• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.2
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• pp.53-60
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• 2003

This paper deals with steady-state analysis of a single-phase line-start permanent magnet synchronous motor. In order to analyze the steady-state characteristics, the asymmetric single-phase line-start synchronous motor is converted to the symmetric two-phase synchronous motor, that is, the asymmetric magnetic field is separated from the positive and the negative symmetric components using symmetrical-component theory. The analysis method of the synchronous motor on the d-q axis coordinates is used for the positive component and the equivalent circuit of the induction motor is applied for the negative component analysis. Moreover, d-q axis inductance considering current phase angle is applied to positive component analysis for precise characteristic analysis. In order to validate the proposed analysis method, the analysis results are compared with the experimental results.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.550-558
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• 2018

This paper presents the current limit strategy of voltage controller of delta-connected H-bridge static synchronous compensator (STATCOM) under an unbalanced voltage fault event. When phase to ground fault happens, the feasibility to heighten the magnitude of sagging phase voltage is considered by using symmetric transformation method in delta-structure STATCOM. And the efficiency to cover the maximum physical current limit of switching device is considered by using vector analysis method that calculate the zero sequence current for balancing the cluster energy in delta connected H-bridge STATCOM. The result is simple and obvious. Only positive sequence current has to be used to support the unbalanced voltage sag. Although the relationship between combination of the negative sequence voltage with current and zero sequence current is nonlinear, the more negative sequence current is supplying, the larger zero sequence current is required. From the full-model STATCOM system simulation, zero sequence current demand is identified according to a ratio of positive and negative sequence compensating current. When only positive sequence current support voltage sag, the least zero sequence current is needed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.8
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• pp.1745-1751
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• 2010

In this paper, a small broadband dipole antenna that simultaneously satisfies DCS1800/PCS/WCDMA/WLAN is designed and fabricated. To reduce the size and to improve the bandwidth of planar microstrip dipole antenna, a new symmetric double-ring radiator structure is used. An antenna can be reduced with increasing effective current length of dipole, and can be obtained a wide band impedance characteristic with decreasing reactance component by using a novel symmetrical double-ring structure. The proposed antenna shows broadband characteristic of 1.07GHz(52%) from 1.5GHz to 2.57GHz with VSWR < 2 (${\leq}-10dB$).

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.54 no.9
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• pp.403-407
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• 2005

Most of the loads in industrial power distribution systems are balanced and connected to three power systems. However, voltage unbalance is generated at the user's 3-phase 4-wire distribution systems with single & three phase. Voltage unbalance is mainly affected by load system rather than power system. Unbalanced voltage will draws a highly unbalanced current and results in the temperature rise and the low output characteristics at the machine. It is necessary to analyse correct voltage unbalance factor for reduction of side effects in the industrial sites. Voltage unbalance is usually defined by the maximum percent deviation of voltages from their average value, by the method of symmetric components or by the expression in a more user-friendly form which requires only the three line voltage readings. If the neutral point is moved by the unbalanced load at the 3-phase 4-wire system. Line and phase voltage unbalance leads to different results due to zero-sequence component. So that it is difficult to analyse voltage unbalance factor by the conventional analytical method, This paper presents a new analytical method for phase and line voltage unbalance factor in 4-wire systems. Two methods indicate exact results.

• Archives of Plastic Surgery
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• v.32 no.3
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• pp.287-292
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• 2005

The definitive correction of secondary lip nasal deformities is a great challenge for plastic surgeons. To rectify the secondary lip nasal deformities, various procedures and its modifications have been reported in many centers. However, no universal agreement exist to correct the various components of secondary nasal deformities. The secondary nasal deformity of the unilateral cleft lip has its own characteristic abnormalities including the retroplaced dome of the ipsilateral nasal tip, hooding of the alar rim, a secondary alar-columellar web, short columella, depressed alar base and so forth. Among these components of secondary nasal deformity, maxillary hypoplasia, especially in the area of piriform aperture, and alveolar bone defect can make the alar base depressed, which in turn, leads to wide and flat nasal profile, obtuse nasolabial angle coupled with subnormal nasal tip projection in aspect of aesthetic consideration. Moreover, the maxillary hypoplasia contributes to reduced size of the nasal airway in combination with other component of external nasal deformity and therefore the nasal obstruction may be developed functionally. Therefore, the current authors have performed corrective rhinoplasty with the augmentation of alar base with various methods which include rearrangement of soft tissue, vertical scar tissue flap and use of allogenic or autologous materials in 42 patients between 1998 and 2003. The symmetric alar base could be achieved, which provides the more accurate evaluation and more appropriate management of the various component of any coexisting secondary nasal deformity. In conclusion, the augmentation of alar base, as a single procedure, is a basic and essential to correct the secondary lip nasal deformities.

• Journal of Biomedical Engineering Research
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• v.25 no.2
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• pp.151-156
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• 2004

The purpose of this study was to develop EMG triggered FES system for restoration of upper extremity function in chronic hemiplegic patients and to identify the optimal location of electrode application for the EMG triggered FES system which produces effective muscle contraction and detects EMG activity for extension in the wrist and finger joints. The stimulus system was composed of EMG measuring component, constant current component and the program for muscle contraction by EMG triggered FES and passive FES. Parameter of electrical stimulation was 35 ㎐ in frequency, 150 ${\mu}\textrm{s}$ in pulse width and symmetric bi-phasic wave. In 15 hemiplegic patients, EMG triggered FES was applied to the proximal half of forearm which was divided into 12 areas. The most sensitive area for measuring EMG activities during extension of the wrist and fingers was area 4, 5 and the optimal location of electrical stimulation for producing extension of the wrist and fingers was area 4, 5, 7, 8. These results suggest that the area 4 and 5 was considered as the most optimal location of electrode application for measuring EMG activities as well as producing extension of the wrist and fingers by EMG triggered FES system.