• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.72.3-73
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• 2017

The spatial distribution of sub-halos in a large host halo is usually described as isotropic in the ${\Lambda}CDM$ cosmology. Recent observations, however, show that satellite galaxies around massive galaxies are often located within a preferred plane. In order to understand the origin of such planar alignment, we investigate the spatial distribution of sub-halos around their hosts by using the hydrodynamic cosmological simulation, Illustris. In particular, we analyze the systems resembling the Milky Way (MW) and its satellites, i.e. consisting of MW-sized central galaxy and its at least 11 satellites. The result shows that ~10 % of MW-like systems have the anisotropic satellite galaxy distribution at z = 0. The satellites that are accreted more recently tend to form a flattened structure more frequently, indicating a link of satellite distribution to the surrounding environment. We discuss the physical origin of the anisotropic satellite distribution from the viewpoint of the ${\Lambda}CDM$ paradigm.

• Journal of Mechanical Science and Technology
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• v.17 no.1
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• pp.32-39
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• 2003

In this study we examined connections between vertebral motion and patterns of muscle activation during voluntary head tracking movements. A Rhesus (Maraca mulatta) monkey was trained to produce sinusoidal tracking movements of the head in the sagittal plane while seated. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted to record from eight neck muscles. Videofluoroscopic images of cervical vertebral motion, and EMG (electromyographic) responses were simultaneously re-corded. Experimental results demonstrated that head and vertebrae moved synchronously and that motion occurred primarily at skull-C$_1$, C$\_$6/-C$\_$7/ and Csub 7/-C$_1$. Our findings illustrate that although the biomechanical constraints of each species may limit the number of solutions available, it is the task requirements that appear to govern CNS (central nervous system) selection of movement behaviors.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.179-182
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• 2005

현재 액정 표시장치는 액정의 유전율 이방성 특성에 따라 Positive LC 와 Negative LC로 구분되어 개발 된다. Positive LC에는 TN(Twisted Nematic)모드와 IP(In Plane Switching) 모드가 있다. Negative LC에는 VA(Vertical alignment) 모드가 있다. 데이타 전압을 교류구동 시키므로, LCD Pixel들은 극성반전을 하게 되며, 이때 특정 Pattern에서 화면상에 비정상적인 색깔이 나타난다. 특정 Pattern이란 데이타 전압이 교류구동을 할 때, Vcom Level이 데이타 전압에 의한 Coupling 때문에 왜곡이 발생되고, 이 왜곡에 의하여 레드, 그린, 블루 Pixel의 충전을 차가 발생해서, 화면의 좌우는 적색편향 하게 보이고, 중앙은 녹색편향 발생된다.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.407-410
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• 2005

We report on a high speed flexible display based on a deformed helix ferroelectric liquid crystal (DHFLC) in a vertically aligned configuration. The mechanical stability of the flexible DHFLC display was achieved using a periodic array of columnar spacers formed directly on the top sides of in-plane electrodes by the photolithography technique. Several unique features of display performances such as flexibility, uniform alignment, fast response, and gray scale capability were obtained.

• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.156-161
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• 2014

Anisotropy profile of a rubbed polyimide film is investigated using both a modified ultra high precision transmission ellipsometer and the analysis software previously developed to determine the optic axis distribution of discotic liquid crystals in the wide view film. The distorted sinusoidal variation of the ellipsometric constants obtained at an oblique angle of incidence indicates that the optic axis varies from $14.7^{\circ}$ to $40.6^{\circ}$ from the sample plane. The magnitude and distribution of anisotropy is expressed in terms of no, ne, and the cosine-shaped tilt angle distribution of the optic axis in a rubbed polyimide film.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.12
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• pp.1001-1008
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• 2001

This paper presents a new camera calibration algorithm for ill-conditioned cases in which the camera plane is nearly parallel to a set of non-coplanar calibration boards. for the ill-conditioned case, most of existing calibration approaches such as Tsais radial-alignment-constraint method cannot be applied. Recently, for the ill-conditioned coplanar calibration Lee&Lee[16] proposed an iterative algorithm based on the least square method. The non-coplanar calibration algorithm presented in this paper is an iterative two-stage procedure with extends the previous coplanar calibration algorithm. Through the first stage, camera, position and orientation parameters as well as one radial distortion factor are determined optimally for a given data of the scale factor and the focal length. In the second stage, the scale factor and the focal length are locally optimized. This process is repeated until any improvement cannot be expected any more Computational results are provided to show the performance of the algorithm developed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.605-606
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• 2005

Depth error correction effect for maladjusted stereo cameras with calibrated pixel distance parameter is presented. Intra and extra parameters should be obtain to determine the relation between image and world coordination through experiment. One difficulty is in camera alignment for parallel installation: placing two CCD arrays in a plane. If the pixel distance parameter which is one of intra parameter is calibrated with known points, such error can be compensated in some amount. Such error compensation effect with the calibrated pixel distance parameter is demonstrated with various experimental results.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.186-186
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• 2009

Most liquid crystal display modes, including the twisted nematic (TN) $mode^1$, the in-plane switching (IPS) $mode^2$, the fringe field switching (FFS) $mode^3$, and the vertically aligned (VA) $mode^4$ are based on either a horizontal or a vertical alignment. However, for some applications, such as no-bias-bend (NBB) pi cell or bistable bend-splay display, an intermediate pretilt angle is essential$^5$. NBB pi cells have been a focus of interest because of their fast response time; however, the reliable control of the intermediate pretilt angle of liquid crystals that is required for the fabrication of NBB pi cells is challenging. The controllable pre-tilt angle of liquid crystals was investigated using a blend of horizontal and vertical polyimide prepared by a rubbing method. Various pretilt angles in the range from 0^{\circ}$ to 90^{\circ}$ were achieved as a function of the vertical polyimide content. We observed uniform liquid crystal alignment on the rubbing-treated blended polyimide layer. A NBB pi cell with an intermediate pretilt angle of 47.8^{\circ}$ was manufactured. This cell had no initial bias voltage and a low threshold voltage, which indicates that it has low power consumption. In addition, the response time of the NBB pi cell was rapid.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.22-28
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• 1992

Barium ferrite thin films were reactively deposited with Fe and BaO composite targets by a facing tergects sputtering unit. When thermally oxidized silicon wafers were used as substrates, minimum substrate heating of $750^{\circ}C$ was necessary for the perfect c-axis alignment in barium ferrite films. To lower the critical substrate temperature for the good c-axis alignment, such seed layers as ZnO, ${\alpha}-Fe_{2}O_{3}$ and ${\gamma}-Fe_{2}O_{3}$ were tested. The excellent c-axis algnment of BaM was obtained at a substrate temperature of $600^{\circ}C$ on ZnO seed layer whose (002) plane was parallel to the substrate surface. The magnetic properties of the BaM film showed saturation magnetization of 295 emu/cc, perpendicular coercivity of 1.7 kOe and squareness of 0.75. Optimum deposition rate of $230\;{\AA}/min$ was obtained with the composite target and this was 5 to 20 times higher than those of other investigators with oxide targets.

• Korean Journal of Optics and Photonics
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• v.3 no.2
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• pp.77-85
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• 1992

The design of a flat-field XUV spectrograph is optimized for a high throughput, aberration-corrected spectral image in the wavelength region of 50-300 $\AA$ The varied-line spacing (VLS) concave grating theory for an XUV spectrograph with a toroidal mirror in front of an entrance slit is derived. Since the derived theory includes the arbitrary shaped source, it is able to correct the limit of the simple optimization theory which considers only a point source at the center of the entrance slit. The reflection matrix at the toroidal mirror and the diffraction matrix at VLS grating are derived and compared with those of a holographic grating. The absolute energy efficiency of a flat-field spectrograph is calculated by considering the reflectivities of the toroidal mirror and the Au coated concave grating and the grating efficiency. The alignment sensitivity of the toroidal mirror and the concave grating is investigated, and the method to achieve the best imaging of XUV spectrum is discussed. The calculated resolving power of the flat-field XUV spectrograph is more than 4000 in the aberration-corrected wavelength range. The focused spot size at the dispersion plane is less than $20\mu \textrm m\times \mu \textrm m$at the wavelength 100$\AA$ It is shown that a high throughput characteristic can also be achieved through a careful adjustment of alignment parameters.