• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.187-194
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• 2008

Because the types and severities of most engine faults are various and complex, it is not easy that the conventional model based fault detection approach like the GPA(Gas Path Analysis) method can monitor all engine fault conditions. Therefore this study proposed newly a diagnostic algorithm for isolating and diagnosing effectively the faulted components of the smart UAV propulsion system, which has been developed by KARI(Korea Aerospace Research Institute), using the fuzzy logic and the neural network algorithms. A precise performance model should be needed to perform the model-based diagnostics. The based engine performance model was developed using SIMULINK. For the work and mass flow matching between components of the steady-state simulation, the state-flow library was applied. The proposed steady-state performance model can simulate off-design point performance at various flight conditions and part loads, and in order to evaluate the steady-state performance model their simulation results were compared with manufacturer's performance deck data. According to comparison results, it was confirm that the steady-state model well agreed with the deck data within 3% in all flight envelop. The diagnosis procedure of the proposed diagnostic system has the following steps. Firstly after obtaining database of fault patterns through performance simulation, then secondly the diagnostic system was trained by the FFBP networks. Thirdly after analyzing the trend of the measuring parameters due to fault patterns, then fourthly faulted components were isolated using the fuzzy logic. Finally magnitudes of the detected faults were obtained by the trained neural networks. Because the detected faults have almost same as degradation values of the implanted fault pattern, it was confirmed that the proposed diagnostic system can detect well the engine faults.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.1
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• pp.58-65
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• 2019

The stability, reliability and efficiency of a smart ship are important issues as the interest in an autonomous ship has recently been high. An automatic collision avoidance system is an essential function of an autonomous ship. This system detects the possibility of collision and automatically takes avoidance actions in consideration of economy and safety. In order to construct an automatic collision avoidance system using reinforcement learning, in this work, the sequential decision problem of ship collision is mathematically formulated through a Markov Decision Process (MDP). A reinforcement learning environment is constructed based on the ship maneuvering equations, and then the three key components (state, action, and reward) of MDP are defined. The state uses parameters of the relationship between own-ship and target-ship, the action is the vertical distance away from the target course, and the reward is defined as a function considering safety and economics. In order to solve the sequential decision problem, the Deep Deterministic Policy Gradient (DDPG) algorithm which can express continuous action space and search an optimal action policy is utilized. The collision avoidance system is then tested assuming the $90^{\circ}$intersection encounter situation and yields a satisfactory result.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.3
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• pp.89-94
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• 2019

K1A1 tank commander's primary thermal sight is a device that enables tank commanders to detect, identify, aim and track the target by observing targets in all directions during day, night and in situations of smokescreen and fog through $360^{\circ}$ rotation independent from the gunner's primary thermal sight and stabilizing the line of sight even under the vibrations occurring when the tank is standstill and moving. The main function of this device is to detect and process visible and thermal images and deliver the final images to the tank commander. One of the core parts to that end is the observation window (daytime/thermal image window). This core part is mounted at the entrance of the optical path for observing the target and plays the role of making visible light during the daytime and infrared light during the night pass through the target and transmitting the resultant images to the internal optical system of the tank commander's primary thermal sight. Such core parts have been selected as depot maintenance items so that they are replaced by new parts instead of being recycled when they are subjected to maintenance in most cases. That is, the military budget is wasted because such parts are replaced by new parts despite that they can be recycled for maintenance. Therefore, this study proposed a mounting tool for polishing and coating observation windows (daytime and thermal image window) using planar polishing equipment and DLC (Diamond-Like Carbon) coating equipment. In addition, this study presented an amendment (proposal) of the Depot Maintenance Work Request (DMWR) already published to verify the performance of recycled products including the establishment of inspection standards for recycling processes.

• The Journal of the Convergence on Culture Technology
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• v.5 no.3
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• pp.155-163
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• 2019

This study was to analyze whether volunteer motivation represents a mediated effect in the relationship between social support and multicultural acceptance by university students as a late adolescent. Among the students attending a university located in North Chungcheong Province, 256 participants have experienced volunteer work. Data analysis conducted multiple regression analysis using SPSS and analysis showed that social support of university students affected multicultural acceptance and that volunteer motivation in their relationship between social support and multicultural acceptance was fully mediated. Based on these results, it has revealed a path that the social support of university students affects multicultural acceptance through volunteer motivation. Therefore, in order to gain social support, university students should improve their ability to maintain a positive view of interpersonal relations and to cope with conflicts efficiently. They will also have to strengthen self-directing capacity in order to increase the level of motivation for volunteer participation.

• Safety and Health at Work
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• v.10 no.3
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• pp.260-264
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• 2019

Background: Professional dance is a physically demanding career path with a high injury prevalence, yet an ingrained culture of hiding or pushing through injuries. Developing better knowledge surrounding the cultural beliefs and behaviors related to injury reporting is critical to understand their incidence and burden. Therefore, the aim of this study was to investigate injury fear and injury reporting behaviors in professional dancers in Australia. Methods: This study utilized data collected in a cross-sectional survey of professional dancers in Australia. Descriptive analysis of injury fear and reporting stigma are presented with comparisons between subgroups (full-time versus part-time dancers; men versus women) conducted using two-sided Fisher's exact tests. Results: A total of 146 professional dancers were included. Over half (63%) of the respondents reported that they fear sustaining a dance-related injury, that they believe there is still a stigma surrounding injuries in dance (62%), and that this stigma has led to a delay in reporting or seeking care for an injury (51%). A lower proportion of part-time than full-time dancers reported that they would usually tell someone within their dance employment about an injury (35.1% vs. 59.6%, p = 0.006). Conclusion: Professional dancers are at risk of losing contracts or roles if they are injured, and therefore, it is common to dance through their occurrence. Many dancers, particularly those dancing part-time, are unwilling to tell their employers about their injuries. Action is required to improve this culture regarding injury reporting and help seeking for more effective injury understanding, prevention, and management in dance.

• Journal of Digital Convergence
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• v.17 no.11
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• pp.315-325
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• 2019

The study attempted to examine the structural model of the effects of health status and retirement aging anxiety on middle-aged workers. The subjects were collected from 263 40-59 year old middle-aged workers who work at three institutions in C and G cities. Results First, the variables affecting aging anxiety were aging preparation and health status, and these variables accounted for 52% of aging anxiety. Second, health status had a significant effect on retirement preparedness, and there was a significant indirect effect on aging anxiety through retirement preparedness. There was a partial control effect due to the difference in the path coefficient between health status and aging anxiety in the multi-group moderating effect of 40~49 and 50~59 years. Therefore, in order to reduce aging anxiety, it is important to find ways to prepare for various retirement, and a systematic management system is necessary.

• International Journal of Computer Science & Network Security
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• v.21 no.6
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• pp.23-28
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• 2021

The article discusses the features of adaptation of the parameters of the physical layer of data transmission in self-organizing networks based on unmanned aerial vehicles operating in the conditions of "smart cities". The concept of cities of this type is defined, the historical path of formation, the current state and prospects for further development in the aspect of transition to "smart cities" of the third generation are shown. Cities of this type are aimed at providing more comfortable and safe living conditions for citizens and autonomous automated work of all components of the urban economy. The perspective of the development of urban mobile automated technical means of infocommunications is shown, one of the leading directions of which is the creation and active use of wireless self-organizing networks based on unmanned aerial vehicles. The advantages of using small-sized unmanned aerial vehicles for organizing networks of this type are considered, as well as the range of tasks to be solved in the conditions of modern "smart cities". It is shown that for the transition to self-organizing networks in the conditions of "smart cities" of the third generation, it is necessary to ensure the adaptation of various levels of OSI network models to dynamically changing operating conditions, which is especially important for the physical layer. To maintain an acceptable level of the value of the bit error probability when transmitting command and telemetry data, it is proposed to adaptively change the coding rate depending on the signal-to-noise ratio at the receiver input (or on the number of channel decoder errors), and when transmitting payload data, it is also proposed to adaptively change the coding rate together with the choice of modulation methods that differ in energy and spectral efficiency. As options for the practical implementation of these solutions, it is proposed to use an approach based on the principles of neuro-fuzzy control, for which examples of determining the boundaries of theoretically achievable efficiency are given.

• Sleep Medicine and Psychophysiology
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• v.28 no.1
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• pp.34-42
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• 2021

Objectives: This study investigated sleep quality in female full-time homemakers and evaluated the relationship of sleep disturbance with psychological and socio-environmental factors. Methods: This cross-sectional study adopted a structured survey and sequential recruitment method for randomized participation of community-dwelling full-time female homemakers. Sleep quality and mental health were measured using the Korean version of the Pittsburgh Sleep Quality Index (K-PSQI), Korean version of the Beck Depression Inventory-II (K-BDI-II), Korean version of the Beck Anxiety Inventory (K-BAI), and Korean version of the Beck Hopelessness Scale (K-BHS). The willingness-to-pay (WTP) method was selected to measure the self-evaluated monetary value of household service work. The relationship among the main relevant factors was statistically analyzed through a mediation model. Results: A total of 166 participants were analyzed and classified having poor versus good sleep quality (poor : 24.1%, n = 40 ; good : 75.9%, n = 126 ; cut-off point = 9 on the K-PSQI). Significant between-group differences were observed in mental health status (K-BDI-II, p < 0.001 ; K-BAI, p < 0.001 ; K-BHS, p = 0.003). The moderated mediation model was verified, indicating that depression may mediate the association between nurturing burden and sleep disturbance. The path from nurturing burden to depression may be moderated by average monthly household income. Conclusion: A relatively high portion of full-time female homemakers may suffer from sleep disturbance and interactions between psychological and socio-environmental factors might determine sleep quality, suggesting the need for public health policies targeting improvement of sleep quality and mental health among full-time homemakers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.3
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• pp.377-383
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• 2021

Recently, in accordance with the 4th industrial revolution, The use of autonomous mobile robots for flexible logistics transfer is increasing in factories, the warehouses and the service areas, etc. In large factories, many manual work is required to use Simultaneous Localization and Mapping(SLAM), so the need for the improved mobile robot autonomous driving is emerging. Accordingly, in this paper, an algorithm for mapless navigation that travels in an optimal path avoiding fixed or moving obstacles is proposed. For mapless navigation, the robot is trained to avoid fixed or moving obstacles through Deep Q Network (DQN) and accuracy 90% and 93% are obtained for two types of obstacle avoidance, respectively. In addition, DQN requires a lot of learning time to meet the required performance before use. To shorten this, the target size change algorithm is proposed and confirmed the reduced learning time and performance of obstacle avoidance through simulation.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.129-138
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• 2021

Today we are getting a lot of information and various activities on our website through the internet. These websites are maintained by individuals or by website specialists. The basic method is to change the files that make up the running website. Changing the entire file in this process takes a long time and changes the files that do not need to be changed, so the efficiency is greatly reduced. When only the files that need to be changed are changed, it takes a lot of effort as a person must manually search each path to check the files and change the files one by one. To solve this problem, automatic distribution systems were developed. Additional resources and learning are required, resulting in additional cost, time and labor. Therefore, in this paper, we propose an automatic update system to minimize resource consumption by using the resources and technologies of the existing website. The proposed system does not require learning new skills. This aims to improve reliability and reduce time compared to human work.