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Best compromising crashworthiness design of automotive S-rail using TOPSIS and modified NSGAⅡ

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Journal of Central South University 2015年第1期22卷 121-133页

作者： abolfazl Khalkhali School of Automotive Engineering Iran University of Science and Technology

In order to reduce both the weight of vehicles and the damage of occupants in a crash event simultaneously, it is necessary to perform a multi-objective optimal design of the automotive energy absorbing components. Modified non-dominated sorting genetic algorithm II(NSGA II) was used for multi-objective optimization of automotive S-rail considering absorbed energy(E), peak crushing force(Fmax) and mass of the structure(W) as three conflicting objective functions. In the multi-objective optimization problem(MOP), E and Fmax are defined by polynomial models extracted using the software GEvo M based on train and test data obtained from numerical simulation of quasi-static crushing of the S-rail using ABAQUS. Finally, the nearest to ideal point(NIP)method and technique for ordering preferences by similarity to ideal solution(TOPSIS) method are used to find the some trade-off optimum design points from all non-dominated optimum design points represented by the Pareto fronts. Results represent that the optimum design point obtained from TOPSIS method exhibits better trade-off in comparison with that of optimum design point obtained from NIP method.

关键词： automotive S-rail crashworthiness technique for ordering preferences by similarity to ideal solution(TOPSIS) method group method of data handling(GMDH) algorithm multi-objective optimization modified non-dominated sorting genetic algorithm(NSGA II) Pareto front

Low-cost sensorless control of four-switch,brushless DC motor drive with direct back-EMF detection

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第2期10卷 201-208页

作者： abolfazl HALVAEI NIASAR abolfazl VAHEDI Hassan MOGHBELLI Department of Electrical Engineering Faculty of EngineeringUniversity of Kashan Center of Excellence for Power System Automation and Operation Iran University of Science and Technology Department of Science and Mathematics Texas A&M University at Qatar

We propose a position sensorless control scheme for a four-switch,three-phase brushless DC motor drive,based on the zero crossing point detection of phase back-EMF voltages using newly defined error functions(EFs). The commutation in-stants are 30° after detected zero crossing points of the EFs. Developed EFs have greater magnitude rather than phase or line voltages so that the sensorless control can work at a lower speed range. Moreover,EFs have smooth transitions around zero voltage level that reduces the commutation errors. EFs are derived from the filtered terminal voltages vao and vbo of two low-pass filters,which are used to eliminate high frequency noises for calculation of the average terminal voltages. The feasibility of the proposed sensorless control is demonstrated by simulation and experimental results.

关键词： Brushless DC motor Four-switch inverter Sensorless control Back-EMF voltage sensing DSP

Analysis of optoelectronic properties of TiO_2 nanowiers/Si heterojunction arrays

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Chinese Physics B 2014年第10期23卷 469-471页

作者： Saeideh ramezani Sani Department of Physics Roudehen Branch Islamic Azad University

The optoelectronic properties of n-TiO2NW/p-Si heterojunction fabricated by depositing TiO2 nanowires on a p-Si substrate are studied. Under excitation at a wavelength of 370 nm, the TiO2 nanowires produce a light emission at 435 nm due to the emission of free excitons. The I-V characteristics are measured to investigate the heterojunction effects under the dark environment and ultraviolet （UV） illumination, n-TiOzNW/p-Si has a p-n junction formed in the n-TiOz/p-Si beterojunction. TiO2NW/Si photodiode produces a pbotocurrent larger than dark current under UV illumination. It is observed that UV photons are absorbed in TiO2 and the heterojunction shows a 0.034-A/W responsivity at 4-V reverse bias.

关键词： TiO2 nanowires photoresponse I-V characteristics heterojunction

A NONLINEAR MICROBEAM MODEL BASED ON STRAIN GRADIENT ELASTICITY THEORY

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Acta Mechanica Solida Sinica 2013年第1期26卷 21-34页

作者： Farshid Rajabi Shojaa ramezani Department of Mechanical Engineering Islamic Azad UniversityBandar Anzali BranchAnzaliIran Department of Mechanical Engineering Faculty of EngineeringUniversity of GuilanRashtIran

A micro scale nonlinear beam model based on strain gradient elasticity is developed. Governing equations of motion and boundary conditions are obtained in a variational framework. As an example, the nonlinear vibration of microbeams is analyzed. In a beam having a thickness to length parameter ratio close to unity, the strain gradient effect on increasing the natural frequency is predominant. By increasing the beam thickness, this effect decreases and geometric nonlinearity plays the main role on increasing the natural frequency. For some specific ratios, both geometric nonlinearity and size effects have a significant role on increasing the natural frequency.

关键词： strain gradient elasticity microbeam geometric nonlinearity

HBIR: Hypercube-Based Image Retrieval

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Journal of Computer Science & Technology 2012年第1期27卷 147-162页

作者： Hossein Ajorloo abolfazl Lakdashti Department of Computer Engineering Sharif University of Technology Tehran Iran University College of Rouzbahan Sari Iran

In this paper, we propose a mapping from low level feature space to the semantic space drawn by the users through relevance feedback to enhance the performance of current content based image retrieval （CBIR） systems. The proposed approach makes a rule base for its inference and configures it using the feedbacks gathered from users during the life cycle of the system. Each rule makes a hypercube （HC） in the feature space corresponding to a semantic concept in the semantic space. Both short and long term strategies are taken to improve the accuracy of the system in response to each feedback of the user and gradually bridge the semantic gap. A scoring paradigm is designed to determine the effective rules and suppress the inefficient ones. For improving the response time, an HC merging approach and, for reducing the conflicts, an HC splitting method is designed. Our experiments on a set of 11 000 images from the Corel database show that the proposed approach can better describe the semantic content of images for image retrieval with respect to some existing approaches reported recently in the literature. Moreover, our approach can be better trained and is not saturated in long time, i.e., any feedback improves the precision and recall of the system. Another strength of our method is its ability to address the dynamic nature of the image database such that it can follow the changes occurred instantaneously and permanently by adding and dropping images.

关键词： image retrieval relevance feedback rule base hypercube (HC)

Kinetics study of CO_(2) absorption in potassium carbonate solution promoted by diethylenetriamine

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Green Energy & Environment 2021年第1期6卷 83-90页

作者： Rouzbeh ramezani Renzo Di Felice Department of Civil Chemical and Environmental EngineeringUniversity of GenoaVia Opera Pia 1516145GenovaItaly

In this work,characterization and kinetics of CO2 absorption in potassium carbonate(K_(2)CO_(3))solution promoted by diethylenetriamine(DETA)were *** measurements were performed using a stirred cell reactor in the temperature range of 303.15–323.15 K and total concentration up to 2.5 kmol m*** density,viscosity,physical solubility,CO_(2) diffusivity and absorption rate of CO_(2) in the solution were *** reaction kinetics between CO_(2) and K2CO3þDETA solution were ***-first order kinetic constants were also predicted by zwitterion *** was revealed that the addition of small amounts of DETA to K_(2)CO_(3) results in a significant enhancement in CO_(2) absorption *** reaction order and activation energy were found to be 1.6 and 35.6 kJ mol1,*** terms of reaction rate constant,DETA showed a better performance compared to the other promoters such as MEA,EAE,proline,arginine,taurine,histidine and alanine.

关键词： Gas absorption CO_(2)capture Reaction rate constant Kinetic study Absorption rate

Effect of fiber hybridization on energy absorption and synergy in concrete

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Frontiers of Structural and Civil Engineering 2019年第6期13卷 1338-1349页

作者： Ahmadreza ramezani Mohammad Reza ESFAHANI Department of Civil Engineering Ferdowsi University of MashhadMashhad 91775-1111Iran

In the present study,steel and polypropylene(PP)fibers have been utilized with the intent of obtaining hybrid fiber-reinforced concrete(HFRC)with desirable mechanical *** attempt has been made to scrutinize the properties of HFRC with the main concentration being on energy absorption characteristics of concrete and the efficacy of fiber hybridization in producing ***,a total of 180 specimens,representing 20 different mixtures have been cast and evaluated through compressive,split tensile,and flexural *** relevant flexural toughness of the specimens was calculated using ASTM C1018,ASTM Cl 609,JSCE,and PCS methods,and the effectiveness of these methods was evaluated based on the experimental *** was observed that steel fibers are more effective in the improvement of flexural toughness in the presence ofPP ***,synergy associated with the combination of fibers at different stages of deflection of the beam specimens was observed and analyzed.

关键词： hybrid fiber-reinforced concrete synergy toughness steel fibers polypropylene fibers

Aerodynamic Characteristics of Conventional and Innovative High Lift Swept Wings

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Journal of Bionic Engineering 2019年第3期16卷 432-441页

作者： Mojtaba ramezani Voloojerdi Mahmoud Mani Aerospace Engineering Department Amirkabir University of Technology 424 Hafez Ave Tehran 158757413 Iran

The new bird inspired wing sweep was introduced and compared with straight and conventional swept wings in gliding flight by an experimental test setup. Due to the similarity with the birds, wing, all test models have S1223 airfoil. Swept models inspired from the bird consist of two parts: the straight part near the root and the swept part near the tip. Aerodynamic forces on each wing were measured from 0° to 24° angles of attack and Reynolds numbers of 4.3×10^4, 8.6×10^4, 1.3×10^5, and 1.7× 10^5. Wind tunnel test results show that wings with an innovative sweep at α> 0 have more lift for Reynolds numbers between 4.3× 10^4 and 8.6×10^4. Also, innovative sweep increases the stall angle, and the wing did not stall until α = 24° for Reynolds between 1.3×10^5 and 1.7×10^5. An increase in lift and having sufficient aerodynamic performance in low Reynolds numbers for birds' inspired wing sweep in gliding flight may be the answer to why the wing sweep of birds is not like conventional sweeps.

关键词： bio-inspired wing wing sweep wing aerodynamics bird wing low Reynolds number

The Generalized-Fisher composite fading model for the next generation of mobile communication systems

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Digital Communications and Networks 2024年第5期10卷 1322-1331页

作者： Fereshteh Salimian Rizi abolfazl Falahati Department of Electrical Engineering Iran University of Science and Technology(IUST)

The new generation of communication systems is moving towards using a millimeter-wave *** the shadowing effects are undeniable in this type of propagation,the proposed Generalized Fisher(GF) distribution can be useful in modeling shadowed fading channels,considering the non-linearity and the multi-cluster nature of the diffusion *** introducing the model,its main statistics,including Probability Density Function(PDF),Cumulative Distribution Function(CDF),Moment Generating Function(MGF),and the distribution of the sum of an arbitrary number of independent and non-identically distributed(i.n.i.d.) random variables with GF distribution are ***,some wireless communication application criteria such as ergodic and outage capacities,are ***,considering the classic Wyner's wiretap model and passive eavesdropping scenario,specific security criteria,such as the probability of non-zero secrecy capacity and secrecy outage probability,are also *** expressions are measured in terms of either univariate or multivariate Fox's H-function.

关键词： Composite fading Ergodic capacity Generalized-Fisher distribution Secrecy analysis Sum of random variables