• Journal of Astronomy and Space Sciences
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• v.40 no.3
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• pp.93-100
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• 2023

A study of uncertainty analysis was conducted on four key thermophysical properties of molten Platinum using a noncontacting levitation technique. More specifically, this work demonstrates a detailed reporting of the uncertainties associated with the density, volumetric thermal expansion coefficient, surface tension and viscosity measurements at higher temperatures for a widely used refractory metal, Platinum using electrostatic levitation (ESL). The microgravity experiments were conducted using JAXA's Electrostatic Levitation Furnace (ELF) facility on the International Space Station and the terrestrial experiments were conducted using NASA's Marshal Space Flight Center's ESL facility. The performance of these two facilities were then quantified based on the measurement precision and accuracy using the metrological International Standards Organization's Guide to the Expression of Uncertainty Measurement (GUM) principles.

• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1053-1063
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• 2002

This paper presents a robust nonlinear controller for a f degree of freedom (DOF) parallel manipulator in the task space coordinates. The proposed control strategy requires information on orientations and translations in the task space unlike the joint space or link space control scheme. Although a 6 DOF sensor may provide such information in a straightforward manner, its cost calls for a more economical alternative. A novel indirect method based on the readily available length information engages as a potential candidate to replace a 6 DOF sensor. The indirect approach generates the necessary information by solving the forward kinematics and subsequently applying alpha-beta-gamma tracker With the 6 DOF signals available, a robust nonlinear task space control (RNTC) scheme is proposed based on the Lyapunov redesign method, whose stability is rigorously proved. The performance of the proposed RNTC with the new estimation scheme is evaluated via experiments. First, the results of the estimator are compared with the rate-gyro signals, which indicates excellent agreement. Then, the RNTC with on-line estimated 6 DOF data is shown to achieve excellent control performance to sinusoidal inputs, which is superior to those of a commonly used proportional-plus-integral-plus-derivative controller with a feedforward friction compensation under joint space coordinates and the nonlinear controller under task space coordinates.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.69-72
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• 2005

The FIMS (Far-ultraviolet IMaging Spectrograph; also known as SPEAR, Spectroscopy of Plasma Evolution from Astrophysical Radiation) is the primary payload of the STSAT-1, the first Korean science satellite, which was launched in September, 2003. The FIMS performs spectral imaging of diffuse far-ultraviolet emission with the unprecedented wide field of view and the relatively good spectral resolution. We present far-ultraviolet spectral observations of highly ionized interstellar medium including supernova remnants, superbubbles, soft X-ray shadows, and the molecular hydrogen fluorescent emission lines. The FIMS has detected He II, C III, 0 III, O IV, Si IV, O VI, and $H_2$ fluorescent emission lines. The emission lines arise in shocked or thermally heated and in photo-ionized gases. We present an overview of the FIMS instrument and its initial observational results.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.501-503
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• 2006

We have processed the GPS data using several high quality GPS data processing softwares for last decade. Bernes and GIPSY II are some of them. Though these programs have different characteristics in terms of structures and processing philosophies, high quality results from these are still comparable. KASI Space Geodesy Research Division has developed several GNSS data processing softwares like the quasi real-time ionospheric parameter estimator, orbit propagator and estimator, and precision positioning estimator. However, we are currently in needs of our own comprehensive GNSS data processing software with the European Galileo system on the horizon. KASI team has worked on a preliminary pilot project for the software and is making block pieces for the software. The roadmap, the description, and brief results of KASIOPEA (KASI Orbit Propagator and EstimAtor) are presented in this paper.

• Journal of People, Plants, and Environment
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• v.21 no.6
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• pp.545-555
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• 2018

The purpose of this study was to analyze land use plans of 61 residential complexes and identify the factors that caused the variation of urban parks and green space ratio depending on the land ownership processing method. The ratio of urban parks and green space of expropriation districts was higher than that of replotting districts. Within the same city and country as well as other regions, the parks and green space ratio of land expropriation districts increased higher than 7% compared to that of replotting districts. The variation of urban parks and green space ratio was mainly related to the ratio of road. Small housing complexes such as detached house and quasi-residential sites resulted to expand space for road construction, thus, the areas of urban parks or green space came to reduce. The average urban parks and green space ratio in the urban development by the expropriation method and replotting method are 24.5% and 16.8% respectively. In order to prevent the reduction of urban parks and green space ratio according to the preference of detached house sites or quasi-residential sites in development zones, it is necessary to make systematic adjustment such as adjusting the urban parks and green space ratio securing standard.

• The Bulletin of The Korean Astronomical Society
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• v.24 no.2
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• pp.89-89
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• 1999

• Bulletin of the Korean Space Science Society
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• 2000.04a
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• pp.53-53
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• 2000

No Abstract, See Full Text

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.911-917
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• 2017

There are generally three folds when developing neural network classifiers. They are as follows: 1) discriminant function; 2) lots of parameters in the design of classifier; and 3) high dimensional training data. Along with this viewpoint, we propose space search optimized polynomial neural network classifier (PNNC) with the aid of data preprocessing technique and simultaneous tuning strategy, which is a balance optimization strategy used in the design of PNNC when running space search optimization. Unlike the conventional probabilistic neural network classifier, the proposed neural network classifier adopts two type of polynomials for developing discriminant functions. The overall optimization of PNNC is realized with the aid of so-called structure optimization and parameter optimization with the use of simultaneous tuning strategy. Space search optimization algorithm is considered as a optimize vehicle to help the implement both structure and parameter optimization in the construction of PNNC. Furthermore, principal component analysis and linear discriminate analysis are selected as the data preprocessing techniques for PNNC. Experimental results show that the proposed neural network classifier obtains better performance in comparison with some other well-known classifiers in terms of accuracy classification rate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.11
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• pp.915-920
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• 2013

Units developed for a real satellite should pass space environmental tests and launch environment tests. Thermal Vacuum Test, one of the space environmental test, simulates extreme thermal environment encountered in on-orbit operation of satellite. Many payloads which adapt non-traditional, brand-new technology are developed by developers who is not familiar to space engineering field. There might be some possibility of mistakes which result in serious problem due to lack of experience, especially from planning to performing thermal vacuum test. In this paper, brief overview of thermal environmental test related to a satellite development is summarized in order to prepare and perform the thermal test.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.413-422
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• 2012

In recent years, a number of missions have been planned and conducted worldwide on the planets such as Mars, which involves the unmanned robotic exploration with the use of rover. The rover is an important system for unmanned planetary exploration, performing the locomotion and sample collection and analysis at the exploration target of the planetary surface designated by the operator. This study investigates the development of mobility system for the rover ground model necessary to the planetary surface exploration for the benefit of future planetary exploration mission in Korea. First, the requirements for the rover mobility system are summarized and a new mechanism is proposed for a stable performance on rough terrain which consists of the passive suspension system with 8 wheeled double 4-bar linkage (DFBL), followed by the performance evaluation for the mechanism of the mobility system based on the shape design and simulation. The proposed mobility system DFBL was compared with the Rocker-Bogie suspension system of US space agency National Aeronautics and Space Administration and 8 wheeled mobility system CRAB8 developed in Switzerland, using the simulation to demonstrate the superiority with respect to the stability of locomotion. On the basis of the simulation results, a general system configuration was proposed and designed for the rover manufacture.