• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.12-17
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• 2018

A natural cavitation-type high-speed underwater vehicle with solid rocket motor is tested, and its speed and running distance are measured. The outputs from pressure sensors on the surface of the vehicle reveal a pressure-time history reflecting the development of supercavitation. Underwater cameras installed on the wall of the test pool record the entire process from the onset of supercavitation to its full development. CNU-SuperCT, based on two-dimensional inviscid theoretical analysis, is used to simulate test results. Considering CNU-SuperCT does not include the control fins of the vehicle, simulation results agree with test results very well. Additionally, pictures from underwater cameras support the test results.

• Computational Structural Engineering
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• v.10 no.2
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• pp.171-178
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• 1997

Three-dimensional dynamic analyses of underground openings subjected to explosive loadings are carried out. Dynamic analyses consist of two steps; one-dimensional source calculation and three-dimensional tunnel analysis. One-dimensional source calculation includes explosive charge and the free field surrounding rock. The input pressure time history for three-dimensional tunnel analysis is obtained from the companion one-dimensional source calculation. The computer program MPDAP-3D incorporated this analysis capability. It is shown that the computer program is a useful tool for the analysis of the structural safety evaluation of underground openings during construction by drill and blasting method.

• Annual Conference on Human and Language Technology
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• 1999.10e
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• pp.199-202
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• 1999

ETRI 통신단말연구부에서는 1999년 7월 22일에 C-STAR 회원국이 함께 참여하는 국제간 음성언어번역 시스템 공동 시연을 가졌다. 이 논문은 다국어 대화체 번역시스템인 음성언어번역 시스템의 국제간 공동 시연에 사용된 한국어 번역 시스템의 성능에 대해 기술한다. 번역 시스템의 성능은 전사문장을 이용한 영어, 일본어, 한국어의 번역 결과와 음성인식 결과를 이용한 각 언어의 번역 결과를 평가하여 얻었다. 그리고 세부 시스템의 성능을 알아보기 위해 음성인식의 결과로부터 C-STAR IF(interchange format)까지의 해석 시스템과 C-STAR IF로부터 한국어, 영어, 일본어로 생성해 내는 생성 시스템의 성능으로 나누어서 평가한다.

• Journal of the Korean Geotechnical Society
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• v.37 no.10
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• pp.65-76
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• 2021

There is a possibility of cavities occurring inside and behind the lining of an aged tunnel structure. In most cases, it is not easy to check the cavity because it exists in a place where visual inspection is impossible. Recently, attempts have been made to evaluate the condition of the tunnel lining and the backfill materials using non-destructive tests such as Ground Penetrating Radar, and various related model tests and numerical analysis studies have been conducted. In this study, the GPR signal characteristics for tunnel lining model testing were analyzed using gprMax software, which was compared with model test results. The numerical model applied to the model test reasonably simulated the electromagnetic wave signal according to the change of the material such as tunnel lining and internal cavity. Using the verified GPR model, B-scan data for the development of the GPR signal analysis technique were obtained, which can evaluate the thickness of the tunnel lining, the presence of the cavity, the effect of the waterproof membrane, and the frequency band.

• Journal of the Korean Society for information Management
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• v.39 no.1
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• pp.45-68
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• 2022

The objective of this study is to investigate the factors which influence biotechnology scientists' data sharing intention. This study employed Ostrom's theory of collective action. The target population of this study includes scientists and students of biotechnology field in South Korea. A total of 411 responses which collected by e-mail were used for the final data analysis. The summary of this study is as follows. First, norm of data sharing and academic reciprocity were found to have significant positive influences on data sharing intention directly. Second, perceived community trust was found to have significant positive influences on data sharing intention when academic reciprocity was the mediator. Third, academic reputation showed the moderating effects on the relationship between norm of data sharing and academic reciprocity, and between norm of data sharing and data sharing intention. These findings show that researchers can approach the data sharing behaviors by using the mechanism of trust, norms, reciprocity, and reputation and indicate necessity for a development of academic reputation system to promote more data sharing behaviors of researchers.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.6
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• pp.482-489
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• 2018

Most of the numerical and experimental studies on supercavitating flows are focused on the cavitator only. However, the partial cavity growing into the supercavity is affected by the shape of the body placed behind the cavitator. In this paper, we develope a numerical method which is based on the boundary element method to predict supercavitating flow around three-dimensional axisymmetric bodies. We estimate the influence of the body shape on the supercavity growth. Here, we consider various parameters of the body such as cavitator shape, shoulder length and body diameter, and compare the results with the case of the cavitator only. In summary, it is found that the body may impede the cavity growth, the shoulder mainly affects the cavity length, and the supercavity occurring in the cone type cavitator is strongly influenced rather than that of the disk type cavitator.

• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.26-32
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• 2019

The vortex flow behind a bluff body has been a subject of interest for a very long time because of its engineering applicability such as to vortex induced vibration. In the near wake of a bluff body, vortices are periodically shed in two shear layers, which originate in the trailing edges. The far wake is made up of the classical Karman vortices, which are connected together by streamwise and spanwise vortices. These vortex formations have been studied in many experimental and numerical ways. However, most of the studies considered non-cavitating flow. In this study, we investigated cavitating flow in the wake of a two-dimensional wedge. Experiments were conducted in a cavitation tunnel of Chungnam National University. Using a particle image velocimetry (PIV), we measured the velocity fields under two different flow conditions: non-cavitating and cavitating regimes. We also investigated the vortex shedding frequencies using an absolute pressure transducer mounted on the top of the test window. Throughout the experiments, it was found that the shedding frequency of the vortex was strongly affected by cavitation, and the Strouhal number could exceed its value in the non-cavitating regime.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.16-21
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• 2002

현재의 웹은 신문, 잡지, 책 등의 온라인 출판뿐 아니라, 전자상거래, 금융, 가상 공동체, 마케팅, 광고 둥의 다양한 분야에서 실생활과 밀접하고, 기업에서도 웹 사이트가 제품 홍보 뿐 아니라 제품의 판매, 마케팅 등 매출에 막대한 영향을 미치는 중요한 위치를 차지하고 있다. 웹 사이트의 규모가 커지고 복잡해져감에 따라서 소수의 웹 디자이너들이 웹 사이트를 개발했던 것에서 개발에 필요한 인력과 그 역할을 나누게 되었고, 다른 제품처럼 납기를 위한 일정 관리가 필요하게 되었다. 그동안 웹 사이트 개발에 있어서 일련의 과정들에 대한 정형화되고 표준화된 작업 방법을 별로 적용하지는 않았다. 소프트웨어 공학을 그대로 웹 사이트 개발에 적용할 수는 없지만, 점차 웹 사이트가 소프트웨어 처럼 되어 가고 있고, 현재 웹 사이트 개발에 있어서 필요한 표준 개발 방법론이나 프로젝트 관리 둥을 소프트웨어 공학에서 적용시킬 수 있다. 본 논문에서 웹 사이트 개발에 있어서 더 나은 생산성과 품질을 얻기 위해 기획, 설계, 개발, 그래픽 디자인, 정보 설계, 컨텐츠, 테스트, 유지보수 등의 일련의 과정들을 프로세스화 하고, 구조적으로 접근하는 방법을 소프트웨어 공학의 표준 개발 방법론이나 프로젝트 관리, 품질관리 등에 관한 연구와, 실제로 이러한 방법론을 적용한 웹 서버을 구축하였다.

• The Journal of Engineering Geology
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• v.5 no.1
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• pp.31-44
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• 1995

The puppose of this study is to propose the numerical modelling criteria for underground opening, rock mass continuum is regarded as homogeneous rock behaved linear elastic. The results of this study are summarized as follows: - Boundaries of the finite element mesh should be located at least 6 radii away from the center of the opening. - For circular openings, tension only developed when $K_0$ was less than one-fourAs the ratio of initial horiwntal to vertical stress increased, the inward springline movement increased and the inward crown movement decreased. - The displacement patterns developing for opening I shaped horse-shoe and opening II shaped powerstation are similar to those for circular openings. For both type opening I and opening II, stress concentrations develop at the intersection of the wall and floor. Greater stress concentrations are found for the type opening II.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.1
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• pp.24-31
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• 2021

In this study, we present experimental observations of artificial supercavitation generated by the injection of compressed air at multiple locations on the body. Experiments were conducted at a cavitation tunnel equipped with a special facility to remove injected air before returning to the test section. Artificial supercavitation, which is generated at a relatively low speed compared to natural supercavitation, is formed asymmetrically on the axis of the body due to the buoyancy effect. In order to accelerate the development of the supercavity and increase the area covering the body, an experimental device capable of additional injection from the body was designed and its performance was evaluated through the model test. The shapes of the supercavity generated by multi-injections of different combinations according to different flow speeds were analyzed using high-speed shadow images. The results show that multiple injections at suitable locations can effectively increase the length of the supercavity and consequently improve propulsion efficiency.