Simulation studies were conducted on the magnetization of (RE)BCO (RE–Ba–Cu–O, where RE represents a rare earth element) bulk superconductors using various split-coil arrangements by solving the critical state equation using the commercial software FlexPDE. A pair of coaxial coils of identical size is identified as an optimum arrangement for practical magnetization at 77 K by the ‘zero-field cooling’ technique. In general, the magnetization process is likely to be most effective when the outer radius of the coils lies between 100% and 50% of the sample radius. A relatively large coil pair is necessary for samples with either a smaller aspect ratio or larger values of Jc0. Two different regimes of flux penetration are found to be involved in the magnetization process. For a sufficiently small sample, the penetration field is determined by flux propagation from beneath the coil to the centre of the sample; for a sufficiently large sample, the definitive propagation route is from beneath the coil to the periphery of the sample. Effective split-coil magnetization occurs only in the former regime, and both penetration regimes are completely different from that involved in the solenoidal-coil magnetization process.
Natural orifice transluminal endoscopic surgery (NOTES) is viewed as a means of breaking one of the physical barriers associated with invasive abdominal operation by decoupling body wall injury from the surgical intervention. However, although the global concept has been clearly elucidated, there remains many separate components that still need piecing together before its routine practice can be realized. In particular, NOTES, in common with other confined access approaches such as single-port laparoscopic surgery, imposes marked constraints on the range and fluidity of operator instrument movement. Therefore, at present, these techniques possess significant limitations on their capacity for ensuring sufficient instrument triangulation as well as the appropriate degrees of tissue positioning and tensioning for facilitating efficient dissection. These technical considerations have recently reinvigorated the investigation of the utility of magnets in affecting surgical operation. The majority of work to date has however focused solely on permanent magnets due to their ease of manufacture and handling, despite the significant limitations inherent in their physical qualities. This review considers these issues and presents the potential engineering solution achievable by employing high-temperature superconducting electromagnets to impose the required physical forces for effective surgical operation in place of conventional rigid assistance instrumentation.
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