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CD8+T cells with stem cell-like properties (TSCM) sustain adaptive immunity to intracellular pathogens and tumors. However, the developmental origins and chromatin regulatory factors (CRFs) that establish their differentiation are unclear. Using an RNA interference screen of all CRFs we discovered the histone methylase Mll1 was required during T cell receptor (TCR) stimulation for development of a TSCMprecursor state and mature memory (TMEM) cells, but not short-lived or transitory effector cell-like states, in response to viral infections and tumors. Mll1 was essential for widespreadde novodeposition of histone H3 lysine 4 trimethylation (H3K4me3) upon TCR stimulation, which accounted for 70% of all activation-induced sites in mature TMEMcells. Mll1 promoted both H3K4me3 deposition and reduced TCR-induced Pol II pausing at genes whose single-cell transcriptional dynamics explained trajectories into nascent TSCMprecursor states during viral infection. Our results suggest Mll1-dependent control of Pol II elongation and H3K4me3 establishes and maintains differentiation of CD8+TSCMcell states.

Introduction The utility of evaluating a sagittal view of CT of the spine is well-known. In many clinical cases, the sagittal view includes noise generated from surrounding objects and may degrade the image quality. Iterative reconstruction (IR) techniques are useful for noise reduction; however, they can reduce spatial resolution. The aim of this study was to evaluate the effectiveness of the adaptive statistical iterative reconstruction (ASiR) for generating sagittal CT images of the spine when compared to filtered back projection (FBP). Methods The image quality of clinical images from 25 patients were subjectively assessed. Three radiologists rated spatial resolution, image noise, and overall image quality using a five-point scale. For objective assessment, z-direction modulation transfer function (z-MTF) was measured using a custom-made phantom. Additionally, z-axis noise power spectrum (z-NPS) was measured using a water phantom. An improved adaptive statistical iterative reconstruction algorithm called ASiR-V was used in this study. Blending levels were 50%, and 100% (ASiR-V50, ASiR-V100, respectively). Results For subjective assessments, images using ASiR-V100 were determined to have the best overall image quality, despite having received the worst score in the assessment of spatial resolution. For objective assessments, the image using ASiR-V50 and ASiR-V100 curves were slightly degraded in terms of low contrast z-MTF when compared to FBP. Conclusion ASiR-V was effective to improve the image quality when compared with FBP when reviewing sagittal reformats of the spine. Implications for practice This study suggests that high resolution is not the only thing that is key when reviewing sagittal CT spinal reformats. Such images should be provided as part of routine CT spine protocols, where available.

Non-invasive range measurement of particle beams is important to prevent deviation of the irradiated area in particle therapy. In this study, we made an experiment of imaging carbon-ion beams by setting the projection ranges into an acrylic target from 4.29 cm to 7.65 cm by a pitch of 0.21 cm. Secondary electron bremsstrahlung (SEB) generated on the beam trajectories were detected for the imaging by use of a pinhole camera system consisting of a pinhole collimator and a position-sensitive cadmium-telluride semiconductor detector (CdTe imager). Beam images were acquired, and their profiles along the longitudinal axis were numerically analyzed, to obtain a suitable parameter that was strongly correlated with the set range. Then we could propose a scheme to measure the particle beam range in the target during irradiation by use of the CdTe imager. As a result, the range shift can be measured in the case of the acrylic target with an accuracy of 0.1 cm.

In proton therapy, range verification is important to monitor the location of the Bragg peak within the patient’s body. Secondary-electron-bremsstrahlung (SEB) imaging is a promising method of proton range verification. Unfortunately, the SEB images measured by the dedicated gamma camera contain neutron-induced backgrounds as well as the SEB counts. To improve the accuracy of range verification in SEB imaging, we propose to apply a time-of-flight (TOF) method to reduce neutron background in measured images of SEB. The SEB and neutron generation and transport were calculated by a Monte Carlo simulation. Proton pencil beams were irradiated to a water phantom and then the time spectra and profiles of SEB and neutron were obtained by scoring on a detector. The total count of neutrons was approximately 10 times higher than that of SEB and increased with higher proton energy. The TOF method, selecting a time window for the TOF spectrum of SEB, reduced the neutron background by more than 97%. We concluded that the TOF methods can dramatically reduce neutron background and improve the accuracy of proton range verification in SEB imaging.

The purpose of this study is to evaluate the effect of a lead radiation shield on the ability of a beam imaging device consist of an imaging plate (IP) and a collimator by Monte Carlo simulations. Simulations were performed using PHITS. A carbon-ion beam was injected to an acrylic target. A tungsten collimator having a pinhole was placed at the distance of 31.2 cm from the beam. A lead radiation shield was placed on the tungsten collimator. An IP was placed under the collimator. Beam images were acquired by recording the position distribution of energy deposition on the IP. We confirmed that therapeutic carbon-ion beam images could be acquired using the imaging device combining the IP and collimator. It was found that removal of the lead shield had no effect on the imaging results.

A 79-year-old woman with a history of open heart surgery presented with severe aortic stenosis (AS). Computed tomography (CT) showed chronic type B aortic dissection (TBAD) between the distal aortic arch and the left common iliac artery. After careful consideration, we planned transfemoral (TF)-transcatheter aortic valve implantation (TAVI) using a 20-Fr long sheath to minimize contact with the false lumen of the aorta. TAVI was performed under general anesthesia, guided by transesophageal echocardiography (TEE). A transcatheter aortic valve was successfully implanted. TEE, immediately after valve implantation, showed no remarkable changes in the descending thoracic aorta. Repeated post-procedural CT examinations showed no obvious changes in the aorta. The patient was stable without sequelae at the 12-month follow-up. This case demonstrates that TF-TAVI using a long sheath under TEE guidance can be a treatment option for patients with severe AS and chronic TBAD.

Background Little has been reported on the outcome of contact force (CF)-guided radiofrequency catheter ablation (RFCA) and second generation cryoballoon ablation (CBA). Purpose The purpose of this study was to compare the outcome of CF-guided RFCA and second generation CBA for paroxysmal atrial fibrillation (PAF). Methods We enrolled the consecutive 364 patients with PAF who underwent initial ablation between September 2014 and July 2018 in our hospital. We compared the late recurrence of atrial tachyarrhythmia more than three months after ablation between RFCA group and CBA group. All RFCA procedures were performed using CF-sensing catheter and all CBA procedures were performed using second generation CB. Results There were significant differences in background characteristics: chronic kidney disease, serum brain natriuretic peptide level, and left ventricular ejection fraction. After propensity score matched analysis (Table), atrial tachyarrhythmia free survival was significantly higher in CBA group than in RFCA group (Figure). Conclusions Second generation CBA showed a significantly lower late recurrence rate compared to CF-guided RFCA. Kaplan-Meier Curve Funding Acknowledgement Type of funding source: None

Background Pulmonary vein isolation (PVI) has become well-established as the main therapy for patients with drug-refractory paroxysmal atrial fibrillation (PAF) and various isolation methods including radiofrequency ablation (RFA), cryoballoon ablation (CBA) and laser balloon ablation (LBA) were available. Pathological findings in each ablation methods such as myocardial injury and inflammation are thought to be different. High sensitive cardiac troponin I (hs-TnI), subunit of cardiac troponin complex, is a sensitive and specific marker of myocardium injury. High-sensitive C-reactive protein (hs-CRP) is a biomarker of inflammation and is elevated following cardiomyocyte necrosis. Relationship between myocardial injury and inflammation after ablation using RFA, CBA and LBA and early recurrence of atrial fibrillation (ERAF) remains unclear. Methods We enrolled consecutive PAF patients from Osaka Rosai Atrial Fibrillation (ORAF) registry who underwent PVI from January 2019 to October 2019. We compared the clinical characteristics including age, gender, hypertension, diabetes mellitus, history of heart failure, CHADS2Vasc score, renal function, serum BNP level and echocardiographic parameters including left ventricular dimensions, left atrial diameter (LAD) and left ventricular ejection fraction (LVEF) between RFA, CBA and LBA groups. We investigated the difference of relationship between myocardial injury marker (hs-TnI), inflammation markers (white blood cell change (DWBC) from post to pre PVI, neutrophil-to-lymphocyte ratio change (DNLR) from after to before PVI and hs-CRP) at 36–48 hours after PVI and ERAF ( Results We enrolled 187 consecutive PAF patients who underwent PVI. RFA, CBA and LBA groups comprised 108, 57 and 22 patients, respectively. There were no significant differences of age, gender, hypertension, diabetes mellitus, history of heart failure, CHADS2Vasc score, renal function, serum BNP level and echocardiographic parameters between each group. Serum hs-TnI in RFA group and LBA group were significantly lower than in CBA group (2.643 ng/ml vs 5.240ng/ml, 1.344 ng/ml vs 5.240 ng/ml, p Conclusion LBA may cause less myocardial injury than RFA and CBA, on the contrary LBA may cause more inflammation than CBA. Incidence of ERAF in LBA was highest between each procedure. Inflammation markers and ERAF Funding Acknowledgement Type of funding source: None

Introduction ILUMIEN III trial has reported that non-inferiority of optical coherence tomography (OCT)-guided percutaneous coronary intervention (PCI) to intravascular ultrasound-guided PCI for postprocedural minimum stent area. In the trial, external elastic lamina (EEL)-based stent sizing criteria was introduced, however OCT has limitations including incomplete visualization of EEL in severale lesions. Purpose The aim of the study is to investigate real-world clinical impact of EEL-based stent sizing criteria. Methods The study included consecutive patients who underwent OCT-guided percutaneous coronary intervention (PCI) for de novo lesions in our institution between September 2016 and April 2018. EEL visibility, mean EEL diameter, mean lumen diameter and plaque morphology were assessed at proximal and distal references. The plaque morphology at references was categorized according to its most prevalent component as follows: normal, fibrous plaque, lipid plaque, and calcified plaque. Both references were divided into 3 groups according to visibility of EEL. Results Among 205 lesions, 31 lesions had artifacts at references (16 proximal and 17 distal references). EEL visibility was summarized in a table. Out of 174 lesions with both analyzable references, 111 lesions (63.8%) had >180-degree EEL visibility at both references. Proportion of plaque morphology were significantly different among 3 groups at proximal and distal references as shown in a figure. Conclusions EEL-based stent sizing criteria was usable for 63.8% of all the lesions. Vessel size and plaque morphology were significantly associated with EEL visibility. Proportion of plaque morphology Funding Acknowledgement Type of funding source: None

Background Complete right bundle branch block (CRBBB) is one of the most frequent alterations of the electrocardiogram (ECG). Several studies have shown that CRBBB was a risk factor for cardiovascular diseases and the appearance of CRBBB in patients hospitalized for exacerbated heart failure (HF) was associated with a worse prognosis. Various alternations of ECG such as early repolarization pattern and intraventricular conduction disturbance were associated with high recurrence ratio of atrial fibrillation (AF) after pulmonary vein isolation (PVI). However clinical outcome after PVI in patients with CRBBB remains unclear. Methods We enrolled consecutive AF patients who underwent PVI from September 2014 to November 2018 rom Osaka Rosai Atrial Fibrillation (ORAF) registry. We excluded patients with other wide QRS (left bundle branch block, ventricular pacing and unclassified intraventricular conduction disturbance) and divided into 2 groups; CRBBB (QRS duration ≥120msec) group and no-CRBBB (QRS duration Results We enrolled 736 consecutive AF patients who underwent PVI. CRBBB patients comprised 55 patients (7.5%). There were no significant differences of age, gender, hypertension, diabetes mellitus, history of heart failure, history of stroke, CHADS2Vasc score, PAF, renal function, plasma BNP level and echocardiographic parameters (LVDd, LVDs, LVEF and LAD) between the 2 groups. Incidence of AF/AT recurrence after PVI was significantly higher in CRBBB group than no-CRBBB group (Figure). CRBBB was an independently and significantly associated with late recurrence of AF/AT after PVI by multivariate Cox analysis (hazard ratio: 1.923, 95% CI: 1.190–2.961, p=0.009) in addition to female (p Conclusion CRBBB may be a strong predictor of AF/AT late recurrence after PVI. AF/Ar recurrence after PVI Funding Acknowledgement Type of funding source: None

Background BIOSCIENCE randomized trial which compared biodegradable-polymer sirolimus-eluting stents with ultra-thin (60μm) strut (ultra-thin BP-SES) and durable-polymer everolimus-eluting stents with thin (81μm) strut (thin DP-EES) have reported that definite stent thrombosis within 1 year had more frequently occurred in ultra-thin BP-SES (0.9%) than in thin DP-EES group (0.4%) although it was not statistically significant. It suggests that neointimal coverage after stent implantation within 1 year might be different between ultra-thin BP-SES and thin DP-EES. Recently, two types of biogradable-polymer sirorimus eluting stents, thin (80μm) strut type (thin BP-SES) and ultra-thin (60μm) strut type (ultra-thin BP-SES), can be available in clinical settings. Purpose We compared neointimal coverage conditions between ultra-thin BP-SES and thin BP-SES by optical coherence tomography (OCT). Methods Consecutive Forty-six patients who underwent 21 ultra-thin BP-SESs or 25 thin BP-SESs implantation were enrolled. We compared incidences of acute coronary syndrome, type B2/C lesion, atherectomy device use, stent size, stent length, maximum inflation pressure, and 8-month follow-up OCT parameters including proportions of uncovered struts (%Uncovered), malapposed struts, (%Mallaposed) and mean neointimal hyperplasia thickness (mean NHT) between the two groups. Results %Uncovered and %malapposed were significantly higher and mean NHT was significantly lower in ultra-thin BP-SES than in thin BP-SES (Table). The other parameters were similar between the two groups. Conclusion Ultra-thin BP-SES showed worse neointimal coverage as compared to thin BP-SES within 1 year after stent implantation, which may increase stent thrombosis. Funding Acknowledgement Type of funding source: None

A TCAD model to simulate program/erase characteristics of 3D charge trap flash memory cells is constructed and calibrated with the experiment. The mechanism of the program characteristics degradation of the semicircular cells are studied using the TCAD model and it is clarified that the current leakage path due to the fringe parasitic transistor causes the degradation. An initial charge injection technique is proposed to suppress the parasitic leakage current to improve the program characteristics of the semicircular cells.

During infections, naive CD8 T cells differentiate into terminal effector cells (TE) and long-lived memory CD8 T cells that recirculate through lymphoid organs using the vasculature (TCIRC), and tissue resident memory (TRM) cells that do not recirculate. The transcriptional control that delineates differentiation of TE cells from memory cell subsets is still unclear. DNA motifs recognized by ETS-family transcription factors (TFs) are highly frequent in cis-regulatory regions that become chromatin accessible in naïve CD8 T cells 24 hours after TCR stimulation, and in mature memory T cell subsets. The ETS-family is encoded by 27 genes, and expression analyses revealed Ets1 is the most highly expressed member. Ets1 is transiently downregulated during activation and is re-expressed in TCIRC cells, but remains lower in intestinal TRM cells. P14 CD8 T cells responding to acute LCMV infection that were depleted of Ets1 using retrovirally-delivered shRNAmirs preferentially became KLRG1hi CD127lo TE-like cells, and their numbers in the circulation rapidly declined, resulting in an absence of long-lived effector cells and residual numbers of central memory-like cells. Concomitantly, Ets1-depleted cells re-distributed into the gut TRM compartment and had increased fractions of CD69hi CD103hi cells. Early after infection in the spleen, a larger fraction of Ets1-depleted P14 cells express CCR9 and α4β7. Depletion or overexpression of Ets1 in P14 cells both indicate it negatively regulates CD25 and Prdm1 expression, and promotes Tcf7 and Bcl6 expression. These results suggest that Ets1 functions early during CD8 T cell activation to establish the normal pattern of TCIRC and TRM cell differentiation during acute viral infection.

During infections, naive CD8 T cells differentiate into terminal effector cells (TE) that are relatively short-lived, and memory precursor (MP) cells that give rise to long-lived memory CD8 T cells, but the transcriptional control of this process is still unclear. In naïve CD8 T cells, cis-regulatory regions that become accessible in chromatin during the first 24 hours of TCR stimulation and that remain accessible in mature memory T cell subsets are highly enriched with motifs encoding binding sites for the ETS- and bZIP-families of transcription factors (TFs), many of which also overlap Runx-TF binding sites. The ETS and bZIP TF families are encoded by 88 genes, and are differentially expressed between naïve, early effector, and memory CD8 T cell subsets. To interrogate their requirements functionally, we applied an in vivo pooled RNA interference screen using short hairpin RNAs in microRNA contexts (shRNAmirs) to suppress individually all TFs from both families in CD8 T cells responding to lymphocytic choriomeningitis virus (LCMV) infection. In addition, we focused on Ets1, the most highly expressed ETS TF in naïve, effector and memory cell subsets. Ets1 suppression with shRNAmirs impaired overall effector CD8 T cell numbers in vivo, and increased the frequency of TE-like cells at early times after LCMV infection, which resulted in reduced long-lived effector cells and an increased fraction of altered central memory-like cells at later time points. Enforced Runx3 expression in Ets1-suppressed cells partially restored normal MP cell formation at early times. These results suggest that Ets1 and Runx3 are each necessary for the normal differentiation of MP cells, and could function cooperatively to program their differentiation.

A Cable-in-Conduit-Conductor (CICC) is a composite conductor consisting of many superconducting strands twisted in multiple steps. The CICC has the characteristics which make it suitable for fusion magnets, but lower critical current than expected have been observed in some experiments. The resistance distribution between the strand and the copper sleeve in a “Wrap Joint” is expected to be inhomogeneous and to affect the current distribution and the critical current in the CICC. We measured the DC resistance distribution between the strand and the copper sleeve in a simple model Wrap Join at liquid helium temperature and observed an inhomogeneous resistance distribution. A 3-D strand path calculated by considering the manufacturing process of CICC and an algorithm from previous work were used to evaluate the resistance distributions between the strand and the copper sleeve. The calculated and measured resistance distributions showed the same overall trends. The homogeneity of the resistance distribution between the strand and the copper sleeve is strongly dependent on whether the strand is in direct contact with the copper sleeve or not. Maximizing the number of direct contacts between the strand and the copper sleeve of the “Wrap Joints” was effective for reducing any possible current imbalances.

Generally, high magnetic flux density is adopted in superconducting magnetic energy storage (SMES) coil design to reduce superconducting coil size and increase energy density. However, critical current density of the SMES coil is degraded by applying the high magnetic flux density to superconducting wire. This means that adopting the high magnetic flux density is not necessarily suitable for the superconducting wire reduction of the SMES coil. In this paper, the relationship between the maximum magnetic flux density within coil and superconducting wire usage of the SMES coil composed of solenoid or toroidal coil wound by MgB2, Bi2223, or REBCO wire was investigated. As a result, most suitable magnetic flux density within SMES coil for realizing the minimum superconducting wire usage in MgB2 , Bi2223, and REBCO wires were clarified. How to estimate the most suitable maximum magnetic flux density within coil for realizing the minimum wire usage in each superconducting wire was also investigated. Comparison between the rate of change of coil radius times maximum magnetic flux density and critical current density with respect to the maximum magnetic flux density is useful for obtaining the suitable maximum magnetic flux density for the minimum superconducting wire usage.

High-temperature superconducting (HTS) tri-axial cable, which consists of three concentric phases, was developed as a potential commercial solution for next generation distribution power network. In our previous research, we simulate the transient thermal behavior of the cable by solving the heat equation using one-dimension difference method. The result shows that it takes time to recover the cable temperature to the steady-state operation level due to a low thermal conductivity of the insulation layer after a fault. However for a long cable system, when middle phase in concentric structure is rated under an over current, accumulated heat from middle phase might continually warm up the liquid nitrogen (LN 2 ) flow by heat transfer even the over current has been stopped. In this research, we improve the numerically calculation which includes the consideration of flowing liquid nitrogen and the heat transfer in both radius and longitudinal directions. A long tri-axial cable system thermal stability is discussed based on the calculation results.

A tri-axial HTS cable with the advantage of compact structure, low heat loss, and low cost is a perfect solution for future distribution power network demand. In our previous research, a typical single line to ground (SLG) fault simulation was carried out in an adiabatic condition. A stabilizer layer thickness design of the tri-axial HTS cable based on a calculation of maximum temperature rise in the worst condition was proposed. However, in practical application, after the quenched cable is removed from the network by a breaker, a recovery time is also a very important parameter to decide if the cable is allowed to reconnect to the power network. In this paper, a one-dimensional computational fluid dynamics (CFD) analysis is carried out to simulate the transient thermal behavior of the cable. The result shows that it takes time to recover the cable temperature to the steady-state operation level due to a low thermal conductivity of the insulation layer. Since the cable is cooled by forced liquid nitrogen (LN 2 ) flow, there is a temperature gradient along the cable. The temperature of LN 2 gradually rises after the fault until the warmed coolant runs out of the cable.

Information of 3D strand locations in a Cable-in-Conduit (CIC) conductor is necessary for accurate estimation of conductor performance, e.g., AC losses, current distribution or strain effect. However, it is difficult to derive strand positions after compaction, and there have been no analytical methods to accurately estimate strand positions. In our previous work, we measured strand positions in the CIC conductor, whose length is about 1 m, with 81 NbTi strands and it was verified that some strands were displaced from their original positions. In order to estimate strand locations in a long conductor, we developed a method to analyze three dimensional strand positions taking into account the cable deformation caused by compaction. In this method, we use strand positions in only one cross section of conductor and twist pitches of each sub-cable to calculate the center of gravity of each sub-cable. The strand positions are obtained in a manner that the same order sub-cables rotate around the center of gravity of one order higher sub-cable according to a function of the cabling pitch. We derive the twist pitches after compaction by using measured and calculated strand positions. The calculated strand locations by using the derived twist pitches agree well with the measured ones, with errors of about 0.7 mm.

A multi-laminated HTS tape conductor wound into double-pancake coils has recently been used for large SMES. If the HTS tapes are simply laminated to form the conductor, the current distribution in the laminated tape conductor of the coil is not homogeneous because of the differences among all the tape inductances. Transposition of these tapes at the innermost or outermost layer of the coil is effective for homogeneous current distribution. However, this method would requires the same number of single-pancake coils as that of the HTS tape conductor, and hence the number of HTS tape conductors is restricted. In this paper, we propose a new method to control the current distribution in the laminated conductor using transposition at the innermost layer of a double-pancake coil and adjusting the gaps between the laminated tapes. We analyze the current distributions for multi-laminated HTS tape conductors for a double-pancake coil, and show the homogeneous current distribution of the laminated tape conductor. In order to verify the theory, we designed homogeneous current distribution coil wound with the multi-laminated (four times) HTS tape conductors by transposing them at the innermost layer and by adjusting the additional thickness 0.075 mm between the parallel conductors. We obtained the homogeneous current distribution in the tape conductor. The experimental data were in good agreement with the theory.

A multi-laminated HTS tape conductor has been recently developed to fabricate large double pancake coils. If the HTS tapes are simply laminated to form the conductor, the current distribution in the laminated tape conductor of the coil is unbalanced because of different inductances of all tapes. It is very important to analyze current distributions in the multi-laminated tape conductor used for the double pancake coil for SMES. In this paper, we analyze the current distribution in the tape conductor by using electrical circuit model, and then discuss how to obtain the homogeneous current distribution. One way is to transpose the tape position at both ends of pancake coil so as to arrange the tapes symmetrically. However, this method is not perfectly geometrical symmetry for more than 3 laminated tapes in the conductor. We propose new method to obtain homogeneous current distribution by adjusting gaps between HTS tapes in the conductor. Finally we numerically demonstrate the homogeneous current distribution in the 4-laminated tapes with inserting additional thickness among tapes.

In plant and industrial complex, further energy saving can be realized by DC interconnection between the ends of AC radial distribution system. We fabricated a power system simulator to verify that the DC interconnection is effective for energy saving in the distribution system. An YBCO toroidal coil composed of eight double pancake coils was fabricated and adopted in the simulator as a DC reactor. Harmonic current with DC-offset component were observed in the YBCO toroidal coil and the frequency component ratio of harmonic current depended on the inductance of the toroidal coil. Energy loss in the YBCO toroidal coil during the DC interconnection in the power system simulator decreased with the inductance of the YBCO toroidal coil because the magnitude of harmonic current component decreased with the inductance. To clarify the loss characteristics in the YBCO toroidal coil, we investigated influence of the magnitude of harmonic-frequency component and DC-offset component on the transport current loss in YBCO tape conductor. The transport current lose was independent of the magnitude of DC-offset component. The energy loss characteristics in the YBCO toroidal coil were closely related to the transport current loss in the YBCO tape conductor with harmonic current.

Large-inductance DC reactors are often required in practical factories, and superconducting magnets represent an interesting alternative for the construction of such devices. It is therefore useful to obtain optimized designs for DC reactors, particularly for the minimization of the winding volume under many constraints. The superconducting magnets of DC reactors can be operated at higher temperature than that of SMES, since the rated current in the case of DC reactors is much smaller. To operate at high temperature (77 K) makes the coolant cost low. However, the flux flow loss becomes large at 77 K, and then it has to be taken into account at the design stage. In this paper, the optimized configurations of toroidal superconducting magnets for DC reactor are presented and the configurations of HTS conductor are investigated under taking the flux flow loss into account.

We have investigated the basic properties of levitation force and vibration transmission in a magnetic levitation type superconducting seismic isolation device. Since it is very difficult in a real device of a seismic isolation device to keep the stationary levitation against any horizontal disturbances, we have devised a permanent magnet-permanent magnet (PM-PM) system with a copper plate and verified that the stable stationary levitation of the seismic isolation object could be achieved by using the PM-PM system with the copper plate. In addition, to improve the damping effect, we adopted vibration absorbing system composed of a copper plate and a permanent magnet. We investigated the basic properties of vibration transmission and damping effect in the model device having the PM-PM system with the copper plate and vibration absorbing system. The vibration transmission was reduced and the damping effect was greatly improved by the magnetic interaction between the copper plate and the permanent magnet in the PM-PM system with the copper plate and vibration absorbing system. We investigated the relationship between the magnetic interaction between the copper plate and the permanent magnet and obtained a suitable thickness of the copper plate in the PM-PM system and a suitable structure of vibration absorbing system for reducing the vibration transmission and improving the damping ratio effectively.

In this study, a duplex model is developed as a constitutive model for the homogenised elastic–viscoplastic behaviour of plate–fin structures. This model consists of plate and fin layers, which are individually ruled by different macroscopic constitutive models. An anisotropic, compressible power law equation that was derived in a recent study by the present authors is used to describe the homogenised viscoplastic behaviour of the fin layer. On the other hand, an isotropic, incompressible power law equation is used as the macroscopic viscoplastic constitutive equation of the plate layer. The duplex model developed is applied to an ultrafine plate–fin structure made of Hastelloy X. It is thus shown that the duplex model is more successful in simulating the homogenised viscoplastic behaviour under multiaxial loading than the corresponding simplex model in which plates and fins are non‐separately homogenised.

This paper describes experiments and analysis of the warpage of Si/solder/Cu layered plates subjected to cyclic thermal loading. As received and annealed Cu plates are used as the Cu layer, and three thickness ratios are considered for the Si and Cu layers. It is experimentally shown that the initial warpage caused by soldering either grows or recovers with an increase in the number of temperature cycles and that the cyclic growth of warpage is apparent when the Cu layer is annealed and is relatively thick. Then, by performing a three‐dimensional finite element analysis, it is demonstrated that the cyclic growth and recovery of warpage shown experimentally can be simulated well if an appropriate constitutive model is employed for kinematic hardening in the Cu layer.

We have devised a magnetic levitation type superconducting seismic isolation device taking advantage of the specific characteristic of HTS bulk that the HTS bulk returns to its original position by restoring force against a horizontal displacement. The superconducting seismic isolation device is composed of HTS bulks and permanent magnets (PM rails). The PMs are fixed on an iron plate to realize the same polarities in the longitudinal direction and the different polarities in the transverse direction. The superconducting seismic isolation device can theoretically remove any horizontal vibrations completely. Therefore, the vibration transmissibility in the longitudinal direction of the PM rail becomes zero in theory. The zero vibration transmissibility and the stationary levitation, however, cannot be achieved in the real device because a uniform magnetic field distribution in the longitudinal direction of PM rail cannot be realized due to the individual difference of the PMs. Therefore, to achieve stationary levitation in the real device we adopted a PM–PM system that the different polarities are faced each other. The stationary levitation could be achieved by the magnetic interaction between the PMs in the PM–PM system, while the vibration transmitted to the seismic isolation object due to the magnetic interaction. We adopted a copper plate between the PMs to reduce the vibration transmissibility. The PM–PM system with the copper plate is very useful for realizing the stationary levitation and reducing the vibration transmissibility.

By the advantage of more compact structure, small leakage field, and low heat loss, tri-axial cable become to be mainstream design in recently HTS practical project. However, the imbalance current problem was also reported by some practice experiments. Since the HTS tri-axial cable is composed of three concentric phases, an unsymmetrical inductance and capacitance distribution which is determined by twist pitches and radii, gives an inherent imbalance in three-phase currents distribution. In our previous research, we proposed a two sections structure design to overcome this limitation. Inductance has been balanced by twist pitch adjusting. In that case, the imbalance ratio of current only can be caused by capacitance distribution which is depending on voltage and line length. In this paper, we evaluate the thickness of insulation, the unsymmetrical capacitance distribution and cable fabrication error. Then we investigate the imbalance ratio due to the capacitance as functions of voltage and length by using Electromagnetic Transients Program (EMTP).

We should prevent non-uniform current distribution due to manufacturing errors of tape size, coil size, and conductor deformation in the toroidal coil composed of multiple YBCO double pancake coils. This is because the non-uniform current distribution causes the increase of AC losses and the decrease of critical current in the YBCO tapes. Therefore, we analytically investigated the relationship between the manufacturing error and the current distribution in the toroidal coils composed of the eight series-connected double pancake coils composed of the transposed conductor with two parallel-connected YBCO tapes and the eight sets of two parallel-connected double pancake coils composed of single YBOC tape conductor connected in series. The parallel-connected multiple double pancake coils composed of single tape conductor is much more effective for preventing the non-uniform current distribution than the double pancake coil composed of the transposed conductor with parallel-connected multiple tapes. The non-uniformity of current distribution can be improved by increasing the length of parallel-connected current path by increasing the number of series-connected double pancake coils in each current path.

Recently, high-temperature superconductor (HTS) cables have been widely studied because of their compactness and high power capacity compared to conventional copper cables. In HTS cables, AC loss is an important issue since large losses reduce the efficiency of the power line. Among HTS cables, tri-axial cable is under intensive investigation recently, since it has a smaller amount of HTS tapes, small leakage fields and small heat loss in leak when compared with the three single-phase cables. For realizing high current capacity, more than one layer is required for each phase; therefore AC loss of the multi-layer tri-axial HTS cable should be carefully examined. In the tri-axial cable, different phase currents produce the out-of-phase magnetic fields on the other phase layers. In case of multi-layer arrangement, net magnetic fields on layer surfaces may exceed the penetration field of the HTS tape. Therefore in this paper, we analyze the AC loss of a tri-axial HTS cable which is composed of two layers per phase. Here, we treat the tri-axial cable which consists of two different longitudinal segments and thus satisfies balanced phase and homogeneous current distribution condition by controlling twist pitch and length of separate segments.

We have investigated levitation force characteristics of a magnetic levitation type superconducting seismic isolation device composed of HTS bulks and permanent magnets. Large levitation force at a small gap of less than 3 mm has been already obtained, while only small levitation force at a large gap of more than 5 mm. In a practical use of the superconducting device, the HTS bulks should be cooled by not LN2 but a cryocooler. This means that large levitation force at a large gap of more than 5 mm is required due to a vacuum layer thickness in a cryostat. Therefore, we investigated the suitable size and arrangement method of the permanent magnet and the HTS bulk to improve the levitation force at a large gap of more than 5 mm effectively. By adopting a permanent magnet arrangement of "Halbach array", we could greatly improve the levitation force at a large gap of more than 5 mm. Based on the experimental and computed results of levitation force and magnetic field distribution, we could achieve further improvement of the levitation force by optimizing the size of the permanent magnet and the HTS bulk. The suitable width and thickness of the permanent magnet were 10 mm against a disk-shaped HTS bulk 32 mm in diameter and the suitable thickness of the HTS bulk was less than 2 mm at a gap of more than 5 mm.

Non-uniform current distribution in a conductor composed of multiple HTS tapes is one of the important problems for increasing current carrying capacity of a large-scale coil system such as Superconducting Magnetic Energy Storage (SMES) and DC reactor. We focused on a manufacturing error in the HTS tape thickness and analytically investigated the relationship between the manufacturing error and the non-uniform current distribution. Even in a transposed conductor, the non-uniform current distribution is easily occurred by a small error in the tape thickness due to high coupling constant among the tapes. The non-uniformity of the current distribution reduces the current carrying capacity. However, the non-uniform current distribution can be improved by adopting a pancake coil with a large radius and small number of turns. An HTS tape with large thickness is also effective for reducing the non-uniformity of current distribution. Adopting parallel double pancake coils composed of single HTS tape is one of the promising candidates for increasing current carrying capacity effectively without any problems of the non-uniform current distribution. The suitable connecting method among the parallel double pancake coils for uniform current distribution, however, should be developed.