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A robust PN length estimation in down link low- SNR DS-CDMA multipath channels
, Article International Conference on Advanced Communication Technology, ICACT, 7 February 2010 through 10 February 2010 ; Volume 2 , February , 2010 , Pages 951-955 ; 17389445 (ISSN) ; 9788955191455 (ISBN) ; Ganji, F ; Safaei, A ; Samsami Khodadad, F ; Sharif University of Technology
2010
Abstract
In this paper an efficient method is proposed for blind detection of multiuser spread spectrum signal and pseudo noise (PN) length estimation in downlink scenario. This method is based on fluctuating observation of second order statistic (SOS) estimator of received signal; estimating length of spreading code with no need to primary information based on observing second order peaks of correlation estimator is presented. In low SNR, the fading multipath phenomenon especially in length of small codes leads to problem in detecting place of correlation estimator peaks. In this paper besides expanding blind estimation to multiuser environment, by using searching method in updating the length of...
Optimization of a cascading TMR system configuration using genetic algorithm
, Article IEEE International Conference on Industrial Informatics (INDIN), 25 July 2012 through 27 July 2012 ; July , 2012 , Pages 470-474 ; 19354576 (ISSN) ; 9781467303118 (ISBN) ; Jahed, M ; Sharif University of Technology
2012
Abstract
The architecture of the Cascading TMR (Triple Modular Redundancy) System is commonly found in aerospace applications. The system is potentially capable of containing a large number of modules and sub modules. In this paper a novel method for optimization of a Cascading TMR system configuration using GA (Genetic Algorithm) is proposed. The proposed algorithm provides a configuration that maximizes reliability and minimizes overhead area simultaneously
A novel Space Time Diversity Generalized Decorrelating Rake receive for multipath downlink DS-CDMA systems
, Article 2011 IEEE GCC Conference and Exhibition, GCC 2011, 19 February 2011 through 22 February 2011, Dubai ; 2011 , Pages 417-420 ; 9781612841199 (ISBN) ; Hosaini, S. N ; Khodadad, F. S ; Baghbanmanesh, M. R ; Sharif University of Technology
2011
Abstract
In this paper a novel Space Time Diversity Generalized Decorrelating Discrete Time Rake (STD-GD-DTR) for Upstream DS-CDMA system is proposed. The chosen algorithm for estimating the correct data is Maximum likelihood. In this method, a robust receiver based on maximum likelihood estimation is represented in which, space time diversity technique has been combined with generalized decorrelating discrete-time RAKE (GD-DTR) receiver to obtain higher performance than other widely used techniques for data estimation. Our proposed STD-GD-DTR ML based receiver provides high gains in the presence of channel estimation errors from similar methods. Simulation results illustrate the appropriate...
A practical approach for coherent signal surveillance and blind parameter assessment in asynchoronous DS-CDMA systems in multipath channel
, Article Proceedings - 2010 18th Iranian Conference on Electrical Engineering, ICEE 2010, 11 May 2010 through 13 May 2010 ; 2010 , Pages 305-310 ; 9781424467600 (ISBN) ; Ganji, F ; Aref, M. R ; Sharif University of Technology
2010
Abstract
A novel, robust and practical method for active user enumeration in asynchronous CDMA in multipath channel condition is proposed in this paper. Most of the previous works do not consider the fact that in practical case, user's signals with the help of receiver arrive asynchronously. The proposed method can be used practically in blind multi-user detection such as eavesdropping; moreover, the method is based on information theory criteria which outperform other methods. Minimum description length (MDL) has better performance than all other information criteria used in such scenarios. Unlike most of the pervious works, we do not exploit array antenna to gather necessary data of the users....
A novel BEM- based channel estimation algorithm for time variant uplink OFDMA system
, Article International Conference on Advanced Communication Technology, ICACT, 7 February 2010 through 10 February 2010 ; Volume 2 , Feb , 2010 , Pages 1289-1293 ; 17389445 (ISSN) ; 9788955191455 (ISBN) ; Tabatabavakili, V ; Samsami Khodadad, F ; Hosseinnezhad, M ; Safaei, A ; Sharif University of Technology
2010
Abstract
IN this paper the effect of different channel estimation approaches in OFDMA uplink system which are based on Basis Expansion Model (BEM) and widely used to consider time varying channels are discussed. It has been shown in previous works that modeling error will be reduced by applying oversampled BEM with cost of increasing sensitivity to noise. This problem will be solved by combining oversampled BEM and MMSE channel estimator with cost of increasing computational complexity. In this paper a novel channel estimation approach is represented in which by combining oversampled BEM and low rank MMSE in frequency domain, almost the same performance as the full rank MMSE has been achieved while...
Hardware Redundancy in Fault-Tolerant Digital Systems: A VHDL Approach to Evaluate TMR Robustness
, M.Sc. Thesis Sharif University of Technology ; Jahed, Mehran (Supervisor)
Abstract
Triple Module redundancy (TMR) is a commonly used approach to increase reliability in space applications. Applying this method, triple modules and voting circuits are implemented in a field programmable gate array (FPGA). In TMR systems when a single event upset (SEU) occurs, the voting circuit neglects the failure value of a module receiving the SEU and takes a correct value from the other two modules. The present TMR approach utilized for the combinational and sequential logic on the gate level shows that it is possible to write hardware description language (VHDL) code in a structured yet high level coding style to obtain the required redundancy. However using VHDL, the level of required...
The direction of arrival estimation in DS-CDMA systems employing the code-matched filters and parallel ESPRIT algorithms
, Article Proceedings - 2010 IEEE International Conference on Wireless Communications, Networking and Information Security, WCNIS 2010, 25 June 2010 through 27 June 2010, Beijing ; 2010 , Pages 274-279 ; 9781424458516 (ISBN) ; Hoseini Karani, S. B ; Safaei, A ; Hadi Karami Ata, M ; Taheri, A ; Sharif University of Technology
2010
Abstract
It was shown that the number of array elements must exceed the number of sources for subspace-based direction-of-arrival (DOA) estimation. But this is not practical for a direct-sequence code-division multiple access (DS-CDMA) wireless system, since the number of mobile users is very large. To remove the aforementioned restriction, a DOA estimator, employing the code-matched filters and parallel ESPRIT algorithms, is proposed. This algorithm does not use to search all angles such as MUSIC method. Besides, it is not necessary to use AIC and MDL criterion to estimate the number of sources in the proposed algorithm. Simulation results illustrates the appropriate performance of the new method
Thermodynamics and Kinetics Study of Gas Hydrates in Presence of Ionic Liquids
, M.Sc. Thesis Sharif University of Technology ; Ghotbi, Cyrus (Supervisor) ; Taghikhani, Vahid (Supervisor) ; Nazari, Khodadad (Supervisor)
Abstract
Gas hydrates are ice-like clathrate compounds. Methane, carbon dioxie and natural gas compounds can form gas hydrate and plug pipelines, in order to preventing of gas hydrate formation, inhibitors like electrolytes are added to the natural gas pipelines. In this work a model proposed to predict the hydrate formation conditions in presence of some inhibitors such as NaCl, KCl, NaBr, KBr, [BMIM][BF4] and [BMIM][Br]. So a new equation of state that can be applied to both electrolyte and associating solutions called GV-SAFT-MSA is developed. Two dialkylimidazolium ionic liquids [BMIM][BF4] and [BMIM][MS] have been investigated for their potential application as novel gas hydrate inhibitors. The...
An imperialist competitive algorithm approach for multi-objective optimization of direct coupling photovoltaic-electrolyzer systems
, Article International Journal of Hydrogen Energy ; Vol. 39, Issue 33 , 11 November , 2014 , pp. 18743-18757 ; ISSN: 03603199 ; Sayedin, F ; Khavas, S. S
2014
Abstract
In the context of sustainable clean hydrogen production pathways, photovoltaic-electrolyzer systems are one of the most promising alternatives for acquiring hydrogen from renewable energy sources. In fact, determining the optimal set of design and operating variables are always a key issue while coupling directly renewable electricity sources to PEM electrolyzers. Few previous studies have attempted to find the optimal size and operational condition of directly coupled photovoltaic-electrolyzer (PV/El) systems in order to maximize the hydrogen production or to minimize energy transfer loss between photovoltaic devices and the electrolyzer. Nevertheless an easy and efficient approach still...
Prediction of Lumbar Muscle Forces Due to Applied Externally Moment and Analaysing Coactivation Between Lumbar Muscles
, M.Sc. Thesis Sharif University of Technology ; Parnianpour, Mohammad (Supervisor) ; Shams Al-Allahi, Mohammad Bagher (Co-Advisor)
Abstract
The role of the lumbar muscles in maintaining posture and balancing externally applied loads has been studied for many years.preliminary studies used electromyograpy (EMG) to establish a relationship between trunk posture and muscle ativity.so developing a better undrestanding of the functional role of those muscles. Determination of lumbar muscle forces, will have an important role in reducing low back pain I future.For this reason,reaserchers have done many studies for understanding the resistence and function on the musulosketal system bye using of various protocls and have utilized of various biomechanical models for determining the effects of applied externally loads on lumbar...
Optimisation of deep mixing technique by artificial neural network based on laboratory and field experiments
, Article Georisk ; Volume 14, Issue 2 , 2020 , Pages 142-157 ; Mojtahedi, S. F. F ; Sadeghi, H ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
Ground improvement techniques are inevitable for weak soils that cannot endure the design load imposed by superstructures. Deep mixing technique (DMT) as one of these methods is promising and effective when a deep soil layer with low bearing capacity is encountered. Such deposits are quite common in the South-west of Iran where the studied site is located. In order to validate the influence of DMT on the enhancement of strength, both in-situ and laboratory tests were conducted. Afterwards, a parametric study was carried out to investigate the influence of key factors including cement content, water–cement ratio, curing time and plasticity index (PI) on the performance of DMT. In summary, a...
Optimisation of deep mixing technique by artificial neural network based on laboratory and field experiments
, Article Georisk ; 2019 ; 17499518 (ISSN) ; Mojtahedi, S. F. F ; Sadeghi, H ; Sharif University of Technology
Taylor and Francis Ltd
2019
Abstract
Ground improvement techniques are inevitable for weak soils that cannot endure the design load imposed by superstructures. Deep mixing technique (DMT) as one of these methods is promising and effective when a deep soil layer with low bearing capacity is encountered. Such deposits are quite common in the South-west of Iran where the studied site is located. In order to validate the influence of DMT on the enhancement of strength, both in-situ and laboratory tests were conducted. Afterwards, a parametric study was carried out to investigate the influence of key factors including cement content, water–cement ratio, curing time and plasticity index (PI) on the performance of DMT. In summary, a...
Voltage balancing of series IGBTs in short-circuit conditions
, Article IEEE Transactions on Power Electronics ; Volume 37, Issue 5 , 2022 , Pages 5675-5686 ; 08858993 (ISSN) ; Peyghami, S ; Iannuzzo, F ; Blaabjerg, F ; Kaboli, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2022
Abstract
This article proposes a scheme for balancing the voltage of series-connected insulated gate bipolar transistors (IGBTs), which is also very effective under short-circuit conditions. An optimized clamp-mode snubber is proposed, including an active-driver to balance the currents of the IGBTs during short-circuit, which in turn allows for a considerable reduction of the snubber capacitance. The approach is proven to be effective under short-circuit conditions by a maximum of 55 V voltage increment and a negligible difference in the current values. The effectiveness of the proposed approach is demonstrated through simulations in PSPICE software and experimental tests performed at 2 kV. ©...
Screening and optimization of effective parameters in biological extraction of heavy metals from refinery spent catalysts using a thermophilic bacterium
, Article Separation and Purification Technology ; Volume 118 , October , 2013 , Pages 151-161 ; 13835866 (ISSN) ; Ghojavand, F ; Mousavi, S. M ; Yaghmaei, S ; Amiri, F ; Sharif University of Technology
2013
Abstract
This research aimed at finding the factors with more impact on the bioleaching of a spent hydrocracking catalyst by thermophilic acidophilic archaea called Acidianus brierleyi and determining the optimal condition in order to reach the maximum metals recovery. Initially, four more significant factors affecting the bioleaching efficiency including pH, pulp density, inoculation and elemental sulfur concentration, were screened and identified among ten key factors using Plackett-Burman factorial design. Next, a central composite design was applied to obtain the optimum conditions for achieving the maximum efficiency of the bioleaching process. pH 1.6, pulp density 0.6% (w/v), inoculation 4%...
A neuro-optimal approach for thrust-insensitive trajectory planning
, Article Aircraft Engineering and Aerospace Technology ; Volume 81, Issue 3 , 2009 , Pages 212-220 ; 00022667 (ISSN) ; Pazooki, F ; Noushabadi, F ; Sharif University of Technology
2009
Abstract
Purpose - The purpose of this paper is to devise a new approach to synthesize closed-loop feedback guidance law for online thrust- insensitive optimal trajectory generation utilizing neural networks. Design/methodology/approach - The proposed methodology utilizes an open- loop variational formulation that initially determines optimal launch/ ascent trajectories for various scenarios of known uncertainties in the thrust profile of typical solid propellant engines. These open-loop optimized trajectories will then provide the knowledge base needed for the subsequent training of a neural network. The trained network could eventually produce thrust-insensitive closed-loop optimal guidance laws...
In vitro biological outcome of laser application for modification or processing of titanium dental implants
, Article Lasers in Medical Science ; Volume 32, Issue 5 , 2017 , Pages 1197-1206 ; 02688921 (ISSN) ; Farahmand, F ; Tabatabaei, F. S ; Sharif University of Technology
2017
Abstract
There are numerous functions for laser in modern implant dentistry including surface treatment, surface coating, and implant manufacturing. As laser application may potentially improve osseointegration of dental implants, we systematically reviewed the literature for in vitro biological responses to laser-modified or processed titanium dental implants. The literature was searched in PubMed, ISI Web, and Scopus, using keywords “titanium dental implants,” “laser,” “biocompatibility,” and their synonyms. After screening the 136 references obtained, 28 articles met the inclusion criteria. We found that Nd:YAG laser was the most commonly used lasers in the treatment or processing of titanium...
Higher prevalence of asymptomatic or mild COVID-19 in children, claims and clues
, Article Journal of Medical Virology ; Volume 92, Issue 11 , May , 2020 , Pages 2257-2259 ; Noorbakhsh, F ; Mohebbi, S. R ; Ghaemi, A
John Wiley and Sons Inc
2020
Mathematical modeling of CSF pulsatile hydrodynamics based on fluid-solid interaction
, Article IEEE Transactions on Biomedical Engineering ; Volume 57, Issue 6 , 2010 , Pages 1255-1263 ; 00189294 (ISSN) ; Bastani, D ; Najarian, S ; Ganji, F ; Farmanzad, F ; Seddighi, A. S ; Sharif University of Technology
2010
Abstract
Intracranial pressure (ICP) is derived from cerebral blood pressure and cerebrospinal fluid (CSF) circulatory dynamics and can be affected in the course of many diseases. Computer analysis of the ICP time pattern plays a crucial role in the diagnosis and treatment of those diseases. This study proposes the application of Linninger et al.s [IEEE Trans. Biomed. Eng. , vol. 52, no. 4, pp. 557565, Apr. 2005] fluidsolid interaction model of CSF hydrodynamic in ventricular system based on our clinical data from a group of patients with brain parenchyma tumor. The clinical experiments include the arterial blood pressure (ABP), venous blood pressure, and ICP in the subarachnoid space (SAS). These...
A control strategy for reducing the torque ripple in low speed operation of direct torque controlled induction motor
, Article 2004 IEEE International Symposium on Industrial Electronics, IEEE-ISlE, 4 May 2004 through 7 May 2004 ; Volume 2 , 2004 , Pages 1203-1208 ; Zolghadri, S. M. R ; Haghbin, T. S ; Homaifar, F. A ; Sharif University of Technology
2004
Abstract
A new switching table is proposed for decreasing the torque ripple in DTC especially in low speed. Each sector is divided to two half sector and a proper vector set is defined for each. Through this new switching table, the torque response is smooth even in the beginning of each sector and it leads to the reduction of torque ripple. None of motor parameters are used in this switching strategy and there is no need to shorten the sampling period. Simulation and experimental results confirm the ability of this method in reducing the torque ripple. ©2004 IEEE
Methanol-to-hydrocarbons product distribution over sapo-34 and zsm-5 catalysts: The applicability of thermodynamic equilibrium and anderson-schulz-flory distribution
, Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 38, Issue 2 , 2019 , Pages 49-59 ; 10219986 (ISSN) ; Yaripour, F ; Ahmadpour, S ; Khorasheh, F ; Sharif University of Technology
Iranian Institute of Research and Development in Chemical Industries
2019
Abstract
The product distribution of methanol to hydrocarbons conversion over SAPO-34 and ZSM-5 catalysts was studied using thermodynamic equilibrium and Anderson-Schulz-Flory (ASF) distributions. The equilibrium compositions were calculated using constrained Gibbs free energy minimization. The effect of catalyst type was considered by setting upper limits to product carbon number due to shape selectivity according to zeotype catalyst channel size; that is, n5 for SAPO-34 but n6 for aliphatic and n10 for aromatic compounds over H-ZSM-5 catalyst. The equilibrium selectivity of kinds of paraffin is negligible over SAPO-34 system while that of olefins is very small over H-ZSM-5, both in agreement...