Search

To reduce the computation load for electromagnetic field analyses of magnets wound with spiral coated-conductor cables, we developed a simplified analysis method. In the method, we analyze a single spiral coated-conductor cable carrying transport current under the external magnetic field, which is generated by the current in adjacent spiral coated-conductor cables while ignoring influence of shielding currents in them. We conducted numerical electromagnetic field analyses with and without the model and directly compared the analysis results: magnetization and ac loss density distributions in coated conductors and the temporal evolution of ac losses. The comparison of the analysis results from each analysis model showed the applicability of the analysis method for ac loss estimation of magnets.

Summary: Camptodactyly is a condition defined by persistent flexion contracture of the proximal interphalangeal joints of the hand. Surgical treatment requires flaps for the dissection of the skin and the resulting soft tissue defect, soft tissue release, and sometimes reconstruction of the extension mechanism. Z-plasty and transposition flap have been reported as methods used in soft tissue defects. In this case, covering the defects of the digits was necessary for keeping the wound clean; thus, we should select a surgical method that facilitates stable and reliable blood flow of the flap. The digital artery perforator flap is pedicled and its transfer does not require the dissection of neurovascular bundles; therefore, it can be used safety and relatively easily. We considered the digital artery perforator flap to be a useful technique in terms of securing stable and reliable blood flow and not twisting the skin. Thus, we performed a digital artery perforator flap transfer for a volar soft tissue defect due to dissociation from proximal interphalangeal joint contracture in camptodactyly.

We experimentally studied the thermal runawayinitiating at a low critical current ( I c ) part. This low I c part is determined by the combination of two reasons in a real coil: (a) the unavoidable defects caused by the manufacturing process, which reduce local critical currents (and might not be uniform across the width of a coated conductor) and (b) the magnetic field distribution along the coated conductor. To simulate the thermal runaway using a short monofilament/multifilament REBa₂Cu₃Oy (RE-123) coated conductor, we artificially created a local defect (low I c part) in a short sample by pressing using a drill bit (creating a defect close to one edge of a coated conductor) or bending (creating a uniform defect across the width of a coated conductor). The sample of the coated conductor was conduction-cooled to 30 K, and a magnetic field was applied (μ₀ H up to 2 T) perpendicular to the wide face of the conductor to control its critical current. Transverse voltages in a multifilament coated conductor were measured to obtain the transverse currents among the filaments through the copper layer. Thermal runaway currents (operating currents above which thermal runaway initiates) of the monofilament sample and those of the multifilament sample with additional Joule loss due to the transverse currents were determined and compared to study the effect of the transverse currents on the initiation of thermal runaway in the multifilament coated conductor. Experiments on the protection against thermal runaway were conducted. When a normal voltage (over a preset threshold) was detected, the supplied current would be decreased exponentially. The thresholds for protecting monofilament and multifilament coated conductors from degradation after thermal runaway were compared.

Shielding-current-induced fields (SCIFs) in magnets wound with coated conductors deteriorate the field quality of the magnets. Particularly, in magnets that are excited repeatedly, and must generate time-varying magnetic fields, for example, in certain types of accelerator magnets, the influence of the temporal behavior of the SCIFs on magnetic field is quite complicated. We focused on the magnetic field drifts and conducted magnetic field measurements using a small dipole magnet wound with coated conductors cooled using a cryocooler. The magnet was operated under various patterns of excitation, and magnetic fields were measured using a rotating pickup coil, which enabled us to measure the dipole and sextupole components of the magnetic field. Numerical electromagnetic field analyses were conducted to examine the current distributions in conductors, which influenced the temporal behavior of the magnetic field.

We carried out repeated excitation experiments of a test magnet for accelerator applications of RE-123 coated conductors in order to study its tolerance against ac loss and the stability as well as the reproducibility of the generated magnetic field. The magnet consists of a pair of 4-stacked racetrack coils with an iron return yoke in the low temperature region. It can generate 2.4 T of dipole magnetic field at its room temperature beam duct with its rated current of 200 A, and the maximum magnetic field to which the coated conductor is exposed is about 4 T. At first, the magnet was excited repeatedly with a saw-tooth waveform to examine the tolerance against ac loss: the magnetic field was ramped up to 4 T at the conductor in 120 s and down to 0 T in 120 s. We also carried out numerical electromagnetic field analyses to estimate the ac loss in the magnet. Next, we examined the influence of shielding currents on the field stability and reproducibility at the steps during ramping down, where the current was held constant. This simulated the excitation pattern of magnets for carbon gantries.

We have been studying the potential of energy consumption reduction in rapid-cycling synchrotrons (RCSs) by using superferric magnets with coils wound with high temperature superconductor (HTS). By conducting three-dimensional electromagnetic field analyses on superferric magnets with different coil cross-sections and iron yoke geometries, ac loss of each magnet design was estimated. Rough estimations of the iron loss were also conducted to obtain overall energy consumption of each magnet design. By the comparison, influence of coil cross-section and iron yoke geometry on electricity consumption of the magnet were evaluated.

We wound copper-plated multifilament coated conductors spirally on a round core to decouple filaments electromagnetically under ac transverse magnetic fields and measured their magnetisation losses. Although the coated conductors were plated with copper, which connects all filaments electrically and allows current sharing among them, the spiral geometry decoupled filaments similar to the twist geometry, and the magnetisation loss was reduced effectively by the multifilament structure. The measured magnetisation loss of a 4 mm wide, 10-filament coated conductor with a 20 μm thick copper wound spirally on a 3 mm core was only 7% of that of the same 10-filament coated conductor with a straight shape under an ac transverse magnetic field with an amplitude and frequency of 100 mT and 65.44 Hz, respectively. We separated the measured magnetisation losses into hysteresis and coupling losses and discussed the influence of filament width, copper thickness, and core diameter on both losses. We compared the hysteresis losses with the analytical values given by Brandt and Indenbom and compared the coupling losses with the values calculated using a general expression of coupling loss with the coupling time constants and geometry factors.

The effect of multifilament coated conductors on reducing shielding currents was studied by numerical electromagnetic field analyses. We compared the behaviours of the shielding currents in stacked double pancake coils and layer-wound solenoid coils (SLCs) wound with the following conductors: a monofilament coated conductor, a copper-plated two-filament coated conductor, and an insulated two-filament coated conductor. Shielding-current-induced fields (SCIFs) in the layer-wound SLCs wound with copper-plated two-filament coated conductors decay more rapidly than in stacked double pancake coils wound with copper-plated two-filament coated conductors. In addition, we examined the behaviour of the shielding currents in the coils with and without normal metal terminals. The normal metal terminals made the decay time constants of the SCIFs in pancake coils longer, while the decay time constants of SCIFs did not change notably in the layer-wound SLCs with and without normal metal terminals.

A cryocooler-cooled high-temperature superconducting magnet was constructed, and it was tested on the beam line of the heavy ion medial accelerator in Chiba (HIMAC). The magnet consists of a pair of four-stacked racetrack coils wound with RE-123 coated conductor that are plated with 41- μ m copper for protection. The magnet has a room temperature beam duct, at which 2.4 T of magnetic field is generated, whereas the maximum magnetic field to which coated conductors are exposed is approximately 4 T. The magnetic field in the beam duct was measured and calculated to examine its stability, which might have been affected by shielding currents in the coated conductors. On the beam line of the HIMAC, at first, the beam guiding by the magnet was demonstrated. The measured beam-guiding characteristics were compared with the beam tracking calculations. Next, a carbon ion beam was injected intentionally into the RE-123 coils of the magnet to simulate the incidents of uncontrolled beam injection into accelerator magnets. Prior to this test, the possible heat deposition to the coil by the beam injection was calculated, and the feasibility of quench protection using a dump resistor was studied through quench experiments using short pieces of the RE-123 coated conductors.

Utilizing high temperature superconducting (HTS) magnets coupled with iron core on the rapid cycling synchrotrons is considered as an effective way to reduce their construction and running costs. However, the heat generation by ac loss in HTS wires is a critical obstacle for the application, and prediction and reduction of ac loss in HTS magnets coupled with iron core are essential. In this work, we built one HTS double pancake coil (DPC), a stack of two DPCs, and an iron core comprising laminated steel to couple with the coil windings. The HTS-coated conductors are 200 A-class 4-mm–wide Shanghai Conductors. We report the ac loss measurement results on the coil windings with/without the iron core at three different frequencies. The ac loss in the HTS windings was significantly increased due to the existence of the iron core. Increasing the number of stack of the DPCs may help reduce the difference in ac loss values in the coil windings with/without iron cores.

A three-dimensional electromagnetic field analysis model was developed to estimate ac losses in high-temperature superconductor (HTS) coils composing superferric magnets for rapid-cycling synchrotrons. The influence of magnetized iron yokes in the superferric magnets on distributions of magnetic flux density in HTS coils was considered as externally applied magnetic flux density to HTS coils in the analysis model. We carried out the ac loss calculations using the models for two superferric magnets having different iron core and HTS coil geometries. The ac loss density distribution in the HTS coils and overall ac losses of the superferric magnets were compared.

We developed a simplified three-dimensional electromagnetic field analysis model for accelerator magnets wound with Conductor on Round Core (CORC) to estimate ac loss of magnets. In our model, the coil winding of the analyzed magnet was separated into several divisions composed of dozens of turns. Then, ac loss density in a division was assumed to be the same as that of a single CORC wire exposed to magnetic field in a representative turn of the division. We carried out the ac loss calculations using the model for a superferric magnet composed of coil wound with CORC wires and iron core.

Purpose Unstable distal radius intra-articular fractures require restoration of alignment. Exact fixation of intra-articular fragments is ideal. Here, we employed intraoperative computed tomography (CT) navigation to insert screws accurately in the intra-articular dorsal fragments during treatment with a volar locking plate for distal radius intra-articular fractures. The main purposes of this study were to evaluate the accuracy of this procedure and the postoperative stability of the articular fragments through CT findings, as well as to assess clinical outcomes. Methods This study included 26 patients with distal radius fractures, who were treated with a volar locking plate using intraoperative CT navigation with a minimum follow-up of 12 months. Mean patient age was 63 years and mean follow-up was 16 months. We examined the position of the inserted distal screws and articular displacement on preoperative, intraoperative, and post–bone union CT images. The 3 distal ulnar screw positions that influence the stability of the dorsoulnar articular fragment were evaluated. The Mayo wrist score and Disabilities of the Arm, Shoulder, and Hand score were also clinically evaluated. Results Computed tomography evaluation revealed that the distal locking screws were appropriately inserted at the subchondral position, with sufficient length to stabilize the dorsal fragments, and reduction and stability of the articular fragment were acceptable. At the final follow-up, mean Mayo wrist score was 90.8 and mean Disabilities of the Arm, Shoulder, and Hand score was 9.6. Conclusions Intraoperative CT navigation was successfully used for volar locking plate fixation of intra-articular distal radius fractures. Computed tomography evaluation revealed that the screws were precisely inserted for articular fragments and bone union was achieved, maintaining good intra-articular alignment. The findings demonstrate the accuracy of volar locking plate fixation assisted by intraoperative CT navigation and the good clinical outcomes of this procedure. Type of study/level of evidence Therapeutic IV.

One of critical issues for HTS transformers is achieving sufficiently low AC loss in the windings. Therefore, accurate prediction of AC loss is critical for the HTS transformer applications. In this work, we present AC loss simulation results employing the H-formulation for a 1 MVA 3-Phase HTS transformer. The high voltage (HV) windings are composed of 24 double pancakes per phase wound with 4 mm – wide YBCO wire. Each double pancake coil has 38 ¼ turns. The low voltage (LV) windings are 20 turn single-layer solenoid windings wound with 15/5 (15 strands of 5 mm width) Roebel cable per phase. The numerical method was first verified by comparing the numerical and experimental AC loss results for two coil assemblies composed of two and six double pancake coils (DPCs). The numerical AC loss calculated for the transformer was compared with the measured AC loss as well as the numerical result obtained using the minimum magnetic energy variation (MMEV) method. The numerical AC loss result in this work and experimental result as well as the numerical result using MMEV at the rated current agree to within 20%. Further simulations were carried out to explore the dependence of the AC loss on the gap between the turns of the LV winding. The minimum AC loss at rated current in the 1 MVA HTS transformer appears when the gap between turns is approximately 2.1 mm turn gap in the LV winding. This is due to the change of relative heights between the HV and LV windings which results in optimal radial magnetic field cancellation. The same numerical method can be applied to calculate AC loss in larger rating HTS transformers.

We have been seeking effective ways to reduce ac losses in REBCO coil assemblies. The ac loss characteristics of assemblies of REBCO double-pancake coils (DPCs) are influenced by the magnetic interactions between coils as well as the electric field (E)−current density (J) characteristics of REBCO coated conductors. We compared the ac loss characteristics of two assemblies of DPCs obtained by electromagnetic field analysis and experiment: one consisting of two DPCs and another consisting of six DPCs. Prior to the electromagnetic field analyses, we measured the current transport properties of the coated conductors and formulated their E−J characteristics. In the assembly of six DPCs, ac loss concentrates in the end PCs. In order to reduce the ac loss there, we replaced the end DPCs with ones wound with coated conductors with higher critical currents. However, the conductor replacing is not effective so much to reduce the ac loss because of magnetic interactions between DPCs.

Because the coefficient matrix is dense in the electromagnetic-field-analysis models of coated conductors using current vector potentials, the analyses of large-scale coils require a large amount of memory and long computation time. In this paper, we introduce hierarchical matrices by using the HACApK library in order to reduce both memory consumption and computation time. The effect of the method with respect to memory consumption and computation time is examined in numerical tests using a pancake coil wound with a coated conductor. The effect of parallel computations is also examined. Finally, we analyzed a large-scale magnet, with 1.5 million unknown values.

We carried out electromagnetic field analyses on the shielding-current-induced field (SCIF) of a cosine–theta dipole magnet, which is wound with coated conductors with finite electric field ( E )–current density ( J ) characteristics and must ramp up its magnetic field. E – J characteristics, which depend on the field amplitude and orientation, were formulated based on the measured E – J data and were used for the analyses. The distributions of E in coated conductors of the magnet during the ramp-up phase as well as the flat top of the magnet excitation was revealed, and the relevant range of E – J characteristics of coated conductors was discussed from the viewpoint of dominating shielding currents. The influences of the variation of the E – J characteristic and the field ramp-up rate on SCIF were examined.

We designed a coil-dominated magnet wound with coated conductors for a spiral sector fixed-field alternating-gradient (FFAG) accelerator for carbon cancer therapy. The magnet consisted of deformed pancake coils with negative bends. Coils were arranged similar to a ladder to generate the required radial profile of magnetic field. The positions and the number of turns of the coils were iteratively adjusted to reduce the magnetic field error. We carried out numerical electromagnetic field analyses of the designed magnet to evaluate the influence of coated-conductor magnetization (screening or shielding current) on its field quality.

The shielding-current-induced field is a serious concern for the applications of coated conductors to magnets. The striation of the coated conductor is one of the countermeasures, but it is effective only after the decay of the coupling current, which is characterised with the coupling time constant. In a non-twisted striated coated conductor, the coupling time constant is determined primarily by its length and the transverse resistance between superconductor filaments, because the coupling current could flow along its entire length. We measured and numerically calculated the frequency dependences of magnetisation losses in striated and copper-plated coated conductors with various lengths and their stacks at 77 K and determined their coupling time constants. Stacked conductors simulate the turns of a conductor wound into a pancake coil. Coupling time constants are proportional to the square of the conductor length. Stacking striated coated conductors increases the coupling time constants because the coupling currents in stacked conductors are coupled to one another magnetically to increase the mutual inductances for the coupling current paths. We carried out the numerical electromagnetic field analysis of conductors wound into pancake coils and determined their coupling time constants. They can be explained by the length dependence and mutual coupling effect observed in stacked straight conductors. Even in pancake coils with practical numbers of turns, i.e. conductor lengths, the striation is effective to reduce the shielding-current-induced fields for some dc applications.

We report the progress of an R&D project of fundamental technologies for cryocooler-cooled accelerator magnets using coated conductors funded by the Japan Science and Technology Agency under its S-Innovation Program. Its target applications include carbon cancer therapy and accelerator-driven subcritical reactor. We have been carrying out design studies of HTS magnets for spiral sector fixed-field alternating gradient accelerators to show their feasibility for the target applications and to clarify the requirements of winding technologies. A three-dimensional winding machine has been developed to fabricate a model magnet in which winding technologies required for the designed magnet are implemented. With respect to the large magnetization of coated conductors, which is one of the big concerns on their uses in accelerator magnets, the magnetic field measurements using rotating pick-up coils have been made to clarify its influence on the multipole components of the magnetic field. A method for numerical electromagnetic field analyses of coils with three-dimensional shapes has been developed to predict the influence of magnetization on the field quality of magnets.

We calculated ac losses in the Roebel cables with various configurations considering their 3-D structures in order to clarify the effect of their geometrical configurations on their ac loss characteristics: the number of strands, the transposition length, and the width of the gap between the two rows of stacks of coated conductors were varied. We also calculated the ac losses in the coated-conductor stacks of which cross-sections were identical to the cross-sections of the straight section of the Roebel cables. Magnetization losses without transport current and transport current losses without externally applied magnetic field were calculated for each case. The difference in the ac loss characteristics of the Roebel cables and those of the coated-conductor stacks is significant for magnetization losses. We discussed this difference via a comparison of the longitudinal ac loss distribution.

We have been developing a model for numerical electromagnetic field analyses of three-dimensional-shape coils wound with coated conductor. To analyze three-dimensional-shape coils in a reasonable computation time, we applied thin-strip approximation and other two approximations to our model: a nested-loops approximation and a block approximation. In a nested-loops approximation, each coil turn was approximated as cumulated closed-loops, in a block approximation, several consecutive turns were modeled with an identical current distribution: the bundle of these consecutive turns was called as a block. Analyses were carried out for a single pancake coil to evaluate the errors caused by these approximations. The current profiles as well as temporal evolution of ac losses were compared in various analyses with or without the nested-loops approximation and the block approximation. These approximations were applied to the numerical electromagnetic field analyses of a part of a saddle-shape coil.

We have been developing a model for numerical electromagnetic field analyses of REBCO Roebel cables wound into coil configurations, considering their three-dimensional structure. Electromagnetic field analyses were carried out for one-turn circular closed loop of a Roebel cable, one turn circular closed loop of a Roebel cable at the end of a stack of Roebel-cable loops which simulated a solenoid coil of a finite length, and an infinite solenoid coil wound with a Roebel cable. From the temporal evolution of the current distribution in the Roebel cables, ac losses were calculated. We studied the ac loss characteristics of Roebel cables in different locations in coils. The influence of the gap between turns on ac losses was discussed.

A single pancake coil wound with a copper-plated multifilament coated conductor, with four filaments, was put in a cusp magnetic field, and the magnetic field was measured near the coil at 30 K. A similar experiment was performed by using another reference single pancake coil wound with a monofilament coated conductor. Numerical electromagnetic field analyses of these coils were carried out, and the calculated shielding current-induced fields (SCIFs) were compared with the measured ones in both coils. The temporal behaviour of the calculated SCIF in the coil wound with the four-filament coated conductor was also compared with a series of exponential components, in which a coupling time constant extrapolated from short sample experiments was used as the time constant of the primary component. Current distributions in the coated conductors wound into the pancake coils were visualised. In particular, the temporal behaviours of the current distributions in the four-filament coated conductor and their influence on the SCIF were discussed.

Summary:. Cutaneous myxoma is a rare neoplasm typically occurring as an asymptomatic nodule on the head, neck, and chest regions of adults. However, multiple cutaneous myxoma of the subungual space is even rarer. Here, we report a case of multiple cutaneous myxoma of the subungual space in which the tumor was removed by creating a mid-radial incision while preserving the nail matrix. The excisional biopsy samples were dispatched for histopathological examination and confirmed to be cutaneous myxoma. To the best of our knowledge, this is the first report on multiple cutaneous myxoma of the subungual space.

Root-to-shoot communication plays an important role in the adaptation to environmental stress. In this study, we established a model system for root-to-shoot signalling to observe global gene expression in Arabidopsis thaliana. The roots of Arabidopsis seedlings were wounded and the expression in the shoots of 68 and 5 genes was up-regulated threefold at 30 min and 6 h post-injury, respectively. These genes were designated early and late Root-to-Shoot responsive (RtS) genes, respectively. Many of the early RtS genes were found to encode transcription factors such as AtERFs, whereas others were associated with jasmonic acid (JA) and ethylene (ET). Some of the late RtS genes were shown to be regulated by 12-oxo-phytodienoic acid (OPDA). In fact, elevated levels of JA and OPDA were detected in the shoots of seedlings 30 min and 6 h, respectively, after wounding of the roots. A mutant analysis revealed that JA and ET are involved in the expression of the early RtS genes. Thus, root-to-shoot communication for many RtS genes is associated with the systemic production of JA, OPDA and possibly ET.

It is known that wounding systemically activates the expression of various defense-related genes in plants. However, most studies of wound-induced systemic response are concerned with a leaf-toleaf response. We have recently reported that the long distance signaling was also observed in the shoots of Arabidopsis seedling with wounded roots. We identified early and late root-to-shoot responsive (RtS) genes that were upregulated in the shoots of root-wounded seedlings at 30 min and 6 h post-injury, respectively. It is likely that the primary signals were rapidly transfered from injured roots to shoots, and then these signals were converted into chemical signals. In fact, increase of JA and OPDA content activated the expression of early and late RtS genes in shoots, respectively. In addition, we visualized wound-induced root-to-shoot response by using RtS promoter- luciferase (Luc) transgenic plants. Analysis of the AtERF13 promoter::Luc transgenic plants clearly shows that the wound-induced root-to-shoot signaling was rapidly activated via the vascular systems. © 2011 Landes Bioscience.

We carried out electromagnetic field analyses on the cross sections of two dipole magnets wound with coated conductors. One was a cosine-theta magnet, and the other was a block design magnet. The electric field–current density characteristics of the coated conductors were formulated using a percolation depinning model based on the measured voltage–current characteristics. We calculated the temporal evolutions of the current-density distributions in all the turns of each magnet and used these evolutions to calculate the multipole components of the magnetic field. We compared the two magnets, which differed in coated-conductor orientations, regarding the influence of coated-conductor magnetization on the field qualities.

Root-to-shoot communication plays an important role in the adaptation to environmental stress. In this study, we established a model system for root-to-shoot signalling to observe global gene expression in Arabidopsis thaliana. The roots of Arabidopsis seedlings were wounded and the expression in the shoots of 68 and 5 genes was up-regulated threefold at 30 min and 6 h post-injury, respectively. These genes were designated early and late Root-to-Shoot responsive (RtS) genes, respectively. Many of the early RtS genes were found to encode transcription factors such as AtERFs, whereas others were associated with jasmonic acid (JA) and ethylene (ET). Some of the late RtS genes were shown to be regulated by 12-oxo-phytodienoic acid (OPDA). In fact, elevated levels of JA and OPDA were detected in the shoots of seedlings 30 min and 6 h, respectively, after wounding of the roots. A mutant analysis revealed that JA and ET are involved in the expression of the early RtS genes. Thus, root-to-shoot communication for many RtS genes is associated with the systemic production of JA, OPDA and possibly ET.

Electromagnetic field analyses were carried out to study the influence of coated-conductor magnetisation, i.e. the screening (shielding) current, on the field quality of a dipole magnet in a rotating gantry for hadron cancer therapy. The analyses were made on the cross section of a cosine-theta dipole magnet in a rotating gantry for carbon ions, which generated 2.90 T of magnetic field. The temporal profile (temporal variation) of the magnet current was determined based on the actual excitation schemes of the magnets in the rotating gantry. The experimentally determined superconducting property of a coated conductor was considered, and we calculated the temporal evolutions of the current-density distributions in all the turns of coated conductors in the magnet. From the obtained current-density distributions, we calculated the multipole components of the magnetic field and evaluated the field quality of the magnet. The deviation in the dipole component from its designed value was up to approximately 25 mT, which was approximately 1% of the designed maximum dipole component. Its variation between repeated excitations was approximately 0.03%, and it drifted approximately 0.06% in 10 s. Some compensation schemes might be required to counteract such influence of magnetisation on the dipole component. Meanwhile, the higher multipole components were small, stable, and sufficiently reproducible for a magnet in rotating gantries, i.e. |b 3| ~ 1.1 × 10−3 and |Δb 3| ~ 0.2 × 10−3 in 10 s.