Study on Volume Variation and Stability of Riverbed in the Yangtze Estuary

In recent years,regional floods and typhoons have occurred in the Yangtze Estuary.Changing dynamic conditions and dramatic reduction of sediment discharge in the basin are affecting the dynamic equilibrium pattern of the Yangtze Estuary.Based on the field measurement data and theoretical derivation,this paper analyzed the changing process of runoff-sediment discharge into the sea after the operation of the Three Gorges Project(TGP),and the tidal dynamics and sediment variation characteristics of the Yangtze Estuary.The erosion of South Branch mainly occurs in the channel below-10 m contour,and the riverbed volume below contours 0 m and-10 m has a good correlation with the sediment discharge of Datong Station in the previous year.On this basis,the ratio of the horizontal distance from the starting point to the section centroid below the average water level(B_c)and the water depth at the section centroid(H_c)was proposed to describe the change of the section shape.The relationships between the water-diverting ratio,the sediment-diverting ratio and the water-diverting angle,the conditions of runoff and sediment discharge from the upper reach and the characteristics of the riverway section were established,and the theoretical calculation equations of the water-diverting ratio,the sediment-diverting ratio and the diverting angle of each bifurcation were also established.

基于Riverbed的机载电子板卡红外图像分割

在机载电子板卡故障诊断过程中,需要对故障芯片进行准确的定位。针对机载电子板卡芯片布局紧密、工作芯片的热辐射范围广的问题,提出一种新型的人机交互式红外图像分割方法。首先,利用基于图像森林变换的Riverbed算法对故障目标图像进行边界追踪,并将Live Wire的特性与之相结合,优化了对边界模糊的目标的轮廓的提取,显著减少了所需的定位点数;然后,鉴于芯片的外形特征,采用基于梯度幅度直方图和类内方差最小化的自适应方法找到芯片的边界,用得到的芯片边界对目标轮廓进行约束,提高目标区域定位的精度。实验结果表明:该方法有效提高了故障边界提取的速度,与其他经典算法相比较有效提高了芯片的核心发热区域提取的精度,避免了多分割的现象。

Effects of riverbed scour on seismic performance of high-rise pile cap foundation

To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity （or supply） of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.

Modeling the triaxial behavior of riverbed and blasted quarried rockfill materials using hardening soil model

Riverbed modeled rockfill material from Noa Dehing dam project, Arunachal Pradesh, India and blasted quarried modeled rockfill material from Kol dam project, Himachal Pradesh, India were considered for this research. Riverbed rockfill material is rounded to sub-rounded and quarried rockfill material is angular to sub-angular in shape. Prototype rockfill materials were modeled into maximum particle size （dmax） of 4.75 mm, 10 mm, 19 mm, 25 mm, 5O mm and 80 mm for testing in the laboratory. Consolidated drained triaxial tests were conducted on modeled rockfill materials with a specimen size of 381 mm in diameter and 813 mm in height to study the stress-strain-volume change behavior for both rockfill materials. Index properties, i.e. uncompacted void content （UVC） and uniaxial compressive strength （UCS）, were determined for both rockfill materials in association with material parameters. An elasto- plastic hardening soil （HS） constitutive model was used to predict the behavior of modeled rockfill materials. Comparing the predicted and observed stress-strain-volume change behavior, it is found that both observed and predicted behaviors match closely. The procedures were developed to predict the shear strength and elastic parameters of rockfill materials using the index properties, i.e. UCS, UVC and relative density （RD）, and predictions were made satisfactorily. Comparing the predicted and experi- mentally determined shear strengths and elastic parameters, it is observed that both values match closely. Then these procedures were used to predict the elastic and shear strength parameters of large- size prototype rockfill materials. Correlations were also developed between index properties and ma- terial strength parameters （dilatancy angle, ~, and initial void ratio, einit, required for HS model） of modeled rockfill materials and the same correlations were used to predict the strength parameters for the prototype rockfill materials. Using the predicted material parameters, the stress-strain-volume change behavior of prototype rockfill material was predicted using elastoplastic HS constitutive model. The advantage of the proposed methods is that only index properties, i.e. UCS, UVC, RD, modulus of elasticity of intact rock, Eir, and Poisson＇s ratio of intact rock, Vir, are required to determine the angle of shearing resistance, Ф, modulus of elasticity, E50^ref and Poisson＇s ratio, , of rockfill materials, and there is E50＆ref no need of triaxial testing. It is believed that the proposed methods are more realistic, economical, and can be used where large-size triaxial testing facilities are not available.

Mobility Issue on Octagonal Structured ZigBee Network Using Riverbed

Wireless Sensor Network (WSN) is a special type of communication medium through distributed sensor nodes. Popular wireless sensor nodes like ZigBee have splendid interoperability after IEEE 802.15.4 standardization in the domain of wireless personal area network (WPAN). ZigBee has another great feature mobility that makes the ZigBee network more versatile. The mobility feature of ZigBee mobile nodes has a greater impact on network performance than fixed nodes. This impact sometimes turns into more severe because of network structure and mobility model. This study mainly focuses on the performance analysis of the ZigBee mobile node under Random and Octagonal mobility management model with the Tree routing method. The Riverbed academic modeler is used to design, implement and simulate the ZigBee network under certain conditions. This study also presents a competitive performance analysis based on ZigBee mobile nodes transmitter and receiver characteristics under the observation of the mobility model. This indicates that Octagonal mobility model exhibits better performance than the Random mobility model. This study will constitute a new way for further designing and planning a reliable and efficient ZigBee network.

Application of Short Sequential Extraction Procedure(SSEP) for the Determination of Zn, Cu, and Cd Contents in Riverbed Sludge in Hejiagou, Harbin, China

A short sequential extraction procedure（SSEP） was applied to the determination of more readily available metal fractions of Zn, Cu, and Cd in the riverbed sludge in Hejiagou, Harbin, China. From the results, a potential order of metal availability in seven sludge samples was proposed： Cd 〈 Cu 〈 Zn, and samples S1 , S2, and S4 were used for the determination of total Zn content, and sample S3 used for the determination of total Cu content in the mobile and the mobilizable fractions showed the highest pollution risk. The results with regard to metal mobility in sludge samples were confirmed by the individual and global contamination factors that were calculated from the nonresidual and residual metal contents. The results obtained from metal-release experiments after exposure of sludge to environmental conditions agreed well with those obtained from both SSEP and the individual and global contamination factors, indicating that the maximum metal release could be an additional factor to evaluate the heavy metal availability in contaminated sludge. A substantial time saving was achieved by using the metal-release method in the present study.

A Micro Study to Determine Porosity, Hydraulic Conductivity, Permeability and the Discharge Rate of Groundwater in Ondo State Riverbeds, Southwestern Nigeria

Laboratory study of three riverbed soil samples denoted as A, B and C have been carried out by determining the soils Porosity, Hydraulic conductivity, Permeability and also investigating if there are points of convergence between the discharge rate and angle of tilt for the above mentioned samples. The experimental results for Porosity were approximately within 34% - 37%, Hydraulic conductivity was within 3.02 × 10-5 - 9.70 × 10-5 (m/s) and Permeability was within 2.74 × 10-12 - 8.80 × 10-12 (m2). Pressure generally increases as distance of flow increases for θ = 5° - 25° but there was decrease in pressure as distance of flow increases for all three samples when θ = 0°. The points of convergence for the discharge rate ranged from 0.001 × 10-10 - 4.54 × 10-10 (m3/s), while the angle of tilt convergence points ranged from 0.1° to 3.6°. There was increase in discharge rate as angle of tilt increases for all three samples.

Riverbed发布业界最全面的数字体验管理解决方案

本刊讯Riverbed科技公司日前宣布推出最新版Riverbed SteelCentral，为用户提供市场上最完整、集成的数字体验管理解决方案。现在，Riverbed SteelCentral可以帮助客户评估数字体验的方方面面，

Energy dissipation caused by boundary resistance in a typical reach of the lower Yellow River and the implications for riverbed stability

The energy dissipation of boundary resistance is presented in this paper based on the flow resistance.Additionally,the river morphology responses to the resistance energy dissipation are explored using the Gaocun-Taochengpu reach in the lower Yellow River as a prototype.Theoretical analysis,measured data analysis and a one-dimensional hydrodynamic model are synthetically used to calculate the energy dissipation rate and riverbed morphological change.The results show that the energy dissipation rate along the channel will increase in both the mean value and the fluctuation intensity with increasing discharge.However,the energy dissipation rate will first decrease and then increase as the flow section or width-depth ratio increases.In addition,the energy dissipation rate has a significant positive correlation with the riverbed stability index.The results imply that the water and sediment transport efficiency of the river channel can be improved by optimizing the cross-sectional configuration to fulfil the minimum energy dissipation rate of the boundary resistance under stable riverbed conditions.

AN INVESTIGATION OF RIPPING UP THE RIVERBED

This paper discusses some characteristics of the phenomenon of ripping up the riverbed, which appears in the Yellow River, reviews the previous researches, and develops a formula for predicting scouring intensity.

Riverbed:应用性能等同于业务性能

随着IT技术快速发展,企业业务的实现方式也逐渐从线下转移到线上,企业中的IT应用越来越多,追求极致的用户体验也开始成为越来越多企业对IT应用的要求。＂很显然,在互联网＋时代,应用性能已经成为衡量企业好坏的一个重要指标。＂Riverbed亚太区副总裁、大中华区总经理袁志陵指出,这些面向员工、客户和普通用户的IT应用,如果性能不好、让人访问时速度很慢、甚至突然中断,都会给企业带来巨大的损失。2015年,Riverbed曾在全球做过一项调查,

基于区域优先的树型ZigBee网络的性能分析

ZigBee终端收集传感数据并发送给协调器,协调器对多个终端发来的请求进行处理,而这些请求都是非同步的,降低了网络的整体性能。文中针对ZigBee树型路由网络,提出区域优先机制,使节点的请求同步,从而构建一个可靠的ZigBee网络。Riverbed仿真软件的仿真结果表明:相比于不带优先级的ZigBee网络,带优先级的ZigBee网络性能具有明显的优越性。

A Study on Priority Based ZigBee Network Performance Analysis with Tree Routing Method

The Wireless Sensor Network (WSN) is spatially distributed autonomous sensor to sense special task. WSN like ZigBee network forms simple interconnecting, low power, and low processing capability wireless devices. The ZigBee devices facilitate numerous applications such as pervasive computing, security monitoring and control. ZigBee end devices collect sensing data and send them to ZigBee Coordinator. The Coordinator processes end device requests. The effect of a large number of random unsynchronized requests may degrade the overall network performance. An effective technique is particularly needed for synchronizing available node’s request processing to design a reliable ZigBee network. In this paper, region based priority mechanism is implemented to synchronize request with Tree Routing Method. Riverbed is used to simulate and analyze overall ZigBee network performance. The results show that the performance of the overall priority based ZigBee network model is better than without a priority based model. This research paves the way for further designing and modeling a large scale ZigBee network.

Bed Forms and Sediment Characteristics along the Thalweg on the Tanana River near Nenana, Alaska, USA

Sediment sampling and longitudinal river-bottom surveys were conducted along the thalweg on the Tanana River near the city of Nenana, Alaska, USA, to provide basic information for the engineering design requirements of hydrokinetic devices to be deployed in the area. The study reach was located at approximately 64°33'50'N and 149°04'W. The Tanana is a large glacier-fed river, with open-water flow conditions from May to October. The river presents a single channel in the study area. Granulometric analyses of sediment moving near the riverbed reveals the coexistence of three distinctive types of sediment along the study reach: 1) nearly uniform fine sand;2) bimodal distributions containing fine sand and medium gravel;and 3) medium gravel. Preliminary relationships between sediment loads and discharge were developed. Dunes with small superimposed dunes were found along the reach. The basic geometric parameters (i.e., wavelength and height) of dunes were measured, and steepness was calculated. In general, dune wavelength increased with increasing discharge. Dune wavelengths ranged from 41 to 67 m, while small-dune wavelengths ranged from 13 to 16 m. Steepness increased slightly with increasing discharge.

Optimization of ZigBee Network Parameters for the Improvement of Quality of Service

Network enabled digital technologies are offering new and exciting opportunities to increase the connectivity of devices for the purpose of home and office automation. ZigBee (IEEE 802.15.4) is such a digital wireless technology that is used for personal area networks. In this paper, an office automation network using the combination of fixed and mobile IEEE 802.15.4 has been deployed and analyzed. The QoS parameters of the network as the performance metrics like throughput, MAC delay and data dropped rate have been investigated. Finally the network has been finalized with the optimized QoS parameters.

Using Hydraulic Engineering Model Experiment to Study the Sediment Trapping Efficiency of Adjustable Check Dam

The construction of fully closed check dam (CD) is a conventional flood prevention mechanism implemented on rivers. Fully closed CDs trap large amounts of sediments in rivers to stabilize the river slopes and control erosion. However, fully closed CDs cannot selectively trap sediment and may easily overflow, causing them to losing their ability to mediate and hold sediments. Previous studies proposed the concept of “breathable CDs”. The researcher introduced metal slit dam (SD) that could be assembled and disassembled quickly and conveniently. Once a CD reaches maximum capacity, operators must ensure that the water channels of the dam are free from blockage. Moreover, they must inspect the internal accumulation conditions of the dam periodically or immediately following heavy typhoon rains. When necessary, either the sediment buildup in the upriver blockage must be cleared, or the transverse structure of the dam must be removed to allow fine particles to be discharged along with a moderate amount of water. These actions can free up the sediment-storing capacity of the dam for the next heavy typhoon rains. In addition, operators should also inspect the damages inflicted on the dam, such as erosion, wear and tear, and deformation conditions. Damaged components should be disassembled and repaired if possible, or recycled and reused. The present study performed channel tests to simulate closed CDs, SDs, steel pipe dam (SPDs), and steel pipe plus slit dam (SPSDs) for 50-year and 100-year frequency floods. Results were then analyzed to determine the sediment trapping (ST) effects of various CDs, the effects of “adjustable CDs”, and the changes of moderated riverbeds.

3D mathematical model for suspended load transport by turbulent flows and its applications

This paper presents a 3D mathematical model for suspended load transport in turbulent flows. Based on Dous stochastic theory of turbulent flow, numerical schemes of Reynolds stresses for anisotropic turbulent flows were obtained. A refined wall function was employed to treat solid wall boundaries. The equations for 2D suspended load motion and sorting of bed material have been expanded into 3D cases. Numerical results are validated by the measured data of the Gezhouba Project, and proved to be in good agreement with the experimental. The present method has been employed to simulate sediment erosion and deposition in the dam area of Three Gorges Project, and for the operation of the project, siltation process and deposition pattern in the near-dam area of the reservoir, size distribution of the deposits and bed material, and flow fields and sediment concentration fields at different time and elevations are predicted. The predicted results are close to the experimental observations in physical model studies. Thus, a new method is established for 3D simulation of sediment motion in dam areas of multi-purpose water projects.

三峡大坝下游水位变化与河道形态调整关系研究（英文）

In this study, data measured from 1955–2016 were analysed to study the relationship between the water level and river channel geometry adjustment in the downstream of the Three Gorges Dam（TGD） after the impoundment of the dam. The results highlight the following facts：（1） for the same flow, the low water level decreased, flood water level changed little, lowest water level increased, and highest water level decreased at the hydrological stations in the downstream of the dam;（2） the distribution of erosion and deposition along the river channel changed from ＂erosion at channels and deposition at bankfulls＂ to ＂erosion at both channels and bankfulls;＂ the ratio of low-water channel erosion to bankfull channel erosion was 95.5% from October 2002 to October 2015, with variations between different impoundment stages;（3） the low water level decrease slowed down during the channel erosion in the Upper Jingjiang reach and reaches upstream but sped up in the Lower Jingjiang reach and reaches downstream; measures should be taken to prevent the decrease in the channel water level;（4） erosion was the basis for channel dimension upscaling in the middle reaches of the Yangtze River; the low water level decrease was smaller than the thalweg decline; both channel water depth and width increased under the combined effects of channel and waterway regulations; and（5） the geometry of the channels above bankfulls did not significantly change; however, the comprehensive channel resistance increased under the combined effects of riverbed coarsening, beach vegetation, and human activities; as a result, the flood water level increased markedly and moderate flood to high water level phenomena occurred, which should be considered. The Three Gorges Reservoir effectively enhances the flood defense capacity of the middle and lower reaches of the Yangtze River; however, the superposition effect of tributary floods cannot be ruled out.

A STUDY ON NONEQUILIBRIUM TRANSPORT OF NONUNIFORM BEDLOAD IN STEADY FLOW

In the case of steady flow, an equilibrium state for an alluvial reach referring to the input of sediment over a sufficiently long time (time interval in the order of months) is equal to the output of sediment. A nonequilibrium state exists under steady flow when the sediment transport rate changes with time and space, so that there is no balance between input and output of sediment. The experiments were performed in an open circuit tilting flume with the bed slope of 0. 001-0. 009, the flume length of 30m and flume width of 0. 5m. The boundary condition at upstream and in all experiments, the rate of sedimant supply was zero. The coal or sand was se- lected as the Wed material. The grain diameter of the bed material varied in the range of 0.05- 20. 00ram. The equation of nonequilibrium transport of nonuniform bedload is derived. The grain distribution of the size distribution of bedload is calculated by modified Gessler's formula. The grain size distribution of bed material is calculated by CARICHAR mixed layer model. These equations are applied to numerical simulation of armoring of riverbeds. The results of the bedload transport rate and the grain size distribution of the bedload at the end of the down- stream in the process of time, as well as the grain size distribution of the bed material in the pro- cess of time and distance are all in close agreement with the measurements.