• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.566-572
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• 2020

In a wireless power transmitter, the characteristics and effects of wireless power transmission between two induction coils are investigated, and a power converter circuit and a battery charger/discharger circuit using wireless power transmission technology are proposed. The advantage of wireless power transmitters and wireless chargers is that, instead of the existing plug-in-mounted wired charger (OBC; on-board charger), the user can wirelessly charge the battery without connecting the power source when charging power to the battery. There is. In addition, the advantage of wireless charging can bring about an energy efficiency improvement effect by using the secondary side rectifier circuit and the receiving coil, but the large-capacity long-distance wireless charging method has a limitation on the transmission distance, so many studies are currently being conducted. The purpose of the study is to study the transmitter circuit and receiver circuit of a wireless power transmission device using a primary coil, a secondary coil, and a half bridge series resonance converter, which can transmit power of a non-contact type power transmitter. As a result, a new topology was applied to improve the power transmission distance of the wireless charging system, and through an experiment according to each distance, the maximum efficiency (95.8%) was confirmed at an output of 3 kW at an 8 cm transmission distance.

• Journal of Practical Agriculture & Fisheries Research
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• v.26 no.1
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• pp.22-29
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• 2024

In this study, we summarized the definition of smart vegetable seedling production technology, analysis of smart seedling production system, a hardware and software configuration model for smart seedling production system, research and development trends in smart seedling production system, and proposed future research and development plans for smart seedling production technology. Smart vegetable seedling production is a data-based seedling production, management, and distribution system that utilizes 4th Industrial Revolution technology to improve seedling productivity and quality. The production of vegetable seedlings using smart seedling production technology can be efficiently managed by collecting, analyzing, and managing information on seedlings, environment, and tasks at each stage of production by linking with the smart seedling integrated management system. However, there is still a lack of standardization of seedling standards and quality for each vegetable crop to establish smart seeding production technology, as well as development of smart seedling production element technology, which requires national wide R&D support.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.49 no.3
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• pp.188-193
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• 2004

Fifty-day-old plug seedlings of yacon (Polymnia sonchiflolia Poeppig ＆ Endlicher) were transplanted on Mar. 23, Apr,8, Apr,23, May 8, May 23, and June 7,2002 at Jeju to evaluate the effect of transplanting date on the growth and yield of yacon in Jeju island. Delaying the transplanting until May 23 greatly decreased plant height stem height, main stem diameter and number of nodes per plant. The number of marketable tuberous roots was about 6.0 per plant with the early transplanting from March 23 to April 231 but decreased to 1.9 per plant with the latest transplanting time, June 7. The yield of marketable tuberous roots of early transplanted (March 23 to April 23) yacon was about 27 MT/ha, and was 32.4 MT/ha at April 23 transplanting, but was remarkably reduced at the three later transplantings, May 8, May 23, and June 7. Dry matter and soluble solid contents of marketable tuberous roots were 14％ and 15％, respectively, regardless of transplanting date. The weight of a marketable tuberous root ranged from 153 to 183.9 g at the first three transplantings, but gyeatly reduced with delaying transplanting until May 7. The optimum transplanting date for yacon in Jeju island seems to be from mid-April to late April considering tuberous root yields, the risk of late-spring frost, and cost of seedling raising.

• Journal of Science Education
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• v.32 no.2
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• pp.17-32
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• 2008

The purpose of this study was to analyze the use of the e-learning courseware which is about the properties of earth environmental change. I made these materials using Lectora program, and to have more visual effect, I used movies and animations as much as possible. A lot of movies and pictures are added to help student understand the geographical age. Especially the forms of performance test questions are various, and student can check the answer right after taking test. Because of this, they can get a immediate feedback. In addition, this allows you to adapt yourself to the age of information by using the internet. Every plug-in is already linked together, so you only need to once. Pictures and moving reflections can be edited with ease. I hope this study will provide valuable aid for the education of earth science and a chance to develop better materials.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.4
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• pp.397-403
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• 2012

The vitality of immature tooth could be lost by dental caries, trauma and fracture of malformed tooth. The vitality loss might lead to halt of the development of the root. The recommended endodontic treatment for a non-vital immature permanent tooth is apexification. Apexification is a method of inducing apical closure through the formation of mineralized tissue in the apical pulp region. Calcium hydroxide is the material of choice for apexification. Long-term exposure to calcium hydroxide may form the apical hard tissue, but weaken the dentin due to its alkaline nature and thus make the roots more susceptible to fracture. It is important to preserve any weakened tooth, so a permanent restoration is needed to reinforce teeth that are prone to fracture. The purpose of this case report was to describe the treatment for reinforcing immature teeth treated with long-term calcium hydroxide. In these cases, the apexes of teeth were sealed with MTA plugs and the root canals were restored with composite resin and fiber post.

• Restorative Dentistry and Endodontics
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• v.27 no.5
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• pp.535-542
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• 2002

The purpose of this study was to evaluate the effect of EDTA irrigant according to application time and temperature. 31 human mature extracted teeth with a single canal were sectioned with microtome in 3mm thickness and gained 62 samples of root canals. They were distributed randomly into 6 groups of 10 specimens each and control group of 2 specimens. Each specimen was prepared with GT rotary file (Dentsply, Maillefer Co., Swiss) and irrigated with 3 ml sodium hypochlorite every minute. Then smear layer was removed with EDTA solution (PULPDENT$^{\circledR}$, PULPDENT Co., USA.) except two control specimens. Specimens of each group were irrigated with 17% EDTA. The time and temperature of application were as follows : (Table omitted) All specimens were split longitudinally and prepared for examination by scanning electron microscopy. A set of reference micrographs was used to award a debris score as follows: 0 = no smear layer, all tubules clean and open; 1 = no superficial smear layer, tubule openings visible, but some contain debris plug or soft tissue remnants: 2 = moderate smear layer, some tubules open and others closed; 3 = heavy smear layer, most/all tubule openings obscured. Results were evaluated with Kruskal-Wallis test to determine whether there was statistically significant difference among six groups. Pairs of groups were analyzed using the Student-Newman-Keuls Method and Mann-Whitney test. The results were as follows : 1. Control specimens showed heavy smear layer at the canal walls 2. Among the groups applied with EDTA for 2 minutes, group 1 showed the heaviest smear layer, and there was statistically significant difference between group 1 and the other groups(p<0.05). 3. Among the groups applied with EDTA for 5 minutes, group 4 and group 6 showed smear layer but there was no significant difference between them. 4. Among the groups applied with EDTA for the same temperature, group 1 showed heavier smear layer than group 4, and there was statistically significant difference(p<0.05). 5. Among the groups applied with EDTA for the same temperature, group 2 showed heavier smear layer than group 5 and group 3 showed heavier smear layer than group 6. But there was no statistically significant difference among them. From the results above, it could be concluded, EDTA solution is effective in removing of smear layer when it is applied for 5 minutes. If EDTA is applied for 2 minutes, it should be applied above room temperature.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.607-614
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• 2013

Nowadays, automotive manufacturers have developed various technologies to improve fuel economy and reduce harmful emissions. The ultra-lean direct injection engine is a promising technology because it has the advantage of improving thermal efficiency through the deliberate control of fuel and ignition. This study aims to investigate the development of a spray-guided-type lean-burn LPG direct injection engine through the redesign of the combustion system. This engine uses a central-injection-type cylinder head in which the injector is installed adjacent to the spark plug. Fuel consumption and combustion stability were estimated depending on the ignition timing and injection timing at various air-fuel ratios. The optimal injection timing and ignition timing were based on the best fuel consumption and combustion stability.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.6
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• pp.432-436
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• 2002

This study was conducted in 2001 to determine the influence of seed-piece size (SPS) and number (SPN) per mini-tuber produced by hydroponics on growth and yield of potato (Solanum tuberosum L.). Treatments consisted of the combination of six SPS (3, 5, 7, 9, 11, 13g/seed-piece) and four SPN (whole tuber, and two, three, and four pieces/tuber). Percentage sprout emergence at transplanting was higher for seed pieces weighing 7 to 13 g (83.0 to 85.4%) and for three and four pieces per tuber (85.4 and 84.8%). As SPS were increased from 3 to 9 g/piece, total yields markedly increased from 2,052 to 2,924 kg/10a and seed tuber (31 to 250 g) yield from 1,589 to 2,428kg/10a with no further increase with SPS. As SPN was increased from one to three/ tuber, total yields increased from 1,918 to 2,982 kg/10a and seed tuber yields from 1,422 to 2,579 kg/10a with no further increase with SPN. Average tuber weight increased with SPS (46.3 to 71.5 g/tuber) and SPN (56.5 to 64.9 g/tuber).

• Journal of Bio-Environment Control
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• v.17 no.4
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• pp.283-287
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• 2008

To investigate the effects of different wavelengths of photosynthetically active radiation on the morphology and leaf color changes of a single tomato (Lycopersicon esculentum) seedling, we stored the seedling at $10{\pm}0.5^{\circ}C$ under eight different wavelengths (peak wavelengths; 405, 450, 505, 545, 600, 645, 680, and 700 nm) with a constant photosynthetic photon flux of $3{\mu}mol\;m^{-2}s^{-l}$ for 28 d. Under the 405, 450, and 505 nm wavelength conditions, the leaves of the seedlings showed vigorous shape with an upright morphology. Rachis elongation was suppressed and hence compact appearance was observed under the 450 and 505 urn conditions. Although the difference in leaf color between before storage and on 28 days after storage was observed under all wavelength conditions, the 405 and 700 um irradiations changed the leaf color to light green. Application of light-emitting diode (LED) light irradiated from around 450 to 545 nm can contribute to vigorous shape with an upright morphology of tomato seedlings during low light irradiation-low temperature storage.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.5-5
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• 2011

The research and development of hybrid electric vehicle (HEV), plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV) are intensified due to the energy crisis and environmental concerns. In order to meet the challenging requirements of powering HEV, PHEV and EV, the current lithium battery technology needs to be significantly improved in terms of the cost, safety, power and energy density, as well as the calendar and cycle life. One new technology being developed is the utilization of composite cathode by mixing two different types of insertion compounds [e.g., spinel $LiMn_2O_4$ and layered $LiMO_2$ (M=Ni, Co, and Mn)]. Recently, some studies on mixing two different types of cathode materials to make a composite cathode have been reported, which were aimed at reducing cost and improving self-discharge. Numata et al. reported that when stored in a sealed can together with electrolyte at $80^{\circ}C$ for 10 days, the concentrations of both HF and $Mn^{2+}$ were lower in the can containing $LiMn_2O_4$ blended with $LiNi_{0.8}Co_{0.2}O_2$ than that containing $LiMn_2O_4$ only. That reports clearly showed that this blending technique can prevent the decline in capacity caused by cycling or storage at elevated temperatures. However, not much work has been reported on the charge-discharge characteristics and related structural phase transitions for these composite cathodes. In this presentation, we will report our in situ x-ray diffraction studies on this mixed composite cathode material during charge-discharge cycling. The mixed cathodes were incorporated into in situ XRD cells with a Li foil anode, a Celgard separator, and a 1M $LiPF_6$ electrolyte in a 1 : 1 EC : DMC solvent (LP 30 from EM Industries, Inc.). For in situ XRD cell, Mylar windows were used as has been described in detail elsewhere. All of these in situ XRD spectra were collected on beam line X18A at National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory using two different detectors. One is a conventional scintillation detector with data collection at 0.02 degree in two theta angle for each step. The other is a wide angle position sensitive detector (PSD). The wavelengths used were 1.1950 ${\AA}$ for the scintillation detector and 0.9999 A for the PSD. The newly installed PSD at beam line X18A of NSLS can collect XRD patterns as short as a few minutes covering $90^{\circ}$ of two theta angles simultaneously with good signal to noise ratio. It significantly reduced the data collection time for each scan, giving us a great advantage in studying the phase transition in real time. The two theta angles of all the XRD spectra presented in this paper have been recalculated and converted to corresponding angles for ${\lambda}=1.54\;{\AA}$, which is the wavelength of conventional x-ray tube source with Cu-$k{\alpha}$ radiation, for easy comparison with data in other literatures. The structural changes of the composite cathode made by mixing spinel $LiMn_2O_4$ and layered $Li-Ni_{1/3}Co_{1/3}Mn_{1/3}O_2$ in 1 : 1 wt% in both Li-half and Li-ion cells during charge/discharge are studied by in situ XRD. During the first charge up to ~5.2 V vs. $Li/Li^+$, the in situ XRD spectra for the composite cathode in the Li-half cell track the structural changes of each component. At the early stage of charge, the lithium extraction takes place in the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component only. When the cell voltage reaches at ~4.0 V vs. $Li/Li^+$, lithium extraction from the spinel $LiMn_2O_4$ component starts and becomes the major contributor for the cell capacity due to the higher rate capability of $LiMn_2O_4$. When the voltage passed 4.3 V, the major structural changes are from the $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, while the $LiMn_2O_4$ component is almost unchanged. In the Li-ion cell using a MCMB anode and a composite cathode cycled between 2.5 V and 4.2 V, the structural changes are dominated by the spinel $LiMn_2O_4$ component, with much less changes in the layered $LiNi_{1/3}Co_{1/3}Mn_{1/3}O_2$ component, comparing with the Li-half cell results. These results give us valuable information about the structural changes relating to the contributions of each individual component to the cell capacity at certain charge/discharge state, which are helpful in designing and optimizing the composite cathode using spinel- and layered-type materials for Li-ion battery research. More detailed discussion will be presented at the meeting.