• Journal of Industrial Technology
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• v.24 no.B
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• pp.207-214
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• 2004

An active stick which supplies force feedback to the operator is developed in this study. A mathematical model of the active stick is derived, and compared with the experimental result. It turns out that the frictional torque due to the mechanical contacts of several parts of the stick is one of the major barriers to achieve high precision operation of the stick. The frictional effect of the stick is cancelled out by using a friction observer. The efficacy of the friction observer is verified through the numerical simulation. Because of the observer dynamics, there are some limitations in exact recovering the static friction and Stribeck effect. However, the friction observer follows the real friction on the average. It's anticipated that the application of the friction observer to the closed loop control of the active stick improves the performance of the displacement versus force characteristics, which will be proved experimentally in the further study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.616-619
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• 2000

The optimum design of a structure requires to determine economical member size and shape of a structure which satisfies the design conditions and functions. In this study, it is attempted to minimize a dead weight of the bogie frame. Therefore, shape optimization is performed for a bolster rib at first and then size optimization for the thickness of top and bottom plate. For the efficient reduction of a weight of a bogie frame, various ellipses centered at a centroid of a bolster rib are made and tried. For the shape optimization, a major axis and an eccentricity of an ellipse are chosen as design variables. From the numerical results of shape and size optimization of a bogie frame, it is known that the weight can be reduced up to 12.476 Y4717.21 kg) with displacement and stress constraints.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.69.1-69.1
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• 2014

We present the spatially resolved kinematics of ionized gas and stars along the major axis of 9 pseudo bulge galaxies. Using the high quality long-slit spectra obtained with the FOCAS at the Subaru telescope, we measured the flux, velocity, and velocity dispersion of the [OIII] and $H{\beta}$ lines to determine the size of the narrow-line region, rotation curve, and the radial profile of velocity dispersions. We compare ionized gas kinematics and stellar kinematics to investigate whether ionized gas shows any signs of outflows and whether stars and ionized gas show the same sigma-dip feature (i.e., decrease of velocity dispersion) at the very center.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.32.1-32.1
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• 2016

Early-type galaxies (ETGs) are supposed to follow the virial relation M ~ sigma^2 * R_e, with M being the galaxy mass, sigma being the stellar velocity dispersion, and R_e being the (2D) effective radius. I apply this relation to (a) the ATLAS3D sample and (b) the sample of Saglia et al. (2016). The two datasets reveal a statistically significant tilt of the empirical relation relative to the theoretical virial relation such that M ~ (sigma^2 * R_e)^0.92 with zero intrinsic scatter. This tilt disappears when replacing R_e with the semi-major axis of the projected half-light ellipse, a. Accordingly, a, not R_e, is the correct proxy for the scale radius of ETGs. By geometry, this implies that early-type galaxies are axisymmetric and oblate in general, in agreement with recent results from modeling based on kinematics and light distributions.

• International Journal of Fluid Machinery and Systems
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• v.5 no.2
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• pp.49-59
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• 2012

The present study is devoted to the influence of a superposed radial inflow in a rotor-stator cavity with a peripheral opening. The flow regime is turbulent, the two boundary layers being separated by a core region. An original theoretical solution is obtained for the core region, explaining the reason why a weak radial inflow has no major influence near the periphery of the cavity but strongly affects the flow behavior near the axis. The validity of the theory is tested with the help of a new set of experimental data including the radial and tangential mean velocity components, as well as three components of the Reynolds stress tensor measured by hot-wire anemometry. The theoretical results are also in good agreement with numerical results obtained with the Fluent code and experimental data from the literature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.9
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• pp.1814-1821
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• 2002

NC cutting simulation is an important factor in the development of products. The geometric modelling of cutter swept surface should be done in NC cutting simulation. A part of cutter swept surface is a ruled surface blended with silhouette curve and cutter path. Finding an intersection point between cutter swept surface and a line is one of major problems in Z-map based cutting simulation. In this paper, cutter swept surface is defined parametrically and it's intersection point with Z-map is found in an exact form. Triangular grid Z-map based 3-axis NC cutting simulation is performed.

• International Journal of CAD/CAM
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• v.6 no.1
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• pp.81-87
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• 2006

This paper describes a method for extracting surfaces from multi-material CT (Computed Tomography) data. Most contouring methods such as Marching Cubes algorithm assume that CT data are composed of only two materials. Some extended methods such as [3, 6] can extract surfaces from the multi-material (non-manifold) implicit representation. However, these methods are not directly applicable to CT data that are composed of three or more materials. There are two major problems that arise from fundamentals of CT. The first problem is that we have to use n(n-1)/2 threshold values for CT data contains n materials and select appropriately one threshold value for each boundary area. The second is that we cannot reconstruct only from CT data in which area three or more materials are adjacent each other. In this paper, we propose a method to solve the problems by using image analysis and demonstrate the effectiveness of the method with application examples construct polygon models from CT data of machine parts.

• Journal of Integrative Natural Science
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• v.9 no.4
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• pp.241-248
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• 2016

Corticotropin-releasing factor receptors (CRFRs) activate the hypothalamic-pituitary-adrenal axis, which is an integral part of the fight or flight response to stress. Increase in CRH level is observed in Alzheimer's disease and major depression and hypoglycemia. Here, we report on the relevant physicochemical parameters required for the CRFR inhibitors. Comparative molecular similarity indices analysis (CoMSIA) was performed with the derivatives of 8-substituted-2-aryl-5-alkylaminoquinolinesas CRFR inhibitors. The best predictions were obtained for the best CoMSIA model with a $q^2$ of 0.576 with 6 components and $r^2$ of 0.977. The statistical parameters from the generated CoMSIA models indicated that the data are well fitted and have high predictive ability. CoMSIA contour maps could be useful in the designing of more potent and novel CRFR derivatives.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.77.2-77.2
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• 2010

We report a possible low-mass companion around the K2 III star $\varepsilon$ CrB (HD 143107). This star belongs to our sample of 55 K-giants studied for their radial velocity variations using the fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) attached to the 1.8-m telescope at Bohyunsan Optical Astronomy Observatory (BOAO). Our precise radial velocity measurements were obtained from February 2005 to June 2010. We find an orbital solution with a period of P = 419 days, a semi-amplitude of K = 137 m/s, and an eccentricity of e = 0.14. Assuming a moderate stellar mass of $M_{\bigstar}=0.77\;M\odot$, we calculate the minimum mass for the companion of m sini = $4.2\;M_{Jup}$ with an orbital semi-major axis of 1.0 AU.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.49.1-49.1
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• 2018

The MATS (Mesosphere Airglow/Aerosol Tomography Spectroscopy) satellite is the next Swedish science microsatellite. We report optical performance test results of the limb telescope, which is the major payload. This telescope is designed with "linear astigmatism-free" (LAF) off-axis optical system in order to have high optical performance across the wide field of view. We measured Modulation Transfer Function (MTF) and Encircled Energy Diameter (EED) of the limb telescope. Full field imaging tests show expected results without linear astigmatism across the full field of view ($5.67^{\circ}{\times}0.91^{\circ}$). Since the amount of stray light is from the earth and the sun, we also simulated and measured the stray light in the field image.