Institute for Systems Studies and Analyses

Delhi, India

Institute for Systems Studies and Analyses

Delhi, India
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Modi C.,Jaypee Institute of Information Technology | Kumari P.,Jaypee Institute of Information Technology | Sharma V.K.,Institute for Systems Studies and Analyses
AIP Conference Proceedings | Year: 2017

Present work deals with torsional surface wave propagation in a viscoelastic isotropic layer with Voigt type viscosity sandwiched between inhomogeneous half spaces. Exponential variation in rigidity and density is taken in the upper half space, whereas inhomogeneities in the lower half space associated with rigidity and density are assumed to follow linear variation. Displacement components in the viscoelastic layer, upper and lower half spaces are found in closed form and used to derive the dispersion and absorption relations for torsional wave under the assumed geometry in terms of generalized implicit function. The effects of inhomogeneity, viscosity parameters and dimensionless wave number have been explored in numerical section and explained by suitable graphs. © 2017 Author(s).

Kumari P.,Jaypee Institute of Information Technology | Modi C.,Jaypee Institute of Information Technology | Sharma V.K.,Institute for Systems Studies and Analyses
European Physical Journal Plus | Year: 2016

The propagation of torsional waves generated during earthquakes or mechanical explosions encounter various anomalies like layered structure, crustal inhomogeneities, geomagnetic field, viscosity etc. These anomalies significantly change the governing characteristics of propagating seismic waves. In the present study the authors explored the torsional-surface-wave propagation in a homogeneous magneto-viscoelastic layer over an inhomogeneous magneto-isotropic substratum. A closed-form solution for displacements in layer and substratum is found and the generalized absorption-dispersion relation is derived analytically. The characteristics of torsional waves in some simpler geometry have been deduced as particular cases to the present study. The impact of inhomogeneities-free lower substratum and the absence of magnetic field from layer and substratum is further investigated using numerical simulations and results were analyzed using implicit contour plotting. © 2016, Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg.

Chattopadhyay A.,Indian School of Mines | Kumari P.,Jaypee Institute of Information Technology | Sharma V.K.,Institute for Systems Studies and Analyses
International Journal of Geomechanics | Year: 2014

This paper discusses reflection and transmission phenomena of a three-dimensional (3D) plane quasi-P (qP) wave incident at a triclinic half-space superimposed by a fluid layer underneath another distinct triclinic half-space. The closed-form expressions are obtained for reflection and transmission coefficients of corresponding reflected and transmitted waves. These reflection and transmission coefficients are computed numerically and shown graphically for fixed values of relevant parameters. Certain problems have been discussed as special cases to the present problem. The findings of the current study can be used to analyze problems with similar geometry in different elastic mediums, such as monoclinic, transversely isotropic, and isotropic. DOI: 10.1061/(ASCE)GM.1943-5622.0000311. © 2014 American Society of Civil Engineers.

Kumari P.,Jaypee Institute of Information Technology | Sharma V.K.,Institute for Systems Studies and Analyses
Acta Mechanica | Year: 2014

This paper presents a theoretical study on propagation of torsional surface waves in a homogeneous viscoelastic isotropic layer with Voigt type viscosity over an inhomogeneous isotropic infinite half space. The non-homogeneity in half space is assumed to arise due to exponential variation in shear modulus and density. A closed-form solution has been obtained for the displacement in the layer as well as for a infinite half space. The dispersion and absorption relations for an torsional wave under the assumed geometry have been found. Numerical results are presented for propagation characteristics in terms of a number of non-dimensionalized parameters and have been produced graphically. This study investigates the effect of various parameters, namely non-homogeneity parameter, internal friction, the layer width and complex wave number on dissipation function and phase velocity of the torsional wave. Results in some special cases are also compared with existing solutions available from analytical methods, which show a close agreement. © 2013 Springer-Verlag Wien.

Chandra B.,Indian Institute of Technology Delhi | Gupta M.,Institute for Systems Studies and Analyses
Expert Systems with Applications | Year: 2011

Naïve-Bayes Classifier (NBC) is widely used for classification in machine learning. It is considered as the first choice for many classification problems because of its simplicity and classification accuracy as compared to other supervised learning methods. However, for high dimensional data like gene expression data, it does not perform well due to two major limitations i.e. underflow and overfitting. In order to address the problem of underflow, the existing approach adopted is to add the logarithms of probabilities rather than multiplying probabilities and the estimate approach is used for providing solution to overfitting problem. However, in practice for gene expression data, these approaches do not perform well. In this paper, a novel approach has been proposed to overcome the limitations using a robust function for estimating probabilities in Naïve-Bayes Classifier. The proposed method not only resolves the limitation of NBC but also improves the classification accuracy for gene expression data. The method has been tested over several benchmark gene expression datasets of high dimension. Comparative results of proposed Robust Naïve-Bayes Classifier (R-NBC) and existing NBC for gene expression data have also been illustrated to highlight the effectiveness of the R-NBC. Simulation study has also been performed to depict the robustness of the R-NBC over the existing approaches. © 2010 Elsevier Ltd. All rights reserved.

Iyer S.,Institute for Systems Studies and Analyses | Rao D.V.,Institute for Systems Studies and Analyses
2015 IEEE Underwater Technology, UT 2015 | Year: 2015

Underwater acoustic sensor networks (UWSNs) are crucial for a multitude of underwater applications that require wireless operation. The deployment of sensor nodes in an optimal arrangement while overcoming the unique challenges posed by the surrounding medium and energy constraints on the sensors is a non-trivial task for real-world applications. As these characteristics are anisotropic with respect to change in temperature, salinity, depth, pH, and transmission frequency, they need to be accounted for in a dynamic simulation to preconfigure a stable physical network layout of nodes. A strategy based on computational intelligence techniques that takes into consideration these factors to achieve a viable configuration with the available resources is of prime importance. The proposed methodology uses a genetic algorithm (GA) based optimization technique for the positioning and deployment of UWSN nodes to maximize the coverage provided to protect a high-value asset (HVA) in a military application. In the case of a civil application for ocean monitoring, the proposed technique is used to identify the minimum number of nodes required and their positions for effective communication. © 2015 IEEE.

Das S.K.,Institute for Systems Studies and Analyses
IEEE Intelligent Systems | Year: 2014

The article is halfway between agent technology and the mathematical reasoning needed to model tactical decision-making tasks. These models are applied to the air defense domain for command and control (C2). The article also addresses the issues related to evaluating agents, which are designed and implemented using the agent-programming paradigm. The agents are deployed in a simulated environment for performing C2 tasks, such as electronic counter-countermeasures, threat assessment, and weapon allocation. The simulated defense system runs without any human intervention and represents a state-of-the-art model for C2 autonomy. The use of agents as autonomous decision-making entities is particularly useful in view of futuristic network-centric warfare. © 2001-2011 IEEE.

Dutta D.,Institute for Systems Studies and Analyses
Defence Science Journal | Year: 2014

Effective missile defence systems are primary requirement for naval ships to counter lethal anti-ship cruise missile attacks in today's naval warfare scenario. Anti-ship ballistic missiles would further add worry to ship missile defence. The paper discusses a probabilistic analysis of missile defence system effectiveness by considering a simple scenario of a single ship defence with multiple interceptors against a single non-maneuvering missile attack. The ship's interceptor hard kill lethality is taken as the measures of effectiveness in the analysis. The paper discusses effect of different firing policies, multi-sensor and layered defence to achieve maximum ship survivability. © 2014, DESIDOC.

Saha B.,Institute for Systems Studies and Analyses | Sharma S.,Jaipur Institute of Engineering and Technology
Defence Science Journal | Year: 2012

Steganography is an art that involves communication of secret data in an appropriate carrier, e.g., image, audio, video or TCP/IP header file. Steganography's goal is to hide the very existence of embedded data so as not to arouse an eavesdropper's suspicion. For hiding secret data in digital images, large varieties of steganographic techniques are available, some are more complex than others, and all of them have their respective pros and cons. Steganography has various useful applications and the technique employed depends on the requirements of the application to be designed for. For instance. applications may require absolute invisibility of the secret data, larger secret data to be hidden or high degree of robustness of the carrier. This paper intends to give thorough understanding and evolution of different existing digital image steganography techniques of data hiding in spatial, transform and compression domains. It covers and integrates recent research work without going in to much detail of steganalysis, which is the art and science of defeating steganography. © 2012, DESIDOC.

Vijay Rao D.,Institute for Systems Studies and Analyses
Studies in Computational Intelligence | Year: 2015

Today’s military teams are required to operate in environments that are increasingly complex. Such settings are characterized by the presence of ill-structured problems, uncertain dynamics, shifting and ill-defined or competing goals, action/feedback loops, time constraints, high stakes, multiple players and roles, and organizational goals and norms. Warfare scenarios are real world systems that typically exhibit such characteristics and are classified as Complex Adaptive Systems. To remain effective in such demanding environments, defence teams must undergo training that targets a range of knowledge, skills and abilities. Thus oftentimes, as the complexity of the transfer domain increases, so, too, should the complexity of the training intervention. The design and development of such complex, large scale training simulator systems demands a formal architecture and development of a military simulation framework that is often based upon the needs, goals of training. In order to design and develop intelligent military training systems of this scale and fidelity to match the real world operations, and be considered as a worthwhile alternative for replacement of field exercises, appropriate Computational Intelligence (CI) paradigms are the only means of development. A common strategy for tackling this goal is incorporating CI techniques into the larger training initiatives and designing intelligent military training systems and wargames. In this chapter, we describe an architectural approach for designing composable, multi-service and joint wargames that can meet the requirements of several military establishments using product-line architectures. This architecture is realized by the design and development of common components that are reused across applications and variable components that are customizable to different training establishments’ training simulators. Some of the important CI techniques that are used to design these wargame components are explained swith suitable examples, followed by their applications to two specific cases of Joint Warfare Simulation System and an Integrated Air Defence Simulation System for air-land battles is explained. © Springer International Publishing Switzerland 2016.

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