• Tunnel and Underground Space
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• v.25 no.4
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• pp.383-396
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• 2015

It is analyzed the risk of building damage due to ground surface subsidence occurred during constructing a tunnel below buildings in sand-gravel layer. The overburden and the thickness of sand-gravel layer is about 20m and the width and the height of the tunnel are 12m and 8.6m, respectively. The tunnel is pre-reinforced by umbrella method with three rows of long steel pipes and grouting. Surface subsidence is measured at 36 points surrounding buildings and measured data are used to calculate optimized three dimensional subsidence surface. Depending on the building location, deflection ratio and horizontal strain are calculated to evaluate the risk of building damage. No damage occurs at the buildings because of both the small deflection ratios involved 1~4mm subsidence and compressive horizontal strains.

• Explosives and Blasting
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• v.37 no.4
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• pp.10-16
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• 2019

Information on overpressure, positive phase duration, and impulse are required to assess the effects of shock waves or pressure waves on the structure. In this study, the overpressure and positive phase duration were determined by applying the Multi-Energy Method, which is found to be effective in analyzing the explosion of vapor clouds. Based on the total heat of combustion estimated in the cyclohexane vapor cloud explosion in the Nypro Ltd(UK), overpressure and positive phase duration at the distance of 40, 80, 120, 160, 200, 240, 280, 320, 360(m) from the source of explosion were evaluated. Overpressure was shown to decrease exponentially and positive phase duration increased almost linearly with distance. A probit function was used to assess the probability of damages for the structures at each distance using the overpressure and impact obtained at the above mentioned distances. The Analyses of probability of damages have shown that there is a high probability of collapse at distances within 120m, major damage to structures within 240m, and minor damage and breakage of window panes of structures occur over the entire distances.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.4
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• pp.191-197
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• 2018

This paper details the development of an isotropic elastic-damage constitutive model for polymeric foam based on irreversible thermodynamics to consider the growth and coalescence of voids. The constitutive equations describe the material behavior sustaining unilateral damage. To facilitate finite element analysis, the material properties for specific types of polymeric foams are applied to the developed model; the model is then implemented in ABAQUS as a user-defined material subroutine. To validate the developed damage model, the simulated results are compared to the results of a series of tensile tests on various polymeric foams. The proposed damage model can be utilized to further research on continuum damage mechanics and finite element analysis of polymeric foams in computational engineering.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.2
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• pp.127-132
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• 2013

Traumatic injuries to immature permanent teeth are common and the results can be destructive. Although Hertwig's epithelial root sheath is usually sensitive to trauma, it may resist damage from trauma thereby retaining its vitality and continuing to calcify a root under favorable conditions. This case report describes two cases of trauma to immature permanent incisors. The first case presents an avulsed maxillary central incisor which has been replanted. The other case shows completely avulsed mandibular central incisors which have not been replanted. However, both cases subsequently show continued growing roots separated from the main roots. This report highlights the ability of the immature pulp tissue to continue to form dentin and the robustness of Hertwig's epithelial root sheath to initiate root development despite a traumatic injury.

• Composites Research
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• v.20 no.4
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• pp.42-50
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• 2007

This paper describes the results of experiments and numerical simulation studies on the low-velocity impact damage of two different sandwich composite panels for application to bodyshell and floor structure of the BIMODAL tram vehicle. Square test samples of 100mm sides were subjected to low-velocity impact loading using an instrumented testing machine at four impact energy levels. Part of this work presented is focused on the finite element analysis of low-velocity impact response onto a sandwich composite panels. It is based on the application of explicit finite element (FE) analysis codes LS-DYNA 3D to study the impact response of sandwich structures under low-velocity impact conditions. Material testing was conducted to determine the input parameters for the metallic and composite material model, and the effective equivalent damage model for the orthotropic honeycomb materials. Numerical and experimental results showed a good agreement for damage area and the depth of indentation of sandwich composite panels created by the impact loading.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.485-488
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• 2008

Fire intensity in tunnel fire is very severe, which might cause the spalling on the surface of shotcrete and concrete lining exposed to the heat as well as rapidly-reducing stress due to heat transfer by steel material such as anchor embedded in tunnel which plays the critical role in securing the stability of the tunnel. In this study, a fire test to identity the heat intensity(Modifired Hydrocarbon Curve) and the fire resistance of steel materials embedded as parameters, was carried out. And the evaluation to identify the thermal damage, which was based on critical temperature range for thermal damage of steel materials determined according to the road tunnel fire resistance standard established by ITA(International Tunneling Association).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2A
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• pp.109-116
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• 2012

The dynamic properties of lead rubber bearings, which are used as isolator, are dependent on the main rubber's dynamic behaviors and nonlinear qualities. Rubber materials tend to undergo an aging process under the influence of mechanical or environmental factors, so they can end up inevitably facing damage. A main cause of such aging is known to be oxidization, which occurs through the heat of reaction at high temperatures. Accordingly, in this study an accelerated thermal aging test was carried out in order to compare the characteristic values of the bearings with each other before and after thermal aging occurs. As a result of this experiment, it was found that a thermal aging phenomenon could have an effect on shear stiffness, energy absorption, and equivalent damping coefficients. Furthermore, a decline in the dynamic properties of the lead rubber bearings by means of the thermal aging process was applied to an actual bridge and the effects of such thermal aging on the seismic performance of the bridge were also compared and analyzed based on numerical analysis. As a result of this analysis, it was found that the changes in the basic properties of the lead rubber bearings have a minor effect on the seismic performance of bridges.

• Journal of Hydrogen and New Energy
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• v.32 no.5
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• pp.347-355
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• 2021

This paper is a study on the thermal design of printed circuit heat exchanger (PCHE) to supply cryogenic high pressure liquid hydrogen stored from hydrogen liquefaction process by using computational fluid dynamics (CFD). This PCHE should be thermally designed to raise the temperature of cryogenic liquid hydrogen to a desired temperature and also to be anti-icing to avoid any local freezing in hot channel. This research presents the effect of inlet velocity and inlet temperature of hydrogen, and the effect of flow configurations of co/counter-flow on thermal design of PCHE heat exchanger based on various CFD simulation analysis.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.48-53
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• 1998

We have fabricated electrostatic lens with novel structure by mixing surface- and bulk-micromachining technology. Polysilicon was used for both the structure and sacrificial layer, and the structure layer was passivated with thermal oxide in order not to be attacked during the silicon wet etching. Compared with conventional electrostatic lens used in microcolumn, this device has the advantages in ; 1) hole alignment, throughput, reliability, damage of lens, 2) the possibility of arrayed lithography through the integration of microcolumn.

• 방재와보험
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• s.108
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• pp.64-67
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• 2005

여름철에는 덥고 습한 날씨가 이어져 사람들은 최대한 신체를 노출시켜 시원함을 유지하고자 한다. 따라서 뜨거운 수증기나 국물에 데거나 다리미 등의 뜨거운 쇠붙이에 의해 접촉화상을 입는 경우가 흔하다. 이런 경우 심한 통증과 상처가 생기게 되는데, 대부분의 사람들은 당황하여 어떻게 대처해야 할지 몰라 우왕좌왕하기 마련이다. 일부의 사람들은 간장이나 된장, 알로에 등을 상처에 바르는 등 전근대적인 방법으로 상처를 치료하다가 상처를 키워서 병원에 가기도 하고, 심지어는 창상을 그대로 노출시켜 세균에 의한 감염이 발생되어 얕은 화상이 더욱 깊어져 치료만으로 나을 수 있는 상처를 피부이식술 등의 수술을 필요로 하게 되는 결과를 낳기도 한다. 또한 수술을 하는 정도는 아니더라도 화상흉터가 많이 남게 될 수도 있어 초기의 화상관리가 중요하다 하겠다. 과연 독자들은 화상상처에 어떻게 대처하는지? 초기에 상처를 어떻게 돌보는가에 따라 평생 화상흉터의 멍에를 지고 갈수 있다는 것을 알고 있는지? 이러한 많은 문제점들에 대한 관리적인 차원에서 일반인들이 어렵고 복잡하다고 생각할 수 있는 화상관리에 대해 이야기해 보고자 한다. 화상이 생겼을 때의 처치는 일반적인 열창 때의 처치와는 다른 점이 있다. 우선 열에 의해 피부가 손상을 받아 이를 식히는 과정이 필요하며 이 과정(찬물로의 창상세척)이 간과될 경우 이차적 점은 화상에 의한 상처는 손상된 피부로 인해 노출된 생살을 어떻게 세균감염으로부터 보호하느냐 하는 점이 문제가 되며 이를 예방하는 과정이 필요하다는 것이다.