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排序方式: 共有209条查询结果,搜索用时 0 毫秒
1.
Ahmad Nozad Golikand Elaheh Lohrasbi Mohammad Ghannadi Maragheh Mehdi Asgari 《Journal of Applied Electrochemistry》2008,38(6):869-874
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by
cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms,
polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface
area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The
formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of
a gas diffusion electrode for oxygen reduction reaction. 相似文献
2.
R.Babaei N.Hatami K.Asgari N.Varahram P.Davami 《铸造》2006,55(4):373-377
铸造过程中熔融金属内的固体渣粒的运动轨迹是非常重要的。文中给出了粒子传输轨迹的数学模型,该数学模型采用显示法来确定粒子的位置。模拟研究结果与用其它数学模型的模拟结果比较,吻合良好。该模型可用于固体粒子位置的确定,并应用到SUTCAST软件中。 相似文献
3.
Abolghasem Sayadian Fatemeh Mozaffari 《International Journal of Speech Technology》2017,20(3):587-592
This article puts forward a new algorithm for voice conversion which not only removes the necessity of parallel corpus in the training phase but also resolves the issue of insufficiency of the target speaker’s corpus. The proposed approach is based on one of the new voice conversion models utilizing classical LPC analysis-synthesis model combined with GMM. Through this algorithm, the conversion functions among vowels and demi-syllables are derived. We assumed that these functions are rather the same for different speakers if their genders, accents, and languages are alike. Therefore, we will be able to produce the demi-syllables with just having access to few sentences from the target speaker and forming the GMM for one of his/her vowels. The results from the appraisal of the proposed method for voice conversion clarifies that this method has the ability to efficiently realize the speech features of the target speaker. It can also provide results comparable to the ones obtained through the parallel-corpus-based approaches. 相似文献
4.
Mohammad Reza Ganjali Maryam Ghorbani Parviz Norouzi Azadeh Daftari Magid Faal-Rastegar Abolghasem Moghimi 《Sensors and actuators. B, Chemical》2004,100(3):315-319
A novel poly(vinyl chloride)-based 2,3,5,6,8,9-hexahydro-1,4,7,10-benzotetra oxacyclododecine-12-carbaldehyde-12-(2,4-dinitrophenyl)hy (PBC) with sodium tetraphenyl borate (NaTPB) as an anion excluder, benzyl acetate (BA), acetophenon (AP) and o-nitrophenyloctyl ether (NPOE) as plasticizing solvent mediators was prepared and investigated as a beryllium selective sensor. The best performance was observed with the membrane having the PVC–NaTPB–NPOE–PBC composition 30%:3%:62%:5%, which worked well over a very wide concentration range (1.0×10−7 M to 1.0×10−1 M). The sensor exhibits a Nernstian slope of 29.9 mV per decade of Be2+ activity. The detection limit of the sensor is 7.0×10−8 M (630 ppt). The proposed electrode shows excellent discriminating ability toward Be2+ ion with regard to alkali, alkaline earth, transition and heavy metal ions. It was successfully applied to the determination of beryllium in a mineral sample. 相似文献
5.
Mehdi Panji Hamid Koohsari Mohammad Adampira Hamid Alielahi Jafar Asgari Marnani 《岩石力学与岩土工程学报(英文版)》2016,(4):480-488
In this paper, stress behavior of shallow tunnels under simultaneous non-uniform surface traction and symmetric gravity loading was studied using a direct boundary element method(BEM). The existing fullplane elastostatic fundamental solutions to displacement and stress fields were used and implemented in a developed algorithm. The cross-section of the tunnel was considered in circular, square, and horseshoe shapes and the lateral coefficient of the domain was assumed as unit quantity. Double-node procedure of the BEM was applied at the corners to improve the model including sudden traction changes. The results showed that the method used was a powerful tool for modeling underground openings under various external as well as internal loads. Eccentric loads significantly influenced the stress pattern of the surrounding tunnel. The achievements can be practically used in completing and modifying regulations for stability investigation of shallow tunnels. 相似文献
6.
Zoya Sadighi Abolghasem Ataie Mohammad Reza Barati 《Metals and Materials International》2014,20(1):77-81
In this study, barium-doped lanthanum manganite, La0.8Ba0.2MnO3, was synthesized via a mechano-thermal route employing high energy ball milling and subsequent heat treatment. The structural evolution, morphology and thermal behaviour of the powders were evaluated using XRD, FESEM, and DTA/TGA, respectively. DTA/TGA results showed that the calcination temperature of the carbonates significantly decreased by increasing the milling time. The results revealed that single phase perovskite was formed at 900 °C in a milled sample for 2 h and this temperature decreased to 600 °C by increasing the milling time to 30 h. The mean crystallite size also decreased from 32 to 20 nm by increasing the milling time from 2 to 30 h. The reaction sequence of La0.8Ba0.2MnO3 formation via the mechano-thermal route is proposed using XRD and DTA/TGA results. FESEM micrographs showed that the mean particle size of the perovskite phase is increased slightly from 30 to 40 nm by increasing the heat treatment temperature from 600 to 900 °C. 相似文献
7.
One of the main applications of time alignment is parallel corpus based voice conversion. In the literature, various methods such as dynamic time warping (DTW) and hidden Markov model have been suggested for time alignment of two speech signals. In this paper, we introduce some modifications to DTW in order to decrease the time alignment error. These modifications are refinement, which is done by exerting a threshold, normalization, and comparisons between the preceding and the following frames to make sound correspondence between two different parallel corpus-based speakers’ speeches. Evaluation of this approach which has been done on some corpus sentences indicates a significant improvement of time alignment. At least about 4% and in some cases 15% decrease of error in comparison with DTW has been achieved. 相似文献
8.
Abolghasem Nourmohammadi Saeid Jalali Asadabadi Mohammad Hasan Yousefi Majid Ghasemzadeh 《Nanoscale research letters》2012,7(1):689
The photoluminescence emission of nanoporous anodic aluminum oxide films formed in phosphoric acid is studied in order to explore their defect-based subband electronic structure. Different excitation wavelengths are used to identify most of the details of the subband states. The films are produced under different anodizing conditions to optimize their emission in the visible range. Scanning electron microscopy investigations confirm pore formation in the produced layers. Gaussian analysis of the emission data indicates that subband states change with anodizing parameters, and various point defects can be formed both in the bulk and on the surface of these nanoporous layers during anodizing. 相似文献
9.
Mahsa S. Asgari Manouchehr Nikazar Payam Molla-abbasi Mohammad Mahdi Hasani-Sadrabadi 《International Journal of Hydrogen Energy》2013
Here we show preparation and characterization of a new type of composite membrane based on Nafion®/histidine modified carbon nanotube by imidazole groups (Im-CNT), for direct methanol fuel cell (DMFC) applications. Due to the presence of this imidazole-based amino acid on the surface of CNT, new electrostatic interactions can be formed in the interface of Nafion® and Im-CNT. Physical characteristics of these nanocomposite membranes are investigated by water uptake, methanol permeability, ion exchange capacity, proton conductivity, as well as fuel cell performance results. 相似文献
10.
In this study, nanocomposite hydrogels from grafting of acrylamide onto kappa-carrageenan biopolymer were prepared in the presence of sepiolite clay. Methylenebisacrylamide and ammonium persulfate were used as cross-linker and initiator, respectively. The sepiolite nanoclay was introduced into hydrogel matrix without any chemical treatment. The structure of nanocomposites was investigated by FTIR, SEM, TEM, and TGA techniques. The TEM image showed that sepiolite exists as individual needle’s shape. The swelling of hydrogels were studied in distilled water, salt solutions, and various pHs. The obtained nanocomposites were evaluated to remove of cationic crystal violet (CV) dye from water. The kinetic and isotherm of adsorption of dye onto nanocomposites were studied and analyzed according to kinetic and isotherm models. The results showed that the pseudo-second-order adsorption kinetic was predominated for the adsorption of CV onto nanocomposites. The experimental equilibrated adsorption capacity of nanocomposites was analyzed using Freundlich and Langmuir isotherm models. The results corroborated that the experimental data fit the Langmuir isotherm the best. By varying the pH of initial dye solution, while the clay-free hydrogel showed relatively pH-independent adsorption behavior, the nanocomposites depicted pH-dependent adsorption. 相似文献