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Godunov-type solutions for gas-liquid two-phase transient flows with gas release effects

Journal of Hydrodynamics 2023年第6期35卷 1179-1190页

作者： Yan-qing Lu Ling Zhou Tong-Chuan Che Zi-jian Xue Yun-jie Li yin-ying hu College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing210098China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina

The gas-liquid two-phase homogenous flow has been extensively investigated without the effect of gas ***,the dissolved gas will release when internal water pressure drops below saturation pressure during hydraulic *** results in inaccuracy or even invalidity of the existing model for homogenous flows,especially for the reproduction of two-phase mass transfer *** address this problem,this paper couples the gas release model with conservation equations of homogenous flows,which are numerically solved by the second-order Godunov-type scheme(GTS).Specifically,a virtual-cell method is adopted at system boundaries to achieve the same second-order accuracy as interior cells,which is realized by the monotonic upwind scheme for conservation laws(MUSCL-Hancock scheme).Simulated pressure curves by the proposed model are compared with a series of analytical,numerical and experimental *** indicates that the proposed model with gas release effects reproduces actual pressure responses most accurately,with minimum relative error and root mean squared error compared with experimental ***,the gas release leads to dynamic synchronous fluctuations of void fraction,wave speed and pressure head,including the opposite trends of void fraction and pressure,and higher void fraction leading to greater wave speed ***,sensitivity analysis is concluded with recommended Courant number,and different gas release effects in different initial void *** research increases the basic understanding of two-phase mass transfer processes and their implications for hydraulic transients.

关键词： Two-phase homogeneous flow transient flow gas release second-order Godunov-type scheme

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Changes in extreme high temperature warning indicators over China under different global warming levels

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Science China Earth Sciences 2024年第6期67卷 1895-1909页

作者： Yuxia ZHANG ying SUN Ting hu Chinese Academy of Meteorological Sciences Beijing 100081China National Climate Center Laboratory for Climate StudiesChina Meteorological AdministrationBeijing 100081China

High temperature warning indicators play a pivotal role in meteorological departments,serving as crucial criteria for issuing warnings that guide both social production and daily *** their importance,limited studies have explored the relationship between different global warming levels and changes in high temperature warning *** this study,we analyze data from 2,419 meteorological stations over China and utilize the Coupled Model Intercomparison Project Phase 6(CMIP6)models to examine historical changes in high temperature warning indicators used by the China Meteorological *** evaluate model performance and estimate future changes in these indicators using an annual cycle bias correction *** results indicate that since 1961,the number of high temperature days(TX35d and TX40d)and length of season(TX40d and TX40l)with daily maximum temperature reaching or exceeding 35℃ and 40℃ have increased over *** intensity of high temperatures(TXx)has strengthened and the geographical extent affected by high temperatures has *** 2022,the occurrence of 40℃ high temperatures surges,with Eastern China experiencing a two-day increase in TX40d and an extended seasonal length in TX40l by over five *** CMIP6 models have underestimated the high temperature indictors associated with 35℃ during historical periods,notable difference is not observed between the models and observations for TX40d and TX40l,given their rare ***,future projections,after bias correction,indicate that the increasing trends for 35℃ and 40℃ high temperature days and length of season become more pronounced than the raw projection,suggesting a more severe increase than that anticipated *** global warming intensifies,the high temperature days and length of season are projected to increase non-linearly,while the intensity of high temperatures is expected to increase *** every 1℃ increase in global temperature,the intensity is

关键词： Extreme high temperatures Meteorological warning CMIP6 Global warming levels Future projection

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Semi-Varying Coefficient Panel Data Model with Technical Indicators Predicts Stock Returns in Financial Market

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Journal of Systems Science & Complexity 2024年第4期37卷 1638-1652页

作者： hu Xuemei PAN ying LI Xiang School of Mathematics and Statistics Chongqing Technology and Business UniversityChongqing 400067China Chongqing Key Laboratory of Social Economy and Applied Statistics Chongqing 400067China Research Center for Economy of Upper Reaches of the Yangtse River Chongqing Technology and Business UniversityChongqing 400067China

Accurately predicting stock returns is a conundrum in financial *** this conundrum can bring huge economic benefits for investors and also attract the attention of all circles of *** this paper the authors combine semi-varying coefficient model with technical analysis and statistical learning,and propose semi-varying coefficient panel data model with individual effects to explore the dynamic relations between the stock returns from five companies:CVX,DFS,EMN,LYB,and MET and five technical indicators:CCI,EMV,MOM,ln ATR,ln RSI as well as closing price(ln CP),combine semi-parametric fixed effects estimator,semi-parametric random effects estimator with the testing procedure to distinguish fixed effects(FE) from random effects(RE),and finally apply the estimated dynamic relations and the testing set to predict stock returns in December 2020 for the five *** proposed method can accommodate the varying relationship and the interactive relationship between the different technical indicators,and further enhance the prediction accuracy to stock returns.

关键词： Fixed effects random effects semi-varying coefficient panel data model stock returns technical indicators

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The important role of Turbidity Maximum Zone in sedimentary dynamic of estuarine mangrove swamp

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Frontiers of Earth Science 2024年第1期18卷 219-226页

作者： Tao LIU ying LIU Baoqing hu Key laboratory of Environment Change and Resources Use in Beibu Gulf(Ministry of Education) Nanning Normal UniversityNanning 530001China School of Civil Engineering and Architecture Guangxi UniversityNanning 530004China

Sedimentation is a key process affecting wetland sustainability and carbon burial *** context of sea level rise,climate change and human activities,further understanding about the sedimentary dynamic in wetland is critical in predicting the landscape evolution or the change in carbon burial *** this study,based on the field hydrological observation in a mangrove system in the Nanliu River estuary,we found the net flux of suspended sediment to mangrove is 39−72 kg/m in tidal cycles with Turbidity Maximum Zone(TMZ)forming in surface layer and only is 9−18 kg/m in tidal cycles without *** higher net flux of suspended sediment to mangrove in tidal cycles with TMZ forming in surface layer is attributed to high SSC in rising tide and intense flocculation in *** significant discrepancy in sedimentation rate in the mangrove patches also can be explained by the probability of TMZ forming in the surface layer of *** future,rapid sea level rising may lead to the change of TMZ pattern in estuary,which will result in non-negligible variation in sedimentation rate in *** to the present data of sedimentation rate in wetlands,the fragility of wetlands in river estuary may be miscalculated.

关键词： mangrove wetland sedimentation Turbidity Maximum Zone Nanliu River

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Transient features of graphitization and nitrogen-vacancy color centers in a diamond fabricated by localization femtosecond laser direct writing

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Science China(Technological Sciences) 2024年第8期67卷 2530-2536页

作者： CUI Lin yin SiYu hu ZiFan WANG Lei State Key Laboratory of Integrated Optoelectronics College of Electronic Science and EngineeringJilin UniversityChangchun 130012China

Femtosecond laser direct writing provides an efficient approach to fabricating single nitrogen vacancy(NV) color centers with a relatively high yield. Different from previously reported NV color centers with a random distribution in a bulk diamond or nanocrystals, this gives an opportunity to study the photophysical properties of single NV color centers with precise numbers and positions. However, ultrafast studies on single NV color centers prepared by localization femtosecond laser direct writing are still rare, especially for the graphitization inside a diamond and its relationship with single NV color centers. Here, we report the broadband transient absorption(TA) spectroscopic features of the graphitization and NV color centers in a diamond fabricated by localization femtosecond laser direct writing at room temperature under 400 nm excitation. In comparison with the graphene oxide film, the bleaching features of the graphitization point array in a diamond are similar to reduced graphene oxide,accompanied by excited state absorption signals from local carbon atom vacancy defects in graphene-like structures induced by laser writing. On the other hand, transient features of laser processing array containing single NV color centers with a yield of~50% are different from those of the graphitization point array. Our findings suggest that for ultrashort pulse processing of diamonds, broadband TA spectral signals are sensitive to the surrounding atomic environment of processing sites, which could be applied to laser writing point defects in other materials used as solid-state single photon sources.

关键词： nitrogen-vacancy color center graphitization diamond femtosecond laser direct writing ultrafast spectroscopy

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Laminar Flame Instability of n-Hexane,n-Octane,and n-Decane in Spherical Expanding Flames

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Journal of Thermal Science 2024年第3期33卷 1189-1199页

作者： yin Geyuan hu Erjiang LI Xiaotian LV Xin huANG Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China United Automotive Electronic Systems Co. LtdShanghai201206China Chongqing Changan Automobile Co. Ltd.Chongqing401120China

This paper focuses on the laminar flame instability of three high molecular weight n-alkanes,namely n-hexane,n-octane,and *** experiment was carried out in a constant volume combustion bomb to get the flame *** critical radius under different conditions was extracted using the image processing *** with the existing critical Peclet number theory,the dominant factors of flame instability under current conditions for three n-alkanes can be figured ***,the average cell size(equivalent cell radius,R_(cell))was extracted to provide quantitative analysis of the flame cellular structure,based on the method developed in this *** theoretical R_(cell)were also calculated and compared with the experimental results to validate the proposed method.

关键词： cellular instability equivalent cell radius critical Peclet number spherical flame

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A novel metal-free porous covalent organic polymer for efficient room-temperature photocatalytic CO2 reduction via dry-reforming of methane

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Green Energy & Environment 2024年第9期9卷 1407-1418页

作者： Sheng-Yan yin Ziyi Li yingcai hu Xiao Luo Jishan Li College of Chemistry and Chemical Engineering Hunan University Institute of Basic Medicine and Cancer (IBMC) Chinese Academy of Sciences

At room temperature,the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane（DRM） is quite promising and ***,we developed a novel covalent organic porous polymer （TPE-COP） with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature,which can efficiently generate syngas （CO and H2）.Both electron donor (tris（4-aminophenyl）amine,TAPA) and acceptor (4,4',4'',4'''-(（1 E,1'E,1''E,1'''E）-(ethene-1,1,2,2-tetrayltetrakis （benzene-4,1-diyl）)tetrakis （ethene-2,1-diyl）)tetrakis (1-（4-formylbenzyl）quinolin-1-ium),TPE-CHO) were existed in TPE-COP,in which the push–pull effect between them promoted the separation of photogenerated electron–hole,thus greatly improving the photocatalytic *** functional theory （DFT） simulation results show that TPE-COP can form charge-separating species under light irradiation,leading to electrons accumulation in TPE-CHO unit and holes in TAPA,and thus efficiently initiating *** 20 h illumination,the photocatalytic results show that the yields reach 1123.6 and 30.8μmol g-1for CO and H2,respectively,which are significantly higher than those of TPE-CHO small *** excellent result is mainly due to the increase of specific surface area,the enhancement of light absorption capacity,and the improvement of photoelectron-generating efficiency after the formation of ***,this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.

关键词： Metal-free Photocatalytic CO 2 reduction Covalent organic polymer Dry-reforming of methane Electron donor and acceptor

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Structural characteristics and drivers of greenhouse gas emissions at county-level and long-time scales:A case study of the Anji County,China

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Journal of Environmental Sciences 2024年第6期140卷 319-330页

作者： Zhouxiang Cai Liting hu Di Chen ying Zhang Xuekun Fang College of Environmental&Resource Sciences Zhejiang UniversityHangzhou 310058China Center for Global Change Science Massachusetts Institute of TechnologyCambridgeMA 02139United States Anji Meteorological Bureau Anji 313300China

To achieve carbon neutrality,the Chinese government needs to gain a comprehensive understanding of the sources and drivers of greenhouse gas(GHG)emissions,particularly at the county *** County in eastern China is a typical example of an industrial transformation from quarrying to a low-carbon *** study analyzed the decoupling types and structural characteristics of GHG emissions and the driving factors of carbon dioxide(CO_(2))emissions in the Anji from 2006 to 2019,and explored the differences between countylevel and provincial-level or city-level *** was observed that energy-related activities are the main source of GHG emissions in Anji and that economic development is the driving factor behind the increasing CO_(2)***,industrial transformation and upgradation coupled with the alternative use of clean energy limit the growth of GHG *** study details the GHG emissions of county during the industrial transformation stage and provides corresponding policy recommendations for county governments.

关键词： County GHG emissions Decoupling Driving factors Policy recommendations

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Microstructure and mechanical properties of Ti/Al/Ti clad plates prepared via powder-in-tube method

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Journal of Iron and Steel Research International 2024年第3期31卷 670-687页

作者： Xian-lei hu Qin-cheng Xie Yi Yuan ying Zhi State Key Laboratory of Rolling and Automation Northeastern UniversityShenyang 110819LiaoningChina Suzhou Dongbao Haixing Metal Material Technology Co. Ltd.Suzhou 215600JiangsuChina School of Material Science and Engineering Northeastern UniversityShenyang 110819LiaoningChina

The Ti/Al/Ti clad plates exhibit a broad spectrum of potential ***,the conventional techniques of hot-pressing composite and explosive composite are intricate and environmentally hazardous.A novel method was introduced for preparing clad plates,namely,the powder-in-tube *** method involves a combination of cold rolling,annealing at a temperature of 550℃,and double *** morphology of the intermetallic compound layer was analyzed through the utilization of interface stripping test,tensile test,and microscopic *** interface morphology,interface bonding properties,tensile fracture structures,and properties of plates under the first and second rolling were compared,along with the effects of intermetallic compounds on the interface *** results indicate that the powder-in-tube method,when annealed at 550℃,can produce a composite plate featuring a complete and uniform Ti/Al *** obtained plate exhibits a peeling strength of 21.5 N/mm,tensile strength of 424 MPa,and elongation of 11.5%.Furthermore,a systematic analysis was conducted to determine the causes of performance degra-dation observed during annealing at temperatures of 600 and 650℃.

关键词： Powder-in-tube method-Ti/Al/Ti clad plate Annealing Cold rolling-Mechanical property

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Mechanical behaviors of warm and ice-rich frozen soil stabilized with sulphoaluminate cement

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Journal of Mountain Science 2024年第1期21卷 335-345页

作者： WANG Honglei ZHANG hu ZHANG Jianming ZHANG Qi yin Zhenhua State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhou 730000China University of Chinese Academy of Sciences Beijing 100049China School of Civil Engineering and Transportation Northeast Forestry UniversityHarbin 150040China National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment CCCC First Highway Consultants Co.LtdXi'an 710065China Railway Engineering Research Institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China

The warm and ice-rich frozen soil is characterized by high unfrozen water content, low shear strength and large compressibility, which is unreliable to meet the stability requirements of engineering infrastructures and foundations in permafrost regions. In this study, a novel approach for stabilizing the warm and ice-rich frozen soil with sulphoaluminate cement was proposed based on chemical stabilization. The mechanical behaviors of the stabilized soil, such as strength and stress-strain relationship, were investigated through a series of triaxial compression tests conducted at -1.0℃, and the mechanism of strength variations of the stabilized soil was also explained based on scanning electron microscope test. The investigations indicated that the strength of stabilized soil to resist failure has been improved, and the linear Mohr-Coulomb criteria can accurately reflect the shear strength of stabilized soil under various applied confining pressure. The increase in both curing age and cement mixing ratio were favorable to the growth of cohesion and internal friction angle. More importantly, the strength improvement mechanism of the stabilized soil is attributed to the formation of structural skeleton and the generation of cementitious hydration products within itself. Therefore, the investigations conducted in this study provide valuable references for chemical stabilization of warm and ice-rich frozen ground, thereby providing a basis for in-situ ground improvement for reinforcing warm and ice-rich permafrost foundations by soil-cement column installation.

关键词： Permafrost regions Frozen soil Mechanical behavior Chemical stabilization Ground improvement Ground modification

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