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壁面湍流模型对湍流分离流动数值模拟的影响 被引量:11
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作者 王泽 刘卫明 《空气动力学学报》 CSCD 北大核心 2002年第2期198-205,共8页
本文用三种近壁湍流模型计算了二个二维的湍流分离流动 :单包流动和多包流动。结果表明 :二层模型和低Reynolds数模型具有类似的特性。它们基本上给出合理的分离流动结构。
关键词 数值模拟 影响 壁面湍流模型 k-ε模型 湍流分离流动
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现代电力设备管理系统的构建 被引量:14
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作者 张惠刚 K.Feser 《电力自动化设备》 EI CSCD 北大核心 2002年第12期6-9,共4页
在分析了电力系统设备管理基本要求和特点的基础上,提出了现代电力设备管理系统的基本结构和组成。按设备元件成本与其功能贡献成正比的观点,建立了设备层次化模型。根据设备在线测量和离线测试的数据,采用模糊逻辑推理方法,在线评估设... 在分析了电力系统设备管理基本要求和特点的基础上,提出了现代电力设备管理系统的基本结构和组成。按设备元件成本与其功能贡献成正比的观点,建立了设备层次化模型。根据设备在线测量和离线测试的数据,采用模糊逻辑推理方法,在线评估设备状态及其价值跌落。从设备可用性的观点出发,在考虑设备状态及其重要性等因素后,提出了设备维护决策的综合指标。以变电站为例,阐明了设备管理模型、算法及其维护决策。 展开更多
关键词 电力设备 管理系统 在线状态监视 模糊逻辑推理 设备状态估计 电力系统
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多边形和多面体顶点法矢的数值估计 被引量:14
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作者 姜寿山 Peter Eberhard 《计算机辅助设计与图形学学报》 EI CSCD 北大核心 2002年第8期763-767,共5页
证明了两个定理 :定理 1揭示了三点多边形的外接圆在中点处的法矢与两个边界法矢的关系 ;定理 2揭示了四面体外接球面在中点处的法矢与三个相邻三角平面的法矢量的关系 .给出了一个判别二维多边形和三维多面体顶点法矢计算方法优劣的准... 证明了两个定理 :定理 1揭示了三点多边形的外接圆在中点处的法矢与两个边界法矢的关系 ;定理 2揭示了四面体外接球面在中点处的法矢与三个相邻三角平面的法矢量的关系 .给出了一个判别二维多边形和三维多面体顶点法矢计算方法优劣的准则 .在此基础上 ,提出一种用于估计三维多面体顶部的法矢量的计算方法 . 展开更多
关键词 多边形 多面体顶点 数值估计 法向量 计算机辅助设计
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α-Fe/Nd_2Fe_(14)B复合纳米晶的界面研究
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作者 李伟 张湘义 +3 位作者 关颖 张静武 Sprengel W Schaefer H-E 《中国稀土学报》 CAS CSCD 北大核心 2003年第4期410-412,共3页
采用正电子寿命谱和双探头Doppler展宽测量在原子尺度上研究了α Fe/Nd2Fe14B复合纳米晶的界面结构。正电子寿命研究表明,α Fe/Nd2Fe14B复合纳米晶存在两类界面。一类为非晶界面层,正电子湮没寿命为155ps;另一类为具有原子空位的松懈界... 采用正电子寿命谱和双探头Doppler展宽测量在原子尺度上研究了α Fe/Nd2Fe14B复合纳米晶的界面结构。正电子寿命研究表明,α Fe/Nd2Fe14B复合纳米晶存在两类界面。一类为非晶界面层,正电子湮没寿命为155ps;另一类为具有原子空位的松懈界面,含有空位尺寸大于1~2个铁原子空位的结构自由体积,正电子湮没寿命为246ps。电子 正电子湮没光子的共谐Doppler展宽测量表明这类松懈界面富集非磁性原子Nd和B,这将削弱α Fe/Nd2Fe14B复合纳米晶晶粒间的磁交换耦合。 展开更多
关键词 凝聚态物理 材料物理 界面 正电子湮没 纳米晶 稀土
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DINI机构仓储库认证 被引量:2
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作者 Susanne Dobratz Frank Scholze 吴霞(译) 《现代图书情报技术》 CSSCI 北大核心 2008年第3期95-102,共8页
目的——旨在概述机构仓储库的认证技术以支持德国开放存取活动,同时还描述了德国网络信息初始化计划(DINI)开展的"DINI认证2006"活动。设计方法——DINI对文献和出版物仓库的认证向潜在用户表明,该仓储的运行质量是有所保证... 目的——旨在概述机构仓储库的认证技术以支持德国开放存取活动,同时还描述了德国网络信息初始化计划(DINI)开展的"DINI认证2006"活动。设计方法——DINI对文献和出版物仓库的认证向潜在用户表明,该仓储的运行质量是有所保证的,同时使其区别于一般机构的网络服务。本认证也能够被用作支持开放获取的一个工具。结果——仓储库认证技术虽然不会成为全球性学术信息实现开放获取的主要影响因素,但它能够促进机构仓储库的推广,并提高机构仓储库服务的知名度。研究局限性/意义——DINI认证作为一种"软性"认证,关注的是数字仓储库的互操作性,这是一种正在流行的有指导意义的观点。但是它并不能为可信赖的数字资源长期保存系统提供详尽的审计工具。实践意义——依据特定的组织及技术标准,"DINI针对文档及出版物仓储的认证"推进了德国机构仓储库的发展,同时也为世界范围内数字仓储库的互操作性做出了贡献。原创性/价值——本文描述了德国采用的一个独特方法,同时也适用于其他国家及组织。 展开更多
关键词 数字存储 档案管理 德国
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Intestinal barrier in inflammatory bowel disease 被引量:40
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作者 Lena Antoni Sabine Nuding +1 位作者 Jan Wehkamp Eduard F Stange 《World Journal of Gastroenterology》 SCIE CAS 2014年第5期1165-1179,共15页
A complex mucosal barrier protects as the first line of defense the surface of the healthy intestinal tract from adhesion and invasion by luminal microorganisms. In this review, we provide an overview about the major ... A complex mucosal barrier protects as the first line of defense the surface of the healthy intestinal tract from adhesion and invasion by luminal microorganisms. In this review, we provide an overview about the major components of this protective system as for example an intact epithelium, the synthesis of various antimicrobial peptides (AMPs) and the formation of the mucus layer. We highlight the crucial importance of their correct functioning for the maintenance of a proper intestinal function and the prevention of dysbiosis and disease. Barrier disturbances including a defective production of AMPs, alterations in thickness or composition of the intestinal mucus layer, alterations of pattern-recognition receptors, defects in the process of autophagy as well as unresolved endoplasmic reticulum stress result in an inadequate host protection and are thought to play a crucial role in the pathogenesis of the inflammatory bowel diseases Crohn&#x02019;s disease and ulcerative colitis. 展开更多
关键词 Intestinal barrier Antimicrobial peptide Mucus layer Inflammatory bowel disease Crohn’ s disease Ulcerative colitis Goblet cell Paneth cell
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AN ANALYSIS OF THE MODELING OF STRESS AND STRAIN FIELDS IN A REAL MICROSTRUC-TURE USING AHYBRID METHOD 被引量:2
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作者 E.Soppa S.Schmauder 《Acta Mechanica Solida Sinica》 SCIE EI 2002年第3期277-282,共6页
The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values ... The distribution of stress and strain fields in a micro-structuralarea of a particle reinforced composite is studied by a combinationof experimental and numerical method (hybrid method). With the ex-perimental values of displacements in a micro-region as the boundaryloading condition, strain and stress fields inside the micro-regionare calculated by the finite element method under tow different kindsof model- ing, namely, as pale stress and plane strain condition. Thedifferences between the two kinds of modeling conditions as appliedto micro-structural areas are discussed. 展开更多
关键词 particle reinforced composite real microstructure hybrid method deformation and yield- ing
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THE GENERALIZED(NONLINEAR)POISSON PROBLEM:A DUAL VARIATIONAL APPROACH
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作者 Hans Bufler 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 1994年第3期227-236,共10页
A series of problems in mechanics and physics are governed by the ordinary Poisson equation which demands linearity,isotropy,and material homo- geneity.In this paper a generalization with respect to nonlinearity,aniso... A series of problems in mechanics and physics are governed by the ordinary Poisson equation which demands linearity,isotropy,and material homo- geneity.In this paper a generalization with respect to nonlinearity,anisotropy,and inhomogeneity is made.Starting from the canonical basic equations in the primal and dual formulation respectively we derive systematically the corresponding generalized variational principles;under certain conditions they can be extended to so called complementary extremum principles allowing for global bounds.For simplicity a restriction to two dimensional problems is made,including twice-connected domains. 展开更多
关键词 Generalized Poisson problem dual and complementary variational principles
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Mechanism of Work-hardening for Austenitic Manganese Steel under Non-severe Impact Loading Conditions
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作者 谢敬佩 姜启川 +2 位作者 何镇明 hun(罗全顺) K.Sommer 《Journal of Materials Science & Technology》 SCIE EI CAS CSCD 1992年第6期406-410,共5页
The effect of C,Mn and heat-treatment on work-hardening of austenitic Mn steel and the work-hardening mechanism have been investigated under non-severe impact loading condition.The results show that the ability of wor... The effect of C,Mn and heat-treatment on work-hardening of austenitic Mn steel and the work-hardening mechanism have been investigated under non-severe impact loading condition.The results show that the ability of work-hardening in- creases with the increase of C and aging tempera- ture but decreases with Mn.The work-hardening with high austenitic stability results mainly from dislocations,and that with low austenitic stability results mainly from combined effects of strain-in- duced martensite and high density of dislocations under non-severe impact loading conditions.The wear resistance of medium manganese steel (Mn7) is 1.64-2.46 times that of Hadfield steel (Mnl3). 展开更多
关键词 austenitic manganese steel mechanism of work-hardening
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Separability of Dominant Crop Cultures in Southern Germany Using TerraSAR-X Data
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作者 Kuria Thiong’o René Pasternak +2 位作者 Alfred Kleusberg Frank Thonfeld Gunter Menz 《Advances in Remote Sensing》 2015年第2期97-107,共11页
The research aims at differentiating dominant crop cultures in two test sites of Baden-Wuert- temberg, Southern Germany by creating crop signatures from radar backscatter values. It seeks to establish whether the crop... The research aims at differentiating dominant crop cultures in two test sites of Baden-Wuert- temberg, Southern Germany by creating crop signatures from radar backscatter values. It seeks to establish whether the crop signatures collected in one test site are comparable or transferable to another test site. The two test sites are located in different agro-ecological zones as described in the climate maps of the “Klimaatlas Baden-Wuerttemberg”. TerraSAR-X images (VV polarization) for the months of July and August 2010 were overlaid with crop fields’ ground truth data. As pre-processing steps, radiometric correction was carried out on the images in order to normalize the topographical effects. Classification of the crops was performed on a field scale, according to the mean and standard deviation of their backscatter values. From the results, potatoes could be uniquely differentiated from the cereals in the two different test sites for both the months of July and August 2010. Cereals (rapes, maize, barley, wheat and oats) had comparable backscatter values and their differentiation varied from one test site to another. The results’ accuracy obtained with a maximum kappa coefficient of 0.82 agrees with results of a similar research carried out in North East Germany. 展开更多
关键词 TERRASAR-X Radar Backscatter CROP SIGNATURES CROP Differentiation
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Geographical Reconnaissance of Household in Northern Nigeria towards Optimizing Indoor Residual Spraying Method for Malaria Elimination
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作者 Williams Ojo Moses Onazi Olakunle Olaniyi 《Journal of Geographic Information System》 2016年第6期737-748,共12页
As a part of an effort to roll back malaria in Nigeria, exploring the use of geographically related tools triggered the use of modern approaches of knowing the spatial distribution of target populations to attain sign... As a part of an effort to roll back malaria in Nigeria, exploring the use of geographically related tools triggered the use of modern approaches of knowing the spatial distribution of target populations to attain significant malaria elimination intervention. GIS tool was used for geographical reconnaissance (GR), providing demographic data on respondents’ household and spatial information on the distribution of households in the selected location. A cross-sectional study design was used to collect spatial data in the two locations, while a quantitative questionnaire was used to collect the household data. The analysis of field data indicated that 49,500 unique households were enumerated and thus included in the Indoor Residual Spraying to prevent malaria infection, covering 424 towns in the two Local Government Areas (LGAs). 383,301 persons were recorded during the GR exercise in Doma and Nassarawa Eggon LGAs out of which 79,339 were children of agesless than five years, with 13,526 pregnant women. Further data analysis revealed that the average number of persons per household in both LGAs was approximately eight. The spatial information from the GR provides a foundation for an updateable database for any future survey for developmental activities in Nigeria. The use of modern GR approach has proved to be accurate, reliable and more cost effective and less cumbersome than the traditional approach in the collection and geo-positioning of household data. Use of Garmin e-Trex GPS handheld instruments to collect household data in the designated areas removed the constraints of expensive Personal Digital Assistants and reduced errors of wrong location coordinates. Several African countries which did not use GR or applied the use of Geospatial tool appropriately had setbacks. The previous study in other countries showed limitations which was characterized by substantial inherent logistical and technical challenges culminating in missed targets. This setback was addressed in our study. 展开更多
关键词 Geographical Reconnaissance Geographic Information System Global Positioning Systems Indoor Residual Spraying Local Government Area
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Prof.Ackermann,vision-based navigation and the PG master’s degree programme at HfT Stuttgart
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作者 Michael Hahn 《Geo-Spatial Information Science》 SCIE EI CSCD 2023年第2期156-159,共4页
The two topics of the article seem to have absolutely nothing to do with each other and,as can be expected in a contribution in honor and memory of Prof.Fritz Ackermann,they are linked in his person.Vision-based Navig... The two topics of the article seem to have absolutely nothing to do with each other and,as can be expected in a contribution in honor and memory of Prof.Fritz Ackermann,they are linked in his person.Vision-based Navigation was the focus of the doctoral thesis written by the author,the 29th and last PhD thesis supervised by Prof.Ackermann.The International Master’s Program Photogrammetry and Geoinformatics,which the author established with colleagues at Stuttgart University of Applied Sciences(HfT Stuttgart)in 1999,was a consequence of Prof.Ackermann’s benevolent promotion of international knowledge transfer in teaching.Both topics are reflected in this article;they provide further splashes of color in Prof.Ackermann’s oeuvre. 展开更多
关键词 Vision-based navigation visual odometry photogrammetry and geoinformatics international master’s degree program
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Assessment of PV Shading Device on Building Energy Consumption Taking into Account Site Layout
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作者 Maria Carla Di Vincenzo Dilay Kesten David Infield 《Journal of Energy and Power Engineering》 2012年第3期346-352,共7页
This paper presents the results of a combined study of building energy consumption and the electricity production from PV modules integrated into a shading device, taking account of different site layouts. Various com... This paper presents the results of a combined study of building energy consumption and the electricity production from PV modules integrated into a shading device, taking account of different site layouts. Various combinations of surrounding building configurations and the tilt angles of the shading device (that determines the PV module orientation) are examined. 展开更多
关键词 Shading device PV site layout building energy demand energy supply annual performance.
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Towards greener polymers:Trends in the German chemical industry
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作者 Adam W.Franz Stefan Buchholz +1 位作者 Rolf W.Albach Rolf Schmid 《Green Carbon》 2024年第1期33-44,共12页
Global plastics production is expected to exceed 400 million tons and reach 600 million tons by 2060.Their synthesis currently accounts for approximately 3%of global greenhouse gas emissions.Approximately 60%of all po... Global plastics production is expected to exceed 400 million tons and reach 600 million tons by 2060.Their synthesis currently accounts for approximately 3%of global greenhouse gas emissions.Approximately 60%of all polymers are produced for single-use.Examples include shopping bags,packaging materials,mulch films,and soluble polymers for cosmetics and other purposes.Currently,only a portion of single-use plastic is recycled or disposed of in incinerators or landfills.An estimated 20%is not disposed of properly and pollutes the global environment,especially the oceans.In response to these challenges,the United Nations,European Union,and many nation-states are developing regulatory frameworks that encourage the chemical industry to produce plastics with a smaller environmental footprint and often support this through research funding.Possible solutions include:(1)the use of green energy,green hydrogen,bio-based feedstocks,or CO_(2) in synthesis;(2)the reuse or recycling of plastics through conversion or pyrolysis;and(3)the production of biodegradable polymers.The German chemical industry contributes approximately one-third of polymer production in the EU.It is embedded in the EU regulatory and research landscape and anchored in the European Green Deal,which aims for carbon neutrality by 2050.In this paper,we describe how BASF and Evonik,two leading German chemical companies with strong but different polymer portfolios,respond to the call for greener polymers and how technologies are being developed to make polyurethanes,a particularly important and difficult-to-recycle family of elastomers and duromers,renewable and circular.Reducing the environmental footprint of plastics requires not only innovative materials but also proper governance,regulatory and collection systems,and public willingness to cooperate.In an international comparison of these competencies,expressed by the"polymer management index"(PMI),Germany achieved a top position. 展开更多
关键词 Plastics recycling Biobased plastics Biodegradable plastics Polymer management index European Green Deal
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Progress and perspectives of point cloud intelligence
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作者 Bisheng Yang Nobert Haala Zhen Dong 《Geo-Spatial Information Science》 SCIE EI CSCD 2023年第2期189-205,共17页
With the rapid development of reality capture methods,such as laser scanning and oblique photogrammetry,point cloud data have become the third most important data source,after vector maps and imagery.Point cloud data ... With the rapid development of reality capture methods,such as laser scanning and oblique photogrammetry,point cloud data have become the third most important data source,after vector maps and imagery.Point cloud data also play an increasingly important role in scientific research and engineering in the fields of Earth science,spatial cognition,and smart cities.However,how to acquire high-quality three-dimensional(3D)geospatial information from point clouds has become a scientific frontier,for which there is an urgent demand in the fields of surveying and mapping,as well as geoscience applications.To address the challenges mentioned above,point cloud intelligence came into being.This paper summarizes the state-of-the-art of point cloud intelligence,with regard to acquisition equipment,intelligent processing,scientific research,and engineering applications.For this purpose,we refer to a recent project on the hybrid georeferencing of images and LiDAR data for high-quality point cloud collection,as well as a current benchmark for the semantic segmentation of high-resolution 3D point clouds.These projects were conducted at the Institute for Photogrammetry,the University of Stuttgart,which was initially headed by the late Prof.Ackermann.Finally,the development prospects of point cloud intelligence are summarized. 展开更多
关键词 Point cloud big data point cloud intelligence semantic labeling structured modeling machine learning
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Solving the inverse grating problem by white light interference Fourier scatterometry 被引量:8
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作者 Valeriano Ferreras Paz Sandy Peterhansel +1 位作者 Karsten Frenner Wolfgang Osten 《Light(Science & Applications)》 SCIE EI CAS 2012年第1期17-23,共7页
Scatterometry is a well-established,fast and precise optical metrology method used for the characterization of sub-lambda periodic features.The Fourier scatterometry method,by analyzing the Fourier plane,makes it poss... Scatterometry is a well-established,fast and precise optical metrology method used for the characterization of sub-lambda periodic features.The Fourier scatterometry method,by analyzing the Fourier plane,makes it possible to collect the angle-resolved diffraction spectrum without any mechanical scanning.To improve the depth sensitivity of this method,we combine it with white light interferometry.We show the exemplary application of the method on a silicon line grating.To characterize the sub-lambda features of the grating structures,we apply a model-based reconstruction approach by comparing simulated and measured spectra.All simulations are based on the rigorous coupled-wave analysis method. 展开更多
关键词 Fourier scatterometry inverse problem optical sub-lambda metrology RCWA white light interference
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Encapsulating segment-like antimony nanorod in hollow carbon tube as long-lifespan,high-rate anodes for rechargeable K-ion batteries 被引量:20
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作者 Wen Luo Feng Li +4 位作者 Weiran Zhang Kang Han Jean-Jacques Gaumet Hans-Eckhardt Schaefer Liqiang Mai 《Nano Research》 SCIE EI CAS CSCD 2019年第5期1025-1031,共7页
K-ion battery (KIB) is a new-type energy storage device that possesses potential advantages of low-cost and abundant resource of potassium.To develop advanced electrode materials for accommodating the large size and h... K-ion battery (KIB) is a new-type energy storage device that possesses potential advantages of low-cost and abundant resource of potassium.To develop advanced electrode materials for accommodating the large size and high activity of potassium ion is of great interests.Herein,a segment-like antimony (Sb) nanorod encapsulated in hollow carbon tube electrode material (Sb@HCT) was prepared.Beneficial from the virtue of abundant nitrogen doping in carbon tube,one-dimensional and hollow structure advantages,Sb@HCT exhibits excellent potassium storage properties:in the case of potassium bis(fluorosulfonyl)imide (KFSI) electrolyte,Sb@HCT displays a reversible capacity of up to 453.4 mAh·g^-1 at a current density of 0.5 A·g^-1 and good rate performance (a capacity of 211.5 mAh·g^-1 could be achieved at an ultrahigh rate of 5 A·g^-1).Additionally,Sb@HCT demonstrates excellent long-cycle stability at a current density of 2 A·g^-1 over 120 cycles.Meanwhile,electrolyte optimization is an effective strategy for greatly improving electrochemical performance.Through ex-situ characterizations,we disclosed the potassiation of Sb anode is quite reversible and undergoes multistep processes,combining solid solution reaction and two-phase reaction. 展开更多
关键词 K-ion battery ANTIMONY anode hollow carbon TUBE encapsulation electrolyte optimizati on potassium storage mechanism
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