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Author

J. Valarmathi

Other affiliations: Madras Institute of Technology
Bio: J. Valarmathi is an academic researcher from VIT University. The author has contributed to research in topics: Kalman filter & Extended Kalman filter. The author has an hindex of 3, co-authored 22 publications receiving 110 citations. Previous affiliations of J. Valarmathi include Madras Institute of Technology.

Papers
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Proceedings ArticleDOI
01 Oct 2016
TL;DR: This survey paper attempted to understand the existing research towards vision based navigation and finally proposed a Modular Multi-Sensor Data Fusion technique for UAV navigation in the GPS denied environment.
Abstract: In the Unmanned Air Vehicle (UAV) navigation the main challenge is estimating and maintaining the accurate values of UAVs position and orientation. The onboard Inertial Measurement Unit (IMU) provide the measurements but it is mainly affected from the accumulated error due to drift in measurements. Traditionally the Global Position System (GPS) measurements of vehicles position data can be fused with IMU measurements to compensate the accumulated error, But the GPS signals is not available everywhere and it will be degraded or fully not available in hostile areas, building structures and water bodies. Researchers already evolved methods to handle the UAV navigation in GPS denied environment by using Vision based navigation like Visual Odometry (VO) and Simultaneous Localisation and Mapping (SLAM). In this survey paper we attempted to understand the existing research towards vision based navigation and finally proposed a Modular Multi-Sensor Data Fusion technique for UAV navigation in the GPS denied environment.

126 citations

Journal ArticleDOI
TL;DR: The experimental results demonstrate the capability of the proposed scheme to the available security attributes in both frequency and encryption domain while minimizing image distortion and also resists to various attacks.
Abstract: Modern healthcare systems are based on managing diagnostic information of patients through E-health. E-health refers to the Internet enabled healthcare applications involving transacting personal health records or information and other internet based services including e-Pharmacy where security threats is a major concern . This paper introduces a hybrid watermarking and encryption technique for copyright protection and authentication of medical images. The medical image is watermarked in wavelet domain where in the Electronic Health Record (EHR) is used as watermark and hospital logo as the reference image. Embedding of the EHR data is based on energy band selection and in reference to the bit location in the reference image A Composite algorithm for improved image security is proposed by taking the advantages of DNA based image encryption and genetic algorithms (GA). A number of deoxyribonucleic acid (DNA) masks are created using logistic map function and DNA conversion rules. Then encryption is performed on the watermarked image to generate a number of cipher images. Genetic algorithm (GA) is applied to find the best DNA mask in iterative manner until the condition is met. The experimental results demonstrate the capability of the proposed scheme to the available security attributes in both frequency and encryption domain while minimizing image distortion and also resists to various attacks.

18 citations

Journal ArticleDOI
TL;DR: A brief review of methods used for estimating the target state in single and multi-sensor bearing only tracking (BOT) is presented in this paper, where the target tracking scenarios are divided into three different categories based on the nature of target motion and the number of target and sensors involved.
Abstract: The brief review of methods used for estimating the target state in single and multi-sensor bearing only tracking (BOT) is presented in this paper. It deals with the target state estimation using bearing only measurements. BOT is difficult because of its poor observability in target state and nonlinearity in measurements. The complete survey is done on existing techniques, involved to overcome the difficulties caused by BOT. Here, the target tracking scenarios are divided into three different categories based on the nature of target motion and the number of target and sensors involved. The existing techniques involved are reviewed in detail. Finally the future trends for BOT are also discussed.

6 citations

Proceedings ArticleDOI
01 Oct 2015
TL;DR: In this paper, an orthogonal frequency division multiplexing waveform (OFDM) with linear frequency modulated (LFM) signal is designed which has a high time-bandwidth product.
Abstract: In recent years, multistatic radar systems are extensively used for detection process, as it includes multiple transmitters and multiple receivers spaced at different locations. Due to multiple transmitted signals by multiple transmitters, waveform design with a large time-bandwidth product, low cross-correlation interferences, and a low peak-average power ratio, is a challenging task. Even though many waveform design techniques exist, they lack high time-bandwidth product, which is one of the primary requirements for multistatic airborne radars. In this paper to meet these requirements, in the present study an orthogonal frequency division multiplexing waveform (OFDM) with linear frequency modulated (LFM) signal is designed which has a high time-bandwidth product. This method jointly utilizes the effectiveness of conventional LFM and OFDM signals, to achieve spectral efficiency through multi carrier modulation as well as better range and Doppler resolution. A generalized formulation of OFDM-LFM waveform is presented and the performance is analyzed in time and frequency domains in terms of various ambiguity function parameters.

4 citations

Proceedings Article
09 Jul 2012
TL;DR: Simulated results show that in high noise level scenario, the interpolated adaptive filter gives better estimation in comparison to the existing methods.
Abstract: Relative velocity obtained through estimated Doppler frequency is often prone to error because of high noise and the target maneuverings. Better performance is achieved by applying adaptive length window functions [1] to the target echo signal. The optimum length is primarily dependent on target dynamics, expressed in terms of its acceleration and signal to noise ratio of the obtained echo. Papic et al [1] gave lookup table to select the window length for different signal-to-noise ratios (SNR) at three fixed accelerations. Other than these target accelerations, approximating the window length leads to error in the velocity estimation to low SNR. In this paper we have used Lagranges interpolation technique to get better window length adaptation for any range of target acceleration. The estimated velocity is then smoothened using Kalman filter and adaptive Kalman filter. Simulated results show that in high noise level scenario, our interpolated adaptive filter gives better estimation in comparison to the existing methods[1].

4 citations


Cited by
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22 Oct 2007
TL;DR: The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence and expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering.
Abstract: The fifth edition of "Numerical Methods for Engineers" continues its tradition of excellence. Instructors love this text because it is a comprehensive text that is easy to teach from. Students love it because it is written for them--with great pedagogy and clear explanations and examples throughout. The text features a broad array of applications, including all engineering disciplines. The revision retains the successful pedagogy of the prior editions. Chapra and Canale's unique approach opens each part of the text with sections called Motivation, Mathematical Background, and Orientation, preparing the student for what is to come in a motivating and engaging manner. Each part closes with an Epilogue containing sections called Trade-Offs, Important Relationships and Formulas, and Advanced Methods and Additional References. Much more than a summary, the Epilogue deepens understanding of what has been learned and provides a peek into more advanced methods. Approximately 80% of the end-of-chapter problems are revised or new to this edition. The expanded breadth of engineering disciplines covered is especially evident in the problems, which now cover such areas as biotechnology and biomedical engineering. Users will find use of software packages, specifically MATLAB and Excel with VBA. This includes material on developing MATLAB m-files and VBA macros.

578 citations

Journal ArticleDOI
TL;DR: Experimental evaluation shows that using combination of NSCT, RDWT, SVD and chaotic encryption makes the approach robust, imperceptible, secure and suitable for medical applications.
Abstract: In this paper, a chaotic based secure medical image watermarking approach is proposed. The method is using non sub-sampled contourlet transform (NSCT), redundant discrete wavelet transform (RDWT) and singular value decomposition (SVD) to provide significant improvement in imperceptibility and robustness. Further, security of the approach is ensured by applying 2-D logistic map based chaotic encryption on watermarked medical image. In our approach, the cover image is initially divided into sub-images and NSCT is applied on the sub-image having maximum entropy. Subsequently, RDWT is applied to NSCT image and the singular vector of the RDWT coefficient is calculated. Similar procedure is followed for both watermark images. The singular value of both watermarks is embedded into the singular matrix of the cover. Experimental evaluation shows when the approach is subjected to attacks, using combination of NSCT, RDWT, SVD and chaotic encryption it makes the approach robust, imperceptible, secure and suitable for medical applications.

76 citations

Journal ArticleDOI
TL;DR: The proposed scheme is effective in telemedicine applications and is blind and free from false positive detection, imperceptibility, robustness, tamper detection, localization, recovery and computation time.
Abstract: In this paper we propose a novel region based hybrid medical image watermarking (MIW) scheme to ensure authenticity, integrity and confidentiality of medical images. In this scheme a digital medical image is partitioned into region of interest (ROI) and the region of non interest (RONI). To detect and localize ROI tampering with high accuracy pixel wise positional and relational bits are calculated. Positional bit is calculated with respect to MSBs, row and column of the pixel. Relational bit shows the relation between MSBs. Two original LSBs of each ROI pixel are replace by their corresponding positional and relational bits. Original LSBs of ROI pixels are concatenated and embedded in RONI for ROI recovery in the case of tampering. Multiple watermarks i.e. electronic patient record (EPR), hospitals logo and LSBs of ROI are embedded simultaneously as a robust watermark in RONI using IWT-SVD hybrid transform. The proposed scheme is blind and free from false positive detection. Various experiments have been carried out on different medical imaging modalities to evaluate the performance of the proposed scheme in terms of imperceptibility, robustness, tamper detection, localization, recovery and computation time. ROI tampering is detected and recovered with high accuracy. Thus, the proposed scheme is effective in telemedicine applications.

57 citations

Journal ArticleDOI
TL;DR: The experimental results reveal that the proposed scheme besides being semi-reversible and computationally efficient is capable of handling high payload and as such can be used effectively for electronic healthcare applications.

55 citations

Journal ArticleDOI
TL;DR: This work proposes a novel baseline approach for the navigation of resource constrained robots, introducing the aerial underground scout, with the main goal to rapidly explore unknown areas and provide a feedback to the operator.

51 citations