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This paper reports the development and validation of a new questionnaire to assess students' perceptions of the online learning environment in Indonesia during the COVID-19 pandemic. In total, 669 participants (454 women, 215 men) from various universities were recruited online to complete a 25-item questionnaire. Item factor analysis verified a five-factor model, while multidimensional Rasch analysis showed that all items fit this model and have good reliability. The factors of Access, Interaction, Lecturer Support, Equity, and Investigation formed the valid and reliable Online Classroom Learning Environment Inventory (OCLEI). All aspects of online learning readiness were related to the five factors of the OCLEI, therefore supporting convergent validity. With these results, we concluded that the OCLEI is a novel measure that can be used in future educational research in Indonesia. Limitations and implications are noted. [ABSTRACT FROM AUTHOR]

The objective of this paper is to introduce with a quaternion orientation based quadrotor that can be controlled by Model Predictive Control (MPC). As MPC offers promising performance in different industrial applications, quadrotor can be another suitable platform for the application of MPC. The present study consistently adopts unit quaternion approach for quadrotor orientation in order to avoid any axes overlapping problem, widely known as singularity problem whereas Euler angle orientation approach is unable to resolve so. MPC works based on the minimal cost function that includes the attitude error and consequently, the cost function requires quaternion error in order to proceed with process of MPC. Therefore, the main contribution of this study is to introduce a newly developed cost function for MPC because by definition, quaternion error is remarkably different from the attitude error of Euler angle. As a result, a unit quaternion based quadrotor with MPC can ascertain a smooth singularity-free flight that is influenced by model uncertainty. MATLAB and Simulink environment has been used to validate the cost function for quaternion by simulating several trajectories. [ABSTRACT FROM AUTHOR]

This paper presents novel wind tunnel test results on the aerodynamics of a symmetric thin porous airfoil and a porous rectangular half wing using a symmetric thin airfoil as its cross section, obtained by a six-component force balance. The variation of lift coefficient, drag coefficient, pitching moment, lift versus drag, the gradient of lift, and location of the aerodynamic center with respect to the angle of attack are presented as a function of the porosity. The data, where possible, are compared with the analytical results. The trend of the experimental results behaves in the same manner as the analytical solution. The measured drag coefficients of the airfoil and wing are also presented. The applicability of the standard equation relating the lift coefficient of a non-porous wing with that of a non-porous airfoil to the case of porous wings is verified by applying the equation to porous wings and validating the results using experimental data. Lift slope decreases as the porosity increases. The drag decreases at a low value of porosity and then increases as porosity increases. The standard equation for obtaining the lift coefficient of a wing from the lift coefficient of an airfoil is applicable and valid for porous wings and airfoils. [ABSTRACT FROM AUTHOR]