93 research outputs found
Government Responses Matter: Predicting Covid-19 cases in US under an empirical Bayesian time series framework
Since the Covid-19 outbreak, researchers have been predicting how the epidemic will evolve, especially the number in each country, through using parametric extrapolations based on the history. In reality, the epidemic progressing in a particular country depends largely on its policy responses and interventions. Since the outbreaks in some countries are earlier than United States, the prediction of US cases can benefit from incorporating the similarity in their trajectories. We propose an empirical Bayesian time series framework to predict US cases using different countries as prior reference. The resultant forecast is based on observed US data and prior information from the reference country while accounting for different population sizes. When Italy is used as prior in the prediction, which the US data resemble the most, the cases in the US will exceed 300,000 by the beginning of April unless strong measures are adopted
Modeling diurnal hormone profiles by hierarchical state space models.
Adrenocorticotropic hormone (ACTH) diurnal patterns contain both smooth circadian rhythms and pulsatile activities. How to evaluate and compare them between different groups is a challenging statistical task. In particular, we are interested in testing 1) whether the smooth ACTH circadian rhythms in chronic fatigue syndrome and fibromyalgia patients differ from those in healthy controls, and 2) whether the patterns of pulsatile activities are different. In this paper, a hierarchical state space model is proposed to extract these signals from noisy observations. The smooth circadian rhythms shared by a group of subjects are modeled by periodic smoothing splines. The subject level pulsatile activities are modeled by autoregressive processes. A functional random effect is adopted at the pair level to account for the matched pair design. Parameters are estimated by maximizing the marginal likelihood. Signals are extracted as posterior means. Computationally efficient Kalman filter algorithms are adopted for implementation. Application of the proposed model reveals that the smooth circadian rhythms are similar in the two groups but the pulsatile activities in patients are weaker than those in the healthy controls
fmixed: A SAS Macro for Smoothing-Spline-Based Functional Mixed Effects Models
In this article we implement the smoothing-spline-based functional mixed effects models (Guo 2002) by a SAS macro by exploiting the connection between mixed effects models and smoothing splines. The macro can handle flexible design matrices and is easy to use. Input parameters and output results are described and explained. A numeric example and a real data example are used for illustration
Local Equilibrium Spin Distribution From Detailed Balance
As the core ingredient for spin polarization, the local equilibrium spin
distribution function is derived from the detailed balance principle. The
kinetic theory for interacting fermionic systems is applied to the
Nambu--Jona-Lasinio model at quark level. Under the semi-classical expansion
with respect to and non-perturbative expansion with respect to ,
the kinetic equations for the vector and axial-vector distribution functions
are derived with collision terms. It is found that, for an initially
unpolarized system, non-zero spin polarization can be generated at the order of
from the coupling between the vector and axial-vector charges. The
local equilibrium spin polarization is derived from the requirement of detailed
balance. It arises from the thermal vorticity and is orthogonal to the particle
momentum.Comment: 13 page
Research on the Innovation of Business Ecosystem Model in China’s 0nline Food Reservation Market at Sharing Economic Era
At the sharing economy era, the online food reservation market has experienced great changes, such as the mobilization of ordering,cooperation of logistics , diversification of revenue stream. The ordering patterns has also changed from network order to improve user experience. At present, online food reservation market has difficulties inquickly dealing with the impacts and challenges bought by external environment due to lack of coordination and sharing mechanisms and competition over cooperation among economic individuals.Based on the theory of business ecosystem, this paper focuses on the impacts and challenges brought by the sharing economic era and takes “Huijiachifan” as a case study and proposes new framework of business ecosystem model in China\u27s online food reservation market
CVRecon: Rethinking 3D Geometric Feature Learning For Neural Reconstruction
Recent advances in neural reconstruction using posed image sequences have
made remarkable progress. However, due to the lack of depth information,
existing volumetric-based techniques simply duplicate 2D image features of the
object surface along the entire camera ray. We contend this duplication
introduces noise in empty and occluded spaces, posing challenges for producing
high-quality 3D geometry. Drawing inspiration from traditional multi-view
stereo methods, we propose an end-to-end 3D neural reconstruction framework
CVRecon, designed to exploit the rich geometric embedding in the cost volumes
to facilitate 3D geometric feature learning. Furthermore, we present
Ray-contextual Compensated Cost Volume (RCCV), a novel 3D geometric feature
representation that encodes view-dependent information with improved integrity
and robustness. Through comprehensive experiments, we demonstrate that our
approach significantly improves the reconstruction quality in various metrics
and recovers clear fine details of the 3D geometries. Our extensive ablation
studies provide insights into the development of effective 3D geometric feature
learning schemes. Project page: https://cvrecon.ziyue.cool
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