Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based ...Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based on cable-rib tension structures is proposed and verified by a physical prototype. The parabolic cylindrical antenna adopts simple parallel four-bar mechanisms to construct the basic deployable unit, and the cylindrical direction dimension can be easily extended by modularization, which has obvious advantages in storage ratio and area density. Considering the complexity of the entire antenna structure design, including cable networks and flexible trusses, the form-finding design optimization model of a parabolic cylindrical antenna is established using the force density sensitivity method, and then the kinematics analysis of the deployable mechanism is carried out. Finally, a single-module prototype with a deployable diameter of 4 m × 2 m was designed and fabricated. The results of the ground deployment process test and surface accuracy measurements show that the antenna has good feasibility and practicability.展开更多
Based on chiral pool strategy,a synthesis of the C1-C9 domain of the proposed structure of didemnaketal A,a natural product with potent HIV-1 protease inhibitory activity,has been achieved.Key transformations are a Sh...Based on chiral pool strategy,a synthesis of the C1-C9 domain of the proposed structure of didemnaketal A,a natural product with potent HIV-1 protease inhibitory activity,has been achieved.Key transformations are a Shar-pless asymmetric dihydroxylation and a chelation-controlled allylation.展开更多
Starting from chiral methyl molecules 3 and 4,both derived from(R)-4-methyl-δ-valerolactone,we have ac-complished the synthesis of(R)and(S)-3-methylheptanoic acids.Our methods are amendable to the syntheses of a wide...Starting from chiral methyl molecules 3 and 4,both derived from(R)-4-methyl-δ-valerolactone,we have ac-complished the synthesis of(R)and(S)-3-methylheptanoic acids.Our methods are amendable to the syntheses of a wide variety of chiral 3-methyl alkanoic acids.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 51705388 and 51675398)the Youth Talent Fund of Science and Technology Association of Shaanxi University of Chinathe Aerospace information Research Institute, Chinese Academy of Sciences for its financial support
文摘Deployable mechanisms with light weight and high storage ratio have received considerable attention for space applications. To meet the requirements of space missions, a parabolic cylindrical deployable antenna based on cable-rib tension structures is proposed and verified by a physical prototype. The parabolic cylindrical antenna adopts simple parallel four-bar mechanisms to construct the basic deployable unit, and the cylindrical direction dimension can be easily extended by modularization, which has obvious advantages in storage ratio and area density. Considering the complexity of the entire antenna structure design, including cable networks and flexible trusses, the form-finding design optimization model of a parabolic cylindrical antenna is established using the force density sensitivity method, and then the kinematics analysis of the deployable mechanism is carried out. Finally, a single-module prototype with a deployable diameter of 4 m × 2 m was designed and fabricated. The results of the ground deployment process test and surface accuracy measurements show that the antenna has good feasibility and practicability.
文摘Based on chiral pool strategy,a synthesis of the C1-C9 domain of the proposed structure of didemnaketal A,a natural product with potent HIV-1 protease inhibitory activity,has been achieved.Key transformations are a Shar-pless asymmetric dihydroxylation and a chelation-controlled allylation.
文摘Starting from chiral methyl molecules 3 and 4,both derived from(R)-4-methyl-δ-valerolactone,we have ac-complished the synthesis of(R)and(S)-3-methylheptanoic acids.Our methods are amendable to the syntheses of a wide variety of chiral 3-methyl alkanoic acids.
