• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1159-1166
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• 2006

In this paper, we have designed a RFID reader receiver system for improving the performance of the passive Tag based 9$'908.5{\sim}914MHz'$ RFID reader, and analyzed the system performance according to the frequency, the reader, and tag properties. The commercial receive system causes a loss in sensitivity because of 24 capacitors and 6 inductors. So we have designed an improved system using a circulator, LNA and a SAW filter. The experimental results show that the use of a circulator to separate the Tx/Rx paths eliminates interference, the LNA improves the sensitivity of the Rx module and SAW filter eliminates the noise and spurious components in the received signal.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.47 no.5
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• pp.622-629
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• 2014

This study induced biological denitrification and nitrification via a biofiltration process with the view of removing nitrogen from land-based fish farm effluent. To achieve this, we operated an aquaculture nitrogen-removal system that includes a denitrification and nitrification reactor [working volume 40 L, flow rate 64.8 L, HRT (hydraulic retention time) 14.8 h, HRT considering recycling of NOx 7.4 h]. In the continuous process, the nitrification rate of ammonium nitrogen exceeded 90% at a steady state and the denitrification efficiency exceeded 80% with recycling to a pre-anoxic reactor. In addition, the pH in the final effluent was lower with a low influent water alkalinity averaging 100 mg/L (as $CaCO_3$). For effective denitrification reactions, carbon must be supplied via particulate organic matter (POM) hydrolysis because of the low C/N (carbon/nitrogen) ratio in the water.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.6
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• pp.580-588
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• 2009

A Missile Warning Radar is an essential sensor for active protection system to detect antitank missile in all weather environments. This paper presents the design, development, and test results of L-band pulsed Doppler radar system for main battle tank. This radar system consists of 3 LRUs, which include antenna unit, transmitter and receiver unit and radar signal & data processing unit. The developed core technologies include the patch antenna, SSPA transmitter, coherent I/Q detector, DSP based Doppler FFT filter, adaptive CFAR, SIW tracking capability, and threat decision. The design performance of the developed radar system is verified through various ground fixed and moving vehicle test.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.503-510
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• 2014

This study proposes a bi-directional interleaved current-fed resonant converter (CRC) with reduced size of the output filter for a fuel cell electric vehicle. The proposed CRC achieves zero-current switching turn on and off of switches and diodes and makes ripple current of the output capacitor theoretically zero. As a result, the cost and volume of the output capacitor are significantly reduced. The two-stage power conversion technique is also applied for wide input and output voltage range operations. A 2kW prototype of the proposed converter is built and tested to verify the validity of the proposed operation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12A
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• pp.1217-1224
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• 2008

The carrier tracking has to be basically completed for accurate positioning of Galileo satellite system. The FLL for tracking frequency errors is robust to dynamic stress causing changes of propagation time but hardly tracks accurate carrier tracking. The PLL for tracking phase errors provides accurate carrier tracking but is sensitive to dynamic stress and its tracking performance is decreased when high dynamics exist. In this paper, we design the carrier tracking loop with the FLL-assisted PLL loop filter and co-operations of FLL and PLL to achieve accurate carrier tracking in high dynamic stress. we prove the performance of designed carrier tracking loop via simulations.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.4
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• pp.108-116
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• 2013

Many algorithms have been introduced to improve performance by using massively parallel systems, which consist of several hundreds of processors. A typical example is a GPU system of many processors which uses shared memory. In the case of image filtering algorithms, which make references to neighboring points, the shared memory helps improve performance by frequently accessing adjacent pixels. However, using shared memory requires rewriting the existing codes and consequently results in complexity of the codes. Recent GPU systems support both L1 and L2 cache along with shared memory. Since the L1 cache memory is located in the same area as the shared memory, the improvement of performance is predictable by using the cache memory. In this paper, the performance of cache and shared memory were compared. In conclusion, the performance of cache-based algorithm is very similar to the one of shared memory. The complexity of the code appearing in a shared memory system, however, is resolved with the cache-based algorithm.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.20-28
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• 2008

We propose a radial image processing method in a discrete polar coordinate system based on L1-norm. For this purpose, we first verified that the polar coordinate based on L2-norm can not exist in discrete system and then develop a method converting the Cartesian coordinate to the discrete polar coordinate. We apply the proposed method to smooth mass images of breast tissue and to detect the boundaries of extremely deformable objects. Compared to the Gaussian smoothing method performed in the Cartesian coordinate system, the proposed method stabilized the image signal while maintaining the overall radial shape of mass images. The proposed boundary detection method can detect shapes with high precision while conventional edge detectors can not accurately detect the shape of deformable objects. We also exploit the method to perform pupil detection and have had good experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.10-17
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• 2013

In this paper, a new active damping method of LCL filter without capacitor voltage sensors is proposed for 3 phase PWM Inverter. Normally, L filter or LCL filter is used as an output filter of grid connected PWM inverter. An LCL filter has more excellent performance than L filter to reduce harmonic current, so the small inductance value can be used. However, the resonance problem in LCL filter is happen due to the zero impedance by the addition of LC branch. To solve the resonance problem, the various active damping method has been proposed so far. Generally, the virtual resistor active damping methods is required to additional hardware sensors for measurement of capacitor voltage and current. In this paper, the new active damping method is proposed without any capacitor voltage or current sensors. In the proposed method, the resonance component of the capacitor voltage of LCL filter can be observed by a simple MRAS(Model Reference Adaptive System) observer without additional hardware sensors, and this component is suppressed by feedforward compensation. The validity of the proposed method is proven by simulation and experiment on the 3-phase PWM inverter system.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.1
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• pp.64-70
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• 2014

In this paper, the new LLCL filter is proposed for grid connected three-phase PWM inverter for passive damping. LLCL filter inserts a small inductor in the branch of the capacitor of the traditional LCL filter to compose a series resonant circuit to reduce the switching-frequency component on grid current. Using LLCL filter, the switching-frequency current ripple components can be attenuated much better than the LCL filter, leading to a decrease in the total inductance. However, the resonance phenomena caused by zero impedance from the addition of LC branch in LLCL filter can be a big problem. Resonance phenomena of LLCL filter can be a source of grid system instability, so proper damping methods are required. However, it is difficult to apply a passive damping method in the conventional LLCL filter, because the damping resistor increase impedance of the LC branch. Therefore, switching frequency component of grid current can not much attenuated by low Q of LC series resonance effect. In this paper, a new LLCL filter is proposed to overcome the conventional LLCL filter with passive damping. The validity of the proposed method is proven by simulation and experimental result.

• Journal of Soil and Groundwater Environment
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• v.9 no.2
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• pp.28-40
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• 2004

Box experiments were performed to evaluate the removal efficiency of SVE (soil vapor extraction) for gasoline in soil. An activated carbon sorption tower and a biofilter were operated as post-treatment processes to remove VOCs extracted from extraction wells of SVE. An acrylic resin box (65 cm${\times}$20 cm${\times}$30 cm) was used to make artificial soil layers and two injection wells and one extraction well were built for SVE process in the box. Gases from extraction wells flew into the activated carbon sorption tower or the biofilter. Gasoline concentrations of VOCs emitted from the extraction well were compared with those after post treatments. More than 92% of initial gasoline mass in soil were removed by SVE within few days, suggesting that SVE is very available to remove VOCs from contaminated soils. To treat VOCs from extraction wells of SVE, an activated carbon sorption tower and a biofilter were attached to SVE process and their gasoline removal efficiencies were measured. These post treatment systems lowered gasoline concentrations to below 1.0 ppm within few days. Average remediation efficiency was 98% of gasoline for the activated carbon sorption tower and 84.1% for the biofilter. The maximum removal capacity of a biofilter was 10.7 g/L/hr, which was ten times higher than general biofilter removal capacity. Results from the study suggest that the activated carbon sorption tower and the biofilter would be available for the post treatment process to remove VOCs generated from SVE process.