Observation of recoil-induced resonances and electromagnetically induced absorption of cold atoms in diffuse light

In this paper we report an experiment on the observation of the recoil-induced resonances (RIR) and electromagnetically induced absorption (EIA) of cold Rb87 atoms in diffuse light. The pump light of the RIR and the EIA comes from the diffuse light in an integrating sphere, which also serves the cooling light. The probe light beam is a weak laser split from the cooling laser in order to keep the cooling and probe lasers correlated. We measured the RIR and the EIA signal varying with the detuning of the diffuse laser light, and also measured the temperature of the cold atoms at the different detunings. The mechanism of RIR and EIA in the configuration with diffuse-light pumping and laser probing is discussed, and the difference of nonlinear spectra of cold atoms between in diffuse-light cooling system and in optical molasses as well as in a magneto-optical trap (MOT) are studied.Comment: 9 pages, 6 figure

Lifshitz effects on holographic pp-wave superfluid

In the probe limit, we numerically build a holographic $p$-wave superfluid model in the four-dimensional Lifshitz black hole coupled to a Maxwell-complex vector field. We observe the rich phase structure and find that the Lifshitz dynamical exponent $z$ contributes evidently to the effective mass of the matter field and dimension of the gravitational background. Concretely, we obtain the Cave of Winds appeared only in the five-dimensional anti-de Sitter~(AdS) spacetime, and the increasing $z$ hinders not only the condensate but also the appearance of the first-order phase transition. Furthermore, our results agree with the Ginzburg-Landau results near the critical temperature. In addition, the previous AdS superfluid model is generalized to the Lifshitz spacetime.Comment: 14 pages,5 figures, and 1 table, accepted by Phys. Lett.

A hybrid deep learning method for finite-horizon mean-field game problems

This paper develops a new deep learning algorithm to solve a class of finite-horizon mean-field games. The proposed hybrid algorithm uses Markov chain approximation method combined with a stochastic approximation-based iterative deep learning algorithm. Under the framework of finite-horizon mean-field games, the induced measure and Monte-Carlo algorithm are adopted to establish the iterative mean-field interaction in MCAM and deep learning, respectively. The Markov chain approximation method plays a key role in constructing the iterative algorithm and estimating an initial value of a neural network, whereas stochastic approximation is used to find accurate parameters in a bounded region. The convergence of the hybrid algorithm is proved; two numerical examples are provided to illustrate the results

Modeling and simulation of brake judder considering the effects of thermo-mechanical coupling

Reproducing the real behavior of brake judder in time domain is useful for brake judder reduction, but it is hard to establish a time-domain model of brake judder due to the effects of thermo-mechanical coupling. To solve this problem, a modeling method is proposed taking into account the effects of thermo-mechanical coupling before hotspot occurs. In this method, an eight-degree-of-freedom dynamics model of brake caliper assembly with multi-contact points is established, and a semi-empirical model of friction coefficient is proposed by magic formula tyre model. The input of the dynamics model is the initial disc thickness variation (DTV) and the DTV caused by uneven heating, which is calculated by a transient FE model of thermo-mechanical coupling considering initial DTV. On this basis, a simulation of brake judder is conducted and an experiment is designed to validate the method. The simulated brake pressure and brake torque without and with thermo-mechanical coupling are compared with the experiment results respectively, and it indicates that the simulated results considering thermo-mechanical coupling have a good agreement with experiment results. Brake pressure variation (BPV) and brake torque variation (BTV) increase gradually in time domain because of the effects of thermo-mechanical coupling and the increments of BPV and BTV can reach 45 % and 50 % respectively in the simulation

Influence of surface run-out on disc brake squeal

As a complicated phenomenon of friction-induced noise, disc brake squeal has remained a challenge to automotive industry. To investigate the intermittent characteristics of disc brake squeal, a three-degree-of-freedom dynamics model considering both the friction coefficient and the disc surface run-out (SRO) is established in this paper. Their influences on system complex eigenvalues and transient responses are numerically investigated. At the same time, an experiment is conducted based on a pin-on-disc setup. The experimental results show that disc brake squeal is mainly dependent on modal coupling, and influenced by the incline angle of disc SRO. When disc brake squeal occurs, the time history of sound pressure is consistent with that of the disc vibration, which is due to the synchronization of the incline angle of macro and micro disc SRO that has the equivalent effect on system stability as friction coefficient does

A comment on "Ab initio calculations of pressure-dependence of high-order elastic constants using finite deformations approach" by I. Mosyagin, A.V. Lugovskoy, O.M. Krasilnikov, Yu.Kh. Vekilov, S.I. Simak and I.A. Abrikosov

Recently, I. Mosyagin, A.V. Lugovskoy, O.M. Krasilnikov, Yu.Kh. Vekilov, S.I. Simak and I.A. Abrikosov in the paper: "Ab initio calculations of pressure-dependence of high-order elastic constants using finite deformations approach"[Computer Physics Communications 220 (2017) 2030] presented a description of a technique for ab initio calculations of the pressure dependence of second- and third-order elastic constants. Unfortunately, the work contains serious and fundamental flaws in the field of finite-deformation solid mechanics.Comment: 3 pages, 0 figure