Conference Papers
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/28506
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Item A novel solution to routing in Cognitive Radio ad-hoc networks in high primary user traffic environments(Institute of Electrical and Electronics Engineers Inc., 2015) Sridhar, A.; Sridhar, S.; Lal, S.Cognitive Radio technology holds great promise in solving the problem of spectrum scarcity. A plethora of routing protocols exist for Cognitive Radio networks, however most of them relay on establishing an end-to-end path using a Common Control Channel. This paper focuses on scenarios where the Primary User traffic is very high and erratic and therefore trying to set up end-to-end paths is not feasible. A novel solution to this problem is proposed where the cognitive users form a Cognitive Delay Tolerant Network through a modification in the network stack. Well researched delay tolerant networking routing protocols designed for networks with unreliable links, configured for multiple channel can used for routing in high primary user traffic environments. Through extensive simulation we show the that proposed architecture provides very high delivery ratio (close to 1) in the presence of very high primary user traffic with negligible computational complexity and the absence of a common control channel. We also show that trying to rely on routing protocols that try to establish end to end paths such as Multi-Channel AODV is not feasible. The performance of Multi-Channel AODV and proposed architecture is compared and analyzed with bundle/packet delivery ratio, end-to-end delay and hop count as performance metrics. © 2015 IEEE.Item Advertisement detection in commercial radio channels(Institute of Electrical and Electronics Engineers Inc., 2016) Koolagudi, S.G.; Sridhar, S.; Elango, N.; Kumar, K.; Afroz, F.In this paper, real time identification of advertisement segments in a radio broadcast is performed. There are certain distinctive characteristics of advertisements that distinguish from the rest of the broadcasting information, Speech technology related to recognition of specific patterns in speech signal can characterize this distinction. Machine learning tools such as Hidden Markov Models, Artificial Neural Networks and Ensemble Method are used to classify advertisement and non-advertisement patterns. An ensemble classification technique gave a better classification performance. The system was created using blind audio segmentation for optimization of real time analysis. This work is done mainly using audio characteristics and can be extended to visual data. © 2015 IEEE.Item Analysis of Five Leg Voltage Source Inverter Fed Dual Motor Drive System(EDP Sciences, 2021) Harish, S.P.; Sridhar, S.; Indela, O.; Kodeeswara Kumaran, G.; Parthiban, P.With the advent of electric vehicle multi-machine drives are attaining overwhelming responses from the researchers and industries in recent years, as compared to their counterpart of single machine drive. In this regard, the industries are looking for multi motor control with single inverter system with precise speed control. The solution of aforesaid problem lies with multi-leg inverter fed dual induction motor drives that are capable for high power ratings and other specific applications. Any faults in the system leads to the failure of the operation of the entire drive system. Hence condition monitoring of the entire drive system becomes of paramount significance. Considering the aforementioned points, this paper focuses on the fault analysis of five leg voltage source inverter feeding dual induction motors. The drive system is simulated using MATLAB/SIMULINK for different pulse width modulation techniques like SPWM, SVPWM and Two Arm Modulation (TAM) Techniques. The effect on fault in the inverter like opening of the switch and shorting the switch, on the performance of the induction motors are analysed. Total Harmonic Distortion (THD) of the stator current for different modulation techniques are compared for the analysis purpose. From the results it is observed that the THD is less for SVPWM techniques as compared with SPWM and TAM method. But independent control of both the machine cannot be attained by SPWM and SVPWM method. For independent speed control TAM method is used. So a trade-off has to be done considering the requirement and THD. It is finally concluded that independent speed control is achieved at the cost of higher THD. © The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/)Item Numerical Modeling of Centrifuge Experiment on Vacuum Consolidation of Soft Clay(Springer Science and Business Media Deutschland GmbH, 2022) Sridhar, S.This paper presents the finite element (FE) modeling of centrifuge experiments on vacuum consolidation of soft clay deposits. FE analysis of centrifuge tests as a model scale was performed, and the comparison is made with the centrifuge tests modeled as a prototype. The effect of different material parameters namely unit weight of water and density, initial void ratio and permeability of clay at model and prototype were studied. FE analysis confirmed that the use of unit weight of pore water at 1-g as an input parameter results in an incorrect distribution of vertical effective stress. To correctly compute vertical effective stress, unit weight of water at N-g should be used. In order to model the centrifuge test exactly it would be appropriate to give the values of initial dry density, initial void ratio and the initial vertical stress corresponding to those at 1-g so that the final conditions after self-weight consolidation results in proper distribution of void ratio and other field variables. To correctly model the increase in seepage velocity with gravity in centrifuge tests, permeability must be increased by the same factor as the gravity. Four pore water pressure boundary conditions to model the vacuum pressure were analyzed through numerical runs. The numerical model at the model scale considering all factors analyzed earlier were used in modeling vacuum consolidation of soft clay. It was found that to accurately model the vacuum pressure, the vacuum pressure should be applied only at the top of the soil layer for accurate prediction of the field variables. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Numerical Modelling of Mechanically Stabilized Earth Walls for Slope Protection(Springer Science and Business Media Deutschland GmbH, 2022) Reshma, P.R.; Sridhar, S.Slope failure also known as ‘mass wasting’ is the downward movement of rock or debris under the influence of gravity as a result of several natural and manmade triggers. Mechanically stabilized earth wall is one of the popular methods for stabilizing unstable slopes using of extensible or inextensible reinforcements. This paper presents the analytical and numerical analysis carried out on a mechanically stabilized earth wall for the protection of unstable natural sloping ground. The analytical modelling was done as per the Federal Highway Administration (FHWA) guidelines. The numerical modelling was carried out using the finite element method (FEM) software, PLAXIS 2D. The major objective of the numerical study was to analyse the most influential parameters to be taken care of during the design of MSE wall for slope stability. The numerical studies of slopes were carried out with and without reinforcement. The effects of variation of parameters, such as length, axial stiffness and spacing of reinforcement, cohesion and angle of internal friction of reinforced fill, were analysed. It is observed that, with increase in cohesion and angle of internal friction of retained soil, slope stability has improved significantly. Also, increase in reinforcement parameters such as length and axial stiffness resulted in improved slope stability. But the increase in reinforcement spacing had a negative effect, which resulted in the decreased factor of safety of soil slopes. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item A Critical Review on Potential Use of Iron Ore Tailings as Structural Fill Material(Springer Science and Business Media Deutschland GmbH, 2023) Athira, S.; Sridhar, S.India is well enriched with abundant resources of magnetite and hematite iron ore. Mining activities are tremendously increasing to cater the demand of market, which in turn is responsible for huge generation of mining waste. Mine tailings impoundments produced during beneficiation and extraction of iron ores create environmental threat and are disposed at high monetary and ecological cost. There is a need to find a sustainable and economical solution to handle large quantity of generated waste. Depleting natural resources like granular soil as backfill material needs a substitution in many application-like pavements, mechanically stabilized wall, embankments, etc. This paper presents a critical review on literatures highlighting on use and reuse potential of iron ore tailings as a backfill material in structural application such as MSE wall, embankments, pavements. Characterization and engineering behaviour of the tailings are the central necessity for estimating its effectiveness as its properties vary from ore structure. Mineralogical characterization, shear strength, permeability, workability, and compressive strength are the properties discussed in this paper. Results show that iron ore tailings have properties which can be considered as an effective substitute in structural applications. Adopting it as backfill material can be considered an environmentally friendly method of stabilization. It protects the surface structures and abate subsidence in abandoned underground mines. It has its potential in handling large volume of tailings and significantly reduces the quantity of waste generated in the state. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Finite Element Modelling of Laboratory One-Dimensional Consolidation of Soft Clays(Springer Science and Business Media Deutschland GmbH, 2023) Kasyap Vasudevan, A.S.; Sridhar, S.Consolidation of soft clays is always a challenge in foundation engineering. Different material models have been developed to capture the compression and recompression properties of clays. However, the deformation behaviour of clay is captured relatively well by modified cam clay. Validation of the material models and software tools which uses numerical analysis is very crucial before one use them to analyse field problems. A successful validation can open the possibilities for wide range application of the model. This study attempts to validate numerical model of a one-dimensional consolidation of soft clay using the results of consolidation test already conducted in laboratory. The time settlement data for different compression loads is obtained by simulating the laboratory experimental setup in ABAQUS finite element software. The boundary conditions are defined to simulate the drainage conditions in the experimental setup. The results from both experimental and numerical analysis are compared. The time settlement behaviour from numerical analysis for different loads were found comparable with experimental results. The dissipation of pore pressure and development of effective stress is also presented. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Investigations of hand transmitted vibrations and associated health risks in load haul dumper operators based on different components of a work cycle(Elsevier Ltd, 2023) Sridhar, S.; Govinda Raj, M.; Mangalpady, M.Load Haul Dumpers (LHDs) are operated in underground mines to transport ore/waste rock under extreme conditions. The operating conditions of the LHDs make the operators susceptible to occupational vibration exposure, including Hand Transmitted Vibrations (HTVs). To date, no research literature is available concerning the evaluation of HTVs based on different components of the LHD work cycle. In the present research study, HTV data were collected by mounting a hand strap on tri-axial accelerometer to the operator's hand in contact with the steering device of the LHDs. Frequency-weighted root mean square (WRMs) acceleration values for all the three measurement axes were collected during different components of the LHD work cycle, namely mucking, loaded travel, unloading, and empty travel. High vibration responses were recorded during the mucking operations, followed by empty hauling. Out of the eight LHDs considered for the study, three LHDs had total daily vibration values A(8) more than that of the stipulated Exposure Action Values (EAV) of 2.5 m/s2, the highest recorded being 2.9 m/s2 in the LHD designated L-6. Health risk assessment was carried out based on EU Directive 2002 and ISO 5349:2001, which showed that operators of three LHDs were at risk of developing health issues such as finger blanching within 12 years of their work life. Strategies to mitigate HTVs should focus on the component of the work cycle and the dominant axis of vibration along with the total daily vibration magnitudes. Operating the LHDs using remote controls during mucking can significantly reduce the total vibration magnitude within daily exposure limits. © © 2023 Elsevier Ltd. All rights reserved.Item Comparative Study of Analytical and Numerical Modelling of Bearing Pressure of Shallow Foundation(Springer Science and Business Media Deutschland GmbH, 2025) Rao, M.S.; Sridhar, S.Settlement is the predominant criterion that governs the design of footing on frictional and cohesive frictional soil. Hence bearing pressure plays a key role in design of footing. To evaluate the bearing pressure, Teng, Meyerhof and other researchers proposed empirical formula and charts in terms of N values obtained from Standard Penetration Test (SPT). In the present study, soil investigation data obtained from four sites have been used to estimate the bearing pressure through empirical formula and finite element analysis. Finite element model is validated through the case studies available in the literature. Bearing pressure values for strip footing of width varying from 1.5 to 5.5 m were estimated. Further, an attempt has been made to check the reliability of empirical formula by comparing it with values obtained through numerical analysis. It is observed that if the SPT-N values are directly taken from the field tests, the results from Meyerhof expression were found to be in good agreement with the numerical model. Whereas, if only shear strength parameters are obtained from site, SPT-N value calculated indirectly using friction angle excludes the effect of cohesion. Hence, Meyerhof expression resulted in comparatively lower bearing pressure values. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.