• 대한기계학회논문집A
• /
• 제24권8호
• /
• pp.1923-1930
• /
• 2000

A bar with periodically nonuniform material properties is selected as a one-dimensional model of a flat-panel speaker. This paper describes a theoretical approach to the bending waves propagating i n the nonuniform bar. The phase speed of the wave is obtained using perturbation techniques for small amplitude, sinusoidal modulation of the flexural rigidity and mass density. It is shown that the wave speed is decreased due to the nonuniformity of the material properties by the amount proportional to the square of the modulation amplitude. The resonance occurring when the wavelength is half of the period of the material properties is analyzed by the method of multiple scales. It is also shown that the wave speed at the resonance mode is decreased by the amount proportional to the modulation amplitude but the wave of this mode does not propagate far enough due to attenuation.

• 한국전자파학회:학술대회논문집
• /
• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
• /
• pp.611-621
• /
• 2003

A spurious-suppressed transversal filter using the multiple-coupled line is proposed. The frequency characteristics of the multiple-coupled line are analyzed in detail. In order to compare the performances, the novel spurious-suppressed transversal filter using triple-coupled half-wavelength directional couplers is designed at 5 GHz. The spurious-suppression characteristics of the proposed transversal filter are verified by the full wave analysis and the measurement. The spurious response of the fabricated filter is effectively suppressed up to 13 GHz and the large attenuation is attained in the stopband.

• Applied Science and Convergence Technology
• /
• 제25권2호
• /
• pp.42-45
• /
• 2016

A two-dimensional metal hole array (2DMHA) structure is fabricated by conventional photo-lithography and electron beam evaporation. The transmittance of the 2DMHA is measured at long wave infrared (LWIR) wavelengths (${\lambda}{\sim}10$ to $24{\mu}m$). The 2DMHA sample shows transmittance of 70 and 67% at $15.4{\mu}m$ due to plasmonic resonance with perforated silver and gold thin films, respectively, under surface normal illumination at LWIR wavelengths. The measured infrared spectrum is separated into two peaks when the size of the hole becomes larger than a half-pitch of the hole array. Six degenerated plasmon modes (1,0) at the metal/Si surface split to three modes at an incident beam angle of $45^{\circ}$ with respect to the surface normal direction, and wavelength shifts of the transmitted spectrum are observed in a red shift and blue shift at the same time.

• Journal of the Optical Society of Korea
• /
• 제3권1호
• /
• pp.15-19
• /
• 1999

The formation of spontaneous transverse optical patterns was investigated in a single feedback mirror system using nematic liquid crystals as nonlinear optical media. By varying the size of an input beam and the feedback distance, we obtained various interesting transverse optical patterns as well as the hexagonal pattern which are predicted theoretically assuming plane wave input. We can explain theoretically these characteristics of various pattern by introducing a ratio of the beam half width and spatial wavelength of the patterns. We have observed that as this ratio increased, the number of spot constituting the patterns also increased. Finally the patte군 evolved into the sucessive hexagon in the transverse plane.

• 약학회지
• /
• 제25권3호
• /
• pp.101-108
• /
• 1981

Quantitative determination of capsaicin in biological fluid was investigated. The pharmacokinetic study of capsaicin in rabbits was performed by high-pressure liquid chromatography, equipped with a microparticulate reversed-phase column and a fixed wavelength detector. Elution was carried out using methanolwater(70:30). It allows the quantitative determination at 8-400 ng level. When single dose of capsaicin(4mg/kg) was given to rabbits intravenously, the elimination phase was extremely short with average half-life to 17.35 minute. Urine excretion of capsaicin itself during first 2 hours after intravenous administration (4mg/kg) was 0.004-0.04% of the administered amount. The maximum plasma concentration of capsaicin after oral administration (300mg/kg) was $4{\times}10^{-7}$g/ml at 40 minutes. The $LD_{50}$ of capsaicin in mouse was 0.40mg/kg (i.v.) and 47.2 mg/kg (p.o.) which was determined by Litchfield and Wilcoxon's method, suggesting that the gastrointestinal absorption of capsaicin is poor.

• Journal of Electrical Engineering and Technology
• /
• 제8권2호
• /
• pp.371-375
• /
• 2013

The design of a new compact UWB bandpass filter is proposed, which has cascaded center-tapped microstrip composite right/left-handed transmission-line zeroth-order resonators (CRLH-TL ZORs). In an attempt to reduce the size, instead of the conventional half-wavelength resonators or periodic and multiple CRLH-TL cells, only one cell ZOR geometry is adopted as each resonator in the filter. Additionally, two center-tapped ZORs are coupled to increase the slope of the skirt. Besides, stepped impedance matching parts are placed in the paths to the input and output ports to enhance passband and stopband performances. The proposed filter is shown to have the overall size of $0.69{\lambda}_g{\times}0.70{\lambda}_g$, the insertion loss much less than 1 dB, and an acceptable return loss performance in the predicted and measured results.

• KIEE International Transactions on Electrophysics and Applications
• /
• 제3C권6호
• /
• pp.241-245
• /
• 2003

ZnO thin films on (l00) p-type Si and sapphire substrates have been deposited by a pulsed laser deposition technique using an Nd:YAG laser with a wavelength of 266 nm. The influence of the deposition parameters such as oxygen pressure, substrate temperature and laser energy density on the properties of the grown films was studied. The experiments were performed for substrate temperatures in the range of 200∼50$0^{\circ}C$ and oxygen pressure in the range of 100∼700 sccm. All of the films grown in this experiment show strong c-axis orientation with (002) textured ZnO peak. With increasing substrate temperature, the FWHM (full width at half maximum) and surface roughness were decreased. In the case of using sapphire substrate, the intensity of PL spectra increased with increasing ambient oxygen flow rate. We investigated the structural and morphological properties of ZnO thin films using X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM).

• ETRI Journal
• /
• 제36권6호
• /
• pp.1062-1065
• /
• 2014

A novel substrate-integrated waveguide (SIW) cavity-backed slot antenna is proposed in this study to achieve enhanced-gain performance. The peak gain is remarkably improved with the use of an SIW cavity and metallic superstrate. The superstrate comprises a single rectangular slot window and two half-wavelength patches. The gain can be enhanced by combining the in-phase radiating fields. Further, the 10 dB bandwidth of the proposed antenna ranges from 2.32 GHz to 2.49 GHz, which covers the wireless local area network band. The measured peak gain is 9.44 dBi at 2.42 GHz.

• ETRI Journal
• /
• 제33권2호
• /
• pp.163-168
• /
• 2011

A Fabry-Perot cavity (FPC) antenna producing both high-gain and circularly-polarized (CP) behavior is proposed. To increase antenna gain and obtain CP characteristics, a superstrate composed of square patches with a pair of truncated corners is placed above the linearly polarized patch antenna with an approximately half-wavelength distance from the ground plane at the operating frequency. The proposed antenna has the advantages of high gain, a simple design, and an excellent boresight axial ratio over the operating frequency bandwidth. Moreover, used in an FPC antenna, the proposed superstrate converts a linear polarization produced by a patch antenna into a circular polarization. In addition, the cavity antenna produces left-hand circular-polarization and right-hand circular-polarization when a patch antenna inside the cavity generates x-direction and y-direction polarization, respectively. The measured and simulated results verify the performance of the antenna.

• Journal of information and communication convergence engineering
• /
• 제17권4호
• /
• pp.227-233
• /
• 2019

In long-haul optical communication system consisting of standard single-mode fiber spans and fiber amplifiers, such as the erbium-doped fiber amplifier, performance is deteriorated by signal distortion due to chromatic dispersion and nonlinearity of the fiber. A combination of dispersion management and optical phase conjugation is an effective technique to compensate for the distortion. In an optical link configured by this combination, a dispersion map mainly affects the compensation of the distorted optical signals. This paper proposes new dispersion maps configured by the decaying or expanding distribution of residual dispersion per span (RDPS) in a dispersion-managed link combined with a midway optical phase conjugator. The effect of the proposed dispersion maps on the compensation for distorted 24 channel × 40 Gbps wavelength-division multiplexed signals was assessed through numerical simulation. It was confirmed that all the proposed dispersion maps are most appropriate for the compensation and, furthermore, for the flexibility of link configuration than conventional links.