• Journal of Korean Neurosurgical Society
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• 제51권4호
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• pp.219-221
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• 2012

A 20-month-old boy presented with a intraparenchymal mass in the right frontoparietal area manifesting as complex partial seizure, secondary generalization and left hemiparesis. Magnetic resonance images (MRI) of the brain showed inhomogeneously enhancing mass in the right frontoparietal area which has irregular margin and perilesional edema. Based on the radiological findings, a preoperative diagnosis was an intraaxial tumor, such as pilocytic astrocytoma or dysembryoplastic neuroepithelial tumor. The patient underwent a surgery including frontal craniotomy. The tumor had a partially extreme adherence to the surrounding brain tissue but it showed no dural attachment. Gross-total resection of the tumor was achieved. Postoperative follow-up computed tomography scans showed no residual tumor. The pathological findings confirmed the tumor as a WHO grade I meningioma, transitional type. Nine months after the surgery, follow-up brain MRI showed no recurrence of the tumor, porencephaly in site where the tumor was resected; the patient's symptoms had fully recovered. We report the case of a meningioma in a 20-month-old boy.

• Journal of Korean Neurosurgical Society
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• 제47권6호
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• pp.464-466
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• 2010

A 59-year-old female presented with headache and dizziness for one year. Magnetic resonance imaging revealed a $52{\times}28$ mm, wellcircumscribed, homogenously enhancing mass lesion without dural attachment located in the left lateral cerebellomedullary cistern. The tumor was excised, and a histological diagnosis was a mixed pattern meningioma of meningothelial and fibroblastic type. A meningioma in the posterior fossa without dural attachment is quite rare. We report a rare case of lateral cerebellomedullary cistern meningioma without dural attachment with literature review.

• 생물정신의학
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• 제8권2호
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• pp.233-238
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• 2001

The routine interictal electroencephalogram(EEG) continues to play an important role in the diagnosis and treatment of epilepsy. The clinical investigation of brain disease in the last decade has been marked by dramatic advances in functional imaging, magnetic resonance scanning and digitized EEG. Epilepsy is a disorder of electrical hyperirritability of cerebral cortex and the interictal EEG remains the most convenient means available to demonstrate cortical hyperirritability. The sensitivity and specificity of the EEG in the diagnosis of epilepsy have been disputed. In this review, the type of EEG findings in epilepsy are reviewed and the sensitivity and specificity of interictal epileptiform discharge are discussed. And also the role of EEG in various clinical situations are summarized.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.272-277
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• 2003

This paper reports the fluid flow and heat transfer around a module cooled by forced air flow generated by a piezoelectric(PZT) cooling fan. A flexible PZT fan with distortion in a fluid transport system of comparatively simple structure which was mounted on a PCB in a parallel-plate channel($450{\times}80{\times}700mm^3$) accelerates surrounding fluid locally. Input voltages of 20-100V and a resonance frequency of 23Hz were used to vibrate the cooling fan. Input power to the module was 4W. The cooling effect using a PZT fan was larger than that of free convection. Fluid flow around the module were visualized by using PIV system. The temperature distribution around heated module were visualized by using liquid crystal film(LCF). We found that the flow type was y-shaped and the cooling effect was increased by the wake generated by a piezoelectric cooling fan.

• Journal of Power Electronics
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• 제2권3호
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• pp.189-198
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• 2002

New concept of energy recovery for plasma display panel (PDP) Is proposed. Different from conventional LC resonant sustaining drivers, the current built up before inverting the polarity of the panel electrodes is utilized to change the panel Polarity together with energy Previously charged in Panel capacitance. This operation Provides zero -voltage-switching of switches and reduction of EMI by rejecting the surge current when the sustain switches are turned on. The build-up current helps to reduce transition time of panel polarity and may produce more stable light waveforms. This method shows a desirable characteristic that the circuit loss is similar to that of series resonant type energy recovery circuit which is very effective method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.569-574
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• 1998

This paper presents a two-paralleled 4 quadrant DC chopper type PWM power conversion circuit in order to generate a gradient magnetic field in the Magnetic Resonance Imaging (MRI) system. This power amplifier is connected in parallel with the conventional 4-quadrant DC chopper using IGBTs at their inputs/outputs to realize further high-power density, high speed current tracking control, and to get a low switching ripple amplitude in a controlled current in the Gradient Coils (GCs). Moreover, the power conversion circuit has to realize quick rise/fall response characteristics in proportion to various target currents in GCs. It is proposed in this paper that a unique control scheme can achieve the above objective. DSP-based control systems realize a high control facility and accuracy. It is proved that the new control system will greatly enlarge the diagnostic target and improve the image quality of MRI.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.250-253
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• 2007

본 논문에서는 플라즈마 디스플레이 패널의 구동시 발생되는 전력손실을 최소화시키기 위한 에너지 회수기능을 가지는 새로운 서스테인 구동회로를 제안한다. 제안된 회로는 패널의 등가 커패시턴스와 외부 인덕터의 직렬공진을 이용하여 패널에 에너지를 공급/회수하게 된다. 제안된 에너지 회수 회로는 기존에 널리 이용되는 에너지 회수와 비교하여 저가형 구조로 구성이 가능하며 우수한 에너지 회수 성능을 가진다. 7.5인치 AC-PDP를 이용한 실험을 통해 제안된 회로의 타당성을 검증한다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.290-293
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• 2002

For small capacity rectifier circuits such as these for consumer electronics and appliances, capacitor input type rectifier circuits are generally used. Consequently, various harmonics generated within the power system become a serious problem. Various studies of this effect have been presented previously. However, most of these employ switching devices, such as FETs and the like. The absence of switching devices makes systems more tolerant to over-load, and brings low radio noise benefits. We propose a power factor connection scheme using a LC resonant in commercial frequency without switching devices. In this method, It makes a sinusoidal wave by widening conduction period using the current resonance in commercial frequency, Hence, the harmonic characteristics can be significantly improved, where the lower order harmonics, such as the fifth and seventh orders are much reduced. The result are confirmed by the theoretical and experimental implementations.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.58-60
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• 2002

In this paper the bending vibration analysis of stator for a ring type ultrasonic motor is described. Considering the electromechanical coupling effect, the concepts of generalized stress and strain are explained in detail using the generalized piezoelectric equations, which is the relationship between generalized stress and strain, the differential motion equation were derived. The vibration modes and resonance frequencies of the stator were calculated using the finite element code ATILA.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.1059-1066
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• 2003

A power generation system are proposed to convert ambient mechanical vibration into electrical energy using cantilever-type piezoelectric materials. The vibration-based power device can be used for self-powered systems without batteries. This paper presents the theoretical analysis for the coupled equations of piezoelectric and structural motions and investigates the dynamic characteristics of the self-power system using transfer function method. The theoretical model is verified by the finite element analysis of the resonance frequency, the dynamic response of the structure and the sensor sensibility. Experimental results measured using a prototype system agrees with the theoretical predictions. The system is shown to produce 2.53㎼ in average. Finally, we perform the optimal design for system variables to maximize output power.