• Journal of Ship and Ocean Technology
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• v.8 no.1
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• pp.10-30
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• 2004

High-fidelity RANS simulations are presented for a ducted marine propulsor, including verification ＆ validation (V＆V) using available experimental fluid dynamics (EFD) data. CFDSHIP-IOWA is used with $\textsc{k}-\omega$ turbulence model and extensions for relative rotating coordinate system and Chimera overset grids. The mesh interpolation code PEGASUS is used for the exchange of the flow information between the overset grids. Intervals V＆V for thrust, torque, and profile averaged radial velocity just downstream of rotor tip are reasonable in comparison with previous results. Flow pattern displays interaction and merging of tip-leakage and trailing edge vortices. In interaction region, multiple peaks and vorticity are smaller, whereas in merging region, better agreement with EFD. Tip-leakage vortex core position, size, circulation, and cavitation patterns for $\sigma=5$ also show a good agreement with EFD, although vortex core size is larger and circulation in interaction region is smaller.

• Journal of the korean Society of Automotive Engineers
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• v.10 no.4
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• pp.66-74
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• 1988

The ignition quality of ignition system is influenced by spark energy, discharge pattern of spark energy and spark duration. In this paper, the characteristics of multiple spark ignition system have been investigated for various number of spark and spark interval. The results, which were compared with those obtained with a standard single spark ignition, show that engine output is increased, and lean misfire limit is extended with the multiple spark ignition system. The most effective number of spark at the most effective spark interval that are determined by engine performance test, were 6 times spark at 0.02ms spark interval. For the above condition of spark, engine torque was increased about 20% comparing with conventional ignition system and lean misfire limit was extended to air-fuel ratio 22.5:1. This study researched the rate of heat release and quantity of heat release influenced by a condition of spark on the mass burned in order to investigate the relationship between the rate of mass burned and number of spark times.

• Journal of Industrial Technology
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• v.31 no.A
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• pp.129-133
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• 2011

In this paper, a surface mounted permanent magnet synchronous motor(SPMSM) drive system for industrial sewing machine was developed. Even through a lowr-esolution encoder is used for a low cost, using a full order observer enables to estimate accurate speed and position. And it also compensates a disturbance torque caused by the belt between a load and a motor. In order to control precisely stop positions of a needle, a speed trajectory is calculated from the acceleration pattern which is obtained from the position reference. The performance of the developed system is verified by experimental results.

• Journal of ILASS-Korea
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• v.9 no.4
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• pp.77-82
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• 2004

This paper describes the improvement of engine cooling system. To improve engine cooling performance, the authors approached in two ways. One is to increase water pump performance, changing of impeller shape and lightening of material were carried out. The second one is cooling efficiency rise, which were investigated with head gasket coolant flow passage optimization with flow visualization technique. The test results show that water pump performance was increased effectively, reduction of pump drive torque, and increase of pump flow-rate and pressure rise. Gasket hole pattern optimization test results represent an optimized head coolant flow which stands cross flow from exhaust to intake port side and small vortex were removed.

• Proceedings of the KIEE Conference
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• summer
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• pp.1070-1072
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• 2004

In this paper, the characteristic of slotless permanent magnet brushless motors analyze and compare parallel with radial way. This paper derive magnetic field solutions due to the PM. Torque, flux linkage and back emf are then derived. The results are shown in good conformity with those obtained from the commonly used finite element analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.4
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• pp.617-624
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• 2008

This paper proposes design and implementation of wind turbine simulators which incorporate the turbine dynamic characteristics. At first, the turbine output characteristic in steady state is modelled as a function of wind speed and then dynamic characteristics are modelled such as pitch angle control, torsional vibration, tower shadow effect, wind shear effect, and inertia effect. In addition, a wind speed simulator is developed which can generate the real wind speed pattern. The wind turbine simulator is implemented with 3[kW] M-G set(cage-type induction motor coupled with doubly-fed induction generator) at laboratory.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.192-194
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• 2007

This paper proposes a new wind turbine simulator using a squirrel cage induction for control performance test of DFIG (doubly-fed induction generator). The turbine static characteristics are modeled using the relation between the turbine torque versus the wind speed and the blade pitch angle. The turbine performance is subjected to a real wind speed pattern by modeling the wind speed as a sum of harmonics with a wide range of frequency. The turbine model includes the effect of the tower shadow and wind shear. A pitch angle controller is designed and used to protect the coupled generator by limiting the turbine speed to the maximum value. Experimental results are provided for a 3[kW] wind turbine simulator at laboratory.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.411-416
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• 2005

Nowadays, diesel power plant using low speed two stroke diesel engine is widely used in islands and restricted areas. Considerations were given to its benefit of high thermal efficiency, reliability and durability compared to the other prime movers. However, various types of engine vibration affect neighboring buildings to their structural vibration. For this, diesel power plant are held liable for the troubles caused by these vibration. These are mainly due to the X- and H-type engine vibrations which we excited by the X- and H- guide force moment. Authors have identified a structural vibration of new pattern called ‘T-mode vibration’ due to the torsional vibration of shafting system. In this paper, T-mode vibration is analyzed through an experimental method based on the global vibration measurement.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.15-20
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• 2014

The wind industry grew in the first decade of the 21st century at rates consistently above 20% a year. For wind turbine, gearbox failure can be extremely costly in terms of repair costs, replacement parts, and in lost power production due to downtime. In this paper, gear tooth micro-modification for the high speed stage was used to compensate for the deformation of the teeth due to load and to ensure a proper meshing to achieve an optimized tooth contact pattern. The gearbox was firstly modeled in a software, and then the various combined tooth modification were presented, and the prediction of transmission under the loaded torque for the helical gear pair was investigated, the normal load distribution and root stress were also obtained and compared before and after tooth modification under one torque. The simulation results showed that the transmission error and normal load distribution under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.

• Journal of Oral Medicine and Pain
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• v.24 no.1
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• pp.37-47
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• 1999

This study was performed to investigate the factors related to vibration of temporomandibular joint during mandibular opening movement. For this study, 144 patients with temporomandibular disorders were randomly selected. Angle's classification, lateral guidance pattern, range of maximal mouth opening, preferred chewing side, and affected side were investigated clinically. Mandibular torque rotational movement during opening was recorded with $BioEGN^{(R)}$ and vibration of temporomandibular joint during opening was recorded with $Sonopak^{(R)}$. After clinical diagnosis was made, visual analogue scale(VAS) was used for evaluation of clinical progress of the subject's chief complaints. The author calculated VAS treatment index(VAS Ti) from the record of VAS. The more VAS Ti was, the less remission of subjective symptom was, The data were analyzed with SAS/Stat program and the results of this study were as follows: 1. There were no significant difference in all the variables of joint vibration by age and sex. 2. Integral and peak amplitude in patients of Angle's class I were higher than those of class II or III patients. Integral in patients of group function was higher than that in patients of canine guidance or other types of lateral excursion. 3. As to Angle's classification or lateral guidance type, there were almost not significant difference between subgroup of same class or type and subgroup of different class or type on both sides. And there were also almost not difference between one side and the other side related to preferred chewing side or affected side. 4. Patients with disk displacement with reduction showed higher value of integral and peak amplitude than any other patients. 5. Joint vibration variables significantly correlated with VAS Ti of pain. with clinical range of mouth opening, and with ingredients of mandibular torque rotational movement.