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Numerical Investigation of Convective Heat Transfer and Friction in Solar Air Heater with Thin Ribs

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Computer Modeling in Engineering & Sciences 2018年第3期114卷 295-319页

作者： Sanjay k.sharma V.R.kalamkar VNIT Nagpur

The three-dimensional numerical investigation of an incompressible flow through rib roughened solar air heater is carried out.A combination of thin transverse and truncated ribs is attached on the absorber plate to study its effect on the heat transfer and friction *** parameters in the form of Reynolds number(Re)of 4000-16000,relative roughness pitch(P/e)of 8-18 and relative roughness height(e/dh)of 0.0366-0.055 is considered for the *** CFd code ANSYS FLUENT is used to solve the governing equations of turbulent *** RNG k-εturbulence model is used to solve the transport equations with enhanced wall treatment,keeping the Y+d friction factor obtained is 1.91 and 3.61 *** detailed investigation on average heat transfer,friction factor and flow structures have been discussed.

关键词： CFd 3d heat transfer friction factor

Artificial Neural Network （ANN） and Regression Tree （CART） applications for the indirect estimation of unsaturated soil shear strength parameters

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Frontiers of Earth Science 2014年第3期8卷 439-456页

作者： d.P. kANUNGO Shaifaly sharma Anindya PAIN Geotechnical Engineering Group CSIR - Central Building Research Institute (CBRI) Roorkee 247667 India

The shear strength parameters of soil （cohesion and angle of internal friction） are quite essential in solving many civil engineering problems. In order to determine these parameters, laboratory tests are used. The main objective of this work is to evaluate the potential of Artificial Neural Network （ANN） and Regression Tree （CART） techniques for the indirect estimation of these parameters. Four different models, considering different combinations of 6 inputs, such as gravel %, sand %, silt %, clay %, dry density, and plasticity index, were investigated to evaluate the degree of their effects on the prediction of shear parameters. A performance evaluation was carried out using Correlation Coefficient and Root Mean Squared Error measures. It was observed that for the prediction of friction angle, the performance of both the techniques is about the same. However, for the prediction of cohesion, the ANN technique performs better than the CART technique. It was further observed that the model considering all of the 6 input soil parameters is the most appropriate model for the prediction of shear parameters. Also, connection weight and bias analyses of the best neural network （i.e., 6/2/2） were attempted using Connec- tion Weight, Garson, and proposed Weight-bias approaches to characterize the influence of input variables on shear strength parameters. It was observed that the Connection Weight Approach provides the best overall methodology for accurately quantifying variable importance, and should be favored over the other approaches examined in this study.

关键词： cohesion friction angle Artificial NeuralNetwork Regression Tree Connection Weight Weight-bias Approach

Luminescence properties of near-UV excitable yellow-orange light emitting warm CaSrAl_2SiO_7:Sm^(3+) phosphors

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Journal of Rare Earths 2019年第4期37卷 365-373页

作者： Shweta sharma Nameeta Brahme d.P.Bisen Pradeep dewangan School of Studies in Physics and Astrophysics Pt.Ravishankar Shukla University Center for Nanoscience and Nanotechnology Pt.Ravishankar Shukla University

Single-phase CaSrAl_2 SiO_7:Sm^(3+) phosphors were synthesized by traditional high temperature solid state reaction method. Formation of samples and phase analysis were confirmed by X-ray diffraction technique. Morphology was done by field emission scanning electron microscopy and elemental compositions were confirmed by energy dispersive X-ray analysis. Present phosphors have tetragonal crystallography with space group P42_1 m. Average crystallite size was calculated by using Scherrer and Williamson-Hall method. Photoluminescence study of CaSrAl_2 SiO_7:Sm^(3+) phosphor was *** different excitation wavelengths, PL spectra consist of four emission bands at 564, 570, 601 and650 nm. The emission bands located at 564 and 570 nm are associated with the transition ~4 G_(5/2)→~6 H_(5/2)while emission bands at 601 and 650 nm are due to ~4 G_(5/2)→~6 H_(7/2) and ~4 G_(5/2)→~6 H_(9/2),*** emission was obtained when phosphor was excited under 404 nm wavelength. Non-radiative energy transfer process involved in concentration quenching, was also discussed. CIE coordinate is found in yellow-orange region, hence CaSrAl_2SiO_7:Sm^(3+) phosphors emit yellow-orange light when efficiently excited by near UV(～400 nm) LEd chip. Color purity and CCT of the phosphor were determined; CCT suggests that present phosphor is a good candidate as a warm yellow-orange color emitting phosphor. Effect of different heating rates and different UV exposure time on the TL glow curve of the phosphor was investigated. Activation energies and.kinetic parameters for different traps were calculated by using peak shape method. TL emission spectrum was also recorded. Present article explains all the possible mechanisms associated with luminescence process in CaSrAl_2 SiO_7:Sm^(3+) phosphors.

关键词： Thermoluminescence Photoluminescence Aluminosilicate Yellow-orange emitting phosphor Samarium CaSrAl2SiO7:Sm3+

Endoscopic management of acute cholangitis in elderly patients

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World Journal of Gastroenterology 2006年第40期12卷 6551-6555页

作者： Naresh Agarwal Barjesh Chander sharma Shiv k Sarin department of Gastroenterology GB Pant Hospital New Delhi India

AIM: To evaluate clinical presentation, etiology, compli-cations and response to treatment in elderly patients with acute ***: demographics, etiology of biliary obstruc-tion, clinical features, complications and associated systemic diseases of 175 patients with acute cholangitis were recorded. Endoscopic biliary drainage was performed using nasobiliary drain or stent. The complications related to ERCP, success of biliary drainage, morbidity, mortality and length of hospital stay were evaluated. RESULTS: Of 175 patients, 52 aged ≥ 60 years (groupⅠ, age d 105 were men. Fever was present in 38 of 52 patients of group Ⅱ compared to 120 of 123 in groupⅠ. High fever (fever ≥ 38.0℃) was more common in groupⅠ(118/120 vs 18/38). Hypotension (5/123 vs 13/52), altered sensorium (3/123 vs 19/52), peritonism (22/123 vs 14/52), renal failure (5/123 vs 14/52) and associated comorbid diseases (4/123 vs 21/52) were more common in group Ⅱ. Biliopancreatic malignancy was a common cause of biliary obstruction in group Ⅱ (n = 34) and benign diseases in groupⅠ(n = 120). Indications for biliary drainage were any one of the following either singly or in combination: a fever of ≥ 38.0℃ (n = 136), hypotension (n = 18), peritonism (n = 36), altered sensorium (n = 22), and failure to improve within 72 h of conservative management (n = 22). High grade fever was more common indication of biliary drainage in groupⅠand hypotension, altered sensorium, peritonism and failure to improve within 72 h of conservative management were more common indications in group Ⅱ. Endoscopic biliary drainage was achieved in 172 patients (nasobiliary drain: 56 groupⅠ, 24 group Ⅱ, stent: 64 groupⅠ, 28 group Ⅱ) without any significant age related difference in the success rate. Abdominalpain, fever, jaundice, hypotension, altered sensorium, peritonism and renal failure improved after median time of 5 d in 120 patients in groupⅠ(2-15 d) compared to 10 d in 47 patien

关键词： Acute cholangitis Endoscopic biliary drainage Endoscopic retrograde cholangio-pancreatography Common bile duct stones Carcinoma gall bladder

Complex variable approach in studying modified polarization saturation model in two-dimensional semipermeable piezoelectric media

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Applied Mathematics and Mechanics(English Edition) 2017年第11期38卷 1517-1532页

作者： S. SINGH k. sharma R. R. BHARGAVA department of Sciences and Humanities National Institute of Technology UttarakhandSrinagar(Garhwal)246174India department of Mathematics Indian Institute of Technology RoorkeeRoorkee 247667India

A modified polarization saturation model is proposed and addressed math- ematically using a complex variable approach in two-dimensional （2d） semipermeable piezoelectric media. In this model, an existing polarization saturation （PS） model in 2d piezoelectric media is modified by considering a linearly varying saturated normal electric displacement load in place of a constant normal electric displacement load, applied on a saturated electric zone. A centre cracked infinite 2d piezoelectric domain subject to an arbitrary poling direction and in-plane electromechanical loadings is considered for the analytical and numerical studies. Here, the problem is mathematically modeled as a non-homogeneous Riemann-Hilbert problem in terms of unknown complex potential functions representing electric displacement and stress components. Having solved the Hilbert problem, the solutions to the saturated zone length, the crack opening displace- ment （COd）, the crack opening potential （COP）, and the local stress intensity factors （SIFs） are obtained in explicit forms. A numerical study is also presented for the proposed modified model, showing the effects of the saturation condition on the applied electrical loading, the saturation zone length, and the COP. The results of fracture parameters obtained from the proposed model are compared with the existing PS model subject to electrical loading, crack face conditions, and polarization angles.

关键词： complex variable fracture parameter local stress intensity factor (SIF),piezoelectric polarization saturation (PS) model

Effects of combined drug therapy on HIV-1 infection dynamics

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International Journal of Biomathematics 2016年第5期9卷 1-23页

作者： deepmala kamboj M. d. sharma MLN College Yamuna Nagar Haryana India department of Mathematics kurukshetra University India

Infection of human immunodeficiency virus （HIV） is determined through the decay of healthy Cd44- T-cells in a well-mixed compartment, such as a bloodstream. A mathe- matical model is considered to illustrate the effects of combined drug therapy, i.e. reverse transcription plus protease inhibitor, on viral growth and T-cell population dynamics. This model is used to explain the existence and stability of infected and uninfected steady states in HIV growth. An analytical technique, called variational iteration method （VIM）, is used to solve the mathematical model. This method is modified to obtain the rapidly convergent successive approximations of the exact solution. These approximations are obtained without any restrictions or the transformations that may change the physical behavior of the problem. Numerical simulations are computed and exhibited to illustrate the effects of proposed drug therapy on the growth or decay of infection.

关键词： HIV infection Cd4+ T-cells steady state stability iteration method efficacy.

Assessing forest fragmentation in north-western Himalaya:a case study from Ranikhet forest range,Uttarakhand,India

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Journal of Forestry Research 2017年第2期28卷 319-327页

作者： Mohit sharma Anusheema Chakraborty J.k.Garg P.k.Joshi University School of Environment Management Guru Gobind Singh Indraprastha University department of Natural Resources TERI University School of Environmental Sciences Jawaharlal Nehru University

The northwestern Himalaya harbors high levels of biodiversity due to its unique topography, climatic conditions and heterogeneity. Forest fragmentation is one of the major threats causing a decline in biodiversity in the Himalayan region. We assesses forest fragmentation and changes in land use land cover（LULC） patterns using multi-temporal satellite data over a time span of four decades（1976–2013）. Fragmentation analysis using the Landscape Fragmentation Tool（LFT） reveals a decrease in core and edge areas by 14 and 2.3 %, respectively; while an increase in non-forest, patch area and perforation area by 2.1, 0.4, and 14 %, respectively. The LULC dynamics show that the areas under dense forest and scrub forest have decreased by 2.8 % and 1.9 %, respectively; and there is an increase in open forest, crop land and fallow land area by 2.6, 1.7 and 2.1 %, respectively. The quantification of landscape heterogeneity is undertaken with the help of landscape metrics computed using FRAGSTATS at class and landscape level, showing signs of increased fragmentation. Our study provides baseline database that can support the future biodiversity conservation and sustainable forest management initiatives.

关键词： fragmentation landscape patch biodiversity heterogeneity Himalayan climatic FRAGSTATS showing northwestern

Modified strip saturated models for two equal collinear cracks with coalesced zones in piezoelectric media

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Applied Mathematics and Mechanics(English Edition) 2019年第8期40卷 1097-1118页

作者： S.SINGH1 k.sharma R.R.BHARGAVA department of Sciences and Humanities National Institute of Technology Uttarakhand Srinagar 246174India department of Mathematics Indian Institute of Technology Roorkee Roorkee 247667India

Two equal collinear cracks with coalesced interior electric saturation zones are analytically studied for two-dimensional (2d) arbitrary polarized semipermeable piezo- electric media based on a modified strip saturated model. The strip saturated model is modified here by varying the strip saturated constant electric displacement condition to the polynomially varying electric displacement conditions. Based on the linear, quadratic, and cubic electric displacement conditions on the inner and outer saturated zones, dif- ferent modified strip saturated models are proposed and studied for two equal collinear cracks. With the Stroh formalism and the complex variable technique, these fracture problems are reduced into different types of non-homogeneous Riemann Hilbert problems in unknown generalized complex potential functions. These mathematical problems are then solved with the Riemann-Hilbert approach to obtain the stress and electric displace- ment components at any point of the domain. The explicit expressions for the outer saturated zone length, the crack opening potential (COP), the crack opening displace- ment (COd), and the local intensity factors (LIFs) are derived. A numerical study is presented for the modified strip saturated model in 2d arbitrary polarized semiperme- able PZT-4 material. The obtained results are compared with those of the strip saturated model, and the effects of the polynomially varying saturation condition on the saturated zones and the applied electrical loadings are presented.

关键词： complex variable coalesced zone piezoelectric Riemann-Hilbert problem strip saturated model

dealing with the Contagion: China and India in the Aftermath of the Subprime Meltdown

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China & World Economy 2009年第2期17卷 1-14页

作者： Shalendra d.sharma department of Politics and Economics University of San Francisco

What began as a downturn in the US housing sector in the summer of 2007 had mushroomed into a global financial crisis by September 2008： the most severe since the 1930s. developing countries, including China and India, at first seemingly sheltered from the worst of the turmoil, have not been immune to the contagion＇s spillover effects. What are China and India＇s precise vulnerabilities, and what can each do to better insulate their economies from the vagaries of global financial marker turmoil？ Equally important, what long-term strategies must each country adopt to make their economies more resilient to global market downturns？

关键词： China contagion India subprime crisis