Large Beam Research Articles

Studies on the performance of water retention type tailings dams subjected to filling and inertial loading in a geotechnical centrifuge

The past decade has witnessed the failure of numerous tailing storage facilities and earthen dams. The most common factors causing failure include seepage and slope instability, apart from seismic activities. In the present study, a series of centrifuge model tests have been conducted to study the performance of water retention type (WRT) tailings dams impounded with fine tailings material (and water) on the upstream side. A custom-designed test setup to simulate upstream reservoir filling and inertial loading is employed in a 4.5 m radius large beam geotechnical centrifuge facility available at the Indian Institute of Technology Bombay, India. The centrifuge models were instrumented with pore pressure and displacement transducers to record porewater pressure (PWP) and surface settlement, respectively, and to ensure long-term safety and integrity of tailings dam. Additionally, an onboard digital camera was used to capture the front elevations of the centrifuge models to perform digital image analysis (DIA) for deducing slope face movements, surface settlements, and failure patterns. The results effectively demonstrate the performance of the WRT dam, delineate the slip surface and failure pattern, and quantify the critical design parameter related to inertial loading, which is the horizontal seismic coefficient (i.e. KHyield and KHmax). Based on these physically observed results, the analytical equations were also deduced for the WRT dams to quantify the stability (in terms of factor of safety, FS) and deformation response. The analytically obtained results agree reasonably well with the performance of WRT tailings dam models in the geotechnical centrifuge.

Determination of the Probabilistic Properties of the Critical Fracture Energy of Concrete Integrating Scale Effect Aspects

This paper presents an extension of the validation domain of a previously validated three-dimensional probabilistic semi-explicit cracking numerical model, which was initially validated for a specific concrete mix design. This model is implemented in a finite element code. The primary objective of this study is to propose a function that enables the estimation of the critical fracture energy parameter utilized in the model and validate its effectiveness for various concrete mix designs. The model focuses on macrocrack propagation and introduces significant aspects such as employing volume elements for simulating macrocrack propagation and incorporating two key factors in governing its behavior. Firstly, macrocrack initiation is linked to the uniaxial tensile strength (ft). Secondly, macrocrack propagation is influenced by a post-cracking dissipation energy in tension. This energy is taken equal to the mode I critical fracture energy (GIC) based on the linear elastic fracture mechanics theory. Importantly, both ft and GIC are probabilistic properties influenced by the volume of concrete under consideration. Consequently, in the numerical model, they are dependent on the volume of the finite elements employed. To achieve this objective, numerical simulations of fracture mechanical tests are conducted on a large double cantilever beam specimen. Through these simulations, we validate the proposed function, which is a crucial step towards expanding the model’s applicability to all concrete mix designs.

Evaluation of strength parameters of plain and reinforced concrete with the addition of polypropylene fibers

This research investigates the influence of incorporating small-diameter polypropylene fibers on the mechanical properties of concrete. The studied concrete properties include compressive strength, tensile strength, flexural strength (both plain and reinforced), shear strength, and the mitigation of shrinkage cracks. A total of 92 specimens were meticulously fabricated in the laboratory, comprising cylinders (12 inches in length and 6 inches in diameter), beams (20 x 4 x 4 inches), larger beams (60 x 9 x 9 inches), and slab panels (48 x 48 x 4 inches). During the specimen casting process, a consistent mix with a ratio of 1:2:4 and a water-cement ratio of 0.60 was consistently applied. The polypropylene fiber content varied at 0%, 0.2%, 0.4%, and 0.6% for each property examination. Results indicate a positive impact on all concrete properties studied upon the addition of polypropylene fibers. However, the optimal percentage of polypropylene fibers exhibited variability for each variable and property under investigation. This research contributes insights into the nuanced effects of polypropylene fibers on concrete properties, providing a basis for further exploration and practical application in optimizing concrete performance and durability.

(Invited) Neutrons as a Powerful Tool for Better Understanding Electrochemistry on Various Length and Time Scales

Today, sophisticated methods are applied to gain a deeper understanding of processes in in-situ electrochemistry. There are few ways to study electrochemically relevant processes on different length and/or time scales without affecting the processes themselves. Probes that cover a sufficient volume of the sample non-destructively and are sensitive to the important charge carriers are in great demand. For such purposes, neutrons are an ideal candidate to perform this task because they have relatively high sensitivity to the light chemical elements, can distinguish neighboring elements of the periodic table, have a large beam cross-section, and possess high penetration depth for many types of materials.Therefore, many open questions are addressed to unique neutron techniques tailored to solve the open problems. This article gives an overview of some examples to show the advantages of using neutrons for special questions on different length and time scales [1]. For surface investigations of electrodes, the neutron depth profiling method (NDP) is suitable for characterizing the Li distribution up to the nano range [2]. Neutron diffraction is a powerful tool to better understand cylindrical cells at the atomic level, e.g. during the intercalation process [3]. Another strong field of neutrons is the monitoring of the wetting process during the electrolyte filling of prismatic hard case cells on the macroscopic length scale using the neutron imaging technique [4].

Effect of atom diffusion on the efficiency of Bragg diffraction in atom interferometers.

The transition efficiency of atomic Bragg diffraction as mirrors and beam splitters in Bragg atom interferometers plays an essential role in impacting the fringe contrast and measurement sensitivity. This can be attributed to the properties of atomic sources, Bragg pulse shapes, the pulse duration, and the relative position deviation of the atoms and Bragg pulses. Here, we investigate the effect of the atomic source's diffusion and velocity width on the efficiency of Bragg diffraction of the moving cold atomic cloud. The transfer efficiency of Bragg mirrors and beam splitters are numerically simulated and experimentally measured, which are well consistent in comparison. We quantify these effects of atomic diffusion and velocity width and precisely compute how Bragg pulses' efficiencies vary as functions of these parameters. Our results and methodology allow us to optimize the Bragg pulses at different atomic sources and will help in the design of large momentum transfer mirrors and beam splitters in atom interferometry experiments.

Signatures of resonantly driven laser-wakefield excitation by a pulse train generated by an optical delay mask

Electron plasma waves can be efficiently excited by a resonant train of ultrashort pulses, spatially separated by a plasma wavelength. Generating a pulse train from a single amplified ultrashort pulse may be challenging when dealing with large beams. Here we discuss a pulse splitting technique using a simple delay mask that can be adapted to large diameter petawatt beams. We show via detailed numerical simulations that unique signatures of electrons accelerated by a resonantly excited wakefield can be obtained from realistic focused double-pulse trains obtained from a single-region delay mask.

Low-frequency Radio Recombination Lines Away from the Inner Galactic Plane

Diffuse radio recombination lines (RRLs) in the Galaxy are possible foregrounds for redshifted 21 cm experiments. We use EDGES drift scans centered at −26.°7 decl. to characterize diffuse RRLs across the southern sky. We find that RRLs averaged over the large antenna beam (72° × 110°) reach minimum amplitudes of R.A. = 2–6 hr. In this region, the Cα absorption amplitude is 33 ± 11 mK (1σ) averaged over 50–87 MHz (27 ≳ z ≳ 15 for the 21 cm line) and increases strongly as frequency decreases. Cβ and Hα lines are consistent with no detection with amplitudes of 13 ± 14 and 12 ± 10 mK (1σ), respectively. At 108–124.5 MHz (z ≈ 11) in the same region, we find no evidence for carbon or hydrogen lines at the noise level of 3.4 mK (1σ). Conservatively assuming that observed lines come broadly from the diffuse interstellar medium, as opposed to a few compact regions, these amplitudes provide upper limits on the intrinsic diffuse lines. The observations support expectations that Galactic RRLs can be neglected as significant foregrounds for a large region of sky until redshifted 21 cm experiments, particularly those targeting cosmic dawn, move beyond the detection phase. We fit models of the spectral dependence of the lines averaged over the large beam of EDGES, which may contain multiple line sources with possible line blending, and find that including degrees of freedom for expected smooth, frequency-dependent deviations from local thermodynamic equilibrium (LTE) is preferred over simple LTE assumptions for Cα and Hα lines. For Cα we estimate departure coefficients 0.79 < b n β n < 4.5 along the inner Galactic plane and 0 < b n β n < 2.3 away from the inner Galactic plane.

A low-frequency normal conducting cavity with higher-order mode damping for fourth-generation synchrotron radiation sources.

The utilization of a low-frequency (<200MHz) RF system in storage facilitates the attainment of ultra-low emittances in synchrotron light sources through on-axis injection. This paper focuses on the development of a low-frequency normal conducting (NC) cavity with higher-order mode (HOM) damping for fourth-generation synchrotron light sources. We propose a novel approach to achieve efficient HOM damping in a NC cavity by optimizing the lowest frequency HOM and implementing a beam-line absorber. Notably, unlike conventional NC cavities, the presence of a large beam tube for the beam-line absorber does not compromise the accelerating performance in a coaxial resonant cavity, enabling effective HOM damping while maintaining a high shunt impedance. Through simulations, the prototype design of a 166.6MHz HOM-damped cavity demonstrates a fundamental mode impedance of ∼8 MΩ, with longitudinal and transverse HOM impedances below 2.0 and 50 kΩ/m, respectively.

Compact design of the 166.6 MHz superconducting cavity and its beamline elements for HEPS

The High Energy Photon Source (HEPS) is a 6 GeV diffraction-limited synchrotron light source under construction in Beijing. It will use five 166.6 MHz superconducting radio frequency (rf) cavities to accelerate the 200 mA electron beam in the storage ring. In the current lattice design, each straight section is 6 meters long to accommodate two 166.6 MHz cavities. The cavity adopts β=1 quarter-wave geometry, and the damping of the higher order modes is realized by using an enlarged cavity beam pipe to 505 mm and a ferrite absorber installed on the beam pipe. The low rf frequency, as well as the large beam aperture, added great challenges to the design of the 166.6 MHz cavity module to fit into a strictly limited longitudinal space. In addition, heat load optimization for the transition from room temperature to the cryogenic temperature, smooth tapering from the 505 mm beam aperture to the small diameter of the gate valves for impedance control, proper collimation of the synchrotron light to prevent thermal damage of delicate components, are also demanding requirements for a compact design. Accessibilities are also preserved for tuners and vacuum components to enable online maintenance. Finally, rf field leakage in the vacuum seal groove of the cavity is carefully examined to prevent overheating on the superconducting flange, which, in the worst scenario, may cause a thermal runaway, thus limiting the achievable accelerating gradient of the cavity. This paper presents the first compact design of the 166.6 MHz srf section for HEPS.

Multi-Asymmetric Irradiation Method Using a Ring Array to Obtain an Emission-Capable LED Beam Power Effect to Observe Cancer Removal Status in a Surgical Microscope.

The light emitting diodes (LEDs) used in surgical fluorescence microscopes have weak power, to induce fluorescence emission. The LED induces fluorescence emission throughout a lesion due to its large beam width; however, the beam irradiation intensity is not uniform within the beam width, resulting in a fluorescence emission induction difference. To overcome this problem, this study proposes an asymmetric irradiation array for supplying power uniformly throughout the beam width of the LED and increasing the intensity of the LED. To increase the irradiation power of the LEDs, a multi-asymmetric irradiation method with a ring-type array structure was used. The LED consisted of eight rings, and the space between the LEDs, the placement position, and the placement angle were analyzed to devise an experimental method using 3D printing technology. To test the irradiation power of the LED, the working distance (WD) between the LED and target was 30 cm. The bias voltage of the LED for irradiating the light source was 5.0 V and the measured power was 4.63 mW. The brightness (lux) was 1153 lx. Consequently, the LED satisfied the fluorescence emission induction conditions. The diameter of the LED-irradiated area was 9.5 cm. Therefore, this LED could be used to observe fluorescent emission-guided lesions. This study maximized the advantages of LEDs with optimal conditions for fluorescence emission by increasing the beam width, irradiation area, and energy efficiency, using a small number of LEDs at the maximum WD. The proposed method, optimized for fluorescence expression-induced surgery, can be made available at clinical sites by mass producing them through semiconductor processes.

Beam Size Optimization for High-Altitude Platforms to Ground Links in FSO Communications

Free-space optical (FSO) communication has been used in practice mainly for short-distance transmission because it requires light of sight (LoS) between the transmitter and receiver. For long-distance communication, to avoid terrestrial obstacles, high-altitude platforms (HAPs) flying at stratosphere are used to carry intermediate FSO transceivers which relay data through several hops from the source to the destination stations. A HAP can communicate with a large ground area if its FSO transceiver projects a wide beam onto the ground. However, an excessively large beam makes the FSO transceiver consume a lot of energy. This study investigates the problem of finding individual optimal beam sizes for FSO transceivers on HAPs so that the total cost of the HAP network, including the amortization, energy, and maintenance costs, is minimized. An optimization algorithm was proposed and implemented. The simulation results show the network designed by the algorithm achieves a nearly optimal number of HAPs, leading to a low network cost.

Hagiography and the Tijaniyah Order of Shaikh Badruzzaman in Garut, West Java, 1990-1935

Shaykh Badruzzaman is a figure of great influence who teaches the Tijaniyah Order in Garut. Syaikh Badruzzaman's specialty or Karomah was already visible when he was born until the colonial period. His journey in studying which made Syaikh Badruzzaman explore knowledge from various teachers, so that he had rejected the teachings of the Tijaniyah order at first and even came to the leaders of the Tijaniyah order to discuss. This is interesting, where he initially rejected and finally accepted and even received an Ijazah and spread the Tijaniyah order in Garut. The purpose of this research is to find out that there is Karomah what is in Syaikhuna Badruzzaman that appears since he was born, then how his thoughts in accepting and developing the teachings of the Tijaniyah tarekat. In this research, the methods used are the stages of heuristics, criticism, interpretation and historical historiography. The results of this study show that Syaikh Badruzzaman has several Karomahs, among others, when he was born, a very large light beam appeared, when reciting the Al-Quran he always slept, but when asked, he could explain in detail and correctly, when the lights went out in the pesantren when the students were reciting the Koran, there was light from Syaikh Badruzzaman's body, and other karomahs. In the teachings of the Tijaniyah tariqah he refused, but after a while he changed without knowing why, then hesitated, then accepted it and came to Shaykh Ali bin Abdullah At-Thayyib and then spread it.

Laser-induced damage growth of fused silica optics near growth threshold at 351 nm.

Laser-induced damage growth on the exit surface of fused silica optics triggered by nanosecond pulses at 351 nm is widely described with exponential dynamics. In this Letter, a particular experimental setup allowed us to study damage growth with a large beam and fluences near damage growth threshold for a high number of shots. This allowed us to observe and characterize a regime with a slow and linear growth dynamic not documented in the literature and yet fundamental for the operation of high-power laser installations.

Electric field in the RF cavity with large beam duct for high current beam acceleration

A acceleration scheme using a bunch of single-cell cavities as the first-stage acceleration of ion beams. The single-cell cavity has been shown the possibility of accelerating high-current beams of 1 A or more. As an elemental test before we started a cavity fabrication, we compared simulations of the electric field distribution with experiments utilizing the existing cavity.

Damage Analysis and Quality Control of Carbon-Reinforced Concrete Beams Based on In Situ Computed Tomography Tests

Carbon-reinforced concrete (CRC) is increasingly utilized in construction, due to its unique properties, such as corrosion resistance, high-tensile strength, and durability. Understanding its behavior under different loads is crucial to ensuring its safe and effective use in various construction applications. In this study, three-point bending tests were performed in combination with large-scale in situ computed tomography (CT). This paper presents the related three- and four-dimensional evaluation methods, with emphasis on crack width and quality control. The focus was on large CRC beams, with cross-sectional sizes of up to 80 mm by 160 mm. Such dimensions require extremely high energy during a CT scan. Therefore, a new experimental setup with energies of up to 8 MeV was used in this study. However, such high energies posed new challenges to the analysis methods. Therefore, two methods (digital volume correlation and grayscale profile analysis) for accurate crack width estimation were adapted and applied to the 3D reconstructions. In addition, a photogrammetric stereo image sequence was acquired and analyzed, using digital image correlation to cross-validate the results derived from the 3D crack width estimates. The 3D CT images also played a key role in the quality control measures, including the localization of the carbon-reinforcement and the assessment of porosity within the concrete structure.

Modal Behavior of Microcantilevers Arrays with Tunable Electrostatic Coupling

We analyse the spectral content and parametric resonant dynamics of an array of elastically and electrostatically coupled interdigitated micro cantilevers assembled into two identical half-arrays. In this uncommon arrangement, within each of the half-arrays, the beams are coupled only elastically. The half-arrays are intercoupled only electrostatically, through fringing fields. First, by using the reduced order (RO) model, we analyse the voltage-dependent evolution of the eigenvalues and the eigenvectors of the equivalent mass-spring system, starting from the small two, three and four beams arrays and up to large beams assemblies. We show that at the coupling voltages below a certain critical value, the shape of the eigenvectors, the frequencies of the veering and of the crossing are influenced by the electrostatic coupling and can be tuned by the voltage. Next, by implementing the assumed modes techniques we explore the parametric resonant behavior of the array. We show that in the case of the sub critical electrostatic coupling the actuating voltages required to excite parametric resonance in the damped system can be lower than in a strongly coupled array. The results of the work may inspire new designs of more efficient resonant sensors.

Development and comparison of algorithms for beam stabilization in ultrashort pulsed laser equipped on a six-axis robot

We demonstrate an innovative beam stabilization concept consisting of complementary metal-oxide semiconductor cameras and piezo actuators for a six-axis articulated ultrashort pulsed laser robot system. The beam stabilization system is fixed on robot axes 4 and 5. Moving robot axis 5 in an angular range between 0° and 90°, the laser beam position coupled to the actual robot position is monitored by two cameras integrated on robot axis 5 and used for laser beam characterization and model generation. A mathematical description and models generated with machine learning methods, namely, linear regression and neural network, are compared for predicting the beam position drift as a function of robot axis motion, where the neural network model shows a low prediction tolerance of about 7 pixels. In addition, a stand-alone time-triggered beam correction algorithm is developed and implemented on the system, which shows an excellent correction performance for large beam position drifts (below 500 pixels).

Switchable terahertz orbital angular momentum Bessel beams based on spin-decoupled multifunctional reflective metasurfaces.

In this study, switchable terahertz (THz) multi-orbital angular momentum (OAM) Bessel beams (BBs) were developed based on a spin-decoupled reflective multifunctional metasurface (MTS). Switchability was achieved by switching the feed between left-hand circular polarization (LCP), right-hand circular polarization (RCP), and linear polarization (LP) incidences. A switchable physical model was established for calculating the beam direction, OAM mode, polarization, and non-diffractive distance of the outgoing BBs. As an example, a spin-decoupled MTS was designed to generate dual BBs under LCP incidence, which was subsequently switched to RCP or LP for switchability. The outgoing BBs could be switched among three types of beams: Type-1 under LCP incidence (LCP, θL = 40°, φL = 0°, lL = 1, dL = 18 cm) and (RCP, θR = -40°, φR = 0°, lR = -1, dR = 20 cm); Type-2 under RCP incidence (RCP, θR = 40°, φR = 0°, lR = 1, dR = 18 cm) and (LCP, θL = -19°, φL = 0°, lL = 3, dL = 16.4 cm); and Type-3 under LP incidence (LP, θ = 40°, φ = 0°, l = 1, d = 18 cm), (RCP, θR = -40°, φR = 0°, lR = -1, dR = 20 cm) and (LCP, θL = -19°, φL = 0°, lL = 3, dL = 16.4 cm). Compared with previous MTSs, the proposed spin-decoupled MTS has the advantages of switchability among BBs, high non-diffractive distance/aperture size ratio of 15, large beam deflection angle of up to 40°, and high BB conversion efficiency of up to 96%. The simulated results were consistent with those calculated using the physical model, thus validating the physical model. The designed switchable BBs have potential THz near-field applications, such as high-capacity near-field wireless communications, wireless power transfer, high-resolution imaging, non-destructive testing, and speed detection of high-speed rotating objects.

Component Modeling for Fire Behavior of Shear Tab Connections

During a building fire scenario, the behavior and capacity of gravity connections can significantly contribute to the integrity of steel-framed building structures. Because gravity connections are subjected to axial and flexural force demands and have a limited rotational capacity due to large beam rotations during a fire scenario, a connection model is needed to simulate their behavior when using analytical models to simulate the behavior of a steel structure in fire. This study develops a component model for shear tab connections at ambient and elevated temperatures in the opensource finite element program, OpenSees, to further enable the use of OpenSees for simulating steel structures in fire. Although the developed component model is not limited to implementation within OpenSees. The developed component model is benchmarked against experimental tests of isolated connections and a structural assembly with shear tab connections subjected to mechanical and thermal loads. Through benchmarking, it is shown that (1) the developed component model could be used to simulate connection behavior during a fire scenario and (2) simulating the ductility of connections and connecting components due to damage is critical when simulating the behavior of shear tab connections exposed to fire.

Designing a sky-scanning Fabry–Perot interferometer system with a large size integrating sphere

Integrating spheres can be manufactured at sizes ranging from 1 mm to 3 m in diameter. It has been agreed widely by manufacturers that fitting a large-sized integrating sphere as per the customer requirement is a complex process. Thus, these spheres due to its large beam divergence from the exit port, have never been deployed for the calibration of aeronomy applications. In this article a optical system is described to integrate a large-sized integrating sphere with the Fabry–Perot etalon and thus devise a set-up to generate the concentric ring pattern and record it on the detector. The experimental set-up was verified by optical simulation using ZEMAX (OpticStudio) so as to validate the system’s performance in the laboratory. The important parameter finesse is calculated and its accuracy is found to be 80%.