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排序方式: 共有1016条查询结果,搜索用时 15 毫秒
41.
This article presents a scheme for improving the power output of grid-connected induction generator commonly used in wind energy conversion systems. Generally, the stator of the induction generator is connected in a star with a line voltage of √3 times the rated winding voltage to reduce the line current and, hence, conductor size. To extend the generating operation over a wider speed range, delta-star switchable stator windings are also in vogue. In such cases, the stator is star connected in the lower speed range and switched to a delta connection above a threshold speed. In this study, a new switching scheme is proposed wherein the stator coils are always connected in a star, while the stator is connected to different voltages in low- and high-speed conditions. At low wind speeds, nominal winding voltage is applied to the stator, whereas at higher speeds, the stator applied voltage is √3 times higher than the rated winding voltage. The efficacy of the scheme is demonstrated experimentally with a suitable microcontroller-based switching arrangement. Typical results indicate an increase in output with reduced switching transients. A case study on a 3-Φ, 50-kW induction generator is presented to emphasize the performance improvement with the proposed scheme. 相似文献
42.
The use of patterned media is a new approach proposed to extend the recording densities of hard disk drives beyond 1 Tb/in.2. Bit-patterned media (BPM) overcome the thermal stability problems of conventional media by using single-domain islands for
each bit of recorded information, thereby eliminating the magnetic transition noise (Albrecht et al., Magnetic Recording on
Patterned Media, 2003). Considering steady state conditions, we have transferred the pattern from the disk surface onto the
slider surface and have investigated the pressure generation due to the bit pattern. To reduce the numerical complexity, we
have generated the bit pattern only in the areas of the slider near the trailing edge, where the spacing is small. Cylindrical
protrusions were modeled using very small mesh size on the order of nanometers to obtain the flying characteristics for the
entire slider air bearing surface (ABS) using the “CMRR” finite element Reynolds equation simulator (Duwensee et al., Microsyst
Technol, 2006; Wahl et al., STLE Tribol Trans, 39(1), 1996). The effect of pattern height, pattern diameter, slider skew angle,
and slider pitch angle on flying height of a typical slider is investigated. Numerical results show that the flying height
decreases for a patterned slider and the change in flying height is a function of the pattern height and ratio of the pattern
diameter to the pattern pitch. In comparison to discrete track media, the flying height loss is larger for a patterned slider
disk interface for the same recessed area of pattern. 相似文献
43.
Ramachandran Kasirajan Sivakumar Pandian Suganya Tamilarasan Renganathan Sahadevan 《Korean Journal of Chemical Engineering》2014,31(3):509-513
The lipid content was extracted from the saga seed by superheated condition and soxhlet apparatus. The mixture of hexane, chloroform and methanol was utilized as a mixed solvent for these extraction operations. Different parameters such as different solvent, temperature, mean particle size and solvent flow have been examined. The optimized lipid extraction was achieved as 26.2 wt% by using superheated condition from the saga seed powder at 90 °C for 120min. Then the fatty acids profile of the optimized Adenanthera pavonina oil were analyzed by gas chromatography. Unsaturated fatty acid was high as 83.7% compared with saturated fatty acid barely 15.4% by relative. 相似文献
44.
Nitroarenes as Antitubercular Agents: Stereoelectronic Modulation to Mitigate Mutagenicity
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Dr. Sudhir Landge Dr. Vasanthi Ramachandran Dr. Anupriya Kumar Dr. João Neres Kannan Murugan Dr. Claire Sadler Dr. Mick D. Fellows Vaishali Humnabadkar Dr. Prakash Vachaspati Dr. Anandkumar Raichurkar Sreevalli Sharma Sudha Ravishankar Supreeth Guptha Dr. Vasan K. Sambandamurthy Dr. Tanjore S. Balganesh Dr. Bheemarao G. Ugarkar Dr. V. Balasubramanian Dr. Balachandra S. Bandodkar Dr. Manoranjan Panda 《ChemMedChem》2016,11(3):331-339
Nitroarenes are less preferred in drug discovery due to their potential to be mutagenic. However, several nitroarenes were shown to be promising antitubercular agents with specific modes of action, namely, nitroimidazoles and benzothiazinones. The nitro group in these compounds is activated through different mechanisms, both enzymatic and non‐enzymatic, in mycobacteria prior to binding to the target of interest. From a whole‐cell screening program, we identified a novel lead nitrobenzothiazole (BT) series that acts by inhibition of decaprenylphosphoryl‐β‐d ‐ribose 2′‐epimerase (DprE1) of Mycobacterium tuberculosis (Mtb). The lead was found to be mutagenic to start with. Our efforts to mitigate mutagenicity resulted in the identification of 6‐methyl‐7‐nitro‐5‐(trifluoromethyl)‐1,3‐benzothiazoles (cBTs), a novel class of antitubercular agents that are non‐mutagenic and exhibit an improved safety profile. The methyl group ortho to the nitro group decreases the electron affinity of the series, and is hence responsible for the non‐mutagenic nature of these compounds. Additionally, the co‐crystal structure of cBT in complex with Mtb DprE1 established the mode of binding. This investigation led to a new non‐mutagenic antitubercular agent and demonstrates that the mutagenic nature of nitroarenes can be solved by modulation of stereoelectronic properties. 相似文献
45.
Mingxuan Lu Prabhakar V. Gulgunje Pedro J. Arias-Monje Jeffrey Luo Jyotsna Ramachandran Yudhisthira Sahoo Sandip Agarwal Satish Kumar 《Polymer Engineering and Science》2020,60(9):2143-2151
Bi-component, polyacrylonitrile (PAN)/carbon nanotube (CNT) fibers were processed, at different core-sheath area ratios, by gel spinning. A percolated CNT network at 10 wt% CNT in the sheath enhanced electrical conductivity as compared to the neat PAN fiber, while PAN polymer in the core contributed to the good mechanical properties. Fibers with relatively thin sheath allowed overall CNT loading as low as 3.7 wt% to be made with good electrical conductivity, and PAN stabilization by Joule heating was demonstrated. Such fibers with combined good mechanical properties and electrical conductivity can also potentially be used for electrical heating of fabrics, for making smart textiles, and for electromagnetic interference shielding. 相似文献
46.
Anuj V. Prakash Anwesha ChaudhuryDana Barrasso Rohit Ramachandran 《Chemical Engineering Research and Design》2013
Population Balance Models (PBMs), a class of integro partial differential equations, are utilized for simulating dynamics of numerous particulate systems. PBMs describe the time evolutions and distributions of many particulate processes and their efficient and quick simulation are critical for enhanced process control and optimization, especially for real-time applications. However, their intensive computational resource requirement is largely a prohibitive factor in the utility of PBMs for control and optimization. This paper describes how distributed computing systems may be leveraged to execute PBM-based simulations thus achieving time savings, using MATLAB's Distributed Computing Toolbox. A parallel computing algorithm was developed for a three dimensional and four dimensional population balance model with built-in constructs such as SPMD that ran efficiently on a cluster of two quad-core machines linked via a gigabit ethernet cable. Speedup of 6.2 and 5.7 times were achieved with 8 workers, over an un-parallelized code, for a 3 and 4 dimensional PBM respectively. Evaluations on work efficiency and scalability further affirm the algorithms’ respectable performance on larger clusters despite significant memory transfer overheads. 相似文献
47.
The nature of thermophilic amylolytic enzymes produced by a strain of Aspergillus niger Van Tieghem was influenced by media composition. While glucose, maltose, dextrin and soluble starch induced the production of amyloglucosidase, pectin and sodium polypectate almost exclusively induced the formation of α-amylase. Alkali ions suppressed the formation of amyloglucosidase. NH4NO3, (NH4)2HPO4 and (NH4)2C4H4O6 served as good inorganic nitrogen sources, while casein, groundnut protein and corn steep liquor served to a similar capacity as nitrogen sources from organic material. Deletion of the growth factors pyridoxine-hydrochloride and inositol suppressed enzyme production, while the absence of riboflavin had the opposite effect. 相似文献
48.
Rajangam Vinodh Kalambettu Aravind Bhat Dharmalingam Sangeetha 《Journal of Polymer Research》2011,18(6):1469-1477
Quaternized Polysulfone (QPSU) is a widely investigated material in the industry because of its unique properties such as
resistance to corrosion and high mechanical properties. The ionic nature of the compound can be exploited for medical applications
such as in haemodialysis, drug delivery and tissue engineering. In this study, composite membranes of QPSU with varying concentrations
of Titanium oxide (TiO2) were prepared and characterized using FT-IR, 1H-NMR, XRD, TGA and SEM. The bioactivity of the membranes was studied by immersing them in simulated body fluid (SBF) for
7 days and subsequently observing under SEM for the formation of calcium-phosphate (Ca–PO4) layer on the surface of the membranes. The formation of Ca–PO4 on the samples was confirmed using FT-IR and EDAX. The results were compared with those obtained for QPSU membranes and the
effect of TiO2 concentration on the membrane properties was analyzed. It was observed that the percentage crystallinity of the composites
increased upto a filler concentration of 5 wt% beyond which it decreased. TGA studies revealed an increase in the thermal
stability of the composites with increasing filler concentrations. While optimum bioactivity was observed in the samples containing
5 wt% of TiO2, higher filler content resulted in the formation of denser calcium—phosphate layer on the surface of the composites. The
study shows that quaternized polysulphone/TiO2 composites are promising bio composites having great potential for application in health care. 相似文献
49.
S. Dhanasekaran Aravind Vadiraj G. Balachandran M. Kamaraj 《Transactions of the Indian Institute of Metals》2010,63(5):779-785
Austempering of a ferrite-pearlitic grade of ductile iron was carried out to assess the potential use of the material for
crank shaft application reported. A commercial material was austempered at 340°C to realize the properties. The austempered
ductile iron gave good strength although the ductility values were lower. The material developed had complete ausferritric
structure free of pearlite. The various phase constitution and phase transformation associated with the treatment and during
mechanical deformation was examined. Using XRD analysis the volume fraction of the austenite in the matrix was estimated.
The various aspects of processing a commercial cast iron during ausetmpering, the phase transformation, microstructural evolution
have been examined along with the property of the material. The mechanical behaviour of the material and the scope for further
improvement is discussed. 相似文献
50.
Chen S. Kozuch M. Gibbons P.B. Ryan M. Strigkos T. Mowry T.C. Ruwase O. Vlachos E. Falsafi B. Ramachandran V. 《Micro, IEEE》2009,29(1):62-72
Instruction-grain lifeguards monitor executing programs at the granularity of individual instructions to quickly detect bugs and security attacks, but their fine-grain nature incurs high monitoring overheads. This article identifies three common sources of these overheads and proposes three techniques that together constitute a general-purpose hardware acceleration framework for lifeguards. 相似文献