• Journal of Astronomy and Space Sciences
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• v.20 no.3
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• pp.205-216
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• 2003

The attitude motion of a spin-stabilized, upper-stage spacecraft is investigated based on a two-body model, consisting of a symmetric body, representing the spacecraft, and a spherical pendulum, representing the liquid slag pool entrapped in the aft section of the rocket motor. Exact time-varying nonlinear equations are derived and used to eliminate the drawbacks of conventional linear models. To study the stability of the spacecraft's attitude motion, both the spacecraft and pendulum are assumed to be in states of steady spin about the symmetry axis of the spacecraft and the coupled time-varying nonlinear equation of the pendulum is simplified. A quasi-stationary solution to that equation and approximate resonance conditions are determined in terms of the system parameters. The analysis shows that the pendulum is subject to a combination of parametric and external-type excitation by the main body and that energy from the excited pendulum is fed into the main body to develop the coning instability. In this paper, numerical examples are presented to explain the mechanism of the coning angle growth and how angular momenta and disturbance moments are generated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.226-232
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• 2017

Surface pressure distributions over the RAE-A wing-body configuration were investigated and the grid convergence along the streamwise, spanwise, and circumferential directions was numerically studied. Flow analysis in subsonic and transonic conditions was conducted using the $k-{\omega}$ Wilcox-Durbin+ turbulence model. Surface pressure distributions for subsonic flows were well matched, but those for transonic shocked flows showed a little discrepancy with the experimental data. A cubic spline extrapolation method was applied in order to investigate the grid convergence. This method presented that the grid resolution in the circumferential direction is the most important grid parameter. A refined grid system was made based on the grid convergence study and provided more accurate prediction, especially on the symmetric body surface of RAE-A configuration.

• Journal of Animal Environmental Science
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• v.8 no.3
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• pp.171-176
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• 2002

Physical parameters of milk cow were measured to design and build RMS(Robotic Milking System) with a tape-measurer and body parameter measurer. The parameters are very important variables to design an RMS. For the working zone space of an RMS manipulator and the movement blunting of milk cow, an interval frame was installed on the stall bottom, and then cow's behavioral reactions were tested. The results from this study is summarized as follow. 1. On the general physical condition measurement, the maximum, minimum and average body length of cow which is related to the space that the manipulator could work into the RMS were 175cm, 144cm, and 163cm respectively. It appeared that the average distance between bottom and chest was 60cm. 2. The average length between fore teats, fore and hind teats and hind teats were 178mm, 150mm and 95mm respectively. It appeared that the average length between bottom and teat attachments was 544mm, and the average length between fore teats and tail-end was 331mm. 3. Although a cow kept a some extent length between hind legs for milking, it looked a stable pose. However, the cow kept a some extent distance between front legs for milking, it looked a unstable pose. Based on results of this test, an interval frame of stall bottom should be installed around the position which was located at its hind legs.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.455-462
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• 2016

Output Characteristics of the spaceborn image sensor such as infrared(IR) sensor are varied according to time elapses and sensor repetition on/off operation. As a result, the quality of IR sensor image is decreased. Therefore, spaceborne image sensor require a periodic calibration using a black body system by correcting a non-uniformity of the sensor. In this paper, we proposed a MEMS-based black body system that can implement the high temperature uniformity at various standard temperatures ranging from low to high temperature and easily estimate the representative surface temperature. In addition, it has advantages lightweight, low-power and high accuracy. The feasibility of the proposed MEMS-based black body system was verified through the thermal analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.6
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• pp.101-106
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• 2002

In a bank-to-turn(BTT) missile, if a 2-gimbaled seeker was stabilized using a 2-axis rate gyro mounted along its primary axis, the change of line of sight(LOS) measured by the seeker would be induced by rolling effects due to bank-to-turn(BTT) steering as well as an actual change. It is observed that the body-coupled effects in a homing loop of BTT missile are mainly concerned with the spurious target maneuver and the coupling due to the rate gyro misalignments. In this paper, we formulate a simple linear BTT homing loop model with seeker model including each body-coupling. With the model, we analyze the effects of the couplings on the homing loop stability, and propose a direct linear compensator for the coupling to recover the stability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.385-394
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• 2012

A computer program that can estimate static, dynamic stability and control derivatives using a subsonic-supersonic panel method is developed. The panel method uses subsonic-supersonic source and elementary horse shoe vortex distributions, and their strengths are determined by solving the boundary condition approximated with a thin body assumption. In addition, quasi-steady analysis on the body fixed coordinate system allows the estimation of damping coefficients of aircraft 3 axes. The code is validated by comparing the neutral point, roll and pitch damping of delta wings with published analysis results. Finally, the static, dynamic stability and control derivatives of F-18 are compared with experimental data as well as other numerical results to show the accuracy and the usefulness of the code.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.4
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• pp.317-325
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• 2014

For a missile with a strapdown seeker, line-of-sight rate for guidance is obtained by compensating the look angle rate from the strapdown seeker by the body angular rate from rate gyros. However, the body angular rate from rate gyros has different signal properties when it compared to the body angular rate implicitly included in the look angle rate. Typically this discrepancy causes instability of homing loop. In this paper, we propose a design method of homing loop where seeker delay is compulsively placed in the output signal of the rate gyros for accordance of both body rates. Also, PID control loop is considered for obtaining stabilized guidance command even though uncertainties of seeker delay is associated. The stability analysis for the linear homing loop before and after the compensation has been done. The stability and performance of the designed terminal homing loop is verified through full nonlinear 6-DOF simulations.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.11
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• pp.1066-1072
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• 2009

A panel method based on potential flow theory is developed for the steady/unsteady aerodynamic analysis of arbitrary three-dimensional Blended Wing Body aircraft. The panel method uses the piecewise constant source and doublet singularities as a solution. This potential based panel method is founded on the Dirichlet boundary condition and coupled with the time-stepping method. The present method uses the time-stepping loop to simulate the unsteady motion of the aircraft. The present method can solve the three-dimensional flow over the complex bodies with less computing time and provide various aerodynamic derivatives to secure the stability of Blended Wing Body aircraft. That will do much for practical applications such as aerodynamic designs and analysis of aircraft configurations and flight simulation.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.20-28
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• 2021

With an increase in the commercialization of electricity, and the development of advanced and large electric devices and various wireless radio wave services, concerns over the effects of electromagnetic fields on human health have increased. Accordingly, the World Health Organization encouraged the development of international standards by establishing the 'International Electromagnetic Fields Project' in 1996 based on studies on the harmful effects of electromagnetic fields on the human body. Moreover, the National Institute of Environmental Health Sciences (NIEHS) classified electromagnetic fields as possible carcinogens under Group 2B category, even though they have been found to have a weak correlation with those effects on human health. Mid-to-large-sized electric facilities used at industrial sites mostly adopt a commercial frequency of 60 Hz, and workers handling these facilities are exposed to such extremely low frequency (ELF) fields for a long time. A previous study suggested that exposure to ELF electromagnetic fields with frequency ranges from 0 to 300 Hz, even for a short time, at densities higher than 100 μT may have harmful effects on human body as it affects the activation of nerve cells in the central nervous system by inducing an electric field and current and stimulating muscles and the nervous system in the body. Such studies, however, focused on home appliances used by ordinary people, and research on facilities utilizing high-capacity current and operated by workers at industrial sites is lacking. Therefore, in this study, a 3000 kilowatt generator, which is a high-capacity electric facility employed at industrial sites, was investigated, and the size of the magnetic fields generated during its no-load and high-load operations per distance to produce a map was measured to reveal spots deemed hazardous according to domestic and international exposure standards. The findings of this study is expected to alleviate workers' anxiety about the harmful effects of magnetic fields on their body and to minimize the level of exposure during operations.

• The Korean Journal of Air & Space Law and Policy
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• v.24 no.1
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• pp.119-152
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• 2009

Korea now has a rapidly expanding and developing space programme with exploration aspirations. The government is giving priority to the aerospace industry and, to put it on a better footing, enacted an Aerospace Industry Development Promotion Act in I987, a Space Development Promotion Act in 2005 and a Space Compensation for Damage Act in 2007. I would like to describe briefly the legislative history, main contents and comment for these three space acts including especially launch licensing, registration of space objects, use of satellite information, astronaut rescue, liability for compensation, third party liability insurance and establishment of committee and plans to assist the Korean space effort. Furthermore author proposed to legislate a new draft for the establishment of a Korean Aerospace Development Agency (KADA: tentative title) to create a similar body to Japan Aerospace Exploration Agency (JAXA), British National Space Centre (BNSC) of UK, French Centre National d'Etudes Spatiales (CNES), German Aerospace Center (DLR), Swedish Space Corporation (SSC), China Aerospace Science and Industry Corporation (CASIC), Indian Space Research Organization (ISRO) as well as the Korean Space Agency (KSA: Tentative title) to create a similar body to Canadian Space Agency, European Space Agency, Russian Space Agency, Italian Space Agency, Israel Space Agency, Indian Department of Space, National Aeronautics and Space Administration (NASA) of USA, China National Space Administration in order to develope efficiently space industry. If the Korean government will be establish the Korean Space Agency as an governmental organization in future, it is necessary to revise the contents of the Government Organization Act. It is desirable and necessary for us to establish an Asian Space Agency (ASA), in order to develop our space industry and to promote research cooperation among Asian countries, based on oriental idea and creative powers.