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Quantification of how mechanical ventilation influences the airborne infection risk of COVID-19 and HVAC energy consumption in office buildings

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Building Simulation 2023年第5期16卷 713-732页

作者： Zhihong Pang Xing Lu Zheng O’Neill mike walker’66 department of mechanical engineering texas a&m universitycollege stationtx 77843usa

This paper presents an EnergyPlus-based parametric analysis to investigate the infection risk of Coronavirus Disease 2019(COVID-19)under different mechanical ventilation scenarios for a typical medium-sized office building in various climate zones.A Wells-Riley(WR)based Gammaitoni-Nucci(GN)model was employed to quantitatively calculate the airborne infection risk.The selected parameters for the parametric analysis include the climate zone,outdoor air fraction,fraction of infectors,quanta generation rate,and exposure time.The loss and deposition of particles are not considered.The results suggest that the COVID-19 infection risk varies significantly with climate and season under different outdoor air fraction scenarios since the building heating and cooling load fundamentally impacts the supply airflow rate and thus directly influences the amount of mechanical ventilation,which determines the dilution ratio of contaminants.This risk assessment identified the climate zones that benefit the most and the least from increasing the outdoor air fraction.The climate zones such as 1A(Honolulu,HI),2B(Tucson,AZ),3A(Atlanta,GA),and 7(International Falls,MN)are the most energy-efficient locations when it comes to increasing the outdoor air fraction to reduce the COVID-19 infection risk.In contrast,the climate zones such as 6A(Rochester,MN)and 6B(Great Falls,MT)are the least energy-efficient ones.This paper facilitates understanding a widely recommended COVID-19 risk mitigation strategy(i.e.,increase the outdoor airflow rate)from the perspective of energy consumption.

关键词： COVID-19 smart ventilation built environment infection risks building simulation office building

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Configuration-dependent stretchable all-solid-state supercapacitors and hybrid supercapacitors

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Carbon Energy 2023年第5期5卷 1-47页

作者： Ahmad Amiri Ashley Bruno Andreas A.Polycarpou J.mike walker’66 mechanical engineering department Texas A&M UniversityCollege StationTexasUSA

Given the rise in the popularity of wearable electronics that are able to deform into desirable configurations while maintaining electrochemical functionality,stretchable and flexible(hybrid)supercapacitors(SCs)have become increasingly of interest as innovative energy storage devices.Their outstanding power density,long lifetime with low capacitance loss,and appropriate energy density,in particular in hybrid cases make them ideal candidates for flexible electronics.The aim of this review paper is to provide an in-depth discussion of these stretchable and flexible SCs ranging from fabrication to electro-mechanical properties.This review paper begins with a short overview of the fundamentals of charge storage mechanisms and different types of multivalent metal-ion hybrid SCs.The research methods leading up to the current state of these stretchable and flexible SCs are then presented.This is followed by an in-depth presentation of the challenges associated with the fabrication methods for different configurations.Proposed novel strategies to maximize the elastic and electrochemical properties of stretchable/flexible or quasi-solid-state SCs are classified and the pros and cons associated with each are shown.The advances in mechanical properties and the expected advancements for the future of these SCs are discussed in the last section.

关键词： 1D fiber-like SCs 2D planar supercapacitors 3D sponge and textile structures flexible/stretchable supercapacitors kirigami/origami-inspired structures

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From occupants to occupants:A review of the occupant information understanding for building HVAC occupant-centric control

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Building Simulation 2022年第6期15卷 913-932页

作者： Tao Yang Arkasama Bandyopadhyay Zheng O’Neill Jin Wen Bing Dong mike walker’66 department of mechanical engineering texas a&m universitycollege stationtx77843usa department of civil architectural&environmental engineeringdrexel universityphiladelphiapa19104usa department of mechanical and aerospace engineering syracuse universitysyracuseny13244usa

Occupants are the core of the built environment.Traditional heating,ventilation,and air-conditioning(HVAC)systems operate with predefined schedules and maximum occupancy assumptions with no consideration of specific occupant information.These generalized assumptions usually do not align with the actual demand and result in over-conditioning and occupant discomfort.In recent years,with the aid of Information&Communication Technology(ICT)and Computer Science(CS),it is possible to acquire real-time and accurate occupant information to satisfy the exact thermal requirement through specific HVAC control in one particular built environment.This mechanism is called HVAC“Occupant-centric Control(OCC).”HVAC OCC strategy starts with collecting the occupant’s information(e.g.,presence/absence)and then applies it to meet the occupant’s requirement(e.g.,thermal comfort).However,even though some research studies and field pilot demonstrations have been devoted to the field of OCC,there is a lack of systematic knowledge about occupant data,which is the principal component of OCC for HVAC researchers and practitioners.To fill this gap,this review paper discusses OCC with a particular emphasis on occupant information and investigates how this information can assist HVAC operation in providing an acceptable built environment in required spaces during the required time.We provide a fine-grained,comprehensive picture of occupant information,discuss its features,the modalities of information feed-in into the HVAC control,and the application of commonly utilized occupant information for OCC.

关键词： occupant information occupant-centric control smart building HVAC energy efficiency

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A review of current understanding in tribochemical reactions involving lubricant additives

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Friction 2023年第4期11卷 489-512页

作者： Yan CHEN Peter RENNER Hong LIANG department of Materials Science and engineering Texas A&M UniversityCollege Station 77843USA J.mike walker’66 department of mechanical engineering Texas A&M UniversityCollege Station 77843USA

Lubricants have played important roles in friction and wear reduction and increasing efficiency of mechanical systems.To optimize tribological performance,chemical reactions between a lubricant and a substrate must be designed strategically.Tribochemical reactions are chemical reactions enabled or accelerated by mechanical stimuli.Tribochemically activated lubricant additives play important roles in these reactions.In this review,current understanding in mechanisms of chemical reactions under shear has been discussed.Additives such as oil-soluble organics,ionic liquids(ILs),and nanoparticles(NPs)were analyzed in relation to the tribochemical reaction routes with elements in metallic substrates.The results indicated that phosphorus,sulfur,fluorine,and nitrogen are key elements for tribochemical reactions.The resulting tribofilms from zinc dithiophosphates(ZDDP)and molybdenum dithiocarbamate(MoDTC)have been widely reported,yet that from ILs and NPs need to investigate further.This review serves as a reference for researchers to design and optimize new lubricants.

关键词： lubricant additives tribochemical reactions oil-soluble organics ionic liquids(ILs) nanoparticles(NPs)

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Zinc-ion hybrid supercapacitors with ultrahigh areal and gravimetric energy densities and long cycling life

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Journal of Energy Chemistry 2022年第7期31卷 480-491,I0012页

作者： Ahmad Amiri M.Naraghi Andreas A.Polycarpou J.mike walker’66 mechanical engineering department texas a&m universitycollege stationTX 77843USA department of aerospace engineering texas a&m universitycollege stationTX 77843USA

Zinc ion hybrid supercapacitor (ZIHSC) with promising energy and power densities is an excellent answer to the ever-growing demand for energy storage devices.The restricted lifespan due to the dendrite formation on metallic zinc (Zn) is one of the main roadblocks.Herein,we investigate the electrochemical capability of oxygen-enriched porous carbon nanofibers (A-CNF) and nitrogen,oxygen-enriched porous carbon nanofibers (N-CNF) cathode materials for structural ZIHSCs.To this end,a series of samples with different chemical compositions (N and O contents) are prepared to present deep insight into the electrochemical mechanism between N/O doping and Zn-ion storage.The as-prepared ZIHSC in the presence of N-CNF cathode and Zn Cl_(2) electrolyte offers a battery-level gravimetric energy density of 143.2 Wh kg^(-1)at a power density of 367.1 W kg^(-1).The free-standing N-CNF electrodes in ZIHSCs enjoy delivering an outstanding areal energy density of 110.4μWh cm^(-2)at 0.24 m W cm^(-2),excellent rate capability,and noticeable cycling stability over 10,000 cycles at 10 A g^(-1)with less than 7%decay.It was also concluded that active pyrrolic N dopants might deliver and facilitate more pseudocapacitance in ZIHSCs than other N configurations,resulting in higher adsorption/desorption and insertion/extraction process of Zn Cl^(+).Taking advantage of the beneficial properties of a free-standing continuous cathode,this novel generation of structural cathode material offers high areal and gravimetric energy densities and mechanical properties in a single zinc-ion-based package.

关键词： Porous carbon nanofibers Zinc chloride electrolyte Zinc ion hybrid supercapacitors Nitrogen-doping Activation Energy density

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Synergistic effects of zeolitic imidazolate frameworks(ZIFs)with different transition metals on intumescent flame-retarded polypropylene composites:A comparative study

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Journal of Materials Science & Technology 2023年第24期155卷 102-110页

作者： Yufeng Quan Ruiqing Shen Christian Schweizer Pradeep Parajuli Zhuoran Zhang Waruna Kulatilaka Qingsheng Wang Artie McFerrin department of Chemical engineering Texas A&M University College Station TX 77843-3122 USA J. mike walker ’66 department of mechanical engineering Texas A&M University College Station TX 77843-3123 USA

The use of intumescent flame retardants(IFRs)is considered an environmentally friendly and cost-effective strategy to suppress potential fire hazards from synthetic polymers.However,some conventional IFRs are neither efficient in developing a thermally stable char layer nor reducing the release of toxic byproducts during polymer combustion.In this work,we aim to discuss the effects of zeolitic imidazolate frameworks(ZIFs)on synergistically improving the flame retardancy behaviors in polypropylene(PP)composites,including thermal degradation(evolved gas analysis),free radical reactions in the gaseous phase(in-situ chemiluminescent image analysis),and carbonaceous structure in the condensed phase(micro-morphology and composition analysis).It is found that the transition metals in ZIFs can catalytically accelerate the crosslinking reaction at a lower initial temperature and decrease the amount of hydrocarbon volatiles in the gaseous phase.Once ignited,the embedded ZIFs can firstly bridge adjacent phosphorus chains in the polymer matrix to expand crosslinking degrees and then they are anchored in the developed N-doped phospho-carbonaceous networks after pyrolysis.As a result,more compact char residue structures are observed in the condensed phase for ZIF-reinforced composites.For example,by replacing 2 wt%of IFR with ZIF-67,the peak heat release rate,peak smoke production rate,and peak CO production rate are reduced by 69%,80%,and 72%,respectively,when compared to the conventional composite.These results indicate an excellent solution to resolve inherent fire hazards associated with IFRs in polymers and achieve necessary efficiency for industrial applications.It also provides a new strategy for determining flammability characteristics and combustion mechanisms of polymer composites using in-situ chemiluminescence analysis.

关键词： Polymer flammability Intumescent flame retardants Zeolitic imidazolate frameworks Thermal degradation Free radical analysis Flame retardant mechanism

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Microencapsulated paraffin as a tribological additive for advanced polymeric coatings

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Friction 2023年第10期11卷 1939-1952页

作者： Reza GHEISARI Mariela VAZQUEZ Vasilis TSIGKIS Ali ERDEMIR Karen L.WOOLEY Andreas A.POLYCARPOU J.mike walker’66 department of mechanical engineering Texas A&M UniversityCollege Station 77843USA department of Chemistry Texas A&M UniversityCollege Station 77843USA department of Materials Science&engineering Texas A&M UniversityCollege Station 77843USA department of Chemical engineering Texas A&M UniversityCollege Station 77843USA

Numerous tribological applications,wherein the use of liquid lubricants is infeasible,require adequate dry lubrication.Despite the use of polymers as an effective solution for dry sliding tribological applications,their poor wear resistance prevents the utilization in harsh industrial environment.Different methods are typically implemented to tackle the poor wear performance of polymers,however sacrificing some of their mechanical/tribological properties.Herein,we discussed the introduction of a novel additive,namely microencapsulated phase change material(MPCM)into an advanced polymeric coating.Specifically,paraffin was encapsulated into melamine-based resin,and the capsules were dispersed in an aromatic thermosetting co-polyester(ATSP)coating.We found that the MPCM-filled composite exhibited a unique tribological behavior,manifested as“zero wear”,and a super-low coefficient of friction(COF)of 0.05.The developed composite outperformed the state-of-the-art polytetrafluoroethylene(PTFE)-filled coatings,under the experimental conditions examined herein.

关键词： microencapsulated phase change material(MPCM) friction reduction additive advanced polymeric coating

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Bioactive superparamagnetic iron oxide-gold nanoparticles regulated by a dynamic magnetic field induce neuronal Ca^(2+)influx and differentiation

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Bioactive Materials 2023年第8期26卷 478-489页

作者： Elias Georgas Muzhaozi Yuan Jingfan Chen Ya Wang Yi-Xian Qin department of Biomedical engineering The State University of New York at Stony BrookStony BrookNYUnited States J.mike walker’66 department of mechanical engineering Texas A&M UniversityCollege StationTXUnited States department of Biomedical engineering Texas A&M UniversityCollege StationTXUnited States department of Electrical and Computer engineering Texas A&M UniversityCollege StationTXUnited States

Treating neurodegenerative diseases,e.g.,Alzheimer’s Disease,remains a significant challenge due to the limited neuroregeneration rate in the brain.The objective of this study is to evaluate the hypothesis that external magnetic field(MF)stimulation of nerve growth factor functionalized superparamagnetic iron oxide-gold(NGF-SPIO-Au)nanoparticles(NPs)can induce Ca^(2+)influx,membrane depolarization,and enhance neuron differentiation with dynamic MF(DMF)outperforming static MF(SMF)regulation.We showed the that total intracellular Ca^(2+)influx of PC-12 cells was improved by 300%and 535%by the stimulation of DMF(1 Hz,0.5 T,30min)with NGF-SPIO-Au NPs compared to DMF alone and SMF with NGF-SPIO-Au NPs,respectively,which was attributed to successive membrane depolarization.Cellular uptake performed with the application of sodium azide proved that DMF enhanced cellular uptake of NGF-SPIO-Au NPs via endocytosis.In addition,DMF upregulated both the neural differentiation marker(β3-tubulin)and the cell adhesive molecule(integrin-β1)with the existence of NGF-SPIO-Au NPs,while SMF did not show these effects.The results imply that noninvasive DMF-stimulated NPs can regulate intracellular Ca^(2+)influx and enhance neuron differentiation and neuroregeneration rate.

关键词： Calcium influx Membrane potential Dynamic magnetic fields Neuroregeneration SPIO-Au Core-shell nanoparticles

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Bayesian optimization with active learning of design constraints using an entropy-based approach

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npj Computational Materials 2023年第1期9卷 1866-1879页

作者： Danial Khatamsaz Brent Vela Prashant Singh Duane D.Johnson Douglas Allaire Raymundo Arróyave J.mike walker’66 department of mechanical engineering Texas A&M UniversityCollege StationTX 77843USA department of Materials Science and engineering Texas A&M UniversityCollege StationTX 77843USA Ames Laboratory U.S.Department of EnergyIowa State UniversityAmesIA 50011USA department of Materials Science&engineering Iowa State UniversityAmesIA 50011USA department of Industrial and Systems engineering Texas A&M UniversityCollege StationTX 77843USA

The design of alloys for use in gas turbine engine blades is a complex task that involves balancing multiple objectives and constraints.Candidate alloys must be ductile at room temperature and retain their yield strength at high temperatures,as well as possess low density,high thermal conductivity,narrow solidification range,high solidus temperature,and a small linear thermal expansion coefficient.Traditional Integrated Computational Materials engineering(ICME)methods are not sufficient for exploring combinatorially-vast alloy design spaces,optimizing for multiple objectives,nor ensuring that multiple constraints are met.In this work,we propose an approach for solving a constrained multi-objective materials design problem over a large composition space,specifically focusing on the Mo-Nb-Ti-V-W system as a representative Multi-Principal Element Alloy(MPEA)for potential use in next-generation gas turbine blades.Our approach is able to learn and adapt to unknown constraints in the design space,making decisions about the best course of action at each stage of the process.As a result,we identify 21 Pareto-optimal alloys that satisfy all constraints.Our proposed framework is significantly more efficient and faster than a brute force approach.

关键词： alloys solidification alloy

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Harnessing the flatbandλ-Ti_(3)O_(5):A breakthrough in solar steam generation

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Science China Materials 2023年第11期66卷 4515-4516页

作者： Chuxin Lei Guihua Yu Materials Science and engineering Program and walker department of mechanical engineering The University of Texas at AustinAustinTX 78712USA

As global population rises,accompanied by escalating environmental pollution and climate change,numerous countries find themselves grappling with an acute scarcity of natural freshwater resources^([1]).Seawater desalination presents a compelling solution to this looming crisis,especially considering the oceans are Earth’s largest water reservoir^([2]).

关键词： reservoir Earth breakthrough

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