9,768 research outputs found
Primordial Lepton Family Asymmtries in Seesaw Model
In leptogenesis scenario, the decays of heavy Majorana neutrinos generate
lepton family asymmetries, and . They are sensitive to
CP violating phases in seesaw models. The time evolution of the lepton family
asymmetries are derived by solving Boltzmann equations. By taking a minimal
seesaw model, we show how each family asymmetry varies with a CP violating
phase. For instance, we find the case that the lepton asymmetry is dominated by
or depending on the choice of the CP violating phase. We
also find the case that the signs of lepton family asymmetries and
are opposite each other. Their absolute values can be larger than
the total lepton asymmetry and the baryon asymmetry may result from the
cancellation of the lepton family asymmetries.Comment: 26 pages, 8 figures, ptp.styl
Imaging crystal orientations in multicrystalline silicon wafers via photoluminescence
We present a method for monitoring crystal orientations in chemically polished and unpassivated multicrystalline silicon wafers based on band-to-band photoluminescence imaging. The photoluminescence intensity from such wafers is dominated by surface recombination, which is crystal orientation dependent. We demonstrate that a strong correlation exists between the surface energy of different grain orientations, which are modelled based on first principles, and their corresponding photoluminescence intensity. This method may be useful in monitoring mixes of crystal orientations in multicrystalline or so-called “cast monocrystalline” wafers.H. C. Sio acknowledges scholarship support from
BT Imaging and the Australian Solar Institute, and the
Centre for Advanced Microscopy at ANU for SEM access.
This work has been supported by the Australian Research
Council
High efficiency single quantum well graded-index separate-confinement heterostructure lasers fabricated with MeV oxygen ion implantation
Single quantum well AlGaAs/GaAs graded-index separate-confinement heterostructure lasers have been fabricated using MeV oxygen ion implantation plus optimized subsequent thermal annealing. A high differential quantum efficiency of 85% has been obtained in a 360-µm-long and 10-µm-wide stripe geometry device. The results have also demonstrated that excellent electrical isolation (breakdown voltage of over 30 V) and low threshold currents (22 mA) can be obtained with MeV oxygen ion isolation. It is suggested that oxygen ion implantation induced selective carrier compensation and compositional disordering in the quantum well region as well as radiation-induced lattice disordering in AlxGa1–xAs/GaAs may be mostly responsible for the buried layer modification in this fabrication process
Results and Lessons from a Decade of Terra MODIS On-Orbit Spectral Characterization
Since its launch in December 1999, the NASA EOS Terra MODIS has successfully operated for more than a decade. MODIS makes observations in 36 spectral bands from visible (VIS) to longwave infrared (LWIR) and at three nadir spatial resolutions: 250m (2 bands), 500m (5 bands), and 1km (29 bands). In addition to its on-board calibrators designed for the radiometric calibration, MODIS was built with a unique device, called the spectro-radiometric calibration assembly (SRCA). It can be configured in three different modes: radiometric, spatial, and spectral. When it is operated in the spectral modes, the SRCA can monitor changes in Sensor spectral performance for the VIS and near-infrared (NIR) spectral bands. For more than 10 years, the SRCA operation has continued to provide valuable information for MODIS on-orbit spectral performance. This paper briefly describes SRCA on-orbit operation and calibration activities; it presents decade-long spectral characterization results for Terra MODIS VIS and NIR spectral bands in terms of chances in their center wavelengths (CW) and bandwidths (BW). It is shown that the SRCA on-orbit wavelength calibration capability remains satisfactory. For most spectral bands, the changes in CW and BW are less than 0.5 and 1 nm, respectively. Results and lessons from Terra MODIS on-orbit spectral characterization have and will continue to benefit its successor, Aqua MODIS, and other future missions
Correlated Differential Privacy: Feature Selection in Machine Learning
© 2005-2012 IEEE. Privacy preserving in machine learning is a crucial issue in industry informatics since data used for training in industries usually contain sensitive information. Existing differentially private machine learning algorithms have not considered the impact of data correlation, which may lead to more privacy leakage than expected in industrial applications. For example, data collected for traffic monitoring may contain some correlated records due to temporal correlation or user correlation. To fill this gap, in this article, we propose a correlation reduction scheme with differentially private feature selection considering the issue of privacy loss when data have correlation in machine learning tasks. The proposed scheme involves five steps with the goal of managing the extent of data correlation, preserving the privacy, and supporting accuracy in the prediction results. In this way, the impact of data correlation is relieved with the proposed feature selection scheme, and moreover the privacy issue of data correlation in learning is guaranteed. The proposed method can be widely used in machine learning algorithms, which provide services in industrial areas. Experiments show that the proposed scheme can produce better prediction results with machine learning tasks and fewer mean square errors for data queries compared to existing schemes
The Dichotomy between Nodal and Antinodal Quasiparticles in Underdoped (LaSr)CuO Superconductors
High resolution angle-resolved photoemission measurements on underdoped
(LaSr)CuO system show that, at energies below 70 meV, the
quasiparticle peak is well defined around the (/2,/2) nodal region
and disappears rather abruptly when the momentum is changed from the nodal
point to the (,0) antinodal point along the underlying ``Fermi surface''.
It indicates that there is an extra low energy scattering mechanism acting upon
the antinodal quasiparticles. We propose that this mechanism is the scattering
of quasiparticles across the nearly parallel segments of the Fermi surface near
the antinodes.Comment: to appear in Phys. Rev. Let
Experimental verification of a Jarzynski-related information-theoretic equality using a single trapped ion
Most non-equilibrium processes in thermodynamics are quantified only by
inequalities, however the Jarzynski relation presents a remarkably simple and
general equality relating non-equilibrium quantities with the equilibrium free
energy, and this equality holds in both classical and quantum regimes. We
report a single-spin test and confirmation of the Jarzynski relation in quantum
regime using a single ultracold ion trapped in a harmonic
potential, based on a general information-theoretic equality for a temporal
evolution of the system sandwiched between two projective measurements. By
considering both initially pure and mixed states, respectively, we verify, in
an exact and fundamental fashion, the non-equilibrium quantum thermodynamics
relevant to the mutual information and Jarzynski equality.Comment: 2 figure
Multiple Bosonic Mode Coupling in Electron Self-Energy of (La_2-xSr_x)CuO_4
High resolution angle-resolved photoemission spectroscopy data along the
(0,0)-(,) nodal direction with significantly improved statistics
reveal fine structure in the electron self-energy of the underdoped
(LaSr)CuO samples in the normal state. Fine structure at
energies of (4046) meV and (5863)meV, and possible fine structure
at energies of (2329)meV and (7585)meV, have been identified. These
observations indicate that, in LSCO, more than one bosonic modes are involved
in the coupling with electrons.Comment: 4 pages, 3 figures, Fig. 2 update
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