• Journal of the Optical Society of Korea
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• v.7 no.4
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• pp.211-215
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• 2003

Statistical characteristics of the backscattered light from turbid tissues obtained by polarizationsensitive optical coherence tomography are investigated. The amplitude of the backscattered light is found to faithfully follow the Rayleigh distribution predicted by the scattering theory of electromagnetic waves in random media. The probability density function of the phase difference between the two orthogonal polarization components of the backscattered light is explicitly derived and then verified in comparison with the experimental data measured from in-vitro tissues of porcine ligament.

• Clinics in Shoulder and Elbow
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• v.20 no.4
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• pp.244-249
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• 2017

Shoulder kinematics is important, as it is associated with shoulder arthropathy and pain mechanisms. Various static and dynamic analysis methods are prevalent for shoulder kinematics. These include 2-dimensional plane x-ray, computed tomography, and magnetic resonance imaging, cadaver study, electromagnetic motion analysis, transcortical bone pins technique, and in vivo 3-dimensional motion analysis. Although these methods provide the value of the shoulder kinematics angle, they are unable to explain why such changes occur. Since each method has its pros and cons, it is important to understand all factors accurately, and to choose a method that best meets the purpose of the researcher.

• Journal of The Korean Astronomical Society
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• v.47 no.1
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• pp.15-39
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• 2014

Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and $X/{\gamma}$ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

• Electronics and Telecommunications Trends
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• v.32 no.6
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• pp.66-72
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• 2017

The frequency range of a radio wave is from 3kHz to 300GHz, and radio technologies use this range to improve the quality of human lives. Radio technologies have entered a new phase of communication. The core infrastructure used as the basis for technologies leading the fourth industrial evolution, such as artificial intelligence, the Internet of Things, autonomous cars/drones, augmented reality, robots, and remote medical diagnoses, is the 5G network. The 5G network enables transmitting and receiving large amounts of data at very high speed. In particular, application technologies with artificial intelligence have been studied, including radar, wireless charging, electromagnetic devices and their effects on humans, EMI/EMC, and microwave imaging. In this study, we present a future radio technology that is needed to prepare for the upcoming industrial revolution and digital transformation.

• ETRI Journal
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• v.41 no.1
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• pp.10-22
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• 2019

Since Leith and Upatnieks demonstrated the first optical hologram in 1964, hologram technology has attracted a great deal of interest in a wide range of optical fields owing to its potential use in future optical applications such as holographic imaging and optical data storage. Although there have been considerable efforts to develop holographic technologies using conventional optics, critical issues still hinder future development. Recently, metasurfaces composed of artificially fabricated subwavelength structures have been considered as novel holographic devices that show an unprecedented ability to control electromagnetic waves. In this review, we outline the recent progress in metasurface holography. A general introduction to several types of metasurface holography categorized based on their physics and application is provided. Then, our personal perspective on the future of this field is discussed.

• Current Applied Physics
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• v.18 no.11
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• pp.1185-1189
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• 2018

Thickness-dependent magnetic domain structure of ultrathin Co wedge films (0.3 nm-1.0 nm) sandwiched by Pt layers was investigated by scanning transmission x-ray microscopy (STXM) employing X-ray magnetic circular dichroism (XMCD), utilizing elliptically polarized soft x-rays and electromagnetic fields, with a spatial resolution of 50 nm. The magnetic domain images measured at the Co $L_3$ edge showed the evolution of the magnetic domain structures from maze-like form to the bubble-like form as the perpendicular magnetic field was applied. The asymmetric domain expansion of a 500 nm-scale bubble domain was also measured when the in-plane and perpendicular external magnetic field were applied simultaneously.

• Sleep Medicine and Psychophysiology
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• v.17 no.2
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• pp.91-99
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• 2010

Objectives: Deficit schizophrenia (DS) constitutes a disease separate from non-deficit schizophrenia (NDS). The aim of the current study was to compare the quantitative EEG and low resolution electromagnetic tomography (LORETA) imaging between DS and NDS. Methods: This study was performed by 32 channels EEG for 42 schizophrenia patients who we categorized into DS and NDS using proxy instrument deficit syndrome (PDS). We performed the absolute power spectral analyses for delta, theta, alpha, low beta and high beta activities. We compared power spectrum between two groups using Independent t-test. Partial correlation test was performed with clinical parameters. Standardized LORETA (sLORETA) was used for comparison of cortical activity, and statistical nonparametric mapping (SnPM) was applied for the statistical analysis. Results: DS showed significantly increased delta and theta absolute power in fontal and parietal region compared with NDS (p<0.05). Power spectrum showed significant correlation with 'anergia' and 'hostility/suspiciousness' subscale of brief psychiatric rating scale (BPRS)(p<0.05). sLORETA found out the source region (anterior cingulate cortex/limbic part) that delta activity was significantly increased in DS (p=0.042). Conclusions: DS showed different cortical activity compared with NDS. Our results may suggest QEEG and LORETA could be the marker in differentiating between DS and NDS.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.309-315
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• 2002

Conventional electromagnetic (EM) method using small loops as a source and receiver has been used in detection of conductive buried objects like a metal detector or in qualitative estimation of the subsurface conductivity variation. Recently, however, since detection of buried objects and imaging of the subsurface conductivity distribution in a relatively conductive area are in a high demand for environmental and engineering purposes, the quantitative interpretation technique of EM data is actively studied. In this regard, we introduce a brief principle of EM survey and show an example of the detection of buried conductive material and imaging of the subsurface conductivity distribution based on data measured at a test survey area. Through this study, we show that multi-frequency EM surveys using small loops may be a good solution to give quick and detail information of subsurface in a conductive survey area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.2 s.105
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• pp.184-192
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• 2006

Synthetic Aperture Radars(SAR) are used mainly for high-resolution imaging of the terrain. This paper describes the $16{\times}16$ array antenna designed for an X-band, automobile-based SAR(AutoSAR) system. This antenna has the structure of several layers such as radome, radiators, slots, feed network, and honeycomb cores. Each layer is adhesively bonded to meet different combination of structural and electrical design requirements. Using the Strip-Slot-Foam-Inverted-Patch(SSFIP) structure and honeycomb cores, a wide bandwidth and a structural hardness were achieved. Measurement results were compared with simulation results. It was observed that this antenna had a bandwidth of 1.7 GHz, side-lobe levels of less than -20 dB, half-power beamwidth of $5^{\circ}$ and $5^{\circ}$, and gains of 25.0 dBi. The observed results show that the designed array antenna will be applicable to the wideband SAR system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.2
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• pp.218-225
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• 2015

Inverse synthetic aperture radar(ISAR) is coherent imaging system formed by conducting signal processing of received data which consists of radar cross section(RCS) reflected from maneuvering target. A novel algorithm is proposed to compensate inter-pulse motion(IPM) for the purpose of forming an well-focused ISAR image through signals generated by stepped chirp waveform( SCW). The velocity and acceleration of the target related to IPM are estimated based on particle swarm optimization (PSO) which has been widely used in optimization technique. Furthermore, a modified PSO which enables us to improve the performance of PSO is used to compensate IPM in a very short-time. Simulation results using point scatterer model of a Boeing-737 aircraft validate the performance of the proposed algorithm.