• Composites Research
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• v.18 no.6
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• pp.34-39
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• 2005

In this study, we analyzed the relation between physical/mechanical properties and ballistic properties for several engineering ceramics that were expected to use as armor material. After physical/mechanical measurement, we measured ballistic properties about KE(Kinetic Energy, L/D=10.7, tungsten heavy alloy) and HEAT(High Explosive Anti-Tank, K215) projectiles. Increasing Young's modulus/density, hardness/density and flexural strength/density ratios, ballistic properties were generally increased. Especially it appeared that the ballistic property about KE projectile was lineally increased, as HEL/density ratio increased.

• Composites Research
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• v.18 no.6
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• pp.40-47
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• 2005

In this study, we tried to invent ceramic armor material with brilliant ballistic properties by the silica of the high compression-expansion ratio and based on alumina that has the most economical and higher ballistic efficiency. After we choose three compositions, proper sintering temperature for each composition was decided. After physical/mechanical measurement, we measured ballistic properties about KE(Kinetic Energy, L/D=10.7, tungsten heavy alloy) and HEAT(High Explosive Anti-Tank, K215) projectiles. As a result, $46\%\;Al_2O_3\;-\;51\%\;SiO_2$ of three compositions had the highest ballistic efficiency md better properties than alumina.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.80-85
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• 2010

The study of the safety perceptions between two groups, trained and untrained student pilots were compared as pre-studies of that how the safety perceptions of the flight instructors affect that of the student pilots. As a results, the factors of the communication and the safety procedures shows higher values on the one-year trained group than the other because the trained students get used to the safety procedures which are necessary to the practical training. In reliability for the flight instructor, the factors of two groups show the high tendency without regard to groups. Despite of the lack of the specific research, the result implies that the student pilots are influenced by the safety perceptions of the flight instructors. In addition, the factors of the accident report were investigated as that the trained group has lower mean, however the factors of the receiving penalties of the trained group were higher than the other. These results imply that the trained group feels concern for the penalties and the punishments by reporting the accidents in spite of amounts of the training.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.777-780
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• 2011

The supersonic wind tunnel is a common facility to studies the aerodynamic phenomenon around the high speed vehicle or weapon system whose operating speed is greater than sonic speed. In this study, a design procedure and selecting the components of a new supersonic wind tunnel whose nozzle exit is $125mm{\times}100mm$ is considered. An operating test of this wind tunnel is being conducted to compare the result with the design values, mach number, etc.

• Aerospace Engineering and Technology
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• v.9 no.1
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• pp.17-27
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• 2010

KSLV-I KM plume including alumina particle has been studied using the continuum solver. Alumina particles are assumed to have 7 different diameters, and the specific ratio of the plume gas is assumed to be 1.2, with which the internal nozzle flow characteristics are similar to those of the chemically equilibrium analysis results. The results showed that the expansion angle of the particles is smaller than that of the gas phase, and that the big sized alumina particles are gathered in the plume core and the expansion angles of the big sized particles are smaller than those of the light particles. When the emissivity of the particles are assumed to be 0.1, the radiative heat flux is equivalent to those measured during the flight test of KSLV-I.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.24-27
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• 2012

In this study, the full scale flight type Dual-Pulse Rocket Motor(DPRM) with the bulkhead type Pulse Separation Device(PSD) was designed, manufactured, and fire-tested. The bursting time and pressure of PSD were analyzed by the pressure, thrust and vibration results of static fire tests and ablation of PSD was measured with 3-D coordinate measuring machine. As a result, PSD requirements, bursting conditions and thermal safety, were satisfied.

• Journal of the Korean Society of Child Welfare
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• no.36
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• pp.7-27
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• 2011

This study empirically examines the effects of after-school self-care on children's development. More specifically, we examine whether the level of after-school self-care experiences that a child had during the 4 to 6 grade period affects the levels of school achievement, internalizing problem behaviors, externalizing problem behaviors, and delinquent behaviors during the child's middle school years. The study utilized the data from the Korea Welfare Panel Study's 1st and 4th year child supplementary surveys. The results show that the level of after-school self-care experiences negatively affects children's school achievement and internalizing problem behaviors. The study finds that, as the level of after-school self-care experiences increase, school achievement decreases and internalizing problem behaviors increase. The effects of after-school self-care on school achievement and internalizing behaviors were statistically significant even after controlling for the other variables that are known to be important factors on child development including child, parent, and family characteristics. The findings suggest that there is an independent effect of the level of after-school self-care on school achievement and internalizing problem behaviors. We also provide policy implications of the study. The policy considerations for latchkey children should include not only increasing the quantity of after-school programs, but also paying attention to the need of child development support programs beyond basic protection and care.

• Journal of the Korean Society of Child Welfare
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• no.53
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• pp.1-23
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• 2016

With using a subsample of 1,373 poor single mothers and their children from the Fragile Families and Child Wellbeing study, the present study examined the associations among mothers' economic hardship, depressive symptoms, and parenting stress, child abuse and neglect, and their children's behavior problems, delinquency, and social skill. These families were tracked through follow-up interviews at the time of birth, and when the children were three, five, and nine years old. The results indicated that mothers' economic hardship, depressive symptoms, and parenting stress were significant predictors to determine their children's abuse and neglect. Findings also suggest that higher levels of child abuse and neglect are positively associated with more behavior problems and delinquency, and negatively associated with social skills. Further discussions include policy and services to prevent child abuse and neglect and to alleviate mothers' financial difficulties, depression, and parenting stress.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.05a
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• pp.207-210
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• 2009

This paper presents development status of sounding rockets containing scientific payload and telemetry at home and abroad. The case of outside, united state is launching sounding rockets in 20-30 flight per year by the NASA program which offer to carry payload weights of 38-680 kg and altitude of 88-1,500 km. Europe is launching in 4-5 flight per year by the ESA program. Japanese sounding rockets are being applied an Antarctic exploration and flight verification in 1-2 flight per year. The case of korean sounding rockets was successful with the launch of three times(KSR-I,II,III), but our development techniques for space launch vehicle lag behind other industries. Therefore, Launch vehicle development should enable with the support and acquirement of advanced technology.

• The Journal of the Korea Contents Association
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• v.5 no.5
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• pp.133-139
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• 2005

The neutron capture cross section of $^{99}Tc$ has been measured relative to the $^{10}B(n,\gamma)$ standard cross section by the neutron time-of-flight(TOF) method in the energy range of 0.007 eV to 47 keV using a 46-MeV electron linear accelerator(linac) at the Research Reactor. Institute, Kyoto University(KURRI). In order to experimentally prove the result obtained, the supplementary cross section measurement has been made from 0.3 eV to 1 keV using the Kyoto University Lead stowing-down spectrometer (KULS) coupling to the linac. The relative measurement by the TOF method has been normalized to the reference value(20.01 b) at 0.0253 eV and the KULS measurement to that by the TOF method. The existing experimental data and the evaluated capture cross sections in ENDF/B-VI, JENDL-3.2, and JEF-2.2 have been compared with the current measurements by the linac TOF and the KULS experiments.