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CT사진을 이용한 한국인의 C형 치근관의 분포에 대한 연구
전록원,허경회,이원진,허민석,이삼선,최순철 대한구강악안면방사선학회 2009 Imaging Science in Dentistry Vol.39 No.2
Purpose : To investigate the incidence and prevalence of C-shaped root canal using computed tomographic images of head and neck in Korean population. Materials and Methods : Regardless of each examination purpose, randomly selected 268 examples which have serial axial computed tomographic images with 8 normal molars in maxilla and mandible were selected and investigated. Defined C-shaped root canal and we could get 82 proper image examples in view of this definition. These were detected and investigated of incidence and prevalence of C-shaped root canal. Results : C-shaped root canals were found in 82 examples among 268 (30.6%) and 147 teeth. They were only found on molar area, and the highest incidence was 37.41% of left mandibular second molars, and the lowest was 2.04%of right maxillary second molars. On prevalence of tooth position, mandibular second molar was the highest, 65% of C-shaped root canal teeth and maxillary second molar was 6% the lowest. Conclusion : 31% of randomly selected CT images no considering check-up reason have C-shaped root canals. The C-shaped root canals of mandibular second molar are found most frequently and they are also detectable on maxilla. On Korean population, C-shaped root canals are one of conditions that have to concern with dental treatment for it appears at a high prevalence relatively.
Kyung Rok Won,Nam Euy Hong,Han Min Park,Hee Seop Byeon 한국목재공학회 2016 목재공학 Vol.44 No.6
To evaluate the resistance of wood to decay caused by fungi, sapwood and heartwood of red pine (Pinus densiflora) and sapwood and heartwood of larch (Larix kaempferi) were conducted. Wood samples were immersed for 96 h in pyroligneous liquor. Then, the brown-rot fungus, Fomitopsis palustris, was used to examine the decay resistance of red pine and larch. Weight and density of wood from the all conditions increased after immersion treatment. Weight loss after decay resistance test was also dropped with a immersion treatment. The lowest weight loss indicated at immersion-treated heartwood of larch. Immersion treatment using pyroligneous liquor effectively increased the resistance of wood to decay caused by fungi.
Kyung-rok Won,Nam-euy Hong,Su-young Jung,Byung-ro Kim,Hee-seop Byeon 한국목재공학회 2017 목재공학 Vol.45 No.2
This study was conducted to evaluate the resistance of heat-treated wood using the catalyst to decay caused by fungi for sapwood and heartwood of two tree species, Korean red pine (Pinus densiflora) and Japanese larch (Larix kaempferi), respectively. Wood samples were immersed for 10 min in sulfuric acid (7.5%) and then heat-treated at 130℃ for 90 min. Fomitopsis palustris, a brown-rot fungus, was used to examine the decay re-sistance of Korean red pine and Japanese larch wood. Weight and density of wood from the all conditions in-creased after heat treatment using the catalyst. Weight loss after decay resistance test was also dropped with a heat treatment. The lowest weight loss indicated at heat-treated heartwood of Japanese larch. Heat treatment us-ing the catalyst effectively increased the resistance of wood to decay caused by fungi.
Study on Red and Black Heartwood Properties of Cryptomeria Japonica in Southern Region of Korea
Kyung-rok Won,Su-young Jung,Byung-oh Yoo,Nam-euy Hong,Hee-seop Byeon 한국목재공학회 2017 목재공학 Vol.45 No.6
The heartwood (HW) of Japanese cedar (Cryptomeria japonica) has usually a reddish color. But some trees have black-colored heartwood (BHW). BHW of Japanese cedar has a low commercial value because of the appearance. Therefore, in this study, a comparative analysis was conducted to evaluate the differences in the physical, mechanical, and inorganic element properties, and decay resistance of red-colored heartwood tree (RHW) and BHW. The physical properties showed significant difference between sapwood (SW) and HW, but there was no significant difference between RHW and BHW. From the results of mechanical properties, no sig-nificant difference was recognized in SW of RHW, HW of RHW, SW of BHW, and HW of BHW. There were decay resistance differences between RHW and BHW in HW, and between HW and SW in both RHW and BHW, respectively. The magnesium (Mg), potassium (K), and calcium (Ca) contents had significant differences between SW and HW in both RHW and BHW. In this present study, the decay resistances and the contents of Mg and K were higher in HW than in SW both for RHW and BHW, while these measurements were lower in RHW than in BHW. Therefore, BHW was considered to be worthy as a high-quality material as RHW.
Effect of Heat Treatment on the Bending Strength and Hardness of Wood
Kyung Rok Won,Tae Hong Kim,Kyo Kil Hwang,Song Ho Chong,Nam Euy Hong,Hee Seop Byeon 한국목재공학회 2012 목재공학 Vol.40 No.5
Heat treatment improves dimensional stability and sound absorption properties of wood. However, mechanical properties of wood can be deteriorated during the heat treatment. The effect of heat treatment on the bending strength and hardness of wood for Korean paulownia, Pinus densiflora, Lidiodendron tulipifera and Betula costata were measured. The heat treatment temperature has been investigated at 175°C and 200°C, respectively. The results showed that the weight and density of wood decreased after heat treatment. It was found that the density by heat treatment was lower at 200°C than that at 175°C. And, MOE increased with the reduced density. On the contrary, MOR and hardness decreased. In all conditions, It was found that there was a high correlation of 1% level between bending modulus of elasticity and modulus of rupture.
Kyung Rok Won,Kwang Soo Lee,Su Young Jung,Byung Oh Yoo,Han Min Park,Hee Seop Byeon 경상대학교 농업생명과학연구원 2019 농업생명과학연구 Vol.53 No.3
Bamboo forests are fast-growing, renewable resources, and their carbon sequestration potential has attracted increasing attention. Although bamboo can be used for many purposes, bamboo forests in Korea represent a generally underutilized resource. The main objective here was to perform an assessment of the physical and mechanical characteristics of different species of bamboo found in Korea. The main species of domestic bamboo are Phyllostachys bambusoides, P. pubescens, and P. nigra; we measured the air-dried density for each of the species, with obtained values of 0.89 g/cm2, 0.79 g/cm2, and 0.83 g/cm2, respectively, giving the density order of P. bambusoides > P. pubescens > P. nigra, with P. bambusoides having the highest density. We then measured the compressive strength of each species, which were 802.84 kgf/cm2, 624.69 kgf/cm2, and 743.77 kgf/cm2, respectively, in the order of P. bambusoides > P. pubescens > P. nigra, with P. bambusoides having the highest compressive strength. Volume and maximum load decreased with increasing node height in the three bamboo species, whereas air-dried density and compressive strength increased. Our results thus add to the pool of essential knowledge about Korean bamboo species, and consequently to the development of a potentially valuable domestic resource in Korea.
Kyung Rok Won,Song Ho Chong,Nam Euy Hong,Sang Uk Kang,Hee Seop Byeon 한국목재공학회 2013 목재공학 Vol.41 No.5
Nondestructive evaluation (NDE) technique method using a resonance frequency mode was carried out for heat treatment wood produced under different conditions. The effect of heat treatment on the bending strength and NDE technique using the resonance frequency by impact hammer mode of wood for Korean paulownia, Pinus densiflora, Lidiodendron tulipifera and Betula costata were measured. The heat treatment temperature has been investigated at 175°C and 200°C, respectively. There were a close relationship of dynamic modulus of elasticity and static bending modulus of elasticity to MOR. In all conditions, It was found that there were a high correlation at 1% level between dynamic modulus of elasticity and MOR, and static modulus of elasticity and MOR. However, the result indicated that correlation coefficient is higher in dynamic modulus of elasticity to MOR than that in static modulus of elasticity to MOR. Therefore, the dynamic modulus of elasticity using resonance frequency by impact hammer mode is more useful as a nondestructive evaluation method for predicting the MOR of heat-treated wood under different temperature and species conditions.
Kyung-Rok Kim,Chang-Wan Ha,Kyung-Soo Kim,Won-Soo Yun IEEE 2014 IEEE transactions on components, packaging, and ma Vol.4 No.3
<P>In this paper, a method to reduce the contact resistance of lateral thermosonic bonding with an anisotropic conductive film (ACF) is proposed. Despite the various advantages of the ACF-based bonding process, it suffers from higher contact resistance between a chip and a substrate, which increases the power consumption and decreases the reliability. The contact resistance largely relies on the conductive particle density. However, in the thermosonic process, a large portion of conductive particles flow out along with the adhesives at the reflow state. To tackle this issue, an intaglio-shaped bump is newly proposed. Thanks to the proposed bump, more conductive particles remain inside the intaglio shape after the reflow state, which results in increment of the conductive particles' density. Through the experiments with a commercialized ACF, it will be shown that the proposed intaglio-shaped bump does increase the conductive particle density of the lateral thermosonic bonding process.</P>
Effects of Heating Temperature and Time on the Physical Properties of Heat-Treated Wood
Kyung-Rok Won,Nam-Euy Hong,Su-Sang Kwon,Hee-Seop Byeon 경상대학교 농업생명과학연구원 2015 농업생명과학연구 Vol.49 No.6
This study was performed to investigate the effects of heat treatment on the physical properties of two species of wood under different heating conditions including at 180℃ for 12 h and 24h, and at 210℃ for 3h and 6h. Heat treatment tests for Pinus densiflora and Larix kaempferi were performed in order to assess the effects on the properties of dimension, weight, density loss, and water absorption. The results showed heat treatment caused significant changes in physical properties such as the dimension, weight, density loss and amount of water absorption. The dimension, weight and density of wood after heat treatment decreased as the heating temperature and time were increased. The amount of water absorption was lower in heat-treated wood than that in solid wood until 48hours. However, the water absorption of heat-treated wood was higher in heat-treated wood than that in solid wood at 96hours. The amount of water absorption of solid Pinus densiflora was higher than that of solid Larix kaempferi.