Quantum fluctuations in the BCS-BEC crossover of two-dimensional Fermi gases

We present a theoretical study of the ground state of the BCS-BEC crossover in dilute two-dimensional Fermi gases. While the mean-field theory provides a simple and analytical equation of state, the pressure is equal to that of a noninteracting Fermi gas in the entire BCS-BEC crossover, which is not consistent with the features of a weakly interacting Bose condensate in the BEC limit and a weakly interacting Fermi liquid in the BCS limit. The inadequacy of the 2D mean-field theory indicates that the quantum fluctuations are much more pronounced than those in 3D. In this work, we show that the inclusion of the Gaussian quantum fluctuations naturally recovers the above features in both the BEC and the BCS limits. In the BEC limit, the missing logarithmic dependence on the boson chemical potential is recovered by the quantum fluctuations. Near the quantum phase transition from the vacuum to the BEC phase, we compare our equation of state with the known grand canonical equation of state of 2D Bose gases and determine the ratio of the composite boson scattering length $a_{\rm B}$ to the fermion scattering length $a_{\rm 2D}$. We find $a_{\rm B}\simeq 0.56 a_{\rm 2D}$, in good agreement with the exact four-body calculation. We compare our equation of state in the BCS-BEC crossover with recent results from the quantum Monte Carlo simulations and the experimental measurements and find good agreements.Comment: Published versio

Evaluation of corrosion expansion of reinforced concrete specimen using fiber optical Brillouin sensing technique

This paper investigated the evaluation of the concrete damage degree due to steel bar corrosion for reinforced concrete structures. Brillouin optical fiber time domain analysis (BOTDA) sensors were developed to monitor the steel bar corrosion expansion strain. Electrochemical accelerating experimental results showed the sensors could be used for early detection and the lifelong monitoring. The damage factor was proposed to quantitatively evaluate the concrete damage degree before initial cracking and during the development of cracks. Finite element analysis was performed on concrete specimens to map the monitoring results with the damage factor, which supported the capability of the damage factor

Research of piezoelectric acoustic liner

The piezoelectric acoustic liner is a new type of acoustic liner that uses piezoelectric patches to replace the traditional mechanical structure. Its working principle is to change the resonator volume of acoustic liner by inverse piezoelectric effect. In this paper, the finite element method is used to analyze the deformation of piezoelectric patches and the acoustic performance of piezoelectric acoustic liner, when the piezoelectric patch deformation is 0.1 mm, the noise elimination frequency band offset of the acoustic liner is about 30 Hz, and related experiments are designed. The experimental results confirm that noise elimination frequency range of piezoelectric acoustic liner is 1100 Hz to 1300 Hz within the voltage range of 0 V to 200 V

The Effect of Human Walking on Distribution Characteristics of Indoor Particulate Matter

In modern society, house dust particulate matters pollution had become serious. Ventilation is an important method for removing house dust particulate matters and it is very important to explore the removal efficiency of house dust particulate matters under different ventilation modes. This study analyses the removal effect of house dust particulate matters under the two typical ventilation modes called ceiling exhaust and slit exhaust strategy through experiments and date analysis. In the process of experiments, riboflavin particles were used as the house dust particulate matters, instantaneous microbial detection (IMD) was used to measure the house dust particulate matters. Walking test was carried on after the ventilation system running for some time, which aimed to explore the influence of human behaviour on the house dust particulate matters distribution under two different ventilation modes. It is concluded that larger size particles had larger sedimentation velocity and sedimentation velocity of particles would be faster significantly after the ventilation system working. After walking experiment, particles concentration returned to background concentrations due to the effect of the ventilation system. Particles concentration in slit exhaust strategy was lower than ceiling exhaust so that the effect of slit exhaust strategy is superior to the ceiling exhaust

Study on multivariate regression model of indoor and outdoor particulate pollution in severe cold area of China

At present, the widespread existence of haze phenomenon has a serious impact on indoor air quality. Indoor particulate pollution has been paid more and more attention by the society. However, the correlation and diffusion mechanism of indoor and outdoor particulate matter are still controversial. In order to explore the correlation between indoor and outdoor particulate matter of different building types in heating season and non-heating season, the indoor and outdoor particulate concentrations and meteorological parameters of 110 stations in severe cold area of China were monitored by experiments. The analysis shows that indoor and outdoor temperature, humidity, air velocity, wind direction and atmospheric pressure are the main factors affecting indoor and outdoor particulate concentration. And based on these factors, it can model the indoor predicted particulate concentrations by multivariate regression. It also shows a significant difference in the relationship between the concentration of particulate matter and factors of indoor and outdoor particulate matter. Therefore, this study provides a good premise for exploring the health risks and control measures of particulate matter