11,647 research outputs found
VHE gamma ray absorption by galactic interstellar radiation field
Adopting a recent calculation of the Galactic interstellar radiation field,
we calculate the attenuation of the very high energy gamma rays from the
Galactic sources. The infra-red radiation background near the Galactic Center
is very intense due to the new calculation and our result shows that a cutoff
of high energy gamma ray spectrum begins at about 20 TeV and reaches about 10%
for 50 TeV gamma rays.Comment: 6 pages, 1 figure, figure is changed, conclusion not change
Suggestions for solution space exploration in the early stage of architectural design based on a literature review
Early design decisions have higher potential to influence building performance compared with the decisions made at later design stages. Performance simulation and optimization algorithms have been integrated to assist early design in reducing carbon emissions, improving indoor thermal comfort, etc. However, early decision making within a limited time frame is still challenging due to the large number of design options, the lack of decision-making guidance, and the trade-offs among various requirements. Selecting appropriate methods to explore design space is the key to find an ideal solution. This paper reviewed the challenges and identified the key questions to access the ability of existing decision-making methods to cope with different challenges. It is concluded that the interactive exploration of design space could be more effective and efficient by (1) combining the surrogate models and the automated optimization algorithms to improve the efficiency of the building performance calculation and the optimal design space position; and by (2) extending the optimal design space to increase the solution diversity, and (3) filtering the near optimal design space with consideration of the stakeholders\u27 preferences and values. Further integration of tools for building performance simulation, diversity description and decision-making guidance is needed to support the decision -making process
Multi-Level Cross Residual Network for Lung Nodule Classification.
Computer-aided algorithm plays an important role in disease diagnosis through medical images. As one of the major cancers, lung cancer is commonly detected by computer tomography. To increase the survival rate of lung cancer patients, an early-stage diagnosis is necessary. In this paper, we propose a new structure, multi-level cross residual convolutional neural network (ML-xResNet), to classify the different types of lung nodule malignancies. ML-xResNet is constructed by three-level parallel ResNets with different convolution kernel sizes to extract multi-scale features of the inputs. Moreover, the residuals are connected not only with the current level but also with other levels in a crossover manner. To illustrate the performance of ML-xResNet, we apply the model to process ternary classification (benign, indeterminate, and malignant lung nodules) and binary classification (benign and malignant lung nodules) of lung nodules, respectively. Based on the experiment results, the proposed ML-xResNet achieves the best results of 85.88% accuracy for ternary classification and 92.19% accuracy for binary classification, without any additional handcrafted preprocessing algorithm
Muon anomalous magnetic moment and lepton flavor violation in MSSM
We give a thorough analysis of the correlation between the muon anomalous
magnetic moment and the radiative lepton flavor violating (LFV) processes
within the minimal supersymmetric standard model. We find that in the case when
the slepton mass eigenstates are nearly degenerate, , coming from
SUSY contributions, hardly depends on the lepton flavor mixing and, thus, there
is no direct relation between and the LFV processes. On the
contrary, if the first two generations' sleptons are much heavier than the 3rd
one, i.e., in the effective SUSY scenario, the two quantities are closely
related. In the latter scenario, the SUSY parameter space to account for the
experimental is quite different from the case of no lepton
flavor mixing. Especially, the Higgsino mass parameter can be either
positive or negative.Comment: 22 pages, 9 figures; Some discussions are modifie
Split Two-Higgs-Doublet Model and Neutrino Condensation
We split the two-Higgs-doublet model by assuming very different vevs for the
two doublets: the vev is at weak scale (174 GeV) for the doublet \Phi_1 and at
neutrino-mass scale (10^{-2} \sim 10^{-3} eV) for the doublet \Phi_2. \Phi_1 is
responsible for giving masses to all fermions except neutrinos; while \Phi_2 is
responsible for giving neutrino masses through its tiny vev without introducing
see-saw mechanism. Among the predicted five physical scalars H, h, A^0 and
H^{\pm}, the CP-even scalar h is as light as 10^{-2} \sim 10^{-3}eV while
others are at weak scale. We identify h as the cosmic dark energy field and the
other CP-even scalar H as the Standard Model Higgs boson; while the CP-odd A^0
and the charged H^{\pm} are the exotic scalars to be discovered at future
colliders. Also we demonstrate a possible dynamical origin for the doublet
\Phi_2 from neutrino condensation caused by some unknown dynamics.Comment: version in Europhys. Lett. (discussions added
Full calculation of clumpiness boost factors for antimatter cosmic rays in the light of Lambda-CDM N-body simulation results
Anti-proton and positron Galactic cosmic ray spectra are among the key
targets for indirect detection of dark matter. The boost factors, corresponding
to an enhancement of the signal and linked to the clumpiness properties of the
dark matter distribution, have been taken as high as thousands in the past. The
dramatic impact of these boost factors for indirect detection of antiparticles,
for instance with the PAMELA satellite or the coming AMS-02 experiment, asks
for their detailed calculation. We take into account the results of high
resolution N-body dark matter simulations to calculate the most likely energy
dependent boost factors linked to the cosmic ray propagation properties, for
anti-protons and positrons. Starting from the mass and space distributions of
sub-halos, the anti-proton and positron propagators are used to calculate the
mean value and the variance of the boost factor for the primary fluxes. We take
advantage of the statistical method introduced in Lavalle et al. (2007) and
cross-check the results with Monte Carlo computations. By spanning some extreme
configurations of sub-halo and propagation properties, we find that the average
contribution of the clumps is negligible compared to that of the smooth dark
matter component. Sub-halos do not lead to enhancement of the signals, unless
they are taken with some extreme (unexpected) properties. This result is
independent of the nature of the self-annihilating dark matter candidate
considered, and provides precise estimates of the theoretical and the
statistical uncertainties of the antimatter flux from dark matter
substructures. Spectral distortions can still be expected in antimatter flux
measurements, but scenarios invoking large and even mild clumpiness boost
factors are strongly disfavoured by our analysis.Comment: Final version, matching the published one. 32 pages, 12 figure
CP Asymmetry in Charged Higgs Decays in MSSM
We discuss and compare the charge-parity (CP) asymmetry in the charged Higgs
boson decays H -> \bar{u}_i d_j for the second and third generation quarks in
the minimal supersymmetric standard model. As part of the analysis, we derive
some general analytical formulas for the imaginary parts of two-point and
three-point scalar one-loop integrals and use them for calculating vectorial
and tensorial type integrals needed for the problem under consideration. We
find that, even though each decay mode has a potential to yield a CP asymmetry
larger than 10%, further analysis based on the number of required charged Higgs
events at colliders favors the \bar{t}b, \bar{c}b, and \bar{c}s channels, whose
asymmetry could reach 10-15% in certain parts of the parameter space.Comment: 25 pages, 9 figures. Discussion about charged Higgs observability
added, typos corrected, accepted for publication in PR
Ages and Masses of 0.64 million Red Giant Branch stars from the LAMOST Galactic Spectroscopic Survey
We present a catalog of stellar age and mass estimates for a sample of
640\,986 red giant branch (RGB) stars of the Galactic disk from the LAMOST
Galactic Spectroscopic Survey (DR4). The RGB stars are distinguished from the
red clump stars utilizing period spacing derived from the spectra with a
machine learning method based on kernel principal component analysis (KPCA).
Cross-validation suggests our method is capable of distinguishing RC from RGB
stars with only 2 per cent contamination rate for stars with signal-to-noise
ratio (SNR) higher than 50. The age and mass of these RGB stars are determined
from their LAMOST spectra with KPCA method by taking the LAMOST -
giant stars having asteroseismic parameters and the LAMOST-TGAS sub-giant stars
based on isochrones as training sets. Examinations suggest that the age and
mass estimates of our RGB sample stars with SNR 30 have a median error of
30 per cent and 10 per cent, respectively. Stellar ages are found to exhibit
positive vertical and negative radial gradients across the disk, and the age
structure of the disk is strongly flared across the whole disk of
\,kpc. The data set demonstrates good correlations among stellar age,
[Fe/H] and [/Fe]. There are two separate sequences in the [Fe/H] --
[/Fe] plane: a high-- sequence with stars older than
\,8\,Gyr and a low-- sequence composed of stars with ages
covering the whole range of possible ages of stars. We also examine relations
between age and kinematic parameters derived from the Gaia DR2 parallax and
proper motions. Both the median value and dispersion of the orbital
eccentricity are found to increase with age. The vertical angular momentum is
found to fairly smoothly decrease with age from 2 to 12\,Gyr, with a rate of
about 50\,kpc\,km\,s\,Gyr. A full table of the catalog is
public available online.Comment: 16 pages, 22 figures,accepted by MNRA
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