• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.11
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• pp.1078-1091
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• 2011

In this paper, a triple band-notched UWB antennas using a spiral resonator and a complementary split ring resonator is proposed as two types. The band-rejection characteristic of the designed antenna is analyzed through the structure and equivalent circuit model of spiral resonator and CSRR. The measured results of first type antenna show that a VSWR less than 2 was satisfied with a resonant frequency in the range of 1.16~12 GHz and it can be obtained the band-stop performance at 3.3~3.85 GHz, 5.15~6.1 GHz, and 8.025~8.5 GHz. The measured results of second type antenna show that a VSWR less than 2 was satisfied with this antenna works from 1.79 to 12 GHz and it can be achieved the band-notched performance at 3.3~3.88 GHz, 5.12~5.94 GHz, and 8.025~8.51 GHz. Through the measured results, the designed antenna was satisfied UWB band except for triple notched bands.

• Journal of Bio-Environment Control
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• v.26 no.4
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• pp.258-267
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• 2017

The price competitiveness of photovoltaic system (PV system) has risen recently due to the growth of industries, however, it is rarely applied to the greenhouse compared to other renewable energy. In order to evaluate the application of PV system in the greenhouse, power generation and optimal installation area of PV panels should be analyzed. For this purpose, the prediction of the heating and cooling loads of the greenhouse is necessary at first. Therefore, periodic and maximum energy loads of a multi-span greenhouse were estimated using Building Energy Simulation(BES) and optimal installation area of PV panels was derived in this study. 5 parameter equivalent circuit model was applied to analyzed power generation of PV system under different installation angle and the optimal installation condition of the PV system was derived. As a result of the energy simulation, the average cooling load and heating load of the greenhouse were 627,516MJ and 1,652,050MJ respectively when the ventilation rate was $60AE{\cdot}hr^{-1}$. The highest electric power production of the PV system was generated when the installation angle was set to $30^{\circ}$. Also, adjustable PV system produced about 6% more electric power than the fixed PV system. Optimal installation area of the PV panels was derived with consideration of the estimated energy loads. As a result, optimal installation area of PV panels for fixed PV system and adjustable PV system were $521m^2$ and $494m^2$ respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.866-872
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• 2007

In this paper, we present a frequency tunable and compact antenna which consists of a first-order Peano curve, two shorting posts, and two inductors which are serially connected between the posts and the edge of the Peano curve. By properly choosing the inductance of two inductors, the operating frequency of the antenna can be controlled without sacrificing the fractional bandwidth. To give good demonstration of the operating mechanism, the equivalent circuit of this antenna is included. To validate the simulation results, we have fabricated the several antennas of being integrated with different inductors, and the measured results show a good agreement with the simulated ones. The measured results reveal that the operating frequency is shifted from 1.47 GHz to 0.586 GHz without the decrease of the input impedance bandwidth. In case of integrating two inductors of 91nH and 470nH, the electric size of the antenna is only $0.0246 {\lambda}{\times}0.0246{\lambda}{\times}0.0114{\lambda}$. The measured fractional bandwidth$(S_{11}{\leq}-10 dB)$ and the radiation efficiency of the antenna are 5.22% and 47.25%, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.887-894
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• 2007

In this paper, design and fabrication of the LPF with controllable four transmission zeros using electric coupling and added open stub is presented. Pass-band of the LPF is GSM band, and two transmission zeros are generated by the electric coupling at the WiBro and S-DMB band, And the other two transmission zeros are generated by the open stub at the upper frequencies. Harmonic frequency of the stop-band is suppressed by the realization of the filter using quasi-lumped element with small parasitic values. $C_M$, which is the electric coupling element of the equivalent circuit, is realized by the distance control between the open stubs of the filter structure. The fabricated LPF used teflon substrate with relative permittivity of 2.6. And it has a size of $38{\times}20{\times}0.79 mm^3$, which is including a feed line. The measured 3 dB cut-off frequency is 1.55 GHz, and locations of the transmission zeros are 2.20, 2.43, 4.11 and 6.84 GHz, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1128-1134
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• 2014

In this paper, the effects of a metamaterial slab with negative permeability in a magnetically coupled wireless power transfer system (WPT) in the overall performance are analyzed quantitatively in terms of the effective quality factors of the loop resonators and coupling coefficient considering the slab losses, based on an equivalent circuit. Using the ideal metamaterial slab(lossless slab), the WPT efficiency is improved considerably by the magnetic flux focusing. However, the practical lossy slab made of RRs or SRRs limits the significant enhancement of WPT efficiency due to the relatively high losses in the slab consisting of RRs or SRRs near the resonant frequency. For the practical loop resonator, other than a point magnetic charge, using the practical lossy metamaterial slab in order to improve the transfer efficiency, the width of the slab needs to be optimized somewhat less than the half of the distance between two loop resonators. For the low-loss slab with its loss tangent of 0.001, the WPT efficiency is maximized at 93 % when the ratio of the slab width and the distance between the two resonators is approximately 0.35, compared with 53 % for the case without the slab. The efficiency in case of employing the high-low slab(loss tangent: 0.2) is maximized at 61 % when the slab ratio is 0.25.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.15-23
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• 2017

This paper reports a SOC(State-of-Charge) estimation method using the extended Kalman filter(EKF) algorithm, which can allow real-time implementation and reduce the error of the model and be robust against noise, to accurately estimate and evaluate the charging/discharging state of the EV(Electric Vehicle) battery. The battery was modeled as the first order Thevenin model for the EKF algorithm and the parameters were derived through experiments. This paper proposes the changed method, which can have the SOC to 0% ~ 100% regardless of the aging of the battery by replacing the rated capacity specified in the battery with the maximum chargeable capacity. In addition, This paper proposes the EKF algorithm to estimate the non-linearity interval of the battery and simulation result based on Ah-counting shows that the proposed algorithm reduces the estimation error to less than 5% in all intervals of the SOC.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.10-18
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• 2018

The primary purposes of this study are to understand a fundamental aspect of current uniformity around a reinforcing bar (rebar) in cement mortar, and to develop an accurate monitoring method in a wet-dry cycling process with the alternative current (AC) impedance method. Three cement mortar specimens with two embedded rebars were prepared in the laboratory. As a main variable, the distance between two rebars was designed to be 10, 20 and 30 mm with the same thickness of 20 mm. To simulate the corrosion of rebars in concrete structures in a marine environment, three cement mortar specimens were exposed to 15 wet-drying cycles (24-hour-immersion in seawater and 48-hour-drying in a room temperature) in the laboratory. It was observed that the potential level shifted to a noble value during corrosion potential monitoring, which is attributed to acceleration of dissolved oxygen diffusion at the drying process. AC impedance was measured in a frequency range from 100 kHz to 1 mHz on a wet-drying process. A theoretical model was proposed to explain the interface condition between the rebars and cement mortar by using the equivalent circuit consisting of a solution resistance, a charge transfer resistance and a CPE (constant phase element). It was observed that the diffusion impedance appeared in a low frequency range as corrosion of rebars progresses. At the drying stage of the wet-drying cycles, the currents line for monitoring tended to be non-uniform at the interface of rebar/mortar, being phase shift, ${\theta}$, close to $-45^{\circ}$.

• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.961-966
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• 2003

A Multi-Layer Ceramic (MLC) chip type Band-Pass Filter (BPF) using BiNb$\_$0.975/Sb$\_$0.025/ $O_4$ LTCC (Low Temperature Co-fired Ceramics) and MLC processing is presented. The MLC chip BPF has the benefits of low cost and small size. The BPF consists of coupled stripline resonators and coupling capacitors. The BPF is designed to have an attenuation pole at below the passband for a receiver band of IMT-2000 handset. The computer-aided design technology is applied for analysis of the BPF frequency characteristics. The attenuation pole depends on the coupling between resonators and the coupling capacitance. An equivalent circuit and structure of MLC chip BPF are proposed. The frequency characteristics of the manufactured BPF is well acceptable for IMT-2000 application.

• Journal of the Korea Society of Computer and Information
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• v.18 no.3
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• pp.107-118
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• 2013

In this paper, we developed the semiconductor monitoring system for the etching process. Around the world, expert companies are competing fiercely since the semiconductor industry is a leading value-added industry that produces the essential components of electronic products. As a result, many researches have been conducted in order to improve the quality, productivity, and characteristics of semiconductor products. Process monitoring techniques has an important role to give an equivalent quality and productivity to produce semiconductor. In fact, since the etching process to form a semiconductor circuit causes great damage to the semiconductors, it is very necessary to develop a system for monitoring the process. The proposed monitoring system is mainly focused on the dry etching process using plasma and it provides the detailed observation, analysis and feedback to managers. It has the functionality of setting scenarios to match the process control automatically. In addition, it maximizes the efficiency of process automation. The result can be immediately reflected to the system since it performs real-time monitoring. UI (User Interface) provides managers with diagnosis of the current state in the process. The monitoring system has diverse functionalities to control the process according to the scenario written in advance, to stop the process efficiently and finally to increase production efficiency.

• Geophysics and Geophysical Exploration
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• v.17 no.4
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• pp.247-252
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• 2014

Gagok Mine, which is skarn deposits, includes sulfide minerals such as sphalerite, galena, chalcopyrite, and pyrrhotite. To explore these minerals, spectral induced polarization (SIP) is relatively effective compared to other geophysical exploration methods because there is a strong IP effect caused by electrode polarization. In the SIP, the chargeability related to sulfide mineral contents and the time constant related to the grain size of the minerals are obtained. For this reason, we aim to compare difference in the mineralized characteristics between two orebodies in the Gagok Mine by using the chargeability and the time constant. For this study, we sampled ores from the south of Wolgok orebody and the north of Sungok orebody. In order to recognize the mineralization characteristics, the metal content of the samples was measured by a potable XRF and the SIP data of the samples were acquired by using a laboratory SIP measurement system. As a result, the metals in the samples such as Pb, Zn, Cu, and Fe were detected by the portable XRF measurement. In particular, the Fe and Zn contents were far higher than the other metals. The Fe and the Zn were caused by the sphalerite and the pyrrhotite through microscopy. The Wolgok orebody had higher sulfide mineral contents than the Sungok orebody and the result corresponded with the chargeability result. However, we considered that the Sungok orebody had a larger sulfide mineral grain size than the Wolgok orebody because the time constant of the Sungok orebody was larger.