• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.18-24
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• 2011

In this paper, we present the load-deflection behavior of GRP pipes. GRP buried pipes are widely used in construction in the advantage of their superior mechanical and physical characteristics such as high chemical resistance, high corrosion resistance, right weight, smooth surface of the pipe, and cost effectiveness from soil-structure interaction. To design flexible pipes to be buried underground, it should be based on the ASTM D2412(2010). When applying ASTM D 2412(2010) to the design, pipe stiffness(PS) must be predetermined by the parallel-plate test which requires tedious and laborious working process. To overcome such problems, the finite element simulations for finding the load-deflection behavior of the GRP flexible pipes is installed at UTM testing machine. In the finite element simulations, basic data, such as the modulus of elasticity of the material and cross-sectional dimension, is used. From the investigation, we found that the difference between experimental result and analytical prediction is less than 15% when the pipe deflected 3% and 5% of its vertical diameter although the pipe material is not uniform across the cross-section.

• The Journal of Korean Association of Computer Education
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• v.18 no.2
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• pp.83-90
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• 2015

In an virtualization environment, several virtual machines use physical resources together. If a specific virtual machine uses to much of the computing resources, other machines may not be working properly. There are various method to solve this problem. Most representative study is to migrate a specified virtual machines to a different server, a target server. In this study, server load can be transferred to a target server by the remigrate of the load imposed on virtual machine. It is still problematic that virtual machine has to remigrate to a different server. This thesis has proposed the algorithm determining the remigration targets by applying dynamic thresholds to solve those problems. The migration algorithm applies dynamic thresholds according to the following criteria. Firstly, the usage of CPU, network and memory; secondly, decide the set of artificial machine and the target server based on the resources surpassed thresholds; thirdly, determine artificial machines based on the resource usage in the target server.

• Progress in Superconductivity and Cryogenics
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• v.14 no.4
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• pp.50-53
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• 2012

This paper describes experimental study on GM-type pulse tube refrigerator (PTR). In a PTR, the pulse tube is only filled with working gas and there exists secondary flow due to a large temperature difference between cold-end and warm-end. The stability of secondary flow is affected by orientation of cold-head and thus, the cooling performance is deteriorated by gas mixing due to secondary flow. In this study, a single stage GM-type pulse tube refrigerator is fabricated and tested. The cooing performance of the fabricated PTR is measured as varying cold-head orientation angle and the results are used as reference data. Then, we divided interior space of pulse tube into three segments, and fixed the various size of screen mesh at interface of each segment to suppress the performance degradation due to secondary flow. For various configuration of pulse tube, no-load test and heat load test are carried out with the fixed experimental condition of charging pressure, operating frequency and orifice valve turns. From experimental results, the fine screen mesh shows the effective suppression of performance degradation for the large orientation angle, but the use of screen mesh cause the loss of cooling capacity rather than the case of no insertion into pulse tube. It should be compromised whether the use of screen mesh in consideration of the installation limitation of a GM-type pulse tube refrigerator.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.7
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• pp.1509-1513
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• 2003

The autopilot system of vessel is proposed to take service safety and security, to elevate service efficiency, to decrease labor and to improve working environment. Ultimate purpose of the proposed system is to minimize the number of crew by guaranteeing economical efficiency of shipping service. Recently, the research is being achieved to compensate various nonlinear parameters of vessel and apply it to course keeping control, track keeping control, roll-rudder stabilization, dynamic ship positioning and automatic mooring control etc. using optimizing control technique. Relation between rudder angle controlled by steering machine of vessel and ship-heading angle, and load condition of ship is nonlinear, which affects various parameters of shipping service. The speed and direction of waves, velocity and quantity of wind, which also cause the non-linearity of it. Therefore the autopilot system of ship requires the robust control algorithm can overcome various non-linearity. On this paper, we design the autopilot system of ship, which overcomes nonlinear Parameters and disturbance of it using Fuzzy Algorithm, evaluate the proposed algorithm and its excellence through simulation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.12
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• pp.106-114
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• 2009

This paper addresses unit commitment for microgrid optimization including renewable energy sources, working under deregulated power market. As microgrid supplies both heat and electricity for consumer, operational optimization must be done to meet their demand economically. So renewable energy sources are considered to be negative load, and batteries are used as the load flattening device to raise possibly operational function. In the state of solution, the program is developed to solve out the maximum profit of microgrid using dynamic programming method. Finally, its validity is verified through case study in isolation mode and interconnected mode. The S/W will be used to operate microgrid economically after the market of microgrid is formed.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.476-483
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• 2017

The decay heat that is produced by nuclear reactor spent fuel must be cooled in a spent fuel storage pool. A wickless heat pipe or a vertical two-phase closed thermosyphon (TPCT) is used to remove this decay heat. The objective of this research is to investigate the thermal performance of a prototype model for a large-scale vertical TPCT as a passive cooling system for a nuclear research reactor spent fuel storage pool. An experimental investigation and numerical simulation using RELAP5/MOD 3.2 were used to investigate the TPCT thermal performance. The effects of the initial pressure, filling ratio, and heat load were analyzed. Demineralized water was used as the TPCT working fluid. The cooled water was circulated in the water jacket as a cooling system. The experimental results show that the best thermal performance was obtained at a thermal resistance of $0.22^{\circ}C/W$, the lowest initial pressure, a filling ratio of 60%, and a high evaporator heat load. The simulation model that was experimentally validated showed a pattern and trend line similar to those of the experiment and can be used to predict the heat transfer phenomena of TPCT with varying inputs.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.18-26
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• 2021

The effect of heavy construction equipment on the excavated slope is investigated by slope stability analysis. A mobile crane with 500 kN capacity is applied as a working load to the background surface of the excavated slope, in both sandy soil and clay, designed to guarantee the safety of slope stability. Major parameters such as the distance between the edge of the slope and the mobile crane, groundwater level, and ground plate size of the mobile crane are considered. Only 23.8% and 14.3% of the analysis models with sandy soil and clay excavated slope, respectively, satisfied the slope stability. By changing the slope of the sandy soil from 1:1.0 to 1:1.2, the number of analysis models securing slope stability increased from 23.8% to 40.5%. For the clay excavated slope, the analysis models securing slope stability increased from 14.3% to 42.9% by changing slope inclination from 1:0.8 to 1:1.2. In addition, it is found that the increase in the size of the ground plate of the mobile crane increases the analysis models that secure slope stability. Therefore, it is an effective way to relax the excavated slope's inclination angle and simultaneously increase the ground plate size to guarantee stability.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.31 no.2
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• pp.156-172
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• 2021

Objectives: To investigate the trends of industrial injuries among long-term health care workers in Korea Methods: T7866 injuries were selected from the total industrial injuries approved by the Industrial Accident Compensation Insurance Act(Occupational Safety and Health Act) among long-term health care workers between 2007 and 2016 in Korea. We analyzied the trends of industrial injuries according to work process, occurrence type, and causes. Results: The industrial injuries among long-term health care workers increased since 2012. The mostly occurred area for industrial injuries were low back areas, which is related that the most serious industrial injuries occurred when the one long-term healthcare worker lift manually the recipient, from bed(ondol, Korean floor heating system) to a wheelchair, bed to bath bed, and wheelchair to bath chair. In addition to this, lack of workforce, increased work intensity due to overwork contributed the increasing of occupational injury. Conclusions: This study suggests that the main causes of industrial injuries were Lack of facilities and equipment for small private long-term care institutions, The physical load that goes into lifting the recipient directly, work intensity such as excessive workload and increased work speed. We suggest that the social publicization of long-term care service for the elderly, avoiding ways to lift recipients directly, introducing lifting machines as well as improving working methods, and reducing the workload of caregivers are required.

• Korean Journal of Agricultural Science
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• v.48 no.4
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• pp.1039-1050
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• 2021

The purpose of this study is to measure load data for a 55 kW class agricultural tractor during a harvesting operation and to analyze the required power according to the working conditions. A field test was conducted at three different tractor speeds (1.2, 1.3, and 1.4 km·h^-1). A load measurement system was developed for the front axles, rear axles, and for power take-off (PTO). The torque and rotational speeds of the axles and PTO were measured during the field test and were calculated as the required power. The results showed that the total required power was in the range of 4.86 - 5.48 kW during the harvesting operation according to the tractor speed, and it was confirmed that this represents a ratio of 8.8 - 10.0% of the engine rated power. Also, it was confirmed that the required power of the axle and PTO increased as the tractor speed increased. In future studies, we plan to supplement the measurement system for a tractor to include a hydraulic system and perform a field test for harvesting various underground crops.

• Safety and Health at Work
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• v.14 no.2
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• pp.185-192
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• 2023

Background: The turnover rate of nurse aides in Taiwan is high. However, the predictors of turnover behavior in the newly employed are still unclear. Objective: To examine the predictors of turnover behavior in newly employed licensed nurse aides. Methods: A longitudinal study design was used and subjects were newly employed certified nurse aides from a nurse aid training association in Taiwan. A total of five questionnaire surveys were conducted. The questionnaire was mainly used to collect information on turnover behavior, personal socioeconomic background, workplace psychosocial hazards, worker health hazards, and musculoskeletal disorders. Results: A total of 300 participants were recruited in the study. Cox regression analysis results showed that short working experience (hazard ratio [HR] = 0.21, p < 0.01), work as non-home nurse aides (HR = 0.58, p = 0.01), low monthly salary (HR = 0.68, p < 0.01), high work mental load (HR = 1.01, p = 0.01), low workplace justice (HR = 0.97, p < 0.01), high workplace violence (HR = 1.60, p < 0.01), high burnout (HR = 1.01, p = 0.04), poor mental health (HR = 1.06, p = 0.04), and high total number of musculoskeletal disorder sites (HR = 1.08, p = 0.01) contribute to a higher risk of turnover. Conclusion: The results indicated that employment period, work as a home nurse aide, monthly salary, work mental load, workplace justice, workplace violence, work-related burnout, mental health, and total number of musculoskeletal disorder sites are predictors of turnover behavior in newly employed certified nurse aides.