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Fabrication of large-bulk ultrafine grained 6061 aluminum alloy by rolling and low-heat-input friction stir welding

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Journal of Materials Science & Technology 2018年第1期34卷 112-118页

作者： C.Y.liu B.Qu p.Xue Z.Y.Ma K.Luo M.Z.Ma r.p.liu Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Key Laboratory of New processing Technology for Nonferrous Metal & Materials Ministry of Education Guilin University of Technology Guangxi Key Laboratory of Universities for Clean Metallurgy and Comprehensive Utilization of Nonferrous Metal resources Guilin University of Technology State Key Laboratory of Metastable Materials Science and Technology Yanshan University

In this study, the ultrafine grained （UFG） 6061 Al alloys fabricated by cold rolling were friction stir welded （FSW） with different rotation rates under both air cooling and rapid cooling in water. Low-heat-input parameters of 400 rpm rotation rate in water （400-Water） could effectively inhibit the coarsening of recrystallized grains, reduce the precipitation rate, and retain more dislocations of the UFG 6061 Al parent metal. 400-Water joint showed high lowest-hardness value, narrow low-hardness zone, and high tensile strength, attributing to the effect of dislocation, grain boundary, solid-solution, and precipitation hardening. This work provides an effective strategy to fabricate large-sized bulk UFG AI alloy by cold rolling with large deformation and low-heat-input FSW.

关键词： Aluminum alloys Ultrafine grained materia Friction stir welding Mechanical properties

Effectiveness and safety of acupuncture in treatment of pregnancyrelated symptoms:a systematic review and Meta-analysis

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Journal of Traditional Chinese Medicine 2024年第1期44卷 16-26页

作者： liu Tingting liu Tongou liu Mingfu School of Traditional Chinese Medicine Clinical Medicine Hubei University of Traditional Chinese MedicineWuhan 430000China First Clinical College of Hubei University of Traditional Chinese Medicine Wuhan 430000China Department of Acupuncture and Tuina Affiliated Hospital of Hubei University of Traditional Chinese MedicineHubei Provincial Hospital of Traditional Chinese MedicineWuhan 430000China

OBJECTIVE:To systematically evaluate the efficacy and safety of acupuncture(AM)in the treatment of pregnancyrelated symptoms such as acute vomiting during pregnancy.METHODS:We comprehensively searched the available literature up to November 2021,including pub Med,Embase,Cochrane Library,Chinese Biomedical Literature Database,and China National Knowledge Infrastructure Database,for randomized controlled trials(rCTs)on AM for the treatment of severe vomiting,insomnia,pharyngeal and pelvic pain,mood abnormalities,and dyspepsia during pregnancy.rESULTS:Sixteen rCTs with a cumulative sample size of 1178 cases were included.Of these,964 patients were included in the Meta-analysis.The Meta-analysis results showed that AM was more efficient than Western medicine in treating discomfort during pregnancy[odds ratio(Or)=1.19,95%confidence interval(CI)(1.11,1.28),pr than the control group in improving the visual analog scale scores[standard mean difference(SMD)=0.62,95%CI(0.53,0.71),pperior to the control group in improving Numerical rating Scale(NrS)symptom scores[Or=7.31,95%CI(3.36,15.94),pre was no significant difference in adverse effects between the AM and sham-AM groups and the analgesic drug group[Or=0.70,95%CI(0.39,1.28),p=0.25],but the treatment and control groups had mild adverse effects with a low incidence.CONCLUSIONS:AM is more effective than other treatments or pharmacotherapy alone in the treatment of pregnancy-related symptoms,and is relatively safe.However,the quality of the included trials was rather poor,and high-quality studies are required to confirm our findings.

关键词： acupuncture pregnancy nausea vomiting sleep initiation and maintenance disorders low back pain pelvic pain mood abnormalities Meta-analysis systematic review

Superior comprehensive properties of LaFe_(11.8)Si_(1.2)/Ce_(60)Co_(40) magnetocaloric composites

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Journal of rare Earths 2024年第6期42卷 1073-1086,I0003页

作者： Xichun Zhong Yuanxin Li Yucai Wu Jiaohong Huang Cuilan liu Jian liu Zhongwu liu Minglong Zhong Zhenchen Zhong r.V.ramanujan School of Materials Science and Engineering South China University of TechnologyGuangzhou510640China Baotou research Institute of rare Earths Baotou014030China Center for Advanced Solidification Technology School of Materials Science and EngineeringShanghai UniversityShanghai200444China Jiangxi KeyLaboratory for rare Earth Magnetic Materials and Devices&Institute for rare Earth Magnetic Materials and Devices(IrEMMD) Jiangxi University of Science and TechnologyGanzhou341000China School of Materials Science and Engineering Nanyang Technological University639798Singapore Singapore-HUJ Alliance for research and Enterprise(SHArE) The Smart Grippers for Soft Robotics(SGSR)ProgrammeCampus for Research Excellence and Technological Enterprise(CREATE)138602Singapor

LaFe_(11.8)Si_(1.2)/Ce_(60)Co_(40) composites were prepared by spark plasma sintering and subsequent diffusion annealing.A novel core-shell structure is observed with the LaFe11.8Si1.2 particles as the core and the(La,Ce)_(2)(Fe,Co,Si)_(17)(2:17)phase as the shell.As diffusion annealing time(t_(a))increases,this core-shell structure is replaced by the formation of the(La,Ce)_(1)(Fe,Co,Si)_(13) phase.Annealing at 1323 K for 12 h results in samples with(-ΔSM)^(max) of 9.30 J/(kg·K)(Δμ0H=2 T),good mechanical properties((σbc)^(max)=402 Mpa,ε=4.21%)and thermal conductivity of 8.7 W/(m·K).Thus,bulk composites with excellent comprehensive properties for magnetic refrigeration are obtained in this work.

关键词： LaFe_(11.8)Si_(1.2)/Ce_(60)Co_(40)composites Spark plasma sintering Diffusion annealing Microstructure evolution Magnetocaloric effect rareearths

Flame Structure of Methane and Kerosene Combustion with a Compact Concave Flame-Holder using the LES-pdf Method

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Journal of Thermal Science 2024年第1期33卷 222-234页

作者： WANG Fang WANG Yunfan WEI Guanyi liu Denghuan JIN Jie JONES p.William School of Energy and power Engineering Beihang UniversityBeijingBeijing 100191China Department of Mechanical Engineering Imperial College LondonLondon SW72AZUK

Compact flame-holders for afterburners are an increasing requirement for modern aero engines.However,flame-holder design is non-trivial since high inlet temperatures,velocities,and elaborate structures induce complex turbulence,combustion,and spray coupling in modern afterburners.In this work,the LES-pdf and stochastic fields-Lagrangian particle spray methods are used to investigate methane and aviation kerosene combustion structures formed by new-type concave flame-holders.The flow pattern,combustion mode,and flame structure of gaseous and liquid fuel around a concave flame-holder are analyzed,discussed,and compared with experimental results.results reveal that the flame stability of a concave flame-holder is better than that of the non-concave one.Furthermore,when using liquid fuel,the concave flame-holder forms a stable and compact flame.These results suggest concave flame-holders are a promising design for compact afterburners.

关键词： concave structure flame-holder LES-pdf spray combustion flame structure AECSC

removal of Cr(Ⅵ)by glutaraldehyde-crosslinked chitosan encapsulating microscale zero-valent iron:Synthesis,mechanism,and longevity

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Journal of Environmental Sciences 2024年第8期142卷 115-128页

作者： Yijun Duan Fang liu Xiang liu Miao Li School of Environment Tsinghua UniversityBeijing 100084China Transportation Institute of Inner Mongolia University Hohhot 010070China

Microscale zero-valent iron(mZVI)has shown great potential for groundwater Cr(Ⅵ)remediation.However,low Cr(Ⅵ)removal capacity caused by passivation restricted the wide use of mZVI.We prepared mZVI/GCS by encapsulating mZVI in a porous glutaraldehydecrosslinked chitosan matrix,and the formation of the passivation layer was alleviated by reducing the contact between zero-valent iron particles.The average pore diameter of mZVI/GCS was 8.775 nm,which confirmed the mesoporous characteristic of this material.results of batch experiments demonstrated that mZVI/GCS exhibited high Cr(Ⅵ)removal efficiency in a wide range of pH(2-10)and temperature(5-35℃).Common groundwater coexisting ions slightly affected m ZVI/GCS.The material showed great reusability,and the average Cr(Ⅵ)removal efficiency was 90.41%during eight cycles.In this study,we also conducted kinetics and isotherms analysis.pseudo-second-order model was the most matched kinetics model.The Cr(Ⅵ)adsorption process was fitted by both Langmuir and Freundlich isotherms models,and the maximum Langmuir adsorption capacity of m ZVI/GCS reached243.63 mg/g,which is higher than the adsorption capacities of materials reported in most of the previous studies.Notably,the column capacity for Cr(Ⅵ)removal of a mZVI/GCS-packed column was 6.4 times higher than that of a mZVI-packed column in a 50-day experiment.Therefore,mZVI/GCS with a porous structure effectively relieved passivation problems of mZVI and showed practical application prospects as groundwater Cr(Ⅵ)remediation material with practical application prospects.

关键词： Chitosan Glutaraldehyde mZVI Cr(Ⅵ) Groundwater

Circumscription of the East Asia clade (Apiaceae subfamily Apioideae) and the taxonomic placements of several problematic genera

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plant Diversity 2024年第2期46卷 206-218页

作者： Jing Zhou Xinyue Wang Shilin Zhou Junmei Niu Jiarui Yue Zhenwen liu Stephen r.Downie School of pharmaceutical Science and Yunnan Key Laboratory of pharmacology for Natural products Kunming Medical University1168 Western Chunrong RoadYuhua StreetChenggong New CityKunming 650500China Yunnan Academy of Forestry and Grassland Kunming 650201China Gaoligong Mountain Forest EcosystemObservation and Research Station of Yunnan ProvinceKunming 650201China Yunnan Key Laboratory of Biodiversity of Gaoligong Mountain Kunming 650201China Department of plant Biology University of Illinois at Urbana-ChampaignUrbanaIL 61801USA College of Modern Biomedical Industry Kunming Medical UniversityKunming 650500China

The East Asia(or physospermopsis) clade was recognized in previous molecular phylogenetic investigations into the higher-level relationships of Apiaceae subfamily Apioideae. The composition of this clade, the phylogenetic relationships among its constituent taxa, and the placement of species previously determined to be problematic have yet to be resolved. Herein, nr DNA ITS sequences were obtained for150 accessions of Apioideae, representing species whose distributions are in East Asia or genera having one or more species included within the East Asia clade. These data, along with published ITS sequences from other Apioideae(for 3678 accessions altogether), were subjected to maximum likelihood and Bayesian inference analyses. The results show that the East Asia clade contains representatives of 11currently recognized genera: Hansenia, Hymenolaena, Keraymonia, Sinolimprichtia, Acronema, Hymenidium, physospermopsis, pimpinella, Sinocarum, Tongoloa, and Trachydium. However, the latter seven genera have members falling outside of the East Asia clade, including the generic types of all except Tongoloa. Within the clade, the species comprising these seven genera are widely intermingled, greatly increasing confusion among relationships than previously realized. The problematic species physospermopsis cuneata is confirmed as falling within the East Asia clade, whereas p. rubrinervis allies with the generic type in tribe pleurospermeae. physospermopsis kingdon-wardii is confirmed as a member of the genus physospermopsis, whereas the generic attributions of p. cuneata and Tongoloa stewardii remain unclear. Two species of Sinocarum(S. filicinum and S. wolffianum) are transferred into the genus Meeboldia. This is the most comprehensive molecular phylogenetic investigation of the East Asia clade to date, and while the results increase systematic understanding of the clade, they also highlight the need for further studies of one of the most taxonomically intractable groups in Apioideae.

关键词： physospermopsis pimpinella Sinocarum Tongoloa Trachydium

Frequency regulation of VSC-MTDC System with Offshore Wind Farms

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Journal of Modern power Systems and Clean Energy 2024年第1期12卷 275-286页

作者： Haoyu liu Chongru liu North China Electric power University Beijing 102206China

Frequency regulation of voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC)system with offshore wind farms enhances the frequency stability by compensating the power for a disturbed AC system.However,it is difficult to reasonably allocate frequency-regulation resources due to a lack of coordination mechanisms between wind farms and the MTDC system.Moreover,it is difficult for the frequency control of the wind farms to manage changes in wind speed;and the risk of wind-turbine stalls is high.Thus,based on the kinetic energy of wind turbines and the power margin of the converters,the frequency-regulation capability of wind turbines is evaluated,and a dynamic frequency-support scheme considering the real-time frequency-support capability of the wind turbines and system frequency evolution is proposed to improve the frequency-support performance.A power adaptation technique at variable wind speeds is developed;the active power in the frequency-support stage and restoration stage is switched according to the wind speed.A hierarchical zoning frequency-regulation scheme is designed to use the frequency-regulation resources of different links in the MTDC system with wind farms.The simulation results show that the novel frequency-regulation strategy maintains frequency stability with wind-speed changes and avoids multiple frequency dips.

关键词： Wind generation voltage source converter-based multi-terminal high-voltage direct current(VSC-MTDC) frequency regulation cooperative control adaptive control variable wind speed

Characteristics and sources of peroxyacetyl nitrate(pAN)in the rural North China plain:results from1-year continuous observations

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Journal of Environmental Sciences 2024年第4期138卷 719-731页

作者： Xin liu Xiaowei He Chenglong Zhang Yifei Song Shuyang Xie Chengtang liu pengfei liu Yuanyuan Zhang Yujing Mu Junfeng liu research Center for Eco-Environmental Sciences Chinese Academy of SciencesBeijing 100085China University of Chinese Academy of Sciences Beijing 100049China

peroxyacetyl nitrate(pAN)is an important photochemical pollutant in the troposphere,whereas long-term measurements are scarce in rural areas in North China plain(NCp),resulting in unclear seasonal variations and sources of pAN in rural NCp.In this study,we conducted a 1-year observation of pAN during 2021-2022 at the rural NCp site.The average concentrations of pAN were 1.10,0.75,0.65,and 0.88 ppbv in spring,summer,autumn,and winter,respectively,with a 1-year average of 0.81±0.60 ppbv.Calculations indicate that the loss of pAN through thermal decomposition in summer accounts for 43.2% of the total formed pAN,which is an important reason for the low concentration of pAN in summer.We speculate that since the correlation between pAN and O_(3) in winter is significantly lower than that in other seasons,the observed regional transport of pAN cannot be ignored in winter.Through budget analysis,regional transport accounted for 12.8% and 55.9% of the observed pAN on the spring and winter pollution days,respectively,which showed that regional transport played key roles during the photochemical pollution of the rural NCp in winter.The potential source contribution function revealed that the transported pAN mainly comes from southern Hebei in spring.In winter,the transported pAN was mainly from Langfang,Hengshui,and southern Beijing.Our findings may aid in understanding pAN variations in different seasons in rural areas and highlight the impact of regional transport on the pAN budget.

关键词： photochemical pollution peroxyacetyl nitrate(pAN) Seasonal variations regional transport rural area

Severe acute respiratory syndrome-coronavirus-2(SArS-COV-2)infection of pneumocytes with vaccination and drug therapy:Mathematical analysis and optimal control

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International Journal of Biomathematics 2024年第2期17卷 299-334页

作者： r.Viriyapong p.Inkhao Department of Mathematics Faculty of Science Naresuan University Phitsanulok65000Thailand

We propose a mathematical model studying a within-host infection dynamics of SArSCoV-2 in pneumocytes.This model incorporates immune response,vaccination and antiviral drugs.The crucial properties of the model-the existence,positivity and boundary of solutions are established.Equilibrium points and the basic reproduction number are calculated.The stability of each equilibrium point is analyzed.Optimal control is applied to the model by adding three control variables:vaccination,treatment by Favipiravir and treatment by Molnupiravir.Numerical results show that each individual control could reduce SArS-CoV-2 infection in some aspects;however,with a combination of three controls,we obtain the best results in reducing SArS-CoV-2 infection.This study has emphasized the importance of prevention by vaccine and the antiviral treatments.

关键词： SArS-CoV-2 vaccination drug therapy immune response optimal control