• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 1993년도 추계학술강연 및 발표대회강연 및 발표논문 초록집
• /
• pp.4-4
• /
• 1993

Ferrous powder metallurgy in Japan has developed in the last four decades, where every decade is featured by certain breakthroughs in materials. The progress in PM materials is closely related to newly developed powders. Low alloy steel powders for high strength PM components are grouped into three types: Ni and/or Mo containing completely alloyed powders, Ni containing partially alloyed powders, and Cr containing completely alloyed powders. Every type has its special characteristics. The tensile strength of PM materials is improved up to 2 GPa. The hardness is also increased to exceed 500 HV with normal hardening methods, and 700 HV with novel surface treatment techniques. The present maximum of fatigue strength is 550 MPa, and that of impact energy is 100 J. Novel PM materials with improved properties are applied to a variety of automobile and other components: power steering pumps, rocker anns, valve guides and inserts, bearings, torque sensors, etc. The future outlook for the ferrous PM is Quite positive, and the industry is expected to show renewed growth by applying many types of alloy steel powders and new ferrous PM materials.

• 한국입자에어로졸학회지
• /
• 제15권2호
• /
• pp.79-90
• /
• 2019

It is important to control fine particles in children care centers, elementary schools, elderly care facilities and so on where vulnerable children and the aged stay during most of their time. This study has investigated $PM_{2.5}$ and $PM_{10}$ concentrations in two classrooms equipped with an air cleaner and two air cleaners, respectively and they were compared to those in a classroom without an air cleaner as well as those outdoors. Eight air cleaners which have various clean air delivery rates (CADRs) between 9.9 and $21.3m^3/min$ were tested in classrooms in two elementary schools in Seoul. Average $PM_{2.5}$ and $PM_{10}$ were $7.3{\pm}0.7$ and $45.5{\pm}4.1{\mu}g/m^3$ in classrooms equipped with an air cleaner and $4.2{\pm}0.6$ and $24.6{\pm}2.5{\mu}g/m^3$ in classrooms with two air cleaners, whereas they were $22.1{\pm}2.6$ and $109.1{\pm}9.6{\mu}g/m^3$ in classrooms without an air cleaner and $36.9{\pm}5.1$ and $74.1{\pm}10.6{\mu}g/m^3$ outdoors, respectively. $PM_{2.5}$ in classrooms could be reduced effectively by using an air cleaner or two air cleaners, because $PM_{2.5}$ was mainly infiltrated from outdoors, however $PM_{10}$ could not because $PM_{10}$ was mainly caused indoors by students' activities. Air cleaners were more effective for removal of $PM_{2.5}$ and $PM_{10}$ in classrooms with a high airtightness than those in classrooms with a relatively low one. Average $CO_2$ in classrooms was about 1500 to 2000 ppm for class hours dependent on the student number per a classroom, which was about 1.5 to 2 times higher than the standard, regardless of the use of air cleaner.

• International Journal of Industrial Entomology and Biomaterials
• /
• 제38권1호
• /
• pp.6-13
• /
• 2019

In the present study, we investigated the antifungal activity of methanol and ethanol extracts of different parts (leaves, twigs, and root bark) of mulberry plant against Alternaria alternata and Fusarium sp. Among them, the methanol and ethanol extracts of mulberry root bark exerted the highest inhibitory activity against the mycelial growth of A. alternata ($70.6{\pm}1.6$ to $80.8{\pm}6.7%$ and $58.7{\pm}0.0$ to $80.8{\pm}6.7%$, respectively) and Fusarium sp. ($15.5{\pm}2.7$ to $39.3{\pm}3.4%$ and $26.4{\pm}2.7$ to $47.6{\pm}4.8%$, respectively). In contrast, the methanol and ethanol extracts from mulberry leaves and twigs did not suppress the mycelial growth of these fungal species. Importantly, the methanol and ethanol extracts of mulberry leaves tended to even accelerate the mycelial growth of A. alternata and Fusarium sp. Therefore, the results of this study indicate that methanol and ethanol extracts of mulberry root bark can be used as control agents against A. alternata and Fusarium sp.

• Bulletin of the Korean Chemical Society
• /
• 제30권5호
• /
• pp.1097-1100
• /
• 2009

New types of conducting polyaniline-polymannuronate (PANI-PM) composites were synthesized by in situ deposition techniques in an aqueous media. By dissolving different weight percentage of polymannuronate (PM) (5, 10, 15, and 25%), the oxidative polymerization of aniline was carried out using ammonium per sulfate as an oxidant. The obtained composites were studied for their thermal stability and electrochemical behavior. The thermal stability of PANI-PM composites is lower than PANI, which supports a strong interaction between PANI and PM. However, the composites show an appreciable electrochemical behavior. Based on these observation the PANI-PM composites can be explored in different fields such as electric devices, sensors, functional coatings, etc.

• 한국재료학회지
• /
• 제5권3호
• /
• pp.371-378
• /
• 1995

YBCO 산화물 초전도체의 초소성 변형에 대한 최적 변형조건을 파악하고자 80$0^{\circ}C$~93$0^{\circ}C$의 온도범위에서 1.0 $\times$ $10^{-3}$s^{-1}$!1.0 $\times$ $10^{-7}$s^{-1}$의 초기변형속도로 압축시험을 수행하였다. 변형속도 민감지수는 m=0.50 $\pm$ 0.1로 나타났다. 이는 결정립계 미끄러지\ulcornerㄹ 주 변형기구로 하는 초소성임을 의미한다. 결정립크기에 따른 유동응력과의 관계는 $\sigma$\propto$d^{1.8 $\pm$ 0.3}$의 지수함수식을 이루고 있으며 Nabarro-Hering 크\ulcorner과 상응하는 격자확산이 확산경로임을 보였다. 초소성 변형에 대한 활성화에너지는 Q=571 $\pm$ 30 kJ/mole이었다. 본 실험온도 구간에서 압축 변형시 변형속도, 변형응력 및 결정립크기에 따른 고온 변형거동 관계식은 $\varepsilon$=A$\sigma$^{2.00 $\pm$ 0.04 - 1.8 $\pm$ 0.3}$ exp(-571 $\pm$ 30kJ/RT)와 같이 유도 되었다. 본 실험조건에서 최적 초소성 변형조건은 86$0^{\circ}C$ 부금, 초기변형속도 ~1.0 $\times$ $10^{-4}$S^{-1}$이었다.

• Journal of Acupuncture Research
• /
• 제34권4호
• /
• pp.180-184
• /
• 2017

Background: Recently, Cervi Parvum Cornu pharmacopuncture has been widely used. But no studies on the indicator materials for Cervi Parvum Cornu pharmacopuncture have been conducted. The aim of this study was to select indicator materials that would aid in the uniform preparation of standardized Cervi Parvum Cornu pharmacopuncture. Methods: Three lots of Cervi Parvum Cornu pharmacopuncture were analysed. Each lot was prepared using the same methods and materials. Chondroitin sulfate, alanine, and leucine were selected as the indicator materials for Cervi Parvum Cornu. For standardization, chondroitin sulfate analysis was performed using the colorimetric method, while alanine and leucine were analyzed using liquid chromatography-mass spectrometry (LC-MS). Results: Analysis of the three lots of Cervi Parvum Cornu pharmacopuncture found chondroitin sulfate levels of $108.9{\pm}17.3ug/ml$, $118.8{\pm}5.0ug/ml$ and $112.3{\pm}11.9ug/ml$. Alanine levels were $44.9{\pm}2.8ug/ml$, $44.6{\pm}0.3ug/ml$, and $43.9{\pm}0.2ug/ml$. Leucine levels were $29.6{\pm}0.7ug/ml$, $29.0{\pm}0.1ug/ml$, and $29.4{\pm}0.1ug/ml$. Conclusion: These results suggest that chondroitin sulfate, alanine, and leucine may be useful for the standardization of Cervi Parvum Cornu pharmacopuncture.

• 한국재료학회지
• /
• 제18권9호
• /
• pp.486-491
• /
• 2008

The effect of annealing treatment conditions on the interfacial adhesion energy between electrolessplated Ni film and polyimide substrate was evaluated using a $180^{\circ}$ peel test. Measured peel strength values are $26.9{\pm}0.8,\;22.4{\pm}0.8,\;21.9{\pm}1.5,\;23.1{\pm}1.3,\;16.1{\pm}2.0\;and\;14.3{\pm}1.3g/mm$ for annealing treatment times during 0, 1, 3, 5, 10, and 20 hours, respectively, at $200^{\circ}C$ in ambient environment. XPS and AES analysis results on peeled surfaces clearly reveal that the peeling occurs cohesively inside polyimide. This implies a degradation of polyimide structure due to oxygen diffusion through interface between Ni and polyimide, which is also closely related to the decrease in the interfacial adhesion energy due to thermal treatment in ambient conditions.

• 한국표면공학회지
• /
• 제48권3호
• /
• pp.115-120
• /
• 2015

We studied white tandem organic light-emitting diodes using red and blue fluorescent materials. White 2 units tandem OLEDs were fabricated using $Alq_3$:Rubrene (3 vol.% 5 nm) and SH-1 : BD-2 (3 vol.% 25 nm) as emitting layer (EML). The device with $Alq_3$ : Rubrene (3 vol.% 5 nm) / SH-1 : BD-2 (3 vol.% 25 nm) showed yellowish white emission with a Commission Internationale de l'Eclairage (CIE) coordinates of (0.442, 0.473) at $1,000cd/m^2$, and variation of CIE coordinates was low with ($0.44{\pm}0.002$, $0.472{\pm}0.001$) from 500 to $3,000cd/m^2$. White 3 units tandem OLEDs were fabricated by additory stacking the blue or white layer as EML. CIE coordinates of 3 units tandem OLEDs with stacked blue and white layer was low variation of ($0.293{\pm}0.008$, $0.36{\pm}0.005$) and ($0.412{\pm}0.002$, $0.423{\pm}0.001$) from 500 to $3,000cd/m^2$, respectively. Our findings suggest that stacked OLED was possible to controlling CIE coordinates and producing excellent color stability.

• 한국결정성장학회지
• /
• 제11권2호
• /
• pp.78-84
• /
• 2001

The binary forsterite($Mg_2SiO_4$)/spinel ($MgAl_2O_4$) system, a possible refractory for industrial applications, is investigated for their density and grain growth the same firing conditions as the each component material between $1400^{\circ}C$ and $1700^{\circ}C$ ($1650^{\circ}C$). The forsterite grain growth exponent is established to be equal to 5 for all compositions within this binary system. Generally; the spinel addition to forsterite inhibited the forsterite grain growth. The activation energies for the forsterite grain growth of the eight compositions(weight ratio of forsterite/spinel) within the binary system are determined to be: 952$\pm$79(95/5), 363$\pm$37(90/10), 219$\pm$21(80/20), 220$\pm$44(70/30), 112$\pm$16(50/50), 112$\pm$23(30/70), 198$\pm$26(10/90), and 121$\pm$12(5/95) KJ/mol. The more forsterite is contained within the binary system, the higher value the activation energy for forsterite grain growth. It is considered that the forsterite grain growth at the higher forsterite compositions are more inhibited by spinel than that of the lower forsterite compositions.

• 한국산학기술학회논문지
• /
• 제11권4호
• /
• pp.1483-1491
• /
• 2010

이 연구의 목적은 현재 한국 혼합치열기 어린이의 치아우식 충전 및 예방재료의 사용 실태를 파악하고자 하는 것이다. 한국의 4개 대도시 지역 7개 초등학교를 무작위로 선정하여 부모의 동의를 얻은 9세와 10세 어린이 711명을 대상으로 한 명의 검진자가 구강검진을 시행하였다. 연구 결과 우식경험유치면수는 $7.9{\pm}8.0$ ($ds=1.3{\pm}2.5,\;fs=6.6{\pm}7.6$)이고 우식경험영구치면수는 $1.4{\pm}2.2\;(DS=0.2{\pm}0.8,\;FS=1.1{\pm}2.1$)로 나타났다. 아말감, 레진, 실란트, 및 기타재료의 평균 충전 치면수는 각각 $2.8{\pm}3.9,\,1.6{\pm}2.8,\;2.9{\pm}3.2$, 및 $4.5{\pm}7.0$이었다. 지역별 충전 재료의 사용에 있어 아말감의 사용은 대구에서 가장 높았으며 레진은 부산에서 제일 높게 나타났다. 영구치의 치아우식 충전 및 예방 재료의 사용은 치아우식예방을 위한 치면열구전색재의 총 치면수가 전체의 약 70%를 차지하여 가장 많음을 알 수 있었고 충전재료로는 레진이 약 20%, 아말감은 약 10%의 비율을 보였다.