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AIP Conference Proceedings [AIP Publishing 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Fes, Morocco (25–27 March 2019)] 15th International Conference on Concentrator Photovoltaic Systems (CPV-15) - Characterization of absorption losses in rear side n-type polycrystalline silicon passivating contacts
摘要： Passivating contacts consisting of polycrystalline silicon (poly-Si) and thin silicon-oxide (SiOx) layers facilitate a significant reduction of recombination losses in silicon solar cells. Nevertheless, these gains come with short circuit current density (Jsc) losses due to parasitic absorption by the poly-Si. Even if the passivating contacts are employed at the rear side only, absorption, particularly due to free carriers (FCA) in the heavily doped poly-Si, may still lead to significant Jsc losses. In this work, these losses are characterized as a function of the poly-Si thickness (tpoly) by the analysis of front reflectance spectra in the infrared (IR). For this study, two sets of samples with different n-type full-area poly-Si passivating contacts at the rear are compared to references with a phosphorus(P)-diffused back surface field (BSF) instead. For the two sets, Jsc losses with respect to the references (ΔJsc) are 0.10 mA/cm2 and 0.42 mA/cm2 per 100 nm thick poly-Si, respectively. The difference between the two values is studied by Hall measurements and interpreted to be due to the over three times as high free carrier concentration (ND,act) in the poly-Si layers of the second set of samples as the first set. On the other hand, lifetime measurements showed an excellent passivation yielding an implied open circuit voltage (iVoc) up to 736 mV only for the samples with the more heavily doped poly-Si, whereas iVoc of 683 mV was measured for the first set, which indicates a trade-off between absorption losses and passivation quality.
关键词： infrared reflectance,passivating contacts,solar cells,absorption losses,polycrystalline silicon
更新于2025-09-12 10:27:22
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Discrimination of wood species using laser-induced breakdown spectroscopy and near-infrared reflectance spectroscopy
摘要： A new method is proposed for the discrimination of wood species by combining near-infrared reflectance spectroscopy (NIRS) and laser-induced breakdown spectroscopy (LIBS) and using chemometrics for data analysis. The method was applied to the analysis of 42 samples from six different species: Amburana cearensis, Copaifera lucens, Phyllocarpus riedelii, Cariniana legalis, Bowdichia virgilioides, and Aspidosperma pyricollum. The spectra from both techniques were merged on a single data matrix and pretreated by standard normal variate (SNV) and Savitzky– Golay first derivative with smoothing. Principal component analysis was applied to the exploratory data analysis and showed a clear formation of sample groups according to the wood species only when the data from both analytical techniques and the data pretreatment were used. Sample discrimination using partial least squares discriminant analysis was proved possible, but with an average misclassification of about 10%. Sample grouping and discrimination were shown to be probably related to different concentrations of iron, copper, zinc, and/or sodium (affecting the LIBS spectra) and lignin, water, cellulose, and/or hemicellulose (affecting the NIRS spectra).
关键词： wood species discrimination,laser-induced breakdown spectroscopy,near-infrared reflectance spectroscopy,chemometrics
更新于2025-09-12 10:27:22
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Flash spectral imaging for optical metrology of solar cells
摘要： Flash spectral imaging of full area (156 mm by 156 mm) silicon solar wafers and cells is realized in a setup integrating pseudo-monochromatic LEDs over the wavelength range of 370 to 1050 nm and a high-resolution monochrome camera. The captured information allows the computation of sample reflectance as a function of wavelength and coordinates, thereby constituting a spectral reflectance map. The derived values match that obtained from monochromator-based measurements. Optical inspection is then based on the characteristic reflectance of surface features at optimally contrasting wavelengths. The technique reveals otherwise hidden stains and anti-reflection coating (ARC) non-uniformities, and enable more selective visualization of grains in multicrystalline Si wafers. Optical contrast enhancement of metallization significantly improves accuracy of metal detection. The high effective resolution of the monochrome camera also allows fine metallization patterns to be measured. The rapid succession of flash-and-image-capture at each wavelength makes the reported optical metrology technique amenable in photovoltaic manufacturing for solar wafers/cells sorting, monitoring and optimization of processes.
关键词： Flash spectral imaging,monochrome camera,ARC non-uniformities,optical metrology,metallization,reflectance,LEDs,solar cells
更新于2025-09-11 14:15:04
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Enhance the solar cell efficiency by reduction of reflection losses
摘要： The enhancement of the solar cell efficiency field has been achieved in many methods due to the different factors and conditions that led to loss the solar energy .This work deals with the increasing of the efficiency of solar cell that made of single crystalline silicon .This increment achieved by the reduction of biggest type of losses of the conversion efficiency named reflection . by using two methods first ; forming grooves on the surface using pulse Nd:YAG laser with max energy 1J and pulse width 10ns, using the fast and accurate movement of the 3D optical galvo mirror scanning system to form the grooves , the second method was by deposition nanomaterials as Silver (Ag) and Cadmium telluride (CdTe) to constitute an antireflection layer for the incident solar spectrum . The effect of antireflection layer material type and the effect of incident light angle on the reflection had been studied in this work .The reflectance had been measured by a system designed and built to give the reflection for angles ranged 0 – 180 degree controlled by Microcontroller. The result inducate that increase in conversion efficiency was 28.3% for Ag/Si , and 32.9% for CdTe/Si than the original efficiency of Si solar cell.
关键词： silicon solar cell,reflectance,laser texture,nanoparticles,antireflection surfaces
更新于2025-09-11 14:15:04
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Identification of tea varieties by mid‐infrared diffuse reflectance spectroscopy coupled with a possibilistic fuzzy c‐means clustering with a fuzzy covariance matrix
摘要： Mid-infrared diffuse reflectance spectroscopy was used to rapidly and nondestructively identify tea varieties together with the proposed possibilistic fuzzy c-means (PFCM) clustering with a fuzzy covariance matrix. The mid-infrared diffuse reflectance spectra of 96 tea samples with three different varieties (Emeishan Maofeng, Level 1, and Level 6 Leshan trimeresurus) were acquired using the FTIR-7600 infrared spectrometer. First, multiplicative scatter correction was implemented to pretreat the spectral data. Second, principal component analysis was employed to compress the mid-infrared diffuse reflectance spectral data after preprocessing. Third, linear discriminant analysis was utilized for extracting the identification information required by the fuzzy clustering algorithms. Ultimately, the fuzzy c-means (FCM) clustering, the allied fuzzy c-means (AFCM) clustering, the PFCM clustering, and the PFCM clustering with a fuzzy covariance matrix were used to cluster the processed spectral data, respectively. The highest identification accuracy of the PFCM clustering with a fuzzy covariance matrix reached at 100% compared with those of FCM (96.7%), AFCM (94.9%), PFCM (96.3%), and partial least squares discrimination analysis (PLS-DA) algorithm (33.3%). It is sufficiently demonstrated that the mid-infrared diffuse reflectance spectroscopy coupled with the PFCM clustering with a fuzzy covariance matrix was a valid method for identifying tea varieties.
关键词： possibilistic fuzzy c-means clustering,tea varieties,Mid-infrared diffuse reflectance spectroscopy,fuzzy covariance matrix,nondestructive detection
更新于2025-09-11 14:15:04
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High-performance subambient radiative cooling enabled by optically selective and thermally insulating polyethylene aerogel
摘要： Recent progress in passive radiative cooling technologies has substantially improved cooling performance under direct sunlight. Yet, experimental demonstrations of daytime radiative cooling still severely underperform in comparison with the theoretical potential due to considerable solar absorption and poor thermal insulation at the emitter. In this work, we developed polyethylene aerogel (PEA)—a solar-reflecting (92.2% solar weighted reflectance at 6 mm thick), infrared-transparent (79.9% transmittance between 8 and 13 mm at 6 mm thick), and low-thermal-conductivity (kPEA = 28 mW/mK) material that can be integrated with existing emitters to address these challenges. Using an experimental setup that includes the custom-fabricated PEA, we demonstrate a daytime ambient temperature cooling power of 96 W/m2 and passive cooling up to 13°C below ambient temperature around solar noon. This work could greatly improve the performance of existing passive radiative coolers for air conditioning and portable refrigeration applications.
关键词： subambient cooling,solar reflectance,thermal insulation,polyethylene aerogel,radiative cooling
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE Southwest Symposium on Image Analysis and Interpretation (SSIAI) - Las Vegas, NV (2018.4.8-2018.4.10)] 2018 IEEE Southwest Symposium on Image Analysis and Interpretation (SSIAI) - A Reflectance Based Method For Shadow Detection and Removal
摘要： Shadows are common aspect of images and when left undetected can hinder scene understanding and visual processing. We propose a simple yet effective approach based on reflectance to detect shadows from single image. An image is first segmented and based on the reflectance, illumination and texture characteristics, segments pairs are identified as shadow and non-shadow pairs. The proposed method is tested on two publicly available and widely used datasets. Our method achieves higher accuracy in detecting shadows compared to previous reported methods despite requiring fewer parameters. We also show results of shadow-free images by relighting the pixels in the detected shadow regions.
关键词： image enhancement,shadow removal,reflectance classifier,shadow detection
更新于2025-09-11 14:15:04
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Association between Visual Acuity and Retinal Layer Metrics in Diabetics with and without Macular Edema
摘要： Purpose. Diabetes is known to cause alterations in retinal microvasculature and tissue that progressively lead to visual impairment. Optical coherence tomography (OCT) is useful for assessment of total retinal thickening due to diabetic macular edema (DME). In the current study, we determined associations between visual acuity (VA) and retinal layer thickness, reflectance, and interface disruption derived from enface OCT images in subjects with and without DME. Materials and Methods. Best corrected VA was measured and high-density OCT volume scans were acquired in 149 diabetic subjects. A previously established image segmentation method identified retinal layer interfaces and locations of visually indiscernible (disrupted) interfaces. Enface thickness maps and reflectance images of the nerve fiber layer (NFL), combined ganglion cell and inner plexiform layer (GCLIPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), photoreceptor outer segment layer (OSL), and retinal pigment epithelium (RPE) were generated in the central macular subfield. The associations among VA and retinal layer metrics were determined by multivariate linear regressions after adjusting for covariates (age, sex, race, HbA1c, diabetes type, and duration) and correcting for multiple comparisons. Results. In DME subjects, increased GCLIPL and OPL thickness and decreased OSL thickness were associated with reduced VA. Furthermore, increased NFL reflectance and decreased OSL reflectance were associated with reduced VA. Additionally, increased areas of INL and ONL interface disruptions were associated with reduced VA. In subjects without DME, increased INL thickness was associated with reduced VA, whereas in subjects without DME but with previous antivascular endothelium growth factor treatment, thickening of OPL was associated with reduced VA. Conclusions. Alterations in retinal layer thickness and reflectance metrics derived from enface OCT images were associated with reduced VA with and without presence of DME, suggestive of their potential for monitoring development, progression, and treatment of DME.
关键词： retinal layer reflectance,visual acuity,retinal layer thickness,optical coherence tomography,diabetic macular edema,interface disruption
更新于2025-09-11 14:15:04
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MULTISPECTRAL IMAGING SYSTEM FOR QUANTITATIVE ASSESSMENT OF TRANSCUTANEOUS BLOOD OXYGEN SATURATION
摘要： This paper presents the use of Extended Modified Lambert Beer (EMLB) model for quantification of transcutaneous blood oxygen saturation (StO2) via a noninvasive approach. Continuous wave (CW) reflectance spectroscopy system is employed for measurement of intensity reflected from left index finger of an Asian nonsmoking volunteer at resting condition. Multispectral images captured in the wavelength range of 520 ? 600 nm at an interval of 10 nm are mathematically analyzed and fitted using the developed fitting algorithm to give the best estimation of StO2. The result from this preliminary study revealed a mean StO2 value of 75 ± 5% for the participating individual, which value agreed considerably well with that presented in previous works. This work concluded that the developed spectroscopy system and quantification technique can potentially be used as an alternative means to clinical assessment of wound healing progress.
关键词： Transcutaneous blood oxygen saturation,reflectance spectroscopy,Extended Modified Lambert Beer model,skin oximetry
更新于2025-09-11 14:15:04
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[IEEE 2018 IEEE 20th International Workshop on Multimedia Signal Processing (MMSP) - Vancouver, BC, Canada (2018.8.29-2018.8.31)] 2018 IEEE 20th International Workshop on Multimedia Signal Processing (MMSP) - Measuring Ear-Canal Reflectance and Estimating Ear-Canal Area Functions and Eardrum Reflectance
摘要： Ear-canal reflectance contains information about ear-canal cross-sectional area functions and eardrum reflectance. These are important in audiology and the design of modern hearing aids and headphones. This paper investigates the inversion method for jointly estimating ear-canal cross-sectional area function and eardrum reflectance, given the acoustic reflectance measured at the entrance of the ear canal. It is found through physical experiments and simulations that the estimated cross-sectional area function is spatially band-limited to 2Fc/c, where Fc is the frequency bandwidth of the low-pass filtered reflectance used in the inversion, and c is the speed of sound. If the actual spatial bandwidth of the area function under estimation is higher than this, then Gibbs ripples appear in the estimated area function. A method is presented for the accurate measurements of ear-canal reflectance, and results are presented for two subjects along with the estimated ear-canal area functions and eardrum reflectance.
关键词： Headphone and hearing aids signal processing,Gibbs phenomena,measurements of ear-canal reflectance,eardrum reflectance,inversion method,ear-canal area function
更新于2025-09-10 09:29:36