Pre-positioning of relief items under road/facility vulnerability with concurrent restoration and relief transportation

Planning for response to sudden-onset disasters such as earthquakes, hurricanes, or floods needs to take into account the inherent uncertainties regarding the disaster and its impacts on the affected people as well as the logistics network. This article focuses on the design of a multi-echelon humanitarian response network, where the pre-disaster decisions of warehouse location and item pre-positioning are subject to uncertainties in relief item demand and vulnerability of roads and facilities following the disaster. Once the disaster strikes, relief transportation is accompanied by simultaneous repair of blocked roads, which delays the transportation process, but gradually increases the connectivity of the network at the same time. A two-stage stochastic program is formulated to model this system and a Sample Average Approximation (SAA) scheme is proposed for its heuristic solution. To enhance the efficiency of the SAA algorithm, we introduce a number of valid inequalities and bounds on the objective value. Computational experiments on a potential earthquake scenario in Istanbul, Turkey show that the SAA scheme is able to provide an accurate approximation of the objective function in reasonable time, and can help drive policy-based implications that may be applicable in preparation for similar potential disaster

Examining the Factors Affecting the Selection of the Recreation Activity Type of University Students

This research was conducted to determine the recreational activity choices of the students studying at various faculties of the university. The main purpose of this study is to determine the factors that affect the selection of recreational activity of university students. A total of 156 students, 98 female and 58 male, studying at various faculties in İzmir Universities, participated in the survey. As the data collection tool, “Personal Information Form” and the scale made by Arslan (2010 and 2012) to measure the factors affecting the selection of the recreational activity type were used. The data obtained were analyzed by using the SPSS 23 program. “T-test”, “ANOVA” and “Tukey post hoc” tests were used to obtain statistical results.  “Guidance” sub-dimension mean score values and “general scale” mean score values were higher in women than men (p<0.05). “Personal suitability” and “environment” sub-dimension mean score values of individuals with an income of 1000 TL and below are higher than individuals with higher income (p<0.05). A significant difference was observed only in the mean scores of the “guidance” sub-dimension according to the educational background of the mothers of the individuals (p<0.05). When the mean score values of “personal suitability”, “guidance” sub-dimension and “general scale” were examined, it was concluded that the mean score values of individuals whose fathers are primary and high school graduates were higher than those whose fathers were bachelor and master graduates (p<0.05). Mean scores of “personal suitability”, “environment” sub-dimensions and “general scale” were higher in individuals whose family with an income of 1001 - 2000 TL per month, that is, the lowest income group (p<0.05). When we look at the “guidance”, “environment” sub-dimensions and the general scale, it was concluded that the mean score values of individuals who think that games are a little effective in activities are higher than the mean score values of individuals who think that games in activities are very effective (p<0.05). The opinions of the individuals about "in which faculty the recreation department should be" do not make a difference on the mean score values of the "general scale" and its sub-dimensions. According to the type of recreational activity that individuals do in their leisure time, the mean score values of the “general scale” and its sub-dimensions do not show a significant difference (p>0.05). As a result of the findings, when the factors that affect the selection of the recreational activity type of the students were examined, it was found that the highest factor was “age-appropriateness”. The statement with the lowest mean in the scale is “healthy life programs on TV”. In addition, it was concluded that the most effective factors in individuals' choices on the recreational activities were that the activities were personally suitable for them and the environment was also suitable

Potential effects of logistics clusters: The case of Turkish Freight Villages

Freight Villages (FV) are logistics clusters in which all activities related with freight transportation are realized. Various operators conduct business under one roof in FVs. Coordination and collaboration are the essential part for creating harmony to achieve sustainability. The establishment of such facilities in Turkey has been realized in late 2000s. In this paper, the aim is to provide a broad overview of the FVs in Turkey and shed light into their potential for the future. To do so site visits to all existing operational public FVs and a private FV have been made, where interviews with the management units have been conducted and comparisons to global counterparts have been made. As a result of these, it has been observed that currently, FVs in Turkey are overwhelmed due to lack of coordination and collaboration. However, also light has been shed into possible alternative working principles for Turkish FVs, and it has been showed that if coordination and collaboration could be realized, significant positive effects can be achieved in terms of different aspects regarding sustainability and social equity

A stochastic programming approach for chemotherapy appointment scheduling

Chemotherapy appointment scheduling is a challenging problem due to the uncertainty in pre-medication and infusion durations. In this paper, we formulate a two-stage stochastic mixed integer programming model for the chemotherapy appointment scheduling problem under limited availability and number of nurses and infusion chairs. The objective is to minimize the expected weighted sum of nurse overtime, chair idle time, and patient waiting time. The computational burden to solve real-life instances of this problem to optimality is significantly high, even in the deterministic case. To overcome this burden, we incorporate valid bounds and symmetry breaking constraints. Progressive hedging algorithm is implemented in order to solve the improved formulation heuristically. We enhance the algorithm through a penalty update method, cycle detection and variable fixing mechanisms, and a linear approximation of the objective function. Using numerical experiments based on real data from a major oncology hospital, we compare our solution approach with several scheduling heuristics from the relevant literature, generate managerial insights related to the impact of the number of nurses and chairs on appointment schedules, and estimate the value of stochastic solution to assess the significance of considering uncertainty

Koridorları birbirine paralel dizilmiş depolarda sipariş toplama problemi.

Order-picking operations constitute the costliest activities in a warehouse. The order-picking problem (OPP) aims to determine the route of the picker(s) in such a way that the total order-picking time, hence the order-picking costs are minimized. In this study, a warehouse that consists of parallel pick aisles is assumed, and various versions of the OPP are considered. Although the single-picker version of the problem has been well studied in the literature, the multiple-picker version has not received much attention in terms of algorithmic approaches. The literature also does not take into account the time taken by the number of turns during the picking route. In this thesis, a detailed discussion is made regarding the computational complexity of the OPP with a single picker. A heuristic procedure, which makes use of the exact algorithm for the OPP with no middle aisles, is proposed for the single-picker OPP with middle aisles, and computational results on randomly generated problems are given. Additionally, an evolutionary algorithm that makes use of the cluster-first, route-second and route-first, cluster-second heuristics for the VRP is provided. The parameters of the algorithm are determined based on preliminary runs and the algorithm is also tested on randomly generated problems, with di fferent weights given to the cluster-first, route-second and route-first, cluster-second approaches. Lastly, a polynomial time algorithm is proposed for the problem of minimizing the number of turns in a parallel-aisle warehouse.M.S. - Master of Scienc

Order picking in a parallel-aisle warehouse with turn penalties

In many real-life routing problems, incorporating the negative effects of turns is an important, but often overlooked aspect. This is especially true for order picking in warehouses, where making the turns not only decreases the picking efficiency by reducing the speed of the vehicle, but it also results in other unquantifiable effects such as vehicle tipovers, increased congestion and increased risk of collision with pedestrians or other vehicles. In this paper, we consider the order picking problem in a parallel-aisle warehouse by taking into account the number and effect of the turns. In particular, we show that the problem of minimising the number of turns, minimising travel time under turn penalties, the biobjective problem that involves turn and travel time minimisation as separate objectives, and the triobjective problem with U-turn minimisation as a third objective can all be solved in polynomial time. Our computational results show that the algorithms we develop can generate the corresponding Pareto front very quickly, and significantly outperform heuristic approaches used in practice

The storage replenishment problem in rectangular warehouse

In warehouses, storage replenishment operations involve the transportation of items to capacitated item slots in forward storage area from reserve storage. These items are later picked from these slots as their demand arises. While order picking constitutes the majority of warehouse operating costs, replenishment operations might be as costly in warehouses where pick lists generally consist of only a few lines (e.g., order fulfillment warehouses). In this study, we consider the storage replenishment problem in a parallel-aisle warehouse, where replenishment and order picking operations are carried out in successive waves with time limits. The aim is to determine the item slots that will be replenished and the route of the replenishment worker in each replenishment wave, so as to minimize the total labor and travel costs, and ensure the availability of items at the start of the wave they will be picked. The problem is analogous to the inventory routing problem due to the inherent trade-o between labor and travel costs. We present complexity results on different variants of the problem and show that the problem is NP-hard in general. Consequently, we use a heuristic approach inspired by those from the inventory routing literature. We use randomly generated warehouse instances to analyze the elect of different storage policies (random and turnover-based) and demand patterns (highly skewed or uniform) on replenishment performance, and to compare the proposed replenishment approach to those in practice