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Using Terahertz Time-Domain Spectroscopy to Discriminate among Water Contamination Levels in Diesel Engine Oil
摘要： Terahertz time-domain spectroscopy (THz-TDS) in the range of 0.5 to 2.0 THz was evaluated for discriminating among water contamination levels (0%, 0.1%, and 0.2%) in diesel engine oil (SAE 15W-40). The absorption coefficient demonstrated potential to discriminate among the three water contamination levels with significant differences among all three levels across the 1.111 to 1.332 THz and 1.669 to 1.934 THz ranges. At each of these frequency ranges, each water contamination level was significantly different from the other two. The 0% water contamination level had the lowest absorption coefficient, while 0.2% water had the highest absorption coefficient. The refractive index demonstrated greater potential to discriminate among water contamination levels with significant differences among all three water levels across the 0.5 to 1.5 THz range. The refractive index of 0% water was the lowest and 0.2% water was the highest across the THz range. Linear regression analysis of the refractive index as a predictor of water contamination level yielded a highly significant equation (p < 0.0001, R2 = 0.99, RMSE = 0.01) when using the refractive indices at 0.5 THz. The refractive indices of these oil samples were promising for discrimination of water contamination. THz spectroscopy should be evaluated for discriminating other engine oil contaminants.
关键词： Terahertz spectroscopy,Diesel,Engine oil,Water contamination
更新于2025-09-09 09:28:46
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The role of cloud contamination, aerosol layer height and aerosol model in the assessment of the OMI near-UV retrievals over the ocean
摘要： Retrievals of aerosol optical depth (AOD) at 388 nm over the ocean from the Ozone Monitoring Instrument (OMI) two-channel near-UV algorithm (OMAERUV) have been compared with independent AOD measurements. The analysis was carried out over the open ocean (OMI and MODerate-resolution Imaging Spectrometer (MODIS) AOD comparisons) and over coastal and island sites (OMI and AERONET, the AErosol RObotic NETwork). Additionally, a research version of the retrieval algorithm (using MODIS and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) information as constraints) was utilized to evaluate the sensitivity of the retrieval to different assumed aerosol properties.
关键词： MODIS,CALIOP,aerosol layer height,aerosol model,AERONET,OMI,aerosol optical depth,cloud contamination
更新于2025-09-04 15:30:14
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Dew as a Detrimental Influencing Factor for Soiling of PV Modules
摘要： Soiling of photovoltaic (PV) modules can significantly reduce their energy yield by reflecting or absorbing the incident light and is of great importance for operation and maintenance of PV systems in dusty environments. In this paper, we examine the influence of dew—which is formed on PV modules during night and early morning hours—on soiling processes. Outdoor experiments were performed in desert conditions in Qatar using unheated and heated glass samples supplied with different heating powers, as well as outdoor microscopy studies. In addition, laboratory soiling experiments were performed using different dust types, controlled dust removal by centrifugal forces at different relative humidity levels, and defined dew cycles. Results from both the field tests and laboratory soiling experiments showed a significant impact of dew on particle adhesion, removal, and corresponding soiling rates, which was independent of the dust type. Microstructural investigations using electron microscopy were performed to determine the cause of increased particle adhesion. Heating of glass surfaces during the night can significantly reduce the processes of cementation, particle caking, and capillary aging and, thus, reduce soiling. This study indicates that the prevention of condensation can be a method to mitigate soiling.
关键词： Photovoltaic systems,surface contamination,solar panels,solar energy
更新于2025-09-04 15:30:14
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Observations on Si-based micro-clusters embedded in TaN thin film deposited by co-sputtering with oxygen contamination
摘要： Using scanning electron microscopy (SEM) and high-resolution x-ray photoelectron spectroscopy with the synchrotron radiation we investigated Si-based micro-clusters embedded in TaSiN thin films having oxygen contamination. TaSiN thin films were deposited by co-sputtering on fixed or rotated substrates and with various power conditions of TaN and Si targets. Three types of embedded micro-clusters with the chemical states of pure Si, SiOx-capped Si, and SiO2-capped Si were observed and analyzed using SEM and Si 2p and Ta 4 f core-level spectra were derived. Their different resistivities are presumably due to the different chemical states and densities of Si-based micro-clusters.
关键词： oxygen contamination,HRXPS,TaN thin film,SEM,co-sputtering,Si-based micro-clusters
更新于2025-09-04 15:30:14
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Measurements of Microstructural, Chemical, Optical, and Electrical Properties of Silicon-Oxygen-Nitrogen Films Prepared by Plasma-Enhanced Atomic Layer Deposition
摘要： In this study, silicon nitride (SiNx) thin films with different oxygen concentration (i.e., SiON film) were precisely deposited by plasma enhanced atomic layer deposition on Si (100) substrates. Thus, the effect of oxygen concentration on film properties is able to be comparatively studied and various valuable results are obtained. In detail, x-ray reflectivity, x-ray photoelectron spectroscopy, atomic force microscopy, and spectroscopic ellipsometry are used to systematically characterize the microstructural, optical, and electrical properties of SiON film. The experimental results indicate that the surface roughness increases from 0.13 to 0.2 nm as the oxygen concentration decreases. The refractive index of the SiON film reveals an increase from 1.55 to 1.86 with decreasing oxygen concentration. Accordingly, the band-gap energy of these films determined by oxygen 1s-peak analysis decreases from 6.2 to 4.8 eV. Moreover, the I-V tests demonstrate that the film exhibits lower leakage current and better insulation for higher oxygen concentration in film. These results indicate that oxygen affects microstructural, optical, and electrical properties of the prepared SiNx film.
关键词： silicon nitride,silicon oxynitride,oxygen contamination,optical properties,plasma enhanced atomic layer deposition
更新于2025-09-04 15:30:14