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排序方式: 共有227条查询结果,搜索用时 15 毫秒
71.
72.
Uh-Chan Ryu Im Y. Oh K. DiGiovanni D.J. Baishi Wang Hariharan A. 《Electronics letters》2003,39(13):975-977
A new technique to suppress temperature dependence of EDFA gain is proposed and experimentally demonstrated. A specially designed EDF, the glass host of which is Sb-doped silica, showed an opposite sign of temperature dependent gain coefficients in C-band compared to Al-doped silica EDFs. Concatenation of those two EDFs showed an improved gain variation less than /spl plusmn/0.37 dB for the saturated gain over 15 dB, within -40 to +80/spl deg/C. 相似文献
73.
74.
Results of an exhaustive experimental study of the effect of conducting grills on theE -plane radiation patterns ofE -plane sectoral horns are presented. It is observed that the grills satisfying certain optimum conditions are capable of focusing the patterns with considerable improvement in beamwidth and directive gain. The impedance conditions are also improved by the presence of the grills. Data for a number of horns operating at a wide range of frequencies are presented. 相似文献
75.
A simple dipstick type vapour cryostat and a versatile electronic temperature controller which uses a proportional, integral and differential type of control are described. They have been used together for the calibration of thermometers in the liquid helium temperature range and for the measurement of the transition temperature of superconductors. Temperature stability of 2 mK (typical) is achieved easily at a working temperature of 7 K for a period exceeding an hour. The use of the system is quite general and can readily cover the temperature range up to 300 K with a suitable choice of temperature sensor and heat input. 相似文献
76.
The advent of Web technology has made Web servers core elements of future communication networks. Although the amount of traffic that Web servers must handle has grown explosively during the last decade, the performance limitations and the proper tuning of Web servers are still not well understood. In this paper we present an end-to-end queueing model for the performance of Web servers, encompassing the impacts of client workload characteristics, server harware/software configuration, communication protocols, and interconnect topologies. The model has been implemented in a simulation tool, and performance predictions based on the model are shown to match very well with the performance of a Web server in a test lab environment. The simulation tool forms an excellent basis for development of a Decision Support System for the configuration tuning and sizing of Web servers. 相似文献
77.
K. Hariharan R. K. M. Rajkumar Dr. V. Abhaikumar 《Instruments and Experimental Techniques》2011,54(2):176-182
This paper presents a novel Time Tick based Built In Self Test (TT BIST) for measuring the static errors of an Analog to Digital
Converter (ADC). The proposed method determines the period elapsed during transition between two consecutive digital levels
and compares it with the ideal period of transition. A counter that works, at higher speed relative to the sampling rate of
the ADC under test, is used. It counts the number of time ticks occurred during every transition. The required ramp signal
is generated dynamically, using current source with digital switch for selecting the equivalent test signal. Further to support
testing of errors in ratiometric ADC, a slope conditioning module is also implemented. The entire computation cycle is done
in a single ramp cycle whereas in conventional histogram method multiple waveforms are required. Thus, the proposed TT method
requires less time to achieve desired accuracy levels by choosing the appropriate slope of the ramp signal. 相似文献
78.
Krishnaswamy Hariharan Ngoc-Trung Nguyen Nirupam Chakraborti Frédéric Barlat 《Materials and Manufacturing Processes》2015,30(4):403-413
The texture induced anisotropy of yield strength in cold rolled sheet metals is modeled using anisotropic yield criteria. The classical and other optimization methods used so far to determine the yield coefficients are limited by fixed set of experimental data, initial guess values, and pre-determined weight factors. A robust multiobjective optimization based on evolutionary algorithm proposed in this paper minimizes the error in yield stress and plastic strain ratio simultaneously and thereby overcomes the limitations in the approaches used before. The new approach is tested using Hill48 and Barlat89 yield criteria for five different materials from literature. The new approach is observed to improve the prediction capability of yield coefficients when compared to earlier approaches. The Pareto frontier obtained in the new approach can serve as a comparative tool to evaluate the accuracy of different yield criteria. 相似文献
79.
Automated texture‐based characterization of fibrosis and carcinoma using low‐dose lung CT images
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Lakshmi Devan Roy Santosham Ranganathan Hariharan 《International journal of imaging systems and technology》2014,24(1):39-44
Lung cancer is the most common cause of cancer deaths worldwide and account for 1.38 million deaths per year. Patients with lung cancer are often misdiagnosed as pulmonary tuberculosis (TB) leading to delay in the correct diagnosis as well as exposure to inappropriate medication. The diagnosis of TB and lung cancer can be difficult as symptoms of both diseases are similar in computed tomography (CT) images. However, treating TB leads to inflammatory fibrosis in some of the patients. There comes the need of an efficient computer aided diagnosis (CAD) of the fibrosis and carcinoma diseases. To design a fully automated CAD for characterizing fibrous and carcinoma tissues without human intervention using lung CT images. The 18 subjects in this study include seven healthy, two fibrosis and eight carcinoma, and one necrosis cases. The dataset is built by CT cuts representing healthy is 113, fibrosis is 103, necrosis is 39, and carcinoma is 185 totalling 440 images. The gray‐level spatial dependence matrix and gray level run length matrix approach are used for extracting texture‐based features. These features are given to neural network classifier and statistical classifier. These classifier performances are evaluated using receiver‐operating characteristics (ROC). The proposed method characterizes these tissues without human intervention. Sensitivity, specificity, precision, and accuracy followed by ROC curves were obtained and also studied. Thus, the proposed automated image‐based classifier could act as a precursor to histopathological analysis, thereby creating a way to class specific treatment procedures. 相似文献
80.
Spectrally resolved white-light phase-shifting interference microscopy has been used for measurements of the thickness profile of a transparent thin-film layer deposited upon a patterned structure exhibiting steps and discontinuities. We describe a simple technique, using an approach based on spectrally resolved optical coherence tomography, that makes it possible to obtain directly a thickness profile along a line by inverse Fourier transformation of the complex spectral interference function. 相似文献