• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.5
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• pp.447-454
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• 2009

Rate-independent crystal plasticity model suffers from the non-uniqueness of activated slip systems and the determination of the shear slip rates on the active slip systems. In this paper, a time-integration algorithm which circumvents the problem of the multiplicity of the slip systems was developed and implemented into the user subroutine VUMAT of a commercial finite element program ABAQUS. The magnitude of the slip shears on the active slip systems in f.c.c Cu single crystal aligned with the specific crystallographic orientation was investigated to validate our solution procedure. Also, texture developments under various deformation modes such as simple compression, simple tension and plane strain compression were compared with the results of the rate-dependent model by using the rate-independent crystal plasticity model. The computation time employing the rate-independent model is much more reduced than the those of the rate-dependent model.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.95-103
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• 1999

Low pressure combustion characteristics of the composite solid propellants were studied in terms of the propellant burning rate, ignition processes, and the structure of the extinguished surfaces. Optical Vacuum Strand Burner(OVSB) system was designed and configured for this purpose. Burning rates of the propellants were measured at subatmospheric pressure by developed test method in OVSB. The ignition and combustion phenomena of the studied propellants in the combustion chamber of OVSB were recorded and analyzed with the camera and VCR(30 frames/s). Burning surfaces of the propellants were extinguished by rapid depressurization method and analyzed with Scanning Electron Microscope(SEM).

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.458-462
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• 2003

기존의 고정적 웹 페이지에, 실시간적으로 변화하는 내용의 제공을 가능하게 하기 위해, 추가적으로 코드를 첨가할 수 있도록 만든 것이 웹 응용 프로그램이다. 그 예로는 cgi, php, jsp, java, python 등이 있다. 많은 수의 언어와 다수의 프로그램들이 빠른 속도로 개발됨에 따라 많은 수의 보안 문제점들이 발생하였고 실제로 대단히 많은 서버들이 침입의 대상이 되었다. 웹 응용 프로그램의 보안에 많은 문제점이 발생한 이유는 첫번째, 기존의 서버 응용 프로그램들에 비하여 웹 응용 프로그램은 휠씬 많은 수가 아주 빠르게 개발되었다는 점이다. 두 번째는 웹 응용 프로그램에서 발생한 새로운 종류의 보안 위험성을 들 수 있다. 기존의 서버 응용 프로그램에서 발생하는 위험성들은 서버프로그램의 버그를 이용한 것이었고, 이들은 외부 입력의 내용보다는 그 크기 등의 간단히 검사 가능한 특징에 의존하는 경우가 많았다. 하지만, 웹 응용 프로그램이 외부 입력의 내용을 코드의 일부로 사용하는 경우가 많음으로 인해서, 웹 응용 프로그램에서는 간단히 검사하기 어려운 특징인 입력의 내용에 의존하는 위험성들이 많이 발생한다. 본 논문에서는 이러한 새로운 방식의 위험성을 소스코드를 이용해서 어떻게 자동적으로 검사할 수 있을 지에 관해서 새로운 아이디어를 제시한다. 이 아이디어는 현재 구현 중에 있으며, 초기 실험 결과 기존의 검사 프로그램들이 찾아내지 못하는 취약점들을 찾아낼 수 있음이 확인되었다.

• Geotechnical Engineering
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• v.12 no.4
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• pp.101-114
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• 1996

In this study, the characteristics of bearing capacity and deformation of intermediate soils are investigated through centrifuge tests. The experimental parameters are footing width, initial stress condition of soils and relative loading rate defined relationship of loading rate and permeability of soils. It is examined that loading rate influences on the bearing capacities and deformations. Based on the test results, some problem of existing specification are introduced in the view of related loading rates and load intensities. Especially it is showed that load intensities magnitude rlre reversed in the same settlement ratio(s/B(%)), due to partial drained effect as well as loading rates in undrained con dition based on the excess pore pressure and deformations measured under loading.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.9-17
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• 2000

The crystal growth and dissolution rates were calculated by solving a model equation, which involved the dissolution of the metastable phase($\beta$-HNIW) and growth of the stable phase($\varepsilon$-HNIW), together with the mass balance equation. The model has been successfully used to simulate available kinetic data for the $\beta$$\longrightarrow$$\varepsilon$ polymorphic transformation via a solution phase. From the effectiveness factor based on the two-step model, it was found that the surface integration contribution to the process was comparatively small, and a diffusion dependency decreased with an increase of the mass fraction of chloroform in the mixed solvents of ethyl acetate and chloroform. Appling these kinetics in process simulation allowed for the prediction of the product size of $\varepsilon$-HNIW.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.41-49
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• 2005

We have developed a random heterogeneous velocity model with bimodal distribution in methane hydrate-bearing Bones. The P-wave well-log data have a von Karman type autocorrelation function and non-Gaussian distribution. The velocity histogram has two peaks separated by several hundred metres per second. A random heterogeneous medium with bimodal distribution is generated by mapping of a medium with a Gaussian probability distribution, yielded by the normal spectral-based generation method. By using an ellipsoidal autocorrelation function, the random medium also incorporates anisotropy of autocorrelation lengths. A simulated P-wave velocity log reproduces well the features of the field data. This model is applied to two simulations of elastic wane propagation. Synthetic reflection sections with source signals in two different frequency bands imply that the velocity fluctuation of the random model with bimodal distribution causes the frequency dependence of the Bottom Simulating Reflector (BSR) by affecting wave field scattering. A synthetic cross-well section suggests that the strong attenuation observed in field data might be caused by the extrinsic attenuation in scattering. We conclude that random heterogeneity with bimodal distribution is a key issue in modelling hydrate-bearing Bones, and that it can explain the frequency dependence and scattering observed in seismic sections in such areas.

• Journal of the Korea Computer Graphics Society
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• v.6 no.1
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• pp.19-27
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• 2000

This paper proposes a non-self-intersecting multiresolution deformable model to extract and reconstruct three-dimensional boundaries of objects from volumetric data. Deformable models offer an attractive method for extracting and reconstructing the boundary surfaces. However, convensional deformable models have three limitations- sensitivity to model initialization, difficulties in dealing with severe object concavities, and model self-intersections. We address the initialization problem by multiresolution model representation, which progressively refines the deformable model based on multiresolution volumetric data in order to extract the boundaries of the objects in a coarse-to-fine fashion. The concavity problem is addressed by mesh size regularization, which matches its size to the unit voxel of the volumetric data. We solve the model self-intersection problem by including a non-self-intersecting force among the customary internal and external forces in the physics-based formulation. This paper presents results of applying our new deformable model to extracting a sphere surface with concavities from a computer-generated volume data and a brain cortical surface from a MR volume data.

• Defense and Technology
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• no.3 s.169
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• pp.36-45
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• 1993

유도탄에 의존하는 전투 경향은 향후 계속적으로 증대될 것이며 더구나 유도탄은 지금까지 설명한 것 같이 장거리화, 고속화, 스텔스화, 고고도 또는 저고도 탄도선택, 명중 직전까지 탐지 곤란 및 최종유도 단계에서 고가속도 운동 등 성능은 향상 일로에 있습니다. 함정의 생존성을 제고시키기 위한 각국의 대함유도탄 방어체계 개발 노력은 함정 탑재 무기체계인 근접방어 무기체계, 함대공유도탄, ESM 및 유도탄 기만 장치의 지속적인 성능개량과 함께 지속될 것입니다

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.11a
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• pp.240-241
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• 2019

최근 객체 추적 분야에서의 딥러닝 활용도가 증가하고 있다. 대표적인 딥러닝 기반 객체 추적 시스템은 객체 검출 알고리즘과 추적 알고리즘의 연쇄된 형태로 구성된 형태이다. 따라서 추적 시스템의 성능은 객체 검출기의 성능에 매우 의전적이라는 한계점이 존재한다. 본 논문에서는 위와 같은 검출-추적의 직관적인 구조로 구성된 시스템에서 딥러닝 기반 검출기에 대한 의존성을 낮추고 또한 추적기의 동작 속도를 증가시키는 방법을 제안한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.3
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• pp.238-245
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• 2000

유도초음파를 이용하면 배관 및 박판과 같은 파유도체에 대한 광범위한 비파괴탐상을 할 수 있게되어 시간과 경비를 절약할 수 있는 장점이 있다. 그래서 유도초음파를 이해하고 활용하기 위한 연구가 활발히 진행되고 있다. 유도초음파가 기존의 체적 초음파와 크게 다른 점은 분산성있어 초음파의 전파속도가 진동수와 파유도체의 두께에 의존한다는 것과 전파 특성이 다른 무한개의 모드가 존재한다는 것이다. 본 논문에서는 박판과 배관에서의 유도초음파를 이해하고 비파괴탐상에 적용하기 위해 필요한 모드의 분산과 선택 그리고 확인에 대해 이론적인 결과와 및 실험적인 예를 제시하여 그 개념을 소개하였다.