Using a GIS for Real Estate Market Analysis: The Problem of Spatially Aggregated Data

Many databases used for real estate market analysis are not available at the address level. For example, information on employment and unemployment may be available only for labor market areas; and Census data is typically tabulated for blocks or higher levels of spatial aggregation. A Geographic Information System (GIS) associates these spatially aggregated data with the geographical center of the area. This poses special problems when we use a GIS to evaluate linkages between supply and demand. This article presents some solutions to this problem; methods that are relatively easy to implement on a GIS are emphasized. A GIS can be used to calculate a theoretical average travel distance to the population in the geographical area. We propose ways to determine when these theoretical distances are inadequate approximations; and we provide alternatives for these situations.

Influence of mean distance between fibers on the effective gas thermal conductivity in highly porous fibrous materials

This work was supported by the Russian Goverment Grant No. 14.Z50.31.0036.Peer reviewedPostprin

Stationary probability density of stochastic search processes in global optimization

A method for the construction of approximate analytical expressions for the stationary marginal densities of general stochastic search processes is proposed. By the marginal densities, regions of the search space that with high probability contain the global optima can be readily defined. The density estimation procedure involves a controlled number of linear operations, with a computational cost per iteration that grows linearly with problem size

Modelling of radionuclide migration through the geosphere with radial basis function method and geostatistics

The modelling of radionuclide transport through the geosphere is necessary in the safety assessment of repositories for radioactive waste. A number of key geosphere processes need to be considered when predicting the movement of radionuclides through the geosphere. The most important input data are obtained from field measurements, which are not available for all regions of interest. For example, the hydraulic conductivity, as input parameter, varies from place to place. In such cases geostatistical science offers a variety of spatial estimation procedures. To assess the a long term safety of a radioactive waste disposal system, mathematical models are used to describe the complicated groundwater flow, chemistry and potential radionuclide migration through geological formations. The numerical solution of partial differential equations (PDEs) has usually been obtained by finite difference methods (FDM), finite element methods (FEM), or finite volume methods (FVM). Kansa introduced the concept of solving PDEs using radial basis functions (RBFs) for hyperbolic, parabolic and elliptic PDEs. The aim of this study was to present a relatively new approach to the modelling of radionuclide migration through the geosphere using radial basis functions methods and to determine the average and sample variance of radionuclide concentration with regard to spatial variability of hydraulic conductivity modelled by a geostatistical approach. We will also explore residual errors and their influence on optimal shape parameters

Sedimentation and Flow Through Porous Media: Simulating Dynamically Coupled Discrete and Continuum Phases

We describe a method to address efficiently problems of two-phase flow in the regime of low particle Reynolds number and negligible Brownian motion. One of the phases is an incompressible continuous fluid and the other a discrete particulate phase which we simulate by following the motion of single particles. Interactions between the phases are taken into account using locally defined drag forces. We apply our method to the problem of flow through random media at high porosity where we find good agreement to theoretical expectations for the functional dependence of the pressure drop on the solid volume fraction. We undertake further validations on systems undergoing gravity induced sedimentation.Comment: 22 pages REVTEX, figures separately in uudecoded, compressed postscript format - alternatively e-mail '[email protected]' for hardcopies

Planning Approximations to the Length of TSP and VRP Problems

This paper studies parsimonious, intuitive, and effective formulas to approximate the length of Traveling Salesman Problems (TSP) and Vehicle Routing Problems (VRP). Using intuition derived from continuous models and graph theory, a formula to approximate the length of vehicle routes is proposed. In instances with different patterns of customer spatial distribution, time windows, customer demands, and depot locations are used to test the proposed approximation. Regression results show that the approximation can reasonably predict the length of TSP and VRP problems in randomly generated problems and real urban networks. Expressions for the incremental cost of serving an additional customer or increasing the number of routes are derived and estimated. The main contribution of this paper is to develop and test intuitive approximations to TSP and VRP problem in general settings. The approximations are valuable for strategic and planning analysis of transportation and logistics problems