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Incipient sediment motion based on turbulent fluctuations

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International Journal of Sediment Research 2020年第2期35卷 125-133页

作者： Wan Hanna Melini Wan Mohtar Ji Wang Lee Najwa Izzaty Mohammad Azha nian-sheng cheng Department of Civil & Structural Engineering Faculty of Engineering and Built EnvironmentUniversiti Kebangsaan Malaysia School of Civil and Environmental Engineering College of EngineeringNanyang Technical University

The current study modifies the representation of the Shields parameter using turbulent strength,*** root-mean-square(rms) fluid *** were done under a steady,uniform flow using eight sediment sizes with particle Reynolds numbers(Rep) ranging between 1.0(fine sediment) and 183.4(coarse sediment).Utilising the peak rms horizontal(u) values,the critical Shields parameter,θ,was calculated and a trend similar to the well-established Shields curve was *** analysis was extended to the Shields curve obtained based on the critical shear velocity,Reynolds shear stress,and data extracted fro m the oscillating grid-turbulence *** show that turbulent fluctuations are crucial for the incipient sediment motion and are essentially better predictors than the commonly used critical shear velocity.A quadrant analysis to identify the role of turbulent bursting events in incipient sediment motion also was done where sweeps and ejections are dominant for finer and coarser sediment sizes,respectively.

关键词： Incipient sediment motion Root-mean-square fluid velocity Grid-turbulence Quadrant analysis Turbulent fluctuations

Revisited Vanoni-Brooks sidewall correction

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International Journal of Sediment Research 2011年第4期26卷 524-528页

作者： nian-sheng cheng 1 Assoc.Prof,School of Civil and Environmental Engineering,Nanyang Technological University,Nanyang Avenue,Singapore 639798. Assoc. Prof. School of Civil and Environmental Engineering Nanyang Technological University Nanyang Avenue Singapore 639798

The evaluation of the sidewall friction could be inconvenient in the implement of the Vanoni-Brooks sidewall correction *** the Colebrook-White equation and Nikuradse’s pipe friction data,two explicit formulae are developed in this note for finding the sidewall friction *** are applicable for various sidewalls that are either hydrodynamically-smooth or rough,or in the transitional regime.

关键词： Sidewall correction Friction factor Open channel flow Pipe flow Sediment transport

大尺度糙率条件下流速分布规律的试验与理论研究

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水动力学研究与进展（A辑） 2022年第5期37卷 633-638页

作者：徐璞儿程年生魏茂兴浙江大学海洋学院舟山316021

大尺度糙率条件下,床面糙率对水流特性的影响不再局限于近床区域,而会传播至包括自由表面的整个水深,这将导致被广泛认可的对数型流速分布规律不再适用。为避免自由表面对流场测量的影响,该文选用矩形断面粗糙管开展大尺度糙率水流试验... 详细信息

大尺度糙率条件下,床面糙率对水流特性的影响不再局限于近床区域,而会传播至包括自由表面的整个水深,这将导致被广泛认可的对数型流速分布规律不再适用。为避免自由表面对流场测量的影响,该文选用矩形断面粗糙管开展大尺度糙率水流试验。首先采用粒子图像测速技术(PIV)进行二维流场测量,并对实测流速的垂线分布进行了时间和空间的双平均处理;然后基于Prandtl紊流掺混理论,假设掺混长度为常数,推导出指数型流速分布公式。结果表明,理论公式与试验资料吻合良好,说明所采用的假设较好地描述了大尺度糙率水流的扩散特性。试验结果还表明,受大糙率元的影响,紊动强度和雷诺切应力的峰值位置明显偏离床面,紊动强度沿水深的分布趋向均匀。

关键词：紊流矩形管道大尺度糙率流速分布

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Pancreatic stent improves the success rate of needle-knife papillotomy in patients with difficult biliary cannulation

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World Journal of Gastroenterology 2025年第1期31卷 58-67页

作者： Mu-Hsien Lee cheng-Hui Lin Chi-Huan Wu Yung-Kuan Tsou Kai-Feng Sung sheng-Fu Wang Nai-Jen Liu Department of Gastroenterology and Hepatology Chang Gung Memorial Hospital and Chang Gung University College of MedicineTaoyuan 33305Taiwan School of Medicine Chang Gung UniversityTaoyuan 33305Taiwan

BACKGROUND Needle-knife precut papillotomy(NKP)is typically performed ***,it remains unclear whether pancreatic stent(PS)placement can improve the outcomes of *** To explore whether PS placement improves the success rate of NKP in patients with difficult biliary *** This single-center retrospective study included 190 patients who underwent NKP between January 2017 and December 2021 after failed conventional biliary *** cases with incidental pancreatic duct cannulation during conventional biliary cannulation,the decision for pre-NKP PS placement was made at the endoscopist's *** primary outcome was the difference in the NKP success rate between patients with and without PS placement;the secondary outcome was the adverse event *** Among the 190 participants,82 received pre-NKP PS(PS-NKP group)whereas 108 did not[freehand or freehand NKP(FH-NKP)group].Post-NKP selective biliary cannulation was successful in 167(87.9%)patients,and the PS-NKP had a significantly higher success rate than the FH-NKP group(93.9%vs 83.3%,P=0.027).The overall adverse event rates were 7.3%and 11.1%in the PS-NKP and FH-NKP groups,respectively(P=0.493).A periampullary diverticulum(PAD)and significant intraoperative bleeding during NKP were independently associated with NKP failure;however,a pre-NKP PS was the only predictor of NKP *** the 44 participants with PADs,the PS-NKP group had a non-significantly higher NKP success rate than the FH-NKP group(87.5%and 65%,respectively;P=0.076).CONCLUSION PS significantly improved the success rate of NKP in patients with difficult biliary cannulation.

关键词： Difficult biliary cannulation Endoscopic retrograde cholangiopancreatography Needle-knife papillotomy Pancreatic stent Selective biliary cannulation

Change of MicroRNA-134,CREB and p-CREB expression in epileptic rat

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Asian Pacific Journal of Tropical Medicine 2015年第4期8卷 292-298页

作者： Yan Zhu cheng-Shan Li Yuan-Ye Wang sheng-nian Zhou Department of ICU(Jining medical college affiliated hospital) Department of Neurology Qilu Hospital of Shandong University Brain Science Research Institute Shandong University

Objective:To To investigate the changes of MicroRNA-134,CREB and p-CREB expression in epileptic rat brains in order to elucidate the molecular mechanisms of epilepsy,providing new ideas for clinical ***:Sixty-four Spraque-Dawley(SD)rats were divided into groups randomly,including control group,six hours after seizure group,24-hour group,threeday group,one-week group,two-week group,four-week group,and eight-week *** groups were placed under a pilocarpine-induced epilepsy model except the control group,and all rats were decapitated in different points of *** specimens were taken for quantitative PCR experiments,immunohistochemistry and Western blot *** results of the epilepsy model groups and the control group were ***:There were no significant differences between the six hours after seizure group,the 24-hour group and the control group about the MicroRNA-134 ***-134 in the hippocampus tissue of the three-day group significantly reduced compared with the control group;same result was observed with the one-week,two-week,four-week and eight-week *** CREB and p-CREB levels in the three-day group's rat hippocampus significantly increased compared with the control group;and the high levels of CREB and p-CREB were constantly maintained in the one-week,two-week,four-week and eight-week ***:The MicroRNA-134 level of the epileptic rat hippocampus is significantly lower than normal after three days,and continues to maintain a low level:while CREB and p-CREB levels are rsignificantly increased after three days,and continue to remain at a high ***-134 plays a role in inhibiting synaptic plasticity by inhibiting CREB and p-CREB expressions.

关键词： MicroRNA-134 CREB p-CREB Quantitative PCR Western blot Immunohistochemistry

Transmitting electric power system dynamics in SCADA using polynomial fitting

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Science China(Technological Sciences) 2009年第4期52卷 937-943页

作者： DUAN XianZhong SU sheng MEI nian College of Electrical and Electronic Engineering Huazhong University of Science and TechnologyWuhan 430074China

The paper proposes an approach to transmit electric power system dynamics in the SCADA. With the prevalent application of digital substation automation system, it is feasible for the remote terminal units (RTUs) to collect phasors within a substation. However, limited communication capacity remains the bottleneck that prevents SCADA from transmitting system dynamics. This paper proposes to compress dynamics data with curve fitting in the RTUs and reconstruct the dynamics in the SCADA server for reducing communication demand. Dispatchers in the control center can thus get system dynamics with a delay of several seconds. Simulation result shows that for a power system under disturbance with short-circuit that once occurred and was cleared, the SCADA can approximate the original dynamics with satisfying precision using limited degree polynomial fitting. The approach is highly scalable and adaptable, and can be implemented on existing communication infrastructure with a few software modifications. The approach has extensive application potential.

关键词： SCADA WAMS (wide area measurement system) polynomial fitting system dynamics

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Improved Edge Confinement due to Ion Cyclotron Radio Frequency boronization in the HT—7 Tokamak

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Chinese Physics Letters 2003年第6期20卷 881-884页

作者： XUGuo-sheng WANBao-nian SONGMei LINGBi-Li InstituteofPlasmaPhysics ChineseAcademyofSciencesHefei230031

The phenomena of improved edge confinement due to ion cyclotron radio frequency boronization were observed with a fast reciprocating Langmuir probe in the HT-7 tokamak. A strong shear layer of radial electric field was produced in the plasma edge region, which resulted in the formation of an edge transport barrier. Consequently, the edge profiles of electron density were steepened, and both the absolute and relative fluctuation levels were suppressed by the shearing E×B flows. Concomitant reduction of the coherence between electron density and poloidal electric field fluctuations and the change of their cross-phase resulted in turbulent particle flux dropping by more than a half at the plasma edge. This demonstrates the de-correlation effect of turbulence and its contribution to edge transport. The results presented here suggest a link between wall conditions and boundary plasma physics, especially an interaction between atomic processes and turbulence through the formation of radial electric field shear at the plasma edge.

关键词： Carrier concentration

Statistical Characterization of Boundary Fluctuations in the HT—7 Tokamak

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Chinese Physics Letters 2003年第6期20卷 869-872页

作者： SONGMei WANBao-nian XUGuo-sheng LINGBi-Li InstituteofPlasmaPhysics ChineseAcademyofSciencesPOBox1126HeFei230031

The statistical properties of plasma fluctuations are characterized in the boundary region of HT-7 tokamak. A non-Gaussian feature is observed in fluctuations of ion saturation current and floating potential in most of the scrape-off layer regions. The statistical properties of fluctuations have a clear radial dependence, showing a near-Gaussian character in the proximity of the velocity shear layer location and another region where the poloidal velocity has a trend to zero. Fluctuations show a bursty character with pulses asymmetric in time and the time asymmetry reaches the minimum around the shear layer. From the results, we can see an obvious coupling of the pulses and the poloidal flow.

关键词： Shear flow

Modification of Boundary Fluctuations by LHCD in the HT—7 Tokamak

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Chinese Physics Letters 2003年第6期20卷 865-868页

作者： SONGMei WANBao-nian XUGuo-sheng LINGBi-Li InstituteofPlasmaPhysics ChineseAcademyofSciencesPOBox1126Hefei230031

Measurements of boundary fluctuations and fluctuation driven electron fluxes have been performed in ohmic and lower hybrid current drive enhanced confinement plasma using a graphite Langmuir probe array on HT-7 tokamak. The fluctuations are significantly suppressed and the turbulent fluxes are remarkably depressed in the enhanced plasma. We characterized the statistical properties of fluctuations and the particle flux and found a non-Gaussian character in the whole scrape-off layer with minimum deviations from Gaussian in the proximity of the velocity shear layer in ohmic plasma. In the enhanced plasma the deviations in the boundary region are all reduces obviously. The fluctuations and induced electron fluxes show sporadic bursts asymmetric in time and the asymmetry is remarkably weakened in the lower hybrid current driving (LHCD) phase. The results suggest a coupling between the statistical behaviour of fluctuations and the turbulent flow.

关键词： Tokamak devices