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Improving Arctic Sea-Ice Thickness Estimates with the Assimilation of CryoSat-2 Summer Observations

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Ocean-Land-Atmosphere Research 2023年第1期2卷 298-308页

作者： Chao Min Qinghua Yang Hao Luo Dake Chen Thomas Krumpen Nabir Mamnun Xiaoyu Liu lars Nerger School of Atmospheric Sciences Sun Yat-sen Universityand Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)ZhuhaiChina Alfred Wegener Institute Helmholtz Centre for Polar and Marine ResearchBremerhavenGermany.

Rapidly shrinking Arctic sea ice has had substantial impacts on the Earth ***,reliably estimating the Arctic sea-ice thickness(SIT)using a combination of available observations and numerical modeling is urgently ***,for the first time,we assimilate the latest CryoSat-2 summer SIT data into a coupled ice-ocean *** particular,an incremental analysis update scheme is implemented to overcome the discontinuity resulting from the combined assimilation of biweekly SIT and daily sea-ice concentration(SIC)*** with improved estimates of sea-ice volume,our SIT estimates corrected the overestimation of SIT produced by the reanalysis that assimilates only SIC in summer in areas where the sea ice is roughest and experiences strong deformation,e.g.,around the Fram Strait and *** study suggests that the newly developed CryoSat-2 SIT product,when assimilated properly using our approach,has great potential for Arctic sea-ice simulation and prediction.

关键词： prediction. Arctic CryoSat

Anticipation and Response: Emergency Services in Severe Weather Situations in Germany

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International Journal of Disaster Risk Science 2018年第1期9卷 116-128页

作者： Thomas Kox Catharina Lüder lars Gerhold Interdisciplinary Security Research Institute of Computer Science Freie Universitat Berlin Hans-Ertel-Centre for Weather Research Optimal Use of Weather Forecasts

Communicating meteorological uncertainty allows earlier provision of information on possible future events. The desired benefit is to enable the end-user to start with preparatory protective actions at an earlier time based on the end-user's own risk assessment and decision threshold. The presented results of an interview study,conducted with 27 members of German civil protection authorities, show that developments in meteorology and weather forecasting do not necessarily fit the current practices of German emergency services. These practices are mostly carried out based on alarms and ground truth in a superficial reactive manner, rather than on anticipation based on prognoses or forecasts. Emergency managers cope with uncertainty by collecting, comparing, and blending different information about an uncertain event and its uncertain outcomes within the situation assessment to validate the information. Emergency managers struggle most with an increase of emergency calls and missions due to the impacts of severe weather. Because of the additional expenditures, the weather event makes it even harder for them to fulfill their core duties. These findings support the need for impact-based warnings.

关键词： Emergency services Forecast uncertainty Germany Weather warning response Weather warnings

Simulation-supported measurements in large circulating fluidized bed combustors

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Particuology 2009年第4期7卷 324-331页

作者： Joachim Werther Ernst-Ulrich Hartge lars Ratschow Reiner Wischnewski Institute of Solids Process Engineering and Particle Technology Hamburg University of TechnologyD 21071 HamburgGermany Now with Pyry Energy GmbH HamburgGermany Now with Hydro Aluminium AS OsloNorway

The concept of simulation-supported measurement is suggested for the elucidation of processes occurring in the combustion chambers of large-scale circulating fluidized bed combustors where the desired information cannot be obtained by direct measurements. The concept is illustrated with the example of secondary air injection where the way the air is released, the penetration depth and the evenness of air distribution over the cross-sectional area of the combustion chamber are of interest. The measured information consists of lateral profiles of oxygen concentrations measured with gas sampling probes at two ports which were located 5 and 9 m, respectively, above the level of secondary air injection. The simulation is carried out on the basis of a 3D semi-empirical fluid-mechanical model of the circulating fluidized bed which is combined with models of gas and solids mixing, fuel distribution, devolatilization and combustion of char and volatiles. The combination of the simulation with the measurements yields a clear picture of the mechanism of secondary air injection, its penetration into the combustion chamber and its effect on the local combustion processes. The results confirm the usefulness of the concept of simulation-supported measurement for this application.

关键词： Fluidized bed Combustion Local measurements 3D modeling

Reactive gas-solids flows in large volumes—3D modeling of industrial circulating fluidized bed combustors

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Particuology 2010年第1期8卷 67-77页

作者： Reiner Wischnewski lars Ratschow Ernst-Ulrich Hartge Joachim Werther Hydro Aluminium AS Pyry Energy GmbH Institute of Solids Process Engineering and Particle Technology Hamburg University of Technology

A model is presented for the simulation of reactive gas-solids flows in large industrial reactors. Circulating fluidized bed （CFB） combustors with several thousands of cubic meters reaction volume are probably the largest reactors of this type. A semi-empirical modeling approach has been chosen to model the three-dimensional concentration distributions of gas and solids components and temperatures inside the combustion chamber of such boilers. Two industrial CFB boilers are investigated in detail： the 105 MWe Duisburg combustor in Germany and the 235 MWe Turow combustor in Poland. The semi-empirical model approach is described first. Then the model is used to show how the three-dimensional concentration and temperature fields are formed by the interaction of several local phenomena. Good agreement between simulation and measurements has been achieved.

关键词： Circulating fluidized bed Large-scale Combustion 3D modeling

CFD-simulation of a circulating fluidized bed riser

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Particuology 2009年第4期7卷 283-296页

作者： Ernst-Ulrich Hartge lars Ratschow Reiner Wischnewski Joachim Werther Hamburg-University of Technology Institute of Solids Process Engineering and Particle TechnologyD-21071 HamburgGermany

In the current work, a model of the fluid mechanics in the riser of a circulating fluidized bed （CFB） has been implemented using computational fluid dynamics （CFD）. The model developed shall be used in future as the basis of 3D-reactor model for the simulation of large scale CFB combustors. The two-fluid model （TFM） approach is used to represent the fluid mechanics involved in the flow. The computational implementation is accomplished by the commercial software FLUENT. Different closure formulations are tested on a simplified geometry. Two different turbulence formulations, namely the swirl modified RNG k-e model and the Realizable k-e model, are tested in combination with two different approaches to solid phase turbulence, namely the dispersion and per phase approach. One focus of the current work is put on the study of different drag correlations. Besides the drag correlations by Syamlal et al. [Syamlal, M., Rogers, W., ＆ O＇Brien, T. J. （1993）. MFIX documentation theory guide. Technical Report DOE/METC-9411004, U.S. Department of Energy （DOE）. Morgantown Energy Technology Center： Morgantown, WV] and Gidaspow [Gidaspow, D. （1994）. Multiphaseflow andfluidization. New York： Academic Press] the EMMS model has been used to determine the momentum exchange between the two phases. The resulting formulation is then used to simulate a 1-m × 0.3-m cold CFB setup and is validated by experimental results [Schlichtharle, P. （2000）. Fluid dynamics and mixing of solids and gas in the bottom zone of circulating fluidized beds. Unoublished doctoral dissertation, Technische Universitaet Hamburg-Harburg, Shaker Verlag： Aachen].

关键词： Circulating fluidized bed Two-fuid model EMMS model Drag correlations

NPRportrait 1.0:A three-level benchmark for non-photorealistic rendering of portraits

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Computational Visual Media 2022年第3期8卷 445-465页

作者： Paul L.Rosin Yu-Kun Lai David Mould Ran Yi Itamar Berger lars Doyle Seungyong Lee Chuan Li Yong-Jin Liu Amir Semmo Ariel Shamir Minjung Son Holger Winnemöller School of Computer Science and Informatics Cardiff UniversityCardiffUK School of Computer Science Carleton UniversityOttawaCanada Department of Computer Science and Technology Tsinghua UniversityBeijingChina Reichman University(the Interdisciplinary Center) HerzliyaIsrael Department of Computer Science and Engineering Pohang University of Science and TechnologyPohangRepublic of Korea Lambda Labs Inc.San FranciscoUSA Hasso Plattner Institute University of PotsdamPotsdamGermany Multimedia Processing Laboratory Samsung Advanced Institute of TechnologySuwonRepublic of Korea Adobe Systems Inc.San JoseUSA

Recently,there has been an upsurge of activity in image-based non-photorealistic rendering(NPR),and in particular portrait image stylisation,due to the advent of neural style transfer(NST).However,the state of performance evaluation in this field is poor,especially compared to the norms in the computer vision and machine learning ***,the task of evaluating image stylisation is thus far not well defined,since it involves subjective,perceptual,and aesthetic *** make progress towards a solution,this paper proposes a new structured,threelevel,benchmark dataset for the evaluation of stylised portrait *** criteria were used for its construction,and its consistency was validated by user ***,a new methodology has been developed for evaluating portrait stylisation algorithms,which makes use of the different benchmark levels as well as annotations provided by user studies regarding the characteristics of the *** perform evaluation for a wide variety of image stylisation methods(both portrait-specific and general purpose,and also both traditional NPR approaches and NST)using the new benchmark dataset.

关键词： non-photorealistic rendering(NPR) image stylization style transfer portrait evaluation benchmark

Diabetes, its impact on peripheral nerve regeneration： lessons from pre-clinical rat models towards nerve repair and reconstruction

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Neural Regeneration Research 2018年第1期13卷 65-66页

作者： Kirsten Haastert-Talini lars B. Dahlin Institute of Neuroanatomy and Cell Biology Hannover Medical School Hannover Germany Center for Systems Neuroscience (ZSN) Hannover Germany Department of Translational Medicine-Hand Surgery Lund University Lund Sweden Department of Hand Surgery Skane University Hospital Malmo Sweden

The global number of patients with type 1 and type 2 diabetes is about to increase substantially in the coming decades. The reasons for this are two-fold, at first there is actual increase in incidence of type 1 diabetes and at second there is global increase in living expectancy and a high prevalence of patients with type 2 diabetes among the elderly. The diabetic condition is affiliated with reduced peripheral nervous system maintenance, such as peripheral neuropathies （Juster-Switlyk and Smith, 2016） that may be more common in men.

关键词： Diabetes length

High-resolution peat records for Holocene monsoon history in the eastern Tibetan Plateau

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Science China Earth Sciences 2006年第6期49卷 615-621页

作者： lars G. Franzen A.J.Tim Jull Department of Earth Sciences Goteborg University P.O. Box 460 SE-405 30 Goteborg Sweden NSF-AMS Facility University of Arizona Arizona AZ85721 USA

The variations of summer and winter monsoons during the Holocene in the eastern Ti-betan Plateau are shown to follow two basic models based on the reliable dating and high-resolution monsoon proxies determinations, one being a synchronous model in that both summer and winter monsoons are strengthening or decreasing, and the other to form a complementary pattern. These two different patterns evenly interact with each other on different time scales and together compose a complicated monsoon climatic model in this region. The climatic condition integrated by winter and summer monsoons is synchronous to the global pattern, which also shows the instability of the Holocene climate on centennial-millennial timescale. The abrupt monsoon event in about 6.2 ka cal. BP is much more severe than that in ca. 8.0 ka cal. BP, which indicates the regional character of the Asian monsoon and that the Asian monsoon climate is indeed a window on the global climate system.

关键词： eastern Tibetan Plateau, Holocene, winter and summer monsoons, asynchronous, peat, climate instability.

Damage due to rolling in total knee replacement-The influence of tractive force

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Friction 2013年第2期1卷 178-185页

作者： Markus AWIMMER lars BIRKEN Kay SELLENSCHLOH Erich SCHNEIDER Section of Tribology Rush University Medical CenterChicagoIL 60612USA Section of Biomechanics Hamburg University of TechnologyHamburg21071Germany

The femoral condyles of a knee prosthesis articulate with a combination of rolling and sliding on the tibial polyethylene *** is known about potential polyethylene damage due to rolling *** rolling does not exclude the presence of tangential surface loads,this study sought to investigate the influence of tractive rolling on the wear of polyethylene.A“wheel-on-flat”apparatus,consisting of a metal wheel and a polyethylene flat,mimicked contact conditions present in total knee *** increasingly tractive force under conditions of pure rolling was *** was found that under rolling kinematics a tangential surface load of up to 17%of the normal load could be transferred through the *** damage was dependent on the amount of tractive force and appeared more severe with higher *** the region of highest tractive force,wear features were identified that resembled perpendicular ridges on surfaces of retrieved tibial polyethylene *** suggests that tractive rolling may be a relevant wear mode in total knee replacement.

关键词： polyethylene wear knee prosthesis tractive rolling