Faculty Publications
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Item An analytical model for spiral wound reverse osmosis membrane modules: Part II - Experimental validation(2011) Sundaramoorthy, S.; Srinivasan, G.; Murthy, D.V.R.This paper presents the experimental studies carried out for validation of a new mathematical model [1] developed for predicting the performance of spiral wound RO modules. Experiments were conducted on a laboratory scale spiral wound RO module taking chlorophenol as a model solute. Experiments were carried out by varying feed flow rate, feed concentration and feed pressure and recording the readings of permeate concentration, retentate flow rate, retentate concentration and retentate pressure. A total of 73 experimental readings were recorded. The membrane transport parameters Aw (solvent transport coefficient) and Bs (solute transport coefficient) and the feed channel friction parameter b were estimated by a graphical technique developed in this work. The mass transfer coefficient k, estimated using the experimental data, was found to be strongly influenced by solvent flux and solute concentration apart from the fluid velocity. Taking the effects of solvent flux, solute concentration and fluid velocity, a new mass transfer correlation for Sherwood number is proposed in this work for the estimation of mass transfer coefficient. Comparison of model predictions with experimental observations demonstrated that the model was capable of predicting permeate concentration within 10% error, retentate rate flow within 4% error and rejection coefficient within 5% error. © 2011 Elsevier B.V.Item Reprint of: “An analytical model for spiral wound reverse osmosis membrane modules: Part II — Experimental validation”(Elsevier B.V., 2011) Sundaramoorthy, S.; Srinivasan, G.; Murthy, D.V.R.This paper presents the experimental studies carried out for validation of a new mathematical model [1] developed for predicting the performance of spiral wound RO modules. Experiments were conducted on a laboratory scale spiral wound RO module taking chlorophenol as a model solute. Experiments were carried out by varying feed flow rate, feed concentration and feed pressure and recording the readings of permeate concentration, retentate flow rate, retentate concentration and retentate pressure. A total of 73 experimental readings were recorded. The membrane transport parameters Aw (solvent transport coefficient) and Bs (solute transport coefficient) and the feed channel friction parameter b were estimated by a graphical technique developed in this work. The mass transfer coefficient k, estimated using the experimental data, was found to be strongly influenced by solvent flux and solute concentration apart from the fluid velocity. Taking the effects of solvent flux, solute concentration and fluid velocity, a new mass transfer correlation for Sherwood number is proposed in this work for the estimation of mass transfer coefficient. Comparison of model predictions with experimental observations demonstrated that the model was capable of predicting permeate concentration within 10% error, retentate rate flow within 4% error and rejection coefficient within 5% error. © 2011 Elsevier B.V.Item Tuned liquid dampers for multi-storey structure: numerical simulation using a partitioned FSI algorithm and experimental validation(Springer India sanjiv.goswami@springer.co.in, 2017) Eswaran, M.; Sathyanath, S.; Niraj, P.; Reddy, G.R.; Ramesh, M.R.Wind-induced and earthquake-induced vibrations of structures such as super-tall towers and bridges can be efficaciously controlled by tuned liquid dampers (TLDs). This work presents a numerical simulation procedure to study the performance of TLDs–structure system through sigma (?)-transformation-based fluid–structure coupled solver. For this, a ‘C’-based computational code has been developed. The structural equations, which are coupled with the fluid equations in order to achieve the transfer of sloshing forces to structure for damping, are solved by the fourth-order Runge–Kutta method, while the fluid equations are solved using finite-difference-based sigma-transformed algorithm. Different iterative and error schemes are used to optimize the code for larger convergence rate and higher accuracy. For validation, a few experiments are conducted with a three-storey structure using TLDs arrangement. The present numerical results of response of TLD-installed structures match well with the experimental results. The minimum displacement of structure is observed when the resonance condition of the coupled system is achieved through proper tuning of TLDs. Since real-time excitations are random in nature, the performance study of TLDs under random excitation has also been carried out in which the Bretschneider spectrum is used to generate the random input wave. © 2017, Indian Academy of Sciences.Item Numerical simulation and experimental validation of free surface flows during low pressure casting process(Elsevier Ltd, 2017) Viswanath, A.; Manu, M.V.; Savithri, S.; Pillai, U.T.S.The present work analyzes the free surface flow characteristics during mold filling in a low pressure casting process (LPC) through water model experiments and numerical simulations. The flow patterns visualized through the water analog experiments using different input pressure sequences have been verified with numerical simulation results for the entire LPC process. The benchmarked numerical model has been further used to study the impact of different in-gate shapes on fluid free surface behavior inside the mold cavity. The mold filling and solidification simulation is then carried out using magnesium alloy as liquid for the same geometry and the same input pressure profile to highlight the effect of thermo physical properties of actual melts on the free surface flow behavior. © 2017Item Nonlinear bending and free vibration response of SUS316-Al2O3 functionally graded plasma sprayed beams: theoretical and experimental study(SAGE Publications Inc. claims@sagepub.com, 2018) Malik, P.; Kadoli, R.Functionally graded SUS316-Al2O3 beams with ceramic content varying from 0 to 40% were prepared by a plasma spraying technique. Nonlinear finite element analysis was used to obtain the static deflection and free vibration of a clamped-free functionally graded beam. Von Kármán geometric nonlinearity and power law variation in material gradation through the beam thickness are considered in the analysis. The maximum error between the experimental and nonlinear finite element results for deflection is 6.68% and 14.31% on the fundamental frequency. Numerical results have also been attempted using ANSYS 3D solid element and they compare more closely with the experimental results. © 2016, © The Author(s) 2016.Item A novel GA-ELM model for patient-specific mortality prediction over large-scale lab event data(Elsevier Ltd, 2019) S. Krishnan, G.; Kamath S?, S.Patient-specific mortality prediction models are an essential component of Clinical Decision Support Systems developed for caregivers in Intensive Care Units (ICUs), that enable timely decisions towards effective patient care and optimized ICU resource management. While high prediction accuracy is a fundamental requirement for any mortality prediction application, being able to so with minimal patient-specific data is a major plus point that can help in improving care delivery and cost optimization. Most existing scoring techniques and prediction models utilize a multitude of lab tests and patient events to predict mortality and also suffer from reduced performance when available patient data is less. In this paper, a Genetic Algorithm based Wrapper Feature Selection technique is proposed for determining most-optimal lab events that contribute predominantly to mortality, even for large-scale patient cohorts. Using this, an Extreme Learning Machine (ELM) based neural network is designed for predicting patient-specific ICU mortality. The proposed GA-ELM model was benchmarked against four popular traditional mortality scores and also state-of-the-art machine learning models for experimental validation. The GA-ELM model achieved promising results as it outperformed the traditional scoring systems by 11%–29% and state-of-the-art models by up to 14%, in terms of AUROC. © 2019 Elsevier B.V.Item Predicting ICD-9 code groups with fuzzy similarity based supervised multi-label classification of unstructured clinical nursing notes(Elsevier B.V., 2020) Gangavarapu, T.; Jayasimha, A.; S. Krishnan, G.S.; Kamath S?, S.In hospitals, caregivers are trained to chronicle the subtle changes in the clinical conditions of a patient at regular intervals, for enabling decision-making. Caregivers’ text-based clinical notes are a significant source of rich patient-specific data, that can facilitate effective clinical decision support, despite which, this treasure-trove of data remains largely unexplored for supporting the prediction of clinical outcomes. The application of sophisticated data modeling and prediction algorithms with greater computational capacity have made disease prediction from raw clinical notes a relevant problem. In this paper, we propose an approach based on vector space and topic modeling, to structure the raw clinical data by capturing the semantic information in the nursing notes. Fuzzy similarity based data cleansing approach was used to merge anomalous and redundant patient data. Furthermore, we utilize eight supervised multi-label classification models to facilitate disease (ICD-9 code group) prediction. We present an exhaustive comparative study to evaluate the performance of the proposed approaches using standard evaluation metrics. Experimental validation on MIMIC-III, an open database, underscored the superior performance of the proposed Term weighting of unstructured notes AGgregated using fuzzy Similarity (TAGS) model, which consistently outperformed the state-of-the-art structured data based approach by 7.79% in AUPRC and 1.24% in AUROC. © 2019 Elsevier B.V.Item High sensitivity detection of chemicals based on sinusoidally apodized structured grating assisted liquid filled directional coupler(Springer, 2021) Raghuwanshi, S.K.; Singh, Y.; Singh, M.; Chack, D.; Kumar, R.; Prakash, O.The grating has a significant role in sensing applications. Similarly, the grating-assisted coupler has excellent potential in chemical sensing applications. The power coupling between two closely coupled waveguide couplers can be significantly tuned by incorporating grating between them. The grating has been taken of silica material with sinusoidal shape in variation. The grating layer is assumed to be embedded within the sensing layer while considering a changeable effective refractive index depending on the sensing layer substances. In the present paper, grating assisted directional coupler has been numerically analysed using its own developed MATLAB-based algorithm of finite difference method (FDM) scheme. FDM method has been applied to solve the Eigenvalue equation to obtain allowed Eigenvalues and corresponding Eigen vectors (TE and TM cases). In FDM, the analysis domain has been fine discretized into the mesh of 1-D equal spacing for reasonable accurate computation results. In experimental validation, Fibre Bragg grating (FBG) has been suspended between two high refractive index coupler regions, which act as a power coupling zone. Also, the coupling length has been changed from 5 to 20 ? m for tuning purposes and then optimized for grating parameters viz. length, period, etc. The whole structure is 2-Dimensional (x and y directions) with invariant in the y-direction. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Item A low voltage harvesting in photovoltaic generation systems using negative embedded Z-source inverter(John Wiley and Sons Ltd, 2021) Reddivari, R.; Jena, D.Commercial two-stage grid-connected photovoltaic (PV) inverters suffer from a narrow band maximum power point (MPP) voltage operation. If the voltage falls outside this narrow band, the inverter switches its operation from MPP to power limitation mode. At the same time, these inverters need high start-up voltages to turn them ON again. The evolutionary algorithms are widely used to track the global MPP at wide input (PV) voltage range. However, the global MPP at low PV voltages cannot be boosted to grid voltage level due to the limited duty ratio of conventional DC-DC converters that restricts the inverter MPP voltage range. This paper summarizes the potential challenges of narrow range MPP voltage solar inverters under partial shading scenarios. Also, demonstrates a proposed single-stage negative embedded Z-source single-stage inverter (NEZSI) to extend the MPP voltage range. The proposed topology wakes up the inverter at lower threshold voltages that enables it to extract energy from low PV string voltages. In addition, the proposed inverter tracks the MPP at a faster rate with low input current ripple, inrush current, and device stresses. Further in this paper, qualitative and quantitative comparisons between state-of-the-art topologies are provided to highlight the superiority of the proposed inverter. Simulation and experimental validation of the proposed inverter are demonstrated with traditional perturb and observe (P&O) and variable step P&O algorithms. © 2021 John Wiley & Sons Ltd.Item Finite element modeling and experimental validation of rectangular pin buckle arrestors for offshore pipelines(Taylor and Francis Ltd., 2022) Rao, N.R.; Kaliveeran, V.Finite element modeling was performed, and experiments were conducted on pipeline models made of stainless steel of grade SS304. Present research work focuses on the improvement in structural properties of offshore pipelines stiffened with rectangular pin buckle arrestors by varying length and placing them at different locations along the length of pipeline. The optimum length of buckle arrestors was identified from finite element analysis and pipeline models were fabricated for conducting buckling experiments. Bending experiments were conducted on the pipeline models to determine flexural capacity of the pipeline models. Finite element analysis results showed good agreement with experimental results. © 2020 Taylor & Francis Group, LLC.