56,942 research outputs found

    Dynamic complex opto-magnetic holography

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    Computer-generated holograms with their animated, three-dimensional appearance have long appealed to our imagination as the path towards truly immersive displays with bi-directional natural parallax. Impressive progress in updateable 3-D imagery has been achieved with liquid crystal modulators and high-resolution, but quasi-static holograms are being recorded in photosensitive materials. However, the memory requirements and computational loads of real-time, large-area holography will be hard to tackle for several decades to come with the current paradigm based on a matrix calculations and bit-plane writing. Here, we experimentally demonstrate a conceptually novel, holistic approach to serial computation and repeatable writing of computer-generated dynamic holograms without Fourier transform, using minimal amounts of computer memory. We use the ultrafast opto-magnetic recording of holographic patterns in a ferrimagnetic film with femtosecond laser pulses, driven by on-the-fly hardware computation of a single holographic point. The intensity-threshold nature of the magnetic medium allows sub-diffraction-limited, point-by-point toggling of arbitrarily localized magnetic spots on the sample, according to the proposed circular detour-phase encoding, providing complex modulation and symmetrical suppression of upper diffractive orders and conjugated terms in holographically reconstructed 3-D images

    Index to NASA Tech Briefs, 1975

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    This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

    Focal Spot, Summer 1986

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    https://digitalcommons.wustl.edu/focal_spot_archives/1043/thumbnail.jp

    Towards compliant data retention with probe storage on patterned media

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    We describe how the compliance requirements for data retention from recent laws such as the US Sarbanes Oxley Act may be supported by a tamper-evident secure storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual dots. We report on an experiment to show that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. The write-once operation can be used to support flexible data retention by tamper-evident writing and physical data deletion

    Towards Tamper-Evident Storage on Patterned Media

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    We propose a tamper-evident storage system based on probe storage with a patterned magnetic medium. This medium supports normal read/write operations by out-of-plane magnetisation of individual magnetic dots. We report on measurements showing that in principle the medium also supports a separate class of write-once operation that destroys the out-of-plane magnetisation property of the dots irreversibly by precise local heating. We discuss the main issues of designing a tamper-evident storage device and file system using the properties of the medium

    Creation and pinning of vortex-antivortex pairs

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    Computer modeling is reported about the creation and pinning of a magnetic vortex-antivortex (V-AV) pair in a superconducting thin film, due to the magnetic field of a vertical magnetic dipole above the film, and two antidot pins inside the film. For film thickness =0.1ξ= 0.1\xi, κ=2\kappa = 2, and no pins, we find the film carries two V-AV pairs at steady state in the imposed flux range 2.10Φ0<Φ+<3.0Φ02.10\Phi_0 < \Phi^+ < 3.0\Phi_0, and no pairs below. With two antidot pins suitably introduced into the film, a single V-AV pair can be stable in the film for Φ+1.3Φ0\Phi^+ \ge 1.3\Phi_0. At pin separation 17ξ\ge 17\xi, we find the V-AV pair remains pinned after the dipole field is removed, and, so can represent a 1 for a nonvolatile memory.Comment: 8 pages, 6 figure
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