Development of a New Type of Incisal Table for Prosthetic Articulators

This study illustrates the effectiveness of an advanced incisal table surface, featuring adjustable curvature, in the sake of more accurate articulator kinematics in anterior teeth reconstruction. Prosthetic articulators, used by dental technicians in reconstructive dentistry, are adjustable instruments that simulate the motion of mastication between dental casts: usually, the forward motion (protrusion) of the mandible is guided by sliding a pin over a flat table in order to recreate those movements when incisal teeth are missing. However, such protrusion is an approximation of the exact motion, since flat incisal tables have a limited set of adjustments. Customized software has been developed in order to simulate the kinematics of articulators in three-dimensional space: animations and measures of the envelope of teeth profiles show the unfeasibility of reconstructing with good approximation the profile of incisive teeth, when a simple ‘flat' incisal table is used. A new incisal table with an adjustable curvature has been proposed, simulated, and built, and computer simulations demonstrated the superior precision of the new design when compared to a conventional articulator which uses a flat incisal table

N-body gravitational and contact dynamics for asteroid aggregation

The development of dedicated numerical codes has recently pushed forward the study of N-body gravitational dynamics, leading to a better and wider understanding of processes involving the formation of natural bodies in the Solar System. A major branch includes the study of asteroid formation: evidence from recent studies and observations support the idea that small and medium size asteroids between 100 m and 100 km may be gravitational aggregates with no cohesive force other than gravity. This evidence implies that asteroid formation depends on gravitational interactions between different boulders and that asteroid aggregation processes can be naturally modeled with N-body numerical codes implementing gravitational interactions. This work presents a new implementation of an N-body numerical solver. The code is based on Chrono::Engine (2006). It handles the contact and collision of large numbers of complex-shaped objects, while simultaneously evaluating the effect of N to N gravitational interactions. A special case of study is considered, investigating the relative dynamics between the N bodies and highlighting favorable conditions for the formation of a stable gravitationally bound aggregate from a cloud of N boulders. The code is successfully validated for the case of study by comparing relevant results obtained for typical known dynamical scenarios. The outcome of the numerical simulations shows good agreement with theory and observation, and suggests the ability of the developed code to predict natural aggregation phenomena

Oscillations Control of Rocking-Block-Type Buildings by the Addition of a Tuned Pendulum

This study deals with the dynamical evolutions exhibited by a simple mechanical model of building, comprising a parallelepiped standing on a horizontal plane. The main goal is the introduction of a pendulum in order to reduce oscillations. The theoretical part of the work consists of a Lagrange formulation and Galerkin approximation method, and dry friction has also been considered. From the analytical/numerical simulations, we derive some important conclusions, providing us with the tools suitable for the design of absorbers in practical cases

A NON-ABELIAN GROUP ALGEBRA FOR KINEMATIC COORDINATE TRANSFORMATION

Abstract: This paper proposes an algebra T (T, ≻) which can be used to express kinematic transformations in chains of frames that move in threedimensional space. The algebraic structure of T will be discussed end the most relevant properties will be presented. This algebra can be translated into a set of algorithms that fit well into a compact formalism, by exploiting the operator-overloading feature of modern object-oriented programming languages. Implementation and application are discussed by means of examples

REAL-TIME SIMULATION OF A RACING CAR

Abstract: This work describes the development and the application of a computer-based vehicle simulator. Such real-time simulation software is currently used in our Department as a tool for optimizing the design of a racing car, namely a single-seat vehicle for the SAE-ATA formula. Being based on our custom multibody library Chrono::Engine, the vehicle simulator exploits a recent formulation founded on vector-measure differential inclusions and cone-complementarity problems (CCP)

Efficient simulation of contacts,friction and constraints using a modified spectral projected gradient method

This work introduces a modified version of the Spectral Projected Gradient method that can be used for simulating dynamical systems with complex joints and frictional contacts. The proposed method is able to solve for unknown reactions in systems with large number of colliding shapes and articulated mechanisms. This method couples the ability of solving complementatity constraints, typical of fixed point iterations used in real-time applications, with the superior convergence of Krylov iterations for linear problems, hence making it attractive as a general purpose solver for both linear and non linear problems