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Earthquake Engineering and Engineering Vibration 2013年第1期12卷 143-154页

作者： chandra shekhar Goit Masato Saitoh Department of Civil and Environmental Engineering Saitama University

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant *** practical pile inclinations of 5掳 and 10掳 in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are *** obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of *** impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination *** values of horizontal impedance functions are obtained for the ＇positive＇ and ＇negative＇ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined *** of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental *** analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

关键词： inclined single piles harmonic loads horizontal impedance functions local nonlinearity finite element model

Fabrication of Self-cleaning Antireflective Polymer Surfaces by Mimicking Underside Leaf Hierarchical Surface Structures

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Journal of Bionic Engineering 2019年第3期16卷 400-409页

作者： Srinadh Mattaparthi chandra shekhar Sharma Creative & Advanced Research Based on Nanomaterials (CARBON) Laboratory Department of Chemical Engineerings Indian Institute of Technology Hyderabad Kandi Telangana 502285 India

In this work, we utilized underside of four different plant leaves with different scale of hierarchical surface roughness to fabricate large area self-cleaning antireflective polymer surfaces. A simple and precise two-step soft-lithography replica molding technique was deployed by using polydimethylsiloxane (PDMS) polymer as a replicating material. In the first step, a negative PDMS replica was fabricated by using the underside of an original leaf as a template material. In the second step, a positive PDMS replica was fabricated through a negative PDMS replica used as a template. In order to study the non-wetting and light trapping properties, as-replicated polymer surfaces were characterized using Scanning Electron Microscopy (SEM), contact angle goniometer, and UV-Vis spectroscopy. SEM images confirmed the successful replication of complex hierarchical structures while contact angle measurement studies established retaining high non-wetting properties in polymer replicas. Optical studies suggest near zero reflection in normal mode and less than 5% diffuse reflection when measured using integrated sphere mode. These results have been correlated and explained with the air-liquid fraction and roughness factor as measured using three-dimensional optical profilometer.

关键词： biomimicking natural leaf replica molding non-wetting light trapping hierarchical roughness

Finite Capacity Service System with Partial Server Breakdown and Recovery Policy:An Economic Perspective

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Journal of Systems Science and Systems Engineering 2024年第6期33卷 651-681页

作者： Shreekant Varshney Suman Kaswan Mahendra Devanda chandra shekhar Department of Mathematics School of TechnologyPandit Deendayal Energy UniversityGandhinagarGujarat382426India Department of Mathematics Birla Institute of Technology and Science PilaniPilani CampusPilaniRajasthan333031India Department of Mathematics Maharaja Surajmal Brij UniversityBharatpurRajasthan321201India

Developing a comprehensive service strategy to optimize customer satisfaction presents an ongoing challenge for effective facility *** essence of comprehensive systems is selecting the suitable service design,establishing an effective service delivery process,and building continuous *** research analyzes a finite capacity service system incorporating several realistic customer-server dynamics:customer impatience,server’s partial breakdown,and threshold recovery *** the number of customers is more,the server is under pressure to increase the service rate to mitigate the service system’s *** from this fact,the concept of service pressure condition is also *** characterization,we evaluate state probabilities derived using the matrix-analytic method and henceforth several performance *** address the cost optimization problem involving the developed Chapman-Kolmogorov forward differential-difference equations and determine optimal operational parameters,we employ the recently devised cuckoo search(CS)optimization approach.A comparative analysis is performed with the semi-classical optimizer:quasi-Newton(QN)method,and metaheuristics technique:particle swarm optimization(PSO),to validate the efficacy of ***,several numerical illustrations are depicted in different tables and graphs to understand essential characteristics quickly.

关键词： Customer impatience service pressure condition partial server breakdown threshold-based recovery policy Cuckoo search particle swarm optimization quasi-Newton

Vertical impedance functions of pile groups under low-to-high loading amplitudes:numerical simulations and experimental validation

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Earthquake Engineering and Engineering Vibration 2023年第3期22卷 647-666页

作者： Usama Zafar chandra shekhar Goit Masato Saitoh Riku Fukuda School of Science and Engineering Saitama University255 Shimo-OkuboSaitamaJapan

Piles in a group experience additional displacements in soil due to pile-to-pile interactions apart from those resulting from the external *** effect of these interactions determined assuming soil as an elastic and/or viscoelastic material on pile head impedance functions of the pile group is studied by relating the group stiffness to the static stiffness of a single ***,the prevailing elastic solutions may misestimate the resulting pile group response due to the lack of consideration for either soil(material)and/or soil-pile interface *** is well established that soil behaves nonlinearly under moderate-to-high loading amplitudes,and besides,the soil-pile interface nonlinearity can exist even at small loading *** study addresses the effects of these nonlinearities on the vertical impedance functions of a 3×3-pile group using numerical methods by direct analyses and superposition using pile-to-pile interaction *** numerical results are validated using scaled model tests under 1 g *** results highlight the overestimation of pile-to-pile interactions in the pile group when assuming elastic soil *** cases either by direct analyses or superposition approach involving soil and soil-pile interface nonlinearities agree well with the experimental pile group responses under close-to-elastic and nonlinear conditions.

关键词： impedance functions numerical simulations model-scale experiment superposition approach soil-pile interface nonlinearity

Exploring the potential of artificial intelligence techniques in prediction of the removal efficiency of vortex tube silt ejector

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International Journal of Sediment Research 2023年第4期38卷 615-627页

作者： Sanjeev Kumar chandra shekhar Prasad Ojha Nand Kumar Tiwari Subodh Ranjan Department of Civil Engineering Indian Institute of Technology Department of Civil Engineering National Institute of Technology

A vortex tube silt ejector is a curative hydraulic structure used to remove sediment deposits from canals and is recognized as one of the most efficient substitutes for physically removing canal sediment. The spatially varied flow in the channel and the rotational flow behavior in the tube make the silt removal process complex. It is even harder to accurately predict the silt removal efficiency by traditional models accurately. However, artificial intelligence(AI) and machine learning approaches have emerged as robust substitutes for studying complex processes. Therefore, this research makes use of AI approaches; support vector machine(SVM), random forest(RF), random tree(RT), and multivariate adaptive regression spline(MARS) to compute the vortex tube silt ejection efficiency using the laboratory data sets. The outcomes of the artificial intelligence(AI)-based techniques also were compared with traditional models. It was found that the RT model(root mean square error, RMSE = 2.165, Nash Sutcliffe efficiency, NSE = 0.98) outperforms the other applied approaches which had relatively more significant result errors. The sensitivity analysis of the process depicts the extraction ratio as the key parameter in the computation of vortex tube silt ejector removal efficiency. The findings of the AI-based approaches discussed in the current study might be helpful for hydraulic engineers as well as researchers in the assessment of the removal efficiency of vortex tube silt ejectors.

关键词： Vortex tube silt ejector Support vector machine Random forest Random tree Multivariate adaptive regression spline

Exploring the nexus between Indian forestry and the Sustainable Development Goals

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Regional Sustainability 2021年第4期2卷 308-323页

作者： Giribabu DANDABATHULA Sudhakar Reddy CHINTALA Sonali GHOSH Padmapriya BALAKRISHNAN chandra shekhar JHA Regional Remote Sensing Centre(West) NRSC/ISROJodhpurRajasthan342001India Forest Biodiversity and Ecology Division National Remote Sensing CentreISROHyderabadTelangana500037India Central Zoo Authority New Delhi110003India Chief Conservator of Forests/Secretary(Forests) Government of Madhya PradeshBhopalMadhya Pradesh462012India Regional Centers Head Quarters National Remote Sensing CentreISROHyderabadTelangana500037India

Forests are considered as a sacred asset in India and have guided the way of living throughout its *** forests not only accommodate the myriad species but also act as a survival support system to the communities that depended on *** 2030 Agenda for Sustainable Development proposed by the United Nations(UN)has gained momentum and becomes an integral part of the recent efforts of Indian *** this investigation,we examined the potential nexus between Indian forestry system(biodiversity-enriched assets,ecosystem services,constitutional mechanisms,and governances)and Sustainable Development Goals(SDGs)through theoretical underpinnings from literature that selected from database like Google Scholar,Indian forest survey reports,and information retrieved from Indian government *** significance of this review is that it presents comprehensive information about Indian forestry,biodiversity-rich assets,and sustainable forest management *** results show that Indian forestry as a whole is an integral part of the food-energy-water cycle and contributes to all dimensions of sustainable development,i.e.,economic sustainability,social sustainability,and environmental *** investigation confirms that besides partly contributing to the economy and life support systems to many dependent species,forests also act as boosters in the areas of food security and *** related to the climate action,peace,and partnership goals are well in place through various forestry interventions and environmental commitments by the Government of India.

关键词： Indian forests Sustainable Development Goals(SDGs) Sustainable forest management Economic sustainability Social sustainability Environmental sustainability Climate change

GEOLOGICAL STUDIES OF METAMORPHIC ROCKS IN THE VICINITY OF M.C.T./LESSER HIMALAYAN SHEAR ZONE, PARTS OF SIKKIM HIMALAYAS

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地学前缘 2000年第S1期7卷 33-35页

作者： chandra shekhar Dubey(Department of Geology, University of Delhi, Delhi\|110007, India)

The Eastern Sikkim area forming a part of the Lesser Himalaya is located between 27°10′～27°30′N latitudes and 88°25′～88°40′E longitudes (750km 2). The previous workers agreed that a domal structure is present in Sikkim which is constituted by low to high grade metamorphic rocks characterised by inverted metamorphism. The rocks were repeatedly deformed and were metamorphosed at about 550 to 770℃ (550 to 750MPa). Geologically, the oldest rocks of Eastern Sikkim are represented by Darjeeling Formation showing medium to high grade metamorphism. It is followed by low grade Daling Formation which is characterised by tectonic wedges of Lingtse gneiss. The potassic syenite intrusive i.e. the Sikkim igneous formation is youngest rock type of the area. The Darjeeling Formation associated with amphibolite bands consists of kyanite\|sillimanite, staurolite and garnet zones, while the Daling Formation is characterised by low grade chloritoid and chlorite zones. Lingtse Formation is gneissic in which patches of retrograded and sheared garnet schists are present. Intrusions of potassic syenites (Sikkim Formation) occur in the form of oval and concordant bodies. The F 1, F 2 and F 3 folds are well developed in rocks of Eastern Sikkim area.. The F 1 folds are rootless, tightly isoclinal or reclined and highly obliterated in their attitude. The F 2 folds belong to class IC of Ramsay (1967). Their interlimb angles vary from 20～50 degrees. Intersection lineation due to S 0/S 1 and S 2 surfaces is parallel to the F 2 folds axis. Third generation structures are represented by open to moderately tight and kinked folds. Superimposition of F 3 folds on F 2 folds resulted into type II interference pattern of Ramsay (1967). Structural analysis of these folds have revealed that F 2 folds are non\|cylindrical. The kink or F 3 folds were possibly responsible for the formation of a megakink resembling with the domal structure. The repeatedly deformed rocks of Eastern Sikkim area were folded, faul

关键词： metamorphic rocks M C T/LESSER Himalayan shear zone Sikkim Himalayas

Evaluation of Various Linear Regression Methods for Downscaling of Mean Monthly Precipitation in Arid Pichola Watershed

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Natural Resources 2010年第1期1卷 11-18页

作者： Manish Kumar Goyal chandra shekhar Prasad Ojha Dept. of Civil Engineering Indian Institute of Technology

In this paper, downscaling models are developed using various linear regression approaches namely direct, forward, backward and stepwise regression for downscaling of GCM output to predict mean monthly precipitation under IPCC SRES scenarios to watershed-basin scale in an arid region in India. The effectiveness of these regression approaches is evaluated through application to downscale the predictand for the Pichola lake region in Rajasthan state in India, which is considered to be a climatically sensitive region. The predictor variables are extracted from (1) the National Centers for Environmental Prediction (NCEP) reanalysis dataset for the period 1948–2000, and (2) the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1 and COMMIT for the period 2001–2100. The selection of important predictor variables becomes a crucial issue for developing downscaling models since reanalysis data are based on wide range of meteorological measurements and observations. Direct regression was found to yield better performance among all other regression techniques explored in the present study. The results of downscaling models using both approaches show that precipitation is likely to increase in future for A1B, A2 and B1 scenarios, whereas no trend is discerned with the COMMIT.

关键词： Backward Forward Precipitation Regression Stepwise

Application of PLS-Regression as Downscaling Tool for Pichola Lake Basin in India

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International Journal of Geosciences 2010年第2期1卷 51-57页

作者： Manish Kumar Goyal chandra shekhar Prasad Ojha Department of Civil Engineering Indian Institute of Technology

In this paper, downscaling models are developed using Partial Least Squares (PLS) Regression for obtaining projections of mean monthly precipitation to lake-basin scale in an arid region in India. The effectiveness of this approach is demonstrated through application to downscale the predictand for the Pichola lake region in Rajasthan state in India, which is considered to be a climatically sensitive region. The predictor variables are extracted from (1) the National Centers for Environmental Prediction (NCEP) reanalysis dataset for the period 1948-2000, and (2) the simulations from the third-generation Canadian Coupled Global Climate Model (CGCM3) for emission scenarios A1B, A2, B1 and COMMIT for the period 2001-2100. The selection of important predictor variables becomes a crucial issue for developing downscaling models since reanalysis data are based on wide range of meteorological measurements and observations. In this paper, we use PLS regression for quality prediction and its use for the variable selection based on the variable importance. The results of downscaling models using PLS regression show that precipitation is projected to increase in future for A2 and A1B scenarios, whereas it is least for B1 and COMMIT scenarios using predictors.

关键词： PLS Regression Precipitation VIP Score

Analysis of Mean Monthly Rainfall Runoff Data of Indian Catchments Using Dimensionless Variables by Neural Network

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Journal of Environmental Protection 2010年第2期1卷 155-171页

作者： Manish Kumar Goyal chandra shekhar Prasad Ojha Department of Civil Engineering Indian Institute of Technology

This paper focuses on a concept of using dimensionless variables as input and output to Artificial Neural Network (ANN) and discusses the improvement in the results in terms of various performance criteria as well as simplification of ANN structure for modeling rainfall-runoff process in certain Indian catchments. In the present work, runoff is taken as the response (output) variable while rainfall, slope, area of catchment and forest cover are taken as input parameters. The data used in this study are taken from six drainage basins in the Indian provinces of Madhya Pradesh, Bihar, Rajasthan, West Bengal and Tamil Nadu, located in the different hydro-climatic zones. A standard statistical performance evaluation measures such as root mean square (RMSE), Nash–Sutcliffe efficiency and Correlation coefficient were employed to evaluate the performances of various models developed. The results obtained in this study indicate that ANN model using dimensionless variables were able to provide a better representation of rainfall–runoff process in comparison with the ANN models using process variables investigated in this study.

关键词： Dimensional Variables Artificial Neural Networks Rainfall–Runoff