• Korean Journal of Optics and Photonics
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• v.3 no.2
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• pp.105-110
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• 1992

In order to measure fine rotation angles by magneto-optic effects of magneto-optical recording thin films, a polarization modulation method is used. In the experiment, the polarization of laser (He-Ne laser) beam is modulated by a Faraday rotator and the amplified modulated signals are selectively detected by phase sensitive detector. The magnetic Kerr rotation and Faraday rotation hysteresis loops are investigated by this method for thermally evaporated amorphous TbFeCo thin films and RF sputtered garnet thin films. Rotation angles about $0.25^{\circ}$ are measured easily from TaFeCo thin films. In the case of longitudinal Kerr rotation, very small rotation angle of $2.5\times10^{-3^\circ}$ is measured with good accuracy of the measurement (about $1\times10^{-3^\circ}$). And it is found that each thin films have the hysteresis curves of high coercivity and good squareness.

• Korean Journal of Radiology
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• v.2 no.4
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• pp.210-215
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• 2001

Objective: To investigate the efficacy of gadobenate dimeglumine (GdBOPTA) enhanced MR imaging for the detection of liver lesions in patients with primary malignant hepatic neoplasms. Materials and Methods: Thirty-one patients with histologically proven primary malignancy of the liver were evaluated before and after administration of GdBOPTA at dose 0.05 or 0.10 mmol/kg. T1-weighted spin echo (T1W-SE) and gradient echo (T1W-GRE) images were evaluated for lesion number, location, size and confidence by three off-site independent reviewers and the findings were compared to reference standard imaging (intraoperative ultrasound, computed tomography during arterial portography or lipiodol computed tomography). Results were analyzed for significance using a two-sided McNemar's test. Results: More lesions were identified on Gd-BOPTA enhanced images than on unenhanced images and there was no significant difference in lesion detection between either concentration. The largest benefit was in detection of lesions under 1 cm in size (7 to 21, 9 to 15, 16 to 18 for reviewers A, B, C respectively). In 68% of the patients with more than one lesion, Gd-BOPTA increased the number of lesions detected. Conclusion: Liver MR imaging after Gd-BOPTA increases the detection of liver lesions in patients with primary malignant hepatic neoplasm.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.5
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• pp.628-637
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• 2004

In many drinking water treatment plants, chlorination process is one of the main techniques used for the disinfection of water. This disinfecting treatment leads to the formation of disinfection by-products (DBPs) such as haloacetonitriles (HANs), trihalomethanes (THMs), haloacetic acids (HAAs). In this study, headspace-solid phase microextraction (HS- SPME) technique was applied for the analysis of HANs in drinking water. The effects of experimental parameters such as selection of SPME fiber, the addition of salts, magnetic stirring, extraction temperature, extraction time and desorption time on the analysis were investigated. Analytical parameters such as linearity, repeatability and detection limits were also evaluated. The $50/30{\mu}m$-divinylbenzene/carboxen/polydimethylsiloxane fiber, extraction time of 30 minutes, extraction temperature of $20^{\circ}C$ and desorption time of 1 minute at $260^{\circ}C$ were the optimal experimental conditions for the analysis of HANs. The correlation coefficients ($r^2$) for HANs was 0.9979~0.9991, respectively. The relative standard deviations (%RSD) for HANs was 2.3~7.6%, respectively. Detection limits (LDs) for HANs was $0.01{\sim}0.5{\mu}g/L$, respectively.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.4
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• pp.203-207
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• 2013

The appropriate handling of motion artifacts is essential for clinical diagnosis in magnetic resonance imaging (MRI). In many cases, motion is an inherent part of MR images because it is difficult to control during MR imaging. As the motion in the human body occur in a deformable manner, they are difficult to deal with. This paper proposes a novel detection method for periodically moving regions to produce MR images with less motion artifacts. When the data is acquired by the radial trajectory, the proposed method can extract the deformable region easily using the difference in the modulated sinograms, which have different periodic phase terms. The simulation results applied to the various cases confirmed the good performance of the proposed method.

• Carbon letters
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• v.26
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• pp.43-50
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• 2018

In this research, a novel and efficient quinoline thioacetamide functionalized magnetic graphene oxide composite ($GO@Fe_3O_4@QTA$) was synthesized and utilized for dispersive magnetic solid phase preconcentration of Cd(II) and Ni(II) ions in urine and various food samples. A number of diverse methods were employed for characterization of the new nanosorbent. The design of experiments approach and response surface methodology were applied to monitor and find the parameters that affect the extraction performance. After sorption and elution steps, the concentrations of target analytes were measured by employing FAAS. The highest extraction performance was achieved under the following experimental conditions: pH, 5.8; sorption time, 6.0 min; $GO@Fe_3O_4@QTA$ amount, 17 mg; 2.4 mL $1.1mol\;L^{-l}$ $HNO_3$ solution as the eluent and elution time, 13.0 min. The detection limit is 0.02 and $0.2ng\;mL^{-1}$ for Cd(II), and Ni(II) ions, respectively. The accuracy of the new method was investigated by analyzing two certified reference materials (sea food mix, Seronorm LOT NO 2525 urine powder). The interfering study revealed that there are no interferences from commonly occurring ions on the extractability of target ions. Finally, the new method was satisfactorily employed for rapid extraction and determination of target ions in urine and various food samples.

• Journal of the Korean Magnetic Resonance Society
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• v.24 no.1
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• pp.9-15
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• 2020

Nitrogen vacancy center (NV center) in diamond has recently been appeared as a promising candidate for hyperpolarization applications due to its optical pumping property by laser. Optically Detected Magnetic Resonance (ODMR) has been used as a conventional method to obtain the resonance spectrum of NV centers. ODMR, however, has a shortcoming of sensitivity and a limitation of subjects, such that the degree of hyperpolarization can hardly be estimated, and that the spins other than NV centers are invisible. In contrast, Electron Spin Resonance (ESR) spectroscopy is known to proportionally reflect the degree of spin polarization. In this work, we successfully observed the optically-induced hyperpolarization of NV spins in diamond through CW-ESR spectroscopy with an X-band system. All the NV peaks were identified by calculating the eigenvalues of NV spin Hamiltonian. The intensities of NV peaks were enhanced over 240 times after optical pumping. The enhanced peaks corresponding to the transition from |m_s=0> to |m_s=-1> revealed inverted phases, while other peaks remained in-phase. The optically-induced hyperpolarization on NV spins can be a useful polarization source, leading to ¹³C nuclear hyperpolarization in diamond.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.180-184
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• 2007

For driving a sinusoidal type permanent magnet synchronous motor with a maximum continuous torque, a $120^0$ delayed three phase sinusoidal current input which matched with the absolute rotor position is needed at a stator coil. So, the detection of absolute rotor position is required inevitably. Thus the right angle relationship between stator magnetic field and rotor magnetic field has to be preserved at a stator by this commutation action. The detection of a absolute position for the commutation can be made generally by the output signal analysis of the encoder attached at a motor shaft. This study purposes to design signal processing logic circuits which can detect the absolute position of motor with a modem encoder system and generate the three reference wave for making sinusoidal current input at a stator coil.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.5
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• pp.1018-1024
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• 2011

For the driving of the sinusoidal type permanent magnet synchronous motor with a maximum continuous torque, the 1200 delayed three phase sinusoidal current inputs which matched with the absolute rotor position are needed at the stator coil. Therefore, the detection of a absolute rotor position is required inevitably. And the right angle relationship between stator magnetic field and rotor magnetic field has to be preserved at a stator by this commutation action. The detection of a absolute position for the commutation can be made generally by the output signal analysis of the encoder attached at a motor shaft. The purposes of this study are to design signal processing logic circuits which could detect the absolute position of motor with a modern encoder system and generate the three reference wave for making sinusoidal current input at a stator coil.

• Investigative Magnetic Resonance Imaging
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• v.1 no.1
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• pp.142-147
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• 1997

Purpose: To compare the effectiveness of the in-phase (IP) sequence and the opposed-phase (Op) sequence in the detection of focal hepatic lesions in the single breath-hold hepatic MR imaging with fast gradient T1-weighted pulse sequences. Materials and Methods: IP and OP T1-weighted breath-hold imaging was performed using fast gradient echo sequences in 45 patients referred for known focal hepatic lesions, in which 78 lesions were detected. Three blind readers independently reviewed the images for lesion detectability. The signal-to-noise ratio (SNR) of the liver, the lesion-to-liver contrast-to-noise ratio (CNR) and the liver-to-spleen CNR were also compared. A consensus was reached by three readers to determine which sequence is better in image quality. Results: On OP images, 61(78%), 61(78%), and 63(89%) lesions were correctly identified for reader 1, 2 and 3, respectively. On IP images, 66(85%), 65(83%), and 65(93%) lesions were detected for each reader, respectively. When two image sets were combined, 71(91 %), 69(88 %), and 76(97%) lesions respectively were detected for each reader. In cases of hepatocellular carcinoma, liver-to-Iesion CNR was greater on the OP images(p (0.05), but in other lesions significant difference was not demonstrated. Liver-to-spleen CNR was higher on OP images(p ( 0.1), but the SNR of the liver was higher on the IP images. Conclusion: Use of both IP and OP imaging can be helpful to avoid erroneous missing of some focal hepatic lesions.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4816-4834
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• 2020

This paper proposes transfer learning and fine-tuning techniques for a deep learning model to detect three distinct brain tumors from Magnetic Resonance Imaging (MRI) scans. In this work, the recent YOLOv4 model trained using a collection of 3064 T1-weighted Contrast-Enhanced (CE)-MRI scans that were pre-processed and labeled for the task. This work trained with the partial 29-layer YOLOv4-Tiny and fine-tuned to work optimally and run efficiently in most platforms with reliable performance. With the help of transfer learning, the model had initial leverage to train faster with pre-trained weights from the COCO dataset, generating a robust set of features required for brain tumor detection. The results yielded the highest mean average precision of 93.14%, a 90.34% precision, 88.58% recall, and 89.45% F1-Score outperforming other previous versions of the YOLO detection models and other studies that used bounding box detections for the same task like Faster R-CNN. As concluded, the YOLOv4-Tiny can work efficiently to detect brain tumors automatically at a rapid phase with the help of proper fine-tuning and transfer learning. This work contributes mainly to assist medical experts in the diagnostic process of brain tumors.