Understanding the role of slant angle in oblique slit arrays made of metal at terahertz frequencies

, Article IEEE Transactions on Terahertz Science and Technology ; Volume 5, Issue 3 , May , 2015 , Pages 497-504 ; 2156342X (ISSN) Edalatipour, M ; Mehrany, K ; Sharif University of Technology

IEEE Microwave Theory and Techniques Society 2015

Abstract

Analytical expressions are given for zeroth-order diffraction efficiencies of metallic gratings with slanted and straight slit arrays at microwave and terahertz frequencies when the slit width is small enough to ensure that non-principal eigenmodes supported by the slit remain below cut-off. These expressions show that at lower normalized frequencies when the grating is zeroth order and all off-specular diffraction orders are evanescent, metallic slit arrays with slanted and straight walls could become identical to each other whenever certain relation is held between the geometrical parameters of the two structures. A noteworthy advantage of juxtaposing slanted and slit arrays is that it...

Homogenization of Sub-Wavelength Inhomogeneities for Analysis and Design of Terahertz Spoof Plasmonic Structures

, Ph.D. Dissertation Sharif University of Technology Edalatipour, Masoud (Author) ; Mehrany, Khashayar (Supervisor)

Abstract

In this thesis we investigate the use of periodic array of metallic structures which mimics the propagation of the surface plasmon-polaritons waves. The TEM modes supported by these structured surfaces are referred to as the spoof surface plasmon-polaritons. They have many properties in common with the electron plasma and can be described by a plasma-like effective permittivity, when the structure is on a scale much smaller than the wavelength. In this thesis we extend this concept to include different kinds of structured surfaces like cut through metallic slits array and square array of rectangular metallic pillars which support TEM modes. We show that although these structured surfaces...

Physics of broadband Brewster transmission through square array of rectangular metallic pillars

, Article Journal of the Optical Society of America B: Optical Physics ; Volume 32, Issue 6 , 2015 , Pages 1202-1207 ; 07403224 (ISSN) Edalatipour, M ; Khavasi, A ; Mehrany, K ; Sharif University of Technology

OSA - The Optical Society 2015

Abstract

The physics behind the broadband Brewster transmission through square arrays made of rectangular metallic pillars is explored by appealing to the effective medium theory. First, an analytical solution is given for the principal electromagnetic mode propagating between the pillars, and then, the mode matching technique is invoked to extract the parameters of the effective medium model. In this fashion, the pillars are homogenized via a diagonal anisotropic tensor and the effects of higher diffracted orders are included in the effective medium theory by attributing a surface conductivity to the surface boundary of the array. It is shown that the former effectuates the wideband Brewster effect...

Radiation properties enhancement of a GSM/WLAN microstrip antenna using a dual band circularly symmetric EBG substrate

, Article IEEE Transactions on Antennas and Propagation ; Volume 60, Issue 11 , 2012 , Pages 5491-5494 ; 0018926X (ISSN) Salarrahimi, M ; Rashed Mohassel, J ; Edalatipour, M ; Sharif University of Technology

2012

Abstract

This communication presents a dual band circular patch antenna with improved radiation properties at GSM and WLAN frequency bands, i.e., 1.8 and 2.4 GHz. The improvement has been achieved using a dual band circularly symmetric EBG (CS-EBG) structure. The structure has been simulated, fabricated and measured demonstrating notable enhancement in antenna radiation patterns at both frequency bands. Results show 5 dB and 7 dB improvement in front to back ratio at design frequencies of 1.8 GHz and 2.4 GHz respectively. In addition, measurement results demonstrate 0.8 dB increase in antenna gain and significant reduction in cross polarization level at both frequency bands

Miniaturized patch antenna using a circular spiral-based metamaterial

, Article Microwave and Optical Technology Letters ; Volume 59, Issue 9 , 2017 , Pages 2276-2279 ; 08952477 (ISSN) Kavousi, H ; Rashed Mohassel, J ; Edalatipour, M ; Sharif University of Technology

2017

Abstract

A miniaturized patch antenna is proposed and its radiation properties are experimentally investigated. A new metamaterial configuration based on circular spiral inclusion is used as the patch antenna substrate. The proposed antenna has not only a lighter profile but also a higher gain in comparison with its previously reported counterparts. It is shown that by using this new configuration a miniaturization factor of 3.1 can be realized. © 2017 Wiley Periodicals, Inc

Creation of artificial surface conductivity on metallic metamaterials

, Article Journal of Lightwave Technology ; Volume 30, Issue 12 , February , 2012 , Pages 1789-1794 ; 07338724 (ISSN) Edalatipour, M ; Khavasi, A ; Rezaei, M ; Mehrany, K ; Sharif University of Technology

2012

Abstract

Metal films with a periodic arrangement of cut-through slits are studied to show that artificial surface conductivity is created at the flat interface between the periodic slits and the cover/substrate. The presence of surface conductivity when the periodic structure is modeled by an effective refractive index can describe how non-specular higher diffracted orders affect the specular zeroth diffracted order. The magnitude of this surface conductivity is controlled geometrically. The artificial surface conductivity is pure imaginary and thus reactive if all non-specular orders are evanescent. This is usually the case in the low frequency regime. At higher working frequencies when some...

Optimum operation of single cavity photonic switches

, Article Proceedings of SPIE - The International Society for Optical Engineering, 25 January 2010 through 27 January 2010 ; Volume 7607 , January , 2010 ; 0277786X (ISSN) ; 9780819480033 (ISBN) Naqavi, A ; Monem Haghdoost, Z ; Edalatipour, M ; Khorasani, S ; Mehrany, K ; Sharif University of Technology

2010

Abstract

In this work, an optimum frequency is found for the operation of single cavity photonic switches. At this optimum point, the transmission contrast of ON and OFF states takes its highest value, while keeping the device power threshold relatively low and the device speed acceptably high. Then, the dynamic behavior of a typical single cavity all optical switch is investigated in the optimum operation point through temporal Coupled Mode Theory. Switching speed and power are discussed, and the device is shown to be applicable for telecommunication and data processing applications. The analysis is quite general, and can be used for resonant structures, such as photonic crystals and microring...

Long Term Effective Factors on House Price of Metropolises of Iran

, M.Sc. Thesis Sharif University of Technology Moeeni, Safoura (Author) ; Nili, Masoud (Supervisor)

Abstract

The notable share of housing sector in GDP (approximately five percent) shows this sector’s relation with macroeconomic activities. On the other hand, House as an asset leads housing sector to be affected by monetary and fiscal variables. A dynamic panel data was used in this study to evaluate the relations between housing sector and some macroeconomic variables in metropolises of Iran. As results show, in long term growth of liquidity, GDP per capita and sharp ratio have positive effects, and land per capita has negative effect on housing price in metropolises of Iran. Price increases have not been equal in different cities. Inequality of land price between metropolises and between...

Estimating an Index of Iran’s Informal Economy in 1350-1386 With Concentration on the Impact of Government’s Intervention by EMIMIC Model (The Multiple Indicators-Multiple Causes Model and Error-Correction Model)

, M.Sc. Thesis Sharif University of Technology Khandan, Abbas (Author) ; Nili, Masoud (Supervisor)

Abstract

In this research, an Index of Iran informal economy in response to the government interventions in credit, labor and product markets is stimated by EMIMIC model. To do this, first these interventions are measured using principal components analysis. In the model, the variables GDP and employment are used as indicators and taxation rates, government distortions in credit, labor and product markets, government expenditure, per capita income, unemployment and inflation as causes of the informal economy. We conclude these government interventions have affected Iran informal economy and their influence is more than indirect interventions influence such as taxation. The estimated index of Iran...

Water Quality Modeling of Urban Streams

, M.Sc. Thesis Sharif University of Technology Soltani, Maryam (Author) ; Tajrishy, Masoud (Supervisor)

Abstract

With altering natural state and increasing impervious surfaces, traditional urbanization leads to deteriorating the environment and water catchments. During the years most efforts in order to control the urban runoff outflow, have been focused on quantity; and awareness about improving water quality has been raised just in the last few years and, which emphasizes on pollution source control. Standard water quality sampling methods are time consuming, expensive and because of sampling in broad geographic areas, difficult; however modeling is a more efficient way in assessing water quality and as worries about non-point source pollution grows, different kinds of models have been used to...

The Political Economy Aspects of the Redistributive Role of Government in a General Equilibrium Micro-founded Macro Model

, M.Sc. Thesis Sharif University of Technology Zakeri, Hassan (Author) ; Nili, Masoud (Supervisor)

Abstract

The role of government in economy has been a controversial subject in economics. Lately, there has been some fundamental change in evaluating this subject. One could mention two of these as 1) realizing the importance of micro-founded macro model for evaluating policy, and 2) taking into consideration the rent-seeking behavior of politicians. In this research, a general equilibrium in a micro-founded macro model will be discussed and then in political economics framework, the effect of government on this equilibrium will be investigated. Only the redistribution role of government has been considered. First, the model in which a benevolent government is seeking optimal policy is Discussed....

Measurement of Gini Coefficients by Means of Household’s Special CPI in Iran(1984-2005)

, M.Sc. Thesis Sharif University of Technology Ghasemi, Mojtaba (Author) ; Nili, Masoud (Supervisor)

Abstract

Gini coefficient is the most prevalent index for the measurement of inequality and is usually extracted by means of nominal variables based on income or expenditures of households. In this study we have extracted more accurate Gini coefficients. By using the raw data of Households Budget Survey (HBS) and STATA software, a special CPI for each household of the sample is extracted. Subsequently nominal expenditures are deflated by these special CPIs, and at last, Gini coefficients are extracted from real expenditures. Our findings indicate that in recent years, extracted Gini coefficients are remarkably higher than prevailing ones.

Parametric Evaluation of the Y- Shaped Bracing Frame and Introducing a New Method for Design

, M.Sc. Thesis Sharif University of Technology Sedaghati, Parshan (Author) ; Mofid, Masoud (Supervisor)

Abstract

This paper investigates the behavior of the Y-shaped bracing system. Because of the special type of eccentricity in this system, the behavior of the frame is strongly dependent on the geometrical changes of the braces. So that even in the elastic region, it shows the geometrically nonlinear behavior. The amount of eccentricity is very effective on the nonlinear behavior of the frame. Also the ratio of cross sections of the bracing members has a very important impact on the expected performance of the frame. The results show that this system tolerates large displacements, and can act like a base isolation system. Firstly, using a two-dimensional accurate modeling related to the geometrical...

Assessment of Seismic Behavior Factor of Irregular Midrise Steel Structure

, M.Sc. Thesis Sharif University of Technology Baghi, Alireza (Author) ; Mofid, Masoud (Supervisor)

Abstract

The Overstrength, Ductility and the Response Modification Factor (R) for 70 steel X-braced , Inverted-V-Braced and Offcenter Bracing System frames were evaluated by performing pushover analysis of model structure with various stories (3,6,9,12&15 story) and span length (4,6&8 meter). Some result were compared with those from nonlinear dynamic analysis. According to the analysis result the R factors obtained from nonlinear dynamic analysis are 15% more than obtained from pushover analysis and R factors computed from pushover analysis were generally smaller than the values given in the design codes. R factors in Irregular structure in height are about 90% of R values in regular structure in...

Synthesis of γ-Fe2O3 Nanoparticles by Gelatin Mediator and Synthesis of γ-Fe2O3/SiO2/PCA/Ag-NPs Nanostructure Drug Delivery System

, M.Sc. Thesis Sharif University of Technology Masoud, Nazila (Author) ; Pourjavadi, Ali (Supervisor)

Abstract

Maghemite (γ-Fe2O3) nanoparticles were produced after high temperature oxidation of gelatin-Fe3O4 nanocomposite, obtained from a common coprecipitation process of Fe2+ and Fe3+ ions in an alkaline medium in the presence of a gelatin protein as an effective mediator. Size, shape, surface morphology and magnetic properties of the prepared γ-Fe2O3 nanoparticles were characterized using XRD, FTIR, TEM, SEM and VSM data. The results revealed that primary, gelatin-Fe3O4 nanocomposite had been formed and next, the gelatin decomposition in furnace produced a spinel structure of γ-Fe2O3. The effects of furnace temperature and time of heating together with the amount of gelatin on the produced...

On The Behavior of Low-Rise, Irregular, Dual Structures

, M.Sc. Thesis Sharif University of Technology Khazaei, Siamak (Author) ; Mofid, Masoud (Supervisor)

Abstract

The Response modification factor R represents the behavior of the structure such as ductility, overstrength and the inherent redundancy. This factor shall be defined according to the type of lateral force resisting system. However, there are some complexities and/or uncertainties in codes related to the R factor according to the height, form of irregularities and structural systems. Therefore, from the scientific point of view as well as reliability, it is very clear that the R factor cannot be similar for all kinds of structures, categorized as a specific group. In this investigation, assuming a low-rise, vertically irregular structure with a heliport which has a dual structural system...

Modeling Phosphorous Movement in Watersheds with SWAT (Case Study: Kan Watershed)

, M.Sc. Thesis Sharif University of Technology Delkash, Majid (Author) ; Tajrishy, Masoud (Supervisor)

Abstract

Maintaining the quality of water is of paramount importance for lakes with tourist attraction capacity. Inaccurate prediction of the quality state of lake in design phase may lead to some trouble in future. Kan River known as the main source of water feeding for the urban lake located in the north of Chitgar park passes through various villages and restaurants discharging nutrients via runoff and wastewater in the aforementioned river. Previous investigations reveal that phosphorous plays a central role in the water quality of this river and the associated downstream lake. In this research, Kan watershed,located in in the north-west of Tehran, was simulated. Considering the "Total Maximum...

The Role of Socio-Political Institutions in Economic Performance of Developing Countries

, M.Sc. Thesis Sharif University of Technology Mollaei, Yaser (Author) ; Nili, Masoud (Supervisor)

Abstract

Findings of economics in last decade shows that social and economic institutions have direct influence on economic performance of a society. However, these institutions are determined by the state. In different regimes, the political power is in the hand of different social groups with different preferences and goals; as a result, different social and economic policies and institutions are take place in different political regimes. In this research, we study economic performance of a society under control of two different political regimes: in first, the majority rules the state and in second, there is a totalitarian regime in which; the political power is concentrated in hand of a group of...

Exploring Economic Performance of Resource-Rich Countries by Separating their Political Systems

, M.Sc. Thesis Sharif University of Technology Jahandideh, Mahsa (Author) ; Nili, Masoud (Supervisor)

Abstract

Economic performance of resource rich countries is related to their political systems. In this research, consistent to Hosseini (1388), we develop a theoretical model in which we classify the political systems of those countries to four systems based on corruption, myopic behavior of the incumbent, ideological bias of people, and the popularity shocks in elections. We show that in a fixed institutional framework, democracy leads to higher welfare for people and better economic performance. However, in a society with low corruption, high political convergence, and low popularity shocks both democracy and dictatorship maximize the social welfare in the model

Aerodynamic Improvement of Cooling Systems for a Thermal Power Plant Using CFD

, M.Sc. Thesis Sharif University of Technology Salemkar, Hossein (Author) ; Darbandi, Masoud (Supervisor)

Abstract

This research considers the wind effects on the thermal deficiency of natural draught dry cooling tower (NDDCT) using the CFD tool. To have a realistic study, the NDDCT of Shazand Powerplant, located in Shazand, Iran, is simulated as the sample cooling tower design points. Considering of Shazand NDDCT model, the mal-effects of local wind were studied against its thermal efficiency. As is known, the thermal efficiency of a NDDCT can be affected by local wind in either its upper (i.e., outlet section) or lower (i.e., the radiator section) parts. In this study, a full study is performed to quantify the mal-effects of local wind on either upper or lower parts of one tower. The results show that...