• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.05a
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• pp.429-433
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• 2004

Most utiltity systems are subject to frequent changes, often due to increased loads and demand to up-grade quality of service provided. Urban renewal, expressway construction and suburban growth have also caused significant changes in urban utility distribution systems. Recently, it is required that a guideline for planning of a complete system, the reasonable design and construction methods for the efficient installation common utility tunnels must be estabilished. It prompts drastic measures to guard cities and their inhabitants against the horror of massive fires in the future. Preparedness holds the key to safety.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.112-116
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• 2004

On-line monitoring of fault discharge is an important approach for indicating the condition of electrical insulation of stator winding in high voltage motor. In this paper, several key aspects of on-line monitoring system are discussed, involving the characteristics of fault discharge of stator winding in high voltage motor, spectrum analysis of four simulation fault signals, feature extraction of internal fault discharge from apply voltage to breakdown. The study of the partial discharge activities allows to highlight the ageing stage in the winding fault under test. During the life of the winding insulation fault, the shape of PD signal change relating to the ageing stage. The ageing of stator winding insulation fault of high voltage motor is investigated based on the characteristics of partial discharge pulse distribution and statistical parameters, such as maximum, skewness and kurtosis using discrete wavelet transform coefficients.

• Proceedings of the KAIS Fall Conference
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• 2010.05a
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• pp.210-213
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• 2010

센서 네트워크는 구성의 편리성과 이동성, 확장성이 뛰어난 장점을 가지고 있어서 침입 탐지나 원격감시 등 여러 분야에서 응용이 가능한 네트워크로 앞으로 계속 발전해야할 과제가 남아 있다. 즉, 센서 네트워크 환경에서는 보안성을 위해 센서 노드들은 키를 공유해야 하는데, 기존에 제안된 키 분배기법은 키가 너무 많이 필요하거나, 비 효율적인 문제가 있고 노드간 연결이 안되서 도태 되는 노드가 생기는 등 취약한 점이 많다. 본 논문에서는 무선 센서 네트워크 환경에서 안전한 키 분배를 위한 방법중에 쿼럼 시스템을 응용한 다중선택그리드 쿼럼방식을 사용해 센서 노드들 사이의 인증을 강화시켜 외부의 공격 노드들로부터 안전하고 노드간 연결성이 보장되는 방법을 제시하고 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06c
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• pp.286-288
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• 2012

Facing the counterfeiting acts towards various products, many manufacturers implement ePedigree system to secure their supply chain. Using ePedigree, a distribution history including a valid product identifier from the manufacturer until the final retailer is recorded. And this ePedigree is signed by each involved supply chain party using digital signature. With this digital signature, any unauthorized alteration to the ePedigree document would generate a failed verification process. If there is a counterfeit product using a fake ePedigree document, it wouldn't be able to pass the verification process either. Hence, there wouldn't be any counterfeit product that could enter the legal supply chain and bought by the consumer. We are proposing to use ECDSA instead of RSA since it has faster performance and shorter key size. At a certain same security level, ECDSA only needs 163 bits, while RSA needs 1024 bits.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.24-29
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• 2003

Deep sea water has cold temperature, abundant nutrients and minerals, and good water quality that is pathogen-free and stable. Compared with surface water, deep sea water contains more nutrition salt, such as nitrogen and phosphor. Moreover, if has the good balance of minerals. Because of the ability of the spray drying process to produce a free-flowing power considering of spherical particles with a well-defined size distribution and the rapid drying times for heat-sensitive material, spray drying is attractive for a wide range of applications spray drying is a unique unit operation in which powders are produced from a liquid feed in a single processing step. Key component of the process are atomizer, spray chamber. Design of spray chamber should be based on the atomizer type, the production rate, and the particle size required. Because of the complex processes taking place during spray drying, traditional design method are based on pilot-plant tests and empirical scale-up rules. Modern technique such as CFD have a role to play in design and troubleshooting.

• Proceedings of the KOR-KST Conference
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• 2003.02a
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• pp.127-150
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• 2003

This research presents a novel application of static traffic assignment methods, but with a variable time value, for estimating the market share of a high-speed rail (HSR) in the NW-SE corridor of Korea which is currently served by the airline (AR), conventional rail (CR), and highway (HWY) modes. The proposed model employs the time-space network structure to capture the interrelations among all competing transportation modes, and to reflect their supply- and demand-sides constraints as well as interactions through properly formulated link-node structures. The embedded cost function for each network link offers the flexibility for incorporating all associated factors, such as travel time and fare, in the model computation, and enables the use of a distribution rather than a constant to represent the time-value variation among all transportation mode users. To realistically capture the tripmakers' value-of-time (VOT) along the target area, a novel method for VOT calibration has been developed with aggregate demand information and key system performance data from the target area. Under the assumption that intercity tripmakers often have nearly "perfect" travel information, one can solve the market share of each mode after operations of HSR for each O-D pair under the time-dependent demand with state-of-the-art traffic assignment. Aside from estimating new market share, this paper also investigated the impacts of HSR on other existing transportation modes.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.134-134
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• 2021

Precipitation is a crucial component of water cycle and play a key role in hydrological processes. Traditionally, gauge-based precipitation is the main method to achieve high accuracy of rainfall estimation, but its distribution is sparsely in mountainous areas. Recently, satellite-based precipitation products (SPPs) provide grid-based precipitation with spatio-temporal variability, but SPPs contain a lot of uncertainty in estimated precipitation, and the spatial resolution quite coarse. To overcome these limitations, this study aims to generate new grid-based daily precipitation using Automatic weather system (AWS) in Korea and multiple SPPs(i.e. CHIRPSv2, CMORPH, GSMaP, TRMMv7) during the period of 2003-2017. And this study used a machine learning based Random Forest (RF) model for generating new merging precipitation. In addition, several statistical linear merging methods are used to compare with the results of the RF model. In order to investigate the efficiency of RF, observed data from 64 observed Automated Synoptic Observation System (ASOS) were collected to evaluate the accuracy of the products through Kling-Gupta efficiency (KGE), probability of detection (POD), false alarm rate (FAR), and critical success index (CSI). As a result, the new precipitation generated through the random forest model showed higher accuracy than each satellite rainfall product and spatio-temporal variability was better reflected than other statistical merging methods. Therefore, a random forest-based ensemble satellite precipitation product can be efficiently used for hydrological simulations in ungauged basins such as the Mekong River.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.358-358
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• 2012

The application of BZO (Boron-doped Zinc Oxide) films use as the TCO(Transparent Conductive Oxide) material for display and solar cell industries, where the conductivity of the BZO films plays a critical role for improvement of cell performance. Thin BZO films are deposited on glass substrates by using RF sputter system. Then charging flow rates of O2 gas from zero to 10 sccm, thereby controlling the impurity concentration of BZO. BZO deposited on soda lime glass and RF power was 300 W, frequency was 13.56 MHz, and working pressure was $5.0{\times}10-6$ Torr. The Substrate and glass between distance 200 mm. We measured resistivity, conductivity, mobility by hall measurement system. Optical properties measured by photo voltaic device analysis system. We measured surface build according to oxygen flow rate from XPS (X-ray Photoelectron Spectroscopy) system. The profile of the energy distribution of the electrons emitted from BZO films by the Auger neutralization is measured and rescaled so that Auger self-convolution arises, revealing the detail structure of the valence band. It may be observed coefficient ${\gamma}$ of the secondary electron emission from BZO by using ${\gamma}$-FIB (Gamma-Focused Ion Beam) system. We observed the change in electrical conductivity by correlation of the valence band structure. Therefore one of the key issues in BZO films may be the valence band that detail structure dominates performance of solar cell devices. Demonstrating the secondary electron emission by the Auger neutralization of ions is useful for the determination of the characteristics of BZO films for solar cell and display developments.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.873-877
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• 2008

There were many exposed problems in previous authentication method on LAN. Especially Open System Authentication Method, Shared Key Method, Mac Based Authentication Method are very hard to use in wireless network that needs security. So now, many researches have been performed about $802.1{\times}$ and user authentication method applying PKI. But certificate verification protocol has been used abolished list called CRL since it's first usage of PKI, there were still has a problem about distribution point. In this paper, I applied CVS to use CA direct not to use CRL and OSCP server in order to improve this problems.

• Proceedings of the Safety Management and Science Conference
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• 2002.11a
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• pp.295-304
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• 2002

This case describes key development challenges and patterns as experienced by Internet Auction Company, Ltd. from the startup stage through IPO to the sale to eBay. Currently an eBay company, Internet Auction Co. continues to pursue new auction systems and substitute distribution systems for the future with a renewed entrepreneurial spirit. In 1997, Mr Hyuk Oh saw a business opportunity in the Internet allowing two-way communications. At that time, the success stories of eBay and Onsale in the United States were good stimuli to his startup of an auction site. He opened the Website in April 1, 1998 after four months of development efforts. Auction has merit more than other shopping malls. First, it brings about interesting and benefit. Second, it has interactive trade system. Third, customers will trade for reasonable price through direct own will of them. Fourth, Auction's model brings about multitude sale through aggressive sales. Even if Network Marketing has socially negative effect in case of inappropriate use, it is good mood for further business. In case E-Commerce use as useful purpose, it will have competitive priority revenue model.