TKES:A Novel System for Extracting Trendy Keywords from Online News Sites

As the Smart city trend especially artificial intelligence,data science,and the internet of things has attracted lots of attention,many researchers have created various smart applications for improving people’s life quality.As it is very essential to automatically collect and exploit information in the era of industry 4.0,a variety of models have been proposed for storage problem solving and efficient data mining.In this paper,we present our proposed system,Trendy Keyword Extraction System(TKES),which is designed for extracting trendy keywords from text streams.The system also supports storing,analyzing,and visualizing documents coming from text streams.The system first automatically collects daily articles,then it ranks the importance of keywords by calculating keywords’frequency of existence in order to find trendy keywords by using the Burst Detection Algorithm which is proposed in this paper based on the idea of Kleinberg.This method is used for detecting bursts.A burst is defined as a period of time when a keyword is continuously and unusually popular over the text stream and the identification of bursts is known as burst detection procedure.The results from user requests could be displayed visually.Furthermore,we create a method in order to find a trendy keyword set which is defined as a set of keywords that belong to the same burst.This work also describes the datasets used for our experiments,processing speed tests of our two proposed algorithms.

基于样本熵的肌电信号起始点检测研究

该文提出了一种基于样本熵的动作肌电信号起始点检测方法,为肌电信号应用于智能假肢控制、人机交互,以及临床疾病诊断和评估等领域提供重要前提.首先利用固定长度的滑动窗对动作肌电信号分帧,然后计算每帧信号的样本熵值,之后设定自适应阈值确定动作肌电信号的起始点.实验结果表明,样本熵能够有效表征动作肌电信号的开启模式,对较短时间的肌肉收缩松弛有很好的连续性,较之于其他常见的几类检测算法具有更好的抗噪声性能,特别是对肌肉不自主收缩产生的尖锐毛刺信号具有优异的抑制性能.

基于表面肌电信号双谱分析的动作分类

为了提高人体上肢动作识别正确率,提出了一种基于表面肌电信号双谱分析的动作分类方法,以信息增益作为表面肌电信号起止点分割效果衡量标准,结合TKE算子提取出肌肉运动起止区间的表面肌电信号,对提取到的表面肌电信号进行双谱变换,提取双谱的正反对角切片作为表面肌电信号特征,以概率神经网络作为分类器,以100次10折交叉验证为一次动作分类实验,计算10次分类实验的平均正确率,最终得到正对角切片、反对角切片和正反对角切片的分类正确率分别为94.56%、90.93%和95.48%.

昆虫迁飞场的数值模拟

选用一维ＴＫＥ模式，以国家气象局的常规气象资料为基础，以Ｅ－ε闭合求其数值解，模拟出边界层内任意迁飞高度上的风温要素值，从而得到昆虫迁飞场的时空分布，为昆虫迁飞行为生态学研究和迁飞性害虫的异地预测提供了基础数据。

关于大气边界层方程闭合的对比研究

采用具有１１２阶精度的ＴＫＥ闭合方案以及适当减少垂直网格层数，使计算量大大减少。模拟结果与观测结果仍很吻合；与３阶闭合结果相比，并无明显降低。该方案提供了改进３维大气模式中ＰＢＬ参数化精度的可能性。

基于表面肌电信号进行手部动作发起检测方法

实时且准确地识别手部动作,是表面肌电信号应用的重要方面,而通过其进行手部动作的发起检测是一个技术难点。为了解决这一问题,该文提出一种通过表面肌电信号进行手部动作发起检测的方法,将TKE算子应用于s EMG信号的预处理,通过设计二值化状态函数,并针对消除噪声对肌电信号的影响,提出启发式滤波策略。建立手部动作发起的表面肌电仿真模型,通过比对应用几种算子对仿真模型进行发起检测,证明TKE算子方法的有效性。利用肌电信号采集与处理系统进行实验验证。结果表明,该检测方法能够对手部动作发起进行高精度的实时检测。

Modeling of the eddy viscosity by breaking waves

Breaking wave induced nearsurface turbulence has important consequences for many physical and biochemical processes including water column and nutrients mixing, heat and gases exchange across air-sea interface. The energy loss from wave breaking and the bubble plume penetration depth are estimated. As a consequence, the vertical distribution of the turbulent kinetic energy （TKE）, the TKE dissipation rate and the eddy viscosity induced by wave breaking are also provided. It is indicated that model results are found to be consistent with the observational evidence that most TKE generated by wave breaking is lost within a depth of a few meters near the sea surface. High turbulence level with intensities of eddy viscosity induced by breaking is nearly four orders larger than vw1（ = κu ＊wz）, the value predicted for the wall layer scaling close to the surface, where u ＊w is the friction velocity in water, κ with 0. 4 is the yon Kármán constant, and z is the water depth, and the strength of the eddy viscosity depends both on wind speed and sea state, and decays rapidly through the depth. This leads to the conclusion that the breaking wave induced vertical mixing is mainly limited to the near surface layer, well above the classical values expected from the similarity theory. Deeper down, however, the effects of wave breaking on the vertical mixing become less important.

Estimates of Reynolds Stress and TKE Production in the Seasonally Stratified East China Sea

During the two cruises in March and July of 2011, the tidal cycling of turbulent properties and the T/S profiles at the same location in seasonally stratified East China Sea （ECS） were measured synchronously by a bottom-mounted fast sampling ADCP （acoustic Doppler current profiler） and a RBR CTD （RBR-620） profiler. While focusing on the tide-induced and stratification＇s impact on mixing, the Reynolds stress and the turbulent kinetic energy （TKE） production rate were calculated using the ‘variance method＇. In spring, the features of mixing mainly induced by tides were clear when the water column was well-mixed. Velocity shear and turbulent parameters intensified towards the seabed due to the bottom friction. The components of the velocity shear and the Reynolds stress displayed a dominant semi-diurnal variation related to velocity changes caused by the flood and ebb of M2 tide. Stratification occurred in summer, and the water column showed a strongly stratified pycnocline with a characteristic squared buoy- ancy frequency of N2~ （1-6）x 10 3 S-2 The components of the velocity shear and the Reynolds stress penetrated upwards very fast from the bottom boundary layer to the whole water column in spring, while in summer they only penetrated to the bottom of the pycnocline with a relatively slow propagation speed. In summer, the TKE production within the pycnocline was comparable with and sometimes larger than that in the well-mixed bottom layer under the pycnocline. Considering the associated high velocity shear, it is speculated that the mixing in the pycnocline is a result of the local velocity shear.

Convection:a neglected pathway for downward transfer of wind energy in the oceanic mixed layer

Upper-ocean turbulent mixing plays a vital role in mediating air-sea fluxes and determining mixed-layer properties, but its energy source, especially that near the base of the mixed layer, remains unclear. Here we report a potentially significant yet rarely discussed pathway to turbulent mixing in the convective mixed layer. During convection, as surface fluid drops rapidly in the form of convective plumes, intense turbulence kinetic energy(TKE) generated via surface processes such as wave breaking is advected downward, enhancing TKE and mixing through the layer. The related power, when integrated over the global ocean except near the surface where the direct effect of breaking waves dominates, is estimated at O(1)TW, comparable to that required by maintaining the Meridional Overturning Circulation(MOC). The mechanism in question therefore deserves greater research attention, especially in view of the potential significance of its proper representation in climate models.

Large eddy simulation of the rotation effect on the ocean turbulence kinetic energy budget in the surface mixed layer

A non-hydrostatic, Boussinesq, and three-dimensional large eddy simulation(LES) model was used to study the impact of the Earth's rotation on turbulence and the redistribution of energy in turbulence kinetic energy(TKE) budget. A set of numerical simulations was conducted,(1) with and without rotation,(2) at different latitudes(10°N, 30°N, 45°N, 60°N, and 80°N),(3) with wave breaking and with Langmuir circulation, and(4) under different wind speeds(5, 10, 20, and 30 m/s). The results show that eddy viscosity decreases when rotation is included, indicating that rotation weakens the turbulence strength. The TKE budget become tight with rotation and the effects of rotation grow with latitude. However, rotation become less important under Langmuir circulation since the transport term is strong in the vertical direction. Finally, simulations were conducted based on field data from the Boundary Layer and Air-Sea Transfer Low Wind(CBLAST-Low) experiment. The results, although more complex, are consistent with the results obtained from earlier simulations using ideal numerical conditions.

大包长水口浸入深度对三角形四流中间包钢水质量的影响

为了研究长水口浸入深度对钢水流动和钢水质量的影响,在等比例中间包水模中完成了物理和数学模拟。在等比例中间包水模中,在各种不同水口浸入深度条件下,完成了卷渣试验。采用聚乙烯玻璃粉(920 Kg/m^3)模拟炉渣相,并且在换包过程中搜集每个浸入深度条件下,借助卷渣说明其相对性能。开发了一个三维数学模型、并且在各种不同大包长水口浸入深度条件下,检测湍流等高线(湍流动能(TKE)等高线)。当浸入深度位置较低时,中间包内的湍流现象较为严重,结果导致更多的卷渣。与之相反,当浸入深度位置较高时,中间包内的湍流现象较轻,由此产生的卷渣数量也较少。因此,采用长水口浸入位置较高的中间包操作可能取消湍流抑制器的使用,并降低耐火材料的消耗和成本。

Flow structure and shear stress in the presence of both ice cover on water surface and leafless vegetation in channel bed

This study aimed to investigate the previously unexplored effects of ice cover and submerged vegetation on flow structure.Experiments were undertaken under both open channel and ice-covered flow conditions.The bed material consisted of three non-uniform sands.The findings revealed that when vegetation patches were present on the bed and an ice cover was present,the velocity profiles exhibited a distinctive pattern with two peak values.Turbulent kinetic energy(TKE)also exhibited two peaks,one above the vegetation bending height and another at the sheath section,with a decreasing trend towards the ice cover.Furthermore,quadrant analysis showed that when the flow surface is covered by an ice cover,the contributions of inward and outward events increased compared with those observed in an open channel flow.In most cases,these contributions surpassed the sweep and ejection events.The findings enhance our understanding of vegetation’s response to diverse surface conditions and have practical implications for river management and environmental engineering.

Prediction of bedload transport inside vegetation canopies with natural morphology

Due to vegetation drag and vegetation-generated turbulence,bedload transport in vegetated channels is more complicated than that in nonvegetated channels.It is challenging to obtain accurate predictions of bedload transport in vegetated channels.Previous studies generally used rigid circular cylinders to simulate vegetation,and the impact of plant morphology on bedload transport was typically ignored;these methods deviate from natural scenarios,resulting in prediction errors in transport rates of more than an order of magnitude.This study measured bedload transport rates inside P.australis,A.calamus and T.latifolia canopies and in arrays of rigid cylinders for comparison.The impact of plant morphology on bedload transport in vegetated channels was examined.Inside the canopies of natural morphology,the primary factor driving bedload transport is the near-bed turbulent kinetic energy(TKE),which consists of both bed-generated and vegetation-generated turbulence.A method was proposed to predict the near-bed TKE inside canopies with natural morphology.For the same solid volume fraction of plants,the transport rate inside canopies with a natural morphology is greater than or equal to that within an array of rigid cylinders,depending on the plant shape.This finding indicates that plant morphology has a significant impact on transport rates in vegetated regions and cannot be ignored,which is typical in practice.Four classic bedload transport equations(the Meyer-Peter-Müller,Einstein,Engelund and Dou equations),which are suitable for bare channels(no vegetation),were modified in terms of the near-bed TKE.The predicted near-bed TKE was inserted into these four equations to predict the transport rate in canopies with natural morphology.A comparison of the predictions indicated that the Meyer-Peter-Müller equation had the highest accuracy in predicting the transport rate in vegetated landscapes.

Research on blade tip clearance cavitation and turbulent kinetic energy characteristics of axial flow pump based on the partially-averaged Navier-Stokes model

To reveal the cavitation forms of tip leakage vortex(TLV)of the axial flow pump and the flow mechanism of the flow field,this research adopts the partially-averaged Navier-Stokes(PANS)model to simulate the cavitation values of an axial flow pump,followed by experimental validation.The experimental result shows that compared with the shear stress transport(SST)k-ωmodel,the PANS model significantly reduces the eddy viscosity of the flow field to make the vortex structure clearer and allow the turbulence scale to be more robustly analyzed.The cavitation area within the axial flow pump mainly comprises of TLV cavitation,clearance cavitation and tip leakage flows combined effect of triangular cloud cavitation formed.The formation and development of cavitation are accompanied by the formation and evolution of vortex,and variations in vortex structure also generate and promote the development of cavitation.In addition,an in-depth analysis of the relationship between the turbulent kinetic energy(TKE)transport equation and cavitation patterns was also conducted,finding that the regions with relatively high TKE are mainly distributed around gas/liquid boundaries with serious cavitation and evident gas-liquid change.This phenomenon is mainly attributed to the combined effect of the pressure action term,stress diffusion term and TKE production term.

Flow hydrodynamics drive effective fish attraction behaviour into slotted fishway entrances

Effective fishways rely on attracting fish,utilising the natural rheotactic behaviour of fish to orient into an attraction flow near the entrance.Despite the critical importance of attraction,understanding of the hydrodynamics of vertical slot entrances in relation to fish behaviour remains poor.Herein,hydrodynamic measurements of flows at slotted fishway entrances were experimented with two different designs,two velocities,three water depths,and two fish species,silver perch(Bidyanus bidyanus)and Australian bass(Percalates novemaculeata).Fish behaviours were tracked in relation to hydrodynamic measures of three-dimensional velocity and turbulent kinetic energy(TKE).There were distinct differences in the attraction flow between entrance designs,irrespective of velocity and water depth.A plain slotted entrance produced a more symmetric flow in the centre of the flume,causing fish to approach the entrance by skirting the core of the attraction jet flow and areas of high turbulence.In contrast,streamlined slotted entrance design resulted in an asymmetric attraction flow which guided fish along the wingwall towards the slotted entrance,improving attraction for both species.There were clear patterns in swimming trajectories for silver perch,swimming along the sidewalls of the observation zone towards the entrance,but Australian bass were less predictable,using random routes on their way to the slotted entrance.Both species preferred areas of low turbulence(TKE<0.02 m^(2)/s^(2)).This work has important implications for design of vertical slotted entrance systems.

Structures of convection and turbulent kinetic energy in boundary layer over the southeastern edge of the Tibetan Plateau

Based on a comprehensive analysis on Sonic Anemometer and gradient data, wind profile radar(WPR) and GPS sounding data of March–August 2008 from the boundary layer(BL) tower observation system at Dali on the southeastern edge of Tibetan Plateau(TP), it is found that the strengths of turbulent kinetic energy(TKE), buoyancy term and shear term depend on vegetation cover in association with local stability and thermodynamic condition. Strong kinetic turbulence appears when near surface layer in neutral condition with the large contribution from shear term. In an unstable condition within near surface layer, the atmospheric turbulent motion is mainly thermal turbulence, as buoyancy term is obviously larger than shear term. Under a stable condition the intermittent turbulence is accompanied by weak shear and buoyancy term, and TKE is significantly less than neutral or instable condition. The study also presents that the buoyancy term contribution at Nyingchi station in the southern slopes of the TP large topography in spring is significantly larger than that at Dali over the southeastern TP edge, reflecting that the thermal turbulence makes an important contribution to convection activity in the southern slopes of TP. Dali station is located in complex terrain with mountain and valley leading to larger kinetic turbulence. From the perspective of interaction of turbulence-convection in different scales, the study revealed that the height of convective boundary layer(CBL) could reach up to 1500–2000 m. TKE, shear term, and buoyancy term in near surface layer have the notable correlations with BL height and local vertical motion. The daytime thermodynamic turbulence effect of heat flux and buoyancy term has an obvious impact on the height of CBL, whereas mechanical turbulence only exerts a less impact. Mechanical turbulence in near surface layer has a significant impact on vertical motion especially in the forenoon with impacting height of 2500–3000 m. The peaks in diurnal variations of shear term and buoyancy term correspond to the high instable periods, especially in summer forenoon. Our observation analysis characterized the convection activity triggered by TKE source and their interaction in the southeastern TP edge.

刚性非浸没式植被对弯道水流特性的影响

该文采用180°U形矩形截面弯道玻璃水槽模拟天然弯道河流,运用声学多普勒流速仪(acoustic doppler velocimeter,ADV)研究刚性非浸没式植被(密度4.47%)对弯道水流纵向流速分布,横向环流及湍流动能(turbulence kinetic energy,TKE)的影响。实验结果表明,当水槽流量较小时,植被对水流的阻碍作用较小,由流速降低而导致的水深增加现象不明显,当水槽流量增大时候,植被对水位的抬升现象明显;水流受植被"阻滞"作用,弯道处纵向流速沿水深分布不再服从"对数型"分布规律,且原本水流受弯道作用后呈现的"上减下增"效果也消失;植被加快了最大流速区向凸岸转移,到达弯道出口时,最大流速区逐渐转移至断面中部区域;在植被的影响下,各断面弯道环流消失;植被会加剧水流紊动效应,导致湍动加剧,TKE增大。上述实验结论将增进研究者对植被对弯道水流特性影响的理解,同时也为泥沙疏浚,河道生态系统恢复提供指导。

Innovative configuration of vertical slot fishway to enhance fish swimming conditions

A vertical slot fishway(VSF)is among the most effective and commonly used fishway structures to enable fish to pass through artificial barriers such as dams and weirs in the river.Nevertheless,such structures need further improvements in providing better swimming conditions for fish inside the pool and enhancing attraction at the entrance.Therefore,the main objective of this study was to investigate the influence of slope and whether integrating some cylinder structures inside the fishway could enhance further attraction and provide better swimming conditions for fish.This study consists of several numerical simulations,first considering the fishway without cylinder elements while testing three different slopes under two different discharges.Then,the same numerical simulations were conducted,considering cylinder elements of different diameters and arrangements inside the fishway.The numerical model was validated by comparing computed velocities with those measured experimentally from the literature.The results show that the maximum velocity and turbulent kinetic energy(TKE)in the main jet increase as the discharge increases on the same slope.The flow velocity and TKE decrease in the areas inside the pool and between the two baffles.Introducing cylinder elements inside the fishway reduces the principal flow’s maximum velocity.Also,inside the pool,low-velocity regions were expanding.A comparison between the design with a cylinder and the simple VSF indicates that the presence of a cylinder reduced the maximum velocities for the smallest and highest slopes by 6.21%and 9.86%on average,respectively.However,in terms of TKE,cylinders inside the fishway could provide better performance than simple VSF,mainly for low-flow conditions.Finally,this study’s solution-oriented findings provide insights that could help design cost-effective fishways by improving particularly fish attraction to the fishway.

Diurnal evolution of the barrier layer and its local feedback in the central Taiwan Strait

Diurnal evolution of the barrier layer (BL) and its local feedback features in the central Taiwan Strait (119.2oE,24.3oN) during summertime monsoon are investigated using in situ moored observations conducted by the "Yan-Ping 2" research vessel in late June 2005.During the initiation phase,for the non-solar radiation tends to be trapped in the upper mixed layer,whereas the solar radiation can penetrate deeply through the mixed layer approaching the thermocline,most heat is accumulated inside the BL inducing an inverse-thermal layer.Along with heat convergence inside the BL,thermal exchange increases between the BL and the overlaying mixed layer and finally,a prominently warming mixed layer is formed.Moreover,the BL is associated with a buoyancy frequency minimum with mild stability.Further analysis reveals that the BL's local feedbacks can be divided into two aspects,on one hand,the BL can generate dramatic changes in the local sensible and latent heat fluxes;on the other hand,the sub-halocline and the thermocline serve as two interfaces during the downward transmission of the wind stirring turbulent kinetic energy (TKE) and as a result,most TKE is retarded by the shallow halocline and being trapped above the upper mixed layer,while the residual pierced through the base of the mixed layer is likewise blocked by the thermocline.

Computational study of bubbly jets in stagnant water

The air-water bubbly jets in a stagnant water are numerically investigated by using a CFD software package with the realizable k-e turbulence model.The focus is on the jet evolutionary behaviors in terms of the gas void fraction,the axial water velocity,the turbulent kinetic energy(TKE),the entrainment coefficient,and the momentum and buoyancy fluxes in a wide range of the bubbly jets(with the initial gas volume fractions ranging from 0 to 0.83).The computational results are found generally in good agreement with the experimental results reported in the literature.Both the gas void fraction and the axial water velocity follow the Gaussian distribution in the radial direction as expected,however a double-peak distribution is found for the TKE at some distance away from the nozzle.With the increase of the longitudinal distance,their peak values generally are decreased until reaching approximately their terminal values.The non-dimensional relations are revealed in both the radial and longitudinal directions.The potential core and the spreading rates of the bubbly jets are then investigated.The liquid volume flux of the bubbly jets is found to increase almost linearly along the centerline with an entrainment coefficient of 0.037-0.065.The momentum flux of the bubbly jets increases due to the buoyancy force,and the relative importance of the momentum and buoyancy fluxes is also discussed.