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Sol-Gel법에 의한 Thermochromic 박막 제조
장원식,김석범,강승구,조동수 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.1
$VO_2$ thin films have been prepared on borosilicate glass substrate using alkoxide method to characterize the effects of fabricating factors on thermochromic performance. The gel films formed by spin coating were converted to $V_2O_5$ phase during oxidizing heat-tratment and the $VO_2$ phase were formed by reducing heat-treatement. The thermochromic switching properties of $VO_2$ thin films are strongly affected by the crystal phase and microstructure and those could be controlled by reducing heat-treatment conditions. The ther-mochromic switching characteristics of $VO_2$ thin films synthesized were measured at IR (2.5$\mu\textrm{m}$) as the transition temperature of $63^{\circ}C$ the transition width of $3.6^{\circ}C$and the maximum and minimum transmittance of 84% and 14% respectively.
장원식,최경화,양승철,한웅규 대한비뇨의학회 2011 Investigative and Clinical Urology Vol.52 No.4
Purpose: Percutaneous nephrolithotomy (PCNL) is conventionally conducted in the prone position. However, the prone position increases anesthesia-related morbidity and position changes lengthen the operation time. We report perioperative outcomes and the learning curve for flank PCNL on the basis of a single surgeon’s experience. Materials and Methods: This study investigated 53 cases of flank PCNL performed for renal stones at our institution from April 2008 to September 2010. We compared mean operative time, stone-free rate, drop in hemoglobin level, length of hospital stay, complications, and need for additional procedures after the surgery. The 53 cases were divided into three groups by case number to compare therapeutic effect, stability, and the learning curve for flank position PCNL. Results: The mean operation time for the 53 patients was 97.3±43.1 minutes. The mean operation time gradually decreased as the surgeon accumulated experience. From the 36th case, the mean operation time showed a statistically significant decrease to 72.2± 24.1 minutes (p=0.003). The overall stone-free rate was 64.2% for all procedures (range, 61.1-76.5%). There were no significant differences in the drop in hemoglobin level, stone-free rate, re-treatment, hospital stay, or complication rate. There was no injury to the bowel or renal vessels, and no other major complications occurred. Conclusions: Flank PCNL can be used to remove renal stones effectively while overcoming the disadvantages of the existing prone position PCNL. After 36 cases, the learning curve showed acquisition of surgical competence. The clinical experience reported here suggests that flank PCNL is a safe and feasible technique.
Prediction of Stent Failure for Malignant Ureteral Obstruction in Non-Urological Cancer
장원식,허지은,전대영,이종수,한현호 연세대학교의과대학 2023 Yonsei medical journal Vol.64 No.11
Purpose: To analyze prognostic factors associated with ureteral stent failure and to develop a prediction model for malignant ure teral obstruction (MUO) in patients with non-urological cancers. Materials and Methods: We retrospectively reviewed patients with non-urological cancers who underwent ureteral stenting or percutaneous nephrostomy (PCN) for MUO between 2006 and 2014. Variables predicting stent failure were identified using Cox regression analysis. Results: Of the 743 patients, 468 (63.0%) underwent ureteral stenting only, and 275 (37.0%) underwent PCN owing to technical (n=215) or functional (n=60) stent failure. The median overall survival was 4 [interquartile range (IQR) 1–11] months, and the me dian interval duration to stent failure was 2 (IQR 0–7) months. In univariate analysis, lower gastrointestinal cancer, previous radio therapy to the pelvis, bladder invasion, lower ureteral obstruction, and low previous estimated glomerular filtration rate (eGFR) (<30 mL/min/1.73 m2) were significantly associated with a decreased survival rate. In multivariate analysis, bladder invasion and previous eGFR were significant predictors. With these two predictors, we divided patients into three groups based on their pres ence: low-risk (neither factor; n=516), intermediate-risk (one factor; n=206), and high-risk (both factors; n=21). The median stent failure-free survival rates of patients in the low-, intermediate-, and high-risk groups were 26 (8-unreached), 1 (0–18), and 0 (0–0) months, respectively (p<0.001). Conclusion: In cases of ureteral obstruction caused by non-urological cancers, patients with bladder invasion and a low eGFR showed poor stent failure-free survival. Therefore, PCN should be considered the primary procedure for these patients.
기공이 있는 carbon 섬유강화 glass 복합재의 마모 거동
김석범,장원식 경기대학교 부설 산업기술종합연구소 1997 산업기술종합연구소 논문집 Vol.13 No.-
Wear test was carried out on the borosilicate glass with voids which was reinforced with continuous cabon fiber(Taekwang Ind., Acelan TZ-307) in one direction and high carbon chromium steel ball(SUJ-2) was used as a counterface. Wear properties were measured in 3 different directions between the wear direction and the reinforced fiber direction: parallel(P), anti-parallel (AP) and normal(N). Wear speed was fixed as 0.04 m/s, and 20Kgf, 25Kgf and 30Kg of loads were used. Ball-on-three flat wear tester was used with paraffin oil as a lubricant. Wear rate in the P direction was the biggest, the second was in the AP direction and the least was in the N direction under all different loads.