• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.11
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• pp.1-7
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• 1995

The problem of amplitude-and frequency-modulated waveforms is analyzed when a linearly polarized electromagnetic wave is scattered by a slowly rotating rotor with metal plates. ECM in conjunction with a quasi-stationary method is used to analyze the modulated waveforms. The modulated waveforms depend on the orientation and dimension of the object. its rotation speed, and very strongly on the incident and scattering directions. The modulate waveforms of a rotating non-skewed metal plate and a rotor with two blades are functions of twice the rotating frequency of those. Similar results are discussed for a rotating skewed metal plate, but the modulated waveforms is a function of the rotating frequency. Numerical results based on our ECM are presented and compared with those of Sikta's and PO solution.

• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.405-409
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• 2009

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ${\sim}3$ dB, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

• International Journal of Automotive Technology
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• v.4 no.4
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• pp.203-211
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• 2003

This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP (Carbon-fiber reinforced plastics) laminate plates based on considerations of stress wave propagation theory, which were converted to measurements of load and displacement verses time. The delamination area of impacted specimens for the different ply orientations was measured with an ultrasonic C-scanner to determine the correlation between impact energy and delamination area. The energy absorbed by a quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen embedding GFRP (Glass-fiber reinforced plastics) layer was higher than that of normal specimens. Also, a falling weight impact tester was built to evaluate the characteristics and impact strength of CFRPs.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1991.04a
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• pp.31-39
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• 1991

When predicting shipboard noise levels, the accuracy depends largely on the value of the structureborne noise transmission loss. Although empirical formulars are frequently used because of their simplicities, researches on the analytical methods to estimate the transmission loss of structureborne noise such as wave guide theory and SEA has long been one of the major topics in shipboard acoustics to overcome the inherent limitations of empirical ones. This paper describes an application of SEA to predict the transmission loss of the structurebornenoise of a simple ship-like structural model consisted of 22 flat plates. The result shows that discrepancies between experimental and theoretical transmission losses are less than 3 dB.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.29-34
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• 2011

Various types of coastal structures have been constructed to prevent coastal disasters. Among these coastal structures, submerged breakwaters have been used more widely than all of the other coastal structures because of their excellent advantages in scenery effects, construction efficiency, and environmental benefits. This study investigated the potential of the horizontal plate submerged breakwater model. Usually, it is necessary for a submerged breakwater to minimize and compensate for the negative impacts on the marine environment and ecosystem caused by the marine construction. Thus, the prevention of coastal disasters was verified for this submerged breakwater model, regardless of its function as a fish reef. The purpose of this study was to investigate the hydraulic characteristics with changes in the crest width and porosity of a horizontal plate submerged breakwater and compare the results of this study with the results of other studies on permeable and impermeable submerged breakwaters.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.3
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• pp.210-220
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• 2001

This paper aims at the evaluation on the characterization of CFRP laminate plates using falling weight impact tester. The experimentation was conducted on several laminates of different fiber and ply orientation. A system was built for the impact strength of CFRP laminates in consideration of stress wave propagation with using drop-weight impact tester as one of impact test. Absorbed energy of orthotropic composites with using T300 fiber, which are composed of the same fiber and stacking number is higher than that or quasi-isotropic specimen over impact energy 7J, but in case or using T700 fiber, much difference does not show. Also, absorbed energy of orthotropic composites with using T300 fiber, which are composed or stacking number and orientation became more than that of T700 fiber specimen; however great change doesn't show in case of quasi-isotropic specimens. It is found that influence was confirmed between impact energy and absorbed energy as the impact energy is increased with adding the falling weight.

• Journal of Astronomy and Space Sciences
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• v.29 no.1
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• pp.69-77
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• 2012

This report describes the inception, development and extensive use over 30 years of elliptical polarimeters at the University of Pennsylvania. The initial Mark I polarimeter design utilized oriented retarder plates and a calcite Foster-Clarke prism as the analyzer. The Mark I polarimeter was used on the Kitt Peak 0.9 m in 1969-70 to accomplish a survey of approximately 70 objects before the device was relocated to the 0.72 m reflector at the Flower and Cook Observatory. Successive generations of automation and improvements included the early-80's optical redesign to utilize a photoelastic modulated wave plate and an Ithaco lock-in amplifier-the photoelastic modulating polarimeter. The final design in 2000 concluded with a fully remote operable device. The legacy of the polarimetric programs includes studies of close binaries, pulsating hot stars, and luminous late-type variables.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.10
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• pp.144-151
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• 1996

In this paper, the theoretical analysis and the computer simulation of a new modified cochran's triangular interferometer as an incoherent holography, which can eliminate bias and conjugate image problems of the conventional cochran's triangular interferometer, are spresented. In other words, it is theoretically derived by using jones matrix operation that bias and conjugate image can be removed by adding simple optical components including a polarizing beam splitter, wave plates, and linear polarizers to the conventional with a point source, we demonstrated the validity of the suggested method by comparing the modified cocharan's triangular interferometer with the conventional one.

• The Journal of the Acoustical Society of Korea
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• v.29 no.3E
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• pp.140-145
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• 2010

In the present study, tubular polyvinyl chloride (PVC) cortical bone mimics that simulate the cortical shell of long bones were used to validate the axial transmission technique for assessing the cortical thickness by measuring the ultrasonic velocities along the cortical shell of long bones. The ultrasonic velocities in the 9 PVC cortical bone mimics with wall thicknesses from 4.0 to 16.1 mm and inner diameters from 40 to 300 mm were measured as a function of the thickness by using a pair of custom-made transducers with a diameter of 12.7 mm and a center frequency of 200 kHz. In order to clarify the measured behavior, they were also compared with the predictions from a theory of guided waves in thin plates. This phantom study using the PVC cortical bone mimics provides useful insight into the dependencies of ultrasonic velocities on the cortical thickness in human long bones.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.774-779
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• 2003

Arc-shaped line array slits have been used for the laser generation of focused Lamb waves. The spatially expanded Nd:YAG pulse laser was illuminated through the arc-shaped line array slit on the surface of a sample plate to generate the Lamb waves of the same pattern as the slit. Then the generated Lamb waves were focused at the point of which distance from the slit position is dependent on the curvature of slit arc. The proposed method showed better spatial resolution than the conventional linear array slit in the detection of laser machined linear defect and drill machined circular defect on aluminum plates of 1mm thickness.