• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.166-173
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• 2006

In this study, a probe array has been developed for use in a data storage device that is based on scanning probe microscope (SPM) and MEMS technology. When recording data bits by poling the PZT thin layer and reading them by sensing its piezoresponse, commercial probes of which the tip heights are typically shorter than $3{\mu}m$ raise a problem due to the electrostatic forces occurring between the probe body and the bottom electrode of a medium. In order to reduce this undesirable effect, a poly-silicon probe with a high aspect-ratio tip was fabricated using a molding technique. Poly-silicon probes fabricated by the molding technique have several features. The tip can be protected during the subsequent fabrication processes and have a high aspect ratio. The tip radius can be as small as 15 nm because sharpening oxidation process is allowed. To drive the probe, electrostatic actuation mechanism was employed since the fabrication process and driving/sensing circuit is very simple. The natural frequency and DC sensitivity of a fabricated probe were measured to be 18.75 kHz and 16.7 nm/V, respectively. The step response characteristic was investigated as well. Overshoot behavior in the probe movement was hardly observed because of large squeeze film air damping forces. Therefore, the probe fabricated in this study is considered to be very useful in probe-based data storages since it can stably approach toward the medium and be more robust against external shock.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.6
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• pp.105-112
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• 2003

Diode rectifier which can't be controlled output voltage and phase control converter as AC/DC converter have low power factor and harmonics of lower order in the line current. In this paper, three phase PWM(Pulse Width Modulation) AC/DC boost converter is studied to solve these problems. The characteristics of a proposed converter are to control the phase of current without current sensor as a very simple control algorithm using circuit parameters only and to apply sinusoidal PWM method with fixed switching frequency due to a difficult design of input filter and switching device. We simulate for the proposed algorithm that high power factor is achieved and DC link voltage has fast dynamic response without ripple in rectifying and regenerating operation. As a result of experiment with circuit parameter(inductor, capacitor) decided in simulation, the proposed converter had high power factor and reduction of low order harmonics as against diode rectifier.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1708-1714
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• 2010

In this paper, the full color LED billboard or a general quality improvement methods of quality gamma correction, brightness, and brightness adjustment, etc., regardless of the overall color of images uniformly bright or dark have been taken care of. The video itself, but simply expressed as a uniform brightness of a certain size, how to adjust the brightness of input video signal does not reflect the characteristics of the entire screen with just a lighter or darker line is only feeling was brought. So, unlike conventional video transmission system with new LED display technology in the histogram analysis of image data is input by the input image data by determining the luminance values of the attributes are reflected, as appropriate based on the histogram of the distribution of brightness values By controlling the LED display is expressed in the uniform image can improve the brightness control, histogram distribution of the image as full color billboards driven processing technology is proposed.

• Journal of Internet of Things and Convergence
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• v.3 no.1
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• pp.25-31
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• 2017

In the future a future type new city and the latest apartment will be built, and the IoT technology will be constructed and combined in large numbers indoors of ordinary households. An air cleaner that makes people in it comfortable is built in, and the suction port that sucks in the air of the air purifier and the discharge port that discharges it are set up around the room and come out. However, this is impossible to adjust because there is only a central switch on / off. Also, consuming a lot of electricity so that many electricity charges are caused by huge electricity consumption will eventually be a waste of resources. This would like to be adjusted and driven through the fine dust detection device to the room built-in air purifier and that has provided a solution to save electricity. In addition, since it exists in and around the room, you can grasp the position of the person and connect to the home network to enhance the convenience. Also, through analysis of the air, we provide a health-check solution that checks the user's health and adjusts it appropriately.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.3
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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 the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.301-306
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• 2003

We have designed embedded web server system and ported Linux operating system version 2.4.1 at our system. And then We implemented to control and monitor widely separated hardware. Web server is the Boa web server with General Public License. We designed for this system using of Cirrus logic's EP7312 ARM core base processor and connecting input and output device at GPIO port of EP7312. Device driver of General purpose I/O for Linux OS is designed. And then the application program controlling driver is implemented to use of common gate interface C language. User is available to control and monitor at client PC. This method have benefit to reduce the Expenditure of hardware design and development time against PC base system and have various and capacious application against firmware base system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.8
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• pp.3391-3397
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• 2011

These excavators have been widely used due to their flexibility in handing various tasks via simple changes of their attachments. Since the performance of manually-operated excavators heavily depend on the operators' skill level, there is a strong need for developing automatic excavators in the industry. In order to achieve such goals, exiting approaches have studied direct modification of existing hydraulic systems in the excavator for feed back control of each link. This paper presents a miniaturized automatic excavator that can be used for the development and demonstration of advanced control algorithm for excavators under a safer environment with reduced cost. Two PCs were installed and connected to the excavator through wireless communications for its control and monitoring. Tracking control of each link using a time varying sliding mode controller was performed through experiments on the developed system to demonstrate its ability.

• The Journal of the Korea Contents Association
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• v.8 no.7
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• pp.93-102
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• 2008

With the advance of ubiquitous environment, a lot of changes occur in various kinds of applications. The marketing for festivals is not an exception. Due to the needs for changes in the festival marketing, researches about active marketing suitable for ubiquitous environment are increasing. The purpose of this paper is to develop a u-pamphlet based on PDA and QR code. In this paper, we focus on Jeju Jeongweol Daeboreum Fire Festival, shortly Jeju Fire Festival, as a pamphlet content, which is one of the best domestic festivals. When tourists attend Jeju Fire Festival, the proposed u-pamphlet provides various forms of Jeju Fire Festival information either by accessing digital content stored in PDA directly or by interpreting QR code in the Festival area and connecting remote digital content indirectly. In addition, in order to analyze the necessity, the usefulness, the functionality, and the technical barriers of the u-pamphlet, we make a questionnaire after we exhibit our u-pamphlet.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.353-356
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• 2009

A pivotal mechanical balance of plant for 75kW class molten carbonate fuel cells comprise of a catalytic burner and an ejector which has been designed and tested in KEPRI(Korea Electric Power Research Institute). The catalytic burner, which oxidizes residual fuel in the anode tail gas, was operated at several conditions. Some problems arose due to local overheating or auto-ignition, which could limit the catalyst life. The catalytic burner was designed by considering both gas mixing and gas velocity. Test results showed that the temperature distribution is very uniform. In addition, an ejector is a fluid machinery to be utilized for mixing fluids, maintaining vacuum, and transporting them. The ejector is placed at mixing point between the anode off gas and the cathode off gas or the fresh air Several ejectors were designed and tested to form a suction on the fuel tail gas and balance the differential pressures between anode and cathode over a range of operating conditions. The tests showed that the design of the nozzle and throat played an important role in balancing the anode tail and cathode inlet gas pressures. The 75kW MCFC system built in our ejector and catalytic burner was successfully operated from Novembe, 2008 to April, 2009. It recorded the voltage of 104V at the current of 754A and reached the maximum generating power of 78.5kW DC. The results for both stand-alone and integration into another balance of plant are discussed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.10
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• pp.891-898
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• 2007

Optimal aerodynamic design for the pitch-controlled horizontal axis wind turbine and its aerodynamic performance for various pitch angles are performed numerically by using the blade element momentum theory. The numerical calculation includes effects such as Prandtl‘s tip loss, airfoil distribution, and wake rotation. Six different airfoils are distributed along the blade span, and the special airfoil i.e. airfoil of 40% thickness ratio is adopted at the hub side to have structural integrity. The nonlinear chord obtained from the optimal design procedure is linearized to decrease the weight and to increase the productivity with very little change of the aerodynamic performance. From the comparisons of the power, thrust, and torque coefficients with corresponding values of different pitch angles, the aerodynamic performance shows delicate changes for just $3^{\circ}$ increase or decrease of the pitch angle. For precisive pitch control, it requires the pitch control algorithm and its drive mechanism below $3^{\circ}$ increment of pitch angle. The maximum torque is generated when the speed ratio is smaller than the designed one.