• 천문학회보
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• 제40권1호
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• pp.73.1-73.1
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• 2015

Isolated galaxies in low-density regions are significant in the sense that they are least affected by the hierarchical pattern of galaxy growth and interactions with perturbers at least for the last few Gyr. To form a comprehensive picture of the star formation history of isolated galaxies, we construct a catalog of isolated galaxies and their comparison sample in relatively denser environments. The galaxies are drawn from SDSS DR7 in the redshift range of 0.025 < z < 0.044. We performed visual inspection and classified their morphology following the Hubble classification scheme. We have investigated the color-magnitude diagram and found elliptical and unbarred spiral galaxies in isolated systems are relatively fainter and bluer than those in denser regions. For the spectroscopic study, we make use of the OSSY catalog (Oh et al. 2011). Our analysis on the absorption-line properties based on the comparison with stellar population models suggests that isolated elliptical galaxies are likely to be younger and metal poorer, while isolated Sc-type galaxies seem to have older luminosity-weighted ages, than their high-density counterpart. In addition, according to the BPT diagnostics, early-type galaxies among isolated galaxies are rather evenly classified into star forming, composite, Seyfert and LINER, whereas their comparisons are mainly populated in the LINER region. On the other hand, late-type galaxies do not show any prominent difference. We discuss the evolutionary histories of isolated galaxies in the context of the standard ${\Lambda}CDM$ cosmology.

• 천문학회지
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• 제30권1호
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• pp.95-106
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• 1997

We investigate the velocity distribution of dark matter in the disk of a galaxy like the Milky Way at the solar radius. Using N-body simulations with the total mass and z-component of angular momentum conserved, we calculate the response of a dissipationless dark matter galactic halo during the dissipational collapse of the baryonic matter in spiral galaxy formation. The initial distribution of dark matter and baryonic particles is assumed to be a homogeneous mixture based on a King model. The baryonic matter is assumed to contract, forming the final luminous components of the galaxy, namely the disk and, in some cases, a bulge and central point. Both slow and fast growth of the luminous components are considered. We find that the velocity distribution of dark matter particles in a reference frame rotating slowly about the galaxy center in the plane of the disk is similar to a Maxwellian, but it is somewhat boxier, being flatter at the peak and truncated in the tails of the distribution. We tabulate parameters for the best-fitting Maxwellian and modified-Maxwellian distributions. There is no significant difference between slow collapse and fast collapse for all these results. We were unable to detect any effect of disk formation on the z-dependence of the dark matter density distribution.

• International Journal of Contents
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• 제11권4호
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• pp.44-55
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• 2015

There has been a significant paradigm shift in the book industry from print to digital, with the increased use of electronic books (e-books) on e-book readers. The major online booksellers and publishers are devoting their energies to the growth of the e-book market, resulting in an upward spiral in e-book usage, and a resultant increase in the number of downloaded e-books in an e-book reader library. However, there are comparatively few features for e-book management and search in most e-book reader libraries, particularly in smartphone environments. In addition, the user interfaces of e-book management in e-book readers are highly diverse, which has led to major usability issues. In this paper, we analyze user preferences for e-book management and search in the libraries of the five most commonly used e-readers for the Android smartphone platform via a questionnaire survey. Then, we suggest ideal alternatives in addition to user-friendly features based on user preferences for managing e-book libraries, to allow users to more easily browse collections, thereby enhancing the usability of e-book readers.

• 치과방사선
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• 제28권2호
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• pp.491-503
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• 1998

A cystic compound odontoma in the maxillary sinus occurred in a 13-year-old boy. who had missing right upper third molar without having the history of extraction of the wisdom tooth. He complained nasal stuffiness. headache. and pain on the affected face. resembling any sign and symptoms of the maxillary sinus problems. The cystic compound. sized 2 x 1.5 cm in diameter was pedunculated and attached on the posterior wall of the right maxillary sinus and above the antral floor. The location of the compound odontoma in the maxillary sinus was confirmed after panoramic. waters. spiral tomographic. CT examinations and surgical exploration. Its location was on the medial. posterior. superior to the normal position of the maxillary third molar or the maxillary dental arch. The cystic odontoma in the maxillary sinus made the patient have the signs and symptoms of maxillary sinusitis. The cystic compound odontoma might be originated from the dental lamina of the missing upper right third molar. The 'V principle' of the upper jaw growth and the pneumatization process of the maxillary sinus could explain why the compound odontoma had peduncular shape and the location of odontoma was on the medial. superior to the normal position of the maxillary dental arch.

• 천문학회보
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• 제43권2호
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• pp.34.1-34.1
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• 2018

We investigate the properties of bright galaxies with various morphological types in Abell 1139 and Abell 2589, using the pixel color-magnitude diagram (pCMD) analysis. The 32 bright member galaxies ($Mr{\leq}-21.3mag$) are deeply imaged in the g and r bands in our CFHT/MegaCam observations, as a part of the KASI-Yonsei Deep Imaging Survey of Clusters (KYDISC). We examine how the features of their pCMDs depend on galaxy morphology and infrared color. We find that the g - r color dispersion as a function of surface brightness (${\mu}r$) shows better performance in distinguishing galaxy morphology, than the mean g - r color does. The best set of parameters for galaxy classification appears to be a combination of the minimum color dispersion at ${\mu}r{\leq}21.2mag\;arcsec-2$ and the maximum color dispersion at $20.0{\leq}{\mu}r{\leq}21.0mag\;arcsec-2$: the latter reflects the complexity of stellar populations at the disk component in a typical spiral galaxy. Moreover, the color dispersion of an elliptical galaxy appears to be correlated with its WISE infrared color ([4.6]-[12]). This indicates that the complexity of stellar populations in an elliptical galaxy is related to its recent star formation activities. From this observational evidence, we infer that gas-rich minor mergers or gas interactions may have usually occurred during the recent growth of massive elliptical galaxies.

• 한국응용약물학회:학술대회논문집
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• 한국응용약물학회 1996년도 춘계학술대회
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• pp.197-197
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• 1996

Helicobacter pylori (H. pylori) is a microaerophilic spiral bacterium and infection by it in the human stomach causes gastritis, furthermore, it is considered to be involved in the pathogenesis of peptic ulcers and the development of gastric carcinoma. We assessed the inhibitory activity of new antiulcer drugs against Helicobacter pylori. The activities of new antiulcer agents against Helicobacter pylori strains were determined by the standard agar dilution method with blood agar base #2, supplemented with 5% sheep blood and 4 antibiotics to support growth of these organisms. They were inoculated by multipoint inoculator and incubated at 37$^{\circ}C$ for 3 days under microaerophilic atmosphere. The MIC of antiulcer agents was the lowest concentration that inhibited visible growth of these organisms. According to results of various biochemical tests, these bacteria were identified as Helicobacter pylori strains. And the MIC results showed that the strains were very susceptible to omeprazole and YJA20379s. Some of YJA20379s were more potent than omeprazole. These results suggest that our new antiulcer drugs have potent inhibitory activity against Helicobacter pylori, so that our new antiulcer drugs might be useful for the clinical eradication of gastrointestinal Helicobacter pylori.

• Journal of the Korean Wood Science and Technology
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• 제45권5호
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• pp.525-534
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• 2017

잎갈나무와 일본잎갈나무의 종 구분을 위하여 해부학적 특성을 관찰하고, 재질의 특성을 밝히기 위하여 연륜폭, 가도관 길이, 밀도, 강도 등을 비교분석하였다. 수간해석와 시험편 채취를 위하여 강원도 정선군 정선읍 지역에서 생장한 잎갈나무와 일본잎갈나무를 경급별(대 중 소)로 1본씩 선발하여 벌채하였다. 잎갈나무와 일본잎갈나무의 평균 수령은 각각 74년, 51년, 평균 흉고지름은 각각 442 mm, 352 mm, 평균 수고는 각각 26.1 m, 20.8 m이었다. 두 수종의 수목해부학적 차이는 나선비후가 잎갈나무에 존재하지 않지만, 일본잎갈나무의 방사가도관에 드물게 존재한다는 점이다. 하지만 본 연구에서는 잎본잎갈나무의 방사단면에서 나선비후가 발견되지 않았다. 수고 1.2 m의 원판에서 측정된 잎갈나무와 일본잎갈나무의 연평균 직경생장은 각각 5.167 mm, 5.954 mm로 일본잎갈나무의 생장이 잎갈나무에 비하여 우수하였다. 강도측정을 위한 시험편의 물리적 특성에서 연평균 직경생장이 작은 잎갈나무가 일본잎갈나무에 비하여 만재율과 전건밀도가 크게 측정되었다. 역학적 특성은 잎갈나무가 일본잎갈나무에 비하여 2 - 7% 크게 측정되었다. 본 연구를 통하여 축적된 자료는 향후 수행될 DNA 분석을 통한 잎갈나무와 일본잎갈나무 종 구분의 기초자료로 활용될 것으로 기대된다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
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• pp.216-227
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• 2004

A new cavitating model by using bubble size distribution based on bubbles-mass has been proposed. Both liquid and vapor phases are treated with Eulerian framework as a mixture containing minute cavitating bubbles. In addition vapor phase consists of various sizes of vapor bubbles, which are distributed to classes based on their mass. The bubble number-density for each class was solved by considering the change of the bubble-mass due to phase change as well as generation of new bubbles due to heterogeneous nucleation. In this method, the bubble-mass is treated as an independent variable, and the other dependent variables are solved in spatial coordinates and bubble-mass coordinate. Firstly, we employed this method to calculate bubble nucleation and growth in stationary super-heated liquid nitrogen, and bubble collapse in stationary sub-cooled one. In the case of bubble growth in super-heated liquid, bubble number-density of the smallest class based on its mass is increased due to the nucleation. These new bubbles grow with time, and the bubbles shift to larger class. Therefore void fraction of each class is increased due to the growth in the whole class. On the other hand, in the case of bubble collapse in sub-cooled liquid, the existing bubbles are contracted, and then they shift to smaller class. It finally becomes extinct at the smallest one. Secondly, the present method is applied to a cavitating flow around NACA00l5 foil. Liquid nitrogen and liquid oxygen are employed as working fluids. Cavitation number, $\sigma$, is fixed at 0.15, inlet velocities are changed at 5, 10, 20 and 50m/s. Inlet temperatures are 90K in case of liquid nitrogen, and 90K and 1l0K in case of liquid oxygen. 110K of oxygen is corresponding to the 90K of nitrogen because of the same relative temperature to the critical one, $T_{r}$=$T/T_c^{+}$. Cavitating flow around the NACA0015 foils was properly analyzed by using bubble size distribution. Finally, the method is applied to a cavitating flow in an inducer of the LE-7A hydrogen turbo-pump. This inducer has 3 spiral foils. However, for simplicity, 2D calculation was carried out in an unrolled channel at 0.9R cross-section. The channel moves against the fluid at a peripheral velocity corresponding to the inducer revolutions. Total inlet pressure, $Pt_{in}$, is set at l00KPa, because cavitation is not generated at a design point, $Pt_{in}$=260KPa. The bubbles occur upstream of the foils and collapse between them. Cavitating flow in the inducer was successfully predicted by using the bubble size distribution.

• Journal of Microbiology and Biotechnology
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• 제15권5호
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• pp.992-1000
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• 2005

Campylobacter is one of the emerging foodborne pathogens, and its worldwide incidence rate is extremely high. This study was undertaken to isolate and identify Campylobacter strains from chicken carcasses in the local markets, and analyze their characteristics regarding oxygen tolerance. They were isolated after aerobic enrichment and identified by biochemical, physiological, and morphological characteristics, PCR, and 16S rDNA sequencing. Their oxygen tolerances were analyzed in terms of the cell surface hydrophobicity, cell fatty acid composition, and oxidoreductase. Five strains of C. jejuni were isolated and identified from 61 isolates from 50 chickens. Among them, C. jejuni IC21 grew well in Brucella broth and commercial milk under aerobic condition. However, in the aerobic exposure, the cell surface hydrophobicity of C. jejuni IC21 was almost the same as the other isolates, even though its morphology changed from the spiral-bacilli form into the coccoid form. Fatty acid analyses showed that all Campylobacter strains had a high composition of $C_{19:1}$, cyclopropane fatty acid, and that the amount of the other fatty acids were very similar between them. Interestingly, however, only oxidoreductase activities of C. jejuni IC21 increased highly under aerobic exposure even though its activities were almost the same as the other C. jejuni strains just after microaerobic culture. It had 11.8 times higher catalase activity, 4.4 times higher for SOD, and 2.0 times higher for NADH oxidase activities. Therefore, in the case of the aero-adaptive C. jejuni IC21, expression of oxidoreductase significantly increased under oxidative stressed condition, which might allow it to survive for a longer time and grow on food under aerobic exposure. Such new strain might be one of the explanations for the increase of campylobacteriosis.

• 한국전산구조공학회논문집
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• 제26권4호
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• pp.309-318
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• 2013

본 논문에서는 일체식 교대 교량의 장대화 및 내진성능 향상을 위해 가장 중요한 역할을 하는 교대-H형 강말뚝 연결부의 성능을 향상시키기 위하여 기존의 연결부의 균열형상을 파악하고, 이를 기반으로 새로운 형태의 연결부를 제안하기 위하여 철근을 활용하여 강성을 증가시키는 방법과 강말뚝의 형상을 개선하여 연성을 개선시키는 방법을 모색하였다. 먼저, 기존 연결부의 성능을 향상시키기 위하여 연결부 주변에 PennDOT에 규정된 철근상세와 나선철근의 배치와 HSS 튜브를 사용하였으나, PennDOT의 철근 상세와 HSS 튜브는 연결부의 성능을 향상시키지 못 했으나, 나선철근은 균열을 효과적으로 차단시키는 것을 확인할 수 있었다. 하지만, 철근의 구속효과로 인해 강말뚝의 저항력이 변위에 선형적으로 비례하여 증가하므로 교량의 상부구조에 축력을 발생시키는 효과를 가져왔다. 따라서, 강말뚝의 형상을 개선하기 위하여 콘크리트 교대에 매입된 부분의 플랜지를 제거하는 방법과 콘크리트 외부에서 플랜지의 폭을 축소시키는 형태를 검토하였다. 두 가지 방안 모두 균열을 억제하는데 효과적인 방법이었으나, 플랜지를 제거하는 쪽의 연결부가 더욱 효과적이었다.