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Effects of site productivity on individual tree maximum basal area growth rates of Eucalyptus pilularis in subtropical Australia

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Journal of Forestry Research 2023年第6期34卷 1659-1668页

作者： P.w.west Forest Research Centre Southern Cross UniversityLismoreNSW 2480Australia

Inventory data were available from 96 plots of even-aged,monoculture,tall-open forests of Eucalyptus pilularis Smith,aged 2-63 years,growing in sub-tropical regions along the east coast of Australia.A model was developed relating the maximum possible stem basal area growth rate of individual trees to their stem basal *** any tree size,this maximum increased as site productivity ***,the size at which this maximum occurred decreased as productivity *** research has shown that,at any stand age,trees of a particular stem basal area are taller on more productive sites than on less productive *** trees incur greater respiratory costs to ensure maintenance of the photo synthetic capacity of their canopies;this reduces their growth *** was concluded that trees with larger basal areas will have the maximum possible growth rate on a less productive site,whilst trees with smaller basal areas will have the maximum possible on a more productive *** model developed may constitute the first stage of a complete individual tree growth model system to predict wood yields from these forests.

关键词： Growth model Individual tree Maximum growth rate Eucalyptus pilularis Physiological eff ects

Applications of Chapman-Richards model to geotechnical engineering

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第6期11卷 1286-1292页

作者： w.Nie w.Guo School of Civil Engineering Nanyang Technical UniversitySingapore Key Laboratory of Coast Civil Structure and Safety of Ministry of Education Tianjin UniversityTianjinChina School of Civil Engineering Tianjin UniversityTianjinChina

In this paper,the Chapman-Richards model is adapted to best fit three types of nonlinear curves that are generally encountered in geotechnical engineering practices,*** degree of consolidation versus time factor curves in one-dimensional consolidation and plane strain consolidation under strip loading,the compressibility and permeability curves of soft clay,and the geometry parameters of geosynthetic tube versus pumping pressure *** methods of determining unknown parameters using the Chapman-Richards model are fully *** is found that the Chapman-Richards model has its range of applications in geotechnical engineering and may provide unique insights into the complexity of geotechnical problems.

关键词： Mathematical modeling Chapman-Richards model Curve-fitting

Adventures Beyond Amdahl's Law:How Power-Performance Measurement and Modeling at Scale Drive Server and Supercomputer Design

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Journal of Computer Science & Technology 2023年第1期38卷 80-86页

作者： Kirk w.Cameron Computer Science Virginia TechWashington D.C.VA 24061U.S.A.

Amdahl’s Law painted a bleak picture for large-scale *** implication was that parallelism was limited and therefore so was potential *** Amdahl’s contribution was seminal and important,it drove others vested in parallel processing to define more clearly why large-scale systems are critical to our future and how they fundamentally provide opportunities for speedup beyond Amdahl’s *** the early 2000s,much like Amdahl,we predicted dire consequences for large-scale systems due to power *** our early work was often dismissed,the implications were clear to some:power would ultimately limit *** this retrospective,we discuss how power-performance measurement and modeling at scale led to contributions that have driven server and supercomputer design for more than a *** the influence of these techniques is now indisputable,we discuss their connections,limits and additional research directions necessary to continue the performance gains our industry is accustomed to.

关键词： Amdahl’s Law speedup power-aware computing power modeling performance modeling performance prediction power measurement

Limits on light emission from silicon

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Chinese Optics Letters 2009年第4期7卷 268-270页

作者： Peter würfel Institut für Angewandte Physik Universitt KarlsruheD-76128 KarlsruheGermany

Although silicon is an indirect semiconductor, light emission from silicon is governed by the same gener- alized Planck＇s radiation law as the emission from direct semiconductors. The emission intensity is given by the absorptance of the volume in which there is a difference of the quasi Fermi energies. A difference of the Fermi energies may result h＇om the absorption of external light （photoluminescence） or from the injection of electrons and holes via selective contacts （electroluminescence）. The quantum efficiency may be larger than 0.5 for carrier densities below 10^15 cm^-3. At larger densities, non-radiative recombination, in particular Auger recombination dominates. At all carrier densities, the relation between emission intensity and difference of the quasi Fermi energies is maintained. Since this difference is equal to the voltage of a properly designed solar cell, luminescence is the key indicator of material quality for solar cells.

关键词： Carrier concentration Fermi level Light Light emission Photoluminescence Semiconducting silicon Silicon

PREDICTION OF CHARACTERISTICS FOR VERTICAL ROUND NEGATIVE BUOYANT JETS IN HOMOGENEOUS AMBIENT

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Journal of Hydrodynamics 2001年第1期13卷 103-110页

作者： Huai, w.X. Li, w. Dep. of River Eng. Coll. of Water Resource Eng. Wuhan 430072 China

The k-Ε turbulence model is used to establish a mathematical model of a vertical round jet with negative buoyancy in a static homogeneous ambient. The hybrid finite analytic method, with a non-uniform staggered grid, is used to calculate the whole flow field. The variations of centerline velocity, density and turbulent kinetic energy along the axial line for a given exit densimetric Froude number are found to converge to single curves under the unified scaling law derived by Chen and Rodi. The profiles of mean velocities, mean density difference and the half-width of negative buoyant jets for velocity and density are given. The calculation confirmed that the maximum height of rise is proportional to M03/4 B0-1/2, where M0 and B0 are the momentum flux and the buoyancy flux at the source, respectively.

关键词： Computer simulation Jets Mathematical models Numerical methods

Superexchange and charge transfer in the nickelate superconductor La_(3)Ni_(2)O_(7) under pressure

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Science China(Physics,Mechanics & Astronomy) 2024年第11期67卷 1-8页

作者： wéi wú Zhihui Luo Dao-Xin Yao Meng wang Center for Neutron Science and Technology Guangdong Provincial Key Laboratory of Magnetoelectric Physics and DevicesSchool of PhysicsSun Yat-sen UniversityGuangzhou 510275China

Recently, a bulk nickelate superconductor La_(3)Ni_(2)O_(7) is discovered at pressures with a remarkable high transition temperature T_(c)~ 80 K. Here, we study a Hubbard model with tight-binding parameters derived from ab initio calculations of La_(3)Ni_(2)O_(7),by employing large scale determinant quantum Monte Carlo and cellular dynamical mean-field theory. Our result suggests that the superexchange couplings in this system are comparable to that of cuprates. The system is a charge transfer insulator as the hole concentration becomes four per site at large Hubbard U. Upon hole doping, two low-energy spin-singlet bands emerge in the system exhibiting distinct correlation properties: while the one composed of the out-of-plane Ni-d_(3z^(2)-r^(2)) and O-p_(z) orbitals demonstrates strong antiferromagnetic correlations and narrow effective bandwidth, the in-plane singlet band consisting of the Ni-d_(x^(2)-y^(2)) and O-p_(x)/p_(y) orbitals is in general more itinerant. Over a broad range of hole doping, the doped holes occupy primarily the d_(x^(2)-y^(2)) and p_(x)/p_(y) orbitals, whereas the d_(3z^(2)-r^(2)) and p_(z) orbitals retain underdoped. we propose an effective t-J model to capture the relevant physics and discuss the implications of our result for comprehending the La_(3)Ni_(2)O_(7) superconductivity.

关键词： superconductivity nickelate superconductors Hubbard model superexchange charge transfer insulator quantum Monte Carlo

Effect of suction change on water content and total volume of an expansive clay

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第5期8卷 699-706页

作者： ZHAN Liang-tong CHEN Ping NG C.w.w. ~ Department of Civil Engineering Zhejiang University Hangzhou 310027 China Department of Civil Engineering Zhejiang Sci- Tech University Hangzhou 310018 China Department of Civil Engineering Hong Kong University of Science and Technology Hong Kong China

A laboratory study was carried out on both natural and compacted specimens to investigate the complex soil-water interaction in an unsaturated expansive clay. The laboratory study includes the measurement of soil-water characteristic curves, 1D free swelling tests, measurement of swelling pressure and shrinkage tests. The test results revealed that the air-entry value of the natural specimen was quite low due to cracks and fissures present. The hydraulic hysteresis of the natural specimen was relatively insignificant as compared with the compacted specimen. within a suction range 0 to 500 kPa, a bilinear relationship between free swelling strain (or swelling pressure) and initial soil suction was observed for both the natural and compacted specimens. As a result of over-consolidation and secondary structures such as cementation and cracks, the natural specimens exhibited significant lower swelling (or swelling pressure) than the compacted specimen. The change of matric suction exerts a more significant effect on the water phase than on the soil skeleton for this expansive clay.

关键词： Expansive soil water content Suction Swelling Shrinkage

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Texas Helimak

Plasma Science and Technology 2008年第3期10卷 284-289页

作者： Kenneth w.GENTLE Fusion Research Center University of Texas at Austin Texas USA

Helimak is an experimental approximation to the ideal cylindrical slab, a onedimensional magnetized plasma with magnetic curvature and shear. The Texas Helimak realizes this approximation to a large degree; the finite size of the device can be neglected for many phenomena. Specifically, the drift-wave turbulence characteristic of a slab is observed with scale lengths small compared with the device size. The device and the general features of its behavior are described here. The device is capable of studying drift-wave turbulence, scrape-off layer （SOL） turbulence, and the stabilization of turbulence by imposing velocity shear.

关键词： plasma turbulence drift waves particle transport turbulence suppression

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混沌个人计算机的一个程序集

国外科技新书评介 2008年第12期 3-4页

作者： Hans Jtirgen korsch （）吕金虎不详中国科学院数学与系统科学研究院副研究员

著名物理学家***曾指出：”混沌的发现是20世纪物理学的第三次革命。”近半个世纪以来，人们对混沌运动的自然规律及其在自然科学和社会科学中的表现有了广泛而深刻的认识，而如何应用混沌研究的成果为人类服务已经成为21世纪非线性科... 详细信息

著名物理学家***曾指出：”混沌的发现是20世纪物理学的第三次革命。”近半个世纪以来，人们对混沌运动的自然规律及其在自然科学和社会科学中的表现有了广泛而深刻的认识，而如何应用混沌研究的成果为人类服务已经成为21世纪非线性科学发展所面临的巨大挑战。一方面，混沌的应用将会直接促进人们对混沌本质的深刻认识；另一方面，混沌应用中提出的许多新问题也将进一步促进混沌研究的深入和发展。本书是第一次出版13年后第三次修订本。

关键词：混沌运动个人计算机程序集混沌应用物理学家社会科学自然科学自然规律