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A numerical and experimental comparison of heat transfer in a quasi two-dimensional packed bed

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Particuology 2024年第1期84卷 136-144页

作者： Matthias Tyslik Mirko Ebert Martin Schiemann siegmar wirtz Christian Lessig Department of Energy Plant Technology Ruhr-University BochumGermany Institute for Simulation and Graphics Otto-von-Guericke-Universität MagdeburgGermany

Heat transfer plays a major role in many industrial processes taking place in packed *** accurate and reliable simulation of the heat exchange between particles is therefore crucial for a reliable operation and to optimize the processes in the *** discrete ordinates method(DOM)provides an established numerical technique to model radiative heat transfer in granular media that offers the possibility to consider the directional dependence of the radiation *** this work,DOM is compared with Monte Carlo ray tracing,which provides an alternative method for heat transfer ***-rically simple configurations are used to investigate the influence of the angular discretization on the accuracy of the results and the computation time in both *** obtained insights are then transferred to a more complex configuration of a quasi two-dimensional test rig consisting of metal rods for which also experimental results are *** results show that both DOM and Monte Carlo ray tracing allow for an accurate simulation of heat transfer in packed *** Carlo ray tracing requires thereby computation times that are surprisingly competitive(although still somewhat slower)compared to DOM and allows for an easier computation of highly accurate reference *** our preliminary comparison to the experimental test rig,Monte Carlo ray tracing also provides the advantage that it can more easily model highly specular materials such as stainless *** methods are comparable for diffuse materials such as magnesium oxide.

关键词： Heat transfer Discrete ordinates method Monte Carlo ray tracing

Investigating the inflow into a granular bed using a locally resolved method

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Particuology 2024年第2期85卷 89-101页

作者： Maximilian Brommer Maik Scharnowski Enric Illana Mahiques siegmar wirtz Viktor Scherer Ruhr University Bochum Institute of Energy Plant TechnologyUniversitätsstraβe 15044780BochumGermany

Discrete Element Method-Computational Fluid Dynamics(DEM/CFD)simulations of industrial-scale granular systems employ spatial averaging(porous media approach)for the fluid-particle interaction in the whole domain,which can lead to poor accuracy,for instance at flow inlets,as local particle bulk morphology is not *** paper presents an approach where the interstitial flow in crucial areas with large gradients can be resolved locally in an otherwise unresolved domain,so that a mixed resolved-unresolved method is *** a generic example to show the feasibility and performance of the new approach,the inflow of ambient air into a flat-bottom hopper through a narrow orifice is *** an experimental setup,the vertical profile of the pressure decay through the inlet and across the packing is chosen for com-parison with respective *** obtained with the conventional porous media method and the locally resolved approach are compared to these experiments for varying volume flow rates and for two different particle *** of different size as well as dodecahedrons are *** is found that although averaging methods already provide good approximations,the locally resolved method can improve the result especially when conventional drag laws are not applicable due to wall effects or if large velocity gradients exist.

关键词： DEM/CFD Packed bed Pressure drop

Shape-changing particles for locally resolved particle geometry in DEM simulations

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Particuology 2024年第6期89卷 185-190页

作者： Enric Illana Klidi Qyteti Maik Scharnowski Maximilian Brömmer siegmar wirtz Viktor Scherer Institute of Energy Plant Technology Ruhr-University BochumBochumGermany

Taking into account the complex shape of particles in discrete element method (DEM) simulations of large-scale granular systems is computationally demanding due to the time-consuming contact detection algorithms for polyhedral particles. In this short communication, a novel approach that locally resolves the particle shapes where needed and uses a simplified representation elsewhere, to accelerate simulations without compromising accuracy, is presented. For this purpose, a method employing a smooth transition of the particle shape representation from analytical spheres to shape-resolving polyhedra is introduced in DEM. The feasibility and correct implementation of this approach are demonstrated through simulations of hopper discharge involving spherical and dodecahedral particles from a flat bottom silo or shaft kiln. The model capabilities, in terms of accuracy as well as reduction in computational effort, are quantified for a moving bed with continuous outflow.

关键词： Polyhedron Size change Shape change Locally resolved DEM

Convective drying of wood chips:Accelerating coupled DEM-CFD simulations with parametrized reduced single particle models

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Particuology 2024年第1期84卷 158-167页

作者： Lucas Reineking Jonas Fischer Ali Mjalled Enric Illana siegmar wirtz Viktor Scherer Martin Monnigmann Automatic Control and System Theory Ruhr-Universität-BochumUniversitätstraße 150Bochum44801Germany Energy Plant Technology Ruhr-Universität-BochumUniversitätstraße 150Bochum44801Germany

The simulation of industry-scale reactive bulks is challenging due to the complex interaction between fluid and *** particles in the bulk and their interaction with the fluid flow can be described by combined Discrete Element Method-Computational Fluid Dynamics(DEM-CFD)***,the computational cost of the Finite Volume(FV)methods deployed in these models can become prohibi-tively expensive,especially for high inner-particle *** particle Reduced Models(RMs)can be used to achieve both fast and accurate descriptions of the processes in each *** an example of bulk systems comprising heat and mass transfer,we compared FV and RM simulations for the drying of wood chips in a bulk reactor.A manifold-based nonlinear interpolation was applied to resolve changing boundary conditions for the *** simulations showed that RMs provide accurate values for the thermodynamic state variables of the ***,the time required for the bulk simulation was reduced by 67%with the *** is evident that simulations with high inner-particle resolution can be accelerated by RMs if manifold-based nonlinear interpolation is used to address changing boundary conditions.

关键词： Reduced model Reactive bulk Discrete element method Manifold-based interpolation Drying of porous mediaDEM-CFD

Comparing two IBM implementations for the simulation of uniform packed beds

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Particuology 2024年第3期86卷 1-12页

作者： Christian Gorges Maximilian Brommer Christin Velten siegmar wirtz Enric Illana Mahiques Viktor Scherer Katharina Zahringer Berend van Wachem Mechanical Process Engineering Otto-von-Guericke-Universitat MagdeburgUniversitatsplatz 239106MagdeburgGermany Department of Energy Plant Technology Ruhr-Universitat BochumUniversitatsstraBe 15044780BochumGermany Laboratory of Fluid Dynamics and Technical Flows Otto-von-Guericke-Universitat MagdeburgUniversitatsplatz 239106MagdeburgGermany

Nowadays,the design of fixed packed bed reactors still relies on empirical correlations,which,especially for small tube to particle diameter ratios,are mostly too inaccurate because of the presence of wall ***,the simulation of fixed packed bed reactors plays an important role to predict and control the flow and process parameters in such,nowadays and in the *** of its straightforward applicability to non-uniform packings with particles of arbitrary shapes,the immersed boundary method(IBM)has advantages over other numerical methods and is used more and more *** paper compares two approaches of IBMs for the simulation of fixed bed reactors with spherical shaped *** classic,smooth approach is compared to the straightforward to implement blocked-off method for velocity fields above the fixed bed for particle Reynolds numbers of 300 and *** from experimental inline PIV-measurements of the reactor to be simulated serve as a basis for *** good agreement with the experiment is found for both simulation methodologies with higher resolutions,considering the more stable flow at a particle Reynolds number of *** in the different IBM approaches occurred for the more unsteady flow at a particle Reynolds number of *** to the blocked-off method,the smooth IBM reflects the formation of additional jets and recirculation zones better right above the bed,though increasing the fluid mesh resolution improves the accuracy of the blocked-off ***,a more diffusive behaviour is found for the blocked-off simulations due to the stairstep representation,which is avoided by using interpolation stencils as in the smooth *** higher mesh refinement in the blocked-off IBM this effect can be reduced,but this also increases the computational effort.

关键词： Immersed boundary method Packed bed reactor Uniform particle packing

Three-dimensional analysis of the gap space under forearm casts

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Chinese Journal of Traumatology 2022年第2期25卷 77-82页

作者： Roman wirtz Silvia Pianigiani Bernardo Innocenti Frédéric Schuind Department of Orthopaedics and Traumatology UniversitéLibre de BruxellesCampus Hospitalo-Facultaire Erasme1070BruxellesBelgium BEAMS Department UniversitéLibre de BruxellesÉcole Polytechnique de Bruxelles1050BruxellesBelgium

Purpose:Secondary displacement represents a frequent complication of conservative treatment of fractures,particularly of the distal *** gap space between skin and cast may lead to a certain degree movements and this increased mobility might favor *** aim of this study was to develop a new 3D method,to measure the gap space in all 3 geometrical planes,and to validate this new technique in a clinical setting of distal radius ***:This study applies 3D imaging to measure the space between plaster and skin as a potential factor of secondary displacement and therefore the failure of conservative *** developed and validated a new methodology to analyze and compare different forearm casts made of plaster of Paris and *** unpaired t-test was performed to document differences between the investigated parameters between plaster of Paris and fiberglass *** significance level was set at p<***:In a series of 15 cases,we found the width of the gap space to average 4 mm,being slightly inferior on the radial *** the two different casting materials,plaster of Paris and fiberglass,we found a significantly larger variance of space under casts made of the first material(p=0.39).A roughness analysis showed also a markedly significantly higher irregularity of the undersurface of plaster of Paris as compared with ***:This study allows for a better understanding of the nature of the"gap space"between cast and skin and will contribute to develop and improve new immobilization techniques and materials.

关键词： Forearm Wrist casts Radius fractures Conservative treatment Gap space

Expanding Non-Patient COVID-19 Data: Towards the FAIRification of Migrants' Data in Tunisia, Libya and Niger

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Data Intelligence 2022年第4期4卷 955-970,1034,1038,1044,1047,1054页

作者： Mariem Ghardallou Morgane wirtz Sakinat Folorunso Zohra Touati Ezekiel Ogundepo Klara Smits Ali Mtiraoui Mirjam van Reisen University of Sousse Faculty of Medicine of SousseDepartment of Community MedicineResearch Laboratory LR12ES03Tunisia4002Sousse Tilburg University 1002 Tunisthe Netherlands Department of Mathematical Sciences Olabisi Onabanjo UniversityP.M.B 2002Ago-IwoyeOgun StateNigeria 120005Nigeria Data Science Nigeria Lagos 105102 Leiden University 1310 Leidenthe Netherlands Leiden University Medical Centre Leiden University1310 Leidenthe Netherlands Virus Outbreak Data Network-Africa

This article describes the FAIRification process(which involves making data Findable, Accessible, Interoperable and Reusable—or FAIR—for both machines and humans) for data related to the impact of COVID-19 on migrants, refugees and asylum seekers in Tunisia, Libya and Niger, according to the scheme adopted by GO FAIR. This process was divided into three phases: pre-FAIRification, FAIRification and postFAIRification. Each phase consisted of seven steps. In the first phase, 118 in-depth interviews and 565 press articles and research reports were collected by students and researchers at the University of Sousse in Tunisia and researchers in Niger. These interviews, articles and reports constitute the dataset for this research. In the second phase, the data were sorted and converted into a machine actionable format and published on a FAIR Data Point hosted at the University of Sousse. In the third phase, an assessment of the implementation of the FAIR Guidelines was undertaken. Certain barriers and challenges were faced in this process and solutions were found. For FAIR data curation, certain changes need to be made to the technical process. People need to be convinced to make these changes and that the implementation of FAIR will generate a long-term return on investment. Although the implementation of FAIR Guidelines is not straightforward, making our resources FAIR is essential to achieving better science together.

关键词： FAIRification process FAIR Guidelines FAIR data Tunisia Niger Libya COVID Migrants VODAN-Africa

OsHYPK-mediated protein N-terminal acetylation coordinates plant development and abiotic stress responses in rice

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Molecular Plant 2022年第4期15卷 740-754页

作者： Xiaodi Gong Yaqian Huang Yan Liang Yundong Yuan Yuhao Liu Tongwen Han Shujia Li Hengbin Gao Bo Lv Xiahe Huang Eric Linster Yingchun Wang Markus wirtz Yonghong Wang Institute of Genetics and Developmental Biology Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Crop Biology College of Life SciencesShandong Agriculture UniversityTaianShandong 271018China State Key Laboratory of Molecular Developmental Biology Institute of Genetics and Developmental BiologyChinese Academy of SciencesBeijing 100101China Centre for Organismal Studies Heidelberg University69120 HeidelbergGermany

N-terminal acetylation is one of the most common protein modifications in eukaryotes,and approximately 40%of human and plant proteomes are acetylated by ribosome-associated N-terminal acetyltransferase A(NatA)in a co-translational ***,the in vivo regulatory mechanism of NatA and the global impact of NatA-mediated N-terminal acetylation on protein fate remain ***,we identify Huntingtin Yeast partner K(HYPK),an evolutionarily conserved chaperone-like protein,as a positive regulator of NatA activity in *** found that loss of OsHYPK function leads to developmental defects in rice plant architecture but increased resistance to abiotic stresses,attributable to perturbation of the N-terminal acetylome and accelerated global protein ***,we demonstrated that OsHYPK is also a substrate of NatA and that N-terminal acetylation of OsHYPK promotes its own degradation,probably through the Ac/N-degron pathway,which could be induced by abiotic *** together,our findings suggest that the OsHYPK-NatA complex plays a critical role in coordinating plant development and stress responses by dynamically regulating NatA-mediated N-terminal acetylation and global protein turnover,which are essential for maintaining adaptive phenotypic plasticity in rice.

关键词： rice OsHYPK N-terminal acetylation protein turnover plant architecture stress response

EurBeST——商业养蜂条件下的抗螨蜂种选育

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中国蜂业 2024年第2期75卷 22-23页

作者： R.Buechler A.Uzunov C.Costa M.Meixner Y Le Conte F.Mondet M.Kovacic S.Andonov N.L.Carreck L.Dimitrov B.Basso M.Bienkowska R.Dall’Olio F.Hatjina U.wirtz 陈超(文\图) 单金琼(文\图) 不详

上期我们讲了抗螨蜜蜂的选育以及取得的成效,本期我们继续讨论选育抗螨蜜蜂过程中遇到的问题及建议。一、种蜂王的用户调查对目前蜂王市场的调查显示,客户的期望值很高,但满意度一般。欧洲养蜂人希望买到高品质的蜂王,其中最重要的是抗... 详细信息

上期我们讲了抗螨蜜蜂的选育以及取得的成效,本期我们继续讨论选育抗螨蜜蜂过程中遇到的问题及建议。一、种蜂王的用户调查对目前蜂王市场的调查显示,客户的期望值很高,但满意度一般。欧洲养蜂人希望买到高品质的蜂王,其中最重要的是抗病和高产。但是,他们对抗病性的满意度最低(图1)。近50%的用户认为选择育种是实现免用药养蜂的重要甚至唯一的手段。具有悠久育种传统的国家的用户对选择育种的认可率更高。

关键词：选择育种用户调查蜂王问题及建议抗螨养蜂人蜜蜂商业养蜂