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Plastic 광섬유용 GRIN ROD의 제조 및 그 광학특성에 관한 연구
한동근,임승순,김정엽,Han, Dong-Geun,Im, Seung-Sun,Kim, Jeong-Yeop 한국섬유공학회 1985 한국섬유공학회지 Vol.22 No.5
The photocopolymerization of methyl methacrylate(MMA) with vinyl benzoate(VB), using benzoyl peroxide(BPO) as an initiator, was carried out with UV irradiation to obtain a transparent GRIN rod. The resulting GRIN rod has a parabolic gradient of refractive index in the region near the center axis(radius Rc), and index-distribution constant A and the normalized radius Rc were measured by the reduction rate of an image and the view field of the rod lens. An increase in monomer feed ratio, MMA/VB(wt/wt) ranging from 2.5 to 5.0 results in the increase of A but the decrease of Rc. The value of A grew very high at BPO=1.0wt% and MMA/VB=4.0, and the value of Rc monotonically decreased with the BPO concentration. Elevation of the polymerization temperature caused the decrease in both A and Rc. The index distribution from the center to the periphery showed a similar shape, regardless to the sample compositions. The GRIN rod shows convex lens characteristics which are necessary properties in use of imaging and light-focusing devices.
한동근 영남대학교 지역발전연구소 2002 영남지역발전연구 Vol.29 No.-
We survey theories and cases on the relationship between real estate bubbles and the eruption of financial crisis. Georgists, who follows the Henry George's view that land speculation is the major force of economic depression, offer variety of mechanism through which real estate bubbles give rise to a financial turmoil. But the cause-effect relation goes to the other way around also. Easy monetary policy prompts banks to increase the credit supply, much of which goes to the real estate sector, resulting in bubbles. Once the bubbles pop out, the financial institutions suffer from huge bad loan. The paper summarizes modern theories that offer a micro foundation of why the commercial banks are prone to be overexposed to the real estate risks.
한동근,안광덕 한국생체재료학회 2005 생체재료학회지 Vol.9 No.1
Heart disease is presently the major cause of death worldwide, with heart valve disease being one of the crucial afflictions of the cardiovascular system. If valve malfunction occurs, surgical repair or replacement of the diseased valve with a heart valve prosthesis is necessary to restore valve function. An estimated 87,000 heart valve replacement procedures were performed in U.S.A. in 2000, whereas about 275,000 procedures are done globally each year. A numbers of models for heart valve substitutes for past 40 years have been studied and developed, but currently two prosthetic heart valves were commercialized and used clinically: mechanical and tissue (bioprosthetic) valves in which approximately 55% are mechanical and 45% are tissue. However, both types of heart valves have many major complications and problems until now that limit their prolong success. A number of researches are being progressed to regenerate the ideal heart valves using tissue engineering. In this article, the following will give each characteristics of 4 kinds of valves including polymeric heart valves, an update of the recent developments, and current aspects of tissue-engineered heart valves.