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[Author] Hiroshi NAKATSUKA(2hit)

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  • Morphological Study of YBa2Cu3Oy Thin Films Grown by Excimer Laser Ablation Method

    Shingo TOMOHISA  Hiroshi NAKATSUKA  Minoru TACHIKI  Takeshi KOBAYASHI  

     
    PAPER-Device technology

      Vol:
    E79-C No:9
      Page(s):
    1264-1268

    A close correlation between the YBa2Cu3Oy film morphology and location of the (100) MgO substrate during growth by excimer laser ablation was obtained. When the susbtrate was placed inside the fringe portion of the laser plume, the spiral shape was most clearly seen on the entire film surface for both the conventional and eclipse ablation methods. When the substrate was placed outside the plume, the spiral growth was less pronounced. On the other hand, when the substrate was placed inside the plume core, marked deformation of the morphology occurred, and the superconducting critical temperature was lowered. This correlation was explained to some extent by the spatial variation of kinetic energy of the flying growth species.

  • Ultrasmall: A Tiny Soft Processor Architecture with Multi-Bit Serial Datapaths for FPGAs

    Shinya TAKAMAEDA-YAMAZAKI  Hiroshi NAKATSUKA  Yuichiro TANAKA  Kenji KISE  

     
    PAPER-Architecture

      Pubricized:
    2015/09/15
      Vol:
    E98-D No:12
      Page(s):
    2150-2158

    Soft processors are widely used in FPGA-based embedded computing systems. For such purposes, efficiency in resource utilization is as important as high performance. This paper proposes Ultrasmall, a new soft processor architecture for FPGAs. Ultrasmall supports a subset of the MIPS-I instruction set architecture and employs an area efficient microarchitecture to reduce the use of FPGA resources. While supporting the original 32-bit ISA, Ultrasmall uses a 2-bit serial ALU for all of its operations. This approach significantly reduces the resource utilization instead of increasing the performance overheads. In addition to these device-independent optimizations, we applied several device-dependent optimizations for Xilinx Spartan-3E FPGAs using 4-input lookup tables (LUTs). Optimizations using specific primitives aggressively reduce the number of occupied slices. Our evaluation result shows that Ultrasmall occupies only 84% of the previous small soft processor. In addition to the utilized resource reduction, Ultrasmall achieves 2.9 times higher performance than the previous approach.