AMIRKABIR
Year:2007 | Volume:17 | Issue:65-E-65-D (TOPICS IN: GROUPS OF BASIC SCIENCE, APPLIED ENGINEERING AND CHEMICAL, POLYMER, TEXTILE ENGINEERING)|Papers Count:11

The inverse DEA models discuss about problems such as estimating inputs (outputs) quantities when the outputs (inputs) quantities are increased and efficiency level remains unchanged. The same point in all inverse DEA problems is that the changes in inputs and outputs are assessed whereas the efficiency level of DMU is remained unchanged but in some real problems we need to estimate the changes of inputs due to outputs changes and efficiency growth.One of the problems of this kind is TFP problem. In this problem the inputs and outputs quantities of a DMU in the next period should be increased such that we have predefined percent of efficiency growth. In this paper we discuss about this type of problems and we generalize the inverse DEA models such that they can be used for solving foregoing problems.

A class of boundary value problems involving propagation of two dimensional surface water waves, associated with deep water and a plane vertical rigid barrier is investigated under the assumption that a thin sheet of ice covers the surface. We assume that the ice cover behaves like a thin isotropic elastic plate. The problems under consideration lead to those of solving the two dimensional Laplace equation in a quarter plane, under a Neumann boundary condition on the vertical boundary and a 'condition involving up to the fifth order derivatives of unknown function on the horizontal ice covered boundary, along with two appropriate edge conditions, ensuring the uniqueness of the solutions. The method employed here to solve the mixed boundary value problem is to determine the unique solution of a special type of singular Fredholm integral equation of the first kind.

A set of locally product structures on tangent manifold TM of a space form M is pointed out. This is found in a study of a type of Sasaki metric whose second term is a special deformation of the first one. Introducing an adequate almost product structure we find at first a large class of locally almost product structures on TM for a (pseudo)-Riemannian manifold M. When M is a space form, a subset of it is made of locally product structures.

The rare earth metals have special importance for their high magnetic moments, various magnetic and crystal structures. The experiments show in constant conditions, such as electro negativity, ionic radii, hybridasion that are important factors that determine the existence of a stable phase of a crystal; there are anomalous behaviors in formation of Rare-earth Compounds. The gadolinium with 7 electron in its 4f shell has spherical symmetry and stability in magnetic and crystal structure but Gd2X(X=AI, Ga, ln) compounds show anomalous behavior in ones, Gd2Al intermetallic compound crystallize in orthorhombic structure and Gd2In in hexagonal, while there is no report about Gd2Ga IMC.The manner of preparing of Gd2Ga intermetallic compound that is not inscripted in Gd-Ga phase diagram was probed by Arc melted furnace. XRD and SEM data show that its structure is orthorhombic and very sensitive to annealing temperature. Then stability of crystal structures of Gd2X (X=AI, Ga, In) compounds were researched by calculating of total energy of systems, based on the DFT calculations by use of wien2k program that data are in good agreement with the experimental ones.

An stochastic model of an interface moving through porous media is studied in this paper. This model differs from the standard Kardar-Parisi-Zhang by the fact that the fluctuations are quenched random variables. It is concluded that the Family-Vicsek scaling form is valid for porous media. Scaling exponents in porous media and in the absence of quenched noise are calculated and compared for dimension d=1. It's obtained that the rate of average height increment of interface in porous media for RD (Random Deposition) model is in the form of tk-1; k<1. It shows, this rate is a decreasing function of time.

In this paper after an introduction to the Uncertainty Studies, a methodology for estimating quality and quantity of the reservoir uncertainties is introduced in five stage: 1) choose or prepare best reservoir dynamic and static model 2) define uncertainty parameters 3) design the experiments 4) run designed experiments 5) analyze of the results and estimate the distribution of response parameter. In the case study, this integrated methodology, based on some statistical approaches such as Experimental Design, Response Surface Methodology and Monte Carlo Sampling, is applied to the reservoir model and the defined uncertainty parameters. Therefore, impact of each uncertainty on the cumulative oil production as response parameter is obtained and finally, uncertainty in the reserves is estimated based on the stochastic modeling of the uncertain parameters.

Application of conductive carbon black in polymer blends remarkably increases electric conductivity of polymers. According to the results presented in this paper, electric conductivity of polymer blends containing. carbon black is increased in a non-linear way as the extent of carbon black increases. Also, there is an optimal amount of carbon black beyond which a significant change is observed in electric property of polymer blends, i.e. carbon black contents smaller than this critical value (agglomeration thereshold) can not affect the electric property of polymer blends. In addition, carbon black with higher structures reduces the agglomeration thereshold as well as addition of ionic materials. Moreover, increasing temperature, and consequently reduction of the blend viscosity, reduces the agglomeration threshold, as it facilitates the formation of conductive networks. Finally, effect of the test temperature on the blend conductivity depends on the glass transition of the blend. Indead, increasing test temperature, reduces electric conductivity at first, but in the vicinity of glass transition temperature of polymer blend causes the electric conductivity to increase.

The aim of this research was to synthesize a modified PVA as a self-polishing antifouling resin. Modification of PVA was performed in two stages, namely etherification of PVA by an acyl chloride and quaternization of chlorine pendant group by tertiary amines. The effect of PVA molecular weight, amine type and the extent of reaction with amine on the self-polishing property of the prepared resin was investigated. FTIR analysis was used to identify the modified resins and self-polishing rate of the modified PVA was also measured. It was obtained that the yield of quaternization reactions was more than 92%. The rate of polishing of the resin films was found to be in the range of 5-12 micron per month. The polishing rate of the resins increased with the increase of the extent of quaternization and decrease of PVA molecular weight.

The look-up table (LUT) method is implement for characterizing a four-color halftone printer. In order to create a LUT, 216 colored samples are created and their colorimetric coordinates were measured. Then, cubic interpolation algorithm is used to calculate the approximation. Because of differences in color gamut's of printer and the gamut of samples, a gamut-mapping algorithm is used. The CLGB technique is used to map out of gamut colors.

A general multiresolution approach is developed and applied to upscaling of multiscale 2D heterogeneous reservoirs. The method uses the wavelet transformations to the original detailed description of the reservoir, with finer resolution introduced in region of potentially high flow rate (high permeability) and coarser, homogenized property descriptions applied throughout the bulk of the model. Wavelet transformations are currently recognized as the most efficient method of data compression. The method is applied to flow problem (steady single-phase flow) and transport problem (miscible displacement process). In this way, pressure is computed on the coarse-grid using upscaled properties. These pressures are then used to compute the pressure at the small scale within each coarse block. Thus, an approximation for the pressure is obtained without ever having to solve the full fine-grid problem, saving CPU time and memory. Finally, velocity field, the most important key component of fluid flow process, is calculated using obtained pressure field. The results of two problems show good agreement with full fine-grid solution.