• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.297-302
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• 2005

Right hand circularly polarized Ka band microstrip patch array antenna was designed, manufacture and measurement were carried out. In order to lower axial ratio performance sequential rotation array technique was used. With mono-pulse feed There are sum and delta channel. Waveguide to microstrip transition was used. The 512 array antenna was performed which axial ratio is about 1.ldB in the half power beam width and also 1.ldB at the normal direction. Directivity gain of designed antenna is 32dB.

• Journal of electromagnetic engineering and science
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• v.10 no.3
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• pp.183-185
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• 2010

A 2.4 GHz dual-polarized antenna for a Doppler radar is studied. The proposed dual-polarized antenna using a stacked annular ring patch with two co-centric gap-coupled feed lines and a $90^{\circ}$ hybrid exhibits fairly good performance of 22 dB isolation at a center frequency of 2.4 GHz. Using a $90^{\circ}$ hybrid, a right-handed circular polarization for the transmitter and a left-handed circular polarization for the receiver are implemented. The gain of the designed antenna is about 0 dBi over operating frequencies. The antenna size including a ground plane is only $40{\times}40\;mm^2$.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.114-121
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• 1998

Using Hebb-Wagner's asymmetric cell, partial conductivities of holes and electrons in yttria stabilized zirconia doped with 10 mol% TiO2 have been estimated by a dc polarization measurement. The current interrruption method and ac impedance measurements have been also made to evaluate the ionic conductivity and to examine the consistency of the partial conductivities. Partial conductivities of electrons(σn) and holes (σp) were found to be pro-peortional to -1/4 and 1/4 power of partial pressure of oxygen gas, respectively, except for σn at reducing conditions. In comparison with 5 mol% doped YSZ, σn was found to increase with the increase of TiO2 concentration, but σp stayed at almost a constant value.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.99-105
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• 2008

Southern exposure test specimens were used to evaluate corrosion performance of epoxy-coated reinforcing bars in chloride contaminated concrete by electrochemical impedance spectroscopy method. The test specimens with conventional bars, epoxy-coated bars and corrosion inhibitors were subjected 48 weekly cycles of ponding with sodium chloride solution and drying. The polarization resistance obtained from the Nyquist plot was the key parameter to characterize the degree of reinforcement corrosion. The impedance spectra of specimens with epoxy-coated bars are mainly governed by the arc of the interfacial film and the resistance against the charge transfer through the coating is an order of magnitude higher than that of the reference steel bars. Test results show good performance of epoxy-coated bars, although the coatings had holes simulating partial damage, and the effectiveness of corrosion-inhibiting additives. The corrosion rate obtained from the impedance spectroscopy method is equivalent to those determined by the linear polarization method for estimating the rate of corrosion of reinforcing steel in concrete structures.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.217-227
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• 2004

The bowl in a ship purifier suffers from high stress and high temperature in a detrimental heavy fuel oil environment. Duplex stainless steel(DSS) is a primary material to withstand this harsh condition. Newly-manufactured STS 329 grade DSS has been evaluated by various mechanical and electrochemical test methods. Eight heat treatment(HT) conditions with different temperature and time were applied to the DSS samples to improve corrosion resistance. Microstructure and polarization test results concluded the optimum HT condition was $1.090^{\circ}C$-60 minutes. Confirmation experiments for applying to a real bowl including stress corrosion cracking test exhibited the reproducibility of the optimum HT condition.

• Economic and Environmental Geology
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• v.19 no.3
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• pp.193-197
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• 1986

A simple and fast solution is derived to evaluate the effects of time-domain electromagnetic coupling in induced polarization surveys on a uniform earth. The simplified solution gives an explicit statement of the dependence of time-domain electromagnetic coupling on the model parameters, and yields sufficiently accurate results for most situations encountered in practice. The co-linear dipole-dipole and Wenner arrays are used as examples in this paper, but th numerical solution can be applied to any electrode configuration.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.594-597
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• 2003

In the present study, the piezoelectricity and polarization of multilayer ceramic actuator, being designed to stack PMN-PZ-PT ceramic layers and Ag-Pd electrode layers alternatively, were investigated under a consideration of geometric factor, the volume ratio of the ceramic to the electrode layers. The actuators were fabricated by tape casting of 0.2Pb(Mg1/3Nb2/3)O3-0.38PbZrO3-0.42PbTiO3 followed by lamination and burnout & co-firing processes. The actuators of 10 10 0.62 nm3 in size were formed in a way that 60 200 m thick ceramics were stacked alternatively with 5 m thick electrode layer. Increases in polarization and electric field-induced displacement with thickness of the ceramic layer were attributed to change of 90o/180o domain ratio, which was affected by interlayer internal stress. The piezoelectricity and actuation behaviors were found to depend upon the volume ratio (or thickness ratio) of ceramic to electrode layers.

• Nuclear Engineering and Technology
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• v.53 no.1
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• pp.172-177
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• 2021

The microstructure and texture of three 316L foils of 25 ㎛ thickness, which were subjected to different manufacturing process, were systematically characterized using advance analytical techniques. Then, the electrochemical property of the 316L foils in simulated pressurized water reactor (PWR) solution was analyzed using potentiodynamic polarization. The results showed that final rolling strain and annealing temperature had evident effect on grain size, fraction of recrystallization, grain boundary type and texture distribution. It was suggested that large final rolling strain could transfer Brass texture to Copper texture; low annealing temperature could limit the formation of preferable orientations in the rolling process to reduce anisotropy. Potentiodynamic polarization test showed that all samples exhibited good corrosion performance in the simulated primary PWR solution.

• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.65.1-65.1
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• 2020

We present high-resolution, high-sensitivity continuum data of NGC 4522 observed at 3 cm (X-band) and 10 cm (S-band) in full polarization mode using the JVLA. This observation has 2 - 4 times better spatial resolution and 2 - 5 times better sensitivity compared to previous continuum observations. NGC 4522 is a Virgo spiral galaxy undergoing active ram pressure stripping. This galaxy is particularly well known for the CO emission detected outside its stellar disk, some of which coincides with the extraplanar HI gas and Halpha patches. The major goal of our JVLA observation is to leverage our understanding of the influence of the ram pressure on the general ISM field and multi-phase medium. By combining our new deep radio continuum data and previous observations, we will investigate how the B-field properties can be affected by the ram pressure, and what roles the B-field plays in the stripping process of the multi-phased ISM and in the star formation activity when the ram pressure is present.

• Journal of the Korean Magnetics Society
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• v.11 no.5
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• pp.196-201
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• 2001

The dependence of CoFe interfacial layer thickness and plasma oxidation condition on tunneling magnetoresistance (TMR) in Ta/NiFe/FeMn/NiFe/Al$_2$O$_3$/NiFe/Ta tunnel junctions was investigated. As the CoFe layer thickness increases, TMR ratio rapidly increases to 13.7 % and decreases with further increase of the CoFe layer thickness. The increase of TMR with the CoFe thickness up to 25 was thought to be due mails to the high spin-polarization of CoFe. The maximum MR of 15.3% was obtained in the Si(100)/Ta(50 )/NiFe(60 )/FeMn(250 )/NiFe(70 )/Al$_2$O$_3$/NiFe(150 )/Ta(50 ) magnetic tunnel junction with a 16 Al oxidized for 40 sec using a Ar/O$_2$ (1:4) mixture gas.