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An Ensemble Forecast of the South China Sea Monsoon

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Advances in Atmospheric Sciences 1999年第2期16卷 159-182页

作者： t.n.Krishnamurti Mukultewari EdBensman Department of Meteorology Florida State University Tallahassee FL

this paper presents a generalized ensemble forecast procedure for the tropical latitudes. Here we propose an empirical orthogonal function-based procedure for the definition of a seven-member ensemble. the wind and the temperature fields are perturbed over the global tropics. Although the forecasts are made over the global belt with a high-resolution model, the emphasis of this study is on a South China Sea monsoon. Over this domain of the South China Sea includes the passage of a tropical Storm, Gary, that moved eastwards north of the Philippines. the ensemble forecast handled the precipitation of this storm reasonably well. A global model at the resolution triangular truncation 126 waves is used to carry out these seven forecasts. the evaluation of the ensemble of forecasts is carried out via standard root mean square errors of the precipitation and the wind fields. the ensemble average is shown to have a higher skill compared to a control experiment, which was a first analysis based on operational data sets over both the global tropical and South China Sea domain. All of these experiments were subjected to physical initialization which provides a spin-up of the model rain close to that obtained from satellite and gauge-based estimates. the results furthermore show that inherently much higher skill resides in the forecast precipitation fields if they are averaged over area elements of the order of 4° latitude by 4° longitude squares.

关键词： Ensemble forecast triangular truncation

Multisubband electron mobility in a parabolic quantum well structure under the influence of an applied electric field

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Journal of Semiconductors 2014年第1期35卷 1-6页

作者： n.Sahoo t.Sahu Department of Electronic Science Berhampur University Department of Electronics and Communication Engineering National Institute of Science and Technology

We study the multisubband electron mobility in a barrier delta doped AlχGal-χAs parabolic quantum well structure under the influence of an applied electric field perpendicular to the interface plane. We consider the alloy fraction χ = 0.3 for barriers and vary x from 0.0 to 0.1 for the parabolic well. Electrons diffuse into the well and confine within the triangular like potentials near the interfaces due to Coulomb interaction with ionized donors. the parabolic structure potential, being opposite in nature, partly compensates the Coulomb potential. the external electric field further amends the potential structure leading to an asymmetric potential profile. Accordingly the energy levels, wave functions and occupation of subbands change. We calculate low temperature electron mobility as a function of the electric field and show that when two subbands are occupied, the mobility is mostly dominated by ionised impurity scattering mediated by intersubband effects. As the field increases transition from double subband to single subband occupancy occurs. A sudden enhancement in mobility is obtained due to curtailment of intersubband effects. thereafter the mobility is governed by both impurity and alloy disorder scatterings. Our analysis of mobility as a function of the electric field for different structural parameters shows interesting results.

关键词： parabolic quantum well multisubband electron mobility AlGaAs

Bound States Energies of a Harmonic Oscillator Perturbed by Point Interactions

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Communications in theoretical Physics 2017年第3期67卷 241-249页

作者： n.Ferkous t.Boudjedaa laboratory of theoretical Physics Department of Physics University of Jijel PB 98 Ouled Aissa DZ-18000 Jijel Algeria

We determine explicitly the exact transcendental bound states energies equation for a one-dimensional harmonic oscillator perturbed by a single and a double point interactions via Green's function techniques using both momentum and position space representations. the even and odd solutions of the problem are discussed. the corresponding limiting cases are recovered. For the harmonic oscillator with a point interaction in more than one dimension,divergent series appear. We use to remove this divergence an exponential regulator and we obtain a transcendental equation for the energy bound states. the results obtained here are consistent with other investigations using different methods.

关键词： Green's function delta potential harmonic oscillator regularization

Effects of Heat treatment on Hardness and Dry Wear Properties of a Semi-Solid Processed Fe-27 wt pct Cr-2.9 wt pct C Cast Iron

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Journal of Materials Science & technology 2008年第3期24卷 330-334页

作者： A.Wiengmoon t.Chairuangsri n.Chomsang n.Poolthong J.t.H.Pearce Department of Physics Faculty of ScienceNaresuan University Department of Industrial Chemistry and Electron Microscopy Research and Service Center Faculty of ScienceChiang Mai University Department of Physics Faculty of ScienceChiang Mai University Division of Materials technology School of EnergyEnvironmental and MaterialsKing Mongkut's University of Technology Thonburi national Metal and Materials technology Center

EfFects of heat treatments on hardness and dry wear properties of a semi-solid processed Fe-26.96 wt pct Cr- 2.91 wt pct C cast iron were studied. Heat treatments included tempering at 500℃, destabilisation at 1075℃ and destabilisation at 1075℃ plus tempering at 500℃, all followed by air cooling. Electron microscopy revealed that, in the as-cast condition, the primary proeutectic austenite was round in shape while the eutectic M7C3 carbide was found as radiating clusters mixed with directional clusters. tempering did not change the microstructure significantly when observed by scanning or transmission electron microscopy. Destabilisation followed by air cooling led to a precipitation of secondary M23C6 carbide and a transformation of the primary austenite to martensite. Precipitation behaviour is comparable to that observed in the conventionally cast iron. tempering after destabilisation resulted in a higher amount of secondary carbide precipitation within the tempered martensite in the eutectic structure. Vickers macrohardness and microhardness in the proeutectic zones were measured. Dry wear properties were tested by using a pin-on-disc method. the maximum hardness and the lowest dry wear rate were obtained from the destabilisation-plus-tempering heat treatment due to the precipitation of secondary carbides within the martensite matrix and a possible reduction in the retained austenite.

关键词： Semi-solid process High chromium cast iron Heat treatment Hardness Wear

large dinosaur egg accumulations and their significance for understanding nesting behaviour

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Geoscience Frontiers 2024年第5期15卷 467-488页

作者： l.Ezquerro R.Coimbra B.Bauluz C.núñez-lahuerta t.Román-Berdiel M.Moreno-Azanza Departamento de Geodinámica Estratigrafía y PaleontologíaFacultad de Ciencias GeológicasUniversidad Complutense de MadridC/JoséAntonio Novais1228040MadridSpain Aragosaurus-IUCA:Recursos Geológicos y Paleoambientales.Departamento de Ciencias de la tierra.Facultad de Ciencias Universidad de ZaragozaC/Pedro Cerbuna 1250009 ZaragozaSpain Museu da lourinha LourinhaPortugal GeoBiotec Department of Earth SciencesNOVA School of Science and TechnologyUniversidade Nova de LisboaCaparicaPortugal GeoBiotec Departamento de GeocienciasUniversidade de AveiroAveiroPortugal Insitut Catalàde Paleoecologia Humana i EvolucióSocial(IPHES-CERCA) Zona Educacional 4Campus Sescelades URV(Edifici W3)43007 TarragonaSpain Departament d´Història i Història de l´Art Universitat Rovira i VirgiliAv.Catalunya 3543002 TarragonaSpain Geotransfer IUCA Departamento de Ciencias de La TierraFacultad de CienciasUniversidad de ZaragozaZaragozaSpain

the accurate identification of dinosaur egg accumulations as nests or clutches is crucial for understanding the reproductive behaviour of these extinct ***,existing methods often rely on the presence of complete eggs and embryo remains,and sedimentological criteria that are only applicable to well-structured *** this study,we introduce an innovative approach to characterize egg accumulations in structureless sediments,where traditional nest structures may not be *** methodology employs a unique combination of sedimentological,taphonomic,geochemical,and geophysical proxies for the study of egg *** applied this approach to the egg accumulation from Paimogo(Jurassic,Portugal),traditionally interpreted as a *** findings reveal that the Paimogo egg assemblage is a secondary deposit,resulting from a flooding event in a fluvial plain that dismantled several allosauroid and crocodylomorph *** eggshell vapor conductance results,coupled with sedimentological evidence,suggest that allosauroid dinosaurs buried their eggs in the dry terrain of overbank areas close to a main channel during the breeding season,likely during the dry season to prevent the embryos from *** research underscores the necessity of multidisciplinary approaches in interpreting egg accumulations and offers a novel methodology for studying these accumulations in structureless *** findings provide new insights into the breeding behaviour and nesting preferences of these extinct organisms,contributing to our understanding of dinosaur ecology.

关键词： Breeding behaviour theropod taphonomy Stable isotopes Magnetic susceptibility Jurassic

timoshenko beam model for chiral materials

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Acta Mechanica Sinica 2018年第3期34卷 549-560页

作者： t.Y.Ma Y.n.Wang l.Yuan J.S.Wang Q.H.Qin Department of Mechanics Tianjin University School of Engineering Deakin University Research School of Engineering Australian National University

natural and artificial chiral materials such as deoxyribonucleic acid （DnA）, chromatin fibers, flagellar filaments, chiral nanotubes, and chiral lattice materials widely exist. Due to the chirality of intricately helical or twisted microstructures, such materials hold great promise for use in diverse applications in smart sensors and actuators, force probes in biomedical engineering, structural elements for absorption of microwaves and elastic waves, etc. In this paper, a timoshenko beam model for chiral materials is developed based on noncentrosymmetric micropolar elasticity theory. the governing equations and boundary conditions for a chiral beam problem are derived using the variational method and Hamilton＇s principle. the static bending and free vibration problem of a chiral beam are investigated using the proposed model. It is found that chirality can significantly affect the mechanical behavior of beams, making materials more flexible compared with nonchiral counterparts, inducing coupled twisting deformation, relatively larger deflection, and lower natural frequency. this study is helpful not only for understanding the mechanical behavior of chiral materials such as DnA and chromatin fibers and characterizing their mechanical properties, but also for the design of hierarchically structured chiral materials.

关键词： timoshenko beam model Chiral material Chirality Deflection Microrotation

A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of Gan_xAs_yP_(1-x-y)/GaP quantum wells on GaP substrates

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Chinese Physics B 2014年第7期23卷 640-644页

作者： O l nsal B Gnül M temiz Department of Engineering Physics University of Gaziantep

the GaP-based dilute nitride direct band gap material Ga（nAsP） is gaining importance due to the monolithic integra- tion of laser diodes on Si microprocessors. the major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga（nAsP）/GaP QW lasers. therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GanxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen （n） concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GanxAsyP1-x-y/GaP QWs with that of the GanxAsyP1-x-y/Al2Ga1-2P QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of n into the well and AI into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.

关键词： quantum well band alignment carrier confinement dilute nitride phosphide alloy

On the derivation of the entropy of ideal quantum gases confined in a three-dimensional harmonic potential

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Communications in theoretical Physics 2020年第4期72卷 106-111页

作者： le tri Dat Vinh n t Pham laboratory of Applied Physics Advanced Institute of Materials ScienceTon Duc Thang UniversityHo Chi Minh City 756636Vietnam Faculty of Applied Sciences Ton Duc Thang UniversityHo Chi Minh City 756636Vietnam Ho Chi Minh City University of Education Ho Chi Minh City 748342Vietnam

In this work,the entropy functions of ideal quantum gases in a three-dimensional harmonic trap are analytically calculated using temperature as an explicit ***,the applicability of the analytical formulas is validated by comparison with the numerical *** results illustrate that the obtained functions could be applied for the whole temperature regime with a maximum relative deviation of less than 7.5%in the vicinity of the critical temperature tcin the case of Bose ***,for Fermi gases,although the analytical formula fits well at very low-and high-temperature regimes,it cannot be applied at temperature in the range[0.3-0.5]t_F,where t_F is the Fermi *** addition,the consistency between our formulas and classical ones at significantly high temperatures is also discussed.

关键词： thermodynamic properties entropy 3D harmonic trap ideal quantum gases

large-Scale Estimation of Distribution Algorithms with Adaptive Heavy tailed Random Pro jection Ensembles

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Journal of Computer Science & technology 2019年第6期34卷 1241-1257页

作者： Momodou l.Sanyang Ata Kabán School of Computer Science University of BirminghamEdgbastonBirmingham B152TTU.K. School of Information technology and Communication University of The GambiaSerekundaThe Gambia

We present new variants of Estimation of Distribution Algorithms (EDA) for large-scale continuous optimisation that extend and enhance a recently proposed random projection (RP) ensemble based approach. the main novelty here is to depart from the theory of RPs that require (sub-)Gaussian random matrices for norm-preservation, and instead for the purposes of high-dimensional search we propose to employ random matrices with independent and identically distributed entries drawn from a t-distribution. We analytically show that the implicitly resulting high-dimensional covariance of the search distribution is enlarged as a result. Moreover, the extent of this enlargement is controlled by a single parameter, the degree of freedom. For this reason, in the context of optimisation, such heavy tailed random matrices turn out to be preferable over the previously employed (sub-)Gaussians. Based on this observation, we then propose novel covariance adaptation schemes that are able to adapt the degree of freedom parameter during the search, and give rise to a flexible approach to balance exploration versus exploitation. We perform a thorough experimental study on high-dimensional benchmark functions, and provide statistical analyses that demonstrate the state-of-the-art performance of our approach when compared with existing alternatives in problems with 1000 search variables.

关键词： covariance adaptation estimation of distribution algorithm random projection ensemble t-distribution