• 한국표면공학회지
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• 제29권5호
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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.

• 한국초전도ㆍ저온공학회논문지
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• 제22권4호
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• pp.1-5
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• 2020

Heart consists of myocardium cells and the electrophysiological activity of the cells generate magnetic fields. By measuring this magnetic field, magnetocardiogram (MCG), functional diagnosis of the heart diseases is possible. Since the strength of the MCG signals is weak, typically in the range of 1-10 pT, we need sensitive magnetic sensors. Conventionally, superconducting quantum interference devices (SQUID)s were used for the detection of MCG signals due to its superior sensitivity to other magnetic sensors. However, drawback of the SQUID is the need for regular refill of a cryogenic liquid, typically liquid helium for cooling low-temperature SQUIDs. Efforts to eliminate the need for the refill in the SQUID system have been done by using cryocooler-based conduction cooling or use of non-cryogenic sensors, or room-temperature sensors. Each sensor has advantage and disadvantage, in terms of magnetic field sensitivity and complexity of the system, and we review the recent trend of MCG technology.

• Progress in Superconductivity
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• 제3권1호
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• pp.56-59
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• 2001

We have constructed a multi-channel SQUID magnetometer system for localization and classification of magnetic targets. Ten SQUID magnetometers were arranged to measure 5 independent components of 3 $\times$ 3 magnetic field gradient tensor. To get gradient from the difference of magnetic field measurements, we carefully balanced magnetometers. SQUIDs with slotted washer were used for operation in an unshielded laboratory environment, and noise characteristic in the laboratory was measured. With the multi-channel SQUID magnetometer system, we have successfully traced the motion of a bar magnet moving around it at a distance of about 1 m. In the urban environment, the drift of uniform magnetic field due to the irregular motion of a large magnetic body at distance and earth field causes an error in the position calculation, and this results in the distortion of the calculated trajectory. In this paper, we present the architecture and the performance of the system.

• Fisheries and Aquatic Sciences
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• 제2권1호
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• pp.12-16
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• 1999

Denaturation of actomyosin from the obliquely striated mantle muscle of squids (Todarodes pacificus) was studied by measuring the changes in $Ca^{2+}$-ATPase activity, relative viscosity, and solubility during frozen storage at three different temperature zones of maximum ice crystal formation $(-3^{\circ}C,\;-\;-5^{\circ}C)$, the eutectic point $(-11^{\circ}C)$, and $-20^{\circ}C$. The logarithms of $Ca^{2+}$-ATPase activity, relative viscosity and solubility of the actomyosin solutions (0.6 M KCl) and suspensions (0.05 M KCl) tended to decrease during frozen storage. The denaturation of squid actomyosin at the zone of maximum ice crystal formation significantly differed by only two degree of temperature difference between $-3^{\circ}C$ and $-5^{\circ}C$, and it (0.05 M KCl) at $-3^{\circ}C$ was less than those of other temperature. The denaturation at $-11^{\circ}C$ was more rapid than at $-5^{\circ}C$. The logarithms of $Ca^{2+}$ -ATPase activity, relative viscosity, and solubility were changed slower in the suspensions (0.05 M KCl) than the solutions (0.6 M KCl) at all experimental temperatures.

• 한국응용과학기술학회지
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• 제33권2호
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• pp.304-310
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• 2016

식염 5%를 첨가한 저염 오징어 젓갈을 $10^{\circ}C$에서 8주간 숙성시키면서 핵산관련물질의 변화를 분석하였다. 숙성발효에 따른 정미성분의 변화를 보면, 핵산관련물질 중 ATP 및 ADP는 소실되어 검출되지 않았으며 초기에만 AMP가 존재하고 숙성중반까지 현저히 감소한 반면에 inosine 및 hypoxanthine은 숙성중반까지 증가하였다가 다시 감소하였으며 핵산관련물질의 대부분을 차지하였다. pH는 식염농도가 낮고 숙성온도가 높을수록 숙성후반까지 계속 유의성 높게 증가하여 숙성이 촉진되었으며 적정산도는 숙성후반까지 감소하였다. 이상의 결과처럼 저염 오징어 젓갈의 적정 발효조건을 추정해 보면 발효온도 $10^{\circ}C$, 식염 10%, 발효기간 5주로 추정되어 활용가치가 높다고 사료된다.

• 한국수산과학회지
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• 제30권4호
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• pp.523-527
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• 1997

본 연구는 분리된 세 개의 군이 서로 다른 독특한 생식생태를 가지는 지를 파악하기 위하여 각군의 산란기, 난경 조성, 포란수 및 성숙 외투장을 조사하였다. 하계군의 산란기는 7월$\~$8월 (주산란기, 7월), 난경 분포는 $0.4\~2.4mm$ (최빈값, 0.8 mm)이었고, 포란수는 $F=0.1\times10^{-6}{\times}ML^{0.5036}$이었다. 추계군의 산란기는 9월$\~$이듬해 1월 (주산란기, 9월), 난경 분포는 $0.2\~1.4mm$ (최빈값, 0.8mm)이었고, 포란수는 $F=1.0017{\times}ML^{3.2864}$ 이었다. 동계군은 3월$\~$4월 (주산란기, 3월)이었으며, 난경 분포는 $0.4\~2.0mm$ (최빈값, 1.0 mm)이었다. 포란수는 $F=1.0499{\times}ML^{1.2953}$ 이었다. 성숙외투장은 하계군, 추계군 및 동계군 모두 $20\~22cm$이었다. 이상의 결과를 종합하여 보면, 산란기, 포란수 및 난경의 분포는 군간에 차이가 있었으나 성숙외투장은 군간에 차이가 없었다.

• Progress in Superconductivity
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• 제9권1호
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• pp.50-55
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• 2007

We have installed a 61-channel magnetocardiography (MCG) system inside a magnetically shielded room (MSR) with a size of $2.4\;m\;{\times}2.4\;m\;{\times}2.4\;m$. The MCG system consists of 1st-order axial gradiometers containing double relaxation oscillation SQUIDs (DROSs) with pick-up coils of a base line of 70 mm. The MSR holds a shielding factor of 50 at 0.1 Hz and 10000 at 100 Hz, when its door in the middle on a front wall is closed. On opening the MSR door, we have obtained the characteristics of the MCG system with a 2.9 Hz noise generated from an air conditioning unit at 13 m distance off the MSR. In an open-door MSR ($140^{\circ}$ opening), a noise at the center channel increases up to $700\;fT/Hz^{l/2}$ at 2.9 Hz and $1.7\;pT/Hz^{1/2}$ at 60 Hz. MCG signals for a healthy human do not show distortion until the door opens to $45^{\circ}$, but show the effect of noise when the door opens further at $90^{\circ}$ and $140^{\circ}$. With the door opens to $45^{\circ}$, MCG measurement can be performed with ease of door operation and without creating claustrophobia for the patient.

• Progress in Superconductivity
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• 제7권1호
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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.

• Progress in Superconductivity
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• 제13권3호
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• pp.139-145
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• 2012

Electric activity of cardiac muscles generates magnetic fields. Magnetocardiography (or MCG) technology, measuring these magnetic signals, can provide useful information for the diagnosis of heart diseases. It is already about 40 years ago that the first measurement of MCG signals was done by D. Cohen using SQUID (superconducting quantum interference device) sensor inside a magnetically shielded room. In the early period of MCG history, bulky point-contact RF-SQUID was used as the magnetic sensor. Thanks to the development of Nb-based Josephson junction technology in mid 1980s and new design of tightly-coupled DC-SQUID, low-noise SQUID sensors could be developed in late 1980s. In around 1990, several groups developed multi-channel MCG systems and started clinical study. However, it is quite recent years that the true usefulness of MCG was verified in clinical practice, for example, in the diagnosis of coronary artery disease. For the practical MCG system, technical elements of MCG system should be optimized in terms of performance, fabrication cost and operation cost. In this review, development history, technical issue, and future development direction of MCG technology are described.

• 수산해양기술연구
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• 제52권2호
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• pp.162-168
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• 2016

This study attempted to help determine Korean fishery policies by proposing improvement plans after examining the current regulations, fishing vessels, fishing gear and fishing methods of the middle sized trawl fishery in the East Sea for targeting only squid. In general, the size, engine horse power, and net length of the middle sized trawlers are between 50 and 60 GT, 1,200 and 1,600 PS, and approximately 165 m with four seamed trawl nets, respectively. While a jigging vessel attracted squids using lights, the trawler approached a jigging vessel. The trawler let the jigging vessel know its decision for fishing, and then jigging vessel rolled up jigs. The net of the trawler was casted at 45 degrees between the bow and the stern of the jigging vessel. Once the trawler towed close to the stern of the jigging vessel upon its passing of the jigging vessel, the bow of the trawler turned 45 degrees left again. Then, squid aggregations were entered into the net. When the cod end was passed a light vessel, the trawler hoisted the net up to the otter board. Then the trawler turned 180 degrees. It repeated three to five times of fishing operations as the previous method. We recommend that the regulations allow nineteen side trawlers to catch like stern trawler, as well as the cooperative trawler and jigging vessel operations.