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안동길,이정희 한국비파괴검사학회 2000 한국비파괴검사학회지 Vol.20 No.3
공업용 서멧 절삭공구는 다성분계 탄화물과 강자성체(ferromagnetic material)인 철족의 Co, Ni 결합상 금속으로 구성 되어 있다. 본 연구에서는 새로운 시도로서 금속 결합상 량과 소결조건에 따른 TiCN계 서멧의 자기적 특성의 측정에 의한 기계적 성질의 평가방법을 연구하였다. 실험에서는 결합상이 다른 상용 서멧조성의 합금을 분말 야금법에 의해 제조하였다. 소결된 서멧의 자기적 특성은 합금의 조직과 탄소량에 따라 크게 변화하였다. 포화자화(magnetic saturation, 4πσ)와 항자력(coercive force, Hc)은 비례하였으며, 고탄소 소결합금에 있어서는 Co-Ni 결합상에서의 W, Mo, Ti등의 용매원자의 농도가 낮아짐에 따라 포화자화는 증가하였다. 항자력이 높을수록 경도는 증가하였고, 서멧의 강도 및 인성은 포화자화가 증가할수록 우수하였다. 서멧공구에서 자기적 특성을 측정하여 기계적 성질을 비파괴적으로 평가할 수 있었다. The commercial cermet cutting tools consist of multi-carbide and a binder metal of iron group, such as cobalt and nickel which are ferromagnetic. In this paper, a new approach to evaluate the mechanical properties of TiCN based cermet by magnetic properties were studied in relation to binder content and sintering conditions. The experimental cermet was prepared using commercial composition with the other binder contents by PM process. It was found that the magnetic properties of the sintered cermets remarkably depended on the microstructure and the total carbon content. The magnetic saturation was proportional to increment of coercive force. At high carbon content in sintered cermet, the magnetic saturation was increased by decreasing the concentration of solutes such as W, Mo, Ti in Co-Ni binder. As the coercive force increases, the hardness usually increases. The strength and toughness of the cermet also increased with increasing the magnetic saturation. The measurement of magnetic properties made it possible to evaluate the mechanical properties in the cermet cutting tools.
鐵棒 1回, 2回 및 3回 뒤공중돌아내리기의 比較 分析
申榮吉,金柄斗,安禹洪,金正子,吳東燮,朴宇奎 慶北大學校 體育科學硏究所 1987 체육과학연구지 Vol.3 No.-
The purpose of this study was to offer gymnasts data for successfully performing triple back somersault dismount(TBSD) and for designing training programs to progress gymnasts to the advanced dismount skills from the horizontal bar through comparative analysis of selected biomechanical factors of single back somersault dismount(SBSD), double back somersault dismount(DBSD) and TBSD. The subjects employed were a total of 4 male middle and high school gymnasts aged between 15 and 16 years. A motion-picture camera, fliming at a nominal rate of 54 frames/s, was used to record the performance of subjects on each trial. This camera was placed at a distance of 15 m from the inward pole of horizontal bar with its optical axis at right angle to this pole. The results obtained are summarized as follows: The mean release angle was 80.5° for the SBSD, 77.3° for the DBSD and 71.3° for TBSD. There were significant differences between the SBSD and the TBSD(p<0.01), the DBSD and the TBSD(p<0.05) but no significant difference between the SBSD and the DBSD. The angular velocity at release was 4.533 ㎭/s for the SBSD, 5.338 ㎭/s for the DBSD and 6.020 ㎭/s for the TBSD. There was a significant difference among these velocities(p<0.05, p<0.01). The linear velocity at release was 5.458m/s for the SBSD, 5.750m/s for the DBSD and 6.083m/s for the TBSD. In this case, we had a significant difference only between the SBSD and the other two somersaults(p<0.05, p<0.01). The shoulder angle at release was 170.5° for the SBSD, 167.0° for the DBSD and 154.3° for the TBSD. There were significant differences between the SBSD and the TBSD(p<0.05), the DBSD and the TBSD(p<0.05) but no significant difference between the DBSD and the TBSD. The hip and knee angle at release were increased respectively by increasing the number of somersault but showed no significant difference among these angles. The mean flight time from release to landing for each somersault was calculated; it took the subjects 1.315s to perform the SBSD, 1.345s to perform the DBSD and 1.416s to perform the TBSD. There was a significant difference among these somersaults with respect to time(p<0.05, p<0.01). The mean maximum height was 3,633m for the SBSD, 3,720m for the DBSD and 3,780m for the TBSD. There was a significant difference only between the SBSD and the other two somersaults. The mean horizontal distance was decreased respectively by increasing the number of somersault but showed no significant difference among these somersaults with respect to distance. The smallest hip angle during flight in the SBSD was 115.3° at 0.317s after the subject left the bar, for the DBSD it was 48.2° at 0.621s while that of the TBSD was 32.3° at 1,102s after release. The relationship between the time the smallest hip angle observed and the total flight time was determined; it took 24.1% of the total flight time of the SBSD to reach the smallest hip angle. In the DBSD, it took 46.2% of the total flight time to reach for the smallest hip angle and in the TBSD 77.8% of the total flight time to reach the smallest hip angle. From the above results, the gymnast would need to (1) increase angular velocity before release by manipulating of body shape, (2) change the release angle and (3) stay tuck position longer by shortening as quickly as possible the angle of each body joint to perform successfully the TBSD. Also to be able to perform quadruple back somersault dismount, a gymnast would need flight time of a minimum 1,782s.
최동혁,정길수,박병수,유남재 강원대학교 산업기술연구소 2005 産業技術硏究 Vol.25 No.B
This paper is an experimental result of investigating lateral soil movements at piled bridge abutments by using the centrifuge model facility. Three different centrifuge model experiments, changing the methods of ground improvement at bridge abutment on the soft clayey soil (no improvement, preconsolidation and plastic board drain (PBD), sand compaction pile (SCP) + PDB), were carried out to figure out which method is the most appropriate for resisting against the lateral soil movements. In the centrifuge modelling, construction process in field was reconstructed as close as possible. Displacements of abutment model, ground movement, vertical earth pressure, cone resistance after soil improvement and distribution of water content were monitored during and after centrifuge model tests. As results of centrifuge model experiments, preconsolidation method with PBD was found to be the most effective against the lateral soil movement by analyzing results about displacements of abutment model, ground movement and cone resistance. Increase of shear strength by preconsolidation method resulted in increasing the resistance against lateral soil movement effectively although SCP could mobilize the resistance against lateral soil movement. It was also found that installment with PBD beneath the backfill of bridge abutment induced effective drainage of excess pore water pressure during the consolidation by embanking at the back of the abutment and resulted in increasing the shear strength of clay soil foundation and eventually increasing the resistance of lateral soil movement against piles of bridge abutment.
조종수,김사익,윤승락,노정관,나종범,김동귀,최길동 진주산업대학교 산업과학기술연구소 2007 산업과학기술연구소보 Vol.- No.14
To investigate the antimicrobial effects of essential oil in the leaves of Chamaecyparis obtusa extractives by paper disc method, the extractives were fractionated into four portions. In antimicrobial test, essential oil in the leaves of Chamaecyparis obtusa was found to have strong inhibitory effects against the growth of Bacillus subtilis and Staphylococcus aureus. A part of analyzed inhibition components of essential oil in the leaves of Chamaecyparis obtusa from GC-MS was supposed to be α,β-pinene, α-terpinolene, camphor, β-myrcene, 1-α-terpinolene, 4-thujen-2-α-yl, limonene, Cardinene.
나종범,김사익,조종수,윤승락,노정관,김동귀,최길동 진주산업대학교 산업과학기술연구소 2007 산업과학기술연구소보 Vol.- No.14
This study was performed to investigate the effect of wax layer of bamboo on leaching of boron compounds. The removal of wax layer increased the loading of boron on bamboo surface. However, it had an effect on increasing the leaching rates of boron compounds during leaching test. The addition of water repellent retarded leaching of boron compounds to some extent from treated samples. Although borate/WRP system did not qualify borate treated wood for ground contact use, it showed a potential to improve performance of borate treated bamboo in above-ground applications not subjected to continuous wetting conditions.