Shape Corners Research Articles

Metamaterial as perfect absorber for high sensitivity refractive index based biosensing applications at infrared frequencies

In this paper, we introduce a novel design of a metamaterial unit cell absorber, which is based on a metal/insulator/metal sandwich structure. The design is subjected to comprehensive finite element method computational analysis to ensure accurate and reliable results. The proposed metamaterial sandwich structure demonstrates exceptional absorption performance, achieving a nearly perfect absorption rate of 99.996% at the resonance infrared frequency of 39.8 THz. To provide a detailed theoretical explanation of nearly perfect absorption, we employ the effective medium theory, impedance matching, and field distribution analysis. Additionally, we have optimized the structural parameters of the sensor to maximize its absorption peak. This includes optimizing the thickness of the gold (Au) layer (from 0.03 to 0.28 μm), the distance between the L shape corners (from 0.60 to 0.90 μm), and the thickness of SiC dielectric spacer (from 0.20 to 0.45 μm). Furthermore, we showcase the remarkable sensitivity of the proposed metamaterial unit cell in detecting subtle changes in the refractive index through the implementation of a sensing medium setup in our model. Remarkably, we achieve a frequency shift sensitivity of 3.74 THz/RIU, along with a quality factor of 10.33, for a wide range of refractive indices (1.0–2.0). Moreover, for cancer detection, we attain a sensitivity of 3.5 THz/RIU. These findings highlight the exceptional performance of our approach in accurately detecting changes in refractive index, making it a promising candidate for various sensing applications. The novelty of our work lies in the design of a metamaterial unit cell structure. This configuration exhibits several noteworthy features, including wide incident angle () coverage up to 60°, polarization insensitivity, exceptional frequency shift sensitivity, high absorption peaks across a wide range of refractive indices, and the ability to distinguish cancer cells from healthy ones.

Tunable compressive properties of a novel auxetic tubular material with low stress level

The auxetic tubular materials have attracted wide attention owing to their unusual mechanical properties and potential applications in designing foldable devices. However, most of auxetic tubular structures designed by incorporating re-entrant, chiral or penetrated microstructures remain great challenging in stress concentration because of the presence of shape corners in these structures. In this study, a novel auxetic tubular structure is designed by incorporating the smooth peanut-shaped hole pattern and then is fabricated via 3D printing technique. Subsequently its mechanical properties and deformation characteristics are investigated by uniaxial compression experiments and finite element simulation. Results reveal that the designed tube exhibits significant auxetic performance under compression and the stress level within the structure is significantly reduced, in contrast to the auxetic tubular structure with orthogonal elliptical hole pattern. Finally, the effect of controlling parameters of the designed auxetic tubular structure on Poisson’s ratio is studied to better understand its auxetic behavior and also provide tunable design of auxetic tubular structures.

Revealing the effect of minor Ca and Sr additions on microstructure evolution and mechanical properties of Zn-0.6 Mg alloy during multi-pass equal channel angular pressing

In this study, the microstructure evolution and mechanical properties of Zn-0.6 (wt.%) Mg alloys with minor calcium (Ca) and strontium (Sr) additions (0.1 wt%) during multi-pass equal channel angular pressing (ECAP) were comparatively investigated. The obtained results illustrate that in addition to α-Zn matrix and network-shaped ternary α-Zn + Mg2Zn11 + MgZn2 eutectic structure, CaZn13 and SrZn13 particles are formed in as-cast Zn-Mg-Ca and Zn-Mg-Sr alloys, respectively. The CaZn13 particles exhibit cuboid shape, and their sizes are much larger than the ellipsoidal SrZn13 particles. After multi-passes ECAP, both α-Zn grains and eutectic structure are obviously refined owing to the dynamic recrystallization (DRX) process and mechanical crushing effect, while the CaZn13 and SrZn13 particles exhibit no obvious change. Moreover, the existence of cuboid CaZn13 particles with sharp corners are more effective to refine α-Zn matrix via the particle stimulated nucleation DRX mechanism, resulting in finer microstructure of Zn-Mg-Ca alloy. Since the CaZn13 particles could induce large stress concentration at their shape corners during deformation, which even causes crack of the particles in ECAP alloys, the ductility of Zn-Mg-Ca alloys is significantly deteriorated. Overall, the 12p ECAP Zn-Mg-Sr alloy exhibits optimal mechanical properties with ultimate tensile strength above 300 MPa and elongation higher than 20%. Nevertheless, the deformed Zn-Mg-Ca alloys possess poor ductility owing to the existence of CaZn13 particles, which should be avoided in future design of Zn-based biodegradable metals.

Enhanced Global and Local Curvature Properties for Corner Detection

Corner detection is basically a methods used to extract certain kind of features in images which could produce some information including the location or position of the corner points. Thus, in this paper an enhancement shape corner detection method is proposed to detect true corners of shape images. The overall performance of the proposed enhanced shape corner detector and six other existing shape detectors and descriptors including Harris, SUSAN, Harris-Laplace, CSS, SIFT and global and local curvature properties is presented. The experimental results of corner detection methods are tested using the benchmark binary image MPEG-7 Core Experiment Shape-1 Part B dataset. To measure the performance of corner detection evaluation, an appropriate number of true corners were determined.

New record of <i>Ulva sublittoralis</i> (Ulvales, Chlorophyta) in Korea

A marine ulvalean species (Chlorophyta) was collected from the eastern coast of Korea. This species is morphologically characterized by a distromatic, dark to medium green and mostly irregularly orbicular or irregularly expanded thallus with entire or undulate margin without serrations. Vegetative cells are irregularly polygonal with distinctly rounded corners in shape, and have chloroplast completely covering the outer cell wall and one to two pyrenoids per cell. In a phylogenetic tree based on ITS (Internal Transcribed Spacer) sequences, this Korean alga nests in the same clade with Ulva sublittoralis, as a sister clade of U. californica, U. flexuosa and U. tanneri, which share the irregularly orbicular or expanded thallus normally without teeth cells. The genetic divergence between them is intraspecific within Ulva. Accordingly, it is identified as U. sublittoralis based on the morphological and molecular data. This is the first record of Ulva sublittoralis in the Korean marine algal flora.

AgPO microcrystals with complex polyhedral morphologies diversity obtained by microwave-hydrothermal synthesis for MB degradation under sunlight

Abstract This research addresses the synthesis of silver phosphate microcrystals with complex polyhedral morphologies as rhombic dodecahedral, trapezoidal, tetrahedral and cuadri-hexahedral polyhedrons as well as structures of shape corners and edges. These structures are obtained simultaneously by means of few modifications to the hydrothermal method using microwave and basic medium for the chemical synthesis. The photo-degradation activity of silver phosphate microcrystals was measured using methylene blue (MB) under sunlight while stirring. The degradation time of the MB was reported at 4 min using 0.1 gr of microparticles suspended on 50 mL of MB at 5 × 10 5 mol/L concentration. These Ag3PO4 polyhedric microcrystals were characterized by different techniques: energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Nitrogen adsorption at 77 K. Reaction order and rate law were determined as well. A particle pore size distribution with order diameter of 4.862 nm and pore families between 5 and 20 nm linked to interstitial mesopores were well identified. Furthermore, these type of materials synthesis is environmental friendly due to its basic nature.

Improved Global and Local Curvature Properties for Shape Corner Detection

Improved Global and Local Curvature Properties for Shape Corner Detection

Effect of the Orientation of Hexagonal Fibers on the Effective Elastic Properties of Unidirectional Composites

AbstractExisting studies reveal that the shape corners of hexagonal fiber affect the degree of constraint on the matrix material. However, none of these studies included the effect of orientation of hexagonal fibers. In this study, a computational micromechanics model of oriented hexagonal fibers in periodic unidirectional composite materials is established for the determination of effective orthotropic elastic properties of the composite. In the present numerical modeling, the representative unit composite cell including the matrix material and the single oriented hexagonal fiber or random oriented hexagonal fibers is solved by micro-scale finite element analysis with different stress loads and periodic displacement boundary conditions, which are applied along the cell boundary to meet the requirement of straight-line constraint during deformation of the cell. Subsequently, the effective elastic properties of the composite are evaluated for periodic regular packing and random packing using the homogenization approach for investigating the influence of unified orientation and random orientation of the hexagonal fibers on the overall elastic properties of the fiber-reinforced composites. The numerical results are verified by comparing with other available results.

Synthesis and atomic-scale characterization of CeO2 nano-octahedrons

We report the synthesis of ceria nano-octahedrons using a simple yet efficient hydrothermal technique free of surfactant and template. A comprehensive microscopic characterization reveals that the nano-octahedrons exposed with eight {111} planes have shape corners and well-defined edges at the nanoscale. Atomic-resolution imaging uncovers that a couple of atomic layers are disappeared at corner, the atomic density of oxygen is reduced at surface, and there occur stacking faults inside the nano-octahedrons, which should have implications for our understanding of catalytic activity of ceria. We also propose a growth mechanism for the nano-octahedrons and provide an explanation to the easy formation of nano-octahedrons with the eight {111} facets.

Influence of the Milling Weld Toe and WIG Remelting Reconditioning Technology to Welded Pieces in the Case of Fatigue Testing

The paper presents the researches to determine the best technologies to improve the lifetime of the corner welding. Generally it is says that the convex corner welding presents high mechanical properties because of the greater area section. The practice activity shows that in fact, because of the stress concentrators, these shapes of the welding are not the best solution. A better shape of the corner welding is the concave one that provides better results in the working conditions. To provide better results of the convex shape corner welding different recondition techniques are known. The paper is focused on fatigue testing performed on different samples realized with different beads on different working parameters. There are studied different reconditioned probes and the results are reported in fatigue curves.

S055014 90°T字形分岐部を有するチャネル乱流の分岐損失低減と流動特性([S055-01]内部流れ(1))

An experimental study is performed for dividing turbulent channel flow in 90 degree T-junction with sharp and various shape corners. Experiments are conducted for flow rate ratios of 0.2, 0.4, 0.6 and 0.8 (ratio between the flow rates in the branch and main channels) keeping the Reynolds number of the main flow at 4.0x10^4. The width of main channel H_1 is kept to 30mm, and the width of the branch channel H_2 is changed 15mm, 30mm and 45mm. The wall static pressure is measured and loss coefficient is evaluated. The velocity profiles are measured by a PIV system. The results show that rounding the corner reduces the pressure loss in the branch flow. As the ratio of width of the main channel to branch channel decreases, the reduction of pressure loss in the branch flow becomes large. It relates that the reattachment length is shorter compared with that of the sharp corner. Whereas the pressure loss in the main flow basically remains unaffected.

Numerical study of flow around an oscillating diamond prism and circular cylinder at low Keulegan-Carpenter number

In order to identify the influence of shape corners on the instantaneous forces in the case of oscillating bodies, the simulated flow field is compared for two kinds of cross sections: diamond prism and circular cylinder. For these two flow configurations, the same Reynolds number and a Keulegan-Carpenter are considered. To compute the dynamic flow field surrounding the body, the Navier-Stokes transport equations in a non-inertial reference frame attached to the body are considered. Hence, a source term is added locally to the momentum equation to take into account the body acceleration. The proposed model is solved using the PHOENICS code. For the oscillating circular cylinder, the simulated results are in good agreement with the experimental data available in the litterature. After validation of this proposed model, flow field for diamond prism is determined. For both bodies, the process of the vortex formation is similar, with the formation of a recirculation zone in the near-wake containing a symmetric pair of vortices of equal strength and opposite rotation. The length of recirculation zone varies approximately linearly with time. However, the in-line force coefficient of the oscillating diamond prism is found to be greatest, since the recirculation zone is longer compared with that of the oscillating circular cylinder.

SEM <i>In Situ</i> Investigation on Fatigue Cracking Behavior of X80 Pipeline Steel with Inclusions

The micro-mechanical behavior of inclusions in X80 pipeline steel under fatigue loading was investigated by means of SEM in situ observation. The influence of sizes and shapes of inclusion on crack initiation and propagation was analyzed. The result shows that for large-size single-particle inclusion, cracks initiate from the interior under the fatigue loading. When a certain circulation cycles are reached, cracks initiate at the matrix near the sharp corner of the inclusion. The cracks extend at the matrix during the stable extension period and unstable extension period following the crack initiation, until fracture occurred. For chain inclusion, cracks first initiate at the interface between inclusion and matrix within the chain area, and the circulation cycles needed for initiation are far less than single inclusion. Cracks steadily extend after the initiation, and then fracture after very short circulation cycles. A chain of inclusion with the shape corners is serious harmful to the fatigue properties.

Numerical Simulation of Gas-assisted Injection Molding Process for A Door Handle

A unified mathematical model is proposed to predict the short shot, primary and secondary gas penetration phenomenon in gas-assisted injection molding (GAIM) process, where the Cross-WLF model and two-domain modified Tait equation are employed to simulate the melt viscosity and density in the whole process, respectively. The governing equations of two-phase flows including gas, air and polymer melt are solved using finite volume method with SIMPLEC technology. At first, two kinds of U-shaped gas channels are modeled, where the shape corner and generous corner cases are studied. At last, as a case study, the short shot, primary and secondary gas penetration processes of a door handle are simulated. The numerical results show that the mathematical model can successfully depict the race-tracking and corner effects, which are very helpful for the design of GAIM.

Anisotropic diffusion for effective shape corner point detection

This work presents a new method for detecting shape corner points. These points are characterized as having high curvature value and their detection is an important task in several applications, including motion tracking and object recognition. As noisy points also have high curvature value we propose a framework that includes smoothing and corner point localization. First, we defined a function that associates each shape contour point with its curvature value, then the proposed method automatically smooths this function via an anisotropic filter based on an evolutionary equation, simultaneously localizing the corner points. The results obtained show that the proposed model has good performance when compared with three other techniques.

Polygonal Approximation of Contour Shapes Using Corner Detectors

A great amount of corner detectors that appear in literature are based on using the Freeman chain code of eight directions, which is used to represent contour shapes. We propose a new method for corner detection based on a three-symbol chain code representation, which requires lower storage memory and an easy way to obtain shape corners. We compare it with five existing methods, which are well known in the literature, giving our method a better performance. Furthermore, in order to reconstruct the original shapes through polygonal approximations, we propose an error parameter to quantify the efficiency. This can be accomplished by considering the redundancy of points produced when looking for corners and when computing the difference between the original region and the approximated polygon.

Farthest point distance: A new shape signature for Fourier descriptors

Shape description is an important task in content-based image retrieval (CBIR). A variety of techniques have been reported in the literature that aims to represent objects based on their shapes. Each of these techniques has its pros and cons. Fourier descriptor (FD) is one of these techniques a simple, yet powerful technique that offers attractive properties such as rotational, scale, and translational invariance. Shape signatures, which constitute an essential component of Fourier descriptors, reduce 2-D shapes to 1-D functions and hence facilitate the process of deriving invariant shape features using the Fourier transform. A good number of shape signatures have been reported in the literature. These shape signatures lack important shape information, such as corners, in their representations. This information plays a major role in distinguishing between different shapes. In this paper, we present the farthest point distance (FPD), a novel shape signature that includes corner information to enhance the performance of shape retrieval using Fourier descriptors. The signature is calculated at each point on a shape contour. This signature yields distances calculated between the different shape corners, and captures points within the shape at which the human focuses visual attention in order to classify shapes. To reach a comprehensive conclusion about the merit of the proposed signature, the signature is compared against eight popular signatures using the well-known MPEG-7 database. Furthermore, the proposed signature is evaluated against standard boundary- and region-based techniques: the curvature scale space (CSS) and the Zernike moments (ZM). The FPD signature has demonstrated superior overall performance compared with the other eight signatures and the two standard techniques.

Numerical simulations of flow-field interactions between moving and stationary objects in idealized street canyon settings

Numerical simulations of an ideal model of street canyons with moving objects in the horizontal plane were conducted. The simulations were based on the unsteady two-dimensional incompressible Navier–Stokes equations, discretized on an overlapping grid with a numerical scheme that is second-order accurate in both space and time. The computational domain consists of a rectangular background with eight fixed objects arranged in two parallel columns representing the street canyon. Four identical objects were put in each column equidistantly. One or two identical objects were moving along the symmetry line of the computational domain. The objects were either circular or rectangular with rounded corners in shape. The numerical method was first validated by comparing with existing experimental and simulation data. A parametric study was carried out to investigate the influence of the characteristic parameters (such as canyon width, velocity of the moving objects, and separation distance between them) on the wake of the moving objects.

1115 LBMによる薄板製コーナーベーン形状の最適化(OS6-1 複雑流れ解析I 格子ボルツマン法,オーガナイズドセッション:6 複雑流れ解析の新展開)

1115 LBMによる薄板製コーナーベーン形状の最適化(OS6-1 複雑流れ解析I 格子ボルツマン法,オーガナイズドセッション:6 複雑流れ解析の新展開)

Incorporating a corner correction scheme into enhanced pattern area density proximity effect correction

Enhanced pattern area density proximity effect correction (EPADPEC) is an algorithm for performing electron proximity effect correction for direct write electron beam systems. The algorithm is described in C. S. Ea and A. D. Brown [J. Vac. Sci. Technol. B 17, 323 (1999)]. In this article, we describe a corner correction scheme for EPADPEC. The scheme reduces the pullback radius and the absolute area difference at shape corners by at least a factor of 2, at a computation cost increase of 1.7–5.9.