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51.
Ahmad Feyz Dizaji Hossein Ali Sepiani Farzad Ebrahimi Akbar Allahverdizadeh Hasan Ali Sepiani 《Journal of Mechanical Science and Technology》2009,23(8):2299-2307
An initial-boundary value problem that is Duffing’s oscillator with time varying coefficients will be studied. Using Banach’s
fixed-point theorem, the existence of periodic solution of the equation will be predicted. The method applied in this paper
is the Schauder second fixed point theorem, which includes the response of structures under vibratory force systems. As an
example, the dynamics of nonlinear simply supported rectangular thin plate under influence of a relatively moving mass is
studied. By expansion of the solution as a series of mode functions, the governing equations of motion are reduced to an ordinary
differential equation for time development vibration amplitude, which is Duffing’s oscillator. Finally, a parametric study
is developed, after that some numerical examples are solved, and the validity of the present analysis is clearly shown.
This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho
Hossein Ali Sepiani received his B.S. degree in Mechanical Engineering from University of Kashan, Iran, in 2003. He then received his M.S. degree
from University of Tehran, in 2006. Currently, Hossein is continuing his research at University of Tehran. His research interests
include new materials (FGMs, Nano-materials, SMAs, SMPs, etc), Composites (Woven Fabrics and Fiber Metal Laminates), Smart
Materials (Shape Memory Alloy, Magnet/Electro-rheological and Piezoelectric Sensors and Actuators), Intelligent structures
(Structures integrated with smart materials), Vibration and control of Intelligent Structures and their application.
Ahmad Feyz Dizaji got his B.S. degree from University of Tehran, Iran, in 1970. Then he continued his study in U.S. and received his PhD. degree
from Michigan State University in 1983, in Applied Mathematics under the supervision of Professor Shui-ni Chow and Professor
J. Mallet-Paret. Since then he has been a member of the Faculty of Engineering in University of Tehran, teaching mathematics
in both undergraduate and graduate levels. 相似文献
52.
M. Hadi A. R. Kamali J. Khalil-Allafi A. R. Ebrahimi M. Hadavi 《Russian Journal of Non-Ferrous Metals》2009,50(1):24-29
Titanium aluminide intermetallic compounds have an excellent capability for use in engineering structures at high temperatures.
In the present work the formation of Nb rich inclusions in microstructure and evaporation of Al during melting of γ-TiAl based
alloy (Ti-48Al-2Cr-2Nb-1B (at %)) was studied. The results show that the inclusions cannot be removed even with a four-stage
melting process, when elemental Nb is used as raw material. However, by replacing Nb with NbAl3 and using a three-stage melting process, the inclusions were removed from microstructure and also evaporation of Al was reduced
remarkably. Otherwise, with removing elemental Al from raw material by using TiAl compound, evaporation of Al will be very
low. Increasing vessel pressure from 400 to 600 mbar will not influence evaporation of Al.
The article is published in the original. 相似文献
53.
54.
Microelectromechanical systems are utilized alongside with transistor amplifiers and resistive connections for implementing of oscillatory associative memories. Phase locking is studied in such a network and all requirements of the circuit level implementation are satisfied. A very high gain trans-impedance amplifier operating in 1 GHz in addition to a novel automatic amplitude control circuit is employed to remove amplitude dynamics of the system. Requiring resonator characteristics are extracted and calculated as well. A new method for initialization of the network is proposed. Each neuron consumes 1.08 mW from a 1.8 V power supply. The convergence time of a typical network trained by Hebbian rule is less than 1.5 ns which results in an ultra high speed analog signal processing system. 相似文献
55.
P. Ebrahimi S. M. Razavi S. Ismaeili M. Azarpour 《Petroleum Science and Technology》2013,31(11):1188-1195
Recognition of hydrocarbon migration is so vital for petroleum exploration. Developing intelligent systems (artificial neural network) enable experts to achieve more details from seismic data. Although detection of migration direction using seismic data is difficult, Chimney-cube analysis overcomes this problem. The authors used several filters, seismic attributes, neural network (supervised and unsupervised), and interpreters' viewpoints. In supervised method artificial and human intelligence cover their limitations and in unsupervised method the authors eliminate the experts' views. Chimney recognizes the migration direction and locates the spill points, mud volcanoes, gas seepages, sealing, and nonsealing faults and finally the origin of hydrocarbon. 相似文献
56.
N. Martinez A. J. Williams S. A. Seyyed Ebrahimi I. R. Harris 《Journal of Materials Science》1999,34(10):2401-2406
A hydrogen treatment followed by calcination, has been developed in order to enhance the intrinsic coercivity of Sr-hexaferrite (SrFe12O19). Fully hydrogen-treated Sr-hexaferrite consists of a mixture of 73%, by weight, of Fe and 27% of Sr7Fe10O22 phases. Calcination of this material to reform the SrFe12O19 phase occurs in two stages. Between room temperature and 600°C, oxygen was absorbed resulting in a large increase in weight with the formation of a mixture of SrFeO3–x and Fe2O3( and ). During the second stage, the intermediate phases reacted to form SrFe12O19 at a temperature of between 700 and 800°C. A partial desorption of oxygen occurred until calcination reached completion at 1000°C. The magnetization at 1100 kA m–1 and the remanence were similar to those of the untreated material, but, because of a much refined grain size, the intrinsic coercivity was considerably larger, with values around 400 kA m–1. Grain growth occurs at temperatures > 1000°C, resulting in a decrease in the intrinsic coercivity. 相似文献
57.
58.
We develop a new efficient numerical methodology for automated simultaneous registration and intensity correction of images. The approach separates the intensity correction term from the images being registered in a regularized expression. Our formulation is consistent with the existing non-parametric image registration techniques, however, an extra additive intensity correction term is carried throughout. An objective functional is formed for which the corresponding Hessian and Jacobian is computed and employed in a multi-level Gauss–Newton minimization approach. In this paper, our experiments are based on elastic regularization on the transformation and total variation on the intensity correction. Validations on dynamic contrast enhanced MR abdominal images for both real and simulated data verified the efficacy of the model. 相似文献
59.
Mostafa Kahani Afshin Tatar Milad Sadeghzadeh 《Numerical Heat Transfer, Part A: Applications》2013,63(4):1190-1206
AbstractIn this study, Multilayer Perceptron Artificial Neural Network (MLP-ANN) model and Least Square Support Vector Machine (LSSVM), were developed to predict the thermal performance and pressure loss of nanofluid flow through coils as non-straight pathways. There different coils with various curvature ratios and coil pitches were constructed and used. Stable TiO2 (50?nm)/water nanofluid in different concentrations from 0.0 to 2.0% were prepared using appropriate method. As it is expected, considerable enhancement of heat transfer was achieved by application of nanofluids instead of water in system. Volume concentration of nanofluid, Prandtl number (ranging from 4.82 to 9.11) and Helical number (106.80 to 1282.87) were introduced to the developed models to obtain Nusselt number (9.89 to 53.30) and pressure drop (291.35 to 18784?kPa) as the output data of the models. According to the output results of developed models, MLP-ANN model was able to predict both Nusselt number and pressure drop of nanofluid flow more precisely in comparison to LSSVM model. The developed MLP model of this study exceeded LSSVM model to high correlation coefficient value of 0.97. 相似文献
60.
Elham Poonaki Mohammad Esfandyar Hadi Hejazinia Seyed Esmaeil Sadat Ebrahimi Morteza Pirali Hamedani Jafar Farzaneh Mehdi Shafiee Ardestani 《IET nanobiotechnology / IET》2020,14(6):470
Gadolinium as a contrast agent in MRI technique combined with DTPA causes contrast induced nephropathy (CIN) and nephrogenic systemic fibrosis (NSF) which can reduce by usage of antioxidants such as N‐acetyl cysteine by increasing the membrane''s permeability leads to lower cytotoxicity. In this study, N ‐acetyl cysteine‐PLGA Nano‐conjugate was synthesized according to stoichiometric rules of molar ratios andafter assessment by FTIR, NMR spectroscopy and Atomic Force Microscopy (AFM) imaging was combined with Magnevist® (gadopentetate dimeglumine) and its effects on the renal cells were evaluated. MTT [3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐Diphenyltetrazolium Bromide] and cellular uptake assays have indicated relatively significant toxicity of magnevist (P < 0.05) on three cell lines including HEK293, MCF7 and L929 compared to other synthesized ligands that shown no toxicity. Moreover, systemic evaluation has shown no notable changes of blood urea nitrogen (BUN) and creatinine in kidney of mice. In consequence, antioxidant effect was increased as well as the renal toxicity of the contrast agent reduced at the cell level. As a result, PLGA‐NAC nano‐conjugate can be a promising choice for decreasing the magnevist toxicity for treatment and prevention of CIN and will be able to open a new horizon to research on reduction of toxicity of contrast agents by using nanoparticles.Inspec keywords: blood, toxicology, nanofabrication, cellular biophysics, biomedical materials, nanoparticles, chromatography, cancer, biodegradable materials, biomedical MRI, kidney, pH, nanomedicine, patient treatment, diseases, atomic force microscopy, Fourier transform infrared spectraOther keywords: cellular toxicity, gadopentate dimeglumine, contrast agent, magnetic resonance imaging technique, diethylenetriamine pentaacetate, contrast‐induced nephropathy, nephrogenic systemic fibrosis, stoichiometric rules, molar ratios, dimethyl sulphoxide solution, chromatography techniques, nuclear magnetic resonance spectroscopy, atomic force microscopy imaging, Magnevist®, gadopentetate dimeglumine, renal cells, MTT cytotoxicity, human embryonic kidney‐293, L929 cell lines, in vitro conditions, cellular uptake assays, Magnevist uptake, antioxidant effect, renal toxicity, cell level, PLGA nanocarrier, acetylcysteine nanoconjugate, Magnevist toxicity, N‐acetylcysteine–PLGA nano‐conjugate, N‐acetyl cysteine‐poly‐lactic‐co‐glycolic acid nanoconjugate 相似文献