• Journal of the Korean Wood Science and Technology
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• v.38 no.1
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• pp.1-10
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• 2010

In this study, to study an effective use and improve strength performances of woods and wood-based materials, three-ply hybrid laminated woods which are composed of spruce in the face and three kinds of wood-based boards (MDF, PB, OSB) in the core were manufactured, and the effect of constitution elements used for the core laminae on bending creep performances was investigated. The shape of creep curves showed exponential function plots which the upper right side was increased, and differed among the kinds of wood-based boards used for the core laminae of hybrid laminated wood. The creep deformation perpendicular to the grain of faces of hybrid laminated woods was in order $C_{\perp}$(P) > $C_{\perp}$(M) > $C_{\perp}$(O) with PB, MDF and OSB in the core, respectively. It was found that the creep deformation arranged with OSB in the core had 2 times smaller than those arranged with MDF and PB in the core. By hybrid laminating, the creep deformation of spruce perpendicular to the grain was markedly decreased. On the other hand, the creep deformation parallel to the grain of the faces ($C_{\parallel}$ type) of hybrid laminated woods was in order $C_{\parallel}$(P) > $C_{\parallel}$(O) > $C_{\parallel}$(M) with PB, OSB and MDF in the core. The ratios among three hybrid laminated woods were considerably decreased, especially the difference between $C_{\parallel}$(P) and $C_{\parallel}$(O) hybrid laminated woods arranged with PB and OSB in the core was very small. These values showed 0.108~0.464 times smaller than creep deformation of three wood-based boards and it was found that creep deformation of three wood-based boards was considerably decreased by hybrid laminating. Creep anisotropy of hybrid laminated woods was greater in creep deformation than in initial deformation, whereas it was found that the values was much smaller than that of spruce parallel laminated woods.

• Radiation Oncology Journal
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• v.12 no.2
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• pp.151-158
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• 1994

Since Jan. 1992, authors have conducted a pilot study to treat malignant glioma with multiple daily fractionated(MDF) radiation therapy and this paper presents the outcome compared MDF to conventional factionated(CF) radiation therapy Between Sep. 1989 and Jan. 1993, forty three patients with high grade glioma of brain except brain stem glioma were treated: nineteen patients were treated with CF radiation therapy and 24 patients were treated with MDF radiation therapy. In CF radiation therapy, total dose was 6300cGy/35fx in 7 weeks, which 5040cGy was delivered to the initial target volume and 1260cGy to reduced target volume. And in MDF radiation therapy, total dose was 6400cGy/40fx in 4 weeks, which 3200cGy was delivered to the initial target volume as 160cGy 2 times daily 6hr apart. All patients had histologically confirmed anaplastic astrocytoma(AA) of glioblastoma multiforme (GBM) with stereotactic biopsy or craniotomy for subtotal or gross tumor resection. The range of follow-up was 7 months to 4 years with a median follow-up of 9 months. The Median survival from surgery was 9 months for all patients. The median survival was 9 months and 10 months for MDF group and CF group and 10 months and 9.5 months for glioblastoma multiforme and anaplastic astrocytoma, respectively. In 36 patients with follow-up CT scan or MRI scan, disease status was evaluated according to treatment groups, Four patients(GBM:3, AA:1) of 21 patients in MDF group, were alive with no evidence of disease, while none of patient was alive with no evidence of disease in CF group. The progression of disease had occurred in 20 patients, 11 patients and 9 patients in MDF group and CF group, respectively All of these patients showed in-field progression of disease, Four of 11 patients($27\%$) in MDF group showed the new leasion outside of the treatment field, while 5 of 9 patients($56\%$) in CF group. In our study the prognosis was not influenced by age, KPS, grade, extent of surgery and different fractional scheduled radiation therapy. Authors concluded that MDF regimen was well tolerated and shortened the treatment period from 7 weeks to 4 weeks without compromising results. We believe that further follow-up is needed to assess the role of MDF.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.E2
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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.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.3 no.1
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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.

• Physical Therapy Korea
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• v.10 no.3
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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.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.5 no.1
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• pp.20-25
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• 2012

Gender differences have been studied by using spectral features such as median frequency (MDF) respectively. MDF is the most commonly used as a feature to describe muscle conduction velocity. The aim of this paper is to detect gender differences from surface EMG signals during isotonic contractions of the bicep Brachii. Eight volunteers participated in surface EMG recordings placed on the biceps brachii and each recording experiment continued until their exhaustion. We used feature values and regressive slopes and compared the feature changes from the onset to the endurance time to find gender differences. The result of experiments shows that the regressive slope of these features is valid to measure gender differences.

• Journal of the Korean Wood Science and Technology
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• v.48 no.2
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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.

• Transactions of Materials Processing
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• v.29 no.2
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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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• v.13 no.4
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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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• v.42 no.5
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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.