• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 1996년도 International Conference on Agricultural Machinery Engineering Proceedings
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• pp.238-246
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• 1996

When the important structures or components of agricultural machinery are designed, the full-filed methods of stress analysis can provide enough information in order to obtain lighter weight and prevent failure. The photoelasticity has been applicated to solve many practical engineering problems. The coating method provides full-field information, enabling the engineers to determine the complete distribution of surface strains and directly highlighting severely strained areas, especially for the welded frames of agricultural machinery. A combined method of model and prototype for strain analysis of excavator has been successfully applied to improve design. A measuring and recording system controlled by micro-computer and application software for dynamic event was studied. It can be widely used in structural failure analysis under cyclical loading . Typical application concerned stress field of crack tip and failure analysis of some mechanical structures are introduced are in roduced briefly in this paper.

• Advances in aircraft and spacecraft science
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• 제6권1호
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• pp.69-86
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• 2019

This paper discusses the use of the Digital Image Correlation (DIC) technique for the displacement and strain measurements of a wet lay-up composite wing. As opposed to classical strain gages, DIC allows to conduct full field strain analysis of simple to complex structural parts. In this work, wing-up bending tests and measurements of the composite wing of the Dardo Aspect by CFM Air are carried out through an ad-hoc test rig and the Q-400 DIC system by Dantec Dynamics. Also, the results are used to validate a finite element model of the structure under investigation.

• Investigative Magnetic Resonance Imaging
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• 제1권1호
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• pp.114-118
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• 1997

목적: 기능적 MR 영상은 외부자극에 따라, 이에 상응하는 특정한 뇌피질 부위의 혈류량의 변화를 신호강도의 차이로 나타내는 방법이다. 시각피질에 대한 기능적 MR은 환자가 광자극을 응시함으로써 수행될 수 있는 것으로, 이의 수행에는 적절한 형태의 광자극원이 필수적이다. 이에 저자는 광자극원의 크기가 시각피질 활성화에 영향을 미칠 수 있는지 알아보기 위하여 본 연구를 하였다. 대상 및 방법: 정상적인 시력을 가진 자원자 5명을 대상으로 시각활성화 기능적 MR을 시행하였다. 광자극원은 $11{\times}8cm$ 크기의 기판에 적색 LED(light-emitting diodes) 39개를 박고 직류전원을 사용하도록 만들었다. 이를 크기에 따라 full field, half field 및 focal central field의 3가지로 구분하고 8Hz로 점멸하였다. EPI 기법으로 6회의 광자극 기간과 6회의 휴식기간을 번갈아 3차례 시행하여 총 36회의 검사를 하고, Z-score로 통계처리하였다. 이 때 얻은 활성화 영상을 같은 부위의 T1강조영상에 결합시켰다. 각 경우에서 시각피질에서 활성화된 pixel의 수를 full field, half field 및 focal central field에서 얻어진 pixel 수의 합으로 나누어 활성화지수를 구하였다. 이 활성화지수를 토대로 광원크기와의 관계를 분석하였다. 결과: Full field로 자극을 주었을 때 시각피질의 평균 신호강도의 증가는 약 9.6%였다. 4명에서 활성화지수는 full field, half field, focal central field의 순으로 감소하였으며, 나머지 1명에서는 half field 시의 값이 full field 시의 값보다 컸다. 광원크기에 따른 활성화지수의 범위는 full field 43-73%(평균 55%), half field 22-40%(평균 32%), focal central field 5-24%(평균 13%)였다. 결론: 기능적 MR영상을 이용하여 시각피질의 활성화를 용이하게 확인할 수 있었으며 광자극원의 크기에 따라 증가되는 시각피질 활성화를 입증할 수 있었다.

• 조명전기설비학회논문지
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• 제24권6호
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• pp.35-42
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• 2010

본 논문에서는 등각사상 방법(conformal mapping method)을 사용하여 도체로 보강된 결합 도파 선로(conductor-backed coupled coplanar waveguide)의 정전기장 분포와 전위 분포를 계산하는 해석적인 수식을 유도하였다. 그리고 유도한 수식을 사용하여 결합 도파 선로 구조 전체에 분포하는 정전기장과 전위분포를 계산하고 이를 분석하였다. 논문에서 사용한 방법은 반복계산 과정을 필요로 하지 않으므로 이를 사용하면 전파해석방법(full-wave analysis method)보다 전기장분포를 빠르고 간편하게 계산할 수 있다. 이 방법은 결합기, 필터, 마이크로스트립 안테나와 같은 결합선로를 사용한 마이크로파집적회로의 분석에 폭넓게 응용될 수 있다.

• Wind and Structures
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• 제27권3호
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• pp.199-211
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• 2018

This paper deals with wind fragility and risk analysis of high rise buildings subjected to stochastic wind load. Conventionally, such problems are dealt in full Monte Carlo Simulation framework, which requires extensive computational time. Thus, to make the procedure computationally efficient, application of metamodelling technique in fragility analysis is explored in the present study. Since, accuracy by the conventional Least Squares Method (LSM) based metamodelling is often challenged, an efficient Moving Least Squares Method based adaptive metamodelling technique is proposed for wind fragility analysis. In doing so, artificial time history of wind load is generated by three wind field models: i.e., a simple one based on alongwind component of wind speed; a more detailed one considering coherence and wind directionality effect, and a third one considering nonstationary effect of mean wind. The results show that the proposed approach is more accurate than the conventional LSM based metamodelling approach when compared to full simulation approach as reference. At the same time, the proposed approach drastically reduces computational time in comparison to the full simulation approach. The results by the three wind field models are compared. The importance of non-linear structural analysis in fragility evaluation has been also demonstrated.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1905-1913
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• 2011

The dynamic characteristic of bogie that is driving system of railway vehicle is very important regarding decision of vehicle characteristics as running safety and comport. The dynamic characteristic test of bogie is tested on full size in place on field testing on track. But, the testing on the full size caused many problems. To overcome these problem by full size test, the Railway Safety Research Center in Seoul National University of Science & Technology developed 1/5 scale size of small scale derailment simulator and is currently testing running stability of 1/5 scaled bogie. Also To take effectively advantage of running stability test using small scale derailment simulator in actuality design and reliability estimation, it is necessary comparison and examination with field test and theoretical analysis result In this paper. to achieve running stability analysis of 1/5 scaled bogie on small scale derailment. the program using MATLAB that is fast compose and analysis the motion equation of Saemaul power bogie is developed. It is achieved analysis according to various specification (weight, size, suspension, etc..) and is evaluated corelation between test result and dynamic characteristic of actual railway vehicle.

• 복합신소재구조학회 논문집
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• 제7권1호
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• pp.1-8
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• 2016

In this paper, the full-size structural performance test for a lightweight soundproof tunnel composed of partitioned pipe truss members is carried out to investigate the structural performance. In addition, a nonlinear structural analysis of the same finite element model as the full-size testing model is performed to compare the test result. The test and analysis results showed that the lightweight soundproof tunnel ensures the structural safety against wind loads, snow loads and load combinations. As a result, the full-size test and analysis results meet all the design load conditions, hence the proposed lightweight soundproof tunnel is ready for the field application.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.241-246
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• 1996

A new solution for the dynamic analysis of as asphalt concrete pavements under moving loads has been developed. The asphalt concrete pavement can be modeled in elastic or viscoelastic medium of multi-layered structure. The subgrade can be modeled as either a rigid base or a semi-infinite halfspace. The loads may be constant or arbitrary circular loads into one direction. The method utilizes the Complex Response Method of transient analysis with a continuum solution in the horizontal direction and a finite-element solution in the vertical direction. This proposed method incorporates such important factors as wave propagation, inertia and damping effects of the medium as well as frequency-dependent asphalt concrete properties. The proposed method has been validted with the full-scale field truck test, which was conducted on instrumented asphalt concrete section on a test track at PACCAR Technical Center in Mount Vernon, Washington. Comparison with field strain data from full-scale pavement tests has shown excellent agreement. Theoretical results have shown that the effect of vehicle speed is significant and that it is in part due to the frequency-dependent

• International Journal of Aeronautical and Space Sciences
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• 제2권2호
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• pp.28-38
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• 2001

A numerical method for the assessment and correction of tunnel wall interference effects on forced-oscillation testing is presented. The method is based on the wall pressure signature method using computed wall pressure distributions. The wall pressure field is computed using unsteady three-dimensional full Navier-Stokes solver for a 70-degree pitching delta wing in a wind tunnel. Approximately-factorized alternate direction implicit (AF-ADI) scheme is advanced in time by solving block tri-diagonal matrices. The algebraic Baldwin-Lomax turbulence, model is included to simulate the turbulent flow effect. Also, dual time sub-iteration with, local, time stepping is implemented to improve the convergence. The computed wall pressure field is then imposed as boundary conditions for Euler re-simulation to obtain the interference flow field. The static computation shows good agreement with experiments. The dynamic computation demonstrates reasonable physical phenomena with a good convergence history. The effects of the tunnel wall in upwash and blockage are analyzed using the computed interference flow field for several reduced frequencies and amplitudes. The corrected results by pressure signature method agree well with the results of free air conditions.

• 현장농수산연구지
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• 제10권1호
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• pp.137-151
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• 2008

This research was conducted to suggest a policy plan for intensive major course in recurrent education system of KNAC. A survey was answered by students, graduates, field professors and (full-time) professors. The results are summarized as follows; 1. In the item of educational operation system, there were some differences in preference among 4 examinee groups. Students preferred 'semester system', graduates and field professors did 'once per week system', and professors 'cyber+centralized training system'. 2. As entering time, students and graduates preferred 'immediately after graduation'. However, field and full-time professors preferred '1 to 3 years after graduation' that became reality. 3. As board and lodging, all examinee groups wanted 'dormitory in college'. Students and graduates were open to pay educational expenses as a level of national colleges. 4. As a curriculum, the most preferred subject by all groups was 'major field technique', which was followed by 'marketing/sale' and 'farm management' in the order of preference.