9,949 research outputs found
Estimation and model selection in generalized additive partial linear models for correlated data with diverging number of covariates
We propose generalized additive partial linear models for complex data which
allow one to capture nonlinear patterns of some covariates, in the presence of
linear components. The proposed method improves estimation efficiency and
increases statistical power for correlated data through incorporating the
correlation information. A unique feature of the proposed method is its
capability of handling model selection in cases where it is difficult to
specify the likelihood function. We derive the quadratic inference
function-based estimators for the linear coefficients and the nonparametric
functions when the dimension of covariates diverges, and establish asymptotic
normality for the linear coefficient estimators and the rates of convergence
for the nonparametric functions estimators for both finite and high-dimensional
cases. The proposed method and theoretical development are quite challenging
since the numbers of linear covariates and nonlinear components both increase
as the sample size increases. We also propose a doubly penalized procedure for
variable selection which can simultaneously identify nonzero linear and
nonparametric components, and which has an asymptotic oracle property.
Extensive Monte Carlo studies have been conducted and show that the proposed
procedure works effectively even with moderate sample sizes. A pharmacokinetics
study on renal cancer data is illustrated using the proposed method.Comment: Published in at http://dx.doi.org/10.1214/13-AOS1194 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Quantum computation in decoherence-free subspace with superconducting devices
We propose a scheme to implement quantum computation in decoherence-free
subspace with superconducting devices inside a cavity by unconventional
geometric manipulation. Universal single-qubit gates in encoded qubit can be
achieved with cavity assisted interaction. A measurement-based two-qubit
Controlled-Not gate is produced with parity measurements assisted by an
auxiliary superconducting device and followed by prescribed single-qubit gates.
The measurement of currents on two parallel devices can realize a projective
measurement, which is equivalent to the parity measurement on the involved
devices.Comment: v2: thoroughly rewritten version with title and motivation changed;
v3: published version with detail dirivation
Shallow landslides modeling using a particle finite element model with emphasis on landslide evolution
Abstract. Numerical modelling is a powerful tool to study the mechanism of landslides and constructs the foundation of many physically-based assessment methods applied to natural hazards. Usually, numerical analyses of landslides are carried out on the failure mechanism and on the propagation process separately. With the advantage of dealing with large deformation problems, the particle finite element method (PFEM), that is the particle extension of the traditional FEM, has the capability of simulating the entire evolution of the landslide from the generation to the deposition phase. To figure out the difference between a unified PFEM simulation and the usually adopted approaches that separate failure mechanism (static analysis) and run-out analysis (dynamic analysis), we implement a PFEM code that is applied first to a simple homogeneous slope model. Numerical results reveal that under the so-called critical condition the landslide comes to a stop with a slight modification of the original profile, while its profile is drastically changed if strength reduction is further applied. To test the capability of our model, we choose the 2013 Cà Mengoni landslide, northern Apennines, Italy, as a case study, since it behaved as if it were formed by homogeneous material. In virtue of the back-analysis of the run-out distance that we perform by using different material strength parameters, we show that the PFEM model is able to capture the variation of the observed landslide profile, and contributes to the understanding of the dynamics of the whole sliding process
Associations Between General and Central Obesity and Hypertension Among Children: The Childhood Obesity Study in China Mega-Cities
In this study, we examined the associations of general and central obesity and hypertension among Chinese children. Data was collected from 1626 children aged 7-16 years and their parents in four mega-cities across China. Mixed effect models examined associations of general and central obesity with hypertension, and between body mass index (BMI), waist circumference (WC), waist-To-height ratio (WHtR), systolic blood pressure (SBP) and diastolic blood pressure (DBP). The prevalence of general obesity, central obesity, and hypertension among the children was 11.1%, 19.7%, and 9.0%, respectively. More boys had general and central obesity than girls (15.2% vs. 6.9%; 27.4% vs. 11.7%, respectively; both P \u3c 0.0001). Sex difference in hypertension rate was not statistically significant (9.3% in boys vs. 8.8% in girls, P = 0.7341). Both SBP and DBP were positively associated with BMI, WC, and WHtR, regardless of sex and region. General obesity (OR = 5.94, 95% confidence interval [CI]: 3.69-9.55) and central obesity (OR = 3.45, 95% CI: 2.27-5.23) were strongly associated with hypertension. The prevalence of general obesity, central obesity, and hypertension was high among Chinese children in the four mega-cities across China. Children\u27s BMI, WC, and WHtR were positively associated with their SBP and DBP. Obese children were 3-6 times more likely to have hypertension
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Multistaged discharge constructing heterostructure with enhanced solid-solution behavior for long-life lithium-oxygen batteries.
Inferior charge transport in insulating and bulk discharge products is one of the main factors resulting in poor cycling stability of lithium-oxygen batteries with high overpotential and large capacity decay. Here we report a two-step oxygen reduction approach by pre-depositing a potassium carbonate layer on the cathode surface in a potassium-oxygen battery to direct the growth of defective film-like discharge products in the successive cycling of lithium-oxygen batteries. The formation of defective film with improved charge transport and large contact area with a catalyst plays a critical role in the facile decomposition of discharge products and the sustained stability of the battery. Multistaged discharge constructing lithium peroxide-based heterostructure with band discontinuities and a relatively low lithium diffusion barrier may be responsible for the growth of defective film-like discharge products. This strategy offers a promising route for future development of cathode catalysts that can be used to extend the cycling life of lithium-oxygen batteries
Scheme for remote implementation of partially unknown quantum operation of two qubits in cavity QED
By constructing the recovery operations of the protocol of remote
implementation of partially unknown quantum operation of two qubits [An Min
Wang: PRA, \textbf{74}, 032317(2006)], we present a scheme to implement it in
cavity QED. Long-lived Rydberg atoms are used as qubits, and the interaction
between the atoms and the field of cavity is a nonresonant one. Finally, we
analyze the experimental feasibility of this scheme.Comment: 7 pages, 2 figure
Topological quantum memory interfacing atomic and superconducting qubits
We propose a scheme to manipulate a topological spin qubit which is realized
with cold atoms in a one-dimensional optical lattice. In particular, by
introducing a quantum opto-electro-mechanical interface, we are able to first
transfer a superconducting qubit state to an atomic qubit state and then to
store it into the topological spin qubit. In this way, an efficient topological
quantum memory could be constructed for the superconducting qubit. Therefore,
we can consolidate the advantages of both the noise resistance of the
topological qubits and the scalability of the superconducting qubits in this
hybrid architecture.Comment: v2: Accepted for publication in Science China-Physics, Mechanics &
Astronom
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