3D Geometric Analysis of Tubular Objects based on Surface Normal Accumulation

This paper proposes a simple and efficient method for the reconstruction and extraction of geometric parameters from 3D tubular objects. Our method constructs an image that accumulates surface normal information, then peaks within this image are located by tracking. Finally, the positions of these are optimized to lie precisely on the tubular shape centerline. This method is very versatile, and is able to process various input data types like full or partial mesh acquired from 3D laser scans, 3D height map or discrete volumetric images. The proposed algorithm is simple to implement, contains few parameters and can be computed in linear time with respect to the number of surface faces. Since the extracted tube centerline is accurate, we are able to decompose the tube into rectilinear parts and torus-like parts. This is done with a new linear time 3D torus detection algorithm, which follows the same principle of a previous work on 2D arc circle recognition. Detailed experiments show the versatility, accuracy and robustness of our new method.Comment: in 18th International Conference on Image Analysis and Processing, Sep 2015, Genova, Italy. 201

An experimental/analytical program to assess the utility of lidar for pollution monitoring

The development and demonstration of lidar techniques for the remote measurement of atmospheric constituents and transport processes in the lower troposphere was carried out. Particular emphasis was given to techniques for monitoring SO2 and particulates, the principal pollutants in power plant and industrial plumes. Data from a plume dispersion study conducted in Maryland during September and October 1976 were reduced, and a data base was assembled which is available to the scientific community for plume model verification. A UV Differential Absorption Lidar (DIAL) was built, and preliminary testing was done

Multi-beam miniaturized volumetric scanning microscopy with a single 1-dimensional actuation

Miniaturized optical imaging systems often use a 2-dimensional (2-D) actuator such as a piezoelectric tube or microelectromechanical system actuator for the acquisition of 2-D and higher dimensional images over an areal field of view (FOV). Piezoelectric tubes are the most compact, but usually produce impractical sub-millimetre FOVs and are difficult to fabricate at scale, leading to high costs. Planar piezoelectric bending actuators ('benders') are substantially lower cost and capable of much larger actuations, albeit 1-dimensional (1-D) and traditionally inadequate for 2-D steering tasks. We present a piezoelectric bender imaging system that exploits mechanical motion coupling to produce multi-millimetre scale 2-D scan coverage. Leveraging optical coherence tomography with a long coherence length laser, we further extend the FOV using three depth-multiplexed imaging beams from optical fibres resonating in synchronicity across the width of the bender. Each fibre had a FOV of ~2.1 x 1.5 mm, contributing to a stitched field of ~2.1 x 2.9 mm with a beam resolution of 12.6 um full-width at half-maximum. Imaging of biological samples including stomach tissue, an ant and cell spheroids was performed. This multi-fold improvement in imaging coverage and cost-effectiveness promises to accelerate the advent of piezoelectric scanning in compact devices such as endoscopes for biomedicine, and headsets for augmented/virtual reality and neuroscience

Laser-aided additive manufacturing of glass

“This thesis presents various approaches for the laser-aided additive manufacturing of glass. First, a technique is investigated to create free-form, low to zero coefficient of thermal expansion structures out of silica-gel. A CO2 laser was coupled through a gantry system and focused onto a binder-free silica-gel powder bed (15-40 μm particles). Prior to writing each layer, powder is dispensed by sifting it onto the build platform as opposed to a conventional wiper system, avoiding contacting and potentially damaging sensitive parts. After deposition, the parts are annealed in a furnace to increase their strength. The influence of various process parameters including scan speed and laser power on final shape is investigated. In addition, the flexural strength of annealed parts is measured via three-point bending tests. Next, it was endeavored to transform the intensity profile of a TEM00 CO2 laser beam with a field-mapping beam shaper, the primary goal being to obtain a beam transformation which created a more uniform intensity distribution. Beam profile measurements were conducted in two regimes (focal plane and far-focal range) in an attempt to identify various profile transformations that correspond to theoretical models. Finally, a fiber-fed laser-heated process was developed for the additive manufacturing (AM) of glass parts. Soda-lime and stripped quartz SMF-28 optical fibers with diameters ranging from 100-125 μm were fed into a laser generated melt pool. A CO2 laser beam is focused onto the intersection of the fiber and the work piece, which is positioned on a four-axis computer controlled stage. Through the careful control of process parameters such as laser power, feed rate and scan speed, bubble free parts such as walls and lenses may be printed, as well as complicated free-standing structures”--Abstract, page iii

Design and Development of a new Scalp Cooling Cap - Stage 1 : Confidential Design and Development Report

This project is funded by Technology Strategy Board Smart grant of £500,000 awarded to Paxman Coolers to develop and improve the Paxman scalp cooler to enable the product to meet the needs of a global market, together with improvements to efficacy and patient experience. The development includes improvements to the cap which will take into account anthropometric data, 3D head scanning and 3D modelling to create an innovative solution that offers significant improvements to current design. 3D laser sintering technology is used to create tools and in close collaboration with a major silicon manufacturer a novel system for cap production for producing a new design which gives a better user experience through improved comfort, fit and heat conductivity. The product will be protected by world patent cover and is subject to non-disclosure agreements with the University’s partners

Innovative techniques to devise 3D-printed anatomical brain phantoms for morpho-functional medical imaging

Introduction. The Ph.D. thesis addresses the development of innovative techniques to create 3D-printed anatomical brain phantoms, which can be used for quantitative technical assessments on morpho-functional imaging devices, providing simulation accuracy not obtainable with currently available phantoms. 3D printing (3DP) technology is paving the way for advanced anatomical modelling in biomedical applications. Despite the potential already expressed by 3DP in this field, it is still little used for the realization of anthropomorphic phantoms of human organs with complex internal structures. Making an anthropomorphic phantom is very different from making a simple anatomical model and 3DP is still far from being plug-and-print. Hence, the need to develop ad-hoc techniques providing innovative solutions for the realization of anatomical phantoms with unique characteristics, and greater ease-of-use. Aim. The thesis explores the entire workflow (brain MRI images segmentation, 3D modelling and materialization) developed to prototype a new complex anthropomorphic brain phantom, which can simulate three brain compartments simultaneously: grey matter (GM), white matter (WM) and striatum (caudate nucleus and putamen, known to show a high uptake in nuclear medicine studies). The three separate chambers of the phantom will be filled with tissue-appropriate solutions characterized by different concentrations of radioisotope for PET/SPECT, para-/ferro-magnetic metals for MRI, and iodine for CT imaging. Methods. First, to design a 3D model of the brain phantom, it is necessary to segment MRI images and to extract an error-less STL (Standard Tessellation Language) description. Then, it is possible to materialize the prototype and test its functionality. - Image segmentation. Segmentation is one of the most critical steps in modelling. To this end, after demonstrating the proof-of-concept, a multi-parametric segmentation approach based on brain relaxometry was proposed. It includes a pre-processing step to estimate relaxation parameter maps (R1 = longitudinal relaxation rate, R2 = transverse relaxation rate, PD = proton density) from the signal intensities provided by MRI sequences of routine clinical protocols (3D-GrE T1-weighted, FLAIR and fast-T2-weighted sequences with ≤ 3 mm slice thickness). In the past, maps of R1, R2, and PD were obtained from Conventional Spin Echo (CSE) sequences, which are no longer suitable for clinical practice due to long acquisition times. Rehabilitating the multi-parametric segmentation based on relaxometry, the estimation of pseudo-relaxation maps allowed developing an innovative method for the simultaneous automatic segmentation of most of the brain structures (GM, WM, cerebrospinal fluid, thalamus, caudate nucleus, putamen, pallidus, nigra, red nucleus and dentate). This method allows the segmentation of higher resolution brain images for future brain phantom enhancements. - STL extraction. After segmentation, the 3D model of phantom is described in STL format, which represents the shapes through the approximation in manifold mesh (i.e., collection of triangles, which is continuous, without holes and with a positive – not zero – volume). For this purpose, we developed an automatic procedure to extract a single voxelized surface, tracing the anatomical interface between the phantom's compartments directly on the segmented images. Two tubes were designed for each compartment (one for filling and the other to facilitate the escape of air). The procedure automatically checks the continuity of the surface, ensuring that the 3D model could be exported in STL format, without errors, using a common image-to-STL conversion software. Threaded junctions were added to the phantom (for the hermetic closure) using a mesh processing software. The phantom's 3D model resulted correct and ready for 3DP. Prototyping. Finally, the most suitable 3DP technology is identified for the materialization. We investigated the material extrusion technology, named Fused Deposition Modeling (FDM), and the material jetting technology, named PolyJet. FDM resulted the best candidate for our purposes. It allowed materializing the phantom's hollow compartments in a single print, without having to print them in several parts to be reassembled later. FDM soluble internal support structures were completely removable after the materialization, unlike PolyJet supports. A critical aspect, which required a considerable effort to optimize the printing parameters, was the submillimetre thickness of the phantom walls, necessary to avoid distorting the imaging simulation. However, 3D printer manufacturers recommend maintaining a uniform wall thickness of at least 1 mm. The optimization of printing path made it possible to obtain strong, but not completely waterproof walls, approximately 0.5 mm thick. A sophisticated technique, based on the use of a polyvinyl-acetate solution, was developed to waterproof the internal and external phantom walls (necessary requirement for filling). A filling system was also designed to minimize the residual air bubbles, which could result in unwanted hypo-intensity (dark) areas in phantom-based imaging simulation. Discussions and conclusions. The phantom prototype was scanned trough CT and PET/CT to evaluate the realism of the brain simulation. None of the state-of-the-art brain phantoms allow such anatomical rendering of three brain compartments. Some represent only GM and WM, others only the striatum. Moreover, they typically have a poor anatomical yield, showing a reduced depth of the sulci and a not very faithful reproduction of the cerebral convolutions. The ability to simulate the three brain compartments simultaneously with greater accuracy, as well as the possibility of carrying out multimodality studies (PET/CT, PET/MRI), which represent the frontier of diagnostic imaging, give this device cutting-edge prospective characteristics. The effort to further customize 3DP technology for these applications is expected to increase significantly in the coming years

Installation Quality Inspection for High Formwork Using Terrestrial Laser Scanning Technology

Current inspection for installation quality of high formwork is conducted by site managers based on personal experience and intuition. This non-systematic inspection is laborious and it is difficult to provide accurate dimension measurements for high formwork. The study proposed a method that uses terrestrial laser scanning (TLS) technology to collect the full range measurements of a high formwork and develop a genetic algorithm (GA) optimized artificial neutral network (ANN) model to improve measurement accuracy. First, a small-scale high formwork model set was established in the lab for scanning. Then, the collected multi-scan data were registered in a common reference system, and RGB value and symmetry of the structure were used to extract poles and tubes of the model set, removing all irrelevant data. Third, all the cross points of poles and tubes were generated. Next, the model set positioned on the moving equipment was scanned at different specified locations in order to collect sufficient data to develop an GA-ANN model that can generate accurate estimates of the point coordinates so that the accuracy of the dimension measurements can be achieved at the millimetre level. Validation experiments were conducted both on another model set and a real high formwork. The successful applications suggest that the proposed method is superior to other common techniques for obtaining the required data necessary for accurately measuring the overall structure dimensions, regarding data accuracy, cost and time. The study proposed an effective method for installation quality inspection for high formwork, especially when the inspection cannot be properly operated due to cost factors associated with common inspection methods

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF PLASMA-JET FORMING

Sheet metal forming has found increasing applications in modern industries. To eliminate use of expensive tools during product development, thermal forming, a rapid prototyping process that is flexible enough to decrease costs has been developed. Thermal forming processes use a heat source to perform the required deformation mainly by creating a thermal difference along the thickness of the sheet. Gas flames, lasers and plasma heat sources have been used for sheet metal bending by thermal forming. An alternative to laser and gas flames, plasma-jet forming has been developed that uses a non-transferred plasma arc as a heat source. The plasma-jet forming system uses a highly controllable non-transferred plasma torch as a heat source to create the necessary thermal gradient in the sheet metal that causes the required plastic deformation. Various experiments to produce simple linear bends and other complex shapes have been conducted by using different scanning options and coupling techniques. A computer simulated model using finite element method is being developed to study key parameters affecting this process and also to measure the thermal transient temperature distribution during the process. A predictive model to relate the deformation to the temperature gradient for various materials is being developed. Simulation results that are in accordance to experimental observations will further improve this material forming process to be highly controllable and more accurat

Studies in picosecond chronoscopy

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