• Journal of The Korean Association For Science Education
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• v.31 no.6
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• pp.864-875
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• 2011

The purpose of this study was to investigate high school students' understanding of acid-base related concepts using three different titration technologies. The test population was composed of 209 students from three classes in the 10th grade. The different titration experiments using indicator, or pH-meter or MBL were performed in each class unit, respectively. The analyses of the effect on the understanding of different titration technologies were carried out by comparing the mean scores of the concept test taken before and after the titration for the three groups. The results of the acid-base related concept test indicated that statistically significant effects on the understanding of the concepts were shown by all groups. Comparing the effect on the comprehension of the three groups, the MBL group showed the most significant effect, while the pH-meter group showed the least significant. It was also attempted to analyze the effect on comprehension of the concepts by the cognitive and the motivational levels of students. This study revealed that the students in the formal operation stage showed higher understanding of the acidbase related concepts, while those in the concrete operation stage showed lower comprehension. It was also shown that the students at the active motivational level scored higher in comprehension than those who had a low score. The results of this study implied that each group showed differently enhanced comprehension of concepts by titration technologies. Therefore, teachers need to promote an appropriate experiment technology for the cognitive and motivational levels of students as well as try to help students express freely their own perspectives.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.42-51
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• 2017

This paper deals with the power supply facility providing wireless power transmission for a type of electric vehicles called the on-line electric vehicle(OLEV) and proposes optimal protection coordination methods which analyze the faultsin the 60Hz and 20kHz bands using PSCAD/EMTDC, which is the typical commercial software for the distribution system. The simulation results show that the proposed methods can reduce the fault current by introducing an NGR (Neutral Ground Resistor) in the 60Hz band and prevent the malfunctioning of the protection device by installing a CT in the neutral wire in the 20kHz band when a ground fault occurs.

• Analytical Science and Technology
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• v.10 no.3
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• pp.209-215
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• 1997

Li-AGICs as a anode of secondary battery were synthesized by high-pressure method as a function of the Li-contents. The characteristics of these prepared compounds were determined from the studies with X-ray diffraction method, UV/VIS spectrophotometric and differential scanning calorimeter(DSC) analysis. From the results of X-ray diffraction, it was found that the lower stage intercalation compounds were formed with increase of Li-contents. The mixed stages in these compounds were also observed. In the case of the $Li_{30wt%}$-AGIC, the compounds in the stage 1 structure were formed predominantly, but the structure of only pure stage 1 for structural defect of artificial graphite is not observed. According to UV/VIS spectrophotometric analysis, $Li_{30wt%}$-AGIC shows distinguishable energy state spectrum with the position of $R(%)_{min}$ values, but the characteristic spectra of almost all Li-AGICs are not observed. The enthalpy and entropy changes of the compounds can be obtained from the differential scanning calorimetric analysis results. From the results, it was found that exothermic and endothermic reactions of Li-AGICs are related to thermal stability of lithium between artificial graphite layers.

• Analytical Science and Technology
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• v.10 no.2
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• pp.126-130
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• 1997

Electrochemical behavior of 1.0mM bis(2,2'-bipyridyl)copper( II )(${Cu(bpy)_2}^{2+}$) in 100mM NaCl+27mM $MgCl_2$ solution with and without sodium dodecyl sulfate(SDS) is investigated. In the presence of SDS, $E_{pa}$ and $E_{1/2}$ of ${Cu(bpy)_2}^{2+/1+}$ shifts to the positive direction compared to the SDS free. Teh intersection of two lines on ${\Delta}E_p$ vs. -log[SDS] plot for 1.0mM $Cu(bpy)_2(NO_3)_2$ in 100mM NaCl+27mM $MgCl_2$ solution is a critical micelle concentration(CMC). Reduced form ${Cu(bpy)_2}^{1+}$ in the presence of $MgCl_2$ is more easily associated to dodecyl sulfate anion($DS^-$) than oxidized ${Cu(bpy)_2}^{2+}$. As the ionic strength is increased by the addition of multiply charged cations($MgCl_2$), the double layer becomes more compact and micelle formation is more difficult.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.83-88
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• 2017

The purpose of this paper is to study for a failure examples producing in electronic control air conditioner in vehicle. The first example, it looked for the repetitive fuse cutting phenomenon that the diode using for a surge voltage prevention of inner A/C relay damaged because of no absorbing the surge voltage by short of diode when the A/C is off. The second example, it knew the icing phenomenon of evaporator that the A/C ECU didn't control the A/C because of inner cutting of fin thermo sensor. The third example, it verified the operation trouble phenomenon because of the A/C switch and for sensor burned in flames by short phenom enon when the sheath of the cable has peeled off. Therefore, the driver have to manage the optimism system of a car by thoroughgoing inspection and improvement the failure phenomenon.

• Transactions of the KSME C: Technology and Education
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• v.1 no.1
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• pp.99-105
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• 2013

In this paper, we carried out the basic design of 36 MTD natural gas BOG re-liquefaction system to recover the generated natural gas during performance test of LNG pump and natural gas compressor. The re-liquefaction process of natural gas is designed to have 1500 kg/h of liquefaction rate with reverse Brayton refrigeration cycle. With the designed process, the variation of liquefaction rate is calculated for various inlet conditions of feed gas. From results, the liquefaction rate is more sensitive for inlet temperature than gas composition. The specifications of equipments such as gas blower, natural gas compressor, cryogenic heat exchanger and nitrogen compander are determined on the basis of the designed process. The requirement of power consumption and cooling water are also determined through the basic design.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.12
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• pp.22-31
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• 2015

Recently, 3rd Generation Partnership Project (3GPP) has developed device-to-device (D2D) communication to cope with the explosively increasing mobile data traffic. The D2D communication uses sidelink based on single carrier-frequency division multiple access (SC-FMDA) due to its low peak-to-average power ratio (PAPR). In addition, demodulation reference signal (DMRS) is designed to support multiple input multiple output (MIMO). In this paper, we propose the DFT-based channel estimation scheme for sidelink in D2D communication. The proposed scheme uses the 2-Dimensional Minimum Mean Square Error (2-D MMSE) interpolation scheme for the user moving at a high speed. We perform the system level simulation based on 20MHz bandwidth of 3GPP LTE-Advanced system. Simulation results show that the proposed channel estimation scheme can improve signal-to-interference-plus-noise ratio (SINR), throughput and spectral efficiency of conventional scheme.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.135-143
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• 2017

The domestic unique research reactor, HANARO (Hi-flux Advanced Neutron Application ReactOr), has been constructed with the open-pool, the core is submerged in, for the multi-purpose neutron application. The reactor has a primary cooling system to remove the fission heat from the core and its connected fluidic systems. Since the works are required at the reactor pool top as a characteristic of the research reactor, the radiation shall be minimized with the operation of the hot water layer system to avoid unnecessary radiation exposure on the workers during work at the pool top. Moreover, the pool water management system is connected to the reactor pool to maintain the pool temperature below $50^{\circ}C$ to minimize the uprising radioactive gas or impurity from the colder pool bottom. For the efficient flow rate of the PWMS, the thermal capacity of heat exchanger is selected with 260 kW in the normal operation condition. In this paper, the modeling is formulated to figure out whether or not each pool temperature maintains below the temperature limit and the calculation results show that the designed PWMS heat exchanger has enough capacity with the design margin regardless of the reactor operation mode.

• Journal of Convergence for Information Technology
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• v.9 no.2
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• pp.65-74
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• 2019

This study is an experimental study on the single group pre-post test design for the convegenced of an integration support program for home-based cancer patients and the verification of its effects. Targeting total 33 home-based cancer patients in J city, total 30 sessions of the convegenced integration support program composed of cancer-related knowledge education, stress management, cognitive behavioral approach, and exercise for revitalization were provided three times a week for ten weeks. In the results of this study, the convegenced integration support program reduced stresses of the subjects and also improved their hopes and self-esteem. Thus, this program is considered as a onvegenced integration support program suitable for home-based cancer patients. In the future, it would be necessary to seek for the nursing interventional strategies for the expansion for this program to regional health centers or community institutes performing the convegenced integration support program for cancer survivors, so that they could continuously participated in the program.

• Journal of Environmental Impact Assessment
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• v.32 no.3
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• pp.157-165
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• 2023

In Korea, a major contaminant of farmland soils in the vicinity of abandoned mines is arsenic, for which the general soil reclamation method is contaminated soil stabilization and cover the stabilized soil with clean soil at a thickness of 40 cm. In a previous pot experiment study we confirmed the feasibility of a lower thickness (20 cm) of covering soil for such reclamation in abandoned coal mines, where arsenic contamination levels are generally lower than in metal mines. In this subsequent study a field experiment including rice plant cultivation in field test plots was conducted. For over 4 months, the transfer of arsenic from the contaminated soil to the unpolished rice grains was reduced by 44% when a clean soil covering with a thickness of 20 cm was applied. The maximum decrease (56%) was shown when the stabilization process was performed before the covering. These results reveal a lower thickness of clean soil covering has a high feasibility and it can increase cost-efficiency in the reclamation of an abandoned coal mine.