• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.1-8
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• 2020

In this study, a configuration design of a CH₄/LOx small rocket engine was made and test system was established for the performance evaluation. A coaxial swirl injector was chosen because of its remarkable atomization performance and low combustion instability. Three aspect ratios for the combustion chamber configuration, i.e., 1.5, 1.8, and 2.1 were also set for the comparison of the combustion efficiency. The reliability of the thrust measurement rig was enhanced by pre-and post-calibration process. From the preliminary ground hot-firing test, the measured thrust and specific impulse values were 89.2 N and 181.8 s, respectively, which were 21.6% lower than the ideal values. In addition, the efficiency of characteristic velocity was measured as 84.2%.

• Journal of Adhesion and Interface
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• v.19 no.2
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• pp.55-59
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• 2018

In this study, to overcome a complicated shoe adhesion process such as buffing, pre-treatment by primer in the rubber component of the shoe, we studied adhesion mechanical properties with rubber compound added water-soluble salt for the purpose of improving the adhesion between midsole and outsole. Acid salts, basic salt and neutral salts were evaluated, rubber containing basic salts showed excellent adhesion to water-based adhesion. Since the basic salt is present as the hydroxy salt, the surface of rubber is hydrophilized. The results are confirmed by contact angle and IR spectroscopy measurement. In addition, in the case of rubber compound added basic salts, NBS abrasion resistance and hardness were increased by increasing crosslink density, but crosslink time was delayed.

• Journal of Magnetics
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• v.7 no.2
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• pp.45-50
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• 2002

A magnetic field annealing is firstly used for nanostructured Sm-Co/Co films, prepared by magnetron sputtering method. The effects of magnetic field annealing on single-layered Sm-Co films are different from those on multi-layered Sm-Co/Co films. A detailed analysis of microstructures and magnetic properties is made by means of HRTEM, Auger electron spectroscopy, XRD and Physical Property Measurement System (PPMS). From magnetic properties and microstructure analysis, it was confirmed that these differences originate from the effects of magnetic field annealing on crystallization behavior of the films. The relationship between magnetic properties and microstructures explains a different demagnetization process of single-layered and multilayered films. For the single-layered Sm-Co films, magnetic-field-annealing makes the main phases change from $CaCu_5/ to Zn_2Th_{17}$ structure, resulting in a decrease of coercivity. The results show that the magnetic-field-annealing is useful to improve the properties of nanostructured Sm-Co(30 nm)/Co(10 nm) films, which ascribe to improving the pinning effectiveness in coercivity mechanism and decreasing the magnetostatic interaction of films. A very high coercivity about 0.7 T was obtained from nanoscaled multi-layered Sm-Co(30 nm)-/Co(10 nm) films.

• Applied Science and Convergence Technology
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• v.26 no.2
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• pp.34-41
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• 2017

A 2.45 GHz microwave plasma with linear antenna has been prepared for hydrophobic and wear-resistible surface coating of carbon steel. Wear-resistible properties are required for the surface protection of cutting tools and achieved by depositing a hydrogenated amorphous carbon film on steel surface through linear microwave plasma source that has $TE_{10}-TEM$ waveguide. Compared to the existing RF plasma source driven by 13.56 MHz, linear microwave plasma source can easily generate high density plasma and provide faster deposition rate and wider process windows. In this study, $Ar/CH_4$ gas mixtures are used for hydrogenated amorphous carbon film deposition. When microwave power of 1000 W is applied, 40 cm long uniform $Ar/CH_4$ plasma could be obtained in gas pressure of 200~400 mTorr. The Vickers hardness measurement of hydrogenated amorphous carbon film on steel surface was evaluated. It was found the optimized deposition condition at $Ar:CH_4=25:25$ sccm, 300 mTorr with microwave power of 1000W and RF bias power of 100W. By deposition of hydrogenated amorphous carbon film, contact angle on steel surfaces increases from $43.9^{\circ}$ to $93.2^{\circ}$.

• Journal of the Korea Convergence Society
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• v.11 no.5
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• pp.381-389
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• 2020

Patients, particularly elderly patients, need nursing appropriate to their characteristics and pace, whereas 'fast nursing' is actually emphasized in Korea. Hence, this study attempts to identify the characteristics of 'slow nursing' in Korea. Walker & Avant's approach to concept analysis was performed through a literature review on the concept of 'slow nursing.' A literature search and concept analysis, using the keywords of 'slow,' 'slow nursing' and 'slow prescription' in Pubmed, Riss, NDSL, DBPIA, and Google Scholar from 2000 to 2019, yielded the following attributes of 'slow nursing': 'respect for the speed of the subject,' 'carefulness,' 'comfort in the process,' 'participation' and 'consideration of the meaning of life.' Model cases were derived based on these attributes. Predisposing factors involved in 'slow nursing' include patient malfunction, psychological deflection, indifference, fear of treatment, and lack of willingness to live. The outcomes were a discovery of patients' potential capacities, recovery of confidence, health promotion, improved communication with medical staff, confidence, and self-integrity. It is expected that the development of measurement tools using the attributes of 'slow nursing' would contribute to patient nursing and research in the future.

• Journal of the Korean Electrochemical Society
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• v.18 no.4
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.5 s.120
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• pp.539-546
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• 2007

In this paper, a 3-D EM simulation methodology for on-chip spiral inductor analysis has provided and it is shown that the methodology can be adapted to the highly predictable design for CMOS VCO. LC-resonator type VCO have fabricated by using standard 0.25 um CMOS process. And the LC VCO layout case which has pattern ground shielded inductors and the other layout case which has no pattern grounded inductors were fabricated for the verification of their effects on the VCO's phase noise by reducing the Q-factor of inductors. Fabricated VCO has 3.094 GHz, -12.15 dBm output at the tuning voltage of 2.5 V, and from the simulation, Q-factor of the pattern grounded inductor has increased 8% at 3 GHz, and from the measurement results, the phase noise has reduced by 9 dB at the 3 MHz off-set frequency for the pattern grounded inductor layout case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.941-944
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• 2016

This paper proposes 24 GHz power amplifier for automotive collision avoidance and surveillance short range radar using Samsung 65-nm CMOS process. The proposed circuit has a 2-stage differential power amplifier which includes common source structure and transformer for single to differential conversion, impedance matching, and power combining. The measurement results show 15.5 dB maximum voltage gain and 3.6 GHz 3 dB bandwidth. The measured maximum output power is 13.1 dBm, input $P1_{dB}$ is -4.72 dBm, output $P1_{dB}$ is 9.78 dBm, and maximum power efficiency is 17.7 %. The power amplifier consumes 74 mW DC power from 1.2 V supply voltage.

• Journal of the Korean Home Economics Association
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• v.20 no.4
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• pp.193-204
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• 1982

This study attempts to clarify the relationship between mother;s child-rearing practices and children's critical thinking abilities. More specifically this study wants to answer the questions: (a) Is there any relationship between mother's child-rearing practices and children's critical thinking abilities? (b) What dimensions of child-rearing practices are more important for children's critical thinking abilities? (c) Does the developmental process of children's critical thinking abilities show any difference according to the mother's child-rearing practices? This study is based on the conceptual model of child-rearing practices from the cognitive disciplinary viewpoint proposed by Lee et al.(1973). They polarized the child-rearing practices into the“mediated”types. These types were specified along seven dimensions of child-rearing. In general terms, the two types refer to the degree to which mother resorts to the description of concrete and immediate phenomena and immediate expression of momentary impulses, and positively reinforces such behaviors of her children. Two kinds of data were collected from 60 primary school boys and girls, and their mothers. A child-rearing practices questionnaire with 28 items was sent to the mothers. And the children were administered a critical thinking abilities test containing measures of 4 dimensions from the Ahn's Critical Thinking Measurement Technique. The major findings are those (a) the children of mothers who reported to have used more“mediated”types of child-rearing show relatively higher level of critical thinking abilities than their counterparts; (b) of the seven dimensions of child-rearing practices, the most significant are“mode of description”,“rationality-orientation”and“reward and punishment”; and (c) the“mediated”type of child-rearing practices tends to facilitate critical thinking abilities development. In conclusion, it is believed that a further refinement of this study will contribute to the development of child-rearing training program for mothers.

• Journal of Korea Game Society
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• v.18 no.5
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• pp.103-112
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• 2018

"Ito2", an early childhood educational coding game that allows students to learn sequential, loop, and conditional statement concepts through games is introduced. The developed game is a two-stage process of mock and practical classes for children in actual nursing cares, and coding education is conducted for actual children to determine its effectiveness. The degree of change is observed by observing trends in childhood cognitive development performance in all six areas, including parts and the overall, space, observation, shape and measurement, classification, comparison, and listing, as the coding training is conducted. In this paper, the improvement of cognitive development and spatial perceptual abilities were achieved by children playing games with infant functional coding with fun elements plus learning factors.