• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.48-52
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• 2005

The research topic of super-RENS technology is shifting from the signal intensity (CNR; Carrier to Noise Ratio) to the signal uniformity (Jitter or bER). To achieve an uniform signal characteristics, it is important to reduce signal fluctuation in a super-RENS disc. In this study, we investigated the relation between signal fluctuation and low frequency noise (LFN), and analyzed LFN increase in recording and readout processes. It was found that signal fluctuation had a close relationship with the LFN. Also, it was found that the recorded mark shape such a bubble type and high readout power increased the LFN in recording and readout process of a super-RENS disc. So, using non-bubble type recording material and low super-resolution readout material, we markedly improved the LFN in a super-RENS disc.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1700-1706
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• 2016

In this paper, a dual-stator, spoke-type linear vernier machine (DSSLVM) for wave energy extraction application was proposed. This machine is capable of producing a competitively high thrust force and force density at a low operation speed in direct drive systems. The operation principal and working of the proposed DSSLVM were studied. The stator core height is adjusted to improve the overall force density of the proposed machine while reducing the force ripple. To evaluate the advantages of the proposed DSSLVM, the main performance was compared with that of a recently developed linear primary permanent magnet vernier machine (LPPMVM). The proposed machine exhibited greater thrust force and force density, an improved power factor and lower force ripple with the same permanent magnet (PM) volume compared to the LPPMVM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.283-283
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• 2010

Smart street light controller is a product with advance micro controller base for energy saving in conventional street lighting systems. Intelligent Street light controller are specially developed for automation and energy saving in conventional street light systems and lighting systems. It is so designed that it operates on sunrise & sun set timings according to longitude of particular location with facilitate to set month wise civil twilight timings to cope up with all seasons. Dimming (Power down) mode selection switch on/off at fixed times with relay or contactor. Night dimming, staggering and intelligent control reduces burn hours and increases the lifetime of lamps with about 30% and low annual operating cost type base are among the most inexpensive wireless technologies available. Low initial costs As PLC wireless, there is no need to establish cable connection.

• Journal of electromagnetic engineering and science
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• v.6 no.4
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• pp.203-208
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• 2006

Channel estimation and data detection for OFDM systems over time- and frequency-selective channels are investigated. Relying on the complex exponential basis expansion channel model, a pilot-embedded channel estimation scheme with low computational complexity and spectral efficiency is proposed. A periodic pilot sequence is superimposed at a low power on information bearing sequence at the transmitter before modulation and transmission. The channel state information(CSI) can be estimated using the first-order statistics of the received data. In order to enhance the performance of channel estimation, we recover the transmitted data which can be exploited to estimate CSI iteratively. Simulation results show that the proposed method is suitable for doubly-selective channel estimation for the OFDM systems and the performance of the proposed method can be better than that of the Wiener filter method under some conditions. Through simulations, we also analyze the factors which can affect the system performances.

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.6
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• pp.568-573
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• 2007

Environmental information (temperature, humidity, vibration, $CO_2$, gas leakage, etc.) of building is an essential item to manage and monitor a building. For intelligent building, it is necessary to get temperature and illumination information to save energy and crack information to prevent structural problems. Moreover, temperature and gas leakage information to alarm a tire precaution, or humidity information to maintain comfortable environment. However, there have not been many researches on systems for gathering environmental information and building maintenance due to high costs. In this paper, wireless sensor network technology is applied to collecting building environmental information. Wireless sensor network is one of the latest issues and has low-power consumption, low-cost, self-configuration features.

• Journal of Power Electronics
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• v.16 no.2
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• pp.731-747
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• 2016

The droop-based control strategy is widely applied in the interfacing inverters for distributed generation. This can be a problem since low-frequency stability issues may be encountered in droop-based microgrid. The objective of this paper is to classify, evaluate and compare various low-frequency damping methods. First, low-frequency stability problems are analyzed and an equivalent model of a droop-controlled inverter is investigated to classify the damping methods into the source-type damping strategies and the impedance-type damping strategies. Moreover, the lead-lag compensation network insertion control is proposed as a beneficial part of the source-type damping strategies. Then, the advantages and disadvantages of the different types of damping methods are theoretically evaluated and experimentally tested. Furthermore, the damping methods are comprehensively compared to illustrate the application field of each method. Finally, the synthesis of different damping methods to enhance the low-frequency stability is discussed and experimental validation is presented.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.2
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• pp.70-76
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• 2014

In industrial situation, electronic and electro-mechanical systems have been using different type of batteries in rapidly increasing numbers. These systems commonly require high reliability for long periods of time. Wider application of battery for low-power design as a prime power source requires us knowledge of failure mechanism and reliability of batteries in terms of load condition, environment condition and other explanatory variables. Battery life is an important factor that affects the reliability of such systems. There is need for us to understand the mechanism leading to the failure state of battery with performance characteristic and develop a method to predict the life of such battery. The purpose of this paper is to develope the methodology of monitoring the health of battery and determining the condition or fate of such systems through the performance reliability to predict the remaining useful life of primary battery with load condition, operating condition, environment change in light of battery life variation. In order to evaluate on-going performance of systems and subsystems adopting primary batteries as energy source, The primitive prototype for performance reliability analysis device was developed and related framework explained.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.687-689
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• 2000

Molten Carbonate Fuel Cell (MCFC) with high electrical efficiency and low environmental effect has been developed for the commercial application of power generation fields. Recently we have built a 25 kW molten carbonate fuel cell power generation system and tested it. The MCFC system is composed of diverse peripheral units such as reformer, pre-heater, water purifier. electrical loader, gas supplier, and recycling systems. The stack itself was made of 40 cells of $6.000 cm^2$ area each. The stack showed an output of 28.6 kW power and a reliable performance at atmospheric operation. while in pressurized operation the stack showed an output 25.6 kW lower than the atmospheric operation. The reason of lower performance of pressurized operation was caused from a gas cross over shown in few cells in the stack.

• Journal of Communications and Networks
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• v.7 no.1
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• pp.36-44
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• 2005

In this paper, we present a retransmission power adjustment (RPA) scheme for DS/SSMA ALOHA packet radio systems with packet combining. In the proposed RPA scheme, retransmission power is adjusted in such a way that the erroneously-received packet can be recovered with a minimized interference to other user packets. We analyze the performance of the system with the RPA by employing the equilibrium point analysis (EPA), and confirm that the results obtained from the EPA are very close to the simulation results in low power cases. Simulation results demonstrate that the RPA scheme brings forth performance gain in the throughput and the average delay while saving a significant amount of transmission power. We also investigate the stability of the system from the EPA results, and conclude that the system becomes stable as the offered load increases or the level of retransmission power decreases.

• Journal of Power Electronics
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• v.16 no.1
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• pp.277-286
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• 2016

This paper offers two Maximum Power Point Tracking (MPPT) systems for Photovoltaic (PV) applications. The first MPPT method is based on a fixed frequency Model Predictive Control (MPC). The second MPPT technique is based on the Predictive Hysteresis Control (PHC). An experimental demonstration shows that the proposed techniques are fast, accurate and robust in tracking the maximum power under different environmental conditions. A DC/DC converter with a high voltage gain is obligatory to track PV applications at the maximum power and to boost a low voltage to a higher voltage level. For this purpose, a high gain Switched Inductor Quadratic Boost Converter (SIQBC) for PV applications is presented in this paper. The proposed converter has a higher gain than the other transformerless topologies in the literature. It is shown that at a high gain the proposed SIQBC has moderate efficiency.