3D Shape Measurement of Objects in Motion and Objects with Complex Surfaces

This thesis aims to address the issues caused by high reflective surface and object with motion in the three dimensional (3D) shape measurement based on phase shifting profilometry (PSP). Firstly, the influence of the reflectivity of the object surface on the fringe patterns is analysed. One of the essential factors related to phase precision is modulation index, which has a direct relationship with the surface reflectivity. A comparative study focusing on the modulation index of different materials is presented. The distribution of modulation index for different material samples is statistically analysed, which leads to the conclusion that the modulation index is determined by the diffuse reflectivity. Then the method based on optimized combination of multiple reflected image patterns is proposed to address the saturation issue and improve the accuracy for the reconstruction of object with high reflectivity.A set of phase shifted sinusoidal fringe patterns with different exposure time are projected to the object and then captured by camera. Then a set of masks are generated to select the data for the compositing. Maximalsignal-to-noise ratio combining model is employed to form the composite images pattern. The composite images are then used to phase mapping.Comparing to the method only using the highest intensity of pixels for compositing image, the signal noise ratio (SNR) of composite image is increased due to more efficient use of information carried by the images

Unconstrained Proximal Operator: the Optimal Parameter for the Douglas-Rachford Type Primal-Dual Methods

In this work, we propose an alternative parametrized form of the proximal operator, of which the parameter no longer needs to be positive. That is, the parameter can be a non-zero scalar, a full-rank square matrix, or, more generally, a bijective bounded linear operator. We demonstrate that the positivity requirement is essentially due to a quadratic form. We prove several key characterizations for the new form in a generic way (with an operator parameter). We establish the optimal choice of parameter for the Douglas-Rachford type methods by solving a simple unconstrained optimization problem. The optimality is in the sense that a non-ergodic worst-case convergence rate bound is minimized. We provide closed-form optimal choices for scalar and orthogonal matrix parameters under zero initialization. Additionally, a simple self-contained proof of a sharp linear convergence rate for a $(1/L)$-cocoercive fixed-point sequence with $L\in(0,1)$ is provided (as a preliminary result). To our knowledge, an operator parameter is new. To show its practical use, we design a dedicated parameter for the 2-by-2 block-structured semidefinite program (SDP). Such a structured SDP is strongly related to the quadratically constrained quadratic program (QCQP), and we therefore expect the proposed parameter to be of great potential use. At last, two well-known applications are investigated. Numerical results show that the theoretical optimal parameters are close to the practical optimums, except they are not a priori knowledge. We then demonstrate that, by exploiting problem model structures, the theoretical optimums can be well approximated. Such approximations turn out to work very well, and in some cases almost reach the underlying limits

Degradation assessment of industrial composites using thermography

Thermographic inspection is a relatively new technique for Non-Destructive Testing (NDT) which has been gathering increasing interest due to its relatively low cost hardware and extremely fast data acquisition properties. This technique is especially promising in the area of rapid automated damage detection and quantification. In collaboration with a major industry partner from the aerospace sector advanced thermography-based NDT software for impact damaged composites is introduced. The software is based on correlation analysis of time-temperature profiles in combination with an image enhancement process. The prototype software is aiming to a) better visualise the damages in a relatively easy-to-use way and b) automatically and quantitatively measure the properties of the degradation. Knowing that degradation properties play an important role in the identification of degradation types, tests and results on specimens which were artificially damaged have been performed and analyzed.EPSR

Polymer Dielectric in Organic Field‐Effect Transistor

In this chapter, we aim to present an overview of the polymer dielectrics in organic field‐effect transistors and their applications. In the first section, we give a short introduction of polymer dielectrics in organic field‐effect transistors. We illustrate multilayer, hybrid, and cross‐linked polymer dielectrics adopted in organic field‐effect transistors. Then we introduce the available biomaterials engaged as polymer dielectrics in organic field‐effect transistors. We mainly focus on the utilization of silk fibroin, DNA, and DNA base pair dielectrics. We end the chapter by presenting the applications of polymer dielectrics. We elaborate that the polymer dielectrics can function as the electrode buffer layer, as well as the organic field‐effect transistor‐based gas sensor, inverter, and memory

Self-Assembly of Graphene Nanoribbons Induced by the Carbon Nanotube

In this chapter, a series of molecular dynamics simulations have been carried out to explore the self‐assembly of graphene nanoribbons (GNRs) induced by the single‐walled carbon nanotubes (SWCNTs). Simulation results show that GNRs can insert and wrap SWCNTs spontaneously, forming helical configurations and maximizing the π‐π stacking area between graphene and SWCNT. The helical configuration takes the least amount of energy and achieves the maximum occupancy. The size and function group of GNR and SWCNT should meet the required conditions to guarantee the self‐assembly in insertion and wrapping processes. Several GNRs can spiral in an SWCNT simultaneously, and two formulas have come up in this study to estimate the quantity threshold for multiple GNR spiralling. The rolled GNRs can also spontaneously insert into SWCNTs, forming a DNA‐like double helix, or collapsing to a linked double graphitic nanoribbon and wrapping in a helical manner around the tube