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排序方式: 共有236条查询结果,搜索用时 750 毫秒
51.
Babak Kaboudin Foad Kazemi Abolfazl Ghaderian Zahra Zand 《Journal of the Iranian Chemical Society》2014,11(4):1121-1127
52.
The paper considers an inventory model with backorders in a fuzzy situation by employing two types of fuzzy numbers, which are trapezoidal and triangular. A full-fuzzy model is developed where the input parameters and the decision variables are fuzzified. The optimal policy for the developed model is determined using the Kuhn-Tucker conditions after the defuzzification of the cost function with the graded mean integration (GMI) method. Numerical examples and a sensitivity analysis study are provided to highlight the differences between crisp and the fuzzy cases. 相似文献
53.
A highly efficient photocatalytic reduction of nitroarenes using TiO2/polyethylene glycol 400-water (TiO2/PEG–H2O) is reported. This system at deoxygenated and illuminated (sunlight or violet LED) conditions efficiently reduced nitroarenes using oxalic acid or ammonium formate as a sacrificial electron donor. Reducible functional groups such as chloro, hydroxy, flouro, bromo and carbonyl were intact under the optimized reaction conditions. The 0.1 and 0.5–1 mmol amount of nitroarenes was used under sunlight and violet LED (400 nm) irradiation, respectively. Reusability of the nanotitania was successfully carried out four times. The analyses of the recovered catalyst after five runs including TEM, XRD, TGA and CHN were done and results showed that PEG is located on TiO2; no change in morphology, crystallinity and particle sizes was observed. 相似文献
54.
A. Bahraminasab M. Sadegh Movahed S. D. Nasiri A. A. Masoudi Muhammad Sahimi 《Journal of statistical physics》2006,124(6):1471-1490
We carry out an exact analysis of the average frequency ν+
αxi
in the direction x
i
of positiveslope crossing of a given level α such that, h(x, t) − = α, of growing surfaces in spatial dimension d. Here, h(x, t) is the surface height at time t, and is its mean value. We analyze the problem when the surface growth dynamics is governed by the Kardar-Parisi-Zhang (KPZ) equation without surface tension, in the time regime prior to appearance of cusp singularities (sharp valleys), as well as in the random deposition (RD) model. The total number N
+ of such level-crossings with positive slope in all the directions is then shown to scale with time as t
d/2 for both the KPZ equation and the RD model.
PACS number(s): 52.75.Rx, 68.35.Ct 相似文献
55.
Malihe S. Kazemi Golamhossein Rounaghi 《Russian Journal of Inorganic Chemistry》2010,55(12):1987-1991
The liquid membrane transport of Pb2+ cation using decyl-18-crown-6 as selective ion carrier was studied. The transport of lead ion across the liquid membrane in the presence of S2O 3 2? , P2O 7 4? , CN?, SCN?, and DDC? as stripping agents in the receiving phase shows that the nature and the concentration of the stripping agents affect on Pb2+ cation transport and the maximum transport occurs when the sodium thiosulfate (Na2S2O3) was used. The effects of various parameters influencing the transport efficiency such as the pH of the source and receiving phases, the concentration of picrate ion as counter ion in the source phase were also studied. Five replicated experiments show that a value 82.12 ± 2.09% of the initial concentration of the Pb2+ cation in the source phase is extracted into the receiving phase after 4 hours. Also the selectivity and efficiency of lead ion transport from the source phase containing equimolar mixtures of Na+, K+, Ca2+, Ni2+, Cu2+, Cd2+ and Ag+ metal cations were investigated. 相似文献
56.
57.
Sulfamic acid immobilized on diethylenetriamine functionalized Fe3O4 nanoparticles (SA‐DETA‐Fe3O4) was successfully prepared and characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), vibrating sample magnetometer (VSM), thermo gravimetric analysis (TGA), X‐Ray diffraction (XRD) and scanning electron microscopy (SEM). The sulfamic acid was found as a magnetically separable and highly active catalyst for the oxidative coupling thiols, oxidation of sulfides. Furthermore, the SA‐DETA‐Fe3O4 showed the high catalytic activity in Knoevenagel condensation of aromatic aldehydes with active methylene compounds (malononitrile and ethyl cynoacetate). The nanosolid catalyst could be easily recovered by a simple magnetic separation and reused for many cycles without deterioration in catalytic activity. 相似文献
58.
Dr. Masoud Kazemi Dr. Xiang Sheng Prof. Fahmi Himo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(51):11945-11954
Acyl transferase from Mycobacterium smegmatis (MsAcT) is a promising biocatalyst because it catalyzes an acyl transfer reaction in aqueous solution, thereby accepting many primary and secondary alcohols as substrates. MsAcT also exhibits high enantioselectivity for a selected number of secondary alcohols. To increase the applicability of this enzyme for the production of optically active compounds, a detailed understanding of the reaction mechanism and the factors that affect enantioselectivity is essential. Herein, quantum chemical calculations are employed to study the reactions of two secondary alcohols, 1-isopropyl propargyl alcohol and 2-hydroxy propanenitrile, for which the enzyme displays opposite enantiopreference, favoring the S enantiomer in the former case and R enantiomer in the latter. A model of the active site has been designed and for both substrates various binding modes are evaluated and the intermediates and transition states along the reaction path are then located. The calculated energy profiles agree with the experimental observations, and reproduce the selectivity outcome. Through a detailed analysis of the geometries of key transition states, insights into the origins of the enantiopreference are obtained. 相似文献
59.
NaY zeolite functionalized by sulfamic acid/Cu(OAc)_2[NaY/SA/Cu(Ⅱ)] was synthesized and used as a new,efficient and recyclable catalyst for preparation of formamides. This novel organic-inorganic hybrid catalyst was characterized by several techniques such as FT-IR, XRD, SEM, EDX and TG analysis.Chemoselectivity, easy procedure, excellent yields, very short reaction times, solvent-free and mild reaction conditions are some benefits of this new protocol. 相似文献
60.
Mohammad Ebrahim Torki Mohammad Taghi Kazemi Junuthula N. Reddy Hassan Haddadpoud Saeid Mahmoudkhani 《Journal of sound and vibration》2014
In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known. 相似文献