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Effect of Cathode Flow Field Configuration on Air- Breathing Proton Exchange Membrane Fuel Cell
장웅기,최종필,서영호,김병희 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
Air-breathing proton exchange membrane fuel cells (AB-PEMFCs) have been known to reduce the cost, complexity, noise, volume, and weight of fuel cells and can enhance their reliability. However, AB-PEMFCs still have some crucial issues such as the depletion of local oxygen concentration adjacent to the cathode in the absence of convection and hydrogen starvation at the anode side caused by the improper mass and water management in the dead-end mode. To manage mass and water efficiently, the effect of the opening ratio of the cathode opening geometry was investigated by considering the effects of the reaction area and contact resistance. When the opening ratio of the air flow field increased, the cell performance improved. However, at the high opening ratio of 72%, even though the voltage did not drop as quickly at high current densities as that at a low opening ratio, the cell performance was lower than that at the low opening ratio. And the slit-type fuel cells showed better performance by comparing the performances of the slit and square types of the cathode opening geometry. By introducing mesoscale channels on the flow field surface of the cathode, the formation of water droplets on the gas diffusion layer was minimized considerably.
하이드로겔과 미세유체채널을 이용한 단속적 약물 공급소자
장웅기,서영호,김병희 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.3
In this study, we propose a device that uses the expansive force of a hydrogel to inject a small amount of a drug over a long duration. The proposed microfluidic drug injection device has a hydrogel in the injection chamber. The expansive force of the hydrogel provides the injection pressure to control the drug injection period, time required for supplying water to the hydrogel, and hydrogel expansion time. The use of a hydrogel is difficult due to its powdery texture. Hence, the hydrogel was mixed with polydimethylsiloxane (PDMS) and converted into hydrogel disks. A stop valve was also designed to generate flow resistance in the microfluidic device, which supplies water to the hydrogel. The drug injection intermittently supplied the hydrogel’s expansive force along with the drug, with ~2.1 ㎕ of the drug being administered. Results demonstrate that the hydrogel expansive force can be used to achieve intermittent drug supply.
하부요관결석의 자연배출을 위한 이뇨제, 알파차단제, 부신피질 호르몬제 삼중요법의 효과
장웅기,홍영권 대한비뇨의학회 2008 Investigative and Clinical Urology Vol.49 No.11
Purpose: We prospectively evaluated the efficacy of administering tamsulosin with or without deflazacort, combined with furosemide, for treating distal ureteral stones. Materials and Methods: A total of 241 patients with symptomatic distal ureteral stones were enrolled in this study between January 2004 and September 2007. They were divided into three treatment groups: group A(n=42) who received furosemide(40mg/day), group B(n=66) who received furosemide and tamsulosin(0.4mg/day) and group C(n=72) who received furosemide and tamsulosin plus deflazacort(24mg/day) for a maximum of 2 weeks. Follow-up visits were made at the 1st and the 2nd week after all the medication had been administered. The efficacy was evaluated in terms of the success rate and the time for achieving expulsion after administering the medication, according to the stone size. Results: The three groups were comparable in terms of age, gender and stone size. The stone diameter was 4.90±0.47mm for group A, 5.08±0.30mm for group B and 5.04±0.36mm for group C. The overall success rate was 64.3%, 80.3% and 91.7%, respectively, and the differences were statistically significant(p=0.001). The mean expulsion time for the smaller stones (<5mm) was 9.13 days, 6.25 days and 5.43 days for each group, respectively, while that for the larger stones(≥5mm) was 10.25 days, 8.93 days and 7.32 days, respectively, and the values for both sized stones showed statistically significant differences(p=0.027 for the smaller stones, 0.018 for the larger stones). There was no serious adverse event associated with the medication. Conclusions: Medical expulsive therapy with tamsulosin and deflazacort combined with furosemide is a time saving, safe and effective method for treating distal ureter stone. Purpose: We prospectively evaluated the efficacy of administering tamsulosin with or without deflazacort, combined with furosemide, for treating distal ureteral stones. Materials and Methods: A total of 241 patients with symptomatic distal ureteral stones were enrolled in this study between January 2004 and September 2007. They were divided into three treatment groups: group A(n=42) who received furosemide(40mg/day), group B(n=66) who received furosemide and tamsulosin(0.4mg/day) and group C(n=72) who received furosemide and tamsulosin plus deflazacort(24mg/day) for a maximum of 2 weeks. Follow-up visits were made at the 1st and the 2nd week after all the medication had been administered. The efficacy was evaluated in terms of the success rate and the time for achieving expulsion after administering the medication, according to the stone size. Results: The three groups were comparable in terms of age, gender and stone size. The stone diameter was 4.90±0.47mm for group A, 5.08±0.30mm for group B and 5.04±0.36mm for group C. The overall success rate was 64.3%, 80.3% and 91.7%, respectively, and the differences were statistically significant(p=0.001). The mean expulsion time for the smaller stones (<5mm) was 9.13 days, 6.25 days and 5.43 days for each group, respectively, while that for the larger stones(≥5mm) was 10.25 days, 8.93 days and 7.32 days, respectively, and the values for both sized stones showed statistically significant differences(p=0.027 for the smaller stones, 0.018 for the larger stones). There was no serious adverse event associated with the medication. Conclusions: Medical expulsive therapy with tamsulosin and deflazacort combined with furosemide is a time saving, safe and effective method for treating distal ureter stone.