When centers can fail: a close second opportunity

This paper presents the p-next center problem, which aims to locate p out of n centers so as to minimize the maximum cost of allocating customers to backup centers. In this problem it is assumed that centers can fail and customers only realize that their closest (reference) center has failed upon arrival. When this happens, they move to their backup center, i.e., to the center that is closest to the reference center. Hence, minimizing the maximum travel distance from a customer to its backup center can be seen as an alternative approach to handle humanitarian logistics, that hedges customers against severe scenario deteriorations when a center fails. For this extension of the p-center problem we have developed several different integer programming formulations with their corresponding strengthenings based on valid inequalities and variable fixing. The suitability of these formulations for solving the p-next center problem using standard software is analyzed in a series of computational experiments. These experiments were carried out using instances taken from the previous discrete location literature.Peer ReviewedPostprint (author’s final draft

La p-médiane humanitaire

Dans ce mémoire, nous présentons plusieurs variantes du problème de la p-médiane (PPM) classique. Le PPM classique est un problème de localisation-partitionnement. Il consiste à localiser p entrepôts parmi n groupes d'usagers (p et n entiers avec p ≤ n), de sorte que si l'on rattache chaque groupe d'usagers à son entrepôt le plus proche, la somme totale des distances des groupes d'usagers à leur entrepôt soit minimale. Les entrepôts ne peuvent être placés qu'aux emplacements des groupes d'usagers. Suite à une catastrophe humanitaire (ou naturel) provoquée, par exemple, par un séisme ou un ouragan, de nombreuses infrastructures du pays touché sont détruites. Nous nous intéressons au problème de localisation d'entrepôts destinés à l'organisation d'interventions en prévision à de telles catastrophes. Le but est de permettre que les groupes d'usagers (ou de victimes) aient une grande probabilité de recevoir les soins et besoins vitaux nécessaires assez rapidement tout en respectant le budget disponible pour l'aide humanitaire. Le modèle du PPM classique n'est pas adapté à ce type de problème puisqu'il ne tient pas compte des infrastructures qui risquent d'être détruites lors d'un désastre naturel. Ainsi, les solutions qu'il produit ne pourront pas être intégrées dans les décisions logistiques de prépositionnement de dépôts et de matériel d'intervention et de support à la population (ou groupes d'usagers). Dans cette étude, nous tenterons de trouver des solutions à ce type de problème en proposant des variantes du PPM dites "humanitaires" qui prendront en compte de nouvelles contraintes et la probabilité de survie de certaines infrastructures face à un séisme. Un paramètre important, la matrice des distances d'accès, sera modifié en conséquence. L'objectif est de minimiser la distance d'accès totale tout en respectant le budget disponible. Nous présentons des modèles linéaires utilisant des variables binaires. Des expériences numériques sont effectuées, à l'aide du logiciel d'optimisation CPLEX, sur des réseaux expérimentaux et un réseau réel. Les résultats obtenus nous montrent comment varie la distance d'accès totale en fonction du nombre d'entrepôts que l'on souhaite localiser et certains autres paramètres. Ainsi, ayant conscience de l'impact des variantes étudiées, le gestionnaire prendra de meilleures décisions de localisation d'entrepôts en prévision d'une catastrophe de ce type.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Problème de la p-médiane classique (PPM), problème de la p-médiane humanitaire (PPMH), prépositionnement d'entrepôts, catastrophe humanitaire, séisme, aide humanitaire, probabilité de survie d'infrastructures, matrice des distances d'accès

Positioning, Planning and Operation of Emergency Response Resources and Coordination between Jurisdictions

Railroad related rail incidents, particularly those involving hazardous material (hazmat), cause severe consequences and pose significant threats to safety, public health and the environment. Rail safety is a huge issue in Midwestern states such as Illinois, Wisconsin, and Minnesota. This project aims at strategically positioning and allocating emergency responders and resources in anticipation of potential accidents in a region that may be impacted by rail incidents. Mathematical models and solution techniques are developed to enable systematic analysis of the emergency response system associated with railroad incidents; e.g., to strategically position and allocate emergency responders and resources in anticipation of potential accidents along spatially distributed railroad networks. We consider the added complexity due to vulnerability of the emergency response system itself, such as the risk of disruptions to the transportation network for first-responders (e.g., blockage of railroad crossings). The outcomes from these tasks will provide fundamental understanding, operational guidelines, and practical tools to policy makers (e.g., federal and state agencies) to induce socio-economically favorable system that support safe and efficient railroad industry operations

Responsive Contingency Planning for Supply Chain Disruption Risk Mitigation

Contingent sourcing from a backup resource is an effective risk mitigation strategy under major disruptions. The production volumes and speeds of the backup resource are important protection design considerations, as they affect recovery. The objective of this dissertation is to show that cost-effective protection of existing supply networks from major disruptions result from planning appropriate volume and response speeds of a backup production facility prior to the disruptive event by considering operational aspects such as congestion that may occur at facilities. Contingency strategy are more responsive and disruption recovery periods can be shortened through such prior planning. The dissertation focuses on disruption risk arising from intelligent or pre-meditated attacks on supply facilities. An intelligent attacker has the capability to create worst case loss depending on the protection strategy of a given network. Since the attacker seeks the maximum loss and the designer tries to identify the protection scheme which minimizes this maximum loss, there exists an interdependence between attack and protection decisions. Ignoring this characteristic leads to suboptimal mitigation solutions under such disruptions. We therefore develop a mathematical model which utilizes a game theoretic framework of attack and defense involving nested optimization problems. The model is used to decide optimal selection of backup production volume and the response speeds, the facilities to build such capability within the available budget. The reallocation of demands from a disrupted facility to an undisrupted facility in a contingency strategy leads to congestion of the undisrupted facility, which may result in longer lead times and reduced throughput during disruption periods, thereby limiting the effectiveness of a contingency strategy. In the second part of the dissertation, we therefore analyze congestion effects in responsive contingency planning. The congestion cost function is modeled and integrated into the mathematical model of responsive contingency planning developed in the first part of the dissertation. The main contribution of this dissertation is that a decision tool has been developed to plan protection of an existing supply networks considering backup sourcing through gradual capacity acquisition. The solution methodology involving recursive search tree has been implemented which allows exploring protection solutions under a given budget of protection and multiple combinations of response speeds and production capacities of a backup facility. The results and analysis demonstrate the value of planning for responsive contingency in supply chains subject to risks of major disruptions and provide insights to aid managerial decision making

Qualitative assessment of the impact of political disruptions on textiles supply chain performance in Pakistan

With growing regional competition, burgeoning global demand, increased pressure for service improvement and heavy reliance on the textile industry, it is important to understand the complex relationships between political disruptions and supply chain performance. Political disruptions within or outside the textile production system not only affect the processes of ginning, spinning, and weaving, but also the distribution of goods to the end consumers. For firms it is relatively easy to control the production systems, but it is challenging to manage disruptions that emanates from external stimuli. An improved understanding of this relationship will enable Pakistan to enhance its competiveness in a globalised market. There are a number of studies that have investigated transportation risks, disruptions associated with systems failure, and the impacts that natural disasters such as flooding and bushfires have on supply chain performance. The impacts of political disruptions on supply chain performance in Pakistan however are rarely examined empirically. In particular, there is a lack of interdisciplinary research that provides a deeper understanding of the role of political structures and processes resulting in a political disruption while linking it to the efficiency of production and distribution systems of the textile industry. This thesis investigates the complex relationship between political disruptions and the supply chain disruptions that are linked with supply chain performance. This research was conducted using a structuration theory framework, with reference to domination, signification, and legitimation, which collectively provide the basis for exploring the role of agents, the methods they adopt to communicate message and how they used power and resources to fulfil their demand for change through creating disruptions. In-depth semi-structured interviews were conducted with twenty five agents representing textile organisations, third party logistics providers, and interest groups. An investigation into the role played by agents shows the complexity of the interwoven relationships between political disruptions and supply chain performance. Interviewees have recognised political disruptions as a key threat to the efficiency of textile supply chain. Yet they are inadequately understood and insufficiently managed. They have multiple forms, sources and variegated effects. It is found that they collectively create interlinked and interlocking vicious cycles within which political disruptions across different stages of supply chain are embedded as a repetitive system. The interpretation of interview data enabled the development of a typology of political disruptions that further indicates external political disruptions to have a much wider impact on external supply chain operations than they do on internal processes. These disruptions can slow down or in some cases stop external supply chain operations such as procurement of materials and distribution of finished goods to markets. External disruptions also have a direct effect on the internal operations in that they cause an interruption in the production process. Internal textile production operational performance is based on external supply chain activities; this is because external disruptions lie outside the direct influence of the textile manufacturers. The findings of this study indicate that textile supply chain disruptions reflect the multitude of methods used by agents to exchange the messages to bring social and economic change through political resistance. It is often achieve through systematically organised disruptions of the supply chain systems by agents which directly or indirectly interrupt the seamless flow of raw materials between facilities or the distribution of finished goods to end-customers political groups, manufacturers, the labour force, labour unions, supply chain operators, interest groups and customers. The findings from the interview data indicate that, disruptions in the Pakistan textile industry can emanate from internal or external environment, especially when agents are intentionally or unintentionally enabled to allocate resources. Manufacturers exercise their transformative capabilities to bring about desirable changes towards achieving the optimum utilisation of finite resources (raw materials, labour input) through production planning, scheduling, and execution. With reference to signification, agents can have the most impact on supply chain performance through their interpretive schemes used to plan and deploy different methods of communication to transmit their messages to the targeted audience. It is found that politically motivated strikes are often considered as a means to communicate the messages for change and social transformation to the authorities in power to achieve certain purposes such as a pay rise in case of labour strike or resistance to certain laws by political parties or interest groups. These disruptions, some subtle others extreme, create major transportation bottlenecks, delivery delays, and labour supply issues which in turn have had significant implications on supply chain performance. Lower performance was shown to be attributed to the constant threat of political disruptions that were affecting the efficiency of supply chain operations. Interview results show that, textile supply chain disruptions are a result of agent’s mismanagement or intentional use of their allocative powers and the methods that they used to communicate the message. The means of communication depends on the agent’s situation and thus the impact occurs accordingly. Results show that, militants groups use extreme methods as a tool to communicate their messages to the targeted audience which in turn create direct effect on the transportation infrastructure and service operations. Pakistan’s political system has been affected as a result of conflicts from both inside and outside the country. These conflicts have included wars with neighbouring countries, a lack of political leadership, internal political conflicts, and interference from non-political agents. The results indicate that, political disruptions are not isolated events but are part of the political processes and institutional structures within which the disruptions germinate and grow. The political disruptions are not just linked to political systems but also the way textile manufacturers organise work within their organisations. This politically organised structure within the production systems has significant impact on supply chain performance. In this thesis, a supply chain strategic framework was developed to help mitigate the likely impact of political disruptions on textile supply chain performance. This strategic framework can work as a comprehensive guide for textile manufacturing firms to engage in continuous improvement, information sharing, process integration, process synchronisation, and the establishment of mutual trust. Firms can adjust supply chain operations by devising and deploying tactics and strategies to adapt to the potential threat from political disruptions. Further research however is required to evaluate the effectiveness of these strategies to help firms employing politically-engaging practical methods to tackle the threat of political disruptions to textile supply chain. Future research will consider collecting objective data to gather information of the scale and intensity of political disruptions to find ways to enhance textile supply chain performance in Pakistan