• Macromolecular Research
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• v.16 no.5
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• pp.434-440
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• 2008

Three-armed, star-shaped molecules containing 4-(N,N-diphenyl)amino-4'-nitroazobenzene chromophores were synthesized to study the diffraction behavior after inscribing surface relief gratings. The two molecules differed in terms of their mode of chromophore attachment to the core. In compound 5, they were bound to the core laterally through alkylene spacers, whereas the chromophores were tethered perpendicularly to the core in compound 4. Although 60 wt% of the polar azobenzene chromophores was comprised of large molecules, no aggregation behavior was observed in the absorption spectra of the thin films. The surface relief gratings were elaborated on the surface of the molecular films by the two-beam interference method. The dynamics of grating formation were studied in terms of the diffraction efficiency using two different film samples made up of two star-shaped molecules. The maximum diffraction efficiency of D-$(ENAZ)_3$, compound 4, was measured to be about 30%, which was significantly high. The mode of chromophore attachment affected the dynamic properties of the diffraction gratings.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.39.2-40
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• 2016

The molecular gas surrounding an H II region is thought to be a place where star formation can be induced. Such triggered star formation can arise form the overpressurization of existing density enhancements or thought the collapse of a swept up layers of material. In this talk, We will discuss the results of a study of star-formation activity associated with the outer Galaxy ring-shaped H II regions KR 7, KR 81, KR 120 and KR 140 using archival Spitzer and WISE data along with the JHK observations. We used CO data cubes from the FCRAO and TRAO in order to define extent of the molecular cloud associated each HII region. Using the infrared data sets, We identified and classified YSO populations within each molecular cloud using measures such as the class I/II ratio and YSO spatial density. Along with this, one of the main question in the study of star formation is how protostar accrete material from their parent molecular clouds and observations of infall motions are needed to provide direct evidence for accretion. Combining our observation of the YSO population distribution with time scales associated with YSO evolution and HII expansion, we investigated the possible significance of triggered star formation in the molecular cloud surrounding each region.

• Rapid Communication in Photoscience
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• v.1 no.1
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• pp.19-20
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• 2012

Novel star-shaped imide compounds containing electron-donating triphenylamine and/or electron-withdrawing bis(trifluoromethyl)phenyl side groups were synthesized via a two-step process. First, 3,6-dibromo-benzene-1,2,4,5-tetracarboxylic acid (2B4BA) was reacted with 4-aminophenyl (diphenylamine) (ATPA) or 3,5-bis(trifluoromethyl)aniline (6FA) by imide reaction. Then, Suzuki coupling reaction was carried out on these compounds with 4-(N,N-diphenylamino)-1-phenyl boronic acid (BTPA) or 3,5-bis(trifluoromethyl)phenyl boronic acid (6FBB), resulting in 3,6-bis[4-(diphenylamino)phenyl]-N,N'-bis[4-(diphenylamino) phenyl]-pyromellitimide (TPTPPI), 3,6-bis[3,5-bis(trifluoro methyl) phenyl]-N,N'-bis[3,5-bis(trifluoromethyl) phenyl]-pyro mellitimide (6F6FPI) or 3,6-bis[4-(diphenylamino)phenyl]-N,N'-bis[3,5-bistrifluoromethyl)phenyl]-pyromellitimide (6FTPPI). The imide compounds obtained were characterized by NMR, FT-IR, DSC, TGA, melting point analyzer, EA, and solubility measurements. In addition, their optical and electrical properties were evaluated by fluorescence spectroscopy, UV-vis spectroscopy, and cyclic voltammetry (CV). 6F6FPI exhibited deep blue emission (443 nm), along with high $T_m$ ($382^{\circ}C$) and relatively high $T_g$ ($148^{\circ}C$).

• Management & Information Systems Review
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• v.34 no.3
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• pp.101-123
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• 2015

Amidst the growing uncertainty in external environments, securing and retaining superior human resources is becoming emphasized as a key means for organizations to achieve competitive advantages. Particularly, star employees-human resources that are characterized by their ability to create extraordinary performance relative to other peers-are increasingly gaining attention in both academia and industry because of its importance in knowledge-based industries. However, despite the prevailing recognition for star employees, few previous literature have attempted to empirically test the direct relationship between the ratio of star employees in an organization and organizational performance. Considering both the potential for positive and negative influence of star employees on organizations, the relationship between the ratio of star employees and organizational performance can not only be a simple linear relationship but can also exist in a curvilinear form. Building on the existing literature on star employees, this paper establishes competing hypotheses for the two possibilities of curvilinear relationship; as the ratio of star employees increases, marginal effects can either increase (i.e., U-shaped curvilinear relationship) or decrease (i.e., inverted U-shaped curvilinear relationship). Employing an unbalanced panel data of 35 Korean brokerage firms between years 2008 and 2013 with 134 observations, the relationship between the ratio of best analysts (i.e. star employees) as selected by Maeil Business Newspaper and financial performance (i.e. organizational performance) of corresponding brokerage firms is examined. Empirical results indicate that while organizational performance increases as the ratio of star employees increases, its positive effect diminishes over time which provides support for the curvilinear relationship with decreasing marginal effects. Our research findings imply that star employees create value in knowledge-based industries; at the same time, implications are given as results calls for caution for excessive dependence on star employees beyond a certain level.

• Polymer(Korea)
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• v.38 no.5
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• pp.671-675
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• 2014

Well-defined star shaped and linear block copolymers were synthesized to study the dispersion stability of copper phthalocyanine (CuPc). We synthesized dispersants using (2-dimethylamino) ethyl methacrylate (DMAEMA) and poly(ethylene glycol) methyl ether methacrylate) (PEGMA) by activators generated by electron transfer (AGET) atom transfer radical polymerization (ATRP). pDMAEMA-b-pPEGMA copolymers were characterized by GPC and NMR. Furthermore, we studied the effect of the dispersion stability of copper phthalocyanine by controlling the degree of polymerization of PEGMA as a stabilizing group. The 4-arm star shaped polymeric dispersant showed better dispersion stability of CuPc at $25^{\circ}C$ for 7 days.

• Journal of the Korean Mathematical Society
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• v.18 no.2
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• pp.135-140
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• 1982

• Macromolecular Research
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• v.9 no.2
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• pp.100-106
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• 2001

Several star-polymers with aliphatic cores were synthesized by ring opening polymerization (ROP) of $\xi$-caprolactone using stannous 2-ethyl-hexanoate as a catalyst. The star-polymers were thoroughly analyzed by MALDI-TOF mass spectrometry, temperature gradient interaction chromatography and $\^$13/C-NMR to obtain detailed information of the molecular structure. The imperfection of the star-polymers seemed to be originated from restricted participation of sterically hindered hydroxyl groups of initiator. The synthesized star-polymers had narrow molecular weight distributions. Various reaction conditions to control the imperfection were studied.

• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.17-26
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• 2023

The star-shaped propellant grain can be used for designing burning surface areas with various profiles and are easy to manufacture, so it can be usefully applied to actual solid rocket motors. However, since there are many design-related configuration variables and slivers at the end of combustion, it is difficult to achieve an optimal design using a general optimization technique. In this study, the new method for designing star grains using a database was proposed to increase usability and success rate of optimization design. In the proposed method, a solution that satisfies the requirements is obtained after defining the performance variables, constructing the database. By applying the proposed method, the design of star grains with various profiles of the burning surface area was performed, and the validity of the design method was confirmed.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.47.2-47.2
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• 2015

At local, galaxy properties are well known to be clearly different in different environments. However, it is still an open question how this environment-dependent trend has been shaped. In this presentation, we will show the results of our investigation about the evolution of star-formation properties of galaxies over a wide redshift range, from z~2 to z~0.5, focusing its dependence on their stellar mass and environment. In the UKIDSS/UDS region, we estimated photometric redshifts and stellar population properties, such as stellar masses and star-formation rates, using the deep optical and near-infrared data available in this field. Then, we identified galaxy cluster candidates at z~0.5-2. Through the analysis and comparison of star-formation (SF) properties of galaxies in clusters and in field, we found interesting results regarding the evolution of SF properties of galaxies: (1) regardless of redshifts, stellar mass is a key parameter controlling quenching of star formation in galaxies; (2) At z<1, environmental effects become important at quenching star formation regardless of stellar mass of galaxies; and (3) However, the result of the environmental quenching is prominent only for low mass galaxies (M* < $10^{10}M_{\odot}$) since the star formation in most of high mass galaxies are already quenched at z > 1.

• Journal of the Korean Society of Costume
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• v.5
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• pp.141-152
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• 1981

Various ceremonial flags were of great importance to the rulers who wished to have the absolute authorities for governing the people. Perhaps nothing indicated the ideas, thoughts and symbols of a certain period and people than the ceremonial flags. The ceremonial flags used in the old China and Korea took the shapes of the heaven and the earth, representing the social backgrounds and thoughts. This study was limited only to the discussion of the heaven-shaped patterns of the ceremonial flags. The 28 constellations of the heaven, in the Oriental way of thinking, were considered to express the immortal powers of Providence and the political domination of the earth. Hence the Polaris, the center of the heaven, symbolized the whole family of king, prince, child born of a concubine and royal harem. Among the constellation pictures were those of Han period, wall painting of old tombs in Koguryeo kingdom and old Japanese kingdom. Referring to the Emperor's ceremonial flags in Daemyeongjibyei, symbolic meanings changed historically and the complete systems of the ceremonial flags were established in Song period when the divine person was drawn on the flags. Animals concerned properly with the particular star and the shapes of the star were both drawn on the flags in Won period and only the shapes of the particular star in Myeong period. In the Imperial enthronement of Kojong the ceremonial flags might be made by the examples of those of Myeong period and remains are now found at Changdeok Palace, which need a further study because the references in detail are not available.