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- 저자 : Kutsuna, Kenji (검색결과 6 건)
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A Fair and Efficient Congestion Avoidance Scheme Based on the Minority Game
Kutsuna, Hiroshi,Fujita, Satoshi Korea Information Processing Society 2011 Journal of information processing systems Vol.7 No.3
In this paper, we propose a new congestion control scheme for high-speed networks. The basic idea of our proposed scheme is to adopt a game theory called, "Minority Game" (MG), to realize a selective reduction of the transmission speed of senders. More concretely, upon detecting any congestion, the scheme starts a game among all senders who are participating in the communication. The losers of the game reduce the transmission speed by a multiplicative factor. MG is a game that has recently attracted considerable attention, and it is known to have a remarkable property so that the number of winners converges to a half the number of players in spite of the selfish behavior of the players to increase its own profit. By using this property of MG, we can realize a fair reduction of the transmission speed, which is more efficient than the previous schemes in which all senders uniformly reduce their transmission speed. The effect of the proposed scheme is evaluated by simulation. The result of simulations indicates that the proposed scheme certainly realizes a selective reduction of the transmission speed. It is sufficiently fair compared to other simple randomized schemes and is sufficiently efficient compared to other conventional schemes.
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Study on the Performance of Laser Welded Joint of Aluminum Alloys for Car Body
Kutsuna, M.,Kitamura, S.,Shibata, K.,Sakamoto, H.,Tsushima, K. The Korean Welding and Joining Society 2002 International journal of Korean welding society Vol.2 No.2
Considering the fuel consumption of car, a light structure of aluminum alloys is desired fer car body nowadays. However, fusion welding of aluminum alloys has some problems of reduction of joint efficiency, porosity formation and hot cracking. In the present work, investigation to improve the joint performance of laser welded joint has been carried out by addition of Cu, Ni, and Zr to A6NO 1 alloy welds. Aluminum alloy plate of 2.Omm in thickness with filler metal bar was welded by twin beam Nd: YAG laser facility (total power: 5kW). The filler metals were prepared by changing the chemical compositions for adding the elements into the weld metal. Thirteen filler metal bars were prepared and pre-placed into the base metal before welding. Ar gas shielding with a flow rate of 10 1/min was used. The defocusing distance is kept at 0 mm. At travel speeds off 3 to 9 and at laser power of 5kW (front beam 2kW rear beam 3kW), full penetration welds were obtained, whereas at travel speeds of 12 to 18 m/min and same power, partial penetration was observed. The joint efficiency of laser-welded joint was improved by the addition of Cu, Ni, and Zr due to the solid solution hardening, grain refining and precipitation hardening. The type of hardening has been further considered by metallurgical examination.
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김경근,쿠츠나 켄지,Kim, KyungKeun,Kutsuna, Kenji The Korean Society of Business Venturing 2014 벤처창업연구 Vol.9 No.1
한국의 벤처캐피탈은 투자규모가 세계적인 수준이나 창업초기단계 벤처기업에 대한 투자가 미흡하고 첨단기술 분야 및 수도권에 투자가 집중된 데다 신규상장 및 M&A 시장의 높은 진입장벽 등으로 벤처캐피탈의 투자자금 회수 등이 어려운 상황이다. 첨단기술 벤처기업의 경우 투자자와 벤처기업간 정보의 비대칭성으로 투자자금 조달에 어려움을 겪을 수 있으나 벤처금융 선진국은 정부 자금지원시 시장과 민간투자자와의 연계, 해외 저명 벤처캐피탈사와의 공동투자 유도 등 다양한 유인설계(incentive mechanism design)를 통해 동 문제를 해결하고 있다. 이러한 점들을 감안하여 우리 정부 및 지자체는 민간부문과의 공동펀드 확대, 지역별로 특화된 매칭펀드 조성, M&A 등 벤처캐피탈사의 출구경로 다양화 등을 통해 창업벤처생태계를 개선하는 데 주력할 필요가 있으며, 벤처캐피탈사도 외국 벤처캐피탈사와의 공동투자 등을 통해 투자대상 기업선정 및 가치증대 활동에 노력을 경주할 필요가 있다. Though South Korea has world-class volume of Venture Capital Investment, as a share of GDP, early stage venture investments are still short, and investments are concentrated in high technology area and Capital area. Because of the high barriers to entry of the new IPO and M&A market, the venture capital companies undergo difficulties in profit. High-tech ventures face difficulties in raising money from outside investors due to information asymmetry between venture investors and venture companies. To resolve these problems, developed countries's government make a co-funding investment scheme with private sectors and design incentive mechanism such as receiving knowledge of the reputable investors' joint venture. Korean central and local government can benchmark those of things. For example, the expansion of the investment volume with private sector, region-specific matching fund and venture capital's exit path diversification such as M&A through the establishment of a business venture eco-system. At the same time, venture companies are to make an efforts to enhance the ability of screening for venture companies and the value for investment activities through a joint venture investments.
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김종도(Jong-Do Kim),무네하루 쿠쯔나(Muneharu KUTSUNA),유지 사노(Yuji SANO) 대한용접·접합학회 2015 대한용접·접합학회지 Vol.33 No.4
Advances in laser technology have yielded a multitude of innovative processes and applications in various industries. Laser peening is a typical example invented in the mid-1990s as a surface technology, which converted residual stress from tension to compression by just irradiating successive laser pulses to metallic materials under aqueous environment without any surface preparation. The effects of laser peening have been experimentally studied on residual stress, stress corrosion cracking(SCC) susceptibility and fatigue properties with water-penetrable frequency-doubled Nd:YAG laser. In addition, laser peening has been widely used in aviation and aerospace industries, automobile manufacturing and nuclear plant. One of the most important causes to improve the above-mentioned properties is the deeper compressive residual stress induced by laser peening. Taking advantage of the process without reacting force against laser irradiation, a remote operating system was developed to apply laser peening to nuclear power reactors as a preventive maintenance measure against SCC.
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