Beam System Research Articles

Exponential and polynomial stabilization of laminated beams with two history memories

<p style='text-indent:20px;'>In this paper, a laminated beam system with two history-type controls is studied. One of the controls acts on the effective rotation angle and the other on the slip equation. The latter control replaces the structural damping usually considered in this model in the literature. Using the semigroup of linear operators approach, we prove the system is globally well-posed. We establish the exponential stability of the system provided the equal-speed waves propagation holds. Otherwise, the system lacks exponential stability. The polynomial decay with rate <inline-formula><tex-math id="M1">\begin{document}$ t^{-\frac{1}{4}} $\end{document}</tex-math></inline-formula> is also proved using the theorem due to Borichev and Tomilov.</p>

Safety action over oscillations of a beam excited by moving load via a new active vibration controller.

This paper presents a mixed active controller (NNPDCVF) that combines cubic velocity feedback with a negative nonlinear proportional derivative to reduce the nonlinear vibrating behavior of a nonlinear dynamic beam system. Multiple time-scales method treatment is produced to get the mathematical solution of the equations for the dynamical modeling with NNPDCVF controller. This research focuses on two resonance cases which are the primary and 1/2 subharmonic resonances. Time histories of the primary system and the controller are shown to demonstrate the reaction with and without control. The time-history response, as well as the impacts of the parameters on the system and controller, are simulated numerically using the MATLAB program. Routh-Hurwitz criterion is used to examine the stability of the system under primary resonance. A numerical simulation, using the MATLAB program software, is obtained to show the time-history response, the effect of the parameters on the system and the controller. An investigation is done into how different significant effective coefficients affect the resonance's steady-state response. The results demonstrate that the main resonance response is occasionally impacted by the new active feedback control's ability to effectively attenuate amplitude. Choosing an appropriate control Gaining quantity can enhance the effectiveness of vibration control by avoiding the primary resonance zone and unstable multi-solutions. Optimum control parameter values are calculated. Validation curves are provided to show how closely the perturbation and numerical solutions are related.

Development and characterization of a narrow-pulsed molecular beam system

A narrow-pulsed and velocity-controlled molecular beam system is constructed by using a high-speed chopper and a temperature adjustable pulsed valve. The duration of the hydrogen molecular beam pulse is reduced to approximately 6.3 µs and characterized using resonance-enhanced multiphoton ionization (REMPI) at a distance of ~193 mm downstream from the nozzle. To precisely determine the velocity of the hydrogen molecules, a pump-probe technique combining stimulated Raman pumping and REMPI is employed at a fixed distance (193 mm) with nanosecond lasers. By adjusting the temperature of the pulsed valve, the velocity of the hydrogen beam varies continuously from 1290 m/s to 3550 m/s. The system exhibits potential for multiple applications in the field of chemical reaction dynamics, including its potential to integrate with ion traps and surface scattering experiments.

Heavily Doped Zinc Oxide with Plasma Frequencies in the Telecommunication Wavelength Range

Heavy and hyper doping of ZnO by a combination of gallium (Ga) ion implantation using a focused ion beam (FIB) system and post‐implantation laser annealing is demonstrated. Ion implantation allows for the incorporation of impurities with nearly arbitrary concentrations, and the laser‐annealing process enables dopant activation close to or beyond the solid‐solubility limit of Ga in ZnO. Heavily doped ZnO:Ga with free‐carrier concentrations of ≈1021 cm−3, resulting in a plasma wavelength of 1.02 μm, which is substantially shorter than the telecommunication wavelength of 1.55 μm is demonstrated. Thus, this approach enables the control of the plasma frequency of ZnO from the far infrared down to 1.02 μm, thus, providing a promising plasmonic material for applications in this regime.

LTB analysis of pre-stressed mono-symmetric thin-walled beams with deviators under non-uniform bending moments using a simplified FEM

A FE formulation has been newly presented for the lateral-torsional buckling (LTB) analysis of an externally pre-stressed (PS) steel beam, possessing deviators under non-uniform bending moments. Firstly, the total potential energies of the PS mono-symmetric thin-walled beams in possession of un-bonded/bonded deviators are derived depending on the number of deviators. Afterwards, the in-plane solutions of the PS mono-symmetric simple/cantilever beams under the lateral load can be analytically derived through the use of discontinuous functions. A simplified FE procedure is then developed based on the total potential energy, taking into consideration the effects of double tendons. Finally, the critical buckling loads of simple and cantilever PS mono-symmetric beams which were subjected to the non-uniform moments with the increasing of deviators are evaluated using the FEM and Rayleigh-Ritz method. As a result, the FE solutions were found to be very well matched to solutions by Ritz method and Abaqus. Additionally, the effects of double tendons, eccentricity, and the initial tension on LTB of the PS beam system were investigated with the increase of un-bonded/bonded deviators.

Vibration attenuation characteristics of finite locally resonant meta beam: Theory and experiments

Dynamic vibration absorbers are of utmost importance in civil and mechanical engineering applications; however, their intricate mechanisms are always challenging for practical realization. This paper investigates the vibration suppression characteristics of a base-excited cantilever beam having a series of lumped masses and spring–mass resonator systems. Both analytical and experimental investigations are carried out to compare the transmittance of the dynamic displacement response of the entire system. In the analytical method, a single unit cell comprises an Euler Bernoulli beam attached by a lumped mass and a spring–mass resonator (SMR) system. The transfer matrix method establishes the force–displacement relationship between each unit cell. Furthermore, experiments were conducted by applying a monochromatic frequency to the beam and detecting transmitted vibrations at the beam and SMR systems. The experimental results are validated with the analytical results, providing essential confidence in our proposed methodology. Moreover, several parametric studies were also conducted to obtain the rationale for the variation in the number and location of SMR systems in the vibration characteristics of the entire system.

Research on Vibration Characteristics of an Underground Powerhouse of Large Pumped-Storage Power Station

With the rapid development of pumped storage, the vibration problems caused by the operation of power stations have become increasingly prominent. In this paper, a large-scale pumped-storage power station is taken as the research object, and a three-dimensional refined finite element model of the underground powerhouse including the surrounding rock mass is established. Based on the analysis of the vibration source of the powerhouse and the water diversion pipeline, the modal and dynamic response analysis of the underground powerhouse of the hydropower station is carried out, and the distribution law of the larger vibration displacement position is revealed. The calculation results show that under the premise that the vibration source is selected reasonably and the numerical model is accurate, the main frequency of the underground powerhouse structure can be obtained more accurately. After optimizing the design of the underground powerhouse based on the calculation results, the resonance problem of the underground powerhouse of the hydropower station can be avoided. The dynamic elastic modulus of the rock mass around the underground powerhouse has little influence on the mode shape of the powerhouse, but has a great influence on its fundamental frequency. When the dynamic elastic modulus of the rock mass increases by 50%, the fundamental frequency of the plant increases by about 29%. At the same time, the mode shape of each order of the underground powerhouse structure does not change much, mainly manifested as the vibration of the beam system structure, which is mainly caused by the stiffness of the beam system components being much smaller than the structural stiffness of the windshield, machine pier, and mass concrete around the volute. The research results can provide references for the design of underground powerhouses of large-scale pumped-storage power stations and the analysis of vibration problems.

Reinforcement on existing concrete that has been reinforced with CFRP

Implementing a box culvert system on bridges is an economical choice due to the reduced material use. This system has a joint that blends between the slab and the abutment walls and pillars. With a stiffer joint, the moment that occurs is smaller than a simple beam system. Box culvert foundations are commonly shallow foundations. Consequently, it is vulnerable to settlement, particularly the abutments that receive soil loads from the bridge embankment. Therefore, making the displacement in the abutments greater than in the pillars.
 The existing box culvert structure at the study site in Semarang, Indonesia has a span of 2 x 15 meters. Reinforcement has been previously carried out using Carbon Fiber Reinforced Polymer (CFRP) to treat cracks. Though, as time passed, the treated cracks reopened and new cracks developed. Structural cracks occur at a negative moment, so that the reinforcement yielded.
 A reinforcement using CFRP does not increase stiffness—thus, a reinforcement with adding external reinforcement system is used. This reinforcement is done by adding 400 x 200 WF profile—connected mechanically by attaching anchors to the slab. Reinforcement with a WF profile is safer due to its mechanical system, which makes it easier to implement and monitor.

Automating building element detection for deconstruction planning and material reuse: A case study

To address the need for a shift from a linear to a circular economy in the built environment, this paper develops a semi-automated assistive process for planning building material deconstruction for reuse using sensing and scanning, Scan-to-BIM, and computer vision techniques. These methods are applied and tested in a real-world case study in Geneva, Switzerland, with a focus on reconstruction and recovery analysis for floor beam systems. First, accessible sensing and scanning tools, such as mobile photography and smartphone-based consumer-grade Lidar devices, are used to capture imagery and other data from an active demolition site. Then, photogrammetry and point cloud data analysis are performed to construct a 3D BIM model of relevant areas. The structural relationships between reconstructed BIM elements are evaluated to score the feasibility for recovery of each element. This study illustrates what is feasible and where further development is necessary for automating building material reuse planning at scale to increase the uptake of circular economy practices in the construction sector.

Distance and Efficiency Enhancement With Aspherical Retroreflectors for Resonant Beam SWIPT

The resonant beam system (RBS) with double spherical retroreflectors presents a potential mobile simultaneous wireless information and power transfer (SWIPT) technology without any tracking control. However, the movement distance and performance are limited due to the effect of spherical aberration. To improve mobility performance in RBS, including movement distance and output power, we adopt an aspherical lens as the focusing mirror in a retroreflector. By shifting the beam phase distribution, the aspherical lens focuses all passing beams, particularly edge beams, on the focal mirror, enhancing energy concentration in the resonant cavity. The beam field propagation through cat’s-eye retroreflectors, gain medium, and air is studied for analyzing the transfer efficiency and output power, and we demonstrate that the axial movement distance in the aspherical resonator is about 7 m, which is more than twice as far away as the spherical resonator. Within a field of view of 3° at a distance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1~\rm {m}$ </tex-math></inline-formula> , the output power of the aspherical resonator is greater than that of the spherical resonator with the same movement angle, up to two times. The maximum output electric power and spectral efficiency are approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4~\rm {W}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12~\rm {bps/Hz}$ </tex-math></inline-formula> , respectively.

Performance improvement of NES based on eddy current damping

This paper investigates the application of an eddy current damping (ECD) to improve the performance of a nonlinear energy sink (NES). The effect of the damping on the vibration suppression performance of the NES is presented. Next, the principle of the ECD is introduced and combined with the NES, namely ECD enhanced NES (ECD-NES). On this basis, the effect of the ECD-NES parameters on its vibration reduction performance is analyzed. Then, the proposed ECD-NES is applied to a cantilever beam system, and the vibration suppression performance of the ECD-NES is compared with that of the NES without ECD. An optimization strategy for the ECD-NES is proposed under the condition of comprehensive consideration of displacement control and energy dissipation. Lastly, the effectiveness of the ECD-NES is verified experimentally on the cantilever beam system. The results show that adding the ECD is effective in improving the performance of the NES. After ECD enhanced NES is installed, the amplitude decay speed is increased by 24.18% in simulations and 18.85% in experiments; the energy dissipation rate is increased by 7.3% compared with the NES without ECD.

Focused Ion Beam Engineering of Carbon Nanotubes for Optical Rectenna Applications

The optical rectenna is a device that converts the optical range of electromagnetic radiations to a direct current. Optical antennas, as for the radio frequency (RF) antennas, require an antenna’s structure in the range of optical light EM wavelengths, i.e., a few hundred nanometers to a few micrometers. Herein, we demonstrate the optical rectenna effect of single-wall carbon nanotubes (SWCNTs) by cutting them in the resonance lengths of monopole nano-antennas (i.e., λ/4) of 100, 150, and 200 nm to convert incident red, green, and blue lights into a direct current. The physical engineering (cutting) of SWCNTs dispersed on SiO2/Si, comparable to one-quarter of the incident monochromatic light wavelength (i.e., red, green, and blue), is carried out with high-energy gallium (Ga) ion beams, with the help of a focused ion beam (FIB) system. The rectenna characteristics of these engineered SWCNTs are investigated using conductive mode atomic force microscopy (C-AFM). This unprecedented approach to investigating the optical rectennas will open more directions to study the rectenna effect at the nanometer scale.

An evolving learning-based fault detection and diagnosis method: Case study for a passive chilled beam system

Traditional fault detection and diagnosis (FDD) methods learn from training data obtained under limited operating conditions, after which they stop learning. In this study, we developed an evolving learning-based FDD method for HVAC systems, which learns as the performance of a building system and its components changes. Specifically, an evolving learning algorithm—growing Gaussian mixture regression—is used to construct both a data-driven model representing normal performance and a transfer function for fault diagnosis. The evolving learning-based FDD method was demonstrated for detecting and diagnosing common faults of passive chilled beam systems. We employ generalized performance indices, such as the deviations between predictions (expectations) and measurements, the differences between two parameters, and other features extracted from parameters. A novel feature selection method was developed for selecting fault signatures. An uncertainty threshold determining whether a performance index was within the range of normal operation influences false alarm rates. By increasing the uncertainty thresholds from zero to two standard deviations, false alarm rates for normal operations were reduced from 14.8% to 1.3% and the percentage of normal operation data categorized as an unknown operation was reduced from 25% to 0%. Eight known faults were detected and diagnosed with an accuracy of 100%. A new fault was first categorized as an unknown fault before evolving. After evolving the transfer function by updating the key parameters of the Gaussian components, the unknown fault was also accurately diagnosed. The evolving learning-based FDD method and novel feature selection method can be employed for detecting and diagnosing common faults of other systems or subsystems in the built environment.

Timoshenko systems with Cattaneo law and partial Kelvin–Voigt damping: well-posedness and stability

This work considers thermoelastic Timoshenko beam systems with full and partial Kelvin–Voigt damping. The heat conduction is governed by the Cattaneo law. By applying the semi-group method, we establish the existence and uniqueness of weak global solution, then with the multiplier method, we as well prove exponential stability results. In most cases, stabilizing a Timoshenko system with Cattaneo law requires obtaining stability number or some equal wave speed propagation condition. However, interestingly in this work our stability result does not require any stability number nor equal wave speed propagation condition.

Nonlinear piezoelectric energy harvesting induced through the Duffing oscillator.

In this paper, nonlinear piezoelectric energy harvesting induced by a Duffing oscillator is studied, and the bifurcation trees of period-1 motions to chaos for such a piezoelectric energy-harvesting system are obtained analytically. Distributed-parameter electromechanical modeling of a piezoelectric energy harvester is presented first, and the electromechanically coupled circuit equation excited by infinitely many vibration modes is developed. The governing electromechanical equations are reduced to ordinary differential equations in modal coordinates, and eventually an infinite set of algebraic equations is obtained for the complex modal vibration responses and the complex voltage responses of the energy harvester beam. One single mode case is considered in this paper, and periodic motions with bifurcation trees are obtained through an implicit discrete mapping method. The frequency-amplitude characteristics of periodic motions are obtained for the nonlinear piezoelectric energy-harvesting systems, which provide a better understanding of where and how to achieve the best energy harvesting. This study describes about how the nonlinear oscillator induces piezoelectric energy harvesting through a beam system. The nonlinear piezoelectric energy harvesting is presented through a nonlinear oscillator. Due to the nonlinear oscillator, chaotic piezoelectric energy-harvesting states can get more energy compared to the linear piezoelectric energy-harvesting system.

Investigation of the Optimal PID-Like Fuzzy Logic Controller for Ball and Beam System with Improved Quantum Particle Swarm Optimization

Fuzzy Logic Controllers (FLCs) are intelligent control methods, where membership functions and corresponding rules are defined to get a proper control signal. The parameters were defined for these controllers, and they are named as PID-like FLC since the input and output parameters are connected to the Fuzzy controller with integral and derivative action of the error signal to change the behavior/performance of FLC. In this research, three different rule sets for Fuzzy controllers; 3 × 3, 5 × 5, and 7 × 7 are used and parameters are optimized with; differential evolution, genetic algorithm, particle swarm optimization and quantum-behaved particle swarm optimization. In addition to these controllers, a novel algorithm named as improved quantum particle swarm optimization is proposed as a part of this research. The simulation and real-life implementation on the experimental set results of these controllers are discussed in this paper.

Design concepts of a new imaging system for a high-intensity XUV source beam by colour centres excitation in lithium fluoride crystals

Stable colour centre production in lithium fluoride (LiF) crystals can employ as a high-spatial-resolution imaging tool for extreme ultraviolet (XUV) irradiation, as well as the possibility for images of the unfocused beam and the beam focused by a multi-layer mirror.The LiF crystal sensitivity has sufficient to impress high-contrast photo-luminescent patterns with XUV single-pulse irradiation on an area up to 40mm2. The suggested imaging technique, using LiF as a detector, can contribute to reducing the lack of sufficient knowledge for XUV beam characterization and profile featurization which can open a very wide range of XUV metrology and tomography applications.The experimental results explain the concepts of detection of high-intensity source at13.5nm using a YAG:Ce scintillator crystal embedded with a CMOS camera, additionally using LiF as a 2D high-resolution detector, and the work shows investigations outcomes and improvement procedure and analysis.The results demonstrate the potential of LiF crystals as a sub-micrometre resolution two-dimensional imaging tool for XUV irradiation applications. Moreover, the research study explains the optimization sequences of the new imaging technique that will play an important role to predict the achievable spot size, geometry, beam profile and intensity distribution, as well as the characterization complexity of XUV source features.

Innovative bolted-steel box for seismic-resistant dry-precast concrete beam-column connection

Currently, many buildings are constructed with precast concrete methods. However, they still use the cast in-situ method, especially for the beam and column connection system where there are some obstacles in the casting process and the possibility of installing the reinforcement bars on site not following the design. Hence, there is potential for structural failure in that part of the connection. To reduce the connection constraints, it is proposed that the method of connecting precast concrete with an innovative connection system that is simple, lightweight, fast in the manufacturing process, can be constructed quickly and effectively on-site, and easily meets the specifications of connection quality. This proposed type of connection is a dry joint type that only uses bolts for the connection system with steel box components. This study will prove that the dry joint system can receive the moment and shear load due to earthquakes still in the elastic phase, not experiencing plasticity. The concept of connection planning does not change the concept of the Special Moment Frame System which applies the concept of Strong Column Weak Beam and Plastic Hinges. The connection is ensured in strong conditions, there is no yielding and damage at the time of a large earthquake, so the failure is not in the connection but occurs in the precast concrete block element that is at the end of the beam outside the planned connection in flexural failure with ductile behavior, not shear failure.

Electrical Characteristics of Atmospheric-Pressure Plasma Enhanced Chemical Vapor Deposition Fabricated Indium-Gallium-Zinc-Oxide Thin-Film Transistors with In-Situ Hydrogenation and Neutral Beam Oxidation

Low temperature poly-crystalline silicon thin-film transistors (LTPS-TFTs) and indium-gallium-zinc-oxide TFTs (IGZO-TFTs) are potential candidates for future technology of various displays. Due to its simple manufacturing process, low cost and good uniformity, IGZO-TFTs have been developed as main stream display technology. From the viewpoint of device electrical characteristics, a-IGZO TFTs have better field-effect mobility (&gt;10 cm2/V * s), larger Ion/Ioff ratio (&gt;106), smaller subthreshold swing (S.S) and good stability. In this study, atmospheric-pressure PECVD (AP-PECVD) is used to deposit a-IGZO active layer, during the deposition process In-Situ hydrogenation is applied to enhance the layer characteristics. Also, the layer is then surface oxidation treated by neutral beam system (NBS). The optimal TFTs device characteristics is reached with In-Situ hydrogenation of H2 90 sccm, and surface oxidation of 400 W NBS treatment. The field-effect mobility is 34.05 cm2/V * s, threshold voltage is 1.74 V, subthreshold swing is 62 mV/decade, and current ratio Ion/Ioff is 2.04×107. Compared with conventional plasma, NBS used in this study provides charge-free plasma which could enhance device electric characteristics.

Asymptotic behavior of a laminated beam with nonlinear delay and nonlinear structural damping

Our concern in the present work is a Timoshenko laminated beam system with nonlinear delay and nonlinear structural damping acting in the equation describing the dynamics of slip. The aim is to establish an explicit and general energy decay rates of the solution under suitable assumptions on the weight of delay and speeds of wave propagation. To achieve our desired stability results, we exploit some properties of convex functions, coupled with the multiplier technique, which involves constructing an appropriate Lyapunov functional equivalent to the energy of the system.