• Korean Journal of Remote Sensing
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• v.18 no.2
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• pp.91-96
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• 2002

The performance characteristics of a satellite imager using a Time Delay and Integration(TDI) Charge Coupled Device (CCD) with fixed integration time is investigated for the variation of satellite altitude and tilt angle. In consequence of the investigation TDI synchronization using tilt imaging is proposed as a solution to compensate geometric performance degradation due to altitude decrease. The tilt angle optimized for the TDI synchronization at decreased altitude is presented. This result can be used for a TDI CCD imager with variable integration time in a certain range as well.

• Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.1-5
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• 2009

The flight control of the T-50 advanced trainer is conducted by the digital FBW (Flight-by-Wire) control system. The system input data consist of flight conditions such as altitude, airspeed, and angle of attack. And the flight conditions of the aircraft are obtained from IMFP (Integrated Multi-Function Probe). The T-50 aircraft equip three IMFP sensors. To ensure reliability in flight condition data obtained from each IMFP sensor, the mean value of flight conditions is used as the input of the control system. In this study, the effect of an installation angle of IMFP sensors on estimation of flight altitude was investigated by flight test results in the supersonic region.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.68-75
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• 2017

Dual bell nozzle is a type of altitude compensation nozzle, which is a nozzle that minimize the losses of the specific impulse at the off-design point of a typical bell nozzle. In this paper, numerical computations are performed to understand the transition characteristics of dual bell nozzles with fixed expansion ratios. The major design variables are the length of extension and the angle of inflection. As the length of the extension increased, the transition altitude and transition duration increased and the reduction of the thrust coefficient decreased. As the angle of inflection increased, the transition altitude and transition duration decreased and the reduction of the thrust coefficient increased.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.216-221
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• 2002

A spherical Earth surface is used fur realistic analysis of the geometrical performance characteristics about the variation of satellite altitude and 2-dimensional line-of-sight(LOS) tilt angle in a satellite imager using Time Delay and Integration(TDI) technique with fixed integration time. In the spherical Earth surface model TDI synchronization using LOS tilt is investigated as a solution to compensate geometric performance degradation due to altitude decrease. This result can be used fur a TDI CCD imager with variable integration time in a certain as well.

• KIEAE Journal
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• v.12 no.1
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• pp.113-118
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• 2012

The photovoltaic is one of the most important sustainable technologies appliable to architectures. The power performance mainly depends on the installation conditions of them. This study aims to evaluate the power performance of photovoltaic system by the installation conditions, the tracking methods and reflecting mirrors. For the study, the Solar Pro computer simulations have been conducted on installation angles, solar azimuth and solar altitude. Also, the field mock-up tests are performed to of its application to verify the simulation results. Both the results of the experiment and the simulation have proved that the efficiency of 90-degree fixed angle method was higher than that of 30-degree fixed angle, the efficiency of altitude tracking was better than that of azimuth tracking method, and changing both the altitude and the azimuth together is more efficient rather than the shortened tracing way. In addition, the light-concentrating method in which the incidence angle of the sun is controlled by an adhered reflector has been analyzed to have better efficiency than the general method of tracing according to the orbit of the sun. Therefore, this thesis is expected to offer the basic data to set a more effective tracing-type of photovoltaic power generation system in the future. For this, more researches are to be conducted hereafter on a high efficiency drive motor and the establishment of an economic system.

• Journal of Korea Water Resources Association
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• v.55 no.12
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• pp.1105-1114
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• 2022

A study on a method to overcome the limitations of the topographical and hydrological observation environment for estimating the QPE with high consistency with the ground rainfall by utilizing the spatiotemporal observation advantages of the rainfall radar for use in flood forecasting, and quantitative observations of localized rainfall due to these limiting conditions Uncertainty should be identified in terms of flood analysis. Against this background, in this study, 22 major heavy rain events in 2016 were analyzed for each of Mt. Biseul (BSL), Mt. Sobaek (SBS), Mt. Gari (GRS), Mt. Mohu (MHS), and Mt. Seodae (SDS) to determine the observation distance and altitude. The uncertainty of observation was quantified and an error map was derived. As a result of the analysis, it was found that, on average, the rainfall radar exceeded 10% up to 100 km and 30% over 150 km. Based on the average radar operating altitude angle, it was found that the error for the altitude was approximately 10% or less up to the second altitude angle, 20% at the third or higher altitude angle, and more than 50% at the fourth altitude angle or higher.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.8
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• pp.838-848
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• 2014

We present a simulation study of an algorithm for the range and angle of arrival(AOA) estimation with an interferometric synthetic aperture radar(InSAR) altimeter using a real digital elevation model(DEM). We also illustrate a step-by-step procedure of generating raw InSAR data, as well as their range and azimuth compressed data, which is to be used for the subsequent altitude and angle estimation. The AOA is estimated using a deterministic maximum likelihood estimator(DMLE) applied to the first arrived point for each pulse in the compressed data obtained with three antennas. The range bin size and the pulse repetition interval(PRI) are much smaller than the cell size of the DEM used in this study. To make the DEM compatible to the radar parameters, we first generate a higher resolution DEM by linearly interpolating the given DEM. After a brief description of the principle of the InSAR altimeter, the algorithms for altitude and angle estimation are presented, and their performance is assessed through simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.2
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• pp.115-124
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• 2018

In this study, a cold flow test was carried out on a high-speed vehicle facility with a high-altitude environment simulator. Variable test was carried out according to the blockage ratio, angle, and length of the test model. It is confirmed that the blockage rate can be operated in the range of 40%, and that the model should be selected at an angle of 45 degrees or less. The variables of length are less dominant compared to the variables of blockage rate and angle. Through this, a database is obtained according to the parameters of the conical model of the high-speed vehicle test facility.

• Journal of Biosystems Engineering
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• v.25 no.3
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• pp.233-240
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• 2000

A commercially available Doppler radar was modified and evaluated for on-board monitoring of ground speed. The radar output was corrected for pitch angle of aircraft based on the output of an electrolytic tilt sensor. The effects of aircraft speed, height and mounting angle on error in the ground speed were evaluated. The speed error decreased with an increase of the mounting angle since the radar contact angle with respect to the ground approached to the mounting angle. The error increased with an increase of the nominal aircraft speed. The altitude insignificantly affected the speed error. The Doppler radar provided acceptable percent errors within 5% in most measurements. The error can be reduced within ${\pm}$1.5% by increasing the mounting angle ($43^{\circ}$). The error of -3.8% at the mounting angle of $29^{\circ}$could be reduced by adjusting the mounting angle with respect to the radar contact angle.

• Journal of computational fluids engineering
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• v.9 no.3
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• pp.18-25
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• 2004

Multi plume effects on the base heating have been Investigated with a CFD program. As the flight altitude increases, the plume expansion angle increases regardless of the single or clustered engine. The plume interaction of the clustered engine makes a high temperature thermal shear in the center of four plumes. At low altitude, the high temperature shear flow stays in the center of plumes, but it increases up to engine base with the increasing altitude. At high altitude, the flow from plume to base and the flow from base into outer free stream are supersonic, which transfers the high heat in the center of plumes to the base region. The radiative heat of the clustered engine varies from 220 kW/m² to 469 kW/m² with increasing altitude while those of the single engine are 10 kW/m² and 43.7 kW/m². And the base temperature of the clustered engine varies from 985K to 1223K, and those of the single engine are 483K and 726K. This big radiative heat of clustered engine can be explained by the active high temperature base flow and strong plume interactions.