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Towards a universal optimization of the performance of sand storage dams in arid and semi-arid areas by systematically minimizing vulnerability to siltation:A case study in Makueni,Kenya

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International Journal of Sediment Research 2018年第3期33卷 221-233页

作者： Josep de Trincheria Walter Filho Leal ralf Otterpohl Institute of Wastewater Management and Water Protection Hamburg University of Technology Research and Transfer Centre "Sustainable Development and Climate Change Management" Hamburg University of Applied Sciences

Sand storage dams are hydraulic retention structures that increase the volume of coarse sediments in seasonal sandy streams by exclusively blocking the bedload transport during runoff events. However,siltation of fine grain particles, which are transported as part of the suspended load, is a major factor causing sand storage dams to perform poorly. Therefore, this study aimed to evaluate the hydrological performance and cost-efficiency of 30 sand storage dams. This study also aimed to increase the understanding of critical factors which may affect the performance and lead to siltation of sand storage reservoirs. The analysis was based on a physical survey of 30 sand storage dams that were built in onestage in southeastern Kenya. Most of the study sites had the capacity to produce sand. However, the reservoirs suffered from severe siltation, which caused generalized low annual yields, reduced supply capacities, and low cost-efficiency. It is argued that the main factors for the poor performance were the high inter-and intra-annual variability of bedload transport, which coupled with the construction of onestage spillways, led to siltation of the reservoirs. Thus, large volumes of fine grain particles accumulated in the reservoirs during runoff events with bedload layer heights lower than the height of the one-stage spillways. To systematically maximize the robustness to the inherent variability of bedload transport, and ensure optimal performance levels by systematically minimizing siltation, spillways should be built in stages of reduced height. Thus, the lower the stage height, the higher the probability of maximizing the accumulation of coarse sediment. It is estimated that a multi-stage construction process with stage heights of 20 cm would have produced a performance 26 times higher. This implies that the 30 reservoirs would have had the capacity to supply 8516 people as compared to the current supply capacity of 330 people. Improvements in the performance of sa

关键词： Bedload transport variability Spillway Multi-stage construction

Hybrid model for prediction of welding distortions in large structures

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Frontiers of Materials Science 2011年第2期5卷 209-215页

作者： Vesselin MICHAILOV Nikolay DOYNOV Christoph STAPELFELD ralf OSSENBRINK Chair of Joining and Welding Technology Brandenburg Technical University of Cottbus Konrad-Wachsmann-Allee 17 03046 Cottbus Germany

The paper presents a short overview of the contemporary approaches for calculating welding distortions. In order to meet the existing challenges, an advanced hybrid model for prediction of welding distortions in large structures is described. For the purpose of illustrating the capability of this model, a simulation case is put into discussion. The results are validated by comparison with experimental data, as well as with common simulation technique. Analysis of the calculation costs is also presented. The directions for development of calculation technique, based on the presented model, are also suggested.

关键词： hybrid model welding distortion calculation

Analysis of the microbial communities in soils of different ages following volcanic eruptions

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Pedosphere 2020年第1期30卷 126-134页

作者： Marcela HERNáNDEZ Marcela CALABI ralf CONRAD Marc G.DUMONT Max Planck Institute for Terrestrial Microbiology Karl-von-Frisch-Str.10Marburg 35043(Germany) Scientific and Technological Bioresource Nucleus Universidad de La FronteraTemuco(Chile) School of Biological Sciences University of SouthamptonSouthampton SO171BJ(UK)

Volcanism is a primary process of land *** provides a model for understanding soil-forming processes and the role of pioneer bacteria and/or archaea as early colonizers in those new *** objective of this study was to identify the microbial communities involved in soil *** was extracted from soil samples from the Llaima volcano in Chile at sites destroyed by lava in different centuries(1640,1751,and 1957).Bacterial and archaeal 16 S r RNA genes were analyzed using quantitative polymerase chain reaction(q PCR)and Illumina Mi Seq *** showed that microbial diversity increased with soil age,particularly between the 1751 and 1640 *** archaeal communities,Thaumarchaeota was detected in similar abundances in all soils,but Euryarchaeota was rare in the older *** analysis of bacterial 16 S r RNA genes showed high abundances of Chloroflexi(37%),Planctomycetes(18%),and Verrucomicrobia(10%)in the youngest *** and Acidobacteria were highly abundant in the older soils(16%in 1640 and 15%in 1751 for Acidobacteria;38%in 1640 and 27%in 1751 for Proteobacteria).The microbial profiles in the youngest soils were unusual,with a high abundance of bacteria belonging to the order Ktedonobacterales(Chloroflexi)in the 1957 soil(37%)compared with the 1751(18%)and 1640(7%)*** this study,we show that there is a gradual establishment of the microbial community in volcanic soils following an eruption and that specific microbial groups can colonize during the early stages of recovery.

关键词： 16S rRNA gene extreme environment high-throughput sequencing Ktedonobacterales microbial diversity pioneer microbe recolonization soil formation volcanic deposit

Si-based polymer-derived ceramics for energy conversion and storage

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Journal of Advanced Ceramics 2022年第2期11卷 197-246页

作者： Qingbo WEN Fangmu QU Zhaoju YU Magdalena GRACZYK-ZAJAC Xiang XIONG ralf RIEDEL State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China College of Materials Key Laboratory of High-Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China Technische Universität Darmstadt Institut für MaterialwissenschaftOtto-Berndt-Straβe 3D-64287DarmstadtGermany EnBW Energie Baden-Württemberg AG Durlacher Allee 9376131 KarlsruheGermany

Since the 1960s,a new class of Si-based advanced ceramics called polymer-derived ceramics(PDCs)has been widely reported because of their unique capabilities to produce various ceramic materials(e.g.,ceramic fibers,ceramic matrix composites,foams,films,and coatings)and their versatile ***,due to their promising structural and functional properties for energy conversion and storage,the applications of PDCs in these fields have attracted much attention in recent *** review highlights the recent progress in the PDC field with the focus on energy conversion and storage ***,a brief introduction of the Si-based polymer-derived ceramics in terms of synthesis,processing,and microstructure characterization is provided,followed by a summary of PDCs used in energy conversion systems(mainly in gas turbine engines),including fundamentals and material issues,ceramic matrix composites,ceramic fibers,thermal and environmental barrier coatings,as well as high-temperature ***,applications of PDCs in the field of energy storage are reviewed with a strong focus on anode materials for lithium and sodium ion *** possible applications of the PDCs in Li–S batteries,supercapacitors,and fuel cells are discussed as ***,a summary of the reported applications and perspectives for future research with PDCs are presented.

关键词： polymer-derived ceramics(PDCs) high-temperature resistance structural properties electrochemical properties microstructure

Boron-modified perhydropolysilazane towards facile synthesis of amorphous SiBN ceramic with excellent thermal stability

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Journal of Advanced Ceramics 2022年第7期11卷 1104-1116页

作者： Ying ZHAN Wei LI Tianshu JIANG Claudia FASEL Emmanuel III RICOHERMOSO Jan BERNAUER Zhaoju YU Zhenghao WU Florian MÜLLER-PLATHE Leopoldo MOLINA-LUNA ralf GROTTENMÜLLER ralf RIEDEL Department of Materials and Earth Sciences Technical University of DarmstadtD-64287 DarmstadtGermany College of Materials Key Laboratory of High Performance Ceramic Fibers(Xiamen University)Ministry of EducationXiamen 361005China Eduard-Zintl-Institut für Anorganische und Physikalische Chemie Technical University of DarmstadtD-64287 DarmstadtGermany Merck KGaA Performance MaterialsD-64293DarmstadtGermany

SiBN ceramics are widely considered to be the most promising material for microwavetransparent applications in harsh environments owing to its excellent thermal stability and low dielectric *** work focuses on the synthesis and ceramization of single-source precursors for the preparation of SiBN ceramics as well as the investigation of the corresponding microstructural evolution at high temperatures including molecular dynamic ***-and chlorine-free perhydropolysilazanes were reacted with borane dimethyl sulfide complex at different molar ratios to synthesize single-source precursors,which were subsequently pyrolyzed and annealed under N2 atmosphere(without ammonolysis)to prepare SiBN ceramics at 1100,1200,and 1300℃with high ceramic yield in contrast to previously widely-used ammonolysis synthesis *** obtained amorphous SiBN ceramics were shown to have remarkably improved thermal stability and oxidation resistance compared to amorphous silicon ***,the experimental results have been combined with molecular dynamics simulation to further study the amorphous structure of SiBN and the atomic-scale diffusion behavior of Si,B,and N at 1300℃.Incorporation of boron into the Si–N network is found to suppress the crystallization of the formed amorphous silicon nitride and hence improves its thermal stability in N2 atmosphere.

关键词： polymer-derived ceramics(PDCs) SiBN crystallization molecular dynamics oxidation resistanc

A creative method to tune Fe–O interaction in ferrites

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先进陶瓷(英文) 2023年第8期12卷 1612-1624页

作者： Farshad Farshidfar Arash Fattahi ralf Brüning Dominic H.Ryan Khashayar Ghandi Department of Chemistry University of GuelphGuelph N1G 2W1Canada Physics Department Mount Allison UniversitySackville E4L 1E6Canada Physics Department McGill UniversityMontreal H3A 2T8Canada

To be able to regulate the anionic oxygen position in ferrites,an original compositing method is developed by introducing a porous p-type phase in the n-type matrix of ferrite spinel semiconductors.A result of this method is the synergetic effect of the enhanced mass and charge transport that impacted the morphology and anionic oxygen position within the MgFe_(2)O_(4) *** hypothesis is that fine tuning of the anionic oxygen position in ferrites allows us to regulate their physicochemical properties significantly,with the implications for diverse *** electron exchange interaction(J)between O-centered and octahedral-occupying iron(Fe)-centered orbitals affected both the electrical and magnetic properties of the matrix significantly,supporting our *** three-dimensional variable range electron hopping is one such effect.

关键词： Fe_(2)O_(4) spinel structural distortion electron hopping

Infectious diseases during the European Union training mission Mali(EUTM MLI)–a four-year experience

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Military Medical Research 2018年第4期5卷 293-303页

作者： Hagen Frickmann ralf Matthias Hagen Florian Geiselbrechtinger Nagpal Hoysal Department of Microbiology and Hospital Hygiene Bundeswehr Hospital Hamburg Institute for Medical Microbiology Virology and Hygiene University Medicine Rostock Department of Preventive Medicine Bundeswehr Medical Academy NATO Center of Excellence for Military Medicine (MilMedCOE) Deployment Health Surveillance Capability (DHSC) Institute of Medical Information Processing Biometry and Epidemiology

Background: The European Union Training Mission Mali(EUTM MLI) is a multinational military training deployment to the Western African tropical nation of Mali. Based on routinely collected disease and non-battle injury surveillance data, this study quantifies the true impact of infectious diseases for this tropical mission and potential seasonal variations in infectious disease ***: Categorized health events during the EUTM MLI mission and associated lost working days were reported using the EpiNATO-2 report. Infection-related health events were descriptively analyzed for a 4-year period from the 12 th week in 2013 to the 13 th week in 2017. Aggregated EpiNATO-2 data collected from all missions other than EUTM MLI were used as a ***: Among the infectious diseases reported by EUTM MLI, non-severe upper respiratory infections and gastrointestinal diseases dominated quantitatively, accounting for 1.65 and 1.42 consultations per 100 person-weeks, respectively. The number of recorded infectious disease-associated lost working days during the whole study interval was 723. Seasonal changes in disease frequency were detectable. More gastrointestinal infections were seen in the rainy season, and more respiratory infections occurred in the dry season; these were associated with peaks of more than 2.5 consultations per 100 person-weeks for both ***: Despite initial concerns focused on tropical infectious diseases during this mission in tropical Mali, upper respiratory tract and gastrointestinal infections predominate. The relatively low number of reported lost working days may indicate that these infections are at the milder end of the spectrum of infectious diseases despite a likely reporting bias.

关键词： Tropical deployment Infectious diseases Tropical medicine Gastrointestinal infections Upper respiratory tract infections Mali

Two birds with one stone: Simultaneous fabrication of HfC nanowires and CNTs through efficient utilization of polymer-derived ceramics

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Journal of Materials Science & Technology 2022年第34期129卷 163-172页

作者： Yanqin Fu Yulei Zhang Xuemin Yin Liyuan Han Qiangang Fu Hejun Li ralf Riedel Shaanxi Province Key Laboratory of Fiber Reinforced Light Composite Materials Northwestern Polytechnical UniversityXi’an 710072China Technische Universität Darmstadt Institut für MaterialwissenschaftOtto-Berndt-Straβe 3Darmstadt D-64287Germany

Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer *** formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal *** pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of ***,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor *** present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.

关键词： HfC nanowires Carbon nanotubes Waste gasses Effective utilization Polymer-derived ceramics

Importance of Air-Sea Coupling in Simulating Tropical Cyclone Intensity at Landfall

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Advances in Atmospheric Sciences 2022年第10期39卷 1777-1786页

作者： Charlie C.F.LOK Johnny C.L.CHAN ralf TOUMI School of Energy and Environment City University of Hong KongHong KongChina Department of Physics Imperial CollegeLondon SW72AZUK

An atmosphere-only model system for making seasonal prediction and projecting future intensities of landfalling tropical cyclones(TCs)along the South China coast is upgraded by including ocean and wave models.A total of 642 TCs have been re-simulated using the new system to produce a climatology of TC intensity in the South China *** comparisons of the simulations from the atmosphere-only and the fully coupled systems reveal that the inclusion of the additional ocean and wave models enable differential sea surface temperature responses to various TC characteristics such as translational speed and *** particular,interaction with the ocean does not necessarily imply a weakening of the TC,with the coastal bathymetry possibly playing a role in causing a near-shore intensification of the *** results suggest that to simulate the evolution of TC structure more accurately,it is essential to use an air-sea coupled model instead of an atmosphere-only model.

关键词： tropical cyclone intensity tropical cyclone landfall seasonal prediction air-sea coupling