Search Results (1,546)

To address the demand for wide-swath, high-resolution short-wave infrared (SWIR) imaging on resource-constrained spaceborne platforms, this study presents the design and on-orbit validation of a compact dual-channel push-broom (line-scanning) imaging system. The system adopts a transmissive optical architecture and a centralized, compact electronic control unit (ECU) configuration. By interleaving and mosaicking sixteen InGaAs linear array detectors, the system achieves an imaging swath of approximately 187 km and a nominal ground sampling distance of about 24 m, while maintaining a total instrument mass of 10.62 kg and a power consumption of approximately 12 W, thereby demonstrating a high level of integration and efficient resource utilization. To address focal plane consistency issues arising from multi-detector mosaicking, a closed-loop leveling method was developed using the modulation transfer function (MTF) as the primary performance metric. Through defocus estimation and quantitative correction of protrusions on a SiC substrate, convergence toward a unified confocal focal plane among multiple detectors was achieved. On-orbit image quality assessment indicates that the full width at half maximum (FWHM) of the line spread function (LSF) for both channels is approximately 1.38 pixels, with favorable signal-to-noise ratio (SNR) performance. These results validate the effectiveness of the proposed focal plane leveling strategy as well as the opto-mechanical-thermal design of the system. The proposed approach provides a practical pathway for the engineering implementation and consistency control of multi-detector mosaicked SWIR payloads under stringent resource constraints. Full article

This paper presents a comparative evaluation of a wave union (WU) time-to-digital converter (TDC) implemented on two Microchip flash-based field-programmable gate arrays (FPGAs): the radiation-tolerant RTG4 (RT4G150-1CG) and the low-power SmartFusion2 (M2S150TS-1FCG1152). Both implementations use an identical VHDL architecture consisting of parallel tapped delay lines (TDLs) each with a WU pattern generator, edge-coded logic encoding, and real-time statistical bin width calibration. Single-shot precision (SSP), defined as the standard deviation of consecutive period measurements derived from calibrated timestamps, is evaluated across four independent input channels. Measurements are performed at five input frequencies (1, 2, 10, 20, and 40 MHz) and six ambient temperatures ranging from 20 °C to 60 °C. At a low input frequency, the RTG4 implementation achieves a mean SSP of 6.97 ps, while IGLOO2 yields 10.12 ps under identical conditions. As the input frequency increases, the SSP of both platforms decreases and converges to approximately 4.5 ps. However, at elevated temperatures, both devices experience observable degradation in SSP. To quantify thermal robustness, a thermal sensitivity coefficient (TSC) is introduced, defined as the rate of SSP variation with temperature. The results show that the same WU TDC core implemented on a space-graded FPGA exhibits improved thermal stability and reduced channel-to-channel variance compared to its equivalent on a commercial platform. Full article

Asymptotic solutions are derived to model the development of atmospheric internal gravity waves generated by latent heating in a two-dimensional configuration involving a vertically-sheared background flow. The mathematical model comprises nonlinear partial differential equations derived from the conservation laws of fluid dynamics under the anelastic approximation where the background density and temperature vary with altitude. The latent heating is represented by a horizontally-periodic but vertically-localized nonhomogeneous forcing term in the energy conservation equation. This generates gravity waves that are considered as perturbations to the background flow and are expressed as perturbation series, with the leading-order contributions being the solutions of linearized equations. Taking into account the nonlinear terms at the next order gives expressions for the effects of the waves on the background mean flow. Due to the vertical shear, there is a critical level where momentum and energy are transferred from the wave modes to the mean flow. The asymptotic solutions show that the wave–mean-flow interaction is nonlocal and occurs over the range of altitudes from the thermal forcing level up the critical level. This is in contrast to what occurs in the case of waves forced by an oscillatory lower boundary, where the interaction is typically localized around the critical level. It is found that the wave drag is negative above the thermal forcing level, making the mean flow velocity more negative, but it becomes positive as the waves approach the critical level, indicating wave absorption in this region. There is wave transmission through the critical level, as well as absorption, and the extent of transmission depends on the depth of the latent heating profile. The mean potential temperature is reduced above the thermal forcing level and enhanced at the critical level, a situation that could ultimately lead to the development of convective instabilities. Full article

Harmonising heterogeneous met-ocean time series to a common temporal resolution is a prerequisite for integrated marine renewable energy assessments. Such datasets often differ in their sampling frequency, statistical distribution, and non-stationarity, complicating joint analysis. This study presents a practical multi-criteria framework for selecting temporal interpolation strategies for met-ocean datasets, explicitly balancing prediction accuracy and computational efficiency. Six environmental variables relevant to offshore renewable energy—wind speed, significant wave height, energy period, peak period, global horizontal irradiance, and upper-ocean thermal gradients—are analysed using ten-year reanalysis datasets for the Madeira Archipelago. Six commonly used deterministic time-domain interpolation methods are evaluated within a unified validation framework combining training–test splits, k-fold cross-validation, and Monte Carlo resampling. Their performances are quantified using the relative root mean square error and computational time, integrated through a composite performance score. The results show that makima interpolation provides the most consistent compromise between accuracy and efficiency for most variables in dense, regularly sampled met-ocean datasets, while spline-based approaches perform better for highly skewed solar irradiance. Preprocessing steps, such as detrending and distribution normalisation, yield only marginal improvements for dense, regularly sampled datasets, and method rankings remain stable under moderate changes in accuracy–speed weightings. Rather than proposing a universal interpolator, this work delivers a reproducible decision-support workflow for temporal resampling of multi-variable met-ocean datasets, supporting early-stage marine renewable energy assessments. Full article

Piezoelectric pressure sensors are commonly used as blast wave pressure sensors in explosion testing. Accurate measurement of blast wave overpressure is of great significance. In explosion testing, piezoelectric pressure sensors exhibit a baseline drift phenomenon. This paper analyzes the mechanism of the baseline drift phenomenon observed in explosion testing through experiments and simulation, identifying the mechanism behind it. From an experimental perspective, it is determined that the thermal effect of light induces the baseline drift phenomenon. Furthermore, modeling and simulation of the piezoelectric pressure sensor using COMSOL 6.2 Multiphysics software confirms that the photothermal effect causes changes in the temperature field within the sensor’s internal structure, which in turn brings the thermal stress. The thermal stress superimposes on the output of piezoelectric pressure sensors. This is the fundamental cause of the baseline drift phenomenon in piezoelectric pressure sensors. This research provides a crucial foundation for understanding the mechanisms by which explosions affect piezoelectric pressure sensors. Full article

As one of the core technologies in modern national defense and security fields, infrared stealth technology aims to realize the controllable regulation of the radiation characteristics of targets in the infrared band. This paper focuses on a novel electrochromic device with a structure of WO₃/nickel mesh/Al³⁺-Zn²⁺gel electrolyte/zinc foil. The structural composition and working mechanism are systematically analyzed, and the infrared stealth regulation performance is emphatically studied. The WO₃ thin film and device structure were characterized by scanning electron microscopy (SEM). The infrared emissivity modulation and optical response properties of the device were measured using an infrared thermal imager and a UV-Vis-NIR spectrophotometer. The prepared WO₃ film exhibits a dense spherical morphology, indicating excellent uniformity and compactness. After 1000 cycles, the areal capacitance of the device remains 83.7% of its initial value, demonstrating good cycling stability. Under the voltage regulation of −0.1 V to 1.1 V, the emissivity ε of the device at the typical mid-wave infrared wavelength of 4.0 μm decreases from 0.89 (−0.1 V) to 0.67 (1.1 V), with an absolute modulation amplitude Δε of 0.22. At the typical long-wave infrared wavelength of 8.7 μm, ε decreases from 0.96 (−0.1 V) to 0.69 (1.1 V), with an absolute modulation amplitude Δε of 0.29. The electrochromic switching times for coloring and bleaching are 10.1 s and 2.44 s, respectively. According to infrared thermal imaging tests, in the temperature range of 30–40 °C, the surface temperature difference ΔT between the colored state and bleached state increases from 4.3 °C to 4.6 °C. The maximum regulation amplitude reaches 4.6 °C at 40 °C. The device achieves efficient regulation of infrared emissivity through the electrochromic effect, providing a new device design strategy for infrared stealth technology. Full article

This study provides a theoretical assessment of the structural, electronic, and thermal properties of MgMH₃ (M = Mn and Ni) compounds using the full-potential linearized augmented plane wave (FP-LAPW) method, with a range of modern functionals. The thermoelectric properties that are surveyed here relate to the power factor, the dimensionless thermoelectric figure of merit, the thermal conductivity, and the electrical conductivity that are associated with these compounds. The study finds that MgNiH₃ has superior thermoelectric properties compared to MgMnH₃. The analysis of the band structure reveals that both materials conduct electricity like metals, as there is no energy gap (0 eV), indicating that the conduction and valence bands overlap. The thermal conductivity was found to be linearly related to an increase in temperature, whereas the electrical conductivity varied with temperature. At elevated temperatures, the maximum power factor values reach 1.45 × 10⁻³ W/(K².m) for MgMnH₃ and 1.96 × 10⁻³ W/(K².m) for MgNiH₃ at 900 K. Upon examination of the electronic states, the contributions to the metallic nature of these hydrides come largely from the Ni and Mn orbitals. This type of prospective information on the potential of MgNiH₃ and MgMnH₃ in industrial applications, especially thermoelectric applications, is a valuable contribution. Understanding their thermal and electronic structure will demonstrate their potential for industry. Full article

To investigate the strength evolution of concrete structures operating in long-term service in humid environments while facing threats such as earthquakes, explosions, and impacts, this study utilized a Hopkinson pressure bar (SHPB) and an MTS testing system to conduct experiments on concrete with four different moisture contents (relative saturation of 0%, 50%, 80%, and 100%) across a strain rate range of approximately 10⁻⁵ to 2 × 10² s⁻¹. Based on these results, a relationship equation was established describing how the strength factor of wet concrete varies with strain rate. The study identified sensitive and non-sensitive regions for the strain rate effect in wet concrete. As the water content increases, the threshold for the sensitive region decreases. Specifically, the inflection strain rate for dried concrete is approximately 32 s⁻¹, whereas for saturated concrete, it drops below 5 s⁻¹. A functional equation describing the variation in the strain rate sensitivity coefficient with water content was derived, showing that the strain rate effect on strength becomes more pronounced as water content increases. The rate-wet coupling effect on concrete compressive strength was analyzed, and zones dominated by the strain rate strengthening effect and the water-weakening effect were identified. The mechanism of strength variation in wet concrete across different strain rate ranges was investigated. The analysis indicates that free water participates in the action processes of each mechanism from low to high strain rates. As the strain rate increases, the mechanisms of pore water interaction and thermal activation undergo a transition. At higher strain rates, the significant increase in the dynamic strength of wet concrete results from the combined and coupled effects of the material’s “true strain rate effect” and the stress wave effect in wet concrete, which are driven by the mutual coupling of pore water, thermal activation, and viscous drag mechanisms. This paper aims to provide a reference for the in-depth understanding of the strength evolution and control of hydraulic concrete structures. Full article

With the development of deep geothermal resources, including hot dry rock, the issues of low rock-breaking efficiency and wellbore instability encountered when drilling into high-temperature granite reservoirs have become increasingly prominent. The study aims to elucidate the physical degradation and fracture failure mechanisms of granite exposed to high temperatures and thermal shock. The mineral composition and microstructure of granite were analyzed by X-ray diffraction (XRD) combined with field emission scanning electron microscopy (FE-SEM). Systematic experiments were conducted to investigate the thermal damage mechanisms and mechanical properties of thermal-treated (25 °C to 600 °C) granite under different cooling conditions (natural cooling, water cooling, LN₂ cooling). The experimental results show that the physical parameters of granite exhibit significant path dependence on temperature and cooling rate. When the temperature exceeds 400 °C, the rock undergoes pronounced nonlinear volumetric expansion and a sharp increase in porosity, with P-wave velocity decaying exponentially as the temperature rises. Mechanical tests reveal that high temperature considerably weakens the rock tensile strength. For granite at 600 °C, the maximum reduction in strength reaches 80.79%, and faster cooling leads to greater strength degradation. Additionally, 3D morphology analysis indicates that the section roughness of granite increases exponentially with temperature, where the arithmetic mean height S_a more comprehensively reflects the overall characteristics of surface morphology and demonstrates the strongest ability for characterizing strength. These findings provide a theoretical basis for the efficient volumetric fracturing and rapid drilling technologies applicable to hot dry rock. Full article

Botulinum toxin type A (BoNT/A) injection into the bladder wall is a milestone in the treatment of urinary incontinence in patients with neurogenic detrusor overactivity (NDOi) or overactive bladder syndrome (OABi) who are refractory to or unable to tolerate oral or transdermal therapies. However, the efficacy of BoNT/A is hampered by the low long-term adherence of patients to a treatment that requires repeated bladder injections under cystoscopy control. The discontinuation is particularly evident among incontinent patients with spontaneous voluntary voiding, regardless of whether the cause is NDOi or OABi, although clearly more marked among the latter group. In addition to the bother and pain associated with repeated cystoscopies, these patients show low tolerance to the high incidence of urinary tract infections (UTIs) and transient urinary retention, the two most common adverse events. Fewer injection points may render treatments less painful, apparently without reducing efficacy, but will not avoid the need for repeated cystoscopies, and no studies have demonstrated that such modification increases adherence. Eventually, accessing the bladder wall for BoNT/A administration via a transabdominal approach, under real-time ultrasound guidance, may overcome trans-urethral limitations, but the technique’s reproducibility remains unknown. An intensive investigation is ongoing to identify aids that facilitate the passage of the large, fragile BoNT/A molecule across the urothelium to reach the bladder nerves without injections. Electromotive Drug Administration (EMDA) of BoNT/A demonstrated efficacy and safety over a 6-year follow-up in NDOi patients at a single center, but the results were not reproduced at other institutions. The application of shock waves to the bladder using shock waves generated by Extracorporeal Shock Wave Lithotripsy (ESWL) machines to tear the urothelium and facilitate the passage of BoNT/A instilled in the bladder is ingenious, but the experience is very limited. Dimethyl sulfoxide, liposomes, and thermal-reversal hydrogel to deliver the toxin failed in pilot trials. BoNT/A in nano-formulations has high heat stability, resistance to pH changes, and to enzymatic degradation. Extended efficacy in dermal and intramuscular pilot applications is promising but needs to be replicated in the bladder. Full article

Human respiratory syncytial virus (RSV) is the predominant etiological agent responsible for lower respiratory tract infections in young children. Recurrent infections throughout an individual’s lifespan can lead to significant morbidity, particularly in the elderly and in adults, influencing the trends of hospitalization rates. Consequently, it is imperative to develop technologies that can sanitize environments from this pathogen while being compatible with human presence. Structure Resonant Energy Transfer (SRET) is the scientific principle underlying a sanitization technology that has demonstrated efficacy against several enveloped viruses, including SARS-CoV-2 and Influenza A viruses. SRET employs specific frequencies of electromagnetic waves to effectively disrupt the structural integrity of viral envelopes through dipole coupling. This disruption leads to the inactivation of the virus, rendering it non-infectious. The objective of this study is to analyse the effect of a specific SRET sanitization method on RSV. The sanitization test was conducted in aerosol form within a BSL-3 laboratory, exploring the frequency band from 8 to 16 GHz. An optimal sub-band was identified, giving an inactivation efficiency up to 99.5%. In conclusion, it has been demonstrated that the microwave non-thermal sanitization method is effective against RSV. These results confirm its potential as a viable approach for environmental decontamination. Full article

Polydimethylsiloxane (PDMS) films doped with graphene nanoplatelets (GNP) with an embossed surface-relief grating were investigated as photothermal actuated sensors. The films were initially characterized using controlled environmental heating where the wavelength of a diffracted white-light probe beam measured at a fixed angle increased monotonically with temperature due to thermal expansion of the grating. An asymmetric double sigmoidal function tracked the shift in peak diffraction wavelength. The observed thermal response is consistent with the thermal expansion of a freestanding PDMS composite film. When a continuous-wave (CW) laser was incident on the film, intensity-dependent photothermal expansion caused a transient deformation in the grating. The photomechanical behavior of the grating, tracked by the diffracted probe beam with a miniature spectrometer, was then shown to act as a laser power meter. These results demonstrate that photomechanical materials can be used as add-ons to existing optical spectroscopy devices for power-sensing applications. Full article

The present study examines the regulatory effects of laser heating parameters (power, position, and spot radius) on hydrothermal wave instability, heat and mass transfer, and interfacial deformation in bilayer thermocapillary systems under normal gravity. It provides theoretical support for the efficient utilization of energy and the optimization of industrial thermal systems, meeting the demands of sustainable development. The results show that increasing laser power induces asymmetric flow bifurcation nears the laser heating point, enhancing hydrothermal waves in the left region while suppressing them in the right region, with oscillation periods decreasing monotonically and amplitudes showing non-monotonic variation. Laser heating position alters convection intensity distribution, in which the convection in the hot zone is weakened as the laser point nears the cold end, while the convection in the cold zone is strengthened as the laser point nears the hot end. Reducing spot radius significantly decreases temperature gradients near the interfacial heat source, while attenuating horizontal velocity amplitude and increasing oscillation period, effectively suppressing oscillatory thermocapillary convection. This study demonstrates that precise control of laser heating parameters can effectively suppress thermocapillary instability and optimize heat transfer without introducing additional mechanical disturbances. It provides a theoretical basis for efficient, low-energy, non-contact thermal flow control technologies. Full article

To advance our understanding of atmospheric processes and climate dynamics, improved knowledge of outgoing long-wave radiation (OLR) spectral emission is essential. The FORUM mission, selected for the ninth cycle of the European Space Agency’s Earth Explorer programme, is specifically designed to address the long-standing observational gap in the far-infrared (FIR) spectral region. When combined with measurements from the IASI-NG instrument, FORUM will provide complete spectral coverage of Earth’s OLR emission (spanning 100 to 2760 cm⁻¹ wavenumber, or 3.62 to 100 μm wavelength), thereby enabling robust climate model validation and enhanced understanding of climate change processes. While IASI-NG’s primary mission is to support numerical weather prediction, FORUM is designed to measure key climate variables, which also enable the retrieval of atmospheric parameters in the troposphere and lower stratosphere. In this study, we assess the information content of FORUM and IASI-NG measurements for atmospheric profiling through a simulation-based approach. Synthetic retrieval products are generated using a linearized formulation of the retrieval transfer function, allowing an efficient and physically consistent evaluation of the sensitivity of the two instruments to atmospheric temperature and water vapor profiles. The analysis reveals a non-negligible sensitivity of FORUM to atmospheric temperature extending into the stratosphere, resulting in significant information content at altitudes higher than previously reported. This finding highlights the potential of far-infrared observations to contribute to atmospheric temperature profiling beyond the lower troposphere. The complementary capabilities of FORUM and IASI-NG suggest that their combined use can enhance the characterization of the atmospheric thermal structure. These results represent a first step toward evaluating the potential role of FORUM Level-2 products in future numerical weather prediction applications. Full article

Non-destructive and destructive test methods are applied to wood to characterize this heterogeneous natural material. There have been multiple studies to characterize and investigate the change after the treatment (impregnation, thermal modification, etc.). In terms of thermal modification, there have been few studies on thermo–vacuum treatment, which is performed in a continuous vacuum atmosphere. With this method, the objective was to attempt to reduce the strength decrease after the thermal treatment. The aim of this study was to estimate the flexural properties of thermo–vacuum-treated Scots pine wood with destructive and acoustic-based non-destructive test methods. Wood was treated at 180 °C and 360 mm Hg. Both treated and untreated samples were cut into small specimens to ensure they were free of defects and were tested with acoustic-based non-destructive (longitudinal vibration and stress wave) and static bending test methods. The results show a decrease in equilibrium moisture content, demonstrating the efficiency of the treatment. When the results were compared with destructive test results, higher correlations (R² > 0.858) were found when estimating the modulus of elasticity (MOE) for both the untreated and treated wood, while lower correlations (R² < 0.440) were found for the modulus of rupture (MOR). When an additional equation was developed, stronger correlations (R² > 0.8986) were obtained between the non-destructive and destructive test results. Full article