• Journal of The Korean Association For Science Education
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• v.28 no.5
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• pp.383-394
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• 2008

We analyzed the description of diffusion phenomena in a 7th-grade textbook, and investigated teachers' understanding and teaching methods on diffusion concepts. The data were collected from textbook analysis and questionnaires from 46 science teachers and interviews with 5 teachers. Based on texts' analysis by definition, example, and representation of the diffusion, we found that most of the representations were macroscopically explained by observing the movement of ink in water and smelling the fragrance of perfume in the air. The analysis of questionnaire and interviews also revealed that the definition and the explanation of the diffusion were too abstract for teachers to understand and teach the concept without further information about the microscopic concept of collision of the matter with the medium. Such examples and models lead science teachers to form indistinctive concepts such as dissolution, effusion, and evaporation. Furthermore, the analytical data showed that teachers' understanding of the diffusion concept has been heavily dependent upon the textbook and the level of the understanding was very similar with that of textual description.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.9
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• pp.848-857
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• 2011

Vision-based collision avoidance system for air traffic management requires a excellent multiple target detection algorithm under low signal-to-noise ratio (SNR) levels. The track-before-detect (TBD) approaches have significant applications such as detection of small and dim targets from an image sequence. In this paper, two detection algorithms with the TBD approaches are proposed to satisfy the multiple target detection requirements. The first algorithm, based on a dynamic programming approach, is designed to classify multiple targets by using a k-means clustering algorithm. In the second approach, a hidden Markov model (HMM) is slightly modified for detecting multiple targets sequentially. Both of the proposed approaches are used in numerical simulations with variations in target appearance properties to provide satisfactory performance as multiple target detection methods.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.47-53
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• 2022

With the recent development of defense technology, various aircraft armaments/equipments are being developed. Among them, cruise guided weapons(missile) for launching aircraft can be installed on aircraft aftersecuring reliability and safety through varioustests. In order to avoid collision with aircraft, missile separated from aircraft must release restraint of wing at the specified time, control wing in the specified direction. In order to confirm this, a test system that can control MIL-STD-1760 according to safety separation procedure and verify release performance is required. test system needs a function to check circuit for release of restraints and a function to check driving performance by controlling MIL-STD-1760. In addition, test system should be simulate environment separated from aircraft. This paper presented a testsystemthat can verify circuit and driving performance mounted on missile according to the safety separation procedure, and it was confirmed that it was normally separated from aircraft through flight tests.

• Journal of Adhesion and Interface
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• v.14 no.4
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• pp.183-191
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• 2013

In order to elucidate the granular heaping phenomenon, the movement behaviors of 3 different types of granule (millet, sand and thin foil disc) have been investigated by applying the vertical or the rotational vibration to each of the 3 vessels, respectively containing one of the 3 types of granule. In case of vertical vibrations, all of them showed the heaping phenomenon like Gerner's simulation, and that in the order of the millet, sand and thin foil disc, regardlessly of weight. Especially, a heaping of disc granules was proven to be relatively delayed, and that with several small complex clutters. For rotational vibration, the central area of vessel turned out to rise up due to the repulsive force by vessel wall as well as the collision between elastic granules, right after the turning point of vibration. Even spiral pattern was made when the rotational vibration amplitude got higher. From these facts, one can see that the heaping be characterized by the inclusion of attractive granules as well as the vibrational type applied to granule vessel.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.397-416
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• 2020

Investigations of the commercial aircraft impact effect on nuclear island infrastructures have been drawing extensive attention, and this paper aims to perform the safety assessment of Generation III nuclear power plant (NPP) buildings subjected to typical commercial aircrafts crash. At present Part II, based on the verified finite element (FE) models of aircrafts Airbus A320 and A380, as well as the NPP containment and auxiliary buildings in Part I of this paper, the whole collision process is reproduced numerically by adopting the coupled missile-target interaction approach with the finite element code LS-DYNA. The impact induced damage of NPP plant under four impact locations of containment (cylinder, air intake, conical roof and PCS water tank) and two impact locations of auxiliary buildings (exterior wall and roof of spent fuel pool room) are evaluated. Furthermore, by considering the inner structures in the containment and raft foundation of NPP, the structural vibration analyses are conducted under two impact locations (middle height of cylinder, main control room in the auxiliary buildings). It indicates that, within the discussed scenarios, NPP structures can withstand the impact of both two aircrafts, while the functionality of internal equipment on higher floors will be affected to some extent under impact induced vibrations, and A380 aircraft will cause more serious structural damage and vibrations than A320 aircraft. The present work can provide helpful references to assess the safety of the structures and inner equipment of NPP plant under commercial aircraft impact.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.1
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• pp.63-73
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• 2021

This paper presents a algorithm for automatic target recognition robust to the influence of the flame in order to track the target by EOTS(Electro-Optical Targeting System) equipped on UAV(Unmanned Aerial Vehicle) when there is aerial target or marine target with flame at the same time. The proposed method converts infrared images of targets and flames into a gradient vector field, and applies each gradient magnitude to a polynomial curve fitting technique to extract polynomial coefficients, and learns them in a shallow neural network model to automatically recognize targets and flames. The performance of the proposed technique was confirmed by utilizing the various infrared image database of the target and flame. Using this algorithm, it can be applied to areas where collision avoidance, forest fire detection, automatic detection and recognition of targets in the air and sea during automatic flight of unmanned aircraft.

• Korean Journal of Materials Research
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• v.27 no.9
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• pp.501-506
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• 2017

Surface morphology and optical properties such as transmittance and haze effect of glass etched by physical and chemical etching processes were investigated. The physical etching process was carried out by pen type sandblasting process with $15{\sim}20{\mu}m$ dia. of $Al_2O_3$ media; the chemical etching process was conducted using HF-based mixed etchant. Sandblasting was performed in terms of variables such as the distance of 8 cm between the gun nozzle and the glass substrate, the fixed air pressure of 0.5bar, and the constant speed control of the specimen stage. The chemical etching process was conducted with mixed etching solution prepared by combination of BHF (Buffered Hydrofluoric Acid), HCl, and distilled water. The morphology of the glass surface after sandblasting process displayed sharp collision vestiges with nonuniform shapes that could initiate fractures. The haze values of the sandblasted glass were quantitatively acceptable. However, based on visual observation, the desirable Anti-Glare effect was not achieved. On the other hand, irregularly shaped and sharp vestiges transformed into enlarged and smooth micro-spherical craters with the subsequent chemical etching process. The curvature of the spherical crater increased distinctly by 60 minutes and decreased gradually with increasing etching time. Further, the spherical craters with reduced curvature were uniformly distributed over the etched glass surface. The haze value increased sharply up to 55 % and the transmittance decreased by 90 % at 60 minutes of etching time. The ideal haze value range of 3~7 % and transmittance value range of above 90 % were achieved in the period of 240 to 720 minutes of etching time for the selected concentration of the chemical etchant.

• The Korean Journal of Air & Space Law and Policy
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• v.30 no.1
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• pp.303-325
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• 2015

The latest slogan put forth by the international space community is the safety, security, and sustainability of outer space activities. The security of outer space activities, in particular, would be defined as the secure state from space-based threats. The latter comprises passive threats (such as collision with other satellites and space debris) and aggressive threats (such as electromagnetic interference, arms race on the earth or in outer space, and military attacks). Has outer space been used for military purposes in practice? If so, does international law regulate the military space activities it? The use of outer space for military purposes is referred to as space militarization and space weaponisation. Satellites has been used in Gulf War, Kosovo War, and Afghan War, recently, and research and development on space weapons are under way. Since only the placement of weapons of mass destruction on orbit around the earth is prohibited in accordance with 1967 Outer Space Treaty, it may be asked whether other weapons may be placed on orbit. It will be necessary to analyze the stance of on the above question, by studying UN space-related treaties including UN Charter. New international space norms represented by PPWT, ICoC, and UN GGE Report are at the center of progressive development of international law. In conclusion, the author will signpost the various points on international norms to be codified on the use of outer space for military purposes.

• Journal of the Korean Society of Combustion
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• v.21 no.3
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• pp.1-6
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• 2016

The effect of applied electric fields on jet flow instability was investigated experimentally by varying the direct current (DC) voltage and the alternating current (AC) frequency and voltage applied to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames in laminar jet flow configuration, which occur when AC electric fields are applied. The results indicate that a twin-lifted jet flames originates from cold jet instability, caused by interactions between negative ions in the jet flow via electron attachment as $O_2+e{\rightarrow}O_2{^-}$ when AC electric fields are applied. This was confirmed by experiments in which a variety of gaseous jets were ejected from a nozzle to which DC voltages and AC frequencies and voltages were applied, with ambient air between two deflection plates connected to a DC power source. Experiments in which jet flows of several gases were ejected from a nozzle and AC electric fields were applied in coflow-nitrogen provided further evidence. The flow instability occurred only for oxygen and air jets. Additionally, jet instability occurred when the applied frequency was less than 80 Hz, corresponding to the characteristic collision response time. The effect of AC electric fields on the overall structure of the jet flows is also reported. Based on these results, we propose a mechanism to reduce jet flow instability when AC electric fields are applied to the nozzle.

• The Korean Journal of Air & Space Law and Policy
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• v.24 no.1
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• pp.35-58
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• 2009

A treaty that governs the compensation on damage caused by aircraft to the third parties on surface was first adopted in Rome in 1933, but without support from the international aviation community it was replaced by another convention adopted again in Rome in 1952. Despite the increase of the compensation amount and some improvements to the old version, the Rome Convention 1952 with 49 State parties as of today is not considered universally accepted. Neither is the Montreal Protocol 1978 amending the Rome Convention 1952, with only 12 State parties excluding major aviation powers like USA, Japan, UK, and Germany. Consequently, it is mostly the local laws that apply to the compensation case of surface damage caused by the aircraft, contrary to the intention of those countries and people who involved themselves in the drafting of the early conventions on surface damage. The terrorist attacks 9/11 proved that even the strongest power in the world like the USA cannot with ease bear all the damages done to the third parties by the terrorist acts involving aircraft. Accordingly as a matter of urgency, the International Civil Aviation Organization(ICAO) picked up the matter and have it considered among member States for a few years through its Legal Committee before proposing for adoption as a new treaty in the Diplomatic Conference held in Montreal, Canada 20 April to 2 May 2009. Accordingly, two treaties based on the drafts of the Legal Committee were adopted in Montreal by consensus, one on the compensation for general risk damage caused by aircraft, the other one on compensation for damage from acts of unlawful interference involving aircraft. Both Conventions improved the old Convention/Protocol in many aspects. Deleting 'surface' in defining the damage to the third parties in the title and contents of the Conventions is the first improvement because the third party damage is not necessarily limited to surface on the soil and sea of the Earth. Thus Mid-air collision is now the new scope of application. Increasing compensation limit in big gallop is another improvement, so is the inclusion of the mental injury accompanied by bodily injury as the damage to be compensated. In fact, jurisprudence in recent years for cases of passengers in aircraft accident holds aircraft operators to be liable to such mental injuries. However, "Terror Convention" involving unlawful interference of aircraft has some unique provisions of innovation and others. While establishing the International Civil Aviation Compensation Fund to supplement, when necessary, the damages that exceed the limit to be covered by aircraft operators through insurance taking is an innovation, leaving the fate of the Convention to a State Party, implying in fact the USA, is harming its universality. Furthermore, taking into account the fact that the damage incurred by the terrorist acts, where ever it takes place targeting whichever sector or industry, are the domain of the State responsibility, imposing the burden of compensation resulting from terrorist acts in the air industry on the aircraft operators and passengers/shippers is a source of serious concern for the prospect of the Convention. This is more so when the risks of terrorist acts normally aimed at a few countries because of current international political situation are spread out to many innocent countries without quid pro quo.