• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.4
• /
• pp.86-92
• /
• 2019

Polymers with various compositions of azobenzene and hexamethylene groups in the main chain were synthesized by a Schotten-Baumann reaction and their properties were investigated. The chemical structures and physical properties of the synthesized polymers were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry, thermogravimetric analysis, polarized optical microscopy, and x-ray diffraction. The polymers showed an inherent viscosity of 1.28-1.36 dl/g and were relatively insoluble in most organic solvents. The melt transition temperature increased rapidly with increasing number of azobenzene groups in the polymer. When the azobenzene monomer content was more than 50 mol%, no melting transition occurred below the decomposition temperature. Among the polymers with a melt transition temperature, the MP-A3C7 and MP-A5C5 polymers were liquid crystalline materials and exhibited a nematic phase with weak liquid crystallinity over a wide liquid crystal temperature range. This difference in the properties of the synthesized polymers is likely due to the changes in intermolecular forces resulting from the linearity and polarity of the trans-form of azobenzene.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.18 no.4
• /
• pp.206-213
• /
• 2013

Glass eels (Anguilla japonica) are caught in the west coast of Korea on their migratory route from the breeding grounds in the Mariana Trench along the North Equatorial Current and the Kuroshio Current. To identify the food source of natural glass eels, we analyzed the stable C and N isotopes of glass eels caught in April 2012 and investigated possible food sources in the survey area. In particular, with respect to the stable C and N isotopes of particulate organic matter, we extended the surveying area to the northern parts of East China Sea as well as the west coast of Korea. The stable C and N isotope ratios of the glass eels caught in the west coast were found to be $-20.7{\pm}0.1$‰ and $5.0{\pm}0.2$‰, respectively. The stable C and N isotope ratios of the particulate organic matter in the west coast of Korea, in which the glass eels are assumed to eat the particulate organic matter as food source, were estimated to be $-24.0{\pm}0.3$‰ and $2.8{\pm}0.4$‰, respectively. Similar data were obtained from the northern part of the East China Sea, $-24.5{\pm}0.5$‰ and $0.8{\pm}0.3$‰. The stable isotope ratios showed values differing from the stepwise increasing rates up the food web in natural aquatic ecosystem, showing that particulate organic matter in the west coast of Korea and East China Sea was not served as the glass eels food source. This result suggested that the glass eels caught in the west coast might not assimilate nutrition from the marine environment during long migration.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.2 no.2
• /
• pp.151-159
• /
• 1997

Benthic respiration and chemical fluxes were measured at the sediment-water interface underlying the marine fish cages floating on the open coastal waters off Tong-Young, the South Coast of Korea. The effects of cage farming on coastal benthic environment and on mass balance of organic carbon in the benthic boundary layer under the marine fish cages are addressed. In a growing season of caged fishes of June, 1995, benthic chambers and sediment traps were deployed on the sediment-water interfaces of the two sites chosen for this study: 1) Cage Site, directly underlying the fish cages of the farm at 18 m water depth, and 2) Control Site, about 100 m away from the farm at 32 m water depth. Benthic respiration rates and chemical fluxes were calculated from the evolution of dissolved oxygen and chemicals in the chamber water, and mass balance of organic carbon in the benthic boundary layer was constructed based on the vertical flux of particulate organic matter (POM) and chemical fluxes out of the sediment. High organic dumping (6400 mg C $m^{-2}d^{-1}$) and high benthic respiration (230 mmol $O_2\;m^{-2}d^{-1}$) were observed at the Cage Site. Equivalent to 40% of vertical flux of organic carbon into the Cage Site seemed to be decomposed concurrently and released back to overlying waters (2400 mg C $m^{-2}d^{-1}$). Consequently, up to 4000 mg C $m^{-2}d^{-1}$ of organic carbon could be buried into the farm sediment (equivalent to 60% of organic carbon flux into the Cage Site). At the Control Site, relatively less input of organic carbon (4000 mg C $m^{-2}d^{-1}$) and low benthic respiration rate (75 mmol $O_2\;m^{-2}d^{-1}$) were observed despite short distance away from the cages. The influence of cage farming on benthic chemical fluxes might be restricted and concentrated in the sea bottom just below the fish cages in spite of massive organic dumping and high current regime around the fish cage farm.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.19 no.4
• /
• pp.302-307
• /
• 2014

To examine the trophic ecology of the ascidian Styela clava in an aquaculture system of Korea, stable carbon and nitrogen isotopes were analyzed monthly in S. clava, coarse ($>20{\mu}m$, CPOM) and fine particulate organic matters ($0.7<<20{\mu}m$, FPOM). CPOM (means: $-18.5{\pm}1.2$‰, $9.3{\pm}0.7$‰) were significantly higher ${\delta}^{13}C$ and ${\delta}^{15}N$ values than those ($-20.5{\pm}1.5$‰, $8.4{\pm}0.5$‰) of FPOM. S. clava had mean ${\delta}^{13}C$ and ${\delta}^{15}N$ values of $-18.9({\pm}1.7)$‰ and $11.6({\pm}0.7)$‰, respectively. S. clava were more similar to seasonal variations in ${\delta}^{13}C$ and ${\delta}^{15}N$ values of FPOM than those of CPOM, suggesting that they rely largely on the FPOM as a dietary source. In addition, our results displayed that the relative importance between CPOM and FPOM as dietary source for the ascidians can be changed according to the availability of each component in ambient environment, probably reflecting their feeding plasticity due to non-selective feeding irrespective of particle size. Finally, our results suggest that dynamics of pico- and nano-size plankton (i.e., FPOM) as an available nutritional source to S. clava should be effectively assessed to maintain and manage their sustainable aquaculture production.

• The Mathematical Education
• /
• v.24 no.2
• /
• pp.74-104
• /
• 1986

This study aims at investigating the correlation between such variables as a child's family circumstance and personality and that of the child's mathematical ability. For the objects of the study five hundreds and sixteen students (male 273, female 243) were andomly selected from the fifth grade primary school students in the city of Seoul. For the tool of measure the investigation of Korean family circumstances with particular characteristics, the personality test by Chong Pom Mo and Kim Ho Kwon, and the intelligence test by Lee Sang Ro, Chin Whal Kyo and Pyon Chang Jin were employed. For the statistical analysis S. A. S. C., the statistical analysis package of KAIST was employed. The resutis of the test can be summarized as follows. The correlation between the variable of family Circumstance and that of mathematical alility 1) In case of the significance level 0.05 the education of the childs mother and the order of the child's birth have much to do with the perception speed. In case of the significance level 0.1 it makes some difference in the child's perception spead whether the clild's mother has a job or not. 2) In case of the significance level 0.05 the education of the child's father and mother, the father's job and the type of habitation have influence on the child's perception of space. 3) In case of the significance level 0.05 the education of the child's father and mother, the father's job, the order of the child's birth, the type of habitation, their religion, and their cultural, and economic standard have influence on the child's ability of inference. 4) In case of the significance level 0.05 the education of the child's father and mother, the father's job, the type of habitation, their religion and their cultural and economic standard have influence on the child's ability of calculation. 5) In case of the significance level 0.05 any variable of the child's family circumstance has nothing to do with the child's memory. In case of the significance level 0, 1 the type of family and the type of habitation have effect on the child's memory. 6) In case of the significance level 0.05 the education of the child's parents, the jobs of the parents, the type of habtation, their religion, and their cultural and economic standard have influence on the child's linguistic notion. The correlation between the variable of the child's personality and that of the child's mathematical ability 1) In regard to the priority of the variables influencing the child's perception speed, the child's discretion comes first in order, and then sociability and impulsiveness of the child. 2) The child's discretion has effect on the child's space perception. 3) The child's discretion has effect on the child's ability of inference. 4) In regard to the child's ability of calculation the child's discretion comes first in order, and then impulsiveness and sociability of the child. 5) The child's discretion has effect on memory. 6) The child's discretion has effect on the child's linguistic notion.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.11 no.3
• /
• pp.75-86
• /
• 2003

In the near future, the capacity of conventional anaerobic digester is thought to be insufficient because of the increase of the total solids from expansion of intercepting sewer, sewage quantity and direct input of night soil from near apartment districts. The objectives of this study was to investigate the improvement of digestion efficiency using microbial agent(Bio-dh). The system was a pilot-scale, two-staged, anaerobic sludge digestion system. The first-stage digester was heated and mixed. The agitation velocity of the first-stage digester was 120rpm. The second-stage digester was neither heated nor mixed. The Digestion temperature was kept at $35{\pm}1^{\circ}C$ The detention time of digester was 19 days. The dosage of sewage sludge and microbial agent were $0.65m^3/day$ and $0.5{\ell}/day$, respectively. The experiments was run for 25days. Three times a week, $COD_{Mn}$ and SS of effluent, TS, VS, and biogas production rate were measured. Temperature, pH, and alkalinity were measured daily. The results were as follows ; Without microbial agent, digestion efficiencies ranged 46.0%~50.9%(mean=48.6%), with microbial agent(Bio-dh), digestion efficiencies ranged 52.8%~57.3%(mean=54.2%). Consequently, microbial agent(Bio-dh) increased the sludge digestion efficiency about 12%. Also, Without microbial agent, the mean concentration of $COD_{Mn}$ and SS of second-stage digester effluent were 1,639mg/L, 4,888mg/L respectively. With microbial agent, the mean concentration of $COD_{Mn}$ and SS of second-stage digester effluent were 859mg/L, 2,405mg/L respectively. Consequently, microbial agent(Bio-dh) increased the removal efficiency of $COD_{Mn}$ and SS about 47.6% and 50.8%, respectively.