Sharif Digital Repository

The price elasticity of gasoline demand is a key parameter in evaluation of various policies. However, most of the literature uses aggregate data to identify this elasticity. Temporal and spatial aggregation make such elasticity estimates biased. We employ a unique dataset of all gasoline transactions in Iran during a 4-month period around an unexpected exogenous price change to identify that price elasticity. We also identify a significant withholding behavior by consumers in response to anticipated price changes. The consumers reduce or postpone their purchases when they expect a decrease in prices. Controlling for date fixed effects would eliminate homogeneous withholding responses.... 

We estimate the price elasticity of the demand for gasoline smuggling in Iran. For this purpose, we employ a detailed panel of monthly gasoline consumption data from 160 distribution hubs during the period 2005–2014. We apply two different approaches which are diff-in-diff and panel data estimations. The results suggest that the foreign-to-home gasoline price ratios have a significant impact on the time-varying elasticity of demand. This finding supports the hypothesis that an increase in domestic gasoline prices will significantly reduce the demand for smuggling. In addition, as the distance of a region from its closest higher-price neighboring country diminishes, the price elasticity of... 

To what extent can a short-term decline in the output of a small open economy be explained by trade barriers? To answer this, we extend the Business Cycle Accounting method of Chari et al. (2007) to a small open economy model. We include an additional time-varying wedge to model financial trade frictions caused by barriers on imports. International sanctions on Iran provide an empirical opportunity to apply this method to data on Iran's recession in 2012-13. The results indicate that efficiency and investment wedges account for most of the fluctuations in aggregate variables during the sanctions, and trade barriers had little contemporaneous explanatory power. The effect of oil boycotts... 

To what extent can a short-term decline in the output of a small open economy be explained by trade barriers? To answer this, we extend the Business Cycle Accounting method of Chari et al. (2007) to a small open economy model. We include an additional time-varying wedge to model financial trade frictions caused by barriers on imports. International sanctions on Iran provide an empirical opportunity to apply this method to data on Iran's recession in 2012-13. The results indicate that efficiency and investment wedges account for most of the fluctuations in aggregate variables during the sanctions, and trade barriers had little contemporaneous explanatory power. The effect of oil boycotts... 

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... 

Short circuit current is one of the major threats for power system stability. Power system should have the ability to detect and clear these faults within a specified time. The protection system can clear the faults only if the interruption capability of the circuit breakers is higher than the fault level. Expansion of the grid and installation of new power on the scale that is envisaged will require practical solutions to a number of technical challenges. One of the technical challenges is fault level management as system expansion often results in increased fault levels beyond the design limits of the existing switchgears. Replacing the old equipments particularly circuit breakers with the... 

We use the weighted integral form of spherical Bessel functions and introduce a new analytical set of complete and biorthogonal potential-density basis functions. The potential and density functions of the new set have finite central values and they fall off, respectively, similar to r-(1+ l) and r-(4+ l) at large radii, where l is the latitudinal quantum number of spherical harmonics. The lowest order term associated with l = 0 is the perfect sphere of de Zeeuw. Our basis functions are intrinsically suitable for the modelling of three-dimensional, soft-centred stellar systems and they complement the basis sets of Clutton-Brock, Hernquist & Ostriker and Zhao. We test the performance of our... 

One of the shortcomings of photoconductive (PC) antennas in terahertz (THz) generation is low effective radiated power in the desirable direction. In this paper, we propose a defective photonic crystal (DPC) substrate consisting of a customized 2D array of air holes drilled into a solid substrate in order to improve the radiation characteristics of THz PC antennas. The effect of the proposed structure on the performance of a conventional THz PC antenna has been examined from several aspects including radiation efficiency, directivity, and field distribution. By comparing the radiation performance of the THz antenna on the proposed DPC substrate to that of the conventional solid substrate, it... 

Iran has been experiencing slow growth for the past ten years. Using plant-level information, we show that on average firm-specific productivity in manufacturing sectors declined at the rate of 2.6 percent annually, while large top decile firms experienced a modest growth in productivity between 2005 and 2011. We decompose this trend and find that within-plant variation is its main driving force while the between firms and industries component is insignificant. We test several alternative explanations that may contribute to these negative trends. We show that the subsidy reform had a negative effect, while privatization seems to have had no effect. Private management not affected on... 

In this paper, arrays of two different terahertz (THz) antennas based on defective photonic crystal (DPC) substrates are proposed and their radiation characteristics are investigated by using full-wave simulation. We show that employing DPC substrates in THz photoconductive antenna (PCA) arrays reduces the amount of power coupled to the substrate surface waves and, as a result, decreases the mutual coupling between the elements of the antenna array and increases the directivity in the boresight direction. By studying 1 × 2 arrays of bowtie and four-leaf-clover-shaped antennas, we show that either the improvement of directivity in a broad bandwidth or the enhancement of photomixer antenna... 

Using plant level panel data of manufacturing firms in Iran from 2003 to 2013, we test the Dutch disease predictions, including the impact of a rise in oil prices on intensive and extensive margins of trade. Our findings indicate that during periods of high oil prices domestic currency appreciates, but contrary to resource curse theories, domestic firms export more, and new firms enter foreign markets. We reconcile this paradox by proposing a new channel, which we call “subsidy disease.” Despite rising oil prices, the government of Iran kept domestic energy prices at low levels, which increased the implicit subsidy accruing to energy intensive firms. In effect, these firms gain a competitive... 

A set of bi-orthogonal potential-density basis functions is introduced to model the density and its associated gravitational field of three dimensional stellar systems. Radial components of our basis functions are weighted integral forms of spherical Bessel functions. We discuss on the properties of our basis functions and demonstrate their shapes for the latitudinal Fourier number l = 2. © 2008 Copyright International Astronomical Union 2008  

At least four source impedances are required to characterize the noise parameters of a two-port network. The accuracy of the noise parameters depends on the configuration of the employed source impedances (pattern). The configuration of a specified pattern, generated generally by an impedance tuner, changes with frequency, and as such, the accuracy is usually degraded in a wideband characterization. To realize a low-error wideband noise characterization, the present article thoroughly investigates the method of choosing a four-source impedance pattern. A Monte Carlo simulation-based approach is proposed to obtain the desired impedance patterns. The measurement and simulation results show... 

Low scalability and power efficiency of the shared bus in SoCs is a motivation to use on chip networks instead of traditional buses. In this paper we have modified the Orion power model to reach an analytical model to estimate the average message energy in K-Ary n-Cubes with focus on the number of virtual channels. Afterward by using the power model and also the performance model proposed in [11] the effect of number of virtual channels on Energy-Delay product have been analyzed. In addition a cycle accurate power and performance simulator have been implemented in VHDL to verify the results. ©2008 IEEE  

This paper presents a small open economy, dynamic general equilibrium model with cash-in advance constraint and a currency attack to explain the dynamic effects of changes in trade barriers in the short and long run. The model is calibrated using data on macroeconomic variables in Iran's economy from 1990 to 2013 to identify and analyze the effects of barriers imposed on trade. We analyze the effects of counterfactual fiscal, monetary and exchange rate policies in response to trade barriers and show how the economy would respond in different time horizons. We also evaluate the effects of eliminating each of the factors causing this stagflation. Our findings show that the short-term drop in... 

Thermodynamic and kinetic studies have been carried out on the adsorption of uranium(VI) by Amberlite IRA-910 resin. The adsorption process has been investigated as a function of adsorbate concentration, solution acidity, contact time, adsorbent dosage, and temperature. The experiments were preformed in batch mode, where uranium initial concentration on the solution samples were 185.5, 277.6 and 456.8 (mg/lit), sulfuric acid concentration range was 0.02-9 (mol/lit) and sorbent dosages were 0.2, 0.3 and 0.5 g. Equilibrium isotherm data were analyzed using Freundlich and Dubinin-Radushkevich isotherm models. The results showed that the adsorption process was well described by Freundlich... 

Heating, Ventilating and Air Conditioning (HVAC) plant is a multivariable, nonlinear and non minimum phase system, which control of this plant, is very difficult. This paper presents a new approach to control of HVAC system. The proposed method is a hybrid of fuzzy logic and PID controller. Simulation results show that this control strategy is very robust, flexible and alternative performance. To evaluate the usefulness of the proposed method, we compare the response of this method with PID controller. The simulation results show that our method has the better control performance than PID controller  

Bioremediation of soil and groundwater sites contaminated by petroleum hydrocarbons is known as a technically viable, cost-effective, and environmentally sustainable technology. The purpose of this study is to investigate laboratory-scale bioremediation of petroleum-hydrocarbon contaminated soil through development of eight bioreactors, two bioreactors for each bioremediation mode. The modes were: (1) natural attenuation (NA); (2) biostimulation (BS) with oxygen and nutrients; (3) bioaugmentation (BA) with hydrocarbon degrading isolates; (4) a combination of biostimulation and bioaugmentation (BS-BA). Total petroleum hydrocarbons (TPH) mass balance over the bioreactors showed about 2% of... 

The solubility of hydrogen sulphide in three ionic liquids, viz. 1-hexyl-3-methylilmidazolium hexafluorophosphate ([hmim][PF6]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF4]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N]), at temperatures ranging from 303.15 K to 343.15 K and pressures up to 1.1 MPa were determined. The solubility values were correlated using the Krichevsky-Kasarnovsky equation and Henry's constants were obtained at different temperatures. Partial molar thermodynamic functions of solvation such as standard Gibbs free energy, enthalpy, and entropy were calculated from the solubility results. Comparison of the values obtained... 

Land subsidence associated with using natural groundwater resources for serving the growing population needs has been receiving extensive research attention in the literature over the past few decades. The water content fluctuation in the of subsurface soil layers significantly impacts the land subsidence. The key objective of this study is to predict changes in water content profiles in soil layers over a long period of time using a deep learning-based approach. A convolution neural network algorithm that is commonly used in Artificial Intelligence (AI) applications is modified in the present study for processing in-situ measurement water content profiles. The approach used in the proposed...