• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.347-349
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• 1999

본 논문에서는 대규모 영상 데이터베이스로부터 모양 영상에 대한 검색을 빠르고 효율적으로 수행하기 위해 해싱기법을 변형한 색인구조와 검색방법을 제안한다. 제안된 색인 구조는 이진 모양 영상(binary shape image)의 불변 모멘트 집합(invariant moments set)을 특징 벡터로 사용하여 다차원으로 구성된다. 이 색인 구조를 기반으로 제안된 해싱을 변형한 검색방법은 기존의 방법들에 비해 검색공간을 줄임으로써 검색속도를 높인다. 본 논문에서 제안한 색인구조와 검색방법을 1000개의 이진 모양 영상들에 적용해 본 결과 검색공간이 전체 공간의 10% 미만으로 줄어드는 효과가 있었다.

• Journal of the Korea Society for Simulation
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• v.30 no.1
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• pp.127-137
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• 2021

The method of utilizing the strain and vibration values of rails is primarily used to diagnose the condition of wheels and railroad facilities. The dynamic load is measured under the assumption that the strain of the rail and the load of the railroad vehicle are proportional. Wheel condition is measured under the assumption that the magnitude of the defect and the magnitude of the rail vibration are proportional. However, environmental factors affecting the strain and vibration of the rail such as vehicle speed, wheel load, climate, and track conditions are not reflected, many errors occur depending on the measurement conditions. In this study, the effect of track distortion, which is a major indicator of the track condition among the environmental factors that affect the strain and vibration of the rail, on the strain and vibration of the rail, was examined through dynamic simulation. As a measure to reduce the measurement deviation, the effect of securing additional measurement points was analyzed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.06b
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• pp.51-64
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• 1999

가스터빈에 사용되는 소재는 여타 금속소재에 비하여 고온 기계적 특성은 우수한 반면 상대적으로 단조성이 떨어지기 때문에, 금속소재의 단조성에 대한 이해와 단조 공정별 장단점을 파악하여 단조공정 설계에 반영하여야 한다. 가스터빈용 Ni합금의 경우 고온기계적 성질은 결정립 크기에 크게 의존한다. 결정립 크기는 기계적 성질에 직접적으로 영향을 미치는데, 동적재결정의 경우 초기 결정립크기, 변형률, 변형속도, 온도 뿐만 아니라 결정립계에 석출된 제2상에 의해서 크게 영향을 받기 때문에 이들 상의 고용온도를 파악하여 단조공정 설계에 반영하여야 한다. 유한요소법으로 변형률과 온도분포를 해석함으로써 단조품 내의 결정립 분포를 효과적으로 예측할 수 있다. 다단계 단조 경우, 최종 단조품의 결정립 크기는 단계별 단조 온도 및 변형률 배분 등에 따라 변하므로 이를 고려하여야 한다.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.48-53
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• 2006

A methodology is described for predicting the fatigue life of the resistance spot weldment including strain rate effect. Because it is difficult to perform a physical failure test with high strain rate, an analytical method is necessary to get the mechanical properties of various strain rate, To this end, quasi-static tensile-shear tests at several strain rate were performed on spot weldments of SPC. These test provided the empirical data with the strain rate. With these results, we formulated the function of fatigue life prediction using the lethargy coefficient which is the global material property from tensile test. And, we predicted the fatigue life of spot weldment at dynamic strain rate. To confirm this method for fatigue life prediction, analytical results were compared with the experimental fatigue data.

• Tunnel and Underground Space
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• v.30 no.1
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• pp.15-28
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• 2020

In this study, a procedure was introduced to estimate strength and deformation modulus of the 3-D discrete fracture network(DFN) systems using the distinct element method(DEM). Fracture entities were treated as non-persistent square planes in the DFN systems. Systematically generated fictitious fractures having similar mechanical characteristics of intact rock were combined with non-persistent real fractures to create polyhedral blocks in the analysis domain. Strength and deformation modulus for 10 m cube domain of various deterministic and stochastic 3-D DFN systems were estimated using the DEM to explore the applicability of suggested method and to examine the effect of fracture geometry on strength and deformability of DFN systems. The suggested procedures were found to effective in estimating anisotropic strength and deformability of the 3-D DFN systems.

• The Korean Journal of Rheology
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• v.2 no.2
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• pp.56-65
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• 1990

열방성 액정고분자와 폴리카보네이트를 대상 수지로 하여 용융혼합기로 액정고분자 의 함량, 혼합속도 및 온도등의 변환에 따른 훈련 특성을 측정하고 고분자 혼합물의 혼련조 건과 유변학적 특성 모폴로지 사이의 관계를 조사하였다. 혼련 토크는 100rpm의 혼합속도 에서 극소값을 보이며 혼합기 내의 전단속도가 낮기 때문에 혼력에의해서는 LCP가 섬유상 으로 형성되지 못하고 구형의 입자로 존재함을 알수 있었다. 혼합물의 점도는 시험된 전단 속도 영역에서 순수한 고분자보다 현저히 낮으며 5wt%의 소량 첨가로도 5배의 점도 감소 효과를 보이고 LCP함량이 약 30wt%일 경우 점도 및 혼합에너지가 최소로 되었다. Capillary 레오미터의 실험결과 LCP/PC의 점도비가 1보다 작거나 같튼 전단장하에서 LCP 는 섬유상을 형성하였으며 높은 점도비의 경우 LCP의 변형이 어려워 구형의 입자로 존재하 였다. 또한 혼합물의 PC Tg 이동은 에스터르 교환 반응에 의한 부분적인 혼화성의 증가에 기인함을 알수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.649-656
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• 2016

Thick composite disks are utilized in the fast-rotating machines such as turbine disks, flywheels, and so on. The effects of rotating speed on the dynamic characteristics of thick composite disks are deeply studied in this paper. The dynamic governing equations of a rotating composite disk including transverse shear and rotary inertia are derived and then formulated into the finite element equation. Isotropic, circumferentially reinforced disk, and radially reinforced disk are selected for the numerical analysis. The inclusion of the transverse shear and rotary inertia into the governing equation of the rotating disks makes the natural frequency reduced as well as the critical speed. The present results show that the rotation of a thick disk may not reduce the effect of transverse shear and rotary inertia depending on anisotropy, thickness ratio and mode, unlike the results reported in other studies.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.409-416
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• 2019

An improved numerical model for non-linear analysis of reinforced concrete (RC) slabs subjected to blast loading is proposed. This approach considers a strain rate dependent orthotropic constitutive model that directly determines the stress state using the stress-strain relation acquired from the data obtained using the biaxial strength envelope. Moreover, the bond-slip between concrete and reinforcing steel is gradually enlarged after the occurrence of cracks and is concentrated in the plastic hinge region. The bond-slip model is introduced to consider the crack direction of the concrete under a biaxial stress state. Correlation studies between the numerical analysis and the experimental results were performed to evaluate the analytical model. The results show that the proposed model can effectively be used in dynamic analyses of reinforced concrete slab members subjected to explosive loading. Moreover, it was determined that it is important to consider biaxial behavior in the material model and the bond-slip effect.

• Nuclear Engineering and Technology
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• v.26 no.1
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• pp.1-8
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• 1994

The flame speed correlation considering thermal-hydraulic phenomena under severe accidents is proposed and correction coefficients are defined. This correlation modifies the pressure dependency in Iijima-Takeno correlation and adds the steam suppression effects to it in the anticipated hydrogen and steam concentration ranges under severe accidents. The existing models of flame speed due to hydrogen combustion under severe accidents are based on the experiments which were performed merely at room temperature and atmospheric pressure. They have difficulty in predicting a accurate flame speed in a case of high temperature and pressure during severe accidents. Thus the flame structure is assumed as a prerequisite to the reliable determination of flame speed and theoretical model is developed. To examine the validity, flame speeds in various conditions calculated by this model are compared with those obtained by the calculation of the existing correlations of the codes such as improved HECTR and MAAP. Also the steam suppression ratio is quantified and the steam suppression coefficient is defined as a composition of mixture. Initial temperature and pressure dependencies are investigated and correction coefficents are determined. More experimental studies can be recommended to improve this correlation to its further works.

• Food Science of Animal Resources
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• v.23 no.1
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• pp.50-55
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• 2003

Fresh ground pork was irradiated with the electron beam(3.0 and 5.0 kGy) using 2 different conveyer speeds (10 and 20 ㎐), respectively, in order to determine the effect of conveyer speeds on the development of lipid oxidation and microbial stability. During refrigerated storage, the development of lipid oxidation decreased significantly (p<0.05) with the increase in the electron beam conveyer speed from 10 to 20 ㎐. The ground pork with electron beam inhibited the growth of total aerobic bacteria and mesophiles. The inhibitory effect increased when the electron beam dose increased from 0 to 5.0 kGy. The finding that higher speed(20 ㎐) of electron beam had some antioxidative effect is very promising, however, other means to control the lipid oxidation must also be employed to fully utilize the sterilization effect of electron beam in ground pork.