215 research outputs found
Pressure-induced changes in the magnetic and valence state of EuFe2As2
We present the results of electrical resistivity, ac specific heat, magnetic
susceptibility, X-ray absorption spectroscopy (XAS) and X-ray magnetic circular
dichroism (XMCD) of the ternary iron arsenide EuFe2As2 single crystal under
pressure. Applying pressure leads to a continuous suppression of the
antiferromagnetism associated with Fe moments and the antiferromagnetic
transition temperature becomes zero in the vicinity of a critical pressure Pc
~2.5-2.7 GPa. Pressure-induced re-entrant superconductivity, which is highly
sensitive to the homogeneity of the pressure, only appears in the narrow
pressure region in the vicinity of Pc due to the competition between
superconductivity and the antiferromagnetic ordering of Eu2+ moments. The
antiferromagnetic state of Eu2+ moments changes to the ferromagnetic state
above 6 GPa. We also found that the ferromagnetic order is suppressed with
further increasing pressure, which is connected with a valence change of Eu
ions.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
High-pressure x-ray diffraction of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals
The effect of pressure on the structural stability of icosahedral Zr-Al-Ni-Cu-Ag quasicrystals forming from a Zr65Al7.5Ni10Cu7.5Ag10 metallic glass with a supercooled liquid region of 44 K has been investigated by in situ high-pressure angle-dispersive x-ray powder diffraction at ambient temperature using synchrotron radiation. The icosahedral quasicrystal structure is retained up to the highest hydrostatic pressure used (approximately 28 GPa) and is reversible after decompression. The bulk modulus at zero pressure and its pressure derivative of the icosahedral Zr-Al-Ni-Cu-Ag quasicrystal are 99.10+/-1.26 GPa and 4.25+/-0.16, respectively. The compression behavior of different Bragg peaks is isotropic and the full width at half maximum of each peak remains almost unchanged during compression, indicating no anisotropic elasticity and no defects in the icosahedral Zr-Al-Ni-Cu-Ag quasicrystals induced by pressure
Systems-theoretic Safety Assessment of Robotic Telesurgical Systems
Robotic telesurgical systems are one of the most complex medical
cyber-physical systems on the market, and have been used in over 1.75 million
procedures during the last decade. Despite significant improvements in design
of robotic surgical systems through the years, there have been ongoing
occurrences of safety incidents during procedures that negatively impact
patients. This paper presents an approach for systems-theoretic safety
assessment of robotic telesurgical systems using software-implemented
fault-injection. We used a systemstheoretic hazard analysis technique (STPA) to
identify the potential safety hazard scenarios and their contributing causes in
RAVEN II robot, an open-source robotic surgical platform. We integrated the
robot control software with a softwareimplemented fault-injection engine which
measures the resilience of the system to the identified safety hazard scenarios
by automatically inserting faults into different parts of the robot control
software. Representative hazard scenarios from real robotic surgery incidents
reported to the U.S. Food and Drug Administration (FDA) MAUDE database were
used to demonstrate the feasibility of the proposed approach for safety-based
design of robotic telesurgical systems.Comment: Revise based on reviewers feedback. To appear in the the
International Conference on Computer Safety, Reliability, and Security
(SAFECOMP) 201
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