Sample Shape Research Articles

Crystalline and magnetic properties of CoO nanoparticles locally investigated by using radioactive indium tracer

We herein report a comprehensive investigation on the magnetic, structural, and electric properties of CoO nanoparticles with different sizes by local inspection through hyperfine interactions measured in a wide range of temperatures (10–670 K) by using radioactive ^{111}In(^{111}Cd) tracers with the perturbed angular correlations technique. Small cobalt oxide nanoparticles with the characteristic size of 6.5 nm have been prepared by the wet chemical route that turned out to be essential to incorporate radioactivity tracers during nucleation and growth of the particles. Nanocrystalline samples with 22.1 nm size were obtained by thermal treatments under low pressure of helium at 670 K. The hyperfine data were correlated with X-ray diffraction, ZFC–FC magnetic measurements, and transmission electron microscopy to describe the structure, magnetic properties, size, and shape of samples. An analysis of the temperature evolution of hyperfine parameters revealed that the structural distortion and the magnetic disorder in the core and on the surface layer play an important role in the magnetic behavior of CoO nanoparticles.

Dipolar interaction and sample shape effects on the hysteresis properties of 2d array of magnetic nanoparticles

We study the ground-state and magnetic hysteresis properties of 2d arrays ( $$L^{}_x\times L^{}_y$$ ) of dipolar interacting magnetic nanoparticles (MNPs) by performing micromagnetic simulations. Our primary interest is to understand the effect of sample shape, $$\Theta $$ , the ratio of the dipolar strength to the anisotropy strength and the direction of the applied field $$\vec {H} = H_{0}{\hat{e}}^{}_H$$ on the ground state and the magnetic hysteresis in an array of MNPs. To study the effect of the shape of the sample, we have varied the aspect ratio $$A^{}_r=L^{}_y/L^{}_x$$ , which in turn, is found to induce shape anisotropy in the system. Our main observations are: (a) When the dipolar interaction is strong $$(\Theta >1)$$ , the ground-state morphology has an in-plane ordering of magnetic moments, (b) the ground-state morphology has randomly oriented magnetic moments that are robust regarding system sizes and $$A^{}_r$$ for weakly interacting MNPs ( $$\Theta <1$$ ), (c) micromagnetic simulations suggest that the dipolar interaction decreases the coercive field $$H^{}_c$$ , (d) the remanence magnetisation $$M^{}_r$$ is found to be strongly dependent not only on the strength of dipolar interaction but also on the shape of the sample and (e) due to the anisotropic nature of dipolar interaction, a strong shape anisotropy effect is observed when the field is applied along the long axis of the sample. In such a case, the dipolar interaction induces an effective ferromagnetic coupling when the aspect ratio is enormous. These results are of vital importance in high-density recording systems, magneto-impedance sensors, etc.

Improvement of radio frequency heating uniformity for millets by changing shape and adding polypropylene blocks

Radio frequency (RF) treatment is a burgeoning method in food processes. RF heating non-uniformity is a main obstacle for industrial implementations and influenced by the geometry of treated materials. In this study, the effect of convex-concavo shapes of the sample top surface and step shapes at the bottom of the rectangular container by adding polypropylene (PP) blocks on the heating uniformity was investigated using a 6 kW, 27.12 MHz free-running oscillator RF system. The results showed that the RF heating uniformity index values of millets decreased with increasing convex degree and decreasing concave degree of the sample top shape. Moreover, adding PP blocks at the bottom of the sample container was a better choice of improving RF heating uniformity owing to the wider adjustable range of sample sizes and better temperature distribution. This study provided a new method to improve the RF heating uniformity by simply changing the shapes of samples in either the top or bottom surface.

Mechanical grinding alters physicochemical, structural, and functional properties of tobacco (Nicotiana tabacum L.) leaf powders

Utilizing tobacco industrial waste can increase added value without increasing the environmental burden. The physicochemical, structural, and functional properties of tobacco leaf powders produced by coarse and superfine grinding treatments with different particle size were investigated. The particle size was significantly reduced by superfine grinding to micron scale (10.3 μm), and the specific surface area sharply increased. With decreasing particle size, the bulk density, tap density, angles of repose and slide increased, but water and oil holding capacities decreased, indicating the worse flowability and hydration property. The increasing lightness and yellowness but decreasing redness were observed after superfine grinding. Differential scanning calorimetry curves showed that superfine grinding insignificantly affected the conformation stability and denaturation degree of proteins. Fourier transform infrared spectroscopy proved unchanged main structure and decreased chain length of polysaccharide polymer. Morphology revealed that the shape of superfine ground sample was changed from an irregular polygon to spherical-like, and surface roughness was reduced. All cell walls were disrupted after superfine grinding, but the dissolution yields of nicotine and total phenolic, and antioxidant activities were not enhanced. The median particle size of 93.9 μm was the most effective for the ingredient dissolution and antioxidant capacity. This study was expected to supply new insights in guiding the development of discarded tobacco in practice.

Shape deviations of DLW microstructures in dependency of fabrication parameters

Deep understanding of the effects associated with fabrication parameters and their influence on the resulting structures shape is essential for the further development of direct laser writing (DLW). In particular, it is critical for development of reference materials, where structure parameters are precisely fabricated and should be reproduced with use of DLW technology. In this study we investigated the effect of various fabrication and preparation parameters on the structural precision of interest for reference materials. A well-studied photo-curable system, SZ2080 negative photo-resist with 1 wt.% Michler’s ketone (Bis) photo-initiator, was investigated in this work. The correlation between applied laser power, laser velocity, fabrication direction on the deviations in the structure shape were observed by means of white light interferometry microscopy. Moreover, influence of slicing and hatching distances as well as prebake time were studied as function of sample shape. Deviations in the structure form between the theoretically expected and the one detected after DLW fabrication were observed in the range up to 15%. The observed shape discrepancies show the essential importance of fine-tuning the fabrication parameter for reference structure production.

Flash sintering and dielectric properties of K0.5Na0.5NbO3

AbstractK0.5Na0.5NbO3 (KNN) of 4‐μm average particle size was flash sintered in parallel plate capacitor configuration (PPCC) under 100 V/mm (0.8 mA/mm2 cut‐off) with 10°C/min heating rate in air. Precipitous densification occurred from Tf = 662–670°C (Tf–furnace temperature) in 60 s with 55 mW/mm3 peak power absorption at Tf = 667°C, resulting in 98% dense ceramic of &lt; 5‐μm grains size. No grain growth was observed. A cubic grain morphology was inherited from the starting KNN powder. No sign of liquid phase formation on grain boundaries (GBs) was detected. A 147°C rise above Tf = 667°C due to Joule heating is predicted. At 25°C and 1 kHz, relative permittivity (εr) and dielectric loss (tan(δ)) are 4096 and 2.9%, respectively. From 0.1 to 100 kHz, εr and tan(δ) undergo relaxation, reaching εr = 577 and tan(δ) = 0.2% at 1000 kHz. Variation of εr with temperature revealed Amm2 → P4mm and P4mm → Pm3m transitions at ∼204°C and 409°C, respectively. As per Curie–Weiss analysis, Curie temperature and Curie–Weiss constant are θ = 375°C and C = 3.1 × 10−5°C for the P4mm → Pm3m transition, respectively. The transition is first order as Ttr &gt; θ with a diffusiveness exponent γ = 1.04, indicating normal ferroelectric behavior. The low‐frequency dielectric relaxation is attributed to the space charge in the vicinity of GBs, which is a remnant of flash sintering. Joule heating cannot alone account for the densification in 60 s, which we substantiate within the framework of phase equilibrium and diffusion kinetics. We conjecture that oxygen vacancies start ionizing at Tf = 662°C, couple with the applied electric field via the Lorentz force, and increase their electrochemical potential, causing ultrafast densification. The effects of sample shape, size, and PPCC contributing to high sintered density are also discussed.

Processing of intermetallic laminates by Self-Propagating High–Temperature Synthesis initiated with concentrated solar energy

The intermetallic compounds are very interesting in a multitude of structural and functional applications, such as in turbomachines or engine parts, due to their good behaviour at high temperatures, as well as their high resistance to corrosion and oxidation. In the present work, the study of processing of the Ni-Al system intermetallics has been carried out by means of Self-Propagating High–Temperature Synthesis initiated by concentrated solar energy (SHS–CSE). Synthesis by this high-energy exothermic reaction often causes the appearance of porosity, lack of interlayer adhesion, volumetric expansion, and even the total loss of sample shape. To obtain high-quality systems, a study has been carried out on one-layer and multi-layer configurations from powder materials, considering the influence of the heating rate and time. The use of concentrated solar energy has allowed to obtain fully densified nickel parts at 1000°C in just 15 min, compared to the 1325°C and more than 12h required by conventional techniques to obtain lower relative densities (~97%). The best results in multilayer configurations have been achieved in Ni-Ni/Al-Ni system with the synthesis of intermetallic compounds type Ni2Al3, NiAl and Ni3Al. The control of volumetric expansion and porosity, full densified nickel layers perfectly adhered to the interlayer and hardness values up to 900 HV have been obtained in just 2 min. This work highlights the wide possibilities of the use of CSE in metal treatment, which allows efficient and sustainable synthesis of new systems and the improvement of the final properties of the parts.

Limited-angle computed tomography with deep image and physics priors

Computed tomography is a well-established x-ray imaging technique to reconstruct the three-dimensional structure of objects. It has been used extensively in a variety of fields, from diagnostic imaging to materials and biological sciences. One major challenge in some applications, such as in electron or x-ray tomography systems, is that the projections cannot be gathered over all the angles due to the sample holder setup or shape of the sample. This results in an ill-posed problem called the limited angle reconstruction problem. Typical image reconstruction in this setup leads to distortion and artifacts, thereby hindering a quantitative evaluation of the results. To address this challenge, we use a generative model to effectively constrain the solution of a physics-based approach. Our approach is self-training that can iteratively learn the nonlinear mapping from partial projections to the scanned object. Because our approach combines the data likelihood and image prior terms into a single deep network, it is computationally tractable and improves performance through an end-to-end training. We also complement our approach with total-variation regularization to handle high-frequency noise in reconstructions and implement a solver based on alternating direction method of multipliers. We present numerical results for various degrees of missing angle range and noise levels, which demonstrate the effectiveness of the proposed approach.

Combustion characteristics of PMMA sheets with different equivalent diameters in still air

SummaryTo investigate the combustion characteristics of polymethyl methacrylate (PMMA), a series of experiments of PMMA combustion with different sample shapes and sizes in still air are performed. A digital video camera and an electronic balance are used to record the combustion process and variation of mass, particularly. The effects of equivalent diameter on combustion are discussed and analyzed, respectively, to well adapt in dimensionless analysis methods. Flame pulsation during the stable burning stage is studied by similarity theory and dimensionless analysis methods. Experimental and theoretical results show that correlations between flame pulsation and equivalent diameters in PMMA burning are similar to that of pool fires, that is, flame pulsation frequency is inversely related to the square root of equivalent diameter. In addition, the corresponding theoretical analysis of heat and mass transfer processes is studied. Convection and radiation heat transfer were calculated and modeled for each shape and sample size. Based on the heat transfer calculation results, sample mass loss rate for each sample size was predicted, and it is in good agreement with the experimental result. Finally, a dimensionless heat release rate for different sample size was scaled with dimensionless flame height.

Size and shape effects in the orbital magnetization of TMDs monolayers

The intrinsic orbital magnetization of a TMD monolayer is usually calculated for periodic crystals without mentioning the geometrical shape of samples and boundary conditions (BCs) for the electron wave functions. Such approaches, based on Bloch’s theorem, involves a contribution from the Berry curvature, also in the case when the system is described by the two-band minimal model (Xiao et al 2012 Phys. Rev. Lett. 108 196802). In the present paper, we show that the geometrical and topological properties of the specimen, as well as the BCs, play an important role in the problem of valley orbital magnetization even for a macroscopic sample.

Korelasi Point Load Index dan Uniaxial Compressive Strength pada Satuan Batupasir dan Batulempung Formasi Latih untuk Penentuan Koefisien Kekuatan Batuan di Pit X Tambang Batubara PT Berau Coal, Kalimantan Timur

Physical and mechanical properties of rock for engineering purposes are indispensable for any civil/construction, mining and other engineering requirment. The results of the uniaxial compressive strength (UCS) test are very much needed in various geotechnical analyzes or engineering, in particular in the mining industry in relation to the calculation of the pit slope design and other mining infrastructure. Rock samples used in this study were obtained from the results of geotechnical drilling (full core drilling). The rock engineering properties test to obtain UCS and PLI values was carried out in the laboratory. Testing the rock hardness index using the point load index (PLI) can be done more quickly, cheaply, practically and can use rock samples with a variety of sample shapes. The focus and object of the research are mudstone and sandstone units as part of the Lati Formation. These two types of layers are the most dominant rock types as a constituent of the pit slopes in the research area. To ensure that the correlation results are in accordance with the rules of scientific research, the distribution of UCS and PLI data from laboratory test results is verified using a statistical approach / testing. Correlation and analysis between the two rock engineering properties test results are very useful for geotechnical analysis data input. The coefficient or constant values obtained can be used to determine the rock strength values used in various geotechnical analyzes so that the analysis can be carried out more efficiently, effectively and quickly and can support geotechnical engineering work.

PFC: A Novel Perceptual Features-Based Framework for Time Series Classification

Time series classification (TSC) is a significant problem in data mining with several applications in different domains. Mining different distinguishing features is the primary method. One promising method is algorithms based on the morphological structure of time series, which are interpretable and accurate. However, existing structural feature-based algorithms, such as time series forest (TSF) and shapelet traverse, all features through many random combinations, which means that a lot of training time and computing resources are required to filter meaningless features, important distinguishing information will be ignored. To overcome this problem, in this paper, we propose a perceptual features-based framework for TSC. We are inspired by how humans observe time series and realize that there are usually only a few essential points that need to be remembered for a time series. Although the complex time series has a lot of details, a small number of data points is enough to describe the shape of the entire sample. First, we use the improved perceptually important points (PIPs) to extract key points and use them as the basis for time series segmentation to obtain a combination of interval-level and point-level features. Secondly, we propose a framework to explore the effects of perceptual structural features combined with decision trees (DT), random forests (RF), and gradient boosting decision trees (GBDT) on TSC. The experimental results on the UCR datasets show that our work has achieved leading accuracy, which is instructive for follow-up research.

Microstructural observation of complex-shaped green ceramic compact and numerical simulation with special consideration on crack formation

The microstructure of a die-pressed green ceramic compact with a complex shape was visualized by liquid immersion and X-ray micro-computed tomography techniques. Significant microstructural inhomogeneity in terms of the pore distribution and granule shape was observed depending on the sample locations, while cracks were formed only at certain positions. The microstructural differences were explained by the von Mises stress gradient within the compact, which originated from friction between the granule and mold as well as non-uniform pressure delivery because of the complex sample shape. A numerical simulation was performed based on the modified Drucker–Prager/Cap model to explain the origin of the different microstructures, such as pore distribution and crack formation.

Determination of Fracture Limit Line in Principal Strain Space by Shear Tests

The main goal of this paper was to define a new limit line, which expands Forming Limit Curve (FLC) more precisely Fracture Forming Limit Curve (FFLC). The new limit line was defined by damage models transformed from triaxiality-fracture strain space to the major/minor strain space and we focused on the shear area. Because FLC and FFLC have some limitations, for example, some Advanced High Strength Steels (AHSS) fractures before thinning. Another limitation can be seen on the left side of the diagrams in the shear region, where the part can break in the process without crossing the FLC or FFLC. The different shapes of samples were used for finding a new line of the FFLC and Deep Drawing Test (DDT) was used for verification. The fracture points from measurement were used for calibration of simple uncoupled damage models. The simple model means model, which is calibrated based on one or two measurements (tensile test or tensile test + shear test). This paper was used an Advanced High Strength Steel (AHSS) DP1000 sheet with a thickness of 0.8 mm for the experiments.

Recognition of weeds at asparagus fields using multi-feature fusion and backpropagation neural network

In order to solve the problem of low recognition rates of weeds by a single feature, a method was proposed in this study to identify weeds in Asparagus (Asparagus officinalis L.) field using multi-feature fusion and backpropagation neural network (BPNN). A total of 382 images of weeds competing with asparagus growth were collected, including 135 of Cirsium arvense (L.) Scop., 138 of Conyza sumatrensis (Retz.) E. Walker, and 109 of Calystegia hederacea Wall. The grayscale images were extracted from the RGB images of weeds using the 2G-R-B factor. Threshold segmentation of the grayscale image of weeds was applied using Otsu method. Then the internal holes of the leaves were filled through the expansion and corrosion morphological operations, and other interference targets were removed to obtain the binary image. The foreground image was obtained by masking the binary image and the RGB image. Then, the color moment algorithm was used to extract weeds color feature, the gray level co-occurrence matrix and the Local Binary Pattern (LBP) algorithm was used to extract weeds texture features, and seven Hu invariant moment features and the roundness and slenderness ratio of weeds were extracted as their shape features. According to the shape, color, texture, and fusion features of the test samples, a weed identification model was built. The test results showed that the recognition rate of Cirsium arvense (L.) Scop., Calystegia hederacea Wall. and Conyza sumatrensis (Retz.) E. Walker were 82.72% (color feature), 72.41% (shape feature), 86.73% (texture feature) and 93.51% (fusion feature), respectively. Therefore, this method can provide a reference for the study of weeds identification in the asparagus field. Keywords: weeds recognition, image processing, feature extraction, multi-feature fusion, BP neural network, asparagus field DOI: 10.25165/j.ijabe.20211404.6135 Citation: Wang Y F, Zhang X D, Ma G X, Du X X, Shaheen N, Mao H P. Recognition of weeds at asparagus fields using multi-feature fusion and backpropagation neural network. Int J Agric & Biol Eng, 2021; 14(4): 190–198.

Waterproof Galvanometer Scanner-Based Handheld Photoacoustic Microscopy Probe for Wide-Field Vasculature Imaging In Vivo

Photoacoustic imaging (PAI) is a hybrid non-invasive imaging technique used to merge high optical contrast and high acoustic resolution in deep tissue. PAI has been extensively developed by utilizing its advantages that include deep imaging depth, high resolution, and label-free imaging. As a representative implementation of PAI, photoacoustic microscopy (PAM) has been used in preclinical and clinical studies for its micron-scale spatial resolution capability with high optical absorption contrast. Several handheld and portable PAM systems have been developed that improve its applicability to several fields, making it versatile. In this study, we developed a laboratory-customized, two-axis, waterproof, galvanometer scanner-based handheld PAM (WP-GVS-HH-PAM), which provides an extended field of view (14.5 × 9 mm2) for wide-range imaging. The fully waterproof handheld probe enables free movement for imaging regardless of sample shape, and volume rate and scanning region are adjustable per experimental conditions. Results of WP-GVS-HH-PAM-based phantom and in vivo imaging of mouse tissues (ear, iris, and brain) confirm the feasibility and applicability of our system as an imaging modality for various biomedical applications.

Sono-synthesis of MnWO4 ceramic nanomaterials as highly efficient photocatalysts for the decomposition of toxic pollutants

As the subject of energy deficiency and environmental contamination has become a widespread concern, introducing green and quick procedure for synthesizing compounds with a catalyst role in solving environmental problems is followed with great interest. Herein, we offer a controllable sonochemical approach for photocatalyst synthesis. The nanostructured MnWO4 is created via a sonochemical process utilizing a green capping agent, phenylalanine. It was observed that various quantities of precursors, different sonication times, and diverse types of capping agents could modify the shape, photocatalytic yield, and scale of MnWO4 samples. The features of nanostructured MnWO4 were examined with different kinds of analyses. The activity of various MnWO4 structures as photocatalytic substances to eliminate organic contamination in water by visible radiation was also studied. Although all the various structures of manganese tungsten oxide were able to eliminate the organic contamination in the water, the photocatalytic performance of MnWO4 nanostructure was created utilizing phenylalanine via sonochemistry was superior to that of the samples made under other conditions. The optimal sample manifested remarkable yield since the removal rates of Acid Yellow 23, eosin Y, and crystal violet in 50 min under visible radiation were 98.86, 99.15, and 97.56 %, respectively. The manganese tungsten oxide nanostructure is of the paramagnetic kind. Besides, the optimal MnWO4 sample was reused as a photocatalytic substance. It manifested appropriate stability over 13 cycles, denoting its capability as a highly efficient photocatalytic substance to remedy the environment.

Color-difference evaluation for 3D objects.

A psychophysical experiment using 3D printed samples was conducted to investigate the change of perceived color differences caused by two different illuminations and two 3D sample shapes. 150 pairs of 3D printed samples around five CIE color centers [Color Res. Appl. 20, 399-403, 1995], consisting of 75 pairs of spherical samples and 75 pairs of flat samples, with a wide range of color differences covering from small to large magnitude, were printed by an Mcor Iris paper-based 3D color printer. Each pair was assessed twice by a panel of 10 observers using a gray-scale psychophysical method in a spectral tunable LED viewing cabinet with two types of light sources: diffuse lighting with and without an additional overhead spotlight. The experimental results confirmed that the lighting conditions had more effect on the perceived color difference between complex 3D shapes than between 2D objects. The results for 3D and 2D objects were more similar under only diffuse lighting. Current 3D results had good correlations with previous ones [Color Res. Appl. 24, 356-368, 1999; J. Opt. Soc. Am. A 36, 789-799, 2019] using 2D samples with large color differences, meaning that color-difference magnitude had more effect on perceived color differences than sample shape and lighting. Considering ten modern color-difference formulas, the best predictions of the current experimental data were found for CAM02-LCD formula [Color Res. Appl. 31, 320-330, 2006]. For current results, it was also found that predictions of current color-difference formulas were below average inter-observer variability, and remarkable improvements were found by adding power corrections [Opt. Express 23, 597-610, 2015].

Field-Induced Transversely Isotropic Shear Response of Ellipsoidal Magnetoactive Elastomers.

Magnetoactive elastomers (MAEs) claim a vital place in the class of field-controllable materials due to their tunable stiffness and the ability to change their macroscopic shape in the presence of an external magnetic field. In the present work, three principal geometries of shear deformation were investigated with respect to the applied magnetic field. The physical model that considers dipole-dipole interactions between magnetized particles was used to study the stress-strain behavior of ellipsoidal MAEs. The magneto-rheological effect for different shapes of the MAE sample ranging from disc-like (highly oblate) to rod-like (highly prolate) samples was investigated along and transverse to the field direction. The rotation of the MAE during the shear deformation leads to a non-symmetric Cauchy stress tensor due to a field-induced magnetic torque. We show that the external magnetic field induces a mechanical anisotropy along the field direction by determining the distinct magneto-mechanical behavior of MAEs with respect to the orientation of the magnetic field to shear deformation.

A geometry-independent moment correction method for the MPMS3 SQUID-based magnetometer

Modern superconducting quantum interference device (SQUID) magnetometers enable fully automated measurements with currently unmatched sensitivity. The measured moment values are, however, prone to deviations from their actual value due to geometric effects, namely sample size, shape, and radial offset. The current procedure to correct these geometric effects, for the magnetic property measurement 3 (MPMS3) magnetometer, is based on an available simulation tool, valid for both SQUID-VSM and DC-scan methods. Still, determining the correction factor requires samples with well-defined geometric shapes together with accurate sample dimensions and the usually difficult to determine radial offset. There is no established solution to correct geometry effects of irregularly shaped samples or unknown radial offsets. In this work, we find a systematic relation between the difference of SQUID-VSM and DC-scan measurements and their corresponding correction factors for the MPMS3. This relation follows a clear trend, independent of sample geometry and radial offset, for a given pair of DC-scan length and SQUID-VSM amplitude values. Exploiting this trend, a geometry-independent correction method is presented and validated by measurements of two different geometries of the same Al piece, two different radial offsets of a Ni square, and metallic Fe powder using a far from optimal sample mounting.