Suitable Post Processing Research Articles

In situ study on the tensile deformation in high-density polyethylene/hexagonal boron nitride composite

Tensile deformation in the post processing of polymer plays a critical role in determining its mechanical properties. In this work, we investigated the structure evolution of high-density polyethylene/hexagonal boron nitride (HDPE/h-BN) composite during stretching in a wide temperature range from 25 °C to 100 °C in order to reveal the suitable post processing temperature of HDPE/h-BN composites fiber. The structure transition of HDPE crystal and the distribution of h-BN were investigated by in-situ small-angle X-ray scattering (SASX), in-situ wide-angle X-ray diffraction (WAXD) measurements, and scanning electron microscopy (SEM). The result shows that the parent HDPE crystal would be broken and recrystallize into highly oriented daughter crystal along the tensile direction when the tensile temperature (Tten) is in the range from 70 °C to 100 °C, though the recrystallization rate is low at high Tten. When Tten is low (25 °C), the crystallinity decreases continuously as no recrystallization takes place. In addition, the h-BN migrates accompany with the HDPE matrix and becomes oriented during the tensile direction. Combining the result of WAXD, SAXS, and the SEM measurement, it is concluded that the temperature of 70 °C is suitable for post processing of the HDPE/h-BN composite fiber.

Deja Vu: semantics-aware recording and replay of high-speed eye tracking and interaction data to support cognitive studies of software engineering tasks-methodology and analyses.

The paper introduces a fundamental technological problem with collecting high-speed eye tracking data while studying software engineering tasks in an integrated development environment. The use of eye trackers is quickly becoming an important means to study software developers and how they comprehend source code and locate bugs. High quality eye trackers can record upwards of 120 to 300 gaze points per second. However, it is not always possible to map each of these points to a line and column position in a source code file (in the presence of scrolling and file switching) in real time at data rates over 60 gaze points per second without data loss. Unfortunately, higher data rates are more desirable as they allow for finer granularity and more accurate study analyses. To alleviate this technological problem, a novel method for eye tracking data collection is presented. Instead of performing gaze analysis in real time, all telemetry (keystrokes, mouse movements, and eye tracker output) data during a study is recorded as it happens. Sessions are then replayed at a much slower speed allowing for ample time to map gaze point positions to the appropriate file, line, and column to perform additional analysis. A description of the method and corresponding tool, Deja Vu, is presented. An evaluation of the method and tool is conducted using three different eye trackers running at four different speeds (60 Hz, 120 Hz, 150 Hz, and 300 Hz). This timing evaluation is performed in Visual Studio, Eclipse, and Atom IDEs. Results show that Deja Vu can playback 100% of the data recordings, correctly mapping the gaze to corresponding elements, making it a well-founded and suitable post processing step for future eye tracking studies in software engineering. Finally, a proof of concept replication analysis of four tasks from two previous studies is performed. Due to using the Deja Vu approach, this replication resulted in richer collected data and improved on the number of distinct syntactic categories that gaze was mapped on in the code.

Finite element simulation of plasticity and fracture for Inconel 718 deposited by laser powder bed fusion – Chances, use and challenges

Laser Powder Bed Fusion (LPBF), is used to produce a component in layers by selective re-melting of a metal powder bed. A powder layer of an alloy is applied to a metal substrate within a process chamber filled with an inert gas. This powder layer is locally heated by a laser to a temperature above the melting point of the used alloy. Only regions of the applied powder which belong to the desired component are treated by the laser beam. After heating the layer is complete, the build platform is lowered by 30–90 µm and a new powder layer is applied. The procedure is repeated until the part is completed. After suitable post processing the part can be used. The relative density of the finished component is close to 100%. Depending on the deposition system the laser spot diameter measures approximately 40–80 µm, therefore the size of the resulting melt region is relatively small while cooling rates and temperature gradients are very high. Hence some resulting material properties of certain laser-melted alloys differ from the properties which can be achieved by conventional production routes. Furthermore, studies show that adjustment of certain process parameters can be used to influence the material condition, e.g., the anisotropy of the mechanical material properties. On the one hand this degree of freedom might offer opportunities to realize designed component properties, but on the other hand the modeling of the material condition and the resulting mechanical properties is challenging. A testing program covering different stress states as well as different material orientations has been performed at COMTES FHT. The tests revealed a significant orthotropy of plasticity and fracture which both are considered in the derived material card for the material model MF GenYld+CrachFEM – a material model developed by MATFEM. A good agreement between physical tests and finite element simulations of the performed tests was found. Chances and challenges in using the full potential of AM deposited materials based on detailed numerical modeling considering material orthotropic behavior are presented here for Inconel 718 and are supported by experimental testing.

In‐Depth Identification of Phenolics Fractionated from Eucalyptus Kraft Lignin

AbstractKraft lignin, the principal by‐product of the pulping industry, is an abundant yet highly underutilized aromatic resource. It is useful due to the vast scales involved as a source of fuels, chemicals, and functional materials when suitable postprocessing is applied. It is deemed to be a renewable alternative to fossil sources. Because of the extreme complexity of kraft lignin, in‐depth composition analysis and chemical structural identification are crucial for the development of effective valorization strategies. This work embarks on the characterization and identification of lignin‐derived phenolic compounds in representative hardwood (Eucalyptus) kraft lignin after selective fractionation using a single solvent. Advanced 2D heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR), 31P NMR, and mass spectrometry in combination with synthetic authentic compounds are used for the structural identification of the low‐molecular‐weight fraction of kraft lignin. A total of 20 phenolic compounds, including several novel monomers (catechols), dimers (diarylethanes, diarylethenes, etc.), and trimers with triphenyl structures are systematically identified in the Eucalyptus kraft lignin. In addition, polysulfide is detected in the low‐molecular‐weight fraction, indicating that the oxidative polymerization of S2−/HS− occurrs during the kraft pulping process. An improved understanding of kraft lignin, especially the low‐Mw fraction, is expected to provide essential information for the selective fractionation and valorization of lignin.

Superconvergent weak Galerkin methods for non-self adjoint and indefinite elliptic problems

In this paper we present a stabilizer-free weak Galerkin (SFWG) finite element scheme for the approximation of the non-self adjoint and indefinite elliptic equations. Supercloseness convergence of the SFWG method is derived. After a suitable postprocessing of the SFWG solution, the resulting post-processed solution converges with two order higher than the optimal order in both H1 semi-norm and L2 norm on triangular meshes. Numerical experiments are demonstrated to verify the theoretical findings.

Two Ensemble Approaches for Forecasting Sulfur Dioxide Concentrations from Kīlauea Volcano

AbstractKīlauea volcano, located on the island of Hawaii, is one of the most active volcanoes in the world. It was in a state of nearly continuous eruption from 1983 to 2018 with copious emissions of sulfur dioxide (SO2) that affected public health, agriculture, and infrastructure over large portions of the island. Since 2010, the University of Hawaiʻi at Mānoa provides publicly available vog forecasts that began in 2010 to aid in the mitigation of volcanic smog (or “vog”) as a hazard. In September 2017, the forecast system began to produce operational ensemble forecasts. The months that preceded Kīlauea’s historic lower east rift zone eruption of 2018 provide an opportunity to evaluate the newly implemented air quality ensemble prediction system and compare it another approach to the generation of ensemble members. One of the two approaches generates perturbations in the wind field while the other perturbs the sulfur dioxide (SO2) emission rate from the volcano. This comparison has implications for the limits of forecast predictability under the particularly dynamic conditions at Kīlauea volcano. We show that for ensemble forecasts of SO2 generated under these conditions, the uncertainty associated with the SO2 emission rate approaches that of the uncertainty in the wind field. However, the inclusion of a fluctuating SO2 emission rate has the potential to improve the prediction of the changes in air quality downwind of the volcano with suitable postprocessing.

Optical Stepped Thermography of Defects in Photovoltaic Panels

Defects in photovoltaic panels can reduce the effective working area, and decrease the performance of the photovoltaic panels. Therefore, it is significant to identify such defects and to feed the fault information up to the production chain. Active infrared thermographic non-destructive testing has the advantages of non-contact, fast speed and large imaging area, and has been widely used in the detection of defects in various materials. In this article, a stepped thermography of the defects, which result in degradation of energy conversion efficiency of cells in photovoltaic panels, was proposed. The front surface of the photovoltaic panel was optically stimulated by halogen lamps in step heating way, while an infrared camera was employed to monitor the temperature evolution of the front surface and to capture infrared image sequences. The thermal image sequences were processed using data processing algorithms, focusing on enhancing the defect signatures. The techniques of background subtraction, discrete Fourier transform, polynomial fitting, first-order derivative, cross correlation coefficient and histogram equalization were mainly used. Compared to the raw thermal images, the reconstructed images using suitable algorithms are more helpful to evaluate the defects. The results show that the optical stepped thermography combined with suitable post data processing is a fast and effective technique to identify the defects in photovoltaic panels.

Experiment and optimization study on the radial graded porous volumetric solar receiver matching non-uniform solar flux distribution

Radial graded porous volumetric solar receiver is designed to match the non-uniform solar flux distribution. Based on the computed tomography and image-processing techniques, uniform and radial graded porous volumetric solar receivers are reconstructed. The 3D printing technique and suitable post processing are implemented to fabricate complex porous samples using super-alloy Inconel 718 as material. Both experimental and numerical studies are conducted to investigate the fluid flow and heat transfer processes in porous volumetric solar receivers. The results present that the 3D printed porous samples are suitable for solar thermal energy absorption and high temperature utilization. As for uniform porous receivers, porous media with small pore diameter has larger thermal efficiency because of enhanced convective heat transfer. Compared with the uniform porous receiver with highest thermal efficiency, the radial graded porous volumetric solar receiver with large pore diameter inside could further relatively increase the thermal efficiency by 4.1% while relatively decreases the flow resistance by 8.6%. The reasonable distribution of pore diameter of porous media could regulate the mass flow distribution and direct more air to the high heat flux region. Moreover, local overheating phenomenon is observed in the uniform porous receiver using air as heat transfer fluid. By applying the coupled optimization method, an optimum pore diameter distribution is determined for the radial graded porous volumetric solar receiver.

Mechanical and microstructural characterization of microwave post processed Alloy-718 coating

High Velocity Oxy-fuel (HVOF) sprayed coatings are preferred for depositing almost all materials in numerous industries due to their ease of operation. However, the presence of heterogenous microstructure along with the presence of considerable porosity requires a suitable post processing of as-sprayed coatings. In the present work, the principles of microwave hybrid heating (MHH) were successfully applied for the post processing of HVOF sprayed Alloy-718 coating. The as-sprayed and post-processed coatings were characterised in terms of their microstructure, microhardness, fracture toughness and surface roughness. Pin-on-disc tribometer was used to analyse the abrasive wear behaviour of as-sprayed and post-processed coatings. The post processed coating resulted in significant improvement in mechanical properties of the as-sprayed coatings due to healing of micro-cracks and pores during microwave exposure.

Edge disbond detection of carbon/epoxy repair patch on aluminum using thermography

The composite patches are used to repair the damaged metal and composite structures in different industries, especially in the aerospace industry. One of the most dangerous types of defects are the disbond defects in repaired structures because of cutting the flow of stress to the patch. Disbond defects are often initiated at the edge of the repair patch and propagated to the center by degradation in service. Flash thermography inspection at the edge of repair patch is a challenging issue due to the edge effect.In the present study, the disbonds at the edges of composite repair patch have been investigated by step heating thermography method. Since, raw thermal data are usually not suitable for quantitative defects evaluation and so, different image processing methods, including Fourier transform (FT), one- and two-dimensional Daubechie's wavelet transforms have been performed. Furthermore, for the first time, the three dimensional wavelet transform has been used to optimize the results in terms of signal to noise ratio and time processing. Moreover, the simulation of the thermography inspection process has been carried out using finite element modeling (FEM). The model enables a better understanding of the heat transfer process and provides a means of establishing the experimental set-up parameters required for inspecting appropriately the edge of the repair patch on metal structures. Results provided some suggestions in selecting more suitable post processing for interrogating of adhesive bonded composite with different states.

Quantitative subsurface analysis using frequency modulated thermal wave imaging

Quantitative depth analysis of the anomaly with an enhanced depth resolution is a challenging task towards the estimation of depth of the subsurface anomaly using thermography. Frequency modulated thermal wave imaging introduced earlier provides a complete depth scanning of the object by stimulating it with a suitable band of frequencies and further analyzing the subsequent thermal response using a suitable post processing approach to resolve subsurface details. But conventional Fourier transform based methods used for post processing unscramble the frequencies with a limited frequency resolution and contribute for a finite depth resolution. Spectral zooming provided by chirp z transform facilitates enhanced frequency resolution which can further improves the depth resolution to axially explore finest subsurface features. Quantitative depth analysis with this augmented depth resolution is proposed to provide a closest estimate to the actual depth of subsurface anomaly. This manuscript experimentally validates this enhanced depth resolution using non stationary thermal wave imaging and offers an ever first and unique solution for quantitative depth estimation in frequency modulated thermal wave imaging.

Abstract P365: Blood Pressure Evaluation From Ppg Signal Analysis and Artificial Neural Network

The analysis of the PPG signal in the time domain for the evaluation of the blood pressure (BP) is proposed. Some features extracted from the PPG signal are used to train an Artificial Neural Network (ANN) to determine the function that fit the target systolic and diastolic BP. The data related to the PPG signals and BP used in the analysis are provided by the Multi-parameter Intelligent Monitoring in Intensive Care (MIMIC II) database. The pre-analysis of the signal to remove inconsistent data is also proposed. A set of 1750 valid pulse is considered. The 80% of the input samples is used for the training of the network. Instead, the 10% of the input data are used for the validation of the network and 10% for final test of this last. The results show as the error for both the systolic and diastolic BP evaluation is included in the range of ±3 mmHg. Tab.1 shows the results for 20 PPG pulses randomly selected analyzed together with the systolic and diastolic blood pressure furnished by MIMC and evaluated by the trained ANN. Tab.1 experimental results comparing MIMIC and the ANN results. Moreover, a suitable hardware to validate the ANN with the sphygmomanometer is designed and realized. This hardware allows clinicians to collect data according to the requirements of the validation procedure. With the sphygmomanometer the systolic and diastolic values are referred to two different PPG pulses. As a consequence, it is proposed a new hardware interface allowing the synchronized acquisition and storage of the PPG signal and clinician voice. For the validation, the clinician: (i) evaluates the BP on both the arms and assesses that no significant differences occur; (ii) plugs the PPG sensor on the finger of one arm; (iii) starts the recording of both the PPG signal and the audio signal; (iv) evaluates the BP on the other arm with sphygmomanometer and says the systolic and diastolic values when detected. Through suitable post processing algorithm, the Systolic and Diastolic values are associated to the corresponding PPG Pulses. Following this procedure, the dataset to further validate the ANN according the standard is obtained. Once the ANN is validated it will be implemented on smartphone to have always in the pocket a reliable measurement system for Blood Pressure, oximetry and heart rate.

Development of CNTs-filled photopolymer for projection stereolithography

PurposePolymeric parts produced by 3D stereolithography (SL) process have poorer mechanical properties as compared to their counterparts fabricated via conventional methods, such as injection or compression molding. Adding nanofillers in the photopolymer resin for SL could help improve mechanical properties. This study aims to achieve enhancement in mechanical properties of parts fabricated by SL, for functional applications, by using well-dispersed nanofillers in the photopolymers, together with suitable post-processing.Design/methodology/approachCarbon nanotubes (CNTs) have high strength and Young’s modulus, making them attractive nanofillers. However, dispersion of CNTs in photopolymer is a critical challenge, as they tend to agglomerate easily. Achieving good dispersion is crucial to improve the mechanical properties; thus, suitable dispersion mechanisms and processes are examined. Solvent exchange process was found to improve the dispersion of multiwalled carbon nanotubes in the photopolymer. The UV-absorbing nature of CNTs was also discovered to affect the curing properties. With suitable post processing, coupled with thermal curing, the mechanical properties of SL parts made from CNTs-filled resin improved significantly.FindingsWith the addition of 0.25 wt.% CNTs into the photopolymer, tensile stress and elongation of the 3D printed parts increased by 70 and 46 per cent, respectively. With the significant improvement, the achieved tensile strength is comparable to parts manufactured by conventional methods.Practical implicationsThis allows functional parts to be manufactured using SL.Originality/valueIn this paper, an improved procedure to incorporate CNTs into the photopolymer was developed. Furthermore, because of strong UV-absorption nature of CNTs, curing properties of photopolymer and SL parts with and without CNT fillers were studied. Optimized curing parameters were determined and additional post-processing step for thermal curing was discovered as an essential step in order to further enhance the mechanical properties of SL composite parts.

A stable and linear time discretization for a thermodynamically consistent model for two-phase incompressible flow

A new time discretization scheme for the numerical simulation of two-phase flow governed by a thermodynamically consistent diffuse interface model is presented. The scheme is consistent in the sense that it allows for a discrete in time energy inequality. An adaptive spatial discretization is proposed that conserves the energy inequality in the fully discrete setting by applying a suitable post processing step to the adaptive cycle. For the fully discrete scheme a quasi-reliable error estimator is derived which estimates the error both of the flow velocity, and of the phase field. The validity of the energy inequality in the fully discrete setting is numerically investigated.

Experimental and numerical investigations of a pseudo-2D spout fluidized bed with draft plates

Spout fluidized beds are often utilized for gas-solid contacting operations involving physical and/or chemical transformations with simultaneous heat and mass transfer such as drying, coating, granulation, combustion, gasification etc. This is because these beds combine advantages of both spouted and fluidized beds. Since the development of the spout fluidized bed, several geometrical modifications have been proposed to optimize the bed performance. One of these modifications often applied in granulation and coating industries includes a draft tube insertion inside the bed, which results in improved performance by providing a restriction on lateral particle flow providing clear distinction for wet spout and dry annulus zones. Moreover, the insertion of the draft tube leads to a stable spouting at lower flow rates, due to the reduced bypassing of the inlet gas (from spout to annulus).In this work, the hydrodynamic characteristics of a spout fluidized bed with draft plates was studied to identify the flow characteristics by constructing a flow regime map by image analysis and a fast Fourier transform of the measured pressure signal. In addition, the captured images were used to determine the particle velocity via particle image velocimetry (PIV). Furthermore, simulations were carried using a discrete particle model with a sub grid scale turbulence model for two regimes, namely the spouting-with-aeration and fluidized bed-spouting-with-aeration (dispersed spout), which are of most interest from an industrial view point. The obtained results were compared with previously obtained experimental data i.e. PIV. This study highlights various flow pattern observed during operation of spout fluidized bed with a draft plate over a wider operating conditions, which is useful to select proper operating conditions; whereas the experimental data can be used for computational fluid dynamic (CFD) model validation, which serve as a building block for design and scale-up at higher operational scales. Besides this, the quantitative information such as particle velocity, residence time distribution, solid mixing and circulation can be obtained after suitable post processing hence useful in optimizing the bed performance.

Superconvergent discontinuous Galerkin methods for nonlinear elliptic equations

Based on the analysis of Cockburn et. al. (Math. Comp. 78 (2009), pp. 1-24) for a selfadjoint linear elliptic equation, we rst discuss su- perconvergence results for nonselfadjoint linear elliptic problems using discon- tinuous Galerkin methods. Further, we have extended our analysis to derive superconvergence results for quasilinear elliptic problems. When piecewise polynomials of degree k 1 are used to approximate both the potential as well as the ux, it is shown, in this article, that the error estimate for the discrete ux in L 2 -norm is of order k + 1: Further, based on solving a discrete linear elliptic problem at each element, a suitable postprocessing of the discrete potential is developed and then, it is proved that the resulting post-processed potential converges with order of convergence k + 2 in L 2 -norm. These results conrm superconvergent results for linear elliptic problems.

Subgradient Techniques for Passivity Enforcement of Linear Device and Interconnect Macromodels

This paper presents a class of nonsmooth convex optimization methods for the passivity enforcement of reduced-order macromodels of electrical interconnects, packages, and linear passive devices. Model passivity can be lost during model extraction or identification from numerical field solutions or direct measurements. Nonpassive models may cause instabilities in transient system-level simulation, therefore a suitable postprocessing is necessary in order to eliminate any passivity violations. Different from leading numerical schemes on the subject, passivity enforcement is formulated here as a direct frequency-domain <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> norm minimization through perturbation of the model state-space parameters. Since the dependence of this norm on the parameters is nonsmooth, but continuous and convex, we resort to the use of subdifferentials and subgradients, which are used to devise two different algorithms. We provide a theoretical proof of the global optimality for the solution computed via both schemes. Numerical results confirm that these algorithms achieve the global optimum in a finite number of iterations within a prescribed accuracy level.

A Review of David Gottlieb’s Work on the Resolution of the Gibbs Phenomenon

AbstractGiven a piecewise smooth function, it is possible to construct a global expansion in some complete orthogonal basis, such as the Fourier basis. However, the local discontinuities of the function will destroy the convergence of global approximations, even in regions for which the underlying function is analytic. The global expansions are contaminated by the presence of a local discontinuity, and the result is that the partial sums are oscillatory and feature non-uniform convergence. This characteristic behavior is called the Gibbs phenomenon. However, David Gottlieb and Chi-Wang Shu showed that these slowly and non-uniformly convergent global approximations retain within them high order information which can be recovered with suitable postprocessing. In this paper we review the history of the Gibbs phenomenon and the story of its resolution.

Noise-Free Determination of Isochromatic Parameter of Stereolithography-Built Models

Recently, stereolithography, one of the rapid prototyping (RP) techniques, has simplified the process of making three-dimensional (3-D) photoelastic models. One of the issues in stereolithography-made models is the noise due to porosity of the model. This is undesirable for data handling in digital photoelasticity. A preliminary study showed that the thickness of the slice has an influence on the appearance on the noise. In this paper, use of 10-step phase-shifting technique (PST) and refined three-fringe photoelasticity (RTFP) is explored to determine the isochromatic data as accurately as possible. A slice cut from a 3-D model of a spline shaft made of stereolithographic material is used for isochromatic determination. It is found that with suitable postprocessing, the quantitative results obtained from 10-step PST and RTFP are comparable. The relative merits of these two techniques for analysing stereolithographic models are brought out.

Suitable post processing algorithms for X-ray imaging using oversampled displaced multiple images

X-ray imaging systems such as photon counting pixel detectors have a limited spatial resolution of the pixels, based on the complexity and processing technology of the readout electronics. For X-ray imaging situations where the features of interest are smaller than the imaging system pixel size, and the pixel size cannot be made smaller in the hardware, alternative means of resolution enhancement require to be considered. Oversampling with the usage of multiple displaced images, where the pixels of all images are mapped to a final resolution enhanced image, has proven a viable method of reaching a sub-pixel resolution exceeding the original resolution. The effectiveness of the oversampling method declines with the number of images taken, the sub-pixel resolution increases, but relative to a real reduction of imaging pixel sizes yielding a full resolution image, the perceived resolution from the sub-pixel oversampled image is lower. This is because the oversampling method introduces blurring noise into the mapped final images, and the blurring relative to full resolution images increases with the oversampling factor. One way of increasing the performance of the oversampling method is by sharpening the images in post processing. This paper focus on characterizing the performance increase of the oversampling method after the use of some suitable post processing filters, for digital X-ray images specifically. The results show that spatial domain filters and frequency domain filters of the same type yield indistinguishable results, which is to be expected. The results also show that the effectiveness of applying sharpening filters to oversampled multiple images increase with the number of images used (oversampling factor), leaving 60–80% of the original blurring noise after filtering a 6 × 6 mapped image (36 images taken), where the percentage is depending on the type of filter. This means that the effectiveness of the oversampling itself increase by using sharpening filters, and more images taken can be considered worth the effort.