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    A novel dual-band transmission line with equal-phase responses

    , Article IEEE Transactions on Microwave Theory and Techniques ; Volume 69, Issue 2 , 2021 , Pages 1265-1272 ; 00189480 (ISSN) Rezvani Pakdeh, M ; Tajik, A ; Fakharzadeh, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    This article presents a novel dual-band transmission line (TL), consisting of a multibranch stub, which can provide equal unwrapped phases at two different frequencies. The frequency ratio can be close to one without any significant degradation in the device performance. Besides, the bandwidth of the proposed line can be manipulated at both frequencies by adjusting the design parameters. The behavior of the structure over the frequency bands is investigated theoretically, and the design procedure and relations are derived. The simulation and measurement results of a quarter-wavelength open-ended stub and a branch-line coupler (BLC) are presented and compared to verify the performance of the... 

    RS-Satellites propulsion subsystem performance sizing via design plane technique, a generic method

    , Article IEEE Aerospace and Electronic Systems Magazine ; Volume 36, Issue 2 , 2021 , Pages 56-70 ; 08858985 (ISSN) Ahmadi, A ; Kosari, A ; Malaek, S. M. B ; Khoshsima, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Remote sensing satellites propulsion subsystem preliminary design based on performance sizing is discussed. The process is a fairly complicated one considering a variety of operational as well as performance requirements. This research aims to reduce the number of iterations required by the current practice to reach a compromise. It is based on a rapid-sizing method that helps lessen lengthy iteration cycles. The proposed technique, similar to such class of preliminary design processes, leads to an acceptable approximation that must be properly conveyed to other disciplines involved for further elaborations. With proper selection of design and performance parameters together with fundamental... 

    RS-Satellites propulsion subsystem performance sizing via design plane technique, a generic method

    , Article IEEE Aerospace and Electronic Systems Magazine ; Volume 36, Issue 2 , 2021 , Pages 56-70 ; 08858985 (ISSN) Ahmadi, A ; Kosari, A ; Malaek, S. M. B ; Khoshsima, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    Remote sensing satellites propulsion subsystem preliminary design based on performance sizing is discussed. The process is a fairly complicated one considering a variety of operational as well as performance requirements. This research aims to reduce the number of iterations required by the current practice to reach a compromise. It is based on a rapid-sizing method that helps lessen lengthy iteration cycles. The proposed technique, similar to such class of preliminary design processes, leads to an acceptable approximation that must be properly conveyed to other disciplines involved for further elaborations. With proper selection of design and performance parameters together with fundamental... 

    Structured design of integrated subscriber line interface system and circuit

    , Article Analog Integrated Circuits and Signal Processing ; Volume 45, Issue 1 , 2005 , Pages 47-59 ; 09251030 (ISSN) Tajalli, A ; Atarodi, M ; Sharif University of Technology
    2005
    Abstract
    A structured design of Subscriber Line Interface System and Circuit will be described. A high level synthesis allows extracting overall system and circuit requirements to satisfy the desired specifications, standards, and a robust implementation. For this purpose, first the output driving stage will be analyzed and then, dc, ac, and longitudinal balance feedbacks will be considered. Then based on extracted system specifications, optimum circuit design of line-driver will be described. High-level design of line-driver as the most important circuit block which is optimized for stability, accuracy, area, and power dissipation will be elaborated. © 2005 Springer Science + Business Media, Inc  

    Optimum seismic design of concentrically braced steel frames: Concepts and design procedures

    , Article Journal of Constructional Steel Research ; Volume 61, Issue 2 , 2005 , Pages 151-166 ; 0143974X (ISSN) Moghaddam, H ; Hajirasouliha, I ; Doostan, A ; Sharif University of Technology
    Elsevier BV  2005
    Abstract
    A methodology is presented for optimization of the dynamic response of concentrically braced steel frames subjected to seismic excitation, based on the concept of uniform distribution of deformation. In order to obtain the optimum distribution of structural properties, an iterative optimization procedure has been adopted. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that the seismic performance of such a structure is optimal, and behaves generally better than those designed by conventional methods. In... 

    Computational inverse design for cascaded systems of metasurface optics: comment

    , Article Optics Express ; Volume 30, Issue 20 , 2022 , Pages 36966-37005 ; 10944087 (ISSN) Zarei, S ; Khavasi, A ; Sharif University of Technology
    Optica Publishing Group (formerly OSA)  2022
    Abstract
    In a recently published article by Backer [Opt. Express 27(21), 30308 (2019).], a computational inverse design method is developed for designing optical systems composed of multiple metasurfaces. The forward propagation model used in this method was a discretized version of the angular spectrum propagator described by Goodman [Introduction to Fourier Optics, 1996]. However, slight modifications are necessary to increase the accuracy of this inverse design method. This comment examines the accuracy of the results obtained by the above-mentioned method by a full-wave electromagnetic solver and explains the reason of their difference. Thereafter, slight modifications to the method proposed by... 

    Direct Displacement Based Design of Steel Moment Resisting Frames and Comparison of Use in Building Codes

    , M.Sc. Thesis Sharif University of Technology Chegini, Narges (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    Recent research in the field of earthquake engineering has seen the development of a number of different displacement-based seismic design (DBD) methods. Such methods aim to overcome limitations with the force-based design methods incorporated in current codes, and the most developed DBD method currently available is the Direct DBD approach, presented by Priestley. The objective of this work is to investigate the performance of the Direct DBD design procedure for steel moment-resisting frame structures. For this purpose, a series of regular steel MRF frames, varying from 4 to 20 stories in height are designed based on DDBD approach and utilizing displacement design spectrum of the Iranian... 

    Investigation of the Effect of Asphaltene on the Stability of Water-oil Emulsion

    , M.Sc. Thesis Sharif University of Technology Hosseini, Amir (Author) ; Taghikhani, Vahid (Supervisor) ; Baghban Salehi, Mahsa (Supervisor) ; Masihi, Mohsen (Supervisor)
    Abstract
    During the production of crude oil from reservoirs, the production of quantities of formation water along with this oil, causes the crude oil does not have the necessary indicators for transportation, refining and ultimately export. The presence of water and salt along with crude oil causes corrosion of refinery and transmission equipment and makes oil unfavorable in terms of economic efficiency (both for domestic use and for export). water and salt produce stable emulsion with oil that can be stable for a long time and can not be easily separated from crude oil. Therefore, separation of water and salt from crude oil is one of the most important issues in the oil industry. Breaking this... 

    Graph homomorphisms and nodal domains [electronic resource]

    , Article Linear Algebra and its Applications ; 2006, Volume 418, Issue 1, Pages 44–52 Daneshgar, A. (Amir) ; Sharif University of Technology
    Abstract
    In this paper, we derive some necessary spectral conditions for the existence of graph homomorphisms in which we also consider some parameters related to the corresponding eigenspaces such as nodal domains. In this approach, we consider the combinatorial Laplacian and co-Laplacian as well as the adjacency matrix. Also, we present some applications in graph decompositions where we prove a general version of Fisher’s inequality for G-designs  

    An efficient tabu search algorithm for the single row facility location problem [electronic resource]

    , Article European Journal Of Operational Research ; Vol. 205, No. 1, pp. 98-105 Samarghandi, H. (Hamed) ; Eshghi, Kourosh ; Sharif University of Technology
    Abstract
    The general goal of the facility layout problem is to arrange a given number of facilities to minimize the total cost associated with the known or projected interactions between them. One of the special classes of the facility layout problem is the Single Row Facility Layout Problem (SRFLP), which consists of finding an optimal linear placement of rectangular facilities with varying dimensions on a straight line. This paper first presents and proves a theorem to find the optimal solution of a special case of SRFLP. The results obtained by this theorem prove to be very useful in reducing the computational efforts when a new algorithm based on tabu search for the SRFLP is proposed in this... 

    Optimization of operating conditions in ultrafiltration process for produced water treatment via Taguchi methodology

    , Article Desalination and Water Treatment ; Volume 54, Issue 10 , June , 2015 ; ISSN: 19443994 Reyhani, A ; Sepehrinia, K ; Seyed Shahabadi, S. M ; Rekabdar, F ; Gheshlaghi, A ; Sharif University of Technology
    Abstract
    This paper describes how to find optimal operating conditions of three controlling parameters, i.e. temperature, transmembrane pressure (TMP), and cross-flow velocity (CFV) for maximizing the permeate flux and total organic carbons (TOC) rejection, and minimizing the fouling resistance using Taguchi method in ultrafiltration (UF) treatment of the real produced water. At first, the optimal operating conditions were found at a temperature of 45°C, TMP = 4 bar, and CFV of 2.25 m/s. To determine the most significant parameters affecting the response parameters, an analysis of variance was employed. In the second stage, performance of applied polymeric membrane in the UF system was studied under... 

    Minimum power Miller-compensated CMOS operational amplifiers

    , Article Scientia Iranica ; Vol. 21, Issue. 6 , 2014 , pp. 2243-2249 ; e-ISSN :23453605 Meghdadi, M ; Bakhtiar, M. S ; Sharif University of Technology
    Abstract
    A new approach for the design of two-stage Miller-compensated CMOS op amps is presented. The paper studies the basic relations between power consumption, unitygain bandwidth, the biasing region, technology parameters, and the external capacitive load. As a result, simple and efficient design guides are provided to achieve the minimum possible power consumption for the given specifications and for short-channel devices. It is shown that the conventional design procedures do not always result in minimum power op amps. The presented results are also verified by Spectre simulations  

    Performance calculations within the conceptual design process of hand-launched aircraft

    , Article Applied Mechanics and Materials ; Vol. 629, issue , October , 2014 , p. 145-151 Nadji, M ; Banazadeh, A ; Sharif University of Technology
    Abstract
    Matching diagram is a key part of the conceptual design process to determine the wing area and the required power. However, it requires drag polar estimation and the assumption of maximum lift coefficient. In case of conventional manned aircraft, early estimation techniques are based on statistical data that are not suitable for hand-launched aircraft. In this study, it has been attempted to present the performance calculations and a proper conceptual design model by acquiring sound values for the aerodynamic coefficients in low Reynolds number, using statistical wetted area as well as a raw design of fuselage, wing and tails. The process is applied to a sample scenario and the results are... 

    Hybrid orthogonal-phased array MIMO RADAR

    , Article IET Conference Publications ; Volume 2013, Issue 617 CP , 2013 ; 9781849196031 (ISBN) Roshanzamir, A. S ; Bastani, M. H ; Sharif University of Technology
    2013
    Abstract
    Multiple Input Multiple Output (MIMO) radar is a multiple aperture technology characterized by the ability to transmit diverse signals at each aperture. This is in contrast to traditional phased array radar whereby a single signals is transmitted with a phase shift applied at each element to enable steering of the transmit beampattern. The hybrid MIMO phased array radar (HMPAR) concept is an outgrowth of the monostatic MIMO construct, in which all sensors have the same view of the far field target which is known as colocated antenna. In the HMPAR, the full transmit array is partitioned into sub-arrays which can be electronically steered in different directions and driven by separate transmit... 

    Application of a new rapid transit network design model to bus rapid transit network design: Case study Isfahan metropolitan area

    , Article Transport ; Volume 30, Issue 1 , Oct , 2013 , pages 93-102 ; 16484142 (ISSN) Kermanshahi, S ; Shafahi, Y ; Bagherian, M ; Sharif University of Technology
    2013
    Abstract
    The problem of Rapid Transit Network Design (RTND) is studied in this paper. Due to the noticeable contribution of rapid transit lines in public transportation network of large urban areas, this problem is interesting to the transportation specialists. On the other hand, the success stories of Bus Rapid Transit (BRT) systems in different countries have motivated us to study BRT network planning. BRT systems can be developed with less investment costs and construction time in comparison with rail-based systems. Therefore, planning Bus Rapid Transit lines, either to develop a new rapid transit network or extend a current one can be an interesting research topic. This problem, like other... 

    Experiments design for hardness optimization of the Ni-Cr alloy electrodeposited by pulse plating

    , Article Acta Metallurgica Sinica (English Letters) ; Volume 26, Issue 5 , 2013 , Pages 558-564 ; 10067191 (ISSN) Imanieh, I ; Yousefi, E ; Dolati, A ; Mohammadi, M. R ; Sharif University of Technology
    2013
    Abstract
    The hardness of the Ni-Cr alloy which is electrodeposited in chloride solution, is optimized by design of experiment method (central composite design). Various parameters were evaluated in order to find significant factors in this process. Frequency, duty cycle, current density and temperature were selected as effective factors. Analyses of variance (ANOVA) were performed on the results of the designed experiments. The best model which can predict the hardness of the Ni-Cr alloy electrodeposits was found whereas the frequency and quadratic behaviour of the current density were the most significant model terms. Serious interaction of the current density with frequency and duty cycle also were... 

    Subsonic and transonic airfoil inverse design via Ball-Spine Algorithm

    , Article Computers and Fluids ; Volume 84 , 2013 , Pages 87-96 ; 00457930 (ISSN) Nili Ahmadabadi, M ; Ghadak, F ; Mohammadi, M ; Sharif University of Technology
    2013
    Abstract
    Inverse design in external flow regimes usually involves finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this research, a novel iterative inverse design method is developed for inviscid subsonic and transonic external flow regimes. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a 2D inviscid analysis code. The Euler equations are solved for a physical domain of which some unknown boundaries are iteratively modified via BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called... 

    Design methodology and preliminary sizing of an unmanned mars exploration plane (UMEP)

    , Article APPLIED MECHANICS AND MATERIALS; 332; 15; Biomechanics, neurorehabilitation, mechanical engineering, manufacturing systems, robotics and aerospace: optimization of the engineering systems; OPTIROB 2013 ; Volume 332 , 2013 , Pages 15-20 ; 16609336 (ISSN) ; 9783037857335 (ISBN) Behroo, M ; Banazadeh, A ; Golkhandan, A. R ; Sharif University of Technology
    2013
    Abstract
    This paper discusses the mission requirements and design constraints for an Unmanned Martian research aircraft based on a tailor-made classical airplane design methodology. First, the exploration mission is described using the information from previous real-world experiences and the desired payload is proposed accordingly. The environmental conditions that dictate severe constraints to the design space are characterized afterwards. The conventional airplane design cycle is modified to address the lack of statistical data and to define a proper design recycling criteria. Eventually, the outcome is presented in the form of a novel configuration that is well suited to carry out the specified... 

    Estimation of current-induced pile groups scour using a rule-based method

    , Article Journal of Hydroinformatics ; Volume 15, Issue 2 , September , 2013 , Pages 516-528 ; 14647141 (ISSN) Ghaemi, N ; Etemad-Shahidi, A ; Ataie-Ashtiani, B ; Sharif University of Technology
    2013
    Abstract
    Scour phenomenon around piles could endanger the stability of the structures placed on them. Therefore, an accurate estimation of the scour depth around piles is very important for engineers. Due to the complexity of the interaction between the current, seabed and pile group; prediction of the scour depth is a difficult task and the available empirical formulas have limited accuracy. Recently, soft computing methods such as artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) have been used for the prediction of the scour depth. However, these methods do not give enough insight into the generated models and are not as easy to use as the empirical formulas. In... 

    Analytical modeling of performance characteristics of axial flow two-stage turbine engine using pressure losses models and comparing with experimental results

    , Article World Applied Sciences Journal ; Volume 21, Issue 9 , February , 2013 , Pages 1250-1259 ; 18184952 (ISSN) Jouybari, J ; Eftari, M ; Kaliji, H. D ; Ghadak, F ; Rad, M ; Sharif University of Technology
    2013
    Abstract
    The main objective of this paper is to make a detailed systematic analysis of two-stage, axial flow turbine by using of different losses models and a new suggested algorithm based on one-dimensional simulation. The suggested method is found to be effective, fast and stable, in obtaining performance characteristics of multi-stage axial flow turbines. In one-dimensional modeling, mass flow rate, pressure ratio and efficiency are unknown, with define turbine geometry, inlet total pressure and temperature the turbine performance characteristics can be modeled. This modeling is based on common thermodynamics and aerodynamics principles in a mean stream line analysis under steady state condition....