Texture Direction Research Articles

Analysis of influence factors of target polarization characteristics

The target polarization characteristics reflect the important information about the medium material, surface texture, and structural characteristics of the target itself. In this paper, 9 kinds of samples with different materials, roughness, and surface texture direction are selected to measure the polarization characteristics in an outdoor environment, and the influencing factors of the target polarization characteristics are analyzed, where the influence of the surface texture direction on the spatial distribution of the target polarization characteristics is emphatically analyzed. The results show that the target polarization characteristics are affected by many factors such as material, roughness, surface texture direction, and detection position, and the greater the angle between the surface texture direction and the principal plane, the more concentrated the target polarization characteristics are in and around the principal plane, which could provide a theoretical basis for comprehensively mastering the target polarization characteristics, improving the ability of target polarization detection and recognition, and enhancing the confidence of the target polarization modeling and simulation.

Bipolar Rashba Semiconductors: A Class of Nonmagnetic Materials for Electrical Spin Manipulation.

The realization of the electrical control of spin is highly desirable. One promising approach is by regulating the Rashba spin-orbit coupling effect of materials through external electric fields. However, this method requires materials to possess either a high electric field response and a large Rashba constant or the simultaneous presence of Rashba splitting and ferroelectric polarization. These stringent requirements result in a scarcity of suitable materials. In order to surpass these limitations and exploit a new prospect for spin manipulation via the Rashba effect, a conceptual class of materials named bipolar Rashba semiconductors (BRS) is proposed, whose valence band and conduction band possess opposite spin texture directions when approaching the Fermi level. The unique electronic structure of BRS makes it feasible to reverse the spin precession by simply applying a gate voltage. The existence of BRS is confirmed through first-principles calculations on the two-dimensional (2D) material AlBiS3.

Online micro defects detection for ductile cast iron pipes based on twin light photometric stereo

Ductile cast iron pipes (DCIPs) are widely utilized in water and gas supply due to their exceptional mechanical and material properties. Quality control during production is paramount for optimal performance, with surface defect detection being of utmost importance. Currently, production sites primarily rely on manual visual inspection, which presents several challenges, including high labor intensity, low efficiency, and subjectivity in defect judgment. 2D detection algorithms based on single images struggle to effectively detect small defects such as pores, pinholes, and scratches, resulting in high missed detection rates and vulnerability to interference from oil and water stains. To address these issues, this paper proposes a symmetrical twin-light photometric stereo (TLPS) detection algorithm based on photometric stereo theory, and image correction algorithm for mitigating the effects of ambient light. A visual inspection prototype system was designed and successfully implemented at a production site. The system comprises eight visual inspection units, each equipped with a high-speed line scan camera and two bar light sources for image acquisition of moving DCIP. Under the Lambertian model and parallel light source assumption, the gradient expression in the texture direction of the DCIP surface is derived based on light source symmetry. Production experiment results demonstrate that the gradient map obtained through the proposed TLPS effectively enhances defect contrast and accurately detects and locates micro defects such as pores, pinholes, and scratches on cast pipe surfaces. This verifies the effectiveness of the TLPS algorithm, addresses the shortcomings of traditional 2D detection algorithms, and lays the foundation for subsequent online detection of DCIP surface defects.

The effect of thickness on the defects and anisotropy of thin-wall Hastelloy X fabricated via laser powder-bed fusion

Laser powder-bed fusion (LPBF) possesses unique advantages in manufacturing complex structures. The mechanical properties of thin-wall structures are crucial for the application. This study investigates the influence of wall thickness on defects and mechanical properties of LPBF Hastelloy X (HX) superalloy. As the wall thickness decreases from 1.5 mm to 0.25 mm, the diameter of sub-grains inside the molten pool increases, exhibiting a progressively enhanced <100>//transverse direction (TD) texture in thin wall structure. Meanwhile, decreasing wall thickness leads to increased porosity and cracks due to unstable molten pool and higher residual stress. The crack initiates at columnar to equiaxed transition (CET) position and propagates along the building direction (BD). The tensile strength of the LPBF HX specimens in the horizontal and vertical directions is 773.5 MPa and 642.1 MPa with thickness of 1.5 mm, respectively, while the elongation of both specimens is close to 35%. When the wall thickness decreases to 0.25 mm, the elongation significantly decreases due to the evolution of microstructure anisotropy and the cracks along the BD, reaching 10.1% and 24.3% for horizontal and vertical specimens. This work illustrates the defects, microstructural evolution and the mechanical properties anisotropy in thin-wall structures of LPBF HX, providing a foundation for adjusting and optimizing the performance of subsequent thin-wall printing processes.

Roughness evaluation of turned composite surfaces by analysis of the shape of autocorrelation function

In this paper, the application of an Autocorrelation Function for the characterisation of surface topography was validated. The roughness evaluation of turned composite surfaces was supported by sophisticated studies of the Autocorrelation Function properties, considering especially the shape of the function. Details were measured with the optical method. The selection of the surface roughness evaluation procedures was carried out based on the Autocorrelation Function for both profile and areal analyses. Moreover, the application of various types of regular analysis methods, proposed in commercial software, like regular Gaussian regression and robust Gaussian functions, median de-noising, regular isotropic Spline, and fast Fourier transform filters, was proposed for the evaluation of surface topography parameters from the ISO 25178 standards. It was found that many common techniques, like commonly used filters, spectral analysis, and characterisation of texture direction, were supported by the proposed Autocorrelation Function studies. Moreover, the hard thresholding technique was found to be valuable in the comprehensive noise-suppression analysis.

Surface Morphology Analysis of Laser Shock Peened 20CrMnTi Steel: A Statistical Evaluation

Surface morphology impacts material performance and durability significantly. To gain a deeper understanding of the impact of laser shock peening (LSP) treatment on the surface morphology of materials and to explore more optimized LSP treatment strategies, this study presents an investigation into the surface morphology of 20CrMnTi steel following LSP treatment. Through the application of statistical analysis, the study examines the induced surface morphology variations resulting from both single-point repetitive LSP and multiple LSP treatments. Experimental results demonstrate significant alterations in surface roughness and peak height distribution after LSP treatments, accompanied by the presence of high amplitude compressive residual stress (CRS). Moreover, the depth of laser-induced indentations is found to be closely related to the number of impacts, and the incidence angle of the laser exhibits a discernible influence on the directional texture and periodicity of the impacted surfaces. This investigation also proposes a method for estimating surface morphology variations after LSP treatment by means of analysis of impact patterns, thereby offering the potential for enhancing the friction and wear performance of the impacted surfaces through the adjustment of the impact region position during multi-layer LSP treatment.

Diagnostics of Multi Drug Resistant Tuberculosis in Chest Radiographs using Local Textures &amp; Extreme Gradient Boosting

Abstract This study attempts to detect and differentiate Multi Drug Resistant (MDR) - Tuberculosis (TB) and Drug Sensitive (DS)-TB Chest Radiographs (CXR) using local texture descriptors and Ensemble Learning method. Studies report that CXR images contain likelihood information of the drug resistance which can be utilized computationally. Initially, CXR images are subjected to lung fields segmentation using Reaction Diffusion Level Set method. Further, Local Directional Texture Pattern (LDTP) features are extracted from the segmented lungs to characterize the localized textural variations. Extreme Gradient Boosting (XGBoost) classifier is employed to differentiate DS-TB and MDR-TB images. The obtained results demonstrate the ability of extracted LDTP features to characterize nonspecific textural inhomogeneities in images by operating on its principal directions. XGBoost algorithm provides maximum accuracy of 93% and true positive rate of 94.6% in detecting MDR-TB. As the proposed study differentiates the MDR-TB condition using CXR images, its computerized diagnostics could be used in the early screening and followup of TB ridden patients for public health infection control in any setting.

Effects of Building Directions on Microstructure, Impurity Elements and Mechanical Properties of NiTi Alloys Fabricated by Laser Powder Bed Fusion.

For NiTi alloys prepared by the Laser Powder Bed Fusion (LPBF), changes in the building directions will directly change the preferred orientation and thus directly affect the smart properties, such as superelasticity, as well as change the distribution state of defects and impurity elements to affect the phase transformation behaviour, which in turn affects the smart properties at different temperatures. In this study, the relationship between impurity elements, the building directions, and functional properties; the effects of building directions on the crystallographic anisotropy; phase composition; superelastic properties; microhardness; geometrically necessary dislocation (GND) density; and impurity element content of NiTi SMAs fabricated by LPBF were systematically studied. Three building directions measured from the substrate, namely, 0°, 45° and 90°, were selected, and three sets of cylindrical samples were fabricated with the same process parameters. Along the building direction, a strong <100>//vertical direction (VD) texture was formed for all the samples. Because of the difference in transformation temperature, when tested at 15 °C, the sample with the 45° orientation possessed the highest strain recovery of 3.2%. When tested at the austenite phase transformation finish temperature (Af)+10 °C, the 90° sample had the highest strain recovery of 5.83% and a strain recovery rate of 83.3%. The sample with the 90° orientation presented the highest microhardness, which was attributed to its high dislocation density. Meanwhile, different building directions had an effect on the contents of O, C, and N impurity elements, which affected the transformation temperature by changing the Ni/Ti ratio. This study innovatively studied the impurity element content and GND densities of compressive samples with three building directions, providing theoretical guidance for LPBFed NiTi SMA structural parts.

Precise and Rapid Replication of Complex‐Shaped Fused Silica Optics

AbstractThe high hardness, brittleness, and thermal resistance of fused silica glasses extremely challenge the mass production of complex‐shaped fused silica optics. This paper reports a new process chain for rapidly replicating complex‐shaped fused silica optics from complex molds at ambient temperature. The process chain mainly consists of the ultraprecision diamond turning of the complex‐shaped molds, the rapid shape replication through the silica precursor photopolymerization, and the transparent complex‐shaped optics derivation from the debinding and sintering. The directional shrinkages and surface texture evolutions in the process are comprehensively characterized for the replicated fused silica optics. After the shrinkage compensation, transparent fused silica optics with the spherical, microlens array, and hierarchical freeform surfaces are precisely replicated, exhibiting micrometric form accuracy, nanometric surface roughness, and high imaging quality. The proposed process chain provides a revolutionary approach for the mass production of precise complex‐shaped fused silica optics with fundamentally improved production efficiency and complex shape formation capability.

Some models for initially stressed and initially strained structurally anisotropic incompressible materials

In this paper, we determine the constitutive relations for structurally anisotropic materials from a reference with initial strain or initial stress. Using reference independence of strain energy density, we first deduce the relationship of various initial strain measures with material symmetry and determine the resulting structural tensors. We use these structural tensors to derive the necessary invariants for initially strained materials. We also Examine the polyconvexity of the derived invariants and determine constitutive relations for the initially strained Ogden model. Next, we determine the constitutive relation for a combination of initial stress-texture symmetry which may be a more popular approach of recent interest. We deduce four reference-independent constitutive relations for initially stressed transversely isotropic incompressible materials. The first two strain energy functions are linear in the left Cauchy stretch and its cofactor, respectively, in the stress-free state. In the absence of initial stress, the third strain energy function involves all standard invariants for transversely isotropy. To deduce this strain energy in the presence of initial stress, we invert a fourth-order tensor and perform several involved tensor calculations. Finally, we obtain the constitutive relation for an initially stressed transversely isotropic limited chain extensible (LCE) model. To determine the initial stretch in the preferred texture direction in terms of initial stress, we utilize the geometrical interpretation of the Almansi strain measure.

Microstructure formation during laser powder bed fusion of Ti-22Al-25Nb with low and high pre-heating temperatures

We compare microstructure formation during laser powder bed fusion (LPBF) of a Ti-22Al-25Nb alloy applying low and high pre-heating build plate temperatures. Fast cooling rates during low-temperature LPBF lead to metastable weakly ordered β phase, i.e., bcc–(Ti,Al,Nb) with pronounced 〈100〉 texture in build direction and nanosized segregations within grains elongated in the build direction. For high-temperature LPBF a Widmanstätten microstructure was observed with lenticular O phase precipitates within the β matrix. Microscopical and in situ high-energy synchrotron diffraction investigations demonstrate that the microstructure formation can be widely explained by the precipitation of O phase from supersaturated β rather than by a sequence of solid-state phase transformations, as it would be expected under thermodynamic equilibrium conditions. A detailed analysis of the microstructural gradient in the subsurface region, however, demonstrates that precipitation from metastable β cannot fully explain the observed microstructures, and that the process energy density, i.e., the intensity of the intrinsic heat treatment of LPBF, plays a relevant role. The investigation of the graded area near the surface of the LPBF materials produced with high pre-heating temperature is particularly interesting as it reveals preferred nucleation of the O phase at subgrain boundaries and dislocations.

Texture direction recognition of wooden beams and columns based on improved meta-learning

Texture direction recognition of wooden beams and columns based on improved meta-learning

A combined experimental and crystal plasticity study of grain size effects in magnesium alloys

This work presents a method to incorporate the micro Hall-Petch equation into the crystal plasticity finite element (CPFE) framework accounting for the microstructural features to understand the coupling between grain size, texture, and loading direction in magnesium alloys. The effect of grain size and texture is accounted for by modifying the slip resistances of individual basal and prismatic systems based on the micro Hall-Petch equation. The modification based on the micro Hall-Petch equation endows every slip system at each microstructural point with a slip system-level grain size and maximum compatibility factor, which are in turn used to modify the slip resistance. While the slip-system level grain size is a measure of the grain size, the maximum compatibility factor encodes the effect of the grain boundary on the slip system resistance modification and is computed based on the Luster-Morris factor. The model is calibrated using experimental stress-strain curves of Mg-4Al samples with three different grain sizes from which the Hall-Petch coefficients are extracted and compared with Hall-Petch coefficients predicted using original parameters from previous work. The predictability of the model is then evaluated for a Mg-4Al sample with different texture and three grain sizes subjected to loading in different directions. The calibrated parameters are then used for some parametric studies to investigate the variation of Hall-Petch slope for different degrees of simulated spread in basal texture, variation of Hall-Petch slope with loading direction relative to basal poles for a microstructure with strong basal texture, and variation of yield strength with change in grain morphology. The proposed approach to incorporate the micro Hall-Petch equation into the CPFE framework provides a foundation to quantitatively model more complicated scenarios of coupling between grain size, texture and loading direction in the plasticity of Mg alloys.

Microstructure, crack formation and improvement on Nickel-based superalloy fabricated by powder bed fusion

Nickel-based superalloy (Haynes 230) parts were fabricated by powder bed fusion using a laser - based system. Crack defects were unavoidable. In order to solve the cracking problem, it was necessary to understand the crack formation mechanism, and the hot isostatic pressing method was used to eliminate the crack defects. The results indicated that the microstructure displayed cellular crystal structure in XY direction and columnar crystal structure with {001} < 001 > cubic texture in XZ direction. Under the thermal stress and micro-segregation, M23C6 carbides and NiSi eutectic phases were precipitated at high angle grain boundaries, which promoted the formation of solidification and liquation cracks. Because the direction of the internal cracks in the horizontal tensile sample was perpendicular to the tensile direction and the microstructure was {001} < 001 > cubic texture, the tensile properties were anisotropic. After hot isostatic pressing treatment, the cracks were obviously eliminated, the ultimate tensile strength and elongation were significantly improved. The carbides transformed from Cr-rich M23C6 to W-rich M6C.

STRUKTUR ANATOMI KAYU YANG DIPERDAGANGKAN DI KABUPATEN ACEH BESAR

This study aims to determine the anatomical structure of wood and its possiblity uses for trade in Aceh Besar District. The research was carried out by observing 13 wood samples from the Bogorience 1915 xylarium wood collection. The observed samples included macroscopic and microscopic characteristics. Macroscopic characteristics include texture, color, pattern, texture, and grain direction of the wood. Microscopic characteristics observed were growth circumference boundaries, vessels, pores, dots, and radii based on the International Association of Wood Anatomists (IAWA) book. Each preparation was observed using a microscope and analyzed descriptively. The results showed that the anatomical structures of the macroscopic and microscopic properties of the 13 Aceh Besar wood species varied in terms of texture, grain direction, radius size, crystal type, fiber length, vessel length, and fiber wall thickness. While the pattern, color, distribution of pores, type of dots, type of perforation area, type of parenchyma cells, and the composition of the cells composing the radius show uniformity, and two kinds of wood have prismatic crystals, namely Surian wood in upright cells and Bangkirai wood in straight cells lie down. The 13 types of wood, 46% include strong class I-II for construction, bridges, pillars, and floors. Meanwhile, 54% is classified as strong class III-V as a material for making furniture, doors, windows, and products that do not require heavy strength.

Detection of GAN generated image using color gradient representation

With the development of generative adversarial network (GANs) technology, the technology of GAN generates images has evolved dramatically. Distinguishing these GAN generated images is challenging for the human eye. Moreover, the GAN generated fake images may cause some behaviors that endanger society and bring great security problems to society. Research on GAN generated image detection is still in the exploratory stage and many challenges remain. Motivated by the above problem, we propose a novel GAN image detection method based on color gradient analysis. We consider the difference in color information between real images and GAN generated images in multiple color spaces, and combined the gradient information and the directional texture information of the generated images to extract the gradient texture features for GAN generated images detection. Experimental results on PGGAN and StyleGAN2 datasets demonstrate that the proposed method achieves good performance, and is robust to other various perturbation attacks.

A hierarchical approach based CBIR scheme using shape, texture, and color for accelerating retrieval process

In the traditional content-based image retrieval (CBIR) framework, images are retrieved based on the combined primitive features. However, such a kind of fusion is always not effective as one feature may overshadow other image feature. To overcome this issue, in this particular paper, we have suggested a hierarchical framework where features like color, texture, and shape are considered in a single hierarchy only. The main concern of the hierarchical system is the proper selection of the order of retrieving visual features. So, semantic-based image retrieval has been carried out. Here, at the first level, the salience map-based region of interest has been identified, and then edge histogram descriptor-based shape features are incorporated. In the second hierarchy, we have proposed a novel directional texture feature extraction based on the Tamura features’ directionality. Further, color is considered another primitive feature of an image, but human visual perception is not sensitive to each color. The image can be visualized by the salient colors, and in this work, we have developed a color image quantization-based approach. Now, to validate the system, extensive experimental results and its comparison with its contemporaries through Corel-1 K, GHIM-10 K, Olivia-2688, and Produce-1400 databases have been carried out.

Droplet pinning on the tilted surface processed by a grinding machine

The study reports the experimental results of pinning/sliding water droplets onto tilted stainless steel substrates with different roughness and texture directions. The substrates were textured by a grinding machine. Droplets were dropped onto the substrate using a syringe. The distance between the needle and the substrate was varied from 20 mm to 200 mm. After impingement, the droplets pinned or slid onto the tilted surfaces in the parallel and perpendicular to the texture direction. For each substrate, the conditions of pinning or sliding of the droplet were obtained using the probability theory. It was established that, in contrast to the case of a water droplet on the surface with perpendicular scratches, the probabilities of droplet pinning on the polished surface and surface with parallel scratches were equal. The perpendicular scratches on the polished surface of stainless steel increased the probability of pinning a droplet by 20 %. The main fundamental result is to establish two spreading modes: with fragmentation and without fragmentation. The limiting cases in which water droplets divided into a few smaller droplets after impingement were obtained.

Statistical Analysis on Impact of Image Preprocessing of CT Texture Patterns and Its CT Radiomic Feature Stability: A Phantom Study.

To examine computed tomography (CT) radiomic feature stability on various texture patterns during pre-processing utilizing the Credence Cartridge Radiomics (CCR) phantom textures. Imaging Biomarker Explorer (IBEX) expansion for the abbreviation IBEX extracted 51 radiomic features of 4 categories from 11 textures image regions of interest (ROI) of the phantom. 19 software pre-processing algorithms processed each CCR phantom ROI. All ROI texture processed image features were retrieved. Pre-processed CT image radiomic features were compared to non-processed features to measure its textural influence. Wilcoxon T-tests measured the pre-processing relevance of CT radiomic features on various textures. Hierarchical cluster analysis (HCA) was performed to cluster processer potency and texture impression likeness. The pre-processing filter, CT texture Cartridge, and feature category affect the CCR phantom CT image's radiomic properties. Pre-processing is statistically unaltered by Gray Level Run Length Matrix (GLRLM ) expansion for the abbreviation GLRLM and Neighborhood Intensity Difference matrix (NID) expansion for the abbreviation NID feature categories. The 30%, 40%, and 50% honeycomb are regular directional textures and smooth 3D-printed plaster resin, most of the image pre-processing feature alterations exhibited significant p-values in the histogram feature category. The Laplacian Filter, Log Filter, Resample, and Bit Depth Rescale Range pre-processing algorithms hugely influenced histogram and Gray Level Co-occurrence Matrix (GLCM) image features. We found that homogenous intensity phantom inserts, CT radiomic feature, are less sensitive to feature swaps during pre-processing than normal directed honeycomb and regular projected smooth 3D-printed plaster resin CT image textures. Because they lose fewer information during image enhancement, This feature concentration empowerment of the images also enhances texture pattern recognition.

Shape Memory Properties and Microstructure of FeNiCoAlTaB Shape Memory Alloys

The three-point-bending shape memory properties, microstructure, and magnetic properties of Fe40.95Ni28Co17Al11.5Ta2.5B0.05 (at.%) alloys were investigated. The magnetic results showed a martensitic transformation in the samples that were aged at 700 °C for 6 and 12 h under the applied magnetic fields of 0.05 and 7 Tesla. The martensitic start temperature increased from −113 °C to −97 °C as aging times increased from 6 to 12 h. Increasing the magnetic fields from 0.05 to 7 Tesla, the transformation temperatures increased to a higher temperature. Both samples reach saturation magnetization (140 emu/g) under 7 Tesla. The 98.5% cold-rolled alloys that were annealed at 1250 °C for 0.5 h presented a strong &lt;100&gt; texture in the rolling direction with an average grain size of 360 μm. Increasing the annealing time to 1 h, the intensity of texture reduced from 31.61 to 23.19. The fraction of low angle grain boundaries (LABs) for the 98.5% CR samples after annealing at 1250 °C for 0.5 h and 1 h was about 24.6% and 16.1%, respectively. Three-point-bending results show that the sample aged at 700 °C for 6 h displayed 0.2% recoverable strain at a stress level of 800 MPa. Failure occurred before the 900 MPa cycle could be completed. The sample aged at 700 °C for 12 h shows no transformation before the applied stress level of 300 MPa. As the stress levels increase to 400 MPa, the sample shows the shape memory effect and displayed 0.8% recoverable strain at a stress level of 400 MPa. The samples are failures during the 500 MPa cycle. The observed recoverable strain values were lower than those that were theoretically predicted, which was possibly due to the larger volume fraction of high-angle grain boundary and the slightly lower than expected average grain size.