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251.
The existence of triple solutions for a second-order nonlocal functional boundary value problem is proved by using a fixed-point theorem on cones in Banach spaces due to Leggett and Williams. The obtained results are new even in the ordinary case for three-point boundary value problems discussed quite recently in [Xiaoming He and Weigao Ge (2002). Triple solutions for second-order three-point boundary value problems. J. Math. Anal. Appl., 268, 256–265]. 相似文献
252.
253.
Sven O. Krumke Sleman Saliba Tjark Vredeveld Stephan Westphal 《Mathematical Methods of Operations Research》2008,68(2):333-359
In this paper we investigate a vehicle routing problem motivated by a real-world application in cooperation with the German
Automobile Association (ADAC). The general task is to assign service requests to service units and to plan tours for the units
such as to minimize the overall cost. The characteristics of this large-scale problem due to the data volume involve strict
real-time requirements. We show that the problem of finding a feasible dispatch for service units starting at their current
position and serving at most k requests is NP-complete for each fixed k ≥ 2. We also present a polynomial time (2k − 1)-approximation algorithm, where again k denotes the maximal number of requests served by a single service unit. For the boundary case when k equals the total number |E| of requests (and thus there are no limitations on the tour length), we provide a -approximation. Finally, we extend our approximation results to include linear and quadratic lateness costs. 相似文献
254.
Anwar Abo-Amer Christoph Steinberg Ulrich Westphal 《Journal of fluorine chemistry》2006,127(10):1311-1323
Fluorinated organodifluoroboranes RfBF2 are in general suitable reagents to transform XeF2 and RIF2 into the corresponding onium tetrafluoroborate salts [RfXe][BF4] and [R(Rf)I][BF4], respectively. (4-C5F4N)BF2 and trans-CF3CFCFBF2 which represent boranes of high acidity form no Xe-C onium salts in reactions with XeF2 but give the desired iodonium salts with RIF2 (R = C6F5, o-, m-, p-C6FH4). The reaction of (4-C5F4N)BF2 with XeF2 ends with a XeF2-borane adduct. C6F5Xe(4-C5F4N), the first Xe-(4-C5F4N) compound, was obtained when C6F5XeF was reacted with Cd(4-C5F4N)2. We describe the synthesis of (4-C5F4N)IF2 and reactions of (4-C5F4N)IF2 and C6F5IF2 with (4-C5F4N)BF2. Analogous to [(4-C5F4N)2I][BF4] and [C6F5(4-C5F4N)I][BF4] aryl(perfluoroalkenyl)iodonium salts [R(R′)I][BF4] were obtained from RIF2 (R = C6F5, o-, m-, p-C6FH4) and R′BF2 (R′ = trans-CF3CFCF, CF2CF). The gas phase fluoride affinities pF− of selected fluoroorganodifluoroboranes RfBF2 and their hydrocarbon analogs are calculated (B3LYP/6-31+G*) and discussed with respect to their potential to introduce Rf-groups into hypervalent EF2 bonds. Four aspects which influence the transformation of hypervalent EF2 bonds (E = Xe, R′I) under the action of Lewis acidic reagents RAFn−1 (A = B, P; n = 3, 5) into the corresponding [RE][AFn+1] salts are presented and the important role of the acidity is emphasized. Fluoride affinities may help to plan the introduction of organo groups into EF2 moieties and to expand the types of acidic reagents. Thus C6H5PF4 with a pF− value comparable to that of RfBF2 compounds is able to introduce the C6H5 group into RIF2 (R = C6F5, p-C6FH4). 相似文献
255.
Let X,Y be Banach spaces and {T(t):t≥0} be a consistent, equibounded semigroup of linear operators on X as well as on Y; it is assumed that {T(t)} satisfies a Nikolskii type inequality with respect to X and Y:T(2t)fY(t)T(t)fX. Then an abstract Ulyanov type inequality is derived between the (modified) K-functionals with respect to (X,DX((-A)α)) and (Y,DY((-A)α)),α>0, where A is the infinitesimal generator of {T(t)}. Particular choices of X,Y are Lorentz–Zygmund spaces, of {T(t)} are those connected with orthogonal expansions such as Fourier, spherical harmonics, Jacobi, Laguerre, Hermite series. Known characterizations of the K-functionals lead to concrete Ulyanov type inequalities. In particular, results of Ditzian and Tikhonov in the case , are partly covered. 相似文献
256.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
257.