393 research outputs found
Design of decorative 3D models: from geodesic ornaments to tangible assemblies
L'obiettivo di questa tesi è sviluppare strumenti utili per creare opere d'arte decorative digitali in 3D. Uno dei processi decorativi più comunemente usati prevede la creazione di pattern decorativi, al fine di abbellire gli oggetti. Questi pattern possono essere dipinti sull'oggetto di base o realizzati con l'applicazione di piccoli elementi decorativi. Tuttavia, la loro realizzazione nei media digitali non è banale. Da un lato, gli utenti esperti possono eseguire manualmente la pittura delle texture o scolpire ogni decorazione, ma questo processo può richiedere ore per produrre un singolo pezzo e deve essere ripetuto da zero per ogni modello da decorare. D'altra parte, gli approcci automatici allo stato dell'arte si basano sull'approssimazione di questi processi con texturing basato su esempi o texturing procedurale, o con sistemi di riproiezione 3D. Tuttavia, questi approcci possono introdurre importanti limiti nei modelli utilizzabili e nella qualità dei risultati. Il nostro lavoro sfrutta invece i recenti progressi e miglioramenti delle prestazioni nel campo dell'elaborazione geometrica per creare modelli decorativi direttamente sulle superfici. Presentiamo una pipeline per i pattern 2D e una per quelli 3D, e dimostriamo come ognuna di esse possa ricreare una vasta gamma di risultati con minime modifiche dei parametri. Inoltre, studiamo la possibilità di creare modelli decorativi tangibili. I pattern 3D generati possono essere stampati in 3D e applicati a oggetti realmente esistenti precedentemente scansionati. Discutiamo anche la creazione di modelli con mattoncini da costruzione, e la possibilità di mescolare mattoncini standard e mattoncini custom stampati in 3D. Ciò consente una rappresentazione precisa indipendentemente da quanto la voxelizzazione sia approssimativa. I principali contributi di questa tesi sono l'implementazione di due diverse pipeline decorative, un approccio euristico alla costruzione con mattoncini e un dataset per testare quest'ultimo.The aim of this thesis is to develop effective tools to create digital decorative 3D artworks. Real-world art often involves the use of decorative patterns to enrich objects. These patterns can be painted on the base or might be realized with the application of small decorative elements. However, their creation in digital media is not trivial. On the one hand, users can manually perform texture paint or sculpt each decoration, in a process that can take hours to produce a single piece and needs to be repeated from the ground up for every model that needs to be decorated. On the other hand, automatic approaches in state of the art rely on approximating these processes with procedural or by-example texturing or with 3D reprojection. However, these approaches can introduce significant limitations in the models that can be used and in the quality of the results. Instead, our work exploits the recent advances and performance improvements in the geometry processing field to create decorative patterns directly on surfaces. We present a pipeline for 2D and one for 3D patterns and demonstrate how each of them can recreate a variety of results with minimal tweaking of the parameters. Furthermore, we investigate the possibility of creating decorative tangible models. The 3D patterns we generate can be 3D printed and applied to previously scanned real-world objects. We also discuss the creation of models with standard building bricks and the possibility of mixing standard and custom 3D-printed bricks. This allows for a precise representation regardless of the coarseness of the voxelization. The main contributions of this thesis are the implementation of two different decorative pipelines, a heuristic approach to brick construction, and a dataset to test the latter
Lagrange dynamics of lumped-mass multibody models of overhead cranes in 2D and 3D operational spaces
In this report the multibody Lagrange dynamics of overhead cranes is analyzed in some particular cases, for 2-dimensional and 3-dimensional operational spaces. Cables are modeled with lumped-mass chains
Quantum and classical contributions to entropy production in fermionic and bosonic Gaussian systems
As previously demonstrated, the entropy production - a key quantity
characterizing the irreversibility of thermodynamic processes - is related to
generation of correlations between degrees of freedom of the system and its
thermal environment. This raises the question of whether such correlations are
of a classical or quantum nature, namely, whether they are accessible through
measurements. We address this problem by considering fermionic and bosonic
Gaussian systems. We show that for fermions the entropy production is mostly
quantum due to the parity superselection rule which restricts the set of
physically allowed measurements to projections on the Fock states, thus
significantly limiting the amount of classically accessible correlations. In
contrast, in bosonic systems a much larger amount of correlations can be
accessed through Gaussian measurements. Specifically, while the quantum
contribution may be important at low temperatures, in the high temperature
limit the entropy production corresponds to purely classical position-momentum
correlations. Our results demonstrate an important difference between fermionic
and bosonic systems regarding the existence of a quantum-to-classical
transition in the microscopic formulation of the entropy production. They also
show that entropy production can be mainly caused by quantum correlations even
in the weak coupling limit, which admits a description in terms of classical
rate equations for state populations, as well as in the low particle density
limit, where the transport properties of both bosons and fermions converge to
those of classical particles.Comment: 22 pages, 16 figure
Probabilistic Triangulation for Uncalibrated Multi-View 3D Human Pose Estimation
3D human pose estimation has been a long-standing challenge in computer
vision and graphics, where multi-view methods have significantly progressed but
are limited by the tedious calibration processes. Existing multi-view methods
are restricted to fixed camera pose and therefore lack generalization ability.
This paper presents a novel Probabilistic Triangulation module that can be
embedded in a calibrated 3D human pose estimation method, generalizing it to
uncalibration scenes. The key idea is to use a probability distribution to
model the camera pose and iteratively update the distribution from 2D features
instead of using camera pose. Specifically, We maintain a camera pose
distribution and then iteratively update this distribution by computing the
posterior probability of the camera pose through Monte Carlo sampling. This
way, the gradients can be directly back-propagated from the 3D pose estimation
to the 2D heatmap, enabling end-to-end training. Extensive experiments on
Human3.6M and CMU Panoptic demonstrate that our method outperforms other
uncalibration methods and achieves comparable results with state-of-the-art
calibration methods. Thus, our method achieves a trade-off between estimation
accuracy and generalizability. Our code is in
https://github.com/bymaths/probabilistic_triangulationComment: 9pages, 5figures, conferenc
Real-time Ultrasound Signals Processing: Denoising and Super-resolution
Ultrasound acquisition is widespread in the biomedical field, due to its properties of low cost, portability, and non-invasiveness for the patient. The processing and analysis of US signals, such as images, 2D videos, and volumetric images, allows the physician to monitor the evolution of the patient's disease, and support diagnosis, and treatments (e.g., surgery). US images are affected by speckle noise, generated by the overlap of US waves. Furthermore, low-resolution images are acquired when a high acquisition frequency is applied to accurately characterise the behaviour of anatomical features that quickly change over time. Denoising and super-resolution of US signals are relevant to improve the visual evaluation of the physician and the performance and accuracy of processing methods, such as segmentation and classification. The main requirements for the processing and analysis of US signals are real-time execution, preservation of anatomical features, and reduction of artefacts. In this context, we present a novel framework for the real-time denoising of US 2D images based on deep learning and high-performance computing, which reduces noise while preserving anatomical features in real-time execution. We extend our framework to the denoise of arbitrary US signals, such as 2D videos and 3D images, and we apply denoising algorithms that account for spatio-temporal signal properties into an image-to-image deep learning model. As a building block of this framework, we propose a novel denoising method belonging to the class of low-rank approximations, which learns and predicts the optimal thresholds of the Singular Value Decomposition. While previous denoise work compromises the computational cost and effectiveness of the method, the proposed framework achieves the results of the best denoising algorithms in terms of noise removal, anatomical feature preservation, and geometric and texture properties conservation, in a real-time execution that respects industrial constraints. The framework reduces the artefacts (e.g., blurring) and preserves the spatio-temporal consistency among frames/slices; also, it is general to the denoising algorithm, anatomical district, and noise intensity. Then, we introduce a novel framework for the real-time reconstruction of the non-acquired scan lines through an interpolating method; a deep learning model improves the results of the interpolation to match the target image (i.e., the high-resolution image). We improve the accuracy of the prediction of the reconstructed lines through the design of the network architecture and the loss function. %The design of the deep learning architecture and the loss function allow the network to improve the accuracy of the prediction of the reconstructed lines. In the context of signal approximation, we introduce our kernel-based sampling method for the reconstruction of 2D and 3D signals defined on regular and irregular grids, with an application to US 2D and 3D images. Our method improves previous work in terms of sampling quality, approximation accuracy, and geometry reconstruction with a slightly higher computational cost. For both denoising and super-resolution, we evaluate the compliance with the real-time requirement of US applications in the medical domain and provide a quantitative evaluation of denoising and super-resolution methods on US and synthetic images. Finally, we discuss the role of denoising and super-resolution as pre-processing steps for segmentation and predictive analysis of breast pathologies
Nodal decompositions of a symmetric matrix
Analyzing nodal domains is a way to discern the structure of eigenvectors of
operators on a graph. We give a new definition extending the concept of nodal
domains to arbitrary signed graphs, and therefore to arbitrary symmetric
matrices. We show that for an arbitrary symmetric matrix, a positive fraction
of eigenbases satisfy a generalized version of known nodal bounds for un-signed
(that is classical) graphs. We do this through an explicit decomposition.
Moreover, we show that with high probability, the number of nodal domains of a
bulk eigenvector of the adjacency matrix of signed a Erd\H{o}s-R\'enyi graph is
and .Comment: 38 pages 1 figur
Performance Enhancement Using NOMA-MIMO for 5G Networks
The integration of MIMO and NOMA technologies addresses key challenges in 5G and beyond, such as connectivity, latency, and dependability. However, resolving these issues, especially in MIMO-enabled 5G networks, required additional research. This involved optimizing parameters like bit error rate, downlink spectrum efficiency, average capacity rate, and uplink transmission outage probability. The model employed Quadrature Phase Shift Keying modulation on selected frequency channels, accommodating diverse user characteristics. Evaluation showed that MIMO-NOMA significantly improved bit error rate and transmitting power for the best user in download transmission. For uplink transmission, there was an increase in the average capacity rate and a decrease in outage probability for the best user. Closed-form formulas for various parameters in both downlink and uplink NOMA, with and without MIMO, were derived. Overall, adopting MIMO-NOMA led to a remarkable performance improvement for all users, even in challenging conditions like interference or fading channels
RANSAC for Robotic Applications: A Survey
Random Sample Consensus, most commonly abbreviated as RANSAC, is a robust estimation method for the parameters of a model contaminated by a sizable percentage of outliers. In its simplest form, the process starts with a sampling of the minimum data needed to perform an estimation, followed by an evaluation of its adequacy, and further repetitions of this process until some stopping criterion is met. Multiple variants have been proposed in which this workflow is modified, typically tweaking one or several of these steps for improvements in computing time or the quality of the estimation of the parameters. RANSAC is widely applied in the field of robotics, for example, for finding geometric shapes (planes, cylinders, spheres, etc.) in cloud points or for estimating the best transformation between different camera views. In this paper, we present a review of the current state of the art of RANSAC family methods with a special interest in applications in robotics.This work has been partially funded by the Basque Government, Spain, under Research Teams Grant number IT1427-22 and under ELKARTEK LANVERSO Grant number KK-2022/00065; the Spanish Ministry of Science (MCIU), the State Research Agency (AEI), the European Regional Development Fund (FEDER), under Grant number PID2021-122402OB-C21 (MCIU/AEI/FEDER, UE); and the Spanish Ministry of Science, Innovation and Universities, under Grant FPU18/04737
A spectral Galerkin exponential Euler time-stepping scheme for parabolic SPDEs on two-dimensional domains with a C2-boundary
We consider the numerical approximation of second-order semi-linear parabolic
stochastic partial differential equations interpreted in the mild sense which
we solve on general two-dimensional domains with a boundary
with homogeneous Dirichlet boundary conditions. The equations are driven by
Gaussian additive noise, and several Lipschitz-like conditions are imposed on
the nonlinear function. We discretize in space with a spectral Galerkin method
and in time using an explicit Euler-like scheme. For irregular shapes, the
necessary Dirichlet eigenvalues and eigenfunctions are obtained from a boundary
integral equation method. This yields a nonlinear eigenvalue problem, which is
discretized using a boundary element collocation method and is solved with the
Beyn contour integral algorithm. We present an error analysis as well as
numerical results on an exemplary asymmetric shape, and point out limitations
of the approach.Comment: 23 pages, 7 figure
Novel Magnetic Resonance Imaging-Compatible Mechatronic Needle Guidance System for Prostate Focal Laser Ablation Therapy
Advances in prostate cancer (PCa) screening techniques have led to diagnosis of many cases of low-grade and highly localized disease. Conventional whole-gland therapies often result in overtreatment in such cases and debate still surrounds the optimal method of oncologic control. MRI-guided prostate focal laser ablation (FLA) is a minimally invasive treatment option, which has demonstrated potential to destroy localized lesions while sparing healthy prostatic tissue, thereby reducing treatment-related side effects. Many challenges still exist in the development of FLA, including patient selection; tumour localization, visualization, and characterization; needle guidance; and evaluation of treatment efficacy. The objective of this thesis work was to advance and enhance techniques for needle guidance in MRI-guided focal laser ablation (FLA) therapy of PCa.
Several steps were taken in achieving this goal. Firstly, we evaluated the overlap between identified lesions and MRI-confirmed ablation regions using conventional needle guidance. Non-rigid thin-plate spline registration of pre-operative and intra-operative images was performed to align lesions with ablation boundaries and quantify the degree of coverage. Complete coverage of the lesion with the ablation zone is a clinically important metric of success for FLA therapy and we found it was not achieved in many cases. Therefore, our next step was to develop an MRI-compatible, remotely actuated mechatronic system for transperineal FLA of prostate cancer. The system allows physicians in the MRI scanner control room to accurately target lesions through 4 degrees of freedom while the patient remains in the scanner bore. To maintain compatibility with the MRI environment, piezoelectric motors were used to actuate the needle guidance templates, the device was constructed from non-ferromagnetic materials, and all cables were shielded from electromagnetic interference. The MR compatibility and needle placement accuracy of the device were evaluated with virtual and phantom targets.
The system should next be validated for accuracy and usefulness in a clinical trial where more complex tissue properties and potential patient motion will be encountered. Future advances in modeling the tissue properties and compensating for deformation of the prostate, as well as predicting needle deflection, will further bolster the potential of FLA as option for the management of PCa
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