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Analysis of drop deformation dynamics in turbulent flow

Chinese Journal of Chemical Engineering 2016年第2期24卷 264-277页

作者： Stephanie Nachtigall Daniel Zedel matthias Kraume Chair of Chemical and Process Engineering Technische Universitat Berlin

Drop breakage and coalescence influence the particle formation in liquid-liquid dispersions. In order to reduce the influencing factors of the whole dispersion process, single drops where coalescence processes can be neglected were analyzed in this work. Drops passing the turbulent vicinity of a single stirrer blade were investi- gated by high-speed imaging. In order to gain a statistically relevant amount of drops passing the area of interest and corresponding breakage events, at least 1600 droplets were considered for each parameter set of this work. A specially developed fully automatic image analysis based on Matlab was used for the evaluation of the resulting high amount of image data. This allowed the elimination of the time-consuming manual analysis and further- more, allowed the objective evaluation of the drops＇ behavior. Different deformation parameters were consid- ered in order to describe the drop deformation dynamics properly. Regarding the ratio of both main particle axes （0axes）, which was therefore approximated through an ellipse, allowed the determination of very small de- viations from the spherical shape. The perimeter of the particle （0peri） was used for the description of highly de- formed shapes. In this work the results of a higher viscosity paraffin oil （ηd =127 mPa. s） and a low viscosity solvent （petroleum, ηd = 1.7 mPa-s） are presented with and without the addition of SDS to the continuous water phase. All results show that the experimentally determined oscillation but also deformation times underlie a wide spreading. Drop deformations significantly increased not only with increasing droplet viscosity, but also with decreasing interfacial tension. Highly deformed particles of one droplet species were more likely to break than more or less spherical particles. As droplet fragmentation results from a variety of different macro-scale de- formed particles, it is not assumed that a critical deformation value must be reached for the fragmentati

关键词： Drop deformation Drop breakage Liquid-liquid system Turbulent mixing Image analysis High-speed imaging

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Power Law or Logarithmic Law ?── A Data Analysis for Zero Pressure Gradient Turbulent Boundary Layers with Low Re _(δ2)

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Journal of Thermal Science 2000年第1期9卷 23-29页

作者： matthias Buschmann (Institute of Fluid Mechanics Dresden University of Technology

The paper Presents an analysis of two-dimensional zero pressure gradient (ZPG) turbulent boundary layers (TBL) with regard to the application of Power laws. Only TBL with low Reynolds number 300 < Reδ2 < 6200 are taken into account. It is found that a certain region of the mean velocity profile can be described with a power law of the form u+ = Cpow * y+α This Power law region is not a Priori identical with the overlap region. An algorithm for the determination of the wall skin friction using the power law is proposed. The method was applied with good result to ZPG TBL and to adverse pressure gradient (APG) TBL. To bridge the gap between the wall and the power law region an approach for the turbulent viscosity is suggested.

关键词： power law turbulent boundary layer scaling analysis fluid mechanics

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Simulation of a Shock Tube with a Small Exit Nozzle

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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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Synthesis of dimeric estradiol enzyme model containing imidazolyl and study on its catalytic efficiency in hydrolysis of carboxylates and phosphates

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Chinese Journal of Chemistry 1997年第5期15卷 438-442页

作者： Yan, JM Xie, RG Zhao, HM Wu, DX Xia, pf Sichuan Univ Dept Chem Chengdu 610064 Sichuan Peoples R China Sichuan Normal Coll Dept Chem Chengdu 610041 Sichuan Peoples R China

Dimeric estradiol enzyme model (2) was synthesized by etherification of 2,4-bis(N-imidazolylmethyl)-17β-estradiol (1) with 1,3-dibromopropane in the presence of anhydrous K2CO3. Hydrolysis of carboxylates and phosphates catalyzed by the model showed Michaelis-Menten kinetic behavior. Hydrophobic interaction between the model and ester accelerates the hydrolysis markedly, rate enhancement of up to 65 and 285 fold, relative to imidazole, is observed.

关键词： Dimeric estrogen enzyme model compound catalytic hydrolysis carboxylate phos- phate

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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 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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