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排序方式: 共有251条查询结果,搜索用时 204 毫秒
61.
Reza Hassanzadeh Esmaile Khorram Iraj Mahdavi Nezam Mahdavi-Amiri 《Applied Soft Computing》2011,11(1):551-560
We consider nonlinear optimization problems constrained by a system of fuzzy relation equations. The solution set of the fuzzy relation equations being nonconvex, in general, conventional nonlinear programming methods are not practical. Here, we propose a genetic algorithm with max-product composition to obtain a near optimal solution for convex or nonconvex solution set. Test problems are constructed to evaluate the performance of the proposed algorithm showing alternative solutions obtained by our proposed model. 相似文献
62.
Vahideh Shahedifar Amir MasoudRezadoust Iraj AmiriAmraei 《Propellants, Explosives, Pyrotechnics》2016,41(2):321-326
The inhibition of a double‐base solid propellant is used to control and prevent the burning degree of the exposed area, which is due to longer burning time. In recent years, inhibition with cellulose derivatives has become popular, but these monolithic systems usually suffer from the drawback of a high erosion rate and demand high thickness and low burning time. In this research two composite inhibitors based on natural fibers were manufactured by filament winding technique and their physical, thermal, and thermomechanical properties were compared. In addition, a chlorinated flame retardant (CFR) as well as antimony trioxide were added in inhibitor compositions to control their burning processes. It was found that the cotton/epoxy composite inhibitor displays a compatible thermal expansion coefficient with the propellant and a high amount of residual char compared to cotton/vinyl ester composite. Also, it was understood that the moisture absorption resistance and thermal stability, i.e., initial decomposition temperature of cotton/vinyl ester specimen were better than cotton/epoxy specimen. Furthermore, density and the flame retardant performance of both composite inhibitors were similar. Additionally, the tan(δ) value obtained for cotton/epoxy composite was higher than that of cotton/vinyl ester composite indicating its good dissipation of vibrational energy. 相似文献
63.
Fathollah Pourfayaz Seyed Hassan Jafari Yadollah Mortazavi Abbas Ali Khodadadi Hossein Ali Khonakdar 《Polymer-Plastics Technology and Engineering》2015,54(6):632-638
Different contents of multiwalled carbon nanotube (MWCNTs) functionalized by He-dielectric barrier discharge (DBD) plasma followed by an exposure to NH3 were incorporated into PA6 matrix via a phase inversion based solution method. Optical and electron microscopic results were indicative of the excellent dispersion state of the MWCNTs. The differential scanning calorimetry and thermogravimetric analysis measurements revealed that even addition of a slight amount of the MWCNTs significantly increased the thermal stability and crystallization temperature. Moreover, the low electrical percolation threshold of the PA 6/functionalized MWCNTs nanocomposites was another confirmation for achieving a good dispersion state of MWCNTs using this approach. 相似文献
64.
Rasol Abdullah Mirzaie Firouzeh Kamrani Azam Anaraki Firooz Abbas Ali Khodadadi 《Materials Chemistry and Physics》2012
Visible light sensitive photocatalysts of Fe2O3/ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe2O3 and sodium hydroxide at room temperature. The products were characterized by scanning electron microscopy, powder X-ray diffraction, N2 adsorption–desorption measurement, UV–vis absorption, and photoluminescence spectroscopy and used for photodecolorization of Congo red. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe3+ to Zn2+ ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98–3.81 eV and 2.88–2.98 eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed. These nanocomposites showed high decolorization ability in visible light with wavelength up to about 400 nm. Among the samples, Fe2O3/ZnO nanoflower (molar ratio of Fe3+ to Zn2+ is 1:100) exhibited higher decolorization efficiency than the other nanocomposites. It could be considered as a promising photocatalyst for dyes treatment. 相似文献
65.
M. SaghafiS. Heshmati-Manesh A. Ataie A.A. Khodadadi 《International Journal of Refractory Metals and Hard Materials》2012,30(1):128-132
Nanocrystalline molybdenum with a mean crystallite size of 50 nm was synthesized by mechanical activation of MoO3 powder and its subsequent hydrogen reduction. MoO3 powder was severely activated in a high energy planetary ball mill under a pure argon atmosphere. Temperature-programmed reduction (TPR) by hydrogen was used to investigate hydrogen reduction behavior of the powder samples activated for 5 and 20 h. It was found that by increasing the activation time, the peak temperature for the reduction was shifted slightly to lower temperatures and the peak for the reduction of MoO3 to MoO2 was completely separated from the one for the reduction of MoO2 to molybdenum. In order to evaluate the effect of mechanical activation on the reduction behavior of MoO3, the initial micron-sized powder and the sample activated for 20 h were reduced at similar conditions. It was found that the activated sample with finer particles was reduced faster than the un-milled sample. Hydrogen reduction of the non-activated MoO3 produced a very fine grained molybdenum powder but the crystallite size changes of the sample activated for 20 h was negligible during reduction. 相似文献
66.
Iraj BARGEGOL Seyed Mohsen HOSSEINIAN Vahid NAJAFI MOGHADDAM GILANI Mohammad NIKOOKAR Alireza OROUEI 《Frontiers of Structural and Civil Engineering》2022,16(2):250-265
In this study, the relationship between space mean speed (SMS), flow rate and density of pedestrians was investigated in different pedestrian facilities, including 1 walkway, 2 sidewalks, 2 signalized crosswalks and 2 mid-block crosswalks. First, statistical analysis was performed to investigate the normality of data and correlation of variables. Regression analysis was then applied to determine the relationship between SMS, flow rate, and density of pedestrians. Finally, two prediction models of density were obtained using genetic programming (GP) and group method of data handling (GMDH) models, and k-fold and holdout cross-validation methods were used to evaluate the models. By the use of regression analysis, the mathematical relationships between variables in all facilities were calculated and plotted, and the best relationships were observed in flow rate-density diagrams. Results also indicated that GP had a higher R2 than GMDH in the prediction of pedestrian density in terms of flow rate and SMS, suggesting that GP was better able to model SMS and pedestrian density. Moreover, the application of k-fold cross-validation method in the models led to better performances compared to the holdout cross-validation method, which shows that the prediction models using k-fold were more reliable. Finally, density relationships in all facilities were obtained in terms of SMS and flow rate. 相似文献
67.
Jafar Moghimi-Rad Fatemeh Zabihi Iraj Hadi Sadollah Ebrahimi Taghi Dallali Isfahani Jamshid Sabbaghzadeh 《Journal of Materials Science》2010,45(14):3804-3811
The effect of ultrasound radiation on the size and size distribution of synthesized copper particles was investigated under
various concentrations of ethylene glycol (E.G.) as a capping agent. Monodispersed copper particles were produced by the reduction
of an aqueous copper (II) sulfate solution at the presence of hydrazine monohydrate. X-ray diffraction and scanning electron
microscopy analysis revealed that the morphology, size, and size distribution of produced particles were influenced by the
reducing agent injection rate, capping agent concentration, and sonication. Increasing the injection rate of reducing agent
to an amount higher than a critical value decreases the size of copper particles and also converts the monodispersed particles
to polydispersed particles. Results of using a sonifier at the reduction stage revealed that finer monodispersed copper particles
can be achieved at higher injection rates related to the critical value. Increasing the concentration of E.G. as a capping
agent decreases the size of copper particles, while applying ultrasound radiation along with increasing the concentration
of E.G. increases the size of copper particles. Morphology of particles varies by the concentration and type of the capping
agent. Higher reducing agent injection rates and the application of a sonifier at the instance of reduction result in smaller
spherical particles at various capping agent concentrations. 相似文献
68.
Abstract The objective of this study is to present an information system for assessment of management and organization in a gas refinery. To achieve the objective of this study, Balanced Score Card (BSC) methodology was utilized to categorize management and organization indicators into four categories. The data related to a five year period was then collected to provide a benchmark for the refinery. Furthermore, the data from 19 developed and developing countries were collected for the purpose of benchmarking. A t‐test was then introduced to benchmark the refinery's management and organization indicators. Moreover, Data Envelopment Analysis (DEA) was used to analyze and further assess the violated indicators. Finally, an integrated information system was designed in .Net environment by C#. It was introduced to facilitate the assessment of management and organization indicators. This is the first study that introduces an information system for performance assessment of management and organization in a gas refinery by integration of BSC, DEA and t‐test. 相似文献
69.
In this study, three non‐linear indices consist of compression, one‐dimensional (1D) and two‐dimensional (2D) fractal dimensions are used for the determination of the malignancy or benignity of cancer tumours in breast thermograms. On the other hand, by developing the high‐precision infrared cameras as well as new methods of image processing, biomedical thermography images have found a prominent position among the others. Furthermore, cancerous tissue can be affected by the laser. In this study, in order to treat the cancerous lesion identified by breast thermograms, the laser parameters are designed. The basis of controller designing is the obtained non‐linear indices. If the indices are moved from the chaotic behaviour to normal condition, the treating tissue is going from cancerous to a healthy condition and the treatment process is completed. Radiation frequency and the energy density of laser are designed as two key elements in the cancer treatment. In this study, the type I and type II fuzzy controllers are employed for the control strategies. Using the proposed closed‐loop control, the non‐linear indices of the cancerous lesion will be reduced during the treatment process. The simulation results on two datasets of breast thermograms indicate the superiority of type II fuzzy controller.Inspec keywords: closed loop systems, fractals, infrared imaging, tumours, fuzzy control, medical image processing, cancer, biological tissues, gynaecology, patient treatmentOther keywords: cancer tumours, breast thermograms, high‐precision infrared cameras, image processing, cancerous tissue, cancerous lesion, nonlinear indices, type II fuzzy controller, closed‐loop control, fuzzy controller design, breast cancer treatment, 2D fractal dimensions 相似文献
70.
Bulk Single Crystal‐Like Structural and Magnetic Characteristics of Epitaxial Spinel Ferrite Thin Films with Elimination of Antiphase Boundaries
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Amit V. Singh Behrouz Khodadadi Jamileh Beik Mohammadi Sahar Keshavarz Tim Mewes Devendra Singh Negi Ranjan Datta Zbigniew Galazka Reinhard Uecker Arunava Gupta 《Advanced materials (Deerfield Beach, Fla.)》2017,29(30)
Spinel ferrite NiFe2O4 thin films have been grown on three isostructural substrates, MgAl2O4, MgGa2O4, and CoGa2O4 using pulsed laser deposition. These substrates have lattice mismatches of 3.1%, 0.8%, and 0.2%, respectively, with NiFe2O4. As expected, the films grown on MgAl2O4 substrate show the presence of the antiphase boundary defects. However, no antiphase boundaries (APBs) are observed for films grown on near‐lattice‐matched substrates MgGa2O4 and CoGa2O4. This demonstrates that by using isostructural and lattice‐matched substrates, the formation of APBs can be avoided in NiFe2O4 thin films. Consequently, static and dynamic magnetic properties comparable with the bulk can be realized. Initial results indicate similar improvements in film quality and magnetic properties due to the elimination of APBs in other members of the spinel ferrite family, such as Fe3O4 and CoFe2O4, which have similar crystallographic structure and lattice constants as NiFe2O4. 相似文献