Sharif Digital Repository

Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. However their favorable thermal performance has allowed them to be employed in other buildings like bazaars, or market places in Iran. In this investigation, wind pressure coefficients were determined experimentally for a domed roof model in a boundary layer wind tunnel. The model was a 1/10 scale model of the dome of an old school in the city of Yazd, in the central desert region of Iran. The model included a number of windows at the collar of the dome, and a hole on its apex. A total of 48 pressure tabs were employed to measure the air pressure at various... 

Solar radiation received and absorbed by four domed roofs was estimated and compared with that of a flat roof. The domed roofs all had the same base areas, and equal to that of the flat roof. One of the roofs considered was the dome of the St. Peter's Church in Rome. Compared with the other roofs considered, this dome had a higher aspect ratio. It was found that all domed roofs received more solar radiation than the flat roof. Considering glazed tiles to cover a selected dome in Iran and the dome of the St. Peter's Church, it was found that the solar radiation absorbed by these roofs is reduced appreciably. In the case of the dome of St. Peter's Church, the amount of radiation absorbed was... 

Using domed roofs to reduce building solar load in hot arid area is one of Iranian mechanical engineering masterworks. The first application of these roofs was to cover large buildings such as mosques, shrines, etc. However their thermal performance made them to be employed in other buildings like bazaars. The aim of this study was to determine the air pressure and velocity distribution over domed roofs, by employing numerical methods. The results of this study will be used as the first step for thermal performance evaluation of domed roofs. © 2007 American Institute of Physics  

The decentralized approach to security administration in new computing environments (e.g., pervasive computing and mobile environments) is based on apportioning the environment into multiple security domains. The security policies of each security domain are specified by an authority and enforced by a security agent. The requirements of cooperative administration in such Multi-Security-Domain (MSD) environments, for shared or subdomains, induced us to propose an MSD cooperation framework within a logical security policy language (called MASL) in this paper. MASL is a variation of deontic logic that enables multiple authorities to specify their domain policies, including obligations and... 

An access control model for Semantic Web should take the semantic relationships among the entities, defined in the abstract conceptual level (i.e., ontology level), into account. Authorization and policy specification based on a logical model let us infer implicit security policies from the explicit ones based on the defined semantic relationships in the domains of subjects, objects, and actions. In this paper, we propose a logic based access control model for specification and inference of history-constrained access policies in conceptual level of Semantic Web. The proposed model (named TDLBAC-2) enables authorities to state policy rules based on the history of users' accesses using a... 

An access control model for Semantic Web should be compatible with the corresponding semantic model. The access control procedure(s) should also take the semantic relationships between the entities (specified as ontologies) into account. Considering the benefits of logic-based models and the description logic foundation of Semantic Web, in this paper, we propose an access control model based on a temporal variant of description logics (TL-ALCF). This logical schema enables us to express history constrained policies to enrich the policy-base with dynamic properties based on previous accesses. The specification of each component of the model as well as the approach to define history... 

Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools. They have been also employed in other buildings like bazaars or market places in Iran due to their favorable thermal performance. The aim of this research is to study about domed roofs thermal performance in order to determine how they can be helpful in reducing the maximum air temperature of inside buildings during the warm seasons considering all parameters like air flow around them, solar radiation, radiation heat transfer with the sky and the ground as well as some openings on the building. The results of the study show that the thermal performance of the... 

Domed roofs have been used in Iran and many other countries to cover large buildings such as mosques, shrines, churches, schools, etc. However their favorable thermal performance made them to be employed in other buildings such as bazaars, or market places, in Iran. The aim of this study was to determine the air pressure distribution over domed roofs, employing a numerical method. In this investigation, a three-dimensional model and a laminar inlet air flow were considered. The k-ε RNG method was employed for the turbulent flow simulation method. Simulation was run under three conditions of windows and a hole on top of the dome being open, or closed. The results were compared with the... 

The coaxial electrospinning for producing core-shell nanofibers due to control the release profile of drug by the shell layer has been developed. N-carboxymethyl chitosan (CMC)-polyvinyl alcohol (core)/poly(ε-caprolactone) (PCL) (shell) nanofibers were produced via coaxial electrospinning. Doxorubicin (DOX) and nickel ferrite nanoparticles were incorporated into the nanofibers for controlled release of DOX against MCF-7 breast cancer. The minimum CMC/PCL fiber diameter was found to be 300 nm by optimizing of three variables including voltage to distance ratio (1.5–2.5 kV/cm), CMC concentration (4−6 wt.%) and PCL concentration (8−12 wt.%). The synthesized core-shell fibers were characterized... 

The coaxial electrospinning for producing core-shell nanofibers due to control the release profile of drug by the shell layer has been developed. N-carboxymethyl chitosan (CMC)-polyvinyl alcohol (core)/poly(ε-caprolactone) (PCL) (shell) nanofibers were produced via coaxial electrospinning. Doxorubicin (DOX) and nickel ferrite nanoparticles were incorporated into the nanofibers for controlled release of DOX against MCF-7 breast cancer. The minimum CMC/PCL fiber diameter was found to be 300 nm by optimizing of three variables including voltage to distance ratio (1.5–2.5 kV/cm), CMC concentration (4−6 wt.%) and PCL concentration (8−12 wt.%). The synthesized core-shell fibers were characterized... 

We revisit the mathematical formulation of the famous Jaynes-Cummings-Paul Hamiltonian, which describes the interaction of a two-level atom with a single mode of an electromagnetic cavity reservoir. We rigorously show that under the condition of ultrastrong coupling between the atom and cavity in which the transition frequency is comparable to the coupling frequency, the bosonic field operators undergo non-sinusoidal time variations. As a result, the well-known solutions to the Jaynes-Cummings-Paul model are no longer valid, even when the rotating wave approximation is not used. We show how a correct mathematical solution could be found instead  

This manuscript presents a framework to develop vector error correction (VEC) models applicable to forecasting the short- and long-run movements of the average hourly earnings of construction labor, which is an essential predictor of the construction labor costs. These models characterize the relationship between average hourly earnings and a set of explanatory variables. The framework is applied to develop VEC forecasting models for the average hourly earnings of construction labor in the USA based on the identified variables that govern its movements, such as Global Energy Price Index, Gross Domestic Product, and Personal Consumption Expenditures. More than 150 candidate VEC models were... 

The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The... 

The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The... 

The core-shell nanofibers, produced by the coaxial electrospinning method, are good candidates for delivery of anticancer drugs due to their continuous release without initial burst release. In this work, the N-carboxymethyl chitosan (N-CMCS)-polyvinyl alcohol (PVA)/poly(ε-caprolactone) (PCL) composite and core-shell nanofibers were prepared by two-nozzle and coaxial electrospinning techniques, respectively. Doxorubicin (DOX) as an anticancer drug was loaded into the N-CMCS/PVA/PCL nanofibers fabricated by two-nozzle and coaxial electrospinning. The performance of nanofibers was compared for the adsorption and controlled release of DOX against MCF-7 breast cancer cells death in vitro. The... 

This overview presents a tutorial introduction to the theory of magnetic plasma confinement in toroidal confinement systems with particular emphasis on axisymmetric equilibrium geometries, and tokamaks. The discussion covers three important aspects of plasma physics: Equilibrium, Stability, and Transport. The section on equilibrium will go through an introduction to ideal magnetohydrodynamics, curvilinear system of coordinates, flux coordinates, extensions to axisymmetric equilibrium, Grad-Shafranov Equation (GSE), Green's function formalism, as well as analytical and numerical solutions to GSE. The section on stability will address topics including Lyapunov Stability in nonlinear systems,... 

This paper presents a neuro-predictive controller for temperature control of automotive air conditioning system. A numerical model for the automotive refrigeration cycle, which includes transient operating conditions, has been employed in simulations. In this model, which has been created from numerous laboratory tests on a typical passenger car, the vehicle is divided into two linked modules representing the air conditioning (A/C) system as well as the passenger compartment climate. Moreover, the thermal loads have been considered. This system demonstrates variable and large time delays, which is the case in reality. The simulation results show good performance of the proposed controller. ©... 

We present a new approach for analytical modeling and calculating the response of high-Tc superconductive transition edge sensors in a wide range of modulation frequencies for different configurations of the film patterns. The method used here is based on solving the heat transfer differential equation for two different time varying heat sources, which are related to the absorbed radiated power. The used method employs two-dimensional boundary conditions for describing meander-line patterned devices. The results from the applied method are in better agreement with those obtained from the frequency response measurements of the characterized samples, than the previously developed models. In... 

We have developed a simulation system for nanoscale high-electron mobility transistors, in which the self-consistent solution of Poisson and Schrödinger equations is obtained with the finite element method. We solve the exact set of nonlinear differential equations to obtain electron wave function, electric potential distribution, electron density, Fermi surface energy and current density distribution in the whole body of the device. For more precision, local dependence of carrier mobility on the electric field distribution is considered. We furthermore compare the simulation to a recent experimental measurement and observe perfect agreement. We also propose a novel graded channel design,...