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11.
Increased rates of mortgage foreclosures in the U.S. have had devastating social and economic impacts during and after the 2008 financial crisis. As part of the response to this problem, nonprofit organizations such as community development corporations (CDCs) have been trying to mitigate the negative impacts of mortgage foreclosures by acquiring and redeveloping foreclosed properties. We consider the strategic resource allocation decisions for these organizations which involve budget allocations to different neighborhoods under cost and return uncertainty. Based on interactions with a CDC, we develop stochastic integer programming based frameworks for this decision problem, and assess the practical value of the models by using real-world data. Both policy-related and computational analyses are performed, and several insights such as the trade-offs between different objectives, and the efficiency of different solution approaches are presented. 相似文献
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We extend known results concerning the centre of spaces of regular (resp. weakly compact or compact) operators between two Banach lattices to the setting of L-weakly compact and M-weakly compact operators. We also show that the L-weakly compact, M-weakly compact, and compact operators lying in the centre of a Banach lattice coincide. 相似文献
15.
Bayram Sahin 《Heat and Mass Transfer》2007,43(5):493-502
The present work submits an investigation about the optimal values of design parameters and performance analysis for a heat
exchanger having cylindrical pin fins positioned in a rectangular channel. The experiments covered the following range: Reynolds
number 13,500–42,000, the clearance ratio (C/H) 0, 0.33 and 1, the interfin spacing ratio (S
y
/D) 1.208, 1.944 and 3.417. In the experimentation, Taguchi method was employed, and Nusselt number and friction factor were
considered as performance parameters. While the optimum parameters were determined, due to the goals (above aims) more than
one being, the trade-off among goals was considered. First of all, each goal was optimized, separately. Then, all goals were
optimized together, considering the priority of goals, and the optimum results were found to be Reynolds number of 42,000,
fin height of 50 mm and pitch of 3.417. The performance analysis also was made under a constant pumping power constraint,
and the results showed that the use of cylindrical pin fins may lead to an advantage on the basis of heat transfer enhancement. 相似文献
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17.
We examine the dynamic phase transitions and the dynamic compensation temperatures, within a mean-field approach, in the mixed
spin-3/2 and spin-5/2 Ising system with a crystal-field interaction under a time-varying magnetic field on a hexagonal lattice
by using Glauber-type stochastic dynamics. The model system consists of two interpenetrating sublattices with σ=3/2 and S=5/2. The Hamiltonian model includes intersublattice, intrasublattice, and crystal-field interactions. The intersublattice
interaction is considered antiferromagnetic and to be a simple but interesting model of a ferrimagnetic system. We employ
the Glauber transition rates to construct the mean-field dynamic equations, and we solve these equations in order to find
the phases in the system. We also investigate the thermal behavior of the dynamic sublattice magnetizations and the dynamic
total magnetization to obtain the dynamic phase transition points and compensation temperatures as well as to characterize
the nature (continuous and discontinuous) of transitions. We also calculate the dynamic phase diagrams including the compensation
temperatures in five different planes. According to the values of Hamiltonian parameters, five different fundamental phases,
three different mixed phases, and six different types of compensation behaviors in the Néel classification nomenclature exist
in the system. 相似文献
18.
T.?BayrakdarEmail authorView authors OrcID profile A.?A.?Ergin 《Mediterranean Journal of Mathematics》2018,15(4):183
We show that a surface corresponding to a first-order ODE is minimal in three-dimensional Riemannian manifold which is determined by the first prolongation of \({\text {d}}y/\mathrm{d}x=p(x,y)\) if and only if \(p_{yy}=0\). Accordingly, any linear first-order ODE describes a minimal surface which is not necessarily totally geodesic. 相似文献
19.
Suppose (i) X is a separable Banach space, (ii) C is a convex subset of X that is a Baire space (when endowed with the relative topology) such that aff(C) is dense in X, and (iii) f:C→R is locally Lipschitz continuous and convex. The Fenchel-Moreau duality can be stated as
20.
We consider a scale-free network of stochastic HH neurons driven by a subthreshold periodic stimulus and investigate how the collective spiking regularity or the collective temporal coherence changes with the stimulus frequency, the intrinsic noise (or the cell size), the network average degree and the coupling strength. We show that the best temporal coherence is obtained for a certain level of the intrinsic noise when the frequencies of the external stimulus and the subthreshold oscillations of the network elements match. We also find that the collective regularity exhibits a resonance-like behavior depending on both the coupling strength and the network average degree at the optimal values of the stimulus frequency and the cell size, indicating that the best temporal coherence also requires an optimal coupling strength and an optimal average degree of the connectivity. 相似文献