• 한국농공학회논문집
• /
• 제55권6호
• /
• pp.187-196
• /
• 2013

This study is focused on analyzing the deformation types of seaside armor stones based of field survey in order to establish the cause of abrasion following the deformation of seaside armor stones. 1. The deformation of seaside armor stone in saemangeum sea dike was classified as three different types: floating, deviation, and abrasion. 2. It was discovered that the stones floated to the extent of maximum 50 m, as the result of inspecting floating stones which were situated on different ten places. 3. The average number of deviation in the high ocean wave section was four times more than that in the ordinary ocean wave section, as a result of comparing the deviation number of the ordinary ocean wave section and that of the high ocean wave section for the purpose of inspecting the relation between the deviation of armor stones and the effects of ocean wave. 4. The angular shape of armor stones seen in the initial construction period has been abraded smoothly, as result of comparing of the shape change of armor stones for the purpose of inspecting abrasion state of seaside armor stones. 5. It was discovered that the abrasion of armor stone was severe in the section of many floating stones, as a result of analyzing the levels of abrasion and the cumulative sections of floating stones for the purpose of investigating the cause of abrasion.

• Geomechanics and Engineering
• /
• 제22권5호
• /
• pp.449-460
• /
• 2020

The double-lane arrangement model is frequently used in underground coal mines because it is beneficial to improve the mining efficiency of the working face. When the double-lane arrangement is used, the service time of the reserved roadway increases by twice, which causes several difficulties for the maintenance of the roadway. Given the severe non-uniform deformation of the reserved roadway in the Buertai Coal Mine, the stress distribution law in the mining area, the failure characteristics of roadway and the control effect of support resistance (SR) were systematically studied through on-site monitoring, FLAC 3D numerical simulation, mechanical model analysis. The research shows that the deformation and failure of the reserved roadway mainly manifested as asymmetrical roof sag and floor heave in the region behind the working face, and the roof dripping phenomenon occurred in the severe roof sag area. After the coal is mined out, the stress adjustment around goaf will happen to some extent. For example, the magnitude, direction, and confining pressure ratio of the principal stress at different positions will change. Under the influence of high-stress rotation, the plastic zone of the weak surrounding rock is expanded asymmetrically, which finally leads to the asymmetric failure of roadway. The existing roadway support has a limited effect on the control of the stress field and plastic zone, i.e., the anchor cable reinforcement cannot fully control the roadway deformation under given conditions. Based on obtained results, using roadway grouting and advanced hydraulic support during the secondary mining of the panel 22205 is proposed to ensure roadway safety. This study provides a reference for the stability control of roadway with similar geological conditions.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제37권3호
• /
• pp.205-213
• /
• 2011

Introduction: The enlargement and deformation of the orbit give rise to a visible enophthalmos. As a consequence, a disturbance of eye motility together with double images is likely to occur. This study examined the degree of enophthalmos according to the extent of orbital wall fracture and volume of herniated orbital tissue in blowout fractures of the medial and inferior orbital wall. Materials and Methods: This study was performed on patients diagnosed with medial and inferior orbital wall fractures at the Department of Oral and maxillofacial surgery, Chonbuk National University Hospital from 2007 to 2009. The patients' age, gender, etiology of fracture and degree of enophthalmos were investigated. The changes in the degree of enophthalomos, diplopia and ocular motility restriction after operation were examined. Results: The degree of enophthalomos increased with increasing extent of orbital wall fracture and volume of herniated orbital tissue. Conclusion: Whether to perform the operation is decided after measuring the extent of the orbital wall fracture and volume of herniated orbital tissue using computed tomography (CT), time for the decision of operation can be shortened. This can cause a decrease in the complications of orbital wall fractures.

• 한국재료학회지
• /
• 제28권8호
• /
• pp.435-439
• /
• 2018

MA Al alloys are examined to determine the effects of alloying of Mg and Cu and rolling on tensile deformation behavior at 748 K over a wide strain rate range($10^{-4}-10^3/s$). A powder metallurgy aluminum alloy produced from mechanically alloyed pure Al powder exhibits only a small elongation-to-failure(${\varepsilon}_f$ < ~50%) in high temperature(748 K) tensile deformation at high strain rates(${\acute{\varepsilon}}=1-10^2/s$). ${\varepsilon}_f$ in MA Al-0.5~4.0Mg alloys increases slightly with Mg content(${\varepsilon}_f={\sim}140%$ at 4 mass%). Combined addition of Mg and Cu(MA Al-1.5%Mg-4.0%Cu) is very effective for the occurrence of superplasticity(${\varepsilon}_f$ > 500%). Warm-rolling(at 393-492 K) tends to raise ${\varepsilon}_f$. Lowering the rolling-temperature is effective for increasing the ductility. The effect is rather weak in MA pure Al and MA Al-Mg alloys, but much larger in the MA Al-1.5%Mg-4.0%Cu alloy. Additions of Mg and Cu and warm-rolling of the alloy cause a remarkable reduction in the logarithm of the peak flow stress at low strain rates (${\acute{\varepsilon}}$< ~1/s) and sharpening of microstructure and smoothening of grain boundaries. Additions of Mg and Cu make the strain rate sensitivity(the m value) larger at high strain rates, and the warm-rolling may make the grain boundary sliding easier with less cavitation. Grain boundary facets are observed on the fracture surface when ${\varepsilon}_f$ is large, indicating the operation of grain boundary sliding to a large extent during superplastic deformation.

• Journal of the Korean Wood Science and Technology
• /
• 제45권6호
• /
• pp.689-702
• /
• 2017

In this study, with the view to using effectively small and medium diameter Korean domestic woods as structural materials, cross-laminated woods were manufactured by using six species of Korean domestic softwoods and hardwoods, and bending creep properties were investigated for each species. The creep curves showed the shape of the exponential function plot, and the creep curves after 1 hour were able to estimate by fitting it to the power law. The initial and creep compliances of cross-laminated woods showed the higher values in wood species with a low density than in that with a high density. And by cross-laminating, the initial and creep compliances perpendicular to the grain considerably decreased, the extent of the decrease was found to be greater in creep deformation than in initial deformation. The creep anisotropies of cross-laminated woods were considerably decreased by cross-laminating. The relative creep of $C_{\bot}$ type composed of perpendicular-direction lamina in the faces decreased 0.59 - 0.64 times compared to that of $P_{\bot}$ type composed of perpendicular-direction laminae in all layers, and that for $C_{\parallel}$ type composed of parallel-direction laminae in the faces increased 1.5 - 1.6 times compared to that of $P_{\parallel}$ type composed of parallel-direction laminae in all layers.

• Structural Engineering and Mechanics
• /
• 제88권1호
• /
• pp.53-65
• /
• 2023

With the gradual implementation of long-span suspension bridges into high-speed railway operations, the main beam's bending stiffness contribution to the live load response permanently grows. Since another critical control parameter of railway suspension bridges is the beam-end rotation angle, it should not be ignored by treating the main beam deflection as the only deformation response. To this end, the current study refines the existing method of the main cable shape and simply supported beam bending moment analogy. The bending stiffness of the main beam is considered, and the main beam's analytical expressions of deflection and rotation angle in the whole span are obtained using the cable-beam deformation coordination relationship. Taking a railway suspension bridge as an example, the effectiveness and accuracy of the proposed analytical method are verified by the finite element method (FEM). Comparison of the results by FEM and the analytical method ignoring the main beam stiffness revealed that the bending stiffness of the main beam strongly contributed to the live load response. Under the same live load, as the main beam stiffness increases, the overall deformation of the structure decreases, and the reduction is particularly noticeable at locations with original larger deformations. When the main beam stiffness is increased to a certain extent, the stiffening effect is no longer pronounced.

• Earthquakes and Structures
• /
• 제6권6호
• /
• pp.581-609
• /
• 2014

Reinforced concrete (RC) structures are likely to experience damage when subjected to earthquakes. Damage index (DI) has been recognised as an advanced tool of quantitatively expressing the extent of damage in such structures. Last 30 years have seen many concepts for DI proposed in order to calibrate the observed levels of damage. The current research briefly reviews all available concepts and investigates their relative merits and limitations with a view to proposing a new concept based on residual deformation. Currently available DIs are classified into two broad categories - non-cumulative DI and cumulative DI. Non-cumulative DIs do not include the effects of cyclic loading, whilst the cumulative concepts produce more rational indication of the level of damage in case of earthquake excitations. Ideally, a DI should vary within a scale of 0 to 1 with 0 representing the state of elastic response, and 1 referring to the state of total collapse. Some of the available DIs do not satisfy these criteria. A new DI based on energy is proposed herein and its performances, both for static and for cyclic loadings, are compared with those obtained using the most widely accepted DI in literature. The proposed DI demonstrates a rational way to predict the extent of damage for a number of case studies. More research is encouraged to address some identified issues.

• Elastomers and Composites
• /
• 제40권4호
• /
• pp.242-248
• /
• 2005

스포츠화 중창용으로 사용되는 세가지 종류의 발포체인 PU, IP 및 PH의 경도가 피로특성에 미치는 영향을 검토하였다. 세 가지 종류의 발포체를 50 rpm으로 50,000번 반복 압축하였으며, 발포체의 셀은 반복압축에 따라 형태가 변형되었다. 셀 변형의 정도는 IP의 경우가 PH나 PU 보다 큰 것으로 나타났다. 반복압축에 의해 발포체에서 영구변형이 나타났으며, IP가 PH나 PU 보다 크게 나타났다. 반복압축에 따라 세 가지 종류의 발포체의 최대압축력은 감소하는 경향을 나타내었으며, IP의 경우 가장 현저한 감소를 나타내었다. 세 가지 종류의 발포체는 경도가 증가함에 따라 최대압축력의 저하가 더욱 큰 것으로 나타났다.

• 한국멀티미디어학회논문지
• /
• 제25권2호
• /
• pp.206-214
• /
• 2022

The way to measure the extent of damage from floods and droughts is to identify changes in the extent of water systems. In order to effectively grasp this at a glance, satellite images are used. KOMPSAT-5 uses Synthetic Aperture Radar (SAR) to capture images regardless of weather conditions such as clouds and rain. In this paper, various deep learning models are applied to perform semantic segmentation of the water system in this SAR image and the performance is compared. The models used are U-net, V-Net, U2-Net, UNet 3+, PSPNet, Deeplab-V3, Deeplab-V3+ and PAN. In addition, performance comparison was performed when the data was augmented by applying elastic deformation to the existing SAR image dataset. As a result, without data augmentation, U-Net was the best with IoU of 97.25% and pixel accuracy of 98.53%. In case of data augmentation, Deeplab-V3 showed IoU of 95.15% and V-Net showed the best pixel accuracy of 96.86%.

• 대한기계학회논문집
• /
• 제16권10호
• /
• pp.1869-1876
• /
• 1992

본 연구에서는 고온에서 높은 강도특성을 유지하면서 동시에 내마모성이 뛰어 나 가스터어빈의 부재로서의 사용이 기대되는 탄화규소(SiC) 세라믹에 대하여, 고체입 자의 충격에 의해 생기는 손상에 미치는 입자의 재질 및 크기의 영향을 조사하였다. 또 각 형태의 손상발생 임계치와 강도저하에 미치는 입자크기의 영향에 관해서도 검토 하였다.