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排序方式: 共有1373条查询结果,搜索用时 15 毫秒
51.
Y.N. Trivedi 《AEUE-International Journal of Electronics and Communications》2013,67(8):671-675
We consider orthogonal frequency division multiplexing (OFDM) in a multiple input single output (MISO) system. In the presence of spatially uncorrelated time-varying frequency selective channel, we use subcarrier by subcarrier antenna selection using delayed feedback. We derive closed-form expressions for the pdf of the received SNR and BER for MQAM constellation. The expressions have been obtained as a function of the correlation (ρ) between perfect channel state information (CSI) and delayed CSI, where 0 ≤ ρ ≤ 1. We have verified our analytical expressions by comparing them with simulation results. We have also reduced the BER expression for some special cases and compared them with the results available in the literature. We conclude that the diversity gain of the considered system is reduced to one for ρ < 1, i.e. not having perfect antenna selection for each subcarrier. However, we get some coding gain compared to single input single output system, the coding gain reduces with decreasing the correlation. 相似文献
52.
The grafting of acrylonitrile (AN) onto sodium salt of partially carboxymethylated amylose (Na-PCMA) using ceric ammonium nitrate (CAN) as an initiator has been studied in water/solvent mixtures. The solvents used include methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride. The results have been discussed. The effect of reaction medium on the molecular weight of grafted PAN has also been studied. The chain transfer constants (Cs) for solvents like methanol, ethanol, propanol, butanol, acetone and carbon tetrachloride have been evaluated at 30°C by the help of Mayo's equation. 相似文献
53.
Richard N. L. Lamptey Bivek Chaulagain Riddhi Trivedi Avinash Gothwal Buddhadev Layek Jagdish Singh 《International journal of molecular sciences》2022,23(3)
Neurodegenerative disorders are primarily characterized by neuron loss. The most common neurodegenerative disorders include Alzheimer’s and Parkinson’s disease. Although there are several medicines currently approved for managing neurodegenerative disorders, a large majority of them only help with associated symptoms. This lack of pathogenesis-targeting therapies is primarily due to the restrictive effects of the blood–brain barrier (BBB), which keeps close to 99% of all “foreign substances” out of the brain. Since their discovery, nanoparticles have been successfully used for targeted delivery into many organs, including the brain. This review briefly describes the pathophysiology of Alzheimer’s, Parkinson’s disease, and amyotrophic lateral sclerosis, and their current management approaches. We then highlight the major challenges of brain-drug delivery, followed by the role of nanotherapeutics for the diagnosis and treatment of various neurological disorders. 相似文献
54.
A. Bhattacharya P. Ray H. Brahmbhatt K. N. Vyas S. V. Joshi C. V. Devmurari J. J. Trivedi 《应用聚合物科学杂志》2006,102(4):3575-3579
Pressure driven techniques (viz. reverse osmosis and nanofiltration) have the potentiality to remove the pesticides from water. The observations revealed that pesticides removal mostly depends upon the molecular weight (size exclusion) and hydrophobicity (log P) of the pesticides. Interfacial polymerization of m‐phenylene diamine (MPD) and trimesoyl chloride (TMC) on the polysulfone membranes impart the salt rejection property in it. It is shown that with the greater salt rejection property, the performance removal of pesticides also is in increasing trend. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3575–3579, 2006 相似文献
55.
Jignesh H. Trivedi 《应用聚合物科学杂志》2013,129(4):1992-2003
Polyacrylonitrile (PAN)‐grafted sodium salt of partially carboxymethylated tamarind kernel powder (Na‐PCMTKP‐g‐PAN, %G = 413.76 and %GE = 96.48) was prepared using the established optimal reaction conditions for ceric‐initiated graft copolymerization of acrylonitrile onto Na‐PCMTKP (DS = 0.15) in a homogeneous medium. The graft copolymer was hydrolyzed by 0.7N KOH solution at 90–95°C to yield the superabsorbent hydrogel H‐Na‐PCMTKP‐g‐PAN. The nitrile groups of Na‐PCMTKP‐g‐PAN were completely converted into a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The products were characterized spectroscopically and morphologically. The swelling behavior of the unreported superabsorbent hydrogel, H‐Na‐PCMTKP‐g‐PAN, was studied by carrying out its absorbency measurements in low‐conductivity water, 0.15M salt (NaCl, CaCl2, and AlCl3) solutions, and simulated urine (SU) at different timings. The swelling behavior of the hydrogel in different swelling media followed the second‐order kinetics. The values of the various swelling characteristics were reported. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
56.
REFLICS: Real-time flow imaging and classification system 总被引:1,自引:0,他引:1
Sadahiro Iwamoto David M. Checkley Jr. Mohan M. Trivedi 《Machine Vision and Applications》2001,13(1):1-13
An accurate analysis of a large dynamic system like our oceans requires spatially fine and temporally matched data collection
methods. Current methods to estimate fish stock size from pelagic (marine) fish egg abundance by using ships to take point
samples of fish eggs have large margins of error due to spatial and temporal undersampling. The real-time flow imaging and
classification system (REFLICS) enhances fish egg sampling by obtaining continuous, accurate information on fish egg abundance
as the ship cruises along in the area of interest. REFLICS images the dynamic flow with a progressive-scan area camera (60
frames/s) and a synchronized strobe in backlighting configuration. Digitization and processing occur on a dual-processor Pentium
II PC and a pipeline-based image-processing board. REFLICS uses a segmentation algorithm to locate fish-egg-like objects in
the image and then a classifier to determine fish egg, species, and development stage (age). We present an integrated system
design of REFLICS and performance results. REFLICS can perform in real time (60 Hz), classify fish eggs with low false negative
rates on real data collected from a cruise, and work in harsh conditions aboard ships at sea. REFLICS enables cost-effective,
real-time assessment of pelagic fish eggs for research and management.
Received: 12 April 2000 / Accepted: 6 July 2000 相似文献
57.
The problem of interface pattern selection in nonlinear dissipative systems is critical in many fields of science, occurring in physical, chemical and biological systems. One of the simplest pattern formations is the Saffman-Taylor finger pattern that forms when a viscous fluid is displaced by a less viscous fluid. Such finger-shaped patterns have been observed in distinctly different fields of science (hydrodynamics, combustion and crystal growth) and this has led to a search for a unified concept of pattern formation, as first proposed by the classic work of D'arcy Thomson. Two-dimensional finger-shaped patterns, observed in flame fronts and the ensembled average shape of the diffusion-limited aggregation pattern, have been shown to be similar to Saffman-Taylor finger shapes. Here we present experimental studies that establish that the cell shapes formed during directional solidification of alloys can be described by the form of the Saffman-Taylor finger shape equation when a second phase is present in the intercellular region. 相似文献
58.
Kim C. Ng Mohan Trivedi Hiroshi Ishiguro 《International Journal of Computer Vision》2002,47(1-3):131-147
A new range-space approach is described for synergistic resolution of both stereovision and reflectance (visual) modeling problems simultaneously. This synergistic approach can be applied to arbitrary camera arrangements with different intrinsic and extrinsic parameters, image types, image resolutions, and image number. These images are analyzed in a step-wise manner to extract 3-D range measurements and also to render a customized perspective view. The entire process is fully automatic. An extensive and detailed experimental validation phase supports the basic feasibility and generality of the Range-Space Approach. 相似文献
59.
Experimental studies have been conducted in the two-phase region of the Pb-Bi peritectic system to investigate the effect
of thermosolutal convection on the banded microstructure. A systematic study is carried out by varying convection effects
through the use of thin cylindrical samples of different diameters. A strong oscillatory convection is found in a 6.0-mm-diameter
sample that produces a large treelike primary phase in the center of the sample that is surrounded by the peritectic phase
matrix. The length of the treelike structure is found to decrease as the diameter of a sample is reduced to 0.8 mm. When the
sample diameter is further reduced to 0.4 mm, laminar flow is present that gives rise to discrete bands of the two phases.
The banded microstructure, however, is found to be transient and only the peritectic phase forms after a few bands. Composition
variations in the banded structure are measured to determine the nucleation undercoolings for both phases and to characterize
the banding cycle. The banding cycle is determined by the nucleation undercoolings and is independent of convection in the
melt, but the banding window closely depends on convection. The presence of the transient banding process is analyzed by using
a boundary layer model, and the number of transient bands is found to agree with the model for samples of different compositions
and lengths. 相似文献
60.
Trivedi M. McShane E.A. Vijayalakshmi R. Mulay A. Abedinpour S. Atkinson S. Shenai K. 《Education, IEEE Transactions on》2002,45(1):57-64
An integrated power electronics curriculum has been implemented in the Department of Electrical and Computer Engineering at the University of Illinois, Chicago. This paper describes the development of a set of hands-on laboratory experiments to accompany classroom lectures. Content is based on switching converter topologies and commercial power semiconductor devices. Unlike most experiments, which focus on circuit- or control-level characteristics, our approach emphasizes the circuit-device-load interactions. The concept presented is innovative in that it creates a 3×3 matrix of experiment variation-devices, circuits-control, and machines-loads-with one set of hardware. The lab development is ongoing with future experiments to address three-phase converters and motor control applications. Experiment content is described, as well as the means by which the material has been integrated within the course sequence. Lab station construction and safety issues are also addressed. The experiments require hands-on measurement and circuit connection and complement the established course elements of theory and computer-based circuit modeling. Laboratory experiments and computer simulations collectively provide quantitative evidence of mixed circuit and device optimization 相似文献