• KSBB Journal
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• v.9 no.2
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• pp.211-223
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• 1994

In fermentations with a 4-liter stirred tank bioreactor, a better than two-fold enhancement of the gas-liquid mass transfer coefficient$(k_La)$ in the celite-immobilized fungal cultures of Tolypocladium in flatum over the parallel conventional free-cell was observed at identical biomass concentrations, despite the higher specific oxygen uptake rate of the immobilized fungi during exponential growth. As a result oxygen sufficient conditions, i. e., dissolve oxygen(D.O.) concentrations exceeding 75% air saturation, could be maintained throughout exponential growth period of the immobilized culture, in contrast to the suspended fungal culture, whose D.O. levels fell below 50% air saturation. A linear monotonic dependence of $k_La$ upon impeller agitaion rate was found for both immobilized and conventional cultivation modes over a range of 250 to 550rpm, the slope being a function of biomass concentration for the free but not for the immobilized cell system In contrasts oxygen transfer rate was a much weaker function of aeration rate up to about 2.5 vvm for both culture configurations. Above this level, aeration rate had no further effect on the mass transfer. In addition, the immobilized cultures sustained good morphological and physiological states, leading to almost two times higher cyclosporln A (CyA) productivity overt the parallel free cell system. These experiments suggest that the celite-immobilized fungal system in a stirred tank reactor has considerable promise for scaling up cyclosporin A production in terms of high-density cultivation.

• Electrical & Electronic Materials
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• v.10 no.2
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• pp.141-149
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• 1997

L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders were prepared by both GNP(Glycine-Nitrate Process) and solid state reaction method in various of calcination temperature(800-1000.deg. C) and time in air. Also, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contacts on YSZ(Yttria-Stabilized Zirconia) substrate were prepared by screen printing and sintering method as a function of sintering temperature(1100-1450.deg. C) in air. Sintering behaviors have been investigated by SEM(Scanning Electron Microscope) and porosity measurement. Compositional and structural characterization were carried out by X-ray diffractometer and ICP AES(Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Electrical characterization was carried out by the electrical conductivity with linear 4 point probe method. As the calcination period increased in solid state reaction method, L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ phase increased. Although L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ single phase was obtained only for 48hrs at 1000.deg. C, in GNP method it was easy to get single and ultra-fine L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ powders with submicron particle size at 650.deg. C for 30min. The particle size and thickness of L $a_{0.7}$S $r_{0.3}$Mn $O_{3}$ cathode contact by solid state reaction method did not change during the heat treatment, while those by GNP method showed good sintering characteristics because initial powder size fabricated from GNP method is smaller than that fabricated from solid state reaction method. Based on enthalpy change from thermodynamic data and ICP-AES analysis, it was suggested to make cathode contact in composition of (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$ Mn $O_{3}$ which have little second phase (L $a_{2}$Z $r_{2}$ $O_{7}$) for high efficient solid oxide fuel cells applications. As (L $a_{0.7}$S $r_{0.3}$)$_{0.91}$Mn $O_{3}$ cathode contact on YSZ substrate was sintering at 1250.deg. C the temperature that liquid phase sintering did not occur. It was possible to obtain proper cathode contacts with electrical conductivity of 150(S/cm) and porosity content of 30-40%.m) and porosity content of 30-40%.

• Journal of Environmental Health Sciences
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• v.6 no.1
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• pp.1-9
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• 1979

An experimental study was carried out to develop a rural type toilet of which the effluent could not transmit parasitic diseases at a village in Kangwon Province, Korea, during the period of January through December 1978, A drum tank (dia. 57cm$\times$90cm) and a cement tank (100cm$\times$100cm$\times$100cm) were filled with human excreta collected from toilets of the villages (the ratio of feces to urine was estimated approximately 1: 5) at once and three threecompartment toilets were constructed and used by people. pH, temperatures and viability of parasitic eggs were examined with the content of toilets. Rusults are summarized as follows: 1. pH increased from 7.0 at the beginning of experiment to 7.5 or 8.0 after 4 months of storage in drum tank as well as in cement tank and so did from 7.0~7.5 in the first tank to 8.0~8.5 in the third tank of all three-compartment toilets. 2. Temperatures of content at middle part of toilets in January through March ranged from 2 to 6$\circ$C which were 2-4$\circ$C higher than those of air, and those of lower part were again 1~2$\circ$C higher than of middle part. but temperatures of air, at middle part andat lower part in April were 14$\circ$C, 9~10$\circ$C and 8~9$\circ$C respectively, in July 29$\circ$C, 20~21$\circ$C and 19~20$\circ$C respe ctively and in October 17$\circ$C, 14$\circ$C and 14~13$\circ$C respectively. 3. All the parasitic eggs were degenerated about 4 months after filling drum tank with human excreta on 10th April while 10% of eggs were degenerated on 15th May, and all the eggs were degenerated about 4 months after filling cement tank on 24th August while about 10% were degenerated on 11th September and 20% on 4th October. 4. Degeneration rates of eggs were only 5~15% at 5cm below surface in the first tanks of three-compartment toilets while 45~65% at 50cm below, and concentration rates of eggs in second tanks were 8~12% of those in first tanks and only a few eggs were found in third tank but all of them were degenerated. Specific gravity of liquid of 1.022~1.024 in second tanks was not enough for overflowing eggs into third tanks.

• Journal of Preventive Medicine and Public Health
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• v.29 no.4 s.55
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• pp.863-875
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• 1996

In order to prepare the fundamental data for the health promotion by assessing the exposure level of styrene, the author determined the concentration of mandelic acid and phenylglyoxylic acid in urine of 42 workers who were exposed to styrene by high performance liquid chromatography and surveyed 16 symptoms, by questionnaire and also tested neurobehavioral test(digit symbol, benton visual retention) in 2 FRP plants of Kyung Nam area from July to September, 1995. Control was sampled by age sex matching method. The concentration of styrene in air was determined by gas chromatography. The results were as follows; 1. Geometric mean concentration of styrene in air was 17.4ppm, geometric mean concentration of mandelic acid(MA) in urine were 404.3mg/g creatinine for exposure group, 46.4mg/g creatinine for control group, geometric mean concentration of phenylglyoxylic acid(PGA) in urine were 57.5mg/g creatinine for exposure group, 9.5mg/g creatinine for control group. Mean concentration of MA and PGA showed statistically significant difference between exposure group and control group(p<0.01). 2. Number of symptom were 2.9 for exposure group, 3.3 for control group, number of digit symbol were 24.1 for exposure group, 32.5 for control group, number of Benton visual retention test were 6.1 for exposure group, 6.0 for control group, respectively. As result of adjusting the education year, number of Benton visual retention test showed statistically significant difference between exposure group and control group(p<0.05). 3. Excellent correlation were observed between environmental styrene exposure and urinary MA(r=0.80), PGA(r=0.73), and MA+PGA(r=0.81).

• Journal of Animal Environmental Science
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• v.13 no.3
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• pp.171-178
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• 2007

This study was carried out to investigate the effect of microbial complex diets on improvement of air quality in finishing pig building. Ammonia and hydrogen sulfide concentrations were significantly(p<0.05) decreased by dietary supplementation of 0.1% level of microbial complex compared with those of control according to the time in the finishing pig building. Characteristics of piggery liquid slurry that total nitrogen and $NH_3-N$ of treatment were reduced relatively compared with those of control, and were decreased depending on the time. In conclusion, the result obtained from this study suggest that the dietary supplementation of microbial complex for finishing pigs may improve environment in the finishing pig building.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.4
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• pp.463-470
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• 1998

To improve muscle quality and prolong freshness of sashimi, the effects of freezing-thawing condition on physicochemical and rheological properties of plaice muscle were investigated. Muscle tested were frozen with quick freezing (liquid nitrogen gas) or slow freezing ($-15^{\circ}C$ air). Transition time of zone of ice crystal formation was within 10 minute for quick freezing and 110 minute for slow freezing. Time required for thawing to $0^{\circ}C$ in muscle temperature by various thawing methods was shortest with $25^{\circ}C$ tap water, followed by $15^{\circ}C$ tap water, $10^{\circ}C$ tap water, $25^{\circ}C$ air, $5^{\circ}C$ tap water and $0^{\circ}C$ cold water. Breaking strength of muscle was higher in quickly frozen sample than in slowly frozen sample. According to sashimi term, changes in breaking strength of muscle did not show any difference in quickly frozen sample, while showed significant difference in slowly frozen sample. The remaining content of ATP was not effected by freezing speed, and ATP content was apt to higher in quickly thawed sample than in slowly thawed sample. IMP was the majority of ATP and it's related compounds of sample after freezing and thawing. Collagen matrix was weakened markedly in slowly frozen sample than in quickly frozen sample.

• Journal of Korea Society of Waste Management
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• v.35 no.8
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• pp.744-753
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• 2018

The Stockholm Convention, which was adopted in Sweden in 2001 to protect human health and the environment, includes regulations for Persistent Organic Pollutant Rotors such as toxic and bioaccumulatives. Currently, there are 28 types of materials. This prohibits and limits the production, use, and manufacture of products. Korea is a member of the Convention, and it is necessary to prepare management and treatment plans to address the POP trends. Thus, we experimentally investigate whether the environmentally stable incineration is achieved when the sample is thermally treated using the Lab-scale (1 kg/hr). The target samples is pesticides in liquid phase and solid phase. In this study, organic chlorinated pesticides and their thermal characteristics were analyzed. We calculated the theoretical air volume based on the element analysis results. Because the interior of the reactor is small, more than 10 times of the air ratio was injected. The retention time was set to at least 4 seconds using a margin. The incineration temperature was $850^{\circ}C$ and $1100^{\circ}C$. Thus, we experimentally investigated whether the environmentally stable incineration was achieved when the sample was thermally treated using the Lab-scale (1 kg/hr). We analyzed five types of exhaust gas; the 02 concentration was high, but the CO amount decreased. Complete combustion is difficult because of the small size of the furnace due to the nature of Lab-scale. The organic chlorine-containing pesticide had an average decomposition rate of 99.9935%. Considering the decomposition rates of organic chlorine-containing pesticide in this study, the incineration treatment at over 2 ton/hour, which is typical for a conventional incinerator, is possible. Considering the occurrence of dioxins and unintentional persistent organic pollutants, it can operate at more than $1,100^{\circ}C$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.5
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• pp.333-338
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• 2022

The single jet of decane/methylcyclohexane mixed fuel that is surrogate for kerosene was injected into supercritical environment and visualized using shadowgraph technique. The injection pressure drop of the fuel jet of T_r = 0.484 was kept constant at 0.5 MPa and the experiment was conducted above the critical point of the mixed fuel, and the reduced temperatures of the chamber was changed from 1.00 to 1.23, and the reduced pressures was 1.00 and 1.38. As an index for reducing the density of jets sprayed into the supercritical environment, the brightness intensity of the post-processed jet image was observed with the internal temperature and pressure of the chamber. It was confirmed that the decrease in the brightness intensity of the jet when the temperature inside the chamber increased, and when the pressure inside the chamber was higher at the same temperature, the decrease in the brightness intensity of the jet was delayed. When the pressure inside the chamber is high, it is thought that the change in brightness intensity is delayed due to the increase in the pseudo-critical temperature of the fuel and the increase in the temperature required to reduce the density of the fuel jet.

• Analytical Science and Technology
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• v.18 no.5
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• pp.403-409
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• 2005

Polycyclic Aromatic Hydrocarbons(PAHs) contamination arises from several sources including processing of food(smoking, direct drying, cooking) and environmental contamination of air, water, or soil, the later being considered as the most important. In this study, to establish the analytical method for some PAHs[benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene, indeno(1,2,3-c,d)pyrene] in fish, alkali digestion time, extraction solvents, elution volume of florisil cartridge for clean-up have been optimized. The methodology involved saponification and extraction with n-hexane, clean-up on Sep-Pak florisil cartridges and determination by HPLC/FLD(High Performance Liquid Chromatography/Fluorescence Detector). Overall method recoveries for 8 PAHs spiked into these products ranged from 90 to 106%.

• Solar Energy
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• v.10 no.3
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• pp.13-18
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• 1990

When nonuniform thermal boundary conditions are imposed on the surface of a circular cylinder in crossflow, the heat transfer characteristics can be quite different compared to what is found for isothermal or constant heat flux boundary conditions. In the present analysis, two kinds of nonuniform boundary conditions along the circumference of the cylinder are considered in a uniform stream of air: step changes and linear profiles. Step changes in temperature can arise on the surface of an external, cylindrical, solar central receiver. As the working fluid(water) flows through the vertical tubes that ring the circumference of Solar One(a solar central receiver in Barstow, California), the solar flux on the receiver heats the water from a liquid to a superheated state. In this process, portions of the receiver panels, and thus portions of the circumference of the cylinder, function as a preheater, boiler, or superheater. Hence the surface temperature can vary significantly around the cylinder. Common engineering practice has been to use an average wall temperature with an isothermal cylinder heat transfer coefficient when estimating the convective loss in these kinds of situations.