State-space aerodynamic model reveals high force control authority and predictability in flapping flight.

Flying animals resort to fast, large-degree-of-freedom motion of flapping wings, a key feature that distinguishes them from rotary or fixed-winged robotic fliers with limited motion of aerodynamic surfaces. However, flapping-wing aerodynamics are characterized by highly unsteady and three-dimensional flows difficult to model or control, and accurate aerodynamic force predictions often rely on expensive computational or experimental methods. Here, we developed a computationally efficient and data-driven state-space model to dynamically map wing kinematics to aerodynamic forces/moments. This model was trained and tested with a total of 548 different flapping-wing motions and surpassed the accuracy and generality of the existing quasi-steady models. This model used 12 states to capture the unsteady and nonlinear fluid effects pertinent to force generation without explicit information of fluid flows. We also provided a comprehensive assessment of the control authority of key wing kinematic variables and found that instantaneous aerodynamic forces/moments were largely predictable by the wing motion history within a half-stroke cycle. Furthermore, the angle of attack, normal acceleration and pitching motion had the strongest effects on the aerodynamic force/moment generation. Our results show that flapping flight inherently offers high force control authority and predictability, which can be key to developing agile and stable aerial fliers.

Rheumatic manifestations of hepatitis B and C and their association with viral load and fibrosis of the liver.

The objective of this study is to investigate rheumatologic manifestations of hepatitis B and C and their relation with viral load and degree of hepatic fibrosis. Thirty-six HBV and 36 HBV patients were included. Liver biopsy was performed for all participants. We detected arthralgia 53-50%, myalgia 58-61% and fatigue 64-81% in HBV and HCV groups in order. All manifestations did not differ between groups significantly. Pain intensity was higher in HCV group (P = 0.023). Arthralgia is associated with viral load of the patients in both groups (P = 0.000 and P = 0.001). Viral load and fatigue are correlated in both groups (P = 0.000 and P = 0.001). There is a considerable relation between inflammation and arthralgia (P = 0.000) and myalgia (P = 0.033). We conclude that rheumatologic manifestations are common both in HBV and HCV and related with viral load and fibrosis.