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排序方式: 共有431条查询结果,搜索用时 328 毫秒
71.
S. A. Hosseini M. Alizadeh A. Ghasemi M. A. Meshkot 《Journal of Materials Engineering and Performance》2013,22(2):405-409
Highly porous NiTi with isotropic pore morphology has been successfully produced by self-propagating high-temperature synthesis of elemental Ni/Ti metallic powders. The effects of adding urea and NaCl as temporary pore fillers were investigated on pore morphology, microstructure, chemical composition, and the phase transformation temperatures of specimens. These parameters were studied by optical microscopy, scanning electron microscopy, x-ray diffraction, and differential scanning calorimetry (DSC). Highly porous specimens were obtained with up to 83% total porosity and pore sizes between 300 and 500 μm in diameter. Results show pore characteristics were improved from anisotropic to isotropic and pore morphology was changed from channel-like to irregular by adding pore filler powders. Furthermore, the highly porous specimens produced when using urea as a space holder, were of more uniform composition in comparison to NaCl. DSC results showed that a two-step martensitic phase transformation takes place during the cooling cycles and the austenite finish temperature (A f) is close to human body temperature. Compression test results reveal that the compressive strength of highly porous NiTi is about 155 MPa and recoverable strain about 6% in superelasticity regime. 相似文献
72.
Z. Piravi-Vanak Jahan B. Ghasemi M. Ghavami H. Ezzatpanah E. Zolfonoun 《Journal of the American Oil Chemists' Society》2012,89(3):371-378
Twenty seven Iranian olive oil samples were collected from different provinces to evaluate fatty acids and sterol compositions.
The samples were collected from different geographical locations that varied in altitude, temperature, humidity and rain fall.
The sample collected from the northern part of Iran by the Caspian Sea had higher oleic acid [G2 sample (75.98%)] and lower linoleic acid [Go5 sample (6.5%)] and palmitic acid [G2 sample (10.78%)] concentrations than samples from the southern part of the country such as F1 whose contents of C16:0, C18:1 and C18:2 were 15.27, 62.73 and 16.09%, respectively, in the southern part, the climate is
dry and the temperature variation is wider and the elevation is 1,488 m. The results indicated that oleic acid was the predominant
fatty acid with 62.7% for F1 sample in the warmer climate at the south of Iran to 76.0% for G2 sample in the cooler climate in the north of Iran. According to the results, the highest content of β-sitosterol was 87%
related to samples G9 and Z3 from the north of Iran and the lowest content was 69.95% related to sample F1–24 from the south of Iran. Clustering techniques such as principal component analysis and hierarchical cluster analysis were
carried out on olive composition data to show similarities and discrimination between samples as a function of the cultivation
zone. The two methods applied clearly showed the effect of growing regions on the distribution of the olive oil samples in
the high dimensional space created by fatty acid and sterol compositions. 相似文献
73.
Reza Ghasemi Reza Shoja-Razavi Reza Mozafarinia Hossein Jamali 《Ceramics International》2013,39(8):8805-8813
The main goal of this paper was to evaluate and compare the microstructure and mechanical properties of plasma-sprayed nanostructured and conventional yttria stabilized zirconia (YSZ) thermal barrier coatings (TBCs). To this end, NiCrAlY bond coat, nanostructured, and conventional YSZ coatings were deposited on Inconel 738LC substrate by atmospheric plasma spraying (APS). The mechanical properties of the coating were evaluated using nanoindentation and bonding strength tests. The microstructure and phase composition of the coating were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffractometry (XRD). The nanostructured YSZ coating contained both nanosized particles retained from the powder and microcolumnar grains formed through the resolidification of the molten part of the powder, whereas the microstructure of the conventional YSZ coating consisted of columnar grain splats only. The phase composition of the as-sprayed nanostructured coating consisted of the non-transformable tetragonal phase, while the conventional coating showed the presence of both the monoclinic and non-transformable tetragonal phases. The results of nanoindentation and bonding strength tests indicated that the mechanical properties of the nanostructured coating were better than those of the conventional coating. 相似文献
74.
Graphene oxide (GO) was deposited on inexpensive and mechanically stable stainless steel (SS) electrode by electrophoretic deposition (EPD) technique. GO was reduced electrochemically in NaNO3 to obtain electrochemically reduced graphene oxide (ERGO). Next, Hybrid nickel–cobalt hexacyanofarrate (NiCoHCF) nanoparticles were deposited from solution containing Ni+2 and Co+2 with ratio of 1:1 on ERGO/SS by bipotential method. Morphological investigation of prepared sample by scanning electron microscopy showed the presence of nanoparticles with diameters in the range of 15–50 nm. Crystal structure of nanocomposite was investigated by X-ray diffraction technique. Electrochemical behavior of prepared film indicates that hybrid nanocomposite has higher specific capacitance (411 F g−1) than ERGO (185.2 F g−1) in KNO3 solution at current density of 0.2 A g−1. In other words, pseudocapacitor that is formed based on the faradaic behavior of NiCoHCF can improve the capacitive performance of ERGO. 相似文献
75.
76.
Abdollah Ghasemi Pirbalouti Sayed Hamed Neshat Ebrahim Rahimi Behzad Hamedi Fatemeh Malekpoor 《International Journal of Food Properties》2013,16(9):2063-2071
Chemical composition and antibacterial activity of essential oils from three endemic plants including, Thymus daenensis Celak, Dracocephalum multicaule Montbr & Auch., Satureja bachtiarica Bunge and one native plant, Tanacetum polycephalum Schultz-Bip were determined. Volatile oils analyzed using gas chromatography and gas chromatography-mass spectrometry. The in-vitro antibacterial activity was performed by agar disc diffusion and micro-dilution assays. The results revealed distinct differences in the compounds depending on sample plant. Among the plant species screened, essential oils of S. bachtiarica and T. daenensis showed highest antibacterial activity against Staphylococcus aureus. 相似文献
77.
Tahmineh Sodaee Ali Ghasemi Ebrahim Paimozd Andrea Paesano Jr. Akimitsu Morisako 《Journal of Electronic Materials》2013,42(9):2771-2783
Cobalt ferrite nanoparticles were synthesized by a reverse micelle process. The optimum processing conditions required to fabricate nanocrystalline cobalt ferrite using a reverse micelle technique, especially the effect of water-to-surfactant molar ratios including w = 8, 10, 12, and 14, pH values in the range of 8 to 11, and annealing temperatures in the range of 400°C to 800°C, were evaluated. x-Ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), vibrating-sample magnetometry, and superconducting quantum interference device analysis were employed to evaluate the structural and magnetic properties of synthesized nanoparticles. XRD analysis confirms that the nanoparticles have a single-phase cubic spinel structure. The average particle size increases with increasing pH value and annealing temperature. Magnetization study reveals that the cobalt ferrite nanoparticles exhibit a superparamagnetic trend. The zero-field-cooled magnetization curves of cobalt ferrite nanoparticles indicated that, with an increase in pH value, the blocking temperature increases. Based on the obtained optimum parameters, terbium-substituted cobalt ferrite nanoparticles with composition CoFe2?x Tb x O4 (x = 0.1 to 0.5) were prepared by a reverse micelle process. XRD and field-emission scanning electron microscopy evaluation demonstrated that single-phase spinel ferrites with narrow size distribution were obtained. Mössbauer spectroscopy was used to determine the site preference of terbium cation. The results confirm that terbium cations were distributed at tetrahedral and octahedral sites, but with a preference for the former. It was observed that, with an increase in terbium content, the saturation magnetization increases. 相似文献
78.
Saeed Choopani Neda Keyhan Ali Ghasemi Ali Sharbati Reza Shams Alam 《Materials Chemistry and Physics》2009,113(2-3):717-720
The effect of Mn+2Co+2Ti+4 substitution on microwave absorption has been studied for BaCoxMnxTi2xFe12 ? 4xO19 ferrite–acrylic resin composites, where x varies from 0.3 to 0.5 in steps of 0.1, in frequency range from 12 to 20 GHz. X-ray diffraction (XRD), scanning electron microscope (SEM), vibrating sample magnetometer, and vector network analyzer were used to analyze the structures, electromagnetic and microwave absorption properties. The results showed that, the magnetoplumbite structures for all samples have been formed. Based on microwave measurement on reflectivity, BaCoxMnxTi2xFe12 ? 4xO19 may be a good candidate for electromagnetic compatibility and other practical applications at high frequency. 相似文献
79.
This paper proposes dynamic positioning (DP) on a hovering autonomous underwater vehicle (HAUV) to perform accurate underwater processes such as welding operations. High maneuverability, high controllability, and hovering of the robot were the prerequisites of this operation, which increase its accuracy and velocity and reduce costs and human health risks. Other types of thrusters were used in this robot to reduce the number of thrusters and controller''s complexity. Controlling every 6 degrees of freedom to perform this type of operation was done. Furthermore, such a delicate operation required controlling the translational and rotational movements together. There was also a need to control the velocities to travel in a prescribed distance at a reasonable time. The possibility of dynamic positioning for welding and maintaining position at a point was defined for the robot. Then the robot''s performance under a defective state-servo motor failure, thruster malfunction-and the subsequent effects on the performance during the predetermined missions were investigated. Simulation results demonstrated that the HAUV has the capability to perform dynamic positioning operations. In this article, one of the prevalent classic control methods called PID controller was employed for controlling the movements of the robot. 相似文献
80.
Zalooli Ahmad Khamehchiyan Mashalah Nikudel Mohammad Reza Freire-Lista David Martín Fort Rafael Ghasemi Shahram 《Bulletin of Engineering Geology and the Environment》2020,79(10):5499-5515
Bulletin of Engineering Geology and the Environment - Salt crystallization-induced decay of Vardavard granodiorite and Shirkouh monzogranite, two Iranian building stones, were assessed with two... 相似文献