In this paper, we present an extended car-following model with consideration of the gravitational force. A new macroscopic model taking into account the slope effects is developed using the relationship between the microscopic and macroscopic variables. The proposed model is applied to reflect the effect of the slope on uniform flow, traffic waves and small perturbation. The simulation results demonstrate that both the angle and the length of the slope have important impacts on traffic flow. The effect of the slope becomes more significant with the increase of the slope angle.

An extended macroscopic model for traffic flow on a highway with slopes

Interaction with liquids at the ultra-large surface area of nanoporous material enables a high-efficiency energy dissipation system with wide perspective applications [A. Han, et al., Langmuir 2008, 24, 7044]. In this paper, a nanoporous energy dissipation system composed of a mixture of zeolite ZSM-5 and water is established and studied experimentally. Firstly, quasi-static compression experiments are carried out to analyze the pressure–volume curve and reveal the energy dissipation mechanism. Afterwards, a parametric study is conducted to explore the effects of three parameters, the pretreatment temperature of zeolite ZSM-5 (600–1100 °C), mass ratio of ZSM-5 to water (1:5–6:5), and average zeolite particle size (2.145–5.251 µm before heated or 6.104–9.557 µm after heated). Results show that in order to obtain optimum energy absorption performance, the pretreatment temperature of about 1000 °C, and higher ratio of ZSM-5 with larger particle size are desired. With high energy dissipation and reusability, the zeolite-water system with optimal parameters established herein may become an attractive cushioning device.

Experimental Study on Energy Dissipation Characteristics of ZSM-5 Zeolite/Water System

In our experiment, a single cesium atom prepared in a large-magnetic-gradient magneto-optical trap (MOT) can be efficiently transferred into a 1064-nm far-off-resonance microscopic optical dipole trap (FORT). The efficient transfer of the single atom between the two traps is used to determine the trapping lifetime and the effective temperature of the single atom in FORT. The typical trapping lifetime has been improved from ∼ 6.9 s to ∼ 130 s by decreasing the background pressure from ∼ 1 × 10−10 Torr to ∼ 2 × 10−11 Torr and applying one-shot 10-ms laser cooling phase. We also theoretically investigate the dependence of trapping lifetimes of a single atom in a FORT on trap parameters based on the FORT beam’s intensity noise induced heating. Numerical simulations show that the heating depends on the FORT beam’s waist size and the trap depth. The trapping time can be predicted based on effective temperature measurement of a single atom in the FORT and the intensity noise spectra of the FORT beam. These experimental results are found to be in agreement with the predictions of the heating model.

Extending the trapping lifetime of single atom in a microscopic far-off-resonance optical dipole trap

A plasmonic waveguide coupled system that is composed of a square ring cavity and a metal–insulator–metal (MIM) waveguide with two silver baffles is proposed. The transmission and reflection properties of the proposed plasmonic system are investigated numerically using the finite element method. The normalized Hz field distributions are calculated to analyze the transmission mode in the plasmonic system. The extreme destructive interference between light mode and dark mode causes plasmonically induced reflection (PIR) window in the transmission spectrum. The PIR window is fitted using the coupled mode theory. The analytical result agrees with the simulation result approximately. In addition, the PIR window can be controlled by adjusting structural parameters and filling different dielectric into the MIM waveguide and the square ring cavity. The results provide a new approach to designing plasmonic devices.

https://iopscience.iop.org/article/10.1088/1674-1056/26/12/124212/pdf

Plasmonically induced reflection in metal-insulator-metal waveguides with two silver baffles coupled square ring resonator *

An extended two-lane lattice model of traffic flow with consideration of the slope effect is proposed. The slope effect is reflected in both the maximal velocity and the relative current. The stability condition of the model is derived by applying the linear stability method. By using the nonlinear analysis method, we obtain the Korteweg–de Vries (KdV) equation near the neutral stability line and the modified Korteweg–de Vries (mKdV) equation near the critical point. The analytical and numerical results demonstrate that the stability of traffic flow is enhanced on the uphill but is weakened on the downhill when the slope angle increases.

An extended lattice model for two-lane traffic flow with consideration of the slope effect

This paper derives the dispersion relation of microring coupled-resonator optical waveguides (CROWs) without any approximation by using the transfer matrix method. Based on the established dispersion relation of CROWs it obtains the slow group velocity and dispersion coefficient. It finds that the effect of dispersion on optical pulses can be adjusted to balance the effect of nonlinearity by changing coupling coefficient or loss, so optical soliton with group delay can be obtained in microring CROWs. The optical soliton with group delay is of great significance for applications of microring CROWs in delay lines and optical buffers of future all-optical communication systems.

http://iopscience.iop.org/article/10.1088/1674-1056/18/1/036/pdf

Optical soliton with group delay in microring coupled-resonator optical waveguides

We investigate the reduction of the group velocity propagation resulting from the steep change of the refractive index by the coherent population oscillation in erbium-doped optical fibre. The largest delay is measured to be about 8.75ms corresponding to a group index of 1.312 × 106. The time delay or advancement depends on the pump intensity. Influences of the ion density on the fractional delay and the group velocity reduction of light propagation are studied. Based on our discussion the optimization parameters should be selected in order to obtain more appropriate time delay and the slowdown of group velocity.

Slowdown of Group Velocity of Light Using Coherent Population Oscillation

A novel relative rotation sensor based on slow light is proposed and analysed. A theoretical analysis shows that the high sensitivity of the proposed rotation sensor is achieved through an electromagnetically-induced-transparency medium. Unlike the tradition detection method, the idea of rotation sensing is to detect group delay between counter-propagating wave packets. It can be used to realize an ultra-precise rotation sensor.

http://iopscience.iop.org/article/10.1088/1674-1056/19/1/014216/pdf

Precise relative rotation sensing using slow light

Considering the insertion loss of coupler， we theoretically analyzed the CRIT effect of the ring-in-ring structure resonator. In the process of the theoretical analysis， the transmission coefficient and effective phase shift were deduced using iterative approach， and then the dispersion was obtained， including the effect of the insertion loss. The analysis shows the effective phase shift， group velocity and bandwidth of the whole system can be controlled by the insertion loss， the multiples between the lengths of rings and the number of rings. The control of dispersion in ring-in-ring structure is important for applications of this structure in rotating sensor， optical delay line， optical buffer and filtering.

Research on CRIT property in ring-in-ring structure resonator

To measure the focal ratio degradation of astronomical fibers, we use laser as the light source which can do with bringing the light to a focal point and we can control the injection position. The laser has a high coherency and there are a number of modes in the large-core fiber. Consequently, the output spot will be a speckle. The presence of speckle makes the energy distribution of optical field uneven, so that it's hard to calculate the spot radius. To reduce the influence of the speckle, the contact-type mode scrambler is developed in our research. It's used to make the fiber vibrate at a suitable frequency of 0-80 Hz, and the vibration amplitude is 0.5 cm. The phase of different propagation modes is changed randomly in order to vibrate the modes and reduce the influence of the speckle. Different vibration result is observed by setting different vibration frequency and different CCD exposure time. The estimate of the vibration result can be given by using the method of contrast and Fourier Transform. Three different core diameters (10&#x00B5;m, 125&#x00B5;m, 320&#x00B5;m) are contrast with each other for convenience. The result shows that the vibration frequency between 65-70 Hz is best, and the optimum exposure time is 30 ms for all three diameters. The vibration of fiber using mode scrambler can reduce the speckle obviously under coherent illumination.

Tian He

Papers

Optical soliton with group delay in microring coupled-resonator optical waveguides

Slowdown of Group Velocity of Light Using Coherent Population Oscillation

Precise relative rotation sensing using slow light

Research on CRIT property in ring-in-ring structure resonator

Phase-Disturbing Speckle-Suppressing by Contact Fiber Scrambler