The feasibility of the fabrication of coatings for elevated-temperature structural applications by laser cladding MoSi2 pow- der on steel was investigated. A dense and crack-free fine coating, well-bonded with the sub...The feasibility of the fabrication of coatings for elevated-temperature structural applications by laser cladding MoSi2 pow- der on steel was investigated. A dense and crack-free fine coating, well-bonded with the substrate has been obtained by this technique This coating consists of FeMoSi, Fe2Si and a small amount of MosSi3 due to dilution of the substrate in the coating. The microstructure of the coating is characterized of typical fine dendrites, The dendrites are composed of FeMoSi primary phase, and the interdendritic areas are two eutectic phases of FeMoSi and Fe2Si. The hardness of the coating reaches 845 Hv0.5, 3.7 times larger than that of the steel substrate （180 Hv05）.展开更多
An investigation was conducted to examine the impact of additive mixing with wheat straw(WS)for pellet making.This study manufactured seven types of pellets with different additive combina-tions to evaluate pellet qua...An investigation was conducted to examine the impact of additive mixing with wheat straw(WS)for pellet making.This study manufactured seven types of pellets with different additive combina-tions to evaluate pellet quality characteristics and their relationships.A laboratory-type hammer mill and a pellet mill were used for feedstock preparation and pellet production.Experimental investigations showed that the lignin content increased from 7.0%to 13.1%,which was a primary need for pelletization.Also,the heating value rose from 17.02 to 20.36 MJ/kg.However,the ash content also increased from 7.09%to 16.2%.Results showed that dimension(length and diame-ter),durability,and tensile strength increased significantly with additives while the fines content decreased.The fines content had an inverse relationship with durability and strength.Wheat straw(60%),together with 10%sawdust(SD),10%corn starch(CS),10%bentonite clay(BC),and 10%biochar(BiC),was optimal with good pellet performance(T7).In addition,both the T5 pellets(70%WS,10%SD,10%BiC,and 10%BC)and the T6 pellets(70%WS,10%SD,10%BiC,and 10%CS)provide suitable quality according to EN plus 2015 standard requirements.The ash content of produced pellet was higher than the recommended value,which suggests that further research onto the alternative additive use for ash reduction is needed.展开更多
In this paper, we establish a convergence theory for a finite element method with weighted basis functions for solving singularly perturbed convection-diffusion equations. The stability of this finite element method i...In this paper, we establish a convergence theory for a finite element method with weighted basis functions for solving singularly perturbed convection-diffusion equations. The stability of this finite element method is proved and an upper bound O（h｜lnε｜3/2） for errors in the approximate solutions in the energy norm is obtained on the triangular Bakhvalov-type mesh. Numerical results are presented to verify the stability and the convergent rate of this finite element method.展开更多
基金This work was financially supported by the National Natural Science Foundation of China (No.59836220), the Major Science Re-search Foundation of the Chinese Academy of Science (No.KY951-Al-601-03), and the Science Research Foundation of the Univer-sity of Science and Technology Beijing (No.20041004790)
文摘The feasibility of the fabrication of coatings for elevated-temperature structural applications by laser cladding MoSi2 pow- der on steel was investigated. A dense and crack-free fine coating, well-bonded with the substrate has been obtained by this technique This coating consists of FeMoSi, Fe2Si and a small amount of MosSi3 due to dilution of the substrate in the coating. The microstructure of the coating is characterized of typical fine dendrites, The dendrites are composed of FeMoSi primary phase, and the interdendritic areas are two eutectic phases of FeMoSi and Fe2Si. The hardness of the coating reaches 845 Hv0.5, 3.7 times larger than that of the steel substrate （180 Hv05）.
文摘An investigation was conducted to examine the impact of additive mixing with wheat straw(WS)for pellet making.This study manufactured seven types of pellets with different additive combina-tions to evaluate pellet quality characteristics and their relationships.A laboratory-type hammer mill and a pellet mill were used for feedstock preparation and pellet production.Experimental investigations showed that the lignin content increased from 7.0%to 13.1%,which was a primary need for pelletization.Also,the heating value rose from 17.02 to 20.36 MJ/kg.However,the ash content also increased from 7.09%to 16.2%.Results showed that dimension(length and diame-ter),durability,and tensile strength increased significantly with additives while the fines content decreased.The fines content had an inverse relationship with durability and strength.Wheat straw(60%),together with 10%sawdust(SD),10%corn starch(CS),10%bentonite clay(BC),and 10%biochar(BiC),was optimal with good pellet performance(T7).In addition,both the T5 pellets(70%WS,10%SD,10%BiC,and 10%BC)and the T6 pellets(70%WS,10%SD,10%BiC,and 10%CS)provide suitable quality according to EN plus 2015 standard requirements.The ash content of produced pellet was higher than the recommended value,which suggests that further research onto the alternative additive use for ash reduction is needed.
基金This work is supported by National Natural Science Foundation of China （NSFC10671023） and Beijing Municipal Education Commission （71D0911003）. The second author acknowledges the support from National Natural Science Foundation of China （NSFC10771019）.
文摘In this paper, we establish a convergence theory for a finite element method with weighted basis functions for solving singularly perturbed convection-diffusion equations. The stability of this finite element method is proved and an upper bound O（h｜lnε｜3/2） for errors in the approximate solutions in the energy norm is obtained on the triangular Bakhvalov-type mesh. Numerical results are presented to verify the stability and the convergent rate of this finite element method.
