Symmetric Cross Research Articles

RSF model with SCE‐based global constraint for image segmentation

A novel region-scalable fitting (RSF) active contour model with symmetric cross entropy (SCE)-based global constraint is proposed to segment various kinds of images. The energy functional is mainly composed of two parts, namely the local and global constraints. The local constraint is the weighted region-scalable fitting term, which computes the local intensity information. The global constraint is constructed by measuring the difference between the intensity distribution of the object image and the intensity distribution of the original image using SCE. Moreover, some regularised terms are incorporated into the energy functional. Experimental results for synthetic and real images show that the proposed model achieves better segmentation performance and is insensitive to initial contour and noise.

Biomorphodynamics of river banks in vegetated channels with self-formed width

Laboratory and field studies investigating the mutual interaction between riparian vegetation dynamics and river morphodynamics have revealed that riparian vegetation may play an important role in the evolution of channel beds and river banks. In order to disentangle this still debated question, field and modeling techniques have helped to explore and better understand the time and spatial scales of such processes. Simple morphodynamic models for river evolution have typically used a constant discharge to describe in-channel processes and basic relationships for river bank dynamics. In order to overcome these limits we propose a longitudinally integrated dynamical model that describes the bank pull - bar push mechanisms in channels with symmetric cross section. Different hydrographs (constant, periodic and stochastic discharge) are applied to investigate channel width and vegetation biomass evolution trajectories and equilibrium values. Results show the interplay of riparian vegetation and water flow in controlling channel width evolution and the trajectories of channel adjustment to flow perturbations. These results also highlight the limit of adopting a constant discharge when describing mutual flow and vegetation processes affecting channel evolution. In addition, under stochastic forcing, the model shows the existence of a range of flood frequencies for which the cooperation between the hydrologic time scales and that characterizing vegetation colonization induces a regular pattern in channel width time variations (coherence resonance). Finally, model application to real case studies confirm the possibility to use the model to interpret long-term river evolutionary trajectories in realistic applications.

Fault diagnosis of rolling element bearing based on symmetric cross entropy of neutrosophic sets

A novel symmetric single-valued neutrosophic cross entropy (SVNCE) measure based upon a newly developed symmetric measure of fuzzy cross entropy is established and then applied it for identifying defects of bearings installed in a test rig and axial piston pump. A 3-level wavelet packet transformation (WPT) is used for extracting and decomposing the fault features associated with the vibrational signals. The new evaluated SVNCE values between knowledge of various faults types and real testing samples provide useful evaluation information of fault types. The concluded results reveal that the proposed SVNCE measure furnishes better fault identification accuracy when compared with the existing model based upon correlation coefficient of simplified neutrosophic sets (SNSs). Furthermore, the proposed SVNCE measure offers consistent and feasible results and is capable for holding the optimal fault type selection under sensitive analysis.

Modelling of laminated composite plates with weakly bonded interfaces using scaled boundary finite element method

Scaled Boundary Finite Element Method (SBFEM), a relatively new approach, is investigated for the analysis of the weakly bonded laminated composite plates, under cylindrical bending. A plane strain formulation, which does not require any assumptions on the displacement or stress field, is developed. The interface between two plies is simulated using a linear spring layer model and incorporated in the numerical modelling with the help of zero thickness interface elements. The model is coded and postprocessed in MATLAB to capture general delamination, i.e. separation of the plies at interfaces in both tangential and normal direction. Due to the semi-analytical solution procedure of SBFEM, the model provides highly accurate results. Use of SBFEM reduces the meshing burden and complexities in the discretisation. Moreover, the method can handle hanging nodes, so one can use small interface elements without decreasing the size of adjoining domains. These qualities make the proposed numerical model computationally cheaper as well as very accurate. The presented formulation is demonstrated for a variety of examples in laminated composites including unidirectional laminates, symmetric cross ply laminates and antisymmetric cross ply laminates. The proposed model's close agreement as well as its superiority over the other methods is established for future reference.

Comparative study on performance of controlling geometric nonlinearity of laminated smart composite plate using piezoelectric fiber reinforced composite & active fiber composite material

The present work highlights on comparative investigation for the performance of active constrained layer damping treatment using PFRC and AFC patch material for controlling the nonlinear transient vibrations of laminated composite plate. In this case for making the constraining layer of the ACLD treatment for PFRC and AFC patch material is used. For modelling of ACLD in the time domain Golla-Hughes-McTavish (GHM) method is used. The Von Karman type non-linear strain displacement relations along with a simple first-order shear deformation theory are used for deriving this electromechanical coupled problem. A finite model in 3-dimensions has been developed for smart composite plate integrated with the ACLD treated patches of PFRC and AFC. The results of both the cases have been compared and it has been found that the improved performance of AFC patch over the PFRC in subsiding the transient nonlinear vibrations of symmetric cross ply laminated composite plate.

Comparative investigation on nonlinear transient vibrations of laminated composite shallow shell with active constrained layer damping treatment using PFRC and AFC patch material

Here, the comparative investigation for the performance of active constrained layer damping treatment using PFRC and AFC patch material for controlling the nonlinear transient vibrations of laminated composite shallow shell is carried out. The patch material used in this case for making the constraining layer of the ACLD treatment is PFRC and AFC. For modelling of ACLD in the time domain Golla-Hughes-McTavish (GHM) method is used. The Von Kármán type non-linear strain displacement relations along with a simple first-order shear deformation theory are used for deriving this electromechanical coupled problem. A finite model in 3-dimensions have been developed for smart composite shallow shell integrated with the ACLD treated patches of PFRC and AFC. The results of both the cases have been compared and it has been found that the improved performance of AFC patch over the PFRC in subsiding the transient nonlinear vibrations of symmetric cross ply laminated composite shallow shell.

Dynamic flood wave routing in prismatic channels with hydraulic and hydrologic methods

AbstractTime-dependent, unsteady flow has been studied in prismatic open channels with symmetric trapezoidal and triangular cross sections and small bottom slope. The St Venant equations without lateral inflow have been discretized in explicit as well as in implicit form and solved numerically, for unsteady, subcritical flow. The inflow hydrograph used can be applied for different flood events by adjusting its parameters accordingly. The results presented are derived from the explicit schemes Lax-Diffusive, MacCormack, Lambda as well as the implicit Preissmann scheme, and are compared to those from the Muskingum-Cunge method and the widely used commercial software HEC-RAS. The peak flow computed by the Lax-Diffusive scheme was reduced at the downstream end of the channel and the arrival time of the peak increased if compared to the other methods. The Muskingun-Cunge method forecasted the shortest peak flow arrival time at the downstream end cross section. Mass conservation computed from inflow and outflow hydrographs has been confirmed, since the maximum error did not exceed 2.60%. All codes were implemented in house using Matlab®.

The peptide hormone glucagon forms amyloid fibrils with two coexisting β-strand conformations.

Glucagon and insulin maintain blood glucose homeostasis and are used to treat hypoglycemia and hyperglycemia in diabetic patients, respectively. Whereas insulin is stable for weeks in its solution formulation, glucagon fibrillizes rapidly at the acidic pH required for solubility, and is therefore formulated as a lyophilized powder that is reconstituted in acidic solution immediately before use. Here we use solid-state NMR to determine the atomic-resolution structure of fibrils of synthetic human glucagon grown at pharmaceutically relevant low pH. Unexpectedly, two sets of chemical shifts are observed, indicating the coexistence of two β-strand conformations. Those two conformations have distinct water accessibilities and intermolecular contacts, indicating that they alternate and hydrogen-bond in an antiparallel fashion along the fibril axis. Two antiparallel β-sheets assemble with symmetric homodimer cross sections. This amyloid structure is stabilized by numerous aromatic, cation-π, polar and hydrophobic interactions, suggesting mutagenesis approaches to inhibit fibrillization to improve this important drug.

Improving Facial Image Recognition based Neutrosophy and DWT Using Fully Center Symmetric Dual Cross Pattern

Improving Facial Image Recognition based Neutrosophy and DWT Using Fully Center Symmetric Dual Cross Pattern

An inverse method for the abrasive jet micro-machining of high aspect ratio channels of desired topography – Part II, experiments

Part I of this two-part paper presented an inverse technique to sculpt high aspect ratio (AR) micro-channel cross-sections of desired topography. In this paper, the methodology is experimentally verified for a variety of topographies machined in both brittle and ductile erosive materials. Micro-channels with trapezoidal and semi-circular cross-sections, and semi-circular protrusions were machined in borosilicate glass. Micro-channels with symmetric and asymmetric wedge-shaped cross sections were machined in poly-methyl-methacrylate PMMA. The chosen topographies represent the most challenging cases because they run counter to the natural surface evolution tendency for these two materials. Overall, the average error between the machined and desired profiles was 6.4% in borosilicate glass and 9% in PMMA. The methodology opens up new possibilities for the micro-fabrication of higher efficiency devices containing high-aspect ratio micro-features of virtually any desired shape.

Cavity model analysis of differential dual‐polarised annular‐ring patch antenna

The four-port cavity model is presented to study a differential dual-polarised annular-ring patch antenna operating at higher order mode TM12. Acceptable agreements among calculated, simulated, and measured impedances and radiation patterns are obtained. Theoretical analysis shows that the differential port-to-port coupling impedance is zero, and its isolation is theoretically infinite. The differential input impedance is about four times of the single-ended input impedance at the resonant frequency of higher order mode TM12. The differential operation can suppress the adjacent modes TM02 and TM22 near the operating mode TM12 and lead to a more symmetrical E-plane radiation pattern and lower cross polarisation level.

Seismic behavior of reinforced concrete squat walls with high strength reinforcements: An experimental study

A total of 15 squat reinforced concrete (RC) shear walls (12 of them were reinforced with high strength reinforcement of HRB600 [Grade 600 MPa] and the remaining 3 with normal grade reinforcement of HRB400 [Grade 400 MPa]) have been tested under the cyclic loading. The influencing parameters considered in the test specimens include the grade of reinforcement, axial load ratio, types of cross section, and reinforcement ratio. The seismic performances of the squat RC shear walls have been studied using the test results based on the failure mode, hysteretic behaviors, peak shear strength, deformation capacity, secant stiffness degradation, and inelastic energy dissipation capacity. The test results reveal that the failure modes of the walls with HRB600 steel bars are similar to those walls with HRB400 reinforcement. The walls with high strength reinforcement tend to achieve a larger ultimate deformation but slightly lower load carrying capacity. Both the initial stiffness and energy dissipation of the specimen hysteretic curves decrease as the reinforcement ratio increases and the parameters of cross section and reinforcement ratios have more significant effect on the seismic behavior of shear walls than that by the axial load ratio. Comparing with the walls reinforced with lower reinforcement ratio, the ones with higher reinforcement ratio exhibit larger and better peak load and deformation capacities. Shear walls with symmetrical cross section have better seismic performance than those having the asymmetric ones. When the specimens are subjected to the peak load, the stress in 90% horizontal reinforcement could reach 425 and 385 MPa for the 95% horizontal reinforcement.

Surface stress effects on the mechanical properties of silicon nanowires: A molecular dynamics simulation

A primary challenge to use silicon nanowires as a truly potential building block in nanoscale devices is the implementation of scale effects into operational performance. Therefore, surface stress effects—as a direct result of size reduction—on transport properties became a major field of study. Previous computational simulations have focused so far on geometrical parameters with symmetrical cross sections, while silicon nanowires with nonsymmetrical cross sections are the major result of top-down fabrication techniques. A recent study has drawn a new aspect on the role played by the surface stress with a torsional profile on silicon nanowires to address the existing controversy from experimental and computational studies. Motivated by its success, the implications of this surface stress profile on the tensile properties of silicon nanowires are studied through molecular dynamics simulations. Deformation associated with the surface stress is computed for different length-to-thickness and width-to-thickness ratios. Then, tensile properties are investigated for a constant strain rate. Atomic calculations are carried out on silicon nanowires along the ⟨100⟩ crystal orientation for fixed-fixed and fixed-free boundary conditions. A combination of compressive uniaxial surface stress and torsional surface stress contributes to the mechanical behavior of silicon nanowires. A transition on elastic properties is obtained through changing the cross section from square to rectangular configuration. Further to addressing the controversy regarding the contribution of the surface stress on the mechanical properties, limits associated with available analytical approaches are highlighted for silicon nanowires.

Effects of Axisymmetric Square-Wave Excitation on Transverse Jet Structure and Mixing

The influence of temporal square-wave excitation on structural and mixing characteristics of an equidensity, gaseous jet in crossflow (JICF) was explored in the present study. As in separate unforced and sinusoidally excited JICF experiments, acetone planar laser-induced fluorescence imaging enabled this detailed quantification for the JICF for mean jet-to-crossflow momentum flux ratios ranging from (with a convective unstable upstream shear layer, or USL, in the absence of forcing) to (with a globally unstable USL). Such square-wave excitation of the jet fluid required adaptive feedforward control, not only to create more accurate temporal square waveforms but to enable more accurate comparison among alternative forcing conditions. Square-wave excitation of the JICF demonstrated a significant influence on the naturally globally unstable JICF, where specific nondimensional stroke ratios within -dependent ranges could produce deeply penetrating, periodic vortices with improved jet penetration and spread. Enhanced jet penetration did not always correlate with better molecular mixing, however; there was a stronger correlation of improved mixing at higher values with creation of a more symmetric jet cross section via square-wave excitation, especially one with a clear counter-rotating vortex pair structure.

Differential coupling contributes to synchronization via a capacitor connection between chaotic circuits

Nonlinear oscillators and circuits can be coupled to reach synchronization and consensus. The occurrence of complete synchronization means that all oscillators can maintain the same amplitude and phase, and it is often detected between identical oscillators. However, phase synchronization means that the coupled oscillators just keep pace in oscillation even though the amplitude of each node could be different. For dimensionless dynamical systems and oscillators, the synchronization approach depends a great deal on the selection of coupling variable and type. For nonlinear circuits, a resistor is often used to bridge the connection between two or more circuits, so voltage coupling can be activated to generate feedback on the coupled circuits. In this paper, capacitor coupling is applied between two Pikovsk-Rabinovich (PR) circuits, and electric field coupling explains the potential mechanism for differential coupling. Then symmetric coupling and cross coupling are activated to detect synchronization stability, separately. It is found that resistor-based voltage coupling via a single variable can stabilize the synchronization, and the energy flow of the controller is decreased when synchronization is realized. Furthermore, by applying appropriate intensity for the coupling capacitor, synchronization is also reached and the energy flow across the coupling capacitor is helpful in regulating the dynamical behaviors of coupled circuits, which are supported by a continuous energy exchange between capacitors and the inductor. It is also confirmed that the realization of synchronization is dependent on the selection of a coupling channel. The approach and stability of complete synchronization depend on symmetric coupling, which is activated between the same variables. Cross coupling between different variables just triggers phase synchronization. The capacitor coupling can avoid energy consumption for the case with resistor coupling, and it can also enhance the energy exchange between two coupled circuits.

Buckling analysis of thin FRP cross ply laminated composite panel with circular cut-out subjected to Transverse compressive loading

Abstract In composite laminates, bucklingphenomena is a matter of study while designing thin laminated panels due to their instability to carry compressive loads in practical situations. One such practical condition is a thin FRP symmetric cross ply rectangular laminate panel with different cross ply laminating sequences having a circular cut-out, which is subjected to uniaxial transverse compression. The Circular cutouts can be used both for mechanical& civil applications like fastening, for setting up a path for easy accessibility, safety openings, and at times it may be required to vary the natural frequency response of the structures and also used for joining of two different plates. The variation of buckling load is of interest, along with the study of influence of parameters like, layer thickness, aspect ratio (a/b), change in circle diameter, eccentricity in the cutout position, stacking sequence were analyzed. The aspect ratio, layer thickness and stacking sequence are important parameters that influence the buckling behavior of the composite plate

Enhanced absorption of monolayer molybdenum disulfide (MoS2) using nanostructures with symmetrical cross resonator in the visible ranges

In order to enhance the absorption of monolayer molybdenum disulfide (MoS2), a novel nanostructure with symmetrical cross resonator based on MoS2 in the visible wavelength ranges has been proposed. At a resonant wavelength of 623 nm, the absorption of monolayer MoS2 in the absorption structure is as high as 82%, much higher than the bare MoS2 in the air. The electric field around monolayer MoS2 is enhanced by the guided mode resonance, thereby enhancing the absorption of monolayer MoS2 in the structure. The relevant parameters of the proposed structure are adjusted to achieve the tunability of the resonant wavelength in the visible ranges and the high-efficiency absorption of monolayer MoS2 in the structure, which is of great significance for the applications of MoS2-based optoelectronic devices.

Substrate integrated waveguide leaky wave antenna with low cross polarization in X‐Ku band

In this article, a balanced symmetrical low cross polarization (X-pol) substrate integrated waveguide (SIW) based leaky wave antenna (LWA) is presented. The unit cell of the LWA consists of transverse and longitudinal slots, which provide series and shunt resonant elements, essentially required to radiate at broadside direction efficiently. The radiating slots are arranged in a way such that the unit cell is symmetrical around the centerline so as to achieve the low X-pol levels. Moreover, the shape of the longitudinal slots are changed and optimized to match the unit cell impedance to the characteristic impedance of the SIW. Parametric constraints of the radiating slots are studied for achieving the continuous beam scanning and the best low X-pol in the presented LWA. The final presented LWA is capable of continuous beam scanning from −28° to +30° within a frequency range of 9.5-15.2 GHz including broadside at 12.2 GHz. Moreover, the X-pol levels are better than −40 dB all over the scanning frequency range. Finally, the antenna prototype is fabricated and tested. Simulated and measured results are in good agreement. The maximum gain of the antenna measured is 13.8 dB.

Ultimate Bearing Capacity Assessment of Hull Girder With Asymmetric Cross Section

The objective of this study is to investigate the variation of neutral axis of ship hull girder due to asymmetric geometry or asymmetric load, and its influence on the ultimate strength (ULS) of hull girder. In order to account for asymmetric geometries and loads of hull girders, the force equilibrium and force-vector equilibrium criteria together with a minimum convergence factors (error) method are employed to determine the translation and rotation of neutral axis plane (NAP) of symmetric or asymmetric hull cross section in the application of Smith's method at each step of curvature of the hull girder. The ULSs of Dow's 1/3 frigate model with three predefined structural integrity states, one intact and two damaged, respectively, is investigated by the improved Smith's method (ISM) for a range of variation of heeling angles. The influence of asymmetric geometry and load on the motion of NAP and on the ULS are analyzed and discussed. The results show that the improved iteration strategy together with the minimum convergence factors (error) method is efficient and more accurate in searching the translation and rotation of NAP. Finally, the envelope curves of the bending moments in the three predefined integrity states are obtained, which can be used for assessing ULS of hull girders under combined vertical and horizontal wave bending moments.

Failure Analysis of Buried Polyethylene Pipe Subjected to Combined Loading of Non-uniform Settlement and Landslide Based on FEM

Polyethylene (PE) pipes are widely used in urban gas transportation systems but they are more prone to failure than steel pipes under the ground loads such as settlement, landslide and cyclic traffic load. This paper aims to study the position transfer law of failure location under the combined loading of non-uniform settlement and landslide, a numerical simulation model of buried PE pipe is developed in ABAQUS using a new method of non-uniform settlement displacement. The results show that the failure location will appear on the middle plane when the landslide is relatively small. With the increment of the settlement displacement, the failure location gradually appears on the symmetrical cross section, and the stress of turning point does not reach the yield stress. The crushing caused by the horizontal deformation under the action of landslide undermines the protective effect of the soil on the buried PE pipe, and the damage caused by the landslide to the pipe is more serious than that by the settlement. The result can provide a valuable reference and support for the safety assessment of buried PE pipe.