• Journal of Biomedical Engineering Research
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• v.18 no.4
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• pp.407-412
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• 1997

In this paper, we present a new method to diagnose the characteristics of the soft tissue, especially a liver. In order to diagnose the characteristics of a liver, it is necessary to evaluate the propagation delay time and propagation velocity of bending vibration In a liver. For this purpose, we measure the propagation velocity of bending vibration in a liver for low frequency forced vibration using a standard ultrasonic Doppler diagnosis equipment. We have carried out preliminary experiments by using an ultrasonic probe of 3.5MHz and obtained some results. This new measurement method developed here can be applied to new research and medical fields for acoustic non-invasive diagnosis of soft tissue.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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• pp.52-55
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• 1996

Though the increment of using computer vision system in modern industry, there are lots of difficulties to measure precisely because of measurement error distortion phenomenon. Between these reasons, the distortion of edge is dominant reason which is occured by the blurred image. The blurred image is happened when camera can not discriminate its precise focus. To correct and generalize distortion phenomenon is imprrtant. Thus we must fix the discrimination criteria which is collected by image recognition of precise focus. The edge of image means discontinuous point of intensity, and the component of edge is discribed as high frequency component at special domain specturm of image. The good condition of focus means there are much high frequency energy in image. The method of discribing high frequency energy is gradient operater which determines the condition of focus.

• Wind and Structures
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• v.18 no.4
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• pp.375-389
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• 2014

The high-frequency force-balance (HFFB) technique and its subsequent improvements are reviewed in this paper, including a discussion about nonlinear mode shape corrections, multi-force balance measurements, and using HFFB model to identify aeroelastic parameters. To apply the HFFB technique in engineering practice, various validation studies have been conducted. This paper presents the results from an analytical validation study for a simple building with nonlinear mode shapes, three experimental validation studies for more complicated buildings, and a field measurement comparison for a super-tall building in Hong Kong. The results of these validations confirm that the improved HFFB technique is generally adequate for engineering applications. Some technical limitations of HFFB are also discussed in this paper, especially for higher-order mode response that could be considerable for super tall buildings.

• Journal of Information Processing Systems
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• v.15 no.1
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• pp.189-202
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• 2019

During thermal power coal-fired boiler operation, it is very important to detect the pulverized coal concentration in the air pipeline for the boiler combustion stability and economic security. Because the current measurement methods used by power plants are often involved with large measurement errors and unable to monitor the pulverized coal concentration in real-time, a new method is needed. In this paper, a new method based on microwave circular waveguide is presented. High Frequency Electromagnetic Simulation (HFSS) software was used to construct a simulation model for measuring pulverized coal concentration in power plant pipeline. Theoretical analysis and simulation experiments were done to find the effective microwave emission frequency, installation angle, the type of antenna probe, antenna installation distance and other important parameters. Finally, field experiment in Jilin Thermal Power Plant proved that with selected parameters, the measuring device accurately reflected the changes in the concentration of pulverized coal.

• Proceedings of the IEEK Conference
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• 2001.06d
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• pp.253-256
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• 2001

Characteristics of fruit vibrations are related to the material properties of the fruit. A new method for spectral analysis is developed and used for the non-destructive estimation of fruit firmness. The resonant frequency of the fruit is related to its firmness. However, the determination of the resonant frequency is not easy So the smoothing method is applied to the frequency spectra to obtain a robust estimate for the resonant frequency.

• Journal of Advanced Navigation Technology
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• v.3 no.2
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• pp.120-131
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• 1999

For the phase measurement in the radar system using the magnetron pulse source, the STALO (Stable Local Oscillator) frequency need to be controlled to provide the stable intermediate frequency. In radar receiver, AFC(Automatic Frequency Control) circuit detects the transmitting frequency change and controls the STALO frequency to keep the intermediate frequency stable. In this paper, we designed and implimented AFC circuits for radar receiver. The frequency deviation is detected and compared with the reference frequency and the STALO frequency is controlled by the digital command signal.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.1
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• pp.10-17
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• 2000

In boiler high-temperature pipelines such as main steam pipe, header and steam drum in fossil power plants, conventional measurement techniques(replica method, electric resistance method, and hardness test method) for measuring creep damage have such disadvantages as complex preparation and measurement procedures, too many control parameters. And also, these techniques have low practicality and applied only to component surfaces with good accessibility. It needs to apply a reliable and quantitative ultrasonic nondestructive evaluation method that can be replaced for these equipment. In this study, both artificial creep degradation test using life prediction formula and frequency analysis by ultrasonic tests for crept specimens were carried out for the purpose of nondestructive evaluation for creep damage. As a result of ultrasonic tests for crept specimens, we conformed that the high frequency side spectra decrease and central frequency components shift to low frequency band, and also their bandwidth decreases as increasing creep damage in backwall echos.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.234-234
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• 2011

Electron-neutral collision frequency is one of the important parameters in the plasma physics and in industrial plasma engineering. We can understand the momentum, energy, and charge transport properties of the plasma using electron-neutral collision frequency.[1] The wave-cutoff method is a diagnostic method for the electron density measurement, but the cutoff peak value depends on gas pressure. The wave-cutoff signal becomes unclear as increasing gas pressure. The reason of pressure dependence is that the electron-neutral collision disturbs electron motion so that microwave can propagate through plasma at plasma frequency.[2] Using the pressure dependence of wave-cutoff method we can find the electron-neutral collision frequency. At first we tried to confirm this method using well known gas such as Ar. The cutoff signal decrease as increasing gas pressure (the simulation result). The wave-cutoff signal is unclear at a gas pressure of 500 mTorr. (electron density $1.0{\times}10^{10}/cm^3$, electron temperature 1.7 eV, electron -neutral collision frequency~1 GHz). In this condition, the electron-neutral collision frequency is closed to the wave-cutoff frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.527-532
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• 2010

This paper is concerned with the measurement of static and dynamic displacement by image processing(IP) and study for prediction method of velocity and acceleration. To measure the displacement visually, the measurement system consists of a telephoto zoom camera, ccd image device and a computer. The specific target on the white board is used to calculate the displacement of the structure. The captured image is then converted into a pixel-based data and then analyzed numerically. The limitation of the system depends on the image capturing speed and the pixel-size of image. In this paper, we developed for the displacement measurement using the image processing method. The proposed method enables us to measure the vibration measurement, velocity and acceleration directly without any contact. The current resolution of the displacement measurement is limited to 1/100 millimeter scale.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.547-550
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• 2005

Gauge blocks are the most widely used material measure in length field in industry. The gauge block interferometer, which is the gauge block measuring system, comprises Twyman-Green type interferometer optics and light sources having precisely known wavelengths. This paper describes the work done for advancing the measurement system and automating the measurement process. The advancing of the system was done mainly by exchanging the spectral lamp with the frequency stabilized lasers, and the automation of measurement was achieved by modifying the hardware and developing the automatic measuring software. As the results of this work, the contrast of interferometric fringes of gauge blocks longer than 100 mm s enhanced about 20 times, and the measurement time has reduced down to 50% by automation.