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In general, the critical current of a Bi-2223 tape-stacked-cable is much less than the total summation of critical currents of each tape, which is mainly due to the self magnetic fields of the cable itself. Therefore, to predict the critical current of a Bi-2223 tape-stacked-cable, we need to analyze the self field effects of the stacked cable as well as the critical current density data (J/sub c/) of one tape. To make it more complex, the critical current degradation of a Bi-2223 tape is anisotropic; the critical current is lower in the normal magnetic field (to the tape surface) than in the parallel field. In this paper, a novel approach to predict the critical current of a Bi-2223 tape-stacked-cable from a J/sub c/-B curve of one tape is presented. The approach basically includes the load line analysis of the stacked tapes, and its usefulness is confirmed by the experimental data.

High T/sub c/ superconductors, such as Bi-2223, have been promising candidates for an electrical busbar because the busbar has a relatively low self magnetic field. It has been found that the critical current of Bi-2223 stacked tapes is much less than the total summation of critical currents of each tape, which is mainly attributed to the self magnetic fields. Furthermore, since the critical current degradation of Bi-2223 tape is greater in the normal magnetic field (to the tape surface) than in the parallel one, detailed magnetic field configurations are required to reduce the self-field effects. Conceptually, by rearranging each stacked tape properly, the self field effects could be minimized. In this paper, we calculate the self field effects of a stacked conductor, defining self field factors of normal and parallel magnetic fields to the tape surface. We propose an optimum shape of octagonal structured busbar which has minimum self field effects.

It is needed several large reservoirs and long operating time in order to remove suspended solid (SS) like steel fines and iron oxide at steel making factory. If removing rate of SS in coolant of hot rolling process can be increased, the productivity of working process can be increased and the area of reservoir can be reduced. We investigated the formation ability of magnetic flock which mixed with inorganic materials and polymer coagulants. Iron hydroxide and electrolytic dissociation were used for pretreatment. We assembled reciprocal superconducting HGMS system that had a purpose to remove SS of coolant at steel factory. The wire of filter was used stainless steel 420. Maximum coagulation formation rate of SS was 98%. Removing ratio of Fe3O4 fine particles in artificial wastewater showed over than 99% after four times of repetition of magnetic separation.

Superconductivity research in Korea started in 1984, and the number of research groups engaged in high-Tc superconductor has greatly increased since 1986. Although superconductivity research has a short history, many attempts have been made to develop low-Tc superconducting machines and high-Tc superconducting devices. KERI has developed fabrication technology for superconducting wires and magnets since 1992. Accordingly, an active shielding-type MRI superconducting magnet was fabricated at 1996 and through collaboration with industry, KERI has attempted to produce 24 NbTi filament superconducting wires since 1992. EESRI and KEPCO developed a 0.5MJ SMES system and successfully conducted an energy transfer test between two NbTi coils in 1993. A superconducting current limiter has been under research at Yonse University since 1993. They manufactured a 220V/100A class superconducting current limiter in 1995 and have investigated applicability to power systems. On the other hand, the High-Temperature Superconductivity Research Association (HiTeSRA) was organized to promote the research of high-temperature superconductivity, and has taken the lead in the research activities for high-temperature superconductivity. KRISS and LG Electronics developed a directly coupled SQUID with single-layer YBCO thin film and successfully demonstrated MCG measurement using high-Tc SQUID magnetometers in 1996. ETRI has developed microwave superconducting coupled-line bandpass filters using YBCO thin film fabricated by laser ablation. Since 1995, a project for the development of a superconducting nuclear fusion device has been in progress. Such developments have led Korea to enter a new phase in the research of applied superconductivity.

The influence of preparation conditions on the V - I characteristics of silver-sheathed Bi-2223 tapes made by the powder-in-tube method has been investigated in detail. A variation in oxide layer thickness appeared periodically along the lengthwise direction of the tape and became more prominent for the more heavily cold-worked tape. This phenomenon is called the sausaging effect, and it was assessed quantitatively by determining two parameters; the coefficient of variation (COV) and the correlation period ( z 1 ). The n value was found to relate definitely to both COV and z 1 . A larger COV value resulted in a smaller n value. Strong sausaging caused a significant underestimation of the critical current density.

The characteristic microstructure which develops during the preparation of silver sheathed Bi2223 tapes by the powder-in-tube method is explained. The critical current density (Jc) increases with decreasing tape thickness. During reduction of the thickness, densification and texturing of the microstructure takes place. However, due to the heavy reduction, the degree of variation of oxide layer thickness becomes abruptly large, while Jc degrades. This phenomenon is called work instability. A correction of Jc that eliminates the influence of work instability has been successfully carried out from a statistical viewpoint.

The phase relation and the microstructural features in Bi-Pb-Sr-Ca-Cu-O superconducting ceramics have been investigated. Various samples were prepared by sintering at temperatures between 1073 and 1223 K for a long time and quenching into liquid nitrogen. The phases existing at those temperatures have been identified by means of XRD and EPMA. The 2223 phase was found to be formed by the reaction of the 2212 phase with the liquid, which is produced eutectically from the 2201 phase and Ca2PbO4. It was confirmed that the volume fraction of the 2223 phase became largest in the sample sintered at 1128 K, with small amounts of impurity phases CuO, (Sr,Ca)2CuO3 and (Sr,Ca)3Cu5Ox. The amounts of (Sr,Ca)2CuO3 and (Sr,Ca)CuOx phases increased during the decomposition of the 2223 phase at temperatures above 1133 K. The (Sr,Ca)Ox compound was identified as a new phase for the sample sintered at temperatures higher than 1223 K.

The silver-sheath technique is most powerful for preparing the high Tc superconducting tapes. It comprises a serial step of handlings. A general feature of this process is firstly introduced. The recent developments of Y123, Y124, Bi2212, Bi2223 and T1 oxide tapes have been reviewed. Problems which should be solved for the present technique and a future scope are discussed. Fundamental investigations are emphasized to be still very important in this scientific field.

The critical current density of Ag-sheathed Bi-Pb-Sr-Ca-Cu-O tapes was significantly improved by thermomechanical treatment. After the Ag tube filled with oxide powder was reduced in diameter by swaging, the wire was pressed and heat treated at different temperatures above 830 degrees C. The pressing and heat treatment processes were repeated. High densification and a high laminated structure have been achieved, where the c axis of elongated grains is almost parallel to the surface normal and both 2223 and 2212 phases coexist. At present the best value of the transport critical current densities obtained at 4.2 K was 2.5*105 A cm-2 at zero field and 5.3*104 A cm-2 at 10 T. For this specimen, hysteresis was still observed in the plot of magnetic field against Jc.

The superconducting and magnetic properties of YNi(2)B(2)C single crystal have been investigated by heat capacity and dc-magnetic methods, with magnetic field applied parallel to the c-axis, i.e., H\\ (0 0 1)-direction. In the framework of heat capacity and magnetization analyses, we obtain the thermodynamic critical field H(c) from both heat capacity and magnetization data. The heat capacity data deviate from predictions for both weak- and strong-coupling superconductivity, but are described relatively well in a medium-coupling analysis. The precise t(3)-dependence of the electronic heat capacity C(es) indicates the gap anisotropy with the presence of point nodes for YNi(2)B(2)C single crystal. (C) 2003

A simple model for estimating the hysteresis energy loss of coated conductors under a general load line was studied. We took advantage of the characteristic line Ib(Ha) to determine the major parameters used in this model. The value of Ib(Ha) was based on the scanning Hall probe measurements (SHP) on a Sm1Ba2Cu3O7 − δ coated conductor. During SHP measurement, a magnetic field (Ha) and current (Ia) were applied simultaneously and were varied along 11 different load lines. From the values of SHP measurements, the current density profiles, J(x, Ha, Ia), were calculated using a numerical inversion method. We define the quantity Ib = ∫ − ww|J(x, Ha, Ia)| dx and we calculated Ib at many points (Ha, Ia) in every load line. We found that when Ia is less than Ib and the flux trap regions are absent, the values of Ib for all points (Ha, Ia) constitute a single line Ib(Ha), which can be easily extrapolated to a high field. This line provided a major parameter for our model.

Silver sheathed Bi2223 tapes were prepared by the powder in tube method. In order to get high critical current density (J c ), the microstructure was controlled through a serial step of handlings. Especially, the addition of other elements, the influence of load for pressing and the degree of reduction of size were in detail investigated. High critical current densities have been achieved relating to the improvement of microstructure by addition of another element, densification, formation of well-textures structure and minimization of work instability.

In this paper, AC losses of Bi-2223 tapes with different matrix of superconducting core were measured and analyzed. The two samples produced by a powder-in-tube method are multi-filamentary tape with Ag and AgAu matrix. The measurement was carried out under the environment of constant transport current and applied time-varying magnetic field. From experiment, losses for fields applied parallel to the c-axis of the textured Bi-2223 grains are larger by over an order of magnitude than those applied perpendicular. And it is confirmed that conductor losses with Ag matrix are larger than those with AgAu matrix.

The hysteresis loss in a Sm1Ba2Cu3O7−δ coated conductor was estimated from magnetic field profiles measured by the scanning Hall probe method. Current, Ia, and magnetic field, Ba, were applied simultaneously; Ba was applied in the normal direction with respect to the tape surface. Ba and Ia were varied from Bpeak to −Bpeak and from Ipeak to −Ipeak, respectively, with the ratio α = Ia/Ba fixed during the variation. Three values of α were taken for the three load lines. The values of Bpeak/Ipeak were varied from 0 mT/0 A to 10.7 mT/116 A, 99.1 mT/50 A, and 298.2 mT/46.1 A, respectively, for the three load lines. From the measured values of magnetic field profiles, the current profiles were calculated by the iterative inversion method. From the current profiles, the flux density profiles and the hysteresis loss, Q, were then calculated for various values of Ipeak(= αBpeak) in each load line. The results were compared with theoretical calculations based on Brandt's model. When Bpeak was about 300 mT, the estimated values of Q were several times smaller than the theoretical values of Q with the self-field Ic0. The low value of Q in this case is due to the field dependent Ic and the saturation effect of the current profiles, which results in significant reduction of the induced magnetic moment, M.

In order to investigate more specifically about the microstructure change due to the difference of nominal composition in Bi-Pb-Sr-Ca-Cu-O system and its influences on critical transport current density ( Jc ), we prepared various Ag sheathed tapes by changing the parameter,y in the nominal composition of 1.8 (or 1.6): 0.4: (1.6−0.1y): (2+0.04y). (2.8+0.0.6y) for Bi:Pb:Sr:Ca:Cu. Jc showed maximum at the composition parameter, y = 0 and decreased with increasing amount of Sr or Ca and Cu. By XRD analysis and SEM observation, it was found that Jc depends sensitively on the amount of impurity phases such as (Sr,Ca)3Cu50x, 11905 phase(2.4 nm with c-axis) and the volume fraction of 2223 phase.

We calculated the current distribution in a coated conductor (CC) from magnetic induction profiles measured using the scanning Hall probe method. An external magnetic field was applied in the normal direction with respect to the tape surface and was decreased stepwise from Hpeak to −Hpeak. From the hysteretic behavior of the current distributions, the energy loss, QM, was calculated for various values of Hpeak. Comparison of the present results with Brandt's theoretical calculations revealed that his formula is still valid if one substitutes the magnetic field dependent critical current density into his equation. The theoretical results obtained were consistent with the experimental QM values obtained.

The effects of unilateral sciatic neurectomy on gastrocnemius muscle were studied in adult male rats. The morphological changes of both gastrocnemius muscles were observed by light and electron microscopy. Western blot analysis was performed to study the protein expression. Following the denervation, the affected muscle weights decreased significantly than normal. And the denervation led to a significant reduction in the area and diameter of muscle fibers on light microscopy. The affected muscle fibers showed the decreasing in size and the irregularity of myofibrilar arrangement on electron microscopy. On transverse view, the area of affected muscle fiber were smaller than normal. Their myofibrils were smaller and very irregular in size. The thin and thick myofilaments were not regular and partially lost. Mitochondria between myofibrils and subsarcolemmal area in affected muscle fibers were damaged and partially lost. The sacoplasmic reticulum and T-tubules were mostly lost and irregular. Some satellite cells were observed adjacent the muscle fiber, but they were inactive morphologically. On longitudinal view, most of myofibrils in affected muscle fibers were lost generally or partially although the their most sarcomeres were regularly arranged. Z line and myofilaments were lost partially and were partially irregularly arranged. The loss of thin myofilaments was more than that of thick myofilaments. Much debris of cell organelles were scattered among myofibrils. The expression of MyoD and myogenin were decrease significantly and the expression of p-mTOR and p-FOXO1 were decreased, too. On the other hand, MuRF1 was increased significantly. Taken together, the main effect of gastrocnemius muscle by sciatic neurectomy is the atrophy as a result of the loss of myofilaments and cell organelles through the decrease of protein synthesis and the increase of protein degradation.

In order to improve the critical current density (Jc) of Ag-sheathed B(Pb)SCCO tapes, various thermomechanical treatments were applied. The combination of swaging and pressing was most effective at present for obtaining the high critical current densities. Repeating TMT cycle, the densed and preferred oriented granular structure was obtained. This caused Jc to increase, especially the Jc under magnetic fields at 4.2 K.

Ag sheathed BPSCCO superconducting tapes doped with SnO2, BaCO3 and MgO were prepared by ”powder-in-tube method”. Relation between microstructure change and critical current density has been investigated. Improvement of critical current density for MgO and BaCO3 doped tapes was observed, where fine MgO particles distributed in oxide matrix and dense textured structure were observed, respectively.