Search Results (97)

This paper presents a study on the propagation of acoustic waves in gallium nitride (GaN) layers deposited on sapphire substrate. The influence of GaN layer thickness and the configuration of interdigital transducers (IDTs) on the generation and propagation of different surface wave modes, including Rayleigh, Sezawa, and Love waves, was analyzed. Experimental measurements in the 100 MHz–6 GHz range were complemented by numerical simulations using the finite element method (FEM). The results demonstrated a strong dependence of wave characteristics on technological parameters, particularly the quality of the GaN–sapphire interface. The data obtained can be utilized for optimizing the design of acoustic sensors, resonators, and RF filters. Full article

Love wave surface acoustic wave (LSAW) sensors are crystal resonators known for their high potential for biosensing applications due to their high sensitivity, real-time detection, and compatibility with microfluidic systems. Commercial LSAW devices are costly, and manufacturing them is even more expensive, making accessibility a significant challenge. Additionally, their use requires specialized systems, and with only a few manufacturers dominating the market, most available solutions are proprietary, limiting customization and adaptability for specific research needs. In this work, a low-cost open-source LSAW biosensing system prototype was developed based on a commercially acquired resonator. The development integrates microfluidics through a polydimethylsiloxane (PDMS) chip, low-cost electronics, and both 3D printed ultraviolet (UV) resin and polylactic acid (PLA) parts. The instrument used for measurements was a vector network analyzer (VNA) that features open-source software. The code was customized for this study to enable real-time, label-free biosensing. Experimental validation consisted of evaluating the sensitivity and repeatability of the system, from the setup to its use with different fluids. Results demonstrated that the development is able to advance to more complex applications. Full article

Applying the holographic 2-flavor Einstein–Maxwell-dilaton model, the parameters of which are fixed by lattice QCD, we extract the equations of state for hot quark–gluon plasma around the critical point at $T=182$ MeV, and have corresponding quark star cores constructed. By further adding hadron shells, the mass range of the whole stars spans from 2 to 17 solar masses, with the maximum compactness around 0.22. This result allows them to be black hole mimickers and candidates for gap events. The I–Love–Q–C relations are also analyzed, which show consistency with the neutron star cases when the discontinuity at the quark–hadron interface is not large. Furthermore, we illustrate the full parameter maps of the energy density and pressure as functions of the temperature and chemical potential and discuss the constant thermal conductivity case supposing a heat source inside. Full article

The crust and upper mantle structure of Mars is determined in the depth range of 0 to 100 km, by means of dispersion analysis and its inversion, which is performed for the surface waves present in the traces of the seismic event: S1094b. From these traces, Love and Rayleigh waves are measured in the period range of 4 to 40 s. This dispersion was calculated with a combination of digital filtering techniques, and later was inverted to obtain both models: isotropic (from 0 to 100 km depth) and anisotropic (from 0 to 15 km depth), which were calculated considering the hypothesis of the surface wave propagation in slightly anisotropic media. The seismic anisotropy determined from 0 to 5 km depth (7% of S-velocity variation and ξ ~ 1.1) could be associated with the presence of sediments or lava-flow layering, and wide damage zones surrounding the long-term fault networks. For greater depths, the observed anisotropy (17% of S-velocity variation and ξ ~ 1.4) could be due to the possible presence of volcanic materials and/or the layering of lava flows. Another cause for this anisotropy could be the presence of layered intrusions due to a single or multiple impacts, which could cause internal layering within the crust. Finally, the Moho depth is determined at 50 km as a gradual transition from crust to mantle S-velocities, through an intermediate value (3.90 km/s) determined from 50 to 60 km-depth. Full article

A study of the azimuthal variation in the surface wave fundamental-mode phase velocity is performed for the Philippine Sea Plate (PSP). This azimuthal variation has been anisotropically inverted for the PSP to determine the isotropic and anisotropic structure of this plate from 0 to 260 km. This azimuthal variation is due to anisotropy in the upper mantle. The crust is found in an isotropic structure, but the lithosphere and asthenosphere exhibit anisotropic structures. For the lithosphere, the main cause of anisotropy is the alignment of anisotropic crystals approximately parallel to the direction of seafloor spreading, and the fast axis of the seismic velocity is in the direction of ~163° of azimuth. For the asthenosphere, the seismic anisotropy can be derived from the lattice-preferred orientation (LPO) in response to the shear strains induced by mantle flow, and the fast axis of the seismic velocity is also the direction of ~163° of azimuth. This result suggests that a mantle flow pattern may occur in the asthenosphere and seems to be approximately parallel to the direction of seafloor spreading observed for the lithosphere. Finally, the changes in the parameter ξ with depth are studied to estimate the depth of the lithosphere–asthenosphere boundary (LAB), observing a clear change in this parameter at 80 km depth. Full article

Seismic metamaterials have gained significant attention for their ability to reduce seismic wave energy. However, numerical simulations have dominated the majority of research on seismic metamaterials, with relatively few field experiments validating their effectiveness. Additionally, the focus has primarily been on attenuating Rayleigh waves, with less attention given to Love waves. In this study, we first designed a seismic metamaterial featuring a periodic and symmetric array of square holes using numerical simulations as our research platform. We then explored its attenuation effects on Rayleigh waves, particularly Love waves, through field experiments. The results revealed not only differences in energy attenuation between these wave types but, more importantly, uncovered a phenomenon that we termed Bandgap-Induced Attenuation Mode Inversion within the ultra-broadband gap that was generated by the seismic metamaterials, where Love waves exhibited greater attenuation than Rayleigh waves below 50 Hz, while Rayleigh waves exhibited greater attenuation above 50 Hz. These findings highlight the necessity of considering both wave types when designing cost-effective seismic metamaterials, providing valuable insights for the development and application of metamaterials that can effectively mitigate the energy of different seismic wave modes. Full article

Prostate-specific antigen (PSA) is a well-established tumour marker for prostatic carcinoma. In this study, we present a novel, real-time, and ultrasensitive Love-mode surface acoustic wave (L-SAW) immunosensor for PSA detection enhanced by MoS₂@Cu₂O-Au nanocomposite conjugation. The MoS₂@Cu₂O-Au nanocomposites were analyzed by SEM, XRD, and EDS. The experiments show a significant improvement in sensitivity and detection limit compared with the previous detection methods utilizing nanogold alone to detect PSA biomolecules. The experimental results show a good linear relationship when the range of PSA concentrations between 200 pg/mL and 5 ng/mL was tested. The experimental results also show good specificity against alpha 1 fetoprotein and L-tryptophan disruptors. Full article

In this study, the resonant characteristics of the off-center-driven Chladni plates were systematically investigated for the square and equilateral triangle shapes. Experimental results reveal that the number of the resonant modes is considerably increased for the plates under the off-center-driving in comparison to the on-center-driving. The Green’s functions derived from the nonhomogeneous Helmholtz equation are exploited to numerically analyze the information entropy distribution and the resonant nodal-line patterns. The experimental resonant modes are clearly confirmed to be in good agreement with the maximum entropy states in the Green’s functions. Furthermore, the information entropy distribution of the Green’s functions can be used to reveal that more eigenmodes can be triggered in the plate under the off-center-driving than the on-center-driving. By using the multiplication of the resonant modes in the off-center-driving, the dispersion relation between the experimental frequency and the theoretical wave number can be deduced with more accuracy. It is found that the deduced dispersion relations agree quite well with the Kirchhoff–Love plate theory. Full article

The Spaceborne Global Lightning Location Network (SGLLN) serves the purpose of identifying transient lightning events occurring beneath the ionosphere, playing a significant role in detecting and warning of disaster weather events. To ensure the effective functioning of the wideband electromagnetic pulse detector, which is a crucial component of the SGLLN, it must be tested and verified with specific signals. However, the inherent randomness and unpredictability of lightning occurrences pose challenges to this requirement. Consequently, a high-power electromagnetic pulse radiation system with a 20 m aperture reflector is designed. This system is capable of emitting nanosecond electromagnetic pulse signals under pre-set spatial and temporal conditions, providing a controlled environment for assessing the detection capabilities of SGLLN. In the design phase, an exponentially TEM feed antenna has been designed firstly based on the principle of high-gain radiation. The feed antenna adopts a pulser-integrated design to mitigate insulation risks, and it is equipped with an asymmetric protective loading to reduce reflected energy by 85.7%. Moreover, an innovative assessment method for gain loss, based on the principle of Love’s equivalence, is proposed to quantify the impact of feed antenna on the radiation field. During the experimental phase, a specialized E-field sensor is used in the far-field experiment at a distance of 400 m. The measurements indicate that at this distance, the signal has a peak field strength of 2.2 kV/m, a rise time of 1.9 ns, and a pulse half-width of 2.5 ns. Additionally, the beamwidth in the time domain is less than 10°. At an altitude of 500 km, the spaceborne detector records a signal with a peak field strength of approximately 10 mV/m. Particularly, this signal transformed into a nonlinear frequency-modulated signal in the microsecond range across its frequency spectrum, which is consistent with the law of radio wave propagation in the ionosphere. This study offers a stable and robust radiation source for verifying spaceborne detectors and establishes an empirical foundation for investigating the impact of the ionosphere on signal propagation characteristics. Full article

Channel wave seismic activity often occurs with thin and medium-thick coal seams being the main target layer. To address the problem of channel wave applicability detection in extremely thick coal seams, the propagation and identification characteristics of channel waves remain the focus of research. Therefore, this paper takes the in-seam wave exploration of a 27 m extremely thick coal seam as an example and uses the staggered mesh finite difference method to construct a three-dimensional medium model for numerical simulation. An analysis of the physical parameters of coal and rock, along with the dispersion characteristics of channel waves in extra-thick coal seams, is utilized, through the Zoeppritz equation and the total reflection propagation method, to calculate the imaging. We found the following: (1) The dispersion areas and weak dispersion areas along the detection direction are extremely thick coal seams. (2) There are apparent channel waves in extra-thick coal seams, with a waveform similar to body waves; the length of the wave train is shorter than that of the conventional channel wave, and the arrival time can be estimated accurately. The amplitude of the apparent channel wave is affected by the degree of dispersion, with lower attenuation and higher resolution. The characteristic of total reflection in extremely thick coal seams is that the incident angle is equal to the critical angle, and the dispersion characteristics are weak. (3) The channel waves with weak dispersion characteristics in extra-thick coal seams are mainly Love-type waves. Full article

This paper studies elastic stress wave propagation generated by an impact in a system consisting of a moving striker rod and an initially stationary semi-infinite rod. This research emphasizes the role of different general impedances in affecting the response during the wave propagation process. The Rayleigh–Love rod theory is used in this research to consider lateral inertia and Poisson’s effects on longitudinal waves in rods, as these factors lead to greater stress results compared to the traditional wave equation. To solve the complex wave equations in a Rayleigh–Love rod with different general impedances, the numerical inversion of Laplace transformation is applied and verified using the results of previous research. This study demonstrates that variations in general impedances cause different wave reflection and transmission behaviors at the interface. As the wave interacts with this discontinuity of impedance, it may be amplified or attenuated, and changes in impedance can significantly affect wave propagation behaviors. Full article

This paper presents an in-depth study of the stress wave behavior propagating in a Rayleigh–Love rod with sudden cross-sectional area variations. The analytical solutions of stress waves are derived for the reflection and transmission propagation behavior at the interface of the cross-sectional area change in the rod, considering inertia and Poisson’s effects on the rod material. Examples solved using the finite element method are provided to verify the correctness of the analytical results. Based on the forward analysis of Rayleigh–Love wave propagation in a rod impacted by a striker rod, an impact-echo-type nondestructive testing (NDT) method is proposed to conduct defect assessment in rod-type structural components with sudden cross-sectional area changes within a cover medium. This proposed NDT method can identify the location, extension, and cross-sectional area drop ratios of an irregular zone in the rod to be inspected. Full article

This article is methodological in nature, addressing and discussing the challenges the research team encountered in constructing a new international well-being index called the World Love Index. This index represents the first quantitative operationalization of the concept of Social Love, which seeks to capture actions or social relationships characterized by excess and care for the benefit of individuals outside the primary circle, loved for their irreducibility. Starting with a discussion of the project’s objective rooted in the Beyond GDP debate, the article first analyzes the theoretical definition of Social Love and its semantic dimensions for operationalization. It then focuses on the methodological construction of the index through secondary data analysis, particularly examining the transition from the first wave to the second wave. Through the first wave of the WLI, this concept was systematically investigated on a transnational level. However, the first wave faced criticism for its weaknesses due to decisions made during the index’s construction. This paper, from a purely methodological perspective, demonstrates how the second wave of the WLI aims to address these challenges and turn them into strengths. Full article

This pioneer study determined the azimuthal variation in surface-wave fundamental-mode phase velocity for the Arabian plate, concluding that this variation is not due to seismic anisotropy but to lateral heterogeneity, which is compatible with anisotropic earth models of azimuthal isotropy. The study area was divided in six regions with similar surface-wave phase velocities. We determined their corresponding SH and SV-velocity models versus depth (from 0 to 260 km) by means of the anisotropic inversion of surface-wave phase velocities under the hypothesis of surface-wave propagation in slightly anisotropic media. We observed seismic anisotropy from 10 to 100 km depth. From these models, the parameter ξ was calculated for each region, and the most conspicuous features of the study area were described in terms of this parameter, such as the existence of the plume material propagation in the Arabian shield from the Afar plume, or the existence of a lithospheric keel, which was observed in previous studies beneath the Arabian platform, the Mesopotamian Plain and the Zagros belt. Full article

This paper presents an extended work on the Finite Element Method (FEM) simulation of Love Wave (LW) sensors in a liquid medium. Two models are proposed to simulate the multiphysical response of the sensor. Both are extensively described in terms of principle, composition and behavior, making their applications easily reproducible by the sensor community. The first model is a Representative Volume Element (RVE) simulating the transducer and the second focuses on the sensor’s longitudinal (OXZ) cut which simulates the multiphysical responses of the device. Sensitivity of the LW device to variations in the rheological and dielectric properties of liquids is estimated and then compared to a large set of measurements issued from LW sensors presenting different technological characteristics. This integral approach allows for a deeper insight into the multiphysical behavior of the LW sensor. This article also explores the advantages and drawbacks of each model. Both are in good accordance with the measurements and could be used for various applications, for which a non-exhaustive list is proposed in the conclusion. Full article