A multi-item fuzzy economic production quantity problem with a finite production rate

Inventory Management and production planning are essential tasks for every company in the industry. Therefore, the development of a large set of Economic Order Quantity (EOQ) models is needed. In this paper, a fuzzy multi-item Economic Production Quantity (EPQ) model is developed. This paper contributes to the state-of-the-art with a theoretical study of a problem, where a company has to decide the size of some production batches under uncertain cycle times. The uncertainty will be handled with triangular fuzzy numbers and an analytical solution will be found to the optimization problem.     

基于库存理论的铁路始发直达运输产品设计

将库存理论运用到铁路始发直达运输产品设计,能够有效实现运输服务组织成本与库存成本的有机统一。为实现库存成本在铁路始发直达运输中的加载,在考虑周期非完整情况下的库存成本的同时,将铁路运输和库存成本纳入同一目标函数,在装卸车地库存能力约束下,构建基于库存理论的铁路始发直达运输产品设计模型,确定成本最小的铁路始发直达运输产品设计方案。以赤峰地区至山东省煤炭运输网络为例,设计方案有效降低了成本,有助于吸引客户选择铁路运输,以及辅助铁路运营单位研究调整始发直达运输产品方案。     

Segmentation and time-of-day patterns in foreign exchange markets

This paper sheds light on a puzzling pattern in spot foreign exchange markets: domestic currencies appreciate (depreciate) systematically during foreign (domestic) working hours. This phenomenon spans many years and several exchange rates, and overrides calendar effects. We argue that it is mainly due to liquidity and inventory patterns that emerge from the combination of two factors: domestic agents tend to be net buyers of foreign currency and to trade mostly in their country’s working hours. The prevalence of domestic (foreign) traders demanding the counterpart currency during domestic (foreign) working hours implies sell-price (buy-price) pressure on the domestic currency during domestic (foreign) working hours.     

VMI对医药供应链中零售商和批发商的利益影响研究

随着政府对医药卫生行业监管的加强,医药的流通环节已成为医药行业变革的重点之一。通过对行业产品及供应链特性的分析,本文提出医药行业实施供应商库存管理(VMI)是迎接变革的一个有效途径,然后定性定量地研究VMI如何增加医药零售商、批发商和整个供应链的利润。本文也给出VMI协调医药供应链的条件,以及批发商如何通过自身的管理提升来实现自我激励和促成同零售商的共赢。     

Inventory model for an inventory system with time-varying demand rate

The standard inventory problems of the multi-period have been modeled under different situations. Specifically we have considered the demand subjects of a continuous distribution and a discrete distribution, and whether the demand of each period is unchanged or not. A method to get an economic order quantity in inventory systems with discrete and unchanged demand was presented in a previous paper, and this method has been generalized to an inventory model with varying continuous demand. However, it was not achieved due to there being many classified cases in the general situations. In this article the above method is discussed in the case discrete demand to determine whether it increases or decreases from period to period. A theoretical method is presented by using previous results and some examples are given which suggest how the concept can handle on inventory system. In order to make the decision, an algorithm is also presented under some conditions, and examples are shown by using the computer software program, Mathematica, which helps to explain the findings. In general cases, we view the optimal policy in the inventory problems in only a few periods.     

A supply chain network design considering transportation cost discounts

This study addresses an integrated facility location and inventory allocation problem considering transportation cost discounts. Specifically, this article considers two types of transportation discounts simultaneously: quantity discounts for inbound transportation cost and distance discounts for outbound transportation cost. This study uses an approximation procedure to simplify DC distance calculation details, and develops an algorithm to solve the aforementioned supply chain management (SCM) problems using nonlinear optimization techniques. Numerical studies illustrate the solution procedures and the effects of the model parameters on the SCM decisions and total costs. Results of this study serve as a reference for business managers and administrators.     

The relationship between information technology capability,inventory efficiency,and shareholder wealth: A firm-level empirical analysis

Inventories represent an important strategic resource for firms, with implications for shareholder wealth. As such, firms expend considerable effort in managing their inventories efficiently. Among other factors, information technology (IT) capability can play an important role in enabling inventory efficiency and financial performance. However, insight into the chain-of-effects linking IT capability, inventory efficiency, and stock market returns and risk remains limited. In this paper, we provide a conceptual model outlining the relationships between these constructs. Next, we evaluate the model using secondary information on firms from multiple industries across the 10-year time period of 2000–2009. Our analysis confirms that firms’ IT capability plays a significant role in enhancing their inventory efficiency, which, in turn, is observed to increase stock market returns. Our results also reveal that firms’ IT capability directly reduces their stock market risk and enhances their stock market returns. Taken together, these findings, along with the conceptual model that we advance, have important research and managerial implications.     

A multiple objective particle swarm optimization approach for inventory classification

This paper presents a particle swarm optimization approach for inventory classification problems where inventory items are classified based on a specific objective or multiple objectives, such as minimizing costs, maximizing inventory turnover ratios, and maximizing inventory correlation. In addition, this approach determines the best number of inventory classes and how items should be categorized for the desired objectives at the same time. Experiments are employed to determine the best combination of algorithm parameter values. Extensive numerical studies are conducted and results are compared to other known classification methods. The performance of the algorithm on a practical case is also presented.     

Models and metrics to assess humanitarian response capacity

The race to meet vital needs following sudden onset disasters leads response organizations to establish stockpiles of inventory that can be deployed immediately. These government or non-government organizations dynamically make stockpile decisions independently. Even though the value of one organization's stock deployment is contingent on others' decisions, decision makers lack evidence regarding sector capacity to assess the marginal contribution (positive or negative) of their action. To our knowledge, there exist no metrics describing the system capacity across many agents to respond to disasters. To address this gap, our analytical approach yields new humanitarian logistics metrics based on stochastic optimization models. Our study incorporates empirical data on inventory stored by various organizations in United Nations facilities and in their own warehouses to offer practical insights regarding the current humanitarian response capabilities and strategies. By repositioning inventory already deployed, the system could respond to disasters in the same expected time with a range of 7.4%–20.0% lower cost for the items in our sample.     

Relief aid stocking decisions under bilateral agency cooperation

We aim to quantify the benefits of cooperation between humanitarian relief agencies in terms of stocking decisions. We consider two agencies that stock the same type of relief item at different locations prone to individual disaster risks and agree to transship the shortage amount from available stocks in case of a disaster. We incorporate the disaster risk to the Newsvendor model by conditioning the stock quantity decisions on the event that a major disaster occurs within the lifetime of the stocked relief item. We optimize the stock quantity for each agency in response to the other's quantity and compute a Nash Equilibrium solution numerically. We apply this game theoretic approach to the case of earthquake preparedness in Istanbul to optimize the stocking decisions of an agency for shelter units in cooperation with another agency. We investigate the characteristics of the solutions under various parameter settings and identify cases in which cooperation may be beneficial to one or both of the agencies.