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Developing a multi-method approach to identifying e-scooter hazard hotspots

Journal of Traffic and Transportation Engineering(English Edition) 2024年第4期11卷 667-680页

作者： Michael Hardinghaus Simon Nieland Rebekka Oostendorp Jan Weschke german aerospace center(dlr)Institute of Transport Research Berlin 12489Germany

In recent years,e-scooters have been introduced in many European *** several places we have witnessed a rapid uptake of this new mode of transport mainly as a result of public sharing schemes.A number of incidents,injuries and even fatalities have given rise to questions regarding the safety of these *** questions are being researched mainly using official crash data and data specifying injuries and hospital *** now,the research has focused on investigating typical injury patterns and estimating risk *** little is known about exactly where conflicts and crashes *** of hazard hotspots is crucial when investigating risk levels and improving safety for all road ***,this paper develops an approach to investigating locations with potentially dangerous interactions within the active mobility system in the city of *** approach consists of explorative expert interviews,an online poll,and quantitative *** the latter we combine three ***,we research crash hotspots using official ***,we use data based on acceleration sensors from cyclists'smartphones to find locations of sudden ***,we use trip data from the operators of escooter sharing *** information gathered is used in a conclusive expert workshop to identify hazard *** show that many of the conflicts with pedestrians are caused by parked ***,e-scooter trips are concentrated in the inner city and along specific *** moving traffic,various data sources are used to identify hotspots at intersections and in areas between *** present research lays the foundation for important further studies to investigate interactions at hotspots in detail by determining nine specific locations in the city of berlin.

关键词： E-scooter Accidents Crashes Active mobility Micromobility Road safety

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Evolution of airports from a network perspective--An analytical concept

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Chinese Journal of Aeronautics 2017年第2期30卷 513-522页

作者： Mark Azzam german aerospace center -dlr 53227 Bonn Germany

Analyzing airports＇ role in global air transportation and monitoring their development over time provides an additional perspective on the dynamics of network *** order to understand the different roles airports can play in the network an integrated and multidimensional approach is ***,an approach to airport classification through hierarchical clustering considering several parameters from network theory is presented in this *** applying a 29 year record of global flight data and calculating the conditional transition probabilities the results are displayed as an evolution graph similar to a discrete-time Markov *** this analytical concept the meaning of airports is analyzed from a network perspective and a new airport taxonomy is *** presented methodology allows tracking the development of airports from certain categories into others over *** show that airports of equal classes run through similar stages of development with a limited number of alternatives,indicating clear evolutionary *** from giving an overview of the results the paper illustrates the exact data-driven approach and suggests an evaluation *** methodology can help the public and industry sector to make informed strategy decisions when it comes to air transportation infrastructure.

关键词： Airport classification Air transportation Cluster analysis Complexity science Network development Network science

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Corrosion behavior of metallic alloys in molten chloride salts for thermal energy storage in concentrated solar power plants： A review

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Frontiers of Chemical Science and Engineering 2018年第3期12卷 564-576页

作者： Wenjin Ding Alexander Bonk Thomas Bauer Institute of Engineering Thermodynamics German Aerospace Center (DLR) 70569 Stuttgart Germany Institute of Engineering Thermodynamics German Aerospace Center (DLR) 51147 Cologne Germany

Recently, more and more attention is paid on applications of molten chlorides in concentrated solar power （CSP） plants as high-temperature thermal energy storage （TES） and heat transfer fluid （HTF） materials due to their high thermal stability limits and low prices, compared to the commercial TES/HTF materials in CSP- nitrate salt mixtures. A higher TES/HTF operating temperature leads to higher efficiency of thermal to electrical energy conversion of the power block in CSP, however causes additional challenges, particularly increased corrosiveness of metallic alloys used as contain- ers and structural materials. Thus, it is essential to study corrosion behaviors and mechanisms of metallic alloys in molten chlorides at operating temperatures （500-800℃） for realizing the commercial application of molten chlorides in CSE The results of studies on hot corrosion of metallic alloys in molten chlorides are reviewed to understand their corrosion behaviors and mechanisms under various conditions （e.g., temperature, atmosphere）. Emphasis has also been given on salt purification to reduce corrosive impurities in molten chlorides and development of electrochemical techniques to in-situ monitor corrosive impurities in molten chlorides, in order to efficiently control corrosion rates of metallic alloys in molten chlorides to meet the requirements of industrial applications.

关键词： corrosion mechanisms impurities metallic corrosion salt purification electrochemical techniques

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Evaluation of Turbulence Models in Predicting Hypersonic and Subsonic Base Flows Using Grid Adaptation Techniques

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Chinese Journal of Aeronautics 2012年第3期25卷 325-334页

作者： YOU Yancheng BUANGA Bjorn HANNEMANN Volker LUDEKE Heinrich Institute of Aerodynamics and Flow Technology German Aerospace Center (DLR) Braunschweig 38108 Germam Institute of Aerodynamics and Flow Technology german aerospace center (dlr) Gottingen 37073 Germany Department of Aeronautics Xiamen University Xiamen 361005 China

The flows behind the base of a generic rocket, at both hypersonic and subsonic flow conditions, are numerically studied. The main concerns are addressed to the evaluation of turbulence models and the using of grid adaptation techniques. The investigation focuses on two configurations, related to hypersonic and subsonic experiments. The applicability tests of different turbu- lence models are conducted on the level of two-equation models calculating the steady state solution of the Reynolds-averaged Navier-Stokes（RANS） equations. All used models, the original Wilcox k-co, the Menter shear-stress transport （SST） and the ex- plicit algebraic Reynolds stress model（EARSM） formulation, predict an asymmetric base flow in both cases caused by the support of the models. A comparison with preliminary experimental results indicates a preference for the SST and EARSM results over the results from the older k-co model. Sensitivity studies show no significant influence of the grid topology or the location of the laminar to turbulent transition on the base flow field, but a strong influence of even small angles of attack is reported from the related experiments.

关键词： base flows turbulence models steady calculation grid adaptation numerical simulation

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Measurements of Laminar Burning Velocities of Alternative Fuels:Application in Transport and aerospace

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Journal of Thermal Science 2023年第2期32卷 503-512页

作者： RICHTER Sandra BRAUN-UNKHOFF Marina NAUMANN Clemens german aerospace center(dlr) Institute of Combustion TechnologyDepartment of Chemical Kinetics and AnalyticsStuttgart 70569Germany

The laminar burning velocity belongs to the fundamental combustion properties of fuels being a measure for their heat release,flame length,as well as reactivity and combustion stability,and thus,may impact the design of burners and combustion ***,these experimental data are needed for the validation and optimization within the construction and development of detailed chemical kinetic reaction *** this study,an overview of the different applications of fuel characterization regarding the specific area of interest(road transport,aviation,and aerospace)will be *** on the application,effects of different molecular characteristics on the laminar burning velocity are evaluated:the presence of oxygen atoms and the grade of branching in a specific fuel molecule as well as the difference in the type of a chemical bond,here,single and double *** of alternative fuels being discussed in the present study are:(Ⅰ)oxymethylene ether(OMEn)in the field of road transport;(Ⅱ)a paraffinic Alcohol-to-Jet fuel as sustainable aviation fuel;and(Ⅲ)mixtures of ethane or ethene with nitrous oxide as green propellants for rocket propulsion applications.

关键词： laminar burning velocity alternative sustainable fuels road transport aviation fuels green propellants

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On the applicability of the single parabolic band model to advanced thermoelectric materials with complex band structures

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Journal of Materiomics 2021年第3期7卷 603-611页

作者： Johannes de Boor Institute of Materials Research German Aerospace Center(DLR)51147KoelnGermany

Due to the complex interplay between composition,synthesis parameters and the performance of thermoelectric materials,the optimization of thermoelectric materials needs to be complemented by modelling.A relatively simple and thus popular approach is the so called single parabolic band model,which allows for an efficient optimization of the material properties and a benchmarking of different materials based on relatively few,well available experimental *** complex band structures are common for high performance materials,single parabolic band modelling is also employed with apparent success for material systems where the underlying assumptions are not well *** order to assess the validity of a single parabolic band analysis for such systems,the thermoelectric properties for two model systems are calculated:one with a single band that is twofold degenerate and one with a light and a heavy *** if the density of states masses and the scattering potentials are kept identical,the transport properties and in particular the Hall coefficients differ significantly,which leads to an incorrectly determined carrier *** the carrier concentration is the base for the single parabolic band analysis,all the quantities obtained from it(optimum carrier concentration,effective mass,deformation potential)are determined incorrectly as well.

关键词： Thermoelectrics Electrical transport Single parabolic band model

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Graben on the Lunar Nearside: Do Dikes Lie Beneath?

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Acta Geologica Sinica(English Edition) 2016年第S1期90卷 175-176页

作者： Amanda L.NAHM german aerospace center (dlr)

On the Moon,tectonic structures are concentrated on the nearside,spatially associated with the maria(e.g.,Watters and Johnson,2010),or basalt-filled impact *** graben(or rilles)are long,narrow troughs up to

关键词： Graben on the Lunar Nearside Do Dikes Lie Beneath

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Hydrogen production at intermediate temperatures with proton conducting ceramic cells:Electrocatalytic activity,durability and energy efficiency

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Journal of Energy Chemistry 2023年第11期86卷 437-446,I0010页

作者： Haoyu Zheng Feng Han Noriko Sata Rémi Costa Institute of Engineering Thermodynamics German Aerospace Center (DLR) Institute for Building Energetics Thermotechnology and Energy Storage (IGTE) University of Stuttgart

Proton conducting ceramic cells(PCCs)are an attractive emerging technology operating in the intermediate temperature range of 500 to 700℃.In this work,we evaluate the production of hydrogen at intermediate temperatures by proton conducting ceramic cell electrolysis(PCCEL).We demonstrate a highperformance steam electrolysis owing to a composite positrode based on BaGd_(0.8)La_(0.2)Co_(2)O_(6-δ)(BGLC1082)and BaZr0.5Ce0.4Y0.1O3-δ(BZCY541).The high reliability of PCCEL is demonstrated for 1680 h at a current density as high as-0.8 A cm^(-2)close to the thermoneutral cell voltage at 600℃.The electrolysis cell showed a specific energy consumption ranging from 54 to 66 kW h kg^(-1)that is comparable to state-of-the-art low temperature electrolysis technologies,while showing hydrogen production rates systematically higher than commercial solid oxide ceramic cells(SOCs).Compared to SOCs,the results verified the higher performances of PCCs at the relevant operating temperatures,due to the lower activation energy for proton transfer comparing with oxygen ion ***,because of the p-type electronic conduction in protonic ceramics,the energy conversion rate of PCCs is relatively lower in steam *** faradaic efficiency of the PCC in electrolysis mode can be increased at lower operating temperatures and in endothermic conditions,making PCCEL a technology of choice to valorize high temperature waste heat from industrial processes into *** increase the faradaic efficiency by optimizing the materials,the cell design,or the operating strategy is a key challenge to address for future developments of PCCEL in order to achieve even more superior techno-economic merits.

关键词： Steam electrolysis Hydrogen production Proton conducting ceramics Intermediate temperature Energy efficiency

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Urbanization between compactness and dispersion:designing a spatial model for measuring 2D binary settlement landscape configurations

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International Journal of Digital Earth 2019年第6期12卷 679-698页

作者： Hannes Taubenbock Michael Wurm Christian GeiB Stefan Dech Stefan Siedentop german aerospace center(dlr) German Remote Sensing Data Center(DFD)OberpfaffenhofenGermany ILS-Research Institute for Regional and Urban Development DortmundGermany

Measuring spatial patterns is a crucial task in spatial *** indicators have been developed to measure patterns in a quantitative ***,most comparative studies rely on relative comparisons,limiting their explanatory power to specific case *** by advancements in earth observation providing unprecedented resolutions of settlement patterns,this paper suggests a measurement technique for spatial patterns to overcome the limits of relative *** design a model spanning a feature space based on two metrics-largest patch index and number of *** feature space is defined as‘dispersion index’and covers the entire spectrum of possible two-dimensional binary(settlement)*** model configuration allows for an unambiguous ranking of each possible pattern with respect to spatial *** spatial resolutions of input data as well as selected areas of interest influence measurement results,we test dependencies within the ***,common other spatial metrics are selected for testing whether they allow unambiguous *** scenarios,we apply the model to artificially generated patterns representing all possible configurations as well as to real-world settlement classifications differing in growth dynamics and patterns.

关键词： Land cover spatial patterns landscape metrics dispersion index sensitivity analysis urban settlements remote sensing comparative spatial analysis

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Pragmatic model transformations for refactoring in Scilab/Xcos

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International Journal of Modeling, Simulation, and Scientific Computing 2016年第1期7卷 39-61页

作者： Umut Durak german aerospace center(dlr)Institute of Flight Systems Lilienthalplatz 7 Braunschweig 38108Germany

Model-Based Development has become an industry wide standard *** an open source alternative,Scilab/Xcos is being widely employed as a hybrid dynamic systems modeling *** the increasing efficiency in implementation using graphical model development and code generation,the modeling and simulation community is struggling with assuring quality as well as maintainability and *** is defined as an evolutionary modernization activity where,most of the time,the structure of the artifact is changed to alter its quality characteristics,while keeping its behavior *** has been widely established as a technique for textual programming languages to improve the code structure and *** refactoring is also regarded as one of the key practices of model engineering,the methodologies and approaches for model refactoring are still under ***-Driven Modernization(ADM)has been introduced by the software engineering community as a model-based approach to software modernization,in which the implicit information that lies in software artifacts is extracted to models and model transformations are applied for modernization *** refactoring as a low level modernization task,the practices from ADM are ***,this paper proposes a model-based approach for model refactoring in order to come up with more efficient and effective model refactoring methodology that is accessible and extendable by *** other graphical modeling tools,Scilab/Xcos also possesses a formalized model specification conforming to its implicit *** than proposing another metamodel for knowledge extraction,this pragmatic approach proposes to conduct in place model-to-model transformations for refactoring employing the Scilab/Xcos model *** construct a structured model-based approach,the implicit Scilab/Xcos metamodel is explicitly presented utilizing ECORE as a *** a practical model

关键词： Model refactoring Scilab/Xcos model engineering model transformations

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