22,858 research outputs found
Oriented gap opening in the magnetically ordered state of Iron-pnicitides: an impact of intrinsic unit cell doubling on the square lattice by atoms
We show that the complicated band reconstruction near Fermi surfaces in the
magnetically ordered state of iron-pnictides observed by angle-resolved
photoemission spectroscopies (ARPES) can be understood in a meanfield level if
the \emph{intrinsic unit cell doubling} due to As atoms is properly considered
as shown in the recently constructed S microscopic effective model. The
(0,) or (,0) col-linear antiferromagnetic (C-AFM) order does not open
gaps between two points at Fermi surfaces linked by the ordered wave vector but
forces a band reconstruction involving four points in unfolded Brillouin zone
(BZ) and gives rise to small pockets or hot spots. The S symmetry naturally
chooses a staggered orbital order over a ferro-orbital order to coexist with
the C-AFM order. These results strongly suggest that the kinematics based on
the S symmetry captures the essential low energy physics of iron-based
superconductors.Comment: 5 figures, 5 page
The Distribution of Satellites Around Central Galaxies in a Cosmological Hydrodynamical Simulation
Observations have shown that the spatial distribution of satellite galaxies
is not random, but rather is aligned with the major axes of central galaxies
(CGs). The strength of the alignment is dependent on the properties of both the
satellites and centrals. Theoretical studies using dissipationless N-body
simulations are limited by their inability to directly predict the shape of
CGs. Using hydrodynamical simulations including gas cooling, star formation,
and feedback, we carry out a study of galaxy alignment and its dependence on
the galaxy properties predicted directly from the simulations.We found that the
observed alignment signal is well produced, as is the color dependence: red
satellites and red centrals both show stronger alignments than their blue
counterparts. The reason for the stronger alignment of red satellites is that
most of them stay in the inner region of the dark matter halo where the shape
of the CG better traces the dark matter distribution. The dependence of
alignment on the color of CGs arises from the halo mass dependence, since the
alignment between the shape of the central stellar component and the inner halo
increases with halo mass. We also find that the alignment of satellites is most
strongly dependent on their metallicity, suggesting that the metallicity of
satellites, rather than color, is a better tracer of galaxy alignment on small
scales. This could be tested in future observational studies.Comment: ApJ Letter, accepted. Four figures, no table. The resolution of Fig 1
was downgraded due to the limitation of file size. Updated to match the
version in pres
Random matrices with external source and KP functions
In this paper we prove that the partition function in the random matrix model
with external source is a KP function.Comment: 12 pages, title change
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Research on VCSEL interference analysis and elimination method
Laser methane gas sensors have been increasingly accepted in coal mine safety monitoring. Most laser spectroscopic methane gas sensors are based in BFB lasers at around 1650nm. However, they suffer from high power consumption and high cost due to temperature control is required for laser diode operation at constant temperature. VCSEL lasers have offered low operation current and low power consumption when operating at non-TEC mode. However, it is found that the interference noise is critical for laser methane detection. This paper report typical results of the laser diode ripple characterization method and methods of noise reduction methods are discussed
In vivo optical-resolution photoacoustic computed tomography with compressed sensing
Optical-resolution photoacoustic microscopy is becoming a powerful research tool for studying microcirculation in vivo. Moreover, ultrasonic-array-based optical-resolution photoacoustic computed tomography (OR-PACT), providing comparable resolution at an improved speed, has opened up new opportunities for studying microvascular dynamics. In this Letter, we have developed a compressed sensing with partially known support (CS-PKS) photoacoustic reconstruction strategy for OR-PACT. Compared with conventional backprojection reconstruction, the CS-PKS strategy was shown to produce high-quality in vivo OR-PACT images with threefold less measurement data, which can be leveraged to improve the data acquisition speed and costs of OR-PACT systems
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High Sensitivity Hot-wire based Wind Velocity Sensor using Co-doped Fiber and Fiber Bragg Grating for use in mining applications
In this paper, a mathematical model of the temperature distribution in a fiber-optic version of the familiar 'hot-wire' wind velocity sensor has been established and a practical sensor device realized and investigated for use in coal mining applications. The relationship between the dynamic measurement range, the sensitivity, the sensor probe surface heat transfer coefficient and the wind speed (in the region where the sensor probe is located) has been investigated. The veracity of the predicted performance of the fiber-optic hot-wire mathematical model has then been verified by experiment. The sensitivity of the sensor probe to wind velocity was measured across several wind velocity ranges to be ∼1500pm per unit m/s wind velocity (in the range of 0 - 0.5 m/s), ∼330pm per unit m/s in the range 0.5 - 2 m/s and ∼50pm per unit m/s in the range of 2.0 - 4.5 m/s
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