Modeling and stabilization of a wireless network control system with packet loss and time delay

The problem of modeling and stabilization of a wireless network control system (NCS) is considered in this paper, where packet loss and time delay exist simultaneously in the wireless network. A discrete-time switched system with time-varying delay model is first proposed to describe the system closed by a static state feedback controller. A sufficient criteria for the discrete-time switched system with time-varying delay to be stable is proposed, based on which, the corresponding state feedback controller is obtained by solving a set of linear matrix inequalities (LMIs). Numerical examples show the effectiveness of the proposed method.     

Super-twisting observer-based sliding mode control with fuzzy variable gains and its applications to fully-actuated hexarotors

In this paper, we consider the super-twisting observer-based sliding mode control algorithm with fuzzy variable gains (STOSMC) for the fully-actuated hexarotor. Our hexarotor has full actuation due to six titled propellers that allows to control position and orientation (attitude) simultaneously, and resolves the singularity problem of the rotational matrix by using the quaternion modeling framework. We show that the proposed STOSMC for the hexarotor guarantees finite-time convergence of the estimation error and asymptotic stability of the hexarotor. In simulations, we demonstrate the nonsingularity and fully-actuated control performance of the hexarotor by considering extreme position and attitude control scenarios. Moreover, the simulation results show that the hexarotor achieves the fast and precise tracking performance to the desired position and the desired attitude and the chattering phenomenon is reduced compared with the fixed-gains observer-based super-twisting sliding mode control due to the fuzzy mechanism.     

Programmed sample delivery on a pressurized paper

This paper reports a method to control the fluid flow in paper-based microfluidic devices simply by pressing over the channel surface of paper, thereby decreasing the pore size and permeability of a non-woven polypropylene sheet. As a result, fluid resistance is increased in the pressed region and causes flow rate to decrease. We characterize the decrease of flow rate with respect to different amounts of pressure applied, and up to 740% decrease in flow velocity was achieved. In addition, we demonstrate flow rate control in a Y-shaped merging paper and sequential delivery of multiple color dyes in a three-branched paper. Furthermore, sequential delivery of multiple fluid samples is performed to demonstrate its application in multi-step colorimetric immunoassay, which shows a 4.3-fold signal increase via enhancement step.     

Relations of emergent literacy skill development with conventional literacy skill development in Korean

The present study investigated relative contributions of initial status and growth rates of emergent literacy skills (i.e., phonological awareness, letter-name knowledge, vocabulary, and rapid serial naming) to initial status and growth rates of conventional literacy skills (i.e., word reading, pseudoword reading, and spelling) for young Korean children. A total of 215 four-year-old children were followed for approximately 15 months. Results showed (1) consistent effects of letter-name knowledge, phonological awareness, and rapid serial naming on conventional literacy skills, and (2) the importance of children’s initial level in the emergent literacy skills for achieving conventional literacy skills. These results are discussed in light of characteristics of the Korean language and writing system.     

Critical Literacy Practices Within Problem-Based Learning Projects in Science

Interchange - Digital technologies are part of many children’s everyday lives. They use them for entertainment, information seeking and connecting with friends on social media. These shifts...