• Korean Journal of Environmental Agriculture
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• v.30 no.4
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• pp.382-389
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• 2011

BACKGROUND: Light-emitting diodes (LEDs) with lower electric cost and the specific wavelength have been considering as a novel light source for plant production in greenhouse conditions as well as in a closed culture system. Supplementary lighting for day-length extension was considered as light intensity, light quality, and/or photoperiod control on plant growth and development. Effects of supplementary blue or red LED radiation with lower light intensity on growth of Ageratum (Ageratum houstonianum Mill., cv. Blue Field), African marigold (Tagetes erecta L., cv. Orange Boy), and Salvia (Salvia splendens F. Sello ex Ruem & Schult., cv. Red Vista) were discussed during sunrise and sunset twilight in the experiment. METHODS AND RESULTS: Supplementary lighting by blue and red LEDs for 30 (Treatment B30; R30) or 60 (Treatment B60; R60) min. per day were established in greenhouse conditions. Photosynthetic photon flux for supplementary radiation was kept at $15{\mu}mol\;m^{-2}\;s^{-1}$ on the culture bed. Natural condition without supplementary light was considered as a control. The highest shoot and root dry weights were shown in African marigold exposed by red light for 60 min. per day. Supplementary blue and red lighting regardless of the radiation time significantly stimulated development of lateral branches in African marigold. Stem growth in Ageratum and Salvia seedlings was significantly promoted by red radiation as well as natural light. CONCLUSIONS: Extending of the radiation time at sunrise and sunset twilight using LEDs stimulated reproductive growth of flowering plant species. Different characteristics on growth under supplementary blue or red lighting conditions were also observed in the seedlings during supplementary radiation.

• Korean Journal of Plant Resources
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• v.26 no.6
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• pp.709-717
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• 2013

The objective of this study was to examine the effect of root pruning intensity in combination with different initial seedling size on the growth of transplanting seedlings of Quercus acutissima. One-year-old seedlings were divided into three groups depending on their height, i.e. small (< 15 cm), medium (25-35 cm) and large size (35 cm <). Root of seedlings was pruned by three intensity such as, leaving 5 cm (severe), 10 cm (medium) and 15 cm (light) of taproot from the root-collar. After one year, we investigated survival rate, height and root-collar diameter (RCD) increment and final shoot dry weight. Also we measured characteristics of newly developed lateral roots such as number, total length, dry weight and diameter. Severe root pruning showed the lowest survival rate in all seedling size. Height increment, RCD increment and shoot dry weight were decreased with increasing intensity of root pruning. Seedlings of medium and light root pruning showed similar above-ground growth and dry weight of lateral roots. More large seedlings showed good survival rate, height increment and final shoot dry mass in all root pruning intensity. Therefore, one-year-old seedlings of Q. acutissima should be pruned taproot by 10 cm and transplanted to obtain excellent performance and increase the efficiency of transplanting work. Based on the findings of this study, it is important that applying to different root pruning intensity depending on initial seedling size for producing 2-year-old seedlings with excellent growth and high quality.

• Physical Therapy Korea
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• v.28 no.4
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• pp.251-255
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• 2021

Background: Physical activity and quality of life (QOL) influence the health status of older adults. Recently, the use of wearable devices to monitor physical activity has increased. Objects: This study examined the relationship between the amount of physical activity, measured using a wearable device, and QOL among older adults. Methods: In total, 71 older adults (aged ≥ 65 years) were enrolled. The amount of physical activity was measured using a wearable device with a wrist strap, and daily physical activity was classified according to intensity (sedentary, light, moderate, or very active). Self-reported QOL was evaluated using the Short Form 36 (SF-36) questionnaire. Pearson and Spearman correlation analyses were conducted to analyze parametric and non-parametric variables, respectively. The relationship between amount of daily physical activity and SF-36 scores was assessed. Results: The correlation analyses revealed positive correlations between the amount of moderate-intensity and very active physical activity (minutes/day) and SF-36 scores (p < 0.05). Conclusion: Physical activity of at least moderate intensity is associated with better QOL in older adults. Further studies are required to verify the effects of increased physical activity on QOL in older adults.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.165-166
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• 2009

A hologram was recorded with two-dimensional scanning of an optical fiber connected to a single-photon counting detector under ultra-weak illumination. The object image was clearly reconstructed in a computer from the hologram. The dependence of hologram quality on the illumination light intensity was estimated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.11
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• pp.1-13
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• 2011

The purpose of this study is the realization of LED light environment closely resembling the Autumn daylight which people feel comfortable with. This research was conducted through an optical experiment and Emotional evaluation through human's eyes. Human beings are affected by the color of light, quality and light intensity. Unlike the past when human beings have worked mainly in daylight, the urbanites today spend most of the time in indoor spaces. Therefore, the artificial light is needed to strive toward a spectrum of daylight. This study is purposed to provide the pleasant light environment for human beings and build its database. This study course is expected to contribute to the new design methodology of the related fields under the development of the LED emotional lighting color.

• Horticultural Science & Technology
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• v.33 no.3
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• pp.349-355
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• 2015

Lisianthus (Eustoma grandiflorum) is relatively sensitive to temperature and light conditions. For year round production of good quality potted plants and energy saving, it is necessary to understand the growth and flowering response to the combined conditions of these environmental factors. This study was conducted to examine the growth and flowering responses to temperature, photoperiod, and light intensity during the post-seedling stage. 'El Paso Deep Blue' lisianthus plants with four true leaf pairs were grown in growth chambers maintained at average daily temperatures (ADT) of 14, 20, and $26^{\circ}C$ and provided with three photosynthetic photon fluxes [PPF; 100, 200, and $400{\mu}mol{\cdot}m^{-2}{\cdot}s^{-1}$] for 8 (08:00-16:00) and 16 hours (08:00-24:00) by fluorescent and incandescent lamps, resulting in four daily light integrals (DLI): about 3, 6 (two photoperiods), 12 (two photoperiods), and $24mol{\cdot}m^{-2}{\cdot}d^{-1}$. After treatment for three weeks followed by growth for one week in a greenhouse of $20{\pm}3^{\circ}C$, growth and development were measured. Higher temperature, higher PPF, and longer photoperiod promoted plant growth and flowering; however the impacts of PPF and photoperiod were smaller than those of temperature. As ADT and DLI increased, the number of leaves, number of flowers, lateral shoot length, and shoot dry weight increased. An increase of about $1mol{\cdot}m^{-2}{\cdot}d^{-1}$ DLI could constitute an increase of 0.40 to $0.76^{\circ}C$ ADT depending on these crop characteristics when ADT and DLI are above $20^{\circ}C$ and $12mol{\cdot}m^{-2}{\cdot}d^{-1}$, respectively. Therefore, growers can select a regimen of heating or supplemental lighting without delaying harvesting time or decreasing crop quality.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.11
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• pp.51-57
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• 2001

A light beam reflected from a machined surface generally containes information concerning about its surface roughness. This study examines and proposes a surface roughness measurement technique for on-machine measurement of machined surfaces. The technique is based on the measurement of a reflected laser beam pattern and the statistical analysis of its light intensity distribution. The surface roughness was found to be closely related to the standard deviation of the light intensity on the primary axis of the reflected pattern. An image acquisition device is made up of a laser diode, a half mirror, a screen, and a CCD camera. The exact image with the primary and secondary axes of a reflected laser beam pattern is calculated through such image processing algorithm as thresholding, edge detection, image rotation, segmentation, etc. A median filter and a surrounding light correction algorithm are improve the image quality and reduce the measuring error. Using the developed measuring device the effect of screen materials and workpiece and workpiece materials was investigated. Experimental results regarding to relatively high-quality surfaces machined by grinding, polishing, lapping processes have shown the measurement error is within 10% in the range of $0.1{mu}m~0.8{\mu}m R_q.$Therefore, the proposed method is thought to be effectively used when quick measurements is needed with workpieces fixed on the machine.

• Korean Journal of Plant Resources
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• v.12 no.2
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• pp.139-144
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• 1999

The present study was carried out to determine the effects of lighting directions and light intensities on the growth of in vitro plantlets of strawberry, potato and lily. The growth of plantlets was affected by two different lighting systems, downward and sideward lighting system. There were no difference for the plantlets of strawberry regardless of lighting directions. However, leaf area, fresh weight and dry weight have increased as the light intensity increased. Also, plant height and root length on node culture of potato decreased at high intensity of the sideward lighting, while thickness of stem and root was thicker, fresh weight and dry weight were heavier, and leaf area was increased. Also, bulblet formation on scale culture of lily has been abundant, and fresh weight and dry weight were increased. Thus, the sideward lighting system which loaded three stories for culture vessels with raising light intensity into culture vessels instead of conventional downward lighting system promoted growth and raised the efficiency of production of high quality microplant.

• Journal of Bio-Environment Control
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• v.30 no.4
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• pp.448-454
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• 2021

This study was conducted to the effect of low air temperature and light intensity conditions on yield and quality of tomato at the early stage of growth in Korea. Inplastic greenhouses, low temperature and low temperature with shade treatments were performed from 17 to 42 days after plant. Tomato growing degree days were decreased 5.5% due to cold treatment during the treatment period. Light intensity decreased 74.7% of growing degree days due to shade. After commencing treatments, the plant growth decreased by low temperature and low radiation except for height. Analysis of the yield showed that the first harvest date was the same, but the yield of the control was 3.3 times higher than low temperature with shade treatment. The cumulative yields at 87 days after transplanting were 1734, 1131, and 854 g per plant for control, low temperature, and low temperature with shade, respectively. The sugar and acidity of tomatoes did not differ between treatment and harvesting season. To investigate the photosynthetic characteristics according to the treatment, the carbon dioxide reaction curve was analyzed using the biochemical model of the photosynthetic rate. The results showed that the maximum photosynthetic rate, J (electric transportation rate), TPU (triose phosphate utilization), and R_d (dark respiration rate) did not show any difference with temperature, but were reduced by shading. Vcmax (maximum carboxylation rate) was decreased depending on the low temperature and the shade. Results indicated that low temperature and light intensity at the early growth stage can be inhibited the growth in the early stage but this phenomenon might be recovered afterward. The yield was reduced by low temperature and low intensity and there was no difference in quality.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.245-251
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• 2022

BACKGROUND: Selection an suitable light source is essential in the year-round production of horticultural crops in closed production systems such as plant factory with controlled environments. This study was investigated to confirm the effects of artificial light sources on growth of cherry tomato'CF Jelly'(Lycopersicon esculentum var.) under high-pressure sodium lamps (HPS), metal-halide lamps (MH), and LEDs. METHODS AND RESULTS: Light intensity of the light sources was controlled at 220±30 µmol/m²/s with 12 hrs of photoperiod for a day. Flower development was significantly faster in HPS and MH treatments compared to the LEDs. There was no significant difference between the leaf number and leaf shape under the HPS and MH treatments. Reproductive growth of cherry tomato was significantly promoted by the LEDs treatment of blue plus red lights. Fruit yield per plant also increased under the LEDs compared to the others. CONCLUSION(S): Growth, flowering, and fruit setting of the cherry tomato were accomplished by the artificial lights under plant factory conditions. The HPS treatment showed negative effect on fruit quality in terms of blossom-end rot incidence compared to the LEDs or MH treatment. Effect of the LEDs on promotion of fruit weight and yield was also proved. Additional research should be carried out for improving sugar metabolism or decreasing disease in the fruits under plant factory system using only artificial lights.