• 천문학회보
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• 제39권1호
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• pp.58.2-58.2
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• 2014

The Arches cluster is a young (2-4 Myr), compact (~1 pc), and massive (${\sim}2{\times}10^4M_{\odot}$) star cluster located ~30 pc away from the Galactic center (GC) in projection. Being exposed to the extreme environment of the GC such as elevated temperature and turbulent velocities in the molecular clouds, strong magnetic fields, and larger tidal forces, the Arches cluster is an excellent target for understanding the effects of star-forming environment on the initial mass function (IMF) of the star cluster. However, resolving stars fainter than ~1 $M_{\odot}$ in the Arches cluster partially will have to wait until an extremely large telescope with adaptive optics in the infrared is available. Here we devise a new method to estimate the shape of the low-end mass function where the individual stars are not resolved, and apply it to the Arches cluster. This method involves histograms of pixel intensities in the observed images. We find that the initial mass function of the Arches cluster should not be too different from that for the Galactic disk such as the Kroupa IMF.

• 한국생산제조학회지
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• 제19권3호
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• pp.414-418
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• 2010

Due to the increasing demand for carious methodologies to improve the quality of products were introduced. A Brush the most frequently used type of grinding process is one of the deburring. in order to produce consistent burr shape, various machining conditions have been combined and applied to disk grinding process. Between the workpiece and the grinding disc to earn depends on the angle of the slope has been observed. Drastic increase of tool wear has been also observed along the inclination angle variation. Various burr shapes have been captured and analyzed using image processing technique.

• 한국정보처리학회논문지
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• 제6권10호
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• pp.2716-2721
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• 1999

The problem of determining the conformal maps from the unit disk onto a jordan region has been completed by solving the theodorsen equation that is nonlinear. For the hubners method, which has been well known for the efficient method among the many suggestions for the Theodorsen equation, it has been reproved in our early study that the convergence rate could be remarkably improved by exploring and applying a low-frequency pass filter[1]. However, in the Hubner's method with the low-frequency filter, the discrete numbers and parameters of the low-frequency filter were able to be acquired only by experience. In this paper we show algorithms that determine the discrete numbers and parameters of the low-frequency filter automatically in accordance with the given region. This results from analyzing the function, which decides the shape of the given domain under the assumption that the degree of the problem depends of the transformation of a given domain, as seen in the Fourier Transform.

• 한국구조물진단유지관리공학회 논문집
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• 제2권2호
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• pp.170-176
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• 1998

The team mixed PbO, $ZrO_2$, $TiO_2$, $Nb_2O_5$ and $MnCO_3$, to make $Pb[(Zr_{0.54}\;Ti_{0.46})\;Nb_{0.005}]O_3+4%MnCO_3$. The electroded PZT ceramics were poled by 3 kV/mm at $110^{\circ}C$ for 600 s. We assembled the 0.4mm thick PZT slices into ultrasonic transducers. Central frequency of the probe is 5 MHz, which is proper to the thickness gauge for steel pipes and for flaw detector. The probe can detect a disk shape defect of 1mm diameter at 15cm deep in steel block. The new probe's Fresnel zone that the ultrasonic beam do not broaden is 13mm. Over the Fresnel zone, the ultrasonic beam spreads. Half of the beam spread angle of the probe is $4.3^{\circ}-4.6^{\circ}$. This probe can be used for the ultrasonic transducers for non-destructive testing of steel bridges.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.217-224
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• 2000

This paper proposes a new type of HDD suspension integrated with shape memory alloy(SMA) actuator in order to prevent the friction between the slider and the disk. A finite element analysis is undertaken to investigate modal characteristics of the proposed self loading/unloading slider. The dynamic model is formulated and its validity is proved by comparing the predicted displacement transmissibility with the measured one. A control model is then established by integrating experimentally-obtained SMA actuator dynamics. Subsequently, a sliding mode controller is designed to achieve non-contact start/stop(Non CSS) modes, and control results are presented in time domain.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.817-832
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• 2021

In this paper, a simple practical method to estimate the drag of Super-Cavitating Underwater Vehicles (SCUV) is proposed that can obtain the drag with only principal dimensions in an initial design stage. SCUV is divided into cavitator, forebody, afterbody, base, and control fin and the drag of each part is estimated. The formulas for the drag coefficient are proposed for the disk and cone type cavitators and wedges used as control fins. The formulas are a function of cavitation number, cone or wedge angle, and Reynolds number. This method can confirm the drag characteristics of SCUV that the drag hump appears according to the coverage of the body by the cavity and the cavitator drag remains only when the entire body is covered by cavity. Applying this method to SCUV of various shapes, it is confirmed that the effects of cavitating and non-cavitating conditions, cavitator and body shape, and speed could be found.

• Design & Manufacturing
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• 제17권2호
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• pp.33-41
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• 2023

Metal raw materials and chemical additives, which are raw materials for secondary batteries, are pulverized by the high-speed rotation of the Grinding Disc of the Classifier Separator Mill (CSM). Grinding discs are required to withstand abrasion, corrosion, high-speed rotational force and impact. In order to analyze the stability of domestic and foreign grinding discs, quality tests including surface roughness, surface lubrication, surface state measurement, and surface 3D shape measurement were analyzed. When producing developed products, it shows that excellent products can be produced.

• 열처리공학회지
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• 제36권6호
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• pp.412-421
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• 2023

As the demand for mechatronic systems and high performance increases in the machinery industry, the importance of improving friction characteristics is emphasized. During relative movement of objects, friction and wear occur on two surfaces in contact, and various methods are being designed to increase the lifespan and energy efficiency of machines. The energy increase effect using lubricants is a well-known method. In this study, a micro-sized rectangular grid pattern was produced by applying a precise micro-pattern photo lithography process. Rectangular grid patterns of the same shape and friction behavior according to the size of the pattern were produced in convex and concave shapes, and the tribological characteristics of each were analyzed.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2022년도 추계학술대회
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• pp.57-57
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• 2022

A taxonomic revision of Deutzia in Korea was conducted based on critical observations of wild populations and herbarium specimens. Species delimitations were re-evaluated on the basis of morphological characters and distributions resulting in the recognition of five taxa. The texture of leaf, flower disk and capsules, the shape of leaf, inflorescence and capsules are useful diagnostic traits at the specific level. The five taxa are well distinguished from each other. Deutzia grandiflora var. baroniana can be distinguished by its distribution and calyx from Deutzia uniflora, which are morphologically similar. Deutzia paniculata Nakai, a rare and endemic plant, is characterized by having panicle in inflorescences. On the other hand, Deutzia glabrata Kom. is occasionally confused with Deutzia parviflora, but the most distinctive characters include the surface of leaves, the surface and size of capsules. Photographs and a key to five species of Deutzia were provided in addition to distribution.

• 천문학회보
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• 제40권1호
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• pp.59.1-59.1
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• 2015

We present hydrodynamic simulations of gas clouds that inflowing from the disk to a few hundred parsec region of the Milky Way. Realistic Galactic structures are included in our simulations by thousands of multipole expansions that describe 6.4 million stellar particles of a self-consistent Galaxy simulation (Baba, Saitoh & Wada, in prep.). We find that a hybrid multipole expansion model with two different basis sets and a thick disk correction well reproduces the overall structures of the Milky Way. We find that the nuclear ring evolves into 240 pc at T~1500 Myr, regardless of the initial size. For most of simulation runs, gas inflow rate to the nuclear region is equilibrated as ~0.02 Msun/yr, and thus accumulated gas mass and star formation activity is stabilized as $6{\times}10^7Msun$ and ~0.02M/yr, respectively. These stabilized values are in a good agreement with estimations for the CMZ. The nuclear ring is off-centered to the Galactic center by the lopsided central mass distribution of the Galaxy model, and thus an asymmetric mass distribution is arose accordingly. The lopsidedness also leads the nuclear ring to be tilted to the Galactic plane and to precess along the Galaxy rotation. In early evolutionary stage when gas clouds start to inflow and form the nuclear ring, the z-directional oscillations of the gas clouds results in the twisted, infinity-shaped nuclear ring. Since the infinity-shaped feature is transient only for first 100 Myr, the current infinity-shape observed in the CMZ may indicate that the CMZ forms quite recently.