• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.2
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• pp.141-155
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• 2023

Monitoring technology based on electrical resistivity is widely used for non-destructive data collection and health analysis of underground structures and tunnels. Vulnerable sections such as fault zone generates many problems during construction of the tunnel. These problems cause displacement and stress changes of the ground. Therefore, it is necessary to predict the state of the fault zone section to ensure the mechanical stability of the underground structure. Monitoring the size of joints and the porosity of the fillings is essential for rocks. Previous studies have not considered the variety of fillings in rock joints. In this study, electrical resistivity tests were conducted according to the particle mixing state of the sandy fillings. When the size of fillings is decreased at the constant porosity, the electrical resistivity tends to increase. The results of this study are expected to be useful as basic electrical resistivity data for predicting the ground conditions and evaluation of the ground behavior that is containing sandy fillings in the rock joint for tunnels.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.86-93
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• 2023

Pyrotechnic separation devices have been widely used as holding and release mechanism for deployable appendage. However, pyro-shock can cause temporal or permanent damage on shock sensitive components such as electronics, mechanism, and brittle components. This study proposed a low-stiffness blade based passive shock absorber using a multi-layered stiffener laminated with viscoelastic acrylic tapes for reducing transmitted pyro-shock upon explosion of pyrotechnic separation devices. The multi-layered structure with viscoelastic tape has high-damping characteristics to effectively secure structural integrity of low-stiffness blades under the launch environment. The design effectiveness was verified through a shock test by dropping a pendulum. The structural integrity of the shock absorber under a launch environment was evaluated through structural analysis under load conditions with a deployable payload.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.663-673
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• 2011

In this study, we analysed the effect of the fire source in the warehouse under the bridge and the height of the bridge using FDS code. To compare accuracy of simulation results, we simulated the experimental result with unit combustibles which is heptane as well as the mock-up test. Using this method, we evaluated the fire safety of the bridge which contains spalling and strength damage of concrete as well as damage of reinforcements according to the fire source and the height of the bridge. Most of the bridges are vulnerable to spalling of concrete. The book combustion has the strongest fire intensity which is expected to damage the bridge less than 30m height in the three types of the fire sources. The bridge over the 30m height can ensure the fire safety in the case of the rubber combustion.

• Journal of Environmental Policy
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• v.7 no.4
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• pp.35-55
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• 2008

Assessing vulnerability to climate change is the first step to take when setting up appropriate adaptation strategies. Adaptive capacity to climate change is the important factor comprising vulnerability. An adaptive capacity index in agricultural water management system was developed considering agricultural water supply and demand for rice production in Jeolla-do, Korea. The agricultural water supply was assumed to be equal to the amount of water stored in the major agricultural reservoirs, while data on the agricultural water demand was obtained from the dynamic simulation results by Korea Agriculture Corporation(KAC). The spatial unit for analysis was conducted at the county(Si, Gun, Gu) level and temporal scale was based on every month from 1991-2003. Adaptive capacity for drought stress index(ACDS index) was calculated as the percentage of data points where the irrigated water supply was greater than the crop water demand. The ACDS index was compared with SWSCI(Standard Water Storage Capacity Index) and the relationship showed high degree of fit($R^2$=0.84) using the exponential function, indicating that the developed ACDS index is useful for evaluating the status of the balance between agricultural water supply and demand, especially for the small sized agricultural reservoirs. This study provided the methodological basis for developing climate change vulnerability index in agricultural water system which is projected to be more frequently exposed to drought condition in the future due to climate change. Further research should be extended to the study on the water demand of the crops other than rice and to the projection of the change in ACDS index in the future.

• Journal of Korea Water Resources Association
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• v.52 no.6
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• pp.429-440
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• 2019

The numbers of multi-year droughts due to climate change are increasing worldwide. Boryeong Dam, located in Chungcheongnam-do, South Korea, was also affected by a 4-year drought from 2014 to 2017. Since traditional unilateral decision making processes to alleviate drought damage have, until now, resulted in conflicts between many of the involved groups, the need for active participation from both stakeholders and policymakers is greater than before. This study introduced Shared Vision Planning, a collaborative decision making process that involves participation from various groups of stakeholders, by organizing Water Policy Council for Climate Change Adaptation in Chungcheongnam-do. A Shared Vision Planning Model was then developed with a system dynamics software by working together with relevant stakeholders to actively reflect their requests through three council meetings. Multiple simulations that included various future climate change scenarios were conducted, and future drought vulnerability analysis results of Boryeong Dam and districts, in terms of frequency, length, and magnitude, were arrived at. It was concluded that Boryeong Dam was more vulnerable to future droughts than the eight districts. While the total water deficit in the eight districts was not so significant, their water deficit in terms of spatial discordance was proved to be more problematic. In the future, possible alternatives to the model will be implemented so that stakeholders can use it to agree on a policy for possible conflict resolutions.

• Economic and Environmental Geology
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• v.23 no.4
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• pp.425-452
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• 1990

A tentative hydrogeologic and hydrodispersive study was carried out to evaluate the groundwater pollution potential at a selected site by utilizing empirical assessment methodologies in an advanced stage of quantitative computer aided assessment. The upper most aquifer is defind as saturated overburden and weathered zone including the upper part of highly fractured rock. Representative hydraulic conductivity and storativity of the uppermost aquifer are estimated at 2.88 E-6 m/s and 0.09, respectively. Also calculated Darcian and average linear velocity of groundwater along the major pathway are 0.011 m/d and 0.12 m/d with average hydraulic gradient of 4.6% in the site. The results of empirical assessment methodologies indicate that 1) DRASTIC depicts that the site is situated on non-sensitive and non-vulnerable area. 2) Legrand numerical rating system shows that the probability of contamination and degree of acceptability are classed to "Maybe-Improbable, and Probable Acceptable and Marginally Unacceptable" with situation grade of "B". 3)Waste soil-site interaction matrix assessment categorizes that the study site is located on "Class-8 Site".

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.591-591
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• 2012

본 연구는 Transparent conducting oxide (TCO, 산화물투명전극)를 이용한 박막태양전지 효율향상에 관한 것으로, 이중의 TCO층(Double-stacked TCO layer)의 효과적인 광학 및 전기적 설계에 관한 것이다. 기존 박막 태양전지에서는 투명전극 TCO layer로서, ITO (Indium-Tin-Oxide), FTO (Fluorine- Tin-Oxide), 및 AZO(Aluminum-doped Zinc Oxide) 등을 사용해 왔다. 각 TCO layer마다 장점이 있지만 단점 또한 존재한다. ITO의 경우 높은 전기적 특성을 가지는 반면 수소 플라즈마에 취약하고 기계적 강도에 취약해 ITO 단일층만으로 박막 태양전지에 적용하는 것에 제한을 받는다. 한편, AZO의 경우 전기적 특성도 우수할 뿐만 아니라 수소 플라즈마에도 내구성이 강한 장점이 있지만, 일함수가 p형 반도체보다 낮아 Schottky junction이 되어, 높은 전위장벽이 형성된다. 이는 정공의 이동을 방해하고, 정공의 축적이 일어나서 순방향 전압을 인가할 때 많은 전류의 감소를 가져온다. 또한, AZO와 p형 반도체 사이의 높은 직렬저항으로 인해 광전압(Voc, Open circuit voltage)와 충실률 (FF, Fill factor)가 떨어진다는 단점이 있다. 본 실험에서는 ITO/AZO 2중구조의 TCO층을 적용하여 상기의 문제점을 해결하고자 한다. 이중 구조 TCO층은 Magnetron sputter system을 이용하여, 단계적으로 증착되었다. 빛이 입사하는 유리에 ITO를 제1전도층으로 증착하였는데, ITO는 입사광의 투과도와 전기전도성이 우수하다. 제2전도층으로는 AZO층을 이용하였으며, 실리콘 반도체층과 접하게 된다. AZO는 실리콘 증착시 발생하는 수소 플라즈마에 안정적이고, 물리적 강도 또한 우수한 장점이 있다. 이중 구조층위에 실리콘 광흡수층(Si absorber)을 증착하였으며, pin 구조를 가진다. 기존, 단일막 TCO층과 2중구조 TCO층을 이용하여, 실리콘 박막 태양전지를 구성하였다. 이때, ITO/AZO의 2중구조를 적용하였을 때 태양 전지 특성이 크게 향상된 결과를 얻을 수가 있었다. 특히, 전류밀도의 경우 ITO, FTO, AZO 각각 14.5 mA/cm2, 11.2 mA/cm2, 8.18 mA/cm2를 나타낸 반면 ITO/AZO 2중구조의 경우 약 17mA/cm2 로 크게 향상 되었고, 태양전지 변환 효율도 각각 7.5%, 6.9%, 4%에서 ITO/AZO 2중 구조의 경우 8.05%로 크게 향상되었다. 본 발표에서는 2중구조 TCO를 이용한 현공정에 적용 가능한 박막태양전지 효율향상 기법에 대해 논의하고자 한다.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.193-199
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• 2018

The commonly used delivery system for online merchandise has potential problems, not only missing but also criminal case. Also, the contemporary Kiosk type approach for delivery system has some problems in an initial installation cost, expense of management system and especially security weaknesses in the wireless communication. To resolve these issues, this paper is proposing a securely unmaned smart locker system that can handle up to 64 parcels. This is easily controlled and monitored by a smartphone. In addition to the system, an algorithm is proposed to make the security of wireless communications better. Finally, a method is proposed to minimize the cost of delivery by using centralized server.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.477-477
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• 2022

환경문제가 사회적으로 크게 대두되면서, 환경 보전 및 복원에 대한 국민들의 관심이 높아졌다. 특히 하천의 경우, 시민들의 레저 활동 및 휴식을 위한 공간으로도 활용되고 있어 청정한 환경 유지를 위한 노력이 필요하다. 하천의 생태기능은 하천에서 살아가는 각종 생물의 서식 조건을 유지함으로써 하천이 환경적으로 건강한 상태를 유지하도록 하는데 매우 중요한 역할을 한다. 우리나라는 70년대 이후부터 오염물질로부터의 수량 보장 등의 목적으로 하천 유지유량을 설정하여 관리하고 있다. 최근에는 이러한 단순 수질 환경 및 물수요의 충족을 위한 취수량 확보 목적을 넘어 수생태계 보호를 위한 유량인 환경생태 유량의 확보가 중요한 문제로 대두되고 있다. 일반적으로 생태계 기능을 보존하는데 필요한 최적 또는 최소 유량에 대한 평가는 다양한 종의 어류에 대한 하천의 유량과 서식지 가용성 사이의 관계를 정의하는 서식지 기반 모델에 의해 수행되어왔으며, 이를 위해서 우선적으로 하천 단면에 대한 수위, 유량, 지반고 등의 하천 고유 특성에 대한 정보를 필요로한다. 이에 본 연구는 생태유량 산정에 앞서 HEC-RAS(하천 분석 시스템)를 이용하여 한강권역내 생태유량 산정을 위한 취약지역 3지점에 대한 하천 단면 정보에 대한 분석을 진행하였다. 본 연구 결과는 한강권역 환경생태유량 산정 및 하천 관리를 위한 기초자료로 활용할 수 있을 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.115-124
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• 2003

In this paper, the effects of vehicle loads on flat slab system are investigated on the basis of the previous studies for beam-gilder parking structural system. The influence surfaces of flat slab for a typical design section are constructed lot the purpose of obtaining maximum member forces under vehicle loads. In addition, the equivalent vehicle load factors for flat slab parking structures are suggested using artificial neural network. The network responses we compared with the results obtained by numerical analyses to verify the validation of Levenberg-Marquardt algorithm adopted as training method in this Paper. Many parameter studies for the flat slab structural system show dominant vehicle load effects at the center positive moments in both column and middle strips, like the beam-girder parking structural system.