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Simulation of a Shock Tube with a Small Exit Nozzle

Journal of Thermal Science 2018年第1期27卷 34-38页

作者： Yigang Luan matthias Olzmann Franco Magagnato Harbin Engineering University HarbinChina Karlsruhe Institute of Technology(KIT) Institute of Physical ChemistryKaiserstrasse 1276131 KarlsruheGermany Karlsruhe Institute of Technology(KIT) Institute of Fluid MechanicsKaiserstrasse 1276131 KarlsruheGermany

Shock tubes are frequently used to rapidly heat up reaction mixtures to study chemical reaction mechanisms and kinetics in the field of combustion chemistry [1]. In the present work, the flow field inside a shock tube with a small nozzle in the end plate has been investigated to support the analysis of reacting chemical mixtures with an attached mass spectrometer and to clarify whether the usual assumptions for the flow field and the related ther- modynamics are fulfilled. In the present work, the details of the flow physics inside the tube and the flow out of the nozzle in the end plate have been investigated. Due to the large differences in the typical length scales and the large pressure ratios of this special device, a very strong numerical stiffness prevails during the simulation process. Second-order ROE numerical schemes have been employed to simulate the flow field inside the shock tube. The simulations were performed with the commercial code ANSYS Fluent [2]. Axial-symmetric boundary conditions are employed to reduce the consumption of CPU time. A density-based transient scheme has been used and vali- dated in terms of accuracy and efficiency. The simulation results for pressure and density are compared with ana- lytical solutions. Numerical results show that a density-based numerical scheme performs better when dealing with shock-tube problems [5]. The flow field near the nozzle is studied in detail, and the effects of the nozzle to pressure and temperature variations inside the tube are invcstigatcd. The results show that this special shock-tube setup can be used to study high-temperature gas-phase chemical reactions with reasonable accuracy.

关键词： CFD shock tube low pressure numerical scheme

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Effect of Nb on Austenite Formation and Decomposition in an X80 Linepipe Steel

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Journal of Iron and Steel Research International 2011年第S1期18卷 658-663页

作者： Fateh Fazeli matthias Militzer The Centre for Metallurgical Process Engineering The University of British Columbia VancouverBCCanada V6T 1Z 4

Advanced high strength steels for pipeline applications,e.g.X80 grades,have complex microstructures and are frequently microalloyed with *** the hot rolled product it is sought to have Nb precipitated as Nb(CN).However,when processing these steels Nb may be in solution and critically affects the microstructure evolution,*** decomposition on the run-out table of a hot ***,microstructure changes in the heat affected zone (HAZ) during girth welding of these linepipe steels may occur with Nb precipitated or in *** the HAZ,depending on welding procedures,the material undergoes a number of austenite formation and decomposition cycles and the amount of Nb in solution varies along these *** selected positions of the HAZ,thermal cycles peak at the intercritical region and the partial formation of austenite and subsequent decomposition constitutes additional *** reliable process models for run-out table cooling and the HAZ hinges on an accurate tracking of microstructure evolution,which is strongly influenced by the amount of Nb in *** present study provides more insight into the effect of Nb on austenite formation and ***,a novel experimental methodology is presented to measure quantitatively the effect of Nb on transformation temperatures pertinent to austenite decomposition,notably ferrite.A model for ferrite formation that accounts for solute drag of Nb is proposed to describe the experimental ***,an experimental study will be presented to quantify the effect of Nb in and out of solution on austenite formation in the intercritical *** is found that the morphology of intercritical austenite,as well as the kinetics of its formation is strongly affected by the starting microstructure and the state of Nb.

关键词： Effect of Nb on Austenite Formation and Decomposition in an X80 Linepipe Steel HAZ

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Market-based coordination of price-responsive demand using Dantzig-Wolfe decomposition method

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Energy and AI 2023年第4期14卷 329-340页

作者： Foad Najafi matthias Fripp Department of Electrical Engineering University of Hawaii at Manoa2540 Dole StreetHonoluluHawaiiUnited States

The increasing penetration of Distributed Generation(DG)and Demand Responsive(DR)loads in power systems has necessitated the development of novel approaches to address the coordination problem of Price Responsive Devices(PRD).These PRDs are treated as self-interested players aiming to optimize their consumption patterns based on prevailing *** this paper,we propose a new algorithm based on the Dantzig-Wolfe(DW)Decomposition method,which tackles the coordination problem of self-interested PRDs in a distributed *** the distributed nature of the DW approach,we model the self-interested algorithms of PRDs as sub-problems within the DW *** coordinator,or grid operator,responsible for collecting the energy consumption information(energy bids)of PRDs,solves the master problem of the DW and determines the price signal *** proposed algorithm exhibits fast convergence as the sub-problems within DW,which could involve a large number of PRDs(potentially millions),can be solved ***,based on the DW theory,if the PRDs’subproblems are convex,reaching the optimal point(equivalent to Nash Equilibrium)is guaranteed within a limited number of *** evaluate the proposed model,we conducted a simulation involving 200 participant households,each equipped with two types of loads:Electric Vehicles(EVs)as examples of inter-ruptible loads,and Electric Water Heaters(EWHs)as examples of Thermostatically Controlled Loads(TCLs).The results demonstrate that when the algorithm converges to the optimal point,both the generation cost and user payment(based on the marginal cost of generation)***,there is a significant reduction in the Peak to Average Ratio(PAR)of the aggregate load.

关键词： Demand-side management(DSM) Distributed optimization Dantzig-Wolfe algorithm Price responsive devices(PRD) Appliance coordination

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Altitudinal Levels and Altitudinal Limits in High Mountains

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Journal of Mountain Science 2007年第1期4卷 24-33页

作者： matthias Kuhle Geographie/Hochgebirgsgeomorphologie Geographisches Institut der Universitt Goldschmidtstr.5 37077 Gttingen Germany

In lowlands climate-specific processes due to weathering and erosion are dominant, whilst the geomorphology of mountains is dependent on the geologic-tectonic structure, i.e., the energy of erosion that increases according to the vertical. The expression ＂extremely high mountains＂ has been established as the extreme of a continuous mountain classification. It has to be understood in terms of geomorphology, glaciology and vegetation. Correspondence of the planetary and hypsometric change of forms is of great value as synthetic explanation. It is confirmed with regard to vegetation, periglacial geomorphology and glaciology. Due to the world-wide reconstruction of the snowline its paleoclimatie importance increases, too. Apart from lower limits the periglacial and glacial altitudinal levels also show zones of optimum development and climatic upper limits in the highest mountains of the earth. According to the proportion of the altitudinal levels a classification as to arid, temperate and humid high mountains has been carried out.

关键词： Altitudinal levels altitudinal limits high Mountains

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A New Convergent Explicit Tree-Grid Method for HJB Equations in One Space Dimension

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Numerical Mathematics(Theory,Methods and Applications) 2018年第1期11卷 1-29页

作者： Igor Kossaczky matthias Ehrhardt Michael Gunther Lehrstuhl fur Angewandte Mathematik und Numerische Analysis Fakultat fur Mathematik und NaturwissenschaftenBergische Universitat WuppertalGaußstrasse 2042119 WuppertalGermany

In this work we introduce a new unconditionally convergent explicit Tree-Grid Method for solving stochastic control problems with one space and one time dimension or equivalently,the corresponding Hamilton-Jacobi-Bellman *** prove the convergence of the method and outline the relationships to other numerical *** case of vanishing diffusion is treated by introducing an artificial diffusion *** illustrate the superiority of our method to the standardly used implicit finite difference method on two numerical examples from finance.

关键词： Tree-Grid Method Hamilton-Jacobi-Bellman equation Stochastic control problem

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Axon degeneration:new actor in an old play

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Neural Regeneration Research 2023年第3期18卷 547-548页

作者： Marina Herwerth matthias T.Wyss Institute of Pharmacology and Toxicology University of ZurichNeuroscience Center ZurichUniversity and ETH ZurichZürichSwitzerland Institute of Neuronal Cell Biology Department of NeurologyTechnische Universität MünchenMunichGermany

After an insult of white matter tracts,*** the spinal cord or optic nerve,axons react in general by the activation of a tightly regulated self-destruction *** so-called axon degeneration cascade can be triggered by various causes,including injury,toxins,and genetic defects,and is a shared pathway in many different neurological diseases(Coleman and Hoke,2020).Axonal degeneration is thought to be responsible for disease progression and accumulation of disability across many neurological *** hallmark of early axonal injury is the appearance of local spheroid formations along the axon,often referred to as a“pearl-on-string”pattern or axonal beading or *** this striking shape change has been observed after various types of injury,such as mechanical,chemical,or inflammatory stimuli,we know little about its exact mechanism and its immediate impact on axonal *** this perspective,we would like to contrast the classical calcium-dependent form of axonal degeneration with a recently described form of a calcium-independent mechanism underlying axonal beading.

关键词： degeneration swelling injury

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Modelling and simulation of fixtures during grinding

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Science China(Technological Sciences) 2009年第7期52卷 1821-1829页

作者： matthias KLAERNER Juergen LEOPOLD Lothar KROLL Institute of Mechanical and Polymer Engineering Chemnitz University of Technology09107 ChemnitzGermany Fraunhofer Institute for Machine Tools and Forming Technology 09126 ChemnitzGermany

The complex workpiece-fixture behaviour during machining is an essential component of the fixture development *** detail,the forces acting on fixture components have to be analysed.A method for the prediction of the reaction forces due to process and clamping loads is presented in this *** the beginning,detailed information about the workpiece-fixture behaviour during the process is determined by a complex finite element ***,the reduction of the number of elements leads to a smaller model with less computation time,validated and used for the variation of process ***,an analytical description is developed based on the combination of both *** the help of the empiric equation it is possible to predict the reaction forces and the dependency on several process *** method has been validated by modelling shape grinding of a nozzle guide vane.

关键词： clamping forces grinding finite element method fixture

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Modelling the population fluctuation of winter moth and mottled umber moth in central and northern Germany

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Forest Ecosystems 2019年第1期6卷 38-55页

作者： Anika Hittenbeck Ronald Bialozyt matthias Schmidt Northwest German Forest Research Institute

Background: Winter moth(Operophtera brumata) and mottled umber moth(Erannis defoliaria) are forest Lepidoptera species characterized by periodic high abundance in a 7–11 year cycle. During outbreak years they cause severe defoliation in many forest stands in Europe. In order to better understand the spatio-temporal dynamics and elucidate possible influences of weather, stand and site conditions, a generalized additive mixed model was developed. The investigated data base was derived from glue band catch monitoring stands of both species in Central and North Germany. From the glue bands only female moth individuals are counted and a hazard code is calculated. The model can be employed to predict the exceedance of a warning threshold of this hazard code which indicates a potential severe defoliation of oak stands by winter moth and mottled umber in the coming ***: The developed model accounts for specific temporal structured effects for three large ecoregions and random effects at stand level. During variable selection the negative model effect of pest control and the positive model effects of mean daily minimum temperature in adult stage and precipitation in early pupal stage were ***: The developed model can be used for short-term predictions of potential defoliation risk in Central and North Germany. These predictions are sensitive to weather conditions and the population dynamics. However, a future extension of the data base comprising further outbreak years would allow for deeper investigation of the temporal and regional patterns of the cyclic dynamics and their causal influences on abundance of winter moth and mottled umber.

关键词： Operophtera brumata Erannis defoliaria Generalized additive mixed model Weather effect Insect pest outbreaks

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Critical Approach to Methods of Glacier Reconstruction in High Asia and Discussion of the Probability of a Qinghai-Xizang (Tibetan) Inland Ice

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Journal of Mountain Science 2007年第2期4卷 91-123页

作者： matthias Kuhle Geographie/Hochgebirgsgeomorphologie Geographisches Institut der Universitt Goldschmidtstr.5 37077 Gttingen Germany

This overview discusses old and new results as to the controversy on the past glacier extension in High Asia, which has been debated for 35 years now. This paper makes an attempt to come closer to a solution. H.v. Wissmann's interpretation (1959) of a small-scale glaciation contrasts with M. Kuhle's reconstruction (1974) of a large-scale glaciation with a 2.4 million km2 extended Qinghai-Xizang (Tibetan) inland glaciation and a Himalaya-Karakorum icestream network. Both opinions find support but also contradiction in the International and Chinese literature (Academia Sinica). The solution of this question is of supraregional importance because of the subtropical position of the concerned areas. In case of large albedo-intensive ice surfaces, a global cooling would be the energetical consequence and, furthermore, a breakdown of the summer monsoon. The current and interglacial heat-low above the very effective heating panel of the Qinghai-Xizang (Tibetan) Plateau exceeding 4000 m, which gives rise to this monsoon circulation, would be replaced by the cold-high of an inland ice. In addition, the plate-tectonically created Pleistocene history of the uplift of High Asia — should the occasion arise up to beyond the snowline (ELA) —would attain a paleoclimatically great, perhaps global importance. In case of a heavy superimposed ice load, the question would come up as to the glacio-isostatic interruption of this primary uplift. The production of the loesses sedimentated in NE-China and their very probable glacial genesis as well as an eustatic lowering of the sea-level by 5 to 7 m in the maximum case of glaciation are immediately tied up with the question of glaciation we want to discuss. Not the least, the problems of biotopes of the sanctuary-centres of flora and fauna, i.e., interglacial re-settlement, are also dependent on it. On the basis of this Quaternary- geomorphological-glaciological connection, future contributions are requested on the past glaciation, the curre

关键词： Approach methods inland ice glacier reconstruction High Asia Qinghai-Xizang (Tibetan)

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Amino acid promoted hydrogen battery system using Mn-pincer complex for reversible CO_(2) hydrogenation to formic acid

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Frontiers in Energy 2022年第5期16卷 697-699页

作者： Zupeng CHEN Henrik JUNGE matthias BELLER Jiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources College of Chemical EngineeringNanjing Forestry UniversityNanjing 210037China Leibniz-Institute for Catalysis University of RostockRostock 18059Germany Leibniz-Institute for Catalysis Rostock 18059Germany

The worldwide energy system developed in the past century is highly dependent on non-renewable fossil ***,the concentration of carbon dioxide(CO_(2))in the atmosphere has continuously increased from 280 ppm(parts per million)to>420 ppm since the industrial revolution[1–5].This excessive emission of CO_(2) causes global warming and ocean *** this context,the Paris Agreement on Climate Change adopted in 2015 recognized the necessity of holding the increase of global average temperature below 2℃,preferably 1.5℃,above pre-industrial levels,and reaching a CO_(2)-neutral process by 2050.

关键词： system hydrogenation reversible

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