Sharif Digital Repository

The burning of fossil fuels such as gasoline, coal, oil, natural gas in combustion reactions results in the production of carbon dioxide. The phase behavior of the carbon dioxide + water system is complex topic. Unlike methane, CO2 exhibits a minimum in the water content. These minima cannot be predicted by existing methods accurately. In this communication, two mathematical-based procedures have been proposed for accurate computation of CO2 water content for tempe-ratures between 273.15 and 348.15 K and the pressure range between 0.5 and 21 MPa. The first is based on least squares support vector machine (LSSVM) algorithm and the second applies multilayer perceptron (MLP) artificial neural... 

In this study, effects of replacing cement with colloidal amorphous silica nano-particles have been experimentally investigated on the physical and mechanical properties, durability and microstructure of concrete. Experimental results include workability, fresh concrete density, and hardened concrete properties like compressive strength at different ages of 3, 7, and 28-days, and also 28-days splitting tensile strength. Furthermore, influence of silica nano-particles on durability and microstructure of concrete for 28-days specimens was tested by conducting water absorption test, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Analysis (EDAX), respectively. In order to study... 

The power output of gas turbines reduces greatly with the increase of inlet air temperature. Aquifer thermal energy storage (ATES) is employed for cooling of the inlet air of a gas turbine. Water from a confined aquifer is cooled in winter, and is injected back into the aquifer. The stored chilled water is withdrawn in summer to cool the gas turbine inlet air. The heated water is then injected back into the aquifer. A 20 MW Hitachi gas turbine, along with a two-well aquifer were considered for analysis. It was shown that the minimum power output of the gas turbine on the warmest day of the year could be raised from 16.30 to 20.05 MW, and the mean annual power output could be increased from... 

The coefficient of performance (COP) of a photovoltaic panel or module is defined as the ratio of the total electrical energy produced by the panel during its life to the total energy spent for its manufacture. All processes involved for the manufacture of photovoltaic panels were considered and the energy spent per unit mass of the final product during each process was determined. The total electrical energy spent for the manufacture of a photovoltaic module of 1×0.5 m dimensions, employing 340 micron wafers, with the net wafer area of 0.36 m2, was then determined. Monocrystalline and multicrystalline silicon cells were employed. It was found that for the manufacture of the PV module... 

A circuit model based on the transmission line theory is proposed to analyze the recently introduced metal-insulator-metal (MIM) complementary split-ring resonators (CSRRs). It is shown that integer and noninteger modes of CSRRs can be characterized by transmission line models with short- and open-circuited terminals. The proposed circuit model is then extended to incorporate side-coupling effects between the CSRRs and straight MIM waveguides. Thereby, simple closed-form expressions are provided for the coupling quality factor. It is shown that waveguide resonator structures based on CSRRs at specific resonance frequency and bandwidth can be smaller than waveguide resonator structures based... 

The mean monthly values of sky clearness index, K̄T, were estimated for 36 Iranian cities, utilizing the solar radiation data measured by the Iranian Meteorological Organization. The study shows that the city of Tabas, in the desert regions of Iran, with an annual average K̄T of 0.69 is the sunniest city, followed by the cities of Yazd, Khor, Birjand, Khorramabad, Kerman, and Shiraz. On the other hand, the cities of Babolsar, Gorgan, Ramsar and Rasht, located by the Caspian Sea with average values of K̄T of 0.41, 0.41, 0.39 and 0.39, respectively, are the cloudiest cities in Iran  

Vapor liquid equilibrium (VLE) data has significant role in designing processes which include vapor and liquid in equilibrium. Since it is impractical to measure equilibrium data at any desired temperature and pressure, particularly near critical region, thermodynamic models based on equation of state (EOS) are usually used for VLE estimating. In recent years due to the development of numerical tools like artificial intelligence methods, VLE prediction has been find new alternatives. In the present study a novel method called Least-Squares Support Vector Machine (LSSVM) used for predicting bubble/dew point pressures of binary mixtures containing carbon dioxide (CO 2) + cyclic compounds as... 

Keratinocyte Growth Factor (KGF) is a paracrine-acting, epithelial mitogen that plays a prominent role in the regeneration of damaged epithelial tissues. In spite of different attempts to produce recombinant human KGF in many organisms, including bacteria, mammalian cells, plant cells and insect cells; production of recombinant form suffers from lower yields and recovery relative to other recombinant proteins of similar size and properties. Due to many advantages of Pichia pastoris expression systems for producing industrial enzymes and pharmaceutical proteins, in this study P. pastoris was chosen as a host for KGF expression. For preparing human KGF coding sequence, MCF-7 cell line was... 

Two new designs of wind towers were tested side by side with a conventional wind tower in the city of Yazd, Iran. All the towers were of identical dimensions. The two new designs were one with wetted column, consisting of wetted curtains hung in the tower column, and the other one with wetted surfaces, consisting of wetted evaporative cooling pads mounted at its entrance. The air temperature leaving the wind towers with evaporative cooling provisions were much lower than the air temperature leaving the conventional design, and its relative humidity much higher. The air-flow rate was reduced slightly in these new towers. It was found that the wind tower with wetted column performs better with... 

Physical separation methods, especially membrane technology, can be a good substitute for biological wastewater treatment, due to its simple constructions and operations. There are many papers and patents in this field. Membranes need to be cleaned periodically to be able to operate economically, and need to be replaced after a while. Several factors can influence the membrane cleaning procedure, including pressure of backwash, acid and base concentration, duration of forward washing, and duration of acid-base backwashing. In this study the effect of these parameters was investigated to find an optimum condition which could result in a good polyethersulphone (PES) membrane cleaning with less... 

The objective of this study is to develop a general finite element formulation associated with an incremental adaptive procedure which established for thermoviscoelastic stress analysis of orthotropic cylinders made of polymers. This paper concerned with development of a numerical algorithm for the solution of the quasistatic initial/boundary value problems involving the linear viscoelastic media with thermal and mechanical deformations. The viscoelastic constitutive equations, represented in an integral form and involving relaxation functions, are transformed into an incremental algebraic relation. An incremental relaxation is then developed for the finite element formulation to deal with... 

In this work, the process of starch removal from starchy wastewater using a hydrophilic polyethersulfone membrane was investigated. The pore size of the membrane was 0.65 μm and the pattern of stream in plate and frame handmade membrane module was cross-flow. To design the layout of the experiments, response surface methodology was applied. The performance of the filtration process was evaluated by calculating the (chemical oxygen demand) COD removal percentage (rejection factor) and permeate flux. In this study, five operative parameters were investigated, including trans-membrane pressure, flow rate and temperature of feed, pH, and the COD concentration of starch wastewater. Two models... 

In oil and gas fields, it is a common practice to flow liquid and gas mixtures through choke valves. In general, different types of primary valves are employed to control pressure and flow rate when the producing well directs the natural gas to the processing equipment. In this case, the valve normally is affected by elevated levels of flow (or velocity) as well as solid materials suspended in the gas phase (e.g., fine sand and other debris). Both surface and subsurface chokes may be installed to regulate flow rates and to protect the porous medium and surface facilities from unusual pressure instabilities.In this study a reliable, novel, computer based predictive model using Least-Squares...