• 정보과학회 논문지
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• 제43권10호
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• pp.1073-1078
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• 2016

정수로 표현된 문자열에 대한 (${\delta}$, ${\gamma}$)-매칭은 음악서열이나 주가 연구에 응용될 수 있다. 본 논문에서는 정수문자집합에 대한 문자열의 ${\delta}$-근사주기와 ${\gamma}$-근사주기의 개념을 제시한다. 또한 최소 ${\delta}$-근사주기와 최소 ${\gamma}$-근사주기를 각각 $O(n^2)$ 시간에 찾는 알고리즘들을 제시하고 수행시간을 측정한 결과를 보인다.

• 정보과학회 논문지
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• 제44권8호
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• pp.760-766
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• 2017

반복적인 문자열은 데이터압축, 생물정보학 등 여러 분야에서 연구되어 왔다. 본 논문에서는 음악서열이나 주가지수와 같이 정수로 표현될 수 있는 문자열에 대한 반복에 대해 연구한다. 최근 정수문자열의 최소 ${\delta}$-근사주기와 최소 ${\gamma}$-근사주기를 찾는 문제들이 소개되었고, 문자열의 길이가 n일 때, 두 문제를 각각 $O(n^2)$ 시간에 해결하는 알고리즘들이 제시되었다. 본 논문에서는 위의 두 문제에 대해 각각 $O(n^2)$개의 스레드를 이용하여 O(n) 시간에 해결하는 병렬알고리즘을 제시한다. 실험결과, n = 10,000일 때, 본 논문에서 제시하는 병렬알고리즘은 순차알고리즘보다 최소 ${\delta}$-근사주기를 계산하는데 약 19.7배, 최소 ${\gamma}$-근사주기를 계산하는데 약 40.08배 빠른 수행시간을 보였다.

• Journal of Astronomy and Space Sciences
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• 제29권2호
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• pp.151-161
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• 2012

An intensive analysis of 148 timings of V700 Cyg was performed, including our new timings and 59 timings calculated from the super wide angle search for planets (SWASP) observations, and the dynamical evidence of the W UMa W subtype binary was examined. It was found that the orbital period of the system has varied over approximately $66^y$ in two complicated cyclical components superposed on a weak upward parabolic path. The orbital period secularly increased at a rate of $+8.7({\pm}3.4){\times}10^{-9}$ day/year, which is one order of magnitude lower than those obtained by previous investigators. The small secular period increase is interpreted as a combination of both angular momentum loss (due to magnetic braking) and mass-transfer from the less massive component to the more massive component. One cyclical component had a $20.^y3$ period with an amplitude of $0.^d0037$, and the other had a $62.^y8$ period with an amplitude of $0.^d0258$. The components had an approximate 1:3 relation between their periods and a 1:7 ratio between their amplitudes. Two plausible mechanisms (i.e., the light-time effects [LTEs] caused by the presence of additional bodies and the Applegate model) were considered as possible explanations for the cyclical components. Based on the LTE interpretation, the minimum masses of 0.29 $M_{\odot}$ for the shorter period and 0.50 $M_{\odot}$ for the longer one were calculated. The total light contributions were within 5%, which was in agreement with the 3% third-light obtained from the light curve synthesis performed by Yang & Dai (2009). The Applegate model parameters show that the root mean square luminosity variations (relative to the luminosities of the eclipsing components) are 3 times smaller than the nominal value (${\Delta}L/L_{p,s}{\approx}0.1$), indicating that the variations are hardly detectable from the light curves. Presently, the LTE interpretation (due to the third and fourth stars) is preferred as the possible cause of the two cycling period changes. A possible evolutionary implication for the V700 Cyg system is discussed.