• Journal of Practical Engineering Education
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• v.13 no.3
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• pp.497-505
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• 2021

Test equipment for strain and vibration measurement was designed for educational purposes. Widely available and affordable materials were put into making this device. Three strain gauges placed on an iron ruler made cantilevered beam were used to measure values according to external load. An electromagnet triggered excitation and a function generator created vibration of the beam. We present three different tests conducted with this equipment regarding production of scales, measurement of resonant frequency, and calculation of the difference between excitation frequency and measured frequency. Overall, this paper presents a piece of simple yet inexpensive test equipment and its corresponding portfolio with expectations of being applied to the educational field for efficient measurement of load and vibration.

• 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%.

• Korean Journal of Materials Research
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• v.19 no.12
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• pp.637-643
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• 2009

In this study, we analyzed the effect of silicon oxynitride matrix on the optical properties of Au nanoparticles dispersed on composite film and explored the effectiveness of the silicon in fine tuning the refractive index of the composite film for applications in optical waveguide devices. The atomic fraction of nitrogen in $SiO_xN_y$ films was controlled by varying the relative flow ratio of nitrogen gas in reactive sputtering and was evaluated optically using an effective medium theory with Bruggeman geometry consisting of a random mixture between $SiO_2$ and $Si_3N_4$. The Au nanoparticles were embedded in the $SiO_xN_y$ matrix by employing the alternating deposition technique and clearly showed an absorption peak due to the excitation of surface plasmon. With increasing nitrogen atomic fraction in the matrix, the surface plasmon resonance wavelength shifted to a longer wavelength (a red-shift) with an enhanced resonance absorption. These characteristics were interpreted using the Maxwell-Garnett effective medium theory. The formation of a guided mode in a slab waveguide consisting of 3 $\mu$m thick Au:$SiO_xN_y$ nanocomposite film was confirmed at the telecommunication wavelength of 1550 nm by prism coupler method and compared with the case of using $SiO_2$ matrix. The use of $SiO_xN_y$ matrix provides an effective way of controlling the mode confinement while maintaining or even enhancing the surface plasmon resonance properties.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.4
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• pp.104-116
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• 2020

Fipronil, the phenylpyrazole insecticide, is effective and used in various fields. Especially, fipronil was reliable because it was known to be specific on invertebrate animals than vertebrate animals including mammals. However, fipronil had potential risks that affect vertebrate animals as it blocks the gamma-aminobutyric acid (GABA) receptors that also exists in vertebrates as well as invertebrates. Therefore, it was necessary that harmful effects of fipronil on vertebrates are clarified. For this purpose, the zebrafish (Danio rerio) were used on behalf of vertebrate animals in present study. The zebrafish were exposed to 5 ㎍/L, 25 ㎍/L, and 50 ㎍/L of fipronil during 12, 24 and 72 hours. To closely observe toxic process, 12 hours and 24 hours of additional time point were set in the exposure test. Nuclear magnetic resonance (NMR)-based metabolomics is an approach to detect metabolic changes in organism resulted from external stimuli. In this study, NMR-based metabolomics showed the metabolic changes in zebrafish caused by fipronil exposure. Metabolic analysis revealed that fipronil interfered with energy metabolism and decreased the antioxidant ability in zebrafish. Antioxidant ability decline was remarkable at high exposure concentration. In addition, metabolic analysis results over time suggested that reactions for alleviating the excessive nerve excitation occurred in zebrafish after fipronil exposure. Through this study, it was elucidated that the adverse effects of fipronil on vertebrate animals are evident. The risk of fipronil on vertebrates can be no longer ignored. Moreover, this study has a meaning of practically necessary research for organism by examining the effects of fipronil at low concentrations existed in real environment.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.4
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• pp.99-107
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• 2018

In this study, the injector transfer function (ITF) of a gas-gas coaxial jet-swirl injector is measured by perturbing jet or swirl flow using a speaker as jet flow increases. As a result of measuring the ITF varying feed system length, a peak occurs at a resonance frequency of space where the perturbed flow passes. With jet excitation, the ITF magnitude decreases, but increases thereafter as increasing the jet flow. Therefore the larger the velocity difference between jet and swirl flow, the larger the ITF. With swirl excitation, ITF decreases as increasing the jet flow because of the energy decrease with respect to the constant downstream flow.

• International Journal of Aeronautical and Space Sciences
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• v.15 no.4
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• pp.396-411
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• 2014

Synchronized switch damping (SSD) techniques have recently been developed for structural vibration control using piezoelectric materials. In these techniques, piezoelectric materials are bonded on the vibrating structure and shunted by a network of electrical elements. These piezoelectric materials are switched according to the amplitude of the excitation force to damp vibration. This paper presents a new SSD technique called 'synchronized switch damping on negative capacitance and adaptive voltage sources' (SSDNCAV). The technique combines the phenomenon of capacitance transient charging and electrical resonance to effectively dampen the structural vibration. Also, the problem of stability observed in the previous SSD techniques is effectively addressed by adapting the voltage on the piezoelectric patch according to the vibration amplitude of the structure. Analytical expressions of vibration attenuation at the resonance frequency are derived, and the effectiveness of this new technique is demonstrated, for the control of a resonant cantilever beam with bonded piezoelectric patches, by comparing with SSDI, SSDVenh, and SSDNC techniques. Theoretical predictions and experimental results show the remarkable vibration damping capability of SSDNCAV technique, which was better than the previous SSD techniques. The broadband vibration control capabilities of SSDNCAV technique are also demonstrated, which exceed those of previous SSD techniques.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.178.2-178.2
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• 2010

The wind turbine gearbox is important rotating part to transmit torque from turbine blade to generator. Generally, gear shaft which rotates causes vibration by influence of stiffness and mass with gear shaft. Root cause of this vibration source is well known to gear transmission error that is decided from gear tooth property. Transmission error excites a gear, and makes excitation force that is vibrated shaft. This vibration of shaft is transmitted to gearbox housing through gearbox bearing. If the resonance about which the natural frequency of the gearbox accords with shaft exciting frequency occurs, a wind turbine can lead to failure. The gearbox for wind turbine should be considered influence of vibration as well as the fatigue life and its performance by such reason. The cause to vibration should be closely examined to reduce influence of such vibration. In this paper, the cause of the vibration which occurs by a gearbox is closely examined and the method which can reduce the vibration which occurred is shown. It is compared with vibration test outcome of a 3MW gearbox for verification of the method shown by this paper.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.291-296
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• 2007

This study presents the evaluation process for door module. Its objective evades the resonance generated at module plate due to the operation of window regulator motor. For this study, the design improvement process is composed of experimental methods having three steps. First step is modal analysis at door assembly status for acquisition of dynamic characteristics which are modal frequency and damping. Second step is a vibration experiment to get the test mode considered an efficiency of window regulator motor. Last step is a vibration measurement by the form of $6{\times}6$ array on module plate. A vibration measurement of 6x6 array form can be got to three analysis results which are a transfer path of vibration using cross correlation function, a vibration map using OA level and a contribution by frequency band using coherent output power spectrum on module plate. These results are applied to SDM(structural dynamic modification) for design improvement to get around the resonance on module plate by the excitation of window regulator motor.

• Journal of Power Electronics
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• v.12 no.4
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• pp.677-688
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• 2012

The vibratory conveyors with electromagnetic drive are used for performing gravimetric flow of granular materials in processing industry. By realizing free vibrations of variable intensity and frequency over a wide range through application of the electromagnetic actuator, suitable power converter, and the corresponding controller, continuous conveyance of granular materials have been provided for various operating conditions. Standard power output stages intended for control of vibratory conveyance using thyristors and triacs. Phase angle control can only accomplish tuning of amplitude oscillations, but oscillation frequency cannot be adjusted by these converters. Application of current controlled transistor converters enables accomplishing the amplitude and/or frequency control. Their use implies the excitation of a vibratory conveyor independent of the supply network frequency. In addition, the frequency control ensures operation in the region of mechanical resonance. Operation in this region is favourable from the energy point of view, since it requires minimal energy consumption. The paper presents a possible solution and advantages of the amplitude-frequency control of vibratory conveyors by means of a current controlled power converter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.11
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• pp.1094-1103
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• 2008

A fuel specific detonation wave in a pipe propagates with a predictable wave velocity. This internal detonation wave speed determines the level of flexural wave excitation of pipes and the possibility of resonant response leading to a large displacement. In this paper, we present particular solutions of displacements and the resonance conditions for internally loaded pipe structures. These analytical results are compared to numerical simulations obtained using a hydrocode(multi-material blast wave analysis tool). We expect to identify potential explosion hazards in the general power industries.