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Ravi Kumar Gangwar

Bio: Ravi Kumar Gangwar is an academic researcher from Indian Institutes of Technology. The author has contributed to research in topics: Dielectric resonator antenna & Antenna (radio). The author has an hindex of 19, co-authored 162 publications receiving 1181 citations. Previous affiliations of Ravi Kumar Gangwar include Indian Institute of Technology Dhanbad & Banaras Hindu University.


Papers
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Journal ArticleDOI
TL;DR: It is suggested that MW radiation-induced oxidative stress by increasing ROS production in the body may lead to DNA strand breakage in the brain cells and implantation failure/resorption or abnormal pregnancy in mice.
Abstract: The present experiment was designed to study the 2.45 GHz low-level microwave (MW) irradiation-induced stress response and its effect on implantation or pregnancy in female mice. Twelve-week-old mice were exposed to MW radiation (continuous wave for 2 h/day for 45 days, frequency 2.45 GHz, power density=0.033549 mW/cm(2), and specific absorption rate=0.023023 W/kg). At the end of a total of 45 days of exposure, mice were sacrificed, implantation sites were monitored, blood was processed to study stress parameters (hemoglobin, RBC and WBC count, and neutrophil/lymphocyte (N/L) ratio), the brain was processed for comet assay, and plasma was used for nitric oxide (NO), progesterone and estradiol estimation. Reactive oxygen species (ROS) and the activities of ROS-scavenging enzymes- superoxide dismutase, catalase, and glutathione peroxidase-were determined in the liver, kidney and ovary. We observed that implantation sites were affected significantly in MW-irradiated mice as compared to control. Further, in addition to a significant increase in ROS, hemoglobin (p<0.001), RBC and WBC counts (p<0.001), N/L ratio (p<0.01), DNA damage (p<0.001) in brain cells, and plasma estradiol concentration (p<0.05), a significant decrease was observed in NO level (p<0.05) and antioxidant enzyme activities of MW-exposed mice. Our findings led us to conclude that a low level of MW irradiation-induced oxidative stress not only suppresses implantation, but it may also lead to deformity of the embryo in case pregnancy continues. We also suggest that MW radiation-induced oxidative stress by increasing ROS production in the body may lead to DNA strand breakage in the brain cells and implantation failure/resorption or abnormal pregnancy in mice.

65 citations

Journal ArticleDOI
TL;DR: In this article, a dielectric resonator (DR)-based multiple-input-multiple-output (MIMO) antenna with bi-directional pattern diversity is presented. But the back-to-back arrangement of cylindrical DR antennas DRAs (cDRAs) is not considered.
Abstract: This Letter presents a dielectric resonator (DR)-based multiple-input-multiple-output (MIMO) antenna with bi-directional pattern diversity. The back-to-back arrangement of cylindrical DR antennas DRAs (cDRAs) is one of the unique features of the proposed design. The cDRAs are placed on an FR4 substrate with a common ground plane. Each cDRA element is excited by two ports to establish a four-port MIMO antenna system. At ports 1 and 2, the top cDRA is excited via co-planar waveguide (CPW) fed conformal strip lines. In case of ports 3 and 4, the bottom cDRA is excited by microstrip line fed conformal strip lines. Isolation between all ports is improved (better than 18 dB) by generating orthogonal modes in the cDRAs and use of opposite excitations. Measured results confirm that the proposed four-port MIMO antenna system is useful for the frequency ranges between 5.4 and 6.0 GHz for WLAN applications.

48 citations

Journal ArticleDOI
TL;DR: In this paper, a triple band hybrid multi-input-multi-output MIMO cylindrical dielectric resonator antenna with high isolation is examined, which includes two symmetric folded microstrip line feeding structures along with CDRA at two different ends of substrate.
Abstract: In this communication, triple band hybrid multi-input-multi-output MIMO cylindrical dielectric resonator antenna CDRA with high isolation is examined. The proposed MIMO antenna includes two symmetric folded microstrip line feeding structures along with CDRA at two different ends of substrate. Two inverted L-shaped strips on the ground plane are used to enhance the isolation S12<-15 dB as well as to generates 2.7 GHz frequency band. Metallic strip on the ground plane act as an electromagnetic reflector and also enhance the isolation between two antennas S12<-20 dB. Archetype of proposed MIMO antenna design has been fabricated and tested to validate the simulated results. The proposed antenna operates at three different frequency bands 2.24-2.38 GHz, 2.5-3.26 GHz, and 4.88-7.0 GHz S11<-6 dB with the fractional bandwidth 6.06%, 26.4%, and 35.7%, respectively. Folded microstrip lines generate λ4 path delay between the electric field lines and originate circular polarization characteristics in the frequency range 5.55-5.75 GHz with the fractional bandwidth of 3.55%. In order to satisfy the different performance requirement of MIMO antenna such as envelop correlation coefficient, mean effective gain, effective diversity gain, peak gain are also examined. The proposed antenna is found suitable for LTE2500, WLAN, and WiMAX applications. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.

48 citations


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01 Jan 2016

733 citations

Journal ArticleDOI
TL;DR: A novel method that could be applied to the fleld of MR brain image classiflcation and can assist the doctors to diagnose where a patient is normal or abnormal to certain degrees is presented.
Abstract: Automated and accurate classification of MR brain images is extremely important for medical analysis and interpretation. Over the last decade numerous methods have already been proposed. In this paper, we presented a novel method to classify a given MR brain image as normal or abnormal. The proposed method first employed wavelet transform to extract features from images, followed by applying principle component analysis (PCA) to reduce the dimensions of features. The reduced features were submitted to a kernel support vector machine (KSVM). The strategy of Kfold stratified cross validation was used to enhance generalization of KSVM. We chose seven common brain diseases (glioma, meningioma, Alzheimer’s disease, Alzheimer’s disease plus visual agnosia, Pick’s disease, sarcoma, and Huntington’s disease) as abnormal brains, and collected 160 MR brain images (20 normal and 140 abnormal) from Harvard Medical School website. We performed our proposed methods with four different kernels, and found that the GRB kernel achieves the highest classification accuracy as 99.38%. The LIN, HPOL, and IPOL kernel achieves 95%, 96.88%, and 98.12%, respectively. We also compared our method to those from literatures in the last decade, and the results showed our DWT+PCA+KSVM with GRB kernel still achieved the best accurate classification results. The averaged processing time for a 256× 256 size image on a laptop of P4 IBM with 3GHz processor and 2 GB RAM is 0.0448 s. From the experimental data, our method was effective and rapid. It could be applied to the field of MR brain image classification and can assist the doctors to diagnose where a patient is normal or abnormal to certain degrees. Received 14 June 2012, Accepted 23 July 2012, Scheduled 19 August 2012 * Corresponding author: Yudong Zhang (zhangyudongnuaa@gmail.com).

230 citations

01 Jan 2016
TL;DR: Complete with an up–to–date tutorial overview of the field and substantial new, introductory material for each topic, Microstrip Antennas combines in one source a selection of today's most significant and useful articles on microstrip and antenna design.
Abstract: Description: Electrical Engineering/Antennas and Propagation Microstrip Antennas The Analysis and Design of Microstrip Antennas and Arrays Microstrip Antennas contains valuable new information on antenna design and an excellent introduction to the work done in the microstrip antenna area over the past 20 years. The articles are well–chosen and (are) complete with practical design information that is very useful for the working engineer. Stuart Long, University of Houston The editors have done an outstanding job in assembling this updated reprint book. It is a welcome addition to the list of books on microstrip antennas. There is no doubt that it will be a valuable source of information for graduate students, engineers and researchers the original articles are written lucidly and are very informative, and the reprint articles are well chosen. Kai Fong Lee, The University of Toledo Complete with an up–to–date tutorial overview of the field and substantial new, introductory material for each topic, Microstrip Antennas combines in one source a selection of today’s most significant and useful articles on microstrip and antenna design. Eminent experts David M. Pozar and Daniel H. Schaubert guide you through:

210 citations

01 Jan 2012
TL;DR: In this article, a wavelet transform was employed to extract features from images, followed by applying principle component analysis (PCA) to reduce the dimensions of features and submitted the reduced features were submitted to a kernel support vector machine (KSVM).
Abstract: Automated and accurate classiflcation of MR brain images is extremely important for medical analysis and interpretation. Over the last decade numerous methods have already been proposed. In this paper, we presented a novel method to classify a given MR brain image as normal or abnormal. The proposed method flrst employed wavelet transform to extract features from images, followed by applying principle component analysis (PCA) to reduce the dimensions of features. The reduced features were submitted to a kernel support vector machine (KSVM). The strategy of K- fold stratifled cross validation was used to enhance generalization of KSVM. We chose seven common brain diseases (glioma, meningioma, Alzheimer's disease, Alzheimer's disease plus visual agnosia, Pick's disease, sarcoma, and Huntington's disease) as abnormal brains, and collected 160 MR brain images (20 normal and 140 abnormal) from Harvard Medical School website. We performed our proposed methods with four difierent kernels, and found that the GRB kernel achieves the highest classiflcation accuracy as 99.38%. The LIN, HPOL, and IPOL kernel achieves 95%, 96.88%, and 98.12%, respectively. We also compared our method to those from literatures in the last decade, and the results showed our DWT+PCA+KSVM with GRB kernel still achieved the best accurate classiflcation results. The averaged processing time for a 256£256 size image on a laptop of P4 IBM with 3GHz processor and 2GB RAM is 0.0448s. From the experimental data, our method was efiective and rapid. It could be applied to the fleld of MR brain image classiflcation and can assist the doctors to diagnose where a patient is normal or abnormal to certain degrees.

198 citations

Journal ArticleDOI
TL;DR: Different MIMO antenna design techniques and all of their mutual coupling reduction techniques through various structures and mechanisms are presented with multiple examples and characteristics comparison.
Abstract: In recent years, multiple-input-multiple-output (MIMO) antennas with the ability to radiate waves in more than one pattern and polarization play a great role in modern telecommunication systems. This paper provides a theoretical review of different mutual coupling reduction techniques in MIMO antenna systems. The increase in the mutual coupling can affect the antenna characteristics drastically and therefore degrades the performance of the MIMO systems. It is possible to improve the performance partially by calibrating the mutual coupling in the digital domain. However, the simple and effective approach is to use the techniques, such as defected ground structure, parasitic or slot element, complementary split ring resonator, and decoupling networks which can overcome the mutual coupling effects by means of physical implementation. An extensive discussion on the basis of different mutual coupling reduction techniques, their examples, and comparative study is still rare in the literature. Therefore, in this paper, different MIMO antenna design techniques and all of their mutual coupling reduction techniques through various structures and mechanisms are presented with multiple examples and characteristics comparison.

197 citations