Sharif Digital Repository

Using low power electronic devices for space applications to reduce the mass and energy consumption has lead to electromagnetic interference (EMI) problem. Electronic enclosures are used to shield electronic devices against EMI. In the past, electromagnetic shielding has been mainly the only criteria considered in electronic enclosure design. However, there are several structural and thermal requirements for selection of shielding materials which should also be taken into account. In this research work, three quantitative materials selection methods, i.e. Digital Logic (DL), Modified Digital Logic (MDL), and Z-transformation, are employed to select the best material from among a list of... 

A two-flavor color-superconducting Nambu-Jona-Lasinio model is introduced at finite temperature T, chemical potential μ, and in the presence of a constant magnetic field e∼B. The effect of (T,μ,e∼B) on the formation of chiral- and color-symmetry-breaking condensates is studied. The complete phase portrait of the model in T-μ, μ-e∼B, and T-e∼B phase spaces for various fixed e∼B, T, and μ is explored. A threshold magnetic field e∼Bt0.5GeV2 is found, above which the dynamics of the system are solely dominated by the lowest Landau level, and the effects of T and μ are partly compensated by e∼B  

Utilizing an extended two-flavor Nambu-Jona Lasinio (NJL) model, we review some of the effects of external magnetic fields on two-flavor color superconducting phase (2SC) at moderate baryon densities in the QCD phase diagram. The effective action of the extended NJL model consists of two mass gaps as functions of three intensive quantities, the temperature, the quark chemical potential and the external magnetic field. The nonzero values of the mass gaps, chiral and diquark condensates, induce spontaneous chiral and color symmetry breaking, respectively, and as a result two different phases of quark matter appear. We find the transition curves between these phases as well as the critical... 

The color neutral two-flavor superconducting phase of cold and dense quark matter is studied in the presence of constant magnetic fields and at moderate baryon densities. In the first part of the paper, a two-flavor effective Nambu-Jona-Lasinio model consisting of a chiral symmetry breaking (χSB) mass gap σB, a color superconducting (CSC) mass gap ΔB and a color chemical potential μ8 is introduced in the presence of a rotated U(1) magnetic field B. To study the phenomenon of magnetic catalysis in the presence of strong magnetic fields, the gap equations corresponding to σB and ΔB, as well as μ8 are solved in the lowest Landau level approximation. In the second part of the paper, a detailed... 

Application of the existing materials selection methods is not much popular in space environment. This is in spite of involvement of the selection process in this field with a wide range of influential factors (e.g. conventional mechanical properties and over 21 space environmental effects). In this paper an introductory road map for employing systematic materials selection methods in the field by engaging the selection process with mechanical properties and only one of the space environmental factors is presented. Here, selected case studies, which are involved with outgassing phenomenon of materials in vacuum condition, highlight the incapability of some of the methods in dealing with such... 

The directional weak decay constants of neutral pions are determined at finite temperature T, chemical potential μ and in the presence of a constant magnetic field B. To do this, we first derive the energy dispersion relation of neutral pions from the corresponding effective action of a two-flavor, hot and magnetized Nambu–Jona-Lasinio model. Using this dispersion relation, including nontrivial directional refraction indices, we then generalize the partially conserved axial vector current relation of neutral pions and derive the Goldberger-Treiman as well as the Gell–Mann-Oakes-Renner relations consisting of the directional quark-pion coupling constant g(μ)qqπ0 and the weak decay constant... 

The effect of the anomalous magnetic moment of quarks on thermodynamic properties of the chiral condensate is studied, using a two-flavor Nambu-Jona-Lasinio model at finite temperature T, chemical potential μ, and in the presence of a uniform magnetic field eB. To this purpose, the Schwinger linear-in-B ansatz for the anomalous magnetic moment of quarks is considered in terms of the nonperturbative Bohr magneton. In a two-dimensional flavor space, it leads to the correction TSch=κQeB in the energy dispersion relation of quarks. Here, Q is the quark charge matrix. We consider three different sets for κ, and numerically determine the dependence of the constituent quark mass on T,μ, and eB for... 

Monomer grafting, a unique technique for polysaccharide modification, is always performed under inert (e.g., N2) atmosphere. This work is the first report related to evaluating the possibility and efficiency of the grafting of acrylonitrile (AN) onto starch in presence of oxygen. Thus, corn starch (in both granular and gelatinized states) as well as soluble starch were grafted by AN using a ceric-carbohydrate redox initiating system. Graft copolymerizations were performed under nitrogen, air, and oxygen atmospheres at similar conditions. Grafting occurrence was verified using chemical and spectral proofs. The polymerization mechanism and kinetics were investigated by recording the... 

Acrylonitrile (AN) was grafted onto various natural and modified polysaccharides (i.e., gum arabic, gum tragacanth, xanthan gum, sodium alginate, chitosan, sodium carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose) by using ceric-carbohydrate redox initiating system. After overcoming practical problems, mainly from the high viscosity of the aqueous solutions of the different substrates, the graft copolymerization reactions were run either in air or in N2 atmosphere under similar conditions. Grafting was confirmed using chemical and spectral (FTIR) proofs. The reactions were kinetically investigated using semi-empirical expressions and time-temperature profiles. An anomalous... 

The properties of noninteracting σ and π0 mesons are studied at finite temperature, chemical potential, and in the presence of a constant magnetic field. To do this, the energy dispersion relations of these particles, including nontrivial form factors, are derived using a derivative expansion of the effective action of a two-flavor, hot and magnetized Nambu-Jona-Lasinio model up to second order. The temperature dependence of the pole and screening masses as well as the directional refraction indices of magnetized neutral mesons are explored for fixed magnetic fields and chemical potentials. It is shown that, because of the explicit breaking of the Lorentz invariance by the magnetic field,... 

A cooperative supply chain seeks to coordinate its members to produce and distribute products along the chain, for minimum overall costs to satisfy customer demand. An integrated multi-period, multiple product and multiple stage supply chain is formulated using a flow networks framework. A Cooperative Supply Chain Optimizer (CSCO), as a central software entity taking advantage of Grid technology, connects and gathers necessary operational information from members of the corporate supply chain. The CSCO then guides supply chain members on ordering decisions, for a minimum overall cost of the entire supply chain, while continuously re-directing the members as new data becomes available. The... 

A mechanism for supply chain coordination models the entire supply chain with multiple members in four stages to satisfy customer demand with minimum total costs. Previous coordination mechanisms research applied restrictive assumptions on the number in the supply chain stages and members in each stage, disallowing a case of multi-product. Flow networks concept is proposes as a coordination mechanism for supply chains with multiple members, multiple stages and multi-products, where each product is composed of several basic components. A supply chain optimizer (SCO), actually an e-hub, gathers supply chain state information. After necessary computations, it informs members of the supply chain... 

A combination of silica chloride and wet SiO2 was used as an effective deacetalizating agent for the conversion of acetals to their corresponding carbonyl derivatives under mild and heterogeneous condition