Scanning Step Research Articles

Assessment of Stress-strain State of NPP Pipeline Metal Parts and Elements

As part of the experimental assessment of the stress-strain state of pipeline elements at the NPP using devices based on the magnetoanisotropic method, the criteria for the parameters of the main mechanical stress difference characterizing the increased probability of erosion and corrosion wear were obtained. It is determined that the high level of the main mechanical stress difference values in combination with the results of processing measurements on the parameters of the first derivative and the gradient of the main mechanical stress difference, depending on the scanning step in the grid nodes, are additional criteria for detecting a potentially dangerous area of erosion and corrosion wear.

Wavelet-transform-based speckle vector tracking method for X-ray phase imaging.

We introduce a new X-ray speckle-vector tracking method for phase imaging, which is based on the wavelet transform. Theoretical and experimental results show that this method, which is called wavelet-transform-based speckle-vector tracking (WSVT), has stronger noise robustness and higher efficiency compared with the cross-correlation-based method. In addition, the WSVT method has the controllable noise reduction and can be applied with fewer scan steps. These unique features make the WSVT method suitable for measurements of large image sizes and phase shifts, possibly under low-flux conditions, and has the potential to broaden the applications of speckle tracking to new areas requiring faster phase imaging and real-time wavefront sensing, diagnostics, and characterization.

A revised manuscript submitted to sensors and actuators B: Chemical illumination modification from an LED to a laser to improve the spatial resolution of IGZO thin film light-addressable potentiometric sensors in pH detections

Indium Gallium Zinc Oxide (IGZO) on Indium Tin Oxide (ITO) glass has been applied as the semiconductor substrate of a light-addressable potentiometric sensor (LAPS) with the advantages of immunity to room light inference and high photocurrent. For the first time, investigations into this IGZO LAPS including two-dimensional (2D) chemical imaging and reduction of the potential biorelative damage induced by the requirement of an ultraviolet (UV) light source are presented in this study. For the spatial resolution, a smaller aperture for the light spot provided by a light emitting diode (LED) makes the photocurrent decrease. To overcome this natural limitation, the type of AC modulation of light source is changed from a sine wave to a square wave with different duty cycles. The photocurrent and power consumption of a 365 nm LED with square wave and a duty cycle of 40 % are 42.2 % higher and 16.2 % lower than those of the conventional setup of a sine wave, respectively. The pH sensitivity, linearity, hysteresis and drift are comparable. The illumination wavelengths of 365, 405 and 435 nm are studied for photoresponse. 405 nm illumination with acceptable pH sensing performance can be suggested for IGZO LAPS for less bio damage concern. Additionally, a laser with a wavelength of 405 nm with spot size of 25 μm and scanning step of 2 μm is proven to have a clear pattern recognition down to 50 μm in 2D image. Further optimization of the spot size of the laser, thickness and composition of IGZO are suggested for better spatial resolution.

Femtosecond Ti: Sa ultra short-pulse laser irradiation effects on the properties and morphology of the zirconia surface after ageing

Femtosecond pulses from a Ti:Sapphire laser were used to irradiate specimens of yttria-stabilised (35% mol) tetragonal zirconia (Y-TZP) with the purpose of studying the effects of the irradiations on their surface properties and morphology after ageing. Zirconia disks were divided into eight groups (n = 32) according to their surface treatment and subsequent ageing: Control: no treatment; sandblasting: Al2O3 sandblasting 50 μm; and ultrashort laser pulses irradiation with 25 μJ pulses, considering two different scanning steps based on the width between two grooves. These groups were duplicated and submitted to ageing. The surfaces were analysed using scanning electron microscopy (SEM), and X-ray diffraction. A finite element analysis, a biaxial flexure test, as well as fractographic and Weibull analyses, were performed. The strengths of the disks were statistically different for the treatment factor, and the principal stresses seemed to be concentrated at the centre of the specimens, as predicted by the computer simulations. Ageing decreased the strengths for all groups and increased the Weibull modulus for the laser group with the 40 μm-width between two grooves. The sandblasting group presented the highest monoclinic phase peak. Although the most significant strength was found within the sandblasting group, the phase transformation was favourable to the laser groups. The Weibull modulus was higher for the laser group with the 60 μm-width between two grooves, confirming the highest homogeneity of its failure distribution. Regardless of the surface treatment, strength was decreased with ageing in all groups. The femtosecond Ti:Sa ultra-short pulse laser irradiation can be suggested as an alternative to the gold standard sandblasting in long-term Y-TZP zirconia rehabilitations, such as crowns and veneers.

MulayCap: Multi-Layer Human Performance Capture Using a Monocular Video Camera.

We introduce MulayCap, a novel human performance capture method using a monocular video camera without the need for pre-scanning. The method uses "multi-layer" representations for geometry reconstruction and texture rendering, respectively. For geometry reconstruction, we decompose the clothed human into multiple geometry layers, namely a body mesh layer and a garment piece layer. The key technique behind is a Garment-from-Video (GfV) method for optimizing the garment shape and reconstructing the dynamic cloth to fit the input video sequence, based on a cloth simulation model which is effectively solved with gradient descent. For texture rendering, we decompose each input image frame into a shading layer and an albedo layer, and propose a method for fusing a fixed albedo map and solving for detailed garment geometry using the shading layer. Compared with existing single view human performance capture systems, our "multi-layer" approach bypasses the tedious and time consuming scanning step for obtaining a human specific mesh template. Experimental results demonstrate that MulayCap produces realistic rendering of dynamically changing details that has not been achieved in any previous monocular video camera systems. Benefiting from its fully semantic modeling, MulayCap can be applied to various important editing applications, such as cloth editing, re-targeting, relighting, and AR applications.

Multi-scale analysis of the generated damage when machining pockets of 3D woven composite for repair applications using abrasive water jet process: Contamination analysis

Repair of damaged aircraft structural parts is a regular maintenance activity carried out to preserve airworthiness while being economically viable. Conventional repair techniques used have negative impact on the repair quality and environment due to dust emission. For eliminating aforementioned problem, this study investigates controlled depth abrasive water jet (AWJ) milling for repair procedure of 3D woven CFRP composite structures used in the new aircraft engine developed by Safran Aircraft Engines. The aim is to identify and quantify the damage and surface contamination induced by AWJ milling. For this, the influence of milling parameters on the damage and surface contamination is investigated through full factorial experimental study. Several characterisation techniques like 3D optical profilometry, Scanning Electron Microscopy and X-ray tomography combined with image processing were used for a multi-scale analysis of the machined surface damage and contamination. In fact, the machining quality was quantified using an innovative criterion called “crater volume” (Cv). The obtained results have shown surface contamination by embedded abrasive particles and presence of bare and broken fibres, cracks, craters. The results show that the rate of contamination is influenced by the jet pressure and the scan step and the Cv is influenced by the jet exposure time.

High-sensitivity nanoscale chemical imaging with hard x-ray nano-XANES.

Resolving chemical species at the nanoscale is of paramount importance to many scientific and technological developments across a broad spectrum of disciplines. Hard x-rays with excellent penetration power and high chemical sensitivity are suitable for speciation of heterogeneous (thick) materials. Here, we report nanoscale chemical speciation by combining scanning nanoprobe and fluorescence-yield x-ray absorption near-edge structure (nano-XANES). First, the resolving power of nano-XANES was demonstrated by mapping Fe(0) and Fe(III) states of a reference sample composed of stainless steel and hematite nanoparticles with 50-nm scanning steps. Nano-XANES was then used to study the trace secondary phases in lithium iron phosphate (LFP) particles. We observed individual Fe-phosphide nanoparticles in pristine LFP, whereas partially (de)lithiated particles showed Fe-phosphide nanonetworks. These findings shed light on the contradictory reports on Fe-phosphide morphology in the literature. Nano-XANES bridges the capability gap of spectromicroscopy methods and provides exciting research opportunities across multiple disciplines.

XRD and EBSD studies of severe shot peening induced martensite transformation and grain refinements in austenitic stainless steel

Effects of severe shot peening (SSP) on the phase transformation and grain refinements of stainless steel 304 have been studied, driven by potential performance improvements via grain refinements in advanced surface enhancements, by employing X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). XRD measurements reveal a monotonic increase in martensite transformations (MT) when the shot peening coverage (SPC) is increased from 100% to 1500% and the increase exhibits a strong correlation with that of the compressive residual stress (CRS). They also reveal that the maximum MT locates under the processed surface and shifts deeper into the material when the SPC is increased. This variation trend, except for the different locations in depth, is similar to that of the maximum CRS. The depth-dependence of MT measured by XRD is consistent with that measured by EBSD at a scanning step of 0.3 μm; however, discrepancies are observed when either increasing or decreasing the scanning step by about one order of magnitude. The discrepancies are attributable to the SSP-induced grain refinements, which exhibit a monotonic decrease as a function of the depth under the peened surface, while the severely refined grains are most dominated by martensite.

Generalized linear model for enhancing the temperature measurement performance in Brillouin optical time domain analysis fiber sensor

This study describes the deployment of machine learning algorithm called generalized linear model (GLM) to improve the temperature prediction performance in Brillouin optical time domain analysis (BOTDA) fiber sensor for distributed temperature sensing application. In GLM, the temperature prediction is made from the Brillouin gain spectrum (BGS) and the link function, without the need to determine the Brillouin frequency shift (BFS). In this proof-of-concept experiment, the performance of GLM was investigated by collecting the BGS and comparing it to the conventional Lorentzian curve fitting (LCF) method. From the experimental results, we have found that the GLM method produced a more consistent temperature prediction than the conventional LCF method. Furthermore, the proposed GLM method could still retain an accurate temperature measurement regardless of low signal-to-noise ratio (SNR) and large frequency scanning step while collecting BGS, which is difficult to be achieved by the conventional LCF method at certain level. In addition to that, the prediction obtained is 655 times faster than the conventional LCF method. The small and negligible deterioration to the temperature resolution confirmed the robustness of GLM in performing fast and accurate temperature measurement for BOTDA.

Iterative X-ray spectroscopic ptychography.

Spectroscopic ptychography is a powerful technique to determine the chemical composition of a sample with high spatial resolution. In spectro-ptychography, a sample is rastered through a focused X-ray beam with varying photon energy so that a series of phaseless diffraction data are recorded. Each chemical component in the material under investigation has a characteristic absorption and phase contrast as a function of photon energy. Using a dictionary formed by the set of contrast functions of each energy for each chemical component, it is possible to obtain the chemical composition of the material from high-resolution multi-spectral images. This paper presents SPA (spectroscopic ptychography with alternating direction method of multipliers), a novel algorithm to iteratively solve the spectroscopic blind ptychography problem. First, a nonlinear spectro-ptychography model based on Poisson maximum likelihood is designed, and then the proposed method is constructed on the basis of fast iterative splitting operators. SPA can be used to retrieve spectral contrast when considering either a known or an incomplete (partially known) dictionary of reference spectra. By coupling the redundancy across different spectral measurements, the proposed algorithm can achieve higher reconstruction quality when compared with standard state-of-the-art two-step methods. It is demonstrated how SPA can recover accurate chemical maps from Poisson-noised measurements, and its enhanced robustness when reconstructing reduced-redundancy ptychography data using large scanning step sizes is shown.

Abrasive water and slurry jet micro-machining techniques for fabrication of molds containing raised free-standing micro-features

The demand for metallic micro-molds that can be used for inexpensive mass production of polymeric microfluidic chips is increasing. Existing manufacturing techniques such as soft-lithography and photolithography can require multiple time-consuming steps, especially when the aim is to create three-dimensional features. In this study, the feasibility of using abrasive water jet machining (AWJM) and abrasive slurry jet machining (ASJM) to fabricate such micro-molds in Al6061-T6 and SS316 was studied. Jet raster scans under various combinations of process parameters were used in order to machine micro-pockets containing free-standing structures, representing molds for casting microfluidic chips with channel networks. As expected, for both materials and using both ASJM and AWJM, the pocket roughness decreased as the distance between adjacent raster scans (step size) decreased, but the lowest waviness occurred at an intermediate step size. The best quality pockets were achieved on SS316 using ASJM with the intermediate step size and the highest possible slurry mass flow rate. Unmasked machining could not be used to fabricate molds with sharp-edged intersecting features, and a novel hybrid AWJM/ASJM masked machining technique was thus introduced. An undercut and an undesirable erosion near the edges of the mask formed if the position of the last raster scan closest to the mask was not carefully controlled. Possible reasons for these phenomena were discussed in terms of the likelihood of jet deflection off the machining kerf and mask, and the resulting erosion due to secondary slurry flow. By careful selection of the process parameters, it was demonstrated that high quality molds with both single and intersecting free-standing structures at multiple heights could be fabricated, thus making three-dimensional microfluidic chip mold fabrication feasible.

Rational design of a conformation-specific antibody for the quantification of Aβ oligomers

Protein misfolding and aggregation is the hallmark of numerous human disorders, including Alzheimer's disease. This process involves the formation of transient and heterogeneous soluble oligomers, some of which are highly cytotoxic. A major challenge for the development of effective diagnostic and therapeutic tools is thus the detection and quantification of these elusive oligomers. Here, to address this problem, we develop a two-step rational design method for the discovery of oligomer-specific antibodies. The first step consists of an "antigen scanning" phase in which an initial panel of antibodies is designed to bind different epitopes covering the entire sequence of a target protein. This procedure enables the determination through in vitro assays of the regions exposed in the oligomers but not in the fibrillar deposits. The second step involves an "epitope mining" phase, in which a second panel of antibodies is designed to specifically target the regions identified during the scanning step. We illustrate this method in the case of the amyloid β (Aβ) peptide, whose oligomers are associated with Alzheimer's disease. Our results show that this approach enables the accurate detection and quantification of Aβ oligomers in vitro, and in Caenorhabditis elegans and mouse hippocampal tissues.

Differential Alternative Pulses Voltammetry Application in Organic and Inorganic Analysis

The simultaneous voltammetric determination of species with close peak potentials presents some difficulties, because of the overlapping of their redox peaks at conventional solid electrodes. Therefore, two approaches were proposed to overcome this drawback: (i) chemometric resolution of the overlapped peaks by semi-derivative or multivariate analysis and (ii) development of chemically modified electrodes with better electrochemical performances, permitting peaks separation. However, the mathematical treatment habitually results in a precision decrease, while the electrode modification often requires the use of expensive materials and involves sophisticated techniques. Hence, another strategy for the direct simultaneous species determination is suggested in this work. It involves the application of Differential Alternative Pulses Voltammetry (DAPV) [1], which provides the great resolution of the second order voltammetric techniques, as Radio-Frequency Polarography, Second Harmonic AC Voltammetry, and Differential Faradaic Rectification Polarography (DFRP), in combination with the high sensitivity, precision, and instrumental and operational simplicity of the most common voltammetric technique, the differential pulse voltammetry (DPV).The second order voltammetric techniques including DAPV are based on the nonlinearity of the electrochemical system I/E characteristic yielding voltammograms shaped as a derivative of voltammetric peak resulting from small sinusoidal or rectangular bipolar deviations of the DC potential. Two single pulses of small amplitude, one cathodic and one anodic are successively applied in DAPV for every value of the scanned DC potential with delay time between the pulses equal to the delay time between the scan step and the first one (Fig. 1). The sum of the two pulse faradaic current components with opposite polarities is registered vs. the scanned potential as DAPV voltammogram. The experimentally determined half-width of the DAPV peaks (37 mV at 2 electrons reduction) is 1.22 times smaller than that of the most common voltammetric technique DPV (45.3 mV) at the same conditions and equals that obtained by the application of another second order technique, the DFRP. Thus, the DAPV voltammogram’s shape as second derivative of voltammetric wave combined with the small half-widths of the anodic and the cathodic peaks allows simultaneous quantification of species having very small peak potential difference.Taking advantage from the great resolution power of DAPV, it was applied for the simultaneous determination of a range of organic (catechol and hydroquinone [2]; o-nitrophenol, m-nitrophenol and p-nitrophenol [3]) and inorganic species (Cd2+/In3+; Tl+/Pb2+ [1, 4]) with close peak potential difference, as shown in Figs. 2-5.The proposed approach offers a very simple alternative route for the simultaneous determination of a broad range of species and overcomes the disadvantages of the currently applied strategies involving electrode modification or mathematical data processing.

Multiple Step Interlaced Beam Scan to Minimize the Deviation of Radar Detection Performance

For detection of targets, a radar conventionally scans a specified search volume with a fixed beam lattice of a specified beam spacing. With the fixed beam lattice, the detection performance of the radar within a unit beam lattice changes depending on the line-of-sight angle to a target. In this paper, multiple step interlaced scan is proposed to minimize the deviation of the detection performance due to the change of the target line-of-sight angle. As a figure of merit for the detection performance, the cumulative probability of detection is analyzed for various values of the interlaced scan step with different beam overlap ratios, and the optimal values of the steps to minimize the deviation of the cumulative probability of detection are derived.

THE Pr3Ga1,67Se7 – Pr3Ge1,25Se7 SYSTEM

Interaction of the components in Pr 3 Ga 1,67 Se 7 – Pr 3 Ge 1,25 Se 7 system and crystal structure of the quaternary phase Pr 3 GaGe 0,5 Se 7 have been investigated using X-ray phase analysis. The alloys were synthesized from elementary substances of at least 99.99 wt. % purity in quartz containers in an MP-30 programmable electric muffle furnace. Containers were evacuated to a residual pressure of 10-2 Pa and soldered in oxygen-gas burner flame. The alloys were synthesized by: 1) heating the mixture to 870 K at the rate of 30 K/h; 2) exposure for 100 h; 3) heating to 1370 K at the rate of 12 K/h; 4) exposure for 2 h; 5) cooling to 770 K at the rate of 12 K/h; 6) homogenizing annealing for 500 h. After reaching the equilibrium state, the synthesized alloys were quenched into room-temperature water. The diffraction patterns for X-ray phase analysis were recorded at a DRON 4-13 diffractometer for 2Q range of 10-80° (CuKα radiation, scan step 0.05°, 4 s exposure in each point). Data processing and the determination of the crystal structure utilized WinCSD software package. A continuous solid solution series is formed in the Pr 3 Ga 1,67 Se 7 – Pr 3 Ge 1,25 Se 7 system. At 770 K, the parameter a of the hexagonal cell varies within the solid solution from 1,0354(3) nm to 1,0620(3) nm. The parameter c varies from 0,6391(2) nm to 0,6057(1) nm, and the cell volume from 0,59336 nm 3 to 0,59163 nm 3 . The Pr atoms are centered on trigonal prisms with one additional atom. These prisms are formed by Se atoms. The atoms of the statistical mixture M1 (0,333 Ga + 0,167 Ge) are located practically in the centers of the octahedra of Se atoms ([M16Se1]). Atoms M2 (0,667 Ga + 0,333 Ge) are located in tetrahedraof Se atoms ([M 23 Se 21 Se 3 ]).

Improved voltage scanning method for maximum power point under partial shadow conditions

This paper proposes a novel maximum power point tracking (MPPT) algorithm with global search. The algorithm combines global voltage sweep and incremental conductance method, and introduces a Judging factor as a criterion for global voltage scanning. The Judging factor is compared with the threshold and the scan step size is selected based on the result. Take a large step when far from the peak. When approaches the peak, uses the incremental conductance method to find the local extrema and store it, then continues scanning. When the output power is close to zero, the scan is complete, Comparing all local extrema points then the global maximum power point will be found by this algorithm. Matlab simulation results show that the algorithm can find the global maximum and the search speed is fast.

Investigation on high speed laser printing of silver nanoparticle inks on flexible substrates

The ever-increasing demand for more efficient, cost- and time-effective electronics required in production-grade technology, impels the research in the field of printed electronics. Laser-induced forward transfer (LIFT) technique meets the requirements for precise deposition and high resolution components, however further research has to be conducted in order to improve the process’ speed and reproducibility. In this work, laser printing of silver (Ag) nanoparticle lines on PEN substrate at high repetition rates (10–40 kHz) is introduced and an investigation on the factors that affect the printing results, including the experimental setup’s parameters and inks’ rheological characteristics, is conducted. Specifically, a high-speed imaging setup is employed in order to study the liquid bubble formation and jet expansion, for four Ag nanoparticle inks of different viscosities and four different repetition rates. At the same time, different values of donor-receiver distance and scanning step are applied, in order to succeed optimum lines. The results indicate that, for high repetition rates, best quality lines derive from high viscosity inks when the distance between the donor and the receiver is relatively small.

Scanning Nanowire Probe Interferometer for Scalable Humidity Mapping

AbstractQuantifying humidity has long been an unavoidable task in science, industry, and society. Recent developments of nanoscience and technology that deal with ultrasmall droplets have aroused interest in microscopic moisture. Utilization of nanomaterials has been emerging as a promising strategy to miniaturize hygrometers for high‐sensitive, ultrasmall‐area sensing. However, a lack of high‐precision, on‐demand position control of sensing nanomaterials makes it difficult to explore spatial distribution of humidity at the micro‐ and nanoscale. Here, a scanning probe hygrometry (SPH) is developed that enables not only micro/nanoresolution but also scalable spatial mapping of humidity distribution. The SPH is realized with an unprecedented scanning nanowire probe interferometer (NPI) that is produced by direct 3D nanoprinting of a moisture‐sensitive polymer on a tapered optical fiber. Notably, the interferometric response of the NPI probe in ultrasmall areas quantitatively depends on humidity, arising from its refractive index change and volumetric swelling. By scanning the NPI probe and reading out the interferometric signals, multiscale spatial mapping of humidity distribution with versatile scanning steps from ≈102 nm to a few mm is demonstrated. The NPI is expected to provide a new nanoscale metrology that can answer fundamental questions about evaporation‐related science and engineering.

Rapid High-Resolution Mosaic Acquisition for Photoacoustic Remote Sensing.

Mechanical stages are routinely used to scan large expanses of biological specimens in photoacoustic imaging. This is primarily due to the limited field of view (FOV) provided by optical scanning. However, stage scanning becomes impractical at higher scanning speeds, or potentially unfeasible with heavier samples. Also, the slow scan-rate of the stages makes high resolution scanning a time-consuming process. Some clinical applications such as microsurgery require submicron resolution in a reflection-mode configuration necessitating a method that can acquire large field of views with a small raster scanning step size. In this study, we describe a method that combines mechanical stages with optical scanning for the rapid acquisition of high-resolution large FOVs. Optical scanning is used to acquire small frames in a two-dimensional grid formed by the mechanical stages. These frames are captured with specific overlap for effective image registration. Using a step size of 200 nm, we demonstrate mosaics of carbon fiber networks with FOVs of 0.8 × 0.8 mm2 captured in under 70 s with 1.2 µm image resolution. Larger mosaics yielding an imaging area of 3 × 3 mm2 are also shown. The method is validated by imaging a 1 × 1 mm2 section of unstained histopathological human tissue.

Shape refinement and rigging of raw-scanned 3D volume by a user-specified skeleton

RGB-D camera-based scanning has increased in popularity; however, raw-scanned three-dimensional (3D) models contain several issues, such as fused arms and legs, that hinder animation. Here, we describe a semiautomatic method that allows generation of a rigged 3D mesh from a raw-scanned 3D volume with simple annotations. The method allows a user to annotate a skeleton structure on registered photographs captured in the scanning step, followed by automatic cutting of fused body parts using the skeleton information to beautify the cut surface by applying mesh smoothing. The system then generates a skinned 3D mesh based on the user-specified 3D skeleton. We tested our method using several raw-scanned 3D plush toy models and successfully generated plausible animations.