Availability of systems with partially observable failures

The availability is determined for the following kind of system. When the system is operational (up), it can fail in either one of two modes. However, the system operator does not always diagnose the failure mode correctly. Given that one failure mode has occurred, the authors correctly diagnose the failure mode with a given probability η and misdiagnose it with probability 1-η, where η may vary with failure mode. The problem is modeled by a partially observable Markov process. Numerical results indicate that a high probability of misdiagnosis produces appreciably high system-downtime     

Relatively heavy Higgs boson in more generic gauge mediation

We discuss gauge mediation models where the doublet messengers and Higgs doublets are allowed to mix through a “charged” coupling. The charged coupling replaces messenger parity as a means of suppressing flavor changing neutral currents without introducing any unwanted CP violation. As a result of this mixing between the Higgs doublets and the messengers, relatively large A-terms are generated at the messenger scale. These large A-terms produce a distinct weak scale mass spectrum. Particularly, we show that the lightest Higgs boson mass is enhanced and can be as heavy as 125 GeV for a gluino mass as light as 2 TeV. We also show that the stops are heavier than that predicted by conventional gauge mediation models. It is also shown that these models have a peculiar slepton mass spectrum.     

16.7-fA/cell tunnel-leakage-suppressed 16-Mb SRAM for handling cosmic-ray-induced multierrors

Tunnel-leakage currents become the dominant form of leakage as MOS technology advances. An electric-field-relaxation scheme that suppresses these currents is described. Cosmic-ray-induced multierrors have now become a serious problem at sea level. An alternate error checking and correction architecture for the handling of such errors is also described, along with the application of both schemes in an ultralow-power 16-Mb SRAM. A test chip fabricated by using 0.13-/spl mu/m CMOS technology showed per-cell standby-current values of 16.7 fA at 25/spl deg/C and 101.7 fA at 90/spl deg/C. The chip provided a 99.5% reduction in soft errors under accelerated neutron-exposure testing.     

Optical circuits for equalizing group delay dispersion of opticalfibers

Optical circuits are synthesized for equalizing the group delay dispersion of single-mode fibers. The transfer function of the equalizing circuits are given by Chebyshev polynomials of the second kind. The various realization methods for the group delay equalizer are shown, including periodic structures using birefringent crystals, birefringent fibers, and Mach-Zehnder interferometric planar optical circuits. An optical equalizer employing TiO₂ birefringent crystals was fabricated and evaluated by using an optical network analyzer, which operates by making modulation-envelope phase and amplitude measurements while scanning the optical carrier frequency. The measured optical equalizer characteristics show excellent agreement with the simulation analysis. The effectiveness of the equalizer for substantial reduction of the dispersion penalty for a 10 Gb/s signal transmitted over 30 km of normal dispersion fiber was demonstrated. The periodicity of the equalizer results in periodic dispersion-free bands, and hence, the equalizer is suitable for use in future multichannel FDM systems     

Rapid, Precise, and Stable Control of Optical Frequency for SG-DBR LD Using Quartz Etalon

This paper presents rapid, precise, and stable control of optical frequency for sampled-grating distributed Bragg reflector (SG-DBR) laser diode (LD) using a Z-cut quartz etalon supported at the middle point. The optical frequency of SG-DBR LD was controlled by the mode-hop-free three-electrode control method. As a result, stable mode operation and wide continuous tuning range without mode hopping have been realized. A 0.2-ms optical frequency tuning speed with a 4.35-THz tuning range and a 130-MHz control error of the optical frequency was demonstrated. A 1.1-MHz Allan deviation was reached at an integration time of 12 times 10³ s.     

Conformal gauge mediation

We propose a one-parameter theory for gauge mediation of supersymmetry (SUSY) breaking. The spectrum of SUSY particles such as squarks and sleptons in the SUSY standard-model and the dynamics of SUSY-breaking sector are, in principle, determined only by one parameter in the theory, that is, the mass of messengers. Above the messenger threshold all gauge coupling and Yukawa coupling constants in the SUSY-breaking sector are on the infrared fixed point. We find that the present theory may predict a split spectrum of the standard-model SUSY particles, mgaugino<msfermion$m_{\mathrm{gaugino}}<m_{\mathrm{sfermion}}$, where mgaugino$m_{\mathrm{gaugino}}$ and msfermion$m_{\mathrm{sfermion}}$ are SUSY-breaking masses for gauginos and squarks/sleptons, respectively.     

Characterization of a Water-Dispersed Biodegradable Polyurethane-Silk Composite Sponge Using 13C Solid-State Nuclear Magnetic Resonance as Coating Material for Silk Vascular Grafts with Small Diameters

Recently, Bombyx mori silk fibroin (SF) has been shown to be a suitable material for vascular prostheses for small arteries. In this study, we developed a softer SF graft by coating water-dispersed biodegradable polyurethane (PU) based on polycaprolactone and an SF composite sponge on the knitted SF vascular graft. Three kinds of ¹³C solid-state nuclear magnetic resonance (NMR), namely carbon-13 (¹³C) cross-polarization/magic angle spinning (MAS), ¹³C dipolar decoupled MAS, and ¹³C refocused insensitive nuclei enhanced by polarization transfer (r-INEPT) NMR, were used to characterize the PU-SF coating sponge. Especially the ¹³C r-INEPT NMR spectrum of water-dispersed biodegradable PU showed that both main components of the non-crystalline domain of PU and amorphous domain of SF were highly mobile in the hydrated state. Then, the small-diameter SF artificial vascular grafts coated with this sponge were evaluated through implantation experiments with rats. The implanted PU-SF-coated SF grafts showed a high patency rate. It was confirmed that the inside of the SF grafts was covered with vascular endothelial cells 4 weeks after implantation. These results showed that the water-dispersed biodegradable PU-SF-coated SF graft created in this study could be a strong candidate for small-diameter artificial vascular graft.