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Radial basis function classifier construction using particle swarm optimisation aided orthogonal forward regression
We develop a particle swarm optimisation (PSO)
aided orthogonal forward regression (OFR) approach for constructing radial basis function (RBF) classifiers with tunable nodes. At each stage of the OFR construction process, the centre vector and diagonal covariance matrix of one RBF node is determined efficiently by minimising the leave-one-out (LOO) misclassification rate (MR) using a PSO algorithm. Compared with the state-of-the-art regularisation assisted orthogonal least square algorithm based on the LOO MR for selecting fixednode RBF classifiers, the proposed PSO aided OFR algorithm for constructing tunable-node RBF classifiers offers significant advantages in terms of better generalisation performance and smaller model size as well as imposes lower computational complexity in classifier construction process. Moreover, the proposed algorithm does not have any hyperparameter that requires costly tuning based on cross validation
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Sparse kernel density estimation technique based on zero-norm constraint
A sparse kernel density estimator is derived based on the zero-norm constraint, in which the zero-norm of the kernel weights is incorporated to enhance model sparsity. The classical Parzen window estimate is adopted as the desired response for density estimation, and an approximate function of the zero-norm is used for achieving mathemtical tractability and algorithmic efficiency. Under the mild condition of the positive definite design matrix, the kernel weights of the proposed density estimator based on the zero-norm approximation can be obtained using the multiplicative nonnegative quadratic programming algorithm. Using the -optimality based selection algorithm as the preprocessing to select a small significant subset design matrix, the proposed zero-norm based approach offers an effective means for constructing very sparse kernel density estimates with excellent generalisation performance
Supernova Constraints on Models of Neutrino Dark Energy
In this paper we use the recently released Type Ia Supernova (SNIa) data to
constrain the interactions between the neutrinos and the dark energy scalar
fields. In the analysis we take the dark energy scalars to be either
Quintessence-like or Phantom-like. Our results show the data mildly favor a
model where the neutrinos couple to a phantom-like dark energy scalar, which
implies the equation of state of the coupled system behaves like Quintom
scenario in the sense of parameter degeneracy. We find future observations like
SNAP are potentially promising to measure the couplings between neutrino and
dark energy.Comment: Typos fixed and references updated. Version pressed in PR
Luminous Infrared Galaxies in the Local Universe
We study the morphology and star formation properties of 159 local luminous
infrared galaxy (LIRG) using multi-color images from Data Release 2 (DR2) of
the Sloan Digital Sky Survey (SDSS). The LIRGs are selected from a
cross-correlation analysis between the IRAS survey and SDSS. They are all
brighter than 15.9 mag in the r-band and below redshift ~ 0.1, and so can be
reliably classified morphologically. We find that the fractions of
interacting/merging and spiral galaxies are ~ 48% and ~ 40% respectively. Our
results complement and confirm the decline (increase) in the fraction of spiral
(interacting/merging) galaxies from z ~1 to z ~ 0.1, as found by Melbourne, Koo
& Le Floc'h (2005). About 75% of spiral galaxies in the local LIRGs are barred,
indicating that bars may play an important role in triggering star formation
rates > 20 M_{sun}/yr in the local universe. Compared with high redshift LIRGs,
local LIRGs have lower specific star formation rates, smaller cold gas
fractions and a narrower range of stellar masses. Local LIRGs appear to be
either merging galaxies forming intermediate mass ellipticals or spiral
galaxies undergoing high star formation activities regulated by bars.Comment: 22 pages, 5 figures, accepted for publication in ApJ, title changed,
typos corrected,major revisions following referee's comments,updated
reference
The Physical Connections Among IR QSOs, PG QSOs and Narrow-Line Seyfert 1 Galaxies
We study the properties of infrared-selected QSOs (IR QSOs),
optically-selected QSOs (PG QSOs) and Narrow Line Seyfert 1 galaxies (NLS1s).
We compare their properties from the infrared to the optical and examine
various correlations among the black hole mass, accretion rate, star formation
rate and optical and infrared luminosities. We find that the infrared excess in
IR QSOs is mostly in the far infrared, and their infrared spectral indices
suggest that the excess emission is from low temperature dust heated by
starbursts rather than AGNs. The infrared excess is therefore a useful
criterion to separate the relative contributions of starbursts and AGNs. We
further find a tight correlation between the star formation rate and the
accretion rate of central AGNs for IR QSOs. The ratio of the star formation
rate and the accretion rate is about several hundred for IR QSOs, but decreases
with the central black hole mass. This shows that the tight correlation between
the stellar mass and the central black hole mass is preserved in massive
starbursts during violent mergers. We suggest that the higher Eddington ratios
of NLS1s and IR QSOs imply that they are in the early stage of evolution toward
classical Seyfert 1's and QSOs, respectively.Comment: 32 pages, 6 figures, accepted by Ap
Overcoming the Circular Problem for \gamma-ray Bursts in Cosmological Global Fitting Analysis
Due to the lack of low redshift long Gamma-Ray Bursts (GRBs), the circular
problem has been a severe obstacle for using GRBs as cosmological candles. In
this paper, we present a new method to deal with such a problem in MCMC global
fitting analysis. Assuming that a certain type of correlations between
different observables exists in a subsample of GRBs, for the parameters
involved in the correlation relation, we treat them as free parameters and
determine them simultaneously with cosmological parameters through MCMC
analysis on GRB data together with other observational data. Then the circular
problem is naturally eliminated in this procedure. We take the Ghirlanda
relation as an example while keeping in mind the debate about its physical
validity. Together with SNe Ia, WMAP and SDSS data, we include 27 GRBs with the
reported Ghirlanda relation in our study, and perform MCMC global fitting. We
consider the CDM model and dynamical dark energy models. In each case,
in addition to the constraints on the relevant cosmological parameters, we
obtain the best fit values as well as the distributions of the correlation
parameters and . We find that the observational data sets other than
GRBs can affect and considerably through their degeneracies with the
cosmological parameters. The results on and for different cosmological
models are in well agreement within range. The best fit value of
in all models being analyzed is with . For ,
we have the best value in the range of with . It is
also noted that the distributions of and are generally broader than the
priors used in many studies in literature. (Abriged)Comment: 9 pages, 2 figures, 2 tables, Accepted for publication in Ap
Monolithic millimeter-wave diode grid frequency multiplier arrays
Monolithic diode frequency multiplier arrays, including barrier-N-N(+) (BNN) doubler, multi-quantum-barrier-varactor (MQBV) tripler, Schottky-quantum-barrier-varactor (SQBV) tripler, and resonant-tunneling-diode (RTD) tripler arrays, have been successfully fabricated with yields between 85 and 99 percent. Frequency doubling and/or tripling have been observed for all the arrays. Output powers of 2.4-2.6 W (eta = 10-18 percent) at 66 GHz with the BNN doubler and 3.8-10 W (eta = 1.7-4 percent) at 99 GHz with the SQBV tripler have been achieved
Entanglement control in one-dimensional random XY spin chain
The entanglement in one-dimensional random XY spin systems where the
impurities of exchange couplings and the external magnetic fields are
considered as random variables is investigated by solving the different
spin-spin correlation functions and the average magnetization per spin. The
entanglement dynamics near particular locations of the system is also studied
when the exchange couplings (or the external magnetic fields) satisfy three
different distributions(the Gaussian distribution, double-Gaussian
distribution, and bimodal distribution). We find that the entanglement can be
controlled by varying the strength of external magnetic field and the different
distributions of impurities. Moreover, the entanglement of some
nearest-neighboring qubits can be increased for certain parameter values of the
three different distributions.Comment: 13 pages, 4 figure
Discovery of new cellulases from the metagenome by a metagenomics-guided strategy.
Background Energy shortage has become a global problem. Production of biofuels from renewable biomass resources is an inevitable trend of sustainable development. Cellulose is the most abundant and renewable resource in nature. Lack of new cellulases with unique properties has become the bottleneck of the efficient utilization of cellulose. Environmental metagenomes are regarded as huge reservoirs for a variety of cellulases. However, new cellulases cannot be obtained easily by functional screening of metagenomic libraries. Results In this work, a metagenomics-guided strategy for obtaining new cellulases from the metagenome was proposed. Metagenomic sequences of DNA extracted from the anaerobic beer lees converting consortium enriched at thermophilic conditions were assembled, and 23 glycoside hydrolase (GH) sequences affiliated with the GH family 5 were identified. Among the 23 GH sequences, three target sequences (designated as cel7482, cel3623 and cel36) showing low identity with those known GHs were chosen as the putative cellulase genes to be functionally expressed in Escherichia coli after PCR cloning. The three cellulases were classified into endo-β-1,4-glucanases by product pattern analysis. The recombinant cellulases were more active at pH 5.5 and within a temperature range of 60–70 °C. Computer-assisted 3D structure modeling indicated that the active residues in the active site of the recombinant cellulases were more similar to each other compared with non-active site residues. The recombinant cel7482 was extremely tolerant to 2 M NaCl, suggesting that cel7482 may be a halotolerant cellulase. Moreover, the recombinant cel7482 was shown to have an ability to resist three ionic liquids (ILs), which are widely used for cellulose pretreatment. Furthermore, active cel7482 was secreted by the twin-arginine translocation (Tat) pathway of Bacillus subtilis 168 into the culture medium, which facilitates the subsequent purification and reduces the formation of inclusion body in the context of overexpression. Conclusions This study demonstrated a simple and efficient method for direct cloning of new cellulase genes from environmental metagenomes. In the future, the metagenomics-guided strategy may be applied to the high-throughput screening of new cellulases from environmental metagenomes.published_or_final_versio
Probing for cosmological parameters with LAMOST measurement
In this paper we study the sensitivity of the Large Sky Area Multi-Object
Fiber Spectroscopic Telescope (LAMOST) project to the determination of
cosmological parameters, employing the Monte Carlo Markov Chains (MCMC) method.
For comparison, we first analyze the constraints on cosmological parameters
from current observational data, including WMAP, SDSS and SN Ia. We then
simulate the 3D matter power spectrum data expected from LAMOST, together with
the simulated CMB data for PLANCK and the SN Ia from 5-year Supernovae Legacy
Survey (SNLS). With the simulated data, we investigate the future improvement
on cosmological parameter constraints, emphasizing the role of LAMOST. Our
results show the potential of LAMOST in probing for the cosmological
parameters, especially in constraining the equation-of-state (EoS) of the dark
energy and the neutrino mass.Comment: 7 pages and 3 figures. Replaced with version accepted for publication
in JCA
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