Search Results (1,164)

This study evaluates the drying kinetics of banana slices sliced at various infrared powers and measurable values, as well as the spectral and microstructural changes that some physical quality parameters present. Banana slices were dried at 300, 400, and 500 W (894, 1190 and 1410 W/m² infrared radiation intensity) medium wavelength infrared (MWIR). In addition, banana samples were sliced to be 6–8 and 10 mm. The drying processes were terminated when the samples reached approximately 30% moisture level. After drying, banana samples’ quality values, such as color, shrinkage, and water loss were evaluated. FT-NIR (Fourier Transform-Near Infrared) spectroscopy and microstructure measurements were performed. For banana slices dried at different powers with medium-wavelength infrared, the shortest drying time is for 6 mm thick products and can be operated in the range of 33–36 min⁻¹. When the color values were examined, it was determined that the lowest total color changes occurred at 500 W drying power. In shrinkage measurements, samples dried at 500 W power were observed at the highest frosting. In water loss analyses, statistically similar results were obtained at 500 W drying power for various thicknesses. While the microstructural configurations of sliced banana samples were observed to be smoother during drying, samples dried at 300 W power were detected in a tighter form during drying and they were combined more regularly at 500 W power. FT-NIR spectral measurements were again expressed independently of the reflection values due to the wide pore range in high-power infrared drying (500 W). Full article

This study investigates the non-equilibrium radiation characteristics during the high-speed re-entry of a lunar-return-type capsule under rarefied atmospheric conditions. A line-by-line spectral model was developed to compute atomic emission and absorption coefficients for excited nitrogen and oxygen atoms. Coupled with the Direct Simulation Monte Carlo (DSMC) method, the Photon Monte Carlo (PMC) method was employed to solve the radiative energy transport equation. The model was validated against the FIRE II flight experiment at 1631 s and 1634 s, showing improved agreement with experimental heat flux data compared to previous numerical results. A detailed sensitivity analysis was conducted to examine the influence of spectral discretization and the number of emitted photons per computational cell. Results indicate that low spectral resolution can cause non-physical fluctuations in wall heat flux, while increasing the number of photons improves local smoothness. Optimal parameters were identified as 50,000 spectral points and 5000 photons per cell. The model was further applied to a lunar-return-type capsule re-ntering at 90 km and 95 km altitudes. It was found that radiative heating is spatially decoupled from aerodynamic heating and primarily governed by excited species concentration and line-of-sight geometry. At 90 km, radiative heating accounted for over $15.31\%$ of the aerodynamic heating, more than double that at 95 km. These results underscore the necessity of considering radiation effects in the design of thermal protection systems, particularly at high re-entry velocities and large angles of attack. Full article

To model the response of neural networks to electromagnetic radiation in real-world environments, this study proposes a memristive dual-wing fractional-order Hopfield neural network (MDW-FOMHNN) model, utilizing a fractional-order memristor to simulate neuronal responses to electromagnetic radiation, thereby achieving complex chaotic dynamics. Analysis reveals that within specific ranges of the coupling strength, the MDW-FOMHNN lacks equilibrium points and exhibits hidden chaotic attractors. Numerical solutions are obtained using the Adomian Decomposition Method (ADM), and the system’s chaotic behavior is confirmed through Lyapunov exponent spectra, bifurcation diagrams, phase portraits, and time series. The study further demonstrates that the coupling strength and fractional order significantly modulate attractor morphologies, revealing diverse attractor structures and their coexistence. The complexity of the MDW-FOMHNN output sequence is quantified using spectral entropy, highlighting the system’s potential for applications in cryptography and related fields. Based on the polynomial form derived from ADM, a field programmable gate array (FPGA) implementation scheme is developed, and the expected chaotic attractors are successfully generated on an oscilloscope, thereby validating the consistency between theoretical analysis and numerical simulations. Finally, to link theory with practice, a simple and efficient MDW-FOMHNN-based encryption/decryption scheme is presented. Full article

This study presents the first comprehensive investigation establishing the relationship between color consistency and luminous efficacy of radiation (LER) in phosphor-converted light-emitting diodes (LEDs), introducing novel selection criteria for energy-efficient applications. A systematic analysis of LED sources with nominal correlated color temperature (CCT) values of 3000 K and 4000 K across color-rendering index (CRI Ra) thresholds (≥60 and ≥80) was conducted, evaluating spectral power distributions (SPD) and chromaticities relative to 3-step, 5-step color-consistency circles, and 7-step American National Standards Institute (ANSI) quadrangles. Novel findings reveal a previously uncharacterized strong positive correlation between color consistency and luminous efficacy across all analyzed LED sources. LEDs with chromaticities within 3-step color-consistency circles consistently demonstrated superior LER values compared to 5-step boundaries, while sources outside established circles showed significantly inferior energy performance despite meeting nominal CCT requirements. The research establishes that tighter color-consistency tolerances directly correlate with enhanced luminous efficacy, revealing an intrinsic relationship between color quality and energy performance. These breakthrough findings introduce a paradigm shift in LED selection methodology, providing lighting professionals with evidence-based criteria that simultaneously optimize color consistency and energy efficiency, enabling more sustainable lighting solutions through integrated quality–performance assessment. Full article

This study presents a semi-empirical approach to generalizing the acoustic radiation generated by serrated airfoil configurations, based on small-scale aerodynamic/acoustic experiments and functional regression techniques. In the context of passive noise reduction strategies, such as leading-edge and trailing-edge serrations, acoustic measurements are performed in a controlled subsonic wind tunnel environment. Sound pressure level (SPL) spectra and acoustic power metrics are acquired for various geometric configurations and flow conditions. These spectral data are then analyzed using regression-based modeling techniques—linear, quadratic, logarithmic, and exponential forms—to capture the dependence of acoustic emission on key geometric and flow-related variables (e.g., serration amplitude, wavelength, angle of attack), without relying explicitly on predefined nondimensional numbers. The resulting predictive models aim to describe SPL behavior across relevant frequency bands (e.g., broadband or 1/3 octave) and to extrapolate acoustic trends for configurations beyond those tested. The proposed methodology allows for the identification of compact functional relationships between configuration parameters and acoustic output, offering a practical tool for the preliminary design and optimization of low-noise serrated profiles. The findings are intended to support both physical understanding and engineering application, bridging experimental data and parametric acoustic modeling in aerodynamic noise control. Full article

The inversion factor is an important physical parameter for assessing and revealing the performance of semiconductor lasers, providing insights into the carrier-injected band-filling effect and radiation characteristics. In this paper, the carrier inversion factor (P_f) is measured to elucidate the luminescence mechanism of an InGaAs-based well-island composite (WIC) structure, formed by the self-assembly migration of indium atoms and exhibiting excellent spectral properties. P_f is obtained by collecting the amplified photoluminescence (PL) spectra from dual facets of the device, with carrier concentrations ranging from 9.0 × 10¹⁷ to 9.4 × 10¹⁷ cm⁻³. Compared with classical InGaAs/GaAs quantum well structures under the same operating conditions, the inversion level in the WIC structure can be as high as 2.2. Simulation results reveal enhanced quasi-Fermi-level separation and broadened spectral bandwidth. The research is of great significance in the development of new types of quantum-confined lasers with wide spectral output. Full article

This study investigates the underwater transient vibro-acoustic response of double-layered stiffened cylindrical shells through an integrated experimental-numerical approach. Initially, vibration and noise responses under transient impact loads were experimentally characterized in an anechoic water tank, establishing benchmark datasets. Subsequently, based on the theory of transient structural dynamics, a numerical framework was developed by extending the time-domain finite element/boundary element (FEM/BEM) method, enabling comprehensive analysis of the transient vibration and acoustic radiation characteristics of submerged structures. Validation through experimental-simulation comparisons confirmed the method’s accuracy and effectiveness. Key findings reveal broadband features with distinct discrete spectral peaks in both structural vibration and acoustic pressure responses under transient excitation. Systematic parametric investigations demonstrate that: (1) Reducing the load pulse width significantly amplifies vibration acceleration and sound pressure levels, while shifting acoustic energy spectra toward higher frequencies; (2) Loading position alters both vibration patterns and noise radiation characteristics. The established numerical methodology provides theoretical support for transient impact noise prediction and low-noise structural optimization in underwater vehicle design. Full article

The research objectives of engine plume radiation calculation primarily encompass two aspects: (1) addressing the additional heating induced by plume radiation on rocket thermal protection systems and (2) elucidating the variation patterns of spectral radiation intensity for infrared signature identification and tracking. Focusing on the thermal effects of radiation, this study first calculates the radiative properties of high-temperature combustion gases and particles separately. Subsequently, the radiative properties of mixed droplets with alumina caps are computed and analyzed. Building upon this and incorporating empirical formulas for aluminum droplet combustion, the engine’s radiative properties are calculated, accounting for the presence of mixed droplets. Ultimately, an integrated computational method for engine radiative properties (both internal and external flow fields) is established, which considers the non-equilibrium processes during droplet transformation. The radiative property parameters are then embedded into the fluid dynamics software via multidimensional interpolation. The radiation transfer equation is solved using the discrete ordinates method (DOM) to obtain the radiation intensity distribution within the plume flow field. This work provides technical support for investigating the radiative characteristics of solid rocket engine plumes. Full article

Monitoring water quality in narrow tributary bays of large river-type reservoirs is hindered by sparse sampling and cloud-limited imagery. This study develops a Trophic State Index (TSI) inversion for Xiangxi Bay, a major tributary bay of the Three Gorges Reservoir, using Landsat data and a backpropagation (BP) neural network, with hyperparameters tuned via a grid search algorithm (GSA). Environmental drivers such as water temperature, solar radiation, and photosynthetically active radiation were combined with Landsat spectral bands. Eleven sites measured monthly in 2009 yielded 98 samples after preprocessing, and training achieved R² = 0.94. Predictions for 2009 show clear spatiotemporal heterogeneity: those for April and September (TSI = 48–59) exceeded those for July and October (46–56), with mid–lower reaches (52–59) being higher than mid–upper reaches (47–54). Out-of-period predictions for April/June 2019 and August/November 2020 were consistent with seasonal expectations, with higher spring–summer TSIs (2019: 50–57; 2020 August: 45–55) than in November 2020 (37–47). Key limitations include the small sample size, cloud-related data gaps, and sensitivity to evolving reservoir operations. This framework demonstrates a practical route to the satellite-based monitoring and mapping of trophic status in narrow reservoir tributaries. Full article

The intensification of the urban thermal environment has brought attention to urban land surface temperature (ULST). Complex building geometry and manmade material lead to significant thermal radiation directionality (TRD) of the urban canopy, and the TRD effect directly influences the accuracy of ULST retrieval algorithms. Therefore, it is essential to understand and eliminate the TRD effect to achieve high-accuracy ULST. In this context, the hemispherical brightness temperature maximum–minimum discrepancy (BTD) was quantitatively analyzed via different spectral bands, component temperature thresholds, urban geometries, and component temperature differences. Meanwhile, the DART simulations database was used to systematically evaluate 1 single-kernel- and 30 dual-kernel-driven models (KDMs), which were combined from 5 base-shape kernels (RossThick, Vinnikov, uea, RossThin, and LSF) and 6 hotspot kernels (RL, Roujean, Vinnikov, LiSparseR, LiDense, and Chen). Results show that the BTD discrepancy (ΔBTD) can reach up to 0.91 K with different band emissivities, whereas the ΔBTD is over 10 K with different component temperature differences. The building density and ratio between building heights and road widths (H/W) also exhibit their importance over urban regions. In addition, the RossThick–/Vinnikov–Roujean dual-kernel KDMs demonstrate better performance with an overall RMSE of 1.12 K. The RL-series KDMs can describe the hotspot distribution well, but the uea-series KDMs outperform at the solar principal plane (SPP) and cross-solar principal plane (CSPP). Specifically, the performance of all KDMs is sensitive to the H/W and component temperature thresholds, and urban geometry can affect the TRD RMSE with increasing H/W and a depletion of high building density. The quantitative TRD analysis and comparison provide a comprehensive reference for understanding the distribution of thermal radiation, which is also a reliable basis for developing the new TRD model over urban regions. Full article

In the present study, the reflection and transmission of radiation in submicron indium tin oxide (ITO) films deposited on a borosilicate glass substrate are experimentally investigated for a wide spectral range, including ultraviolet, visible, infrared and terahertz regions. Theoretical modeling of the spectra is performed using the transfer matrix method. The interaction of electromagnetic radiation with ITO is considered in the framework of the Drude model. The simulated spectra are in good agreement with the experimental ones. New non-destructive methods for determining the ITO film parameters (sheet resistivity, thickness, electron concentration and mobility) have been developed. They are based on a fitting procedure for reflectivity and/or transmittance spectra. Full article

Ultraviolet radiation (UVR) represents significant risks to both textile durability and human health. Natural dyes are gaining attention as eco-friendly alternatives to synthetic UV-blocking agents, offering aesthetic and functional benefits. This study explores the UV-protective properties of 100% cotton knit fabrics dyed with natural dyes—indigo, weld, and madder—using different mordanting processes, including materials with mordant abilities such as alum, pomegranate peel, and tannin extracted from quebracho. Twenty samples were evaluated, including undyed, individually treated, and combined dye-mordant formulations. UV protection was assessed through spectral transmittance and Ultraviolet Protection Factor (UPF) measurements before and after washing. The results showed that natural dyes significantly improved the UV resistance of cotton fabrics, particularly when combined with products like pomegranate and the tannin–alum mixture. Notably, some samples demonstrated improved UPF and became darker after washing, such as mordant combinations like tannin with alum. These findings suggest that natural dye, when combined with appropriate mordants, offers a sustainable and effective approach to producing UV-protective textiles. This is particularly valuable in children’s clothing, where chemical safety and sun protection are crucial. Future research should investigate the influence of pH on dye stability and UV-blocking performance to optimise formulations for industrial use and long-term functionality. Full article

When vehicles fly at hypersonic speeds, a high-temperature flow field forms and emits intense radiation across some spectral bands. This strong flow field can be seen as a point source and is transmitted to high altitudes through the radiative transfer process. In this study, the corresponding atmospheric profiles were introduced, the databases in high-temperature conditions were established, and the corresponding gas absorption characteristics were further calculated using the line-by-line method. Correspondingly, the radiative transfer processes were calculated by a Monte Carlo model with surface and point sources. The Monte Carlo model is rigorously validated against the VLIDORT model through detailed comparisons. For radiative simulations in the near-space environment, both high-temperature conditions and 3D scenarios are considered. The simulations reveal that the use of high-temperature databases could introduce an error of approximately 3%, and the radiation field exhibits stronger inhomogeneity in the infrared band. Full article

Ultra-short-term PV power prediction (USTPVPP) results provide a basis for the development of intra-day rolling power generation plans. However, due to the feature information and the unpredictability of meteorology, the current ultra-short-term PV power prediction accuracy improvement still faces technical challenges. In this paper, we propose a combined prediction framework that takes into account the reconfiguration of the predictable components of PV stations and the spatiotemporal heterogeneous maps. A circuit singular spectral decomposition (CISSD) intrinsic predictable component extraction method is adopted to obtain specific frequency components in sensitive meteorological variables, a mechanism based on radiation characteristics and PV power trend predictable component extraction and reconstruction is proposed to enhance power predictability, and a spatiotemporal heterogeneous graph neural network (STHGNN) combined with a Non-stationary Transformer (Ns-Transformer) combination architecture to achieve joint prediction for different PV components. The proposed method is applied to a PV power plant in Gansu, China, and the results show that the prediction method based on the proposed combined spatio-temporal heterogeneous graph neural network model combined with the proposed predictable component extraction achieves an average reduction of 6.50% in the RMSE, an average reduction of 2.50% in the MAE, and an average improvement of 11.93% in the R² over the direct prediction method, respectively. Full article

Short-wave-infrared (SWIR) imaging can extend drone operations into fog and rain, yet the optimum spectral strategy remains unclear. We evaluated a drone-borne quantum-dot SWIR camera inside a climate-controlled tunnel that generated calibrated advection fog, radiation fog, and rain. Images were captured with a broadband 400–1700 nm setting and three sub-band filters, each at four lens apertures (f/1.8–5.6). Entropy, structural-similarity index (SSIM), and peak signal-to-noise ratio (PSNR) were computed for every weather–aperture–filter combination. Broadband SWIR consistently outperformed all filtered configurations. The gain stems from higher photon throughput, which outweighs the modest scattering reduction offered by narrowband selection. Under passive illumination, broadband SWIR therefore represents the most robust single-camera choice for unmanned aerial vehicles (UAVs), enhancing situational awareness and flight safety in fog and rain. Full article