• Applied Chemistry for Engineering
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• v.3 no.4
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• pp.605-613
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• 1992

NCO-terminated prepolymers were synthesized by reacting carbonate-type polyol(PTMCG)($M_w=1,000$ and 2,000) with MDI and N-methyldiethanolamine, as a chain extender. Carbonate-type polyurethane containg zwitterionic group was prepared by reacting the prepolymer with 1,3-propane sultone. From the IR and NMR spectra of model reactions, it was known that the ionization occurred under the same condition. The structure of zwitterionic carbonate-type polyurethane(ZPU) therefore could be confirmed from the model reactions. Glass transition temperature(Tg) ranged between $-15{\sim}-30^{\circ}C$ from the thermal data. Tg was between $-15{\sim}-18^{\circ}C$ for a series of ZPU10 samples and between $-25{\sim}-26^{\circ}C$ for a series of ZPU20 polymers. Tensile strength increased with mole ratio of ionic content. On the contrary, elongation was rather dropped with mole ratio of ionic content. ZPU10-30 having better tensile strength and less elongation was selected as a membrane for the concentration of ethanol aqueous solution through pervaporation. To obtain the better selectivity, it was crosslinked with HMDI. In the swelling test, it showed the higher swelling degree at around 50wt% ethanol concentration due to the plastization effect of ethanol. To optimize the separation capacity, two operating factors-feed concentration and temperature-were considered. The overall separation capacity was as follows : separation factor, 2~83.2 ; the flux, $25.4{\sim}58.8g/m^2hr$.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.374-381
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• 1999

Poly(vinyl alcohol) (PVA) membranes crosslinked with poly(styrene-maleic anhydride) (PSMAn) were prepared, and the pervaporation characteristics of the membranes were studied for the separation of water/ethanol mixtures. The prepared PVA membranes showed that the permeation rate and separation factors were increased with increasing of PSMAn contents in the feed of 92/8 wt. % ethanol/water composition. However, when the water content in the feed composition was increased highly, the overall permeation rate was increased in the order of 2%>1%>0.5% in spite of the increase of the crosslinking contents, and the separation factor was decreased due to the higher sorbed water contents and the consequent plasticization action of membrane. Also, with respect to operating temperature, the permeation rate of the membranes obeyed the Arrhenius type. Especially, in the case of 2% crosslinked membrane, it was shown based on the pervaporation characteristics that both the permeation rate and separation factor were increased with increasing operating temperature from $30^{\circ}C$( to $50^{\circ}C$. From these results, it can be known that the hydrophilic groups introduced in the membrane by PSMAn highly affected the transport of permeants.

• Korean Journal of Ecology and Environment
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• v.38 no.2 s.112
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• pp.249-260
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• 2005

Dynamics of phytoplankton community were monthly examined at two sites in Lake Juam from January to December 2003. One site is located near the Dam, an intake tower, where obtain a drinking water resource, the other site is located in the shallow region, Mundeok-bridge, the upstream or effluent part of lake. During the study, there made little the differences in physicochemical factors between two sites, but numbers of species and standing crops of phytoplankton differ remarkably. Totally, 41% of green algae and 35.8% of diatoms were comprised of total phytoplankton species, while 46.3% of dinoflagellates and 27.6% of cyanobacteria contributed in total standing crops of Phytoplankton community. Cyanobacterium Microcystis aeruginora and diatom Fragilaria crotonensis dominated the Dam site during a warm season, while dinoflagellates Peridinium bipes and Asterionella formosa were at the shallow region during a cold season, respectively. According to the CCA analysis, dissolved oxygen, chemical oxygen demand and total phosphate strongly affected the growth of P. bipes with low water temperature. In addition, the increment of total nitrogen and water temperature affected biomass of a cyanobacterium M. aeruginosa. Collectively, it may suggest that the majority of annual primary production of Lake Juam is covered by two dominant species Peridinium bipes in cold season and Microcystis aeruginosa in warm season.

• Korean Journal of Food Science and Technology
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• v.23 no.2
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• pp.235-240
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• 1991

Starch phosphates were prepared from the corn starch mixed with 2% sodium tripolyphosphate by twin-screw extruder with a feed rate of 20 kg/hr and an extrusion temperature of $130^{\circ}C$, and the effects of extrusion variables on the physicochemical properties (target parameters) of starch phosphates were investigated. Interrelations of system parameters (specific mechanical energy and extrudate moisture) and rheological properities of starch was analyzed by using the response surface analysis. Degree of substitution (DS) was increased with increasing the feed moisture, and showed the maximum value at the screw of near 250 rpm, Degree of gelatinization was proportionally increased with increasing the screw speed and decreasing the feed moisture. Apparent viscosity of the paste was increased with increasing the feed moisture, but it was not significantly affected by the screw speed. It was found by scanning electron microscopy that the starch microgranules were much more degradaded, and as consequent result, the intrinsic viscosity was decreased, whereas, water solubility index was increased. The rate of retrogradation of the gels was retarded with increasing DS and decreasing viscosity.

• Korean journal of food and cookery science
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• v.21 no.4 s.88
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• pp.406-415
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• 2005

To evaluate the storage characteristics of Korean soups for the utilization of the Ready-Prepared Foodservice System, Yukkaejang(spicy beef and vegetable soup), Sagol-woogeojitang (bone soup with young cabbage), Kalbitang(beef short-ribs soup) and Seolleongtang(beef and bone soup) were prepared and their physico-chemical characteristics were investigated according to storage time and temperature$(4^{\circ}\;to\;20^{\circ}C)$ through analysis of pH, TBA values, Hunter color values, microbial counts, and sensory evaluation. No significant difference in pH was shown among the 4 kinds of soup while TBA values were significantly increased with storage time and temperature. Hunter color values(L, a and b values) of the Korean soups were significantly increased except Yukkaejang. In the sensory evaluation, appearance, color, flavor, taste, texture and overall acceptability of the soups decreased significantly with increasing storage time and temperature. Through correlation analysis between quality factors of treatments stored at $4^{\circ}$, the overall acceptability in Yukkaejang and Seolleongtang showed significant positive correlation with appearance, color, flavor and texture. The evaluated shelf-life of all four Korean soups was within 3 days at $10^{\circ}$, suggesting that Korean soups are applicable to ready-prepared foodservice system.

• Research in Plant Disease
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• v.11 no.2
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• pp.208-212
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• 2005

At the survey of June, 2002, total 294 dead frees were found in 20 ha of Black pine (Pinus thunbergii) forest located in the western coastal region of Korean peninsula. The dead trees were scattered over the 27 place as groups of about ten trees each. As a result of the field survey on the relationship between the conditions of dead trees and the occurrence of fruiting bodies of Rhizina undulata around the dead and/or dying trees, from June 2002 to August 2004 in the four plots, the occurrence of infected trees was observed as a shape of an irregular concentric circle from the first infected tree and R. undulata was found mainly around the dead tree. Because there was no observation of any other insects and pathogens which would kill trees, the cause of tree death in groups was considered owing to R. undulata. From the analysis of the physical and chemical proper ties of the soil collected from the damaged areas, the pH of soil was between 4.6 and 5.8 and the contents of soil nutrients were very low. Any "fire" trace was not found at all the 27 damaged places in the area, Taean, Chungcheongnam-Do, which are generally known as an important factor to initiate development of the disease. Therefore, further examination is needed to verify precisely about other environmental factors related with the group dying of the Black pines in this area beside 'fire'.

• 한국해양학회지
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• v.22 no.3
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• pp.207-215
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• 1987

The Keum River Estuary was investigated two times in April and July, 1986, to study process controlling chlorophyll distribution in estuarine waters. During the surveys, distribution patterns were studied for chlorophyll-a, nutrients, ph, SPM (Suspended Particulate Matter), DO (Dissolved Oxygen), temperature, salinity, etc. During April survey(low-discharge period), sea water penetrated to Kangkyung, about 35km upstream from the constructing weir, while in July (high-discharge period) only to 3 km upstream from the weir,In April SPM showed very high concentrations (500mg/l)on the average. But very low concentrations(about10mg/l)were observed in July due to high discharge of fresh water.Chlorophyll-a concentrations showed large variations both in time and space :much higher concentraations in July than in April and sharp decrease in concentrations at the fresh water-sea water interface (April:$6.5\mu\textrm{g}/{\ell}$ for fresh waters and 41.4\mu\textrm{g}/{\ell}$ forestuarine waters). Differebce ub chlorophyll-a concentrations for these two surveys appear to be caused mainly by the difference in effectiveness of penetrating lights controlled by SPM in the waters. Sharp decrease in chlorophll-a at the fresh water-sea water interface is believed to be resulted from mass mortality of fresh water phytoplankton caused by changes in osmotic pressure in the region. Observations in the same regions such as increase in AOU(Apparent Oxygen Utilization)and ammonia, decrease in PH,probably resulted through decomposition processes of dead planktons,furtuer support the idea.

• Journal of Wetlands Research
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• v.6 no.4
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• pp.59-69
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• 2004

Constructed wetlands are regarded as an important water treatment system for agricultural water quality improvement and management. The purpose of this study is to evaluate the application of subsurface flow wetland(SFW), using the Pharagmites australis as macrophytes, and to clarify the basic and essential factors to be considered in the construction and management of constructed wetlands. This study was carried out relatively short hydraulic residence time(HRT), 6hr ~ 72hr (3days), using eutrophic reservoir water with relatively low concentrations of influent and large quantity to be treated. The effluent satisfied the criteria of agricultural water quality. Removal efficiencies of Biochemical oxygen demand(BOD), Chemical oxygen demand(COD), Suspended solids(SS) and Chlorophyll a(Chl-a) were high in HRT 24hr, not any more significant increasement of removal efficiencies in HRT 48hr and 72hr. However, removal efficiencies of nitrogen and phosphorus increased as HRT increased, showing the highest efficiency at the 72hr of HRT in nitrogen, and 48hr in phosphorous. The SFW was very effective system for reservoir water quality improvement, and had the advantages of the reduction of purchasing cost to land required, lack of odors, and harmful insects, especially mosquito, the improvement of the scenic beauty and minimal risk of public exposure. Therefore, it was evaluated that the SFW was very available water treatment system for the water quality improvement of agricultural reservoir. However, it was need to consider with application of the SFW in high cost of construction and troublesome of management.

• Applied Chemistry for Engineering
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• v.23 no.5
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• pp.467-473
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• 2012

Coenzyme Q10 (CoQ10) is a natural lipid cofactor with antioxidant and anti-aging properties as cosmetic and food ingredients, involved in cellular energy metabolism. Here, nano-emulsions with CoQ10 were fabricated with lecithin, ethanol, oil, and sorbitan monostearate (Arlacel 60), as major components. Phase inversion emulsion method with ultrasonicator was utilized in producing CoQ10 solution, and stabilization effects from lecithin and ethanol and other diverse perturbation factors were evaluated over time. Physical properties of the emulsion were characterized such as its size, surface charges by zeta-potential, and the overall structures. Optimal concentrations of CoQ10 and Arlacel 60 were 0.8% and 3%, respectively, for producing the smallest sizes of nanoemersions in a 100 nm diameter with best morphology. No notable changes in the size were observed over 7 days from Ostwald ripening, when the concentration of Arlacel 60 was higher than 2%. Even after 270 days at room temperature, the size of nanoemulsions maintained as 115 nm in diameter, revealing only a 10% increase with high degrees of long termed stability and substantiality. In addition, changes in the surface potential occurred possible due to the flocculation effect on the nanoparticles.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.27-27
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• 2011

For the design of real applicable molecular devices, current-voltage properties through molecular nanostructures such as metal-molecule-metal junctions (molecular junctions) have been studied extensively. In thiolate monolayers on the gold electrode, the chemical bonding of sulfur to gold and the van der Waals interactions between the alkyl chains of neighboring molecules are important factors in the formation of well-defined monolayers and in the control of the electron transport rate. Charge transport through the molecular junctions depends significantly on the energy levels of molecules relative to the Fermi levels of the contacts and the electronic structure of the molecule. It is important to understand the interfacial electron transport in accordance with the increased film thickness of alkyl chains that are known as an insulating layer, but are required for molecular device fabrication. Thiol-tethered RuII terpyridine complexes were synthesized for a voltage-driven molecular switch and used to understand the switch-on mechanism of the molecular switches of single metal complexes in the solid-state molecular junction in a vacuum. Electrochemical voltammetry and current-voltage (I-V) characteristics are measured to elucidate electron transport processes in the bistable conducting states of single molecular junctions of a molecular switch, Ru(II) terpyridine complexes. (1) On the basis of the Ru-centered electrochemical reaction data, the electron transport rate increases in the mixed self-assembled monolayer (SAM) of Ru(II) terpyridine complexes, indicating strong electronic coupling between the redox center and the substrate, along the molecules. (2) In a low-conducting state before switch-on, I-V characteristics are fitted to a direct tunneling model, and the estimated tunneling decay constant across the Ru(II) terpyridine complex is found to be smaller than that of alkanethiol. (3) The threshold voltages for the switch-on from low- to high-conducting states are identical, corresponding to the electron affinity of the molecules. (4) A high-conducting state after switch-on remains in the reverse voltage sweep, and a linear relationship of the current to the voltage is obtained. These results reveal electron transport paths via the redox centers of the Ru(II) terpyridine complexes, a molecular switch.