• Tribology and Lubricants
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• v.36 no.6
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• pp.332-341
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• 2020

High-speed turbomachinery implements gas foil bearings (GFBs) due to their distinctive advantages, such as high efficiency, lesser part count, and lower weight. This paper provides the test results of the static structural stiffnesses and loss factors of bump-type foil thrust bearings with increasing preload and bearing deflection. The focus of the current work is to experimentally quantify variability in structural stiffnesses and loss factors among the four test thrust bearings with identical design values and material of the bump and top foil geometries using the same (open-source) fabrication method. A simple test setup, using a rigidly mounted non-rotating shaft and thrust disk, measures the bearing bump deflections with increasing static loads on the test bearing. The inner and outer diameters of the test bearings are 41 mm and 81 mm, respectively. The loss factor, best-representing energy dissipation in the test bearings, is estimated from the area inside the local hysteresis loop of the load versus the bearing deflection curve. The measurements show that structural stiffnesses and loss factors of the test bearings significantly rely on applied preloads and bearing deflections. Local structural stiffnesses of the test bearings increase with applied preloads but decrease with bearing deflections. Changes of loss factors are less sensitive to applied preloads and bearing deflections compared to those of structural stiffnesses. Up to 35% variability in static load structural stiffnesses is found between bearings, while up to 30% variability in loss factors is found between bearings.

• 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 Acoustical Society of Korea
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• v.40 no.6
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• pp.626-648
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• 2021

Domestically, demands for multi-purpose performance venues which accommodate various performance genres have increased. However, those venues have limited capability and confined to a primary performance. The present work investigated various methods for controlling the acoustics of room for required performance genres by reviewing aurally presented and published materials. The method of varying the acoustics of a space is called Variable Acoustics, and adjusted in either passive and active ways. Passive control encompasses variable absorption, variable volume, coupled volume, and canopy reflectors, where the acoustics of a room is controlled in an architectural way. Active control includes In-line, Regenerative, and Hybrid systems where the acoustics of a room is manipulated electronically. The mechanism and application of each passive control system in existing venues are reviewed and their pros and cons are discussed. Also, the concept of each active systems and product applications are looked at through literature reviews. Lastly, some considerations that need to be taken into in the planning and design stage of a multi-purpose hall using Variable Acoustics are suggested.

• Journal of the Korea Safety Management & Science
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• v.23 no.4
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• pp.23-29
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• 2021

The purpose of this study is to reduce the probability of occurrence of electric fires as a preemptive preventive measure, and to strengthen the capability of preventing electric fires by strengthening the cooperative function between electric fire-related departments and establishing a cooperative system. In this study, the general aspects of electric fires were identified by reviewing the literature such as ignition mechanisms of electric fires. And the major electrical fires that occurred in the last 10 years were classified into ignition factors (short circuit, overload/overcurrent, and earth leakage/ground fault) and ignition sources (wiring/wiring appliances, electrical equipment/household appliances). And the 4M technique was used to analyze the potential causes of ignition at the fire site and to suggest preventive measures. In the case In this study, out of 48 electrical fires in the past 10 years, 16 short-circuit fires, 3 overload/overcurrent fires, 3 short-circuit and earth fault fires, 16 fires in wiring/wiring appliances, and 10 fires in electrical equipment/home appliances classified as cases. And prevention measures were presented in terms of human, machine, media, and management by using the 4M technique. For the preemptive prevention of electric fires, strengthening the compulsory electrical safety inspection and making it mandatory to report when new or expanding electric facilities, charging a fee for electric safety inspection for detached houses and granting benefits subject to inspection completion, improvement of the electric safety voluntary inspection table and safety indications; It was suggested as a policy to organize and operate electrical safety inspection personnel in a two-person team (mixed), establish a close work cooperation system with related organizations, and strengthen electrical safety education and publicity.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.57 no.4
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• pp.302-315
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• 2021

In this study, factors such as improvement of a fishing process and safety, reduction of the labor force and headcount and development of the automation technology for offshore (eel and crab) pot fishing vessels were analyzed. A questionnaire survey was conducted to analyze and select the key factors using independent/paired sample t-test and correlation analysis, and a living lab was operated with ship owners, skippers and experts to discuss practical needs of the site. From the result of questionnaire survey and field requirements, it was possible to understand the level of awareness of ship safety, general safety equipment, fishing work process and fishing safety equipment from the point of view of the field. In addition, there were differences in the measurement results of each items because the working environment and experience were different according to the position of the ship owner and the skipper. The results of the questionnaire survey and various perceptions of field stakeholders were reflected when analyzing the fishing system and fishing process to choose the development equipment applicable to the field. From the analysis results, the selected development equipment based on the fishing equipment and process currently in operation are pot washing device, catch separation and fish hold injection device, length limit regulations and bait ejection device after use, automatic main line winding device, bait crusher, automatic (crab) pot hauling separator and so on.

• Safety and Health at Work
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• v.13 no.2
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• pp.255-260
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• 2022

Background: The coronavirus disease 2019 (COVID-19) pandemic has demonstrated the importance of implementing strategic management that prioritizes the safety of frontline nurse professionals. In this sense, this research was aimed at identifying factors associated with the illness of nursing professionals caused by COVID-19 according to socio-demographic, clinical, and labor variables. Methods: A cross-sectional study was conducted in three Brazilian university hospitals with 859 nursing professionals, which include nurses, technicians, and nursing assistants, between November 2020 and February 2021. We present data using absolute and relative frequency. We used Chi-square test for hypothesis testing and multiple logistic regression for predictive analysis and chances of occurrence. Results: The rate of nursing professionals affected by COVID-19 was 41.8%, and the factors associated with contamination were the number of people in the same household with COVID-19 and obesity. Being a nurse was a protective factor when the entire nursing team was considered. The model is significant, and its variables represent 56.61% of the occurrence of COVID-19 in nursing professionals. Conclusion: Obesity and living in the same household as other people affected by COVID-19 increases the risk of contamination by this new coronavirus.

• Journal of Creative Information Culture
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• v.6 no.3
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• pp.199-207
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• 2020

In this study, the case of capstone design course operation for the execution of SW development-oriented projects in the field of computer engineering is presented, and a 3-tier capstone design model is proposed through the case. Recently, most engineering departments operate capstone design classes, but in many cases, capstone design courses are generally operated in the graduation year. Students taking these capstone design courses are experiencing difficulties in the process of actually coding and implementing together with the collaboration process according to the team project class operation, but before these difficulties, derivation and verification of possible ideas and concrete ideas It is showing more difficulties in the process. In this study, in order to efficiently operate the capstone design and create results, in the second semester prior to graduation, students, professors, and mentors from industry mentors will work together to develop ideas through an idea tone contest, etc. Through the second semester, we propose a 3-tier capstone design model that can advance the idea and actual implementation and implementation of the derived ideas.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.10
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• pp.1432-1440
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• 2022

Recently, as Virtual Desktop Infrastructure(VDI) is widely used not only in office work environments but also in workloads that use high-spec multi-core-based applications, the requirements for real-time and stability of VDI are increasing. Accordingly, the display protocol used for remote access in VDI and performance optimization of virtual machines have also become more important. In this paper, we propose two ways to configure desktop virtualization for multi-core-based application operation. First, we propose a codec configuration of a display protocol with optimal performance in a high load situation due to multi-processing. Second, we propose a virtual CPU scheduling optimization method to reduce scheduling delay in case of CPU contention between virtual machines. As a result of the test, it was confirmed that the H.264 codec of Blast Extreme showed the best and stable frame, and the scheduling performance of the virtual CPU was improved through scheduling optimization.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.113-124
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• 2021

Underground environmental infrastructure and energy production facilities, which are recognized as avoidable facilities such as landfills, are emerging as an important social issue due to urbanization and economic growth. In order to safely construct a large-scale plant facility in the underground space, it is necessary to increase the utilization of the limited space layout and minimize unnecessary columns. In this study, the plant modularization method(Pipe Rack Module) was reviewed to solve the problems of work constraints, assembly and demolition, process system interconnection, and maintenance that occur when plant facilities are underground. In addition, plant module analysis was performed by applying various load conditions (earthquake load, device load, earth pressure load, etc.) to improve spatial layout usability and secure structure stability. Based on the analysis results under various boundary condition, the implications regarding the minimum installation interval and module arrangement (draft) of basic modules required for the construction of an underground combined plant were derived.

• The Journal of the Convergence on Culture Technology
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• v.7 no.4
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• pp.435-440
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• 2021

This study examines the effectiveness of the study through a case of PBL (problem-based learning) class conducted in a balanced culture course called at 00 - University in the second semester of 2020. The effects we can achieve through learning are as follows: First, problem-based learning (PBL) has sufficient active interaction between the teacher and the learner. Second, PBL learning can actively utilize various problems that fit the characteristics of the subject and actively utilize the process of role sharing and collaboration. Third, critical perceptions of problem situations can be extended. The limitations identified in this class case are, first, the nature of the subject, "Understanding Culture and Philosophy," which makes it possible to discuss the global cultural phenomenon, but it should be discussed in terms of philosophy. Second, it is not easy to work as a team on non-face-to-face online.