• Composites Research
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• v.26 no.5
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• pp.279-288
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• 2013

In this paper, the delamination and deformed FSS caused by residual stresses in the Loop type FSS embedded composites and the transmission characteristic changes due to deformation of FSS by residual stresses were studied. FSS may have different electromagnetic characteristics depending on the type of element, design variables, and array. Therefore, design variables of square loop FSS embedded composites structures were determined to obtain the transmission characteristic for X-band (8~12 GHz). Then the design variables of other types of loops (triangular loop and circular loop) were determined based on the dimensions of square loop. Thereafter, the residual stresses and transmission characteristics of FSS embedded composite structures with various single and double loop FSS's, and stacking sequence of composite laminates were compared.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.547-557
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• 2007

This study was conducted to investigate the flow and combustion characteristic of the experimental burner which was manufactured for the reflection of the oven and broil burner features. As slot shape, spacing between slots, and slot arrangement of the exit area which emits the mixing gas are different in case of oven burners and broil turners, the purpose of this study is to know the affection of the flame interaction and combustion characteristic according to the change of shape factors such as slot shape, slot arrangement, and slot-to-slot spacing. With no relation of the slot shape, as the spacing between slots became narrow, the occurrence of a lift-flame was delayed. So the combustion was possible in the leaner region, but the appearance of yellow-tip became a little fast. Slit slot port had the broadest operating range among the other slot shapes. Specially, from the side of lift-flame, as the jet that spreads downstream in the longitudinal slot was nearly circular just a few slot lengths away from the orifice, slot-to-slot spacing of the Slit port was closer than the other ports. These results could be expected through the computer numerical method and had a good agreement. As the spacing between slots increased, in case of Slit and Mix port, NOx emission rate was constant or decreased, but the NOx emission of Hole port was increased. CO emission rate of Slit and Hole port was increased as the slot-to-slot spacing was broadened.

• Journal of The Korean Astronomical Society
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• v.48 no.5
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• pp.299-311
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• 2015

We report first results from KVN and VERA Array (KaVA) VLBI observations obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN) project. We observed eight selected AGN at 22 and 43 GHz in single polarization (LCP) between March 2014 and April 2015. Each source was observed for 6 to 8 hours per observing run to maximize the uv coverage. We obtained a total of 15 deep high-resolution images permitting the identification of individual circular Gaussian jet components and three spectral index maps of BL Lac, 3C 111 and 3C 345 from simultaneous dual-frequency observations. The spectral index maps show trends in agreement with general expectations – flat core and steep jets – while the actual value of the spectral index for jets shows indications for a dependence on AGN type. We analyzed the kinematics of jet components of BL Lac and 3C 111, detecting superluminal proper motions with maximum apparent speeds of about 5c. This constrains the lower limits of the intrinsic component velocities to ~ 0.98c and the upper limits of the angle between jet and line of sight to ~20°. In agreement with global jet expansion, jet components show systematically larger diameters d at larger core distances r, following the global relation d ≈ 0.2r, albeit within substantial scatter.

• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.466-471
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• 2017

SOTM is a device for the satellite communication on the move. Many studies are conducted on microstrip, waveguide and array antenna for the low profile of the SOTM's antenna. But those antennas have a problem that is difficult to adjust the polarization, and for that reason we have studied the parabolic antenna structure. The general form of parabolic reflector structure is circular, but we used cut-off shape reflector by cutting the upper and lower reflector for low profile antenna. Accordingly, this results in the decrease of reflector area which causes reduced gain and G/T ratio. In order to solve this problem, we have transformed and designed the sub reflector for improving the efficiency and gain of the cut- off shape parabolic antenna.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.83-88
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• 2017

This paper describes the azimuth accuracy test of phase comparison direction finding method using F-16 fighter scale-down model. When the antennas are placed on the bottom of a fighter, reflection signals caused by an aircraft structure arises and an azimuth error occurs. In this research, the F-16 fighter scale-down model was made to 5:1, and five antennas were placed on the bottom of the model, then the radio waves of emitters were received by the antennas in the $0-360^{\circ}$ azimuth angles. The accuracy test was performed by numerically analyzing the phases of the radio waves received by the five antennas. The azimuth error of the phase comparison direction finding with scale-down model was measured to be less than $0.5^{\circ}$ when the signal noise ratio was larger then 0dB, and it could be very useful for the design of the phase comparison direction finding method of the fighter.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.12 s.354
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• pp.16-23
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• 2006

This paper presents the development of the fast Direction Finder using direct conversion method, which can intercept for short pulse signal of less' than 1 msec. in RF Down Converter, and CVDF(Correlative Vector Direction Finding) algorithm, which estimates DoA (Direction of Arrival). The configuration and characteristics of direction finder using 5-channel equi-spaced circular array antenna are presented and the direct conversion techniques for removing tuning time using I/Q demodulator are described. The CRLB of our model is derived, the principles of 2 kind of CVDF algorithm are explained and their characteristics are compared with CRLB w.r.t the number of samples and spacing ratio. The RF Down Converter prototype using direct conversion method is manufactured, the 2 kind of CVDF algorithm are applied and their performance are analyzed. Finally it is confirmed the LSE based CVDF algorithm is better than correlation-coefficient based except for ambiguity protection capabilities.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.595-597
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• 2015

LMC X-4 is an eclipsing high-mass X-ray binary exhibiting a superorbital modulation with a period of ~ 30:5 days. We present a detailed study of the variations of the superorbital modulation period with a time baseline of ~ 18 years. The period determined in the light curve collected by the Monitor of All-sky X-ray Image (MAXI) significantly deviates from that observed by the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). Using the data collected by RXTE/ASM, MAXI, and the Burst Alert Telescope (BAT) onboard Swift, we found a significant period derivative, $\dot{P}=(2.08{\pm}0.12){\times}10^{-5}$. Furthermore, the O{C residual shows complex short-term variations indicating that the superorbital modulation of LMC X-4 exhibits complicated unstable behaviors. In addition, we used archive data collected by the Proportional Counter Array (PCA) on RXTE to estimate the orbital and spin parameters. The detected pulse frequencies obtained in small time segments were fitted with a circular orbital Doppler shift model. In addition to orbital parameters and spin frequency for each observation, we found a spin frequency derivative of $\dot{v}=(6.482{\pm}0.011){\times}10^{-13}Hz{\cdot}s^{-1}$. More precise orbital and spin parameters will be evaluated by the pulse arrival time delay technique in the future.

• Korean Journal of Microbiology
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• v.54 no.2
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• pp.161-163
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• 2018

The genome of Flavivirga eckloniae $ECD14^T$ isolated from a seaweed Ecklonia cava was sequenced. The genome comprises a single circular 5,665,358 bp chromosome with a G + C content of 33.9%, 4,647 total genes, 4,595 protein-coding genes, 44 pseudo genes, and 52 RNA genes. CRISPER genes and sequences were not found and there were some phage remnants and transposons. This strain contains alginate lyase and ${\beta}$-glucosidase genes responsible for the degradation of seaweed polysaccharides.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.484-487
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• 2014

In this paper, We describe antenna characteristics for efficiently detecting human signs using small, planar and low power antenna. Then we can measure biological signals including respiration, heart rate, blood pressure, and blood sugar, using UWB (Ultra Wide Band) pulses, while does not contact the human body. The antenna need stable and wideband impedance characteristic, because it use gaussian pulse signal. Usually it has trade-off between wideband impedance and gain. But we don't considered array type antennas because we want to need small size. Generally the antennas that classified as frequency independent satisfy our requirements. Frequency independent antennas include spiral, log-periodic, sinuous, and etc. These antennas are possible to have shape planar type. In this paper, We tested these kind antenna's characteristics in center frequency 5 GHz, Especially circular patch and sinuous antenna designed and analyzed.

• Journal of IKEEE
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• v.23 no.3
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• pp.1112-1115
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• 2019

This paper proposes a novel low-profile omni-directional microstrip antenna to mount on the deployable wing of the observation munition. The proposed antenna is designed on seven hexagonal resonators in a quasi-circular array to achieve a monopolar radiation pattern with a thin substrate. By employing the mesh ground structures, the resonant frequencies and impedance bandwidths of the proposed antenna is investigated. To verify the feasibility of the mesh ground structure, the thin ground wire width is investigated theoretically for improving the 3-dB fractional bandwidth, realized antenna gain and quality-factor. The proposed antenna demonstrates a good monopolar radiation in good agreement with the simulation results. The implemented prototype shows the measured bandwidth of 326 MHz with respect to 5.65% centered at 5.77 GHz and realized gain of 5.49 dBi at 5.84 GHz.