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Instability analysis of viscoelastic CNTs surrounded by a thermo-elastic foundation
Saeed Amir,Mehdi Khani,Ali Reza Shajari,Pedriam Dasht 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.2
Static and dynamic instability of a viscoelastic carbon nanotube (CNT) embedded on a thermo-elastic foundation are investigated, in this research. The CNT is modeled based on Euler-Bernoulli beam (EBB) and nonlocal small scale elasticity theory is utilized to analyze the structure. Governing equations of the system are derived using Hamilton‟s principle and differential quadrature (DQ) method is applied to solve the partial differential equations. The effects of variable axial load and diverse boundary conditions on static/vibration instability are studied. To verify the result of the DQ method, the Galerkin weighted residual approach is used for the instability analysis. It is observed appropriate agreement for results of two different solution methods and satisfactory accuracy with those obtained in prior studies. The results of this work could be useful for engineers and designers in order to produce and design nano/micro structures in thermo-elastic medium.
Saeed Amir,Ehsan Arshid,Mohammad Reza Ghorbanpour Arani 국제구조공학회 2019 Smart Structures and Systems, An International Jou Vol.23 No.5
The present study analyzed free vibration of the three-layered micro annular/circular plate which its core and face sheets are made of saturated porous materials and FG-CNTRCs, respectively. The structure is subjected to magneto-electric fields and magneto-electro-mechanical pre loads. Mechanical properties of the porous core and also FG-CNTRC face sheets are varied through the thickness direction. Using dynamic Hamilton’s principle, the motion equations based on MCS and FSD theories are derived and solved via GDQ as an efficient numerical method. Effect of different parameters such as pores distributions, porosity coefficient, pores compressibility, CNTs distribution, elastic foundation, multi-physical pre loads, small scale parameter and aspect ratio of the plate are investigated. The findings of this study can be useful for designing smart structures such as sensor and actuator.
Saeed Amir,Ehsan Arshid,Zahra Khoddami Maraghi 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.5
Magneto-rheological fluids and magneto-strictive materials are of the well-known smart materials which are used to control and reduce the vibrations of the structures. Vibration analysis of a smart annular three-layered plate is provided in this work. MR fluids are used as the core’s material type and the face sheets are made from MS materials and is assumed they are fully bonded to each other. The structure is rested on visco-Pasternak foundation and also is subjected to a transverse magnetic field. The governing motion equations are derived based on CPT and employing Hamilton’s principle and are solved via GDQ as a numerical method for various boundary conditions. Effect of different parameters on the results are considered and discussed in detail. One of the salient features of this work is the consideration of MR fluids as the core, MS materials as the faces, and all of them under magnetic field. The outcomes of this study may be led to design and create smart structures such as sensors, actuators and also dampers.
Saeed Farzamfar,Majid Salehi,Arian Ehterami,Mahdi Naseri-Nosar,Ahmad Vaez,Amir-Hassan Zarnani,Hamed Sahrapeyma,Mohammad Reza Shokri,Mehdi Aleahmad 대한의용생체공학회 2018 Biomedical Engineering Letters (BMEL) Vol.8 No.4
This is the first study demonstrating the efficacy of menstrual blood-derived stem cell (MenSC) transplantation viadecellularized human amniotic membrane (DAM), for the promotion of skin excisional wound repair. The DAM wasseeded with MenSCs at the density of 3 9 104 cells/cm2 and implanted onto a rat’s 1.50 9 1.50 cm2 full-thicknessexcisional wound defect. The results of wound closure and histopathological examinations demonstrated that the MenSCseededDAM could significantly improve the wound healing compared with DAM-treatment. All in all, our data indicatedthat the MenSCs can be a potential source for cell-based therapies to regenerate skin injuries.
Locating Astragalus hypsogeton Bunge appropriate site using AHP and GIS
Saeed Shojaei,Hamid Alipur,Amir Hossein Hatefi Ardakani,Seyede Negar Hashemi Nasab,Hassan Khosravi 대한공간정보학회 2018 Spatial Information Research Vol.26 No.2
In order to locate Astragalus appropriate areas in Salook watershed, Iran, at the first, six main effective criteria including direction, slope, altitude, temperature, rainfall and soil texture were determined based on fields study and expert experiences. Then using the analytic hierarchy process (AHP) method were weighted based on questionnaire form in the expert choice 11 software, and relative importance of each criteria and their classes were calculated. Finally, obtained maps were overlaid in ArcGIS software to determine Astragalus appropriate areas. The results showed that Northern area have higher priority than other. With the most relative importance (0.5101), the heights above 1800 m the heights above 1800 m suitable sites for Astragalus spp. The three main criteria including altitude, rainfall and temperature with the weight of 0.3043, 0.2201 and 0.1550 have the most relative importance respectively and in terms of the location are in the first to third priority. In general, from the total area of Salook watershed, 553 hectares was identified as Astragalus species suitable site. This research showed that using technology and GIS and AHP and with the least cost and time, the optimal location of medicinal plants can be determined in different lands.
Prediction of Ground Water Table Using NF-GMDH Based Evolutionary Algorithms
Amir-Abbas Jahanara,Saeed Reza Khodashenas 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.12
Groundwater, as the key element of water resources, can play inevitably substantial role in managing groundwater aquafers. In fact, a ferocious demand for acquiring precise estimation of groundwater table is of remarkable significance for analyzing water resources systems. A wide range of artificial intelligence techniques were used to predict groundwater table with highly convincing level of precision. Hence, this investigation aims to present an integration of a neuro-fuzzy (NF) system and group method of data handling (GMDH) in order to forecast the ground water table (GWT). The NF-GMDH network has been improved by means of the particle swarm optimization (PSO) and gravitational search algorithm (GSA) as evolutionary algorithms. The proposed methods were developed using records of two wells in Illinois State, USA. For this purpose, datasets related to time series of GWT have been grouped into three sections: training, testing, and validation phases. Through training and testing phases, the efficiency of the NF-GMDH methods were studied. The performances of proposed techniques were compared to the performance of radial basis function-neural network (RBF-NN). Evaluation of statistical results indicated which NF-GMDH-PSO network (R = 0.973 and RMSE = 0.545) is capable of providing higher level of precision rather than the NF-GMDH-GSA network (R = 0.969 and RMSE = 0.618) and RBF-NN (R = 0.814 and RMSE = 1.41). Also, conducting an external validation for the improved NF-GMDH models showed the most permissible level of precision.
Dielectric and Electromechanical Properties of Zr-Doped BNT-ST Lead-Free Piezoelectric Ceramics
Amir Ullah,Mateen Ullah,Aman Ullah,A. V. Trukhanov,Ghulam Saddiq,Burhan Ullah,Aurang Zeb,Saeed Ullah Jan,김일원 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.6
0.72(Bi$_{0.5}$Na$_{0.5}$)Ti$_{(1-x)}$Zr$_x$O$_3$-0.28SrTiO$_3$ (BNTZ-ST) with $x$ = 0.00, 0.01, 0.02 and 0.03 were produced using a solid solution reaction procedure. Results from the X-ray diffraction (XRD) analysis showed the presence of a perovskite structure with cubic symmetry for all samples. Surface analysis was completed using field emission scanning electron microscopy (FE-SEM), and the grain size was found to decrease slightly with increasing Zr doping. The grain morphology was primarily rectangular, but morphed into a rounder shape with increases in Zr. In a dielectric constant study, the depolarization temperature was found to decrease with increasing Zr$^{+4}$ content and increasing frequency. The strain was found to be 0.34\% for the undoped samples with an equivalent dynamic strain ($S_{max}/E_{max}$) of 618 pm/V, without negative strain. However, the strain decreased slightly and hysteresis loops become slim and more symmetric, attaining a relaxor ferroelectric behavior with increasing Zr content.
An analytical model for shear links in eccentrically braced frames
Saeed Erfani,Amir Ashtari 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.3
When an eccentrically braced frame (EBF) is subjected to severe earthquakes, the links experience inelastic deformations while beams outside of the link, braces and columns are designed to remain elastic. To perform reliable inelastic analyses of EBFs sufficient analytical model which can accurately predict the inelastic performance of the links is needed. It is said in the literature that available analytical models for shear links generally predict very well the maximum shear forces and deformations from experiments on shear links, but may underestimate the intermediary values. In this study it is shown that available analytical models do not predict very well the maximum shear forces and deformations too. In this study an analytical model which can accurately predict both maximum and intermediary values of shear force and deformation is proposed. The model parameters are established based on test results from several experiments on shear links. Comparison of available test results with the hysteresis curves obtained using the proposed analytical model established the accuracy of the model. The proposed model is recommended to be used to perform inelastic analyses of EBFs.
Amir Hossein Abdi,Saeed Reza Motamedian,Ehsan Balaghi,Mahtab Nouri 대한치과교정학회 2018 대한치과교정학회지 Vol.48 No.4
Objective: The aim of this study is to compare the adaptation of a straight wire between brackets positioned at the mid-lingual surface and those placed gingivally by using a three-dimensional simulation software. Methods: This cross-sectional study was performed using OrthoAid, an in-house software. The subjects were 36 adolescents with normal Class I occlusion. For each dental cast, two bracket positioning approaches, namely the middle and gingival, were examined. In the middle group, the reference points were placed on the mid-lingual surface of each tooth, while in the gingival group, the reference points were positioned lingually on the anterior teeth. A 4th degree polynomial was adopted, and the in-plane and off-plane root mean squares (RMSs) of the distances between the reference points and the fitted polynomial curve were calculated using the software. Statistical analysis was performed using the paired-samples t-test (a = 0.05). Results: The mean in-plane RMS of the polynomial curve to the bracket distance in the gingival group was significantly lower than that in the middle group (p < 0.001). The off-plane RMS was higher in the gingivally positioned brackets in the maxilla than in the middle group (p < 0.001). However, the off-plane RMS in mandible was not statistically significantly different between the two groups (p = 0.274). Conclusions: The results demonstrated that the gingival placement of lingual brackets on the anterior teeth could decrease the distance between a tooth and the straight wire.[Korean J Orthod 2018;48(4):236-244]