• Advances in aircraft and spacecraft science
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• v.2 no.2
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• pp.169-182
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• 2015

Aeronautics engine cooling is one of the biggest problems that engineers have tried to solve since the beginning of human flight. Systems like radiators should solve this purpose and they have been studied extensively and various solutions have been found to aid the heat dissipation in the engine zone. Special interest has been given to air coolers in order to guide the air flow on engine and lower the high temperatures achieved by the engine in flow conditions. The aircraft companies need faster and faster tools to design their solutions so the development of tools that allow to quickly assess the effectiveness of an cooling system is appreciated. This paper tries to develop a methodology capable of providing such support to companies by means of some application examples. In this work the development of a new methodology for the analysis and the design of oil cooling systems for aerospace applications is presented. The aim is to speed up the simulation of the oil cooling devices in different operative conditions in order to establish the effectiveness and the critical aspects of these devices. Steady turbulent flow simulations are carried out considering the air as ideal-gas with a constant-averaged specific heat. The heat exchanger is simulated using porous media models. The numerical model is first tested on Piaggio P180 considering the pressure losses and temperature increases within the heat exchanger in the several operative data available for this device. In particular, thermal power transferred to cooling air is assumed equal to that nominal of real heat exchanger and the pressure losses are reproduced setting the viscous and internal resistance coefficients of the porous media numerical model. To account for turbulence, the k-${\omega}$ SST model is considered with Low- Re correction enabled. Some applications are then shown for this methodology while final results are shown in terms of pressure, temperature contours and streamlines.

• Steel and Composite Structures
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• v.23 no.2
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• pp.187-194
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• 2017

To reuse a broken plain concrete (PC) arch, a retrofitting method was proposed to ensure excellent structural performances, in which carbon fiber reinforced polymers (CFRPs) were applied to repair and strengthen the damaged PC arch through bonding and wrapping techniques. Experiments were carried out to reveal the deformation and the load carrying capacity of the retrofitted composite arch. Based on the experiments, repairing and strengthening effects of the CFRP retrofitted broken arch were revealed. Simplified analysing model was suggested to predict the peak load of the CFRP retrofitted broken arch. According to the research, it is confirmed that absolutely broken PC arch can be completely repaired and reinforced, and even behaves more excellent than the intact PC arch when bonded together and strengthened with CFRP sheets. Using CFRP bonding/wrapping technique a novel efficient composite PC arch structure can be constructed, the comparison between rebar reinforced concrete (RC) arch and composite PC arch reveals that CFRP reinforcements can replace the function of steel bars in concrete arch.

• Journal of Advanced Navigation Technology
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• v.19 no.1
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• pp.15-21
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• 2015

WA-DGNSS is a system to service for users using a satellite which received correction data from ground station that calculates the relative errors of the tracked GNSS signals and sends to a satellite. Users are guaranteed the reliability of the GNSS signal and the accuracy of positioning. ICAO recommends the application of WA-DGNSS for the airplane taking off and landing process. In this paper, we suggests methods to verify of the pre-developed WA-DGNSS reference software constituting modules and an integration test process refer to the RTCA DO-278 which is a document for the development process of an aeronautics software. Also, we statistically verified the reference software test through our methods. And then, we confirmed to performance the function of the reference software properly.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.785-795
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• 2008

The swell is a major cause of interruption for the activity in a port and the ship navigation in coastal waters, coastal geographical changes, and the disaster with a loss of lives. However, many researches about the observation and the prediction of swells have not been conducted actively due to the difficulties to collect and synthesize the massive amount of long term field data for waves and meteorological information. In this study, the internet-based realtime monitoring system(Fieldbox) was developed to collect the wave data. The characteristics and main components of swells occurred in Korea were analyzed using wave data observed through the Fieldbox and the meteorological data collected by the KMA(Korea Meteorological Administration) and NASA(National Aeronautics and Space Administration). The characteristics of the swell generation patterns were analyzed using the monthly data of the Kwangan Tower between 2004 and 2006 to estimate the specific features such as sources and locations of swells generated in Korea.

• Smart Structures and Systems
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• v.6 no.9
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• pp.1057-1077
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• 2010

An early detection of structural damages is critical for the decision making of repair and replacement maintenance in order to guarantee a specified structural reliability. Consequently, the structural damage detection, based on vibration data measured from the structural health monitoring (SHM) system, has received considerable attention recently. The traditional time-domain analysis techniques, such as the least square estimation (LSE) method and the extended Kalman filter (EKF) approach, require that all the external excitations (inputs) be available, which may not be the case for some SHM systems. Recently, these two approaches have been extended to cover the general case where some of the external excitations (inputs) are not measured, referred to as the adaptive LSE with unknown inputs (ALSE-UI) and the adaptive EKF with unknown inputs (AEKF-UI). Also, new analysis methods, referred to as the adaptive sequential non-linear least-square estimation with unknown inputs and unknown outputs (ASNLSE-UI-UO) and the adaptive quadratic sum-squares error with unknown inputs (AQSSE-UI), have been proposed for the damage tracking of structures when some of the acceleration responses are not measured and the external excitations are not available. In this paper, these newly proposed analysis methods will be compared in terms of accuracy, convergence and efficiency, for damage identification of structures based on experimental data obtained through a series of laboratory tests using a scaled 3-story building model with white noise excitations. The capability of the ALSE-UI, AEKF-UI, ASNLSE-UI-UO and AQSSE-UI approaches in tracking the structural damages will be demonstrated and compared.

• Atmosphere
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• v.24 no.2
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• pp.265-281
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• 2014

Currently, Korea is developing a Cheollian follow-on satellite program, named as Geostationary Korea Multipurpose Satellite 2 (GK-2), which consists of two satellites. One satellite (GK-2A) is dedicated to the meterological mission, while the second one (GK-2B) hosts two main payloads for the ocean and environmental application. As GK-2A is dedicated to the meteorological mission unlike Cheollian, there have been discussions on the possibility of transferring the responsibilities of the GK-2A program to the Korea Meteorological Administration. To help resolve any consumptive disputes or to find an efficient way for the GK-2A program, the events happened after the successful launch of the first meteorological satellite TIROS-1 in the U.S. in April 1960 are investigated. With the successful demonstration of usefulness of TIROS-1 for the meteorological applications, organizations such as the Weather Bureau and the Department of Defense, responsible for the real time application of the TIROS 1 data, strongly requested for an operational meteorological satellite program which resulted in the plan for the National Operational Meteorological Satellite System (NOMSS). The plan was strongly supported by Kennedy Adminstration and was put forwarded for the new program under the responsibility of Weather Bureau to the Congress. However, the responsible Committee on Science and Aeronautics sided with NASA and requested major revision of the responsibility. Due to many unfavorable conditions, Weather Bureau accepted the requests and signed with NASA on the agreement for the operational meteorological satellite. However, with the delay of Nimbus satellite which is planned to be used for the prototype of the operational satellite and changes of the unfavorable situations, the Weather Bureau could draw a second agreement with NASA. The new agreement reflected most propositions requested by the Weather Bureau for the NOMSS plan. Until now the second agreement is regarded as the basic principles for the operational meteorological satellite program in the U.S. This study investigates the backgrounds and processes of the second agreement and its implications for the GK-2 program.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.289-302
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• 2017

The key risk analysis technologies for the re-entry of space objects into Earth's atmosphere are divided into four categories: cataloguing and databases of the re-entry of space objects, lifetime and re-entry trajectory predictions, break-up models after re-entry and multiple debris distribution predictions, and ground impact probability models. In this study, we focused on reentry prediction, including orbital lifetime assessments, for space situational awareness systems. Re-entry predictions are very difficult and are affected by various sources of uncertainty. In particular, during uncontrolled re-entry, large spacecraft may break into several pieces of debris, and the surviving fragments can be a significant hazard for persons and properties on the ground. In recent years, specific methods and procedures have been developed to provide clear information for predicting and analyzing the re-entry of space objects and for ground-risk assessments. Representative tools include object reentry survival analysis tool (ORSAT) and debris assessment software (DAS) developed by National Aeronautics and Space Administration (NASA), spacecraft atmospheric re-entry and aerothermal break-up (SCARAB) and debris risk assessment and mitigation analysis (DRAMA) developed by European Space Agency (ESA), and semi-analytic tool for end of life analysis (STELA) developed by Centre National d'Etudes Spatiales (CNES). In this study, various surveys of existing re-entry space objects are reviewed, and an efficient re-entry prediction technique is suggested based on STELA, the life-cycle analysis tool for satellites, and DRAMA, a re-entry analysis tool. To verify the proposed method, the re-entry of the Tiangong-1 Space Lab, which is expected to re-enter Earth's atmosphere shortly, was simulated. Eventually, these results will provide a basis for space situational awareness risk analyses of the re-entry of space objects.

• Journal of The Korean Astronomical Society
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• v.50 no.5
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• pp.139-149
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• 2017

The Korea Astronomy and Space Science Institute plans to develop a coronagraph in collaboration with National Aeronautics and Space Administration (NASA) and to install it on the International Space Station (ISS). The coronagraph is an externally occulted one-stage coronagraph with a field of view from 3 to 15 solar radii. The observation wavelength is approximately 400 nm, where strong Fraunhofer absorption lines from the photosphere experience thermal broadening and Doppler shift through scattering by coronal electrons. Photometric filter observations around this band enable the estimation of 2D electron temperature and electron velocity distribution in the corona. Together with a high time cadence (<12 min) of corona images used to determine the geometric and kinematic parameters of coronal mass ejections, the coronagraph will yield the spatial distribution of electron density by measuring the polarized brightness. For the purpose of technical demonstration, we intend to observe the total solar eclipse in August 2017 with the filter system and to perform a stratospheric balloon experiment in 2019 with the engineering model of the coronagraph. The coronagraph is planned to be installed on the ISS in 2021 for addressing a number of questions (e.g., coronal heating and solar wind acceleration) that are both fundamental and practically important in the physics of the solar corona and of the heliosphere.

• The Journal of the Acoustical Society of Korea
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• v.38 no.6
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• pp.621-629
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• 2019

A logical measure is suggested to estimate an accurate Sound Speed Profile (SSP) for the unusual variation of salinity in the Yellow Sea. Based on National Aeronautics and Space Administration (NASA)'s Aqua and Soil Moisture Active Passive (SMAP) satellite data, this measure identifies the area of temperature inversion effect and expansion of low salinity (<30.5 psu) water. Subsequently, on the area, the Conductivity, Temperature, and Depth (CTD) mounted unmanned maritime system estimates accurate SSP. In order to carry out this measure conveniently, a flow chart is demonstrated in this research. By using this measure which finds the high variational salinity area, the inaccuracy issue for calculating SSP from Expandable Bathy Thermograph (XBT) is expected to be solved.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.605-610
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• 2004

Solid propellants allow thrusters to be light-weight, com-pact and robust because they require neither tank nor valve, Moreover, the solid propellant will not leak, spill or slosh. Consequently, the solid propellant thruster is one of the potential candidates for the microthruster. On the other hand, the control of the solid propellant combustion is difficult, since the conventional solid propellant continues to bum until all the stored propellant is consumed. Although particular devices like thrust reverser were designed to control the combustion, these devices were rarely used in the practical rocket motors. These devices rise thruster weight as well as complicate the thruster operation. In this study, a solid propellant microthruster using laser sustained combustion was designed in order to develop a high-efficiency microthruster overcoming the previously-mentioned difficulty. This designed thruster has semiconductor lasers and non-self-combustible solid propellants in addition to the conventional solid propellant thruster. In this designed thruster, the semiconductor laser controls the combustion of the non-self-combustible solid propellant. In order to demonstrate that the solid propellant combustion is controllable with laser, some non-self-combustible solid propellants were irradiated with the laser at a back-pressure of about 1㎪. A 40-W class Neodymium Yttrium Aluminum Garnet (ND:YAG) laser was used as a tentative alternate to the semiconductor laser. This experiment has shown that the solid propellant combustion was controllable with 10- W class laser irradiation.