- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Reflectance and crystallinity of silicon solar cells with LIPSS produced by XeCl excimer laser pulses
摘要： Laser-induced periodic surface structures (LIPSS) were formed on silicon solar cell surfaces by using a XeCl excimer laser to irradiate them with nanosecond UV laser pulses in the fluence range 0.2–0.6 J/cm2 near the melting threshold fluence (Fth = 0.5 J/cm2) in air. We measured the reflectance of the silicon solar cells after laser irradiation and evaluated their crystallinity by Raman spectroscopy. We found that reflectance and crystallinity depended on laser fluence and number of pulses. For fluence of 0.5 J/cm2, the produced LIPSS contributed to a reduction of ΔR = 3.3% in reflectance at a wavelength of 500 nm. The crystallinity of the fine structures with reduced reflectance was maintained at laser fluences near the melting threshold.
关键词： Crystallinity,Nanosecond UV laser,Reflectance,LIPSS,Nanostructured silicon solar cell
更新于2025-09-19 17:13:59
-
Microsecond Resolved Infrared Spectroelectrochemistry Using Dual Frequency Comb IR Lasers
摘要： A dual infrared frequency comb spectrometer with heterodyne detection has been used to perform time resolved electrochemical attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS). The measurement of the potential dependent desorption of a monolayer of a pyridine derivative (4-dimethylaminopyridine, DMAP) with time resolution as high as 4 μs was achieved without the use of step-scan interferometry. An analysis of the detection limit of the method as a function of both time resolution and measurement co-additions is provided and compared to step-scan experiments of an equivalent system. Dual frequency comb spectroscopy is shown to be highly amenable to time-resolved ATR-SEIRAS. Microsecond resolved spectra can be obtained with high spectral resolution and fractional monolayer detection limits in a total experimental duration that is two orders of magnitude less than the equivalent step-scan experiment.
关键词： 4-dimethyamino pyridine (DMAP),noise analysis,Dual frequency comb spectroscopy,time resolved spectroelectrochemistry,RC constant,attenuated total reflectance surface enhanced infrared absorption spectroscopy (ATR-SEIRAS),detection limit
更新于2025-09-19 17:13:59
-
Impact of grain growth of silver reflective electrode by electron bombardment on external quantum efficiency of III-nitride micro-light-emitting diode arrays
摘要： The effect of electron-beam irradiation (EBI) on Ag reflector is investigated in order to improve the efficiency of flip-chip InGaN/GaN multiple-quantum-wells micro light-emitting diode (μ-LED) arrays. After EBI, small size grains are diffused and then become larger grain. Therefore, grain boundaries are reduced which originates the crystal quality and reflectance of Ag reflect to improve. Grain size of Ag reflector is increased with the increase in EBI time that is consistently observed by different kinds of material characterizations. 5 minutes EBI-based Ag reflector shows higher reflectance (~91 %) at 450 nm than without EBI sample (~84 %). Finally, without and with EBI on Ag reflector-based μ-LED arrays are fabricated. After EBI, there is no change in forward bias voltage except optical performances. At driving current, Ag reflector with EBI-based μ-LEDs has higher light-output-power, electroluminescence intensity and electroluminescence distribution over the chip area compared to without EBI-based μ-LEDs. Usually, increased light-extraction-efficiency causes the external-quantum-efficiency of the μ-LEDs to increase. These enhanced optoelectronic performances are consistently described by using microscopic and macroscopic characterizations.
关键词： Ag reflector,Electron-beam irradiation,reflectance,micro light-emitting diodes,grain size
更新于2025-09-19 17:13:59
-
A Cost-Effective and Portable Optical Sensor System to Estimate Leaf Nitrogen and Water Contents in Crops
摘要： Non‐invasive determination of leaf nitrogen (N) and water contents is essential for ensuring the healthy growth of the plants. However, most of the existing methods to measure them are expensive. In this paper, a low‐cost, portable multispectral sensor system is proposed to determine N and water contents in the leaves, non‐invasively. Four different species of plants—canola, corn, soybean, and wheat—are used as test plants to investigate the utility of the proposed device. The sensor system comprises two multispectral sensors, visible (VIS) and near‐infrared (NIR), detecting reflectance at 12 wavelengths (six from each sensor). Two separate experiments were performed in a controlled greenhouse environment, including N and water experiments. Spectral data were collected from 307 leaves (121 for N and 186 for water experiment), and the rational quadratic Gaussian process regression (GPR) algorithm was applied to correlate the reflectance data with actual N and water content. By performing five‐fold cross‐validation, the N estimation showed a coefficient of determination (??2) of 63.91% for canola, 80.05% for corn, 82.29% for soybean, and 63.21% for wheat. For water content estimation, canola showed an ??2 of 18.02%, corn showed an ??2 of 68.41%, soybean showed an ??2 of 46.38%, and wheat showed an ??2 of 64.58%. The result reveals that the proposed low‐cost sensor with an appropriate regression model can be used to determine N content. However, further investigation is needed to improve the water estimation results using the proposed device.
关键词： plant phenotyping,non‐invasive,machine learning,reflectance,leaf nitrogen
更新于2025-09-19 17:13:59
-
The influence of MC1R dermal morphological features of photoexposed skin in women revealed by reflectance confocal microscopy and optical coherence tomography
摘要： Background: The melanocortin 1 receptor (MC1R) gene is one of the major determinants of skin pigmentation. It is a highly polymorphic gene and some of its polymorphisms, have been related to specific skin phenotypes, increased risk of skin cancers and skin photoaging. Currently, its contribution to changes in dermal features in photo-exposed skin is unknown. Objective: The main objective of this study is to evaluate the potential correlation between MC1R status and specific healthy photoexposed skin characteristics. Materials and methods: Skin facial features were estimated by evaluation with standard digital photography with automated features, reflectance confocal microscopy (RCM) and optical coherence tomography (OCT) in 100 healthy women. Skin of the forearms was used as a control. Results: The study found an association between RHC MC1R polymorphisms and dermal features in photoexposed areas being represented by increased vessel density and pixel density in OCT (p=0.025 and p=0.001, respectively) and increased coarse collagen in RCM (p=0.034), as compared to non-RHC subjects. To our knowledge this is previously unreported. Additionally, previously reported correlations between light hair and skin color and pigmented spots with MC1R RHC polymorphisms have been confirmed. Conclusions: Our results suggest the role of RHC MC1R variants in dermal variations of facial skin, as compared to non-RHC variants. To our knowledge this is previously unreported.
关键词： MC1R,melanocortin 1 receptor,reflectance confocal microscopy,skin photoaging,dynamic-optical coherence tomography
更新于2025-09-19 17:13:59
-
Do optical sensor readings change throughout the day? An evaluation of two sensor systems
摘要： Optical sensors are useful tools for rapid and periodic assessment of plant nutritional status. However, the utility and potential of these sensors may be reduced if their readings change throughout the day. Therefore, this study aimed to assess the effects of time of day on measurements of the SPAD-502 chlorophyll meter and the GreenSeeker throughout the bean crop cycle. The treatments consisted of time of day for sensor measurements (8:00, 12:00, and 16:00 h) throughout six dates over the crop cycle. The results showed that measurements from the SPAD-502 and the GreenSeeker significantly changed according to time of day. The SPAD index at 16:00 h showed the lowest coefficient of variation (CV, 2.5%) and was on average, 3.05 ± 0.43, and 1.12 ± 0.25 SPAD units higher when compared to readings obtained at 8:00 and 12:00 h. Differently, the NDVI from the GreenSeeker showed the lowest CV (4.34%) at 8:00 h and was, on average, 0.06 ± 0.028 and 0.03 ± 0.01 units higher than measurements taken at 16:00 h and 12:00 h, respectively. Furthermore, the different times of sensor measurements present variations in air temperature and solar radiation, which directly influence the leaf water content and paraheliotropic movements. Thus, the indices from both sensors tend to show a high variability during different times of the day. Therefore, it is essential to create a consistent sampling protocol to reduce the variability of sensor measurements during the crop cycle.
关键词： Phaseolus vulgaris L,solar radiation,chlorophyll meter,precision agriculture,canopy reflectance sensor
更新于2025-09-19 17:13:59
-
[IEEE 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Bengaluru, India (2018.12.17-2018.12.19)] 2018 4th IEEE International Conference on Emerging Electronics (ICEE) - Silicon Slot Waveguide Mach-Zehnder Using Fixed Electron Beam Moving Stage Patterning Technique
摘要： Ocean water albedo (OWA) plays an important role in the global climate variation. Compared with the achievements in land surface albedo studies, the global distributions of ocean water and sea ice albedo are seldom addressed. This study designed an operational global OWA algorithm based on the three-component reflectance model of the ocean water: sun glint, whitecaps, and water-leaving reflectance. The related achievements in these three areas are reviewed and integrated into the operational algorithm. After the sensitive analysis, the algorithm is compared with previous studies and validated with ground observations at COVE site located 25 km east of Virginia Beach (36.91? N, 75.71? W), and the results indicate that the proposed algorithm is generally consistent with previous parameterization scheme. As an example, the global OWAs in summer and winter 2011 are generated using the remote sensing reflectance data sets via the Moderate Resolution Imaging Spectroradiometer and Modern-Era Retrospective analysis for Research and Applications meteorological reanalysis data set. The generated product includes instantaneous (e.g., local noon) and daily mean OWAs under both clear-sky and white-sky conditions. Upon the examples, the local noon clear-sky OWA shows a significant latitude variation due to the dominance of the solar angle, whereas the white-sky OWA is sensitive to wind speeds and optical constituents. The global distribution of the daily mean OWA exhibits a similar trend to the local noon OWA. However, the daily mean clear-sky OWA is significantly larger than the local noon OWA; this finding should be noted when using OWA products for energy balance research. Additionally, all forms of OWA products exhibit increase in coastal areas with high input of terrestrial matters.
关键词： water-leaving reflectance,whitecaps,Ocean water albedo (OWA),sun glint
更新于2025-09-19 17:13:59
-
[Laser Institute of America ILSC? 2019: Proceedings of the International Laser Safety Conference - South Kissimmee, Florida, USA (March 18–21, 2019)] International Laser Safety Conference - Construction and utilization of probabilistic dynamic bidirectional reflectance distribution functions
摘要： Reflections of high energy lasers from surfaces can present hazards to persons and instruments at significant distances. Heating from these lasers causes changes in the reflection characteristics of surfaces they illuminate. As such, reflections from these surfaces cannot be properly modeled with static bidirectional reflectance distribution functions (BRDFs), but require time-dynamic BRDFs. Moreover, the time-evolution of the surface reflections is not deterministic, but can vary even when the materials and illumination conditions are nearly identical, such that only probabilistic characterization is realistic. Due to the swiftly changing nature of the reflections, traditional BRDF measurements with goniometric instruments are impossible, so BRDFs must be deduced from images of the reflected light incident on a screen intercepting a portion of the reflection solid angle. A new BRDF model describes these complex probabilistic dynamic BRDFs with only four intuitive parameters for a given laser wavelength, irradiance, and duration, where these parameters have central values and statistical variances over discrete regimes corresponding to surface conditions. An automated procedure determines appropriate parameter values and variances from captured screen images, requiring only a single angle of laser incidence. Parameters from sample tests illustrate the model.
关键词： high energy lasers,probabilistic modeling,dynamic BRDFs,bidirectional reflectance distribution functions,laser safety
更新于2025-09-16 10:30:52
-
Surface Roughening of Silicon Wafer Solar Cell by Using ECDM Method
摘要： This research proposes surface roughening of silicon wafer solar cell by electrochemical discharge machining (ECDM). The stainless steel was used as negative electrode. The graphite was used as the positive electrode acting as the auxiliary electrode. The potassium hydroxide was used as the electrolyte. The processing parameters include the machining voltage, the processing time, the machining gap, the electrolyte concentration, the additive agent concentration, pulse frequency and duty factor, etc. The result of experiments reveals that appropriate concentrations of ethanol can expand the size of the pores and enhance surface roughening effect. The appropriate processing parameters are a machining gap of 200μm, voltage of 48V, concentration of potassium hydroxide of 3M, concentration of ethanol of 4%. The electrochemical discharge machined surface roughness was increased from 0.417μm to 0.915μm using one minute processing time. The average reflectance rate of the textured surface was decreased from 29.6% to 12.7%. This study reveals that ECDM method has the advantage of short processing time and can generate a higher surface roughness and the porous structure.
关键词： Electrical chemical discharge machining,Reflectance rate,Surface roughening,Silicon wafer solar cell
更新于2025-09-16 10:30:52
-
[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Identification of the calcified tissues using laser induced breakdown spectroscopy
摘要： Ocean water albedo (OWA) plays an important role in the global climate variation. Compared with the achievements in land surface albedo studies, the global distributions of ocean water and sea ice albedo are seldom addressed. This study designed an operational global OWA algorithm based on the three-component reflectance model of the ocean water: sun glint, whitecaps, and water-leaving reflectance. The related achievements in these three areas are reviewed and integrated into the operational algorithm. After the sensitive analysis, the algorithm is compared with previous studies and validated with ground observations at COVE site located 25 km east of Virginia Beach (36.91? N, 75.71? W), and the results indicate that the proposed algorithm is generally consistent with previous parameterization scheme. As an example, the global OWAs in summer and winter 2011 are generated using the remote sensing reflectance data sets via the Moderate Resolution Imaging Spectroradiometer and Modern-Era Retrospective analysis for Research and Applications meteorological reanalysis data set. The generated product includes instantaneous (e.g., local noon) and daily mean OWAs under both clear-sky and white-sky conditions. Upon the examples, the local noon clear-sky OWA shows a significant latitude variation due to the dominance of the solar angle, whereas the white-sky OWA is sensitive to wind speeds and optical constituents. The global distribution of the daily mean OWA exhibits a similar trend to the local noon OWA. However, the daily mean clear-sky OWA is significantly larger than the local noon OWA; this finding should be noted when using OWA products for energy balance research. Additionally, all forms of OWA products exhibit increase in coastal areas with high input of terrestrial matters.
关键词： water-leaving reflectance,whitecaps,Ocean water albedo (OWA),sun glint
更新于2025-09-16 10:30:52