• Textile Coloration and Finishing
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• v.8 no.6
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• pp.27-32
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• 1996

This research is to investigate the reaction kinetics by air-lift bioreactor using calcium hydroxide, the neutralization agent and immobilization media, for removing ethylene glycol remained after chemical pretreatment. It was found that the optimum hydraulic retention time was obtained as 24.2hours at the optimum F/M ratio of 1.32kg-$TCOD_{Mn}$/day.kg-MLVSS, and then, infiuent $TCOD_{Mn}$ and MLVSS concentration were 3,290mg/l and 2,472mg/l, respectively. During the steady state, the kinetics constants such as maximum specific substrate removal rate, half saturation velocity coefficient, yield coefficient and endogenous respiration coefficient were estimated in the base of $TCOD_{Mn}$ as substrate concentration. And they were 1.47day$^{-1}$, 3.95mg/l, 0.391 and 0.092day$^{-1}$, respectively. And also, the oxgen use coefficients for cell synthesis, a', and energy of maintenance, b', were obtained as 0.4kg-O$_{2}$/kg-$TCOD_{Mn}$ and 0.056day$^{-1}$, at the steady state by the experimental result of oxygen uptake rate.

• Wind and Structures
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• v.31 no.1
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• pp.15-20
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• 2020

The aircraft industry supports aviation by building aircraft and manufacturing aircraft parts for their maintenance. Fuel economization is one of the biggest concerns in the aircraft industry. The reduction in specific fuel consumption of aircraft can be achieved by a variety of means, simplest and more effective is the one to impose minor modifications in the aircraft main wing or the parts which are exposed to the air flow. This method can lead to a reduction in aerodynamic resistance offered by the air and have a smoother flight. The main objective of this study is to propose geometric design modifications on an existing aircraft wing which acts as a vortex generator and it can reduce the drag and increase lift to drag ratio, leading to lower fuel consumption. The NACA 2412 aircraft wing is modified and designed. Rigorous flow analysis is carried out using computational fluid dynamics based software Ansys Fluent. Results show that saw tooth modification to the main wing shows the best aerodynamic efficiency as compared to other modifications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.34 no.6
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• pp.475-479
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• 2021

There are many difficulties in the applications of smart manufacturing technology in the era of the 4th industrial revolution. In this paper, a test bed was built to aim for acquiring smart manufacturing technology, and the test bed was designed to acquire basic technologies necessary for PLC (Programmable Logic Controller), HMI, Internet of Things (IoT), artificial intelligence (AI) and big data. By building a vehicle maintenance lift that can be easily accessed by the general public, PLC control technology and HMI drawing technology can be acquired, and by using cloud services, workers can respond to emergencies and alarms regardless of time and space. In addition, by managing and monitoring data for smart manufacturing, it is possible to acquire basic technologies necessary for embedded systems, the Internet of Things, artificial intelligence, and big data. It is expected that the improvement of smart manufacturing technology capability according to the results of this study will contribute to the effect of creating added value according to the applications of smart manufacturing technology in the future.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.393-399
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• 2007

Concrete bridge decks are directly exposed to the severe environmental conditions such as rain water and deicing chemicals resulting in the freeze-thaw action and the rebar corrosion during their service lift. These deteriorations of bridge decks shorten the service lift and consequently they are the major concerns of the maintenance. The high performance concrete (HPC) deck is proposed as the alternative to minimize the deterioration problems. To develop more durable concrete deck, the performance characteristic tests of HPC mixtures were carried out. In this study, 4 different concrete mixtures were used varying the mineral admixtures as the cement replacement; ordinary portland cement (OPC), 20% fly ash (FA),20% fly ash with 4% silica fume (FS), and 40% ground granulated blast-furnace slag (BS). The design compressive strengths of HPC specimens were 27 MPa and 35 MPa, respectively. The results showed that the compressive strength of concrete did not much affect the durability of concrete. HPC with fly ash and silica lune (FS) were turned out to have the good durability and crack resistance.

• Journal of IKEEE
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• v.24 no.2
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• pp.673-676
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• 2020

In this paper, we propose a whole-body management system using ultra-low temperature cyclical cooling method combined with IT technology. The proposed system has the following characteristics. First, it minimizes maintenance costs by circulating nitrogen gas cooled by ultra-low temperature inside the controller. Secondly, based on the information measured by the temperature sensor and oxygen concentration sensor, nitrogen gas is supplied to provide safe ultra-low temperature whole-body management. Thirdly, after entering the user's height, it provides convenient, ultra-low temperature whole-body care that can be controlled using an automatic lift. Fourth, it provides an easy-to-access, easy-to-manage GUI and a manager-only web program for whole-body management system operation. The results tested by the authorized testing agency to assess the performance of the proposed system were measured in the range of ±5%, the world's highest temperature sensor accuracy, and a range of -110℃ to -150℃ greater than the world's highest whole-body management temperature range(-110℃ ~ -140℃). In addition, humidity was measured at less than 40%, the world's highest, and oxygen concentration was more than 18%, the world's highest. Therefore, the effectiveness of the methods proposed in this paper was demonstrated because they produced the same results as the world's highest levels.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.2
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• pp.145-150
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• 2020

Water wall tube is one of the major factors consisting of a fluidized bed boiler and it plays very important role for the generation of electricity within the boiler. But these water wall tubes within the fluidized bed boiler are subject to the ware and corrosion caused by the high temperature gas and the flowing medium. If water leak is occurred, the secondary damage by the water leak will occur. As a result of that, the power generation efficiency decreases noticeably. Therefore, the maintenance of the water wall tube is very important. In this study, we designed a exciter sensor based on simulation and composed a remote field eddy current system for the defect evaluation of the outer water wall tube. Starting from the shape design of exciter, we conducted simulations for various design factors such as the water wall tube size, material, frequency, lift-off and so on. Based on the results, we designed the optimum exciter sensor for the water wall tube test within the fluidized bed boiler.

• Journal of Convergence for Information Technology
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• v.9 no.2
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• pp.172-179
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• 2019

Recently, design automation of installation drawings and design elements has been required in the elevator industry. This is recognized as an important role in securing adaptability on site, reducing design errors, and enhancing export competitiveness. However, in case of a small company doesn't have enough resources to develop the program, and it is difficult to develop a design automation program. Therefore, it is necessary to have an automatic drawing generation program that enables small companies to easily invest and use, while allowing users to concentrate on productive tasks. In this paper, we propose an automatic drawing generation program using parametric coding technique. This program is linked with the web service and automatically creates the drawing when the user enters the site information on the web. This is useful for elevator installation and maintenance due to reduced drawing time for elevator drawings.

• Journal of the Korea Safety Management & Science
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• v.22 no.2
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• pp.23-29
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• 2020

Korea's elevator industry is one of the world's eighth-largest industrial sectors and the third largest in the world by new installations. This year, the number of elevators has exceeded 700,000, and the number of new installations is 30,000-40,000 every year. However, the news of elevator-related accidents is reported continuously through the media and the accident rate is not decreasing. In particular, among the recent accidents related to elevators, accidents related to elevator workers are increasing, causing social problems. This year, the National Assembly's Environmental Labor Relations Commission's National Auditors lost five lives a year and 12 elevator workers were killed in fall and stenosis accidents during the installation, maintenance and replacement of the elevators for about two years since 2018. It took place to adopt the representatives of four domestic elevator companies as witnesses. An elevator worker is a collective term for workers involved in the design, manufacturing, installation, replacement, maintenance, inspection, management, and supervision related to the elevator industry, and the related accidents are called elevator worker accidents. Analysis of elevator-related accidents in the past has shown that the fault of the user accounted for 70% of the total, and the fault of the worker accounted for about 2.5%, and the accident occurred to the user or the user due to carelessness of the worker during the lift-related work. Currently, elevator-related accidents are reported by the Korea Elevator Safety Agency under Article 48 of the Elevator Safety Management Act under the Ministry of Interior and Safety. If deemed necessary for the prevention and prevention of recurrence of an elevator accident, the cause and condition of the elevator accident may be investigated. However, the current draft law is limited only to elevators after installation inspection, and is separated from the Ministry of Employment and Labor's data on accidents occurring in the manufacturing and installation stages related to the elevator industry. This study analyzes the recent safety accidents of elevator workers and prepares safety measures to prevent them through the risk analysis, and also draws out the problems and improvements of the current elevator worker accident investigation to find the elevator worker accident rate that is on the increase trend.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.71-78
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• 2023

In general, electric submersible pumps (ESPs), which have an average life of 1.0 to 1.5 years, experience a decrease in performance and a reduction in life of the pump depending on oil and gas reservoir characteristics and operating conditions in wells. As the result, the failure of ESP causes high well workover costs due to retrieval and installation, and additional costs due to shut down. In this study, a flow loop system was designed and established to predict the life of ESP in long­term operation of oil and gas wells, and the life cycle data of ESP from the time of installation to the time of failure was acquired and analyzed. Among the data acquired from the system, flow rate, inlet and outlet temperature and pressure, and the data of the vibrator installed on the outside of ESP were analyzed, and then the performance status according to long-term operation was classified into five stages: normal, advice I, advice II, maintenance, and failed. Through the experiments, it was found that there was a difference in the data trend by stage during the long­term operation of the ESP, and then the condition of the ESP was diagnosed and the failure of the pump was predicted according to the operating time. The results derived from this study can be used to develop a failure prediction program and data analysis algorithm for monitoring the condition of ESPs operated in oil and gas wells.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.68-73
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• 2020

This purpose of this paper was to review the development trend of the VTOL MAVs with a ducted propellant that can fly like the VTOL at intermediate and high speeds, hovering, landing, and lifting off vertically over urban areas, warships, bridges, and mountainous terrains. The MAV differs in flight characteristics from helicopters and fixed wings in many respects. In addition to enhancing thrust, the duct protects personnel from accidental contact with the spinning rotor. The purpose of the U.S. Army FCS and DARPA's OAV program is spurring development of a the VTOL ducted MAV. Today's MAVs are equipped with video/infrared cameras to hover-and-stare at enemies hidden behind forests and hills for approximately one hour surveillance and reconnaissance. Class-I is a VTOL ducted MAV developed in size and weight that individual soldiers can store in their backpacks. Class-II is the development of an organic VTOL ducted fan MAV with twice the operating time and a wider range of flight than Class-I. MAVs will need to develop to perch-and-stare technology for lengthy operation on the current hover-and-stare. The near future OAV's concept is to expand its mission capability and efficiency with a joint operation that automatically lifts-off, lands, refuels, and recharges on the vehicle's landing pad while the manned-unmanned ground vehicle is in operation. A ducted MAV needs the development of highly accurate relative position technology using low cost and small GPS for automatic lift-off and landing on the landing pad. There is also a need to develop a common command and control architecture that enables the cooperative operation of organisms between a VTOL ducted MAV and a manned-unmanned ground vehicle.