• Proceedings of the Korean Magnestics Society Conference
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• 1994.10a
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• pp.56-57
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• 1994

• Proceedings of the Korean Magnestics Society Conference
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• 1996.10a
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• pp.90-91
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• 1996

• Proceedings of the Korean Society of Laser Processing Conference
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• 2002.11a
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• pp.105-108
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• 2002

• Bulletin of the Korean Chemical Society
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• v.22 no.8
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• pp.914-916
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• 2001

• Korean Journal of Clinical Pharmacy
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• v.20 no.2
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• pp.159-164
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• 2010

Radiofrequency ablation (RA) is being used to manage atrial fibrillation (AF) with patients failed at the $1^{st}$-line anti-arrhythmic medications. Patients undergoing this procedure are at increased risk of thromboembolism after ablation, and anticoagulation management surrounding the ablation remains controversial. Although no conclusive recommendations can be made, published guidelines and data support therapeutic anticoagulation with warfarin. The purpose of this study was to analyze effectiveness of current therapy and to find factors fluctuate International Normalized Ratio (INR) values in patients undergone RA followed by anticoagulation service (ACS). Retrospective review was conducted utilizing database in a hospital. Among 110 patients under warfarin around ablation between January 2006 to September 2007, 54 patients were selected and allocated into 2 groups: Group A included 47 who discontinued warfarin after ablation, while 7 in B continued the medication. Information on demographics, amount and length of warfarin dosing, INR values and measuring frequencies, and the causing factors on INR fluctuation were abstracted. Differences were analyzed using chi-squared test, Fisher's Exact test, and unpaired Student t-test. Mean amount of warfarin before and after surgery was 4.0 mg, 4.1 mg in Group A and was 5.1 mg, 4.6 mg in Group B, respectively. Average duration of warfarin doing before ablation was 73.7 days in Group A, 129.9 days in B with no significant difference (p = 0.312). The duration time of warfarin on groups after ablation lasted several months. The number of checking INRs was 4.1 and 7.6, respectively. Inter-individual variability of INR fluctuations were $2.1{\pm}0.6$ in Group A and $2.2{\pm}0.7$ in B which were not significantly different (p = 0.062). 164 cases of decreased INR were: 'omission in taking medication, stressfulness and headache, 'increased intake of high vitamin K foods', 'lifestyle change of increased physical activities', and 'increase of food-intakes'. To the contrary, 36 cases of increased INR were: 'reduce of food-intake', 'use of non-prescription drugs', 'reduction in physical activities', and 'excessive restriction on food-intake', consecutively. In conclusion, the study validated therapeutic outcomes of RA patients who we treated with standard guideline and demonstrated 9 factors of INR fluctuations in the patient. A well-trained, pharmacist-monitored anticoagulation service could reduce the risk of adverse effects and prevent complications in patients with AF around RA operation.

• Journal of Yeungnam Medical Science
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• v.24 no.2
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• pp.197-205
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• 2007

Background : The occurrence of atrial fibrillation after ablation of atrial flutter is clinically important. We investigated variables predicting this evolution in ablated patients without a previous atrial fibrillation history. Materials and Methods : Thirty-six patients (Male=28) who were diagnosed as atrial flutter without previous atrial fibrillation history were enrolled in this study. Group 1 (n=11) was defined as those who developed atrial fibrillation after atrial flutter ablation during 1 year follow-up. Group 2 (n=25) was defined as those who has not occurred atrial fibrillation during same follow-up term. Echocardiogram was performed to all patients. We measured left atrial size, left ventricle end diastolic and systolic dimension, ejection fraction and left atrial volume index before and after ablation of atrial flutter. The differences of each variables were compared and analyzed between two groups. Results : The preablation left ventricular ejection fraction (preLVEF) and postablation left ventricular ejection fraction (postLVEF) are $54{\pm}14%$, $56{\pm}13%$ in group 1 and $47{\pm}16%$, $52{\pm}13%$ in group 2. The differences between each two groups are statistically insignificant ($2.2{\pm}1.5$ in group 1 vs $5.4{\pm}9.8$ in group 2, p=0.53). The preablation left atrial size (preLA) and postablation left atrial size (postLA) are $40{\pm}4mm$, $41{\pm}4mm$ in group1 and $44{\pm}8mm$, $41{\pm}4mm$ in group 2. The atrial sizes of both groups were increased but, the differences of left atrial size between two groups before and after flutter ablation were statistically insignificant ($0.6{\pm}0.9mm$ in group 1 vs $-3.8{\pm}7.4mm$ in group 2, p=0.149). The left atrial volume index before flutter ablation was significantly reduced in group 1 than group 2 ($32{\pm}10mm^3/m^2$, $35{\pm}10mm^3/m^2$ in group 1 and $32{\pm}10mm^3/m^2$, $29{\pm}8mm^3/m^2$ in group 2, p<0.05). Conclusion : The difference between left atrial volume index before and after atrial flutter ablation is the robust predictor of occurrence of atrial fibrillation after atrial flutter ablation without previous atrial fibrillation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.119-122
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• 2005

Ablation phenomena is very complicated because it includes momentum, energy and mass transfer, chemical reactions as well as phase change. In this paper, ablation at the rocket nozzle throat is modeled as unsteady one dimensional axi-symmetric with proper boundary conditions and field equation is solved numerically. Analytical results are compared with measured ablation data from firing experimental liquid rocket engine. Test variables are combustion pressure and mixture ratio. for low combustion pressure and low mixture ratio, the discrepancy between analysis and experiments are large but for the normal rocket operation range, two results show a simliar trend with maximum discrepancy of $100\%$.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.11
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• pp.17-23
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• 2010

Titanium alloy is one of the hard processing materials made by the traditional manufacturing method because of the excellent mechanical strength. Ablation of titanium alloy is investigated by using a femtosecond laser which is a regenerative amplified Ti:sapphire laser with 1kHz repetition rate, 184fs pulse duration time and 785nm wavelength. Experiments are carried out under various ablation conditions with different pulse overlap ratios for the rectangular shape and micro hole. Test results show that the ablation characteristic according to pulse overlap ratio of titanium alloy seems to be as non-linear type at the different zone of energy fluence. The optimal condition of rectangular shape processing is obtained at the laser peak power 1.3mW, pulse overlap ratio of 90%, beam gap of $1\;{\mu}m$. The micro hole has a good quality from the pulse overlap ratio of 99% at the same laser peak power. With the optimal processing condition, the fine rectangular shape and micro hole without burr and thermal damage are achieved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.311-314
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• 2009

A two-dimensional thermal response and ablation simulation code for predicting charring material ablation and shape change on solid rocket nozzle is presented. For closing the problem of thermal analysis, Arrhenius' equation and Zvyagin's ablation model are used. The moving boundary problem and endothermic reaction in thermal decomposition are solved by rezoning and effective specific heat method. For simulation of complicated thermal protection systems, this method is integrated with a three-dimensional finite-element thermal and structure analysis code through continuity of temperature and heat flux.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1572-1577
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• 2003

High-power pulsed laser ablation under atmospheric pressure is studied utilizing numerical and experimental methods with emphasis on recondensation ratio, and the dynamics of the laser induced vapor flow. In the numerical calculation, the temperature pressure, density and vaporization flux on a solid substrate are first obtained by a heat-transfer computation code based on the enthalpy method, and then the plume dynamics is calculated by using a commercial CFD package. To confirm the computation results, the probe beam deflection technique was utilized for measuring the propagation of a laser induced shock wave. Discontinuities of properties and velocity over the Knudsen layer were investigated. Related with the analysis of the jump condition, the effect of the recondesation ratio on the plume dynamics was examined by comparing the pressure, density, and mass fraction of ablated aluminum vapor. To consider the effect of mass transfer between the ablation plume and air, unlike the most previous investigations, the equation of species conservation is simultaneously solved with the Euler equations. Therefore the numerical model computes not only the propagation of the shock front but also the distribution of the aluminum vapor. To our knowledge, this is the first work that employed a commercial CFD code in the calculation of pulsed ablation phenomena.