• The Transactions of the Korean Institute of Power Electronics
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• 제7권3호
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• pp.224-236
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• 2002

In this paper, a comparative study on the performance of two-phase and three-phase randomized pulse position PWM scheme for mitigation of audible switching acoustic noise in motor drives is done. In the randomized Pulse Position PW, each of two-Phase or three-phase PWM Pulses is located randomly in each switching interval. Simulation and experimental efforts were executed to investigate the spread effects of Power spectra of inverter output voltage, waveforms of ripple current and audible switching acoustic noise. As results, two-phase RP% scheme is more effective from the viewpoint of switching loss and ease of implementation while the three-phase RPWM scheme is more effective from the viewpoint of the spread effects of power spectra. Also, from the view point of the audible switching acoustic noise in motor drives, two-phase and three-phase RPW schemes are nearly the same.

• Journal of KIISE:Computing Practices and Letters
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• 제10권5호
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• pp.394-405
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• 2004

To make Web Services the real applications, the efficient mechanisms for Web Services discovery, Web Services composition and Web Services execution must be provided. Among these issues, especially, Web Services composition plays the key roles in Web Services applications that are loosely coupled and composed applications consisted of primitive Web Service components. In this paper we demonstrate a new Web Service composition approach using ontologies. We apply ontologies to describe Web Services information such as Web Services input/output parameters, pre conditions, post conditions and other necessary management information. In this paper, we also introduce Action ontology and Object ontology to describe the functional properties of Web Services These ontologies offer semantic description of Web Services functionalities beyond the limitation of the current WSDL. We can achieve semantic interoperabilities between heterogeneous Web Services in terms of conceptual processing and realize semantic services composition. We implement semantic Web Services composition system called Genie based on service description ontologies.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제16권1호
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• pp.627-633
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• 2015

We designed of a LDO regulator with a OVP and UVLO protection function for a PMIC. Proposed LDO regulator circuit consists of a BGR reference circuit, an error amplifier and a power transistor and so on. The proposed LDO regulator is designed for low voltage input power protection. Proposed LDO circuit generated fixed 2.5 V from a supply of 3.3V. It was designed with 3.3 V power supply using a $0.35{\mu}m$ CMOS technology. SPICE simulation results showed that the proposed circuit provides 0.713 mV/V line regulation with output 2.5 V ~ 3.9 V and $8.35{\mu}V/mA$ load regulation with load current 0 mA to 40 mA.

• Fashion & Textile Research Journal
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• 제16권1호
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• pp.145-152
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• 2014

The usage of textile-based sensors has increased due to their many advantages (compared to IT sensors) when applied to body assessment and comfort. Textile-based sensors have different detecting factors such as pressure, voltage, current and capacitance to investigate the characteristics. In this study, textile-based sensor fabrics with sheath-core type conductive yarns were produced and the relationship between capacitance changes and applied load was investigated. The physical and electric properties of textile-based sensor fabrics were also investigated under various laminating conditions. A textile based pressure sensor that uses a sheath-core conductive yarn to ensure the stability of the pressure sensor in the textile-based sensor (the physical structure of the reaction characteristic of the capacitance) is important for the stability of the initial value of the initial capacitance value outside the characteristic of the textile structural environment. In addition, a textile based sensor is displaced relative to the initial value of the capacitance change according to pressure changes in the capacitance value of the sensor due to the fineness of the high risk of noise generation. Changing the physical structure of the fabric through the sensor characteristic of the pressure sensor via the noise generating element of laminating (temperature, humidity, and static electricity) to cut off the voltage output element to improve the data reliability could be secured.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제26권10호
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• pp.771-777
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• 2013

This paper dealt with the development of a LED floodlight for naval vessels to replace the conventional floodlight using an incandescent and a halogen lamp. We found a technical solution for current problems of conventional lights and also improved optical characteristics by developing a LED floodlight which has a typical long-lived light source with high efficiency. To satisfy the requirements specified in Korea Standard Vessels (KS V), the optical structure was designed with selected LED package and lens. A LED module was composed of 10 LEDs in series for stable luminous output, and an aluminium heat sink was adopted for effective heat-radiation design. The LED floodlight was fabricated as a module type so that it can easily replace the conventional light source. The power consumption of the prototype floodlight was only a tenth of a conventional one with the same optical performance. Also, a test showed the floodlight satisfied the electrical, optical and environmental requirements of the standards.

• Journal of Electrical Engineering and Technology
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• 제10권6호
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• pp.2256-2261
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• 2015

In the power plant using high temperature fuel cells such as Molten Carbonate Fuel Cell(MCFC), and Solid Oxide Fuel Cell(SOFC), the generated electric power per area of power generation facilities is much higher than any other renewable energy sources. - High temperature fuel cell systems are capable of operating at MW rated power output. - It also has a feature that is short for length of the line for connecting the interior of the generation facilities. In normal condition, these points are advantages for voltage drops or power losses. However, in abnormal condition such as fault occurrence in electrical system, the fault currents are increased, because of the small impedance of the short length of power cable. Commonly, to minimize the thermal-mechanical stresses on the stack and increase the systems reliability, we divided the power plant configuration to several banks for parallel operation. However, when a fault occurs in the parallel operation system of power main transformer, the fault currents might exceed the interruption capacity of protective devices. In fact, although the internal voltage level of the fuel cell power plant is the voltage level of distribution systems, we should install the circuit breakers for transmission systems due to fault current. To resolve these problems, the SFCL has been studied as one of the noticeable devices. Therefore, we analyzed the effect of application of the SFCL on bus tie in a fuel cell power plants system using PSCAD/EMTDC.

• Progress in Medical Physics
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• 제29권1호
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• pp.16-22
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• 2018

Current dosimetry protocols recommend the use of parallel-plate chambers in electron dosimetry because the electron fluence perturbation can be effectively minimized. However, substitutable methods to calibrate and measure the electron output and energy with the widely used cylindrical chamber should be developed in case a parallel-plate chamber is unavailable. In this study, we measured the correction factors and absolute dose-to-water of electrons with energies of 4, 6, 9, 12, 16, and 20 MeV using Farmer-type and Roos chambers by varying the dose rates according to the AAPM TG-51 protocol. The ion recombination factor and absolute dose were found to be varied across the chamber types, energy, and dose rate, and these phenomena were remarkable at a low energy (4 MeV), which was in good agreement with literature. While the ion recombination factor showed a difference across chamber types of less than 0.4%, the absolute dose differences between them were largest at 4 MeV at approximately 1.5%. We therefore found that the absolute dose with respect to the dose rate was strongly influenced by ion-collection efficiency. Although more rigorous validation with other types of chambers and protocols should be performed, the outcome of the study shows the feasibility of replacing the parallel-plate chamber with the cylindrical chamber in electron dosimetry.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제38권2호
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• pp.107-114
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• 2014

This paper proposes a common rail pressure control algorithm for passenger car diesel engines. For handling the parameter-varying characteristics of common rail systems, the quantitative feedback theory (QFT) is applied to the design of a robust rail pressure control algorithm. The driving current of the pressure control valve and the common rail pressure are used as the input/output variables for the common rail system model. The model parameter uncertainty ranges are identified through experiments. Rail pressure controller requirements in terms of tracking performance, robust stability, and disturbance rejection are defined on a Nichols chart, and these requirements are fulfilled by designing a compensator and a prefilter in the QFT framework. The proposed common rail pressure control algorithm is validated through engine experiments. The experimental results show that the proposed rail pressure controller has a good degree of consistency under various operating conditions, and it successfully satisfies the requirements for reference tracking and disturbance rejection.

• Journal of Sensor Science and Technology
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• 제27권5호
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• pp.311-316
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• 2018

An antenna-coupled bolometer-type terahertz sensor was designed, fabricated, evaluated, and utilized to obtain terahertz transmission images. The sensor consists of a thin film bowtie antenna that resonates accordingly in response to an incident terahertz beam, a heater that converts the applied current in the antenna into heat, and a microbolometer that converts the rise in temperature into a change in resistance. The device is fabricated by a bulk micromachining process on a 4-inch silicon wafer. The fabricated sensor chip has a size of $2{\times}2mm$ and an active area of $0.1{\times}0.1mm^2$. The temperature coefficient of resistance (TCR) of the bolometer film (VOx) is 2.0%, which is acceptable for bolometer applications. The output sensor signal is proportional to the power of the incident terahertz beam. Transmission images were obtained with a 2-axis scanning imaging system that contained the sensor. The small active area of the sensor will enable the development of highly sensitive focal plane array sensors in terahertz imaging cameras in the future.

• Transactions of the Korean Society of Automotive Engineers
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• 제25권1호
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• pp.82-91
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• 2017

This paper is a study on the bi-directional DC-DC converter, one of the key elements of 48V-12V dual systems in mild hybrid electric vehicles. Mild hybrid electric vehicles require a bi-directional DC-DC converter that can efficiently transmit power in two directions between a 48V battery and a 12V battery. To develop a bi-directional DC-DC converter with better price competitiveness, upgraded fuel economy, excellent performance and smaller size, this study designed, produced and presented a circuit that improved on the existing one. In the proposed 8-phase bi-directional DC-DC converter, the size of the passive element was reduced through the 8-phase interleaved topology, whereas downscaling had previously posed a difficulty. This study also designed and produced a 2.5kW class prototype. Based on the proposed 8-phase interleaved topology, a size of 227.5 (W) * 172 (L) * 64.35 (H) was achieved. In the boost mode operation and buck operation modes, the maximum efficiency was recorded at 94.04 % and 95.78 %, respectively.