Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a...Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a U-shaped steel closed support with an inverted U-shaped steel arch in the floor is proposed as a method for improving the support effect of the surrounding rock during the process of floor heaving.This research established a mechanical model for the U-shaped steel closed support,and determined the reaction forces at the connection of a camber angle.Using the limit load method calculated the critical buckling load of the inverted U-shaped steel arch,and use of a strength check method tested the strength of the U-shaped steel material.A numerical simulation was conducted using the finite difference software FLAC3 D.The simulation results show that the U-shaped steel closed support is able to control the floor heave of roadways,which is successfully used in the West 11-2 development roadway of the Zhuji Mine in the Huainan mining area in China.The cumulative floor heave over two years was less than50 mm.展开更多
A current challenge concerns developing new bioresorbable stents that combine optimal mechanical properties and biodegradation rates with limited thrombogenicity. In this context, twinning-induced plasticity (TWIP) st...A current challenge concerns developing new bioresorbable stents that combine optimal mechanical properties and biodegradation rates with limited thrombogenicity. In this context, twinning-induced plasticity (TWIP) steels are good material candidates. In this work, the hemocompatibility of a new TWIP steel was studied in vitro via hemolysis and platelet activation assessments. Cobalt chromium (CoCr) L605 alloy, pure iron (Fe), and magnesium (Mg) WE43 alloy were similarly studied for comparison. No hemolysis was induced by TWIP steel, pure Fe, or L605 alloy. Moreover, L605 alloy did not affect CD62P exposure, αIIbβ3 activation at the platelet surface, or phosphorylation of protein kinase C (PKC) substrates upon thrombin stimulation. In contrast, TWIP steel and pure Fe significantly decreased platelet response to the agonist. Given that similar inhibitory effects were obtained when using a conditioned medium previously incubated with TWIP steel, we postulated TWIP steel corrosion to be likely to release components counteracting platelet activation. We showed that the main ion form present in the conditioned medium is Fe3+. In conclusion, TWIP steel resorbable scaffold displays anti-thrombogenic properties in vitro, which suggests that it could be a promising platform for next-generation stent technologies.展开更多
Objective To study the safety of the novel high nitrogen nickel-free austenitic stainless steel bare metal stents （BMS） in a recognized porcine coronary model and to select a better grid structure of it. Methods Th...Objective To study the safety of the novel high nitrogen nickel-free austenitic stainless steel bare metal stents （BMS） in a recognized porcine coronary model and to select a better grid structure of it. Methods Three types of stents were randomly implanted in different coronary arteries of the same pig： 316L stainless steel BMS （316L-BMS） （n=12）, novel high nitrogen nickel-free stents Grid A （NF-A-BMS） （n=12） and novel high nitrogen nickel-free stents Grid B （NF-B-BMS） （n=12）. In total, eighteen animals underwent successful random placement of 36 oversized stents in the coronary arteries. Coronary angiography was performed after 36 d of stents implantation. Nine animals were respectively sacrificed after 14 d and 36 d for histomorphologic analysis. 〈br〉 Results Quantitative coronary angiography （QCA） showed similar luminal loss （LL） in the three groups：（0.21±0.17） mm for 316L-BMS, （0.16±0.12） mm for NF-A-BMS, （0.24±0.15） mm for NF-B-BMS （P=0.05）. Histomorphomeric analysis after 15 d and 36 d revealed that there was also no significant difference among the three groups in neointimal area （NA） with similar injury scores respectively. High magnification histomorphologic examination showed similar inflammation scores in the three groups, but NF-A-BMS group had poorer endothelialization scores compared with NF-B-BMS group, 2.00±0.63 vs. 2.83±0.41 （P=0.015） at 15 d, which also could be proved by the scanning electron microscope. However, the difference could not been observed at 36 d. Conclusion The novel NF-BMS showed similar safety as 316L-BMS during the short-term study. NF-B-BMS had better endothelialization than NF-A-BMS and this may owe to the specific strut units.展开更多
As it is evident from the practice of construction and maintenance of thin retaining walls, the degree of developing of frictional forces in interlock connections of steel sheet U-shape piles essentially influences th...As it is evident from the practice of construction and maintenance of thin retaining walls, the degree of developing of frictional forces in interlock connections of steel sheet U-shape piles essentially influences the realization of the values of geometric characteristics of the piles cross-section （the moment of inertia and the section modulus） reduced to the length unit of the construction. The article offers new and simple solutions for realization and economically effective technological approaches to provide joint work of the sheet piles being considered, which improve the adequacy of design and reliability of maintenance of thin retaining walls.展开更多
Lately, cardiovascular diseases are becoming a critical issue to human health and patients suffer from such a disease tend to be increasing throughout the world due to the changes in lifestyle. As the remedies to card...Lately, cardiovascular diseases are becoming a critical issue to human health and patients suffer from such a disease tend to be increasing throughout the world due to the changes in lifestyle. As the remedies to cardiovascular diseases, a coronary artery bypass graft surgery （CABG） and a stent implantation have been widely used. In order to achieve successful results through these treatments, a stent must fulfill the certain conditions with its design and mechanical properties. A stent must have sufficient stiffness to secure the strength of narrowed blood vessel and sufficient fatigue strength against the pulsatory motion of the blood vessel. Also its high flexibility is mandatory not to damage the vessel wall while it is being transferred to the lesion through the blood vessel. A design of stent has considerable influence upon the performance of stent. Thickness, curvature and connection method of strut are main variable factors in stent design.展开更多
基金provided by the National Natural Science Foundation of China(No.51404256)the National Basic Research Program of China(No.2013CB227900)Fundamental Research Funds for the Central Universities of China(No. 2014QNA51)
文摘Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a U-shaped steel closed support with an inverted U-shaped steel arch in the floor is proposed as a method for improving the support effect of the surrounding rock during the process of floor heaving.This research established a mechanical model for the U-shaped steel closed support,and determined the reaction forces at the connection of a camber angle.Using the limit load method calculated the critical buckling load of the inverted U-shaped steel arch,and use of a strength check method tested the strength of the U-shaped steel material.A numerical simulation was conducted using the finite difference software FLAC3 D.The simulation results show that the U-shaped steel closed support is able to control the floor heave of roadways,which is successfully used in the West 11-2 development roadway of the Zhuji Mine in the Huainan mining area in China.The cumulative floor heave over two years was less than50 mm.
文摘A current challenge concerns developing new bioresorbable stents that combine optimal mechanical properties and biodegradation rates with limited thrombogenicity. In this context, twinning-induced plasticity (TWIP) steels are good material candidates. In this work, the hemocompatibility of a new TWIP steel was studied in vitro via hemolysis and platelet activation assessments. Cobalt chromium (CoCr) L605 alloy, pure iron (Fe), and magnesium (Mg) WE43 alloy were similarly studied for comparison. No hemolysis was induced by TWIP steel, pure Fe, or L605 alloy. Moreover, L605 alloy did not affect CD62P exposure, αIIbβ3 activation at the platelet surface, or phosphorylation of protein kinase C (PKC) substrates upon thrombin stimulation. In contrast, TWIP steel and pure Fe significantly decreased platelet response to the agonist. Given that similar inhibitory effects were obtained when using a conditioned medium previously incubated with TWIP steel, we postulated TWIP steel corrosion to be likely to release components counteracting platelet activation. We showed that the main ion form present in the conditioned medium is Fe3+. In conclusion, TWIP steel resorbable scaffold displays anti-thrombogenic properties in vitro, which suggests that it could be a promising platform for next-generation stent technologies.
文摘Objective To study the safety of the novel high nitrogen nickel-free austenitic stainless steel bare metal stents （BMS） in a recognized porcine coronary model and to select a better grid structure of it. Methods Three types of stents were randomly implanted in different coronary arteries of the same pig： 316L stainless steel BMS （316L-BMS） （n=12）, novel high nitrogen nickel-free stents Grid A （NF-A-BMS） （n=12） and novel high nitrogen nickel-free stents Grid B （NF-B-BMS） （n=12）. In total, eighteen animals underwent successful random placement of 36 oversized stents in the coronary arteries. Coronary angiography was performed after 36 d of stents implantation. Nine animals were respectively sacrificed after 14 d and 36 d for histomorphologic analysis. 〈br〉 Results Quantitative coronary angiography （QCA） showed similar luminal loss （LL） in the three groups：（0.21±0.17） mm for 316L-BMS, （0.16±0.12） mm for NF-A-BMS, （0.24±0.15） mm for NF-B-BMS （P=0.05）. Histomorphomeric analysis after 15 d and 36 d revealed that there was also no significant difference among the three groups in neointimal area （NA） with similar injury scores respectively. High magnification histomorphologic examination showed similar inflammation scores in the three groups, but NF-A-BMS group had poorer endothelialization scores compared with NF-B-BMS group, 2.00±0.63 vs. 2.83±0.41 （P=0.015） at 15 d, which also could be proved by the scanning electron microscope. However, the difference could not been observed at 36 d. Conclusion The novel NF-BMS showed similar safety as 316L-BMS during the short-term study. NF-B-BMS had better endothelialization than NF-A-BMS and this may owe to the specific strut units.
文摘As it is evident from the practice of construction and maintenance of thin retaining walls, the degree of developing of frictional forces in interlock connections of steel sheet U-shape piles essentially influences the realization of the values of geometric characteristics of the piles cross-section （the moment of inertia and the section modulus） reduced to the length unit of the construction. The article offers new and simple solutions for realization and economically effective technological approaches to provide joint work of the sheet piles being considered, which improve the adequacy of design and reliability of maintenance of thin retaining walls.
文摘Lately, cardiovascular diseases are becoming a critical issue to human health and patients suffer from such a disease tend to be increasing throughout the world due to the changes in lifestyle. As the remedies to cardiovascular diseases, a coronary artery bypass graft surgery （CABG） and a stent implantation have been widely used. In order to achieve successful results through these treatments, a stent must fulfill the certain conditions with its design and mechanical properties. A stent must have sufficient stiffness to secure the strength of narrowed blood vessel and sufficient fatigue strength against the pulsatory motion of the blood vessel. Also its high flexibility is mandatory not to damage the vessel wall while it is being transferred to the lesion through the blood vessel. A design of stent has considerable influence upon the performance of stent. Thickness, curvature and connection method of strut are main variable factors in stent design.
