• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.799-800
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• 2008

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.9
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• pp.1220-1228
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• 2003

The mirage technique is proved to be powerful in measuring the thermal diffusivity of materials. In particular, its contactless nature makes it suitable for delicate samples and microscale structures. In this study, thermal-wave-coupling method is developed in a general form for both thermally thin and thick samples. In the suggested measuring scheme, the probe beam can be positioned close to the pump beam and the absolute position need not be measured. Therefore the new scheme provides a relatively simple yet effective way to determine the thermal diffusivity of thermally thick samples. Thermal diffusivities of bulk samples like Ni and Al were measured and the characteristics of mirage signal for a thin film were observed by using the mirage experimental setup. The apparent thermal diffusivity was measured by varying such parameters as probe beam height, size of pump beam, power of pump beam, and surface condition of sample. From the practical standpoint, it is shown that the size of the pump beam is the most important factor for accurate thermaldiffusivity measurement. Experiments using thin-film samples show that the thermal diffusivity of a substrate covered with thin film can be measured by photothermal mirage signals.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2C
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• pp.85-93
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• 2010

The shear stiffness has become an important design parameter to understand the soil behavior. In particular, the elastic moduli and void ratio has been considered as important parameters for the design of the geotechnical structures. The objective of this paper is the development of the penetration type Field Velocity and Resistivity Probe (FVRP) which is able to assess the elastic moduli and void ratio based on the elastic wave velocities and electrical resistivity. The elastic waves including the compressional and shear wave are measured by piezo disk elements and bender elements. And the electrical resistivity is measured by the resistivity probe, which is manufactured and installed at the tip of the FVRP. The penetration tests are carried out in calibration chamber and field. In the laboratory calibration chamber test, after the sand-clay slurry mixtures are prepared and consolidated. The FVRP is progressively penetrated and the data are measured at each 1 cm. The field experiment is also carried out in the southern part of Korea Peninsular. Data gathering is performed in the depth of 6~20 m at each 10 cm. The elastic moduli and void ratio are estimated based on the analytical and empirical solutions by using the elastic wave velocities and electrical resistivity measured in the chamber and field. The void ratios based on the elastic wave velocities and the electrical resistivity are similar to the volume based void ratio. This study suggests that the FVRP, which evaluates the elastic wave velocities and the electrical resistivity, may be a useful instrument for assessing the elastic moduli and void ratio in soft soils.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.80-87
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• 2005

T-50 supersonic jet trainer aircraft using digital flight-by-wire flight control system receives aircraft flight conditions such as altitude, VCAS(Calibrated Airspeed) and Angle of Attack from IMFP(Integrated Multi-Function Probe). IMFP sensors information have triplex structure using three IMFP sensors. Air-data selection logic is mid-value selection in three information from three IMFP sensors in order to have more reliability. From supersonic flight test at high altitude, air-data information is dropped simultaneously because of supersonic shock wave effect. This error information may affect to aircraft stability and safety in supersonic area at low altitude. This paper propose that sensitivity analysis and HQS(Handling Quality Simulator) pilot simulation in order to analyze flight stability and controllability in supersonic area at low altitude when these information is applied to flight control law.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.422-428
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• 2015

A 2.45GHz microwave plasma source with a linear antenna has been developed for low temperature large scale deposition processing. Microwave power is transmitted through WR340 waveguide and a copper rod, linear antenna, is located in a quartz tube. The power matching is effectively achieved by a linear antenna is located at ${\lambda}_g/4$ or $3{\lambda}_g/4$ from the end of WR340 waveguide. The Ar plasma was generated along the surface of quartz tube and a clear standing wave pattern with nearly 10cm wavelength was observed at Ar pressure of 200mTorr and 200W input power. The electron density and electron temperature were investigated by using the electrostatic probe. The electron density and electron temperature were highly measured near the surface of quartz tube. Ar plasma density along the quartz tube is mostly uniform despite standing wave set-up and antenna of long length. A uniform temperature was measured at 10~40cm distance from the end quartz tube and 5cm distance from the surface of quartz tube.

• Journal of Mechanical Science and Technology
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• v.15 no.4
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• pp.441-447
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• 2001

Ultrasonic wave generation and propagation were modeled to simulate an ultrasonic test. A ray model was used for the modeling. Actual sound pressure distribution of the incident wave from an angle probe was analyzed using an ultrasonic visualization method to incorporate the actual sound pressure distribution in the model. In this method, the sound pressure was expressed by the density of rays and the reflection coefficient of ultrasonic beams. Reflection and mode conversion of rays were computed by the Snells law. Simulation programs for the problem of ultrasonic testing of a butt joint are built using this ray modeling. Simulation results for ultrasonic wave scattering from a defect and A-scan display in ultrasonic testing agreed with the actual experiment results.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.283-292
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• 2009

Laser-based ultrasonic sensing requires the probe with fixed fecal length, but this requirement is not essential in laser-based ultrasonic generation. Based on this fact, we designed a pulsed laser-based ultrasonic wave propagation imaging (UWPI) system with a tilting mirror system for rapid scanning of target, and an in-line band-pass filtering capable of ultrasoaic mode selection. 1D-temporal averaging, 2D-spatial averaging, and 3D-data structure building algorithms were developed far clearer results allowing fur higher damage detectability. The imaging results on a flat stainless steel plate were presented in movie and snapshot formats which showed the propagation of ultrasound visible as a concentric wavefield emerging from the location of an ultrasonic sensor. A hole in the plate with a diameter of 1 mm was indicated by the scattering wavefields. The results showed that this robust UWPI system is independent of focal length and reference data requirements.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.124-125
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• 2000

We introduce a scheme with a maximized efficiency of detecting atoms passing through an optical standing-wave mode cavity. Consider a standing-wave optical cavity illuminated by a weak probe beam through one of its mirrors where the transmission through the other mirror is monitored by a photodetector. If an atom is put in the cavity, the atom-cavity coupling shifts the resonance frequency of the system via the so-called normal mode splitting, and thereby the transmission power will drop. In fact, this type of atom detection scheme has been used in recent single atom trap experiments In practice, however, the field in a standing-wave mode will have a geometrical structure having nodes and antinodes that when the atom traverses the cavity through one of the nodes, there will be no such effect of atom-field interaction. (omitted)

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.607-614
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• 2010

Shear behavior of granular soils largely affects the safety and stability of underground and earth structures. This study presents the characteristics of shear zone in a direct shear test using shear wave and electrical resistivity measurements. An innovative direct shear box made of transparent acrylic material has been developed to prevent direct electric current. Bender elements and electrical resistivity probe are embedded in the wall of direct shear box to estimate the shear wave velocities and the electrical resistivity at the shear and non-shear zones. Experimental results show that the void ratio and shear wave velocity at shear zone increase during shearing while the values remain constant at non-shear zone. The results demonstrate correlation among the contact force, small strain shear modulus, and void ratio at shear zone. This study suggests that the application of the modified direct shear box including shear wave and electrical resistivity measurements may become an effective tool for analyzing soil behavior at shear zone.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.6
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• pp.1-7
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• 2002

The use of an asymmetric Mach-Zehnder interferometric amplitude modulator to measure a relatively low frequency electric field strength is described. The sensitivity of an electric field sensor using a Ti:LiNbO$_3$ optical modulator is strongly affected by the shape of a electrode(probe antenna). To measure the low frequency electric field, a probe antenna of wide effective area is more useful than the usual dipole antenna. As a proof of this, the optical modulator was fabricated with a plate-type probe antenna and the usefulness of this antenna tested for measuring low frequency electric field strength. Measurements were performed in the range 0.1V/cm to 60V/cm at 60Hz through 100KHz. Using a probe antenna of 10mm$\times$10mm, the output voltage of 10㎷ was measured with respect to the electric field strength of 0.1V/cm at 60Hz. By increasing the effective area of the probe antenna, better sensitivity is obtainable over the measured range.