• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2017.05a
• /
• pp.797-802
• /
• 2017

This paper describes the scale effect of hybrid rocket motor which has blow-down oxidizer supply system. ResuIts show that the scale effect on regression rate is negligible using presently accessible scaling relation for $LN_2O$/PE propellant combination amid the absence of exactly proven scaling relation. It was also found that the characteristic velocity efficiency increases as motor scale increases. However, the characteristic velocity efficiency includes complicated parameters such as post-chamber configuration or geometry which can affect the entire flow field. It is therefore hard to conclude that the increase of efficiency is solely due to the enlargement of motor scale nor draw any conclusion on the scale effect which require a profound understanding of hybrid rocket scaling rules.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.24 no.1
• /
• pp.64-77
• /
• 2020

An electric-pump cycle, which is a propellant supply system for driving pumps of a liquid rocket engine using an electric motor, has the advantages of simple system configuration and easy control of supply flow rate and pressure. This paper investigates and analyzes the overseas research trends of the electric-pump cycle. In addition, the research and development country, performing organization, application, engine thrust, pump pressure increase, motor power, and rotation speed are summarized. Among them, the design variables of the overseas research that applied the upper-stage propulsion system with the thrust range of 0.445~2.2 kN could be used in the study of a similar electric-pump cycle in Korea.

• Korean Journal of Materials Research
• /
• v.18 no.3
• /
• pp.148-152
• /
• 2008

A new cost-effective atomic layer deposition (ALD) technique, known as Proximity-Scan ALD (PS-ALD) was developed and its benefits were demonstrated by depositing $Al_2O_3$ and $HfO_2$ thin films using TMA and TEMAHf, respectively, as precursors. The system is consisted of two separate injectors for precursors and reactants that are placed near a heated substrate at a proximity of less than 1 cm. The bell-shaped injector chamber separated but close to the substrate forms a local chamber, maintaining higher pressure compared to the rest of chamber. Therefore, a system configuration with a rotating substrate gives the typical sequential deposition process of ALD under a continuous source flow without the need for gas switching. As the pressure required for the deposition is achieved in a small local volume, the need for an expensive metal organic (MO) source is reduced by a factor of approximately 100 concerning the volume ratio of local to total chambers. Under an optimized deposition condition, the deposition rates of $Al_2O_3$ and $HfO_2$ were $1.3\;{\AA}/cycle$ and $0.75\;{\AA}/cycle$, respectively, with dielectric constants of 9.4 and 23. A relatively short cycle time ($5{\sim}10\;sec$) due to the lack of the time-consuming "purging and pumping" process and the capability of multi-wafer processing of the proposed technology offer a very high through-put in addition to a lower cost.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.1 s.45
• /
• pp.117-126
• /
• 2007

Web Forensics algorithm used to an extraction of technical Web Forensics data to be adopted to proof data regarding a crime cyber a computer at data of a great number of log History is an essential element. Propose Web Forensics algorithm, and design at these papers, and try to implement in a Web server system of an actual company. And make the Web dispatch Loging system configuration experiment that applied integrity regarding Web log History information or authentication regarding an information source. Design Web Forensics algorithm and the Flow which used for Web log History analyses at server of e-mail, webmail, HTTP (Web BBs. Blog etc.), FTP, Telnet and messengers (MSN, NateOn, Yahoo, DaumTouch, BuddyBuddy, MsLee, AOL, SoftMe) of a company, and implement through coding. Therefore have a purpose of these Paper to will contribute in scientific technical development regarding a crime cyber a computer through Web Forensics.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2003.05a
• /
• pp.89-93
• /
• 2003

The Korea Research Institute of Ships and Ocean Engineering (KRISO), the ocean engineering branch of KORDI, has designed and manufactured a model of an autonomous underwater vehicle (AUV) to test underwater docking. This paper introduces the AUV model, ASUM, equipped with a visual servo control system to dock into an underwater station with a camera and motion sensors. To make a visual servoing AUV, this paper implemented the visual servo control system designed with an augmented state equation, which was composed of the optical flow model of a camera and the equation of the AUV's motion. The system design and the hardware configuration of ASUM are presented in this paper. A small long baseline acoustic positioning system was developed to monitor and record the AUV's position for the experiment in the Ocean Engineering Basin of KRISO, KORDI. ASUM recognizes the target position by processing the captured image for the lights, which are installed around the end of the cone-type entrance of the duct. Unfortunately, experiments are not yet conducted when we write this article. The authors will present the results for the docking test of the AUV in near future.

• Wind and Structures
• /
• v.10 no.5
• /
• pp.463-479
• /
• 2007

A series of wind tunnel sectional model dynamic tests of a twin-deck bridge were conducted at the CLP Power Wind/Wave Tunnel Facility (WWTF) of The Hong Kong University of Science and Technology (HKUST) to investigate the effects of gap-width on the self-excited vibrations and the dynamic and aerodynamic characteristics of the bridge. Five 2.9 m long models with different gap-widths were fabricated and suspended in the wind tunnel to simulate a two-degrees-of-freedom (2DOF) bridge dynamic system, free to vibrate in both vertical and torsional directions. The mass, vertical frequency, and the torsional-to-vertical frequency ratio of the 2DOF systems were fixed to emphasize the effects of gap-width. A free-vibration test methodology was employed and the Eigensystem Realization Algorithm (ERA) was utilized to extract the eight flutter derivatives and the modal parameters from the coupled free-decay responses. The results of the zero gap-width configuration were in reasonable agreement with the theoretical values for an ideal thin flat plate in smooth flow and the published results of models with similar cross-sections, thus validating the experimental and analytical techniques utilized in this study. The methodology was further verified by the comparison between the measured and predicted free-decay responses. A comparison of results for different gap-widths revealed that variations of the gap-width mainly affect the torsional damping property, and that the configurations with greater gap-widths show a higher torsional damping ratio and hence stronger aerodynamic stability of the bridge.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.1
• /
• pp.151-156
• /
• 2006

Accurate vessel traffic observation is indispensable to carry out vessel traffic management, design of vessel traffic route, planning of port construction, etc. In order to observe the vessel traffic accurately without many efforts such as the use of a ship or car equipped with special radar observation system and the preparation of observation staff, the authors have been developing completely automated remote radar/AIS network system covering the main traffic area in Tokyo Bay. The composite radar image observed at Yokosuka and Kawasaki radar stations with AIS information can be seen on web site of Internet. In addition to the development of radar/AIS observation system, the software to analyze observed vessel traffic flow has been developed. This software has various functions such as automatic tracking of ship's positions, automatic estimation of ship's size, automatic integration of radar image and AIS data, animation of ships' movements, extraction of dangerous ship encounters, etc. The configuration and functions of the developed remote radar/AIS network system are shown first in this paper. Then various functions of the software to analyze vessel traffic are introduced, and some analyzed results on the vessel traffic in Tokyo Bay are described demonstrating the effectiveness of the developed system.

• Journal of the Korean Society of Earth Science Education
• /
• v.9 no.1
• /
• pp.97-105
• /
• 2016

The purpose of this study was to examine the effects of storytelling skill on science concept and science learning motivation. For this study the 5 grade, 2 class was divided into a research group and a comparative group. The class was pre-tested in order to ensure the same standard. The research group had the science class with storytelling skill, and the comparative group had the class of the teacher centered lectures on 11 classes in 8 weeks. The storytelling skill was focused on set the astronomical target wants to set up a story, through the small group discussion, present subject of the story, set the protagonist of the story for smooth configuration of the story, in order to smooth the flow of the story, make up a story around a hero, to make a clear story, decorated with pictures, shapes, graphs, etc, group story, complete with an astronomical(saints) in storytelling. To prove the effects of this study, science concept was split up according to knowledge, inquiry, attitude. Also, science learning motivation consisted of assignment is worth, learning beliefs about control, self efficacy. The results of this study are as follows. First, using storytelling skill was effective in science concept. Second, using storytelling skill was effective in science learning motivation. Also, after using storytelling skill was good reaction by students. As a result, the elementary science class with storytelling skill had the effects of developing science concept and science learning motivation. It means the science class with storytelling skill has potential possibilities and value to develop science concept and science learning motivation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.32 no.5
• /
• pp.91-96
• /
• 2004

An optimal design of the gas generator for Liquid Rocket Engine (LRE) was conducted. A fuel-rich gas generator in open cycle turbopump system was designed for 10ton in thrust with RP-1/LOx propellant. The optimal design was done for maximizing specific impulse of thrust chamber with constraints of combustion temperature and for matching the power requirement of turbopump system. Design variables are total mass flow rate to gas generator, O/F ratio in gas generator, turbine injection angle, partial admission ratio, and turbine rotational speed. Results of optimal design provide length, diameter, and contraction ratio of gas generator. And the operational condition predicted by design code with resulting configuration was found to maximize the objective function and to meet the design constraints. The results of optimal design will be tested and verified with combustion experiments.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.34 no.2
• /
• pp.11-16
• /
• 2006

An experimental study of the transonic flows over NACA and double wedge airfoils was conducted with a shock tube. The configuration of test section with a slotted wall and chamber was designed and tested to minimize wall and reflected shock wave effects and use the shock tube as simple and less costly wind tunnel generating the relatively high Reynolds numbers transonic flow. Transonic airfoil flows at hot gas Mach numbers of 0.80~0.84, Reynolds number of about $1.2{\times}10^6$ on airfoil chord length and angles of attack of $0^{\circ}$ and $2^{\circ}$ were visualized with the shadowgraph method. The shock wave profiles on the airfoils were compared with the corresponding results from the conventional transonic wind tunnel tests. The experimental results showed that present shock tube exhibited the proper performance characteristics as transonic wind tunnel for tested Mach number range and airfoils.