• Korean Journal of Soil Science and Fertilizer
• /
• v.37 no.2
• /
• pp.124-130
• /
• 2004

This study was carried out to evaluate the effects of condensed molasses soluble (CMS) treatment on the mineralization of N, chemical properties and soil microbial population under the incubation condition with unsaturated water content during the 7 weeks at $25^{\circ}C$ in the different levels of CMS application. The results indicated that the total nitrogen content of soil was increased with increasing application rate of CMS and this trend was maintained up to 7 weeks. With CMS treatment content of $NH_4-N$ was gradually decreased. However, the content of $NO_3-N$ in the soil was gradually increased with incubation time due to the nitrification under the unsturated water condition. The CMS treatment increased the microbial populations such as bacteria, actinomycetes and fungi, which may be due to the availability of more nutrients such as amino acids, sugars and other minor elements from CMS. The pH of soil was found to be reduced by the addition of CMS, Whereas, electrical conduvtivity of soil was correspondingly increased with increasing application rate of CMS.

• Analytical Science and Technology
• /
• v.12 no.1
• /
• pp.34-39
• /
• 1999

Estrone such as estriol and estradiol can not be determined by votammetric methods, because these are electrochemically inactive in the potential windows for mercury drop electrode. Nitro-derivatives of estrone are electro active and nitration of estrone is accomplished by heating the solution involving estrone and sodium nitrite in a water-bath at $100^{\circ}C$ for 30 min. Such nitro-derivatives are determined directly by voltammetry. The electrochemical behavior for nitrated estrone was investigated by cyclic voltammetry. The trace estrone was determinated by differential pulse adsorptive cathodic stripping voltammetry. Nitrated estrone gives a well defined voltammetric wave at ca. - 0.61 V (vs. Ag/AgCl electrode). The electrochemical reaction was irreversible process in sodium borate buffer at pH 11 and nitrated estrone was strongly adsorbed on the surface of mercury electrode. The optimal experimental conditions for the determination of nitrated esterone were found to be 0.05 M sodium nitrate, 0.01 M sodium borate, pH 11.0, and an accumlation potential of 0.10 V (vs. Ag/AgCl). The detection limit was as low as $1{\times}10^{-9}M$ for estrone with 2 min accumulation time.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
• /
• 2003.04a
• /
• pp.141-141
• /
• 2003

신선농산물의 호홉속도를 측정하는 방법 중 하나인 개방계(open system) 호흡속도 측정시스템은 소정의 농도로 조정된 혼합기체를 측정대상시료에 흘려 보내며 측정하는 방법이다. 개방계 측정법의 장점은 혼합 기체조성 영역에서 정확한 호흡속도를 얻을 수 있으며 방치시간이 필요 없으므로 반복 측정이 용이한 것 등이다. 그러나 개방계 측정법은 공급되는 혼합기체의 농도와 유속이 일정하여야 하며 연속으로 호흡속도 측정용 챔버의 혼합기체 공급측과 배기측에서 기체시료를 수집하여 매우 미세한 기체농도의 차이를 측정할 수 있어야 하고 기체 시료 수집에 상당한 주의가 요구된다. 이러한 문제를 개선하기 위하여 개방계 호흡속도 측정 시스템을 자동화하였다. 자동화된 호흡속도 측정 시스템은 혼합기체 발생장치, 온도조절이 가능한 기체기밀용 챔버와 G.C로 구성되어 있다. 환경기체조성을 위한 혼합기체발생장치는 $N_2$, $O_2$, $CO_2$ 압축 실린더에서 공급되는 기체를 압력 조절기를 통해서 일차압력을 조정하고 정밀 압력 조절기를 이용하여 0.1~0.2 kg/$\textrm{cm}^2$의 정압을 유지시켰다. 압력이 일정해진 기체는 metering valve를 이용하여 각 기체의 유량을 소정의 비율로 제어할 수 있도록 하였으며 각각의 기체는 gas mixed cell에서 실험 농도의 환경기체조성으로 혼합되어 항온기내의 호흡속도 측정 챔버($25^{\circ}C$)로 공급될 수 있도록 하였다. 호흡속도 측정용 챔버는 개스킷이 장착된 아크릴 재질이며 온도 조절이 가능한 항온기로 구성되어 있다. 호흡속도 측정용 챔버와 G.C간의 기체흐름은 three way solenoid valve에 의하여 제어되며 전원의 on/off에 따라 공급측의 가스와 배기측의 가스가 선택적으로 G.C에 공급될 수 있도록 구성하였다. 측정 대상 챔버의 기체는 제어된 유로를 따라 multi-position valve를 통과하여 G.C에서 분석되도록 하였다. 본 연구에서 개발된 개방계 호흡속도 자동 측정 시스템의 성능 실험에서 혼합기체발생장치에서 조제된 혼합 기체의 농도를 설정치와 비교한 결과 $O_2$와 $CO_2$의 농도에서 평균오차 0.2%로 정밀한 것으로 나타났으며 호흡속도 측정용 챔버의 혼합기체 공급측과 배기측의 가스 농도를 3회 반복 측정한 결과 재현성에서는 0.1%이하의 편차로 나타났다. 개방계 호흡속도 자동 측정 시스템을 이용하여 환경기체조성하에서 토마토의 호흡속도를 측정하는 실측 실험을 수행한 결과 2$0^{\circ}C$에서 12.7~42.1mg$CO_2$/kg.hr였으며 12$^{\circ}C$에서 2.5~8.2mg$CO_2$/kg.hr로 일반적으로 보고되고 있는 토마토 호흡속도와 일치하는 결과를 나타내었다.

• Proceedings of the KWS Conference
• /
• 2010.05a
• /
• pp.80-80
• /
• 2010

전자제품의 소형화, 경량화, 고집적화가 심화됨에 따라 전자제품을 구성하는 회로의 미세화 또한 요구되고 있다. 이러한 요구는 경성회로기판 (rigid printed circuit board, RPCB) 뿐만 아니라 연성회로기판 (flexible printed circuit board, FPCB) 에도 적용되고 있으며 이에 대한 많은 연구 또한 이루어지고 있다. 연성회로기판은 일반적으로 절연층을 이루는 폴리이미드 (polyimide, PI)와 전도층을 이루는 구리로 이루어져 있다. 폴리이미드는 뛰어난 열적 화학적 안정성, 우수한 기계적 특성, 연속공정이 가능한 장점을 가지고 있으나, 고온다습한 환경하에서 높은 흡습성으로 인해 전도층을 이루는 구리와의 접합특성이 저하되는 단점 또한 가지고 있다. 또한 전도층을 이루는 구리는 고온다습한 환경하에서 산화 발생이 용이하기 때문에 접합특성의 감소를 야기할 수 있다. 따라서 본 연구에서는 고온다습한 조건하에서 sputtering and plating 공정을 통해 순수 Cr seed layer를 가지는 연성회로기판의 seed layer의 두께와 시효시간의 변화로 인해 발생하는 접합특성의 변화를 관찰하고 분석하였다. 본 연구에서는 두께 $25{\mu}m$의 일본 Kadena사(社)에서 제작된 폴리이미드 상에 sputtering 공정을 통해 순수 Cr으로 이루어진 각각 두께 100, 200, $300{\AA}$의 seed layer를 형성한 후 전해도금법을 이용, 두께 $8{\mu}m$의 구리 전도층을 형성한 시료를 사용하였다. 제작된 시료는 고온다습한 환경하에서의 접합 특성의 변화를 관찰하기 위하여 $85^{\circ}C$/85%RH 항온항습 조건하에서 각각 24, 72, 120, 168시간 동안 시효처리 한 후, Interconnections Packaging Circuitry (IPC) 규격에 의거하여 접합강도를 측정하였다. 시료의 전도층은 폭 3.2mm 길이 230mm의 패턴을 가지도록, 절연층은 폭 10mm, 길이 230mm으로 구성되었으며 이를 50.8mm/min의 박리 속도로 각 시편당 8회의 $90^{\circ}$ peel test를 실시하였다. 파면의 형상과 화학적 조성을 분석하기 위해 SEM (Scanning electron microscope)과 EDS (Energy-dispersive X-ray spectroscopy)를 사용하였으며, 파면의 조도 측정을 위해 AFM (Atomic force microscope)을 사용하였다. 또한 계면의 화학적 결합상태를 분석하기 위해 XPS (X-ray photoelectron spectroscopy)를 통해 파면을 관찰 분석하였다.

• The korean journal of orthodontics
• /
• v.26 no.3
• /
• pp.317-324
• /
• 1996

This study was conducted to evaluate the tensile bond strength of three commercially available glass ionomer cements as orthodontic bracket adhesives. 120 premolars extracted for orthodontic treatment were prepared for bonding and standard edgewise brackets were bonded with Shofu Glaslonomer Cement (Shofu Co., U.S.A.), GC Fuji ItGC Co., Japan), KETAC-CEM(ESPE Co., West Germany) with different P/L ratio. The tensile bond strength was tested by Instron testing device after 24hours and 3months from bonding. After debracketing, bracket bases were examined to determine the failure sites. The results of this study were as follows: 1. KETAC CEM showed the highest bond strength other than measurement after 24 hours and at its original P/L ratio, and seemed to have clinically a proper bond strength. It seemed, however, that both Shofu Giaslonomer Cement and GC Fuji I had an inappropriate bond strength. 2. The incorporation of additional powder into the mixture improved the tensile bond strength. 3. Prolonged storage time improved the tensile bond strength. 4. Of the failure, failure occured at the tooth-adhesive interface(54.2%) was the most common type. The second type of failure(36.7%) was combination type, where part of the adhesive remained on the tooth and part on the bracket. And the last type of failure(9.1%) occured at the adhesive-bracket interface.

• Proceedings of the KWS Conference
• /
• 2009.11a
• /
• pp.75-75
• /
• 2009

연성회로기판은 일반적으로 절연체를 이루는 폴리이미드와 전도체를 이루는 구리로 구성되어 있다. 폴리이미드는 뛰어난 열적 화학적 안정성, 기계적 특성, 공정성 등의 장점으로 인해 연성회로기판의 절연체로서 제안되었지만 전도체를 이루는 구리와의 접합 특성이 우수하지 않기 때문에 많은 연구가 현재까지 진행되고 있고, 그 결과 연성회로기판의 접합 특성에 많은 개선이 이루어짐과 동시에 다양한 공정 방법이 제안되고 있다. 하지만 고온다습한 환경에서 사용될 경우 폴리이미드의 높은 흡습성과, 구리와 seed layer의 산화 문제로 인해 접합 특성이 저하된다는 단점 또한 가지고 있다. 따라서 본 연구를 통해 고온다습한 조건하에서 seed layer가 80Ni/20Cr 합금으로 구성된 연성회로기판의 seed layer의 두께와 시효시간으로 인해 발생하는 접합 신뢰성의 차이를 관찰하였다. 본 연구에서는 두께 $25{\mu}m$의 폴리이미드 위에 각각 100, 200, $300{\AA}$ 두께의 80Ni/20Cr의 합금 조성을 가지는 seed layer를 스퍼터링 공정을 통해 형성한 후 전해도금법을 이용하여 $8{\mu}m$ 두께의 구리 전도층을 형성하였다. 접합 특성 평가를 위해 ICP 규격에 따라 전도층 패턴을 폭 3.2mm, 길이 230mm로 시편을 제작하여 50.8mm/min의 이송 속도로 각 시편당 8회의 $90^{\circ}$ peel test를 실시하였다. 또한 $85^{\circ}C$/85% 항온항습 조건하에서 각각 24, 72, 120, 168시간 동안 시효 처리 후 같은 방법으로 연성회로기판의 접합 특성을 평가하였다. 파면의 형상과 조성을 분석하기 위해 SEM (Scanning electron microscope)과 EDS (Energy-dispersive X-ray spectroscopy)를 사용하였으며, 파면의 조도 측정을 위해 AFM (Atomic force microscope)을 사용하였다. 또한 파면의 잔여물 분석을 위해 EPMA (Energy probe microanalysis)를 사용하였고 계면의 화학적 결합상태를 분석하기 위해 XPS (X-ray photoelectron spectroscopy)를 통해 파면을 분석하였다.

• Applied Chemistry for Engineering
• /
• v.2 no.2
• /
• pp.97-107
• /
• 1991

Highly-siliceous dealuminated zeolite, silicalite(end member of ZSM-5) was synthesized from a batch composition of 2.55 $Na_2O-5.0$ TPABr-$100SiO_2-2800H_2O $ at $180^{\circ}C$ and at times ranging from one to seven days of reaction time. Autoclaves containing the synthesis mixture were centrifuged within the specially-equipped convection oven to provide an elevated gravitational force field like 30 and 50 G. Tests were also conducted at normal gravity. For synthesis performed under elevated gravities, average and maximum crystal sizes were substantially greater than those synthesized under normal gravity and product yields were also found to be affected by elevated gravity ; that is, product yields were substantially enhanced under elevated gravity from 4 % to 55 % with respect to normal gravity. The average crystal sizes of silicalite synthesized at normal gravity were 50 to $70{\mu}m$ over an entire range of reaction time, one to seven days while the average crystal sizes synthsized under elevated gravities, 30 and 50 G, were 160 to $190{\mu}m$ respectively. For the elevated gravity, in particular, two separate nucleations and growths were observed. For examples, at 50G, large crystals of $200{\mu}m$ were produced through the second growing stage after 5 days of reaction following the rapid first growing stage where fairly large crystals of $135{\mu}m$ were produced only in 2 days of reaction. The maximum crystal sizes obtained through the above two growing stages were 190 and $300{\mu}m$, respectively. A discussion of how elevated gravity affects nucleation, growth, yield and crystal size of silicalite is presented.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.4
• /
• pp.590-596
• /
• 2019

Uses of fossil fuels like coal and oil increases with industrial development, and problems like abnormal climate come up as greenhouse gas increases. Accordingly, studies are actively conducted on eco-friendly renewable energy as a replacement for the main resources, and especially, wood pellets with high thermal efficiency are in the limelight as an alternative fuel in thermal power stations and gas boilers. However, despite a constant increase in their usage, few studies are conducted on their risks like fire and spontaneous combustion. Thus, this study found the auto-ignition temperature and critical ignition temperature of wood pellets with a change in flow rate in a thermostatic bath, using a sample vessel with 20 cm in length, 20 cm in height and 14 cm in thickness to predict their ignition characteristics. Consequently, at the flow rate of 0 NL/min, as the core temperature of the sample increased to higher than the ambient temperature, they ignited at $153^{\circ}C$, when the critical ignition temperature was $152.5^{\circ}C$. At the flow rates of 0.5 NL/min and 1.0 NL/min, it was $149.5^{\circ}C$, and at the flow rate of 1.5 NL/min, it was $147.5^{\circ}C$. Consequently, at the same storage, the more the flow rate, the lower the critical ignition temperature became.

• Journal of the Society of Disaster Information
• /
• v.19 no.2
• /
• pp.292-304
• /
• 2023

Purpose: This study was conducted to obtain experimental data for the establishment of preventive measures against fire, as large and small fire accidents occur at production and storage sites of superabsorbent polymers developed for the convenience of daily life. Method: The sample container was fixed at 0.2m in both length and width, and was shaped into a rectangular cuboid with heights of 3cm, 5cm, 7cm, and 14cm to access an infinite flat plane. The sample container was fixed in the center of a thermostatic bath that was heated to a predetermined temperature according to a preset temperature control program. If the central temperature of the sample rose more than 20℃ above the set temperature, it was determined to have 'ignited', and if it remained similar to the set temperature, it was determined to have 'unignited'. Result: The critical autoignition temperature was calculated to be 212.5℃ for a sample container with a height of 3cm, 202.5℃ for 5cm, 192.5℃ for 7cm, and 177.5℃ for 14cm. The ignition induction time to reach the highest temperature was approximately 42hours for 3cm, 91hours for 5cm, 151hours for 7cm, and 300hours for 14cm. Conclusion:① As the size of the sample container increased, the autoignition temperature decreased and the ignition induction time to reach the highest temperature increased. ② The apparent activation energy was calculated to be 39.30kcal/mol, with a correlation of 99.5%.

• Journal of Applied Biological Chemistry
• /
• v.66
• /
• pp.424-435
• /
• 2023

As a result of this study, DPPH radical scavenging activity was 81.8% at a concentration of 100 ㎍/mL of Alpinia galanga L. rhizome 70% ethanol extract (AG.E), and ABTS⁺ radical scavenging activity was confirmed to be 99.8%, similar to L-Ascorbic acid (AA), at a low concentration of 50 ㎍/mL AG.E. To measure anti-aging activity, collagenase and elastase inhibitory activities were measured and AG.E showed higher inhibitory effects than epigallocatechin gallate (EGCG) starting at a low concentration of 50 ㎍/mL. In particular, AG.E showed inhibitory effects more than three times that of EGCG at a concentration of 500 ㎍/mL. In order to verify anti-aging effect of AG.E in CCD-986sk cell, good anti-aging effect was obtained in various experiments stimulated with UVB. In a gene expression analysis experiment using RT-PCR, the COL1A mRNA expression level was found to increase 2.90 times compared to no addition at a low concentration of 20 ㎍/mL AG.E, confirming the possibility of developing it as a good functional material related to anti-aging. As a basic study on temporal biological activity preservation ratio of material when applied to formulations, AG.E, and AA were added to a stable W/O type emulsion and stored in a thermostat at 25 ℃ for 60 days. As a result of measuring DPPH and ABTS⁺ radical scavenging activities on the 1st, 30th, and 60th days, it was confirmed that antioxidant effects are maintained at a high level over time in formulations.