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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

Effect of Equal Channel Angular Extrusion on the Microstructures and Properties of Two Extruded Al-Mg-Si Alloys

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Journal of Materials Science & Technology 2005年第5期21卷 623-629页

作者： G.w.Lorimer School of Materials The University of ManchesterGrosvenor StreetMl 7HS ManchesterUK

The effect of equal channel angular extrusion （ECAE） on the microstructure of two Al-Mg-Si extrusion alloys was investigated by high resolution electron backscattered diffraction （EBSD） using a field emission gun scanning electron microscope （FEG-SEM） and a transmission electron microscope （TEM）. Two contrasting alloys： a dilute alloy, based on alloy 6061 and a concentrated alloy, based on alloy 6069 were employed for this research. It has been found that prior ECAE to extrusion promotes high angle grain boundaries （HAGBs） in the extrusions, and the increase in HAGBs ratio is due to the large shear deformation involved in the process of ECAE. Tensile testing results show that a further ageing treatment strengthens the alloys after extrusion and the ECAE processed extrusions are more ductile than conventional extrusions.

关键词： Equal channel angular extrusion Electron backscattered diffraction Al-Mg-Si alloys

An Algorithm for Constructing 3D Struts

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Journal of Computer Science & Technology 2009年第1期24卷 56-64页

作者： George w.Hart Department of Computer Science Stony Brook UniversityStony BrookNY 11794U.S.A.

A simple robust ＂strut algorithm＂ is presented which, when given a graph embedded in 3D space, thickens its edges into solid struts. Various applications, crystallographic and sculptural, are shown in which smooth high-genus forms are the output. A toolbox of algorithmic techniques allow for a variety of novel, visually engaging forms that express a mathematical aesthetic. In sculptural examples, hyperbolic tessellations in the Poincare plane are transformed in several ways to three-dimensional networks of edges embodied within a plausibly organic organization. By the use of different transformations and adjustable parameters in the algorithms, a variety of attractive forms result. The techniques produce watertight boundary representations that can be built with solid freeform fabrication equipment. The final physical output satisfies the ＂coolness criterion,＂ that passers by will pick them up and say ＂wow, that＇s cool!＂

关键词： sculpture solid modeling echinoderm algorithms fine arts computer-aided design

Toward understanding Cretaceous climate An updated review

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Science China Earth Sciences 2017年第1期60卷 5-19页

作者： william w. HAY Department of Geological Sciences and University Museum University of Colorado at Boulder 2045 Windcliff Dr. Estes Park CO 80517 USA

New data and ideas are changing our view of conditions during the *** of the continents was lower than originally thought,eliminating the'cold continental interior paradox'of fossils of plants that could not tolerate freezing occurring in regions indicated by climate models to be well below freezing in *** controversy over the height of Cretaceous sea levels has been resolved by knowledge of the effects of passage of the subducted slab of the Farallon Plate beneath the North American *** cause of shorter term sea level changes of the order of 30 to 50 meters is not because of growth and decay of ice sheets,but more likely the filling and release of water from groundwater reservoirs and lakes although there may have been some ice in the Early and latest *** dioxide was not the only significant greenhouse gas;methane contributed significantly to the warmer *** of very warm tropical ocean temperatures(>40℃)have implications for the nature of plant life on land limited by Rubisco *** land surfaces were much wetter than has been thought,with meandering rivers and many oxbow lakes providing habitat for large dinosaurs.A major rethinking of the nature of conditions on a warmer Earth is underway,and a new suite of paleoclimate simulations for the Cretaceous is needed.

关键词： Cretaceous Paleogeography Paleotopography Sea level Greenhouse Paleohydrology Paleoclimate

A PERSONAL MEMOIR OF wEIMIN ZHENG-“A MAN FOR ALL SEASONS”

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Journal of Systems Science and Systems Engineering 2013年第4期22卷 499-504页

作者： Keith w.HIPEL Department of Systems Design Engineering University of Waterloo

In 1951 Professor weimin Zheng returned to the People＇s Republic of China from the United Kingdom to assist in building his country into a modern nation. Rather than pursue a doctoral degree at the California Institute of Technology, or Caltech as it is popularly called, Professor Zheng, unselfishly and patriotically, decided that he would devote his many talents to providing a first-class education to Chinese students within a strong university system. In particular,

关键词： A MAN FOR ALL SEASONS A PERSONAL MEMOIR OF wEIMIN ZHENG

Morphology,distribution,and chromosome counts of two varieties of Hedychium villosum(Zingiberaceae)

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Journal of Systematics and Evolution 2010年第5期48卷 344-349页

作者： w.John KRESS Department of Botany National Museum of Natural HistorySmithsonian Institution Key Laboratory of Tropical Forest Ecology Xishuangbanna Tropical Botanical GardenChinese Academy of Sciences

Polyploidy is a major mechanism of adaptation and speciation in *** varieties of Hedychium villosum,*** and ***,primarily differ in plant and flower *** number suggests that *** is diploid(2n=34)and *** is tetraploid(2n=68).Although the flowers of the two varieties do not have any difference in floral shape,each can be easily distinguished morphologically because the shoots,leaves,and flowers of the tetraploid *** are consistently larger than the diploid *** two varieties each possess distinct geographic ranges and habitats,and no sympatric distribution has been *** tetraploid *** has a broader geographic distribution range and more diverse ecological habitats than the diploid *** two varieties are also completely reproductively isolated due to the non-overlap of their flowering *** two varieties should be recognized as two distinct species as they fulfill the requirements of various species ***,we suggested that the tetraploid *** should be kept as Hedychium villosum and the diploid *** should be renewed to Hedychium tenuiflorum.

关键词： distribution Hedychium villosum morphology polyploidy Zingiberaceae.