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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 beds.An accurate and reliable simulation of the heat exchange between particles is therefore crucial for a reliable operation and to optimize the processes in the bed.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 propagation.In this work,DOM is compared with Monte Carlo ray tracing,which provides an alternative method for heat transfer simulations.Geomet-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 methods.The 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 available.Our results show that both DOM and Monte Carlo ray tracing allow for an accurate simulation of heat transfer in packed beds.Monte 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 solutions.In 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 steel.Both methods are comparable for diffuse materials such as magnesium oxide.

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

On Integral Graphs which Belong to the Class ■

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Journal of Mathematical Research with Applications 2024年第4期 444-464页

作者： mirko LEPOVI? Tihomira Vuksanovi?a 32

Abstract Let G be a simple graph and let ■ denote its complement.We say that G is integral if its spectrum consists entirely of integers.In this work we establish a characterization of integral graphs which belong to...

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Multi-point temperature measurements in packed beds using phosphor thermometry and ray tracing simulations

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Particuology 2024年第2期85卷 77-88页

作者： Guangtao Xuan mirko Ebert Simson Julian Rodrigues Nicole Vorhauer-Huget Christian Lessig Benoit Fond Institute of Fluid Dynamics and Thermodynamics OVGU MagdeburgUniversitaetsplatz 2Magdeburg39106Saxony-AnhaltGermany Institute of Simulations and Graphics OVGU MagdeburgUniversitaetsplatz 2Magdeburg39106Saxony-AnhaltGermany Institute of Process Engineering OVGU MagdeburgUniversitaetsplatz 2Magdeburg39106Saxony-AnhaltGermany ONERA The French Aerospace LabDepartment of AerodynamicsAeroelasticity and Aeroacoustics(DAAA)Paris-Saclay University8rue des VertugadinsMeudon92190France

Packed bed reactors are commonly found in the process industry,for example in flame-assisted calci-nation for cement production.Understanding the heat transfer inside the bed is essential for process control,product quality and energy efficiency.Here we propose a technique to determine the internal temperature distribution of packed beds based on a combination of lifetime-based phosphor ther-mometry,ray tracing simulations,and assimilation of temperature data using finite element heat transfer simulations.To establish and validate the technique,we considered a reproducible regular packing of 6 mm diameter aluminum spheres,with one of the spheres in the top layer being electrically heated.If a sphere inside the packing is coated with thermographic phosphors and excitation light is directed to-wards the packing,luminescence from the coated sphere exits the packed bed after multiple reflection and the sphere's temperature can be determined.Isothermal measurements showed that the temper-ature obtained by phosphor thermometry is independent of the luminescent sphere location.When imaging the luminescence on a camera,the luminescence distribution in recorded image depended,however,on the position of the sphere.Therefore,in setups with multiple phosphor-coated spheres,their signals can be separated using a least squares fit.We demonstrate the approach using a setup with three luminescent spheres and validated the temperature readings against thermocouple measurements.To obtain the spatial signatures for individual sphere positions required for the least squares fit,ray tracing simulations were used.These provide an efficient alternative to single sphere measurements that are only practical for regular spherical packed beds.Multi-point measurements were used as input to a finite element heat transfer simulations to determine parameters such as particle-to-particle air gap distance.With these,the full temperature distribution inside the bed could be assimilated from the measured values.

关键词： Packed beds Phosphor thermometry Ray tracing Heat transfer simulation Data assimilation

Accelerated intermetallic phase amorphization in a Mg-based high-entropy alloy powder

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Journal of Magnesium and Alloys 2024年第5期12卷 1792-1798页

作者： Prince Sharma Purvam Mehulkumar Gandhi Kerri-Lee Chintersingh mirko Schoenitz Edward L.Dreizin Sz-Chian Liou Ganesh Balasubramanian Institute for Functional Materials&Devices Lehigh University Center of Materials for Advanced Energetics New Jersey Institute of Technology

We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling. The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition. Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure. This transformation, characterized by the emergence of antisite disorder, lattice expansion, and the presence of nanograin boundaries, signifies a departure from the precursor intermetallic structure. Additionally, this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy. The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.

关键词： High-entropy alloy High-energy milling Antisite disorder Amorphous Intermetallic

低水灰比下聚羧酸减水剂对超高性能混凝土分散性能的研究

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科技风 2022年第23期 60-62页

作者： mirko cruber 刘欢 Serina Ng 王进春石家庄市长安育才建材有限公司河北石家庄051530 河北省混凝土用功能性材料工程技术研究中心河北石家庄051530 河北省建筑化学添加剂产业技术研究院河北石家庄051530 四川砼道科技有限公司四川成都611139

通过对不同结构聚羧酸减水剂进行超高性能混凝土(UHPC)小型流动性试验,分析了不同结构聚羧酸减水剂(PCE)对UHPC流动性的影响。PC3聚羧酸减水剂是非常经济的,1.40%的掺量就可以使UHPC具有良好的流动性。小分子量的聚羧酸减水剂,如PC8在... 详细信息

通过对不同结构聚羧酸减水剂进行超高性能混凝土(UHPC)小型流动性试验,分析了不同结构聚羧酸减水剂(PCE)对UHPC流动性的影响。PC3聚羧酸减水剂是非常经济的,1.40%的掺量就可以使UHPC具有良好的流动性。小分子量的聚羧酸减水剂,如PC8在水灰比低至0.16的情况下,仍然能使UHPC保持良好的流动性,但是掺量需要增加到3.10%。不同结构聚羧酸减水剂的经济效益是不一样的,根据不同的水灰比的要求,需要合理设计聚羧酸减水剂的结构,从而使聚羧酸高性能减水剂达到更好的经济性,节约资源,更加环保。

关键词： UHPC 聚羧酸高性能减水剂分子结构

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Functional Dependence of IM and HV Angle in Hallux Valgus Deformity before and after Operative

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Journal of Applied Mathematics and Physics 2024年第5期12卷 1626-1646页

作者： Nenad Stojanović mirko Sovilj Vesna Ivanišević Department of Mathematics Faculty of Philosophy University of Banja Luka Banja Luka Bosnia and Herzegovina Higher Medical School Prijedor Bosnia and Herzegovina Faculty of Medicine University of Banja Luka Banja Luka Bosnia and Hercegovina

Hallux valgus is a relatively common and multifaceted complex deformity of the front part of the foot. It is the result of multiple effects of innate (endogenous) and exogenous etiological factors with different degrees of influence. The degree of hallux valgus deformity is usually assessed by radiological values of hallux valgus (HV) and intermetatarsal (IM) angles. The aim of the paper is to justify the definition of hallux valgus deformity as a function of one angle, (HVA or IMA), and then to determine the functional connection and the most suitable function equalizing the values of the angles IMA and HVA. As hallux valgus is a double angulation deformity, the analytically determined connection between the HVA and IMA angles reduces the study of the deformity to the study of function with one argument, and makes the analysis of deformity changes before and after operative treatment simpler. For the determined connections between the angles, the values of linear proportionality coefficients and regression coefficients of corresponding linear functions of analytical equalization of the value of the IM angle and the degree of deformity for a given value of the HV angle were experimentally determined. The obtained results were checked on a sample of 396 operatively treated hallux valgus deformities. The presented analytical approach and the obtained functional links of IMA and HVA enable quantitative observation of the change in the degree of deformity based on the radiologically determined value of these angles, and the established nonlinear function will be useful for evaluating the expected value of the IM angle and the degree of deformity based only on the measured value of the HV angle. .

关键词： Functional Connection of Deformity Angles Analytical Equalization of IM Angle Values Hallux Valgus Intermetatarsal Angle Correction of Deformity

不同机制砂对混凝土工作性能的影响及改善措施

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科技风 2022年第20期 76-78,124页

作者：王玉乾 Serina Ng 刘磊 mirko cruber 王进春石家庄市长安育才建材有限公司河北石家庄051530 河北省混凝土用功能性材料工程技术研究中心河北石家庄051530 河北省建筑化学添加剂产业技术研究院河北石家庄051530 四川砼道科技有限公司四川成都611139

结合不同工程案例,探讨机制砂常见的问题,分析其对混凝土造成的影响及原因,并根据不同的机制砂提出相应的改善方法。由试验结果可知,通过混凝土配合比和外加剂调整可有效改善混凝土的工作性能。

关键词：机制砂混凝土配合比混凝土外加剂

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Sc元素添加对双辊铸轧Al−Cu−Li−Mg−Zr基合金热处理的影响

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Transactions of Nonferrous Metals Society of China 2024年第6期34卷 1759-1773页

作者： Rostislav KRÁLÍK Barbora KŘIVSKÁ Lucia BAJTOŠOVÁ Mykhailo STOLBCHENKO mirko SCHAPER Olexandr GRYDIN Miroslav CIESLAR Department of Physics of Materials Faculty of Mathematics and PhysicsCharles UniversityKe Karlovu 512116PragueCzech Republic Department of Materials Science Faculty of Mechanical EngineeringUniversity of PaderbornWarburger Straße 10033098PaderbornGermany

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金... 详细信息

提出制备含Sc的Al−Cu−Li−Mg−Zr基合金带材的工艺方案。即先采用双辊铸轧技术制备近净形状的3 mm厚带材,再对其进行均匀化/固溶处理。研究两种Al−Cu−Li−Mg−Zr基双辊铸轧合金,其中一种添加质量分数为0.17%的Sc,另一种未添加Sc。两种合金均先在300℃下退火30 min,然后在450℃下退火30 min以及530℃下退火30 min,随后进行室温水淬。前两段退火后组织中生成了细小、弥散的Al_(3)Zr/Al_(3)(Sc,Zr)颗粒。最后的退火步骤起到了均匀化/固溶处理的作用。双辊铸轧材料的细小晶粒结构使含有主要合金元素的原始颗粒在较短的退火时间内溶解。缩短保温时间可以限制表面层中Li的耗尽和Al_(3)Zr/Al_(3)(Sc,Zr)弥散相的明显粗化。铸态含Sc材料已经具有明显细小的晶粒结构,而经均匀化/固溶处理后生成的Al_(3)(Sc,Zr)弥散相抑制了晶粒在高温下发生粗化。在后续180℃下时效处理后,形成了θʹ(Al_(2)Cu)、T1(Al_(2)CuLi)和S'(Al_(2)CuMg)强化相。在峰值时效状态下,屈服强度提高了200 MPa,这一数值与类似直接冷却铸造材料的相当,从而证实了所提方案的合理性。

关键词：显微组织力学性能 Al−Cu−Li基合金 Sc合金化双辊铸轧

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Older European Adults and Access to Healthcare During the COVID-19 Pandemic

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China CDC weekly 2022年第39期4卷 879-884页

作者： Yushan Yu mirko Petrovic Wei-Hong Zhang International Centre for Reproductive Health(ICRH) Department of Public Health and Primary CareFaculty of Medicine and Health SciencesGhent UniversityGhentBelgium Section of Geriatrics Department of Internal Medicine and PaediatricsFaculty of Medicine and Health SciencesGhent UniversityGhentBelgium School of Public Health Universitélibre de Bruxelles(ULB)BruxellesBelgium

In Europe,population ageing poses a challenge.Given accelerating population ageing in Europe,longterm care(LTC)is a growing concern.Unmet healthcare needs varied among European countries during the coronavirus disease 2019(COVID-19)pandemic,and greater attention should be paid to ensuring that the healthcare needs of vulnerable populations are met.Notably,developing common and comparable indicators is useful for monitoring the LTC and healthcare of older adults at the national and international levels,and understanding the reasons for the differences in indicators between European countries could shed light on how to improve the health of older adults.

关键词： Access ageing COV