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This study introduces a new machine learning-based algorithm for the retrieving significant wave height (SWH) using synthetic aperture radar (SAR) images. This algorithm is based on the azimuthal cut-off wavelength and was developed in quad-polarized stripmap (QPS) mode in coastal waters. The collected images are collocated with a wave simulation from the numeric model, called WAVEWATCH-III (WW3), and the current speed from the HYbrid Coordinate Ocean Model (HYCOM). The sea surface wind is retrieved from the image at the vertical–vertical polarization channel, using the geophysical model function (GMF) CSARMOD-GF. The results of the algorithm were validated against the measurements obtained from the Haiyang-2B (HY-2B) scatterometer, yielding a root mean squared error (RMSE) of 1.99 m/s with a 0.82 correlation (COR) and 0.27 scatter index of wind speed. It was found that the SWH depends on the wind speed and azimuthal cut-off wavelength. However, the current speed has less of an influence on azimuthal cut-off wavelength. Following this rationale, four widely known machine learning methods were employed that take the SAR-derived azimuthal cut-off wavelength, wind speed, and radar incidence angle as inputs and then output the SWH. The validation result shows that the SAR-derived SWH by eXtreme Gradient Boosting (XGBoost) against the HY-2B altimeter products has a 0.34 m RMSE with a 0.97 COR and a 0.07 bias, which is better than the results obtained using an existing algorithm (i.e., a 1.10 m RMSE with a 0.77 COR and a 0.44 bias) and the other three machine learning methods (i.e., a >0.58 m RMSE with a <0.95 COR), i.e., convolutional neural networks (CNNs), Support Vector Regression (SVR) and the ridge regression model (RR). As a result, XGBoost is a highly efficient approach for GF-3 wave retrieval at the regular sea state.

Sentinel-1 synthetic aperture radar (SAR) is one of the most advanced open-access satellite systems available, benefitting from its capability for earth observation under all-weather conditions. In this study, more than 280 Sentinel-1 SAR images are used to derive significant wave heights (Hs) of the sea surface using a polarization-enhanced methodology. Two study areas are selected: one is located near Hawai’i in a deep water region, and the other is in transitional water off the U.S. west coast, where the U.S. National Oceanic and Atmospheric Administration (NOAA) buoy data are available for validations. The enhanced Hs retrieval methodology utilizes dual-polarization SAR image data with strong non-Bragg radar backscattering, resulting in a better estimate of the cut-off wavelength than from those using single-polarization SAR data. The new method to derive Hs is applied to SAR images from 2017 taken from both deep water (near Hawai’i) and coastal water locations (off the U.S. West coast). The assessments of the retrieved Hs from SAR images suggest that the dual-polarization methodology can reduce the estimated Hs RMSE by 24.6% as compared to a single-polarization approach. Long-term reliability of the SAR image-derived Hs products based on the new methodology is also consolidated by large amount of in-situ buoy observations for both the coastal and deep waters.

The series of the glasses with general formula (40-x)Li2O:30B2O3:30Bi2O3:xV2O5, with x = 0, 0.5, 1.0, 1.5 and 2.0 mol% was prepared using conventional quenching technique. The glass transition temperature Tg for these samples were determined from Differential Thermal Analysis. The glass transition temperature increases beyond 0.5 mol%. It was found that the glasses under study consist of randomly connected BO3 & BO4 structural units. The density and molar volume of glasses were found to depend on V2O5 content. Initially the density increases, molar volume and glass transition temperature decrease with the addition of V2O5. This suggests that when V2O5 is added to the glass initially up to 0.5 mol% it may be entering as a modifier. Beyond 0.5 mol% density decreases and molar volume increases as V2O5 goes as former. This reveals the role of V2O5 as a glass network former beyond 0.5 mol%. Optical band gap energy decreases and cut off wavelength increases with increase in V2O5 content.

We consider a solar selective absorber with its thin-film layer containing nanospheres whose sizes follow a Poisson distribution. We show that the size distribution of the nanospheres is correlated with the cut-off wavelength of the solar selective absorber system. The study demonstrates that the absorptance profile mostly covers the solar spectrum and the nanospheres Poisson size distribution parameters, like the mean and the number of nanospheres in a layer, relate to the shift of the cut-off wavelength. This means that we can finely control how the real nanosphere-based solar thermal collector in different working temperatures.

This paper has presented the basic infrastructure of different multilayer graded index fiber profiles design. The optimum graded refractive index fiber profile design for the control of total Losses and dispersion effects are considered. The trade-off between different refractive index fiber profiles is realized in order to achieve loss and dispersion effects management. It is evident that the proposed first optical fiber has presented lower dispersion and splice loss than other proposed fibers. As well as the proposed third optical fiber outlines lower effective mode field diameter and micro bending loss than other proposed fibers. Dominant mode, cutoff wavelength and international telecommunication union-telecommunication (ITU-T) values for each fiber are examined based on finite difference method.

Deep ultraviolet (DUV) photodetection usually relies on wide-bandgap semiconductors, which however face challenges in material growth and doping processes. In this work, we proposed and validated a photodetection scheme based on tunneling barrier modulation, achieving highly sensitive DUV photodetection. Using a two-dimensional van der Waals heterostructure, the device integrates MoS 2 as the transporting layer for its high carrier mobility and low dark current, few-layered graphene (FLG) as the photon absorption layer, and hexagonal boron nitride (hBN) as the dielectric barrier. The device exhibits an photoresponsivity of 4.4 × 10 6  A·W -1 and specific detectivity of 1.4 × 10 17 cm ⋅ H z − 1 / 2 ⋅ W − 1 for 250 nm DUV light, with a rejection ratio R 250 /R 450 exceeding 10 6 for visible light. Unlike conventional photodetectors, the cutoff wavelength is determined by the tunneling barrier rather than the material bandgap. Additionally, this photodetection scheme has been extended to a wide range of materials, utilizing different charge transporting layer (e.g., MoS 2 , ReS 2 ), barrier layer (e.g., hBN, Al 2 O 3 ), and photon absorption materials (e.g., FLG, PdSe 2 , Au, Pd), showcasing its broad adaptability and potential for extensive application. Furthermore, the device has been successfully employed as a power meter for weak UV radiation (0.1 μW·cm -2 ) and for measuring solar UV irradiance with results matching the meteorological agency’s weather reports. Overall, this work introduces an effective approach for developing high-performance DUV photodetectors, highlighting significant potential for applications in the optoelectronic market. Deep ultraviolet (DUV) detectors based on wide-bandgap semiconductors face challenges in the materials growth and optoelectronic properties optimization. Here, the authors realize high-performance DUV photodetectors based on van der Waals heterostructures, where the cutoff wavelength is determined by the tunnelling barrier height rather than the material bandgap.

A novel PV-TEG hybrid system applied in outer space is designed, and relevant physical and numerical models are established to study the effects of cut-off wavelength ( λ c) and concentration ratio ( CR ) on the output behaviors of separate PV module, TEG module, and PV-TEG hybrid system. Combining the changing patterns of the output characteristics of PV and TEG modules in terms of λ c and CR , it is concluded that the hybrid system achieves a 20.1% increase in the maximum electrical power density in comparison to a separate PV module. In outer space, the novel PV-TEG hybrid system significantly improves the output behavior compared with a single PV cell and can provide technical support for converting space solar energy into electricity.

HighlightsA facile method was developed to achieve visible light (green) and near infrared dual-mode afterglow emissions from carbon dots (CDs)-based materials at ambient conditions for the first time.We proposed a promising method in advanced information security applications through a special manner of readout.The as-developed method was confirmed to be applicable to many kinds of CDs for achieving or enhancing their afterglow performances.Near-infrared (NIR), particularly NIR-containing dual-/multi-mode afterglow, is very attractive in many fields of application, but it is still a great challenge to achieve such property of materials. Herein, we report a facile method to prepare green and NIR dual-mode afterglow of carbon dots (CDs) through in situ embedding o-CDs (being prepared from o-phenylenediamine) into cyanuric acid (CA) matrix (named o-CDs@CA). Further studies reveal that the green and NIR afterglows of o-CDs@CA originate from thermal activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) of o-CDs, respectively. In addition, the formation of covalent bonds between o-CDs and CA, and the presence of multiple fixation and rigid effects to the triplet states of o-CDs are confirmed to be critical for activating the observed dual-mode afterglow. Due to the shorter lifetime and insensitiveness to human vision of the NIR RTP of o-CDs@CA, it is completely covered by the green TADF during directly observing. The NIR RTP signal, however, can be readily captured if an optical filter (cut-off wavelength of 600 nm) being used. By utilizing these unique features, the applications of o-CDs@CA in anti-counterfeiting and information encryption have been demonstrated with great confidentiality. Finally, the as-developed method was confirmed to be applicable to many other kinds of CDs for achieving or enhancing their afterglow performances.

Near-infrared transparent films demonstrate important applications in many fields, but how to eliminate light interference from ultraviolet-visible region and how to tackle the trade-off effect between film thickness and transmittance remain as challenges. Herein, we report a near-infrared transparent film that achieves high-efficient combination of thin thickness (16 μm), suitable cut-off wavelength (890 nm), and ideal transmittance (T NIR  > 90%, T Vis  < 1%). Moreover, the film is photo-chemically stable, heating resistance and moisture insensitive. The key component of the film is a complex of a specially designed boron compound containing a perylene monoimide unit (PMI-CBN) with an organic base 1,8-diazabicyclo[5,4,0]undec-7-ene. The complex depicts red-shifted absorption from 709 to 943 nm owing to deprotonation of the N-H group of PMI-CBN. Dispersion of the complex in polymethyl methacrylate results in the high-performance film. As demos, the film is successfully used for night vision imaging and information encryption. Near-infrared transparent films have a number of applications, but combining elimination of UV-vis light and the balance of film thickness and transmittance is challenging. Here, the authors report the development of a thin material with good transmittance and a suitable wavelength cutoff.

The growing demand for optical fibers is due to their superior the ability to transmit information with high efficiency and minimal loss across extensive distances. In this study, four optical fibers with core radii ranging from (2.05-5.05) μm, and with a numerical aperture of 0.1624 were analyzed. The modal properties of these fibers were calculated at a wavelength of 1030 nm using the RP Fiber Calculator software (free version 2025). Furthermore, the impact of increasing the core radius on these properties was examined. The results showed that multimode fibers are formed when the core radius is much larger than the wavelength used. In contrast, single-mode fiber is obtained when this condition is not met. Five modes properties were calculated: cut-off wavelength, effective area, power in the core, propagation constant and effective refractive index. The geometric distribution of the amplitudes of all modes was graphically represented.