• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.4
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• pp.292-299
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• 2017

The KUH-1's Wheel Brake Assembly which is Brake System is an essential component to perform flight mission for pilot. It has function of taxing, differential braking and parking to sustain landing capability. However, the skid and abrasion of tire were occurred in mass-produce operation. Also, if it is occurred on the ground, the flight can not be performed. In this case, the defect is a major cause of the decrease in the operation rate of aircraft. In this paper, the cause of the defect in flight was identified and the failure process was organized. Also, it describes design improvements which was derived from troubleshooting and suggests verification results of flight test.

• 대한공업교육학회지
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• v.34 no.2
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• pp.20-41
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• 2009

The purpose of this study was to propose conceptual Structure of the study of industrial education based on the concepts and characteristics of industrial education. Therefore, the study was conducted through literature research. 1) The characteristic of industrial education in the study was proposed as 'subject for occupational competence in the industrial technology' on the educational purpose. 2) The characteristic of industrial education in the study was proposed as 'subject for practical knowledge in the industrial/engineering technology' on the structure of knowledge. 3) The characteristic of industrial education in the study as was proposed as 'subject for technological problem solving in the system design and engineering context' on the educational methodology 4) The characteristic of industrial education in the study was proposed as 'design, building, testing and troubleshooting' on the educational process.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.6
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• pp.110-117
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• 2003

The operational characteristics of the landing gear retraction/extension depend on the complexity of design variables operational/environmental conditions. In order to meet the requirements of minimum stow area and performance, the integration of the landing gear system requires operational kinematic and dynamic analysis considering an effect of its related system. This study investigates operational dynamic behaviors of the T-50 landing gear system using ADAMS. Taking into account for various operational/environmental conditions, an analysis of dynamic behavior on the landing gear operational characteristics is performed with experience derived from a wide range of proprietary designs. Analytical results are presented for discussing the effects of temperature, aerodynamic and maneuver load on normal/emergency operation of the landing gears and doors. This analysis leads us to the conclusion that the proposed program is shown to be a better quantitative one that apply to a new development and troubleshooting of the landing gear system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.23-30
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• 2019

Automobiles are largely divided into passenger cars with less than five passengers and commercial vehicles such as construction machines, trucks, mixers, special lorries, and large buses. Automobile maintenance companies are also divided into passenger cars and commercial vehicles. Because commercial vehicles are the livelihood vehicles of individual carriers engaged in cargo transportation, passenger transportation, and construction, fast and accurate maintenance is important. Access to the expressway is also important because the car is large and uses highways. In addition, the time required for troubleshooting is long, so sufficient space must be secured for parking the vehicle, and ease of entry and exit of the vehicle in the maintenance shop should be fully considered. For this reason, commercial vehicle maintenance companies have higher initial investment costs than car maintenance companies, and it is difficult to supply and maintain maintenance personnel. Therefore, it is necessary to carefully examine and analyze various related factors for successful commercial vehicle maintenance company selection. However, most existing commercial vehicle maintenance companies often choose their location based on the empirical judgment of the founder, the customs and the case, without a clear analysis. In this study, we show how to derive the location selection factors to be considered when establishing professional maintenance company for commercial vehicles and to select the optimal location by using AHP (Analytic Hierarchy Process) method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.666-673
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• 2011

To perform effective integration test of avionics equipments, the importance of a setup for integration test environment has been increasing in recently developed aircraft. Especially, the development of integration test equipment is necessary for minimizing the development period and reliability of integration test. This paper treats the model development for optimal working of integration test after analyzing the characteristics of each MEP equipments for Surion(KUH). Models, whose main role is troubleshooting of equipment and simulation for missing equipments, consists of dynamic, behavior, and ICD models depending on the dynamic characteristics. Software test for both unit level and system level are performed to verify the model reliability. By conducting integration test using SIL, it is confirmed that the developed models are suitable for integration function test of the MEP system.

• Tribology and Lubricants
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• v.31 no.3
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• pp.79-85
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• 2015

RC delay is a critical issue for achieving high performance of ULSI devices. In order to minimize the RC delay time, we uses the CMP process to introduce high-conductivity Cu and low-k materials on the damascene. The low-k materials are generally soft and fragile, resulting in structure collapse during the conventional high-pressure CMP process. One troubleshooting method is electrochemical mechanical polishing (ECMP) which has the advantages of high removal rate, and low polishing pressure, resulting in a well-polished surface because of high removal rate, low polishing pressure, and well-polished surface, due to the electrochemical acceleration of the copper dissolution. This study analyzes an electrochemical state (active, passive, transpassive state) on a potentiodynamic curve using a three-electrode cell consisting of a working electrode (WE), counter electrode (CE), and reference electrode (RE) in a potentiostat to verify an electrochemical removal mechanism. This study also tries to find optimum conditions for ECMP through experimentation. Furthermore, during the low-pressure ECMP process, we investigate the effect of current density on surface roughness and removal rate through anodic oxidation, dissolution, and reaction with a chelating agent. In addition, according to the Faraday’s law, as the current density increases, the amount of oxidized and dissolved copper increases. Finally, we confirm that the surface roughness improves with polishing time, and the current decreases in this process.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.3
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• pp.367-374
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• 2009

Every year there are great socio-economic loss and damage caused by landslides in steep slopes. According to recent statistics, the percentage of casualty due to breakdown in steep slopes was 27.3% of all natural disasters occurring over the past decade($1998{\sim}2007$). Therefore, the nationwide scale survey on the landslide susceptibility was made to recognize the status quo for appropriate troubleshooting measure against the collapse of steep slopes. Nevertheless, few dent that the data collected is not sufficient to grasp the overall understanding of the onsite situation due to lack of spatial information. As a result, the study aims to develop a program enabling to send on site topological data and prefixed data-gather criteria directly to the central management server in real-time basis. It will be conducted through mobile devices and portable GPS system, accordingly. This program is expected to be implemented as an efficient application tool of slope spatial information acquisition.

• Journal of Communications and Networks
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• v.9 no.4
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• pp.446-456
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• 2007

Increased access to broadband networks has led to a fast-growing demand for voice and video over IP(VVoIP) applications such as Internet telephony(VoIP), videoconferencing, and IP television(IPTV). For pro-active troubleshooting of VVoIP performance bottlenecks that manifest to end-users as performance impairments such as video frame freezing and voice dropouts, network operators cannot rely on actual end-users to report their subjective quality of experience(QoE). Hence, automated and objective techniques that provide real-time or online VVoIP QoE estimates are vital. Objective techniques developed to-date estimate VVoIP QoE by performing frame-to-frame peak-signal-to-noise ratio(PSNR) comparisons of the original video sequence and the reconstructed video sequence obtained from the sender-side and receiver-side, respectively. Since processing such video sequences is time consuming and computationally intensive, existing objective techniques cannot provide online VVoIP QoE. In this paper, we present a novel framework that can provide online estimates of VVoIP QoE on network paths without end-user involvement and without requiring any video sequences. The framework features the "GAP-model", which is an offline model of QoE expressed as a function of measurable network factors such as bandwidth, delay, jitter, and loss. Using the GAP-model, our online framework can produce VVoIP QoE estimates in terms of "Good", "Acceptable", or "Poor"(GAP) grades of perceptual quality solely from the online measured network conditions.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.113-118
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• 2015

High-power semiconductor devices and microprocessors in factory electrical installation so sensitive to power quality measurements such as harmonic currents, voltage fluctuations, flicker, current imbalance. Therefore, the little change of power quality can influences the productivity of factory electrical machines. Troubleshooting these problems requires accurate measurements and analysis of power quality with monitoring instruments that can effectively locate issues and identify solutions. In this paper, the author presents hand-held power quality monitoring system to locate issues and identify solutions. The proposed system consists of two parts, One is to develop hand-held power meters by using NI(National Instrument) DAQ(Data Acquisition) and WLAN. Another is develop power quality monitoring MMI(Man-Machine Interface) using LabView software. To demonstrate the validity of the proposed algorithm, variable tests are carried out.

• Restorative Dentistry and Endodontics
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• v.45 no.3
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• pp.31.1-31.20
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• 2020

Matrix metalloproteinases (MMPs) are enzymes that can degrade collagen in hybrid layer and reduce the longevity of adhesive restorations. As scientific understanding of the MMPs has advanced, useful strategies focusing on preventing these enzymes' actions by MMP inhibitors have quickly developed in many medical fields. However, in restorative dentistry, it is still not well established. This paper is an overview of the strategies to inhibit MMPs that can achieve a long-lasting material-tooth adhesion. Literature search was performed comprehensively using the electronic databases: PubMed, ScienceDirect and Scopus including articles from May 2007 to December 2019 and the main search terms were "matrix metalloproteinases", "collagen", and "dentin" and "hybrid layer". MMPs typical structure consists of several distinct domains. MMP inhibitors can be divided into 2 main groups: synthetic (synthetic-peptides, non-peptide molecules and compounds, tetracyclines, metallic ions, and others) and natural bioactive inhibitors mainly flavonoids. Selective inhibitors of MMPs promise to be the future for specific targeting of preventing dentin proteolysis. The knowledge about MMPs functionality should be considered to synthesize drugs capable to efficiently and selectively block MMPs chemical routes targeting their inactivation in order to overcome the current limitations of the therapeutic use of MMPs inhibitors, i.e., easy clinical application and long-lasting effect.