• 천문학회보
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• 제46권2호
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• pp.67.2-67.2
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• 2021

We present preliminary results on the chemical and kinematic analysis of accreted and heated metal-rich (-1.0 < [Fe/H] < -0.3) stars in the Galactic disk. These stars are in the ranges of e > 0.7, -100 < V_𝜙 < 100 km/s, and |Z| < 3 kpc, and are presumably heated (accreted) by (from) past merger events such as Gaia Enceladus and Sausage (GSE). These stars are largely separated into two groups based on the level of [α/Fe] and radial velocity dispersion. The first group has low [α/Fe] and high radial velocity dispersion, and the second group shows high [α/Fe] and low radial velocity dispersion. We propose that the first group of stars are accreted from the GSE galaxy, whereas the second group of stars are dynamically heated by the GSE merger event.

• 천문학회보
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• 제31권2호
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• pp.62.2-62.2
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• 2006

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.663-666
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• 2002

Hard disk drived (HDD) in computer are used extensively as data storage capacity. The trend in the computer industry to produce smaller disk drives rotating at higher speeds requires an improved understanding of fluid motion in the space between disks. The distribution of pressure disturbance on disks has relation to flow structure. To investigate the flow structure, time-resolved hot-wire measurements of the circumferential velocity component were obtained for the flow between the center pair of four disks of common radius $R_2$ coretating at angular velocity ${\Omega}$ in a fixed cylindrical enclosure. Hot-wire supporter acts as an obstruction in this case. The effects of rotating speed and size of hot-wire supporter diameter between disks on the flow driven by disks were investigated. Velocity spectra at the fixed space were measured to obtain the structure of inner and outer region in flow field.

• 천문학회지
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• 제42권2호
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• pp.17-26
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• 2009

We estimate the enclosed mass profile in the central 10 pc of the Milky Way by analyzing the infrared photometry and the velocity observations of dynamically relaxed stellar population in the Galactic center. HST/NICMOS and Gemini Adaptive Optics images in the archive are used to obtain the number density profile, and proper motion and radial velocity data were compiled from the literature to find the velocity dispersion profile assuming a spherical symmetry and velocity isotropy. From these data, we calculate the the enclosed mass and density profiles in the central 10 pc of the Galaxy using the Jeans equation. Our improved estimates can better describe the exact evolution of the molecular clouds and star clusters falling down to the Galactic center, and constrain the star formation history of the inner part of the Galaxy.

• 전자공학회논문지B
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• 제29B권11호
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• pp.36-45
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• 1992

A numerical trajectory planning method for path-constrained trajectory planning is proposed which ensures collision-free and time-optimal motions for two robotic manipulators with limited actuator torques and velocities. For each robot, physical constraints of the robots such as limited torques or limited rotational velocities of the actuators are converted to the constraints on velocity and acceleration along the path, which is described by a scalar variable denoting the traveled distance from starting point. Collision region is determined on the coordination space according to the kinematic structures and the geometry of the paths of the robots. An Extended Coordination Space is then constructed` an element of the space determines the postures and the velocities of the robots, and all the constraints described before are transformed to some constraints on the behaviour of the coordination-velocity curves in the space. A dynamic programming technique is them provided with on the discretized Extended Coordination Space to derive a collision-free and time-optimal trajectory pair. Numerical example is included.

• 로봇학회논문지
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• 제10권4호
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• pp.230-244
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• 2015

Continuous-path motion control such as resolved motion rate control requires online solving of the inverse differential kinematics for a robot. However, the solution space of the inverse differential kinematics related to Jacobian J is not well-established. In this paper, the solution space of inverse differential kinematics is analyzed through categorization of mapping conditions between joint velocities and end-effector velocity of a robot. If end-effector velocity is within the column space of J, the solution or the minimum norm solution is obtained. If it is not within the column space of J, an approximate solution by least-squares is obtained. Moreover, this paper introduces an improved mapping diagram showing orthogonality and mapping clearly between subspaces, and concrete examples numerically showing the concept of several subspaces. Finally, a solver and graphics user interface (GUI) for inverse differential kinematics are developed using MATLAB, and the solution of inverse differential kinematics using the GUI is demonstrated for a vertically articulated robot.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.290-292
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• 2004

Near-IR observations of the central few parsecs of our Galaxy from the HST/NICMOS have been analyzed to produce H, K photometry. We have cross-identified our photometry with the Keck high-resolution spectrometry of the central 0.5 pc of our galaxy to distinguish evolved late-type stars from early-type stars, and use late-type stars as tracer population. We perform several statistical tests to find the best fitting parameters of stellar density distribution and velocity dispersion models, then derive volume number densities and velocity dispersions. The volume number density distribution has power law index $1.55\~1.7$. We then derive the mass distribution in the Central region of our Galaxy using the Jeans equation.

• 천문학회보
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• 제39권1호
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• pp.71.2-71.2
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• 2014

For better understanding of the physics of pores, we have investigated horizontal and vertical motions of plasma in a pore obtained on 2013 August 24 by using high time and spatial resolution data from the Fast Imaging Solar Spectrograph (FISS) of the 1.6 meter New Solar Telescope (NST). We infer the LOS velocity by applying the bisector method to the wings of Ca II 8542 ${\AA}$ profile, and inspect oscillations of the intensity and the LOS velocity in the pore. In this presentation, we discuss the physical implications of our results in view of a connection between LOS and horizontal plasma flows in a concentrated magnetic flux.

• 한국식품조리과학회지
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• 제31권1호
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• pp.33-40
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• 2015

For the globalization of Korean food restaurants, the kitchens should be equipped with proper ventilation systems and space to keep clean and ensure food safety. This study aimed to examine the ratio of kitchen to total space of restaurant and the suitability of the ventilation systems employed at Korean food restaurants. Data were collected by on-site survey of 12 Korean foods restaurants in Seoul. Length and width of the restaurants were measured with scale. Temperatures and air velocity around the heating equipment, working area, and hood were measured with a thermal imaging camera anemometer and thermometer. Statistical analyses were conducted with the SPSS program. The average space of the restaurants was $25.7m^2$. The ratio of kitchen to space was 0.22 for restaurants sized $32m^2$, 0.28 for $33-66m^2$, 0.21 for $66.1-99m^2$, 0.16 for $99.1-148.5m^2$, and 0.35 for those above $148.5m^2$. Average maximum and minimum air velocity around the hood were 0.28 m/sec and 0.22 m/sec, respectively. Under these conditions, the temperature of the working area was $41^{\circ}C$, presenting an uncomfortable indoor temperature for kitchen employees to work. When classifying 3 groups based on the minimum and maximum air velocity, the temperatures near the cooking area and in the hood of the restaurants showed significant differences among the three groups. When the maximum air velocity was over 0.3 m/sec, the temperature of the cooking area was as $30.1^{\circ}C$, showing a significantly lower temperature (p<0.01). Based on these results, the kitchen space rate of 0.25 to the total space and a ventilation system maintaining a maximum air velocity over 0.3 m/sec were recommended for ensuring the food safety of Korean foods restaurants sized 66 to $99m^2$.

• 대한기계학회논문집B
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• 제21권3호
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• pp.427-435
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• 1997

Conditional sampling techniques are utilized to investigate the relation between the wall skin-friction and stream wise velocity fluctuations in a turbulent boundary layer. Conditionally averaged results using a peak detection and the VITA (variable-interval time-averaging) technique show that a high skin friction is associated with high frequency components of the wall skin-friction fluctuations. The conditionally averaged wall skin-friction fluctuations obtained by using the VITA technique have a positively-skewed characteristics compared with the conditionally averaged stream wise velocity fluctuations. It is confirmed that there exists a phase shift between the wall skin-friction and stream wise velocity fluctuations, which was also found from the long-time averaged space-time correlations. The amount of phase shift between the wall skin-friction and stream wise velocity fluctuations is the same as that from the long-time averaged space-time correlations and does not change despite the variation of the detection threshold.