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Virtual welding equipment for simulation of GMAW processes with integration of power source regulation

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Frontiers of Materials Science 2011年第2期5卷 79-89页

作者： uwe REISGEN Markus SCHLESER Oleg MOKROV Alexander ZABIROV ISF - Welding and Joining Institute RWTH Aachen University Germany

A two dimensional transient numerical analysis and computational module for simulation of electrical and thermal characteristics during electrode melting and metal transfer involved in Gas-Metal-Arc-Welding （GMAW） processes is presented. Solution of *** transient heat transfer equation is carried out using a control volume finite difference technique. The computational module also includes controlling and regulation algorithms of industrial welding power sources. The simulation results are the current and voltage waveforms, mean voltage drops at different parts of circuit, total electric power, cathode, anode and arc powers and arc length. We describe application of the model for normal process （constant voltage） and for pulsed processes with U/I and Ill- modulation modes. The comparisons with experimental waveforms of current and voltage show that the model predicts current, voltage and electric power with a high accuracy. The model is used in simulation package SimWeld for calculation of heat flux into the work-piece and the weld seam formation. From the calculated heat flux and weld pool sizes, an equivalent volumetric heat source according to Goldak model, can be generated. The method was implemented and investigated with the simulation software SimWeld developed by the ISF at RWTH Aachen University.

关键词： GMAW process simulation regulation algorithm power source

High non-photochemical quenching of VPZ transgenic potato plants limits CO_(2) assimilation under high light conditions and reduces tuber yield under fluctuating light

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Journal of Integrative Plant Biology 2022年第9期64卷 1821-1832页

作者： Günter G.Lehretz Anja Schneider Dario Leister uwe Sonnewald Department of Biology Division of BiochemistryFriedrich-Alexander-University Erlangen-NürnbergStaudtstrasse 5Erlangen91058 Germany Plant Molecular Biology Faculty of BiologyLudwig Maximilians University of MunichGroßhaderner Str.2-482152 Planegg-MartinsriedMunichGermany

Under natural conditions,photosynthesis has to be adjusted to fluctuating light *** exposed to high light dissipate excess light energy in form of heat at photosystem II(PSII)by a process called non-photochemical quenching(NPQ).Upon fast transition from light to shade,plants lose light energy by a relatively slow relaxation from *** overexpression of violaxanthin de-epoxidase(VDE),PSII subunit S(PsbS)and zeaxanthin epoxidase(ZEP)in tobacco accelerates relaxation from photoprotection,and increases photosynthetic *** Arabidopsis,expression of the same three genes(VPZ)resulted in a more rapid photoprotection but growth of the transgenic plants was *** we report on VPZ expressing potato plants grown under various light *** to tobacco and Arabidopsis,induction and relaxation of NPQ was accelerated under all growth conditions tested,but did not cause an overall increased photosynthetic rate or growth of transgenic *** yield of VPZ expressing plants was unaltered as compared to control plants under constant light conditions and even decreased under fluctuating light *** control conditions,levels of the phytohormone abscisic acid(ABA)were found to be elevated,indicating an increased violaxanthin availability in VPZ ***,the increased basal ABA levels did not improve drought tolerance of VPZ transgenic potato plants under greenhouse *** failure to benefit from improved photoprotection is most likely caused by a reduced radiation use efficiency under high light conditions resulting from a too strong NPQ *** this negative effect in the future might help to improve photosynthetic performance in VPZ expressing potato plants.

关键词： drought photosynthesis potato non-photochemical quenching xanthophyll cycle

Entropy dominated behaviors of confined polymer-nanoparticle composites

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Chinese Physics B 2012年第11期21卷 513-517页

作者：曹学正 Merlitz Holger Sommer Jens-uwe 吴晨旭 Department of Physics and ITPA Xiamen University Leibniz-Institut fr Polymerforschung Dresden

Stretched polymers will lose their possible configurations if they are mixed with nanoparticles or touch a hard wall, which leads to a strong depletion attraction responsible for the enrichment of nanoparticles near substrates. Moreover, it is found that there exists a sacrifice mechanism in confined pure polymer samples or polymer-nanoparticle mixtures, that part of the polymers, in order to reach a minimum free energy for the total system, are adsorbed on hard walls even though they lose their conformation. The current study provides a simple yet effective approach for the design of thin polymer composites.

关键词： conformation entropy nanoparticle depletion attraction thin polymer layer

Evaluating Emissions of Nitrous Oxide from Cropland Soils Under Different Rotations in Mato Grosso, Brazil:A Scenario Simulation Study

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Pedosphere 2019年第4期29卷 432-443页

作者： Katharina H. E. MEURER Eric BOENECKE uwe FRANKO Department of Ecology Swedish University of Agricultural Sciences Uppsala 75007 (Sweden) Department of Soil System Science Helmholtz Center for Environmental Research (UFZ) Halle (Saale) 06120 (Germany)

Expansion of cropland involves immense land use changes, and the resulting intensified management practices have a strong influence on the functioning of the underlying soil. For instance, increased application of nitrogen(N) fertilizer is known to enhance fluxes of nitrous oxide(N2O) from the soil to the atmosphere. The emission factor(EF) proposed by the Intergovernmental Panel on Climate Change(IPCC) assumes a linear relationship between added N and N2O-N fluxes, but it does not account for environmental factors, such as soil properties or climate. Due to the high spatial and temporal variability of N2O-N fluxes, mechanistic models are preferable in terms of extrapolation to larger scales. In this study, we evaluated simulated N2O-N fluxes from soils under agricultural use in the Brazilian state, Mato Grosso, using the CANDY(Carbon and Nitrogen Dynamics) model. A control tool was developed in order to enable the simulation of 1 650 scenarios covering different sites(soil + climate) and management regimes(crop rotation +amount of applied fertilizer + sowing and harvesting dates). Results suggested that the sites had a very strong influence on calculated emissions, which is not accounted for by static EF. Furthermore, most fertilizer-induced N2O-N fluxes derived from the scenario simulations were best described by a non-linear function. For sounder budgeting on the federal and national scale, there is still a strong need for long-term observations of continuous crop rotations and spatial distribution of soil types and their specific characteristics. The presented results provide a valuable starting point for developing further scenario simulations and adapting experimental campaigns for N2O emission study.

关键词： agricultural systems Carbon and Nitrogen Dynamics CANDY model climate emission factor management soil property soil types

Understanding source-sink interactions: Progress in model plants and translational research to crops

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Molecular Plant 2023年第1期16卷 96-121页

作者： Laise Rosado-Souza Ryo Yokoyama uwe Sonnewald Alisdair R.Fernie Max-Planck-Institute of Molecular Plant Physiology Am Mühlenberg 114476 Potsdam-GolmGermany Department of Biochemistry University of Erlangen-NurembergStaudtstrasse 591058 ErlangenGermany

Agriculture is facing a massive increase in demand per hectare as a result of an ever-expanding population and environmental *** we have learned much about how environmental conditions and diseases impact crop yield,until recently considerably less was known concerning endogenous factors,including within-plant nutrient *** this review,we discuss studies of source-sink interactions covering both fundamental research in model systems under controlled growth conditions and how the findings are being translated to crop plants in the *** this respect we detail efforts aimed at improving and/or combining C3,C4,and CAM modes of photosynthesis,altering the chloroplastic electron transport chain,modulating photorespiration,adopting bacterial/algal carbon-concentrating mechanisms,and enhancing nitrogen-and water-use ***,we discuss how modulating TCA cycle activities and primary metabolism can result in increased rates of photosynthesis and outline the opportunities that evaluating natural variation in photosynthesis may *** source,transport,and sink functions are all covered in this review,we focus on discussing source functions because the majority of research has been conducted in this ***,considerable recent evidence,alongside the evidence from classical studies,demonstrates that both transport and sink functions are also incredibly important determinants of *** thus describe recent evidence supporting this notion and suggest that future strategies for yield improvement should focus on combining improvements in each of these steps to approach yield optimization.

关键词： photosynthesis assimilate transport nitrogen-use efficiency water-use efficiency source-sink natural variance transgenic intervention

Immunomagnetic removal of cryo-damaged human spermatozoa

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Asian Journal of Andrology 2005年第1期7卷 61-69,页

作者： uwe Paasch Sonja Grunewald Katja Wuendrich Tbrsten Jope Hans-Jurgen Glander Division of Andrology Department of Dermatology University of Leipzig Leipzig D-04103 Germany

Aim: To estimate the dissipation of mitochondrial transmembrane potential (mTMR,Δψ_m) and activation of sperm caspases (aCP) as signs of apoptosis in human spermatozoa during cryopreservation and to evaluate the efficiency of immunomagnetic cell separation (MACS) of these spermatozoa via annexin V-binding. Methods: The mTMP and aCP in fresh and cryopreserved spermatozoa were detected by fluorescence microscopy and by Western blots. The sperm suspensions were divided into two sperm fractions (with intact and deteriorated membranes) by magnetic cell separation (MiniMACS, Miltenyi Biotec, Bergisch Gladbach, Germany) in dependence on their binding to superparamagnetic annexin V-microbeads (AN-MB). Results: The cryopreservation decreased the portion of spermatozoa with intact mTMP from 80.1% ± 7.2 % to 53.5 % ± 13.1% and increased the spermatozoa with activated pancaspases (aCP) from 21.8 % ± 2.6 % to 47.7 % ± 5.8 % (n = 10; mean ± SEM; P < 0.01). The activation of caspases 1, 3, 8, and 9 in the cryopreserved spermatozoa was confirmed by Western blots (n = 22). MACS reduced significantly the percentage of cryopreserved spermatozoa with dissipated mTMP to 8.1 ± 3.9 (P < 0.01) and also those with aCP to 9.3 % ± 2.2 %. Western blot analyses confirmed the increase of the activated caspase3, 9, and 8 in the AN-MB-positive fraction (P < 0.05) compared with the AN-MB-negative fraction. The MACS separation effect was confirmed by anti-annexin V-antibodies. There was no significant influence of the separation column and the magnetic field on the sperm functions. Conclusion: The cryopreservation impaired the mTMP and enhanced the activation status of caspases in human spermatozoa. The immunomagnetic sperm separation via binding of AN-MB could deplete low quality spermatozoa from cryopreserved semen samples.

关键词： spermatozoa cryopreservation immunomagnetic separation plasma membrane annexin V apoptosis caspases mitochondria

Forest edge–interior differentiation in the epiphytic lichen diversity of the forest steppe in the Khangai Mountains, Mongolia

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Journal of Plant Ecology 2014年第3期7卷 287-297页

作者： Markus Hauck uwe de Bruyn Samjaa Javkhlan Dorjburgedaa Lkhagvadorj Department of Plant Ecology Albrecht von Haller Institute of Plant SciencesGeorg August University of GöttingenUntere Karspüle 237073 GöttingenGermany Von-Müller-Straße 30 26123 OldenburgGermany Institute of Botany Mongolian Academy of SciencesZhukov Street 7Ulan Bator 51Mongolia School of Economics and Business Mongolian State University of AgricultureUlan BatorMongolia

Aims The effects of traditional land use by mobile livestock keepers on biodiversity in forest steppe ecotones are insufficiently *** are an important part of forest plant *** we analyze differences in the diversity and composition of the epiphytic lichen vegetation between the edge and the interior of Siberian larch forests in the Khangai Mountains,western Mongolia,which are highly subdivided into *** asked whether the epiphytic lichen vegetation at the forest edge differs significantly from that in the interior,whether the edge is inhabited by more nitrophilous species than the interior and whether the density of nomad camps around the forest affects epiphytic lichen *** Cover percentages of epiphytic lichen species were recorded from 20 trees per plot on 6 plots in the interior and 6 plots at the edge of Larix sibirica *** position of nomad summer camps was surveyed using Global Positioning *** were analyzed with pairwise significance tests,analysis of similarities,nonmetric multidimensional scaling and canonical correspondence *** Findings The composition of the epiphytic lichen vegetation clearly differed between the two habitats,with more species being more frequent at the edge than in the ***,there was no difference in species richness(α-diversity).The epiphyte vegetation at the edge was more uniform and characterized by lower variation of tree-levelα-diversity and lowerβ-diversity than in the *** the edge,only nitrophytic lichens were dominant,whereas in the interior,nitrophytes and acidophytes were among the dominant *** pattern is probably attributable to the spatial heterogeneity of the intensity of forest grazing and was shown to be influenced by the density of nomad summer camps in the vicinity of the ***-levelα-diversity increased with stem diameter,but high-diameter trees were *** results suggest that the present level of forest pat

关键词： alpha-diversity beta-diversity edge effect nitrophytes pastoral nomadism

Casting of microstructured shark skin surfaces and possible applications on aluminum casting parts

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China Foundry 2011年第1期8卷 62-65页

作者： Todor Ivanov Andreas Bührig-Polaczek uwe Vroomen Foundry Institute of RWTH Aachen University

Within the project "Functional Surfaces via Micro-and Nanoscaled Structures" which is part of the Cluster of Excellence "Integrative Production Technology" established and financed by the German Research Foundation (DFG),an investment casting process to produce 3-dimensional functional surfaces down to a structural size of 1μm on near-net-shape-casting parts has been *** common way to realize functional microstructures on metallic surfaces is to use laser ablation,electro discharge machining or micro *** handicap of these processes is their limited *** approach of this project to raise the efficiency is to use the investment casting process to replicate microstructured surfaces by moulding from a laser-microstructured grand master *** main research objective deals with the investigation of the single process steps of the investment casting process with regard to the moulding *** results concerning making of the wax pattern,suitability of ceramic mould and core materials for casting of an AlSi7Mg0.3 alloy as well as the knock-out behavior of the shells are *** using of the example of an intake manifold of a gasoline race car engine,a technical shark skin surface has been realized to reduce the drag of the intake *** intake manifold consists of an air-restrictor with a defined inner diameter which is microstructured with technical shark skin *** this reason the inner diameter cannot be drilled after casting and demands a very high accuracy of the casting part.A technology for the fabrication and demoulding of accurate microstructured castings are *** factors of different moulding steps of the macroscopic casting part as well as the microscopic riblet structure have been examined as well.

关键词： investment casting microstructured surfaces shark skin

Optical Transmittance and Band Gap of Ferroelectric BaTi2O5 Bulk Glass

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Chinese Physics Letters 2008年第12期25卷 4421-4424页

作者： Javed Ahmad Hidetoshi Minami Sher Alam Jianding Yu Yasutomo Arai Hiromoto uwe Institute of Materials Science University of Tsukuba Tsukuba Ibaraki 305-8573 Japan Department of Physics Bahauddin Zakariya University Multan 60800 Pakistan Advanced Materials Laboratory National Institute for Materials Science (NIMS) Tsukuba Ibaraki 305-0044 Japan Japan Aerospace Exploration Agency ISS Science Project Office 2-1-1 Sengen Tsukuba Ibaraki 305-8505 Japan

Optical transmittance and reflectance on ferroelectric BaTi2O5 glasses prepared recently by a containerless synthesis technique are measured at room temperature in the wavelength range 190-800nm. The fundamental absorption edge located around 340nm demonstrates the coloudess and transparent character of the glass. The optical band gap of 3.32eV has been estimated. The tail of the optical absorption near the fundamental absorption edge is found to follow the Urbach rule. Our analysis of the experimental spectra supports an indirect allowed interband transition between the valence band formed by O-2p orbitals and the conduction band formed by Ti-3d orbitals.

关键词： field emission molybdenum dioxide enhancement factor