• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.29-35
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• 2011

In this paper, an integrated simulation model for designing multi-agent system based DEMS (distributed energy management system) in stand-alone micro-grid system is proposed. In the design of the EMS(energy management system), the multi-agent based DEMS are more effective than conventional centralized EMS, but it is difficult to design the DEMS by general design tools for power system because of various states of a microgrid system during operation of stand-alone mode. Also, since performance test of the DEMS using a real system is inefficient, an integrated simulation model is required for designing an effective multi-agent system based DEMS. The proposed model consists of Matlab/SimPowerSystems based simulation model of the microgrid system and the Multi-agnet based DEMS designed by Matlab/StateFlow tool. In order to show the effect of the proposed model, the model outputs are analyzed for specified operation conditions.

• Journal of Energy Engineering
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• v.25 no.1
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• pp.9-14
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• 2016

This study has been carried out to develop TM (Thermal to Mechanical) conversion systems for electric power generation using one of the Low Temperature Differential (LTD) Stirling engines called MM-7 capable of harnessing low temperature waste heat whose temperature is only $20{\sim}30^{\circ}C$ above the ambient. Measurements were made on the torque and rpm for a number of temperature differentials between the engine hot and cold ends, which could be effectively applied in developing the most suitable configuration for the high performance TM (Thermal to Mechanical) conversion system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.11 no.1
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• pp.41-55
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• 2003

A calibration jet system using separate blower is developed to calibrate a flow sensor effectively. Designed open circuit type mini calibration jet system, which has the dimension of $0.5m(W){\times}1.17m(H)$ is small compared with conventional calibration jet systems. The exit of nozzle has exchangeable contractions with a cross section area of $38.5cm^2$ , and a cross section area of $113.1cm^2$, respectively. The ranges of wind speed at exit of exchangeable nozzles are $7.5{\sim}42\;m/s$ and $1.8{\sim}16.5\;m/s$, respectively. The input power for the high pressure blower is 1.18kW. The turning vanes for corner was rolled flat plate parallel to the flow direction. The flow conditioning screen was located immediately downstream of the wide-angle diffuser. The honeycomb and two flow conditioning screens were located in the stagnation chamber. From the economical point of view and the simplicity of the calibration jet system set up and handling, it can be said that the developed calibration jet system is an effective calibration jet system. This system can also be used to calibrate the flow sensor with high resolution.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.323-323
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• 2013

High power light-emitting diodes (LEDs) are widely used in many device applications due to its ability to operate at high power and produce high luminance. However, releasing the heat accumulated in the device during operating time is a serious problem that needs to be resolved to ensure high optical efficiency. Ceramic or Aluminium base metal printed circuit boards are generally used as integral parts of communication and power devices due to its outstanding thermal dissipation capabilities as heat sink or heat spreader. We investigated the characterisation of electroless plating of Ni-B film according to plating bath temperature, ranging from $50^{\circ}C$ to $75^{\circ}C$ on Ag paste/anodised Al ($Al_2O_3$)/Al substrate to be used in metal PCB for high power LED packing systems. X-ray diffraction (XRD), Field-Emission Scanning Electron Microscopy (FE-SEM) and X-ray Photoelectron Spectroscopy (XPS) were used in the film analysis. By XRD result, the structure of the as deposited Ni-B film was amorphous irrespective of bath temperature. The activation energy of electroless Ni-B plating was 59.78 kJ/mol at the temperature region of $50{\sim}75^{\circ}C$. In addition, the Ni-B film grew selectively on the patterned Ag paste surface.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.1-8
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• 2013

This paper presents a variable gain amplifier(VGA) without passive devices. This VGA employes the architecture of current feedback amplifier and variable gain can be achieved by using the GM ratios of two trans-conductance(gm) circuits. To obtain linearity and high gain, it uses current division technique and source degeneration in feedback GM circuits. Input trans-conductance(GM) circuit was biased by using a tunable voltage controller to obtain variable gain. The prototype of the VGA is designed in $0.35{\mu}m$ CMOS technology and it is operating in sub-threshold region for low power consumption. The the gain of proposed VGA is varied from 23dB to 43dB, and current consumption is $2.82{\mu}A{\sim}3{\mu}A$ at 3.3V. The area of VGA is 1$120{\mu}m{\times}100{\mu}m$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8B
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• pp.812-821
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• 2009

This paper proposes a novel dynamically reconfigurable switch for various multimedia applications in hybrid NoC systems. Current NoC systems, which adopt hybrid NoC structure with fixed switch and job distribution algorithms, require designers to precisely predict the property of applications to be processed. This paper proposes a reconfigurable switch which minimizes buffer overflow in various multimedia applications running on an NoC system. To verify the performance of the proposed system, we performed experiments on various multimedia applications running on embedded systems, such as MPEG4 and MP3 decoder, GPS positioning system, and OFDM demodulator. Experimental results show that buffer overflow has been decreased by 41.8% and 29.0%, respectively, when compared with NoC systems having sub-clusters with mesh or star topology. Power usage has been increased by 2.3% compared with hybrid NoC systems using fixed switches, and chip area has been increased from -0.6% to 5.7% depending on sub-cluster topology.

• Progress in Superconductivity and Cryogenics
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• v.9 no.4
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• pp.32-36
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• 2007

We fabricated and tested a novel hybrid superconducting fault current limiter (SFCL) of three-phase $24kV_{rms}/630A_{rms}$ rating. In order to apply conventional resistive SFCLs into electric power systems, the urgent issues to be settled are as follows, such as initial installation price of SFCL, operation and maintenance cost due to ac loss of superconductor and the life of cryostat, and high voltage and high current problems. The ac loss and high cost of superconductor and cryostat system are main bottlenecks for real application. Furthermore in order to increase voltage and current ratings of SFCL, a lot of superconductor components should be connected in series and parallel which resulted in extreme high cost. In addition, the method to quench all components at the same instant needs very sophisticated skill and careful operation. Due to these problems, the practical applications of SFCL were pending. Therefore, in order to make practical SFCL, the price of SFCL should be lowered and should meet the demand of utilities. We designed novel hybrid SFCL which combines superconductor and conventional electric equipment including vacuum interrupter, power fuse and current limiting reactor. The main purpose of hybrid SFCL is to drastically reduce total usage of superconductor by adopting current commutation method by use of superconductor and high fast switch. Consequently, it was possible to get the satisfactory test results using this method, and further works for field tests are in the process.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.219-222
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• 2004

There are several factors that disturb an Ultra-Wideband (UWB) radio propagation in an indoor environment such as path loss, shadowing and multipath fading. These factors directly affect the quality of the received signal. In this paper, we investigated the influence of the human body shadowing on UWB propagation based on measured wireless channel in an anechoic chamber. The characteristics of the UWB channel including the transmitter and the receiver antenna effects are acquired over the frequency bandwidth of 3${\sim}$11 GHz. The major factors such as the power delay profile (PDP), the angular power distribution (APD), the pulse distortion and the RMS delay spread caused by the human body shadowing are presented.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1453-1459
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• 2015

Loss of excitation (LOE) relay is prevalently used to protect synchronous generator. The widely used method for synchronous generator LOE protection is a negative offset mho relay with two zones. The basis of this relay is identical to mho impedance relay. In other words, this relay calculates impedance by measuring voltage and current at the generator terminal. On the other hand, the presence of series compensation, changes measured voltage and current signals during loss of excitation. This paper reveals that the presence of series compensators such as fixed series capacitors (FSCs) and static synchronous series compensator (SSSC) causes a significant delay on the performance of generator LOE relay. It is also shown that the presence of SSSC causes the LOE relay to be under-reached. Different operating modes of the power system, the SSSC and also different percentages of series capacitive compensations have been considered in the modeling. All the detailed simulations are carried out in the MATLAB/Simulink environment using the SimPowerSystems toolbox.

• Nuclear Engineering and Technology
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• v.39 no.1
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• pp.85-94
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• 2007

The Korean nuclear fuel cycle was modeled by the dynamic analysis method, which was applied to the once-through and alternative fuel cycles. First, the once-through fuel cycle was analyzed based on the Korean nuclear power plant construction plan up to 2015 and a postulated nuclear demand growth rate of zero after 2015. Second, alternative fuel cycles including the direct use of spent pressurized water reactor fuel in Canada deuterium uranium reactors (DUPIC), a sodium-cooled fast reactor and an accelerator driven system were assessed and the results were compared with those of the once-through fuel cycle. The once-through fuel cycle calculation showed that the nuclear power demand would be 25 GWe and the amount of the spent fuel will be ${\sim}65000$ tons by 2100. The alternative fuel cycle analyses showed that the spent fuel inventory could be reduced by more than 30% and 90% through the DUPIC and fast reactor fuel cycles, respectively, when compared with the once-through fuel cycle. The results of this study indicate that both spent fuel and uranium resources can be effectively managed if alternative reactor systems are timely implemented along with the existing reactors.