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排序方式: 共有429条查询结果,搜索用时 78 毫秒
11.
Majid Azarang Mehran Sookhakian Mousa Aliahmad Masoumeh Dorraj Wan Jeffrey Basirun Boon Tong Goh Yatimah Alias 《International Journal of Hydrogen Energy》2018,43(32):14905-14914
Nitrogen-doped graphene-ZnS composite (NG-ZnS) was synthesized by thermal treatment of graphene-ZnS composite (G-ZnS) in NH3 medium. In the second step, the as-synthesized samples were deposited on indium tin oxide glass (ITO) by electrophoretic deposition for photocatalytic hydrogen evolution reaction. The as-prepared NG-ZnS-modified ITO electrode displayed excellent photocatalytic activity, rapid transient photocurrent response, superior stability and high recyclability compared to the pure ZnS and G-ZnS-modified ITO electrode due to the synergy between the photocatalytic activity of ZnS nanorods and the large surface area and high conductivity of N-graphene. 相似文献
12.
Mohammad Hossein Aboonasr Shiraz Mehran Rezaei Fereshteh Meshkani 《Korean Journal of Chemical Engineering》2016,33(12):3359-3366
Mesoporous nanocrystalline nickel-alumina promoted catalysts with high surface area were prepared by microemulsion (ME) method and employed in dry reforming of methane reaction. The catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller surface area analysis (BET), temperature programmed reduction (TPR) and temperature programmed oxidation (TPO) techniques. The results showed that the prepared catalysts had high porosity with great surface area and small crystallite size. Among the K2O, MgO, CaO and BaO promoters, the MgO promoter showed considerable effect on catalytic performance and coke suppression of catalyst. 相似文献
13.
Siamak Pedrammehr Mehran Mahboubkhah Navid Khani 《Journal of Mechanical Science and Technology》2012,26(3):711-721
In this paper, a Newton-Euler approach is utilized to generate the improved dynamic equations of the generally configured
Stewart platform. Using the kinematic model of the universal joint, the rotational degree of freedom of the pods around the
axial direction is taken into account in the formulation. The justifiable direction of the reaction moment on each pod is
specified and considered in deriving the dynamic equations. Considering the theorem of parallel axes, the inertia tensors
for different elements of the manipulator are obtained in this study. From a theoretical point, the improved formulation is
more accurate in comparison with previous ones, and the necessity of the improvement is clear evident from significant differences
in the simulation results for the improved model and the model without improvement. In addition to more feasibility of the
structure and higher accuracy, the model is highly compatible with computer arithmetic and suitable for online applications
for loop control problems in hardware. 相似文献
14.
S. Siavash Saei‐Dehkordi Aziz A. Fallah Mahbubeh Heidari‐Nasirabadi Mehran Moradi 《International Journal of Food Science & Technology》2012,47(8):1579-1585
This study aimed to determine the chemical composition, antimicrobial and antioxidative activity of Satureja khuzestanica Jamzad essential oil. The oil was analysed by GC and GC/MS. Twenty‐eight constituents were identified. The oxygenated monoterpenes (78.22%) were the principal compound group. Among them, carvacrol (53.86%) and thymol (19.84%) were the most abundant constituents. The oil exhibited an acceptable antimicrobial activity against most of the tested microorganisms. The checkerboard method was applied to determine fractional inhibitory concentration indices (FICIs) to interpret the synergetic, additive, indifference or antagonistic interactions between essential oil and each of antimicrobials (lysozyme, ciprofloxacin, fluconazole and amphotericin B) against food‐related microorganisms. The synergetic phenomenon (FICI ≤ 0.5) was observed in majority of combinations with the exception of the essential oil and lysozyme. The oil exhibited good 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity (IC50 = 28.71 μg mL?1). Also, the oil had strong antioxidative activity in β‐carotene‐linoleic acid assay relative antioxidant activity (RAA% = 95.45). This study demonstrated that the essential oil has beneficial biological properties and its simultaneous application with standard antimicrobials against food‐related microorganisms result in reduction in inhibitory doses of the antimicrobials in vitro. 相似文献
15.
Mehran Dadkhah Mohammad Hossein Mosallanejad Luca luliano Abdollah Saboori 《金属学报(英文版)》2021,34(9):1173-1200
Nowadays, as an emerging technology, additive manufacturing(AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites(MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coe fficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works. 相似文献
16.
Mutations Closer to the Active Site Improve the Promiscuous Aldolase Activity of 4‐Oxalocrotonate Tautomerase More Effectively than Distant Mutations
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Mehran Rahimi Jan‐Ytzen van der Meer Dr. Edzard M. Geertsema Harshwardhan Poddar Dr. Bert‐Jan Baas Prof. Dr. Gerrit J. Poelarends 《Chembiochem : a European journal of chemical biology》2016,17(13):1225-1228
The enzyme 4‐oxalocrotonate tautomerase (4‐OT), which catalyzes enol–keto tautomerization as part of a degradative pathway for aromatic hydrocarbons, promiscuously catalyzes various carbon–carbon bond‐forming reactions. These include the aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde. Here, we demonstrate that 4‐OT can be engineered into a more efficient aldolase for this condensation reaction, with a >5000‐fold improvement in catalytic efficiency (kcat/Km) and a >107‐fold change in reaction specificity, by exploring small libraries in which only “hotspots” are varied. The hotspots were identified by systematic mutagenesis (covering each residue), followed by a screen for single mutations that give a strong improvement in the desired aldolase activity. All beneficial mutations were near the active site of 4‐OT, thus underpinning the notion that new catalytic activities of a promiscuous enzyme are more effectively enhanced by mutations close to the active site. 相似文献
17.
Nima Bayat Mehran Rezaei Fereshteh Meshkani 《Korean Journal of Chemical Engineering》2016,33(2):490-499
Nickel catalysts supported on mesoporous nanocrystalline gamma alumina with various nickel loadings were prepared and employed for thermocatalytic decomposition of methane into CO x -free hydrogen and carbon nanofibers. The prepared catalysts with different nickel contents exhibited mesoporous structure with high surface area in the range of 121.3 to 66.2m2g?1. Increasing in nickel content decreased the pore volume and increased the crystallite size. The catalytic results revealed that the nickel content and operating temperature both play important roles on the catalytic performance of the prepared catalysts. The results showed that increasing in reaction temperature increased the initial conversion of catalysts and significantly decreased the catalyst lifetime. Scanning electron microscopy (SEM) analysis of the spent catalysts evaluated at different temperatures revealed the formation of intertwined carbon filaments. The results showed that increasing in reaction temperature decreased the diameters of nanofibers and increased the formation of encapsulating carbon. 相似文献
18.
Wan J Basirun Mehran Sookhakian Saeid Baradaran Mohammad R Mahmoudian Mehdi Ebadi 《Nanoscale research letters》2013,8(1):397
Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. 相似文献
19.
Roxana Family Mehran Solati-Hashjin Shahram Namjoy Nik Ali Nemati 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(6):688-691
In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD). Results show that the morphology of HA-Alumina-Zirconia coatings is more homogenous in the second process with 2 hours final sol stirring time, 20 hours aging time under stirring at 60, 675°C calcination temperature for coating and 850°C for powder and 60mm/min rate of dip coating. 相似文献
20.
Alieh Aminian Mehran Solati-HashjinAli Samadikuchaksaraei Farhad BakhshiFazel Gorjipour Arghavan FarzadiFattolah Moztarzadeh Martin Schmücker 《Ceramics International》2011,37(4):1219-1229
Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO3)2, (NH4)3PO4 or (NH4)2HPO4 and Si(OCH2CH3)4 (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO43−) groups with silicate (SiO44−) groups resulting in Si-HA described as Ca10(PO4)6−x(SiO4)x(OH)2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH− loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite. 相似文献