Search Results (371)

Parity-time ($\mathcal{PT}$) symmetry offers a well-established route for enhancing light-matter interaction by means of formation of exceptional points. The model of plane waves is commonly used for finding and investigating exceptional points in open multilayer systems. Here we study behaviors of TE-polarized Bessel light beams in $\mathcal{PT}$-symmetric multilayer structures. It is shown that, due to the translational invariance of the planar interfaces, the exceptional and diabolic points of the Bessel beam are identical to those of a conventional plane wave with the same angle of incidence. Basing on this equivalence, we adopt the method of scattering matrices to TE-polarized non-paraxial Bessel beams and determine positions of exceptional points depending on the transverse wave number and non-Hermiticity parameter for both propagating and evanescent beams. We reveal the evolution of exceptional and diabolic lines when the number of layers changes and find their link to the transmission and reflection spectra. This research may pave the way for exploiting light beams in non-Hermitian photonics. Full article

Background/Objectives: A dual-layer flat-panel detector (DFD), in which two flat-panel detectors are stacked vertically, enables single-shot dual-energy imaging without a fan-beam scanning and switching mechanism in conventional dual-energy X-ray absorptiometry (DXA), the clinical standard for bone mineral density (BMD). However, because single-shot BMD measurement systems using DFDs show substantial spectral overlap, their BMD measurement performance is inherently inferior to that of dual-shot systems. In this paper, we optimize the tube voltage, metal filter thickness, and CsI(Tl)-scintillator thickness so that the BMD estimation error of the single-shot method is similar to that of the double-shot method. Here, we also optimize the dual-shot approach to serve as a meaningful reference in the comparison. Methods: BMD measurement simulations were performed using a polynomial estimator based on second-order polynomial fitting of dual-energy logarithmic intensities. Performance comparison was based on noise sensitivity, quantified by the condition number and mean square error under a multiplicative noise model, and was further assessed using the equivalent energies and the bone-tissue attenuation ratios. Results: The simulation results indicate that, in the dual-shot approach, decreasing the low tube voltage is the most effective strategy for improving BMD measurement performance, whereas in the single-shot approach, reducing the upper scintillator thickness has the largest impact. Conclusions: When both approaches are evaluated under their respective optimized configurations based on synthetic simulations, the single-shot approach demonstrates that the BMD estimation error is sufficiently similar to that of the dual-shot approach, supporting its potential as a hardware-efficient alternative for BMD measurement. Full article

Continuous rigid-frame bridges experience web, bottom-slab, and deck-slab deterioration in service, yet strengthening locations are rarely compared within a single structure. A 3.68-m acrylic (polymethyl methacrylate, PMMA) model of a three-span rigid-frame bridge was tested at four static load levels with a three-axle vehicle. The web void was patched, and the bottom and deck slabs were then stiffened, forming cumulative Stages 0–3; a beam model matched the measurements within 3.6–9.7%. At the mid-span section, full strengthening reduced the 20-kg deflection by 39.8% and raised equivalent flexural stiffness by 51.5%. The bottom-slab stage gave the largest incremental gain, raising bottom-flange strain improvement at the mid-span and side-span one-third control sections from 2–4% to 28–31%; the deck-slab stage added a comparable stiffness gain. Web patching acted locally (21.9% strain reduction beside the defect and 0.5% at the mirror gauge) but left the control-section flexural indices unresolved; as a web void mainly affects shear, which is unmeasured here, it is reported as localized restoration. Response-line shapes were preserved while Stage-3 envelope areas contracted by 30–40%. The specimen was not replicated, and the mid-span improvement spans 37.4–48.0% across three data treatments. The results support mechanism-based screening of strengthening locations in similar box girders under service loading. Full article

Pile-anchor retaining systems represent a fundamental support technology for urban deep excavations, where accurate quantification of anchor axial force is essential to achieving both structural safety and economical design. Here, we systematically assessed the predictive performance of several established design approaches—namely the static equilibrium method, the equivalent beam method, the earth pressure envelope method, an empirical chart-based method, and the CPD method—against in-situ monitoring data acquired from a deep excavation project. Under the site-specific conditions, the chart-based method delivered the closest agreement with the measured anchor forces. We further implemented a finite element model to perform a parametric sensitivity analysis, elucidating the influence of anchor embedment depth, excavation depth, and groundwater table position on anchor axial force. The results revealed that increasing anchor embedment depth produced only a marginal variation in anchor force, indicating weak sensitivity. In contrast, deepening the excavation produced a pronounced escalation in anchor force and significantly modulated pile bending moments. Elevating the depth to the groundwater table (i.e., lowering the water level) caused the anchor force to decline monotonically, with the rate of decrease progressively attenuating at greater depths, thereby demonstrating a moderate dependency on groundwater conditions. Full article

FLASH radiotherapy, which delivers radiation at ultrahigh dose rates (UHDRs) exceeding 40 Gy/s, has attracted considerable attention because of its potential to spare normal tissues while maintaining tumour control. Gold nanoparticles (GNPs) are promising radiosensitizers that enhance radiation-induced biological effects through increased production of reactive oxygen species (ROS) and subsequent DNA damage. However, the influence of GNPs on DNA damage under FLASH irradiation remains poorly understood. In this study, Geant4-DNA Monte Carlo simulations were performed to investigate the effects of GNP size and dose rate on DNA damage during UHDR electron-beam irradiation. DNA damage was quantified through both direct and indirect mechanisms based on energy deposition in DNA backbone segments and interactions between radiation-induced radical species and DNA, and was evaluated relative to equivalent water nanoparticle (WNP) controls. The results demonstrated a dose rate-dependent reduction in both relative single-strand breaks (RSSBs) and relative double-strand breaks (RDSBs) arising from direct and indirect DNA damage mechanisms. For the 10 keV monoenergetic model condition, the 10 nm GNP produced the greatest radiosensitization among the particle sizes investigated, with the matched GNP/WNP analysis showing a maximum 5-fold enhancement in direct SSB yields. In contrast, substantially weaker GNP-specific enhancement and no comparable size-dependent effect were observed at 1 MeV. These findings demonstrate that GNP-mediated radiosensitization depends on both nanoparticle size and electron energy under the irradiation conditions investigated. The greater enhancement observed for the 10 nm GNP at 10 keV should therefore not be interpreted as identifying a universally optimal GNP size for FLASH radiotherapy. Full article

In deepwater open-loop drilling of ultra-shallow high-build-rate horizontal wells, the drill string spans the exposed seawater section, the mudline transition, and the constrained downhole section. Existing studies have not yet established a unified coupled dynamic model covering the full string, and the response patterns and parameter-control mechanisms remain insufficiently understood. This study examines a surface-hole operation in a block of the South China Sea. A six-degree-of-freedom spatial Euler–Bernoulli beam finite element model was established from the measured wellbore trajectory. Structural and fluid inertia, geometric stiffness due to axially varying force, Morison-type current loading, a wake-oscillator model for vortex-induced vibration (VIV), wellbore contact and friction, and bit loads were coupled within one framework. The generalized-alpha method was used for time discretization, and the nonlinear dynamic equilibrium equations were solved by within-step iteration for multiple operating conditions. Under the baseline condition, the peak in-line displacement was 6.3–6.4 m and occurred in the middle of the seawater section; the peak cross-flow displacement was approximately 0.43 m, the maximum bending moment was approximately 36 kN m, and the maximum equivalent stress was approximately 230 MPa. The high internal-force values were concentrated in the mudline transition and the upper BHA, demonstrating spatial separation between deformation and internal force. Surface current velocity controlled the in-line response amplitude: increasing the velocity from 0.4 to 0.8 m/s increased the peak in-line displacement by approximately 230%. WOB had a limited effect on global deformation and acted mainly on the local near-bit section. These results provide numerical reference for mechanistic analysis and parameter control of drill-string dynamics in comparable deepwater open-loop drilling operations. Full article

External loads acting on shield tunnel linings in service are difficult to determine, while existing back analysis methods often require multiple monitoring quantities and repeated numerical calculations. This study develops an analytical method for identifying the equivalent horizontal load and lateral pressure coefficient from a single rotation measurement. The lining is modelled as a continuous Euler–Bernoulli curved beam on a radial Winkler foundation, with circumferential compression and bending considered. The radial components of the vertical and horizontal loads are decomposed into uniform and second-order terms. Closed-form solutions are obtained for displacement, rotation, and internal forces, followed by an explicit inverse relation between rotation at one circumferential position and the load difference. The analytical responses agree closely with an independent plane-frame finite element model. Prescribed horizontal loads and lateral pressure coefficients are also recovered accurately from finite element rotations. A FLAC3D model of the complete ring with continuous elastic ground further shows that the circumferential response pattern is retained and that the equivalent horizontal load can still be estimated when the Winkler ground representation is relaxed. The method identifies the load difference from one rotation measurement, and when the vertical load is independently estimated, determines the equivalent horizontal load. It provides a basis for assessing lining ovalization, bending response, and abnormal loading states. Full article

Railway turnouts are subject to disproportionately high maintenance costs, partly driven by ballast void formation under asymmetrically loaded sleepers. Existing turnout models rely on detailed three-dimensional finite element track representations and do not readily support iterative long-term settlement analyses across the complete turnout geometry. This paper presents a computationally efficient physics-based vehicle–track interaction (VTI) framework extended to railway turnouts, incorporating a dual track model with equivalent foundation stiffnesses, a rail pad layer, and a crossing nose impact model. A modular sleeper dynamics model, formulated as an Euler–Bernoulli beam on a tensionless Winkler foundation, is coupled with the VTI framework to compute spatially resolved dynamic ballast pressure distributions along individual sleepers. A local pressure-based settlement model then allows the study of sleeper–ballast void formation over repeated axle passes. The framework is applied as a proof of concept to two in-service railway turnouts, one with and one without under sleeper pads, and complemented by a parametric study varying train speed, vehicle type, and rail pad stiffness. Void formation concentrates in the crossing nose region, consistent with laboratory measurements and particle-scale simulations. Under sleeper pads reduce peak ballast pressure by 38 to 44% and substantially reduce void formation across the crossing panel, thereby lowering overall track settlement and supporting the maintenance of track geometry in the turnout during operation. Vehicle type is the dominant influencing factor, with the locomotive producing up to 83% higher peak pressure than the passenger car model. The proposed framework provides an efficient tool for comparative turnout design, offering insight into the force transfer and settlement mechanisms of railway turnouts. Full article

High-frequency broadband acoustics can provide fine spatial resolution for near-range fish measurements, but the performance and limitations of beam-position-resolved backscatter measurements require careful evaluation. This proof-of-concept study examined one commercially sourced, dead, previously frozen specimen of each of three cultured fishes: golden pompano (Trachinotus ovatus; 24.4 cm), mandarin fish (Siniperca chuatsi; 29.1 cm), and large yellow croaker (Larimichthys crocea; 31.2 cm). A 650–750 kHz narrow-beam system was referenced to a 10.3 mm tungsten-carbide sphere, and matched-filter pulse compression and 1° stepwise scanning were used to estimate a beam-position-resolved backscatter metric along each body. At broadside incidence, the section-summed backscatter indices were −33.61, −22.45, and −33.07 dB for the T. ovatus, S. chuatsi, and L. crocea specimens, respectively. The section-summed abdominal backscatter index, in the region occupied by the swimbladder in the post-thaw X-ray images, exceeded the arithmetic mean of the head and tail group indices by 9.71 ± 1.84 dB (range: 8.27–11.86 dB). Tailward beam positions fell below the noise floor at approximately 12.5% of the expected scan positions for S. chuatsi and 22.2% for L. crocea. A 15° departure from broadside reduced the section-summed index by 3.73–11.43 dB. Kirchhoff-ray-mode (KRM) simulations based on post-thaw dual-view X-ray geometry were broadly consistent with the specimen-level contrast observed among the preserved specimens, but were 0.92–2.74 dB lower than the corresponding broadside section-summed measurement indices at 700 kHz. These differences are not a quantitative validation because the measured and modeled estimators, frequency weighting, geometry, and tissue parameters were not equivalent. These results demonstrate the feasibility of a calibrated beam-position workflow for preserved specimens, while not establishing live-fish target strength, species benchmarks, or biomass-estimation performance. Full article

This study focuses on accelerating adaptive beamforming in the Multicarrier Wireless Internet Local Loop (McWiLL) professional radio communication system using “Korona” ring smart antennas. The work investigates algorithms for calculating complex weight coefficients in an eight-element uniform circular antenna array. The main objective is to reduce beam pattern adaptation time while maintaining interference suppression depth and robustness under multipath propagation. To achieve this, an ensemble machine learning approach based on the Random Forest algorithm is employed to approximate the optimal Minimum Variance Distortionless Response (MVDR) solution using elements of the sample covariance matrix of received signals. The training dataset is generated through McWiLL channel simulations considering mutual coupling between array elements, signal-to-noise ratio (SNR) variation, and different angles of arrival of the desired and interfering signals. The proposed method is evaluated against the classical MVDR algorithm in terms of radiation pattern null depth, robustness to phase distortions, and inference time on a Field-Programmable Gate Array (FPGA) hardware platform. Results demonstrate that the Random Forest-based approach achieves more than a fourfold reduction in computation time while forming radiation-pattern nulls of about 30–35 dB toward the interferers (versus 44–46 dB for the classical MVDR); the synthesized core uses no hardware multipliers (DSP48), and its functional equivalence to the software model is confirmed by bit-exact RTL co-simulation. The findings show promise for deployment in McWiLL base stations and other professional radio systems requiring fast, adaptive beamforming under dynamic channel conditions. Full article

Theranostics has transformed nuclear medicine from an imaging-focused discipline into a data-rich radiation medicine platform in which target expression, pharmacokinetics, tumor dose, and response can be measured in the same patient. This critical narrative review evaluates patient-specific integration of radiopharmaceutical therapy (RPT) with external-beam radiotherapy (EBRT), with emphasis on quantitative imaging, absorbed-dose estimation, spatial registration, biological interpretation, adaptation thresholds, and reporting. We performed a targeted search of PubMed/MEDLINE, ClinicalTrials.gov, U.S. Food and Drug Administration records, professional-society guidance, and reference lists for English-language evidence available through 31 July 2026, prioritizing guidelines, regulatory documents, randomized and prospective trials, technical validation studies, and clinically informative retrospective series. Established RPT platforms are distinguished from investigational combined-modality applications and emerging or speculative technologies. Liver-directed Y-90 radioembolization combined with focal EBRT remains the most developed model, whereas head and neck, prostate, meningioma, lymphoma, and bone-dominant strategies illustrate distinct clinical geometries and levels of readiness. Across platforms, direct addition of absorbed dose in gray (Gy) is a geometric description, not automatically a biological endpoint; biologically effective dose (BED) and equivalent dose in 2-Gy fractions (EQD2) should be treated as model-based estimates with explicit assumptions. Future theranostic radiation medicine should therefore be built on prospective trials with prespecified dosimetry, uncertainty analysis, adaptation rules, and shared cross-modality reporting standards. Full article

The mechanical compatibility between dental restorative materials and the natural tooth structure is a relevant factor for long-term clinical performance. Although zirconia (yttria-stabilized tetragonal zirconia polycrystal, Y-TZP) and lithium disilicate are widely used for full-coverage crowns, their biomechanical interaction with the underlying dentin and pulp under functional loading remains insufficiently characterized. This study reports a comparative finite element analysis (FEA) of a mandibular first molar under vertical (200 N, axial) and oblique (200 N, 30°) loading, evaluating three configurations: an intact healthy tooth, a zirconia Y-TZP full-coverage crown, and a lithium disilicate full-coverage crown. The three-dimensional geometry was obtained from a cone-beam computed tomography (CBCT) study of a caries-free mandibular first molar, previously described and verified by the present group, and was analyzed in ANSYS Workbench (Static Structural). Von Mises equivalent stress, maximum principal stress and total deformation were obtained for enamel or restoration, dentin, and pulp in each configuration. Zirconia produced the highest stress concentrations in the coronal restoration (88.4 MPa vertical; 174.5 MPa oblique), exceeding the healthy enamel baseline by 57.6% and 89.7%, respectively. Both restorative materials reduced dentin stress relative to the healthy tooth, consistent with the stress-shielding effect driven by elastic-modulus mismatch. Under oblique loading, the maximum principal stress in healthy enamel reached 61.7 MPa, approaching or exceeding the upper bound of the reported tensile strength range (~10–40 MPa) and identifying oblique loading as the more demanding of the two conditions analyzed. Within the limitations of the present finite element model, lithium disilicate demonstrated a more favorable stress distribution, with dentin stress values closer to the intact-tooth baseline. The model does not include a luting cement layer, a periodontal ligament, the dentin–enamel junction, anisotropic tissue behavior or cyclic loading, and no experimental validation was performed; the results are therefore presented as a controlled numerical comparison between three configurations under the specific conditions simulated, and not as direct clinical selection criteria. Full article

Laminated carbon fiber reinforced polymer (CFRP) beams are widely used in lightweight structures, yet their vibration response depends strongly on laminate architecture, boundary conditions, thickness, and material anisotropy. Previous studies often examined these effects separately or relied on a single analytical or numerical approach. This study presents a multi fidelity framework integrating classical laminate theory (CLT), the Vinson–Sierakowski (VS) equivalent modulus method, and three-dimensional finite element analysis for modal prediction and parametric design of symmetric CFRP laminated beams. Three stacking sequences, [0/0/0/0], [0/45/45/0], and [0/90/90/0], were evaluated under clamped-free (CF) and clamped-clamped (CC) conditions. ANSYS models using quadratic HEX20 solid elements served as the numerical reference. Across 36 validation frequencies, the mean absolute percentage errors were 3.05% for CLT and 2.28% for VS, giving VS a 25.1% lower average error. The [0/0/0/0] laminate produced the highest frequencies. The first numerical frequency increased from 36.37 to 230.20 Hz when the boundary condition changed from clamped-free to clamped-clamped. Increasing thickness from 2 to 8 mm raised the first frequency from 18.20 to 72.62 Hz, while increasing $E_1/E_2$ from 10 to 30 raised it from 30.80 to 53.85 Hz. The framework supports rapid screening, laminate level interpretation, and detailed numerical verification for vibration-oriented composite beam design. Full article

The bent sub is a main deflection component in the near-bit assembly of small-diameter push-the-bit guided coring tools, and its parameters affect build-up capability and local structural response. Existing studies mainly focus on conventional rotary steerable drilling systems, whereas slim-hole constraints, including narrow annular clearance and cross-sectional weakening induced by internal coring channels, remain insufficiently considered. To address this problem, a static bending model of the near-bit section was established based on Euler–Bernoulli beam theory. Channel-induced cross-sectional weakening was represented using the actual concentric annular geometry of the primary load-bearing outer tube, and the bent-sub initial curvature, dual push-the-bit loads, axial weight on bit, and borehole-wall contact and friction effects were incorporated. The build-up rate (BUR), maximum equivalent stress, and maximum curvature served as response indicators. A control-variable approach was used to analyze the bent-sub length L_b, bend angle γ, and distance from the bit D_b. The results showed that D_b had the strongest effect on BUR, and all parameters exhibited a trade-off between steering performance and structural safety. Increasing L_b from 0.30 m to 0.80 m reduced BUR from 12.65°/30 m to 9.79°/30 m, whereas increasing γ from 0.5° to 2.5° increased BUR from 4.12°/30 m to 10.70°/30 m. Considering structural constraints and normalized BUR retention, the recommended engineering ranges are L_b = 0.65–0.80 m, γ = 1.3°–1.9°, and D_b = 0.50–0.70 m. Full article

As the construction industry seeks to reduce carbon emissions, timber has emerged as a key material due to its capacity for biogenic carbon storage and end-of-life (EoL) reuse. However, assessing the practical circularity potential of timber structures remains challenging. This is largely because recovered components suffer geometric and material losses at their connection points. This study evaluates the EoL reuse and recycling potential of a multi-storey timber building by combining Building Information Modelling (BIM) with Life Cycle Assessment (LCA). A digital model was used to quantify structural elements (beams, columns, and walls), explicitly accounting for material losses at connections to calculate the net recoverable timber. The recovered material (837.39 m³) was assigned to various cascading use scenarios based on material strength: structural reuse, non-structural reuse, engineered wood production, and energy recovery. To align with ISO 14044 principles, a functional equivalence factor (Q-factor) was applied to measure the environmental benefits of substituting new materials. Results indicate an overall material loss of 16.62% due to connections. Among the evaluated EoL pathways, structural reuse yielded the greatest net carbon benefit (−128.7 tCO₂e), significantly outperforming lower-value alternatives such as energy recovery (−29.3 tCO₂e). Additionally, a Design for Disassembly (DfD) sensitivity analysis showed that reducing connection losses by 50% could increase net global warming potential (GWP) savings by up to 19.7%. In conclusion, connection design is a critical factor in enabling timber circularity. Furthermore, combining BIM material tracking with LCA methods offers a practical approach to quantifying the long-term carbon benefits of timber reuse strategies. Full article