• 정보보호학회논문지
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• 제28권2호
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• pp.437-447
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• 2018

가상현실(Virtual Reality, VR)은 게임 업계의 새로운 표준이 되고 있다. PokeMon GO는 가상현실 기술을 적용한 대표적인 사례이다. PokeMon GO는 출시 후 다음날 미국에서 가장 많은 iOS App Store 다운로드 수를 기록하였다. 이는 가상현실의 위력을 보여주는 사례이다. 가상현실은 자이로스코프, 가속도, 촉감 센서 등으로 구성되며 사용자가 게임을 깊이 몰입할 수 있게 한다. 새로운 기술이 등장함에 따라 새롭고 다양한 위협요소가 생긴다. 그래서 우리는 가상현실 기술과 게임 시스템에 대한 보안 연구가 필요하다. 본 논문에서 가상현실 기기(Oculus Rift)와 게임 시스템(Quake)의 정보보증을 위해 위협 분석을 진행한다. STRIDE, attack library, attack tree 순서로 체계적으로 분석한다. DREAD를 통해 보안 대책을 제안한다. 또한 VCG(Visual Code Grepper) 도구를 사용하여 소스 코드의 논리 오류 및 취약한 함수를 파악하고 해결 방법을 제안한다.

• 정보보호학회논문지
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• 제31권4호
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• pp.687-699
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• 2021

프로그램에서 취약점이 발생하면 그에 대한 정보가 문서화되어 공개된다. 그러나 일부 취약점의 경우 발생한 원인과 그 소스코드를 공개하지 않는다. 이러한 정보가 없는 상황에서 취약점을 찾기 위해서는 바이너리 수준에서 코드를 분석해야 한다. 본 논문에서는 Out-of-bounds Read 취약점 유형을 바이너리 수준에서 찾는 것을 목표로 한다. 바이너리에서 취약점을 탐지하는 기존의 연구는 주로 동적 분석을 이용한 도구로 발표되었다. 동적 분석의 경우 프로그램 실행 정보를 바탕으로 취약점을 정확하게 탐지할 수 있지만, 모든 실행 경로를 탐지하지 못할 가능성이 있다. 모든 프로그램 경로를 분석하기 위해서는 정적 분석을 사용해야 한다. 기존의 정적 도구의 경우 소스코드 기반의 도구들이며, 바이너리에 수준의 정적 도구는 찾기 어렵다. 본 논문에서는 바이너리 정적 분석을 통해 취약점을 탐지하며, 메모리 구조를 모델링하는 방법으로 Heap, Stack, Global 영역의 취약점을 탐지한다. 실험 결과 기존의 탐지도구인 BAP_toolkit과 비교하였을 때 탐지 정확도 및 분석 시간에서 의미 있는 결과를 얻었다.

• Journal of Radiation Protection and Research
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• 제28권3호
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• pp.189-197
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• 2003

Level 3 PSA(사고결말분석)는 원자력 발전소의 사고 시 누출된 방사성 핵종으로 인해 야기되는 환경 및 인체에 미치는 영향(공중위험도)을 평가하는 것이다. 본 논문에서는 원자력 발전소의 중대사고시 환경으로 방출되는 방사성물질의 방출특성과 그 결과로 인체에 미치는 영향에 대하여 확률론적 사고영향분석코드인 MACCS를 이용하여 평가하였다. 이러한 평가는 관련 변수들의 상대적 중요도를 파악하는데 유용할 뿐만 아니라 소외리스크(Offsite Risk)를 최소화시키기 위한 대책개발에 있어 중요한 지표가 될 수 있다. 특히 방출고도, 열 함량, 방출기간의 3가지 중요 변수를 선정하여, 이들 변수들의 변화에 따라 영향을 받는 조기사망자 수와 암 사망자 수의 변화를 분석하였다. 또한, 참조원전의 위험성 평가를 위하여 IPE(Individual Plant Examination)에서 제시된 STC(Source Term Category) 19가지 시나리오에 대한 각 사고별 빈도와 MACCS코드를 수행한 결과값을 이용하여 참조원전의 위험성 평가를 수행하였다.

• 한국IT서비스학회지
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• 제14권2호
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• pp.129-142
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• 2015

The purpose of this study is to suggest an effective regression testing method in order to minimize the scope of test resulting from the modification of software and to prevent mismatch of test case and test objects. As a way to improve the efficiency of regression testing which uses a change-centric testing technique, the method flow is analyzed and grasped through a static analysis based on source code in order to identify modified parts. After the order of priority is set according to the results of user action log-based dynamic analysis on identified regression testing objects, test effect can be raised by adjusting the order of priority using code complexity. Quality assurance coverage can be checked using the user action log suggested in this study, and the progress of test and whether or not each function has been verified can be checked, too. In addition, by minimizing test parts and adjusting the order of test, costs and time can be saved, making it possible to conduct regression testing effectively.

• Nuclear Engineering and Technology
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• 제48권5호
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• pp.1120-1125
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• 2016

The neutron decay constant, ${\alpha}$, and effective delayed neutron fraction, ${\beta}_{eff}$, are important parameters for the control of the dynamic behavior of nuclear reactors. For the heavy water zero power reactor (HWZPR), this document describes the measurements of the neutron decay constant by noise analysis methods, including variance to mean (VTM) ratio and endogenous pulse source (EPS) methods. The measured ${\alpha}$ is successively used to determine the experimental value of the effective delayed neutron fraction as well. According to the experimental results, ${\beta}_{eff}$ of the HWZPR reactor under study is equal to 7.84e-3. This value is finally used to validate the calculation of the effective delayed neutron fraction by the Monte Carlo methods that are discussed in the document. Using the Monte Carlo N-Particle (MCNP)-4C code, a ${\beta}_{eff}$ value of 7.58e-3 was obtained for the reactor under study. Thus, the relative difference between the ${\beta}_{eff}$ values determined experimentally and by Monte Carlo methods was estimated to be < 4%.

• Nuclear Engineering and Technology
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• 제53권10호
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• pp.3449-3459
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• 2021

With the increasing availability of high-performance computing (HPC) platforms, uncertainty quantification (UQ) and sensitivity analyses (SA) can be efficiently leveraged to optimize design parameters of complex engineering problems using modeling and simulation tools. The workflow involved in such studies heavily relies on HPC resources and hence requires pre-processing and post-processing capabilities of large amounts of data along with remote submission capabilities. The NEAMS Workbench addresses all aspects of the workflows involved in these studies by relying on a user-friendly graphical user interface and a python application program interface. This paper highlights the NEAMS Workbench capabilities by presenting a semiautomated coupling scheme between Dakota and any given package integrated with the NEAMS Workbench, yielding a simplified workflow for users. This new capability is demonstrated by running a SA of a turbulent flow in a pipe using the open-source Nek5000 CFD code. A total of 54 jobs were run on a HPC platform using the remote capabilities of the NEAMS Workbench. The results demonstrate that the semiautomated coupling scheme involving Dakota can be efficiently used for UQ and SA while keeping scripting tasks to a minimum for users. All input and output files used in this work are available in https://code.ornl.gov/neams-workbench/dakota-nek5000-study.

• 한국생산제조학회지
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• 제19권2호
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• pp.288-294
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• 2010

In recent years, wind energy has been the world's fastest growing source of energy. This paper describes the structural design and analysis of composite blade for 2 kW-level HAWT (horizontal axis wind turbine). The aerodynamic design and force, which are required to design and analyze a composite blade structurally, are calculated through BEMT(blade element momentum theory) implemented in public code PROPID. To obtain the equivalent material properties of filament wound composite blades, the rule-of-mixture is applied using the basic material properties of fiber and matrix, respectively. Lay-up sequence, ply thickness and ply angle are designed to satisfy the loading conditions. Structural analysis by using commercial software ABAQUS is performed to compute the displacement and strength ratio of filament wound composite blades.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.392-403
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• 2013

For the analysis of radiating noise problems in medium-to-high frequency ranges, the Energy Flow Boundary Element Method (EFBEM) was developed. EFBEM is the analysis technique that applies the Boundary Element Method (BEM) to Energy Flow Analysis (EFA). The fundamental solutions representing spherical wave property for radiating noise problems in open field and considering the free surface effect in underwater are developed. Also the directivity factor is developed to express wave's directivity patterns in medium-to-high frequency ranges. Indirect EFBEM by using fundamental solutions and fictitious source was applied to open field and underwater noise problems successfully. Through numerical applications, the acoustic energy density distributions due to vibration of a simple plate model and a sphere model were compared with those of commercial code, and the comparison showed good agreement in the level and pattern of the energy density distributions.

• Journal of Ship and Ocean Technology
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• 제12권1호
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• pp.45-56
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• 2008

Recently, International Association Classification Societies (IACS) has adopted the Common Structural Rules (CSR) for Bulk Carriers and Tankers, which specifies the requirement associated with the ultimate strength of hull girder structure. The theoretical background and the results of verification study are neither well summarized nor released. Furthermore, the requirement is not a form of deterministic formula but a form of program in which source code is not disclosed. The reliability of the non-linear structural analysis program is verified through the comparison with the results of the analysis and the model test. Then, the reliability of the ultimate strength requirement in CSR is checked by comparing with the results of rigorous non-linear analysis.

• 한국전산유체공학회지
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• 제4권1호
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• pp.1-7
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• 1999

The numerical methodology for computing tile impact forces and water entry behaviors of high speed water entry bodies was been developed. Since the present method assumed the impact occurs within a very short time interval. the viscous effects do not have enough time to play a significant role in the impact forces, that is, the flow around a water-entry object was assumed as an incompressible potential flow and is solved by the source panel method. The elements fully submerged into the water are routinely treated, but the elements intersected by the effective planar free surface are redefined and reorganized to be amenable to the source panel method. To validate the present code, it was applied to disk, cone and ogive model and compared with experimental data. Good agreement was obtained. The water entry behavior such as the bouncing phenomena from the free surface was also simulated using the impact forces and two degree of freedom dynamic equation. Physically acceptable results were obtained.