• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.1
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• pp.27-33
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• 2019

Several studies have been completed on the topic of container terminals in Northern Vietnam. Few of them, however, deal with competition in terms of costs related to vessel waiting time or cargo handling. This paper estimates the average waiting cost per TEU for all the container terminals in Northern Vietnam. After average waiting time was first estimated by applying queuing theory, uncertainty theory was applied to estimated vessel daily cost. A simulation was performed to create a series of data representing waiting cost per TEU in relation to the rate of volume handled/capacity of each terminal. Non-linear regression based on this series was used to present a function for the relationship between the average waiting cost of each terminal and the rate of volume handled /capacity.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.20-28
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• 2021

With an increase in the commercialization of electricity, and the development of advanced and large electric devices and various wireless radio wave services, concerns over the effects of electromagnetic fields on human health have increased. Accordingly, the World Health Organization encouraged the development of international standards by establishing the 'International Electromagnetic Fields Project' in 1996 based on studies on the harmful effects of electromagnetic fields on the human body. Moreover, the National Institute of Environmental Health Sciences (NIEHS) classified electromagnetic fields as possible carcinogens under Group 2B category, even though they have been found to have a weak correlation with those effects on human health. Mid-to-large-sized electric facilities used at industrial sites mostly adopt a commercial frequency of 60 Hz, and workers handling these facilities are exposed to such extremely low frequency (ELF) fields for a long time. A previous study suggested that exposure to ELF electromagnetic fields with frequency ranges from 0 to 300 Hz, even for a short time, at densities higher than 100 μT may have harmful effects on human body as it affects the activation of nerve cells in the central nervous system by inducing an electric field and current and stimulating muscles and the nervous system in the body. Such studies, however, focused on home appliances used by ordinary people, and research on facilities utilizing high-capacity current and operated by workers at industrial sites is lacking. Therefore, in this study, a 3000 kilowatt generator, which is a high-capacity electric facility employed at industrial sites, was investigated, and the size of the magnetic fields generated during its no-load and high-load operations per distance to produce a map was measured to reveal spots deemed hazardous according to domestic and international exposure standards. The findings of this study is expected to alleviate workers' anxiety about the harmful effects of magnetic fields on their body and to minimize the level of exposure during operations.

• Progress in Superconductivity and Cryogenics
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• v.25 no.3
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• pp.49-55
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• 2023

This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.

• Journal of the Ergonomics Society of Korea
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• v.18 no.2
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• pp.1-9
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• 1999

The objective of this study was to make comparison of the physical work capacities(PWCs) for three different types of tasks. For this purpose, an ergometer exercise, a treadmill exercise, and lifting activities with four different frequencies (2, 5, 8, 11 lifts/min) for the lifting range from floor to 76cm were considered. Oxygen consumption rates and heart rates were measured during the exercises and lifting activities. The PWC values for ergometer exercise test was $2562.71ml-O_2/min$ and the one for treadmill exercise was $2874.89ml-O_2/min$. The value of lifting PWC increased from $1774.07ml-O_2/min$ to $2296.76ml-O_2/min$ as the lifting frequency increased from 2 to 11 lifts/min. The ratio of the lifting PWCs to the ergometer PWC increased from 69.36% to 89.77% as the lifting frequency increased. To the treadmill PWC, the ratio increased from 62.21% to 85.24% as the lifting frequency increased. From this result, it appears that the PWCs based on the lifting tasks rather than PWCs by ergometer or treadmill exercise should be considered to determine the physiological criterion for safe weights for lifting tasks. Therefore, the physiological criteria of the NIOSH Guideline should be reexamined.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.333-336
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• 2003

For long time, the takeoff and landing control of airship was worked by human handling. With the development of the autonomous control system, the exact controls during the takeoff and landing were required and lots of methods and algorithms were suggested. This paper presents the result of airship take-off and landing by buoyancy control using air ballonet volume change and performance control of pitch angle for stable flight within the desired altitude. For the complexity of airship's dynamics, firstly, simple PID controller was applied. Due to the various atmospheric conditions, this controller didn’t give satisfactory results. Therefore, new control method was designed to reduce rapidly the error between designed trajectory and actual trajectory by learning algorithm using an artificial neural network. Generally, ANN has various weaknesses such as large training time, selection of neuron and hidden layer numbers required to deal with complex problem. To overcome these drawbacks, in this paper, the RBFN (radial basis function network) controller developed.

• Journal of The Korean Association of Information Education
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• v.15 no.3
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• pp.493-503
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• 2011

The Korea Ministry of Education, Science and Technology (MEST) determines admission quota of cyber universities. MEST's decision is made based on each university's physical and administrative capacity for handling admission numbers. However, the unique characteristics of cyber universities (e.g., online teaching and learning environments) are not considered in MEST's current decision process. MEST also lacks specifics in their policies that are required to ensure university's autonomous control for admission number as well as learners' rights and quality assurance. This study intended to improve decision making process on admission quota of cyber universities so as to increase quality assurance of education. The alternative admission quota decision frameworks have been formulated based on (a) the analysis of the current practices of cyber universities, (b) focus group interviews, and (c) recommendations of the expert.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.306-315
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• 2004

A Bridge Transported Servo Manipulator (BTSM) for Advanced spent fuel Conditioning Process (ACP) has been developed to overcome the limitation of access that is a drawback of Mechanical master-slave manipulators (MSMs) for the equipment maintenance. Wire-driven mechanisms have been adopted to increase the handling capacity to weight. The main disadvantage of the wire driven mechanism is that if one link is in motion, other links can be affected because wires and links are coupled. In this paper, the relationship between pulleys and links are formiliarized to overcome this drawbacks, Derived equations are proven and analyzed through experiments.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.1 no.1
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• pp.37-44
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• 1978

The purpose of this study is to search for an efficient application method in solving delay-phenomenon problems which influence upon total production cost through case study. The method of this study is an experimental study based on cutting time data in lead cutting operations from "Lead Cutting Machine (Stripper)" and its service rate data from a large electronic products company which utilizes conveyor line system for the products "Car Stereo" The procedure of this experimental study is as follows; 1) Using loading(Man-Hour) analysis technique j,1 order to analyse and evaluate Production capacity, efficiency, operation and idle rate assembly charge, waiting and service cost -when its are controlled by stripper operator(server) 2) Establishing adequate waiting time model of finite population caused by the interference of 4 stripper machine which is drawn from mathematical statistics testing, that is, goodness of fit test in the waiting and service rate and to search for optimal solution by utilizing the above mentioned model The experimental result was that amount to 8,546,618won Per year was brought down, that is, by optimum point, it shows a decrease as compared with Present point. The major limitation of this experimental study is that the Queue in the Finite Population, so to speak. it comes from the interference of 4 stripper machine dealt with this case were limited only on the Car Stereo conveyor line. Further study of application of this application method to the areas such as material handling, personnel management marketing and transportation management is strong1y recommended.trong1y recommended.

• Journal of Energy Engineering
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• v.27 no.3
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• pp.57-62
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• 2018

The development of coal-fired power plants to ensure energy security and electricity consumption is a matter for the Vietnam economy. However, the huge amount of ash discharged is a major environmental challenge. It is estimated that by the end of 2017, the amount of ash in the country is about 40 million tons and annually emitted over 16.4 million tons. While the quantity of coal-fired power plant is rising, the ash content will increase year by year if the ash doesn't treat well. The ash will be increased from 61 million tons in 2018 to 109 million tons in 2020, 248 million tons in 2025 and 422 million tons in 2030. The difficulties of coal-fired power plants are the problem of ash handling, some plants are at risk of closure because there are not enough dump capacity to storage. Therefore, Vietnam is in need of urgent measures to treat a large amount of waste from coal-fired power plants. The specific objectives of this study were as follows: (1) provide an overview of coal ash situation produced by coal-fired power plants in Vietnam; (2) study about regulations related to coal ash treatment; (3) comprehend the literature review of the cement sector status.

• Journal of the Ergonomics Society of Korea
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• v.16 no.3
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• pp.23-36
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• 1997

The objective of this study was to make a comparison of the oxygen consumption rates during the lifting activities and the physiological criteria of the recommended weights of RWL, AL, and MPL by NIOSH Guideline. The physical Work Capacity (PWC) based on the bicycle ergometer was 2562.71ml/min, and the one based on the treadmill was 2874.89ml/min for the college male students of Korea. Lifting activities with four different lifting frequencies(2, 5, 8, 11 lifts/min) for one lifting range from floor to 76cm height were studied. The oxygen consumption rates and the heart rates were measured or recorded while subjects were lifting the weight of RWL, AL, and MPL. The heart rates and the oxygen consumption rates increased as the frequency increased from 2 to lifts/min. However, those slightly decreased at the frequency of 11 lifts/ min. The measured oxygen consumption rates were ranging from 2.3% to 29.6% higher than the physiological criteria 620, 700, and 1000ml/min, respectively, of the RWL, AL, and MPL for all the lifting frequencies (5, 8, 11 lift/min) except 2 lifts/min. It si suggested that the physiological criteria of NIOSH Guideline should be based on the lifting PWC, which can consider the type of lifting activity and the frequency of the task, rather than using the PWC by ergometer or treadmill. The measured oxygen consumption rates were ranging from 13.26% to 40.11% higher than the values estimated using the models by Garg and Kim. From these findings it is suggested that the NIOSH Equation should not be directly applied to Korean without resonable modifications.