• Composites Research
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• v.16 no.5
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• pp.15-20
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• 2003

In this paper, the fracture strength of the surface damaged laminates was predicted by applying the fracture strengths of the unflawed and flawed laminates. For prediction, the theoretical equation about the fracture strength of laminates was simplified applying classical laminate theory and was applied to the surface damaged laminates. Lagace's and Tsai's experimental data were used for verifying the theoretical equation. Moreover, to verify the theoretical prediction, an experiment was performed. Surface unflawed laminate and flawed laminates were fabricated and the experiments were made and these results were compared with theoretical predictions. The specimens' fiber direction was same to the tensile direction and the theoretical predictions and the experimental results were showed good agreement. Therefore, by this equation, the fracture strength of structures made of composites will be able to be predicted when the surface of the structures was damaged.

• Proceedings of the Korea Inteligent Information System Society Conference
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• 2000.11a
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• pp.151-157
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• 2000

본 논문에서는 웹사이트에 접근하는 사용자 접근 패턴을 학습하여 정보 제공이 보다 용이한 구조로 자동 개선시켜 나가는 적응형 웹사이트를 구축하고자 한다. 즉, 기존 웹사이트의 구조를 가늠한 한 파괴하지 않는 범위 내에서 김 사이트를 변경하고자 관련성은 높으나 접근 경로가 긴 문서들의 클러스터를 찾아내고, 이들에 대한 별도의 색인 페이지를 생성하여 웹사이트 내에 위치시킨다. 이를 위하여, 먼저 대용량의 웹 서버 로그 데이터들을 대상으로 순차 패턴 탐색 방법인 AprioriAll 알고리즘을 적용함으로써 웹문서간의 충분한 연관성 지지도를 갖는 사용자 순차 접근 패턴을 분석해낸다. 사용자 순차 접근 패턴 분석을 통해 관련성 있는 문서들의 집합을 알아낸 후, 웹사이트의 하이퍼 링크 구조 정보를 고려하여 접근 경로가 긴 문서들만을 골라 웹 문서 클러스터를 생성시킨다. 이러한 웹문서 클러스터들에 대한 색인 페이지를 추가 생성하여 제공함으로써 사용자들의 보다 효과적인 정보 접근을 지원한 수 있는 웹사이트로의 변경이 가능하다.

• Annual Conference on Human and Language Technology
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• 2021.10a
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• pp.215-220
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• 2021

다중 도메인에 대해 답변 생성 모델이 동작 가능하도록 하는 가장 쉬운 방법은 모든 도메인의 데이터를 순서와 상관없이 한번에 학습하는 것이다. 하지만 이경우, 발화에 상관 없이 지나치게 일반적인 답변을 생성하는 문제가 발생한다. 이에 반해, 도메인을 분리하여 도메인을 순차적으로 학습할 경우 일반적인 답변 생성 문제를 해결할 수 있다. 하지만 이경우 새로운 도메인의 데이터를 학습할 때, 기존에 학습한 도메인에 대한 성능이 저하되는 파괴적 망각 현상이 발생한다. 파괴적 망각 현상을 해결하기 위하여 다양한 지속학습기법이 제안되었으며, 그 중 메모리 리플레이 방법은 새로운 도메인 학습시 기존 도메인의 데이터를 함께 학습하는 방법으로 파괴적 망각 현상을 해결하고자 하였다. 본 논문에서는, 사람의 기억 시스템에 대한 모형인 앳킨슨-쉬프린 기억 모형에서 착안하여 사람이 기억을 저장하는것과 유사한 방법으로 메모리 리플레이 방법의 메모리 관리방법을 제안하였고, 해당 메모리 관리법을 활용하는 메모리 리플레이 방법을 통해 답변 생성 모델의 파괴적 망각 현상을 줄이고자 하였다. 다중 도메인 답변 생성에 대한 데이터셋인 MultiWoZ-2.0를 사용하여 제안 모델을 학습 및 평가하였고, 제안 모델이 다중 도메인 답변 생성 모델의 파괴적 망각 현상을 감소시킴을 확인하였다.

• Composites Research
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• v.17 no.4
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• pp.68-73
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• 2004

An analytical study was conducted to characterize the fatigue crack growth behavior of pre-cracked aluminum plates repaired with asymmetric bonded composite patch. For single-sided repairs, due to the asymmetry and the presence of out-of$.$plane bending, crack front shape would become skewed curvilinear started from a uniform through-crack profile, as observed from Previous studies. Therefore, for the accurate investigation of fatigue behavior, it is necessary to predict the actual crack front evolution and take it into consideration in the analysis. In this study, the fatigue analysis of single-sided repairs considering crack front shape development was conducted by implementing three-dimensional successive finite element method coupled with linear elastic fracture mechanics (LEFM) concept, which enables the growing crack front to be directly traced and modeled in a step by step way. Through conducting present analysis technique, crack path of the patched plate as well as the fatigue life was evaluated with sufficient accuracy. The analytical predictions of both the crack front shape evolution and the fatigue life were in good agreement with the experimental observations.

• Journal of Korea Water Resources Association
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• v.39 no.2 s.163
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• pp.89-98
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• 2006

To evaluate the pipe failure impact, current methodologies consider only a broken pipe as the impacted area. However, these approaches are accurate if the broken pipe is the only area isolated from tile system. Depending on the number and locations of on-off valves, more pipes which are adjacent to a broken pipe may be isolated. Using the concept of Segment suggested by Walski, the methodology evaluating the pipe failure impact incorporated with on-off valve locations has been suggested by Jun. However, a segment cannot account for all possible pipe failure impacted areas since it does not consider additional failures, namely the network topological failure and the hydraulic pressure failure. For this reason, a methodology which can consider the network topology and hydraulic pressure limitation as well as on-off valve locations is suggested. The suggested methodology is applied to a real network to verify its applicability As results, it is found that a single pipe failure can affect huge areas depending on the configuration of on-off valves and the network topology. Thus, the applicability of the suggested methodology for evaluating the pipe failure impacts on a water distribution network is proved.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.373-378
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• 2012

The objective of this research is to examine the probabilistic approach to evaluating turbine ejection frequency considering common-cause failure. This paper identifies basic turbine ejection mechanisms under high and low speeds and presents a detailed probabilistic methodology (fault tree) for assessing ejection frequency. The alpha factor methodology is applied to common-cause failure evaluations. The frequencies under different test schemes are compared and the propagation of uncertainty through the fault tree model is evaluated. The following conclusions were reached: (1) the turbine blade ejection frequency due to ductile failure under high speed is around 8.005E-7/yr; (2) if common-cause failure is considered, the frequency will be increased by 11% and 33% depending on the test scheme; and (3) if the parameter uncertainties are considered, the frequency is estimated to be in the range of 9.35E-7 to 1.13E 6, with 90% confidence.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.203-211
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• 2013

Shear behavior of joint plane has been investigated considering the magnitude of normal stresses and initial surface roughness. Shear strength of joint plane has been measured by performing the multi-stage shear test in which applied normal stress level has been increased stepwise. Multi-stage shear test within the specified normal stress range has been repeated and two types of strength parameter variation have been observed: type 1 - both cohesion and friction angle decrease, type 2 - cohesion decrease and friction angle increase. Trends of strength parameter variation for the three rock types, gneiss, granite and shale, have been investigated and the influence of initial roughness of joint plane on the sequential shear strength change for the repeated multi-stage shear tests also has been analyzed.

• Explosives and Blasting
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• v.39 no.2
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• pp.1-14
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• 2021

Recently, with the development of high-performance processing devices such as GPGPU, a three-dimensional dynamic analysis technique that can replace expensive rock material impact tests has been actively developed in the defense and aerospace fields. Experimentally observing or measuring fracture processes occurring in rocks subjected to high impact loads, such as blasting and earth penetration of small-diameter missiles, are difficult due to the inhomogeneity and opacity of rock materials. In this study, a three-dimensional dynamic fracture process analysis technique (3D-DFPA) was developed to simulate the fracture behavior of rocks due to impact. In order to improve the operation speed, an algorithm capable of GPGPU operation was developed for explicit analysis and contact element search. To verify the proposed dynamic fracture process analysis technique, the dynamic fracture toughness tests of the Straight Notched Disk Bending (SNDB) limestone samples were simulated and the propagation of the reflection and transmission of the stress waves at the rock-impact bar interfaces and the fracture process of the rock samples were compared. The dynamic load tests for the SNDB sample applied a Pulse Shape controlled Split Hopkinson presure bar (PS-SHPB) that can control the waveform of the incident stress wave, the stress state, and the fracture process of the rock models were analyzed with experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1093-1098
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• 2013

A single-crystal sapphire is used as a transparent bulletproof window material; however, few studies have investigated the dynamic behavior and fracture properties under high-speed impact. High-speed and high-resolution sequential images are required to study the interaction of the bullet with the brittle ceramic materials. In this study, a device is developed to capture the sequence of high-speed impact/penetration phenomena. This system consists of a speed measurement device, a microprocessor-based camera controller, and multiple CCD cameras. By using a linear array sensor, the speed-measuring device can measure a small (diameter: up to 1 2 mm) and fast (speed: up to Mach 3) bullet. Once a bullet is launched, it passes through the speed measurement device where its time and speed is recorded, and then, the camera controller computes the exact time of arrival to the target during flight. Then, it sends the trigger signal to the cameras and flashes with a specific delay to capture the impact images sequentially. It is almost impossible to capture high-speed images without the estimation of the time of arrival. We were able to capture high-speed images using the new system with precise accuracy.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.325-328
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• 2001

본 논문에서는 웹 사이트에 접근하는 이용자의 패턴을 분석하여 정보 제공이 보다 용이한 구조로 자동 개선시켜 나가는 적응형 웹 사이트의 구현 방안을 제시한다. 특히, 본 연구에서는 기존 웹 사이트의 구조를 가능한 파괴하지 않는 범위 내에서 웹 사이트론 변경하고자 이용자의 접근 패턴상 연관성은 높으나 접근 경로가 긴 문서들을 추출하여 색인 페이지를 추가 생성한다. 이를 위하여, 먼저 대용량의 웹 서버 로그 데이터를 대상으로 하이퍼 링크 구조에 따라 필터링된 최후 전진 문서만을 가지고 데이터 시퀀스를 구성한다. 이러한 데이터 시퀀스에 새로운 순차 접근 패턴 탐색 알고리즘인 TPA를 적용함으로써 웹 문서간 충분한 지지도를 갖는 연관성 있는 문서들의 시퀀스를 구한다. 이와같은 빈발 시퀀스들에 대한 색인 페이지를 추가로 생성시켜주는 서비스를 통하여 이용자들의 효과적인 정보 접근을 지원할 수 있는 웹 사이트로의 변경이 가능하다.