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The sputtering yield of crystalline Si(1?0?0) surface by monoatomic and diatomic nitrogen ions impact
摘要： We have investigated the sputtering rate of thin crystalline silicon film forming silicon-on-insulator structure impinged by atomic and molecular nitrogen ions with medium energies of 25, 50, and 100 keV/(N atom) at several incident angles of 0, 30, 45, and 60°. The thickness of the surface silicon layer after ion irradiation was quantitatively estimated by Rutherford backscattering spectroscopy using 2.56-MeV 10B2+ ions with a grazing angle geometry to accurately analyze the thickness decrement in several nanometers for ultrathin Si layers. The sputtering rates were compared with a full-cascade TRIM simulation based on a binary collision approximation. We found that the sputtering yields of monoatomic N ion with higher energies (> 50 keV/N) took significantly higher than that of diatomic N2 ion, probably suggesting that a wake-like effect of relatively fast N^N molecular ions surviving for a long period due to a considerably strong triple bond. In addition, the observed sputtering yields for all present conditions were a few times smaller than that estimated by the full-cascade TRIM calculation using typical lattice parameters. We quantitatively discuss the details of sputtering phenomenon of crystalline silicon by nitrogen ions at medium energy region.
关键词： Medium energy,Molecular ion,Sputtering,Rutherford backscattering spectroscopy,Silicon
更新于2025-09-23 15:23:52
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Study on sliding-window length based on Rayleigh backscattering spectrum correlation in distributed optical-fiber strain measurement
摘要： A theoretical model is established for estimating the strain measurement error based on the Rayleigh backscattering spectrum correlation in distributed optical fiber strain measurements. Assuming the signal is much larger than the noise, the theoretical model predicts the strain measurement error using noise variance and the defined quality factor Q of the Rayleigh backscattering spectrum. Furthermore, an algorithm based on the quality factor Q is proposed to select an optimized sliding-window. The sliding-window length can be obtained by calculating the threshold value of the quality factor using a theoretical model corresponding to the required strain measurement accuracy. Compared with the traditional method where the sliding-window length is defined by the user based on spatial resolution requirements or an empirical definition, the sliding-window length determined by the algorithm is more reasonable and can be automatically defined, alleviating the requirement for user inputs. To verify the correctness of the theoretical model, two experiments are set up: a self-correlation experiment, that analyzes the effect of the quality factor on the strain measurement accuracy, and a virtual experiment of the noise influence, which analyzes the effect of different noise variances. The experimental results are in good agreement with those of the model.
关键词： Distributed optical fiber strain measurement,Rayleigh backscattering spectrum correlation,Optical frequency domain reflectometer
更新于2025-09-23 15:23:52
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Accuracy Assessment of Bio-optical Models to Retrieve Backscattering Coefficients in Case 1 Waters of the Bay of Bengal
摘要： The backscattering coef?cient (bb) has been obtained either in situ observations/measurements or semi-analytical/analytical and empirical algorithms that depend on the relationship between ‘bb’ and the remote sensing re?ectance (Rrs). Several models were developed to estimate backscattering coef?cient from the satellite imagery. The present study aims to assess the accuracy of bio-optical models and infer the best suitable model for Ocean Colour Monitoring (OCM-2) and for the upcoming OCM-3 sensors of Indian Space Research Organization. For this purpose, the bio-optical algorithms/models such as quasi-analytical algorithm (QAA), QAA version 5, Generalized Inherent Optical Properties (GIOP) and optimization of semi-analytical models in case 1 waters of the Bay of Bengal (BoB) were considered. For this analysis, three satellite sensors Moderate Resolution Imaging Spectroradiometer (MODIS)-Aqua, Visible Infrared Imaging Radiometer Suite (VIIRS), and OCM-2 datasets has been used to assess the model’s accuracy. The results showed that the optimization technique performs better (bias = 0.002, 0.179 and root-mean-square error (RMSE) = 8%, 20%) for MODIS-A and OCM-2, respectively, whereas GIOP performs better (bias = 0.08, RMSE = 14%) for VIIRS in case 1 waters of the BoB. From the statistical analysis of each model for all stations, it is recommended to use the optimization technique rather than GIOP technique for estimation of satellite based ‘bb’ in Indian waters.
关键词： Case 1 waters,QAA,QAA_v5,GIOP,Backscattering coef?cient,Optimization
更新于2025-09-23 15:23:52
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The Dependence of Resonance Frequency to Landing Angle in Reciprocal Scattering Phenomena of the Waves From an Elliptical Plasma Dielectric Antenna
摘要： Scattering of an electromagnetic plane wave in transverse electric mode which is obliquely incident to an elliptical plasma antenna with a dielectric rod is comprehensively investigated. The field solutions of the incident, transmitted, and the scattered waves will be derived in terms of Mathieu and modified Mathieu functions. Using asymptotic expansions of Mathieu functions, the scattering cross section per unit length is obtained. It will be shown that in such an elliptical plasma antenna, the backscattering cross section depends on the incident angle and the bistatic scattering cross section varies with scattering angle significantly. Such effects are not seen in antennas with circular cross section due to the circular symmetry in them. The validation of the presented formulations and numerical computation will be examined with the circular case that is an asymptotic well-known case. The graphs of backscattering cross section, scattering pattern, and their corresponding to the polarized charge densities are presented. The dependence of the backscattering cross section and the scattering pattern upon the density and geometrical dimension of the plasma and dielectric are investigated. In addition, it will be shown that the resonance frequencies, under which the plasma antenna response will be maximum, essentially depend on the incident angle of the incident wave.
关键词： dielectric rod,resonance frequency,polarized charge density,Backscattering cross section,scattering pattern,elliptical plasma antenna
更新于2025-09-23 15:22:29
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[IEEE 2018 OCEANS - MTS/IEEE Kobe Techno-Ocean (OTO) - Kobe (2018.5.28-2018.5.31)] 2018 OCEANS - MTS/IEEE Kobe Techno-Oceans (OTO) - Underwater Image Denoising Based on Non-Local Methods
摘要： Due to the medium scattering and light absorption, the acquired underwater optical images suffer from poor visibility. Absorption and scattering effects are caused not only by the water itself but also by other floating particles. Moreover, backscattering is strengthened during the light is reflected and deflected multiple times by the suspended particles before reaching the camera. The backscattering gives rise to specific strong correlated noise together with a constant level degrading the image contrast. Although there are many effective dehazing methods to remove the veil background, they have ignored the influence of backscattering noise, which still exists in the dehazed images. In addition, because of the special characteristics of backscattering noise, the traditional image denoising methods are difficult to make sense, even cause distortion. Accordingly, this paper employed the non-local denoising methods which are referred to Non-Local Means algorithm and Block-Matching 3D collaborative filtering to suppress the backscattering noise. The experimental results show that they can effectively remove the backscattering noise of underwater image and achieve better image quality.
关键词： backscattering noise,BM3D,NLM,underwater image
更新于2025-09-23 15:22:29
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Spaceborne GNSS-Reflectometry for Ship-Detection Applications: Impact of Acquisition Geometry and Polarization
摘要： In this paper, a comparative study of spaceborne Global Navigation Satellite System (GNSS)-Reflectometry for ship detection applications is provided. The analysis is conducted by evaluating the impact of 1) the acquisition geometry and 2) the received signal polarization on ship detectability in GNSS-R data. In particular, the backscattering acquisition geometry is demonstrated to be more suitable for ship detection applications, thus allowing for the detection of 20 m-length ships. Even very large ships are hardly detectable in the conventional forward-scattering geometry. Moreover, receiving right-hand circular polarization is demonstrated to provide significant improvements of the signal-to-noise-plus-clutter with respect to the conventional left-hand circular polarization channel, conventionally exploited in GNSS-R remote sensing. The study is based on a numerical tool for the bistatic radar cross section of the ship, which is presented in a companion paper.
关键词： backscattering geometry,GNSS-Reflectometry,bistatic radar,ship detection,maritime surveillance
更新于2025-09-23 15:21:21
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[IEEE IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - Valencia, Spain (2018.7.22-2018.7.27)] IGARSS 2018 - 2018 IEEE International Geoscience and Remote Sensing Symposium - A GPS-Reflectometry Simulator for Target Detection Over Oceans
摘要： The development and implementation of a GPS-Reflectometry (GPS-R) simulator for the ocean target detection application is proposed, with the objective of assessing and characterizing the capability of GPS-R as a new method for sea surface target detection. The novel idea is to use a backscattering configuration to enhance the electromagnetic return from the target compared to the surrounding ocean. Hence the backscattering simulator simulates images of GPS echoes from one or more targets embedded in an ocean clutter, and its outputs will be analysed as a function of hardware parameters, geometry, and signal processing approaches to determine the target detectability. Some preliminary results related to the backscattering simulations from both ocean and target will be presented.
关键词： target detection,GPS-Reflectometry,backscattering
更新于2025-09-23 15:21:21
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Application of laser backscattering imaging for the physico-chemical characterisation of antimicrobial silica particles functionalised with plant essential oils
摘要： The capacity of orthogonal imaging applied to laser-backscattering for characterising antimicrobial particles based on immobilised essential oils was tested. Different particles were synthesised using various particle and oils. Samples were characterised physico-chemically and by an imaging technique. The technique recorded the generated patterns because of the laser-particles interaction during the sedimentation process. The series of images were transformed into an orthogonal image. Data extraction varied depending on the fragmentation degree of image length. After the multivariate analysis, the physico-chemical results showed variability due to particle size. That variability diminished the effect of oils for large sizes. The imaging data collected these properties, which could be used to recognise both particle size and oil type. Thus the prediction of the properties was successful. The position in the physico-chemical space of variance was also predicted. Hence this technique could complement a low-cost method to evaluate the properties of functionalised particles with oils.
关键词： Essential oils,Silica particles,Laser backscattering,Orthogonal imaging,Physico-chemical characterisation
更新于2025-09-23 15:21:01
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Analytical Thomson backscattering spectra and new scaling laws in laser and magnetic fields
摘要： The analytical asymptotic expression of Thomson backscattering spectra in arbitrarily polarized laser and uniform magnetic fields is given. It is used to theoretically analyze the spectra structures and properties. The results of asymptotic expression and numerical calculations show good agreement in the large harmonic-order region. The scaling laws about laser intensity and electron initial axial momentum are obtained. Furthermore, the optimal harmonic order corresponding to the maximum radiation intensity can be found, then new scaling laws about this optimal harmonic order with laser intensity and resonance parameter are revealed.
关键词： scaling laws,magnetic fields,laser fields,Thomson backscattering
更新于2025-09-23 15:21:01
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The role of the femtosecond laser induced nano/micro structures on the optical features of the steel surface; experimental polarimetry study
摘要： We are witnessing that ultrashort laser material processing (ULMP) is getting an established technique to modify many characteristics of a surface. Being applicable for various materials with any geometry or physical characteristics, besides being rapid and having simple experimental set-ups makes ULMP appropriate for small and large scale controlled modifications. Using this method to adjust the optical features of a surface has been also suggested in last years. So that mimicking the functional surfaces existing in nature which have distinctive surface morphologies and thus have special optical features, efforts are going on to create similar samples using ULMP. Here in this study, the potential of ULMP technique in changing the optical properties of metallic substrates is explored. Selecting 316L stainless steel as a substrate, five samples which are irradiated in different circumstances are fabricated. The role of the laser induced nano/micro structures on the optical features of these samples are studied systematically. Visible light backscattering in the range of 0°-65° was studied at first. Extracting the Mueller matrix elements for all samples at two different incident angles of 45° and 60°, the polarimetry parameters including retardancy, depolarization and diattenuation are calculated at the next step. Due to the multi-scale nature of the morphologies, more than the illuminating light angle, dependence of the samples optical response to its orientation is also discussed in detail Results clearly reflect that the optical response of laser induced periodic surface structure (LIPSS) coated layers have an anisotropic behavior regarding the incident angle and the polarization of the illuminating light. Furthermore, the surface orientation itself can play very serious role on the final response of the sample. It comes out that the characteristics of a surface such as its morphology, roughness or the correlation of the LIPSS structures has important effect in these regards.
关键词： backscattering,structure,femtosecond laser,surface,optical features,polarimetry
更新于2025-09-23 15:21:01