• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.2
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• pp.147-151
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• 2001

An optical fiber sensor is capable of nondestructive measurement of a structure and it has an advantage of the immunity to electromagnetic interference because light is not affected by electromagnetic wave. In addition, if optical fibers are buried in an object like a concrete, this sensor tan analyze defects and physical status of the object without disassembling it. Especially, the fiber Bragg grating sensor is a promising optical fiber sensor capable of nondestructive test of such an object. A fiber Bragg grating has the characteristics of reflecting or blotting light of a specific wavelength. If we apply physical quantity like strain to the fiber Bragg grating, the center wavelength of the reflected light is shifted and then we can find the physical quantity applied to the fiber Bragg grating by measuring the center wavelength shift of the reflected light. The fiber Bragg grating sensor capable ot static and dynamic strain measurement is being used in health-monitoring of buildings, structures, etc. Recently increasing is interest in dynamic strain measurement inevitable to the civil structures such as roads and bridges. In this study we implemented the optical fiber sensor system which can measure dynamic strain at multiple points using Fabry-Perot wavelength demodulation. And we measured the static and dynamic strain using this sensor system with a test structure(cantilever). Measurement results were similar to those obtained with the conventional electrical measurement methods.

• Journal of Radiation Protection and Research
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• v.39 no.1
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• pp.21-29
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• 2014

A new cold neutron triple-axis spectrometer (Cold-TAS) was recently constructed at the 30 MWth research reactor, HANARO. The spectrometer, which is composed of neutron optical components and radiation shield, required a redesign of the segmented monochromator shield due to the lack of adequate support of its weight. To shed some weight, lowering the height of the segmented shield was suggested while adding more radiation shield to the top cover of the monochromator chamber. To investigate the radiological effect of such change, we performed MCNPX simulations of a few different configurations of the Cold-TAS monochromator shield and obtained neutron and photon intensities at 5 reference points just outside the shield. Reducing the 35% of the height of the segmented shield and locating lead 10 cm from the bottom of the top cover made of polyethylene was shown to perform just as well as the original configuration as radiation shield excepting gamma flux at two points. Using gamma map by MCNPX, it was checked that is distribution of gamma. Increased flux had direction to the top and it had longer distance from top of segmented shield. However, because of reducing the 35% of the height, height of dissipated gamma was lower than original geometry. Reducing the 35% of the height of the segmented shield and locating lead 10cm from the bottom of the top cover was selected. After changing geometry, radiation dose was measured by TLD for confirming tester's safety at any condition. Neutron(0.21 ${\mu}Svhr^{-1}$) and gamma(3.69 ${\mu}Svhr^{-1}$) radiation dose were satisfied standard(6.25 ${\mu}Svhr^{-1}$).

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.668-673
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• 1995

$UO_2$-CeO$_2$ 모의혼합분말에 첨가제를 미량 첨가하여 소결체의 미세구조 변화를 $UO_2$분말의 경우와 비교, 관찰하였다. 소결 첨가제로서 Ta, Ti 및 Nb를 사용하였으며, 이들을 미세한 산화물의 형태로 $UO_2$ 및 $UO_2$-CeO$_2$에 첨가하여 환원성 및 산화성 분위기에서 각각 소결하였다. Ta, Ti 및 Nb는 환원소결에서 $UO_2$의 결정립을 성장시켰으나 산화소결에서는 첨가효과가 크게 나타나지 않았다. $UO_2$-0.lw%TiO$_2$와 $UO_2$-0.6w%Ta$_2$O$_{5}$의 환원소결체에서 eutectic phase가 관찰되었으나 산화소결체에서는 나타나지 않았다. $UO_2$-4wt%CeO$_2$의 환원소결에서는 Ti만이 결정립성장에 기여하는 것으로 나타났으며 Ta, Nb와 같이 $UO_2$에 치환형으로 고유되는 원소는 Ce 이온과 Cluster를 형성함으로 결정립성장에 거의 기여하지 못하고, Ti와 같이 UO2$_2$ 침입형으로 고용되는 원소는 일부가 인접한 Ce$_{U}$' 이온과 cluster를 형성하더라도 나머지가 V$_{U}$'의 형성에 기여하므로서 결정립을 성장시킬 수 있다.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.194.1-194.1
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• 2012

우주비행체의 내부 장치 고장 혹은 외부 환경에 의한 고장이 발생할 경우를 대비하여 가상 모의 시뮬레이터를 이용한 고장 대응 훈련이 요구된다. 시뮬레이터 개발 초기에 이러한 고장 발생 메커니즘을 설계에 반영하지 않는 경우 교관이 작성한 고장 시나리오에 의한 유기적 고장 발생 및 고장 전파 기능을 납품 후 추가 요구하기는 용이하지 않다. 본 논문에서는 사용자가 시뮬레이터를 이용하여 의도하는 고장을 의미있는 시각(Epoch)에 주입하기 위한 고장 발생 메커니즘 구조를 설명한다. 또한 천리안위성 시뮬레이터 소프트웨어의 고장 발생 예제를 통해 고장 감지, 고장 복구, 관제원의 대응 방법 등을 설명한다.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.663-668
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• 2002

In this paper, insulating effects and strength development of concrete placed at mock up model structure are discussed using anti freezing agent and insulating forms. According to test results, concrete containing 8% of anti freezing agent shows lower freezing temperature, earlier setting time and higher strength development than plain concrete. As for the temperature history of mock up structures, when plain concrete is placed at euro form, the temperature drops to -4${\circ}$ before early 24 hours, and when concrete containing anti freeze agent at euro form, it to -3${\circ}$ before early 24 hours. Nevertheless, when concrete containing anti freeze agent is placed at insulating form, it does not go below zero, and the concrete containing anti freeze agent enhances higher strength development.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.629-632
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• 2006

This study investigated the engineering properties of crushed sand, based on improvement quality technology, and washed sand concrete by conducting mock-up test, in order to verify the availability of crushed sand for full sized structure. Test results showed that fluidity, air content, supersonic waves and corrosion state of concrete using crushed sand had favorable results. In addition, it is found that compressive strength, drying shrinkage length change, hydration heat and neutralization of crushed sand concrete exhibited similar tendency, with that of washed sand concrete. The crushed concrete using developed quality improvement technology shows comparable performance to washed sand concrete.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.40-48
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• 2022

Recent studies have reported about UAV-based disaster rescue system adopting AR technology. Performing a disaster rescue training in an environment similar to an actual disaster site results in high costs and risk of accidents. In this paper, we propose a simulation software using VR technology so that rescuer can safely and inexpensively train the operation of the disaster rescue system. Through the analysis of the existing system, we derived the requirements for virtualizing training, and developed the simulation software using Unreal Engine and Airsim API. Simulation results show that the proposed simulation software can effectively simulate the operation of the conventional disaster rescue system.

• Journal of the Korean Society of Safety
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• v.6 no.2
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• pp.37-40
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• 1991

산업용 안전모는 그 기능상 耐貫通性과 衝擊吸收性이 중요하다. 이중내관통성은 별로 어려움이 없으나 충격흡수성은 무게 및 크기가 제한되고 극히 간단한 안전모의 구조에 충격을 충분히 흡수하는 Bumper작용까지 하여야 하므로 기준에 합격할수 있는 안전모를 제작하기 위하여는 여간 어려운게 아니다. 이에 論者는 일정한 무게의 추가 일정한 높이에서 자유낙하하여 안전모에 충격을 加하고서 반발할때까지의 안전모의 수직운동(변형)이 어느정도 이루어저야 하는지에 대하여 관심을 갖었다. 즉 모체든 착장체든 또는 모체와 착장체의 연결장소에서든 일정한 충격량을 받았을때 모체의정점(낙하물과 최초로 접한부분)이 수직으로 S'의 거리 만큼 움직여 주고 운동이 정지된다고 보았을때 S'과 m(추의중량), S(추가 떨어지는 높이) Fi(충격이 흡수되고 남은 충격력)와의 관계식을 뉴톤의 운동법칙으로 부터 수학적 방법으로 유도 함으로서 시험조건 및 검정 기준에 주어진 수치인 m, S, Fi,을 대입하므로서 S'을 알 수 있는바 이것을 기초로 안전모의설계및 제조된 안전모의 충격흡수 정도를 용이하게 판단 할 수있다.

• Korean Journal of Construction Engineering and Management
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• v.17 no.4
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• pp.87-94
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• 2016

The necessity to consider stability of underground structures constructed below or adjacent ammunition depots has been increased since the expansion of urban area and construction of infrastructure. However, there are a few studies on influence of accidental explosion on underground structures. In this study, the process of assessing the stability of underground structures is suggested and its applicability is verified through the case study. AUTODYN and SPACECLAIM are used to execute the structure and geotechnical modelling, and explosion effect is simulated and vibration velocities are calculated. According to the result of this case study, it is concluded that underground structure constructed 70m below ground might be rarely influenced by the simulated explosion. The process used in this study could be used to design the underground ammunition complex and analyse the stability of underground facilities being influenced by periodical vibration.

• Fire Science and Engineering
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• v.33 no.3
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• pp.63-73
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• 2019

This study examined the activity of the simulated training scenarios and special rescue crew assuming a chemical accident inside the building. To improve the response ability and safety of rescue personnel in the event of a chemical accident, a total of eight stages of simulated training scenarios were conducted and the activity was measured. As a result of the activity measurement according to the simulation training scenario, the average maximum heart rate of the rescuers was the highest at 177.50 ppm in the 4^th stage, and then 176.67 ppm for the 5^th step, 171.17 ppm for the 2^nd step, 169.33 ppm for the 3^rd step, 162.17 ppm for the 6^th step, 159.58 ppm for the 7^th step, 148.75 ppm for the 8^th step, and 139.33 ppm for the 1^st step. The mean maximum respiratory rate was the highest at 38.17 rpm in the 4^th stage, followed by 37.58 rpm in the 5^th stage, 32.00 rpm in the 6^th stage, 31.58 ppm in the 7^th stage, 31.33 rpm in the 3^rd stage, 31.08 rpm in the 2^nd stage, and 28.00 rpm in the 8^th stage. The 1^st stage was 22.67 rpm. In addition, body water reduction measurements were reduced by up to 0.7 g due to the training intensity.