广东前汛期强对流天气分类流型及物理量阈值

本文利用常规高空、地面和自动站观测资料,对2004-2013年广东前汛期分类强对流天气的影响系统及其位置和动态的详细分析和比较,归纳总结了不同类型强对流天气与影响系统之间的有机联系和显著区别,结果表明:大范围短时强降水大部分在高空槽影响下伴有纬向型切变线和低空急流,而区域性短时强降水更依赖于地面低槽的发展;大范围混合强对流天气多数与径向型切变线密切相关,低槽发展所带来的不稳定能量积蓄和冷锋的触发易使对流天气更强烈发展。建立了不同类型强对流天气的流型,总结了各流型天气系统特点和简化物理量指标及阈值,为今后广东强对流天气分析和分类预报提供了明确的思路和参考依据。

油水两相水平管流流动特性分类系数研究

基于新的油水两相水平管流流型分类法,提出牛顿流体流动的流型分类系数Zn和牛顿—非牛顿流体流型分类系数Zc。Zn可用来粗略判断表现出牛顿流体性质的油水两相流的流型;Zc则可用来判断油水两相流能否出现非牛顿流体性质的流型。Zn与Zc虽然是在特定条件下只考虑流体流动主要影响因素得出的数值,但能够在一定程度上反应出油水两相水平管流的流型。

基于脱离速度的垂直气液两相管流流型识别

流型是影响垂直气液两相管流流动与传热特性的主要因素,因而流型识别是两相流研究的首要任务。经典模型中,通过折算速度、表面张力和密度来耦合流型转换边界,通过试验数据,以折算速度为轴量,绘制出目前普遍接受的流型图。文中提出一种基于脱离速度大小来识别垂直气液两相管流流型的新方法。该方法的优点在于,以速度为参考标准,更有利于在压力、温度变化的环境中找到两相流运动的规律。文中深入分析了垂直气液两相管流的流动机理,以脱离速度来定义流型转换边界,区分垂直管中的4种常见流态,并与实测数据完全吻合,同时这种理论分析方法也对垂直气液两相管流中的举升效率、共流液体、临界状态和流型本质差别有着更为合理的解释。

基于混沌吸引子形态特性的两相流流型分类方法研究

利用高灵敏度差压传感器,在垂直上升管中采集到了80组气液两相流差压波动信号.利用放置参考截面的方法,建立了描述混沌吸引子形态的一般方法,在此基础上,提出了不同维数下的吸引子形态特征量进行组合的气液两相流流型分类新方法.研究结果表明:该方法对包括复杂过渡流型在内的气液两相流流型有很好分类效果,预示着混沌吸引子形态描述是研究非线性时间序列的实用有效途径.

集输立管内流型分类及流型控制实验研究

根据归一化压差及出口相含率信号特征规律对集输-立管内所发生的流型进行了判别及分类,将流型划分为典型严重段塞流(SS1)、第二类严重段塞流(SS2)、第三类严重段塞流(SS3)、震荡流型(OSC)及稳定流型(STB),并对所观察到的典型严重段塞流(SS1)进行了手动节流、基于立管底部压力的PID控制及基于立管压差的PID控制调节。通过对比消除典型严重段塞流后立管底部压力、立管压差、入口流量波动及调节阀平均开度等参数对三种控制策略的控制效果进行评价得出结论:基于立管压差的PID控制调节效果最好,基于立管底部压力的PID自动控制次之,手动节流控制严重段塞流效果最差。

基于多尺度的气液两相流图像信号质量指数谱分析

针对多重分形质量指数谱曲率和面积的概念,应用分形特征最为典型的LORENZ信号与HENON信号以及Cantor集对两个参数进行验证,结果证明两个参数在探测混沌时间序列复杂性方面是完全有效的。引入了多尺度的分析方法,详细研究了气液两相流图像灰度波动信号在不同尺度频率下的两个参数的变化情况,确定采用尺度5信号进行分析。在不同流型的5尺度灰度波动信号下获得了非线性特征值,通过分类指标和单因素方差分析(ANOVA)检验结果,并同其余文献中应用的混沌吸引子形态周界特征(吸引子面积、长轴、短轴)相对比,发现此特征值对不同流型具有较好的分类效果,且在不同液相流速下随气相速度的增加能够揭示出气液两相流型机理结构变化情况,是一种有效的研究气液两相流的方法。

Clustering algorithm for multiple data streams based on spectral component similarity

A new algorithm for clustering multiple data streams is proposed.The algorithm can effectively cluster data streams which show similar behavior with some unknown time delays.The algorithm uses the autoregressive （AR） modeling technique to measure correlations between data streams.It exploits estimated frequencies spectra to extract the essential features of streams.Each stream is represented as the sum of spectral components and the correlation is measured component-wise.Each spectral component is described by four parameters,namely,amplitude,phase,damping rate and frequency.The ε-lag-correlation between two spectral components is calculated.The algorithm uses such information as similarity measures in clustering data streams.Based on a sliding window model,the algorithm can continuously report the most recent clustering results and adjust the number of clusters.Experiments on real and synthetic streams show that the proposed clustering method has a higher speed and clustering quality than other similar methods.

Evolution of Main Characteristics of the Registered Cotton Cultivars in National Cotton Regional Trials in Yangtze River Valley

[Objective] The aim of this study was to characterize the national regis- tered varieties selected from cotton regional trials in Yangtze River Valley （YaRV） in recent years. [Method] Cotton cultivar classification and comprehensive evaluation index were set up based on national cotton registration standard. GGE biplot method was adopted to analyze the correlation of major breeding target characters of 53 national registered cotton varieties in cotton regional trials in YaRV during 1981-2012. According to the shift of check cultivars in cotton regional trials in the past, the cotton regional trial practice since 1981 was divided into five periods. The dynamic of cultivar type＇s proportion and the evaluation index scores was analyzed across the five periods. [Result] There existed intricate interrelationship among cotton breeding target traits, which constrained it necessary to construct indices for com- prehensive evaluation of cotton varieties. The dynamic of cultivar types in the five periods indicated that type II varieties emerged since Simian 3 period and then its proportion decreased gradually; type Ⅲ varieties maintained a certain proportion in each period and kept on the rise overall; type Ⅳvarieties occupied the majority pro- portion of registered cultivars before 1993, but a minor proportion since Simian 3 period. On the other side, the change trend of the evaluation index demonstrated that the varieties registered before 2003 did not pass the qualified line at present. The peak scores appeared in the varieties registered during 2004-2008. The scores of the varieties registered after 2009 were only slightly over the qualified line. [Conclusion] More attention should be paid to the improvement and evaluation of micronaire, so as to guide the simultaneous development of high yielding and fiber quality in cotton breeding and registration procedure in YaRV.

Investigation of droplet breakup in liquid–liquid dispersions by CFD–PBM simulations：The influence of the surfactant type

The accurate prediction of the droplet size distribution(DSD)in liquid–liquid turbulent dispersions is of fundamental importance in many industrial applications and it requires suitable kernels in the population balance model.When a surfactant is included in liquid–liquid dispersions,the droplet breakup behavior will change as an effect of the reduction of the interfacial tension.Moreover,also the dynamic interfacial tension may be different with respect to the static,due to the fact that the surfactant may be easily desorbed from the droplet surface,generating additional disruptive stresses.In this work,the performance of five breakup kernels from the literature is assessed,to investigate their ability to predict the time evolution of the DSD and of the mean Sauter diameter,when different surfactants are employed.Simulations are performed with the Quadrature Method of Moments for the solution of the population balance model coupled with the two-fluid model implemented in the compressible Two Phase Euler Foam solver of the open-source computational fluid dynamics(CFD)code Open FOAM v.2.2.x.The time evolution of the mean Sauter diameter predicted by these kernels is validated against experimental data for six test cases referring to a stirred tank with different types of surfactants(Tween 20 and PVA 88%)at different concentrations operating under different stirrer rates.Our results show that for the dispersion containing Tween 20 additional stress is generated,the multifractal breakup kernel properly predicts the DSD evolution,whereas two other kernels predict too fast breakup of droplets covered by adsorbed PVA.Kernels derived originally for bubbles completely fail.

Length-Based Vehicle Classification in Multi-lane Traffic Flow

For the realtime classification of moving vehicles in the multi-lane traffic video sequences, a length-based method is proposed. To extract the moving regions of interest, the difference image between the updated background and current frame is obtained by using background subtraction, and then an edge-based shadow removal algorithm is implemented. Moreover, a tbresholding segmentation method for the region detection of moving vehicle based on lo- cation search is developed. At the estimation stage, a registration line is set up in the detection area, then the vehicle length is estimated with the horizontal projection technique as soon as the vehicle leaves the registration line. Lastly, the vehicle is classified according to its length and the classification threshold. The proposed method is different from traditional methods that require complex camera calibrations. It calculates the pixel-based vehicle length by using uncalibrated traffic video sequences at lower computational cost. Furthermore, only one registration line is set up, which has high flexibility. Experimental results of three traffic video sequences show that the classification accuracies for the large and small vehicles are 97.1% and 96.7% respectively, which demonstrates the effectiveness of the proposed method.

Internet Multimedia Traffic Classification from QoS Perspective Using Semi-Supervised Dictionary Learning Models

To address the issue of finegrained classification of Internet multimedia traffic from a Quality of Service(QoS) perspective with a suitable granularity, this paper defines a new set of QoS classes and presents a modified K-Singular Value Decomposition(K-SVD) method for multimedia identification. After analyzing several instances of typical Internet multimedia traffic captured in a campus network, this paper defines a new set of QoS classes according to the difference in downstream/upstream rates and proposes a modified K-SVD method that can automatically search for underlying structural patterns in the QoS characteristic space. We define bagQoS-words as the set of specific QoS local patterns, which can be expressed by core QoS characteristics. After the dictionary is constructed with an excess quantity of bag-QoSwords, Locality Constrained Feature Coding(LCFC) features of QoS classes are extracted. By associating a set of characteristics with a percentage of error, an objective function is formulated. In accordance with the modified K-SVD, Internet multimedia traffic can be classified into a corresponding QoS class with a linear Support Vector Machines(SVM) clas-sifier. Our experimental results demonstrate the feasibility of the proposed classification method.

Membrane redistributions through multi-intercellular exchanges and serial trogocytosis

Trogocytosis is a rapid transfer between cells of membranes and associated proteins. Trogocytic exchanges have been investigated between different cell types, mainly in two-cell systems, involving one donor and one acceptor cell type. Here, we studied trogocytosis in a more complex system, involving not only several immune cell subsets but also multiple tumor cells. We show that CD4~ T cells, CD8＋ T cells and monocytes can acquire membrane patches and the intact proteins they contain from different tumor cells by multiple simultaneous trogocytoses. The trogocytic ca- pabilities of CD4~ and CD8~ T cells were found to be similar, but inferior to that of autologous monocytes. Activated peripheral-blood mononuclear cells （PBMCs） may also exchange membranes between themselves in an all-autolo- gous system. For this reason, monocytes are capable of acquiring membranes from multiple tumor cell sources, and transfer them again to autologous T cells, along with some of their own membranes （serial trogocytosis）. Our data illustrate the extent of membrane exchanges between autologous activated immune effector cells and their environ- ment, and how the cellular content of the local environment, including ＂bystander＂ cells, may impact the functions of immune effector cells.

Building a Tree Adjusted Logistic Classification Model in Biomarker Data Analyses

Researchers in bioinformatics, biostatistics and other related fields seek biomarkers for many purposes, including risk assessment, disease diagnosis and prognosis, which can be formulated as a patient classification. In this paper, a new method of using a tree regression to improve logistic classification model is introduced in biomarker data analysis. The numerical results show that the linear logistic model can be significantly improved by a tree regression on the residuals. Although the classification problem of binary responses is discussed in this research, the idea is easy to extend to the classification of multinomial responses.

Collapse Analysis of Imperfect Subsea Pipelines Based on 2D High-Order Nonlinear Model

To study the collapse of imperfect subsea pipelinos, a 2D high-order nonlinear model is developed. In this model, the large deformation of the pipes is considered by raiaining the high-order nonlinear terms of strain. In addi-tion, the J2 plastic flow theory is adopted to describe the elasioplastic constitutive relations of material. The quasi-static process of collapse is analyzed by the increment method. For each load step, the equations based on the principle of virtual work are presented and solved by the discrete Newton＇s method. Furthermore, finite element simulations and full-scale experiments were preformed to validate the results of the model. Research on the major influencing factors of collapse pressure, including D/t, material type and initial ovality, is also presented.

Analysis of a Class of Symmetric Equilibrium Configurations for a Territorial Model

Motivated by an animal territoriality model,we consider a centroidal Voronoi tessellation algorithm from a dynamical systems perspective.In doing so,we discuss the stability of an aligned equilibrium configuration for a rectangular domain that exhibits interesting symmetry properties.We also demonstrate the procedure for performing a center manifold reduction on the system to extract a set of coordinates which capture the long term dynamics when the system is close to a bifurcation.Bifurcations of the system restricted to the center manifold are then classified and compared to numerical results.Although we analyze a specific set-up,these methods can in principle be applied to any bifurcation point of any equilibrium for any domain.

Static Model Classification Status： Taking Into Account Emerging External Factors

Analysis of the problem of predicting bankruptcy shows that foreign and domestic models included only internal factors of enterprises. But the same indicators of internal factors in the rapidly changing external environment can lead to bankruptcy, and not in others. External factors are the most dangerous, because the possible influence on them is minimal and the impact of their implementation can be devastating. This paper focuses on the same factors to assess the impact of the macroeconomic indicators （extemal factors） on the parameters of static models predicting a local approximation of the crisis at the plant. To accomplish the purpose, a Spark set of 100 companies was compiled, including 50 companies which officially declared bankruptcy in the period of 2000-2009 and 50 stable operating companies with a random sample of the same time period. External factors were extracted from the Joint Economic and Social Data Archive1 The author compared two data sets： （1） microeconomic indicators--money to the total liabilities, retained earnings to total assets, net profit to revenue, Earnings Before Interest and Taxes （EBIT） to assets, net income to equity, net profit to total liabilities, current liabilities to total assets, the totality of short-term and long-term loans to total assets, current assets to current liabilities, assets to revenue, equity to total assets, and current assets to revenue; and （2） external factors--index of real gross domestic product （GDP）, industrial production index, the index of real cash incomes, an index of real investments, consumer price index, the refinancing rate, unemployment rate, the price of electricity, gas prices, oil price, gas price, dollar to ruble, ruble euro Standard ＆ Poor （S＆P） index, the Russian Trading System （RTS） index, and region. The aim of the comparison results paging classes ＂insolvent＂ and ＂non-bankrupt＂ is achieved using two methods： classification and discrimination. In both methods, computational procedures are realized with the use of algorithms linear regression, artificial neural network, and genetic algorithm. In the 2-m model, data set includes both internal and external factors. The results showed that the inclusion of only the microeconomic indicators, excluding external factors, impedes models about two times.

Discrete Boltzmann Method with Maxwell-Type Boundary Condition for Slip Flow

The rarefied effect of gas flow in microchannel is significant and cannot be well described by traditional hydrodynamic models. It has been known that discrete Boltzmann model(DBM) has the potential to investigate flows in a relatively wider range of Knudsen number because of its intrinsic kinetic nature inherited from Boltzmann equation.It is crucial to have a proper kinetic boundary condition for DBM to capture the velocity slip and the flow characteristics in the Knudsen layer. In this paper, we present a DBM combined with Maxwell-type boundary condition model for slip flow. The tangential momentum accommodation coefficient is introduced to implement a gas-surface interaction model.Both the velocity slip and the Knudsen layer under various Knudsen numbers and accommodation coefficients can be well described. Two kinds of slip flows, including Couette flow and Poiseuille flow, are simulated to verify the model.To dynamically compare results from different models, the relation between the definition of Knudsen number in hard sphere model and that in BGK model is clarified.

Examples of Boundary Layers Associated with the Incompressible Navier-Stokes Equations

The author surveys a few examples of boundary layers for which the Prandtl boundary layer theory can be rigorously validated.All of them are associated with the incompressible Navier-Stokes equations for Newtonian fluids equipped with various Dirichlet boundary conditions(specified velocity).These examples include a family of(nonlinear 3D) plane parallel flows,a family of(nonlinear) parallel pipe flows,as well as flows with uniform injection and suction at the boundary.We also identify a key ingredient in establishing the validity of the Prandtl type theory,i.e.,a spectral constraint on the approximate solution to the Navier-Stokes system constructed by combining the inviscid solution and the solution to the Prandtl type system.This is an additional difficulty besides the wellknown issue related to the well-posedness of the Prandtl type system.It seems that the main obstruction to the verification of the spectral constraint condition is the possible separation of boundary layers.A common theme of these examples is the inhibition of separation of boundary layers either via suppressing the velocity normal to the boundary or by injection and suction at the boundary so that the spectral constraint can be verified.A meta theorem is then presented which covers all the cases considered here.