Haze control is a difficult and arduous battle,and it is a major decision concerning the people's livelihood and national ecological civilization construction.Taking Heilongjiang Province as an example,this paper ...Haze control is a difficult and arduous battle,and it is a major decision concerning the people's livelihood and national ecological civilization construction.Taking Heilongjiang Province as an example,this paper introduced a new idea for haze control.Haze in Heilongjiang Province was mainly resulted from straw burning.Market-oriented,large-scale,and industrialized haze control relying on science and technology is new opportunity and challenge for realizing ecological civilization and revitalizing the economy of Heilongjiang Province.展开更多
To investigate the mechanical process that occurs between rocks and tooth hobs,the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-si...To investigate the mechanical process that occurs between rocks and tooth hobs,the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-sized sandstone samples.When a piece of sandstone is crushed by the tooth of a hob rolling at a constant speed,the resultant reaction forces of the sandstone on the tooth first hinder and then contribute to the rolling of the hob.The absolute value of the longitudinal reaction force is significantly higher than that of the lateral reaction force.Because the tooth was subjected to reaction forces from the sandstone,forces and moments were applied to the hob in order to keep the hob rolling.The applied forces were equal in value and opposite in direction to the reaction forces of the sandstone on the tooth.Three typical curves of the work done by the applied forces and moment were obtained,and the contribution of the applied lateral force and moment to the total work done for crushing sandstones was variable;however,no work was done by the applied longitudinal force.Moreover,the applied longitudinal force and total work were positively correlated with the strength of sandstone samples.The total work,applied forces,and moment increased with the maximum penetration depth of the tooth in the sandstone.展开更多
The accuracy of subgrade quality evaluation is important for road safety assessment.Since there is little research work devoted to testing lightweight cellular concrete(LCC)by an ultrasound-based method,the quantitati...The accuracy of subgrade quality evaluation is important for road safety assessment.Since there is little research work devoted to testing lightweight cellular concrete(LCC)by an ultrasound-based method,the quantitative relation between ultrasonic testing results and the quality of LCC subgrade is not well understood.In this paper,the quality of LCC subgrade was evaluated with respect to compressive strength and crack discrimination.The relation between ultrasonic testing results and LCC quality was explored through indoor tests.Based on the quantitative relation between ultrasonic pulse velocity and compressive strength of LCC,a fitting formula was established.Moreover,after the LCC became cracked,the ultrasonic pulse velocity and ultrasonic pulse amplitude decreased.After determining the lower limiting values of the ultrasonic pulse velocity and ultrasonic pulse amplitude through the statistical data,it could be calculated whether there were cracks in LCC subgrade.The ultrasonic testing results showed that the compressive strength of the LCC subgrade was suitable for purpose and there was no crack in the subgrade.Then core samples were taken from the subgrade.Comparisons between ultrasonic testing results of subgrade and test results of core samples demonstrated a good agreement.展开更多
文摘Haze control is a difficult and arduous battle,and it is a major decision concerning the people's livelihood and national ecological civilization construction.Taking Heilongjiang Province as an example,this paper introduced a new idea for haze control.Haze in Heilongjiang Province was mainly resulted from straw burning.Market-oriented,large-scale,and industrialized haze control relying on science and technology is new opportunity and challenge for realizing ecological civilization and revitalizing the economy of Heilongjiang Province.
基金This study was sponsored by the National Natural Science Foundation of China(Grant No.51609071)Fundamental Research Funds for the Central Universities(Nos.B200202087 and B200204032).
文摘To investigate the mechanical process that occurs between rocks and tooth hobs,the crushing of sandstone with a tooth hob was simulated using reconstructed multi-mineral mesoscopic numerical models of various grain-sized sandstone samples.When a piece of sandstone is crushed by the tooth of a hob rolling at a constant speed,the resultant reaction forces of the sandstone on the tooth first hinder and then contribute to the rolling of the hob.The absolute value of the longitudinal reaction force is significantly higher than that of the lateral reaction force.Because the tooth was subjected to reaction forces from the sandstone,forces and moments were applied to the hob in order to keep the hob rolling.The applied forces were equal in value and opposite in direction to the reaction forces of the sandstone on the tooth.Three typical curves of the work done by the applied forces and moment were obtained,and the contribution of the applied lateral force and moment to the total work done for crushing sandstones was variable;however,no work was done by the applied longitudinal force.Moreover,the applied longitudinal force and total work were positively correlated with the strength of sandstone samples.The total work,applied forces,and moment increased with the maximum penetration depth of the tooth in the sandstone.
基金This study was funded by the National Natural Science Foundation of China(Grant No.51609071)the Fundamental Research Funds for the Central Universities(Nos.B200202087,B200204032).
文摘The accuracy of subgrade quality evaluation is important for road safety assessment.Since there is little research work devoted to testing lightweight cellular concrete(LCC)by an ultrasound-based method,the quantitative relation between ultrasonic testing results and the quality of LCC subgrade is not well understood.In this paper,the quality of LCC subgrade was evaluated with respect to compressive strength and crack discrimination.The relation between ultrasonic testing results and LCC quality was explored through indoor tests.Based on the quantitative relation between ultrasonic pulse velocity and compressive strength of LCC,a fitting formula was established.Moreover,after the LCC became cracked,the ultrasonic pulse velocity and ultrasonic pulse amplitude decreased.After determining the lower limiting values of the ultrasonic pulse velocity and ultrasonic pulse amplitude through the statistical data,it could be calculated whether there were cracks in LCC subgrade.The ultrasonic testing results showed that the compressive strength of the LCC subgrade was suitable for purpose and there was no crack in the subgrade.Then core samples were taken from the subgrade.Comparisons between ultrasonic testing results of subgrade and test results of core samples demonstrated a good agreement.
