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In location-routing problems, the objective is to locate one or many depots within a set of sites (representing customer locations or cities) and to construct delivery routes from the selected depot or depots to the remaining sites at least system cost. The objective function is the sum of depot operating costs, vehicle acquisition costs and routing costs. This paper considers one such problem in which a weight is assigned to each site and where sites are to be visited by vehicles having a given capacity. The solution must be such that the sum of the weights of sites visited on any given route does not exceed the capacity of the visiting vehicle. The formulation of an integer linear program for this problem involves degree constraints, generalized subtour elimination constraints, and chain barring constraints. An exact algorithm, using initial relaxation of most of the problem constraints, is presented which is capable of solving problems with up to twenty sites within a reasonable number of iterations. 相似文献
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Nor-Mycosporin Glutamin, a new unstable compound isolated from sporulating cultures of , has the structure (I). 相似文献
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J. Gerum Susanne Marie Beckurts O. Lüning A. Heiduschka J. Deininger C. H. Bailey H. Kalning Arpin T. Pecaud E. Vautier Th. Merl A. Reuß W. Brendler H. Langfurth J. Grossfeld A. Fornet W. Herter Marchadier Goujon G. Testeni P. Menaul C. T. Dowell Th. v. Fellenberg J. Abel K. Fricke O. Lüning E. Arbenz A. Juckenack A. Fornet und A. Nestler 《Fresenius' Journal of Analytical Chemistry》1924,65(1-2):84-91
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We extend all-optical quasi-phase matching of high-order harmonic generation into spectral regions where conventional phase matching is not possible. The high laser intensities required to generate harmonics at energy >130 eV, coupled with the resulting high level of ionization, preclude conventional phase matching in all nonlinear media. Selective enhancement factors between 40 and 150 in the flux of harmonics at photon energies around 140 eV are demonstrated using a train of two counterpropagating pulses. 相似文献
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Chen MC Arpin P Popmintchev T Gerrity M Zhang B Seaberg M Popmintchev D Murnane MM Kapteyn HC 《Physical review letters》2010,105(17):173901
We demonstrate fully phase-matched high harmonic emission spanning the water window spectral region important for nano- and bioimaging and a breadth of materials and molecular dynamics studies. We also generate the broadest bright coherent bandwidth (≈300 eV) to date from any light source, small or large, that is consistent with a single subfemtosecond burst. The harmonic photon flux at 0.5 keV is 103 higher than demonstrated previously. This work extends bright, spatially coherent, attosecond pulses into the soft x-ray region for the first time. 相似文献