• Investigative Magnetic Resonance Imaging
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• v.22 no.4
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• pp.260-265
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• 2018

Chordoid meningioma, an uncommon subtype of meningioma, occurs rarely in the spine. In this case report, the authors present a case of spinal chordoid meningioma in a young female patient, and include a detailed description of imaging findings and a literature review.

• Journal of Korean Neurosurgical Society
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• v.66 no.3
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• pp.239-246
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• 2023

Germinal matrix and intraventricular hemorrhage (GM-IVH) are the major causes of intracranial hemorrhage in premature infants. Cranial ultrasound (cUS) is the imaging modality of choice for diagnosing and classifying GM-IVH. Magnetic resonance imaging (MRI), usually performed at term-equivalent age, is more sensitive than cUS in identifying hemorrhage in the brain. Post-hemorrhagic ventricular dilatation is a significant complication of GM-IVH and correlates with adverse neurodevelopmental outcomes. In this review, we discuss the various imaging findings of GM-IVH in premature infants, focusing on the role of cUS and MRI.

• Investigative Magnetic Resonance Imaging
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• v.23 no.4
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• pp.395-400
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• 2019

Acromegaly is a rare endocrine disorder caused by excessive secretion of the growth hormone. There is a wide range of clinical manifestations from somatic symptoms to respiratory or cardiac failure. Among them, cardiovascular involvement is a leading cause of morbidity and mortality. There are relatively few cases reporting cardiac magnetic resonance imaging (CMR) findings of cardiomyopathy in patients with acromegaly. Thus, we report a case of acromegaly showing dilated cardiomyopathy focusing on the findings of CMR.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.370-377
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• 2004

The density approach and the homogenization design method are representative methods in topology optimization problems. In the topology optimization in magnetic fields, those methods are applied based on the results of the applications In elastic fields. In this study, the density method is modified considering the concept of the homogenization design method. Also, the results of the topology optimization in magnetic fields by the modified density method as well as the homogenization method are compared especially focusing the change of the penalization parameter in the density approach. The effect of the definition of the design domain such as global/local design domain is also discussed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.11-19
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• 2008

This paper proposes small VCM(voice coil motor) type, auto-focusing and zoom actuators for mobile information devices. In order to meet the large output displacement within small height restriction, the proposed auto-focusing actuator adopts curved suspensions, which are similar to a leaf-spring type suspension of optical disk drives. The sensitivity of design parameters on output displacement and dynamic performance is implemented using ANSYS (3D FEM tool) to determine the optimal geometry and stiffness of the curved suspensions. This paper also investigates a new zoom actuator without a suspension supporting a bobbin. The zoom actuator uses a moving rail and a stoper mechanism by generating rotational force at lens holder. Magnetic flux density of the zoom actuator are calculated by both the FEM and permeance method. Experiments using prototypes of the proposed focusing and zoom models show that both actuators meet the required displacement and performance.

• Journal of Powder Materials
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• v.20 no.2
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• pp.125-128
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• 2013

Magnetic and dielectric properties of rubber composites are controlled by using two kinds of high-permeability metal particles with different electrical conductivity (Sendust, Permalloy), and their effect on microwave absorbance has been investigated, focusing on the quasi-microwave frequency band (0.8-2 GHz). Noise absorbing sheets are composite materials of magnetic flake particles of high aspect ratio dispersed in polymer matrix with various filler amount of 80-90 wt.%. The frequency dispersion and magnitude of complex permeability is almost the same for Sendust and Permalloy composite specimens. However, the complex permittivity of the Permalloy composite (${{\varepsilon}_r}^{\prime}{\simeq}250$, ${{\varepsilon}_r}^{{\prime}{\prime}}{\simeq}50$) is much greater than that of Sendust composite (${{\varepsilon}_r}^{\prime}{\simeq}70$, ${{\varepsilon}_r}^{{\prime}{\prime}}{\simeq}0$). Due to the large dielectric permittivity of Permalloy composite, the absorbing band is shifted to lower frequency region. However, the investigation of impedance matching reveals that the magnetic permeability is still small to satisfy the zero-reflected condition at the quasi-microwave frequency band, resulting in a small microwave absorbance lower than 10 dB.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.1
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• pp.36.2-36.2
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• 2011

A cancelling magnetic feature (CMF) is believed to be a result of magnetic reconnection in the low atmosphere of the Sun. In this work, we investigate the physical properties of CMFs, focusing on the rates of flux cancellation in CMFs and the dynamics of chromospheric phenomena coupled with CMFs. First, we have determined the specific rates of flux cancellation using the magnetograms taken by the Solar Optical Telescope (SOT) aboard the Hinode satellite. The specific rates determined with the SOT turned out to be systematically higher than those based on the data taken by the Michelson Doppler Imager (MDI) aborad the SOHO. Second, we analyzed transient Ca II brightenings associated with small-scale CMFs using the SOT/Hinode. We found that in most Ca II brightenings related to CMFs, and the Ca II intensity peaks after magnetic flux cancellation proceeds. Moreover, brightenings tend to appear as pairs of bright points of similar size and similar brightness overlying magnetic bipoles. To further study the brightening and dynamics of chromospherie features associated with CMFs, we have analyzed Fast Imaging Solar Spectrograph (FISS) data. From this data the Doppler motion of chromospheric features above a CMF changed from redshift to blueshift. The duration of such dynamics is very short being less than 2 minutes. These results are unexpected one and can not be explained by any pre-existing pictures of CMFs.

• Investigative Magnetic Resonance Imaging
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• v.20 no.1
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• pp.1-8
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• 2016

The spine is the most common location for skeletal metastases, and the incidence of spinal metastasis shows an increasing tendency. Because metastatic spinal tumors progress from an anterior element to a posterior element resulting in continuing destruction of the pedicles, epidural extension and involvement of neural structures of the metastatic tumor are eventually visible. Therefore, it is clinically significant for radiologists to understand the pathophysiology of spinal metastasis and to assess the involvement of neural structures and the disintegration of spinal instability related to the pathophysiology. As MRI is also the best imaging modality for diagnosing spinal metastasis, radiologists should accurately assess spinal metastasis and provide practical information to physicians. Therefore, we will describe some analysis points focusing on the understanding of pathophysiology of spinal metastasis and the next step toward a more extensive clinical approach using MR imaging.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.780-785
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• 2001

A moving-magnet type pickup actuator is proposed, which has the back-yoke to improve th sensitivity. Through the magnetic path analysis, we can find that the flux density is increased i the air gap by the pole assignment of magnet and the adding of back-yoke can reduce the flu leakage and induce 40％ up of flux density. Experimental results show that the sensitivity i improved in the tracking direction, however, the improvement doesn't occur in the focusing direction. Finally, the compensation performance is tested in HD-DVD system. And it is verifie that the actuator can compensate the disc tilt of ${\pm}$0.7$^{\circ}$.

• Investigative Magnetic Resonance Imaging
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• v.23 no.3
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• pp.264-269
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• 2019

Cavernous hemangioma of the gallbladder is an extremely rare benign tumor. The tumor has only a few cases being reported in literature. However, to the best of our knowledge, no reports focusing on the MRI findings of cavernous hemangioma of the gallbladder have been published. This study reports a case of gallbladder hemangioma with pathologic and radiologic reviews, including MRI findings.