Surface analysis and fingerprint recognition from multi-light imaging collections

Multi-light imaging captures a scene from a fixed viewpoint through multiple photographs, each of which are illuminated from a different direction. Every image reveals information about the surface, with the intensity reflected from each point being measured for all lighting directions. The images captured are known as multi-light image collections (MLICs), for which a variety of techniques have been developed over recent decades to acquire information from the images. These techniques include shape from shading, photometric stereo and reflectance transformation imaging (RTI). Pixel coordinates from one image in a MLIC will correspond to exactly the same position on the surface across all images in the MLIC since the camera does not move. We assess the relevant literature to the methods presented in this thesis in chapter 1 and describe different types of reflections and surface types, as well as explaining the multi-light imaging process. In chapter 2 we present a novel automated RTI method which requires no calibration equipment (i.e. shiny reference spheres or 3D printed structures as other methods require) and automatically computes the lighting direction and compensates for non-uniform illumination. Then in chapter 3 we describe our novel MLIC method termed Remote Extraction of Latent Fingerprints (RELF) which segments each multi-light imaging photograph into superpixels (small groups of pixels) and uses a neural network classifier to determine whether or not the superpixel contains fingerprint. The RELF algorithm then mosaics these superpixels which are classified as fingerprint together in order to obtain a complete latent print image, entirely contactlessly. In chapter 4 we detail our work with the Metropolitan Police Service (MPS) UK, who described to us with their needs and requirements which helped us to create a prototype RELF imaging device which is now being tested by MPS officers who are validating the quality of the latent prints extracted using our technique. In chapter 5 we then further developed our multi-light imaging latent fingerprint technique to extract latent prints from curved surfaces and automatically correct for surface curvature distortions. We have a patent pending for this method

Predicting the exposure of diving grey seals to shipping noise.

There is high spatial overlap between grey seals and shipping traffic, and the functional hearing range of grey seals indicates sensitivity to underwater noise emitted by ships. However, there is still very little data regarding the exposure of grey seals to shipping noise, constraining effective policy decisions. Particularly, there are few predictions that consider the at-sea movement of seals. Consequently, this study aimed to predict the exposure of adult grey seals and pups to shipping noise along a three-dimensional movement track, and assess the influence of shipping characteristics on sound exposure levels. Using ship location data, a ship source model, and the acoustic propagation model, RAMSurf, this study estimated weighted 24-h sound exposure levels (10-1000 Hz) (SELw). Median predicted 24-h SELw was 128 and 142 dB re 1 μPa2s for the pups and adults, respectively. The predicted exposure of seals to shipping noise did not exceed best evidence thresholds for temporary threshold shift. Exposure was mediated by the number of ships, ship source level, the distance between seals and ships, and the at-sea behaviour of the seals. The results can inform regulatory planning related to anthropogenic pressures on seal populations

CF6-6D engine short-term performance deterioration

Studies conducted as part of the NASA-Lewis CF6 jet engine diagnostics program are summarized. An 82-engine sample of DC-10-10 aircraft engine checkout data that were gathered to define the extent and magnitude of CF6-6D short term performance deterioration were analyzed. These data are substantiated by the performance testing and analytical teardown of CF6-6D short term deterioration engine serial number (ESN) 451507

An Investigation of the Dimensional Stability of Dental Alginates

Dimensional stability was defined by Nicholls (1977) as “the ability (of a material) to maintain accuracy over time”, and the result of loss of accuracy, “distortion”, as “the relative movement of a single point, or group of points, away from some originally specified reference position such that permanent deformation is apparent”. Maintaining dimensional stability of dental impression materials is vital if the impression cannot be cast (in stone) soon after removal from the mouth. Dental irreversible hydrocolloid (alginate) is a major dental impression material used worldwide in many clinical procedures. However, alginate is dimensionally unstable and changes its dimensions (suffers “distortion”) after removal from the mouth. With storage times of more than ten minutes, alginate begins to distort, and after one to three hours (depending on the product and storage conditions) cannot be used for many clinical purposes, especially fixed prosthodontics such as crowns and bridges (Hampson 1955, Skinner & Hoblit 1956, Wilson & Smith 1963, Rudd et al. 1969, Miller 1975, Inohara 1977, Schoen et al. 1978, Coleman et al. 1979, Linke et al. 1985, Habu et al. 1986, Peutfeldt & Asmussen 1989, Mathilde & Peters 1992, Khan & Aziz Sahu 1995, Eriksson et al. 1998, Schleier et al. 2001, and Donovan & Chee 2004). This loss of accuracy, due to dimensional instability, manifests as a time-dependent distortion of the poured stone cast, and thus any prosthesis fabricated will not fit in the mouth. With the introduction of the more stable elastomers in the 1950s (Stackhouse 1970, Glenner 1997, Brown 2003) that could be stored for days if necessary, without loss of accuracy, the alginates fell out of favour for fixed prosthodontics. Recently, there has been a resurgence of interest in alginate for use in dental procedures where dimensional stability is critical (Peutzfeldt and Asmussen 1989, Eriksson et al. 1998). This in part is due to the favourable properties of alginate not found in the elastomers. Of greatest significance is that alginate hydrocolloid is hydrophilic, whereas elastomers are hydrophobic (Phillips & Ito 1958, Glenner 2004). Thus, alginate materials are able to reproduce wet oral areas with greater precision and to produce a superior "fit" of, say, a gold casting produced by the Lost Wax technique (Skinner and Phillips 1982). A number of reports have been published which investigate newer alginate materials that are claimed to be more dimensionally stable than older formulations. Puetzfeldt and Asmussen (1989) found that a newer alginate , if stored at 100% relative humidity, retained accuracy over 24 hours that was equivalent to that of the elastomers. More recently, the manufacturer of another alginate has claimed equivalent dimensional stability to the elastomers for up to 100 hours, and, whilst this claim has not been reported on in the literature, the present thesis will show that, under favourable conditions of storage, the material maintained clinically useful accuracy for up to 100 hours. Another approach to improving the accuracy of alginate impressions has been to combine reversible hydrocolloid with alginate (the “Bilaminar” technique). Frederick and Caputo (1997) confirmed that the new agar reversible hydrocolloids are just as accurate (at the time of removal from the mouth) as the new elastomers. Mathilde et al. (1992) and Eriksson et al. (1998) have shown that several of the “bilaminar” impression techniques for fixed prosthodontics, where alginate is used as a tray material supporting a reversible hydrocolloid (agar) wash, are as accurate and dimensionally stable as elastomers for up to three hours. However, these studies are difficult to interpret due to lack of uniformity in the testing methods, and the fact that there is no regulatory standard available to measure dimensional stability for dental alginates. The International Standard (IS) for alginate impression materials (ISO 1563:1990E) contains no specification for dimensional stability, and thus places no requirement for manufacturers to state dimensional stability properties on their labels. In contrast, ISO 4823:1992(E) specifies the IS for elastomeric dental impression materials, and it does specify a requirement for dimensional stability (less than 1.5% distortion after 24 hours). Further, the IS sets a method for determination of dimensional stability. Briefly, this method (the Optical Method) uses a travelling optical microscope to measure the accuracy of the distance between score lines on an impression of a test grid, at various time periods. The American Dental Association Specification No. 19 for dental elastomeric impression materials is identical to the IS. There is currently no specific Australian Standard (AS) for the dimensional stability of any dental impression material. Overview of Experimental Methods A. The Optical Method The aim of Part A of this investigation was to: 1. Adapt the Optical Method of the IS for elastomers to be reproducible for dental alginates. This was achieved by using a perforated test tray (to simulate clinical conditions), and measuring the grid pattern on a dental stone button after casting the test impression, rather than direct measurement of the impression, as for the IS. 2. To measure and rank the dimensional stability of a number of locally available dental alginates. Measurements of the test stone buttons proved reproducible, and the results were different for each sample, allowing them to be ranked according to dimensional stability after 50 and 100 hours of storage. The results show that the traditional optical method for measuring dimensional stability, as specified in the IS for dental elastomers, can be adapted to measure the dimensional stability of dental alginates However, the Optical Method of measuring dimensional stability of dental alginates is cumbersome and time-consuming. It was hypothesised that dimensional stability of dental alginates could be measured more conveniently by finding a thermal property that is directly proportional to dimensional stability. This method could be useful for the rapid determination of relative performance, and allow comparison with a determined benchmark. B. The Thermal Method Recently, modern methods of Thermal Analysis, Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) have been used to rapidly age various polymers, including food alginates (Chinachoti 1996), in order to measure thermal stability. This thesis shows that thermal stability is an indicator of dimensional stability. The aim of Part B of this investigation was therefore to adapt thermal analysis techniques to dental alginates, and develop a method to measure their thermal stability. These results were then compared with those for dimensional stability measured by the Optical Method to determine the relationship between thermal and dimensional stability for dental alginates. The results show that current thermal analysis methods of TGA and DSC can be adapted to measure relative dental alginate dimensional stability, and are both rapid and convenient. This study also provides evidence that commercial products differ as regards the property of dimensional stability, and can be ranked accordingly. C. Practical Application of the Methods The aim of part C of this thesis was to validate the methods (both optical and thermal) developed in this study by using them to investigate the effect of varying the water/powder ratio on the dimensional stability of dental alginates. It was shown that dimensional stability is affected by changes to the recommended water/powder ratio, that both the methods detected and measured the changes, and that the results were proportional, in that any percentage change detected by the optical method, was mirrored by the thermal method, confirming that the more convenient thermal methods can be used to measure dimensional stability

An Investigation of the Dimensional Stability of Dental Alginates

Dimensional stability was defined by Nicholls (1977) as “the ability (of a material) to maintain accuracy over time”, and the result of loss of accuracy, “distortion”, as “the relative movement of a single point, or group of points, away from some originally specified reference position such that permanent deformation is apparent”. Maintaining dimensional stability of dental impression materials is vital if the impression cannot be cast (in stone) soon after removal from the mouth. Dental irreversible hydrocolloid (alginate) is a major dental impression material used worldwide in many clinical procedures. However, alginate is dimensionally unstable and changes its dimensions (suffers “distortion”) after removal from the mouth. With storage times of more than ten minutes, alginate begins to distort, and after one to three hours (depending on the product and storage conditions) cannot be used for many clinical purposes, especially fixed prosthodontics such as crowns and bridges (Hampson 1955, Skinner & Hoblit 1956, Wilson & Smith 1963, Rudd et al. 1969, Miller 1975, Inohara 1977, Schoen et al. 1978, Coleman et al. 1979, Linke et al. 1985, Habu et al. 1986, Peutfeldt & Asmussen 1989, Mathilde & Peters 1992, Khan & Aziz Sahu 1995, Eriksson et al. 1998, Schleier et al. 2001, and Donovan & Chee 2004). This loss of accuracy, due to dimensional instability, manifests as a time-dependent distortion of the poured stone cast, and thus any prosthesis fabricated will not fit in the mouth. With the introduction of the more stable elastomers in the 1950s (Stackhouse 1970, Glenner 1997, Brown 2003) that could be stored for days if necessary, without loss of accuracy, the alginates fell out of favour for fixed prosthodontics. Recently, there has been a resurgence of interest in alginate for use in dental procedures where dimensional stability is critical (Peutzfeldt and Asmussen 1989, Eriksson et al. 1998). This in part is due to the favourable properties of alginate not found in the elastomers. Of greatest significance is that alginate hydrocolloid is hydrophilic, whereas elastomers are hydrophobic (Phillips & Ito 1958, Glenner 2004). Thus, alginate materials are able to reproduce wet oral areas with greater precision and to produce a superior "fit" of, say, a gold casting produced by the Lost Wax technique (Skinner and Phillips 1982). A number of reports have been published which investigate newer alginate materials that are claimed to be more dimensionally stable than older formulations. Puetzfeldt and Asmussen (1989) found that a newer alginate , if stored at 100% relative humidity, retained accuracy over 24 hours that was equivalent to that of the elastomers. More recently, the manufacturer of another alginate has claimed equivalent dimensional stability to the elastomers for up to 100 hours, and, whilst this claim has not been reported on in the literature, the present thesis will show that, under favourable conditions of storage, the material maintained clinically useful accuracy for up to 100 hours. Another approach to improving the accuracy of alginate impressions has been to combine reversible hydrocolloid with alginate (the “Bilaminar” technique). Frederick and Caputo (1997) confirmed that the new agar reversible hydrocolloids are just as accurate (at the time of removal from the mouth) as the new elastomers. Mathilde et al. (1992) and Eriksson et al. (1998) have shown that several of the “bilaminar” impression techniques for fixed prosthodontics, where alginate is used as a tray material supporting a reversible hydrocolloid (agar) wash, are as accurate and dimensionally stable as elastomers for up to three hours. However, these studies are difficult to interpret due to lack of uniformity in the testing methods, and the fact that there is no regulatory standard available to measure dimensional stability for dental alginates. The International Standard (IS) for alginate impression materials (ISO 1563:1990E) contains no specification for dimensional stability, and thus places no requirement for manufacturers to state dimensional stability properties on their labels. In contrast, ISO 4823:1992(E) specifies the IS for elastomeric dental impression materials, and it does specify a requirement for dimensional stability (less than 1.5% distortion after 24 hours). Further, the IS sets a method for determination of dimensional stability. Briefly, this method (the Optical Method) uses a travelling optical microscope to measure the accuracy of the distance between score lines on an impression of a test grid, at various time periods. The American Dental Association Specification No. 19 for dental elastomeric impression materials is identical to the IS. There is currently no specific Australian Standard (AS) for the dimensional stability of any dental impression material. Overview of Experimental Methods A. The Optical Method The aim of Part A of this investigation was to: 1. Adapt the Optical Method of the IS for elastomers to be reproducible for dental alginates. This was achieved by using a perforated test tray (to simulate clinical conditions), and measuring the grid pattern on a dental stone button after casting the test impression, rather than direct measurement of the impression, as for the IS. 2. To measure and rank the dimensional stability of a number of locally available dental alginates. Measurements of the test stone buttons proved reproducible, and the results were different for each sample, allowing them to be ranked according to dimensional stability after 50 and 100 hours of storage. The results show that the traditional optical method for measuring dimensional stability, as specified in the IS for dental elastomers, can be adapted to measure the dimensional stability of dental alginates However, the Optical Method of measuring dimensional stability of dental alginates is cumbersome and time-consuming. It was hypothesised that dimensional stability of dental alginates could be measured more conveniently by finding a thermal property that is directly proportional to dimensional stability. This method could be useful for the rapid determination of relative performance, and allow comparison with a determined benchmark. B. The Thermal Method Recently, modern methods of Thermal Analysis, Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) have been used to rapidly age various polymers, including food alginates (Chinachoti 1996), in order to measure thermal stability. This thesis shows that thermal stability is an indicator of dimensional stability. The aim of Part B of this investigation was therefore to adapt thermal analysis techniques to dental alginates, and develop a method to measure their thermal stability. These results were then compared with those for dimensional stability measured by the Optical Method to determine the relationship between thermal and dimensional stability for dental alginates. The results show that current thermal analysis methods of TGA and DSC can be adapted to measure relative dental alginate dimensional stability, and are both rapid and convenient. This study also provides evidence that commercial products differ as regards the property of dimensional stability, and can be ranked accordingly. C. Practical Application of the Methods The aim of part C of this thesis was to validate the methods (both optical and thermal) developed in this study by using them to investigate the effect of varying the water/powder ratio on the dimensional stability of dental alginates. It was shown that dimensional stability is affected by changes to the recommended water/powder ratio, that both the methods detected and measured the changes, and that the results were proportional, in that any percentage change detected by the optical method, was mirrored by the thermal method, confirming that the more convenient thermal methods can be used to measure dimensional stability

A simulation method to estimate closing forces in car-sealing rubber elements

The door-closing process can reinforce the impression of a solid, rock-proof, car body or of a rather cheap, flimsy vehicle. As there are no real prototypes during rubber profile bidding-out stages, engineers need to carry out non-linear numerical simulations that involve complex phenomena as well as static and dynamic loads for several profile candidates. This paper presents a structured virtual design tool based on FEM, including constitutive laws and incompressibility constraints allowing to predict more realistically the final closing forces and even to estimate sealing overpressure as an additional guarantee of noise insulation. Comparisons with results of physical tests are performed

The Use of Optical Coherence Tomography in Dental Diagnostics: a State-of-the-Art Review

Optical coherence tomography provides sections of tissues in a noncontact and noninvasive manner. The device measures the time delay and intensity of the light scattered or reflected from biological tissues, which results in tomographic imaging of their internal structure. This is achieved by scanning tissues at a resolution ranging from 1 to 15 μm. OCT enables real-time in situ imaging of tissues without the need for biopsy, histological procedures, or the use of X-rays, so it can be used in many fields of medicine. Its properties are not only particularly used in ophthalmology, in the diagnosis of all layers of the retina, but also increasingly in cardiology, gastroenterology, pulmonology, oncology, and dermatology. The basic properties of OCT, that is, noninvasiveness and low wattage of the used light, have also been appreciated in analytical technology by conservators, who use it to identify the quality and age of paintings, ceramics, or glass. Recently, the OCT technique of visualization is being tested in different fields of dentistry, which is depicted in the article

A high-resolution photogrammetric workflow based on focus stacking for the 3D modeling of small Aegean inscriptions

Any attempt of decipherment and language identification of the scripts from the Aegean dating to the second millennium BCE (namely Cretan Hieroglyphic, Linear A, and Cypro-Minoan) has relied, until today, on traditional catalogues of inscriptions, consisting of incomplete or subjective 2D representations, such as photographs and hand-drawn copies, which are not suitable for documenting such three-dimensional writing systems. In contrast, 3D models of the inscribed media allow for an accurate and objective “autopsy” of the entire surface of the inscriptions. In this context, this work presents an efficient, accurate, high-resolution, and high-quality texture photogrammetric workflow based on focus-stacked macro images, designed for the 3D modeling of small Aegean inscriptions, to properly reconstruct their geometry and to enhance the identification of their signs, making their transcription as unbiased as possible. The pipeline we propose also benefits from a pre-processing stage to remove any coloration difference from the images, and a reliable and simple 3D scaling procedure. We tested this workflow on six inscribed artifacts (two in Cretan Hieroglyphic, three in Linear A, one of uncertain affiliation), whose average size ranges approximately from 1 to 3 cm. Our results show that this workflow achieved an accuracy of a few hundredths of mm, comparable to the technical specifications of standard commercial 3D scanners. Moreover, the high 3D density we obtained (corresponding to the edge average length of the 3D model mesh), up to ≈ 30 µm, allowed us to reconstruct even the smallest details of the inscriptions, both in the mesh and in the texture layer of the 3D models