检索结果-南通市图书馆

Effect of processing parameters on the electromagnetic radiation emission during plastic deformation and crack propagation in copper-zinc alloys

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 Zhejiang University-Science A(Applied Physics & Engineering) 2006年第11期7卷 1800-1809页

作者： KUMAR Rajeev MISRA ashok Department of Mechanical Engineering Birla Institute of Technology Mesra 835215 Ranchi India

This paper presents some investigations on the effect of processing parameters on the emission of electromagnetic radiation （EMR） during plastic deformation and crack propagation in copper-zinc alloys. Timing of the EMR emissions, maximum stress during crack instability, stress-intensity factor, elastic strain energy release rate, maximum EMR amplitude, RMS value of EMR amplitude, EMR frequency and electromagnetic energy release rate were analysed for the effect of rolling directions at different percentage of zinc content in Cu-Zn alloy specimens. The same parameters were also analysed for 68-32 Cu-Zn alloy specimens at different annealing temperatures and at different angles 0, to the rolling direction. EMR emissions are observed to be highly anisotropic in nature. At θ=45° to 60°, marked changes in mechanical and electromagnetic parameters were observed. Specimens annealed at 500℃, just above the recrystallization temperature, and at 700℃, when grain-size growth is rapid, EMR responses have been found to have well-defined patterns.

关键词： Radiation Plastic deformation Rolling direction Annealing Fracture

Investigation on the Reduction of Center of Mass Oscillations of Flexible Flapping Fins

在线全文

学校读者我要写书评

暂无评论

Journal of Bionic Engineering 2016年第4期13卷 544-557页

作者： ashok K Kancharala Michael K Philen Aerospace and Ocean Engineering Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA

Nature has been a source of inspiration for developing advanced autonomous aerial and underwater vehicles. The bodies with flapping appendages produce Center of Mass （COM） oscillations as the flapping fins generate forces oscillatory in nature. The vehicles with larger COM oscillations pose the problems of control and maneuverability and this paper discusses the effect of flexibility and other operating parameters such as heaving, pitching amplitudes and operating frequency on COM oscillations. A detailed theoretical investigation has been carried out to predict the optimal operating parameters along with the fin stiffness to reduce the COM oscillations for a given Self-Propelled Speed （SPS）. Experiments have been performed to validate the theoretical results. It has been observed that the flexible fins operating at larger frequencies produce lower COM oscillations compared to stiffer fins operating at lower frequencies for a given mean thrust/SPS, and that the trailing edge amplitude along with the deformation pattern play a role in the generation of COM oscillations.

关键词： flapping fin fluid-structure interaction optimization digital image correlation

Morphology of single inhalable particle inside public transit biodiesel fueled bus

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 Environmental Sciences 2010年第2期22卷 263-270页

作者： Kaushik K.Shandilya ashok Kumar Department of Civil Engineering The University of Toledo

In an urban-transit bus, fueled by biodiesel in Toledo, Ohio, single inhalable particle samples in October 2008 were collected and detected by scanning electron microscopy and energy dispersive X-ray spectrometry （SEM/EDS）. Particle size analysis found bimodal distribution at 0.2 and 0.5 μm. The particle morphology was characterized by 14 different shape clusters： square, pentagon, hexagon, heptagon, octagon, nonagon, decagon, agglomerate, sphere, triangle, oblong, strip, line or stick, and unknown, by quantitative order. The square particles were common in the samples. Round and triangle particles are more, and pentagon, hexagon, heptagon, octagon, nonagon, decagon, strip, line or sticks are less. Agglomerate particles were found in abundance. The surface of most particles was coarse with a fractal edge that can provide a suitable chemical reaction bed in the polluted atmospheric environment. The three sorts of surface patterns of squares were smooth, semi-smooth, and coarse. The three sorts of square surface patterns represented the morphological characteristics of single inhalable particles in the air inside the bus in Toledo. The size and shape distribution results were compared to those obtained for a bus using ultra low sulfur diesel.

关键词： individual particle environmental scanning electron microscope urban-public transit bus ultra low sulfur diesel

Influence of rare-earth ions on structural and magnetic properties of CdFe_2O_4 ferrites

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2010年第2期29卷 168-173页

作者： ashok Gadkari Tukaram Shinde Pramod Vasambekar Department of Physics GKG CollegeKolhapur 416012 India Department of Physics KRP Kanya Mahavidylaya Islampur 415409 India Department of Electronics Shivaji University Kolhapur 416004 India

Nano-sized powders of rare-earth ions added CdFe2O4 ferrites were synthesized by oxalate co-precipitation *** influence of R ions（R = Sm3＋, Y3＋, and La3＋） on the microstructure and magnetic properties of CdFe2O4 ferrites was ***, SEM, FTIR, and magnetic hysteresis loops were used for analyzing the *** addition of R ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain *** magnetic properties such as saturation magnetization, remanent magnetization, and magnetic moment increased due to addition of rare-earth ions in CdFe2O4 *** formation of secondary phase on the grain boundaries supports the abnormal *** spectra show two absorption *** suggest that the magnetic properties depend on the particular method of preparation and additives.

关键词： nanoparticle rare-earth ions magnetization grain size hysteresis

Are men talking their reproductive health away？

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2015年第3期17卷 433-434页

作者： ashok Agarwal Damayanthi Durairajanayagam Center for Reproductive Medicine Cleveland Clinic Cleveland Ohio USA MARA University of Technology Sungai Buloh Malaysia

The advent of mobile phones has revolutionized communication trends across the globe. As the popularity of mobile phone usage continues to escalate, there is now growing concern about the effects of radiofrequency electromagnetic waves （RF-EMW） exposure on biological tissues, such as the brain and testes. Researchers have sought to link the much debated decline in human sperm quality in the last decade, with increased exposure to RF-EMW, particularlythrough mobile phone usage. In a recent systematic review and meta-analysis on the effect of mobile phone RF-EMW radiation on sperm quality, Adams et al.1 demonstrated an association between mobile phone exposure and reduced sperm motility and viability, with inconsistent effects on sperm concentration.1 Results from 10 pooled experimental （in vitro） and observational （in vivo） human studies （n = 1492） led these researchers to suggest that exposure to RF-EMW radiation from carrying a mobile phone in the trouser pocket negatively impacts sperm quality.

关键词： RADIATION PHONES IMPACT

Erratum to:Superlubricity of epitaxial monolayer WS_(2)on graphene

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第6期17卷 5754-5754页

作者： Holger Büch Antonio Rossi Stiven Forti Domenica Convertino Valentina Tozzini Camilla Coletti Center for Nanotechnology Innovation@NEST Istituto Italiano di TecnologiaPiazza S.Silvestro 1256127 PisaItaly NEST Istituto Nanoscienze–CNR and Scuola Normale SuperiorePiazza San Silvestro 1256127 PisaItaly Graphene Labs Istituto Italiano di TecnologiaVia Morego 3016163 GenovaItaly

The article"Superlubricity of epitaxial monolayer WS2 on graphene",written by Holger Büch,Antonio Rossi,Stiven Forti,Domenica Convertino,Valentina Tozzini,and Camilla Coletti,was originally published electronically on the publisher’s internet portal(currently SpringerLink)on June 18th 2018 without open *** the author(s)’decision to opt for Open choice the copyright of the article changed in August 2018 to©The Author(s)2018 and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License(http://***/licenses/by/4.0/),which permits use,duplication,adaptation,distribution and reproduction in any medium or format,as long as you give appropriate credit to the original author(s)and the source,provide a link to the Creative Commons license and indicate if changes were made.

关键词： monolayer epitaxial license

Numerical modelling of pullout of helical soil nail

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 Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 648-658页

作者： Saurabh Rawat ashok Kumar Gupta Department of Civil Engineering Jaypee University of Information Technology Waknaghat Solan 173234 India

An investigation into the pullout response of helical soil nail using finite element subroutine Plaxis 2D is *** numerical modelling of actual pullout response is achieved by axisymmetric and horizontal loading *** effect of varying number of helical plates,helical plate spacing and helical plate diameter is studied to understand the pullout capacity *** failure surfaces for various helical soil nail configurations and their pullout mechanisms are also analysed and *** pullout capacity is found to increase with increase in number of helical *** helical plate spacing ratio（s/D;） and diameter ratio（D;/D;） are found to increase the pullout only up to a critical *** response of helical soil nail using axisymmetric finite element simulation is found similar to the uplift behaviour of helical piles and helical soil *** the absence of literature regarding numerical modelling of helical soil nail,simulation results are validated with uplift responses of helical piles and soil anchors.A good agreement in their comparative study for pullout response is also observed.

关键词： Finite element Helical soil nail Pullout response Plate spacing Plate diameter Failure mechanism

Historical temporal variation in precipitation over Western Himalayan Region：1857-2006

在线全文

学校读者我要写书评

暂无评论

Journal of Mountain Science 2016年第4期13卷 672-681页

作者： naresh kumar ashok kumar jaswal India Meteorological Department Lodi Road New Delhi 110003 India India Meteorological Department Pune 411005 India

This study has examined the temporal variation in monthly, seasonal & annual precipitation over the Western Himalayan Region(WHR) and the influence of global teleconnections, like the North Atlantic Oscillation(NAO) and Southern Oscillation(SO) Indices on seasonal & annual precipitation. The Mann–Kendall non-parametric test is applied for trend detection and the Pettitt–Mann–Whitney test is used to detect possible shift. Maximum entropy spectral analysis is applied to find the periodicity in annual & seasonal precipitation. The study shows a non-significant decreasing trend in annual precipitation over WHR for the period 1857-2006. However, in seasonal precipitation, a significant decreasing trend is observed in monsoon and a significant increasing trend in post-monsoon season during the same period. The significant decrease in monsoon precipitation may be due to weakening of its teleconnection with NAO as well as SO Indices mainly during last three decades. It is observed that the probable change of year in annual & monsoon precipitation over WHR is 1979. The study also shows significant periodicities of 2.3-2.9 years and of 3.9-4.7 years in annual & seasonal precipitation over WHR.

关键词： Monsoon Precipitation Western Himalayan region Temporal Variation

Wear behavior of asbestos-free eco-friendly composites for automobile brake materials

在线全文

学校读者我要写书评

暂无评论

Friction 2016年第2期4卷 144-152页

作者： ashok Kumar ILANKO Srinivasan VIJAYARAGHAVAN Department of Manufacturing Engineering Annamalai University Annamalai Nagar 608002 India

The goal of this work is to study the wear behavior of materials that have the potential to be used as brake pad materials under different contact loads and speeds instead of asbestos. The three different brake pad materials studied are flax fiber reinforced phenolic composites (FFRC), basalt fiber reinforced phenolic composites (BFRC), and flax/basalt reinforced hybrid phenolic composites (HFRC). A wear mechanism map was developed by using the fuzzy c-means clustering algorithm method (FCM) to study the wear mechanism of composites. The results showed BFRC to be a better brake pad material than the other fiber reinforced composites studied, because the good thermal characteristics and bonding nature of basalt fiber increased the wear resistance of BFRC considerably.

关键词： wear resistance non-asbestos brake frictional materials eco-friendly composites wear mechanism maps coefficient of friction wear