87799 research outputs found
Sort by
Control point modifications that preserve the Pythagorean–hodograph nature of planar quintic curves
Although planar Pythagorean–hodograph (PH) curves are compatible with the standard Bernstein–Bézier representations, freely modifying the control points will compromise their PH nature. The present study focuses on identifying control point displacements that ensure a given planar PH curve remains a PH curve. In particular, for planar quintic PH curves r(t), t∈[0,1] it is shown that finitely-many simultaneous displacements of two control points yield modified quintic PH curves, identified as the solutions of quadratic and cubic equations. As a more practical approach, modification of PH quintics in canonical form with r(0)=0 and r(1)=1 by the displacement of a single interior control point is considered, with the remaining interior control points being used to minimize a measure of deviation from the original PH quintic. As illustrated by several examples, this approach provides an efficient and intuitive means of effecting reasonable shape modifications within the space of planar quintic PH curves
Behavioral Dynamic Portfolio Selection via Epsilon-Contaminations
We consider a dynamic portfolio selection problem in a finite horizon binomial market model, composed of a non-dividend-paying risky stock and a risk-free bond. We assume that the investor’s behavior distinguishes between gains and losses, as in the classical cumulative prospect theory (CPT). This is achieved by considering preferences that
are represented by a CPT-like functional, depending on an S-shaped utility function. At the same time, we model investor’s beliefs on gains and losses through two different epsilon-contaminations of the “real-world” probability measure. We formulate the portfolio selection problem in terms of the final wealth and reduce it to an iterative search problem over the set of optimal solutions of a family of non-linear optimization problems
Stability for some classes of degenerate nonlinear hyperbolic equations with time delay
We consider several classes of degenerate hyperbolic equations involving delay terms and suitable nonlinearities. The idea is to rewrite the problems in an abstract way and, using semigroup theory and energy method, we study well-posedness and stability. Moreover, some illustrative examples are given
The operational principles of MICROMEGAS gas detectors at low pressure: A comprehensive exploration
Extensive efforts at INFN Pisa have focused on optimizing a gas detector for low pressures down to 100 mbar. MICROMEGAS technology, with its tunable avalanche volume, is inherently suited for these conditions. However initial standard simulations predicted low gain at these pressures. An extensive test campaign with X-ray sources and refined simulations based on experimental results have provided a better understanding of the detector's performance across different gas pressures. © 202
Strategies for exploiting auxiliary information and achieving spatial balance in environmental surveys
Many schemes have been proposed in literature to achieve
“well spread” samples, and some of them can take advantage of auxiliary
information. Alternatively, well spread samples can be straightforwardly
obtained by means of schemes widely adopted in environmental and ecological surveys, such as one-per-stratum stratified sampling or systematic
sampling. In both cases the auxiliary information can be adopted at the
estimation level and therefore the comparison of the performances of alternative strategies exploiting auxiliary information at different levels is
welcomed
Evidence based management of medical devices: A follow-up experiment
Ensuring the optimal operation and longevity of medical devices is essential for maintaining high safety standards in healthcare. This study presents a significant advancement in the field by enhancing an existing evidence-based maintenance (EBM) framework, which is crucial for the effective management of medical equipment. Building upon previous methodologies, this research introduces a novel, comprehensive taxonomy for categorizing maintenance reports by revising and updating existing failure codes. This refinement addresses gaps in previous models, enabling more precise and effective maintenance strategies. A key innovation of this study is the development of a standard XML protocol, which addresses the current lack of standardization in the field, providing a consistent and unified approach to data management. This standardization is critical for improving communication and data exchange across different healthcare systems and technologies. To validate the enhanced EBM framework, the study applies it to corrective maintenance work orders related to Digital Angiography Systems, Magnetic Resonance Imaging, and Computed Tomography, using data from the Pisa University Hospital's Computerized Maintenance Management System from 2021 to 2022. This validation demonstrates the reproducibility and adaptability of the framework across different medical equipment, healthcare contexts, and timeframes. The findings represent a significant advancement in healthcare technology management, offering a robust, standardized approach that optimizes the safety, functionality, and longevity of medical devices. This research not only expands maintenance standards in the healthcare sector but also provides a critical tool for addressing the current challenges in medical device maintenance, paving the way for more reliable and effective healthcare technologies
111Ag phantom images with Cerenkov Luminescence Imaging and digital autoradiography within the ISOLPHARM project
Gas-related pathological events and therapeutic failures: a case of oxygen at the microcirculatory and lymphatic level
No abstract availabl
Study and use of spectral symbol properties for isogeometric matrices on trimmed geometries
We study the spectral behavior of (sequences of) matrices resulting from immersed isogeometric discretizations on
trimmed geometries. They enjoy an asymptotic spectral distribution, described by a (spectral) symbol, and we
discuss some properties of this symbol. In particular, we show that the structure and properties of the symbol
are completely analogous to the untrimmed case when a suitable natural restriction of the parametric domain is
considered. This spectral knowledge can be exploited to identify potentially fast preconditioners for the considered
immersed discretization matrices and we propose a specific CG preconditioner based on the symbol. We also provide
numerical experiments that support the correctness of the theoretical results and illustrate the performance of the
proposed preconditioner