X-shaped Cavity Research Articles

A Wideband Circularly Polarized Corporate-Fed Waveguide Aperture Array in the 60 GHz Band

A wideband circularly polarized planar antenna with hexagonal apertures arrayed over a plate-laminated waveguide slot array is developed in the 60 GHz band. The 2×2-element subarray functioning as the principal component is precisely and efficiently analyzed by the method of moments using numerical eigenmode expansion. This numerical approach is particularly applied to the regions of both the X-shaped cavity and hexagonal radiating aperture for circular polarization. Moreover, the bandwidths of both axial ratio (AR) and impedance matching in the subarray are significantly widened by applying the genetic algorithm in two steps. The bandwidths for both AR <; 3 dB and VSWR <; 1.5 are improved from 4.8% to 14.5% compared with the previous design. Their mechanisms are investigated in detail as well. A 32×32-element array with a uniform illumination is designed and fabricated by the diffusion bonding of thin copper plates. The wideband antenna performance is verified by the experimental evaluation.

Motion of circular cylinders during natural convection flow in X-shaped cavity filled with a nanofluid using ISPH method

PurposeThis study aims to illustrate the impacts of the motion of circular cylinders on the natural convection flow from variable heated partitions inside the X-shaped cavity filled with Al2O3-water nanofluid. A partial layer of a homogeneous/heterogeneous porous medium is located in the top area of the X-shaped cavity.Design/methodology/approachThree different cases of the porous media including homogeneous, horizontal heterogeneous and vertical heterogeneous porous media were considered. Three different thermal conditions of the embedded circular cylinders including hot, cold and adiabatic conditions are investigated. An incompressible scheme of smoothed particle hydrodynamics (ISPH) method is modified to compute the non-linear partial differential equations of the current problem. Two variable lengths of the left and right sides of the X-shaped cavity have a high-temperature Th and a low-temperature Tc, respectively. The other wall parts are adiabatic. The numerical simulations are elucidating the dependence of the heat transfer and fluid flow characteristics on lengths of hot/cold source Lh, porous cases, Darcy parameter, thermal conditions of the embedded circular cylinders and solid volume fraction.FindingsOverall, an increment in length of hot/cold source leads to augmentation on the temperature distributions and flow intensity inside the X-shaped cavity. The hot thermal condition of the circular cylinder augments the temperature distributions. The homogeneous porous medium slows down the flow speed in the top porous layer of the X-shaped cavity. The average Nusselt number decreases as Lh increases.Originality/valueISPH method simulated the motion of circular cylinders in the X-shaped cavity. The X-shaped cavity is saturated with a partial layer porous medium. It is found that an increase in hot source length augments the temperature and fluid flow. ISPH method can easily handle the motion of cylinders in the X-shaped cavity. Different thermal conditions of cylinders can change the temperature distributions in X-cavity.

Double-diffusive convection of solid particles in a porous X-shaped cavity filled with a nanofluid

In this work, numerical results are discussed for thermo-solutal convection resulting from embedded solid particles and partial length in X-shaped cavity. A heterogeneous porous medium and Aluminium oxide Al2O3-water nanofluid are filled the X-shaped cavity. The solid particles with a high temperature Th and concentration Ch are filling the center part of X-shaped cavity. Variable length in the left-wall of X-shaped cavity is carrying Th and Ch and similar variable length in the right-wall has Tc and Cc and the other wall parts are adiabatic.In this study, an incompressible smoothed particle hydrodynamics (ISPH) is utilized to solve the governing equations of velocities, temperature and concentrations. The novelty of this work is to couple between solid-fluid particles inside X-shaped cavity filled by a nanofluid and heterogeneous porous media. Numerical simulations have been obtained for the variation of buoyancy ratio , Darcy parameter , Lewis number , solid volume fraction , partial lengths and Length of solid particles . Main results indicated that coupled solid-fluid particles are depending on the values of buoyancy ratio parameter. Therefore, maximum of velocity field increases by 20.95% as buoyancy ratio increases from −1 to 1. A decrease on Darcy parameter from Da = 10−2 to Da = 10−5 slows down the coupling between solid and fluid particles and it decreases the maximum of velocity field by 94.5%. Adding nanoparticles reduces the coupled solid-fluid particles and it reduces maximum of velocity field by 56.71%.

Analytical model for evaluating XCC pile shaft capacity in soft soil by incorporating penetration effects

The derivation of a new analytical model for predicting the soil displacement of X-section cast-in-place concrete (XCC) piles installed vertically into soft clay as well as for predicting limit shaft resistance during loading phases is presented in this paper. The analytical model is formulated by assuming that the XCC pile penetration process is an X-shaped cylindrical cavity expansion process. Based on the theoretical framework of the Strain Path Method (SPM), the strain, displacement and stress induced by X-shaped cavity expansion can be obtained. The proposed analytical model is validated by comparing the degenerate solution of this study with that of conventional circular (cylindrical) cavity expansion theory. Analytical model-based design methods are then proposed for evaluating soil displacement and XCC pile shaft capacity. Theoretical predictions are compared with field test measurements to verify the suitability of the proposed design method. The proposed new analytical model reveals the fundamental penetration mechanics of XCC piles and gives improved design methods for determining XCC pile shaft capacities.

Perpendicular-Corporate Feed in Three-Layered Parallel-Plate Radiating-Slot Array

We propose a perpendicular-corporate feed in a three-layered parallel-plate radiating-slot array to remove the x-shaped cavity walls completely in the radiating part of the conventional planar corporate-feed waveguide slot array antenna. Coupling apertures on the bottom excite radiating slots spaced with the half of their spacing on the middle in the parallel plates. We place dielectric with proper permittivity in the region between the coupling aperture and the radiating-slot layer to excite a standing wave strongly there for a large number of slots. A parasitic-slot layer is added on the top to improve the bandwidth. A $16 \times 16$ slot array antenna is designed for uniform excitation with the perpendicular and the planar corporate feeds, and fabricated in the 60 GHz band. At the design frequency of 61.5 GHz, the measured directivity is 33.5 dBi with the aperture efficiency of 90.6%.

Complex variable solution for boundary value problem with X-shaped cavity in plane elasticity and its application

A new type of displacement pile, the X-section cast-in-place concrete (XCC) pile, has recently been developed in China. Extensive field tests and laboratory experiments are undertaken to evaluate its performance and quantify the non-uniform deformation effect (NUDE) of the X-shaped cross section during installation. This paper develops a simplified theoretical model that attempts to capture the NUDE. Based on the theory of complex variable plane elasticity, closed-form solutions of the stress and displacement for the X-shaped cavity boundary value problem are given. Subsequently, the analytical solution is used to evaluate the NUDE, the concrete filling index (CFI), and the perimeter reduction coefficient of the XCC pile cross section. The computed results are compared with field test results, showing reasonable agreement. The present simplified theoretical model reveals the deformation mechanism of the X-shaped cavity and facilitates application of the newly developed XCC pile technique in geotechnical engineering.

Syntheses, structures and properties of four second-sphere coordination complexes via metal halide anion and naphthalene-based ligand

Second-sphere coordination refers to any intermolecular interactions with the ligands directly bound to the primary coordination sphere of a metal ion. Four supramolecular complexes, 0.5[L·2H]2+·0.5[MCl4]2−·[CH3OH]·0.5[CH2Cl2] (M = Co, crystal 1; M = Mn, crystal 2), 0.5[L·2H]2+·0.5[ZnBr4]2−·[CH3OH]·0.5[CH2Cl2] (crystal 3), and 0.5[L·2H]2+·0.5[Cu2Br4]2−·H2O (crystal 4), based on naphthalene-based ligand N,N,N′,N′-tetra-p-methylnaphthyl-ethanediamine (L), have been synthesized. X-ray analysis reveals that 1–3 are isostructural, in which the methanol molecules are bridges, connecting the protonated L and metal chloride anions via N–H⋯O and O–H⋯Cl (Br) interactions to construct the host framework, and forming X-shaped cavity accessible for the inclusion of weakly polar guest molecules of dichloromethane. Dichloromethane is connected with the host framework through van der Waals forces. In 4, a dinuclear anion [Cu2Br4]2− is connected with the ligand through N–H⋯Br interactions, in which the water molecules are accommodated between chains formed by the ligand and [Cu2Br4]2−. Structure stability, thermal analysis, and photoluminescent properties were studied for 1–4.

CONSTRUCTAL DESIGN OF A X-SHAPED CAVITY COOLED BY CONVECTION

This paper applies Constructal design to study the geometry of a X-shaped cavity that penetrates into a solid conductive wall. The objective is minimizing the dimensionless maximal excess of temperature between the solid body and the cavity. There is uniform heat generation on the solid body. The cavity surfaces are cooled by convection heat transfer while the solid body is subjected to adiabatic conditions on its outer surfaces. The total volume and the cavity volume are fixed, but the lengths and thickness of the X-shaped cavity can vary. The emerged optimal configurations and performance are reported. The effect of the area fraction φ which denotes the ratio between the cavity area and the total area of the geometry, and the ratio between the length and thickness of the branch cavity, H1/L1, on the dimensionless maximal excess of temperature is numerically investigated. The results show that the dimensionless maximal excess of temperature θmax,min decreases approximately 60% when the cavity fraction increases from φ = 0.05 to 0.25. The results also show that the X-shaped cavity performs approximately 45% better when compared to a C-shaped cavity under the same thermal conditions. The optimal X-shaped cavity is also in accordance with the optimal distribution of imperfections principle.

Constructal design of isothermal X-shaped cavities

This paper applies Constructal design to study the geometry of a X-shaped cavity that penetrates into a solid conducting wall. The objective is to minimize the maximal dimensionless excess of temperature between the solid body and the cavity. There is uniform heat generation on the solid body. The total volume and the cavity volume are fixed, but the geometric lengths and thickness of the X-shaped cavity can vary. The cavity surfaces are isothermal while the solid body has adiabatic conditions on the outer surface. The emerged optimal configurations and performance are reported graphically. When compared to the Y- and C- and H-, the X-shaped cavity performs approximately 53% better than the Y-shaped cavity and 68% better than the C-shaped cavity for the area fraction ? = 0.05, while its performance is 22% inferior to the performance of the H-shaped cavity for the area fraction ? = 0.1. The results indicate that the increase of the complexity of the cavity geometry can facilitate the access of heat currents and improve the performance of the cavities.