• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.13-22
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• 2004

In case of the lateral movement accurring at soft ground where a row of piles are installed, the crown failure at external arch zone of soil arching is firstly developed, and the cap failure at wedge zone in front of piles is lastly developed. Therefore, the lateral earth pressure acting on a row of piles due to soil movement should be calculated in each condition of crown and cap failures around piles. A theoretical equation of crown failure can be proposed using a cylindrical cavity expansion theory. The theoretical equation of crown failure is mainly affected by two factors. One is related to soil properties such as internal friction angle, cohesion and horizontal pressure, and the other is related to pile factors such as diameter, installation interval. Meanwhile, the yield range of lateral earth pressure is established in the estimation of theoretical equation based on crown and cap failures around piles. The theoretical values based on crown and cap failures are compared with the experimental values. The experimental values are located in the range proposed by theoretical values. Thus, it is confirmed that the theoretical values proposed in the study are very reasonable.

• Journal of Korean Society of Forest Science
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• v.98 no.5
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• pp.576-583
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• 2009

Based on the stem analysis and biomass measurement of 36 trees and 1,576 branches in Pinus sylvestris var. mongolica (Mongolian pine) plantations of Northeast China, this study was conducted to develop estimation model equation for leaf biomass of a single tree and branch, to examine the vertical distribution of leaf biomass in the crown, and to evaluate the proportional ratios of biomass by tree parts, stem, branch, and leaf. The results indicated that DBH and crown length were quite appropriate to estimate leaf biomass. The biomass of single branch was highly correlated with branch collar diameter and relative height of branch in the crown, but not much with stand density, site quality, and tree height. Weibull distribution function would have been appropriate to express vertical distribution of leaf biomass. The shape parameters from 29 sample trees out of 36 were less than 3.6, indicating that vertical distribution of leaf biomass in the crown was displayed by bell-shaped curve, a little inclined toward positive side. Apparent correlationship was obtained between leaf biomass and branch biomass having resulted in linear function equation. The stem biomass occupied around 80% and branch and leaf made up about 20% of total biomass in a single tree. As the level of tree class was increased from class I to class V, the proportion of the stem biomass to total biomass was gradually increased, but that of branch and leaf became decreased.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.277-285
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• 2019

This study was conducted to understand the growth characteristics of Picea jezoensis that was one of representative subalpine species in Korea, in the light of the effects of wind and micro-topography in its habitats on Mt. Deogyu, Korea. The prevailing wind directions were southwest and west at the study sites. We randomly selected P. jezoensis (height ≥ 1.5 m) on windward, intermediate, and leeward slopes and measured diameter at breast height (DBH), height, crown length by 8 directions in upper, middle and lower sectors of the crown. We examined the micro-topography of P. jezoensis stood on and classified it into 3 types: type 1 was mounded and fully exposed to surrounding environments without neighboring trees; type 2 was somewhat wind-protected by surrounding rocks, but no neighboring vegetation; type 3 was on gentle slope or flat where P. jezoensis grew with neighboring trees or shrubs. The ratios of height to DBH, and estimated crown growth to actual crown growth (hereafter crown growth ratio) were compared among the three types of micro-topography on windward, intermediate and leeward sites. The height growth per DBH and crown growth ratio in the upper and middle crowns were the smallest on the windward site, and the highest on the leeward site (p < 0.01). The crown growth ratio on type 1 on the windward site was only 46% of that on type 3 on the leeward site. Although on the same windward slope, trees on type 1 had more deformed crown shapes than that on Type 3, showing asymmetric crown cross-sectional areas. Wind and micro-topography played critical roles on the crown growth of P. jezoensis.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.599-610
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• 2001

Due to an increasing interest in esthetics and concerns about toxic and allergic reactions to certain alloys, patients and dentists have been looking for metal-free tooth-colored restorations. Recent improvement in technology of new all-ceramic materials and composite materials has broadened the options for esthetic single crown restorations. The aim of this investigation was to study the fracture strength of the metal-free posterior single crowns fabricated using two recently introduced systems, Empress 2 ceramic and Targis-Vectris. Forty premolar-shaped stainless steel dies with the 1mm-wide circumferential shoulder were prepared. Ten cylindrical crowns having a diameter of 8.0mm and total height of 7.5mm were fabricated for each crown system respectively(PFM, Empress staining technique, Empress 2 layering technique, and Targis- Vectris). The crowns were filled with cement and placed on the stainless steel dies with firm finger pressure. The crowns were then stored in distilled water at room temperature for 24 hours before testing. The crowns were tested for fracture strength in an Instron universal testing machine (Instron 6022). With a crosshead speed of 1mm/min the center of the occlusal surface of the crown was loaded using a 4-mm-diameter stainless steel ball until fracture occurred. The fracture surfaces of the crowns were gold coated and examined using scanning electron microscopy(Jeol JSM-840 Joel Ltd., Akishima, Tokyo, Japan). Within the parameters of this study the following conclusions were drawn: 1. The mean fracture strength for PFM crowns was 5829(${\pm}906$)N; for Empress staining technique the fracture strength was 1697(${\pm}604$)N; for Empress 2 Layering technique the fracture strength was 1781N(${\pm}400$)N, and the fracture strength for Targis- Vectris was 3093(${\pm}475$)N. 2. The fracture strength of the PFM crowns was significantly higher than that of the Empress 2 and the Targis-Vectris crowns (P<0.05). 3. The fracture strength of the Targis-Vectris crowns was significantly higher than that of the Empress 2 crowns (P<0.05). 4. No statistical difference was found when Empress staining technique was compared with Empress 2 layering technique. 5. The SEM image of fracture surface of Empress 2 crown showed a very dense microstructure of the lithium disilicate crystals and the SEM image of fracture surface of Targis-Vectris crown showed indentations of Vectris and some fibers tom off from Vectris.

• Korean Journal of Environment and Ecology
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• v.35 no.4
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• pp.398-407
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• 2021

This study intended to identify causes of poor tree vigor in the Hanbando coastal forest by investigating its geographical environment, climate condition, soil physicochemical characteristics, and growth condition of Pinus thunbergii. It divided the forest into an area with poor tree vigor or dead standing trees and a control area with good tree vigor and examined them separately. The survey showed that stand density was significantly higher in the area with poor tree vigor. In contrast, the crown width in the area with good tree vigor was wider. The number of dead standing trees and the stand density showed a negative correlation. The stand density and diameter at breast height (DBH), tree height, crown height, and crown width also showed a negative correlation. The result indicated that, as the tree's stand density increases, the crowns of individual trees overlapped and the lower branches died. Then crown height and crown width decreased, and the number of leaves and photosynthesis was reduced, leading to lower tree height and weaker growth of breast diameter. As a result, tree vigor weakened, and combined with environmental pressures from the lack of moisture and nutrients in coastal soil and salty wind, P. thunbergii in coastal areas is expected to die massively. Although the causes of dead standing trees and poor tree vigor of P. thunbergii in the Hanbando coastal forest are complicated, poor management of adequate tree density in response to the growth of P. thunbergii is the primary cause. The secondary cause is external environmental pressures, including unfavorable soil conditions and salty and strong wind that obstruct the growth of P. thunbergii.

• Journal of Korean Society of Forest Science
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• v.101 no.2
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• pp.244-250
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• 2012

The objective of this study was to analyze the above-ground biomass and crown fuel characteristics of Pinus densiflora stands in Yangyang, Gangwon province. A total of thirteen representative trees were destructively sampled in Yangyang region. The results showed that the stem density ($g{\cdot}cm^{-3}$) was 0.347~0.409, whereas the above-ground biomass expansion factors ranged from 1.251~1.419. In terms of crown fuel biomass, the above-ground biomass was $161.6Mg{\cdot}ha^{-1}$ while the stem biomass, branch biomass and needle biomass were $126.4Mg{\cdot}ha^{-1}$, $29.3Mg{\cdot}ha^{-1}$ and $5.9Mg{\cdot}ha^{-1}$, respectively. Needles and twigs with less than 1 cm diameter accounted 45.2% of the total crown fuel load. The available crown bulk density, which was calculated by dividing the crown fuel load to the crown volume, was $0.178kg{\cdot}m^{-3}$. The results of this study on the biomass and carbon stocks estimation of the Pinus densiflora together with the crown fire hazard assessment based on crown fuel loads are very significant information for the forest managers.

• Korean Journal of Plant Resources
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• v.12 no.4
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• pp.297-302
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• 1999

This study was carried out to find morphological characters of flower and its distribution in mixed population of Paeonia lactiflora Pallas. In distribution of flowering periods, early, medium, and late matured type were 18%, 56%, and 26%, respectively. Flowering duration was less than eight days in 9% of flowers. In next 9 to 11 days, 12 to 14 days and more than 15 days showed, 50%, 37% and 4% respectively. For flower sizes, small size below 9cm diameter were 11%, medium size between 9 to 13cm diameter and large size above 13cm diameter were 65% and 24%, respectively. Among six kinds of flower colors - red, red pink, pink, light pink, pale yellow and white, pink color flowers was dominant, showed 56%. In flower types, single flower was 76%, and anemone, crown, bomb and japanese types were also present. Flower stem diameter were positively correlated with flowering duration, flower size and number of stamens, and negatively correlated with number of stamens and pistils, number of pistils and petals.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1689-1699
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• 1990

Sendzimir rolling mill is widely used for rolling hard materials such as stainless steel due to its small work roll diameter and shape controllability using two effective actuators, AS-U-Roll crown adjustment and lst. intermediate roll shifting. However, in comparison with 4-high or 6-high mills, it is noteasy to get good strip or excellent flatness because Z-mill has small diameter of work rolls which are easily deformed by load. A new mathematical model based on the method of dividing roll and strip into multo-portions was used to develop strip profile prediction software. Using the developed software, several influencing factors related to rolled strip profile for Z-Mill were tested analytically and characterized for the effective shape control. The effects of adjusting shape control actuators of Z-Mill on strip profile were also examined and discussed in detail.

• The korean journal of orthodontics
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• v.36 no.1 s.114
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• pp.84-90
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• 2006

The aims of this study were to investigate the prevalence of spaced, closed, and crowded primary dentitions by sex and arch in Korean children from Kanghwa, and to determine the frequency of the primate and developmental spaces. The differences in the mesiodistal crown diameters and the arch dimensions between the spaced, closed, and crowded primary dentitions were also evaluated. Dental casts of 102 preschool children (57 males and 45 females, aged $4{\sim}5$ years) were studied. The prevalence of spacing in the primary dentition was 63.2% In males and 57.8% in females. The frequency of spacing was greater in males than in females, and greater in the maxillary arch than in the mandibular arch. The crowns were significantly larger and the arches significantly narrower in closed and crowded dentitions than in those with spacing (p<0.05). The results showed that the prevalence of spacing was lower than that found in previous studies and the presence of spacing in the anterior region was related to the mesiodistal crown diameter and the intercanine width.

• Korean Journal of Medicinal Crop Science
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• v.6 no.3
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• pp.198-203
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• 1998

This experiment was conducted to determine the effect of different size of divided crowns used as planting material on the growth characteristics, yield and quality of Paeania lactiflora Pallas (P. lactiflora Pallas). The ratio of sprouting, rooting, and growth of above-ground parts increased with the increase of crown size. The root yields of under-ground parts from different size of divided crown were 2,674kg/10a for large size and 2,304kg/10a for medium size and the yield index was improved by 39% and 30%, respectively, compared to 1,921kg/10a in small size. Commodity ratio of roots over 10mm in diameter were higher for large and medium size crown: index increased by 26 % and 11 %, respectively, compared to 1,406kg/10a in small size. Income analyzed by crown size was \ 1,133,000 per 10a at the use of small crown size but income were increased 25 % and 48 %, respectively. by using medium and large size crown as compared with small crown.