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The study of the dynamic response characteristics of “W”-type deep canyon terrain to double-span concrete arch bridges under earthquake action holds great practical significance. In this research, a bridge in Sichuan Province is taken as the object of study. The boundary-integral equation method and peak frequency shift method are combined to apply an embedded linear time–history analysis algorithm to the finite element spatial dynamic calculation model of the entire bridge, resulting in an improved model. By comparing these two methods with model test results, the seismic response characteristics of the middle part of a “W” concrete arch bridge under different foundation depths and seismic intensities are examined. The boundary integral equation method was utilized to calculate ground motion response at any point on site, revealing a significant amplifying effect of increased seismic wave intensity on acceleration response at the top of the arch bridge. When input seismic wave intensity increased from 0.1 g to 0.3 g, maximum acceleration at buried depths of 3 m and 8 m in the middle of the arch bridge foundation increased by 102.63% and 79.16%, respectively, indicating that shallow buried depth structures are more sensitive to seismic wave intensity. Furthermore, using peak frequency shift rules for analyzing seismic wave propagation characteristics in “W”-type deep canyon topography confirms the sensitivity of shallow buried depth structures to seismic wave intensity and reveals the mechanism through which topography influences seismic wave propagation. This study provides a helpful method for understanding the propagation law and energy distribution characteristics of seismic waves in complex terrain. It was observed that the displacement at the top of the arch bridge increased significantly with an increase in seismic intensity. When subjected to 0.1 g, 0.2 g, and 0.3 g EI-Centro seismic waves, the maximum displacement at the top of the arch bridge model with a foundation buried depth of 3 m was 8 mm, 32 mm, and 142 mm, respectively. For arch bridge models with an 8-m foundation buried depth, these displacements were measured at 6.2 mm, 21 mm, and 68 mm, respectively. The results from model tests verified that increasing the depth of foundation burial effectively reduces the displacement at the top of the structure. Furthermore, by combining a boundary-integral equation method and peak-frequency shift method, this study accurately predicted significant influences on W-shaped double deep canyon topography from seismic response, and successfully captured stress concentration and seismic wave amplification/focusing effects on arch foot structures. The calculated results from both methods align well with model test data which confirm their effectiveness and complementarity when analyzing seismic responses under complex terrain conditions for bridge structures.

Direct and precise monitoring of intracranial physiology holds immense importance in delineating injuries, prognostication and averting disease 1 . Wired clinical instruments that use percutaneous leads are accurate but are susceptible to infection, patient mobility constraints and potential surgical complications during removal 2 . Wireless implantable devices provide greater operational freedom but include issues such as limited detection range, poor degradation and difficulty in size reduction in the human body 3 . Here we present an injectable, bioresorbable and wireless metastructured hydrogel (metagel) sensor for ultrasonic monitoring of intracranial signals. The metagel sensors are cubes 2 × 2 × 2 mm 3  in size that encompass both biodegradable and stimulus-responsive hydrogels and periodically aligned air columns with a specific acoustic reflection spectrum. Implanted into intracranial space with a puncture needle, the metagel deforms in response to physiological environmental changes, causing peak frequency shifts of reflected ultrasound waves that can be wirelessly measured by an external ultrasound probe. The metagel sensor can independently detect intracranial pressure, temperature, pH and flow rate, realize a detection depth of 10 cm and almost fully degrade within 18 weeks. Animal experiments on rats and pigs indicate promising multiparametric sensing performances on a par with conventional non-resorbable wired clinical benchmarks. A bioresorbable, wireless hydrogel (metagel) sensor, encompassing both biodegradable and stimulus-responsive hydrogels for ultrasonic monitoring of intracranial signals, was implanted into intracranial space with a puncture needle and deformed in response to physiological environmental changes.

The production mechanism of fast radio bursts (FRBs)—mysterious, bright, millisecond-duration radio flashes from cosmological distances—remains unknown. Understanding potential correlations between burst occurrence times and various burst properties may offer important clues about their origins. Among these properties, the spectral peak frequency of an individual burst (the frequency at which its emission is strongest) is particularly important because it may encode direct information about the physical conditions and environment at the emission site. Analyzing over 4000 bursts from the three most active sources—FRB 20121102A, FRB 20201124A, and FRB 20220912A—we measure the two-point correlation function ξ(Δt, Δνpeak) in the two-dimensional space of time separation Δt and peak frequency shift Δνpeak between burst pairs. We find a universal trend of asymmetry about Δνpeak at high statistical significance; ξ(Δνpeak) decreases as Δνpeak increases from negative to positive values in the region of short time separation (Δt ≲ 0.3 s), where physically correlated aftershock events produce a strong time correlation signal. This indicates that aftershocks tend to exhibit systematically lower peak frequencies than mainshocks, with this tendency becoming stronger at shorter Δt. We argue that the “sad trombone effect”—the downward frequency drift observed among subpulses within a single event—is not confined within a single event but manifests as a statistical nature that extends continuously to independent yet physically correlated aftershocks with time separations up to Δt ∼ 0.3 s. This discovery provides new insights into underlying physical processes of repeater FRBs.

The Chang’e-4 lander successfully landed in the Von Kármán crater on the farside of the Moon in 2019, collecting a large amount of scientific data to analyze the surface material and subsurface structures of the Von Kármán crater. In this study, we processed the high-frequency radar data from the first 25 lunar days collected by the Lunar Penetrating Radar along the route of the Yutu-2 rover. Using the peak frequency shift method, we calculated the loss tangent of the shallow regolith layer ranged from 3×10 −3 to 5.5×10 −3 . The estimated TiO 2 and FeO content in the regolith is 11.2 wt% - 14.7 wt%, revealing a heterogeneous distribution of iron and titanium content along the CE-4 landing site.

Channel erosion not only amplifies debris‐flow magnitude and impact but also reshapes local geomorphology. However, the destructive and infrequent nature of debris flows makes in situ monitoring of channel‐bed erosion processes and flow characteristics challenging. Here, we investigate seismic signals for monitoring erosion‐driven geomorphic changes, using data from 18 well‐documented debris flows at Illgraben, Switzerland, between 2019 and 2023. We find that integrated seismically derived impact forces over each event correlate with channel‐bed elevation changes, revealing erosion thresholds. Seismic peak frequencies correlate with absolute channel‐bed elevations at seismic source regions, reflecting changes in wave propagation paths due to erosion. The correlation is evident, with peak frequency shifts exceeding 15 Hz while channel‐bed elevation changes were under 4 m during the 5‐year period. These findings demonstrate the capacity of seismic signals to characterize debris‐flow erosion and track absolute channel‐bed elevations, offering new insights into geomorphic processes.

Objectives To compare image quality between a deep learning image reconstruction (DLIR) algorithm and conventional iterative reconstruction (IR) algorithms in dual-energy CT (DECT) and to assess the impact of these algorithms on radiomics robustness. Methods A phantom with clinical-relevant densities was imaged on seven DECT scanners with the same voxel size using typical abdominal-pelvis examination protocols. On one DECT scanner, raw data were reconstructed using both conventional IR (adaptive statistical iterative reconstruction-V, ASIR-V) and DLIR. Nine sets of corresponding images were generated on other six DECT scanners using scanner-equipped conventional IR. Regions of interest were delineated through rigid registrations. Image quality was compared. Pyradiomics platform was used for radiomics feature extraction. Test-retest repeatability was assessed by Bland-Altman analysis for repeated scans. Inter-reconstruction algorithm reproducibility between conventional IR and DLIR was tested by intraclass correlation coefficient (ICC) and concordance correlation coefficient (CCC). Inter-scanner reproducibility was evaluated by coefficient of variation (CV) and quartile coefficient of dispersion (QCD). Robust features were identified. Results DLIR significantly improved image quality. Ninety-four radiomics features were extracted and nine features were considered as robust. 93.87% features were repeatable between repeated scans. ASIR-V images showed higher reproducibility to other conventional IR than DLIR (ICC mean, 0.603 vs 0.558, p = 0.001; CCC mean, 0.554 vs 0.510, p = 0.004). 7.45% and 26.83% features were reproducible among scanners evaluated by CV and QCD, respectively. Conclusions DLIR improves quality of DECT images but may alter radiomics features compared to conventional IR. Nine robust DECT radiomics features were identified. Key Points • DLIR improves DECT image quality in terms of signal-to-noise ratio and contrast-to-noise ratio compared with ASIR-V and showed the highest noise reduction rate and lowest peak frequency shift. • Most of radiomics features are repeatable between repeated DECT scans, while inter-reconstruction algorithm reproducibility between conventional IR and DLIR, and inter-scanner reproducibility, are low. • Although DLIR may alter radiomics features compared to IR algorithms, nine radiomics features survived repeatability and reproducibility analysis among DECT scanners and reconstruction algorithms, which allows further validation and clinical-relevant analysis.

To investigate the sound source characteristics of infrasound waves generated during the operation of the gas explosion liquid level monitoring instrument, with a focus on the aerodynamic noise produced by the monitoring device, a mixed numerical method was used to simulate and study the impact of different nozzle diameters, gas explosion pressures, and casing pressures on the instrument’s infrasound frequency range. The results indicate that gas explosion pressure, casing pressure, and nozzle diameter primarily affect the spectral characteristics within the 10 Hz to 20 Hz range. As the gas explosion pressure and nozzle diameter increase, the sound pressure level in the internal sound field also increases, and the peak frequency shifts higher. Conversely, with an increase in casing pressure, the sound pressure level in the internal sound field decreases, and the peak frequency shifts lower. The research findings can provide a theoretical basis for the development of the instrument.

The higher efficiency of superconducting radio-frequency (SRF) cavities compared to normal-conducting ones enables the development of high-energy continuous-wave linear accelerators (linacs). Recent progress in the development of high-qualityNb3Snfilm coatings along with the availability of cryocoolers with high cooling capacity at 4 K makes it feasible to operate SRF cavities cooled by thermal conduction at relevant accelerating gradients for use in accelerators. A possible use of conduction-cooled SRF linacs is for environmental applications, requiring electron beams with energy of 1–10 MeV and 1 MW of power. We have designed a 915 MHz SRF linac for such an application and developed a prototype single-cell cavity to prove the proposed design by operating it with cryocoolers at the accelerating gradient required for 1 MeV energy gain. The cavity has a∼3μmthickNb3Snfilm on the inner surface, deposited on a∼4mmthick bulk Nb substrate and a bulk∼7mmthick Cu outer shell with three Cu attachment tabs. The cavity was tested up to a peak surface magnetic field of 53 mT in liquid He at 4.3 K. A horizontal test cryostat was designed and built to test the cavity cooled with three Gifford-McMahon cryocoolers. The rf tests of the conduction-cooled cavity, performed at General Atomics, achieved a peak surface magnetic field of 50 mT and stable operation was possible with up to 18.5 W of rf heat load. The peak frequency shift due to microphonics was 23 Hz. These results represent the highest peak surface magnetic field achieved in a conduction-cooled SRF cavity to date and meet the requirements for a 1 MeV energy gain.

Metamaterial biosensors have been extensively used to identify cell types and detect concentrations of tumor biomarkers. However, the methods for in situ and non-destruction measurement of cell migration, which plays a key role in tumor progression and metastasis, are highly desirable. Therefore, a flexible terahertz metamaterial biosensor based on parylene C substrate was proposed for label-free and non-destructive detection of breast cancer cell growth and migration. The maximum resonance peak frequency shift achieved 183.2 GHz when breast cancer cell MDA−MB−231 was cultured onto the surface of the metamaterial biosensor for 72 h. A designed polydimethylsiloxane (PDMS) barrier sheet was applied to detect the cell growth rate which was quantified as 14.9 µm/h. The experimental peak shift expressed a linear relationship with the covered area and a quadratic relationship with the distance, which was consistent with simulation results. Additionally, the cell migration indicated that the transform growth factor-β (TGF-β) promoted the cancer cell migration. The terahertz metamaterial biosensor shows great potential for the investigation of cell biology in the future.

We present and experimentally demonstrate a seismic ambient noise monitoring optical fibre sensor for early warning detection of sinkholes. The developed optical fibre sensor is designed for warning alert of subsidence and cover collapse sinkholes. The progressive process of sinkhole development causes structural change in the subterranean surface. The impact of this change and its influence on the subsurface acoustic modes was detected in the form of variations in the spectral content of the ambient noise signals monitored in the subsurface. Structural surface integrity was monitored through frequency response as the void increased. Vibrational states relating to unsteady structural conditions were identified. Significant instability events were captured giving timely warnings before collapse. The polarisation based single mode fibre sensor and monitoring method is proposed for implementation in a phase sensitive distributed acoustic sensor setup. Peak frequencies in the micro-seismic noise band of 0.1 Hz to 1.0 Hz were observed through cavity development and growth. Extended peak frequency shifts and bandwidth in the band >1Hz were recorded, indicating weakness and imminence of collapse. Early warning detection by the structural field model was achieved prior to the sudden subsurface failure which results in collapse sinkholes. By monitoring variations in the vibrating frequency modes when a subsurface cavity develops within the structure, trigger events and collapse precursor conditions are identified. We have successfully demonstrated an early response warning annunciator by using an algorithm to analyse combinational characteristics of the spectral components of the detected signals. The fibre sensor reduces the risk and socio-economic impact of infrastructural damage due to sudden collapse of sinkholes and has extended potential of monitoring earthquakes and landslides.