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Application of IITM-rANS3D to free-fall water entry of prismatic and non-prismatic finite wedges

Journal of Hydrodynamics 2023年第3期35卷 417-430页

作者： Shaswat Saincher Kshitij Srivastava r.vijayakumar V.Sriram Center for Maritime Experiments to Maritime Experience(ME2ME) Indian Institute of Technology MadrasChennaiIndia Department of Ocean Engineering Indian Institute of Technology MadrasChennaiIndia

High-speed watercraft and ships undergo coupled motions which make the front portion of the hull exit and violently re-enter *** induces short-term slamming loads that may compromise the structural integrity of the *** slamming of the bow can be modeled as straight wedges of different deadrise angles(DrAs)falling into water from different *** advent of computational fluid dynamics has allowed the problem of wedge-slamming to be simulated using the full Navier-Stokes equations thus complementing the pioneering studies based on ***,most researchers are opting to use commercial software to simulate the wedge-impact problem as it allows access to overset meshing algorithms which are robust in modeling the wedge as a moving *** boundary methods(EBMs)offer some advantages over overset meshing in that the mesh only needs to be generated once and Cartesian mesh-based solvers can be ***,the application of EBMs to wedge-impact has been limited in the literature and merits further *** this context,we investigate the applicability of the fast-fictitious-domain(FFD)based embedded boundary treatment to simulate the violent water-entry of *** extend our in-house Navier-Stokes model IITM-rANS3D to handle floating bodies through integration of a rigid-body dynamics solver and an algorithm to embed three-dimensional stereolithography(STL)geometries as solids over a Cartesian *** proposed algorithm is extensively benchmarked against variable DrA wedge-slamming experiments reported in the literature as well as constant DrA wedge-slamming experiments performed *** good agreement is reported in terms of the time-history of hydrodynamic impact pressures measured at various locations on the hull as well as the wedge motion responses thus demonstrating the suitability of FFD for simulating the coupled hydrodynamics of slamming for simplified hull geometries.

关键词： Wedge water entry slamming fast-fictitious-domain IITM-rANS3D experiments

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船体风机叶片对中速船水动力性能影响的计算分析

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哈尔滨工程大学学报（英文版） 2023年第4期22卷 762-774页

作者： S.Gopinath r.vijayakumar Department of Ocean Engineering Chennai Indian Institute of Technology MadrasChennai Tamil Nadu 600036India

The importance of reducing ship resistance is growing considerably as a result of the increase in atmospheric emissions and the drive towards green shipping through *** this point,Energy Saving Devices(ESD),in particular,Hull Vane®(HV),have been widely applied as a potential technique for reducing wave-making resistance for vessels with higher Froude Number(Fr).The advantages of HV for a medium-speed vessel,where the wave-making component accounts for almost 50%of total resistance,have yet to be *** study presents the computational analysis of the KCS model(1∶75.5);for a particular trim condition by using the VOF method and rANS *** hull acts as a candidate vessel for the class of medium-speed characteristics.A total of 36 numerical simulations were carried out to study the changes in resistance and motion characteristics of the vessel with and without *** validate the numerical setup,the experimental work of Hou et al(2020)on the DTMB hull was *** effectiveness of HV can be comprehended by the reduction percentage in total resistance,trim,sinkage,and transom wave height,in comparison to bare hull *** reduction in total resistance extends up to 6%for Fr=0.32 with configuration 2 with negative *** CFD results indicate that there is a reduction in trim up to 57%for the maximum speed with a corresponding Fr=0.34 with a positive angle of foil(AoF).The trim correction effect is increasing with the depth of submergence of *** sinkage,there occurs nearly a 31%reduction for Fr=0.34 with a positive *** exists a substantial reduction in the height of the transom wave with the inclusion of HV,the results of which are discussed in *** the presented results,retrofitting the Hull Vane®is effective in the selected speed range but pronouncing as the speed of the vessel increases.

关键词： Decarbonization Green shipping Ship resistance Energy saving devices(ESD) Hull vane®.(HV) Angle of foil(AoF)

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CLEANrOOM AIr FILTErS:DESIGN AND TESTING

CLEANROOM AIR FILTERS:DESIGN AND TESTING

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第二届中国国际过滤材料研讨会

作者： r.vijayakumar Ph.D. Air Techniques International Air Techniques International

＜正＞ Air filters for particle removal are the primary means for providing clean air for a host of activities requiringclean environments or cleanrooms. Although cleanrooms are commonly associated with the high tech microelectron-ics or the regulated pharmaceutical industries, a growing number of other industries, such as spray painting andpackaging food, are requiring cleanrooms. Filters designed and tested to satisfy the needs of these clean environ-ments are loosely termed cleanroom filters. Unlike filters used for general HVAC applications, cleanroom filters focus less on capacity and more on pene-

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Bio Caryota Fiber reinforced Polymer Composites: Mechanical Properties and Vibration Behavior Analysis

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Journal of Bionic Engineering 2019年第3期16卷 480-491页

作者： Kayaroganam Palanikumar.vijayakumar Subbiah Department of Mechanical Engineering Sri Sai Ram Institute of Technology Chennai Tamil Nadu India Department of Mechanical Engineerings Sathyabama Institute of Science and Technology Chennai Tamil Nadu India

Polymer composites reinforced with the biofibers are found to have improved applications in many fields and also they can reduce the environmental effect. In this work, caryota-a new natural fiber for polymer composites is fabricated and their tensile, flexural and impact properties are estimated to be used in economical and lightweight load carrying structures. Laminates at different weight fraction (wt%) of 10 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt% and 45 wt% are manufactured using a compression molding technique. results asserted that the unidirectional arrangement having 40 wt% fiber posses good properties. Also the dynamic characteristics such as natural frequency and damping study are carried out for different wt% of unidirectional caryota fiber reinforced composite laminates by ex? perimental modal analysis. From this study, it has been asserted that by using the caryota fiber reinforced polyester composites, the traditional synthetic fiber can be replaced especially in automobile sector. If the caryota fiber reinforced composite material is applied properly, then its application fields will be improved.

关键词： natural fiber caryota fiber reinforcements polymer-matrix composites (PMCs) mechanical properties vibration analysis

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LSTM Based Spectrum Prediction for real-Time Spectrum Access for IoT Applications

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Intelligent Automation & Soft Computing 2023年第3期35卷 2805-2819页

作者： r.Nandakumar.vijayakumar Ponnusamy Aman Kumar Mishra KSr Institute for Engineering and Technology Tiruchencode637215India ECE Department SRMISTChengalpattuChennai603202India

In the Internet of Things(IoT)scenario,many devices will communi-cate in the presence of the cellular network;the chances of availability of spec-trum will be very scary given the presence of large numbers of mobile users and large amounts of *** prediction is very encouraging for high trafﬁc next-generation wireless networks,where devices/machines which are part of the Cognitive radio Network(CrN)can predict the spectrum state prior to transmission to save their limited energy by avoiding unnecessarily sen-sing radio *** short-term memory(LSTM)is employed to simulta-neously predict the radio Spectrum State(rSS)for two-time slots,thereby allowing the secondary node to use the prediction result to transmit its information to achieve lower waiting time hence,enhanced performance capacity.A frame-work of spectral transmission based on the LSTM prediction is formulated,named as positive prediction and sensing-based spectrum *** proposed scheme provides an average maximum waiting time gain of 2.88 *** proposed scheme provides 0.096 bps more capacity than a conventional energy detector.

关键词： Cognitive radio network encoder-decoder LSTM waiting time capacity

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The Variability of the Interannual Oscillations of the Indian Summer Monsoon rainfall

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Advances in Atmospheric Sciences 1995年第1期12卷 95-102页

作者： r. vijayakumar J. r. Kulkarni Indian Institute of Tropical Meteorology Pune-411008 India Indian Institute of Tropical Meteorology Pune-411008 India

A new method of analysis namely, Singular Spectrum Analysis (SSA) is applied to the Indian Summer Monsoon (June-September) rainfall (ISMr) series. The method is efficient in extracting the statistically significant oscillations with periods 2.8 and 2.3 year from the white noise of the ISMr series. The study shows that 2.8 / 2.3 year cycle captures the variability of the ISMr related to Southern Oscillation / Quasi Biennial Oscillation. The temporal structure of these oscillations show that these are in phase in extreme (excess and drought) monsoon conditions as well as in El Nino Southern Oscillation (ENSO) years. Both these oscillations show minimum variability during the period 1920-1940 and there is an increasing trend in the variability of these oscillations in the recent decades. The study enables to obtain pure signal consisting of reconstructed time series using these two Oscillations, from the original white noise series.

关键词： Singular Spectrum Analysis Monsoon Variability.

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PV based water pumping system for agricultural irrigation

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Frontiers in Energy 2016年第3期10卷 319-328页

作者： T A BINSHAD K vijayakumar M KALEESWArI Department of Electrical Engineering Malaviya National Institute of Technology Jaipur 302017 India Department of Electrical Engineering Poomima University Jaipur302017 India

This paper investigates the operation and analysis of the photovoltaic water pumping system in detail. Power electronic controllers were designed and developed for the water pumping system using a boost converter along with an inverter followed by an induction motor pump set. The proposed system could be employed in agricultural irrigation under any operating condition of varying natures of solar irradiances and temperatures. The configuration and implementation of the system were described in detail. Further, the detailed method of analysis and simulation characteristics of such PV water pumping system was also presented. With the concern of shortage of fossil fuel, global warming and energy security, the proposed PV based water pumping significant demand of electricity agricultural sector. system can meet the and serve for the

关键词： photovoltaic water pumping system power electronic controller solar irradiances and temperature

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Detection of Diabetic retinopathy from retinal Images Using DenseNet Models

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Computer Systems Science & Engineering 2023年第4期45卷 279-292页

作者： r.Nandakumar P.Saranya vijayakumar Ponnusamy Subhashree Hazra Antara Gupta Department of ECE K S R Institute for Engineering and TechnologyTiruchengode637215India Department of Computer Science and Engineering SRM Institute of Science and TechnologyChennai603203India Department of Electronics and Communication and Engineering SRM Institute of Science and TechnologyChennai603203India

A prevalent diabetic complication is Diabetic retinopathy(Dr),which can damage the retina’s veins,leading to a severe loss of *** treated in the early stage,it can help to prevent vision *** since its diagnosis takes time and there is a shortage of ophthalmologists,patients suffer vision loss even before ***,early detection of Dr is the necessity of the *** primary purpose of the work is to apply the data fusion/feature fusion technique,which combines more than one relevant feature to predict diabetic retinopathy at an early stage with greater *** procedures for diabetic retinopathy analysis are fundamental in taking care of these *** profound learning for parallel characterization has accomplished high approval exactness’s,multi-stage order results are less noteworthy,especially during beginning phase *** Connected Convolutional Networks are suggested to detect of Diabetic retinopathy on retinal *** presented model is trained on a Diabetic retinopathy Dataset having 3,662 images given by *** results suggest that the training accuracy of 93.51%0.98 precision,0.98 recall and 0.98 F1-score has been achieved through the best one out of the three models in the proposed *** same model is tested on 550 images of the Kaggle 2015 dataset where the proposed model was able to detect No Dr images with 96%accuracy,Mild Dr images with 90%accuracy,Moderate Dr images with 89%accuracy,Severe Dr images with 87%accuracy and Proliferative Dr images with 93%accuracy.

关键词： Convolutional Neural Networks vision loss pathogenic blood vessels DenseNet AlexNet resNet

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Some Physical Aspects of Summer Monsoon Clouds-Comparison of Cloud Model results with Observations

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Advances in Atmospheric Sciences 1991年第1期8卷 111-124页

作者： A. Mary Selvam r. vijayakumar A. S. r. Murty Indian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 India

The physical characteristics of the summer monsoon clouds were investigated. The results of a simple cloud model were compared with the aircraft cloud physical observations collected during the summer monsoon seasons of 1973, 1974, 1976 and 1981 in the Deccan Plateau *** model predicted profiles of cloud liquid water content (LWC) are in agreement with the observed profiles. There is reasonable agreement between the model predicted cloud vertical thickness and observed *** observed cloud-drop spectra were found to be narrow and the concentration of drops with diameter > 20um is either low or absent on many occasions. In such clouds the rain-formation cannot take place under natural atmospheric conditions due to the absence of collision-coalescence process. A comparison of the model predicted and observed rainfall suggested that the precipitation efficiency in cumulus clouds of small vertical thickness could be as low as 20 per *** clouds forming in the Deccan Plateau region during the summer monsoon are, by and large, cumulus and strato-cumulus type. The vertical thickness of the cumulus clouds is in the range of 1.0-2.0 km. The LWC is found to be more in the region between 1.6-1.9 km A. S. L. , which corresponds to the level at almost 3 / 4 th of the total vertical thickness of the cloud and thereafter the LWC sharply decreased. Nearly 98 per cent of the tops of the low clouds in the region are below freezing level and the most frequent range of occurrence of these cloud-tops is in the range of 2.0-3.0 km A. S. L. The dominant physical mechanism of rain-formation in these summer monsoon clouds is the collision-coalescence process.

关键词： heat Some Physical Aspects of Summer Monsoon Clouds-Comparison of Cloud Model results with Observations

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Thermal Degradation Kinetics of Structurally Diverse Poly(bispropargyl ethers-bismaleimide) Blends

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Chinese Journal of Polymer Science 2016年第3期34卷 253-253,254-267页

作者： Jeyaraj Pandiyan Dhanalakshmi Mahendran Arunjunai raj Chinnaswamy Thangavel vijayakumar Department of Chemistry Kamaraj College of Engineering and Technology S.P.G.C.Nagar Wood Carinthian Competence Centre Kompetenzzentrum Holz GmbH Department of Polymer Technology Kamaraj College of Engineering and Technology S.P.G.C.Nagar

Structurally diverse bispropargyl ethers using resorcinol,quinol,4,4￠-dihydroxy biphenyl,bisphenol-A,4,4￠-dihydroxy diphenyl ketone,4,4￠-dihydroxy diphenylsulphone,trimethyl indane bisphenol and tetramethyl spirobiindane bisphenol were prepared by using phase transfer *** materials were separately blended with 4,4￠-bismaleimido diphenyl methane（BMIM）in mole ratios（0.5：0.5）.The materials were thermally cured and the structural characterisation and the thermal properties of these cross-linked materials are investigated using Fourier-transform infrared（FTIr）spectrophotometer and thermogravimetric analyzer（TGA）.Among the different materials investigated poly MrPE,poly MBPEBPA and poly MSPE show higher onset degradation temperature of 300°C indicating higher thermal *** degradation kinetics is investigated using Flynn-Wall-Ozawa（FWO）,Vyazovkin（VYZ）and Friedman（FrD）*** the various cured materials investigated,the activation energy（Ea-D）values obtained for poly MrPE and poly MKPE were observed to increase continuously froma=0.2 to 0.8 and the values range from 199 kJ/mol to 245 k J/mol and 153 k J/mol to 295 k J/mol *** crosslinked materials resulting from these bispropargyl monomers definitely need more energy for bond cleavage due to the presence of more aromatic *** volatile products obtained during the thermal degradation of the polymers were analyzed using thermogravimetric-Fourier transform infrared analyses（TG-FTIr）.The phenols,substituted phenols,carbon monoxide,carbon dioxide and small amount of aniline were found to be the major products during thermal degradation of these cured blends.

关键词： Bispropargyl ethers Bismaleimide TG Degradation kinetics TG-FTIr

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