• Wind and Structures
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• 제22권4호
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• pp.477-501
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• 2016

Though hilly topography influences both wind speeds and directions aloft, only the influence on wind speeds, i.e. the speed-up effect, has been thoroughly investigated. Due to the importance of a model showing the spatial variations of wind directions above hilly terrains, it is worthwhile to systematically assess the applicability and limitations of the model describing the influence of hilly topographies on wind directions. Based on wind-tunnel test results, a model, which describes the horizontal and vertical variations of the wind directions separately, has been proposed in a companion paper. CFD (Computational Fluid Dynamics) techniques were employed in the present paper to evaluate the applicability of the proposed model. From the investigation, it has been found that the model is acceptable for describing the vertical variation of wind directions by a shallow hill whose primary-to-secondary axis ratio (aspect ratio) is larger than 1. When the overall hill slope exceeds $20^{\circ}$, the proposed model should be used with caution. When the aspect ratio is less than 1, the proposed model is less accurate in predicting the spatial variation of wind directions in the wake zone in a separated flow. In addition, it has been found that local slope of a hill has significant impact on the applicability of the proposed model. Specifically, the proposed model is only applicable when local slope of a hill varies gradually from 0 (at the hill foot) to the maximum value (at the mid-slope point) and then to 0 (at the hill top).

• Asian-Australasian Journal of Animal Sciences
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• 제25권7호
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• pp.1009-1014
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• 2012

Environmental stress boosts the levels of stress hormones and accelerates energy expenditure which subsequently imbalance the body's homeostasis. L-ascorbic acid (L-AA) has been recognized to mitigate the negative impact of environmental stress on production performances in birds. The present investigation was carried out to elucidate the effect of different dietary levels of L-AA on production performance, egg quality traits and fertility in Japanese quail at low ambient temperature. Sixty matured females (15 wks) were equally divided into three groups (20/group) based on the different dietary levels of L-AA (0, 250 and 500 ppm) and coupled with an equal number of males (1:1) obtained from the same hatch. They were managed in uniform husbandry conditions without restriction of feed and water at 14 h photo-schedule. Except for feed efficiency, body weight change, feed consumption and hen-day egg production were recorded highest in 500 ppm L-AA supplemented groups. Among the all egg quality traits studied, only specific gravity, shell weight and thickness differed significantly (p<0.05) in the present study. Fertility was improved significantly ($p{\leq}0.01$) to a dose dependent manner of L-AA. The findings of the present study concluded that dietary L-AA can be a caring management practice at least in part to alleviate the adverse effect of cold induced stress on production performance in Japanese quail.

• 한국전자통신학회논문지
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• 제13권1호
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• pp.213-220
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• 2018

하천부유쓰레기 관련 조사 및 정책은 수거나 처리비용에 초점이 맞춰져있으며, 부유쓰레기로 인한 수환경 오염에 대한 평가는 진행되지 않았다. 이에 본 연구에서는 부산광역시에 위치한 낙동강 유역(금곡, 호포)의 부유쓰레기 집적구간에 대한 수환경 오염 조사를 진행하였다. 수질조사 결과 부유쓰레기 상습 정체 구간이 비정체 구간에 비해 낮은 DO 농도를 나타냈으며, COD와 Chl-a는 유사한 농도를 나타냈다. 상습 정체 구간에 약 3달간 부유 상태로 둔 포집조사 결과 절지동물문이 가장 많은 종(4종)이 출현하였으며, 깔따구류(Chironomidae sp.)가 우점하는 것으로 나타났다. 또한 질적 저하에 대한 내성이 강하며, 유속이 느리고 정체된 수역에서 주로 블루길(Lepomis macrochirus)이 출현하였다.

• 해양환경안전학회지
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• 제21권5호
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• pp.492-500
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• 2015

본 논문에서는 새만금 개발사업이 해양환경에 미치는 영향에 대한 국민들의 인식을 분석하였다. 이를 위해 새만금 인근지역인 전북 군산시, 김제시, 부안군 400가구 및 새만금 인근지역 외 전국 600가구 등 총 1,000가구를 대상으로 설문조사를 수행하여 얻은 결과를 분석하였다. 또한 새만금 개발사업의 경제적 효과 및 해양환경 영향을 동시에 고려할 때 새만금 개발사업에 대해 판단하는 공공의 태도에 영향을 미치는 요인을 분석하기 위해 서열프로빗 모형을 적용한 통계적 분석을 수행하였다. 인식조사 결과, 새만금 개발사업의 경제적 효과와 해양환경 영향을 동시에 고려할 때, 새만금 인근지역조사 및 전국조사 응답자의 70 % 이상이 새만금 개발사업을 반대하였다. 또한 설문조사 응답자의 90 % 이상이 새만금 방조제 외해역의 해양환경관리가 필요하다고 인식하고 있었다. 따라서 새만금 방조제 외해역 환경관리를 위한 적절한 대책이 마련되어야 할 것이다.

• 천문학회지
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• 제52권5호
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• pp.181-205
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• 2019

There is evidence that the luminosities of Type Ia supernova (SN Ia) depend on their environments. While the impact of this trend on estimating cosmological parameters is widely acknowledged, the origin of this correlation is still under debate. In order to explore this problem, we first construct the YONSEI (YOnsei Nearby Supernova Evolution Investigation) SN catalog. The catalog consists of 1231 spectroscopically confirmed SNe Ia over a wide redshift range (0.01 < z < 1.37) from various SN surveys and includes light-curve fit data from two independent light-curve fitters, SALT2 and MLCS2k2. For a sample of 674 host galaxies, we use the stellar mass and the star formation rate data in Kim et al. (2018). We find that SNe Ia in low-mass and star-forming host galaxies are $0.062{\pm}0.009mag$ and $0.057{\pm}0.010mag$ fainter than those in high-mass and passive hosts, after light-curve corrections with SALT2 and MLCS2k2, respectively. When only local environments of SNe Ia (e.g., locally star-forming and locally passive) are considered, this luminosity difference increases to $0.081{\pm}0.018mag$ for SALT2 and $0.072{\pm}0.018mag$ for MLCS2k2. Considering the significant difference in the mean stellar population age between the two environments, this result suggests that the luminosity evolution of SNe Ia with redshift is most likely the origin of the environmental dependence.

• 한국터널지하공간학회 논문집
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• 제24권3호
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• pp.293-304
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• 2022

최근 국내·외에서 지하도로 및 장대터널의 계획 및 시공으로 인해 설치 빈도가 증가하고 있는 터널 환기탑관련 설치기준에 대한 조사 및 분석, 국내 및 해외의 터널에 대한 환기탑 설치사례분석을 통해 시사점 및 개선점을 고찰하였다. 검토 결과 환기탑위치 및 높이선정 시 오염물질 배출로 인한 환경영향성, 주변 경관과 조화로운 배치, 지상부지의 효율적인 활용 등을 고려하여 주민과의 협의과정 등을 통해 최종 환기탑의 형식을 확정하는 것이 합리적일 것으로 판단된다. 또한, 설계단계에서부터 주변지형과의 자연스런 조화 및 민원방지를 위해 대기질 시뮬레이션을 통한 환기탑 높이 축소 등에 대한 상세한 검토가 필요할 것으로 판단된다.

• Structural Engineering and Mechanics
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• 제85권2호
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• pp.275-287
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• 2023

The use of environmental-friendly building materials is becoming increasingly popular worldwide. Compared to the normal concrete, rubber-based concrete is considered more durable, environmentally friendly, socially and economically viable. In this investigation, M20 grade concrete was designed and the fine aggregates were replaced with crumb rubber of two different micron sizes (0.221 mm and 0.350 mm). Fly ash (FA) and silica fume (SF) replaces the binder as supplementary cementitious materials at a rate of 0, 5, 10, 15, and 20% by weight. The mechanical properties of concrete including compressive strength, tensile, and flexural strength were determined. The polynomial work expectation validates the response surface approach (RSM) concept for optimizing SF and FA substitution. The maximum compressive strength (22.53 MPa) can be observed for the concrete containing 10% crumb rubber, 15% fly ash and 15% silica fume. The reduced unit weight of the rubberized concrete may be attributed to the lower specific gravity of the rubber particles. Two-way ANOVA with a significance criterion of less than 0.001 has been utilized with modest residual error from the lack of fit and the pure error. The predictive model accurately forecasts the variable-response relationship. Since, the crumb rubber is obtained from wasted tires incorporating FA and SF as a cementitious ingredient, it helps to significantly improve mechanical properties of concrete and reduce environmental degradation.

• Advances in aircraft and spacecraft science
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• 제9권3호
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• pp.195-215
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• 2022

The increasing interest in CubeSat platforms ant their capability of enlarging the frontier of possible missions impose technology improvements. Miniaturized electrical propulsion (EP) systems enable new mission for multi-unit CubeSats (6U+). While electric propulsion systems have achieved important level of knowledge at equipment level, the investigation of the mutual impact between EP system and CubeSat technology at system level can provide a decisive improvement for both the technologies. The interaction between CubeSat and EP system should be assessed in terms of electromagnetic emissions (both radiated and conducted), thermal gradients, high electrical power management, surface chemical deposition, and quick and reliable data exchanges. This paper shows how a versatile CubeSat Test Platform (CTP), together with standardized procedures and specialized facilities enable the acquisition fundamental and unprecedented information. Measurements can be taken both by specific ground support equipment placed inside the vacuum facility and by dedicated sensors and subsystems installed on the CTP, providing a completely new set of data never obtained before. CTP is constituted of a 6U primary structure hosting the EP system, representative CubeSat avionics and batteries. For the first test campaign, CTP hosts the ambipolar plasma propulsion system, called Regulus and developed by T4I. After the integration and the functional test in laboratory environment, CTP + Regulus performed a Test campaign in relevant environment in the vacuum chamber at CISAS, University of Padua. This paper is focused on the test campaign description and the main results achieved at different power levels for different duration of the firings.

• 대한토목학회논문집
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• 제26권1B호
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• pp.1-6
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• 2006

낙동강, 섬진강, 영산강, 그리고 금강 권역의 충적 대수층에서 해안선을 통하여 바다로 유출되는 지하수 해안유출량이 평가되었다. 증반산, 하천 유출과 같은 수문학적 주요 인자와 양적으로 비교하면 지하수 해안유출량은 상대적으로 많은 양이 아니다. 하지만 수문순환 과정에서 최하류라는 특징에 의하여 지하수 해안 유출의 개발은 환경적인 영향을 상대적으로 적게 받으며, 현재 물 부족으로 어려움을 겪고 있는 많은 해안지역에서 유용하게 사용될 수 있는 중요한 수자원이다. 유출량 평가를 위하여 기 조사된 지하수위 조사 자료와 Darcy의 법칙에 기반을 둔 평가방법을 이용하였다. 주요 변수의 산정에는 해안선의 복잡성과 해수쐐기의 영향을 고려할 수 있는 기술을 적용하였다. 연구결과 조사 대상 4개 하천 권역의 지하수 해안 유출량은 연간 18억$m^3$에 달하는 것으로 나타났다. 이는 권역별 강수총량의 2.3%에 이르는 수치이다. 지하수 개발 측면에서 는 낙동강 권역이 가장 유리한 것으로 나타났다.

• 한국환경과학회지
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• 제33권1호
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• pp.27-41
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• 2024

In this study, we evaluated productivity, soil physiochemical properties, and soil microbial characteristics in Kimchi cabbage(Brassica rapa subsp. pekinensis) cultivation within a highland environment during summer. Specifically, we examined the effect of different cropping systems, namely monoculture and rotation with soybean, over an 8-year cropping period. The results of our investigation revealed that significant differences were absent in terms of yield and soil physiochemical properties between the two cropping systems. However, microbial characteristics exhibited distinctive patterns. Bacterial diversity was significantly higher in the rotation system that in the monoculture, whereas fungal diversity demonstrated a preference for rotation although the result was not significant. Our findings identified the presence of Bradyrhizobium stylosanthis, a nitrogen-fixation symbiont, as an indicator ASV (amplicon sequence variant) in the rotation system, where it displayed significantly higher abundances. These observations suggest a potential positive effect of the rotation system on nitrogen fixation. Notably, throughout the cultivation period, both cropping systems did not exhibit critical disease incidences. However, Fusarium oxysporum, a well-known pathogen responsible for inducing fusarium wilt disease in Kimchi cabbage, was detected with significantly higher abundance in the monoculture system. This finding raises concerns about the potential risk associated with Kimchi cabbage cultivation in a long-term monoculture system.