Cylindrical Beam Research Articles

Quantification and Sensitivity Analysis of the Model Uncertainty in the Projectile-Barrel Coupled Artillery Dynamics System Based on Random Matrix Theory

Simplifications in the engineering of artillery firing dynamics modeling introduce model uncertainty, which seriously affects the model’s predictive performance. To this end, a typical variable-section hollow cylindrical cantilever beam structure in artillery firing dynamics is investigated in this paper. The statistical approximation methods quantify parameter and model uncertainty separately, and their respective confidence intervals were calculated and compared. The results show that the traditional parameter uncertainty approach overestimates the parameter uncertainty ranges, and introducing the model uncertainty approach dramatically improves the model prediction performance. Additionally, a projectile-barrel coupled artillery dynamics model considering model uncertainty is established, and its effectiveness is validated through the actual launch experiments. The sensitivity of the dynamic responses to the system matrix, namely model uncertainty, is further analyzed. This paper provides theoretical references for the study of uncertainty in artillery launch dynamics and proposes effective methods to enhance the predictability of computational models for complex structural systems.

Spin angular momentum and optical chirality of Poincaré vector vortex beams

Abstract The optical chirality and spin angular momentum of structured scalar vortex beams has been intensively studied in recent years. The pseudoscalar topological charge $\ell$ of these beams is responsible for their unique properties. Constructed from a superposition of scalar vortex beams with topological charges $\ell_\text{A}$ and $\ell_\text{B}$, cylindrical vector vortex beams are higher-order Poincar'e modes which possess a spatially inhomogeneous polarization distribution. Here we highlight the highly tailorable and exotic spatial distributions of the optical spin and chirality densities of these higher-order structured beams under both paraxial (weak focusing) and non-paraxial (tight focusing) conditions. Our analytical theory can yield the spin angular momentum and optical chirality of each point on any higher-order or hybrid-order Poincar'e sphere. It is shown that the tunable Pancharatnam topological charge $\ell_{\text{P}} = (\ell_\text{A} + \ell_\text{B})/2$ and polarization index $m = (\ell_\text{B} -\ell_\text{A})/2$ of the vector vortex beam plays a decisive role in customizing their spin and chirality spatial distributions. We also provide the correct analytical equations to describe a focused, non-paraxial scalar Bessel beam.

Controlled generation of cylindrical vector vortex beams using an optically active material.

An efficient method for the generation of tunable cylindrical vector vortex beams is proposed and demonstrated experimentally using an optically active (OA) material. The uniqueness of the proposed methodology lies in the control over the tunability of the cylindrical vector vortex beams using different concentrations of the optically active material. The efficiency of the generated beams is enhanced by using a single low oblique incidence angle of the input beam on a spatial light modulator with a single-phase profile. Two global parameters are measured experimentally to show the quantitative tunability and efficiency of the generated beams. The proposed method can find applications in the fabrication of various kinds of spiral nanostructures.

Aeroacoustic modeling of a low Reynolds number rotor in the wake of a cylindrical beam

In micro air vehicles, low Reynolds number rotors operating in close proximity to the fuselage raises the question of interaction noise as a prominent acoustic source. This paper proposes to comprehensively explore the interaction noise generation mechanisms, employing numerical simulations, experimental approaches, and analytical modelling. The focus is on scenarios where a low Reynolds number rotor is located in the wake of a cylindrical beam, and oppositely when the beam is in the wake of the rotor. In both scenarios, it is observed experimentally that the amplitudes of the BPF harmonics are increased with respect to that obtained without beam. This increase is higher when the rotor is in the wake of the beam compared to when the beam is in the wake of the rotor. The numerical simulation is shown to reproduce quite well the envelope of the amplitudes of the BPF harmonics obtained experimentally in both scenarios. Interestingly, by applying Ffowcs-Williams and Hawkings analogy on elementary surfaces, and not on the whole rotor-beam surface, the main sound generation mechanism was found to be the unsteady loading on the beam in both scenarios. Finally, an analytical modeling of the noise source mechanism is compared with experimental and numerical results.

Introduction of a new cylindrical beam and study of its propagation through a paraxial optical system

Introduction of a new cylindrical beam and study of its propagation through a paraxial optical system

Topological Structures of Energy Flow: Poynting Vector Skyrmions.

Topological properties of energy flow of light are fundamentally interesting and may introduce novel physical phenomena associated with directional light scattering and optical trapping. In this Letter, skyrmionlike structures formed by Poynting vectors are unveiled in the focal region of two pairs of counterpropagating cylindrical vector vortex beams in free space. The appearance of local phase singularities, and the distinct traveling and standing wave modes of different field components passing through the focal spot lead to a Néel-Bloch-Néel transition of Poynting vector skyrmion textures along the light propagating direction. By shaping the wave front of the incident beams with patterned amplitudes, the topological invariant of the Poynting vector skyrmions can be further tuned in a prospective area. This work expands the family of optical skyrmions and holds great potential in energy flow associated applications.

Suppression of Parasitic Modes in a Cylindrical Gyrotron Beam Tunnel by a Wall Corrugation With Schroeder Diffuser Structures

Suppression of Parasitic Modes in a Cylindrical Gyrotron Beam Tunnel by a Wall Corrugation With Schroeder Diffuser Structures

Designed 3D Dumpling‐Shaped Femtosecond Laser Structured Light Field for Nanoscale Sensing

AbstractNanoscale optical sensing plays a crucial role in achieving high‐precision non‐contact distance and displacement measurements. As one of the promising alternatives, structured light can greatly simplify optical sensing systems. In this study, a novel optical phenomenon of a structured beam called the “Dumpling‐shaped Structured Light Field” (DSLF) is revealed, which forms during the focusing of cylindrical lens beams. The 3D DSLF comprises two mutually perpendicular primary and secondary foci, offering unique possibilities in micro/nano processing and sensing applications. A thorough investigation of the DSLF is conducted, revealing a correlation between the secondary foci and the phase status at the objective lens's entrance pupil. The propagation of DSLF under tight focus conditions has been verified and discussed through methods of femtosecond laser two‐photon polymerization and light field analysis. Finally, thanks to the unique 3D intensity distribution of 3D DSLF, the applicability of DSLF in high‐precision position and vibration sensing has been demonstrated. By detecting the horizontal and vertical dimensions of the reflected DSLF, position and vibration sensing is achieved with a Z‐direction accuracy of 10 nm (λ/80). This research contributes to understanding structured light, and offers practical applications in various fields, including micro/nano laser processing, optical imaging, sensing, etc.

Axial and transverse acoustic radiation forces on an elliptical cylinder arbitrarily positioned in a cylindrical quasi-Gaussian beam

Axial and transverse acoustic radiation forces on an elliptical cylinder arbitrarily positioned in a cylindrical quasi-Gaussian beam

Dimensioning of Biomimetic Beams under Bending for Additively Manufactured Structural Components.

Additively manufactured mechanical components show great lightweight characteristics and can often be enhanced by integrating biomimetic geometrical features. This study focuses on one specific subcase, namely the substitution of solid cylindrical beams that are under bending with geometrically more complex biomimetic beams. Based on the pseudo-stem of the banana plant as a role model, six geometric beam designs were derived. Given the manufacturing constraints of the PBF-LB/M process, two abstractions were selected for detailed investigation in the main part of this study. The beam lengths were set to 100 mm. Based on parametric optimization simulations, optimal design parameters were identified for the two biomimetic abstractions for 26 different bending load cases ranging from 14 to 350 Nm. Analogous parameter optimizations were performed for a solid cylindrical beam design, which was used as a reference. The results provide detailed design solutions within the investigated intervals for biomimetic beams that can be substituted into more complex mechanical component designs with ease. The analysis provides information on which structures to use for the investigated loads. With the help of the developed numerical models, designers can easily generate biomimetic beam designs for specific bending load values.

Numerical evaluation of strain transfer model for steel-reinforced optical fiber cable embedded in a cylindrical concrete beam with two void inclusions

In distributed optical fiber sensors, strain transfer is usually described through a simplified one-dimensional equation, derived from continuum mechanics. This equation, in which a parameter known as the strain-lag parameter takes into account the cable’s geometric and mechanical characteristics, establishes a relationship between the measured longitudinal strain profile within the optical fiber and the real strain profile occurring in the host material. In the case of steel-reinforced optical fiber cables, appreciated for their resistance to breakage during on-site instrumentation, a notable discrepancy between the measured and actual strain profiles is revealed especially in the presence of a strain gradient, indicating that the ability to transfer strain from the host material to the optical fiber is restrained using this type of cable. This paper assesses numerically the strain transfer model for steel-reinforced optical fiber sensors in the presence of a strain gradient generated by two void inclusions in a concrete beam. The good accuracy of the strain transfer model is observed by the comparison with a 3D finite element simulation. However, the result points out the critical necessity of precisely determining the strain-lag parameter.

TORSION OF A CYLINDRICAL BEAM HAVING TWO LINEAR CRACKS WITH DIFFERENT LENGTHS

TORSION OF A CYLINDRICAL BEAM HAVING TWO LINEAR CRACKS WITH DIFFERENT LENGTHS

Study on the Hydrodynamic Performance of the Beam Used in the Antarctic Krill Beam Trawl

The beam trawl is one of the primary operational trawls for Antarctic krill, and its beam provides horizontal expansion support for the trawl net. The hydrodynamic performance of the beam significantly affects the vertical expansion and sinking performance of the trawl, as well as impacts the energy consumption of the fishing vessel. In this study, the beam of the Antarctic krill trawl used on the “Shen Lan” fishing vessel served as a prototype. Three types of beams, cylindrical, airfoil, and elliptical, were designed. The hydrodynamic performances of beams with different shapes at different angles of attack were studied using numerical simulation, and the accuracy of the numerical simulation was validated through the flume test. The results show that the cylindrical beam has a higher drag coefficient and a lower lift coefficient, compared to the airfoil beam and the elliptical beam. Under different angles of attack, the cylindrical beam’s drag coefficient is, on average, 49.54% higher than that of the airfoil beam and 59.74% higher than that of the elliptical beam. Its lift coefficient is 87.79% lower than that of the airfoil beam and 85.06% lower than that of the elliptical beam, respectively. At different angles of attack, the hydrodynamic coefficients of the airfoil beam and the elliptical beam are similar, and their trends, with respect to the angle of attack, are generally consistent. The drag coefficients increase with an increasing angle of attack, while the lift coefficients show a trend of initially increasing and then decreasing with an increasing angle of attack. The absolute values of the lift coefficients for the airfoil beam and the elliptical beam both reach their maximum values at an angle of attack of 45°, with values of 0.703 and 0.473, respectively. Compared to the cylindrical beam, the hydrodynamic performances of the airfoil beam and elliptical beam are superior.

Vortex circular airy beams through leaky-wave antennas

A novel method to design leaky-wave antennas radiating vortex cylindrical Airy beams at microwave frequencies is here presented. Two different approaches are adopted to produce waves with a nonzero orbital angular momentum (OAM): one based on a bull’s eye design excited by a uniform circular array of vertical coaxial probes with proper azimuthal phase delay, and one based on a single coaxial feeder exciting a multi-spiral radiator. Both of them take advantage of backward radial propagation of cylindrical leaky waves promoting circular Airy beams with vortex patterns. The OAM state can be changed by either varying the probe phasing or the number of spiral units. A reference profile is designed under transverse-electric and transverse-magnetic excitation independently. Numerical full-wave analysis are performed using different angular states to validate the antenna design, as well to highlight the different advantages of the two alternative design approaches.

Spin-Hall Effect of Cylindrical Vector Vortex Beams

Spin-Hall effect (SHE) of light is one of the main manifestations of the spin-orbit interaction of photons, and has been extensively studied for optical beams with homogeneous polarization. Here, we present a theoretical study of the SHE of cylindrical vector vortex beams (CVVBs) possessing inhomogeneous polarization. We derive the analytical expressions of the SHE of CVVBs reflected and refracted at a dielectric interface with radial and azimuthal polarization of incidence. The spin-dependent shifts of the SHE of light linearly depend on the topological charge of the CVVBs. In contrast to the conventional SHE of horizontally or vertically polarized beams, the SHE shifts of the CVVBs are asymmetrical when the topological charge is nonzero. This asymmetry results in the transverse Imbert–Fedorov (IF) shifts that are proportional to the topological charge. Furthermore, based on weak measurement, we propose an experimental scheme to enhance the SHE and related IF shifts with proper pre- and post-selection polarization states. Our results advance the study of the SHE of structured light and may find applications in SHE-based techniques such as precision measurement.

Spin angular momentum at the sharp focus of a cylindrical vector vortex beam

Sharp focusing of a light field with double (phase and polarization) singularity is studied. Using the Richards-Wolf method, an exact analytical expression for the longitudinal projection of the spin angular momentum (SAM) vector at the focus is obtained. The expression derived suggests that 4 (n –1) subwavelength regions are formed at the focus, where n is the cylindrical vector beam order, with their centers located on a certain circle centered on the optical axis. Notably, the SAM projections are found to have the opposite sign in the neighboring regions. This means that in the neighboring focal regions, the light has alternating left or right elliptical polarization (manifestation of a spin Hall effect). At the center of the focal spot near the optical axis, the field is right-handed elliptically polarized at m > 0, or left-handed elliptically polarized at m < 0, where m is the vortex charge. The total longitudinal spin, i.e., the longitudinal SAM component averaged over the beam-cross section, is zero and preserved upon focusing. Due to the beam containing an optical vortex with charge m, the transverse energy flow rotates on a spiral path near the focal plane, rotating on a circle in the focal plane. The rotation direction near the optical axis is counterclockwise for m > 0, and clockwise for m < 0.

Flat-topped Beams using Phase Compensation based on Low-profile Transmitarray

This paper proposes a method to add an additional phase compensation to conventional phased arrays to achieve flat-topped beam forming, which can convert the spherical waves emitted by common conical horn antennas into cylindrical flat-topped beams, at the same time, there is also a certain power enhancement. A centrosymmetric unit composed of four layers of F4B and metal patches is designed. By changing the value of the parameters, a 360∘ phase change can be achieved, and it has the advantages of small size and low-profile. To validate the design concept, a prototype of the transmitarray (TA) was designed, fabricated, and measured by calculating the phase distribution of the front. The measurement results show that the designed TA can achieve flat-topped beams at 5.2GHz, the maximum gain is 1.15dB higher than that of the horn antenna, and the flat-topped range is about ±10∘. The results are in good agreement with the simulation within the test range.

Development and assessment of a methodology for abstraction of topology optimization results to enable the substitution of optimized beams

Improving mechanical topology optimization (TO) results by substituting biomimetic beams is one possibility to achieve designs of mechanical components that are highly sustainable and show good mechanical performance. Because of their geometric complexity, such designs were found to be well-suited for production by laser additive manufacturing. One obstacle of incorporating biomimetics beams in TO designs is the lack of detailed design methodologies. Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October–3 November (ASME, New York, 2022)] proposed a corresponding design concept. Building on their concept, we present in this work a detailed methodology for abstraction of TO results to a design consisting of ball nodes and cylindrical beams. Using such an auxiliary design, the internal forces and moments of the beams can be evaluated to allow for the substitution of suitable biomimetic beams to generate biomimetic component designs in a next step. We present a skeletonization algorithm based on the potential field approach. Using the skeletonization and an additional analysis of the dimensions of the beams in the TO result, the algorithm develops an auxiliary design of the original TO result. The final algorithm was applied to three common TO results to obtain one auxiliary component design each. The developed algorithm was found to generate abstractions that were well-suited for use in the methodology proposed in Röver et al. [“Methodology for integrating biomimetic beams in abstracted topology optimization results,” in Proceedings of the ASME 2022 International Mechanical Engineering Congress and Exposition. Volume 4: Biomedical and Biotechnology; Design, Systems, and Complexity Columbus, OH, 30 October–3 November (ASME, New York, 2022)], because internal forces and moments in the abstracted beams could be evaluated with less effort. Therefore, our work contributes to a detailed design methodology for biomimetic mechanical components in the field of design for additive manufacturing.

Comparative Analysis of the Interferogram Sensitivity to Wavefront Aberrations Recorded with Plane and Cylindrical Reference Beams

Comparative Analysis of the Interferogram Sensitivity to Wavefront Aberrations Recorded with Plane and Cylindrical Reference Beams

Commissioning of a RayStation structure template for the iBEAM evo Couchtop.

Accurate radiotherapy treatment planning requires attenuation through the treatment couch to be accounted for in dose calculation. This is commonly performed by using contouring tools to add a virtual structure in the shape of the treatment couch and assigning the preferred absorption properties. The RayStation treatment planning system (TPS) allows users to assign a material that comprises both an elemental structure and a physical density. The selection of such parameters should be made so that modelled attenuation through the couch closely matches measured data. When these measurements involve the use of plastic phantoms and rotational beams, the validity of the data is dependent upon aspects of TPS and linear accelerator performance that can be difficult to quantify. A fundamental measure of couch attenuation using an ionisation chamber in water and perpendicular beam geometry that required no gantry movement was implemented to eliminate the identified uncertainties. This data was used to determine the combination of elemental composition and density assigned to a modelled couch structure that provided the most accurate representation of beam attenuation in this simple geometry. The preferred material was then validated using a cylindrical phantom and rotational beams. The findings were equivalent between the static gantry with water phantom and rotating gantry with cylindrical phantom. Of the elemental compositions investigated, it was possible to achieve suitable agreement with the measured data for each option provided the density was optimised. Choice of the elemental composition was not observed to be an important factor in achieving a good model.