Asymmetric Beam Research Articles

A boosted muon collider

A muon collider could produce the heavier Standard Model particles with a boost, for example in resonant processes such as μ−μ+→ h or μ−μ → Z. We propose machine configurations that produce the boost (asymmetric beam energies, tilted beams) and estimate how much the luminosity is reduced or perhaps enhanced. The feasibility of the proposed configurations, as well as an estimation of the beam-induced backgrounds and beam energy spread, needs to be evaluated in order to derive more solid conclusions on the physics potential of such boosted collider configurations. If achievable, the boost can provide new interesting observational opportunities. For example it can significantly enhance the sensitivity to long-lived new particles decaying in a far-away detector, such as dark higgses or sterile neutrinos produced in h or Z decays.

Composition optimization of PMMA base denture reinforced with different percentages of Nano Hydroxyapatite and alumina particles to obtain highest KIc and KIIc values using hybrid IWO/PSO algorithm

Composition of three-phase dental denture (Polymethyl methacrylate or PMMA + Nano Hydroxyapatite + Nano Alumina) was optimized using hybrid IWO/PSO algorithm to obtain the highest KIc and KIIc. First, initial fracture toughness tests were performed on nine groups of PMMA base dentures with different percentages of ingredients. Symmetric single edge notch beam and asymmetric three-point bend beam with inclined crack were used for KIc and KIIc testing, respectively. The initial design parameters were considered as: {75–100% PMMA, 0–10% Nano Hydroxyapatite and, 0–15% Nano Alumina}. As the initial guess values for starting the hybrid optimization algorithm, B-spline curves (as the cost function) were fitted to the experimental results of both modes I and II. Then the IWO/PSO algorithm was run to find the optimum composition and maximum fracture toughness value of each mode. The best KIc was found for the composition of {78.5% PMMA + 9% Nano Hydroxyapatide + 12.5% Nano Alumina}. Similarly, using the hybrid IWO/PSO algorithm the optimum composition of {83.4% PMMA + 8.7% Nano Hydroxyapatide + 7.9 % Nano Alumina} was obtained to gain the highest KIIc. The experimental fracture toughness values obtained from the proposed compositions via employing the hybrid algorithm were approximately 40% higher than the all tested nine groups of PMMA base dentures under both modes I and II. The fracture toughness ratio KIIc/KIc of the optimum mix-designs predicted by the hybrid algorithm was equal to 0.78 and showed good agreement with the experimental KIIc/KIc ratio. The fracture toughness for any desired mixed mode condition can also be predicted in-terms of the KIc and stress intensity factors and T-stress of the desired mode mixity.

LOCALISED FIRE ASSESSMENT OF A STEEL STRUCTURAL SOLUTION IN A PILOT BUILDING

AbstractMany tragic fires in the past decades have highlighted the importance of fire safety engineering and its meaningful application in the engineering field. With a constant and significant growth of the research the classical approach based on prescriptive time‐temperature curve, where the gas temperature is assumed to be constant within the entire compartment and always increasing on time has been challenged by a performance‐based one. Performance‐based approach is aiming to represent the fire accounting for more physics than the prescriptive approach, considering ignition, fire growth burning and cooling phase. Nowadays practitioners facing the design stage of a project have to face the choice between designing with prescriptive or performance‐based approach. In this work a comparison between design using performance based and a prescriptive approach will be provided. In particular, the building is under development in the framework of a demonstration RFCS (Research Found for Coal and Steel) project called DREAMERS, founded by the European Commission. The chosen structure for this example is an 800 m2 steel building, which will be built in the Campus of the University of Salerno (Italy). The main peculiarity of the building is the implementation of all the most advanced technologies for the construction of a resilient structure in terms of seismic, robustness and fire safety. The building is designed in steel and steel composite solutions, following a holistic design approach and foreseeing a life time monitoring of its behavior. The flooring system is made of Asymmetric Floor Beams (AFB) and Cofradal® 260, whereas vertical elements are hot rolled HEB sections. The work here presented is showing some of the main challenges related to the fire design as well as application of next generation localised fire models.

Terahertz cascaded metasurfaces for both spin-symmetric and asymmetric beam diffractions with active power distribution

Ultra-compact and tunable devices for terahertz (THz) beam manipulation are highly desired in wireless communication and radar scanning. Although the appearance of the Pancharatnam-Berry (PB) metasurface has provided strategies for THz beam scanning, active output power distribution is still difficult to achieve, and the flexibility of beam manipulation is limited by a single metasurface. In this work, we demonstrated an all-dielectric cascaded metasurface consisting of a spin-decoupled metasurface and a PB metasurface. The conjugated characteristic of the PB phase for two photonic spin states is broken with highly efficient high-order diffractions of wave vector superposition through the cascaded metasurfaces, and both spin-symmetric and spin-asymmetric transmissions are obtained by designing the differences in metasurface bandwidth. Moreover, the output power between the deflection beams can be actively tuned by changing the incident polarization state, achieving power modulation ratios of 99.3% and 95.1% for the two conjugated spin beams, respectively. Therefore, this work realizes controllable wave division multiplexing and power distribution and opens new avenues for the design of ultra-compact multifunctional devices.

A refined shear deformation theory of an asymmetric sandwich beam with porous core: Linear bending problem

This paper is devoted to a sandwich beam with an asymmetric structure under uniformly distributed load. The first end of this beam is simply supported, while second end is clamped. The individual nonlinear deformation function of a plane beam cross section – the shear effect with consideration of the classical shear stress formula is analytically developed. Displacements, strains and stresses taking into account the individual nonlinear deformation function for successive layers of this beam are elaborated in detail. The system of two differential equation of equilibrium of this beam, based on the principle of stationary potential energy, is obtained. This system of equations is precisely solved analytically, according to the theory of differential equations. The individual nonlinear deformation functions, shear stresses and deflections of two cases of sample beams are determined in detail: the first with variable core porosity in the direction of the beam depth, the second with constant core porosity – standard sandwich structure. The calculations results specified in Tables and graphically presented in Figures.

Dynamic Stability of an Asymmetric Sandwich Beam Resting on a Paternak Foundation

The parametric dynamic stability of a pinned-pinned asymmetric sandwich beam resting on a Pasternak foundation with viscoelastic core, subjected to an axial pulsating load is investigated. The effects of thickness ratio of two elastic layers (h31), elastic modulus ratio(E3/E1), the ratio of modulus of the shear layer of Pasternak foundation to the Youngs modulus of elastic layer (Gs/E1), the ratio of length of the beam to the thickness of the elastic layer (lh1), the ratio of in phase shear modulus of the viscoelastic core to the Youngs modulus of the elastic layer (G2/E1), the ratio of thickness of Pasternak foundation to the length of beam (δ/l), coreloss factor (η) the ratio of thickness of viscoelastic layer to that of elastic layer (h21) on the non-dimensional static buckling load are considered. In addition to these the effects of the above parameters on the regions of parametric instability have been studied.

Coal Pillar Size Determination and Surrounding Rock Control for Gob-Side Entry Driving in Deep Soft Coal Seams

In response to the large-scale instability failure problem of designing coal pillars and support systems for gob-side entry driving (GSED) in high-stress soft coal seams in deep mines, the main difficulties in the surrounding rock control of GSED were analyzed. The relationship between the position of the main roof breaking line, together with the width of the limit equilibrium zone and a reasonable size for the coal pillar, were quantified through theoretical calculations. The theoretical calculations showed that the maximum and minimum widths of the coal pillar are 8.40 m and 5.47 m, respectively. A numerical simulation was used to study the distribution characteristics and evolution laws of deviatoric stress and plastic failure fields in the GSED surrounding rock under different coal pillar sizes. Theoretical analysis, numerical simulation, and engineering practice were comprehensively applied to determine a reasonable size for narrow coal pillars for GSED in deep soft coal seams, which was 6.5 m. Based on the 6.5 m coal pillar size, the distribution of deviatoric stress and plastic zones in the surrounding rock of the roadway, at different positions of the advanced panel during mining, was simulated, and the range of roadway strengthening supports for the advanced panel was determined as 25 m. The plasticization degree of the roof, entity coal and coal pillar, and the boundary line position of the peak deviatoric stress zone after the stability of the excavation were obtained. Drilling crack detection was conducted on the surrounding rock of the GSED roof and rib, and the development range and degree of the crack were obtained. The key areas for GSED surrounding rock control were clarified. Joint control technology for surrounding rock is proposed, which includes a combination of a roof channel steel anchor beam mesh, a rib asymmetric channel steel truss anchor cable beam mesh, a grouting modification in local fractured areas and an advanced strengthening support with a single hydraulic support. The engineering practice showed that the selected 6.5 m size for narrow coal pillars and high-strength combined reinforcement technology can effectively control large deformations of the GSED surrounding rock.

Dynamic Stability Study on an Exponentially Tapered Rotating Asymmetric Sandwich Beam Under the Action of a Pulsating Axial Load with Variable Temperature Gradient

In this research article stability study of an exponentially tapered rotating sandwich beam having different elastic parameters in temperature environment has been done. The sequential steps followed up to reach the goal are extended Hamilton’s principle, non-dimensionlization of equations, selection of shape functions for the mathematical modeling of the system from the past research work depending upon the boundary conditions, use of general Galerkins method, help of modal matrix and finally the use of Saito-Otomi conditions. Here the effects of variable thermal gradient, on the Young’s modulus of the elastic layers have been considered in place of constant thermal gradient as earlier. Consideration of effect of variable thermal gradient, while analyzing the stability of the system is the most significant contribution of this research article to the society as non-uniform elastic layers are considered here. The influence of different parameters on the regions of instability are studied and presented graphically. Comparison of the results with uniform and variable thermal gradient is carried out.

The influence of asymmetric faces on low-velocity impact failure of CFRP/aluminum foam composite sandwich beams

The influence of asymmetric faces on dynamic failure of fully clamped CFRP/aluminum foam composite sandwich beams subjected to low-velocity impact was studied. Three kinds of geometrically asymmetric sandwich cross-sections with an equal area density were designed. The low-velocity impact experiments of the composite sandwich beams were carried out to explore the dynamic response and the failure modes. Initial failure modes of top face fracture, indentation and core shear were found. The final failure modes, including top face fracture, core shear, bottom face fracture at one end and debonding between core and bottom face, were observed. It is shown that the composite sandwich beams experience the elastic bending to large deflection. The impact load is strengthened and increases rapidly at the large deflection stage due to effect of the fully clamped boundary. Furthermore, the quasi-static theoretical models were employed to predict the dynamic response of the composite sandwich beams. the theoretical models can capture the elastic bending of the composite sandwich beams reasonably, while the initial failure loads are slightly underestimated. The comparisons of peak load and midspan deflection suggest that the asymmetric composite sandwich beams with a thinner top face have better impact resistance than other designs of the faces.

Mode decoupling in interlaminar fracture toughness tests on bimaterial specimens

The present work has a two-fold objective: (i) to critically review the methods for fracture mode decoupling in unconventional laboratory specimens, such as the asymmetric double cantilever beam (ADCB) specimen; and (ii) to propose mode decoupling conditions and associated specimen design formulae to obtain pure fracture modes when bimaterial specimens are tested in ADCB and asymmetric end-notched flexure (AENF) configurations. In the first part of the paper, the literature on fracture mode decoupling is reviewed to shed light on some controversial points. We start with discussing various pure-mode conditions suggested by different authors and continue with the simplest case of the bimaterial joint. Our review also considers complex cases, such as the presence of bending–extension coupling or residual (hygrothermal) stresses. In the second part of the paper, bimaterial specimens loaded in ADCB and AENF test configurations are investigated. Employing energetically orthogonal mode decomposition, Engesser–Castigliano’s theorem, and the laminated beam theory, we illustrate specimen design criteria enabling to obtain pure fracture modes. The obtained specimen design formulae are validated through finite element analyses.

Mixed mode fracture toughness of epoxy molding compound/printed circuit board interface of semiconductor packages with respect to temperature and moisture

Interfacial delamination is a critical factor for dissimilar bi-material interfaces in terms of structural mechanical behavior and reliability. In this study, the mixed mode interfacial fracture toughness of a thin epoxy molding compound/printed circuit board bilayer with different mixities was measured via the asymmetric double cantilever beam test with a reinforced metal jig. Additionally, mode II fracture toughness properties were measured through the end notched flexure test. All tests were performed under various temperature and moisture absorption conditions below 100℃/85 %RH. Then, a finite element simulation was performed with the cohesive zone model technique to validate the experimentally measured fracture toughness values by comparing the load–displacement curves from the experiment and simulation. Additionally, the single leg beam test and its finite element simulation were conducted and compared for validation of the measured mixed mode fracture toughness values. It was demonstrated that the developed mixed mode fracture toughness measurement method could provide accurate fracture toughness, which could effectively predict the overall load–displacement curve and damage propagation behavior.

Research on Dual-Functional Properties of an Asymmetric Piezoelectric Metamaterial Beam for Simultaneous Vibration Reduction and Power Generation

Research on Dual-Functional Properties of an Asymmetric Piezoelectric Metamaterial Beam for Simultaneous Vibration Reduction and Power Generation

An ultra-compact broadband polarizing beam splitter utilizing hybrid plasmonic waveguide

Polarizing beam splitter has rather significant applications in polarization diversity circuits and polarization multiplexing systems. In this paper, we present an asymmetric polarizing beam splitter utilizing hybrid plasmonic waveguide. The special hybrid structure with a hybrid waveguide and a dielectric waveguide can limit the energy of TE and TM modes to a different layer. Therefore, we can achieve beam splitting by adjusting the corresponding parameters of the two waveguides. First, we studied the influences of different structure parameters on the real part of the effective mode refractive index of the two waveguides, and obtained a set of parameters that satisfy the condition of strong coupling of TM mode and weak coupling of TE mode. Then, the performance of our proposed polarizing beam splitter is evaluated numerically. The length of the coupling section is only 4.1 µm, and the propagation loss of TM and TE modes is 0.0025 dB/µm and 0.0031 dB/µm respectively. Additionally, the extinction ratios of TM and TE modes are 10.62 dB and 12.55 dB, respectively. Particularly, the proposed device has excellent wavelength insensitivity. Over the entire C-band, the fluctuation of the whole normalized output power is less than 0.03. In short, our proposed asymmetric polarizing beam splitter features ultra-compactness, low propagation loss, and broad bandwidth, which would provide promising applications in polarization multiplexing system and polarization diversity circuits relevant to optical interconnection.

Optimal method for reconstructing polychromatic maps from broadband observations with an asymmetric antenna pattern

Broadband time-ordered data obtained from telescopes with a wavelength-dependent, asymmetric beam pattern can be used to extract maps at multiple wavelengths from a single scan. This technique is especially useful when collecting data on cosmic phenomena such as the cosmic microwave background (CMB) radiation, as it provides the ability to separate the CMB signal from foreground contaminants. We develop a method to determine the optimal linear combinations of wavelengths (``colors'') that can be reconstructed for a given telescope design and the number of colors that are measurable with high signal-to-noise ratio. The optimal colors are found as eigenvectors of a matrix derived from the inverse noise covariance matrix. When the telescope is able to scan the sky isotropically, it is useful to transform to a spherical harmonic basis, in which this matrix has a particularly simple form. We propose using the optimal colors determined from the isotropic case even when the actual scanning pattern is not isotropic (e.g., covers only part of the sky). We perform simulations showing that maps in multiple colors can be reconstructed accurately from both full-sky and partial-sky scans. Although the original motivation for this research comes from mapping the CMB, this method of polychromatic mapmaking will have broader applications throughout astrophysics.

Generalized Asymmetric Hermite–Gaussian and Laguerre–Gaussian Beams

We derive analytical formulae for the complex amplitudes of variants of generalized Hermite–Gaussian (HG) and Laguerre–Gaussian (LG) beams. We reveal that, at particular values of parameters of the exact solution of the paraxial propagation equation, these generalized beams are converted into conventional elegant HG and LG beams. We also deduce variants of asymmetric HG and LG beams that are described by complex amplitudes in the form of Hermite and Laguerre polynomials whose argument is shifted into the complex plane. The asymmetric HG and LG beams are, respectively, shown to present the finite superposition of the generalized HG and LG beams. We also derive an explicit relationship for the complex amplitude of a generalized vortex HG beam, which is built as the finite superposition of generalized HG beams with phase shifts. Newly introduced asymmetric HG and LG beams show promise for the study of the propagation of beams carrying an orbital angular momentum through the turbulent atmosphere. One may reasonably believe that the asymmetric laser beams are more stable against turbulence when compared with the radially symmetric ones.

A semi-analytical method for determining the mixed mode I/II fracture resistance and mode mixture of ADCB laminates

The crack tip of the asymmetric double cantilever beam (ADCB) under mode-I loading is often accompanied by a proportion of mode II component, thus it is a typical mixed-mode I/II problem. Characterizing the mixed-mode I/II fracture resistance behavior and mode partition in ADCB laminates is of great significance for studying the mode mixture phenomenon. In this work, a semi-analytical method is proposed to determine the mixed-mode fracture resistance curve (R-curve) and mode mixture of ADCB composite laminates. Considering the use of the equivalent crack length related to compliance, the global crack growth rate ratio correction model is proposed. The results derived from the proposed semi-analytical method is compared with other theoretical methods to verify its effectiveness and wide applicability for ADCB laminates with various material systems and stacking sequences. In contrast, the semi-analytical method with the global crack growth rate ratio correction requires fewer measurement data and gives accurate R-curve results. In addition, it makes the mode partition during the whole delamination growth process with physical meaning.

Self-focusing of asymmetric finite Airy-Gaussian laser beams in magnetized plasma

In this work, the role of asymmetry in the beam profile of finite Airy-Gaussian (AiG) laser is presented to explore its propagation dynamics in collisionless magnetized plasma. Emphasis is on analyzing the self-trapping condition for both extraordinary (E) and ordinary (O) modes of propagation of AiG laser beam. Theoretical formulation is based on obtaining nonlinear coupled differential equations for beam-width parameters in both transverse dimensions of the beam with the help of parabolic equation approach under WKB and paraxial approximations. It is found that asymmetry in the modulation parameters significantly affects self-focusing of finite AiG beam. Moreover, the same initial intensity parameter for simultaneous self-trapping of both modes of propagation is noteworthy.

Compressive forces influence on the vibrations of double beams

Abstract The influence of compressive forces on the lower and upper natural frequencies of the double beams has been studied in this article. Euler–Bernoulli’s hypotheses have been used to derive the natural frequency equations. Two asymmetric beams were assumed in this work, and four different boundary conditions were applied in these equations: Pinned–Pinned, Clamped–Clamped, Clamped–Free, and Clamped–Pinned. When the axial compressive force is increased about 18 times, it is observed that the lower natural frequencies decreased by 19% for PP beam, 8% for CC beam, 81% for CF beam, and 12% for CP beam. However, the greatest effect of the axial force on the higher frequencies is by reducing it in the CC beam by a ratio that does not exceed 2%. A rise in the values of axial compressive force causes a reduction in the lower natural frequencies, mostly for the CF beam, while it has a little effect on the higher natural frequencies. Similarly, when the compressive forces on the upper and lower beams fluctuate simultaneously, their effect is doubled on the frequencies when the axial compressive force on one of the two beams changes only.

Sensitivity analysis of vibration response of timoshenko beam to mass ratio and velocity of moving mass and boundary conditions: Semi-analytical approach

In real-world physics phenomena, the boundary conditions of structural members in the structural beam systems affect the system response. Also, moving load or mass problems are used widely in many engineering fields, such as structural, transportation, mechanical engineering, etc. Therefore, it is necessary to study the effect of boundary conditions on beam vibrations. Hence, a semi-analytical approach for the Timoshenko beam with various boundary conditions under moving mass is presented in this paper. Dynamic Green Function is introduced for modeling the beam under moving mass. An accurate formulation is illustrated for modeling a Timoshenko beam under moving mass with different boundary conditions. Finally, some examples demonstrate to assess of the effect of different boundary conditions, the mass ratio of moving mass, and the speed of moving mass. The numerical results are shown the efficiency and simplicity of the present approach. Based on the results, it is found that the mass ratio affects the dynamic response shape. For moving mass, the delay of the maximum dynamic deflection with respect to the mass position, increases with the speed at the higher speeds. But for smaller values of the speed, the same results of the maximum dynamic deflection for the moving load model along with the moving mass model are obtained. On the other hand, the maximum dynamic deflection points of the curves move slightly towards the right end of the beam with an increasing mass ratio. Also, the location of the constraint in the asymmetric beams is more significant in dynamic response. It is found that the dynamic behavior of the beam under moving mass changes dramatically based on the type of boundary conditions. Furthermore, the displacement obtained for each boundary condition decreases with increasing mass speed.

Tailoring freeform beam-shaping lenses for edge-emitting lasers

The edge-emitting laser diodes (EELs) are widely used in various applications, however, the strongly asymmetric beam profile along the fast and slow axes gives a big challenge to the beam shaping of EEL. Traditional optical devices mainly focus on adjusting the asymmetric divergence angle of the fast and slow axes of the EEL, and it is difficult to achieve flexible and precise control of the luminous distribution of the EEL due to the limited freedom of the conventional beam-shaping element. In this article, we employ freeform lenses to flexibly reshape EEL beams and develop an approach to tackle the obstacles caused by the strongly asymmetric beam profile by generalizing the Monge–Ampère method to tailor freeform beam-shaping lenses. Three typical but challenging beam-shaping tasks show that both the intensity and wavefront of an EEL beam can be reshaped in a desired manner by using a single compact freeform lens without any symmetric restrictions on the architecture of the beam-shaping system.