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Background: Segmental arterial mediolysis (SAM) causes subarachnoid hemorrhage (SAH) due to intracranial aneurysm rupture and arterial dissection. We encountered a case of SAM-related SAH due to ruptured dissection of the A1 segment of the anterior cerebral artery concomitant with internal carotid artery (ICA) dissection. Case Description: A 53-year-old man presented with SAH due to a ruptured right A1 dissecting aneurysm. The aneurysm was trapped; however, 7 days after the onset of SAH, he experienced right hemiparesis and aphasia. Angiography showed left ICA dissection; urgent carotid artery stenting was performed, leading to symptom improvement. Abdominal computed tomography angiography showed aneurysms of the celiac and superior mesenteric arteries. He was diagnosed with SAM based on clinical, imaging, and laboratory findings. Conclusion: In the acute phase of SAM-related SAH, cerebral ischemia could occur due to both cerebral vasospasm and intracranial or cervical artery dissection.

Introduction It has not been reported how long the follow-up study after carotid artery stenting (CAS) should be continued. The purpose of the present study is to clarify the dynamic change of the in-stent neointimal layer and residual arterial lumen by two years following CAS using three-dimensional computed tomography angiography (3D CTA) with volume rendering. Methods Thirty-six stented carotid arteries in 34 consecutive patients were examined by 3D CTA with volume rendering at two weeks and 3, 6, 12, 24 months of follow-up. Results An in-stent hypodense area could be detected in 10 of 36 (27.8%) carotid arteries at two weeks after CAS. In-stent hypodense areas gradually declined thereafter by three months. In the course of longer follow-up, the layer of the in-stent hypodense area (neointimal hyperplasia) continued to grow in size for up to 24 months. Patients with an in-stent hypodense area at two weeks have a thicker layer of neointimal hyperplasia at 24 months than patients without in-stent hypodense area at two weeks’ follow-up. The predictive factors for growing neointimal hyperplasia at 24 months in multiple regression analysis are ulcer formation in pretreatment stenosis and the thickness of in-stent hypodense area at two weeks following CAS. Conclusion Our results suggest that follow-up study should be continued for a longer period even if in-stent restenosis could not be detected at one year following CAS. Especially in cases with ulcer formation in pretreatment stenosis and with a subacute in-stent hypodense area after CAS, longer follow-up is strongly recommended.

本研究は、インド・ベンガル地方の「バウル」と呼ばれる宗教的芸能集団のライフヒストリーの研究である。個々のバウルのライフヒストリーは、それぞれ個人の経験を表現したもので、それ自体で完結した世界をあらわしている。しかし、ひとりの人間の人生の物語には、その人をとりまく社会の描写があるはずである。ひとりの人間のライフヒストリーは、絵画や写真にたとえれば、その人の「肖像」であると同時に、その人に焦点をあわせた「群像」でもある。本研究では、あつめた資料を読者に提示する方法として、「ライフヒストリーの重ねあわせ」という手法を採用する。すなわち、複数のバウルのライフヒストリーを並列させて、ベンガル社会における「バウルという人間集団」を描きだす。

本研究は、インド・ベンガル地方の「バウル」と呼ばれる宗教的芸能集団のライフヒストリーの研究である。 個々のバウルのライフヒストリーは、それぞれ個人の経験を表現したもので、それ自体で完結した世界をあらわしている。しかし、ひとりの人間の人生の物語には、その人をとりまく社会の描写があるはずである。ひとりの人間のライフヒストリーは、絵画や写真にたとえれば、その人の「肖像」であると同時に、その人に焦点をあわせた「群像」でもある。本研究では、あつめた資料を読者に提示する方法として、「ライフヒストリーの重ね合わせ」という手法を採用する。すなわち、複数のバウルのライフヒストリーを並列させて記述し、ベンガル社会における「バウルという人間集団」を描きだす。

When a quench occurs in a superconducting magnet, excessive joule heating in normal region may damage the magnet. It is necessary to detect the quench as soon as possible and discharge magnetic energy stored in the magnet. The authors have presented a quench detection/protection system based on an active power method which detects the quench regardless of a self-inductive and mutual-inductive voltages and electromagnetic noise. In the conventional active power method, the inductive voltages are removed by cancel coils. In this paper, the authors propose a method to cancel an inductive voltage using a capacitor circuit. The quench detection/protection system becomes more precise and smaller than the conventional system through the capacitor circuit.

When a quench occurs in a superconducting magnet, excessive joule heating may damage the magnet. We have presented the quench protection system based on an active power method. Our previous quench protection tests have been carried out for small superconducting magnets whose self inductances are less than several hundred mH to verify principles of our proposed system. In this paper, we present experimental results of quench protection tests of a cryocooler cooled 6 T NbTi superconducting magnet (self inductance 15.5 H), which is a commercial size magnet made by Tamakawa Co., Ltd. We confirmed that our proposed system could inhibit the maximum temperature of the superconducting magnet (initial temperature 4.3 K) after the quench to less than about 44 K at operation magnetic field 5.5 T. Experimental results suggest that our proposed system is useful for practical used superconducting magnets.

本研究は、インド・ベンガル地方の「バウル」とよばれる宗教的芸能集団の民族誌である。詩人タゴール(Rabindranath Tagore 1861-1941)が、20世紀初頭にバウルの歌の豊潤さを紹介して以来、それまで「奇妙な集団の風変わりな歌」とみなされていたバウルの歌が再評価されるようになった。タゴールの影響により、その後ベンガル人学者によって膨大な数のバウルの歌が採集され、なかには注釈つきのりっぱな歌集として出版された。また、バウルの歌を分析し、バウルの宗教を考察した専門書もいくつか出版された。もちろんこれらの研究は、バウルについてのわれわれの理解におおいに貢献したのであるが、そこには「人間としてのバウル」を専門的に紹介しようとした民族誌的文献は、事実上、皆無である。本研究は、ベンガルのバウルの民族誌的記述と分析を通じて、カースト制度と表裏一体の関係にある世捨ての制度を考察し、インド文明の構造的理解を試みようとするものである。

When a quench occurs in a superconducting magnet, excessive joule heating may damage the magnet. The authors have presented a quench detection/protection system based on an activ e power method, which can detect the quench quickly and precisely by measuring an active power dissipated within the magnet after the quench. In this paper, the authors show usefulness of a softwa re quench detection/protection system for a cr yocooled NbTi superconducting magnet which is a commercial size magnet made by Tamakawa Co., Ltd.. Experimental results show that the proposed system is useful for the practical used superconducting magnet.

In high temperature superconductors, local and excessive temperature rise occurs after normal transition because normal zone propagation velocities are slow at high operation temperature and then the superconductors may be degraded or burned. Therefore, it is essential to detect the temperature rise in high temperature superconducting coils and protect them as soon as possible. The authors have presented a detection method based on time-frequency visualization of AE signals. In this paper, the authors discuss detection and frequency analysis of AE signals accompanying with epoxy cracks caused by thermal expansion in an HTS coil by using the method.

The normal zone propagation velocities in high T c superconductors are slow at high operation temperature and therefore local and excessive temperature rise generates at quench occurrence, and then the superconductors are degraded or burned. Therefore it is essential to detect the temperature rise in high T c superconducting (HTS) coils as soon as possible and protect them. The authors have presented a quench detection method for HTS coils by time–frequency visualization of AE signals and have shown its usefulness for a HTS coil with height and outer diameter of 40–50 mm. In this paper, the authors present a quench detection/protection system based on superior method in quench detection time to the previous method and show its usefulness for a larger HTS coil (height and outer diameter: 160–190 mm) than the previous coil.

本研究は、インド・ベンガル地方の「バウル」とよばれる宗教的芸能集団の民族誌である。詩人タゴール(Rabindranath Tagore 1861-1941)が、20世紀初頭にバウルの歌の豊潤さを紹介して以来、それまで「奇妙な集団の風変わりな歌」とみなされていたバウルの歌が再評価されるようになった。タゴールの影響により、その後ベンガル人学者によって膨大な数のバウルの歌が採集され、なかには注釈つきの立派な歌集として出版された。また、バウルの歌を分析し、バウルの宗教を考察した専門書もいくつか出版された。もちろんこれらの研究は、バウルについてのわれわれの理解におおいに貢献したのであるが、そこには「人間としてのバウル」を専門的に紹介しようとした民族誌的文献は、事実上、皆無である。本研究は、バウルの民族誌的記述と分析を通じて、カースト制度と表裏の関係にある世捨ての制度を考察し、インド文明の構造的理解を試みようとするものである。

When the quench occurs in the superconducting coil, the excessive joule heating in the normal region may damage the coil. It is necessary to detect the quench in the coil as soon as possible and discharge the magnetic energy stored in the coil. We have presented a quench protection system based on the active power method which detects a quench regardless of the self-inductive and mutual-inductive voltage for multi-layer superconducting coils. In this paper, the usefulness of the developed system is confirmed for two-layer superconducting coils wound with Bi2Sr2Ca2Cu3Ox HTS tapes.

High temperature superconducting (HTS) motors electromagnetically consist of a rotator wound with HTS wires and an armature with conventional copper wires like Litz wire. The HTS rotor windings, as field coils, consist of a straight part and an end-ring part. Because a major rotation torque is induced by an interaction between magnetic fields and current-carrying conductors in the straight part, most of mechanical stresses in the motor occur at the straight part. An end-ring is placed in the edge of the straight part and used to connect to each adjacent straight-part coils. The magnetic fields by coil currents concentrate on the end-ring part, therefore, it is expected that the critical current of the entire coil, straight and end-ring, can be determined by the magnitude of the field in the end-ring. This paper deals with the overall Jc degradation in the end-ring part by self-field generated from the coil. In addition to electromagnetic analyses, we have performed a numerical analysis in order to evaluate mechanical stresses in the straight part of field coil by armature reaction on steady-state operation. The analytical results will be presented in this paper.

The stability and the protection of superconducting applications are very important issues. High temperature superconductor (HTS) is stable than low temperature superconductor (LTS). However, due to the high stability of HTS, HTS coils have complicate behaviors of normal transition – such as a recovery into the superconducting state or thermal runaway – which is determined by the magnitude of disturbance, coil size, the structure of winding wire and cooling condition. In this paper, we propose the quench protection system based on the active power method which can detect the quench by measuring the generating instantaneous active power in HTS coils. And the quench detection circuit adopted a software circuit by LabVIEW which was added a new quench protection technique to the circuit in order to improve its detection performance. Furthermore, it can monitor interior states of HTS coils with acquiring the only coil voltages in real time. To confirm the validity of the suggested technique, the experiments were performed with the hardware circuit for quench detection simultaneously. The experimental results are presented and discussed in this paper.

This paper presents the quench detection method with using normal transition behavior for HTS coil. If the HTS coil starts to propagate a normal zone by an initial quench, it will be recovered the superconducting state or runaway thermally. These behaviors were mainly determined by variety parameters like the magnitude of a disturbance, HTS coil size, the structure of winding wire and cooling condition. However, the first step of detection or protection for coils should be started from detecting the presence of a non-recovering normal zone. This paper classifies the initial quench behaviors of HTS wires or coils as a model of 3-type tendencies, and suggests suitable detection techniques for each tendency with using the end-to-end voltage of coil. In additional, this method is able to detect a quench without a decisive criterion used at other quench detection methods. In order to confirm the validity of the method, we used the HTS sample coil wound with YBCO tapes. This paper presents these results and the quench protection properties with fabricated detection method.

Recently, the superconducting devices using cryogenic and superconducting technologies were widespread in the field of electric power. The 2G wires with YBCO superconducting layer, metal substrate and stabilizer layer are expected to be used in future superconducting applications, because it has high Jc properties in high temperature and high magnetic fields. In order to operate safely at high transport currents, the thermal stability of the wounding wire should be addressed in terms of detection and protection against the quench. On the other hand, the understanding of the 3-dimensional normal zone expansion during a quench is very important to design the superconducting devices such as magnets and cables. This paper presents the results of an experimental study for normal zone propagation properties in the longitudinal and transverse directions using the pancake coil wound with 2G wires which have Cu and SUS stabilizers under the cryocooler cooling. And the minimum quench energy (MQE) of the pancake coils wound with two different kinds of stabilizers as functions of operating temperature and transport current will be described.

本研究は、インド・ベンガル地方の「バウル」とよばれる宗教的芸能集団の民族誌である。詩人タゴール(Rabindranath Tagore 1861-1941)が、20世紀初頭にバウルの歌の豊潤さを紹介して以来、それまで「奇妙な集団の風変わりな歌」とみなされていたバウルの歌が再評価されるようになった。タゴールの影響により、その後ベンガル人学者によって膨大な数のバウルの歌が採集され、なかには注釈つきの立派な歌集として出版された。また、バウルの歌を分析し、バウルの宗教を考察した専門書もいくつか出版された。もちろんこれらの研究は、バウルについてのわれわれの理解におおいに貢献したのであるが、そこには「人間としてのバウル」を専門的に紹介しようとした民族誌的文献は、事実上、皆無である。本研究は、バウルの民族誌的記述と分析を通じて、カースト制度と表裏の関係にある世捨ての制度を考察し、インド文明の構造的理解を試みようとするものである。

To understand the effects of the hot pressing on the pinning behavior for the SiC doped MgB2 tape wire, magnetic field and temperature dependences on a critical current density Jc and the pinning force have been studied. The MgB2 tapes were fabricated using an in situ powder-in-tube (PIT) method, the hot pressing process with nano-SiC powders and the carbon steel sheath. Jc of the hot pressing processed wire is enhanced especially at low field compared with that of the no hot-pressed wire. It is suggested that the enhancement of Jc is caused by the improvement of the MgB2 grain connectivity came from the hot pressing. The pinning analysis using the pinning models of a surface pinning and a normal point pinning lead to that the scaled curve of the pinning force for the SiC-doped MgB2 tape with the hot pressing process showed anisotropy in a lower field. This result suggests that the pinning center of the hot pressing processed MgB2 wire forms into inequi-axial shape, which is different from that in the tape without the hot pressing having the equi-axial pinning center in our previous report. It was also found that the scaled pinning force of the SiC-doped MgB2 tape with the hot pressing is larger than the surface pinning model in a higher field. This suggests that the pinning force was enhanced by the hot pressing in a higher field.

Recently, the superconducting devices using cryogenic and superconducting technologies were widespread in the field of electric powers. The quench protection is one of the important issues for safety operating of the superconducting devices, because the excessive joule heating brings about damage to the superconducting magnets when the quench occurs. However, if the HTS coil starts to transit normally by an initial quench, it will be recovered into the superconducting state or runaway thermally. These behaviors were mainly determined by the magnitude of a disturbance, HTS coil size, the structure of winding wire and cooling condition. Therefore, in order to detect the transition into the normal state at HTS coil more accurately, it needs to investigate these effects as parameters. This paper describes the electromagnetic and thermal behaviors of HTS during normal transition by the initial quench. The aim is the development of the quench detection method about HTS coil for 5 MW HTS motor after an initial quench. It adopted the hardware and the software that were able to estimate the quench by monitoring the voltage and temperature for the behavior between the thermal runaway and the recovery. This paper will be presented these results and the quench protection properties with fabricated detection method.

The magnetic chromatography (MC) is a very useful system for an ion and/or fine magnetic particle separation due to its strong magnetic field gradients in a very small flow channel. We have not only developed the MC system to separate the fine particles and ions, we have also developed the numerical analysis computer code based on the fluid dynamics and electromagnetism to investigate the separating characteristics and to optimize design of magnetic column. In this paper, we studied MC technology for magnetic particles and ion separations using micro-scale magnetic column with ferromagnetic wires experimentally. The influences of the strength of magnetic gradient, flow velocity and coefficient of viscosity of solvent were studied by the developed computer code.

The minimum quench energy (MQE) and normal zone propagation velocity (NZPV) of three kinds of Nb3Al superconductors fabricated by the rapid heating, quenching and transformation (RHQT) process were measured under various conditions of applied magnetic field (10-14 T), temperature (7-11 K), and transport current (80-95% of the critical current), while cooled by a cryocooler for developing the over 20-T class cryogen-free magnet. As a result, MQE values were related to the critical current density (J c); high MQE was obtained for low J c. It is assumed that J c has a stronger influence on the MQE than specific heat, thermal conductivity, resistivity, and other parameters of the composite superconductor including the matrix and the stabilizer. NZPV was mainly proportional to the transport current density varying with applied field and temperature. The second contribution to NZPV is assumed to be heat capacity depending on the wire configuration.

本研究は、インド・ベンガル地方の「バウル」とよばれる宗教的芸能集団の民族誌である。詩人タゴール(Rabindranath Tagore 1861-1941)が、20世紀初頭にバウルの歌の豊潤さを紹介して以来、それまで「奇妙な集団の風変わりな歌」とみなされていたバウルの歌が再評価されるようになった。タゴールの影響により、その後ベンガル人学者によって膨大な数のバウルの歌が採集され、なかには注釈つきの立派な歌集として出版された。また、バウルの歌を分析し、バウルの宗教を考察した専門書もいくつか出版された。もちろんこれらの研究は、バウルについてのわれわれの理解におおいに貢献したのであるが、そこには「人間としてのバウル」を専門的に紹介しようとした民族誌的文献は、事実上、皆無である。本研究は、バウルの民族誌的記述と分析を通じて、カースト制度と表裏の関係にある世捨ての制度を考察し、インド文明の構造的理解を試みようとするものである。

The resistive type fault current limiter based on YBCO thin film with high critical current density was proposed and developed because of its fast recovery characteristics. We have been developing a magnetic field measurement system with hall sensor to study the critical current density distribution or magnetic properties of high-Tc superconductors such as thin film, tape conductor and coated conductors. In this study, the transport current distribution in straight line and U-corner region of meander type resistive fault current limiter using YBCO thin film was investigated experimentally. The both axial and radial self-magnetic field components according to the direct (DC) and alternating (AC) transport currents were measured by two-axis hall probe to estimate the current distribution. And also, the self-magnetic field at the corner of bispiral type fault current limiter was measured by two-axis hall probe with a high spatial resolution to compare with the meander type fault current limiter.

In an attempt to understand the effects of SiC addition on the pinning behavior for the in-situ PIT MgB2 tape wire, field and temperature dependencies on critical current density, Jc and the pinning force were studied by considering applied magnetic field direction for the rectangular-shaped wire. As a result, it was clarified that the SiC-doped wire has the equiaxial pinning center and the un-doped wire has the inequi-axial pining center. Taking the pinning scaling law into account, it is found that the SiC-doped MgB2 wire has two kinds of the pinning center and the dominant pinning center changes with temperature, that is, the pinning centers are the grain boundary and the precipitates at high and low temperatures, respectively. The un-doped MgB2 wire is assumed to have anisotropy of the pinning mechanism.

本研究は、インド・ベンガル地方の「バウル」とよばれる宗教的芸能集団の民族誌である。詩人タゴール(Rabindranath Tagore 1861-1941)が、20世紀初頭にバウルの歌の豊潤さを紹介して以来、それまで「奇妙な集団の風がわりな歌」とみなされていたバウルの歌が再評価されるようになった。タゴールの影響により、その後ベンガル人学者によって膨大な数のバウルの歌が採集され、なかには注釈つきの歌集として出版された。また、バウルの歌を分析し、バウルの宗教を考察した専門書もいくつか出版された。もちろんこれらの研究は、バウルについてのわれわれの理解におおいに貢献したのであるが、そこには「人間としてのバウル」を専門的に紹介しようとした民族誌的文献は、事実上、皆無である。本研究は、バウルの民族誌的記述と分析を通じて、カースト制度と表裏の関係にある世捨ての制度を考察し、インド文明の構造的理解を試みようとするものである。

When the quenching occurs in a superconducting coil, excessive joule heating in normal area may damage the coil. It is necessary to detect quenching in the coil as soon as possible and discharge the magnetic energy stored in the coil. Therefore, we propose a superconducting coil protection system based on an active power method. The system is highly resistant to the noise and does not require cancel voltage taps, so it is useful for both AC and DC coils. We have presented the effectiveness of the system using some test coils cooled in LN 2 or LHe. However, we have not discussed the effectiveness of the proposed system for helium-free cryocooled magnets, in which a larger temperature rise occurs after quenching than in liquid-cooled magnets. In this paper, we verify the effectiveness and practicality of the proposed system through coil protection tests for a cryocooled Nb 3 Al LTS coil.

We have been developing a 3D superconducting actuator with HTS (high temperature superconducting) bulk and two-dimensionally arranged multiple electromagnets. The application of HTS bulk enables stable levitation and suspension due to its strong pinning force. The performance of the actuator is determined mainly by the spatial distribution of the generated magnetic field of the electromagnets. For the sake of improving the levitation force, we proposed to attach a sliced iron sheet (we called this cap core) on the top surface of the core in each electromagnet. The proposed cap core was expected to lead to an intensive concentration and abrupt gradient increase of the perpendicular component in the magnetic field through the HTS bulk of the electromagnets. We experimentally confirmed and measured the effect of the cap core. For the optimized design of the cap core, we calculated the spatial distribution of the magnetic field on the surface of the electromagnet using 3D FEM analysis for several cap cores and estimated the levitation force of the HTS bulk using the calculated result.

The magnetic chromatograph (MC) system is one of the promising methods for ion separation because of its strong magnetic field gradients. We have been developing the MC system to separate the fine particles and ions, and have also developed the numerical analysis computer code based on fluid dynamics and electromagnetism to investigate the separating characteristics and optimization of MC system. We investigated MC technology for magnetic particles separation using superconducting magnet and micro-scale magnetic column with ferromagnetic wires experimentally. A channel height of magnetic column for ion separation was optimized by the developed computer code.

Recently, HTS coils have been developed for electric power apparatuses. In superconducting coils, local and excessive joule heating may give damage to the superconducting windings when a quench occurs and therefore it is essential that the quench is detected quickly and precisely so that the coils can be safely discharged. Resistive voltage measurement method is universally used for the quench detection, however, it is vulnerable to an electromagnetic noise which causes insufficient quench detection and at least needs a central voltage tap in windings. In a large superconducting coil, a lead-wire from the central voltage tap may cause a short-circuit when high voltage will be applied. In this paper, we present a quench protection system based on the active power method which detects a quench by measuring the instantaneous active power generated in a superconducting coil. The protection system based on this method is very strong against to the noise and no more needs a central voltage tap. The performance of system developed by us is confirmed by using test coil wound with Bi-2223 HTS tapes.

The new in situ MgB 2 tapes with/without SiC addition and the hot pressing process have been fabricated using the carbon steel sheath. The critical temperature ( T c ), critical current density ( J c ) and the AC transport current loss of those tapes have been studied and discussed in various conditions. The MgB 2 tapes with the carbon steel sheath that improved the core hardness and homogeneity, resulting in high J c , and the SiC addition, and the hot pressing brought narrow T c transition width. As the carbon steel has ferromagnetism, it affected the loss of the MgB 2 tape. The large losses that were two to three orders of magnitude higher than Norris’ theoretical curve were obtained. It was clarified that the main loss of the MgB 2 tape was the hysteresis loss of the carbon steel sheath.

We have been developing a three-dimensional (3-D) superconducting actuator with HTS bulk and electromagnets. Proposed 3-D superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. To realize the 3-D superconducting actuator with high performance, we have to investigate the shape-dependences of electromagnets and HTS bulk on levitating characteristics. In this study, we fabricated the individually controlled eight-polarities electromagnets and the two kinds of bolted joints cap cores to improve the control ability and levitation characteristics. And also, we prepared the disk-shaped and ring-shaped (with 20 mm inner diameter) HTS bulk with 60 mm diameter, and evaluated how magnetic field distribution influences the levitating characteristics as functions of levitation force and height.

We have been investigating a three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and move in free space. Proposed superconducting actuator consists of the stator constructed by two-dimensional arranged electromagnets and HTS bulk superconductor as a mover. The 2-D arranged electromagnets were individually controlled to move the HTS bulk. It is expected that our proposed 3-D superconducting actuator will be useful as a transporter used in clean rooms where silicon wafers are manufactured. Wafers must be protected from contact with dust and other contamination. To realize the superconducting actuator with HTS bulks, the electromagnetic characteristics of HTS bulk, such as trapped field strength and patterns, should be clarified and the optimized controlling system is also required. Therefore, in this study, to construct the optimal 3-D actuator system, the fundamental characteristics of the levitation for HTS bulks with individually controlled four and eight-polarities electromagnets were investigated experimentally. And two kinds of cap cores attached the top of the core to improve the control ability of proposed actuator were fabricated and tested.

Pre-bending effects of Nb3Sn composite wires, enhancement in Jc at the as-cooled condition and Jc peak, Jcm, against applied tensile strain, are well known in especially Cu-Nb reinforced Cu stabilized Nb3Sn wire. In an attempt to understand the effects, three directional strain analyses using FEM were studied by considering thermally-induced residual strain due to temperature difference between the reaction temperature and the cryogenic temperatures including the pre-bending process at room temperature for three types of Nb3Sn composite wires. To evaluate effects of change in three directional strain, the von Mises strain was introduced. As a result, the minimum von Mises strain against the applied tensile strain corresponded to Jcm; low strain shows Jcm enhancement by the pre-bending for Cu-Nb reinforced Nb3Sn wire. It was found that there is a direct correlation between the minimum von Mises strain and Jcm related to the pre-bending.

Many high-Tc superconducting (HTS) tape manufactures make an effort to improve the transport characteristics of HTS tapes. When AC or DC current flows in the HTS tape, AC or DC magnetic self-fields are induced around the conductor by the current and these self-fields affect on the AC loss and the critical current like the transport characteristics of HTS tapes. The spatial distribution and magnitude of the self-field are variable due to the neighboring materials on the HTS tape. In this paper, the relation between the transport characteristics and the self-field distribution of HTS tapes with paralleled ferromagnetic material (Ni tape) and/or diamagnetic material (BSCCO tape) is experimentally investigated. The self-fields according to the DC and AC transport currents were measured by hall probe with axial and radial magnetic field components. The critical currents of HTS tapes with paralleled the Ni tape are slightly decreased and the transport current losses markedly increased. However, the critical currents and transport current losses of HTS tapes with paralleled BSCCO tape showed more improved performance than those of single HTS tape. We explain these results using the change of the spatial distribution and magnitude of self-field on HTS tapes by the neighboring magnetic materials.

We have been developing a magnetic field measurement system with two-axis hall-probes to study the critical current density distribution or magnetic properties of high- T c superconductors. In this study, the current distributions at corners of the meander type resistive fault current limiters were measured by hall probe with high spatial resolution. The both of axial and radial magnetic field components ( B x and B z ) according to the direct (DC) and alternating (AC) transport currents were measured by hall probe to estimate the current density distribution with high accuracy. And, it is confirmed that the measured radial components are very useful to estimate the current distribution.

Reducing AC loss in a superconducting apparatus is one of the most important issues, and the precise measurement and estimation of AC losses are essential to reduce them. The four-terminal method is universally used as an electric measurement method of AC losses for superconducting tapes and wires. In this method, noise and inductive voltage superposed on the terminal voltage of the superconductor are eliminated by a lock-in amplifier and cancel coil, respectively, and then measurement of very small resistive voltage is achieved. However, using this conventional method, a plurality of measuring instruments and apparatuses are needed, and therefore the measuring system becomes complicated and much time is consumed in the calibration process. In this paper, we present a simple and precise measurement system based on an active power detection method, which is proposed as a quench detection method. The proposed system consists of a small number of instruments and apparatus and is less susceptible to noise. Its usefulness is verified by comparing the proposed method and the conventional four-terminal method in measuring the AC transport current loss of a Bi2223/Ag tape.

AC transport current loss (self field loss) of ex-situ-processed MgB2 superconducting tapes with Ni sheath was measured under different conditions of transport current value, transport current frequency, and temperature. Experimental results were compared with Norris' theoretical curves and previous measured losses of MgB2 tapes with CuNi and stainless-steel sheaths, which were larger than the theoretical ones and previous data. The loss vs. normalized transport current (transport current normalized by critical current) curves varied with temperature and the loss at 9 K was larger than that at 14 K. The measured loss approached Norris' curves in the high normalized transport current region. In order to gain insight into these origins, FEM analysis of magnetic flux concentration by Ni and estimations of hysteresis loss of ferromagnetic nickel-sheath and of homogeneity of the core were carried out. As a result, the hysteresis loss of Ni was very small based on the estimation and the loss measurement of Ni. Main contributions to large loss are considered to be self-field enhancement due to magnetic flux concentration by the Ni-sheath and critical current density distribution of the MgB2 core caused by the inhomogeneity of critical current density and critical temperature

A superconducting actuator with multiple motions is proposed and experimentally investigated for the development of microelectrical machines. The disk-shaped YBCO bulk was located above the electromagnets and cooled down in the field-cooling method, which enabled the flux pinning. The YBCO bulk superconductor was driven in vertical, horizontal and/or self-rotation by PC-controlled coil currents using multiple electromagnets. The most suitable levitation stability was obtained when we used four electromagnets and NNSS trapped field type. It was confirmed that the levitation force and horizontal moving force strongly depended on the coil current and the air gap length, respectively.

The critical current density, Jc, of metal-organic deposition process using trifluoroacetates (TFA-MOD) based YBCO films was measured between 20 K and 77 K in magnetic fields up to 9.5 T as a function of the field direction. C-axis oriented YBCO films was deposited on LaAlO/sub 3/ single crystalline substrates and also on CeO/sub 2/ buffered IBAD (YSZ/Hastelloy) substrates by TFA-MOD method. The obtained Jc values at 77 K and 0 T were 7 and 1.7 MA/cm/sup 2/ for LaAlO/sub 3/ and IBAD substrates, respectively. High Jc values over 10/sup 5/ A/cm/sup 2/ were maintained up to 4 T (B//c-axis) for the LaAlO/sub 3/ substrate and up to 3 T (B//c-axis) for the CeO/sub 2/ buffered IBAD substrate. These results imply that TFA-MOD with simple fabrication process is very promising for the practical YBCO coated conductor. And the dependences on temperature and angular of the Jc at various external magnetic fields for some different thicknesses YBCO films was reported.

Composite superconductors such as Cu/Nb/sub 3/Sn and Ag/Bi-oxides are subjected to thermally-induced residual strain by other component materials due to the around 1,000 K temperature difference between the reaction temperature and the cryogenic temperatures, and to applied tensile strain by the hoop stress of longitudinal (z) direction during the coil operation. To clarify especially the radial (r) and tangential (/spl theta/) strain behaviors including z-strain, we analyzed elastic-plastically multi-core model by computing of FEM for various composite conductors. As a result, applied tensile stress on the z-direction of the composite conductor gave monotonous decrease of thermally-induced rand /spl theta/-strains, which changed tensile to compressive strain. With increase in the z-strain effective strain showed the minimum value, not zero, at around z-strain-free state. Moreover it was found that all conductors are classified into three types by combination of component materials.

Composite superconductors like Cu/Nb/sub 3/Sn and Ag/Bi-oxides are subjected to thermally-induced residual strain by other component materials due to the around 1000 K temperature difference between the high temperatures where the superconductor is formed and the cryogenic temperatures where they are operated. To clarify especially the radial (r) and (/spl theta/) tangential strain behaviors, we analyzed elastic-plastically two models, the concentric core model (single-core model) and multi-core model and used two analysis methods, calculation of the force balance equation for the former model and computing of FEM for the former and the latter models. Strains in r and /spl theta/ directions varied with combination of component materials having large and small thermal expansion coefficients; the superconductor sandwiched by high thermal expansion materials is subjected to larger tensile r-strain and larger compressive /spl theta/-strain, as compared with superconducting core only embedded in the matrix. Furthermore it was found that there was a strain distribution by the core location at the inner or the outer. Finally, a better combination of the superconductor with other materials was obtained.

The purpose of this study is to characterize the time course of N-isopropyl-p-[123I]-iodoamphetamine (123I-IMP) uptake of primary central nervous system lymphomas (PCNSL) comparing with those of other common brain tumors such as malignant gliomas and meningioma.

The measurement and analysis of AC transport current loss (self-field loss) in MgB2 superconducting composites were studied. In experimental results, the normalized Ic dependency of AC loss in the MgB2 deviated from Norris' theoretical curve. Then a numerical analysis was performed by taking into consideration the model of a round superconducting wire that consisted of three concentric layers. The analysis clearly showed the experimentally obtained results, such as that the phenomenon originated in the inhomogeneity of the critical current density in the wire rod section.

Several types of reinforced Nb 3 Sn wires have been developed to prevent reduction of superconducting properties by applying a strong electromagnetic force. To fabricate a cryocooled magnet using those reinforced wires, we experimentally measured the minimum quench energy (MQE) under cryocooled conditions of some reinforced Nb 3 Sn wires. As a result, it became clear that thermal stability expressed as MQE was controlled by the temperature margin between the temperature of the operating condition and the transition temperature from superconductivity to normal. Using the FEM analysis, it was realized that the cause of the decline in thermal stability for the reinforced wires was the low thermal conductivity of the reinforced materials.

Quench properties of Bi/sub 2/Sr/sub 2/CaCu/sub 2/O/sub 8//AgMg tape were experimentally investigated under a cryocooled condition in high magnetic fields. The critical current (I/sub c/), quench current (I/sub q/), and minimum quench energy (MQE) were measured at various initial temperatures of 4.2 K, 10 K, and 20 K and at magnetic fields of 7 T and 9 T. MQE was the minimum disturbance energy enough to make thermal quench and was evaluated from the input energy by a resistive heater. It was found that MQE exhibited the minimum value around 20 K. The temperature margin, difference between the initial temperature and the thermal runaway temperature, decreased monotonously with increase at the operating temperature. Since the temperature dependence of MQE did not agree with that of temperature margin, we focused on the internal energy calculated by integrating specific heat of the sample. The temperature dependence of the internal energy was in agreement with that of MQE qualitatively.