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排序方式: 共有1719条查询结果,搜索用时 15 毫秒
41.
S.C. Nandy G.N. Nandakumar B.B. Bhattacharya 《Computers & Mathematics with Applications》1997,34(12):121-135
This paper outlines an algorithm for optimum linear ordering (OLO) of a weighted parallel graph with O(n log k) worst-case time complexity, and O(n + k log(n/k) log k) expected-case time complexity, where n is the total number of nodes and k is the number of chains in the parallel graph. Next, the two-layer OLO problem is considered, where the goal is to place the nodes linearly in two routing layers minimizing the total wire length. The two-layer problem is shown to subsume the maxcut problem and a befitting heuristic algorithm is proposed. Experimental results on randomly generated samples show that the heuristic algorithm runs very fast and outputs optimum solutions in more than 90% instances. 相似文献
42.
Akshay Atwe Ankur Gupta Rishi Kant Mainak Das Ishan Sharma Shantanu Bhattacharya 《Microsystem Technologies》2014,20(7):1373-1381
We report a novel pH-sensitive hydrogel based micro-valve for metered flow that has applications in a laboratory made “Intelligent valving system”. The hydrogel solution was prepared through Chitosan and poly vinyl alcohol in acetic acid and crystallized using gluteraldehyde as the crosslinking agent in the form of thin wafers and it was found to be very sensitive to pH changes. The pore structure of hydrogel was investigated through Field Emission Scanning Electron Microscopy and thin wafers of the gel were physically placed inside PDMS microchannels. Flow metering in these channels was observed by controlled expansion of the hydrogel plug till complete valving was realized. This valving device was further precisely characterized with micro Particle Image Velocimetry using a solution containing fluorescent polymeric micro beads. The principle advantage of this hydrogel device is the smaller range of pH (varying between pH 3 and 7) over which the valving response is observed. 相似文献
43.
A multispeed testing method for obtaining tool-life parameters using radioactive tools has been developed. By suitable interpolation of the instantaneous rates of absolute wear measured for a number of discrete cutting speeds, the corresponding tool-life values can be deduced in a test employing a single cutting edge. Using failure criteria based on wear-land width, crater volume and total wear volume, tool-life parameters were obtained in orthogonal cutting tests with irradiated high speed steel tools. Subsidiary experiments, including conventional tool-life testing, confirmed the validity of the multispeed method over the cutting speed range investigated. 相似文献
44.
S. K. Srivastav A. Bhattacharya M. V. V. Kamaraju G. Sreenivasa Reddy A. K. Shrimal D. S. Mehta 《International journal of remote sensing》2013,34(17):3253-3267
This paper reports the results of a pilot study carried out in RajpuraDariba area, Rajasthan, for locating favourable zones of lead-zinc-copper (Pb-Zn-Cu) mineralization using remote sensing, Geographical Information System (GIS) and geostatistical modelling techniques. Remotely sensed data, both aerial and satellite, were used to update the existing geological map. ATLAS GIS software and multivariate geostatistical techniques were used to analyse and integrate different types of geological and geophysical datasets. The Favourability Index (FI) maps prepared during this study show the occurrence of three favourable zones for Pb-Zn-Cu mineralization. They are: (i) around and north of Rawan ka Khera; (ii) isolated spots between Ruppura and Bhupalsagar; and (iii) north of Dhani. Selective geochemical sampling and resistivity profiling carried out in these favourable zones indicated the presence of geochemical anomalies (anomalous concentrations of Zn and Cu) and low/moderate resistivity zones, respectively. Recent drilling carried out by the Department of Mines and Geology (DMG), Rajasthan, at about 2.5 km north of Rawan ka Khera (one of the predicted favourable zones) indicated evidence of Cu mineralization at a depth of about 70 m. 相似文献
45.
Recently, feature grouping has been proposed as a method for improving retrieval results for logos and web images. This relies on the idea that a group of features matching over a local region in an image is more discriminative than a single feature match. In this paper, we evolve this concept further and apply it to the more challenging task of landmark recognition. We propose a novel combination of dense sampling of SIFT features with interest regions which represent the more salient parts of the image in greater detail. In place of conventional dense sampling used in category recognition that computes features on a regular grid at a number of fixed scales, we allow the sampling density and scale to vary based on the scale of the interest region. We develop new techniques for exploring stronger geometric constraints inside the feature groups and computing the match score. The spatial information is stored efficiently in an inverted index structure. The proposed approach considers part-based matching of interest regions instead of matching entire images using a histogram under bag-of-words. This helps reducing the influence of background clutter and works better under occlusion. Experiments reveal that directing more attention to the salient regions of the image and applying proposed geometric constraints helps in vastly improving recognition rates for reasonable vocabulary sizes. 相似文献
46.
Premature failure of a cylindrical roller bearing of a gear box input shaft from a hot strip mill has been investigated. The pins of the cylindrical rollers of the bearing broke from the welded joints at their ends on the cage ring. Investigations were carried out on the failed roller pin and the welded joint. The investigation consists of visual observation, chemical analysis, characterization of macro- and microstructures, measurement of hardness profile, fractography, and energy dispersive spectroscopy (EDS). The fracture surface of the roller pins exhibits beach marks. Scanning electron microscopy (SEM) of the fracture surfaces reveals striations suggesting fatigue failure. The measured hardness profile along the welded joint shows very high hardness due to the presence of untempered martensite at the fusion boundary as revealed by the microstructural examination. Analyses of the results infer that the roller pins failed by the initiation of fatigue cracks from the welded joint because of the presence of untempered martensite originated due to improper welding process. 相似文献
47.
Maitreyee Bhattacharya 《Metallurgical and Materials Transactions B》2011,42(2):380-384
The synthesis of magnetic Ni nanoparticles is being investigated by the reduction of NiO nanoparticles in the presence of hydrogen gas. In this study, nanocrystalline NiO particles have been synthesized by a homogenous carbonate precipitation method employing nickel electrolyte (NiSO4) as the source of nickel and ammonium hydrogen carbonate as the precipitating agent. Nickel electrolyte (NiSO4) was obtained after processing of sea nodules by the roasting-ammonia leaching-solvent extraction method. The physicochemical characterization of NiO and Ni particles, i.e., bright field image by transmission electron microscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray analysis, Fourier transform-infrared (FT-IR) study, and magnetic measurements by vibration sample magnetometer (VSM) are studied. The particles are observed to be superparamagnetic. 相似文献
48.
Pramod K. Singh B. Bhattacharya R.K. Nagarale Kang-Wook Kim Hee-Woo Rhee 《Synthetic Metals》2010,160(1-2):139-142
Biopolymer composite membranes based on chitosan doped with an ionic liquid (IL) 1-ethyl 3-methylimidazolium thiocyanate (EMImSCN) have been developed and characterized. The doped ionic liquid films show remarkable enhancement in ionic conductivity (σ). The Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM) and X-ray diffraction studies (XRD) affirmed the composite nature, good incorporation of ionic liquid and reduction in crystallinity of films, respectively. The interaction between ionic liquid, chitosan and iodide polymer electrolyte matrix was evaluated by cyclic voltammetry. The fabricated dye sensitized solar cell (DSSC) using this new biopolymer electrolyte membranes shows promising performance. 相似文献
49.
Jan-Bernd Hövener Eduard Y. Chekmenev Kent C. Harris William H. Perman Thao T. Tran Brian D. Ross Pratip Bhattacharya 《Magma (New York, N.Y.)》2009,22(2):123-134
Object Define MR quality assurance procedures for maximal PASADENA hyperpolarization of a biological 13C molecular imaging reagent.
Materials and methods An automated PASADENA polarizer and a parahydrogen generator were installed. 13C enriched hydroxyethyl acrylate, 1-13C, 2,3,3-d3 (HEA), was converted to hyperpolarized hydroxyethyl propionate, 1-13C, 2,3,3-d3 (HEP) and fumaric acid, 1-13C, 2,3-d2 (FUM) to hyperpolarized succinic acid, 1-13C, 2,3-d2 (SUC), by reaction with parahydrogen and norbornadiene rhodium catalyst. Incremental optimization of successive steps in
PASADENA was implemented. MR spectra and in vivo images of hyperpolarized 13C imaging agents were acquired at 1.5 and 4.7 T.
Results Application of quality assurance (QA) criteria resulted in incremental optimization of the individual steps in PASADENA implementation.
Optimal hyperpolarization of HEP of P = 20% was achieved by calibration of the NMR unit of the polarizer (B
0 field strength ± 0.002 mT). Mean hyperpolarization of SUC, P = [15.3 ± 1.9]% (N = 16) in D
2O, and P = [12.8 ± 3.1]% (N = 12) in H
2O, was achieved every 5–8 min (range 13–20%). An in vivo 13C succinate image of a rat was produced.
Conclusion PASADENA spin hyperpolarization of SUC to 15.3% in average was demonstrated (37,400 fold signal enhancement at 4.7 T). The
biological fate of 13C succinate, a normally occurring cellular intermediate, might be monitored with enhanced sensitivity. 相似文献
50.
C. R. Kumaran Maneesh Chandran M. Krishna Surendra S. S. Bhattacharya M. S. Ramachandra Rao 《Journal of Materials Science》2015,50(1):144-156
It is important to understand the growth of CNT-diamond composite films in order to improve the inter-link between two carbon allotropes, and, in turn, their physical properties for field emission and other applications. Isolated diamond particles, continuous diamond thin films, and thin films of carbon nanotubes (CNTs) having non-uniformly distributed diamond particles (CNT-diamond composite films) were simultaneously grown on unseeded, seeded, and catalyst pre-treated substrates, respectively, using a large-area multi-wafer-scale hot filament chemical vapor deposition. Films were deposited for four different growth durations at a given deposition condition. The changes in surface morphology and growth behavior of diamond particles with growth duration were investigated ex situ using field emission scanning electron microscopy and 2D confocal Raman depth spectral imaging, respectively. A surface morphological transition from faceted microcrystalline nature to nanocrystalline nature was observed as a function of growth duration in the case of isolated diamond particles grown on both unseeded and catalyst pre-treated substrates. However, such a morphological transition was not observed on the simultaneously grown continuous diamond thin films on seeded substrates. 2D confocal Raman depth spectral imaging of diamond particles showed that the local growth of CNTs did not affect the growth behavior of neighboring diamond particles on catalyst pre-treated substrates. These observations emphasize the importance of surface chemical reactions at the growth site in deciding sp2 or sp3 carbon growth and the final grain size of the diamond films. 相似文献