• 한국자동차공학회논문집
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• 제2권3호
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• pp.62-74
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• 1994

This paper addresses on the model synthesis and performance analysis of an engine mount featuring electro-rheological(ER) fluids which undergo a phase change when subjected to electric fields. A novel type of ER fluid-filled engine mount is devised and its hydraulic model is constructed. An equivalent mechanical model is subsequently obtained from the governing equation of the hydraulic model. The model parameters associated with the ER fluids are distilled from experimental investigations on the Bingham properties of the fluids. The distilled data are then incorporated into the governing model to undertake feasible work through computer simulations,. It is shown that the proposed engine mount has an inherent capability of controlling both the damping force and the resonance frequency. Other superior performance characteristics accrued from the proposed methodology are also evaluated.

• The Journal of the Acoustical Society of Korea
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• 제16권2E호
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• pp.21-26
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• 1997

We propose to use transverse waves instead of longitudinal waves in a scanning tomographic acoustic microscope (STAM) and new type of multiple-transducer with the functions of muliple-angle and multiple-frequency tomography. Proposed multiple-transducer scheme has three insonification angles and three resonance frequencies in order to operate in the transverse wave mode and multiple-angle and multiple frequency tomography for the STAM. In order to evaluate the performance of proposed transducer scheme we have simulated tomographic reconstruction with back-and-forth propagation(BFP) algorithm. Simulation results showed proposed multiple-transducer scheme is capable of obtaining good resolution with transverse wave mode and multiple-frequency tomography. It is also showed that proposed scheme is an efficient rotation scheme by proportion to the number of projections.

• Journal of Korean Neurosurgical Society
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• 제42권3호
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• pp.220-223
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• 2007

We report a case of dural marginal zone lymphoma which showed the usual radiological findings resembling meningioma. A 59-year-old woman presented with headache. Initial computed tomography and magnetic resonance images showed a frontal convexity meningioma. The patient underwent a craniotomy and subtotal (simpson grade II) resection of tumor was done. Pathological examination confirmed an extranodal marginal zone B-cell lymphoma of Mucosa-Associated Lymphoid Tissue (MALT). The lesion was composed of a lymphoid mass with irregularly shaped follicles surrounded by many monomorphic small lymphocytes and a stained marginal zone for B-cell markers CD20 and CD29a. The natural history of primary CNS lymphoma and MALT type lymphoma are different. B-cell MALT lymphoma can mimic meningioma in its radiological features. Accordingly, MALT lymphoma of the CNS must be considered in the differential diagnosis of meningioma.

• Journal of Korean Neurosurgical Society
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• 제52권2호
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• pp.161-163
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• 2012

Spinal angiolipomas are rare lesions usually found in the epidural space of the thoracic spine. The infiltrating type of spinal angiolipomas is extremely rare. This report presents the case and reviews the related literature. A 58-year-old man was presented with a 7-month history of progressive weakness and sensory change of lower extremities. Magnetic resonance images showed a well-enhanced mass infiltrating the vertebral foramen at the T4-5 level. Resection of the tumor was performed. Histological study revealed the tumor as an angiolipoma. The patient was relieved from symptoms after tumor resection.

• 한국전기전자재료학회논문지
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• 제13권12호
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• pp.1025-1031
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• 2000

An ultrasonic linear motors consist of a slider and an ultrasonic vibrator which generates an elliptical oscillations. The ultrasonic linear motors mainly consist of an ultrasonic vibrator which generates elliptical oscillations. The ultrasonic linear motor fabricated in this paper was the use of the 1st longitudinal(L1) and 4th bending vibrations(B4). In order to low driving voltage and improve the life time of the ultrasonic motor, we used stacked piezoceramics. Stacked piezoceramics are adhered to aluminum elastic material. The finite element method was used to optimize dimension of ultrasonic vibrator and direction of vibratory displacement. As a result of estimating the characteristics of the ultrasonic linear motor, no-load velocity was 0.204[m/s] when applied voltage was 70[ $V_{rms}$] in resonance frequency.y.

• Journal of Korean Neurosurgical Society
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• 제49권2호
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• pp.124-127
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• 2011

A 43-year-old male presenting with headache and dizziness underwent craniotomy and gross total resection of an extraaxial tumor was achieved via left occipital interhemispheric approach. The tumor was diagnosed as papillary meningioma arising from the left falcotentorium with such pathologic characteristics of bronchoalveolar adenocarcinoma. At postoperative day 40, he developed generalized tonic clonic seizure and then progressed to a status epilepticus pattern. Brain magnetic resonance imaging showed irregular leptomeningeal enhancement with a significant peritumoral area. Through a cerebrospinal fluid (CSF) study, we identified the meningioma cells of the papillary type from the CSF. At the postoperative day 60, he fell into semicomatose state, and the computed tomography imaging showed low density on both cerebral hemispheres, except the basal ganglia and cerebellum, with overall brain swelling and an increased intracranial pressure. He died on the following day. We experienced a rare case of a papillary meningioma with leptomeningeal seeding.

• 산업기술연구
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• 제28권B호
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• pp.117-122
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• 2008

This paper presents the conductance model at high frequency of the Ceramic Metal Halide Lamp and the designing method of the electronic ballast with the LCC resonant tank type by using that model. Conductance model is based on a physical phenomenon in the discharge tube of the lamp and model constants of conductance model are obtained by Least Squares Method. After equivalent impedances are determined by the conductance model, The LCC resonance tank is designed by using the equation of the lamp power. Simulation result using PSpice software and experimental results show that the conductance model in this paper is very useful to design the electronic ballast at high frequency for the Ceramic Metal Halide Lamps.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.79-83
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• 2001

A cone-shaped active magnetic bearing spindle system for high speed internal grinding is designed and tested. The cone-shaped AMB system consists of only 4 couples of magnet, it can be smaller and lighter than conventional radial-axial-type AMB system. In this paper, the cone-shaped electromagnets are designed by magnetic circuit theory, and de-coupled direct feedback PID controller is applied to control the coupled magnetic bearings. The designed cone-shaped AMB spindle system is built and constructed with a digital control system, and tested its stbility and dynamic performances. As the results of the tests, this spindle runs up to 40,000 rpm with about 5 ${\mu}{\textrm}{m}$ of runout, and the AMB system provides high damping ratio eliminating overshoot and resonance speed.

• 한국초전도ㆍ저온공학회논문지
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• 제3권2호
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• pp.49-54
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• 2001

The purpose of this study is to analyze the characteristics of the linear compressor for Stirling refrigerator. To ensure high performance and long life of the FPFD(Free Piston. Free Displacer) type Stirling refrigerator, the operating parameters of the linear compressor should be optimized. The experimental results show that the operating frequency of the linear compressor has significant effect on the input power characteristics. and that the compressor with higher charging pressure of working fluid has high pressure ratio. For the high performance of the linear compressor. compressor should be operated at the resonance frequency with respect to the given charging pressure.

• 한국통신학회논문지
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• 제21권5호
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• pp.1304-1316
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• 1996

In this paper, A VCO(Voltage Controlled Oscillator) in use of clock recovery/data regeneration circuit for 10 Gbps fiber optic receivers was developed. The improved hair-pin resonator with a parallel coupled lines, which has been applied to microstrip filters, was used as a resonance part. As a frequcncy tuning device by substituting 3-terminalMESFET vaaractor for varactor diode, an MMIC manufacturing process will be simplified. Since a hair-pin resonator is planar type compared to the dielectric resonator and has a relatively flat reactance verus frequency, it will be favorable to apply a hair-pin resonator to an MMIC, in addition wideband frequency tuning range is able to be obtained.