Analysis Of Two-dimensional Structures Research Articles

High Field Confinement Enhancement in Silicon-based Photonic Crystal with Different Point Defects

Two-dimensional silicon-based photonic crystals as optical analogs to electronic semiconductors are presented in this paper, emphasizing the design and analysis of two-dimensional structures. Employing the Lumerical FDTD solver, we initially crafted defect-free photonic crystals within a hexagonal lattice of air holes on a silicon slab (6.57 μm along x, 6.57 μm along y, 0.75 μm along z). The lattice parameters (a = 0.365 μm, r = 0.1095 μm, with r = 0.3a) established a target resonant wavelength of 1.5 μm. Utilizing Finite Difference Time-Domain (FDTD), we evaluated electric field decay, resonant modes, and the Q factor. The defect-free structure exhibited a peak Q factor of 736.004 at a resonant wavelength of 1262.87 nm. Removal of a central hole enhanced the Q factor to 1286.96 at 1391.07 nm. Introducing various line defects, the structure with three holes removed from vertical positions emerged as the optimal candidate for silicon-based photonic crystal cavity resonators, displaying the highest Q factor near the target resonant wavelength. Additionally, the structure with seven holes removed showed stable linear decays at both resonant wavelengths, suggesting its potential as a cavity resonator design candidate.

Analyses of Deformation Due to Screening-Current-Induced Force in Layer-Wound REBCO Insert Coil for 1.3-GHz LTS/HTS NMR

REBCO wires have high critical current density and thermal stability, and are being applied in various fields such as NMR, MRI, and accelerators. We are currently designing a 1.3-GHz LTS/HTS NMR magnet that operates in a persistent current (PC) mode. However, there are issues with using REBCO coils that need to be resolved. One problem unique to REBCO coils is non-uniform electromagnetic forces caused by screening currents. During the charging and discharging of the coil, screening currents are induced, resulting in a significantly non-uniform current distribution within the coil. As a result, non-uniform electromagnetic forces are generated within the coil due to these screening currents. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In this study, we performed an electromagnetic stress analysis using a two-dimensional axisymmetric structural analysis that considered tension during winding, thermal stress during cooling, and electromagnetic force during charging. First, we compared the results of the numerical simulation of the layer-wound REBCO coil with the experimental results. Then, we conducted numerical simulations of an insert REBCO coil in a design example of a 1.3-GHz NMR to evaluate the stress and deformation of the REBCO coil.

Electroelastic Analysis of Two-Dimensional Piezoelectric Structures by the Localized Method of Fundamental Solutions

Electroelastic Analysis of Two-Dimensional Piezoelectric Structures by the Localized Method of Fundamental Solutions

Matrix equations models for nonlinear dynamic analysis of two-dimensional and three-dimensional RC structures with lateral load resisting cantilever elements

In control engineering and structural dynamics, mathematical models such as the state-space representation, equation of motion, and the phase plane are matrix equations describing the system equilibrium. This paper develops novel matrix equations models for linear/nonlinear dynamic analysis of reinforced concrete (RC) buildings with cantilever elements lateral load resisting systems (e.g., RC shear wall, RC core). The models offer a new approach for introducing two-dimensional and three-dimensional cantilever structures to control the theory’s state-space representation and structural dynamics’ equation of motion. The development primarily addresses the stiffness and mass matrices. The proposed displacement-related stiffness matrix of cantilever elements satisfies the necessary conditions of symmetricity and elemental boundary conditions. The nonlinear matrix structural analysis employs a smooth hysteretic model for deteriorating inelastic structures, referring to the relation between the bending moment and the bending curvature through the bending stiffness. The parameters controlling the cyclic behavior regard a composite RC cross section subject to gravitational load and bending simultaneously. The paper includes four examples that exemplify the practical utilization of the matrix equations models in analyzing two-dimensional and three-dimensional structures of linearly elastic and inelastic properties. The four examples demonstrated the idealized applicability of the matrix equations models for modal analysis, pushover analysis, and inelastic earthquake response analysis.

Stochastic receptivity of laminar compressible boundary layers: An input-output analysis

In this study, a receptivity analysis of streaks, oblique and two-dimensional flow structures is presented with a stochastic receptivity framework for different inputs for supersonic adiabatic boundary layer flows. In particular, an active role of temperature fluctuation is identified for the amplification of oblique patterns, while a passive role is observed for the onset of streaks and two-dimensional flow structures. From a practical point of view, this study can help to improve the effectiveness of actuators aiming at a particular response in supersonic boundary layer flows.

Vibration Prediction of Space Large-Scale Membranes Using Energy Flow Analysis

In this work, vibration prediction of space large-scale membranes from the energy point of view is investigated. Based on the Green kernel of vibrating membranes, a new analytical representation of energy response of infinite membranes is derived. Averaged energy is used as the main variable so that the response fluctuation can be smoothed. Then membranes of various shapes can be taken into account by introducing the mean free path into the formulation to describe travel distances of energy waves. The energy response of finite membranes is obtained with the superposition of energy waves subsequently. Considering uncertainties usually becomes significant in large-scale structures, the formulation expressed with random variables is obtained for membranes with uncertain properties. The mathematical expectation and variance of energy response are derived subsequently. And the confidence interval of random response is obtained. Finally, numerical simulations are performed to validate the proposed formulations and characteristics of the random energy responses are analyzed by taking a space large-scale membrane structure as a model. The developed formulations make the analysis of membranes with uncertainties more convenient than Finite Element Method (FEM) since they are expressed in analytical forms. Compared with existing formulations of energy flow derived from deterministic travel distances of waves that only apply to regular shapes of structures, the proposed formulations are suitable for membranes of various shapes. This work provides an alternative analytical approach to vibration prediction for space large-scale membranes with uncertainties. And the approach is thought helpful for the vibration analysis of other two-dimensional structures.

Vibration analysis of two-dimensional micromorphic structures using quadrilateral and triangular elements

PurposeThe paper aims to presents a numerical analysis of free vibration of micromorphic structures subjected to various boundary conditions.Design/methodology/approachTo accomplish this objective, first, a two-dimensional (2D) micromorphic formulation is presented and the matrix representation of this formulation is given. Then, two size-dependent quadrilateral and triangular elements are developed within the commercial finite element software ABAQUS. User element subroutine (UEL) is used to implement the micromorphic elements. These non-classical elements are capable of capturing the micro-structure effects by considering the micro-motion of materials. The effects of the side length-to-length scale parameter ratio and boundary conditions on the vibration behavior of 2D micro-structures are discussed in detail. The reliability of the present finite element method (FEM) is confirmed by the convergence studies and the obtained results are validated with the results available in the literature. Also, the results of micromorphic theory (MMT) are compared with those of micropolar and classical elasticity theories.FindingsThe study found that the size effect becomes very significant when the side length of micro-structures is close to the length scale parameter.Originality/value The study is to analyze the free vibrations of 2D micro-structures based on MMT; to develop a 2D formulation for micromorphic continua within ABAQUS; to propose quadrilateral and triangular micromorphic elements using UEL and to investigate size effects on the vibrational behavior of micro-structures with various geometries.

The Spatial Spillover Effect of Environmental Regulation and Technological Innovation on Industrial Carbon Productivity in China: A Two-Dimensional Structural Heterogeneity Analysis

Environmental regulation and technological innovation are two crucial factors for improving industrial carbon productivity. However, prior research ignored the spatial spillover effects of these factors, and heterogeneity caused by industrialization level and resource dependence did not acquire attention either. Thus, we use the STIRPAT model and spatial panel Durbin model to study the spatial spillover effects of two independent variables. Then, a two-dimensional structural heterogeneity analysis is conducted according to the industrialization level and resource dependence. The results are as follows: improving environmental regulation and technological innovation is good for industrial carbon productivity. Simultaneously, there are obvious regional differences under two-dimensional structural heterogeneity. From the perspective of space, industrial carbon productivity has high spatial autocorrelation, and it can be enhanced through local environmental legislation, as well as technological innovation. Environmental regulation’s spatial spillover impact inhibits the improvement of industrial carbon productivity in surrounding provinces, resulting in a pollution haven effect. However, there is no evident regional spillover effect of technological innovation. Therefore, we provided new perspectives from spatial spillover and structural heterogeneity to optimize low-carbon policies.

Fracture mechanics analysis of two-dimensional cracked thin structures (from micro- to nano-scales) by an efficient boundary element analysis

In this paper, the boundary element method (BEM) based on the elasticity theory is developed for fracture analysis of cracked thin structures with the relative thickness-to-length ratio in the micro- or nano-scales. A special crack-tip element technique is employed for the direct and accurate calculation of stress intensity factors (SIFs). The nearly singular integrals, which are crucial in applying the BEM for thin-structural problems, are calculated accurately by using a nonlinear coordinate transformation method. The present BEM procedure requires no remeshing procedure regardless of the thickness of thin structure. Promising SIFs results with only a small number of boundary elements can be achieved with the relative thickness of the thin film is as small as 10−9, which is sufficient for modeling most of the thin bodies as used in, for example, smart materials and micro/nano-electro-mechanical systems.

Complete vibration band gap characteristics of two-dimensional periodic grid structures

In this article, the spectral element method combined with Bloch theorem is applied to calculate complete vibration band gap characteristics of two-dimensional periodic grid structures, which is verified by structural vibration transmission results based on spectral element method and finite element method. According to the differential equation of motion, complete spectral stiffness matrix of beam element is established at first, then stiffness matrix of grid structure can be obtained by coordinate transformation and assembly method, so as to form governing equation of motion based on Bloch boundary conditions. The band gap characteristics of periodic structures can be calculated by solving motion equation. Through band gap distribution analysis of two-dimensional periodic grid structures, the dispersion relations of different unit arrangements and effects of material and structural parameters on band gap characteristics are obtained which can be applied to acoustic design or vibration and noise reduction areas.

Vibration analysis of two-dimensional structures using micropolar elements

Vibration analysis of two-dimensional structures using micropolar elements

Shape transformers for phononic band gaps tuning in two-dimensional Bloch-periodic lattice structures

In this paper, shape transformers, a set of non-dimensional geometrical parameters that define beam cross-section efficiencies based on their size and shape, are employed in the wave propagation analysis of two-dimensional periodic lattice structures. Here, shape transformers of lattice unit-cell beams are used as design variables to tailor the frequency band gaps of the lattice structure, in the form of their mid frequencies and aspect ratios, by means of numerical Bloch-periodic simulation. Case studies are presented for lattices with square and hexagon Bravais symmetries where a total of six different unit-cell topologies are studied, considering 12 classes of different cross-section shapes. It is observed that a significant shift of the waveband branches towards lower frequencies are obtained with the variation of shape transformers from a void to a filled envelope configuration. Moreover, while changing the cross-section geometric variables, it is possible to determine associated values of maximum aspect ratios of band gap frequencies, thus identifying cross-section shapes that have better performance with respect to lattice dynamic characteristic. It is also found that the “H” and “I” cross-section shapes, in comparison to other shape families presented, resulted in the maximization of the band gap aspect ratio while maintaining a low frequency range, hence being ideal candidates for designing lattice metamaterials with lower frequency ranges of elastic wave attenuation. Furthermore, among all lattice topologies investigated, it is noted that the employment of diamond cross-section and its derivatives resulted in the greatest sensitivity of the mid-frequency shift of the band gap with respect to variations in cross-section geometric efficiency. It is also observed, as a general behavior for all unit-cells studied, that when scaling up the in-plane height of the cross-section, the aspect ratio of the band gap was maximized. Finally, using the Modal Assurance Criterion, we demonstrated that the variation in the shape transformers conserves the consistency between the eigenwaves of unit-cells at different characteristic points of the Irreducible Brillouin Zone. The presented study paves the way for the development and the systematic implementation of a novel wave attenuation tuning technique.

Numerical Evaluation of Thermal and Electromagnetic Stress in Frame-Reinforced Stacked REBCO Pancakes Coils

To achieve high-field rare-earth barium copper oxide (REBCO) coils, the mechanism of the deterioration of or damage to such coils needs to be clarified. A REBCO coil experiences various stresses and strains during the winding, cooling down, charging, and discharging processes. Furthermore, the additional force and stress due to a screening current has become an issue in REBCO coils. To protect REBCO coils from large electromagnetic stress in a high field, a reinforcement structure called the Y-based oxide superconductor and reinforcing outer integrated (YOROI) coil was proposed. This study numerically evaluated the effect of the YOROI coil structures against thermal and electromagnetic stress using a two-dimensional axisymmetric structural analysis. This simulation considered the following: 1) the mechanical stress induced by 10 N of winding tension, 2) thermal stress during cooling from 300 K to 10 K, and 3) electromagnetic stress, which included the additional stress due to a screening current during the charging process. The mechanical behavior due to each process was investigated, and the effect of the YOROI structures was also examined.

Medium-Frequency Vibration Analysis of Timoshenko Beam Structures

Medium-frequency (mid-frequency) vibration analysis of complex structures plays an important role in automotive, aerospace, mechanical, and civil engineering. Flexible beam structures modeled by the classical Euler–Bernoulli beam theory have been widely used in various engineering problems. A kinematic hypothesis made in the Euler–Bernoulli beam theory is that the plane sections of a beam normal to its neutral axis remain planes after the beam experiences bending deformation, which neglects shear deformation. However, previous investigations found out that the shear deformation of a beam (even with a large slenderness ratio) becomes noticeable in high-frequency vibrations. The Timoshenko beam theory, which describes both bending deformation and shear deformation, would naturally be more suitable for medium-frequency vibration analysis. Nevertheless, vibrations of Timoshenko beam structures in a medium frequency region have not been well studied in the literature. This paper presents a new method for mid-frequency vibration analysis of two-dimensional Timoshenko beam structures. The proposed method, which is called the augmented Distributed Transfer Function Method (DTFM), models a Timoshenko beam structure by a spatial state-space formulation in the [Formula: see text]-domain. The augmented DTFM determines the frequency response of a beam structure in an exact and analytical form, in any frequency region covering low, middle, or high frequencies. Meanwhile, the proposed method provides the local information of a beam structure, such as displacement, shear deformation, bending moment and shear force at any location, which otherwise would be very difficult with energy-based methods. The medium-frequency analysis by the augmented DTFM is validated in numerical examples, where the efficiency and accuracy of the proposed method is demonstrated. Also, the effects of shear deformation on the dynamic behaviors of a beam structure at medium frequencies are examined through comparison of the Timoshenko beam and Euler–Bernoulli beam theories.

A New Approach to Transient Vibration Analysis of Two-Dimensional Beam Structures at Medium and High Frequencies

Abstract Transient analysis of medium-frequency (mid-frequency) and high-frequency vibrations plays an important role in the research and development of complex structures in aerospace, automobile, civil, mechanical, and ship engineering. Low-frequency analysis tools, like the finite element methods, do not work well for mid- and high-frequency problems because they require a huge number of degrees-of-freedom and consequently costly computation, and are sensitive to material properties and boundary conditions. High-frequency analysis tools, such as the statistical energy analysis (SEA) and its variations, are unsuitable for midfrequency problems because they describe the vibrational behaviors of multibody structures in a global manner and cannot provide detailed local information about displacements and internal forces. In this paper, a new method, which is called the augmented distributed transfer function method (DTFM), is proposed for transient vibration analysis of two-dimensional beam structures at medium and high frequencies. Without the need for discretization and numerical integration, the augmented DTFM consistently delivers analytical transient solutions from low to high-frequency regions. A unique feature of the proposed method is that it can provide local information about system response, such as the displacements and internal forces of a structure, at any point and in any frequency region. Additionally, the proposed method provides a platform for model reduction, by which, a balance of efficiency and accuracy in mid- and high-frequency analyses can be achieved. The proposed method is demonstrated in numerical examples.

III-N heterostructures for monolithic integration of enhancement/depletion-mode high-electron-mobility transistors

Simulation analysis of III-N two-dimensional electron gas-based structures that could be used for stable monolithically integrated enhancement/depletion-mode circuits was carried out. Three different designs were proposed and analysed, including a novel p-GaN/AlN-GaN SPSL/GaN, which is expected to have lower ON-state resistance and higher transconductance than conventional normally-off GaN-based transistors.

Improved Methods for Simulating Live Loads for Two-Dimensional Structural Analysis of Buried Culverts

The current AASHTO LRFD Bridge Design Specifications stipulates a “special distribution width” for two-dimensional (2D) live-load analysis of reinforced concrete (r/c) boxes and arches with less than 2 ft of soil cover. This special distribution width allows a significantly greater reduction of the applied surface load than permitted for other culvert shapes and materials. Neither the AASHTO commentary nor the underlying developmental report provide the physical reasoning for the special distribution width, or why it only applies to r/c boxes and arches. This paper provides a clear, physical understanding of the three-dimensional (3D) phenomena associated with the special distribution width and the interaction with longitudinal load spreading through soil. This is achieved with the aid of a flat-plate model, representative of the top slab of a box culvert, with a variable line-load width. The closed-form solution reveals that the physical reason is “3D stiffness effects” (3DSE), which occur when the line-load width is relatively short compared with the culvert’s longitudinal lay length. Moreover, it is shown that 3DSE disappear when the line load reaches a special width called the “critical distribution width” or Wcritical. Wcritical is dependent on the culvert’s span and length, and is a key parameter along with parameter Wmin needed to identify the limiting line-load width that evokes 3DSE. The key concepts of 3DSE, Wcritical, and Wmin are used to develop improved 2D analysis procedures using either the traditional reduced surface load approach or the more recent continuous load spreading approach.

Tile vaults as integrated formwork for reinforced concrete: Construction, experimental testing and a method for the design and analysis of two-dimensional structures

Tile vaults are traditional, unreinforced masonry structures made of thin bricks (tiles), mortar and fast-setting cement or gypsum. They can be constructed without the need for a formwork, except at the boundaries, making them inherently economic. Tile vaults have historically provided a solution for the efficient construction of vaulted structures. Today, they can be used as permanent formwork for concrete shells, allowing for a significant reduction of the construction cost and waste produced, due to the possibility of reducing or even eliminating the need for traditional formwork. The concrete can be poured directly onto a tile-vaulted formwork to form a composite structure.This paper presents a technique for the construction of single-curvature shells consisting of a composite structure combining tile vaulting and reinforced concrete. A method for the design of these composite vaults and the assessment of their strength and stability against external loading is also presented. This method is based on limit analysis but takes into account the reinforcement’s contribution to the composite cross-section’s bending capacity.The equilibrium method is implemented computationally to provide fast results for the user. It provides graphical and intuitive results and opens the possibility for the future extension to fully three-dimensional problems. The design and structural analysis method is called Extended Limit Analysis for Reinforced Masonry (ELARM).Both the proposed construction technique and the computational method have been validated through experimental research. The feasibility of the building technique has been validated by the construction of two full-scale prototypes. In addition, the prototypes have been load-tested to failure to compare the results with those predicted by ELARM.

Screening and Identification of ssDNA Aptamers against HN Protein for Detection of Bovine Parainfluenza Virus Type 3 Antibodies in Serum.

Bovine Parainfluenza Virus type 3 (BPIV3) is a major but often overlooked pathogen that causes respiratory disease in cattle, especially during transportation and in feedlot situations. There is a demand for the rapid detection and serological diagnosis of BPIV3 to monitor the presence of the virus and its antibodies in cattle, which is critical in designing suitable interventions and control. In the present study, ssDNA aptamers with high affinity and specificity against the HN protein of BPIV3 were selected using microplates as the matrix. After eleven rounds selection, thirty-four different DNA sequences were obtained in total, wherein w-32, w-33, and w-34 were repeated seven, eleven, and nine times, and with Kd values of 56.57 ± 2.7 nM, 24.64 ± 2.84 nM, and 31.3 ± 3.32 nM, respectively. Two-dimensional structural analysis showed that the three aptamers had several loop structures that were probably more energetically favorable for target binding. Of the three candidates, aptamer w-33 showed the best affinity in an indirect enzyme-linked aptamer assay (ELAA). The percent inhibition cutoff value of the ELAA, assessed using twenty negative sera, was 31%. In a comparative study with commercial ELISA kits, the positive detection rate of the ELAA was slightly higher than that of the commercial ELISA kits, and the coincidence rate of ELAA and ELISA was 88%. Further optimization of the ELAA method with more serums is needed.

Spatial and temporal changes in extracellular elastin and laminin distribution during lung alveolar development

Lung alveolarization requires precise coordination of cell growth with extracellular matrix (ECM) synthesis and deposition. The role of extracellular matrices in alveogenesis is not fully understood, because prior knowledge is largely extrapolated from two-dimensional structural analysis. Herein, we studied temporospatial changes of two important ECM proteins, laminin and elastin that are tightly associated with alveolar capillary growth and lung elastic recoil respectively, during both mouse and human lung alveolarization. By combining protein immunofluorescence staining with two- and three-dimensional imaging, we found that the laminin network was simplified along with the thinning of septal walls during alveogenesis, and more tightly associated with alveolar endothelial cells in matured lung. In contrast, elastin fibers were initially localized to the saccular openings of nascent alveoli, forming a ring-like structure. Then, throughout alveolar growth, the number of such alveolar mouth ring-like structures increased, while the relative ring size decreased. These rings were interconnected via additional elastin fibers. The apparent patches and dots of elastin at the tips of alveolar septae found in two-dimensional images were cross sections of elastin ring fibers in the three-dimension. Thus, the previous concept that deposition of elastin at alveolar tips drives septal inward growth may potentially be conceptually challenged by our data.