• Journal of Power Electronics
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• v.15 no.1
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• pp.31-38
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• 2015

In this paper, a buck-boost type battery charger is developed for charging battery set with a lower voltage. This battery charger is configured by a rectifier circuit, an integrated boost/buck power converter and a switched capacitors circuit. A boost power converter and a buck power converter sharing a common power electronic switch are integrated to form the integrated boost/buck power converter. By controlling the common power electronic switch, the battery charger performs a hybrid constant-current/constant-voltage charging method and gets a high input power factor. Accordingly, both the power circuit and the control circuit of the developed battery charger are simplified. The switched capacitors circuit is applied to be the output of the boost converter and the input of the buck converter. The switched capacitors circuit can change its voltage according to the utility voltage so as to reduce the step-up voltage gain of the boost converter when the utility voltage is small. Hence, the power efficiency of a buck-boost type battery charger can be improved. Moreover, the step-down voltage gain of the buck power converter is reduced to increase the controllable range of the duty ratio for the common power electronic switch. A prototype is developed and tested to verify the performance of the proposed battery charger.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.599-608
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• 2011

FPS(friction pendulum system) is an isolation system which is possible to isolate structures from earthquake by pendulum characteristic. Natural frequencies of the structures could be determined by designing the radius of curvature of FPS. Thus, response vibration could be reduced by changing natural frequency of structures from FPS. But effective periods of recorded seismic wave were various and estimation of earthquake characteristic could be difficult. If effective periods of seismic wave correspond to natural frequency of structures with FPS, resonance can be occurred. Therefore, CFPBS(cone-type friction pendulum bearing system) was developed for controlling the acceleration and displacement of structure by the slope of friction surfaces. Structural natural frequency with CFPBS can be changed according to position of ball on the friction surface which was designed cone-type. Therefore, superstructures on CFPBS could be isolated from earthquake. In this study, seismic performance of CFPBS was evaluated by numerical analysis and shaking table test.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.70-74
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• 2004

There are many researches being in process to develop the information storage devices applying to the portable devices recently. Based on this need, the information storage devices have to be satisfied with the fast access time, the robustness of the system, high data transfer rate and lower media price. The total size of the drive must design to adapt the portable devices such as CF II card or PC II card size. This paper proposes the swing arm type actuator to insert the designed actuator in the drive of the CF II size. Hereafter the research will be going on to be suitable to the physical standard and design the focus magnetic circuit newly. The swing arm type actuator including this circuit is designed to have the dynamic characteristic satisfying the mechanical specification as well as the BD 1x. Finally, the adaptability to the portable devices was demonstrated by the finite element analysis and optimization of structural part.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.722-725
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• 2004

Voltage step-down characteristics in Ring/Dot type piezoelectric transformer were examined as a function of the area of input electrode when the area of output electrode is fixed. The effects of driving frequency and load resistance on the voltage step-down characteristics were also examined. Voltage gain was greatly dependent on the driving frequency and load resistance, and showed a maximum gain at resonance frequency of the step-down transformer. The frequency where the maximum output voltage appears increased about 0.2% as the load resistance increased from 10 to $150\Omega$. As the area of input electrode increased, the voltage gain and the efficiency of the transformer increased. Frequency dependence of efficiency of the step-down transformer revealed a similar tendency with the voltage gain curves. The maximum efficiency remarked 94% when the input voltage and the load resistance were 20 $V_{PP}$ and $120\Omega$, respectively.

• Journal of Genetic Medicine
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• v.18 no.2
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• pp.137-141
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• 2021

Genetic causes of developmental and epileptic encephalopathy (DEE) have been rapidly uncovered from mid-2010s. The mutations of gene enconding calcium channel, voltage-dependent, P/Q type, alpha 1A subunit (CACNA1A) are recently detected in DEE, which gene is already known well in familial hemiplegic migrine type 1 or episodic ataxia type 2. Ketogenic diet therapy (KDT) is effective in some DEE, which data is short in CACNA1A encephalopathy. A 3-month-old male with global developmental delay and multidrug-resistant focal seizures was diagnosed as epilepsy of infancy with migrating focal seizures (EIMFS). Brain magnetic resonance imaging and metabolic screening were all normal. Whole exome sequencing revealed two variants of CACNA1A: c.899A>C, and c.2808del that is from his mother. His seizures disappeared within 3 days whenever on KDT, which recurred without it. To our knowledge, this rare case of EIMFS with novel mutations of CACNA1A, is the first report in CACNA1A encephalopathy becoming seizure-free on KDT.

• Journal of the Korean Society of Radiology
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• v.82 no.5
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• pp.1321-1327
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• 2021

Neurofibromatosis type 1 (NF1) is a relatively common inherited disorder characterized by the formation of neurofibromas, pigmentary abnormalities of the skin, Lisch nodules of the iris, and skeletal abnormalities. Multiple cutaneous neurofibromas are benign nerve sheath tumors and the main manifestation of NF1. Cardiac neurofibroma associated with NF1 is very rare, and few cases have been reported in the literature. Herein, we present the CT and MRI findings of a surgically confirmed left ventricular neurofibroma in a 32-year-old female with NF1.

• Dementia and Neurocognitive Disorders
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• v.22 no.3
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• pp.87-99
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• 2023

Background and Purpose: According to the amyloid cascade hypothesis, fibrillary amyloid-beta load in the brain causes Alzheimer's disease (AD) with toxic effects. Recently, perivascular spaces (PVSs), fluid-filled cavities around small penetrating arterioles and venules in the brain, and the glymphatic system relationship with type 2 diabetes mellitus (DM2) and AD has been an important research topic from a physiopathological point of view. There are two types of PVSs that are associated with sporadic atherosclerosis and cerebral amyloid angiopathy. In this study, we evaluated the relationship between the number and localization of enlarged PVSs in AD. Methods: A total of 254 patients with AD and 125 healthy controls were included in this study All the patients were evaluated with neurological and cognitive examinations and magnetic resonance imaging (MRI). PVSs on MRI were graded by recording their number and location. The study was a retrospective study. Results: In our study, the number of white matter convexity-central semiovale localized PVSs was higher in patients than in the control group. In addition, the number of PVSs in this localization score was higher in patients with DM2. Cerebral PVS counts were higher in patients with AD than in the control group. Conclusions: These results suggest the important role of cerebral amyloid angiopathy, one of the vascular risk factors, and the glymphatic system in the pathogenesis of AD. In addition, the results of our study suggest that the evaluation of PVSs levels, especially at the (centrum semiovale), using imaging studies in AD is a potential diagnostic option.

• Journal of the Korean Society of Radiology
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• v.81 no.1
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• pp.135-146
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• 2020

Purpose To describe magnetic resonance imaging (MRI) findings in 10 cases of Toxocara canis myelitis and to analyze these findings to aid in the diagnosis of this condition. Materials and Methods From June 2015 to March 2018, we retrospectively analyzed the electronic medical records and MR images of patients who were diagnosed with Toxocara canis myelitis. The analysis of the MR images was based on a discussion between an experienced spinal radiologist and a radiology resident. Results This study classified MRI findings into the following two types. Type 1 was defined as central and diffuse T2 high signal intensity on the axial plane, which was observed in 50% of all cases. All lesions showed avid enhancement, mostly in the posterolateral or posterior region (4 cases, 80%). Type 2 was defined as wedge-shaped or focal T2 high signal intensity in the posterolateral or posterior region and corresponded to the remaining 50% of the cases. In this case, the extent of the lesion was relatively small and contrast enhancement was observed in only one case. Conclusion This study revealed that various imaging findings could be observed in cases of Toxocara canis myelitis, and the findings were classified into two types.

• Clinics in Shoulder and Elbow
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• v.18 no.4
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• pp.197-205
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• 2015

Background: The purpose of this study was to evaluate the postoperative magnetic resonance imaging (MRI) results of minimal-tying (one medial-row tie among 4 medial-row sutures) on the medial-row in double-row suture-bridge configuration ($2{\times}2$ anchor with $4{\times}4$ suture stands). Methods: From 2011 March to 2012 July, 79 patients underwent arthroscopic rotator cuff repair using $2{\times}2$ anchor double-row configuration. The mean age was 61.3 years (range, 31-81 years). Two double-loaded suture anchors were used for medial-row. Four medial-row stitches were made with only one medial-row knot-tying (the most anterior suture). Lateral-row was secured using the conventional suture-bridge anchor technique; all 4 strands were used for each anchor. Repair integrity was evaluated with MRI at mean 6.2 months postoperatively. Retear and the pattern of retear, change of fatty infiltration, and muscle atrophy of supraspinatus were evaluated using pre- and postoperative MRI. Results: Repaired tendon integrity was 38 for type I, 30 for type II, 6 for type III, 4 for type IV, and 1 for type V, according to Sugaya classification. Considering type IV/V as retear, the rate was 6.3% (5 out of 79 patients). Medial cuff failure was observed in 4 patients. Fatty atrophy of supraspinatus was significantly improved postoperatively according to Goutallier grading (p=0.01). The level of muscle atrophy of supraspinatus was not changed significantly after surgery. Conclusions: Minimal tying technique with suture configuration of four-by-four strand double-row suture-bridge yielded a lower retear rate (6.3%) in medium to large rotator cuff tears.

• Journal of Sensor Science and Technology
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• v.27 no.2
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• pp.112-117
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• 2018

In this study, a bender-type piezoelectric energy harvester was fabricated and evaluated to compensate for the disadvantages of high-power generation only in the resonance frequency range of a piezoelectric harvester using a piezoelectric cantilever. The generated power was investigated according to various changes in the vibration environment. Compared with the piezoelectric cantilever module, the bender-type piezoelectric module showed a larger number of peak voltages. The primary peak voltage shifted toward the low frequency when the spring was coupled to the bender-type piezoelectric module. The harvester of the three bender-type modules had a vibration frequency exceeding 1 mW in the 34-45 Hz range and generated 3.112 mW of power at the vibration frequency of 38 Hz. The harvester of the six bender-type modules had a vibration frequency exceeding 1 mW in the 31-45 Hz range and generated 3.081 mW of power at the vibration frequency of 35 Hz.