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141.
142.
Shahram Amini Michel W. Barsoum Tamer El-Raghy 《Journal of the American Ceramic Society》2007,90(12):3953-3958
Because the layered machinable ternary carbide, Ti2 SC, has a significantly shorter c -lattice parameter—as compared with most of the 50+ other so-called Mn+1 AXn (MAX) phase family (M=early transition metal; A=A group element and X=C or N and n=1–3) to which it belongs—it was postulated that its mechanical properties would be significantly different than the other MAX phases. In this work, fine-grained (FG) and coarse-grained (CG) polycrystalline fully dense Ti2 SC samples were fabricated. Hot pressing Ti2 SC powders, at 1500°C under a stress of ∼45 MPa for 5 h resulted in FG (2–4 μm) samples which and upon further annealing for 20 h at 1600°C resulted in CG (10–20 μm) ones. No peaks other than those associated with Ti2 SC and an impurity anatase phase, with a volume fraction of ∼6 vol% were observed in the XRD patterns and micrographs. The average Vickers hardness in the 2–300 N range is 8±2 GPa with the FG samples being slightly harder. This hardness is the highest of any of the MAX phases characterized to date. Also in contrast to all MAX phases, cracks extended from the corners of Vickers indents in the FG samples. From these cracks the fracture toughness was estimated and found to increase more or less linearly with load from ≈4 to 6 MPa·m1/2 as the Vickers force was increased from 50 to 300 N, respectively. The room temperature compressive stress of the FG samples was 1.4±0.2 GPa; the failure mode was brittle. Its Young's modulus—also one of the highest for a M2 AX phase measured to date—was 316±2 GPa. There was no evidence for incipient kink band formation during simple compression. The latter is attributed, in part, to the fine grain size of the hot-pressed material. 相似文献
143.
ABSTRACTA new eco-friendly bucky gel nano sorbent consisting of magnetic grapheneoxide (MGO) and an ionic liquid (IL) was used based on dispersive extraction technique followed by cold vapor atomic absorption spectroscopy for determination of mercury in river water, milk, omega-3 supplements, and lipstick. The optimum conditions for extraction were 50 mg of sorbent (mass ratio IL/MGO: 26), 8 min vortexing, acetate buffer pH = 4, and for desorption 3 min vortexing of HNO3 (1 mL). The limits of detection, quantification, preconcentration factor and extraction recovery were found at 0.57, 1.88 µg L?1, 21 and 84%. Relative standard deviation (RSD) was 6.5% (n = 3). 相似文献
144.
Shahram Arbab Parviz Noorpanah Naser Mohammadi Ahmad Zeinolebadi 《Journal of Polymer Research》2011,18(6):1343-1351
The simultaneous effects of non-solvent concentration in the spinning dope, jet-stretching and hot-drawing on porosity, morphology
development and mechanical properties of wet-spun poly(acrylonitrile) fibers were studied. Addition of non-solvent to the
spinning dope increased dope viscosity, the entanglement density of the polymeric solution and the number of entanglements
per chain. Drawability of the as-spun fiber depended on the number of entanglements per polymer chain. Therefore, addition
of non-solvent improved or spoiled drawability of the wet-spun fibers based on the concentration of the initial spinning dope.
Hot-drawing and jet-stretching did not affect the fraction of nanovoids but shifted their size distribution towards smaller
values. However, hot-drawing was more effective in reducing the overall porosity of the fibers in comparison with jet-stretching.
Fiber tenacity increased when overall porosity decreased. Finally, strength-diameter correlation showed good agreement with
the Griffith’s theory. 相似文献
145.
Davood Iranshahi Mohsen Karimi Shahram Amiri Mitra Jafari Razieh Rafiei Mohammad Reza Rahimpour 《Chemical Engineering Research and Design》2014
Naphtha reforming is one of the most important processes in refineries in which high value-added reformate for gasoline pool and aromatics such as benzene, toluene, and xylene are produced. It is necessary to establish new naphtha reforming units and develop the traditional units to increase the efficiency of the processes. In this study, according to the recent progresses in the naphtha reforming technology, mathematical modeling of this process in continuous catalyst regeneration mode of operation is accomplished in two dimensions (radial and axial) by considering cross flow pattern. In addition, a new catalyst deactivation model has been proposed and a new reaction network model based on 32 pseudo-components with 84 reactions is investigated. Then, this model has been validated by comparing with industrial data, and its results have acceptable agreement. 相似文献
146.
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148.
Based on a fifteen month investigation of a post production facilities for both the entertainment industry and broadcasters, we identified a number of challenges with the design and implementation of a server in support of multiple editing stations. These include, how to: share the same content among multiple editors, support continuous display of the edited content for each editor, support complex editing operations, compute the set of changes (deltas) proposed by an editor, compare the deltas proposed by multiple editors, etc. It is beyond the focus of this paper to report on each challenge and its related solutions. Instead, we focus on one challenge, namely how to support continuous display of the edited content for each editors, and techniques for physical organization of data to address this challenge. 相似文献
149.
In this paper, a new voltage-mode configuration for realizing a first-order phase shifter is suggested. The proposed phase
shifter contains low number of components, i.e. two n-type metal-oxide semiconductor field effect transistors (NMOS transistors) both operating in saturation region, a grounded
capacitor and three resistors. The presented circuit can be equipped with electronic tunability by using externally controllable
electronic resistor. Computer simulation results, using SPICE program, are given to demonstrate the performance of the proposed
phase shifter. 相似文献
150.
Esmaili Shabnam Tavallali Vahid Amiri Bahram Bazrafshan Foroud Sharafzadeh Shahram 《SILICON》2022,14(16):10245-10256
Silicon - Drought stress limits the growth and yield of essential oils of valuable medicinal plants such as feverfew (Tanacetum parthenium). So, foliar application efficiency of nano-silicon... 相似文献