• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1555-1560
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• 2000

Recently, optical pickup actuators have been designed to have structures that extruded lens to decrease their height, because they are used in very thin drive for notebook computers. However, because of discordant and undesirable of forces that are supposed to happen in this design feature, subsidiary resonance such as rolling and pitching mode exert bad influence on actuator. In this paper, we presented force constituents to clarify the cause of subsidiary resonance and proposed new finite element analysis method to calculate force precisely, and performed frequency response analysis to evaluate characteristics of actuators. As a result, we could find out design parameters to diminish the influence of subsidiary resonance. Sample actuators designed with appropriate parameters were fabricated and put to practical tests. Comparing analysis with experimental results, we verified the accuracy of the analysis and the effectiveness of the method presented.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.484-489
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• 2003

In this paper, a single phase driven piezoelectric motor design was presented for linear motion Two metal/ceramic composite actuators, a piezoelectric ring which was bonded to a metal endcap from one side, were used as the active elements of this motor. The motor was composed of a piezoelectric ceramic, a metal ring which has 4 arms, and a guider. Motors with 30 [mm] and 35 [mm] diameter were studied by finite element analysis and experiments. As results, the maximum speed of motor was obtained at resonance frequency. When the applied voltage of the motor increased, the speed was increased. Also, bidirectional motion of the motor was achieved by combining two motors which have different resonance frequency. But the characteristics of bidirectional motion were not equaled, because of the problem of reproduction on the fabrication and the experiment. If present motor is used at the auto-zoom device of a camera, it will have much advantage. Because the direct linear motion can be achieved with a simple structure of motor and no gearbox of total system.

• Journal of the Korean Magnetic Resonance Society
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• v.19 no.1
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• pp.36-41
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• 2015

The causative agent of shigellosis, Shigella flexneri, is a Gram-negative anaerobic bacterial pathogen that causes one of the most infectious bacterial dysenteries in humans. It originates infection by invading cells of the colonic epithelium using a type III secretion system. Despite S. flexneri is closely linked with the human disease, structural study is very deficient. Here, we have initiated NMR study of SF1002 which is the uncharacterized protein from S. flexneri strain 5a M90T. Based on a series of triple resonance spectra, sequence-specific assignments of the backbone amide resonances of SF1002 could be completed. This NMR study would contribute to the structural genomics of S.flexneri.

• Transactions on Electrical and Electronic Materials
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• v.11 no.1
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• pp.37-41
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• 2010

The authors investigated the photoluminescence (PL) and the electron paramagnetic resonance (EPR) from an magnesium (Mg)-doped GaN thin film with a delta-doped layer. The regularly doped sample shows a PL peak at 2.776 eV for the as-grown sample, and the peak shifts to 2.904 eV and increases in intensity for the annealed sample. The delta-doped sample also shows the same PL peak as does the regularly doped sample. However, only the annealed delta-doped layer shows a sharp EPR with a small isotropic Lande g-factor, $g_{II}$, of 2.029. This resonance is attributed to the delta-doped layer, which forms a hole-bound Mg-N atomic structure instead of the $Mg_{Ga}-V_N$ defect complex, indicating that the delta-doped sample was not optically activated to form PL centers but was instead electrically activated to form a hole-bound state.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1391-1401
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• 2017

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1058-1070
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• 2017

This paper proposes a novel active damping scheme to suppress LCL-filter resonance with only grid-current feedback control in grid-connected voltage-source converters. The idea comes from the concept of the model reference adaptive control (MRAC). A detailed theoretical derivation is given, and the effectiveness of this method is explained based on its physical nature. According to the control structure of this method, the active damping compensator, which is essentially a second order resonant integrator (SORI) filter, provides an effective solution to damp LCL resonance and to eliminate the need for additional sensors. Compared with extra feedback methods, the cost and complexity are reduced. A straightforward tuning procedure for the active damping method has been presented. A stability analysis is illustrated in the discrete domain while considering a one-step delay. Finally, experimental results are presented to validate the analysis and to demonstrate the good performance of the proposed method.

• Progress in Medical Physics
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• v.31 no.4
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• pp.189-193
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• 2020

An MR-based attenuation correction (MRAC) map plays an important role in quantitative positron emission tomography (PET) image evaluation in PET/magnetic resonance imaging (MRI) systems. However, the MRAC map is affected by the magnetic field inhomogeneity of MRIs. This study aims to evaluate the characteristics of MRAC maps of physical phantoms on PET/MRI images. Phantom measurements were performed using the Siemens Biograph mMR. The modular type physical phantoms that provide assembly versatility for phantom construction were scanned in a four-channel Body Matrix coil. The MRAC map was generated using the two-point Dixon-based segmentation method for whole-body imaging. The modular phantoms were scanned in compact and non-compact assembly configurations. In addition, the phantoms were scanned repeatedly to generate MRAC maps. The acquired MRAC maps show differently assigned values for void areas. An incorrect assignment of a void area was shown on a locally compact space between phantoms. The assigned MRAC values were distorted using a wide field-of-view (FOV). The MRAC values also differed after repeated scans. However, the erroneous MRAC values appeared outside of phantom, except for a large FOV. The MRAC map of the phantom was affected by phantom configuration and the number of scans. A quantitative study using a phantom in a PET/MRI system should be performed after evaluation of the MRAC map characteristics.

• Journal of Veterinary Clinics
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• v.40 no.5
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• pp.370-374
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• 2023

Oral melanoma is the most common type of oral tumor in dogs. In this report, computed tomography (CT) and magnetic resonance imaging (MRI) were performed to diagnose a right oral pigmented mass in an 8-year-old dog. The oral mass appeared as a homogeneous soft tissue density parenchyma on pre-contrast CT images, and with heterogeneous enhancement on post-contrast images. Bone destruction of the right mandibular body around the mass and mild enlargement of the right mandibular lymph node were also found. On MRI, the bulky oral mass showed mixed hyperintensity and isointensity compared to the adjacent muscle, where irregular hyperintensity on T1-weighted images corresponded to hypointensity on the T2-weighted images. Based on the physical examinations and imaging results, melanoma was suspected and confirmed via fine-needle aspiration. These unique MRI signals were due to the high paramagnetic melanin content in the tumor, therefore MRI examination could be useful for diagnosis of melanoma.

• Journal of radiological science and technology
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• v.22 no.1
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• pp.27-33
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• 1999

The classification of herniated intervertebral lumbar disc type is clinically important, as treatment method may be slightly different according to the type of herniated intervertebral disc. When 450 patients who suffered from herniated intervertebral lumbar disc were tested with Magnetic Resonance Imaging (MRI) to find out the type of herniated disc, the following findings were given : 1. The age of the patients investigated ranged from 15 to 83, and their mean age was 40. 2. The male patients were twice as many as the female patients, since the ratio of males to females was 300 : 150. 3. 118 patients suffered from a single herniated disc, and 332 patients were attacked with multi-herniated disc. 4. The types of single herniated disc were a protrusion for 50 patients (40%) and an extrusion for 40 patients (34%). The part of being herniated was an intervertebral disc between $L_4-L_5$ for 95 patients(80%) and the same disc between $L_5-S_1$ for 22 patients(19%). 5. The types of multi : -herniated disc were an protrusion for 67 patients(20%) and an extrusion for 70 patients(21%). Besides, 90 patients (28%) were the case that protrusion and extrusion coexisted simultaneously. The parts of being herniated were $L_3-L_4,\;L_4-L_5$ and $L_5-S_1$ for 53 patients(16%), $L_3-L_4$ and $L_4-L_5$ for 57 patients(17%), and $L_4-L_5$ and $L_5-S_1$ for 139 patients(42%).

• Korean Journal of Cleft Lip And Palate
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• v.8 no.2
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• pp.53-62
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• 2005

Submucosal type cleft palate is a kind of cleft palate. A submucosal cleft may result in shortening of the anteroposterior dimension of the hard or soft palates or both. The increased distance along with the lack of muscle connection in the soft palate usually accounts for the lack of palatopharyngeal function in patients with submucosal cleft. Resonance disorders which is found in cleft patients show hypernasality or hyponasality. Many cases of submucosal type cleft palate patients visit our clinics due to hypernasality. In this study, resonance disorders was evaluated through nasalance test. Experimental group was composed of submucosal type cleft palate patients. The patients were treated by a so-called combined therapy, i.e., operation and speech training. To observe the changing pattern by surgery, nasalance test was carried out one time before surgery and three times after surgery. Nasometer II was used as a examination. The questionaire was filled with single vowels & diphthongs. The mean nasalance score of the child was significantly lower than that of the adult at every vowel. An early age at operation (under 10 years) was that a better functional result was achieved with patients. The mean nasalance score of /i/ was highest and that of /a/ was the lowest. The result of corrective surgery in selected cases has achieved improvement in all cases. Hypernasality has been consistently diminished. he operation.