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Analysis of drop deformation dynamics in turbulent flow

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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

Quenching Simulation of PM Coated Tools

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材料热处理学报 2004年第05B期25卷 752-757页

作者： Axel Htter Werner Theisen Christoph Broeckmann chair of Materials Technology Ruhr University Bochum GermanyChair of Materials Technology Ruhr University Bochum GermanyKoppern Entwicklungs-GmbH Hattingen Germany

HIP cladding is a powder metallurgical coating technique used in the production of wear parts and tools. In many cases the composite components consist of carbide-free hot-work steel as base material and wear resistant carbide-rich PM cold-work steel as coating material. To ensure operativeness a heat treatment matched to the substrate and coating material is required. Dissimilar phase transformation behaviour and different thermal expansion coefficients of layer and substrate entail inner stresses affecting the transformation kinetics in turn. In order to get a deeper insight into these effects Finite Element simulation tools are used. On the one hand, the transient heat conduction problem of the quenching process has to be solved. Non-linear boundary conditions and phase transformation of both, substrate and layer are considered. On the other hand, the mechanical response is calculated. The overall aim of the investigation is an improvement of common heat treatment techniques used for HIP cladded wear parts.

关键词：数值模拟淬火 HIP包覆磨损工具钢

An IEEE value loop of human-technology collaboration in geospatial information science

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Geo-Spatial Information Science 2020年第1期23卷 61-67页

作者： Liqiu Meng chair of Cartography Technical University of MunichMunichGermany

Geosensing and social sensing as two digitalization mainstreams in big data era are increasingly converging toward an integrated system for the creation of semantically enriched digital *** with the rapid developments of AI technologies,this convergence has inevitably brought about a number of *** the one hand,value-adding chains from raw data to products and services are becoming value-adding loops composed of four successive stages–Informing,Enabling,Engaging and Empowering(IEEE).Each stage is a dynamic loop for *** the other hand,the“human versus technology”relationship is upgraded toward a game-changing“human and technology”*** information loop is essentially shaped by the omnipresent reciprocity between humans and technologies as equal partners,co-learners and co-creators of new *** paper gives an analytical review on the mutually changing roles and responsibilities of humans and technologies in the individual stages of the IEEE loop,with the aim to promote a holistic understanding of the state of the art of geospatial information ***,the author elicits a number of challenges facing the interwoven human-technology *** transformation to a growth mind-set may take time to realize and *** works on large-scale semantic data integration are just in the *** experiences of geovisual analytic approaches are far from being systematically ***,the ethical concerns for the handling of semantically enriched digital Earth cover not only the sensitive issues related to privacy violation,copyright infringement,abuse,*** also the questions of how to make technologies as controllable and understandable as possible for humans and how to keep the technological ethos within its constructive sphere of societal influence.

关键词： Geosensing social sensing geovisual analytics semantic web embodied cognition ethics uncertainty

Quadratic stabilization of a nonlinear aeroelastic system using a novel Neural-Network-based controller

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Science China(Technological Sciences) 2011年第5期54卷 1126-1133页

作者： D. SFFKER chair of Dynamics and Control University of Duisburg-Essen

This contribution proposes a novel neural-network-based control approach to stabilize a nonlinear aeroelastic wing section. With the prerequisite that all the states of the system are available, the proposed controller requires no comprehensive information about structural nonlinearity of the wing section. Furthermore, the proposed control approach requires no human intervention of designing goal dynamics and formulating control input function, which is difficult to be realized by the typical neural-network-based control following an inverse control scheme. Simulation results show that the proposed controller can stabilize the aeroelastic system with different nonlinearities.

关键词： quadratic stabilization neural-network nonlinear aeroelastic control cognition

Kinetic Instability of Anisotropic Drift Wave Accompanied by Field Aligned Currents in Solar Coronal Loop

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Communications in Theoretical Physics 2018年第10期70卷 470-476页

作者： Hafsa Naim Ch.Uzma G.Murtaza Salam chair Department of Physics GC University

Solar coronal loops are frequently accompanied by the field-aligned currents, which drive instabilities if the drift velocity u0 > v A the Alfv′en velocity. For our choice of parameters, the critical threshold value of u0/v A is ～ 3.0 for growth and the corresponding current filling factor ～ 10-3-10-4. Below this value we are no longer in the kinetic *** coronal loops also have short-scale density gradients within each loop. The electron resonance in the presence of density gradient causes the drift mode to grow. We study the effect of these two free energy sources, the electron drift and the density gradient, in the presence of temperature anisotropy T⊥_α > T∥_α. These effects simultaneously exist in the coronae. Using gyrokinetic theory, we investigate the influence of these effects, examine how they interplay with each other and study the consequent growth of the magnetosonic wave. We observe that kinetic instability driven by density gradient can be suppressed by field-aligned currents. The temperature anisotropy with chosen signatures causes further stabilizing effect. The results may prove useful to study the heating mechanism of solar coronal loops, acceleration of particles and confinement of particles in the thermonuclear reactors.

关键词： solar corona coronal loops temperature anisotropy density inhomogeneity field-aligned currents gyrokinetic

EDISON-WMW: Exact Dynamic Programing Solution of the Wilcoxon–Mann–Whitney Test

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Genomics, Proteomics & Bioinformatics 2016年第1期14卷 55-61页

作者： Alexander Marx Christina Backes Eckart Meese Hans-Peter Lenhof Andreas Keller chair for Clinical Bioinformatics Medical Faculty Saarland University Department of Human Genetics Saarland University University Hospital chair for Bioinformatics Saarland University

In many research disciplines, hypothesis tests are applied to evaluate whether findings are statistically significant or could be explained by chance. The Wilcoxon-Mann-Whitney （WMW） test is among the most popular hypothesis tests in medicine and life science to analyze if two groups of samples are equally distributed. This nonparametric statistical homogeneity test is commonly applied in molecular diagnosis. Generally, the solution of the WMW test takes a high combinatorial effort for large sample cohorts containing a significant number of ties. Hence, P value is frequently approximated by a normal distribution. We developed EDISON-WMW, a new approach to calcu- late the exact permutation of the two-tailed unpaired WMW test without any corrections required and allowing for ties. The method relies on dynamic programing to solve the combinatorial problem of the WMW test efficiently. Beyond a straightforward implementation of the algorithm, we pre- sented different optimization strategies and developed a parallel solution. Using our program, the exact P value for large cohorts containing more than 1000 samples with ties can be calculated within minutes. We demonstrate the performance of this novel approach on randomly-generated data, benchmark it against 13 other commonly-applied approaches and moreover evaluate molec- ular biomarkers for lung carcinoma and chronic obstructive pulmonary disease （COPD）. We foundthat approximated P values were generally higher than the exact solution provided by EDISON- WMW. Importantly, the algorithm can also be applied to high-throughput omics datasets, where hundreds or thousands of features are included. To provide easy access to the multi-threaded version of EDISON-WMW, a web-based solution of our algorithm is freely available at http：// ***/software/wtest/.

关键词： Wilcoxon-Mann-Whitneytest:Wilcoxon rank-sum test Dynamic programing Exact permutation Parallel optimization

Variability of European beech wood density as influenced by interactions between treering growth and aspect

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Forest Ecosystems 2016年第3期3卷 165-173页

作者： Daniela Diaconu Marc Wassenberg Heinrich Spiecker chair of Forest Growth and Dendroecology Albert-Ludwigs-University

Background： Wood density is considered to be the most important predictor of wood quality but despite its importance, diffuse-porous tree species have been the subject of only a limited number of studies. The importance of European beech forests for Central Europe calls for profound research to examine the potential impact of a warmer climate on the quality of beech timber. Methods： In this study we analysed the influence of tree-ring width and tree-ring age on the wood density of beech, and whether the wood density response to these two parameters is modified by aspect. A linear mixed-effects model for wood density was constructed for mean density data measured with high frequency densitometry on stem discs from 72 beech trees sampled from two different aspects （northeast -NE and southwest -SW） of a valley in southwestern Germany. Results： Part of the variability of mean annual wood density was explained by cambial age： an increase in cambial age resulted in an increase in mean wood density. Tree-ring width and aspect had only a small influence on wood density, Wood density on the SW aspect was lower than on the NE with a difference of approximately 0.006 g/cm3. The between-tree variability was very high. Conclusions： The significant interaction between cambial age and aspect reflects the importance of site conditions at older tree ages： with increasing cambial age the difference between aspects becomes stronger. Our results give a better understanding of the importance of site conditions on the wood quality of beech.

关键词： Fagus sylvatica HF densitometry Wood quality Wood density Aspect

Flow frictional characteristics of microencapsulated phase change material suspensions flowing through rectangular minichannels

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Science China(Technological Sciences) 2006年第4期49卷 445-456页

作者： Frank Dammel Peter Stephan chair of Technical Thermodynamics Darmstadt University of Technology Germany

An experimental investigation was conducted on the laminar flow frictional characteristics of suspensions with microencapsulated phase change material (MEPCM) in water flowing through rectangular copper minichannels. The MEPCM was provided at an average particle size of 4.97 μm, and was mixed with distilled water to form suspen- sions with various mass concentrations ranging from 0 to 20%. The experiment was per- formed to explore the effect of MEPCM mass concentration on friction factor and pressure drop in the minichannels. The Reynolds number ranged from 200 to 2000 to provide laminar and transitional flows. It was found that the experimental data for the suspensions with 0 and 5% concentration agree well with the existing theoretical data for an incom- pressible, fully developed, laminar Newtonian flow. For the suspensions with mass con- centrations higher than 10%, there is an obvious increase in friction factor and pressure drop in comparison with laminar Newtonian flow.

关键词： microencapsulated phase change material suspension, friction factor, rectangular minichannel.

Group control for procedural rules:parameterized complexity and consecutive domains

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Frontiers of Computer Science 2024年第3期18卷 133-141页

作者： Yongjie YANG Dinko DIMITROV chair of Economic Theory Saarland UniversitySaarbrücken 66123Germany

We consider GROUP CONTROL BY ADDING INDIVIDUALS(GCAI)in the setting of group identification for two procedural rules-the consensus-start-respecting rule and the liberal-start-respecting *** is known that GCAI for both rules are NP-hard,but whether they are fixed-parameter tractable with respect to the number of distinguished individuals remained *** resolve both open problems in the *** addition,we strengthen the NP-hardness of GCAI by showing that,with respect to the natural parameter the number of added individuals,GCAI for both rules are W[2]-***,the W[2]-hardness for the liberal-startrespecting rule holds even when restricted to a very special case where the qualifications of individuals satisfy the so-called consecutive ones ***,for the consensus-startrespecting rule,the problem becomes polynomial-time solvable in this special *** also study a dual restriction where the disqualifications of individuals fulfill the consecutive ones property,and show that under this restriction GCAI for both rules turn out to be polynomial-time *** reductions for showing W[2]-hardness also imply several algorithmic lowerbounds.

关键词： group control by adding individuals group identification parameterized complexity consecutive ones property FPT W-hard