• Journal of Astronomy and Space Sciences
• /
• v.28 no.3
• /
• pp.163-172
• /
• 2011

An intensive analysis of 185 timings of WZ Cep, including our new three timings, was made to understand the dynamical picture of this active W UMa-type binary. It was found that the orbital period of the system has complexly varied in two cyclical components superposed on a secularly downward parabola over about 80y. The downward parabola, corresponding to a secular period decrease of $-9.{^d}97{\times}10^{-8}y^{-1}$, is most probably produced by the action of both angular momentum loss (AML) due to magnetic braking and mass-transfer from the massive primary component to the secondary. The period decrease rate of $-6.^{d}72{\times}10^{-8}y^{-1}$ due to AML contributes about 67% to the observed period decrease. The mass flow of about $5.16{\times}10^{-8}M_{\odot}y^{-1}$ from the primary to the secondary results the remaining 33% period decrease. Two cyclical components have an $11.^{y}8$ period with amplitude of $0.^{d}0054$ and a $41.^{y}3$ period with amplitude of $0.^{d}0178$. It is very interesting that there seems to be exactly in a commensurable 7:2 relation between their mean motions. As the possible causes, two rival interpretations (i.e., light-time effects (LTE) by additional bodies and the Applegate model) were considered. In the LTE interpretation, the minimum masses of $0.30M_{\odot}$ for the shorter period and $0.49M_{\odot}$ for the longer one were calculated. Their contributions to the total light were at most within 2%, if they were assumed to be main-sequence stars. If the LTE explanation is true for the WZ Cep system, the 7:2 relation found between their mean motions would be interpreted as a stable 7:2 orbit resonance produced by a long-term gravitational interaction between two tertiary bodies. In the Applegate model interpretation, the deduced model parameters indicate that the mechanism could work only in the primary star for both of the two period modulations, but could not in the secondary. However, we couldn't find any meaningful relation between the light variation and the period variability from the historical light curve data. At present, we prefer the interpretation of the mechanical perturbation from the third and fourth stars as the possible cause of two cycling period changes.

• Journal of Astronomy and Space Sciences
• /
• v.16 no.2
• /
• pp.227-240
• /
• 1999

We performed CCD photometric observations of W UMa type contact binary BV Dra during eight nights from May 1996 to June 1999 using 61cm telescope at Sobaeksan Optical Astronomy Observatory, and completed BV R light curves of the system. From our observations, we derived nine new times of minimum lights (five timings for primary eclipse, four for secondary) and determined new light elements with the times of minima observed since 1999. Our BV R light curves and Batten & Lu(1986)'s radial-velocity ones were simultaneously analyzed with contact mode (Mode 3) of Wilson-Devinney's binary model, and the photometric and spectroscopic solutions for BV Dra were solved. In the analysis, we derived the solutions of 1999 light curves with and without spots, respectively. As the results, asymmetry of light curves may be interpreted as produced by the existence of two spots; hot spot on the secondary and cool on the primary. Combining solutions of light curves and radial-velocity ones, absolute dimensions of BV Dra are $M_1=0.40M_{odot}$, $M_2=1.01M_{odot}$, $R_1=0.72R_{odot}$, $R_2=0.40R_{odot}$. In mass-radius diagram, the less massive and hotter primary component of BV Dra is near TAMS and the secondary is near ZAMS, which is very similar to the other W-type W UMa binaries.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.1
• /
• pp.44-58
• /
• 1997

The BVR CCD photometric observations of W UMa-type eclipsing binary SS Ari were made on ten nights from November 1996 to December 1996. Eight new times of minimum lights were derived. The analysis of times of minima of SS Ari confirms the suggestions of other previous investigators that the orbital period of SS Ari have been suffering from a sinusoidal varition. The amplitude and period for the cyclic period changes were calculated as about $58^{y}$ and $0.^{d}053$, respectively. The period variation has been discussed in terms of two potential mechanisms: 1) the light-time effect due to a hypothetical third body and 2) deformations in the convective envelope of a magnetically active component. In the earlier case, the third body has a mass of $1.3M_{\odot}$, if exist, in the form of a white dwarf or a binary system. It seems that the system velocities from the spectroscopic observations supports this interpretation. Meanwhile in the latter case, the primary component is mainly responsible for the magnetic activity of this system with a theoretical amplitude of $\pm0.^{m}08$. However, we cannot make a conclusion which is reasonable explanation at this point, due to lack of observational data. Moreover, the period variation of SS Ari shows duplication about $14^y$, cyclic period with an amplitude of about $0.^d001$ to the above periodic change. We also cannot make an acceptable conclusion for it at this time.

• Journal of Astronomy and Space Sciences
• /
• v.29 no.2
• /
• pp.151-161
• /
• 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.

• Journal of Microbiology and Biotechnology
• /
• v.12 no.4
• /
• pp.699-701
• /
• 2002

The current study demonstrates the ability of the marine cyanobacterium Oscillatoria willei BDU130511 to disinfect raw sewage. Within a holding time of 3 h under laboratory conditions, the organism drastically reduced in the total bacterial and coliform counts at various pH levels, in both unbuffered and buffered sewage, thereby suggesting a potential role for cyanobacteria in wastewater treatment.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3343-3347
• /
• 2011

A simple efficient and neat synthesis of ${\alpha}$-hydroxy phosphonates has been accomplished from aromatic/heterocyclic aldehydes and diethyl phosphite using $KHSO_4$ as a catalyst under solvent-free conditions at ambient temperature. These compounds are characterized by spectral and analytical data and tested for their anti-oxidant activity.

• East Asian mathematical journal
• /
• v.23 no.1
• /
• pp.83-101
• /
• 2007

In this paper the concept of somewhat pairwise fuzzy continuous functions and somewhat pairwise fuzzy open functions are introduced. Some interesting properties of these functions are investigated besides giving some characterizations of these functions.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.2
• /
• pp.225-232
• /
• 1997

A total of 1088 observations (272 in B, 272 in V, 272 in R, and 272 in I) were made from January to February in 1995 at Chungbuk National University observatory(CbNUO). We constructed BVRI light curves with our data. The photometric solution of these light curves was obtained by means of the Wilson-Devinney method. Our result was compared with those by previous investigators.

• East Asian mathematical journal
• /
• v.23 no.2
• /
• pp.151-158
• /
• 2007

In this paper we introduce the concept of fuzzy ${\beta}-compact^*$ spaces. Besides giving some interesting properties of fuzzy ${\beta}-compact^*$ spaces we also give a characterization on fuzzy $\beta$-compact spaces by making use of newly introduced concept of fuzzy $\beta$-filters.

• East Asian mathematical journal
• /
• v.23 no.2
• /
• pp.159-174
• /
• 2007

In this paper, the concepts of pairwise fuzzy $G_{\delta}$-connected spaces and pairwise fuzzy $G_{\delta}$-extremally disconnected spaces are introduced. The concept of pairwise fuzzy $G_{\delta}$-basically disconnected spaces is defined. Characterizations of the above spaces are given besides giving several examples. Interrelations among the spaces introduced are discussed and some relevant counter examples are given.