Influence of the Source to Substrate Distance on the Growth,Tribological Properties and Optical Properties of Be Films

The Be films were prepared by thermal evaporation at different sources to substrate distances（SSD） on glass substrates. The decrease of SSD from 90 mm to 50 mm caused the increase of substrate temperature and the rising density of incident Be atoms, thus the properties of Be films greatly changed accordingly. The experimental results showed that the grain diameter in the Be films transited from below 100 nm to 300 nm, the film growth rate increased from 2.35 nm/min to 4.73 nm/min and the roughness increased from 7 nm to 49 nm. The performance study suggested that the friction coefficient of Be films increased from 0.13 to 0.27 and was related to the surface roughness and inner structure, the near-infrared reflectance of Be films increased from 40% to 85% with the increase of wavelength and concurrently decreased with the decrease of SSD, respectively. The performance study indicated that the Be film had the potential application in specific near-infrared reflectance optical system.

Numerical simulation research on response characteristics of surrounding rock for deep super-large section chamber under dynamic and static combined loading condition

The stability control of surrounding rock for large or super-large section chamber is a difficult technical problem in deep mining condition.Based on the in-site geological conditions of Longgu coal mine,this paper used the dynamic module of FLAC3D to study the response characteristics of deep super-large section chamber under dynamic and static combined loading condition.Results showed that under the static loading condition,the maximum vertical stress,deformation and failure range are large,where the stress concentration coefficient is 1.64.The maximum roof-to-floor and two-sides deformations are 54.6 mm and 53.1 mm,respectively.Then,under the dynamic and static combined loading condition:(1)The influence of dynamic load frequency on the two-sides is more obvious;(2)The dynamic load amplitude has the greatest influence on the stress concentration degree,and the plastic failure tends to develop to the deeper;(3)With the dynamic load source distance increase,the response of surrounding rock is gradually attenuated.On this basis,empirical equations for each dynamic load conditions were obtained by using regression analysis method,and all correlation coefficients are greater than 0.99.This research provided reference for the supporting design of deep super-large section chamber under same or similar conditions.

Vapor intrusion in buildings: Development of semi-empirical models including lateral separation between the building and the pollution source

Future constructions in the context of the industrial wastelands reuse may be exposed to Vapor Intrusion(VI).VI can be evaluated by combining in-situ measures and analytical models to evaluate exposure risk in future indoor environments.However,the assumptions in the existing models may reduce their accuracy when they do not meet the characteristics of real situations.Wrong estimations of indoor concentration levels may lead to inappropriate solutions against VI.In this context,new semi-empirical models(SEM)are proposed in order to better specify pollution scenarios and thus increase the accuracy of VI estimations.This development is based on a parametric study(numerical CFD)and a dimensionless analysis combined to existing VI models that consider a continuous source distribution in the soil.These expressions allow to better take into account the source position in the soil(i.e.depth and lateral source/building separation),soil properties(air permeability,diffusion coefficient of the pollutant,…)and building features(building foundation,indoor pressure,air exchange rate,…)in the estimation of indoor concentration levels.The obtained results with the proposed SEM were compared with a numerical CFD model and available experimental data,showing good accuracy in the estimation of VI.Given the advantages of these new models,they can provide better precision in the health risk assessments associated with VI.Furthermore,these expressions can be easily integrated into building ventilation codes allowing to consider air exchange rate and indoor pressure variations over time.