• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.1
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• pp.16-27
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• 2018

A basic numerical analysis was performed to confirm the possibility of combining a dual bell nozzle and an Expansion-Deflection(E-D) nozzle. The dual bell nozzle was designed based on the first-stage nozzle of the Korean Space Launch Vehicle that is being developed, and the E-D nozzle concept was applied to the dual bell nozzle. The inlet condition was analyzed by applying eight types of frozen flow analysis, and k-${\omega}$ SST was selected as the turbulence model. The number of optimal grids was obtained as 240,000 through the grid sensitivity analysis. As a result, it was confirmed that the transition altitude increased owing to over-expansion when the E-D nozzle concept was applied to the dual bell nozzle, and the specific impulse gain was obtained at high altitudes compared with the KSLV-II first-stage engine.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.4
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• pp.1-9
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• 2019

Recently, in the space market, there has been a rapid reduction of the launch price. The major reason is that a few commercial companies, especially SpaceX, began to enter into the space market about ten years ago, which has changed the space market from monopolization to competition, and accelerated the adoption of commercial efficiency in the technology and management. Also, the successful landing and recovery of a first stage in 2016 by SpaceX proved to be a prelude to opening a new era of reusable launch vehicles, and SpaceX declared the groundbreaking launch price through using the reusable launch vehicle. This study calculates the total launch cost required to put a certain satellite into the LEO, compares the launch cost in three cases with different payload weights, and reviews the impacts of the payload on the cost effectiveness of a reusable vehicle. The total launch cost is divided into 6 subsections cost, namely development cost, production cost, refurbishment cost, operation cost, fixed-cost of factory and launch site, and insurance cost. The cost estimation relationships used in the calculation are taken from the commonly proven cost models such as TRANSCOST.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.2
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• pp.155-166
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• 2021

In this paper, design study of a small two-stage launch vehicle is undertaken for the dedicated launch of the Compact Advanced Satellite 500 (CAS500)-class satellite into the Low Earth Orbit (LEO) by modifying the second and third stages of the Korean Space Launch Vehicle II (KSLV-II). Since the KSLV-II has three stages, velocity increment is newly distributed for the two-stage small launch vehicle. For this end, the staging design is carried out for the design parameters such as stage mass ratios, structural coefficients and engine options for each stage followed by trajectory analysis. Investigation of the results provides the combination of design parameters for the small launch vehicle for the dedicated launch of 500 kg-class satellite into LEO.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.1
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• pp.189-201
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• 1997

The purpose of this study was to evaluate the position and shape of mental foramen in panoramic radiographs. For this study, panoramic radiographs were obtained from the 200 adults and evaluated the position and shape of mental foramen. According to various positional changes in panoramic radiographs of the patients, the author also obtained panoramic radiographs from the 100 adults and then evaluated the positional and shape changes of mental foramen. The following results were obtained: 1. Shapes of mental foramen were observed elliptical(43.3％), round or oval(42.5％), unidentified(7.5％) and diffuse (6.7％) type in descending order of frequency. 2. Horiwntal position of mental foramen were most frequently observed at the 2nd premolar area(54.2％), and area between the 1st premolar and 2nd premolar(43.1％), area between the 2nd premolar and 1st molar(2.7％) in descending order of frequency. 3. Vertical position of mental foramen were most frequently observed at the inferior of apex(88.2％), and at apex (9.7％), overlap with apex(1.9％), superior of apex(0.2％) in descending order of frequency. 4. According to various positional changes in panoramic radiographs of the patients, shape changes of mental foramen were more obviously observed at the forward 10mm and chin down 100 positioned panoramic radiographs. And changes of horiwntal and vertical position were observed in similar to compared with normal positioned panoramic radiographs.

• Journal of Radiation Protection and Research
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• v.8 no.1
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• pp.33-37
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• 1983

Neutron reflecting effects in terms of effective multiplication factor have been calculated with varying water or concrete thickness, and gap distance between concrete reflector and a fissile solution system. A numerical calculation of effective multiplication factors has been carried out by using the discrete ordinates method with the help of the computer code, ANISN. It is revealed that the reflecting .effect by thin concrete is lower than that of the identical thickness of water while the effect by thick water is low compared to that of the identical thickness of concrete. It seems that the effective multiplication factors are first decreasing rapidly with gap distance, which is filled with water, between concrete reflector and the fissile solution system, and then decrease slowly over the distance of about 15cm.

• Korean journal of applied entomology
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• v.36 no.1
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• pp.37-42
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• 1997

Korean entomopathogenic fungi were serveryed from soil samples throughout the five provinces and within three city limits using larvae of great wax moth, Galleria mellonella as baits. The fungi were also isolated from the eight species of dead insects. Of the total 200 soil samples, 40(20.0%) were positive for entomopathogenic fungi with 21(10.5%) containing Beauveria and 19(9.5%) containing Metarhizium. Positive sample sites in each habitat included 25 of the 110(22.7%) from forests, 2 of the 20(11.0%) from agricultural fields, 6 of the 11(54.5%) from agricultural fallow areas, and 7 of the 19(36.8%) from riparian areas. In addition, Metarhizium was isolated from Japanese walking stick (Phraortes elongatus) and Beauveria from the other 7 species of dead insects.

• Journal of the Korean Magnetics Society
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• v.2 no.1
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• pp.69-74
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• 1992

This paper describes the energy and speed characteristics of an induction coil-gun. The coil-gun has some merits that it can be easily installed and repeatedly used many times, it does not damage mechanically in the course of launch and the force exerted on the projectile is distributed uniformly. An equivalent circuit is employed for modeling the coil-gun. The circuit equations and equation of motion are then derived based on the equivalent circuit. These equations are solved numerically by using Runge-Kutta method. Finally the energy transfer ratios are obtained according to the variations of the resonant frequency of driving circuit and charging voltage of capacitors. The muzzle velocities of projectile are also obtained according to the variations of electrical conductivity and initial position of projectile, firing angle of driving circuit, charging voltage of capacitor and resistance of driving coil, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.89-98
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• 1987

X-Ray photogrammetry is the method that register and analize the anatomical or physiological information about the human body by the photography form. In this paper, using X-Ray, accuracy of three dimensional coordinates of objects which are deformed and a part of human body is analyzed. An objective of this analysis lies in improving the accuracy of three dimensional coordinates and enhancing the practical use. Through the observation, X-Ray Photogrammetry is used in practical use. And X-Ray photograph is used the reform of graphical model by the determination of the three dimensional coordinates about all sides of object.

• Aerospace Engineering and Technology
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• v.12 no.1
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• pp.73-80
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• 2013

In this study, a numerical analysis based on CFD methods has been conducted to predict the aerodynamic coefficients and aerodynamic loads of KSLV-II configuration designed at the system design phase. By the effects of exclusion of engine cowls of prior configuration, axial force and normal force decreased and center of pressure was much moved to the nose direction. Also, aerodynamic loads at flight and on the launch pad were predicted for structural load analysis. The computed results will be used for mission analysis and structural analysis at the next design phase.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.1205-1211
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• 2017

The Propulsion System Test Complex(PSTC) was constructed for the verification test of each stage's propulsion system of KSLV-II. Main Control System(MCS) is the system to operate the onboard equipment and the ground equipment of the PSTC simultaneously. This paper describes the critical design, the development status, and test results of Main Control System. The MCS will be used for the interface connection between ground control systems and onboard equipment. Test sequence and operation process of the Work Manager will be conducted by MCS.