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A magnetic bubble generator consisting of a Permalloy disk and a current conductor loop has been used recently in a mass memory design utilizing magnetic bubble technology. The bias field range in which the disk can hold the seed bubble is measured in this report as a function of of the rotating field frequency. Above a critical frequency fc , the bias field margins begin to decrease. The dependence of fc on disk size is obtained for disks with diameters from 16 μm up to 43 μm at rotating fields of 20 and 30 Oe. The separation between Permalloy disks and the garnet film is kept at 0.8 μm or 1.6 μm. Results show that at a fixed rotating field, a smaller disk is preferable at higher frequency for a magnetic bubble material with a given mobility. The critical frequency fc obtained is in good agreement with a theoretical calculation using the viscous damping model by Rossol et al. For frequencies below fc , the bias field margin on the disk is equal to that of the propagating channel and circuit failure due to the loss of the generator seed bubble can be eliminated. 相似文献
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Crack propagation in strengthened concrete disks is a problem that has not yet been addressed properly. To investigate it, a cracked half-infinite disk of concrete is strengthened with a linear elastic material bonded to the surface, and analyzed using two different finite element modeling approaches. The first method is 3D modeling of strengthening, interface and disk, and the second method is modeling of an equivalent disk in 2D, with an effective cohesive crack, equivalent thickness and equivalent stiffness. The 2D modeling approach simplifies modeling of the problem significantly and reduces the computational efforts and time. A good prediction of the cracking response, global response and load was obtained with the 2D model, whereas prediction of the size and shape of the interface debond was only approximate. It is concluded that the effective cohesive modeling approach can be used instead of 3D calculations to predict the response of a structure and that it opens up for simpler evaluation of strengthened concrete structures using the finite element method. 相似文献
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To improve the understanding of the bubble domain propagation a stroboscopic investigation of bubble displacement with a permalloy T-bar overlay was undertaken at various values of drive field rotation rate. In addition to stepwise change of bubble wall velocity, variation distortion of the bubble shape in the process of propagation and an asynchronous lag of the bubble relative to the drive field vector were also observed, the lag increasing with the rotation rate. To explain these results a simplified method for determining the bubble position in a magnetostatic well was proposed whereby elements of the permalloy overlay was divided into elementary rectangular components. The computed data are in good agreement with the experimental findings and this permits explanation of a number of phenomena observed in bubble circuits. 相似文献
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Bubble domain memory chips with micron dimension patterns have been fabricated by additive electroplating through photoresist windows using the conductor first processing. Etching defines the detector strips and removes the plating base. The various fabrication steps are described and discussed. The uniformity of the plated films is good and gives a reasonable yield. Nonmagnetic underlayers were plated below the NiFe bars. The gap width could be reduced by overplating the photoresist windows. 4 kbit chips have been fabricated with the processes described. 相似文献
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I. E. Dzhamaletdinova L. Ya. Alimova A. I. Kamardin T. D. Radzhabov 《Journal of Engineering Physics and Thermophysics》1989,57(6):1404-1407
We have studied the gas-separation properties of industrial polyvinyltrimethylsilane (PVTMS) membranes, as well as of experimental specimens of polyarylate siloxane, modified with ions C+, Ar+, B+, and N+.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 6, pp. 888–892, December, 1989. 相似文献
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The accuracy to which a desired dopant concentration can be attained through ion implantation depends largely upon the time constant for switching the ion beam on and off. Different means for switching the ion beam are discussed and a fast-switching device is described. The new device allows for a switching time constant of about 2 ms. During the switching process, no ions of other species can reach the target. 相似文献
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Ion dynamics of pulsed plasma sheath during the plasma source ion-implantation (PSII) affects the resultant surface properties and structures. In this work, a two-dimensional fluid model is applied to the problem of computing ion dynamics in the sheath of a target with a rectangular groove. The evolution of sheath edge, x and y components of ion velocity on the target surface are simulated to describe the physics of sheath in PSII. 相似文献
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Three-dimensional holographic disks 总被引:3,自引:0,他引:3
We describe optical disks that store data holographically in three dimensions by using either angle multiplexing or wavelength multiplexing. Data are stored and retrieved in parallel blocks or pages, and each page consists of approximately 10(6) bits. The storage capacity of such disks is derived as a function of disk thickness, pixel size, page size, and scanning parameters. The optimum storage density is approximately 120 bits/μm(2). 相似文献
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We have investigated the atomic structures of displacement cascades and amorphous-crystalline interfaces in silicon, ion implanted at 4 K, using high-resolution electron microscopy. The nature of the cascades and the process of amorphization are shown to be strong functions of ion-implantation and substrate variables. At 4 K the specific damage energy density for the crystalline to amorphous phase transition in silicon has been determined to be 12 eV/atom. The details of atomic structures of amorphous silicon and amorphous-crystalline interfaces are presented. The calculations of the mean free path between collisions and the energy deposited per atom are found to be consistent with experimental observations on amorphization of silicon. 相似文献
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Foam-like carbon (carbon nanofoam, CNF) which belongs to the porous carbon family is formed by pulsed laser ablation of graphite in liquid nitrogen. Each bubble is about 3-10 nm in size and has a layered structure with typically one to four graphene layers. The CNF forms nanoparticles of about 100 nm in size. CNF encapsulating platinum nanoparticles (Pt@CNF) is formed when a mixture of graphite, platinum, and hexadecanoic acid is used as a target. Each bubble encapsulating a platinum nanoparticle is approximately 15 +/- 4 nm in diameter and contains typically 6 +/- 3 graphene walls. The platinum nanoparticles in the CNF are 9 +/- 4 nm in diameter. The annealing of the Pt@CNF at 300 degrees C for a week in vacuum reveals that the CNF effectively prevents the platinum nanoparticles from aggregating. 相似文献
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Feng Wenran Li Zhen Chen Yingying Chen Jinyang Lang Haoze Wan Jianghong Gao Yan Dong Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in... 相似文献
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Hyuga F. Shinohara M. Kozen A. Hirano M. Tsuzuki N. 《IEEE transactions on magnetics》1984,20(4):545-546
It is well-known that bubble propagation margins for ion-implanted bubble devices depend strongly on ion-implantation conditions. A new ion-implantation method is reported that can significantly improve bubble propagation margins for minor loops with 4 × 4 μm bit cell size. The implantation was done through a Mo thin film layer so that the lattice strain and the anisotropy field change would be more uniform through the depth of the implanted layer. With this method, minor loops can be formed by hydrogen single implantation. Consequently simplification of the implantation process is achieved. 相似文献