干/湿纺制初生中空纤维膜数学模型的数值模拟

In an effort to find the effect of mass transfer ,surface tesion and drag forces on the velocity distribution,the mathematical model of the velocity profile of a nascent hollow fiber during membrane formation in the air gap region was numerically simulated by using the Runge-Kutta method (fourth-order method).The effect of mass transfer on velocity distribution based on the complicated function(G(Ch^s))was presented and the dffects of a complicated function were studied in two cases:in the first case,G(Ch^s) was constant;in the second,G(Ch^s) was variable.The latter was done by varying with the concentration of solvent in a nascent hollow fiber through the air-gap region.One empirical equation was used to describe this change and the predected values had a better agreement with the experimental values.To verify the moedl hypotheses,hollow fiber membranes were spun from 20:80 polybenzimidazole/polyetherimide dopes with 25.6 wt％ solid in N,N-dimethylacetamide (DMAc) using water as the external and internal coagulants.Based on the experimental results of dry-jet wet-spinning process for the fabrication of hollow fiber membranes,it is found that the model calculated values were in a good agreement with the experimental values.     

Controlling traffic jams on a two-lane road using delayed-feedback signals

This paper focuses mainly on the stability analysis of two-lane traffic flow with lateral friction, which may be caused by irregular driving behavior or poorly visible road markings, and also attempts to reveal the formation mechanism of traffic jams. Firstly, a two-lane optimal velocity (OV) model without control signals is proposed and its stability condition is obtained from the viewpoint of control theory. Then delayed-feedback control signals composed of distance headway information from both lanes are added to each vehicle and a vehicular control system is designed to suppress the traffic jams. Lane change behaviors are also incorporated into the two-lane OV model and the corresponding information about distance headway and feedback signals is revised. Finally, the results of numerical experiments are shown to verify that when the stability condition is not met, the position disturbances and resulting lane change behaviors do indeed deteriorate traffic performance and cause serious traffic jams. However, once the proper delayed-feedback control signals are implemented, the traffic jams can be suppressed efficiently.     

Numerical analysis on car-following traffic flow models with delay time

INTRODUCTION For the past few decades, many researchers have made studies of modelling driver behavior to repro- duce the observed features of traffic flow. Recently Kerner and Rehborn (1997) observed that there are three distinct dynamic phases on highways: free traf- fic flow, coexisting traffic flow and traffic jams. The occurrence of traffic jams without obvious reasons had been explained in terms of the conventional phase transition (Nagatani, 1998). Various traffic flow models, suc…     

Dynamics in Two Periodically Driven and Weakly Coupled Bose-Einstein Condensates

In this paper, dynamics in the oscillations of the relative atomic population in two periodically driven and weakly coupled Bose-Einstein eondensates (BECs) was qualitatively studied. Using the well-known Melnikov method, the conditions of existence of the periodic and chaotic coherent atomic tunnellings were given in the model. Our results indicate the typical route from bifurcation of the limited circles to chaos, and are in agreement with the previous numerical results.     

Quasi-Bayesian software reliability model with small samples

In traditional Bayesian software reliability models, it was assume that all probabilities are precise. In practical applications the parameters of the probability distributions are often under uncertainty due to strong dependence on subjective information of experts’ judgments on sparse statistical data. In this paper, a quasi-Bayesian software reliability model using interval-valued probabilities to clearly quantify experts’ prior beliefs on possible intervals of the parameters of the probability distributions is presented. The model integrates experts’ judgments with statistical data to obtain more convincible assessments of software reliability with small samples. For some actual data sets, the presented model yields better predictions than the Jelinski-Moranda (JM) model using maximum likelihood (ML). Project supported by the National High-Technology Research and Development Program of China (Grant Nos.2006AA01Z187, 2007AA040605)     

δ-映射算法及其在非一致道路条件交通流问题中的应用

1　Introduction　Inhomogenetiesintrafficrefertothosefactorsre sultingfromthechangeintrafficflowvolumes ,suchasthechangeinthenumberoflanes ,thedegradationofroads,andthedisturbanceatazebracrossingoratollstation ,etc .Theconsiderationoftheinhomo geneitiesgivesrisetospatiallyvaryingfluxintrafficcontinuummodels ,whichareusuallynon strictlyhy perbolicandhavenotbeenwellunderstoodmathemat ically .Therelatedstudiesinliteraturewerefewandthebehaviorandtheinfluenceoftheseinhomo geneitieswerenotclearenough…     

A matrix padé-type-routh model reduction method for multivariable linear systems

In the present paper, the formulae for matrix Padé-type approximation were improved. The mixed model reduction method of matrix Padé-type-Routh for the multivariable linear systems was presented. A well-known example was given to illustrate that the mixed method is efficient. Project supported by National Natural Science Foundation of China (Grant No. 10271074)     

Simulation of sludge blanket height in clarifiers

Sludge blanket height (SBH) is an important parameter in the clarifier design, operation and control. Based on an overview and classification of SBH algorithms, a modified SBH algorithm is proposed by incorporating a threshold concentration limit into a relative concentration sharp change algorithm to eliminate the disturbance of compression interfaces on the correct simulation of SBH. Pilot-scale test data are adopted to compare reliability of three SBH algorithms reported in literature and the modified SBH algorithm developed in this paper. Calculated results demonstrate that the three SBH algorithms give results with large deviation (> 50%) from measured SBH, especially under low solid flux conditions. The modified algorithm is computationally efficient and reliable in matching the measured data. It is incorporated into a one-dimensional clarifier model for stable simulation of pilot-scale experimental clarifier data and into dynamic simulation of a full-scale wastewater treatment plant (WWTP) clarifier data. Project supported by the National Natural Science Foundation of China (Grant No.501380107)     

流体动力润滑的紊流理论模式

1　IntroductionItiswellknownthatfluidflowsinsealsandbear ingsturnfromlaminarregimeintoturbulentonewhentheirReynoldsnumberbecomeshigherthanacriticalvalue .Theearliesttheoriesofhydrodynamiclubricationhavebeenbasedonthepresumptionofex istenceoflaminarflowregime .Inturbulentregime ,however ,thecharacteristicsofsealsandbearingsdif ferfromthepredictionsbytheoriessobased .Speciallubricationtheoriesbasedoncontemporaryturbulencemodelssincethelaterhalfof 190 0’swerethereforedevelopedtotaketheeffectsof…     

用改进的元胞自动化模型模拟不同信号灯控制策略下的交通流(英文)

1Introduction Recently,more attention has been paid to urbantraffic,especially the traffic flow controlled by trafficlights.Traffic light control strategy is crucial for i m-proving the efficiency of urbantransportation network.The cellular automaton(CA)m…     

用改进的元胞自动化模型模拟不同信号灯控制策略下的交通流

Traffic flows controlled by traffic light strategies were investigated via a cellular automaton model with anticipation, which is suitable for describing urban traffic. Three kinds of strategies, i. e., synchronized, green-wave and random switching lights, were designed, simulated and compared with each other. It is shown that the green-wave strategy is only valid at lower density and there is not an effective way with the three strategies to improve the efficiency of traffic flow at high density.     

Polynomial-time interior-point algorithm based on a local self-concordant finite barrier function

The choice of self-concordant functions is the key to efficient algorithms for linear and quadratic convex optimizations, which provide a method with polynomial-time iterations to solve linear and quadratic convex optimization problems. The parameters of a self-concordant barrier function can be used to compute the complexity bound of the proposed algorithm. In this paper, it is proved that the finite barrier function is a local self-concordant barrier function. By deriving the local values of parameters of this barrier function, the desired complexity bound of an interior-point algorithm based on this local self-concordant function for linear optimization problem is obtained. The bound matches the best known bound for small-update methods. Project supported by the National Natural Science Foundation of China (Grant No.10771133), the Shanghai Leading Academic Discipline Project (Grant No.S30101), and the Research Foundation for the Doctoral Program of Higher Education (Grant No.200802800010)     

Application of uncertainty reasoning based on cloud model in time series prediction

Time series prediction has been successfully used in several application areas, such as meteorological forecasting, market prediction, network traffic forecasting, etc., and a number of techniques have been developed for modeling and predicting time series. In the traditional exponential smoothing method, a fixed weight is assigned to data history, and the trend changes of time series are ignored. In this paper, an uncertainty reasoning method, based on cloud model, is employed in time series prediction, which uses cloud logic controller to adjust the smoothing coefficient of the simple exponential smoothing method dynamically to fit the current trend of the time series. The validity of this solution was proved by experiments on various data sets. Project (No. 2001AA112030) supported by the National Hi-Tech Development Program (863) of China     

NDMP-Plus： An Improved Protocol for Network Based Data Management

Network based data management is the backup/restore mechanism used in a data storage center. This paper presents a new network based data management-NDMP-Plus, a revision of network data management protocol. Components and the working mechanism of the NDMP-Plus architecture are first discussed. Two new techniques in NDMP-Plus-virtual storage layer （VSL） and negotiation mechanism are then studied. VSL is a crucial component to achieve flexibility, and the negotiation mechanism is a key to improve performance. Furthermore, experiments are carried out to evaluate the performance of NDMP-Plus. The result suggests that NDMP-Plus has stronger flexibility and better performance than NDMP.     

基于更新论证法考虑负索赔的一类与时间相关的风险模型的罚金折现期望函数

In this paper,the expected discounted penalty function is considered in the risk process with the time-correlated claims,that is,every main claim can cause a by-claim but the occurrence of the by-claim may be delayed.By the renewal argument,it is shown that the expected value satisfies a system of integro-differential equations.Moreover,the explicit expression for the Laplace transform of the expected value is derived by means of Rouchés theorem.A numerical example is     

公交线路发车间隔优化的双层规划模型与算法

针对发车间隔这一公交车辆调度中需要考虑的关键因素,提出了一种优化线路发车间隔的双层规划模型.该模型从公交公司和乘客两者利益出发,上层模型以最小化公交系统中因发车频率设置而产生的时间和经济总成本为目标;下层模型是公交客流分配模型,用来描述发车间隔优化后的客流分配情况.设计了一种混合遗传算法,即模拟退火遗传算法,来求解模型.最后,以常州市某几条线路为例,利用公交数据对模型和算法进行了检测.结果表明：所提出的线路发车间隔优化模型体现了公交供需关系是合理的,而且求解算法是有效的.     

Analysis of Network Traffic with Extreme Value Theory

Withincreasingdemandofwidebandwidthservicesuchasmultimediaandvideo ,itisverydesirabletore searchondifferenttransporttechniquesforhigh speednetworks.Congestioncontrol,bandwidthassignment ,networkmanagementand performanceevaluationaresomeexamplesthathavebeenresearchedwidely .Asthefoundationoftheseresearchfields ,itisthemostessentialtobuildamodelthatcanaccuratelycharacterizerealnet worktraffic .Hence ,itisalsonecessarytounderstandandanalyzestatisticalpropertiesofthenetworktrafficbecauseitcanindic…     

Hydrostatic settling velocity of sediments

The settling of sediments is an accelerative process in which the concentration of the main sediments zone will heavily influence settling velocity，but the explicit relationship between the concentration and settling velocity has not been reported in literature. Here a theoretical function was built for the time dependent concentration and time dependent settling velocity of sediments；then the entire settling process reflecting concentration was shown on the basis of sediments instant-settlement theory and mathematical method. Agreement of computed results and experimental data was found. Several governing parameters，including particle size，particle density，initial suspended sediments concentration and suspension height，were discussed with a series of calculated velocity curves. The research indicated that ⑴ the presented concentration-velocity time relationship is rational，⑵ settling process of the sediments group with variation of concentration consists of acceleration stage，uniform motion stage and deceleration stage，and ⑶ particle size，particle density and initial suspended sediments concentration have more influence on the settling velocity than the suspension height and water temperature.     

行人最大速度对行人流影响的研究

应用改进的格子气模型(即将行人的最大速度扩展到大于1)研究行人的最大速度对过道中单向和双向行人流的影响。模拟结果显示:最大速度为5时所对应基本图的临界密度跟实验值比较符合,说明该扩展是必要的;在一定范围内随着行人最大速度的增大道路的整体通行能力增强同时临界密度减小;双向行人流的时空斑图显示行人最大速度的增大加快了拥堵的形成过程(即缩短了行人从局部拥堵演化为完全拥堵的时间)。     

Optimal velocity functions for car-following models

The integral part of the optimal velocity car-following models is the optimal velocity function （OVF）, which can be derived from measured velocity-spacing data. This paper discusses several characteristics of the OVF and presents regression analysis on two classical datasets, the Lincoln and Holland tunnels, with different possible OVFs. The numerical simulation of the formation of traffic congestion is conducted with three different heuristic OVFs, demonstrating that these functions give results similar to those of the famous Bando OVF （Bando et al., 1995）. Also an alternative method is present for determining the sensitivity and model parameters based on a single car driving to a fixed barrier.