• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.12
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• pp.1673-1680
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• 2003

It is essential to operate chemical lasers with supersonic ejector system as the laser output power goes up. In this research, ejector design parameter study was carried out for optimal ejector design through understanding the ejector characteristics and design requirements for chemical lasers operating. Designed ejector was 3D annular type with 2$^{nd}$ -throat geometry and pressurized air was used for primary flow. Ejector design was carried out with two steps, quasi-1D gas dynamics was used for first design and commercial code was used to verify the first design. In this study, to get the effect of ejector geometry on its performance, three cases of primary nozzle area ratio and 2$^{nd}$ -throat cross sectional area and two cases of 2$^{nd}$ -throat L/D ratio experiments were carried out. Primary and secondary pressures were measured to get the mass flow rate ratio, minimum secondary pressure, ejector starting pressure and unstarting pressure at every case. In the result, better performance than design level was shown and optimal ejector design method for chemical lasers was obtained.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.10
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• pp.1231-1237
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• 2004

Determination of geometric design parameters of a second-throat type annual supersonic ejector is described. Tested geometric parameters were primary nozzle area ratio, cross-sectional area of second-throat, L/D ratio of second-throat and primary flow injection angle. Varying these four geometric parameters, we build a test matrix made of 81 test conditions, and experimental apparatus was fabricated to accommodate them. For each test condition, the stagnation pressure of primary flow and the static pressure of the secondary flow were measured simultaneously along with their transition to steady operation and finally to unstarting condition. Comparing the performance curve of every case focused on starting pressure, the unstarting pressure and the minimum secondary pressure, we could derive correlations that the parameters have on the performance of the ejector and presented the optimal design method of the ejector. Additional experiments were carried out to find effects of temperature and mass flow rate of the secondary flow.

• Journal of Korean Academy of Nursing
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• v.33 no.3
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• pp.386-394
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• 2003

Purpose: This study was designed to explore the association of diet with menopausal symptoms in Korean women, Method: For this cross-sectional survey, 276 women aged between 45-55 years visiting two branches of K-university hospital located in Seoul and Ansan of Kyunggi province were recruited from April to July, 2002. A menopause-specific quality-of-life questionnaire and a food frequency questionnaire were used to measure menopause-related symptoms and the intake of 28 types of foods. Result: No differences were found in the levels of bothersome total menopausal symptoms, physical symptoms, psychosocial symptoms, and sexual symptoms according to the intake of each food. Only higher intake of fishes, seaweeds, and vegetable oils were inversely associated with bothersome levels of vasomotor symptoms. Women with higher intake of yellow-green vegetables and lower intake of coffee, confectionery, and processed foods reported lower hot flush rate. Conclusion: The results suggest that higher intake of yellow-green vegetables and lower intake of coffee, confectionery and processed foods may relieve hot flushes. Further study needs to be pursued to study the relationship with nutrients of these foods and hot flushes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.447-447
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• 2009

In this study, transparent and conductive Al-doped zinc oxide (AZO) films were prepared on Corning glass and silicon wafer substrate by RF magnetron sputtering method using an Al-doped ZnO target (Al: 2 wt.%) at room temperature as the thickness of 150 nm. We investigated the effects of the RF power between 100 Wand 350 W in steps of 50 W on structural, electrical and optical properties of AZO films. Also, we studied the effects of the working pressure (3, 4 and 5 mtorr) on that condition. The thickness and cross-sectional images of films were observed by field emission scanning electron microscopy (FE-SEM) and all of the films were kept to be constant to $150\pm10$ nm on Coming glass and silicon wafer. A grain size was calculated from X-ray diffraction (XRD) on using the Scherrer' equation and their electrical properties investigated hall effect electronic transport measurement system. Moreover, we measured transmittance of AZO films by UV/VIS spectrometer.

• Journal of Ocean Engineering and Technology
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• v.17 no.5 s.54
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• pp.57-65
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• 2003

This paper proposes an optimum design method of structural and control systems, using a 2-D truss structure as an example. The structure is subjected to initial static loads and disturbances. For the structure, a FEM model is formed. Using modal transformation, the equation of motion is transformed into modal coordinates, in order to decrease D.O.F. of the FEM model. To suppress the effect of the disturbances, the structure is controlled by an output feedback $H_{\infty}$ controller. The design variables of the combined optimal design of the control-structure systems are the cross sectional areas of truss members. The structural objective function is the structural weight. The control objective function is the $H_{\infty}$ norm, the performance index of control. The second structural objective function is the energy of the response related to the initial state, which is derived from the time integration of the quadratic form of the state in the closed-loop system. In a numerical example, simulations have been perform. Through the consideration of structural weight and $H_{\infty}$ norm, an advantage of the combined optimum design of structural and control systems is shown. Moreover, since the performance index of control is almost nearly optimiz, we can acquire better design of structural strength.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1199-1204
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• 1997

SiC conversion layer was fabricated by the chemical vapor reaction between graphite substrate and silica powder. The CVR process was carried out in nitrogen atmosphere at 175$0^{\circ}C$ and 185$0^{\circ}C$. From the reduction of silica powder with graphite substrate, the SiO vapor was created, infiltrated into the graphite substrate, then, the SiC conversion layer was formed from the vapor-solid reaction of SiO and graphite. In the XRD pattern of conversion layer, it was confirmed that 3C $\beta$-SiC phase was created at 175$0^{\circ}C$ and 185$0^{\circ}C$. Also, in the back scattered image of cross-sectional conversion layer, it was found that the conversion layer was easily formed at 185$0^{\circ}C$, the interface of graphite substrate and SiC layer was observed. It was though that the coke particle size and density of graphite substrate mainly affect the XRD pattern and microstructure of SiC conversion layer. In the oxidation test of 100$0^{\circ}C$, the SiC converted graphites exhibited good oxidation resistance compared with the unconverted graphites.

• Journal of Korean Biological Nursing Science
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• v.11 no.2
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• pp.183-194
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• 2009

Purpose: It is aimed to empirically apply and examine the effects of Creative Training Techniques (CTT) that focus on student-centered educational environment to an anatomy subject for biological nursing science education. Methods: A triangulation that combines cross-sectional survey and content analysis was used and the data were collected in 2008. Participants were 301 freshmen students attending one junior nursing college in Seoul, Korea. A questionnaire was distributed to 301 students, 289 of whom responded (response rate 96.0%), and used for data analysis. Factor analysis, reliability analysis, and descriptive statistics were conducted by using data analysis SPSS 14.0 KO for Windows programs. In addition contents analysis was conducted. Results: 1) CTT Increased the relationship between professor and students ($3.12{\pm}0.92$), 2) Students preferred the various team leader choosing method ($3.25{\pm}0.93$), 3) Model and image materials helped the learning ($3.71{\pm}0.89$). Conclusion: CTT can be used to enhance students' learning effectiveness. Intervention programs intensified by CTT may be useful to improve students' learning abilities in nursing science education.

• Journal of Korean Biological Nursing Science
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• v.11 no.1
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• pp.14-22
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• 2009

Purpose: This study was conducted to examine the clinical factors which affected the amount and the duration of infusion of intravenous (IV) heparin on ischemic stroke. Method: A cross-sectional descriptive study was designed to examine the factors. A total of 101 patients with ischemic stroke from a University hospital in G-city, Korea from January to December, 2006 were participated in this study. Data were analyzed by t- and ANOVA test, correlation coefficient, and stepwise multiple linear regression analysis. Result: This study showed that the patients who have been temporarily stopped to infuse iv heparin for more than one hour, had cardioembolic stroke, and had the lower count of initial red blood cell (RBC) had significantly lower amount of iv heparin infusion per body surface. In addition, this study founded that the patients with lower count of initial RBC and the lower level of initial blood sugar were significantly less likely to have the lower length of iv heparin infusion. Conclusion: Continuous monitoring and controlling the count of RBC and the level of blood sugar are needed to increase the efficacy of iv heparin therapy on ischemic stroke. Further empirical studies should be conducted to support the results of this study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.8
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• pp.1952-1966
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• 1994

The body segment parameters of twelve young male Korean were measured to compare with the results of foreign cadaver studies. A human body was assumed to have fourteen body segments. The mass of each segment was measured with a water immersion test and the mass center of a segment was determined on the balance platform by changing postures. In the case of Korean, because of the difference in body proportion, the mass center of whole-body is located further from the distal end of head(Korean : 44.9% vs. Caucasian : 41.2%), and the mass center of each segment also located in different proportional locations. The existing regression equations, which can estimate segment mass based upon the anthropometric dimensions, estimates segment mass (the mass of shank) for Korean with 13% error. Therefore, it is not recommended to estimate the mass, and the moment of inertia of body segment of Korean based on the existing equations. However, the density information of body constituents was similar enough to apply it to Korean density. It was validated by the comparison between the results of the direct immersion method and 3-dimensional volume reconstruction of segment form the cross sectional images of CT-scan. The average body density measured form twelve subjects was $1.035{\;}kg/m^3$ and showed deceasing trendency.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.23 no.3
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• pp.218-222
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• 2014

A 3D printer was used to fabricate a micro-TAS system for biomedical applications. A polymeric medical device fabrication based on a 3D printer can be performed at atmospheric conditions. A CAD- and CAM-based system is a flexible method to design medical components, and a 3D printer is a suitable device to perform this task. In this research, a 100-micron-wide fluidic channel was fabricated with a high-aspect ratio. A cross-sectional SEM image confirmed its possible usage in a micro-reactor using 3D printers. CNC-machined samples were compared to 3D printer-fabricated samples, and the advantages and disadvantages were discussed. Based on the SEM images, the surface roughness of the 3D printed reactor was not affected by wet or dry conditions due to its manufacturing principle. An aspect ratio of 5 to 1 was achievable with 100-${\mu}$ m-wide fluid channels. No melting was found, and the shape of channels was straight enough to be used for micro reactors.