Fractional alpha stable network traffic model and its application in QoS routing

It is not a simple and trivial work to set up an appropriate network traffic model. A fractional Alpha model is proposed in this paper and two proofs based on flow and session level, respectively, are given. Based on this model, the lower bound for the residual of the queueing distribution is deduced. Comparing the residual distribution function (RDF) based on our model with it based on other models, we find our formula matches the real RDF better. Based on this formula, we can predict the need for forwarding performance. Then a novel QoS routing algorithm based on this prediction is proposed. Last we demonstrate a simple example to denote how our algorithm can effectively improve the utility of bandwidth and amount of traffic and guarantee QoS.     

Repair evaluation of concrete cracks using surface and through-transmission wave measurements

Surface opening cracks are common defects in large civil structures like bridges. They allow penetration of water or other agents that result in loss of durability earlier than expected. Their repair can be conducted by the injection of epoxy material that seals the crack sides keeping out any aggressive substances in addition to the recovery of strength. In order to evaluate crack parameters before impregnation as well as to determine the final repair effectiveness, a combination of Rayleigh and longitudinal waves is applied. Rayleigh waves demonstrate the filling condition of the material into the shallow layer near the surface while tomography using longitudinal waves through the thickness yields information about the area inside the structure. Wave propagation dispersion features are exploited by the proposed tomography at different frequencies, demonstrating that higher frequencies lead to more accurate characterization.     

On the behaviour of hygroscopic wheels: Part I – channel modelling

In this paper a detailed mathematical formulation is developed for the numerical modelling of the behaviour of a channel of a hygroscopic compact matrix. A comparison between the detailed version and a simplified one is performed considering a two-dimensional airflow between desiccant parallel plates. The distinct heat and mass transfer phenomena are strongly coupled, and some properties of the airflow and of the desiccant medium exhibit important changes during the sorption processes. Both physical models take into account the gas side and solid side resistances to heat and mass transfer. The wall domain is treated similarly in both models, by taking into account the simultaneous heat and mass transfer together with the water adsorption/desorption process. Two phases co-exist in equilibrium inside the desiccant porous medium, the equilibrium being characterized by sorption isotherms without hysteresis. The detailed model is based on the solution of the differential equations for the conservation of mass, energy and momentum, assuming that no momentum transport exists in the porous wall domain. In the simplified model, the airflow is treated as a bulk flow, the interaction with the wall being evaluated by using appropriated convective coefficients.Both models are compared in the simulation of a parallel plate channel during an adsorption process. The results show a good agreement for channel lengths greater than 0.1 m. In part II of the paper, the simplified model is adapted to the simulation of the three-dimensional problem in the channel of a hygroscopic rotor, and it is used to perform parametric studies.     

Public key distribution scheme for delay tolerant networks based on two-channel cryptography

A delay tolerant network (DTN) is a store carry and forward network characterized by highly mobile nodes, intermittent connectivity with frequent disruptions, limited radio range and physical obstructions. Emerging applications of DTN include rural DTN, vehicular DTN and pocket DTN. The development of DTN raises a number of security-related challenges due to inconsistent network access and unreliable end-to-end network path. One of the challenges is initial secure context establishment as it is unrealistic to assume that public key infrastructure (PKI) is always globally present and available, hence, the public key management becomes an open problem for DTN. In this paper, for the first time, we propose a dynamic virtual digraph (DVD) model for public key distribution study by extending graph theory and then present a public key distribution scheme for pocket DTN based on two-channel cryptography. By distinguishing between owners and carriers, public key exchange and authentication issues in the decentralized pocket DTN environment can be solved by a two-channel cryptography process and our simulation results have proven it.     

Location-Dependent Lane-Changing Behavior for Arterial Road Traffic

Lane-changing behavior plays an important role in characterizing urban arterial road traffic dynamics. This paper investigates efficiency-driven and objective-driven motives for drivers to change lanes on arterial roads. The former motive is determined by the circumstances of the surrounding traffic flow, whereas the latter depends on position. A location-dependent lane changing model is then established by weighing the two motives for lane changing. Both continuous and discrete versions of the arterial traffic model are obtained using the LWR (Lighthill–Whitham–Richards) model with the two types of lane changing. Simulations show that the proposed model can reproduce macroscopic traffic phenomena such as spillover and a decrease in the concomitant departure flow, which is the reason for capacity loss. It is concluded that 1) there exists a critical condition under which there is no capacity loss and that 2) a different flow composition could result in a different capacity loss, which varies according to the flow direction. Hence, traffic management and control should take this loss into account.     

混合交通下右转机动车信号配时方法

为了减少右转机动车与直行自行车之间的干扰,提高交叉口的运行效率,本文分析了两相位信号控制交叉口右转机动车与自行车之间的冲突规律以及自行车交通流的行驶特性,确定设置右转机动车信号的直行自行车流量临界值.以减少冲突和提高交叉口运行效率为目标,确定右转机动车相位绿灯起亮时刻和绿灯时长,并建立了相应的参数标定模型.以实际调查数据为基础,应用VISSIM模拟软件进行模拟验证,结果表明,设置右转机动车信号后,右转机动车延误和机非冲突明显减少.     

Set methods of left-turn waiting zone at signalized intersection

To maximize the number of vehicles passing by the stop-line in a cycle and improve the operation efficiency of intersection in China,the settlement of left-turn lane waiting-zone is becoming prevailing. Based on conflicting-point method,the internal mechanism of left-turn flow after stopping line was analyzed through taking postposition left-turn lane waiting-zone intersection for instance. The relationship between the first left-turn vehicle and the last vehicle of previous phase passing the conflicting point was expounded. According to the time of successive arriving of two vehicle flows at conflicting-point,the reasonable layout for waiting area of left-turn vehicles was researched when the clearance index was less than 0. The results suggest that the appropriate layout for waiting area of left-turning vehicles can improve the operation efficiency of intersections.     

Research and Application of Dynamic Equation for Full Frontal Impact

Full frontal impact theory needs researching and exploring to satisfy the primary safety design of occupant restraint system,avoiding the increasingly "engineering"trend in order to develop and design safety vehicle. After occupant restraint system is simulated by using linear elastic stiffness k,the occupant-vehicle frontal rigid barrier impact model is established. Dynamic equation of dummy chest coupling vehicle is built for full frontal impact based on ordinary vehicle deceleration by Hooke law,and the equation is solved by comparing coefficient and satisfying boundary qualifications. While relative vehicle characteristic parameters are kept unchanging,the actual vehicle deceleration is fitted to the simplified equivalent square wave( ESW),tipped equivalent square wave( TESW) and equivalent dual trapezoids wave( EDTW). Phase angle  and amplitude A of dynamic equations based on ESW,TESW and EDTW are calculated and deduced. The results show that: the dynamic equation of dummy chest coupling vehicle can be well utilized to instruct the primary safety design of full frontal impact for objective vehicle to satisfy chest deceleration demands and the equation based on TESW is best for this design.     

GEE type inference for clustered zero-inflated negative binomial regression with application to dental caries

Use of zero-inflated count data models is common in applications where the number of zero counts exceeds that predicted from a traditional count data model such as Poisson or negative binomial. When count data exhibiting inflated zero counts are correlated among subjects, a natural approach will be to fit a marginal model with the help of generalized estimating equations (GEE) that can incorporate subject-to-subject correlations. A GEE based zero-inflated negative binomial (ZINB) model is proposed to fit clustered counts with excessive zeros. However, the corresponding sandwich variance estimator appears to underestimate the true variance. The theoretical reasons for its failure are explained and a correction under additional modeling assumptions is offered. In addition, a clustered resampling (bootstrap) procedure is proposed to estimate the variance and it is shown that the bootstrap procedure captures the correct variance under no additional model assumptions. Utility of this marginal GEE based ZINB model over two other competing models has been assessed using a thorough simulation study. The resulting inference procedure is applied to study the association between the dental caries and fluoride exposures using a dataset extracted from the Iowa Fluoride Study. A number of risk factors of clinical significance are reliably identified using the proposed model.     

Real-time congestion prediction for urban arterials using adaptive data-driven methods

Multimedia Tools and Applications - Congestion prediction can support traffic departments to take effective traffic management measures, and it aids users to adopt smarter trip strategies,...