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[en] Nuclear medicine requires the most up-to-date specialized technical facilities. The paper underlines the factor of reliability in purpose-designed equipment used for basic examinations. The possibility is also discussed of the automation of standard nuclear medicine instruments
[en] As developments in magnetic recording increase, the demands for high density recording media continue to rise. One particular medium developed towards meeting these needs is the commercially successful metal evaporated (ME) tape. To provide a deeper understanding of the magnetic processes occurring in recording media, theoretical studies are carried out to complement experimental observations. Therefore, this thesis is concerned with developing a micromagnetic model to simulate the magnetic behaviour of ME tape. ME tape consists of bundles of granular columns which are tilted towards the film normal. The morphology of the film influences the magnetic behaviour and a 3D model is developed in this thesis to represent the columnar structure and the granular nature of ME tape. A Monte Carlo algorithm, consisting of a 'move and grow' procedure, is developed to generate an irregular system of spherical grains whose radii were generated from a log-normal distribution. This structure provides the foundation for modelling columns of ME tape. Initially an isolated column of ME tape was investigated. Grains were considered to be single domain and the dynamic process of the magnetic moments was explored by the Landau-Lifschitz equation. The model demonstrated that as the strength of the exchange coupling parameter increased, then moments which were strongly coupled resisted large negative fields and square hysteresis loops with a high coercivity were produced. Reversal of the moments was observed to be initiated at the ends of a column and then propagated throughout the column. This was attributed to large demagnetising fields and was particularly evident in the model with aligned easy axes. If the easy axes were randomly orientated then more disorder was present in the model and moments rotated incoherently. This produced hysteresis loops that were less square than those of the aligned model. The results also showed how the microstructure influenced the reversal processes. Simulations on assemblies of interacting columns of ME tape highlighted that, when exchange coupling was weak, moments reversed incoherently throughout the structure. However, increasing the strength of the exchange coupling caused a high degree of cooperative reversal to occur in individual columns. As moments reverse their direction they initially relax towards the long axis of a column due to column demagnetising effects. The model demonstrates that as moments reverse there is a changing balance between magnetostatic (demagnetising) and exchange interactions within and between columns. The model was considered to be a good representation of ME tape, and the results obtained not only complement previous studies but provide a deeper understanding of the reversal processes occurring both within and between columns of ME tape. (author)
[en] Since the introduction of perpendicular recording, conventional perpendicular scaling has enabled the hard disk drive industry to deliver products ranging from ∼130 to well over 500 Gb/in2 in a little over 4 years. The incredible areal density growth spurt enabled by perpendicular recording is now endangered by an inability to effectively balance writeability with erasure effects at the system level. Shingled magnetic recording (SMR) offers an effective means to continue perpendicular areal density growth using conventional heads and tuned media designs. The use of specially designed edge-write head structures (also known as 'corner writers') should further increase the AD gain potential for shingled recording. In this paper, we will demonstrate the drive-based recording performance characteristics of a shingled recording system at areal densities in excess of 800 Gb/in2 using a conventional head. Using a production drive base, developmental heads/media and a number of sophisticated analytical routines, we have studied the recording performance of a shingled magnetic recording subsystem. Our observations confirm excellent writeability in excess of 400 ktpi and a perpendicular system with acceptable noise balance, especially at extreme ID and OD skews where the benefits of SMR are quite pronounced. We believe that this demonstration illustrates that SMR is not only capable of productization, but is likely the path of least resistance toward production drive areal density closer to 1 Tb/in2 and beyond. - Research highlights: → Drive-based recording demonstrations at 805 Gf/in2 has been demonstrated using both 95 and 65 mm drive platforms at roughly 430 ktpi and 1.87 Mfci. → Limiting factors for shingled recording include side reading, which is dominated by the reader crosstrack skirt profile, MT10 being a representative metric. → Media jitter and associated DC media SNR further limit areal density, dominated by crosstrack transition curvature, downtrack transition length and media exchange coupling parameters. → Drive track misregistration (TMR) was also observed to be a dominant factor in the ultimate areal density capability of these drive systems with OD performance degrading strongly vs measurements made at the ID. → The ultimate potential for commercialization of SMR drive systems will be gated by success in control of these dominating factors.
[en] This interface module in its present form enables any device with a GPIB port to accept numbers or 8-bit characters. Both modules use primarily TTL integrated circuits readily available. (T.A.)