Air Inclusions Research Articles

Izdelava velikih glivnih biokompozitov z nizko gostoto

As the need for a circular economy grows, so does the need for new sustainable materials. Biocomposites made from fungi are a sustainable alternative to synthetic foams. The key to commercializing this technology is knowing how to produce large quantities of such materials with the appropriate properties. As part of our experimental work, we have produced a larger mycelium biocomposite with a low density, a volume of 47 litres and a length of two metres. The final fungal biocomposite was produced by growing the mycelium in three stages; first in culture bags, then in two larger moulds, which were combined in a third stage. We used a culture of Ganoderma resinaceum and a specially formulated substrate to achieve a low density. The final biocomposite with a density of 80 kg/m³ met the target dimensions, remained infection-free and withstood lighter loads. The main disadvantage of the material was the small surface indentations caused by air inclusions in the substrate when the mycelium-laden substrate was transferred to the moulds.

Multiscale analysis of interlocking effects for polymer additive manufacturing on aluminum foam

AbstractHybrid structures are increasingly relevant for lightweight design and functional components. Various manufacturing techniques for creating hybrid components exist, often focusing on combining metal and polymer components. The present study examines a novel approach for manufacturing hybrid functional structures by directly printing thermoplastic onto aluminum profiles using closed‐cell aluminum foam, with the mechanical interlocking resulting in a structural bond. The filling of pores in the aluminum foam with the polymer affects the bond strength of this hybrid compound. Within a simulation‐based process design the additive manufacturing process parameters are investigated using a computational fluid dynamics (CFD) model with Fluid‐Structure Interaction for the pore‐filling process and a finite element (FE) model to evaluate the resulting bond strength. The material throughput, the nozzle distance, and the polymer temperature are the key process parameters taken into account. A parameterized, virtual foam model is used within this framework, where a linear movement of the extruder nozzle and the resulting polymer strand is investigated. This method includes the mesh conversion from the CFD results to the FE mesh for structural analysis by exporting the iso‐surface for the polymer geometry embedded in the pores of the aluminum foam structure. This approach made it possible to investigate the phenomena that occur in the process in more detail, particularly to quantify the influence of air inclusions. Thus, a decisive contribution to the hybridization of aluminum foams has been made, which opens up further potential for research and application in the long term.

Environmental and behavioral mitigation strategies for patients with atopic dermatitis

Although numerous medications have recently been approved for the treatment of atopic dermatitis (AD), the current treatment guidelines often lack information on non-pharmacologic approaches to disease management. In contrast, patients and caregivers frequently express strong interest in environmental and behavioral mitigation strategies. Herein, we summarize the evidence-base for these interventions with a focus on the role of specific chemicals in driving AD. We outline avoidance strategies for the various routes of exposure such as air pollution, water contamination, or inclusion in home goods, skin care products, and cleansers. Evidence for and against dietary modification and emollient use as primary prevention are discussed. To remember these interventions we propose a mnemonic, HELPSS AD: Home decor, Emollients, Laundering, Probiotics, Soaks, Social support, Air quality, and Diet. Each of these categories presents nuanced molecular differences that must be considered. For example, probiotic responses vary by the specific species while home products and pollution must be analyzed by the specific toxins. Although the interventions discussed lack the level of evidence required for inclusion into formal guidelines, awareness of these approaches may offer aid to, and build trust with, patients and caregivers.

Акустические свойства композита алюминий-полистирол

The paper presents the results of experimental studies of the acoustic properties of an aluminum-polystyrene composite with a connectivity of 0-3. The dependences of the speed and attenuation of longitudinal volumetric acoustic waves (BAW) in the composite at a frequency of 17 MHz, as well as its density and acoustic impedance, on the volumetric content of aluminum particles in it, in the range of 0-80%, were obtained. It has been shown that an increase in the volume fraction of filler particles in the aluminum-polystyrene composite leads to significant changes in its physical properties - density and acoustic impedance - almost 2 times, longitudinal wave speed - by 17% and acoustic attenuation - by 25 times. Velocity and attenuation are, respectively, the least and most sensitive parameters to the composition of the composite. The dependences are nonlinear; this is due to the appearance of air inclusions, intergranular interaction of aluminum particles and, as a consequence, deterioration of interphase interaction and structural organization of the composite material.

Exploring the performance of the topological energy method for object and damage detection from noisy and poor databases.

In this work, we study the performance of numerical methods based on the computation of topological energies to process data from synthetic and real experiments where only noisy limited-view data corresponding to a few frequencies are available. We show numerical experiments in two problems of practical interest. The first one corresponds to experimental measurements of the electromagnetic scattering produced by different objects extracted from the Fresnel database. The second one is related to synthetic experiments in a simplified model where steel welding joints are acoustically tested to identify possible flaws (air bubbles and inclusions) produced during the welding process. This article is part of the theme issue 'Non-smooth variational problems with applications in mechanics'.

Electrical Strength of Polymer Film with Randomly Distributed Air Inclusions

Electrical Strength of Polymer Film with Randomly Distributed Air Inclusions

Finite Element Analysis of Sandwich Plates with Different Percentages of Delamination

Abstract: The present study pinpoints the effect of delamination in multilayer glass fiber-reinforced composite slabs. The unit cell method of homogenization has been used to find the effect of air inclusion in the glass fiber-reinforced polymer composite. The natural frequency has been obtained up to different modes on every condition. The modal analysis module of ANSYS has been used to obtain the natural frequency for different boundary conditions The present study considered 0% to 10 % of total volume as delamination in four steps (0.5, 1.0, 5.0, and 10%). Two types of boundary were considered in the present study, in the first condition the plate is fixed from all four sides, the second two sides are assumed to be free, and the remaining two sides are fixed.

Wind Tunnel Evaluation of Plant Protection Products Drift Using an Integrated Chemical–Physical Approach

The use of plant protection products (PPPs) has become fundamental to guarantee excellent field productivity. Nevertheless, their usage presents critical issues, such as the quantity of substances used, the relative toxicity, and the contamination of nearby fields caused by atmospheric drift. This study focuses on the characterization of aerosol droplets of PPPs produced by spraying a chemical marker, fluorescein, with an orchard airblast sprayer equipped with conventional hollow cone (HC) and anti-drift air inclusion (AI) nozzles, using a wind tunnel as a controlled environment. A particle/droplet image analysis was employed to study the droplet production of the nozzles, while a liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis allowed us to evaluate samples collected using a cascade impactor located at 5 m, 10 m, and 20 m from the emission point. Overall, HC nozzles are very accurate at producing specific drop size distributions (DSDs), while AI nozzles produce a much wider DSD, concentrating the largest part of the distributed volume into droplets of a larger size. The marker concentration was much lower for the AI nozzles compared to the HC nozzles; moreover, the two nozzles show a similar trend in the coarse droplet range, while significantly differing in the fine droplet spectrum.

Acute complicated jejunum diverticulitis: a case report with a short literature review.

Jejunal diverticulosis is a rare condition. Most of the time, it is asymptomatic; but it can cause severe complications such as intestinal perforation, mechanical occlusion, and hemorrhage. A patient aged 78 years, with a history of biological aortic valve prosthesis, atrial fibrillation, type 2 diabetes mellitus, and chronic obstructive pulmonary disease, presented in the emergency department for acute abdominal pain in the lower abdominal floor, nausea, and inappetence. Abdominal computed tomography revealed an inflammatory block in the hypogastrium, agglutinated small intestinal loops, fecal stasis, and air inclusions. Pulled mesentery and associated internal hernia are suspected. Exploratory laparotomy was performed, revealing an inflammatory block in the hypogastrium, whose dissection revealed inner purulent collection and the appearance of jejunal diverticulitis, a diagnosis confirmed by histopathological examination. Segmental resection of the jejunum with double-layer terminal-terminal enteroenteric anastomosis, lavage, and drainage was performed. The evolution was favorable. Based on our brief review, the diagnosis of complicated jejunal diverticulosis is difficult and sometimes not accurately established, even by high-resolution imaging techniques, with diagnostic laparotomy being necessary for these situations. Surgical treatment should be considered before severe complications develop.

Efficient testing of weld seam models with radii of curvature in the millimeter range using laser ultrasound

Laser ultrasound is a widely used tool for industrial quality assurance when a contactless and fast method is required. In this work, we used a laboratory setup based on a confocal Fabry–Perot interferometer to examine weld seam models. The focus was placed on small samples with curved surfaces (small in the sense that the radius of curvature is comparable to the largest ultrasonic wavelength) and on efficient ways to detect the presence and volume of process pores, with the goal to transfer this method to industrial applications. In addition to this experimental method for investigating welds, a numerical method that models the experimental setup was implemented in MATLAB. For this purpose, first the thermal effects of the excitation process were taken into account by solving the thermal diffusion equation with an explicit scheme. Then, the elastodynamic equations were solved using the Elastodynamic Finite Integration Technique, taking into account the stresses induced by the excitation process. The B-Scans generated with this numerical model were compared with experimental B-Scans for simple test cases and good agreement was found. In a next step, the additional structures in the B-Scans resulting from air inclusions were identified and investigated with both methods using flat test specimens at first. Besides the direct echoes, structures from skimming surface waves and multiple reflections were visible. These additional structures are unwanted in defect reconstruction methods like the Synthetic Aperture Focusing Technique (SAFT) as they would lead to artifacts. In samples much larger than the largest ultrasound wavelength, however, these unwanted structures are still negligible in amplitude or can be well separated temporally, but for small samples this is no longer the case. As a result, reconstruction methods based on direct echoes like SAFT are difficult to apply. For many industrial applications, the reconstruction is not decisive at all, but only the knowledge of the total volume of process pores (TVPP). It is shown with both experimental and numerical methods, that this TVPP can be estimated from the variation in the B-Scans from various small weld seam models.

Quality Testing in Aluminum Die-Casting – A Novel Approach using Acoustic Data in Neural Networks

In quality control of aluminum die casting various processes are used. For example, the density of the parts can be measured, X-ray images or images from the computed tomography are analyzed. All common processes lead to practically usable results. However, the problem arises that none of the processes is suitable for inline quality control due to their time duration and to their costs of hardware. Therefore, a concept for a fast and low-cost quality control process using sound samples is presented here. Sound samples of 240 aluminum castings are recorded and checked for their quality using X-ray images. All parts are divided into the categories "good" without defects, "medium" with air inclusions ("blowholes") and "poor" with cold flow marks. For the processing of the generated sound samples, a Convolutional Neuronal Network was developed. The training of the neural network was performed with both complete and segmented sound samples ("windowing"). The generated models have been evaluated with a test data set consisting of 120 sound samples. The results are very promising. Both models show an accuracy of 95% and 87% percent, respectively. The results show that a new process of acoustic quality control can be realized using a neural network. The model classifies most of the aluminum castings into the correct categories. Keywords: acoustic quality control, aluminum die casting, convolutional neural networks, sound data

Multi-scale ultrasonic imaging of sub-surface concrete defects

This paper introduces a new method for creating the ultrasonic image of concrete that utilizes both linear and nonlinear wave properties in a single measurement. Linear ultrasonic imaging relies on wave velocity. The resolution of linear ultrasonics for various inclusion sizes and inclusion-to-base material ratios is numerically and experimentally studied. The nonlinear ultrasonic testing (NLUT) image is based on the acoustic nonlinearity coefficient, calculated using inputs of the first and second harmonic amplitudes, wave number, and the distance between the transmitter and receiver. The ultrasonic waveform is decomposed into its harmonics using wavelet transform. Their wave velocities, wave numbers, and amplitudes are extracted to calculate the linear wave velocity and the acoustic nonlinearity coefficient. Four calibration samples with different inclusions are tested to evaluate the effectiveness of combining two imaging methods: pure concrete, concrete with small foam inserts simulating air inclusions, and two concrete samples with larger foam inclusions. The angle dependence of acoustic nonlinearity coefficient is shown. The results show that constructing both linear and nonlinear ultrasonic imaging is necessary when the defect’s properties are unknown.

Structuring step dependent characteristics in joining using pin-like structures in the vibration welding process

Abstract With this study, correlations in the structuring step of pin-like joining were derived. Increased friction energy due to higher amplitude or force leads to a reduction in structuring time. Changes in thermo-mechanical properties for humid specimens result in increased process times. The theoretical geometry of the pin-like structures is well reproduced in the lower pin area, regardless of the process control. In the upper pin area, increased force and amplitude results in increased defects and air inclusions as a result of an accelerate and more inhomogeneous pin formation. Humidity does not affect the general pin geometry, but should be avoided due to increased air inclusions that can weaken the structure. For the multi-material joints, high bond strengths of up to 30 % of the base material (max. 50 % possible with the geometry used) can be achieved. Therefore, a minimum undercut is required. Once this is reached, the pin defects and the corresponding pin-foot ratio are decisive for the resulting bond quality.

Automatic generation of high-fidelity representative volume elements and computational homogenization for the determination of thermal conductivity in foamed concretes

Foamed concretes are highly porous materials with excellent insulation properties. Their thermal conductivity is strongly dependent on the pore structure, characterized by the porosity as well as the shape and size distribution of pores. To define the representative volume element (RVE) of foamed concretes with high fidelity, we develop NRGene, an automatic generator of cubic samples with spherical air inclusions whose number and size obey a given distribution. We compute the effective thermal conductivity tensor for a given RVE using finite-element-based computational homogenization. The hi-fi RVE of foamed concretes may contain hundreds of millions of finite elements, making it better suited for benchmarking than for everyday engineering applications. Then, having the hi-fi model as benchmark, we propose a simplified model consisting of the hi-fi model called with a truncated histogram as input, which is largely cheaper while keeping a satisfactory accuracy. We model 21 different foamed concretes with a wide range of porosities and different compositions of the cement paste. Further, we demonstrate that it is the volume of all the pores of a given size, and not its quantity, what affects the effective thermal conductivity of foamed concretes.

Simulation of crude oil slick on ice infested sea water

A three-dimensional numerical model based on the smoothed particle hydrodynamics (SPH) method is utilized to model such interactions. The effects from air and water are well captured using suitable force components and without explicit inclusion of air and water phases. This reduces the four-phase SPH model into a two-phase model, significantly reducing computational costs and potentially enabling the use of this model for large-scale simulations. This study includes two simulation domain size. The results show that the remained oil slick in the icy domain is completely depend on properties of different crude oils and current velocity. Then we performed a numerical experiment to study the effects of different ice parameters (e.g., ice concentration, floe shape) on the drift of fresh and weathered oil. Ice fields with the size of 750 m × 1350 m are used in the experiment. The ice concentration varies between 30%, 50% and 70%. Quadrilateral and circular ice floes, in addition to real-shape floes digitize from an aerial image are all used in the experiment. Oil spills of 1257 m3 are released in the open water and later drift into the ice under the influence of steady current of 50 cms. The type of spilled crude oil varies from fresh Troll B, Troll B 250 °C, and Troll B 250 °C and 75%emuls. The behavior of oil spills while crossing through the ice infested area are investigated by measuring the thickness of crude oil, the average and maximum distance traveled by crude oil.

Using fiber or rod—The influence of different filler materials during CO2 laser welding of quartz glass

Welding of quartz glass is still mainly carried out with gas torches and manually by glass specialists. The use of gas torches is highly energy inefficient as much heat energy is released around the component and into the environment. In addition, the manual process can result in inhomogeneous welds. An automated laser process would make quartz glass welding more energy-efficient and repeatable and address the growing shortage of skilled labor. In this study, quartz glass plates up to 4.5 mm in thickness are welded together at an angle of 125° to each other using a fiber or rod as the filler material. Glass thickness and angle were selected based on a project-specific application. The aim is to achieve a homogeneous weld with as few defects as possible using a lateral fiber- or rod-based deposition welding process. The main challenge is to achieve the melting of the filler material at the bottom contact point of the two glasses so that no air inclusions occur. A 400 μm fiber and a 1 mm rod are investigated as filler materials. The advantage of the fiber compared to the rod is that the contact point of the glasses is easier to reach and bond during the welding process. Due to the large gap between the glass fibers compared to the fiber diameter, a high fiber feed rate is required to fill the V-gap with the viscous glass material. The disadvantage is that the fiber is subjected to high pressure when digging into the melt, which can lead to fiber breakage. In addition, there is a high consumption of filling material. Adjustable and relevant process parameters include the ratio between substrate and fiber feed, the laser power, the spot diameter, and the process gas pressure. The fabricated samples are analyzed using optical and laser confocal microscopy.

Type of pectin determines structuring potential of soy proteins into meat analogue applications

The addition of pectin to soy protein isolate (SPI) is a route to create fibrous products using shear cell technology. In this study, we investigated pectins derived from soybean, sugar beets, and citrus (two variants) that vary in sugar composition, degree of methylation and acetylation. The objective was to examine how these different pectins impact the functional properties of the SPI dispersions. The SPI-pectin blends were shear structured and their visual appearance, microstructural, rheological, and mechanical properties were analyzed. The addition of pectins from citrus (the highly methyl-esterified form) and soybean resulted in fibrous products when mixed with SPI. The addition of the low methyl-esterified pectin derived from citrus led to less pronounced fibrous product, and pectin from sugar beet did not lead to fibrous products. To explain the effect, several properties of the blends and products were tested. It was found that the fibrous products contained more air (i.e. higher void fraction) than products that were not fibrous, and that air bubbles were deformed in the shear direction. The rheological measurements of the blends revealed that the pectins lowered the yield and flow point of SPI, and the flow transition index. The blend with the highest elasticity after heating also had the highest deformation of air bubbles. Based on all results it was concluded that pectin influenced the structure formation in two ways: 1) affecting the ability to facilitate air inclusion and 2) influencing the storage modulus and elasticity of the matrix.

Online thickness measurements of acrylate-based coatings on knitted polyester fabric using terahertz time-domain spectroscopy

Three different institutions combined their expertise in a joint R&D project to demonstrate the suitability of terahertz time-domain spectroscopy for thickness measurements of acrylate-based coatings on polyester fabric. First, we spectroscopically analyzed the materials involved using a high-precision terahertz spectrometer and determined optical properties such as the refractive index and loss coefficient. Raster scans were then performed across the sample, and terahertz images were created to identify material boundaries and thickness inhomogeneities. Finally, we applied a fast scanning terahertz time-domain spectrometer based on electronically controlled optical sampling and a customized reflection head for online thickness measurements in a coating line. The textile moved at a speed of 0.5 m/min, while the measurement system records terahertz pulses at a rate of 1600 traces/s. Coating thicknesses of between 63 µm and 99 µm were calculated in a post-processing step. To classify these non-contact and non-destructive measurements, these thicknesses were compared with the results of standard methods. Online and offline (62-83 µm) terahertz and SEM (66-75 µm) measurements delivered the best agreement for average coating thickness. In contrast, mechanical testing methods gave either too low or too high values for layer thickness, which were not comparable. Terahertz time-domain spectroscopy and imaging technology enable the first non-destructive quality control of acrylate-based textile coatings immediately following coating in the production line. Measurable variables are coating thicknesses and the detection of defects such as air inclusions.

Millimetric Inclusion Detection Through a Contactless Microwave Spiral Sensor for Biomedical Applications

This article introduces the design and fabrication of a microwave contactless sensor used to detect the presence of millimetric inclusions in a biological medium for biomedical applications. The hardware system comprises a self-resonant planar spiral resonator (SR) (sensing element) inductively coupled to an external concentric single-loop probe (reading probe), working at 648 MHz. The microwave sensor configuration relies on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> -factor maximization of the spiral coil, that is, the sensing element, through an optimization process, to obtain a stronger sensitivity and, thus, a millimeter resolution for the inclusions’ detection. The detection is achieved by recording both the amplitude variation and the frequency shift of the input impedance of the reading probe. To validate the proposed solution, full-wave simulations have been performed to design and preliminary evaluate the radiating system performance in detecting millimetric biological inclusions. As an applicative example, we focus on air bubbles detection in hemodialysis procedures; in particular, we carried out the experimental verification by employing an agar phantom to replicate the dielectric characteristics of the blood tissue and polylactic acid (PLA) samples of various sizes to represent the air inclusions. We proved that the theoretical assumptions were in excellent agreement with both the numerical and experimental results, encouraging further analysis of the potential use of such sensors in biomedical applications. Indeed, the radiating device can be very helpful for all operations where it is necessary to detect the presence of undesired and dangerous contaminants in a contactless way, making the procedure safer for patients.

Effect of ultrasonic treatment on soybean okara to be used as a gluten‐free bread improver

SummaryThe production of soybean protein isolates generates an insoluble residue called okara that is rich in proteins and dietary fibre. These macromolecules have functional properties that can be modified and improved by emerging technologies, such as high‐intensity ultrasound. The objectives of this work were to analyse the ability of soybean okara (UOK) to act as a gluten‐free bread improver and to evaluate the effect of a sonication process on this property (OKS). Both okaras were assayed at two percentages (2% and 3%) leading to a reinforcement of interactions in the matrix of batters, producing bread of better technological and sensorial quality. The addition of OKS 3%, improved specific volume (20%), reduced the hardness (30%) and increased the cohesiveness of the crumb and improved the air inclusion. These results demonstrated the efficiency of the sonication process to obtain a gluten‐free bread improver from a bulky by‐product of the soybean industry.