• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1177-1183
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• 2013

In this paper, the analysis of inspection period bases on reliability is suggested in the field of traction power system. Even though there are several maintenance models, the most commonly used maintenance assessment has been focused on time based maintenance in real traction power systems. The maintenance intervals are selected on the basis of long-time experience. It ensures high availability and exact planning of staff. Reliability centered maintenance, which evaluates criticality and severity of each failure mode, achieves the operation, maintenance, and cost-effective improvement that will manage the risks of equipment. This paper deals with electrification in railway inspection frequency and applied reliability based inspection frequency instead of constant intervals. The distribution function of failure rate in traction power system belongs to Weibull function. Also, the fault data and the number of installed equipments for electrifications are collected. The failure history is investigated and classified in detail. Though these complicated procedures, it contribute to extend equipment lifetime and to reduce maintenance costs.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.236-241
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• 2009

After analyzing the characteristics of the cooling dryer, the mixed cooling dryer was developed by adding the desiccant dryer which supplement the cooling dryer's demerits. Also, the hybrid desiccant cooling dryer was developed to use effectively the exhaust heat energy of the cooling dryer. It could make a more that 20 percent reduction in energy compared with the mixed desiccant cooling dryer. It has become essential to supply this equipment and search the suitable drying product.

• Journal of the Korean Chemical Society
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• v.16 no.2
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• pp.106-116
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• 1972

The universality of the pseudo wet bulb temperature has been established in the drying of macroporous inerts, microporous inerts, and microporous swellable materials using water and methyl alcohol as the liquids. The pseudo wet bulb temperature is a new constant temperature intermediate between the wet bulb and dry bulb temperatures of the air during the second falling rate period. This temperature is calculated from consideration of the heat transfer to, and vapor diffusion from, liquid evaporating at the liquid-air boundary. The experimental results agree with that calculated from the equation proposed by Nissan, Bolles and George.

• Journal of the Optical Society of Korea
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• v.8 no.1
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• pp.29-33
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• 2004

We propose and demonstrate a novel optical pulse multiplier applicable to OTDM (Optical Time Division Multiplexing) systems using cascaded long-period fiber gratings. We have exploited the fact that each mode in a fiber has a different propagation constant to obtain time delays among optical pulses. The proposed scheme could realize high-frequency optical pulse multiplication for optical short pulse trains. We have successfully implemented two, four, and eight times multiplications with the maximum repetition rate of 416.7 ㎓. The obtained pulse delays are well matched with the simulated ones.

• Journal of Biosystems Engineering
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• v.28 no.4
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• pp.361-368
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• 2003

This study was intended to investigate the temporal and spatial variabilities of dry matter, nitrogen content, chlorophyll of paddy rice and yield caused by different rates of nitrogen application. An experimental field was divided into 45 plots of 3.48 ${\times}$ 12 m in size and application rate of nitrogen varied from 0 to 235% with an increment of 25% based on the standard rate of N-P$_2$O$_{5}$-K$_2$O=12-8-8 kg/10a. The measurements were made 8 times every 9-10 days after the transplanting. About 60 days after the transplanting, there exhibited little variabilities in the dry matter caused by different rates of nitrogen application. After that. however, there showed large variabilities and the dry matter increased with the application rate. The nitrogen content of paddy also increased with the application rate but it was inconsistent. After the tillering period, the nitrogen content remained constant. In the early stage of the tillering period the nitrogen content decreased in spite of increase in the dry matter. However. after a certain period of time it increased with the dry matter. There were little variabilities of chlorophyll after the transplanting. However, the SPAD increased with application rate of nitrogen as the paddy grew. After the tillering period SPAD was not affected by the different rates. More yield was obtained at the plots where larger nitrogen content was measured.d.

• International Journal of Automotive Technology
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• v.6 no.4
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• pp.305-314
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• 2005

Injection rate shape control is one feature of a diesel fuel injection system that is strongly desired at this time. In the conventional common rail system, it is difficult to control the injection rate since the fuel pressure is constant during the injection period, resulting in a nearly rectangular rate shape. In order to look into possible injection modulations, injectors equipped with standard and geometrically modified control valves were investigated in detail by means of computer modelling and simulation. Experiments were carried out to validate the feasibility of such a shaping. The results of this study show a noteworthy dependence of the fuel rate on geometrical modifications in the piloting stage of the injector.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1181-1192
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• 2008

A laboratory investigation was carried out into effects of strain rate on undrained shear behavior of Holocene clay underneath Kobe Airport with an objective to evaluate the factor of safety of the retaining structure built on it. It was examined in a series of triaxial compression and extension tests performed using different rate of axial straining. A comparative compression test in which the strain rate was changed in steps was also carried out. Similar tests were performed in constant-volume direct shear box (DSB) test. And, the deformation characteristics of the clay were also examined in order to evaluate the variation of stiffness during undrained shearing. It was found that the undrained strength increased with not only the shear rate but also the consolidation period. ISOTACH properties seemed a key to govern the undrained shear behavior.

• Journal of the Korean Society of Food Science and Nutrition
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• v.26 no.6
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• pp.1021-1027
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• 1997

$CO_2$production in fermentation of dongchimi was measured and interrelated with changes in pH and titratable acidity. The effects of salt content and temperature on $CO_2$production rate were analysed. Fermentation of dongchimi showed drastic pH decrease in early stage and subsequent levelling off around 3.9, with linearly increased acidity up to 0.3~0.4% optimum quality. $CO_2$production of dongchimi could be analysed to consist of two consecutive stages of constant rate. The first stage $CO_2$production of higher rate moved to the second stage of lower rate when acidity rose beyond 0.3%. When compared to those of 1 and 2% salt content, dongchimi of 3% salt showed lower $CO_2$production rate in the 1st stage and slower acidity change through the whole fermentation period. However, it resulted in the product of highest $CO_2$accumulation at optimal ripeness because of consistent $CO_2$production of longer 1st stage period and relatively high $CO_2$production rate in 2nd stage. $CO_2$production depended on temperature less compared to acidity change(activation energy: 57.3 and 44.3kJ/mol for $CO_2$production of 1st and 2nd stages, respectively; 79.3kJ/mol for acidity change), which means higher ratio of $CO_2$production rate relative to acidity increase at lower temperature. Slower increase in acidity at low temperature also was shown to extend the period of 1st stage $CO_2$production. Therefore, low temperature fermentation was effective in producing the high $CO_2$content dongchimi at adequate acidity, which is desirable organoleptically.

• The Korean Journal of Ecology
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• v.9 no.3
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• pp.161-184
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• 1986

An experiment was made in order to analyze the growth characteristics and productivity of Zoysia japonica under control, mowing and TIBA treatment conditions at the experimental farm of Kyung Hee univ. from May 26 to Oct. 1 in 1985. The field was planned by the randomized block design method and each treatment was given to three plots (2${\times}$2, 4${\times}$4 and 10${\times}$10 cm) and was replicated three times. Each plot was 1$m^2$ for Zoysia japonica. The sampling of each plot was taken once a week after sowing. In order to know the dry matter of total standing crops, kept 9$0^{\circ}C$ and weighted each organ of the plants. Total leaf area of a plant was measured by drawing method. The author adopted the growth analysis of English School. The increasing rates of numbers of leaf and stem were remarkably high in each plot between 10th and 12th weak after sowing and it was highest in TIBA treated plot. The increasin rate of leaf area in each plot was remarkably high beween 10th and 12th week and the maximum value of leaf area was 274.00c$m^2$ in TIBA treated plot of 100 plants/$m^2$. The increasing rate of standing crop was remarkably high between 10th and 12th week and the high increasing tendency in TIBA plot resulted from TIBA. The positive correlationship was founded between standing crop and leaf area. The evaporation rather than temperature acted as a main factor of negative correlation with standing crop during the experiment period. Solar radiation had a high positive correlation in the lower density of plot. C/F ratio was low, during the growth period, from 10th to 12th week after sowing and was low in the higher density under each treated plot. T/R ratio was not constant during the sampling period but was high in the lower density. The increasing rates of RGR and NAR were high between 11th and 12th week after sowing. Leaf area ratio was high in higher density in each plot and not constant in all treated plot.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.3 no.4
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• pp.329-333
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• 2005

To identify the effect of engineered barriers on the leach rate of cesium from spent PWR fuel under a synthetic granitic groundwater, the related leach tests with and without bentonite or metals have been performed up to about 6 years. The leach rates were decreased as a function of leaching time and then became a constant after a certain period. The period in a bare spent fuel was much longer than that with bentonite or metal sheets. The cumulative fraction of cesium released from the spent fuel with bentonite or with copper and stainless steel sheets was steadily increased, but the fraction from bare fuel was rapidly and then sluggishly increased. However, the values deducted its gap inventory from the cumulative fraction of cesium released from the bare fuel was almost very close to the others. These suggest that the initial release of cesium from bare fuel might be dependant on its gap inventory and the effect of engineered barriers on the long-term leach rate of cesium would be insignificant but the rate with engineered barriers could be reduced in the initial transient period due to their retardation effect. And the long-term leach rate of cesium from spent fuel in a repository would be approached to a constant rate of $2\times10^{-2}g/m^2-day$.