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optimal tool design in micro-milling of difficult-to-machine materials

Advances in Manufacturing 2023年第2期11卷 222-247页

作者： Lorcan o'Toole Feng-Zhou Fang Centre of Micro/Nano Manufacturing Technology(MNMT-Dublin) University College DublinDublin 4Ireland State Key Laboratory of Precision Measuring Technology and Instruments Laboratory of Micro/Nano Manufacturing Technology(MNMT)Tianjin UniversityTianjin300072People's Republic of China

The limitations of significant tool wear and tool breakage of commercially available fluted micro-end mill tools often lead to ineffective and inefficient manufacturing,while surface quality and geometric dimensions remain unacceptably poor.This is especially true for machining of difficult-to-machine(DTM)materials,such as super alloys and ceramics.Such conventional fluted micro-tool designs are generally down scaled from the macro-milling tool designs.However,simply scaling such designs from the macro to micro domain leads to inherent design flaws,such as poor tool rigidity,poor tool strength and weak cutting edges,ultimately ending in tool failure.Therefore,in this article a design process is first established to determine optimal micro-end mill tool designs for machining some typical DTM materials commonly used in manufacturing orthopaedic implants and micro-feature moulds.The design process focuses on achieving robust stiffness and mechanical strength to reduce tool wear,avoid tool chipping and tool breakage in order to efficiently machine very hard materials.Then,static stress and deflection finite element analysis(FEA)is carried out to identify stiffness and rigidity of the tool design in relation to the maximum deformations,as well as the Von Mises stress distribution at the cutting edge of the designed tools.Following analysis and further optimisation of the FEA results,a verified optimum tool design is established for micro-milling DTM materials.An experimental study is then carried out to compare the optimum tool design to commercial tools,in regards to cutting forces,tool wear and surface quality.

关键词： Precision machining Micro-milling Difficult-to-machine(DTM) Tool wear Micro-tool design Surface quality

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Benchmark assessment of performance indices of a selection of hybrid nanofluids in a hybrid photovoltaic/thermal system

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Clean Energy 2022年第2期6卷 247-270页

作者： o.M.Amoo R.o.Fagbenle M.o.oyewola Department of Mechanical Engineering University of IbadanIbadanOyo StateNigeria School of Mechanical Engineering Fiji National UniversityFiji

This research is a study assessing the performance of hybrid nanofluids in hybrid photovoltaic(PV)-thermal systems.This study addresses 10 hybrid nanofluids applied to hybrid PV-thermal systems.The transition to carbon-free energy can mitigate the worst effects of climate change,ensuring that global sustainability is addressed.Clean energy is now responsible for one-third of the global capacity,of which 20%is attributed to solar energy.Renewables continue to be economically viable,with declining costs driving growth.This study aims to compare the yearly performances of a model hybrid PV-thermal system using 10 different hybrid nanofluids.Hybrid nanofluids constitute two or more dissimilar materials stably suspended in a base fluid(e.***.water).MATLAB and CoMSoL Multiphysics®computational fluid dynamics software are employed together for the benchmarking assessment with good agreement observed.Various fluid inlet temperatures(Tin∈[300,360]K),nanofluid volume concentrations(φ∈[0,4]%)and storage-tank volumes(V∈[50,300]L)were simulated.The meteorological data applied were those for Lagos,Nigeria(6°27’55.5192”N,3°24’23.2128”E).The assessment based on analytical-numerical solutions reveals that the thermal enhancement by hybrid nanofluids ranges from 6.7%(graphene oxide[Go]-multiwalled carbon nanotube[MWCNT]/water)to 7%(Zno-Mn-ZnFe2o4/water)forφ=2%and V=300 L.The yearly exergy efficiency ranges from 2.8%(Zno-Mn-ZnFe2o4/water)to 2.9%(Go-MWCNT/water),also forφ=2%and V=300 L.These findings have implications for a vast range of industrial processes,expanding the knowledge that is critical to a sustainable future.

关键词： energy transformation hybrid photovoltaic-thermal(PV/T)system hybrid nanofluids CoMSoL Multiphysics® MATLAB enhancements

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Magnetohydrodynamic‑based Internal Cooling System for a Ceramic Cutting Tool:Concept Design,Numerical Study,and Experimental Evalidation

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Nanomanufacturing and Metrology 2023年第4期6卷 60-80页

作者： John o’Hara Fengzhou Fang Center of Micro/Nano Manufacturing Technology(MNMT-Dublin) University College DublinDublin 4Ireland State Key Laboratory of Precision Measuring Technology and Instruments Laboratory of Micro/Nano Manufacturing Technology(MNMT)Tianjin UniversityTianjin 300072China

The efective removal of the heat generated during mechanical cutting processes is crucial to enhancing tool life and produc-ing workpieces with superior surface fnish.The internal cooling systems used in cutting inserts employ a liquid water-based solvent as the primary medium to transport the excess thermal energy generated during the cutting process.The limitations of this approach are the low thermal conductivity of water and the need for a mechanical input to circulate the coolant around the inner chamber of the cutting tool.In this context,this paper proposes an alternative method in which liquid gallium is used as the coolant in combination with a magnetohydrodynamic(MHD)pump,which avoids the need for an external power source.Using computational fuid dynamics,we created a numerical model of an internal cooling system and then solved it under conditions in which a magnetic feld was applied to the liquid metal.This was followed by a simulation study performed to evaluate the efectiveness of liquid gallium over liquid water.The results of experiments conducted under non-cooling and liquid gallium cooling conditions were analyzed and compared in terms of the tool wear rate.The results showed that after six machining cycles at a cutting speed Vc=250 m min−1,the corner wear VBc rate was 75µm with the coolant of and 48µm with the MHD-based coolant on,representing a decrease of 36%in tool wear.At Vc=900 m min−1,the corner wear VBc rate was 75µm with the coolant of and 246µm with the MHD-based coolant on,representing a decrease of 31%in tool wear.When external cooling using liquid water was added,the results showed at Vc=250 m min−1,the diference between the tool wear rate reduction with the internal liquid gallium coolant relative to the external coolant was 29%.When the cutting speed was increased to Vc=900 m min−1,the diference observed between the internal liquid gallium coolant relative to the external coolant was 16%.The study proves the feasibility of using liquid gallium as a coolant to efectively remove the

关键词： Internal cooling Heat transfer Liquid metal Magnetic feld Cutting tool

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An overview of Rationalization Theories of Non-simply Connected Spaces and Non-nilpotent Groups

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Acta Mathematica Sinica,English Series 2022年第10期38卷 1705-1721页

作者： Sergei o.IVANoV Laboratory of Modern Algebra and Applications St.Petersburg State University14th Line29bSaint Petersburg199178Russia

We give an overview of five rationalization theories for spaces(Bousfield-Kan’s Q-completion;Sullivan’s rationaliz ation;Bousifeld’s homology rationaliz ation;Casacuberta-Peschke’s Ω-rationalization;Gomez-Tato-Halperin-Tanré’s π-fiberwise rationalization)that extend the classical rationalization of simply connected spaces.We also give an overview of the corresponding rationalization theories for groups(Q-completion;HQ-localization;Baumslag rationalization)that extend the classical Malcev completion.

关键词： Rationalisation localisation rational homotopy theory group theory

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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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A comprehensive simulation-based assessment of office building performance adaptability to teleworking scenarios in different Canadian climate zones

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Building Simulation 2022年第6期15卷 995-1014页

作者： Farzam Kharvari Sara Azimi William o’Brien Department of Civil and Environmental Engineering Carleton University1125 Colonel by DriveOttawaOntarioK1S 5B6Canada

Recent studies have shown that office building systems do not adapt well to partial occupancy(e.g.,from teleworking)and thus perform suboptimally.As a result,this study aims to assess office building performance adaptability by investigating the impact of four different technologies,including occupancy-based lighting,smart plugs(occupancy-based plug load),demand-controlled ventilation(DCV),occupancy-based thermostat,and their cumulative effect in office buildings in six different Canadian climates.A three-story office building is simulated in EnergyPlus version 9.3.0 under five occupancy scenarios,including 0%occupancy,100%occupancy,50%uniformly distributed occupancy across the floor,50%consolidated occupancy scenario where occupants work in core zones,and 50%consolidated occupancy scenario where occupants work in perimeter zones.The results are compared using energy use intensity(EUI),energy use intensity per occupant(EUP),and the corresponding greenhouse gas(GHG)emissions.A total of 180 simulations demonstrate the occupancy-adaptive technologies are generally most beneficial for low occupancy scenarios and milder climates.The results also show the cumulative impact of all these technologies on the potential energy savings is significant in the climates under consideration.overall,the results show office buildings can improve their performance adaptability during partial occupancy by implementing the studied technologies.Aside from filling in the current knowledge gap in the literature on partial occupancy,the for the first time results of this study systemically demonstrate how each technology performs under different partial occupancy scenarios and how they perform together at each climate.

关键词： partial occupancy thermostat setpoint smart plug demand-controlled ventilation(DCV) lighting

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A synthetic microbial community used as a bioinoculant can overcome rice production constraints in acid soils

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Science China(Life Sciences) 2024年第5期67卷 1085-1086页

作者： Maureen o’Callaghan Shengjing Shi Resilient Agriculture Group AgResearchLincolnChristcurch 8140New Zealand

A customised synthetic microbial community(SynCom)composed of carefully selected rhizosphere-competent bacterial strains improved rice growth,yield and resistance to soil acidity and Al toxicity.

关键词： soil soils rhizosphere

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Learning Effectiveness of Semester and Year-Long Study Abroad Programmes:Perspectives of International Students in a UK and China Context

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Fudan Journal of the Humanities and Social Sciences 2023年第3期16卷 359-379页

作者： Xianghan o’Dea Chen Wang Mike o’Dea Huddersfield Business School University of HuddersfieldQueensgateHuddersfieldHD13DHUK School of Education Durham UniversityStockton RoadDurhamDH13LEUK School of Arts Design and Computer ScienceYork St John UniversityLord Mayor’s WalkYorkYO317EXUK

Research on international students’learning experiences pays much less attention to those studying semester and/or year-long programmes in a country that differs significantly from their home country with respect to culture and the education system.Adopting transformative learning theory as the theoretical framework,this paper explores the learning effectiveness of students on such programme in a Chinese and in a UK university.It analyses the narratives of 27 students in relation to their cognitive and behavioural activities and also their self-reflective and collaborative reflective activities.The findings indicate that these students only partially achieved transformative learning.The main reasons are:(1)the duration of this type of programme was not long enough to achieve a full transformation and(2)both host universities did not include reflection in the learning process properly.This paper makes a contribution to cross-border learning literature in the Chinese and the UK contexts.

关键词： International students Learning experiences Self-refections Study abroad programmes Transformative learning

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Non-invasive respiratory support for CoVID-19-related acute respiratory failure

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Chinese Medical Journal 2022年第4期135卷 416-418页

作者： João Carlos Winck Joaquim Moreira Department of Medicine Faculty of Medicine-Porto UniversityPorto 4200-319Portugal Unidade Local de Saúde do Alto Minho Viana do CasteloPortugal

The European Respiratory Society/American Thoracic Society clinical practice guidelines,which are only recommendatory,suggest utilization of non-invasive respiratory support therapies(NRST)as a preventive strategy for avoiding intubation in hypoxemic acute respiratory failure(ARF).[1]Theoretical concerns against the use of NRST are essentially related to safety reasons for the risk of the virus spreading among healthcare workers(HCW)and for the risk of delaying intubation in case of failure.

关键词： respiratory acute clinical

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Effect of thermal load on performance parameters of solar concentrating photovoltaic:High-efficiency solar cells

Energy and Built Environment

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Energy and Built Environment 2022年第2期3卷 201-209页

作者： Ali.o.M.Maka Tadhg S o’Donovan Institute of Mechanical Process and Energy EngineeringSchool of Engineering and Physical SciencesHeriot-Watt UniversityEdinburgh EH144ASUnited Kingdom

The triple-junction solar cell is designed to exploit a wide range of the solar spectrum photons.These triple-layers consisting of GaInP/GaInAs/Ge,it is monolithically stacked,leading to high conversion efficiency.To describe and understand it’s operating behaviour,this paper presents a performance analysis of a triple-junction solar cell,based on estimation modelling.A model was developed to determine the performance characteristic of the solar cell.Hence,the J-V curve is characterising the performance of solar cells,which used to optimise and improve the design of the cells.It has been discussed the effects of thermal load related to cell temperature increases on the cell’s operating performance parameters.Cell temperature increases from 25 to 125℃ have resulted variances,which causes a significant decrease in efficiency to approximately−17%,open circuit voltage by−15%and fill factor by−4.5%.on the other hand,the current density slightly increased by+5.5%.Finally,ought to consider the thermal management while designing and developing solar CPV technology;therefore,it’s significant to improve cell efficiency and to maintain cell integrity from thermal damage.

关键词： Performance parameters Temperature rises Triple-junction solar cells Performance analysis Cell temperature

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