Sowmya R.,Sir MVIT |
Proceedings of 16th National Conference on Communications, NCC 2010 | Year: 2010
This paper considers the design and analysis of a filter at the receiver of a source coding system to mitigate the excess distortion caused due to channel errors. The index output by the source encoder is sent over a fading discrete binary symmetric channel and the possibly incorrect received index is mapped to the corresponding codeword by a Vector Quantization (VQ) decoder at the receiver. The output of the VQ decoder is then processed by a receive filter to obtain an estimate of the source instantiation. The distortion performance is analyzed for weighted mean square error (WMSE) and the optimum receive filter that minimizes the expected distortion is derived for two different cases of fading. It is shown that the performance of the system with the receive filter is strictly better than that of a conventional VQ and the difference becomes more significant as the number of bits transmitted increases. Theoretical expressions for an upper and lower bound on the WMSE performance of the system with the receive filter and a Rayleigh flat fading channel are derived. The design of a receive filter in the presence of channel mismatch is also studied and it is shown that a minimax solution is the one obtained by designing the receive filter for the worst possible channel. Simulation results are presented to validate the theoretical expressions and illustrate the benefits of receive filtering. ©2010 IEEE.
Newman N.C.,IISC |
Porter A.L.,Search Technology Inc. |
Porter A.L.,Georgia Institute of Technology |
Newman D.,University of California at Irvine |
And 2 more authors.
Journal of Engineering and Technology Management - JET-M | Year: 2014
We are developing indicators for the emergence of science and technology (S&T) topics. To do so, we extract information from various S&T information resources. This paper compares alternative ways of consolidating messy sets of key terms [e.g., using Natural Language Processing on abstracts and titles, together with various keyword sets]. Our process includes combinations of stopword removal, fuzzy term matching, association rules, and term commonality weighting. We compare topic modeling to Principal Components Analysis for a test set of 4104 abstract records on Dye-Sensitized Solar Cells. Results suggest potential to enhance understanding regarding technological topics to help track technological emergence. © 2013 Elsevier B.V.
News Article | August 7, 2015
To solve its energy crisis in a coal-dependent country and to reach its goal toward becoming one of the world's largest solar markets, India is launching a new concentrated solar power project in a few weeks. Run by the Indian Institute of Science (IISC) as part of the Solar Energy Research Institute for India and the United States (Seriius), the project consists of rows of aluminum troughs that will generate solar-powered electricity. Sunlight that reflects from the troughs will bounce to water pipes located above. The water in the pipes will be heated to 392 degrees Fahrenheit and go through a heat exchanger that is attached to a small machine used for producing power from fast-flowing water, which will then create 100 kilowatts of electricity. The researchers will then be able to test various reflective heat-transferable liquids, such as molten salt, to produce electricity. They will gather and analyze data sent to a dashboard at IISC from small wireless sensors with the goal of finding the best components to produce solar power in India as many of the solar panels the country received are not suited for the extreme conditions of its climate. Along with testing concentrated solar power, solar photovoltaic installations will also be added, and researchers will focus on creating polymers to protect the panels from extreme conditions like high temperatures and dust. While the project may lead to the solution for the deterioration of solar panels, the researchers have another problem on their hands — monkeys. The installation set in Challakere, north of Bangalore, is often invaded by monkeys that are wreaking havoc on the solar panels. The monkeys are said to chew on the electrical cables and even lick the panels that collect dew. "We've tried giving them food to lure them away, but they just sit there," professor of materials engineering at IISC Praveen Ramamurthy said. "I don't know what to do." To address the monkey problem, the researchers have even tried an ultrasonic monkey repellent to keep the animals away from the project, but they just keep coming back. While the panels provide a hangout spot for the primates, the project will help India progress toward providing clean energy to the more than 300 million people who live without it.
Yau C.-K.,Georgia Institute of Technology |
Porter A.,Georgia Institute of Technology |
Porter A.,Search Technology Inc. |
Newman N.,IISC |
And 2 more authors.
Scientometrics | Year: 2014
Topic modeling is a type of statistical model for discovering the latent "topics" that occur in a collection of documents through machine learning. Currently, latent Dirichlet allocation (LDA) is a popular and common modeling approach. In this paper, we investigate methods, including LDA and its extensions, for separating a set of scientific publications into several clusters. To evaluate the results, we generate a collection of documents that contain academic papers from several different fields and see whether papers in the same field will be clustered together. We explore potential scientometric applications of such text analysis capabilities. © 2014 Akadémiai Kiadó, Budapest, Hungary.
Sundaresh L.,IISC |
Nagendra Rao P.S.,IISC
Electric Power Systems Research | Year: 2014
A modified Newton-Raphson (NR) load flow scheme which automatically incorporates generator reactive power limits is proposed. Traditionally, handling generator reactive power limits is considered as an adjusted load flow solution and this adjustment is carried out through bus type switching method. Incorporating bus type switching in a NR algorithm is not straight forward, as it involves several subjective decisions and hence, there is no commonly used implementation. The modified NR scheme proposed here combines this adjustment feature in the load flow problem formulation directly. This is achieved by augmenting the set of complementary reactive power relations at voltage controlled buses with the conventional set of active power balance equations at all buses and reactive power balance equations at load buses in a Mixed Complementarity Problem (MCP) framework. Effectiveness of the scheme has been demonstrated through extensive simulations considering a number of test systems. © 2013 Elsevier B.V.