Search for: design
Total 2918 records
Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 36, Issue 3 PART 1 , 2000 , Pages 889-897 ; 00189251 (ISSN) ; Mohammad, K ; Bastani, H ; Sharif University of Technology
A new constant false alarm rate (CFAR) processor is presented, that exhibits a noticeable detection performance in the presence of interfering targets, as well as an excellent false alarm rate (FAR) regulation at the clutter power transition regions. The presented CFAR processor, which is designed to work on the logarithmic amplified video signals, can also easily adapt itself to new environmental conditions. Furthermore, in the steady state, its performance does not depend on the background noise power. Simulation results show the obvious preference of the presented processor to the conventional GOCA-LOG/CFAR, regarding FAR regulation at the clutter power transition regions. Noncoherent...
Bayesian reliability-based robust design optimization of mechanical systems under both aleatory and epistemic uncertainties, Article Engineering Optimization ; 2022 ; 0305215X (ISSN) ; Khodaygan, S ; Ghaderi, A ; Sharif University of Technology
Taylor and Francis Ltd 2022
Uncertainties can be divided into two general categories: aleatory and epistemic. Conventional reliability-based robust design optimization approaches, which disregard epistemic uncertainties due to lack of knowledge about the physical nature of systems, have previously been developed. To overcome this weakness, unlike previous methods, a Bayesian reliability-based robust design optimization method is proposed in the presence of both aleatory and epistemic uncertainties. The proposed formulation is presented as a multi-objective optimization problem. The univariate dimension reduction method is used to approximate the mean and variance of the design function. The non-dominated sorting...
Article Robotics and Computer-Integrated Manufacturing ; Vol. 27, Issue 2 , April , 2011 , Pages 357-366 ; ISSN: 07365845 ; Behzadipour, S ; Alasty, A ; Sadough Vanini, S. A ; Sharif University of Technology
The design of a new cable-driven robot for large-scale manipulation is presented with focus on the tension condition in the cables. In this robot, the arrangement of the cables is such that the moving platform has three translational motions. The robot has potentials for large-scale robotic manipulations, machining of large parts and material handling. The design analysis presented here is towards the synthesis of the robot as well as the sizing of the actuators and cables. The synthesis of this robot is dependent on the results of the tensionable workspace analysis previously published by the Alikhani et al. . The analysis of the cable forces is presented in detail, which is then used to...
Article Aerospace Science and Technology ; Volume 26, Issue 1 , 2013 , Pages 244-258 ; 12709638 (ISSN) ; Malaek, M. B. S ; Ashrafizaadeh, M ; Taheri, M. S ; Sharif University of Technology
In this work we show how Artificial Intelligence (AI) could effectively be used to expedite the decision making process in the early stages of the aircraft design process. We employ both Fuzzy Logic (FL) and Neural Network (NN) as two different schemes of the AI. The developed tools are intended to help to select the proper combination of engine thrust, wing area and the aircraft weight without going through elaborate details of other direct approaches. We further show how the AI could be applied to the specific class of light business jets which serves to validate these schemes. The results indicate the effectiveness of the AI approach in the preliminary aircraft design process. The actual...
Article International Journal of Structural Stability and Dynamics ; Volume 12, Issue 3 , 2012 ; 02194554 (ISSN) ; Salehipoor, H ; Sharif University of Technology
This paper deals with the optimum design of vibration absorbers utilized to reduce undesirable random vibrational effects that are originated in linear structures. Analytical expressions, for the case of nonstationary white-noise accelerations, are derived. The criterion is different from most conventional optimum design criteria, since it is based on minimizing the displacement or the acceleration variance of the main structure responses, without considering performances required against failure. In this study, in order to control the structural vibrations induced on a mechanical structure excited by nonstationary based acceleration random process, the MOO (multi-objective optimum) design...
Article IEEE Communications Letters ; Volume 19, Issue 1 , November , 2015 , Pages 50-53 ; 10897798 (ISSN) ; Mashhadi, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2015
This letter investigates the deterministic design of pilot power and pattern for sparse channel estimation in OFDM systems based on minimizing the coherence of the DFT sub-matrix. It has been suggested that the pilot pattern forming a cyclic difference set (CDS) or almost difference set (ADS) is optimal. So, we proposed a deterministic procedure that jointly optimized for pattern and power of pilots as a solution. First, pilot patterns forming CDS/ADS were gathered through a search. Then, the power was numerically allocated to the different pilots from all the patterns. Finally, the pilot pattern and power pair leading to minimum coherence was selected from the available pairs. Simulation...
Article Procedia CIRP, 16 September 2015 through 18 September 2015 ; Volume 34 , 2015 , Pages 236-243 ; 22128271 (ISSN) ; Abedian, A ; Giorgetti, A ; Citti, P ; Suh, N. P ; Matt, D ; Kathryn, M ; Sharif University of Technology
When cracks along rivet holes and other highly stressed regions of mostly aged aircrafts are found, usually repairs are being made to arrest these cracks. Patches provide an innovative repair technique, which can enhance the way aircrafts are maintained. Composite patch design along with axiomatic design technique deployment is a possibility. Axiomatic Design (AD) is expressed as a system design methodology that is applicable to creation of a new design, analysis and improvement of an existing design. While, here Patch Design system architecture is expressed as application of principles of axiomatic design on top level requirements with consideration of design parameters and constraints. A...
A statistical solution to mitigate functional requirements coupling generated from process (manufacturing) variables integration-part 2: a case study on clarifying the effect of process (manufacturing) variables integration on functional requirements independency, Article Procedia CIRP, 16 September 2015 through 18 September 2015 ; Volume 34 , September , 2015 , Pages 76-80 ; 22128271 (ISSN) ; Houshmand, M ; Sharif University of Technology
In this part of the work, to illustrate the strength of the "partial and semipartial correlation analysis, as the proposed solution described in detail in part 1, we consider design problem of the manufacturing system of a given product based on a set of hypothetical data and show how to explore the most appropriate integration choices in which the (causal) dependencies of the concerned PVs are minimal. Based on the results of this study, we emphasize that incorporating the identified sensitive PVs into the integration process will eventually lead to coupling among a subset of the product's FRs and isolation of these PVs is recommended as an ideal solution. However, sometimes, in the real...
Article Structural and Multidisciplinary Optimization ; Volume 39, Issue 5 , 2009 , Pages 519-530 ; 1615147X (ISSN) ; Davami, P ; Sharif University of Technology
The optimal feeder design in gravity casting processes is considered. The design problem is formulated as an additive, growth-like, evolutionary topology optimization problem. The initial design of the presented method is a casting part which is placed in a suitable environmental mould box. The method is composed of three stages: determining the feeder-neck connection point on the casting surface, constructing the feeder-neck and the feeder growth. During the growth stage, the feeder topology is changed gradually until satisfying some predefined criteria. The design of multiple feeders is also considered in this work. In the presented method, feeders are designed in a descending order of...
Using Axiomatic Design Approach and Conventional Methods to Optimize Process Planning of Cylindrical Parts in ServoHydraulic Pouya Co, M.Sc. Thesis Sharif University of Technology ; Houshmang, Mahmoud
Decision making is one of the most critical issues in engineering field. The Axiomatic Design is recently known as one of the most robust tools for decision making task. Axiomatic design is a engineering theory that provides a systematic framework for decision making using two axioms. These two axioms called Independence and Information axioms are both used to do the task.In this thesis, the information axiom is used to select the best machine (operation) for manufacturing cylindrical parts. To do that, three criteria including surface roughness, dimensional accuracy and cost have been chosen.Finally a comparison to the result of this methodology and the result of Analytical Hierarchy...
M.Sc. Thesis Sharif University of Technology ; Abedian, Ali
When today’s aircrafts reach the end of their service lifes, fatigue cracks are found to have developed along rivet holes and other highly stressed regions of the aircraft. In order to extend life of these aircrafts, repairs have been made to arrest these cracks. Composite repair patches provide an innovative repair technique, which can enhance the way aircrafts are maintained. In this thesis, composite patch design is presented based on axiomatic design technique. Axiomatic design is investigated design methodology for large or complex system design. Tools to enable successful application of axiomatic design are expressed as axioms and process for axiomatic system design. The patch design...
One Dimensional Numerical Simulation of Gas Exchange and Combustion Processes in a Port Fuel Injected Gasoline Engine to Optimize Intake Valve Lift, Timing, and Duration, M.Sc. Thesis Sharif University of Technology ; Hosseini, Vahid ; Mozaffari, Ali Asghar
In the modern world, one of the largest concerns is the ever depleting supply of oil. The automotive industry is especially impacted. In recent years the price of gasoline has fluctuated substantially and the price of crude oil has reached record highs. The high price of gasoline coupled with the uncertainty of its availability and future price have put a high priority on fuel economy of an engine. In addition the emissions released from internal combustion (IC) engines are polluting the atmosphere. Many studies have linked the greenhouse gases produced by an automobile engine to the partial destruction of our atmosphere and to global warming. As a result the US government is passing...
M.Sc. Thesis Sharif University of Technology ; Khodaygan, Saeed
A mechanical system inherently affected by the conditions, factors and parameters of uncertainty. Without including the uncertainty effects in the optimal design procedure, the mechanical system will not be reliable. To include uncertainty effects in an optimum design, there are two different approaches; the robust design optimization and the reliability based design optimization. In robust design optimization process, the main aim is to enhance the system performance by minimizing the variations. In reliability based design optimization process, the target is that the optimal design variables to be in appropriate reliably levels. In this paper, a new model for the reliability based robust...
Article Microwave and Optical Technology Letters ; Vol. 56, issue. 9 , JUN , 2014 , pp. 1997-2001 ; ISSN: 08952477 ; Sharif University of Technology
Operation of two different optical fiber sensor designs for distance measurements with a good sensitivity, resolution, and wide dynamic range is reported. Design is based on the intensity modulation due to reflectance measurement from a target surface. Two reported designs are fabricated with a triple-fiber assembly, in which one uses a double-transmitter, while another one uses a double-receiver fiber design. Reflection signals from different targets are tested with these sensors and results for the mirror and A4 paper surfaces are described. The response curve for both experiments starts from a near zero level, shows a maximum at a certain distance and gradually drops to the background...
Article Proceedings of the ASME Turbo Expo, San Antonio, Tx ; Volume 6 C , 2013 ; ISBN: 9780791855249 ; Hajilouybenisi, A ; Mojaddam, M ; Sharif University of Technology
In this research an analytical model for performance prediction of centrifugal compressors is developed. The loss mechanisms are investigated in impeller, diffuser and volute separately for wide operating rotational speeds of the compressor. The contributions of compressor components in total entropy generation are further studied using different experimental correlations and methods. The results are verified using experimental test results, carried out at Sharif University of technology Turbocharger laboratory which has been designed to derive performance curves of turbocharger compressors. The test rig is equipped to measure static and stagnation pressures at inlet and outlet of each...
Article ASME 2012 Gas Turbine India Conference, GTINDIA 2012, 1 December 2012 through 1 December 2012 ; December , 2012 , Pages 265-270 ; 9780791845165 (ISBN) ; Parizi, P. N ; Taheri, R ; Sharif University of Technology
Because of their high performance and unique abilities like producing none-rotating wake, Counter Rotating Propellers (C.R.P.) are being used in many advanced propulsion or ventilation systems. But due to complicated design procedure of C.R.P. fans up to now it was not possible to apply the concept in reversible systems. For the first time in this research, a new method presented to design a reversible counter rotating propeller system. This method is based on designing a basic C.R.P. by a reliable edition of blade element theory to achieve maximum performance in main rotating course and then to optimize it in order to have almost same performance in reverse rotating course. After expressing...
Article Procedia Engineering ; Volume 14 , 2011 , Pages 3237-3244 ; 18777058 (ISSN) ; Estekanchi, H. E ; Seyedain Boroujeni, S ; Sharif University of Technology
In Endurance Time (ET) method gradually intensifying acceleration functions are created in a manner that the linear and nonlinear response spectra of them, while being proportional to average of real earthquakes spectra, intensifies in a uniform manner with time. These functions are used as input functions for nonlinear time history analysis of structures and performance of structures is assessed based on the maximum time duration that they can meet the specified performance objectives. In this paper, application of the ET method in nonlinear seismic analysis of structures has been investigated. Numerical procedures and optimization techniques that are used for the production of acceleration...
Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 229, Issue 6 , July , 2015 , Pages 993-1002 ; 09544100 (ISSN) ; Hajilouy Benisi, A ; Movahhedy, M. R ; Sharif University of Technology
SAGE Publications Ltd 2015
In this research, design methods of radial flow compressor volutes are reviewed; the main criteria in volute primary designs are recognized and the most effective ones are selected. The effective parameters, i.e., spiral cross-section area, circumferential area distribution, exit cone, and tongue area of the compressor volute are parametrically studied to identify the optimum values. A numerical model has been prepared and verified through experimental data which are obtained from the designed turbocharger test rig. Different volutes are modeled and numerically evaluated using the same impeller and vane-less diffuser. For each model, the volute total pressure ratio, static pressure recovery...
Article 19th International Conference on Microelectronics, ICM, Cairo, 29 December 2007 through 31 December 2007 ; 2007 , Pages 137-140 ; 9781424418473 (ISBN) ; Babagoli, M ; Hessabi, S ; Sharif University of Technology
In this paper, an infrastructure for debug of complex SoCs that employs assertions is introduced. The proposed infrastructure combines traditional off-chip analysis techniques with on-chip at-speed debug facilities. The main part of on-chip debug hardware consists of data and transaction monitors. The monitor hardware is automatically generated by synthesizing the assertions that were used for verification and validation before manufacturing. We have integrated the proposed method in a system-level design methodology. By synthesizing various assertions from different kinds in a case study we have studied the overhead of our method. © 2007 IEEE
Article Proceedings - 2006 International Conference on Design and Test of Integrated Systems in Nanoscale Technology, IEEE DTIS 2006 ; 2006 , Pages 69-73 ; 0780397266 (ISBN); 9780780397262 (ISBN) ; Hessabi, S ; Moghadam, E. K ; Sharif University of Technology
IEEE Computer Society 2006
The ODYSSEY design methodology is an object-oriented design methodology which models a system in terms of its constituting objects and their corresponding method calls. Some of these method calls are implemented in hardware functional units, while others are simply executed by a general-purpose processor. There is a communication overhead because functional units must communicate with each other and with the processor core. In this paper we utilize the custom instructions capability of Nios II processor to enhance the performance of our ASIP. Since these instructions are in the processor itself, there will be no communication overhead for using them. We analyze the performance of the...