• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.9
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• pp.661-667
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• 2018

Tactical communication radio systems that employ software defined radios(SDRs) have been developed for achieving high-speed data transmissions and voice communications. Such systems possess multiband and multichannel features, and can potentially replace several existing radio systems. This paper proposes a design for wideband antennas by incorporating a diplexer matching network for tactical vehicles. The proposed antenna design includes two radiators(upper and lower) and a diplexer matching network connected to the end of the feed line such that the LC matching networks are interleaved in the lower radiator and spring mount. By employing the diplexer matching network, the designed antenna can perform wideband impedance matching for the fifty ohm feed line. The designed LC networks aid in varying the effective electrical length of the antenna according to the operation frequency. The primary objective behind adjusting the electrical length is to vary the current distribution above and below the LC networks. The proposed antenna was fabricated and tested in an open site. The obtained evaluation results show that the designed antenna can achieve a relative bandwidth of 190% with a VSWR value of 3.5:1, and can attain good antenna gains over VHF and UHF bands.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.3
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• pp.50-56
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• 2010

In this paper, compact broad-band antenna using circular spiral slot and CPW (coplanar waveguide) feed is proposed. The proposed antenna is designed on the same plane of the substrate by using CPW fed structure, archimediean spiral slot structure. So it was achieved both the size of compact antenna and the broad band. A archimediean spiral slot structure is introduced for resonance of medium band operation. The distances of a CPW feeder line and a ground plane are modified for impedance matching and lower/higher band operation. The proposed antenna has a compact size ($8mm\;{\times}\;13mm$) and it is etched on the FR-4 (relative dielectric constant 4.4, thickness 0.8mm) dielectric substrate. The simulated impedance bandwidth (VSWR $\leq$ 2) and maximum gain of the proposed antenna are 5.98GHz (4.1GHz ~ 10.08GHz) and 3.97dBi, respectively. The measured impedance bandwidth (VSWR $\leq$ 2) and maximum gain of the proposed antenna are 6.02GHz (4.48GHz ~ 10.5GHz) and 2.68dBi, respectively. The simulation and measured result shows good impedance matching and radiation pattern over the interesting frequency bands. It can be applied to antenna of broad-band wireless communication system.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.227-234
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• 2011

Many technologies for wireless internet are increasing as more and more laptop computers, net books, smart phone and other terminals, which provide wireless network, are created. IEEE 802.11 is computer wireless network technology that used in small area, called wireless LAN or Wi-Fi. IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). AP (Access Point) is installed at cafes and public places providing wireless environment. It is more convenient to use wireless internet, however, It can be seen easily around us and possible to communicate with AP. IEEE 802.11 has many vulnerability, such as packet manipulation and information disclosure, so we should pay more attention when using IEEE 802.11. Therefore this paper developing monitoring system which can find out AP and Stations that connect with it, and capturing AP's information to find out vulnerability. This paper suggests monitoring system which traffic analysis in wireless environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2223-2231
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• 2015

In this paper, we propose a built-in antenna for wireless USB dongle which has a modified structure from the existing planar monopole antenna. The proposed antenna implemented a dual-band characteristic by inserting Strip1, Strip2, Strip3 into the monopole structure combined with 'n' shape and feeded 50-Ω using coaxial cable. The antenna is designed on an FR-4 substrate of which the dielectric constant is 4.6, and its overall size is 10 mm × 50 mm × 1mm. Based on the measurement results of the return loss, it was confirmed to satisfy the dual band resonance characteristics of 740 MHz (2.3 ~ 2.7 GHz) and 1,200 MHz (5.15 ~ 5.825 GHz) by -10 dB. In addition, we obtain the omni-directional radiation pattern measurements in the operating frequency bands, and the maximum gain of the proposed antenna has 2.26~3.81 dBi in the 2.4 GHz band and 2.21~5.79 dBi. in the 5.5 GHz band, respectively.

• Progress in Medical Physics
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• v.12 no.1
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• pp.1-8
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• 2001

Diamond thin films were synthesized by a chemical vapor deposition (CVD). Raman spectrum showed the diamond line at 1332 $cm^{-1}$ / and x-ray diffraction pattern exhibited a strong (111) peak of diamond. The scanning electron microscopy analysis showed that the CVD diamond thin film was grown to be unepitaxial crystallites with pyramidal hillocks. A wavelength-resolved thermoluminescence (TL) of the CVD diamond thin film irradiated with X-rays showed one peak at 430 nm around 560 K. The glow curve of the CVD diamond thin film produced one dominant 560-K peak that was caused by first-order kinetics. Its activation energy and the escape frequency were calculated to be 0.92 ～ 1.05 eV and 1.34 $\times$ 10$^{7}$ sec$^{-1}$ , respectively. The emission spectrum at 560 K was split into 1.63-eV, 2.60-eV, and 3.07-eV emission bands which is known to be attribute to silicon-vacancy center, A center, and H3 center, respectively.

• Composites Research
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• v.30 no.6
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• pp.356-364
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• 2017

Composite lattice structures are tried to be used in various fields because of its benefit in physical properties. With increase of demand of the composite lattice structure, nondestructive testing technology is also required to certificate the quality of the manufactured structures. Recently, research on the development of the composite lattice structure in Republic of Korea was started and accordingly, fast and accurate non-destructive evaluation technology was needed to finalize the manufacturing process. This paper studied non-destructive testing methods for composite lattice structure using laser ultrasonic propagation imaging systems. Pulse-echo ultrasonic propagation imaging system was able to inspect a rib structure wrapped with a skin structure. To reduce the time of inspection, a band divider, which can get signal in different frequency bands at once, was developed. Its performance was proved in an aluminum sandwich panel. In addition, to increase a quality of results, curvature compensating algorithm was developed. On the other hand, guided wave ultrasonic propagation imaging system was applied to inspect delamination in a rib structure. To increase an area of inspection, multi-source ultrasonic wave propagation image was applied, and defects were successfully highlighted with variable time window amplitude mapping algorithm. These imply that ultrasonic propagation imaging systems provides fast and accurate non-destructive testing results for composite lattice structure in a stage of the manufacturing process.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.335-335
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• 2001

Direct-normal, total horizontal and diffuse horizontal irradiance data obtained from a multi-filter rotating shadowband radiometer over seven different wavelength bands (416nm, 151nm, 616nm, 675nm, 870nm and 940nm and the entire spectrum) has been analyzed at Kwangju, South Korea from June 1998 December 2000. The maximum hourly global radiation flux ranged from 0.44 MJ/$m^2$ to 2.68 MJ/$m^2$ at around 11:00-12:00 Hr local time while the maximum hourly diffuse radiation flux ranged from about 0.96 MJ/$m^2$ to 1.37 MJ/$m^2$. The maximum hourly direct irradiance ranged from 1.42 MJ/$m^2$ to 2.92 MJ/$m^2$ from June1998-2000. During the period under consideration, the average monthly global radiation recorded were 13.09 MJ/$m^2$/day, 10.58MJ/$m^2$/day and 9.78MJ/$m^2$/day for years 1998, 1999 and 2000 respectively, while the diffuse irradiance were 6.54 MJ/$m^2$/day, 5.33 MJ/$m^2$/day and 5.14 MJ/$m^2$/day for f998, 1999 and 2000 respectively. The direct irradiance values at the site were 11.63 MJ/$m^2$/day, 8.24MJ/$m^2$/day and 7.75 MJ/$m^2$/day for 1998, f999 and 2000 respectively. It was observed that each of the years has its own unique meteorological parameters that affect the quality and quantity of radiation received for each month. The annual average daily fractions of the diffuse to the global radiation (KD) were 0.51, 0.61 and 0.59 for years 1998, 1999 and 2000 respectively. Analysis indicated that the average daily KD ranged from 0.13 to a maximum value of 0.99 in May for irradiance measured at the broadband channel while the maximum and minimum KD value of 0.91 and 0.23 was recorded at wavelength band 870nm and 940nm in January and September respectively. The lowest average daily clearness index (Kt) value recorded was 0.03 in May (Spring) and the annual average daily clearness indexes are 0.45, 0.34 and 0.35 for years 1998, f999 and 2000 respectively. The frequency of clear days annually at Kwangju is 67.95%, 29.57% and 40.72% for years 1998, 1999 and 2000 respectively.

• Journal of Oriental Neuropsychiatry
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• v.21 no.3
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• pp.45-64
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• 2010

Objectives : The purpose of this study was to examine the effects of auricular acupuncture at the Shinmun on patients with dementia by using power spectrum analysis. Electroencephalogram(EEG) power spectrum show site-specific and state-related differences in various frequency bands. Methods : Study was carried out in 38 subjects.(31 patients with dementia and 7 normal people, 27 females and 11 males ; mean age=75.9 years old). To know the effect of auricular acupuncture at the Shinmun in patients with dementia, we measured electroencephalogram(EEG) of normal people and patients with dementia about 'before', 'after' and 'after 15 minutes' giving auricular acupuncture at the Shinmun, and compared the brain wave($\alpha$, $\beta$, $\delta$, $\theta$) of EEG 30 channels. Results : In the case of patients with dementia, in the power values of $\alpha$(alpha) band at F4, FP2, FCZ, F8, FC4 channels (p<0.05) during the Shinmun-auricular acupuncture treatment increased significantly. In $\beta$(beta) band, the power values at T8 channel(p<0.05) during the Shinmun-auricular acupuncture treatment increased significantly. In $\delta$(delta) band, the power values at F7, FP1, FZ, FP2, FCZ, C4, FC4, CP4, T8, P7, P3, O1, OZ, O2, P4, P8 channels(p<0.05) during the Shinmun-auricular acupuncture treatment decreased significantly. In $\Theta$(theta) band, the power values at O1, OZ, O2channel(p<0.05) during the Shinmun-auricular acupuncture treatment decreased significantly. Conclusions : Through these results, we concluded that auricular acupuncture at the Shinmun on patients with dementia could have effect the functional mechanism of the cerebral cortex.

• Geophysics and Geophysical Exploration
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• v.22 no.4
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• pp.177-185
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• 2019

Ground roll is a surface wave which is usually observed in the land seismic data. It is one of the typical coherent noise. During the reflection data processing, ground roll is removed because it is considered as noise. This removal process often causes the loss of reflection signals if the ground roll overlaps reflection signals. In this study, we look over Karhunen-Loeve Transform (KLT) and analyze its effects to suppress the ground roll appropriately while reducing the reflection loss. Numerical tests in homogeneous elastic media show that the ground roll has been properly rejected. However, the field data application reveals that there is no significant suppression of ground roll when compared to band-pass filtering. This can be considered that it is hard to calculate horizontally aligned gathers in the field data because the ground roll contains a wide range of frequency bands. On the contrary, the result of singular value decomposition (SVD) filtering shows that the ground roll has been significantly reduced. It is thought that the SVD filtering performs better in the ground roll suppression than KLT because it is easy to calculate the horizontally aligned gathers in the SVD filtering.

• Journal of Life Science
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• v.21 no.4
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• pp.502-508
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• 2011

The purpose of this study was to evaluate the methods of identifying zygotic seedlings of crosses between 'Morita unshiu' (Citrus. unshiu Marc.) and 'Ponkan' (C. reticulata Blanco). In order to investigate the frequency and position of zygotic seedlings and to determine the efficiency of zygotic seedling identification, random amplified polymorphic DNA (RAPD) and sequence-related amplified polymorphism (SRAP) were performed using UBC (9, 27, 229, 230, and 254) primers and F4/R27, F7/R14, F12/R10, and F44/R62 primer sets, respectively. A total of 37 putative zygotic seedlings out of 55 individuals were selected by RAPD and SRAP. The F7/R14 primer pair showed a screening ability of 45.5% (25/55), whereas the primer UBC27 revealed the highest efficiency of zygotic seedling identification (50.9%, 28/55). When both UBC27 and F7/R14 were properly used for selection of hybridized seedlings of 'Morita unshiu' (C. unshiu Marc.) and 'Ponkan' (C. reticulata Blanco), screening efficiency was increased to 60% (33/55) for putative zygotic seedlings. Thus, it is possible to select putative hybrid zygotic seedlings in an accurate and effective manner by RAPD and SRAP.