• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.1
• /
• pp.50-63
• /
• 2015

Explosive bolts are one of pyrotechnic release devices, which are highly reliable and efficient for a built-in release. Among them, ridge-cut explosive bolts which utilize shock wave generated by detonation to separate bolt body produce minimal fragments, little swelling and clean breaks. In this study, separation phenomena of ridge-cut explosive bolts or ridge-cut mechanism are computationally analyzed using Hydrocodes. To analyze separation mechanism of ridge-cut explosive bolts, fluid-structure interactions with complex material modeling are essential. For modeling of high explosives (RDX and PETN), Euler elements with Jones-Wilkins-Lee E.O.S. are utilized. For Lagrange elements of bolt body structures, shock E.O.S., Johnson-Cook strength model, and principal stress failure criteria are used. From the computational analysis of the author's explosive bolt model, computational analysis framework is verified and perfected with tuned failure criteria. Practical design improvements are also suggested based on a parametric study. Some design parameters, such as explosive weights, ridge angle, and ridge position, are chosen that might affect the separation reliability; and analysis is carried out for several designs. The results of this study provide useful information to avoid unnecessary separation experiments related with design parameters.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.1
• /
• pp.111-120
• /
• 2008

A particle image velocimetry (PIV) technique was employed to investigate the effects of blowing jet on the flow characteristics over stationary and pitch-oscillating airfoils. The Reynolds number was $7.84{\times}10^5$ based on the chord length. It was found that for stationary airfoil cases, continuous and pulsating blowing jets successfully reduced separated wake region at high angles of attack. A comparison study of two different types of jet blowing indicated that pulsating jet is more effective than continuous jet for flow separation control. Pulsating leading-edge blowing postpones flow separation and increased stall angle of attack by $2^{\circ}{\sim}3^{\circ}$. For pitch-oscillating airfoil cases, the PIV results showed that blowing jet efficiently delays the separation onset point during pitch-up stroke, whereas it does not prevent flow separation during pitch-down stroke, even at angles of attack smaller than static ones.

• Korean Journal of Oriental Medicine
• /
• v.9 no.2
• /
• pp.17-27
• /
• 2003

Eumyang-ohaeng[陰陽五行-Eumyang and five phases], as a standing rule that establishes the theory of Oriental medicine and origin of the oriental philosophy, it provides the perspective of the oriental medicine's outlook of the world. Without knowing the Eumyang-ohaeng, we cannot discuss Oriental medicine, nor can we understand the oriental way of thinking. Time and Space is what the human being created in order to explain the existence and change of matters. There is a common denominator between this universal concept of time and space and the theory of Eumyang-ohaeng. Consequently this paper investigates how characteristics of Eumyang-ohaeng and that of time and space matches Eumyang represents all matter and its characteristic, by comparison with each other space, and Ohaeng shows the change of matter with time gradually and sequancely. But this separation is only a separation by words, they really melt into one like two sides of a coin is actually just one coin. After all the theory of Eumyang-ohaeng is a theory that leads us to realize time and space, matter and power are all just one. So consequently, despite the difference in mass or size or longevity of matters, Eumyang-ohaeng pulls all matter into one body. It's why Eumyang-ohaeng is defined as the unified theory of time and space.

• Honam Mathematical Journal
• /
• v.35 no.4
• /
• pp.707-716
• /
• 2013

The present paper consists of two parts. Since the recent paper [4] proved that an Alexandroff $T_0$-space is a semi-$T_{\frac{1}{2}}$-space, the first part studies semi-open and semi-closed structures of the Khalimsky nD space. The second one focuses on the study of a relation between the LS-property of ($SC^{n_1,l_1}_{k_1}{\times}SC^{n_2,l_2}_{k_2}$, k) relative to the simple closed $k_i$-curves $SC^{n_i,l_i}_{k_i}$, $i{\in}\{1,2\}$ and its normal k-adjacency. In addition, the present paper points out that the main theorems of Boxer and Karaca's paper [3] such as Theorems 4.4 and 4.7 of [3] cannot be new assertions. Indeed, instead they should be attributed to Theorems 4.3 and 4.5, and Example 4.6 of [10].

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.1
• /
• pp.58-64
• /
• 2004

• Transactions of the Korean Society of Automotive Engineers
• /
• v.9 no.1
• /
• pp.84-93
• /
• 2001

The aim of this study is to provide fundamental informations that make it possible to use a cool stream and a hot stream simultaneously. We changed the pressure of compressed air that flows into a tube, the inner diameter of orifice that a cold stream exits, and the mass flow rate ratio. And in each case, we measured the temperature of a cold stream and a hot stream in each exit of a tube. Also we measured the axial temperature distribution and the radial temperature distribution in internal space of a tube. From the study, following conclusive remarks can be made. Average flow rate that flows into a tube is in proportion to square root of inlet pressure. As inlet pressure increases axial and radial temperature distribution in the inner space of vortex-tube increase. As mass flow rate ratio change, separation point moves.

• International Journal of Aeronautical and Space Sciences
• /
• v.9 no.2
• /
• pp.107-113
• /
• 2008

program package for store separation analysis, SAFESEP, has been developed. The package includes CTS system software, 3-Dimensional visualization software, off-line store trajectory software and aerodynamic database software. In this paper, we describe the functions and the capabilities of the store separation analysis program package.

• Journal of Astronomy and Space Sciences
• /
• v.40 no.3
• /
• pp.123-129
• /
• 2023

This paper presents an analysis of the trans-lunar trajectory insertion performance of the Korea Pathfinder Lunar Orbiter (KPLO), the first lunar exploration spacecraft of the Republic of Korea. The successful launch conducted on August 4, 2022 (UTC), utilized the SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station. The trans-lunar trajectory insertion performance plays a crucial role in ensuring the overall mission success by directly influencing the spacecraft's onboard fuel consumption. Following separation from the launch vehicle (LV), a comprehensive analysis of the trajectory insertion performance was performed by the KPLO flight dynamics (FD) team. Both orbit parameter message (OPM) and orbit determination (OD) solutions were employed using deep space network (DSN) tracking measurements. As a result, the KPLO was accurately inserted into the ballistic lunar transfer (BLT) trajectory, satisfying all separation requirements at the target interface point (TIP), including launch injection energy per unit mass (C3), right ascension of the injection orbit apoapsis vector (RAV), and declination of the injection orbit apoapsis vector (DAV). The precise BLT trajectory insertion facilitated the smoother operation of the KPLO's remainder mission phase and enabled the utilization of reserved fuel, consequently significantly enhancing the possibilities of an extended mission.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.33 no.9
• /
• pp.1-8
• /
• 2005

This paper explored the effects of separation control through the use of pulsating jet blowing on a two dimensional elliptical airfoil. To develop an active control technique of flow separation, a flow control actuator utilizing continuous/pulsed jet of pressurized air was designed and installed in a wind tunnel testing model of elliptic wing. PIV measurement and flow visualization of the wing near field were conducted to access the feasibility and effectiveness of the pulsed jet blowing on controlling the stall of the elliptical wing in subsonic flow. PIV experimental results show that separation control can provide significant reduction in turbulent flow wake and separation bubbles by jet blowing. The pulsating jet blowing is more effective on the separation control than continuous one. Increased jet frequency suppressed the turbulent separated flow wake effectively at even higher AOAs.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.47 no.9
• /
• pp.617-628
• /
• 2019

The currently considered pyrotechnic separation nut is separated through the complicated process, because it has many internal moving parts and two variable-volume chambers connected by the vent hole. Therefore, it has many design parameters. Some of these are the contact angles between internal moving parts, the masses of the internal moving parts, the inner diameter of the push rod protrusion, the initial volumes of the chambers, the mass of the explosive charge, and the diameter of the vent hole. To improve the pyrotechnic separation nut, it is necessary to understand how the behavior of the separation nut is changed according to design parameters. In this point of view, parametric studies are carried out using the previously proposed prediction model for pyrotechnic separation nut behaviors. In each case, the parameter of the interest is changed while the others are kept unchanged. From the results, it is investigated how each design parameter influences the separation behavior.