• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1107-1114
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• 2005

The running condition of multi-system air conditioner is prone to vary largely as it is designed for individual conditioning in each space of middle and small sized buildings. This leads to overcooling in case of partial load run, while the lack of capacity happens in case of full load run. Besides these, there exist such problems as instabilities due to the uneven refrigerant distribution caused by fluctuation of load and the change in piping line. Based upon the basic study on the function characteristics found in parts needed for maximized system working design in order to troubleshoot, the system functioning pattern should be identified through the different tests with various operating circumstances and the analysis models should be developed. With this ground, the control logic has to be made to have a control over capacity and make possible the efficient distribution of refrigerant.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.42-49
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• 2014

The gasoline direct injection (GDI) system is considerably spreading in automotive market due to its advantages. Nevertheless, since GDI system emit higher particle matter (PM) due to its combustion characteristics, it is difficult to meet strengthened emission regulation in near future. For this reason, a combined GDI with MPI system, so-called, dual injection (DUI) system is being investigated as a supplemental measure for the GDI system. This paper focused on power and fuel consumption effect by injection mode strategy of DUI system in part load and idle engine operating condition. In this study, port fuel injectors are installed on 2.4 liters GDI production engine in order to realize DUI system. And, at each injection mode, DOE (design of experiment) method is used to optimize engine control parameters such as dual injection ratio, start of injection timing, end of injection timing, CAM position and so on. As a consequence, DUI mode shows slightly better or equivalent fuel efficiency compared to conventional GDI engine on 9 points fuel economy mode as well as MPI mode shows less fuel consumption than GDI mode during idle operation. Furthermore, DUI system shows improvement potential of maximum 2.0% fuel consumption and 1.1% performance compared to GDI system in WOT operating condition.

• Journal of Environmental Health Sciences
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• v.34 no.6
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• pp.423-432
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• 2008

In this study, we investigated the possibility of auto control and the proper operating factors in the BNR(Biological Nutrient Removal) process using an NADH(Reduced Nicotinamide Adenine Dinucleotide) fluorometer, which characterized the emitted fluorescence when activated by flashes of UV light at 460 nm. In terms of finding adequate operating parameters, results indicted that nitrification efficiency decreased in the controlled DO while denitrification efficiency decreased in the controlled pH. The above results indicated that controlled operating condition after combination with NADH, DO and pH was resonable. Result obtained from the correlation between NADH and pH showed that variation trend of influent loading was similar to those of NADH and pH, and also the variation cycle was repeated on a daily basis. Consequently, this result showed the increase of BOD loading caused the nitrification efficiency to decrease because air-flow, required for nitrification, was reduced, and so the NADH value was increased. From these results, it is possible to use NADH flourimetry to assess the variation of organic load and nitrification efficiency in the case of small change in influent pH such as in sewage and also to handle and operate the load variation in the auto control system using the NADH fluorometer.

• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.353-362
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• 2010

This paper presents a centralized control algorithm for power system performance in the Korean power system using Flexible AC Transmission Systems (FACTS) devices. The algorithm is applied to the Korean power system throughout the metropolitan area in order to alleviate inherent stability problems, especially concerns with voltage stability. Generally, control strategies are divided into local and centralized control. This paper is concerned with a centralized control strategy in terms of the global system. In this research, input data of the proposed algorithm and network data are obtained from the SCADA/EMS system. Using the full system model, the centralized controller monitors the system condition and decides the operating point according to the control objectives that are, in turn, dependent on system conditions. To overcome voltage collapse problems, load-shedding is currently applied in the Korean power system. In this study, the application of the coordination between FACTS and switch capacitor (SC) can restore the solvability without load shedding or guarantee the FV margin when the margin is insufficient. Optimal Power Flow (OPF) algorithm, for which the objective function is loss minimization, is used in a stable case. The results illustrate examples of the proposed algorithm using SCADA/EMS data of the Korean power system in 2007.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.47 no.3
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• pp.248-256
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• 2011

The inherent efficiency of a ship would be prior to any other quality factors in ship's safety, because lack of it may give rise to a serious sea casuality even if it were a light mistake in operation. And the representative casualty comes from a deficiency of stability and an operating error combined would be capsizing. The Korean offshore large purseiner looks to have a structural weak point with small range of stability in spite of her big initial metacentric height, and have various type of roll reduction devices in order to cover up the defect. The aim of this study is to grasp for the roll reduction characteristics of the purseiner with bilge keel only and a stern keel additionally attached. The results are summarized as follows; The rolling angle of the model ship was increased in accordance with increase of the wave period and height, especially at close to the natural wave period of her, and the trends were more distinguished in the situation of bilge keel only installation than in the stern keel additionally installed. And stern keel has not noticeable effect on the reduction of the roll in the light ship condition, but has a little effect in full load condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.10
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• pp.1016-1019
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• 2011

In this paper, we predict a maximum electric field strength of WCDMA base station using a pilot channel in a code domain. In order to verify the feasibility of our method, we compare our predicted value on a self-designed test base station with a general electric field strength measurement value at a full-traffic load condition and with a calculated value by a ray-tracing technique. Predicted results show above 90 % agreement with the general measurement and calculation values. We also show that our prediction method can be applied to electric field measurement on a real operating base station. Therefore, it is concluded that our prediction method be an effective method to measure a maximum electric field strength in a base station inspection test.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.125-130
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• 2008

The main components of the KSTAR helium refrigeration system (HRS) can be classified into the warm compression system (WCS) and the cryogenic devices according to the operating temperature levels. The WCS itself consists of the compressor station (C/S) and the oil removal system (ORS). The process helium is compressed from 1 bar to 22 bar maximum in the C/S and downstream, the ORS removes the oil mixed in the helium to less than 10 ppbw as per the operation criteria of the cryogenic devices of the KSTAR HRS. After the installation, the pre-commissioning and commissioning activities were started on July, 2007. Before the start-up of the C/S, vibration measurement and the skid reinforcement jobs were performed for stable operation of the C/S. The results of the WCS performance tests met the requirements of the KSTAR HRS but satisfied the vibration level criteria only at the compressors' full load condition.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.8-14
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• 2015

Synthetic natural gas(SNG), acquired from coal, is regarded as an alternative to natural gas since a rise in natural gas due to high oil price can be coped with it. In the present study, 11-liter heavy duty compressed natural gas(CNG) engine was employed in order to examine the combustion and emission characteristics of SNG. The simulated SNG, made up 90.95% of methane, 6.05% propane and 3% hydrogen was used in the experiment. Power output, thermal efficiency, combustion stability and emission characteristics were compared to those with CNG at the same engine operating conditions. Knocking phenomenon was also analyzed at 1260 rpm, full load condition. Combustion with SNG was more stable than CNG. Nitrogen oxides emissions increased while Carbon dioxides emissions decreased. Anti-knocking characteristics were improved with SNG.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.800-808
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• 2022

The International Maritime Organization adopted the interim standards for ship maneuverability in November 1993 for preventing collision of ships at sea and for protecting the marine environment, and based on the accumulated data, in December 2002, the established standards for ship maneuverability were adopted. However, the standards adopted are those at full load, even keel, and at least 90 % of the ship speed at 85 % of the ship's maximum power. Moreover, these standards have limitations in providing information on maneuverability under actual navigational conditions. Therefore, in this study, frequency analysis AHP analysis techniques were studied by consulting navigational officers, captains, and experts, who have significant knowledge on ship maneuverability, utilization of the current standards, and the information necessary for the operation of the actual ship. The results of this study confirmed that the necessary information on maneuverability for the navigational officer operating the vessel is information about the turning circle at a small angle of 5°-10° and z-test information at maneuvering speed, not sea speed. Additionally, in relation to speed control, additional information on deceleration inertia and acceleration inertia is needed than the information on the stopping ability at sea speed and full loaded condition. The derived results are considered to be useful as basic data for preparing guidelines for ship maneuverability necessary for navigational of icers who operate ships.

• Journal of Energy Engineering
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• v.25 no.3
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• pp.73-82
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• 2016

The energy consumption efficiency in a variety of operational test mode was considered for domestic gas boiler below 70 kW. The energy efficiency test carried out in the experimental conditions similar to the actual operation status was analyzed and compared with the current Korean efficiency test method. Four types of test modes for each boiler(Non-condensing and condensing boiler) were carried out in the condition of laboratory mode(full load, steady state) and actual operating mode. Futhermore divided into two operational status for each of these, it was applied by maximum gas consumption and consumer sales conditions. Test equipment has the function referred to gas boiler standards, such as KS or European standard EN. The equipment should be continuously measured and record the measuring factors which are the flow volume of gas and water, laboratory temperature, water flow volume for heating, return water volume after heating and quantity of the exhaust gases(CO, NO, $NO_2$). The experimental results were found that non-condensing boiler efficiency of laboratory mode is about 10% higher than that of actual mode. In case of condensing boiler, the efficiency of laboratory condition is about 20% higher than that of the actual using conditions. I suggest that the government will gradually take the efficiency test method considering the actual conditions.