• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.227-231
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• 2014

Underwater radiated noise is one of the vital factors in underwater weapon systems like submarine. A passive elastic mount is an effective reduction method for the vibration from a ship-board machinery transmitted to the hull which is radiated as noise outside the hull. A passive elastic mount shows the limitation on the vibration reduction and needs multi stage mounting system including double stage one to meet the required underwater radiated noise criteria. It is necessary for the multi stage mounting system to consider the large displacement in the underwater shock explosion. So it is difficult to apply the multi stage mounting system in submarine because of space limitation. Also recent navy sonar system are trying to have the capability to detect the ship-borne acoustic signals in the low frequency range. An alternative to the passive mount is an active mount with moving-coil type electromagnetic actuator based on a conventional rubber mount in the low frequency range. In the previous paper, 4 active mounts with moving-coil type electromagnetic actuator based on the rubber mount were installed on the hard floor of the facility, which means no consideration on the elastic foundation effect for the control of the active mounts was taken into account. In this study, an experimental performance analysis on the active mount was carried out using 4 active mounts installed on the cylindrical structure to investigate the elastic foundation effect.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.90-92
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• 2008

A novel solving technique has been developed to analyze the dynamic characteristics of high speed Thomson-coil arc eliminator. The electromagnetic repulsion actuator based on Thomson-coil is taken as the driving part of the arc eliminator, due to which, the opening and closing time is quite short compare to other type actuators. The electromagnetic repulsion actuator is composed of one repulsion plate and two fixed coils, corresponding to the opening coil and closing coil, respectively. The new solving technique is derived based on the equivalent electric circuit model of the system which is set up by dividing the repulsion plate into multi segments using adaptive segmentation method. This solving technique is applied to the dynamic characteristic analysis of electromagnetic repulsion actuators in high speed Thomson-coil arc eliminators. The calculation results are testified by the FEM calculation results and experiment results.

• Journal of The Korean Radiological Technologist Association
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• v.29 no.1
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• pp.61-66
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• 2003

Purpose : To evaluate was the newly designed gastroduodenal coil catheter: in-vitro test. Material and Method : the coil catheter that we made in our laboratory was 150 cm. The coil that is made of stainless steel wire was composed 1.3m inner diameter and

• Proceedings of the Korean Nuclear Society Conference
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• 2002.05a
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• pp.143.1-143
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• 2002

• The Journal of the Korea Contents Association
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• v.12 no.7
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• pp.247-254
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• 2012

This study presents the assessment results of coil length characteristics according to the volume of cerebral artery among the inpatients that received angiography and coil embolization following intracranial aneurysm from March, 2010 to September 2011. The volume rendering method was applied to the patients that received embolization to their cerebral arteries to obtain volume measurements. After coil embolization, the volume ratios were calculated with the volumes and lengths of coils. The embolic volume ratios were $43.11{\pm}3.11%$, $36.07{\pm}2.03%$, 40.91%, and 38.25% when the aneurysm sizes were 6mm or less, 6~10mm, 10~15mm and 20mm or more, respectively, being similar to the recommended volume ratios. Regardless of the types of aneurysm, the coil length according to volume was 0.65cm per $1mm^3$ of 20~$100mm^3$ when one type of 0.25mm diameter coil was used. They were 0.62cm per $1mm^3$ of 20~$150mm^3$ when one type of coil was used in the aneurysm volume of the saccular type and 0.60cm per $1mm^3$ of 20~$90mm^3$ when one type of coil was used in the aneurysm volume of the multi-lobulated type.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.55-59
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• 2005

CFD analysis has been conducted to find the two stage impeller configuration which is the most suitable for a stirred tank with an internal helical cooling coil and a cooling jacket, which is frequently used in chemical industries for highly exothermic reactions ranged from low to medium viscosity. Two typical types of impellers are considered; pitched paddle impellers and Rushton turbine impellers. Interestingly, pitched paddle impellers show a good mixing performance for multi-species, whereas Rushton turbine impellers achieve a good mixing performance for multi-phases. Besides the type of an impeller, the location of an impeller is another important factor to be considered in order to accomplish an effective mixing. The best set of types and locations of two impellers is recommended based on the coefficient of variation(CoV) value and the heat removal capability obtained from CFD results. The former is a measure to quantify the degree of mixing.

• Journal of Electrical Engineering and Technology
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• v.11 no.2
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• pp.367-376
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• 2016

This paper presents a cell balancing method for a single switch flyback converter with a multi-winding transformer. The conventional method using a flyback converter with a multi-winding transformer is simple and easy to control, but the voltage of each secondary winding coil might be non-uniform because of the unequal effective turn-ratio. In particular, it is difficult to control the non-uniform effect using turn-ratios because secondary coil has a limited number of turns. The non-uniform secondary voltages disturb the cell balancing procedure and induce an unbalance in cell voltages. Individual cell control by adding a switch for each cell can reduce the undesirable effect. However, the circuit becomes bulky, resulting in additional loss. The proposed method here uses the conventional flyback converter with an adjustment made to the output filters of the cells, instead of the additional switch. The magnitude of voltage applied to a particular cell can be reduced or increased according to the adjusted filter and the selected switching frequency. An analysis of the conventional converter configuration and the filter design method reveals the possibility of adequate cell balancing control without any additional switch on the secondary side.

• Progress in Superconductivity and Cryogenics
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• v.16 no.1
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• pp.27-31
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• 2014

2G HTS tapes are widely used for various electric machines. In addition, stacked or parallel connected HTS tapes are essentially used to raise transport current level for large capacity electric machines. Therefore, critical current characteristic of stacked tapes need to be studied. Recently developed 2G HTS tapes are fabricated with various defects doping so that tapes possess pinning center to improve the critical current characteristic. During this process, the critical current is determined minimum value in not perpendicular magnetic field but a specific magnetic field angle according to the reported research. However, the effects of magnetic field angle to critical current of multi-stacked 2G HTS tapes have not been examined. In this paper, field coil which is a race-track coil wound by using an HTS tape with iron-core was fabricated to apply angle adjustable magnetic field to the 2G HTS tape samples. We measured critical current of single and multi-stacked two tapes that have different characteristic depending on various magnetic field angle and magnitude in liquid nitrogen environment. Furthermore, results of single and multi-stacked tapes were compared and analyzed.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.195-198
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• 1994

The design and construction of a 13 Tesla / 46 mm bore superconducting magnet is presented. The system consists of an 5 Tesla outer NbTi coil with a bore I.D. of 144m, a winding O. D. of 208mm and the length of 200mm which is connected in series with a 200mm long insert coil constructed of multi filamentary $Nb_3Sn$. The insert coil was reacted after winding. Also, epoxy impregnation is accomplished at $Nb_3Sn$ coil using a low viscosity crack resistant epoxy which is forced into the coil with a series of vacuum and over atmosphere pressure cycle.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.3
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• pp.303-308
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• 2008

The induction heating is more efficient for a plate bending because of its easy operation and control of working parameters, compared with the heating by a gas torch. The existing axis symmetric analysis method could neither handle initial curved plates nor be used in the optimization of coil shapes because of its limit of an axis symmetric coil shape. But the proposed method using some discrete part models and analysis processes could overcome these difficulties and show more accurate results in temperatures and deflections of flat or curved plates with initial curvature than those in the existing axis symmetric analysis method. This method is composed of the multi-disciplinary analyses such as an electro magnetic analysis, a heat transfer analysis and a deformation analysis based on inherent strain approach per each step. Traditionally, the coil shape in the induction heating is circular shape and it needs the moving process along heating lines. To overcome this, the 'Long Type Coil' with some linear parallel coils was proposed. It did not need the moving process along heating lines and reduced the heating process time. The results of experiments were compared with those of the simulation.