• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.11
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• pp.982-989
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• 2013

Omni-directional antennas of UHF-Band are located on the top and bottom side of the Smart UAV in order to connect a link always. Therefore one of each antennas should be connected to a ground antenna. Because the communication link of the omni-directional antennas is influenced by the objectives around aircraft, the clearance of LOS(Line of Sight) should be achieved in order to avoid a loss of link. In this paper, the analysis results on the influence of the complex objectives placed around the antenna on the communication link are presented according to the change of attitude angles. The best positions of antennas are selected based on the electromagnetic analysis using XGTD tool which supports the modeling of antenna pattern. The flight tests of the Smart UAV were successfully performed with the selected antenna position.

• Journal of the Korean Chemical Society
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• v.21 no.4
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• pp.246-255
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• 1977

The adsorption of methylmethacylate on layer silicates containing various interlayer cations has been studied by means of infrared spectroscopy and X-Ray. Several characteristic carbonyl bands of adsorbed methylmethacrylate appeared differently at the region of 1723∼1547$cm^{-1}$depending on the species of cation and the dehydration temperature. The carbonyl stretching band shifted about 190$cm^{-1}$ to lower frequencies has been observed only for polyvalent cations, which has been attributed to $>C=O{\cdot}{\cdot}{\cdot}M^{n+}$ complex formation. The band appeared at 1703∼1640$cm^{-1}$ is responsible for hydrogen bonding between carbonyl oxygen and cationic water or cationic hydroxyl group, and the degree of shift indicates good correlation with the polarizing power of the interlayer cations. However, the band appeared at 1723$cm^{-1}$ has not been correlated with the species of cation but assigned to the carbonyl stretching which reacted with the surface hydroxyl group. On the basis of interlamellar spacing, it is suggested that the molecular plane of MMA molecule is parallel to silicate layers.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.828-831
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• 1999

5,15-Bis(mesityl)-10,20-bis(4-amino)porphyrin was synthesized with meso-(mesityl)dipyrromethane and 4-nitrobenzaldehyde. It was characterized with $^1H$-NMR spectroscopy, UV spectrophotometer, and GC-MASS. In UV spectrum, Soret-band(438 nm) and Q-bands(526, 572, 611 nm) were confirmed. In NMR spectrum, the characteristic peak of porphyrin was detected at -2.65 ppm. Copolyimide containing porphyrin structure was synthesized with mesityl-$TPP(NH_2)$, 3,3',4,4'-benzophenonetetracarboxylic dianhydride(BTDA) and 2,2-bis(4-(4-aminophenoxy)phenyl) hexafluoropropane(BAPHF) and characterized with UV and FT-IR spectrophotometer. The $T_g$ and $T_m$ of the synthesized copolyimide were 220.7 and $369.2^{\circ}C$, respectively.

• Journal of Photoscience
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• v.9 no.2
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• pp.118-121
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• 2002

A state of bacteriorhodopsin at high temperature was studied by various spectral measurements. The stability measurements indicated that the onset temperature of the denaturation was 70$^{\circ}C$ in the dark and 60$^{\circ}C$ under illumination. The reactivity of hydroxylamine with the Schiff's base also significantly increased in the temperature range between 60 and 70$^{\circ}C$. A spectral band at about 470 nm appeared in the temperature range higher than 60$^{\circ}C$. The circular dichroism spectra in the visible region started to change from a bilobed exiton type to a positive band at about 60$^{\circ}C$, suggesting that the two-dimensional configuration of bacteriorhodopsin molecules changed from crystalline to amorphous. All the measurements suggested a new state between 60 and 70$^{\circ}C$ in which bacteriorhodopsin is stable only in the dark.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.284-284
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• 2012

본 연구에서는 다이오드 소자의 온도 증가에 따른 C-V 특성을 분석하였다. 180 kHz 주파수 조건에서 온도는 300 K에서 450 K까지 50 K 간격으로 가변하였다. 측정 결과 reverse bias 영역에서는 커패시턴스의 온도 의존성이 없었으나, forward bias 영역에서는 온도가 증가함에 따라 동일 전압에서의 커패시턴스가 증가하였다. 이로부터 온도가 증가 할수록 소자가 반전(inversion) 상태에서 축적(accumulation) 상태로 빨리 전환함을 확인하였으며, 1/C2-V 그래프로부터 온도 증가에 따른 전위장벽(Built-in potential, Vbi) 감소를 확인하였다. 전위장벽은 0.63 V에서 0.31 V로 온도 상승에 따라 약 0.1 V씩 감소하였다. 이는 energy band diagram에서 p-type 영역과 n-type 영역의 energy band 차가 감소해 공핍층 영역의 폭이 좁아짐을 의미한다. 공핍층의 두께 감소로 다이오드 전류의 급격한 증가뿐 아니라 위에서 언급한 바와 같은 C-V 특성을 보였다. 이번 연구에서는 기존의 보편화 된 I-V 측정을 통한 다이오드 소자 분석과는 달리 온도 변화에 따른 C-V 분석을 통해 소자 내부의 전위 장벽 및 공핍층 폭 감소에 따른 소자 특성 변화를 분석하였다.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.158-165
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• 1997

The Sun interference event predictions for the KOMPSAT TT&C station were performed to analyze the frequency of the event and the impact on the TT&C link. The KOMPSAT orbit was propagated including only J2 geopotential term for maintaining the Sun-synchronism and no other perturbations were included. Local time of ascending node of the KOMPSAT satellite was set to 10h50m00s. The TT&C station was assumed to locate in Taejon and have 9 meter antenna for S-band link. One year of simulation from 1999/07/01 were performed out of 3 year of mission lifetime of KOMPSAT satellite. Total four times of Sun interference events were occurred during 1 year of simulation and those lasted about 50 seconds altogether. The C/N degradation of the TT&C system was calculated about 4dB. The Sun interference event of 50 seconds of year are 0.0076 percents of the S-band contact time when the 30 minute of contact time is assumed in a day.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.132-132
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• 1994

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.385-388
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• 2000

In this paper, the Ka-band Dielectric resonator oscillator has been designed and fabricated. The resonator network was simulated using HFSS program. The design method of an oscillator is the small-signal S-parameter design. The Push-push DRO employs a hetero junction FET (NE32484A). The fabricated Push-push DRO shows such characteristics as the phase noise -106 ㏈c/Hz at the 100 ㎑ frequency offset. the output power and fundamental frequency surpression were -6 ㏈m and -29 ㏈c, respectively.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.82-82
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• 2004

• Progress in Superconductivity
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• v.4 no.2
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• pp.132-136
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• 2003

Extremely selective high temperature superconducting (HTS) band -pass filters were developed for the base transceiver station applications of Digital Cellular communication Service (DCS). The filters have a bandwidth of 25 MHz at a center frequency of 834 MHz. There are 12 resonators which have spiral-meander microstrip-line structures in order to reduce far-field radiations with a reasonable tunability. As a result, the size of filters is 5 mm $\times$ 17 mm $\times$ 41 mm. Device characteristics exhibited a low insertion loss of -0.4 dB with a -0.2 dB ripple and a return loss better than -10 dB in the pass-band at 65 K. The out-of-band signals were attenuated better than 60 dB about 3.5 MHz from the lower band edge, and 3.8 MHz from the higher band edge.