• 상하수도학회지
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• 제21권3호
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• pp.273-278
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• 2007

Modern society has moved from a phosphorus recycling loop, where animal manure and human wastes were spread on farming land to recycle nutrients, to a once-through system, where phosphates are extracted from mined, non-renewable phosphate rock and end up either in landfill(sewage sludge, incinerator ash) or in surface waters. In this research, crystallization of nitrogen and phosphate with natural sources of $Mg^{2+}$ in synthetic water was tested. The operational parameters of pH, mixing time, and the magnesium molar ratio were investigated to find optimal conditions of the MAP precipitation using synthetic wastewater. The removal efficiency of phosphate increased with pH up to 11. By MAP precipitaiton of the synthetic waste water, 94% of the phosphate were eliminated at pH 11. It was found that at least 10 minutes mixing time was required and 20 minutes mixing time was recommended for efficient phosphate removal. High efficiency removal of phosphate was possible when the magnesium molar ratio was 1.0~2.0. The comparative study of different magnesium sources showed that coagulants (PAC) was the more efficient sources than only magnesium. The result showed that 97% of phosphate removal. In conclusion, coagulants (PAC) induced crystallization of struvite and hydroxyapatite was shown to be a technically viable process that could prove cost effective for removing phosphate in wastewater.

• 한국의류학회지
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• 제13권3호
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• pp.242-251
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• 1989

The purpose of this study was to investigate the changes in easy-care and strength properties of the wet fixation processed viscose rayon fabrics. Rayon fabrics were treated with mixed resins of melamine formaldehyde (MF) and DMDHEU by one bath and two bath wet fixation processes. The MF/DMDHEU mixed resin concentrations were 50/100, 50/150, 100/100, 100/150 and 150/100(g/1). Magnasium chloride was used as a catalyst. Treated fabrics were evaluated by nitrogen content, DP rating, wrinkle recovery angle, breaking strength, tearing strength and abrasion resistance. The properties were compared to the fabrics treated by conventional Pad-Dry-Cure (PDC) method. Wet fixation processed fabrics showed DP ratings of higher than 3 and higher than 275 degrees of wrinkle recovery angles in all the mixed resin concentrations. Wet fixation processed fabrics showed increase in breaking strength and tearing strength but decrease in abrasion resistance. However, the decrease in abrasion resistance was much less than the conventional PDC treated fabrics. The one bath wet fixation processed fabrics showed better physical properties than the two bath processed fabrics in general. The optimum treatment condition was the mixed resin concentration of MF/DMDHEU, 100/100 g/l in one bath wet fixation process.

• Journal of Microbiology and Biotechnology
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• 제12권3호
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• pp.522-525
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• 2002

A very rapid and efficient separation technique for cellular rhizobial cyclosophoraoses was developed based on fractional precipitation and partition chromatography. Cyclosophoraoses are known to function in the osmotic regulation and root nodule formation of legumes during the nitrogen fixation process. Cyclosophoraoses are produced as unbranched cyclic (1longrightarrow12)-${\beta}$-D-glucans in Agrobacterium or Rhizobium species. Recent research has shown that cyclosophoraoses can form inclusion complexation with various unstable or insoluble guest chemicals, thereby implying great potential for industrial application. Typical separation of pure cellular cyclosophoraoses has been so far carried out by several time-consuming steps, including size exclusion, anion exchange, and desalting liquid chromatographies, with a relatively poor recovery. However, the proposed method demonstrated that the successive application of fractional ethanol precipitation and one step of silica gel-based flash column chromatography was enough to simultaneously purify neutral or anionic forms of cyclosophoraoses. This novel technique is very rapid and provides a high recovery.

• Environmental Engineering Research
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• 제20권1호
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• pp.65-72
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• 2015

A comparative study on response of a toxic compound thiocyanate ($SCN^-$) was carried out in continuous and fed batch moving bed reactor systems. Both systems had three sequential anaerobic, anoxic and aerobic reactors and operated at same hydraulic retention time. Feed $SCN^-$ was first increased from 600 mg/L to 1,000 mg/L for 3 days (shock 1) and then from 600 to 1,200 mg/L for 3 days (shock 2). In anaerobic continuous reactor, increase of effluent COD (chemical oxygen demand) due to shock load was only 2%, whereas in fed batch reactor it was 14%. In anoxic fed batch reactor recovery was partial in terms of $SCN^-$, phenol, COD and $NO{_3}{^-}$-N and $NO{_2}{^-}$-N removals and in continuous reactor complete recovery was possible. In both systems, inhibition was more significant on aerobic reactors than anaerobic and anoxic reactors. In aerobic reactors ammonia removal efficiency deteriorated and damage was irreversible. Present study showed that fed batch reactors showed higher substrate removal efficiency than continuous reactors during regular operation, but are more susceptible to toxic feed shock load and in nitrifying reactor damage was irreversible.

• 한국수산과학회지
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• 제29권6호
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• pp.828-836
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• 1996

The histological changes of gill, liver, spleen and muscle, and respiration and blood variables and liver glycogen content were examined in black seabream, Acanthopagrus schlegeli. Fish were exposed to a high level of total ammonia nitrogen (10.4 mg/l) and recovered from exposure $(0.4{\pm}0.2mg/l)$ in a closed recirculating seawater system. In the process of exposure, mortality was $9\%$, and hyperplasia, necrosis or inflammation appeared in all tissues except for muscle. Oxygen consumption was decreased by $49\%$, and red blood cell (RBC) number, hematocrit and hemoglobin concentration were significantly decreased, while plasma glucose contents, activities of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) increased. Liver glycogen content significantly increased from $6.6\%\;to\;10.4\%$. A large amount of hemosiderin was observed in the splenic tissue. During the recovery period, RBC number, hematocrit, hemoglobin concentration, GOT and GPT activities were returned to the normal status. Histological status of liver tissue was returned to the normal, but liver glycogen content was not recovered. During the recovery period, spleen melanin-macrophages temporarily increased, but subsequently decreased to the normal status.

• Asian Journal of Atmospheric Environment
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• 제8권2호
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• pp.96-107
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• 2014

Extreme recovery of the thermal energy from the combustion of flue gas may bring about early gas condensation resulting in the increased formation of nitric acid vapor. The behavior of the nitric acid formed inside the stack and in the atmosphere was investigated through a computer-aided simulation in this study. Low temperatures led to high conversion rates of the nitrogen oxide to nitric acid, according to the Arrhenius relationship. Larger acid plumes could be formed with the cooled flue gas at $40^{\circ}C$ than the present exiting gas at $115^{\circ}C$. The acid vapor plume of 0.1 ppm extended to 25 m wide and 200 m high. The wind, which had a seasonal local average of 3 m/s, expanded the influencing area to 170 m along the ground level. Its tail stretched 50 m longer at $40^{\circ}C$ than at $115^{\circ}C$. The emission concentration of the acid vapor in the summer season was a little lower than in the winter. However, a warm atmosphere facilitated the Brownian motion of the discharged flue gas, finally leading to more vigorous dispersion.

• 한국식품영양과학회지
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• 제23권2호
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• pp.328-332
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• 1994

The purpose of present paper is to compare and analyze the quality of imported Chinese products with the Korean local products in terms of proximate composition, character of external appearance , ingredient composition of dried bracken , dried radish cubers, meju , dried pollack, dried mussel , and dried brown seaweed(Undaria puinnatidifida) which were imported between Oct., and Dec. 1992 and distributed in the market. Moisture recovery of dried products resulted in changed shape and incomplete moisture recovery due to an excessive drying in consideration of hygroscopic property in the course of distribution. The amounts of water soluble brown pigment were two times greater in Korean dried pollack and bracken than those of Chinese products. The content of volatile basic nitrogen (VBN) were twice in Chinese dried pollack, and this may be due to foregin odor from a long transport time and distribution process. The contents of aflatoxin in Korean products were not detectable and these of Chinese products were 5 $\mu\textrm{g}$(%) in dried pollack, bracken and radish cuber. the remaining agricultural chemicals were not detectable in all products. Because of poor technique and facilities, the external appearance of Chinese products especially dried mussels and dried pollack were not uniformed in size and color. Discoloration and foregin substance such as hair, dust were checked , Korean products were mostly packed in small size in PP or bag, and Chinese products were packed in bulk size and distributed as a bulk.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2113-2119
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• 2024

This study presents the development and characterization of a prototype TL/OSL reader for the retrospective dose assessment of individuals in radiological emergencies. The reader is portable, semi-automatic, and capable of accurate measurements. The dimension of the reader is 25 × 25 × 37 cm³ and the weight is about 15 kg. The reader consists of a sample moving stage, a heating module, an optical stimulation module, a detection module, a data acquisition (DAQ) unit, a nitrogen gas control module, and a PC with a GUI program. The reader has three measurement modes: TL, CW_OSL, and custom mode. The reader was characterized using commercial thermal luminescence dosimeters (TLD, LiF:Mg,Cu,Si) and optically stimulated dosimeters (OSLD, Al₂O₃:C), as well as fortuitous materials, such as display glasses and resistors of mobile phone. The results showed that the reader is capable of measuring signals with a detection limit of up to 0.02 mGy using a commercial dosimeter. In the dose recovery test using fortuitous materials, the reconstructed doses obtained three days post-irradiation closely aligned with the initially administered doses. As a result, this study suggests that the developed TL/OSL reader is a promising instrument for emergency dose assessment at accident sites.

• 소성∙가공
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• 제33권5호
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• pp.322-329
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• 2024

Because a high strain rate suppresses cross slip and delays dynamic recovery in the alloys with a face-centered cubic (FCC) structure, it is generally accepted that the influence of strain rate on strain hardening rate and tensile strength is greater than that on the yield strength of FCC alloys. The present study examined the tensile behavior of an austenitic stainless steel exhibiting an FCC structure, and revealed that the increment in yield strength was greater than that in tensile strength as the strain rate increased from 5.21×10^-5s^-1 to 4.17×10^-1s^-1. This indicated that the strain hardening rate was reduced by increasing the strain rate, which was inconsistent with the conventional explanation. Adiabatic heating was detected at high strain rates from 5.21×10^-5s^-1, and the resulting temperature increase could elevate stacking fault energy. The tendency for sip planarity was investigated by applying the Ludwigson model to the tensile curves, which suggested that higher stacking fault energy due to adiabatic heating could accelerate cross slip and dynamic recovery, thereby reducing the strain hardening rate.

• 센서학회지
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• 제33권5호
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• pp.242-247
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• 2024

Pure and 0.3 wt% Au-doped In₂O₃ hollow spheres were synthesized via ultrasonic spray pyrolysis of droplets containing an In-source and sucrose in air and their gas sensing characteristics to 1 ppm ethanol, 1 ppm toluene, 1 ppm xylene, 2 ppm nitrogen dioxide (NO₂), and 30 ppm carbon monoxide (CO) were measured at 400 - 450℃. The pure In₂O₃ hollow spheres exhibited relatively low gas responses and sluggish recovery kinetics. In contrast, the doping of Au into In₂O₃ hollow spheres significantly increased the gas response (S= resistance ratio) to 1 ppm ethanol (S= 20.6) at 400℃ with low cross-responses (S = 1.3-8.8) to other interference gases. Furthermore, the hollow spherical morphology of In₂O₃ provides a large surface area and facilitates rapid gas diffusion, resulting in fast response and recovery times. The sensor exhibited excellent performance with a low detection limit of 1.6 ppb. These findings indicate that the Au-In₂O₃ hollow spheres are promising candidates for advanced ethanol-sensing applications, particularly in breath-alcohol monitoring for ignition interlock devices.