Search Results (240)

To break through the bottleneck in the mapping of the mechanoluminescent (ML) intensity field to the strain field, a quantification method for full-field strain measurement based on pixel-level data fusion is proposed, integrating ML imaging with digital image correlation (DIC) to achieve precise reconstruction of the strain field. Experiments are conducted using aluminum alloy specimens coated with ML film sensor on their surfaces. During the tensile process, ML images of the films and speckle images of the specimen backsides are simultaneously acquired. Combined with DIC technology, high-precision full-field strain distributions are obtained. Through spatial registration and region matching algorithms, a quantitative calibration model between ML intensity and DIC strain is established. The research results indicate that the ML intensity and DIC strain exhibit a significant linear correlation (R² = 0.92). To verify the universality of the model, aluminum alloy notched specimen tests show that the reconstructed strain field is in good agreement with the DIC and finite element analysis results, with an average relative error of 0.23%. This method enables full-field, non-contact conversion of ML signals into strain distributions with high spatial resolution, providing a quantitative basis for studying ML response mechanisms under complex loading. Full article

The research investigated the potential of five novel additively manufactured (AM) fiber-reinforced thermoplastic composite (FRTPC) configurations as alternatives for ablative thermal protection system (TPS) applications. The thermal stability and ablative behavior of ten samples developed via fused deposition modeling (FDM) three-dimensional (3D) printing out of fire-retardant thermoplastics were investigated using an in-house oxyacetylene torch bench. All samples featured an innovative internal thermal management architecture with three air chambers. Furthermore, the enhancement of thermal benefits was achieved through several approaches: ceramic coating, mechanical hybridization, or continuous fiber reinforcement. For each configuration, two samples were exposed to flame at 1450 ± 50 °C for 30 s and 60 s, respectively, with the front surface subjected to direct exposure at a distance of 100 mm during the ablation tests. Internal temperatures recorded at two back-side contact points remained below 50 °C, well under the 180 °C maximum allowable back-face temperature for TPS during testing. Continuous reinforced configurations 4 and 5 displayed higher thermal stability the lowest values in terms of thickness, mass loss, and recession rates. Both configurations showed half of the weight losses measured for the other tested configurations, ranging from approximately 5% (30 s) to 10–12% (60 s), confirming the trend observed in the thickness loss measurements. However, continuous glass-reinforced configuration 5 exhibited the lowest weight loss values for both exposure durations, benefiting from its non-combustible nature, low thermal conductivity, and high abrasion resistance intrinsic characteristics. In particular, the Al₂O₃ surface coated configuration 1 showed a mass loss comparable to reinforced configurations, indicating that an enhanced surface coat adhesion could provide a potential benefit. A key outcome of the study was the synergistic effect of the novel air chamber architecture, which reduces thermal conductivity by forming small internal air pockets, combined with the continuous front-wall fiber reinforcement functioning as a thermal and abrasion barrier. This remains a central focus for future research and optimization. Full article

This study focused on the thermal stability and ablative behavior assessment of five newly developed composite TPS configurations. All ten test samples were 3D printed via FDM using various fire-retardant thermoplastic materials, with and without reinforcement. Eight samples integrated a new thermal management internal air chamber conceptualized architecture. A prompt feasible approach for the flame resistance preliminary assessment of ablative TPS samples was developed, using an in-house oxy-acetylene torch test bench. Experimental OTB ablation tests involved exposing the front surface samples to direct flame at 1450 ± 50 °C at 100 mm distance. For each configuration, two samples were tested: one subjected to 30 s of flame exposure and the other to 60 s. During testing, internal temperatures were measured at two backside sample contact points. Recorded temperatures remained below 46 °C, significantly under the maximum allowable back face temperature of 180 °C set for TPSs. The highest mass losses were measured for PC and PETG FR materials, achieving around 19% (30 s) and, respectively, 36% (60 s), while the reinforced configurations showed overall only a third of this reduction. The study’s major outcomes were the internal air chamber concept validation and identifying two reinforced configurations as strong candidates for the further development of 3D-printed ablative TPSs. Full article

Bifacial photovoltaic panels are preferred over monofacial panels due to the ability of their back surfaces to absorb radiation and generate electricity. However, optimizing the rear-side energy contribution remains a critical area of research. This study systematically investigates how four key parameters (albedo, tilt angle, panel height, and mounting configuration) affect rear-side energy generation and overall panel efficiency. In the first scenario, the impact of surface reflectivity was evaluated. High-reflectivity materials such as aluminum (21.2%) and fresh snow (20.5%) significantly increased rear-side energy yield. The second scenario examined tilt angle, showing that increasing the tilt up to 50° enhanced back-side generation, reaching a gain of 5.5%. The third scenario focused on the effect of panel height, revealing a linear relationship with energy generation. The fourth assessed orientation, comparing horizontal and vertical installations. Horizontal mounting provided a higher rear-side energy yield (4.5%) due to increased exposure to ground-reflected radiation. The findings of this study provide important information for the optimization of bifacial photovoltaic panels and the information will provide guidance for easier and more efficient installation of solar power plants. Full article

To accommodate the extreme thermodynamic effects and erosion damage in throttling equipment for ultra-high-pressure natural gas wells (175 MPa), a coupled multiphase flow erosion numerical model for nozzles was established. This model incorporates a real gas compressibility factor correction and is based on the renormalized k-ε RNG (Renormalization Group k-epsilon model, a turbulence model that simulates the effects of vortices and rotation in the mean flow by modifying turbulent viscosity) turbulence model and the Discrete Phase Model (DPM, a multiphase flow model based on the Eulerian–Lagrangian framework). The study revealed that the nozzle flow characteristics follow an equal-percentage nonlinear regulation pattern. Choked flow occurs at the throttling orifice throat due to supersonic velocity (Ma ≈ 3.5), resulting in a mass flow rate governed solely by the upstream total pressure. The Joule–Thomson effect induces a drastic temperature drop of 273 K. The outlet temperature drops below the critical temperature for methane hydrate phase transition, thereby presenting a substantial risk of hydrate formation and ice blockage in the downstream outlet segment. Erosion analysis indicates that particles accumulate in the 180° backside region of the cage sleeve under the influence of secondary flow. At a 30% opening, micro-jet impact causes the maximum erosion rate to surge to 3.47 kg/(m²·s), while a minimum erosion rate is observed at a 50% opening. Across all opening levels, the maximum erosion rate consistently concentrates on the oblique section of the plunger front. Results demonstrate that removing the front chamfer of the plunger effectively improves the internal erosion profile. These findings provide a theoretical basis for the reliability design and risk prevention of surface equipment in deep ultra-high-pressure gas wells. Full article

This work presents the use of a novel impedance coupling technique and electrical length increase by using stub loading placed from the radiator to the ground plane. This method is applied to the design of a small four-element ultrawideband (UWB) MIMO antenna arranged in axial symmetry to achieve a compact array size while obtaining a bandwidth starting from a very low cutoff frequency compared to a conventional radiator operating at the same frequency. The four-element MIMO antenna, with an operational bandwidth of 1.9 GHz to 30 GHz, is based on a wideband monopole with a semicircular geometry, fed by a coplanar structure and an L-shaped half-ground plane section. To increase the electrical length of the structure and achieve a compact antenna design, reactive stub loading is introduced, placing it on the backside of the substrate, located orthogonally between the radiator and the L-shaped ground plane, obtaining a small-sized configuration. The axial symmetry is employed to increase the antennas’ isolation by taking advantage of the orthogonal positioning and making the radiated fields have a low correlation. The antenna array footprint measures 48 mm × 48 mm, corresponding to 0.3λ₀ × 0.3λ₀ at the lower cutoff frequency. The array exhibits a low envelope correlation coefficient (ECC) of around 0.033 at 2 GHz, and less than 0.001 at the rest of the bandwidth; a diversity gain (DG) of approximately 10; a stable total active reflection coefficient (TARC) below −10 dB; interport isolation between 20 and 40 dB; and an average gain of 2.8 dBi. Full article

Shoulder-assisted heating friction plug welding (SAH-FPW) experiments were conducted to repair keyhole-like volumetric defects in 6082-T6 aluminum alloy, employing a novel concave backing hole technique on a flat backing plate. This approach yielded well-formed plug welded joints without significant macroscopic defects. Notably, the joints exhibited no thinning on the top surface while forming a reinforcing boss structure within the concave backing hole on the backside, resulting in a slight increase in the overall load-bearing thickness. The introduction of the concave backing hole led to distinct microstructural zones compared to joints welded without it. The resulting joint microstructure comprised five regions: the nugget zone, a recrystallized zone, a shoulder-affected zone, the thermo-mechanically affected zone, and the heat-affected zone. Significantly, this process eliminated the poorly consolidated ‘filling zone’ often associated with conventional plug repairs. The microhardness across the joints was generally slightly higher than that of the base metal (BM), with the concave backing hole technique having minimal influence on overall hardness values or their distribution. However, under identical welding parameters, joints produced using the concave backing hole consistently demonstrated higher tensile strength than those without. The joints displayed pronounced ductile fracture characteristics. A maximum ultimate tensile strength of 278.10 MPa, equivalent to 89.71% of the BM strength, was achieved with an elongation at fracture of 9.02%. Analysis of the grain structure revealed that adjacent grain misorientation angle distributions deviated from a random distribution, indicating dynamic recrystallization. The nugget zone (NZ) possessed a higher fraction of high-angle grain boundaries (HAGBs) compared to the RZ and TMAZ. These findings indicate that during the SAH-FPW process, the use of a concave backing hole ultimately enhances structural integrity and mechanical performance. Full article

This paper presents the design and performance analysis of a compact wireless power transfer (WPT) system operating at 1.6 GHz. The transmitter (Tx) structure consists of a circular slot and a circular radiating element, excited from the backside of the substrate, while the receiver (Rx) comprises a slotted patch antenna miniaturized using two vertical vias. The initial power transfer efficiency (PTE), represented by the transmission coefficient $S_{21}$, was measured to be −31 dB with a 25 mm separation between Tx and Rx. To enhance the efficiency of the system, a dielectric matching media (MM) was introduced between the transmitter and receiver. Through the implementation of the MM, the PTE improved significantly, with $S_{21}$ increasing to −24 dB. A parametric study was conducted by varying the thickness of the MM from 1 mm to 10 mm and the relative permittivity (${\epsilon }_r$) from 5 to 30. The results demonstrate that both the thickness and dielectric constant of the MM play a crucial role in improving the coupling and overall efficiency of the WPT system. The optimal configuration was achieved with a matching media thickness of 10 mm and a relative permittivity of 25, which yielded the best improvement in transmission performance. This work offers a practical approach to enhance near-field WPT efficiency using simple matching structures and is particularly relevant for compact and low-profile energy transfer applications. Full article

Given the exceptional capabilities of femtosecond laser processing in achieving high-precision ablation for air-film cooling hole fabrication on turbine blades, it is imperative to develop an advanced monitoring methodology that enables real-time feedback control to automatically terminate the laser upon complete penetration detection, thereby effectively preventing backside damage. To tackle this issue, a spectrum-domain coherent imaging technique has been developed. This innovative approach adapts the fundamental principle of fiber-based Michelson interferometry by integrating the air-film hole into a sample arm configuration. A broadband super-luminescent diode with a 830 nm central wavelength and a 26 nm spectral bandwidth serves as the coherence-optimized illumination source. An optimal normalized reflectivity of 0.2 is established to maintain stable interference fringe visibility throughout the drilling process. The system achieves a depth resolution of 11.7 μm through Fourier transform analysis of dynamic interference patterns. With customized optical path design specifically engineered for through-hole-drilling applications, the technique demonstrates exceptional sensitivity, maintaining detection capability even under ultralow reflectivity conditions (0.001%) at the hole bottom. Plasma generation during laser processing is investigated, with plasma density measurements providing optical thickness data for real-time compensation of depth measurement deviations. The demonstrated system represents an advancement in non-destructive in-process monitoring for high-precision laser machining applications. Full article

Scattered light makes up a significant amount of recorded intensities during tomographic imaging, thereby leading to severe misinterpretation and artifacts in the reconstructed volume images. Correcting artificial intensities that stem from scattered light, therefore, is of primary interest and demands quantitative measurements. While numerous methods have been developed to reduce X-ray scattering artifacts, fewer methods deal with optical scattering. In this study, a measurement method for determining optical scattering in scintillators is presented with the aim of further developing correction algorithms. A theoretical model based on internal multiple reflections was developed for this purpose. This model assumes an additive exponential kernel with a certain scattering length to the system’s point spread function. This assumption was confirmed, and the scatter length was estimated from three new different kinds of experiments (hgap, rect, and LSF) on the BM18 beamline of the European synchrotron. The experiments further revealed significant differences in scattering proportion and length when different coatings are applied to the front and back faces of crystalline LuAG scintillators. Anti-reflective coatings on the backside show an effect of reducing the scattering magnitude while reflective coatings on the front side increase the proportion of the unscattered signal and, thus, show proportionally less scattering than black coating or no front coating. In particular, roughened black coating is found to worsen optical scattering. In summary, our results indicate that a combination of reflective (front) and anti-reflective (back) coatings yields the least optical scattering and, hence, the best image quality. Full article

Conventional ultraviolet microplasma sources typically lack a back-reflection structure, resulting in radiative power loss from the backside. To enhance the emission efficiency of ultraviolet microplasma devices around 220 nm, we propose a multilayer reflective coating composed of alternating high- and low-refractive-index layers of Al₂O₃ and SiO₂, within a V-shaped groove. Key structural parameters, including the number of alternating film layer pairs, groove width, and light source position, are investigated to show their effects on ultraviolet reflection characteristics. The results show that reducing the groove width greatly enhances light reflection. When the groove width is 6.5 μm, the device exhibits a reflection efficiency of 47.82% and power enhancement of 91.66%, representing improvements of 2.5-fold and 4.2-fold, respectively, compared to non-optimized cases. Device performance is also influenced by the offset of the light source, which is more sensitive along the horizontal direction. This study provides a practical solution for developing high-efficiency ultraviolet emission devices. Full article

In deep foundation pit engineering, the rational arrangement of internal struts plays a crucial role in controlling diaphragm wall displacement and minimizing environmental impacts. This study investigates the effects of servo steel struts through model tests, analyzing diaphragm wall displacement, bending moment, surface settlement, and surrounding soil pressure during both excavation and active servo control phases. The results show that installing servo struts near the pit bottom significantly improves deformation control, whereas strut placement in shallow zones more effectively mitigates surface settlement. The servo system dynamically adjusts strut displacements, thereby inducing internal force redistribution in the diaphragm wall and modifying the stress field in surrounding soils. This mechanism leads to an increase in positive bending moments on the wall’s backside, which may necessitate the localized reinforcement of the diaphragm wall at servo strut connections to ensure structural integrity. The lateral wall and surrounding soil pressure exhibit further increase, effectively compensating for the pressure loss induced by excavation unloading. Notably, the influence on soil pressure demonstrates a dissipating trend with an increasing distance from the excavation. Full article

Snowboard Big Air (SBA), recognized as an Olympic discipline since 2018, emphasizes maneuver difficulty as a key scoring criterion, requiring athletes to integrate technical skill with adaptive responses to dynamic environments in order to perform complex aerial rotations. The takeoff phase is critical, determining both flight trajectory and rotational performance through coordinated lower limb extension and upper body movements. Despite advances in motion analysis technology, quantitative assessment of key takeoff parameters remains limited. This study investigates parameters related to performance, joint kinematics, and rotational kinetics during the SBA takeoff phase to identify key factors for success and provide practical guidance to athletes and coaches. Eleven athletes from the Chinese national snowboard team performed multiple backside tricks (720°, 1080°, 1440°, and 1800°) at an outdoor dry slope with airbag landings. Three-dimensional motion capture with synchronized cameras was used to collect data on performance, joint motion, and rotational kinetics during takeoff. The results showed significant increases in most measured metrics with rising trick difficulty from 720° to 1800°. The findings reveal that elite SBA athletes optimize performance in high-difficulty maneuvers by increasing the moment of inertia, maximizing propulsion, and refining joint kinematics to enhance rotational energy and speed. These results suggest that training should emphasize lower limb power, core and shoulder strength, flexibility, and coordination to maximize performance in advanced maneuvers. Full article

Acoustic energy penetrates into the Si substrate at cavity boundaries. Due to this, the air cavity-based bulk acoustic resonators experience higher harmonic mode, parasitic resonance, and spurious mode. To overcome these effects and enhance the performance parameters, a backside air cavity is fabricated using the deep reactive ion etching (DRIE) method. The DRIE method helps to achieve the optimized active area of the resonator. SiO₂ film on a silicon substrate as the support layer and ZnO as the piezoelectric (PZE) film are used for the resonator. The crystal growth and surface morphology of ZnO film were investigated with X-ray diffraction, scanning electron microscopy, and atomic force microscopy. FBAR is modeled in a 1-D modified Butterworth–Van Dyke (mBVD) equivalent circuit. As RF measurement results, we successfully demonstrated a FBAR with optimized active area of 320 × 320 μm², center frequency of 1.261 GHz, having a quality factor of 583.8. Overall, this suppression of higher harmonic mode shows the great potential for improving the selectivity of the sensor and also in RF filter design applications. This integration of DRIE-based cavity formation with ZnO-based FBAR architecture not only enables compact design but also effectively suppresses spurious and higher-order modes, which demonstrates a performance-enhancing fabrication strategy not fully explored in the current literature. Full article

This study investigated the thermal performance of reduced super intumescent (RSI) coating, focusing on the correlation between porosity evolution and thermal conductivity under elevated temperature conditions. Porosity development was quantified using scanning electron microscopy (SEM) combined with MATLAB-based image analysis, achieving a maximum porosity of 62% after 60 min of exposure. Thermal degradation was characterized using thermogravimetric analysis (TGA), which recorded a mass loss of 35% between 250 °C and 400 °C, capturing the decomposition kinetics and correlating degradation stages with char formation. Fire protection efficiency was evaluated by employing heat flow meter tests (thermal conductivity reduced from 0.15 W/mK to 0.05 W/mK), methane torch experiments (backside temperature increase delayed by up to 50% compared to uncoated steel), and COMSOL-based heat transfer simulations. The results revealed that the RSI coating’s thermal conductivity decreased as its porosity increased, enhancing its insulation effectiveness. Additionally, the formation of a thermally stable char layer at 400 °C significantly reduced heat transfer to the metal substrate by 66%. These findings support the optimization of bio-derived fire-retardant coatings for passive fire protection applications. Full article