• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2011.04a
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• pp.388-392
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• 2011

화재 발생 시 연소확대 방지 및 이를 지연시켜 재실자의 피난시간을 확보하고자 실시하는 방염처리의 성능평가는 연소시험방법을 통해 잔염시간, 잔신시간, 탄화면적, 탄화길이가 일정기준에 적합하여야만 방염성능을 부여받게 되며 목재나 MDF와 같은 합판은 방염도료나 방염필름을 부착하여 사용하는 현장방염처리방법이 사용되고 있다. 따라서 본 연구에서는 시중에서 일반적으로 사용되고 있는 비방염 접착필름, 방염 필름, 방염 도료 등을 MDF 합판에 적용하여 방염처리 하였을 때의 연소특성 및 방염성능을 측정하였다.

• Journal of the Korean Wood Science and Technology
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• v.41 no.2
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• pp.105-110
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• 2013

A repeated impregnation and carbonization process was performed to prepare high-density woodceramics using MDF. The physical properties were estimated to further confirm morphologically structurally occurred changes of one-time and two-time phenolic resin treated and carbonized woodceramics. As compare one-time and two-time carbonized woodceramics, the increasing rate of weight and density declined after second carbonization as the resin impregnation ratio grew higher, and when the resin impregnation ratio was 40 percent, the weight and density of the second carbonization increased more than in the first step by 20.5% and 33.9% respectively which were the highest rates.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.58.3-58.3
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• 2020

We present spatial variations of chemical abundances ([Fe/H] and [α/Fe]) in the Galactic disk, using a large number of dwarfs and giants from Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST). Specifically, we investigate how the metallicity distribution function (MDF) and the alpha abundance distribution function (ADF) change with the distance from the Galactic center to understand the chemical evolution history of the Galactic disk. We also study the difference (if any) in the MDF and ADF between dwarfs and giants to provide valuable clues to the formation history of the Galactic disk.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.3 no.1
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• pp.49-59
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• 2005

This study assigns each 8 of 24 normal persons to control group(Group I), strength increase group(Group II) and endurance increase group(Group III) to analyze differences in changes of strength and endurance with surface electromyography and kinetics according to application modes of neuromuscular electrical stimulation(NMES). Group I had not any treatment, group II performed 15 repeated contraction with 60% intensity of maximal voluntary isometric contraction(MVIC) by setting 10-sec on time and 50-sec off time and group III conducted 30 repeated contraction with 30% intensity of MVIC by setting 10-sec on time and 20-sec off time. For neuromuscular electrical stimulation, 2,500 Hz of Russian current, 35 pps of pulse rate and 200 of pulse width. Neuromuscular electrical stimulation was conducted by five times for total 4 weeks. Before and after experimentmotor unit action potential of vastus medialis, rectus femoris and vastus lateralis were measured with sEMG, median frequency(MDF) was analyzed, and thus the following results were obtained. There was significant difference in the period of measuring vastus medialis and rectus femoris in change of MDF and interaction among groups with analysis of surface electromyography before and after neuromuscular electrical stimulation(p<.001) and in particular, there was a remarkable change among groups according to the period of measurement. In conclusion, NMES influenced changes of strength and endurance according to its application modes and in particular, it was found that strength increment application had a significant influence on strength increment in applying short-time NMES.

• Journal of the Korean Wood Science and Technology
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• v.45 no.3
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• pp.327-334
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• 2017

This study was carried out to investigate the formaldehyde emission of building materials and effect of carbonized-board (c-board) on formaldehyde reduction using a chamber method. As a result, reduction performance of formaldehyde was in the order of c-board (90%), c-bamboo board (84%), diatomite-based panel (82%), allophane-based tile (78%), Pinus densiflora timber (58%), MDF (54%) and gypsum-based board (46%) for approximately 12 days. In $1.9m^3$ chamber filled with particleboard (PB), the formaldehyde reduction performance of c-board was significantly increased with increasing input amount of c-board for 68 days. In particular, the formaldehyde emissions can be reduced above 40% and 75% by input rate of 10% and 30% c-board, respectively, in given ratio of chamber volume and PB area.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.511-518
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• 2017

In recent years, many interests and researches on the insulations required the multiple performances other than insulation performance. The purpose of this paper is to find the optimal ratio between wood fiber and rice-husks charcoal to develop a structural board with carbonized rice-husks. Based on these rice-husks charcoals, basic research was carried out to develop thermal insulation materials with structural performance, and the following conclusions were obtained. The MC of the board using the carbonized rice-husks was 3.2-4.1% and the density was 0.58-0.68, indicating the possibility of excellent structural material. The bending strength was 9.1-32.6 MPa in the length direction and 9.2-34.1 MPa in the width direction. It is possible to obtain the bending strength of the normally used MDF level and to find the possibility of development of the thermal insulation material having the structural performances.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.4 no.1
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• pp.27-38
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• 2006

This study analyzed changes in action potential of supraspinal neuron and motor unit depending on maximum tolerance isometric contraction(MTIC) by electrical stimulation and examined influence of functional electrical stimulation (FES) on spinal neuron adaptation. It selected 40 university students in their twenties and divided into experimental groups of 25% MTIC(I), 50% MTIC I (II), 75% MTIC(III) and 100% MTIC(IV) depending on MTIC by electrical stimulation, and performed isometric contraction of plantar flexor muscle to each experimental group with given contraction for 20 times. It measured V/Mmax and MDF pre and post exercise, compared volume of contraction. 1. V/Mmax ratio showed no significant difference in comparison among experimental groups. 2. There was significant difference in median frequency of gastrocnemius and soleus in action potential motor unit according to comparison among experimental groups(p<.001). When contraction by electrical stimulation was maximum, change was greatest. This results suggest that muscle contraction by electrical stimulation was influence to action potential of spinal motor neuron system which appear optimal level though aspect and difference degree were not in accordance. Consequently, optimal stimulation level of MTIC(50%) by FES would be lead to central nerve adaptation. muscle contraction by electrical stimulation was influence highly to MDF which should be consider to fatigue of motor unit for muscle contraction by electrical stimulation.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.9 no.2
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• pp.1-6
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• 2011

Purpose : This study aims to examine changes in electromyogram (EMG) signals detected from the tibialis anterior muscle during repetitive contraction exercises in normal female adults. Methods : The subjects of this study were 10 normal adult females without any musculoskeletal or nervous system disorders. A total of 30 contractions were made repetitively with maximal voluntary contraction exercise for six seconds and a resting time for three seconds. Changes in muscle contractions were measured using dynamometer and EMG signals such as root mean square (RMS), integrated EMG (IEMG), and median frequency (MDF). Results : The result of measurement showed no significant differences in IEMG and RMS in accordance with the increase in the number of contractions. MVIC and MDF showed significant differences in accordance with the increase in the number of contractions (p<0.05). Conclusion : This study demonstrated that repetitive tibialis anterior muscle contraction resulted in a significantly different MVIC and MDF but no significant differences in IEMG and RMS. Therefore, compared to other lower leg muscles, the tibialis anterior muscle is a low-frequency muscle and therefore electrophysiological characteristics of the muscle should be considered in different exercise methods.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.15-23
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• 2009

This paper presents a novel high-speed, low-complexity flexible 128/64-point $radix-2^4$ FFT/IFFT processor for the applications in high-throughput MIMO-OFDM systems. The high radix multi-path delay feed-back (MDF) FFT architecture provides a higher throughput rate and low hardware complexity by using a four-parallel data-path scheme. The proposed processor not only supports the operation of FFT/IFFT in 128-point and 64-point but can also provide a high data processing rate by using a four-parallel data-path scheme. Furthermore, the proposed design has a less hardware complexity compared with traditional 128/64-point FFT/IFFT processors. Our proposed processor has a high throughput rate of up to 560Msample/s at 140MHz while requiring much smaller hardware expenditure satisfying IEEE 802.11n standard requirements.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.3
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• pp.21-28
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• 2008

To evaluate the seismic performance of multi-degree of freedom(MDF) systems, repeated nonlinear response history analyses are often conducted, which require extensive computational efforts. To reduce the amount of computation required, equivalent single degree of freedom(SDF) systems representing complex multi-degree of freedom(MDF) systems have been developed. For the equivalent SDF systems, bilinear models and trilinear models have been most commonly used. In these models, the P-$\Delta$ effect due to gravity loads during earthquakes can be accounted for by assigning negative stiffness after elastic range. This study evaluates the adequacy of equivalent SDF systems having these hysteretic models to predict the actual response of steel moment resisting frames(SMRF). For this purpose, this study conducts cyclic pushover analysis, nonlinear time history analysis and incremental dynamic analysis(IDA) for SAC-Los Angeles 9-story buildings using nonlinear MDF models(exact) and equivalent SDF models(approximate). In addition, this study considers the strength limited model.