• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.73.2-73.2
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• 2010

In order to understand internal dynamics of starless cores, molecular line emissions are usually observed. From profiles of the molecular lines, internal motions of starless cores have been deduced using a simple radiative transfer model such as the two-layer model (Myers et al.1996). This brings complexities arising from the chemical evolution. The motivation of this study is to follow the chemical evolution of a starless core that goes through gravitational contraction. For this purpose, we have performed hydrodynamical simulations with a marginally unstable Bonnor-Ebert sphere as an initial condition. We follow the chemical evolution of this core with changing conditions such as the chemical reaction rate at the dust surface and the strength of radiation field that penetrate into the core. At the core center, the molecules suffer from a higher degree of molecular depletion on the dust covered by ice rather than on the bare silicate dust. The stronger radiation field dissociates more molecules at the core envelope. From analysis on the line profile using the two-layer model, we found that the speed of inward motion deduced from the HCN F = 2-1 line adequately traces the true infall speed, when the dust is covered by ice and the core is exposed to the diffuse interstellar radiation field. Under different conditions, the two-layer model significantly underestimate the infall speed.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.42.1-42.1
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• 2017

We investigate the evolutionary properties of red supergiant stars (RSGs), using stellar evolution model of Modules for Experiments in Stellar Astrophysics (MESA). In this study, we calculate models with mass range of 9-39M_sun and several different convection parameters (e.g. mixing length, overshooting, and semiconvection) at SMC, LMC, Milky Way, and M31 metallicities. We compare the calculated evolutionary tracks with observed RSGs in SMC, LMC, Milky Way and M31, and discuss appropriate input physical parameters in model calculation. We find that a larger mixing length parameter is necessary for M31 metallicity to fit the positions of RSGs in H-R diagram, compared to lower metallicity environments. Theoretically predicted numbers of yellow supergiant stars (YSGs) are also compared with the observed population. We find that Ledoux models with semiconvection can better explain the number of YSGs. Finally, we investigate the final radius, final star mass, and final hydrogen envelope mass of RSGs and discussed the their properties as type II-P supernova progenitors.

• Journal of The Korean Digital Architecture Interior Association
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• v.10 no.3
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• pp.79-86
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• 2010

From the research which sees the building which uses a natural control method with ecological architecture, continuity tried to divide the building which uses a physical control method with sustainable architecture. Ecological architecture analyzes the microclimate of the area and applies mining and natural ventilation leads and that the interior environment controls, the condition of the site actively and there is a possibility of seeing. Also sustainable architecture which is possible to lead and recycling and reuse of the resources and energy cyclic process of the construction resources to lead and the interior environment to control. Therefore the case where the facility system and structural system become integrated design organically in natural circulating method is many. Specially the sunshade system and double skin system are combined and structural system of the building and there is a possibility of having the envelope which form is feature. Today the buildings lead and the system integration process where the integral parts are systematic is demanded the interior environment which and an external form and that, they make they are there is a possibility of seeing. the environmental building which hits joins in with natural control method and the structure and facility system are integrated and has the tendency which is developed and there is a possibility of saying that a meaning with the alternative construction will be able to reduce the resources and an energy.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.3
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• pp.22-35
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• 1994

To improve the bandwidth efficiency in the environment of digital mobile communications, a correlative coded FM system is designed. The signal of this system has continuous phase and high power efficiency due to the constant envelope. But this signal also has a little loss of the SNR and some degradation of the BER. In this paper, a modified MLSE method which uses correlative coded signal is adopted to improve the performance of the receiver. The MLSE method improved the BER performance in the used channel. Without the decision feedback, the receiver performance was improved by 2dB and with it, by 4dB Particularly, the MLSE method and the decision feedback showed better performance in bad channels than in a stable telephone channel.

• Geotechnical Engineering
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• v.14 no.5
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• pp.17-28
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• 1998

The design of a ground anchor wall calculating the design anchor force and anchored walls depends primarily on the earth pressure acting on anchored w deflection of the wall, the wall stiffness, distribution exists for anchored walls. In the apparent earth pressure envelope design of anchored walls. In this study, full scale anchored w pressure distribution was obtained from function. Earth pressures obtained from pressure and with the apparent earth pre the anchored wall in sand. It is conclude is appropriate for the anchored wall design.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1032-1037
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• 2016

In this paper, the method of isolation enhancement for the mobile phone MIMO antenna of LTE class 40(2300~2400MHz) was studied. Design of MIMO antenna was based on the hybrid antenna that operates both a monopole and an IFA(Inverted F Antenna). A structure for the isolation enhancement which controls induced electric field on the ground plane is located between MIMO antenna, and was not connected with the ground but apart 0.3mm. A MIMO antenna that operates on class 3~40(1710~2400MHz) of LTE service bands and a structure for the isolation enhancement at the class 10 band were designed. VSWR measurement of implemented antenna on the FR4 board showed within 3:1 at entire design bands, and isolation between antennas at the class 40 band was less than -30dB. Isolation was enhanced more than 20dB by the studied structure. ECC(Envelope Correlation Coefficient) for MIMO performance was under 0.1, and antenna average gain and efficiency measured in the anechoic chamber were -4.28~-1.40dBi and 37.32~72.36% respectively.

• Particle and aerosol research
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• v.15 no.4
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• pp.149-157
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• 2019

Infiltration characteristics of airborne particulate matter had been investigated in real-life for about 90 days over 2 years in a Korean apartment building where a 3-person household had lived and the exclusive private area was 84.9 ㎡. Airtightness was measured by fan depressurization, and the ACH₅₀ was 2.41 times per hour. In and outdoor particle concentrations were measured by optical particle counters. Infiltration factors and filtration efficiencies of the house, which reflect the removal of outdoor particles penetrating building envelope and the deposition inside a building, were obtained from data screened based on an empirical evaluation process. Infiltration factor of fine particles showed a range from about 42% at 0.4 m/s of wind speed to 72% at 4.2 m/s of wind speed with closed windows and doors. Filtration efficiency was like a MERV 13 grade filter with an open window outside at a balcony at low outdoor wind speed under 1 m/s. The grade decreased to MERV 11 by opening another outside window at the other balcony. Filtration efficiencies decreased as much as 29% in average at a range of 0.3~2.5 ㎛.

• Structural Engineering and Mechanics
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• v.26 no.6
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• pp.687-707
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• 2007

High-tech facilities engaged in the production of semiconductors and optical microscopes are extremely expensive, which may require time-domain analysis for seismic resistant design in consideration of the most critical directions of seismic ground motions. This paper presents a framework for generating three-dimensional critical seismic ground acceleration time histories compatible with the response spectra specified in seismic design codes. The most critical directions of seismic ground motions associated with the maximum response of a high-tech facility are first identified. A new numerical method is then proposed to derive the power spectrum density functions of ground accelerations which are compatible with the response spectra specified in seismic design codes in critical directions. The ground acceleration time histories for the high-tech facility along the structural axes are generated by applying the spectral representation method to the power spectrum density function matrix and then multiplied by envelope functions to consider nonstationarity of ground motions. The proposed framework is finally applied to a typical three-story high-tech facility, and the numerical results demonstrate the feasibility of the proposed approach.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.654-667
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• 2003

This paper presents a consequence of the systematic approach to identify the aerodynamic parameters of an unmanned aerial vehicle (UAV) equipped with the automatic flight control system. A 3-2-1-1 excitation is applied for the longitudinal mode while a multi-step input is applied for lateral/directional excitation. Optimal time step for excitation is sought to provide the broad input bandwidth. A fully automated programmed flight test method provides high-quality flight data for system identification using the flight control computer with longitudinal and lateral/directional autopilots, which enable the separation of each motion during the flight test. The accuracy of the longitudinal system identification is improved by an additional use of the closed-loop flight test data. A constrained optimization scheme is applied to estimate the aerodynamic coefficients that best describe the time response of the vehicle. An appropriate weighting function is introduced to balance the flight modes. As a result, concurrent system models are obtained for a wide envelope of both longitudinal and lateral/directional flight maneuvers while maintaining the physical meanings of each parameter.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.3
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• pp.327-333
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• 2015

As industrial robots come into wider use, their control techniques are being developed along with enhancements in their performance. Specially, the dynamic performance of a 6-axis articulated industrial robot is greatly changed according to the position and orientation of the robot. This means that the PI parameter tuning of the robot and orientation of the robot. This mconsidering the dynamic characteristics of robot mechanism. In this study, $LabView^{(R)}$ programming was applied to automatically conduct parameter scheduling for various robot motions. Using forward and inverse kinematics of RS2, we can divide the working envelope of RS2 into 24 subspaces. We then conduct the gain-tuning according to each subspace. Finally, we program the actual gain scheduling, in which the optimized gain-tuning for each subspace to be passed should be changed for various robot motions using $LabView^{(R)}$.