Delays caused by motorized vehicles unable to clear intersections in China： Graphical analysis

In many Chinese cities,motorized vehicles （M-vehicles） move slowly at intersections due to the interference of a large number of non-motorized vehicles （NM-vehicles）.The slow movement makes a part of M-vehicles fail to leave intersections timely after the traffic signal tums red,and thereby conflicts between vehicles from two directions occur.The phenomenon was analyzed graphically by using the cumulative vehicle curve.Delays in three cases were modeled and compared：NM-vehicle priorities and M-vehicle priorities with all-red intervals unable to release all vehicles,and longer all-red intervals ensuring release all vehicles.Marginal delays caused by two illegal behaviors that occasionally happened in mixed traffic intersections were also investigated.It is concluded that increasing the speed of M-vehicles leaving intersections and postponing the entering of NM-vehicles are the keys in mathematics,although they are uneasy in disordered mixed traffic intersections due to a dilemma between efficiency and orders in reality.The results could provide implications for the traffic management in the cities maintaining a large number of M-and NM-vehicles.     

Strategy to control crawling vehicles with automated mechanical transmission

In order to move vehicles with automated mechanical transmission (AMT) a little bit of distance, such as reversing into or moving in a garage, a control strategy for crawling vehicles was proposed. Based on the dynamic analysis of vehicle starting process and requirements of crawl driving for the vehicle,a control strategy of the clutch was designed. The strategy increased the slipping friction torque first and then decreased it, in order to realize the crawl driving. The speed increased by the engagement of the clutch, and then the clutch turned to disengage to the half disengage point, when the speed met the requirements. Based on the control strategy, a control software was designed. In the end, the software was tested on a vehicle with AMT. The lowest steady vehicle speed was reduced to 40% of the original value, which was set in the control strategy.     

Specific energy optimization in sawing of rocks using Taguchi approah简

This work aims at selecting optimal operating variables to obtain the minimum specific energy （SE） in sawing of rocks. A particular granite was sampled and sawn by a fully automated circular diamond sawblades. The peripheral speed, the traverse speed, the cut depth and the flow rate of cooling fluid were selected as the operating variables. Taguchi approach was adopted as a statistical design of experimental technique for optimization studies. The results were evaluated based on the analysis of variance and signal-to-noise ratio （S/N ratio）. Statistically significant operating variables and their percentage contribution to the process were also determined. Additionally, a statistical model was developed to demonstrate the relationship between SE and operating variables using regression analysis and the model was then verified. It was found that the optimal combination of operating variables for minimum SE is the peripheral speed of 25 m/s, the traverse speed of 70 cm/min, the cut depth of 2 cm and the flow rate of cooling fluid of 100 mL/s. The cut depth and traverse speed were statistically determined as the significant operating variables affecting the SE, respectively. Furthermore, the regression model results reveal that the predictive model has a high applicability for practical applications.     

Ribbon model based path tracking method for autonomous ground vehicles

To resolve the path tracking problem of autonomous ground vehicles, an analysis of existing path tracking methods was carried out and an important conclusion was got. The vehicle-road model is crucial for path following. Based on the conclusion, a new vehicle-road model named ＂ribbon model＂ was constructed with consideration of road width and vehicle geometry structure. A new vehicle-road evaluation algorithm was proposed based on this model, and a new path tracking controller including a steering controller and a speed controller was designed. The difficulties of preview distance selection and parameters tuning with speed in the pure following controller are avoided in this controller. To verify the performance of the novel method, simulation and real vehicle experiments were carried out. Experimental results show that the path tracking controller can keep the vehicle in the road running as fast as possible, so it can adjust the control strategy, such as safety, amenity, and rapidity criteria autonomously according to the road situation. This is important for the controller to adapt to different kinds of environments, and can improve the performance of autonomous ground vehicles significantly.     

Spray deposition for making large size billet with swing atomizer

The movement mode of the atomizer is a very important parameter during spray deposition process,which has direct influence on the size and surface texture of the billets. To resolve the problem of manufacturing large size billets,a method of spray deposition by the atomizer with off-center swing was put forward. The atomizer was driven by the alternating current servomotor to swing within 7° at varying speed. The influence of the atomizer parameters,such as translation of the atomizer,swing angle of the atomizer,substrate falling speed and spraying pressure,on the spray deposition was studied. The optimized parameters of the spray deposition process were obtained. The results show that the large size billets with uniform surface quality can be made through adjusting swing frequency and angle of the atomizer,offset distance of the atomizer and inclined angle of the substrate; the valid spray area will decrease and the dimension of top surface will reduce when pressure is less than 0.4 MPa within certain spray distance; meantime,the moving time and cooling time of the droplets are extended,which will lead to loose structure and bad densification. When the pressure,the swing angle and the eccentric offset of the atomization equal 0.5 MPa,7° and 60 mm,respectively,large size billets with fine texture and diameter of 500 mm can be produced.     

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.     

A Model for Capacity Considering the Interference by Pedestrian Traffic at Signal Intersections

The capacity is impacted badly by pedestrians’ violation behavior at signal intersections. In order to quantify the impact, the time-headway and the vehicular speed from start-up to reach the stable saturation flow with and without pedestrian traffic are used as the direct measurements. Using the statistical analysis, the time-headway of saturation flow is mainly affected by the position of pedestrians and the degree of pedestrians’ influence is classified into four levels. Then the speed-time profile for the vehicular acceleration at each level is fitted by Curve Fitting Software. Based on the effect to the time-headway and acceleration time, the model of capacity influenced by pedestrians is established and the influence is quantified, which enriches the fundamental theory of traffic engineering. The result shows that the vehicular capacity can be decreased by 14% at the worst case (level I ). The conclusions obtained in this paper are valuable for better management of the signal intersection.     

Analyzing influence of bicycles on traffic flow using microscopic simulation approach

Mixed traffic consisting of cars and bicycles is a typical pattern of urban traffic in China.To study the impact of bicycles on traffic performance,a microscopic simulating model based on the principle of cautious driving and collision free was proposed.The interaction between cars and bicycles were described by lateral friction and overlapping driving.The dynamical features of speed and time-headway were investigated by numerical simulations.The results show that bicycles have a significant impact on travel speed and time-headway.The effect of bicycles can cause different results in the free flow phase and congestion phase respectively.The results also indicate the necessity to mitigate the interaction between motorized vehicles and non-motorized vehicles.     

A new braking force distribution strategy for electric vehicle based on regenerative braking strength continuity

Regenerative braking was the process of converting the kinetic energy and potential energy, which were stored in the vehicle body when vehicle braked or went downhill, into electrical energy and storing it into battery. The problem on how to distribute braking forces of front wheel and rear wheel for electric vehicles with four-wheel drive was more complex than that for electric vehicles with front-wheel drive or rear-wheel drive. In this work, the frictional braking forces distribution curve of front wheel and rear wheel is determined by optimizing the braking force distribution curve of hydraulic proportional-adjustable valve, and then the safety brake range is obtained correspondingly. A new braking force distribution strategy based on regenerative braking strength continuity is proposed to solve the braking force distribution problem for electric vehicles with four-wheel drive. Highway fuel economy test （HWFET） driving condition is used to provide the speed signals, the braking force equations of front wheel and rear wheel are expressed with linear equations. The feasibility, effectiveness, and practicality of the new braking force distribution strategy based on regenerative braking strength continuity are verified by regenerative braking strength simulation curve and braking force distribution simulation curves of front wheel and rear wheel. The proposed strategy is simple in structure, easy to be implemented and worthy being spread.     

Mechanism analysis on pillar instability induced by micro-disturbance under critical condition

A simplified mechanical model of ultra-high pillar was established and its potential energy expression was derived under axial load on the basis of energy theory. Under critical conditions according to the nonlinear theory, the critical behaviors and the forming mechanism of pillar instability were discussed by external disturbance , such as stresses waves by blasting , axial force eccentricity ratherish and imperfections in pillar. The results show that the micro-disturbances attenuate with time and they are independence each other when pillar is in the stability state. Their effects on the stability of system are inessential. The correlation degree of disturbances increases sharply and various micro-disturbances are relative and nested reciprocally when the system is in critical state and they also cooperate with each other, which induces system to reach a new state.     

Installation position determination of wind speed sensors on steel pole along a high-speed railway

In order to consider the influence of steel pole on the measurement of wind speed sensors and determinate the installation position of wind speed sensors, the flow field around wind speed sensors was investigated. Based on the three-dimensional steady Reynolds-averaged Navier-Stokes equations and k-ε double equations turbulent model, the field flow around the wind speed sensor and the steel pole along a high-speed railway was simulated on an unstructured grid. The grid-independent validation was conducted and the accuracy of the present numerical simulation method was validated by experiments and simulations carried out by previous researchers. Results show that the steel pole has a significant influence on the measurement results of wind speed sensors. As the distance between two wind speed sensors is varied from 0.3 to 1.0 m, the impact angles are less than ±20°, it is proposed that the distance between two wind speed sensors is 0.8 m at least, and the interval between wind speed sensors and the steel pole is more than 1.0 m with the sensors located on the upstream side.     

Impact Dynamics of Supercavitating Projectile with Fluid/Structure Interaction

As supercavitating projectiles move at high speed, the periodic impacts ("tail-slap") on the interior surface of the cavity generally occur due to disturbances. The interactions between the projectile and the water/cavity interface are the sources of structural vibrations, which affect the guidance of the vehicle and undermine the structural reliability. The Fluid/Structure Interaction calculation procedure of the tail-slaps of supercavitating projectile is established, and the dynamic behaviours of the projectile operating in tail-slap conditions with and without considering Fluid/Structure Interaction are obtained and compared. The responses of the projectile riding a reducing cavity are studied, and the effect of Fluid/Structure Interaction is also analyzed. The results show that the angular velocity of projectile increases as the body slowing down, and the amplitude of the elastic displacement response decreases at the beginning and increases when the cavity size is close to the diameter of the tail of projectile. The effect of Fluid/Structure Interaction reduces the amplitudes and frequencies of the impact loads and the vibration responses of the body, and when the speed is higher, the effect is more apparent.     

Bifurcation\instability forms of high speed railway vehicles

The China high speed railway vehicles of type CRH2 and type CRH3, modeled on Japanese high speed Electric Multiple Units (EMU) E2 series and Euro high speed EMU ICE3 series possess different stability behaviors due to the different matching re-lations between bogie parameters and wheel profiles. It is known from the field tests and roller rig tests that, the former has a higher critical speed while large limit cycle oscillation appears if instability occurs, and the latter has lower critical speed while small limit cycle appears if instability occurs. The dynamic model of the vehicle system including a semi-carbody and a bogie is established in this paper. The bifurcation diagrams of the two types of high speed vehicles are extensively studied. By using the method of normal form of Hopf bifurcation, it is found that the subcritical and supercritical bifurcations exist in the two types of vehicle systems. The influence of parameter variation on the exported function Rec1(0) in Hopf normal form is studied and numerical shooting method is also used for mutual verification. Furthermore, the bifurcation situation, subcritical or supercritical, is also discussed. The study shows that the sign of Re(λ) determinates the stability of linear system, and the sign of Rec1(0) determines the property of Hopf bifurcation with Rec1(0)>0 for supercritical and Rec1(0)<0 for subcritical.     

Investigation on Skidding of Rolling Element Bearing in Loaded Zone

Skidding which occurs when rolling element entering into the loaded zone is prone to cause wear and incipient failure to the raceways and rolling elements. This paper presents a dynamic model to investigate the skidding of a rolling element bearing under radial load when the rolling element is entering into the load zone. In this dynamic model, the effects of the contact forces, friction forces on the rolling element-race and rolling element-cage interfaces, gravity, and the centrifugal forces of rolling elements are taken into consideration. The Hertzian contact theory is applied to calculate the non-linear contact forces. The Coulomb friction law is used to calculate the friction forces. The differential equations of rotational motion of the rolling element with regard to its central axis and the central axis of the outer ring are established respectively. The dynamic equations are then solved by using a fourth-order Runge-Kutta algorithm. The skidding characteristics of rolling element at the entry into the loaded zone are exposed, and the effects of the operating parameters on skidding behavior are carefully investigated.     

Hollow fiber liquid-supported membrane technology for enantioseparation of racemic salbutamol by combinatorial chiral selectors

Enantioseparation of salbutamol solute was carried out in liquid-supported membrane by using a polyvinylidene fluoride hollow-fiber module. The enantioselective transport of solute was facilitated by combinatorial chiral selectors, which were dissolved in toluene organic solvent. The effects of molar concentration ratios of salbutamol to combinatorial chiral selectors, and the pH value of buffer solution on enantioseparation were investigated. The results show that when the molar concentration ratio is 2 ： 1 ： 1, the maximum separation factor and enantiomer excess are 1.49 and 19.74%, respectively, and the R-enantiomer flux is more than S-enantiomer; the pH value of buffer solution influences the performances of enantioseparartion obviously, and the appropriate range of pH value is 7.0-7.2.     

Impact energy analysis of turbulent water sprays for continuous centrifugal concentration

A SLon full-scale continuous centrifugal concentrator was used to reconcentrate hematite from a high gradient magnetic separation concentrate to study the effect of impact angle, concentrate mass and drum rotation speed on the impact energy of turbulent water sprays for continuous centrifugal concentration, under conditions of feed volume flow rate around 9 m3/h, feed solid concentration of 25%-35% and reciprocating velocity of water sprays at 0.05 m/s. The results indicate that a minimal critical impact energy is required in the water sprays for achieving continuous concentration of the concentrator; an unfitted impact angle reduces the impact efficiency, and the highest impact efficiency of 0.6416 is found at the mpact angle of 60°; the increase in concentrate mass leads to an increase in impact energy, and the highest impact efficiency is maintained when the concentrate mass varies in the range of 0.44-0.59 kg/s; when the concentrate mass and the pressure of water sprays are kept at around 0.45 kg/s and in the range of 0.4-0.6 MPa respectively, the impact energy increases proportionally with the increase of drum rotation speed.     

Influence of orifice-to-wall distance on synthetic jet vortex ring simpinging on a fixed wall

Two-dimensional particle image velocimetry (PIV) is used to investigate the influence of the orifice-to-wall distance on synthetic jet vortex rings impinging on a fixed wall. Both evolutions of vortical structures and statistical characteristics of flow fields at different orifice-to-wall distances are presented. It is found that different orifice-to-wall distances have different effects in terms of the vortex strength and impinging speed when the vortex rings are approaching the wall. The secondary vortex ring can be observed within the shear layer only when the dimensionless orifice-to-wall distance is close to or less than the dimensionless stroke length. Consequently, an appropriate orifice-to-wall distance plays a vital role in the sense of impingement effect. The statistical analysis of the flow field indicates that a wall jet forms after impingement, while both the decay rate of the maximum radial velocity and the spreading rate of the half-width decrease with the increasing orifice-to-wall distance. The non-dimensional wall jet velocity profiles at different orifice-to-wall distances all exhibit self-similar behaviors, which is consistent with the theoretical solution of the laminar wall jet.     

Critical safe distance design to improve driving safety based on vehicle-to-vehicle communications

A critical safe distance （CSD） model in V2V （vehicle-to-vehicle） communication systems was proposed to primarily enhance driving safety by disseminating warning notifications to vehicles when they approach calculated CSD. By elaborately analyzing the vehicular movement features especially when braking, our CSD definition was introduced and its configuration method was given through dividing radio range into different communication zones. Based on our definition, the needed message propagation delay was also derived which could be used to control the beacon frequency or duration. Next, the detailed CSD expressions were proposed in different mobility scenarios by fully considering the relative movement status between the front and rear vehicles. Numerical results show that our proposed model could provide reasonable CSD under different movement scenarios which eliminates the unnecessary reserved inter-vehicle distance and guarantee the safety at the same time, The compared time-headway model always shows a smaller CSD due to focusing on traffic efficiency whereas the traditional braking model generally outputs a larger CSD because it assumes that the following car drives with a constant speed and did not discuss the scenario when the leading car suddenly stops. Different from these two models, our proposed model could well balances the requirements between driving safety and traffic throughput efficiency by generating a CSD in between the values of the two models in most cases.     

Bending analysis and control of rolled plate during snake hot rolling

In order to study the bending behavior of aluminum alloy 7050 thick plate during snake hot rolling, several coupled thermo-mechanical finite element(FE) models were established. Effects of different initial thicknesses, pass reductions, speed ratios and offset distances on the bending value of the plate were analyzed. ‘Quasi smooth plate' and optimum offset distance were defined and quasi smooth plate could be acquired by adjusting offset distance, and then bending control equation was fitted. The results show that bending value of the plate as well as the extent of the increase grows with the increase of pass reduction and decrease of initial thickness; the bending value firstly increases and then keeps steady with the ascending speed ratio; the bending value can be reduced by enlarging the offset distance. The optimum offset distance varies for different rolling parameters and it is augmented with the increase of pass reduction and speed ratio and the decrease of initial thickness. A proper offset distance for different rolling parameters can be calculated by the bending control equation and this equation can be a guidance to acquire a quasi smooth plate. The FEM results agree well with experimental results.     

Bicycle capacity of borrowed-priority merge at unsignalized intersections in China

To investigate bicyclists’ behavior at unsignalized intersections with mixed traffic flow,a bicycle capacity model of borrowed-priority merge was developed by the addition-conflict-flow procedure.Based on the actual traffic situation,the concept of borrowed priority,in which the major-road bicycles borrow the priority of major-road cars to enter the intersections when consecutive headway for major-steam cars is lower than the critical gap for minor-road cars,was addressed.Bicycle capacity at a typical unsignalized intersection is derived by the addition-conflict-flow procedure.The proposes model was validated by the empirical investigation.Numerical results show that bicycle capacity at an intersection is the function of major-road and minor-road car streams.Bicycle capacity increases with increasing major-road cars but decreases with increasing minor-road cars.