• Korean Journal of Agricultural and Forest Meteorology
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• v.16 no.1
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• pp.22-28
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• 2014

This study was conducted to investigate the photosynthetic characters of Populus alba${\times}$glandulosa cuttings in response to elevated $CO_2$ concentration and air temperature for selecting tree species adaptive to climate change. The cuttings were grown in environment controlled growth chambers with two combinations of $CO_2$ concentration and air temperature conditions: (i) $22^{\circ}C$ + $CO_2$ 380 ${\mu}mol$ $mol^{-1}$ (control) and (ii) $27^{\circ}C$ + $CO_2$ 770 ${\mu}mol$ $mol^{-1}$ (elevated) for almost three months. The cuttings under the elevated treatment showed reduced tree height and photosynthetic pigment contents such as chlorophyll and carotenoid. In particular, the elevated treatment resulted in a marked reduction in the chlorophyll a closely associated with $CO_2$ fixative reaction system. Different levels of reduction in photosynthetic characters were found under the elevated treatment. A decrease was noted in photochemical reaction system parameters: net apparent quantum yield (7%) and photosynthetic electron transport rate (14%). Moreover, a significant reduction was obvious in $CO_2$ fixative reaction system parameters: carboxylation efficiency (52%) and ribulose-1,5-bisphosphate(RuBP) regeneration rate (24%). These results suggest that the low level of photosynthetic capacity may be attributed to the decreased $CO_2$ fixative reaction system rather than photochemical reaction system.

• Korean Journal of Environmental Biology
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• v.23 no.1
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• pp.64-70
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• 2005

To investigate the synergistic effects of low dose gamma irradiation and growth regulators on the growth and photosynthesis in rice (Oryza sativa L.), laboratory and greenhouse experiments were conducted using 4-year-old rice seeds. In the laboratory experiment, the germination rate was increased in 0.001 ppm IBA treatment, showing the synergistic effect of gamma irradiation and growth regulators. The seedling growth was increased by treatment of GA₃ and IBA, the irradiated groups having higher than the non-irradiated ones. Particularly, it was remarkable in 0.001 ppm IBA. In greenhouse experiment, seedling growth was increased in response to a combination of gamma irradiation and 0.001 ppm IBA. Effective quantum yield of PSⅡ(Ф/sub PSⅡ/) and photochemical quenching (qP) were increased, while non-photochemical quenching (qN) was decreased by 0.001 ppm IBA. A synergistic effect of gamma irradiation and IBA was only found in seedling growth. The present results suggest that low dose gamma irradiation and growth regulator could synergistically stimulate seedling growth.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.2
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• pp.79-89
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• 2012

This study was conducted to investigate the chlorophyll contents, photosynthetic characteristics, chlorophyll fluorescence, and growth performance of Parasenecio firmus under changing light environment. Parasenecio firmus was grown under non-treated (full sunlight) and three different shading conditions (88~93%, 65~75% and 45%~55% of full sunlight) for the experiment. Total chlorophyll content, photochemical efficiency (Fv/Fm), T/R ratio, specific leaf area (SLA), leaf area ratio (LAR), and leaf weight ratio (LWR) were increased with increasing shading level, but decreased dark respiration. Therefore, light absorption and light utilization efficiency were improved under the low intensity light. Plants under 65~75% of full sunlight had best maximum photosynthetic rate and net apparent quantum yield in May. On the other hand, the non-treated plants had lower maximum photosynthetic rate, photochemical efficiency, and chlorophyll content than the treated ones. Parasenecio firmus considered to be a sciophyte, is fairly sensitive to high intensity light. If 88-93% of full sunlight lasts for a long period, photosynthetic capacity will be sharply decreased, though limiting light. These results suggest that growth of Parasenecio firmus adapted to 65~75% of full sunlight.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.315-315
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• 2010

결정질 실리콘을 포함하는 태양전지의 광전효율은 표면에 입사되는 태양광의 반사를 제외하면 흡수된 광자에 의해 생성되는 전자-정공쌍의 상대적인 비율인 내부양자효율에 의존하게 된다. 실제 생성된 전자-정공쌍은 기판재료의 결정상태와 전기광학적 물성 등에 의해 일부가 재결합되어 2차적인 광자의 생성이나 열로서 작용하고 최종적으로 전자와 정공이 완전히 분리되고 전극에 포집되어 실질적인 유효전류로 작용한다. 16% 이상의 고효율 결정질 실리콘 태양전지양산이 요구되고 있는 현실에서 광전효율 개선 위해 가장 우선적으로 고려되어야 할 변수는 입력 태양광스펙트럼에 대한 결정질 실리콘 표면반사율을 최소화하여 광흡수를 극대화하는 것이라 할 수 있다. 이의 해결을 위하여 대기와 실리콘표면 사이의 굴절률차이가 크면 클수록 태양광스펙트럼에 대한 결정질 실리콘의 광반사는 증가하기 때문에 상대적으로 낮은 굴절률의 $SiO_x$나 $SiN_x$와 같은 반사방지막을 광입력 실리콘표면에 증착하여 광반사율 저감공정을 적용하고 있다. 이와 더불어 결정질 실리콘표면을 화학적으로 혹은 플라즈마이온으로 50-100nm 직경의 바늘형 피라미드형상으로 texturing 함으로 광자들의 다중반사 등에 기인하는 광흡수율의 증가를 기대할 수 있기 때문에 태양전지효율 개선에 긍정적인 영향을 미치는 것으로 이해된다. 본 실험에서도 고효율 다결정 실리콘 태양전지 양산공정에 적용 가능한 ICP-RIE기반 결정질 실리콘표면에 대한 texturing 공정기술을 연구하였다. Double Langmuir 플라즈마 진단시스템(DLP2000)을 적용하여 사용한 $SF_6$와 $O_2$ 개스유량과 챔버압력, 플라즈마 파워에 따른 이온밀도, 전자온도, 포화이온전류밀도, 플라즈마포텐셜의 공간분포를 모니터링하였고 texturing이 완료된 시료에 대하여 A1.5G 표준태양광스펙트럼의 300-1100nm 파장대역에서 반사율을 측정하여 그 변화를 관찰하였다. 본 연구에서 얻어진 결과를 간략히 정리하면 Si texturing에 가장 적합한 플라즈마파워는 100W, $SF_6/O_2$ 혼합비는 18:22, 챔버압력은 30mtorr 등이고 이에 상응하는 플라즈마의 이온밀도는 $2{\sim}3{\times}10^8\;ions/cm^3$, 전자온도는 14~15eV, 포화전류밀도는 $0.014{\sim}0.015mA/cm^2$, 플라즈마포텐셜은 38~39V 범위 등이었다. 현재까지 얻어진 최소 평균반사율은 14.2% 였으며 최적의 texturing패턴 플라즈마공정 조건은 이온에 의한 Si표면원자들의 스퍼터링과 화학반응에 의한 증착이 교차하는 플라즈마 에너지 및 밀도 상태인 것으로 해석된다.

• Journal of agriculture & life science
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• v.43 no.6
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• pp.95-103
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• 2009

To develop natural intermediate flavoring substances, optimal hydrolysis conditions and taste compounds for two step enzyme hydrolysate(TSEH) using Grass puffer(Takifugu niphobles) were investigated. The optimal conditions for TSEH method were revealed in temperature at $55^{\circ}C$ 3 hour digestion with Alcalase (pH 7.5) at the 1st step and 2 hour at $45^{\circ}C$ digestion with Flavourzyme(pH 6.0~6.5) at the 2nd step. TSEH method was superior to hot-water extraction on the aspect of yield, nitrogen contents and organoleptic taste quality such as umami and control of bitter taste formation. In taste active-components in Glass puffer TSEH, total free amino acid content was 4,502 mg%, major free amino acids were Pro, Leu, Lys, Hypro, Tau, Arg, Phe, Ala, Glu and Val in ordor. As for nucleotides, IMP(372 mg%) was the principal component and also contents of TMAO, total creatinine, and betaine were 43, 278 and 41 mg% in Glass puffer TSEH, respectively. The major inorganic ions in TSEH were Na(949 mg%), K(222 mg%), Cl(1,180 mg%) and $PO_4$(1,081 mg%).

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.309-314
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• 2022

Carbon dots (CDs) are few nanometer-sized carbon-based nanoparticles and emerging candidate materials in various fields such as biosensors and bioimaging due to their excellent optical properties and high biocompatibility. However, most CDs, emitting blue light, have limited their application in biomedical fields due to the low penetration of short-wavelength lights into the biological system. Therefore, there has been enormous need to develop long-wavelength emitting CDs. In this study, red-emitting CDs were successfully synthesized through the hydrothermal reaction of p-phenylenediamine with hydrochloric acid. In addition, the effect of the amount of hydrochloric acid on the formation of carbon dots, resulting in the variation of the chemical structures of CDs, were investigated, which was confirmed with the intensive structural analyses using infrared and X-ray photoelectron spectroscopy. It was found that the chemical structure of CDs governed their optical properties and quantum yield. Therefore, this study provides an insight into the role of acid in forming red-emitting CDs as the optimal probe for biomedical application.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.4
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• pp.1-13
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• 2022

This study was conducted to investigate the chlorophyll content, photosynthetic characteristics, and growth characteristics of Aster koraiensis and Dendranthema zawadskii var. latiloba according to shading treatment. A. koraiensis and D. zawadskii grew in four different shading treatment plots (0%, 50%, 75% and 95% of full sunlight) for experiments. It was found that as the shading level increased, the total chlorophyll content increased and dark respiration decreased in both A. koraiensis and D. zawadskii, indicating that A. koraiensis and D. zawadskii increase the utilization efficiency for photosynthesis under low light conditions. In addition, as the shading level increased, the net apparent quantum yield increased, resulting in the highest in the 95% shading plot, but the highest photosynthetic rate, water use efficiency, and leaf mass per area (LMA) were shown in the control group than in the shading treatments. The results showed that A. koraiensis and D. zawadskii are heliophytes showing plasticity to light, and if the light is restricted to continue to shade, it may be detrimental to growth. For healthy growth, it is considered suitable to grow A. koraiensis under full light conditions, and D. zawadskii under the light condition that blocks 0-50% of full sunlight.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.14 no.2
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• pp.118-126
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• 2009

Benthic diatoms are very important primary producers in understanding estuary ecosystems and their productions are largely varied by their photo-physiological characteristics. The short-term effects of increased temperature on the photosynthetic and photo-physiological characteristics of cultured different species of benthic diatoms (Navicula sp., Nitzschia sp., Cylindrotheca closterium, and Pleurosigma elongatum) were investigated by measuring their PSII-fluorescence kinetics using a Diving-PAM. Photosynthesis versus irradiance curves were measured every two hours at six different temperatures (10, 15, 20, 25, 30, and $35^{\circ}C$) for twenty-four hour. The effective quantum yield of PSII ($\Phi_{PSII}$) for most of the species showed a decreasing trend with increased temperature. The relative maximum electron transport rate (rETRmax) was significantly increased up to the optimum temperature level and then sharply decreased. Relative to the values of other parameters, the maximum light use coefficient ($\alpha$) was not substantially changed at lower temperature levels (<$30^{\circ}C$) but significantly decreased only at higher temperatures (30 and $35^{\circ}C$). The light saturation coefficient ($E_K$) mirrored the rETRmax temperature response. In regards to the temperature acclimation abilities of the four species with time, Navicula sp. and C. closterium acclimated to short-term changes in temperature through their photo-physiological adjustments.

• Korean Journal of Plant Resources
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• v.37 no.2
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• pp.203-213
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• 2024

In this study, we investigated the growth and physiological responses of Iris laevigata Fisch. to shading treatments in order to suggest optimal light conditions for ex-situ conservation of the northern lineage plants. For this purpose, a control plant receiving full sunlight and different shading treatments (50%, 75%, 95%) were installed, and leaf mass per area, chlorophyll content and fluorescence response, and photosynthetic characteristics were investigated. I. laevigata developed leaves with higher photosynthetic efficiency to adapt to lower light intensity as shading levels increased. Chlorophyll content increased with increasing shading levels, and leaf mass per area decreased with increasing leaf area. The chlorophyll fluorescence responses Fv/Fm and NPQ did not change with shading, and the activity of the carbon fixation system did not differ between treatments. I. laevigata exhibited a light-saturation point equivalent to that of sun plants and maintained photosynthetic capacity similar to that of controls up to 75% shading. The apparent quantum yield of I. laevigata decreased significantly at 95% shading, indicating adaptation to lower light conditions. It seems that the photosynthetic capacity of I. laevigata decreases when grown under 95% shading level compared to full sunlight, and it is judged that the longer the light is restricted by continuous shading, the more unfavorable the growth will be.

• Korean Journal of Optics and Photonics
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• v.35 no.4
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• pp.175-183
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• 2024

Research into optical signal processing using photonic integrated circuits (PICs) has been actively pursued in various fields, including optical communication, optical sensors, and quantum optics. Among the materials used in PIC fabrication, polymers have attracted significant interest due to their unique characteristics. To fabricate polymer-based PICs, establishing an accurate manufacturing process for the cross-sectional structure of an optical waveguide is crucial. For stable device performance and high yield in mass production, a process with high reproducibility and a wide tolerance for variation is necessary. This study proposes an efficient method for fabricating polymer optical-waveguide devices by introducing the atomic layer deposition (ALD) process. Compared to conventional photoresist or metal-film deposition methods, the ALD process enables more precise fabrication of the optical waveguide's core structure. Polyimide optical waveguides with a core size of 1.8 × 1.6 ㎛² are fabricated using the ALD process, and their propagation losses are measured. Additionally, a multimode interference (MMI) optical-waveguide power-splitter device is fabricated and characterized. Throughout the fabrication, no cracking issues are observed in the etching-mask layer, the vertical profiles of the waveguide patterns are excellent, and the propagation loss is below 1.5 dB/cm. These results confirm that the ALD process is a suitable method for the mass production of high-quality polymer photonic devices.