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Fabrication and functional characterization of engineered features on pyrolytic carbon

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Advances in Manufacturing 2016年第2期4卷 134-141页

作者： vivek Bajpai Bablu Prasad Ramesh Singh Department of Mechanical Engineering Indian Institute ofTechnology Bombay Powai Mumbai 400076 India Centre for Environmental Science and Engineering IndianInstitute of Technology Bombay Powai Mumbai 400076India

Engineered features on pyrolytic carbon （PyC） have been reported to improve the functional performance of the bio-implants. This paper is focused on the functional characterization of micro-features created on the surface of PyC. Two different types of micro-features （wide channels and arrayed holes） have been created by micro-electrical discharge machining （micro-EDM）. Two other micro-fea- tures （fine channels and micro-pillars） have been created by micromilling process. Coliform bacterial strain was iso- lated from a sample of water and grown on all four tex- tured. Cell growth was carried out on an unmachined surface to see the behavior of the isolated bacterial strain on the textured/non-textured surfaces. The samples were examined under SEM before and after wash to see cell growth and cell adhesion capability of the textures. The wide channels by micro-EDM show the maximum cell growth but poor cell adhesion. 184% higher cell growth has been observed on the wide channels in comparison with unmachined surface. The fine channels by micro-milling show comparatively lower growth but the cell adhesion on this surface was found excellent. 71% cells remain unwa- shed after washing of the surface having fine channel textures. It means that the channels structure shows the maximum cell growth and adhesion independent of machining process.

关键词： Pyrolytic carbon Micro-features Surfacetexturing Cell growth and adhesion

Effects of cartilaginous rings on airflow and particle transport through simplified and realistic models of human upper respiratory tracts

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Acta Mechanica Sinica 2013年第6期29卷 883-892页

作者： vivek Kumar Srivastav Akshoy Ranjan Paul Anuj Jain Department of Applied Mechanics Motilal Nehru National Institute of Technology

In the present study, computational fluid dynamics （CFD） is used to investigate inspiratory and expiratory airflow characteristics in the human upper respiratory tract for the purpose of identifying the probable locations of particle deposition and the wall injury. Computed tomography （CT） scan data was used to reconstruct a three dimensional respiratory tract from trachea to first generation bronchi. To compare, a simplified model of respiratory tract based on Weibel was also used in the study. The steady state results are obtained for an airflow rate of 45 L/min, corresponding to the heavy breathing condition. The velocity distribution, wall shear stress, static pressure and particle deposition are compared for inspiratory flows in simplified and realistic models and expiratory flows in realistic model only. The results show that the location of cartilaginous rings is susceptible to wall injury and local particle deposition.

关键词： Upper respiratory tract Cartilaginous rings Computational fluid dynamics (CFD) Computed tomogra- phy (CT) Wall shear stress Particle deposition.

Scaling laws for gas-solid riser flow through two-fluid model simulation

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Particuology 2011年第2期9卷 121-129页

作者： P.R.Naren vivek.V.Ranade CREST National Chemical Laboratory Chemical Engineering Department Institute of Chemical Technology

Scale up of gas-solid circulating fluidized bed （CFB） risers poses many challenges to researchers. In this paper, CFD investigation of hydrodynamic scaling laws for gas-solid riser flow was attempted on the basis of two-fluid model simulations, in particular, the recently developed empirical scaling law of Qi, Zhu, and Huang （2008）. A 3D computational model with periodic boundaries was used to perform numerical experiments and to study the effect of various system and operating parameters in hydrodynamic scaling of riser flow. The Qi scaling ratio was found to ensure similarity in global parameters like overall cross- sectional average solid holdup or pressure drop gradient. However, similarity in local flow profiles was not observed for all the test cases. The present work also highlighted the significance of error bars in reporting experimental values.

关键词： RisersScalingCFDPeriodic boundaryTwo-fluid modelError bar

Reconciliation of size-density bivariate distributions over a separating node

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Particuology 2008年第3期6卷 167-175页

作者： Bidarahalli Venkoba Rao vivek Ganvir Sirigeri Jois Gopalakrishna Engineering and Industrial Services Tata Consultancy Services Limited 1Mangaldas RoadPune 411001India Tata Research Development and Design Centre Tata Consultancy Services Limited 54BHadapsar Industrial EstatePune 411013India Department of Mineral Processing Post Graduate CenterSandurKarnataka 583119India

Data reconciliation considers the restoration of mass balance among the noise prone measured data by way of component adjustments for the various particle size or particle density classes or assays over the separating node. In this paper, the method of Lagrange multipliers has been extended to balance bivariate feed and product size-density distributions of coal particles split from a settling column. The settling suspension in the column was split into two product fractions at 40% height from the bottom after a minute settling of homogenized suspension at start. Reconciliation of data assists to estimate solid flow split of particles to the settled stream as well as helps to calculate the profiles of partition curves of the marginal particle size or particle density distributions. In general, Lagrange multiplier method with uniform weighting of its components may not guarantee a smooth partition surface and thus the reconciled data needs further refinement to establish the nature of the surface. In order to overcome this difficulty, a simple alternative method of reconciling bivariate size-density data using partition surface concept is explored in this paper.

关键词： Data reconciliation Size-density partition surface Settling test

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

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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

Food resource and temporal partitioning amongst a guild of predatory agroecosystem-inhabiting ant species

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Current Zoology 2009年第5期55卷 366-375页

作者： vivek Mohan AGARWAL Neelkamal RASTOGI Center of Advanced Study in Zoology Banaras Hindu University

Prey diversity and temporal foraging patterns of six abundant,predatory ant species were investigated seasonally in an agroecosystem with two main vegetable *** *** the highest predation success and therefore appears to be the dominant species while Tapinoma melanocephalum showed the lowest success under the natural field *** of prey diversity and temporal activity patterns with the null model tests of niche overlap revealed a significant overlap indicating that the activity periods and prey diversity may not be solely influenced by interactions among the co-existing ant ***,niche partitioning in the daily peak activity periods was demonstrated during all the three seasons(summer,rainy and winter)particularly between Pheidole *** *** *** a high intensity,broadly extended mono-modal foraging *** compressus and *** showed bi-modality in their foraging activity during the rainy season and mono-modal patterns during summer and winter *** tesserinoda,Tetramorium *** *** exhibited peak foraging activities in the morning hours during the summer and rainy *** activity profiles of *** and *** were skewed towards late afternoon hours during the winter season indicating avoidance of foraging activity during the favourable periods when the more aggressive Pheidole *** *** the sponge gourd agroecosystem,the ants captured predominantly hymenopteran,orthopteran and coleopteran *** Pheidole *** mainly the large orthopteran prey,other ant species captured worker ants in the sponge gourd *** the cauliflower agroecosystem,while other species captured prey chiefly belonging to six orders,i.e.,Lepidoptera,Hymenoptera,Coleoptera,Hemiptera,Isoptera and Diptera,Pheidole *** *** were the only species to also hunt many orthopteran *** agroecosystem-inhabiting ant speci

关键词： Niche partitioning Temporal niche Prey diversity Annual cropping system

Gastroesophageal reflux disease and severe obesity:Fundoplication or bariatric surgery?

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World Journal of Gastroenterology 2010年第30期16卷 3757-3761页

作者： vivek N Prachand John C Alverdy Center for the Surgical Treatment of Obesity Department of SurgeryUniversity of Chicago Pritzker School of MedicineChicagoIL 60637United States

Increases in the prevalence of obesity and gastroesophageal reflux disease (GERD) have paralleled one another over the past decade, which suggests the possibility of a linkage between these two processes. In both instances, surgical therapy is recognized as the most effective treatment for severe, refractory disease. Current surgical therapies for severe obesity include (in descending frequency) Roux-en-Y gastric bypass, adjustable gastric banding, sleeve gastrectomy, and biliopancreatic diversion with duodenal switch, while fundoplication remains the mainstay for the treatment of severe GERD. In several large series, however, the outcomes and durability of fundoplication in the setting of severe obesity are not as good as those in patients who are not severely obese. As such, bariatric surgery has been suggested as a potential alternative treatment for these patients. This article reviews current concepts in the putative pathophysiological mechanisms by which obesity contributes to gastroesophageal reflux and their implications with regards to surgical therapy for GERD in the setting of severe obesity.

关键词： Morbid obesity Gastroesophageal reflux disease Fundoplication Bariatric surgery Gastric bypass Sleeve gastrectomy

ON THE (p,q)-MELLIN TRANSFORM AND ITS APPLICATIONS

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Acta Mathematica Scientia 2021年第5期41卷 1719-1732页

作者： Pankaj JAIN Chandrani BASU vivek PANWAR Department of Mathematics South Asian University Akbar BhawanChanakya PuriNew Delhi-110021India

In this paper,we introduce and study a(p,q)-Mellin transform and its corresponding convolution and *** terms of applications of the(p,q)-Mellin transform,we solve some integral ***,a(p,q)-analogue of the Titchmarsh th... 详细信息

关键词： q-Mellin transform (p q)-Mellin transform inversion formula convolution integral equation

A review of friction models in interacting joints for durability design

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Friction 2017年第1期5卷 1-22页

作者： Zulfiqar A.KHAN vivek CHACKO Hammad NAZIR NanoCorr Energy & Modelling(NCEM)Research Department of Design & Engineering Bournemouth University Bournemouth United Kingdom

This paper presents a comprehensive review of friction modelling to provide an understanding of design for durability within interacting *** is a complex phenomenon and occurs at the interface of two components in relative *** the last several decades,the effects of friction and its modelling techniques have been of significant interests in terms of industrial *** is however a need to develop a unified mathematical model for friction to inform design for durability within the context of varying operational *** dynamic mechanisms model for the design of control systems has not incorporated friction phenomena due to non-linearity ***,the tribological performance concurrently with the joint dynamics of a manipulator joint applied in hazardous environments needs to be fully *** the dynamics and impact models used in mechanical joints with clearance have also been *** inclusion of reliability and durability during the design phase is very important for manipulators which are deployed in harsh environmental and operational *** revolute joint is susceptible to failures such as in heavy manipulators these revolute joints can be represented by lubricated conformal sliding *** presence of pollutants such as debris and corrosive constituents has the potential to alter the contacting surfaces,would in turn affect the performance of revolute joints,and puts both reliability and durability of the systems at greater risks of *** literature is identified and a review on the latest developments of the science of friction modelling is presented *** review is based on a large volume of *** in the relevant field have been identified to capitalise on for future ***,this review will bring significant benefits to researchers,academics and industry professionals.

关键词： friction dynamics joint clearance numerical models impact durability