• Progress in Superconductivity
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• 제9권1호
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• pp.23-28
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• 2007

In order to have a superconductive connection between the wire-wound pickup coil and input coil, typically Nb terminal blocks with screw holes are used. Since this connection structure occupies large volume, large stray pickup area can be generated which can pickup external noise fields. Thus, SQUID and connection block are shielded inside a superconducting tube, and this SQUID module is located at some distance from the distal coil of the gradiometer to minimize the distortion or imbalance of uniform background field due to the superconducting module. To operate this conventional SQUID module, we need a higher liquid He level, resulting in shorter refill interval. To make the fabrication of gradiometers simpler and refill interval longer, we developed a novel method of connecting the pickup coil into the input coil. Gradiometer coil wound of 0.125-mm diameter NbTi wires were glued close to the input coil pads of SQUID. The superconductive connection was made using an ultrasonic bonding of annealed 0.025-mm diameter Nb wires, bonded directly on the surface of NbTi wires where insulation layer was stripped out. The reliability of the superconductive bonding was good enough to sustain several thermal cycling. The stray pickup area due to this connection structure is about $0.1\;mm^2$, much smaller than the typical stray pickup area using the conventional screw block method. By using this compact connection structure, the position of the SQUID sensor is only about 20-30 mm from the distal coil of the gradiometer. Based on this compact module, we fabricated a magnetocardiography system having 61 first-order axial gradiometers, and measured MCG signals. The gradiometers have a coil diameter of 20 mm, and the baseline is 70 mm. The 61 axial gradiometer bobbins were distributed in a hexagonal lattice structure with a sensor interval of 26 mm, measuring $dB_z/dz$ component of magnetocardiography signals.

• Progress in Superconductivity
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• 제13권1호
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• pp.34-39
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• 2011

본 연구를 통해서 초전도 선재 시료의 국소적인 영역에 대한 전류 밀도의 공간적인 분포를 시료의 손상 없는 비파괴적인 방법으로 LTSHPM을 통해서 1차원 2차원으로 형상화해 보았다. 그 결과 외부자기장에 의한 차폐전류의 흐름을 분석할 수 있었다. 또한 MPMS에서 외부자기장에 따른 자기모멘트를 측정한 결과와 LTSHPM을 통해 전류 밀도 분포를 분석한 결과를 비교해 볼 때 외부자기장에 의한 반자성의 크기와 자기모멘트로 인해 생기는 차폐전류가 100 Oe에서 최댓값을 가지는 일치하는 결과를 얻을 수 있었다. 그리고 세 가지의 평행한 브릿지에 흐르는 차폐전류를 2차원적으로 분석해 본 결과 시료 전체적으로 가장 바깥쪽으로 차폐전류가 흐르는 공통점을 확인해 볼 수 있었다.

• 한국군사과학기술학회지
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• 제9권2호
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• pp.11-19
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• 2006

The underwater electromagnetic signatures of a naval ship are mainly generated from three sources which are the permanent and induced magnetic field in the ship's hull and other ferrous components, the cathodic current electromagnetic field established by the Impressed Current Cathodic Protection(ICCP) system or the Sacrificial Anode and the stray electromagnetic fields generated by onboard equipment. These signatures can be minimized by certain design methods or installation of signature reduction equipment. In this paper, we represented the characteristic of the underwater electromagnetic signature and the signature reduction techniques for a naval ship. Also, we measured the electromagnetic field changes emitted from the real ship using the Electric and Magnetic field Measurement System(EMMS). We found that the underwater electromagnetic signature for a naval ship can be used as input or trigger signal in a surveillance system and an influence mine.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.20-24
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• 2009

The superconducting property measurement system is used to acquire electrical and thermal properties on short HTS tape samples and the system is composed of specimen holder for mounting HTS tape and a magnet for applying magnetic fields externally. The magnet consists of two split racetrack windings and is designed to produce maximum 3T of center field. The temperature of specimen holder can be varied in range from 10K to 77K. The field homogeneity is required less than 300 gauss stray field contour within 20cm axially and 3cm radially from origin. We have worked on the conceptual designs of the conduction-cooled magnet for the superconducting characteristic measurement system. The measurement system will be fabricated in near future based on the design parameters presented in this paper.

• 한국초전도ㆍ저온공학회논문지
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• 제17권2호
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• pp.25-30
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• 2015

In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

• Parasites, Hosts and Diseases
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• 제55권3호
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• pp.287-294
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• 2017

The present study was performed to record new definitive hosts of Isthmiophora hortensis, and to describe morphological characteristics derived from a variety of worm samples for clarification of its taxonomic validity. Morphological characteristics with dimensions were observed in worm samples (n=21) from naturally infected wild animals, including a raccoon dog Nyctereutes procyonoides from Gimhae-si (City), Gyeongsangnam-do, stray cats and a striped field mouse from several localities, and a wild boar Sus scrofa, from Gurye-gun (County), Jeollanam-do. In addition, adult flukes (n=45) recovered in albino rats experimentally infected with the metacercariae from a freshwater fish species were also subjected to morphological studies. The mean ratios of the body length (BL) to body width (BW) were 5.86 and 5.76 in worms from wild animals and experimental rats, respectively. Those of the ventral sucker to oral sucker were 2.92 and 3.01 in worms from 2 groups. The mean percentages of the hindbody length (HBL) to BL were 42.1 and 41.2 in 2 groups. Those of uterine fields to BL were 9.8 and 12.2 in the 2 worm groups. By the present study, the 2 species of wild animals, the raccoon dog and wild boar, have been added as new definitive hosts for I. hortensis. The morphological characteristics of adult flukes derived from a variety of host source were redescribed to support the taxonomic validity of this echinostome species.

• Parasites, Hosts and Diseases
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• 제57권6호
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• pp.647-656
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• 2019

Isthmiophora hortensis (Digenea: Echinostomatidae) is a dominant echinostome in animal reservoir hosts and humans in the Republic of Korea (Korea). We intended to investigate the infection status with this echinostome species in the several species of wild animals and describe the morphological characteristics in the faunistic view point. A total of 175 animal carcasses belonging to 3 families, i.e., Canidae, Felidae and Mustelidae, were collected from the southern regions of Korea from March 2010 to July 2017. Isthmiophora spp. worms were recovered from the small intestines of each animal under a stereomicroscope after washing of intestinal contents. Isthmiophora hortensis was recovered from 4 species of wild carnivores, i.e., Nyctereutes procyonoides (3/107: 2.8%), Mustela sibirica (11/31: 35.5%), Meles lucurus (2/3: 33.3%) and Martes flavigula (1/2: 50%). The other 3 carnivores comprising stray dogs, cat and leopard cat were negative for I. hortensis infection (0/2, 0/10 and 0/12, respectively). Specimens obtained from the Lutra lutra (6/8: 75%) were identified as a distinct species, I. inermis, by morphological comparison. Isthmiophora inermis has thinner body, elongate testes and different anterior limits of vitelline fields. Detailed morphological descriptions and comparisons with the morphological characteristics are provided. Conclusively, it was confirmed for the first time that 3 species of mustelid mammals, i.e., M. sibirica, M. lucurus, and M. flavigula, are to be the new definitive hosts of I. hortensis in Korea. Additionally, I. inermis is to be newly added in the Korean echinostome fauna.

• 대한금속재료학회지
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• 제49권6호
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• pp.505-513
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• 2011

A magnetic device which enables the application of a strong and uniform magnetic field to thin film during sputtering was designed for controlling the magnetic anisotropy using a three dimensional finite element method, and the effects of the external magnetic field on the magnetic properties of sputtered thin films were investigated. Both the intensity and the uniformity of the magnetic flux density in the sputter zone (50 mm ${\times}$50 mm) was dependent on not only the shape and size of the magnet device but also the magnitude of stray fields from the magnet. For the magnet device in which the distance between two magnets or two pure iron bars was 80-90 mm, the magnetic flux density along the direction normal to the external magnetic field direction was minimum. The two row magnets increased the magnetic flux density and uniformity along the external magnetic field direction. An Fe thin film sputtered using the optimized magnet device showed a higher remanence ratio than that fabricated under no external magnetic field.

• 한국전기전자재료학회논문지
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• 제37권1호
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• pp.112-117
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• 2024

The Internet of Things (IoT) device is a key component for Industry 4.0, which is the network in homes, factories, buildings, and infrastructures to monitor and control the systems. To demonstrate the IoT network, batteries are widely utilized as power sources, and the batteries inevitably require repeated replacement due to their limited capacity. Magneto-mechano-electric (MME) generators are one of the candidate to develop self-powered IoT systems since MME generators can harvest electricity from stray alternating current (AC) magnetic fields arising from electric power cables. Herein, we report a magneto-mechano-triboelectric generator enabled by a ferromagnetic-ferroelectric composite. In the triboelectric nylon matrix, a ferromagnetic carbonyl iron powder (CIP) was introduced to induce magnetic force near the AC magnetic field for MME harvesting. Additionally, a ferroelectric ceramic powder was also added to the MME composite material to enhance the charge-trapping capability during triboelectric harvesting. The final ferromagnetic-ferroelectric composite-based MME triboelectric harvester can generate an open-circuit voltage and a short-circuit current of 110 V and 8 μA, respectively, which were enough to turn on a light emitting diode (LED) and charge a capacitor. These results verify the feasibility of the MME triboelectric generator for not only harvesting electricity from an AC magnetic field but also for various self-powered IoT applications.