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Welding mechanics for advanced component safety assessment

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Frontiers of Materials Science 2011年第2期5卷 224-235页

作者： dieter SIEGELE Fraunhofer Institute for Mechanics of Materials IWM WShlerstr. 11 79108 Freiburg Germany

Numerical methods are nowadays a useful tool for the calculation of distortion and residual stresses as a result from the welding process. Modern finite element codes not only allow for calculation of deformations and stresses due to the welding process but also take into account the change of microstructure due to different heating and cooling rates. As an extension to the pure welding simulation, the field of welding mechanics combines the mechanics and the material behaviour from the welding process with the assessment of service behaviour of welded components. In the paper, new results of experimental and numerical work in the field of welding mechanics are described. Through examples from automotive, nuclear and pipe-line applications it is demonstrated that an equilibrated treatment and a close interaction of ＂process＂, ＂properties＂ and ＂defects＂ are necessary to come up with an advanced fitness-forservice assessment of welded components.

关键词： welding simulation residual stress defect assessment fracture mechanics

Lab experiments on the innovative rapid thick strip casting process

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International Journal of Minerals,Metallurgy and Materials 2012年第5期19卷 391-398页

作者： Richard Nagy dieter Senk Department of Ferrous Metallurgy IEHK RWTH Aachen UniversityAachen 52056Germany

Rapid thick strip casting （RTSC） by Anton Hulek, Inventmetall, is an innovative concept for the production of hot strips with a final as-cast thickness of about 25 mm before rolling. The innovation of the mechanism consists in a vertical mould performing a caterpillar motion. This moving mould has an unconventional parallelogram-shaped cross-section. The conventional rectangular shape is formed in the shaping machine, which is placed straight below the mould. Further elements of the technology are state-of-the-art. For the investigation of this new casting system theoretical calculations were complemented with practical experiments. The investigation focused mainly on two key aspects： the characteristics of the mould and the shaping process. For the practical analysis a static mould with three pairs of elements in laboratory scale was developed and commissioned by the Dept. of Ferrous Metallurgy @ RWTH Aachen University. The shaping experiments were carried out in model scale with two different materials and in variable boundary conditions. The results of these experiments delivered important mechanical as well as thermal informations about the casting system.

关键词： continuous casting rapid solidification strip metal moulds near-net-shape casting

Natural water purification and water management by artificial groundwater recharge

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2008年第3期9卷 221-226页

作者： Klaus-dieter BALKE Institute for Geosciences University of TübingenSigwartstr.10D-72076 TübingenGermany

Worldwide,several regions suffer from water scarcity and *** infiltration and subsurface storage of rain and river water can reduce water *** groundwater recharge,possibly combined with bank filtration,plant purification and/or the use of subsurface dams and artificial aquifers,is especially advantageous in areas where layers of gravel and sand exist below the earth's *** infiltration of surface water into the uppermost aquifer has qualitative and quantitative *** contamination of infiltrated river water will be reduced by natural *** minerals,iron hydroxide and humic matter as well as microorganisms located in the subsurface have high decontamination *** this,a final water treatment,if necessary,becomes much easier and *** quantitative effect concerns the seasonally changing river discharge that influences the possibility of water extraction for drinking water *** changes can be equalised by seasonally adapted infiltration/extraction of water in/out of the aquifer according to the river discharge and the water *** method enables a continuous water supply over the whole ***,artificially recharged groundwater is better protected against pollution than surface water,and the delimitation of water protection zones makes it even more save.

关键词： Artificial groundwater recharge Natural attenuation Water management

Kinetics of hydrogen peroxide quenching following UV/H_(2)O_(2)advanced oxidation by thiosulfate,bisulfite,and chlorine in drinking water treatment

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Frontiers of Environmental Science & Engineering 2023年第12期17卷 59-69页

作者： Tianyi Chen Lizbeth Taylor-Edmonds Susan Andrews Ron hofmann Department of Civil and Mineral Engineering University of TorontoTorontoOntario M5S 1A4Canada

Residual H_(2)O_(2)from UV/H_(2)O_(2)treatment can be quenched by thiosulfate,bisulfite,and chlorine,but the kinetics of these reactions have not been reported under the full range of practical *** this study,the rates of H_(2)O_(2)quenching by these compounds were compared in different water matrices,temperatures,pH,and when using different forms of bisulfite and *** general,it was confirmed that thiosulfate would be too slow to serve as a quenching agent in most practical *** pH 7-8.5,chlorine tends to quench H_(2)O_(2)more than 20 times faster than bisulfite in the various conditions *** important observation was that in lightly-buffered water(e.g.,alkalinity of 20 mg/L as CaCO_(3)),the form of chlorine can have a large impact on quenching rate,with gaseous chlorine slowing the reaction due to its lowering of the pH,and hypochlorite having the opposite *** impacts will become less significant when water buffer capacity(i.e.,alkalinity)increases(e.g.,to 80 mg/L as CaCO_(3)).In addition,water temperature should be considered as the time required to quench H_(2)O_(2)by chlorine at 4℃is up to 3 times longer than at 20℃.

关键词： UV/H_(2)O_(2) H_(2)O_(2) quenching Chlorine type Water alkalinity Temperature

Eigenvalue sensitivity analysis based on the transfer matrix method

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International Journal of Mechanical System Dynamics 2021年第1期1卷 96-107页

作者： dieter Bestle Engineering Mechanics and Vehicle Dynamics Brandenburg University of Technology Cottbus‐SenftenbergCottbusGermany

For linear mechanical systems,the transfer matrix method is one of the most efficient modeling and analysis ***,in contrast to classical mod-eling strategies,the final eigenvalue problem is based on a matrix which is a highly nonlinear function of the ***,classical strategies for sensitivity analysis of eigenvalues *** parameters cannot be *** paper develops two specific strategies for this situation,a direct differentiation strategy and an adjoint variable method,where especially the latter is easy to use and applicable to arbitrarily complex chain or branched multibody *** the system analysis itself,it is able to break down the sensitivity analysis of the overall system to analytically determinable derivatives of element transfer matrices and recursive formula which can be applied along the transfer path of the topology *** examples of different complexity validate the proposed approach by comparing results to analytical calculations and numerical *** obtained procedure may support gradient‐based optimization and robust design by delivering exact sensitivities.

关键词： adjoint variable method direct differentiation sensitivity analysis transfer matrix method

Characterization and modeling of the temperature-dependent thermal conductivity in sintered porous silicon-aluminum nanomaterials

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Nano Research 2022年第6期15卷 5663-5670页

作者： Danny Kojda Tommy hofmann Natalia Gostkowska-Lekner Klaus Habicht Department Dynamics and Transport in Quantum Materials Helmholtz-Zentrum Berlin für Materialien und Energie GmbHBerlin D-14109Germany Institute of Physics and Astronomy University of PotsdamPotsdam D-14476Germany

Nanostructured silicon and silicon-aluminum compounds are synthesized by a novel synthesis strategy based on spark plasma sintering(SPS)of silicon nanopowder,mesoporous silicon(pSi),and aluminum *** interplay of metal-assisted crystallization and inherent porosity is exploited to largely suppress thermal *** and temperaturedependent thermal conductivity studies allow us to elucidate the impact of porosity and nanostructure on the macroscopic heat *** electron microscopy along with quantitative image analysis is applied to characterize the sample morphology in terms of domain size and interpore distance *** demonstrate that nanostructured domains and high porosity can be maintained in densified mesoporous silicon *** contrast,strong grain growth is observed for sintered nanopowders under similar sintering *** observe that aluminum agglomerations induce local grain growth,while aluminum diffusion is observed in porous silicon and dispersed nanoparticles.A detailed analysis of the measured thermal conductivity between 300 and 773 K allows us to distinguish the effect of reduced thermal conductivity caused by porosity from the reduction induced by phonon scattering at nanosized *** a modified Landauer/Lundstrom approach the relative thermal conductivity and the scattering length are *** relative thermal conductivity confirms the applicability of Kirkpatrick’s effective medium *** extracted scattering lengths are in excellent agreement with the harmonic mean of log-normal distributed domain sizes and the interpore distances combined by Matthiessen’s rule.

关键词： thermal conductivity mesoporous silicon porosity spark plasma sintering nanoscale modeling

Groundwater protection:What can we learn from Germany?

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2008年第3期9卷 227-231页

作者： Klaus-dieter BALKE Institute for Geosciences University of TübingenSigwartstr.10D-72076 TübingenGermany

For drinking water security the German waterworks proceed on a comprehensive concept,i.e.,the protection of all the regions from the recharge area to the *** includes the protection of the recharge area by a precautionary management,a safe water treatment,a strict maintenance of the water distribution network,continuous control and an intensive training of *** protection zones together with effective regulations and control play a very important *** protection zones with different restrictions in land-use are *** in reservoirs and lakes is also protected by Surface Water Protection *** the surrounding area the land-use is controlled,*** treatment is necessary if acidification happens caused by acid rain,or eutrophication caused by the inflow of *** important is the collaboration between waterworks and the farmers cultivating land in the recharge area in order to execute water-protecting ecological farming with the aim to reduce the application of fertilizers and plant protection *** financial losses have to be compensated by the waterworks.

关键词： Drinking water security Germany Groundwater protection zone Water protection

Price transmission in hog and feed markets of China

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Journal of Integrative Agriculture 2015年第6期14卷 1122-1129页

作者： ZHOU De dieter Koemle College of Economics and Management Nanjing Agricultural University Department of Agricultural Economics and Rural Development University of Gttingen

There is an increasing demand for feed as the industrialization of hog production in China. Land scarcity limits China＇s ability to continue increasing its hog production without feed imports, particularly soybean, and the feed markets are increasingly integrated into the global market. This study performs an analysis of price transmission between the hog price in China and feed prices, specifically domestic maize price and international soybean price, from January 2000 to April 2014. We identified a long-term stable equilibrium relationship between the three markets. However, further analyses show that there is no significant Granger causality between hog and feed market, and the long-run equilibrium partially results from Granger causality between the international soybean market and domestic maize market. This suggests that the domestic hog market has been distorted by different policies. The results also indicate that the efficiency of price transmission is very low and it takes about 11 months to correct one-half of any long-run disequilibrium for the hog market in China. Therefore, to stabilize hog price in China, only market intervention to regulate the maize and soybean markets would be insufficient and comprehensive measures need to be taken into account such as hog production modernization, agricultural insurance, epidemic surveillance etc.

关键词： soybean maize prices surveillance scarcity imports modernization insurance agricultural stabilize

A review of Palaeoarchaean felsic volcanism in the eastern Kaapvaal craton:Linking plutonic and volcanic records

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Geoscience Frontiers 2018年第3期9卷 667-688页

作者： Andrea Agangi Axel hofmann Marlina A.Elburg Department of Applied Geology Curtin UniversityBentleyWAAustralia Department of Geology University of Johannesburg JohannesburgSouth Africa

In the Kaapvaal craton of southern Africa, as well as other Archaean cratons worldwide, the progression from dominant tonalite-trondhjemite-granodiorite(TTG) to granite-monzogranite-syenogranite(GMS)rock types is interpreted to reflect progressive reworking and differentiation of the continental *** we re-evaluate the early Archaean evolution of the Kaapvaal craton and propose a unified view of the plutonic and volcanic records based on elemental and isotopic(Nd, Hf) data and zircon U-Pb *** also report new whole-rock major and trace element analyses, zircon U-Pb ages and Hf-in-zircon analyses of igneous clasts from a conglomerate of the 3.2 Ga Moodies Group of the Barberton Greenstone Belt. Many of these clasts are derived from shallow intrusive rocks of granitic composition, which are scarcely represented in outcrop. Despite alteration, the volcanic rocks can be classified based on their trace element contents into two main groups by comparison with plutonic rocks. One group has characteristics resembling TTGs: relatively low and fractionated rare earth element concentrations with no Eu anomaly and relatively low concentrations of high field strength elements(Nb mostly ≤12 ppm). The second group has GMS-like characteristics: less fractionated REE, marked negative Eu anomalies and HFSE-increasing trends with progressing fractionation(Nb ≤ 50 ppm or more, Th up to 30-40 ppm). In addition, igneous clasts of Moodies Group conglomerate have chemical, mineralogical and isotopic characteristics that link them to GMS. New analyses of some of these clasts indicate elevated high field strength elements(Nb up to 20 ppm) and_(εHf)(t)of zircon down to -3.5. These rocks imply the presence of an already differentiated felsic crust at >3.5 Ga, which has Nd and Hf model ages indicating mantle extraction ages extending back to the Eoarchaean. The combined record of plutonic and volcanic rocks of the Kaapvaal craton provides a more complex scenario than previously suggest

关键词： Archean Kaapvaal craton TTG Greenstone Barberton