• 생태와환경
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• 제46권1호
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• pp.75-85
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• 2013

이 연구는 경안천 토양에서 기후 조건의 차이, 식물의 유무, 질소 농도의 차이에 따른 토양의 생물학적 유기물 분해속도의 변화가 대기 중 온실가스($CH_4$, $CO_2$) 발생에 미치는 영향을 알아보고자 하였다. 본 연구 결과, 유기물 분해속도와 $CH_4$, $CO_2$ flux 모두 환경 조건이 동시에 변화하는 경우에 영향을 받음을 알 수 있었다. 유기물 분해 속도는 기후 조건의 차이와 질소농도의 차이, 기후 조건 차이와 식물의 유무가 있는 경우에 영향을 받음을 알 수 있었다. $CH_4$ flux는 기후 조건 차이와 질소 농도의 차이, 기후 조건 차이와 식물의 유무, 식물의 유무와 질소 농도의 차이가 있는 경우에 영향이 있었으며 $CO_2$ flux는 기후 조건 차이와 식물의 유무, 식물의 유무와 질소 농도의 차이가 있는 경우에 영향이 있음을 통해 기후 조건 차이와 식물의 유무, 질소 농도의 차이가 유기물 분해속도에 영향을 주어 대기 중 온실가스 발생에 영향을 줄 수 있음을 알 수 있었다. 기후 조건 차이는 토양의 분해를 증진시켜 대기로 방출되는 온실가스 또한 가중시킬 수 있다고 알려져 있으나, 본 연구를 통해 기후변화가 유기물의 분해와 대기로의 온실가스 방출을 감소시킬 수 있다는 결과를 도출할 수 있었으며 기후 조건 차이 외의 질소가 유입될 경우, 순영향(positive effect)을 주게 됨을 알 수 있었다. 그러나 식물의 영향이 작용할 경우 질소의 유입으로 인한 순영향을 감소시킬 수 있음을 알 수 있었으며, 이에 따른 추가적인 연구가 필요할 것으로 판단된다.

• 한국물환경학회지
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• 제35권4호
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• pp.316-331
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• 2019

Carbon dioxide($CO_2$) emission from rivers to the atmosphere is a key component in the global carbon cycle. Most of the rivers are supersaturated with $CO_2$. At a global scale, the amount of $CO_2$ emission from rivers is reported to be five-fold greater than that from lakes and reservoirs, but relevant data are rare in Korea. The objectives of this study is to estimate the $CO_2$ net atmospheric flux(NAF) from the upstream of Gangjeong-Goryeong Weir(GGW), Dalseong Weir(DSW), Hapcheon-Changnyeong Weir(HCW), and Changnyeong-Haman Weir(CHW) located in Nakdong River South Korea) using field and laboratory experiments and to apply data mining techniques to develop parsimonious prediction models that can be used to estimate $CO_2$ NAF with physical and water quality variables that can be collected easily. As a result, the study sites were all heterotrophic systems that often released $CO_2$ to the atmosphere, except when the algal photosynthesis was active.The median $CO_2$ NAF was minimum $391.5mg-CO_2/m^2$ day at GGW and maximum $1472.7mg-CO_2/m^2$ day at DSW. The $CO_2$ NAF showed a negative correlation with pH and Chl-a since the overgrowth of the algae consumed $CO_2$ in the water and increased the pH. As the parsimonious multiple regression model and random forest model developed, this study showed an excellent performance with the $Adj.R^2$ value higher than 0.77 in all weirs. Thus, these methods can be used to estimate $CO_2$ NAF in the river even if there is no $pCO_2$ measurement data.

• 한국환경과학회지
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• 제25권10호
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• pp.1349-1368
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• 2016

Concentrations of fine particulate matter ($PM_{2.5}$) and several of its particle constituents measured outside homes in Houston, Texas, and Los Angeles, California, were characterized using multiple regression analysis with proximity to point and mobile sources and meteorological factors as the independent variables. $PM_{2.5}$ mass and the concentrations of organic carbon (OC), elemental carbon (EC), benzo-[a]-pyrene (BaP), perylene (Per), benzo-[g,h,i]-perylene (BghiP), and coronene (Cor) were examined. Negative associations of wind speed with concentrations demonstrated the effect of dilution by high wind speed. Atmospheric stability increase was associated with concentration increase. Petrochemical source proximity was included in the EC model in Houston. Area source proximity was not selected for any of the $PM_{2.5}$ constituents' regression models. When the median values of the meteorological factors were used and the proximity to sources varied, the air concentrations calculated using the models for the eleven $PM_{2.5}$ constituents outside the homes closest to influential highways were 1.5-15.8 fold higher than those outside homes furthest from the highway emission sources. When the median distance to the sources was used in the models, the concentrations of the $PM_{2.5}$ constituents varied 2 to 82 fold, as the meteorological conditions varied over the observed range. We found different relationships between the two urban areas, illustrating the unique nature of urban sources and suggesting that localized sources need to be evaluated carefully to understand their potential contributions to $PM_{2.5}$ mass and its particle constituents concentrations near residences, which influence baseline indoor air concentrations and personal exposures. The results of this study could assist in the appropriate design of monitoring networks for community-level sampling and help improve the accuracy of exposure models linking emission sources with estimated pollutant concentrations at the residential level.

• 한국농공학회논문집
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• 제63권6호
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• pp.117-129
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• 2021

The movement of animals is one of the primary factors that influence the variation of livestock emissions. This study evaluated the relationship between animal activity and three major emissions, PM₁₀, PM_2.5, and ammonia gas, in weaning, growing, and fattening pig houses through continuous monitoring of the animal activity. The movement score of animals was quantified by the developed image analysis algorithm using 10-second video clips taken in the pig houses. The calculated movement scores were validated by comparison with six activity levels graded by an expert group. A comparison between PMs measurement and the movement scores demonstrated that an increase of the PMs concentrations was obviously followed by increased movement scores, for example, when feeding started. The PM₁₀ concentrations were more affected by the animal activity compared to the PM_2.5 concentrations, which were related to the inflow of external PM_2.5 due to ventilation. The PM₁₀ concentrations in the fattening house were 1.3 times higher than those in the weaning house because of the size of pigs while weaning pigs were more active and moved frequently compared to fattening pigs showing 2.45 times higher movement scores. The results also indicated that indoor ammonia concentration was not significantly influenced by animal activity. This study is significant in the sense that it could provide realistic emission factors of pig farms considering animal's daily activity levels if further monitoring is carried out continuously.

• 전기전자학회논문지
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• 제21권2호
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• pp.123-129
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• 2017

고분자 막 연료전지는 높은 전력밀도, 낮은 배출 및 낮은 동작온도 때문에 미래 자동차 및 전력생산의 강력한 보류이다. FEMFC 내부의 기체확산층(GDL)의 중요한 관심은 물의 조절이다. GDL은 소수성 PTFE와 전기전도성을 위해서 탄소로 보통 구성되어 있다. 이 시뮬레이션에서 GDL 흐름은 확립된 방정식 모델의 단순화된 접근법으로 조사되었다. GDL의 성능은 모델 방정식을 이용하여 전지의 내부열, 수증기 밀도 와 산소밀도의 결과를 보였다. FEMFC 촉매층 모델은 유효인자, Butler-volmer 와 수소유동 밀도의 결과를 나타냈다. 이 결과들은 몇 가지 요소들과 함께 영향의 차이는 흥미 가지게 되며 정보는 연료전지를 설계하는데 도움을 줄 것이다.

• International Journal of Advanced Culture Technology
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• 제3권1호
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• pp.1-12
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• 2015

The current scenario of the transportation sector reflects the urgent need to address issues such as depletion of traditional fuel reserves and ever growing pollution levels. Researchers around the world are focussing on alternatives as well as optimisation of currently employed devices to reduce the pollution levels generated by the commonly used fuels. One such optimisation involves the study of air flow within the intake manifolds of SI engines. It is a well-known fact that alterations in the air manifolds of engines have a significant impact on the engine performance parameters, fuel consumption and emission levels. Previous works have demonstrated the impacts of runner lengths, diameter, plenum volume, taper angle of distribution manifolds and other factors on in-cylinder fluid motion and engine performance. However, a static setup provides an optimal configuration only at a specific engine speed. This paper aims to investigate the variations in the same parameters on a four stroke, naturally aspirated single cylinder SI engine through varying the cross section design over the intake runner with the aid of Computational Fluid Dynamics. The system consists of segments that form the intake runner with projections on the inside that allow various permutations of the intake runner segments. The various configurations provide the optimised fluid flow characteristics within the intake manifold at specific engine speed intervals. The variations such as turbulence, air fuel mixing are analysed using the three dimensional CFD software FLUENT. The results can be used further for developing an automated or manually adjustable intake manifold.

• 한국산업정보학회논문지
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• 제25권2호
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• pp.115-127
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• 2020

본 연구에서는 모바일폰의 생산, 유통 및 사용 후 처리과정을 효율적으로 관리하기 위한 지속가능한 폐쇄루프 공급망 (Sustainable close-loop supply chain: SCLSC) 모델을 제안한다. 제안된 SCLSC모델의 지속가능성 (Sustainability)을 강화하기 위해 경제적 요인인 총이익 최대화, 환경적 요인인 총 CO2 방출량 최소화, 사회적 요인인 사회적 영향력 최대화를 각각 고려하였다. 이들 세 가지의 요인은 제안된 SCLSC모델의 수리화 모델링 과정에서 목적함수로 표현된다. 따라서 제안된 SCLSC모델은 다목적 최적화 (Multi-objective optimization) 문제로 고려될 수 있으며, 이를 해결하기 위해 혼합유전알고리즘 (Hybrid genetic algorithm: HGA) 접근법을 사용하였다. 수치실험에서는 세가지 상이한 규모의 SCLSC모델을 제시하고, 이를 다양한 수행도 척도들을 사용하여 HGA 접근법의 우수성을 확인하였다.

• Advances in materials Research
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• 제8권1호
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• pp.47-73
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• 2019

Joining of Mg/Ti hybrid structures by welding for automotive and aerospace applications has attracted great attention in recent years due mainly to its potential benefit of energy saving and emission reduction. However, joining them has been hampered with many difficulties due to their physical and metallurgical incompatibilities. Different joining processes have been employed to join Mg/Ti, and in most cases in order to get a metallurgical bonding between them was the use of an intermediate element at the interface or mutual diffusion of alloying elements from the base materials. The formation of a reaction product (in the form of solid solution or intermetallic compound) along the interface between the Mg and Ti is responsible for formation of a metallurgical bond. However, the interfacial bonding achieved and the joints performance depend significantly on the newly formed reaction product(s). Thus, a thorough understanding of the interaction between the selected intermediate elements with the base metals along with the influence of the associated welding parameters are essential. This review is timely as it presents on the current paradigm and progress in welding and joining of Mg/Ti alloys. The factors governing the welding of several important techniques are deliberated along with their joining mechanisms. Some opportunities to improve the welding of Mg/Ti for different welding techniques are also identified.

• 농업과학연구
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• 제48권4호
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• pp.655-668
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• 2021

The present study was conducted to investigate the effects of the supplementation of Achyranthes japonica extract (AJE) on overall performance levels with different nutrition concentrations in the diets of finishing pigs. Here, 140 finishing pigs with initial body weights of 50.18 ± 2.37 kg were used in a ten-week trial involving a 2 × 2 factorial design in two phases with the following factors: diet types with different nutrition concentrations (Positive control [PC] vs. Negative control [NC]) and 0 or 0.05% AJE supplementation to NC and PC diets. The PC diet was a basal diet, whereas the NC diet consisted of a 5% and 7% crude protein (CP) reduced basal diet during phase 1 (1 - 35 days) and phase 2 (36 - 70 days), respectively. A significant effect (p < 0.05) on the gain-to-feed ratio (G : F) was observed with interaction effects between the diets and AJE supplementation. However, during phase 1 and in all periods, the pigs fed the PC and NC diets with average daily feed intake (ADFI) tended to decrease compared to those fed diets with AJE. A significant effect (p = 0.0380) of E. coli was observed in pigs fed the PC and NC diets compared to AJE supplementation in phase 2 of the experiment. The backfat thickness (BFT) tended to decrease and the lean meat percentage (LMP) was significantly improved in phase 2 for pigs fed the PC and NC diets. In summary, BFT and LMP showed beneficial effects and fecal microbiota of E. coli counts were positively affected when pigs were fed diets with different nutrient concentrations.

• 한국구조물진단유지관리공학회 논문집
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• 제19권2호
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• pp.33-39
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• 2015

최근 급속한 기후변화 및 광범위한 사회간접시설의 개발 등으로 인해 사면붕괴가 곳곳에서 발생하고 있으며, 이에 대한 모니터링 및 예방시스템 구축에 대한 사회적인 관심이 증가하고 있는 상태이다. 사면붕괴 메카니즘에 영향을 미치는 중요한 영향인자는 지표내 수분 및 온도이며 이에 대한 변화 추이를 통해 사면붕괴를 예측할 수 있다. 따라서, 사면붕괴 모니터링을 위해서는 지표 깊이별 온도 및 함수비를 연속적으로 측정할 수 있는 복합센싱 기법이 필요하다고 볼 수 있다. 현재까지 온도 및 함수비에 대해 각각의 계측이 가능한 개별 센서는 다양하게 개발되어 있는 상태이지만, 온도 및 함수비를 동시에 연속적으로 측정할 수 있는 복합계측 시스템의 경우에는 많은 연구가 필요한 상태이다. 본 논문에서는 전류소모가 최소화된 측온 회로와 고주파 신호를 토양에 방사하는 수분 측정 센서를 적용한 고정밀 온도-함수비 복합센서를 개발하여 효율적이고 정확도를 향상시킨 사면붕괴 모니터링 시스템에 적용할 수 있도록 하였다. 개발된 복한센서의 성능검증을 위하여 기본성능 표준시험, 실내검증실험, 현장장기실험 등의 다양항 실험적 연구를 수행하였으며, 실험결과를 통해 개발된 복합센서를 이용한 모니터링 시스템은 지반의 온도 및 함수비를 정확하게 모니터링할 수 있는 것으로 나타났다.