• Journal of Radiation Protection and Research
• /
• v.26 no.3
• /
• pp.225-229
• /
• 2001

In Korea, an advanced reactor system of 330MWt power called SMART (System integrated Modular Advanced ReacTor) is being developed by KAERI to supply energy for seawater desalination as well as electricity generation. A shielding design of the SMART core with 49 CEDM is established by a two-dimensional discrete ordinates radiation transport analyses. The DORT two-dimensional discrete ordinates transport code is used to evaluate the SMART shielding designs. Three axial regions represent the SMART reactor assembly, each of which is modeled in the R-Z geometry. The BUGLE-96 library is used in the analyses, which consists of 47 neutron and 20 gamma energy groups. The results indicate that the maximum neutron fluence at the bottom of reactor vessel is $5.89 {\times} 10^{17}\;n/cm^2$ and that on the radial surface of reactor vessel is $4.49 {\times} 10^[16}\;n/cm^2$. These results meet the requirement, $1.0 {\times} 10^{20}\;n/cm^2$, in 10 CFR 50.61 and the integrity of SMART reactor vessel during the lifetime of the reactor is confirmed.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.13 no.5
• /
• pp.30-37
• /
• 2004

This paper presents the thermal characteristic analysis of a high-speed horizontal machining center with spindle speed of 50,000rpm and feedrate of 120m／min. The spindle system is designed based on the built-in motor, angular contact ceramic ball bearings, oil-air lubrication and oil-jacket cooling method. The X-axis and Y-axis feeding systems are composed of the linear motors and linear motion guides, and the Z-axis feeding system is composed of the servo-motor, ball screw and linear motion guides. The thermal characteristics such as the temperature distribution, temperature rise, thermal deformation and step response, are estimated based on the finite element model of machining center and the heat generation rates of heat sources related to the machine operation conditions. Especially, the thermal time constant assessed from the step response function is introduced as an index of thermal response characteristics.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.49.1-49.1
• /
• 2017

In order to investigate the origin of multiple stellar populations in the halo and bulge of the Milky Way, we have constructed chemical evolution models for the low-mass proto-Galactic subsystems such as globular clusters (GCs). Unlike previous studies, we assume that supernova blast waves undergo blowout without expelling the pre-enriched gas, while relatively slow winds of massive stars, together with the winds and ejecta from low and intermediate mass asymptotic giant branch stars, are all locally retained in these less massive systems. We first applied these models to investigate the origin of super-helium-rich red clump stars in the metal-rich bulge as recently suggested by Lee et al. (2015). We find that chemical enrichments by the winds of massive stars can naturally reproduce the required helium enhancement (dY/dZ = 6) for the second generation stars. Disruption of these "building blocks" in a hierarchical merging paradigm would have provided helium enhanced stars to the bulge field. Interestingly, we also find that the observed Na-O anticorrelation in metal-poor GCs can be reproduced, when multiple episodes of starbursts are allowed to continue in these subsystems. Specific star formation history with decreasing time intervals between the stellar generations, however, is required to obtain this result, as would be expected from the orbital evolution of these subsystems in a proto-Galaxy. The "mass budget problem" is also much alleviated by our models without ad-hoc assumptions on star formation efficiency and initial mass function.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.1
• /
• pp.46.1-46.1
• /
• 2018

In order to investigate the origin of multiple stellar populations in the halo and bulge of the Milky Way, we have constructed chemical evolution models for the low-mass proto-Galactic subsystems such as globular clusters. Unlike previous studies, we assume that supernova blast waves undergo blowout without expelling the pre-enriched gas, while relatively slow winds of massive stars, together with the winds and ejecta from low and intermediate mass asymptotic-giant-branch stars, are all locally retained in these less massive systems. We find that the observed Na-O anti-correlations in metal-poor GCs can be reproduced when multiple episodes of starbursts are allowed to continue in these subsystems. A specific form of star formation history with decreasing time intervals between the stellar generations, however, is required to obtain this result, which is in good agreement with the parameters obtained from our stellar evolution models for the horizontal-branch. The "mass budget problem" is also much alleviated by our models without ad-hoc assumptions on star formation efficiency and initial mass function. We also applied these models to investigate the origin of super helium-rich red clump stars in the metal-rich bulge as recently suggested by Lee et al. (2015). We find that chemical enrichments by the winds of massive stars can naturally reproduce the required helium enhancement (dY/dZ = 6) for the second-generation stars. Disruption of proto-globular clusters in a hierarchical merging paradigm would have provided helium enhanced stars to the bulge field.

• Wind and Structures
• /
• v.8 no.5
• /
• pp.357-372
• /
• 2005

Mean and extreme pressure distributions on a large cantilevered flat roof model are measured in a boundary layer wind tunnel. The largest peak suction values are observed from pressure taps beneath conical "delta-wing type" corner vortices that occur for oblique winds, then the characteristics and causes of the local peak suctions are discussed in detail. Power spectra of fluctuating wind pressures measured from some typical taps located at the roof edges under different wind directions are presented, and coherence functions of fluctuating pressures are also obtained. Based on these results, it is verified that the peak suctions are highly correlated with the conical vortices. Furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and the corners of the roof is recommended. The experimental results show that the suggested strategy can effectively control the generation of the conical vortices and make a reduction of 50% in mean pressures and 25% in extreme local pressures at wind sensitive locations on the roof.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.353-360
• /
• 2007

KIGAM has installed a FLARE+ continuous geomagnetic observation system in 1998 in Daejeon of which the IAGA identification code is DZN. The coordinates of the absolute measurement plinth precisely determined by the PDGPS(Post-Processing Differential Global Positioning System) is (127-21-37.19E, 36-22-43.96N, 45.93 m) in WGS84 for the horizontal and from the geoid surface for the vertical. Periodically we have conducted the absolute geomagnetic measurement on the plinth above. We have processed the continuous time-variation 3-axis geomagnetic data measured on arbitrary sensors' coordinates in the observatory and absolute geomagnetic data together to get as the results the time-variation H(orizontal), D(eclination), Z(vertical down), F(scalar calculated from 3 components) and P(Proton Precession Magnetometer Data). We have compared our own data with those calculated from the 10th generation IGRF(International Geomagnetic Reference Field). All the measured data in the DZN Observatory can be acquired through the website http://geomag.kigam.re.kr.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.9
• /
• pp.1341-1349
• /
• 2001

In this paper, 3 D.O.F. actuator, which has three degrees of freedom in one joint, is proposed. The proposed 3 D.O.F. spherical actuator is composed of the rotor and atator. The upper plate of the stator supports the rotor and five electromagnets are located at the base of the stator. The rotor has two permanent magnets, and each rotational axis of the rotor gimbal system is supported by the bearing. To find out the governing equations for the torque generation, Coulombs law and Lorentz force with respect to magnetism is applied. As the experimental results, if the distance between electromagnet and permanent maget is far enough, the force between these magnets can be expressed from current of coils and z-axial distance. For the purpose of control 3 D.O.F. actuator, PID control law is applied. The experimental results are presented to show the validity of the proposed 3 D.O.F. actuator.

• ETRI Journal
• /
• v.32 no.1
• /
• pp.73-83
• /
• 2010

Combinatorial testing has been an active research area in recent years. One challenge in this area is dealing with the combinatorial explosion problem, which typically requires a very expensive computational process to find a good test set that covers all the combinations for a given interaction strength (t). Parallelization can be an effective approach to manage this computational cost, that is, by taking advantage of the recent advancement of multicore architectures. In line with such alluring prospects, this paper presents a new deterministic strategy, called multicore modified input parameter order (MC-MIPOG) based on an earlier strategy, input parameter order generalized (IPOG). Unlike its predecessor strategy, MC-MIPOG adopts a novel approach by removing control and data dependency to permit the harnessing of multicore systems. Experiments are undertaken to demonstrate speedup gain and to compare the proposed strategy with other strategies, including IPOG. The overall results demonstrate that MC-MIPOG outperforms most existing strategies (IPOG, IPOF, IPOF2, IPOG-D, ITCH, TConfig, Jenny, and TVG) in terms of test size within acceptable execution time. Unlike most strategies, MC-MIPOG is also capable of supporting high interaction strengths of t > 6.

• Korean Journal of Computational Design and Engineering
• /
• v.8 no.2
• /
• pp.115-121
• /
• 2003

A new Layered Manufacturing(LM) system, named PaperMill, is developed applying micro milling technology. A micro endmill(127 11m in diameter) is introduced as the cutter of build material. The selected build material for this system is an adhesive-coated paper roll which provides advantages such as good bonding between layers, machinability, and low material cost. A 3-axis CNC controller and three step-motors are used for the movement of X-Y-Z table of the system. For simplicity of the control of mechanism, the control system for feeding the paper roll is uncoupled from CNC controller. Two code converters are developed for the toolpath generation of the new LM system. The NC converter generates a set of NC codes for PaperMill using commercial CAM software while the SML converter generates an NC code from Quickslice's SML format. The NC codes generated from the converters consist of a series of profile data and trigger code for paper feeding. Two sample gears were fabricated to prove the concept of the system, which shown that the dimensional errors of the fabricated gears is under 3.4 percent.

• Journal of the Korea Society of Computer and Information
• /
• v.20 no.11
• /
• pp.69-75
• /
• 2015

This paper suggests heuristic polynomial time algorithm for crew scheduling problem that is a kind of optimization problems. This problem has been solved by linear programming, set cover problem, set partition problem, column generation, etc. But the optimal solution has not been obtained by these methods. This paper sorts transit costs $c_{ij}$ to ascending order, and the task i and j crew paths are merged in case of the sum of operation time ${\Sigma}o$ is less than day working time T. As a result, we can be obtain the minimum number of crews $_{min}K$ and minimum transit cost $z=_{min}c_{ij}$. For the transit cost of specific number of crews $K(K>_{min}K)$, we delete the maximum $c_{ij}$ as much as the number of $K-_{min}K$, and to partition a crew path. For the 5 benchmark data, this algorithm can be gets less transit cost than state-of-the-art algorithms, and gets the minimum number of crews.