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Development and validation of a transient simulation model of a full-scale PCM embedded radiant chilled ceiling

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Building Simulation 2023年第6期16卷 813-829页

作者： Seyedmostafa Mousavi Behzad Rismanchi stefan Brey Lu Aye Renewable Energy and Energy Efficiency Group Department of Infrastructure EngineeringFaculty of Engineering and Information Technology(FEIT)The University of MelbourneMelbourneVIC3010Australia InvAus Pty Ltd. MelbourneVIC3000Australia

The recent significant rise in space cooling energy demand due to the massive use of air-conditioning systems has adversely changed buildings’energy use patterns *** updated energy technology perspectives highlight the need for innovative cooling systems to address this growing cooling *** change material embedded radiant chilled ceiling(PCM-RCC)has lately acquired popularity as they offer more efficient space cooling together with further demand-side *** advancements in PCM-RCC applications have increased the necessity for reliable simulation models to assist professionals in identifying improved designs and operating *** this study,a transient simulation model of PCM-RCC has been developed and validated using measured data in a full-scale test cabin equipped with newly developed PCM ceiling *** model,developed in the TRNSYS simulation studio,includes Type 399 that uses the Crank-Nicolson algorithm coupled with the enthalpy function to solve transient heat transfer in PCM ceiling *** developed model is validated in both free-running and active operation modes,and its quality is then evaluated using several validation *** results obtained in multiple operating scenarios confirm that the model simulates the transient behaviour of the PCM-RCC system with an accuracy within±10%.Aided by this validated model,which offers the user detailed flexibilities in the system design and its associated operating schemas,PCM-RCC’s potentials regarding peak load shifting,energy savings,and enhanced thermal comfort can be investigated more reliably.

关键词： phase change material(PCM) radiant cooling ceiling panel modelling and simulation validation

In situ characterization of particle formation in spray flame synthesis using wide-angle light scattering

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Particuology 2024年第3期86卷 304-312页

作者： Simon Aβmann Franz J.T.Huber stefan Will Lehrstuhl für Technische Thermodynamik(LTT) Friedrich-Alexander-Universitat Erlangen-Nürnberg(FAU)Erlangen91058Germany Erlangen Graduate Schoolin Advanced Optical Technologies(SAOT) Friedrich-Alexander-Universitat Erlangen-Nurnberg(FAU)Erlangen91052Germany Competence Unit Engineering of Advanced Materials(EAM) Friedrich-Alexander-Universitat Erlangen-Nürnberg(FAU)Erlangen91052Germany

Wide-angle light scattering(WALS)was used for in situ measurements of droplet and nanoparticle size distributions during the synthesis of titania and iron oxide particles from liquid precursor solutions in the standardized SpraySyn burner for spray flame *** was synthesized from titanium tetraisopropoxide(TTIP)and iron oxide from iron(II)nitrate nonahydrate(INN)using ethanol(EtOH)as *** images were taken at heights up to 120 mm above the burner surface and classified into droplet and particle *** size distributions were derived from a sequential analysis of scattering data containing the oscillating Mie pattern,the lognormal size distribution parameters for spherical and fractal particle fractions from a multivariate approach on averaged particle scattering *** results show that the precursor addition leads to altered evaporation behavior and even droplet disruption probably induced by puffing or micro-explosions compared to pure *** the case of TTIP(a hygroscopic alkoxide),the synthesis of a large fraction of spheres was observed,while the nitrate INN leads to the formation of mostly fractal aggregates.

关键词： Spray flame synthesis Metal oxide particles Elastic light scattering Droplet size distribution Nanoparticle morphology Particle size distribution

Quantitative spatiotemporal impact of dynamic population density changes on the COVID-19 pandemic in China’s mainland

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Geo-Spatial Information Science 2023年第4期26卷 642-663页

作者： Guangyuan Zhang stefan Poslad Yonglei Fan Xiaoping Rui IoT Laboratory School of Electronic Engineering and Computer ScienceQueen Mary University of LondonLondonUK School of Earth Sciences and Engineering Hohai UniversityNanjingChina

The coronavirus disease 2019(COVID-19)and its mutant viruses are still wreaking global havoc over the last two years,but the impact of human activity on the transmission of the pandemic is difficult to *** human dynamic spatiotemporal distribution can help in our understanding of how to mitigate COVID-19 spread,which can help in maintaining urban health within a county and between counties within a *** distribution can be computed using the Volunteered Geographic Information(VGI)of the citizens in conjunction with other variables,such as climatic conditions,and used to analyze how human’s daily density distribution quantitatively affects COVID-19 *** on the estimated population density,when the population density increases daily by 1 person/km^(2) in a county or prefectural-level administrative unit with an average size of 26,000 km^(2),the county would have an additional 3.6 confirmed cases and 0.054 death cases after 5 days,which is the illness onset time for a new COVID-19 *** 14 days,which is the maximum incubation period of the COVID-19 virus,there would be 5 new confirmed cases and 0.092 death ***,in neighboring regions,there can be 0.96 fewer people infected with COVID-19 on average per day as a result of strong intervention of local and neighboring *** primary innovation and contribution are that this is the first quantitative assessment of the impacts of dynamic population density on the COVID-19 ***,the direct and indirect effects of the impact are estimated using spatial panel *** models that control the unobserved factors improve the reliability of the estimation,as validated by random experiments and the use of the Baidu migration dataset.

关键词： COVID-19 Geographic Information Systems(GIS) panel data Spatial Durbin Model(SDM)

Sensitivity analysis of sediment flux derived by laser diffraction and acoustic backscatter within a reservoir

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International Journal of Sediment Research 2018年第1期33卷 18-26页

作者： stefan Haun Laura Lizano Institute for Modelling Hydraulic and Environmental Systems University of Stuttgart Department of Hydraulic and Environmental Engineering Norwegian University of Science and Technology Ministry of Environment and Energy

A combination of two indirect methods to measure sediment flux is presented in this study to evaluate suspended sediment transport in a hydropower reservoir. The acoustic backscatter signal(ABS)from an Acoustic Doppler Current Profiler(ADCP) is therefore applied in pre-defined transects within the reservoir in combination with a Laser In-Situ Scattering Transmissometry-stream lined device(LISSTSL). The stationary LISST-SL derived suspended sediment concentration(SSC) measurements are used to calibrate the ABS. From the LISST-SL measurements a time series of SSC is obtained. This enables, in addition, a comprehensive data analysis to evaluate the influence of natural fluctuations of the SSC on the calculated sediment flux, which should be taken into account when assessing sediment transport. Furthermore SSC measurements are done with the LISST-SL close to the reservoir bed. In areas close to the bed no information regarding the ABS is available from the ADCP measurements due to the side-lobe interference. In various studies the information from the last three valid cells is used for ***, as result of a comparison of the LISST-SL measurements with extrapolated SSC values from the ADCP measurements it can be seen that, especially in deep reservoirs, this method has to be adapted to the in-situ conditions.

关键词： Reservoir Suspended sediment concentrations Sediment flux Laser diffraction Acoustic backscatter signal

Less workplace parking with fully autonomous vehicles?

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Journal of Intelligent and Connected Vehicles 2022年第3期5卷 283-301页

作者： stefan Tscharaktschiew Felix Reimann Institute of Transport and Economics Technische Universität DresdenDresdenGermany

Purpose–Recent studies on commuter parking in an age of fully autonomous vehicles(FAVs)suggest,that the number of parking spaces close to the workplace demanded by commuters will decline because of the capability of FAVs to return home,to seek out(free)parking elsewhere or just *** would be good news because,as of today,parking is one of the largest consumers of urban land and is associated with substantial costs to *** of the studies,however,is concerned with the special case of employer-provided parking,although workplace parking is a widespread phenomenon and,in many instances,the dominant form of commuter *** purpose of this paper is to analyze whether commuter parking will decline with the advent of self-driving cars when parking is provided by the ***/methodology/approach–This study looks at commuter parking from the perspective of both the employer and the employee because in the case of employer-provided parking,the firm’s decision to offer a parking space and the incentive of employees to accept that offer are closely interrelated because of the fringe benefit character of workplace *** study develops an economic equilibrium model that explicitly maps the employer–employee relationship,considering the treatment of parking provision and parking policy in the income tax code and accounting for adverse effects from commuting,parking and public *** study determines the market level of employer-provided parking in the absence and presence of FAVs and identifies the factors that drive the *** study then approximates the magnitude of each factor,relying on recent(first)empirical evidence on the impacts of ***–This paper’s analysis suggests that as long as distortive(tax)policy favors employer-provided parking,FAVs are no guarantee to end up with less commuter ***/value–This study’s findings imply that in a world of self-driving cars,policy intervention related to work comm

关键词： Autonomous vehicles Employer-provided parking Fringe benefit Self-driving cars Transport policy

Implementation and validation of a bonded particle model to predict rheological properties of viscoelastic materials

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Particuology 2024年第6期89卷 198-210页

作者： Michael Mascara Arno Mayrhofer stefan Radl Christoph Kloss Institute of Process and Particle Engineering Graz University of TechnologyInffeldgasse 13Graz8010Austria DCS Computing GmbH Industriezeile 35Linz4020Austria

This work focuses on implementing a particle-based method able to characterize viscoelastic materials whose rheological properties,such as storage modulus G′and loss modulus G″,are *** is based on the bonded particle model,with the elastic constitutive relation here substituted with a viscoelastic one to capture time-scale *** Burgers model,vastly used in literature to model viscoelastic systems,is discretized and *** test case used for calibration comprises of a cubic lattice,sheared with a periodic motion,to mimic the effect of a shear *** appropriate filtering of the stress response,the rheological properties are obtained,highlighting the effect of the lattice geometry,as well as the particle size,on the accuracy of the ***,the Burgers parameters are calibrated by analytically fitting the experimental dataset,showing the limitation of the Burgers *** micro-contact parameters are obtained from the macro parameters through appropriate *** completing a frequency sweep,the simulated G′and G″show a relatively large error,around 25%for G’for *** this reason,a more robust model,namely the generalized Maxwell model,has been *** calibration procedure is performed in the same fashion as for the Burgers ***,the tangential micro-contact parameters are scaled *** normal *** scaling parameter,calledα,is calibrated by minimizing the root mean square error between simulation and experimental data,giving errors below 10%in both G′and G″for a large ***,a full ring plate-plate rheometer setup is simulated,and the simulation is compared with the given experimental dataset,again finding a good agreement.

关键词： DEM Rheology Numerical modeling Viscoelasticity

Three-way Subsynchronous Torsional Interactions Between LCC HVDC,MMC HVDC and a Thermal Generator

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Journal of Modern Power Systems and Clean Energy 2023年第4期11卷 1331-1340页

作者： stefan Kovacevic Dragan Jovcic Pierre Rault Olivier Despouys School of Engineering University of AberdeenAberdeen AB243UEU.K. Réseau de Transport d’Électricité ParisFrance

This paper performs a study on three-way subsynchronous torsional interactions(SSTI)between a hybrid dual-infeed high-voltage direct current(HVDC)system and a nuclear *** test case is based on the French IFA2000 line commutated converter(LCC)HVDC(2 GW)and the new Eleclink modular multilevel converter(MMC)HVDC(1 GW)interacting with the Gravelines generator(1 GW).The analysis is performed by the means of the eigenvalue stability assessment on an analytical model,while the accuracy of the conclusions is verified using the detailed non-linear electromegnetic transient program(EMTP)*** study shows that the dual-infeed system may introduce higher risk of the SSTI compared with the point-to-point HVDC *** shows that MMC operating as static synchronous compensator(STATCOM)may further reduce the torsional damping at 6.3 Hz *** conclusion may be unexpected since it is known fact from literature that STATCOM has a beneficial impact on the transient performance of *** studies show that in a sequential HVDC loading,it may be beneficial to load the MMC HVDC ***,the risk of the SSTI may be minimized by changing HVDC controller gains,in particular,by increasing phaselocked-loop(PLL)gains on the LCC rectifier.

关键词： Subsynchronous torsional interaction(SSTI) eigenvalue stability hybrid dual-infeed high-voltage direct current(HVDC) line commutated converter(LCC) modular multilevel converter(MMC) nuclear generator

Hydrogen effect on the mechanical behaviour and microstructural features of a Fe-Mn-C twinning induced plasticity steel

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 835-846页

作者： Xiaofei Guo stefan Zaefferer Fady Archie Wolfgang Bleck Steel Institute RWTH Aachen UniversityIntze-str.1Aachen 52072Germany Max-Planck-Institut für Eisenforschung GmbH Max-Planck-Straße 1Düsseldorf 40237Germany NLMK Europe Eutelis-Platz 2Ratingen 40878Germany

The influences of hydrogen on the mechanical properties and the fracture behaviour of Fe-22Mn-0.6C twinning induced plasticity steel have been investigated by slow strain rate tests and fractographic *** steel showed high susceptibility to hydrogen embrittlement,which led to 62.9%and 74.2%reduction in engineering strain with 3.1 and 14.4 ppm diffusive hydrogen,*** fracture surfaces revealed a transition from ductile to brittle dominated fracture modes with the rising hydrogen *** underlying deformation and fracture mechanisms were further exploited by examining the hydrogen effects on the dislocation substructure,stacking fault probability,and twinning behaviour in pre-strained slow strain rate test specimens and notched tensile specimens using coupled electron channelling contrast imaging and electron backscatter diffraction *** results reveal that the addition of hydrogen promotes planar dislocation structures,earlier nucleation of stacking faults,and deformation twinning within those grains which have tensile axis orientations close to//rolling direction and//rolling *** developed twin lamellae result in strain localization and micro-voids at grain boundaries and eventually lead to grain boundary decohesion.

关键词： twinning induced plasticity steel hydrogen mechanical behaviour dislocation twinning electron channelling contrast imaging

A neuron's ambrosia: non-autonomous unfolded protein response of the endoplasmic reticulum promotes lifespan

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Neural Regeneration Research 2022年第2期17卷 309-310页

作者： stefan Homentcovschi Ryo Higuchi-Sanabria Department of Molecular&Cellular Biology University of CaliforniaBerkeleyCAUSA

The ability to protect cellular components in the face of deleterious conditions, such as exposure to chemical poisons, damaging radiation, or excessive heat, is crucial to organismal viability.

关键词： autonomous delete exposure