检索结果-南通市图书馆

Strong coupling,charm- and bottom-quark masses from electron-positron annihilation

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Physics C 2010年第6期34卷 675-679页

作者： J.H.k.hn Institut für Theoretische Teilchenphysik Karlsruhe Institute of Technology

The cross section for electron-positron annihilation into hadrons allows for a precise determination of the strong coupling constant and the charm- and bottom-quark masses. Recent theoretical and experimental results ... 详细信息

关键词： strong coupling quark masses

Bio-inspired tetracarbene compounds as a new family of energy saving catalysts

在线全文

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2023年第4期79卷 559-561页

作者： Bo Zhang Fritz E.k.hn CAS key Laboratory of Science and Technology on Applied Catalysis Dalian Institute of Chemical PhysicsChinese Academy of SciencesDalian 116023LiaoningChina' University of Chinese Academy of Science Beijing 100049China Molecular Catalysis Catalysis Research Center and Department of ChemistrySchool of Natural SciencesTechnical University of MunichLichtenbergstr 485748 Garching bei MünchenGermany

Efficient use of energy is a pressing *** of chemical processes is currently an important target for energy *** chemical processes are independent of pathways with respect to the final energy output or consumption,the application of catalysts can reduce involved activation energies considerably and therefore save large amounts of energy.

关键词： Catalysis Iron Carbenes Multidentate ligands

Organorhenium(Ⅶ) oxides

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2006年第Z1期25卷 411-421页

作者： k.hn Fritz E. JAIN kavita R. Department für Chemie der Technischen Universitt München Lichtenbergstrasse 4 D-85747 Garching bei München Germany

Methyltrioxorhenium (MTO) and its derivatives were utilized as catalysts for a broad variety of organic reactions after the discovery of an easy synthetic access way to this class of compounds. Among the numerous characterization techniques, 17O-NMR spectroscopy and vibrational spectroscopy were exemplary discussed. The immobilization of MTO and its derivatives is of significant current interest as is the synthesis of chiral derivatives.

关键词： catalysis epoxidation immobilization olefination rhenium

Hydromechanical behaviors of andesite under different stress states during fluid injection

在线全文

学校读者我要写书评

暂无评论

Journal of Rock Mechanics and Geotechnical Engineering 2021年第4期13卷 727-744页

作者： Miao He Qi Li Xiaying Li Liang Xu Michael k.hn State key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China University of Chinese Academy of Sciences Beijing100049China Fluid Systems Modelling Section GFZ German Research Centre for GeosciencesPotsdamGermany Institute of Earth and Environmental Science University of PotsdamPotsdamGermany

Water reinjection into the formation is an indispensable operation in many energy engineering *** operation involves a complex hydromechanical(HM)coupling process and sometimes even causes unpredictable disasters,such as induced *** is acknowledged that the relative magnitude and direction of the principal stresses significantly influence the HM behaviors of rocks during ***,due to the limitations of current testing techniques,it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions,such as in triaxial extension stress *** this end,a numerical study of HM changes in rocks during injection under different stress states is *** this model,the saturated rock is first loaded to the target stress state under drainage conditions,and then the stress state is maintained and water is injected from the top to simulate the formation injection *** attention is given to the difference in HM changes under triaxial compression and extension *** includes the differences in the pore pressure propagation,mean effective stress,volumetric strain,and stress-induced *** numerical results demonstrate that the differential stress will significantly affect the HM behaviors of rocks,but the degree of influence is different under the two triaxial stress *** HM changes caused by the triaxial compression stress states are generally greater than those of extension,but the differences decrease with increasing differential stress,indicating that the increase in the differential stress will weaken the impact of the stress state on the HM *** addition,the shear failure potential of fracture planes with various inclination angles is analyzed and summarized under different stress *** is recommended that engineers could design suitable injection schemes according to different tectonic stress fields versus fault occurrence to reduce the risk of

关键词： Water reinjection Stress state Hydromechanical(HM)coupling Injection-induced seismicity Numerical modeling

Laser additive manufactured high-performance Fe-based composites with unique strengthening structure

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第30期89卷 242-252页

作者： Hongyu Chen Dongdong Gu Liang Deng Tiwen Lu Uta k.hn konrad kosiba College of Materials Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China Jiangsu Provincial Engineering Laboratory for Laser Additive Manufacturing of High-Performance Metallic Components Nanjing University of Aeronautics and AstronauticsNanjing 210016China Leibniz IFW Dresden Institute for Complex MaterialsP.O.Box 270116D-01069 DresdenGermany

Steel matrix composites(SMCs),reinforced by ceramic particles,have received a consistent attention in recent *** conventional methods to prepare SMCs is generally challenging,and the mechanical properties of conventionally fabricated SMCs are *** this study,we successfully fabricated highperformance SMCs by laser powder bed fusion(LPBF)of a composite powder consisting of Fe-based alloy powder and submicron-sized WC *** effect of laser energy density on the phase formation,microstructural evolution,overall density and resulting mechanical properties of LPBF-fabricated composites was *** present results show that a novel Fe_(2)W_(4)C carbidic network precipitates in the solidified microstructure entailing segregations along the boundaries of cellular *** presence of this carbidic network hampers the growth of sub-grains even at elevated temperatures,and hence,stabilizes the grain size though prepared at a broad range of different energy *** exact distribution of the Fe_(2)W_(4)C carbides depends on the employed laser energy densities,as for instance they are more uniformly distributed at higher energy *** density of LPBF samples reaches the maximum value of 99.4%at 150 J/mm^(3).In this parameter set,high microhardness of~753 HV,compression strength of~3350 MPa and fracture strain of~24.4%are *** enhanced mechanical properties are ascribed to less metallurgical defects,higher volume fraction of the martensitic phase and increasing pile-up dislocations resulting from the pinning effect by Fe_(2)W_(4)C carbide.

关键词： Laser additive manufacturing Laser powder bed fusion Steel matrix composite Microstructures Mechanical properties

Glass-forming ability, phase formation and mechanical properties of glass-forming Cu-Hf-Zr alloys

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2019年第5期29卷 576-581页

作者： k.kosiba kaikai Song U.k.hn Gang Wang S.Pauly Leibniz IFW Dresden Institute for Complex Materials School of Mechanical Electrical & Information Engineering Shandong University (Weihai) Laboratory for Microstructures Institute of Materials Shanghai University

The influence of Hf additions on the glass-forming ability（GFA）,phase formation and mechanical properties of Cu;Hf;Zr;（x=2,5,10,20 at.%）alloys has been systematically *** report on a distinct correlation between phase formation and GFA of Cu;Zr;-based *** additions of Hf reduce the thermal stability of the high-temperature B2Cu（Hf,Zr）phase,while the thermal stability of the corresponding undercooled melt is *** GFA of these alloy series gradually raises up to 10 at.%Hf,whereas at 20 at.%Hf,the GFA is drastically lowered,since the B2Cu（Hf,Zr）phase becomes unstable and the precipitation of the lowtemperature equilibrium phases is *** interrelation determines the microstructure and results in the formation of Cu-Hf-Zr-based bulk metallic glass *** composites not only show appreciable macroscopic plastic strain,but also high yield strength.

关键词： Metallic glasses Glass-forming ability Composites Continuous cooling transformation (CCT) diagram Mechanical properties

Estimation of Throughfall Erosivity in a Highly Diverse Forest Ecosystem Using Sand-Filled Splash Cups

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Journal of Earth Science 2010年第6期21卷 897-900页

作者： Christian Geiβler Peter k.hn 史学正 Thomas Scholten Chair of Physical Geography and Soil Science Eberhard Karls University Tübingen Institute of Soil Science Chinese Academy of Sciences

Sand-fflled splash cups were used to study the erosive power of rainfall and throughfall in the humid subtropics of Southeast China. The splash cup measurements yielded precise and reproducible results under both open field conditions and forest vegetation. The splash cups were exposed to specific forest stands of different ages and to selected species （Schima superba, Castanopsis eyrei, Daphniphyllum oldhamii, Lithocarpus glaber） in the Gutianshan （古田山） National Nature Reserve （GNNR）. The results of the measurements under forest vegetation show that the erosive power of throughfall drops to be 2.59 times higher compared to the open field. This accentuates the importance of shrub, herb and litter layers in forest ecosystems to protect the soil against erosion. Coalescing drops from leaves and branches （drips） are responsible for this notable gain in erosive power. Moreover, differences in sandloss between the investigated tree species （deciduous, evergreen） revealed that the erosion potential and the spatial heterogeneity of throughfall are species-specific. This highlights the importance of selecting specific species for afforestation projects considering the prevention of soil erosion.

关键词： Biodiversity and Ecosystem Functioning (BEF)-China biodiversity soil erosion soil erosion experiment splash cup throughfall erosivity.

Plastic deformation of a Zr-based bulk metallic glass fabricated by selective laser melting

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2021年第1期60卷 139-146页

作者： L.Deng k.kosiba R.Limbach L.Wondraczek U.k.hn S.Pauly IFW Dresden Institute for Complex MaterialsHelmholtzstraße 20D-01069DresdenGermany Otto Schott Institute of Materials Research University of JenaFraunhoferstraße 6D-07743JenaGermany University of Applied Sciences Aschaffenburg Würzburger Straße 45D-63743AschaffenburgGermany

Fully amorphous Zr_(52.5)Cu_(17.9)Ni_(14.6)Al_(10)Ti_(5) bulk metallic glass(BMG) samples with a relative density exceeding 98% were fabricated via selective laser melting(SLM).High fracture stresses of around1700 MPa and a reproducible plastic strain of about 0.5% were obtained for cylindrical SLM *** analysis of the observed serrations during compressive loading implies that the shear-band dynamics in the additively manufactured samples distinctly differ from those of the as-cast *** phenomenon appears to originate from the presence of uniformly dispersed spherical pores as well as from the more pronounced heterogeneity of the glass itself as revealed by instrumented *** these heterogeneities,the shear bands are straight and form in the plane of maximum shear *** manufacturing,hence,might not only allow for producing large BMG samples with complex geometries but also for manipulating their deformation behaviour through tailoring porosity and structural heterogeneity.

关键词： Powder bed fusion Selective laser melting Bulk metallic glass Serrated flow Heterogeneity

The effects of 12 weeks of functional strength training on muscle strength,volume and activity upon exposure to elevated Gz forces in high-performance aircraft personnel

在线全文

学校读者我要写书评

暂无评论

Military Medical Research 2021年第4期8卷 481-489页

作者： Monika Rausch Frank Weber Sven k.hn Carla Ledderhos Christoph Zinner Billy Sperlich Multinational Medical Coordination Centre/European Medical Command Andernacher Strasse 10056070 KoblenzGermany. German Air Force Center of Aerospace Medicine 82256 FuerstenfeldbruckGermany. Department of Radiology Bundeswehr Central Hospital56072 KoblenzGermany. Department of Sport University of Applied Sciences for Police and Administration of Hesse65199 WiesbadenGermany. Integrative&Experimental Exercise Science&Training Institute of Sport ScienceUniversity of Wuerzburg97082 WuerzburgGermany

Background:Technological advancements in modern military and acrobatic jet planes have resulted in extraordinary psychophysiological loads being exerted upon flying personnel,including inducing neck and back *** purpose of this study was to examine the effects of 12 weeks of functional strength training on 1)the volume and strength of the neck and shoulder muscles and 2)muscular activity upon exposure to helmets of different masses and elevated Gz forces in a long-arm centrifuge in high-performance aircraft ***:Eighteen participants underwent 12 weeks of functional strength training(n=12)or the control protocol(n=6)without additional strength ***-and post-intervention tests included evaluations of isometric strength of the head extensor muscles,flexion,and lateral flexion and rotation,as well as magnetic resonance imaging(MRI)to measure the volume of the ***,***,and deep neck ***,during a long-arm centrifuge(+1.4 and+3Gz)protocol,the muscular activity levels of the ***,*** and *** spinae muscles were assessed without a flight helmet,with a helmet,and with a helmet and night vision *** participant’s perception of muscular strain was noted immediately after the long-arm centrifuge ***:The maximal isometric strength in all exercises and muscle volumes increased in the training group but not the control group(Pk muscles induced by the long-arm centrifuge did not differ between the ***:Twelve weeks of functional strength training improves the maximal isometric strength and volume of neck and shoulder m

关键词： Fighter pilots Long-arm centrifuge Muscular strain Strength training Neck muscle High-performance aircraft Gz forces