Large Rotation Angle Research Articles

End-to-end affine registration framework for histopathological images with weak annotations

Background and ObjectiveHistopathological image registration is an essential component in digital pathology and biomedical image analysis. Deep-learning-based algorithms have been proposed to achieve fast and accurate affine registration. Some previous studies assume that the pairs are free from sizeable initial position misalignment and large rotation angles before performing the affine transformation. However, large-rotation angles are often introduced into image pairs during the production process in real-world pathology images. Reliable initial alignment is important for registration performance. The existing deep-learning-based approaches often use a two-step affine registration pipeline because convolutional neural networks (CNNs) cannot correct large-angle rotations. MethodsIn this manuscript, a general framework ARoNet is developed to achieve end-to-end affine registration for histopathological images. We use CNNs to extract global features of images and fuse them to construct correspondent information for affine transformation. In ARoNet, a rotation recognition network is implemented to eliminate great rotation misalignment. In addition, a self-supervised learning task is proposed to assist the learning of image representations in an unsupervised manner. ResultsWe applied our model to four datasets, and the results indicate that ARoNet surpasses existing affine registration algorithms in alignment accuracy when large angular misalignments (e.g., 180 rotation) are present, providing accurate affine initialization for subsequent non-rigid alignments. Besides, ARoNet shows advantages in execution time (0.05 per pair), registration accuracy, and robustness. ConclusionWe believe that the proposed general framework promises to simplify and speed up the registration process and has the potential for clinical applications.

Growth and characterization of holmium-doped yttrium iron garnet single crystal

Yttrium iron garnet (YIG) crystals are the primary candidate for non-reciprocal device. With the miniaturization and integration of optical communication devices, the modified YIG crystals with excellent comprehensive performances are highly desired. To explore the possible mechanism of rare earth ions doping on Faraday effect, holmium oxide-doped YIG (Ho0.6Y2.4Fe5O12, abbreviated as HYIG) crystal was grown by molten salt method. Its structure, optical transparency, magnetic, magneto-optical properties and oxygen atmosphere annealing processes were first investigated systematically. The HYIG crystal wafers annealed at 800 °C for 2 h can achieve the large Faraday rotation angle (186 deg/cm at 1310 nm; 148 deg/cm at 1550 nm) and good optical transparency (73.64 % at 1310 nm; 74.83 % at 1550 nm), which is increased by approximately 10 % compared to the unannealed sample. This result may provide a new insight into the investigation of rare earth doped YIG crystals and their atmosphere annealing processes.

Theoretical Stiffness Modeling and Application Research of a Novel Stacked Flexure Hinge

This study investigates and designs a novel stacked hinge with low stiffness, large rotation angle, high strength, and length-adaptive functionality. Firstly, based on the large deformation theory of cantilever beams and relevant theories of leaf springs, a stiffness theoretical model for stacked flexure hinges is established. Subsequently, the stiffness theoretical model is further modified by considering the frictional force, aiming to reduce errors. Secondly, a stiffness-testing experimental platform for this flexure hinge is designed to verify the correctness of the theoretical model. Finally, the stacked flexure hinge is applied to the trailing-edge mechanism of a variable camber wing, achieving a deformation target of 15° downward bending of the wing and demonstrating good shape retention, thereby proving the feasibility of the application.

Hydrodynamics Analysis of an Underwater Foldable Arm

Improved designs for underwater manipulators are becoming increasingly important due to their utility in academic and industrial applications. In this work, an experiment was conducted in conjunction with a numerical simulation to investigate the hydrodynamic performance and structural reliability of the proposed foldable arm during the unfolding process at various movement velocities. A large-scale geometric model of the foldable arm with a single degree of freedom (DOF) was constructed. The distribution of the flow field, the movement stability and the equivalent stress of the foldable arm were quantitatively analyzed with a designed tank experiment and the Computational Fluid Dynamics (CFD) simulation. Simulation results show that the maximum deviation of the resistance and torque is 8.04% and 5.73%, respectively, compared with the experimental results of static postures. Comparison results prove the reliability of the numerical model. The results of transient simulation demonstrate that the optimal speed of the foldable arm is 3 Kn and the pressure distribution on the surface of foldable arm is relatively regular. Furthermore, a fluid–structure interaction (FSI) validation study of the foldable arm was presented. For the coupling between the fluid and structural mechanics domains, a nonmatching discretization approach was adopted. The results show that the directional deformation (Z axis) of the foldable arm is less than 0.50 mm. The proposed foldable arm has a large angle of rotation and high stability compared to the existing manipulators.

Experimental study and characteristic analysis of vacuum arc between cup-type axial magnetic contacts under different diameter-to-gap ratios

Since vacuum circuit breakers gradually advanced to higher voltage levels, axial magnetic field (AMF) contacts have drawn a great deal of attention due to their excellent breaking ability. The cup-type AMF contact is a common kind of AMF contact, which has much potential in contact design and application of high voltage grade systems due to the advantages of strong structural strength, uniform magnetic field distribution, lower resistance, etc. This study analyzes the arcing characteristics of a cup-type AMF contact with a large slotted rotation angle at various diameter-to-gap ratios (DGRs). The arcing process is divided into five stages as follows: initial diffusion, contracting, fully constricted, re-diffusion, and extinguished. Arc self-rotation and anode separation phenomena in the re-diffusion stage appear when the DGR is 58/24. The reasons for these occurrences were discussed and explained with regard to the magnetic field vector's spatial distribution. The duration of each stage and the current threshold of a fully constricted arc will both differ with the change of the DGR. The structural parameters of the fully constricted arc were computed through the method of imaging the luminous intensity distribution after the arc was fully constricted. The source of the change in the arc voltage can be seen in the variation of arc structural parameters, which also reflect anode activity intensity to a certain extent. The transient magnetic field simulation method was used to explain why the arc under the same instantaneous current shows variable morphology at the extinguished stage and contracting stage in one arcing process. The research results presented in the article can be used as a reference for developing high-voltage cup-type AMF contacts.

Experimental study on seismic performance and deformation damage of loose dovetail-tenon joints in ancient timber structures

A looseness is typical damage for mortise-tenon joints in ancient timber structures. The tenon of the loose dovetail-tenon joints is prone to be pulled out, leading to joint failure in the earthquake. Hence, it is necessary to investigate the seismic performance and deformation damage of loose dovetail-tenon joints. This study conducts pseudo-static and acoustic emission (AE) tests on three full-scaled dovetail-tenon joints to determine the four stress stages of each joint, including slight damage, medium damage, severe damage, and nearly failure. It examines the hysteretic and skeleton curve, stiffness and strength degradation, energy dissipation performance, and the variation raw of the amount of tenon pulled out at each stage. The deformation damage mode, damage degree, and damage evolution equation of the joint at each stage are obtained based on the AE characteristic parameters measured at each stage. The results indicate that as the rotation angle increases, each joint's stiffness and energy dissipation capacity decrease, while the joint bending moment rises and then reduces, and the amount of tenon pulled out increases. The greater the degree of looseness, the lower the bearing capacity of each joint, and the more pronounced the degradation of stiffness and strength. At each stage, the maximum decrease of initial stiffness is 85.75%, and the maximum amount of tenon pulled out is 93 mm. The failure modes of joints are mainly tenon pulled out failure, and extrusion deformation greatly influences the tenon pulled out failure. As the degree of looseness grows, joints are more prone to severe deformation damage under large rotation angles. At the slight and medium stages, the joints primarily suffer from tensile damage of material, but at the severe damage and nearly failure stage, they mainly suffer from shear damage of material. The damage value of each joint increases with the relative stress ratio, and looseness significantly impacts the damage degree of the joint.

Large Faraday rotation angle with high transmittance in Weyl semimetal assisted by resonant tunneling

Over the past decades, a series of nanostructures have been proposed to intensively enhance the Faraday rotation angle. However, the mutual inhibition between the Faraday rotation angle and the transmittance poses a challenge to achieve large Faraday rotation angle with high transmittance. In this paper, a sandwich structure consisting of two Weyl semimetal (WSM) layers of the same thickness and a dielectric layer is designed. Empowered by the resonant tunneling, the enhanced Faraday rotation effect is accompanied by an increase in transmittance. In the presence of realistic level of optical loss, the transmittance can be up to reach 97.4% when the resonant tunneling conditions of left-handed and right-handed polarized light are satisfied simultaneously, and its corresponding Faraday rotation angle can also be as high as −51.1 degrees. By adjusting the axial vector of the WSM layer, we design an optical isolator with a transmittance of up to 97% and a Faraday rotation angle of 45 degrees. This simple triple-layer structure provides some theoretical basis and reference value for future research into non-reciprocal devices.

Динамика плоского движения космического крана-манипулятора типа руки с учетом изгиба звеньев

The paper considers the plane motion dynamics of a three-link crane-manipulator consisting of two rods elastic in bending and a massive solid body attached to them at their end (load capture). All links are interconnected by hinge joints with the given (controlled) relative rotation angles. The first link is also connected to the mobile base. The system mathematical model was developed to calculate its non-stationary oscillations and dynamic loading of links at arbitrary in time and large relative angles of the links rotation as the solid bodies. The rods bending deformations (elastic transverse displacements and rotation angles of the axes) were considered to be insignificant (linear). Each rod ending was represented by the Ritz method using two given shape functions with the unknown coefficients, which were taken as the generalized coordinates. In this case, the “cantilever” bending forms of each rod with the given transverse displacement and angle of rotation at their ends were used. A simplified version was considered: each rod bending was represented by only one given form of its bending by a single moment applied at the end. System oscillation equations were obtained based on the principle of probable displacements in the generalized coordinates (four equations or two in a simplified form). Since rotation angles at the ends of the elastic rods were added to the given rotation angles of the non-deformable rods, total angles were left under the signs of sines and cosines without linearization for convenience of calculations and increasing accuracy. As a result, such equations of non-stationary oscillations remained non-linear. They were integrated by numerical methods using standard programs in one of the computer algebra systems. Examples are provided with the comparative results estimates obtained in the two-term and one-term approximations of the function in regard to the bending form of the system bending rod joints.

A general formulation for simulating the dynamic deployment of thick origami

The deployment of origami is usually a rapid and complicated dynamic process. However, little has been done to simulate the entire deployment process of thick origami which is a typical over-constrained mechanical system. Based on the constrained Hamilton’s equations in conjunction with the natural coordinate formulation, a general formulation capable of tracing the dynamic deployment of thick origami is established. Particular efforts are paid to dealing with the problems including geometric description, redundant constraint, large rotational angle, and possible bifurcation paths. The proposed formulation is applied to three thick origami structures: thick Miura-ori, thick diamond origami, and thick waterbomb origami. The results show that the dynamic characteristics during the deployment can be successfully obtained, and the numerical accuracy is also validated by the ADAMS simulation and prototype experiments. Furthermore, parametric analyses are performed to investigate the effects of actuating positions and geometric parameters on deployment behaviors. The proposed formulation provides a clear view of the deployment process for thick origami structures, which will benefit the optimal design in practical applications.

The seismic performance evaluation of unbonded laminated rubber bearings with end rotation

Laminated rubber bearing is a common quasi-isolation system in the small and medium span highway bridges in China, whose mechanical properties may change when the service disease occurs. Under such special supporting condition, the seismic performance evaluation of laminated rubber bearings becomes necessary. Therefore, compression shear tests and numerical simulation are conducted to investigate the effect of end rotation on the mechanical properties of unbonded laminated rubber bearings, in which eleven bearings are divided into B0, B1 and B2 groups. Experiment results show that the equivalent stiffness of bearings decreases with increasing end rotation angle, the maximum reduction ratio of B1s and B2s reaches 15.5% and 12.3% respectively; whereas the equivalent damping ratio exceeds 0.10 and varies slightly. Moreover, numerical results are in good agreement with testing ones, and the large end rotation angle will cause the yielding of steel shims according to the numerical results.

Sediment supply mechanism and its influence on hydrocarbon accumulation in the Paleogene of the northern Huanghekou Sag, Bohai Bay Basin, China

Tectonic activity and sediment supply have significantly affected the rifted basin fillings and hydrocarbon accumulations. The Huanghekou Sag in the southeastern Bohai Bay Basin is a hydrocarbon rich sag and was bounded by the Bonan Uplift to the north in the Paleogene, which strongly affected sediment disribution and hydrocarbon accumulation in this region. The sediment supply mechanism of the Paleogene parent rocks in this area has not been revealed yet. Therefore, the Huanghekou Sag is a natural laboratory to reveal the relationship between the tectonic activties and hydrcoarbon accumulations in a rifted basin. In this study, the tectonic evolution characteristics of the Bonan Uplift in different geological periods are revealed during the main fault depression periods. Then, the direction of the provenance and distribution of the depositional system of the Bonan Uplift are analyzed based on the sedimentary system and mineralogy analysis. Finally, the sediment supply in the Bonan Uplift in different geological periods has been systematically studied. The results indicated that sediment supply is the dominant factor of hydrocarbon accumulation in the Paleogene in the Huanghekou Sag. During the Paleocene-Middle Eocene, extensive denudation occurred in the Bonan Uplift, sediments were mainly sourced from the Bonan Uplift in the northern margin of the Huanghekou Sag. During the Late Eocene to Early Oligocene, the Bonan Uplift had a large angle rotation and subsidence due to the strong rifting of the Bozhong Sag in the north, and the sand supply capacity was seriously reduced. Due to the different sediment supply in different geological periods, high quality reservoir and cap conditions were formed in the Paleogene in the central and northern parts of the Huanghekou Sag, which is conducive to the accumulation and preservation of oil and gas.

DIC measurement method for large rotation based on improved grid-based motion statistics.

As a noncontact optical measurement method, the digital image correlation (DIC) method can provide full-field displacement and strain measurement during object deformation. In the case of small rotation deformation, the traditional DIC method can obtain accurate deformation measurement results. However, when the object rotates at a large angle, the traditional DIC method cannot obtain the extreme value of the correlation function, resulting in the occurrence of decorrelation. In order to address the issue, a full-field deformation measurement DIC method based on improved grid-based motion statistics is proposed for large rotation angles. First, the speeded up robust features algorithm is applied to extract and match the feature point pairs between the reference image and the deformed image. Furthermore, an improved grid-based motion statistics algorithm is proposed to eliminate the wrong matching point pairs. Then, the deformation parameters of the feature point pairs obtained by the affine transformation are taken as the initial deformation value for DIC calculation. Finally, the intelligent gray-wolf optimization algorithm is used to obtain the accurate displacement field. The effectiveness of the proposed method is proved by simulation and practical experiments, and the comparative experiments show that the proposed method is faster and more robust.

Modulation of light by coherent perfect polarization rotation in Ce:YIG

We present a scheme in which light is modulated through coherent perfect activity. By irradiating two coherent beams from both sides to a magnetic material and controlling their relative phases, we can manipulate the output light. Through coherent perfect polarization rotation process, large polarization rotation angles can be observed, which makes possible the light modulation. It is realized that this coherent process provides the light modulation by using a very low intensity coherent light.

What Determines the Critical Electric Field of AFE-to-FE in Pb(Zr,Sn,Ti)O3-Based Perovskites?

Electric-field-induced antiferroelectric-ferroelectric (AFE-FE) phase transition is a prominent feature of antiferroelectric (AFE) materials. The critical electric field of this phase transition is crucial for the device performance of AEFs in many applications, but the determining factor of the critical electric field is still unclear. Here, we have established the correlation between the underlying structure and the critical electric field by using in situ synchrotron X-ray diffraction and high-resolution neutron diffraction in Pb(Zr,Sn,Ti)O3-based antiferroelectrics. It is found that the critical electric field is determined by the angle between the average polarization vector in the incommensurate AFE state and the [111]P polarization direction in the rhombohedral FE state. A large polarization rotation angle gives rise to a large critical electric field. Further, density functional theory (DFT) calculations corroborate that the lower energy is required for driving a smaller angle polarization rotation. Our discovery will offer guidance to optimize the performance of AFE materials.

Cross-dipole π-π stacking of crossed perylene diimides with D-A-D structures by crystal engineering towards ambipolar charge transport performance and aggregation-induced emission

A cross-dipole π-π close-stacking of 1,7-diphenylazophenol (AZO) perylene diimides (PDI, AZO-PDIs) formed in a single-crystal integrating good ambipolar charge transport and aggregation-induced emission (AIE) behaviors has been unveiled. The weak electron donating and moderate steric hindrance of AZOs endows AZO-PDIs with crossed Donor-Acceptor-Donor (D-A-D) structures, which facilitates the charge injection of both electrons and holes and a distinct cross-dipole π-π close-packing with the distance of only 3.29 Å. Accordingly, the wave function overlaps and electronic coupling of PDI cores are significantly enhanced to provide a quasi-1D charge transport channel, resulting in ambipolar performance with the hole and electron mobility of 6.74 cm2 V−1 s−1 and 5.96 cm2 V−1 s−1 respectively. The average conductivity of 0.5 S m−1 has further confirmed the good charge transport properties of the single crystals. Moreover, it also exhibits AIE behaviors due to the weak transition dipole resonance induced by the cross-dipole stacking of a large rotation angle (79.8°) and restriction of intramolecular rotation of the bulk AZOs. This work initially provides a promising strategy for achieving both charge transport and AIE performance on account of D-A-D molecules with crossed conformations at the molecular level and efficient π-overlaps induced by cross-dipole stacking at the supramolecular level.

Precipitate sheared by low-angle grain boundary in Mg-Al alloys

The interaction between Mg17Al12 precipitate and low-angle grain boundaries (LAGBs) in Mg-Al alloys was studied using molecular dynamics (MD) simulations. The precipitate was observed to be not sheared by the LAGBs with a small rotation angle < 8°, but sheared by the LAGBs with a large rotation angle ≥ 9° To explain these two different interaction styles, a critical GB shear was proposed analytically using the Eshelby theory, which indicates that the critical GB rotation angle is 8.4° and agrees well with the current MD simulations. The critical GB shear was found to be related to the aspect ratio of precipitate.

Restoring force characteristic model for bending moment–rotation angle relationship of concrete‐filled square steel tube beam‐columns

AbstractThis paper proposes a new simplified restoring force characteristic model of the bending moment–rotation angle relationship for square concrete‐filled steel tube (CFT) beam‐columns to estimate the elastoplastic flexural‐shear behavior from short to slender beam‐columns. The square CFT beam‐column model incorporates a reduction in strength after the ultimate strength. The proposed simplified model is multilinear and involves a cracking strength point, a yield strength point, an ultimate strength point, and strength reduction points. In the proposed model, each flexural strength is calculated by a general superposed strength method, and new empirical expressions for each rotation angle are proposed from the results of previous experimental cyclic and monotonic loading tests. The proposed model for the bending moment–rotation angle relation is found to agree approximately with experimental results up to large rotation angles.

Improved SURF method in digital image correlation for estimation of large rotation angle

Digital image correlation (DIC) is widely used in optical measurement techniques with the advantages of high precision, robustness and expansibility. The conventional DIC, however, is highly dependent on the accuracy of initial parameters, and there are reports [1,2] that it may fail when the rotation angle of the target specimen exceeds 7°. The combination of Speeded-Up Robust Features (SURF) with Random Sample Consensus (RANSAC) algorithm has been applied to solve this problem with limited success due to the effects of residual mismatches. An enhanced algorithm based on SURF is proposed in this study to address this problem. The transformation model between two images is obtained by RANSAC similar to existing methods. Then an angle compensation strategy is proposed to estimate the rotation angle of the deformed image to form the compensated image. Finally, an iterative process is proposed to refine the initial parameters from the reference and deformed images with a new convergence threshold. In addition, an evaluation criterion developed from a multiple ring template is proposed to compute the similarity of feature point pairs to improve the speed of convergence and sampling accuracy. Results from numerical simulation and experimental analysis show that the accuracy and robustness of the proposed method are significantly improved. Further application of the proposed method to monitor the rotating blades of a scaled model wind turbine illustrates further the capability of the proposed method.

Element-selective magnetization states in a Gd23Fe67Co10 alloy, probed by soft X-ray resonant magneto-optical Kerr effect

The core-level resonant magneto-optical Kerr effect of a ferrimagnetic metal alloy, Gd23Fe67Co10, was measured at the Fe M-shell and Gd N-shell absorption edges using rotating analyzer ellipsometry. A large Kerr rotation angle of several degrees was detected at room temperature. The signal was found to be strong enough for element-selective magneto-optical experiments to trace various magnetic events, such as all-optical magnetization switching.

Scaling of the disorder operator at deconfined quantum criticality

We study scaling behavior of the disorder parameter, defined as the expectation value of a symmetry transformation applied to a finite region, at the deconfined quantum critical point in (2+1)d in the J-Q_3J−Q3 model via large-scale quantum Monte Carlo simulations. We show that the disorder parameter for U(1) spin rotation symmetry exhibits perimeter scaling with a logarithmic correction associated with sharp corners of the region, as generally expected for a conformally-invariant critical point. However, for large rotation angle the universal coefficient of the logarithmic corner correction becomes negative, which is not allowed in any unitary conformal field theory. We also extract the current central charge from the small rotation angle scaling, whose value is much smaller than that of the free theory.