• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.4
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• pp.69-76
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• 2005

In this paper, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TM_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of If modes. The size and location of intercavity slot is determined by the coupling equation from E-and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1273-1278
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• 2005

In this thesis, a 2 stage 6-pole bandpass filter(BPF) is designed and implemented by using triple-mode cavity for satellite payload system. The BPF has a 100MHz bandwidth at the center frequency of 14.5GHz(Ku-band) and the response of the filter is the Chebyshev function. The cavity filter uses two orthogonal $TE_{113}$ modes and one $TM_{012}$ mode. The coupling between the adjacent cavityes(intercavity coupling) results in a Chebyshev response and is accomplished by only H-filed component of TE modes. The size and location of intercavity slot is determined by the coupling equation from E- and H-field of TE and TM resonant modes in circular cavity. The 2-stage 6-pole triple-mode cavity BPF has the insertion loss of 2.4dB and the reflection loss of 15dB in the passband. The triple-mode BPF proposed in this thesis can be used as channel filters for satellite payload system and can minimize filter assembly in general wireless communication system.

• Smart Structures and Systems
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• v.20 no.3
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• pp.273-283
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• 2017

This paper presents and compares three feedback control strategies for active control of noise inside a 3-D vibro-acoustic cavity. These are a) control strategy based on direct output feedback (DOFB) b) control strategy based on linear quadratic regulator (LQR) to reduce structural vibrations and c) LQR control strategy with a weighting scheme based on structural-acoustic coupling coefficients. The first two strategies are indirect control strategies in which noise reduction is achieved through active vibration control (AVC), termed as AVC-DOFB and AVC-LQR respectively. The third direct strategy is based on active structural-acoustic control (ASAC). This strategy is an LQR based optimal control strategy in which the coupling between the various structural and the acoustic modes is used to design the controller. The strategy is termed as ASAC-LQR. A numerical model of a 3-D rectangular box cavity with a flexible plate (glued with piezoelectric patches) and with other five surfaces treated rigid is developed using finite element (FE) method. A single pair of collocated piezoelectric patches is used for sensing the vibrations and applying control forces on the structure. A comparison of frequency response function (FRF) of structural nodal acceleration, acoustic nodal pressure, and piezoelectric actuation voltage is carried out. It is found that the AVC-DOFB control strategy gives equal importance to all the modes. The AVC-LQR control strategy tries to consume the control effort to damp all the structural modes. It is seen that the ASAC-LQR control strategy utilizes the control effort more intelligently by adding higher damping to those structural modes that matter more for reducing the interior noise.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.3
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• pp.112-115
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• 2021

Herein, a correlation between B-site cation order and spin-phonon coupling in La₂NiMnO₆ double perovskite has been investigated. Raman spectra of La₂NiMnO₆ double perovskite annealed at 950 and 1400℃ have been measured in the 140-598 K range. A substantial softening of the phonon modes has been observed below the Curie temperature, which emphasized the presence of the spin-phonon coupling in the system. The spin-phonon coupling was found to be stronger in relatively more ordered La₂NiMnO₆ double perovskite. Thus, the magnitude of spin-phonon coupling was influenced by the Ni/Mn cation order.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.81-84
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• 2005

In order to effectively resist seismic loads, coupling beams must be sufficiently stiff, strong and posses a stable load-deflection hysteretic response. This paper reports experimental data on the seismic performance of precast HPFRCC coupling beams with variable details. Precast HPFRCC coupling beam was tested to evaluate their failure modes. shear behavior, micro crack pattern and energy dissipation. Based on the experimental results, precast coupling beam with diagonal and rhombic details offer greater performance and ductility than coupling beam with normal detail.

• Journal of Hydrospace Technology
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• v.2 no.1
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• pp.18-26
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• 1996

It is normal practice to consider bending wave modes only, when one applies SEA (Statistical Energy Analysis) to ship structures because of complexities in SEA modeling and evaluation of coupling loss factors for inplane modes. According to the result of Tratch[1], the inplane wave modes becomes important for the analysis of a foundation structure as the distance from the source and receiver increases. In this paper, the effect of inplane wave modes on structure-borne noise propagation in ship structures is presented. It is shown that the inplane wave could increase the noise level more than 10 dB compared with the results without inplane wave modes at high frequency bands for compartments far from the source location.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.293-298
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• 2004

We investigate the effect of the wing width and thickness of a Double-Sided Deep-Ridge(DSDR) vertical directional coupler on the coupling length dependent on the polarization, We have found that the DSDR vertical directional coupler without a wing does not have polarization independent coupling lengths. The variation of the coupling length of TE and TM modes and the difference between the coupling lengths of the two modes are negligible as the wing width increases beyond the specific wing width for the same wing thickness. Thus, we can see that a DSDR vertical directional coupler has a wing width larger than the minimum wing width to obtain the polarization independent coupling length. The minimum wing width increases as the wing thickness increases for the same core thickness and as the core thickness decreases for the same wing width. Also, we have found that the minimum wing thickness is determined by the core thickness and the minimum wing thickness decreases as the core thickness increases.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.5
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• pp.603-613
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• 1998

Resonant characteristic of Whispering modes(W. G. mode) on a dielectric disk resonator is influenced by an external circuit that is placed near the disk to excite this type of modes. In order to evaluate this phenomenon, we divide the disk resonator as two parts; a coupling part in which the mode coupling occurs and on uncoupled region. In the coupled part, we regard the part of the disk as a curved waveguide which is loaded with matched circuit, and derive a coupled mode equation for nonparallel dielectric waveguides. From the coupled mode equation, we calculate coupling coefficients and a coupled electromagnetic field. By using the complex coupling coefficients, we can calculate power transfer. We also calculate a resonant frequency in consideration of the mode coupling phenomenon. The calculated resonance frequence is confirmed by experiment for the resonance characteristics. As the results, it is found that the discrepancy between the theoretical and the experimental resonance frequencies is about 1.28% and the discrepancy between theory and experiment of FSR is about 0.6%.

• Earthquakes and Structures
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• v.14 no.3
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• pp.261-271
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• 2018

Fiber reinforced cementitious composites (FRCC) materials that exhibit strain-hardening and multiple cracking properties under tension were recently developed as innovative building materials for construction. This study aims at exploring the use of FRCC on the seismic performance of coupling beams with conventional reinforcement. Experimental tests were conducted on seven FRCC precast coupling beams with small span-to-depth ratios and one ordinary concrete coupling beam for comparison. The crack and failure modes of the specimens under the low cycle reversed loading were observed, and the hysteretic characteristics, deformation capacity, energy dissipation capacity and stiffness degradation were also investigated. The results show that the FRCC coupling beams have good ductility and energy dissipation capacities compared with the ordinary concrete coupling beam. As the confinement stirrups and span-to-depth ratio increase, the deformation capacity and energy dissipation capacity of coupling beams can be improved significantly. Finally, based on the experimental analysis and shear mechanism, a formula for the shear capacity of the coupling beams with small span-to-depth ratios was also presented, and the calculated results agreed well with the experimental results.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.53-56
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• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.