1,721,071 research outputs found
Indicators basis for functional shape analysis
No full textStep functions are widely used in several applications from geometry processing and shape analysis. Shape segmentation, partial matching and self similarity detection just to name a few. The standard signal processing tools do not allow us to fully handle this class of functions. The classical Fourier series, for instance, does not give a good representation for these non smooth functions. In this paper we define a new basis for the approximation and transfer of the step functions between shapes. Our definition is fully spectral, allowing for a concise representation and an efficient computation. Furthermore our basis is specifically built in order to enhance its use in combination with the functional maps framework. The functional approach also enable us to handle shape deformations. Thanks to that our basis achieves a large improvement not only in the approximation of step functions but also in the transfer, exploiting the functional maps framework. We perform a large set of experiments showing the improvement achieved by the proposed basis in the approximation and transfer of step functions and its stability with respect to non isometric deformations
Spectral-based segmentation for functional shape-matching
No full textIn Computer Graphics and Computer Vision, shape co-segmentation and shape-matching are fundamental tasks with diverse ap-
plications, from statistical shape analysis to human-robot interaction. These problems respectively target establishing segment-
to-segment and point-to-point correspondences between shapes, which are crucial task for numerous practical scenarios. No-
tably, co-segmentation can aid in point-wise correspondence estimation in shape-matching pipelines like the functional maps
framework. Our paper introduces an innovative shape segmentation pipeline which provides coherent segmentation for shapes
within the same class. Through comprehensive evaluation on a diverse test set comprising shapes from various datasets and
classes, we demonstrate the coherence of our segmentation approach. Moreover, our method significantly improves accuracy
in shape matching scenarios, as evidenced by comparisons with the original functional maps approach. Importantly, these en-
hancements come with minimal computational overhead. Our work not only introduces a novel coherent segmentation method
and a valuable tool for improving correspondence accuracy within functional maps, but also contributes to the theoretical
foundations of this impactful field, inspiring further research
Driving simulator: Analysing the impact of mechanical latency on the perception of lateral dynamics
Full text linkMechanical latency is the time elapsed between the driver’s input and the subsequent movement of a driving simulator. Large latencies may overlap with the time constants of a vehicle, thus altering its dynamics. As latency introduces inconsistencies between the driver’s input and the vehicle’s response, it may also result in motion sickness. The paper describes the design and the results of a test campaign conceived to understand how mechanical latency impacts the perception of lateral dynamics. In particular, the research aimed at identifying the minimal variation of latency perceived by ordinary drivers. Tests were performed with an innovative cable-driven simulator moving over a 6 × 6 metre platform. A rigorous test procedure was designed while several volunteers of different ages and driving experiences were required to perform a specific manoeuvre with different latencies. The results showed that 20% of the population can perceive latency variations below 40 ms
Crank-Lever Electromagnetic Damper (CLEMD) Design for Automobile Suspension System
No full textAn effective damper is among the most important components of the suspension system. It ensures the right amount of damping force is acting on the suspension system to provide comfort to the passengers and proper road holding to tires. Unfortunately, the energy absorbed by the dampers from the suspension system gets wasted in the form of heat. In this article, it is proposed to use innovative electromagnetic damper (EMD) with a crank-lever mechanism to recover energy from the suspension system. The goal is to develop a lightweight design of EMD that can recover a high amount of power. For the design, an off-road vehicle is used since in off-road vehicles the amount of power wasted in the suspension system is high. Three different design approaches are used, which include single-stage gearbox type, two-stage gearbox type, and three-stage gearbox type of CLEMD. Out of them, the best design, i.e. three-stage gearbox type of CLEMD is selected because of minimum weight and inertia of the components. This article is focused on the design and analysis of the three-stage gearbox type of CLEMD. On the basis of the output of numerical simulations of vehicle model, specifications for crank-lever electromagnetic damper (CLEMD) are driven and design is carried out. Also, performance analyses of CLEMD are carried out by interfacing model of CLEMD with the model of a vehicle. The advantage of CLEMD is it can act as an actuator to provide active force in an active suspension system
Characteristics Analyses of Innovative Crank-Lever Electromagnetic Damper for Suspension System of an Off-Road Vehicle
No full textIn this article performance of the innovative Crank-Lever Electromagnetic Damper (CLEMD) for an off-road vehicle suspension system is analyzed. To determine the characteristic behavior of the CLEMD, the damping force it provides on the suspension system is varied by changing the values of the damping coefficient in the simulations. Various parameters considered in the analyses include power regenerated, voltage, current, comfort, road-holding, etc. The behavior of all the parameters of the CLEMD is observed for an off-road vehicle by carrying out simulations on country roads since the off-road vehicles are subjected to higher road irregularities and hence provide an opportunity to regenerate a higher amount of power. A two-dimensional (2-D) model of a vehicle developed in SimMechanics is interfaced with a Simulink model of CLEMDs for the analyses. This device allows not only to recover energy while damping the relative motion between the car body and unsuspended masses but also to tune the damping coefficient to alter the response of the vehicle in terms of heave and pitch dynamics. The tuning of CLEMDs was changed to show the trade-off between the power regenerated, comfort, and road-holding. A cost function analysis is carried out to determine the optimum values of the damping coefficient. Also various characteristics including cyclical characteristics of the CLEMD are studied, which are useful for further developments in Electromagnetic Dampers (EMDs)
Freight trains for intermodal transportation: optimisation of payload distribution for reducing longitudinal coupling forces
No full textIncreasing the length and hauled mass represents an effective method for boosting freight train transportation. However, several analyses showed that longer and heavier trains pose safety concerns mainly related to large buffer forces generated during emergency braking. The paper investigates the effect of payload sequence on these forces referring to freight trains for intermodal transportation. A simplified trainset model is developed to predict the maximum buffer forces during emergency braking, for a set of 500 trains generated with random payload distribution. An optimisation algorithm developed for combinatorial problems is then applied to change the payload sequence on each train so that buffer forces are minimised. Optimised train sequences are then inputted into a more accurate model for longitudinal trainset dynamics, showing that a proper wagon arrangement can decrease buffer forces by more than 40%. The analysis also provided general guidelines for optimising wagon sequence
High-speed freight trains for intermodal transportation: Wind tunnel study on the aerodynamic coefficients of container wagons
Full text linkThe paper investigates the response to crosswind of a high-speed freight train for intermodal transportation, through wind tunnel tests. A 1:20 model of a freight train composed by an engine and two flat-car vehicles was instrumented with force balances to measure the aerodynamic coefficients of the flat-car plus container assembly and of the container alone. Aerodynamic coefficients strongly affects the train stability and the anchorage limits of the container itself. During the wind tunnel tests, eight different loading configurations were considered and aerodynamic coefficients were determined for yaw angles (i.e. angle between train and wind) ranging from 0° to 90°. Experimental results show the benefits in terms of drag reduction due to the presence of a laden vehicle upstream. As far as the rollover risk is concerned, the less critical condition is found for a vehicle preceded by a fully laden wagon and followed by an empty one. More in particular, at low yaw angles, the worst condition for a vehicle occurs when the wagon ahead is empty while, for yaw angles between 45° and 55° which are the most critical for ‘low speed’ trains, the differences with respect to the other configurations reduce significantly
Foreword to the Special Section on Smart Tools and Applications in Graphics (STAG 2021)
No full textThe Special Section contains extended and revised versions of the best papers presented at the 8th Conference on Smart Tools and Applications in Graphics (STAG 2021), held virtually on October 28–29, 2021. Five papers were selected by appointed members from the Program Committee; extended versions were submitted and further reviewed by external experts. The result is a collection of paper spanning different Visual Computing domains: from vector graphics on surfaces to image vectorization, from 3D geometric modelling of geological data to computation of the geometric kernel of polyhedra, up to lens-based scene exploration of annotated visual data
MapTree: Recovering multiple solutions in the space of maps
No full textIn this paper we propose an approach for computing multiple high-quality near-isometric dense correspondences between a pair of 3D shapes. Our method is fully automatic and does not rely on user-provided landmarks or descriptors. This allows us to analyze the full space of maps and extract multiple diverse and accurate solutions, rather than optimizing for a single optimal correspondence as done in most previous approaches. To achieve this, we propose a compact tree structure based on the spectral map representation for encoding and enumerating possible rough initializations, and a novel efficient approach for refining them to dense pointwise maps. This leads to a new method capable of both producing multiple high-quality correspondences across shapes and revealing the symmetry structure of a shape without a priori information. In addition, we demonstrate through extensive experiments that our method is robust and results in more accurate correspondences than state-of-the-art for shape matching and symmetry detection
Newton's fractals on surfaces via bicomplex algebra
No full textWe show how bicomplex numbers can be exploited for computing Newton's fractals in three and four dimensions.
The patterns derived from these fractals can be computed very efficiently on GPU as pixel shaders, and they are well suited for surface decoration, material masking and volumetric rendering
- …
