检索结果-南通市图书馆

Extraterrestrial microspherules from Bajada del Diablo,Chubut,Argentina

Geoscience frontiers 2017年第1期8卷 137-149页

作者： M.j.Orgeira L.N.Castro G.A.Goldmann C.B.Prezzi E.Sileo D.R.Vega C.franzosi R.D.Acevedo O.Martinez j.Rabassa j.f.ponce O.R.Tofalo Departamento de Ciencias Geologicas-lGEBA Facultaci de Ciencias Exactas y NaturalesOniversidad de Buenos AiresCiudad UniversitariaPabelldn 11C1428EHABuenos AiresArgentina Consejo Nacional de lnvestigaciones Cientificas y Tecnicas de Argentina CONICEE Argentina Departamento de lngenierfa Agrfcola y Uso de la Tierra Facultad de AgronomiaUniversidad de Buenos AiresAv.San Martin 4453CI417DSEBuenos AiresArgentina INQUIMAE Departamento de Qufmica Inorganica.Analitica y Quimica Fisica.Facultad de Ciencias Exactas y Naturales.Universidad de Buenos AiresPabellon IICiudad Universitaria.C1428EHABuenos Aires.Argentina Gerencia de lnvestigacion y Aplicaciones Comision Nacional de Energfa AtomicaUniversidad Nacional General San MartinBuenos AiresArgentina Centro Austral de lnvestigaciones Cientificas CADIC-ConicetUshuaiaArgentina Universidad Nacional de la Patagonia"San juan Bosco"Sede Esquel ChubutArgentina Universidad Nacional de la Patagonia"San juan Bosco"Sede Ushuaia UshuaiaArgentina

The Quaternary infilling of a circular structure located in Bajada del Diablo,Chubut Province,Argentina has been proposed as a crater strewn field in previous *** we report the finding of about 65 microspherules collected in a trench excavated in the center of the *** majority of handpicked specimens are single,but some of them exhibit compound *** single specimens are spherical with a mean size of 137 nm,whereas the more complex samples show peduncles and drop *** crystal growth is recognized in the internal structure of some broken *** chemical composition from the surface and center of microspherules was determined by energy dispersive spectrometry employing *** EMPA and XRD analysis indicate that the microspherules are mainly composed of fe and O with magnetite,fe0with subordinate *** consideration of possible anthropogenic and volcanic origins,these spherulites are ascribed to an extraterrestrial *** accumulation rate of 47 microspherules per m2/yr is estimated for the studied *** value is two orders of magnitude higher than the reference flux for cosmic dust estimated for the last 1 Ma in the Transantarctic *** microspherules might have been generated as a byproduct of asteroid entry in the atmosphere.

关键词： Extraterrestrial microspherules Chemistry Bajada del Diablo Chubut Patagonia-Argentina

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Pressure drop analysis on the positive half-cell of a cerium redox flow battery using computational fluid dynamics: mathematical and modelling aspects of porous media

引用

frontiers of Chemical Science and Engineering 2021年第2期15卷 399-409,F0004页

作者： fernando f.Rivera Berenice Miranda-Alcantara German Orozco Carlos ponce de Leon Luis f.Arenas National Council of Science and Technology(CONACYT) Mexico City 03940Mexico Center of Research and Technological Development in Electrochemistry(CIDETEQ) Queretaro 76703Mexico Electrochemical Engineering Laboratory Energy Technology Research GroupFaculty of Engineering and Physical SciencesUniversity of SouthamptonSouthampton SO171BJUK

Description of electrolyte fluid dynamics in the electrode compartments by mathematical models can be a powerful tool in the development of redox flow batteries(RfBs)and other electrochemical *** order to determine their predictive capability,turbulent Reynolds-averaged Navier-Stokes(RANS)and free flow plus porous media(Brinkman)models were applied to compute local fluid velocities taking place in a rectangular channel electrochemical flow cell used as the positive half-cell of a cerium-based RfB for laboratory *** different platinized titanium electrodes were considered,a plate plus a turbulence promoter and an expanded metal *** pressure drop was validated against experimental data obtained with typical cerium *** was found that the pressure drop values were better described by the RANS approach,whereas the validity of Brinkman equations was strongly dependent on porosity and permeability values of the porous media.

关键词： CfD simulation porous media porous electrode pressure drop redox flow battery

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Analysing changes in spatial point patterns:A proposal using data from a forest thinning experiment

引用

forest Ecosystems 2022年第6期9卷 878-887页

作者： Christian Salas-Eljatib joaquín Riquelme-Alarcon Pablo j.Donoso Diego ponce Daniel P.Soto Centro de Modelacion y Monitoreo de Ecosistemas Escuela de Ingeniería ForestalUniversidad MayorSantiagoChile Vicerrectoría de Investigacion y Postgrado Universidad de La FronteraTemucoChile Departamento de Silvicultura y Conservacion de la Naturaleza Universidad de ChileSantiagoChile Instituto de Bosques y Sociedad Universidad Austral de ChileValdiviaChile Corporacion Nacional forestal ValdiviaChile Departamento de Ciencias Naturales y Tecnología Universidad de AysenCoyhaiqueChile

Spatial patterns reveal critical features at the individual and community ***,how to evaluate changes in spatial characteristics remains largely *** assess spatial changes in spatial point patterns by augmenting current statistical functions and *** fitted functions to describe unmarked and marked(tree size)spatial patterns using data from a large-scale silvicultural experiment in southern ***,we compute the mingling index to represent spatial tree *** proffer the pair correlation function difference before and after treatment to detect changes in the unmarked-point pattern of trees and the semivariogram-ratio to evaluate changes in the marked-point *** research provides a quantitative assessment of a critical aspect of forest heterogeneity:changes in spatial unmarked and marked-point *** proposed approach can be a powerful tool for quantifying the impacts of disturbances and silvicultural treatments on spatial patterns in forest ecosystems.

关键词： Spatial diversity Marked-point process Spatial heterogeneity Conspecific Variable-density thinning Nothofagus

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Critical pathway for primary open angle glaucoma diagnosis

引用

International journal of Ophthalmology(English edition) 2017年第6期10卷 968-972页

作者： Alejandro R.Allocco julia A.ponce Maria j.Riera Mauricio G.Magurno Instituto Santa Lucia Parana Alameda de la Federaci6n 493 Parana 3100 Entre Rios Argentina

AIM： To develop a critical pathway for primary open angle glaucoma （POAG） diagnosis intended to be efficient, to unify criteria, reduce resource use and minimize costs to the health system. METHODS： We performed a systematic search on PubMed, Cochrane, Embase and *** databases and classified the quality of evidence from level I through III. RESULTS： A critical pathway was designed by setting a key-decision step by step model on the basis of the best current evidence. CONCLUSION： A critical pathway, evidence-based guideline, may be a useful tool intended to reduce costs while maintaining or even improving the quality of care for diagnosing a highly prevalent pathology such as open angle glaucoma.

关键词： glaucoma diagnosis critical pathway guideline

来源：

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

Investigation on the influence of the initial RDX crystal size on the performance of shaped charge warheads

引用

Defence Technology（防务技术） 2019年第5期15卷 802-807页

作者： f.Majiet f.j.Mostert Rheinmetall Denel Munition Somerset WestSouth Africa Centre for Scientific&Industrial Research PretoriaSouth Africa

Copper lined wave shaped shaped charges of particular design and liner metallurgy were used to investigate the effect of explosive crystal size on the resultant shaped charge jet *** A3 with RDX of three different average crystal sizes,i.e.30μm,100μm and 300μm were used in the *** other parameters in the charge were kept constant and in particular,care was given to obtain consistent dimensional quality and liner microstructure,in order to prohibit the variation of other *** flash-X-ray diagnostics were used in field tests to obtain the jet parameters from multiple firings of similar *** is found that the varying crystal size of the RDX has a marginal influence in the total jet length of the ***,it is also found that there is less variation between firings in the jet parameters for jets from the charges loaded with the crystal size of 100 μm.

关键词： shaped size crystal

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Implementation of a Roughness Element to Trip Transition in Large-eddy Simulation

引用

journal of Thermal Science 2015年第1期24卷 30-36页

作者： j.Boudet j.-f.Monier f.Gao LMfA Ecole Centrale de Lyon Université de Lyon–UMR CNRS 5509 69134 Ecully Cedex France PhD.Candidate Université de Lyon–UMR CNRS 5509 69134 Ecully Cedex France

In aerodynamics, the laminar or turbulent regime of a boundary layer has a strong influence on friction or heat transfer. In practical applications, it is sometimes necessary to trip the transition to turbulent, and a common way is by use of a roughness element （e.g. a step） on the wall. The present paper is concerned with the numerical im- plementation of such a trip in large-eddy simulations. The study is carried out on a flat-plate boundary layer con- figuration, with Reynolds number Rex=l.3x 106. first, this work brings the opportunity to introduce a practical methodology to assess convergence in large-eddy simulations. Second, concerning the trip implementation, a volume source term is proposed and is shown to yield a smoother and faster transition than a grid step. Moreover, it is easier to implement and more adaptable. finally, two subgrid-scale models are tested： the WALE model of Nic0ud and Ducros （flow Turbul. Combust., vol. 62, 1999） and the shear-improved Smagorinsky model of Ldv^que et al. （j. fluid Mech., vol. 570, 2007）. Both models allow transition, but the former appears to yield a faster transition and a better prediction of friction in the turbulent regime.

关键词： large-eddy simulation boundary layer roughness element transition tripping

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Nucleation and growth kinetics of La0.7Sr0.3Cr0.4Mn0.6O3-δ SOfC perovskite:Symmetry alteration evolution induced by Cu2+ and Ni2+ impregnation

引用

Progress in Natural Science:Materials International 2016年第6期26卷 665-670页

作者： A.Concha-Balderrama G.Rojas-George j.Alvarado-flores H.Esparza-ponce M.H.Bocanegra-Bernal A.Reyes-Rojas Centro de Investigación en Materiales Avanzados S.C.(CIMAV) Laboratorio Nacional de NanotecnologíaMiguel de Cervantes 120 Complejo Industrial ChihuahuaCd.de Chihuahua

La0.7Sr0.3Cr0.4Mn0.6O3-δperovskite nanoparticles have been synthetized using an ethylene glycol modified solgel method and impregnated by Cu0.75Ni0.25nanoparticles. The phase transitions and nucleation kinetics were studied by time resolved x-ray diffraction, Rietveld, Raman spectroscopy and high resolution transmission electron microscopy. findings have shown that, an atomic disorder dominates from room temperature to 400 °C. Nanoparticles with crystal size formation of La0.7Sr0.3Cr0.4Mn0.6O3-δand SrCrO4solid solutions with Pm3m cubic and P21/n monoclinic symmetry respectively in the range of 600–650 °C. Symmetry reduction from the Pm3m→R3c space group had been obtained at a lower temperature（750 °C） than those reported in the literature in oxygen atmosphere and it was confirmed by an octahedral distortion, which takes place in the crystallographic direction[221]/（122）. The johnson-Mehl-Avrami model had described the whole process, where the existence of two phases was shown before it reached its complete D3d6point group symmetry.

关键词： Perovskite structure Sol-gel method Composite Kinetics Rietveld

来源：

同方期刊数据库评论

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Surface morphology and impurity distribution of electron beam recrystallized silicon films on low cost substrates for solar cell absorber

引用

Rare Metals 2006年第Z1期25卷 195-200页

作者： GROMBALL f MüLLER j Department of Mikrosystemtechnik Technische Universitt Hamburg-Harburg Hamburg 21073 Germany

A line shaped electron beam recrystallised polycrystalline silicon film on the low cost substrate was investigated for the use of the solar cell absorber. The applied EB energy density strongly influences the surface morphology of the film system. Lower EB energy density results in droplet morphology and the rougher SiO2 capping layer due to the low fluidity. With the energy increasing, the capping layer becomes smooth and continuous and less and small pinholes form in the silicon film. Tungstendisilicide (WSi2) is formed at the interface tungsten/silicon but also at the grain boundaries of the silicon. Because of the fast melting and cooling of the silicon film, the eutectic of silicon and tungstendisilicide mainly forms at the grain boundary of the primary silicon dendrites. The SEM-EDX analysis shows that there are no chlorine and hydrogen in the area surrounding a pinhole after recrystallization because of outgassing during the solidification.

关键词： polycrystalline silicon film solar cell recrystallization energy surface morphology outgassing

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Characterization of Phases in an As-cast Copper-Manganese-Aluminum Alloy

引用

journal of Materials Science & Technology 2006年第6期22卷 779-784页

作者： j.Iqbal f.Hasan f.Ahmad Department of Metallurgical and Materials Engineering University of Engineering and TechnologyLahorePakistan

Copper-manganese-aluminum （CMA） alloys, containing small additions of fe, Ni, and Si, exhibit good strength and remarkable corrosion resistance against sea water. The alloys are used in as-cast condition, and their microstructure can show wide variations. The morphology, crystallography and composition of the phases presented in an as-cast （CMA） alloy of nominal composition Cu-14%Mn-8%Al-3%fe-2%Ni were investigated using optical, electron optical, and microprobe analytical techniques. The as-cast microstructure consisted of the grains of fcc α and bcc β-phases alongwith intermetallic precipitates of various morphologies. The room temperature microstructure exhibited four different types of precipitates inside the α-grains： the ＇large＇ dendritic-shaped particles and the cuboid-shaped precipitates, which were rich in fe and Mn and had an fcc structure, while the ＇small＇ dendritic-shaped particles and the globular precipitates were based on feaAI and had DO3 structure. These four different morphologies of intermetallic precipitates exhibited discrete orientation-relationships with the α-matrix. The β-grains only contained very small cuboid shaped precipitates, which could only be resolved through transmission electron microscopy. These precipitates were found to be based on fe3Al and had the DO3 structure.

关键词： Orientation relationship DO3 structure Intermetallic phases

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

ＯＮＴＨＥＨＹＰＥＲＢＯＬＩＣＯＢＳＴＡＣＬＥＰＲＯＢＬＥＭＯＦＦＩＲＳＴＯＲＤＥＲ

引用

Chinese Annals of Mathematics,Series B 2002年第2期23卷 253-266页

作者： j.f.RODRIGUES CMAf/Universidade

This paper presents new results for strong solutions and their coincidence sets of the obstacle problem for linear hyperbolic operators of first order. An inequality similar to the LewyStampacchia ones for elliptic and parabolic problems is shown. Under nondegeneracy conditions the stability of the coincidence set is shown with respect to the variation of the data and with respect to approximation by semilinear hyperbolic problems. These results are applied to the asymptotic stability of the evolution problem with respect to the stationary coercive problem with obstacle.

关键词： Hyperbolic obstacle problem Linear hyperbolic operator Strong solution

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：