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101.
This paper proposes a new methodology to schedule activities in projects with stochastic activity durations. The main idea
is to determine for each activity an interval in which the activity is allowed to start its processing. Deviations from these intervals result in penalty costs. We employ
the Cross-Entropy methodology to set the intervals so as to minimize the sum of the expected penalty costs. The paper describes
the implementation of the method, compares its results to other heuristic methods and provides some insights towards actual
applications. 相似文献
102.
Robust multi-echelon multi-period inventory control 总被引:2,自引:0,他引:2
Ben-Tal Aharon Golany Boaz Shtern Shimrit 《European Journal of Operational Research》2009,199(3):922-935
We consider the problem of minimizing the overall cost of a supply chain, over a possible long horizon, under demand uncertainly which is known only crudely. Under such circumstances, the method of choice is Robust Optimization, in particular the Affinely Adjustable Robust Counterpart (AARC) method which leads to tractable deterministic optimization problems. The latter is due to a recent re-parametrization technique for discrete time linear control systems. In this paper we model, analyze and test an extension of the AARC method known as the Globalized Robust Counterpart (GRC) in order to control inventories in serial supply chains. A simulation study demonstrates the merit of the methods employed here, in particular, it shows that a good control law that minimizes cost achieves simultaneously good control of the bullwhip effect. 相似文献
103.
Boaz Galdino de Oliveira Regiane de Cássia Maritan Ugulino de Araújo Elisa Soares Leite Mozart Neves Ramos 《International journal of quantum chemistry》2011,111(1):111-116
A theoretical analysis of linear and bifurcate halogen‐oxygen bonds is presented in this work. B3LYP/6‐311++G(d,p) and MP2/6‐311++G(d,p) calculations were used to determine the optimized geometries of intermolecular systems formed by CFCl3 and O3. Molecular properties often analyzed in hydrogen‐bonded complexes were used here to describe the interaction between chlorine (CFCl3) and oxygen (O3). The halogen‐oxygen bond in the CFCl3···O3 complex was characterized using the topological parameters derived from the quantum theory of atoms in molecules. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
104.
Jochen Vogl Boaz Paz Maren Koenig Wolfgang Pritzkow 《Analytical and bioanalytical chemistry》2013,405(9):2995-3000
A modified Pb–matrix separation procedure using NH4HCO3 solution as eluent has been developed and validated for determination of Pb isotope amount ratios by thermal ionization mass spectrometry. The procedure is based on chromatographic separation using the Pb·Spec resin and an in-house-prepared NH4HCO3 solution serving as eluent. The advantages of this eluent are low Pb blanks (<40 pg?mL?1) and the property that NH4HCO3 can be easily removed by use of a heating step (>60 °C). Pb recovery is >95 % for water samples. For archaeological silver samples, however, the Pb recovery is reduced to approximately 50 %, but causes no bias in the determination of Pb isotope amount ratios. The validated procedure was used to determine lead isotope amount ratios in Trojan silver artefacts with expanded uncertainties (k?=?2) <0.09 %. 相似文献
105.
We show the optimality of sphere-separable partitions for problems where n vectors in d-dimensional space are to be partitioned into p categories to minimize a cost function which is dependent in the sum of the vectors in each category; the sum of the squares of their Euclidean norms; and the number of elements in each category. We further show that the number of these partitions is polynomial in n. These results broaden the class of partition problems for which an optimal solution is guaranteed within a prescribed set whose size is polynomially bounded in n. Applications of the results are demonstrated through examples. 相似文献
106.
Boaz Cohen 《Israel Journal of Mathematics》2017,220(2):605-615
Let Y → X be a finite normal cover of a wedge of n ≥ 3 circles. We prove that for any nonzero v ∈ H 1(Y; Q) there exists a lift \(\widetilde F\) to Y of a basepoint-preserving homotopy equivalence F: X → X such that the set of iterates \(\left\{ {{{\widetilde F}^d}\left( v \right)} \right\}:d \in \mathbb{Z} \subseteq {H_1}\left( {Y,\mathbb{Q}} \right)\) is infinite. The main achievement of this paper is the use of representation theory to prove the existence of a purely topological object that seems to be inaccessible via topology. 相似文献
107.
Selective CH Functionalization of Methane,Ethane, and Propane by a Perfluoroarene Iodine(III) Complex 下载免费PDF全文
Dr. Michael M. Konnick Dr. Brian G. Hashiguchi Dr. Deepa Devarajan Nicholas C. Boaz Prof. T. Brent Gunnoe Prof. John T. Groves Niles Gunsalus Prof. Daniel H. Ess Prof. Roy A. Periana 《Angewandte Chemie (International ed. in English)》2014,53(39):10490-10494
Direct partial oxidation of methane, ethane, and propane to their respective trifluoroacetate esters is achieved by a homogeneous hypervalent iodine(III) complex in non‐superacidic (trifluoroacetic acid) solvent. The reaction is highly selective for ester formation (>99 %). In the case of ethane, greater than 0.5 M EtTFA can be achieved. Preliminary kinetic analysis and density functional calculations support a nonradical electrophilic CH activation and iodine alkyl functionalization mechanism. 相似文献
108.
This paper addresses the problem of scheduling activities in projects with stochastic activity durations. The aim is to determine
for each activity a gate—a time before it the activity cannot begin. Setting these gates is analogous to setting inventory
levels in the news vendor problem. The resources required for each activity are scheduled to arrive according to its gate.
Since activities’ durations are stochastic, the start and finish time of each activity is uncertain. This fact may lead to
one of two outcomes: (1) an activity is ready to start its processing as all its predecessors have finished, but it cannot
start because the resources required for it were scheduled to arrive at a later time. (2) The resources required for the activity
have arrived and are ready to be used but the activity is not ready to start because of precedence constraints. In the first
case we will incur a “holding” cost while in the second case, we will incur a “shortage” cost. Our objective is to set gates
so as to minimize the sum of the expected holding and shortage costs. We employ the Cross-Entropy method to solve the problem.
The paper describes the implementation of the method, compares its results to various heuristic methods and provides some
insights towards actual applications. 相似文献
109.
L.Paul Chew Klara Kedem Micha Sharir Boaz Tagansky Emo Welzl 《Journal of Algorithms in Cognition, Informatics and Logic》1998,29(2):238-255
The combinatorial complexity of the Voronoi diagram ofnlines in three dimensions under a convex distance function induced by a polytope with a constant number of edges is shown to beO(n2α(n)log n), where α(n) is a slowly growing inverse of the Ackermann function. There are arrangements ofnlines where this complexity can be as large as Ω(n2α(n)). 相似文献
110.
In this theoretical work, the characterization of multiple proton donors in three isomers of BeH2···2HCl trimolecular dihydrogen-bonded complex was developed through the analysis of structural parameters, electronic criteria,
and analysis of vibrational harmonic spectrum, where all these data were obtained from the B3LYP/6-311++G(3d,3p) calculations.
As dihydrogen bonds are formed by the interaction between two hydrogen atoms, proton donors and hydride hydrogen, the isomers
of BeH2···2HCl trimolecular dihydrogen-bonded complexes are stabilized by two, three, and four centers of proton donors. By analyzing
the charge density integrations calculated by the theory of Atoms in Molecules, these multiple centers of proton donors were
identified by quantification of the intermolecular electronic density, Laplacian operators, and charge transfers. 相似文献