Irregular Holes Research Articles

Load image inpainting: An improved U-Net based load missing data recovery method

Dealing with large percentage data missing is always a challenge for load data recovery. This paper, drawing on ideas from image inpainting, formulates load missing data recovery problem as load image inpainting and the improved U-Net is proposed to restore the load image. First, the 1-dimensional load data is constructed into 2-dimensional load image. Additionally, missing data presents as irregular black holes on the load image. Then, the improved U-Net which introduces residual network (ResNet) and convolutional block attention module (CBAM) is proposed to specifically restore the incomplete load image. Meanwhile, mean absolute error (MAE) and structural similarity (SSIM) are utilized to evaluate data recovery accuracy and load pattern recovery similarity respectively. Load missing data recovery results based on the actual industrial load dataset are presented to verify the effectiveness of the proposed method.

Analysis and characterization of 20 ppi open cell aluminum foam under mechanical loading

In this research the analysis and characterization of open cell aluminium foam with 20 pores per inch (ppi) of Alporas rout under mechanical loading is presented in order to provide a basic understanding with respect to pore size per unit length for the right selection in various engineering applications. For this purpose, three point bending test, tensile test, compression test, vickers hardness test and charpy impact test were performed to seek out the respective properties of each test. All samples and test procedure were performed as per ASTM standards. The scanning electron microscopy (SEM) will performed of the fractured surfaces of the specimens to investigate the failure mode. The SEM photograph shows that; some internal defects were found such as the tinny cracks some irregular shape holes in the cell wall which have been created during foaming process. The shredded cell wall is looked over which was ductile in nature and have occurred during flexural, tensile and charpy impact test. In compression; all pores are collapsed in plateau region, and some crumples and brittle tiny cracks are detected in densifications stage. Dislocation band also detected on the walls and struts of the effected sample of tensile and charpy impact test.

Numerical study on the flow characteristics of pressurized hydrogen leaking into the confined space through different shaped orifices

The safety concerns associated with accidental hydrogen leakage remain a challenge. Although numerous studies have been carried out on the flow behavior of compressed hydrogen leaking in unconfined spaces, the knowledge of the flow characteristics when it leaks into confined spaces through irregular holes is lacking. Therefore, this study uses the three-dimensional Large-Eddy Simulation (LES) model to simulate high-pressure hydrogen leakage in a confined space. Effects of the leakage hole shape on the flow features are investigated, including the circle, square, and triangle with the same equivalent area. Results indicate that the Mach disk shows circular, hexagonal, and octagonal shapes depending on the leakage port geometry. When the leak hole shape is square and triangular, the distribution of pressure waves deflects 45° and 60° near the hole, respectively. It means that non-circular holes affect the pressure distribution after hydrogen leakage. In addition, changing the shape of the leak hole results in a difference in hydrogen jet morphology. Compared to circular jets, in square and triangular jets, the jet boundary narrows along the diagonal plane and the gravity plane, respectively. It indicates that leakage ports with sharp corners can complicate the flow. Therefore, it is essential to consider the influence of the leakage port shape when performing a risk assessment of high-pressure hydrogen leaks in confined spaces.

Supramolecular Host–Guest Assembly Based on Phosphotungstate Nanostructures for Pseudocapacitive and Electrochemical Sensing Applications

Flexible ligands and multinuclear complexes were assembled into nanoscale {P2W18O62} polyoxometalates (POMs) to generate two phosphotungstate hybrid derivatives, (H2bip)2{H2P2 W18O62}·2H2O (1) and (bipy)0.5{Ag(bipy)2}{Ag4(bipy)7}{NaP2W18O62}·H2O (2) (bip = 1,5-bis(imidazole-1-yl)pentane; bipy = 2,2′-bipy), via a precursor hydrothermal method. Compound 1 is a bip ligand modified 4,8-connected supramolecular net with {415;612;8}{45;6}2 topology. In compound 2, the monocore complexes {Ag(bipy)2} and tetranuclear complexes {Ag4(bipy)7} self-associate to generate two supramolecular chains A and B, respectively, which are further alternately joined together to form a unique metal–organic framework with irregular cavities via weak actions and π–π stacking. The Na-linked {P2W18O62} dipolymers as guest units were embedded into the holes, leading to a 3D supramolecular host–guest assemblies. The capacitive performance test reveals that 2-GCE/-CPE presents improved specific capacitance (802.4 and 752.1 F/g at 3 A/g), cycle efficiency (93.6 and 94.8% after the 5000th cycle), and electrical conductivity compared to the precursor and bip ligand modified compound 1. The electrocatalytic comparative data shows that 2-GCE has enhanced electrochemical redox capacity compared to the precursor and compound 1. Further sensing tests display that 2-GCE shows strong electrochemical responses to H2O2/AA at voltages of −0.41/0.36 V with a lower detection line of 0.33/0.05 μM, a wider linear range of 1.0 μM to 3.18 mM/0.15 μM to 2.33 mM, merit selectivity, and reproducibility. The excellent capacitive and sensing performances are related to increased redox centers, improved ion/electron conversion efficiency, and host–guest structural stability resulting from the introduction of multinuclear complexes, irregular holes, and abundant π–π stacking. This study not only enriches the variety of Dawson-type POMs but also provides a feasible idea for enhancing their electrochemical capacitance and sensing performance.

Progressive feature generation with mask awareness for image inpainting

Most existing image inpainting methods have achieved remarkable progress in repairing small image defects. However, when the holes are large, their filling contents suffer from structural distortion and center blur due to the weak correlation between known and unknown pixels. In this paper, we propose a Progressive Feature Generation (PFG) network which is mask awareable during the process of filling irregular holes. Specifically, in order to strengthen the constraint for the hole center, we propose dynamic partial convolution which can adaptively adjust the inpainting proportion according to mask ratio in each recurrence. To synthesize high-quality features in the feature generation phase, two parallel encoders are designed which could effectively improve the capability of model to restore large holes. We argue that during feature merging, the signals generated earlier at the same location are more credible. To this end, we develop the sub-regional weighted merging(SWM) method for PFG-Net to accurately merge the feature maps generated during the whole reconstruction process. Experiments on CelebA, Places2, and Paris StreetView datasets show that our model has excellent performance especially for large holes.

Scalable and cost-effective fabrication of self-floating three-dimensional interconnected polyethylene/multiwall carbon nanotubes composite foam for high evaporation performance

Currently, high-cost and complex preparation processes of photothermal materials are still challenges that limit the promotion and large-scale application of solar evaporation. Herein, an efficient strategy combining melt blending and sacrificial template is proposed for mass and successive fabrication of polyethylene (PE)/multiwall carbon nanotubes (MWCNTs) composite foam. A three-dimensional interconnected PE/MWCNTs framework structure is formed when NaCl particles are completely removed as a sacrificial template, and the MWCNTs nanofillers are uniformly dispersed in the PE matrix. Meanwhile, the PE/MWCNTs composite foam exhibits ultralow reflectance (≈3%) in the wavelength range of 250–2500 nm due to the refraction and reflection of incident light back and forth in the microscale irregular holes and the high-efficiency light absorption of the MWCNTs. Owing to excellent photothermal conversion and low thermal conductivity, the evaporation rate of the PE/MWCNTs composites foam is as high as 1.68 kg m−2 h−1 under 1 Solar Constant irradiation, which corresponds to an evaporation efficiency of ∼72.49%. Specifically, the salinity of the purified water is surprisingly reduced by six orders of magnitude, which is even lower than that of city water and drinking water. The proposed method can be an excellent candidate for the large-scale and low-cost fabrication of high-performance and functional composite foam.

Selective laser melting of the Al0.3CoCrFeNiCu high-entropy alloy: Processing parameters, microstructure and mechanical properties

The as-printed Al0.3CoCrFeNiCu high-entropy alloy (HEA) was fabricated from gas-atomized powders by selective laser melting (SLM) with the tailored printing parameters. The processing parameters, microstructural characteristics, mechanical properties and formed defects of the SLM-processed Al0.3CoCrFeNiCu HEA were examined in detail. The SLM-processed HEAs presented a simple disordered face centered cubic solid solution with columnar grains growing along the building direction and exhibiting a 〈001〉 preferred orientation. Dendritic-segregation, a common phenomenon occurring in as-cast counterparts was eliminated, thus providing a significant method to form a single-phase solid solution. The cellular structure in the columnar grains germinated perpendicular to the boundary of molten pools. In addition, dislocations induced by internal stress were observed. Accordingly, the SLM-processed Al0.3CoCrFeNiCu HEA exhibited superior microhardness and compressive strength. Finally, two types of defects were found in this SLM alloy, including irregular holes and hot cracks. The latter occurring on solid–liquid interface of molten pool were retarded by grain boundaries and then turned into muti-branches. Nevertheless, no crack-free sample could be prepared even though the printing parameters were optimized to achieve a high relative density of 99.08%, indicating this HEA was not suitable for SLM technology to prepare.

Micro-structured and self-assembled patterns in PLA-cast films as a function of CTAB content, magnesium and substratum hydrophobicity

The fabrication of biomaterials with structured surfaces for medical purposes is a topic of great interest. Producing topographies with certain characteristics can benefit tissue formation and/or reduce the probability of developing an infection due to the hindrance shown by certain micro-structures to microbial adhesion.This work presents a new, economically attractive way to fabricate micro-structured patterns on the surface of one of the currently most interesting bioabsorbable polymeric materials, polylactic acid (PLA). Formation of homogeneously distributed holes is presented as a function of three factors: the concentration of cetyltrimethylammonium bromide (CTAB), the presence or not of the dispersant magnesium, and the hydrophobicity of the support used in the PLA-film fabrication, silicone or glass. The size of the holes increases with the CTAB concentration: from 1 to 5 µm on silicone and 2 to 20 µm on glass. Magnesium particles make CTAB to disperse better inside the PLA matrix, provoking the irregular holes observed on glass become regular with sizes between 0.5 and 2 µm. The topographies obtained on silicone are highly stable over time, while on glass they degrade after 28 days. Consequently, it is possible to design a wide spectrum of micro-structured topographies, covering both antimicrobial and tissue integration targets.

Preparation of efficient and economical adsorbent for Cu2+ and Pb2+ adsorption via modifying the silicon–oxygen structure of leaching residues

One eco-friendly and cheap cost leaching residue (LR) was obtained from serpentine leaching system and used to adsorb Cu2+ and Pb2+ in wastewater. LR had a large specific surface area, and uneven interface with irregular holes provided more adsorption sites. Moreover, silicon–oxygen structure of LR presented as one bridge oxygen (Q1), which was more electronegativity and act as the adsorption active site for metal actions. All these characteristics indicated that LR had good adsorption performance, whose equilibrium adsorption capacity (Qe) for Cu2+ and Pb2+ could reach to 38.85 and 27.97 mg/g, respectively. Moreover, the Qe of Pb2+ was much lower than that of Cu2+ in single or binary systems. Selective adsorption mechanism was studied by DFT calculations, the adsorption energy (Eads) of Si–O–Cu and Si–O–Pb equaled to −2.4834 and −2.1822 Ha, indicating that the interaction of Cu2+ ions with LR was stronger and more stable than Pb2+ ions. In this work, leaching residue was transformed into an efficient and cheap absorbent via modifying the silicon–oxygen structure of clay minerals.

Photonic crystal L3 cavity laser fabricated using maskless digital photolithography

Abstract Projection photolithography using an extreme-ultraviolet light source is the core technology that has enabled patterning on the scale of a few nanometers that is required for modern electronic chips. However, this high-end system is neither affordable nor needed for photonics where critical feature sizes are of 100s of nanometers (or of submicron). Although electron-beam lithography can provide a means for photonic device fabrication, it suffers from extremely low throughput. Therefore, a lithographic technique for submicron pattern generation at high throughput and low cost is in high demand. This group recently showed that maskless digital photolithography (MDPL), a convenient and versatile photolithographic technique that requires no photomask, could potentially address this demand by demonstrating photonic crystal (PhC) patterns with submicron periodicity and associated PhC band-edge lasers. In this paper, we report the fabrication of a PhC L3 cavity laser, which contains irregular air holes in terms of their positions and sizes, using the MDPL technique. Successful generation of such an aperiodic and nontrivial submicron pattern requires thorough understanding and scrupulous manipulation on light diffraction. Our achievements should provide the concrete foundation upon which compact, versatile, convenient, speedy, and economical lithographic tools for arbitrary submicron pattern generation can be developed.

Semantic Image Inpainting with Multi-Stage Feature Reasoning Generative Adversarial Network

Most existing image inpainting methods have achieved remarkable progress in small image defects. However, repairing large missing regions with insufficient context information is still an intractable problem. In this paper, a Multi-stage Feature Reasoning Generative Adversarial Network to gradually restore irregular holes is proposed. Specifically, dynamic partial convolution is used to adaptively adjust the restoration proportion during inpainting progress, which strengthens the correlation between valid and invalid pixels. In the decoding phase, the statistical natures of features in the masked areas differentiate from those of unmasked areas. To this end, a novel decoder is designed which not only dynamically assigns a scaling factor and bias on per feature point basis using point-wise normalization, but also utilizes skip connections to solve the problem of information loss between the codec network layers. Moreover, in order to eliminate gradient vanishing and increase the reasoning times, a hybrid weighted merging method consisting of a hard weight map and a soft weight map is proposed to ensemble the feature maps generated during the whole reconstruction process. Experiments on CelebA, Places2, and Paris StreetView show that the proposed model generates results with a PSNR improvement of 0.3 dB to 1.2 dB compared to other methods.

Improved fixation stability for repairing pedicle screw loosening using a modified cement filling technique in porcine vertebrae

Polymethylmethacrylate (PMMA) has been applied clinically and biomechanically repair loose pedicle screws. Controversies have arisen over data due to uncontrolled cement properties, various locations and sizes of fenestrated holes in repair screws, irregular holes and different bone densities of specimens. In this study, the pullout strength was compared for two techniques, the modified technique to use PMMA to augment a threaded hole and the traditional technique with retrograde injection of a PMMA filling, for standard loose screws in porcine vertebrae. Both techniques provided statistically significant results for sufficiently randomized specimens and experimental procedures. The difference in the pullout strength between conical and cylindrical screws for the aforementioned cement augmentation techniques was also investigated. Twenty-four single-level fresh-frozen lumbar vertebrae from L1 to L6 were harvested from four mature pigs. A total of 0.8 ml of PMMA was retrograde injected into screw holes with a 5.5 mm diameter, followed by insertion of a 5.0 mm diameter repair screw in the traditional group (n = 12). A stiff threaded PMMA hole was created with a 4.5 mm tapping screw before insertion of repair screws in the modified group (n = 12). Two screw geometries were randomly assigned as cylindrical (n = 6) and conical (n = 6) in each group. The correlations between filling techniques, screw geometries and axial pullout strength were analyzed. An appropriate screw trajectory and insertion depth were confirmed using X-ray imaging prior to pullout testing in both groups. For a given screw geometry (cylindrical or conical), the pullout force of the modified group was significantly higher than that of the traditional group. There was no significant difference in the pullout force between the screw geometries for a given filling technique. The cement augmentation technique is far more influential than the screw outer geometry. The modified PMMA technique created a greater anchor force than the traditional method and could be an alternative for revision of pedicle screw loosening.

Stress Intensity Factors for a Non-Circular Hole with Inclusion Layer Embedded in a Cracked Matrix

The failure analysis of a non-circular hole with an inclusion layer embedded in an infinite cracked matrix under a remote in-plane uniform load is presented. In this study, a series solution of stress functions for both the matrix and inclusion layer is obtained using the complex variable theory in conjunction with the method of conformal mapping. The stress intensity factor (SIF) can then be determined numerically by solving the singular integral equation (SIE) for the interaction among different crack sites, material properties, and geometries of irregular holes with an inclusion layer. In particular, the failure behavior of composite structures associated with an approximately triangular hole and an approximately square hole with inclusion layers, such as those of oxides, nitrides, and sulfides, is examined in detail. The results demonstrate that a softer layer would enhance the SIF and a stiffer layer would restrain the SIF when a crack is near the inclusion layer. It can be concluded that crack propagation would be suppressed by a stiffer layer even when a micro-defect such as a hole resides in the inclusion layer.

Influence of Super Absorbent Polymer on the Sulfate Resistance of Cement Mortar

Structures are easily corroded in the Salt Lake areas of China, especially in sulfate solution. This study was intended to settle the problem of sulfate corrosion failure of concrete structures, the influences of different contents of super absorbent polymer (abbreviated as SAP) on the working performance, mechanical properties, corrosion resistance and expansion performance of cement mortar were studied. The mechanism of SAP in mortar was analyzed and studied by SEM. The results showed that although SAP could slightly decrease the fluidity and strength of cement mortar, but it could remarkably improve the coefficient of resistance erosion of specimens and the inflation coefficient of cement paste. When the content of SAP was 0.3%, the sulfate corrosion resistance and expansion performance of specimens showed the best (the coefficient of resistance erosion and inflation coefficient of mortar specimens were 0.95 and 0.97, respectively). Besides, SAP could release much water in the hydration process, form irregular holes, and increase the porosity of mortar specimens. There would more hydration products generated and filled in the pores during the hydration process, thereby improving the sulfate resistance of mortar specimens. Therefore, this research provides theoretical guidance and basis for the study of sulfate corrosion damage of concrete structures in the future.

The structure, properties and rheological characterisation of exopolysaccharides produced by Chryseobacterium cucumeris AP-2 from deteriorated milk

A novel exopolysaccharide (APS) was secreted by Chryseobacterium sp. AP-2. The yield of APS reached 3.247 g L−1 in MRS medium with 2% (w/v) maltose during 72 h incubation. The APS was a 4.871 × 105 Da heteropolysaccharide with rhamnose, fucose, mannose, glucose and galactose; using Fourier transform infrared spectroscopy, the main groups in APS were found to be hydroxyl and phosphate groups. APS exhibited a flaky structure with irregular holes, and its structural composition was confirmed by 1H and 13C nuclear magnetic resonance analysis. The degradation temperature (197.3 °C) of APS was determined by thermogravimetric analysis. APS exhibited stable emulsification property with the higher emulsification indexes (EI) than 50% in the diesel oil and kerosene. Ultimately, physicochemical factor (temperature, pH values and salts) had an impact on rheological properties of APS. The properties and structure characterisation of APS laid the experimental foundation for further exopolysaccharide exploration.

Fused spatial point process intensity estimation with varying coefficients on complex constrained domains

The availability of large spatial data geocoded at accurate locations has fueled a growing interest in spatial modeling and analysis of point processes. The proposed research is motivated by the intensity estimation problem for spatial point patterns on complex domains in R2 (e.g., domains with irregular boundaries, sharp concavities, and/or interior holes due to geographic constraints) and linear networks, where many existing spatial point process models suffer from the problems of “leakage” and computation. We propose an efficient intensity estimation algorithm to estimate the spatially varying intensity function and to study the varying relationship between intensity and explanatory variables on complex domains. The method is built upon a graph regularization technique and hence can be flexibly applied to point patterns on complex domains such as regions with irregular boundaries and holes, or linear networks. An efficient proximal gradient optimization algorithm is proposed to solve the penalized composite likelihood problem for parameter estimations. Finally, we apply the method to study and visualize the intensity patterns of the accidents on the Western Australia road network, and the spatial variations in the effects of income, night light condition, and population density on the Toronto homicides occurrences.

Influence of ultrasonic pretreatments on microwave hot-air flow rolling drying mechanism, thermal characteristics and rehydration dynamics of Pleurotus eryngii.

In order to improve the drying efficiency and reduce the drying energy consumption of Pleurotus eryngii, microwave hot-air flow rolling drying (MHARD) coupled with ultrasonic pretreating time (0, 20, 40, and 60 min) was used to investigate the drying profile, thermal characteristics, water migration, microstructure and rehydration dynamics of P. eryngii using differential scanning calorimetry (DSC), low-field nuclear magnetic resonance (LF-NMR) analysis and scanning electron microscopy (SEM). Results showed that the drying time of P. eryngii was 80, 70, 60 and 50 min, accordingly. Energy consumption was significantly reduced by ultrasonic pretreatment, and moisture effective diffusivity (Deff ) was increased with the increase of ultrasonic pretreating time. DSC curves showed that the drying process was accelerated by ultrasonic pretreatment significantly by enhancing the heat transfer. Meanwhile, SEM images showed that the cell was broken and numbers of irregular holes appeared in the ultrasound-pretreated samples. In terms of rehydration dynamics, Page model could well model the rehydration kinetics of dried P. eryngii with R2 > 0.99. The findings indicate that ultrasonic pretreatment is a promising method for MHARD of P. eryngii as it can enhance the drying process, and show potential for industrial application. © 2021 Society of Chemical Industry.

Polyimide mesh-based sample holder with irregular crystal mounting holes for fixed-target serial crystallography

The serial crystallography (SX) technique enables the determination of the room-temperature structure of a macromolecule while causing minimal radiation damage, as well as the visualization of the molecular dynamics by time-resolved studies. The fixed-target (FT) scanning approach is one method for SX sample delivery that minimizes sample consumption and minimizes physical damage to crystals during data collection. Settling of the crystals on the sample holder in random orientation is important for complete three dimensional data collection. To increase the random orientation of crystals on the sample holder, we developed a polyimide mesh-based sample holder with irregular crystal mounting holes for FT-SX. The polyimide mesh was fabricated using a picosecond laser. Each hole in the polyimide mesh has irregularly shaped holes because of laser thermal damage, which may cause more crystals to settle at random orientations compared to regular shaped sample holders. A crystal sample was spread onto a polyimide-mesh, and a polyimide film was added to both sides to prevent dehydration. Using this sample holder, FT-SX was performed at synchrotron and determined the room-temperature lysozyme structure at 1.65 Å. The polyimide mesh with irregularly shaped holes will allow for expanded applications in sample delivery for FT-SX experiments.

Non-Local and Multi-Scale Mechanisms for Image Inpainting.

Recently, deep learning-based techniques have shown great power in image inpainting especially dealing with squared holes. However, they fail to generate plausible results inside the missing regions for irregular and large holes as there is a lack of understanding between missing regions and existing counterparts. To overcome this limitation, we combine two non-local mechanisms including a contextual attention module (CAM) and an implicit diversified Markov random fields (ID-MRF) loss with a multi-scale architecture which uses several dense fusion blocks (DFB) based on the dense combination of dilated convolution to guide the generative network to restore discontinuous and continuous large masked areas. To prevent color discrepancies and grid-like artifacts, we apply the ID-MRF loss to improve the visual appearance by comparing similarities of long-distance feature patches. To further capture the long-term relationship of different regions in large missing regions, we introduce the CAM. Although CAM has the ability to create plausible results via reconstructing refined features, it depends on initial predicted results. Hence, we employ the DFB to obtain larger and more effective receptive fields, which benefits to predict more precise and fine-grained information for CAM. Extensive experiments on two widely-used datasets demonstrate that our proposed framework significantly outperforms the state-of-the-art approaches both in quantity and quality.

Resistance end correction factor of microperforated panel made using additive manufacturing

Fabrication of microperforated panel (MPP) using an additive manufacturing (AM) process produced imperfect perforations with an irregular shape, inconsistent size, and rough inner surface (due to burr formation). This imperfect hole condition leads to a significant deviation between measured and modeled acoustic properties. This study aims to introduce the resistance end correction factor (α) for quantifying this deviation. The MPP model’s current development excludes the irregular and inconsistent holes from the actual MPP. The improved resistance end correction factor (α) is determined based on the actual MPP samples. The MPP’s acoustic properties fabricated using AM process (3D Printing – PolyJet technology) are measured. The improved resistance end correction factor (α) is presented in surface plots for different geometrical parameters, perforation diameter (d), plate thickness (t), and perforation ratio (σ). The interpolation method is used to predict the “α” value based on the surface plot. The improved relative acoustic resistance value for the actual MPP sample with imperfect perforation condition (with recorded lowest hole roundness value at 0.207) is calculated using the predicted “α” value. Comparative results showed that the improved relative acoustic resistance determined based on the interpolated “α” agreed well with the experimental measurement results. The correlation coefficient for each comparison varied from 0.885 to 0.987. This finding is better than comparing calculated relative acoustic resistance values by using Maa’s theory and other MPP models with different proposed resistance end correction factors (α). Therefore, the proposed technique can reflect the imperfect perforation condition in actual MPP samples.