• 천문학회보
• /
• 제44권2호
• /
• pp.64.2-64.2
• /
• 2019

HD 81817 is known as a hybrid star. Hybrid stars have both cool stellar wind properties and UV or even X-ray emission features of highly ionized atoms in their spectra. A white dwarf companion has been suggested as the source of UV or X-ray features. HD 81817 has been observed since 2004 as a part of our radial velocity (RV) survey program to search for exoplanets around K giant stars using the Bohyunsan Observatory Echelle Spectrograph (BOES) at the 1.8 m telescope of Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. We obtained 84 RV measurements between 2004 and 2018 for HD 81817 and found two periodic RV variations. The obtained amplitudes of RV periods are around 200 m/s, which are significantly lower than that expected from a white dwarf companion. Furthermore, our re-analysis of the IUE spectra used by Reimers (1984) shows that the excess in UV emission can easily be explained by a pseudo-continuum of unresolved emission lines originating in the extended chromosphere of the star. We thus conclude that there are no companions of stellar mass to HD 81817. Meanwhile, we analyzed two periodicities in RV measurements and conclude that the period of 627.9 days is caused by intrinsic stellar activities based on H alpha equivalent width (EW) variations of a similar period. On the other hand, the period of 1047.8 days is likely to be caused by substellar companion which has a minimum mass of 27.6 M_JUP, a semi-major axis of 3.3 AU, and an eccentricity of 0.17 assuming the stellar mass of 4.3 M_⊙ for HD 81817. The inferred mass puts HD 81817 b in the brown dwarf desert.

• 천문학논총
• /
• 제15권spc1호
• /
• pp.113-118
• /
• 2000

A magnetic cataclysmic variable has a rotating magnetic white dwarf which accretes matter from its late type companion. Kim & Beuermann (1995) presented a phenomenological model of the accretion from its surrounding structure e.g., a disk into the magnetosphere of the white dwarf, and presented results for the spin modulated X-ray spectrum and light curves. Using this model, we calculate the optical continuum and line emission which result from reprocessing of X-rays in the accretion stream within the magnetosphere. Penning (1985) suggested the observed spin-modulated radial-velocity variations might result from reprocession of X-rays in the disk. We, however, find the radiation can be originated from the magnetosphere accretion stream. We use the same geometrical model to calculate the optical and the X-ray behaviour. The results from the two wavelength bands are internally consistent. We conclude that this approach will increase the diagnostic accuracies of the results.

• International Journal of Costume and Fashion
• /
• 제14권2호
• /
• pp.81-96
• /
• 2014

The meanings of colors vary with time and space. For the most important events in a person's life, such as wedding or funeral, people use color to symbolize their identities or roles. Traditionally, the colors of dress had indicated the wearer's age, class, or marital status in Korea. However, Korea's exposure to western cultures has affected in many dimensions of its modern history. Especially, influenced by social change, the traditional dress has undergone many modifications in forms, silhouettes, materials, and color. However, women's mourning dress has been maintained as a long lasting tradition and the use of white in mourning dress has been regarded as a norm until recently, while men have worn a regular black suit with a black tie. But, the shift from white to black in mourning dress has been observed in recent mourning practices. To examine this change of color in Korean traditional mourning dress, a historical approach utilizing multiple resources, such as interview, observations of events, documents, and archival records was applied.

• 한국게임학회 논문지
• /
• 제20권2호
• /
• pp.91-100
• /
• 2020

바둑에서의 사활문제는 컴퓨터바둑을 구현하기 위해 극복되어야 하는 기본적인 문제이다. 그것을 해결하기 위한 중요 고려 사항은 흑백 대국자 간에 누가 둘러싸고 있고 또는 둘러싸여 있는지를 파악하는 것이다. 흑백 그룹간의 경계선을 알아내기 위해 세력함수와 외곽선 추적 알고리즘을 적용하였다. 여러 외곽선 추적 알고리즘 중에서 무어의 이웃 추적을 적용하면 경계선을 생성할 수 있음을 알아냈으며, 아울러 게임트리의 탐색공간을 획기적으로 줄일 수 있는 가능성을 제시했다.

• 한국전기전자재료학회논문지
• /
• 제28권1호
• /
• pp.21-27
• /
• 2015

We propose a fabrication process of a 3-electrode type reflective display and ascertain the realized color panel. The first design is proceeded with basis on Ti electrode for fast panel fabrication, easy align process, and high reflection of a white image. To observe the particle movement at the lower electrodes and optimize the space between electrodes, we design the second patterns, from which we establish a fabrication process with the mixing of electronic ink, loading of this ink, electronic ink assembly, driving, and packaging. After aging process, we ascertain a normally driving panel with black, white, and blue color.

• ETRI Journal
• /
• 제41권1호
• /
• pp.42-51
• /
• 2019

The rainbow hologram provides views of reconstruction with rainbow color within a large viewing zone. In our recent paper, a Fourier rainbow holographic display using diffraction grating and a white-light LED source was introduced. In this technique, the rainbow effect is realized by the dispersion of white-light source on diffraction grating, while the slit is implemented numerically by reducing the demands of the space-bandwidth product of the display. This paper presents a novel analysis on the visual perception of the Fourier rainbow holographic display using Wigner distribution. The view-dependent appearance of the image, including multispectral field of view and viewing zone, is investigated considering the observer and the display parameters. The resolution of the holographic view is also investigated. For this, a new quantitative assessment for image blur is introduced using Wigner distribution analysis. The analysis is supported with numerical simulations and experimentally captured optical reconstructions for the holograms of the computer model and real object generated with different slit size, reconstruction distance, and different observation conditions.

• International Journal of Advanced Culture Technology
• /
• 제8권4호
• /
• pp.287-293
• /
• 2020

More and more people are paying attention to the psychological pleasure and relaxation that sound hearing brings. In most cases, humans seem to have a special preference for natural sounds. Natural sounds are mainly white noise and pink noise such as wind, rain, waves, waterfall sounds, etc. All of these are often considered to be beneficial to human health, but in reality the same category of natural sounds is no different. It will be very different due to space, time and other factors. Each sound can be unique, so people's hearing experience is also different. This paper quantitatively analyzes the spectrum and brain waves to analyze the feeling of hearing the natural Broken Falls sound. In particular, we aim to objectively analyze the objective feeling of Broken Falls sound falling on the human auditory system through sound spectrum and brain waves.

• 천문학회보
• /
• 제44권2호
• /
• pp.72.1-72.1
• /
• 2019

Symbiotic stars are wide binary systems of a white dwarf and a mass losing giant, exhibiting various activities mainly attributed to accretion of a fraction of slow stellar wind emanating from the giant. We perform 3 dimensional hydrodynamical simulations using the FLASH code to investigate the formation and physical structures of an accretion disk in symbiotic stars with binary separation in the range of 2-4 au. Radiative cooling is introduced in the flow in order to avoid acute pressure increase in the vicinity of the accretor that may prevent stable disk formation. By setting the same density condition in front of the bow shock generated in two different velocity fields, the role of ram pressure balancing between the disk and the wind is examined. We find that three main streams (direct stream from the giant, stream following the accretion wake, and stream passing through the bow shock front) all feed the disk, and their individual contributions on the mass accretion onto the white dwarf are explored.

• 천문학회보
• /
• 제46권1호
• /
• pp.43.2-43.2
• /
• 2021

In this study, we report oscillations of the total intensity of white light loops in the off-limb solar flare observed in 2017-Sep-10 with the SDO/HMI. The total intensity oscillations are correlated with the area of the flaring loop in the plane of the sky. The oscillatory pattern is well fitted by two consecutive damped oscillations. The period and damping time of the first oscillation are 12.9 minutes and 9.9 minutes, respectively. Those of the second oscillation are 11.7 minutes and 15.4 minutes. The excitation of the oscillations coincides with two consecutive type III radio bursts observed in meter range. Assuming the oscillations are magnetoacoustic waves in the flaring loops with the loop lengths ranging from 30 to 90 Mm, the temperature of the white light emitting loops could be in the range from 0.3 MK to 2.6 MK.

• 천문학논총
• /
• 제27권4호
• /
• pp.357-360
• /
• 2012

This paper presents $H{\alpha}$ emission line detections for four galaxies at z > 3.5 made with AKARI as part of the FUHYU mission program. These are the highest-redshift $H{\alpha}$ detections to date in star-forming galaxies. AKARI's unique near-infrared spectroscopic capability has made these detections possible. For two of these galaxies, this represents the first evidence of their redshifts and confirms their physical association with a companion radio galaxy. The star formation rates (SFRs) estimated from the $H{\alpha}$ lines under-predict the SFRs estimated from their far-infrared luminosities by a factor of ~ 2 - 3. We have also detected broad $H{\alpha}$ components in the two radio galaxies which indicate the presence of quasars.