Large Beam Research Articles

Monte‐Carlo Study on Temperature Effect on Scanning Electron Microscopy Contrast for One Spherical Nanoparticle in Multiframe Stacking Mode

Modern scanning electron imaging (SEM) has become an essential tool in various fields. In order to obtain high‐quality images with minimal vibration and drift, the multi‐frame stacking technique is commonly used. However, one aspect that has been overlooked in this process is the electron beam‐induced temperature effect. This study aims to explore the impact of the temperature effect on SEM contrast for a single spherical nanoparticle, specifically a gold nanosphere on a carbon substrate. Through Monte‐Carlo simulation, we investigated how the number of frames in multi‐frame stacking mode affects two types of electron signals: secondary electrons (SE) and backscattering electrons (BSE). Our findings revealed that the SEM contrast is indeed sensitive to the number of frames used in the stacking process. It is observed that the SE contrast decreases while the BSE contrast increases compared to cases without considering temperature effects. It is also found that when using the large primary electron beam energy, the impact of temperature effect was less significant. The electron‐solid interaction theory was utilized to systematically explain the underlying mechanism. This study not only sheds light on how temperature effects can influence SEM imaging but also provides valuable insights for optimizing image acquisition techniques.

A Beam Hopping Scheme Based on Adaptive Beam Radius for LEO Satellites.

Toward the vision of seamless global connectivity in the 6G era, the non-terrestrial network (NTN) in space-air-ground integrated networks (SAGINs) network architecture is one of the highly promising solutions. From the perspective of relay nodes, NTN includes satellite nodes and space-based platform nodes. As a resource management technology in satellite communication, beam-hopping has garnered significant attention from researchers due to its effectiveness in ad-dressing the disparity between offered capacities and uneven terrestrial traffic demands. Recognizing that the larger beams offer broader coverage but the smaller ones provide better an-ti-interference capabilities and higher throughput, this paper introduces an adaptive cluster-ing-based approach. It provides large, medium, and small user beams to target ground users. The proposed algorithm aims to minimize total system latency and enhance system throughput. Sim-ulation results show that employing the proposed algorithm in the baseline model results in a 3.44% increase in system throughput and a 35.5% reduction in system latency. Furthermore, simulation results based on alternative models indicate that while the proposed algorithm may lead to a slight decrease in system throughput, it brings significant improvements in system latency.

Computed tomography of the equine caudal spine and pelvis: Technique, image quality and anatomical variation in 56 clinical cases (2018-2023).

Cross-sectional imaging improves the diagnostic accuracy of complex anatomical regions. Computed tomography (CT) of the pelvis and caudal spine in a large group of live horses and ponies has not been previously reported. To describe the procedure for acquiring CT images of horses' caudal spine/pelvis under general anaesthesia (GA) and to detail the image quality, artefacts and anatomical variations in this region. Retrospective case series. Horses with CT of the caudal spine/pelvis were included. Horses under 6 months and CT examination performed post-mortem were excluded. Protocols, image quality, region of interest, anatomical features and morbidities were analysed. Fifty-six horses (8 months to 20 years, 85-680 kg) met the inclusion criteria. GA ranged from 10 to 60 min (mean: 30, median: 32). There were no adverse events recorded in any of the horses associated with the procedure. Images of all horses were considered of diagnostic quality. Anatomical variations were common and included the location of diverging (widest) interspinous space, the presence of spina bifida in the lumbar and sacral spine, the shape of the last lumbar vertebra and the location of intertransverse joints in terms of where they were present and the degree of fusion/modelling. Not all horses underwent CT examination of the same regions, the upper size limit of horses is unknown and will vary depending on bore size and table infrastructure. Image noise, particularly in large horses and beam hardening artefacts from hardware and pelvis degraded image quality. Images were of insufficient quality in large horses for soft tissue interpretation. CT of the caudal spine and pelvis in live horses with wide-bore CT machines and modified patient infrastructure was safe and produced diagnostic images.

Design and kinematics analysis of a cable-stayed notch manipulator for transluminal endoscopic surgery

The friction between the joints of the continuum manipulator with discrete joints brings great difficulties to kinematic modeling. The traditional driving wire arrangement limits the load capacity of the manipulator. A cable-stayed notch manipulator for transluminal endoscopic surgery is proposed, and a driving force coupling kinematic mode is established. The manipulator is fabricated from a superelastic Nitinol tube with bilaterally cut rectangular notches and is actuated by a stay cable. By applying the comprehensive elliptic integral solution (CEIS) for large deformation beams, the bending angle of each elastic beam is obtained, and the kinematics from the driving space to the joint space is formed. According to the bending angle of each elastic beam, the expression of the manipulator in Cartesian space can be obtained by geometric analysis. The kinematics from the joint space to the Cartesian space is established. The outer diameter of the manipulator is only 3.5 mm, and the inner diameter can reach 2 mm, allowing instruments to pass through. The maximum error of the manipulator movement is less than 5%. The load capacity of the manipulator has been verified through the stiffness experiments, and the maximum load of the manipulator can reach 400 g. The cable-stayed notch manipulator can be accurately modeled on the base of CEIS, and its motion accuracy can meet the needs of engineering applications. The compact size and excellent load capacity of the manipulator make it potential for application in transluminal endoscopic surgical robots.

Procedimentos para modelagem BIM de lajes nervuradas de concreto armado em edificações

It is impossible not to admit that commercial computational tools for structural analysis and detailing have become indispensable in the various applications of Structural Engineering nowadays. The importance of these tools equipped with graphical interfaces based on the BIM (Building Information Modeling) environment is mainly due to the flexibility and ease in making common corrections and changes during the elaboration stage, as well as the proposition of different structural conceptions, not always innovative, but almost always bold, as in the case of reinforced concrete ribbed slabs. The use of ribbed slabs in reinforced concrete is an old practice in Structural Engineering, which has encouraged the adaptation of commercial computational tools, both in the development of structurally consistent mathematical formulations, as well as in the development of specific databases, equipped with information from mold manufacturers and materials intended for the execution of this type of slabs. It is highly efficient in building structures in which there are numerous problems of interference of structural elements with elements of installations, such as large-diameter pipes for wastewater, sewage, gas, fire, and even air conditioning ducts, exhaust and architectural elements. This efficiency is mainly due to the fact that large beams are not considered in their supports, making the lower face of the slab practically without obstacles to the building pipes, and is also due to the low average thickness of concrete used in the pavement compared to conventional rectangular supported slabs and flat mushroom slabs. However, it is not always possible to obtain an optimal final result, even with all the adaptations previously described, mainly due to executive and computational modeling problems. This work intends to present a possible structural modeling methodology, which provides results within the limits of the feasibility of the slab, both in the construction aspect of the computational structural model, as well as the possibility of using materials from manufacturers and labor, using a commercial computational tool for structural analysis and detailing.

Ultrahigh Extinction Ratio Leaky-Guided Hollow Core Fiber Mach-Zehnder Interferometer Assisted by a Large Core Hollow Fiber Beam Splitter.

We proposed a novel fiber Mach-Zehnder interferometer (FMZI) that can perform an ultrahigh extinction ratio (ER), ultracompact, and ultra-broadband interference characteristics. The FMZI structure is based on an extremely tiny hollow core fiber (HCF) with a small diameter of 10 μm (named HCF10) connected with a beam splitter of a large core of 50 μm HCF (named HCF50). The refractive index (RI) of the air core is lower than that of the HCF cladding; a leaky-guided fiber waveguide (LGFW) occurs in such a short-section HCF10 waveguide to simultaneously have the core and cladding modes. To achieve better fringe visibility of the interference, the section of HCF50 assists in splitting the optical light into core and cladding beams launched into the HCF10 with appropriate intensities. Experimental and simulation results show that the optical characteristics of the proposed LGFW-FMZI are very similar. Based on the results of the study, the length of the HCF10 primarily influences the free spectral range (FSR) of the interference spectra, and the HCF50 splitter significantly controls the optimal extinction ratio (ER) of the interference fringes. By exactly adjusting the lengths of HCF10 and HCF50, the proposed fiber interferometers can perform the capability of an ultrahigh ER over 50 dB with the arbitrary FSR in the transmitted interference spectra over an ultra-broad wavelength range of 1250 nm to 1650 nm.

Disruption runaway electron generation and mitigation in the Spherical Tokamak for Energy Production (STEP)

Abstract Generation of Runaway Electrons (REs) during plasma disruptions is of great concern for ITER and future reactors based on the tokamak concept. The current STEP (Spherical Tokamak for Energy Production) concept design features a plasma current higher than 20 MA, thus expected to be in a regime of very high avalanche multiplication. This is confirmed by modelling runaway electron generation in unmitigated disruptions using the code DREAM, with hot-tail generation found to be the dominant primary generation mechanism and avalanche confirmed to be extremely high. Varying assumptions for the prescribed thermal quench phase (duration, final electron temperature) as well as the wall time, the plasma-wall distance, and shaping effects, all STEP unmitigated disruptions are found to generate large runaway electron beams (from 10 MA up to full conversion). The possibility of RE avoidance is first studied by idealized, i.e. radially uniform, impurity injection of a mixture of argon and deuterium, with ad-hoc particle transport arising from the stochasticity of the magnetic field during the thermal quench (TQ). Unfortunately, no such injection scenario allows runaways to be avoided while respecting the other constraints of disruption mitigation. STEP disruption mitigation system (DMS) has then been tested with DREAM, by modelling 2-stage Shattered Pellet Injections consisting of pure D2 followed by Ar+D2. Such a scheme is found to reduce the generation of REs by the hot-tail mechanism, reducing the final RE current to about 13 MA, but isn't sufficient by itself. Options for mitigating such a RE beam (benign termination scheme), as well as estimations of required RE losses during the current quench (from a potential passive RE mitigation coil) will also be briefly discussed.

Comprehensive measurement of three-dimensional thermal conductivity tensor using a beam-offset square-pulsed source (BO-SPS) approach

Accurately measuring the three-dimensional thermal conductivity tensor is essential for understanding and engineering the thermal behavior of anisotropic materials. Existing methods often struggle to isolate individual tensor elements, leading to large measurement uncertainties and time-consuming iterative fitting procedures. In this study, we introduce the Beam-Offset Square-Pulsed Source (BO-SPS) method for comprehensive measurements of three-dimensional anisotropic thermal conductivity tensors. This method uses square-pulsed heating and precise temperature rise measurements to achieve high signal-to-noise ratios, even with large beam offsets and low modulation frequencies, enabling the isolation of thermal conductivity tensor elements. We demonstrate and validate the BO-SPS method by measuring X-cut and AT-cut quartz samples. For X-cut quartz, with a known relationship between in-plane and cross-plane thermal conductivities, we can determine the full thermal conductivity tensor and heat capacity simultaneously. For AT-cut quartz, assuming a known heat capacity, we can determine the entire anisotropic thermal conductivity tensor, even with finite off-diagonal elements. Our results yield consistent principal thermal conductivity values for both quartz types, demonstrating the method's reliability and accuracy. This research highlights the BO-SPS method's potential to advance the understanding of thermal behavior in complex materials.

Tailoring an arbitrary large vectorial structured light beam array utilizing the tensor theory of multiplexed polarization holograms

Vectorial structured light beams, characterized by their topological charge and non-uniform polarization distribution, are highly promising beam modes for several applications in different domains of optics and photonics. To harness its potential specifically in optical communication, data encryption, and optical trapping, it is necessary to tailor a multitude of these beams with arbitrary and large topological charge and polarization distribution. However, achieving the above-mentioned requires bulky optical setups that necessitate the superposition of two beams or involve complex material fabrication techniques that can directly generate these beams. In this paper, we report the generation of a large structured light beam array by utilizing multiplexed polarization holograms, computer-generated holography, and azo-carbazole polymer film. We have developed a theoretical framework for double-exposure polarization holography that enables the possibility of tailoring such a vectorial light beam array. Utilizing the developed theory, we showcase the experimental generation of a structured vector beam array of size 8 × 8 with arbitrary topological charges and polarization distribution in 3 mm × 3 mm area of the polymer film. Exploiting the large space bandwidth of the polymer film, we also demonstrate the generation of vector vortex beam arrays with exceptionally large topological charges (l=100). All the above has been experimentally realized by simply illuminating the hologram with a plane Gaussian beam, and no additional optics are needed. This reported method offers huge potential and opens up new possibilities for the utilization of vectorial structured light beams.

Centrifuge modeling of levees with geocomposite chimney drain subjected to flooding

The objective of present study is to evaluate the performance of a levee subjected to flooding and seepage through centrifuge model tests. For this, six model tests were conducted on a 240 mm high levee model at 30g in a 4.5 m radius large beam centrifuge. A custom-developed simulator is employed to induce identical flood rates on the upstream side of models. Further, using (a) geocomposite (GC) and (b) sand-sandwiched geocomposite (SSGC) as internal chimney drain, the suitability of GC material for dissipation of pore-water pressure (PWP) is also studied. The results of the centrifuge tests are discussed in terms of the development of upstream flood function, PWP within the levee body, and the surface settlements at the levee's crest. Further, the influence of an internal chimney drain, the material used for its construction, and its type and composition on the seepage response of the levee are discussed. It is observed that a GC-based chimney drain with sand cushioning on both sides in the horizontal portion of the chimney drain performs well. Further, digital image analysis of SEM micrographs of exhumed GC after centrifuge tests and the analyzed PWP data during sustained flooding-induced seepage is found to corroborate well.

Dynamic loading platforms coupled to ultra-high speed X-ray imaging at beamline ID19 of the European Synchrotron ESRF

ABSTRACT The intersection of dynamic compression, high-rate material response and X-ray science has seen rapid growth, leading to the establishment of specialized end-stations at international facilities such as Linac Coherent Light Source LCLS (Matter at Extreme Conditions – MEC) and Advanced Photon Source APS (Dynamic Compression Sector – DCS), both USA. Although these facilities excel in working with X-rays tailored for small material volumes (i.e. < 1 mm 3 ), it needs a different approach to delve into subsequent processes. This is particularly the case in the transition from the micro- to mesoscale: here the ESRF distinguishes itself. The large beam size (several cm2) of the ID19 beamline, in conjunction with a strong high energy component, source flux density, and outstanding imaging sensitivity, enables sub-surface visualization of engineering-scale structures as well as natural systems in representative volume, under high rate and shock. This is particularly valuable when studying materials with complex mesostructures and heterogeneities on relevant volumetric scales, which often dominate the dynamic material response. The study of the behavior of materials under dynamic loading presents a unique challenge due to inherently spanning over multiple lengths- and timescales. The evolution of sudden (thermo)mechanical excitation, starting from the lattice scale and progressing through grains, phase domains, and ultimately to structures, exhibits a spectrum of responses spanning from the microscopic to bulk length scales. Consequently, a diverse range of diagnostics as well as driver instrumentation is required to identify, study, and characterize this material response spectrum. This article shall introduce platforms available at beamline ID19 and underline their potential by selected showcase applications. Community access proposals such as the beamtime Block Allocation Group (BAG) allow for access in a routine manner.

Designing ITER motional Stark effect line shift (MSE-LS) spectrometers.

As a part of ITER beam aided diagnostics, the design of Motional Stark Effect (MSE) diagnostic observing the emission from the Balmer-α line is underway. The physics of Stark splitting shows that the Stark manifold is polarization dependent, and the energy splitting results in a line shift proportional to the electric field. Due to the challenges of maintaining the calibration of the plasma facing mirrors in ITER, the conventional MSE polarimetry measurement technique is replaced with a spectral approach that is deemed more favorable in the ITER environment. The MSE line shift (LS) diagnostic is designed to quantify the Lorentz electric field magnitude by measuring the Stark manifold using visible spectroscopy. In the presence of large magnetic fields and high energy heating beams of 1MeV, the expected Stark splitting is much larger than in typical devices. The MSE-LS design has unique challenges requiring careful consideration and modeling of its viewing geometry and photon budget. The MSE-LS approach on ITER is promising but has stringent demands on the allowable errors for the statistical and systematic fitting uncertainties. In this study, a full system model and numerical simulations of data for each sightline are completed. For a range of optical transmission fractions, photon noise analysis is conducted to determine the statistical uncertainties. This provides guidance on the spectrometer throughput, dispersion at the detector, optics, and other design choices. A conceptual design of a high throughput spectrometer with a volume phase transmission grating is presented.

Complementary split resonant ring inspired wide-angle frequency-scanning patch array leaky-wave antenna with open-stopband suppression

In this paper, a wide-angle scanning and dual-linearly polarized leaky-wave antenna (LWA) is proposed based on symmetrical complementary split resonant ring (CSRR) feeding lines. The CSRR excites high-dispersed spoof surface plasmon polaritons (SSPPs) and is inspired to enlarge the scanning angle of the circular patch array antenna. The coupling between CSRR and circular patch determines the unit cell dispersion characteristics of LWA, and the coupling between CSRR and circular patch is controlled by designing their respective periods, p/b, to suppress the open-stopband and reduce the grating lobe, The value of p/b controls the frequency range of the open-stopband. Two parallel CSRR feeding lines are located on the bottom layer of the antenna and feed the array antenna of 11 circular patches above the feeding layer with both differential and common modes excitations. The two modes switch with 1-bit phase shifters on the two parallel feeding lines fed with a Wilkinson power splitter and electronically switch dual-linearly polarized radiations. The proposed scenario of the LWA prototype is validated through simulations and experiments. According to the measurements, horizontally polarized radiation achieves large beam scanning angle from −59.5° to +40° in the frequency range from 8 to 11 GHz with common mode excitation. And vertically polarized radiation scanning the main beam from −47° to +41° in the frequency range from 7.8 to 10.8 GHz with differential-mode excitation. The measured peak gains of the two polarizations are 14.4 dBi and 14.2 dBi, respectively, and the cross-polarization ratios are above 21 dB.

Modeling Abduction Mechanism of Soft Actuator with Elastica for Robotic Hands

Abstract Soft actuators, composed of pliable materials, are increasingly adopted in industrial grippers owing to their inherent flexibility, elasticity, and safety attributes, rendering them conducive for anthropomorphic robotic applications. Notably, a discernible void in extant literature pertains to the nuanced exploration of hand abduction movements. Addressing this lacuna, the present investigation delineates three salient contributions. Primarily, it introduces the Abduction Soft-Actuator (ASA) &amp;#x96; an innovative design specifically tailored for robotic hand abduction. Secondly, it posits an analytical framework augmented by Large Deformation Virtual Beam (LDVB) theory for soft Elastica, facilitating a rigorous dissection of the intrinsic physical properties of the actuator's internal membrane. Thirdly, the study underscores the versatility of the ASA, drawing attention to its innate capability to seamlessly integrate membranes and springs, extending its applicability across multifarious design paradigms. Empirical findings accentuate the ASA's proficiency in prognosticating operational angles under an assortment of spring conditions, thereby refining spring selection protocols for a gamut of applications. Diverging from traditional soft actuators which predominantly deploy a singular material, the ASA epitomizes modularity, allowing for facile spring alternations to cater to diversified requirements. In juxtaposition with prevailing case-by-case analytical approaches, the ASA conspicuously amplifies its domain of applicability. Validation experiments employing inflated silicone membranes substantiate the LDVB theoretical framework, intimating those estimations, reliant on empirical metrics, are amenable to analytical prognostication. Collectively, this methodological intervention not only bridges the prevailing technological chasm but also enriches the comprehension matrix associated with soft actuator mechanism across myriad applications.

Pathways to exploit the multi-spot scanning strategy in electron beam additive manufacturing for control of microstructure and defect density

The goal of this study is to investigate the impact of beam deflection pattern characteristics on microstructure and porosity formation during Powder Bed Fusion Electron Beam Melting (PBF-EB/M) processing of Inconel 718. Specifically, the complex interplay between “beam return time” and “beam jump distance” and their influence on heat accumulation, porosity, and grain formation is explored. The findings reveal that beam jump distance plays a critical role in the transition from columnar to equiaxed solidification, while beam return time is essential for achieving optimal heat accumulation and minimizing porosity. By controlling these two universal beam deflection pattern characteristics, a novel multi-spot scanning strategy was developed, enabling the formation of a fine-grained equiaxed microstructure. It is demonstrated that sufficient heat accumulation is essential for a pore-free bulk material and can be achieved by short beam return times or small beam jump distances. However, for equiaxed grain formation, a large beam jump distance, i.e., a wide distribution of melt pools, is required. Therefore, heat accumulation must be controlled by means of the beam return time if equiaxed grains are aimed for. Additionally, it is found that higher beam currents are beneficial for equiaxed grain formation, but the strongest impact on the columnar to equiaxed transition is attributed to the beam movement pattern itself. This approach offers insights into microstructure control and process reliability, regardless of the specific PBF technique employed, and enables application-specific microstructure design of Inconel 718.

Geochemical analysis of extremely fine-grained cryptotephra: New developments and recommended practices

Tephrochronology is a powerful tool used to synchronise and date stratigraphic records by accurate and precise geochemical analysis of deposited volcanic glass shards. However, in many distal stratigraphic records (e.g., polar ice cores) tephra shards are often extremely fine-grained (<10 μm). Geochemical characterisation of these shards is challenging because conventional preparation and analytical techniques require highly polished glass areas >5 μm for electron probe microanalysis (EPMA) to ensure high analytical totals and minimise alkali element loss. Recent method developments have put forward alternative approaches to accurately measure major oxides of small shards: a smaller 3 μm diameter beam, overlapping large (20 μm) beam areas onto supporting epoxy resin, and using scanning electron microscopy with energy dispersive spectrometry (SEM-EDS). However, there has been no direct intercomparison of these alternative techniques, which to date have only been tested on a limited range of glass compositions and tephras that are much larger than the extremely fine-grained material found in distal archives. These issues complicate decision making about the best analytical approach to take when faced with small shards. Here, we provide a new workflow protocol for the analysis of <10 μm tephra by determining the accuracy and precision of alternative SEM-EPMA methods. By analysing a variety of glass standards including those prepared to replicate fine-grained ice-core cryptotephras, we show that a 3 μm EPMA beam is suitable for use on all glass compositions provided the beam current is reduced to 1 nA. When glass areas are too small for a 3 μm beam we show that overlapping this small beam onto epoxy resin is preferable to SEM-EDS analysis. We also provide evidence confirming that using 3–0.2 μm polishes for <5 min increases analytical precision of the most abundant major oxides by up to three times, whilst, crucially, preserving the smallest shards in a sample. By directly applying these alternative methods to ice-core cryptotephra, we demonstrate the data are of suitable accuracy and precision to make robust geochemical correlations. This workflow can be applied to future tephrochronology studies, significantly increasing the quality and quantity of data that are obtained from cryptotephra horizons in distal records.

Research on the Method of Prestressing Tendon Layout for Large-Span Prestressed Components Continuous Rigid Frame Bridge Based on “Zero Bending Moment Dead Load Theory”

Based on the theory of zero bending moment under constant load, various optimization methods exist for the top beam of large-span continuous rigid frame bridges. These include achieving zero bending moment at the root of the cantilever beam, at the control stage section, and through the zero deflection method. This study aims to explore the methods and effects of optimizing roof beam design using the constant load zero bending moment method and the “three group bundle method”. Using finite element modeling, the total number and eccentricity of prestressed tendons required for each suspended pouring block are determined. Additionally, the “three group beam matching method” is employed to adjust the steel beam, adhering to the design concept of “large cantilever beam matching and small cantilever beam matching”, to achieve a reasonable configuration of the top plate beam. Through specific engineering examples, the results demonstrate that utilizing the constant load zero moment method and the “three group bundle method” can significantly enhance the structural performance and economy of large-span continuous rigid frame bridges. Moreover, it offers practical operability, providing an important reference basis for similar project designs.

Beyond Event-Centric Narratives: Advancing Arabic Story Generation with Large Language Models and Beam Search

In the domain of automated story generation, the intricacies of the Arabic language pose distinct challenges. This study introduces a novel methodology that moves away from conventional event-driven narrative frameworks, emphasizing the restructuring of narrative constructs through sophisticated language models. Utilizing mBERT, our approach begins by extracting key story entities. Subsequently, XLM-RoBERTa and a BERT-based linguistic evaluation model are employed to direct beam search algorithms in the replacement of these entities. Further refinement is achieved through Low-Rank Adaptation (LoRA), which fine-tunes the extensive 3 billion-parameter BLOOMZ model specifically for generating Arabic narratives. Our methodology underwent thorough testing and validation, involving individual assessments of each submodel. The ROCStories dataset provided the training ground for our story entity extractor and new entity generator, and was also used in the fine-tuning of the BLOOMZ model. Additionally, the Arabic ComVE dataset was employed to train our commonsense evaluation model. Our extensive analyses yield crucial insights into the efficacy of our approach. The story entity extractor demonstrated robust performance with an F-score of 96.62%. Our commonsense evaluator reported an accuracy of 84.3%, surpassing the previous best by 3.1%. The innovative beam search strategy effectively produced entities that were linguistically and semantically superior to those generated using baseline models. Further subjective evaluations affirm our methodology’s capability to generate high-quality Arabic stories characterized by linguistic fluency and logical coherence.

A new buckling model for thin-walled micro-beams based on modified gradient elasticity: Coupling effect and size effect

More and more thin-walled micro-beams, including the I-section thin-walled micro-beams, are applied in MEMS. The buckling of a thin-walled micro-beam exhibits some different phenomena from that of a large scale thin-walled beam, such as the size effect, and the coupling effects caused by strain gradient. To investigate the influence of the coupling effects and size effect on the buckling of thin-walled micro-beams, a new buckling model is proposed. Based on modified gradient elasticity (MGE), the governing equations and boundary conditions of the new model are derived from the variational principle. The governing equations and boundary conditions can be simplified to the classical Vlasov's theory, the MGE Bernoulli–Euler beam model, MGE Bernoulli–Euler beam model considering bi-directional flexure respectively. Solved by the feature expansion method, the size effects of the thin-walled micro-beam can be captured by the new model, that is the buckling load increases with internal length scales. Besides the classical flexural–torsional coupling effect, two new coupling effects, such as the higher-order flexure–flexure coupling and the higher-order flexural–torsional coupling, are also captured by the new model. These two new high-order coupling effects of the new model reduce the critical buckling load of thin-walled micro-beams. The higher-order flexural–flexural coupling effect is far greater than the other two coupling effects, and the higher-order flexural–flexural coupling effect is on the same order of magnitude as the effect of MGE (size effect), with the former being negative and the latter positive. The size effect and higher-order coupling effect cannot be ignored and need to be considered carefully for the buckling of thin-walled micro-beams.

High-Purity Large Mode Field Super-Stable Vortex Beam Generator

High-Purity Large Mode Field Super-Stable Vortex Beam Generator