• The Korean Journal of Ecology
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• v.16 no.3
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• pp.317-327
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• 1993

Stands profiles, yearly changes in growth of annual rings, age and diameter structure, and spatial distribution pattern of individuals in the Pinus densiflora stands around the Yeocheon industrial complex were investigated. Growth of annual ring in Pinus densiflora, which survived when vegetation of this area was damaged by air pollutants, was suppressed for about 10 years since 1974 when factories in this area began to operate, but since then such suppressed growth tended to be recovered. It was supposed that the suppresed growth was originated from air pollution and that improvement of growth since the suppressed period was due to the release from competition with them by death of neighbouring trees and the resuction of the amount of air pollutants. Physiognomy of Pinus densiflora stands showed mosaic pattern composed of different patches. Spatial distribution pattern of individuals an stand profiles were similar to those of Pinus densiflora stands regenerated after natural and artificial disturbances. In an age distribution diagram, age of Pinus densiflora population ranged from 1 to 33 years, Among these individuals were recrited corresponded to the suppresed period of growth of annual ring in Pinus densiflora survived when the vegetation was damaged by air pollution. On the other hand, from the result of analysis of frequency distribution diagram of diameter, it was postulated that even if whis Pinus densiflora community can be maintained as it is for the time being, it might be changed to Quercus community with the lapse of time. Regeneration; Pinus densiflora; Air pollution; Annual ring; Age structure; Diameter structure; Quercus spp. In these analyses, factors for individual recognition and species recognition were suggested.

• ALGAE
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• v.22 no.2
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• pp.107-116
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• 2007

Annual growth segments of Ascophyllum nodosum (L.) Le Jolis (Fucales, Fucaceae) are denoted by air bladders that form each spring. By examining annual growth segments, it may be possible to infer information about the physical conditions during the growth period; however, it is uncertain whether the annual segments will expand in size after the initial growth. We examined A. nodosum segments from three populations in Nova Scotia, and statistically evaluated whether the annual growth (length, mass, and maximum diameter) of segments was independent of the age of the frond, whether the segments increased in size after the initial growth, and whether the segment lengths were correlated with mean water temperatures and mean air temperatures when the segments were formed. We found that the growth in length of A. nodosum is dependent on the age of the frond, but frond age explained less than 12 % of the overall variation in length. However, the mass and maximum diameter of segments were independent of the age of the frond. Differences occurred between the lengths of segments formed in different years, but there was no significant correlation with regional mean water or air temperatures. This study indicates that the length of A. nodosum segments may be an indicator of the annual physical characteristics of a site, but future studies are needed to identify which factors have the strongest influence on growth patterns.

• Journal of Preventive Medicine and Public Health
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• v.39 no.4
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• pp.309-316
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• 2006

Objectives: Korean epidemiological studies have used reduced samples according to the subject's characteristics, such as the health services provided, the historical note with asthma, and age, to examine the acute effect of air pollution on asthma using the Korean National Health Insurance records. However, there have been few studies on whether the effects shown in these reduced samples are different from those of all samples. This study compared the effects of air pollution on asthma attacks in three reduced samples with those of entire samples. Methods: The air pollution data for $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, and weather conditions including temperature, relative humidity, and air pressure in Seoul, 2002, were obtained from outdoor monitoring stations in Seoul. The emergency hospital visits with an asthma attack in Seoul, 2002 were extracted from the Korean National Health Insurance records. From these, the reduced samples were created by health service, historical notes with asthma, and age. A case-crossover design was adopted and the acute effects of air pollution on asthma were estimated after adjusting for weather, time trend, and seasonality. The model was applied to each reduced sample and the entire sample. Results: With respect to the health service, the effects on outpatients were similar to those for the total sample but were different for inpatients. These similar effect sizes were also observed in the reduced samples according to the historical note with asthma and age. The relative risks of $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, among the reduced and entire samples were 1.03, 1.04-1.05, 1.02-1.03, 1.04-1.06, and 1.10-1.17, respectively. Conclusions: There was no clear evidence to show a difference between the reduced samples and the entire samples.

• Wind and Structures
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• v.21 no.3
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• pp.289-309
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• 2015

Vertical profiles of mean and fluctuating wind velocities over water waves were studied, by performing Large-Eddy Simulations (LES) on a fully developed turbulent boundary layer over simplified water waves. The water waves were simplified to two-dimensional, periodic and non-evolving. Different wave steepness defined by $a/{\lambda}$ (a : wave amplitude; ${\lambda}$ : wavelength) and wave age defined by $c/U_b$ (c: phase velocity of the wave; $U_b$ : bulk velocity of the air) were considered, in order to elaborate the characteristics of mean and fluctuating wind profiles. Results shows that, compared to a static wave, a moving wave plays a lesser aerodynamic role as roughness as it moves downstream slower or a little faster than air, and plays more aerodynamic roles when it moves downstream much faster than air or moves in the opposite direction to air. The changes of gradient height, power law index, roughness length and friction velocity with wave age and wave amplitude are presented, which shed light on the wind characteristics over real sea surfaces for wind engineering applications.

• Proceedings of the SCSK Conference
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• 2003.09b
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• pp.529-543
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• 2003

Real-time measurements of skin movement induced by air blown on the surface was measured with time. We investigated age-related changes in displacement of the skin surface on the face or the inner upper arm caused by air on 98 Japanese women volunteers aged from 10 to 70 years old. The maximum distance (the denting state) that the skin moved reached 2-5 mm within 10-15 msec on the cheek skin. After that, the skin generally recovered to the original state within 40-50 msec. The maximum speed of movement was 0.5 m/sec and the recovery speed was about 0.25 m/sec on the cheek skin. Significant changes with age were not observed in the denting state, but a significant correlation with age was observed in the recovery state. For example, the maximum recovery speed decreased significantly with age (p=-0.568, p<0.001) and the time required for recovery increased significantly with age (p=0.561, p<0.001). Although the inner upper arm also showed similar results to a cheek, a few parameters were different. This apparatus is a more practical macroscopic system for evaluating skin mechanical properties without contact. This apparatus is effective not only for measuring the mechanical properties of facial skin but also of body skin, such as swelling or sagging of body parts.

• Journal of The Korean Society of Agricultural Engineers
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• v.59 no.6
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• pp.61-71
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• 2017

The tracer gas method has an advantage that can estimate total and local ventilation rate by tracing air flow. However, the field measurement using tracer gas has disadvantages such as danger, inefficiency, and high cost. Therefore, the aim of this study was to evaluate ventilation rate in pig house by using the thermal distribution data rather than tracer gas. Especially, LMA (Local Mean Age), which is an index based on the age of air theory, was used to evaluate the ventilation rate in pig house. Firstly, the field experiment was conducted to measure micro-climate inside pig house, such as the air temperature, $CO_2$ concentration and wind velocity. And then, LMA was calculated based on the decay of $CO_2$ concentration and air temperature, respectively. This study compared between LMA determined by $CO_2$ concentration and air temperature; the average error and root mean square error were 3.76 s and 5.34 s. From these results, it was determined that thermal distribution data could be used for estimation of LMA. Finally, CFD (Computational fluid dynamic) model was validated using LMA and wind velocity. The mesh size was designed to be 0.1 m based on the grid independence test, and the Standard $k-{\omega}$ model was eventually chosen as the proper turbulence model. The developed CFD model was highly appropriate for evaluating the ventilation rate in pig house.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.5
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• pp.206-211
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• 2014

The objective of the present study was to identify ventilation problems, and also to suggest new axial fan systems for the improvement of IAQ in the underground parking lots. Numerical results for air mean-velocity, local mean age, and sound power level are presented along with some of fan angles. The results showed the influence of airflow patterns on the fan performances installed in the underground parking lots. Discharge air volume is increased with the angle of the blade. And also, the main factors affecting the noise of the ventilation fan was found to be a rotational speed.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.651-654
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• 1999

It is required that the compressive strength of concrete should be estimated accurately from the view point of efficient quality control and maintenance of buildings. In this paper, the equations to estimate the compressive strength of concrete using granite aggregates were suggested for both rebound hammer method and ultrasonic pulse velocity method. The results were compared with those for different age or curing condition. The rebound numbers for concrete cured in air were larger than for concrete cured in water. The difference between rebound numbers for concrete cured in water and in air was larger than for concrete cured in water. The difference between rebound numbers for concrete cured in water and in air was larger when water cement ratio was high. Also, with the increase of age, the velocity of ultrasonic pulse for concrete cured in air was measured larger when compared with that in water.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.16 no.3
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• pp.232-242
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• 1987

• Proceedings of the SAREK Conference
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• 2006.11a
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• pp.56-56
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• 2006