• Bulletin of the Korean Chemical Society
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• 제35권12호
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• pp.3595-3600
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• 2014

Monitoring of pH, especially under highly alkaline conditions, is necessary in various processes in the industrial, biotechnological, agricultural, and environmental fields. However, few pH indicators that can function at highly alkaline levels are available, and most of which are organic-based pH indicators. Several years ago, it was reported that gold nanoparticles prepared using trisodium citrate dihydrate were rapidly aggregated at pH values higher than ~12.7. A shift of surface plasmon resonance for such aggregated gold nanoparticles can be applied to pH indicators, allowing for the substitution of traditional organic-based pH indicators. The most important characteristic of pH indicators is the transition pH range. Herein, gold and silver nanoparticles are prepared using different reducing agents, and their transition pH ranges are examined. The results showed that all nanoparticles prepared in this study exhibit similar transition pH ranges spanning 11.9-13.0, regardless of the nanoparticle material, reducing agents, and concentration.

• 한국의류학회지
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• 제28권11호
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• pp.1361-1371
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• 2004

This was a follow-up study to the 'Study on the Body Types of Chinese Adult Women I,' which looked into the body types and classified them into representative body type groups, with the subjects of the women residing in Beijing and Shanghai, and it intends to compare the features of the body types by the residential area of each age range. The results were as follows: 1. The measurements physical items of the women residing in Beijing and Shanghai were compared by the age range, and differences were found in all age ranges. In particular, as the age ranges got higher, the differences in the physical measurements were significant. 2. The comparison of the factor score for the women residing in Beijing and Shanghai by the age range indicated the differences in all the age ranges, and the differences were larger as the age got higher. 3. The comparison of the type distribution for the women residing in Beijing and Shanghai by the age range indicated the differences in their 30's and 40's, while any differences in the type distribution were not found in their 20's.

• Tribology and Lubricants
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• 제26권2호
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• pp.105-110
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• 2010

In order to investigate the wear behavior of aluminum alloy depended on different hardness of the mating tool steel, sliding wear tests were conducted. It was found that the wear characteristics pattern of aluminum alloy for sliding speed was not affected by the hardness of the mating tool steel. However, the effects of the hardness of the mating tool steel exhibited only in relatively low sliding speed ranges. At these ranges, the wear rate of aluminum alloy decreased when increasing the hardness of the mating tool steel. This was attributed by the fact that $Al_2O_3$ particles released from the aluminum worn surface were crushed and embedded on the mating worn surface with high hardness level. At the high sliding speed ranges, wear of aluminum alloy was hardly occurred by the formation of thick $Al_2O_3$ film on the worn surface, regardless of the hardness of the mating tool steel.

• 산업기술연구
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• 제6권
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• pp.19-31
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• 1986

The residence time distribution of liquid flow in a 4.0cm diameter column packed with porous $Al_2O_3$ spheres of 0.37cm diameter were measured with pulse injections of a tracer under cocurrent trickling flow conditions. The mean residence time of liquid flow and liquid hold-up calculated by the transient curve of tracer were unaffected by gas flow rates under experimental ranges of liquid flow rates from 2.4 to $4.5(kg/m^2\;sec)$ and gas flow rates from 0 to $0.13(kg/m^2\;sec)$. The axial dispersion coefficient of liquid stream and apparent diffusivity of tracer in a micropore of solid particle were estimated from the response curve of tracer. The calculated Peclet No. were increased in ranges of 68-to 82 with a increasing of liquid mass velocity, and the external effective contacting efficiency between liquid and solid which can be expressed. by $(D_i)_{app}/D_i$ varied in ranges of 0.54 to 0.68 depending on the liquid flow rates. The gas to liquid(water) volumetric mass transfer coefficient were determined from desorption experiments with oxygen at $25^{\circ}C$ and 1 atm. The measured mass transfer coefficients were increased with liquid flow rates and the effect of gas flow rates on the mass transfer coefficient was insignificant.

• 한국항행학회논문지
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• 제14권2호
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• pp.176-182
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• 2010

본 논문에서는 역 E-급 증폭기 출력 회로의 병렬 공진기를 주파수에 대해 가변되도록 회로를 구성하여 넓은 주파수 범위에서 높은 전력부가효율과 출력전력을 유지하는 방법을 제안하였다. 여기서 사용된 병렬 공진기는 동작 주파수에 따라서 Q 값은 동일하고, 가변 특성을 얻기 위해서 바렉터 다이오드를 사용하여 인덕터와 캐패시터를 만들었으며, 전류 영점 교차를 위한 인덕턴스 성분은 집중소자로 또, 위상 보상을 위한 캐패시턴스는 분포소자로 구현하였다. 역 E-급 증폭기의 주파수 가변 특성을 통해서 효율과 출력 전력을 확인한 실험 결과는 65-120MHz의 주파수 범위에서 증폭기는 최대 75%의 전력부가효율과 25dBm의 출력전력을 얻었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1045-1050
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• 2003

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests are conducted on 2124-T851 aluminum alloy specimens. Three test spectra are generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results are compared with the data obtained from the flight-simulation loading. The experimental results show that omission of the load ranges below 5% of the maximum load does not significantly affect crack growth behavior, because these are below the initial stress intensity factor range. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decrease, and therefore crack growth curve deviates from the crack growth data under the flight-simulation loading. To optimize the load range that can be omitted, crack growth curves are simulated by the stochastic crack growth model. The prediction shows that the omission level can be extended to 8% of the maximum load and test time can be reduced by 59%.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1051-1055
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• 2003

Aluminum carbody for rolling stocks is light and perfectly recycled, but includes severe defects which are very dangerous to fatigue strength. Structural integrity assessment for the carbody by static load test has been performed up to date. In this study, to evaluate fatigue strength of the aluminum carbody of urban transit unit. a testing method to simulate dynamic loading condition was proposed and the fatigue strength of the carbody was evaluated. The dynamic load test results showed that the alternating stress ranges were different from the estimated ranges based on the static test results. Excessive stress ranges at the center are thought to come from the flexible motion of the carbody. published fatigue test data for aluminum components, but variation of alternating acceleration along the length due to flexibility of carbody yielded unexpected results. Because fatigue strength based on the static test results may be overestimated at the center, modification of testing method is necessary.

• 동력기계공학회지
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• 제8권4호
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• pp.11-16
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• 2004

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests were conducted on 2124-T851 aluminum alloy specimens. Three test spectra were generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results were compared with the data obtained from the flight-simulation loading. The experimental results show that the ranges equal to or smaller than 5% of the maximum load do not contribute to crack growth behavior because these are below the initial stress intensity factor range. Omitting these from the flight-simulation loading, test time can be reduced by 54%. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decreased, and crack growth curve deviated from the crack growth data under the flight-simulation loading because loading cycles above fatigue fracture toughness were omitted.

• 자원환경지질
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• 제7권2호
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• pp.63-78
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• 1974

Daehwa tungsten-molybdenum deposits is fissure filled quartz veins occurring in Precambrian granite gneiss adjacent to the contact with Mesozoic biotite granite mass. Essential ore minerals are molybdenum and wolframite accompaning scheelite, cassiterite, chalcopyrite, pyrrhotite, pyrite and bismuthinites. Gangue minerals are quartz and little muscovte, fluorite, beryl and Carbonate minerals. Fluid inclusions in quartz, fluorite, beryl, scheelite and calcite have filling temperature ranges of $170-353^{\circ}C$. According to the studies of mineral paragenesis and filling temperature of fluid inclusion indicate that main tungsten and molybdnum mineralization have taken place with the minerals whose filling temperature ranges 205 to $353^{\circ}C$. Liquid $CO_2$ bearing fluid inclusions are characteristic in the quartz and early fluorite of tungsten and tungsten bearing molybdenum veins but hardly recognized from molybdemun veins. Estimated $CO_2$ concentration according to diagram proposed by the Takenouchi ranges from 10 to 20wt%. These facts suggest that tungsten mineralization may be related to the $CO_2$ content of the hydrothermal solution during the mineralizing period.

• Journal of Biosystems Engineering
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• 제32권2호
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• pp.77-83
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• 2007

The purpose of this study is to find optimal conditions for various outlet clearances of prototype garlic clove separator with a rotating cone in the constant inlet clearance and cone height. Optimal outlet clearance from medium to small size garlics was 25 mm at the $200{\sim}400rpm$. For large garlic, optimal outlet clearances of Namdo and Uiseong garlic were 34 mm and 37 mm, respectively, in the range of $300{\sim}400rpm$. The proportion of garlic separation was over 95% for all quality of garlics. The proportions of damaged garlics at 25 mm and 28 mm outlet clearances were below 5% and below 10%, respectively. Therefore, in order to maintain high performance of garlic separation for the various varieties and qualities, the rotating cone type separator should be designed with cone speed ranges of $200{\sim}400rpm$ and the outlet clearance ranges of $25{\sim}37 mm$. The outlet clearance of the separator should be easily controlled within those ranges.