• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.309-310
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• 2005

Generally, the dielectric constant and loss tangent are gotten by resonators. This paper presents analysis of the comparing the dielectric constant and loss tangent from the Ring, T and series gap structures. The T structure can be analyzed easily at wideband characteristic with simple design. the Ring can ignore the radiation loss from the open-ended effect. the Series gap can get more accurate permittivity than a Ring structure. The Used materials were dupont9599 LTCC ceramic and daeju0086 Ag.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.11-14
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• 2008

Acoustic design parameters of a half-wave resonator are studied experimentally for acoustic stability in a model acoustic tube. According to standard acoustic-test procedures, acoustic-pressure signals are measured. Quantitative acoustic properties of sound absorption coefficient are evaluated and thereby, the acoustic damping capacity of the resonator is characterized. The diameter and the number of a half-wave resonator and the diameter of the tube are selected as design parameters for optimal tuning of the resonator. Optimum acoustic damping capacity is observed at smaller open area ratio as the resonator diameter increases.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.35-38
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• 2011

Damping characteristic according to acoustic cavity's geometries was investigated to control the high frequency combustion instability occurring in the Liquid Rocket Combustion Chamber by experimental test and linear analysis. Its diameter was determined as a design parameter and its orifice length and diameter were appointed as fixed parameter in this study. Result shows that the damping capacity has been almost constant through all the experiments despite using the same orifice and helmholtz resonators which have different volume.

• Journal of the Optical Society of Korea
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• v.15 no.1
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• pp.82-89
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• 2011

In this paper, we numerically study both band-pass and band-stop plasmonic filters based on Metal-Insulator-Metal (MIM) waveguides and circular ring resonators. The band-pass filter consists of two MIM waveguides coupled to each other by a circular ring resonator. The band-stop filter is made up of an MIM waveguide coupled laterally to a circular ring resonator. The propagating modes of Surface Plasmon Polaritons (SPPs) are studied in these structures. By substituting a portion of the ring core with air, while the outer dimensions of the ring resonator are kept constant, we illustrate the possibility of red-shift in resonant wavelengths in order to tune the resonance modes of the proposed filters. This feature is useful for integrated circuits in which we have limitations on the outer dimensions of the filter structure and it is not possible to enlarge the dimension of the ring resonator to reach to longer resonant wavelengths. The results are obtained by a 2D finite-difference time-domain (FDTD) method. The introduced structures have potential applications in plasmonic integrated circuits and can be simply fabricated.

• Current Optics and Photonics
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• v.4 no.4
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• pp.373-379
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• 2020

In this study, we investigate terahertz (THz) generation by a photoconductive antenna with electrodes in the shape of split-ring resonators. According to our theoretical investigation based on a lumped-circuit model, the inductance of this electrode structure leads to resonant behavior of the photo-induced current. Hence, near the resonance frequency the spectral components generated by a resonant photoconductive antenna can be greater than those produced by a non-resonant one. For experimental verification, a resonant photoconductive antenna, which possesses a resonance mode at 0.6 THz, and a non-resonant photoconductive antenna with stripe-shaped electrodes were fabricated on a semi-insulating GaAs substrate. The THz generation by both of the photoconductive antennas demonstrated a good agreement with the theoretically expected results. The observed relationship between the resonant electrodes of the photoconductive antenna and the generated THz spectrum can be further employed to design a narrow-band THz source with an on-demand frequency.

• Current Optics and Photonics
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• v.2 no.6
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• pp.576-581
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• 2018

A new approach for identification of a microwave frequency using an integrated optical waveguide chip, combined with a phase modulator (PM) and two microring resonators (MRRs), is proposed, theoretically deduced, and verified. By wavelength tuning to set the PM under the condition of a double side band (DSB), the measurement range can be started from the dc component, and the measurement range and response slope can be adjusted by designing the radius and transmission coefficient of the MRR. Simulations reveal that the amplitude comparison function (ACF) has a monotonic relationship from dc to 32.5 GHz, with a response slope of 5.15 dB under conditions of DSB modulation, when the radius values, transmission coefficients, and the loss factors are designed respectively as $R_1=400{\mu}m$, $R_2=600{\mu}m$, $t_1=t_2=0.63$, and ${\gamma}_1={\gamma}_2=0.66$. Theoretical calculations and simulation results both indicate that this new approach has the potential to be used for measuring microwave frequencies, with the advantages of compact structure and superior reconfigurability.

• Korean Journal of Materials Research
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• v.31 no.1
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• pp.43-53
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• 2021

Dynamic behavior of piezoelectric ZnO nanowires is investigated using finite element analyses (FEA) on FE models constructed based on previous experimental observations in which nanowires having aspect ratios of 1:2. 1:31, and 1:57 are obtained during a hydrothermal process. Modal analyses predict that nanowires will vibrate in lateral bending, uniaxial elongation/contraction, and twisting (torsion), respectively, for the three ratios. The natural frequency for each vibration mode varies depending on the aspect ratio, while the frequencies are in a range of 7.233 MHz to 3.393 GHz. Subsequent transient response analysis predicts that the nanowires will behave quasi-statically within the load frequency range below 10 MHz, implying that the ZnO nanowires have application potentials as structural members of electromechanical systems including nano piezoelectric generators and piezoelectric dynamic strain sensors. When an electric pulse signal is simulated, it is predicted that the nanowires will deform in accordance with the electric signal. Once the electric signal is removed, the nanowires exhibit a specific resonance-like vibration, with the frequency synchronized to the signal frequency. These predictions indicate that the nanowires have additional application potential as piezoelectric actuators and resonators.

• Structural Engineering and Mechanics
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• v.82 no.4
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• pp.417-434
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• 2022

In this work, a review of mechanical metamaterials and seismic protection systems that use them is carried out, focusing on passive protection systems. During the last years, a wide variety of classical systems of seismic protection have demonstrated to be an effective and practical way of reducing the seismic vulnerability of buildings, maintaining their health and structural integrity. However, with the emergence of metamaterials, which allow obtaining uncommon mechanical properties, new procedures and devices with high performance have been developed, reducing the seismic risk through novel approaches such as: seismic shields and the redirection of seismic waves; the use of stop band gaps and the construction of buried mass resonators; the design of pentamodal base isolators. These ideas are impacting traditional areas of structural engineering such as the design and building of highly efficient base isolation systems. In this work, recent advances in new seismic protection technologies and researches that integrate mechanical metamaterials are presented. A complete bibliometric analysis was carried out to identify and classify relevant authors and works related with passive seismic protection system based on mechanical metamaterial (pSPSmMMs). Finally, possible future scenarios for study and development of seismic isolators based on mechanical metamaterials are shown, identifying the relevant topics that have not yet been explored, as well as those with the greatest potential for future application.

• Journal of electromagnetic engineering and science
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• v.19 no.2
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• pp.115-121
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• 2019

This paper presents the effects of the position of the split of a split-ring resonator (SRR) on the performance of a composite broadband printed dipole antenna. The antenna is made of two printed dipole arms enclosed by two rectangular and identically printed SRRs. One dipole arm and the SRR are printed on the top side of the substrate, while the other dipole arm and SRR are printed on the bottom side of the same substrate. By changing the position of the split on the SRR, different antenna characteristic values are obtained, namely, for impedance bandwidth and radiation patterns. The split position is thus a critical parameter in antenna design, because it influences the antenna's major performance immensely. Different split positions and their consequences for antenna performance are demonstrated and discussed. The antenna generates linearly polarized radiations, and it is computationally characterized for broadband characteristics. The optimized compact antenna has overall dimensions of 9.6 mm × 74.4 mm × 0.508 mm (0.06λ × 0.469λ × 0.0032λ at 1.895 GHz) with a measured fractional bandwidth of 60.31% (1.32 to 2.46 GHz for |S₁₁| <-10 dB) and a radiation efficiency of >88%.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1552-1554
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• 2004

The modeled resonant frequency and electrical properties of Pb(Zr, Ti)$O_3$ (PZT) film with various thicknesses have been investigated in film bulk acoustic wave resonators (FBARs). PZT films and Pt electrodes were fabricated by rf-magnetron sputtering. Fabrication process of electrodes and PZT were patterned by simple lift-off process and then back side of silicon was etched by 45wt% KOH. The crystal structure of PZT films with 0.5, 1 and 2 ${\mu}m$ thickness was investigated by x-ray deflection (XRD) and scanning electron microscopy (SEM). The dielectric constant and performance characteristics of PZT FBAR strongly depended on the film thickness. The resonant frequency of PZT films decreased with increasing film thickness. These sputtered PZT FBAR with simple lift-off process enable us to fabricate high Q values with resonant frequencies. (0.71 - 1.48 GHz).