Presence Of Alignment Errors Research Articles

Self-correction of alignment errors and retardations for a channeled spectropolarimeter.

Alignment errors of birefringent retarders and retardation errors introduced by environmental perturbations can cause significant influences on reconstructed Stokes parameters for the channeled spectropolarimeter. In this paper, we propose what we believe is a novel self-correction model that is independent of input polarization parameters to reduce the effects of alignment errors and environmental perturbations. This self-correction method can realize calibration and compensation of alignment errors and retardations simultaneously by measuring the target light in orbit. Simulation results show that alignment errors and retardations can be calibrated accurately, and the reconstructed Stokes parameters by using the presented method are more precise than by using the traditional method. The validity and feasibility of the presented method are further confirmed through experiments in the presence of alignment errors and environmental perturbations.

Range map superresolution-inpainting, and reconstruction from sparse data

Range images often suffer from issues such as low resolution (LR) (for low-cost scanners) and presence of missing regions due to poor reflectivity, and occlusions. Another common problem (with high quality scanners) is that of long acquisition times. In this work, we propose two approaches to counter these shortcomings. Our first proposal which addresses the issues of low resolution as well as missing regions, is an integrated super-resolution (SR) and inpainting approach. We use multiple relatively-shifted LR range images, where the motion between the LR images serves as a cue for super-resolution. Our imaging model also accounts for missing regions to enable inpainting. Our framework models the high resolution (HR) range as a Markov random field (MRF), and uses inhomogeneous MRF priors to constrain the solution differently for inpainting and super-resolution. Our super-resolved and inpainted outputs show significant improvements over their LR/interpolated counterparts. Our second proposal addresses the issue of long acquisition times by facilitating reconstruction of range data from very sparse measurements. Our technique exploits a cue from segmentation of an optical image of the same scene, which constrains pixels in the same color segment to have similar range values. Our approach is able to reconstruct range images with as little as 10% data. We also study the performance of both the proposed approaches in a noisy scenario as well as in the presence of alignment errors.

Connectivity preservation for multi-agent rendezvous with link failure

This paper proposes a new connectivity-preserving protocol in terms of rectangle-like regions. The protocol consists of a set of distributed control rules; their working together guarantees the network connectivity as well as rendezvous of a discrete-time multi-agent system. It is assumed that all agents share a common minimum sensing radius, but the information exchange may suffer from link failure and recovery. Consequently, the interaction topology is in fact directed and time-varying. By rigorous mathematical arguments, we show the effectiveness and robustness of the protocol in the presence of alignment errors in local coordinate orientations of agents and measurement errors in relative positions of neighbors. We also present simulations to demonstrate the effectiveness of the theoretical results.

EFFECTS OF ALIGNMENT ERRORS IN PROTON NON-SCALING FFAG ACCELERATORS

Non-scaling FFAGs have gained interest in the past decade for their potential application to charged particle therapy using proton and ion beams. However, linear ns-FFAGs naturally cross betatron resonances throughout acceleration. With an acceleration cycle of thousands rather than tens of turns, we find that resonance crossing produces severe orbit distortion in a linear proton/ion ns-FFAG in the presence of alignment errors. To overcome this, the PAMELA (Particle Accelerator for MEdicaL Applications) lattice design avoids resonance crossing with a non-linear ns-FFAG design. This design is outlined and a comparative analysis of alignment tolerances presented.

Optimal algorithm of panoramic sewing of images in the presence of inaccuracies of mutual positioning

An optimal algorithm of panoramic sewing of images in the presence of alignment errors has been synthesized on the basis of the criterion of a posteriori probability maximum. It was shown that in case of stationary images and equal a priori probabilities of image shifts, the shift estimate is determined by a maximum of the cross-correlation function of a pair of overlapping images. The sewing algorithm proposed was illustrated by the sewing of real images.

Modeling and Prediction of Hole Profile in Drilling, Part 2: Modeling Hole Profile

A hole profile model that integrates the dynamics of the drill in the presence of alignment errors, the drill wandering, and the drill margin-hole wall interaction has been developed. The ultimate profile of the hole is generated by the vibrations of the drill at its tip due to its dynamics and wandering, and by the continual updating of the already generated surface to account for any potential drill margin-hole wall interaction. The model predicts the lobbing pattern of the hole in close agreement to that observed during the experiments. The effect of the drill dynamics in the presence of alignment errors, drill wandering, drill margin-hole wall interaction as well as the individual effect of the alignment errors (α, ϕ, and γ) has been studied.