• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.264-270
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• 2002

This paper presents roughness effects on flow characteristics and efficiency of multi-stage axial compressor using numerical simulation. which is carried out with a commercially available software, CFX-TASCflow. In this paper, the third of four stages of GE low pressure compressor is considered including me stator and rue rotor. Mixing-plane approach is adopted to model the interface between the stator and the rotor: it is appropriate for steady state simulation. First, a flat plate simulation was performed to validate how exact the numerical simulation predicts the roughness effect for smooth and rough walls. Then GE compressor model was calculated about at each roughness height. Concluding, very small roughness height largely affects the performance of compressor and the increasing rate of loss decrease as roughness height increase.

• The Korean Journal of Pain
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• v.24 no.4
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• pp.235-238
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• 2011

Vertebral compression fractures result in vertebral height loss and alter sagittal spinal alignment, which in turn can lead to increased morbidity and mortality. Acute osteoporotic vertebral compression fractures are known to increase mobility and instability of the spine. There are limited published data correlating the degree of dynamic mobility and the efficacy of kyphoplasty on vertebral compression fractures. Here we report a 73-year-old female with a severe acute osteoporotic L2 compression fracture who obtained total vertebral height restoration following kyphoplasty, with resolution of back pain.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.441-448
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• 2018

Recently, measurements on clutter loss due to buildings in urban/suburban areas at 3, 6, 10, 18, and 24 GHz have been performed by the Radio Research Agency with the purpose of predicting the clutter loss close to actual urban/suburban propagation for 5G mobile communication. In this work, we have compared the urban clutter loss to suburban clutter loss for a transmit antenna height of 85 m. Furthermore, we have estimated the error between the predicted loss as per ITU-R P.2108 and the measured clutter loss. Our results indicate that for higher frequencies, the measured clutter loss in urban/suburban areas is higher and so lower than the predicted clutter loss. In conclusion, it is necessary to improve the prediction model for clutter loss by taking into account the measured clutter loss in urban/suburban areas in the prediction model.

• Journal of Periodontal and Implant Science
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• v.52 no.6
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• pp.509-521
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• 2022

Purpose: Systemic health has a profound effect on dental treatment. The aim of this study was to evaluate peri-implant bone loss and health screening data to discover factors that may influence peri-implant diseases. Methods: This study analyzed the panoramic X-rays of patients undergoing health screenings at the Health Promotion Center at Seoul St. Mary's Hospital in 2018, to investigate the relationship between laboratory test results and dental data. The patients' physical data, such as height, weight, blood pressure, hematological and urine analysis data, smoking habits, number of remaining teeth, alveolar bone level, number of implants, and degree of bone loss around the implant, were analyzed for correlations. Their associations with glycated hemoglobin, glucose, blood urea nitrogen (BUN), creatinine, and severity of periodontitis were evaluated using univariate and multivariate regression analysis. Results: In total, 2,264 patients opted in for dental health examinations, of whom 752 (33.2%) had undergone dental implant treatment. These 752 patients had a total of 2,658 implants, and 129 (17.1%) had 1 or more implants with peri-implant bone loss of 2 mm or more. The number of these implants was 204 (7%). Body mass index and smoking were not correlated with peri-implant bone loss. Stepwise multivariate regression analysis revealed that the severity of periodontal bone loss (moderate bone loss: odds ratio [OR], 3.154; 95% confidence interval [CI], 1.175-8.475 and severe bone loss: OR, 7.751; 95% CI, 3.003-20) and BUN (OR, 1.082; 95% CI, 1.027-1.141) showed statistically significant predictive value. The severity of periodontitis showed greater predictive value than the biochemical parameters of blood glucose, renal function, and liver function. Conclusions: The results of this study showed that periodontal bone loss was a predictor of peri-implant bone loss, suggesting that periodontal disease should be controlled before dental treatment. Diligent maintenance care is recommended for patients with moderate to severe periodontal bone loss.

• International Journal of Fluid Machinery and Systems
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• v.2 no.1
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• pp.13-20
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• 2009

The effects of positively bowed blade on the aerodynamic performance of annular compressor cascades with large camber angle were experimentally investigated under different incidences. The distributions of the exit total pressure loss and secondary flow vectors of compressor cascades were analyzed. The static pressure was measured by tapping on the cascade surfaces, and the ink-trace flow visualizations were conducted. The results show that the value of the optimum bowed angle and optimum bowed height decrease because of the increased losses at the mid-span with the increase of the caber angle. The C-shape static pressure distribution along the radial direction exists on the suction surface of the straight cascade with large r camber angles. When bowed blade is applied, the larger bowed angle and larger bowed height will further enhance the accumulation of the low-energy fluid at the mid-span, thus deteriorate the flow behavior. Under $60^{\circ}$ camber angle, flow behavior near the end-wall region of some bowed cascades even deteriorates instead of improving because the blockage of the separated flow near the mid-span keeps the low-energy fluid near the end-walls from moving towards the mid-span region, and as a result, a rapid augmentation of the total loss is easy to take place under large bowed angle. With the increase of camber angle, the choice range of bowed angle corresponding to the best performance in different incidences become narrower.

• Journal of the East Asian Society of Dietary Life
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• v.24 no.6
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• pp.802-810
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• 2014

This study investigated the quality characteristics of muffins prepared with tagatose. The effect of tagatose were evaluated in terms of height, volume, weight, specific volume, baking loss rate, moisture contents, colorimeter, sensory evaluation, and texture of muffins during storage (1, 3, 5 days) and texture was measured using a texture analyzer. As the ratio of tagatose increased, the volume, specific volume, baking loss rate, and height decreased, whereas moisture content increased. During storage, control without tagatose showed the highest springiness lowest hardness by TPA, whereas hardness of muffins increased and springiness decreased as the contents of tagatose increased. Lightness of crust and crumb decreased significantly as contents of tagatose increased. According to the sensory evaluation, the control group showed the highest score in terms of texture but was not significant with 2% tagatose (T2). For appearance, color, flavor, taste, and overall acceptance, T2 showed the best result.

• Journal of Korean Dental Science
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• v.17 no.1
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• pp.45-52
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• 2024

Purpose: To investigate the 5-year outcome of dental implants placed in a grafted maxillary sinus using recombinant human bone morphogenetic protein-2 (rhBMP-2). Materials and Methods: We retrospectively analyzed 27 implants after maxillary sinus floor augmentation (MSFA) using rhBMP-2 in 16 patients between January 2016 and March 2017. The study evaluated two outcome variables: (1) 5-year cumulative survival and success rate of the implant after functional loading and (2) marginal bone loss (MBL) for implant failure. Results: The average residual bone height was 4.78±1.53 mm. The healing period before loading was 8.35±2.34 months. The crown-to-implant ratio was 1.31±0.26. The 5-year cumulative survival and success rate after functional loading were 100% and 96.3%, respectively. The 5-year average MLB was 0.89±0.82 mm. Conclusion: Placing dental implants with MSFA using rhBMP-2 is a reliable procedure with favorable long-term survival and success rates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.115-120
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• 2014

To enhance the performance of an automobile turbocharger compressor, the circumferential inlet heights of the volute were modified and the flow field for the combined region of the diffuser and volute was numerically investigated using commercial software. Basically, a well-designed volute should have a high pressure recovery coefficient and a low loss coefficient for the total pressure. In this study, two circular volutes with the same cross sectional shape and tongue angle, but circumferentially different volute inlet heights, were selected. One volute had the middle inlet in the cross-section at the circumferential angle of $90^{\circ}$ but gradually lower inlet heights for the angles between $90^{\circ}$ to $360^{\circ}$ with respect to the cross sectional center of the volute, while maintaining the same height between the tangential line connecting the lowest positions of the cross section and the line connecting the volute inlets in the circumferential direction (case 1 volute). The other volute has an inlet height that is 2 mm lower than in case 1 volute such that the tongue section has a tangential inlet (case 2 volute). The results showed that the case 2 volute had a higher total pressure ratio because of its higher pressure recovery coefficient and higher isentropic efficiency, resulting from the lower loss coefficient along the circumferential position than the case 1 volute.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1051-1057
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• 2004

A numerical optimization procedure for the shape of three-dimensional channel with angled ribs mounted on one of the walls to enhance turbulent heat transfer is presented. The response surface method is used as an optimization technique with Reynolds-averaged Wavier-Stokes analyses of flow and heat transfer. SST turbulence model is used as a turbulence closure. Computational results for local heat transfer rate show reasonable agreements with experimental data. The pitch-to-height ratio of the rib and rib height-to-channel height ratio are set to be 9.0 and 0.1, respectively, and width-to-rib height ratio and attack angle of the rib are chosen as design variables. The objective function is defined as a linear combination of heat-transfer and friction-loss related terms with weighting factor. Full-factorial experimental design method is used to determine the data points. Optimum shapes of the channel have been obtained in the range from 0.0 to 0.1 of weighting factor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.270-273
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• 2003

The characteristic of constant volume micro combustor was investigated experimentally. The shape of micro combustor was cylindrical and has row aspect ratio or has relatively large diameter compared with chamber height. Diameter and chamber height was varied to investigate the geometric effect of combustor on the flame propagation. Diameter of 15 mm and 7.5 mm was designed while chamber height was designed to be 1mm, 2mm, and 3mm. The effect of initial pressure was also investigated parametrically from 1bar to 3bar. The gas used in this study was stoichiometric mixture of methane and air. The maximum pressure achieved in down scaled combustors was lower than that of conventional combustor because heat loss to wall was dominant as expected. The maximum pressure responded favorably with the change of height of combustor and the initial pressure, the maximum pressure was also increased. The flame propagation was possible when the specific condition was satisfied. Although the quenching distance of stoichiometric mixture of CH4 and Air is 2.5 mm, the flame could propagate even under quenching distance as the initial pressure increased.