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  • 1
    Publication Date: 2019
    Description: Background: Although several equations for predicting VO2max in children and adolescents have been reported, the validity of application of these equations to the Korean population has not been verified. The purpose of study was to develop and validate regression models to estimate maximal oxygen uptake (VO2max) using a newly developed 20 m progressive shuttle test (20 m PST) protocol in Korean male (n = 80, 15.3 ± 1.86 years) and female (n = 81, 15.5 ± 1.73 years) adolescents aged 13–18 years. Methods: The modified 20 m PST was performed and the VO2max was assessed in a sample of 161 participants. The participants underwent a treadmill test (TT) in the laboratory and the modified 20 m PST in a gymnasium. For the validation study, the participants performed the TT with a stationary metabolic cart and the 20 m PST with a portable metabolic cart once. In addition, they performed the 20 m PST two more times to establish test–retest reliability. Results: The mean VO2max (49.6 ± 8.7 mL·kg−1·min−1) measured with the potable metabolic cart was significantly higher than that measured in the graded exercise test with the stationary metabolic cart (46.6 ± 8.9 mL·kg−1·min−1, p 〈 0.001) using the new 20 m PST protocol. The standard error of the estimate (SEE) between these two measurements was 1.35 mL·kg−1·min−1. However, the VO2max derived from the newly developed equation was 46.7 ± 7.3 mL·kg−1·min−1 (p 〉 0.05) and the SEE was 2.90 mL·kg−1·min−1. The test and retest trials of the 20 m PST yielded comparable results (laps, r = 0.96; last speed, r = 0.93). Conclusions: Our data suggest that the new 20 m PST protocol is valid and reliable and that the equation developed in this study provides a valid estimate of VO2max in Korean male and female adolescents aged 13–18 years.
    Print ISSN: 1661-7827
    Electronic ISSN: 1660-4601
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Published by MDPI
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  • 2
    Publication Date: 2019
    Description: In a cable-driven parallel robot (CDPR), force sensors are utilized at each winch motor to measure the cable tension in order to obtain the force distribution at the robot end-effector. However, because of the effects of friction in the pulleys and the unmodeled cable properties of the robot, the measured cable tensions are often inaccurate, which causes force-control difficulties. To overcome this issue, this paper presents an artificial neural network (ANN)-based indirect end-effector force-estimation method, and its application to CDPR force control. The pulley friction and other unmodeled effects are considered as black-box uncertainties, and the tension at the end-effector is estimated by compensating for these uncertainties using an ANN that is developed using the training datasets from CDPR experiments. The estimated cable tensions at the end-effector are used to design a P-controller to track the desired force. The performance of the proposed ANN model is verified through comparisons with the forces measured directly at the end-effector. Furthermore, cable force control is implemented based on the compensated tensions to evaluate the performance of the CDPR in wrench space. The experimental results show that the proposed friction-compensation method is suitable for application in CDPRs to control the cable force.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI
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  • 3
    Publication Date: 2019
    Description: Improvement of energy harvesting performance from flexible thin film-based energy harvesters is essential to accomplish future self-powered electronics and sensor systems. In particular, the integration of harvesting signals should be established as a single device configuration without complicated device connections or expensive methodologies. In this research, we study the dual-film structures of the flexible PZT film energy harvester experimentally and theoretically to propose an effective principle for integrating energy harvesting signals. Laser lift-off (LLO) processes are used for fabrication because this is known as the most efficient technology for flexible high-performance energy harvesters. We develop two different device structures using the multistep LLO: a stacked structure and a double-faced (bimorph) structure. Although both structures are well demonstrated without serious material degradation, the stacked structure is not efficient for energy harvesting due to the ineffectively applied strain to the piezoelectric film in bending. This phenomenon stems from differences in position of mechanical neutral planes, which is investigated by finite element analysis and calculation. Finally, effectively integrated performance is achieved by a bimorph dual-film-structured flexible energy harvester. Our study will foster the development of various structures in flexible energy harvesters towards self-powered sensor applications with high efficiency.
    Electronic ISSN: 1424-8220
    Topics: Chemistry and Pharmacology , Electrical Engineering, Measurement and Control Technology
    Published by MDPI
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  • 4
    Publication Date: 2018
    Description: The occurrence of landslide in the hilly region of South Korea is a matter of serious concern. This study tries to produce landslide susceptibility maps for Jumunjin Country in South Korea. Three machine learning algorithms, namely Logistic Regression (LR), LogitBoost (LB), and NaïveBayes (NB) are used, and their final model outcomes are compared to each other. Firstly, a landslide inventory map and the associated input data layers of the landslide conditioning factors were developed based on field verification, historical records, and high-resolution remote-sensing data in the geographic information system (GIS) environment. Seventeen landslide conditioning factors were prepared, including aspect, slope, altitude, maximum curvature, profile curvature, topographic wetness index (TWI), topographic positioning index (TPI), distance from fault, convexity, forest type, forest diameter, forest density, land use/land cover, lithology, soil, flow accumulation, and mid slope position. The result showed that the area under the curve (AUC) values of LR, LB, and NB models were 84.2%, 70.7%, and 85.2%, respectively. The results revealed that the LR and LB models produced reasonable accuracy than respect to NB model in landslide susceptibility assessment. The final susceptibility maps would be useful for preliminary land-use planning and hazard mitigation purpose.
    Electronic ISSN: 2071-1050
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by MDPI
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  • 5
    Publication Date: 2018
    Description: Brain-specific angiogenesis inhibitors (BAIs) 1, 2, and 3 are members of the adhesion G protein-coupled receptors, subfamily B, which share a conserved seven-transmembrane structure and an N-terminal extracellular domain. In cell- and animal-based studies, these receptors have been shown to play diverse roles under physiological and pathological conditions. BAI1 is an engulfment receptor and performs major functions in apoptotic-cell clearance and interacts (as a pattern recognition receptor) with pathogen components. BAI1 and -3 also participate in myoblast fusion. Furthermore, BAI1–3 have been linked to tumor progression and neurological diseases. In this review, we summarize the current understanding of the functions of BAI1–3 in pathological and physiological conditions and discuss future directions in terms of the importance of BAIs as pharmacological targets in diseases.
    Electronic ISSN: 2073-4425
    Topics: Biology
    Published by MDPI
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  • 6
    Publication Date: 2019
    Description: In this paper, we propose a novel data augmentation method with respect to the target context of the data via self-supervised learning. Instead of looking for the exact synonyms of masked words, the proposed method finds words that can replace the original words considering the context. For self-supervised learning, we can employ the masked language model (MLM), which masks a specific word within a sentence and obtains the original word. The MLM learns the context of a sentence through asymmetrical inputs and outputs. However, without using the existing MLM, we propose a label-masked language model (LMLM) that can include label information for the mask tokens used in the MLM to effectively use the MLM in data with label information. The augmentation method performs self-supervised learning using LMLM and then implements data augmentation through the trained model. We demonstrate that our proposed method improves the classification accuracy of recurrent neural networks and convolutional neural network-based classifiers through several experiments for text classification benchmark datasets, including the Stanford Sentiment Treebank-5 (SST5), the Stanford Sentiment Treebank-2 (SST2), the subjectivity (Subj), the Multi-Perspective Question Answering (MPQA), the Movie Reviews (MR), and the Text Retrieval Conference (TREC) datasets. In addition, since the proposed method does not use external data, it can eliminate the time spent collecting external data, or pre-training using external data.
    Electronic ISSN: 2073-8994
    Topics: Mathematics
    Published by MDPI
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  • 7
    Publication Date: 2016-12-19
    Print ISSN: 2469-9926
    Electronic ISSN: 2469-9934
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
    Publication Date: 2015-10-19
    Print ISSN: 1098-0121
    Electronic ISSN: 1550-235X
    Topics: Physics
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