• 한국소음진동공학회논문집
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• 제20권1호
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• pp.58-65
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• 2010

This paper presents dynamic modeling and control analysis of a military vehicle suspension featuring MR valve structure. Firstly, the dynamic model of the suspension system which is included gas spring, MR valve and gas chamber is established with respect to the disturbance. Secondly, the friction model of the suspension system is derived by considering experiment result of the MR suspension system. And then, response characteristics of the damping force with respect to the magnetic field and friction force with the proposed friction model are provided to show the feasibility of practical application. In addition, control performance of the proposed MR suspension system is evaluated with quarter vehicle.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 추계학술대회 논문집 학회본부
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• pp.366-369
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• 1991

A nonlinear controller based on feedback linearization method is proposed for an electromagnetic suspension system. After exactly linearizing the system with nonlinear feedback, linear control technique is applied. Modeling of stagger typed magnet is introduced and controlled for not only levitation, but guidance. By the feedback linearization, the nonlinear, MIMO system is linearized and decoupled, so we can use linear control law. The simulation of this system control skim is demonstrated. Robustness properties of the proposed controller with respect to the load variations and external disturbance is also analyzed for a multi input multi output system. In this properties, the boundary of variation is proposed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1993년도 한국자동제어학술회의논문집(국제학술편); Seoul National University, Seoul; 20-22 Oct. 1993
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• pp.321-326
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• 1993

A gain scheduling approach for the suspension control of a nonlinear MAGLEV System is presented. We show that this technique is ver useful for improving not only performance to the operational disturbances originating aerodynamic force but also robustness to the uncertainty of payload. As a scheduling variable, even though the external disturbance need to be estimated in real time, but the additive measurement is not required to do it. Some simulations show that the gain scheduling control system performs very well comparing with other method using a nonlinear feedback linearization or a fixed gain linear feedback.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.763-766
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• 2006

The principal of a Maglev train is that floats on a magnetic field and is propelled by a linear induction motor. One of advantages is that it generates less noise compared to the wheel-on-rail train, because there are no wheels running along the rail. However, noises due to aero-dynamic disturbance and electrical system such as VVVF inverter and SLIM still occur. In this study, the Maglev cabin noises are measured during running and zero speed conditions. Pass-by noise measurements are performed to obtain outside noise during the operation of the train on the test tract. Data include a single microphone measurement as well as microphone array measurements. The array data are useful for sound source localization and more detailed noise reduction planning.

• Journal of Korean Neurosurgical Society
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• 제48권2호
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• pp.153-156
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• 2010

The authors present a rare case of clear cell ependymoma that developed in the cauda equina. A 54-year-old man was admitted to hospital with intermittent lower back pain. A neurological examination conducted on admission revealed no sensory or motor disturbance. Deep tendon reflexes in both lower extremities were normal. Magnetic resonance images demonstrated a 1.0 cm-sized intradural mass at the filum terminale. Gross total resection was performed via total laminectomy of L1 and L2. The tumor was confirmed to be clear cell ependymoma by histopathologic examination. His symptom was relieved after surgery.

• Journal of Korean Neurosurgical Society
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• 제41권3호
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• pp.190-192
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• 2007

Rarely, downbeat nystagmus can occur due to compression of the lower brainstem by the ectatic vertebral artery and be resolved by microvascular decompression. We present a case of a 67-year-old man with downbeat nystagmus associated with brainstem compression by ectatic vertebral artery. He presented with oscillopsia and vertigo. When he turned his head upward, his symptoms were aggravated and a gait disturbance occurred. Magnetic resonance imaging and computed tomographic angiography demonstrated compression of the medulla oblongata by the left ectatic vertebral artery and other medical causes of downbeat nystagmus were ruled out. Retromastoid craniotomy was performed and after lifting the vertebral artery off the medulla, a trough-shaped indentation in the lower brainstem was identified. The ectatic vertebral artery was repositioned and a Teflon was inserted between the brainstem and the ectatic vertebral artery. Postoperatively, downbeat nystagmus had disappeared.

• 전기학회논문지
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• 제58권3호
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• pp.598-604
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• 2009

This paper proposes a vehicle detector with an anisotropic magnetoresistive (AMR) sensor and addresses experimental results to show the detector's performance. The detector consists of an AMR sensor and mechanical and electronic apparatuses. The AMR sensor, composed of four magnetoresistors, senses disturbance of the earth's magnetic field caused by a vehicle moving over the sensor and then produces an output indicative of the moving vehicle. This paper verifies performance of the detector on the basis of experimental results obtained from the field tests carried under the two traffic conditions on local highways in Korea. First, I show the vehicle counting performance on a low speed congested highway by comparing the vehicle counts measured by the detector with the exact counts. Second, both vehicle counts and average speeds calculated from the measured point-occupancy on another continuously free running highway are compared with the reference values obtained from a loop detector which has two independent loop coils, where I have used several performance indices including mean absolute percentage error (MAPE) to show the performance consistency between the two types of detectors.

• Journal of Korean Neurosurgical Society
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• 제41권1호
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• pp.39-42
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• 2007

Primary intracranial melanoma is uncommon. These tumors most commonly occur at the temporal lobe, cerebellum and cerebellopontine angle. We report a case of intracranial malignant melanoma of the occipital lobe in a 60-year-old man who presented with headache and visual disturbance. The mass showed hyperintensity on T1-weighted images and hypointensity on T2-weighted magnetic resonance images. He underwent gross total removal of tumor and received radiotherapy. Follow-up imaging studios showed neither recurrence nor any signs of residual disease for 4 months.

• Journal of Korean Neurosurgical Society
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• 제51권2호
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• pp.94-97
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• 2012

Tumors that metastasize to the pituitary gland are unusual, and are typically seen in elderly patients with diffuse malignant disease. The most common metastases to the pituitary are from primary breast and lung cancers. We report a 65-year-old woman with pituitary metastasis from breast cancer who presented with recent-onset left progressive deterioration of visual acuity and visual field. The clinical diagnosis was made after brain and sellar magnetic resonance imaging showed a large sellar mass compressing the optic chiasm and invading the pituitary stalk. An otorhinolaryngology and neurosurgery team removed the tumor via a transsphenoidal approach, and this procedure obtained symptomatic relief. Postoperatively, metastasis from breast invasive ductal adenocarcinoma was confirmed histologically. We report this unusual case with a review of the relevant literature.

• Journal of Korean Neurosurgical Society
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• 제43권3호
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• pp.165-168
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• 2008

The location of ganglioglioma (GG) within the infratentorial compartment is unusual. The authors report a rare case of GG in the cerebellar hemisphere. A 12-year-old boy suffered from headache and gait disturbance. Neuroimaging studies demonstrated a large enhancing cerebellar mass with cystic components compressing the forth ventricle. After complete resection of the tumor, the patient became symptom free. Histological examination on the tumor disclosed glial cells and dysplastic ganglion cells. Although it is a rare tumor, in the appropriate clinical setting, a GG should be considered in the presence of a cerebellar mass with both solid and cystic components on magnetic resonance images in children.