Diagonal Square Research Articles

Bionic design of thin-walled bilinear tubes with excellent crashworthiness inspired by glass sponge structures

In order to enhance energy absorption, this study draws inspiration from the diagonal bilinear robust square lattice structure found in deep-sea glass sponges, proposing a design for thin-walled structures with superior folding capabilities and high strength-to-weight ratio. Firstly, the crashworthiness of bionic glass sponge tube (BGSTO) is compared with that of equal-wall-thickness equal-mass four-X tube through both experiments and simulations, and it is obtained that the specific energy absorption of BGSTO is increased by 78.64%. And the crashworthiness of BGSTO is also most significant compared to that of multicellular tubes with the similar number of crystalline cells. Additionally, we found that the double-line spacing of the glass sponge can be freely adjusted without changing the material amount. Therefore, based on BGSTO, we designed two other double-line structures, BGSTA and BGSTB. Then with equal wall thickness and mass as a prerequisite, this study proceeds to design and compare the energy absorption properties of three bilinear thin-walled tubes in both axial and lateral cases. The deformation modes and crashworthiness of the three types of tubes with variable bilinear spacing (βO/A/B ) are comparatively analysed. The improved complex proportional assessment (COPRAS) synthesis decision is used to obtain that BGSTO exhibits superior crashworthiness over the remaining two kinds of tubes. Finally, a surrogate model is established to perform multi-objective optimization on the optimal bilinear configuration BGSTO selected by the COPRAS method.

A Four Element Stringray-Shaped MIMO Antenna System for UWB Applications.

This paper presents a CoPlanar-Waveguide (CPW)-fed stingray-shaped Ultra-WideBand (UWB) Multiple-Input-Multiple-Output (MIMO) antenna system designed for microwave imaging applications. Featuring a diagonal square with four inner lines and a vertical line at the center from toe to tip with a CPW feed line, the unit antenna element looks like a stingray fish skeleton and is, therefore, named as a stingray-shaped antenna. It offers a bandwidth spanning from 3.8 to 12.7 GHz. Fabricated on a 31mil RO5880 RF teflon substrate with a relative permittivity of 2.2, the proposed antenna has dimensions of 26 × 29 × 0.787 mm3. The maximum realized gain achieved is 3.5 dBi with stable omnidirectional radiation patterns. The antenna element is used in a four-antenna MIMO configuration with an isolation-improving structure at the center. The MIMO system has dimensions of 58 × 58 × 0.787 mm3 with a maximum realized gain of 5.3 dBi. The antenna's performance in terms of MIMO parameters like Envelope Correlation Coefficient (ECC) and Diversity Gain (DG) is within satisfactory limits for medical imaging applications. Time domain analysis also yields positive results, allowing its integration into a breast phantom tumor detection simulation. The simulation and measurement results demonstrate excellent agreement, making this antenna a promising candidate for microwave imaging and biomedical applications.

Investigation on the DNB-type critical heat flux in a fuel assembly with 5 by 5 rods

In this paper, Eulerian two-phase model coupled with wall boiling model was employed to simulate the departure from nucleate boiling (DNB) in a 5 × 5 fuel assembly. The numerical simulation accurately predicted the critical heat flux (CHF) and also its location. Compared with the calculated results from W-3 formula and FLICA subchannel code, the CFD (Computational Fluid Dynamics) calculations showed good agreement against experimental measurements with the deviation of 5%, but presented more detailed flow distribution. Based on CFD results, the method of CHF prediction was discussed with an eye on wall superheat, void fraction and vapor convective heat flux in rod surfaces. The distribution of flow field and liquid–vapor fraction affected by mixing vane were further studied. Mixing vane can continually influence the downstream thermal hydraulic characteristics, forming the diagonal circulation and square circulation with the flow development. As a result, the bubble aggregation firstly occurred on the surface of corner hot rod instead of central hot rod, which induced the local heat transfer crisis. The CFD calculations presenting the evolution process of physical parameters can provide guidance for rod bundle CHF test and fuel assembly design.

Dimensions and Proportions of the Ptolemaic Temple at Gebel el-Nour

The paper focuses on the analysis of plan proportions of the Ptolemaic temple near the settlement of Gebel el-Nour (Egypt), the construction of which is dated to the period of reign of Egyptian king Ptolemy II Philadelphus (king from 284 to 246 B.C.). In an attempt to understand the possible logic of the dimensional and geometrical construction of the temple, the development of arithmetical, graphic and modular methods of proportionality is considered in the examples of structures from the Early Dynastic to Ptolemaic periods. Thus, during the construction of the largest Early Dynastic structures the simplest modular system based on sequentially constructed squares in combination with a system of diagonal constructions was used. During the Old Kingdom architecture begins to reflect the proportions of the Egyptian rectangular triangle 3:4:5. To replace the simple ratio of integers and rectangular triangles, laid in the proportions of buildings, in the New Kingdom era comes a system of building on the diagonals of the square. The growing influence of the Mediterranean region in the Ptolemaic period led to the introduction of the Greek system of construction modulo. Meanwhile, during this period there was a conscious archaization — a return to the methods of the Old Kingdom. The analysis of the temple in Gebel el-Nour shows that its geometry is based on a square, the side of which, giving the width of the ground area (16.68 m), and the diagonal of which gives its length (23.60 m). The centre of the square is the centre of the circle (diameter 34.88 m) into which the whole temple is inscribed (pronaos together with the naos). Premises and internal walls of the temple can be built according to the module, the role of which is probably played by the diameter of the base of the column (1.19 m) or on the basis of a rectangular triangle 3:4:5. Thus a complex of methods could be applied to the construction of the temple. Each of these methods solved its task: to obtain general geometry of the building, aesthetics (facades), construction (wall thickness), and functioning (size and configuration of the hall). The use of geometric principles from a much earlier period (the archaic construction of the diagonal square and the use of a rectangular triangle 3:4:5 to divide the interior spaces) is probably a deliberate archaization typical of the period.

Eccentric compression behaviour of diagonal rib-stiffened thin-walled square concrete filled steel tubes

Thin-walled square concrete filled steel tubular (CFST) members have attracted more attention in practice because of less steel consumption, high construction efficiency, and convenient arrangement for furniture or curtain wall. Compared with circular members, the local buckling of thin-walled square CFST members is a big concern since tube buckling often results rapid strength and ductility degradation. So in this investigation, diagonal ribs were welded on the internal tube corners to improve the performance of square CFST members. Nine diagonal rib-stiffened square CFST specimens, with large width-to-thickness ratio B/t=100, were experimentally investigated under eccentric compression. The main test parameters included column slenderness ratios (λ=13.9, 34.6, 55.4) and loading eccentricities (2e/B=0, 0.25, 0.50, 1.00). Detailed finite element models were established and verified. The composite effect of the stiffened column was elaborated through combining test results and the finite element analysis, followed by feasibility of column–column connection details and parametric studies. Finally, design methods for calculating the member resistances subjected to axial and eccentric compression were proposed.

On Chamfer Distances on the Square and Body-Centered Cubic Grids: An Operational Research Approach

Linear programming is used to solve optimization problems. Thus, finding a shortest path in a grid is a good target to apply linear programming. In this paper, specific bipartite grids, the square and the body-centered cubic grids are studied. The former is represented as a “diagonal square grid” having points with pairs of either even or pairs of odd coordinates (highlighting the bipartite feature). Therefore, a straightforward generalization of the representation describes the body-centered cubic grid in 3D. We use chamfer paths and chamfer distances in these grids; therefore, weights for the steps between the closest neighbors and steps between the closest same type points are fixed, and depending on the weights, various paths could be the shortest one. The vectors of the various neighbors form a basis if they are independent, and their number is the same as the dimension of the space studied. Depending on the relation of the weights, various bases could give the optimal solution and various steps are used in the shortest paths. This operational research approach determines the optimal paths as basic feasible solutions of a linear programming problem. A directed graph is given containing the feasible bases as nodes and arcs with conditions on the used weights such that the simplex method may step from one feasible basis to another one. Thus, the optimal bases can be determined, and they are summarized in two theorems. If the optimal solution is not integer, then the Gomory cut is applied and the integer optimal solution is reached after only one Gomory iteration. Chamfer distances are frequently used in image processing and analysis as well as graphics-related subjects. The body-centered cubic grid, which is well-known in solid state physics, material science, and crystallography, has various applications in imaging and graphics since less samples are needed to represent the signal in the same quality than on the cubic grid. Moreover, the body-centered cubic grid has also a topological advantage over the cubic grid, namely, the neighbor Voronoi cells always share a full face.

Husimi-lattice solutions and the coherent-anomaly-method analysis for hard-square lattice gases.

Although lattice gases composed of particles preventing up to their kth nearest neighbors from being occupied (the kNN models) have been widely investigated in the literature, the location and the universality class of the fluid-columnar transition in the 2NN model on the square lattice are still a topic of debate. Here, we present grand-canonical solutions of this model on Husimi lattices built with diagonal square lattices, with 2L(L+1) sites, for L⩽7. The systematic sequence of mean-field solutions confirms the existence of a continuous transition in this system, and extrapolations of the critical chemical potential μ_{2,c}(L) and particle density ρ_{2,c}(L) to L→∞ yield estimates of these quantities in close agreement with previous results for the 2NN model on the square lattice. To confirm the reliability of this approach, we employ it also for the 1NN model, where very accurate estimates for the critical parameters μ_{1,c} and ρ_{1,c}-for the fluid-solid transition in this model on the square lattice-are found from extrapolations of data for L⩽6. The nonclassical critical exponents for these transitions are investigated through the coherent anomaly method (CAM), which in the 1NN case yields β and ν differing by at most 6% from the expected Ising exponents. For the 2NN model, the CAM analysis is somewhat inconclusive, because the exponents sensibly depend on the value of μ_{2,c} used to calculate them. Notwithstanding, our results suggest that β and ν are considerably larger than the Ashkin-Teller exponents reported in numerical studies of the 2NN system.

Circularly polarized MIMO antenna utilizing parasitic elements for simultaneous improvements in isolation, bandwidth and gain

A circularly polarized (CP) multiple-input multiple-output (MIMO) antenna with wideband operation and high isolation characteristics is presented. The proposed antenna is first designed with two diagonal slotted square patches and then, four parasitic elements are utilized to significantly improve the antenna performances. Notably, besides enhancing the operating bandwidth and the gain radiation, the parasitic elements also contribute to reduce the mutual coupling between the MIMO elements. The measurements demonstrate that the proposed two-element MIMO antenna with edge-to-edge spacing of 0.09λo and profile of 0.05λo at the center operating frequency has operating bandwidth of 12.8% (5.1–5.8 GHz) and high isolation of better than 22 dB. The antenna also achieves high gain of better than 7.5 dBic and good diversity performances. Compared to other CP MIMO antennas reported in literature, our design possesses several exclusive features including wideband operation, high gain, very small edge-to-edge element spacing as well as low-profile configuration.

Stability and stabilisation of heterogeneous switched systems with arbitrary switching constraints

Heterogeneous switched systems are a class of special hybrid systems containing different dimensional subsystems. To research the stability and stabilisation of heterogeneous switched systems, a novel approach is presented to design static output feedback controllers for asymptotically stabilising heterogeneous continuous-time and discrete-time switched systems under arbitrary switching rules. This approach, which has less computation complexity, includes a main diagonal square block common Lyapunov function for stability analysis of heterogeneous switched systems and a main diagonal square block common homogeneous polynomial Lyapunov function for stabilisation of heterogeneous switched systems. In the study of stabilisation of heterogeneous switched systems, a two-step iterative method including two convex optimisation functions is established by sums of squares to express existing properties condition and solvable properties condition for determining block controller. At last, a practical example and two numerical examples are presented to show the feasibility of the proposed results.

Analysis of Key Elements of Truss Structures Based on the Tangent Stiffness Method

In recent years, the topic of progressive structural collapse has received more attention around the world, and the study of element importance is the key to studying progressive collapse resistance. However, there are many elements in truss structures, making it difficult to predict their importance. The global stiffness matrix contains the specific information of the structure and singularity of the matrix can reflect the safety status of the structure, so it is useful to evaluate the key elements based on the global stiffness matrix for truss structures. In this paper, according to the tangent stiffness-based method for the element importance, the square pyramid grid was chosen as an example, and the distribution rules of key elements under different support conditions, stiffness distributions, and geometric parameters were studied. Then, three common symmetric grid forms, i.e., diagonal square pyramid grids, biorthogonal lattice grids, and biorthogonal diagonal lattice grids, were selected to investigate their importance indices of elements. The principle in this work can be utilized in progressive collapse analysis and safety assessment for spatial truss structures.

MHD Natural Convection of a Fe3O4–Water Nanofluid within an Inside Round Diagonal Corner Square Cavity with Existence of Magnetic Source

This study concerns a numerical investigation of a magnetohydrodynamic (MHD) natural convection of a Fe3O4–water nanofluid filled within a round diagonal corner square cavity. The cavity was subjected to imposed temperatures (hot and cold walls) and one magnetic source. The nanofluid flow and heat transfer problem was mathematically modeled and its dimensionless problem was established. The finite element method was implemented in order to solve the MHD problem. The effects of the Rayleigh number, Hartmann number and round corner radius on the nanofluid flow (streamlines and velocity magnitude) and heat transfer (isotherms and temperature distribution) were evaluated. Heat transfer was assessed when the convection or the conduction dominates with regard to the nature of the flow.

Characterization of the Observational Covariance Matrix of Hyper-Spectral Infrared Satellite Sensors Directly from Measured Earth Views

The observational covariance matrix, whose diagonal square root is currently named radiometric noise, is one of the most important elements to characterize a given instrument. It determines the precision of measurements and their possible spectral inter-correlation. The characterization of this matrix is currently performed with blackbody targets of known temperature and is, therefore, an output of the calibration unit of the instrument system. We developed a methodology that can estimate the observational covariance matrix directly from calibrated Earth-scene observations. The technique can complement the usual analysis based on onboard blackbody calibration and is, therefore, a useful back up to check the overall quality of the calibration unit. The methodology was exemplified by application to three satellite Fourier transform spectrometers: IASI (Infrared Atmospheric Sounder Interferometer), CrIS (Cross-Track Infrared Sounder), and HIRAS (Hyperspectral Infrared Atmospheric Sounder). It was shown that these three instruments are working as expected based on the pre-flight and in-flight characterization of the radiometric noise. However, for all instruments, the analysis of the covariance matrix reveals extra correlation among channels, especially in the short wave spectral regions.

Experimental study on aerodynamic characteristics of two tandem square cylinders

Aerodynamic characteristics of two tandem square cylinders are investigated in horizontal and diagonal arrangement respectively, with the variation of the spacing ratio (i.e. the center-to-center space P versus the width B of the square cylinder) P/B = 1.75–5 at Re = 8 × 104 in the present study. The study focuses on the aerodynamic characteristics of diagonal tandem cylinders and the comparison with those of horizontal tandem cylinders. The results show that the aerodynamic characteristics of two diagonal square cylinders are distinctly different from those in the horizontal arrangement. At the small spacing, the mean and fluctuating aerodynamic coefficients, the maximum of mean negative pressures and the fluctuating pressures for diagonal tandem cylinders are noticeably larger than those of horizontal tandem cylinders due to a pair of recirculation flows. It is interesting that there are multiple peaks in the power spectra of diagonal tandem cylinders. The Strouhal numbers corresponding to the predominate peak of diagonal tandem cylinders are clearly smaller than those of horizontal tandem cylinders at the same spacing ratio. Additionally, the inter- and intra-cylinder correlations of aerodynamic forces for two types of arrangements change diversely with the variation of the spacing ratio. Moreover, the flow modes should be different from those of two horizontal tandem cylinders, which could be concluded to three regions in the investigated spacing ratio.

Effects of magnetic field on the convective heat transfer rate and entropy generation of a nanofluid in an inclined square cavity equipped with a conductor fin: Considering the radiation effect

In this paper, the effects of radiation and magnetic field on the convection heat transfer rate and the nanofluid entropy generation in a diagonal square cavity with a conductor fin have been numerically investigated. A fin with a thermal conductivity coefficient of k* = 100 is located on one of the walls of the cavity. A volumetric heat source is considered in the fluid that is producing heat in the form of radiation. The effect of this source is added as a source to the energy equation and its value is shown by the Rd radiation parameter. Mass, momentum, and energy conservation equations in two-dimensional mode are discretization with finite difference method based on the control volume and solved using the simple algorithm. The model used for the thermal conductivity coefficient is the phenomenon model, taking into account the Brownian motion of the particles. In this paper, the effects of Rayleigh numbers, Hartmann numbers, radiation parameter and volume percentages of nanoparticles on the entropy generation and heat transfer have been investigated. The results show that increasing the Rayleigh number and reducing the Hartmann number increases the Nusselt number. Alternatively, adding 6% of the nanoparticles to the base fluid in the absence of radiation increases the heat transfer rate and entropy generation by 5.9% and 16.6%, respectively. By adding the radiation parameter, Rd = 3, and the volume percentage of nanoparticles of 6%, the heat transfer rate and total entropy generation increased by 3.4% and 11.2%, respectively. It was also observed that increasing the radiation parameter at high Rayleigh numbers increases the Nusselt number and entropy generation and decreases the Bejan number. Increasing the heat transfer rate is more significant by increasing the radiation parameter at higher Rayleigh numbers.

Influence of the Design of Square p+ Islands on the Characteristics of 4H-SiC JBS

A novel diagonal square array junction barrier Schottky (JBS) diode is created to enhance the forward current and reverse breakdown voltage by increasing the Schottky contact area and shortening the diagonal spacing between two adjacent p+ islands in the active area of a JBS diode. The shape of the p+ islands is square and the positional arrangement of the p+ islands is a diagonal array. Half of the upper and lower p+ islands with smaller areas are connected with the innermost p+ guard ring to create more Schottky contact area and laterally extend the electric field to the edge termination. Results show that the forward current density and reverse breakdown voltage for the diagonal square array JBS diode are 4.2% and 10.7% higher than those for the conventional square array JBS diode, respectively. As the spacing increases, the breakdown voltage for the diagonal square array JBS diode and the conventional square array JBS diode decrease by 3.5% and 7.3%, respectively, indicating that the diagonal square array JBS has more uniform depletion regions and electric field to retain the breakdown voltage.

Spherically Symmetric Solution in (1+4)-Dimensionalf(T)Gravity Theories

A nondiagonal spherically symmetric tetrad field, involving four unknown functions of radial coordinaterplus an angleΦ, which is a generalization of the azimuthal angleϕ, is applied to the field equations of (1+4)-dimensionalf(T)gravity theory. A special vacuum solution with one constant of integration is derived. The physical meaning of this constant is shown to be related to the gravitational mass of the system and the associated metric represents Schwarzschild in (1+4)-dimension. The scalar torsion related to this solution vanishes. We put the derived solution in a matrix form and rewrite it as a product of three matrices: the first represents a rotation while the second represents an inertia and the third matrix is the diagonal square root of Schwarzschild spacetime in (1+4)-dimension.

Polarizers on a segment of square waveguide with diagonal ridges and adjustment iris

Configuration of a polarizer that converts the dominant wave of input rectangular waveguide into the wave with elliptical polarization of output square waveguide. The phase-shifting section is implemented on a segment of a square waveguide with two diagonal square ridges and output iris with finite thickness. The full-wave model of the polarizer is created using partial regions and generalized scattering matrices methods. Based on results of numerical optimization of polarizers with input rectangular waveguide dimensions 19×9.5 mm2 it is revealed that they can provide bandwidth of at least 13% for ellipticity coefficient r < 1 dB and return loss not worse than 25 dB in lower, middle and upper parts of rectangular waveguide’s operating band.

Failure Mechanisms and Progressive Collapse Judgment Criterion of Space Trusses under Strong Earthquakes

Aiming at failure mechanisms and judgment criterion of progressive collapse for space trusses, the responses and the failure mechanisms of diagonal square pyramid space trusses, leaning laid pyramid space trusses and orthogonal square pyramid space trusses with circumferential simple supports under different seismic waves were analyzed in this paper. The results show that space trusses have a good performance of earthquake resistance, but progressive collapse occurs easily. Based on the failure mechanisms of space truss, a judgment criterion of space truss is proposed under strong earthquakes, according to the characteristics of energy, displacements and plastic levels of members. The judgment criterion is expressed by judgment coefficient J. When J&gt;6, space trusses tend to be ductile failure, however, When J&gt; 6, space trusses tend to be progressive collapse.

The effects of surface injection through a perforated square cylinder on some aerodynamic parameters

The surface pressure distribution and the vortex shedding frequency were investigated for the flow around perforated horizontal and diagonal square cylinders with surface injection through various surfaces. For this purpose, surface pressure measurements on each square cylinder (horizontal and diagonal) and vortex shedding frequency measurements in the wake region were performed at three different Reynolds numbers in a wind tunnel. The parameters considered were injection coefficient, position of perforated surface (i.e., top, rear, top-rear and all), pressure coefficient, drag coefficient, and the Strouhal number. The results showed that pressure coefficient distribution, drag coefficient, and the Strouhal number were influenced by the position of the perforated surface and by the injection coefficient. The surface injections through the top-rear, rear and all surfaces of a diagonal square cylinder reduce the drag coefficient for the all Reynolds numbers, while the injection through all surfaces only reduces the drag coefficient of a horizontal square cylinder. The other aerodynamic parameter Strouhal number can also be controlled by injection through certain surfaces of a horizontal square cylinder.

Minimum ber block precoders for zero-forcing equalization

We determine the linear precoder that minimizes the bit error rate (BER) at moderate-to-high signal-to-noise ratios (SNRs) for block transmission systems with zero-forcing (ZF) equalization and threshold detection. The design is developed for the two standard schemes for eliminating inter-block interference, viz, zero padding (ZP) and cyclic prefix (CP). We show that both the ZP minimum BER precoder and the CP minimum BER precoder provide substantially lower error rates than standard block transmission schemes, such as orthogonal frequency division multiplexing (OFDM). The corresponding SNR gains can be on the order of several decibels. We also show that the CP minimum BER precoder can be obtained by a two-stage modification of the water-filling discrete multitone modulation (DMT) scheme in which the diagonal water-filling power loading is replaced by a full matrix consisting of a diagonal minimum mean square error power loading matrix post multiplied by a discrete Fourier transform (DFT) matrix.