Kathrin Fischer

Inventory relocation for overlapping disaster settings in humanitarian operations

The number and scale of humanitarian operations has significantly increased during the past decades due to the rising number of humanitarian emergencies and natural disasters worldwide. Therefore, the development of appropriate planning methods for optimization of the respective supply chains is constantly growing in importance. A specific problem in the context of humanitarian operations is the supply of relief items to the affected areas after the occurrence of a sudden change in demand or supply, for example, due to an epidemic or to unexpected shortages, during an ongoing humanitarian action. When such overlapping disasters occur, goods must be relocated to existing depots in a way which enables rapid supply to regions with new and urgent demand. At the same time, ongoing operations have to continue, i.e., the other regions should not suffer from shortages, and possible future emergencies must be taken into account. This is a planning situation under uncertainty as it is not known in advance if and where a disruption—and hence additional demand—will occur. In this paper, an optimization model for such situations is developed based on penalty costs for non-satisfied demand. A rolling horizon approach for solving the model is presented, and it is shown that taking into account the possibility of future disruptions can help to balance inventories and to reduce total non-served demand.

Sequential Discrete p-Facility Models for Competitive Location Planning

Two new models for duopolistic competitive discrete location planning with sequential acting and variable delivered prices are introduced. If locations and prices are assumed to be set “once and for all” by the players, the resulting bilevel program is nonlinear. Under the assumption that further price adjustments are possible, i.e., that a Nash equilibrium in prices is reached, the model can be simplified to a linear discrete bilevel formulation. It is shown that in either situation players should not share any locations or markets if they strive for profit-maximization.For the situation with price adjustments, a heuristic solution procedure is suggested. In addition, the bilevel models are shown to serve as a basis from which different well-known location models – as, for example, the p-median problem, the preemptive location problem and the maximum covering problem – can be derived as special cases.

Combined location-routing problems—a neural network approach

While in location planning it is often assumed that deliveries are made on a direct-trip basis, in fact deliveries, e.g., to the different supermarkets belonging to a specific chain or to retail outlets of any kind, usually are performed as round-trips. Therefore, it is often necessary to combine the two issues of locating a depot and of planning tours in one problem formulation.In this paper, a neural network approach based on a self-organizing map is proposed for solving such single-depot location-routing problems in the plane. The results derived by this approach are compared with those which can be found by different well-known heuristics, and it is shown that the self-organising map approach competes well with these concepts. Moreover, some modifications which rely on ideas from Tabu Search can be shown to be especially useful for increasing the number of feasible solutions found by the self-organising map approach. Finally, the implementation of the Weiszfeld procedure for a final improvement of the optimal depot location proves to be a useful device.

Scheduling yard cranes considering crane interference

Automated stacking cranes form the heart of modern container terminals. Hence, their productivity has a major influence on the performance of the terminal. In the first part of this paper, the yard crane scheduling problem and its practical relevance from the point of view of the Container Terminal Altenwerder (CTA) in Hamburg, Germany, is described. In Altenwerder, 26 yard blocks orthogonal to the quay with transfer areas at both ends of each block are operated with double rail mounted gantries (DRMG). In the second part of the paper, an outline of a new scheduling algorithm for yard cranes on this particular layout is given. The procedure minimizes delays for the jobs and the cycle times of the cranes. In addition to in-motion times also other parts of the cycle time, as waiting and blocking times resulting from other cranes, are taken into account in the scheduling approach. A branch and bound algorithm is used to create sequences of jobs for each crane. Using a simulation model, both the influence of the length of these sequences and the impact of technical breakdowns on the results are analysed. Finally, the results are verified with operational data and the applicability for practice at the CTA is evaluated.

Scheduling of Different Automated Yard Crane Systems at Container Terminals

In this work, different variants of a branch-and-bound procedure for yard crane scheduling at seaport container terminals and their effect on the terminal’s performance are studied. In particular, this work investigates the level of detail needed to take the exact crane characteristics, e.g., movements and crane interference, into account in the scheduling algorithm. This is examined for four different automated yard crane systems with one or more cranes that operate on rectangular yard blocks with transfer positions at both ends of the block and with the yard blocks arranged orthogonally to the quay. Using a simulation model with realistic scenario data and an automated guided vehicles system for horizontal transport, the results are compared with respect to different key performance indicators, e.g., yard crane productivity and average lateness of jobs. It turns out that especially the consideration of crane interference leads to significant improvements in yard crane productivity. As a result of the lo...

A Revenue Management Slot Allocation Model with Prioritization for the Liner Shipping Industry

The main characteristics for the successful use of revenue management are present in the liner shipping industry. Hence, revenue management methods can be applied to obtain the best container acceptance strategy. The segmentation which is normally used is based on the different container types, routes and customers. The literature shows that reliability and delivery speed are important factors for customers, and that containers with different commodities often have different priority. Therefore, the optimization model which is developed in this work creates booking limits for standard segmentations and incorporates an additional segmentation approach. These new segments are express and standard containers: The express segment is intended for urgent cargo and gets priority on the next ship. A container in the standard segment only needs to be shipped until a fixed delivery date and can be postponed. This new segmentation approach generates advantages for both parties involved.

Remarks on "A measure of risk and a decision-making model based on expected utility and entropy" by Jiping Yang and Wanhua Qiu (EJOR 164 (2005), 792-799)

Abstract Yang and Qiu [Yang, J., Qiu, W., 2005. A measure of risk and a decision-making model based on expected utility and entropy. European Journal of Operational Research 164, 792–799] suggest a new concept for decision making under risk. This concept relies on a combination of the well-known expected utility criterion and the so-called entropy. The authors claim that the approach might be used as a descriptive as well as a normative decision model. In this paper, the theoretical soundness of the concept of entropy is critically examined. The analysis is underpinned by a discussion of the properties of the respective entropy function. Furthermore, normative and descriptive features of the concept are discussed and it is shown that the usefulness with respect to both aspects is questionable.

Optimierungsmodelle zur Bilanzgestaltung

Die Gestaltung der Bilanz im Rahmen des handels- und steuerrechtlichen Jahresabschlusses ist fur Unternehmen von groser Bedeutung. Zum einen erfullt die Bilanz eine Informationsfunktion, da sie Auskunft uber die wirtschaftliche Situation des Unternehmens gibt; sie beeinflust auf diese Weise das Bild des Unternehmens gegenuber der Umwelt und damit moglicherweise z.B. das kunftige Investitionsverhalten von Kapitalgebern. Zum anderen hat die Bilanz fur das Unternehmen intern eine Erfolgs- oder Gewinnermittlungsfunktion, d.h. anhand der Bilanz soll der Unternehmenserfolg beurteilt und der fur die Unternehmenseigner erwirtschaftete Gewinn festgelegt werden. Die gewahlte Bilanzpolitik tragt somit zur Erreichung finanz- und publizitatspolitischer Zielsetzungen bei und beeinflust den Unternehmenserfolg.1

Prepositioning of Relief Items Under Uncertainty: A Classification of Modeling and Solution Approaches for Disaster Management

Natural and man-made disasters often have devastating effects on the affected population and the economy. Optimization models for determining the locations of relief facilities and the amount of first-aid items to be stored before the occurrence of an emergency can help decisively to mitigate the impact of a disaster. As research interest in disaster management has grown significantly over the last decade, this paper reviews the state-of-the-art literature concerning prepositioning of relief items in conjunction with facility location decisions, taking the uncertain nature of a disaster into account. A classification of the respective modeling approaches and solution methods is provided to facilitate the identification of relevant research gaps. One of the main findings is the lack of efficient solution methods especially for large scale problems, although generating optimal solutions in a reasonable timeframe is crucial for the success of a relief operation. Based on the detected gaps, future research directions are suggested.

Central Places: The Theories of von Thünen, Christaller, and Lösch

The question of why economic activities are concentrated in certain places and not in others, why so-called “central places” exist at which an agglomeration of people and trade takes place, and where these central places are to be found, has long been a focus of spatial economists. In the nineteenth and twentieth centuries, three German scientists concentrated on that area, and the results of their research became famous and influential in Germany and all over the world. The three scholars in question are: Johann Heinrich von Thunen (“Der isolierte Staat in Beziehung auf Landwirtschaft und Nationalokonomie,” Teil I, 1826), Walter Christaller (“Die zentralen Orte in Suddeutschland,” 1933) and August Losch (“Die raumliche Ordnung der Wirtschaft,” 1940). Von Thunen was the first to develop a theory of land use, and was praised as “one of the patron saints of econometrics” by Schumpeter (1955). Christaller founded the Theory of Central Places which, in the 1950s, was the only theory “concerning systems of cities that was at all well developed” (Berry 1964) and, especially in the 1960s and 1970s, became the major concept to be applied in regional planning in Germany. Losch, who is described as an “extraordinary personality” by Stolper in the foreword to Losch’s book, developed the first general equilibrium concept regarding the system of locations of economic activities that had ever been presented.