• Journal of Elementary Mathematics Education in Korea
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• v.4 no.1
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• pp.1-19
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• 2000

This paper aims to enhance students' interest in the use of calculators in mathematics education and promote their use of calculators in real-life situations. Towards these ends, problem types and instructional models developed for the efficient utilization of calculators. The instructional models focus on teaching mathematics relying on the path through which expert teachers have gone through to gain relevant knowledge. By developing problem types and instructional models suitable for calculator use, We can contribute to a better attainment of instructional goals in mathematics education. The instructional models and problem types will aid teachers in making decisions about instructional development plan and basic features of instructional activities. The use of a new medium will also lead to increased interest and confidence in learning, thus contributing to the enhancement of students' ego.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.45-52
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• 2006

In this study, a nonlinear control by feedback linearization method, one of nonlinear control schemes based on the nonlinear model, is proposed to suppress the flutter of a supersonic composite panel using piezoelectric materials. Most of the previous panel flutter controllers are the LQR(Linear Quadratic Regulator) which is based on the linear model. A nonlinear feedback linearizing controller proposed in this study considers the nonlinear characteristics of the system model. We use the actuator implemented by piezoceramic PZT. Using the principle of virtual displacements and a finite element discretization with the conforming four-node rectangular element, we first derive the discretized dynamic equations of motion, which are transformed into a nonlinear coupled-modal equations of motion of state space form. The effectiveness of the proposed method is also compared with the LQR based on the linear model through numerical simulations in the time domain using the Newmark method.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.7
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• pp.608-617
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• 2006

This study was conducted to investigate the effects of sowing date on soybean-sprout growth characters and for improving cultural techniques to produce high quality soybean-sprout. Six sprout-soybean cultivars were planted on three sowing dates in 2000 and 2001. The growth of hypocotyl in soybean sprouts was accelerated at higher temperature and the differences among cultivars became greater at later culture days. The longest of hypocotyl and root lengths of soybean sprouts was obtained from July 5 sowing, followed by May 25 and June 15 sowing. Doremikong and Hannamkong had the thickest and the thinness hypocotyls, respectively. Total length of soybean-sprouts was longer in seeds harvested from later sowing, respectively. Eunhakong produced the longest soybean-sprouts, while Tawonkong produced the shortest. Percentage of rotten seed and imperfectly germinated seed harvested at later sowing was lower. Somyeongkong and Tawonkong showed the highest and the lowest percentages of rotten seeds, respectively, while Pungsannamulkong and Hannamkong showed the lowest and the highest percentages of imperfectly germinated seeds. The soybean-sprouts yields were higher in seeds harvested in 2001 and later sowing. Although Eunhakong and Doremikong showed higher soybean-sprout yield, Pungsannamulkong and Somyeongkong showed stable soybean-sprout yield regardless of the sowing dates.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.59 no.4
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• pp.477-482
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• 2014

Variation of anthocyanin contents were analyzed by different growing environments, three locations over three years with 3 black colored soybeans. Anthocyanin contents were different according to growing location, genotypes and planting time, so it can be concluded that anthocyanin content was effected by environmental and genetic variation. Planting date seemed to have a much greater influence on anthocyanin content than cultivar and location. Among different planting dates, anthocyanin contents increased in the seeds planted on June 15 rather than did May 30 and May 15. Compared with 3 cultivars and 3 locations, Ilpumgeomjungkong and Yeonchun had higher contents such as 11.58 mg/ and 9.85 mg/g, respectively. The correlations between color index and anthocyanin content were analyzed by Hunter'value. L (lightness) and b (yellowness) values were correlated negatively with D3G, C3G, Pt3G and total anthocyanin content while a (redness) value was correlated positively. The correlations between meteorological factors and anthocyanin content were analyzed. Anthocyanin content was correlated negatively with mean temperature and accumulated temperature whereas mean daily temperature difference showed positive correlation. We could conclude that the area in which mean temperature was low and daily temperature difference was high is good for attempts to improve black soybean seed quality by the increase of anthocyanin contents.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.1
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• pp.35-43
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• 2003

Recent geomorphological changes and late Quaternary depositional sequences of Gwangyang Bay are studied based on bathymetric maps, surface sediments, and seismic profiles. As a result of the reclamation of coastal area for an industrial complex construction, the coastline of Gwangyang Bay has rapidly been changed and the area of it has now been reduced by about 25 ％ in the last 30 years. In addition, the bottom topography is actively modified by dredging for navigation channels. In surfical sediment distribution, the western part of Gwangyang Bay is dominated by mud facies, whereas the eastern part of the Bay is dominated by sand-mud mixing facies. Depositional sequences above the basement are divided into two units: Unit I in upper layer and Unit II in lower one. These depositional units are unconformably bounded by middle reflector-M. Unit II, mostly occupying the channel areas, is interpreted as fluvial-origin deposits during sea-level lowstand. Unit I typically shows a progradational pattern from the Seomjin River mouth to the Yeosu Strait, which is interpreted as deltaic deposits supplied from the Seomjin River during the Holocene sea-level highstand. The shallow gas within the sediments Is widely distributed in most area, and locally exposed onto the sea-bed due to dredging.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.45-51
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• 2012

BACKGROUND: This study was carried out to establish pre-harvest residue limit of fungicides pyrimethanil and trifloxystrobin in persimmon, based on dissipation and biological half-lives of two fungicides residue. METHODS AND RESULTS: Both pyrimethanil and trifloxystrobin were extracted with acetonitrile, clean-up with $NH_2$ SPE cartridge and residue were analyzed by HPLC/DAD. Limit of Detection was 0.01 mg/kg. Average recovery were $81{\pm}1.62%$, $98{\pm}1.58%$ of pyrimethanil, and $91{\pm}2.94%$, $98{\pm}1.25%$ of trifloxystrobin at fortification levels at 0.1 and 0.5 mg/kg, respectively. CONCLUSION: The biological half-lives of pyrimethanil were 15.6 and 11.6 days at sprayed with recommended and double dosage, respectively. The biological half-lives of trifloxystrobin were 10.4 and 10.3 days at sprayed with recommended and double dosage, respectively. The pre-harvest residue limit of pyrimethanil and trifloxystrobin were recommended as 2.69 and 0.83 mg/kg for 10 days before harvest, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.1
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• pp.445-453
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• 2021

This study investigates the factors influencing quality of life for cancer patients based on demographic characteristics, physical-mental health, and oral health. These factors are analyzed using the results from 235 cancer patients in Korea's 7th national health and nutrition survey. Data were analyzed using PASW Statistics Ver. 18.0. Studies show that cancer patients experienced stress (74.5%), depression (84.3%), and activity limitations (15.3%). In oral health, problems chewing were often experienced in groups with low incomes (3.35±.21), activity limitations (2.71±.31), and depression (3.01±.27). The factors influencing quality of life were higher by 3.43 times in the low-income group and by 8.39 times in the activity-restricted group, by 2.74 times in the high-stress group, by 4.58 times in the depression group, by 2.68 times in the chewing-problems group, and were 4.92 times higher in the speech problems group (p<0.05). To improve quality of life, not only mental and physical health care, but also oral care is necessary. An integrated management plan for medical staff in the treatment process of cancer patients is required to prevent mental, physical, and oral discomfort.

• Journal of the Korean Applied Science and Technology
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• v.38 no.2
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• pp.476-487
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• 2021

To prepare acrylic resin coatings containing 70% of solids, we used n-butyl methacrylate(BMA), methyl methacrylate(MMA), 2-hydroxyethyl methacrylate(2-HEMA), and acetoacetoxyethyl acrylate(AAEA), caprolactone acrylate(CLA) as raw materials, the glass transition temperature(T_g) of acrylic copolymer was adjusted around 50 ℃. The viscosity and molecular weight of the acrylic resins was increased with increasing OH values. Di-tert-amyl peroxide was found to be the suitable initiator to get high-solids acrylic resins. The optimum reaction conditions found in the study are 5 wt% of initiator, 4 wt% of chain transfer agent, 4 hrs of dropping time, and 140 ℃ of reaction temperature. The structure of the synthesized resins were characterized by FT-IR and ¹H-NMR spectroscopy. Number average molecular weight of 1900~2600 and molecular wight distribution of 1.4~2.1 were obtained. Crosslinked acrylic urethane clear coatings were obtained by curing reaction between the synthesized acrylic resins and hexamethylene diisocyanate trimer(Desmodur N-3300), the equivalent ratio of NCO/OH was 1.2/1.0. The physical properties from the following studies were carried out: viscosity(Zahn cup #2), adhesion, drying time, pot-life, pensil hardness, and 60° specular gloss. Various properties of the acrylic urethane clear coatings were also evaluated on the coating specimens. Adhesion property to a substrate, drying time, pot-life, pencil hardness, and 60° specular gloss of prepared paint showed quite good properties. Futhermore, prepared paint containing 10% of CLA showed quite good properties for adhesion, low viscosity and high hardness.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.621-626
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• 2012

In this study, the composite coating materials with improved thermal insulation property were prepared by incorporating the hollow micro-spheres with high heat transfer resistance. The UV curable resin system consisting of hexa aliphatic urethane acrylate (UP118), trimethylolpropane triacrylate (TMPTA), 1,6-hexanediol diacrylate (HDDA), and photoinitiator (Irgacure184) was employed as an organic binder. The glass substrates were coated by the prepared composites via bar coating method and cured under UV radiation. The optical transparency, thermal insulation property, adhesion, and surface hardness of the glass coated with composites containing different type of micro-spheres were investigated. The incorporation of micro-spheres with only 20 vol% of content resulted in remarkable improvement in the thermal insulation property of the coated glass. In addition, the transparent coated glass with light transmittance of about 80% could be obtained when silica micro-sphere (SP) was used as a thermal barrier.

• The Korean Journal of Pesticide Science
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• v.10 no.3
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• pp.165-171
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• 2006

A new 3-amino-1,3-thiazoline chemical library was synthesized through parallel synthetic technology and in vivo antifungal activity of the compounds were investigated against the typical 6 plant diseases (100 ppm). The characteristic feature of these derivatives was that both a benzyl moiety in C-2 imino and an amino group in C-3 of 2-imino-1,3-thiazoline scaffold were substituted in the molecule respectively. Some compounds showed antifungal activity with selectivity against tomato late blight and rice blast. The fungitoxicity would be attributed to 3,4-dichlorophenyl moiety of the benzyl group.