• Fisheries and Aquatic Sciences
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• 제23권6호
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• pp.15.1-15.14
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• 2020

Background: Large rivers are ecological treasures with high human value, but most have experienced decades of degradation from industrial and municipal sewage, row-crop agricultural practices, and hydrologic alteration. We reviewed published analyses of long-term fish diversity publications from three intensively managed large river ecosystems to demonstrate the conservation potential of large river ecosystems. Results: We show how the incorporation of recent advances in river concepts will allow a better understanding of river ecosystem functioning and conservation. Lastly, we focus on the Wabash River ecosystem based on high conservation value and provide a list of actions to maintain and support the ecosystem. In the Wabash River, there were originally 66 species of freshwater mussels, but now only 30 species with reproducing populations remain. Although there were multiple stressors over the last century, the largest change in Wabash River fish biodiversity was associated with rapid increases in municipal nutrient loading and invasive bigheaded carps. Conclusions: Like similarly neglected large river systems worldwide, the Wabash River has a surprising amount of ecological resilience and recovery. For instance, of the 151 native fish species found in the 1800s, only three species have experienced local extinctions, making the modern assemblage more intact than many comparable rivers in the Mississippi River basin. However, not all the changes are positive or support the idea of recovery. Primary production underpins the productivity of these ecosystems, and the Wabash River phytoplankton assemblages shifted from high-quality green algae in the 1970s to lower less nutritional blue-green algae as nutrient and invasive species have recently increased. Our recommendations for the Wabash River and other altered rivers include the restoration of natural hydrology for the mainstem and tributaries, nutrient reductions, mechanisms to restore historical hydrologic patterns, additional sediment controls, and improved local hydraulics.

• Journal of Electrochemical Science and Technology
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• 제11권2호
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• pp.132-139
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• 2020

Solid oxide fuel cells (SOFCs) are among one of the promising technologies for efficient and clean energy. SOFCs offer several advantages over other types of fuel cells under relatively high temperatures (600℃ to 800℃). However, the thermal behavior of SOFC stacks at high operating temperatures is a serious issue in SOFC development because it can be associated with detrimental thermal stresses on the life span of the stacks. The thermal behavior of SOFC stacks can be influenced by operating or material properties. Therefore, this work aims to investigate the effects of the thermal conductivity of each component (anode, cathode, and electrolyte) on the thermal behavior of samarium-doped ceria-based SOFCs at intermediate temperatures. Computational fluid dynamics is used to simulate SOFC operation at 600℃. The temperature distributions and gradients of a single cell at 0.7 V under different thermal conductivity values are analyzed and discussed to determine their relationship. Simulations reveal that the influence of thermal conductivity is more remarkable for the anode and electrolyte than for the cathode. Increasing the thermal conductivity of the anode by 50% results in a 23% drop in the maximum thermal gradients. The results for the electrolyte are subtle, with a ~67% reduction in thermal conductivity that only results in an 8% reduction in the maximum temperature gradient. The effect of thermal conductivity on temperature gradient is important because it can be used to predict thermal stress generation.

• 환경영향평가
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• 제25권4호
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• pp.280-295
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• 2016

최근 육류 소비에 의한 환경 영향이 증가하였고, 쇠고기 소비를 줄이는 것은 지속가능한 식량 공급을 위한 대안의 하나이다. 우리나라에서는 지난 50여 년간 쇠고기 소비는 1961년 대비 2009년 약 13배 증가하였고, 쇠고기 소비에 의한 생태발자국(경작지발자국, 초지발자국, 탄소발자국의 합)도 동기간 약 12배 증가하였다. 특히 수입 쇠고기 소비 증가가 1970년 대비 2009년 약 346배, 수입 쇠고기 소비로 인한 생태발자국은 369배로 현저히 증가하였다. 2023년 한국인이 쇠고기 소비를 절반으로 줄이는 경우 쇠고기 소비에 의한 생태발자국은 기준전망치(BAU, Business As Usual) 대비 40~65% 감소하였다. 또한 시나리오별 저감된 생태발자국으로 지탱가능한 인구수를 추정하면, 한국인과 세계평균 소비 수준에 따라 약 57~156만 명의 식량(농작물, 육류, 어류), 화석 에너지, 산림 및 건조환경 부문의 소비를 지탱할 수 있고, 342~683만 명의 농작물 소비를 지탱할 수 있을 것으로 기대된다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 춘계학술발표대회 논문집
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• pp.162-167
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• 2011

Thermal storage plays an important role in building energy saving, which is greatly assisted by the incorporation of latent heat storage in building materials. A phase change material is a substance with a high heat of fusion which, melting and solidifying at a certain temperature, can be storing and releasing large amount of energy. Heat is stored or released when the material changes from solid to liquid. Integration of building materials incorporating PCMs into the building envelope can result in increased efficiency of the built environment. The aim of this research is to identify thermal performance of PCMs impregnated building materials which is applied to interior of building such as gypsum and red clay. In order to analyze thermal performance of phase change materials, test-cell experiments and simulation analysis were carried out. The results show that micro-encapsulated PCM has an effect to maintain a constant indoor temperature using latent heat through the test-cell experiments. PCM wallboard makes it possible to reduce the fluctuation of room temperature and heating and cooling load by using EnergyPlus simulation program. Phase change material can store solar energy directly in buildings. Increasing the heat capacity of a building is capable of improving human comfort by decreasing the frequency of indoor air temperature swings so that the interior air temperature is closer to the desired temperature for a long period of time.

• 한국통신학회논문지
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• 제38C권1호
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• pp.118-130
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• 2013

고속 모바일 네트워크 및 고성능 모바일 디바이스 기반의 새로운 컨텐츠 서비스 제공환경의 도래로, 사용자들은 실생활공간에서 개인화된 정보를 좀 더 효율적으로 제공해 주는 서비스, 즉 엠비언트 서비스를 요구하고 있다. 이와 같은 지속가능한 형태의 엠비언트 서비스를 구현하여 제공하기 위해서는 보편타당한 서비스 구현 및 제공모델에 대한 연구가 필요하다. 본 논문은 실생활 공간에서 사용자에게 효과적으로 엠비언트 서비스를 제공하기 위하여 실생활 공간을 개인화하는 모델을 제안한다. 제안된 개인화 모델은 Public Info-space, Universal Info-space, Private Info-space의 3계층으로 구성되어있으며, 각 정보공간을 현재의 활용 가능한 기술로 구축하는 방법론에 대해서 논의한다. 제안 모델의 구현 가능성을 확보하기 위해 Wireless Mesh Network와 RTLS로 구성된 테스트베드 인프라를 대학 캠퍼스 내에 구축하고 그것을 활용한 엠비언트 서비스 구현 사례로써 길거리 게임에 대해서 설명한다.

• 한국소프트웨어감정평가학회 논문지
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• 제17권2호
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• pp.117-124
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• 2021

가축의 행동 분석은 가축 건강관리와 농업 생산성 증대에 큰 영향을 미치는 요소이다. 그러나 가축의 행동 분석을 위해 도입되는 대부분의 디지털 기기들은 원시 데이터를 제공하지 않으며 분석 결과 또한 제한적으로 제공한다. 이러한 폐쇄적인 시스템은 첨단 IT 기술의 도입에 필수불가결한 데이터 통합과 빅데이터 구축을 더욱 어렵게 한다. 이에 저비용으로 손쉽게 사용할 수 있는 농장 규모의 데이터 수집 장치 보급이 필요하다. 본 연구는 가축의 행동 분석을 위한 데이터 수집 시스템을 제시한다. 이 시스템은 무선으로 동작하는 다수의 초소형 컴퓨팅 유닛으로 구성되어 있으며 이를 통해 가축의 체온과 가속도 데이터, 위치 정보, 축사 환경 데이터를 수집한다. 또한 본 연구에서는 수집된 가속도 데이터를 바탕으로 가축의 행동을 추정하는 알고리즘을 제시한다. 실험을 위해 경기도 이천의 한우 농가에 시스템을 구축하고 20두의 한우에 대해 데이터를 수집하였으며 이를 토대로 실증 및 분석 결과를 제시하였다.

• 국제학술발표논문집
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• The 9th International Conference on Construction Engineering and Project Management
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• pp.967-974
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• 2022

It is no news that Nigeria's infrastructure challenge is enormous. In the global ranking, Nigeria ranked low in quantity and quality of its infrastructural provision which has a great impact on the ease of business transaction. Low investments in transportation have brought about the current infrastructural deficit. Recently, the Nigerian government has made effort to address at least to some extent the infrastructural deficit through Public-Private Partnership, but this has not yielded the desired result. Moreover, the sustainability issues relating to railway projects such as, emissions, noise pollution, ecosystem, and other environmental issues calls for urgent attention. Hence, this necessitated consideration on sustainability appraisal for the Chinese rail project in Nigeria. This study reviews sustainability of railway projects built by the Chinese firm in Nigeria with particular emphasis on the environmental and social impact of these projects. The study further identified issues and challenges in project implementation with a particular focus on civil dialogue and community engagements. A detailed literature search was conducted on railway projects and infrastructure by systematically reviewing selected published articles.The analysis of the selected articles identified sustainability issues and potential for improvement of Chinese railway projects and how they contribute to or inhibit competitiveness in the Nigerian railway market. From the literature searched, some of the projects constructed by Chinese firm revealed that there is economic and social impact of railway projects delivered by the Chinese firm in terms of capacity development and knowledge transfer potentiality. For instance, in the just concluded Lagos-Ibadan railway projects, the study gathered that the project brought about 5000 jobs and local staff were trained by the Chinese company, this will boost man power and local content capability. Also, it will significantly improve Nigeria's infrastructure and boost its economic development. The study suggests that Nigerian government should ensure and provide an enabling environment that is conducive for investment on the continent. Peace, improved security, and decent governance are the best conditions for sustainable transportation growth.

• Computers and Concrete
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• 제32권6호
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• pp.577-594
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• 2023

Engineered cementitious composites with calcined clay limestone cement (LC³-ECC) as a kind of green, low-carbon and high toughness concrete, has recently received significant investigation. However, the complicated relationship between potential influential factors and LC³-ECC compressive strength makes the prediction of LC³-ECC compressive strength difficult. Regarding this, the machine learning-based prediction models for the compressive strength of LC³-ECC concrete is firstly proposed and developed. Models combine three novel meta-heuristic algorithms (golden jackal optimization algorithm, butterfly optimization algorithm and whale optimization algorithm) with support vector regression (SVR) to improve the accuracy of prediction. A new dataset about LC³-ECC compressive strength was integrated based on 156 data from previous studies and used to develop the SVR-based models. Thirteen potential factors affecting the compressive strength of LC³-ECC were comprehensively considered in the model. The results show all hybrid SVR prediction models can reach the Coefficient of determination (R²) above 0.95 for the testing set and 0.97 for the training set. Radar and Taylor plots also show better overall prediction performance of the hybrid SVR models than several traditional machine learning techniques, which confirms the superiority of the three proposed methods. The successful development of this predictive model can provide scientific guidance for LC³-ECC materials and further apply to such low-carbon, sustainable cement-based materials.

• Steel and Composite Structures
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• 제52권2호
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• pp.145-163
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• 2024

This paper presents six novel hybrid machine learning (ML) models that combine support vector machines (SVM), Decision Tree (DT), Random Forest (RF), Gradient Boosting (GB), extreme gradient boosting (XGB), and categorical gradient boosting (CGB) with the Harris Hawks Optimization (HHO) algorithm. These models, namely HHO-SVM, HHO-DT, HHO-RF, HHO-GB, HHO-XGB, and HHO-CGB, are designed to predict the ultimate strength of both rectangular and circular reinforced concrete (RC) columns. The prediction models are established using a comprehensive database consisting of 325 experimental data for rectangular columns and 172 experimental data for circular columns. The ML model hyperparameters are optimized through a combination of cross-validation technique and the HHO. The performance of the hybrid ML models is evaluated and compared using various metrics, ultimately identifying the HHO-CGB model as the top-performing model for predicting the ultimate shear strength of both rectangular and circular RC columns. The mean R-value and mean a20-index are relatively high, reaching 0.991 and 0.959, respectively, while the mean absolute error and root mean square error are low (10.302 kN and 27.954 kN, respectively). Another comparison is conducted with four existing formulas to further validate the efficiency of the proposed HHO-CGB model. The Shapely Additive Explanations method is applied to analyze the contribution of each variable to the output within the HHO-CGB model, providing insights into the local and global influence of variables. The analysis reveals that the depth of the column, length of the column, and axial loading exert the most significant influence on the ultimate shear strength of RC columns. A user-friendly graphical interface tool is then developed based on the HHO-CGB to facilitate practical and cost-effective usage.

• Ecology and Resilient Infrastructure
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• 제6권4호
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• pp.267-276
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• 2019

상주 공검지는 8세기에 축조된 고대 유적 저수지로서 습지보호지역으로 지정되어 있다. 이곳에서 지속가능한 보전 전략을 수립하는데 필요한 기초자료를 수집하기 위하여, 현존 식생을 분류하고 식생도를 작도하며 식생의 구조적 특징을 파악하고 환경과의 관계를 규명하였다. 공검지 습지보호지역에서는 저습지, 하천, 산림, 초지, 농경지, 과수원 식생에 속하는 총 26개 식물군집이 분류되었다. 탈경향대응분석 (detrended correspondence analysis) 결과에 따르면 습지 식생의 구조는 주로 수심과 인간 교란에 따라서 영향을 받았다. 저수지 습지에서는 통발, 마름과 같은 부수식물과 연꽃, 부들류와 같은 정수식물이 수면을 완전히 피복하고 있었다. 2014년 이후에 점차 정수식물과 습생식물의 분포 면적이 늘어나는 육역화가 빠르게 진행되고 있었다. 습지보호지역의 지속가능한 보전과 복원을 위하여, 지형과 식생을 복원하고, 수문 체계를 회복시키며, 습지로부터 산지까지의 생태계 연결성을 회복한 것이 필요하다고 생각된다.