• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1337-1342
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• 2012

In this paper, we propose a novel reconfigurable antenna that can change the electrical shape of the matching network using RF switches of PIN diodes. The designed antenna operates at two different modes that are Mode 1 (HSDPA band, 2.1~2.2 GHz) and Mode 2(WiBro WiFi band, 2.3~2.5 GHz). The antenna is built on both sides of a polyarcylate substrate. The measured reflection coefficient shows a matching bandwidth of 547 MHz($S_{11}$ <-3 dB, 2.035~2.582 GHz) for Mode 1 and 600 MHz($S_{11}$ <-3 dB, 2.2~2.8 GHz) for Mode 2, and it shows average vertical gains of -4.4 dBi and -4.5 dBi in x-y plane, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.2
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• pp.289-295
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• 2001

The aim of this study is to investigate the ductile fracture behaviour under pure Mode II loading using A533B pressure vessel steel. Single punch shear(SPS) test was performed to obtain the J-R curve under pure Mode II loading which was compared with that of the Model I loading. Simulation using Rousellier Ductile Damage Theory(RDDT) was carried out with 4-node quadrilateral element(L(sub)c=0.25mm). For the crack advance, the failed element removal technique was adopted with a $\beta$ criterion. Through the $\beta$ value tuning-up procedures, $\beta$(sub)crit(sup)II was determined as 1.5 in contrast with $\beta$(sub)crit(sup)I=5.5. In conclusion, it was found that the J-R curve under Mode II loading was located at lower part than that under Mode I loading obtained from the previous study and that the $\beta$ values strongly depended on the loading type. In addition, the predicted result using RDDT showed a good agreement with the SPS experimental one under pure Mode II loading.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.557-564
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• 1998

A low loss x-cut $LiNbO_3$optical waveguide was fabricated by Yi in-diffusion, and the properties of guided-mode and the total insertion loss of the pigtailed waveguide with polarization maintaining fiber(PMF) were measured at optical wavelength 1550nm. for forming the waveguides, the parameters of diffusion, Ti thickness, waveguide line-width, length, diffusion temperature, time and atmosphere were set $1400{\AA}$, $8{\mu}m$, 3.3cm, $1050^{\circ}C$, 8 hours and wet bubbled oxygen, respectively. And then after the polishing and piatailing, it showed that the total insertion loss was -4.1dB for TM mode, -5.5dB for TE mode, and mode size, that is, the horizontal/ vertical size were $13.8{\mu}m/18{\mu}m$ for TM mode, $9.6{\mu}m/6.5{\mu}m$ for TE mode.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.3
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• pp.74-78
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• 2011

In this paper, the bandpass filter for ITS system of 5.8 GHz is proposed by using the dual-mode resonator with the radial stub. As alternating the open stub with the radial stub, the size of the dual mode resonator can be reduced about 39.6% and the out-of-band characteristics of the bandpass filter using dual mode resonator can be enhanced from 19.4 dB to 29.1 dB by using the stub of $6.9{\Omega}$ i.e. realized by parallel two radial stubs with $60^{\circ}$ angle. The fabricated bnadpass filter using the dual mode resonator has the center frequency of 5.72 GHz with the fractional bandwidth of 4.1%. Also, the filter has the insertion loss and return loss of 1.79 dB and 19.4 dB, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.540-547
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• 2004

In this paper, a current - mode class D(CMCD) power amplifier over 70 % power added efficiency at 900 ㎒ is designed and implemented. Based on push-pull class B structure, main power loss due to charge and discharge of output capacitance in switching mode power amplifier is minimized by applying a parallel harmonic control circuit. Experimental CMCD amplifier with 73 % power added efficiency at 3.2 W and 72 % power added efficiency at 5 W are achieved respectively. In addition a characteristic of switching mode power amplifier whose output power is proportional to magnitude of U power is verified.

• Journal of Power Electronics
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• v.14 no.5
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• pp.890-898
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• 2014

Critical conduction mode boost power factor correction converters operating at the boundary of continuous conduction mode and discontinuous conduction mode have been widely used for power applications lower than 300W. This paper proposes an enhanced variable on-time control method for the critical conduction mode boost PFC converter to improve the total harmonic distortion characteristic. The inductor current, which varies according to the input voltage, is analyzed in detail and the optimal on-time is obtained to minimize the total harmonic distortion with a digital controller using a TMS320F28335. The switch on-time varies according to the input voltage based on the computed optimal on-time. The performance of the proposed control method is verified by a 100W PFC converter. It is shown that the optimized on-time reduces the total harmonic distortion about 52% (from 10.48% to 5.5%) at 220V when compared to the variable on-time control method.

• Asian Journal of Atmospheric Environment
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• v.11 no.4
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• pp.313-321
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• 2017

$PM_{10}$ and $PM_{2.5}$ were collected at the Gosan Site on Jeju Island from 2013 to 2015, and their ionic and elemental species were analyzed to examine the variations in their chemical compositional characteristics related to different meteorological conditions. Concentrations of nss-$SO_4{^{2-}}$ and $NH_4{^+}$ were respectively 6.5 and 4.7 times higher in the fine particle mode ($PM_{2.5}$) compared to the coarse particle mode ($PM_{10-2.5}$), however $NO_3{^-}$ concentrations were 2.4 times higher in the coarse mode compared to the fine particle mode. During Asian dust days, the concentrations of nss-$Ca^{2+}$ and $NO_3{^-}$ increased to 8.2 and 5.0 times higher in $PM_{10}$, and 3.5 and 6.0 times higher in $PM_{2.5}$, respectively. During haze days, the concentrations of secondary pollutants increased by 3.1-4.7 and 3.2-7.9 in $PM_{10}$ and $PM_{2.5}$, respectively, and they were, respectively, 1.2-2.1 and 0.9-2.1 times higher on mist days. The aerosols were acidified largely by sulfuric and nitric acids, and neutralized mainly by ammonia in the fine particle mode during the haze days, but neutralized by calcium carbonate in coarse particle mode during the Asian dust days. Clustered back trajectory analysis showed that concentrations of nss-$SO_4{^{2-}}$, $NO_3{^-}$, and $NH_4{^+}$ were relatively high when air masses travelled from China.

• Structural Engineering and Mechanics
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• v.36 no.5
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• pp.575-598
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• 2010

The shape and size of the plastic zone around the crack tip are analyzed under pure mode I, pure mode II and mixed mode (I+II) loading for small scale yielding and for both plane stress and plane strain conditions. A new analytical formulation is presented to determine the radius of the plastic zone in a non-dimensional form. In particular, the effect of T-stress on the plastic zone around the crack tip is studied. The results of this investigation indicate that the stress field with a T-stress always yields a larger plastic zone than the field without a T-stress. It is found that under predominantly mode I loading, the effect of a negative T-stress on the size of the plastic zone is more dramatic than a positive T-stress. However, when mode II portion of loading is dominating the effect of both positive and negative T-stresses on the size of the plastic zone is almost equal. For validating the analytical results, several finite element analyses were performed. It is shown that the results obtained by the proposed analytical formulation are in very good agreements with those obtained from the finite element analyses.

• Journal of Animal Environmental Science
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• v.12 no.3
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• pp.133-140
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• 2006

The climate of stall significantly influences on animal production ability. High concentration of ammonia gas, $CO_2$ and lots of dust are found in modern densely raising stall system, as results, they provide a negative influence on animal and farmer health, and production ability. Therefore, it is necessary to keep clean the inside air of stall to increase the productivity. An air cleaner of wet type, consisting of a fan, a motor, rotating discs, a dust collector, a water bowl, an ozone generator etc, has been developed to clean the stall air. The work principle is that the inside air is sucked through the fan, and the rotating discs make water into fineness spray and blow into the stall. The rest water flows down to the dust collector. In the present study, we measured the dust, ammonia gas, odor, temperature and humidity in a swine stall that were installed two wet air cleaners with 700 fattening swine with On-mode and Off-mode of wet air cleaners. The dust measure was divided into 3 categories, TSP, $PM_{10}$, and $PM_{2.5}$. In summer, the TSP in on-mode were maximum $0.259mg/m^3$ and minimum $0.128mg/m^3$, and the average was $0.195mg/m^3$. These are comparable to the data from Off-mode stall that maximum $0.308mg/m^3$, minimum $0.139mg/m^3$, and average $0.277mg/m^3$. However, $PM_{10}$ and $PM_{2.5}$ showed any significant differences between the tests. The concentrations of ammonia gas in Off-mode stall were maximum 13.8 ppm and minimum 5.9 ppm, and the average was 8.47 ppm. However in On-mode stall the ammonia gas concentrations were maximum 10.5 ppm and minimum 5.5 ppm, and the average was 7.63 ppm. The concentration of ammonia gas in On-mode was 10% in average lower than off-mode stall. Odor was measured by olfactometer. In the Off-mode stall, the odor unit were maximum 420 $Ou/m^3$ and minimum $300\;OU/m^3$, and the average was $367\;OU/m^3$, but in the On-mode stall the odor unit were maximum $330\;OU/m^3$ and minimum $210\;OU/m^3$, and the average was $253\;OU/m^3$. Odor removal efficiency was about 31% in On-mode stall.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.355-358
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• 2008

In the current GPON market and standard, the line bit rate requirement is changing from 1.25 Gbps to 2.5 Gbps. We fabricate a 2.5 Gbps burst-mode receiver with commercially available blocks and optimize it with an APD bias control. A burst-mode measurement setup is made for the full compliance test with the GPON standard. The device meets the partially defined 2.5 Gbps specs in the current ITU G.984.2 standard, also, supports 1.25 Gbps specs for the coexistence issue in an access network. The full-compliant measurement values can be used as a guideline for fixing "for further study" specs in the current GPON standard at 2.5 Gbps.