• Korean Journal of Ecology and Environment
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• v.55 no.4
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• pp.259-273
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• 2022

Interactions between species in a community are very complex, and they are visualized and analyzed through a food web in simple way. Food web is a network of species connected by trophic links showing energy flow from prey to predator. Various models were developed to characterize the food web in ecosystems. In this study, we classified food web models to static models such as Ecopath and dynamic models such as AQUATOX. We presented characteristics of several different types of food web models in each category, and reviewed their applications used in aquatic ecosystems. Finally, we presented issues to be considered to develop food web models.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.3
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• pp.41-49
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• 2010

Recently, RFID systems are spreading in various industrial areas faster but cause some serious problems of information security because of its unstable wireless communication. Moreover, traditional RFID systems have a restriction that one tag per each application object. This restriction deteriorates their usability because it is difficult to distinguish many tags without some kind of effort. Therefore, efficient information sharing of objects based on information security has to be studied for more spreading of RFID technologies. In this paper, we design a new RFID tag structure for supporting multiple objects which can be shared by many different RFID applications. We also design an encryption/decryption algorithm to protect the identifying information of objects stored in our tag structure. This algorithm is a light revision of the existing SEED algorithm which can be operated in RFID tag environment. To evaluate the performance of our algorithm, we measure the encryption and decryption times of this algorithm and compare the results with those of the original SEED algorithm.

• Economic and Environmental Geology
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• v.56 no.4
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• pp.447-456
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• 2023

Even after 2000, oil prices rose enough to be comparable to the past, but the impact on economic variables was relatively stable. Therefore, this study tries to empirically examine that the response of the Korean economy to oil prices has changed since the 1998 financial crisis, when there was a structural change in the Korean economy. Through empirical analysis, it was tested that the influence of oil prices and producer prices on consumer prices had changed in the period before and after 1998, and that the influence of producer prices on the value-added ratio by industry sector also changed. This means that the transfer of the increase in production cost to consumer prices has been alleviated, and the impact on added value has also been alleviated. Various studies should be conducted to understand the causes of the empirical results, such as changes in the relationship between producer prices and consumer prices, factors in the industrial sector due to rising oil prices, and changes in products.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.27-27
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• 2021

세굴은 유체와 유사의 상호작용으로 발생하는 중요한 자연 현상 중 하나로, 구조 및 지반 붕괴, 홍수, 생태계 파괴 등의 문제를 야기할 수 있다. 이러한 세굴 현상을 예측하기 위해 많은 수치적 연구가 진행되어왔지만, 대부분의 연구가 기존 격자기반방법인 유한체적법 (FVM)과 개별요소법 (DEM)이 연성된 모델을 이용하였고, 이는 격자 의존도로 인한 정확도와 효율성의 문제점을 보였다. 해결책으로 입자기반 유체해석 방법인 약압축성 SPH (WCSPH)와 개별요소법의 결합모델을 이용한 모의가 연구되어 왔지만, 단순 밀도차를 활용한 유체해석방법이 압력의 불안정성을 야기하여 유사의 운동에도 영향을 주는 결과를 보였다. 또한, 개별요소법의 특성상 모의 입자의 크기를 실제 실험 입자의 크기와 동일하게 설정하면서 입자수가 지나치게 증가해 계산의 효율성이 현저히 낮아지게 되었고, 이로 인해 실제 자연 지형에 적용하는데 어려움을 보여주었다. 본 연구에서는 향상된 세굴 수치모의해석을 위해 반복법을 통해 안정적인 유체 압력을 계산하는 비압축성 SPH (ISPH)와 개별요소법을 연성한 ISPH-DEM 모델을 사용하였다. 또한, 계산속도 향상을 위해 하나의 입자가 다수의 작은 입자의 움직임을 대표하는 Coarse-grained 방법을 적용하여 기존 모델을 개선하였다. 개선된 모델을 NFLOW ISPH PURPLE 소프트웨어를 이용하여 세굴 현상을 수치 모의하였고 실험 결과와 검증을 진행한 결과, 세굴의 깊이, 너비, 형상 등을 비교하였을 때 약 10% 이내의 오차를 보였고, Coarse-grained 방법을 통한 입자 수 감소로 최소 13배 증가된 해석 속도를 보였다. 이를 통해 본 연구에서 제시된 모델이 실제 자연 지형에서의 적용가능성을 확인할 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.469-476
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• 2023

Soil plasticity models for cyclic and dynamic loads are essential in non-linear numerical analysis of geotechnical structures. While a single yield surface model shows a linear behavior for cyclic loads, J₂-bounding surface plasticity model with zero elastic region can effectively simulate a nonlinearity of the ground response with the same material properties. The radius of the yield surface inside the boundary surface converged to 0 to make the elastic region disappear, and plastic hardening modulus and dilatancy define plastic strain increment. This paper presents the stress-strain incremental equation of the developed model, and derives plastic hardening modulus for the hyperbolic model. The comparative analyses of the triaxial compression test and the shallow foundation under the cyclic load can show stable numerical convergence, consistency with the theoretical solution, and hysteresis behavior. In addition, plastic hardening modulus for the modified hyperbolic function is presented, and a methodology to estimate model variables conforming 1D equivalent linear model is proposed for numerical modeling of the multi-dimensional behavior of the ground.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.2
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• pp.157-164
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• 2010

Recently, the number of shallow tunnel construction increases to improve the structural safety and environment-friendliness. In semi-cut-and-cover Method, ground is excavated to the crown arch level and arch slab is set to backfill before the excavation of lower face. In this study, laboratory model tests was performed to clarify the behavior of the arch slab constructed perpendicular to the slope. Results show that Arch slab is affected by perpendicular to the slope and bedrocks. Negative moment at the upper part of the arch slab at hillside and positive moment at the upper part at the other side are generated as perpendicular to the slope increases. Reaction load at the hillside support was larger than that at the other side.

• Korean Journal of Ichthyology
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• v.34 no.4
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• pp.270-276
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• 2022

In 2020 and 2022, the habitat of brown trout (Salmo trutta) was investigated in the Soyanggang River in Chuncheon, Gangwon province. As a result of the fish survey, A total of 43 individuals brown trout were identified. The total length of brown trout was widely confirmed from 60 cm or more to less than 10 cm. In January 2020, sperm release and spawn were observed in male and female confirmed at the St. 1. Brown trout were identified stably settled in the Soyanggang River and continues to live. In addition, benthic macroinvertebrates that can act as food sources of brown trout and abundantly inhabited. The riverbed structure is evenly composed of fine gravel and gravel, which constitutes the conditions necessary for habitat and spawning. However, the spawning grounds, spawned eggs and hatched fry have not yet been clearly identified, so continuous research is needed.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.465-470
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• 2024

Kitchen cabinets are widely used for their spacious storage and efficient use of space, but their high installed location makes it difficult for the elderly and disabled to access. Therefore, in this paper, we propose a new height-adjustable kitchen cabinet that can be used more easily and safely. The lift-down range of cabinet was set considering the installation location of cabinet for efficient use of kitchen space and the maximum height accessible to the elderly and disabled, and the link geometry and driving method of the complex link mechanism were determined through the mechanism design procedure to ensure that the selected floor come down safely along the optimal descend path. In addition, the appropriate motor and control algorithm were added to allow the user to descend to the desired height with a simple button operation. It was confirmed through actual production that the proposed linkage mechanism performs the desired lift-down motion.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.147-151
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• 2007

인위적인 온실가스 증가의 영향으로 지구의 기온이 상승하고 있으며, 우리나라에서도 이러한 전 지구적인 온난화 추세를 상회하는 경향을 보이고 있다. 20세기 후반부터 기후변화에 따른 강수량 및 집중호우의 증가 추세가 보고되고 있으며, 이에 따른 피해 또한 증가하고 있다. 이러한 이상기후 현상이 전 세계적으로 빈번히 발생하여 가용 수자원의 변동이 커지고 있다. 추가적인 댐 건설이 어려운 상황이고, 댐 운영의 불확실성에 의한 현실적인 운영의 어려움으로 인하여 보수적인 댐 운영이 이루어지고 있는 실정이므로, 한정된 수자원의 효율적인 이용과 예측이 요구되고 있다. 본 연구에서는 기상연구소에서 개발된 A2, B2 기후변화 시나리오에 따른 다목적댐에서의 용수공급능력의 변화에 대한 평가를 수행하였다. 대규모 유역의 대표적인 다목적댐을 선정하고 기후변화 시나리오별 유입량을 분석하였으며, 이를 저수지 모의운영 기법을 이용하여 기후변화 시나리오에 따른 각 댐의 신뢰도 95% 용수공급능력과 예상발전량을 산정함으로써 가용수자원을 평가하였다. 또한 다목적댐의 과거 실적 유입량 자료를 이용한 모의운영 결과와 비교하여 제시하였다. 과거 실적에 의한 결과와 비교할 때, 기후변화 시나리오에 따른 향후 국내 가용 수자원량에도 큰 변화가 있을 것으로 예측되었다. 이로부터 댐 운영에 있어서 홍수기의 안정적인 댐관리와 갈수기의 적절한 수자원 분배를 위한 방향을 제시할 수 있다. 본 연구의 결과는 향후 기후변화에 따른 저수지의 효율적인 운영을 위한 유역의 수자원 영향 평가에 활용할 수 있을 것으로 기대된다.댐의 순기능에 대한 정량적인 분석을 수행하였다. 또한 댐별 방류량을 변동하여 하류 주요지점에 미치는 유황개선효과를 정량화하였다. 마지막으로 댐의 효율을 최대화한 하류확보가능하천유지유량을 월별평균량으로 산정하였다. 이는 향후 오염총량제 기준유량 및 환경용수의 법제화를 통한 하천유지용수의 증가시 비구조적 대책의 공급가능 최대량으로 활용가능할 것으로 사료된다.원에서 인위적으로 방류한 양이 많았기 때문으로 추정할 수 있다. 두 지점의 1월 유출이 100 % 이상인 것은 동절기 하천 결빙으로 인한 유량파악이 힘든 것으로 나타났다. 1월의 하천수위는 계측기에 기록된 수위값으로 유량을 산정한 것이다. 3월, 10월, 12월의 유출이 많은 것은 전월말 발생한 강우의 영향으로 크게 나타났다.다. 5. 초장의 절대치는 품종간에 차이는 있으나 비교적 조파구간에는 초장에 큰 변이가 없었고 파종기가 늦어짐에 따라 짧아졌다. 초장의 신장속도는 파종기가 늦어짐에 따라 현저하게 빨라지고 특히 조생종이 만생종보다 더욱 가속적인 경향이었다. 따라서 최고초장과 최저초장과의 절대치의 차이는 조생종일수록 적고 만생종일수록 큰 격차를 보이었다. 6. 간직경에 있어서도 만생종은 일반적으로 조기파종할수록 굵고, 조생종과 중생종은 4월 25일 파종기가 가장 굵은 편이며 이보다 파종기가 지연 가늘어지는 경향이었다. 7. 간중은 품종의 조만생에 따라 약간의 차이는 있으나 대체로 적기(4월 25일~5월 15일)보다 조기 혹은 만기 파종하면 작아지나 파종기 이동에 따른 간중의 변화는 품종의 조만성에 따라 양상을 달리하여 조생종은

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.65-75
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• 2017

C-S-H phase is the most abundant reaction product, occupying about 50~60% of cement paste volume. The phase is also responsible for most of engineering properties of cement paste. This is not because it is intrinsically strong or stable, but because it forms a continuous layer that binds together the original cement particles into a cohesive whole. The binding ability of C-S-H phase arises from its nanometer-level structure. In terms of chloride penetration in concrete, C-S-H phase is known to adsorb chloride ions, however, its mechanism is very complicated and still not clear. The purpose of this study is to examine the interaction between chloride ions and C-S-H phase with various Ca/Si ratios and identify the adsorption mechanism. C-S-H phase can absorb chloride ions with 3 steps. In the C-S-H phase with low Ca/Si ratios, momentary physical adsorption could not be expected. Physical adsorption is strongly dependent on electro-kinetic interaction between surface area of C-S-H phase and chloride ions. For C-S-H phase with high Ca/Si ratio, electrical kinetic interaction was strongly activated and the amount of surface complexation increased. However, chemical adsorption could not be activated for C-S-H phase with high Ca/Si ratio. The reason can be explained in such a speculation that chloride ions cannot be penetrated and adsorbed chemically. Thus, the maximum chloride adsorption capacity was obtained from the C-S-H phase with a 1.50 Ca/Si ratio.