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Determination of the sensible heat effectiveness and pressure loss of a rotary regenerative heat exchanger using CFD

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Building Simulation 2023年第6期16卷 869-887页

作者： Vladimír Zmrhal Petr Zelenský Jindřich Boháč Martin Barták Miroslav Kučera roman vavřička Faculty of Mechanical Engineering Department of Environmental EngineeringCzech Technical University in PragueTechnická416000Prague 6Czech Republic

The paper presents a new method to determine the sensible effectiveness and pressure loss of rotary regenerative heat exchangers using computational fluid dynamics(CFD).it is based on CFD simulations of a single thermal wheel microchannel with a small cross-sectional area and thin walls,with cyclic inlet and outlet boundary *** unique measurement set-ups were designed and built for the experimental measurement of the heat exchanger *** different types of thermal wheels were manufactured,measured,and simulated in ANSYS *** wheels achieve an effectiveness greater than 73%under certain(air flow)conditions,which is the minimum effectiveness required by Ecodesign(in the EU).For the examined exchangers,the effectiveness ranges from 66.5%to 83.3%,depending on the boundary conditions and geometric parameters of the *** highest sensible effectiveness is achieved by heat exchangers with the largest heat exchange surface Ac;on the other hand,these wheels have the largest pressure *** paper discusses the use of a simplifiedε-NTU correlation model for the HVAC systems(typically C*=1).The correlation model and CFD results were compared and found to be different from each *** results of the CFD simulation were compared with measurements to prove that the proposed simulation method can predict the behaviour of the real heat exchanger as a *** was demonstrated that the sensible effectiveness and pressure loss of the rotary heat exchanger predicted by the CFD simulations correspond well to the measured values within the measurement uncertainty±1.3%.The proposed method can be used for the comparison of different rotary regenerative heat exchangers before their manufacturing and for verification that they meet the EU Ecodesign requirements set by the current *** reduces the cost of the initial optimisation and testing of new designs.

关键词： rotary heat exchanger heat wheel microchannel heat recovery sensible effectiveness pressureloss computer fluid dynamics experiment

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Features of Thermocatalytic Cracking of Polypropylene in the Presence of Potassium Polytitanate and Zeolite Catalysts

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Journal of Harbin institute of Technology(New Series) 2025年第1期32卷 58-66页

作者： Nikita Zherdetsky Alexander Gorokhovsky roman Borisov Valentin Atlasov Department of Chemistry and Chemical Technology of Materials Yuri Gagarin Saratov State Technical UniversitySaratov 410054Russian Federation A.V.Topchiev institute of Petrochemical Synthesis RAS Moscow 119991Russian Federation

A comparative study of products of thermal and thermocatalytic cracking of polypropylene(PP) in the presence of potassium polytitanate(PPT) synthesized by treatment of TiO_(2)(rutile) powder with molten mixture of KOH and KNO_(3) taken in a weight ratio of 30∶30∶40 has been carried *** was shown that the studied type of PPT powder exhibits catalytic properties in the reaction of thermal decomposition of PP,compared to the effect of commercial zeolite catalyst CBV-780 traditionally used for this *** on the analysis performed,the differences in the mechanism of catalytic action of PPT and the zeolite were *** reasons for the observed differences in the composition of PP cracking products and in the rate of coke formation on the surface of studied catalysts were *** the obtained results,it has been proposed that the CBV-780 catalyst promoted more intensive production of the gaseous hydrocarbons compared to PPT,due to higher specific surface area(internal surface) accessible for relatively light and small-sized hydrocarbon products of ***,intensive coke formation on the outer surface of the microporous zeolite contributes to the blocking of transport channels and the rapid loss of catalytic *** the same time,PPT,which initially has a smaller specific surface area,retains its catalytic activity significantly longer due to slit-shaped flat pores and higher transport accessibility of the inner surface.

关键词： polypropylene catalytic cracking potassium polytitanate zeolite reaction mechanism recycling

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The effect of climate factors on the size of forest wildfires(case study:Prague-East district,Czech Republic)

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Journal of Forestry Research 2022年第4期33卷 1291-1300页

作者： Zohreh Mohammadi Peter Lohmander Jan kašpar roman Berčák Jaroslav Holuša Robert Marušák Faculty of Forestry and Wood Sciences Czech University of Life Sciences PragueKamýcká12916500 Praha-SuchdolCzech Republic Optimal Solutions in Cooperation with Linnaeus University UmeaSweden

This paper presents a new approach to identifying the climate variables that influence the size of the area burned by forest *** linear regression was used in combination with nonlinear variable transformations to determine relevant nonlinear forest wildfire size *** from the Prague-East District of the Czech Republic was used for model *** burned forest area was hypothesized as a function of water vapor pressure,air temperature and wind *** speed was added to enhance predictions of the size of forest wildfires,and further improvements to the utility of prediction methods were added to the regression *** results show that if the air temperature increases,it may contain less water and the fuel will become *** size of the burned area then *** the relative humidity in the air increases and the wind speed decreases,the size of the burned area is *** model suggests that changes in the climate factors caused by ongoing climate change could cause significant changes in the size of wildfire in forests.

关键词： Climatic variables Burned forest area Climate change Multiple linear regression

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Taxonomy,distribution,and contemporary exposure of terrestrial mammals to floods and human pressure across different areas for biodiversity conservation in China

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integrative Zoology 2024年第3期19卷 458-467页

作者： roman SHARNUUD Eric i.AMECA MOE Key Laboratory for Biodiversity Science&Ecological Engineering College of Life SciencesBeijing Normal UniversityBeijingChina Climate Change Specialist Group Species Survival CommissionInternational Union for Conservation of NatureGlandSwitzerland

A significant research focus is placed on identifying animal species and areas at future risk to human-induced alterations of the environment and long-term changes in climatic ***,the extent to which exposure to extreme climatic events and intense human pressure can increase the risk of harmful impacts on species remains poorly *** on terrestrial mammals in China,one of the world’s megadiverse countries,we investigated patterns of contemporary exposure to floods and human pressures and determined their taxonomic representation and distribution across three major area-based conservation schemes,namely,national nature reserves(NNRs),priority areas for biodiversity conservation(PABCs),and key biodiversity areas(KBAs).Among the 440 species assessed with moderate or high exposure to floods,327(∼75%)also qualified as moderate or high in exposure to intense human *** species mainly belong to the orders Chiroptera,Eulipotyphla,and ***,there were 305,311,and 311 species with moderate or high exposure to flood and intense human pressure represented across NNRs,PABCs,and KBAs,*** findings support the prioritization of KBAs for expansion of site-based protection efforts such as NNRs in China,considering threats to species from exposure to adverse effects from both extreme climate and human pressure.

关键词： conservation floods human pressure mammals taxonomy

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Risk factors for carotid plaque progression after optimising the risk factor treatment: substudy results of the Atherosclerotic Plaque Characteristics Associated with a Progression Rate of the Plaque and a Risk of Stroke in Patients with the carotid Bifurcation Plaque Study (ANTiQUE)

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Stroke & Vascular Neurology 2022年第2期7卷 132-139页

作者： David Školoudik Petra Kešnerova Tomaš Hrbač David Netuka Jaroslav Vomačka kateřina Langova roman Herzig Tomaš Belšan Center for Health Research Faculty of MedicineUniversity of OstravaOstravaCzech Republic Department of Neurology University Hospital OstravaOstravaCzech Republic Department of Neurology Second Faculty of MedicineCharles UniversityPrahaCzech Republic Department of Neurology Motol University HospitalPrahaCzech Republic Department of Neurosurgery Faculty of MedicineUniversity of OstravaOstravaCzech Republic Department of Neurosurgery University Hospital OstravaOstravaCzech Republic Department of Neurosurgery Military University Hospital PraguePrahaCzech Republic Department of Radiological Assistance Faculty of Health SciencesPalacky University OlomoucOlomoucCzech Republic Deaprtment of Radiology University Hospital OlomoucOlomoucCzech Republic Department of Biophysics Faculty of MedicinePalacky University OlomoucOlomoucCzech Republic Department of Neurology University Hospital Hradec KrálovéHradec KraloveCzech Republic Department of Neurology Faculty of Medicine in Hradec KrálovéCharles UniversityHradec KrálovéCzech Republic Department of Radiology Military University Hospital PraguePrahaCzech Republic

Background and aim Carotid plaque progression contributes to increasing stroke *** study aims to identify factors influencing carotid plaque thickness progression after changing the preventive treatment to the‘treating arteries instead of risk factors’strategy,that is,change in treatment depending on the progression of *** The study participants who completed sonographic controls over the course of 3 years were enrolled to the *** sonography of cervical arteries was performed in 6-month intervals with measurement of carotid plaque *** thickness measurement error(σ)was set as 3 *** evidently stable and progressive plaques(defined as plaque thickness difference between initial and final measurements of˂σand>2σ,respectively)were included to *** and multivariate logistic regression analysis was performed to identify factors influencing plaque *** A total of 1391 patients(466 males,age 67.2±9.2 years)were enrolled in the *** plaque in at least one carotid artery was detected in 255(18.3%)*** age,male sex,greater plaque thickness,coronary heart disease,vascular surgery/stenting history and smoking were more frequently present in patients with progressive plaque(p˂0.05 in all cases).Multivariate logistic regression analysis identified only the plaque thickness(OR 1.850 for left side,95%Ci 1.398 to 2.449;and OR 1.376 for right side,95%Ci 1.070 to 1.770)as an independent factor influencing plaque *** Carotid plaque thickness corresponding to stenosis severity is the only independent risk factor for plaque thickness progression after optimising the prevention treatment.

关键词： prevention treatment Duplex

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On the Homology of the Dual de Rham Complex

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1666-1676页

作者： roman MiKHAiLOV Laboratory of Modern Algebra and Applications St.Petersburg State University14th Line29bSaint Petersburg199178Russia St.Petersburg Department of Steklou Mathematical institute Fontanka 27SaintPetersburg191023Russia

We study the homology of the dual de Rham complex as functors on the category of abelian *** give a description of homology of the dual de Rham complex up to degree 7 for free abelian groups and present a corrected ve... 详细信息

关键词： Dual de Rham complex polynomial functor divided powers derived functors

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Dynamic Modelling of the DEP Controlled Boiling in a Microchannel

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Journal of Thermal Science 2018年第2期27卷 167-174页

作者： Marcin Lackowski roman Kwidzinski institute of Fluid Flow Machinery Polish Academy of Sciences

The paper presents theoretical analysis of flow dynamics in a heated microchannel in which flow rate may be controlled by dielectrophoretic(DEP) forces. Proposed model equations were derived in terms of lumped parameters characterising the system comprising of DEP controller and the microchannel. in result, an equation for liquid height of rise in the controller was obtained from momentum balances in the two elements of the considered system. in the model, the boiling process in the heated section of microchannel is taken into account through a pressure drop, which is a function of flow rate and uniform heat flux. Presented calculation results show that the DEP forces influence mainly the flow rate in the microchannel. in this way, by proper modulation of voltage applied to the DEP controller, it is possible to lower the frequency of Ledinegg instabilities.

关键词： dielectrophoresis boiling microchannel two-phase flow pressure drop

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Modeling static friction behavior of elastic–plastic spherical adhesive microcontact in full-stick condition

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Friction 2024年第11期12卷 2594-2610页

作者： Guo XiANG roman GOLTSBERG izhak ETSiON Department of Mechanical Engineering TechnionHaifa 32000Israel

The static friction behavior of an elastic–plastic spherical adhesive microcontact between a rigid flat and a deformable sphere under combined normal and tangential loading is studied by the finite element method(FEM).The contact between the sphere and the rigid flat is assumed to be full-stick,and the sliding inception is related to a loss of tangential *** intermolecular force between the rigid flat and the sphere is assessed by the Lennard–Jones(LJ)potential,which is applied to the sphere and the rigid flat by a user *** evolution of the adhesive force with tangential displacement in the full-stick condition is *** results indicate that the increasing effect of adhesive energy on the static friction coefficient gradually diminishes with an increase in the adhesive energy and the external normal ***,based on an extensive parametric study,an empirical dimensionless expression is obtained to predict the static friction coefficient of the spherical adhesive microcontact considering the intermolecular force.

关键词： adhesive spherical microcontact Lennard–Jones(LJ)potential elastic–plastic static friction

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Titanium oxide artificial synaptic device:Nanostructure modeling and synthesis,memristive cross-bar fabrication,and resistive switching investigation

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Nano Research 2023年第7期16卷 10222-10233页

作者： Vadim i.Avilov roman V.Tominov Zakhar E.Vakulov Lev G.Zhavoronkov Vladimir A.Smirnov Research Laboratory Neuroelectronics and Memristive Nanomaterials(NEUROMENA Lab) Southern Federal UniversityTaganrog 347922Russia institute of Nanotechnologies Electronics and Electronic Equipment EngineeringSouthern Federal UniversityTaganrog 347922Russia

The paper shows the results of the mathematical model development and the numerical simulation of the oxygen vacancies,and the distribution of TiO,Ti_(2)O_(3),and TiO_(2)oxides in the titanium oxide nanostructure obtained by local anodic oxidation(anodization).The effect of the anodization voltage pulse duration and amplitude on the titanium oxide composition distribution and the conduction channel formation was *** device prototypes based on electrochemical titanium oxide are fabricated and *** was shown that forming free resistive switching between the low resistances state(LRS)1.43±0.54 kΩand the high resistance state(HRS)28.75±9.75 kΩwere observed during 100,000 switching cycles and LRS 1.49±0.23 kΩwas maintained for 10,000 *** resistive switching of the synaptic device prototype was *** was shown that increasing Uset from 0.5 to 1.5 V leads to different LRS from 3.96±0.19 to 0.71±0.10 kΩ.The results obtained can be used in the development of technological foundations for the formation of high-performance multilevel artificial synapses for elements of neuroelectronics and hardware neural networks.

关键词： artificial intelligence neuromorphic systems memristive cross bar resistive switching scanning probe microscopy titanium oxide

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An in vitro demonstration of a passive,acoustic metamaterial as a temperature sensor with mK resolution for implantable applications

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Microsystems & Nanoengineering 2024年第1期10卷 41-54页

作者： Lucrezia Maini Vicente Genovés roman Furrer Nikola Cesarovic Christofer Hierold Cosmin roman Micro-and Nanosystems Department of Mechanical and Process EngineeringETH ZurichTannenstrasse 38092 ZurichSwitzerland. Translational Cardiovascular Technology Department of Health Science and TechnologyETH ZurichLeopold-Ruzicka-Weg 48093 ZurichSwitzerland. Transport at Nanoscale interfaces Swiss Federal Laboratories for Materials Science and TechnologyEMPAÜberlandstrasse 1298600 DübendorfSwitzerland Department of Cardiothoracic and Vascular Surgery Deutsches Herzzentrum der Charite(DHZC)13353 BerlinGermany

Wireless medical sensors typically utilize electromagnetic coupling or ultrasound for energy transfer and sensor *** transfer and management is a complex aspect that often limits the applicability of implantable sensor *** this work,we report a new passive temperature sensing scheme based on an acoustic metamaterial made of silicon embedded in a polydimethylsiloxane *** to other approaches,this concept is implemented without additional electrical components in situ or the need for a customized receiving unit.A standard ultrasonic transducer is used for this demonstration to directly excite and collect the reflected *** metamaterial resonates at a frequency close to a typical medical value(5 MHz)and exhibits a high-quality *** the design features of the metamaterial with the high-temperature sensitivity of the polydimethylsiloxane matrix,we achieve a temperature resolution of 30 *** value is below the current standard resolution required in infrared thermometry for monitoring postoperative complications(0.1 K).We fabricated,simulated,in vitro tested,and compared three acoustic sensor designs in the 29-43℃(~302-316 K)temperature *** this concept,we demonstrate how our passive metamaterial sensor can open the way toward new zero-power smart medical implant concepts based on acoustic interrogation.

关键词： passive resolution utilize

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