• Journal of Aquaculture
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• v.15 no.4
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• pp.253-260
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• 2002

To find the optimal rearing conditions for Saxidomus purpuratus juvenile, filtering activity was estimated as functions of algal concentration and temperature by measuring the rates of clearance (CR) and ingestion (IR), when S. purpuratus was feeding. The clams were fed on unialgal diet of Isochrysis galbana at 6 algal concentrations (4.6$\times$$10^4$~2.6$\times$$10^6$ cells/ml) and at 6 temperatures (5, 10, 15, 20, 25, and 30^{\circ}C ). Algal concentration significantly affected the CR and the IR at all temperatures. At lower algal concentrations, CR increased, but decreased beyond a particular concentration. The maximum CR ($CR_{max}$) at 5, 10, 15, 20, 25, and 30^{\circ}C were 0.30, 1.73, 5.95, 15.17, 21.12, and 0.33 $l/g/h$, respectively. Below the level of 5.6$\times$10$^{5}$ cells/ml, IR increased as algal concentration increased, but was saturated at higher concentrations. To maintain high growth rate of S. purpuratus, I. galbana should be supplied with more than 5.6$\times$10$^{5}$ cells/ml. The maximum IR ($IR_{max}$) at 5, 10, 15, 20, 25 and30^{\circ}C were $2.2$\times$10^8, $1.5\times$10^9, 3.4$\times$10^9, 4.9$\times$10^9, 5.3$\times$10^9, and 1.0$\times$10^8$ cells/g/h, respectively. As for temperature, both $CR_max$ and $IR_max$ increased remarkably with raising temperature from 5 to 25^{\circ}C, but rapidly decreased at 30^{\circ}C. Between 15 and 25^{\circ}C $CR_{max} and IR_{max}$ were higher and most stable, At this temperature range, the $Q_{10}/s for CR_{max} and IR_{max}$ were 3.5 and 1.6, respectively. Therefore the optimal thermal range for the juvenile is 15~$25^{\circ}C$. The annual variation in IR$_{max}$ predicted by natural seawater temperature shows that inactive period (with lower $IR_max$) lasts for 5 months (from December to April). To ensure higher growth of juvenile during this inactive period at hatcheries, rearing temperature should be elevated to $15^{\circ}C$.>.

• Journal of Korea Water Resources Association
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• v.47 no.3
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• pp.257-267
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• 2014

The impact of the combination of changes in temperature and rainfall due to climate change on surface water resources is important in hydro-meteorological research. In this study, 4 hydro-meteorological (HM) models from the Rainfall Runoff Library in the Catchment Modeling Toolkit were used to model the impact of climate change on runoff in streams for 5 river basins in the Republic of Korea. Future projections from 2021 to 2040 (2030s), 2051 to 2070 (2060s) and 2081 to 2099 (2090s), were derived from 12 General Circulation Models (GCMs) and 3 representative concentration pathways (RCPs). GCM outputs were statistically adjusted and downscaled using Long-Ashton Research Station Weather Generator (LARS-WG) and the HM models were well calibrated and verified for the period from 1999 to 2009. The study showed that there is substantial spatial, temporal and HM uncertainty in the future runoff shown by the interquartile range, range and coefficient of variation. In summary, the aggregated runoff will increase in the future by 10~24%, 7~30% and 11~30% of the respective baseline runoff for the RCP2.6, RCP4.5 and RCP8.5, respectively. This study presents a method to model future stream-flow taking into account the HM model and climate based uncertainty.

• Korean Journal of Materials Research
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• v.7 no.12
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• pp.1063-1069
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• 1997

For me1t-spun Fe-Nd-C alloys, variation of phase development and magnetic properties with the variety of alloy compositions and production conditions were investigated. To find out whether hard magnetic $Fe_{14}Nd_2C$ is crystallized direct1y from the melt by rapid quenching, the phase development of the as-spun ribbons spun at various speed was a1so studied. For the ribbons spun at 10m/s, ${\alpha}-Fe$ was the primary crystallization phase followed by the secondary $Fe_{17}Nd_2C$. At 20m/s ${\alpha}-Fe$ was suppressed so that the primary $Fe_{17}Nd_2C$ coexisted with the secondary ${\alpha}-Fe$ and the amorphous phase. Above 30m/s the ribbons were a1most amorphous, and the amorphization was complete at 40m/s. $Fe_{14}Nd_2C$ therefore was not found in as-spun state but obtained after heat treating the ribbons. The effective temperature range ($700{\sim}900^{\circ}C$) in which $Fe_{14}Nd_2C$ can be obtained was wider than that of a cast alloy. An alloy made with the wheel speed of 20 or 30m/s yielded higher coercivities after heat treatment. In iron-rich Fe-Nd-C, the composition range in which a high coercivity (more than 10kOe) is expected is narrow, i.e., 77~78 Fe and 7~8 C(at.%).

• Journal of Wetlands Research
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• v.26 no.3
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• pp.204-218
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• 2024

In this study, we evaluate the applicability of domestic and international forest fire indices in Korea. To accomplish this objective, we first compare the structures of widely-used forest fire indices worldwide. Then, the application results of these forest fire indices are evaluated by comparing them with the annual and seasonal variations in actual forest fire occurrences in Korea. Finally, we select indices suitable for domestic application and propose directions to improve their appropriate applicabilities. The considered forest fire indices include MI, KBDI, FFWI, and mFFWI developed in the United States, NI, ZhI, and MNI developed in Russia, and DWI developed in Korea. This study considers the East Coast region as a study area, and the number of forest fire occurrences is referenced from the forestry statistics yearbook provided by the Korea Forest Service. As results, first, most forest fire indices do not adequately reproduce the actual annual forest fire occurrences as its variation is so small. However, most indices are found to effectively represent the monthly variations. Based on the correlation analysis between forest fire indices and actual forest fire occurrences, mFFWI, MI, ZhI, and DWI are selected as suitable indices for the East Coast region. However, these indices are still not satisfactory to adequately represent the forest fire occurrences in Korea, suggesting the need for further improvements. Each index has its own different aspects to be improved and, therefore, evaluation of these indices may be available only after further improvements are completed.

• Korean Journal of Construction Engineering and Management
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• v.16 no.1
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• pp.74-81
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• 2015

As one of urban infrastructure system, the electricity substation is critical for urban life and industrial activity as the electricity demands get higher than ever. However the substation is generally regarded as unpleasant or dangerous facility, which finally results in the continuous opposition movement by resident due to the belief of unidentified negative effect in apartment prices. Accordingly, as the scientifically objective and quantitative analysis is required to solve the social conflict, this study intends to examine the variation affected by urban infrastructure system, expecially for substation. After the independent variable defining the price of apartment and the dependent variable, which is apartment price, are identified and their spatial data has been filed, the forecasting model has been developed through the hedonic price function as well as artificial neural networks system. The research finding indicated that the spatial range affected by substation is not notable and the range of some case was applicable for less than 600m. It is expected that these research findings can be applied for establishing the one of solid cases for the analysis of economical effect to local housing market by the urban infrastructure system.

• Journal of the Korean Ceramic Society
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• v.38 no.11
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• pp.967-972
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• 2001

The crystal and defect structures of U $O_{x}$(x=2.0, 2.03, 2.14, 2.19, 2.20 and 2.26) were analysed by rietveld refinement and the results were compared to the U-O phase diagram. Neutron diffraction data were collected in the temperature range of RT~100$0^{\circ}C$. The specimens of x=2.14, 2.19, and 2.20 consisted of two phase: $UO_{2+x}$(Fm3m, a≒5.4$\AA$) and $U_4$$O_{9}$(I43d, a≒21.8$\AA$). The proportion of the $UO_{2+x}$(Fm3m) phase increased with increasing the temperature. The variation of the proportion of the two phases with temperature in the U $O_{2.2}$ and U $O_{2.18}$ samples showed some deviation from the expected values from the phase diagram especially at the high temperature range. The phase transitions ${\gamma}$longrightarrow$\beta$longrightarrow$\alpha$ of $U_4$$O_{9}$ were discussed in relation with the phase separation.eparation.ion.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.893-901
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• 2017

In order to understand the fluctuation characteristics of water temperature in August, water temperature, tide level, air temperature and wind data were analyzed using a power spectrum and coherence analysis for a region off the southern coast of Korea. Spectrum analysis showed that the water temperature and tide level in Wando, Goheung, Yeosu, Tongyeong and Masan have peaks over a semi-diurnal period. Coherence showed that water temperature was affected by tide in Wando, Goheung, Yeosu and Tongyeong where tidal range is relatively high. In Masan and Busan, where tidal range is relatively low, however, the tide did not affect water temperature significantly. In particular, wind was the most important factor in relation to water temperature in Masan. Time lags were calculated from phase. In Wando, water temperature decreased 1.5 hrs after a flood tide began. Water temperature decreased 0.3 hrs after a flood tide began in Goheung and Tongyeong. In Masan, water temperature increased 3 hrs after a south wind began. Water temperature in Yeosu was affected by tide, but air temperature, tide and wind in Busan affected water temperature very little.

• Korean Journal of Optics and Photonics
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• v.2 no.3
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• pp.139-148
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• 1991

A fiber-optic magnetic sensor system for the detection of small ac magnetic field(200Hz-2 kHz) was constructed. Magnetic field sensing part was fabricated by bonding a section of optical fiber to amorphous metallic glass(2605SC) having large magnetostriction effect. And with the directional coupler, all fiber type Mach-Zehnder interferometer was constructed to measure the variation of the external magnetic field by translating it into the optical phase shift in the interferometer. The signal fading problem of the interferometer, which is due to random phase drifts originated from the environment, i.e., temperature fluctuation, vibrations, etc., was elliminated by feedback phase compensation. This allows the sensitivity to be maintained at the maximum by keeping the interferometer in quadrature phase condition. The frequency response of metallic glass was found to be nearly flat in the range of 90 Hz-2 kHz and dc bias field for the maximum ac response was 3.5 Oe. The interferometer output showed good linearity over the range $\pm$0.5 Oe. For 1 kHz ac magnetic field the scale factor S and the minimum detectable magnetic field were measured to be 8.0 rad/Oe and $3X10^{-6} Oe/\sqrt{Hz}$at 1 Hz detection bandwidth respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.3
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• pp.33-44
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• 1987

To improve the ability of oxygen transfer in Biological Fluidised Bed(BFB) processes, air lift aeration system was introduced, experimental investigations were performed for the oxygen transfer in reactor, the fluidisation as to Biomass Volatile Solids variation and the relationship between substrate removal rate and oxygen utilization. The experiments for this purpose were executed for the synthetic wastewater by continuous type reactor at $20^{\circ}C$ using reticulated polypropylene sheets as media. The obtained results showed that the oxygen transfer by air lift aeration would be more effective than any other aeration systems used in BFB reactor. Also, it has observed that the critical biomass concentration in reactor took a range of 20 to 23g/l. Applying cages to BFB reactor, biomass would be maintained uniformly in the bed and the fluidisation characteristics of media could be improved. Varying F/M ratio from 0.36 to 0.73, BOD removals were 91% or more. Therefore, this process was suited to the treatment of which F/M ratios are variable and specific oxygen uptake rates ($K_r$) were 0.23 to 0.26g $O_2/g\;VSS{\cdot}day$ at range of 15 to 20g BVS/l.

• KSBB Journal
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• v.11 no.3
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• pp.303-310
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• 1996

The marine microalga Isochrysis galbana Parke was studied to optimize its growth conditions in flask culture. Important medium components studied include nitrogen source, buffer, trace elements and vitamins. Environmental conditions include pH, temperature, light intensity, mixing extent and working volume. The medium prepared from natural sea-waters gave a higher final cell density than the medium prepared from synthetic sea-water Nitrate was a better source than ammonium. In the range of 0.4∼2mM, the final cell density was proportional to the initial nitrate concentration and the cell yield was estimated to be 8.5g dry cell wt/g N. For phosphate, optimal growth was observed in 0.1∼1.0mM but a considerable variation in pH was resulted. The addition of Tris at 5mM or 7mM could stabilize the medium pH, but this significantly reduced both growth rate and final cell density, The effect of trace elements and vitamins was negligible. Optimal temperature and initial pH were $20^{\circ}C$ and 8. When the intensity of incident light was varied in the range of 400∼2100 lux, the growth rate increased from 10mL to 70mL, the final cell density decreased although the initial growth rate did not change. Optimal agitation speed was 100rpm when working volume was 30mL. With optimal conditions, the maximum specific growth rate obtained was 0.021hr-1 and the final cell density was 1.1g/L.