• 한국산학기술학회논문지
• /
• 제4권4호
• /
• pp.387-390
• /
• 2003

동ㆍ식물성 기름으로부터 산이나 알카리 촉매를 사용하여 제조한 친환경 에너지인 바이오디젤의 미생물학적 안정성을 테스트하기 위하여 온도와 저장기간에 따른 미생물에 의한 변질정도를 측정하였다. 측정방법으로 역상 현미경 관찰과, 3M petrifilm분석법으로 생균수를 측정하였고, 균체 단백질의 양을 측정하기 위하여 Bradford protein assay법을 사용하였다. 바이오디젤과 석유디젤, 그리고 각각의 시료를 혼합한 시료를 서로 다른 온도조건(25℃와 35℃)에서 혐기적인 조건으로 90일동안 장기간 저장했을 때 바이오디젤, 석유디젤 그리고 혼합한 시료에서 미생물의 생육은 관찰되지 않았다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2003년도 추계학술대회 논문집(III)
• /
• pp.333-338
• /
• 2003

Polymeric composite structures used in ground transportation applications such as the carbody of tilting train may be exposed to a ground environmental conditions during long-term missions. In this study, the degradation of mechanical and physical properties of graphite/epoxy composite and glass fabric/phenol composite under ground environmental conditions was investigated. Accelerated environmental conditions of ultraviolet radiation, temperature, and moisture were considered. Several types of specimens were used to investigate the effects of environmental conditions on mechanical properties of the composites. Also, storage shear modulus, loss shear modulus, and tan 8 were measured as a function of exposure times through a dynamic mechanical analyzer. Finally, composite surfaces exposed to environmental conditions were examined using a scanning electron microscope.

• 분석과학
• /
• 제24권3호
• /
• pp.212-218
• /
• 2011

본 연구에서는 5종류의 황화합물질($H_2S$, $CH_3SH$, DMS, $CS_2$, DMDS)을 10 ppb (nmol/mol) 수준으로 포함하는 기체상 표준시료를 Teldlar bag에 담은 후 시차를 두고 30일 동안의 기간에 걸쳐 농도변화를 분석하였다. 황성분의 시간적 안정도를 파악하기 위해, 백에 보존한 시료의 보존방식과 분석시점에 대한 결정을 두 가지 상이한 접근방식으로 비교하였다. 이를 통해 시료의 장기적 보관방식과 분석시스템의 일관성에 대한 특성을 동시에 평가하고자 하였다. 이를 위하여, 첫 번째로 전체 보관기간 동안 분석할 시료를 일괄적으로 준비하여 이들을 시간대별로 하나씩 분석하는 Forward(F)보전방식으로 진행하였다. 두 번째로는 시료를 시간의 경과에 따라 순차적으로 준비하고, 종료시점에 모두 일괄적으로 분석하는 Reverse(R)방식으로 접근하였다. 이를 유의수준 90% 기준으로 t-테스트를 적용하여, 두 가지 분석방식의 자료들간에 차이점을 짝비교 방식으로 검정하였다. 이때 $H_2S$, $CH_3SH$, DMDS성분의 결과는 유의한 차이가 존재하는 것으로 나타났다. 본 실험의 결과, 분자량이 가벼운 황성분들($H_2S$와 $CH_3SH$)과 무거운 황성분들(DMS, $CS_2$, DMDS)간의 경시적 안정도에는 현저한 차이가 존재하는 것을 확인였다. 그러나 두 방식 모두 농도가 감소하는 상대적 경향은 성분 별로 일치하였다.

• Journal of Biosystems Engineering
• /
• 제29권4호
• /
• pp.293-300
• /
• 2004

In order to solve the shortage of roughage supply for dairy farm in Korea, the mechanized model system for the production of winter cereal wrap silage in the fellow paddy field was developed in the previous studies. In this study, storage properties after long term storing of the winter cereal wrap silage were investigated. Also, the qualities of the wrap silage which was stored during 4 months were evaluated by sensory testings, analyzing chemical properties(moisture content, pH and organic acids) and investigating the increase of feeding value. The result of this study were summarized as follows; 1. After 300 hours storage, the acid level of the silage decreased slowly to 4.6 -4.8 pH. Also, the temperature was stabilized around 27-28$^{\circ}C$. The silage having below 5.0 pH is a desirable level for the most of good silage. 2. According to the sensory test and chemical property analyzation it was evaluated as the first class silage like a com silage. 3. Also, when the wrap silage are fed to the cattle, the cattle produced milk more 25% than that of conventional feed. 4. As an overall conclusion, winter cereal wrap silage in the fallow paddy field cm be one of the major roughage source in replacement of com and other conventional silage to dairy cattle in Korea.

• 대한기계학회논문집A
• /
• 제28권9호
• /
• pp.1297-1305
• /
• 2004

Reliability of MEMS devices is receiving more attention as they are heading towards commercial production. In particular are the reliability and long-term stability of wafer level vacuum packaged MEMS gyroscope sensors subjected to cyclic mechanical stresses at high frequencies. In this study, we carried out several reliability tests such as environmental storage, fatigue, shock, and vibration, and we investigated the failure mechanisms of the anodically bonded vacuum gyroscope sensors. It was found that successful vacuum packaging could be achieved through reducing outgassing inside the cavity by deposition of titanium as well as by pre-taking process. The current gyroscope structure is found to be safe from fatigue failure for 1000 hours of operation test. The gyroscope sensor survives the drop and vibration tests without any damage, indicating robustness of the sensor. The reliability test results presented in this study demonstrate that MEMS gyroscope sensor is very close to commercialization.

• 한국소음진동공학회논문집
• /
• 제26권3호
• /
• pp.298-307
• /
• 2016

In the building process of FPSOs(floating production, storage and offloading units) is the increasing demand of high performance piping joints that can be installed on its turret system and maintain smooth and long-term flow of ultra-high pressure crude oil, being subjected to external excitations such as wind and wave on the sea. Following such a trend, in this paper, a new-type piping joint of four effective degrees of freedom has been designed, and its dynamic characteristics predicted through mathematical modeling and computer simulations. Moreover, via an example it was shown how the yaw motion in particular can be independently controlled for future durability test despite strong kinetic couplings.

• 펄프종이기술
• /
• 제44권6호
• /
• pp.70-78
• /
• 2012

The Annals of Joseon Dynasty, which recorded governmental affairs for 472 years (AD 1392-1863) during the Joseon dynasty is an representative paper cultural heritage in Korea. Being recognised their authenticity and values they were designated as the No 151 national treasure of Korea in 1973 and registered as 'The Memories of the World' by UNESCO in 1997. Unusually, some volumes of the Annals were treated by beeswax for the permanent preservation. However, the examinations on the deterioration of the beeswax-treated volumes had been exposed the serious damage than the untreated volumes. In particular, the larger amount of beeswax were worst in deterioration condition. In order to solve these problems, NRICH(National Research Institute of Cultural Heritage) of Korea launched the investigation study for the conservation of beeswax-treated volumes of the Annals. Now then, the five study areas have been set up; 1) to understand the damaged condition of the Annals; 2) to analyse the raw materials and production techniques; 3) to test the degradation degree using the duplication samples for understanding the aging factors and mechanism; 4) to develop the conservation techniques through dewaxing and thereafter strengthening the base paper of Hanji; 5) to develop the long-term storage technique using inert gases. On the basis of outcomes from this study, NRICH will plan to establish the systematic conservation and management plan for the beeswax-treated volumes of the Annals in future.

• Journal of Pharmaceutical Investigation
• /
• 제38권3호
• /
• pp.157-162
• /
• 2008

The aim of the study was to formulate the stable amlodipine maleate tablet by selecting and combining of suitable ingredients. Amlodipine tablets were designed by using different manufacturing methods or formulations. Dissolution rate at 30 min of newly formulated tablets was over 98% in 0.1 M HCl medium. After 4 months storage under accelerated condition, the changes of appearance, loss on drying, content and total impurity were investigated. For long-term stability tests, two formulations of K017 (direct compressed tablets consisting of microcrystalline cellulose and pregelatinized starch) and K018 (wet granulated tablets by OpadryAMB) were stored under $25^{\circ}C$, 60% RH for 24 months. Under the accelerated condition, moisture content in K017 formulation was increased as 5.96% for 4 months, while other formulations with anhydrous monobasic phosphoric potassium or by wet granulation showed higher increase in moisture content compared to K017. In addition, K017 formulation showed a low decrease in contents and total relative substance as 0.8% and 0.7%, respectively. Similar stability of amlodipine in K017 was obtained under the long-term stability test. These results indicate that the K017 combined with microcrystalline cellulose and pregelatinized starch as ingredients is very stable formulation to protect active substance from moisture contact and sustain stability. Therefore, suitable combination of ingredients such as microcrystalline cellulose and pregelatinized starch could attribute to enhance the stability of moisture-labile drug such as amlodipine maleate.

• Journal of Periodontal and Implant Science
• /
• 제40권3호
• /
• pp.111-118
• /
• 2010

Purpose: The aim of this study was to investigate whether vitrification in the cryopreservation of periodontal ligament (PDL) cells could be useful for tooth banking. Methods: In step 1, primary cultured human PDL cells were cryopreserved in 100% conventional cryopreservation media and 100% vitrification media (ESF40 media) in different temperatures for 2 weeks. In step 2, a series of modified vitrification formulae named T1 (75% vitrification media + 25% F-media), T2 (50% vitrification media + 50% F-media) and T3 (25% vitrification media + 75% F-media) were used to store PDL cells for 2 weeks and 4 weeks in liquid nitrogen. MTT assay was performed to examine the viability of PDL cells. Results: Maximum cell viability was achieved in cells stored in 100% conventional cryopreservation media at $-196^{\circ}C$ (positive control group) in step 1. Compared to the positive control group, viability of the cells stored in 100% vitrification media was very low as 10% in all test conditions. In step 2, as the percentage of vitrification media decreased, the cell viability increased in cells stored for 2 weeks. In 4-week storage of cells in step 2, higher cell viability was observed in the T2 group than the other vitrification formulae while the positive control group had the highest viability. There was no statistically significant difference in the cell viability of 2-week and 4-week stored cells in the T2 group. Conclusions: These observations indicate 100% vitrification media is not successful in PDL cell cryopreservation. Conventional cryopreservation media is currently the most appropriate media type for this purpose while T2 media would be interesting to test for long-term storage of PDL cells.

• Nuclear Engineering and Technology
• /
• 제28권4호
• /
• pp.349-358
• /
• 1996

The leaching behavior of uranium from unirradiated CANDU UO$_2$ fuel pellet in the spent fuel wet storage and disposal conditions has been investigated. A modified IAEA leach test method was used, and then the extent of leaching was monitored by analysis for uranium in the leachant. The leach test has been performed in various leachants(demineralized water and boric acid solution at pH=6, synthetic granite groundwater) for a long-term period of 5.4 years, and the effect of temperature on the leach rate of uranium has been analyzed. The leach rates of uranium at $25^{\circ}C$ were dependent on the leachants. Over initial 100 days of leach periods, the leach rate in groundwater was the highest in three leachants and no significant differences of leach rates ore observed in the demineralized oater and boric acid solution. But these leach rates in three leachants around 2,000 days at $25^{\circ}C$ appeared to be reached the steady rates in the range of 1~5$\times$10$^{-8}$ g/$\textrm{cm}^2$ day. The leach rate of uranium in groundwater shooed to be independent of the temperature, but those in both demineralized water and boric acid solution increased with temperature. These results show that the leaching behavior of uranium from UO$_2$ fuel in both the demineralized water ann boric acid may be controlled tv the surface oxidative.dissolution reaction of UO$_2$ and the leach rate of uranium in groundwater at room temperature could mainly be controlled by the complex reaction of dissolved uranyl ions with carbonate ions and no variation of leach rate of UO$_2$ in groundwater with temperature may be due to the local deposition of passivating uranyl phases on the surface.