• 한국작물학회지
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• 제61권4호
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• pp.270-276
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• 2016

The objective of this study was to find a rapid determination of the hot air stress in maize (Zea mays L.) leaves using a portable chlorophyll fluorescence imaging instrument. To assess the photosynthetic activity of maize leaves, an imaging analysis of the photochemical responses of maize was performed with chlorophyll fluorescence camera. The observed chlorophyll imaging photos were numerically transformed to the photochemical parameters on the basis of chlorophyll a fluorescence. Chlorophyll a fluorescence imaging (CFI) method showed that a rapid decrease in maximum fluorescence intensity ($F_m$) of leaf occurred under hot air stress. Although no change was observed in the maximum quantum yield ($F_v/F_m$) of the hot air stressed maize leaves, the other photochemical parameters such as maximum fluorescence intensity ($F_m$) and Maximum fluorescence value ($F_p$) were relatively lowered after hot air stress. In hot air stressed maize leaves, an increase was observed in the nonphotoquenching (NPQ) and decrease in the effective quantum yield of photochemical energy conversion in photosystem II (${\Phi}PSII$). Thus, NPQ and ${\Phi}PSII$ were available to be determined non-destructively in maize leaves under hot air stress. Our results clearly indicated that the hot air could be a source of stress in maize leaves. Thus, the CFI analysis along with its related parameters can be used as a rapid indicating technique for the determining hot air stress in plants.

• 조명전기설비학회논문지
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• 제19권2호
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• pp.7-12
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• 2005

광원의 복사에너지가 물질에 입사하면, 그 물질의 고유한 특성에 따라 그 에너지의 일부는 흡수되고 나머지는 반사되거나 투과된다. 물질을 구성하는 분자가 빛을 흡수하면 그 빛의 파장에 따른 복사에너지에 의하여 열적 반응이나 광화학적 반응을 일으킨다. 특히 자외선복사에 의한 광화학적 작용은 물질의 변퇴색과 같은 광화학적 열화를 초래한다. 물질에 손상이 일어나면 그 물질의 가치상실 뿐 아니라, 손상된 것을 다시 복원하기 쉽지 않기 때문에 이에 대한 적절한 조명 환경을 마련하여 손상의 최소화나 보존에 많은 노력을 기울여야 한다. 본 연구에서는 자외선에 의한 광화학적 손상과 그 방호에 대하여 살펴보고, 전시조명용으로 많이 사용되는 인공광원과 자연주광을 대상으로, 이들 광원들이 방출하는 복사조도와 자외선을 포함하는 광복사량을 측정하고 그 결과를 분석하였다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제1권1호
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• pp.19-33
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• 1997

The high oxidants, which occur the daily maximum concentrations in the afternoon, are transported into the other region via long range transport mechanisms or trapped within the shallow mixing boundary layer and then removed physically (deposition, transport by mountain wind, etc.) and chemically (reaction with local sources). Therefore, modeling formation of photochemical oxidants requires a complex description of both chemical and meteorological processes. In this study, as a part of air quality studies, we reviewed various aspects of photochemical modeling on the basis of currently available literature. The result of the review shows that the model is based on a set of coupled continuity equations describing advection, diffusion, transport, deposition, chemistry, emission. Also photochemical oxidant models require a large amount of input data concerned with all aspects of the ozone life cycle. First, emission inventories of hydrocarbon and nitrogen oxides, with appropriate spatial and temporal resolution. Second, chemical and photochemical data allowing the quantitative description of the formation of ozone and other photochemically-generated secondary pollutants. Third, dry deposition mechanisms particularly for ozone, PAN and hydrogen peroxide to account for their removal by absorption on the ground, crops, natural vegetation, man-made and water surfaces. Finally, meteorological data describing the transport of primary pollutants away from their sources and of secondary pollutants towards the sensitive receptors where environmental damage may occur. In order to improve our present study, shortcomings and limitation of existing models are pointed out and verification process through observation is emphasized.

• 한국정밀공학회지
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• 제22권9호
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• pp.60-68
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• 2005

To investigate the effects of beam focusing in the etching of polymers with short pulse Excimer lasers, a polymer etching model of SSB's is combined with a beam focusing model. Through the numerical simulation, it was found that in the high laser fluence region, SSB model considering both photochemical and thermal contribution is considered to be suitable to predict the etched hole shape than a simple photochemical etching model. The average temperature distribution into the substance obtained by assuming 1-D heat transfer is found to be fairly similar to the fluence distribution on the ablated surface. The experimental etching data fur polymers are used to give material properties for ablation model. The fitted etch depth curve gives a nice agreement with the experimental data.

• 한국대기환경학회지
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• 제13권1호
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• pp.41-49
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• 1997

Status of photochemical air pollution in the Greater Seoul Area (GSA) between 1990 and 1995 was assessed in terms of frequency distributions, number of days exceeding standards, average concentration and meteorological effects. In Seoul compared with other areas in Korea, daily maximum concentration was higher but average concentration was not so high due to lower daily minimum from April to October. The top 5th percentile was high especially in summer season. Average number of days exceeding 100 ppb at monitoring stations in GSA was highest in 1994, the hottest year, but it was only 4 days a year. Mean meteorological pattern of high ozone days could be summarized as low wind speeds, high temperatures, strong solar radiation, and low precipitation. Westerlies were more frequent on high ozone days and at Pangi station located in the eastside of GSA, both number of high ozone days and average concentration were high. Effect of precursor transport on the rise of ozone concentration was, however, not consistently important on the whole in GSA.

• Journal of Photoscience
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• 제1권1호
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• pp.39-45
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• 1994

Haloarene in which the phenyl group and halophenyl group are connected by alkyl groups were synthesized to study the photochemical behavior. The photochemical reactions of 1-halo-2-(phenylalkyl)enzenes (1 and 2) were studied in several aerated or unaerated solvents. In the case of 2-benzyl-1-halobenzene photoreduced product (biphenyl) is major in acetonitrile or benzene. In cyclohexane or acetonitrile with triethylamine, photoreduced product is obtained exclusively, while in acetonitrile with toluene, xylene, or sodium hydroxide photocyclized product (fluorene) is mainly obtained. In the case of 1-halo-2-phenethylbenzenes (5 and 6), photocyclized product (9,10-dihydrophenanthrene and phenanthrene) are major in acetonitrile or benzene. While the haloarenes 1 or 2 connecting the two arene rings by methylene is photoreduced, the other haloarene 5 or 6 connecting by ethylene is photocyclized. In cyclohexane or acetonitrile with a small amount of triethylamine, photoreduced reactions of 5 or 6 mainly occur. In acetonitrile with sodium hydroxide, toluene, or xylene, photocyclization of 5, 6 occur exclusively. The triplet state is mainly involved in the photocyclization of 5 or 6, because of the inhibition of oxygen.

• 한국식품영양학회지
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• 제11권3호
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• pp.267-271
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• 1998

Seyferth 시약인 phenyl(tribromomethyl) mercury 및 diazomethane의 식품보존제인 dehydroacetic acid 및 coumarin과의 발암성과 그 반응기작을 분자 구조적 관점에서 알아보기 위하여 UV/vis 조건과 laser flash photolysis 시켰을 때의 결과는 다음과 같다. 1. Diazomethane과 Phenyl(tribromomethyl) mercury와 dehydroacetic acid와 diazomethane과의 반응은 광화학적 분해 반응에서 생성된 : CBr2와 : CH2 카르벤 중간체의 이탈기 효과에 따라 발암성이 크게 나타났다. 2. laser flash photolysis 상에서 반응시켰을 때 식품보존제의 발암성이 UV/vis 상에서의 photolysis 때보다 크게 나타났다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제3권3호
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• pp.151-158
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• 1999

Biogenic source emissions refer to naturally occuring emissions from vegetation, microbial activities in soil, lightening, and so on. Vegetation is especially known to emit a considerable amout of volatile organic compounds into the atmosphere. Therefore, biogenic source emissions are an important input to photochemical air quality models. since most biogenic source emissions are calculated at the county-level, they should be geographically allocated to the computational grid cells of a photochemical air quality model prior to running the model. The traditional method for the spatial allocation for biogenic source emissions has been to use a "spatial surrogate indicator" such as a county area. In order to examine the applicability of such approximations, this study developed more detailed surrogate indicators to improve the spatial allocation method for biogenic source emissions. Due to the spatially variable nature of biogenic source emissions, Geographic Information Systems(GIS) were introduced as new tools to develop more detailed spatial surrogate indicators. Use of these newly developed spatial surrogate indicators for biogenic source emission allocation provides a better resolution than the standard spatial surrogate indicator.indicator.

• 환경영향평가
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• 제5권1호
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• pp.69-77
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• 1996

The variations of ozone concentration and the sensitivity test for VOC emission intensities was investigated by means of a PBM(Photochemical Box Model). Compared to monitoring data, the typical variations of $NO_2$, CO, $O_3$ for days were successfully reproduced. Model results revealed that maximum ozone concentration got increased with the increase of VOC emission, that is, VOC played the important role in producing the photochemical smog.

• Journal of Photoscience
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• 제6권4호
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• pp.177-181
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• 1999

The photochemical transformation of carbon monoxide in aqueous ammonia solution has been investigated at 25${\pm}$0.1$^{\circ}C$ using 184.9 nm UV light. Amination and carbonylation processes were carried out by irradiating the aqueous ammonia solution saturated with carbon monoxide, and the formation of formamide, urea, hexamethylenetetramine, formaldehyde, glyoxal and hydrazine was observed. The formation of hydrazine was affected by the presence of ammonia, and the formation of carbonyl compounds such as formaldehyde and glyoxal was influenced by the presence of carbon monoxide. The formation of formamide, urea and hexamethylenetetramine was affected by both ammonia and carbon monoxide. The initial quantum yields of the products were determined and probable mechanisms for the photochemical reaction were presented on the basis of product analysis.