• Journal of Fisheries and Marine Sciences Education
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• v.5 no.2
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• pp.128-137
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• 1993

This paper presents a new concept to reduce turbulent frictional drag by injecting micro-bubble into buffer layer of turbulent boundary layer on flat plate. The buffer layer of boundary was specified by minus velocity gradient of law of the wall. When the buffer layer region of turbulent boundary layer is filled with micro-bubble of air and viscous of the region is kept low, the velocity profile in the region should be changed substantially. Then the Reynolds stress in the buffer layer region becomes less, which guide to higher velocity gradient there. It results in reduction of velocity gradient at the viscous sublayer, which gives the reduction of shear stress at the wall.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.83-88
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• 2016

This paper describes the test results of plant minimum stable load (Pmin) for Ilijan Power Plant. The test was conducted on May 13 through 14, 2015 to investigate the plant operating and equipment condition in accordance with "Ilijan Plant Performance Test Procedure on Plant Minimum Stable Load" [1]. This paper also contains the assessment of the impact of Pmin to plant operating parameters and possible technical operating issues when operating at lower loads and to recommend the safe minimum load operation of Ilijan per block. In addition, this paper describes the performance calculation results of efficiency and heat rate depending on the load level.

• Journal of Sensor Science and Technology
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• v.18 no.3
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• pp.197-201
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• 2009

This paper studies on the noncontact displacement sensor system to detect the displacement of the cylinder rod. For an inexpensive and a simple process, magnetic scales are printed on the cylinder rod, and magnetized by the specially designed magnetizer that has an yoke through the alternation of N and S pole. Noncontact displacement sensor system consists of cylinder with magnetic scales, Hall sensor, linear guide, controller and display. The system can detect the displacement of moving cylinder with 5 cm/sec in the case of 1 mm magnetic scale. It shows a possibility of position detection of hydraulic cylinder and air cylinder.

• Magazine of the Korean Society of Agricultural Engineers
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• v.7 no.1
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• pp.843-849
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• 1965

Some simple devices to demonstrate important hydraulic principles to students are necessitated in fluid mechanics or hydraulics classes. These devices should\ulcorner be easy to make and operate with inexpensive cost. The writer has studied some simple demonstrhation apparatus of hydraulic principles which were made with cheap materials. The purpose of this paper is to present the results of the study. In this paper, hydraulic principles that can be demonstrated by using these apparatus are described, the plans of them are presented, and how to make them and what materiaIs to be used are briefly explained. An axial-flow fan is a device with which the flow of air is supplied for several purposes. It consists of a duct, a fan and a guide vane. It may be possible to demonstrate the principles of propeIler,drag force, lift, etc.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.120-128
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• 2007

In order to reduce the lead-time and cost, the technology of rapid prototyping(RP) has been widely used. This paper describes the methodology to fabricate a large object by using the principle of rapid prototyping. By laminating thick and sloping polystyrene foam plates, we can make the large model which has three dimensional, continuous surfaces faster and easier than conventional processes. Estimated error was much smaller than other RP products which have stepped effect. For accuracy improvement and post processing, machined metal plates are added between the thick plates. To keep the continuity of surface and strengthen the model, pilot holes and guide rods are applied. By the methodology described in this paper, a missile body with flush air intake was fabricated.

• Journal of Korean Dental Science
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• v.15 no.1
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• pp.75-83
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• 2022

Crown-type implant-assisted removable partial dentures (CIRPDs) can be a feasible treatment option for partially edentulous patients. Here we report a case with remaining unilateral mandibular teeth. Two implants were placed in the posterior portion of the mandible using a surgical guide, and a distal-extension removable partial denture with implant-supported surveyed crowns was fabricated. After 12 months, both the abutment teeth and implants were in good condition. The treatment outcomes were satisfactory in terms of masticatory function and esthetics. The advantages of CIRPDs and considerations for obtaining successful clinical outcomes with these dentures are also discussed.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.3
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• pp.211-219
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• 2017

In this study, we performed numerical simulations on a circulating air classifier using a commercial computational fluid dynamics program. The variations in the grade efficiency, the cut-size and the cut-sharpness were calculated and discussed. By controlling the rotating speed of the main fan, the cut-size could be rapidly increased. However the linearity of the cut-size variation with respect to the main fan speed was not sufficient for application to contaminated soil classification processes. On the other hand, by varying the rotating speed of the classifying fan, the cut-size gradually decreased and could be precisely adjusted. Using both the main fan and the classifying fan, we could achieve larger cut-sharpness values and better classifying performances.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.172-181
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• 2015

Solid Oxide Fuel Cells (SOFC) continue to be among the most promising alternative energy devices. This paper addresses i-V characteristics of SOFC with a focus on air flow rate along the planar anode electrodes. To address this, detailed Butler-Volmer kinetics are implemented in a general-purpose CFD code FLUENT. The numerical results were validated against experimental data from the literature showing excellent match with i-V polarization data ranging 1V-0.4V. Numerical calculations of fuel cell operation under different flow rare conditions were performed in three-dimensional geometries. Results are presented in terms of concentration distribution of hydrogen, oxygen, and water. The simulations and results indicate that advanced CFD with UDF(User-Defined Function) of Butler-Volmer kinetics can be used to identify the conditions leading to air flow rate and specific surface area and guide development of operating conditions and improve the fuel cell system performance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.212-225
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• 2015

UAV (Unmanned Aerial Vehicle), the pilotless plane or drone, draws researchers' attention at these days for its extended use to various area. The research was initiated for military use of the UAV, but the area of applicable field is extended to surveillance, communication, and even delivery for commercial use. As increasing the interest in UAV, the needs of research for operating the flying object which is not directly visible when it conducts a certain mission to remote place is obviously grown as much as developing high performance pilotless plane is required. One of the project supported by government is related to the use of UAV for logistics fields and controlling UAV to deliver the certain items to isolated or not-easy-to-access place is one of the important issues. At the initial stage of the project, the previous researches for controlling UAV need to be organized to understand current state of art in local researches. Thus, this study is one of the steps to develop the unmanned system for using in military or commercial. Specifically, we focused on reviewing the approaches of controlling UAV from origination to destination in previous in-country researches because the delivery involves the routing planning and the efficient and effective routing plan is critical to success to delivery mission using UAV. This routing plan includes the method to avoid the obstacles and reach the final destination without a crash. This research also present the classification and categorization of the papers and it could guide the researchers, who conduct researches and explore in comparable fields, to catch the current address of the research.

• Journal of Advanced Navigation Technology
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• v.24 no.3
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• pp.205-211
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• 2020

Wiring defect is a major concern for safe aircraft operations. However, troubleshooting process of a wiring defect is very difficult due to extensive and complex wiring system and installed location. Recently, time domain reflectometer (TDR) equipment that enables effective defected wiring troubleshooting has been introduced. Unfortunately, TDRs have not practically adopted by most of airlines' maintenance departments because the effectiveness and usefulness of TDRs have not been verified. This study was conducted to verify if TDRs can identify the location and type of defected aircraft wiring, and whether they can be applied for troubleshooting purposes. Experimental plan was established by using various wires and connections applied to actual aircraft and the observed results were compared with the TDR operation guide. The usability of the TDR in actual aircraft wiring defect detection may be acceptable as the experimental results showed similar results to the TDR operation guide.