• Journal of information and communication convergence engineering
• /
• 제16권2호
• /
• pp.67-71
• /
• 2018

The various techniques to compensate for the signal distortion due to the group velocity dispersion (GVD) and nonlinear Kerr effects of optical fibers in the optical links have been proposed in the literature. We propose a flexible dispersion-managed link configuration consisted of single-mode and dispersion-compensating fibers with irregular dispersion coefficients over all fiber spans, and an optical phase conjugator added midway along the optical links. By distributing the lengths of the single mode fibers, we achieve a flexible optical link. The simultaneous ascending and descending distribution of the single-mode fiber lengths before and after the optical phase conjugator, respectively, best compensates the distorted wavelength division multiplexed signals in the optical link with non-fixed coefficients. Our result is consistent with those of our previous work on fixed coefficients. Therefore, to improve the compensation at any magnitude of dispersion coefficient, we must artificially distribute the lengths of the single-mode fibers into a dispersion-managed link.

• Current Optics and Photonics
• /
• 제5권2호
• /
• pp.180-185
• /
• 2021

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.

• Journal of Electrical Engineering and Technology
• /
• 제10권1호
• /
• pp.325-330
• /
• 2015

With approval from the Asia Pacific Metrology Program Working Group on Materials Metrology (APMP WGMM), an international comparison for sheet resistance standards for silicon wafers was firstly conducted among Korea Research Institute of Standards and Science (KRISS) in Korea, CMS/ITRI in Taiwan, and NIM in China, which are national metrology institutes (NMIs), from August 2011 to January 2012. The sheet resistance values of the standards are $10{\Omega}$, $100{\Omega}$, and $1000{\Omega}$; the measurement was conducted in sequence at KRISS, CMS/ITRI, NIM, and KRISS again using the four-point probe method with single and dual configuration techniques. The reference value for the measurement results of the three NMIs was obtained through averaging the values of the three results for each sheet resistance range. The differences between the reference value and the measured values is within 0.22% for $10{\Omega}$, 0.17% for $100{\Omega}$, and 0.12% for $1000{\Omega}$. Therefore, the international consistency for conducting sheet resistance measurements is confirmed within 0.22% through the APMP WGMM approved comparison.

• Journal of electromagnetic engineering and science
• /
• 제12권4호
• /
• pp.234-239
• /
• 2012

This paper presents a compact K-band Doppler radar sensor for human vital signal detection that uses a radar configuration with only single coupler. The proposed radar front-end configuration can reduce the chip size and the additional RF power loss. The radar front-end IC is composed of a Lange coupler, VCO, and single balanced mixer. The oscillation frequency of the VCO is from 27.3 to 27.8 GHz. The phase noise of the VCO is -91.2 dBc/Hz at a 1 MHz offset frequency, and the output power is -4.8 dBm. The conversion gain of the mixer is about 11 dB. The chip size is $0.89{\times}1.47mm^2$. The compact Ka-band Doppler radar system was developed in order to demonstrate remote human vital signal detection. The radar system consists of a Ka-band Doppler radar module with a $2{\times}2$ patch array antenna, baseband signal conditioning block, DAQ system, and signal processing program. The front-end module size is $2.5{\times}2.5cm^2$. The proposed radar sensor can properly capture a human heartbeat and respiration rate at the distance of 50 cm.

• Journal of Magnetics
• /
• 제17권4호
• /
• pp.242-244
• /
• 2012

We report on the basis of experiments that magnetic domain structures exhibit a transition between single and dendrite domains with respect to the width of ferromagnetic nanowires. This transition is directly observed in CoFe/Pt multilayered nanowires having a width in the range of 580 nm to 4.2 ${\mu}m$ with a magnetic force microscope. Nanowires wider than 1.5 ${\mu}m$ show typical dendrite domain patterns, whereas the nanowires narrower than 690 nm exhibit single domain patterns. The transition occurs gradually between these widths, which are similar to the typical widths of the dendrite domains. Such a transition affects the strength of the domain wall propagation field; this finding was made by using a time-resolved magneto-optical Kerr effect microscope, and shows that the domain wall dynamics also exhibit a transition in accordance with the domain configuration.

• 한국전기전자재료학회논문지
• /
• 제18권12호
• /
• pp.1087-1091
• /
• 2005

Four-probe device of single ZnO nanowire was fabricated by electron beam lithography. Electrical characterizations in a two-probe and a four-probe configuration with a back-gate were carried out to clarify the relative contribution of the contact and the intrinsic part in a ZnO nanowire. I-V characteristic in four-probe measurement showed an ohmic behavior with a high conductivity, 100 S/cm, which was better than those of two-probe measurement by 10 times. At the same values of the current between two-probe and four-probe, the net voltage applied inside the nanowire were extracted with calculated voltages at the contact. Four-probe current-gate voltage characteristics showed bigger tendencies than those of two-probe measurement at low temperatures, indicating the reduced gate dependence in two-Probe measurements by the existence of the contact resistance.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제54권11호
• /
• pp.654-659
• /
• 2005

An improved power supply for APD(Avalanche Photo Diode) with a received optical power monitoring circuit allows the received optical power increase temporary without of the degradation of the electrical signal. For the cost reduction and simple fabrication, an improved power supply has been proposed that it was designed for driving a APD as a receiving device of a wireless optical transmission system. It was demonstrated that it was possible to improve a dynamic range by compensating the temperature coefficient of the APD up to 1.0 V/$^{\circ}C$ through the power supply. Also, for an efficient transmission at the receiver end, a simple structure of a single cylindrical micro-lens configuration was used in conjunction with the laser diode to partially compensate a laser beam ellipticity. For this purpose, an astigmatism introduced by the micro-lens is utilized for the additional compensation of the beam ellipticity at the receiver end. In this paper, it is demonstrated that an efficient beam shaping is realized by using the proposed configuration consisting of the single lens attached to the laser diode.

• 한국안전학회지
• /
• 제20권1호
• /
• pp.62-67
• /
• 2005

An eccentrically-loaded single edge crack tension specimen (ESET) is similar to a compact tension(CT) specimen loaded in tension-tension. The standard ESET specimen exhibits advantages over other types of cracked specimen, such as n, single-edge crack, and middle-crack tension specimen. The details of ESET specimen configuration, test procedure, and calculations are described in ASTM E647 standard. However, a difficulty in attaching COD gage to the knife-edge on the front foe of the specimen can be found when the size of ESET specimen is small for rapid cooling and heating in thermal fatigue testing. The finite element analysis is performed for the ESET specimen with projected knife-edge on the front foe and a crack-length-compliance equation is suggested for the new specimen configuration. Calibration test are conducted with 347 stainless steel to compare the measured crack length with the calculated crack length from the suggested compliance expression. The test results showed good agreements with those of analysis.

• Nano
• /
• 제13권12호
• /
• pp.1850149.1-1850149.10
• /
• 2018

Ferroelectric particles have been applied in the photocatalytic field because the spontaneous polarization results in the internal electric field, which can accelerate the separation and migration of photogenerated carriers. In this study, the $BaTiO_3$ (BT) fibers are synthesized by electrospinning. The BT fibers calcined above $800^{\circ}C$ exhibit a strong ferroelectric property, which is verified by a typical butterfly-shaped displacement-voltage loop. It is found that the BT fibers with the single-domain structure exhibit better photocatalytic performance than that with the multi-domain configuration. When the single-domain transforms into multi-domain, the integrated internal electric field correspondingly breaks up, inducing that the internal electric field might cancel each other out and diminish the separation of photogenerated carriers. Also, the Au nanoparticles can improve the photocatalytic activity further on account of the surface plasmon resonance. Therefore, it is suggested that Au nanoparticles decorated on ferroelectric BT nanomaterials are promising photocatalysts.

• 한국산학기술학회논문지
• /
• 제13권11호
• /
• pp.5465-5470
• /
• 2012

FPGA(Field Programmable Gate Array) 디바이스는 회로의 개발 기간을 단축할 수 있으며, 낮은 비용으로 자체적인 회로를 구현할 수 있다는 장점이 있다. FPGA 중에서도 SRAM기술을 사용하는 FPGA는 게이트의 집적도가 높아 복잡한 회로의 구현이 가능하고, 구현한 회로를 동적으로 변경할 수 있는 특징이 있어, 최근 인공위성의 탑재컴퓨터에 그 사용빈도가 증가하고 있는 추세다. 그러나, SRAM 기반 FPGA는 우주 방사선 입자들에 의한 오류 현상인 단일사건오류에 취약하여, 우주에서 사용할 때에는 이를 검출하고, 정정할 수 있는 회로를 탑재해야 한다. 이 논문에서는 FPGA의 내부 모듈 중에서 SEU에 가장 취약한 재구성 메모리를 보호하는 제어기를 설계하였다. 제어기는 SEU에 강한 Anti-Fuse방식의 FPGA에 구현하였으며, 실제 회로 구현 후, 방사능 시험을 수행한 결과, 본 연구에서 제안한 재구성 메모리 보호 제어기를 기존의 TMR회로와 함께 사용하면, 보다 우수한 고장허용성을 갖는 것을 입증하였다.