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An explicit formula for the Webster torsion of a pseudo-hermitian manifold and its application to torsion-free hypersurfaces Dedicated to Professor Sheng GONG on the occasion of his 75th birthday

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Science China Mathematics 2006年第11期49卷 1662-1682页

作者： luk Hing-Sun Department of Mathematics Lady Shaw Building The Chinese University of Hong KongShatinN THong KongChina

This paper gives an explicit formula for calculating the Webster pseudo torsion for a strictly pseudoconvex pseudo-hermitian hypersurface. As applications, we are able to classify some pseudo torsion-free hypersurface... 详细信息

关键词： pseudo Herrnitian manifolds torsion formula torsion-free hypersufaces.

Formability Investigations of High-Strength Dual-Phase Steels

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Acta Metallurgica Sinica(English Letters) 2015年第12期28卷 1471-1481页

作者： Miklós Tisza Zsolt lukács Department of Materials Processing Technology Institute of Materials Science and Technology University of Miskolc

Car manufacturing is always regarded as the key industry behind sheet metal forming, and thus, the requirements of and developments in car manufacturing play a decisive role in the development of sheet metal forming. The automotive industry is faced with contradictory demands and requirements： better performance with lower consumption and less harmful emissions, more safety and comfort; these are extremely difficult to supply simultaneously with conventional materials and conventional manufacturing processes. The fulfillment of these often contradictory requirements is one of the main driving forces in the automotive industry and thus in the material and process developments in sheet metal forming, as well. In recent years, significant developments can be observed in the application of high-strength steels. In this respect, the application of various dual-phase steels is one of the best examples. However, the application of these highstrength steels often leads to formability and manufacturing problems. One formability problem is the springback occurring after sheet metal forming. In the current research, we have dealt mainly with advanced high-strength steels, primarily with dual-phase steels. When applying them, the springback phenomenon is one of the most critical issues. To reduce the tremendous amount of experimental work needed, we also applied numerical simulation using isotropic–kinematic hardening rules. The isotropic–kinematic hardening behavior of a given material in the applied Auto Form numerical package may be characterized with three independent material parameters c, v and K（a detailed explanation of their meaning will be given in the main part of this paper）. However, we found that the material data included in simulation packages for these new high-strength steels are not fully adequate. For the determination of more reliable material parameters and to achieve better simulation results, a new testing device was developed. Numerical simulations were

关键词： Springback Large-strain cyclic deformation High-strength dual-phase steels

Accurate large-scale simulations of siliceous zeolites by neural network potentials

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npj Computational Materials 2022年第1期8卷 1662-1673页

作者： Andreas Erlebach Petr Nachtigall lukášGrajciar Department of Physical and Macromolecular Chemistry Charles UniversityHlavova 812800Prague 2Czech Republic

The computational discovery and design of zeolites is a crucial part of the chemical *** highly accurate while computational feasible protocol for identification of hypothetical siliceous frameworks that could be targeted experimentally is a great *** tackle this challenge,we trained neural network potentials(NNP)with the SchNet architecture on a structurally diverse database of density functional theory(DFT)*** database was iteratively extended by active learning to cover not only low-energy equilibrium configurations but also high-energy transition *** demonstrate that the resulting reactive NNPs retain DFT accuracy for thermodynamic stabilities,vibrational properties,as well as reactive and non-reactive phase *** a showcase,we screened an existing zeolite database and revealed>20k additional hypothetical frameworks in the thermodynamically accessible range of zeolite ***,our NNPs are expected to be essential for future high-throughput studies on the structure and reactivity of siliceous zeolites.

关键词： synthesis zeolite zeolites

A procedural footprint enhancement of global topographic surface with multiple levels of detail

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International Journal of Digital Earth 2020年第4期13卷 527-545页

作者： lukáš Brůha Jan Kolář Faculty of Science Department of Applied Geoinformatics and CartographyCharles University in PraguePragueCzech Republic Grifinor Project CopenhagenDenmark

Virtual globes are technologies for visual navigation through a threedimensional,multi-resolution model of the entire *** representations used in virtual globes,however,lack geometric flexibility at high-resolution levels of the planet-wide terrain *** is a problem especially if boundaries between individual geospatial features and the terrain are important.A novel integration of individual polygonal boundaries with a specific multi-resolution representation of the planet-wide terrain is developed in this *** the preparation stage,the integration relies on an original simplification algorithm applied to the polygonal boundaries between geospatial features and the *** output is a multiple level-of-detail(LOD)geometry,which can be combined with a known multi-LOD representation of the terrain that uses run-time *** data representation is suitable for storage in existing database systems,avoids any data redundancy across LODs,and is even independent of the subdivision schema that partitions the planet’s surface for the sake of dealing with *** runtime,a novel reconstruction algorithm stitches geometric parts from different LODs together in a manner that augments the multi-LOD representation of the *** a certain proximity range from a given position,the method reconstructs a scene that preserves topological relations between the boundaries of geospatial features with the *** method also guarantees that certain nearest proximity to the given position consists of the best geometries that correspond to the original *** properties of the method close up the gap between a mere exploratory visualization of static,pre-generated models and the models supporting geospatial analysis,which is deemed crucial for applications in Geographic Information Systems,Building Information Modelling and other software industries.A prototype implementation and experiment results that prove this method are also prese

关键词： Feature-based topography multiple level-of-detail procedural modeling vector data organization geometry reconstruction

Advanced Antennas Push Forward Wireless Connectivity

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Engineering 2022年第4期8卷 1-2页

作者： Kwai Man luk Baoyan Duan the Royal Academy of Engineering the Chinese Academy of Engineering

Antennas are critical components for wireless *** general,antennas with a wide bandwidth,compact size,and high efficiency are required in order to achieve a high level of system performance with modern wireless communication systems,sensor networks,radio astronomy,deep space probes,and so *** importance of antennas is reflected by the numerous research articles that have been published on this topic in recent years—not only in antenna journals,but also in other related journals on sensors,vehicular technologies,microwave techniques,and terahertz *** huge number of downloads for the papers published in major antenna journals also demonstrates the attractiveness of antenna research.

关键词： antenna Antennas Push

Electropulsing-Induced Microstructural Changes and Their Effects on Electrical Conductivity of Thin Films of an Al-doped ZnO

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Acta Metallurgica Sinica(English Letters) 2018年第12期31卷 1361-1367页

作者： Y.H.Zhu C.M.luk Department of Industrial and Systems Engineering TheHong Kong Polytechnic UniversityHong KongChina Department of Applied Physics The Hong Kong PolytechnicUniversityHong KongChina

Electropulsing-induced phase decompositions and microstructural changes in AZO-5 thin films were studied by X-raydiffraction, scanning electron microscopy, atomic force microscopy, Hall effect measurement and photoluminescence （PL）measurement techniques. It was found that the electropulsing induced phase decomposition started with spinodaldecomposition, which was accompanied by discontinuous precipitation in the AZO-5 thin films. Both circular phasedecompositions and the crystal orientation occurred. Inappropriate electropulsing might damage zones, which resulted intremendous decrease in electrical conductivity. Circular changes in both the peak position and the width of the PLwavelength were observed in the EPT AZO-5 thin films. Formation of zones favored reducing the roughness of the thinfilm.

关键词： Electropulsing Phase transformation Electrical conductivity Photoluminescence Thin-films AZO

Nomore blind dates with calcite: Fluid-flow vs. fault-slip along the Očkov thrust, Prague Basin

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Geoscience Frontiers 2021年第4期12卷 163-174页

作者： Nick M.W.Roberts JiříŽák František vacek JiříSláma Geochronology and Tracers Facility British Geological SurveyEnvironmental Science CentreNottingham NG125GGUK Institute of Geology and Paleontology Faculty of ScienceCharles UniversityAlbertov 6Prague 12843Czech Republic Department of Mineralogy and Petrology National MuseumVáclavskénáměstí68Prague 11579Czech Republic Institute of Geology Czech Academy of Sciencesv.v.i.Rozvojová269Prague 16500Czech Republic

Dating of fracture-filling calcitewith U-Pb geochronology is becoming a rapidly adopted technique for determining the absolute timing of brittle deformation in the upper *** calcite is a desirable target,as it precipitates between individual fault slip displacement events,and provides additional kinematic *** we present a case study of slickenfibres formed on the Očkov thrust in the Lower Palaezoic Prague Basin,Bohemian Massif,utilising a combination of petrographic and in situ *** demonstrate that slickenfibre external textures can be preserved,whilst internally primary textures are removed by fluid infiltration and recrystallization,leading to variable U and Pb *** slickenfibre yielded a date of ca.250 Ma,which we interpret as recording fault slip along the Očkov *** cross-cutting slickenfibre yielded more scattered U-Pb data,with an imprecise apparent age around ca.95 *** slickenfibre is recrystallised,destroying the primary textures,and exhibits element *** meaning of this younger apparent age is therefore questionable;whereas it likely reflects Cretaceous U and Pb mobility assisted by fluid-flow along the fault plane,it may not reflect a period of fault *** results demonstrate that slickenfibre-based U-Pb dates do not unequivocally relate to fault motion,and that petrographic and elemental analyses are important requirements for interpreting calcite U-Pb data.

关键词： U-Pb geochronology Calcite Fault dating Fluid-flow Prague Basin LA-ICP-MS

Effect of Osmotic Stress in Early Stages of Ontogenesis on Root Respiration, Growth, Sugar Content,and Cell Injury in Maize Seedlings Differing in Drought Sensitivity

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Journal of Integrative Plant Biology 2006年第7期48卷 814-822页

作者： lukás, Kolarovic Miroslava Luxová Peter Valentovic Institute of Botany Slovak Academy of Sciences Dubravská cesta 14 Bratislava 84523 Slovakia

Cultivars of maize （Zea mays L.） with different sensitivity to drought were exposed to 0.3 mol/L sorbitol （-1.4 MPa water potential） for 24 h. Exposure to water deficiency significantly reduced the growth of both shoots （coleoptile and hypocotyl） and roots. Shoot growth was inhibited more than the growth of roots. Osmotic stress enhanced accumulation of soluble sugars. Electrolyte leakage, a cell injury index, was slightly increased after 0.3 mol/L sorbitoh Respiration was measured in the presence and absence of 2,6-dlchloro-phenol indophenoh 2,6-Dichloro-phenol indophenol did not influence respiration rates, because statistically equal results were observed under both conditions. Total respiration （VT） decreased after osmoticum treatment. There were no significant differences in the VT among the cultlvars analysed. The decrease In VT was caused by a decline In the activities and capacities of both cytochrome （Vcyt, Vcyt） and alternative pathway （Valt, Valt） of respiration. A high residual respiration （Vres） was observed, up to 27% of total uninhibited respiration. The result of uncoupler use clearly indicated that coupling was maintained after 24 h of osmotic stress. The recovery of the respiration rate was comparable with that of non-stressed control rates. According to these observations, no possible mltochondrial damage is expected. Water deficiency did not induce a stimulation of the alternative oxidase, so we assume that the stimulation of the alternative pathway is not related to drought stress resistance; rather, the function of the alternative pathway is to balance carbon metabolism and electron transport in a response to a changing environment.

关键词： alternative oxidase (AOX) alternative respiration 2,6-dichloro-phenol indophenol (DCPIP) maize osmotic stress sugars uncoupler.

Silver fir tree-ring fluctuations decrease from north to south latitude—total solar irradiance and NAO are indicated as the main influencing factors

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Forest Ecosystems 2023年第6期10卷 717-731页

作者： Vaclav Simůnek Anna Prokůpkova Zdenek vacek Stanislav vacek Jan Cukor Jirí Remes Vojtech Hajek Giuseppe D'Andrea Martin Salek Paola Nola Osvaldo Pericolo Sarka Holzbachova Francesco Ripullone Faculty of Forestry and Wood Sciences Czech University of Life Sciences PragueKamýcka 129CZ—16500Prague 6SuchdolCzech Republic Forestry and Game Management Research Institute v.v.iStrnady 13625202JílovisteCzech Republic Czech Academy of Sciences Institute of Vertebrate BiologyKvetna 860365BrnoCzech Republic Department of Earth and Environmental Sciences University of PaviaVia S.Epifanio 14I-27100PaviaItaly Forests of the Czech Republic SOEPremyslova 1106/19NovýHradec Kralove50008Hradec KraloveCzech Republic School of Agricultural Forestry and Environmental SciencesUniversity of BasilicataViale dell’Ateneo Lucano 10I-85100PotenzaItaly Faculty of Environmental Sciences Czech University of Life Sciences PragueKamýcka 129CZ—16500PragueSuchdolCzech Republic

Silver fir(Abies alba Mill.)is a flexible European tree species,mainly vegetating within the mountainous regions of Europe,but its growth responses across its latitudinal and longitudinal range have not yet been satisfactorily verified under changing environmental *** study describes the tree-ring increment of silver fir in research plots across a latitudinal gradient from the northern range in Czechia(CZ),through Croatia(HR)to the southernmost range in Italy(IT).The research aims to analyze in detail the dynamics and cyclicity of the ringwidth index(RWI)and how it relates to climatic factors(temperature and precipitation),the North Atlantic Oscillation(NAO),and total solar irradiance(TSI),including the determination of *** results show that the main drivers affecting fir growth are the seasonal NAO index and *** temperatures affect RWI early in the vegetation season,while lack of precipitation during the summer is a limiting factor for fir growth,especially in *** temperatures and temperatures in June and July negatively impact,while seasonal precipitation totals in the same months positively influence the RWI in all research plots across *** longest growth cycles in fir RWI were recorded in the northernmost studied plots in *** cyclical fluctuations recede approaching the *** cyclic increase in RWI is related to the TSI,which decreases its effect from north to *** TSI's effects vary,positively impacting CZ but negatively influencing HR while remaining relatively neutral in *** the other hand,seasonal NAO tends to negatively affect silver fir growth in HR and CZ but has a mildly positive effect in *** conclusion,the TSI and the influence of the seasonal NAO index are prevalent in the fir RWI and are accompanied by a greater cyclicity of RWI in Central Europe(temperature optimum)than in the Italian Mediterranean region,where this tree species is limited by climatic conditions,especially lack of pre

关键词： Abies alba Mill Tree-rings Solar cycle North Atlantic oscillation Precipitation Temperature