Objective:To understand the rate of cognition and protection of COVID-19 in a community in Hubei province.Methods:The related knowledge,epidemic situation and self-protective measures of COVID-19 were investigated by ...Objective:To understand the rate of cognition and protection of COVID-19 in a community in Hubei province.Methods:The related knowledge,epidemic situation and self-protective measures of COVID-19 were investigated by mobile phone questionnaire among 836 people in a community in Hubei province.Results:The rate of the awareness of COVID-19’s relevant knowledge and the ways to obtain the epidemic situation varied among different age groups.After multi-channel intervention in the community,the rate of the awareness of COVID-19’s relevant knowledge increased from 75.0%to 96.2%,and the implementation rate of personal protection increased from 59.6%to 92.6%.Conclusion:It is of great significance to improve residents’awareness and protection consciousness and block the spread of COVID-19 in the community through multi-channel intervention.展开更多
Axial piston pumps have been widely used in aircraft hydraulic systems to supply the system with pressurized fluid. The continuous improvement of the aircraft performance has put forward the demand on aviation piston ...Axial piston pumps have been widely used in aircraft hydraulic systems to supply the system with pressurized fluid. The continuous improvement of the aircraft performance has put forward the demand on aviation piston pumps for high power density, safety, and reliability. The lubricating interfaces in axial piston machines are the key design issue that greatly determines the pump performance and service life. The cylinder block/valve plate interface is one of these critical lubricating interfaces and has received considerable attention from many researchers in the last half century. This study aims to review the state-of-the-art literature on the cylinder block/valve plate interface comprehensively and systematically. First, we introduce various theoretical models developed to investigate the lubrication behaviors of the interface and compare them in terms of their assumptions and limitations. Second, the experimental studies on the cylinder block/valve plate interface are presented comprehensively, where the involved test rigs are divided into three types according to their fidelity levels and measurement functionality. Third, we summarize some typical approaches of structure optimization, surface shaping, and surface strengthening, which help improve the load-carrying and anti-wear capacities of the interface under severe operating conditions. Finally, the challenges and future trends of the cylinder block/valve plate interface research are discussed briefly.展开更多
In this paper, it is shown that for a 3-dimensional small cover M over a polytope P, there are only 2-torsions in H_1(M; Z). Moreover, the mod 2 Betti number growth of finite covers of M is studied.
It is Thurston's result that for a hyperbolic knot K in S^3, almost all Dehn fillings on its complement result in hyperbolic 3-manifolds except some exceptional cases. So almost all produced 3-manifolds have the s...It is Thurston's result that for a hyperbolic knot K in S^3, almost all Dehn fillings on its complement result in hyperbolic 3-manifolds except some exceptional cases. So almost all produced 3-manifolds have the same geometry. It is known that its complement in S^3, denoted by E(K), admits a Heegaard splitting. Then it is expected that there is a similar result on Heegaard distance for Dehn fillings. In this paper, Dehn fillings on genus two Heegaard splittings are studied. More precisely, we prove that if the distance of a given genus two Heegaard splitting of E(K) is at least 3, then for any two degenerating slopes on ?E(K), there is a universal bound of their distance in the curve complex of ?E(K).展开更多
文摘Objective:To understand the rate of cognition and protection of COVID-19 in a community in Hubei province.Methods:The related knowledge,epidemic situation and self-protective measures of COVID-19 were investigated by mobile phone questionnaire among 836 people in a community in Hubei province.Results:The rate of the awareness of COVID-19’s relevant knowledge and the ways to obtain the epidemic situation varied among different age groups.After multi-channel intervention in the community,the rate of the awareness of COVID-19’s relevant knowledge increased from 75.0%to 96.2%,and the implementation rate of personal protection increased from 59.6%to 92.6%.Conclusion:It is of great significance to improve residents’awareness and protection consciousness and block the spread of COVID-19 in the community through multi-channel intervention.
基金supported by Chinese Civil Aircraft Project [No. MJ-2017-S49]China National Postdoctoral Program for Innovative Talents [No. BX20200210]China Postdoctoral Science Foundation [No. 2019M660086]。
文摘Axial piston pumps have been widely used in aircraft hydraulic systems to supply the system with pressurized fluid. The continuous improvement of the aircraft performance has put forward the demand on aviation piston pumps for high power density, safety, and reliability. The lubricating interfaces in axial piston machines are the key design issue that greatly determines the pump performance and service life. The cylinder block/valve plate interface is one of these critical lubricating interfaces and has received considerable attention from many researchers in the last half century. This study aims to review the state-of-the-art literature on the cylinder block/valve plate interface comprehensively and systematically. First, we introduce various theoretical models developed to investigate the lubrication behaviors of the interface and compare them in terms of their assumptions and limitations. Second, the experimental studies on the cylinder block/valve plate interface are presented comprehensively, where the involved test rigs are divided into three types according to their fidelity levels and measurement functionality. Third, we summarize some typical approaches of structure optimization, surface shaping, and surface strengthening, which help improve the load-carrying and anti-wear capacities of the interface under severe operating conditions. Finally, the challenges and future trends of the cylinder block/valve plate interface research are discussed briefly.
基金supported by the National Natural Science Foundation of China(Nos.11371094,11771088)
文摘In this paper, it is shown that for a 3-dimensional small cover M over a polytope P, there are only 2-torsions in H_1(M; Z). Moreover, the mod 2 Betti number growth of finite covers of M is studied.
基金supported by National Natural Science Foundation of China(Grant Nos.11371094,11571110 and 11601065)
文摘It is Thurston's result that for a hyperbolic knot K in S^3, almost all Dehn fillings on its complement result in hyperbolic 3-manifolds except some exceptional cases. So almost all produced 3-manifolds have the same geometry. It is known that its complement in S^3, denoted by E(K), admits a Heegaard splitting. Then it is expected that there is a similar result on Heegaard distance for Dehn fillings. In this paper, Dehn fillings on genus two Heegaard splittings are studied. More precisely, we prove that if the distance of a given genus two Heegaard splitting of E(K) is at least 3, then for any two degenerating slopes on ?E(K), there is a universal bound of their distance in the curve complex of ?E(K).
