• Journal of the Korean Wood Science and Technology
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• 제38권1호
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• pp.1-10
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• 2010

이 연구에서는 목재의 효율적인 이용의 일환으로 스프루스 직교형적층재의 중층을 중밀도섬유판(medium density fiberboard, MDF), 파티클보드(particle board, PB) 및 오에스비(oriented strand board, OSB)의 3종류의 시판용 목질보드를 복합적층한 3층 목질계 복합적층재(패널)를 제작하여, 중층 목질보드라미나의 구성엘리멘트가 복합적층재의 휨 크리프성능에 미치는 영향을 조사하였다. 복합적층재의 휨 크리프곡선은 우측상변이 급증하는 지수함수 그래프를 나타내었고, 각 복합적층재의 중층 목질보드라미나의 종류에 따라 다른 경향을 나타내었다. 복합적층재의 크리프변형은 표층섬유직각방향($C_{\perp}$ 타입)에서는 중층에 PB, MDF, OSB를 배열한 $C_{\perp}$(P)타입 > $C_{\perp}$(M)타입 > $C_{\perp}$(O)타입의 순으로, OSB를 중층에 배열한 타입의 크리프변형이 MDF나 PB를 중층에 배열한 것의 2배 이상 적은 것이 확인되었고, 복합적층에 의해 스프루스 섬유직각방향의 크리프변형의 현저한 감소가 나타났다. 한편, 표층섬유방향($C_{\parallel}$ 타입)의 크리프변형은 중층에 PB, OSB, MDF를 삽입한 $C_{\parallel}$(P)타입 > $C_{\parallel}$(O)타입 > $C_{\parallel}$(M)의 순이었으나, 복합적층에 의해 적층재상호간의 비는 현저히 감소하였고, 중층에 PB와 OSB를 배열한 복합적층재의 크리프변형의 차이는 매우 적은 것이 확인 되었다. 이 값은 목질보드의 크리프변형보다는 0.108~0.464배의 적은 크리프변형을 나타내어 복합적층에 의해 목질보드의 크리프변형의 현저한감소가 나타났다. 복합적층재의 표층섬유방향에 대한 표층섬유직각방향의 크리프이방성은 초기변형보다 크리프변형이 현저히 컸지만, 스프루스 평행형적층재의 크리프이방성보다는 현저히 감소하는 것이 확인되었다.

• Radiation Oncology Journal
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• 제12권2호
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• pp.151-158
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• 1994

본 연구는 1989년 1월부터 악성성상세포종과 다형성 교아종에 대해 시행된 방사선 치료에 다분할 방사선 치료와 단순분할 방사선 치료와 단순분할 방사선 치료에 대한 효과를 비교하고 이들 뇌종양의 방사선치료후 예후에 영향을 미치는 인자를 확인하기 위해 시행되었다. 뇌간의 교종 환자를 제외한 전체 43명의 환자는 조직학적으로 악성성상세포종과 다형성교아종으로 확인되었고, 모두 방사선치료를 받았다. 환자는 일반적으로 알려진 예후인자인 연령, 성별, 수행능력, 조직학적 형태, 종양의 절제정도에 따라 분류하였다. 정위적 조직 생검만 시행한 경우는 13명으로 다분할 방사선 치료군과 단순분할 방사선 치료군에서 각각 8명, 5명이었고 개두술에 의해 종양절제술을 받은 경우는 30명으로 다분할 방사선 치료군과 단순분할 방사선 치료군에서 각각 16명과 15명이었다. 조직학적 소견에 따라 악성성상세포종은 15명으로 다분할 방사선 치료군과 단순분할 방사선 치료군에서 각각 6명, 9명이었고 다형성교아종은 25명으로 다분할 방사선 치료군과 단순분할 방사선 치료군에서 각각 16명, 10명이었다. 수행 능력이 70이하인 경우는 8명으로 다분할 방사선 치료군과 단순분할 방사선 치료군에서 각각 4명이었으며 대부분이 수행능력 70이상이었다. 50세 이상인 경우 26명이었고 50세 이하인 경우가 18명이었다. 환자의 중앙연령은 52.5세이고, 범위는 2에서 78세였다. 방사선 치료는 1989년 1월부터 1991년 12월까지 단순분할 방사선이 19명의 환자에게 시행되었고 1992년 1월부터 1993년 1월까지 24명의 환자에서는 다분할 방사선 치료가 시행되었다. 단순분할 방사선치료는 종양부위에 하루 일회 1.8Gy씩 조사되어 7주에 걸쳐 총 63Gy가 조사되었다. 그리고 다분할 방사선 치료는 종양 부위에 1.6Gy씩 1일 6시간 간격으로 2회씩 조사하여 4주에 걸쳐 총 64Gy가 조사되었다. 중앙추적 관찰기간은 9개월이었고 범위는 7개월부터 4년이었다. 전체 환자의 중앙생존 기간은 9개월 이었고 단순분할 방사선 치료군과 다분할 방사선 치료군에서 각각 9개월, 10개월 다형성교아종파 악성성상 세포종에서 각각 10개월 9.5개월이었다. 방사선 조사방법에 따른 비교와 조직학적 형태에 따른 비교에서 의미있는 통계적 차이는 발견할 수 없었다. 컴퓨터 단층촬영이나 핵자기 공명촬영으로 추적 관찰이 가능했던 36명의 환자에서 질병의 상태를 평가하였으며 다분할 방사선 치료군에서 21명중 4명이 무병상태로 생존해 있었고 단순분할 방사선 치료군에서는 13명중 무병상태로 생존한 환자는 없었다. 20명의 환자에서 질병이 진행되거나 재발하였는데 이들중 8명은 방사선이 조사되지 않은 새로운 부위에서 재발하였다. 본 연구에서는 일반적으로 예후 인자로 알려진 연령, 수행능력, 조직학적 형태, 종양의 절제정도가 예후에 영향 미치는 지를 확인할 수 없었다. 본 연구에서 추적기간이 짧기 때문에 정확한 결론을 도출하기 어려우나 고등급 교종에서 다분할 방사선 치료 방법으로 1.6Gy씩 1일 2회로 총 64Gy 조사는 단순분할 방사선 치료방법에 의한 결과보다 더 나은 결과를 보여주지는 못하였다. 그러나 단순분할 방사선 치료와 비교해서 치료에 큰 장애 없이 치료기간을 약 3주 정도 단축시킬 수 있었다. 정확한 결론을 얻기위해 지속적인 추적관찰이 필요하며 치료결과를 향상시키기 위하여 방사선 조사 방법에 있어서 총 방사선량, 1회 방사선 조사량의 조정을 고려한 연구가 필요하며 총 방사선량을 증가시키는 한 방법으로 다분할 방사선 치료와 감마 나이프나 침입형 근접치료를 병용하는 방법도 고려될 수 있겠다.

• Journal of Korean Society for Atmospheric Environment
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• 제23권E2호
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• pp.57-65
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• 2007

In Korea, there is a general lack of information available on air emissions from industry. The reasons for this include the lack of regulatory requirements for emission monitoring, limited information on specific industries, and difficulties in monitoring certain sources. This paper presents the first detailed air pollutant emission factors from composite wood product manufacturing in Korea. This study introduced emission factors for wood-based panels such as plywood, particle board (PB), and medium density fiberboard (MDF). The emission factors of particulate matters (PM) and hazardous air pollutants (HAPs) from MDF were higher than that from other wood products. The concentration of total volatile organic compounds (TVOCs) for hot press from wood-based panels was higher than drying or gluing processes. Emissions data from NPIP were compared to the data from the suggested emission factors in this study and the US EPA's. The data from our emission factors were closer to the observed results than the data using the US EPA's emission factor.

• 대한임상전기생리학회지
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• 제3권1호
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• pp.31-47
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• 2005

Fatigue is a common experience in our daily life and in therapeutic exercises. Human muscle fatigue has been studied using a wide variety of exercise models, protocols and assessment methods. This study conducts quantitative evaluation of fatigue of knee extensor with surface electromyography and dynamometer and is to provide basic materials in physical therapy diagnosis and assessment of skeletal muscle. Measurement of two stages was conducted with 88 normal adults between their twenties and seventies, correlations and differences using collected data according to age was compared and correlations among measured items were analyzed and then the following conclusions were obtained. Analysis of sEMG and dynamometry of knee extensor showed that MDF, FI, MVIC, ET had the closest relations with age and MDF, FI, MVIC were significantly increase with aging. In addition, it was found that there were high correlation among items of analysis.

• 한국전문물리치료학회지
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• 제10권3호
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• pp.141-149
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• 2003

Median frequency can be regarded as a valid indicator of local muscle fatigue. As local muscle fatigue develops, the muscle fiber conduction velocity decreases, the fast twitch fibers are recruited less, and consequently the median frequency shifts toward the lower frequency area. The aim of this study was to test the characteristics of the median frequency according to exercise load (30% and 60% of MVC on the biceps brachii, 40% and 80% of MVC on the vastus lateralis) during the fatiguing isometric exercise. Thirteen healthy male volunteer students of Yonsei University were recruited. After the testing maximal voluntary isometric contraction, three variables (initial median frequency, regression slope, fatigue index) from the regression line of MDF data were measured in each exercise load. The results showed that the regression slope and fatigue index were significantly different for the biceps brachii, but not for the vastus lateralis initial MDF was not significant difference according to the exercise load on both muscles. The regression slope and fatigue index could monitor physiologic muscle change during fatiguing isometric exercise. The results showed that two MDF variables reflect the local muscle fatigue according to the exercise load.

• 한국정보전자통신기술학회논문지
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• 제5권1호
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• pp.20-25
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• 2012

표면근전도의 중앙주파수 특징을 이용하여 근지구력시간에 대한 남녀 성별차별을 구분할 수가 있다. 중앙주파수는 근육의 피로속도를 측정하는데 주로 사용하는 인자이다. 본 연구에서는 상완이두근의 등장성 운동을 통한 근전도의 성별차이를 알아보았다. 등장성운동은 피실험자가 근육피로가 피곤해 질 때까지를 측정하였다. 남녀 성별차이는 근지구력시간에 대한 중앙주파수의 선형회귀선의 기울기로 구분되어지는 특성을 보였다.

• Journal of the Korean Wood Science and Technology
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• 제48권2호
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• pp.231-244
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• 2020

As a way of finding value-added materials from waste medium density fiberboard (MDF), this study characterized cellulose nanocrystals (CNCs) isolated by ammonium persulfate (APS) oxidation using recycled MDF fibers. Chemical composition of the recycled MDF fibers was done to quantify α-cellulose, hemicellulose, lignin, nitrogen, ash and extractives. The APS oxidation was performed at 60 ℃ for 16 h, followed by ultrasonication, which resulted in a CNC yield of 11%. Transmission electron microscope images showed that rod-like CNCs had an average length and diameter of 167±47 nm and 8.24±2.28 nm, respectively, which gave an aspect ratio of about 20. The conductometric titration of aqueous CNCs suspension resulted in a carboxyl content of 0.24 mmol/g and the degree of oxidation was 0.04. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy clearly showed the presence of carboxyl group on the CNCs prepared by the APS oxidation. The change of pH of the aqueous CNC suspension from 4 to 7 converted the carboxyl group to sodium carboxylate group. These results showed that the APS oxidation was facile and CNCs had a one-step preparation method, and thus suggested an optimization of the oxidation condition in future.

• 소성∙가공
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• 제29권2호
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• pp.76-88
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• 2020

The need for advanced high strength steel (AHSS) forming technology is increasing as interest in light weight and safe automobiles increases. Multipoint dieless forming (MDF) is a novel sheet metal forming technology that can create any desired longitudinal and transverse curvature in sheet metal. However, since the springback phenomenon becomes larger with high strength metal such as AHSS, predicting the required MDF to produce the exact desired curvature in two directions is more difficult. In this study, a prediction model using artificial neural network (ANN) was developed to predict the springback that occurs during AHSS forming through MDF. In order to verify the validity of model, a fit test was performed and the results were compared with the conventional regression model. The data required for training was obtained through simulation, then further random sample data was created to verify the prediction performance. The predicted results were compared with the simulation results. As a result of this comparison, it was found that the prediction of our ANN based model was more accurate than regression analysis. If a sufficient amount of data is used in training, the ANN model can play a major role in reducing the forming cost of high-strength steels.

• Asian Pacific Journal of Cancer Prevention
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• 제13권4호
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• pp.1569-1573
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• 2012

Luteolin (LUT), a bioflavonoid has been used as a chemopreventive agent world-wide against chemically induced cancer. Hence we designed an experiment to assess chemopreventive action of LUT on lipid peroxidation (LPO) and glycoconjugates in azoxymethane (AOM)-induced colon carcinogenesis. Colon cancer was induced by 15 mg/body kg. body weight of AOM and administration of LUT (at the dose of 1.2 mg/kg. body weight) was till end of the study. Analysis of lipid peroxidative end products such as protein carbonyl (PC), malonadehyde (MDA) and conjucated dienes (CD) demonstrated significant increase in in AOM-induced animals with reduction by LUT (p<0.05). Increased levels of glycoconjugates such as hexose, hexosamine, sialic acid, fucose and mucoprotein were analyzed in serum and colon tissues examined histopathologically by periodic acid Schiff's (PAS) staining were also reversed by LUT l(p<0.05). The secondary marker of colon cancer mucin depleted foci (MDF) was assessed in control and experimental group of animals. A characteristic increase of MDF was observed in AOM-induced colon cancer animals. Treatment with LUT decreased the incidence of MDF. These results suggest that LUT alters the expression of glycoconjugates and suppress colon cancer. Hence, we speculate that LUT can be used as a chemopreventive agent to treat colon cancer.

• Journal of the Korean Wood Science and Technology
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• 제42권5호
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• pp.615-623
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• 2014

Increases of public attention on healthy environment lead to the regulation of indoor air quality such as Clean Healthy House Construction Standard. This standard covers emission of total volatile organic compounds (TVOCs) (e.g., formaldehyde, benzene, and toluene), ventilation, and use of environmentally-friendly products or functional products. Moisture absorption and desorption abilities are a recommended functionality for improving indoor air quality. In this study, moisture absorption and desorption capacities of carbonized board from wood-based panels and other materials were determined by using UNT-HEAT-01 according to ISO 24358:2008. Pine had higher moisture absorption and desorption capacities ($49.0g/m^2$ and $35.3g/m^2$, respectively) than hinoki cypress, cement board, gypsum board, oriented strand board, and medium density fiberboard (MDF). The moisture absorption and desorption capacities differed considerably according to the wood species. After carbonization process at $400^{\circ}C$, the absorption and desorption ability of MDF increased to 38% and 60%, respectively. However, moisture absorption and desorption capacities decreased with increasing carbonization temperature, but they were still higher than original MDF. Therefore, it is suggested that carbonization below $600^{\circ}C$ can improve moisture absorption/desorption capacities.