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This work presents an approach to the fast determination of a medical accelerator irradiation isocenter as a quality assurance (QA) procedure in radiotherapy. The isocenter determination tool is the tissue equivalent high-resolution 3D polymer gel dosimeter (PABIGnx) in a dedicated container combined with kilovoltage imaging systems and the polyGeVero-CT software package (v. 1.2, GeVero Co., Poland). Two accelerators were employed: Halcyon and TrueBeam (Varian, USA), both equipped with cone beam computed tomography (CBCT) and iterative reconstruction CBCT (iCBCT) algorithms. The scope of this work includes: (i) the examination of factors influencing image quality (reconstruction algorithms and modes), radiation field parameters (dose and multi-leaf collimator (MLC) gaps), fiducial markers, signal averaging for reconstruction algorithms and the scanning time interval between consecutive scans, (ii) the examination of factors influencing the isocenter determination, image processing (signal averaging, background subtraction, image filtering) and (iii) an isocenter determination report using a 2D and 3D approach. An optimized protocol and isocenter determination conditions were found. The time and effort required to determine the isocenter are discussed. [ABSTRACT FROM AUTHOR]

A new approach for solving the fractal Euler-Bernoulli beam equation is proposed. The mapping of fractal problems in non-differentiable fractals into the corresponding problems for the fractal continuum applying the fractal continuum calculus ( F d H 3 -CC) is carried out. The fractal Euler-Bernoulli beam equation is derived as a generalization using F d H 3 -CC under analogous assumptions as in the ordinary calculus and then it is solved analytically. To validate the spatial distribution of self-similar beam response, three different classical beams with several fractal parameters are analysed. Some mechanical implications are discussed. [ABSTRACT FROM AUTHOR]

In this paper, a differential quadrature method of high-order precision (DQ−Pade), which is equivalent to the generalized Pade approximation for approximating the end of a time or spatial interval, is used to solve nonlinear fully intrinsic equations of beams. The equations are a set of first-order differential equations with respect to time and space, and the explicit unknowns of the equations involve only forces, moments, velocity and angular velocity, without displacements and rotations. Based on the DQ−Pade method, the spatial and temporal discrete forms of fully intrinsic equations were derived. To verify the effectiveness and applicability of the proposed method for discretizing the fully intrinsic equations, different examples available in the literatures were considered. It was found that when using the DQ−Pade method, the solutions of the intrinsic beam equations are obviously superior to those found by some other usual algorithms in efficiency and computational accuracy. [ABSTRACT FROM AUTHOR]

We introduce and investigate a novel Laguerre-Gaussian (LG) beam, different from the conventional modal LG beams, which conserve the transverse intensity structure (up to scale) on propagation. The proposed beam does not conserve its structure on free space propagation but possesses some interesting properties. This beam is Fourier-invariant, and it has an increased dark area both in the initial (waist) plane and in the far field. Thus, without changing the topological charge of the beam, varying the radial (lower) index of the associated Laguerre polynomial allows increasing or decreasing the effective diameter of the central dark spot in the intensity pattern. In addition, the beam is autofocusing, i.e., the intensity distribution at the Rayleigh distance from the waist has a shape of the light ring (at any value of the radial index) with the minimal diameter and with the maximal on-ring intensity. Such a beam can be adopted for microparticle manipulation. Increasing the dark area in the focus of a high-aperture spherical lens allows the simultaneous trapping of several absorbing microparticles into this dark area. [ABSTRACT FROM AUTHOR]

We retrieve unknown nonlinear large space-time dependent forces burdened with the vibrating nonlinear Euler-Bernoulli beams under varied boundary data, comprising two-end fixed, cantilevered, clamped-hinged, and simply supported conditions in this study. Even though some researchers used several schemes to overcome these forward problems of Euler-Bernoulli beams; however, an effective numerical algorithm to solve these inverse problems is still not available. We cope with the homogeneous boundary conditions, initial data, and final time datum for each type of nonlinear beam by employing a variety of boundary shape functions. The unknown nonlinear large external force can be recuperated via back-substitution of the solution into the nonlinear Euler-Bernoulli beam equation when we acquire the solution by utilizing the boundary shape function scheme and deal with a smallscale linear system to gratify an additional right-side boundary data. For the robustness and accuracy, we reveal that the current schemes are substantiated by comparing the recuperated numerical results of four instances to the exact forces, even though a large level of noise up to 50% is burdened with the overspecified conditions. The current method can be employed in the online real-time computation of unknown force functions in space-time for varied boundary supports of the vibrating nonlinear beam. [ABSTRACT FROM AUTHOR]

Due to their unlimited shelf life, high impact resistance, recyclability, and fast processing time, the use of carbon fibers in combination with a thermoplastic matrix promises a fiber metal laminate (FML) with improved properties and potentially automated series production. Accordingly, the formability and performance of fast forming technologies, i.e., the hot stamping of thermoplastic FMLs, are increasingly attracting research interest. In this study, a new one-step hot stamping process is first proposed to produce curved thermoplastic FML beams fabricated by Al sheets, PEEK films, and CF/PEEK prepregs (Al/CF/PEEK). Then, the effects of the forming temperature and punching speed on the formability, as well as on the performances of the curved beams, i.e., their macro- and micro-defects, interlaminate strength and failure, thickness distribution, and spring-back, are experimentally investigated via SEM observations, four-point bending tests, and digital image correlations. It is found that curved Al/CF/PEEK laminate beams with the least spring-back (<0.2°) and thickness reduction (<0.2 mm), the fewest defects, the highest curved beam strength (195 N·mm/mm), and the highest interlaminate strength (16.5 MPa) can be produced under the forming temperature of 380°C and punching speed of 10 mm/s. [ABSTRACT FROM AUTHOR]

Slippery liquid‐infused porous surface (SLIPS) has shown great application prospects because of the great liquid repellency and ice resistance. However, there are a few types of research on different metal material to fabricate SLIPS. Here, a simple and effective method is developed on a stainless steel surface to manufacture microporous structure by femtosecond Bessel laser beam direct induce. By fluoroalkylsilane modification and infusing lubricant, SLIPS is successfully obtained. The ice restraint properties of the SLIPS are studied, including the characterization of icing delay and ice‐adhesion strength, which significantly increase the icing‐delay time and reduce the ice‐adhesion strength. Moreover, SLIPS exhibits great durability after hydraulic pressure, salt fog, high‐, and low‐temperature cycle. Based on this method, SLIPS can be produced on different metal substrates including Al, Zn, Ti, Cu with excellent liquid resistance and anti‐icing property, which greatly expand the application of SLIPS in the field of ice resistance. [ABSTRACT FROM AUTHOR]

Finite-aperture microwave vortex beams of various structures in the near-, middle-, and far-field propagation zones have been simulated. The decay of external sidelobes leading to the end of non-diffractive propagation within a fraction of the near-field zone is observed. A ring source of the vortex beams with phase-shift and frequency-sweep control of angular modes and polarization patterns through the use of patch antenna arrays of varying polarization is suggested. A new form of the beam wavefront variation with azimuthal undulation has been proposed that allows one to significantly diversify and dynamically control the beam structure. The consequences of a limited number of antenna patches in a circular array have been considered. The effects of a gradual drop of radiation power along the array and the use of multiple feed points for improving the beams have been simulated. [ABSTRACT FROM AUTHOR]

In this report, we describe a successful orthodontic treatment through the maxillary sinus and show the utility of cone-beam computed tomography (CBCT) for this procedure. A 20-year-old man with Class I molar relationships and crowding of the maxillary and mandibular anterior teeth came to us to improve his malocclusion. Maxillary molar distalization was necessary to reduce the crowding of the teeth. This was achieved by the use of temporary anchorage devices (TADs) and the uprighting of the mandibular molars. However, several roots of the maxillary molars protruded into the maxillary sinus. The maxillary sinus is a known barrier to orthodontic tooth movement, leading to root resorption and/or tipping movement. We aimed to distalize the maxillary molars through the maxillary sinus by bodily movement. The findings were three-dimensionally confirmed by using the superimposition of CBCT obtained before and after the treatment. [ABSTRACT FROM AUTHOR]

• Combination of an SLM with an axicon to generate multi-Bessel beams. • Freeform shaped micro holes. • Dynamic adaption of SLM phase holograms for highest flexibility during the process. • Quadratic shaped micro holes with sizes down to 4 μm. • Round micro holes with circularity up to 96 %. Bessel beams are advantageous tools for micro drilling applications due to their diffraction-free properties, their long focal length, and their small focal spot diameter. However, their application in industry is limited because they are challenging to integrate into flexible beam shaping systems. This work is intended to overcome limitations in flexibility by presenting a new approach paving the way to high-aspect ratio freeform holes. Therefore, a spatial light modulator was integrated into an axicon-based setup to merge diffraction-free ablation with the flexibility of holographic spatial beam shaping. A dynamic change of the phase hologram displayed on the spatial light modulator during the process allows for the generation of arbitrary ablation geometries. In contrast to other holographic approaches, the diffraction-free nature of the Bessel beam allows ablation over an extended focal depth without any focus control needed. The applicability of the approach was demonstrated by processing arbitrary hole shapes, such as ellipses, squares, or star-shapes. The hole sizes of the freeform holes range from 4 µm to 80 µm. Furthermore, up-scaling of the process is demonstrated by using the setup for generation of multi-Bessel spots. [ABSTRACT FROM AUTHOR]

In the underwater wireless optical communication (UWOC) system, strong optical scattering caused by impurity particles in the water leads to the rapid divergence of the beam. This results in a significant decrease in the received light power when using a restricted-size aperture. The challenge is overcome by utilizing a new structured optical beam called a "pin-like" beam. This beam can achieve auto-focused and evolve into a Bessel-like beam, which has a narrow beam size. To demonstrate the capabilities of this system, we conducted experiments using a structured anti-diffraction pin-like beam and a pin-like vortex beam with a limited-size receiver (Rx) aperture achieving a 5Gbit/s OFDM underwater wireless communication link. In our experiments, we directly modulated 16QAM-OFDM signals into a 520 nm laser. The Gaussian beam with a half maximum (FWHM) of 1.4 mm was converted into zero-order Bessel, pin-like and pin-like vortex +2 beams using a spatial light modulator (SLM). The experimental results showed that compared to conventional Gaussian and Bessel beams, the pin-like beam reduced the optical power loss (OPL) in UWOC with an Rx aperture diameter of 1 mm by 3.65 dB and 1.8 dB, respectively. Similarly, the OPL decreased by 2.05 dB and 1.1 dB, respectively, for pin-like vortex +2 beams. [ABSTRACT FROM AUTHOR]

As laser applications continue to advance, other spatial intensity distributions that are not Gaussian are increasingly being used. For instance, Bessel beams, which have a small diameter and a very long focal zone allow the fabrication of high aspect ratio modifications in transparent materials. Higher-order Laguerre–Gauss modes are used in particle manipulation and even for multiplexing in optical communication. However, pulse shaping, apart from pulse compression, has been overlooked but can lead to laser micromachining, particle manipulation, and improvements in optical communication quality and efficiency. In this paper, we demonstrate a method of constructing a helical intensity distribution beam that is modified in space and time. In space, it comprises a different number of intensity maxima, while in the time domain, it exhibits rotation around the propagating axis. We show the numerical simulations of the resultant beam and a way of realizing such a beam experimentally. Results show a tunable rotation speed helical beam with angular speeds up to at least 4.5 mrad/fs. With the increase of the pulse energy, these beams show potential for material ablation applications. • Novel dynamic helical intensity pulsed beam with tunable rotation speeds up to 4.5 mrad/fs. • Helical pulsed beams are generated by two coherent chirped pulses with different vorticity numbers. • High-efficiency beam generation using birefringent elements. • Demonstrated potential for laser material ablation with helical rotating beams. • Scalability to higher energy pulses. [ABSTRACT FROM AUTHOR]

The purpose of this investigation is to examine the properties of finite asymmetric exotic scalar (acoustic) beams with unusual properties using the angular spectrum decomposition in plane waves. Such beams possess intrinsic uncommon characteristics that make them attractive from the standpoint of particle manipulation, handling and rotation, and possibly other applications in particle clearing and separation. Assuming a specific apodization function at the acoustic source, the angular spectrum function is calculated and used to synthesize the radiated pressure field (i.e., excluding evanescent waves that decay away from the source) in the forward direction of wave motion (i.e., away from the source). Moreover, a generalized hybrid method combining the angular spectrum approach with the multipole expansion formalism in spherical coordinates is developed, which is applicable to any finite beam of arbitrary wavefront. The improved approach allows adequate computation of the resonance scattering, radiation force, and spin torque components on an object of arbitrary shape, located on or off the axis of the incident beam in space. Considering the illustrative example of a viscous fluid sphere submerged in a non-viscous liquid and illuminated by finite asymmetric beams such as the Airy and the Bessel vortex beam with fractional order, numerical computations for the scattering, radiation force, and torque components are performed with an emphasis on the distance from the source, the arbitrary location of the particle ,and the asymmetric nature of the incident field. Moreover, beamforming calculations are presented with supplementary animations for the pressure field distribution in space, with an emphasis on the intrinsic properties of the selected beams. The numerical predictions illustrate the scattering, radiation force, and spin torque properties depending on the beam parameters and the distance separating the sphere from the source. This study provides a generalized hybrid method to analyze quantitatively the scattering, radiation force, and spin torque by any finite asymmetric (or symmetric) acoustic beam with potential applications in various fields of applied physics (such as beam-forming, imaging, and mechanical effects of asymmetric sound beams). [ABSTRACT FROM AUTHOR]

In this paper, we consider a new type of Bessel beams having Fourier-invariance property and, therefore, called Fourier-Bessel beams. In contrast to the known Bessel beams, these beams have weak side lobes. Analytical expressions for the complex amplitude of the proposed field in the initial plane of the source and in the far field region have been obtained. It is shown that the proposed Fourier-Bessel beams have a finite energy, although they do not have a Gaussian envelope. Their complex amplitude is proportional to a fractional-order Bessel function (an odd integer divided by 6) in the initial plane and in the Fraunhofer zone. The Fourier-Bessel modes have a smaller internal dark spot compared to the Laguerre-Gauss modes with a zero radial index. The proposed beams can be generated with a spatial light modulator and may find uses in telecommunications, interferometry, and the capture of metal microparticles.

• A simplified model of constructing OAM-multiplexed PAV is developed based on Bessel beams. • The circular lobe distribution in pressure and phase is only determined by differences of TCs. • Intensive changes of circular phase distribution are located at lobe boundaries of pressure valleys. • The pressure peak at φ = 0 increases as the TC number with the phase slope of the mean of TCs. • The remarkable lobe distribution may advance a fast and effective method for OAM communication. Profiting from the fixed vortex-radius, perfect acoustic-vortex (PAV) beams can improve the efficiency of orbital angular momentum (OAM) communication. While, characteristics of OAM-multiplexed PAVs with more than two topological charges (TCs) have not been studied. By applying the spatial Fourier transform to Bessel beams, the principle of constructing OAM-multiplexed PAVs is developed. The characteristics of OAM-multiplexed PAVs are investigated by theoretical analyses and numerical simulations, and also demonstrated by the experimental measurement based on quasi-Bessel beams constructed by the saw-tooth phase modulation for the ring-array of sectorial transducers. Numerical and experimental studies demonstrate that the high-pressure annuli are segmented to lobes, with the lobe number equal to the difference of the maximum and minimum TCs. Circular lobe distributions of pressure and phase only rely on TC differences, which may be identical for different TC combinations. The peak-pressure of the primary lobe centered at φ = 0 increases as the increase of the included TC number, with the angular phase slope equal to the arithmetic mean of included TCs. The excellent characteristics of the TC-independent vortex-radius and the remarkable lobe distributions of pressure and phase may guide the choice of TCs for encoding and decoding, and advance a fast, effective and low-cost method for underwater OAM communication. [ABSTRACT FROM AUTHOR]

• A theoretical model of Bessel beam processing α-quartz is proposed. • Rapid evolutions in electron density and temperature affect the optical properties. • The optical penetration depth decreases rapidly at the edge of focused region. • The localized laser intensity leads to the high electron density from ionization. • A new perspective for the propagation of Bessel beam in dielectrics is presented. Femtosecond laser processing of dielectric has been widely studied. Nevertheless, a direct theoretical model for Bessel beam on α-quartz is still essential. The purpose of this study is to explore the interaction mechanism between Bessel beam and α-quartz. Bessel beam is generated by a combination of femtosecond laser Gaussian beam and beam shaping techniques. In the simulation, the optical and thermophysical properties are studied. The simulation results show that rapid evolutions in electron density and electron temperature affect the optical properties during laser energy deposition in α-quartz. In a few tens of femtoseconds, the optical properties change from transparent to opaque. The optical penetration depth rapidly drops to hundreds of nanometers at the edge of focused region during this period. Therefore, the laser intensity decreases exponentially along the propagation path. The electron density is high at the edge and low at the center of focused region. After sufficient laser energy deposition, microholes are finally formed. The ablation region is predicted by the critical electron density criterion and the critical volumetric energy density criterion. The experimental results verify the results calculated by the theoretical model. In addition, this study provides a new perspective for the theoretical modeling of Bessel beam and provides an important reference for the broad applications in the field of micro-/nano-processing. [ABSTRACT FROM AUTHOR]

• A new MAE model is established based on the coupling of helical wave fronts of Bessel beams in a coaxial toroidal magnet. • The MAE field induced by the Bessel beam of l th order is determined by those of (l -1)th and (l + 1)th orders. • The center-converging rotary MAE field with a constant peak-intensity at the center can only be constructed by the Bessel beam of 1st order. • The MAE field may advance a new synergistic stimulation strategy assisted by center-captured drug particles, with improved accuracy and reduced acoustic energy. The magneto-acousto-electric (MAE) effect shows great significance in neural modulation, whereas the high-precision stimulation cannot be realized by the unidirectional electric distribution perpendicular to the orthogonal acoustic and magnetic fields. A new MAE model is established based on helical wave fronts of Bessel beams in a coaxial magnetic field. Numerical and experimental studies are conducted for quasi-Bessel beams constructed by the saw-tooth phase modulation for a sectorial planar transducer array in a coaxial toroidal magnet. The MAE field induced by the Bessel beam of l th order is determined by those of (l -1)th and (l + 1)th orders. The rotary MAE field with a constant peak-intensity center can only be constructed by the Bessel beam of 1st order, which is effective for neural stimulation. Assisted by therapeutic effects of center-captured drug particles by acoustic-vortex tweezers, the center-converging MAE field may advance a new collaborative stimulation strategy with improved accuracy and reduced acoustic energy. [ABSTRACT FROM AUTHOR]

Vortex beams with orbital angular momentum (OAM) have infinite mode orthogonality, which can greatly boost communication capacity through mode-division multiplexing. However, current exploration of OAM beam transmission primarily focuses on free-space or specialty fibers limited by the OAM spiral phase wavefront characteristics. Due to the mode field phase sensitivity, these methods are constrained by turbulence interference and fabrication error tolerance, restricting transmission distance of OAM beam at practical application. Herein, we propose an OAM transmission scheme using commercial multimode fiber (MMF) exploiting the eigenmodes superposition theory. Leveraging linear superposition of HE and EH vector modes with ± (π/2) phase shift over MMF, OAM excitation and transmission can be supported with low interference. Simultaneously, due to the decreased demand for fabrication precision in the gradient core structure, the tolerance for machining errors is enhanced. As a proof-of-concept, we have demonstrated a multidimensional OAM multiplexing communication with 640-channel (4 OAM modes, 80 wavelengths and 2 polarization states) over a 5 km MMF, successfully transmitting QPSK-OFDM signals at a total rate of 15 Tbit/s. The system demonstrated OAM mode purity exceeding 65% and bit error rate (BER) below the forward error correction (FEC) threshold (3.8 × 10−3). Multiplexed OAM signals can be effectively transmitted in MMF over short to medium distances with acceptable mode crosstalk, while remaining compatible with wavelength and polarization dimensions, enabling the construction of multi-dimensional multiplexing local area networks. • Exploiting the eigenmodes superposition theory, an OAM transmission scheme using commercial multimode fiber was proposed. • A 640-channel multi-dimensional OAM multiplexing system is constructed over 5-km MMF. • 15 Tbit/s QPSK-OFDM signals are successfully transmitted withBERs below the FEC threshold and pattern purity above 65%. • The BERs are reduced by about 2 orders of magnitude after LDPC encoding for channel equalization. [ABSTRACT FROM AUTHOR]

The Flat-topped Vortex (FTV) beam has shown remarkable utility in a diverse range of industrial procedures, primarily attributed to its central intensity plateau. Nevertheless, the substantial potential of the FTV beam in particle trapping and manipulation has been largely underappreciated. In this work, we conducted the first study on the focusing properties and dynamic characteristics of the Flat-topped double vortex (FTDV) beam under different polarization for the absorption of Rayleigh particles. Through superimposing linearly two FTV beams with equal but opposite topological charges, the FTDV beam emerged naturally. Moreover, a comprehensive numerical analysis was subsequently performed to decode the interactions between the focusing field of the FTDV beam and Rayleigh particles. The analysis demonstrated that the focusing field of FTDV beam can perform multi-particle capture and effectively manipulate particles by modulating the topological charge | m | , the flatness order n , and the polarization state of the FTDV. Furthermore, a comparison between the focusing field of FTDV beam with that of vector vortex (VV) beam revealed that the FTDV beam was capable to generate spin angular momentum (SAM) density and spin torque at least an order of magnitude higher. These findings highlight the superior capabilities of FTDV beam in optical manipulation, and provide essential theoretical support for its utilization in particle capture and management. • The focusing and dynamic characteristics of FTDV beam are investigated for the first time. • The tightly focused FTDV beam can generate a larger SAM density and spin torque. • The mechanical state of the trapped particles can be effectively regulated by controlling the topological charge.|m|, the flatness order n, and the polarization state of the FTDV beam. [ABSTRACT FROM AUTHOR]

In view of the powerful light field manipulation ability of metasurface and the wide applications of Bessel beams, parallel Bessel beams are generated based on a simple metasurface design. The proposed metasurface consists of cross nanoholes and the orders of the generated parallel Bessel beams can be modulated. Theoretical analysis provides the detailed design principle of metasurface to generate parallel Bessel beams. Parallel Bessel beams and parallel cosine Bessel beams are generated and the simulation and experimental results give the verification. With respect to the single Bessel beam, the generated parallel Bessel beams with controllable orders may bring more conveniences for the applications of Bessel beams. The simple geometry, parallel output and the controllable order will inspire wider applications of Bessel beams. • The method to generate parallel Bessel beams and cosine Bessel beams is proposed based on focusing axicon lens. • The metasurface consisting of nanoholes regulate light field into parallel Bessel beams or cosine Bessel beams. • The orders of parallel Bessel beams can be effectively controlled by changing the rotation angles of nanoholes. [ABSTRACT FROM AUTHOR]

• We have presented the equivalency between MF-LS and GLS by investigating the influence of different parameters. We investigated the influence of various parameters applied to MF-LS and GLS on imaging results through theoretical simulation. Consequently, MF-LS and GLS demonstrated an "equivalent" imaging performance when matching specific parameters. • We have also designed experiments to verify the "equivalent" conclusion by imaging fluorescent microspheres and biological samples. We found that MF-LS exhibited similar imaging performance with GLS when no extra-processing such as rolling shutter or subtraction were employed. • We anticipate that the petal lobes of MF-LS will resemble those of Bessel beam, Airy beam, and other patterns. However, due to the irregular distribution of side lobes, deconvolution becomes more complex. Nevertheless, benefiting from the uniform beam distribution, MF-LS holds great potential in multi-photon imaging. Overlapped multi-focus light sheet (MF-LS) along beam propagation microscope has generated significant interest due to its reportedly superior axial resolving power when compared to conventional Gaussian light sheet (GLS) systems. By axially overlapped multiple light sheets in the illumination path, it would weld the combined field of view (FOV) and be wider than stationary counterparts. However, the effect of diffractive energy entering the focal space of desired beam, impacting the optical sectioning capabilities of the system has not been studied. It introduces the question that does a MF-LS performance better than standard GLS? Here we quantitatively and systematically analyzed the properties between optimized MF-LS and traditional GLS on z -axis resolution, signal to background ratio (SBR), and FOV. We first optimized the MF-LS by analyzing the diffractive energy to acquire the best sectioning capability. Then, we demonstrated a comparable optical sectioning performance between the two types of LS when matching with specific optical parameters including the illumination numerical aperture (NA) and foci numbers. A novel equation has been proposed to describe the equivalence relation. Analysis in the research suggests "putative FOV-extension" characteristics of MF-LS due to energy effects and interference between beams. Finally, we performed simulation and imaging experiments approaches on both fluorescence microspheres and biological samples to validate the viewpoint of this research. [ABSTRACT FROM AUTHOR]

The Polarization Topological Charge (PTC) is a crucial parameter of a Cylindrical Vector Beam (CVB). Defined as the repetition number of polarization state changes along the azimuth axis, its sign indicates the polarization's rotation direction. This paper delves into the effects of polarization mutation within Fractional Vector Beams (FVB) with angular uncertainty on PTC sorting systems. We compare three optical geometric coordinate transformation methods: Log-Polar (LP), Beam-Copying (BC), and Spiral Transformation (ST), focusing on their robustness and suitability. Our findings show that the azimuth angle of polarization mutation markedly influences the PTC sorting system's output, leading to measurable uncertainties. Importantly, these uncertainties are not intrinsic to the FVB, but rather stem from the sorting system itself. Our study concludes that the BC method is optimal for PTC spectra analysis, whereas the ST method with carefully selected parameters is preferable for average PTC analysis. [ABSTRACT FROM AUTHOR]

• Quasi-Bessel beam generation by an axicon with an exponential phase function. • Theoretical calculation of quasi-Bessel beam propagation by a phase-modified axicon. • Phase parameter optimization for a uniform axial-intensity-profile Bessel beam. • Experimental demonstration of a quasi-Bessel beam by a phase-modified axicon. A simple phase function for a diffractive axicon to allow generation of a quasi-Bessel beam with a uniform axial intensity profile is reported. By adding the new exponential phase function for the diffractive axicon, we theoretically show that a quasi-Bessel beam with a uniform axial intensity profile can be generated without amplitude oscillation or energy loss. We apply this spatial phase function to a spatial light modulator, illuminated by a fundamental Gaussian laser beam, and produce a quasi-Bessel beam with a long, uniform axial intensity profile, which is in very good agreement with theoretical calculation. Dependence of the phase parameters on the axial intensity profile and their optimization are discussed. [ABSTRACT FROM AUTHOR]

In this article, we propose a three‐dimensional meshing algorithm for discrete models combining the lattice approach with the polyhedral particle approach. Our aim is to be able to leverage readily available, well‐supported meshers to handle various geometries. We use them to generate a tetrahedral mesh, which our mesher then converts to a polyhedral mesh. The input mesh serves as geometrical support to generate the nodes of the discrete mesh. The desired shape is obtained with an assembly of convex polyhedral particles—without having to clip them. We show that this approach enables meshing convex or concave geometries with sharp edges, curved features, and more. Several three‐dimensional geometries are presented to support this claim and illustrate the capabilities of the mesher. We provide a detailed analysis of its isotropy. The geometric isotropy is studied by analyzing the orientation of the generated beams. The mechanical isotropy is verified by assessing the properties of the elasticity tensor. Finally, we show that the new mesh retains its ability to be a good support for the generation of realistic cracking patterns. [ABSTRACT FROM AUTHOR]

In most cases, openings are made in the Web of deep beams for installations to pass through. These members require to be strengthened since the openings reduce load-bearing capacity. This study utilizes carbon fiber-reinforced polymer (CFRP) composites and steel protective frames (SPF) as strengthening configurations in reinforced concrete (RC) deep beams to improve the strength lost due to the square openings. To this end, eleven specimens with 10 × 50 × 120 cm in size were subjected to the three-point monotonic loading. In each beam, one or two square openings of 18 cm in each side are positioned either symmetrically or asymmetrically along the beam before it is strengthened with CFRP composites or SPFs. The strengthening composites were installed using externally bonded reinforcement (EBR) or externally bonded reinforcement on grooves (EBROG) techniques in two wrapped or inclined configurations. The obtained results indicate that specimens retrofitted by the SPF exhibited a superior performance as their loading capacity and energy absorption were enhanced by 115% and 337% in comparison with the reference beam, respectively, while these values for the specimens retrofitted by the EBROG technique were 58% and 182%, respectively, and 42% and 105% for those strengthened with the EBR technique. [ABSTRACT FROM AUTHOR]

Cone-beam computed tomography (CBCT) has been shown to be a powerful tool for 3D imaging of the appendicular skeleton, allowing for detailed visualization of bone microarchitecture. This study was designed to compare artifacts in the presence of osteosynthetic implants between CBCT and multidetector computed tomography (MDCT) in cadaveric wrist scans. A total of 32 scan protocols with varying tube potential and current were employed: both conventional CBCT and MDCT studies were included with tube voltage ranging from 60 to 140 kVp as well as additional MDCT protocols with dedicated spectral shaping via tin prefiltration. Irrespective of scanner type, all examinations were conducted in ultra-high-resolution (UHR) scan mode. For reconstruction of UHR-CBCT scans an additional iterative metal artifact reduction algorithm was employed, an image correction tool which cannot be used in combination with UHR-MDCT. To compare applied radiation doses between both scanners, the volume computed tomography dose index for a 16 cm phantom (CTDIvol) was evaluated. Images were assessed regarding subjective and objective image quality. Without automatic tube current modulation or tube potential control, radiation doses ranged between 1.3 mGy (with 70 kVp and 50.0 effective mAs) and 75.2 mGy (with 140 kVp and 383.0 effective mAs) in UHR-MDCT. Using the pulsed image acquisition method of the CBCT scanner, CTDIvol ranged between 2.3 mGy (with 60 kVp and 0.6 mean mAs per pulse) and 61.0 mGy (with 133 kVp and 2.5 mean mAs per pulse). In essence, all UHR-CBCT protocols employing a tube potential of 80 kVp or more were found to provide superior overall image quality and artifact reduction compared to UHR-MDCT (all p <.050). Interrater reliability of seven radiologists regarding image quality was substantial for tissue assessment and moderate for artifact assessment with Fleiss kappa of 0.652 (95% confidence interval 0.618–0.686; p < 0.001) and 0.570 (95% confidence interval 0.535–0.606; p < 0.001), respectively. Our results demonstrate that the UHR-CBCT scan mode of a twin robotic X-ray system facilitates excellent visualization of the appendicular skeleton in the presence of metal implants. Achievable image quality and artifact reduction are superior to dose-comparable UHR-MDCT and even MDCT protocols employing spectral shaping with tin prefiltration do not achieve the same level of artifact reduction in adjacent soft tissue. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the 6D inter-fraction tumour localisation errors in 20 tongue and 20 prostate cancer patients treated with intensity-modulated radiation therapy and volumetric-modulated arc therapy. The patient tumour localisation errors in lateral, longitudinal and vertical translation axes and pitch, roll and yaw rotational axes were analysed by automatic image registration of daily pretreatment kilovoltage cone-beam computed tomography (kV-CBCT) with planning CT in 1000 fractions. The overall mean error (M), systematic error (Σ), random error (σ) and planning target volume (PTV) margins were evaluated. The frequency distributions of setup errors were normally distributed about the mean except for pitch in the tongue and prostate. The overall 3D vector length ≥ 5 mm was 14.2 and 49.8% in the ca-tongue and ca-prostate, respectively. The frequency of rotational errors ≥1 degree was a maximum of 37 and 59.5%, respectively, in ca-tongue and ca-prostate. The M , Σ and σ for all translational and rotational axes decreased with increasing frequency of verification correction in ca-tongue and ca-prostate patients. Similarly, the PTV margin was reduced with no correction to alternate day correction from a maximum of 4.7 to 2.5 mm in ca-tongue and from a maximum of 8.6 to 4.7 mm in ca-prostate. The results emphasised the vital role of the higher frequency of kV-CBCT based setup correction in reducing M , Σ , σ and PTV margins in ca-tongue and ca-prostate patients. [ABSTRACT FROM AUTHOR]

This article presents a novel total Lagrangian cell‐centered finite volume formulation of geometrically exact beams with arbitrary initial curvatures undergoing large displacements and finite rotations. The choice of rotation parameterization, the mathematical formulation of the beam kinematics, conjugate strain measures, and the linearization of the strong form of governing equations are described. The finite volume based discretization of the computational domain and the governing equations for each computational volume are presented. The discretized integral form of the equilibrium equations is solved using a block‐coupled Newton–Raphson solution procedure. The efficacy of the proposed methodology is presented by comparing the simulated numerical results with classic benchmark test cases available in the literature. The objectivity of strain measures for the current formulation and mesh convergence studies for both initially straight and curved beam configurations are also discussed. [ABSTRACT FROM AUTHOR]

Laser-based amorphization on the back surface of a 525-μm thick crystalline silicon sample is studied. To deposit sufficient energy for a local change from a crystalline to an amorphous state, laser irradiation at 2-μm wavelength with 25-ps pulse duration is combined with Bessel beam shaping. Deterministic single-site modifications and homogeneous continuous lines of amorphous silicon are demonstrated. Optical and electron microscopy together with Raman spectroscopy measurements highlight the material transformations featuring the formation of subwavelength periodic surface structures. The investigations open up possibilities for processing in-built microelectronic devices. [ABSTRACT FROM AUTHOR]

Background: Iterative reconstruction for cone-beam computed tomography (CBCT) has been applied to improve image quality and reduce radiation dose. In a case where an object's actual projection is larger than a flat panel detector, CBCT images contain truncated data or incomplete projections, which degrade image quality inside the field of view (FOV). In this work, we propose truncation effect reduction for fast iterative reconstruction in CBCT imaging. Methods: The volume matrix size of the FOV and the height of projection images were extrapolated to a suitable size. These extended projections were reconstructed by fast iterative reconstruction. Moreover, a smoothing parameter for noise regularization in iterative reconstruction was modified to reduce the accumulated error while processing. The proposed work was evaluated by image quality measurements and compared with conventional filtered backprojection (FBP). To validate the proposed method, we used a head phantom for evaluation and preliminarily tested on a human dataset. Results: In the experimental results, the reconstructed images from the head phantom showed enhanced image quality. In addition, fast iterative reconstruction can be run continuously while maintaining a consistent mean-percentage-error value for many iterations. The contrast-to-noise ratio of the soft-tissue images was improved. Visualization of low contrast in the ventricle and soft-tissue images was much improved compared to those from FBP using the same dose index of 5 mGy. Conclusions: Our proposed method showed satisfactory performance to reduce the truncation effect, especially inside the FOV with better image quality for soft-tissue imaging. The convergence of fast iterative reconstruction tends to be stable for many iterations. [ABSTRACT FROM AUTHOR]

In stochastic structural mechanics, the treatment of uncertainty is often the main objective of numerical simulations to estimate the responses of a system or physical phenomenon. These predictions can form the basis for decision making, and therefore, a relevant issue to be studied is how reliable they are. Uncertainties, in general, are assessed under two aspects: from the available statistical information and considering the mathematical model that represents the problem numerically. The model identifies a set of relationships based on principles, conservation laws, and metrics of physical magnitude. For the stochastic bending problem of elastic and stationary beams, it is possible to associate randomness to the properties of the material, geometry, and loads on the structure. Thus, the estimates of the responses will be present in the field of stresses and deformations. In the present work, the variational formulation of the stochastic problem of the linear elliptical contour value with random coefficients is studied in light of the stochastic version of the Lax–Milgram lemma. The propagation and uncertainty quantification are investigated based on the recent numerical methodology of asymptotic complexity λ-Neumann–Monte Carlo. The results of the numerical simulation are obtained for the stochastic bending beam problem based on the Levinson–Bickford theory. The theory of high-order elastic bending has the advantage of meeting the condition of zero shears on the lateral surfaces of the beam. Numerical results are presented related to the accuracy, convergence, estimators of statistical moments, error estimate, and the processing time of the approximate solution for the high-order beam. [ABSTRACT FROM AUTHOR]

This work investigates the problem of optimal placement and geometry of piezoelectric sensors and actuators (S/A) to improve active vibration control performance of smart laminated beam. Theoretical formulation is based on efficient layer-wise finite element model along with an optimal control theory. Control theory is implemented in state space format considering a reduced order model. A laminated beam with collocated piezoelectric S/A placed at the top and bottom surfaces has been considered. A series of simulation based on Taguchi design of experiment has been carried out to determine the optimal placement and geometry of the S/A to achieve best control performance that is maximum modal active damping ratio ξ /minimum settling time with minimum actuator voltage. A multi-criteria optimisation has been performed using Proximity Indexed Value (PIV) integrated with entropy methods. Further, the analysis of mean (ANOM) and analysis of variance (ANOVA) are performed to identify the most significant input parameter based on their percentage contribution. For the smart cantilever beam considered in the analysis, the location of the S/A is the most significant having maximum percentage contribution (35.69%) followed by its length (33.04%) and thickness (24.55%). [ABSTRACT FROM AUTHOR]

The possibility of studying the predicted for ITER effect of anomalous scattering of a microwave beam of ordinary polarization in the plasma of the edge transport barrier at the T-15MD tokamak is shown. [ABSTRACT FROM AUTHOR]

Spectral CT has shown promise for high-sensitivity quantitative imaging and material decomposition. This work presents a new device called a spatial-spectral filter (SSF) which consists of a tiled array of filter materials positioned near the x-ray source that is used to modulate the spectral shape of the x-ray beam. The filter is moved to obtain projection data that is sparse in each spectral channel. To process this sparse data, we employ a one-step direct model-based material decomposition (MBMD) to reconstruct basis material density images directly from the SSF CT data. To evaluate different possible SSF designs, we define a new Fisher-information-based predictive image quality metric called separability index which characterizes the ability of a spectral CT system to distinguish between the signals from two or more materials. This spectral CT performance metric can be used to optimize spectral CT system design. We conducted simulation-based design optimization study to find optimized combinations of filter materials, filter thicknesses, filter widths, and source settings. Finally, we present MBMD results using simulated SSF CT measurements from the optimized designs to demonstrate the ability to reconstruct basis material density images and to show the benefits of the optimized designs. Our results indicate that optimizing SSF CT for separability leads to high-performance at material discrimination tasks. [ABSTRACT FROM AUTHOR]

Imaging examinations are of remarkable importance for diagnostic support in Dentistry. Imaging techniques allow analysis of dental and maxillofacial tissues (e.g., bone, dentine, and enamel) that are inaccessible through clinical examination, which aids in the diagnosis of diseases as well as treatment planning. The analysis of imaging exams is not trivial; so, it is usually performed by oral and maxillofacial radiologists. The increasing demand for imaging examinations motivates the development of an automatic classification system for diagnostic support, as proposed in this paper, in which we aim to classify teeth as healthy or with endodontic lesion. The classification system was developed based on a Siamese Network combined with the use of convolutional neural networks with transfer learning for VGG-16 and DenseNet-121 networks. For this purpose, a database with 1000 sagittal and coronal sections of cone-beam CT scans was used. The results in terms of accuracy, recall, precision, specificity, and F1-score show that the proposed system has a satisfactory classification performance. The innovative automatic classification system led to an accuracy of about 70%. The work is pioneer since, to the authors knowledge, no other previous work has used a Siamese Network for the purpose of classifying teeth as healthy or with endodontic lesion, based on cone-beam computed tomography images. [ABSTRACT FROM AUTHOR]

Based on vector Debye integral, focusing properties of linearly polarized Bessel–Gaussian beam modulated by Bessel gratings combining a radial phase shift modulated spiral zone plate (RSSZP) passing through a large numerical aperture lens system are investigated. The data obtained lead that the intensity and the phase distributions in the focal section are significantly controlled by the order of the beam (m, n), the topological charge p and the shifting parameter β of the RSSZP. Simulations show that by increasing the topological charge, the radius of the ring increases and that the shifting parameter has an effect on the ring size. Also, the linear polarized incident beam lost its polarization after crossing a high-numerical-aperture objective. [ABSTRACT FROM AUTHOR]

A two-dimensional mixed problem for a thin elastic strip resting on a Winkler foundation is considered within the framework of plane stress setup. The relative stiffness of the foundation is supposed to be small to ensure low-frequency vibrations. Asymptotic analysis at a higher order results in a one-dimensional equation of bending motion refining numerous ad hoc developments starting from Timoshenko-type beam equations. Two-term expansions through the foundation stiffness are presented for phase and group velocities, as well as for the critical velocity of a moving load. In addition, the formula for the longitudinal displacements of the beam due to its transverse compression is derived. [ABSTRACT FROM AUTHOR]

The use of deep learning (DL) to improve cone‐beam CT (CBCT) image quality has gained popularity as computational resources and algorithmic sophistication have advanced in tandem. CBCT imaging has the potential to facilitate online adaptive radiation therapy (ART) by utilizing up‐to‐date patient anatomy to modify treatment parameters before irradiation. Poor CBCT image quality has been an impediment to realizing ART due to the increased scatter conditions inherent to cone‐beam acquisitions. Given the recent interest in DL applications in radiation oncology, and specifically DL for CBCT correction, we provide a systematic theoretical and literature review for future stakeholders. The review encompasses DL approaches for synthetic CT generation, as well as projection domain methods employed in the CBCT correction literature. We review trends pertaining to publications from January 2018 to April 2022 and condense their major findings—with emphasis on study design and DL techniques. Clinically relevant endpoints relating to image quality and dosimetric accuracy are summarized, highlighting gaps in the literature. Finally, we make recommendations for both clinicians and DL practitioners based on literature trends and the current DL state‐of‐the‐art methods utilized in radiation oncology. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) is used to investigate the free and forced vibration characteristics of functionally graded graphene-nanoplatelet-reinforced composite (FG-GPLRC) beams. The weight fraction of graphene nanoplatelets (GPLs) is assumed to vary continuously along the beam thickness according to a linear, parabolic, or uniform pattern. For the FG-GPLRC beam, the modified Halpin–Tsai micromechanics model is used to calculate the effective Young's modulus, and the rule of mixture is used to determine the effective Poisson's ratio and mass density. Based on the principle of virtual work under the assumptions of the Euler–Bernoulli beam theory, finite element formulations are derived to analyze the free and forced vibration characteristics of FG-GPLRC beams. A two-node beam element with six degrees of freedom is adopted to discretize the beam, and the corresponding stiffness matrix and mass matrix containing information on the variation of material properties can be derived. On this basis, the natural frequencies and the response amplitudes under external forces are calculated by the FEM. The performance of the proposed FEM is assessed, with some numerical results obtained by layering method and available in published literature. The comparison results show that the proposed FEM is capable of analyzing an FG-GPLRC beam. A detailed parametric investigation is carried out to study the effects of GPL weight fraction, distribution pattern, and dimensions on the free and forced vibration responses of the beam. Numerical results show that the above-mentioned effects play an important role with respect to the vibration behaviors of the beam. [ABSTRACT FROM AUTHOR]

An improved non-convex optimized phase recovery algorithm is used to compensate for wavefront aberrations caused by atmospheric turbulence and pointing errors in the vortex beam. The algorithm is divided into two parts: initialization and iteration. To reduce the effect of outliers, truncation rules are formulated in the initialization phase using the robustness of the sample median to obtain an initial value that is close to the global optimum. The relationship between the results of adjacent iterations is used in the iterations to calculate new weight coefficients, which are applied to the gradient descent to ensure the accuracy of the recovery results. Simulation experiments are carried out for different channel environments and different modes, and the results show that the improved phase recovery algorithm can accurately compensate for distorted wave fronts. The improved algorithm recovers the best results at different turbulence intensities and under the influence of different pointing errors. The recovered Strehl ratio can reach 0.9 and the mode purity can reach 0.92. Single-mode and multi-mode simulations were carried out, and the results show that the improved algorithm is effective and robust. [ABSTRACT FROM AUTHOR]

The dynamic characteristics of a hub-functionally graded material beam undergoing large overall motions are studied. The deformation field of the flexible beam is described by using the assumed mode method (AMM), the finite element method (FEM) and the point interpolation method (PIM). Assuming that the physical parameters of functionally graded materials follow certain kind of power law gradient distribution and vary along the thickness direction. The longitudinal deformation and transversal deformation of the beam are both considered, and the nonlinear coupling term which is known as the longitudinal shortening caused by transversal deformation is also taken into account. The rigid-flexible coupling dynamics equations of the system described by three different discrete methods which have a uniform form are derived via employing Lagrange's equations of the second kind. The validity of the point interpolation method established in this paper is verified by comparing with the numerical simulation results of the assumed mode method and the finite element method. On this basis, the influence of the functional gradient distribution rules on the dynamic characteristics of flexible beams undergoing large overall motions is discussed. The results show that the assumed mode method cannot deal with large deformation problem. Remaining other physical parameters of functionally graded materials beam unchanged, the maximum displacement of the beam increases with the increase of functionally graded materials index. The natural frequency of transverse bending of beam increases with the increase of rotational speed, when rotational speed is constant, the natural frequency will decrease with the increase of functional gradient index. [ABSTRACT FROM AUTHOR]

In this paper, we study the well-posedness and the asymptotic behavior of a one-dimensional laminated beam system with a distributed delay term in the first equation, where the heat conduction is given by Fourier's law effective in the rotation angle displacements. We first give the well-posedness of the system by using the semigroup method. Then, we show that the system is exponentially stable under the assumption of equal wave speeds. [ABSTRACT FROM AUTHOR]

Lattice lightsheet microscopy (LLSM) featuring three-dimensional recording is improved to manipulate cellular behavior with subcellular resolution through optogenetic activation (optoLLSM). A position-controllable Bessel beam as a stimulation source is integrated into the LLSM to achieve spatiotemporal photoactivation by changing the spatial light modulator (SLM) patterns. Unlike the point-scanning in a confocal microscope, the lattice beams are capable of wide-field optical sectioning for optogenetic activation along the Bessel beam path.We show that the energy power required for optogenetic activations is lower than 1 nW (or 24 mWcm-2) for time-lapses of CRY2olig clustering proteins, and membrane ruffling can be induced at different locations within a cell with subcellular resolution through light-triggered recruitment of phosphoinositide 3-kinase. Moreover, with the epidermal growth factor receptor (EGFR) fused with CRY2olig, we are able to demonstrate guided cell migration using optogenetic stimulation for up to 6 h, where 463 imaging volumes are collected, without noticeable cellular damages. Using a Bessel beam as a simulation source allows the use of lattice lightsheet microscopy for spatiotemporal control of photoactivation, illustrated by the control of cellular migration behavior. [ABSTRACT FROM AUTHOR]

Modern cone-beam CT systems are capable of ultra-high-resolution 3D imaging in addition to conventional radiography and fluoroscopy. The combination of various imaging functions in a multi-use setup is particularly appealing for musculoskeletal interventions, such as CBCT arthrography (CBCTA). With this study, we aimed to investigate the feasibility of CBCTA of the wrist in a "one-stop-shop" approach with a gantry-free twin robotic scanner that does not require repositioning of subjects. Additionally, the image quality of CBCTA was compared to subsequent arthrograms on a high-end multidetector CT (MDCTA). Fourteen cadaveric wrists received CBCTA with four acquisition protocols. Specimens were then transferred to the CT suite for additional MDCTA. Dose indices ranged between 14.3 mGy (120 kVp/100 effective mAs; full-dose) and 1.0 mGy (70 kVp/41 effective mAs; ultra-low-dose) for MDCTA and between 17.4 mGy (80 kVp/2.5 mAs per pulse; full-dose) and 1.2 mGy (60 kVp/0.5 mAs per pulse; ultra-low-dose) for CBCTA. Subjective image quality assessment for bone, cartilage and ligamentous tissue was performed by seven radiologists. The interrater reliability was assessed by calculation of the intraclass correlation coefficient (ICC) based on a two-way random effects model. Overall image quality of most CBCTA was deemed suitable for diagnostic use in contrast to a considerable amount of non-diagnostic MDCTA examinations (38.8%). The depiction of bone, cartilage and ligaments in MDCTA with any form of dose reduction was inferior to any CBCTA scan with at least 0.6 mAs per pulse (all p < 0.001). Full-dose MDCTA and low-dose CBCTA were of equal quality for bone tissue visualization (p = 0.326), whereas CBCTA allowed for better depiction of ligaments and cartilage (both p < 0.001), despite merely one third of radiation exposure (MDCTA–14.3 mGy vs. CBCTA–4.5 mGy). Moderate to good interrater reliability was ascertained for the assessment all tissues (ICC 0.689–0.756). Overall median examination time for CBCTA was 5.4 min (4.8–7.2 min). This work demonstrates that substantial dose reduction can be achieved in CT arthrography of the wrist while maintaining diagnostic image quality by employing the cone-beam CT mode of a twin robotic X-ray system. The ability of the multi-use X-ray system to switch between fluoroscopy mode and 3D imaging allows for "one-stop-shop" CBCTA in minimal examination time without the need for repositioning. [ABSTRACT FROM AUTHOR]

The capacity of self-healing fields to reconstruct after passing through scattering media may prove useful in reducing speckle formation. Here, we study the speckle response of the space–time (ST) light sheet compared to a Gaussian wave packet, Airy beam, and Bessel Gauss beam. We find that the Pearson's correlation coefficient for the ST light sheet is 50%, 48% and 40% larger than that of the Gaussian, Airy beam and Bessel Gauss beams, respectively, demonstrating a strong correlation to an input beam that has not been speckled. These results suggest that the ST light sheet exhibits considerable resistance to speckle generation. We also investigate the speckle response of the ST light sheet at its second-harmonic frequency and observe a mean Pearson's correlation coefficient close to 0.6, comparable to the second-harmonic Bessel Gauss beam, and 2.8 × the value obtained for the second-harmonic Gaussian beam. Our results lend themselves to a variety of applications including bioimaging, communications, and optical tweezers. [ABSTRACT FROM AUTHOR]

In classical thermoelasticity, the bimodular effect of materials is rarely considered. However, all materials will present, in essence, different properties in tension and compression, more or less. The bimodular effect is generally ignored only for simple analysis. In this study, we theoretically analyze a two-dimensional curved beam with a bimodular effect and under mechanical and thermal loads. We first establish a simplified model on a subarea in tension and compression. On the basis of this model, we adopt the Duhamel similarity theorem to change the initial thermoelastic problem as an elasticity problem without the thermal effect. The superposition of the special solution and supplement solution of the Lamé displacement equation enables us to satisfy the boundary conditions and stress continuity conditions of the bimodular curved beam, thus obtaining a two-dimensional thermoelastic solution. The results indicate that the solution obtained can reduce to bimodular curved beam problems without thermal loads and to the classical Golovin solution. In addition, the bimodular effect on thermal stresses is discussed under linear and non-linear temperature rise modes. Specially, when the compressive modulus is far greater than the tensile modulus, a large compressive stress will occur at the inner edge of the curved beam, which should be paid with more attention in the design of the curved beams in a thermal environment. [ABSTRACT FROM AUTHOR]

This paper presents an analytical transfer matrix modeling framework for the forced vibration of a bending-torsional-warping coupling Euler-Bernoulli thin-walled beam carrying an arbitrary number of three degree-of-freedom (DOF) spring-damper-mass (SDM) subsystems. The thin-walled beam is divided into a series of distinct sub-beams whose ends are connected to the SDM subsystems. The transfer matrix for each sub-beam is developed based on the exact shape functions of the bending-torsional-warping coupling Euler-Bernoulli theory. Each SDM system is modelled by a set of effective springs based on the dynamic condensation method. The governing matrix equation is formulated based on the compatibility conditions of the placement and the force at the common interfaces of two adjacent sub-beams. Then, a closed-form expression for the frequency response function of the thin-walled beam system is proposed. The results computed by the proposed method achieve good agreement with those obtained by the conventional finite-element method, which shows the accuracy and reliability of the proposed method. The effects of the system parameters on the vibration transmission and vibration isolation properties of the thin-walled beam system are studied. The presented method can simultaneously consider arbitrary number of SDM subsystems and boundary conditions. Furthermore, none of the associated matrices are larger than 12 × 12, which provides a significant computational advantage. [ABSTRACT FROM AUTHOR]

Light detection and ranging systems based on optical phased arrays and integrated silicon photonics have sparked a surge of applications over the recent years. This includes applications in sensing, free-space communications, or autonomous vehicles, to name a few. Herein, we report a design of two-dimensional optical phased arrays, which are arranged in a grid of concentric rings. We numerically investigate two designs composed of 110 and 820 elements, respectively. Both single-wavelength (1550 nm) and broadband multi-wavelength (1535 nm to 1565 nm) operations are studied. The proposed phased arrays enable free-space beam steering, offering improved performance with narrow beam divergences of only 0.5° and 0.22° for the 110-element and 820-element arrays, respectively, with a main-to-sidelobe suppression ratio higher than 10 dB. The circular array topology also allows large element spacing far beyond the sub-wavelength-scaled limits that are present in one-dimensional linear or two-dimensional rectangular arrays. Under a single-wavelength operation, a solid-angle steering between 0.21π sr and 0.51π sr is obtained for 110- and 820-element arrays, respectively, while the beam steering spans the range of 0.24π sr and 0.57π sr for a multi-wavelength operation. This work opens new opportunities for future optical phased arrays in on-chip photonic applications, in which fast, high-resolution, and broadband beam steering is necessary. [ABSTRACT FROM AUTHOR]