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Enhanced thermoelectric performance of spark plasma sintered p-type Ca_(3-x)Y_(x)Co_(4)O_(9+δ)systems

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journal of Materials Science & Technology 2020年第20期52卷 212-222页

作者： j.S.Cha D.h.Kim h.Y.hong K.Park Faculty of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul05006Republic of Korea

highly textured dense Ca3-xYxCo4 O9+δ(0≤x≤0.3)samples were fabricated by combining sol-gel process with spark plasma sintering(SPS).Y^3+substitution for Ca^2+simultaneously increased the Seebeck coefficient and reduced the thermal *** latter was attributed to the increase in lattice anharmonicity,structural distortion,and grain boundary area,which enhanced the phonon ***2.7Y0.3Co4 O9+δshowed the largest dimensionless figure-of-merit(ZT=0.194)at 1073 K because it had the largest Seebeck coefficient and the lowest thermal *** ZT value was 55%larger than that of undoped Ca3 Co4 O9(0.125 at 1073 K).Therefore,Y^3+substitution,sol-gel powder synthesis,and SPS are highly effective for enhancing the thermoelectric prope rties of Ca_(3)Co_(4)O_(9).

关键词： Electrical conductivity Ca_(3)Co_(4)O_(9) Thermoelectric properties Seebeck coefficient Thermal conductivity Spark plasma sintering

Achieving ultrahigh strength and ductility in high-entropy alloys via dual precipitation

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journal of Materials Science & Technology 2023年第35期166卷 67-77页

作者： j.M.Guo B.C.Zhou S.Qiu h.j.Kong M.C.Niu j.h.Luan T.L.Zhang h.Wu Z.B.jiao Department of Mechanical Engineering Research Institute for Advanced ManufacturingThe Hong Kong Polytechnic UniversityHong KongChina The hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057China Department of Materials Science and Engineering City University of Hong KongHong KongChina State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

The strength-ductility trade-offhas been a longstanding dilemma in metallic *** we report an innovative approach to achieve a high strength-ductility synergy via dual precipitation of sheared and bypassed precipitates.(Ni_(2) Co_(2) FeCr)_(96-x) Al_(4) Nb_(x)(at.%)alloys strengthened by nanoscale L12 particles and Laves precipitates were selected as a model for this study,and their precipitate microstructures and mechanical properties were thoroughly *** dual-precipitation-strengthened alloys exhibit a yield strength of more than 1400 MPa,an ultimate tensile strength of over 1800 MPa,and a uniform elon-gation of 18%,thus achieving a high strength-ductility *** analysis reveals that the nanoscale L1_(2) precipitates contribute to the strength via the particle shearing mechanism,whereas the Laves phase provides the strengthening through the Orowan bypass *** study of deformation microstruc-tures shows that the L1_(2) precipitates are sheared by stacking faults,which facilitates long-range disloca-tion gliding through the *** a result,deformation induces the formation of hierarchical stacking fault networks and immobile Lomer-Cottrell locks,which effectively enhance the work hardening ca-pability and plastic stability,thereby resulting in a high ductility at high strength *** are piled-up against the interface between the Laves precipitates and matrix,which increases the work hardening capability at the early stages of plastic deformation but causes stress *** dual precipitation strategy may be useful for many other alloys for achieving superior mechanical properties for technological applications.

关键词： high-entropy alloy Dual precipitation Precipitation strengthening Deformation mechanism

A new technique for islanding operation of distribution network connected with mini hydro

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Frontiers of Information Technology & Electronic Engineering 2015年第5期16卷 418-427页

作者： j.A.LAGhARI h.MOKhLIS M.KARIMI A.h.A.BAKAR hasmaini MOhAMAD Department of Electrical Engineering Faculty of Engineering University of Malaya Department of Electrical Engineering Quaid-e-Awam University of Engineering Science & Technology University of Malaya Power Energy Dedicated Advanced Centre (UMPEDAC) University of Malaya Faculty of Electrical Engineering University of Technology MARA (UiTM)

An islanding operation of a distribution network is a topic of interest due to the significant penetration of distributed generation(DG) in a power system network. however, controlling the frequency of an islanded distribution system remains an unresolved issue, especially when the load exceeds the generation. This paper presents a new technique for a successful islanding operation of a distribution network connected with multiple mini hydro based DGs. The proposed technique is based on three main parts. The first part uses an islanding detection technique to detect the islanding event correctly. The second part consists of a power imbalance estimation module(PIEM), which determines the power imbalance between the generation and load demand. The third part consists of a load shedding controller, which receives the power imbalance value and performs load shedding according to load priority. The proposed technique is validated on an 11 k V existing Malaysia distribution network. The simulation results show that the proposed technique is effective in performing a successful islanding operation by shedding a significant number of loads.

关键词： Islanding operation Mini hydro Distributed generation(DG) Islanding detection Load shedding

Reviewing the Oceanic Nino Index(ONI) to Enhance Societal Readiness for El Nino’s Impacts

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International journal of Disaster Risk Science 2020年第3期11卷 394-403页

作者： Michael h.Glantz Ivan j.Ramirez Consortium for Capacity Building/INSTAAR.University of Colorado BoulderCO 80309USA Department of health and Behavioral Sciences University of Colorado DenverDenverCO 80204USA

NOAA’s Oceanic Nino Index(ONI)is used to record for historical purposes the occurrence and duration of El Nino episodes,based on the monitoring of sea surface temperatures(SSTs)in the central Pacific *** ONI is used to identify the onset of an above average SST threshold that persists for several months,encompassing both the beginning and end of an El Nino *** first appearance of an anomalous seasonal value of 0.5℃suggests with a high probability that an El Nino could emerge,but for heightened warnings,one must wait for several *** this article,we proposed that the ONI value of 0.7℃identifies a tipping point at which the El Nino event becomes locked in,which can provide additional lead time for mitigative actions to be taken by societal decision *** preliminary findings suggest that a first appearance of 0.7℃value could serve as a credible marker of El Nino’s locked-in phase,which can provide additional credibility to the current 0.5℃El Nino onset indicator for at-risk societies to get ready for El Nino’s foreseeable societal and ecological impacts.

关键词： Advisory Disasters Early warning El Nino El Nino Southern Oscillation ENSO hydrometeorological hazards Oceanic Nino Index ONI

Acoustic Measurements for Determination of the Materials Damping Using A Sound Source Localisation System

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Acta Metallurgica Sinica(English Letters) 2013年第2期26卷 113-121页

作者： j. Gken j. Swiostek h. hurdelbrink U. Keil Faculty of Maritime Studies University of Applied Sciences Emden/Leer Bergmannstr. 36 26789 LeerGermany Stalomax TM Company of High-Precision Mechanics ul. Parkingowa 45 37450 Stalowa WolaPoland

Noise measurements are especially a problem when the object under investigation is largely dimensioned and can only be measured from the distance. To obtain information about the location of noise generation, a measurement technique which makes sound visible in order to introduce further specific technical measures is advantageous. The question is if the time dependence of the signal got from such a non touching and non destructive acoustic method has the potential to calculate the materials damping from. Using a small sound source localization system （Microflown^TM probe）, specimens of magnesium alloys with different grain sizes obtained by hydrostatic extrusion were investigated. It has been demonstrated that the fine grained microstructure led to a lower damping and its dependence on the strain was reduced. In this context, acoustic measurements by a sound source localisation system which makes materials characterization possible could be used as a quality tool to detect changes in highly stressed components. This approach allows to promote a selective substitution of conventional materials by more innovative ones. The offshore sector is considered to be a field of application： Wind turbines produce noise emission which stems mainly from turbulences at the tips of the rotor blades and vibrations of components inside the nacelle （e.9. gearbox, generator, ...）. If the vibration amplitudes are too high, microcracks of components can lead to failure over the long term. The monitoring of microstructural changes using a larger type of a sound source localisation system is considered as an innovative technical approach with respect to maintenance activities.

关键词： Magnesium Noise measurements MicroflownTM Damping

Observability Analysis of Integrated Electricity and heating Systems with Thermal Quasi-dynamics in Pipelines

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CSEE journal of Power and Energy Systems 2024年第3期10卷 1145-1158页

作者： Zhigang Li Wenjian Zheng junbo Zhao j.h.Zheng Q.h.Wu School of Electric Power Engineering South China University of TechnologyGuangzhou 510641China Fuzhou Changle District Power Supply Company of State Grid Fujian Electric Power Co. Ltd.Fuzhou 350000China Department of Electrical and Computer Engineering University of ConnecticutStorrsCT 06269USA CSEE IEEE

Observability analysis(OA)is vital to obtaining the available input measurements of state estimation(SE)in an integrated electricity and heating system(IEhS).Considering the thermal quasi-dynamics in pipelines,the measurement equations in heating systems are dependent on the estimated results,leading to an interdependency between OA and *** OA methods require measurement equations be known exactly before SE is performed,and they are not applicable to *** bridge this gap,a scenario-based OA scheme for IEhSs is devised that yields reliable analysis results for a predefined set of time-delay scenarios to cope with this *** its core procedure,the observable state identification and observability restoration are formulated in terms of integer linear *** tests are conducted to demonstrate the validity and superiority of the proposed formulation.

关键词： Integrated electricity and heating system measurement observability analysis state estimation thermal quasi-dynamics

Ξ^-t quasibound state instead of ΛΛnn bound state

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Chinese Physics C 2020年第2期44卷 94-100页

作者： h.Garcilazo A.Valcarce j.Vijande Escuela Superior de Física y Matemáticas Instituto Politécnico NacionalEdificio 907738 México D.F.Mexico Departamento de Física Fundamental Universidad de Salamanca37008 SalamancaSpain Departamento de Física Atómica Molecular y NuclearUniversidad de Valencia(UV)and IFIC(UV-CSIC)46100 ValenciaSpain IRIMED joint Research Unit(IIS La Fe-UV) 46100 ValenciaSpain

The coupledΛΛnn-Ξ-pnn system was studied to investigate whether the inclusion of channel coupling is able to bind theΛΛnn *** use a separable potential three-body model of the coupledΛΛnn-Ξ-pnn system and a variational four-body calculation with realistic *** results exclude the possibility of aΛΛnn bound state by a large ***,we found aΞ-t quasibound state above theΛΛnn threshold.

关键词： baryon-baryon interactions few-body systems Faddeev equations

The Performance of EOS Models in the Prediction of Vapor-Liquid Equilibria in Asymmetric Natural Gas Mixtures

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Chinese journal of Chemical Engineering 1998年第3期6卷 29-37页

作者：王利生 h.Gardeler j.Gmehling Department of Technical Chemisity University of OldenburgP.O.Box 2503D-26111 OldenburgGermany

The aim of this work is to apply cubic equations of state(EOS)to vapor-liquid equilibriacalculations of gas-heavy hydrocarbon systems,which are asymmetric in molecular size and areusually found in natural *** has been done to test the validity of the original PSRKand the cubic simplified perturbed hard-chain(CSPhC)models for global phase *** results show that both equations overpredict vapor pressure in the near critical *** the prediction of the solubilities of high molecular weight(MW)hydrocarbons in the naturalgas,the PSRK model gives good agreement for the dew point pressure-vapor composition *** of the pure component parameters of the CSPhC EOS for heavy components to fit thevapor-liquid equilibrium(VLE)data has been proved to give significant promoting in ***,further improvement of a van der Waals EOS,such as SRK,PT and DG modelsfor the asymmetric systems by adjusting the three pure component properties,T_c, p_c and ?

关键词： equation of state natural gas vapor-liquid equilibria asymmetric systems

Nitrogen Contents on Tribological Properties of Magnetron Sputtered SICN Coatings

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材料热处理学报 2004年第05B期25卷 854-857页

作者： TIETUNSUN Y.Q.FU j.WEI h.j.DU Departmentofphysics ShanghaiJiaotongUniversityShanghaiChina／／SchoolofMechanicalandProductionEngineeringNanyangTechnologicalUniversitySingapore639798 SchoolofMechanicalandProductionEngineering NanyangTechnologicalUniversitySingapore639798／／SingaporeInstituteofManufacturingTechnologySingapore71NanyangDriveSingapore638075 SingaporeInstituteofManufacturingTechnology -Singapore71NanyangDrivesingapore638075

Silicon carbonitride (SiCN) coatings were deposited on silicon and tungsten carbide substrates by co-sputtering silicon and carbon in argon and nitrogen mixture atmosphere using magnetron-sputtering system. The effect of the N2 concentration, RF substrate bias voltage and target current on film deposition rate, roughness, adhesion, mechanical and tribological properties of coatings were investigated. The deposition rate was found to increase with the increasing nitrogen concentration. X-ray photoelectron spectroscopy analysis showed that high nitrogen concentration in the nitrogen-argon gas mixture enhanced the incorporation of C and N but reduced the incorporation of Si. SiCN coatings have good tribological properties at a N2 concentration of approximately 60%.

关键词： SiCN涂层磁控管溅射含氮量硬度磨损