• Journal of Korean Society of Forest Science
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• v.65 no.1
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• pp.54-59
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• 1984

Research was conducted in a minirotation plantation with four different planting densities at Tatae-ri, Chongwoon-myon, Yangpyong-gun, Kyonggi-do, to investigate the relation between volume and biomass production. Nine-year-old Alnus hirsuta var. sibirica analyzed to determine volume yield and weight equations for aboveground parts. The results suggest that the most suitable harvesting or thinning period at highly dense plots, more than 6,000 trees per hectare, is five years after planting, and the most fitted regression equation model for estimating aboveground biomass or total tree biomass is $logY=b_0+b_1logd^2h$.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.119-131
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• 2007

Design build (DB) is a construction project delivery system which has become one of the favored ones and the growth of DB by the public agencies has been steadily increasing. DB can be viewed as an evolutionary project delivery system, since DB project team members collaborate on work with each other, keep seeking cost effective and innovative alternatives that meet the construction needs of the project. Thus DB outperformed others in delivery speed, cost saving, and turnover quality. In Korea, DB projects likewise have steadily increased that it is needed to analyze characteristics of DB delivery system in Korea. For that purpose, this research would offer an analysis of characteristics of DB delivery system in Korea using system dynamics model with investigating the public market trend, comparing DB performance to DBB, and analyzing questionnaire survey.

• Imaging Science in Dentistry
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• v.38 no.1
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• pp.49-56
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• 2008

Purpose: Diagnostic estimation of destruction and formation of bone has the typical limit according to capacity of x-ray generator and image detector. So the aim of this study was to find out how much it can reproduce the shape and the density of bone in the case of using recently developed dental type of cone beam computed tomography, and which image is applied by new detector and mathematic calculation. Materials and Methods: Cone beam computed tomography (PSR 9000N, Asahi Roentgen Ind. Co., Ltd., Japan) and soft x-ray radiography were executed on dry mandible that was already decalcified during 5 hours, 10 hours, 15 hours, 20 hours, and 25 hours. Estimating and comparing of those came to the following results. Results: The change of inferior border of mandible and anterior border of ramus in the region of cortical bone was observed between first 5 and 10 hours of decalcification. The reproduction of shape and density in the region of cortical bone and cancellous bone can be hardly observed at cone beam computed tomography compared with soft x-ray radiography. The difference of decrease of bone density according to hours of decalcification increase wasn't reproduced at cone beam computed tomography compared with soft x-ray radiography. Conclusion: CBCT images revealed higher spatial resolution. However, contrast resolution in region of low contrast sensitivity is the inferiority of images' property.

• Journal of the Korean Wood Science and Technology
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• v.15 no.2
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• pp.99-104
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• 1987

Fiber mats were made at various density levels, using fibers from papermill sludge, ricestraw and various mixtures of the two. The paper mill sludges were collected from Moorim Papermill Co, and Jeonjoo Papermill Co. They were soaked in the liquid sulfur compounds, sulfur-tall oil and sulfurpolyester compounds, and made into fiber-reinforced, sulfur-based composition board. Under optimum conditions of fiber mat preparation and saturation with molten sulfur and modified sulfur, the Young's moduls of the manufactured tiber-reinforced composition board are superior to those of conventional wood-based composition boards. For example, the moduli of elasticity of the composition board made from papermill sludge, with a density of 0.40gm/$cm^3$, were greater than 1,400,000psi as compared 800,000psi for high density hardboard(1.28gm/$cm^3$). The modulus of rupture of the best reinforced composition board manufactured was over 9000psi, comparable to 6000psi of high density hardboard. The proposed Bryant and Lee's theory, "Modified Rule of Mixtures" can be applicable to the nonoriented and short fibrous composition board, when it was modified from "Rule of Mixtures" established by Paul an Jones, and supplemented by Smith and Cox's theory, In the Bryant and Lee's theory of $E_c=\frac{1}{3}aE_fV_f+bE_mV_m$, the constants "a" and "b" for the composition boards made from papermill sludge and the mixtures of ricestraw and the sludge were identified to be in the ranges of 3.29~3.54 and -2.47~-2.80 respectively.

• Journal of the Korean Society of Safety
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• v.29 no.3
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• pp.114-120
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• 2014

The purpose of this study is to conduct the study of the combustion and thermal characteristics through transportation oil for the analysis of fire hazard. Transportation oil breaks down into fuels such as diesel for civilian demands, gasoline, DF1(diesel for military), high sulfur diesel(for marine), kerosene and JP1(for aviation), and lubricants like brake fluid, power steering oil, engine oil, and automatic and manual transmission oil. The experiments of flash point, ignition point, flame duration time, heat release rate were carried out using TAG closed cup flash point tester(AFP761), Cleveland open cup auto flash point analyzer(AFP762), KRS-RG-9000 and Dual cone calorimeter. As a result, the fuel's ignition points were lower than lubricants, especially that of gasoline was not conducted as it has below zero one. Gasoline has the highest ignition point of about $600^{\circ}C$, while the other fuels showed $400{\sim}465^{\circ}C$. For flame duration time, lubricants had over 300 seconds, but fuels had less than 300 seconds except high sulfur diesel(350 seconds). Total heat release rate ranged $287{\sim}462kW/m^2$ for lubricants and gasoline showed the highest total heat release rate, $652kW/m^2$.

• Imaging Science in Dentistry
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• v.37 no.2
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• pp.87-92
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• 2007

Purpose: To measure the absorbed doses of cone beam computed tomography (CBCT), which is recently being more frequently used, and to compare them with those of panoramic radiography. Materials and Methods: To measure the absorbed doses of CBCT ($PSR-9000N^{TM}$, Asahi Roentgen Ind. Co., Japan), we placed TLD chips on the skin regions above the parotid and thyroid glands, and on the dorsum of tongue in a dental head phantom. We used two image acquisition modes of the Dental and Panoramic modes of CBCT, which differed in the field of view. Also, panoramic radiographs (Auto IIIN, Asahi Roentgen Ind. Co., Japan) were taken to compare with the absorbed doses of CBCT. Result: In the Dental mode of CBCT, the absorbed doses of the parotid gland, dorsum of tongue, and thyroid gland were 3.53, 3.13, and 0.36 mGy, respectively. In the Panoramic mode of CBCT, they were 9.57, 9.15, and 0.85 mGy, respectively. The panoramic mode showed higher absorbed doses than those of the Dental mode. In the panoramic radiography, the absorbed doses of the parotid gland, dorsum of tongue, and thyroid gland were 1.21, 1.19, and 0.16 mGy, respectively. And they were about 1/3 of the Dental mode and 1/9 of the Panoramic mode of CBCT. Conclusion: Absorbed doses of CBCT are higher than those of panoramic radiography, and dependent upon the field of view.

• Imaging Science in Dentistry
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• v.37 no.2
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• pp.103-110
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• 2007

Purpose: To examine the danger zone of mesial root of mandibular first molar of patient without extraction using CBCT (cone-beam computed tomography) to avoid the risk of root perforation. Materials and Methods: 20 mandibular first molars without caries and restorations were collected, CT images were obtained by CBCT ($PSR9000N^{TM}$, Asahi Roentgen Co., Japan), reformed and analyzed by V-work 5.0 (CyberMed Inc., Korea), Distance between canal orifice and furcation was measured. In cross sectional images at 3, 4 and 5 mm below the canal orifice, distal wall thickness of mesiobuccal canal (MB-D), distal wall thickness of mesiolingual canal (ML-D), distal wall thickness of central part (C-D), mesial wall thickness of mesiobuccal canal (MB-M) and mesial wall thickness of mesiolingual canal (ML-M) were measured, Results: The mean distance between the canal orifice and the furcation of the roots is 2.40 mm, Distal wall is found to be thinner than mesial wall. Mean dentinal wall thickness of distal wall is about 1 mm, The wall thickness is thinner as the distance from the canal orifice is farther. But significant differences are not noted between 4 mm and 5 mm in MB-D and C-D, MB-D is thinner than ML-D although the differences is not significant. Conclusion: The present study confirmed the anatomical weakness of distal surface of the coronal part of the mesial roots of mandibular first molar by CBCT and provided an anatomical guide line of wall thickness during endodontic treatment.

• Journal of Korea Society of Industrial Information Systems
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• v.8 no.4
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• pp.1-7
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• 2003

This study is concerned with the operational methods of Quality Management employed by the small and medium-sized companies in Gang won-do to improve their power of competition. This study is particular, studied the consortium-participating companies on their Plans of Quality Management as to how they carry them out in order to advance to the first-class business enterprises. The results of this study showed that the of shortage manpower and funds that the local small and mediumsized companies commonly face played a significant role as major obstacles in implementing their Quality Management programs. The study results also suggest that it is necessary to promote some periodic manpower train- ing programs in cooperation with local universities, to utilize professors and experts to build management strategies that can bring and secure the power of competition, and to construct a system of educational-industrial cooperation, as ways leading these companies to the 21s1 century's type of business enterprise.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.106-112
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• 2003

A combined discharge type ozonizer was designed and manufactured. The increase or decrease of temperature greatly influences the characteristics of ozone concentration ( $O_{3con}$), ozone generation ( $O_{3g}$) and ozone yield ( $O_{3Y}$) of a discharge type ozonizer. The characteristics of ozone concentration, ozone generation and ozone yield rate were investigated by varying the gas flow rate (Q), the discharge power ( $W_{d}$) and the temperature (T). At T=25[$^{\circ}C$] the values of $O_{3con}$ were found as 5632, 4200, 2500 and l800[ppm] at Q = 1, 2, 4 and 6[l/min] respectively. At the same temperature the corresponding values of $O_{3g}$ were found as 662, 988, 1176 and l270[mg/h] and those of $O_{3Y}$ were found as 67, 102, 119 and 135[g/kWh] respectively. When the temperature is decreased to -50[$^{\circ}C$], the values of $O_{3con}$ were found as 9000, 6700, 4000 and 2800[ppm] respectively at Q = 1, 2, 4 and 6[l/min]. At the same value of temperature the corresponding values of $O_{3g}$ were found as 1220, 1576, 1882 and 2050[mg/h] and those of $O_{3Y}$ were found as 120, 159, 188 and 202[g/kWh] respectively. Hence as the temperature was decreased from 25 to -50[$^{\circ}C$], the efficiencies of ozone generation were increased by 79, 55, 58 and 49[%] respectively at Q = 1, 2, 4 and 6[l/min].]. 6[l/min].].

• Korean Journal of Materials Research
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• v.6 no.8
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• pp.825-832
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• 1996

적외선 센서의 재료로 활용되고 있는 PLT박막 (두께:8000$\AA$-9000$\AA$)을 Pt/Ti/SiO2/Si와 Pt/M\ulcorner의 하부 구조상에 50$0^{\circ}C$, 55$0^{\circ}C$ 및 $600^{\circ}C$에서 스퍼터링 증착하여 결정성 및 전기적 특성을 조사하였다. $600^{\circ}C$로 in-situ 성장된 PLT박막은 Si기판을 이용한 경우 randomly oriented perovskite 결정구조를 나타내었으며, Pt/MgO 구조위에서는 c-축(00ι)방향으로 배향 성장되었다. $600^{\circ}C$에서 in-situ 성장된 PLT박막의 비유전상수($\varepsilon$r)와 유전정접(tan $\delta$)을 10kHz-100kHz의 주파수에서 측정한 결과 Pt/Ti/SiO2/Si 구조상에 증착된 박막은$\varepsilon$r=90과 tan $\delta$=0.02의 값을 Pt/MgO 구조상에 증착된 박막은 $\varepsilon$e=35와 tan$\delta$=0.01의 값을 나타내었다. 잔류분극량(2Pr)과 초전계수(${\gamma}$)는 상온부근에서 Si 기판을 이용한 경우 각각 0.6$\mu$C/$\textrm{cm}^2$.。C과 0.5x10-8C/$\textrm{cm}^2$.。C정도로 매우 작게 나타났으나 PLT/Pt/MgO 구조에서는 2Pr=5$\mu$C/$\textrm{cm}^2$, r=4x10-8C/$\textrm{cm}^2$.。C로 비교적 양호한 초전박막의 전기적 특성을 나타내었다.