We present the results of new multi-color CCD photometry for the contact binary XZ Leo, together with reasonable explanations for the period and light variations. Six new times of minimum light have been determined. A period study with all available timings confirms Qian's (2001) finding that the O-C residuals have varied secularly according to dP/dt = +8.20×10-8 d yr-l. This trend could be interpreted as a conservative mass transfer from the less massive cool secondary to the more massive hot primary in the system with a mass flow rate of about 5.37×10-8 M⊙ yr-l. By simultaneous analysis of our light curves and the previously published radial-velocity data, a consistent set of light and velocity parameters for XZ Leo is obtained. The small differences between the observed and theoretical light curves are modelled by a blue third light and by a hot spot near the neck of the primary component. Our period study does not support the tertiary light but the hot region which may be formed by gas streams from the cool secondary. The solution indicates that XZ Leo is a deep contact binary with the values of q=0.343, i=78°.8, Δ (T1-T2)=126 K, and f=33.6 %, differing much from those of Niarchos et al. (1994). Absolute parameters of XZ Leo are determined as follows: M1=1.84 M⊙, M2=0.63 M⊙, R1=1.75 R⊙, R2=1.10 R⊙, L1=7.19 L⊙, and L2=2.66 L⊙.

We completed four color light curves of the near-contact binary CN And during three nights from September to December 2004 using the 61-cm reflector and BV RI filters at Sobaeksan Observatory. We determined four new times of minimum light (two timings for primary eclipse, two for secondary). Newly obtained BV RI light curves and the radial velocity curves from Rucinski et a1. (2000) were simultaneously analyzed to derive the system parameters of CN And. We used the semi-detached mode 4 of the 2003-version of the Wilson-Devinney binary model, and interpreted the asymmetry of the light curve by introducing two spots; a cool spot on the primary component and a hot spot on the secondary component. New photometric parameters are not much different from those of Cicek et a1. (2005), and it is considered that the system is in the era of broken contact. From the orbital period study with all available timings including our data, we found a continous period decrease with a rate of Pobs = - -1.82 x 10-7 d yr-1 that can be explained with two possible mechanisms. We think the most likely cause of the period decrease is a thermal mass transfer from the primary to the secondary component, rather than angular momentum loss due to a magnetic stellar wind.

해상운송 서비스의 특수한 환경적 특성으로 인해 해운기업은 불확실한 경영환경에 노출되기 쉬우며, 환경 불확실성에 대응할 수 있는 적절한 경쟁전략을 활용하여 기업의 경영성과를 달성하는 것은 중요하다. 따라서 본 연구는 해운기업에서 높은 경영성과 달성을 위해 환경 불확실성에 따라 어떠한 전략을 취할 것인지를 분석하는데 목적이 있다. Porter의 본원적 경쟁전략인 원가우위전략과 차별화전략을 바 탕으로 하여 우리나라 외항해운기업을 대상으로 환경 불확실성과 기업의 추구하는 경쟁전략의 관련성을 분석하고, 경쟁전략의 활용정도가 경 영성과에 미치는 영향력에 대해 검증하였다. 연구목적 달성을 위해 선행연구와 전문가 개별 인터뷰를 통하여 측정항목을 설정하였고, 설문을 통하여 실증분석을 수행하였으며, 가설 검증에는 OLS회귀분석과 Tobit모형분석을 이용하였다. 본 연구 결과 첫째, 환경 불확실성의 요인 중 변동성은 원가우위전략과 차별화전략의 활용에 영향을 미치고, 다양성은 차별화전략에 유의한 영향력이 있음을 도출하였다. 둘째, 기업의 경 영성과는 원가우위전략의 활용을 통해서 달성할 수 있으므로, 해운 서비스를 제공하는데 비용절감의 노력이 요구된다.

We presented fundamental stellar parameters and evolutionary statuses of six solar type detached eclipsing binaries whose masses are in the range of 0.97-1.43 M⊙. EK Cep and FL Lyr belong to the zero age main sequence. HS Hya, IT Cas and CD Tau are on the main sequence. Their ages are 1.3, 1.9 and 2.2 Gyr, respectively. Both component stars of AI Phe evolved to sub giants and its age is 4.0 Gyr. Those ages of the detached binary systems show good agreement with the time scale for synchronization and circularization of the binary systems.