• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.955-956
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• 2006

Fe-doped $TiO_2$ nanopowders were prepared by mechanical alloying (MA) varying Fe contents up to 8.0 wt.%. The UV-vis absorption showed that the UV absorption for the Fe-doped powder shifted to a longer wavelength (red shift). The absorption threshold depends on the concentration of nano-size Fe dopant. As the Fe concentration increased up to 4 wt.%, the UV-vis absorption and the magnetization were increased. The benefical effect of Fe doping for photocatalysis and ferromagnetism had the critical dopant concentration of 4 wt.%. Based on the UV absorption and magnetization, the dopant level is localized to the valence band of $TiO_2$.

• Journal of Korean Physical Therapy Science
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• v.24 no.1
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• pp.59-68
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• 2017

Purpose : The aims of this study was to conduct a systematic literature review with meta-analysis to investigate the effect of virtual reality based rehabilitation program on balance of patient with stroke in Korean studies. Method : The studies for analysis were searched in electronic databases(Research Information Sharing Service; RISS, Korean Studies Information Service; KISS, DBpia, e-articles, National Assembly Library). The key words for search were 'virtual reality', 'stroke', and 'balance' and only randomized controlled trials and clinical controlled trials were included. Of 40 studies identified in the search, 20 studies met the criteria of this study and included in this meta-analysis. Result : The results were as follows: 1) The overall effect size of virtual reality based rehabilitation program was 0.557(95% critical interval; 0.340~0.774). 2) In the analysis of sub-categorical variables, effect size was as follows; the commercial game type(0.621) > virtual environment type(0.335); the dynamic balance measurement(0.750) > static balance measurement(0.226); randomized controlled trial(0.653) > clinical controlled trial(0.275); and thesis type(0.706) > article of journal type(0.339). 3) In the analysis of sub-continuous variables, as time of program(per session) increased, the balance increased(p<0.05). Conclusion : The results of this study showed that virtual reality based rehabilitation program moderately improves the balance of stroke patient. Further studies are recommended to investigate the effect of sub-variables related to virtual reality programs on motor functions of patient with stroke.

• Korean Journal of Materials Research
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• v.24 no.9
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• pp.465-468
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• 2014

The crystallization effects of boron (B) powder on the phase, full width at half maximum (FWHM) values, and critical properties were investigated for in-situ reacted $MgB_2$ bulk superconductors. The semi-crystalline B powder was heat-treated at different temperatures of 1000, 1300 and $1500^{\circ}C$ for 5 hours in an Ar atmosphere. Then, using as-received and heat-treated B powders, the $MgB_2$ samples were prepared at $600^{\circ}C$ for 40 hours in an Ar atmosphere. As the heat-treatment temperature of the B powder increased, both the particle size of the B powder and crystalline phase increased. In the case of $MgB_2$ samples using B powders heat-treated at above $1300^{\circ}C$, unreacted magnesium (Mg) and B remained due to the improved crystallinity of the B powder. As the heat-treatment temperature of B powder increased, the critical current density of $MgB_2$ decreased continuously due to the reduction of grain boundary density and superconducting volume caused by unreacted Mg and B.

• The Journal of the Acoustical Society of Korea
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• v.25 no.2E
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• pp.60-68
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• 2006

High-frequency bistatic scattering measurements from a corrugated surface were made in an acoustic water tank. First the azimuthal scattering pattern was measured from an artificially corrugated surface which has varying impedance. The corrugated surface was installed both transverse to the direction of incident wave and longitudinal to the direction of incident wave. The angle between the corrugated surface and the direction of the incident wave was about $45^{\circ}$. Second, the scattering strengths were measured from the flat sediment and the corrugated sediment. A critical angle of about $37^{\circ}$ was calculated in the acoustic water tank. The measurements were made at three fixed grazing angles: $33^{\circ}$ (lower than critical angle), $37^{\circ}$ (critical angle), and $41^{\circ}$ (higher than critical angle). The scattering angle and the grazing angle are equal in each measurement. Frequencies were from 50 kHz to 100 kHz with an increment of 1 kHz. The corrugated sediment was made transverse to the direction of the incident wave. The first measurement indicates that the scattering patterns depend on the relations between the corrugated surface and the direction of the incident wave. In the second measurement, the data measured from the flat sediment were compared to the APL-UW model and to the NRL model. The NRL model's output shows more favorable comparisons than the APL-UW model. In case of the corrugated sediment, the model and the measured data are different because the models used an isotropic wave spectrum of sediment roughness in the scattering calculations. The isotropic wave spectrum consists of $w_2$ and ${\gamma}_2$. These constants derived from sediment names or bulk size. The model which used the constants didn't consider the effect of a corrugated surface. In order to consider a corrugated surface, the constants were varied in the APL-UW model.

• Progress in Superconductivity
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• v.12 no.1
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• pp.6-11
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• 2010

The milling effects of a precursor $Y_2BaCuO_5$ (Y211) powder having 1 wt.% $CeO_2$ on the microstructure and critical current density ($J_c$) of liquid infiltration growth (LIG) processed $YBa_2Cu_3O_{7-y}$ (Y-123) bulk superconductors were investigated. The microstructure analysis revealed that the Y211 size in the final Y-123 products decreased with increasing the milling time and a relatively high density and uniform distribution of Y211 inclusions were observed in the sample prepared using 8 h milled powder. However, the unexpected Y211 particles coarsening was observed from the 4 h milled sample which was further increased for 10 h milled sample. Critical current density ($J_c$) of the LIG processed Y-123 bulk superconductors was found to be dependent on the milling time of the Y211 precursor powder. The $J_c$ increased with the increase of milling time and reached up to a maximum at 8 h in the self field while 10 h milled sample showed lower $J_c$ at the same field which might be due to the exaggerated growth and non-uniform distribution of Y211 particles.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.19 no.3
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• pp.322-333
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• 2012

Purpose: The purpose of this study was to evaluate the effects of a newly developed Introduction to Clinical Nursing (ICN) program on critical thinking skills, communication competence, self-efficacy, and clinical performance self-confidence in nursing students in their third year. Methods: One group pre-test and post-test design was used with three data collection time points (pre-test, post-test1 and post-test2). Participants were 74 third year nursing students approaching their first clinical practicum. The new program included (a) simulated clinical encounters regarding situations of assessing hospitalized patents and caring for patients with oxygenation needs, (b) objective structured clinical examination of skills, (c) lectures, and (e) field trips. Data were analyzed using paired t-tests. Results: After the ICN course, critical thinking skills(significant only between pretest and post-test2), communication competence, and clinical performance self-confidence improved significantly (p<.05). There was no improvement in the self-efficacy total score but there was significant improvement in the subscale, self-regulatory efficacy. Conclusions: The study results indicate that the ICN course may be effective in increasing critical thinking skills, communication competence, and clinical performance self-confidence in nursing students. However, the effect size was very small and modifications of this program should be considered to develop more cost-effective educational programs.

• Progress in Medical Physics
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• v.15 no.2
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• pp.100-104
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• 2004

The detector size effect due to the spatial response of detectors is a critical source of inaccuracy in clinical dosimetry that has been the subject of numerous studies. Conventionally, the detector response kernel contains all the information about the influence that the detector size has on the measured beam profile. Various analytical models for this kernel have been proposed and studied in theoretical and experimental works. Herein, a method to simply determine the detector response kernel using the Monte Carlo simulation and convolution theory has been proposed. Based on this numerical method, the detector response kernel for a Farmer type ion chamber embedded in a water phantom has been obtained. The obtained kernel shows characteristics of both the pre-existing parabolic model proposed by Sibata et al. and the Gaussian model used by Garcia-Vicente et al. From this kernel and deconvolution technique, the detector size effect can be removed from measurements for 6MV, 10${\times}$10 $\textrm{cm}^2$ and 0.5${\times}$10 $\textrm{cm}^2$photon beams. The deconvolved beam profiles are in good agreements with the measurements performed by the film and pin-point ion chamber, with the exception of in the tail legion.

• Progress in Superconductivity
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• v.9 no.1
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• pp.80-84
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• 2007

Charcoal was used as a carbon source for improving the critical current density of $MgB_2$ and the effect of annealing temperature on the $J_c$ of $MgB_2$ was investigated. The charcoal powder used in this study was $1{\sim}2$ microns in size and was prepared by wet attrition milling. $MgB_2$ bulk samples with a nominal composition of $Mg(B_{0.95}C_{0.05})_2$ were prepared by in situ process of Mg and B powders. The powder mixture was uniaxially compacted into pellets and heat treated at temperatures of $650^{\circ}C\;-\;1000^{\circ}C$ for 30 minutes in flowing Ar gas. It was found that superconducting transition temperature of $Mg(B_{0.95}C_{0.05})_2$ decreased by charcoal additions which indicates the carbon substitution for boron site. $J_c$ of $Mg(B_{0.95}C_{0.05})_2$ was lower than that of the undoped $MgB_2$ at the magnetic fields smaller than 4 Tesla, while it was higher than that of the undoped sample especially at the magnetic field higher than 4 T. High temperature annealing seems to be effective in increasing $J_c$ due to the enhanced carbon diffusion into boron sites.

• The Journal of Information Systems
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• v.29 no.2
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• pp.265-286
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• 2020

Purpose Among various psychosocial factors, negative social comparison, attention blocking to stimuli, and cognitive interference via information overload are considered most critical in hindering the effective performance improvement of computer-based idea generation. Given that the effect of negative social comparison along with a plausible solution based on the notion of performance feedback and goal setting has been successfully addressed, this study focused on the remaining issues of "attention blocking to stimuli and cognitive interference via information overload" and attempted to find a way to alleviate the effect of such process losses on performance. Design/methodology/approach A 2 × 4 between-subjects design was used, crossing cognitive ability (high and low) and personality (extroversion and introversion). Five subjects per each treatment were randomly selected to make the sample size equal. The group simulator was used to measure individual-level performance. The dependent variables were the quantity of and quality score of ideas. The manner by which these performance measures were operationalized was consistent with prior studies. An additional analysis using the number of diverse ideas was also conducted. Findings Three arguments were made in this study: (1) high cognitive individuals would perform better than low cognitive individuals, (2) extraverted individuals would perform better than introverted individuals, and (3) cognitive ability and personality would interact such that individuals in Q1 would have the highest performance. Cognitive ability had an effect on quality not quantity. Personality had an effect on both quantity and quality. An interaction between cognitive ability and personality was not found due to small sample size despite the use of the group simulator.

• Journal of applied mathematics & informatics
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• v.35 no.3_4
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• pp.241-260
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• 2017

An analysis is made to study the solute transport in a Casson fluid flow through an annulus in presence of oscillatory flow field and determine how this flow influence the solute dispersion along the annular region. Axial dispersion coefficient and the mean concentration expressions are calculated using the generalized dispersion model. Dispersion coefficient in oscillatory flow is found to be a function of frequency parameter, Schmidt number, and the pressure fluctuation component besides its dependency on yield stress of the fluid, annular gap and time in the case of steady flow. Due to the oscillatory nature of the flow, the dispersion coefficient changes cyclically and the amplitude and magnitude of the dispersion increases initially with time and reaches a non - transient state after a certain critical time. This critical value varies with frequency parameter and independent of the other parameters. It is found that the presence of inner cylinder and increase in the size of the inner cylinder inhibits the dispersion process. This model may be used in understanding the dispersion phenomenon in cardiovascular flows and in particular in catheterized arteries.