Study on hysteresis phenomenon in the acceleration phase of supercavitation vehicle

This paper aims to explore cavity shape variation regularity in the acceleration phase of supercavitat- ing vehicle. According to the theory of Homogenous Equilibrium Flow,with Mixture Multiphase Model,by setting up the flow speed at the inlet boundary as a function of time,this study carried out the experiments for the supercavitation vehicle's numeral model and obtained the variation regularity of cavity shape,the viscous drag coefficient and the cavity hysteresis time when the supercavitating vehicle was in the phase of acceleration. Results show that when the vehicle is in the phase of acceleration,at the same cavitation number,the cavity size decrease with the increase of acceleration. With the decrease of cavity number,the effect of acceleration on cavity shape is smaller,but the viscous drag increases along with the increase of acceleration. On the condition when the velocity reaches equality uniform status,the cavity hysteresis decreases as the acceleration becomes smaller. On the condition of the same acceleration,the cavity hysteresis time decreases as the velocity increases.

A measurement method for distinguishing the real contact area of rough surfaces of transparent solids using improved Otsu technique

An experimental method of measuring the real contact area of transparent blocks based on the principle of total internal reflection is presented, intending to support the investigation of friction characteristics, heat conduction, and energy dissipation at the contact interface. A laser sheet illuminates the contact interface, and the transmitted laser sheet is projected onto a screen. Then the contact information is acquired from the screen by a camera. An improved Otsu method is proposed to process the data of experimental images. It can compute the threshold of the overall image and filter out all the pixels one by one. Through analyzing the experimental results, we describe the relationship between the real contact area and the positive pressure during a continuous loading process, at different loading rates, with the polymethyl methacrylate（PMMA）material. A hysteresis phenomenon in the relationship between the real contact area and the positive pressure is found and explained.

STABILITY OF EQUILIBRIA OF NEMATIC LIQUID CRYSTALLINE POLYMERS

We provide an analytical study on the stability of equilibria of rigid rodlike nematic liquid crystalline polymers （LCPs） governed by the Smoluchowski equation with the Maier-Saupe intermolecular potential. We simplify the expression of the free energy of an orientational distribution function of rodlike LCP molecules by properly selecting a coordinate system and then investigate its stability with respect to perturbations of orientational probability density. By computing the Hessian matrix explicitly, we are able to prove the hysteresis phenomenon of nematic LCPs： when the normalized polymer concentration b is below a critical value b＊ （6.T314863965）, the only equilibrium state is isotropic and it is stable; when b＊ 〈 b 〈 15/2, two anisotropic （prolate） equilibrium states occur together with a stable isotropic equilibrium state. Here the more aligned prolate state is stable whereas the less aligned prolate state is unstable. When b 〉 15/2, there are three equilibrium states： a stable prolate state, an unstable isotropie state and an unstable oblate state.

ONE-DIMENSIONAL CELLULAR AUTOMATON MODEL OFTRAFFIC FLOW BASED ON CAR-FOLLOWING IDEA

An improved one-dimensional CA ( Cellular Automaton) traffic model was proposed to describe the highway traffic under the periodic boundary conditions. This model was based on the idea of the car-following model, which claims that the motion of a vehicle at one time step depends on both its headway and the synchronous motion of the front vehicle, thus including indirectly the influence of its sub-neighboring vehicle. It? addition, the so-called safety distance was introduced to consider the deceleration behavior of vehicles and the stochastic factor was taken into account by introducing the deceleration probability. Meanwhile, the conditional deceleration in the model gives a better description of the phenomena observed on highways. It is found that there exists the metastability and hysteresis effect of traffic flow in the neighborhood of critical density under different initial conditions. Since this model gives a reasonable depiction of the motion of a single vehicle, it is easy to be extended to the case of traffic flow tinder the control of traffic lights in cities.

Traffic flow cellular automaton model with bi-directional information in an open boundary condition

With Connected Vehicle Technologies being popular,drivers not only perceive downstream traffic information but also get upstream information by routinely checking backward traffic conditions,and the backward-looking frequency or probability is usually affected by prevailing traffic conditions.Meanwhile,the bi-directional perception range of drivers is expected to significantly increase,which results in more informed and coordinated driving behaviours.So,we propose a traffic flow bi-directional CA model with two perception ranges,and perform the numerical simulations with the field data collected from a one-lane highway in Richmond,California,USA as the benchmark data.Numerical results show that the CA model can effectively reproduce the oscillation of relatively congested traffic and the traffic hysteresis phenomenon.When adjusting the backward-looking probability and the perception range,the CA model can well simulate the travel times of all vehicles,and the generation and dissolution of traffic jams under various scenarios.