• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.130-137
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• 2003

Because of falling-off in power quality by harmonics, obstacles like lowering of capability, noise, vibration of power facilities and so on are occurred. Also generation of harmonics is inevitable and the point at harmonics is seriously gathering strength because energy saving installation using semiconductor circuit as countermeasures to enhance energy efficiency will be broadly spread and the use of energy conversion equipment like motor speed control contrivance, energy keeping installation and so on will increase, in the future. In order to eliminate harmonics obstacle, precision measurement and analysis on voltage, current, power factor, the each ingredient of harmonic order, the percentage of total harmonic distortion, and so forth are needed. In this paper, we developed low-cost measurement system to measure and analyze power quality connected with harmonics and verified it's performance by measuring and analyzing power quality in the three-phase and four-wire system.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.593-600
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• 2014

This paper proposes a torque assist strategy for operating a hybrid agricultural tractor in the field. In general, different field operations such as baling and rotary tillage require different patterns and amounts of torque. Thus, a large agricultural tractor is used to improve the farming efficiency. Therefore, this research has the goal of developing a hybrid tractor that uses a small electric motor to provide additional torque for specific field operations. To achieve this objective, a rule-based torque assist strategy is proposed and validated for a simulation model in the Autonomie framework, which is a commercial simulation tool. Finally, the work efficiencies and fuel consumptions of a conventional tractor and the hybrid tractor with the proposed torque assist strategy are compared using simulations.

• International Journal of Automotive Technology
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• v.8 no.6
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• pp.687-696
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• 2007

To increase the reliability of auto-ignition in CAI engines, the thermodynamic properties of intake flow is often controlled using recycled exhaust gases, called internal EGR. Because of the internal EGR influence on the overall thermodynamic properties and mixing quality of the gases that affect the subsequent combustion behavior, optimizing the intake and exhaust valve timing for the EGR is important to achieve the reliable auto-ignition and high thermal efficiency. In the present study, fully 3D numerical simulations were carried out to predict the mixing characteristics and flow field inside the cylinder as a function of valve timing. The 3D unsteady Eulerian-Lagrangian two-phase model was used to account for the interaction between the intake air and remaining internal EGR during the under-lap operation while varying three major parameters: the intake valve(IV) and exhaust valve(EV) timings and intake valve lift(IVL). Computational results showed that the largest EVC retardation, as in A6, yielded the optimal mixing of both EGR and fuel. The IV timing had little effect on the mixing quality. However, the IV timing variation caused backflow from the cylinder to the intake port. With respect to reduction of heat loss due to backflow, the case in B6 was considered to present the optimal operating condition. With the variation of the intake valve lift, the A1 case yielded the minimum amount of backflow. The best mixing was delivered when the lift height was at a minimum of 2 mm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.8
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• pp.1080-1089
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• 2013

Interior Permanent Magnet Synchronous Machines (IPMSMs) with rare earth magnet are widely used in electric vehicles and hybrid electric vehicles. IPMSMs having high efficiency, high torque, and a wide speed range are employed in propulsion system. And the rotor in an IPMSM is generally made of a rare earth magnet to achieve a large energy product and high torque. This paper discusses issues regarding design and performance of IPMSMs using different factors of BH magnetic characteristic. It is necessary to choose factors of magnetic material according to permanent magnet shape in rotor for high performance. Response Surface Methodology (RSM) is selected to obtain factors of magnetic material according to variety of rotor shapes. The RSM is a collection of mathematical and statistical techniques useful for the analysis of problems in which a response of interest in influenced by several variables and the objective is to optimize response. Therefore, it is necessary to analyze the torque characteristics of an IPMSM having magnet BH hysteresis curve with different rotor shape. Factors of residual flux density (Br) factor and intrinsic coercive force (Hc) are important parameters in RSM for rotor shape. The rotor shapes for IPMSMs having magnet BH characteristic were investigated using the RSM, and three shapes were analyzed in detail using FEA. The results lead to design consequence of IPMSMs in the various rare earth magnet materials.

• Journal of Korean Neurosurgical Society
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• v.63 no.2
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• pp.248-260
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• 2020

Objective : To investigate the efficiency of diffusion tensor imaging (DTI) fiber-tracking based neuronavigation and assess its usefulness in the preoperative surgical planning, prognostic prediction, intraoperative course and outcome improvement. Methods : Seventeen patients with cerebral masses adjacent to corticospinal tract (CST) were given standard magnetic resonance imaging and DTI examination. By incorporation of DTI data, the relation between tumor and adjacent white matter tracts was reconstructed and assessed in the neuronavigation system. Distance from tumor border to CST was measured. Results : The sub-portion of CST in closest proximity to tumor was found displaced in all patients. The chief disruptive changes were classified as follows : complete interruption, partial interruption, or simple displacement. Partial interruption was evident in seven patients (41.2%) whose lesions were close to cortex. In the other 10 patients (58.8%), delineated CSTs were intact but distorted. No complete CST interruption was identified. Overall, the mean distance from resection border to CST was 6.12 mm (range, 0-21), as opposed to 8.18 mm (range, 2-21) with simple displacement and 2.33 mm (range, 0-5) with partial interruption. The clinical outcomes were analyzed in groups stratified by intervening distances (close, <5 mm; moderated, 5-10 mm; far, >10 mm). For the primary brain tumor patients, the proportion of completely resected tumors increased progressively from close to far grouping (42.9%, 50%, and 100%, respectively). Five patients out of seven (71.4%) experienced new neurologic deficits postoperatively in the close group. At meantime, motor deterioration was found in six cases in the close group. All patients in the far and moderate groups received excellent (modified Rankin Scale [mRS] score, 0-1) or good (mRS score, 2-3) rankings, but only 57.1% of patients in the close group earned good outcome scores. Conclusion : DTI fiber tracking based neuronavigation has merit in assessing the relation between lesions and adjacent white matter tracts, allowing prediction of patient outcomes based on lesion-CST distance. It has also proven beneficial in formulating surgical strategies.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.223-227
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• 2006

In this study, the combustion characteristics was studied with various oxidizer in hybrid propulsion system. In this experiments $GN_2O$ and GOX were used as oxidizer, and PE was used as fuel. The combustion behavior was explained by flame temperature with mass O/F ratio, and the use of $GN_2O$ as the oxidizer caused a increase in combustion efficiency with GOX in the same hybrid motor. The mass flow rate of gaseous oxidizer was controlled by the several chocked orifices that have different diameter, and the oxidizer supply range was $0.0138{\sim}0.0427kg/sec$. As result, the empirical relation for oxidizer type was represented by mass flux of solid fuel, it was obtained with mass transfer number, and mass flux of oxidizer.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.5
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• pp.424-431
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• 2007

This thesis proposed H-Bridge Multi-Level Inverter for Fluidized Bed Combustion Boiler Secondary Air Fan in 200MW thermal power plant. The adjustable speed drive systems improve the efficiency in lightly load condition and extend the life span of motor by limiting the over current at starting. H-Bridge Multi-level Inverter is composed of the several series low voltage power cell inverters, which have the independent isolated do link, in each phase. KEPRI(Korea Electric Power Research Institute) has successfully completed to develop, install, and commission H-Bridge Multi-level Inverter(6.6kV, 1MVA). This thesis gives a full detail about H-Bridge Multi-level Inverter, proposed boiler DCS(Distributed Control System) logic, and commissioning test result.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.9
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• pp.1391-1397
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• 2015

Recently, various researches are conducted in the application of regenerative energy produced during the operation of an electric locomotive. Regenerative energy is produced by a generator in the brake procedure. The generator is operated by kinetic energy of an electric railroad using an electric motor. The process of producing regenerative energy varies with the current type of a railroad and its running condition. The quality of electric power can be improved and electric energy can be utilized effectively, especially in the use of an energy storage system (ESS). Thus, it is necessary to apply ESS into AC section and high speed railway. This study analyses the composition of the regenerative ESS equipment installed in Yong-Jeong sectioning post, operational principle, charge and discharge algorithm and energy efficiency. The analysis shows that CO2 emissions can be reduced about 0.5 ton per a day. In addition, ESS helps saving the energy and the compensation of the voltage drop caused by the operation of high speed train when it is installed at the end of the feeder section. The number of high speed train will be increased continuously related to the electrification rate. Therefore, applying the ESS to high speed railway is expected to solve the instability of the feeder voltage and the equipment capacity problem caused by the high speed trains.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1605-1614
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• 2009

The technique of simultaneous localization and mapping is the most important research topic in mobile robotics. In the process of building a map in its available memory, the robot memorizes environmental information on the plane of grid or topology. Several approaches about this technique have been presented so far, but most of them use mapping technique as either grid-based map or topology-based map. In this paper we propose a frame of solving the SLAM problem of linking map covering, map building, localizing, path finding and obstacle avoiding in an automatic way. Some algorithms integrating grid and topology map are considered and this make the SLAM performance faster and more stable. The proposed scheme uses an occupancy grid map in representing the environment and then formulate topological information in path finding by A${\ast}$ algorithm. The mapping process is shown and the shortest path is decided on grid based map. Then topological information such as direction, distance is calculated on simulator program then transmitted to robot hardware devices. The localization process and the dynamic obstacle avoidance can be accomplished by topological information on grid map. While mapping and moving, pose of the robot is adjusted for correct localization by implementing additional pixel based image layer and tracking some features. A laser range finer and electronic compass systems are implemented on the mobile robot and DC geared motor wheels are individually controlled by the adaptive PD control method. Simulations and experimental results show its performance and efficiency of the proposed scheme are increased.

• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.159-164
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• 2001

An extensive range of pumping facilities are employed in the regional water supply system in metropolitan areas, and optimization and the systematic combination of the pump facilities have direct bearing on the stability and economy of the water supply system concerned. These systems must be able to guarantee stability, efficiency and offer high reliability. Preparation of metropolitan area regional water supply system construction project must include a basic plan which takes into account the suitability of pumping facilities to be used, the environment in which facilities will be installed, man-power requirements and basic operational and management policies. This paper contains over-all analysis of the management of metropolitan area regional water supply systems and highlights the cause of Inefficiency and energy waste and puts forward a remedial plan of action. In addition, pump/motor specification programs were developed using Visual Basic to assist selection of the same.