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고분자 전해질 연료전지 하이브리드 무인 비행기의 설계, 제어, 평가 기법 리뷰
차문용,김민진,손영준,양태현 한국수소및신에너지학회 2014 한국수소 및 신에너지학회논문집 Vol.25 No.4
Fuel cells are suitable for a power plant of a unmanned aerial vehicle (UAV) as it is not onlyenvironmentally friendly and quiet but also more efficient than an internal combustion engine. A fuel cell hybridUAV has better performance in endurance than a fuel cell only or battery only UAV. One of the key purposesof making fuel cell hybrid UAVs is having long endurance and now maximum 26 hours of flight is possible. Because optimal design and control methods for fuel cell hybrid UAVs are absolutely needed for their longendurance we have to check the methods. The aircraft made by using application-integrated design method hasless BOP mass and better performances. The optimal design and control methods are generally based on computersimulations or Hardware-In-The-Loop simulations by using dynamic models for their design and control. TheHardware-In-The-Loop simulation (HILS) is to use a hardware device like a fuel cell stack as well as a simulationprogram and it allows for making optimally designed applications. This paper introduce efficient methods of design,control and evaluation for the fuel cell hybrid UAVs.
Patterns of International Trade and a Nation’s Wealth
이덕선,차문용,이재우 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.3
The characteristics of global wealth distributions are correlated with the patterns of international trade. To understand this relationship, we analyzed data sets on world trade and the gross domestic products (GDP) of 190 countries from 1950 to 2000. We found that trade volumes and wealth were unevenly distributed and that they were positively correlated. Interestingly, the trade volumes turn out to be more strongly affected by the wealth of the importing countries than that of the exporting ones, which may be relevant to the wealth distribution. We set up and simulated a simple agentbased model for money-exchange systems and found that broad wealth distributions could emerge under an asymmetric money flow.
Persistent and Survival Properties in a Stock Market Index
이재우,차문용,맹성은,방유식 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.56 No.3
We consider the persistent and the survival properties of the Korean stock market index (KOSPI),and investigate the crossing and the persistence probability for a time series of the KOSPI. The crossing probability of the stock index follows a power law, Y (t) ~t−α. The Korean stock market shows weak antipersistent behavior. We also report the survival probability of the stock index. The survival probability S(t) measures the probability of a stock’s price remaining above (or below) a reference value up to a time to + t. We observed that the survival probability in the Korean stock market followed a power law, S(t) ~ -β, where the exponent depended on the reference level. The persistence and the survival of the stock index comes from the correlated memory of the stock index in the market.
Effects of Intraday Patterns on a Time Series Analysis of the Korean Stock Market Index
김두환,맹성은,방유식,최형욱,차문용,이재우 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.2
The effects of intraday patterns were considered in a time series analysis of the Korean stock market. One minute tick data from January 2, 2004, to October 30, 2009, on the Korea composite stock price index were studied. The autocorrelation function (ACF) of the absolute return and the probability distribution function (PDF) of returns were calculated by using a time series with the intraday patterns removed. Two methods of eliminating the intraday patterns are suggested: elimination from the index itself and from the absolute returns. The ACF of the absolute return showed a power law with an exponent that did not vary with the method used to eliminate the intraday patterns. Eliminating intraday patterns from the absolute return removed the periodicity of the ACF. However, the periodicity remained if intraday patterns were removed from the index itself. The PDF of returns showed a power law, but its exponents depended on the method of removing the intraday patterns.