• Progress in Superconductivity
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• v.2 no.2
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• pp.76-80
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• 2001

We have fabricated YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) ramp-edge Josephson junctions by modifying ramp edges of the base electrodes without depositing any artificial barrier layer. YBa$_2$Cu$_3$O/7-x//SrTiO$_3$ (YBCO/STO) films were deposited on SrTiO$_3$(100) by on-axis KrF laser deposition. After patterning the bottom YBCO/STO layer, the ramp edge was cleaned by ion-beam and then reacted with deionized water under various conditions prior to the deposition of counter-electrode layers. The top YBCO/STO layer was deposited and patterned by photolithography and ion milling. We measured current-voltage (I-V) characteristics, magnetic field modulation of the critical current at 77 K. Some showed resistively shunted junction (RSJ)-type I-V characteristics, while others exhibited flux-flow behaviors, depending on the dipping time of the ramp edge in deionized water. Junctions fabricated using optimized conditions showed fairly uniform distribution of junction parameters such as I$_{c}$R$_{n}$ values, which were about 0.16 mV at 77 K with 1$\sigma$~ 24%. We made a dc SQUID with the same deionized water treated junctions, and it showed the sinusoidal modulation under applied magnetic field at 77 K. 77 K.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.437-442
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• 1996

High quality $YBa_2Cu_3O_y$(YBCO) thin films for directly coupled dc superconducting quantum interference device (SQUID) were fabricated by pulsed laser deposition. Several critical parameters have been optimized through systematic studies. Thus, the films showing the $T_c$ of above 91K and $J_c$ of above$2\times10^6A/cm^2$ at 77K were routinely obtained. Extensive AFM and X-ray diffraction studies have been conducted for morphological and structural analyses. The directly coupled DC-SQUIDs were fabricated from the YBCO thin films deposited on $SrTiO_3$ bicrystals under the optimized conditions. The measurement on $2I_c$ and swing voltage give 200$\mu$A and 17$\mu$V at 77K, respectively.

• Progress in Superconductivity and Cryogenics
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• v.4 no.1
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• pp.35-39
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• 2002

We have simulated and laid out a Single Flux Quantum(SFQ) AND gate for Arithmetic Logic Unit by using XIC, WRspice and Lmeter. SFQ AND gate circuit is a combination of two D Flip-Flop. D Flip-Flop and dc SQUID are the similar shape form the fact that it has the loop inductor and two Josephson junction We obtained perating margins and accomplished layout of the AND gate. We got the margin of $\pm$38%. over. After layout, we drew mask for fabrication of SFQ AND sate. This mask was included AND gate, dcsfq, sfqdc, rs flip-flop and jtl.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.190-190
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• 2010

본 연구에서는 Ti이 도핑된 ZnO의 성장 및 후처리 과정에 따른 구조적, 전기적, 자기적 특성에 관하여 보고한다. ZnTiO 박막은 Pt/SiO2/Si기판에 $500^{\circ}C$, 20 mTorr에서 RF 마그네트론 스퍼터법과 DC 마그네트론 스퍼터법으로 코스퍼터링을 통하여 증착 하였다. 그리고 박막 성장 후 질소분위기에서 $600{\sim}900^{\circ}C$($50^{\circ}$ step)에서 급속 열처리 공정(RTA)을 이용하여 후열처리에 따른 특성변화를 관찰하였다. 구조적 특성변화를 확인하기 위하여 XRD 측정을 하였으며, Ti이 Zn와 치환되어 성장 한 것을 관측하였다. 한편 자기적 특성 확인을 위한 SQUID 측정 결과, ZnTiO 박막에서 강자성 특성인 자기-이력곡선을 확인하였다. 또한 강유전 특성 분석을 위한 I-V 측정에서 ZnTiO 박막에서 강유전 특성인 전류-이력 현상을 관측하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.11a
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• pp.268-271
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• 2002

The goal of the research is to study and describe a new stressed state of High Temperature Superconducting (High-Tc) YBCO Films, to create of SQUIDs (Superconducting Quantum Interference Device) on the bases of these Films with maximal sensitivity. The experimental investigation of the stressed films grown by laser ablation method and its properties, the fabrication of the dc-SQUIDs with maximal sensitivity on the bases of the stressed YBCO films were carried out. The stressed film having the value of the critical current density $J_{c}=3{\cdot}10^{5}A/cm^{2}$ was the more stable than others.

• Nutrition Research and Practice
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• v.14 no.6
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• pp.637-653
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• 2020

BACKGROUND/OBJECTIVES: This study examined the associations between food consumption frequency of Korean adults and self-perceived chewing difficulty, using the food frequency questionnaire (FFQ, 112 items) from 2013-2016 of the Korea National Health and Nutrition Examination Survey (KNHANES). SUBJECTS/METHODS: Subjects were divided into not difficult in chewing (NDC) and difficult in chewing (DC) groups, with 24.17% being classified into DC. Males and females consumed 35 and 37 items less frequently than the other sex, respectively. Due to the remarkable gender difference in food consumption, gender-stratified one-sided survey regression analysis was performed after adjusted for the effect of age, household income, and self-rated health status. RESULTS: Thirty-four items of FFQ were significantly less consumed by the DC group. Females exclusively consumed less beverages and alcohol while males showed the same for fruits and milk·dairy products. Consumption frequency of 8 items such as steamed potatoes·grilled potatoes, stir fried beef, other kimchi·fresh vegetable kimchi, orange, sour pork·pork cutlet, tteokbokki and green tea were significant only in males. In contrast, 17 items including cooked rice with other grains and legumes, boiled egg·steamed egg, Korean cabbage kimchi, banana, and tofu stew·soft tofu stew were significant only for females. Finally, items that showed significance for both were 9 items including loaf bread, ready-to-eat cereal, steamed sweet potatoes·grilled sweet potatoes, stir-fried lotus roots·stir-fried burdock, green laver salad·brown seaweed salads, apples, tomato·cherry tomatoes, squid (raw, dried shredded, boiled, stir-fried), and curd type yogurt. CONCLUSIONS: Findings in this study suggest chewing difficulty may be an important nutritional issue that has to be dealt with for healthful food consumption, with distinct interest of gender.

• Progress in Superconductivity
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• v.7 no.1
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• pp.46-51
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• 2005

We have developed control electronics to operate flux-locked loop (FLL), and analog signal filters to process FLL outputs for 64-channel Double Relaxation Oscillation SQUID (DROS) magnetocardiography (MCG) system. Control electronics consisting of a preamplifier, an integrator, and a feedback, is compact and low-cost due to larger swing voltage and flux-to-voltage transfer coefficients of DROS than those of dc SQUIDs. Analog signal filter (ASF) serially chained with a high-pass filter having a cut-off frequency of 0.1 Hz, an amplifier having a gain of 100, a low-pass filter of 100 Hz, and a notch filter of 60 Hz makes FLL output suitable for MCG. The noise of a preamplifier in FLL control electronics is $7\;nV/{\surd}\;Hz$ at 1 Hz, $1.5\;nV/{\surd}\;Hz$ at 100 Hz that contributes $6\;fT/{\surd}\;Hz$ at 1 Hz, $1.3\;fT/{\surd}\;Hz$ at 100 Hz in readout electronics, and the noise of ASF electronics is $150\;{\mu}V/{\surd}\;Hz$ equivalent to $0.13\;fT/{\surd}\;Hz$ within the range of $1{\sim}100\;Hz$. When DROSs are connected to readout electronics inside a magnetically shielded room, the noise of 64-channel DROS system is $10\;fT/{\surd}\;Hz$ at 1 Hz, $5\;fT/{\surd}\;Hz$ at 100 Hz on the average, low enough to measure human MCG.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.481-492
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• 2004

We report the successful fabrication and I-V curve superconductivity test results of the Nb/Al-based superconducting tunnel junctions. STJs with side-lengths of 20, 40, 60 and $80{\mu}m$ were fabricated by deposition of polycrystalline Nb/Al/AlOx/Al/Nb 5-layer thin films incorporated on a 3-inch Si wafer. STJ was designed by $Tanner^{TM}$ L-Edit 8.3 program, and fabricated in SQUID fabrication facility, KRISS. S-layer STJ thin-films were fabricated using UV photolithography, DC magnetron sputtering, Reactive ion etching, and CVD(Chemical Vapor Deposition) techniques. Superconducting state test for STJ was succeeded in 4K with liquid helium cooling system. Their performance indicators such ie energy gap, normal resistance, normal resistivity, dynamic resistance, dynamic resistivity, and quality factor were measured from I-V curve. Fabricated Nb/Al STJ shows $11\%$ higher FWHM energy resolution than genuine Nb STJ.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.243-243
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• 2007

We have studied the electrical properties and microstructure of $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y[(YNS)-123]$ Oxides by rod-type seeded melt growth process(RSMG) in air atmosphere. Rod-type $NdBa_2Cu_3O_y${Nd-123) seed crystals made a extrusion process method, were used for achieving the ab-plane alignment having large grains perpendicular to the center of (YNS)-123 samples. The observations using SEM and TEM micrographs of the melt-textured (YNS)-123 samples revealed that the nonsuperconducting $(Y_{0.5}Nd_{0.25}Sm_{0.25})Ba_2Cu_3O_y[(YNS)-211]$ inclusions are uniformly distributed in the superconducting matrix. The microstructure and electrical properties were investigated by XRD, SEM, TEM and DC SQUID magnetometer. The sample showed a sharp superconducting transition at 90 K. The magnetization values of the (YNS)-123 sample exhibited the enhanced electrical properties, compared with $YBa_2Cu_3O_y$(Y-123) sample.