• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.44.4-44.4
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• 2019

The supernova remnant Cassiopeia A (Cas A) provides a unique opportunity to observe the fine details of the explosion of core-collapse supernova (SN). Previous optical and near-infrared (NIR) observations of Cas A have shown that the spatial distribution of the metal-enriched SN ejecta is very complicated, indicating that the SN explosion should have been asymmetric and turbulent, especially near the core. Recently, we obtained a long-exposure (~10 hr) image of Cas A by using the UKIRT 3.6-m telescope with a narrow-band filter centered at [Fe II] 1.644 um emission. This 'deep [Fe II] image' provides an unprecedented panoramic view of Cas A, revealing the distribution of dense SN ejecta over the entire remnant. We have carried out NIR multi-object spectroscopic observations of the dense ejecta knots in the northeastern (NE) and eastern (E) outer regions of the remnant using the MMIRS attached on the MMT 6.5-m telescope. A total of 67 ejecta knots are detected. By analyzing their spectra, we have found that the knots in the NE area show strong [S II]/[S III] and [Fe II] lines but little or no [P II] line, while those in the E outer region show strong [Fe II] lines but weak [S II]/[S III] lines. In this talk, we present the preliminary results of our NIR spectroscopic observations and discuss the implications.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.34.2-34.2
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• 2019

Several observational results show a tighter pitch angle at wavelengths of optical and near-infrared than those that are associated with star formation, which is in agreement with the prediction of the density wave theory. In my recent numerical studies, the dependence of the shock positions relative to the potential minima is due to the tendency that stronger shocks form farther downstream. This causes a systematic variation of the perpendicular Mach number, with radius and makes the pitch angle of the gaseous arms smaller than that of the stellar arms, which supports the prediction of the density-wave theory, independently. However, some observations still give controversial results which show similar pitch angles at wavelengths, and there is no statistical study comparing observations and numerical models directly. By analyzing optical image of disk galaxies in the Carnegie-Irvine Galaxy Survey (CGS), I measured the physical values of stellar and gaseous arms such as their strength, length, and pitch angles. For direct comparison with numerical results, I analyzed more than 30 additional numerical models with varying the initial parameters in model galaxies. In this talk, I will present results both of observational and numerical samples and discuss the physical properties of spiral structures based on the density-wave theory.

• Journal of Distribution Science
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• v.21 no.10
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• pp.51-61
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• 2023

Purpose: Research focuses on private universities' professional education in a competitive educational environment. Due to increased competition in the higher education industry, private universities are under pressure to improve their marketing strategies and better understand their prospective students. This study intends to investigate how information sources are used and modified by Indonesian university students when making decisions. Research design, data and methodology: This research is a case study in Riau province, which includes active university students registered in the government database. Data was collected using a questionnaire distributed via Google Forms to students at a private university, and 164 students completed the questionnaire. Results: The results show that the influence of technical quality, functional quality, and image cannot affect word of mouth, and technical quality cannot affect consumer attitudes. The results show that the distribution of high service quality and high image will encourage people to share their experiences by word of mouth to build evaluation attachment in college selection. and found that a good campus image has no direct impact on word of mouth. The spread of an excellent campus image only attracts students to evaluate it. The more talk about the distribution of service quality, the higher the decision to choose the service.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.59-63
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• 2009

The UTP cable has been widely used, recently it is being developed for use in the UHF frequency band. One important characteristic of the UTP cable is NEXT. This research is to develop a pitch selection technique for an UTP cable which leads to a satisfactory NEXT. The transmission line model involving mutual inductances and capacitances between line pairs is used, and the simulation was carried out for frequencies from 1 MHz to 600 MHz. With respect to the worst margin of the NEXT for a Cat. 6 cable the simulation and measurement results show a good agreement.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.49.1-49.1
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• 2015

The origin of magnetic fields in the intracluster medium (ICM) is uncertain: it can be either primordial or astrophysical. Turbulence plays important roles in the origin of magnetic fields in the ICM. This is because turbulence can amplify a weak seed magnetic field very efficiently. The efficiency of the turbulence dynamo critically depends on the magnitude of viscosity: the smaller the viscosity is, the more efficient the turbulence dynamo is. In this talk, I'll discuss turbulence dynamo in both very small viscosity limit and very large viscosity limit. I'll show that when the viscosity in the ICM is comparable to the Spitzer viscosity, the origin of magnetic field in the ICM is likely to be astrophysical. On the other hans, when the viscosity is much smaller than the Spitzer value, the origin of magnetic field can be either astrophysical or primordial.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1169-1172
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• 2005

In this paper, we propose an improved anti-collision algorithm for multi tag interrogation in ubiquitous sensor network(USN) and show the result of simulation for multi tag interrogation in RFID systems. We have analyzed an EPC(Electronic Product Code) protocol which specifies the physical and logical requirements for a passive-backscatter Reader-Talk-First(RTF) RFID(Radio Frequency Identification) system operating in the $860MHz{\sim}960MHz$ frequency range. We have also designed and implemented the simulator of the RFID system based on the EPC protocol. Finally, we find that proposed algorithm works better than an existing algorithm.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.74.2-74.2
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• 2013

Recent spectroscopic observations have provided evidences for the multiple stellar populations having different abundances in some massive globular clusters (GCs). In particular, some of these GCs show clear separations of red giant-branches (RGBs) in calcium narrow band photometry. In order to confirm the differences in heavy element abundances and radial velocities among multiple RGBs, we have performed the low-resolution spectroscopy for the RGB stars in these GCs. The spectral data were taken from the multi-object spectroscopic mode with WFCCD mounted on the du Pont 2.5m telescope in Las Campanas Observatory. In this talk, we will present our progress in the spectroscopic analysis of the RGB stars in these GCs.

• Proceedings of the Korean Society for Bioinformatics Conference
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• 2002.06a
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• pp.63-63
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• 2002

RNA pseudoknots are not only important structural elements for forming the tertiary structure, but also responsible for several functions of RNA molecules such as frameshifting, read-through, and the initiation of translation. There exists no automatic method for drawing RNA pseudoknot structures, and thus representing RNA pseudoknots currently relies on significant amount of manual work. In this talk, I will introduce the first algorithm for automatically generating a drawing of RNA pseudoknot structures. Two basic criteria were adopted when designing the algorithm: (1) Overlapping of structural elements should be minimized to increase the readability of the drawing, and (2) The whole RNA structure as well as the pseudoknots themselves should be recognized quickly and clearly. The algorithm has been implemented in a JAVA program, which can be executed on any computing systems. Experimental results show that this program generates a clear and compact drawing of RNA pseudoknots and allows a biologist to gain insights into RNA pseudoknot structures. The program can also be used as useful aids in designing biochemical experiments to elucidate more precise mechanism of RNA functions associated with pseudoknots.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1011-1011
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• 2001

In general, NIR reflectance spectra (whether recorded using log(1/R) or the Kubelka-Munk function) are not linear functions of the concentration of the absorbers which we are measuring. There are several causes for this non-linearity, the most commonly cited one being front surface reflection. However, non-linearity also arises from the effects of particle size, sample thickness, void fraction, and experimental arrangement. In this talk, we will attempt to isolate the effects of the various causes, and show the effects of each, using both theoretical calculations and actual data. The listener should then be able to assess where we stand in our quest to produce “linear” data through pre-processing and/or alternate collection schemes.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.19-19
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• 2003

The injection of spins into nonmagnetic semiconductors has recently attracted great interest due to the potential to create new classes of spin-dependent electronic devices. A recent strategy to achieve control over the spin degree of freedom is based on dilute ferromagnetic semiconductors. Ferromagnetism has been reported in various semiconductor groups including II-Ⅵ, III-V, IV and II-IV,-V$_2$, which will be reviewed. On the other hand, to date the low solubility of magnetic ions in non-magnetic semiconductor hosts and/or low Curie temperature have limited the opportunities. Therefore the search for other promising ferromagnetic semiconducting materials, with high magnetic moments and high Curie temperatures (Tc), is of the utmost importance. In this talk, we also introduce new pure ferromagnetic semiconductors, MnGeP$_2$ and MnGeAs$_2$, exhibiting ferromagnetism and a magnetic moment per Mn at 5K larger than 2.40 ${\mu}$B. The calculated electronic structures using the FLAPW method show an indirect energy gap of 0.24 and 0.06 eV, respectively. We have observed spin injection in MnGeP$_2$ and MnGeAs$_2$ magnetic tunnel junctions through semiconducting barriers.