• Journal of Korean Neurosurgical Society
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• v.56 no.6
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• pp.504-508
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• 2014

A 59-year-old male patient had 5-month history of gait disturbance and memory impairment. His initial brain computed tomography scan showed $3.5{\times}2.8cm$ sized mass with high density in the pineal region. The tumor was hypointense on T2 weighted magnetic resonance images and hyperintense on T1 weighted magnetic resonance images with heterogenous enhancement of central portion. The tumor was totally removed via the occipital transtentorial approach. Black mass was observed in the operation field, and after surgery, histopathological examination confirmed the diagnosis of malignant melanoma. Whole spine magnetic resonance images and whole body 18-fluoro-deoxyglucose positron emission tomography could not demonstrate the primary site of this melanoma. Scrupulous physical examination of his skin and mucosa was done and dark pigmented lesion on his left leg was found, but additional studies including magnetic resonance images and skin biopsy showed negative finding. As a result, final diagnosis of primary pineal malignant melanoma was made. He underwent treatment with the whole brain radiotherapy and extended local boost irradiation without chemotherapy. His preoperative symptoms were disappeared, and no other specific neurological deficits were founded. His follow-up image studies showed no recurrence or distant metastasis until 26 weeks after surgery. Primary pineal malignant melanomas are extremely rare intracranial tumors, and only 17 cases have been reported since 1899. The most recent case report showed favorable outcome by subtotal tumor resection followed by whole brain and extended local irradiation without chemotherapy. Our case is another result to prove that total tumor resection with radiotherapy can be the current optimal treatment for primary malignant melanoma in the pineal region.

• Proceedings of the KIEE Conference
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• 2004.11b
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• pp.249-251
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• 2004

Harmonic resonant overvoltage during restoration of primary restorative transmission system originates in switching operations and nonlinear characteristics of equipments. Actually it is difficult to predict the occurrence of harmonic overvoltage, since they result from nonlinear characteristics of transformers and other equipments. This paper describes the analysis of domestic primary restorative transmission system using PSCAD/EMTDC. The harmonic resonance is verified and showed the relation with equipments which have nonlinear characteristics such as generator and transformer in this paper. And the solution to prevent harmonic resonance is proposed too. As a result, the PSCAD/EMTDC simulation showed slightly conflictive results that had been presented by IEEE Power System Restoration Working Group report.

• Investigative Magnetic Resonance Imaging
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• v.17 no.3
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• pp.243-248
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• 2013

Primary retroperitoneal mucinous cystadenocarcinoma is a very rare malignancy. To date, 51 cases have been reported, including 3 in pregnant women. Herein, we report magnetic resonance findings of a 31-year-old Korean woman (15 weeks and 3 days pregnant) with primary retroperitoneal mucinous cystadenocarcinoma. On abdominal magnetic resonance imaging (MRI), a mass was identified in the retroperitoneal area with a nodular lesion showing heterogeneous signal intensity and focal wall thickening on T1- and T2-weighted images. Exploratory laparotomy and tumor excision were performed. Histological examination revealed primary retroperitoneal mucinous cystadenocarcinoma. The patient subsequently underwent total hysterectomy, bilateral salpingo-oophorectomy, and omentectomy for metastatic mucinous cystadenocarcinoma of both ovaries 15 months after her initial surgery.

• Investigative Magnetic Resonance Imaging
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• v.20 no.4
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• pp.259-263
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• 2016

Primary diffuse large B-cell lymphoma of the seminal vesicle is an extremely rare disorder, with only two cases reported in the English literature. Here, we present imaging findings of a case of primary diffuse large B-cell lymphoma of the seminal vesicle. On transrectal ultrasonography, the mass presented as a 3.0-cm-sized heterogeneous, hypoechoic lesion in the right seminal vesicle. Computed tomography (CT) revealed a mass with rim-like enhancement in the right seminal vesicle. On magnetic resonance imaging (MRI), the tumor showed iso-signal intensity on T1-weighted images and heterogeneously intermediate-high signal intensity on T2-weighted images. The tumor showed rim-like and progressive enhancement with non-enhancing portion on dynamic scanning. Diffusion restriction was observed in the mass. On fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET/CT) imaging, a high standardized uptake value (maxSUV, 23.5) by the tumor was noted exclusively in the right seminal vesicle.

• Journal of Electrical Engineering and Technology
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• v.8 no.2
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• pp.262-270
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• 2013

A boundary protection method for power distribution line based on equivalent boundary effect is presented in this paper. In the proposed scheme, the equivalent resonance component with a certain central frequency is sleeve-mounted at the beginning of protected zone. The 'Line Boundary' is built by using boundary effect, which is created by introducing impedance in the primary-side of line. The 'Line Boundary' is significantly different from line wave impedance. Therefore, the boundary protection principle can be applied to power distribution line without line traps. To analyze the frequency characteristic corresponding to traveling-waves of introducing impedance in the primary-side of line, distributed parameters model of equivalent resonance component is established. The results of PSCAD/EMTDC simulation prove the obvious difference of voltage high frequency component between internal faults and external faults due to equivalent resonance component, and validate the scheme.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.913-917
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• 2013

During the restoration process of primary restorative transmission system, some over voltages may happen due to nonlinear interaction between unloaded transformers and transmission systems. These over voltages caused by harmonic resonance can be suppressed by inserting damping loads before energizing transformers. But it is very difficult to predict the occurrence possibility of harmonic resonance and complex simulation must be repeated to estimate the sufficient damping loads. This paper presents a damping loads prediction system to prevent harmonic resonance. Detailed analysis of the relationship between harmonic resonance and the amount of damping loads is discussed. The prediction system is developed using a curve fitting and a neural network based on this relationship. A curve fitting used a Gaussian function based on non-linear least square method and multi-layer back-propagation neural network is applied. The system is applied to primary restorative transmission lines in korean power system and the result showed satisfactory performance.

• Investigative Magnetic Resonance Imaging
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• v.23 no.4
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• pp.367-373
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• 2019

Yolk sac tumors are rare malignant germ cell neoplasms that usually arise from the gonads. Extragonadal yolk sac tumors (EGYSTs) frequently occur in the mediastinum in post-pubertal females. EGYSTs in the pelvis are extremely rare, and to date, only thirteen cases have been reported in the English literature. Among them, the primary EGYST of the pelvic peritoneum in post-pubertal females has only been reported in ten cases. The present case describes a 26-year-old female diagnosed with primary peritoneal yolk sac tumor located in the rectouterine pouch. We report clinical and tumor imaging features, including ultrasound, computed tomography (CT), magnetic resonance images (MRI), positron emission tomography-computed tomography (PET-CT), and present a review of the literature.

• Proceedings of the KSMRM Conference
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• 2003.10a
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• pp.25-25
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• 2003

Purpose： In order to characterise primary central nervous system Iymphomas (PCNSL) and to evaluate if 1H spectroscopy improves the preoperative differential diagnosis of other diseases. Method： We reviewed 11 MR imaging and 7 MR spectroscopy of 9 patient with Iymphoma confirmed by stereotatic biopsy.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.1
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• pp.40-46
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• 2011

This paper is to investigate the effects of the asymmetrical support stiffness on the stability of a supercritical driveshaft with asymmetrical shaft stiffness and anisotropic bearings. The equations of motion is derived for a system including a rigid disk, a massless flexible asymmetric shaft, anisotropic bearings and a support beam. The Floquet theory is applied to perform the stability analysis with the variation of the support stiffness, the shaft asymmetry, the shaft damping and the shaft speed. The results show that the asymmetric support stiffness is closely related to the stability caused by primary resonance as well as the supercritical operation. First, the stiffness variation can stabilize the system around primary resonance by weakening the parametric resonance from the shaft asymmetry. Second, it also improve the stability characteristics at a supercritical operation when the support stiffness is not so high relative to the shaft stiffness.

• Investigative Magnetic Resonance Imaging
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• v.13 no.1
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• pp.93-96
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• 2009

Primary localized amyloidosis of the ureter and bladder is a very rare condition. CT and cystoscopic findings are indistinguishable from malignant neoplasm or inflammatory lesions. We report a case of unilateral distal ureteral thickening caused by primary localized amyloidosis. MR image features of hypointensity on T2-weighted images and mural enhancing pattern on contrast enhanced T1-weighted images can be helpful for diagnosis of ureteral amyloidosis.