Browsing by Author "Sridhar, S."

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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. Â© 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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. Â© 2015 IEEE.
Advertisement detection in commercial radio channels
(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.
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. Â© 2015 IEEE.
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. Â© 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/)
Analyzing dynamic stall on tubercle mounted VAWT blades: A simplistic experimental approach using an oscillating rig
(Elsevier Ltd, 2024) Joseph, J.; Sridhar, S.; A, S.; Radhakrishnan, J.
Leading-edge tubercles, inspired by the flippers of humpback whales, are widely adopted passive flow control devices to enhance the aerodynamic performance of various lifting surfaces. This experimental study investigates the implementation of sinusoidal and triangular tubercles on H-type Vertical Axis Wind Turbine blades to analyze their effects on dynamic stall characteristics. Experimental tests were conducted using a specially designed oscillating rig to replicate blade motion at different reduced frequencies. The results reveal that tubercle blades exhibit a lower stall angle and maximum normal force compared to the baseline configuration. Moreover, the dynamic stall characteristics of tubercle blades are notably smoother, leading to reduced hysteresis losses. A variation in the tubercle amplitude-wavelength ratio further decreases hysteresis, albeit at the cost of reduced normal force generation. At the highest tested reduced frequency of 0.065, tubercles reduce hysteresis by up to 38%. Despite the reduction in normal force, tubercles effectively mitigate the effects of dynamic stall vortices, resulting in smoother stall behavior. The observed reduction in hysteresis can contribute to enhancing the turbine's lifespan and increasing power production efficiency. This experimental approach provides a cost-effective alternative to more expensive methods for studying dynamic stall characteristics. © 2024 The Authors
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 5.5Â 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. Â© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.
Comprehensive Assessment on Utilization of Iron Ore Tailing as Backfill Material in Mechanically Stabilized Earth Wall
(Springer, 2025) Satheesh, A.; Sridhar, S.; Packiam, S.
World is bestowed with self-sufficient magnetite and hematite iron ores. Huge volume of mining waste, namely iron ore tailings (IOT), is generated during processing of iron ore, leading to environmental concerns. At the same time, due to excessive usage and environmental regulations, there is scarcity of naturally available granular material. This paper presents the detailed laboratory study carried out to ascertain the feasibility of adopting iron ore tailings as an alternate granular backfill material in mechanically stabilized earth wall. A comprehensive study on mineralogical, physiochemical, and geotechnical characteristics was carried out on IOT procured from Lakhya dam, Chikkamagaluru district, Karnataka, India. X-ray fluorescence study indicates the presence of silica as major mineral along with hematite as major iron-bearing mineral. IOT is classified as a poorly graded sand with high friction angle value varying between 44° and 50° under loose and dense states and negligible particle breakage under compaction. The environmental risk connected with IOT was assessed through leaching studies and it was characterized as low contamination low ecological risk material. Design of mechanically stabilized earth (MSE) wall with IOT and granular soil as backfill using tie-back wedge method revealed that identical number of reinforcement layers are required when iron ore tailing or granular soil is used as backfill. Further, finite element modeling of MSE wall with IOT and river sand as backfill was carried out to compare the deformation behavior. MSE wall with IOT as backfill showed 70% reduction in horizontal facing displacement in comparison with sand backfill. © The Author(s), under exclusive licence to Indian Geotechnical Society 2024.
Comprehensive Evaluation of Iron Ore Tailing and Cement Treated Lithomargic Soil for Pavement Application
(Springer Science and Business Media Deutschland GmbH, 2025) Satheesh, A.; Sridhar, S.
Lithomargic soil, extensively found along the coastal regions of Karnataka, India, is inherently weak with a low California Bearing Ratio (CBR) value and hence, unsuitable as a subgrade or sub-base material in a pavement. To utilize the lithomargic soil as a subgrade or sub-base material, the present study focuses on its stabilization using Iron Ore Tailing (IOT) and cement. IOT, collected from Kudremukh region, Karnataka, India, was assessed for its suitability in pavement stabilization, with proportions ranging from 10 to 50%. Lithomargic soil stabilized with optimum proportion of IOT was subsequently treated with cement, with proportions ranging from 2 to 12% and in increments of 2%. Compaction test, CBR test, Unconfined compression test and durability tests were carried out on lithomargic soil stabilized by IOT alone and both IOT and Cement. Furthermore, X-ray Diffraction, Field Emission Scanning Electron Microscope and Fourier Transform Infrared Spectroscopy analyses were carried out to understand the stabilization mechanisms. Optimal results were obtained for lithomargic soil treated with 20% IOT. The unconfined compression test revealed that the soil-IOT mix satisfied the strength requirements for a subbase material with 6% cement, whereas lithomargic soil alone required 8% cement content to meet the strength requirements. Incorporating 2% cement into the soil-IOT mix enhanced the CBR to 31%, up from 2% for lithomargic soil, satisfying subgrade requirement. All stabilized mix containing more than 2% cement met the durability requirements for 12 cycles of wet-dry and freeze-thaw. The microstructural analyses showed cementitious compounds within the soil structure, indicating the formation of hydration products along with additional hydroxyl compounds. The pavement design and analysis for high-volume roads was carried out as per IRC: 37-2018 and IITPAVE software and results indicate 28% reduction in design pavement thickness and a reduced maximum deflection value after stabilization. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Experimental and numerical analysis of humpback whale inspired tubercles on swept wings
(Emerald Publishing, 2022) Joseph, J.; A, S.; Sridhar, S.
Purpose: With aims to increase the aerodynamic efficiency of aerodynamic surfaces, study on flow control over these surfaces has gained importance. With the addition of flow control devices such as synthetic jets and vortex generators, the flow characteristics can be modified over the surface and, at the same time, enhance the performance of the body. One such flow control device is the tubercle. Inspired by the humpback whale’s flippers, these leading-edge serrations have improved the aerodynamic efficiency and the lift characteristics of airfoils and wings. This paper aims to discusses in detail the flow physics associated with tubercles and their effect on swept wings. Design/methodology/approach: This study involves a series of experimental and numerical analyses that have been performed on four different wing configurations, with four different sweep angles corresponding to 0°, 10°, 20° and 30° at a low Reynolds number corresponding to Rec=100,000. Findings: Results indicate that the effect of tubercles diminishes with an increase in wing sweep. A significant performance enhancement was observed in the stall and post-stall regions. The addition of tubercles led to a smooth post-stall lift characteristic compared to the sudden loss in the lift with regular wings. Among the four different wings under observation, it was found that tubercles were most effective on the 0° configuration (no sweep), showing a 10.8% increment in maximum lift and a 38.5% increase in the average lift generated in the post-stall region. Tubercles were least effective on 30° configuration. Furthermore, with an increase in wing sweep, co-rotating vortices were distinctly observed rather than counter-rotating vortices. Originality/value: While extensive numerical and experimental studies have been performed on straight wings with tubercles, studies on the tubercle effect on swept wings at low Reynolds number are minimal and mainly experimental in nature. This study uses numerical methods to explore the complex flow physics associated with tubercles and their implementation on swept wings. This study can be used as an introductory study to implement passive flow control devices in the low Reynolds number regime. © 2022, Emerald Publishing Limited.
Factors Affecting Investment Decision Making of Urban Individual Investors in India
(National Institute of Technology Karnataka, Surathkal, 2014) Shetty, Sukanya; Kiran, K. B.; Sridhar, S.
For the sake of financial security individuals must save and invest. Due to the changes in the socio-economic environment, not only have individuals become increasingly responsible for their well-being but the landscape of financial markets has changed radically. These changes have been characterized by an increase in the complexity of financial products. Investment decision making (IDM) in such an environment has become extremely difficult. Although modern portfolio theory assumes that investors are rational, in reality it is not so. The literature review provides ample evidence to show that individuals are not rational and markets are not efficient. Further, it provides the theoretical framework to identify the various factors that influence IDM among urban individuals. Although the financial innovations are important and relevant, they ignore the essence of the financial products; of whether it is suitable to those whom it is designed and marketed. For this reason, it is important to understand individuals from a holistic point of view rather than from a single viewpoint. The purpose of the study is to describe the factors that influence IDM of urban individuals in the current scenario. The factors that affect the IDM considered in this study are (a) demographics (b) personality (c) social environment (d) experience (e) choice criteria (f) contextual factors and (g) biases based on information processing errors. The data is substantiated by an in-depth interview of intermediaries who facilitate IDM among individual investors. Data was collected primarily through a survey in the form of a self-administered questionnaire from 1146 urban individual investors as well as from interviewing 40 financial intermediaries. The secondary sources of information were gathered from books, journals, newspapers, working papers, study reports and websites. The validity of the instrument was obtained with the help of experts and pilot tested for a small group of respondents and the reliability was tested using Cronbach’s alpha. The populationconsidered for the study was urban middle class individuals with a minimum disposable income of Rs. two lakhs per annum. Since the data collected is very personal and highly confidential, snowball sampling is used for the purpose of the study. Data is analyzed using Kruskal Wallis test, Pearson’s correlation, Principal Component Analysis and Regression Analysis using SPSS version 17. The results of the study indicate that demographics, personality traits, and experience influence the IDM of individuals. The intermediaries’ opinion agrees with the results of demographic factors and experience. Among the social environment factors, family and non-commercial sources are found to influence the IDM of individuals. As per the intermediaries’ opinion, non-commercial sources and informal sources influence individuals to a larger extent. Among the choice criteria factors, convenience and risk factors influence the IDM of individuals. But, as per the intermediaries’ opinion, return affects IDM to a large extent. Among the contextual factors, task complexity and information processing affects the IDM of individuals. As per the intermediaries’ opinion, task complexity and time constraint affect individual investors. Among the biases, representativeness, framing, availability and loss aversion affect the IDM of individuals. The regression results show that the biases of representativeness, framing, anchoring and loss aversion could be explained using the explanatory variables of personality, social environment, choice criteria and contextual factors. The intermediaries further mention that individuals are affected by emotion while investing. An individual would be able to make better investment decisions by being aware of his/her own biases. By understanding the individual investor, the financial intermediaries could customize financial plans and products to suit the needs of their clients. The policy makers could design policies so as to encourage a positive investment environment that is in favor of individual investors.
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. Â© 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
For rapid industrialization, a high degree of mechanisation has become inevitable, further increasing the capital investment. Mining statistics project a figure of 60 to 80% of the capital invested in a few new coal mining projects on mining machinery and around 5 to 15% on the development necessary to install the equipment. However, a mining property has a definite value only by virtue of its ability to produce profit over a span of years. The components and areas in which cost can be reduced are dealt with.
(Cost reduction in mining industry: a conceptual analysis) Uma Maheshwar Rao, K.; Sridhar, S.; Suryanarayana Murthy, Ch.
1989
Implementation of tubercles on Vertical Axis Wind Turbines (VAWTs): An Aerodynamic Perspective
(Elsevier Ltd, 2022) Sridhar, S.; Joseph, J.; Radhakrishnan, J.
In recent days, enhancement of Vertical Axis Wind Turbines (VAWTs) by mitigating flow deteriorating effects like dynamic stalling, unsteady wake is given great importance. The following article focuses on implementing four different tubercles on the blades’ leading edge and studying its performance and flow characteristics using CFD techniques. Results indicate that the addition of tubercles generated counter-rotating vortices and delayed flow separation and helped control dynamic stalling. Between azimuth angles 70°–160°, the flow was seen to separate only along the trough regions of the blade and remained attached along the peak regions, thus providing more torque and power. In addition to the enhancements in the flow characteristics, a 28% increase in power coefficient was observed for the optimal configuration at the optimal tip speed ratio. Additionally, a 14% increase in maximum lift generated by the blade was observed. Preliminary aeroacoustics analysis revealed a 12% and 20% decrease in the noise emissions along the blade tip and mid-plane of the turbine, respectively. Hence, it can be shown that tubercles effectively control dynamic stall, reduce noise emissions, and increase the power output of VAWTs. © 2022 Elsevier Ltd
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. Â© Â© 2023 Elsevier Ltd. All rights reserved.
Maximum Aerobic Capacity and Relative Aerobic Strain among Mobile Mine Equipment Operators in Underground Mines
(Springer, 2023) Sridhar, S.; Raj, M.G.; Mangalpady, M.
The maximum aerobic capacity and relative aerobic strain could be employed as indicators to establish a balance between work and individuals. Unfortunately, information about the physiological demands of mobile mine equipment operators working in underground mines is nearly nonexistent. The present research aimed to determine the maximum aerobic capacity and relative aerobic strain of the mobile mine equipment operators and assess their relationship with their age and body mass index. Forty operators involved in transporting ore, overburden, mine personnel, explosives, repair material, etc., were examined. The maximum aerobic capacity was determined indirectly using the heart rate of the operators. The mean aerobic capacity of the operators was 38.75 mL/kg/min, and the lowest mean aerobic capacity was found in LHD operators, 37.98 ± 3.93 mL/kg/min. The maximum aerobic capacity was negatively correlated with age and body mass index. Eleven out of 40 operators had relative aerobic strain exceeding 50% of the maximum aerobic capacity. The mean relative aerobic strain was 46.9 ± 5.54, and the highest mean relative aerobic strain of 49.37 ± 5.55 was found among LHD operators. The relative aerobic strain had a positive correlation with age and BMI. Knowing the operators’ maximal capacities while executing their tasks could be crucial in assessing the physiological demands of individuals working in underground mines in terms of acceptable work constraints. © 2022, The Institution of Engineers (India).
Musculoskeletal Disorder Risk in the Upper Extremities of Mobile Mining Equipment Operators Exposed to Hand-Transmitted Vibrations in Underground Metal Mines: a Case–Control Study
(Springer Science and Business Media Deutschland GmbH, 2022) Sridhar, S.; Raj, M.G.; Mangalpady, M.
Hand-transmitted vibration (HTV) exposure is associated with various health risks for operators of mobile mining equipment (MME). The case–control research was conducted to determine the musculoskeletal disorder (MSD) risks associated with exposure to HTVs in the exposed (case) and non-exposed (control) groups. HTV readings were measured at the interface between the hand and the steering device using the SV 105B triaxial hand accelerometer connected to the SV106 human vibration analyzer involving 40 MME operators in accordance with ISO 5349:2001 guidelines. A questionnaire survey was also carried out among both the study groups using Cornell Musculoskeletal Discomfort Questionnaire. The European Union's 2002/44/E.C. was used to assess the health risks posed to the MME operators. Twenty-eight out of the 40 MMEs were generating HTVs exceeding the stipulated daily limits of vibration, putting 70% of the operators at increased risk for developing MSDs. The case group was found to have an elevated risk of exposure with odds ratio (OR) 7.56 (95% confidence interval (CI), 1.159, 49.39) and OR 12.80 (95% CI, 2.436, 67.285) times more likely than the control group to suffer discomfort in the left shoulder and left wrist, respectively, indicating increased risk of exposure to HTV. Additionally, cases had elevated risk associated with exposure to tobacco, OR 9.35(95% CI, 1.856, 47.129) compared to those who did not use tobacco. MSDs were more prevalent in the case group compared to the control group. This observation was validated by the field investigations and the responses of MME operators to the questionnaires. © 2022, Society for Mining, Metallurgy & Exploration Inc.
A novel solution to routing in Cognitive Radio ad-hoc networks in high primary user traffic environments
(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.
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. Â© 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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 â€˜mass wastingâ€™ 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. Â© 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.