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A novel slit-resonator acoustic metastructure (SRAM) composed of Helmholtz resonators and porous materials is proposed to achieve a continuous perfect sound absorption at 200–3000 Hz. The Helmholtz resonator utilizes the resonance effect for low-frequency acoustic energy attenuation, and when its neck is small enough, it can be considered as an air slit. The air slit acts as a channel, from which most acoustic waves enter the metastructure and are absorbed by porous materials. Porous materials absorb high-frequency sound waves through thermoviscous dissipation. Unlike traditional filling forms, porous materials are filled around the air slits. To analyze the acoustic performance of this metamaterial, theoretical models and finite element models are developed and experimentally verified. The SRAM with melamine foam and rock wool can reach an absorption effect better than 0.5 at 331–3000 Hz and reaches a peak of 0.946 at 501 Hz with a thickness of 50 mm. Using the genetic algorithm, the parameters of SRAM are optimized for efficient sound absorption over a wider bandwidth. The optimized SRAM obtains an absorption coefficient of 0.8 in the range of 400–3000 Hz with a thickness of 50 mm. This study provides a new method of low-frequency ultra-broadband sound absorption. [ABSTRACT FROM AUTHOR]

In this study, we propose a coaxial composite resonator (CCR) structural unit and experimentally demonstrate that a periodic structural plate composed of CCR units effectively suppresses low-frequency vibrations. Each CCR unit comprises a cylindrical resonant element, a steering wheel-shaped elastic connection, and a framework structure. These components collectively generate elastic wave bandgaps through the intrinsic damping properties of the resonant elements. Finite element analysis was employed to investigate the influence of key parameters on the bandgap (BG) characteristics of the CCR structure. The results indicate that the resonator mass is the primary determinant of the BG onset frequency, with larger resonator masses leading to a lower onset frequency. Additionally, the lattice constant was identified as the most sensitive parameter influencing the BG width, such that an increased lattice constant results in an expanded frequency range of the BG. The validity of the finite element models and the predicted BG properties were confirmed through experimental testing. The CCR structure exhibits significant potential for applications in low-frequency vibration and noise control. [ABSTRACT FROM AUTHOR]

Lamb wave resonators (LWRs) based on lithium niobate on insulator (LNOI) substrates operating in an A1 mode at frequencies above 5 GHz typically exhibit high electromechanical coupling coefficients (K2) ranging from 20% to 30%. This makes them promising candidates to replace current bulk acoustic wave technology in next-generation broadband RF filters. However, the K2 of conventional LWRs still struggles to meet application requirements for bandwidths exceeding 1 GHz, such as WiFi-6E. This paper presents an analytical optimization approach for rapid and comprehensive scanning of the full 3D Euler space to find the maximum effective K2 of LWR devices. Such a full scan is difficult to achieve by the conventional time-consuming finite element method (FEM). The K2 results for a selected subset of Euler angles obtained through this analytical approach align with FEM simulation results. The optimized results show that LWRs on LNOI can achieve the highest K2 of 59.92% at Euler angles of (0, −151°, −60°), providing bandwidths exceeding 1 GHz at 5 GHz. To validate this optimization approach, LWRs with various orientations were fabricated on both 41° YX-cut and Z-cut LNOI wafers, with measured K2 values at different Euler angles agreeing well with both analytical and FEM results. The proposed K2 optimization method serves as a valuable guideline for selecting substrate cuts and device orientations in the design of ultra-broadband filters for next-generation telecommunications. [ABSTRACT FROM AUTHOR]

Direct methods to manipulate internal heat conduction in solids remain nearly elusive. In this work, we propose a two-dimensional (2D) gradient thermal metamaterial lens designed to control the internal non-Fourier heat conduction. This gradient thermal metamaterial comprises cylindrical structures made of dermis immersed in a stratum background with an effective refractive index adhering to the hyperbolic secant profile rule. Subsequently, the effective refractive index of the thermal metamaterial is defined and numerically assessed using the extended plane wave expansion method. Thereafter, the non-Fourier heat conduction is analyzed numerically via the finite element method in the time-domain. Our findings indicate that the proposed gradient thermal metamaterial can focus the heat effectively and is akin to a flat thermal lens. The proposed flat thermal lens offers promising avenues for enhancing the material properties by laser-based technologies. [ABSTRACT FROM AUTHOR]

Plasmonic coupling among nanocavities creates a significant collective response of near-field enhancement, leading to numerous applications such as extraordinary optical transmittance, enhanced spectroscopy, energy harvesting, photo-enhanced catalysis, meta-lens, etc. We report here a perturbation theory based on the two-body interaction potential to clarify the plasmonic coupling between/among nanocavities. With this theory, we demonstrated that one can calculate the near-field distribution of a cluster of nanocavities and that the results are in agreement with simulations by the finite element method and those measured by a scanning near-field optical microscope. The perturbation theory offers an effective way in dealing with the plasmonic coupling behavior of nanocavities. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the effect of BruxZir Steel treatment on the fracture resistance of zirconia threeunit bridges prepared using 5Y-PSZ-based zirconia blanks. Materials and Methods: Three-unit zirconia bridges were milled using CAD/CAM from homogeneous bisque zirconia blanks (5Y-PSZ-based) supplied by various manufacturers and sintered. Fracture resistance was analyzed with dynamic loading. For each zirconia blank, the fracture resistance of the sintered test restoration (cementation surface treated with BruxZir Steel) was compared to the sintered control restoration (untreated cementation surface). Finite element analysis (FEA) was used to analyze the stress distribution on the three-unit bridge under an axial load. Results: The fracture resistance of the test restorations was significantly higher than that of the control restorations for all manufacturers considered in this study (P < .05). Furthermore, the restoration made of BruxZir Esthetic treated with BruxZir Steel had the highest fracture resistance compared to the other restorations. In addition, the three-unit bridge restorations prepared from 5Y-PSZ-based zirconia blanks exhibited differences in grain size and fracture toughness depending on the presence or absence of BruxZir Steel treatment. The locations of high stresses under FEA correlated well with the fracture locations in the corresponding experimental test. FEA also demonstrated the improved performance of the BruxZir Steel-treated sample compared to the control. Conclusions: The fracture resistance of 5Y-PSZ-based BruxZir Steel-treated three-unit bridges was significantly higher (min = 30%, max = 198%) than the control. [ABSTRACT FROM AUTHOR]

Acoustic metasurfaces are widely used for noise attenuation due to their outstanding acoustic performance and subwavelength characteristics. The paper introduces a topology-optimized inverse design approach for broadband sound-absorbing metasurfaces, aiming to achieve efficient sound absorption performance across a wide frequency spectrum. By integrating genetic algorithms with the finite element method and driven by objectives such as the absorption frequency range and absorption coefficient, we can transcend the limitations of manual design and fully exploit the design potential of structures. Furthermore, the study investigates the sound absorption mechanism and thermal-viscous dissipation through finite element simulations and experimental validations. The research findings reveal that the proposed broadband sound-absorbing metasurfaces demonstrate excellent sound absorption capabilities across the designated frequency range, boasting an average sound absorption coefficient exceeding 85%. These findings offer fresh perspectives and methodologies for advancing the research and practical application of broadband sound-absorbing metasurfaces. [ABSTRACT FROM AUTHOR]

This work presents a high-sensitivity solution sensor based on a phoxonic crystal nanobeam with lateral fins. The fins improve the stability of the suspended nanobeam and its detection performance is unaffected. Acoustic–optic dual-mode cross-detection improves the detection accuracy over the single-mode method. The acoustic and optical energies are concentrated in the defect and slot regions due to the combination of the gradient cavity and slot, which enhances the acoustic–optic interaction with the object to be measured, improving the detection sensitivity. Using the mode bandgaps of photonic and phononic crystals, the sensing characteristics are investigated using the finite element method. The impact of various concentrations on the transmission spectra of optical electromagnetic waves and acoustic elastic waves is investigated. The maximum sensitivity is 2149.5 kHz/ms−1, with Q of over 105 in the acoustic mode and 457.1 nm/RIU in the optical mode. The proposed nanobeam cavity with lateral fins can be used to realize miniaturized multi-mode acoustic–optic sensors. It also provides mechanical support, thermal transport, and channels for lateral carrier injection for the suspended nanobeam. [ABSTRACT FROM AUTHOR]

Magnetic Johnson noise is an important consideration for many applications involving precision magnetometry, and its significance will only increase in the future with improvements in measurement sensitivity. The fluctuation–dissipation theorem can be utilized to derive analytic expressions for magnetic Johnson noise in certain situations, but when used in conjunction with finite element analysis tools, the combined approach is particularly powerful as it provides a practical means to calculate the magnetic Johnson noise arising from conductors of arbitrary geometry and permeability. In this paper, we demonstrate this method to be one of the most comprehensive approaches presently available to calculate thermal magnetic noise. In particular, its applicability is shown to not be limited to cases where the noise is evaluated at a point in space but also can be expanded to include cases where the magnetic field detector has a more general shape, such as a finite-size loop, a gradiometer, or a detector that consists of a polarized atomic species trapped in a volume. Furthermore, some physics insights gained through studies made using this method are discussed. [ABSTRACT FROM AUTHOR]

X-ray self-heating is a common by-product of X-ray Free Electron Laser (XFEL) techniques that can affect targets, optics, and other irradiated materials. Diagnosis of heating and induced changes in samples may be performed using the x-ray beam itself as a probe. However, the relationship between conditions created by and inferred from x-ray irradiation is unclear and may be highly dependent on the material system under consideration. Here, we report on a simple case study of a titanium foil irradiated, heated, and probed by a MHz XFEL pulse train at 18.1 keV delivered by the European XFEL using measured x-ray diffraction to determine temperature and finite element analysis to interpret the experimental data. We find a complex relationship between apparent temperatures and sample temperature distributions that must be accounted for to adequately interpret the data, including beam averaging effects, multivalued temperatures due to sample phase transitions, and jumps and gaps in the observable temperature near phase transformations. The results have implications for studies employing x-ray probing of systems with large temperature gradients, particularly where these gradients are produced by the beam itself. Finally, this study shows the potential complexity of studying nonlinear sample behavior, such as phase transformations, where biasing effects of temperature gradients can become paramount, precluding clear observation of true transformation conditions. [ABSTRACT FROM AUTHOR]

Partial shading can significantly impair the efficiency of thin-film solar cells. When exposed to partial shading, cells within the array tend to become reverse biased, leading to thermal runaway events and the emergence of hotspots. In Cu (In , Ga) Se 2 (CIGS) solar cells such hotspots are also associated with so-called worm-like defects. Both theoretical and experimental studies have shown that in CIGS, a positive-feedback loop leads to instability and thermal runaway events. However, we observe an inconsistency between published simulation results and recently published experimental work. In a recent experimental study, it was shown that under certain conditions, a hotspot develops within 1 m s , showing signs of melting of the CIGS in an area with a 5 μ m radius. However, in published simulation results, the time for such high temperatures to develop is in the order of seconds, a discrepancy of three orders of magnitude. In this work, we argue that this discrepancy is explained by the size of the seed defect, demonstrating that the origin of these experimentally observed, fast-developing hotspots is likely microscopic defects. To this end, we developed an electro-thermal finite element model, with very high temporal and spatial resolution. We demonstrate that, assuming a seed defect with a 10 n m radius, we can reproduce the experimental results with respect to the size of the defect and the time it took to develop. [ABSTRACT FROM AUTHOR]

The ionic conductivity at the grain boundaries (GBs) in oxide ceramics is typically several orders of magnitude lower than that within the grain interior. This detrimental GB effect is the main bottleneck for designing high-performance ceramic electrolytes intended for use in solid-state lithium-ion batteries, fuel cells, and electrolyzer cells. The macroscopic ionic conductivity in oxide ceramics is essentially governed by the underlying polycrystalline microstructures where GBs and grain morphology go hand in hand. This provides the possibility to enhance the ion conductivity by microstructure engineering. To this end, a thorough understanding of microstructure–property correlation is highly desirable. In this work, we investigate numerous polycrystalline microstructure samples with varying grain and grain boundary features. Their macroscopic ionic conductivities are numerically evaluated by the finite element homogenization method, whereby the GB resistance is explicitly regarded. The influence of different microstructural features on the effective ionic conductivity is systematically studied. The microstructure–property relationships are revealed. Additionally, a graph neural network-based machine learning model is constructed and trained. It can accurately predict the effective ionic conductivity for a given polycrystalline microstructure. This work provides crucial quantitative guidelines for optimizing the ionic conducting performance of oxide ceramics by tailoring microstructures. [ABSTRACT FROM AUTHOR]

Electromagnetic applications of composites often impose constraints on the internal electric fields, such as an upper limit on the field strength to prevent local heating or dielectric breakthrough. However, owing to heterogeneity, the local fields in a composite differ from those in a homogeneous material. Moreover, they are accessible neither by experiment nor by effective medium theories, at least for arbitrary microstructures. In this work, we use numerical simulations to evaluate the electric field distribution and the effective permittivity for 3D systems of monodisperse impenetrable spheres dispersed in a continuous matrix phase. We restrict ourselves to loss-free dielectric materials and to a random spatial distribution of particles. Samples are placed in a parallel plate waveguide and exposed to a transverse electromagnetic wave. The local field amplitudes are calculated via the finite element method and are normalized to those of a homogeneous sample exhibiting the same effective permittivity and geometry. We analyze the distribution of the local electric field strength in both constituents, namely, particles and matrix. Thus, we evaluate mean values and standard deviations as well as the field strengths characterizing the highest and lowest percentiles. Increasing particle concentration or permittivity enhances heterogeneity, and so the local electric field strength in some domains can become much higher than its average value. The methods we apply here can also be used in further investigations of more complex systems, including lossy materials and agglomerating particles. [ABSTRACT FROM AUTHOR]

Topology optimization, as a scientific and efficient intelligence algorithm, can be used to distribute the structures or materials with periodic units within the design domain to obtain the desired properties or functions. To induce interface states with high transmission and localization at the specified objective frequency, we propose a topology optimization design of the mirror-symmetric periodic waveguides based on the combination of the multiple population genetic algorithm and the finite element method. In addition to the traditional Bragg gaps, which are generated by the same low-order mode resonances, interface states can also be induced through the proposed topology optimization method in the non-Bragg gaps formed by the resonances of the more complex modes. The non-Bragg interface states possess higher localization due to the involvement of high-order modes in the non-Bragg resonances. This topology optimization method is expected to realize the wavefield manipulation of sound wave localization from a new perspective and provide a novel method for the design of devices for intense localization and high transmission. [ABSTRACT FROM AUTHOR]

This paper presents a new class of graded metamaterial beams by leveraging actively controllable resonators (ACR). The metamaterial comprises a homogeneous host beam that is mounted with negative capacitance shunted piezoelectric cantilever beams, each of which has a tip mass block. Properly changing the negative capacitances (NCs) in the stiffening/softening shunt circuits can control the formed bandgaps, providing greater adjustability and flexibility. Specifically, using modal analysis and considering higher modes of flexural vibrations, the ACR is simplified to an equivalent lumped parameter system with a correction factor applied to the reaction force. We demonstrate the relationship between the derived equivalent parameters of the ACR and NC for different circuitry configurations. A finite element model is built to validate the theoretical models of the ACR and the proposed metamaterial. Subsequently, a grading strategy is proposed to determine the NC values of ACR arrays for achieving broadband vibration suppression. A mechanical damping enhancement phenomenon that can contribute to forming an aggregated band is observed when resistances are introduced into the stiffening circuits. Three circuit configurations are examined, i.e., stiffening, softening, and hybrid circuits. The results showed that a proper grading coefficient can effectively suppress broadband vibration in the low-frequency range. [ABSTRACT FROM AUTHOR]

Within the low-frequency limit, this work analyzes the viscous absorbing properties of circular clusters and semi-infinite slabs made of rigid scatterers embedded in a fluid, such as air or water. These structures are made of rigid scatterers distributed in a hexagonal lattice, and they are proposed as useful absorbing devices in the core of acoustic black holes or acoustic metasurfaces. It is demonstrated that in both types of structures, an optimum value of the filling fraction produces the maximum absorption in a given frequency band. To avoid heavy numerical simulations, the broadband absorbing power has been obtained using a homogenization theory providing not only the effective acoustic parameters (effective mass and effective sound speed) but also the decay coefficient due to viscosity. An enhancement of the broadband sound absorption can be obtained by using a refractive index gradient allowing an increase of the acoustic energy into the semi-infinite slabs. The theoretical predictions are well supported by numerical simulations based on the finite-element and boundary-element methods, respectively, for the semi-infinite slabs and clusters. These predictions have potential applications in the design of structures and metasurfaces with enhanced absorbing power at low frequencies. The analytical model is further supported by experiments made with a 3D-printed sample. [ABSTRACT FROM AUTHOR]

Surface pattern formation of Smart Cut™ silicon-on-insulator (SOI) substrates is investigated using a new process derived from this technology. The local control of SOI surface roughness is achieved by using hetero-temperature surface activated bonding to introduce locally bespoke shear stresses into bonded silicon wafers. The finite element method is used to back up experimental measurements of these large deformations to determine the amount of shear stresses introduced into the structure, and to determine its impact on the fracture mechanism. [ABSTRACT FROM AUTHOR]

Exploring the plasmon energy dissipation mechanism of bimetallic nanostructures after photoexcitation is of great significance for controlling energy transfer in plasmonic applications. The absorption, scattering, and extinction spectra of Ag@Cu, Ag@Pt, and Ag@Co core–shell nanostructures are calculated by finite element method, and the energy dissipation process is visualized by using particle trajectory and the absorbed power density distribution. The absorption/scattering ratio of the core–shell nanostructures, the shell absorptivity, the time-domain electric field as well as the extra-core electron arrangements of Ag, Cu, Pt, and Co atoms are analyzed for figuring out the energy dissipation mechanism. The results show that when a non-plasmonic metal is coated on the surface of a plasmonic metal, the plasmon energy dissipates preferentially in the shell, and the degree of dissipation depends on the imaginary part of the dielectric constant of the shell and the core. A larger dielectric constant of the shell can cause more energy to be transferred from the plasmonic metal to the shell region. This study provides the fundamental physical framework and design principles for plasmonic nanostructures. [ABSTRACT FROM AUTHOR]

Conductor on round core (CORC®) cables have emerged as a leading contender in high-temperature superconducting (HTS) cable designs, offering exceptional performance with current densities surpassing 300 A / mm 2 and the ability to withstand high axial tensile and compressive strain. Despite their remarkable properties, optimizing CORC® cables remains a challenge, particularly in accurately estimating their AC losses under real-world conditions, which necessitates advanced numerical modeling techniques. Building upon recent advancements in simulating straight CORC® cables, where Bean's-like current profiles were observed across the actual thickness of wound superconducting tapes, we introduce a tailored computational approach to enhance the processing speed of three-dimensional (3D) finite element models of wound HTS tapes. This tailored approach is specifically designed to address the complexities of bent CORC® cables, which exhibit helicoidal winding and are subjected to varying mechanical strain. We focus on analyzing their electromagnetic performance by transitioning from idealized straight-former designs to more realistic scenarios where cable-formers are bent to accommodate flexible cable routing or coil configurations. Our simulations consider a typical cable design comprising three 4 mm-wide SuperPower tapes (SCS4050) with a twist pitch of 40 mm. We demonstrate the capability to accurately model the full electromagnetic behavior of bent CORC® cables without the reduction of degrees of freedom, providing valuable insights into their performance under bending conditions. Our findings contribute to the ongoing optimization of CORC® cable designs for a wide range of practical applications in high-current and high-magnetic field environments. [ABSTRACT FROM AUTHOR]

The development of lithium-ion battery technology has ensured that battery thermal management systems are an essential component of the battery pack for next-generation energy storage systems. Using dielectric immersion cooling, researchers have demonstrated the ability to attain high heat transfer rates due to the direct contact between cells and the coolant. However, feedback control has not been widely applied to immersion cooling schemes. Furthermore, current research has not considered battery pack plant design when optimizing feedback control. Uncertainties are inherent in the cooling equipment, resulting in temperature and flow rate fluctuations. Hence, it is crucial to systematically consider these uncertainties during cooling system design to improve the performance and reliability of the battery pack. To fill this gap, we established a reliability-based control co-design optimization framework using machine learning for immersion cooled battery packs. We first developed an experimental setup for 21700 battery immersion cooling, and the experiment data were used to build a high-fidelity multiphysics finite element model. The model can precisely represent the electrical and thermal profile of the battery. We then developed surrogate models based on the finite element simulations in order to reduce computational cost. The reliability-based control co-design optimization was employed to find the best plant and control design for the cooling system, in which an outer optimization loop minimized the cooling system cost while an inner loop ensured battery pack reliability. Finally, an optimal cooling system design was obtained and validated, which showed a 90% saving in cooling system energy consumption. [ABSTRACT FROM AUTHOR]

We propose a novel hybrid acoustic metamaterial that can achieve broadband sound insulation below 452 Hz and almost perfect sound absorption at 864 Hz. The metastructure was fabricated using additive manufacturing. Finite element method simulations were used to study the acoustic properties of the fabricated metamaterials. An equivalent electrical circuit was built using an electro-acoustic analogy to evaluate the sound absorption coefficient. The unique design of this meta-structure possesses two resonant frequencies. Low-frequency sound insulation is found due to the effective negative density at frequencies lower than the cutoff frequency of the elastic membrane. In contrast, a negative effective bulk modulus is the reason behind the broadband sound absorption. The theoretical and simulation results were validated through experiments. Experiments carried out showed an overall average sound transmission loss of 26.31 dB between 50 and 1600 Hz and 24.72 dB in the low-frequency zone (<400 Hz). Furthermore, over 69% of the sound intensity is absorbed in the 500–1000 Hz frequency range. The designed meta-structure exhibits broadband effective negative density below 452 Hz and effective negative bulk modulus from 864 to 1220 Hz. The design specifies a sample thickness of 3.8 cm, corresponding to a subwavelength thickness of approximately λ/10. As a result, the developed meta-structure can potentially be employed for sound insulation and absorption at low frequencies in the aerospace and automotive industries and in-room acoustic applications. [ABSTRACT FROM AUTHOR]

Purpose: To compare abutment screw loosening in 24-degree angulation-correcting and straight implants subjected to nonaxial cyclic loading. Materials and Methods: Seven external connection 24-degree angulation-correcting implants (AI) and seven external connection straight implants (SI) were embedded in acrylic resin within a brass housing. A hemispherical titanium fatigue abutment was secured to each implant using a titanium abutment screw tightened to 32 Ncm. Each implant-abutment complex was positioned within a tooth wear machine and subjected to 1,000,000 cycles of 50-Ncm nonaxial loading to simulate 1 year of function. The abutment screw removal torque values were measured before and after cyclic loading, and the differences were statistically analyzed using two-way ANOVA and post hoc pairwise Dunn tests. Scanning electron microscopy and finite element analyses were performed to assess the wear of the abutment screws. Results: The mean torque loss for the AI group was 21.44% (P < .001) compared to 24.56% (P < .001) for the SI group. There was a statistically significant difference between the AI and SI groups (P = .006). Conclusions: Both groups exhibited significant abutment screw loosening. Within the limitations of this study, 24-degree angulation-correcting implants resisted screw loosening significantly more than straight implants. [ABSTRACT FROM AUTHOR]

For large-diameter (150 mm) SiC epitaxial wafers with thick n− epilayers, stress analysis based on the finite element method and defect characterization near the epi/sub interface by synchrotron x-ray topography were performed. Observations on epitaxial wafers with epilayer thicknesses of 10, 20, 50, and 100 μm revealed that basal plane dislocation (BPD) half-loops were formed near triangular defects or from the edge of the wafer at an epilayer thickness of 50 μm and above. Two types of BPD half-loops with different edge components were observed: one with an extra half-plane above the core and present on the substrate side, and the other with a Burgers vector of opposite sign and present in the epilayer and at the epi/sub interface, forming an interfacial dislocation. The signs of these BPDs are consistent with those predicted from the calculation results, which mitigate compressive and tensile stresses in the epilayer and the substrate, respectively. It is considered that a thicker epilayer increases tensile stress in the substrate, which induces the formation of the BPD with an extra half-plane above the core on the substrate side. The distribution of the BPD half-loop width was also analyzed and compared with the calculated shear stress distribution caused by the radial temperature gradient. Calculations considering the local stress near the triangular defect revealed that the tensile stress near the epi/sub interface locally increases, exceeding the critical stress to form BPD, with an extra half-plane above the core for wafers with an epilayer thickness above 50 μm. [ABSTRACT FROM AUTHOR]

The rapid advances in the additive manufacturing technology has led to the emergence of structural materials with arbitrary geometries that were previously challenging to produce using conventional machining techniques. Elastic constants are key mechanical parameters in structural material design; however, their accurate determination becomes challenging when dealing with materials possessing intricate geometries, which make traditional mechanical testing methods less practical. In this study, we accurately determined the elastic constants of a cuboid-shaped SUS304 specimen by combining resonant ultrasonic spectroscopy with the vibration-pattern-pairing method. The proposed method was then applied to a truss-shaped SUS304 specimen. To ensure the consistency of vibration modes, vibration patterns were matched by assessing the cosine similarity between contour plots, which depict the vibration patterns obtained from each of the three planes of the experimental specimen and those generated from a finite element model based on their color map. The measured elastic constants of the truss-shaped specimen were in reasonable agreement with those of the cuboid-shaped specimen and those obtained from tensile tests conducted on specimens obtained from an SUS304 block—the source material for the cuboid- and truss-shaped specimens. The optimization process for the elastic constants exhibited reproducibility, highlighting the efficacy of our approach for quantifying the elastic constants of materials with arbitrary geometries. The proposed method can assist material designers in accurately and efficiently determining the elastic constants of materials with intricate three-dimensional geometries and mechanical anisotropy. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of restora0on design on fracture resistance and stress distribu0on of veneered and monolithic three-unit zirconia fixed par0al dentures (FDPs) using finite element analysis (FEA). Materials and Methods: Iden0cal epoxy resin replicas of mandibular second premolars and second molars (to serve as abutments for the three-unit bridges) were divided into four groups (n = 10): monolithic zirconia (MZ) restora0ons; conven0onal layering veneering technique (ZL); heat pressed-on technique (ZP); or CAD/CAM lithium-disilicate glass-ceramics (CAD-on). Specimens were subjected to compressive cyclic loading on the mesio-buccal cusp of the pon0c (load range 50 to 600 N; aqueous environment; 500,000 cycles) in a universal tes0ng machine. Data were sta0s0cally analyzed at 5% significance level with Fisher exact test and Kaplan-Meier survival analysis. 3D models were constructed in accordance with experimental groups. The stress distribu0on in each model was analyzed and evaluated according to the loca0on and magnitude of the maximum principal stresses (MPSs) using ANSYS so\ware. Results: Specimens from ZL and ZP groups failed at different stages of the 500,000 cycles fa0gue, while CAD-on and MZ restora0ons survived the fa0gue test. Sta0s0cally, there was a significant difference between the groups (P < .001). The MPS were located under the mesial connector in both monolithic and bilayered three-unit zirconia FDPs. These stresses were found to be higher in monolithic geometries compared to bilayered zirconia FDPs. Conclusions: Monolithic threeunit zirconia and CAD-on zirconia frameworks resulted in superior fracture resistance. Restora0on design significantly affected the stress distribu0on of three-unit zirconia FDPs. [ABSTRACT FROM AUTHOR]

Thin films of amorphous silicon (a-Si) coated on metals such as nickel (Ni) are one of the most promising anode architectures for high-energy-density lithium-ion (Li-ion) batteries. The performance and longevity of batteries with this type of electrode depend on the integrity of the Ni/a–Si interface. The integrity of the a-Si /Ni bonded interface during cycling is critical, but the experimental characterization of interfacial failure of this material system is highly challenging and there is a sparsity of interface strength data in the literature. Here, we describe a laser spallation (LS) technique to characterize the interfacial adhesion strength of Ni/a–Si multilayer films created by chemical vapor deposition (CVD). The LS technique enables the non-contact measurement of the tensile interfacial strength with high precision when compared to conventional methods for characterizing adhesion. Interferometric measurement combined with finite element analysis shows that the Ni/a–Si interface, created via the CVD of a-Si on Ni surfaces can withstand ≈46–72 MPa in tension before failure initiation. To ensure successful and precise characterization of interfacial adhesion strength using LS, we further develop a design criterion for multi-layer samples by analyzing the thin-film mechanics. Our study provides insights into the strength of the Ni/a–Si interface that governs the performance and durability of high-energy-density anodes and offers design guidelines for improving thin-film electrode integrity. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (PZT) thin films offer advantages in microelectromechanical systems (MEMSs) including large motion, lower drive voltage, and high energy densities. Depending on the application, different substrates are sometimes required. Self-heating occurs in the PZT MEMS due to the energy loss from domain wall motion, which can degrade the device performance and reliability. In this work, the self-heating of PZT thin films on Si and glass and a film released from a substrate were investigated to understand the effect of substrates on the device temperature rise. Nano-particle assisted Raman thermometry was employed to quantify the operational temperature rise of these PZT actuators. The results were validated using a finite element thermal model, where the volumetric heat generation was experimentally determined from the hysteresis loss. While the volumetric heat generation of the PZT films on different substrates was similar, the PZT films on the Si substrate showed a minimal temperature rise due to the effective heat dissipation through the high thermal conductivity substrate. The temperature rise on the released structure is 6.8× higher than that on the glass substrates due to the absence of vertical heat dissipation. The experimental and modeling results show that the thin layer of residual Si remaining after etching plays a crucial role in mitigating the effect of device self-heating. The outcomes of this study suggest that high thermal conductivity passive elastic layers can be used as an effective thermal management solution for PZT-based MEMS actuators. [ABSTRACT FROM AUTHOR]

Optical eigenstates with a high quality (Q) factor provide substantial advantages for a broad spectrum of optical devices, particularly those demanding strong light–matter interactions. Recently, it has been demonstrated that ultrahigh- Q resonances can be realized in planar photonic structures by merging multiple bound states in the continuum (BICs) in the momentum space. Photonic lattices with thin-film geometry are known to support abundant TE-polarized and TM-polarized BICs. While prior research has explored the merging of TE-polarized BICs, this paper presents analytical and numerical results concerning the merging of TM-polarized BICs in laterally periodic one-dimensional photonic lattices. As the thickness of photonic lattices increases, TM-polarized accidental BICs descend along the dispersion curves and eventually merge at the upper edge of the second stop band. Employing coupled-mode analysis, we calculate the analytical merging thickness at which multiple TM-polarized BICs come together at the second-order Γ point. We confirm the merging of TM-polarized BICs through finite-element method simulations. Our results can be beneficial for achieving ultrahigh- Q resonances through the merging of BICs. [ABSTRACT FROM AUTHOR]

The current research aims to predict the residual stress accumulation and evolution in the powder bed fusion processed multi-layer thin wall structures through a conforming mesh modeling approach. It involves the discrete element method (DEM) interfaced with the volume of fluid (VOF) method using computational fluid dynamics (CFD) coupled with the finite element method (FEM). The conforming mesh approach developed in the research predicts multi-physics, its induced porosity, and the cumulative effect on the residual stress in the powder bed fusion processed Ti-6Al-4V thin wall structures. The results of the residual stress in the multi-layered component from this method were further quantitatively compared with the non-conforming finite element method. The results show the conforming mesh approach was not only effective in capturing the layer geometry, and defects induced during the printing, but also predicted the residual stress in the region of the defect more accurately than the non-conforming mesh methods.

One of the primary hurdles in microdevice fabrication lies in ascertaining the most impactful tactics for adapting metal surfaces. Through a one-pot tackle and distinct mechanochemical reactions evoked by 15 min aqueous wet sand-milling (SM-15), we successfully grafted Mo-based metal–organic frameworks (Mo-MOFs) onto graphene oxides (GOs). Following this, a convenient and readily scalable methodology of electrophoretic deposition was implemented to create controllable thickness of SM-15 GOs@Mo-MOFs lubricating films, achieving considerable enhancements of 143% and 91% in hardness and Young's modulus, respectively, when compared to those of SM-15 Mo-MOFs. The successful synthesis of SM-15 GOs@Mo-MOFs was corroborated using strategies such as x-ray diffraction, Fourier transform infrared spectroscopy, and field emission scanning electron microscopy. Analyses using the micro-tribotester indicated that the new film exhibited a lowest friction coefficient of roughly 0.5 when imposed with a load of 5 N and sliding speed of 8 mm/s. In addition, the optical profiler nano-indentation in situ scanning probe microscope revealed that SM-15 GOs@Mo-MOFs films had smaller and shallower scratches and grooves compared to SM-15 Mo-MOFs ones. The calculated results of key descriptors (EHOMO, ELUMO, ΔE, etc.) in density functional theory quantitatively disclosed the interaction mechanisms between GOs@Mo-MOFs molecules and microdevices. We first scrutinized the innate properties of molecule adsorption energy and frictional mechanical behaviors using synergetic cross-scale simulations, such as Monte Carlo and finite element methods. The expectation was that this process would motivate a valuable technique for shielding in the thriving micromanufacturing. [ABSTRACT FROM AUTHOR]

Electroporation is a complex, iterative, and nonlinear phenomenon often studied through numerical simulations. In recent years, simulations of tissue electroporation have been conducted with static models. However, the results of a static model simulation are restricted to a fixed protocol signature of the pulsed electric field. In this paper, we describe a novel dynamic model of tissue electroporation that also accounts for tissue dispersion and temperature to allow time-domain simulations. We have implemented the biological dispersion of potato tubers and thermal analysis in a commercial finite-element method software. A cell electroporation model was adapted to account for the increase in tissue conductivity. The model yielded 12 parameters divided into three dynamic states of electroporation. The thermal analysis describes the dependence of tissue conductivity on temperature. The model parameters were evaluated using experiments with vegetal tissue (Solanum tuberosum) under electrochemotherapy protocols. The proposed model can accurately predict the conductivity of tissue under electroporation from 100 to 1000 V/cm. A negligible thermal effect was observed at 1000 V/cm, with a temperature increase of 0.89 ° C. We believe that the proposed model is suitable to describe the electroporation at the tissue level and provides a hint of the effects on the cell membrane. [ABSTRACT FROM AUTHOR]

We report the experimental characterization and finite element modeling of magnetic fluid hyperthermia (MFH) in tissue-like media using tetramethyl ammonium hydroxide coated superparamagnetic iron oxide magnetic nanoparticles (MNPs) of size ∼19.6 ± 1.2 nm, prepared using a co-precipitation technique. MFH properties are probed for the MNPs in ∼1 wt. % agar, resembling the tumor and surrounding normal tissues. The field-induced temperature rise (ΔT) is experimentally measured in real-time utilizing an infrared camera. A finite element model (FEM) is utilized to simulate the spatiotemporal variations in the thermal profiles, which are found to be in good agreement with the experimental data. FEM-based parametric studies reveal that the thermal conductivity of the medium is the most significant parameter influencing the thermal profiles. The spatiotemporal variations in the thermal profiles are numerically studied for seven different tissues, and the obtained results indicate the highest ΔT for the breast tissue in the tumor and the surrounding regions, which is due to the lowest volumetric specific heat and the highest thermal conductivity of the breast tissue, respectively. Numerical studies on the thermal profiles for sub-surface tumors with parametrically varying depths indicate a strong exponential correlation between the surface and tumor temperature, where the regression coefficients are found to be correlated with the thermo-physical properties of the tissues. The obtained findings are beneficial for developing a simplistic and easily deployable framework for a priori generation of the thermal profiles for various tissues during MFH, which is useful for appropriate planning and parameter selection for MFH-based therapy. [ABSTRACT FROM AUTHOR]

The surface-enhanced Raman scattering (SERS) technique provides outstanding molecular fingerprint identification and high sensitivity of analytes. Herein, colloidal sphere-shaped gold nanoparticles (Au-NPs) trapped in concentric rings of the Bessel beam generated from the optical fiber-based negative axicon has been reported as a SERS substrate. With the trapping of Au-NPs, the SERS ability of colloidal Au-NPs improved, and the average enhancement factor (AEF) of the rhodamine-6G (R6G) and 4-aminothiophenol (4-ATP) molecules can reach up to the order of 107. Control experiments were also carried out with the trapping of Au-NPs by Gaussian beam illumination, without any illumination of the light and with the trapping of Au-NPs by the Bessel beam illumination on a silver (Ag)-coated silicon (Si) substrate with a self-assembled monolayer (SAM) of 4-ATP. Theoretical studies were also carried out using the finite element method (FEM) to identify the hotspots generated in the gaps formed between the Au-NPs, leading to an enhancement in the SERS signal of the molecules, and the results were consistent with the experimentally determined AEFs. The obtained results demonstrate that the proposed SERS technique is stable. This study has significant potential applications in clinical diagnosis, food safety, environment safety, chemical sensing, and biosensing. [ABSTRACT FROM AUTHOR]

The role of strain in material properties is well-established, serving as a tool for altering atomic positions and defect formation, adjusting electronic structures and lattice vibrations, and influencing phase transitions, physical characteristics, and chemical properties. In this study, we conducted theoretical calculations of the binding energy and photoionization cross section (PCS) within a spherical core/shell quantum dot (CSQD) for the different transitions between the ground state of a donor impurity and the four low-lying conduction band states. During our study, we employed the finite element method to determine the energy levels and wave functions of the system within the effective mass approximation. Subsequently, we investigated the changes in PCS and binding energy while varying shell width under the influence of an applied electric field, considering both cases with and without the effect of strain. The strain effect was incorporated based on Hooke's law, and we developed specific expressions and utilized the continuum linear elasticity mechanical model for a single spherically symmetric shell. The results demonstrate that the strain correction enhances the binding energy of the four low-lying energy levels, leading to a shift of the PCS peaks toward higher energies. Conversely, the application of an external electric field has varying effects depending on the specific transition being considered. We compared our theoretical results with available experimental data and found them to be in good agreement. The pronounced blue-shift and substantial enhancement in magnitude of PCS spectra concerning shell width, electric field, and strain make CSQDs highly promising candidates for applications in adjustable nano-optoelectronic devices. [ABSTRACT FROM AUTHOR]

Thermal issue has been regarded as one of the bottlenecks for GaN high-electron-mobility transistor (HEMT) performance and reliability, which highlights the importance of accurate thermal modeling. In the present work, we propose a GP (Gaussian process)-resistor–capacitor compact thermal model integrated with the ensemble Kalman filter (EnKF) to handle the nonlinear problems attributed to the temperature-dependent properties of GaN HEMTs under large-signal working conditions. The GP predictor is employed for the nonlinear correction term, with strong ability and extendibility to characterize various temperature-dependent relations resulting from different design configurations and materials. The model is identified via the EnKFs by inputting a sequence of channel temperature oscillations induced by imposing a large-signal continuous wave heating source to the device. Furthermore, an adaptation mode is devised for the in situ and timely update of the model parameters to adapt to the thermal variability of GaN devices, avoiding storing a large amount of historical data and repeated offline regressions. The validation of our modeling scheme is conducted through the case study on GaN-on-SiC HEMT's detailed 3D finite element method simulations. [ABSTRACT FROM AUTHOR]

Purpose: Multiple materials are found in the root canal after fiber-post cementation. The layer of a bioceramic-based (BC) sealer may affect the bond strength (oBS) of the fiber post in the root canal. The purpose of this study was to employ multilayer composite-disk models in diametral compression to investigate whether the bond strength between a fiber post and root dentin can be increased by the application of a primer on the BC sealer. Materials and Methods: The multilayers of materials in the root canal required 3D finite-element (FE) stress analyses (FEA) to provide precise oBS values. First, BC sealer was characterized using x-ray powder diffraction (XRD) to determine when the sealer completely set and the types of crystals formed to select which primer to apply to the sealer. We selected a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-based primer to treat the BC sealer before post cementation. Ultra-highspeed (UHS) imaging was utilized to analyze the crack initiation interface. The obtained failure force was used in FE analysis to calculate oBS. Results: UHS imaging validated the fracture interface at the post-dentin junction as FEA simulations predicted. oBS values of the fiber posts placed with various material combinations in the root canal were 21.1 ± 3.4 (only cement/post), 22.2 ± 3.4 (BC sealer/cement/post) and 28.6 ± 4.3 MPa (10-MDP primer treated BC sealer/cement/post). The 10-MDP-treated BC sealer exhibited the highest oBS (p < 0.05). Conclusion: The multilayer composite disk model proved reliable with diametral compression testing. The presence of BC sealer in the root canal does not reduce oBS of the fiber post. Conditioning the BC sealer layer with 10-MDP primer before fiber-post cementation increases oBS. [ABSTRACT FROM AUTHOR]

Purpose: To compare the biomechanical responses of a normal mandible to an osteoporotic mandible with two-implant--supported magnetic attachments. Materials and Methods: A 3D finite-element model of a two-implant--supported mandibular overdenture with magnetic attachments was developed, and normal and osteoporotic bone samples were prepared. Four types of load were applied to the overdenture in each model: 100 N vertical and oblique loads on the right first molar, and a 100 N vertical load on the right canine and incisors. Biomechanical behaviors of the peri-implant bone, implant, and mucosa were recorded. Maximum equivalent stresses and elastic strains were analyzed. Results: Equivalent elastic strain in osteoporotic cortical and cancellous bone was 9% to 71% and was 142% and 207% greater than in normal cortical bone, respectively. Equivalent elastic strain in the first molar oblique loading condition was 101% to 190% greater than in the first molar vertical loading condition. Conclusions: Osteoporotic cancellous bone was weaker and less resistant to deformation than normal bone, and oblique loading was more harmful than vertical loading. [ABSTRACT FROM AUTHOR]