检索结果-南通市图书馆

Effects of cooling rate on microstructure and microhardness of directionally solidified galvalume alloy

在线全文

学校读者我要写书评

暂无评论

China Foundry 2024年第3期21卷 213-220页

作者： Ji-peng Li de-gao Qiao Jian Li Xiao-yang Luo Peng Peng Xian-tao Yan Xu-dong Zhang gansu Jiu Steel group Hongxing Iron and Steel Co. Ltd.Jiayuguan 735111GansuChina School of Materials and Energy Lanzhou UniversityLanzhou 730000China

The influences of cooling rate on the phase constitution,microstructural length scale,and microhardness of directionally solidified galvalume(Zn-55Al-1.6Si)alloy were investigated by directional solidification experiments at different withdrawal speeds(5,10,20,50,100,200,and 400μm·s^(-1)).The results show that the microstructure of directionally solidified galvalume alloys is composed of primary Al dendrites,Si-rich phase and(Zn-Al-Si)ternary eutectics at the withdrawal speed ranging from 5 to 400μm·s^(-1).As the withdrawal speed increases,the segregation of Si element intensifies,resulting in an increase in the area fraction of the Si-rich *** addition,the primary Al dendrites show significant refinement with an increase in the withdrawal *** relationship between the primary dendrite arm spacing(λ_(1))and the thermal parameters of solidification is obtained:λ_(1)=127.3V^(-0.31).Moreover,as the withdrawal speed increases from 5 to 400μm·s^(-1),the microhardness of the alloy increases from 90 HV to 151 *** is a combined effect of grain refinement and second-phase strengthening.

关键词： galvalume alloy directional solidification microstructure length scale microhardness

Optimal Control of Service Rates of Discrete-Time(s,Q)Queueing-Inventory Systems with Finite Buffer

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science and Systems Engineering 2024年第3期33卷 261-280页

作者： L.Iniya B.Sivakumar g.Arivarignan School of Mathematics Madurai Kamaraj UniversityMaduraiTamilnaduIndia department of Statistics Manonmaniam Sundaranar UniversityTirunelveliTamilnaduIndia

This article,we develop an optimal policy to control the service rate of a discrete time queueing-inventory system with finite *** customers arrive according to a Bernoulli process and the service time for the customers are *** the buffer size attains its maximum,any arriving new customers are considered to be *** customers are served one by one according to FCFS rule and each customers request random number of *** inventory is replenished according to a(s,Q)inventory policy with geometric lead *** main objectives of this article are to determine the service rates to be employed at each slot so that the long run expected cost rate is minimized for fixed inventory level and fixed buffer size and to minimize the expected waiting time for a fixed inventory level and fixed buffer *** problems are modelled as Markov decision *** establish the existence of a stationary policy and employ linear programming method to find the optimal service *** provide some numerical examples to illustrate the behaviour of the model.

关键词： Queueing-inventory system discrete time batch demand-Markov decision process

Effective utilization of dolomitic lead-zinc waste rock by replacing dolomite as flux in iron ore sintering process

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Iron and Steel Research International 2024年第8期31卷 1861-1872页

作者： Xin Wang Cong-cong Yang Jian Pan de-qing Zhu Zheng-qi guo guang-hui Xia Shi-juan Qu School of Minerals Processing and Bioengineering Central South UniversityChangsha 410083HunanChina Low-Carbon and Hydrogen Metallurgy Research Center Central South UniversityChangsha 410083HunanChina

With increasingly stringent environmental protection policies,cost-effective and value-added treatment of massive lead-zinc waste rock(LZWR)generated from the preconcentration process has attracted substantial attention.A type of dolomitic LZWR with 18 wt.%MgO,27 wt.%CaO,0.29 wt.%Zn and 1.43 wt.%S was used as a replacement flux in the iron ore sintering *** sinter pot tests were carried out based on an industrial ore *** results show that replacing 0%-60%of dolomite with LZWR does not adversely affect the sintering productivity,fuel consumption rate,and the quality of the sinter products,while the Zn and S elements contained in LZWR can be effectively removed with the residual Zn and S contents of the resultant sinter products being less than 0.02 and 0.055 wt.%,***,substituting LZWR for dolomite as a flux inevitably increases the SO_(2) concentration in the sintering flue gas due to its high sulfur *** the processing capacity of the sintering flue gas desulfurization system,the replacement ratio of dolomite can reach 40%,equal to LZWR consumption of 24.3 kg per ton of *** SO_(2) in sintering flue gas can be recovered to produce(NH_(4))_(2)SO_(4) or HSO_(4),while the volatilized Zn collected into the zinc-containing dust can be subsequently recycled by the rotary hearth furnace ***,it is technologically and economically feasible to use the LZWR as a replacement flux in the iron ore sintering process,providing a new way for the safe,large-scale and low-cost treatment of LZWR.

关键词： Lead Zinc waste rock Dolomite Sintering Flue gas Sinter product

Prognostic value of a nomogram model for postoperative liver metastasis of colon cancer

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of gastrointestinal Surgery 2024年第4期16卷 1055-1065页

作者： de-Xin Cheng Kang-Di Xu Han-Bo Liu Yi Liu department of Interventional Medicine Zhejiang Provincial People’s Hospital(Affiliated People’s HospitalHangzhou Medical College)Hangzhou 310014Zhejiang ProvinceChina general Surgery Cancer CenterDepartment of Vascular SurgeryZhejiang Provincial People’s Hospital(Affiliated People’s HospitalHangzhou Medical College)Hangzhou 310014Zhejiang ProvinceChina

BACKgROUND Colon cancer is one of the most common malignant tumors of the digestive *** metastasis after colon cancer surgery is the primary cause of death in patients with colon *** To construct a novel nomogram model including various factors to predict liver metastasis after colon cancer *** We retrospectively analyzed 242 patients with colon cancer who were admitted and underwent radical resection for colon cancer in Zhejiang Provincial People’s Hospital from december 2019 to december *** were divided into liver metastasis and non-liver metastasis ***,age,and other general and clinicopathological data(preoperative blood routine and biochemical test indexes)were *** risk factors for liver metastasis were analyzed using singlefactor and multifactorial logistic regression.A predictive model was then constructed and evaluated for *** Systemic inflammatory index(SII),C-reactive protein/albumin ratio(CAR),red blood cell distribution width(RDW),alanine aminotransferase,preoperative carcinoembryonic antigen level,and lymphatic metastasis were different between groups(Pgery(Pder the curve was 0.93 for the column-line diagram prediction model constructed based on these risk factors to distinguish whether liver metastasis occurred *** actual curve of the column-line diagram predicting the risk of postoperative liver metastasis was close to the ideal curve,with good *** prediction model curves in the decision curve analysis showed higher net benefits for a larger threshold range than those in extreme cases,indicating that the model is *** Liver metastases after colorectal cancer surgery could be well predicted by a nomogram based on the SII,CAR,and RDW.

关键词： Systemic immunoinflammatory index C-reactive protein/albumin ratio Erythrocyte distribution width Colon cancer Liver metastasis Novel nomogram model

The great catastrophe: causes of the Permo-Triassic marine mass extinction

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

National Science Review 2024年第1期11卷 37-50页

作者： Paul B.Wignall David P.g.Bond School of Earth & Environment University of Leeds School of Environmental Sciences University of Hull

The marine losses during the Permo-Triassic mass extinction were the worst ever experienced. All groups were badly affected, especially amongst the benthos(e.g. brachiopods, corals, bryozoans, foraminifers,ostracods). Planktonic populations underwent a fundamental change with eukaryotic algae being replaced by nitrogen-fixing bacteria, green-sulphur bacteria, sulphate-reducing bacteria and prasinophytes. detailed studies of boundary sections, especially those in South China, have resolved the crisis to a ～55 kyr interval straddling the Permo-Triassic boundary. Many of the losses occur at the beginning and end of this interval painting a picture of a two-phase extinction. Improved knowledge of the extinction has been supported by numerous geochemical studies that allow diverse proposed extinction mechanisms to be studied. A transition from oxygenated to anoxic-euxinic conditions is seen in most sections globally, although the intensity and timing shows regional variability. decreased ocean ventilation coincides with rapidly rising temperatures and many extinction scenarios attribute the losses to both anoxia and high *** kill mechanisms include ocean acidification for which there is conflicting support from geochemical proxies and, even less likely, siltation(burial under a massive influx of terrigenous sediment) which lacks substantive sedimentological evidence. The ultimate driver of the catastrophic changes at the end of the Permian was likely Siberian Trap eruptions and their associated carbon dioxide emissions with consequences such as warming, ocean stagnation and acidification. Volcanic winter episodes stemming from Siberian volcanism have also been linked to the crisis, but the short-term nature of these episodes(decades) and the overwhelming evidence for rapid warming during the crisis makes this an unlikely cause. Finally, whilst the extinction is well studied in equatorial latitudes, a different history is found in northern Boreal latitudes

关键词： ocean anoxia ocean acidification siltation productivity collapse volcanic winter

Introduction to the Special Issue on Computer-Aided Uncertainty Modeling and Reliability Evaluation for Complex Engineering Structures

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2024年第10期141卷 1-5页

作者： debiao Meng Abílio Manuel Pinho de Jesus Zeng Meng School of Mechanical and Electrical Engineering University of Electronic Science and Technology of ChinaChengdu611731China INEgI Faculty of EngineeringUniversity of PortoPorto4200-465Portugal School of Civil Engineering Hefei University of TechnologyHefei230009China

1 Summary With the advancement of science and technology,complex engineering structures are widely used in extreme environments[1].In equipment service,many uncertainty factors significantly affect safety and reliability[2–5].Therefore,ensuring high reliability of structures has become an important research direction in engineering *** the same time,the importance of equipment health management of complex engineering structures is becoming increasingly prominent[6–8].Computer-aided uncertainty modeling and reliability assessment have become key tools,and finite element simulation and algorithmic innovation play a key role in the reliability analysis of complex equipment[9,10].These techniques can accurately simulate stress and damage accumulation under various operating environments,providing engineers with important decision support and optimization solutions.

关键词： extreme Reliability environments

Understanding the catalysis of chromium trioxide added magnesium hydride for hydrogen storage and Li ion battery applications

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2024年第3期12卷 1117-1130页

作者： D.Pukazhselvan IhsanÇaha Catarina de Lemos Sergey M.Mikhalev Francis Leonard deepak Duncan Paul Fagg department of Mechanical Engineering TEMA-Centre for Mechanical Technology and AutomationUniversity of AveiroAveiro 3810-193Portugal LASI-Intelligent Systems Associate Laboratory Guimarães 4800-058Portugal Nanostructured Materials group International Iberian Nanotechnology Laboratory(INL)Avenida Mestre Jose VeigaBraga 4715-330Portugal

This study explores how the chemical interaction between magnesium hydride(MgH_(2))and the additive CrO_(3) influences the hydrogen/lithium storage characteristics of MgH_(2).We have observed that a 5 wt.%CrO_(3) additive reduces the dehydrogenation activation energy of MgH_(2) by 68 kJ/mol and lowers the required dehydrogenation temperature by 80℃.CrO_(3) added MgH_(2) was also tested as an anode in an Li ion battery,and it is possible to deliver over 90%of the total theoretical capacity(2038 mAh/g).Evidence for improved reversibility in the battery reaction is found only after the incorporation of additives with MgH_(2).In depth characterization study by X-ray diffraction(XRD)technique provides convincing evidence that the CrO_(3) additive interacts with MgH_(2) and produces Cr/MgO *** free energy analyses confirm the thermodynamic feasibility of conversion from MgH_(2)/CrO_(3) to MgO/Cr,which is well supported by the identification of Cr(0)in the powder by X ray photoelectron spectroscopy(XPS)*** high resolution transmission electron microscopy(HRTEM)and energy dispersive spectroscopy(EDS)we found evidence for the presence of 5 nm size Cr nanocrystals on the surface of MgO rock salt *** is also convincing ground to consider that MgO rock salt accommodates Cr in the *** observations support the argument that creation of active metal–metal dissolved rock salt oxide interface may be vital for improving the reactivity of MgH_(2),both for the improved storage of hydrogen and lithium.

关键词： Hydrogen storage Rechargeable batteries Binary hydrides Metal oxides Catalytic mechanism.

Review of Networked Microgrid Protection:Architectures,Challenges,Solutions,and Future Trends

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2024年第2期10卷 448-467页

作者： Jorge de la Cruz Ying Wu John E.Candelo-Becerra Juan C.Vasquez Josep M.guerrero Center for Research on Microgrids(CROM) Department of Energy TechnologyAalborg University9220 AalborgDenmark Facultad de Minas Departamento de Energia Eléctrica y AutomaticaUniversidad Nacional de ColombiaSede MedellinCarrera 80 No.65-223RobledoMedellin 050041Colombia. Center for Research on Microgrids at UPC(UPC CROM) Department of Electronic EngineeringTechnical University of Catalonia(UPC)08019 Barcelona Spain ICREA Pg.Lluis Companys 2308010 BarcelonaSpain Center for Research on Microgrids at AAU(AAU CROM) AAU EnergyAalborg University(AAU)9220 Aalborg EastDenmark

design and selection of advanced protection schemes have become essential for reliable and secure operation of networked *** protection schemes that allow correct operation of microgrids have been proposed for individual systems in different topologies and ***,protection schemes for networked microgrids are still in devel-opment,and further research is required to design and operate advanced protection in interconnected *** of these microgrids in different nodes with various intercon-nection technologies increases fault occurrence and complicates protection *** paper aims to point out challenges in developing protection for networked microgrids,potential solutions,and research areas that need to be addressed for their ***,this article presents a systematic analysis of different microgrid clusters proposed since 2016,including several architectures of networked microgrids,operation modes,components,and utilization of renewable sources,which have not been widely explored in previous review ***,the paper presents a discussion on protection systems currently available for microgrid clusters,current challenges,and solutions that have been proposed for these ***,it discusses the trend of protection schemes in networked microgrids and presents some conclusions related to ***—Adaptive eprotection,microgrid cluster,microgrid,multiple microgrid,networked microgrid,real-time simulation,smart grid.

关键词： Adaptive eprotection microgrid cluster microgrid multiple microgrid networked microgrid real-time simulation smart grid

Comparative Study on Microstructure and Mechanical Properties of Coarse-grained WC-based Cemented Carbides Sintered with Ultrafine WC or (W+C) as Additives

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 399-409页

作者：于淞百闵凡路 LI de NOUdeM guillaume Jacques ZHANg Hailong MA Jichang ZHAO Kui YAO Zhanhu 张建峰 College of Mechanics and Materials Hohai UniversityNanjing 210098China Key Laboratory of geomechanics and Embankment Engineering Hohai UniversityMinistry of EducationNanjing 210098China CRISMAT-ENSICAEN(UMR-CNRS 6508) Universitéde Caen-Basse-NormandieF-14050 CaenFrance Shaanxi Aeronautic Carbide Tool Co.Ltd. Hanzhong 724200China CCCC Tunnel Engineering Co.Ltd. Beijing 100102China

The effects of ultrafine WC(WC_(UF),0.5μm) or W(1μm) and C(0.3μm)(W+C)_(UF) additives on the densification,microstructure and mechanical properties of coarse-grained cemented carbides were compared ***,the cemented carbides with WC_(UF)/(W+C)_(UF) additives are almost fully densification to be higher than 99%,and the average grain size is kept above 2.8μ*** WC_(UF) additive assists grains to(truncated)trigonal prism shape by two dimensional(2D) growth,whereas the(W+C)_(UF) additive assists grains to rounded shape by three dimensional(3D) growth,lowers WC contiguity and increases face-centered-cubic *** hardness and bending strength of(75WC_(C)-15WC_(UF))-10Co are 86.6 HRA and 2 272 MPa,respectively,both higher than those of(75WC_(C)-15(W+C)_(UF))-10Co,which could be ascribed to the enhanced densification and unblemished ***,the fracture toughness of the(75WC_(C)-15(W+C)_(UF))-10Co is 23.5 MPa·m^(1/2),higher than that of the(75WC_(C)-15WC_(UF))-10Co due to the uniform WC-Co structure and flexible binder phase.

关键词： coarse-grained WC-based cemented carbide ultrafine WC ultrafine(W+C) microstructure mechanical properties