AMIRKABIR
Year:2008 | Volume:18 | Issue:67-E|Papers Count:12

Time- resolved spectrum of the neutrons emitted from Plasma Focus devices is a very important piece of information for description of neutron generation mechanism in these devices. In the last two decades, some methods were presented to evaluate this spectrum from the signals of various neutron detectors placed at different distances from the device. All of these procedures are based on the time of flight analysis method, the time- resolved neutron spectrum is derived from solving the integral equation which relates the velocity spectrum of neutrons to time- resolved neutron flux. But the solution of this equation is very complicated and each of presented methods has deficiencies. In this paper a new method is presented on the base of wavelet analysis for solution of this equation to derive the time- resolved energy spectrum. This method is more efficient than the previous ones in different aspects. Using this method for analyzing the results of Poseidon Plasma Focus device (780 kJ, 100 kV), it is observed that its results for neutron energy spectrum and the average energy of neutrons are acceptable.

In this paper the minimum cost flow problem with additional linear constraints on some arcs' flows has been considered. The additional constraints show that the flow on arcs which are belonged to specific subsets of arcs have to be linearly depended on the flow on a specific arc(called reference arc) in the subset. Since the basis structure in this problem is not a spanning tree, we introduce a basis spanning graph and call it a good (q+1)-forest for the problem. Then by regarding the optimality conditions, we restructure the network simplex algorithm to solve the above problem.

This paper consists of two parts. First it talks about simulation of two Multi level preconditioners under the names of HB (Hierarchical basis) and BPX (Bramble, Pasciak, Xu) for linear elliptic boundary value problems on polygon domain with Dirichlet boundary condition that is based on Multigrid idea. On the other hand, this simulation has been done in parallel computing that in addition to saving time it solves the problem of memory allocation. Since these preconditioners are based on domain with structured mesh, a technique is introduced based on fictitious space lemma from which each arbitrary quasi-uniform unstructured triangulation of domain is embedded in auxiliary structured mesh on a square that contains it and then the aforementioned preconditioners for auxiliary mesh is obtained. Finally by defining an operator which makes a one-to-one correspondence between the nodal points of initial mesh on the one hand and those of auxiliary mesh on the other hand, hierarchical basis and BPX preconditioners are constructed for initial mesh that are named "art HB" and "art BPX" respectively.

With underlining the use of reduction and adjustment methods for nonresponse, which occurs in most surveys, and with the use of weighted estimating equations, which are an effective way of adjusting nonresponse bias, influential factors on employment status of people in Iran are discussed. To improve the estimates, weighting adjustment is used in some steps, which include the use of base weight information, nonresponse weight and population predictions. The estimate from a method of non weighted estimating equations, which ignores nonresponse adjustment and population predictions is also compared with the estimate of weighted estimating equations.

In this paper, first, the traffic problem is studied from the Finsler geometric point of view and it is shown that the related metric is a Finsler metric of Randers type. Therefore, the time optimal paths of traffic problem are geodesics of this Randers metric. A real example is given by using the Maple program. Then a nonlinear complementary problem for traffic equilibrium problem is studied and it is shown that a Randers metric can be considered as a gap function in the nonlinear complementarity problem. Next, we extend the nonlinear complementarity problem of traffic equilibrium for a dynamical network. These results may be used in the different equilibrium problems.

A square matrix over the complex field with non-negative integral trace is called a quasi-permutation matrix. For a given finite group G, let c (G) be the minimal degree of a faithful representation of G by complex quasi-permutation matrices. Let r (G) denotes the minimal degree of a faithful rational valued complex character of G. In this paper, we will calculate c (G) and r (G) for the group GL (2,q) when extended by a certain group of order two.

This paper simplifies the Data Envelopment Analysis (DEA) process to the planning of well-drilling operations. It presents an examination of the applicability of DEA to the better planning of well-drilling operations from the managerial point of view. The method can introduce preference individual input levels over alternative path to efficiency. The study focuses on three types of categorized indices in well-drilling program, represented by the well-drilling cost, time and depth for the determination of how far well-drilling resources can increase while still serving as efficient. The data analyses and results based on 35-drilled wells are presented along with their specifications.

Noting that the complete lift of a Riemannian metric g defined on a differentiable manifold M is not 0-homogeneous on the fibers of the tangent bundle TM, in this paper, we introduce a new lift ~g2 which is 0-homogeneous. It determines on ~TM=TM\{0} a pseudo-Riemannian metric, which depends only on the metric g. We study some of the -geometrical properties of this pseudo-Riemannian space and define the natural almost complex structure ~J and natural almost product structure ~Q which preserve the property of homogeneity and find some new results.

Microparticulate form of biodegradable polymers containing drugs is a promising approach toward new controlled release drug delivery systems, and a perfect alternative for daily painful injection of protein drugs. One major challenge in developing such systems is increasing efficiency of fabrication processes and retaining stability and effectiveness of encapsulated proteins and drugs. In this study capabilities of double emulsion (W/O/W)- solvent evaporation method for encapsulation of attenuated avian influenza virus (H9N2) in poly (lactic-co-glycolic acid) 50:50 were investigated and, the protein in vitro release profiles were determined. Some basic salts such as MgCo3 co-encapsulated with protein were used to increase stability and release of the protein. Additives such as NaCl and urea were added to second water phase to ensure and increase loading of the protein. The microspheres were all spherical with almost smooth surface and some small pores. Release profiles reveal that MgCo3 increased the amount of released protein but did not have a significant effect on release rate.

Fifteen tautomeric species of guanine were optimized in the gas phase at MP2, B3LYP and BP86 levels of theory using the 6-31G+(d,p) basis set. The relative stability of these tautomers was calculated. Solvent effect on relative stability of guanine tautomers was investigated at the B3LYP level of theory with 6-3IG+(d,p) basis set using the Onsager reaction field theory. It was found that G2 tautomer has the most stability in the gas phase and GI is in the second degree of stability. But, the inverse results were found in the solvent phase. The transition state (TS) geometry between GI to G2 was calculated in the gas and solvent phases. The predicted barrier energy in the gas phase is increased by increasing the polarity of solvents. The Continuous Set of Gauge Transformation (CSGT) calculations were performed for the nuclei of 1H, 13C, 14Nand 17o at the B3LYP/6-31+G (d,p) level of theory for the B3LYP/6-31+G (d,p) optimized geometry, using the Onsager model. Direct and indirect solvent effects on shielding were also calculated. It was shown that the observed solvent-induced shielding variation is more strongly related to the intensity of the solvent reaction field rather than to the change of molecular geometry induced by the solvent. Chemical shift of the 1H and 13C nuclei for G1 and G2 molecules was calculated and compared with that of TMS molecule.

The surface of activated nanopore sized silica samples was chemically modified by covalent grafting of amine groups, by reaction with N-(2-aminoethyl)-3-aminopropyl-trimethoxy silane. Nanopore sized dipyridyl-functionalized silica gels have been prepared by refluxing grafted amino nanopore sized silica gel with 2,2 -dipyridyl ketone in toluene under the argon atmosphere. The incorporation of nanopore sized organofunctionalized silica gel (DPNSG) particles within carbon paste leads to improved potentiometric detection of copper (II) in acetate medium. The enhanced sensitivity was attributed to selective interaction of copper (II) by the approved surface dipyridyl groups of silica gel. The modified electrode presented high performance, high sensitivity in wide cation activity ranges and good long term stability. The method was satisfactory and was used to determine the copper ion concentration in waste waters, contaminated by this metal.