• Journal of Korean Society of Forest Science
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• v.78 no.4
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• pp.396-400
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• 1989

The oxygen index test was carried out to obtain the relative flammability of wood-based materials (plywood, MDF, particleboard) and their oxygen indices. The oxygen index is the minimum concentration of oxygen, expressed as volume percent, in a mixture of oxygen and nitrogen that will just support flaming combustion of a material under the specified laboratory conditions. In this study the oxygen indices were calculated by using the Dixon and Massey's Up and Down method("N" Large method). The obtained results were as follows : 1. The oxygen indices calculated with Up and Down method were 27.9% for plywood, 26.9% for MDF, and 26.2% for particleboard, indicative of plywood being more difficult to burn than MDF and particleboard Lender the same surrounding conditions. 2. The oxygen indices were not affected by the total gas flow rate.

• The korean journal of orthodontics
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• v.49 no.5
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• pp.326-337
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• 2019

Objective: The objective of this study was to develop new parameters based on the foramina of the trigeminal nerve and to compare them with the conventional cephalometric parameters in different facial skeletal types. Methods: Cone-beam computed tomography (CBCT) scans and cephalograms from 147 adult patients (57 males and 90 females; mean age, 26.1 years) were categorized as Class I ($1^{\circ}$ < ANB < $3^{\circ}$), Class II (ANB > $5^{\circ}$), and Class III (ANB < $-1^{\circ}$). Seven foramina in the craniofacial area-foramen rotundum (Rot), foramen ovale (Ov), infraorbital foramen, greater palatine foramen, incisive foramen (IF), mandibular foramen (MDF), and mental foramen (MTF)-were identified in the CBCT images. Various linear, angular, and ratio parameters were compared between the groups by using the foramina, and the relationship between the new parameters and the conventional cephalometric parameters was assessed. Results: The distances between the foramina in the cranial base did not differ among the three groups. However, the Rot-IF length was shorter in female Class III patients, while the Ov-MTF length, MDF-MTF length, and Ov-MDF length were shorter in Class II patients than in Class III patients of both sexes. The MDF-MTF/FH plane angle was larger in Class II patients than in Class III patients of both sexes. Most parameters showed moderate to high correlations, but the Ov-MDF-MTF angle showed a relatively low correlation with the gonial angle. Conclusions: The foramina of the trigeminal nerve can be used to supplement assessments based on the conventional skeletal landmarks on CBCT images.

• Ceramist
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• v.10 no.3
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• pp.75-85
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• 2007

Over the past few years, due to the great development of optical communications, an increasing R&D activity has been focused on the design and manufacture of the integrated optic amplifiers, with particular reference to their application in wavelength-division-multiplexing (WDM) systems. In this technological context, rare-earth-doped oxide glasses, which had been widely used for solid state lasers, gained much attention as highly performing materials in the third telecom window, around 1.5 micron. The aim of the present paper is to provide a brief overview of the progress made, with particular reference to the authors' work in this area, and to shortly discuss its perspectives.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.8
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• pp.1497-1505
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• 2010

The present study was performed to investigate the effect of aging on muscular activity of older subjects under the condition of fixed load muscle contraction. SEMG signals were recorded from old (46 women) and young (45 women) groups performing sustained isometric elbow flexion contraction with a fixed load during 30 seconds. Linear regression and mean square error (MSE) analysis with four characteristic variables (ARV, RMS, MDF, MNF) were used to compare the age-related difference (of local muscle fatigue and fluctuation of the amplitude and frequency) in the SEMG signal. The main results can be summarized as follows: During sustained muscle contraction with a fixed load: i) the MSE values of amplitude (ARV, RMS) and frequency (MDF, MNF) variables were more than 30% higher for the young than for the old adults; ii) the measures of local muscle fatigue (slope of the MDF and MNF) indicated greater fatigue in the old; and iii) the rate of increase of the SEMG amplitude was higher for the young than the old.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.8
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• pp.60-67
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• 1998

We studied the effects of fractional fourier transform in face recognition, in which only the amplitude spectra of transformed facial images were used.We used two recently developed face recognition methods, the most effective feature (MEF) method (i.e., eigenface method) and most discriminating feature (MDF) method, and the effects of th etransform for th etwo methods were consistent. We confirmed that the recognition rate by the use of MDF method is better than that consistent. We confirmed that the recognition rate by the use of MDF method is better than that by MEF regardless of the order to transform, these methods provided slightly better results when the order was 1 than for any other order values. Only when the order was close to 1, the recognition rates were robust to the shift of the input images, and the trend that the recognition rates decreased as the input size varied was independent of the order. From these results, we fond that it is most advantageous to use the amplitude spectra of the conventional fourier transform whose order is 1.

• Journal of Korean Physical Therapy Science
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• v.10 no.1
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• pp.83-89
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• 2003

An electromyogram (EMG) using surface electrodes is one of the indirect tests most frequently used to ascertain muscle fatigue. An EMG can be used in two ways. The first technique determines the root mean square (RMS), which reflects the amplitude of the EMG signal. The second technique determines the median and mean power frequencies through EMG power spectrum analysis. The purpose of this article is for determine the correlation between work and percent root mean square(%RMS) and between work and MDF of EMG based on muscle contractions. It is used the %RMS, which reflects the amplitude of the EMG signal For MDF, it is used the frequency power spectrum analysis method, which involves the fast Fourier transformation (FFT) of the original Signals.

• Journal of the Korea Furniture Society
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• v.13 no.1
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• pp.19-25
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• 2002

Modern furniture is mostly made of panel products such as a glue-up panel, a particle board and a medium density fiberboard(MDF). Warping is a major defect of these panel products resulting in degrading final products. In this study the factors related to the warping of a glue-up panel and MDF were investigated by comparing the physical properties of warped specimens with those of the unwarped. The differences between the moisture contents measured on the both surfaces of specimens were found to mainly influence the warping of glue-up panel specimens whether conditioned or not. The average oven-dry density of warped glue-up panel specimens was definitely higher than that of the unwarped at l% significance level. For MDF the influencing factor on warping has not been revealed yet, however it was found that the conditioning reduced the number of warped specimens.

• Korean Journal of Agricultural Science
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• v.36 no.1
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• pp.19-25
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• 2009

This study was carried for recycling laminated PB and MDF of disused furniture. PB and MDF particles taken from disused furniture were heat-treated at $250^{\circ}C$ and four levels of treatment time, 2, 4, 6 and 8 hours. The recycled boards were made with heat-treated particles after milling and screening with 100 mesh. The bending strength of the recycled boards were lower than that of virgin boards while their anti-swelling efficiency were much improved. Their formaldehyde emissivity were very low. Thus it was concluded that the recylcled boards are prospective environment-friendly material for interial consturction.

• International Journal of Reliability and Applications
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• v.3 no.4
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• pp.155-164
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• 2002

This paper focuses on how modem data mining can be integrated with real-time relational databases and commercial data warehouses to improve reliability in real-time. An important Issue for many manufacturers is the development of relational databases that link key product attributes with real-time process parameters. Helpful data for key product attributes in manufacturing may be derived from destructive reliability testing. Destructive samples are taken at periodic time intervals during manufacturing, which might create a long time-gap between key product attributes and real-time process data. A case study is briefly summarized for the medium density fiberboard (MDF) industry. MDF is a wood composite that is used extensively by the home building and furniture manufacturing industries around the world. The cost of unacceptable MDF was as large as 5% to 10% of total manufacturing costs. Prevention can result In millions of US dollars saved by using better Information systems.

• Journal of the Korea Furniture Society
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• v.20 no.5
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• pp.490-503
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• 2009

The objective of this work was to investigate the mechanism of heat transfer in hot-pressing process for MDF manufacturing by reference study. Firstly, general heat transfer theory was studied. The numerical analysis of heat transfer in hot-pressing process was studied on temperature profile, moisture profile, physical properties between moisture and board. The mechanism of heat and moisture transfer inside of board was analyzed by conduction, convection, radiation and diffusion of bound water in wood cell walls. Especially, the change of core temperature as hot press time was important factor to setup hot-pressing schedule in MDF manufacturing.