Sharif Digital Repository

In this article, the effects of nonuniform magnetic fields on the hydrodynamics and heat transfer from a heated sphere to its surrounding ferrofluid flow have been investigated. Kelvin body forces originate from the nonuniformity of the applied magnetic field and can generate the vortices behind the sphere leading to a considerable change in the velocity and temperature fields. The applied magnetic field disturbs the thermal boundary layer and decreases heat-transfer resistance, leading to a significant enhancement in the heat-transfer coefficient. Variations of the local and average Nusselt number value (Nu), separation angle, recirculation length, and drag coefficient were considered to... 

The Iranian government has set a target of a 20% share of non-fossil fuel electricity generation by 2030, whose main result is reducing Green House Gas (GHG) emissions (about 182 million tonnes in 2017) to achieve the targets pledged under the Paris Climate Accord. So, this paper presents a comprehensive model on the expansion of non-fossil technology to evaluate the impact of increasing their share in Iran’s electricity supply system. This analytical approach is based on system dynamics (SD) that was developed based on dynamic behavior of electricity market, with an emphasis on the expansion of non-fossil fuels (solar photovoltaics, wind turbines, expansion turbines, and hydro power) in the... 

In this paper, we introduce a technique for improving power distribution characteristics of space time block codes (STBCs) which include peak to average power ratio (PAPR), average to minimum power ratio (Ave/min), and probability of transmitting “zero” by antenna. We consider STBCs in multiple input multiple output (MIMO) and multiple input single output (MISO) systems that achieve full diversity for linear or maximum likelihood (ML) receivers. It is proved that by multiplying a specific non-singular square matrix by the code matrix, a new code is obtained that achieves full diversity and the power distribution characteristics are improved. The proposed technique is general can be applied... 

Improving power distribution characteristics of space time block codes (STBCs), namely peak to average power ratio (PAPR), average to minimum power ratio (Ave/min), and probability of transmitting 'zero' by antenna, makes easier their practical implementation. To this end, this study proposes to multiply full diversity STBC with a non-singular matrix in multiple input multiple output (MIMO) or multiple input single output (MISO) systems with linear or maximum likelihood (ML) receivers. It is proved that the obtained code achieves full diversity and the order of detection complexity does not change. The proposed method is applied to different types of STBCs. The bit error rate (BER) and power... 

As part of its Paris Agreement commitment, Iran pledged to decrease 4 % of its carbon dioxide (CO2) emissions from 2020 to 2030. About 29% of total emission in Iran belongs to electricity supply while energy consumption in other sectors (transport, household, and industry) have a lower share in CO2 emission. The main concern here is finding the optimal mix of power plants in the electricity supply system that should be deployed to meet Iran’s mentioned respective targets and considering simultaneously interests of consumers and producers in this energy system. So, we developed a non-linear mathematical programming model for Iran’s electricity system to address this concern with changing... 

The bronchial tree plays a main role in the human respiratory system because the air distribution throughout the lungs and gas exchange with blood occur in the airways whose dimensions vary from several centimeters to micrometers. Organization of about 60,000 conducting airways and 33 million respiratory airways in a limited space results in a complex structure. Due to this inherent complexity and a high number of airways, using target-oriented dimensional reduction is inevitable. In addition, there is no general reduced-order model for various types of problems. This necessitates coming up with an appropriate model from a variety of different reduced-order models to solve the desired... 

The curve of exhaled inert gas concentration against exhaled volume is called gas washout curve. The slope at the end part of gas washout curve (Sn) is a measure of structural abnormalities. Sn depends on the spatial concentration distribution and dynamic of gas washout, which depends on several mechanisms including asymmetry of airways, nonhomogeneous ventilation, sequential emptying, and gas exchange with blood. Due to a large number of airways in human lungs, using simplified models is inevitable. On the other hand, these simplified models cannot capture some of the mentioned mechanisms and subsequently were not able to predict experimental trend of change in Sn with breath number in... 

Acinar region consists of ~ 33 million airways and provides low resistance against the gas exchange with blood. A three-dimensional anatomically accurate model of pulmonary acinus is useful for simulation of fluid distribution, gas exchange, particle deposition, drug delivery, and detection of structural abnormalities in the lungs. In this study, the stochastic parametric Lindenmayer system has been used to generate the respiratory airways filling a given space. This model takes into account the mechanical properties and details of human acinus which can accurately predict the gas distribution throughout the lungs for the first time. The procedure of finding the dimensions and orientations... 

Gas exchange, particle deposition, and drug delivery in the human lungs depend on the structure of the human bronchial tree. The conducting airways occupy the main portion of the human lungs and transport air from outside into pulmonary acini where the O2–CO2 exchange with blood occurs. Therefore, the generation of three-dimensional accurate structure of the conducting airways is required for simulation of the transport phenomena in the human respiratory system. The present study proposes an intelligent method for generation of conducting airways based on stochastic parametric Lindenmayer system (L-system). The conducting airways grow into the bronchopulmonary segments simultaneously using... 

The bronchial tree plays a main role in the human respiratory system because the air distribution throughout the lungs and gas exchange with blood occur in the airways whose dimensions vary from several centimeters to micrometers. Organization of about 60,000 conducting airways and 33 million respiratory airways in a limited space results in a complex structure. Due to this inherent complexity and a high number of airways, using target-oriented dimensional reduction is inevitable. In addition, there is no general reduced-order model for various types of problems. This necessitates coming up with an appropriate model from a variety of different reduced-order models to solve the desired... 

The curve of exhaled inert gas concentration against exhaled volume is called gas washout curve. The slope at the end part of gas washout curve (Sn) is a measure of structural abnormalities. Sn depends on the spatial concentration distribution and dynamic of gas washout, which depends on several mechanisms including asymmetry of airways, nonhomogeneous ventilation, sequential emptying, and gas exchange with blood. Due to a large number of airways in human lungs, using simplified models is inevitable. On the other hand, these simplified models cannot capture some of the mentioned mechanisms and subsequently were not able to predict experimental trend of change in Sn with breath number in... 

Acinar region consists of ~ 33 million airways and provides low resistance against the gas exchange with blood. A three-dimensional anatomically accurate model of pulmonary acinus is useful for simulation of fluid distribution, gas exchange, particle deposition, drug delivery, and detection of structural abnormalities in the lungs. In this study, the stochastic parametric Lindenmayer system has been used to generate the respiratory airways filling a given space. This model takes into account the mechanical properties and details of human acinus which can accurately predict the gas distribution throughout the lungs for the first time. The procedure of finding the dimensions and orientations... 

Gas exchange, particle deposition, and drug delivery in the human lungs depend on the structure of the human bronchial tree. The conducting airways occupy the main portion of the human lungs and transport air from outside into pulmonary acini where the O2–CO2 exchange with blood occurs. Therefore, the generation of three-dimensional accurate structure of the conducting airways is required for simulation of the transport phenomena in the human respiratory system. The present study proposes an intelligent method for generation of conducting airways based on stochastic parametric Lindenmayer system (L-system). The conducting airways grow into the bronchopulmonary segments simultaneously using... 

Chiral discrimination has always been a hot topic in chemical, food and pharmaceutical industries, especially when dealing with chiral drugs. Enantiomeric recognition not only leads to better understanding of the mechanism of molecular recognition in biological systems, but may further assist in developing useful molecular devices in biochemical and pharmaceutical studies. By emerging nanotechnology and exploiting nanomaterials in sensing applications, a great deal of attention has been given to the design of optical nanoprobes that are able to discriminate enantiomers of chiral analytes. This review explains how engineering nanoparticles (NPs) with desired physicochemical properties allows...