First detection of 22 GHz H2O masers in TX Camelopardalis

Simultaneous time monitoring observations of H$_{2}$O $6_{16}-5_{23}$, SiO $J$ = 1--0, 2--1, 3--2, and $^{29}$SiO $v$ = 0, $J$ = 1--0 lines were carried out in the direction of the Mira variable star TX Cam with the Korean VLBI Network single dish radio telescopes. For the first time, the H$_{2}$O maser emission from TX Cam was detected near the stellar velocity at five epochs from April 10, 2013 ($\phi$ = 3.13) to June 4, 2014 ($\phi$ = 3.89) including minimum optical phases. The intensities of H$_{2}$O masers are very weak compared to SiO masers. The variation of peak antenna temperature ratios among SiO $v$ = 1, $J$ = 1--0, $J$ = 2--1, and $J$ = 3--2 masers is investigated according to their phases. The shift of peak velocities of H$_{2}$O and SiO masers with respect to the stellar velocity is also investigated according to observed optical phases. The H$_{2}$O maser emission occurs around the stellar velocity during our monitoring interval. On the other hand, the peak velocities of SiO masers show a spread compared to the stellar velocity. The peak velocities of SiO $J$ = 2--1, and $J$ = 3--2 masers show a smaller spread with respect to the stellar velocity than those of SiO $J$ = 1--0 masers. These simultaneous observations of multi-frequencies will provide a good constraint for maser pumping models and a good probe for investigating the stellar atmosphere and envelope according to their different excitation conditions.Comment: 10 page

Electronic Commerce Strategy for Small and Medium Enterprises: Case Studies of Korean Firms

Business firms are increasingly taking part in online business activities through internet as the size of the e-commerce market is rapidly growing in the recent years. Electronic commerce (EC) activities now become an essential part of the business strategy for survival as well as growth for both large enterprises and small- to medium-sized enterprises (SMEs). Previous studies on e-commerce mostly focused on the adoption of EC by business firms, and also have been carried out with the data from big enterprises. More often than not, the results obtained from the large business firms are used to provide the guidelines for small to medium-sized enterprises (SMEs). SMEs are, however, different from large business firms in many aspects, and need to be studied on their own. This paper extends the previous research on EC in two aspects. Firstly, we study the e-commerce issues in the area of implementation in relation to the business firm\u27s performance, beyond the adoption and diffusion of IT technology which has been the research issues in many previous research. Secondly, we focus on small and medium enterprises which comprise a large portion of national economy with significant influenc

Korean Nova Records in A.D. 1073 and A.D. 1074: R Aquarii

R Aqr is known to be a symbiotic binary system with an associated extended emission nebula, possibly produced by a historic outburst. To find the associated historic records, we searched for and compiled all 'Guest Star' and 'Peculiar Star' records in three Korean 'official' history books that cover almost two thousand years, Samguksagi, Goryeosa, Joseonwangjosillok. In addition to the record of A.D. 1073, previously noted by Li (1985), we have found in Goryeosa another candidate record of A.D. 1074, which has the same positional description as that of A.D. 1073 with an additional brightness description. We examined various aspects of the two records and conclude that they both are likely to be the records of outburst of R Aqr. This means that there were two successive outbursts in A.D. 1073 and in A.D. 1074, separated by approximately one year. Based on these records, we estimate the distance to R Aqr to be 273 pc if the expansion of the nebula has been at a constant rate. The brightness record of A.D. 1074 corresponds to the absolute magnitude at outburst of M_(outburst) = -6.2 mag. ~ -5.2 mag. at this distance. The two Korean records associated with R Aqr may provide astronomically meaningful constraints to the outburst model of R Aqr and the formative process of its nebulosity.Comment: 10 pages, 2 figures, 1 appendix. To appear in Astronomy and Astrophysic

Toward an Evaluation Model of User Experiences on Virtual Reality Indoor Bikes

This paper deals with deriving a model or framework to evaluate user experiences (UX) of virtual reality (VR) systems, especially, VR indoor bikes which are under construction. Recently, VR is one of the most appealing areas attracting people’s interests around the world. Many products armed with it increasingly emerge on the market, and it is expected that the use of VR systems will continue to increase sharply in the future. However, UX of such products cannot be evaluated appropriately at the moment due to a lack of proper evaluation models. In a broad sense, UX that may stem from human machine interface in ergonomics covers affect, usability, and user value in spite of some differences in definition among the researchers. While evaluations of UX on the products without VR have been overall justifiably performed, UX has been evaluated neither systematically nor strictly on the products with VR. Through the analyses of expert reviews, we newly identify an additional component and its elements, and modify some elements of the three existing components for evaluating UX on the VR systems. As a result, we propose a comprehensive evaluation model of UX, which consists of four factors: usability, affect, user value, and presence feeling. In addition, we determine the components and their elements for specific VR indoor bikes similarly through the analyses of expert surveys and focus-group discussions, which results in developing a questionnaire for users. Finally, along with the questionnaire, we propose a specific evaluation model for VR indoor bikes

Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris

We obtained, for the first time, astrometrically registered maps of the 22.2 GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016 January 7 and 26) using the Korean Very-long-baseline Interferometry Network. The SiO masers show a ring-like spatial structure, while the H2O maser shows a very asymmetric one-side outflow structure, which is located at the southern part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO maser spots are distributed in an inner region, compared to those of the 43.1 GHz SiO maser, which is different from all previously known distributions of the 86.2 GHz SiO masers in variable stars. The different distribution of the 86.2 GHz SiO maser seems to be related to the complex dynamics caused by the overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the position of the central star based on the ring fitting of the SiO masers, which is essential for interpreting the morphology and kinematics of a circumstellar envelope. The estimated stellar coordinate corresponds well to the position measured by Gaia

Pilot VLBI Survey of SiO v=3 J=1--0 Maser Emission around Evolved Stars

In this Letter, we report detections of SiO v=3 J=1--0 maser emission in very long baseline interferometric (VLBI) observations towards 4 out of 12 long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections towards WX Psc and T Cep are new ones. We also present successful astrometric observations of SiO v=2 and v=3 J=1--0 maser emissions associated with two stars: WX Psc and W Hya and their position-reference continuum sources: J010746.0+131205 and J135146.8-291218 with the VLBI Exploration of Radio Astrometry (VERA). The relative coordinates of the position-reference continuum source and SiO v=3 maser spots were measured with respect to those of an SiO v=2 maser spot adopted as fringe-phase reference. Thus the faint continuum sources were inversely phase-referenced to the bright maser sources. It implies possible registration of multiple SiO maser line maps onto a common coordinate system with 10 microarcsecond-level accuracy.Comment: 5 Pages, 3 figures, Fig.3 and Tab. 2 were corrected; Publications of the Astronomical Society of Japan, Vol. 64, No. 6 issued on 2012 December 2

A Spectral Line Survey from 138.3 to 150.7 GHZ toward Orion-KL

We present the results of a spectral line survey from 138.3 to 150.7 GHz toward Orion-KL. The observations were made using the 14 m radio telescope of Taeduk Radio Astronomy Observatory. Typical system temperatures were between 500 and 700 K, with the sensitivity between $0.02 - 0.06$ K in units of $\rm T_A^*$. A total of 149 line spectra are detected in this survey. Fifty lines have been previously reported, however we find 99 new detections. Among these new lines, 32 are `unidentified', while 67 are from molecular transitions with known identifications. There is no detection of H or He recombination lines. The identified spectra are from a total of 16 molecular species and their isotopic variants. In the range from 138.3 to 150.7 GHz, the strongest spectral line is the J=3-2 transition of CS molecule, followed by transitions of the $\rm H_2CO$, $\rm CH_3OH$, $\rm CH_3CN$, and $\rm SO_2$. Spectral lines from the large organic molecules such as $\rm CH_3OH$, $\rm CH_3OCH_3$, $\rm HCOOCH_3$, $\rm C_2H_5CN$ and $\rm CH_3CN$ are prominent; with 80 % of the identified lines arising from transitions of these molecules. The rotational temperatures and column densities are derived using the standard rotation diagram analysis for $\rm CH_3OH$ ($\rm ^{13}CH_3OH$), $\rm HCOOCH_3$, $\rm CH_3CN$ and $\rm SO_2$ with $\rm 10\sim 270 K$ and $\rm 0.2\sim 20\times 10^{15} cm^{-2}$. These estimates are fairly comparable to the values for the same molecule in other frequency regions by other studies.Comment: 10 figures, 2 tex files for a manuscript and tables, accepted to Ap

Nanomorphology dependence of the environmental stability of organic solar cells

Previous studies have reported contradictory effects of small-molecule acceptors on the environmental stability of polymer:small-molecule blends, with one showing that a small-molecule acceptor stabilizes and another showing that it destabilizes the polymer donor. In this work, to investigate the origin of these contradictory results, the effects of the nanomorphologies of small-molecule acceptors on the environmental stability of polymer:small-molecule blends are demonstrated. Investigations on the environmental stabilities of polymer:fullerene blends of poly[[4, 8-bis[(2-ethylhexyl)oxy]benzo[1, 2-b:4, 5-b′]dithiophene-2, 6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3, 4-b]thiophenediyl]] (PTB7):phenyl-C₆₁-butyric acid methyl ester (PCBM) with contrasting nanomorphologies of PCBM reveal that dispersed PCBM in a mixed phase is the critical factor that causes triplet-mediated singlet oxygen generation and, hence, the severe photooxidation of PTB7, whereas an aggregated PCBM phase stabilizes PTB7 by reducing the formation of PTB7 triplet excitons. In addition, the photooxidation of PTB7 substantially degrades hole transport in the PTB7:PCBM blends by destroying the crystalline PTB7 phases within the films; this effect is strongly correlated with the efficiency losses of the PTB7:PCBM organic solar cells. These conclusions are also extended to polymer:nonfullerene blends of PTB7:ITIC and PTB7:Y6, thereby confirming the generality of this phenomenon for polymer:small-molecule organic solar cells