• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.397-397
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• 2015

The frequency of urban floods is recently increased as a consequence of climate change and haphazard development in urban area. To mitigate and prevent the flood damage, we generally utilized a numerical model to investigate the causes and risk of urban flood. Contrary to general flood inundation model simulating only the surface flow, the model needs to consider flow of the sewer network system like SWMM and ILLUDAS. However, this kind of model can not consider the interaction between the surface flow and drainage network. Therefore, we tried to evaluate the impact of bidirectional interaction between sewer and surface flow in urban flooding analysis based on simulations using the quasi-interacted model and the interacted model. As a general quasi-interacted model, SWMM5 and FLUMEN are utilized to analyze the flow of drainage network and simulate the inundation area, respectively. Then, FLO-2D is introduced to consider the interaction between the surface flow and sewer system. The two method applied to the biggest flood event occurred in July 2011 in Sadang area, South Korea. Based on the comparison with observation data, we confirmed that the model considering the interaction the sewer network and surface flow, showed a good agreement than the quasi-interacted model.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.507-518
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• 2012

It is now widely accepted that the resulting displacement field within elastic, inhomogeneous, anisotropic solids subjected to equipartitioned, uniform illumination from uncorrelated sources, has intensities that follow diffusion-like equations. Typically, coda waves are invoked to illustrate this concept. These waves arrive later as a consequence of multiple scattering and appear at "the tail" (coda, in Latin) of seismograms and are usually considered an example of diffuse field. It has been demonstrated that the average correlations of motions within a diffuse field, in frequency domain, is proportional to the imaginary part of Green's function tensor. If only one station is available, the average autocorrelation is equal to the average squared amplitudes or the average power spectrum and this gives the Green's function at the source itself. Several works address this point from theoretical and experimental point of view. However, a complete and explicit analytical description is lacking. In this work we study analytically some properties of the Green's function, specifically the imaginary part of Green's function for 2D antiplane problems. This choice is guided by the fact that these scalar problems have a closed analytical solution (Kausel 2006). We assume the diffusiveness of the field and explore its analytical consequences.

• 상하수도학회지
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• 제33권4호
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• pp.259-268
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• 2019

One of the most effective methods to consistently ensure the safety of a tap water supply can be achieved by application of a comprehensive risk assessment and risk management approach for drinking water supply systems. This approach can be termed water safety plans(WSP) which recommended by WHO(world health organization) and IWA(international water association). For the introduction of WSP into Korea, 150 hazards were identified all steps in drinking water supply from catchment to consumer and risk assessment tool based on frequency and consequence of hazards were developed. Then, developed risk assessment tool by this research was implemented at a water treatment plant($Q=25,000m^3/d$) to verify its applicability, and several amendments were recommended; classification of water source should be changed from groundwater to stream to strengthen water quality monitoring contaminants and frequencies; installation of aquarium to monitor intrusion of toxic substances into raw water; relocation or new installation on-line water quality analyzers for efficient water quality monitoring; change of chlorination chemical from solid phase($Ca(OCl)_2$) to liquid phase(NaOCl) to improve soundness of chlorination. It was also meaningful to propose hazards and risk assessment tool appropriate for Korea drinking water supply systems through this research which has been inconsistent among water treatment authorities.

• 한국안전학회지
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• 제34권1호
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• pp.45-52
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• 2019

Accident analysis models were developed to improve the construction site safety and case studies was conducted. In 2016, 86% of fatality accidents occurred due to simple unsafe acts. Structure related accidents are less frequent than the non structure related causes, but the number of casualties per accident is two times higher than non structure one. In the view of risk perception, efforts should be given to reduce accidents caused by low frequency - high consequence structure related causes. In case of structure related accident, structural safety inspection and management (including quality), ground condition management / inspection technology, and provision of risk information delivery system in case of non structure related accident were proposed as a solution. In analysis of relationship between safety related stakeholder, the main problem were the lack of knowledge of controller and player, loss of control due to duplicated controls, lack of communication system of risk information, and relative position error of controller and player.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2047-2052
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• 2023

Risk-informed approach has been widely applied in the safety design, regulation, and operation of nuclear reactors. It has been commonly accepted that risk-informed design optimization should be used in the innovative reactor designs to make nuclear system highly safe and reliable. In spite of the risk-informed approach has been used in some advanced nuclear reactors designs, such as Westinghouse IRIS, Gen-IV sodium fast reactors and lead-based fast reactors, the process of risk-informed design of nuclear reactors is hardly to carry out when passive system reliability should be integrated in the framework. A practical method for new passive safety reactors based on probabilistic safety assessment (PSA) and passive system reliability analyze linking is proposed in this paper. New three-dimension frequency-consequence curve based on risk concept with three variables is used in this method. The proposed method has been applied to the determination optimization of design options selection in a 10 MWth lead-based research reactor(LR) to obtain one optimized system design in conceptual design stage, using the integrated reliability and probabilistic safety assessment program RiskA, and the computation resources and time consumption in this process was demonstrated reasonable and acceptable.

• 한국식생활문화학회지
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• 제22권5호
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• pp.582-589
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• 2007

The purpose of this study was to measure the causal relationships among affective belief, environmental belief, subjective norm, attitude and meat consumption behavior. A total of 318 questionnaires were completed. Structural equation model was used to measure the causal relationships among the constructs. Results of the study demonstrated that the structural analysis result for the data also indicated excellent model fit. The effects of affective belief, environmental belief and subjective norm on attitude were statistically significant. The effects of affective belief, environmental belief and subjective norm on meat consumption were statistically significant. As expected, attitude had a significant effects on behavioral intention. Moreover, attitude played a mediating role in the relationship between affective belief and meat consumption, environmental belief and meat consumption, subjective norm and meat consumption. Consumption played a mediating role in the relationship between attitude and behavioral intention. In conclusion, based on structural analysis, a model was proposed of interrelations among affective belief, environmental belief, subjective norm, attitude, meat consumption and intention. It should be noted that the original model was modified and should, preferably, be validated in future research. Other variables may be incorporated to form models that consist of new antecedent and consequence pairs.

• Journal of Korean Dental Science
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• 제4권1호
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• pp.26-32
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• 2011

Purpose: The quality of implant surface is one of the factors that influence wound healing of implant site and subsequently affect osseointegration. The objective of modification of the surface properties of an implant is to affect the biological consequence. The purpose of this study is to evaluate the biologic response of osseous tissue to anodized implants. Materials and Methods: Two machined titanium implants for control group were installed in a tibia of each rabbit and two anodized implants for test group were installed in the other tibia of each rabbit. At the moment the implants were installed, resonance frequency analysis (RFA) values were measured. After healing periods of 1, 2, 3, and 7 weeks, the implants were uncovered and RFA values were measured again. Removal torque was measured for one implant in the test group and one implant in the control group. Histological evaluation was executed in the other implants. Results: Both of test group and control group have the tendency of greater RFA change rate and removal torque value as healing periods became longer, but were statistically insignificant (P>0.05). However, in the case of the same healing period, the test group tended to have greater RFA change rate and removal torque than the control group (P<0.05). More active new bone formation from endosteal surface was noted on the anodized surface than machined surface in specimen after 1 week. There were no significant differences between the test group and control group in histological evaluations. Conclusion: In summary, the anodized surface showed slightly favorable results and it is postulated that it may facilitate improved stability in bone.

• 대한전자공학회논문지SD
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• 제48권5호
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• pp.18-24
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• 2011

DEM(Dynamic Element Matching) 기법중의 하나인 DWA(Data Weighted Averaging)는 멀티비트 Sigma-Delta Modulator에서 피드백 DAC의 단위요소 커패시터 부정합으로 인한 비선형성을 제거하기 위하여 널리 이용된다. 본 논문에서는 기존 DWA 구조에서 적용된 클록 타이밍을 조정하여 양자화기 데이터 코드 출력을 Latch 하는 $2^n$ Register 블록을 $2^n$ S-R latch 블록으로 대체하여 MOS Tr.를 줄임과 더불어 여분의 클록을 제거하였고, n-bit 데이터 코드를 지연시키기 위해 사용되는 2개의 n-비트 Register 블록을 1개의 n-비트 Register 블록으로 감소시켰다. 개선된 DWA 구조를 이용하여 3차 3-비트 SC(Switched Capacitor) Sigma-Delta Modulator를 설계한 후, 입력 주파수 20kHz, 샘플링 주파수 2.56MHz에서 0.1% DAC 단위 요소 커패시터 부정합을 갖도록 하여 시뮬레이션 한 결과 기존의 구조와 동일한 해상도를 얻을 수 있었고, 222개의 MOS Tr. 수를 줄일 수 있었다.

• Korean Chemical Engineering Research
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• 제52권6호
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• pp.750-754
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• 2014

초고농도 과산화수소 제조를 위한 투과증발 공정의 정량적 위험성 분석을 수행하였다. 잠재적 주요 사고는 분해반응에 따른 폭발 및 화재이며 실험실 규모일 때 사고결과는 카테고리 3에 속하는 것으로 판단된다. 대상공정에서 분해반응이 일어나는 과정을 사건트리 형태로 모델링하고 사고원인들의 확률함수를 유사사건 발생빈도 자료를 근거로 설정하였다. 구축된 모델을 사용하여 사고율을 계산한 결과, 수용 가능한 위험수준, 즉 사고빈도가 $10^{-4}/yr$ 이하가 되려면 추가 안전장치가 필요한 것으로 파악되었다. 이를 위해 방호계층분석을 적용한 결과, 촉매반응을 막기 위한 본질적 안전설계, 과열을 막기 위한 SIF (safety instrumented function), 그리고 분해반응이 일어나더라도 폭발로 이어지지는 것을 막는 릴리프 시스템이 요구되었다. 제안된 방법은 과산화수소 농축을 포함한 다양한 화학공정의 안전관리시스템 개발에 기여할 수 있을 것으로 기대된다.

• 비파괴검사학회지
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• 제23권5호
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• pp.429-438
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• 2003

본 연구에서는 연속형 일방향 및 수자직 유리섬유강화 복합재료로 인장 시험편을 만들어 AE 특성에 대한 섬유배향 효과를 살펴보았다. AE 신호들을 STFT 처리하여 특성별로 분류하였으며, 반사식 및 투과식 편광현미경을 이용하여 시험편의 손상영역을 관찰하였다. 저주파수 대역의 약한 AE 신호들은 모재 및 계면에서의 손상으로 나타났으며, 높은 진폭의 고주파수 대역 AE 신호들은 섬유 파단에 기인하였다. 섬유 파단 과정에서 발생하는 고진폭의 AE 사상률을 기본 특성 데이터로 하여 다른 섬유배향과 노치방향을 가진 복합재에서의 파괴과정을 특징지을 수 있었다. 결론적으로, AE범은 연속형 유리섬유 강화 복합재의 파괴거동을 탐지하는데 있어 유용함을 알 수 있었다.