-This paper dealt with a state-of-the-art maintenance robots for power transmission lines (PTL). The paper summarized the PTL maintenance robots that have been developed by eight major research institutions. The main features of the robot navigation were derived and classified through analysis of researches conducted by those institutions. The derived six main features were analyzed quantitatively and qualitatively through readiness level assessment. For this, system readiness level (SRL) was used to evaluate the readiness level of overall system. The SRL was obtained using technology readiness level (TRL) and integration readiness level (IRL). In addition, the readiness level for each feature was reviewed through statistical analysis using box and whisker plot. In conclusion, we confirmed the status and direction of research and development on PTL maintenance robots by analyzing conventional robots with respect to six main features.

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Background The virtual reality (VR) content market is rapidly growing due to an increased supply of VR devices such as head-mounted displays (HMDs), whereas VR sickness (reported to occur while experiencing VR) remains an unsolved problem. The most widely used method of reducing VR sickness is the use of a rest frame that stabilizes the user's viewpoint by providing fixed visual stimuli in VR content (including video). However, the earth-fixed grid and natural independent visual background that are widely used as rest frames cannot maintain VR fidelity, as they reduce the immersion and the presence of the user. A visual guide is a visual element (eg, a crosshair of first-person shooter [FPS]) that induces a user's gaze movement within the VR content while maintaining VR fidelity, whereas there are no studies on the correlation of visual guide with VR sickness. Objective This study aimed to analyze the correlation between VR sickness and crosshair, which is widely used as a visual guide in FPS games. Methods Eight experimental scenarios were designed and evaluated, including having the visual guide on/off, the game controller on/off, and varying the size and position of the visual guide to determine the effect of visual guide on VR sickness. Results The results showed that VR sickness significantly decreased when visual guide was applied in an FPS game. In addition, VR sickness was lower when the visual guide was adjusted to 30% of the aspect ratio and positioned in the head-tracking direction. Conclusions The experimental results of this study indicate that the visual guide can achieve VR sickness reduction while maintaining user presence and immersion in the virtual environment. In other words, the use of a visual guide is expected to solve the existing limitation of distributing various types of content due to VR sickness.

We propose an application for power facility monitoring using distributed sensor networks. The proposed application is a virtual frequency disturbance recorder (FDR) system that estimates the frequency of a power grid using the data from a modeled grid and sends the information to the server for monitoring via wireless communication. To verify the validity of the proposed application, we conducted experiments using actual system data. The functionality of the proposed system was also verified by establishing a ZigBee-based wireless network for power monitoring and diagnosis of disturbances.

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