Edge Corner Research Articles

Experimental Investigations of Hydrokinetic Turbine Providing Fillet at the Leading Edge Corner of the Runner Blades

Water streams with low heads can be found in India, both naturally as well as through irrigation canals. These natural resources can be used to generate electricity by utilising Hydrokinetic water turbines. The current investigation includes an experimental investigation of the axial flow turbine in order to make use of these naturally available resources. For Axial Flow Turbines (AFT), the influence of the fillet radius at the leading edge corner of the runner blade is studied. The experiments are carried out under various turbine loads and corresponding head conditions. The 3D printed runners with six different fillet radius (Rtu), i.e. 0 mm, 2 mm, 4 mm, 6 mm, 8 mm, and 10 mm are examined experimentally. The results are presented in the form of obtained efficiency (η ) with a diverse Fillet Radius Ratio (FRR) for different Tip Speed Ratio (TSR) and equivalent head (H). The results indicate that, at the head, 0.012 m, with a sharp edge, i.e., FRR = 0 (Rtu = 0 mm), the minimum efficiency of 34.90% is recorded. However, at the same water head, the maximum efficiency of 84.82% is achieved with FRR = 0.046 (Rtu = 2 mm).

A high performance neural network and fuzzy logic based edge corner detector (NF-ECD)

A high performance neural network and fuzzy logic based edge corner detector (NF-ECD)

Development of a New Micro Drilling Tool with H-Shaped Chisel Edge

In order to improve the tool life and micro-hole machining quality, the H-shaped chisel edge micro-drill (HCE-MD) was developed in this paper. The HCE-MD was characterized by the inner edge formed through the chisel edge thinning. In the micro-drilling process, the inner edge can perform positive rake cutting, so the machining area of the workpiece extruded by cutting edge with a negative rake angle is reduced. Based on this, the distribution of rake angle near the chisel edge corner is improved. Then, the HCE-MD was fabricated on the six-axis CNC grinding machine. The grinding process parameters of the micro-drill were optimized based on the orthogonal grinding test and grey relational grade theory. The size and shape accuracy of the micro-drill were controlled by the multi-axis linkage grinding method and the movement-axis micro compensation method. Finally, the 0.25 mm HCE-MD was fabricated with the cutting edge radius of 1.94 μm and the flank surface roughness of 0.25 μm. The drilling performance of HCE-MD was evaluated through comparative drilling experiments. The experimental results show that, compared with common micro drill, the HCE-MD produced lower thrust force and better micro-hole roundness accuracy, and reduced the micro-drill wear on the chisel edge and the flank.

Effect of the Position of Amine Groups on the CO2, CH4, and H2 Adsorption Performance of Graphene Nanoflakes

CO2 separation from CO2/CH4 and CO2/H2 mixtures is essential in H2 production from biogas. Although amine-functionalized carbon materials are excellent candidates for selective CO2 adsorption, their adsorption performance depends on the amine edge position, which requires further clarification. Herein, 19 graphene nanoflakes (GNFs) bearing two amines at various positions on the zigzag, corner, and armchair edges were evaluated. All structures exhibited better CO2 adsorption compared to CH4 and H2. In the GNFs with isolated amines, only one main bond (H2N–CO2) was involved in CO2 adsorption, which was influenced by charge transfer from the GNFs to CO2. GNFs with adjacent amines had an additional hydrogen bond (H2N–CO2) that became stronger with decreasing steric hindrance. The CO2 adsorption performance of amines decreased as the number of methyl groups on the nitrogen increased, which interfered with CO2 adsorption. The presence of H2O hindered the interaction of amines and CO2 owing to the strong hydrogen bond between H2O and amines.

Active topological phase transitions in high-order elastic topological insulators driven by pneumatic methods and liquid metals

Active topological phase transitions widely occur in active matters and biological systems, such as developing embryos. Since the discovery of the intriguing bulk-boundary effects of topological insulators in Hermitian and non-Hermitian systems, various electric, optical, acoustic, and mechanical topological metamaterials with efficient energy transmission and robust defect-immunization have been designed. To date, however, it remains a challenge to precisely and fast manipulate the topological phase transitions in elastic topological insulators. In this paper, on the basis of theoretical analysis and numerical simulations, we propose an active strategy to achieve this aim through a combination of pneumatic actuation and liquid metals. The proposed method can precisely tune the connecting stiffness and vertex mass in the tight Su–Schrieffer–Heeger model. Thus, we realize the effective and fast control of topological phase transitions and elastic wave bandgap switching. We also uncover the active spinning bulk-boundary effects and higher-order topological states in the elastic topological insulators, demonstrating the high effectiveness and practicability of the proposed method. In addition, the differences between the 1D edge and 0D corner higher-order states are specified by information entropy theory. This work not only gains insights into the active manipulation of topological phase transitions but also inspires novel strategies to design active topological materials through untethered methods, e.g., magnetism or biological cells.

An efficient antenna system with improved radiation for multi-standard/multi-mode 5G cellular communications

This paper introduces a multi-input multiple-output (MIMO) antenna array system that provides improved radiation diversity for multi-standard/multi-mode 5G communications. The introduced MIMO design contains four pairs of miniaturized self-complementary antennas (SCAs) fed by pairs of independently coupled structures which are symmetrically located at the edge corners of the smartphone mainboard with an overall size of 75 × 150 (mm2). Hence, in total, the design incorporates four pairs of horizontally and vertically polarized resonators. The elements have compact profiles and resonate at 3.6 GHz, the main candidate bands of the sub-6 GHz 5G spectrum. In addition, despite the absence of decoupling structures, adjacent elements demonstrate high isolation. To the best of the authors’ knowledge, it is the first type of smartphone antenna design using dual-polarized self-complementary antennas that could possess anti-interference and diversity properties. In addition to exhibiting desirable radiation coverage, the presented smartphone antenna also supports dual polarizations on different sides of the printed circuit board (PCB). It also exhibits good isolation, high-gain patterns, improved radiation coverage, low ECC/TARC, and sufficient channel capacity. The introduced antenna design was manufactured on a standard smartphone board and its main characteristics were experimentally measured. Simulations and measurement results are generally in good agreement with each other. Moreover, the presented antenna system delivers low SAR with adequate efficiency when it comes to the appearance of the user. Hence, the design could be adapted to 5G hand-portable devices. As an additional feature, a new ultra-compact phased array millimeter-wave antenna with super-wide bandwidth and end-fire radiation is being introduced for integration into the MIMO antenna systems. As a result, the proposed antenna system design with improved radiation and multi-standard operation is a good candidate for future multi-mode 5G cellular applications.

Experimental research and numerical simulations of the actual response flat slab in case of column loss

AbstractThis study reports the influence of tie reinforcement on the load‐bearing capacity of a flat plate slab in a failure situation due to the removal of an edge column. The results are based on numerical model analysis, experimental investigations, and analytical estimation. A numerical model was developed using the ATENA FEM program and validated based on the test results of the materials used. Experimental studies on the edge column removal were carried out for three models of 16 field flat plate slabs with varying degrees of tie reinforcement. Furthermore, the columns removed in Models M1 and M2 were near the corner edge columns, whereas in Model M3, they were the middle edge columns. The behavior of a reinforced concrete flat plate subjected to large deflections was estimated analytically based on the current literature and compared with the results obtained from numerical analyses and experimental investigations. During the experimental investigations, many traditional and modern techniques were used to measure the strains and displacements of reinforcing steel and concrete.

Numerical and experimental investigation of second-order mechanical topological insulators

Recently, higher-order topological insulators (HOTIs) as a novel frontier of topological phases of matter have been induced in mechanical systems, opening new routes to manipulate the propagation of elastic waves. Here, second-order mechanical topological insulators (SMTIs) implemented by mechanical metamaterials are systematically investigated in the rectangular lattice, the kagome lattice, the square lattice and the hexagonal lattice. The mechanical metamaterials are constructed from the generalized 2D Su–Schrieffer–Heeger (SSH) models. The topological mechanical metamaterials are characterized by the theories of topological indices and Wannier centers. With simulations and experiments, the corner states and edge states are observed in the topological mechanical metamaterials. Interestingly, the numbers of corner, edge and bulk states are respectively equal to the number of sites located at the corners, edges and bulk. This work offers an inspiring and unified model to study the higher-order topology in mechanical systems, and provides a new way for designing functional and integrated topological devices.

Drilling of alumina and zirconia ceramics using diamond-coated carbide drill

The drilling characteristics and availability of a diamond-coated carbide drill for drilling holes in ceramics were investigated and verified. An alumina and yttria-stabilized zirconia ceramics were used as workpiece materials. The drilling characteristics were evaluated based on the cutting-edge behavior, thrust force, integrity of the inner surface of the drilled hole, and chip morphologies. Alumina drilling had appropriate drilling conditions under which the diamond coating did not flake; under these conditions, extremely long tool life was obtained. Even when the diamond coating flaked off, the thrust force was reduced owing to the sharp cutting edges on the remaining coating ridgelines on the flank face. This flaking occurred around the corner edge region and expanded toward the thinning and chisel edge region with an increase in the number of holes drilled. In addition, the diamond flaking on the rake face occurred earlier when the feed rate of the drill was increased. In drilling alumina, the surface roughness of the inner surface deteriorated as the feed rate increased but improved as the diamond coating flaked off. Whereas in drill zirconia, a considerably better inner surface was obtained, regardless of the flaking of the diamond coating and drilling conditions. In both ceramics, thinning the diamond coating from 20 to 10 μm resulted in premature flaking of the coating. The drill life was reached when the flaking region reached the chisel edge from the corner side. The results of this investigation will assist with the drilling of holes in brittle ceramics using a diamond-coated carbide drill.

Non-Contact Measurement and Identification Method of Large Flexible Space Structures in Low Characteristic Scenes.

The end-operation accuracy of the satellite-borne robotic arm is closely related to the satellite attitude control accuracy, and the influence of the vibration of the satellite's flexural structure on the satellite attitude control is not negligible. Therefore, a stable and reliable vibration frequency identification method of the satellite flexural structure is needed. Different from the traditional non-contact measurement and identification methods of large flexible space structures based on marker points or edge corner points, the condition of non-marker points relying on texture features can identify more feature points, but there are problems such as low recognition and poor matching of features. Given this, the concept of 'the comprehensive matching parameter' of scenes is proposed to describe the scene characteristics of non-contact optical measurement from the two dimensions of recognition and matching. The basic connotation and evaluation index of the concept are also given in the paper. Guided by this theory, the recognition accuracy and matching uniqueness of features can be improved by means of equivalent spatial transformation and novel relative position relationship descriptor. The above problems in non-contact measurement technology can be solved only through algorithm improvement without adding hardware devices. On this basis, the Eigensystem Realization Algorithm (ERA) method is used to obtain the modal parameters of the large flexible space structure. Finally, the effectiveness and superiority of the proposed method are verified by mathematical simulation and ground testing.

Electronic Structures and NLO Properties of a Series of TMDs Lateral‐Core–Shell Heterostructures Quantum Dots

AbstractThe electronic structures and nonlinear optical (NLO) responses of eight triangle group‐VI transition metal dichalcogenides (TMDs) lateral‐core–shell heterostructures quantum dots (QDs) [MaX2MbX2 and MXa2MXb2; M (Ma, Mb) = Mo and W; X (Xa, Xb) = S and Se] have been explored by using quantum chemistry method. Frontier molecular orbital (FMOs) analyses indicate that the triangular frameworks with more active W and/or Se atoms at shell have smaller energy gaps than those with Mo and/or S atoms, and the active sites of the ultra‐small TMD heterostructures mainly locate at the edge and/or the corner of the frameworks. Generally speaking, active atoms at the shell are beneficial to the enhancement of the frequency‐dependent first hyperpolarizabilities compared with the active atoms in the cores. First hyperpolarizability density analyses show that the local contributions of the first hyperpolarizability in x direction is mainly located at the left and right corners, while that in y direction is mainly located at the bottom edge and top corner, confirming the important role that the shell of the TMDs lateral‐core–shell heterostructure QDs play in its NLO response. Further, the electronic transitions contributed to the SHG responses also occur at the shell of these triangular frameworks.

Evolution of the edge states and corner states in a multilayer honeycomb valley-Hall topological metamaterial

The valley-Hall effect provides topological protection to a broad class of defects in valley-Hall photonic topological metamaterials. Unveiling precisely how such protection is achieved and its implications in practical implementations is paramount to move from fundamental science to applications. To this end, we investigate a honeycomb valley-Hall topological metamaterial and monitor the evolution of the topological valley-Hall edge states and higher-order corner states under different perturbation $\ensuremath{\delta}R$. The evolutions of the edge states of the armchair and zigzag interfaces are demonstrated, respectively. By adjusting the geometric parameters and introducing disturbances to break the inversion symmetry, we achieve the edge states with different modes including the conventional crossed edge state and the specific gapped edge state. It is found that the edge states of topological valley kinking will gradually separate with the increase of $\ensuremath{\delta}R$, and finally a complete gap between the edge states appears. The gap has rarely been reported previously in topological materials fabricated by printed circuit board technology. In addition, the higher-order topological corner states can also be observed in the proposed topological metamaterial. The higher-order topological phase is theoretically characterized by nontrivial bulk polarization and the Wannier centers. Our results show that the corner state localization becomes stronger with the increase of $\ensuremath{\delta}R$. It is expected that our results will provide a platform for the realization of optical topological insulators.

High-frequency topological corner and edge states in elastic honeycomb plates

Higher-order topological insulators (HOTIs) have attracted considerable attention because of their topological properties of low-dimensional topological corner states and edge states that exist in bandgaps. High-frequency edge states and corner states can be realized by controlling the interface configuration. However, most studies on HOTI focus on the bandgap at low frequencies, and the valley-selectivity of corner states is generally realized through a big-angle rotation. Here, we propose an elastic valley phononic crystal plate with an out-of-plane wide band gap to realize the edge states and corner states in the high-frequency bandgap. The sliding displacement of the resonators is tuned to control the topological phase transition. The rainbow trapping of topologically protected edge waves (TPEWs) is realized through the modulation of group velocities in the gradient structure based on the sliding parameter, and the valley-selectivity of corner states at high frequencies is further explored by engineering positions of the valley polarization. The simulation and experimental results indicate that TPEWs can be transmitted to different locations according to the switch of frequencies and corner states still hold valley-selectivity in high-frequency bandgaps. The proposed honeycomb plates provide generality for realizing high-frequency edge states and corner states and broaden the application for vibration transmission control and elastic energy trapping.

Spatial-Temporal Tensor Ring Norm Regularization for Infrared Small Target Detection

Infrared small target detection (ISTD) technique is widely used in infrared searching and tracking (IRST) and military surveillance. Existing detection methods must sufficiently address the challenges of the heterogeneous background with high concealment targets. In this letter, we propose a novel spatial-temporal tensor ring norm regularization (STT-TRNR) to detect infrared small targets. First, to utilize the spatial and temporal context information in a sequence, nonrepetitive spatial-temporal patches are formed by sliding windows in the consecutive frames. The patches are stacked into a tensor structure with spatial and temporal information. Second, the tensor ring nuclear norm is introduced to approximate the rank of the background tensor. The tensor ring regularization improves the correlation between dimensions, protects the internal structure of the tensor, and avoids the dimension disaster caused by train decomposition. Third, the local contrastive feature is used as a priori information to suppress the false alarms caused by the corner edges and other noises and avoid the distortion caused by target movement. Finally, the alternating direction multiplier method (ADMM) is employed to reconstruct the sequence images and retrieve the targets. The experimental results reveal that the suggested model provides improved detection performance and higher robustness across various complicated scene types.

Interactive visualization of forearm internal rotation angle in Tai Chi training

Modeling the visual features of the forearm internal rotation angle during Tai Chi training is difficult, and its accurate detection is lacking. To address this issue, this paper proposes an interactive visualization analysis method based on Harris corner detection and edge contour feature extraction to visualize and adjust the internal rotation of the forearm during Tai Chi training in real time. In the proposed method, the visual images of limb movement and forearm rotation during the Tai Chi training are collected as features, and the wavelet image denoising method is used to denoise the images to improve the signal-to-noise ratio of the output. Meanwhile, the image pixel uniform traversal method is used to continuously traverse the image subblocks to extract the edge contour features during the forearm internal rotation interaction. By means of superpixel feature decomposition and grayscale information superposition, the fitting effect of the forearm internal rotation angle is fed back, and based on this, the forearm internal rotation angle is modified to realize the interactive visual analysis of the forearm internal rotation angle. Experimental results show that, compared with existing methods, the interactive visualization performance of the proposed method is better. The proposed method can fit, track, and solve the rotation angle in real time; the required analysis training images are more accurate, and the Tai Chi training data detection and dynamic analysis abilities are improved.

Two-dimensional non-Abelian topological insulators and the corresponding edge/corner states from an eigenvector frame rotation perspective

We propose the concept of two-dimensional (2D) non-Abelian topological insulators which can explain the energy distributions of the edge states and corner states in systems with parity-time symmetry. From the viewpoint of non-Abelian band topology, we establish the constraints on the 2D Zak phase and polarization. We demonstrate that the corner states in some 2D systems can be explained as the boundary mode of the one-dimensional edge states arising from the multiband non-Abelian topology of the system. We also propose the use of the off-diagonal Berry phase as complementary information to assist the prediction of edge states in non-Abelian topological insulators. Our work provides an alternative approach to study edge and corner modes and this idea can be extended to three-dimensional systems.

Comparison and uncertainty quantification of roof pressure measurements using the NIST and TPU aerodynamic databases

The pressure coefficient of a low-rise building in the ASCE wind load design provision is usually obtained from boundary-layer wind-tunnel tests. Although these tests tend to be standardized, inconsistent results from different facilities have been acknowledged as a long-standing issue. This work compares roof pressure for a low-rise building model archived in the National Institute of Standards and Technology (NIST) aerodynamic database and the Tokyo Polytechnic University database, followed by quantifying the measurement and data reduction uncertainties of the NIST datasets. The Monte Carlo simulation propagates four elemental uncertainties to the mean Cp¯, standard deviation Cp′ and peak pressure coefficient Cp,peak. Results indicate that pronounced differences in the roof pressure from two datasets are attributed to different inflow characteristics (including the Jensen number variation) and the inherent measurement uncertainties. High measurement uncertainties of Cp¯ and Cp,peak are strongly correlated with vortical flow structures, either separated flow or conical vortices at the roof corner and windward edges. Two dominant measurement uncertainty sources are distinguished: the dynamic pressure ratio uncertainty and the surface pressure tap uncertainty. Alternative flow and pressure measurement techniques are noted to potentially reduce the two dominant uncertainty sources. This work is intended to clarify measurement uncertainty sources of obtaining pressure coefficients in wind-tunnel model tests and shed lights on why large differences exist from different tests.

Three-dimensional bubble jetting inside a corner formed by rigid curved plates: Boundary integral analysis

Three-dimensional dynamics of a transient bubble inside a corner formed by two rigid curved parabolic plates (walls) is studied numerically using boundary integral method (BIM) based on the potential flow theory. The bubble dynamics, including the expansion and collapse phases until the jet impact, are investigated for different corner angles associated with different focal lengths k of the parabolas. However, for all the simulations, the dimensionless initial vertical standoff distance of the bubble’s center from the corner edge (h∗) is fixed at 4. The bubble remains almost spherical during expansion, except for parts of its surface that flattens near the walls. When the bubble is initiated at the bisector plane of the two intersecting walls, it oscillates symmetrically with respect to the bisector plane and becomes oblate during the late stages of the collapse phase. A high-speed liquid jet forms towards the end of bubble collapse, pointing to the corner. If the corner angle decreases, the bubble becomes more oblate along the bisector plane making the ensuing liquid jet wider and slower. In addition, a bubble initiated closer to one of the two walls is mainly influenced by the closer wall, oscillates non-symmetrically with respect to the bisector plane and the liquid jet formed in this case is inclined towards the closer wall due to the greater Bjerknes force of that wall.

Study on stiffness distribution and failure mechanisms of the twisted profiled textile composite structure under cantilever load

The mechanical behaviors of the twisted profiled textile composite structures with different twist angles were studied by using a novel cantilever beam experiment. The strain distributions on the upper surface of the specimen were monitored by using DIC. Several strain gauges were located at different positions on the lower surface of the specimen. With the increase of cantilever load, the deformation of twisted specimen experienced from the initial torsion to the bending-torsion coupling deformation. The effects of twist angles on stiffness and strength of the twisted composite structures were analyzed. The stiffness distributions of the twisted composite structures are determined by using the finite element analysis (FEA) combining with the experimental results. There is a cubic polynomial function relationship between the macroscopic local twisted angle and the local material stiffness. The stiffness and strength of 135° twisted specimen are higher than that of 45°twisted specimen. The dominant failure mode was the compression fracture at the edge of the lower right corner of the twisted specimen. This study can be helpful of guiding the design of the twisted profiled textile composites structures.

A mathematical model for generation of interactive fractals using a fourth order fractal square: A case study

Fractals can be interactive by using fractal squares which evolved from mathematics. Fractal square (FS) F can be deduced from the F = (F + D)/n, where # D = m. The F n,m shows the FS having n order square boxes in the fractal square are maintained with m boxes and the rest of the boxes are to be discarded. Moreover, FS squares are a common used techniques in mathematical formulation (Pattern recognition and analytical imaging) for creating image patterns that are self-similar in nature. Nonetheless, recently there have been a number of studies produced on the 3 rd order fractals to explore the properties of different classes of fractals formed from it, however only the distinct patterns that are generated from it are being studied, along with Hausdorff dimension (HD) also been popular in order to determine the size of a fractal set. Although, all these existing techniques are limited in order to analysis of fractal set i.e., derived corner type, edge type and interior type. In this paper, we propose a novel dimension method called 4 th order FS and their dimensional analysis. As a new dimension approach, we present the Practical Grid Dimension (PGD) method, which utilizes the grids to calculate dimensions. As a last comparison, we have compared the HD approach with the PGD method in order to validate the proposed model. Researchers will be able to use this model to conduct more in-depth study for successful implementation in a wide range of fractal applications.