• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.139-142
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• 2004

X-band Waveguide slot way antenna is developed for heliborne MTD radar applications. The antenna is composed of multi-layer waveguide structures. Each of them has it's own functions, such as, radiation, power/phase distribution, coupling, etc. Broad-wall offset slots are used for radiators, inclined slots on broad-wall for power distribution to radiating(branch) waveguide, some kind of coaxial probe structures for in-phase coupling and H-plane T-junction power dividers. Antenna is realized by precision machining and careful assembly. It is tested and measured by 3m${\times}$l.7m planar near-field probe, which is set-up in MTG. Far-field calculations have good agreement in tolerable bounds. Special but necessary process such as brazing, will increase the accuracy and performance. Results show promising possibilities of future applications for real systems.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.379-384
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• 2011

This paper performs numerical prediction of fuel temperature in the fuel tanks of unmanned air vehicles for both ground static non-operating and in flight transient conditions. The calculation is carried out using a modified Dufort-Frankel scheme. For this calculation, it is assumed that a non-operating vehicle on the ground is subjected to repeating daily cycles of ambient temperature with solar radiation and wind under 1%, with a 20% probability of hot day conditions. The energy conservation equation is used as the governing equation to calculate heat transfer between the fuel tank surface and the ambient environment. Results of the present analysis may be used as the estimated initial values of fuel temperatures in a vehicle's fuel tank for the purpose of analyzing transient fuel temperatures during various flight missions. This research also demonstrates that the fuel temperature of the front tank is higher than that of the rear tank, and that the difference between the two temperatures increases in the later phases of flight due to the consumption of fuel.

• Journal of Advanced Navigation Technology
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• v.7 no.2
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• pp.101-107
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• 2003

In this study, we provide a single element log-periodic antenna that the feeding networks and array structures are aperture coupled and series dipole array type. We made the antenna for direct receiving the Moogoongwha satellite broadcasting signal. The transmission power was able to feed the patch dipole in series due to lay perpendicularly 8 series patch dipole on tapered slot. The patch dipole radiation pattern which fed in series power, make the main beam direction up $37^{\circ}{\sim}42^{\circ}$ within the BS/CS bandwidth. The main beam gain was measured 9.31~11.03 dBi. Using 32 elements to array the elements properly, we acquire $4{\times}8$ array structure on limited PCB board. As a result, it has been found that the new planar DBS antenna structure have high gain over 10dBi and acceptable elevation angle over 42 degree, and we can apply this result to commercial DBS reception antenna manufacturing.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.638-642
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• 2017

FOD is a generic term for substances with potential threats that can pose a fatal risk to aircraft. Therefore, FOD should be noted in all areas of the airport. Especially, the method of detecting and collecting FOD in runway and aircraft movements is very low efficiency and economical efficiency of airport operation, so it is essential to develop FOD automatic detection system suitable for domestic environment. As part of the aviation safety technology development project, the development of an automatic detection system for foreign matter in the moving area of the aircraft inside the airport is underway. In this paper, it is confirmed that EO / IR camera is used for detection of foreign objects at Taean Airfield of Hanseo University. EO camera is used during the day and IR camera is used at night.

• Korean Journal of Materials Research
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• v.14 no.7
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• pp.522-528
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• 2004

Heat analysis of the plate type and wave type heat sink were carried out by using computational simulation. The heat resistance and air flow of two heat sink models were analysed according to natural and forced convection condition and positions of fan. When a fan was at the position of z-axis and y-axis in forced convection, the heat resistances of plate type heat sink were $0.17^{\circ}C/W$, and $0.28^{\circ}C/W$ respectively. In the case of wave type heat sink, they were $0.18^{\circ}C/W$ and $0.53^{\circ}C/W$. As the air flow velocities were averagely $0.386\;m/s\~3.269\;m/s$, air flow velocity of plate type heat sink was faster than that of wave type. In this experiment, it was observed that the plate type heat sink showed a good ability of heat radiation comparing with wave type one.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.490-493
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• 2005

We have experimentally studied supercontinuum generation in a photonic crystal fiber as a function of pump wavelength and intensity with 100 fs pulsewidth. A supercontinuum over 750 nm spectral width with amplitude variation less than 10 dB has been achieved. It was generated by coupling femtosecond pulses from a mode-locked Ti:Sapphire laser into a 2 m long photonic crystal fiber. Adjusting the parameters of the pump source, it was also possible to control different spectral features of the supercontinuum radiation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1995.05a
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• pp.171-175
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• 1995

Semiconductor diode lasers that can generate one watt or more of optical energy for tens of milliseconds (quasi continuous wave) are now readily available. Several researchers have demonstrated that this power level, when properly coupled, can reliably initiate pyrotechnic mixtures. This means that the initiator containing the pyrotechnic can be protected against inadvertent initiation from electromagnetic radiation or electrostatic discharge by a conducting Faraday cage surrounding the explosive. Only a small dielectric window penetrates the housing of the initiator, thereby eliminating the conductors necessitated by a bridgewire electroexplosive device. The diode laser itself, however, functions at a low voltage (typically 3 volts) and hence is susceptible to inadvertent function from power supply short circuits, electrostatic discharge or induced RF energy. The rocket motor arm-fire device de-scribed in this paper uses a diode laser, but protects it from unintentional function with a Radio Frequency Attenuating Coupler (RFAC).The RFAC, invented by ML Aviation, a UK company, transfers power into a Faraday cage via magnetic flux, thereby protecting the diode, its drive circuit and the pyrotechnic from all electromagnetic and electrostatic hazards. The first production application of a diode laser and RFAC device was by the Korean Agency for Defense Development.

• Journal of the Korean Ceramic Society
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• v.43 no.3 s.286
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• pp.177-184
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• 2006

Dy $L_3$-edge XANES and EXAFS spectra of chalcogenide Ge-As-S glass doped with ca. 0.2 wt% dysprosium have been investigated along with some reference Dy-containing crystals. Amplitude of the white-line peak in XANES spectrum of the glass sample turns out to be stronger than that of other reference crystals, i.e., $DY_2S_3,\;Dy_2O_3\;and\;DyBr_3$. It has been verified from the Dy $L_3$-edge EXAFS spectra that a central Dy atom is surrounded by $6.7{\pm}0.5$ sulfur atoms in its first coordination shell in the Ge-As-S glass, which is relatively smaller than 7.5 of the $Dy_2S_3$ crystal. Averaged Dy-S inter-atomic-distance of the glass ($2.78{\pm}0.01{\AA}$) also turns out to be somewhat shorter than that of the $Dy_2S_3$ crystal ($2.82{\pm}0.01{\AA}$). Such nanostructural changes occurring at Dy atoms imply there being stronger covalency of Dy-S chemical bonds in the Ge-As-S glass than in the crystal counterpart. The enhanced covalency in the nanostructural environment of $Dy^{3+}$ ions inside the glass would then be responsible for optical characteristics of the $4f{\leftrightarrow}4f$ transitions of the dopants, i.e., increase of oscillator strengths and spontaneous radiative transition probabilities.

• Journal of Advanced Navigation Technology
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• v.24 no.1
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• pp.1-8
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• 2020

In this research, we develop an airborne equipment radiating S/C-band signal to a target located at a long distance. RF interface of the equipment comprises band-specific transmitters and an broadband antenna to satisfy EIRP(effective isotropic radiated power) requirements. The equipment is in a shape of a POD like an aircraft fuel tank. The measured weight of the equipment is 119.8 kg, the CG(center of gravity) is 1391.35 mm and the MOI(moment of inertia) are 46.07 ± 0.05(I_yy) kg·㎡, 45.36 ± 0.09(I_zz) kg·㎡. All results are found to meet the requirements for aircraft installation. To verify flight safety, EMI(electromagnetic interference) tests (RE102, CE102), environmental tests (high/low temperature operation, altitude), intra-system EMC(electromagnetic compatibility) and HERP(hazards electromagnetic radiation personnel) tests have been conducted and all the test results met the requirements. It is confirmed that the equipment could be mounted on the aircraft by meeting all electrical and mechanical requirements.

• Elastomers and Composites
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• v.46 no.1
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• pp.29-36
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• 2011

The term 'thermal insulating materials' describes a class of materials which can improve the thermal efficiency by reducing the thermal conduction, convention and radiation between the inside and outside of the system. As a thermal insulating material, numerous industrial applications are possible including the automobile, aerospace, aviation, and petrochemical. Especially, the silica aerogel, with their superior thermal insulating behavior, has been widely used as thermal insulating materials. Because the mechanical properties of the silica aerogel cannot meet the industrial demand, use of the silica aerogel is limited. This article aims to review the thermal insulating materials and silica aerogel, and to introduce the silica aerogel/polymer composites.