• Carbon letters
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• 제3권2호
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• pp.93-98
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• 2002

Short pitch fibers were prepared from petroleum based isotropic precursor pitch by melt-blown technology. The pitch fibers were stabilized in oxidizing condition, followed by steam activations at various conditions. The fiber surface and pore structures of the activated carbon fibers (ACFs) were respectively characterized by using SEM and applying BET theory from nitrogen adsorption at 77 K. The weight loss of the oxidized fiber was proportional to activation temperature and activation time, independently. The adsorption isotherms of the nitrogen on the ACFs were constructed and analyzed to be as Type I consisting of micropores mainly. The specific surface area of the ACFs proportionally increased with the weight loss at a given activation temperature. The specific surface area was ranged 850~1900 $m^2/g$ with pores of narrow distribution in sizes. The average pore size was ranged 5.8~14.1 ${\AA}$ with the larger value from the more severe activation condition.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.49-59
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• 2009

Vibrations of the tower structures of 750kW and 6kW wind turbines(WT) are investigated by measurement and analysis. Acceleration responses of the WT towers under various operation condition are monitored in real time by the remote monitoring system using LabVIEW. Using the monitoring system, resonance condition of the tower structures is diagnosed with the wind speed data within the operating speed range. To predict the tower resonance frequency, 750 kW tower is modeled as an equivalent beam with a lumped mass and Rayleigh energy method is applied. For 6 kW WT, Rayleigh-Ritz analysis is carried out on the tower-cable coupled system. Calculated tower bending frequency is in good agreement with the measured value. Using the analysis model, parametric study is available in order to prevent the severe resonance.

• Fibers and Polymers
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• 제4권4호
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• pp.215-221
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• 2003

A vertical skin model with two detachable environmental chambers was developed to simulate a Human-Clothing-Environment system and to evaluate heat and moisture transport properties of textile materials under severe conditions and during transient states. The construction of the system was described and data reproducibility and accuracy of the instrument were verified by using PEG treated nonwovens. Also advantages over a traditional static type experiment were demonstrated based on a series of experiments.

• Clinical and Experimental Pediatrics
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• 제59권sup1호
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• pp.145-148
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• 2016

Takayasu arteritis (TA) is a chronic inflammatory disease of unknown etiology that affects mainly the aorta, main aortic branches, and pulmonary arteries. Diverse neurological manifestations of TA have rarely been reported in children. Posterior reversible encephalopathy syndrome (PRES) is a neuroradiological condition that presents with headache, seizure, visual disturbances, and characteristic lesions on imaging. Inflammatory condition and severe hypertension in TA can cause PRES. We report of a 5-year-old girl with presumed TA who presented with PRES and chronic total occlusion in the renal artery. The findings on magnetic resonance imaging suggested PRES. Left nephrectomy was performed for total occlusion of the left renal artery, and the confirmatory diagnosis of TA was based on the pathologic findings of the renal artery.

• Journal of Korean Neurosurgical Society
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• 제47권6호
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• pp.458-460
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• 2010

Langerhans cell histiocytosis (LCH), a disorder of the phagocytic system, is a rare condition. Moreover, spinal involvement causing myelopathy is even rare and unusual. Here, we report a case of atypical LCH causing myelopathy, which was subsequently treated by corpectemy and fusion. A 5-year-old boy presented with 3 weeks of severe neck pain and limited neck movement accompanying right arm motor weakness. CT scans revealed destruction of C7 body and magnetic resonance imaging showed a tumoral process at C7 with cord compression. Interbody fusion using cervical mesh packed by autologus iliac bone was performed. Pathological examination confirmed the diagnosis of LCH. After the surgery, the boy recovered from radiating pain and motor weakness of right arm. Despite the rarity of the LCH in the cervical spine, it is necessary to maintain our awareness of this condition. When neurologic deficits are present, operative treatment should be considered.

• 한국표면공학회지
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• 제45권6호
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• pp.278-283
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• 2012

This investigation evaluated the effect of cavitation condition on electrochemical characteristics of 304 stainless steel, which is widely used for marine environment. The cavitation test with time were conducted on 304 stainless steel in seawater solution. Surface morphologies of specimen were observed by scanning electron microscope (SEM) and 3D microscope. Pitting depth, weight loss and damage rate were analyzed after each cavitation experiment. The surface damage was more severe as the current density increased. A dramatical increase in the damage depth and weight loss was observed after 7 hours of cavitation experiment.

• 한국분말재료학회지
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• 제11권5호
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• pp.369-375
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• 2004

A new concept of tungsten heavy alloy composite was suggested and manufactured in this study for the kinetic energy penetrator. The composite heavy alloy was composed of two parts, the center was molybdenum added heavy alloy compositions which were designed to promote the self-sharpening effect and outside was conventional heavy alloy in order to sustain the severe stress condition in the muzzle during the firing. The center part showed an intergranular and brittle mode at tungsten/tungsten interfaces by which self-sharpening effect could be activated. On the other hand, that of outside showed conventional ductile fracture mode under high strain rate condition. From the sub-scale penetration test, the depth of penetration in heavy alloy composites showed greater values than those of conventional tungsten heavy alloys. It is suggested that the heavy alloy composite could be considered as one of the future penetrator materials.

• Nuclear Engineering and Technology
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• 제37권2호
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• pp.127-138
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• 2005

Approaches to several recent issues in the operation of nuclear power plants using computational intelligence are discussed. These issues include 1) noise analysis techniques, 2) on-line monitoring and sensor validation, 3) regularization of ill-posed surveillance and diagnostic measurements, 4) transient identification, 5) artificial intelligence-based core monitoring and diagnostic system, 6) continuous efficiency improvement of nuclear power plants, and 7) autonomous anticipatory control and intelligent-agents. Several changes to the focus of Computational Intelligence in Nuclear Engineering have occurred in the past few years. With earlier activities focusing on the development of condition monitoring and diagnostic techniques for current nuclear power plants, recent activities have focused on the implementation of those methods and the development of methods for next generation plants and space reactors. These advanced techniques are expected to become increasingly important as current generation nuclear power plants have their licenses extended to 60 years and next generation reactors are being designed to operate for extended fuel cycles (up to 25 years), with less operator oversight, and especially for nuclear plants operating in severe environments such as space or ice-bound locations.

• 전기학회논문지
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• 제65권5호
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• pp.883-887
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• 2016

The power supply system in Korean electrified railway has adopted AT feeding. If a fault occurs in some substation for any reason, the vicinity substation must feed electric power on the outage substation through catenary. So, the feeding distance grows twice of the normal state at extended feeding condition. If substation's feeding distance is longer than normal condition, the catenary impedance and train to supply electric power from the substation. Therefore, the severe voltage drop can occur and power supply shall be not allowed. This paper presents the model of compensator against voltage drop using multi-port network algorithm. Whole traction power supply system can be analyzed with this model. Computer simulation including this model is performed based on real train schedule and increased schedule in case studies.

• 한국기계가공학회지
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• 제11권6호
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• pp.115-122
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• 2012

The purpose of this study is to optimize the design of the jack-up platform for 5MW offshore wind turbine system. Considering all the environmental loads such as currents, waves, winds and so on, the members of structures have been designed and optimized based on the AISC and API-RP-2A to be within the allowable stress even in the most critical and severe condition. In addition to the above strength check of structural members, the joint punching shear check and the hydrostatic collapse check are also performed where they are required for the design. The design life of the jack-up platform is 50 years for the static strength check and the fatigue design life is 100 years including to the DFF(Design Fatigue Factor) of 2.0 to have enough stability and workability for the design optimization.