• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.425-431
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• 2018

Composite particles of porous silica and cerium oxide nanoparticles blocking UV/blue light were prepared through a dry coating process. Various composite particles were prepared by varying conditions such as the mixing ratio of cerium oxide and silica, and the chamber rotating speed of mechano fusion system. The surface morphology of the composite particles was observed with SEM and the composition was analyzed using X-ray fluorescence (XRF). When the cerium oxide/silica composite particles were dispersed in water, the transparency and dispersion stability of the colloidal solution were improved. In addition, the fluidity and spreadability of the particle powder were enhanced by making composite particles. These results show that cerium oxide/silica composite particles can be used as functional cosmetic ingredients for UV/blue light protection.

• Korean Journal of Environmental Agriculture
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• v.29 no.3
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• pp.239-246
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• 2010

Aphids are one of the major pests in agricultural crops. A number of synthetic pesticides have been used for control of aphids in agriculture, but increasing public concerns over their adverse effects on the environment have required more environmentally-friendly methods for pest management. In this study, we examined plant oil formulations for the control of green peach aphid (Myzus persicae). Oil formulations were prepared by hydrolyzing the plant oils in ethanolic KOH solution and diluted at the rate of 1:500 for aphid control. The oil formulations showed aphid mortalities ranging from 24.44 to 43.33% in vitro. Significantly increased aphid mortalities were observed by the treatment of oil formulations combined with low-dosed imidacloprid. No significant difference in the aphid mortality was observed between the oil formulations. Mass spectrometry analyses of aphids treated with the low dosedimidacloprid plus the plant oil formulations detected similar concentrations of imidacloprid between the treatments. In field trial bioassays against aphids, significantly decreased aphid population were observed in the pepper plants treated with soybean oil formulation combined with the low-dosed imidacloprid, while aphid population dramatically increased in the pepper plants treated with the low-dosed imidacloprid alone. These results suggested that the plant oil formulations can be used as an environmentally-friendly method for enhancing the insecticidal effectiveness, which may play a role in reducing the use of synthetic pesticide in agriculture.

• Korean journal of food and cookery science
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• v.31 no.2
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• pp.112-117
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• 2015

The analytical method for ethyl carbamate (EC) in maesil (Prunus mume) extract was developed with deuterium-labeled ethyl carbamate as an internal standard. Samples were neutralized with an addition of 1 N sodium hydroxide solution, followed by a solid phase extraction with a Chem Elut cartridge. A standard curve exhibited a good linearity with correlation coefficient of 0.9991. The limit of detection (LOD) and limit of quantification (LOQ) were 2.91 ng/g and 8.83 ng/g, respectively. The recovery rate of EC ranged from 91.40% to 120.90%. The precision never exceeded 12.57% (intra-day) and 11.03% (inter-day). Samples were comprised of 24 home-made and 7 commercially-available maesil extracts. Eight home-made samples contained EC at levels between 3.39 and 75.76 ng/g. Three commercially-available samples had EC at levels between 11.67 and 20.16 ng/g. Average daily intakes of EC from maesil extracts for consumers were 0.23 g/kg of body weight. Based on a benchmark dose confidence limit ($BMDL_{10}$) of 0.25 mg/kg of body weight/day, the margin of exposure (MOE) of EC in maesil extract for consumers was 94,150, which is not of concern. Considering that a daily intake of maesil extract has been increasing, further studies on the formation of EC in maesil extract is needed.

• Journal of Ocean Engineering and Technology
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• v.27 no.4
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• pp.76-82
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• 2013

Motion reduction of an offshore structure at resonant frequency is essential for avoiding critical damage to the topside and mooring system. A damping plate has a distinct advantage in reducing the motion of a floating structure by increasing the added mass and the damping coefficient. In this study, the heave motion responses of a circular cylinder with an impermeable and a permeable damping plate attached at the bottom of the cylinder were investigated thru a model test. The viscous damping coefficients for various combinations of porosity were obtained from a free-decay test by determining the ratio between any pair of successive amplitudes. Maximum energy dissipation occurred at a porous plate with a porosity P = 0.1008. Experimental results for regular and irregular waves were compared with an analytical solution by Cho (2011). The measured heave RAO and spectrum reasonably followed the trends of the predicted values. A significant motion reduction at resonant frequency was pronounced and the heaving-motion energy calculated by the integration of the area under the heave motion spectrum was reduced by more than 75% by the damping plate. However, additional energy dissipation by eddies of strong vorticity and flow separation inside a porous damping plate was not found in the present experiments.

• The Korean Journal of Emergency Medical Services
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• v.11 no.1
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• pp.73-80
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• 2007

This study is a descriptive survey research to know the levels of job satisfaction and influential factors for emergency medical technicians(EMT). This study sampled Level 1 and Level 2 Rescue Members from fire stations and EMT from general hospitals in the Gwangju City and JeollaNamdo area. Interviews for the 75 participants of this convenience sample were conducted for a two month period from July to September 2006. Data was collected on interviewing questionnaires. When looking at the results above internal factions were most influential towards satisfaction and self-responsibility, fulfillment, displays of Aptitude were highest for satisfaction. However, organizational factors were the lowest. There is a need for reform in promotion term periods and policy as well as promotion opportunities. Influential factors for job satisfaction were Role Performance Ability, Intentions for Changing Jobs, and Job Selection Motivation. Therefore, the more insufficient your ability to perform your job the less satisfied you are with it and the more fear you feel from experiences on the job the less satisfied you are with your job. Henceforth, there is a need to reform the educational programs offered to EMT for job training emphasizing job performance ability and the ability to judge for oneself on emergency situations, and reform the promotional system. Finally, there is a need for psychological consultation to offer stability to those after treating an emergency situation and encouragement for personal religion.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.57-70
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• 1989

The purpose of this study was to investigate the effect of salivary gland on the calcification of dentin in rats. 80 Sprague-Dawley male rats that weighed approximately 120gm were used in this study. 5 rats among them were shared as controls. 75 rats received sialoadenectomy were divided into submaxillary adenectomy group, parotidectomy group, and submaxillary-parotid gland combined removal group. In experimental groups, 25 rats in each of the 3 groups were sacrificed at the following intervals; 3 days, 1, 2, 3 and 4 weeks. All animals were sacrificed by vascular perfusion with 10% formalin. The maxillary incisors including periapical tissues were removed and defatted in 20% KOH solution at $0^{\circ}C$ for 24 hours, and dehydrated with acetone. Each tooth specimen was attached on the stab for scanning electron microscopic study. Gold was coated on the each specimen in the thickness of 300${\AA}$ at D.C. 1400V, 6mA for 6 minutes with coating machine (Eiko IB-3). Inner dentinal surfaces of the specimens were observed with SEM (Hitachi S-450). The results were as follows, 1. Parotidectomy groups were found to be inhibited the formation of dentinal calcification compared to submaxillary adenectomy groups in the eady stages. 2. Combined removal of submaxillary and parotid gland was appeared to cause more severe inhibition effect on the dentinal calcification than that of each salivary gland separately. 3. Inhibition of the calcification and mineralization of dentin caused by sialoadenectomy was more extreme from 3 day to 2 weeks after beginning of the experiments. However it was tended to be normalized after that. 4. Salivary gland was responsible for alterations in calcification and mineralization of dentinal growth.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.4
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• pp.72-80
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• 2009

The main purpose of this study is as follows : Finding a solution for fresh wood chips to be used as an alternative growing-media through a study of the formation method of a compost base that is applicable on both construction site and composting factory to ferment fresh wood chips produced from construction site as well as a study on adjuvant or secondary materials. The result from the experiment plot using wood chips sized 50mm or less, manure and fertilizer mixed manure as a source of nitrogen to compost fresh wood chips has shown that the temperatures 9days and 3days after the beginning of the experiment reached to $49.0^{\circ}C$ and $40.4^{\circ}C$ respectively, the heating duration was 7days and 4days respectively, and the C/N ratio was 26.5 and 25.3, each satisfying the standard for composted manure (25.0~40.0). Also, the other result from another experiment plot using mixture of sandy soil and microorganism as an inoculation source of microorganism has shown that the temperature 10days after the beginning of the experiment reached to $67.6^{\circ}C$ and lasted 16days. The experiment plot using sandy soil has shown the highest figure of $5.3{\sim}108$ CFU/g in terms of number of microorganism. The result from the experiment plots for on-site composting of fresh wood chips have shown that the experiment plot that used sandy soil with fertilizer due to supply restriction of manure as a nitrogen source in construction site reached the high temperature of $54.7^{\circ}C$ after 3days of experiment beginning and maintained heating state for 17days and reached 30.6 of C/N ratio, satisfying the standard for composted manure.

• The Korean Journal of Nuclear Medicine
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• v.28 no.2
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• pp.167-171
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• 1994

Ethylcystein dimer (ECD) was synthesized by dimerizatlon of L-thiazolidine-4-carboxylic acid in liquid ammania with sodium metal and successive esterification in ethanolic solution of hydrogen chlorde. The purified product was labeled with $^{99m}Tc$ in the presence of sodium glucarate(pH= 5.6) and stannous chloride. Best result was obtained from the preparation con sisting of 0.1mg ECD, $40{\mu}l$ of 0.4M sodium glucarate (pH=5.6), and $20{\mu}g$ of stannous chloride. The labeling efficiency was 90% with previous condition. The labeled $^{99m}Tc$-ECD was stable at least for 3 hours in PBS(pH=7.4) at room temperature. About 10mCi of $^{99m}Tc$-ECD was injected to normal volunteer, and SPECT image of brain was obtained by triple head camera 10 minutes after inection. The image showed similar distribution of radioactivity in brain with that of HMPAO image.

• Communications of Mathematical Education
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• v.30 no.4
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• pp.435-452
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• 2016

This study was designed to explore students' instrumentalization in relation to the van Hiele's teaching method within a technology environment using GeoGebra. To carry out the study, a total of 4 lesson units was developed based on van Hiele teaching method for two slow learners in Gyeonggi province, Korea. The results of study were as follows. Instrumentalization of students was actualized from preparation, to adaptation, and to application stages. In preparation, and adaptation stages, depending on visualization, students used a trial-and-error method a lot, however in application stage the role of GeoGebra was just to check the solution of what they conjectured. Therefore, a teacher should prepare geometric tasks according to the processes of instrumentalization based on geometric teaching method. During instrumentalization and instrumentation of users, usage scheme(US) and instrumented action scheme(IAS) should be concrete.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.49 no.1
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• pp.51-57
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• 2013

A demand for bio-diesel oil increases as one of solution for exhaustion of fossil fuel and reduction of $CO_2$ emission, and research on bio-diesel is being carried out. Bio-diesel oil is mainly esterified from vegetable oil with methanol in order to use for fuel on diesel engine and has demerit that costs are increased as compared with directly using like non-esterified one. Bio-diesel oil within 3% mixed with gas oil is used at present, proportion of bio-diesel oil will be increase by 5% in future. We judged that wasted soybean oil non-esterified could be used on diesel engine with an electronic fuel injection according to previous researches with a mechanical fuel injection. A performance test using only gas oil, gas oil with esterified bio-diesel oil 5% and wasted soybean oil non-esterified 5% on diesel engine with the electronic fuel injection were carried out. It is noticed that gas oil with wasted soybean oil non-esterified 5% has more similar characteristics to gas oil than gas oil with esterified bio-diesel oil 5%.