• Applied Chemistry for Engineering
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• v.9 no.4
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• pp.579-584
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• 1998

Polymer dispersed liquid crystal(PDLC) composite films were made by polymerization induced phase separation method using UV-curing to investigate the effect of fabrication conditions, such as photoinitiator concentration, film thickness, polymerization temperature, and electric field during polymerization, etc., on the electro-optic properties. As the amount of photoinitiator increased, the driving voltage of PDLC device increased due to the increase of small-size liquid crystal phases. This was considered as the results from the increased interfacial area between liquid crystal (LC) and polymer matrix, since LC molecules at the interfacial regions were relatively difficult to response for the applied electric field. When the higher molecular weight oligomer (PTDA-1000) was used as matrix, the initial transmittance was observed to be relatively higher than that for the lower molecular weight oligomer (PTDA-250). Saturation transmittance for PTDA-1000 was observed at relatively lower voltage than that for PTDA-250, of which transmittance was not saturated even at 60 V. As polymerization temperature increased, the initial transmittance of resulting PDLC film increased due to the larger LC droplets formation and the more matched refractive index between LC and matrix than those cases for the lower polymerization temperature. Though driving voltage decreased for the thinner film, it was considered that optimum thickness of the film should be maintained to get some practical contrast, which is the ratio of off- and on-state transmittance. Furthermore, electro-optic properties such as initial transmittance, driving voltage, and response time were observed to be considerably affected by application of external field during polymerization.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.1
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• pp.96-103
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• 2014

A liquefied natural gas(LNG) in cryogenic liquid is converted back into gaseous form for distribution to residential and industrial consumers. In this re-gasification process, LNG supplies a plenty of cold thermal energy about $83.7{\times}10^4kJ/kg$. The LNG cold thermal energy is utilized for the re-liquefaction process of cryogenic fluids such as Nitrogen, Hydrogen and Helium, and ice manufacturing process and air-conditioning system in some advanced countries. Therefore, it is also necessary to establish the recovery systems of the LNG cold thermal energy around Incheon, Pyungtaek and Tongyung LNG import terminals in our country. Methane is used as working fluid in this paper, which is the major component of LNG over 85 % by volume, in order to investigate the flow behavior characteristics of LNG with phase change at low heat flux. This paper presents the effects of pipe diameters, pipe inclinations and saturation pressures on the flow boundaries of methane flowing in a cryogenic heat exchanger tube, together with those of nitrogen, propane, R11 and R134a. The outcomes obtained from this theoretical researches are also compared with previous experimental data. It was also found that the effect of pipe inclination on the methane flow boundaries was significant.

• Journal of the Korean Magnetics Society
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• v.16 no.3
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• pp.168-172
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• 2006

We studied the magnetic and the related electronic properties of Ni-doped rutile $TiO_{2-{\delta}}$ films (including oxygen deficiency $\delta$) prepared using a sol-gel method. A room-temperature ferromagnetism was observed in the $TiO_{2-{\delta}}$ : Ni films with the saturation magnetization ($M_S$) decreasing with increasing Ni doping and remaining constant above 6 at% Ni doping. The observed ferromagnetism below 6 at% Ni doping is interpreted as due to magnetic polaron formed by a trapped electron in oxygen vacancy and magnetic impurity ions around it. For small Ni doping, $M_S$ up to $3.7{\mu}B/Ni$ was obtained. The ferromagnetism for Ni doping above 6 at% is interpreted as due to the existence of Ni clusters that can explain the p-n conductivity transition observed by Hall effect measurements.

• Journal of Digital Convergence
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• v.8 no.1
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• pp.109-120
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• 2010

Mobile phone-related industries have been mainly concentrated on attracting the new customers and increasing the market share such as for the aggressive marketing activities, but it is the time to find an effective strategy to preserve existing customers since the mobile phone market had already reached the saturation. In this study, the properties of mobile phone that influence on the choice of handset and telecom company were analyzed. General properties of respondents were explored and the mobile phone properties were grouped by common factors. And analyzed the effect of factors on customer satisfaction with structural equation model. 10.4% of respondents are used their handset more than two years and 48.7% wanted to purchase other manufacturer's handset if they repurchase mobile phone. These results might come form the fact that the life cycle of mobile phone become shorter by the heating competition in mobile phone market and, to some degree, the influence of smart phone which recently become globally popular. Four factors, 'Hardware Quality', 'Practicality', 'Convergence Functions' and 'Level of Awareness', are induced from the mobile phone properties. In Structural Equation Model analysis, 'Hardware Quality' and 'Practicality' have significant and positive effects on Customer Satisfaction. But, 'Awareness' such as brand and trend appeared quite less influence on the customer satisfaction.

• Child Health Nursing Research
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• v.19 no.1
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• pp.1-11
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• 2013

Purpose: This study was done to develop a scenario and evaluate student performance in simulation learning of care for children with respiratory distress syndrome in neonatal intensive care units. Methods: To test the application effect, a one group pre-test design was applied. The scenario based on actual patients and textbook material was developed through several meetings of experts. The scenario was used with 17 groups of 55 senior nursing students who participated voluntarily. Results: Contents were organized focusing on the nursing process for simulation learning. In the application of knowledge and skills, nursing students had high scores in the contents of observation of oxygen saturation, and care to relieve dyspnea. Participants' ability, especially in suction and oxygen supply in the evaluation of objective structured clinical examination was not adequate. There was a significant positive correlation between problem-solving ability and satisfaction in learning. Conclusion: The respiratory distress syndrome simulation scenario developed in this study was an effective tool to give students experience in problem solving and critical thinking ability under conditions similar to reality. The development of various scenarios for child nursing care is needed.

• Tuberculosis and Respiratory Diseases
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• v.67 no.3
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• pp.183-190
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• 2009

Background: Repeated arousals during sleep have been known to be associated with excessive daytime sleepiness and cardiovascular complications. We investigated the relationship between arousal indices and clinical parameters. Methods: We retrospectively reviewed medical records of 41 patients who performed polysomnography for a diagnosis of obstructive sleep apnea syndrome. We defined total arousal index (TAI) as the number of arousals per hour and respiratory arousal index (RAI) as the number of arousals associated with apnea or hypopnea per hour. Results: There were significant positive correlations between arousal indices and apnea-hypopnea index (AHI) (RAI vs. AHI, r=0.958, p<0.001; TAI vs. AHI, r=0.840, p<0.001). RAI and mean oxygen saturation showed a significant negative correlation with each other (r=-0.460, p=0.002). TAI revealed a significant positive correlation with mean systolic blood pressure (MSBP) and mean diastolic blood pressure (MDBP) (TAI vs. MSBP, r=0.389, p=0.014; TAI vs. MDBP, r=0.373, p=0.019). There was no significant correlation between arousal indices and parameters of sleepiness. RAI had a significant positive correlation with body mass index (BMI) and neck circumference (NC) (RAI vs. BMI, r=0.371, p=0.017; RAI vs. NC, r=0.444, p=0.004). When partial correlation analysis was performed to adjust for other variables, there was significant correlation between RAI and AHI (r=0.935, p<0.001). Conclusion: This study shows that respiratory arousal index could be a useful index reflecting of severity of obstructive sleep apnea syndrome. Arousal during sleep would be concerned in the development of cardiovascular complication of obstructive sleep apnea. And some anthropometric factors would contribute to the development of arousals during sleep. Further studies are needed to clarify any cause-effect relationship.

• Journal of the Korean Magnetics Society
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• v.21 no.2
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• pp.77-82
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• 2011

The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.30 no.6
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• pp.567-571
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• 2008

Purpose: The purpose was to assess the usefulness of midazolam in patients undergoing minor oral surgery under conscious sedation. Materials and methods: Bispectral index was examined in 20 patients receiving oral minor surgery with conscious sedation supplemented with local anesthesia. All patients included were ASA I and had no contraindications to the study medications. The patients were escorted to the day surgery operation room where, before the commencement of the sedation and surgical procedures, routine monitoring was applied, including the noninvasive monitoring of arterial blood pressure, arterial oxygen saturation, and 3-lead electrocardiogram (Electrocardiogram). Bispectral index electrodes were applied on the frontotemporal region after cleansing the skin with alcohol. Bispectral index was calculated with the Electrocardiogram monitor (A-2000; Aspect Co.). Midazolam was then titrated (initially 3mg wait 2min and 2mg). Vital sign and Bispectral index checked every 5 minute until the end of the procedure. The results were then compared. Results: The Bispectral index index values throughout the sedation study period alter many level. The index was dropped at 5 minutes after administration, but raised at injection and odontomy procedure. During the operation, mean Bispectral index index was higher than conscious sedation index range($60{\sim}80$). The amnesic effect was shown 17 cases out of 20 cases(85%). Conclusion: Conscious sedation technique using midazolma is a safe and effective method of controlling behavior in oral and maxillofacial surgery.

• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.243-248
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• 1997

The effect of $O_2$ partial pressure on microstructure and soft magnetic properties of as-deposited Fe-Hf-O thin film alloys, which are produced by rf magnetron sputtering method in $Ar+O_2$ mixed gas atmosphere, are investigated. Saturation magnetization ($4{\pi}M_s$) of Fe-Hf-O film were decreased with increasing $O_2$ partial pressure, the best soft magnetic properties exhibit at $O_2$ partial pressure of 10%. With further increase of $O_2$ partial pressure, soft magnetic properties decreased continuously. The $Fe_{82}Hf_{3.4}O_{14.6}$ film with $P_{O2}=10%$ exhibits good soft magnetic properties with $4{\pi}M_s=17.7kG$, $H_c=0.7Oe$ and ${\mu}_ {eff}$ (1~100 MHz)=2,500, respectively. The addition of O is effective in grain refinement. In case of $P_{O2}=15%$, it is observed that $Fe_3O_4$ compound is formed and high frequency soft magnetic properties are decrease. The electrical resistvity($\rho$) of Fe-Hf-O film is increased with increasing $O_2$ partial pressure. Electrical resistivity of $Fe_{82}Hf_{3.4}O_{14.6}$ film was 5 times higher than that of the film without oxygen. Thus, it is considered that the good magnetic properties of $Fe_{82}Hf_{3.4}O_{14.6}$ film results from decreasing the $\alpha$-Fe grain size by precipitates (Hf and O), high electrical resistivity.

• Journal of the Korean Magnetics Society
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• v.5 no.4
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• pp.275-280
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• 1995

The sites for $Fe^{+3}$ are partly substituted by $Co^{+2}$ and $Ti^{+4}$ cations to control coercivity of Ba-ferrite particles for use in high density magnetic recording. The substituted $Co^{+2}$ cation has very much different effects on magnetic properties and particle characteristics from that $Ti^{+4}$ cation has. The decrease in the coercivity with the $Co^{+2}$ substitution is attributed to the formation of excessive spinel-block(S-block) in pure Ba-ferrite crystal, while saturation magnetization is increased and the distributions of coercivity and particle size become broad. The substitution with the $Ti^{+4}$ decreases the sauration magnetization, but has less effect on a change in coercivity than the $Co^{+2}$. The $Ti^{+4}$ acts as a nucleation agent in amorphous phase of formulated compound, and consequently particle size and aspect ratio are decreased. Furthermore, the enhancement of substitution of the $Co^{+2}$ for the $Fe^{+3}$ sites in rhombohedral-block(R-block) by the $Ti^{+4}$ retards the nucleation of spinel phase of Ba-ferrite, which results in uniform magnetic properties of Ba-ferrite particles. It is suggested that the contents of the cations to be substituted for the $Fe^{+3}$ sites are optimized on the bases of magnetic properties and particle characteristics rather than on the base of electrical charge balance.