• Journal of Sensor Science and Technology
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• v.29 no.1
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• pp.33-39
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• 2020

Typically, photoacoustic images are obtained in water or gelatin because the impedance of these mediums is similar to that of the human body. However, these acoustic mediums can have an additional mass effect that changes the resonance frequency of the transducer. The acoustic radiation impedance in air is negligible because it is very small compared to that of the transducer. However, the high acoustic impedance of mediums such as the human body and water is quite large compared to that of air, making it difficult to ignore. Specifically, in a case where the equivalent mass is very small, such as with a micro-machined ultrasound transducer, the additional mass effects of the acoustic medium should be considered for an accurate resonance frequency design. In this study, a piezoelectric micro-machined ultrasonic transducer (pMUT) was designed to have a resonance frequency of 10 MHz in the acoustic medium of water, which has similar impedance as the human body. At that time, the resonance frequency of the pMUT in air was calculated at 15.2 MHz. When measuring the center displacement of the manufactured pMUT using a laser vibrometer, the resonance frequencies were measured as 14.3-15.1 MHz, which is consistent with the finite element method (FEM) simulation results. Finally, photoacoustic images of human hair samples were successfully obtained using the fabricated pMUT.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.12
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• pp.1072-1082
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• 2015

In this paper, we propose two noise parameter measurement methods using spectrum analyzer. First method, we measure a noise correlation matrix using the 6-port network, and we calculate noise parameters using measured a noise correlation matrix. Second method, we directly measure noise figures of the DUT for source impedance changes, and then noise parameters are extracted from the measured noise figures. In order to measure a noise figure, we present a method of measuring a noise figure of the DUT that have arbitrary source impedances using spectrum analyzer and a method of eliminating a noise effect of a impedance tuner. Finally, the noise parameters of a passive and active DUT using proposed two methods are compared. The comparison shows that the two results obtained from for the two methods give almost identical noise parameters. The noise parameters measured by 6-port network accurately predict measured noise figures of the DUT for source impedance changes, and noise parameters measured by 6-port network is verified from the comparison.

• Journal of Animal Science and Technology
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• v.63 no.2
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• pp.332-338
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• 2021

The objective of this study was to predict body compositions of live pigs using bioelectrical impedance procedures. In experiment 1, 32 crossbred (Duroc × Landrace × Yorkshire) finishing pigs with an average weight at 84.06 kg were used. In experiment 2, 96 crossbred (Duroc × Landrace × Yorkshire) finishing pigs with an average weight at 88.8 kg were used. A four-terminal body composition analyser was utilized to determine fat percentage. Lean meat percentage and backfat thickness were measured with a lean meat measuring meter. In experiment 1, fat percentage was not significantly correlated with lean meat percentage, although a tendency (p < 0.1) of a negative correlation was found. Backfat thickness was significantly correlated with fat percentage and lean meat percentage (r = 0.745 and r = -0.961, respectively). Coefficients of determination for fat percentage with lean meat percentage, fat percentage with backfat thickness, and backfat thickness with lean meat percentage were 0.503, 0.566, and 0.923, respectively. In experiment 2, fat percentage was significantly correlated with lean meat percentage (r = -0.972). Backfat thickness was also significantly correlated with fat percentage and lean meat percentage (r = 0.935 and r = -0.957, respectively). Results of this study indicate that bioelectrical impedance analysis might be useful for predicting body compositions of live finishing pigs.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2E
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• pp.76-84
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• 1996

The experimental testing results of the large-scale version of a forward-looking ultrasound imaging catheter(FLUIC) are presented, along with the fabrication techniques used, experimental methods, and comparisons of the measured and simulated results. The transducer model is verified by measuring the electrical impedance of the transducer. The pulse width, beamwidth, and the dynamic range for both transmit and pulse-echo response of the fabricated FLUIC are also analyzed. The experimental results conformed its forward-looking imaging capability and the sources of discrepancies between the simulated and experimental beam profiles are addressed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.184-190
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• 2003

In this study, several methods for measuring floor impact sound were introduced. Among them, the simple methods (impedance method and diffuse index method) which can be easily applied to site works were investigated. Moreover, the comparison between the calculation results using diffuse index method and the experimental results measured in real apartment structures was conducted. Consequently, the modified diffuse index method, which can be practically used for predicting the performance of to the floor impact sound of apartment structures and can meet the allowable tolerance of Grade I (${\pm}$5㏈), was proposed.

• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.363-364
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• 2006

We developed 60 GHz analog optical transmitter modules for radio-over-fiber (RoF). They were consisted of an electroabsorption modulator (EAM), impedance matching circuit, and amplifier. The characteristics of fabricated modules were investigated by measuring the signal-to-noise ratio and the noise figure of the 60 GHz RoF link.

• Journal of Electrical Engineering and information Science
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• v.2 no.5
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• pp.40-44
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• 1997

This paper presents the results of studies made for measuring the relative complex permittivity of PCB sheet material in he frequency a range of 100MHz∼1GHz using vector network analyzer. A measurement cell was developed for this purpose using broad-band impedance method and the dielectric constant and loss tangent of two PCBV sheet materials, glass-epoxy and teflon, were measured. The effect of copper cladding was studied.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.8
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• pp.394-400
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• 2001

This paper describes an application of the on line partial discharge measurement method in operating transformer. In the operating transformer, the partial discharge signal may be superimposed by radio intereference voltage(RIV) and pulse shaped noise signals generated by external corona. The partial discharge quantity showed about 3,800pC due to very high sinusoidal interferences at the measuring impedance terminal of the transformer bushing tap. In order to reject these noises, this paper applied RIV filter, band-pass filters and noise gating method. The resulting measuring sensitivity was improved from 3,800pC to 160pC.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.563-566
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• 1999

The functional diagnosis instrument should be preceded first to both the accurate selection of exact acupoint and discrimination. so the measuring and stimulating method are improved to SPAC pattern to evaluate impedance existed in the body. As a result, the resistance factor between skin and probe, the dipolization of cell was reduced so that the judgement of acupoint is advanced. After extraction of optimization parameter of SPAC pattern which the high discrimination efficiency and the lowest affection on the human body is controlled by using microprocessor to enhance conviction. The discrimination efficiency was confirmed by meridian visualization system. Also mechanism of probe was improved to increase efficiency of image recognition processing. The image of discriminated acupoint with probe is obtained by using a camera, the location on the tip of probe is recognized and processed. And then these are converted to virtual color by proportional to measuring current level of scan point on skin.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.05c
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• pp.38-42
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• 2001

This paper describes an application of the on line partial discharge measurement method in operating transformer. In the operating transformer, the partial discharge signal may be superimposed by radio intereference voltage(RIV) and pulse shaped noise signals generated by external corona. The partial discharge quantity showed about 3,800pC due to very high sinusoidal interferences at the measuring impedance terminal of the transformer bushing tap. In order to reject these noises, this paper applied RIV filter, band-pass filters and noise gating method. The resulting measuring sensitivity was improved from 3,800pC to 160pC.