• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.1
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• pp.7-13
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• 2006

Linear compressors with a free piston driven by a linear motor are widely attention in the cooling apparatus such as refrigerator due to the high efficiency The stroke of piston in the linear compressor driven by LPMSM (Linear Permanent-Magnet Synchronous Motor) can be obtained from Integrating the input voltage and current of LPMSM, but it may be diverged due to dc components in the voltage and current. The strategy to prevent the divergence of stroke using both the high-pass filter and do offset compensation was suggested. The equations for the magnitude and phase of the stroke and also dc offset including the stroke are derived as a function of the cut-off frequency of HPF. The accurate stroke of a piston can be calculated by compensating for dc offset. The performance of the newly developed stroke calculation scheme has been verified by experimentally on a linear compressor drive system, where the control was implemented by a 16-bit DSP.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1777-1783
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• 2012

In this paper, a new motor driving circuit is designed to improve the output performance of DC motor, and a controller is developed with the designed circuit. By the designed driving circuit, a controller can continuously drive DC motors by a transformer which has switching signals of a self-generated circuit to operate it. And while the DC motor have a maximum velocity, the reference voltage can be maintained higher value than that of triangle voltage and it makes the DC motor driving transistor ON and maximum power. A 24V-500W DC motor controller is developed with the proposed motor driving circuit, and also a small electric car is made and the driving test of it is executed. The test results shows that it can continuously control go and back speed of motor with 12A driving current. And also, it is verified that the over current and heat detecting function is operating correctly and the rest value of the used battery can be displayed as 6 step from 20 to 100%.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.5
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• pp.229-237
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• 2001

Until recent years, most of the researches for motor drives focus on the high performance drive of the three phase induction motor, and that of the single phase induction motor(SPIM) is out of interest. The SPIM is widely used at low power level because it has the simple construction and economic advantage. In general such machine has both main winding and auxiliary winding. Conventionally, these winding are fed by only one single phase source, and the speed of the motor is not controlled. The SPIM with an auxiliary winding can be treated as an asymmetrical two phase machine. In this paper the space vector Equivalent circuit of SPIM is derived. For vector control of the SPIM the stator current must be decoupled into the flux producing component and the torque producing component. To accomplish decoupling control, the conventional method requires complex calculation and large computation time. We proposed the equivalent circuit referred to the rotor side, in this case only the stator resistances in the direct axis and the quadrature axis are different each other and the other parameters are represented to be equal. Thus the decoupling of the stator current is similar to that of the three phase induction motor. In this paper, the novel vector control system of the single phase induction motor is proposed. To verify the feasibility of this scheme, simulation and experimentation are carried out. The results prove the excellent characteristics for the dynamic response, which confirms the validity of the proposed system.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1729-1750
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• 2018

Voltage source inverters (VSIs) are widely used to drive induction motors in industry applications. The quality of output waveforms depends on the switching sequences used in pulse width modulation (PWM). In this work, all existing optimal space vector pulse width modulation (SVPWM) switching strategies are studied. The performance of existing SVPWM switching strategies is optimized to realize a tradeoff between quality of output waveforms and switching losses. This study generalizes the existing optimal switching sequences for total harmonic distortions (THDs) and switching losses for different modulation indexes and reference angles with a parameter called quality factor. This factor provides a common platform in which the THDs and switching losses of different SVPWM techniques can be compared. The optimal spatial distribution of each sequence is derived on the basis of the quality factor to minimize harmonic current distortions and switching losses in a sector; the result is the minimum ripple loss SVPWM (MRSLPWM). By employing the sequences from optimized switching maps, the proposed method can simultaneously reduce THDs and switching losses. Two hybrid SVPWM techniques are proposed to reduce line current distortions and switching losses in motor drives. The proposed hybrid SVPWM strategies are MRSLPWM 30 and MRSLPWM 90. With a low-cost PIC microcontroller (PIC18F452), the proposed hybrid SVPWM techniques and the quality of output waveforms are experimentally validated on a 2 kVA VSI based on a three-phase two-level insulated gate bipolar transistor.

• Journal of Convergence for Information Technology
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• v.11 no.7
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• pp.104-110
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• 2021

A novel selective oxidation process has been developed for low source/drain (S/D) series resistance of the fin channel metal oxide semiconductor field effect transistor (MOSFET). Using this technique, the selective oxidation fin-channel MOSFET (SoxFET) has the gate-all-around structure and gradually enhanced S/D extension regions. The SoxFET demonstrated over 70% reduction in S/D series resistance compared to the control device. Moreover, it was found that the SoxFET behaved better in performance, not only a higher drive current but also higher transconductances with suppressing subthreshold swing and drain induced barrier lowering (DIBL) characteristics, than the control device. The saturation current, threshold voltage, peak linear transconductance, peak saturation transconductance, subthreshold swing, and DIBL for the fabricated SoxFET are 305 ㎂/㎛, 0.33 V, 13.5 𝜇S, 76.4 𝜇S, 78 mV/dec, and 62 mV/V, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.379-389
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• 2022

The number of public transportation users has dropped drastically due to COVID-19. In this work, my survey was conducted to uncover the factors that influence citizens' travel patterns. Data were collected and logistic regression analysis on the shifts in transportation was undertaken. Additionally, an importance-performance analysis was carried out to investigate how to effectively operate public transportation systems and improve facilities. The main research findings were as follows: First, the more individuals were concerned about COVID-19 (+) and being infected when using public transportation (+), the greater the tendency to switch to private transportation modes. Secondly, when it came to personal traits, respondents who could drive a car (+) or owned a car (+)or did more online shopping (+) or used public transportation for trips (+) tended to switch over, compared with respondents who could not drive or did not own a caror used public transportation to commute. In addition, respondents who were vaccinated (-) or had more household members tended not to switch transportation modes, compared with those who were not vaccinated or had fewer household members. Third, it is important to continue the following efforts to safeguardhygiene linked to public transportation: wearing masks, disinfecting hands, controlling diseases, and general cleaning. The conclusion was that it is important to put traffic congestion and ventilation issues first, especially in regards public transportation, which was not rated as satisfactory enough compared to its importance. The research findings can provide useful basic data when establishing countermeasures to the current COVID-19 circumstances in the areas of public transportation operation and management and in the event of an infectious disease outbreak in the future.

• Journal of the Korean Vacuum Society
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• v.17 no.5
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• pp.461-465
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• 2008

The phase transformation in a film influences its surrounding. Effects of the precrystallization method, which removes influences on gate oxide caused by lateral crystallization, in metal-induced unilaterally crystallized polycrystalline silicon thin-film transistor devices and circuits were studied. Device by the method was shown to have a higher current drive, compared with conventional postcrystallized device. Moreover, we studied DC bias-induced changes in the performance of ring oscillator. PMOS inverters fabricated using precrystallized silicon films have very high dynamic and stable performance, compared with inverters fabricated using postcrystallized silicon films.

• Journal of Digital Convergence
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• v.17 no.12
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• pp.203-210
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• 2019

Most cars today use electronic control to control the state of the engine to achieve optimum performance. This study developed a device for maintaining fault diagnosis and optimal vehicle status by displaying the engine information of a car on the screen in real time using can communication. This system displays information generated from the engine to the driver in real time such as engine intake and exhaust temperature, current battery voltage, tire pressure, RPM, DPF collection amount, torque, and horsepower through the OBD2 socket. You can check immediately. It can help you to drive safely by measuring tire pressure and displaying it on the screen, and it provides a mode to set the shift timing to suit your taste. In particular, in the case of diesel engine cars, the problems caused by smoke can adversely affect the performance and environmental pollution. Therefore, the system was developed to display the DPF collection amount on the system screen to prevent environmental pollution and to manage the vehicle efficiently.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5412-5419
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• 2011

The need is growing for high-speed spindle because various equipment are becoming more precise, miniaturization and high speed with the development of industries. Air-lubricated dynamic bearings are widely used in the optical lithographic manufacturing of wafers to realize nearly zero friction for the motion of the stage. Air-lubricated dynamic bearing can be used in high-speed, high-precision spindle system and hard disk drive(HDD) because of its advantages such as low frictional loss, low heat generation, averaging effect leading better running accuracy. In the paper, numerical analysis is undertaken to calculate the performance of air-lubricated dynamic bearing with herringbone groove. The static performances of herringbone groove bearings which can be used to support the thrust load are calculated. Electrochemical micro machining($EC{\mu}M$) which is non-contact ultra precision machining method has been developed to fabricate the air-lubricated dynamic bearing and optimum parameters which are inter electrode gap size, concentration of electrolyte, machining time are simulated using numerical analysis program.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.534-542
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• 2003

Small electric motors in an automobile perform various tasks such as engine cooling, pumping, HVAC etc. At present, most of them are DC motors supplied by 12V or 24V batteries. However, DC motors suffer from low efficiency, life cycles and reliability. Therefore, there is a growing interest in substituting DC motors for advanced at motors including switched reluctance motors(SRM). Although there are several other forms SRM convertors, they are either unsatisfactory to the control performance or unsuitable for the 12V battery source. Especially, a conventional asymmetric converter of SRM provides the best flexible and effective control to the current waveform of SRM, but it has the most switches and produces conducting voltage drops across two power switches during SRM operation. For automotive applications with a 12V battery source, this circuit is inadequate. For considering the requirement for effective operation and simple structure of converter in the limited internal circumstance of automobiles, the author inclines toward selecting Modified C-dump converter and Energy efficient c-dump converter.