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Graphite Nucleation in Cast Iron Melts Based on Solidification Experiments and Microstructure Simulation

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Journal of Materials Science & Technology 2008年第3期24卷 321-324页

作者： Andreia Sommerfeld bernd Bttger Babette Tonn Institute of Metallurgy Clausthal University of TechnologyClausthal-Zellerfeld ACCESS e.V. Intzestr.552072 Aachen

Microstructure strongly influences the mechanical properties of cast iron. By inoculating the melt with proper inoculants, foreign substrates are brought into the melt and eventually the graphite can crystallize on them. The elements and substrates that really play a role for nucleation are yet unknown. Until now there is very little knowledge about the fundamentals of nucleation, such as composition and morphology of nuclei. In this work we utilized EN-GJL-200 as a base material and examined several produced specimens. The specimens were cast with and without inoculants and quenched at different solidification states. Specimens were also examined with a high and low oxygen concentration, but the results showed that different oxygen contents have no influence on the nucleation in cast iron melts. Our research was focused on the microscopic examination and phase-field simulations. For studying the samples we applied different analytical methods, where SEM-EDS, -WDS were proved to be most effective. The simulations were conducted by using the software MICRESS, which is based on a multiphase-field model and has been coupled directly to the TCFE3 thermodynamic database from TCAB. On the basis of the experimental investigations a nucleation mechanism is proposed, which claims MnS precipitates as the preferred site for graphite nucleation. This theory is supported by the results of the phase-field simulations.

关键词： Graphite nucleation Cast iron melts Solidification Microstructure simulation

On the reversibility of the α_(2)/ω_(o) phase transformation in a high Nb containing TiAl alloy during high temperature deformation

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Journal of Materials Science & Technology 2021年第34期93卷 96-102页

作者： Lin Song Fritz appel Andreas Stark Uwe Lorenz Junyang He Zhanbing He Junpin Lin Tiebang Zhang Florian Pyczak State Key Laboratory of Solidification Processing Northwestern Poly technical University.Xi'an 710072China Institute of Materials Research Helmholtz-Zentrum GeesthachtMax Planck-Str.1Geesthacht 21502Germany Department of Microstructure Physics and Alloys Design Max-Planck-lnsdtut fiir Eisenforschung GmbHDusseldorf 40237Germany State Key Laboratory for Advanced Metals and Materials University of Science and Technology BeijingBeijing 100083China

The transformations between the phasesα_(2)(Ti_(3)Al)andω_(o)were investigated in a lamellar multiphase titanium aluminide alloy based onγ(TiAl).The paper complements an earlier investigation performed on the same material in which the importance of deformation-induced twin structures for theα_(2)→ω_(o) transformation was *** present study shows that the reverse transformationω_(o)→α_(2) can also occur during high-temperature *** transformation is probably triggered by constraint stresses,which exist between the different constituents due to the crystalline *** combined operation of mechanical twinning of theα_(2) phase and the reversible transformation fully converts theα_(2) lamellae into a mixture ofα_(2) andω_(o).This conversion greatly reduces the mechanical anisotropy existing in formerα_(2) *** the technical use of the alloy,the stability of the converted structure with respect to further annealing was also *** reported processes occur at the nano-meter and sub nano-meter scale,thus,advanced characterization techniques were applied,such as high-resolution transmission electron microscopy(HRTEM)and atom probe tomography(APT).

关键词： TiAl alloys Phase transformation Electron microscopy Microstructure

The central role of stem cells in determining plant longevity variation

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Plant Communications 2023年第5期4卷 97-111页

作者： Omid Karami bernd Mueller-Roeber Arezoo Rahimi Plant Developmental Genetics Institute of Biology LeidenLeiden UniversitySylviusweg 722333 BE Leidenthe Netherlands University of Potsdam Institute of Biochemistry and BiologyKarl-Liebknecht-Straße 24–25Haus 2014476 PotsdamGermany Present address:Huygens-Kamerlingh Onnes Laboratory Leiden UniversityNiels Bohrweg 22333 CA Leidenthe Netherlands

Vascular plants display a huge variety of longevity patterns,from a few weeks for several annual species up to thousands of years for some perennial *** how longevity variation is structured has long been considered a fundamental aspect of the life sciences in view of evolution,species distribution,and adaptation to diverse *** animals,whose organs are typically formed during embryogenesis,vascular plants manage to extend their life by continuously producing new tissues and organs in apical and lateral directions via proliferation of stem cells located within specialized tissues called *** cells are the main source of plant *** in plant longevity is highly dependent on the activity and fate identity of stem *** developmental factors determine how stem cells contribute to variation in plant *** this review,we provide an overview of the genetic mechanisms,hormonal signaling,and environmental factors involved in controlling plant longevity through long-term maintenance of stem cell fate identity.

关键词： stem cells plant longevity annual plants perennial plants axillary meristems

Subcellular Distribution of Glutathione Precursors in Arabidopsis thaliana

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Journal of Integrative Plant Biology 2011年第12期53卷 930-941页

作者： Barbara Eva Koffler Romana Maier bernd Zechmann University of Graz Institute of Plant Sciences 8010 Graz Austria Graz University of Technology Institute for Electron Microscopy and Fine Structure Research 8010 Graz Austria

Glutathione is an important antioxidant and has many important functions in plant development, growth and defense. Glutathione synthesis and degradation is highly compartment-specific and relies on the subcellular availability of its precursors, cysteine, glutamate, glycine and γ-glutamylcysteine especially in plastids and the cytosol which are considered as the main centers for glutathione synthesis. The availability of glutathione precursors within these cell compartments is therefore of great importance for successful plant development and defense. The aim of this study was to investigate the compartmentspecific importance of glutathione precursors in Arabidopsis thaliana. The subcellular distribution was compared between wild type plants （Col-0）, plants with impaired glutathione synthesis （glutathione deficient pad2-1 mutant, wild type plants treated with buthionine sulfoximine）, and one complemented line （OE3） with restored glutathione synthesis. Immunocytohistochemistry revealed that the inhibition of glutathione synthesis induced the accumulation of the glutathione precursors cysteine, glutamate and glycine in most cell compartments including plastids and the cytosol. A strong decrease could be observed in γ-glutamylcysteine （γ-EC） contents in these cell compartments. These experiments demonstrated that the inhibition of γ-glutamylcysteine synthetase （GSH1） - the first enzyme of glutathione synthesis - causes a reduction of γ-EC levels and an accumulation of all other glutathione precursors within the cells.

关键词： Arabidopsis cysteine glutamate glutathione glycine.

Surfel-based surface modeling for robotic belt grinding simulation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第7期7卷 1215-1224页

作者： REN Xiang-yang MUELLER Heinrich KUHLENKOETTER bernd Robotics Research Institute University of Dortmund Dortmund 44227 Germany Informatik VII University of Dortmund Dortmund 44227 Germany

The new flee-form surface modelling technology for robotic belt grinding simulation presented in this paper is based on discrete surfel elements generated from the surface approximation point set and can facilitate the simulation implementation. A local process model exploits the advantage of surfel representation to compute the material removal rate and the final surface grinding error can be easily carried out. With the help of this system, robot programmers can improve the path planning and predict potential problems by visualizing the manufacturing process.

关键词： Surface modelling Surfel Belt-grinding simulation

Use of ionic liquid in leaching process of brass wastes for copper and zinc recovery

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International Journal of Minerals,Metallurgy and Materials 2014年第2期21卷 138-143页

作者： Ayfer Kilicarslan Muhlis Nezihi Saridede Srecko Stopic bernd Friedrich Department of Metallurgical and Materials Engineering (Davutpasa Campus) Yildiz Technical University Department of Process Metallurgy and Metal Recycling (IME) RWTH Aachen University

Brass ash from the industrial brass manufacturer in Turkey was leached using the solutions of ionic liquid （IL） 1-butyl-3-methyl-imi-dazolium hydrogen sulfate （[bmim]HSO4） at ambient pressure in the presence of hydrogen peroxide （H2O2） and potassium peroxymonosulfate （oxone） as the oxidants. Parameters affecting leaching efficiency, such as dissolution time, IL concentration, and oxidizing agent addition, were investigated. The results show that [bmim]HSO4 is an efficient IL for the brass ash leaching, providing the dissolution efficiencies of 99%for Zn and 24.82%for Cu at a concentration of 50vol%[bmim]HSO4 in the aqueous solution without any oxidant. However, more than 99%of zinc and 82%of copper are leached by the addition of 50vol%H2O2 to the [bmim]HSO4 solution. Nevertheless, the oxone does not show the promising oxidant behavior in leaching using [bmim]HSO4.

关键词： leaching recovery copper zinc ionic liquids oxidants

Genetic-algorithm-based artificial intelligence control of a turbulent boundary layer

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Acta Mechanica Sinica 2021年第12期37卷 1739-1747页

作者： Jianing Yu Dewei Fan bernd.R.Noack Yu Zhou Center for Turbulence Control Harbin Institute of Technology(Shenzhen)Shenzhen 518055China School of Mechanical Engineering and Automation Harbin Institute of Technology(Shenzhen)Shenzhen 518055China

An artificial intelligence(AI)open-loop control system is developed to manipulate a turbulent boundary layer(TBL)over a flat plate,with a view to reducing friction *** system comprises six synthetic jets,two wall-wire sensors,and genetic algorithm for the unsupervised learning of optimal control *** of the synthetic jets through rectangular streamwise slits can be independently controlled in terms of its exit velocity,frequency and actuation *** are conducted at a momentum-thickness-based Reynolds number Re_(θ)of *** local drag reduction downstream of the synthetic jets may reach 48%under conventional open-loop *** local drag reduction rises to 60%,with an extended effective drag reduction area,under the AI control that finds optimized non-uniform *** results point to the significant potential of AI in the control of a TBL given distributed actuation.

关键词： Turbulent boundary layer Active drag reduction Artificial intelligence

Layerwise third-order shear deformation theory with transverse shear stress continuity for piezolaminated plates

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Chinese Journal of Aeronautics 2024年第9期37卷 490-505页

作者： Yingshan GAO Shunqi ZHANG Wei HU Songyun MA bernd MARKERT School of Mechatronic Engineering and Automation Shanghai UniversityShanghai 200444China Key Laboratory of Silicate Cultural Relics Conservation(Shanghai University) Ministry of EducationShanghai 20044China Institute of General Mechanics RWTH Aachen UniversityAachen 52062Germany

Regarding laminated structures,an electromechanically coupled Finite Element(FE)model based on Layerwise Third-Order Shear Deformation(LW-TOSD)theory is proposed for sta-tic and dynamic ***-TOSD ensures the continuity of in-plane displacements and trans-verse shear *** current LW-TOSD can be applied to arbitrary multi-layer laminated structures with only seven Degrees of Freedom(DOFs)for each element node and eliminates the use of the shear correction ***,a shear penalty stiffness matrix is constructed to sat-isfy artificial constraints to optimize the structural shear strain.A dynamic finite element model is obtained based on LW-TOSD using the Hamilton's ***,the accuracy of the current model is validated by comparing with literature and ABAQUS ***,this study carries out numerical investigations of piezolaminated structures for different width-to-thickness ratios,length-to-width ratios,penalty stiffness matrix,boundary conditions,electric fields and dynamics.

关键词： Laminated structures Piezolaminated structures Third-order shear deformation theory Shear stress continuity Electromechanically coupled

Model of an iron ore sinter plant with selective waste gas recirculation

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Carbon Resources Conversion 2022年第1期5卷 71-83页

作者： Johannes Niel bernd Weiss Walter Wukovits TU Wien Institute of ChemicalEnvironmental and Bioscience EngineeringGetreidemarkt 9/1661060 ViennaAustria Primetals Primetals Technologies Austria GmbHLinzAustria

The use of sinter influences hot metal production substantially and significantly affects an integrated steel mill’s total emissions. Sintering of iron ores is an enormousenergy-intensive and resources consuming process. Introducing a selective waste gas recirculation (SWGR) to the sintering process reduces the energy consumption,stack gas volume flow, and sulfur dioxide emissions of an iron sinter production. Simulating this complex process in flowsheet simulations of integrated iron andsteelworks is a fast and cost-effective opportunity to validate new operation settings. The implementation of a sinter plant in gPROMS ModelBuilder®characterizesthe sintering processes by three main sub-models. A burner model describes the gas combustion, a black-box model consider the main sintering processes, and a windbox model divides the total off-gas into a recycle gas and a stack gas. A specific temperature polynomial represents the temperature distribution across the wind boxesto allow detailed investigations on SWGR in complex flowsheet simulations. Implementing SWGR to the sintering process, the model shows a reduction of cokeconsumption, stack gas flow rate, and sulfur dioxide emissions by 11%, 27%, and 27%, respectively. In the SWGR scenario, the utilization rate of carbon monoxideincreases and less coke is consumed. The chlorine emissions of the sintering process differ with and without SWGR insignificantly.

关键词： dioxide monoxide consuming