Sharif Digital Repository

In the present study, hardness and tribological properties of nanostructured copper reinforced with SiC nanoparticles of various volume fractions (0, 2, 4, and 6 vol%) were investigated. The nanocomposites were fabricated by high-energy mechanical milling and hot pressing method. The Cu-SiC nanocomposites showed enhanced hardness and wear resistance against WC counterface. The hardness and wear resistance of the nanocomposite increased with increasing the amount of SiC nanoparticles up to 2 vol% in the matrix, but they decreased at higher percentages of SiC (4 and 6 vol%). Flake formation-spalling and abrasion were identified as the predominant wear mechanisms. It was found that reducing the... 

In this research heating, cooling and electrical demands of a residential tower are evaluated for Iran various weather conditions. For this purpose, several cities are selected as the representative of the specific weather conditions. To meet the cooling demand, desiccant cooling system plus alternative systems are applied. To analyze desiccant wheel, outlet humidity and temperature have been modeled. Also, the effect of rotational speed and regeneration temperature on entropy generation of the desiccant wheel has been studied based on the obtained results. It is deduced that the entropy generation may be increased by increasing the regeneration temperature and the rotational speed. To... 

A downscaling model capable of explaining the temporal and spatial variability of regional hydroclimatic variables is essential for reliable climate change studies and impact assessments. This study proposes a novel statistical approach based on generalized hierarchical linear model (GHLM) to downscale precipitation from the outputs of general circulation models (GCMs) at multiple sites. GHLM partitions the total variance of precipitation into within- and between-site variability allowing for transferring information between sites to develop a regional downscaling model. The methodology is demonstrated by downscaling precipitation using the outputs of eight GCMs in Lake Urmia basin in... 

The efficient planning of search and rescue (SAR) operations is highly impactful in the disaster response phase, which offers a limited time window with a declining chance for saving trapped people. The present paper introduces a new robust decision support framework for planning SAR resource deployment in post-disaster districts. A two-stage decomposition approach is applied to formulate the problem as iterative interrelated stages of mixed-integer programming (MIP) models. The first stage presents a robust multi-period allocation model for maximizing fair and effective demand coverage in the affected districts during the entire planning horizon. It takes into account the time-sensitiveness... 

Among the various approaches, ZnS treatment is the most convenient method for reducing the charge recombination in quantum dot-sensitized solar cells (QDSSCs). Here an improved method of ZnS treatment is explained for efficiency enhancement in QDSSCs. To get to the goal of device performance improvement, it is essential to have a uniform deposited layer. We utilized Triton X-100 (TX-100) as a surfactant to the convenient aqueous precursors during ZnS deposition by successive ionic layer adsorption and reaction method. It helps to decrease in contact angle and increase in wettability of the aqueous precursor and results in a more uniform deposited layer. The effect of modified ZnS treatment... 

In United States (U.S.), government-funded organizations, such as NLDAC, reimburse travel and subsistence expenses incurred during living-organ donation process. However, in Iran, there is a non-governmental organization called Iranian Kidney Foundation (IKF) that funds the direct and indirect costs of donors through charitable donations and contributions from participants in the exchange program. In this article, for countries outside the U.S. that currently use an equality approach, we propose a potential new compensation-apportionment approach (equitable approach) for kidney-exchange chains and compare it with the currently available system (equality approach) in terms of the... 

In this research, the effect of adding graphene-based aerogel ((G)A) nanoparticles on the tensile and fatigue behavior of the epoxy polymer was investigated. Specimens of nanocomposites were prepared by adding 0.05, 0.1, 0.2, 0.5, 1, and 2 wt.-% (G)A nanoparticles to the epoxy polymer. Tensile tests revealed that the 0.1 wt.-% graphene-based aerogel/ epoxy ((G)A/E) nanocomposites had the highest increase in tensile strength with 19 % growth compared to neat epoxy. Also, the tensile modulus increased by 15 % in the 0.5 wt.-% (G)A/E nanocomposites. A substantial improvement in fatigue life of the epoxy polymer was observed on adding 0.1 wt.-% (G)A nanoparticles. For instance, the fatigue life... 

In this study the first and the second laws of thermodynamics are evaluated for a single effect absorption chiller. Entropy generation and COP are selected as the objective functions and their variations are studied by varying the generator temperature for various condensing temperatures. For this purpose, the enthalpy and the entropy data of the super-heated steam, saturated steam and the saturated water are formulated in the mathematical equations. Also to provide the required steam of generator, prime mover in the form of internal combustion engine is applied and its partial load conditions are analyzed. A residential tower is considered as the case study for selecting the proper prime... 

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

In this paper, the rapid synthesis of nanostructured NiTi–Ni3Ti intermetallic alloy from titanium and nickel powders through mechanical alloying followed by microwave-assisted sintering process was investigated. The sintered samples at different temperatures exhibited major phases of NiTi– B2 and Ni3Ti, and minor phases of NiTi–B19′ and Ti2Ni. The density, porosity and microhardness of the sample varied based on the sintering temperature, in which the highest density and microhardness (~750 H V) were obtained at sintering temperature of 1100 °C. Based on the results of this research, the microwave-assisted sintering can be applied to fabricate Ni–Ti alloys with improved mechanical properties... 

The efficient planning of search and rescue (SAR) operations is highly impactful in the disaster response phase, which offers a limited time window with a declining chance for saving trapped people. The present paper introduces a new robust decision support framework for planning SAR resource deployment in post-disaster districts. A two-stage decomposition approach is applied to formulate the problem as iterative interrelated stages of mixed-integer programming (MIP) models. The first stage presents a robust multi-period allocation model for maximizing fair and effective demand coverage in the affected districts during the entire planning horizon. It takes into account the time-sensitiveness... 

In this paper, the advantages of numerical simulation to improve the process of copper electroforming are demonstrated. In this regard, the finite element model of copper electroforming for a rotating cone electrode was first prepared and then, the effect of the key parameters, such as applied current density, solution conductivity, electrode spacing, and anode height, on the uniformity of the thickness was investigated. The model combines tertiary current distribution with Bulter–Volmer electrode kinetics and computational fluid dynamics at the turbulent condition. In order to validate the model, a cone-shaped shell was produced by electroforming method in the laboratory. The obtained...