High-resolution Optical Scanning Research Articles

SmartWoodID-an image collection of large end-grain surfaces to support wood identification systems.

Wood identification is a key step in the enforcement of laws and regulations aimed at combatting illegal timber trade. Robust wood identification tools, capable of distinguishing a large number of timbers, depend on a solid database of reference material. Reference material for wood identification is typically curated in botanical collections dedicated to wood consisting of samples of secondary xylem of lignified plants. Specimens from the Tervuren Wood Collection, one of the large institutional wood collections around the world, are used as a source of tree species data with potential application as timber. Here, we present SmartWoodID, a database of high-resolution optical scans of the end-grain surfaces enriched with expert wood anatomical descriptions of macroscopic features. These can serve as annotated training data to develop interactive identification keys and artificial intelligence for computer vision-based wood identification. The first edition of the database consists of images of 1190 taxa, with a focus on potential timber species from the Democratic Republic of the Congo with at least four different specimens per species included. Database URL https://hdl.handle.net/20.500.12624/SmartWoodID_first_edition.

An experimental study on the ballistic performance of ultra-high hardness armor steel (Armox 600T) against 7.62 mm × 51 M61 AP projectile in the multi-hit condition

In this study, Armox 600T armor steel was ballistically tested against 7.62 mm × 51 M61 AP projectile. The experimental design was constructed on the basis of the worst-case scenario which is the highest possible impact velocity in the multi-hit condition. The ballistic tests revealed that Armox 600T could defeat the worst-case scenario with a thickness of 12 mm. Furthermore, the damaged and undamaged regions were inspected microstructurally in a detail manner aiming to observe the possible fractographic modes of the studied material. Finally, high resolution optical scanning efforts were also added to the experimental work whose results uncovers the possible improvement areas regarding the quantification of the results of ballistic testing.

Numerical modelling of incipient motion of fracture infillings

Fine-grained infilling materials in rock fractures cannot be penetrated by cement-based grout, while high water velocities in the unfilled parts of the fracture can impose erosion of the infilling materials. Understanding the erosion process of the infilling materials is, therefore, essential for the design of grout curtains. In this paper, the incipient motion of infilling particles in a three-dimensional rock fracture is predicted by a coupled Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) approach. A fracture model is built based on high-resolution optical scanning data of a natural rock joint surface. Infilling particles are modelled as non-cohesive spheric particles in a range of fine-sand sizes. The motion of particles is produced by coupling the CFD, solving the Navier-Stokes equations, with the DEM, prescribing the contact forces between particles. The model could capture the particle-particle and particle-fluid interaction behaviours during particle movement. Simulation results of the fracture model are compared with a parallel-plate model, which shows that the fracture geometry significantly affects the transport and distribution of the infillings. The dimensionless critical shear stress of the fracture model for the studied fracture is 11% larger than the values obtained from the parallel-plate model. Furthermore, the simulations are compared with the Hjulström and Shields diagrams, showing that the use of these two diagrams to predict the infilling erosion in the fracture results in a significant discrepancy. In contrast, a previous equation derived from flume experiments under laminar flows agrees better with the simulations. The present study visualises and quantitatively analyses the erosion process of the fracture infillings, which provides a reference to predict the threshold of the infilling erosion. • The erosion of fracture infillings is quantitatively analysed for the first time. • Fracture geometry significantly affects the transport of the fracture infillings. • The use of Hjulström and Shields diagrams results in a significant discrepancy.

A thin and flexible scanner for fingerprints and documents based on metal halide perovskites

Solution-processed photodetectors could be of use in large-area light-sensing applications because they can be fabricated at low cost on plastic substrates and their absorption spectra can be tuned by chemical design. However, fabricating photodetectors with low dark currents and integrating them into high-resolution backplanes remains challenging. Here we show that solution-processed metal halide perovskite photodiodes on top of an amorphous indium gallium zinc oxide transistor backplane can be used to create a flexible image sensor that is ~100 μm thick and has a resolution of 508 pixels per inch. We have developed a pixel edge cover layer for the system that reduces electrode current leakage and thus dark current density. The low noise current in combination with high external quantum efficiency results in high photodetectivity at wavelengths from 550 nm to 770 nm. We show that our imager can be used for document scanning and biometric fingerprinting and that it can be wrapped around objects with radii as small as 0.6 cm. Low-dark-current perovskite photodetectors can be integrated with an oxide transistor backplane to create a high-resolution optical scanning array capable of imaging flat and curved surfaces.

Experimental program on mechanical properties of large rock fractures

Predictions of fracture displacements are required to support the safety assessments of a deep geological repository for nuclear spent fuel. Laboratory and in-situ experiments are used to estimate these properties. Despite significant contributions in the last decades, there is a knowledge gap in terms of the impact of high normal stresses on the mechanical properties of large-scale fractures under Constant Normal Stiffness (CNS) boundary conditions. Within the framework of the POST project, a cooperative effort was made by SKB (Sweden), NWMO (Canada), and Posiva from Finland (in phase 1) to study these questions. In the second phase of the POST project, a first of a kind direct shear testing machine was manufactured and calibrated that can accommodate samples up to 400 × 600 mm under normal stresses up to 10 MPa, for both CNS and Constant Normal Load (CNL) conditions, with the ability to shear the sample up to 50 mm. Several best practice procedures were developed for fracture characterization pre-, syn-, and post-shear test which utilize high resolution optical scanning, contact pressure measurements, Digital Image Correlation (DIC) measurements, and acoustic emission measurements during the shear test. Natural and tensile-induced fractures of a granitic rock as well as replicas of the hard rock fractures, at three different fracture sizes of 35×60 mm, 70×100 mm, and 300×500 mm, are now being tested. It is hoped that this program will provide a set of high-quality data which will help reduce the knowledge gap in the understanding of fracture behavior.

Prediction of Peak Shear Strength of Natural, Unfilled Rock Joints Accounting for Matedness Based on Measured Aperture

The mechanical behaviour of natural, unfilled rock joints is influenced by the interaction between surface roughness and matedness of the contact surfaces. In the field, natural rock joints normally exhibit a mismatch between the contact surfaces, mainly due to different geological processes such as weathering or deformations. Various attempts have been made to estimate how matedness of rock joints influences their peak shear strength. However, the proposed methodologies imply certain difficulties since they are intended to estimate the matedness of rock joints based mainly on visual inspection, and by relating an initial shear displacement to the length of the analysed sample or by relating the opening of saw-tooth and two-dimensional joint profiles with the degree of interlocking. Therefore, a tested peak shear strength criterion for natural, unfilled rock joints that realistically accounts for the influence of matedness on their peak shear strength is still lacking. This paper presents a methodology where objective measurements of the average aperture of natural, unfilled rock joints are used to estimate their matedness as a step in the prediction of the peak shear strength. This measured average aperture is based on high-resolution optical scanning of the surface roughness. The proposed relationship between measured average aperture and matedness of natural rock joints has been included in a further developed peak shear strength criterion. The verification against ten natural rock joint samples of coarse-grained granite showed that the revised criterion can predict the peak shear strength considering rock joint matedness.

Modelling of the Porousness inside 2.5D Carbon/Carbon Composites

Carbon/Carbon (C/C) composite is a kind of material that has good mechanical property in environment with high temperature above 2000°C. Due to its low density, high specific modulus, high specific strength, high temperature resistance, ablation resistance and corrosion resistance, it has been successfully used for manufacturing parts used in the aero-engine or rocket parts. While fabricating this kind of composite material with the carbonization and graphitization process, porousness with different sizes will be left inside the material. These porousness will affect the milling process, which is a commonly used method for manufacturing the C/C composite parts. To address this problem, a mathematical model is developed to describe the distribution of the porousness inside the 2.5D C/C composite. Firstly, the machined section of the specimen is scanned with the high resolution optical scanning instrument and then transformed to an image. Secondly, the porousness inside the specimen is extracted to calculate their distribution and proportion. Finally, an exponential distribution model is found to be suitable for distribution of porousness inside the material and an algorithm for simulating the pore distribution is established. It is found that the simulated surface is in a good agreement with the measured surface, yielding a relative difference in predicted porosity of 19.6%. The pore distribution of simulated surface also conforms the exponential function distribution. Its coefficients are within the range of the real surface, which verifies the feasibility of the algorithm.

Mechanical properties of hexagonal lattice structures fabricated using continuous liquid interface production additive manufacturing

Additive manufacturing (AM) is a key enabler for architectured lattice materials, because of the geometric complexity of parts that can be produced. Recent advancements in AM have enabled rapid production speeds, high spatial resolution, and a variety of engineering polymers. An open question remains whether production grade AM can accurately and repeatably produce lattice parts. This study presents design, production, and mechanical property testing of hexagonal lattice parts manufactured using continuous liquid interface production (CLIP) based AM. We printed and tested 84 parts, in three polymer materials having relative density ranging from 0.06 to 0.23. Lattice wall structures were reliably printed when truss aspect ratio was in the range 5 to 20 and wall thicknesses were 0.35 or 0.5 mm. The printed lattice parts, each comprising hundreds of slender walls, were measured using high resolution optical scanning. The images were analyzed to evaluate the difference between the printed parts and their designs, and the effect of geometric deviations on the mechanical behavior. The measured elastic moduli of the printed parts are close to the values expected from the materials specifications. The measured strength of the printed parts deviates by 7% from the behavior predicted from the scanned geometry. The failure mode of the printed structures depends upon the material and part geometry. To our knowledge, this is the largest study on the accuracy and performance of AM lattice parts, and the first study of its type for lattice parts made using CLIP.

Characterization of Copper Carbon Composites Manufactured Using the Electroless Precipitation Process

Copper-carbon composites with various copper nano-particulates volume fractions were manufactured using electroless precipitation process. Composites with 10% and 20% carbon volume fractions and copper samples were sintered at two different sintering temperatures 700° and 800°C. The microstructure was studied using high resolution optical scanning investigations. Experimental results indicate that the coefficients of thermal expansion and electrical resistivity intensified with the escalation of the carbon volume fraction in the composites. However, the stress-strain response was found to decrease with the increase of carbon volume fraction in the copper-carbon composites.

Eye and sheath folds in turbidite convolute lamination: Aberystwyth Grits Group, Wales

Eye and sheath folds are described from the turbidites of the Aberystwyth Group, in the Silurian of west Wales. They have been studied at outcrop and on high resolution optical scans of cut surfaces. The folds are not tectonic in origin. They occur as part of the convolute-laminated interval of each sand-mud turbidite bed. The thickness of this interval is most commonly between 20 and 100 mm. Lamination patterns confirm previous interpretations that convolute lamination nucleated on ripples and grew during continued sedimentation of the bed. The folds amplified vertically and were sheared horizontally by continuing turbidity flow, but only to average values of about γ = 1. The strongly curvilinear fold hinges are due not to high shear strains, but to nucleation on sinuous or linguoid ripples. The Aberystwyth Group structures provide a warning that not all eye folds in sedimentary or metasedimentary rocks should be interpreted as sections through high shear strain sheath folds.

The high-numerical approach for the 3D sampling theorem

Point-spread-function engineering constitutes an interesting tool for the improvement of the performance of 3D optical imaging devices like high-resolution optical scanning microscopes. Apart from the gains in resolution, which provide an easy method for the estimation of the superresolving abilities of pupil filters, other analytical tools are necessary for the fast computation of the 3D point spread function. Such tools should take into account the non-paraxial nature of microscopy imaging. In this sense, in this paper we report the high numerical-aperture version of the 3D sampling theorem.

Automated egg counting and sizing from scanned images: Rapid sample processing and large data volumes for fecundity estimates

The production of eggs in a fish population is a fundamental parameter in fisheries management and ecology. Management decisions are based largely on the abundance and composition of the spawning stock; hence it is essential to estimate the contribution of viable eggs by females of various ages, which may depend on the size and maturation schedules in females of younger ages, and the size and reproductive senescence of older ones. The level of recruitment may also be influenced by the size and quality of eggs. Egg quality can be characterised in a number of ways; however, the most useful methods are those that are efficient and widely available. Estimating potential fecundity and egg size in fish and invertebrate populations has been hindered by the processing time, toxicity, and resources required by traditional methods. We have developed an imaging-based technique that counts and measures oocytes from a gravimetric gonadal sub-sample in relatively little time and at low cost. Sub-samples were preserved in a non-toxic formulation of Gilson's solution, which offers an alternative to other preservatives commonly used in fecundity studies. The technique uses high-resolution optical scans of plated oocytes, imaging software, and user-defined object classifications to separate oocyte from ancillary material likely to be present in a processed sample. Estimates of misclassification are as low as 1% (false-negatives) in automated counts.

Self-aligned vertical electrostatic combdrives for micromirror actuation

In this paper, we analyze the effect of misalignment in electrostatic combdrives, and describe a fabrication technology that minimizes misalignment in vertical electrostatic combdrives by creating self-aligned, vertically staggered electrodes. Self-alignment of the interdigitated electrodes simplifies fabrication and minimizes failures due to electrostatic instability, thus enabling fabrication of narrow-gap, high-force actuators with high yield. The process is based on deep-reactive ion etching (DRIE) of buried-patterned silicon-on-insulator (SOI) wafers. Measurements on fabricated combdrives show relative misalignment of less than 0.05 /spl mu/m. This corresponds to less than 0.1% misalignment, which, according to our analysis, results in a travel range of 98% of that for perfectly aligned drives. The validity of the process is demonstrated by fabrication of scanning micromirrors measuring 300 /spl mu/m by 100 /spl mu/m. Optical angular deflections from 4/spl deg/ at low frequency to 40/spl deg/ at resonance were measured for an applied voltage of 75 Vpp. Resonant frequencies ranged from 5 kHz to 15 kHz for these devices, making them suitable for high-speed, high-resolution optical scanning and switching.

Characterization of rock thermal conductivity by high-resolution optical scanning

We compared three laboratory methods for thermal conductivity measurements: divided-bar line-source and optical scanning These methods are widely used in geothermal and petrophysical studies particularly as applied to research on cores from deep scientific boreholes The relatively new optical scanning method has recently been perfected and applied to geophysical problems A comparison among these methods for determining the thermal conductivity tensor for anisotropic rocks is based on a representative collection of 80 crystalline rock samples from the KTB continental deep borehole (Germany) Despite substantial thermal inhomogeneity of rock thermal conductivity (up to 40–50% variation) and high anisotropy (with ratios of principal values attaining 2 and more) the results of measurements agree very well among the different methods The discrepancy for measurements along the foliation is negligible (<1%) The component of thermal conductivity normal to the foliation reveals somewhat larger differences (3–4%) Optical scanning allowed us to characterize the thermal inhomogeneity of rocks and to identify a three-dimensional anisotropy in thermal conductivity of some gneiss samples The merits of optical scanning include minor random errors (16%) the ability to record the variation of thermal conductivity along the sample the ability to sample deeply using a slow scanning rate freedom from constraints for sample size and shape and quality of mechanical treatment of the sample surface a contactless mode of measurement high speed of operation and the ability to measure on a cylindrical sample surface More traditional methods remain superior for characterizing bulk conductivity at elevated temperature.

Development of high-resolution optical scanning fluorescence microscopy

Instrumentation of a high-resolution optical scanning fluorescence microscope is presented. This instrument provides a fluorescent image of the structural surface of various kinds of thin membrane samples with high resolution on the molecular scale. For this instrument, a new excitation optical tip and a three-dimensional scanning unit have been designed. The optical tip consists of a sharpened optical fibre covered with evaporated aluminium in vacuo, on which the top has a pinhole. The optical tip is mounted in the centre of a crosslinked piezoelectric scanning head. On thez-axis, a piezoelectric positioner is equipped with a differential micrometer mechanism. All operations are controlled with a micro-computer system.