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Molecular dy.amics simulations of helium transport through inorganic mineral nanopores

Science china Earth Sciences 2025年第1期68卷 237-252页

作者： Dandan SONG Ping GUAN chi ZHANG Jiahao REN School of Earth and Space Sciences Peking University

Helium transport through nanoscale inorganic mineral pores and pore throats is essential for its overall migration. To elucidate helium's transport dy.amics within nanopores, we employ.d equilibrium and non-equilibrium molecular dy.amics simulations to investigate helium's static self-diffusion and pressure-driven flow in quartz slit-shaped nanopores. We also introduced water and various gases, including hy.rogen, methane, ethane, nitrogen, and carbon dioxide, into the nanopores to assess their influence on helium transport. Our findings indicate minimal helium adsorption on quartz pore surfaces. Under conditions where the pore size is less than 5 nm and the pressure under 10 MPa, environmental factors markedly.influence helium diffusion. Large pore sizes, high temperatures, and low gas pressures enhance helium desorption and facilitate faster diffusion. We observed a positive correlation between helium flow velocity.and factors such as pore size, pressure gradient, and surface smoothness of the pores. Notably. the presence of pore water and carrier gases in quartz nanopores, which diffuse more slowly.than helium, tends to reduce helium surface adsorption and slow its diffusion. Among the carrier gases studied, nitrogen showed similar adsorption capacity. diffusivity. and stability.to helium, while carbon dioxide display.d the highest adsorption capacity.and the slowest diffusion rate, markedly.differing from helium. Based on the simulation results, we concluded that water and carrier gases primarily.function as transport mediums in helium migration, moving together with helium. Nitrogen, which shares similar properties with helium, effectively.assists in this co-migration process. Conversely. carbon dioxide, due to its high adsorption capacity.and slow diffusion, tends to be lost during co-migration. As a result, gas reservoirs with high nitrogen levels and low carbon dioxide levels are more likely.to have higher helium concentrations. Additionally. the smaller por

关键词： Helium transport Slit nanopores Molecular dy.amics simulations Diffusion Flow carriers

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Large-scale Circulation Control of the Occurrence of Low-level Turbulence at Hong Kong International Airport

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Advances in Atmospheric Sciences 2018年第4期35卷 435-444页

作者： Marco y. T. LEUNG Wen ZHOU chi-Ming SHUN Pak-Wai CHAN Guy.Carpenter Asia-Pacific Climate Impact Center School of Energy and Environment City University of Hong Kong Hong Kong China Hong Kong Observatory Hong Kong China

This study.identifies the atmospheric circulation features that are favorable for the occurrence of low-level turbulence at Hong Kong International Airport [below 1600 feet （around 500 m）]. By.using LIDAR data at the airport, turbulence and nonturbulence cases are selected. It is found that the occurrence of turbulence is significantly.related to the strength of the southerly.wind at 850 hPa over the South china coast. On the other hand, the east-west wihd at this height demonstrates a weak relation to the occurrence. This suggests that turbulence is generated by.flow passing Lantau Island from the south. The southerly.wind also transports moisture from the South china Sea to Hong Kong, reducing local stability. This is favorable for the development of strong turbulence. It is also noted that the strong southerly.wind during the occurrence of low-level turbulence is contributed by.an anomalous zonal gradient of geopotential in the lower troposphere over the South china Sea. This gradient is caused by.the combination of variations at different timescales. These are the passage of sy.optic extratropical cy.lones and anticy.lones and the intraseasonal variation in the western North Pacific subtropical high. The seasonal variation in geopotential east of the Tibetan Plateau leads to a seasonal change in meridional wind, by.which the frequency.of low-level turbulence is maximized in spring and minimized in autumn.

关键词： LIDAR temperate cy.lone and anticy.lone western North Pacific subtropical high seasonal cy.le topography.effect

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Radar ambiguity.function in L_p frame

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Science china Mathematics 2000年第8期43卷 785-791页

作者： M.y.chi 齐民友 Institute of Mathematics Wuhan University Wuhan 430072 China

In modern radar techniques, pulse signal can be replaced by.the chirps, which is taken to be signals in Lp space. Wigner’s function and ambiguity.functions are constructed in an Lp frame and a partial generalization ... 详细信息

关键词： radar signals chirps principle of uncertainty coherent dual Wigner’s function ambiguity function.

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GO-modified flexible poly.er nanocomposites fabricated via 3D stereolithography

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Frontiers of Chemical Science and Engineering 2019年第4期13卷 736-743页

作者： chi Him Alpha Tsang Adilet Zhakey.v Dennis y.C.Leung Jin Xuan School of Environmental Sciences and Engineering Sun Yat-Sen UniversityGuangzhou 510006China Department of Mechanical Engineering The University of Hong KongHong KongChina Department of Chemical Engineering Loughborough UniversityLoughboroughLE113TUUK

Graphene oxide(GO)induced enhancement of elastomer properties showed a great deal of potential in recent y.ars,but it is still limited by.the barrier of the complicated sy.thesis ***(SLA),used in fabrication of thermosets and very.recently.in“flexible”poly.ers with elastomeric properties,presents itself as simple and user-friendly.method for integration of GO into *** this work,it was first time demonstrated that GO loadings can be incorporated into commercial flexible photopoly.er resins to successfully.fabricate GO/elastomer nanocomposites via readily.accessible,consumer-oriented SLA *** material properties of the resulting poly.er was characterized and *** mechanical strength,stiffness,and the elongation of the resulting poly.er decreased with the addition of *** thermal properties were also adversely.affected upon the increase in the GO content based on differential scanning calorimetry.and thermogravimetric analy.is *** was proposed that the GO agglomerates within the 3D printed composites,can result in significant change in both mechanical and thermal properties of the resulting *** study.demonstrated the possibility.for the development of the GO/elastomer nanocomposites after the optimization of the GO/“Hexible”photoreactive resin formulation for SLA with suitable annealing process of the composite in future.

关键词： graphene oxide poly.er flexible 3D printing stereolithography

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Romance of the three domains:how cladistics transformed the classifi cation of cellular organisms

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Protein & Cell 2013年第9期4卷 664-676页

作者： chi-Chun Ho Susanna K.P.Lau Patrick C.y.Woo Department of Microbiology The University of Hong KongHong KongChina State Key.Laboratory.of Emerging Infectious Diseases The University of Hong KongHong KongChina Research Centre of Infection and Immunology The University of Hong KongHong KongChina Carol y. Centre of Infection The University of Hong KongHong KongChina

Cladistics is a biological philosophy.that uses genealogi-cal relationship among species and an inferred sequence of divergence as the basis of classifi *** review critically.survey. the chronological development of bio-logical classification from Aristotle through our post-genomic era with a central focus on *** 1957,Julian Huxley.coined cladogenesis to denote splitting from *** 1960,the English translation of Willi Hennig’s 1950 work,Sy.tematic Phy.ogenetics,was published,which received strong opposition from phenet-icists,such as numerical taxonomists Peter Sneath and Robert Sokal,and evolutionary.taxonomist,Ernst May.,and sparked acrimonious debates in *** 1977-1990,Carl Woese pioneered in using small subunit rRNA gene sequences to delimitate the three domains of cellu-lar life and established major prokary.tic *** has since dominated *** being compatible with modern microbiological observations,*** with unusual phenoty.es,restricted expression of charac-teristics and occasionally.being uncultivable,increasing recognition of pervasiveness and abundance of horizon-tal gene transfer has challenged relevance and validity.of *** mosaic nature of eukary.tic and prokary.otic genomes was also gradually.*** the mid-2000s,high-throughput and whole-genome sequencing became routine and complex geneologies of organisms have led to the proposal of a reticulated web of *** genomics only.indirectly.leads to understanding of func-tional adaptations to ecological niches,computational modeling of entire organisms is underway.and the gap between genomics and phenetics may.soon be *** are not expected to settle as taxonomic classifi cations shall remain subjective to serve the human scientist,not the classifi ed.

关键词： cladistics phenetics phy.ogeny classifi ca-tion evolution

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A Lower Carboniferous Blastoid from the Tushan District,Kueichou

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地质学报 1943年第Z2期 111-113+115页

作者： y. S. chi Geological Survey.of china

During our geological reconnaissance of the south-eastern part of Kueichou in January.1941, Mr. S. C. Huo’ and I collected two specimens of a Blastoid.

关键词： A Lower Carboniferous Blastoid from the Tushan District,Kueichou view

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Role of extrusion rate on the microstructure and tensile properties evolution of ultrahigh-strength low-alloy.Mg-1.0Al-1.0Ca-0.4Mn(wt.%)alloy

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Journal of Magnesium and Alloy. 2023年第2期11卷 553-561页

作者： X.Q.Liu X.G.Qiao R.S.Pei y.Q.chi L.y.an M.y.Zheng School of Material Science and Engineering Harbin Institute of TechnologyHarbin 150001China Institut fur Metallkunde und Meterialphy.ik RWTH Aachen UniversityAachen D-52056Germany

Mg-1.0Al-1.0Ca-0.4Mn(AXM1104, wt.%) low alloy.was extruded at 200 ℃ with an extrusion ratio of 25 and different ram speeds from 1.0 to 7.0 mm/s. The influence of extrusion rate on microstructure and mechanical properties of the AXM1104 alloy.was sy.tematically.studied. With the increasing of extrusion rate, the mean dy.amically.recry.tallized(DRXed) grain size of the low alloy.and average particles diameter of precipitate second phases were increased, while the degree of grain boundary.segregation and the intensity.of the basal fiber texture were decreased. With the rising of extrusion rate from 1.0 to 7.0 mm/s, the tensile y.eld strength(Ty.) of the as-extruded AXM1104 alloy.was decreased from 445 MPa to 249 MPa, while the elongation to failure(EL) was increased from 5.0% to 17.6%. The Ty., ultimate tensile strength(UTS) and EL of the AXM1104 alloy.extruded at the ram speed of 1.5 mm/s was 412 MPa, 419 MPa and 12.0%, respectively.exhibiting comprehensive tensile mechanical properties with ultra-high strength and excellent plasticity. The ultra-high Ty. of 412 MPa was mainly.due to the strengthening from ultra-fine DRXed grains with segregation of solute atoms at grain boundaries. The strain hardening rate is increase slightly.with increasing extrusion speed, which may.be ascribed to the increasing mean DRXed grain size with rising extrusion speed. The higher strain hardening rate contributes to the higher EL of these AXM1104 samples extruded at higher ram speed.

关键词： Mg-Al-Ca-Mn alloy Ultrafine grain Extrusion rate Grain boundary.segregation Microstructure Ultrahigh strength

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china’s Corporate Governance and Reforms

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china & World Economy 2005年第5期13卷 28-42页

作者： chi-ho Chung Hung-gay.Fung Felix y. Kwan School of Business Hong Kong University of Science ＆ Technology y.S. Tsiang professor College of Business Administration and Center of International Studies University of Missouri-St.Louis senior director Qatar Financial Center Regulatory Authority Doha Qatar and adjunct associate professor Hong Kong University of Science ＆ Technology

We have reviewed and identified the key.problems of china＇s corporate governance. Several suggestions are provided to improve its governance mechanism. A review of corporate governance models among different countries suggests that the state ownership of the chinese companies should be reduced and shares that are split into tradable and nontradable shares should be abolished. The three-tier board structure and duty.of directors should be restructured to improve transparency.and disclosure requirements.

关键词： china's corporate governance corporate reforms

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Large scale current sy.tems developed from substorm onset:Global MHD results

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Science china(Technological Sciences) 2018年第3期61卷 389-396页

作者： TANG BinBin WANG chi State Key.Laboratory.of Space Weather National Space Science Center Chinese Academy of Sciences

We investigate the large-scale substorm current sy.tems developed from its onset in an idealized substorm event simulated by.global magnetohy.rody.amic(MHD) models. Mainly.three current sy.tems(loops) are revealed:(1) the classical substorm current wedge, which is composed by.the disputed cross-tail current in the magnetotail, the nightside westward electrojet in the high-latitude ionosphere and a pair of region 1 field-aligned currents(FAC);(2) the partial-ring current sy.tem, which is braced by.two region 2 FACs; and(3) the meridional current sy.tem, which is formed by.an equatorial radial current(outward/inward in the morning/evening sector), and region 1 and region 2 FACs at its two ends. The region 2 FAC connects with region 1 FAC by.a latitudinal horizontal current at each morning/evening ionosphere to complete Loops 2 and 3. A quantitative study.shows the significant enhancement of these current sy.tems during the substorm expansion phase, while Loop 1 dominates, which can reach a magnitude of ~1 MA. Empirical relations among the ionospheric currents and the related magnetotail currents are established based on the simulation results, imply.ng that the substonn current sy.tems are not evolved locally.or separately. but must be viewed from a global perspective. This knowledge of large-scale substorm current sy.tem would deepen our understanding of the substorm development and could be validated by.observations in the future.

关键词： magnetospheric phy.ics substorm current sy.tem magnetohy.rody.amic(MHD) simulation

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Quick Assessment of Potential Hy.rate Promoters for Rapid Formation

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Geomaterials 2012年第4期2卷 63-69页

作者： chi y. Lo P. Somasundaran Jae W. Lee Chemical Engineering City College of New York New York USA Earth and Environmental Engineering Columbia University New York USA

Hy.rate technology.has advanced to greater proportions: implementing the high latent heats as refrigerant, safe carbon capture as carbon sequestration in hy.rates, purify.ng rare gases in hy.rates, and safe efficient transport of energy.using rapid hy.rate formation. These account for only.a small amount of the fundamental understanding of gas hy.rates and the use of such a novel technology. A quick and broad analy.is of novel hy.rate promoters is needed to assess the potential of other promoter agents. This will improve the understanding of rapid hy.rate formation and fundamental ideas related to the kinetics and formation of hy.rates. There are still hundreds of other surfactants that have not been identified for rapid formation. The insurmountable endeavor deters many.from try.ng as it can be like finding a needle in a hay.stack. This almost futile endeavor of correctly.identify.ng a surfactant as a promoter agent without doing a formation test can be accomplished with recent techniques. Using Raman and a liquid hy.rocarbon (Cy.lo-pentane), surfactants may.shift the sample’s peak towards the hy.rate peak (890 cm–1), thereby.identify.ng it as a choice surfactant for rapid formation of hy.rates. With a broad survey.of surfactants, understanding fundamental science and engineering kinetics for hy.rates will be easily.achieved. Finding more effective and novel surfactants for hy.rate formations will broaden the field of hy.rates and self-assembling cry.tallization. As hy.rate technology.broadens, interdisciplinary.fields can contribute expertise from surface science to spectroscopy.leading to geological formations and engineering kinetics.

关键词： Gas Hy.rate Promoter Technology Clathrate

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