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Central European Journal of Operations Research - Mankind has faced a huge increase in severe natural and man-made disasters worldwide in the last few years. Emergency responders on a strategic,...  相似文献   
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Mapping closures for turbulent mixing and reaction   总被引:4,自引:0,他引:4  
The mapping closure for the one-point pdf of an inert scalar in homogeneous turbulence is explained and developed. It is shown that the pdf's calculated from the closure are in excellent agreement with those obtained from direct numerical simulations. The closure is then extended to many reactive scalars.I believe in the ultimate possibility of developing general computation procedures based on first principles; and under certain circumstances I believe that it is possible to do this rationally.J.L. Lumley (1978) on computational modeling of turbulent flowsDedicated to Professor J.L. Lumley on the occasion of his 60th birthday.This work was supported in part by U.S. Air Force Office of Scientific Research (Grant No. AFOSR-88-0052).  相似文献   
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We show how N = 8 supersymmetry can break spontaneously to N = 1 at the Planck scale via a Kaluza-Klein compactification of d = 11 supergravity on the squashed seven-sphere. Features unique to Kaluza-Klein supergravity are (i) the massless gravitino of the N = 1 phase comes from a massiveN = 8 supermultiplet, (ii) the scalars developing nonzero VEVs also belong to massive N = 8 supermultiplets, (iii) parity remains unbroken when N = 8 breaks to N = 1.Next we ask whether the resulting N = 1 theory can provide a realistic SU(3) × SU(2) × U(1) unification and speculate that it might if some of the gauge bosons and fermions are composite as in the EGMZ model. In contrast to their model, however, we avoid unwanted helicities and problems with their non-compact E7. Moreover, we suggest a scheme in which the electroweak SU(2) × U(1) is a subgroup of the d = 11 general coordinate group but that the strong SU(3) is a subgroup of the d = 11 local Lorentz group and are not, therefore, to be combined into a GUT. The special properties of the seven-sphere also suggest a possible solution of the cosmological constant problem involving fermion condensates.  相似文献   
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Starting from a 4n-dimensional quaternionic Kähler base space, we construct metrics of cohomogeneity one in (4n+3) dimensions whose level surfaces are theS 2 bundle space of almost complex structures on the base manifold. We derive the conditions on the metric functions that follow from imposing the Einstein equation, and obtain solutions both for compact and non-compact (4n+3)-dimensional spaces. Included in the non-compact solutions are two Ricci-flat 7-dimensional metrics withG 2 holonomy. We also discuss two other Ricci-flat solutions, one on theR 4 bundle overS 3 and the other on anR 4 bundle overS 4. These haveG 2 and Spin(7) holonomy respectively.  相似文献   
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The primary objective of this work is to evaluate the potential of silica gel encapsulated pancreatic islets of Langerhans, or islet tissue, as a means by which insulin secretory capacity might be restored to individuals with insulin dependent, type 1, diabetes mellitus. The encapsulation material under investigation is comprised of sol-gel derived silica ceramic that hardens under conditions of pH, salinity, and temperature that are not harmful to living cells and organisms. Preliminary efficacy has been demonstrated by measurement of insulin secretory response of silica gel encapsulated pancreatic isletsin vitro and blood sugar levels of nonobese diabetic micein vivo.  相似文献   
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Reactions of (NH4)2MS4, AgBr and CuBr in γ-methylpyridine produced one new compound, [MS4Cu4(γ-MePy)8][M6O19] (1, M = W; 2 , M = Mo), of which 1 was characterized by single crystal X-ray analysis. The crystal data: orthorhombic, Pbcn, a = 15.434(4), b = 16.732(2), c = 28.657(7) Å, V = 7400.8(8) Å3, Z = 4 , R = 0.072 for 3121 independent data. The compound is the first example which contains both polyoxotungstate anion and heteropolynuclear cluster cation. In the structure of the cation four edges of the tetrahedral WS2?4 core are coordinated by four copper atoms, giving a WS4Cu4 aggregate of approximate D2h symmetry. The differences between the reaction of Cu+ with MS2?4 and that of Ag+ with MS2?4 in pyridine and its derivatives are discussed.  相似文献   
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