• Korean Journal of Radiology
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• 제24권8호
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• pp.761-771
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• 2023

Objective: To investigate the association among the electrode placement method, electrode type, and local tumor progression (LTP) following percutaneous radiofrequency ablation (RFA) for small hepatocellular carcinomas (HCCs) and to assess the risk factors for LTP. Materials and Methods: In this retrospective study, we enrolled 211 patients, including 150 males and 61 females, who had undergone ultrasound-guided RFA for a single HCC < 3 cm. Patients were divided into four combination groups of the electrode type and placement method: 1) tumor-puncturing with an internally cooled tip (ICT), 2) tumor-puncturing with an internally cooled wet tip (ICWT), 3) no-touch with ICT, and 4) no-touch with ICWT. Univariable and multivariable Cox proportional-hazards regression analyses were performed to evaluate the risk factors for LTP. The major RFA-related complications were assessed. Results: Overall, 83, 34, 80, and 14 patients were included in the ICT, ICWT, no-touch with ICT, and no-touch with ICWT groups, respectively. The cumulative LTP rates differed significantly among the four groups. Compared to tumor puncturing with ICT, tumor puncturing with ICWT was associated with a lower LTP risk (adjusted hazard ratio [aHR] = 0.11, 95% confidence interval [CI] = 0-0.88, P = 0.034). However, the cumulative LTP rate did not differ significantly between tumor-puncturing with ICT and no-touch RFA with ICT (aHR = 0.34, 95% CI = 0.03-1.62, P = 0.188) or ICWT (aHR = 0.28, 95% CI = 0-2.28, P = 0.294). An insufficient ablative margin was a risk factor for LTP (aHR = 6.13, 95% CI = 1.41-22.49, P = 0.019). The major complication rates were 1.2%, 0%, 2.5%, and 21.4% in the ICT, ICWT, no-touch with ICT, and no-touch with ICWT groups, respectively. Conclusion: ICWT was associated with a lower LTP rate compared to ICT when performing tumor-puncturing RFA. An insufficient ablation margin was a risk factor for LTP.

• 대한조선학회논문집
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• 제41권6호
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• pp.8-14
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• 2004

The numerical analysis of a waterjet propulsion system was performed to provide detail understanding of complicated flow phenomena including interactions of intake duct, rotor, stator, and contracted discharge nozzle. The incompressible RANS equations were solved on moving multiblocked grid system. To handle interface boundary between rotor and stator, the sliding multiblock method was applied. The numerical results were compared with experiments and good agreement was obtained. The complicated viscous flow features of the waterjet, such as secondary flow inside the intake duct, the recovery of axial flow by the role of the stator, and tip and hub vortex, etc. were well analyzed by the present simulation. The performance of thrust and torque was also predicted.

• Imaging Science in Dentistry
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• 제41권1호
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• pp.17-21
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• 2011

Purpose : The purpose of this study was to examine the patient- and treatment-related etiologic factors of external root resorption. Materials and Methods : This study consisted of 163 patients who had completed orthodontic treatments and taken the pre- and post-treatment panoramic and lateral cephalometric radiographs. The length of tooth was measured from the tooth apex to the incisal edge or cusp tip on the panoramic radiograph. Overbite and overjet were measured from the pre- and post-treatment lateral cephalometric radiographs. The root resorption of each tooth and the factors of malocclusion were analyzed with an analysis of variance. A paired t test was performed to compare the mean amount of root resorption between male and female, between extraction and non-extraction cases, and between surgery and non-surgery groups. Correlation coefficients were measured to assess the relationship between the amount of root resorption and the age in which the orthodontic treatment started, the degree of changes in overbite and overjet, and the duration of treatment. Results : Maxillary central incisor was the most resorbed tooth, followed by the maxillary lateral incisor, the mandibular central incisor, and the mandibular lateral incisor. The history of tooth extraction was significantly associated with the root resorption. The duration of orthodontic treatment was positively correlated with the amount of root resorption. Conclusion : These findings show that orthodontic treatment should be carefully performed in patients who need the treatment for a long period and with a pre-treatment extraction of teeth.

• Archives of Plastic Surgery
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• 제41권3호
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• pp.285-289
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• 2014

The composite anterolateral thigh flap with vascularized fascia lata has emerged as a workhorse at our institution for complex Achilles defects requiring both tendon and soft tissue reconstruction. Safe elevation of this flap, however, is occasionally challenged by absent or inadequate perforators supplying the anterolateral thigh. When discovered intraoperatively, alternative options derived from the same vascular network can be pursued. We present the case of a 74-year-old male who underwent composite Achilles defect reconstruction using a segmental rectus femoris myofascial free flap. Following graduated rehabilitation, postoperatively, the patient resumed full activity and was able to ambulate on his tip-toes. At 1-year follow-up, active total range of motion of the reconstructed ankle exceeded 85% of the unaffected side, and donor site morbidity was negligible. American Orthopaedic Foot and Ankle Society and Short Form-36 scores improved by 78.8% and 28.8%, respectively, compared to preoperative baseline assessments. Based on our findings, we advocate for use of the combined rectus femoris myofascial free flap as a rescue option for reconstructing composite Achilles tendon/posterior leg defects in the setting of inadequate anterolateral thigh perforators. To our knowledge, this is the first report to describe use of this flap for such an indication.

• 대한조선학회논문집
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• 제41권4호
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• pp.30-37
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• 2004

Flow characteristics of the inflow ahead of a rotating propeller attached to a container ship model were investigated using a two-frame PIV (Particle Image Velocimetry) technique. Ensemble-averaged mean velocity fields were measured at four different blade phases. The mean velocity fields show the acceleration of inflow due to the rotating propeller and the velocity deficit in the near-wake region. The axial velocity distribution of inflow in the upper plane of propeller is quite different from that in the lower plane due to the thick hull boundary layer. The propeller inflow also shows asymmetric axial velocity distribution in the port and starboard side. As the inflow moves toward the propeller, the effect of phase angle variation of propeller blade on the inflow becomes dominant. In the upper plane above the propeller axis the inflow has very low axial velocity and large turbulent kinetic energy, compared with the lower plane. The boundary layer developed along the bottom surface of stern hull forms a strong shear layer affecting vortex structure of the propeller near-wake.

• 동력기계공학회지
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• 제5권3호
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• pp.38-47
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• 2001

One stage axial type turbine is designed by mean-line analysis, streamline curvature method and blade design method using shape parameters. Tip and hub diameter of the turbine are 300mm and 206.4mm, respectively. The rotating speed is 1800RPM, and the output power is 1.4kW. The flow coefficient is 1.68 and the reaction factor at mean-line is 0.373. The number of stator and rotor of the turbine are 31 and 41, respectively. Mach number of stator exit flow near hub is 0.164. A test rig is developed for performance test to validate a developed design method. The experimental result shows that the maximum efficiency is obtained on the design point.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.41-46
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• 2002

Flow field downstream of an inducer was measured to see the flow and performance characteristics of a turbopump inducer. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow - without interaction of the inducer and the volute. A conventional 3-hole probe was used to measure the flow. At inducer exit axial component of absolute velocity decreased on hub region with decrease in flow rate. Tangential velocity component static pressure, and total pressure increased from hub to tip. Relative flow angle from tangential direction was a little higher than outlet blade angle at flow coefficient $\varphi$=0.087 and 0.073. Dynamic pressure was $53\%$ of the mean total pressure at inducer exit at $\varphi$=0.073.

• 열처리공학회지
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• 제8권4호
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• pp.318-325
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• 1995

Information of change of hardness values during applying load is needed often to control the quality of metal products efficiently, but the relation between applied stress and hardness has not been established. In this paper the theoretical relation between the rebound hardness and stress was examined briefly and the experiment was performed with some materials. Materials used in test were mild steel(SB41), 7-3 brass and copper, which were widely used in the commercial plants. Hardness was measured during stress applied using the Equo-Tip hardness tester as a kind of rebound hardness tester. Hardness values decreased as tensile stress increased, the decreasing rate was effected by the Young's modulus of each material, and the rebound hardness values showed linear relationship with the applied stress in elastic region.

• 유공압시스템학회논문집
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• 제8권2호
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• pp.36-41
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• 2011

Analysis of two-dimensional flow in an involute gear pump has been done by using FLUENT. Analysis extended to the turbulent flow includes the mass flow rate with functions of pressure difference between inlet and outlet, rotational velocities of involute gear, and clearances between tip of gear and housing. In general mass flow rate decreases with decreasing rotational velocity, and with increasing clearance and pressure difference. The flow rate efficiency of gear pump, which is defined with the theoretical flow rate, has been presented in terms of the above parameters.

• 산업기술연구
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• 제21권A호
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• pp.41-50
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• 2001

A comparison is made of the temperature distribution and heat loss from a trapezoidal profile fin using two different 3-dimensional methods. These two methods are analytical and finite difference methods. In the finite difference method 78 nodes are used for a fourth of the fin. A trapezoidal profile fin being the height of the fin tip is half of that of the fin base is chosen arbitrarily as the model. One of the results shows that the relative error in the total convection heat loss obtained by using 78 nodes in the finite difference method as compared to the heat conduction through the fin root obtained by analytic method seems to be good (i.e., -3.5%