• Steel and Composite Structures
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• 제42권6호
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• pp.805-826
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• 2022

The free and live load-forced vibration behaviour of porous functionally graded (PFG) higher order nanobeams in the thermal and magnetic fields is investigated comprehensively through this work in the framework of nonlocal strain gradient theory (NLSGT). The porosity effects on the dynamic behaviour of FG nanobeams is investigated using four different porosity distribution models. These models are exploited; uniform, symmetrical, condensed upward, and condensed downward distributions. The material characteristics gradation in the thickness direction is estimated using the power-law. The magnetic field effect is incorporated using Maxwell's equations. The third order shear deformation beam theory is adopted to incorporate the shear deformation effect. The Hamilton principle is adopted to derive the coupled thermomagnetic dynamic equations of motion of the whole system and the associated boundary conditions. Navier method is used to derive the analytical solution of the governing equations. The developed methodology is verified and compared with the available results in the literature and good agreement is observed. Parametric studies are conducted to show effects of porosity parameter; porosity distribution, temperature rise, magnetic field intensity, material gradation index, non-classical parameters, and the applied moving load velocity on the vibration behavior of nanobeams. It has been showed that all the analyzed conditions have significant effects on the dynamic behavior of the nanobeams. Additionally, it has been observed that the negative effects of moving load, porosity and thermal load on the nanobeam dynamics can be reduced by the effect of the force induced from the directed magnetic field or can be kept within certain desired design limits by controlling the intensity of the magnetic field.

• 한국농림기상학회지
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• 제19권4호
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• pp.223-231
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• 2017

본 연구는 미래 기후변화 시나리오에 근거하여 예측되는 온도 상승조건에서 노지 월동채소인 극조생 양파 '싱싱볼'의 생육 및 구 비대에 미치는 영향을 확인하고자 온도구배터널에서 수행하였다. 처리구는 대조구인 대기온도(일평균 $9.8^{\circ}C$) 조건, 온도상승구인 대기온도 $+2^{\circ}C$(일평균 $12.0^{\circ}C$)와 대기온도 $+5^{\circ}C$(일평균 $14.3^{\circ}C$) 조건 등 3수준으로 설정하였다. 생육기 온도 상승에 따른 양파의 생육을 조사한 결과, 대조구인 대기온도 조건에 비해 대기온도 $+2^{\circ}C$ 고온조건에서 자라는 양파가 초장도 길었고, 엽초경도 두꺼워졌으며, 총엽면적, 지상부 생체중 및 지상부 건물중이 증가되었다. 양파의 구 특성을 조사한 결과, 구경이나 구중은 생육후기로 갈수록 커지는 경향을 보였고, 대조구에 비해 대기온도 $+2^{\circ}C$ 고온조건에서 구 크기가 더 커지는 경향을 보였다. 구 비대 개시점인 구 비대지수도 대기온도 $+2^{\circ}C$ 고온조건에서는 타 조건에 비해 가장 빠른 경향을 보였다. 이상의 결과로 보아 대기온도보다 $2^{\circ}C$ 상승하였을 때 극조생 양파의 생육이 원활히 진행되고 수량이 증가되고 품질도 유지되겠으나, 대기 온도보다 $5^{\circ}C$ 이상 고온조건에서는 수량이 감소될 것으로 예측된다.

• Journal of Microbiology and Biotechnology
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• 제19권12호
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• pp.1656-1664
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• 2009

Bioaugmentation of bioreactors focuses on the removal of numerous organics, with little attention typically paid to the maintenance of high and stable nitrite accumulation in partial nitrification. In this study, a bioaugmented membrane bioreactor (MBR) inoculated with enriched ammonia-oxidizing bacteria (AOB) was developed, and the effects of dissolved oxygen (DO) and temperature on the stability of partial nitrification and microbial community structure, in particular on the nitrifying community, were evaluated. The results showed that DO and temperature played the most important roles in the stability of partial nitrification in the bioaugmented MBR. The optimal operation conditions were found at 2-3 mgDO/l and $30^{\circ}C$, achieving 95% ammonia oxidization efficiency and nitrite ratio ($NO_2^-/{NO_x}^-$) of 0.95. High DO (5-6 mg/l) and low temperature ($20^{\circ}C$) had negative impacts on nitrite accumulation, leading to nitrite ratio drop to 0.6. However, the nitrite ratio achieved in the bioaugmented MBR was higher than that in most previous literatures. Denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH) were used to provide an insight into the microbial community. It showed that Nitrosomonas-like species as the only detected AOB remained predominant in the bioaugmented MBR all the time, and coexisted with numerous heterotrophic bacteria. The heterotrophic bacteria responsible for mineralizing soluble microbial products (SMP) produced by nitrifiers belonged to the Cytophaga-Flavobacterium-Bacteroides (CFB) group, and $\alpha$-, $\beta$-, and $\gamma$- Proteobacteria. The fraction of AOB ranging from 77% to 54% was much higher than that of nitrite-oxidizing bacteria (0.4-0.9%), which might be the primary cause for the high and stable nitrite accumulation in the bioaugmented MBR.

• 한국작물학회지
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• 제56권3호
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• pp.255-263
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• 2011

Projected increases in atmospheric $CO_2$ concentration ([$CO_2$]) and temperature ($T_a$) have the potential to alter in rice growth and yield. However, little is known about whether $T_a$ warming with elevated [$CO_2$] modify plant architecture. To better understand the vertical profiles of leaf area index (LAI) and the flag leaf morphology of rice grown under elevated $T_a$ and [$CO_2$], we conducted a temperature gradient field chamber (TGC) experiment at Gwangju, Korea. Rice (Oryza sativa L. cv. Dongjin1ho) was grown at two [$CO_2$] [386 (ambient) vs 592 ppmV (elevated)] and three $T_a$ regimes [26.8 ($\approx$ambient), 28.1 and $29.8^{\circ}C$] in six independent field TGCs. While elevated $T_a$ did not alter total LAI, elevated [$CO_2$] tended to reduce (c. 6.6%) the LAI. At a given canopy layer, the LAI was affected neither by elevated [$CO_2$] nor by elevated $T_a$, allocating the largest LAI in the middle part of the canopy. However, the fraction of LAI distributed in a higher and in a lower layer was strongly affected by elevated $T_a$; on average, the LAI distributed in the 75-90 cm (and 45-60 cm) layer of total LAI was 9.4% (and 35.0%), 18.8% (25.9%) and 18.6% (29.2%) in ambient $T_a$, $1.3^{\circ}C$ and $3.0^{\circ}C$ above ambient $T_a$, respectively. Most of the parameters related to flag leaf morphology was negated with elevated [$CO_2$]; there were about 12%, 5%, 7.5%, 15% and 21% decreases in length (L), width (W), L:W ratio, area and mass of the flag leaf, respectively, at elevated [$CO_2$]. However, the negative effect of elevated [$CO_2$] was offset to some extent by $T_a$ warming. All modifications observed were directly or indirectly associated with either stimulated leaf expansion or crop phenology under $T_a$ warming with elevated [$CO_2$]. We conclude that plant architecture and flag leaf morphology of rice can be modified both by $T_a$ warming and elevated [$CO_2$] via altering crop phenology and the extent of leaf expansion.

• 해양환경안전학회지
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• 제22권4호
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• pp.362-371
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• 2016

섬진강 하구역에서 염분경사에 따른 유색용존유기물(CDOM)의 농도와 특성을 시공간적으로 이해하기 위해 2012년 건기(3월과 6월)와 우기(7월)에 분포특성을 조사하고, 환경요인(수온, 염분)과 영양염, 엽록소와의 상관관계를 고찰하였다. 유색용존유기물의 평균농도는 각각 $1.0{\pm}0.3m^{-1}$(3월), $1.3{\pm}0.4m^{-1}$(6월), $1.4{\pm}0.3m^{-1}$(7월)로 측정되었다. 섬진강 상류의 높은 유색용존유기물 농도(> $1.5m^{-1}$)는 하류로 갈수록 감소(< $0.5m^{-1}$)하였고, 우기에 건기의 평균값에 비해 증가하였다. 또한 유색용존유기물의 화학적 특성과 공급원에 대한 지시자로 사용되는 평균값 $S_{300-500}$은 $0.013{\sim}0.018nm^{-1}$로, 건기에 비해 우기에 높은 값을 나타내었다. 유색용존유기물과 염분은 역상관계를 보였고($R^2$ > 0.8), 우기와 건기 모두 보존성 혼합의 양상을 보였다. 유색용존유기물은 강 하류로 갈수록 해수와 혼합되는 과정에 의해 희석되고, 그 특성 또한 뚜렷한 변화를 보이는 것을 확인하였다. 환경 조건 중 유색용존유기물의 변동에 영향을 주는 주요한 요인은 염분 (혼합)과 온도로 확인되었으며, 전자는 낮은 유색용존유기물 농도의 해수와의 혼합에 의한 희석으로 주로 공간적인 변동을 조절하는 것으로 보였고, 온도의 증가는 유색용존유기물의 생산에 영향을 주는 미생물학적 활동과 광분해에 통한 작용으로 유추된다.