• Title/Summary/Keyword: Field observations

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Finite Element Analysis for Electron Optical System of a Field Emission SEM (전계방출 주사전자 현미경의 전자광학계 유한요소해석)

  • Park, Keun;Park, Man-Jin;Kim, Dong-Hwan;Jang, Dong-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12 s.255
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    • pp.1557-1563
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    • 2006
  • A scanning electron microscope (SEM) is well known as a measurement and analysis equipment in nano technology, being widely used as a crucial one in measuring objects or analyzing chemical components. It is equipped with an electron optical system that consists of an electron beam source, electromagnetic lenses, and a detector. The present work concerns numerical analysis for the electron optical system so as to facilitate design of each component. Through the numerical analysis, we investigate trajectories of electron beams emitted from a nano-scale field emission tip, and compare the result with that of experimental observations. Effects of various components such as electromagnetic lenses and an aperture are also discussed.

Observation of bubble dynamics under water in high-magnetic fields using a high-speed video camera

  • Lee, Seung-Hwan;Takeda, Minoru
    • Journal of Navigation and Port Research
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    • v.28 no.2
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    • pp.141-148
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    • 2004
  • The observations of rapid motion of bubbles under water for approximately 50ms or less in high . magnetic fields of 10 T have been carried out successfully for the first time. The observation system constructed is composed of a high-speed video camera, a telescope, a cryostat with a split-type superconducting magnet, a light source, a mirror and a transparent sample cell. Using this system, the influence of magnetic field on the path and shape of single bubbles of $O_2$(paramagnetism) and $N_2$ (diamagnetism) has been examined carefully. Experimental values describing the path are in good agreement with theoretical values calculated on the basis of the magneto-Archimedes effect, despite the effect of magnetism on the bubble. However, no effect of magnetism on the shape of the bubble is observed In addition, the influence of magnetic field on drag coefficient of the bubble is discussed.

Relationship between the Abnormalities of the Reproductive Organ and the Accumulation of the Environmental Disruptors in the Striped Field Mouse, Apodemus agrarius (등줄쥐의 생식계 이상과 내분비계장애물질 축적과의 관련에 대하여)

  • Yoon Myung Hee
    • Proceedings of the Korea Society of Environmental Biology Conference
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    • 2003.11a
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    • pp.38-47
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    • 2003
  • Relationships between accumulations of endocrine disruptors and abnormalities in the reproductive organs in the adult male striped field mice, Apodemus agrarius, were reviewed. High levels of phenolic compounds were detected in the mice collected at an agricultural village in Gaduck island and at a place having a sewage problem in Samdong-myeon, Namhae. High levels of organo tin compounds were found in the mice collected at Jiri Mt. a tourist resort. Considerably high levels of phenolic or organo tin compounds were detected in mice with shrunken reproductive organs accounting for 14∼42% of the mice examined in each area, which suggests that the abnormality of reproductive organs may be induced by the endocrine disruptors. This hypothesis is strongly supported by histological observations of shrunken reproductive organs, such as necrosis of testicular germ and epithelial cells. This was found not only in the mice with shrunken reproductive organs but also in the mice with enlarged reproductive organs, both had accumulated high levels of endocrine disruptors in general.

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Constraints on scalar field models of dark energy.

  • Lee, Da-hee;Park, Chan-Gyung;Hwang, Jai-chan
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.41.1-41.1
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    • 2019
  • We consider dynamical dark energy models based on a minimally coupled scalar field with three different potentials: the inverse power-law, SUGRA and double exponential potentials. For each model, we derived perturbation initial conditions in the early epoch and performed the Markov Chain Monte Carlo (MCMC) analysis to explore the parameter space that is favored by the current cosmological observations like Planck CMB anisotropy, type Ia supernovae, and baryon acoustic oscillation data. The analysis has been done by using the modified CAMB/COSMOMC code in which the dynamical evolution of the scalar field perturbations are fully considered. The MCMC constraints on the cosmological as well as potential parameters are derived. In the talk we will present a progress report.

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Maemi Dual Field Telescope System (MDFTS) : New survey facility of Kyung Hee Astronomical Observatory

  • Ahn, Hojae;Kim, Na Yeon;Kim, Dohoon;Pak, Soojong;Im, Myungshin
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.2
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    • pp.79.2-79.2
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    • 2019
  • We introduce Maemi Dual Field Telescope System (MDFTS) which is newly installed at Kyung Hee Astronomical Observatory (KHAO). MDFTS consists of two telescope tubes (40cm and 10cm), whose observing fields are aligned with different field of view, 15' x 11' and 83' x 63' respectively. We present the specification of instruments (telescope, mount, camera, and filter system) and the observation environment of KHAO. We expect that MDFTS can be used for transient survey e.g. Intensive Monitoring Survey of Nearby Galaxies (IMSNG). Based on observations conducted so far, the limiting magnitude of 40cm telescope in B-band is B_lim ~ 16 mag at 5-σ detection with 150 seconds total integration time under dark and clear observing condition. Also the integrated observing software for MDFTS, KAOS40 is now under developing.

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Approaches to Southeast Asian Studies: Beyond the "Comfort Zone"

  • Sathian, Mala Rajo
    • SUVANNABHUMI
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    • v.7 no.1
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    • pp.89-103
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    • 2015
  • Over the last decade, the field of Southeast Asian Studies has been inundated with issues of its "territory" (or the definition of what comprises Southeast Asia), relevance and future. The methodology of approaching Southeast Asian Studies has also come under constant scrutiny providing much fodder for debate. One significant suggestion was that the field of Southeast Asian Studies should "break out of the comfort zone" (Van Schendel, Bijdragen, 2012:168(4)). This paper will explore some of the ways of approaching Southeast Asian Studies beyond that comfort zone by examining other/alternative units of studying Southeast Asia in place of the traditional (or statist) perspectives that tend to confine the field within the scope of the national/nation-state boundaries. The paper will also provide some personal observations of the author on the current state and limitations to teaching and researching Southeast Asian Studies in the region.

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Faraday Rotation Measure and Cosmic Magnetic Field

  • Cho, Hyunjin;Ryu, Dongsu;Ha, Ji-hoon;Kang, Hyesung
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.2
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    • pp.39.3-40
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    • 2021
  • The Faraday rotation measure (RM) of extragalactic radio sources is one of tools that can explore the magnetic field in the cosmic web. We have investigated the statistical properties of the RM using the data of simulations for the large-scale structure formation of the universe. Various modelings for the cosmic magnetic field including the redshift dependence, and the intrinsic RM of radio sources have been considered. We here present the structure functions (SFs) of simulated RMs for small angular separations, and compare the SFs with observations, specifically those from the NRAO VLA Sky Survey (NVSS) and LOFAR Two-Metre Sky Survey (LoTSS). We then discuss the implications of our work.

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Designer-User Interaction without Actual Users: A Lesson from a Field Study

  • Jaehyun Park
    • Asia pacific journal of information systems
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    • v.28 no.3
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    • pp.220-239
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    • 2018
  • The purpose of the paper is empirically to explore 'design manner', focusing on the designer's knowledge boundary on the designer-user interactions in the design process. This study conducts a field study and observed designer's interactions with actual users in a leading user-centered design firm over three months. The observations revealed how designers bring ideas about users into design without physically interacting with users during the design process. Based on Bourdieu's theory of practice and the concept of boundary objects, this study introduces the concept of 'design manner', by which designers incorporate user's ideas into the design process without actual involvement of users in the process. This paper contributes to the body of knowledge by introducing the design manner in-between designer's and user's knowledge boundaries and argue bridge between theoretical and actual designer-user interactions in the IS design process.

The Zodiacal Light Observations with the MIRIS

  • Pyo, Jeong-Hyun;Jeong, Woong-Seob;Matsumoto, Toshio;Lee, Dae-Hee;Han, Won-Yong;Ree, Chang-Hee;Park, Young-Sik;Nam, Uk-Won;Moon, Bong-Kon;Park, Sung-Joon;Cha, Sang-Mok;Lee, Sung-Ho;Yuk, In-Soo;Park, Jang-Hyun;Jin, Ho;Lee, Duk-Hang;Lee, Hyung-Mok;Hong, Seung-Soo
    • The Bulletin of The Korean Astronomical Society
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    • v.36 no.1
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    • pp.42.1-42.1
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    • 2011
  • The main payload of the Science and Technology Satellite 3 (STSAT-3), Multipurpose Infrared Imaging System (MIRIS), will be equipped with the wide-field near-infrared camera. Its wide field-of-view ($3.67^{\circ}{\times}3.67^{\circ}$) is optimal for the observation of the zodiacal light (ZL), the sunlight scattered by the interplanetary dust (IPD). The MIRIS will continuously monitor the seasonal variation of the ZL towards both north and south ecliptic poles, which is caused by the asymmetries of the IPD distribution with respect to the Sun and the ecliptic plane. In addition to the monitoring observations, we are planning pointed observations for compelling structures in the ZL, the asteroidal dust bands and the gegenschein. This presentation proposes the zodiacal light observations with the MIRIS and discusses the expected results.

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Polarimetry of solar system small bodies using the Seoul National University 61cm telescope and TRIPOL

  • Jin, Sunho;Ishiguro, Masateru;Kwon, Yuna Grace;Geem, Jooyeon;Bach, Yoonsoo P.;Seo, Jinguk;Sasago, Hiroshi;Sato, Shuji
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.64.2-64.2
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    • 2019
  • It is known that lights scattered by comets and asteroids are partially polarized. From polarimetric observations of those objects, we can investigate physical properties, such as albedos, sizes of cometary dust particles and regolith of asteroids. Since the polarization degrees of those objects highly depend on their phase angles (Sun-object-observer's angles), long-term monitoring observations are required. Moreover, comets show unforeseeable activations (i.e., outbursts) which need follow-up observations to understand the mechanism. In order to realize such monitoring and transient observations, we installed the Triple-Range Imager and POLarimeter (TRIPOL) on the 61cm telescope of Seoul National University (Hereafter, SNU) Gwanak campus. With this combination, we can obtain g', r', i' bands photopolarimetric images simultaneously with $8.0^{\prime}{\times}8.0^{\prime}$ field of view and pixel resolution of 0.94" pixel-1. Here, we make a presentation regarding the photometric and polarimetric performances of TRIPOL on the SNU 61cm telescope. In addition, we introduce initial polarimetric results of asteroid and comets with the instruments. First, we determine the limiting magnitudes (defined as magnitudes for S/N=5) of $15.17{\pm}0.06$ (g'-band), $15.68{\pm}0.01$ (r'-band), $16.24{\pm}0.03$ (I'-band), respectively, with total 240-seconds exposure (four 60-seconds exposure images, each was taken at different rotation angle for the half-wave plate). Second, we found that the instrumental polarization is negligibly small, ($-0.32{\pm}0.04%$ in the g', $-0.36{\pm}0.05%$ in the r' and $-0.21{\pm}0.04%$ in the i'-bands), while the polarization efficiencies are large enough to maximize the performance (i.e., $97.52{\pm}0.03%$ in the g', $98.83{\pm}0.02%$ in the r' and $99.15{\pm}0.02%$ in the i'-bands). With the instruments, we made observations of three Jupiter-family comets, 21P/Giacobini-Zinner, 38P/Stephan-Oterma, and 46P/Wirtanen and plan to observe one near-Earth asteroid, (433) Eros, on a trial basis. Especially for comets, we discriminate signals from dust and gas to eliminate gas contamination, which are known to change observed degree of linear polarization, using multi-band images. We confirm that the phase angle dependency of these comets are consistent with previous observations, probably because polarimetric property of Jupiter-family comets are broadly homogeneous unlike asteroids. We will also describe future observation plans using TRIPOL and SNU 61cm telescope.

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