• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.2
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• pp.127-135
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• 1983

A new approach is developed to analyze the reliability of the earth retaining wall using the concept of probability of failure, instead of conventional factor of safety. Many uncertainties, which are included in the conventional stability analysis, can be excluded by using the stochastic approach. And the reliability, more consistent with the reality, can be obtained by the simulation. The strength parameters of soil properties are assumed to be random variables to follow a generalized beta distribution. The interval [A, B] of the random variables could be determined using the maximum likelihood estimation. The pseudo-random values corresponding to the proposed beta distribution are generated using the rejection method. The probability of failure defined as follows, is obtained by using the Monte Carlo Method. $$P_f=\frac{M}{N}$$ where, $P_f$ : Probability of failure N : Total number of trials M : Total number of failure out of N A computer program is developed for the computation procedure mentioned above. Finally, a numerical example is solved using the developed program.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.37-44
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• 2017

Nonpoint source (NPS) pollution continues to degrade the water quality. NPS pollutants signals high concerns against a sustainable environment. Low impact development (LID) is the leading management practice which regulates and treats stormwater runoff especially in highly impervious urban areas. Constructed wetlands are known to have efficient removal capability of NPS pollutants. Likewise, these LID facilities were intended to maintain the predeveloped hydrologic regime through series of mechanisms such as particle settling, filtration, plant uptake, and etc. In this study, the objective was to investigate the characteristics, fate and treatment performance of the two in-campus constructed wetlands (SW1 and SW2) which were installed adjacent to impervious roads and parking lots to treat stormwater runoff. A total of 42 storm events were monitored starting from July 2010 until November 2015. Manual grab sampling was utilized at the inlet and outlet units of each LID facilities. Based on the results, the wetlands were found to be effective in reducing 37% and 41% of the total runoff volume and peak flows, respectively. Aside from this, outflow EMCs were generally lower than the inflow EMCs in most events suggesting that the two wetlands improved the water quality of stormwater runoff. The average removal efficiency of pollutants in facilities were 63~79% in TSS, 38~54% in TN, 54% in TP and 32%~81% in metals. The results of this study recommend the use of constructed wetlands as efficient treatment facility for urban areas for its satisfactory performance in runoff and pollutant reduction.

• Journal of Korea Technology Innovation Society
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• v.16 no.2
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• pp.444-475
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• 2013

This study explores the trajectories of institutionalization for technology transfer both in the U.S. and Korea, particularly focusing on two universities: Korea Advanced Institute of Science and Technology (KAIST), and the University of California (UC). By comparing the diverging paths of the two universities in setting up institutions, this paper examines the limits of and lessons for technology transfer policies both to Korean government and universities in Korea. The University of California was involved in designing rules and codes, on one hand, to stimulate its members' engagements with technology transfer activity and, on the other hand, to keep its academic integrity since, no later than, the 1960s. The efforts and consequences range from its rules of patenting system to its codes of conducts. Through making rules formal and resolving conflicts on technology transfer activity, the U.S., and the University of California have decreased uncertainties for its members' engagements with industries. By contrast, KAIST has not built up such range of rules or codes due to its shorter experience and its constraining legal contexts. Korea introduced the legal format of the US Bayh-Dole Act in 2002, and its central government has led the initiatives for technology transfer, not allowing much latitude for its universities. This study implies a set of policy recommendations to the Korean government and KAIST: to build entrepreneurial universities, the government should give greater latitude to universities, so universities should be more rigorously engaged in developing their own rules and routines; the government, rather, should focus on providing bridging R&D funds like the Small Business Innovation Research (SBIR), so researchers could draw on resources to move their basic research into next phases; KAIST would be better to promote its members to engage with industries, and introduce conduct codes that allow its academics to engage in industrial activity, rather than building up its commercialization facilities.

• Ecology and Resilient Infrastructure
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• v.7 no.2
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• pp.90-96
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• 2020

Recently, a method that applies laser scanning (LS) that acquires vegetation information such as the vegetation habitat area and the size of vegetation in a point cloud format has been proposed. When LS is used to investigate the physical shape of vegetation, it has the advantage of more accurate and rapid information acquisition. However, to examine uncertainties that may arise during measurement or post-processing, the process of adjusting the data by the actual data is necessary. Therefore, in this study, the physical structure of stems, branches, and leaves of woody vegetation in an artificially formed river channel was manually investigated. The obtained results then compared with the information acquired using the three-dimensional terrestrial laser scanning (3D TLS) method, which repeatedly scanned the target vegetation in various directions to obtain relevant information with improved precision. The analysis demonstrated a negligible difference between the measurements for the diameters of vegetation and the length of stems; however, in the case of branch length measurement, a relatively more significant difference was observed. It is because the implementation of point cloud information limits the precise differentiation between branches and leaves in the canopy area.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.5
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• pp.371-380
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• 2017

The risk-targeted seismic design concept was first included in ASCE/SEI 7-10 to address problems related to the uniform-hazard based seismic concept that has been constructed without explicitly considering probabilistic uncertainties in the collapse capacities of structures. However, this concept is not yet reflected to the current Korean building code(KBC) because of insufficient strong earthquake data occurred at the Korean peninsula and little information on the collapse capacities of structures. This study evaluates the risk-targeted seismic performance of steel ordinary concentrically braced frames(OCBFs). To do this, the collapse capacities of prototype steel OCBFs are assessed with various analysis parameters including building locations, building heights and soil conditions. The seismic hazard curves are developed using an empirical spectral shape prediction model that is capable of reflecting the characteristics of earthquake records. The collapse probabilities of the prototype steel OCBFs located at the Korean major cities are then evaluated using the risk integral concept. As a result, analysis parameters considerably influence the collapse probabilities of steel OCBFs. The collapse probabilities of taller steel OCBFs exceed the target seismic risk of 1 percent in 50 years, which the introduction of the height limitation of steel OCBFs into the future KBC should be considered.

• Clean Technology
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• v.20 no.4
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• pp.449-456
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• 2014

There has been increasing concerns for the problems of water security in countries, caused by the frequent occurrence of localized drought due to the climate change and uncertainty of water balance. The importance of fresh water is emphasized as considerable amount of usable fresh water is utilized for power generation sector producing electricity. PV power system, the source of renewable energy, consumes water for the every steps of life cycle: manufacturing, installation, and operation. However, it uses relatively less water than the traditional energy sources such as thermal power and nuclear power sources. In this study, to find out the use of water for the entire process of PV power system from extracting raw materials to operating the system, the footprint of water in the whole process is measured to be analyzed. Measuring the result, the PV water footprint of value chain was $0.989m^3/MWh$ and the water footprint appeared higher specially in poly-Si and solar cell process. The following two reasons explain it: poly-Si process is energy-intensive process and it consumes lots of cooling water. In solar cell process, deionized water is used considerably for washing a high-efficiency crystalline silicon. It is identified that PV system is the source using less water than traditional ones, which has a critical value in saving water. In discussing the future energy policy, it is vital to introduce the concept of water footprint as a supplementary value of renewable energy.

• Journal of Digital Convergence
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• v.16 no.7
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• pp.97-105
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• 2018

The fourth industrial revolution is expected to bring about great changes in information technology sector and create a variety of jobs. However, the psychological anxiety of IT staff is increasing due to stress and uncertainty created by the new technologies. Accordingly, researchers examined how professional identity moderate the effect of job stress of system maintenance staff on emotion exhaustion. For empirical studies, data was collected from 160 employees responsible for managing and supporting IS, and the hypothesis was verified using SPSS 21. The analysis results showed that role conflicts, role ambiguity, and qualitative work overload, which are components of job stress, have affected the emotion exhaustion. Professional identity had a moderating effect the relationship between qualitative work overload and emotion exhaustion. On the other hand, professional identity did not moderate the relationship between role conflict and emotion exhaustion, role ambiguity and emotion exhaustion. As professional identity lessen the psychological burden and emotion exhaustion of introducing new technologies, organizations need to provide support to enhance professional identity for system maintenance staff.

• Journal of Wetlands Research
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• v.11 no.2
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• pp.67-76
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• 2009

The contribution of pollutant loadings from non-point source (NPS) to the four major rivers in Korea exceeded 22~37 % of the total loadings in 2004 and is expected to reach 60 % in 2020. Most of NPS loadings are coming from urban areas, especially from paved areas. Because of high imperviousness rate, many types of NPS pollutant are accumulating on the surface during dry periods. The accumulated pollutants are wash-off during a storm and highly degrading the water quality of receiving water bodies. For this reason, the Korean Ministry of Environment (MOE) developed the Total Maximum Daily Load (TMDL) program to protect the water quality by managing the point source and NPS loadings. NPS has high uncertainties during a storm because of the characteristics of rainfall and watershed areas. The rainfall characteristics can affect on event mean concentrations (EMCs), mass loadings, flow rate, etc. Therefore, this research was performed to determine EMCs for rainfall ranges from transportation landuses such as road and parking lot. Two sites were monitored over 45 storm events during the 2006/06 through 2008/10 storm seasons. Mean TSS EMCs decrease as rainfall ranges increase and highest at less than 10mm rainfall. The results of this study can be used to determine the efficient scale of BMP facility considering specific rainfall range.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.193-193
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• 2011

국제기구인 정부간 기후변화협의체(Intergovernmental Panel on Climate Change, 이하 IPCC)에서는 기후변화가 기온 상승에 따른 증발산량의 증가, 강수량 및 유출량의 시공간적 분포의 변동 등을 초래하여 수자원의 효율적 관리 및 안정적인 공급에 어려움을 증대시킬 것으로 전망하였다. 또한 IPCC 4차 보고서에 따르면 21세기말 지구의 평균기온은 현재보다 최대 $6.3^{\circ}C$정도 더 상승할 것으로 전망하였다. 전구평균기온이 $3.0^{\circ}C$ 증가할 경우 아시아에서만 연간 700만 명이상이 홍수피해 위기에 직면할 것으로 예상되고 있다. 국내의 경우 기온은 전구평균기온에 비해 2배 이상 높은 $1.5^{\circ}C$ 정도 상승하였으며, 최근 50년간의 강우일수는 감소한 반면 일강수량이 80mm 이상인 호우일수의 발생빈도는 증가되고 있다고 보고되었다. 또한 최근의 물수지 해석과 관련하여 거시적인 관점에서 기온 및 강수량 증가에 따른 물순환 과정을 모의하고, 농업용수, 댐건설, 도시화, 토지이용의 변화 등 인위적인 환경 변화 및 기후변화에 따른 유출량의 변화를 정량화하려는 연구들이 수행되고 있다(한국건설기술원, 2007). 이를 위하여 단기적이 아니라 장기적인 측면에서 유출분석을 할 필요가 있으나, 현재까지 보유하고 있는 실측 자료의 한계 및 이러한 조사를 위해 요구되는 시간 및 비용의 한계 때문에, 유출해석 모형을 주로 이용하고 있다. 본 연구에서는 장래 건설예정인 미계측 호소의 유량과 수질을 모의하기 위하여 하천, 하구, 호소 및 해역에 고루 적용할 수 있는 3차원 수리 동력학적인 모델인 EFDC 모형과 시간의 변화에 따른 수질을 모의하는데 가장 널리 이용하는 WASP 모형을 도입하였다. 향후, 내성천의 영주댐 건설과 같은 큰 변화가 발생하였을 기후 변화의 영향을 파악하기 위하여 EFDC와 WASP모형을 이용하여 대상유역에 대한 유출량과 수온의 변화를 통하여 A2, B1 기후변화 시나리오별로 2020년, 2050년, 2080년의 수질(BOD, TN, TP)변화를 분석하여 보았다. 연구의 결과는 다음과 같이 나타났다. EFDC 및 WASP 모형의 연계를 통한 기후 변화 시나리오에 따른 미래의 저수지 수질예측 모의를 수행한 결과, BOD, TN, TP 등 수질농도 변화는 2020년에서 2080년도로 갈수록 BOD, TN 다소 증가하는 경향을 나타내었고, TP농도는 감소하였다. 시나리오별 변화 특성은 TN, TP 농도는 A2 시나리오가 다소 높고, BOD 농도는 B1 시나리오가 A2보다 높은 것으로 나타났다. EFDC와 WASP을 이용하여 미계측 호소에 대한 기후변화 시나리오별로 적용하여 수질변화를 예측하여 보았는데, 향후 기후변화에 따른 기온, 유량변화와 수질 항목간의 상간관계 정립 및 수질 모의의 불확실성 등에 대한 추가 연구가 필요할 것으로 판단된다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.558-565
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• 2021

The Republic of Korea Navy has deployed naval fleets in the East, West, and South seas to effectively respond to threats from North Korea and its neighbors. However, it is difficult to allocate proper missions due to high uncertainties, such as the year of introduction for the ship, the number of mission days completed, arms capabilities, crew shift times, and the failure rate of the ship. For this reason, there is an increasing proportion of expenses, or mission alerts with high fatigue in the number of workers and traps. In this paper, we present a simulation model that can optimize the assignment of naval vessels' missions by using a continuous time absorbing Markov chain that is easy to model and that can analyze complex phenomena with varying event rates over time. A numerical analysis model allows us to determine the optimal mission durations and warship quantities to maintain the target operating rates, and we find that allocating optimal warships for each mission reduces unnecessary alerts and reduces crew fatigue and failures. This model is significant in that it can be expanded to various fields, not only for assignment of duties but also for calculation of appropriate requirements and for inventory analysis.