Sharif Digital Repository

We study an open quantum spin chain of arbitrary length with nearest neighbor XX interactions of strength g, immersed in an external constant magnetic field Δ along the z direction, whose end spins are weakly coupled to two heat baths at different temperatures. In the so-called global approach, namely, without neglecting interspin interactions, using standard weak-coupling limit techniques, we first derive the open chain master equation written in terms of fermionic mode operators. Then, we focus on the study of the dependence of the resulting open dynamics from the ratio rg/Δ. By increasing r, some of the chain Bohr transition frequencies become negative; when this occurs, both the... 

When a quantum system is coupled to two thermal baths at different temperatures, the temperature gradient as a thermodynamic force causes stationary heat flow within the system. We present a theoretical model to study how quantum features of squeezed thermal reservoirs affect the classical formulation of entropy production in terms of generalized forces and flows. Applying the quantum phase-space method to calculate Wigner entropy production helps us identify heat and squeezing fluxes and their corresponding generalized forces in terms of input-noise correlations of both reservoirs. Our study highlights the essential role played by the correlation of the input-noise operators of the thermal... 

In this study, an extrinsically enriched element free Galerkin (EFG) method is proposed for the thermo-hydro-mechanical simulation of saturated porous media. By taking advantage of partition of unity property of moving least square shape functions, weak discontinuities such as material interfaces are modeled using the Ridge enrichment function and impermeable strong discontinuities are simulated using the Heaviside function. Some guidelines are proposed for the selection of EFG numerical parameters to ensure the stability and accuracy of the results. Numerical examples are provided to illustrate the capability of the proposed approach for fully coupled THM analysis of discontinuous porous... 

A hybrid HDH desalination system integrated with a heat pump was experimentally studied. In this system, heat pump's heating was used to raise the temperature of the air entering the humidifier and its cooling effect was used for dehumidification of humid air and freshwater production. In other words, heat pump's condenser works as the heater of the HDH cycle and its evaporator works as the coolant for the dehumidifier of HDH cycle. The effects of different parameters such as mass flow rate of inlet saline water (relative humidity of the air passing the dehumidification section), volume flow rate of the air passing the dehumidification section and ambient air temperature on freshwater... 

This paper presents a numerical multiscale formulation for analysis of the transient heat and fluid flow in deformable heterogeneous porous media. Due to the heterogeneity of the media, the direct numerical simulation of the micro-structures leads to high computational costs. Hence, the multi-scale method can provide an efficient computational procedure. To this end, the first-order computational homogenization is adopted for two-scale simulation of THM problems. The governing equations of the problem contain a stress equilibrium equation, a mass continuity equation and an advection–diffusion equation in a fully coupled manner. Accordingly, the proper virtual power relations are defined as a... 

By simultaneously applying pinch technology and the exergoeconomic method to a complex process system, beneficial and energy-efficient measures are identified. The "three-link-model" exergoeconomic methodology optimizes the design and operability of a system. In this work, contrary to traditional exergoeconomic methods, a reversed method is used. The approach proposed for the optimization of such a complex system is to iteratively optimize subsystems. Since the reversed exergoeconomic method is used, assumptions considered by Tsatsaronis (based on four assumptions for calculating the cost-optimal exergetic efficiency and relative cost difference) are not applicable and new assumptions are to...