Twin-like Structure Research Articles

EFFICIENCY OF SUPPLEMENTARY OUTPUTS IN SIAMESE NEURAL NETWORKS

In the world of image analysis, effectively handling large image datasets is a complex challenge that requires using deep neural networks. Siamese neural networks, known for their twin-like structure, offer an effective solution to image comparison tasks, especially when data volume is limited. This research explores the possibility of enhancing these models by adding supplementary outputs that improve classification and help find specific data features. The article shows the results of two experiments using the Fashion MNIST and PlantVillage datasets, incorporating additional classification, regression, and combined output strategies with various weight loss configurations. The results from the experiments show that for simpler datasets, the introduction of supplementary outputs leads to a decrease in model accuracy. Conversely, for more complex datasets, optimal accuracy was achieved through the simultaneous integration of regression and classification supplementary outputs. It should be noted that the observed increase in accuracy is relatively marginal and does not guarantee a substantial impact on the overall accuracy of the model.

Siamese Convolutional Neural Network-Based Twin Structure Model for Independent Offline Signature Verification

One of the toughest biometrics and document forensics problems is confirming a signature’s authenticity and legal identity. A forgery may vary from a genuine signature by specific distortions. Therefore, it is necessary to continuously monitor crucial distinctions between real and forged signatures for secure work and economic growth, but this is particularly difficult in writer-independent tasks. We thus propose an innovative and sustainable writer-independent approach based on a Siamese neural network for offline signature verification. The Siamese network is a twin-like structure with shared weights and parameters. Similar and dissimilar images are exposed to this network, and the Euclidean distances between them are calculated. The distance is reduced for identical signatures, and the distance is increased for different signatures. Three datasets, namely GPDS, BHsig260 Hindi, and BHsig260 Bengali datasets, were tested in this work. The proposed model was analyzed by comparing the results of different parameters such as optimizers, batch size, and the number of epochs on all three datasets. The proposed Siamese neural network outperforms the GPDS synthetic dataset in the English language, with an accuracy of 92%. It also performs well for the Hindi and Bengali datasets while considering skilled forgeries.

Phase transition induced by synchroshear in Al-Zn-Mg-Cu alloy

Phase transition of the η-MgZn2 Laves phase from C14 to C15 structure in peak aged Al-Zn-Mg-Cu alloy were studied by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and density functional theory (DFT) calculations. The formation of a well ordered C15 structural MgZn2 as independent precipitate is for the first time observed in Al-Zn-Mg-Cu alloy. The C15 structure is confirmed to be transformed from the C14 by the activation of synchroshear in every other glide plane, which involves the shear induced by two Schockley partial dislocations in the triple-layer of the Laves phase. Besides, the twin-like structure and five-fold symmetry twin are formed for composing C15 structure due to multiple synchroshear. These results expand the structural understanding of the η-MgZn2 precipitates in Al-Zn-Mg-Cu alloy.

Structural, Optical and Photocatalytic Characterization of ZnxCd1−xS Solid Solutions Synthetized Using a Simple Ultrasonic Radiation Method

A simple ultrasonic radiation method was employed for the preparation of zinc and cadmium sulfide solid solution (ZnxCd1−xS; x = 0–0.25 wt.%) with the aim to investigate its efficiency for H2 production via a visible light-driven water-splitting reaction. The catalyst characterization by X-ray diffraction confirmed the formation of solid solution (ZnxCd1−xS) between CdS and ZnS phases. All catalysts exhibited hierarchical morphology (from SEM and TEM) formed by aggregated nanoparticles of ZnxCd1−xS solid solution with crystals showing mainly (111) planes of cubic CdS phase. The crystal size linearly decreased with an increase in Zn incorporation in the crystal lattice (from 4.37 nm to 3.72 nm). The ZnxCd1−xS photocatalysts showed a gradual increase in the H2 evolution, with an increase in the Zn concentration up to 0.2 wt.% making the most effective Zn0.2Cd0.8S catalyst toward H2 production. From the catalyst activity–structure correlation, it has been concluded that the twin-like CdS structure, the (111) plane and specific morphology are the main factors influencing the catalyst effectivity toward H2 production. All those factors compensated for the negative effect of an increase in band gap energy (Ebg) after ZnS incorporation into solid solution (from 2.21 eV to 2.34 eV). The effect of the catalyst morphology is discussed by comparing H2 evolution over unsupported and supported Zn0.2Cd0.8S solid solutions.

Plasticity in cryogenic brittle fracture of ferritic steels: Dislocation versus twinning

The sub-surface deformation structure after cryogenic (77 K) brittle fracture in a ferritic steel was characterized by scanning electron microscopy (SEM). Twin-like structures were found in many grains below the fracture surface. Electron backscatter diffraction (EBSD) was used to identify the crystallography of the structures, and the twin relation in body-centered cubic (BCC) systems was indexed. The twins in the sub-surface area were characterized further by electron channeling contrast imaging (ECCI). This study clarifies the low temperature brittle fracture behavior in the ferritic Fe-3 wt%Si steel consists of both cleavage and plastic deformation in the form of dislocation activities and twinning.

Austenite and precipitation in secondary-hardening ultra-high-strength stainless steel

Ferrium S53 is a new secondary-hardening ultra-high-strength stainless steel, with more Cr than other Co-Ni ultra-high-strength steels. Austenite has a great effect on the fracture toughness of this metal, and the carbides that are precipitated are the main strengthening phase of Ferrium S53 steel; in this study, its microstructural changes during heat treatment were observed and analyzed by X-ray diffraction (XRD), Optical microscope (OM), SEM, and transmission electron microscopy (TEM). About 40.85% retained austenite in the quenched sample is decreased to less than 5% after cryogenic treatment and tempering. In the final sample, block austenite is retained austenite, and film austenite around 5 nm in width is reverted austenite. Inside the martensite lath, parallel twin-like structures are actually segregated M2C precipitates, and most of them are smaller than 20 nm. These precipitates can be aggregated into a several-micron-long parallel zonal microstructure.

Molecular dynamics studies on the grain growth of nanocrystalline Ni and Ni3Al

With molecular dynamics simulations, the growth of face-centered-cubic nanocrystalline materials Ni and Ni3Al has been studied. It is found that grain-rotation induced grain coalescence and curvature-driven grain-boundary migration are dominant mechanisms in the nanograin growth. A detailed comparison of the nanograin growth between the two systems is discussed in terms of grain rotation and grain sliding. We also study the temperature effect and the size effect in the nanograin growth. The tendency of twinning in the nanograin growth is discussed. It is found that in Ni3Al, it seems more possible for nanograins to grow into twin-like structures than single crystal unless at very high temperatures.

Characterization of twin-like structure in a ferrite-based lightweight steel

The present study examined cold to warm compressive deformation behavior of a ferrite- based lightweight steel through characterization of the banded structures. Compression tests were carried out at 25 to 500 °C at a strain rate of 0.01 s-1 up to true strain of 0.6. Analysis of the microstructural evolution using electron back scatter diffraction indicated that the twin-like bands in the large ferrite grains occurred with the {112}[111] system at a 60° misorientation. Density of the twin-like bands is increased by raising the deformation temperature. EBSD results showed that the primary and secondary twins occurred in the [-11-1] and [1-1-1] directions. In addition, the strain at 500 °C distorted the twin-like bands and resulted in wavy boundaries. The strain hardening behavior was also examined using the Crussard-Jaoul (C-J) model and the n-values were calculated for each stage of imposing strain. The results showed high dislocation density in the adjacent of twin-like boundaries intersections which resulted in the n-value increment.

New Ground-State Crystal Structure of Elemental Boron.

Elemental boron exhibits many polymorphs in nature based mostly on an icosahedral shell motif, involving stabilization of 13 strong multicenter intraicosahedral bonds. It is commonly accepted that the most thermodynamic stable structure of elemental boron at atmospheric pressure is the β rhombohedral boron (β-B). Surprisingly, using high-resolution transmission electron microscopy, we found that pure boron powder contains grains of two different types, the previously identified β-B containing a number of randomly spaced twins and what appears to be a fully transformed twinlike structure. This fully transformed structure, denoted here as τ-B, is based on the Cmcm orthorhombic space group. Quantum mechanics predicts that the newly identified τ-B structure is 13.8 meV/B more stable than β-B. The τ-B structure allows 6% more charge transfer from B_{57} units to nearby B_{12} units, making the net charge 6% closer to the ideal expected from Wade's rules. Thus, we predict the τ-B structure to be the ground state structure for elemental boron at atmospheric pressure.

Precipitation Behavior and Magnetic Properties of Cu-Fe-Co Alloys Containing Nanogranular Ferromagnetic-Element Particles

This work investigates the evolution of microstructures and magnetic properties during isothermal annealing of Cu-Fe-Co alloys, using electron microscopy and superconducting quantum interference device (SQUID) magnetometry. Small coherent granular precipitates composed of iron and cobalt formed in the copper matrix in the early stage of precipitation. As annealing proceeded, the precipitates lost coherency to the matrix after reaching a size of 15–20 nm and twin-like structures were consecutively introduced in the particles. The SQUID measurements revealed that the magnetic properties of the specimens correlated with the microstructural evolution. The coercive force initially increased with annealing time but decreased after reaching a peak. Lorentz Microscopy suggested that the initial large increase of magnetization was invoked by a structural transition from fcc to B2 in the precipitates.

Strain Hardening During Hot Compression Through Planar Dislocation and Twin-Like Structure in a Low-Density High-Mn Steel

In this work, we study the flow hardening behavior and microstructural evolution in a low-density Fe-21Mn-0.1C-2.0Al-2.5Si (wt.%) transformation-twinning-induced plasticity steel during hot compression. The substructures were examined by transmission electron microscopy and electron backscatter diffraction methods. The alloy exhibits a combination of strain hardening (at low and medium true compression strains, <0.2) followed by a strain softening at 800 °C. We explain the flow hardening behavior in terms of substructure refinement due to planar dislocation, as well as twin-like structure. The transmission electron microscopy results suggest that short-range ordering triggers slip planarity after straining to 0.05 at 800 °C. Twin-like structure with misorientation angle higher than 20° is formed during further plastic deformation.

Observation of twin-like composition modulation and phase separation with long-range order induced by oxygen deficiency in single crystal manganites

Abstract Single crystal La 2/3 Sr 1/3 MnO 3− δ manganite with an unusual structure was obtained by the optical-floating method with controlled growth in a flowing argon atmosphere. A modulated twin-like structure with phase separation characteristics in the long-range order is found. The energy-dispersive X-ray spectroscopy measurement reveals that there is a strong chemical fluctuation for different stripes, i.e. resulting from the nonstoichiometry due to oxygen deficiency. After annealing, the twin-like stripe phase disappears and the single crystal shows excellent properties. These results may be of great significance for controlled growth of oxide electronics materials with artificial superstructure-like technique.

The microstructure and magnetic properties of nano-scale Fe magnetic particles precipitated in a Cu–Fe alloy

Abstract The evolution of nano-scale Fe particles precipitated in a Cu – Fe alloy has been examined from the viewpoint of the relationship between the microstructure and magnetic properties, using conventional, high-resolution and Lorentz electron microscopy, and magnetic measurements. It has been revealed that spherical Fe particles have a tendency to align along the &lt;001&gt; direction in a Cu matrix at the early stage of precipitation. A twin-like structure developed when spherical Fe particles grew to approximately 40 to 60 nm in size. Lorentz microscopy was successfully applied to determine the direction and magnitude of the magnetic momentum of Fe particles.

Surface, interface and stacking fault energies of magnesium from first principles calculations

Properties of magnesium have been calculated for bulk, surface and stacking faults, regarded as homogeneous interfaces, using density functional theory within a plane wave pseudopotential technique. Using a supercell approach, stacking fault energies have been determined for intrinsic, extrinsic and twin-like structures for the basal plane together with generalised stacking fault energies on basal, pyramidal and prismatic planes.

Fabrication of ZnO Nanoplate–Nanorod Junctions

The ZnO nanorod-nanoplate junctions were synthesized through a vapor-transport and condensation process. 0.83g ZnO and 0.6g graphite powder were mixed and then placed at the sealed end of an alumina tube mounted in the center of a quartz tube within a tube furnace. In a nanoplate-nanorod junction, the boundary energy of a twinlike structure is generally higher than that of an epitaxial junction. When charge carriers migrate through single nanoscale branch points of nanoplate-nanorod junctions, carriers may localize and hop around the junction. A bulk white product was collected at the open end of the quartz tube. The product was characterized using XRD with Cu Ka radiation, SEM, and by means of HRTEM.

Structural symmetry ofYD3epitaxial thin films

A thin-film laminated structure comprised of Pd(5 nm)/Nb(5 nm)/Y(500 nm)/Nb(5 nm) on $\ensuremath{\alpha}{\ensuremath{-}\mathrm{A}\mathrm{l}}_{2}{\mathrm{O}}_{3}(110)$ was synthesized by molecular beam epitaxy to yield a crystalline Y layer with the c axis oriented perpendicular to the growth plane. Neutron diffraction and topographical measurements of the epitaxial ${\mathrm{YD}}_{3}$ layer formed after deuteriding the Y metal layer were consistent with a twinlike structure possessing ${P6}_{3}\mathrm{cm}$ and/or $P3\ifmmode\bar\else\textasciimacron\fi{}c1$ symmetry.

Crystal growth of the neodymium-rich Nd 1+ xBa 2- xCu 3O z solid solution

In the present work on the basis of experimental phase relations in the copper-rich corner of the Nd-Ba-Cu-O system, the insulating Nd 1+ x Ba 2- x Cu 3O z solid solution single crystals, with x = 0.43–0.85, were grown by the top-seeded-solution-growth method. The as-grown Nd 1.85Ba 1.115Cu 3O z crystals were found to be orthorhombic. As a result, the twin-like structure was observed and the twin-plane re-entrant-edge (TPRE) crystal growth mechanism was proposed.

Twins and related morphology of as-grown neodymium-rich Nd 1+ xBa 2− xCu 3O z crystals

In the present work on the basis of experimental phase relations in the copper-rich corner of the Nd–Ba–Cu–O system, insulating crystals of the Nd 1+ x Ba 2− x Cu 3O z solid solution (Nd123ss) with x=0.43, 0.8, 0.85 were grown by the top-seeded solution growth method. The as-grown crystals with x=0.8–0.85 were found to be orthorhombic at room and elevated temperatures. It was confirmed that the orthorhombicity is not related to the tetragonal-to-orthorhombic phase transition but is caused by the heterovalent substitution of barium with neodymium. As a result, a twin-like structure was observed and the twin-plane re-entrant edge growth mechanism was proposed for the first time in this system.

Critical currents and flux creep in orientated BiPbSrCaCuO 110 K phase made by the powder in tube method

Critical currents, magnetic relaxation, magnetic irreversibility and microstructure have been studied for a (Bi,Pb) 2Sr 2Ca 2Cu 3O x phase tape conductor fabricated by the powder in tube method. This conductor, with transport critical current density, J ct (at 77 K and O T), of a few thousand amperes per square centimetre and ab plane orientation to the rolling flat surface, showed pinning potential energies, U o, of 66 meV for the field perpendicular to the ab plane and 181 meV for the field parallel to the ab plane; these values were much larger than those reported for the Bi 2Sr 2CaCu 2O x phase single crystal. Moreover, the field dependence of the magnetic irreversibility temperature was smaller for this tape conductor than that for Bi based crystals. These results imply an improvement in the pinning ability, due to the severe cold working peculiar to this process. Transmission electron microscopy (TEM) showed some defects, such as dislocations and twin-like structures, which may act as pinning centres.

Sulfidation properties of Cr23C6 at 1073 K in H2S-H2 atmospheres of 103.5?10?6 Pa sulfur pressure

The sulfidation behavior of chromium carbide, Cr23C6, was investigated in H2S-H2 gas mixtures over a sulfur partial pressure range of 103.5−10−6 Pa at 1073 K using thermogravimetry, optical and scanning electron microscopy, X-ray diffraction analysis, and electron-probe microanalysis. The kinetics were rapid for short time periods and followed a linear rate law at low sulfur pressures, whereas sulfidation tends to obey a parabolic rate law at high pressures. Sulfidation rates decreased with increasing carbon content in the carbide. Surface morphologies could be divided into three groups: (I) at high sulfur pressures, petal-like. crystals (Cr2S3); (II) at intermediate pressures, a twinlike structure (Cr3S4); (III) and at low pressures, a flat surface with numerous hexagonal pits (Cr1−xS). The scale consisted of two distinct layers: an external scale with a single or multilayer structure and an inner scale with a mixture of Cr1−xS, Cr3C2, and Cr7C3. These higher carbides, Cr3C2 and Cr7C3, may be formed by the sulfidation-carburization of Cr23C6. Pt-marker experiments indicated that the external scale grew by chromium diffusion and that sulfur migration played an important role in the growth of the inner scale.