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排序方式: 共有317条查询结果,搜索用时 15 毫秒
41.
42.
Chang-Hoon Choi Chidambaram P.R. Khamankar R. Machala C.F. Zhiping Yu Dutton R.W. 《Electron Devices, IEEE Transactions on》2002,49(7):1227-1231
Polysilicon depletion effects show a strong gate length dependence according to experimental p-channel MOS capacitance-voltage (C-V) data. The effect can be influenced not only by gate geometries, but also by dopant profiles in poly-gates. These effects have been modeled and verified using device simulation. Nonuniform dopant distributions in the vertical and lateral direction in the poly-gate cause additional potential drops. The potential drop in the poly-gate becomes critical as the gate geometry is scaled down due to edge and corner depletions resulting from fringing electric fields 相似文献
43.
Omari Muhammad Sachin U. Sonavane Yoel Sasson Mandan Chidambaram 《Catalysis Letters》2008,124(1-2):46-51
Results on nonlinear phenomenon (NLP) in the liquid phase hydrogenation of methyl benzoylformate (MBF) and pyruvaldehyde dimethyl acetal (PA) on chiral Pt-cinchona catalyst are reported for the first time (enantiomeric excess 90–95%). The new data support the conclusions of the NLP studies on ethyl pyruvate (EP) and ketopantolactone (KPL). Namely, the order of the adsorption strengths of the parent cinchona alkaloids are: CD > CN > QN ~ QD and the results of the NLP measurements indirectly verify the so-called 1:1 model of enantioselection. The new data, however, call attention to a new, substrate and modifier dependent phenomenon, which necessitates further experiments for a better understanding of the mechanism of the Orito reaction. 相似文献
44.
C Balagopalakrishna OO Abugo J Horsky PT Manoharan E Nagababu JM Rifkind 《Canadian Metallurgical Quarterly》1998,37(38):13194-13202
The role of the beta-93 cysteine residue in the hemoglobin autoxidation process has been delineated by electron paramagnetic resonance. At low temperatures (8 K) after incubation at 235 K, free radical signals were detected. An analysis of the free radical spectrum produced implies that, besides the superoxide radical expected to be formed during autoxidation, an isotropic free radical is produced with a giso of 2.0133. This g value is consistent with that expected for a sulfur radical. Blocking the beta-93 sulfhydryl group with N-ethylmaleimide was found to eliminate the formation of the isotropic radical, but not the superoxide. This finding confirms the assignment of the isotropic radical as a thiyl radical originating from the oxidation of the cysteine SH group. A kinetic analysis of the time course for the formation of both the superoxide and thiyl radicals is consistent with a reversible electron transfer process between superoxide in the heme pocket of the beta-chains and the cysteine residue. This reaction is expected to produce both a thiyl radical and a peroxide. Direct evidence for peroxide production comes from the detection of a transient Fe(III) heme peroxide complex. The significance of the electron transfer process producing a thiyl radical is discussed. It is shown that the formation of the thiyl radical decreases the rate of autoxidation for the beta-chain and reduces heme degradation attributed to the reaction of superoxide with the heme. The insights gained from these low-temperature studies are believed to be relevant to room-temperature autoxidation. 相似文献
45.
R Chidambaram 《Bulletin of Materials Science》1984,6(4):633-641
The shock Hugoniot curves of a large number of materials up to a few Mbar have been obtained experimentally. Metallurgical
examination and physical measurements on metallic and other samples recovered after shock loading up to several 100 kbar indicate
the existence of large concentrations of point, line and planar defects. Dislocation mechanisms have been invoked to explain
shock wave propagation and the phenomena related to the quick homogenisation of stress and strain behind the shock front.
Computer simulation models using molecular dynamics calculations have also been used to understand some aspects of shock wave
propagation at an atomistic level. For very strong shocks, the material is expected to melt under shock heating, but the experimental
evidence regarding this is inconclusive. A combination of shock temperature measurement and theory may be able to answer this
question. 相似文献
46.
In this work, a globally linearized controller (GLC) for a first-order nonlinear system with dead time is proposed. This is similar to the GLC proposed by Ogunnalke [Ind. Eng. Chem. Process. Des. Dev. 25, 241-248 (1986)] for nonlinear systems without dead time. Two methods are proposed. One is based on the Smith prediction from the model in the transformed domain and the other is based on Newton's extrapolation method. The simulation study is made on the conical tank level process and the results are compared with those obtained using a conventional PI controller and the Smith PI controller based on the transfer function model about the operating point 39%. Finally, experimental results on the laboratory conical tank level process are also given. 相似文献
47.
An understanding of the work hardening behavior of particulate reinforced metal -matrix composites is crucial in optimizing the parameters for deformation processing of these materials. In the case of particulate reinforced composites with an age hardenable aluminum alloy matrix, the microstructure and mechanical properties can be altered by a suitable aging treatment as well as by changing the content of alloying elements in the matrix. In this study MMCs with different levels of Cu in the matrix were prepared and aged to peak hardness. A modified continuum model was then used to relate the work hardening behavior of the composites to microstructural parameters. The model is shown to be accurate for all the composite materials investigated in the present study. 相似文献
48.
M. D. Baldwin P. R. Chidambaram G. R. Edwards 《Metallurgical and Materials Transactions A》1994,25(11):2497-2506
Spreadability and reaction layer growth rates of copper-oxygen alloys on polycrystalline alumina were measured above the melting
point of copper to better understand the direct bonding process. Spreading was measured as a function of composition and temperature
by monitoring the diameter of molten droplets as a function of time. As the oxygen content of the melt increased from 0 to
3 wt pct, the spreading diameter increased linearly, at fixed time and temperature. Constant diameters were observed for oxygen
compositions between approximately 3 and 6 wt pct. The diameters again increased linearly for oxygen concentrations greater
than 7 wt pct. This behavior was explained by reference to the copper-oxygen binary phase equilibrium. An interfacial product
was identified to be the complex oxide, CuA102. A detailed investigation of the interlayer growth kinetics was performed to understand the fundamental phenomena controlling
the spreading rates. The growth rate of the CuAlO2 phase and the spreading rate were simultaneously measured for alumina in contact with a copper-2 wt pct oxygen alloy drop
as a function of temperature. The reaction layer thickening was found to be diffusion controlled, with an apparent activation
energy of 309 kJ/mol, and the spreading rate did not correlate with the thickening rate.
Formerly Research Associate, Center for Welding and Joining Research, Department of Metallurgical and Materials Engineering 相似文献
49.
Rajangam Udayakumar Sampath Kasthurirengan Thankaraj Salammal Mariashibu Manoharan Rajesh Vasudevan Ramesh Anbazhagan Sei Chang Kim Andy Ganapathi Chang Won Choi 《International journal of molecular sciences》2009,10(5):2367-2382
Withania somnifera is an important medicinal plant, which is used in traditional medicine to cure many diseases. Flavonoids were determined in the extracts of W. somnifera root (WSREt) and leaf (WSLEt). The amounts of total flavonoids found in WSREt and WSLEt were 530 and 520 mg/100 g dry weight (DW), respectively. Hypoglycaemic and hypolipidaemic effects of WSREt and WSLEt were also investigated in alloxan-induced diabetic rats. WSREt and WSLEt and the standard drug glibenclamide were orally administered daily to diabetic rats for eight weeks. After the treatment period, urine sugar, blood glucose, haemoglobin (Hb), glycosylated haemoglobin (HbA1C), liver glycogen, serum and tissues lipids, serum and tissues proteins, liver glucose-6-phosphatase (G6P) and serum enzymes like aspartate transaminase (AST), alanine transaminase (ALT), acid phosphatase (ACP) and alkaline phosphatase (ALP) levels were determined. The levels of urine sugar, blood glucose, HbA1C, G6P, AST, ALT, ACP, ALP, serum lipids except high density lipoprotein-bound cholesterol (HDL-c) and tissues like liver, kidney and heart lipids were significantly (p < 0.05) increased, however Hb, total protein, albumin, albumin:globulin (A:G) ratio, tissues protein and glycogen were significantly (p < 0.05) decreased in alloxan-induced diabetic rats. Treatment of the diabetic rats with WSREt, WSLEt and glibenclamide restored the changes of the above parameters to their normal level after eight weeks of treatment, indicating that WSREt and WSLEt possess hypoglycaemic and hypolipidaemic activities in alloxan-induced diabetes mellitus (DM) rats. 相似文献
50.
Jamil Ahmad Wajahat Ur Rehman Shaik Khadheer Basha Basheer Ahamed Kuppanna Chidambaram 《Polymer-Plastics Technology and Engineering》2019,58(4):366-383
Polyamide-b-ethylene (Pebax) is a promising material for membrane-based gas separation application with excellent CO2 capturing potential. Pebax is a rubbery elastomer which offers good mechanical support with its hard crystalline phase and excellent gas transport through its amorphous polyether phase. This review article includes recent advances in Pebax based membrane synthesis, solvent selection for membrane synthesis, compatible fillers with Pebax matrix and the improved gas separation performance of the prepared membranes. The literature review shows that Pebax based membranes are a good candidate for separation of CO2 from flue gases and can be used for commercial applications. 相似文献