• Journal of the Optical Society of Korea
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• 제12권1호
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• pp.19-24
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• 2008

In this paper, we describe the fabrication process and the characteristics of polarization maintaining photonic crystal fibers (PM-PCFs). The PM-PCF is fabricated by stack-and-draw method, i.e., stacking silica capillary tubes (making a PM-PCF preform) and drawing to optical fiber. Firstly, a PM-PCF preform is formed by stacking two kinds of capillary tubes around a solid silica rod and jacketing these stacked tubes with an outer silica tube (out-jacket tube). Later, the desired preform is drawn to a fiber in a high temperature drawing tower. We also compare the polarization properties such as polarization dependent loss, birefringence, and differential group delay of the fabricated PM-PCF with those of the conventional PANDA PM fiber.

• Journal of electromagnetic engineering and science
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• 제17권1호
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Current Optics and Photonics
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• 제3권1호
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• pp.16-21
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• 2019

We present a broad-bandwidth comb-spacing-swept source (CSWS) based on a differential polarization delay line (DPDL) for interferometric three-dimensional (3D) imaging. The comb spacing of the CSWS is repeatedly swept by the tunable DPDL in the multiwavelength source to provide depth-scanning optical coherence tomography (OCT). As the polarization differential delay of the DPDL is tuned from 5 to 15 ps, the comb spacing along the wavelength continuously varies from 1.6 to 0.53 nm, respectively. The wavelength range of various semiconductor optical amplifiers and the cavity feedback ratio of the tunable fiber coupler are experimentally selected to obtain optimal conditions for a broader 3-dB bandwidth of the multiwavelength spectrum and thus provide a higher axial resolution of $35{\mu}m$ in interferometric OCT imaging. The proposed CSWS-OCT has a simple imaging interferometer configuration without reference-path scanning and a simple imaging process without the complex Fourier transform. 3D surface images of a via-hole structure on a printed circuit board and the top surface of a coin were acquired.

• 국제지역연구
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• 제15권1호
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• pp.585-602
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• 2011

본 논문은 Phillips and Sul(2007)에 의해서 개발된 패널 수렴 테스트 방법을 이용하여 한국 21개 도시의 소비자 물가지수 중 집세 지수를 분석함으로써 지역별 집세의 동태적 수렴화 현상을 분석한 것이다. 분석 결과 한국의 21개 도시의 집세는 4개의 그룹별로 수렴하고 있으며 그 수렴 수준에 따라 수도권을 중심으로 한 제1그룹과 부천 등의 제2그룹 및 부산 대구 등의 제3그룹 그리고 청주 전주 목포 등의 제4그룹으로 나뉘어 수렴한다. 그룹에 소속된 도시들의 수렴 속도는 수도권을 중심으로하는 제1그룹, 제4그룹, 제2그룹 제3그룹의 순서로 나타났는데 이는 집세 수렴수준이 높은 제1그룹과 수렴수준이 낮은 제4그룹간에 집세의 양극화 현상이 빠르게 나타나고 있는 것을 보여주는 것이다. 이처럼 도시별로 집세지수가 수렴하며 지역별로 양극화하고 있다는 결과는 향후 세제 및 주택 정책에 반영하여 지역별 소득 격차 완화에 사용할 수 있음을 제시하였다.

• 대한치과보철학회지
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• 제43권2호
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• pp.264-279
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• 2005

Statement of problem. Intraoral corrosion not only affects the esthetic and function of metallic dental restoration, but also has biologic consequences as well. Therefore, corrosion is considered a primary factor when choosing the dental alloy and laboratory technique. Purpose. The objective of this study was to compare the effects of solder and laser weld on corrosion Material and methods. Test specimens were made of 2 types of gold alloys, Co-Cr and Ni-Cr alloy and fabricated 3 methods, respectively: as cast, solder, and laser weld. For the analysis of corroding properties, potentiodynamic polarization test and immersion test conducted. The potentiodynamic polarization scan curve were recorded in 0.9% NaCl solution(pH 7) using Potentiostat/Galyanostat Model 273A. All specimens were exposed to 0.9% NaCl solution(pH 2.3) during 14 days. Elemental release into corrosive solution was measured by atomic emission spectrometry Differences in corrosion potential and mass release were determined using ANOVA. Results and conclusion. Through analyses of the data, following results were obtained. 1. In Pontor MPF and Wiron 99, corrosion potential of the solder group was statistically lower than as cast and laser weld group (p<0.05) , but there was no difference between corrosion potential of solder group and laser weld group in Pontor MPF and no differences between as cast and laser weld group (p>0.05). In Jel-Bios 10 and Wirobond, there was no difference of corrosion potential according to joining methods(p>0.05). 2. In all tested alloys, the amount of released metallic ion was greatest in the solder group(p<0.05). There was no difference between as cast group and laser weld group in Jel-Bios 10 and Wirobond(p>0.05). 3. In scanning electron microscopic examination. except soldered Wiron 99 specimens, it is impossible to discriminate the corrosive property of solder and laser weld. 4. Under the this experimental circumstances, laser weld appears superior to the solder when corrosion is considered.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1843-1845
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• 1999

We have investigated the dielectric characteristics of palmitic acid(PA), stearic acid (SA) and arachidic acid(AA) Langmuir-Blodgett(LB) films because these fatty acid systems have a same hydrophilic group and a different hydrophobic one (alkyl chain length). In this work. fatty acid systems were used as LB films and the status of the deposited films was confirmed by evaluating the transfer ratio. the UV absorption and the capacitance. Also, the dielectric characteristics such as the frequency-capacitance characteristics and the dielectric dispersion and absorption characteristics of PA, SA and AA through-plane were measured. The relative dielectric constants of PA, SA and AA LB films were about $2.6\sim4.6$, $2.4\sim4.1$ and $2.2\sim3.8$, respectively. That is, the relative dielectric constants were decreased in proportion to the chain length of methylene group. And, the dielectric dispersion and absorption of each fatty acid LB films have arisen from spontaneous polarization of dipole polarization in the range of $10^4\sim10^5[Hz]$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.195-195
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• 2010

In recent years, Anodic aluminum oxide(AAO) has become popular and attractive materials. It can be easily fabricated and self-organized pore structures. It has been widely used as a biosensor membrane, photonic crystal for optical circuit and template for nanotube growth etc. In previous papers, the theory was developed that AAO shows anisotropic optical properties, since it has anisotropic structure with numerous cylindrical pores. It gives rise to the anisotropy of the refractive index called as birefringence. It can be used as conventional polarizing elements with high efficiency and low cost. Therefore, we would like to compare the theory and experimental results in this study. One method which can measure effective refractive index of thin film is the prism coupling technique. It can give accurate results fast and simply. Furthermore, we can also measure separately the refractive index with different polarization using polarization of the laser (TE mode and TM mode). We calculated the effective refractive index with effective medium approximations (EMAs) by pore size in the SEM image. EMAs are physical models that describe the macroscopic system as the homogeneous and typical method of all mean field theories.

• 한국결정성장학회지
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• 제6권4호
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• pp.648-662
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• 1996

임피던스 스펙트럼을 이용하여 황산 용액에서 glassy carbon과 인조흑연(PVDF 합성 흑연)의 전극표면에 cyclic 분극을 부하 하였을 경우 전극표면에서 나타나는 표면반응에 대하여 조사하여 . 두 재료 표면에서 산소의 산화 혹은 환원과 관련되거나 또는 탄소재료 표면에 화학흡착된 표면작용기(surface functional group)의 변화와 관련되는 것으로 생각되는 산화환원 피크가 potentio-dynamic곡선에서 나타났다. 이러한 전극 표면에서의 표면작용기의 산화환원은 glassy carbon과 PVDF합성 흑연의 임피던스 스펙트럼에도 커다란 영향을 미치는 것으로 나타났다. 또 glassy carbon과 PVDF합성 흑연에서의 임피던스 파라미터는 분극부하에의해 현저한 변화가 나타났다.가 나타났다.

• Journal of Information Processing Systems
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• 제20권2호
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• pp.200-214
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• 2024

Amid the flood of data, social network analysis is beneficial in searching for its hidden context and verifying several pieces of information. This can be used for detecting the spread model of infectious diseases, methods of preventing infectious diseases, mining of small groups and so forth. In addition, community detection is the most studied topic in social network analysis using graph analysis methods. The objective of this study is to examine signed attributed social networks and identify the maximal balanced cliques that are both absolute and fair. In the same vein, the purpose is to ensure fairness in complex networks, overcome the "information cocoon" bottleneck, and reduce the occurrence of "group polarization" in social networks. Meanwhile, an empirical study is presented in the experimental section, which uses the personal information of 77 employees of a research company and the trust relationships at the professional level between employees to mine some small groups with the possibility of "group polarization." Finally, the study provides suggestions for managers of the company to align and group new work teams in an organization.

• 대한의용생체공학회:의공학회지
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• 제42권1호
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• pp.25-30
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• 2021

Objective: The aim of this study is to consider the effect of skin tissue necrosis by improving blood flow in animal skin models for low frequency pulsed electromagnetic fields (LF_PEMF) stimulation. Methods: Twenty rats (Wistar EPM-1 male, 280-320 g) were randomly divided into control groups (n=10) and the PEMF groups (n=10). To induce necrosis of the skin tissue, skin flap was treated in the back of the rat, followed by isolation film and skin flap suturing. Subsequently, the degree of necrosis of the skin tissue was observed for 7 days. The control group did not perform any stimulation after the procedure. For the PEMF group, LF_PEMF (1 Hz, 10 mT) was stimulated in the skin flap area, for 30 minutes a day and 7 days. Cross-polarization images were acquired at the site and skin tissue necrosis patterns were analyzed. Results: In the control group, skin tissue necrosis progressed rapidly over time. In the PEMF group, skin tissue necrosis was slower than the control group. In particular, no further skin tissue necrosis progress on the day 6. Over time, a statistically significant difference from the continuous necrosis progression pattern in the control group was identified (p<0.05). Conclusions: It was confirmed that low frequency pulsed electromagnetic fields (LF_PEMF) stimulation can induce relaxation of skin tissue necrosis.