• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.500-509
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• 2013

This study reports a numerical analysis of the internal flow characteristics of the integrated urea-SCR muffler system with the various geometries of the multi-perforated tube which is set up between the muffler inlet and in front of SCR catalysts. The multi-perforated tube is generally used to disperse uniformly the urea-water solution spray and to make better use of the SCR catalyst, resulting in the increased $NO_x$ reduction and decreased ammonia slip. The effects of the multi-perforated tube orifice area ratios on the velocity distributions in front of the SCR catalyst, which is ultimately quantified as the uniformity index, were investigated for the optimal muffler system design. The steady flow model was applied by using a general-purpose commercial software package. The air at the room temperature was used as a working fluid, instead of the exhaust gas and urea-water solution spray mixture. From the analysis results, it was clarified that the multi-perforated tube geometry sensitively affected to the formation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.15-21
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• 2008

• Tuberculosis and Respiratory Diseases
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• v.44 no.2
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• pp.329-337
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• 1997

Background : Since endotracheal tube is the most important factor involved in the imposed work of breathing during mechanical ventilation, extubation of endotracheal tube is supposed to reduce respiratory work of patient. However, some patients show labored breathing after extubation despite acceptable blood gases. We investigated the changes of work of breathing before and after extubation and the factors involved in the change of WOB after extubation. Methods : The subjects were 34 patients(M : F = 20 : 14, mean age = $61{\pm}17yre$) who recovered from respiratory failure after ventilatory support and were considered to be ready for extubation. The patients with clinical or radiologic evidences of upper airway obstruction before endotracheal intubation for mechanical ventilation were excluded. Vital sign, physical examination, chest X-ray, work of breathing and other respiratory mechanic indices were measured prior to, immediately, 6, 24 and 48 hours after extubation serially. Definition of weaning failure after extubation was resumption of ventilatory support or reintubation of endotracheal tube within 48 hour after extubation because of respiratory failure. The patients were classified into group 1(decreased work of breathing), group 2(unchanged work of breathing) and group 3(increased work of breathing) depending on the statistical difference in the change of work of breathing before and after extubation. Results : Work of breathing decreased in 33%(11/34, group 1), unchanged in 41%(14/34, group 2) and increased in 26%(9/34, group 3) of patients after extubation compared with before extubation. Weaning failure occurred 9%(1/11) of group, 1, 28.6%(4/14) of group 2 and 44%(4/9) of group 3 after extubation(p = 0.07). The change of work of breathing after extubation was positively correlated with change of mean airway resistance(mRaw). (r = 0.794, p > 0.01). In three cases of group 3 whose respiratory indices could be measured until 48 hr after extubation, the change in work of breathing paralleled with the sequential change of mRaw. The work of breathing was peaked at 6 hr after extubation, which showed a tendency to decrease thereafter. Conclusions : Reversible increase of work of breathing after extubation may occur in the patients who underwent extubation, and the increase in mRaw could be responsible for the increase in work of breathing. In addition, the risk of weaning failure after extubation may increase in the patients who have increased WOB immediately after extubation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.6
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• pp.663-668
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• 2012

Fly ash erosion is a leading cause of boiler tube failure in PC boilers. Therefore, shields or baffle plates are installed in specific areas to mitigate fly ash erosion and prevent boiler tube failure. However, the tube failure problems caused by fly ash erosion cannot be eliminated with this solution alone, because each PC boiler has a different flue-gas flow pattern and erosion can become severe in unexpected zones. This problem is caused by an asymmetric internal flow velocity and local growth of the flue gas velocity. For these reasons, clearly defining the flow pattern in PC boilers is important for solving the problem of tube failure caused by fly ash erosion. For this purpose, the cold air velocity technique (CAVT) can be applied to the fly ash erosion problem. In this study, CAVT was carried out on the Hadong #2 PC boiler and the feasibility of application of CAVT to conventional PC boilers was validated.

• Journal of Korean Academy of Nursing Administration
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• v.8 no.4
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• pp.645-654
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• 2002

Purposes : This study was conducted to examine nursing effects after using a new method of nasogastric tube feeding with recycled PETE bottle making use of gravity, and to compare with those of bolus method using syringe and pressure. Methods : The data collected from patients with nasogastric tube feeding more than a week at an internal medicine unit of C university hospital located in G-city from January 1st, 1998 through June 30th, 2000. For this nonequivalent control group posttest non-synchronized design, 28 patients were assigned to an experimental group and 35 patients to a control group. The homogeneity of two groups and the dependent variables were tested with use of $x^2-test$ and t-test. Results : The duration of hemostatic use was significantly shorter in the experimental group than control group(t=2.63, p=0.02). Also, the patients with PETE bottle feeding had a lower cost of material(t=3.51, p=0.01) and a lower rate of the time of direct nursing care(t=2.44, p=0.04) than those of control group. But, there was no significant difference between two groups in the length of hospital stay. Conclusion : This results indicates that nasogastric tube feeding with PETE bottle is superior to nasogastric tube feeding with syringe. This findings gave us an evidence to enhance nursing effectiveness in clinical setting.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.11
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• pp.570-579
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• 2017

In this study, we examined the multi-stage piston-type air compressors typically used in a railroad vehicle, and the heat transfer efficiency was analyzed according to the design conditions of the heat exchanger (a compressor component module for cooling the compressed high temperature air). For the fin-tube heat exchanger used in the most air compressors, numerical analysis was performed to analyze heat transfer by defining the various rectangle tube sizes and the number of fin-per-unit area as design variables under the same flow rate of compressed air. Also, this analysis compared the temperature of the compressed air. Regarding environmental conditions for analysis, the flow rate of the external cooling air was measured and the mean value of the values was applied. And a "turbulence model" was considered in both the external flow of the cooling air and the internal flow inside the tube. From the results of analysis, it was found that the change of the aspect ratio value of the tube greatly influences the heat transfer efficiency of the compressed air, and influences if the fin density is relatively small. As a result, the optimum design specifications of the heat exchanger for air compressors were confirmed based on the analysis of the heat transfer efficiency, according to the design conditions of fin and tube by the operating temperature range of the compressed air.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.1
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• pp.91-94
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• 2018

We develop a time-temperature indicator (TTI) that can determine whether thawing of fish and other fishery products has occurred during frozen storage. A polypropylene tube with an internal diameter of 3 mm was prepared and cut to a length of 14 to 20 mm. One end of the tube was thermally sealed and 0.1% acetic acid was injected into the other end; the tube was then frozen at $20^{\circ}C$. Then the open side of the frozen tube was blocked by sinking the tube into a 10% gelatin solution. The tube was attached to a polyvinyl packaging bag along blue litmus paper and the bag was put into a freezer at $-20^{\circ}C$. After freezing, the bag was removed to an ambient temperature of $20^{\circ}C$, and the time dependence of the color change of the litmus paper was observed. The color changed from blue to red, with the length of the red region increasing with time. Our TTI can be used as a part of a visible detection system and the detection program can conduct the elapsed time analysis on the length of the red region of the litmus paper indicating the degree of thawing. Thus, the TTI is a useful tool in the temperature management of frozen fish and fishery products.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.6
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• pp.146-152
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• 2009

The steel-tube is exposed to a radiation from X-ray source. The transmitted radiation is detected by a detector, usually film or more recently an imaging plate(IP) of Computed Radiography(CR). The detected radiation overlaps the region of both sides of the object. The radiographic images reflect the projections of the rays, passing twice through both external and internal tube material. Nonlinear distortion due to the radioactive transmission and geometric disposition also appears on images. In this paper, an analytical approach is presented to achieve image reconstruction from the steel-tube CR images. Parameters related to radiation and measuring structure, such as intensities, absorption in material and geometric specifications linked with the collimating components, are calculated and identified in order to construct the renoval images for twofold regions of circle-type steel tubes. A correction procedure for region recovery most similar to the true tube is designed. The application of this approach on CR images is shown and reconstructed results are discussed.

• Journal of Mechanical Science and Technology
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• v.16 no.9
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• pp.1102-1111
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• 2002

The study focuses on the heat transfer performance of two-phase closed thermosyphons with plain copper tube and tubes having 50, 60, 70, 80, 90 internal grooves. Three different working fluids(distilled water, methanol, ethanol) are used with various volumetric liquid fill charge ratio from 10 to 40%. Additional experimental parameters such as operating temperature and inclination angle of zero to 90 degrees are used for the comparison of heat transfer performance of the thermosyphon. Condensation and boiling heat transfer coefficients, heat flux are obtained using experimental data for each case of specific parameter. The experimental results are assessed and compared with existing correlations. The results show that working fluids, liquid fill charge ratio, number of grooves and inclination angle are very important factors for the operation of thermosyphons. The relatively high rate of heat transfer is achieved when the thermosyphon with internal grooves is used compared to that with plain tube. The optimum liquid fill charge ratio for the best heat transfer performance lies between 25% and 30%. The range of the optimum inclination angle for this study is 20$^{\circ}$～30$^{\circ}$ from the horizontal position.

• Korean Journal of Optics and Photonics
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• v.9 no.6
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• pp.403-407
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• 1998

The polarizatin properties of an internal-mirror 543 nm He-Ne laser with and without a transverse magnetic field were investigated for single-mode operation. Two orthogonal eigenpolarizations field to the natural tube axes of laser were observed when the emitted laser output was linearly polarized. Polarization unstability between these polarizations occurred when the applying a 500 gauss transverse magnetic field at 35$^{\circ}$ with respect to the natural tube axes of laser. Under such conditions stable single-mode operation which is useful for the frequency stabilization of a 543 He-Ne laser to $I_2$-saturated absorptions was obtained in the tuning range of 880 MHz.