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Waverider hypersonic vehicles have the characteristics of strong coupling between subsystems and the wide range flight envelope. Therefore, the control analysis and synthesis should be integrated into the early stage of vehicle design, the parameters in control system should be optimized as well as the parameters in aerodynamic, propulsion and structure systems in the vehicle design, and the software tool to facilitate the design process should be developed. Firstly, a series of parameters are used to describe the geometric, and a parameterized model of hypersonic vehicles is established. Then, the objective function is determined according to mission requirements, and then optimal parameter set will be obtained by searching variables in design space to satisfy the constraints. Then, the control relaxed specifications, such as controlability, stability, robustness and time-domain performances etc., are set as the optimization indexes, and the proposal on how to adjust parameters is feedbacked to optimization loop. A optimal vehicle configurations is obtained. Finally, the software, which is used to assist vehicle design, is able to carry out vehicle modeling, analyze static and dynamic characteristics, and provide various controller design templates automatically. [ABSTRACT FROM AUTHOR]

Boom aerial refueling system is a kind of multi-rigid-body system with dynamic interaction. The system, which has eight degrees of free (DoFs), is simplified into two-rigid-body, connected by cardan joint. To research the system dynamics, generalized coordinates and generalized velocities are defined, the aerodynamic force on boom is estimated, and a Kane method based model is established. Simulation results indicate that though responses of boom attitude are stable, they are still dissatisfied because of the dynamic coupling between longitudinal and lateral responses, and the distinct influence on the attitude responses caused by the boom extension. The dynamic coupling also exists between tanker and boom. However, if tanker's control system is robust enough to reject disturbance, the boom control law can be designed separately. [ABSTRACT FROM AUTHOR]

In the super low attitude of the airdrop, the movement of the cargos in the cabin will cause significant changes in the center of gravity (CG), the moment of inertia as well as the aerodynamic torque around the center of mass. As a result, the aircraft may become instability. The center of mass of the aircraft is taken as the reference point to establish dynamics models including before the airdrop, the extraction parachute pulling the cargos and the cargos moving in the cabin based on theoretical mechanics and basic flight dynamic equations. Finally, the effect of the extraction parachute, the cargos and the parachute opening process on the airdrop is simulated. [ABSTRACT FROM AUTHOR]

Transport airdropping heavy cargo at super-low-altitude is a complex technical procedure demanding high precision control. The second class equations of Lagrange analytical mechanics are used for establishing the dynamics model for transport-cargo-two-body systems. The model is simpler than Newtonian mechanics since the constraint force between transport and cargo is ideal. State space description is obtained then and state feedback H∞ flight control law is designed in order to suppress transport's attitude response to heavy cargo's moving in airdropping procedure. Numerical simulation is carried out in the conditions of open-loop and closed-loop respectively and the results show that the proposed H∞ closed-loop flight control law is effective. [ABSTRACT FROM AUTHOR]

Objectives: To construct the three-dimensional structure of the isolated teeth of patients with dentinogenesis imperfecta type Ⅱ (DGI-Ⅱ) and dentin dysplasia type Ⅰ (DD-Ⅰ) by using Micro-CT and explore internal structure and hard tissue mineralization density., Methods: The three-dimensional structures of the third molars collected from patients with DGI-Ⅱ and DD-Ⅰ and healthy individuals of the same age were reconstructed by using Micro-CT (Mimics 17.0). The internal structures of the affected teeth along the sagittal and transverse planes were observed. The grayscale values of the enamel, crown dentin, and root dentin were calculated. Then, the mineralization densities of the different parts of the teeth of the three groups were analyzed., Results: The detailed three-dimensional models of the mandibular third molars with hereditary dentin defects were successfully constructed. The models contained the models of the enamel cap, dentin core, and pulp cavity. Sagittal and transverse section scans revealed that in patients with DGI-Ⅱ, the pulp cavity was incompletely calcified and the root canal was narrow, whereas in those with DD-Ⅰ, the pulp cavity and root canal were obliterated and the root of the tooth was absent. The analysis of the grayscale values showed that compared with those in the healthy group, the grayscale values of the enamel, crown dentin, and root dentin were lower in the DGI-Ⅱ and DD-Ⅰ groups ( P <0.01). No significant differences in the grayscale values of the enamel and crown dentin were found between the DGI-Ⅱ and DD-Ⅰ groups ( P >0.05), whereas the grayscale value of the root dentin showed statistically significant differences between the two groups ( P <0.01)., Conclusions: The application of Micro-CT provided a simple and accurate method for the three-dimensional structure reconstruction and quantitative analysis of the mineralization density of isolated teeth with hereditary dentin defects. Although the dentin mineralization density of DGI-Ⅱ and DD-Ⅰ teeth decreased, the decrement shown by DD-Ⅰ teeth was more significant than that shown by DGI-Ⅱ teeth. The pulp cavity had abnormal calcifications, and the root canal was narrow or even occluded.