Search results for "rotation"

On the existence of invariant curves of twist mappings of an annulus

1983

Matheuristics for the irregular bin packing problem with free rotations

2017

[EN] We present a number of variants of a constructive algorithm able to solve a wide variety of variants of the Two-Dimensional Irregular Bin Packing Problem (2DIBPP). The aim of the 2DIBPP is to pack a set of irregular pieces, which may have concavities, into stock sheets (bins) with fixed dimensions in such a way that the utilization is maximized. This problem is inspired by a real application from a ceramic company in Spain. In addition, this problem arises in other industries such as the garment industry or ship building. The constructive procedure presented in this paper allows both free orientation for the pieces, as in the case of the ceramic industry, or a finite set of orientation…

Completely randomized RRT-connect: A case study on 3D rigid body motion planning

2015

Nowadays sampling-based motion planners use the power of randomization to compute multidimensional motions at high performance. Nevertheless the performance is based on problem-dependent parameters like the weighting of translation versus rotation and the planning range of the algorithm. Former work uses constant user-adjusted values for these parameters which are defined a priori. Our new approach extends the power of randomization by varying the parameters randomly during runtime. This avoids a preprocessing step to adjust parameters and moreover improves the performance in comparison to existing methods in the majority of the benchmarks. Our method is simple to understand and implement. …

Efficient Pruning LMI Conditions for Branch-and-Prune Rank and Chirality-Constrained Estimation of the Dual Absolute Quadric

2014

International audience; We present a new globally optimal algorithm for self- calibrating a moving camera with constant parameters. Our method aims at estimating the Dual Absolute Quadric (DAQ) under the rank-3 and, optionally, camera centers chirality constraints. We employ the Branch-and-Prune paradigm and explore the space of only 5 parameters. Pruning in our method relies on solving Linear Matrix Inequality (LMI) feasibility and Generalized Eigenvalue (GEV) problems that solely depend upon the entries of the DAQ. These LMI and GEV problems are used to rule out branches in the search tree in which a quadric not satisfy- ing the rank and chirality conditions on camera centers is guarantee…

A rigidity problem on the round sphere

2015

We consider a class of overdetermined problems in rotationally symmetric spaces, which reduce to the classical Serrin's overdetermined problem in the case of the Euclidean space. We prove some general integral identities for rotationally symmetric spaces which imply a rigidity result in the case of the round sphere.

Finite Displacements and Corrotational Interfaces: Consistent formulation and Symmetry of the Stiffness Matrix

2017

Mechanical interfaces are theoretical and computational tools able to properly reproduce then progressive delamination of composite structures. Scientific literature is rich of interface models, mostly developed in small displacements, whereas a few of them assess the problem in a geometrically nonlinear setting. In the present paper interface formulation is rigorously developed in a geometrically nonlinear setting, and the relevant interface constitutive relations are defined in the local reference with normal and tangential axes to the middle surface in the current configuration. The interface is defined as a zero thickness layer with tractions acting between the two connected surfaces. M…

Soil carbon dynamics as affected by long-term contrasting cropping systems and tillages under semiarid Mediterranean climate

2014

Abstract In a dryland Mediterranean agrosystem (Sicily, Italy) a comparative study was carried out among two crop systems (wheat/wheat and wheat/bean) after 19 years under three most used tillage managements (conventional, dual layer and no-tillage), in order to ascertain the effects of those experimental factors, single and combined, on various soil organic C pools (total and extractable organic C, microbial biomass C, basal respiration). Field CO 2 fluxes from soil, throughout a year, were also determined. Moreover, C input and output were assessed, as well as microbial and metabolic quotients. Tillage management more than cropping system affected the soil organic C stored in the first 15…

Harvesting and recovery decisions under uncertainty

2010

Abstract A stochastic forest rotation model in the Faustmann tradition is presented and exemplified. The model combines harvesting decisions with the potential to recover or clean up to restore the land after very unfavorable evolutions of the stochastic growth process. Uncertainty is shown to have a generally ambiguous effect on the optimal choice of investment strategy. It is also shown how such models can be related to theory of optimal inventory control.

Magnetic wire-based sensors for the micro-rheology of complex fluids

2013

We propose a simple micro-rheology technique to evaluate the viscoelastic properties of complex fluids. The method is based on the use of magnetic wires of a few microns in length submitted to a rotational magnetic field. In this work, the method is implemented on a surfactant wormlike micellar solution that behaves as an ideal Maxwell fluid. With increasing frequency, the wires undergo a transition between a steady and a hindered rotation regime. The study shows that the average rotational velocity and the amplitudes of the oscillations obey scaling laws with well-defined exponents. From a comparison between model predictions and experiments, the rheological parameters of the fluid are det…

The Spirituality Questionnaire: Core Dimensions of Spirituality

2012

Various approaches are used to assess spirituality via questionnaires, ranging from one-dimensional scales to highly multidimensional models. For the present investigation, an – in spirituality research unorthodox – factor analytic method was chosen: principal axis analysis with oblique rotation. An item collection was examinated and cross-validated via internet. The spirituality questionnaire contains four dimensions: belief in God, search for meaning, mindfulness, and feeling of security. They present with high internal consistencies. The factorial structure of the four dimensions was confirmed. Based on the better fit of this method of extraction the authors assume that these dimensions …