Sharif Digital Repository

In the present work a new strategy for straightforward fabrication of CdS/CdTe solar cells, containing CdS nanowires and nanoparticles as a window layer and CdTe nanoparticles and microparticles as an absorber layer, are reported. CdS and CdTe nanostructures were synthesized by solvothermal method. X-ray diffraction analysis revealed that highly pure and crystallized CdS nanowires and nanoparticles with hexagonal structure and CdTe nanoparticles with cubic structure were obtained. Atomic force microscope and field emission scanning electron microscope images showed that CdS nanowires with length of several μm and average diameter of 35 nm, CdS nanoparticles with average particle size of 32... 

Nowadays, Programmable Electronic AC Load (PEAL) is widely used to test various devices such as solar inverters, UPSs, filters, generators, and generally test all AC power and measuring devices. In this paper, Model Predictive Current Control (MPCC) is used for control of a programmable AC load. In each period, switching state that minimizes the cost function is selected and applied to the converter. Cost function is the square of the current components error. The effect of the horizon of prediction on the quality of the load current is investigated. To decrease the calculations burden, a limited search pool is used. Simulation results confirm that using two steps prediction horizon with... 

In an experimental study, investigation is performed based on the surface-mounted hot-film sensors and surface pressure and rake pressure measurements. The boundary-layer (BL) events such as laminar separation (LS), transition onsets, and variations of the wall shear stress are discussed and compared for both pitching and plunging oscillations for various cases of before, within, and beyond the static stall angle of attack (AOA) conditions. All experiments are conducted in a low-speed wind tunnel. The surface pressures are measured using differential pressure sensors with a range from 0.075 to 1.0 psi and with a maximum error of 0.15% of their full span. In addition, the wake profile behind... 

In an experimental study, investigation is performed based on the surface-mounted hot-film sensors and surface pressure and rake pressure measurements. The boundary-layer (BL) events such as laminar separation (LS), transition onsets, and variations of the wall shear stress are discussed and compared for both pitching and plunging oscillations for various cases of before, within, and beyond the static stall angle of attack (AOA) conditions. All experiments are conducted in a low-speed wind tunnel. The surface pressures are measured using differential pressure sensors with a range from 0.075 to 1.0 psi and with a maximum error of 0.15% of their full span. In addition, the wake profile behind... 

Transitional boundary layer over an airfoil in the combined pitch-plunge oscillating motions at low Reynolds number is experimentally investigated. The study is based on the data obtained from both surface hot-film and surface static pressure. Different oscillation zones prior to, within, and beyond the static stall angle of attack of the airfoil are considered. The hysteresis loops for the laminar separation bubble, transition, relaminarization points, as well as the airfoil lift coefficient are investigated and are compared for different types of dynamic motions. Two different types of combined pitch-plunge motions, constructive and destructive, are considered. In the constructive motion,... 

A new technique for the laminar-turbulent intermittency measurement based on the surface hot-film data is presented. The existing techniques require data acquired from the calibrated hot-films which leads to the real wall shear stress values. However, calibration of the hot-films is usually very complex. In the proposed method, a technique based on the probability distribution function (PDF) of the acquired data using the uncalibrated hot-film sensors is presented and evaluated. The PDF is prepared for a reduced form of the quasi-wall shear stress value instead of the real shear stress value one. This leads to a standard normal distribution curve for the PDF in the turbulent flow region and... 

Transitional boundary layer over a pitching airfoil at low Reynolds number (Re = 2:7 × 105) is experimentally investigated using space-frequency and time-frequency analyses of hot- film signals. Boundary layer events are visualized based on the space-frequency and time-frequency plots. The precursor phenomenon for turbulent and fully separated flows is presented based on the time-frequency analysis. A new technique based on time-frequency analysis of hot- film signals is introduced to measure the transition onset and relaminarization locations. This technique functions based on the analysis of high-frequency disturbances of the measured data. Significant attention has been drawn to the... 

Transitional boundary layer over a pitching airfoil at low Reynolds number (Re = 2:7 × 105) is experimentally investigated using space-frequency and time-frequency analyses of hot- film signals. Boundary layer events are visualized based on the space-frequency and time-frequency plots. The precursor phenomenon for turbulent and fully separated flows is presented based on the time-frequency analysis. A new technique based on time-frequency analysis of hot- film signals is introduced to measure the transition onset and relaminarization locations. This technique functions based on the analysis of high-frequency disturbances of the measured data. Significant attention has been drawn to the... 

The single stranded DNA can be adsorbed on the negatively charged surface of gold nanoparticles (AuNPs), but the rigid structure of double stranded DNA prevents it from adsorption. Signal of a tagged single stranded DNA will be quenched by the plasmon effect of the AuNP surface after its adsorption. This phenomenon has been used to study the DNA hybridization and interactions of two complementary 21mer oligonucleotides each tagged with a different fluorescent dye in the presence of 13 nm gold nanoparticles. The DNA strands used in this study belong to the genome of HIV. The obtained rank deficient three-way fluorescence data sets were resolved by both PARAFAC and restricted Tucker3 models.... 

This paper introduces a shock-wave-detection technique based on the schlieren imaging for continuum and rarefied-gas flows. The scheme is applicable for any existing two-dimensional flowfields obtained by experimental or numerical approaches. A Gaussian distribution for a schlieren function within the shock-wave region is considered. This enables the authors to access any desired locations through the shock (e.g., shock center, or leading- and trailing-edge locations). The bow shock-wave profile is described via a rational function, which could be employed for the estimation of shock angle. The relation between pre- and postshock flow properties along the shock wave with a high resolution... 

A new facile strategy for fabrication of high surface area electrode in the form of mixtures of coated carbon nanotubes (CNTs) and TiO2 nanoparticles with various weight ratios is reported. The so-called polymeric gel process was used to deposit thick film containing uniform distribution of TiO2 nanoparticles and coated CNTs with high porosity by dip coating for dye-sensitized solar cells (DSSCs) applications. Based on simultaneous differential thermal analysis, the minimum annealing temperature to obtain inorganic- and organic-free films was determined at 500°C. X-ray diffraction analysis revealed that deposited films were composed of primary nanoparticles with crystallite size in the range... 

Gallium-67 labeled superparamagnetic iron oxide nanoparticles ([ 67Ga]-SPION were prepared and evaluated for their altered biodistribution in normal rats. Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution were synthesized by a co-precipitation technique using ferrous salts at Fe3+/Fe2+ = 2 molar ratio followed by structure identification using XRD, TGA, DSC, VSM, HRSEM, TEM and FT-IR techniques (≈ 5 nm diameter). In order to trace SPION bio-distribution, the radiolabeled iron oxide nanoparticles were prepared using 67Ga with a high labeling efficiency (over 96%, RTLC method) and they also showed an excellent stability at room temperature for at least 4 d. The... 

Well-known polars in classical shock wave theory, that is, flow deflection angle-shock angle (θ-β), hodograph (u*,v*), and pressure deflection (θ-P*) diagrams, are investigated for the rarefied gas flows using a recently proposed shock wave detection technique by Akhlaghi and coworkers. The agreement between the obtained polars with the analytical relations in classical shock wave theory has been shown in the continuum limit for the cases of supersonic flow over the wedge and cylinder geometries. Investigations are performed using the RGS2D direct simulation Monte Carlo solver for supersonic gas flows over a circular cylinder at continuum limit and Kn = 10-4, 10-3, 0.01, 0.03, 0.07, and... 

This article was originally published online on 25May 2021 with the third author listed at the wrong affiliation. The affiliations appear correct above. All online versions of the article were corrected on 28 May 2021; the article is correct as it appears in the printed version of the journal. © 2021 American Institute of Physics Inc.. All rights reserved  

Well-known polars in classical shock wave theory, that is, flow deflection angle-shock angle (θ-β), hodograph (u*,v*), and pressure deflection (θ-P*) diagrams, are investigated for the rarefied gas flows using a recently proposed shock wave detection technique by Akhlaghi and coworkers. The agreement between the obtained polars with the analytical relations in classical shock wave theory has been shown in the continuum limit for the cases of supersonic flow over the wedge and cylinder geometries. Investigations are performed using the RGS2D direct simulation Monte Carlo solver for supersonic gas flows over a circular cylinder at continuum limit and Kn = 10-4, 10-3, 0.01, 0.03, 0.07, and... 

This article was originally published online on 25May 2021 with the third author listed at the wrong affiliation. The affiliations appear correct above. All online versions of the article were corrected on 28 May 2021; the article is correct as it appears in the printed version of the journal. © 2021 American Institute of Physics Inc.. All rights reserved  

Energy demand in Iran is increasing because of many reasons, for instance, low price, population and GDP growth. Its trend shows that this situation could not continue for many years, so it needs reviewing in energy policy in Iran. The aim of this paper is reviewing the whole energy system of Iran and its possible future and offering some policies for solving current and future problems. First of all, this study investigates the trend of growth of some parameters like GDP, electricity price, population, CO2 emission and electricity consumption in eight years. After that, by calculating the price of electricity generated in Iran under three different circumstances, this study is able to... 

Gallium-67 labeled superparamagnetic iron oxide nanoparticles were prepared and evaluated for their altered biodistribution in normal rats. Superparamagnetic iron oxide nanoparticles with narrow size distribution were synthesized by co-precipitation technique using ferric and ferrous salts at molar ratio Fe3+/Fe2+=2:1 followed by structure identification using XRD, thermo gravimetric analysis , differential scanning calorimetric , vibrating sample magnetometer, high-resolution scanning electron microscopy,transmission electron microscopy and fourier transform infrared absorption techniques. In order to trace superparamagnetic iron oxide nanoparticles bio-distribution, the radiolabeled iron... 

Chitosan was chemically modified by diethylenetetraaminepentaacetic acid (DTPA) in different degrees of modification (DM = 6.1, 10.3, 15.7 and 20.9%). DTPA-chitosans were radiolabeled with gallium-66 radionuclide. The effect of several factors on labeling yield such as degree of modification, acidity and concentration of DTPA-chitosan solution, contact time and radioactivity was investigated. Radiolabeled DTPA chitosans were intratumorally injected to fibrosarcoma bearing mice and the leakage of radioactivity from the injection site was evaluated. In comparison with chitosan, all DTPA chitosans showed better efficiency in preventing the leakage of radioactivity from tumor lesion and... 

Abstract The torque exerted on the walls of a micro cylindrical Couette gas flow is studied using Direct Simulation Monte Carlo (DSMC) method and analytical solutions. An analytical solution for temperature filed under specified wall heat flux condition is proposed using a previously introduced power-law (PL) wall-scaling approach. The results of cylindrical Couette flow under specified wall heat flux condition are compared with those of isothermal flow. The effects of rarefaction, compressibility, tangential momentum accommodation coefficient (TMAC) and gas-surface heat exchange on the torque values are investigated for slip to free molecular flow regimes. The results indicate that the...