检索结果-南通市图书馆

Sintered Fe-0.8%c-1.0%Si-0.4%cu P/M Steel Preform Behaviour During cold Upsetting

在线全文

学校读者我要写书评

暂无评论

journal of Iron and Steel Research International 2008年第5期15卷 81-87页

作者： A Rajeshkannan K S pandey S Shanmugam R Narayanasamy Thiagarajar college of Engineering ThiruparankundramMadurai 625015Tamil NaduIndia Maulana Azad National Institute of Technology Bhopal 462007Madhya PradeshIndia Department of Mechanical Engineering National Institute of TechnologyTiruchirappalli 620015Tamil NaduIndia Department of Production Engineering National Institute of TechnologyTiruchirappalli 620015Tamil NaduIndia

cold upsetting experiments were carried out on sintered Fe 0.8%c1.0%Si-0. 4%cu steel preforms in order to evaluate their deformation characteristics. Powder preforms of 86 % of theoretical density, with two different ratios of height to diameter, were prepared using a suitable die set assembly on a 1.0 MN capacity hydraulic testing machine. Sintering was carried out in an electric muffle furnace for 1.5 h at 1 150 ℃. Each sintered compact was subjected to incremental loading of 0.04 MN under dry friction condition till a crack appeared at the free surfaces. The experimental results were critically analysed, the stress as a function of strain and densification was obtained, then the work hardening behaviour was analyzed. It has been found that in the process of enhancing densification, strength and strain hardening is also induced during upsetting, but the work hardening behaviour is not homogenously enhanced against strain and densification.

关键词： cold upsetting stress height strain densification work hardening behaviour

A numerical method for structural uncertainty response computation

在线全文

学校读者我要写书评

暂无评论

Science china(Technological Sciences) 2011年第12期54卷 3347-3357页

作者： ZHANG XuFang pandey Mahesh D. ZHANG YiMin Department of civil and Environmental Engineering University of Waterloo Waterloo N2L 3G1 Canada School of Mechanical Engineering and Automation Northeastern University Shenyang 110815 China

A novel numerical procedure, which realizes the stochastic analysis with dimensional reduction integration （DRI）, c-type Gram-charlier （cGc） series, and finite element （FE） model, is proposed to assess the probability distribution of structural per- formance. From the relationship between the weighting function of orthogonal polynomial and probability density function （PDF） of random variable, the numerical integration formulas are derived for moment computation. Then, distribution of structural uncertainty response can be approximated by the cGc series with the calculated moments. Three engineering appli- cations for the distribution of, the maximum displacement of a ten-bar planer truss, natural frequency of an auto frame, and Von-Mises stress of a bending pipe, are employed to illustrate the computational efficiency and accuracy of the proposed methodology. As compared with plain Monte carlo simulation （McS）, the method can obtain the accurate distribution of structural performance. Especially at the tail region of cumulative distribution function （cDF）, results have shown the satisfy- ing estimators for small probabilities, say, Pc [104, 10-3]. That implies the method could be trusted for structural failure prob- ability prediction. As the computational efficiency is concerned, the procedure could save more than two orders of computational resources as compared with the direct numerical integration （NI） and McS. Furthermore, realization of the procedure does not require computing the performance gradient or Hessian matrix with respect to random variables, or reshaping the finite element matrix as other stochastic finite element （SFE） codes. Therefore, it should be an efficient and reliable routine for uncertainty structural analysis.

关键词： dimensional reduction method Gaussian quadrature Gram-charlier series stochastic finite element model moment method

在线全文

学校读者我要写书评

暂无评论

氦气在矿物纳米孔隙中运移的分子动力学模拟

中国科学:地球科学 2025年第1期55卷 239-254页

作者：宋丹丹关平张驰任嘉豪北京大学地球与空间科学学院北京100871

氦气在矿物纳米孔隙、孔喉中的赋存状态及流动方式对氦气的整体运移至关重要.为了阐明氦气在纳米级矿物孔隙中的运移机制,本文通过平衡分子动力学与非平衡分子动力学方法,分别模拟了氦气在石英层状纳米孔隙中的平衡自扩散和压力驱动下... 详细信息

氦气在矿物纳米孔隙、孔喉中的赋存状态及流动方式对氦气的整体运移至关重要.为了阐明氦气在纳米级矿物孔隙中的运移机制,本文通过平衡分子动力学与非平衡分子动力学方法,分别模拟了氦气在石英层状纳米孔隙中的平衡自扩散和压力驱动下的平流行为.此外,向含氦气的石英纳米孔中加入了水和氢气、甲烷、乙烷、氮气、二氧化碳等气体,以分析流动载体对氦气运移的影响.研究表明,氦气在石英孔隙壁面上的吸附量很小.在孔径小于5nm且气压低于10MPa的条件下,环境因素会显著影响氦气的扩散系数,大孔、高温和低气压的条件能促进氦的解吸附并加快其扩散.氦气以平流的形式在孔隙中运移时,流动速度与孔径大小、压力梯度和孔壁光滑程度正相关.值得注意的是,孔隙中的水和载气扩散都比氦气慢,并且他们的存在都会减少氦气的表面吸附且减弱氦气的扩散.在几种载气中,氮气的吸附性、扩散性和化学稳定性整体最接近氦气,而二氧化碳吸附能力最强、扩散最慢、与氦气差异最大.根据模拟结果,我们认为水和载气的主要作用是作为运输载体,与氦气共同运移.几种载气中,氮气的总体性质与氦气非常相似,可以有效地促进氦气的运移.而二氧化碳气体吸附性强、扩散慢,在多种气体的共同运移过程中容易损失.因此,氮气含量高而二氧化碳含量低的气藏可能具有更高的氦气含量.此外,小孔径、高气压的盖层孔隙中氦气扩散较慢,有利于氦气的保存.并且盖层孔隙中的水和载气会堵塞孔隙空间,进一步阻止了氦气的逸散.

关键词：氦气运移纳米孔隙分子动力学模拟扩散流动载体

A robust deep structured prediction model for petroleum reservoir characterization using pressure transient test data

在线全文

学校读者我要写书评

暂无评论

Petroleum Research 2022年第2期7卷 204-219页

作者： Rakesh Kumar pandey Anil Kumar Ajay Mandal Department of Petroleum and Energy Studies School of Engineering and TechnologyDIT UniversityDehradun248009India Data Science Research Group School of ComputingDIT UniversityDehradun248009India Department of Petroleum Engineering Indian Institute of Technology(Indian School of Mines)Dhanbad826004India

A robust deep learning model consisting of long short-term memory and fully connected neural net-works has been proposed to automatically interpret homogeneous petroleum reservoirs having infinite,no flow,and constant pressure outer boundary *** pressure change data recorded during the well test operation along with its derivative is input into the model to perform the classification for identifying the reservoir model and,further,regression to estimate output *** noise was added to analytical models while generating the synthetic training *** hyperparameters were regulated to perform model optimization,resulting in a batch size of 64,Adam optimization algorithm,learning rate of 0.01,and 80:10:10 data split ratio as the best choices of *** perfor-mance accuracy also increased with an increase in the number of samples during *** classification and regression metrics have been used to evaluate the performance of the *** paper also demonstrates the prediction performance of the optimized model using simulated and actual oil well pressure drawdown test *** proposed model achieved minimum and maximum relative errors of 0.0019 and 0.0308,respectively,in estimating output for the simulated test cases and relative error of 0.0319 for the real test case.

关键词： Well test Reservoir characterization Automatic interpretation Prediction model Hyperparameter tuning Performance indicator

One Step Synthesis and Growth Mechanism of carbon Nanotubes

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2014年第2期30卷 112-116页

作者： Akshay Kumar K.Singh O.P.pandey Sri Guru Granth Sahib World University School of Physics and Materials Science Thapar University

A simple one step, reproducible, synthesis route for carbon nanotubes was proposed. No external catalyst was used for the synthesis. These nanotubes were obtained after decomposition of acetone at 650 ℃ in a specially designed autoclave. The pressure generated due to decomposition of acetone played a vital role in the synthesis. The X-ray diffraction pattern and transmission electron microscopy of the sample showed that the diameter of nanotubes is in the range of 3-14 nm. The thermo gravimetric analysis showed 3% weight loss below 500 ℃; the content of amorphous carbon is very less. The growth mechanism of cNTs was also proposed in the present paper.

关键词： Nanostructures chemical synthesis Electron diffraction Raman spectroscopy Defects

Performance behaviour of elliptical-bore journal bearings lubricated with solid granular particulates

在线全文

学校读者我要写书评

暂无评论

Particuology 2016年第4期14卷 51-60页

作者： Faisal Rahmani jayanta K. Dutt Raj K. pandey Department of Mechanical Engineering Indian Institute of Technology Delhi New Delhi 110016 India

journal bearings operating in hot environments and at high temperatures experience accelerated degra- dation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for providing lubrication in journal bearings in place of lubricating oils. Granular particulates do not degrade thermally, even at considerably high temperatures. This work explores the static and dynamic perfor- mance characteristics of elliptical-bore journal bearings lubricated with granular particulates. It is found that a bearing lubricated with a larger size （2 μm） particles offers better performance compared with that using smaller size （1μm） particles. Bore ellipticity reduces the load-carrying capacity and increases side leakage and the coefficient of friction; however, rotor stability is marginally improved at low eccentricity ratios （〈0.6）, followed by significant improvement at high eccentricity ratios （〉0.6）.

关键词： Particulate journal bearing Grain size Rigid rotor stability Hydrodynamic lubrication

Anthropogenic disturbances and their impact on vegetation in Western Himalaya,India

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

journal of Mountain Science 2016年第1期13卷 69-82页

作者： Zubair A.MALIK Rajiv pandey Ajay Ballabh BHATT Ecology Laboratory Department of Botany and MicrobiologyHNB Garhwal University Srinagar(Garhwal)Uttarakhand-246174India Department of Botany Govt.Degree CollegeBeerwah Budgam(J&K)-193411India. Department of Forestry andNatural Resources HNB Garhwal University Srinagar(Garhwal)Uttarakhand-246174India

The present study assesses anthropogenic disturbances and their impacts on the vegetation in Western Himalaya,India on the basis of various disturbance parameters such as density,Total Basal cover(TBc) of cut stumps,lopping percentage and grazing *** the basis of canopy cover and frequency of disturbances(%),the studied forests were divided into highly disturbed(HD),moderately disturbed(MD) and least disturbed(LD) *** HD forests had the lowest canopy cover,lowest density and lowest TBc and the LD had the highest canopy cover,highest density and highest *** MD forests occupied the intermediate position with respect to these *** richness was least in HD forests,highest in one of the MD forests while LD forest occupied an intermediate *** percentage of regenerating species was lowest(54%) in HD and highest(72%) in *** density of seedlings and saplings was higher in one of the MD forests as compared to HD and *** concluded that the moderate disturbances do not affect the vegetation adversely;however the increased degree of disturbance causes loss in plant diversity;affects regeneration and changes community *** of hydroelectric projects at various places in the study area was found to be one of the most important sources of anthropogenic disturbances in addition to the routine anthropogenic disturbances like grazing,fuelwood collection and fodder *** all proposed dams in the Indian Himalaya are constructed combined with weak national environmental impact assessment and implementation,it will result in a significant loss of ***,various agents of disturbances should be evaluated in cumulative manner and any developmental activities such as hydropower projects,which trigger various natural and anthropogenic disturbances,should be combined with proper cumulative environmental impact assessment and effective implementation to minimise the anticipated loss of vegetation.

关键词： forests vegetation canopy grazing anthropogenic disturbance moderately timber woody stands

Influence of Metal Oxides on the Arc Erosion Behaviour of Silver Metal Oxides Electrical contact Materials

在线全文

学校读者我要写书评

暂无评论

journal of Materials Science & Technology 2004年第1期20卷 49-52页

作者： P.Verma O.P.pandey A.Verma School of Physics and Material Science Thapar Institute of Engineering and Technology Patiala-147004 IndiaSchool of Physics and Material Science Thapar Institute of Engineering and Technology Patiala-147004 IndiaMaterials Science and Technology Division Thapar Centre for Industrial Research and Development Patiala-147004 India

In the present work investigations have been made to see the role of metal oxides on the performance of the silver metal oxides electrical contact materials. Silver metal oxide materials of three different compositions Ag-10cdO, Ag-7.6SnO2-2.3ln2O3 and Ag-10ZnO were prepared by internal oxidation process under identical processing conditions. These materials were tested for electrical conductivity, hardness, and erosion loss. Performing an accelerated test on the actual contactor assessed the electrical performance, involving erosion loss and temperature rise of the processed materials. The arc-eroded surface was characterized under scanning electron microscope. The study of the eroded surfaces of contacts indicates that the thermal stability of metal oxides depends on nature of silver-metal oxide interface and their mode of erosion. An attempt is made to correlate the surface features of the eroded contacts with the thermal stability of metal oxides.

关键词： contact material Microstructure Erosion rate

Evaluation of reference evapotranspiration methods for the northeastern region of India

在线全文

学校读者我要写书评

暂无评论

International Soil and Water conservation Research 2016年第1期4卷 52-63页

作者： Pankaj K.pandey Parmendra PDabral Vanita pandey Department of Agricultural Engineering North Eastern Regional Institute of Science and Technology(NERIST)NirjuliItanagarArunachal PradeshIndia Department of Soil and Water Engineering College of Agricultural Engineering and Post-Harvest Technology(CAEPHT)RanipoolGangtokSikkimIndia

The study planed to identify a suitable alternative to the FAO 56 Penman-Monteith(FAO56PM)equation for calculating reference evapotranspiration(ET_(0))from chosen te mperature and radiation based models utilizing monthly meteorological data from 30 destinations in diverse agro-ecologial regions of the Northeast(NE)India ie,Assam Bengal Plain(ABP),eastern Himalaya(EH),and the northeastern hilly(NEH)***-based IRMAK3 most appropriate in the ABP(weighted root mean square deviation,WRMSD=0.17 mm d^(-1),r^(2)=0.98,for Nagrakata),and TURc model being in the first three rank of most of the sites,with the lowest error and highest correlation in NEH(WRMSD=0.10 mm d^(-1),r^(2)=0.92,for Shillong),and EH(WRMSD=0.23 mm d^(-1),r^(2)=-0.95,for Gangtok).Findings reveal that IRMAK3 and TURc models performed equally well and were observed to be the best among selected modets for the majority of stations followed by FAO24 Blaney-criddle(FAO24Bc),and 1957MAKK Pair-wise regession equations were developed for preferred FAO56PM ET_(0) estimates to ET_(0) estimates by alternative ***-correlation of eighteen chose methods demonstrated that the five equations(*** radiation-and one temperature-based)performed eceptionally well when contrasted with the FAO56PM model,thus being advised for assessing ET_(0)。under limiting data conditions as have yielded a better estimate of ET_(0) with a small error.

关键词： Reference evapotranspiration Performance statistics calibration and validation Empirical methods North East India