Search results for "Management Science"
showing 10 items of 1017 documents
Optimal Trajectories for Spacecraft Rendezvous
2007
The efficient execution of a rendezvous maneuver is an essential component of various types of space missions. This work describes the formulation and numerical investigation of the thrust function required to minimize the time or fuel required for the terminal phase of the rendezvous of two spacecraft. The particular rendezvous studied concerns a target spacecraft in a circular orbit and a chaser spacecraft with an initial separation distance and separation velocity in all three dimensions. First, the time-optimal rendezvous is investigated followed by the fuel-optimal rendezvous for three values of the max-thrust acceleration via the sequential gradient-restoration algorithm. Then, the ti…
Optimistic NAUTILUS navigator for multiobjective optimization with costly function evaluations
2022
AbstractWe introduce novel concepts to solve multiobjective optimization problems involving (computationally) expensive function evaluations and propose a new interactive method called O-NAUTILUS. It combines ideas of trade-off free search and navigation (where a decision maker sees changes in objective function values in real time) and extends the NAUTILUS Navigator method to surrogate-assisted optimization. Importantly, it utilizes uncertainty quantification from surrogate models like Kriging or properties like Lipschitz continuity to approximate a so-called optimistic Pareto optimal set. This enables the decision maker to search in unexplored parts of the Pareto optimal set and requires …
An Adaptive Alternating Direction Method of Multipliers
2021
AbstractThe alternating direction method of multipliers (ADMM) is a powerful splitting algorithm for linearly constrained convex optimization problems. In view of its popularity and applicability, a growing attention is drawn toward the ADMM in nonconvex settings. Recent studies of minimization problems for nonconvex functions include various combinations of assumptions on the objective function including, in particular, a Lipschitz gradient assumption. We consider the case where the objective is the sum of a strongly convex function and a weakly convex function. To this end, we present and study an adaptive version of the ADMM which incorporates generalized notions of convexity and penalty…
Constrained control of a nonlinear two point boundary value problem, I
1994
In this paper we consider an optimal control problem for a nonlinear second order ordinary differential equation with integral constraints. A necessary optimality condition in form of the Pontryagin minimum principle is derived. The proof is based on McShane-variations of the optimal control, a thorough study of their behaviour in dependence of some denning parameters, a generalized Green formula for second order ordinary differential equations with measurable coefficients and certain tools of convex analysis.
Convex Duality in Stochastic Optimization and Mathematical Finance
2011
This paper proposes a general duality framework for the problem of minimizing a convex integral functional over a space of stochastic processes adapted to a given filtration. The framework unifies many well-known duality frameworks from operations research and mathematical finance. The unification allows the extension of some useful techniques from these two fields to a much wider class of problems. In particular, combining certain finite-dimensional techniques from convex analysis with measure theoretic techniques from mathematical finance, we are able to close the duality gap in some situations where traditional topological arguments fail.
The project scheduling polyhedron: Dimension, facets and lifting theorems
1993
Abstract The Project scheduling with resource constraints can be formulated as follows: given a graph G with node set N, a set H of directed arcs corresponding to precedence relations, and a set H′ of disjunctive arcs reflecting the resource incompatibilities, find among the subsets of H′ satisfying the resource constraints the set S that minimizes the longest path in graph (N, H ∪ S). We define the project scheduling polyhedron Qs as the convex hull of the feasible solutions. We investigate several classes of inequalities with respect to their facet-defining properties for the associated polyhedron. The dimension of Qs is calculated and several inequalities are shown to define facets. For …
Learning as Issue Framing in Agricultural Innovation Networks
2014
AbstractPurposeNetworks are increasingly viewed as entities of learning and innovation in agriculture. In this article we explore learning as issue framing in two agricultural innovation networks.Design/methodology/approachWe combine frame analysis and social learning theories to analyse the processes and factors contributing to frame convergence and hence improved practical collaborative outcomes in networks. Issue framing in the networks was followed during a two-year period with the help of multiple methods assembled under a transdisciplinary case study, action research and grounded methodology framework.FindingsOur research suggests that learning and collective action for more sustainab…
Deliberate or Instinctive? : Proactive and Reactive Coping for Technostress
2019
Employees in organizations face technostress that is, stress from information technology (IT) use. Although technostress is a highly prevalent organizational phenomenon, there is a lack of theory-based understanding on how IT users can cope with it. We theorize and validate a model for deliberate proactive and instinctive reactive coping for technostress. Drawing from theories on coping, our model posits that the reactive coping behaviors of distress venting and distancing from IT can alleviate technostress by diminishing the negative effect of technostress creators on IT-enabled productivity. The proactive coping behaviors of positive reinterpretation and IT control can help IT users by in…
Making Communication Strategy Choices in a Fast Evolving Crisis Situation—Results from a Table-Top Discussion on an Anthrax Scenario
2016
This paper aims at clarifying a timely topic of how communication strategy choices are made in evolving, complex crises, such as those caused by terrorism involving chemical, biological, radiological, or nuclear (CBRN) agents. This is done by examining data gathered from a table-top discussion among crisis communication experts, focusing on a scenario of an anthrax attack and analysed qualitatively. The communication experts followed the evolving crisis situation by gathering inputs from various actors in the crisis management network, thereby creating situational understanding, and interpreted these inputs for decision-making on communication strategies. The underlying process of coping wi…
Impacts of COVID-19 and pandemic control measures on public transport ridership in European urban areas – The cases of Vienna, Innsbruck, Oslo, and A…
2021
The study uses the case of two regions with small and medium sized cities (Agder in Norway and the greater Innsbruck area in Austria) and two European capitals, Vienna and Oslo, to showcase the impact of the COVID-19 pandemic on public transport ridership in northern and central Europe. The comprehensive timeline of actions taken by governments and public transport providers in Austria and Norway, and their impact on public transport ridership in the first and second waves of the pandemic form the basis of a descriptive study. Comparing the data, a strong negative impact on the public transport patronage in the first wave of the pandemic was found, despite a comparable low number of cases p…