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31.
Rodolfo Sánchez Angela Braeuning-Demian Jan Glorius Siegbert Hagmann Pierre-Michel Hillenbrand Anton Kalinin Thomas Köhler Yuri A. Litvinov Nikolaos Petridis Shahab Sanjari Uwe Spillmann Thomas Stöhlker 《X射线光谱测定》2020,49(1):33-36
The atomic physics collaboration SPARC is a part of the APPA pillar at the future Facility for Antiproton and Ion Research. It aims at atomic-physics research across virtually the full range of atomic matter. An emphasis of this contribution are the atomic physics experiments addressing the collision dynamics in strong electro-magnetic fields as well as the fundamental interactions between electrons and heavy nuclei at the HESR. Here we give a short overview about the central instruments for SPARC experiments at this storage ring. 相似文献
32.
Nikolaos V. Tzouras Dr. Fady Nahra Dr. Laura Falivene Prof. Dr. Luigi Cavallo Marina Saab Prof. Dr. Kristof Van Hecke Dr. Alba Collado Dr. Christopher J. Collett Prof. Dr. Andrew D. Smith Prof. Dr. Catherine S. J. Cazin Prof. Dr. Steven P. Nolan 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(20):4515-4519
We have been puzzled by the involvement of weak organic and inorganic bases in the synthesis of metal–N-heterocyclic carbene (NHC) complexes. Such bases are insufficiently strong to permit the presumed required deprotonation of the azolium salt (the carbene precursor) prior to metal binding. Experimental and computational studies provide support for a base-assisted concerted process that does not require free NHC formation. The synthetic protocol was found applicable to a number of transition-metal- and main-group-centered NHC compounds and could become the synthetic route of choice to form M–NHC bonds. 相似文献
33.
34.
At the intersection of nonlinear and combinatorial optimization, quadratic programming has attracted significant interest
over the past several decades. A variety of relaxations for quadratically constrained quadratic programming (QCQP) can be
formulated as semidefinite programs (SDPs). The primary purpose of this paper is to present a systematic comparison of SDP
relaxations for QCQP. Using theoretical analysis, it is shown that the recently developed doubly nonnegative relaxation is
equivalent to the Shor relaxation, when the latter is enhanced with a partial first-order relaxation-linearization technique.
These two relaxations are shown to theoretically dominate six other SDP relaxations. A computational comparison reveals that
the two dominant relaxations require three orders of magnitude more computational time than the weaker relaxations, while
providing relaxation gaps averaging 3% as opposed to gaps of up to 19% for weaker relaxations, on 700 randomly generated problems
with up to 60 variables. An SDP relaxation derived from Lagrangian relaxation, after the addition of redundant nonlinear constraints
to the primal, achieves gaps averaging 13% in a few CPU seconds. 相似文献
35.
Nikolaos M. Missirlis 《Numerische Mathematik》1984,45(3):447-458
Summary A variety of iterative methods considered in [3] are applied to linear algebraic systems of the formAu=b, where the matrixA is consistently ordered [12] and the iteration matrix of the Jacobi method is skew-symmetric. The related theory of convergence is developed and the optimum values of the involved parameters for each considered scheme are determined. It reveals that under the aforementioned assumptions the Extrapolated Successive Underrelaxation method attains a rate of convergence which is clearly superior over the Successive Underrelaxation method [5] when the Jacobi iteration matrix is non-singular. 相似文献
36.
Antonella Fiacca Nikolaos Matzakos Nikolaos S. Papageorgiou Raffaella Servadei 《Proceedings Mathematical Sciences》2001,111(4):489-508
In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities.
First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is
defined on all ℝ. Assuming the existence of an upper and of a lower solution, we prove the existence of a solution between
them. Also for a special version of the problem, we prove the existence of extremal solutions in the order interval formed
by the upper and lower solutions. Then we drop the requirement that the monotone nonlinearity is defined on all of ℝ. This
case is important because it covers variational inequalities. Using the theory of operators of monotone type we show that
the problem has a solution. Finally in the last part we consider an eigenvalue problem with a nonmonotone multivalued nonlinearity.
Using the critical point theory for nonsmooth locally Lipschitz functionals we prove the existence of at least two nontrivial
solutions (multiplicity theorem). 相似文献
37.
Mohit Tawarmalani Shabbir Ahmed Nikolaos V. Sahinidis 《Journal of Global Optimization》2002,24(4):385-416
We develop eight different mixed-integer convex programming reformulations of 0-1 hyperbolic programs. We obtain analytical results on the relative tightness of these formulations and propose a branch and bound algorithm for 0-1 hyperbolic programs. The main feature of the algorithm is that it reformulates the problem at every node of the search tree. We demonstrate that this algorithm has a superior convergence behavior than directly solving the relaxation derived at the root node. The algorithm is used to solve a discrete p-choice facility location problem for locating ten restaurants in the city of Edmonton.The research was supported in part by NSF awards DMII 95-02722 and BES 98-73586 to NVS. 相似文献
38.
In this paper we study the relaxation of optimal control problems monitored by subdifferential evolution inclusions. First
under appropriate convexity conditions, we establish an existence result. Then we introduce the relaxed problem and show that
it always has a solution under fairly general hypotheses on the data. Subsequently we examine when the relaxation is admissible.
So we show that every relaxed trajectory can be approximated by extremal original ones (i.e. original trajectories generated
by bang-bang controls) and that the values of the original and relaxed problems are equal. Some examples are also presented. 相似文献
39.
Kai Zhou Mustafa R. Kılınç Xi Chen Nikolaos V. Sahinidis 《Journal of Global Optimization》2018,70(3):497-516
Solving mixed-integer nonlinear programming (MINLP) problems to optimality is a NP-hard problem, for which many deterministic global optimization algorithms and solvers have been recently developed. MINLPs can be relaxed in various ways, including via mixed-integer linear programming (MIP), nonlinear programming, and linear programming. There is a tradeoff between the quality of the bounds and CPU time requirements of these relaxations. Unfortunately, these tradeoffs are problem-dependent and cannot be predicted beforehand. This paper proposes a new dynamic strategy for activating and deactivating MIP relaxations in various stages of a branch-and-bound algorithm. The primary contribution of the proposed strategy is that it does not use meta-parameters, thus avoiding parameter tuning. Additionally, this paper proposes a strategy that capitalizes on the availability of parallel MIP solver technology to exploit multicore computing hardware while solving MINLPs. Computational tests for various benchmark libraries reveal that our MIP activation strategy works efficiently in single-core and multicore environments. 相似文献
40.
Nikolaos Gialelis Ioannis G. Stratis 《Mathematical Methods in the Applied Sciences》2019,42(15):4939-4956
We show local existence of certain type of solutions for the Cauchy problem of the defocusing nonlinear Schrödinger equation with pure power nonlinearity, in various cases of open sets, unbounded or bounded. These solutions do not vanish at the boundary or at infinity. We also show, in certain cases, that these solutions are unique and global. 相似文献