• Journal of The Korean Association For Science Education
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• v.25 no.5
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• pp.583-594
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• 2005

This study examined 8th-graders' conceptions of force on a simple pendulum and investigated cognitive conflict and conceptual change through kinesthetic experience in swing. Participants of this study were guided to anticipate the direction of total force acting on a pendulum at three critical positions and observed it through swing experience. Having completed this, students read an article explaining the results they observed. Most of them considered gravity, tension, and motion-force to be the real forces acting on a pendulum in pre-test. Though they were interested in the activity and conceded their expectations to be different from observed results, the degrees of their cognitive conflict were not significantly high. In summation, 'interest' was the highest and 'anxiety' was the lowest. Most of the students memorized the direction of forces on a swing, but few could explain the reason behind the occurrence in an immediate post-test and delayed post-test.

• Journal of the military operations research society of Korea
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• v.32 no.1
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• pp.90-112
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• 2006

The main purpose of this study is to develop an economical efficiency and maximize efficient characteristic of national defense supply. It's very important to select a supply unit which is excellent in business because it's maximize its efficiency in procurement. So this study focused on the users' dissatisfactions and the elements which have an effect on procurement, especially when they have a general competition contract. In order to have a good result, we studied the papers from Ministry of National Defense supply headquarters and the National Defense Quality Control Office, and referred to various data which contracted within recent 2 years and collect users' dissatisfactions in 3 years in track and mobile equipment field. And we present a analysis between the dissatisfactions and the elements of procurement method by SPSS 12.0.

• Applied Biological Chemistry
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• v.35 no.1
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• pp.14-22
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• 1992

A series of new N-[1-(benzotriazol-1-yl)aryl]arylamine derivatives were synthesized and their antifungal activities $(pI_{50})$ in vitro against Pyricularia oryzae, Fusarium oxysporum f. sp. sesami, Valsa ceratosperma and Botrytis cinerea were dertermined by the agar medium dilution method. From the results of the quantitative structure-activity relationships $(QSAR_S)$ analysis, $hydrophobicity({\pi})$, $electronic({\Sigma\sigma})$ and molar $refractivity({\Sigma}M_R)$ parameter of X & Y-substituents on the phenyl group were also shown to be important factor in determining the variation in the antifungal activity. 4-Bromo group substituents (1d & 2b) were the most effective compounds and the $half-life(T_{1/2})$ on the hydrolysis of X(1) at netural pH was about 1.5 day. Molecular orbital(MO) functions of substrate compound, linear free energy relationships$(LFER_S)$ on the antifungal reactivity arid the results of molecular design were also discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.257-264
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• 2015

The structure of SpaceEye-1 developed by Satrec Initiative is designed to carry out various earth observation missions in harsh launch and orbit environments. This paper describes methodology of the structure design and analysis performed during the SpaceEye-1 development. The SpaceEye-1 structure is designed not only to endure the static/dynamic loads but also to protect a main payload and all other components under the launch environments. The structural design requirements were derived from the requirements of the launch vehicle, payload, and other subsystems from the initial development phase. Three-dimensional modeling process was used to verify geometric compatibility of the structure with the other subsystems, and finite element analysis was used to confirm whether the designed structure satisfied all the mechanical requirements derived from the launch vehicle and payload.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.3
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• pp.243-256
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• 2015

As a part of the R&D efforts for the hypersonic vehicles, various flight test programs has been carried out using small launch vehicles or sounding rockets. Australian HyShot program is a representative case of the flight test program for scramjet engines carried by international collaborations. A number of hypersonic flight test programs has followed in a similar way. In USA, Falcon HTV-2 was carried by DARPA, X-51A by AFRL and HyFly by ONR. HyCAUSE and HIFiRE were carried in collaboration with Australia. In France, LEA program is on the way similarly to X-51A. Russia, China and India seems like carrying out flight test programs for the development of hypersonic defense system. The goals, technical elements, the status and the relation between the programs were summarized in this paper as a reference for the similar program of the country in the future.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.225-231
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• 2011

The satellite clock anomalies, one of the abnormal signal factors of the GPS satellites, can have a significant impact on the GPS measurements. However, it can be difficult to detect the anomalies of the satellites clock before the range of the satellites clock error becomes bigger than the range of the other factors, due to the measurement including error of the orbit, ionosphere delay, troposphere delay, multipath and receiver clock. In order to perform quick and accurate detection by minimization of critical range in anomalies of the satellites clock, this paper suggested a solution to detect precise anomalies of the satellites clock after application of carrier smoothing filter from measurement by dual-frequency and adjustment of errors which can be occurred by other factor and the receiver clock errors. The performance of the proposed method was confirmed by comparing to the satellite clock biases which are provided by IGS.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.5
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• pp.190-198
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• 2011

The precast production has many advantages by fast construction period, labor-saving and high quality. In recent years, the application of the precast product has been increased in the earth retaining wall field. This paper presents the results of the numerical analysis that was carried out to evaluate the dynamic stability of precast and prestressed earth retaining wall under moving train load. The two-dimensional FEM analysis was used to the numerical analyses. The train load to act on trackbed is combined by the real measured roughness phase angle and quasi-static load. The dynamic stability is analysed by the displacement, acceleration and stress under moving train load at each specified location. The results of the analysis show that the precast and prestressed retaining wall has very stable capability for the railway.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.935-941
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• 2009

In this paper, we study the communication based train control technology which has been improved for the railroad operation efficiency. All the signalling systems currently used in Korea are track circuit based train control systems, which train mobility and safety are considered on. When it comes to the recent abroad trend, development for communication based train control system, which arises new paradigm in the field of high density train separation, have been promoted. Considering the urgent necessity to develop the above mentioned technology, we would like to propose the research and development of communication based train control system and the present domestic and foreign statuses of on-board equipment development. In this paper, therefore, we had been developed localization on-board equipment of communication based train control system, which is the key construction of train control systems. For its verification, we accomplished installation and yard test on-board equipment of communication based train control system on Bundang-line's EMU(Electrical Multiple Unit).

• Journal of Astronomy and Space Sciences
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• v.23 no.1
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• pp.29-38
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• 2006

This paper presents an Image Motion Compensation (IMC) algorithm for the Korea's Communication, Ocean, and Meteorological Satellite (COMS)-1. An IMC algorithm is a priority component of image registration in Image Navigation and Registration (INR) system to locate and register radiometric image data. Due to various perturbations, a satellite has orbit and attitude errors with respect to a reference motion. These errors cause depointing of the imager aiming direction, and in consequence cause image distortions. To correct the depointing of the imager aiming direction, a compensation algorithm is designed by adapting different equations from those used for the GOES satellites. The capability of the algorithm is compared with that of existing algorithm applied to the GOES's INR system. The algorithm developed in this paper improves pointing accuracy by 40%, and efficiently compensates the depointings of the imager aiming direction.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.1-7
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• 2017

While a satellite is carried into orbit by a launch vehicle, it is exposed to the severe launch environment with random vibrations and shock. Accordingly, these vibration sources affect electronic equipment, particularly the printed circuit board (PCB) in the satellite. When the launch load impacts the PCB, it causes negative behavior. This causes perpendicular bending around the boundary of fixation points that finally leads to the failure of solder joints, lead wires, and PCB cracks. To overcome these issues, the electronic equipment design must meet reliability requirements. In this paper, Steinberg's method is used to derive allowable and maximum deflection to verify design from a life perspective concerning the control board of the Antenna Pointing Driver (APD) mounted on KOMPSAT-3.