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Assessment of the ballistic response of honeycomb sandwich structures subjected to offset and normal impact

Defence Technology（防务技术） 2023年第10期28卷 56-73页

作者： Nikhil Khaire Gaurav tiwari Vivek Patel M.A.Iqbal Department of Mechanical Engineering Indian Institute of Technology DelhiNew Delhi110016India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur440026India School of Mechanical Engineering Dr.Vishwanath Karad MIT World Peace UniversityPune411038India Department of Civil Engineering Indian Institute of Technology RoorkeeRoorkee247667India

In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb *** high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of ***,the explicit solver was run in Abaqus to create the finite element *** numerically obtained test results were compared with the experimental to check the accuracy of the *** numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in ***,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was *** result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact *** panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset ***,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy ***,inscribe circle diameter had a negative influence on the ballistic ***,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation *** energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.

关键词： Honeycomb sandwich structure Offset impact Energy dissipation characteristic Deformation and failure mode Geometry effect

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Effect of ionic strength on adsorption of As(Ⅲ) and As(V) on variable charge soils

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Journal of Environmental Sciences 2009年第7期21卷 927-932页

作者： XU Renkou WANG Yong tiwari Diwakar WANG Houyan State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science Chinese Academy of Sciences Nanfing 210008 China Department of Chemistry Mizoram University Tanhril Campus Aizawl 796009 India Graduate University of Chinese Academy of Sciences Beifing 100049 China

The study was to investigate the adsorption behavior of arsenite （As（HI）） and arsenate （As（V）） on two variable charge soils, i.e., Haplic Acrisol and Rhodic Ferralsol at different ionic strengths and pH with batch methods. Results indicated that the amount of As（HI） adsorbed by these two soils increased with increasing solution pH, whereas it decreased with increasing ionic strength under the acidic condition. This suggested that As（Ⅲ） was mainly adsorbed on soil positive charge sites through electrostatic attraction under the acidic condition. Moreover, intersects of As（Ⅴ） adsorption-pH curves at different ionic strengths （a characteristic pH） are obtained for both soils. It was noted that above this pH, the adsorption of As（Ⅴ） was increased with increasing ionic strength, whereas below it the reverse trend was true. Precisely the intersect pH was 3.6 for Haplic Acrisol and 4.5 for Rhodic Ferralsol, which was near the values of PZSE （soil point of zero salt effect） of these soils. The effects of ionic strength and pH on arsenate adsorption by these soils were interpreted by the adsorption model. The results of zeta potential suggested that the potential in adsorption plane becomes less negative with increasing ionic strength above soil PZSE and decreases with increasing ionic strength below soil PZSE. These results further supported the hypothesis of the adsorption model that the potential in the adsorption plane changes with ionic strength with an opposite trend to surface charge of the soils. Therefore, the change of the potential in the adsorption plane was mainly responsible for the change of arsenate adsorption induced by ionic strength on variable charge soils.

关键词： arsenic adsorption ionic strength Haplic Acrisol Rhodic Ferralsol zeta potential

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Detection of asymmetric transmission error in geared rotor system through transverse vibration analysis using full spectrum

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Propulsion and Power Research 2020年第3期9卷 255-280页

作者： Bhyri Rajeswara Rao Rajiv tiwari General Motors Technical Center India Pvt.Ltd. BangaloreKarnataka560066India Department of Mechanical Engineering Indian Institute of Technology GuwahatiGuwahatiAssam781039India

Transmission error(TE)in geared rotors is a predominant source of inherent excitation at the pitch point of the gear *** this paper,a transverse vibration analysis is presented to study the effect of TE on geared *** to asymmetry in the TE,it is expected to have both forward and backward whirls excited during rotor whirling,which could be used for its *** aspect has been envisioned first time in the present *** capture this,an approach of orienting the line of action of a gear-pair along oblique plane is considered and the mathematical modeling has been performed of a simple spur gear-pair connecting two parallel shafts at its mid-span with an asymmetric *** capture the forward and backward whirls,equations of motion are converted into a complex form that facilitates obtaining response in full *** response of system model with assumed transmission error and gear-pair parameters has been obtained through a numerical simulation,which shows distinctly the forward and backward whirls due to the *** a simple test rig experimentation,a similar behaviour was observed in transverse vibrations of geared rotors in the full spectrum,which validate the proposed model.

关键词： Geared rotor Asymmetric transmission error Transverse vibration Forward and backward whirls Full spectrum

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Motion through spherical droplet with non-homogenous porous layer in spherical container

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Applied Mathematics and Mechanics(English Edition) 2020年第7期41卷 1069-1082页

作者： P.K.YADAV A.tiwari P.SINGH Department of Mathematics Motilal Nehru National Institute of Technology AllahabadPrayagraj 211004India Department of Mathematics Birla Institute of Technology SciencePilani 333031Rajasthan Department of Mathematics National Institute of Technology PatnaPatna 800005India

The problem of the creeping flow through a spherical droplet with a non-homogenous porous layer in a spherical container has been studied ***’s model for the flow inside the porous annular region and the Stokes equation for the flow inside the spherical cavity and container are used to analyze the *** drag force is exerted on the porous spherical particles enclosing a cavity,and the hydrodynamic permeability of the spherical droplet with a non-homogeneous porous layer is *** is placed on the spatially varying permeability of a porous medium,which is not covered in all the previous works related to spherical *** variation of hydrodynamic permeability and the wall effect with respect to various flow parameters are presented and discussed *** streamlines are presented to discuss the kinematics of the *** previous results for hydrodynamic permeability and drag forces have been verified as special limiting cases.

关键词： non-homogenous porous medium Stokes equation Darcy’s law perme-ability parameter wall effect

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Estimation of the internal and external damping from the forward and backward spectrum of a rotor with a fatigue crack

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Propulsion and Power Research 2020年第1期9卷 62-74页

作者： Dipendra Kumar Roy Rajiv tiwari Department of Mechanical Engineering Indian Institute of Technology GuwahatiAssam781039India Faculty of Mechanical Engineering Indian Institute of Technology GuwahatiAssam781039India

Both internal and external damping are concurrently present in a rotor ***,the internal damping that originates from various sources often leads to instability in the rotor system,and hence its accurate estimation is *** goal of the present paper is to distinctly estimate both external and internal damping in a Jeffcott rotor containing transverse *** modelling of the fatigue crack is based on the assumption of a switching crack,which additionally provides the internal damping due to rubbing on crack faces,which is hardly addressed in ***,the fatigue crack leads to the forward and backward whirls due to asymmetry in the *** the process of development of the identification procedure in the form of the regression equation for the estimation of internal damping,other important unknown rotor system parameters,like the external damping,unbalance and loss of stiffness of the shaft due to the crack,are also *** reduces the estimation error of the internal damping due to reduction in deviations of other model *** simulated responses are obtained from equations of motion of the rotor system in the form of a closed-form expression and by the Runge-Kutta integration *** full-spectrum response data(both magnitude and phase)are utilized during the testing of the proposed identification *** corrections have been incorporated in the *** noise is added in numerical responses during identification of parameters to check the robustness of the algorithm and found to be working satisfactorily.

关键词： Internal damping External damping Switching crack Unbalance Full spectrum

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Plant endemism in the Nepal Himalayas and phytogeographical implications

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Plant Diversity 2019年第3期41卷 174-182页

作者： Achyut tiwari Yadav Uprety Santosh Kumar Rana Department of Botany Tri-Chandra Campus Tribhuvan University Kathmandu Nepal Central Department of Botany Tribhuvan University Kirtipur Kathmandu Nepal Research Centre for Applied Science and Technology Tribhuvan University Kathmandu Nepal IUCN (International Union for Conservation of Nature) Kathmandu Nepal Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of Botany Chinese Academy of Sciences Kunming 650201 Yunnan China University of Chinese Academy of Sciences Beijing 100049 China

Nepal is located in the central part of the greater Himalayan range with a unique series of mountain chains formed by recent mountain building geological events. As one of the youngest mountains in the world it contributes to diversity of plants and also provided barriers to and corridors through which plants migrated during the ice ages. The higher altitudinal variation with the high mountains, deep river valleys and lowland plains combine with the effects of the summer monsoon and dry winter result with an extraordinary diversity of ecosystems including flora and fauna in a relatively small land area. The existing checklists for Nepal record some 6000 species of flowering plants and about 530 ferns. However, the botanical experts estimate that numbers may go up to 7000 when the poorly known remote regions are fully explored. The information on plant endemism in Nepal Himalaya is not adequately known as Nepal is still struggling to complete long awaited Flora of Nepal project. Endemic species are confined to specific areas and are the first to be affected by land use and other global changes. We sought to explore the spatial distribution of endemic plant species in Nepal in relation to the consequences associated with climatic and geologic changes over time in the region with the help of published literature. It was found that the endemism showed marked spatial variation between open moist habitat and dry inner valleys, the former with higher endemism. The updated records showed 312 flowering plant species to be endemic to Nepal with higher endemism around the elevation of 3800e4200 m at sea level. The recent human population explosion, intensified deforestation, habitat fragmentation and modern day environmental changes are posing greater threats to endemic plant in Nepal. The conservation status and threats to these peculiar species are unknown. Nevertheless, environmental degradation and high poverty rates create a potent mix of threats to biodiversity in this l

关键词： Himalaya Topography Endemism

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Prediction of Alzheimer’s Using Random Forest with Radiomic Features

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Computer Systems Science & Engineering 2023年第4期45卷 513-530页

作者： Anuj Singh Raman Kumar Arvind Kumar tiwari KNIT Sultanpur Sultanpur228118India

Alzheimer’s disease is a non-reversible,non-curable,and progressive neurological disorder that induces the shrinkage and death of a specific neuronal population associated with memory formation and *** is a frequently occurring mental illness that occurs in about 60%–80%of cases of *** is usually observed between people in the age group of 60 years and *** upon the severity of symptoms the patients can be categorized in Cognitive Normal(CN),Mild Cognitive Impairment(MCI)and Alzheimer’s Disease(AD).Alzheimer’s disease is the last phase of the disease where the brain is severely damaged,and the patients are not able to live on their *** is an approach to extracting a huge number of features from medical images with the help of data characterization ***,105 number of radiomic features are extracted and used to predict the alzhimer’*** paper uses Support Vector Machine,K-Nearest Neighbour,Gaussian Naïve Bayes,eXtreme Gradient Boosting(XGBoost)and Random Forest to predict Alzheimer’s *** proposed random forest-based approach with the Radiomic features achieved an accuracy of 85%.This proposed approach also achieved 88%accuracy,88%recall,88%precision and 87%F1-score for AD ***,it achieved 72%accuracy,73%recall,72%precisionand 71%F1-score for AD *** and it achieved 69%accuracy,69%recall,68%precision and 69%F1-score for MCI *** comparative analysis shows that the proposed approach performs better than others approaches.

关键词： Alzheimer’s disease radiomic features cognitive normal support vector machine mild cognitive impairment extreme gradient boosting random forest

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Visibility improvement and mass segmentation of mammogram images using quantile separated histogram equalisation with local contrast enhancement

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CAAI Transactions on Intelligence Technology 2019年第2期4卷 73-79页

作者： Bhupendra Gupta Mayank tiwari Subir Singh Lamba PDPM Indian Institute of Information Technology Design & Manufacturing Jabalpur MP 482005 India

In this work, the authors develop a working software-based approach named ‘linearly quantile separated histogram equalisation-grey relational analysis’ for mammogram image (MI). This approach improves overall contrast (local and global) of given MI and segments breast-region with a specific end goal to acquire better visual elucidation, examination, and grouping of mammogram masses to help radiologists in settling on more precise choices. The fundamental commitment of this work is to demonstrate that results of good quality of breast-region segmentation can be accomplished from basic breast-region segmentation if the input image has good contrast and a better interpretation of hidden details. They have evaluated the proposed strategy for MIAS-MIs. Experimental results have shown that the proposed approach works better than state-of-the-art.

关键词： develop contrast approach

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Overexpression of P-glycoprotein induces acquired resistance to imatinib in chronic myelogenous leukemia cells

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Chinese Journal of Cancer 2012年第2期31卷 110-118页

作者： Amit K.tiwari Hsiang-Chun Wu Department of Pharmacology and Systems Therapeutics Mount Sinai School of MedicineNew YorkNY 10029USA Department of Pharmaceutical Sciences College of Pharmacy and Allied Health ProfessionsSt.John's UniversityQueensNY 11439USA

Imatinib,a breakpoint cluster region(BCR)-Abelson murine leukemia(ABL) tyrosine kinase inhibitor(TKI),has revolutionized the treatment of chronic myelogenous leukemia(CML).However,development of multidrug resistance(MDR) limits the use of *** the present study,we aimed to investigate the mechanisms of cellular resistance to imatinib in ***,we established an imatinib-resistant human CML cell line(K562-imatinib) through a stepwise selection *** characterizing the phenotype of these cells,we found that K562-imatinib cells were 124.6-fold more resistant to imatinib than parental K562 *** addition,these cells were cross-resistant to second-and third-generation BCR-ABL *** blot analysis and reverse transcription-polymerase chain reaction(RT-PCR) demonstrated that P-glycoprotein(P-gp) and MDR1 mRNA levels were increased in K562-imatinib *** addition,accumulation of [14C]6-mercaptopurine(6-MP) was decreased,whereas the ATP-dependent efflux of [14C]6-MP and [3H]methotrexate transport were increased in K562-imatinib *** data suggest that the overexpression of P-gp may play a crucial role in acquired resistance to imatinib in CML K562-imatinib cells.

关键词：慢性粒细胞白血病白血病细胞 P-糖蛋白多药耐药过度表达 K562细胞酪氨酸激酶抑制剂诱导

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Effect of orientation on the drag of a cone settling in a Bingham plastic fluid

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Particuology 2019年第2期17卷 157-170页

作者： Pragya Mishra A.K. tiwari R.P. Chhabra Department of Chemical Engineering. Indian Institute of Technology Kanpur 208016 India M2NeT Laboratory Wilfrid Laurier University 75 University Avenue West Waterloo ON N2L 3C5 Canada

Effects of the orientation and apex angle on the settling velocity of conical particles in Bingham plas-tic fluids are numerically investigated over a Reynolds number range of 1 ≤Re ≤100, Bingham number range of 0 ≤ Bn ≤ 100, and cone angle range of 20 ≤α≤ 150°. Governing equations (of continuity and momentum) are solved numerically using the finite element method to obtain velocity and pressure fields that are postprocessed to obtain values of the drag ***, the effect of cone ori-entation on the flow field is visualized and explored in terms of streamline contours and the morphology of yielded/uny ielded regions. Finally, the obtai ned values of drag are correlated via a simple predictive expression in terms of the modified Reynolds number. The effect of the cone angle on drag is found to be moderate because the drag force acting on the lateral surface is a small fraction of the overall drag.

关键词： Bingham number Reynolds number Yielded/unyielded regions Drag

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