成本呈增长趋势,综合货运量也以较快的速度增长。     

Multi-objective design of an organ transplant network under uncertainty

We propose a novel multi-period location–allocation model for the design of an organ transplant transportation network under uncertainty. The model consists of a bi-objective mathematical programming model that minimizes total cost and time, including waiting time in the queue for the transplant operation, while considering organs’ priorities. A fuzzy multi-objective programming based approach is presented to solve the small and medium size problems to optimality. For larger problems, we propose two meta-heuristics based algorithms. Lower bounds, and several numerical examples with managerial insights are discussed. A real case-study is provided, and the existing and the proposed optimal solutions are compared.     

铁路客运专线成本曲线分析

借鉴国内外客运专线资料,对铁路客运专线运输成本的特性及构成进行论述,并从速度目标值与客运量两方面分析对运输成本的影响,说明速度目标值直接影响客运专线的运输成本,而固定成本与客运量无关,变动成本与客运量成正比变化。     

我国铁路货运需求结构的VAR模型分析

在建立铁路货运量、国民经济、铁路网扩展的协整VAR模型基础上,分析三者之间的长期均衡关系和短期动态关系。结果表明,在长期中,铁路货运量随国民经济增长呈缓慢增长趋势,而随铁路网扩展呈较快增长趋势。在短期中,国民经济是铁路货运量的重要影响因素;铁路货运量和铁路网扩展对国民经济影响不大;铁路货运量是铁路网扩展的重要影响因素,而国民经济变化对其影响不大。     

A novel mathematical model for a multi-period,multi-product optimal ordering problem considering expiry dates in a FEFO system

One of the main challenges of retail units is to determine the order quantities of different types of products, each with a specific expiry date, so that the system cost including shortage cost is minimized. We study a new multi-product multi-period replenishment problem for a First Expired-First Out (FEFO) based warehouse management system. The proposed nonlinear model is first converted to a linear one and then solved by applying two evolutionary algorithms: the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO), in which design parameters are set using Taguchi method. Computational results demonstrate the applicability of the proposed model for perishable items and comparing the results shows the efficiency of the proposed metaheuristics as well.     

铁路项目成本管理分解结构

目前国际通用的工作分解结构(WBS)技术是将主要的项目可交付成果分解为较小的且更易于管理的单元。在论述工作分解结构的作用和优点的基础上,给出项目成本WBS设计方法、设计步骤、工作包分拆原则和结构设计等,以及成本WBS的编码设计。     

Price planning for time-definite less-than-truckload freight services

Price planning simultaneous determines the service demand (with associated prices) and an operational plan to maximize a carrier’s profit. We modeled this integral-constrained concave program in the link formulation and proposed an implicit enumeration embedded with Lagrangian Relaxation upper bounds to determine the optimal prices. Computations on Taiwan’s time-definite less-than-truckload freight market showed that the carrier needs to simultaneously re-evaluate its network capacity while determining prices. The common practice of distance-based pricing that sets price by a base rate over direct shipment distance underestimates operating cost, specifically operating losses for short distance shipments.     

Selecting between batch and zone order picking strategies in a distribution center

An order picking strategy in a distribution center (DC) defines the manner in which pickers navigate the picking area to pick items from storage locations. We focus on the problem of selecting between a batch picking and a zone picking strategy. For this problem, we propose a cost model to estimate the cost of each type of picking strategy. In our cost model we consider the effects of pick-rate, picker blocking, workload-imbalance, and the sorting system requirement. Through an example problem, we show how system throughput, order sizes, item distribution in orders, and wavelength affect the picking strategy selection decision.     

Inventory control for returnable transport items in a closed-loop supply chain

An inventory control model for returnable transport items (RTI) where the manager selects the optimal length for inspection, repair, and purchase cycles is described. Repaired and newly obtained RTI are used in combination to satisfy current production requirements. Uncertain returns are incorporated into the model by determining a satisfactory safety stock level to buffer the inventory of used and repairable containers. The minimum cost solution is obtained when inspection and repair runs begin simultaneously. Cycle times are a function of the expected return rate and repairable percentage, while variability in these random assumptions affects the required safety stock.     

Substitution and complementarity in aviation: airports vs airlines

In this paper a model concerning substitution and complementarity on the linkage between airport facilities and airlines from the viewpoint of pricing policy is formulated. This model is used to analyze whether airport pricing policies, e.g. to ensure cost recovery, are compatible with competition for transfer passengers. It is found that airports with a high volume of demand can pursue cost recovery and still be the most preferred hub. Airports with a low level of demand will not be the preferred hub, even if the larger airport charges higher taxes to recover costs.     

The impact of low cost airline operations to Malta

In 2006 the controversial step was undertaken by the Maltese government to provide incentives for new routes with the intention of attracting low cost carriers to fly to the Islands. This paper examines the impact that low cost airline operations are likely to have on the volume and profile of passengers visiting Malta. The focus is on whether the low cost carriers are merely facilitating existing custom in terms of tourism flows, or whether they are attracting a different kind of visitor. The analysis uses data from a number of air transport and tourism sources and concentrates on the UK; the largest tourist market and where the low cost carriers are likely to have the greatest impact. Initially the effects of low cost carriers to date are examined and then there is an assessment of the longer-term impacts investigating recent developments of other low cost routes from the UK. The evidence shows that traffic to Malta increased significantly in 2007 but these additional travellers do not seem to be more interested in history or culture, nor do they take shorter trips or travel more in off-peak times. This is unlike the situation at a number of other European destinations where the introduction of regular low cost services has provided the flexibility for short break cultural tourism to develop.     

Liner shipping hub network design in a competitive environment

A mixed integer programming formulation is proposed for hub-and-spoke network design in a competitive environment. It addresses the competition between a newcomer liner service provider and an existing dominating operator, both operating on hub-and-spoke networks. The newcomer company maximizes its market share—which depends on the service time and transportation cost—by locating a predefined number of hubs at candidate ports and designing its network. While general-purpose solvers do not solve instances of even small size, an accelerated Lagrangian method combined with a primal heuristic obtains promising bounds. Our computational experiments on real instances of practical size indicate superiority of our approach.     

The impact of slow ocean steaming on delivery reliability and fuel consumption

With a dominant volume of global transportation being conducted by sea, ocean container transport greatly impacts the global economy. Since sea vessels are drastically more fuel efficient when traveling at lower speeds, slow steaming has become a widely adopted practice to reduce bunker costs. However, this leads to a longer transportation time, which together with the unpredictability of the delay has been a big challenge. We propose a model to quantify the relationship among shipping time, bunker cost and delivery reliability. Our findings lead to a simple and implementable policy with a controlled cost and guaranteed delivery reliability.     

A less-than-truckload carrier collaboration planning problem under dynamic capacities

This paper addresses the deterministic dynamic single carrier collaboration problem for the small- to medium-sized less-than-truckload (LTL) industry. It is formulated as a binary (0–1) multi-commodity minimum cost flow problem and solved using a branch-and-cut algorithm. Its inherent network structure is exploited to generate the lower bounds to the branch-and-cut algorithm using the network simplex method and by relaxing the integrality constraints. Results from numerical experiments indicate inherent trade-offs at the higher degrees of collaboration between waiting for more affordable collaborative capacity and incurring higher holding costs. They also suggest that collaborating LTL carriers experience increased capacity utilization.