• Korean Journal of Fisheries and Aquatic Sciences
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• v.2 no.2
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• pp.134-138
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• 1969

Experiments were carried out to asses the impotance of environmental conditions upon the growth rate, length compositions seedling and spore liberation of a red alga Glacilaric verrucosa. The alga grown in water of low salinity mixed with fresh water shows better growth rate, lager length composition and excellent seedling, whereas the one vegetated in an area of tidal exposure shows a somewhat retarded growth rate and poor seedlings. The rate of growth Increases from August to October and begins to diminish from December continuing to diminish through February. Therefore the spore settling time extends from May to lune. Although the sun-drying method is the most eacient way of inducing spore liberation, further investigations are necessary in oiler to use this method for the application to artificial spore settling.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.119-126
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• 2002

The mica/epoxy composite used in generator(rated 22 kV and 500 MW) stator windings was aged at 180$\^{C}$ for up to 1000 hours in air and hydrogen. The degradation mechanism was investigated through the defect of evolution and microstructural analysis by performing SEM(Scanning Electron Microscope). As the thermal aging time increases, the number of voids per unit volume increases at the mica/epoxy interface of generator stator windings. The aged specimens in hydrogen showed retarded generation and growth of voids. Accelerated aging tests were conducted using the combination of thermal and electrical aging in air and hydrogen. The aging was carried out at a combined stress such as thermal aging at 110$\^{C}$, electrical aging at 5.5 kV/mm and frequencies 420 Hz in air, and electrical aging at 5.5 kV/mm and frequencies 420 Hz in hydrogen (pressure 4 kg/㎠). Thermal and electrical aging generates large voids at the mica/epoxy interface in air. Electrical aging in hydrogen also generates small voids, delaminations and cracks in mica tapes.

• Journal of ILASS-Korea
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• v.18 no.1
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• pp.21-26
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• 2013

Diesel low temperature combustion (LTC) is the concept where fuel is burned at a low temperature oxidation regime so that $NO_x$ and particulate matters (PM) can simultaneously be reduced. There are two ways to realize low temperature combustion in compression ignition engines. One is to supply a large amount of EGR gas combined with advanced fuel injection timing. The other is to use a moderate level of EGR with fuel injection at near TDC which is generally called Modulated kinetics (MK) method. In this study, the effects of fuel injection pressure on performance and emissions of a single cylinder engine were evaluated using the latter approach. The engine test results show that MK operations were successfully achieved over a range of with 950 to 1050 bar in injection pressure with 16% $O_2$ concentration, and $NO_x$ and PM were significantly suppressed at the same time. In addition, with an increase in fuel injection pressure, the levels of smoke, THC and CO were decreased while $NO_x$ emissions were increased. Moreover, as fuel injection timing retarded to TDC, more THC and CO emissions were generated, but smoke and $NO_x$ were decreased.

• Journal of the Korean Applied Science and Technology
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• v.21 no.4
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• pp.279-288
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• 2004

Liquid crystal (LC) system was introduced into W/O emulsion in order to enhance the stability and moisturizing effect. The LC system, composed of beeswax, surfactant, and water was formed on the surface of emulsion droplet, which was investigated through a polarized microscope. The phenomenon that the viscosity in W/O emulsion system is decreased with time, was reduced by the formation of LC with the addition of beeswax. Centrifugal separation test showed that the stability of emulsion system was increased with the addition of beeswax to 3%. The color change of vitamin C was delayed in LC emulsion systems, which indicates stabilization effect against the oxidation of vitamin C. Evaporation rate in W/O emulsion was retarded by LC, so that high moisturizing effect is expected in W/O LC system.

• Journal of Korea Foundry Society
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• v.32 no.6
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• pp.284-288
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• 2012

The effects of Si content on the variation of microstructure and processing window of austempered ductile cast iron were investigated. Four different Si contents between 2.42 and 3.37 wt.% were used. The influence of silicon on the microstructure and processing window of these materials were studied. Austenitizing was performed at $900^{\circ}C$ for 60min and austempering temperature were both $340^{\circ}C$ and $360^{\circ}C$ and austempering time were for 4min upto 119min and for 5min upto 160min respectively. After heat treatment, the evolution of stage I and stage II were performed by optical metallography, XRD, hardness test. The results showed that $t_2$ was delayed as Si contents was increased due to the fact that Si retarded the formation of cementite ($Fe_3C$). The high silicon content promoted the stability of the metastable two-phase combination of austenite and ausferrite.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.544-551
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• 2006

The sealing technique between a glass tube and a copper heat pipe in an evacuated tube solar collector is studied. In this study two different sealing techniques, such as flame method and furnace firing, are examined. After the sealing of a copper to a glass, the oxidation state of the copper and its bonding morphology were examined by SEM and XRD. Its oxidation was retarded by coating of borate solution on the copper, and $Cu_2O(cuprite)$ turned into CuO(tenorite) with increase in a firing temperature and firing time. Porous structure was found in the oxide layer when CuO formed. The best sealing morphology was observed when the thickness of the oxidation layer was less than $20{\mu}m$. The sealing technique performed in a furnace was promising and the satisfactory result was obtained when the sample was fired at $950^{\circ}C$ for 5 min under $N_2$ atmosphere. Annealing procedure is recommended to remove the stress left at the bonding zone.

• Journal of the Korea Institute of Building Construction
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• v.7 no.3
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• pp.83-90
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• 2007

This study is to investigate the effects of nylon(NY) and cellulose(CEL) fiber contents on the mechanical properties of the concrete. The results were summarized as following. Test showed that increase of NY and CEL fiber contents decreased fluidity of fresh concrete, so the loss of the fluidity would be considered when they were over added. Air contents were slight increased, but they satisfied the target air content. Bleeding capacity of concrete containing fiber significantly was declined. In addition, concrete containing higher amounts of fiber retarded setting time remarkably. Plastic shrinkage crack was reduced with the use of fiber due to increasing fiber contents and changing fiber classes, and NY fibers to prevent the plastic shrinkage crack effectively. Compressive and tensile strength of almost specimens were increased when air contents of the fresh concrete were fixed according to fiber contents, and flexural strength was increased according to fiber contents. For the impact strength of specimens, the specimen containing $0.6kg/m^3$ of NY fibers, showed the most favorable impact strength, The fiber reinforced concrete using NY fibers exhibited superior mechanical performance, and it was considered that $0.6kg/m^3$ of was desirable as the most favorable adding amount.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.1
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• pp.285-297
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• 1998

This report details a case of 8-year-old girl showing failure of odontogenesis after chemo-radiation therapy for the rhabdomyosarcoma at the age of 4. The observed results were as follows : 1. Past history revealed that she had received for a total radiation dose of 4430cGy, 29 fractions in 6 weeks and chemotherapy with vincristine, actinomycin D and cytoxan, followed as maintenance phase for 2 years. 2. The patient was symptom -free and appointed for the treatment of multiple dental caries. 3. Oral examination showed hypoplastic enamel on whole erupted permanent teeth and showed retarded eruption. 4. Conventional radiograms showed failure of root development including abrupt cessation of root formation and root agenesis, and microdontia, missing teeth, irregular enamel, dislocation of the impacted teeth. Additional finding showed good healing bone pattern on the left mandibular ramus and angle area. 5. Cephalometric analysis revealed failure of bite raising due to incomplete eruption of all the first molars and made it possible to suspect entrapped mandibular growth and then Class II tendency growth. 6. There was correlation between the time of chemo-radiation therapy and the damage of the teeth.

• Journal of ILASS-Korea
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• v.16 no.3
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• pp.126-133
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• 2011

In HCCI Engine, combustion is affected by change of compression speed corresponding to engine speed. The purpose of this study is to investigate the mechanism of influence of engine speed on HCCI combustion characteristics by using numerical analysis. At first, the influence of engine speed was shown. And then, in order to clarify the mechanism of influence of engine speed, results of kinetics computations were analyzed to investigate the elementary reaction path for heat release at transient temperatures by using contribution matrix. In results, as engine speed increased, in-cylinder gas temperature and pressure at ignition start increased. And ignition start timing was retarded and combustion duration was lengthened on crank angle basis. On time basis, ignition start timing was advanced and combustion duration was shortened. High engine speed showed higher robustness to change of initial temperature than low engine speed. Because of its high robustness, selecting high engine speed was efficient for keeping stable operation in real engine which include variation of initial temperature by various factors. The variation of engine speed did not change the reaction path. But, as engine speed increased, the temperature that each elementary reaction would be active became high and reaction speed quicken. Rising the in-cylinder gas temperature of combustion start was caused by these gaps of temperature.

• Preventive Nutrition and Food Science
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• v.10 no.2
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• pp.130-133
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• 2005

The growth inhibitiory effect of chaff vinegar against various food-borne pathogenic bacteria was evaluated. Bacterial growth was evaluated in chaff vinegar at concentrations of 15, 30, 50, 65, 80, and $100\%$ using the paper disc diffusion method and 0.5, 1.0, 1.5, 1.8, 2.0, 2.2 and $2.5\%$ in broth. In the paper disc diffusion assay, chaff vinegar showed a clear zone on both the Gram-positive bacteria; Listeria monocytogenes, Staphylococcus aureus and Gram-negative bacteria; Escherichia coli O157:H7, Salmonella Typhimurium, and Vibrio parahaemolyticus. Chaff vinegar exhibited the greatest growth inhibition for V. parahaemolyticus. The bactericidal effect of chaff vinegar on the E. coli O157:H7 was tested at concentrations ranging from 0.5 to $2.5\%$ (v/v) in the LB broth media. Chaff vinegar retarded the lag phase time of the growth curve in proportion in a concentration-dependent manner. Chaff vinegar at $2.5\%$ completely inhibited the growth of E. coli O157:H7.