• 공학교육연구
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• 제4권2호
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• pp.27-34
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• 2001

효과적 가상 교육 시스템의 구축을 위해서 많은 공학과 자연과학 분야의 가상 교육 시스템은 자바 애플릿을 개발하여 제공한다. 본 논문에서는 이러한 자바 애플릿을 빠르고 효과적으로 개발하기 위해 Java Beans 기술을 사용, 애플릿 개발에 반복적으로 사용되는 기능을 가진 컴포넌트로 개발하였으며 이러한 Java Beans 컴포넌트들을 조합하여 교육 효과를 높일 수 있는 5가지 기본적인 애플릿의 패턴을 제시하였다. 이 개발 환경을 이용하여 전기회로, 전기기기, 공업 수학 등의 공학 과목들의 교육용 애플릿을 개발하는데 효과적으로 사용하고 있으며 개발 애플릿에 대한 개발 시간을 정량적으로 고찰하여 제시하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.1498-1500
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• 2004

A novel technique for efficiently extracting maximum power from PV panels is proposed, consisting of a modified buck-boost converter, witch is controlled by a DSP. A variation of the proposed MPPT technique is directly use the modified buck-boost converter current reference as a control parameter. Also 4 parallel boost converters have division of load. A theoretical analysis of the proposed converter is performed and compared with experimental results obtained from a 1k[W] prototype solar panel under a controlled experimental setup.

• 전력전자학회논문지
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• 제27권1호
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• pp.9-17
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• 2022

The series-connected semiconductor devices structure is one way to achieve a high voltage rating. However, a problem with voltage imbalance exists in which different voltages are applied to the series-connected switches. This paper proposed a new voltage balancing technique that controls the turn-off delay time of the switch by adding one bipolar junction transistor to the gate turn-off path. The validity of the proposed method is proved through simulation and experiment. The proposed active gate driver not only enables voltage balancing across a variety of current ranges but also has a greater voltage balancing performance compared with conventional RC snubber methods.

• 한국전기전자재료학회논문지
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• 제25권2호
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• pp.147-152
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• 2012

This paper dealt with the frequency component analysis of acoustic signals produced by corona and series-arc discharges as a diagnostic technique for closed-switchboards. Corona and series-arc discharge were simulated by a needle-plane electrode and an arc generator specified in UL1699, respectively. Acoustic signal was detected by a wideband acoustic sensor with a frequency bandwidth of 4 Hz~100 kHz (-3 dB). We analyzed frequency spectrums of the acoustic signals detected in various discharge conditions. The results showed that acoustic signals mainly exist in ranges from 30 kHz to 60 kHz. From the experimental results, an acoustic detection system which consists of a constant current power supply (CCP), a low noise amplifier (LNA) and a band pass filter was designed and fabricated. The CCP separates the signal component from the DC source of acoustic sensor, and the LNA has a gain of 40 dB in ranges of 280 Hz~320 kHz. The high and the low cut-off frequency are 30 kHz and 60 kHz, respectively. We could detect corona and series-arc discharges without any interference by the acoustic detection system, and the best frequency is considered in ranges of 30 kHz~60 kHz.

• ETRI Journal
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• 제28권4호
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• pp.533-536
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• 2006

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non-return to zero operation with 12 dB extinction ratio is obtained. A four-channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.

• Journal of Electrical Engineering and Technology
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• 제5권1호
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• pp.36-44
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• 2010

This paper presents the design of an algorithm to detect, identify, and locate faults in radial distribution feeders of Provincial Electricity Authority (PEA). The algorithm consists of three major steps. First, the adaptive algorithm is applied to track/estimate the system electrical parameter, i.e. current phasor, voltage phasor, and impedance. Next process, the impedance rule base is used to detect and identify the type of fault. Finally, the current compensation technique and a geographic information system (GIS) are applied to evaluate a possible fault location. The paper also shows the results from field tests of the automate fault location and illustrates the effectiveness of the proposed fault location scheme.

• Neurospine
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• 제15권4호
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• pp.306-322
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• 2018

This review introduces the current technique of photoacoustic imaging as it is applied in imaging-guided surgery (IGS), which provides the surgeon with image visualization and analysis capabilities during surgery. Numerous imaging techniques have been developed to help surgeons perform complex operations more safely and quickly. Although surgeons typically use these kinds of images to visualize targets hidden by bone and other tissues, it is nonetheless more difficult to perform surgery with static reference images (e.g., computed tomography scans and magnetic resonance images) of internal structures. Photoacoustic imaging could enable real-time visualization of regions of interest during surgery. Several researchers have shown that photoacoustic imaging has potential for the noninvasive diagnosis of various types of tissues, including bone. Previous studies of the surgical application of photoacoustic imaging have focused on cancer surgery, but photoacoustic imaging has also recently attracted interest for spinal surgery, because it could be useful for avoiding pedicle breaches and for choosing an appropriate starting point before drilling or pedicle probe insertion. This review describes the current instruments and clinical applications of photoacoustic imaging. Its primary objective is to provide a comprehensive overview of photoacoustic IGS in spinal surgery.

• 한국공작기계학회논문집
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• 제17권6호
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• pp.132-145
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• 2008

We propose a new technique for autonomous navigation and travelling of mobile robot based on ultrasonic sensors through the narrow labyrinth that leave only distance of a few centimeters on each side between the guides and the robot. In our current implementation the ultrasonic sensor system fires at a rate of 100 ms, that is, each of the 8 sensors fires once during each 100 ms interval. This is a very good firing rate, implemented here for optimal performance. This paper presents an extensively tested and verified solution to the problem of obstacle avoidance. Our solution is based on the optimal placement of ultrasonic sensors at strategic locations around the robot. Both the sensor location and the associated navigation algorithm are defined in such a way that only the accurate radial sonar data is used for accurate travelling.

• Current Optics and Photonics
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• 제1권4호
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• pp.289-294
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• 2017

A high-performance time-division multiplexing (TDM) -based multiuser (MU) multiple-input multipleoutput (MIMO) system for efficient indoor visible-light communication (VLC) is presented. In this work, a MIMO technique based on RGB light-emitting diodes (LEDs) with selection combining (SC) is utilized for data transmission. That is, the proposed scheme employs RGB LEDs for parallel transmission of user data and transmits MU data in predefined slots of a time frame with a simple and efficient design, to schedule the transmission times for multiple users. Simulation results demonstrate that the proposed scheme offers an approximately 6 dB gain in signal-to-noise ratio (SNR) at a bit error rate (BER) of $3{\times}10^{-5}$, as compared to conventional MU single-input single-output (SISO) systems. Moreover, a data rate of 66.7 Mbps/user at a BER of $10^{-3}$ is achieved for 10 users in indoor VLC environments.

• 조명전기설비학회논문지
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• 제22권3호
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• pp.74-78
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• 2008

Conventionally, when we need to know about the dynamic characteristics of motors, the moving band method has been the first considerable technique. In this paper, we have investigated the moving material method that moves the property of the material in moving area elements of BLDC motors, instead of moving mesh elements of the rotor. From this method, we can reduce the demanded HDD memory for FEM analysis and the calculation time with same results.