• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.504-512
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• 2003

Simulation programs have been developed and used as an attempt to improve the accuracy of Non-Destructive Evaluation(NDE) techniques. The applicability of these programs is very limited, however, because it is difficult to describe the delicacy of the propagation of stress waves. To investigate the applicability of the finite element analysis for stress wave-based NDE techniques numerical simulation for Impact-Echo method and SASW method is performed. The numerical studies are performed to determine the essential parameters such as contact time of impact load, mesh size and time step size. These studies show that the choice of parameter is very important for improving the accuracy and confidence of the numerical procedure and, thereby, the applicability of the numerical analysis for stress wave-based NDE techniques

• 대기
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• 제14권4호
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• pp.19-23
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• 2004

Progresses in numerical prediction of weather and climate have been in parallel with those of computing resources, especially the development of supercomputers. Advanced techniques in numerical modeling, computational schemes, and data assimilation cloud not have been practically achieved without the aid of supercomputers. With such techniques and computing powers, the accuracy of numerical forecasts has been tremendously improved. Supercomputers are also indispensible in constructing and executing the synthetic Earth system models. In this study, a brief overview on numerical weather / climate prediction, Earth system modeling, and the values of supercomputing is provided.

• 한국해양공학회지
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• 제24권2호
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• pp.25-33
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• 2010

Collision between vessels may lead to structural damage and penetration of hulls. The structural damage of a hull may eventually bring about global collapse of the hull girder and outflow of oil, which would contaminate seawater. Therefore, various regulations require the strength of a vessel after collision to satisfy given criteria, and owners usually request collision analyses to confirm the structural safety of their vessels. In the process of designing a vessel to satisfy the collision strength criteria, the strength has been assessed mostly by conducting collision analyses using numerical techniques, such as dynamic, non-linear, finite-element analysis. Design is an inherently iterative process during which many changes are necessary due to the endless needs for reinforcement and modification. Numerical techniques are not adequate for coping with a situation in which collision analysis is frequently required to provide the revised results that reflect the repetitive changes in designs. Numerical techniques require a lot of time and money to conduct in spite of recent improvements in computing power and in the productivity of modeling tools. Therefore, in this paper, an analytical technique is introduced and a collision problem is idealized and simplified using reasonable assumptions based on appropriate background. The technique was applied to an example of an actual FPSO and verified by comparing the results with results from the numerical technique. A good correlation was apparent between the results of the analytical and numerical techniques.

• 대한토목학회논문집
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• 제10권1호
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• pp.109-113
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• 1990

지적측량(地籍測量)에 의한 부동산(不動産)의 위치결정(位置決定)에 있어서 토지경계(土地境界)를 명확히 해야하고 정확도(正確度)를 높이기 위해 수치지적측량(數値地籍測量)이 요구되고 있다. 본 연구에서는 수치지적측량(數値地籍測量) 정확도(正確度)를 향상 시키기 위해 사진측량기법(寫眞測量技法) 중 독립모델법, 번들조정법, 부가변수를 갖는 번들조정법을 비교분석(比較分析) 하므로써 보다 신뢰성(信賴性)있고 정확한 수치지적(數値地籍) 측량성과(測量成果)를 얻기 위한 방법을 제시 하고자 한다.

• 천문학논총
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• 제25권3호
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• pp.71-76
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• 2010

The current status of numerical simulations of galaxy formation is reviewed. After a description of the main numerical simulation techniques, I will present several applications in order to illustrate how numerical simulations have improved our understanding of the galaxy formation process.

• 한국전산구조공학회논문집
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• 제17권1호
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• pp.75-82
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• 2004

본 논문에서는 응력파 전파를 수치모의할 때 발생하는 수치적인 분산효과를 제거하기 위해 파동방정식에 기초한 일차원 유한요소모형을 이용하여 수치분산오차의 특성을 분석하고 분산오차를 제어할 수 있는 방법을 제안하였다. 질량행렬을 그대로 사용하는 경우와 집중질량행렬을 사용하는 경우에 대한 수치분산오차를 분석하였다. 개발된 분산제어기법은 공간미분항의 시간단계 가중치 및 질량집중도를 조정하는 음해법과 인위적인 분산항을 추가하는 양해법의 두가지 방법이다. 제안된 분산보정기법을 이용하여 계산한 수치해와 파동방정식의 해석해를 비교한 결과 본 연구에서 제안한 분산보정기법의 타당성을 확인하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.247-252
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• 1996

In the concrete structures, cracks occur in various causes and the cracks seriously affect the functions of structures. The analysis techniques of progressive crack in the concrete have been improved with the advance of numerical techniques. The discrete crack model used in finite element program for the analysis of progressive failure is very effective, but it can not be easily implemented into numerical procedures because of difficult handing of nodal points in finite element meshes for crack growth. This paper introduces one of the techniques which skips the difficulty. In this paper, the modeling of progressive failure using finite element formulation is explained for the analysis of concrete fracture. The discontinuous element using the discontinuous shape function and the dual mapping technique in the numerical integration are implemented into finite element code for this purpose. It is shown that developed finite element program can predict the quasi-brittle behavior of concrete including ultimate load. The comparisons of the analysis results with other data are also shown.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.293-304
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• 2020

In this paper, various modulation techniques, including the legacy Global Navigation Satellite System (GNSS) signal modulation techniques, are introduced and the spectral characteristics and correlation characteristics of signals with various modulation techniques are analyzed based on numerical simulation. With the development of various GNSS services, the limited frequency band has become increasingly saturated, and issues of interoperability and compatibility have emerged in the new GNSS design. Since the efficient allocation of frequency resources is closely related to spectrum design, modulation techniques are one of the important signal design parameters of new signal design. Signal modulation techniques are closely related to various figure of merits (FoMs) as well as spectrum characteristic, and in some cases there is a complicated trade-off between FoMs. Thus, the FoMs associated with modulation technology should be analyzed and the best signal candidates should be chosen carefully via the trade-off analysis for FoMs. In this paper, we define the modulation technique based on Phase Shift Keying (PSK), Binary Offset Carrier (BOC) and Continuous Phase Modulation (CPM) for the design of KPS signals, and the FoMs of signals in terms of spectrum and correlation function are evaluated. Signals with various modulation techniques are implemented through a numerical simulation, and the relevant FoMs are analyzed.

• Structural Engineering and Mechanics
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• 제65권5호
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• pp.535-546
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• 2018

The objective of this study is to understand the behaviour of hollow core slabs strengthened with FRP and hybrid techniques through numerical and analytical studies. Different strengthening techniques considered in this study are (i) External Bonding (EB) of Carbon Fiber Reinforced Polymer (CFRP) laminates, (ii) Near Surface Mounting (NSM) of CFRP laminates, (iii) Bonded Overlay (BO) using concrete layer, and (iv) hybrid strengthening which is a combination of bonded overlay and NSM or EB. In the numerical studies, three-dimensional Finite Element (FE) models of hollow core slabs were developed considering material and geometrical nonlinearities, and a phased nonlinear analysis was carried out. The analytical calculations were carried out using Response-2000 program which is based on Modified Compression Field Theory (MCFT). Both the numerical and analytical models predicted the behaviour in agreement with experimental results. Parametric studies indicated that increase in the bonded overlay thickness increases the peak load capacity without reducing the displacement ductility. The increase in FRP strengthening ratio increased the capacity but reduced the displacement ductility. The hybrid strengthening technique was found to increase the capacity of the hollow core slabs by more than 100% without compromise in ductility when compared to their individual strengthening schemes.

• Structural Engineering and Mechanics
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• 제32권4호
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• pp.489-500
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• 2009

The aim of this paper is to compare wavelet, kurtosis and pseudofractal based techniques for structural health monitoring in the presence of measurement noise. A detailed comparison and assessment of these techniques have been carried out in this paper through numerical experiments for the calibration of damage extent of a simply supported beam with an open crack serving as an illustrative example. The numerical experiments are deemed critical due to limited amount of experimental data available in the field of singularity based detection of damage. A continuous detectibility map has been proposed for comparing various techniques qualitatively. Efficiency surfaces have been constructed for wavelet, kurtosis and pseudofractal based calibration of damage extent as a function of damage location and measurement noise level. Levels of noise have been identified for each technique where a sudden drop of calibration efficiency is observed marking the onset of damage masking regime by measurement noise.