• Korean Journal of Radiology
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• v.21 no.6
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• pp.764-772
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• 2020

Objective: Laser ablation is a therapeutic modality used to reduce the volume of large benign thyroid nodules. Unsatisfactory reduction and regrowth are observed in some treated nodules. The aim of the study was to evaluate the long-term outcomes of laser treatment for solid nodules during a 5-year follow-up period, the regrowth rate, and the predictive risk factors of nodule regrowth. Materials and Methods: We retrospectively evaluated patients with benign, solid, cold thyroid nodules who underwent laser ablation and were followed-up for 5 years. According to the selection criteria, 104 patients were included (median baseline nodule volume, 12.5 mL [25.0-75.0%, 8-18 mL]; median energy delivered, 481.5 J/mL [25.0-75.0%, 370-620 J/mL]). Nodule volume, thyroid function test results, and ultrasound were evaluated at baseline and then annually after the procedure. Results: Of 104 patients, 31 patients (29.8%) had a 12-month volume reduction ratio (VRR) < 50.0% and 39 (37.5%) experienced nodule regrowth. Of these 39 patients, 17 (43.6%) underwent surgery and 14 (35.9%) underwent a second laser treatment. The rate of nodule regrowth was inversely related to the 12-month VRR, i.e., the lower the 12-month VRR, the higher the risk of regrowth (p < 0.001). The mean time for nodule regrowth was 33.5 ± 16.6 months. The 12-month VRR was directly related to time to regrowth, i.e., the lower the 12-month VRR, the shorter the time to regrowth (p < 0.001; R² = 0.3516). Non-spongiform composition increased the risk of regrowth with an odds ratio of 4.3 (95% confidence interval [CI] 1.8-10.2; p < 0.001); 12-month VRR < 50.0% increased the risk of regrowth with an odds ratio of 11.7 (95% CI 4.2-32.2; p < 0.001). Conclusion: The VRR of thyroid nodules subjected to similar amounts of laser energy varies widely and depends on the nodule composition; non-spongiform nodules are reduced to a lesser extent and regrow more frequently than spongiform nodules. A 12-month VRR < 50.0% is a predictive risk factor for regrowth and correlates with the time to regrowth.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.5 no.6
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• pp.37-42
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• 2002

This study has been performed to investigate the physical and mechanical characteristics of compaction, volume change and compressive strength for reinforced soil mixed with polypropylene fiber, and to confirm the reinforcing effects with admixture such as polypropylene fiber. To this end, a series of compaction test and compression test was conducted for clayey soil(CL) and polypropylene fiber reinforced soil. In order to determine proper moisture contents and mixing ratio, pilot test was carried out for natural soil and PFRS(polypropylene fiber reinforced soil). And the mixing ratio of mono-filament fiber and fibrillated polypropylene fiber admixture was 0.1%, 0.3%, 0.5% and 1.0% by the weight of dry soil. From the experimental results, it was found that the optimum moisture contents(OMC) increased with the mixing ratio of fiber, but the maximum dry unit weight and the volume change was decreased with the mixing ratio. It means that the improvement of the workability and the reduction of the weight of embankment was done by the addition of the polypropylene fiber. And, from the compression test results, it was found that the addition of the polypropylene fiber remarkably improved the compressive strength of PFRS. And it was observed in the viewpoint of strength that the fibrillated polypropylene fiber reinforced soil was more effective than the mono-filament polypropylene fiber reinforced soil.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.7-10
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• 2003

The amount of coal ash has been increasing and development of effective use is urgently needed. Various by-products and waste are expected to be used as resources from the point of reduction in environmental load. This is an experimental study to compare the properties of high volume coal ash concrete using the reclaimed coal ash. For this purpose, the mix proportion of concrete according to the content ratio of below 5mm reclaimed coal ash (0.65, 0.70, 0.75 and 0.80). And then air content, slump, compressive strength test were performed. According to test results, it was found that the compressive strength of reclaimed coal ash concrete was similar to the content ratio of below 5mm reclaimed coal ash. And the slump of reclaimed coal ash concrete decreased as the content ratio of below 5mm.

• Journal of Korean Neurosurgical Society
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• v.42 no.5
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• pp.371-376
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• 2007

Objective : Balloon kyphoplasty can effectively relieve the symptomatic pain and correct the segmental deformity of osteoporotic vertebral compression fractures. While many articles have reported on the effectiveness of the procedure, there has not been any research on the factors affecting the deformity correction. Here, we evaluated both the relationship between postoperative pain relief and restoration of the vertebral height, and segmental kyphosis, as well as the various factors affecting segmental deformity correction after balloon kyphoplasty. Methods : Between January 2004 and December 2006, 137 patients (158 vertebral levels) underwent balloon kyphoplasty. We analyzed various factors such as the age and sex of the patient, preoperative compression ratio, kyphotic angle of compressed segment, injected PMMA volume, configuration of compression, preoperative bone mineral density (BMD) score, time interval between onset of symptom and the procedure, visual analogue scale (VAS) score for pain rating and surgery-related complications. Results : The mean postoperative VAS score improvement was $4.93{\pm}0.17$. The mean postoperative height restoration rate was $17.8{\pm}1.57%$ and the kyphotic angle reduction was $1.94{\pm}0.38^{\circ}$. However, there were no significant statistical correlations among VAS score improvement, height restoration rate, and kyphotic angle reduction. Among the various factors, the configuration of the compressed vertebral body (p=0.002) was related to the height restoration rate and the direction of the compression (p=0.006) was related with the kyphotic angle reduction. The preoperative compression ratio (p=0.023, p=0.006) and injected PMMA volume (p<0.001, p=0.035) affected both the height restoration and kyphotic angle reduction. Only the preoperative compression ratio was found to be as an independent affecting factor (95% CI : 1.064-5.068). Conclusion : The two major benefits of balloon kyphoplasty are immediate pain relief and local deformity correction, but segmental deformity correction achieved by balloon kyphoplasty does not result in additional pain relief. Among the factors that were shown to affect the segmental deformity correction, configuration of the compressed vertebral body, direction of the most compressed area, and preoperative compression ratio were not modifiable. However, careful preoperative consideration about the modifiable factor, the PMMA volume to inject, may contribute to the dynamic correction of the segmental deformity.

• Journal of Korean Society on Water Environment
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• v.30 no.1
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• pp.87-94
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• 2014

According to the technical guideline of water pollutant load management, the rainfall captured ratio which can be estimated by the empirical formula is an important element to estimate reduction loads of non-point pollutants water quality control basin. In this study, the rainfall captured ratio is altered to stormwater captured ratio considering its meaning in the technical guideline of water pollutant load management, and the new empircal formula of stormwater captured ratio is suggested. In order to do this, we calculate stormwater captured ratio by using the hourly rainfall data of seven urban weather stations (Busan, Daegu, Daejeon, Gangreung, Seoul, Gwangju, and Jeju) for 43 years. The regression coefficients of the existed empirical formula cannot reflect the catchment properties at all, because they are fixed values regardless of regions. However the empirical formula of stormwater captured ratio has flexible regression coefficients by runoff coefficient(C), so it is allowed to consider the characteristics of runoff in catchment. It is expected that reduction loads of storage based water quality control basin can be more reasonably estimated than before.

• Composites Research
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• v.13 no.2
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• pp.40-50
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• 2000

In an effort to construct a structure under the design principle of minimal use of materials for maximum performances, a discrete gradient structure has been introduced in laminate composite systems. Using a sequential linear programming method, the gradient structure of composites to maximize the buckling load was optimized in terms of fiber volume fraction and thickness of each layer. The buckling load showed maximum value with the outmost [$0^{\circ}$] layer concentrated by almost all the fibers when the ratio of length to width(aspect ratio) was less than 1.0. But when the aspect ratio was 2.0, the optimum was determined in a structure where the thickness and fiber volume fraction were well-balanced in each layer. From the optimization of gradient structure, the optimal fiber volume fraction and thickness of each layer were proposed. Gradient structures have also shown an advantage in the weight reduction of composites compared with the conventional homogeneous structures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.6
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• pp.427-434
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• 2009

A new surface shape of an internal cooling passage which largely reduces the pressure drop and enhances the surface heat transfer is proposed in the present study. The surface shape of the cooling passage is consisted of the concave dimple and the riblet inside the dimple which is protruded along the stream-wise direction. Direct Numerical Simulation (DNS) for the fully developed turbulent flow and thermal fields in the cooling passage is conducted. The numerical simulations for five different surface shapes are conducted at the Reynolds number of 2800 based on the mean bulk velocity and channel height and Prandtl number of 0.71. The driving pressure gradient is adjusted to keep a constant mass flow rate in the x direction. The thermoaerodynamic performance for five different cases used in the present study was assessed in terms of the drag, Nusselt number, Fanning friction factor, volume and area goodness factor in the cooling passage. The value of maximum ratio of drag reduction is -22.86 %, and the value of maximum ratio of Nusselt number augmentation is 7.05% when the riblet angle is $60^{\circ}$. The remarkable point is that the ratio of Nusselt number augmentation has the positive value for the surface shapes which have over $45^{\circ}$ of the riblet angle. The maximum volume and area goodness factors are obtained when the riblet angle is $60^{\circ}$.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2465-2470
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• 2008

A new surface shape of an internal cooling passage which largely reduces the pressure drop and enhances the surface heat transfer is proposed in the present study. The surface shape of the cooling passage is consisted of the concave dimple and the riblet inside the dimple which is protruded along the stream-wise direction. Direct Numerical Simulation (DNS) for the fully developed turbulent flow and thermal fields in the cooling passage is conducted. The Numerical simulations for the 5 different surface shapes are conducted at the Reynolds number of 2800 based on the mean bulk velocity and channel height and Prandtl number of 0.71. The driving pressure gradient is adjusted to keep a constant mass flow rate in the x direction. The thermo-aerodynamic performance for the 5 different cases used in the present study was assessed in terms of the drag, Nusselt number, Fanning friction factor, Volume and Area goodness factor in the cooling passage. The value of maximum ratio of drag reduction is -22.86 [%], and the value of maximum ratio of Nusselt number augmentation is 7.05 [%] when the riblet angle is $60^{\circ}$ (Case5). The remarkable point is that the ratio of Nusselt number augmentation has the positive value for the surface shapes which have over $45^{\circ}$ of the riblet angle. The maximum Volume and Area goodness factor are obtained when the riblet angle is $60^{\circ}$ (Case5).

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.50 no.2
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• pp.176-184
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• 2014

Nowadays, consumption of fisheries products is increasing. There are several factors, one of which is a quantitative development through aquaculture. Another factor is an increase qualitative consumption of fish which require that fish be supplied alive. This requires a lot of technical effort to transport the live fish that have low survival rate (c.f. tuna and mackerel) in coastal waters and in the open sea. To develop a towing cage for transporting the live fish, model test in a circulate water channel and simulation by computer tool were carried out. In order to spread vertically, floats were attached at the upper part of the cage, and iron chains attached at the lower part of the cage. For horizontal spreading, kites were attached on the cage. The tension and spreading performance of the cage were measured. The result shows that the tension and reduction ratio of inside volume of the cage were tended to increase with increased towing speeds. The suitable operation condition in towing cage was 1.0 m/s towing speeds with vertical spreading force 8.7 kN, horizontal spreading force 5.6 kN; in this case the reduction ratio of inside volume of the cage was estimated as 25%.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.58-65
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the combustion characteristics of stratified methane-air mixture under several initial charge conditions in the author's previous reports. The results showed that the improvement of thermal efficiency and reduction of heat loss was realized simultaneously by using 2-stage injection method. This paper deals with the reason why the stratified combustion has showed better combustion rate through the measurement and analysis of chemiluminescence of C $H^{*}$ and $C_{2}$$^{*}$ radicals. An optic fiber bundle is used to measure the local emission of C $H^{*}$ and $C_{2}$$^{*}$ radicals to map the relationship between the excess air ratio and local radical intensity ratio in the combustion vessel at 5 mm apart form the geometric center. The results show that there exist a relationship between the intensity ratio and the air-fuel ratio. It is revealed that the improvement of combustion rate in a lean-stratified mixture is realized through the 2-stage injection method. method.