Far-field Zone Research Articles

Study on Leakage and Diffusion Behavior of Liquid CO2 Vessel in CCES

Numerical simulations of the leakage and diffusion behavior of liquid CO2 vessels and security analyses were conducted in this paper, based on a CO2 compression energy storage system. With isentropic choking model, the leakage of vessels under specific conditions was numerically simulated. The influence of different wind speeds on leakage in near-zone field was studied. Meanwhile, the diffusion characteristics of CO2 under three different influencing factors were investigated with the UDM (Unified Dispersion Model) diffusion model, and the diffusion ranges of certain concentrations were detected in the far-zone field. The results show that the low-temperature zone of the 50 mm leak aperture can reach 0.74 m downwind, and basically does not change with wind speed. In the leakage direction, the maximum damage zone of high-speed flow can reach 7.70 m. For the far-zone field, the diffusion area and downwind distance of a dangerous concentration decrease with the increasing of wind speed, and the hazardous area of the low concentration is greatly affected. Based on specific conditions, the maximum diffusion area is 78.46 m2 at 1 m/s wind speed, and the dangerous range reaches 36.32 m downwind. The larger the leakage aperture, the faster the growth trend of the low concentration area under the same conditions. As the equivalent radius of the leakage aperture is less than 50 mm, the maximum diffusion area is proportional to the cubic of the leakage aperture radius. The higher the height of the leakage source, the smaller the concentration range at 1.5 m, which is the average human breathing height. The overall cloud moves upward, meaning that the ground risk decreases. When the leakage aperture is 50 mm and the wind speed is 1 m/s, the maximum cloud diffusion range is 857.35 m2 at the leakage height of 2 m, and the dangerous range reaches 109.53 m downwind, where the maximum concentration is 14.65%.

Propagation of elliptical Gaussian vortex beam based on angular spectrum representation

Vortex beams with hollow elliptical ring structure have attracted broad interest in applications such as micro-particle trapping and manipulation. The paper investigates the dependence of the hollow elliptic ring structure of vortex beams on the beam order and the topological charge, while propagating in the near- and far-field zones. The electric field of the beam is formulated by using the angular spectrum method, which satisfies rigorously Maxwell's equation. The electric field, linear momentum and orbital angular momentum are calculated. Numerical results show that the hollow elliptical ring structure approximately remains unchanged over a finite propagation distance, accompanied by a rotation whose angle depends on the topological charge. In the far-field zone, the ring structure is broken, leading to two bright spots and several dark islands. It is found that the beam profile in the near-field zone is mainly related to the beam order but in the far-field zone is primarily affected by the topological charge. The results presented in the paper may be useful in predicting and explaining the interaction between the elliptic hollow Gaussian vortex beam and the micro-particles, such as the movement of micro-particles along the orbit and the rolling rotation.

A 3D finite element spectral integral (FESI) method for acoustics

We present a novel hybrid method that integrates the spectral integral method (SIM) with finite element for pressure acoustics in an inhomogeneous medium surrounded by spherical or incomplete spherical surfaces. Our approach, called the finite element spectral integral (FESI) method, enables efficient calculations of the pressure field in near-field and far-field zones. It is more efficient than the conventional finite element method hybridized with the boundary element method (i.e., the FEBI method). Furthermore, we construct a symmetric coefficient matrix using the proposed symmetric coupling to speed up the FESI method. We demonstrate through several examples that our FESI method offers significantly improved efficiency and lower memory consumption compared to the FEM combined with the perfect matching layer method while achieving higher accuracy.

The asymmetric evolution of grain-scale stresses in notched specimens under cyclic loads

Engineering components are often exposed to various cyclic loading conditions. The development of microscale stresses under such conditions depends on the material texture, local microstructure, the degree of crystals elastic and plastic anisotropy, as well as the presence of geometrical irregularities. In this study, the three-dimensional synchrotron X-ray diffraction (3D-XRD) technique is used and coupled with a crystal plasticity finite element (CPFE) model to deconvolute the contribution of such parameters on the magnitude of localized stresses. Special attention is paid to the notch geometry, where two double-edge-notched α-zirconium specimens with different geometries but the same texture were deformed in-situ while grain-scale stresses were measured both in the vicinity of the notches and in the far-field zones. Deep and shallow notches were cut to the dimensions comparable with the specimens’ average grain sizes. For each specimen, the center of mass, orientation, elastic strain, stress, and relative volume of more than 6,000 grains were measured and studied. Post-deformation analysis with Electron Backscatter Diffraction (EBSD) was conducted to further validate the observed trends. It is shown that the distribution of grain-scale stresses is asymmetric within each specimen. This asymmetry develops from the early stages of the applied cyclic load and remains intact with further loading. A new method is introduced for quantifying the effects of grain neighbourhood on load sharing, where it is shown that such effects relax the stresses acting on “hard” grains, altering grain-scale stress concentration factors.

Numerical investigation of seismic wavefield characteristics induced by a tensile source in a heterogeneous mining environment

Mining-induced tremors serve as the main dynamic stress source of coal bursts which represent one type of the most critical mining disasters in underground coal mines. To evaluate coal burst risks and comprehend the response of the coal-rock mass to seismic waves, microseismic monitoring stands as the principal method. By inferring the zones with elevated coal burst risks based on the seismic event clusters, valuable insights can be gained. However, because of limited seismic monitoring results generated from an individual seismic event, the recognition of the corresponding dynamic disturbance process remains ambiguous. The dynamic disturbance process presents immense complexity due to the focal mechanism and heterogeneous medium, particularly under the effect of structural heterogeneity induced by large-scale mining operations. In this study, forward numerical modelling was employed to gain the comprehension of seismic wave propagation affected by extraction zones. The findings revealed heightened intricacy of the wavefields and increased displacement concentrations around the working face. The characteristics of peak particle velocity (PPV) and displacement spectra were investigated in the near- and far-field zones, respectively. Owing to the existence of the extraction zone, both a significant amplification effect and the redistribution of PPV were observed around the near-field zone. The intricate wavefield caused by the focal mechanism and extraction zones resulted in more scattered distributions of the low-frequency spectral level, which can potentially cause an overestimation of source intensity. However, the impact of the complex wavefield on the corner frequency was limited. Through the analysis of the PPV attenuation law, as well as the distribution of both seismic moment and source radius, this study offered valuable insights for seismic risk assessment. The forward modelling approach facilitated the identification of high-risk potential areas resulting from seismic events, which deepened our comprehension of the dynamic disturbance process in the complex underground mine environment.

Far-field wireless power harvesting for inaccessible area wireless monitoring

Far-field wireless power solutions are essential for wireless monitoring of inaccessible industrial areas. However, the intuitive nature of RF power is to degrade with distance square law. Due to this attribute, the wireless power solution in a far-field zone has not been practically conceptualized for industrial deployments. To identify a feasible wireless power solution, a 5×10 rectenna panel has been designed and developed in this work. The panel has been designed with a staggered row arrangement to investigate different rectenna arrangement patterns. With experimentation, an optimized rectenna arrangement pattern has been selected for demonstration of its applicability for network sustenance. This work emphasises that smart charging of storage capacitors plays a vital role in extending the wireless power range. The power demand for resource-constrained devices is on a microwatt scale, which can be easily delivered through wireless power in seconds.

Optimization of the size of the circular antenna array in the problem of determining the direction to the radiation source in the far-field zone

Optimization of the size of the circular antenna array in the problem of determining the direction to the radiation source in the far-field zone

Inverse-Designed Superstrate for Arbitrary Shaped-Beam Radiation Pattern Based on Inverse Scattering Method

By using inverse scattering method, an inverse design for dielectric-type superstrate of antenna is introduced to get the arbitrary shaped-beam radiation pattern in this paper. The desired radiation patterns are taken as the known information to reconstruct the permittivity distribution of the dielectric-type superstrate within a certain region. Based on the desired radiation patterns, the scattering fields in far-zone can be assumed. Therefore, according to the electromagnetic inverse scattering method, the parameters of the dielectric-type superstrate can be reconstructed. To validate the proposed method, for simplicity, three shaped-beams are considered in the two-dimensional (2D) simulation firstly. Then, the reconstructed 2D dielectric-type superstrates are directly extended to three dimensions (3D) for applications. The results by the 2D and 3D simulations are in good agreement with each other. Good shaped-beam radiation patterns are obtained as expected. In addition, from the reconstructed superstrate, it can be concluded that the inverse design method without any prior-knowledge is well beyond the ability of traditional forward design methods. Furthermore, unlike deep learning which requires datasets for training, the proposed method does not have this process, so it is also efficient.

PO-03-101 PEAK FREQUENCY INITIAL US AND EUROPEAN EXPERIENCE: A NOVEL MEASURE TO DISTINGUISH NEAR-FIELD FROM FAR-FIELD EGM COMPONENTS

Discrimination between near-field (NF) vs. far-field (FF) components in electrograms (EGMs) is mostly based upon intuitive perception of local EGM sharpness. As high-density mapping catheter use has expanded, the difficulty of discerning sub-components across many EGMs in realtime has increased. To date no mapping system had employed a means to quantify this distinction. A novel detection algorithm was designed to identify sharpness of NF EGM components by annotating the highest Peak Frequency (PF) of a signal. To provide insight into first clinical use cases of NF annotation algorithm and PF data. Acute procedure data were prospectively collected from 32 operators at 16 institutions in the US and Europe. All cases were performed on EnSite X system with EnSite OT Near Field software (Abbott). PF information was used as an adjunct to activation or voltage maps via an emphasis layer or as a standalone map (Figure). Choice of mapping tools and technique was at physician discretion. Analysis included ablation cases (n=175) with the following indications: AF (60.6% [54.7% PAF, 45.3%, PsAF; 34.9% redo]), SVT (20.6%), and VT/PVC (18.9%). The NF algorithm was the roving detection option of choice for automated point collection in most cases (96.2% of AF cases, 91.7% SVT, 69.7% VT/PVC). Alternative detections were Last Deflection in VT cases (33%) and First Deflection in PVC cases (29%). When NF was used, correctness of EGM annotation was noted as highly accurate in 93.5% of cases. Standalone PF maps were used as a diagnostic tool in 48 (27.4%) Depth of Activation Insights cases. Bounding values for map display were variable based on use-case to highlight various electrophysiologic phenomena (Table). In an AF use case, PF was used for gap identification (n=6); values were applied at 225±28 Hz, consistent with previously published value of 240Hz (Merino, et al. EHRA 2022). Alternatively in VT/PVC cases, low PF far-field zones were highlighted to assess activation at depth in tissue; mean values were 198±10 Hz. Peak frequency mapping helps distinguish near field from far-field electrograms. PF mapping can be used as (1) a standalone mapping technique to accurately identify near field components and (2) PF mapping can be used as an adjunctive technique to complement activation and voltage maps. PF mapping appears to assist in substrate differentiation, pathway localization, and contact assessment. Further research is warranted on optimal settings for various tissue types and rhythms.Tabled 1Table. Standalone PF mapsValues in HzValues in HzUsed InUsed InUsed InIntention of Map UseColor Range HighColor Range LownAFSVTVT/PVCCritical Isthmus Identification424 +/- 70222 +/- 445YesYesYesDepth of Activation Insights490 +/- 300198 +/- 3010YesYesFF LAA vs NF PV EGM475 +/- 268220 +/- 256YesPV Gap Identification400 +/- 257225 +/- 286YesSlow Pathway Modification231 +/- 4345 +/- 7911YesOther**10YesYesYes Open table in a new tab

On Damping of Plasmons and Plasmon-Polaritons in Metallic Nanostructures and Its Influence onto Numerical Simulations

AbstractWe show that the damping of plasmons in metallic nanoparticles highly exceeds that caused by scattering of electrons on defects, phonons, and other electrons and on boundaries of particles. The radiation losses in far-field zone due to the Lorentz friction is especially high at nanometre scale of metal confinement (e.g. attains the maximum at ca. 100 nm diameter of particle, Au in vacuum). This causes a different e-m response of such size structures in comparison to conventional solution of Maxwell-Fresnel equations using the bulk dielectric function for metal. The strong discrepancy occurs also if plasmons are coupled in near-field zone to nearby-located absorbing medium, e.g. semiconductor substrate. This coupling cannot be accounted for by classical electrodynamic treatment (e.g. by numerical solution of Maxwell equations by finite element method for differential equation solution) and needs the application of quantum Fermi golden rule to estimate plasmon damping and related modifications of dielectric functions both of metallic nanoparticles and of absorbing medium. Similarly, the perfect cancellation of radiative losses of plasmon-polaritons in metallic nano-chains is beyond classical Maxwell equation modelling, as it reveals the perfect vanishing of Lorentz friction losses in chain segments by radiative contribution from other segments in near-, medium- and far-field zones. This demonstrates that nano-plasmonic effects cannot be reliably numerically modelled using material parameters from conventional packets referred to optical constants measured in bulk.

Experimental study on hydraulic fracture propagation in heterogeneous glutenite rock

To understand the fracture behavior and discuss the possibility of the reservoir-stimulated volume concept on glutenite rock, true triaxial hydraulic fracturing experiments were performed on glutenite rocks with acoustic emission monitoring. Experimental results indicate that a curved hydraulic fracture (HF) can be created. In addition, in situ stress plays the greatest role in HF propagation direction regardless of gravel characteristics; however, the gravel with high mechanical strength could affect hydraulic fracture path locally. Intense fluctuate extension pressure and discrete surged acoustic emission (AE) events not only occur during the breakdown stage but also during the shut-in stage, indicating embedded gravels tend to influence HF process. The breakdown pressure is the highest for sample with low horizontal stress difference, while breakdown pressure for large-size sample with small gravel numbers is the lowest. The highest AE amplitude can be observed for sample where fracture positions on gravels are at the initial stage, while continuous high AE amplitude is observed for samples with high pump rates during the entire process, indicating intense fracture and gravel interactions. Moreover, four possible interaction behaviors between HF and gravels, namely, fracture penetration, deflection, diversion and arrest, can be identified near wellbore and far-field failure zones. In general, fracture penetration behavior is exclusively observed within the near wellbore failure zone. Additionally, the fracture width for a penetration fracture is the largest due to high fracturing energy, while fracture diversion and arrest exhibit the smallest fracture width. Given the existence of gravels, branch fractures are difficult to merge with residual fracturing energy. An extremely coarse HF surface and tortuous HF path can be found for all samples; thus, the selection of a suitable pump rate and fracturing fluid is necessary to migrate near wellbore tortuosity.

Modified multipoles in photonics

Multipole decomposition method is a promising tool for investigation of radiating or scattering responses of electromagnetic sources or particles. It works even in the case of relatively complicated and compound scatterers like multilayer particles, clusters, or asymmetrical systems. Commonly, the radiation fields of point electric or magnetic sources are decomposed only into electric or magnetic dipole moments, while real sources can be described by a series of multipoles, including higher multipoles and toroidal moments. In this paper, we introduce the concept of modified multipoles describing real sources of electric, magnetic, and toroidal types. Using the analytical expressions of first-order multipoles, we discuss how they depend on the position of the center of radiation, as well as on the shift of the source, relative to the center of coordinates. We present results of multipoles for the sources with defects and asymmetry. The long-awaited question about distinguishing radiation patterns of electric and toroidal dipole moments in a far-field zone is discussed and solved in this paper. We show that radiation patterns of shifted electric and toroidal dipoles can be rotated to different angles relative to each other due to shifting. Moreover, we discuss modified anapoles. Our modified dipole approach will be useful for multipole analysis of complex systems in photonics such as nanoparticle clusters, metamaterials, and nanoantennas, as well as for better understanding issues of toroidal electrodynamics.

Estimation of the Parameters of Focused Beams at Short Distances for Antennas of Diffraction Radiation at the Millimeter-Wave Band

The article considers the results of experimental studies of the parameters of focused beams formed in W-band planar antennas of diffraction radiation using an axial dielectric lens and at focal lengths from tens of centimeters to several meters. The focusing of the beam was carried out utilizing a set of replaceable dielectric lenses with a calculated focusing distance of 1,5 m, 3 m, and 6 m. The focusing mode was also considered with two lenses installed in series, jointly providing focusing of the beam at a distance of about 0,8 m. Evaluation of the operating parameters of an electrodynamic system consisting of a planar dielectric waveguide and a planar diffraction grating both located near an inhomogeneity in the form of a dielectric layer with a variable profile (thickness), which is an axial dielectric lens, was the main aim of the researches, as well as the effect of this inhomogeneity on the quality of the formed focused beams under conditions of changes in the distance (depth of field) in the imaging mode, when the beam is inflected from the lens axis, as well as when the operating frequency changes over a wide range of values. In the course of the research, it was found that dielectric lenses with an axial profile made of high-quality polystyrene or PTFE provide the parameters of focusing antenna beams for the developed antennas of diffraction radiation following theoretical calculations, both in the focusing depth and in the mode of beam inflection from the lens axis up to  9 while changing the frequency in the range of 84100 GHz. In this case, the level of the measured side lobes in the generated beams practically did not differ from the similar values obtained for these antennas during their measurement in the open space (in the far-field zone). At a focal length of 75 cm, the transverse dimension of the focused beam was estimated as 35 mm, which approximately corresponds to the radiation wavelength and demonstrates a high focusing quality approaching the theoretically possible diffraction limit and also indicates a weak influence of the inhomogeneity in the form of a dielectric lens on the electrodynamics properties of the antenna of diffraction radiation.

OMNIDIRECTIONAL MILLIMETER-WAVELENGTH ANTENNAS BASED ON SEGMENTAL DIELECTRIC RESONATORS WHICH SUPPORT WHISPERING GALLERY MODES

Subject and Purpose. The subject of investigation is a new class of resonant-type transmit antennas intended for operation at millimeter wavelengths. The model under consideration is based on the idea of diffractional re-emission of waves into the azimuthal direction by local inhomo-geneities of the basically cylindrical structure. The purpose of the work is to justify the possibility of using such an effect for creating antennas with a circular radiation pattern, and to suggest an appropriate design. Methods and Methodology. The research program included both experimental work and application of advanced computer simulation techniques. The modern methods employed have allowed studying electromagnetic field distributions both in internal domains of the dielectric resonators and in the far-field zones of the resonator-based antennas. Results. Design solutions have been proposed for resonant-type, omnidirectional transmit antennas to operate in the millimeter waveband. The characteristic parameters are sizes of their radiating elements, specifically the segmental members equidistantly disposed along the azimuthal direction on the cylindrical surfaces of dielectric disks. The radiational characteristics of such antennas, with segments of either localized or extended dimension (compared with the operating wavelength) have been investigated. Electric field intensity distributions in the far-field region and the respective gain factors of the antennas have been studied. Conclusions. The antennas based on segmental dielectric resonators have been shown to form multi-lobe radiation patterns covering the angular sector of 0–360 along the azimuth. By placing the local segments at the resonant field’s antinodes (of the operating mode) it is possible to achieve relatively high values of the gain, reaching 15.5 dB at the lobe maxima

Experimental modeling of far-field effects in buried pipelines subjected to reverse faulting

Buried pipelines often traverse a broad geographical area and are subject to permanent ground deformations (PGDs) induced by fault movement, lateral spreading, or landslides. These PGDs distort the pipeline locally and mobilize the soil resistance along the pipe interface and outside of the affected area. This study primarily investigates the influence of far-field and transitional soil-pipe resistance on the response of pipelines crossing reverse fault regions. A series of 2.5 m long, one-tenth experimental-scale buried pipelines, representing 60 cm diameter steel pipe at 1.5 m depth prototype in cohesionless sandy soil was subjected to reverse faulting movement. The reverse faulting was simulated by a split-box apparatus under 1g conditions. The end-joint fixities should represent the far-field and transitional effects in full-scale pipes. Four scenarios of far-field and transitional effects were simulated using different pipe-end fixities: (1) free: movement of the pipe end is free in all three directions, (2) axially-free: pipe ends movement is axially free but radially fixed, (3) axially-fixed: pipe end movement is axially fixed and radially constrained by springs, and (4) spring-restrained: pipe end movements are axially and radially restrained by springs. For representing axial soil-spring forces in far-field and transitional zones, two methods were considered: a) the axial soil-spring forces recommended by ASCE (1984) guidelines; and b) an analytical-experimental method that is a combination of an analytical solution, proposed by Vazouras et al. (2015), and a series of pull-out tests, conducted in this study. The radial springs were designed based on ASCE (1984) guideline for both Scenarios of 3 and 4. The results show that the boundary conditions of the pipe have a significant effect on the mode of failure and required fault offset for occurrence of such failure mode. It is also indicated that the ASCE (1984) guideline recommendations on the axial soil-spring representation results in less soil resistance than analytical-experimental method in far-field zone, which may result in a non-conservative estimation of the pipeline performance in fault zones.

Effects of multi-color femtosecond laser beams and external electric field on transition-Cherenkov THz radiation

Terahertz (THz) radiation via transition-Cherenkov mechanism through effects of multi-color femtosecond laser beams and an external electric field is investigated. In this scheme, the electromagnetic radiation driven by the nonlinear longitudinal current density during two- and three-color filamentation has been evaluated. Variations of the electric field of generated THz waves based on the number of harmonics have been considered. The findings indicate that the addition of the second and third harmonic of laser pulse enhances the THz radiation of filament. The superposition of harmonics of the laser pulse increases the dipole-like current density behind the ionization front, and when the velocity of the ionization front exceeds the light speed, the enhanced Cherenkov radiation electric field generates stronger THz radiation in the far-field zone. The angular distribution of radiation pattern in the forward direction was obtained, and the effects of different parameters on generated THz wave patterns were examined. The polarization of laser pulses and the ionization rate as well as the length of filament play a crucial role in the generation of peak frequency and bandwidth of the THz radiation spectrum. The present study shows that an external electric field induces more dipole-like current density leading to an increase in radiation power with no change in directivity.

Constrained Mode–Damping Solvent Extraction Combined Method for the Soil Incorporation into a Real-Time Hybrid Test of the Soil–Structure System

The real-time hybrid test is an effective testing method for soil–structure interaction research. Due to the data interaction time requirement and formula derivation method, the traditional real-time hybrid test of soil–structure interaction mostly employs a simple numerical substructure model. This study investigated the model construction and numerical simulation of a finite element soil substructure with high simulation accuracy and calculation efficiency. The soil was subdivided into near-field and far-field zones. A constrained mode–damping solvent extraction combined method was applied to the latter zone, reducing the soil’s computational scale and simulating the far-field energy dissipation effect. Then, the basic formula of the near-field zone–structure system was derived using the branch mode method, and the motion equation of the soil–structure system applied to real-time hybrid test was obtained. The soil’s numerical model was realized by the joint application of ANSYS and MATLAB software packages and verified through the real-time hybrid test of the soil–structure system. The results show that the proposed constrained mode–damping solvent extraction combined method had high calculation efficiency and good accuracy. It satisfied the requirements of the soil numerical substructure in real-time hybrid tests.

Ultra-wideband and high-performance microwave vortex beam generator based on single-layer Pancharatnam–Berry metasurface with stacked-arc-shaped meta-atoms

Vortex beam carrying orbital angular momentum (OAM) reveals essential application potential in regimes ranging from communication to high-resolution imaging due to the capability to expand channel capacity. However, many current methods for generating vortex beams suffer from narrow bandwidth, low efficiency, and high profile, which undoubtedly will limit their practical application. In this paper, a microwave ultra-wideband single-layer Pancharatnam–Berry metasurface is proposed to convert incident plane waves into vortex waves. The proposed novel stacked-arc-shaped meta-atoms of the metasurface can realize high-performance spin angular momentum-OAM conversion with the efficiency of more than 83% within a considerable bandwidth from 5.85 to 19.56 GHz (fractal bandwidth of 108%), which achieves high-efficiency operation within a wider bandwidth compared to some other wideband metasurface-based vortex beam generator. Three metasurface prototypes for generating vortex beams with the topological charges of l = ±2, −1, −3 respectively are designed. In addition, a metasurface for generating a vortex beam with the topological charge of l = ±2 is fabricated as an example to demonstrate the feasibility and high performance of our vortex beam generator. The generated vortex beams with the mode order of ±2, −1, −3 both in the near-field and the far-field zone are simulated theoretically and the generated vortex beam with the mode order of l = −2 is measured experimentally. The results of the simulation and experiment coincide with each other, which verified the proposed vortex beam generation method successfully. The proposed vortex beam generator is valuable and user-friendly in practical application because of the advantages of low profile, ultra-wide bandwidth, high efficiency, and easy fabrication.

Rayleigh-Sommerfeld scalar diffraction by rotating apertures

We have analytically explored the Rayleigh-Sommerfeld scalar diffraction for various rotating apertures such as rotating single-slit, rotating double-slit, rotating linear diffraction grating, and rotating regular polygonal aperture. Here the apertures are considered to be uniformly rotating along the axes perpendicular to the plane of the apertures and the diffracted fields are analysed in the far-field zone. We have compared the time-averaged intensity distributions for the rotating apertures with the intensity distributions for static circular apertures of the same area. We also have obtained angular speed of rotation dependent Fraunhofer diffraction formulae for the rotating apertures, in particular, the rotating single-slit, the rotating double-slit, and the rotating linear diffraction grating.

3D structure-soil-structure interaction in an arbitrary layered half-space

The aim of the study is to evaluate the 3D dynamic response of a finite geological region containing two structures and rested on a semi-infinite elastic layered half-space with a dynamic source radiating transient waves. The hybrid modelling approach is applied. It is based on the decomposition of the whole domain under consideration into two sub-regions: a finite-sized near-field elastic isotropic zone with two containment structures and the open semi-infinite far-field layered region. The far-field zone is a semi-infinite elastic isotropic arbitrary layered medium where the near-field finite geological region is located on. The 3D hybrid computational tool is based on the boundary element method (BEM) for the far-field layered zone and the finite element method (FEM) for the finite near-field domain. The model for the semi-infinite layered zone is further extended by the incorporation of a new condensation algorithm which makes it possible to handle 3D wave propagation through arbitrary layered half-space. The condensation algorithm is developed to avoid high computational memory cost while retaining the compatibility with the hybrid FEM-hosted procedure which facilitates the useful solution for the practical three-dimensional engineering problems. The BEM model of the dynamically active far-field zone is inserted as a macro-finite element (MFE) in the FEM commercial program ABAQUS. The accuracy and convergence study of the hybrid numerical scheme is presented. Numerical simulations convincingly illustrate that the dynamic response of structure-soil-structure system depends on different key factors and their mutual interplay. These factors are arbitrary layering of the far-field geological zone, the characteristics of the dynamic source, the site effects phenomena, the structure-soil-structure dynamic interaction, the type and geometrical disposition of foundations and structures and the 3D features of the dynamic motion.