• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.303-310
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• 2004

In this paper, L-shaped slot antenna for 5.15㎓-5.35㎓ is designed, fabricated. and measured. The prototype consist of four L-shaped slot. To obtain suitable bandwidth, the form layer is inserted between ground plane and substrate. Important parameters in the design are four L-slot length. width, position, air-gap height. and feed Point position. From these parameters optimized, a four L-shaped slot antenna is fabricated and measured. The measured results of the antenna are obtained as follows results. The resonant frequency of the fabrication four L-shaped slot antenna is 5.25㎓, bandwidth for approximately 5％(VSWR＜1.5) and the gain is 8-9㏈i. The experimental far-field patterns are stable across the pass band. The 3dB bandwidth in H-Plane and I-Plane are 69$^{\circ}$and 62$^{\circ}$, respectively.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.2
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• pp.134-142
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• 2010

A comparative study on the trade-off between the drive current and the total gate capacitance in double-gate (DG) and triple-gate (TG) FinFETs is performed by using 3-D device simulation. As the first result, we found that the optimum ratio of the hardmask oxide thickness ($T_{mask}$) to the sidewall oxide thickness ($T_{ox}$) is $T_{mask}/T_{ox}$=10/2 nm for the minimum logic delay ($\tau$) while $T_{mask}/T_{ox}$=5/1~2 nm for the maximum intrinsic gate capacitance coupling ratio (ICR) with the fixed channel length ($L_G$) and the fin width ($W_{fin}$) under the short channel effect criterion. It means that the TG FinFET is not under the optimal condition in terms of the circuit performance. Second, under optimized $T_{mask}/T_{ox}$, the propagation delay ($\tau$) decreases with the increasing fin height $H_{fin}$. It means that the FinFET-based logic circuit operation goes into the drive current-dominant regime rather than the input gate load capacitance-dominant regime as $H_{fin}$ increases. In the end, the sensitivity of $\Delta\tau/{\Delta}H_{fin}$ or ${{\Delta}I_{ON}}'/{\Delta}H_{fin}$ decreases as $L_G/W_{fin}$ is scaled-down. However, $W_{fin}$ should be carefully designed especially in circuits that are strongly influenced by the self-capacitance or a physical layout because the scaling of $W_{fin}$ is followed by the increase of the self-capacitance portion in the total load capacitance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.634-639
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• 2006

In this paper an MMIC 2-stage power amplifier is designed and fabricated for 5GHz wireless LAN applications using $0.5{\mu}m$ gate length PHEMT transistors. The PHEMT gate width is optimized in order to meet the linearity and efficiency of the MMIC power amplifier. The $0.5{\mu}m\times600{\mu}m$ PHEMT for the drive stage and $0.5{\mu}m\times3000{\mu}m$ PHEMT for the amplification stage are the optimized sizes to achieve more than 25dBc of third order IMD at the power level of 3dB back-off from the input P1dB and more than 22dBm output power under a supply voltage of 3.3V. The two-stage MMIC power amplifier is designed to be used for the both of HIPERLAN/2 and IEEE 802.11a because of its broadband characteristics. The fabricated PHEMT MMIC power amplifier exhibits a 20.1dB linear power gain, a maximum 22dBm output power, a 24% power added efficiency under 3.3V supply voltage. The input and output on-chip matching circuits are included on a chip of $1400\times1200{\mu}m^2$.

• Journal of Plant Biotechnology
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• v.49 no.4
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• pp.356-361
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• 2022

Bacillus sp. is a useful strain for agriculture because it promotes plant growth and controls plant pathogens through a variety of mechanisms. In this study, we obtained a microbial preparation with a high number of viable cells by culturing newly isolated soil bacteria on an optimized medium. Subsequently, we applied this preparation to lettuce to enhance its growth and yield. First, B. amyloliquefaciens ISP-5 was isolated from soil. Next, optimization of culture medium was carried out using 5 L scale fermenters. When culturing B. amyloliquefaciens ISP-5 on this optimized medium, the number of viable cells was approximately 1000 times higher than that obtained from culturing on the commercial medium. Afterwards, the plant growth promotion properties of the ISP-5 strain were evaluated using lettuce as a test plant. Foliar spray treatment of lettuce was carried out by inoculating half the standard concentration suspension (0.5 × 10⁷ cfu/ml). As a result, leaf width increased by 8.6% and leaf length increased by 12.9% compared to the control group. Live weight also increased by 24.2% and dry weight by 23.9%. Considering the results from field test, B. amyloliquefaciens ISP-5 showed potential as a plant growth-promoting bacteria.

• Journal of Electrical Engineering and Technology
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• v.13 no.4
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• pp.1638-1643
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• 2018

Multi-layer ceramic capacitors as decoupling capacitor were fabricated by dielectric composition with a high dielectric constant. The fabricated decoupling capacitors were embedded in the PCB of the 10G RF transceiver module and evaluated for the characteristics of electrical noise by the level of AC input voltage. In order to further improve the electrical properties of the $BaTiO_3$ based composite, glass frit, MgO, $Y_2O_3$, $Mn_3O$, $V_2O_5$, $BaCO_3$, $SiO_2$, and $Al_2O_3$ were used as additives. The electrical properties of the composites were determined by various amounts of additives and optimum sintering temperature. As a result of the optimized composite, it was possible to obtain a density of $5.77g/cm^3$, a dielectric constant of 1994, and an insulation resistance of $2.91{\times}10^{12}{\Omega}$ at an additive content of 5wt% and a sintering temperature of $1250^{\circ}C$. After forming a $2.5{\mu}m$ green sheet using the doctor blade method, a total of 77 layers were laminated and sintered at $1180^{\circ}C$. A decoupling capacitor with a size of $0.6mm(W){\times}0.3mm(L){\times}0.3mm(T)$ (width, length and thickness, respectively) and a capacitance of 100 nF was embedded using a PCB process for the 10G RF Transceiver modules. In the range of AC input voltage 400mmV @ 500kHz to 2200mV @ 900kHz, the embedded 10G RF Transceiver modules evaluated that it has better electrical performance than the non-embedded modules.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.604-609
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• 2019

In this study, we fabricated a capacitive humidity sensor with interdigitated (IDT) electrodes using a thermosetting polyimide as a humidifying material. First, the number of electrodes, thickness, and spacing of the polyimide film were optimized, and a mask was designed and fabricated. The sensor was fabricated on a silicon substrate using semiconductor processing equipment. The area of the sensor was $1.56{\times}1.66mm^2$, and the width of the electrode and the gap between the electrodes were each $3{\mu}m$. The number of electrodes was 166, and the length of an electrode was 1.294 mm for the sensitivity of the sensor. The sensor was then packaged on a PCB for measurement. The sensor was inserted into a chamber environment with a temperature of $25^{\circ}C$ and connected to an LCR meter to measure the change in capacitance at relative humidity (RH) of 20% to 90%, 1 V, and 20 kHz. The results showed a sensitivity of 26fF/%RH, linearity of < ${\pm}2%RH$, and hysteresis of < ${\pm}2.5%RH$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.156-163
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• 2014

In this paper, a compact circularly polarized metamaterial patch antenna using cross aperture-coupled feed is proposed. The CP antenna utilizes the -1 mode that is induced by the composit right-left handed(CRLH) transmission line. Since the -1 mode has the same properties with the $TM_{010}$ mode of the conventional patch antenna, the circular polarization(CP) can be realized. If two orthogonal modes are excited with $90^{\circ}$ phase difference, the CP property can be obtained. In order to obtain two orthogonal modes and $90^{\circ}$ phase difference, 4 mushroom structures having the shape of square are employed. The width and length of the cross aperture are optimized through the design algorithm. The fabricated antenna is based on RT/duroid5880 substrate and the total area of the 4 mushroom is $0.25{\lambda}_0{\times}0.25{\lambda}_0$. The center frequency of the LHCP(Left-Handed Circular Polarization) antenna is measured as 1.622 GHz and circular polarization bandwidth(3 dB) is measured as 3 MHz. The center frequency of the RHCP(Right-Handed Circular Polarization) antenna is measured as 1.609 GHz and circular polarization bandwidth (3 dB) is measured as 3 MHz, respectively. The measured radiation efficiency of LHCP antenna is 61.1 % and the measured radiation efficiency of RHCP antenna is 54.5 %.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.469-474
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• 2006

A $1{\times}16$ thermo-optic switch with small excess loss using multimode interference(MMI) couplers is designed, fabricated, and measured. This paper introduces the proposed $1{\times}16$ thermo-optic switch, and discusses the measurement results. The $1{\times}16$ thermo-optic switch is farmed as 4-stage which consists of 15 unit devices. The unit devices are the $2{\times}2$ thermo-optic switches with Mach-Zehnder interferometer(MZI) structure. The characteristics of the $1{\times}16$ thermo-optic switch depends strongly on each unit device. The unit deviceconsists of two 3-dB general interference MMI couplers and two single mode waveguide arms as a phase shifter. First of all, the 3-dB optical splitter and $2{\times}2$ MZI thermo-optic switch have been tested to confirm the characteristics of the unit devices of the $1{\times}16$ MZI thermo-optic switch. Using the measurement results of the unit devices, the $1{\times}16$ MZI thermo-optic switch can be produced with better characteristics. The resultant structure of the MMI coupler with the optical light source of wavelength of 1550nm for the $1{\times}16$ thermo-optic switch is that the width and the optimized length are $25{\mu}m\;and\;1580{\mu}m$, respectively. The smallest excess loss fur the unit device is -0.5dB and the average excess loss is -0.7dB.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.266-271
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• 2009

We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610 ${\mu}m$ and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.1
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• pp.173-185
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• 2015

This study aims to investigate the characteristics and types of car accidents and establish a prediction model by analyzing 456 car accidents having occurred in the 11 tunnels in Busan, through statistical analysis techniques. The results of this study can be summarized as below. As a result of analyzing the characteristics of car accidents, it was found that 64.9% of all the car accidents took place in the tunnels between 08:00 and 18:00, which was higher than 45.8 to 46.1% of the car accidents in common roads. As a result of analyzing the types of car accidents, the car-to-car accident type was the majority, and the sole-car accident type in the tunnels was relatively high, compared to that in common roads. Besides, people at the age between 21 and 40 were most involved in car accidents, and in the vehicle type of the first party to car accidents, trucks showed a high proportion, and in the cloud cover, rainy days or cloudy days showed a high proportion unlike clear days. As a result of analyzing the principal components of car accident influence factors, it was found that the first principal components were road, tunnel structure and traffic flow-related factors, the second principal components lighting facility and road structure-related factors, the third principal factors stand-by and lighting facility-related factors, the fourth principal components human and time series-related factors, the fifth principal components human-related factors, the sixth principal components vehicle and traffic flow-related factors, and the seventh principal components meteorological factors. As a result of classifying car accident spots, there were 5 optimized groups classified, and as a result of analyzing each group based on Quantification Theory Type I, it was found that the first group showed low explanation power for the prediction model, while the fourth group showed a middle explanation power and the second, third and fifth groups showed high explanation power for the prediction model. Out of all the items(principal components) over 0.2(a weak correlation) in the partial correlation coefficient absolute value of the prediction model, this study analyzed variables including road environment variables. As a result, main examination items were summarized as proper traffic flow processing, cross-section composition(the width of a road), tunnel structure(the length of a tunnel), the lineal of a road, ventilation facilities and lighting facilities.