• Journal of Korean Neurosurgical Society
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• v.53 no.2
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• pp.89-95
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• 2013

Objective : Similar to back pain, neck pain has recently shown to have increasing prevalence. Magnetic resonance imaging (MRI) is useful in identifying the causes of neck pain. However, MRI shows not only pathological lesions but also physiological changes at the same time, and there are few Korean data. The authors have attempted to analyze the prevalence of disc degeneration in highly selective asymptomatic Korean subjects using MRI. Methods : We performed 3 T MRI sagittal scans from C2 to T1 on 102 asymptomatic subjects (50 men and 52 women) who visited our hospital between the ages of 14 and 82 years (mean age 46.3 years). All images were read independently by three observers (two neurosurgeons and one neuroradiologist) who were not given any information about the subjects. We classified grading for cervical disc herniation (HN), annular fissure (AF), and nucleus degeneration (ND), using disc degeneration classification. Results : The prevalence of HN, AF, and ND were 81.0%, 85.9%, and 95.4%, respectively. High prevalence of HN, AF, and ND was shown compared to previous literature. Conclusion : In asymptomatic Korean subjects, the abnormal findings of 3 T MRI showed a high prevalence in HN, AF, and ND. Several factors might play important roles in these results, such as population-specific characters, MRI field strength, and disc degeneration grading system.

• Korean Journal of Cognitive Science
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• v.18 no.1
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• pp.69-90
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• 2007

The purpose of the present research was to examine whether the visual system importantly use binocular disparity information in color-motion binding. Wu, Kanai and Shimojo (2004) reported an illusory color-motion binding which was observed in the peripheral visual area when observers fixated on the central area of visual stimulus. We have found that illusory rotor-motion binding was not observed at the situation where binocular disparity was available but was where it was not available. These results imply that the visual system uses binocular disparity information when it binds rotor and motion and that the binding process occurs after binocular disparity information is processed.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1075-1085
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• 2018

To deal with the operation performance degradation of permanent magnet synchronous machine (PMSM) drives with uncertainties and unmodeled dynamics, this paper presents a finite-time nonlinear disturbance observer (FTNDO) based discretized integral sliding mode (DISM) composite control scheme. Based on the reaching-law approach, a DISM speed controller featuring a superior dynamic quality and global robustness against disturbances is constructed. This controller can avoid the reaching phase and overlarge control action. In addition, a sliding mode differentiator based FTNDO is devised and extended to the discrete-time domain for disturbance estimation. The attractive features of the FTNDO are that it can provide a finite-time converging estimation and alleviate the chattering effect in conventional sliding mode observers, while retaining robustness to parameter variations. By feeding the estimate forward to the pre-stage DISM controller, both disturbances and chattering can be significantly suppressed. Moreover, considering the estimation error of a FTNDO caused by discrete sampling, a stability analysis of the composite controller is discussed. Experimental results validate the superiority of the presented scheme.

• Journal of the korean society of oceanography
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• v.38 no.3
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• pp.101-110
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• 2003

We made intensive observations on the coastal upwelling off the coast of the southern East Sea from June to August in 2001. The upwelling exhibited a weekly waxing and waning. The coastal upwelling of the year 2001 was characterized by abrupt outbreaks and the small local scale. Upwelling occurred more frequently off the coast of Ulsan and Gampo as reported by the earlier observers. The spread of freshly upwelled colder water was varied by each upwelling event. Generally cold waters were carried away northeastward off Pohang province. The upwelled cold waters were saltier than the resident surface waters. The pH and salinity-normalized alkalinity support the idea that the upwelled waters originate from the interior of the East Sea. The extraordinarily high concentration of dissolved oxygen suggests that the upwelled waters are closely connected to the southward flowing North Korea Cold Current. Although a lower primary productivity was reported for the upwelling region, underway surface fluorescence measurement revealed that the recently upwelled waters supported up to an order of magnitude higher algal biomass than the ambient waters. Because thermohaline circulation of the East Sea is so vigorous, with an estimated time scale of less than one hundred years, that the coastal upwelling should be considered not as an anomaly but as a regular component of a circulatory system. A quantitative understanding of upwelling seems to be a key to elucidate material cycling and the associated biological production in the East Sea.

• The Journal of Korean Medicine
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• v.21 no.4
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• pp.227-235
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• 2000

Background and Purpose : Medical and Neurological complications in patients with acute stroke may affect their prognosis including death rate, function and admission period. Some of these complications may be preventable. But few data exist regarding complications occurring in the first weeks. So we sought to observe the type, timing, and frequency of complications in hospitalized patients after stroke. Methods : We retrospectively examined the case notes of patients admitted in Won Kwang Oriental Medical Hospital after stroke. Two observers inspected the case notes using predifined diagnostic criteria and recorded the type, timing, and frequency of complications that occurred during the inpatient period. Results : Complications were recorded in 43 patients(82.7%). The most common medical complications were constipation(25.0%) and shoulder pain(21.2%). The most frequent serious medical problems were pulmonary infection(9.6%) and UTI(7.7%). The most common neurological complications were insomnia(34.6%) and dysphagia(23.7%). The most frequent serious medical problem was mental deterioration(7.7%). Conclusion : Complications after acute stroke are common. There were more medical complications than neurological complications. So we should compile much knowledge about medical complications and treat them actively. The differences between our study and previous studies are attributable to the different methods including patient selection and diagnostic criteria.

• Journal of Broadcast Engineering
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• v.14 no.2
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• pp.210-218
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• 2009

The 3D shape as well as the depth of an object presented on a 3D display is perceptually distorted depending on viewing distance. It is quite undesirable that different observers perceive different depth and shape from an object displayed on a 3D monitor. To resolve the problem of perceptual distortion of 3D depth and shape, the degree of the distortion should be measured appropriately. As a basis for resolving these problems, the present research suggests an instrument for measuring the degree of the perceptual distortion of 3D depth and shape.

• Smart Structures and Systems
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• v.7 no.2
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• pp.103-116
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• 2011

This paper is concerned with the trajectory tracking and vibration suppression of a single-link flexible arm by using piezoelectric materials. The dynamics of a single flexible arm with PZT patches as sensor and actuator is derived using extended Hamilton's principle. Resulting equations show that the coupled beam dynamics including beam vibration and its rigid in-plane rotation takes place in two different time scales. By using singular perturbation theory, the system dynamics is divided into two subsystems. Then, a composite control scheme is elaborated that makes the orientation of the arm track a desired trajectory while suppressing its vibration. The proposed controller has two parts: one is a tracking controller designed for the slow (rigid) subsystem, and the other one is a stabilizing controller for the fast (flexible) subsystem. The outputs considered for the system are angular position of the hub and voltage of the sensor mounted on the structure. To avoid requiring further measurements of beam vibration and also angular velocity of the hub for the fast and slow control laws, respectively, two sliding mode observers for estimating the unknown states are also designed.

• Journal of Korean Neurosurgical Society
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• v.52 no.2
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• pp.103-106
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• 2012

Objective : To prospectively assess the diagnostic and clinical value of a new technique (3-tesla magnetic resonance myelography, 3T MRM) as compared to computed tomographic discography (disco-CT) in patients with far lateral disc herniation. Methods : We evaluated 3T MRM and disco-CT of 25 patients, whom we suspected of suffering from far lateral disc herniation. Using an assessment scale, 4 observers examined independently both 3T MRM and disco-CT images. We analyzed observer agreement and the accentuation of each image. Results : We found complete matching, and observer agreement, between high resolution images of 3T MRM and disco-CT for diagnosing far lateral disc herniation. Conclusion : We think noninvasive 3T MRM is an appropriate diagnostic tool for far lateral disc herniation as compared to disco-CT.

• Journal of Korean Neurosurgical Society
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• v.53 no.1
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• pp.31-38
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• 2013

Objective : Asymptomatic patients show high degeneration prevalence at lumbar disc in previous literatures. Unfortunately, there are few Korean data, so the authors attempted to analyze the prevalence of disc degeneration in highly selective asymptomatic Korean subjects using MRI. Methods : We performed 3 T MRI sagittal scans from T12 to S1 on 102 asymptomatic subjects (50 men and 52 women) who visited our hospital between the ages of 14 and 82 years (mean age 46.3 years). All images were read independently by three observers (two neurosurgeons and one neuroradiologist) who were not given any information about the subjects. We classified grading for lumbar disc herniation (HN), annular fissure (AF), and nucleus degeneration (ND), using disc degeneration classification. Results : The prevalence of HN, AF, and ND were 81.4%, 76.1%, and 75.8% respectively. Almost all levels showed an age-related proportional tendency with some exceptions. Conclusion : In asymptomatic Korean subjects, the abnormal findings showed high prevalence of AF, ND, and extrusion. Especially in young ages, the authors found that bulging, protrusion, and AF showed high prevalence at L4/5 and L5/S1. And ND showed high prevalence at L5/S1. So, all lumbar disc degenerations are not pathologic, especially in children and adolescents.

• The Transactions of the Korea Information Processing Society
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• v.5 no.1
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• pp.236-248
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• 1998

Human observers perceive a contour where no line or edge is given, such as the border between gratings of thin lines offset by half a cycle. Illusory contours occur in a wide variety of circumstances in nature. A common factor in all such figures is the perception of a surface or contour occluding part of a background, i.e. illusory contours are always accompanied by illusory surfaces. Some examples about these kinds of figures are given by Kanizsa's triangle or square. In this paper, we proposed a neural network model for forming(extracting) the illusory surfaces, based on the mechanism of feature extraction found in a mammals' visual pathway. It will be shown that the model can extract the illusory surfaces from illusory contours successfully.