This paper addresses the kinematic and dynamic modelling and analysis for a robot arm consisting of two hydraulic cylinders driving two revolute joints of the arm. The two cylinders and relevant links of the robot constitute two local closed kinematic chains added to the main robot mechanism. Therefore, the number of generalized coordinates of the mechanical system is increased, and the mathematical modelling is more complex that requires a formulation of constraint equations with respect to the local closed chains. By using the Lagrangian formulation with Lagrangian Multipliers, the dynamic equations are first derived with respect to all extended generalized coordinates. Then a compact form of the dynamic equations is yielded by canceling the Multipliers. Since the obtained dynamic equations are expressed in terms of independent generalized coordinates which are selected according to active joint variables of the arm, the equations could be best suitable for control law design and implementation. The simulation of the forward and inverse kinematics and dynamics of the arm demonstrates the motion behavior of the robot system.
The number of COVID‐19 infections is still increasing with the omicron variant. Although vaccination has shown its effectiveness, efficacious treatments are still required. Kovir, a Vietnamese herbal medicine, has shown potential effects for non‐severe COVID‐19 patients in terms of symptom resolution and prevention of disease progression in previous studies. This phase‐3 trial evaluated the safety and efficacy of Kovir for non‐severe COVID‐19 adults. Participants were randomized to the Kovir (381 patients) or placebo (192 patients) groups. Outcomes were progression to severe/critical COVID‐19, a daily symptom score based on 11 pre‐defined symptoms, time to symptom resolution, a negative reverse transcription polymerase chain reaction, an EQ‐5D‐5L quality of life (QOL) score, and serious adverse events. Only one patient (in the placebo group) progressed to severe COVID‐19, thus we could not conclude the effect of Kovir on the prevention of disease progression. Kovir significantly reduced time to symptom resolution (median: 7 vs. 11 days, hazard ratio [95% confidence interval]: 2.03 [1.66–2.48]) compared to placebo. Kovir also increased the QOL score on days 7 and 14. No safety concerns were observed. To conclude, Kovir is safe and facilitates symptom relief for non‐severe COVID‐19 patients. We advocate using Kovir in the early phase of COVID‐19 for non‐severe adult patients.
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