• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.548-554
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• 1997

The single crystal of $Mg_{0.16}Zn_{0.84}$Te:Co(Co:0.01 mole%) was grown by vertical Bridgman method. The crystal structure of $Mg_{0.16}Zn$_{0.84}$Te:Co and optical absorption properties of this compound were studied. The grown single crystal has a cubic structure and a lattice constant a=6.1422 $\AA$ were determined by X-ray diffraction. As a result of the optical absorption spectra of $Mg_{0.16}Zn_{0.84}$Te:Co, the intracenter transitions due to $Co^{2+}$ ions were detected for $A-band:^4A_2(^4F){\to}^4T_2(^4F),\; B-band:^4A_2(^4F){\to}^4T_1(^4F), C- band:^4A_2(^4F){\to}^4T_1(^4P)$.The charge transfer transition near the absorption edge was observed in the wavelength range of 550 to 770 nm. According to the crystal field theory, the crystal field parameter(Dq) and the Racah parameter(B) were determined.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.347-347
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• 2012

Nickel Oxide (NiO) is a transition metal oxide of the rock salt structure that has a wide band gap of 3.5 eV. It has a variety of specialized applications due to its excellent chemical stability, optical, electrical and magnetic properties. In this study, we concentrated on the application of NiO thin film for transparent conducting oxide. The energy band structure, electronic and optical properties of Nickel Oxide (NiO) thin films grown on Si by using electron beam evaporation were investigated by X-Ray Photoelectron Spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and UV-Spectrometer. The band gap of NiO thin films determined by REELS spectra was 3.53 eV for the primary energies of 1.5 keV. The valence-band offset (VBO) of NiO thin films investigated by XPS was 3.88 eV and the conduction-band offset (CBO) was 1.59 eV. The UV-spectra analysis showed that the optical transmittance of the NiO thin film was 84% in the visible light region within an error of ${\pm}1%$ and the optical band gap for indirect band gap was 3.53 eV which is well agreement with estimated by REELS. The dielectric function was determined using the REELS spectra in conjunction with the Quantitative Analysis of Electron Energy Loss Spectra (QUEELS)-${\varepsilon}({\kappa},{\omega})$-REELS software. The Energy Loss Function (ELF) appeared at 4.8, 8.2, 22.5, 38.6, and 67.0 eV. The results are in good agreement with the previous study [1]. The transmission coefficient of NiO thin films calculated by QUEELS-REELS was 85% in the visible region, we confirmed that the optical transmittance values obtained with UV-Spectrometer is the same as that of estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS within uncertainty. The inelastic mean free path (IMFP) estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS is consistent with the IMFP values determined by the Tanuma-Powell Penn (TPP2M) formula [2]. Our results showed that the IMFP of NiO thin films was increased with increasing primary energies. The quantitative analysis of REELS provides us with a straightforward way to determine the electronic and optical properties of transparent thin film materials.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.24-29
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• 2001

In this paper, the wideband microstrip antennas for the PCS & IMT-200O dual band are studied. Experimental and simulation results on the dual band antenna are presented. Simulation results are in good agreement with measurements. The experimental and simulation results confirm the wideband characteristics of the antenna. The studied antenna satisfies the wideband characteristics that are required characteristics for above 420 MHz impedance bandwidth for the PCS & IMT-2OO0 dual band antenna. In this paper, through the designing of a dual band antenna, we have presented the availability for PCS & IMT-20O0 base station antenna.

• Journal of the Korean Magnetics Society
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• v.18 no.6
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• pp.201-205
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• 2008

In order to investigate the origin of the band gap in the half-metallic Heusler alloy, $Co_2MnSi$, through the electronic structure calculation, we have calculated the electronic structures for the compounds consisted of parts of Heusler structures, i.e. zinc-blende CoMn, half-Heusler CoMnSi, and artificial $Co_2Mn$, using the full-potential first-principles band calculation method. By investigating the band hybridization and energy gap for the calculated density of states for these compounds, we found that the the origin of the band gap is not consistent with the explanation discussed by Galanakis et al. We have also discussed the magnetism for these compounds by the calculated number of majority- and minority-spin electrons.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.1
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• pp.252-264
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• 2023

This paper proposes a design of a dual-band band-pass filter that integrates a λg/2 open SIR structure, a transmission line, and a fork-type structure with symmetric and asymmetric open stubs. To obtain the dual-band effect, the proposed filter uses the SIR structure and adjusts the impedance ratio of the SIR structure. Therefore, the position of the harmonics of the filter is shifted through the adjustment of the impedance ratio, and this can obtain a double-band effect. In order to obtain the dual-band characteristics, the dual-band effect is obtained by inserting a open stub between the SIR structures with the SIR structure divided in half. In addition, the second frequency response is obtained by adjusting the length of the open symmetrical stub in the fork-shaped structure. The asymmetrical open stub in the fork form achieves optimum bandwidth by adjusting the length. Therefore, the first center frequency of the proposed band-pass filter is 5.896 GHz and the bandwidth is 13.6 %. At this time, the measurement results are 0.13 dB and 33.6 dB. The second center frequency is 5.906 GHz and the bandwidth is 13.6 %. At this time, the measurement results are 0.15 dB and 19.8 dB. The reason is that when the impedance ratio (Δ) is higher than 1, the position of the harmonic is shifted to a lower frequency band. However, if the impedance ratio (Δ) is lowered by one step, the position of harmonics will move to a higher frequency band. The function of the filter designed using these characteristics can be obtained from the measurement result. The proposed band-pass filter has no coupling loss and no via energy concentration loss because there is no coupling structure of input/output and no via hole. Therefore, system integration is possible due to its excellent performance, and it is expected that dedicated short-range communication (DSRC) system applications used in traffic communication systems will be possible.

• Journal of electromagnetic engineering and science
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• v.16 no.2
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• pp.100-105
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• 2016

We have designed a three-channel output multiplexer (OMUX) using a band-pass filter and an ultra-wideband (UWB) antenna. The proposed band-pass filter is composed of an inner rectangular loop, an outer open stub, and a defected ground structure. The outer open stub can be used to control the pass band, and the inner rectangular loop can improve the insertion loss characteristics of the band-pass filter. The proposed band-pass filter, UWB antenna, and OMUX are fabricated and measured. The designed OMUX can cover the band group 1 (3,168-4,752 MHz) of WiX system. The measured radiation patterns are close to those of a conventional dipole antenna and the measured antenna gain varies from 1.8 dBi to 3 dBi over the operating frequency range.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1049-1056
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• 2017

In this paper, a microstrip-fed dual-band monopole antenna with two arc-shaped lines for WLAN(: Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a microstrip-fed structure, and composed of two arc-shaped lines and then designed in order to get dual band characteristics. We used the simulator, Ansoft's High Frequency Structure Simulator(: HFSS) and carried out simulation about parameters L2, L5, and with/without slit to get the optimized parameters. The proposed antenna is made of $13.0{\times}34.0{\times}1.0 mm^3$ and is fabricated on the permittivity 4.4 FR-4 substrate($12.0{\times}34.0{\times}1.0mm^3$). The experiment results are shown that the proposed antenna obtained the -10 dB impedance bandwidth 360 MHz (2.29~2.65 GHz) and 1,245 MHz (4.705~5.95 GHz) covering the WLAN bands. Also, the measured gain and radiation patterns characteristics of the proposed antenna are presented at required dual-band(2.4 GHz band/5.0 GHz band), respectively.

• Journal of IKEEE
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• v.27 no.4
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• pp.405-410
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• 2023

This paper presents a novel method of implementing a dual-band antenna using a square patch with an inset feed structure. The proposed method is to simply design a dual-band antenna using an asymmetric inset structure with different lengths of slots dug into the patch for inset feeding. To verify the proposed method, a dual-band inset patch antenna supporting 1.57 GHz GPS and 2.4 GHz WiFi bands was designed and manufactured on a 1 mm thick FR4 substrate. From measurement, it was confirmed that the frequency bands of the antenna that satisfy a return loss of -10dB or less are 1.55~1.57GHz and 2.41~2.45GHz, which has dual-band characteristics. Using the proposed method, it is possible to simply implement a dual-band antenna using inset feeding, and it is expected to be utilized in a variety of application fields.

• Journal of the Korean Ceramic Society
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• v.55 no.3
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• pp.267-274
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• 2018

$TiO_2/CuS$ nanocomposites were fabricated by precipitation of nanosized CuS via sonochemical method on electrospun $TiO_2$ nanofibers, and their structure, chemical bonding states, optical properties, and photocatalytic activity were investigated. In the $TiO_2/CuS$ nanocomposite, the position of the conduction band for CuS was at a more negative than that of TiO; meanwhile, the position of the valence band for CuS was more positive than those for TiO, indicating a heterojunction structure belonging to type-II band alignment. Photocatalytic activity, measured by decomposition of methylene blue under visible-light irradiation (${\lambda}$ > 400 nm) for the $TiO_2/CuS$ nanocomposite, showed a value of 85.94% at 653 nm, which represented an improvement of 52% compared to that for single $TiO_2$ nanofiber (44.97% at 653 nm). Consequently, the photocatalyst with $TiO_2/CuS$ nanocomposite had excellent photocatalytic activity for methylene blue under visible-light irradiation, which could be explained by the formation of a heterojunction structure and improvement of the surface reaction by increase in surface area.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.37-44
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• 2020

In this paper, we proposed a compact printed monopole antenna with an inverted L-shaped slot for dual-band operations. Two operating frequency bands are achieved with the use of an inverted L-shaped slot etched on the radiating strip for bandwidth enhancement and a defected ground structure for return loss improvement in the higher frequency band. The measured results showthat the proposed antenna has impedance bandwidths (S₁₁< -10 dB) of 270 MHz (1.81-2.08 GHz) and 340 MHz (2.36-2.70 GHz), covering the required bandwidths for PCS (1850.5-1989.5 MHz), CDMA 2000 (1850-1990 MHz), TD-SCDMA (1880-2025 MHz) and 2.4 GHz WLAN (2400-2484 MHz). The measured return loss of the proposed antenna has a good value of approximately 27.2 dB at 2.4 GHz WLAN. The antenna's peak gains also have a high value of 1.92 dBi at 2 GHz and 2.12 dBi at 2.45 GHz. The proposed antenna shows omnidirectional radiation patterns over the entire frequency range of interest.