• Journal of Ceramic Processing Research
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• v.19 no.5
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• pp.439-443
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• 2018

The outstanding characteristics of high quality GaN single crystal substrates make it possible to apply the manufacture of high brightness light emitting diodes and power devices. However, it is very difficult to obtain high quality GaN substrate because the process conditions are hard to control. In order to effectively control the formation of GaN polycrystals during the bulk GaN single crystal growth by the HVPE (hydride vapor phase epitaxy) method, a quartz ring was introduced in the edge of substrate. A variety of evaluating method such as high resolution X-ray diffraction, Raman spectroscopy and photoluminescence was used in order to measure the effectiveness of the quartz ring. A secondary ion mass spectroscopy was also used for evaluating the variations of impurity concentration in the resulting GaN single crystal. Through the detailed investigations, we could confirm that the introduction of a quartz ring during the GaN single crystal growth process using HVPE is a very effective strategy to obtain a high quality GaN single crystal.

• Journal of agriculture & life science
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• v.43 no.6
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• pp.1-6
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• 2009

The purpose of this study was to analyze annual tree ring growth characteristics for major tree species distributed in Chungbuk province. A total of 800 sample trees from 56 permanent sampling plots measured by the 5th Korean National Forest Inventory Program in 2007 was used for the calculation of annual growth rates. According to the results of this study, the species of Robinia pseudoacacia(2.30mm/yr) showed the best annual tree ring growth rates and the others are Quercus serrata(2.27mm/yr)>Prunus sargentii(1.98mm/yr)> and Larix leptolepis(1.98mm/yr) in order. Most of the major tree species in Chungbuk province, as tree age and stand density increased, annual tree ring growth rates tended to decreased. This information could be very useful for forest managers to understand annual tree ring growth characteristics in Chungbuk province.

• The Korean Journal of Ecology
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• v.19 no.4
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• pp.285-294
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• 1996

Ring-width chronologies of Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) from two experimental forest plots in Kaunas, Lithuania were developed to study tree growth-climate relationship in different geohydrological conditions using response function analysis. The tree ring-width chronologies of Scots pine ranged from 1883~1987 A.D. and 1864~1989 A.D., and Norway spruce 1838~1987 A.D. and 2870~1989 A.D., respectively. The response function analysis has vividly demonstrated that the growth of Scots pine is favoured by warm summer and Norway spruce by cool and moist summer. Spring temperature has shown direct relationship with tree growth of both the species. There also exists notable intraspecies analogies in growth responses except some minor differences.

• The Korean Journal of Ecology
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• v.16 no.3
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• pp.305-316
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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.

• Korean Journal of Ichthyology
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• v.12 no.3
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• pp.166-172
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• 2000

Growth of Ammodytes personatus was investigated based on the specimens collected in the costal waters of Shinsudo, Sacheon from March 20 to December 14, 1988. Age determination based on otolith. The rings in the otolith were used as the basis for age annulus. The time of ring formation was estimated to one time per year in May far 1st ring group and March for 2nd ring group. The spawning season peaked in December. It takes approximately 16 months for the first ring and 11 months for the second ring to form in the otolith. The opaque zone was formed and marked over summer at 1st ring group and spawning mark at 2nd ring group. The relationship between the total length(TL) and otolith radius(R), and body weight(BW) were represented respectively as follows: TL=29.17+182.9R, BW=$4.9{\times}10^{-8}TL^{3.9587}$. Von Bertalanffy growth model is $TL_t$ = 177.273 ($1_e^{-0.040(t+7.332)}$), Robertson growth model is $TL_t=\frac{150.275}{1+2.085e^{-0.099t}}$ and Gompertz growth model is $TL_t=157.551e^{-1.214exp(-0.069t)}$.

• Korean Journal of Agricultural and Forest Meteorology
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• v.10 no.4
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• pp.177-186
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• 2008

This study was carried out to analyze the relationship between major climatic factors (temperature and precipitation) and tree ring growth of Pinus densiflora in 28 cities and counties in Korea. To examine tree ring growth of Pinus densiflora and the response of the climatic factors to climate change, the regional climatic data (for how many years??) from weather stations were categorized by five groups using cluster analysis for major climatic factors. In terms of relationship between monthly average temperature and tree ring growth of Pinus densiflora, negative correlations were observed for the temperatures in March of the present year in Baekdudaegan region and those in February and March in Gyeongbuk and East coast region. In addition, the temperature in October of the previous year was also negatively correlated with tree ring growth. Precipitation was positively correlated with the April and June temperatures of the present year in Baekdudaegan region and Gyeongbuk, respectively. Precipitation effect on the tree ring growth with current year June in Honam and Gyeongnam inland region and June, September in East coast region.

• Journal of Korean Society of Forest Science
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• v.78 no.3
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• pp.287-301
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• 1989

A tree of Ailanthus altissima Swingle was fastened with a plastic band, 19mm wide, around the stem 180cm above ground level and was left to grow under this condition for one year, By removal of this band the tumorous tissue gradually developed and the tree bearing distinct tumorous tissue, an overgrowth surrounding the stem, was harvested two years after the band removal. For the investigation of this tumorous part and its comparison with adjacent normal parts in the anatomical features of individual elements, the tumorous part and parts directly and 40cm above and below the tumorous part were obtained from the tree. The tumor wood having remarkably wider growth increment occurred in the 3rd growth ring the first year after removal of the fastened band, and the barrier zone which delimited the discolored wood from the normal-colored wood inwards appeared u1 the intra-2nd growth ring produced during the fastened period in the tumorous part and the false ring-like zones equivalent to barrier Zone were shown in the normal-colored 2nd growth rings of the parts directly and 40cm above and below the tumorous part, as well. The tumor wood, the 3rd growth ring, and proportion of the 2nd growth ring formed after barrier zone in the tumorous part shared common characteristics in the irregular growth ring boundary, misshapen and shorter individual fibers and vessel elements, and large ray widths and heights. The springwood pores were smaller in diameter in the tumor wood, and the larger radial and smaller tangential diameters of summerwood solitary pores and individual pores consisting of pore multiples in proportion of the 2nd growth ring formed after the barrier zone were transformed into near-isodiametric in the tumor wood, the 3rd growth ring, in the tumorous part. Only in proportion of the 2nd growth ring formed after the barrier zone were transformed into near-isodiametric in the tumor wood, the 3rd growth ring, in the tumorous part, ray densities greatly increased. And the massive tumor wood was caused not by cell size but by cell number because the radial and tangential diameters of fibers in the tumor wood, the 3rd growth ring, in the tumorous part were not sufficiently different from those in the same aged growth rings of the directly and 40cm above and below the tumorous part.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.597-602
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• 2001

A method for the retardation of fatigue crack growth using ring indentation at the vicinity of a crack is examined. Residual stresses near crack tip are evaluated using fracture mechanics approach. The motivation is to develop a simple and effective method for obtaining an increase in fatigue lives to total failure of materials with crack. Fatigue testing of aluminum specimen showed that the retardation effects are observed after the application of the method.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.10
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• pp.27-33
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• 2003

A method for the retardation of fatigue crack growth using ring indentation at the vicinity of a crack is examined. Residual stresses near crack tip are evaluated using fracture mechanics approach using the Bueckner weight function. The motivation is to develop a simple and effective method for obtaining an increase in fatigue lives to total failure of materials with crack. Fatigue testing of aluminum specimen showed that the retardation effects are observed after the application of the method.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.5-11
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• 2016

The control of the roll velocities is essential in maintaining stability during ring rolling, but such control is difficult. The determination of the best roll velocities can be helped with the use of FE simulations and processing maps, which give the useful information such as power dissipation and flow instability for hot metal forming processes. In the current study, the workability of 7050 aluminum alloy is evaluated by using processing map. With the developed information, the stability of the ring rolling condition, called the Constant Growth Velocity Condition (CGVC), is evaluated.