587 research outputs found
Comparisons of log-normal mixture and Pareto tails, GB2 or log-normal body of Romania's all cities size distribution
Modeling demographic data has been on the agenda of statisticians for many years. Some of the distributions used are Pareto, reverse Pareto, q-exponential and log-normal models. An approach to this problem is to consider three statistical models: one for the upper tail, one for the middle range, and another for the lower tail. This paper deals with the size distribution of urban and rural agglomerations in Romania for the 1992–2017 period, by comparing the recently introduced three log-normal mixture (3LN), Pareto tails log-normal (PTLN), and threshold double Pareto Generalized Beta of second kind (tdPGB2) models. The tdPGB2 statistical model has the PTLN distribution as a limiting case. The maximum likelihood estimates of the distributions are computed, and goodness-of-fit tests are performed using the Kolmogorov–Smirnov (KS), Cramér–von Mises (CM) and Anderson–Darling (AD) statistics. Also, we use the Vuong and Bayes factor log-likelihood tests. Using both graphical and formal statistical tests, our results rigorously confirm that the 3LN model is statistically equivalent to PTLN and tdPGB2 distributions, the preferred model being the PTLN probability law. Both the PTLN and tdPGB2 distributions have Pareto tails but the 3LN model does not. All the three models prove to be very well suited parameterizations of Romania's city size data
Adaptive estimation in circular functional linear models
We consider the problem of estimating the slope parameter in circular
functional linear regression, where scalar responses Y1,...,Yn are modeled in
dependence of 1-periodic, second order stationary random functions X1,...,Xn.
We consider an orthogonal series estimator of the slope function, by replacing
the first m theoretical coefficients of its development in the trigonometric
basis by adequate estimators. Wepropose a model selection procedure for m in a
set of admissible values, by defining a contrast function minimized by our
estimator and a theoretical penalty function; this first step assumes the
degree of ill posedness to be known. Then we generalize the procedure to a
random set of admissible m's and a random penalty function. The resulting
estimator is completely data driven and reaches automatically what is known to
be the optimal minimax rate of convergence, in term of a general weighted
L2-risk. This means that we provide adaptive estimators of both the slope
function and its derivatives
LPV Modeling of the Atmospheric Flight Dynamics of a Generic Parafoil Return Vehicle
Obtaining models that can be used for flight control is of outmost importance to ensure reliable guidance and navigation of spacecrafts, like a Generic Parafoil Return Vehicle (GPRV). In this paper, we convert an existing, high-fidelity nonlinear model of the atmospheric flight dynamics of a GPRV to a Linear Parameter-Varying (LPV) form that enables high-performance navigation control design. Application of existing systematic conversion methods for such complicated nonlinear models often result in complex LPV representations, which are not suitable for controller synthesis. We apply and compare state-of-the-art conversion techniques on the GPRV model, including learning based approaches, to optimize the complexity and conservatism of the resulting LPV embedding. The results show that we can obtain an LPV embedding that approximates the complex nonlinear dynamics sufficiently well, where the balance between complexity, conservatism and model performance is efficiently chosen
Swallowing Disorders after Oral Cavity and Pharyngolaryngeal Surgery and Role of Imaging
Head and neck squamous cell carcinoma is the sixth most common cancer diagnosed worldwide and the eighth most common cause of cancer death. Malignant tumors of the oral cavity, oropharynx, and larynx can be treated by surgical resection or radiotheraphy with or without chemotheraphy and have a profound impact on quality of life functions, including swallowing. When surgery is the chosen treatment modality, the patient may experience swallowing impairment in the oral and pharyngeal phases of deglutition. A videofluoroscopic study of swallow enables the morphodynamics of the pharyngeal-esophageal tract to be accurately examined in patients with prior surgery. These features allow an accurate tracking of the various phases of swallowing in real time, identifying the presence of functional disorders and of complications during the short- and long-term postoperative recovery. The role of imaging is fundamental for the therapist to plan rehabilitation. In this paper, the authors aim to describe the videofluoroscopic study of swallow protocol and related swallowing impairment findings in consideration of different types of surgery
Engineering Azobenzene Derivatives to Control the Photoisomerization Process
In this work, we show how the structural features of photoactive azobenzene derivatives can influence the photoexcited state behavior and the yield of the trans/cis photoisomerization process. By combining high-resolution transient absorption experiments in the vis-NIR region and quantum chemistry calculations (TDDFT and RASPT2), we address the origin of the transient signals of three poly-substituted push-pull azobenzenes with an increasing strength of the intramolecular interactions stabilizing the planar trans isomer (absence of intramolecular H-bonds, methyl, and traditional H-bond, respectively, for 4-diethyl-4′-nitroazobenzene, Disperse Blue 366, and Disperse Blue 165) and a commercial red dye showing keto-enol tautomerism involving the azo group (Sudan Red G). Our results indicate that the intramolecular H-bonds can act as a “molecular lock” stabilizing the trans isomer and increasing the energy barrier along the photoreactive CNNC torsion coordinate, thus preventing photoisomerization in the Disperse Blue dyes. In contrast, the involvement of the azo group in keto-enol tautomerism can be employed as a strategy to change the nature of the lower excited state and remove the nonproductive symmetric CNN/NNC bending pathway typical of the azo group, thus favoring the productive torsional motion. Taken together, our results can provide guidelines for the structural design of azobenzene-based photoswitches with a tunable excited state behavior
Micro and nano-patterning of single-crystal diamond by swift heavy ion irradiation
This paper presents experimental data and analysis of the structural damage caused by swift-heavy ion irradiation of single-crystal diamond. The patterned buried structural damage is shown to generate, via swelling, a mirror- pattern on the sample surface, which remains largely damage-free. While extensive results are available for light ion implantations, this effect is reported here for the first time in the heavy ion regime,where a completely different range of input parameters (in terms of ion species, energy, stopping power, etc.) is available for customized irradiation. The chosen ion species are Au and Br, in the energy range 10–40 MeV. The observed patterns, as characterized by profilometry and atomic force microscopy, are reported in a series ofmodel experiments,which show swelling patterns ranging from a few nm to above 200 nm. Moreover, a systematic phenomenological modeling is presented, inwhich surface swelling measurements are correlated to buried crystal damage. A comparison ismade with data for light ion implantations, showing good compatibilitywith the proposedmodels. The modeling presented in thiswork can be useful for the design and realization of micropatterned surfaces in single crystal diamond, allowing generating highly customized structures by combining appropriately chosen irradiation parameters and masks
Measurement of shower development and its Moli\`ere radius with a four-plane LumiCal test set-up
A prototype of a luminometer, designed for a future e+e- collider detector,
and consisting at present of a four-plane module, was tested in the CERN PS
accelerator T9 beam. The objective of this beam test was to demonstrate a
multi-plane tungsten/silicon operation, to study the development of the
electromagnetic shower and to compare it with MC simulations. The Moli\`ere
radius has been determined to be 24.0 +/- 0.6 (stat.) +/- 1.5 (syst.) mm using
a parametrization of the shower shape. Very good agreement was found between
data and a detailed Geant4 simulation.Comment: Paper published in Eur. Phys. J., includes 25 figures and 3 Table
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