On an Application of Microsoft Excel’s Evolutionary Solver to the Resource-Constrained Project Scheduling Problem RCPSP

The Solver Add-in of Microsoft Excel is widely used in courses on Operations Research and in industrial applications. Since the 2010 version of Microsoft Excel, the Solver Add-in comprises a so-called evolutionary solver. We analyze how this metaheuristic can be applied to the resource-constrained project scheduling problem (RCPSP). We present an implementation of a schedule-generation scheme in a spreadsheet, which combined with the evolutionary solver can be used for devising good feasible schedules. Our computational results indicate that using this approach, non-trivial instances of the RCPSP can be (approximately) solved to optimality.

An MILP-based heuristic for staff scheduling problems with acceptance levels

We present a real-world staff-assignment problem that was reported to us by a provider of an online workforce scheduling software. The problem consists of assigning employees to work shifts subject to a large variety of requirements related to work laws, work shift compatibility, workload balancing, and personal preferences of employees. A target value is given for each requirement, and all possible deviations from these values are associated with acceptance levels. The objective is to minimize the total number of deviations in ascending order of the acceptance levels. We present an exact lexicographic goal programming MILP formulation and an MILP-based heuristic. The heuristic consists of two phases: in the first phase a feasible schedule is built and in the second phase parts of the schedule are iteratively re-optimized by applying an exact MILP model. A major advantage of such MILP-based approaches is the flexibility to account for additional constraints or modified planning objectives, which is important as the requirements may vary depending on the company or planning period. The applicability of the heuristic is demonstrated for a test set derived from real-world data. Our computational results indicate that the heuristic is able to devise optimal solutions to non-trivial problem instances, and outperforms the exact lexicographic goal programming formulation on medium- and large-sized problem instances.

Horizon shells and BMS-like soldering transformations

We revisit the theory of null shells in general relativity, with a particular emphasis on null shells placed at horizons of black holes. We study in detail the considerable freedom that is available in the case that one solders two metrics together across null hypersurfaces (such as Killing horizons) for which the induced metric is invariant under translations along the null generators. In this case the group of soldering transformations turns out to be infinite dimensional, and these solderings create non-trivial horizon shells containing both massless matter and impulsive gravitational wave components. We also rephrase this result in the language of Carrollian symmetry groups. To illustrate this phenomenon we discuss in detail the example of shells on the horizon of the Schwarzschild black hole (with equal interior and exterior mass), uncovering a rich classical structure at the horizon and deriving an explicit expression for the general horizon shell energy-momentum tensor. In the special case of BMS-like soldering supertranslations we find a conserved shell-energy that is strikingly similar to the standard expression for asymptotic BMS supertranslation charges, suggesting a direct relation between the physical properties of these horizon shells and the recently proposed BMS supertranslation hair of a black hole.

Zum 25. Stiftungsfest des "Akademischen Vereins für jüdische Geschichte und Literatur"

Alfred Lipschitz

Sehr geehrter Herr Redacteur!

Benjamin Lipschitz

Guessing Harmonic Oscillator Wavefunctions Using Maple

The guessing of eigenfunctions is not trivial at higher quantum numbers, no matter what the system being considered. Instead of guessing, one can employ a symbolic calculus progam (Maple in this case) to aid in the reasoning process.

Der moderne Rabbinismus

Hermann Lipschitz

Der moderne Rabbinismus

Hermann Lipschitz

Zur ungarisch-jüdischen Seminarfrage : ein Aufruf an die glaubensinnige Judenheit Ungarns

Hermann Lipschitz

Aus der Wiener Cultus-Gemeinde 5624 [Rezension]

Hermann Lipschitz

Ein Wort zur Zeit : dringender Mahnruf an das ungarische glaubenstreue Israel

Hermann Lipschitz

Rede : gehalten - zum Theile - in der, in Folge Erlasses der hohen Statthalterei, am 30. und 31. October a. c. in Brünn stattgehabten Versammlung der mährischen Rabbiner, Lehrer und Gemeindevorsteher

Hermann Lipschitz

Design of long-term animal bioassay for low-dose extrapolation using a multistage model

Conventional designs of animal bioassays allocate the same number of animals into control and dose groups to explore the spontaneous and induced tumor incidence rates, respectively. The purpose of such bioassays are (a) to determine whether or not the substance exhibits carcinogenic properties, and (b) if so, to estimate the human response at relatively low doses. In this study, it has been found that the optimal allocation to the experimental groups which, in some sense, minimize the error of the estimated response for low dose extrapolation is associated with the dose level and tumor risk. The number of dose levels has been investigated at the affordable experimental cost. The pattern of the administered dose, 1 MTD, 1/2 MTD, 1/4 MTD,....., etc. plus control, gives the most reasonable arrangement for the low dose extrapolation purpose. The arrangement of five dose groups may make the highest dose trivial. A four-dose design can circumvent this problem and has also one degree of freedom for testing the goodness-of-fit of the response model.^ An example using the data on liver tumors induced in mice in a lifetime study of feeding dieldrin (Walker et al., 1973) is implemented with the methodology. The results are compared with conclusions drawn from other studies. ^

Una experiencia desde equipo técnico : tensiones y apuesta en torno a procesos de autonomía en personas discapacitadas

Nos proponemos en este trabajo tensionar los conceptos de discapacidad, sujeto y educación desde las miradas interdisciplinarias de un equipo que trabaja en una institución de escolaridad especial. Las concepciones epistemológicas que subyacen a las prácticas en la educación especial, como en otros campos, generan acciones y efectos de viejas y nuevas teorías. Revisamos estos supuestos y la naturalización de las prácticas y de las perspectivas. Como equipo hacemos referencia a la necesidad de un proceso permanente de construcción del rol, que permita pensarnos, interactuar, interrogarnos y discutir las diferentes intervenciones institucionales y comunitarias. Así, la conformación interdisciplinaria del equipo nos permite beneficiarnos con una mirada crítica hacia la diversidad y conformar una multiplicidad de observaciones sobre el objeto, lo que implica un capital simbólico muy importante. En éste trabajo es nuestro interés reflexionar acerca de las prácticas interprofesionales en los ámbitos donde se desarrollan los procesos educativos, tendientes a generar procesos de subjetivación y de construcción de ciudadanía posibilitando instancias de autonomía en los alumnos.

Eros y cultura

Es un lugar común la casi inexistente contribución de España a Ia literatura de corte erótico. Esta cuestión se relaciona, al mismo tiempo, con Ia consideración acerca de qué se considera "pornográfico". Aquí es necesario tener en cuenta, empero, en qué medida lo pornográfico implica la mirada del sujeto que lo percibe como tal. La arqueología, por su parte, ha venido dando pruebas de los cambios en la recepción de Ia iconografía antigua; y de este modo ha venido a echar cierta luz sobre la consideración de lo erótico en la misma España, donde la tabuización de Ia sexualidad por el poder eclesiástico ha acorralado lo erótico a un consumo masivo y trivial.