• Title/Summary/Keyword: Black Hole

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IUE SPECTRA OF SEYEERT 1 GALAXY NGC 7469-BLR CHARACTERISTICS OF NGC 7469 (SEYFERT 1 은하 NGC 7469의 IUE SPECTRA-NGC 7469 BLR의 물리적 특성)

  • Son, Dong-Hoon;Hyung, Siek
    • Journal of Astronomy and Space Sciences
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    • v.22 no.3
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    • pp.187-196
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    • 2005
  • From the line ratios of Si III] 1892 to C III] 1909 (Feibelman & Aller 1987), we estimated the BLR electron densities and their changes of Seyfert 1 galaxy NGC 7469 using IUE spectra observed from June 11 to July 29, 1996 (Wanders et al. 1997). We separated blended Si III] and C III] lines using the STARLINK/DIPSO and measured their fluxes within the error of $12.4\%\;and\;6.6\%,$ respectively. Electron density fluctuated from $10^{9.69}\;to\;10^{10.93}$ during about two month period, i.e. 17.3 times density variation within 50 days. We also derived time delays from UV emission line variations .elative to the continuum $(at\;1315{\AA}):$ 2 days for C IV, 4 days for C III], 8 days for Si III]. This suggests that their stratified UV line emission regions are at 0.002 pc, 0.004 pc and 0.006 pc, respectively, from the central region. Based on the BLR sizes and their rotation velocities deduced from the line profiles, we estimate the central black hole mass as about $10^6M_{\odot}$

Star Formation Rate and AGN in Barred Galaxies (막대은하의 별탄생율과 활동성 은하핵)

  • Bang, Jun;Ann, Hong-Bae
    • Journal of the Korean earth science society
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    • v.30 no.1
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    • pp.69-80
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    • 2009
  • We investigate the dependence of star formation rate and Active Galaxy Nuclei (AGN) frequency on the bar properties, especially the bar strength, using SDSS DR6. To better represent the bar strength, we divided the bars into 6 classes according to their length and axial ratios. There seems to be a fairly good correlation between the star formation rate derived from $H{\alpha}$ emission lines and the bar strength, whereas there is no apparent correlation between the AGN activity and the bar strength. We interpret that the former correlation is due to the dependence of bar-driven gas inflow on the strength of bar. The lack of correlation between AGN and bar properties suggests that the accretion of gas onto a supermassive black hole (SMBH) is regulated by the interplay between the bar and SMBH. The frequency of AGN seems to be dependent on the background density but the star formation rate does not. It suggests that star formation is a localized phenomenon that is mostly determined by the gas density in a galaxy, while AGN activity is more closely related to the host property such as mass and luminosity that are thought to be dependent on the environment through the density-luminosity relation.

Transplantation of Koelreuteria paniculata by Sea Current (모감주나무의 해류에 의한 전파)

  • 이영노
    • Journal of Plant Biology
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    • v.1 no.1
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    • pp.11-20
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    • 1958
  • I. Assumption: Mo-kam-ju, Koelreuteria paniculata is a woody plant mainly cistributed over Northern China. Its sporadic growth along the beaches of Korea and Japan is assumed to have been sowed by the seeds transported adrift on the current across the ocean. II. Use and Growth of the Plant: In China, this plant has been cultivated from early times mainly at temples, it seeds being used as rosaries, its flowers for yellow dyes and medicine for the eyes, and its leaves for black dyes. In Korea and Japan, these plants have been cultivated at temples and used as the material for rosaries. No natural growth of these plants was reported until 1919. III. Discoveries: In this domestic area, Dr. Chung Tae Hyun discovered the plant on the beach between Cho-Do and Chang-san-kot, Hwang-Hae Prov. in 1920. The reporter discovered them on the beach at Buk-Ni, Duk-jok-Do in 1948, at An-Hung in 1956 and on the beach at An-min-Do in 1957. In the Japan area, it was discovered for the first time twenty years ago, mainly along the coast line of the Japan Sea and some along the eastern coast line, at Subo, Yamaguchi Prefecture facing the Pacific Ocean. IV. Study and Experiment: A. Seed The seed coat is thick, non-permeable and floatable. A number of seeds were immersed in artificial sea water and fresh water separately. The seeds remained there for a hundred and forty-five (145) days from April 6, 1957 to August 29, 57. Thirty one seeds out of the fifty immersed in salt water and twenty seeds out of the fifty immersed in fresh water remained on the surface of the water, proving them to be non-permeable to both sea and fresh water. Of course, these had retained their germinating capabilities. Five (5) seeds out of twenty from the fresh water and six (6) out of thirty-one from the sea water were successfully germinated after a hole had been drilled in the seed coat and they had been planted. Thus their floating capability, non-permeability and germinating capability after a possible 145 day trip on the flowing currents has been proved satisfactory according to the assumption made above. B. Current As shown in the Data 2 and 3, the sea current initiated in the Pohai Sea flows westward down along the coast line of Korea reaching the southern part during the autumn and winter seasons. This fact also is in favor of the reporter's assumption. V. Discussion and Conclusion: The reporter concludes that, as discussed above, Koelreuteria paniculata which originates in Northern China is transported adrift on the flowing sea current to our western coast line, and also the coast lines of Shantung and Kuangtung of China and it is germinated on the sandy beaches forming new plants. Thus, the seeds drifted down on the southern beach of Korea and have been transported to the Japanese coast, adrift on the Tae-Ma current. Upon fruition, the seeds of the plants which settle on the coasts of western Korea and Japan will migrate to new places. It can be, however, assumed that while the thickness and nonpermeability of the coat enables the long travel in the water, this also can compose a difficulty in germination, consequently in developing a new distribution of this species.

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A Comparative Analysis of Keywords in Astronomical Journals and Concepts in Secondary School Astronomy Curriculum (최근 천문학 연구 키워드와 천체 분야 교육과정 내용 요소 비교 분석)

  • Shin, Hyeonjeong;Kwon, Woojin;Ga, Seok-Hyun
    • Journal of The Korean Association For Science Education
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    • v.42 no.2
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    • pp.289-309
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    • 2022
  • In recent years, astronomy has been snowballing: including Higgs particle discovery, black hole imaging, extraterrestrial exploration, and deep space observation. Students are also largely interested in astronomy. The purpose of this study is to discover what needs to be improved in the current astronomy curriculum in light of recent scientists' researches and discoveries. We collected keywords from all papers published from 2011 to 2020 in four selected journals-ApJ, ApJL, A&A, and MNRAS- by R package to examine research trends. The curriculum contents were extracted by synthesizing the in-service teachers' coding results in the 2015 revised curriculum document of six subjects (Science, Integrated Science, Earth Science I, Earth Science II, Physics II, Convergence Science). The research results are as follows: first, keywords that appear steadily in astronomy are 'galaxies: formation, galaxy: active, star: formation, accretion, method: numerical.' Second, astronomy curriculum includes all areas except the 'High Energy Astrophysical Phenomena' area within the common science curriculum learned by all students. Third, it is necessary to review the placement of content elements by subject and grade and to consider introducing new concepts based on astronomy research keywords. This is an exploratory study to compare curriculum and the field of scientific research that forms the basis of the subject. We expect to provide implications for a future revision of the astronomy curriculum as a primary ground investigation.

Combining Non-Contrast CT Signs With Onset-to-Imaging Time to Predict the Evolution of Intracerebral Hemorrhage

  • Lei Song;Xiaoming Qiu;Cun Zhang;Hang Zhou;Wenmin Guo;Yu Ye;Rujia Wang;Hui Xiong;Ji Zhang;Dongfang Tang;Liwei Zou;Longsheng Wang;Yongqiang Yu;Tingting Guo
    • Korean Journal of Radiology
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    • v.25 no.2
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    • pp.166-178
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    • 2024
  • Objective: This study aimed to determine the predictive performance of non-contrast CT (NCCT) signs for hemorrhagic growth after intracerebral hemorrhage (ICH) when stratified by onset-to-imaging time (OIT). Materials and Methods: 1488 supratentorial ICH within 6 h of onset were consecutively recruited from six centers between January 2018 and August 2022. NCCT signs were classified according to density (hypodensities, swirl sign, black hole sign, blend sign, fluid level, and heterogeneous density) and shape (island sign, satellite sign, and irregular shape) features. Multivariable logistic regression was used to evaluate the association between NCCT signs and three types of hemorrhagic growth: hematoma expansion (HE), intraventricular hemorrhage growth (IVHG), and revised HE (RHE). The performance of the NCCT signs was evaluated using the positive predictive value (PPV) stratified by OIT. Results: Multivariable analysis showed that hypodensities were an independent predictor of HE (adjusted odds ratio [95% confidence interval] of 7.99 [4.87-13.40]), IVHG (3.64 [2.15-6.24]), and RHE (7.90 [4.93-12.90]). Similarly, OIT (for a 1-h increase) was an independent inverse predictor of HE (0.59 [0.52-0.66]), IVHG (0.72 [0.64-0.81]), and RHE (0.61 [0.54-0.67]). Blend and island signs were independently associated with HE and RHE (10.60 [7.36-15.30] and 10.10 [7.10-14.60], respectively, for the blend sign and 2.75 [1.64-4.67] and 2.62 [1.60-4.30], respectively, for the island sign). Hypodensities demonstrated low PPVs of 0.41 (110/269) or lower for IVHG when stratified by OIT. When OIT was ≤ 2 h, the PPVs of hypodensities, blend sign, and island sign for RHE were 0.80 (215/269), 0.90 (142/157), and 0.83 (103/124), respectively. Conclusion: Hypodensities, blend sign, and island sign were the best NCCT predictors of RHE when OIT was ≤ 2 h. NCCT signs may assist in earlier recognition of the risk of hemorrhagic growth and guide early intervention to prevent neurological deterioration resulting from hemorrhagic growth.

Characteristics and Significance of the Huirang Daesa Sculpture at Haeinsa Temple in Hapcheon (합천(陜川) 해인사(海印寺) 희랑대사상(希朗大師像)의 특징과 제작 의미)

  • Jeong, Eunwoo
    • MISULJARYO - National Museum of Korea Art Journal
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    • v.98
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    • pp.54-77
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    • 2020
  • Produced during the Goryeo period (718-1392), the statue of the monk Huirang Daesa at Haeinsa Temple in Hapcheon is almost life-size, with a height of 82.4 cm, a width of 66.6 cm at the knees, and a maximum width of 44 cm at the torso (front and back). Notably, it is the only known example of an East Asian Buddhist sculpture made from wood and dry lacquer that was formed by joining the front and back halves. However, a similar technique was used on a dry lacquer statue of the Medicine Buddha at Cheongnyangsa Temple in Bonghwa, which is estimated to date from the late Goryeo or early Joseon period. As such, this technique is thought to represent this particular time period. In an eighteenth-century travelogue about a trip to Mt. Gayasan, the author describes a sculpture that is believed to be the statue of Huirang Daesa at Haeinsa Temple, based on various unique features that closely correspond to the sculpture's current appearance. For example, the sculpture is said to have a hole in the chest and rough, knobby tendons and bones, two features that can still be seen today. Another sculpture of a Buddhist monk who was active in the western regions during the third and fourth century also has a hole in the chest, which is said to be a symbol of spiritual strength. The travelogue also states that the statue was lacquered black at the time, which means that it must have been painted with its present colors some time in the nineteenth century. Over time, the sculpture has been enshrined in various halls of Haeinsa Temple, including Haehaengdang, Jinsangjeon, and later Josajeon (Hall of the Patriarchs), and Bojangjeon. Records show that images of Buddhist monks, or "seungsang," were produced in Korea as early as the Three Kingdoms period (18 BCE-660 CE), but few of these works have survived. At present, only four such sculptures are extant, including the images of Huirang Daesa from the Goryeo period, and those of Monk Naong and Uisang Daesa from the Joseon period. Of these, the sculpture of Huirang Daesa has special significance for its early production date (i.e., CE. tenth century), outstanding production techniques, and superb artistic quality, realistically capturing both the external appearance and internal character of the subject. The tradition of producing, sanctifying, and worshipping statues of monks was prevalent not only in Korea, but also in China and Japan. However, each country developed its own preferred materials and techniques for producing these unique images. For example, while China has a large number of mummified Buddhist images (yuksinbul), Japan produced diverse images with various materials (e.g., dry lacquer, wood, clay) according to period. But despite the differences in materials and techniques, the three nations shared the same fundamental purpose of expressing and honoring the inherent spirituality of the monks.

Optimized Controlled Atmosphere Regimen for Storage of Fresh Fischer's Ligularia (Ligularia fischeri Turcz.) Leaves (신선 곰취(Ligularia fischeri Turcz.) 잎 저장을 위한 CA 조성 최적화)

  • Park, Yoon-Moon;Kim, Taewan;Kim, Hyun-Seok;Kim, Tae Hoon;Park, Yoo Jin
    • Horticultural Science & Technology
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    • v.33 no.3
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    • pp.375-382
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    • 2015
  • A controlled atmosphere (CA) regimen was optimized during 3 consecutive harvest seasons as the basis of practical modified atmosphere packaging (MAP) storage for quality maintenance and extension of storage potential of fresh Ligularia fischeri leaves. Leaves were harvested in April or May and forced-air cooled to $4^{\circ}C$ before punch-hole MAP (control, where gas concentrations were same as air) and CA treatments. CA regimens adjusted stepwise during 3 experimental years were: 1 and 3% $O_2$, respectively combined with 5 and 10% $CO_2$ in the first year, 3% $O_2$ fixed in combination with 0, 2.5, and 5% $CO_2$ in the second year, and 3% $O_2$ fixed in combination with 2.5 and 5% $CO_2$ in the third year. In the first year, higher incidence of black discoloration was observed with the reduction of respiration under 10% $CO_2$ CA conditions regardless of $O_2$ levels at 1 or 3%. In the second and third year, the incidence of the disorder seemed not to be clearly relevant to CA conditions showing slightly higher incidence only after 4- or 5-week storage + 5-day shelf life. Although texture and appearance quality were maintained better under the 3% $O_2$ + 2.5% $CO_2$condition after 4-week storage + 5-day shelf life, effects of CA on the extension of storage period was slight. Overall results indicated that Ligularia fischeri leaves are very susceptible to $CO_2$ injury. $CO_2$ concentration should be adjusted below 2.5% for safe and effective CA or MAP storage to maintain quality even during short-term storage.

SF Movie Star Trek Series and the Motif of Time Travel (SF영화 <스타트랙> 시리즈와 시간여행의 모티프)

  • Noh, Shi-Hun
    • Journal of Popular Narrative
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    • v.25 no.1
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    • pp.165-191
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    • 2019
  • The purpose of this article is to elucidate why the motif of time travel is repeated in the science fiction narrative by examining the functions of this motif in the SF movie series of Star Trek in its narrative and non-narrative aspects. Star Trek IV: The Voyage Home (1986) aims to attract the audience's interest in the story through the use of plausible time travel in the form of the slingshot effect which causes the spacecraft to fly at very fast speeds around an astronomical object. The movie also touches upon the predestination paradox that arises from a change of history in which it describes a formula of transparent aluminum that did not exist at the time. The film also serves as an evocation of the ideology of ecology by including humpback whales in the central narrative and responding to the real issue of the whale protection movement of the times. Star Track VIII: First Contact (1996) intends to interest the audience in the narrative with the warp drive, a virtual device that enables travel at speeds faster than that of light and a signature visual of Star Trek, at the time of its birth through time travel. The film emphasizes the continuation of peaceful efforts by warning the destruction of humanity that nuclear war can bring. It tackles with the view of pacifism and idealism by stressing the importance of cooperation between countries in the real world by making the audience anticipate the creation of the United Federation of Planets through encounters with the extraterrestrial. Star Trek: The Beginning (2009) improves interest through the idea of time travel to the past, this time using a black hole and the parallel universe created thereby. The parallel universe functions as a reboot, allowing a new story to be created on an alternate timeline while maintaining the original storyline. In addition, this film repeats the themes pacifism and idealism shown in the 1996 film through the confrontation between Spock (and the Starfleet) and Nero, the destruction of the Vulcan and the Romulus, and the cooperation of humans and Vulcans. Eventually, time travel in three Star Trek films has the function of maximizing the audience's interest in the story and allowing it to develop freely as a narrative tool. It also functions as an ideal solution for commenting on current problems in the non-narrative aspect. The significance of this paper is to stress the possibility that the motif of time travel in SF narrative will evolve as it continues to repeat in different forms as mentioned above.