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Experimental investigations on characteristics of water-air two-phase flows during water-fillings in undulation pipelines

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JOURNAL OF HYDRODYNAMICS 2024年第4期36卷 706-724页

作者： tang, xue-lin Liu, Zong-ku Zhang, ling Li, Xiao-qin China Agr Univ Coll Water Resources & Civil Engn Beijing 100083 Peoples R China China Agr Univ Beijing Engn Res Ctr Safety & Energy Saving Techno Beijing 100083 Peoples R China Mingyang Smart Energy Grp Ltd Zhongshan 528400 Peoples R China

Visual and pressurized pipeline systems with single- and multi-undulation layouts were used to study experimentally and analyze theoretically the transient characteristics of water-air two-phase flow during water fillings in undulation pipelines based on the combination action analyses of both the communicating pipe and the gravity of the water-air two-phase flows in the descending pipe. For the single undulation pipeline, the complex two-phase flow-pattern evolutions including full pipe flow and stratified flow for low, medium, high water-filling velocity cases, respectively, lead to a great difference in transient pressure, flow pattern and the water-filling duration. Especially for low and medium water-filling velocity cases, the hydraulic theories related to hydraulic drop and hydraulic jump were employed to investigate the entrapped air pocket evolutions in the descending pipe, and the mechanism of negative pressure at the top of the undulation pipes was analyzed. For the same multi-undulation pipeline, due to the different elevations of the three undulation points along flow direction, namely three different types of pipeline layout, high-medium-low case (high elevation undulation point, medium one, and low one), low-medium-high and high-low-medium ones, their water-filling durations are significantly different, i.e., approximately 80.02 s, 227.34 s and 617.78 s. Meanwhile, there are significant differences in flow patterns in water filling, namely larger entrapped air pockets in three descending pipes for the high-medium-low case, entrapped air pockets in the first two descending pipes and open channel stratified flow in the last one for low-medium-high case, some bubbles in three descending pipes for the high-low-medium case.

关键词： Water-filling duration trapped air pockets water-air two-phase flow transient flow flow-pattern evolution multi-undulation pipelines

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EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON SECONDARY FLOWS AND SEDIMENTATIONS BEHIND A SPUR DIKE

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Journal of Hydrodynamics 2007年第1期19卷 23-29页

作者： tang xue-lin DING Xiang CHEN Zhi-cong College of Water Conservancy and Civil Engineering China Agricultural University Beijing 100083 China Department of Hydraulic Engineering Tsinghua University Beijing 100084 China

For a physical model of the approach navigation channel of Three Gorges Project（TGP）, flow patterns around a non-submerged spur dike placed as a mountain in a long rectangular glass flume were experimentally investigated with and without ＂sucking-spouting＂ water respectively. Based on rigid lid assumption and Dynamic Smagorinsky Model, all these vortex flows around the spur dike were numerically simulated and analyzed, which probably affect the whole flow field and then probably lead to sedimentations for silt-laden two-phase flows. Meanwhile, silt-laden flows were also investigated experimentally. Both the secondary flow region and the silt sedimentations downstream of the spur dike decrease greatly with ＂sucking-spouting＂ water compared to those ones without ＂sucking-spouting＂ water. The Finite Volume Method （FVM） was used to discretize the governing equations together with a staggered grid system, where the second order difference is employed for the diffusion terms and the source terms while the upwind difference QUICK is used for the convection terms. The computational results are all in fairly good agreement with the experimental data.

关键词： Three Gorges Project (TGP) "sucking-spouting" water spur dike silt-laden flow rigid lid assumption,dynamic large eddy simulations

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Optimization of the co-closing law of guide vanes and blades for bulb turbines based on CFD

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Journal of Hydrodynamics 2024年第2期36卷 363-377页

作者： Hui Liu Yun-fa lin Yong-guang Cheng Song xue Mao-jia tang Jian Zhang Jia-yi Fan State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan430072China Dongfang Electric Machinery Co. Ltd.Deyang618000China

The load rejection transient process of bulb turbine units is critical to safety of hydropower stations,and determining appropriate closing laws of guide vanes(GVs)and runner blades(RBs)for this process is of *** this study,we proposed a procedure to optimize the co-closing law of GVs and RBs by using computational fluid dynamics(CFD),combined with the design of experiment(DOE)method,approximation model,and genetic optimization *** sensitivity of closing law parameters on the histories of head,speed,and thrust was analyzed,and a two-stage GVs’closing law associating with a linear RBs’closing law was *** results show that GVs dominate the transient characteristics by controlling the change of *** GVs’first-stage closing speed while shortening first-stage closing time can not only significantly reduce the maximum rotational speed but also suppress the water hammer pressure;slowing GVs’second-stage closing speed is conducive to controlling the maximum reverse axial *** directly affect the runner *** RBs’closing speed can further reduce the rotational speed and the maximum reverse axial *** safety margin of each control parameter,flow patterns,and pressure pulsations of a practical hydropower station were all improved after optimization,demonstrating the effectiveness of this method.

关键词： Bulb turbine load rejection transient process double regulation closing law optimization computational fluid dynamics(CFD)

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Granular collapse in fluids:Dynamics and flow regime identification

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Particuology 2024年第9期92卷 30-41页

作者： Hu tang Bisong lin Dengming Wang Department of Mechanics and Engineering Science School of Civil Engineering and MechanicsKey Laboratory of Mechanics on Disaster and Environment in Western China of Ministry of EducationLanzhou UniversityLanzhou730000China

The collapse of granular material in fluids is a prevalent phenomenon in both natural and industrial processes,displaying a notable sensitivity to initial configuration of the *** study is specifically oriented towards falling process of collapsing material under various fluid conditions,employing the computational fluid dynamics-discrete element method(CFD-DEM)to primarily investigate the dynamics and scaling laws of deposit morphology of collapsed *** a comprehensive analysis of particle sedimentation in fluids,we introduce a refined inertial characteristic time for granular collapse within the inertial ***,we propose modifications to conventional fluid-particle density ratio and Reynolds number,aiming to enhance the accuracy of depicting collapse dynamics and identifying flow regimes across diverse column heights and fluid ***,we construct a phase diagram of flow regimes using modified dimensionless numbers,emphasizing the role of column height in transition between viscous and inertial *** parameters demonstrate enhanced relevance in governing the collapse of immersed granular columns,thereby contributing to a more nuanced understanding of fluid-particle interations in dense granular flows under different regimes.

关键词： Immersed granular material Collapse Dynamic Flow regime Computational fluid dynamics-discrete element method

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Dexamethasone implant for refractory macular edema secondary to diabetic retinopathy and retinal vein occlusion

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International Journal of Ophthalmology(English edition) 2024年第10期17卷 1837-1842页

作者： Yuan-Yuan Zhong Chong tang Lan-Yue Zhang xue-Dong Zhang Shu-lin Liu The First Affiliated Hospital of Chongqing Medical University Chongqing Key Laboratory for the Prevention and Treatment of Major Blinding Eye DiseasesChongqing 400016China

AIM:To evaluate the efficacy,timing of retreatment and safety of dexamethasone(DEX)implant on macular edema(ME)secondary to diabetic retinopathy(DME)and retinal vein occlusion(RVO-ME)patients who were refractory to anti-vascular endothelial growth factor(VEGF)***:This retrospective study included 37 eyes received at least one DEX implant treatment for DME or RVO-ME between January 1,2019,and January 1,*** refractory DME and RVO-ME cases received at least 5 anti-VEGF injections and failure to gain more than 5 letters or a significant reduction in central retinal thickness(CRT).The best corrected visual acuity(BCVA)and CRT were measured at baseline,and at 1,3,4 and 6mo post-DEX implant *** events such as elevated intraocular pressure(IOP)and cataract were ***:For RVO cases(n=22),there was a significant increase in BCVA from 0.27±0.19 to 0.35±0.20 at 6mo post-DEX injection(P<0.05)and CRT decreased from 472.1±90.6 to 240.5±39.0μm at 6mo(P<0.0001).DME cases(n=15)experienced an improvement in BCVA from 0.26±0.15 to 0.43±0.20 at 6mo post-DEX implant injection(P=0.0098),with CRT reducing from 445.7±55.7 to 271.7±34.1μm at 6mo(P<0.0001).Elevated IOP occurred in 45.9%of patients but was well-controlled with topical *** cases of cataract or other adverse events were ***:DEX implants effectively improve BCVA and reduce CRT in refractory DME and *** research with larger cohorts and longer follow-up periods is needed to confirm these findings and assess long-term outcomes.

关键词： macular edema dexamethasone implant anti-vascular endothelial growth factor retinal vein occlusion diabetic retinopathy

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Improved catalytic performance of CO_(2) electrochemical reduction reaction towards ethanol on chlorine-modified Cu-based electrocatalyst

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Nano Research 2024年第5期17卷 3761-3768页

作者： Yifan Liu Hehua tang Yitian Zhou Bo-lin lin School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China

Effective electrochemical conversion of CO_(2) to value-added liquid multi-carbon products driven by renewable energy is a promising approach to alleviate excessive CO_(2) emission and achieve large-scale renewable energy ***,the selectivity and catalytic activity towards liquid multi-carbon products of CO_(2) electroreduction reaction are still unsatisfactory due to the sluggish C-C coupling process and the formation of complex oxygen-containing ***,designing and fabricating highly effective electrocatalysts is crucial for practical applications in this ***,we developed Cl-modified Cu catalyst(Cu-Cl)for efficient electrochemical reduction of CO_(2) to *** optimal Faradaic efficiency and partial current density of ethanol on the Cu-Cl sample reached 26.2%and 343.2 mA·cm^(-2) at-0.74 V(*** hydrogen electrode(RHE)),which were 1.66 and 1.76 times higher than those of the catalyst without Cl decoration,outperforming those in most previously reported *** functional theory(DFT)calculations revealed that the Cl-modified Cu surface suppressed the parasitic hydrogen evolution reaction(HER)and reduced the energy barrier for the C-C coupling process,making the formation of key intermediates favorable for ethanol ***,the decoration of Cl on the Cu surface facilitated ethanol formation.

关键词： CO_(2)electrochemical reduction halogen chlorine Cu-based catalysts ethanol multi-carbon products

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Voltage-modulated polymer nanopore field-effect transistor for multi-sized nanoparticle detection

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Nanotechnology and Precision Engineering 2024年第3期7卷 79-89页

作者： Feng Zhou lin Li Qiannan xue State Key Laboratory of Precision Measurement Technology and Instruments School of Precision Instruments and Optoelectronics EngineeringTianjin UniversityTianjin 300072China

Solid-state nanopores offer a range of distinct advantages over biological nanopores,such as structural diversity and greater stability and durability;this makes them highly promising for high-resolution nanoparticle *** nanopores can exhibit gating characteristics with stress-responsive switches and can demonstrate specificity toward particular *** inspiration from biological nanopores,this paper introduces a novel polymer nanopore with field-effect characteristics,leveraging a conductive polymer in its construction to showcase intriguing gating ***,in this device,the polymer layer serves as the gate,enabling precise control over the source–drain current response inside and outside the pore by simply adjusting the gate *** unique feature allows fine-tuning of the nanopore’s sensitivity to nanoparticles of varying sizes and facilitates its operation in multiple *** results reveal that the developed polymer nanopore field-effect transistor demonstrates remarkable selectivity in detecting nanoparticles of various sizes under different applied *** proposed single device demonstrates the exceptional ability to detect multiple types of nanoparticle,showcasing its immense potential for a wide range of applications in biological-particle analysis and medical diagnostics.

关键词： Nanopipette Polymer nanopore Voltage modulation Nanoparticle detection

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Relationships between Terrain Features and Forecasting Errors of Surface Wind Speeds in a Mesoscale Numerical Weather Prediction Model

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Advances in Atmospheric Sciences 2024年第6期41卷 1161-1170页

作者： Wenbo xue Hui YU Shengming tang Wei HUANG Chinese Academy of Meteorological Sciences Beijing 100081China University of Chinese Academy of Sciences Beijing 101408China Shanghai Typhoon Institute/CMA Shanghai 200030China Key Laboratory of Numerical Modeling for Tropical Cyclone/CMA Shanghai 200030China

Numerical weather prediction(NWP)models have always presented large forecasting errors of surface wind speeds over regions with complex *** this study,surface wind forecasts from an operational NWP model,the SMS-WARR(Shanghai Meteorological Service-WRF ADAS Rapid Refresh System),are analyzed to quantitatively reveal the relationships between the forecasted surface wind speed errors and terrain features,with the intent of providing clues to better apply the NWP model to complex terrain *** terrain features are described by three parameters:the standard deviation of the model grid-scale orography,terrain height error of the model,and slope *** results show that the forecast bias has a unimodal distribution with a change in the standard deviation of *** minimum ME(the mean value of bias)is 1.2 m s^(-1) when the standard deviation is between 60 and 70 m.A positive correlation exists between bias and terrain height error,with the ME increasing by 10%−30%for every 200 m increase in terrain height *** ME decreases by 65.6%when slope angle increases from(0.5°−1.5°)to larger than 3.5°for uphill winds but increases by 35.4%when the absolute value of slope angle increases from(0.5°−1.5°)to(2.5°−3.5°)for downhill *** sensitivity experiments are carried out with a model output statistical(MOS)calibration model for surface wind speeds and ME(RMSE)has been reduced by 90%(30%)by introducing terrain parameters,demonstrating the value of this study.

关键词： surface wind speed terrain features error analysis MOS calibration model

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A Numerical Calculation Algorithm of the Inclination Function Based on the Representation of SO(3) Group

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 137-148页

作者： Yu-xiao Wei Wen-lin tang Department of Geophysics School of Geology Engineering and GeomaticsChang’An UniversityXi’an710064China Key Laboratory of Electronics and Information Technology for Space Systems National Space Science CenterChinese Academy of SciencesBeijing100190China

In the determination of the Earth gravity field in satellite geodesy, the inclination functions represent the projection of data observed along the orbital plane of a satellite orbit into the sphere in the terrestial reference frame. The inclination functions in this work is studied from a group theoretical perspective. The inclination functions are proved to generate a representation of the SO(3) group. An orthogonal relation of the inclination functions is derived and some recurrence relations for the inclination functions are given, based on which an algorithm to calculate the inclination functions is proposed.

关键词： SO(3)group inclination function satellite geodesy representation of SO(3)

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Manipulating d-d orbital hybridization induced by Mo-doped Co_(9)S_(8) nanorod arrays for high-efficiency water electrolysis

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Journal of Energy Chemistry 2024年第6期93卷 592-600,I0015页

作者： xue Zhou Jing Li Guangyao Zhou Weiran Huang Yucan Zhang Jun Yang Huan Pang Mingyi Zhang Dongmei Sun Yawen tang lin Xu Jiangsu Key Laboratory of New Power Batteries Jiangsu Collaborative Innovation Centre of Biomedical Functional MaterialsSchool of Chemistry and Materials ScienceNanjing Normal UniversityNanjing 210023JiangsuChina 'College of Science Jinling Institute of TechnologyNanjing 211169JiangsuChina State Key Laboratory of Multiphase Complex Systems Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China Nanjing IPE Institute of Green Manufacturing Industry Nanjing 211100JiangsuChina School of Chemistry and Chemical Engineering Yangzhou UniversityYangzhou 225009JiangsuChina Key Laboratory for Photonic and Electronic Bandgap Materials Ministry of EducationSchool of Physics and Electronic EngineeringHarbin Normal UniversityHarbin 150025HeilongjiangChina

Precisely refining the electronic structure of electrocatalysts represents a powerful approach to further optimize the electrocatalytic ***,we demonstrate an ingenious d-d orbital hybridization concept to construct Mo-doped Co_(9)S_(8) nanorod arrays aligned on carbon cloth(CC)substrate(abbreviated as Mo-Co_(9)S_(8)@CC hereafter)as a high-efficiency bifunctional electrocatalyst toward water *** has experimentally and theoretically validated that the 4d-3d orbital coupling between Mo dopant and Co site can effectively optimize the H_(2)O activation energy and lower H^(*)adsorption energy barrier,thereby leading to enhanced hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)*** to the unique electronic and geometrical advantages,the optimized Mo-Co_(9)S_(8)@CC with appropriate Mo content exhibits outstanding bifunctional performance in alkaline solution,with the overpotentials of 75 and 234 mV for the delivery of a current density of 10 mA cm^(-2),small Tafel slopes of 53.8 and 39.9 mV dec~(-1)and long-term stabilities for at least 32 and 30 h for HER and OER,*** impressively,a water splitting electrolylzer assembled by the self-supported Mo-Co_(9)S_(8)@CC electrode requires a low cell voltage of 1.53 V at 10 mA cm^(-2)and shows excellent stability and splendid reversibility,demonstrating a huge potential for affordable and scalable electrochemical H_(2) *** innovational orbital hybridization strategy for electronic regulation herein provides an inspirable avenue for developing progressive electrocatalysts toward new energy systems.

关键词： d-d orbital hybridization Transition metal sulfides Nanorods arrays Water electrolysis

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