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Strain-modulated ultrafast magneto-optic dynamics of graphene nanoflakes decorated with transition-metal atoms

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Chinese Physics B 2021年第9期30卷 520-527页

作者： Yiming Zhang Jing Liu Chun Li Wei Jin Georgios Lefkidis wolfgang Hubner School of Mechanics Civil Engineering and ArchitectureNorthwestern Polytechnical UniversityXi'an 710072China Department of Physics and Research Center OPTIMAS Technische Universität KaiserslauternP.O.Box 304967653 KaiserslauternGermany Department of Mechanical Engineering University of ManitobaWinnipeg MB R3T 5V6Canada School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710119China

We perform first-principles calculations and coherent laser-matter interaction analyses to investigate the laser-induced ultrafast spin flip on graphene nanoflakes(GNFs)with transition metal elements attached on the boundary[TM&GNFs(TM=Fe,Co,Ni)].It is shown that the spin-flip process on TM&GNFs is highly influenced by the involved element species and the position attached to the ***,taking Ni&GNF as an example,the first-principles tensile test predicts that the variation of the C-Ni bond length plays an important role in the spin density distribution,especially for the low-lying magnetic states,and can therefore dominate the spin-flip *** fastest spin-flip scenario is achieved within 80 fs in a Ni&GNF structure under 10%tensile strain along the C-Ni *** local deformation modulation of spin flip provides the precursory guidance for further study of ultrafast magnetization control in GNFs,which could lead to potential applications in future integrated straintronic devices.

关键词： graphene nanoflakes straintronics spin dynamics strain effect first principles

Lensless light-field imaging through diffuser encoding

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Light(Science & Applications) 2020年第1期9卷 637-645页

作者： Zewei Cai Jiawei Chen Giancarlo Pedrini wolfgang Osten Xiaoli Liu Xiang Peng Institut fur Technische Optik Universitat StuttgartPfaffenwaldring 970569 StuttgartGermany College of Physics and Optoelectronic Engineering Shenzhen University518060 GuangdongShenzhenChina

Microlens array-based light-field imaging has been one of the most commonly used and effective technologies to record high-dimensional optical signals for developing various potential high-performance applications in many ***,the use of a microlens array generally suffers from an intrinsic trade-off between the spatial and angular *** this paper,we concentrate on exploiting a diffuser to explore a novel modality for light-field *** demonstrate that the diffuser can efficiently angularly couple incident light rays into a detected image without needing any *** characterize and analyse this phenomenon,we establish a diffuser-encoding light-field transmission model,in which four-dimensional light fields are mapped into two-dimensional images via a transmission matrix describing the light propagation through the ***,a calibration strategy is designed to flexibly determine the transmission matrix,so that light rays can be computationally decoupled from a detected image with adjustable spatio-angular resolutions,which are unshackled from the resolution limitation of the *** proof-of-concept approach indicates the possibility of using scattering media for lensless four-dimensional light-field recording and processing,not just for two-or three-dimensional imaging.

关键词： scattering light field

55 Years of Holographic Non-Destructive Testing and Experimental Stress Analysis:Is there still Progress to be expected?

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Light(Advanced Manufacturing) 2022年第1期3卷 98-113页

作者： wolfgang Osten Giancarlo Pedrini Institute for Applied Optics ITO University Stuttgart Pfaffenwaldring 9 70569 StuttgartGermany

Holographic methods for non-destructive testing,shape measurement,and experimental stress analysis have shown to be versatile tools for the solution of many inspection *** main advantages are the non-contact nature,the non-destructive and areal working principle,the fast response,high sensitivity,resolution and *** contrast to conventional optical techniques such as classical interferometry,the holographic principle of wavefront storage and reconstruction makes it possible to investigate objects with rough ***,the response of various classes of products on operational or artificial load can be examined very *** paper looks back to the history of holographic metrology,honors the inventors of the main principles,discusses criteria for the selection of a proper inspection method,and shows exemplary ***,the main focus is on modern developments that are inspired by the rapid technological process in sensing technology and digitization,on current applications and future challenges.

关键词： Non-Destructive Testing Holography Stress Analysis Digital Holography Speckle Interferometry

Simulation Modeling in Plant Breeding: Principles and Applications

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Agricultural Sciences in China 2007年第8期6卷 908-921页

作者： WANG Jian-kang wolfgang H Pfeiffer Institute of Crop Sciences/National Key Facility for Crop Gene Resources and Genetic lmprovement/CIMMYT China Office Chinese Academy of Agricultural Sciences Beijing 100081 P.R.China 2 HarvestPlus clo the International Center for Tropical Agriculture （CIAT） A. A. 6713 Cali Colombia

Conventional plant breeding largely depends on phenotypic selection and breeder＇s experience, therefore the breeding efficiency is low and the predictions are inaccurate. Along with the fast development in molecular biology and biotechnology, a large amount of biological data is available for genetic studies of important breeding traits in plants, which in turn allows the conduction of genotypic selection in the breeding process. However, gene information has not been effectively used in crop improvement because of the lack of appropriate tools. The simulation approach can utilize the vast and diverse genetic information, predict the cross performance, and compare different selection methods. Thus, the best performing crosses and effective breeding strategies can be identified. QuLine is a computer tool capable of defining a range, from simple to complex genetic models, and simulating breeding processes for developing final advanced lines. On the basis of the results from simulation experiments, breeders can optimize their breeding methodology and greatly improve the breeding efficiency. In this article, the underlying principles of simulation modeling in crop enhancement is initially introduced, following which several applications of QuLine are summarized, by comparing the different selection strategies, the precision parental selection, using known gene information, and the design approach in breeding. Breeding simulation allows the definition of complicated genetic models consisting of multiple alleles, pleiotropy, epistasis, and genes, by environment interaction, and provides a useful tool for breeders, to efficiently use the wide spectrum of genetic data and information available.

关键词： breeding simulation genetic model breeding strategy design breeding

Integrated Debris Flow Disaster Mitigation—A Comprehensive Method for Debris Flow Disaster Mitigation

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Journal of Mountain Science 2007年第4期4卷 293-308页

作者： H. wolfgang Weinmeister University of Natural Resources and Applied Life Sciences Vienna Institute of Mountain Risk Engineering (IAN) Gentzgasse 10/6/7 A-1180 Vienna Austria

Integrated disaster mitigation needs interpreting torrent catchment areas as complex landscape systems. The history of valley-evolution shows the influence of climate and vegetation on the valley-evolution. The energy-concept (energy dissipation concept including the idea of the energy-line) is used for a simple explanation of debris flow. Examples of heavy debris flow disasters in controlled torrents in the Alps and Pyrenees give hints, which expanding the time scale can show that side-effects restrict or counteract the mitigation measures. A pallet of different mitigation measures to avoid or to reduce some of the side-effects is shown. The comprehensive method of disaster mitigation also includes the effect of vegetation. The pallet includes: avoiding hazards (hazard mapping, warning and alarming), appropriate land use and avoiding disaster-enhancing measures in the landscape and technical measures, which take into account their side-effects. The energy line is used as simple design theory. The Jiu-Jitsu Principle is explained too. With this comprehensive method a more sustainable reduction of disasters seems possible.

关键词： Torrent complex system energyconcept energy dissipation energy line vegetation integrated debris flow counter-measure disaster mitigation

Upstream-downstream linkages of hydrological processes in the Himalayan region

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Ecological Processes 2014年第1期3卷 51-66页

作者： Santosh Nepal wolfgang-Albert Flugel Arun Bhakta Shrestha International Centre for Integrated Mountain Development(ICIMOD) KathmanduNepal Department of Geoinformatics Hydrology and ModellingFriedrich Schiller UniversityJena(FSU-Jena)Germany

Understanding the upstream-downstream linkages in hydrological processes is essential for water resources planning in river *** there are many studies of individual aspects of these processes in the Himalayan region,studies along the length of the basins are *** study summarizes the present state of knowledge about linkages in hydrological processes between upstream and downstream areas of river basins in the Himalayan region based on a literature *** paper studies the linkages between the changes in the physical environment of upstream areas(land use,snow storage,and soil erosion)and of climate change on the downstream water availability,flood and dry season flow,and erosion and *** is argued that these linkages are complex due to the extreme altitudinal range associated with the young and fragile geology,extreme seasonal and spatial variation in rainfall,and diversity of anthropogenic *** on the findings,the paper concludes that integrated systems analysis is required to understand the holistic complexity of upstream-downstream linkages of hydrological processes in the river basin *** integrated land and water resources management(ILWRM)approach can be instrumental in developing adaptive solutions to problems and can also enable stakeholders of upstream and downstream areas with various interests and needs to work together for the better utilization and management of land and water *** a part of this,the specific circumstances of the upstream communities,who live in fragile and inaccessible mountain areas with limited resource opportunities,should be taken into account so that incentive mechanisms can be established to encourage and acknowledge their contribution.

关键词： Integrated land and water resources management Himalayan region Integrated systems analysis Geoinformatics Physical linkages Value of environmental services

Imaging disturbance zones ahead of a tunnel by elastic full-waveform inversion:Adjoint gradient based inversion *** space reduction using a level-set method

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Underground Space 2018年第1期3卷 21-33页

作者： Andre Lamert Luan T.Nguyen wolfgang Friederich Tamara Nestorovic Seismology Institute of GeologyMineralogy and GeophysicsRuhr-Uniersity BochumGermany Reservoir Engineering and Rock Physics International Geothermal CenterBochuon University of Applied SciencesGermany Mechanics of Adaptive Systems Institute of Computational EngineeringRudhr-Umiversity BochumGermany

We present and compare twoﬂexible and effective methodologies to predict disturbance zones ahead of underground tunnels by using elastic full-waveform *** methodology uses a linearized,iterative approach based on misﬁt gradients computed with the adjoint method while the other uses iterative,gradient-free unscented Kalmanﬁltering in conjunction with a level-set *** the former does not involve a priori assumptions on the distribution of elastic properties ahead of the tunnel,the latter intro-duces a massive reduction in the number of explicit model parameters to be inverted for by focusing on the geometric form of potential disturbances and their average elastic *** imaging methodologies are validated through successful reconstructions of simple *** an application,we consider an elastic multiple disturbance *** using identical synthetic time-domain seismo-grams as test data,we obtain satisfactory,albeit different,reconstruction results from the two inversion *** computa-tional costs of both approaches are of the same order of magnitude,with the gradient-based approach showing a slight *** model parameter space reduction approach compensates for this by additionally providing a posteriori estimates of model parameter uncertainty.

关键词： Tunnel seismics Full waveform inversion Seismic waves Level-set method Adjoint method Kalman filter

Using machine learning and a data-driven approach to identify the small fatigue crack driving force in polycrystalline materials

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npj Computational Materials 2018年第1期4卷 363-372页

作者： Andrea Rovinelli Michael D.Sangid Henry Proudhon wolfgang Ludwig School of Aeronautics and Astronautics Purdue University701W.Stadium AveWest LafayetteIN 47907USA MINES ParisTech PSL Research UniversityMAT-Centre des matériauxCNRS UMR 7633BP 8791003 EvryFrance University of Lyon INSA LyonMATEISUMR 5510 CNRSF-69621 LYONFrance

The propagation of small cracks contributes to the majority of the fatigue lifetime for structural *** significant interest,criteria for the growth of small cracks,in terms of the direction and speed of crack advancement,have not yet been *** this work,a new approach to identify the microstructurally small fatigue crack driving force is *** network and machine learning techniques are utilized to identify relevant micromechanical and microstructural variables that influence the direction and rate of the fatigue crack propagation.A multimodal dataset,combining results from a high-resolution 4D experiment of a small crack propagating in situ within a polycrystalline aggregate and crystal plasticity simulations,is used to provide training *** relevant variables form the basis for analytical expressions thus representing the small crack driving force in terms of a direction and a rate *** ability of the proposed expressions to capture the observed experimental behavior is quantified and compared to the results directly from the Bayesian network and from fatigue metrics that are common in the *** indicate that the direction of small crack propagation can be reliably predicted using the proposed analytical model and compares more favorably than other fatigue metrics.

关键词： fatigue crack driving

Magnetic Properties of Tree Leaves and Their Significance in Atmospheric Particle Pollution in Linfen City,China

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Chinese Geographical Science 2013年第1期23卷 59-72页

作者： YIN Gang HU Shouyun CAO Liwan wolfgang ROESLER Erwin APPEL State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and LimnologyChinese Academy of Sciences University of Chinese Academy of Sciences Institute for Geosciences University of Tübingen

Fifty-one tree leaves were sampled in the industrial area,residential area,and Fenhe River ecological zone,for the purpose of a magnetic study on atmospheric pollution in Linfen City,Shanxi Province,*** of mass-specific magnetic susceptibility(χ) show a significant variation range(from 11.6 × 10-8 m3/kg to 129.7 × 10-8 m3/kg).Overall values of magnetic susceptibility decline in the following sequence:industrial area > residential area > Fenhe River ecological *** relatively elevated concentration-related magnetic parameters(saturation isothermal remanent magnetization,anhysteretic remanent magnetization and magnetic susceptibility) appear in the industrial area,with their highest values in the vicinity of Linfen Steel *** particles are dominated by multidomain,magnetite-like *** particle concentration and grain size both decrease with the increasing distance from industrial area,indicating the industrial area,especially Linfen Steel Mill,is the main source of atmospheric particle *** area and Fenhe River ecological zone are also affected by industrial emission to a certain *** results of this study indicate that magnetic measurements of tree leaves are practicable for monitoring and determination of atmospheric pollution in Linfen City.

关键词： tree leaves environmental magnetism atmospheric particulate matter environmental pollution Linfen City China