• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.912-921
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• 2009

Pulse-discharge technology (PDT) is an innovative technology which uses enormous energy developed by electric discharge for a very instant moment of time. Lately, it has been applied to make expanded sections at the ends of piles and anchors. The expanded section is formed by the deformation of bore-hole induced by shockwave energy developed in filling material by the pulse discharge. In this study, considering the phenomenon of pulse-discharge as an underwater explosion, finite element analyses were carried out to model the shockwave development by pulse discharge. The simulation technique was verified by comparing results with underwater discharge test results.

• Journal of the Korean Ceramic Society
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• v.25 no.1
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• pp.7-14
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• 1988

In this paper, piezoelectric composite materials of 1-3 connectivity were prepared by using "dicing-filling" technique with PZT ceramics and epoxy polymers, and the dependence of piezoelectric properties on the thickness of specimens was investigated. In case that the PZT volume percent is 18.1%, according to an increment of thickness, the dielectric constant of composites( 33) is unchangeable, which is about 200, the piezoelectric coefficient (d33) is somewhat increased, which is about 240-280 (PC/N) and the electromechanical coupling factor of thickness mode(kt) is proportioned, but radial mode(kp) is constant.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1994.03a
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• pp.63-70
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• 1994

An upper bound elemental technique(UBET) is applied to predict forging load and die-cavity filling for non-axisymmetric ring forging. The finial product is divided into three different deformation regions. That is axisymmetric part in corner, lateral plane-strain part and shear deformation on boundaries between them. The plane-strain and axisymmetric part are combinded by building block method. Also the total energy is computered through combination of three deformation part. Experiments have been carried out with pure plasticine billets at room temperature. The theoretical predictions of the forging load and the flow pattern are in good agreement with the experimental results.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.187-190
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• 2018

최근 프로그래밍 교육에서 학생들의 학습 성취도를 빠르고 정확하게 평가하기 위하여 자동 채점 시스템을 사용한다. 강의를 통해 습득한 이론적인 지식을 이해하기 위해 직접 코드를 작성하는 실습이 진행되는 프로그래밍 교육에서 효과적이기 때문이다. 현재 실습에 필요한 실습문항의 대부분은 강사가 직접 생성해야 한다. 특히 강의내용을 바탕으로 예제 소스코드를 이해하여 빈 칸에 알맞은 코드를 작성하는 실습은 강사가 직접 빈 칸에 해당되는 부분을 예제 코드에서 지정해줘야 하는 추가적인 작업이 필요하다. 이러한 빈 칸 채우기 문항은 일반적으로 빈 칸이 고정된 행태이기 예문에 학생들이 답안을 공유하기 쉽다. 이를 막기 위해서 강사는 유사한 내용의 빈 칸 채우기 문항을 추가적으로 생성해야 한다. 하지만 대부분의 자동 채점 시스템은 이를 지원하지 않거나 강사에게 빈 칸을 직접 지정하도록 하는 경우가 대부분이다. 따라서 본 논문에서는 이러한 문제를 해결하는 빈 칸 채우기 문항 자동생성기법을 제안하고 적용 사례를 보인다.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.597-606
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• 2019

Ultrasonic Time-of-Flight Diffraction (TOFD) techniques are useful methods for non-destructive evaluation of fracture characteristics. This study focuses on the reliability and accuracy of ultrasonic diffraction methods to estimate the depth of rock fractures. The study material includes three different rock types; andesite, basalt and ignimbrite. Four different ultrasonic techniques were performed on these intact rocks. Artificial near-surface fracture depths were created in the laboratory by sawing. The reliability and accuracy of each technique was assessed by comparison of the repeated measurements at different path lengths along the rock surface. The standard error associated with the predictive equations is very small and their reliability and accuracy seem to be high enough to be utilized in estimating the depth of rock fractures. The performances of these techniques were re-evaluated after filling the artificial fractures with another material to simulate natural infills.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.1036-1041
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• 2005

Treemaps, a space filling visualization technique, displays a massive data set of hierarchical data interactively on a single computer screen by mapping it to a matrix of rectangles. It allows users to visually inspect and manipulate data to find new relationships or discrepancies that are to difficult to find using traditional techniques. This paper applies treemaps to the evaluation of highway project bids, which contain hundreds or thousands of elements arranged in a hierarchical structure. Through a case study, treemaps are shown to be a potentially effective tool for bid evaluation by both contractors and State or Federal highway officials.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.393-400
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• 2022

Agent-based modeling (ABM), as a relatively new simulation technique, has recently gained in popularity in the civil engineering domain due to its uniquely advantageous features. Among many civil engineering applications, ABM has been applied to facility operation and management, such as energy consumption management, as well as the enhancement of maintenance and repair processes. The former studies used ABM to manage energy consumption through simulating human energy-related behaviors and their interactions with facilities, as well as electrical, heating, and cooling systems and appliances, while the latter used ABM to enhance maintenance process through facilitating coordination, negotiation, and decision making between facility managers, service providers, and repair workers. The present study aims to provide a short qualitative review on the most recent applications of ABM in the above-mentioned areas. Based on the review and follow-up analysis, the study identifies the advantages, disadvantages, and limitations of ABM applications to facility operation and management, and offers several potential future research topics in the hope of filling the existing literature gaps.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.55-57
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• 2020

실감미디어의 수요가 높아짐에 따라, 실감 미디어 컨텐츠 제작에 반드시 필요한 깊이영상에 대한 중요성이 커지고 있다. 다시점 영상으로부터 계산된 깊이 영상은 물체 주위와 배경 영역에 홀을 가지고 있다. 이러한 깊이영상에서의 홀을 채울 때, 이에 대응하는 컬러영상의 색상 특성을 고려하는 방법을 제안한다. 본 논문에서는 컬러 영상의 화소들을 색상 유사성을 이용하여 클래스로 분류하고, 홀의 깊이정보를 예측할 때 같은 클래스의 유효한 깊이값 만을 사용하는 방법을 소개한다. 제안하는 방법을 사용하면 깊이영상의 홀을 효율적으로 채워 넣을 수 있다. 실감미디어 제작에 있어 제안하는 방법을 사용한다면, 사실감 있는 깊이 정보를 얻을 수 있다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.107-114
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• 2008

In wireless access systems, there has been much interest in enhancing the performance of orthogonal frequency division multiplexing OFDM) in a frequency selective fading channel. If the channel is static and is perfectly known to both the transmitter and the receiver, the water-filling technique with adaptive modulation is known to be optimal. However, for OFDM systems, this requires intensive traffic overheads for reporting channel side information on all subcarriers to the transmitter In this paper, we propose an adaptive modulation and coding scheme for bit-interleaved coded OFDM (BIC-OFDM) for downlink packet transmissions with reduced feedback information. To minimize the feedback information, we employ a rate adaptation method based on the OFDM symbol rather than on each subcarrier. To illustrate the performance gap between the optimal water-filling and the proposed scheme, we will compare cutoff rates for both schemes. It is shown that the loss is less than 2dB while the proposed scheme significantly reduces the feedback payloads. Also, the OFDM system in multiuser environment with subcarrier grouping is considered. It is shown that by exploiting multiuser diversity the throughput of the proposed scheme approaches the channel outage capacity as the number of users and the number of subcarrier groups increase.

• Journal of the korean academy of Pediatric Dentistry
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• v.46 no.4
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• pp.382-391
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• 2019

This study was aimed to assess the new trial for minimal cavity preparation in composite restoration combined with resin infiltration, focusing at application sequence. 32 human primary molars with early carious lesions around small cavity were selected and randomly divided into two groups, according to the sequence of cavity preparation (P), composite filling (F) and resin infiltration (I) as IPF and PFI group. Each group was assessed about amount of tooth reduction, features of resin infiltration, and marginal leakage around restoration. Amount of tooth reduction evaluated using micro-CT was decreased compared with the original lesion size in both groups. Features of resin infiltration were verified under confocal laser scanning microscopy. In both groups, infiltrant resin was found on all around the composite and maintained in spite of extent of decalcification even after artificial caries induction. Marginal micro leakage assessed with silver nitrate immersion and micro-CT was found more frequently in PFI group. The technique combining resin infiltration and composite restoration might ensure better adhesion prognosis as applied by the sequence of resin infiltration, cavity preparation, and composite filling. This new trial was thought meaningful in minimizing the cavity size and contributing to minimal invasive dentistry.