Frequency Of Breaks Research Articles

A Novel Multiband Fusion Method Based on Differential Processing of Scattering Centers to Eliminate Incoherence Between Sub-Bands

In traditional multiband fusion (MF) methods, the differences in the scattering center (SC) among different sub-bands are ignored, which leads to incoherence between sub-band echoes and results in limited estimation accuracy for full-band echo (FBE). To solve this problem, a novel MF method based on differential processing of the SCs in each sub-band is proposed and experimentally demonstrated. In this method, the SCs in each sub-band are classified using a proposed two-layer contrast strategy into two kinds of SCs, which are fused and super-resolved, respectively, to produce the FBE. For application during the classification, fusion, and super-resolution processes, a general iterative shrinkage thresholding algorithm is developed to ensure both the accuracy and speed of estimation of the SC locations and amplitudes. Total FBE is calculated by superimposing the fused FBE and the super-resolved FBE. In experiments, the bandwidth of each sub-band is improved by an average factor of 3.97 when the signal-to-noise ratio is equal to 10 dB and the frequency gap between two sub-bands is equal to 5.08 GHz. Thus, the high estimation accuracy of the proposed method is verified, as well as its high robustness to noise and incoherence.

Air versus Perfluoropropane Gas in Pars Plana Vitrectomy for Primary Rhegmatogenous Retinal Detachment: A 3-Year Retrospective Study

Introduction: This study aimed to compare anatomical outcomes of air and perfluoropropane gas (C3F8) tamponade in pars plana vitrectomy for the treatment of rhegmatogenous retinal detachment (RRD). Methods: In this retrospective study, data were gathered from 578 patients (578 eyes) with RRD. The follow-up records of all 578 patients that underwent primary vitrectomy for RRD with air or C3F8 were examined and analyzed. Surgical outcomes of the two groups were compared. Results: A total of 342 eyes were treated with air and 236 with C3F8. The mean follow-up period was 37.65 ± 2.33 months. Baseline and preoperative clinical characteristics were similar between groups, but the period to intraocular bubble disappearance (p < 0.0001), intraocular pressure on the first postoperative day (p < 0.0001), number of cases with intraocular pressure >21 mm Hg within 3 days post-surgery (p < 0.0001), and the number with intraocular pressure >21 mm Hg during follow-up (p = 0.0002) differed significantly between groups. Primary reattachment rates for air and C3F8 groups were 95.03% and 95.34%, respectively. Clinical characteristics were similar in those with and without successful reattachment, and the frequency of new or unclosed breaks was similar between the two groups. There was no significant difference in two groups according to the presence or absence of inferior retinal breaks and inferior detached quadrants. Univariate and multivariate logistic regression identified no risk factor for surgical failure. Conclusions: Air showed equivalent effects to C3F8, with a shorter period to intraocular bubble disappearance, less risk of postoperative intraocular hypertension, and less expense.

Investigation of multi-periodic self-trigger plasma in an AC-driven atmospheric pressure plasma jet

Atmospheric Pressure Plasma Jets have been intensively studied due to their potential application in biological fields but some of their physics properties are still not well understood. In the present article, a helium plasma jet driven by 15–18 kHz sinusoidal voltage ignites multi-periodic self-triggered mode or random mode depending on the applied voltage, driven frequency and inter-electrode gap distance. Most of the observed multiperiodic bullets operate every 2 or 3 sinusoidal periods. Such bullets show similarities with pulsed operating mode, having a jitter of less than 100 ns. The presence of an outer grounded electrode ring is a key parameter permitting the ignition of multiperiodic bullets; it also enhances the propagation length up to 8 times. Fast imaging reveals that 2–3 self-triggered discharges occur in the gap region prior to ignition of the bullet in both positive or negative polarities; this leads to an accumulation of charges beneath the ground electrode, locally enhancing the electric field. Bullet velocities for different polarities and gap distances are compared using optical emission spectrum.

Resonant Kushi-comb-like multi-frequency radiation of oscillating two-color soliton molecules

Nonlinear waveguides with two distinct domains of anomalous dispersion can support the formation of molecule-like two-color pulse compounds. They consist of two tightly bound subpulses with frequency loci separated by a vast frequency gap. Perturbing such a two-color pulse compound triggers periodic amplitude and width variations, reminiscent of molecular vibrations. With increasing strength of perturbation, the dynamics of the pulse compound changes from harmonic to nonlinear oscillations. The periodic amplitude variations enable coupling of the pulse compound to dispersive waves, resulting in the resonant emission of multi-frequency radiation. We demonstrate that the location of the resonances can be precisely predicted by phase-matching conditions. If the pulse compound consists of a pair of identical subpulses, inherent symmetries lead to degeneracies in the resonance spectrum. Weak perturbations lift existing degeneracies and cause a splitting of the resonance lines into multiple lines. Strong perturbations result in more complex emission spectra, characterized by well separated spectral bands caused by resonant Cherenkov radiation and additional four-wave mixing processes.

Interpretable machine learning text classification for clinical computed tomography reports – a case study of temporal bone fracture

BackgroundMachine learning (ML) has demonstrated success in classifying patients’ diagnostic outcomes in free-text clinical notes. However, due to the machine learning model's complexity, interpreting the mechanism behind classification results remains difficult. MethodsWe investigated interpretable representations of text-based machine learning classification models. We created machine learning models to classify temporal bone fractures based on 164 temporal bone computed tomography (CT) text reports. We adopted the XGBoost, Support Vector Machine, Logistic Regression, and Random Forest algorithms. To interpret models, we used two major methodologies: (1) We calculated the average word frequency score (WFS) for keywords. The word frequency score shows the frequency gap between positively and negatively classified cases. (2) We used Local Interpretable Model-Agnostic Explanations (LIME) to show the word-level contribution to bone fracture classification. ResultsIn temporal bone fracture classification, the random forest model achieved an average F1-score of 0.93. WFS revealed a difference in keyword usage between fracture and non-fracture cases. Additionally, LIME visualized the keywords' contributions to the classification results. The evaluation of LIME-based interpretation achieved the highest interpreting accuracy of 0.97. ConclusionThe interpretable text explainer can improve physicians' understanding of machine learning predictions. By providing simple visualization, our model can increase the trust of computerized models. Our model supports more transparent computerized decision-making in clinical settings.

Theoretical studies of low-frequency shear Alfvén waves in reversed shear tokamak plasmas

The low-frequency Alfvénic fluctuations in the kinetic thermal-ion gap frequency range have aroused the interest of researchers since they can interact with background thermal particles and/or energetic particles. In the theoretical framework of the general fishbone-like dispersion relation (GFLDR), we theoretically investigate and delineate the linear wave properties of the low-frequency shear Alfvén wave excited by energetic and/or thermal particles observed in tokamak experiments with reversed magnetic shear. These low-frequency shear Alfvén waves are closely related to the dedicated experiment on energetic ion-driven low-frequency instabilities conducted on DIII-D in 2019. Therefore, adopting the representative experimental equilibrium parameters of DIII-D, in this work we demonstrate that the experimentally observed low-frequency modes and beta-induced Alfvén eigenmodes (BAEs) are, respectively, the reactive-type unstable mode and dissipative-type unstable mode, each with dominant Alfvénic polarization, thus the former being more precisely called low-frequency Alfvén modes (LFAMs). More specifically, due to diamagnetic and trapped particle effects, the LFAM can be coupled with the beta-induced Alfvén-acoustic mode (BAAE) in the low-frequency range (frequency much less than the thermal-ion transit frequency and/or bounce frequency), or with the BAE in the high frequency range (frequency higher than or comparable to the thermal-ion transit frequency), resulting in reactive-type instabilities. Moreover, due to different instability mechanisms, the maximal drive of BAEs occurs in comparison with LFAMs, when the minimum of the safety factor (&lt;inline-formula&gt;&lt;tex-math id="M1"&gt;\begin{document}$ q_{\rm min} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M1.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M1.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;) deviates from a rational number. Meanwhile, the BAE eigenfunction peaks at the radial position of the maximum energetic particle pressure gradient, resulting in a large deviation from the &lt;inline-formula&gt;&lt;tex-math id="M2"&gt;\begin{document}$ q_{\rm min} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M2.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M2.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; surface. The ascending frequency spectrum patterns of the experimentally observed BAEs and LFAMs can be theoretically reproduced by varying &lt;inline-formula&gt;&lt;tex-math id="M3"&gt;\begin{document}$ q_{\rm min} $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M3.jpg"/&gt;&lt;graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="21-20230255_M3.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt;, and they can also be well explained based on the GFLDR. In particular, it is confirmed that the stability of the BAAE is not affected by energetic ions, which is consistent with the first-principle-based theory predictions and simulation results. The present analysis illustrates the solid predictive capability of the GFLDR and its practical applications in enhancing the ability to explain experimental and numerical simulation results.

Anderson-Higgs Mass of Magnons in Superconductor-Ferromagnet-Superconductor Systems

The dynamic interplay of superconductivity and magnetism is promising for developing quantum magnonics and spintronics. Recent experiments have reported significant, enigmatic shifts of ferromagnetic resonance frequency in layered SFS structures. The author explains that the origin of this effect is spontaneous generation of magnon mass due to the celebrated Anderson-Higgs mechanism, a cornerstone of the Standard Model of particle physics. Upon cooling below the superconducting critical temperature, the magnons acquire a frequency gap and change their propagation direction. This effect enables the creation of magnon resonators, crystals, parametric amplifiers, and other useful devices.

Digital Eye strain among Undergraduate Medical students of Nepal Medical College and Teaching Hospital during COVID-19 Pandemic

During Covid-19 Pandemic, there was declaration of lockdown which led to increased usage of digital devices due to starting of online classes. Increased duration of digital device usage predisposed students to Digital eye strain (DES). This study aimed at estimation of the prevalence of DES among medical students of Nepal Medical College and Teaching Hospital during Covid pandemic. It also analyzed the pattern of digital device usage, risk factors for DES, awareness and practice of preventive measures taken by students during online classes. This was a cross-sectional questionnaire-based survey which included one hundred and sixteen undergraduate medical students. The mean age of the students was 22±1.30 years. Sixty-two students (53.4%) were male and fifty-four (46.6%) were female. There was a significant increase in the duration of digital device usage during Covid -period as compared to pre-Covid period (P=&lt;0.001). The prevalence of the DES was 68.1% of which 60.34% had mild DES and 7.76% had moderate DES. The most common ocular symptoms were burning sensation (69.8%) followed by eyesight worsening (60.3%) and eyepain (56%). This study didn’t find significant association between DES and its risk factors like duration of digital device usage, distance from screen, posture, frequency of break and level of screen during online classes. Preventive measures like uses of lubricating eyedrop and use of anti-reflective coated glasses/ blue ray cut glasses were significantly associated with less frequency of DES (P=0.03,0.01 respectively). DES is an emerging eye health problem due to increase screentime exposure, so limitation of screentime and practice of 20-20-20 rule is recommended to reduce DES related symptoms.

Study on bandgap and vibration attenuation mechanism of novel chiral lattices

The chiral metamaterials have been well applied in engineering applications, but the chiral structure of a single material is difficult to achieve low-frequency sound insulation or vibration reduction. Therefore, a new chiral lattice structure is proposed in this paper. Based on the Bloch's theorem, finite element analysis is carried out, and the energy band structures of different types of structures are calculated. The principle of band gap generation of Model No.1 is emphatically analyzed. The effect of geometric parameters on the band gap is discussed. In addition, the propagation characteristics of elastic waves with a specific frequency in the structure are explored. Finally, according to the corresponding relationship between the finite element simulation of vibration transmission in finite period structures and the band gap frequency range, it is verified that the structure can effectively restrain the vibration transmission. The research results show that the structure has excellent broadband gap performance in the frequency range of 3000 Hz, and has a certain filtering effect on vibration transmission.

The shear Alfvén continuum with a magnetic island chain in tokamak plasmas

The shear Alfvén continuum spectrum is studied for a tokamak with a single island chain using the ideal magnetohydrodynamics theory. We have taken into account the toroidal geometry and toroidal mode coupling with the island considered as a highly-shaped stellarator. Various new frequency gaps open up inside the island due to its asymmetry both poloidally and toroidally, such as the mirror-induced Alfvén eigenmode (MAE) gap and the helicity-induced Alfvén eigenmode (HAE) gap. We have shown that the MAE gap acts as the continuation of the outside toroidal Alfvén eigenmode (TAE) gap into the island. However, the combined TAE/MAE gap is getting narrower as the island grows, leaving only half of its original width with a moderate island size as much as 3.2% of the minor radius. In addition, the two-dimensional eigenfunction of the continuum mode on the lower tip of the MAE gap now has highly localised structures around the island’s long axis, contrary to the usual oscillatory global solutions found with no or a low level of toroidal asymmetry—an indication of the continuous spectrum becoming discrete and dense. These results have implications for the frequency, mode structure and continuum damping of global TAEs residing in the gap.

Offset double sideband carrier assisted differential detection with field recovery at low carrier-to-signal power ratio.

Four system frameworks based on carrier assisted differential detection (CADD) receivers for offset double sideband (DSB) signal transmission, including offset DSB asymmetric CADD (offset DSB A-CADD), offset DSB symmetric CADD (offset DSB S-CADD), offset DSB parallel double delay asymmetric CADD (offset DSB PDD-A-CADD), and offset DSB parallel double delay symmetric CADD (offset DSB PDD-S-CADD) are proposed to reduce the requirement for carrier-to-signal power ratio (CSPR) and improve the spectral efficiency (SE) of the self-coherent detection. These frameworks accommodate signal-signal beat interference (SSBI) and efficiently solve the noise enhancement by placing a frequency gap as wide as the signal bandwidth in the middle of the left and right sideband signal. Massive theoretical derivation and simulation verification illustrated that compared with previous interleaved A-CADD, our system achieve field recovery under the condition of 0 dB CSPR with the improvement of SE by 5%, and the OSNR sensitivity is improved by 4.5 dB with 20% forward error correction (FEC) threshold. In addition, due to the devices' limited bandwidth (BW), the information-bearing signal is attenuated at the high-frequency region. And since SSBI has less influence on the signal in the high-frequency region, the frequency gap of the four offset DSB CADD schemes are compressed to utilize as much low-frequency resource as possible and improve the SE. Efficient compression of the frequency gap from 50% to 32.3% with 20% FEC threshold and 50% to 37.7% with 7% FEC threshold at 0 dB CSPR is achieved, and only a slight performance degradation is observed. At this time, the SE is improved by 22.7% and 17.3% with different FEC thresholds, respectively, compared with the 5% frequency gap interleaved A-CADD.

Plasma shape effects on the Alfvén eigenmode spectrum through Alfvén slow-magnetosonic wave coupling

The effect of the plasma shaping (triangularity and elongation) on the continuous spectrum, frequency gaps, and number of eigenmodes is studied. The plasma shaping affects the coupling between Alfvén and slow magnetosonic waves via the geodesic magnetic curvature and the plasma pressure. The Alfvén-slow coupling creates a large number of new gaps in the continuous spectrum below the Alfvén frequency where discrete modes can reside. In ideal magnetohydrodynamic simulations a large number (a few hundred or more) of potential eigenmodes are found. The number of eigenmodes is correlated with the maximum geodesic curvature and a minimum number of possible discrete eigenmodes is found at a negative triangularity of −0.3. It is hypothesized that these possible eigenmodes form a low amplitude and dense discrete spectrum, which can be studied experimentally.

Nonlinear Tunability of Elastic Waves in One-Dimensional Mass-Spring Lattices Attached with Local Resonators

Vibration propagates in the form of elastic waves. The tuning of elastic waves is of great significance for vibration and noise reduction. The elastic metamaterials (EMs), which can effectively prohibit elastic wave propagation in the band gap frequency range, have been widely studied. However, once the structures of the EMs are determined, the band gap is also determined. In this paper, a discrete nonlinear elastic metamaterial is proposed. The harmonic balance method is used to derive the nonlinear dispersion relation combined with Bloch’s theorem. The low frequency band gap near the linear natural frequency of local resonators is obtained. The theoretical results show that the nonlinearity will change the starting and ending frequencies of the band gap. In addition, amplitude can also influence the band gap. This means that the amplitude can be changed to achieve the tunability of elastic waves in nonlinear elastic metamaterials. Finally, the theoretical results are verified by numerical simulation, and the results are in good agreement with each other.

Micro-structural effects in phononic dielectric structures

Based on the higher-grade continuum theory, propagation of longitudinal as well as transverse anti-plane elastic waves in normal direction to nanoscale periodic laminates of piezoelectric dielectrics is studied in this paper. The strain gradients, micro-inertia and direct flexoelectricity phenomena are incorporated into the phenomenological description. The problem is analysed as one-dimensional and the governing equations together with possible boundary conditions are derived from the Hamilton variation principle. It is shown that the transverse waves are not affected by the electric polarization in contrast to the longitudinal waves. The developed formulation is applied to 1D Bloch waves obeying perfect boundary conditions periodical in bi-material laminates and the transfer matrix method is used for derivation of dispersion equation. An analytical method is developed for solution of the dispersion equation. The influence of the micro-stiffness and micro-inertial length scale parameters as well as flexoelectric coefficients on the dispersion curves and the frequency gaps is investigated in parametric study.

Multiscale topology optimization with stress, buckling and dynamic constraints using adaptive geometric components

This research focuses on the multiscale topology optimization (TO) of structures to meet stress, stability, and vibration requirements. The compliance minimization problems of multiscale structures under the global stress constraints, critical buckling load factor, and natural frequencies are established and solved by employing a method using adaptive geometric components (AGCs). During the TO process, the dynamic and stability frequency gap constraints are added to the optimal model to prevent mode switches. The maximum stress is measured using the global p-norm stress aggregation. The concurrent material modeling technique, which involves AGCs, illustrates the macrostructure and microstructure of material under multiple constraints simultaneously, which are optimized by focusing on the AGC parameters under multiple constraints. Benchmark numerical tests are presented and investigated to validate the applicability of the proposed approach.

Initial experience on abdominal photon-counting computed tomography in clinical routine: general image quality and dose exposure

ObjectivesPhoton-counting computed tomography has lately found its way into clinical routine. The new technique could offer substantial improvements regarding general image quality, image noise, and radiation dose reduction. This study evaluated the first abdominal examinations in clinical routine and compared the results to conventional computed tomography.MethodsIn this single-center retrospective study, 66 patients underwent photon-counting and conventional abdominal CT. Four radiologists assessed general image quality, image noise, and image artifacts. Signal-to-noise ratio and dose properties of both techniques within the clinical application were compared. An ex vivo phantom study revealed the radiobiological impact by means of DNA double-strand break foci in peripheral blood cells by enumerating γ-H2AX+53BP1 foci.ResultsGeneral image quality in accordance with the Likert scale was found superior for photon-counting CT (4.74 ± 0.46 vs. 4.25 ± 0.54; p < 0.001). Signal-to-noise ratio (p < 0.001) and also dose exposure were higher for photon-counting CT (DLP: 419.2 ± 162.2 vs. 372.3 ± 236.6 mGy*cm; p = 0.0435). CT exposure resulted in significantly increased DNA damage in comparison to sham control (p < 0.001). Investigation of the average foci per cell and radiation-induced foci numbers revealed significantly elevated numbers (p = 0.004 and p < 0.0001, respectively) after photon-counting CT.ConclusionPhoton-counting CT in abdominal examinations showed superior results regarding general image quality and signal-to-noise ratio in clinical routine. However, this seems to be traded for a significantly higher dose exposure and corresponding double-strand break frequency. Optimization of standard protocols in further clinical applications is required to find a compromise regarding picture quality and dose exposure.Key Points• Photon-counting computed tomography promises to enhance the diagnostic potential of medical imaging in clinical routine.• Retrospective single-center study showed superior general image quality accompanied by higher dose exposure in initial abdominal PCCT protocols compared to state-of-the-art conventional CT.• A simultaneous ex vivo phantom study revealed correspondingly increased frequencies of DNA double-strand breaks after PCCT.

Acetamiprid'in Cyprinus carpio da Genotoksik Etkisinin Mikronükleus Analizi ve Comet Testi ile Araştırılması

Pesticides are considered to be one of the biggest economic and ecological problems in the aquatic ecosystem. Monitoring for toxic effects and screening for different insecticides is vital and crucial for reducing adverse effects on aquatic organisms and public health. Therefore, in this study, we aimed to determine genotoxic effect of acetamipridine in a model fish species, Cyprinus carpio, using the micronucleus test and Comet assay. Common carp (average weight of 1.35 ±0.11g) were exposed to three different concentrations of acetamipridine (0.2, 0.4, and 0.8 g/L) based on previously detected aquatic environmental concentrations, constituting an acute test for a week. At the end of study, the Damage frequency (%), Arbitrary unit and Genetic damage index (%) were evaluated in gill and liver cells of carp by Comet assay. Also, micronucleus frequencies and erythrocyte abnormalities were determined in erythrocytes cells of carp by micronucleus test. Our results revealed significant increases in the frequencies of micronuclei and DNA strand breaks in C. carpio, following exposure to acetamipridine and thus demonstrated the genotoxic potential of this pesticide on fish. Our findings also indicated the suitability of the fish micronucleus test and comet assay in assessment of aquatic genotoxicity of insecticides.

Cytogenetic Effects in Patients after Computed Tomography Examination.

Millions of people around the world are exposed to low doses of ionizing radiation from diagnostic computed tomography (CT) scans. Currently available data on the potential cancer risk after CT scans are contradictory and therefore demand further investigations. The aim of the current study was to obtain estimations of genome damage after CT scans in 42 non-cancer patients and to conduct a comparison of the results with 22 control subjects. The frequency of dicentric ring chromosomes and chromosome breaks was significantly increased in irradiated patients compared to the controls. The distribution of dicentrics among the cells demonstrated non-Poisson distribution that reflected non-uniform and partial-body radiation exposure. A fraction of patients followed Poisson distribution, which is typical for uniform whole-body exposures. Some patients demonstrated a level of dicentrics similar to the control subjects. The individual variations in the frequency and dicentric distribution suggested complex mechanisms of chromosome aberration induction and elimination that could be associated with individual radiosensitivity, as well as previous diagnostics that used ionizing radiation or the redistribution of small fractions of irradiated lymphocytes within the circulatory pull. In conclusion, CT scans may cause genome damage and possible increases in cancer risk. The introduction of a specific follow-up of such patients, especially in the case of repeated CT scans, is suggested.

Physical Activity, Confidence, and Social Norms Associated With Teachers' Classroom Physical Activity Break Implementation.

Despite the benefits of classroom physical activity breaks on student health and academic outcomes, more research is needed to understand what factors may be associated with classroom physical activity break implementation, to bolster buy-in from school stakeholders and increase implementation. This quantitative study examined frequency of classroom physical activity break implementation in relation to (1) objectively measured teachers' physical activity and sedentary behaviors, (2) confidence for leading classroom physical activity breaks, (3) social norms (perceptions of other teachers' classroom physical activity break implementation), and (4) teacher- and school-level demographics. In total, 153 classroom teachers in 20 elementary and middle schools completed a survey including classroom physical activity break frequency, confidence, and social norms, one item each, dichotomized (1 = "most/all the time" OR "agree/strongly agree"). Accelerometry assessed total activity and daytime sedentary behavior. Analyses included multilevel binary logistic regression. Teachers were 90% female, 68% White, and 55% in elementary schools. Odds of implementing classroom physical activity breaks were lower among middle school teachers, 14 times greater among those with greater confidence, and over 17 times greater when teachers perceived others frequently implementing classroom physical activity breaks. Teacher activity was not associated with classroom physical activity break implementation. Future interventions to increase classroom physical activity break implementation should focus on increasing teachers' confidence to lead classroom physical activity breaks and creating more buy-in from classroom teachers to enhance each school's culture of health. By enhancing teacher confidence and social norms for implementing classroom physical activity breaks, we may increase school-based physical activity opportunities.

Design of periodic arched structures integrating the structural nonlinearity and band gap effect for vibration isolation

In this study, a Roman-bridge-inspired metamaterial for vibration isolation is proposed that simultaneously realizes a geometrical nonlinear structure and band gap effect, through the arrangement of periodic materials in a semicircular arched structure. Finite element analysis and band diagram analysis are performed to verify the effect of the periodic arch-structured metamaterial by calculating the transmissibility and band gap frequency range of cuboid, arched and periodic arched models. Based on the calculation results, the relationship between the geometrical parameters of the periodic arch structure and band gap frequency are analyzed, and an empirical correlation is formulated for the generation of a training database for a machine learning optimization model. The geometrical parameters of the metamaterial were optimized using the machine learning model based on an autoencoder architecture with supervised learning. An optimized metamaterial with a band gap area at three target frequencies is generated by the trained neural network, and the effectiveness of the optimized structure is validated by both numerical analysis and a frequency response test.