Search Results (567)

When inverter switching frequency is constrained, PMSM drives operating at relatively high fundamental electrical frequencies may exhibit a low switching-to-fundamental-frequency ratio (low carrier ratio), resulting in fewer voltage vector updates per fundamental cycle and increased current ripple and low-order harmonics. To address the difficulty of synchronizing offline selective harmonic elimination PWM (SHEPWM) switching angles with a field-oriented control (FOC) current loop, this paper proposes an angle-synchronous FOC-SHEPWM implementation based on electrical angle partitioning. A quarter-wave-symmetric SHEPWM model is first established, and the switching angles are solved using Newton iteration and homotopy continuation. A Halton low-discrepancy initial value pool is then constructed. Combined with cumulative interval mapping, admissibility screening, and continuity assessment, it yields switching angle trajectories suitable for closed-loop look-up table implementation and extends the high-modulation-index range toward six-step operation. For online implementation, the ePWM period is updated according to the electrical angular speed, and the offline angles are mapped to intra-partition compare values. Counter-zero sampling, delay angle compensation, dynamic period correction, and fundamental current extraction are integrated to realize synchronized closed-loop pulse generation. The simulation and experimental results demonstrate the stable operation of the SHEPWM-N3, SHEPWM-N5, and SHEPWM-N7 patterns. At equal numbers of switching events, the proposed patterns exhibit lower low-order harmonic content and current total harmonic distortion than ASVPWM, while the fundamental current extraction and dynamic period correction methods reduce d-q-axis current ripple and partition synchronization error, respectively. Full article

Anastomotic angle and flow allocation change together in end-to-side junctions, complicating interpretation of angle-dependent wall shear. We used MITOS Flow Lab, a two-dimensional D2Q9 two-relaxation-time lattice-Boltzmann environment, to examine this coupling in steady, rigid-walled, Newtonian models at Re ≈ 91. Angles of 30–120° were compared under equal outlet pressures and at approximately matched branch-flow fractions of 0.25 and 0.21, achieved with angle-specific static outlet-pressure offsets. Under equal outlet pressures, the branch-flow fraction decreased from 0.356 to 0.151 across this angle range, while the minimum normalized signed recipient-floor shear increased from 0.140 to 0.450. Matching flow allocation substantially reduced angle-associated variation in this endpoint and in the sub-toe response, whereas sub-heel and sub-ostial responses remained angle dependent under the adjusted boundary conditions. This qualitative contrast persisted when the lumen resolution was increased from 32 to 64 nodes for the 0.25 target, although minimum-shear attenuation changed from approximately 83% to 74%. The 0.21 target was examined only on the production grid. These experiments demonstrate that the interpretation of angle-associated shear depends on the flow-allocation condition used for comparison. They do not identify a boundary-independent geometric effect or a causal mediation fraction. Absolute values and attenuation magnitudes remain sensitive to discretization and have not been independently validated. These controlled comparisons provide a framework for interpreting angle-associated shear together with achieved flow allocation and the specified outlet conditions. Full article

SP-QBIC resonances are highly sensitive to asymmetry parameters. Meanwhile, achieving polarization-wavelength-stable QBIC resonances in metasurfaces remains challenging. To address these issues, this study proposes hetero-material out-of-plane (HOP) metasurfaces. First, the influence of the asymmetry parameter on the resonance spectra of the HOP asymmetric metasurfaces (AMS) is analyzed. Compared with in-plane (IP) AMS, the QBIC resonance wavelength of the HOP AMS remains essentially stable as the asymmetry parameter varies, and both the resonance linewidth and the quality (Q) factor exhibit stronger robustness—especially when the hetero-material is located up the symmetric metasurface (HOP_u). Second, the effect of the refractive index of the hetero-material n_l on the resonance spectra of the HOP_u AMS and (the hetero material is located below the symmetric metasurface) HOP_b AMS is investigated. As the n_l increases, the QBIC resonance wavelengths of HOP AMS red-shift; meanwhile, the Q factor of the HOP_u gradually decreases, whereas that of the HOP_b AMS remains almost unchanged. Simulations reveal that HOP AMS resonances exhibit strong robustness against device fabrication errors. Finally, by varying the incident light polarization angle, it is verified that the proposed HOP AMS enables excitation polarization wavelength stable QBIC resonance. The multipole decomposition elucidates the physical mechanism by which HOP AMS can excite polarization wavelength stable SP-QBIC resonances. The key structural parameters of the HOP AMS for exciting polarization wavelength stable SP-QBIC resonance were confirmed. This study provides a theoretical foundation for designing and fabricating metasurfaces that support resonance stable and polarization wavelength stable QBIC resonances. Full article

Background/Objectives: Accurate intraoperative tumour localisation remains challenging in minimally invasive colorectal surgery because tactile palpation is lost and conventional markers can migrate or provide imprecise localisation. Building on a preceding tri-frequency study that identified 13.56 MHz as the preferred RFID band for the intended application, this work develops a shaft-compatible NFC antenna–reader platform and evaluates its electromagnetic behaviour from bench-top reference media to five-layer tissue-equivalent phantoms. Methods: A Ø3 × 25 mm Fair-Rite Material 67 ferrite-rod antenna was designed from material and geometric parameters using finite-rod demagnetisation, inductance, resonance, and field calculations, followed by FEM cross-validation and experimental characterisation. The primary dataset comprised 480 detection distance measurements (2 media × 4 tag angles × 30 repetitions × 2 encapsulation variants). Phantom testing added 1440 measurements at 22 °C and 600 measurements at 37 °C across three fabrication batches, with the 37 °C non-coaxial subset limited to one batch. Results: The fabricated antenna measured 16.9 µH versus a 17.4 µH analytical estimate (−2.9%), with loaded Q = 23. The coaxial detection range was 16.45 ± 0.29 mm in air and 16.26 ± 0.21 mm in saline; angle was the dominant determinant of range (partial η² = 0.989). In the multi-layer phantom, detection was 100% at 0 and 10 mm perirectal fat thickness under coaxial alignment at 22 °C, whereas performance declined markedly with angular misalignment and no detections occurred at fat thicknesses ≥ 20 mm. Across detectable phantom configurations, FEM showed r² = 0.994, RMSE = 0.81 mm, and mean bias +0.70 mm. Bare and resin-overcoated tags showed no statistically detectable range difference. Multi-tag discrimination reached 100% for up to three tags separated by ≥20 mm under coaxial alignment, but deteriorated with angular misalignment. Conclusions: The study demonstrates a physics-informed route from antenna miniaturisation to measured system performance, and defines the present operating envelope under controlled bench and tissue-equivalent phantom conditions. The electromagnetic measurements apply to the antenna–electronics subassembly; integrated-shaft, multi-prototype, multi-operator, ex vivo, and in vivo validation remain necessary before clinical performance can be determined. Full article

The escalating demand for high-frequency acoustic devices in 5G/6G communications imposes stringent requirements on surface acoustic wave (SAW) resonators, including high operating frequency, large electromechanical coupling coefficient $K^2$, and high quality factor Q. However, conventional SAW devices suffer from severe trade-offs among these metrics. This work proposes and theoretically analyzes an embedded-electrode LiNbO₃/SiC heterostructure SAW resonator tailored for high-order modes, with its frequency response evaluated via finite-element modeling. A quasi-three-dimensional periodic model consisting of LiNbO₃/IDT/SiC structure is established, and the effects of LiNbO₃ crystallographic orientation, normalized LiNbO₃ thickness, and embedded-Al-electrode thickness on the resonator performance are then systematically investigated. For the selected design with Euler angle β = 30°, the optimal normalized LiNbO₃ thickness is found to be $h_{\mathrm{LN}}/\mathrm{\lambda }=0.2$. Under this crystal orientation, the optimized normalized embedded-electrode thickness is $h_{\mathrm{I}\mathrm{D}\mathrm{T}}/\mathrm{\lambda }$ = 0.06. The optimized resonator achieves a resonant frequency of f_r = 12.792 GHz, a phase velocity of V = 12,792 m/s, a $K^2$ of 9.16%, and a Q of 1004.4. These investigation results validate the proposed LiNbO₃/IDT/SiC heterostructure as a viable platform for pushing SAW technology into the 10 GHz regime, thereby bridging the gap between acoustic-wave devices and millimeter-wave RF systems for next-generation communications. Full article

In the present study, the potential applications of Cu thin films and Ag/Cu bilayer thin films obtained by the pulsed laser deposition (PLD) technique are investigated in terms of the physicochemical effects resulting from their interaction with an aqueous solution containing Reactive Blue 21 (RB21) dye and sodium bicarbonate (NaHCO₃). The thin-film deposition process was carried out using a Q-switched Nd:YAG laser system operating at a wavelength of λ = 532 nm, with a pulse duration of τ = 10 ns, a repetition rate of ν = 10 Hz, a pulse energy of E = 180 mJ, a laser spot diameter of d = 336 μm, and an angle of incidence of α = 45°. Two types of thin films were prepared: a Cu thin film and an Ag/Cu bilayer thin film. The thermal effects induced by the interaction of the laser beam with the target materials were investigated by numerical simulations performed in COMSOL, allowing the evaluation of melt-phase formation for each material separately and providing a better understanding of the morphology and topography of the deposited thin films. The simulation results were validated through scanning electron microscopy (SEM) observations and surface roughness analyses. The two thin films were subsequently treated with an aqueous solution containing 10 g/L RB21 dye and 10 g/L NaHCO₃. Physicochemical analyses performed after treatment, including scanning electron microscopy (SEM), optical microscopy (OM), profilometry, Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS), X-ray Photoelectron Spectroscopy (XPS) and UV–Vis spectroscopy, revealed significant degradation of the RB21 dye accompanied by corrosion of the thin films, with the corrosion process being more pronounced in the case of the Cu thin film. The obtained results indicate that the method analyzed in this study may represent an alternative approach for the decomposition of recalcitrant organic dyes using thin Cu films, without relying on conventional photocatalytic processes. Equally important are the potential applications of the RB21/NaHCO₃ solution as an etching and patterning medium for thin Cu layers, while the Ag overlayer may provide a protective effect during such processes. These findings may contribute to the development of novel fabrication techniques for optoelectronic components, including solar cells, photovoltaic windows, and other industrial and laboratory applications. Full article

Background/Objectives: Mandibular angle volumization with hyaluronic acid is used to redefine facial contours and improve the aesthetics of the lower third of the face. However, beyond the aesthetic outcomes, it is important to understand the impact of this intervention on the aesthetic perception of subjects undergoing the procedure. This preliminary prospective, non-randomized, uncontrolled clinical trial aimed to evaluate post-treatment aesthetic satisfaction and facial appearance perception in subjects who underwent mandibular angle volumization with hyaluronic acid. Methods: Ten adults (eight women and two men) with a mean age of 34.30 ± 11.20 years participated in the study. Subjects underwent injection of 2 mL of hyaluronic acid per hemiface, following the Medical Codes protocol. Volumetric analysis of the mandibular angle region was performed using the Vectra 3D imaging system. Aesthetic perception and facial self-image were assessed 60 days after the procedure using the Orofacial Esthetic Scale and FACE-Q questionnaires. Results: Volumetric analysis demonstrated descriptively higher values throughout the clinical follow-up on both sides, although no statistically significant differences were observed (p > 0.05). The questionnaires revealed high levels of aesthetic satisfaction and positive perception of facial appearance. On the Orofacial Esthetic Scale, a predominance of high aesthetic satisfaction was observed among subjects. Likewise, FACE-Q results demonstrated high levels of satisfaction related to facial appearance and self-image. Conclusions: Within the limitations of this preliminary secondary analysis, mandibular angle volumization with hyaluronic acid was associated with high post-treatment aesthetic satisfaction and favorable facial appearance perception at the 60-day follow-up. These findings are descriptive and warrant confirmation in larger controlled studies. Full article

Equal-leg angle-steel members are widely used as main load-bearing and bracing members in transmission towers. Under elevated-temperature environments such as mountain fires and forest fires, the elastic modulus and strength of steel degrade significantly, which may reduce the overall stability capacity of compression members and even lead to instability failure. To investigate the stability performance of equal-leg angle-steel members made of Q420 steel at uniform elevated temperatures, a shell-element finite-element model was established in Abaqus by considering temperature-dependent material properties of steel. Parametric analyses were carried out under constant compressional loading and uniform heating for the cases of pinned–pinned, fixed–fixed and eccentric–pinned conditions. The effects of slenderness ratio, stability load ratio, section dimension, and initial imperfection amplitude on the critical temperature were systematically analyzed. The results show that the critical temperature decreases significantly with increasing stability load ratio. The eccentric–pinned condition leads to a higher critical temperature than the other two conditions. The initial geometric imperfection will reduce the fire resistance of members. Based on the critical temperature method, design curves of the critical temperature for three boundary conditions were developed using the finite-element results, which are demonstrated to be more accurate than the existing Chinese and European codes. Full article

Brown algae, such as Dictyota dichotoma, contain fucoidan, whose bioactivity is linked to its molecular characteristics, which are in turn defined by environmental conditions. D. dichotoma fucoidan from the Sea of Cortez in Mexico (DDFSC) has not been previously investigated. This study aimed to extract DDFSC and investigate its chain conformation, microstructure, and antioxidant activity. The extraction yield was 3.6% (w DDFSC/w lyophilized seaweed). Fourier-transform infrared spectroscopy recorded bands characteristic of fucoidan. Fucose represented the main monosaccharide in DDFSC (49.52% w/w). The sulfate content was 3.40% (w/w). Size-exclusion chromatography with multi-angle light scattering determined the molecular weight, intrinsic viscosity, radius of gyration, and hydrodynamic radius as 880 kDa, 260 mL/g, 34 nm, and 32 nm, respectively. The characteristic ratio (C∞) and the persistence length (q) were 4.5 and 1.5 nm, respectively, suggesting a branched random coil conformation. Dynamic light scattering determined polysaccharide diameters of 27.6 and 173.1 nm. Scanning electron microscopy and atomic force microscopy revealed an irregular morphology and aggregates with rough topography, respectively. The IC₅₀ values for ABTS⁺ and DPPH radical scavenging assays were 4.21 and 5.64, respectively. The present study constitutes the first insight into DDFSC characterization and establishes a starting point for the development of sustainable future applications using this polysaccharide. Full article

Background and Objectives: Thoracic dysfunction may contribute to neck pain, restricted mobility, and altered spinal alignment in individuals with forward head posture (FHP). This study compared thoracic flexibility exercise (TFE) with cervical stabilization exercise (CSE) in terms of their effects on pain, range of motion (ROM), spinal alignment, proprioception, and neck-related disability in patients with chronic neck pain and FHP. Materials and Methods: Twenty-four participants were randomly assigned to either the TFE group (n = 12) or the CSE group (n = 12). Both groups performed their assigned intervention once per day, three days per week, for four weeks. The outcome measures included pain intensity, cervical and thoracic ROM, craniovertebral angle (CVA), cranio-rotation angle (CRA), thoracic kyphosis angle (TKA), proprioception, and the Neck Disability Index (NDI). Paired t-tests were used for within-group comparisons, and independent t-tests were used to compare change scores between groups. The Benjamini–Hochberg false discovery rate (FDR) procedure was applied to the between-group comparisons to account for multiple testing. Results: The TFE group showed significant improvements in all outcome measures following the intervention (p < 0.001). The CSE group showed significant improvements in pain, cervical flexion, extension, and right and left rotation, CVA, CRA, proprioception during extension and right and left rotation, and NDI (p < 0.05); however, no significant improvements were observed in thoracic ROM, TKA, or proprioception during flexion (p > 0.05). After FDR correction, between-group comparisons demonstrated significantly greater improvements in the TFE group than in the CSE group across all outcome measures (q < 0.05). Conclusions: TFE may be more effective than CSE in improving pain, ROM, spinal alignment, proprioception, and neck-related disability in patients with neck pain and FHP. Full article

Tip seal leakage in shrouded steam turbines can significantly affect the aerodynamic performance of downstream blade rows. An unsteady three-dimensional numerical model of a 1.5-stage high-pressure steam turbine is established using ANSYS CFX (ANSYS2021) with the SST k–ω turbulence model. Tip seal clearances of 1.0, 1.5, and 1.9 mm are investigated using the Q-criterion and vorticity transport equation to characterize leakage-vortex evolution and its interaction with the mainstream. The results show that increasing tip seal clearance strengthens leakage flow and expands its interaction region. The expansion term exhibits a relatively stronger influence on vorticity variation near the seal teeth, whereas the vortex stretching term plays a significant role in leakage-vortex evolution near the seal inlet, outlet, and cavity. Leakage vortices interact with the rotor wake, intensifying velocity gradients and aerodynamic loss, with pronounced flow distortion near 85% rotor span. The disturbance is further transported to the downstream stator, causing marked variations in flow angle, circumferential velocity, and static pressure in the upper-span region. At 95% and 99% blade heights, pronounced differences in suction-surface static pressure occur within the forward 80% of the chord length. These findings clarify the aerodynamic consequences of tip seal leakage and its downstream effects. Full article

The shear behavior of loess is closely linked to its microstructural evolution, and understanding this relationship is essential for deciphering the mechanisms of loess hazards. In this study, consolidated-drained (CD) triaxial tests were conducted on intact Q₃ Malan loess from the Dongzhi tableland, China, under varying water contents and confining pressures. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) analyses were performed on specimens before and after shearing to quantitatively and qualitatively characterize the changes in pore and particle properties and their connection to shear deformation. The results reveal three failure modes, including shear, homogeneous, and plastic failure. They are governed by the combined effects of microstructural variation and microcrack development, depending on confining pressure and water content. Quantitatively, as water content increases from 9% to 20%, cohesion decreases by 86.8% and peak shear strength reduces by 68.4%, while the internal friction angle decreases only slightly. Water-induced strength deterioration is governed primarily by cohesion loss rather than friction angle reduction. Thus, 20% water content was identified as the critical threshold marking the transition from cohesion-dominated to friction-dominated strength degradation. A critical threshold at approximately 27% water content is identified, beyond which about 70% of mesopore and macropore volumes undergo collapse, after which the strength is almost entirely sustained by interparticle friction. Based on these findings, the water-induced strength decay mechanism is categorized into three stages: rapid cement degradation, friction-dominated transition, and slow attenuation. These macroscopic phenomena are closely linked to the continuous adjustment of the microstructure, manifested by the softening, dispersion, and disintegration of cementations, particle movement and rearrangement, and the reduction and mutual transformation of inter-aggregate pores under loading and wetting. The three-stage mechanism and threshold characteristics of loess strength degradation upon wetting revealed in this study can provide theoretical support for early slope-instability warning in loess irrigation and heavy rainfall regions, as well as engineering reinforcement prioritizing the recovery of cohesion. Full article

Terahertz (THz) fingerprint spectroscopy enables label-free identification of molecular vibrational signatures, but trace biomolecular absorption is too weak to be reliably resolved in free-space measurements. To address this limitation, we propose a four-degree-of-freedom geometrically encoded THz metasurface for broadband multichannel fingerprint sensing. The substrate-free self-supporting aluminum structure incorporates four independently tunable geometric parameters: gap angle θ, outer ring radius R, scaling factor S, and ring width W. By regulating these parameters, multiple resonance-tuning pathways are established, enabling designable multiband spectral coverage over 0.6–1.4 THz and flexible matching with the fingerprint bands of L-hydroxyproline (L-HYP). Numerical simulations show that the metasurface achieves a refractive-index sensitivity of 512.66 GHz/RIU with a linear fitting coefficient of R² = 0.99708 and a mean Q factor of 4.72. For biomolecular fingerprint sensing, the encoded resonances overlap with the L-HYP absorption bands near 0.73 and 1.17 THz, producing AIT-like spectral modulation and envelope-derived attenuation enhancement. Compared with an unstructured analyte reference, the valid 0.73 THz readout gives enhancement factors of 5.76 and 7.09 for the R and S channels, respectively, while the four encoded channels provide enhancement factors of 3.53–4.45 at 1.17 THz. This design provides a compact strategy for broadband multichannel THz fingerprint enhancement, offering a promising route for monitoring collagen-metabolism-related biomarkers and advancing label-free biochemical sensing, fibrosis-related molecular screening, and integrated broadband THz detection. Full article

Deep metal mines commonly contain vertically stacked goafs whose geometry and rock mass properties are incompletely documented. This study evaluates a field-constrained screening framework for high-displacement material scenarios at the Lehong Pb-Zn mine. The framework combines a Latin hypercube sampling (LHS)-FLAC3D response library with static Bayesian inference. Evidence comprised 93 goaf records, 186 Mathews exposed-surface assessments, laboratory constraints, and 40 archived numerical scenarios, whose maximum downward displacement ranged from 4.48 to 31.75 cm. Friction angle φ showed the strongest marginal Pearson correlation with displacement (r = −0.81), followed by cohesion (r = −0.55) and elastic modulus (r = −0.22). At the response library Q75 threshold of 15.04 cm, the Laplace-smoothed probability increased from 0.262 (95% credible interval, 0.142–0.403) across all scenarios to 0.600 (0.352–0.824) under joint cohesion–friction angle degradation. However, the archived design was not an ideal 40-point LHS, and bootstrap resampling retained the scenario ordering in only 45.8–54.8% of replicates. All 93 inventory identifiers matched the Mathews stability table, enabling reproducible site-level triage when Bayesian network results are combined with treatment and stability evidence. The framework is an exploratory screening tool rather than an absolute failure probability model, collapse propagation model, or dynamic early warning system. Full article

Renewable power plants connected to low-system-strength grids are increasingly dominated by inverter-based resources (IBRs). Their point of common coupling (PCC) voltage is therefore shaped not only by reactive-power support but also by active-power ramps, network impedance, short-circuit capacity, and converter limits. Conventional Q-V droop control, fixed power-factor control, Volt/VAR control, and fixed active-power/reactive-power (P/Q) decoupling schemes often absorb active-power excursions into the voltage error, which can drive excessive reactive-power injection during fault clearing, post-fault power recovery, and phase-angle disturbances. Here, an active-power–voltage-coupling-aware reactive-power compensation (APVQ-RC) method is proposed for plant-level voltage control. The method estimates local P-V and Q-V voltage sensitivities online, reconstructs an effective voltage error, and produces a capacity-constrained reactive-power reference through smooth coupling activation. The reduced-order evaluation includes estimator conditioning, excitation screening, sensitivity-estimation error and empirical 95% estimator-error intervals, sensitivity to the smoothing factor and window length, measurement noise, converter capability saturation, and computational timing. Under P-V-coupled transients, APVQ-RC reduces voltage overshoot and reactive-power compensation energy while retaining Q-V-like support during voltage-sag-dominated events. Compared with the best scanned fixed P/Q baseline, it reduces overshoot, reactive-power compensation energy, and reactive-power peak by 42.03%, 60.35%, and 8.90%, respectively; the representative single-step calculation time is 0.0188 ms within a 1 ms control cycle. These results indicate millisecond-scale plant-level feasibility within the reduced model, while electromagnetic-transient, hardware-in-the-loop, and field validation remain necessary before deployment. Full article