• The Korean Journal of Nuclear Medicine Technology
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• v.18 no.2
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• pp.3-7
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• 2014

Purpose SPECT/CT scan to be performed attenuation correction on the basis of CT induce an overestimation of the site due to the beam hardening artifact by metal cover and reduce the images quality. Therefore, this study using a phantom that has been inserted artificial hip joint investigated that effect on the SPECT/CT image causing by metal artifact for varying the parameters of the Attenuation Map. Materials and Methods Siemens Symbia T16 SPECT/CT equipment was used. Artificial hip joint was inserted to SPECT/PET phantom, 17 mm sphere of Bright Streak area in CT image was filled with Tc-99m so that the radiation activity was 8 times compared to background. And then Hot and Background was measured in varying Wide Beam Coefficient on Attenuation Map and RBR (Region to Background Ratio) of Metal and Non-Metal was calculated and analyzed depending on the presence or absence of the hip joint. Results It tended to hot count of Non-Metal and Metal to increase as the value of the manual mode is increased, hot count ratio with the group of both manual mode 0.5 and 0.4 is the best match. Also, in automatic mode, the ratio of RBRNon-Metal and RBRMetal was 1.135, statistically significant difference was not observed in the manual mode 0.5 and 0.4. Conclusion In the automatic mode of Wide Beam Coefficient in attenuation correction map, it was found that it is over-correction by 13.52%, it was possible to minimize the over-correction by the artifact in 0.5 and 0.4 of manual mode. Further studies should be performed in order to apply to a patient with the help of this and it is considered possible to reduce the over-correction by the metal artifact of an artificial hip joint for Hip-Resurfacing Arthroplasty patients, and to improve the diagnostic performance.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.46-51
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• 2015

Stainless steel is a popular structural materials for liquid-hydrogen storage containers and piping components for transporting high-temperature fluids because of its superior material properties such as high strength and high corrosion resistance at elevated temperatures. In general, tungsten inert gas (TIG) arc welding is used for bonding stainless steel. However, it is often reported that the thermal fatigue cracks or initial defects in stainless steel after welding decreases the reliability of the material. The objective of this paper is to clarify the characteristics of ultrasonic guided wave propagation in relation to a change in the initial crack length in the welding zone of stainless steel. For this purpose, three specimens with different artificial defects of 5 mm, 10 mm, and 20 mm in stainless steel welds were prepared. By considering the thickness of s stainless steel pipe, special attention was given to both the L(0,1) mode and L(0,2) mode in this study. It was clearly found that the L(0,2) mode was more sensitive to defects than the L(0,1) mode. Based on the results of the L(0,1) and L(0,2) mode analyses, the magnitude ratio of the two modes was more effective than studying each mode when evaluating defects near the welded zone of stainless steel because of its linear relationship with the length of the artificial defect.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.903-913
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• 2007

In this study, the researchers compared the S-wave velocity structures obtained by two kinds of dispersion curves: phase and group dispersions from a tidal flat located in the SW coast of the Korean peninsula. The ${\tau}-p$ stacking method was used for the phase velocity and two different methods (multiple filtering technique: MFT and continuous wavelet transform: CWT) for the phase velocity. It was difficult to separate higher modes from the fundamental mode phase velocities using the ${\tau}-p$ method, whereas the separation of different modes of group velocity were easily achieved by both MFT and CWT. Of the two methods, CWT was found to be more efficient than MFT. The spatial resolutions for the inversion results of the fundamental mode for both phase and group velocities were good for only a very shallow depth of ${\sim}1.5m$. On the other hand, the spatial resolutions were good up to ${\sim}4m$ when both the fundamental and the 1st higher mode poop velocities obtained by CWT were used for S-wave inversion. This implies that the 1st higher mode Rayleigh waves contain more information on the S-wave velocity in deeper subsurface. The researchers applied the CWT method to obtain the fundamental and the 1st higher mode poop velocities of the S-wave velocity structure of a tidal flat located in SW coast of the Korean peninsula. Thea the S-wave velocity structures were compared with the borehole description of the study area.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.5
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• pp.214-221
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• 2015

In this paper, we present robust estimation and detection algorithms for discrete-time switched linear systems whose output measurements are corrupted by noises. First, a mode estimation algorithm is proposed based on the minimum distance criterion. Then, state variables are also observed under the active mode estimate. Second, a detection algorithm is constructed to detect the mode switching of the switched system. With the boundedness of measurement noise, the proposed estimation algorithm returns the exact active mode and approximate state information of the switched system. In addition, the detection algorithm can detect the switching time within a pre-determined time interval after the actual switching occurred.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.2 s.344
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• pp.34-41
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• 2006

This paper presents a CMOS multi-mode baseband filter architecture to support PDC/GSM/EDGE/WCDMA and its new automatic tuning method. 5-th order Chebyshev low pass filter is designed for implementing the baseband channel-select filter. Capacitors and resistors were shared efficiently between modes to minimize the area. And, the new cut-off frequency tuning method is proposed to compensate the process variation. This method can reduce the area and the noise level due to MOS switches.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.448-454
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• 2008

This paper deals with a behavior based decentralized control strategy for UAV swarming utilizing the artificial potential functions and the sliding mode control technique. Individual interactions for swarming behavior are modeled using the artificial potential functions. The motion of individual UAV is directed toward the negative gradient of the combined potential. For tracking the reference trajectory of UAV swarming, a swarming center is considered as the object of control. The sliding-mode control technique is adopted to make the proposed swarm control strategy robust with respect to the system uncertainties and the varying mission environment. Numerical simulation is performed to verify the performance of the proposed controller.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.427-434
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• 2000

The paper proposes a zero speed start-up scheme of direct rector controlled induction motor drive without any torque jerk. At standstill condition, a method is derived to calculate a stator flux with only stator current. The programmable 3-stage low pass filters with programmable time constants is used in order to solute the problem of integration for stator flux estimation in the direct vector control mode. Due to the time delay of 3-stage low pass filter, the status flux decreases rapidly and also the torque jerk occurs during the transition from standstill mode to the direct rector control mode. A feedforward control strategy of the stator flux is suggested to prevent the torque jerk at start-up. Through results of simulation and experiment with 32 bit DSP, the performance of the start-up scheme is verified.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.55-60
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• 2012

Longitudinal transmission-line modal theory is applied to analyze maximum power transfer in plasmonic grating-assisted directional couplers (P-GADC) based on silicon waveguide. By defining a coupling efficiency amenable to rigorous analytical solutions and interference between even and odd modes, the power exchange of TE modes as a function of propagation distance is evaluated. The numerical result reveals that maximum power transfer occurs at a grating period ${\Lambda}_{eq}=10.26{\mu}m$, in which the insertion loss of supermodes is equal to each other. That is, it is generally different from conventional phase-matching condition or minium gap condition of GADC.

• Journal of the Microelectronics and Packaging Society
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• v.13 no.4
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• pp.57-63
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• 2006

For chip-stack package applications, Cu filling characteristics into trench vias of $75{\sim}10\;{\mu}m$ width and 3 mm length were investigated with variations of electroplating current density and current mode. At $1.25mA/cm^{2}$ of DC mode, Cu filling ratio higher than 95% was obtained for trench vias of $75{\sim}35{\mu}m$ width. When electroplated at DC $2.5mA/cm^{2}$, Cu filling ratios became inferior to those processed at DC $1.25mA/cm^{2}$. Pulse current mode exhibited Cu filling characteristics superior to DC current mode.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.5
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• pp.143-148
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• 2013

A novel ultracompact polarization beam-splitter (PBS) combining two plasmonic multimode interference couplers (P-MMICs) and DFB guiding structure is implemented. The $2{\times}1$ and $1{\times}2$ P-MMICs are designed to collect the polarized powers of TE and TM modes reflected by or transmitted through an internal DFB structure. The simulation results show that the designed DFB-assisted PBS is very short (about $75{\mu}m$), and has a low insertion loss, a high extinction ratio, and a broad bandwidth of 20 nm.