3D Noisy Discrete Objects: Segmentation and Application to Smoothing

International audienceWe propose in this paper a segmentation process that can deal with noisy discrete objects. A flexible approach considering arithmetic discrete planes with a variable width is used to avoid the over-segmentation that might happen when classical segmentation algorithms based on regular discrete planes are used to decompose the surface of the object. A method to choose a seed and different segmentation strategies according to the shape of the surface are also proposed, as well as an application to smooth the border of convex noisy discrete objects

High Resolution Ozone Mapper (HROM)

Using the backscatter ultraviolet instrument (BUV) aboard NIMBUS 4 as a baseline, point scanner mechanisms and spatial multiplex scanning systems were compared on the basis of sensitivity, field of view and simplicity. This comparison included both spectral and spatial scanning and multiplexing techniques. The selected system which optimally met the performance requirements for a shuttle based instrument was a pushbroom spatial scanner using a 15 element photomultiplier tube array and a Hadamard multiplex spectral scan. The selected system was conceptually designed. This design includes ray traces of the monochromator, mechanical layouts and the electronic block diagram

Assessment of plastics in the National Trust: a case study at Mr Straw's House

The National Trust is a charity that cares for over 300 publically accessible historic buildings and their contents across England, Wales and Northern Ireland. There have been few previous studies on preservation of plastics within National Trust collections, which form a significant part of the more modern collections of objects. This paper describes the design of an assessment system which was successfully trialled at Mr Straws House, a National Trust property in Worksop, UK. This system can now be used for future plastic surveys at other National Trust properties. In addition, the survey gave valuable information about the state of the collection, demonstrating that the plastics that are deteriorating are those that are known to be vulnerable, namely cellulose nitrate/acetate, PVC and rubber. Verifying this knowledge of the most vulnerable plastics enables us to recommend to properties across National Trust that these types should be seen as a priority for correct storage and in-depth recording

Visual analytics methods for shape analysis of biomedical images exemplified on rodent skull morphology

In morphometrics and its application fields like medicine and biology experts are interested in causal relations of variation in organismic shape to phylogenetic, ecological, geographical, epidemiological or disease factors - or put more succinctly by Fred L. Bookstein, morphometrics is "the study of covariances of biological form". In order to reveal causes for shape variability, targeted statistical analysis correlating shape features against external and internal factors is necessary but due to the complexity of the problem often not feasible in an automated way. Therefore, a visual analytics approach is proposed in this thesis that couples interactive visualizations with automated statistical analyses in order to stimulate generation and qualitative assessment of hypotheses on relevant shape features and their potentially affecting factors. To this end long established morphometric techniques are combined with recent shape modeling approaches from geometry processing and medical imaging, leading to novel visual analytics methods for shape analysis. When used in concert these methods facilitate targeted analysis of characteristic shape differences between groups, co-variation between different structures on the same anatomy and correlation of shape to extrinsic attributes. Here a special focus is put on accurate modeling and interactive rendering of image deformations at high spatial resolution, because that allows for faithful representation and communication of diminutive shape features, large shape differences and volumetric structures. The utility of the presented methods is demonstrated in case studies conducted together with a collaborating morphometrics expert. As exemplary model structure serves the rodent skull and its mandible that are assessed via computed tomography scans

Researches on Non-standard Optics for Advanced Gravitational Waves Interferometers

This thesis presents a collection of different researches on non-standard optics in view of enhancing the performances of the Advanced Gravitational waves interferometric detectors, where the thermal noise of the test masses is expected to be a limiting factor for their sensitivity. We provide a quantitative analysis of the impact of non-Gaussian beams on different kinds of thermal noises. We developed the theory of mesa beam, in view of a future implementation in advanced GW interferometers of the mesa beam idea, focusing on the analytical derivation of the quantities (i.e. beam width, divergence, propagation factor), which are chosen as ISO standard reference parameters for the characterization of an optical beam. We also analytically proved a new duality relation between optical cavities with non-spherical mirrors. The interest of the GW community in this new beam technology led us to the construction and testing of a prototype mesa beam Fabry-Perot cavity with Mexican-hat mirror. Part of the work of this thesis was devoted to the development of new simulation programs of optical systems. These programs provided the theoretical expected behaviour of our experiment, in particular cavity modes structure and misalignments sensitivity to be confronted with the experimental results. We also explored another complementary way of reducing the mirror thermal noise, beside the beam shaping, that is the multi-layered coating thickness optimization. We show it to be effective in reducing the coating noise and explore the possible implications for GW interferometers in terms of sensitivity. During this analysis we developed an independent model for the coating effective elastic parameters, which is based on the well understood subject of homogenization theory.Comment: Ph.D. thesis, University of Pisa & LIGO-Caltech, 185 page

Wavefront modelling and sensing for advanced gravitational wave detectors

The Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) directly detected gravitational waves for the first time on the 14th of September 2015. In 2017 the detection of gravitational waves from a binary neutron star merger was subsequently followed up by observations by optical and radio astronomers — the first time an astrophysical event was observed by two completely separate astrophysical signals. This marked the beginning of multi-messenger astronomy. Since then 90 astrophysical events have been observed using gravitational waves. To increase the rate of event detection the sensitivity of gravitational wave detectors must be improved. Current state of the art gravitational wave detectors are optical interferometers in the dual recycled Fabry-Perot Michelson (DRFPMI) configuration with quantum squeezed light injected to reduce vacuum noise. Future plans to improve the sensitivity further rely on increasing the circulating laser power and improving the efficiency of quantum squeezing. Squeezing efficiency is drastically reduced by optical losses in the interferometer of which mode mismatch is a large component. Higher laser power introduces larger thermal distortions in the interferometer, which increase mode mismatch. This thesis covers topics relevant to optical modelling of coupled cavity interferometers such as the DRFPMI with a focus on mode mismatch. Novel applications in aLIGO commissioning based on existing mode mismatch sensing techniques using the output mode cleaner (OMC) are presented. A new mode mismatch sensing technique based on transverse higher order mode sidebands is demonstrated on an optical tabletop and its applications to mode mismatch sensing in aLIGO is discussed. A new optical modelling framework based on linear canonical transformations and signal flow graph theory is also presented.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202

Operating, testing and evaluating hybridized silicon P-I-N arrays

Use of CCD detector arrays as visible imagers in space telescopes has been problematic. Charge-coupled devices rapidly deteriorate due to damage from the high radiation environment of space. CMOS-based imagers, which do not transfer charge, offer an alternative technology that is more tolerant of a high-radiation environment. This dissertation evaluates the performance of four pathfinder 1K by 1K hybridized silicon P-I-N detector arrays made by Raytheon under subcontract to RIT as candidates for use in a space telescope application. Silicon P-I-N arrays have photon capture properties similar to back-thinned CCD\u27s and should be far more robust than CCD\u27s in the high-radiation environment of space. The first two devices, 180 µm thick prototypes, demonstrate crisp imaging with lateral diffusion of 5 microns at 35 Kelvin. The nodal capacitance is estimated to be 41 fF and the quantum efficiency is remarkably good (typically \u3e 0.75) over a spectral range from 410 to 940 nm. A second pair of devices, fabricated with detectors thinned to 40 µm, exhibits similar performance but with blue-enhanced spectral response from an improved anti-reflective coating. Operating, testing, and evaluating imaging devices similar to the ones tested here is also problematic. Precise, low-noise, flexible control systems are required to operate the devices, and interpretation of the data is not always straightforward. In the process of evaluating these pathfinder devices, this dissertation surveys and advances systems engineering and analysis (i.e. the application of linear and stochastic system theory) generally useful for operating and evaluating similar hybridized staring focal plane arrays. Most significantly, a previously unaccounted for effect causing significant errors in the measurement of quantum efficiency - inter-pixel capacitive coupling - is discovered, described, measured, and compensated for in the P-I-N devices. This coupling is also shown to be measurably present in hybridized indium antimonide arrays. Simulations of interpixel coupling are also performed and predict the coupling actually observed in the P-I-N devices. Additional analysis tools for characterizing these devices are developed. An optimal estimator of signal on a multiply-sampled integrating detector in the presence of both photon and read noise is derived, modeling a pixel as a simple linear system, and is shown to agree with known limiting cases. Theories of charge diffusion in detectors are surveyed and a system model based on the steady state diffusion equation, infinite lifetime, and contiguous pixels is derived and compared to other models. Simulations validate this theory and show the effect of finite mean free path, finite lifetime, and non-contiguous pixels upon it. A simple method for modeling and evaluating MTF from edge spread is developed and used. A model that separately measures system and device noise in multichannel systems is developed, and shown to agree with measurements taken with the same device in both a quiet and a somewhat noisy system. Hardware and software systems that operate these devices are also surveyed, and \u27agile\u27 technologies and development methodologies apprate for detector research are employed to build a simple and flexible array control system, primarily from open-source components. The system is used to collect much of the experimental data

Fit-for-Purpose Land Administration- Providing Secure Land Rights at Scale. Volume 2: Country Implementation

This Special Issue provides an insight, collated from 26 articles, focusing on various aspects of the Fit-For-Purpose Land Administration (FFPLA) concept and its application. It presents some influential and innovative trends and recommendations for designing, implementing, maintaining and further developing Fit-For-Purpose solutions for providing secure land rights at scale. The first group of 14 articles is published in Volume One and discusses various conceptual innovations related to spatial, legal and institutional aspects and its wider applications within land use management. The second group of 12 articles is published in Volume Two and focuses on case studies from various countries throughout the world, providing evidence and lessons learned from the FFPLA implementation process