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Temporal evolution of scour at bridge abutments in compound channels

International Journal of Sediment Research 2022年第5期37卷 662-674页

作者： Yifan Yang bruce w.melville Xiaozhou Xiong Lu wang School of Engineering The University of Waikato Risland New Zealand Department of Civil and Environmental Engineering The University of Auckland State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resource and Hydropower Sichuan University

Bridge abutment-induced sediment scour in compound river channels is time-sensitive during floods, and, thus, estimating the scour rate has significance in design. In the current study, large-scale laboratory experiments were done to examine the influence of multiple factors on scour evolution,including channel geometry, bed mobility(clear-water or live-bed), and lateral(embankment intrusion) and vertical(deck submergence) flow contractions. A new method is applied for scour measurement and determination of characteristic scour trends. Results show that the nondimensional time scale is related to flow intensity and may peak before reaching the clear-water scour threshold; the corresponding equations also are derived. It is found that the use of scour countermeasures has a significant impact on the scour rate, and the existing equations for unprotected abutments have limitations. Under clear-water conditions, the scour rate is closely related to the overall flow contraction, which can be better reflected by the ratio of the approaching unit discharge to that at the bridge section. Specifically, the effect of vertical flow contraction on scour rate is more dominant than other factors. Two scour rate curves are derived to suit different structural and flow contraction types for clear-water scour. In contrast, the live-bed scour rate data are generally consistent and fall in a narrow band, showing less dependence on other factors. Finally, a new design approach is established to estimate the time scale and scour rate using the new equations proposed in this paper.

关键词： Abutment scour Temporal evolution Compound channel Time scale Scour rate

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Near-bed hydrodynamics associated with the entrainment of coarse particles at different protrusion heights

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Journal of Hydrodynamics 2022年第6期34卷 1067-1080页

作者： Yushu Xie bruce w.melville Asaad Y.Shamseldin Colin N.whittaker Yifan Yang Department of Civil and Environmental Engineering The University of AucklandAucklandNew Zealand School of Engineering The University of WaikatoHamiltonNew Zealand

This paper presents an investigation of near-bed hydrodynamics for a protruding coarse particle over a regular roughened *** laboratory experiments were undertaken at the threshold flow condition,which induced dislodgement of the protruding *** different protrusion heights,the experimental results show that the protruding particle substantially changed the spatial distributions of time-averaged velocities,turbulent kinetic energy,and Reynolds shear stress when compared with those obtained from a flat rough *** spatial distribution pattern of the flow characteristics shows a reasonable degree of similarity at different protrusion heights examined in this *** the target particle,a zone of low Reynolds shear stress was *** analysis was conducted along the main flow direction,at an elevation close to the top of the target particle.A prevalence of sweep(Quadrant 4)and outwards interaction(Quadrant 1)events were associated with the dislodgement of the protruding *** findings imply that the drag force related to strong streamwise velocities may play a more significant role in protruding particle entrainment than the shear stress.

关键词： Entrainment particle protrusion flow structure shear stress quadrant analysis

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Smart Sediment Particle: A novel approach to investigating fluvial bed entrainment using instrumented sensors

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International Journal of Sediment Research 2023年第1期38卷 66-82页

作者： Yushu Xie bruce w.melville Asaad Y.Shamseldin Colin N.whittaker Yifan Yang Department of Civil and Environmental Engineering The University of Auckland School of Engineering The University of Waikato

The Smart Sediment Particle(SSP) instrumented with multiple sensors to obtain tri-axial linear accelerations is used for studying the mechanism of coarse grain entrainment. Three bed arrangements are tested to examine their influences on entrainment processes and the threshold force and impulse conditions. The SSP shows satisfactory precision to capture the imperceptible movement tendencies immediately(e.g., 0.15 s) after the dislodgement. The experimental results show that bed packing can significantly affect the particle’s entrainment threshold and the path of movement. Lateral movement is predominant for some cases because the entrainment path is based on the least work done by the flow,even if the direction is not aligned with the flow. The concept of effective protrusion height is proposed to quantify the effect of local bed arrangement on entrainment. The mean velocity field around the SSP is also measured together with the acceleration data. The mean threshold velocity and resultant impulse show consistent dependence on the bed arrangement. In general, the SSP shows a good prospect of being used to study small-scale entrainment mechanism.

关键词： Smart Sediment Particle Instrumented sensors Entrainment behaviours Tri-axial acceleration Hydrodynamic force impulse

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FFECTS OF FLOw INTENSITY, OBSTACLE ALIGNMENT AND CROSS-SECTION GEOMETRY ON SCOUR AT BRIDGE ABUTMENTS"?CARDOSO, A.H., SANTOS, J.S. and ROCA, M.

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International Journal of Sediment Research 2002年第4期17卷 336-340页

作者： bruce w.melville Civil Engineering NewZealand The University of Auckland Professor Private Bag

The authors present new measurements of maximum (equilibrium) local scour depth at bridge abutments, the new data being analysed in terms of the multiplying factors given in melville (1992, 1997) and melville and Coleman (2000). The design method presented in these publications is referred to here as the University of Auckland (UoA) Method. The authors?data apply to the following factors: Pf (flow intensity), Pq (abutment alignment) and Pg (approach channel geometry).

关键词： SANTOS and ROCA A.H CARDOSO FFECTS OF FLOw INTENSITY J.S OBSTACLE ALIGNMENT AND CROSS-SECTION GEOMETRY ON SCOUR AT BRIDGE ABUTMENTS

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河床泥沙运动阶段的桥墩局部冲刷

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世界桥梁 1986年第3期 46-53页

作者： bruce w.melville ,郝育森郑州铁路局科研所

本文对来水平均流速大于泥沙起动流速阶段,在无粘性泥沙中,圆形桥墩的局部冲刷深度与来水平均流速的关系,进行了研究。搜集并整理了各种不同的桥墩直径、泥沙粒径及来水平均流速的试验数据。从大量数据得知;冲刷深度与流速之间的关系,... 详细信息

本文对来水平均流速大于泥沙起动流速阶段,在无粘性泥沙中,圆形桥墩的局部冲刷深度与来水平均流速的关系,进行了研究。搜集并整理了各种不同的桥墩直径、泥沙粒径及来水平均流速的试验数据。从大量数据得知;冲刷深度与流速之间的关系,因河床沙波形成或沙波未形成而有所不同,每种情况都建立了函数关系.这两种函数有两个最大冲刷深度。它们分别出现于来水平均流速等于起动流速及过渡平床流速时。与以前各家著述不同的是:在河床沙波形成阶段,最大冲刷深度出现于过渡平床状态。而对沙波未形成阶段,最大冲刷深度出现于泥沙起动流速状态。

关键词：河床平均流速来水河槽冲刷深度泥沙粒径桥墩局部冲刷泥沙运动

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Your personal choices in transportation and food are important for lowering carbon emissions

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Frontiers of Environmental Science & Engineering 2024年第6期18卷 27-32页

作者： bruce Logan Fang Zhang wulin Yang Le Shi Institute of Energy and the Environment The Pennsylvania State UniversityUniversity ParkPA 16802USA School of Environment Tsinghua UniversityBeijing 100084China College of Environmental Sciences and Engineering Peking UniversityBeijing 100871China College of Environmental and Resource Sciences Zhejiang UniversityHangzhou 310058China

There is a global need to reduce greenhouse gas emissions to limit the extent of climate change.A better understanding of how our own activities and lifestyle influence our energy use and carbon emissions can help us enable changes in activities that can lead to reductions in carbon *** we discuss an approach based on examining carbon emissions from the perspective of the unit C,where 1 C is the CO_(2)from food a person would on average eat every *** approach shows that total CO_(2)emissions in China,normalized by the population,is 22.5 C while carbon emissions for a person in the US is 43.9 C.A better appreciation of our own energy use can be obtained by calculating carbon emissions from our own activities in units of C,for example for driving a car gasoline or electric vehicle a certain number of kilometers,using electricity for our homes,and eating different *** this information,we can see how our carbon emissions compare to national averages in different countries and make decisions that could lower our personal CO_(2)emissions.

关键词： Carbon dioxide Climate change Daily energy Greenhouse gas

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Spinal intradural electrodes: opportunities, challenges and translation to the clinic

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Neural Regeneration Research 2024年第3期19卷 503-504页

作者： bruce Harland Chien Yew Kow Darren Svirskis School of Pharmacy University of AucklandAucklandNew Zealand Department of Neurosurgery Auckland City HospitalAucklandNew Zealand

Damage to the spinal cord disrupts the electrically active nerve cells which normally transmit afferent and efferent signals,resulting in loss of motor,sensory,and autonomic *** treatments for spinal cord injury utilizing implanted spinal electrodes can be broadly classified into three different *** first of these approaches is“spinal stimulation”where electrodes,usually positioned above the level of injury,provide electrical stimulation to target and disrupt pain signals before they reach the *** second approach uses“activity-dependent neuro-technologies”,in which electrodes positioned below the level of injury initiate a complex spatiotemporal pattern of stimulation at the lumbar spinal cord to generate a walking gait in the limbs(Minev et al.,2015;wagner et al.,2018).

关键词： stimulation electrodes utilizing

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Clinical implications of reconsideration of enthesitis/enthesopathy/enthesial erosion,as tendon attachmentlocalized avulsions and stress fracture equivalents

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world Journal of Orthopedics 2024年第10期15卷 902-907页

作者： bruce M Rothschild Department of Medicine Indiana University Ball Memorial HospitalMuncieIN 47303United States

Recognizing the mechanical origin of enthesitis/enthesopathy and the avulsion-nature of what had previously been considered erosions,it seems inappropriate to attribute it to stresses related to a person’s normal ***,sudden or unconditioned repetitive stresses appears the more likely *** of enthesial reaction have lacked standardization as to findings present among individuals who appear to be *** evaluation by palpation and mani-pulation may be as effective as application of radiologic *** of the mechanical nature of the disease,including individuals with inflammatory arthritis suggests prescription of mechanical solutions that reduce stresses across the involved enthesis.

关键词： Enthesitis Epicondylitis Erosion Avulsion Clinical examination

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Transforming nanoscale VO_(2)(B) into a scalable sodium-ion electrode

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Nano Research 2024年第10期17卷 8809-8818页

作者： Yunkai Luo Swetha Chandrasekaran Bintao Hu Randy Chen Marcus worsley bruce Dunn Department of Materials Science and Engineering University of CaliforniaLos AngelesCA 90095USA Lawrence Livermore National Laboratory CA 94550USA

The intermittent nature of renewable energies requires highly reliable grid-level energy storage approaches.A critical consideration in developing this technology is the areal capacity which determines battery performance and influences the cost of battery *** related importance is finding new ways of developing scalable *** recent years,threedimensional(3D)printing of conductive scaffolds has emerged as an alternative to overcome the scalability limitations of commercial tape cast *** research carried out in the current study demonstrates a successful scalability pathway for nanoscale VO_(2)(B),a desirable cathode for sodium-ion batteries which has a nano-flower morphology with a crystallite sizewe were able to achieve mass loading of over 100 mg·cm^(-2) and still possess an areal capacity of 10 mAh·cm^(-2) at a current density of 5 mA·cm^(-2).Moreover,after 1000 cycles,these electrodes retained 75% to 80% of their initial *** at high loading levels,the electrodeposited VO_(2)(B)exhibits pseudocapacitive material signatures such as a box-like voltammetry response,linear galvanostatic response,and no phase change upon *** scalability of the VO_(2)(B)electrode is demonstrated in a series of experiments which show the areal capacity to scale upon increase in both mass loading and electrode thickness,with only small changes in specific *** study establishes that nanoscale materials can be scaled up to achieve thick electrodes without compromising their electrochemical properties.

关键词： nano VO_(2)(B) sodium-ion battery scalable electrodes three-dimensional(3D)printed scaffold additive manufacturing

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Are James webb Space Telescope Observations Consistent with warm Dark Matter?

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International Journal of Astronomy and Astrophysics 2024年第1期14卷 45-60页

作者： bruce Hoeneisen Universidad San Francisco de Quito Quito Ecuador

we compare observed with predicted distributions of galaxy stellar masses M* and galaxy rest-frame ultra-violet luminosities per unit bandwidth LUV, in the redshift range z=2 to 13. The comparison is presented as a function of the comoving warm dark matter free-streaming cut-off wavenumber kfs. For this comparison the theory is a minimal extension of the Press-Schechter formalism with only two parameters: the star formation efficiency, and a proportionality factor between the star formation rate per galaxy and LUV. These two parameters are fixed to their values obtained prior to the James webb Space Telescope (JwST) data. The purpose of this comparison is to identify if, and where, detailed astrophysical evolution is needed to account for the new JwST observations.

关键词： James webb Space Telescope JwST warm Dark Matter

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