3,359 research outputs found
A Bayesian framework for functional time series analysis
The paper introduces a general framework for statistical analysis of
functional time series from a Bayesian perspective. The proposed approach,
based on an extension of the popular dynamic linear model to Banach-space
valued observations and states, is very flexible but also easy to implement in
many cases. For many kinds of data, such as continuous functions, we show how
the general theory of stochastic processes provides a convenient tool to
specify priors and transition probabilities of the model. Finally, we show how
standard Markov chain Monte Carlo methods for posterior simulation can be
employed under consistent discretizations of the data
An R Package for Dynamic Linear Models
We describe an R package focused on Bayesian analysis of dynamic linear models. The main features of the package are its flexibility to deal with a variety of constant or time-varying, univariate or multivariate models, and the numerically stable singular value decomposition-based algorithms used for filtering and smoothing. In addition to the examples of "out-of-the-box" use, we illustrate how the package can be used in advanced applications to implement a Gibbs sampler for a user-specified model.
State Space Models in R
We give an overview of some of the software tools available in R, either as built- in functions or contributed packages, for the analysis of state space models. Several illustrative examples are included, covering constant and time-varying models for both univariate and multivariate time series. Maximum likelihood and Bayesian methods to obtain parameter estimates are considered.
Absolute calibration and beam reconstruction of MITO (a ground-based instrument in the millimetric region)
An efficient sky data reconstruction derives from a precise characterization
of the observing instrument. Here we describe the reconstruction of
performances of a single-pixel 4-band photometer installed at MITO (Millimeter
and Infrared Testagrigia Observatory) focal plane. The strategy of differential
sky observations at millimeter wavelengths, by scanning the field of view at
constant elevation wobbling the subreflector, induces a good knowledge of beam
profile and beam-throw amplitude, allowing efficient data recovery. The
problems that arise estimating the detectors throughput by drift scanning on
planets are shown. Atmospheric transmission, monitored by skydip technique, is
considered for deriving final responsivities for the 4 channels using planets
as primary calibrators.Comment: 14 pages, 6 fiugres, accepted for pubblication by New Astronomy (25
March
Peranan pendidikan dalam pembinaan kebudayaan nasional di daerah Jambi
Buku ini ditulis dengan tujuan untuk mengetahui faktor penghambat dan faktor pendukung pengejawantahan kebudayaan nasional yang ditransformasikan melalui pranata keluarga, pranata sekolah, pranata ekonomi , pranata agama, dan pranata politik
An R Package for Dynamic Linear Models
We describe an <b>R</b> package focused on Bayesian analysis of dynamic linear models. The main features of the package are its flexibility to deal with a variety of constant or time-varying, univariate or multivariate models, and the numerically stable singular value decomposition-based algorithms used for filtering and smoothing. In addition to the examples of "out-of-the-box" use, we illustrate how the package can be used in advanced applications to implement a Gibbs sampler for a user-specified model
Physics and modelling of generation and propagation of noise by complex sources in realistic basins
The need to develop more accurate numerical tools for the propagation of noise in underwater environments is driven by the continuous increase of human activity in the sea and coastal areas. Noise has been shown to be dangerous to marine wildlife, and steps should be taken soon to mitigate it. Knowing that the primary sources of noise pollution at sea are marine propellers, one of the problems is assessing how the noise generated interacts with the environment, since up to now, the main focus was the characterization of the acoustic signature in the near field or, alternatively, the propagation of simplified acoustic sources in sea-like domains.
The work conducted in this thesis assesses the modelling of complex acoustic sources and the propagation of acoustic pressure in realistic domains. A propagation model based on the solution of the acoustic wave equation in the time and space domain is implemented and used in conjunction with the Ffowcs Williams and Hawkings (FW-H) to analyze the possible patterns occurring in the underwater environment. Specifically, we analyzed the noise radiated by a marine propeller in a canal, focusing on the effects of the boundaries on the acoustic field and, secondly, the consequence of a rotating body placed underneath a free surface. We defined a new methodology called Full Acoustic Analogy (FAA) to achieve these results. This methodology aims to overcome some intrinsic limitations of the known Acoustic Analogies.
The study presented here attempts to bridge the gap between noise characterization and its propagation by introducing a new methodology for evaluating flow-induced noise in a realistic environment.
The propagation model developed, which used the finite-difference-time-domain method, has been compared against benchmark cases (monopole source propagating in classical waveguides) for which an analytical solution is available, and it provides accurate results of the acoustic field. Furthermore, a second analysis is conducted on two classical waveguides: the Ideal one and the Pekeris one. The solution of the wave equation in time and physical space enables the implementation of different sources, such as dipole and quadrupole; therefore, we analyzed the acoustic response of the Pekeris waveguide. The results show that the propagation of the acoustic pressure is strongly affected by the directivity pattern of the source. This was the first step in evaluating the capabilities of the solution of the acoustic equation in the presence of sources characterized by complex directivity since our ultimate goal is to evaluate the noise emitted by a propeller.
In the second part, the FAA analogy is introduced, and we describe how the acoustic pressure obtained with the FW-H equation is used as a source term in the propagation model.
After the validation of the new proposed methodology in an unbounded homogeneous domain, we investigate the propagation of the linear part of the noise generated by a naval propeller within a canal.
Local maxima and minima of the acoustic fields arise from the interaction between the noise source and the environment; in particular, they derive from the superposition of direct and reflected waves.
Moreover, a rotating body placed underneath a free surface generates a peculiar asymmetry of the acoustic field associated with the interaction between the acoustic waves and the free surface.The need to develop more accurate numerical tools for the propagation of noise in underwater environments is driven by the continuous increase of human activity in the sea and coastal areas. Noise has been shown to be dangerous to marine wildlife, and steps should be taken soon to mitigate it. Knowing that the primary sources of noise pollution at sea are marine propellers, one of the problems is assessing how the noise generated interacts with the environment, since up to now, the main focus was the characterization of the acoustic signature in the near field or, alternatively, the propagation of simplified acoustic sources in sea-like domains.
The work conducted in this thesis assesses the modelling of complex acoustic sources and the propagation of acoustic pressure in realistic domains. A propagation model based on the solution of the acoustic wave equation in the time and space domain is implemented and used in conjunction with the Ffowcs Williams and Hawkings (FW-H) to analyze the possible patterns occurring in the underwater environment. Specifically, we analyzed the noise radiated by a marine propeller in a canal, focusing on the effects of the boundaries on the acoustic field and, secondly, the consequence of a rotating body placed underneath a free surface. We defined a new methodology called Full Acoustic Analogy (FAA) to achieve these results. This methodology aims to overcome some intrinsic limitations of the known Acoustic Analogies.
The study presented here attempts to bridge the gap between noise characterization and its propagation by introducing a new methodology for evaluating flow-induced noise in a realistic environment.
The propagation model developed, which used the finite-difference-time-domain method, has been compared against benchmark cases (monopole source propagating in classical waveguides) for which an analytical solution is available, and it provides accurate results of the acoustic field. Furthermore, a second analysis is conducted on two classical waveguides: the Ideal one and the Pekeris one. The solution of the wave equation in time and physical space enables the implementation of different sources, such as dipole and quadrupole; therefore, we analyzed the acoustic response of the Pekeris waveguide. The results show that the propagation of the acoustic pressure is strongly affected by the directivity pattern of the source. This was the first step in evaluating the capabilities of the solution of the acoustic equation in the presence of sources characterized by complex directivity since our ultimate goal is to evaluate the noise emitted by a propeller.
In the second part, the FAA analogy is introduced, and we describe how the acoustic pressure obtained with the FW-H equation is used as a source term in the propagation model.
After the validation of the new proposed methodology in an unbounded homogeneous domain, we investigate the propagation of the linear part of the noise generated by a naval propeller within a canal.
Local maxima and minima of the acoustic fields arise from the interaction between the noise source and the environment; in particular, they derive from the superposition of direct and reflected waves.
Moreover, a rotating body placed underneath a free surface generates a peculiar asymmetry of the acoustic field associated with the interaction between the acoustic waves and the free surface
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The Mechanism of ER to Cytosol Retrotranslocation of Proteins Targeted to ERAD (ER Associated Degradation)
Retro-translocation from the endoplasmic reticulum (ER) to the cytosol of secretory and membrane proteins takes place on misfolded molecules targeted for proteasomal degradation, in a process called ER associated degradation (ERAD). Because of the difficulties in clearly discriminating the fraction of molecules already retro-translocated from the ones in the ER, we took advantage of the E. coli biotin-ligase (BirA) expressed in the cytosol of mammalian cells, to specifically biotin-label proteins that undergo retro-translocation. The method was validated using four different model proteins, known to undergo retro-translocation upon different conditions: the MHC-1α chain, the non-secretory null-Hong Kong mutant of α1 antitrypsin, the immunoglobulin γH chain and calreticulin. The specific mono-biotinylation of only cytosolically dislocated molecules resulted in a novel quantitative method to determine the extent of retro-translocation.
The method was used to study dislocation of CD4 and BST-2/Tetherin, two membrane proteins targeted to degradation by the HIV-1 protein Vpu. It was found that CD4 retro-translocates with oxidised intra-chain disulphide bridges that only upon proteasomal inhibition accumulates in the cytosol in reduced and de-glycosylated form. Similarly, BST-2/Tetherin is first exposed to the cytosol as a dimeric-oxidised complex, which then becomes de-glycosylated and reduced to monomers. Experiments with the non-secreted NS1 Ig-Îș light chain showed that also this ERAD model protein is retro-translocated with oxidised cysteines. The role of VCP/p97-ATPase in retro-translocation was investigated. In contrast to what previously reported, it was found that it is not required to dislocate ERAD substrates from the ER lumen to the cytosol, while it is required for efficient de-glycosylation and proteasomal degradation of ERAD substrates. The results obtained indicate that complete cysteine reduction and unfolding is not strictly required for retro-translocation, suggesting alternative mechanisms of the ERAD pathway. In addition, the role of VCP/p97-ATPase was found associated to stages downstream of membrane crossing
Transition to a greener fashion:how and why main brands are moving towardsa more sustainable business
The fashion industry has long been identified as a main driver of systemic
environmental damage. Especially for so-called âfast fashionâ giants that operate on a strategic
model based on both overproduction and overconsumption. As environmental concerns become
ever more relevant in public discourse, several key corporate players have taken steps to reduce
their environmental impact and make their supply chains more sustainable.
In order to investigate on this matter, we readapt existing research frameworks to measure the
economic and sustainability performance, and their correlation, of eight-company sample selected
among the great fast-fashion âgiantsâ and evaluate their commitment to sustainability issues
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