• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.52-60
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• 2015

Operation area of corps was expanded under military reformation, and extending range of 155 mm howitzer became important issue. New approach is needed to extend range to 80 kim. Ramjet engine is air breathing engine, and it can provide specific impulse several times more than solid rocket motor so that range is extended using same weight of propellant. If the ramjet engine is gun-launched system, it does not require any other booster because muzzle velocity is near Mach 3. Especially solid fuel ramjet (SFRJ) does not have any moving part so that it is favorable for gun-launching system which is under high stress during launching. In this paper, we design air intake, combustion chamber, and nozzle of 155 mm gun launched ramjet propelled artillery shell with inviscid flow assumption. We conduct parameter study to have range more than 80 km, and maximum high explosive volume.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.147-153
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• 2020

Developments in aircraft require safety verification through flight testing for many hours with prototype design and production. The test evaluation step of performing flight tests was an important process that determines the success in the development of the system. In particular, safety development through flight tests in the armed flight test is important for the development of attack helicopters. In the development of attack helicopters, the evaluation period and cost related to the armed flight test are closely related to the required ammunition requirement. Therefore, this paper presents the amount of ammunition required for the military flight test between attack helicopter developments through an analysis of the AH-1 helicopter in a similar case and ADS-44-HDBK of military specification. The AH-1 can be used to calculate the ammunition demand by considering the exclusion of redundant firing tests and configuration differences. In the case of the machine gun-equipped configuration, approximately 10,500R was required, and approximately 324R was required in the case of a rocket-mounted configuration. In addition, if the armed integrated bench is used properly, it is expected to promote efficiently the flight test in the armed flight by identifying the possible risk factors with armed flight tests and excluding them.

• Journal of The Korean Association For Science Education
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• v.34 no.8
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• pp.719-730
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• 2014

The purpose of this study was to investigate elementary school students' perceptions about science, engineering and technology and their images of scientists, engineers, and technicians. In order to investigate students' images of scientists, engineers, technicians and student's perception of science, engineering, and technology, we used the tools "Draw a scientist at work, Draw an engineer at work, and Draw a technician at work". We have revised the tool DAST (Draw a scientist test), which was used in Fralick et al.'s study (2009). Subjects were 209 6th grade students sampled from an elementary school in G-city in Korea. According to the results of this study, the students' representative image of a scientist was similar to stereotypical scientist image in previous studies, but the students perceived science as a field of research with various professionals. The students' representative image of an engineer was a man with short hair, no beard or mustache, wearing ordinary clothes but no glasses. The engineer was designing or constructing a ship, a robot, a computer, and an airplane. The students' representative image of a technician was a man with short hair, wearing protective goggles and a mask for welding. The technician was fixing a car, a robot, a rocket, etc. and working with wrenches, hammers, screw drivers, welding machines, etc. Many students didn't perceive engineering and technology as fields of research. Also, many students didn't variously perceive engineering and technology as fields and ways of study.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.227-238
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• 2016

This review article highlights different types of nano-sized catalysts for the selective alcohol oxidation to form aldehydes (or ketones) with supported or immobilized metal nanoparticles. Metal nanoparticle catalysts are obtained through dispersing metal nanoparticles over a solid support with a large surface area. The nanocatalysts have wide technological applications to industrial and academic fields such as organic synthesis, fuel cells, biodiesel production, oil cracking, energy conversion and storage, medicine, water treatment, solid rocket propellants, chemicals and dyes. One of main reactions for the nanocatalyst is an aerobic oxidation of alcohols to produce important intermediates for various applications. The oxidation of alcohols by supported nanocatalysts including gold, palladium, ruthenium, and vanadium is very economical, green and environmentally benign reaction leading to decrease byproducts and reduce the cost of reagents as opposed to stoichiometric reactions. In addition, the room temperature alcohol oxidation using nanocatalysts is introduced.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.47-53
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• 2017

A boundary layer integral combined with a 1-D isentropic core flow model has been successfully used to determine heat transfer rate on the surface of a supersonic nozzle. However its accuracy is affected by the core flow condition which is used as a boundary condition for the integral calculation. Because flow behavior near a nozzle throat deviates from 1-D isentropic condition due to 2-D flow turning and interaction between core flow and boundary layer, accuracy of heat transfer calculation decreases at a nozzle throat. Therefore, CFD is adopted to deduce improved core flow condition and increase accuracy of boundary layer integral at nozzle throat in this research. Euler model and SST $k-{\omega}$ model is solved by CFD code and used as a boundary condition for boundary layer integral. Developed code is tested in the supersonic nozzle from the previous research and improvement in accuracy is observed, especially at nozzle throat and diverging section of the nozzle. Error between experimental result and calculation result reduced by 16% when a calculation is made based on the SST $k-{\omega}$ model. Method developed in this research is expected to be used in thermal design of the rocket nozzle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.5
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• pp.419-426
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• 2018

For an orbit transfer in a space exploration mission, a solid or liquid rocket booster is included at the last stage of the launch vehicle. During the orbit transfer, thrust misalignment can cause a severe orbit error. Three axis attitude control or spin stabilization can be implemented to minimize the error. Spin stabilization technique has advantages in structural simplicity and lightness. One of ways to apply the spin stabilization to the payload is to include a spin table system in the launch vehicle. In this paper, effect of the spin table system on separation dynamics of the payload is analyzed. Simple model of the spin table to mimic basic functions is designed and simulation environment is established with the model. Effect of the spin table is tested by evaluating separation dynamics of a payload with and without the spin table. Analysis on tolerance effect of separation spring constant on separation dynamics of a payload is conducted.

• Journal of Science Education
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• v.38 no.3
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• pp.569-584
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• 2014

The Purpose of this study was an analysis of high school student's understanding level about concepts of special relativity through in-depth interview. The 8 participants were 10th grade students in H high school in Ulsan city, who were interviewed and analyzed in the results of the interview about basic concepts of special relativity using achievement checklist in 6 situations(principle of constancy of light velocity, principle of relativity, relativity of simultaneity, garage paradox, rocket paradox). As results of the checklist, the participants showed high achievement in the content level of simple phenomena and simple concepts related to special relativity. But they showed low achievement in the concept level for fundamental understanding of special relativity. As results of the interview, it was found that the participants decided the order of events depending on their intuition and had a difficulty to apply the coordinate system to real situation, even though they mathematically understood it. In addition, some participants who could not understand the inertial coordinate system explained paradoxes of relativity depending on their intuition and had learner's chaos. Finally, though high school students usually being in formal operational stage, some students had difficulty to draw phenomena of space and time in two dimensional plane.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.984-997
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• 2015

Chang'e-3 consisting of a lunar lander and exploration rover was launched on December 1, 2013 aboard a Long March 3B rocket flying from Xichang space launch center. Chang'e-3 was inserted into the lunar orbit after about a 5-day transit to the Moon and landed on the targeted landing site after orbiting around the Moon for 8 days. The successful landing of the Chang'e-3 gives a lot of help to analyze the future needs of the subsystem technologies and to figure out the trajectory from launch to lunar landing as well as operation sequences in the development of Korean lunar exploration is scheduled. Therefore, the configuration and analysis of overall mission of Chang'e-3 is performed based on the public information from the press and website. As a result, overall mission trajectory is reconstructed by solving boundary condition and then estimating control variable. Visibility status and eclipse status also analyzes so communication and power charge condition is as good as to operate lunar lander. Mass budget of the lander is derived using ${\Delta}V$ according to specific impulse.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.7
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• pp.776-781
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• 2006

Perchlorate ion($ClO_4^-$), which is present in the solid propellant for rocket, herbicide and some fertilizers. Perchlorate inhibits iodide uptake by the human thyroid gland. Impairment of thyroid function in expectant mothers may impact the fetus and result in effects including cerebral palsy, give rise to thyroid gland cancer. The US EPA(Environmental Protection Agency) adopted a reference dose(RfD) for perchlorate 0.0007 mg/kg-day, and this guidance lead to a Drinking Water Equivalent Level(DWEL) of 24.5 ${\mu}g/L$. The studies about perchlorate are actively performed in foreign countries, especially in USA but there is no study which surveyed the perchlorate contamination in Korea. Therefore, this study was done to investigate perchlorate contamination in Nak-dong river and tap water. The perchlorate was detected in Nakdong river and ranged from ND to 278.4 ${\mu}g/L$. The highest concentration was observed in Kumichon. The perchlorate concentration was decreased with the down stream of Nakdong river. The perchlorate concentration in tap water was varied with the cities and the concentration levels were $ND{\sim}34.1$ ppb. The highest perchlorate concentration was observed in DalsuGoo in Daegu and the similar concentration($9{\sim}11$ ${\mu}g/L$) was detected in most of the districts in Busan. The result of this study suggests that there is a perchlorate source near the Nakdong river and the urgent policy is needed to control perchlorate for the cities which are supplied from Nakdong river as for their tap water.

• Resources Recycling
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• v.25 no.1
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• pp.48-59
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• 2016

The earth has been warming due to $CO_2$ gas emissions from fossil fuel cars and a ship. So the hydrogen fuel cell vehicle(FCV) using hydrogen as a fossil fuel alternative energy is in the spotlight. Hyundai Motor Company of Korea and a car companies of the US, Japan, Germany is developing a FCV a competitive. Obtained hydrogen as a by-product of the coke plant, oil refineries, chemical plants of steel mill, coal is reacted with steam at high temperatures, methane gas, manufacture of high purity hydrogen Methane Steam Reforming and hydrogen detachable reforming method using the Pressure Swing Adsorption or Membrane Reforming technical or decomposition of water to produce electricity. Hydrogen is the electronic industry, metal and chemical industries, which are used as rocket fuel, etc. are used in factories, hospitals, home of the fuel Ene.Farm system or FCV. And a method of storing hydrogen is to store liquid hydrogen and a method for compressing normal hydrogen to the hydrogen container, by storing the latest hydride or Organic chemical hydride method is used to carry the hydrogen station. Korea is currently 13 hydrogen stations in place and in operation, plans to install a further 43 places.