• 한국세라믹학회지
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• 제55권5호
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• pp.440-445
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• 2018

To control the electrical properties of a SiC heating element, we sintered $SiC-ZrB_2$composites by using the spark plasma sintering method. The addition of $ZrB_2$ particles with lower electrical conductivity to the SiC matrices with comparatively higher electrical resistivity lowers the electrical resistivities of the composite material. The $ZrB_2$ particles aggregate to form large particles and 3-1, 3-2, and 3-3 networks, i.e., conduction paths. In our study, about $1-{\mu}m$-sized $ZrB_2$ powders start to form the conduction path at about 10 vol.% of addition, namely the threshold volume. The Joule heating experiment shows that 20 vol.% $ZrB_2$-added SiC heating element has outstanding heating efficiency.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.1-6
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• 1990

Joints are provided in cement concrete pavements to control transverse and longitudinal cracking that occur due to restrained deformations caused by moisture and temperature variations in the slab. But the construction of joints reduces the load-carrying capacity of the pavement at the joints, and pavements have beem deteriorated by cracks at the slab edges along the joints due to traffic loads. Therefore, it is important to analyze the behavior of joints accurately in the design of cement concrete pavements. In this study, the mechanical behavior of cement concrete pavement slabs is analyzed by the plate-finite element model, and Winkler foundation model is adopted to analyze the subgrades. The load transfer mechanism of joints are composed of dowel action, aggregate interlocking, and tied-key action, and the analytical program is developed using these joint models.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.185-188
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• 2004

The effect of fly ash to prevent detrimental expansion due to alkali -silica reaction was investigated through the ASTM C 1260 method that is one of the most commonly used method because results can be obtained within about 16 days. Reactive aggregate used is a netamorphic rock and sedimentary rock. The replacement proportions of portland cement by fly ash were respectively 0, 5, 10, 15, 25 and 35 percent. Expansion of mortar bars due to alkali-silica reaction decreased with the increase of fly ash content. The results show that the expansion due to alkali-silica reaction is dramatically reduced in the presence of high volume fly ash. When the fly ash content examine from all angles (strength and a flow), the replacement proportions of fly ash is about $25\%$ in order to control on expansion.

• 대한전기학회논문지:전력기술부문A
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• 제50권4호
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• pp.172-179
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• 2001

A component based method out of load modeling is to aggregate component load model according to the composition rate of each component load at load bus based on the circuit theory. But the most of component loads respond complex nonlinear characteristics respect to voltage and frequency variation due to the control techniques and semiconductor elements applied to component load. It needs to verify this approach through actual experiment of the aggregation of component load even if it can be down. To identify this aggregation method well known, this paper is proposed the classifying method of component load characteristics for component loads to group by quantitative analysis. The component load characteristics were divided into several types by KSOM (kohonen self organizing map), which can classify multi-dimension vector, component load pattern, into two-dimension vector. Some ambiguous cases happened from KSOM were classified by the proposed closing degree.

• 기술사
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• 제41권2호
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• pp.45-50
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• 2008

At this point, the Pan-Korea Grand Waterway (PKGW) has negative views and various complicated problems, but the government chose PKGW as important project for having a benefit in physical distribution, tourism, aggregate sale and new employment as well as in view of disaster prevention, flood control, irrigation. The government makes special laws for PKGW in evaluating environment effect and the safety of existing facilities and considers countermeasures for the rehabilitation, movement and redevelopment of facilities by related company and specialist. From analyzing and investigating the collective results in detail and in stages, the PKGW is the best choice by which korea engineers can hand over pleasant and beautiful korea to next generation in world.

• 에너지공학
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• 제25권2호
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• pp.79-85
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• 2016

본 논문은 건물군을 위한 개선된 수요 관리 방안을 연구하였다. 수요 반응 체계하에서 제어가능한 다양한 수요 사이드 자원을 집단화하는 것이 중요하다. 기존의 수요관리 알고리즘은 주로 단일 건물로 제한된데 반하여 본 논문은 많은 수의 건물을 위한 수요관리 알고리즘을 제시하였다. 또한, 제시된 수요관리 알고리즘을 적용하기 위한 절차를 제시하였다.

• Journal of Ceramic Processing Research
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• 제20권5호
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• pp.464-469
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• 2019

In this study, the electrical conductivity of multi-walled carbon nanotubes (MWCNTs) and polyethylene synthesized by an extrusion process was evaluated. The MWCNTs used exhibited differences in their dispersion characteristics depending on the type of catalyst or synthesis gas used. Thus, the choice of catalyst or synthesis gas significantly affect the physicochemical state of the final MWCNTs and MWCNT-based composites. In this investigation, the characteristics of MWCNTs were analyzed in four cases by introducing ethylene and propylene gas to each catalyst synthesized using deposition precipitation and spray drying methods. The MWCNT-based composites synthesized using the catalyst prepared by deposition precipitation and the ethylene synthesis gas showed the best electrical conductivity. In principle, the morphologies of the MWCNTs indicate that the smaller the aggregate size and bundle thickness, the better the electrical conductivity of the MWCNT composites. This implies that the network is well-formed.

• KDI Journal of Economic Policy
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• 제43권1호
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• pp.29-52
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• 2021

The purpose of this paper is to measure the impact of the recent Korea-Japan trade dispute on the Korean economy using supply-driven input-output analysis. In July 2019, Japan announced the decision to tighten the export control of three materials which are indispensable in the manufacturing of semiconductors and electronic display panels. Japan's decision directly affects production in Korea's semiconductor and display sectors and is hence not a demand shock. For this reason, a standard demand-driven input-output analysis is not valid despite the fact that it can still be applied. The impact of Japan's decision on Korea's aggregate and individual sectors' gross output, GDP and employment were computed using both methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.1035-1048
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• 2023

The IEEE 802.11 WLAN adopts a random backoff algorithm for its collision avoidance mechanism, and it is well known that the contention-based algorithm may suffer from performance degradation especially in congested networks. In this paper, we design an efficient backoff algorithm that utilizes a reinforcement learning method to determine optimal values of backoffs. The mobile nodes share a common contention window (CW) in our scheme, and using a Q-learning algorithm, they can avoid collisions by finding and implicitly reserving their optimal time slot(s). In addition, we introduce Frame Size Control (FSC) algorithm to minimize the possible degradation of aggregate throughput when the number of nodes exceeds the CW size. Our simulation shows that the proposed backoff algorithm with FSC method outperforms the 802.11 protocol regardless of the traffic conditions, and an analytical modeling proves that our mechanism has a unique operating point that is fair and stable.

• 융합보안논문지
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• 제4권2호
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• pp.9-15
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• 2004

인터넷은 본질적으로 신뢰할 수 없는 네트워크들의 집합체이다. 인터넷상에서는 정보의 흐름을 통제하기가 대단히 어렵기 때문에, 산재한 자원을 충분히 활용하면서 내부의 중요한 자원을 인터넷으로부터 보호해 줄 수 있는 보안문제가 심각하게 대두되고 있다. 최근 발생하는 바이러스 사고와 시스템 불법 침입에 대한 발생률이 과거보다 훨씬 높으며 다양해지고 있다. 이러한 시기에 불법 행동을 막기 위한 침입 차단에 대한 연구가 활발하게 진행 중이며 계속적인 발전을 하고 있다. 본 논문에서는 침입자의 불법 행동에 대한 로그 정보를 XML 포맷 형식에 맞추어 관리자에게 통보하고, 원격으로 제어 할 수 있는 침입 차단 시스템을 개발하여 관리측면에서 발생하는 문제점을 해결하고자 하였다.