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Ultrafine-grained Ti6Al7Nb-xCu alloy with ultrahigh strength and exceptional biomedical properties

Journal of Materials Science & Technology 2023年第33期164卷 68-78页

作者： Yi Li Hai Wang konrad Koenigsmann Hui Liu Shuyuan Zhang Ling Ren Ke Yang Shi-changxu Innovation Center for Advanced Materials Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China University of Chicago ChicagoIL 60637USA Binzhou Institute of Technology Shandong Key Laboratory of Advanced Aluminum Materials and TechnologyBinzhou 256606China

Grain refinement has been found to be able to improve the strength of metals without reducing their plasticity or *** this work,ultrafine-grained Ti6Al7Nb-xCu(x=0,3 wt%,6 wt%,9 wt%)alloys were fabricated based on the clinically used Ti6Al7Nb alloy via Cu alloying fabrication strategy combined with dynamic recrystallization(DRX)from martensite during hot *** results indicate that Cu alloying is not only effective in reducing the width of martensite laths after quenching in theβphase region but also increases the nucleation rate of DRX during the high-temperature ***,the Ti2Cu phase that precipitates from the matrix can pin the grain boundaries and inhibit their growth during the high-temperature *** optimal Cu concentration of Ti6Al7Nb-xCu alloy is determined to be 6 wt%,and the optimal deformation temperature is determined to be 750°*** this Cu content and deformation temperature,the grain size is only 270 nm,the tensile strength is up to 1266±10 MPa,and the elongation is 17%.Compared with the commercial Ti6Al7Nb alloy,the ultrafine-grained Ti6Al7Nb-6Cu alloy has better overall mechanical properties,good biocompatibility,and unique antibacterial *** work provides a theoretical basis for fabricating the new antibacterial titanium-based alloys with high strength.

关键词： High strength titanium alloy Ultrafine grain Antibacterial Dynamic recrystallization

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Natural variation in social conditions affects male mate choosiness in the amphipod Gammarus roeselii

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Current Zoology 2022年第4期68卷 459-467页

作者： konrad Lipkowski Sophie Steigerwald Lisa M Schulte Carolin Sommer-Trembo Jonas Jourdan Department of Wildlife/Zoo-Animal-Biology and Systematics Institute for EcologyEvolution and Diversity Goethe University FrankfurtMaxvon-Laue-Straße 13Frankfurt am MainD-60438Germany Department of Environmental Science Stockholm UniversitySvante Arrheniusväg 8StockholmSE-11418Sweden Zoological Institute University of BaselVesalgasse 1BaselCH-4051Switzerland Department of Aquatic Ecotoxicology Institute for EcologyEvolution and DiversityGoethe University Frankfurt am MainFrankfurt am MainGermany

The extent of male mate choosiness is driven by a trade-off between various environmental factors associated with the costs of mate acquisition,quality assessment and opportunity *** knowledge about natural variation in male mate choosiness across different populations of the same species,however,remains *** this study,we compared male mate choosiness across 10 natural populations of the freshwater amphipod Gammarus roeselii(Gervais 1835),a species with overall high male mating investments,and evaluated the relative influence of population density and sex ratio(both affecting mate availability)on male mate *** investigated amplexus establishment after separating mating pairs and presenting focal males with a novel,size-matched female from the same *** analysis revealed considerable effects of sex ratio and(to a lesser extent)population density on time until amplexus establishment(choosiness).Male amphipods are able to perceive variable social conditions(e.g.,sex ratio)and modify their mating strategy accordingly:We found choosiness to be reduced in increasingly male-biased populations,whereas selectivity increases when sex ratio becomes female *** this,our study expands our limited knowledge on natural variations in male mate choosiness and illustrates the importance of sex ratio(i.e.,level of competition)for male mating decisions in natural *** for variation in sex ratios,therefore,allows envisioning a distinctive variation of choosiness in natural populations and highlights the importance of considering social background information in future behavioral studies.

关键词： amplexus Crustacea local adaptation mate choice population density sex ratio

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MEASUREMENT OF ADHESION FORCES IN AIR WITH THE VIBRATION METHOD

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China Particuology 2005年第1期3卷 3-9页

作者： Siegfried Ripperger konrad Hein Lehrstuhl für Mechanische Verfahrenstechnik Technische Universit(a|¨)t Kaiserslautern67653 Kaiserslautern Germany Lehrstuhl für Mechanische Verfahrenstechnik Technische Universit(a|¨)t Dresden 01062 Dresden Germany

The vibration method represents a practical method for the measurement of adhesion forces and adhesion force distributions. This method causes sinusoidally alternating stresses and yields detachment and contact forces between particles and substrate of the same order of magnitude. Alternating contact forces of the vibration method can cause an adhesion force intensification through flattening of asperities. The measuring principle of the vibration method and the analysis of experimental results are described in the article. Normal adhesion forces (pull-off forces) are measured using the vibration method and the colloidal probe technique. The results of both methods show good agreement for small particle sizes. The influence of the detachment force direction is shown by comparing tangential and normal adhesion forces measured using particle reentrainment in a turbulent air flow and the vibration method, respectively. The surface roughness of the substrate and the relative humidity are shown to significantly influence the measured adhesion forces. For the calculation of the adhesion forces, an approach by Rabinovich was combined with approximations of plastic micro asperity flattening. The Rabinovich approach accounts for roughness effects on the van der Waals force by incorporating the rms roughness of the interacting surfaces, rms-values of the particles and substrates were measured with atomic force microscopy at different scanning areas.

关键词： adhesion force vibration method roughness

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Cathodic activated stainless steel mesh as a highly active electrocatalyst for the oxygen evolution reaction with self-healing possibility

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Journal of Energy Chemistry 2020年第10期29卷 153-160页

作者： Gui-Rong Zhang Liu-Liu Shen Patrick Schmatz konrad Krois Bastian J.M.Etzold Ernst-Berl-Institut für Technische und Makromolekulare Chemie Technische Universit鋞Darmstadt64287 DarmstadtGermany

The oxygen evolution reaction(OER)represents one of the major bottlenecks for broad-based applications of many clean energy storage/conversion *** key to solving this problem lies in developing high-performing,cost effective and stable catalysts for the ***,we demonstrate that ubiquitous stainless steel mesh(SSM)materials activated by a facile cathodization treatment can be employed as a high performing OER catalyst,as showcased by the impressively low overpotentials of 275 and 319 mV to reach the benchmark current densities of 10 and 100 mA cm^−2(1.0 M KOH),*** SSM also exhibits excellent performance in a two-electrode water electrolyzer,which requires a low cell voltage of 1.58 at 10 mA cm^−2 and outperforms many of water electrolyzers using earth-abundant OER ***,cathodized SSM with minor performance degradation after the stability test can also be readily healed by subjecting it to an additional cathodization *** is disclosed that the superior performance of cathodized SSMs stems from the surface enrichment of OER active Ni(oxy)hydroxide,facile gas-bubble removal and transportation over the unique mesh-structured surfaces,while the abundant reservoir of nickel in the bulk allows healing of the catalyst by a facile cathodization.

关键词： Oxygen evolution reaction Water splitting Stainless steel mesh Cathodization Mass transfer limitation Self-healing

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A Review on Active Customers'Participation in Smart Grids

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Journal of Modern Power Systems and Clean Energy 2023年第1期11卷 3-16页

作者： konrad Schmitt Rabindra Bhatta Manohar Chamana Mahtab Murshed Ilham Osman Stephen Bayne Luciane Canha Electrical and Computer Engineering Department Texas Tech UniversityLubbockTX79409USA Wind Energy Program Texas Tech UniversityLubbockTX79409USA Electromechanical and Power Systems Department Federal University of Santa MariaSanta MariaRS97105-900Brazil Design Release Engineer at Electrification and Power conversion General MotorsGM Tech Center RoadWarrenMI48092USAl IEEE

Industrial,commercial,and residential facilities are progressively adopting automation and generation *** having flexible demand and renewable energy generation,traditional passive customers are becoming active participants in electric power system *** profound coordination among grid operators and active customers,the facilities’capability for demand response(DR)and distributed energy resource(DER)management will be valuable asset for ancillary services(ASs).To comply with the increasing demand and flexible energy,utilities urgently require standards,regulations,and programs to efficiently handle load-side resources without trading off stability and *** study reviews different types of customers’flexibilities for DR,highlighting their capabilities and limitations in performing local ancillary services(LASs),which should benefit the power grid by profiting from it through incentive *** financial incentives and techniques employed around the world are presented and *** potential barriers in technical and regulatory aspects are successfully identified and potential solutions along with future guidance are discussed.

关键词： Active distribution network(ADN) ancillary services energy management flexible demand resiliency

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Contrasting responseS of hoverflies and wild bees to habitat structure and land use change in a tropical landscape （southern Yunnan, SW China）

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Insect Science 2012年第6期19卷 666-676页

作者： Ling-Zeng Meng konrad Martin Jing-Xin Liu Frank Burger Jin Chen University of Hohenheim Institute of Plant Production and Agroecology in the Tropics and Subtropics(380b)StuttgartGermany Xishuangbanna Tropical Botanical Garden the Chinese Academy of SciencesMenglaYunnan 666303China Natural History Museum of Erfurt Germany

The response of insects to monoculture plantations has mainly proceeded at the expense of natural forest areas, and is an outstanding and important issue in ecology and conservation biology, with pollination services declined around the world. In this study, species richness and distribution of hoverfly and wild bee communities were investigated in a changing tropical landscape in southern Yunnan, south-west China by Malaise traps periodically from 2008 to 2009. Species were recorded from the traditional land use types （natural forest, grassland, shrubland and rice field fallows）, and from recently established rubber plantations of different ages. Hoverflies （total 53 species） were most common in young successional stages of vegetation, including rice field fallow and shrubland. Species richness was highest in rice field fallows and lowest in forests and showed a highly significant relationship with the number of forb species and ground vegetation cover. In contrast, the highest richness of wild bees （total 44 species） was recorded from the natural forest sites, which showed a discrete bee community composition compared to the remaining habitat types. There was no significant relationship between the bee species richness and the environmental variables, including the numbers of different plant life forms, coverage of canopy and ground vegetation, successional age of vegetation and land use type. At the landscape scale, open land use systems, including young rubber plantations, are assumed to increase the species richness of hoverflies; however, this might decrease wild bee diversity. The present land use change by rubber cultivation can be expected to have negative impacts on the native wild bee communities.

关键词： Apidae insects pollinators rubber plantations Syrphidae tropical forest

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Investigation of fundo-antral reflex in human beings

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World Journal of Gastroenterology 2005年第42期11卷 6676-6680页

作者： Satish SC Rao Anjana Kumar Brent Harris Bruce Brown konrad S Schulze Department of Internal Medicine University of Iowa Carver College of Medicine Iowa City Iowa United States

AIM： To examine the sensory and motor response（s） of the stomach following fundic distention and to assess whether cholinergic mechanisms influence these responses. METHODS： Fundic tone, gastric sensory responses and antral motility were evaluated in eight healthy volunteers after a probe with two sensors was placed in the antrum and a highly compliant balloon in the fundus. Isobaric balloon distentions were performed with a barostat. Study was repeated in six volunteers after intravenous atropine was given. RESULTS： Fundic antral contractions curve was higher First sensation distention induced large amplitude in all subjects. The area under the （P〈0.05） during fundic distention. was reported at 12±4 mmHg, moderate sensation at 18±4 mmHg and discomfort at 21±4 mmHg. Discomfort was associated with a decrease in antral motility. After atropine was given, the area under the curve of pressure waves and fundic tone decreased （P〈0.05）. Sensory thresholds were not affected. CONCLUSIONS： Fundic balloon distention induces an antral motor response, the fundo-antral reflex, which in part may be mediated by cholinergic mechanisms.

关键词： Gastric motility Reflex Fundo-antral reflex Sensation

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The β-relaxation in metallic glasses

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National Science Review 2014年第3期1卷 429-461页

作者： Hai Bin Yu Wei Hua Wang Hai Yang Bai konrad Samwer I. Physikalisches Institut Universit?t G?ttingen Institute of Physics Chinese Academy of Sciences

Focusing on metallic glasses as model systems, we review the features and mechanisms of the β-relaxations,which are intrinsic and universal to supercooled liquids and glasses, and demonstrate their importance in understanding many crucial unresolved issues in glassy physics and materials science, including glass transition phenomena, mechanical properties, shear-banding dynamics and deformation mechanisms,difusion and the breakdown of the Stokes–Einstein relation as well as crystallization and stability of *** illustrate that it is an atractive prospect to incorporate these insights into the design of new glassy materials with extraordinary properties. We also outline important questions regarding the nature ofβ-relaxations and highlight some emerging research directions in this still-evolving ield.

关键词： metallic glass β-relaxation glass transition shear transformation zone shear band difusion stability ultrastable glass

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Simulation Architecture for Modelling Interaction Between User and Elbow-articulated Exoskeleton

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Journal of Bionic Engineering 2017年第4期14卷 706-715页

作者： Bas J. de Kruif Emilio Schmidhauser konrad S. Stadler Leonard W. O'Sullivan School of Design & Health Research Institute University of Limerick Limerick Ireland Netherlands Organisation for Applied Scientific Research Equipment for Additive Manufacturing 5600 HE Eindhoven The Netherlands Zurich University of Applied Sciences School of Engineering 8401 CH Winterthur Switzerland

The aim of our work is to improve the existing user-exoskeleton models by introducing a simulation architecture that can simulate its dynamic interaction, thereby altering the initial motion of the user. A simulation architecture is developed that uses the musculoskeletal models from OpenSim, and that implements an exoskeleton control algorithm and human response model in Matlab. The musculoskeletal models need to be extended with the response of a user to external forces to simulate the dy- namic interaction. A set of experiments was performed to fit this response model. A validation test showed that more than 80% of the variance of the motion could be explained. With the human response model in the combined simulation architecture, a simulation in which an object connects with the exoskeleton or with the human is performed. The effect of the exoskeleton on, among others, muscle excitation and altered motion can be assessed with this architecture. Our work can be used to better predict the effect an exoskeleton has on the user.

关键词： human-exoskeleton modelling human response modelling exoskeleton musculoskeletal system exoskeletondesign

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Light metal compound casting

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Science China(Technological Sciences) 2009年第1期52卷 46-51页

作者： konrad J. M. PAPIS Joerg F. LOEFFLER Peter J. UGGOWITZER ETH Zurich Laboratory of Metal Physics and Technology Wolfgang-Pauli-Str. 10

‘Compound casting’simplifies joining processes by directly casting a metallic melt onto a solid metal substrate. A continuously metallurgic transition is very important for industrial applications, such as joint structures of spaceframe constructions in transport industry. In this project, ‘compound casting’ of light metals is investigated, aiming at weight-saving. The substrate used is a wrought aluminium alloy of type AA5xxx, containing magnesium as main alloying element. The melts are aluminium alloys, containing various alloying elements (Cu, Si, Zn), and magnesium. By replacing the natural oxygen layer with a zinc layer, the inherent wetting difficulties were avoided, and compounds with flawless interfaces were successfully produced (no contraction defects, cracks or oxides). Electron microscopy and EDX investigations as well as optical micrographs of the interfacial areas revealed their continu- ously metallic constitution. Diffusion of alloying elements leads to heat-treatable microstructures in the vicinity of the joining interfaces in Al-Al couples. This permits significant variability of mechanical properties. Without significantly cutting down on wettability, the formation of low-melting intermetallic phases (Al3Mg2 and Al12Mg17 IMPs) at the interface of Al-Mg couples was avoided by applying a protective coating to the substrate.

关键词： compound casting aluminium alloys magnesium alloys interface structure

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