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Interfacing CRYSTAL/AMBER to Optimize QM/MM Lennard–Jones Parameters for Water and to Study Solvation of TiO2 Nanoparticles
摘要： Metal oxide nanoparticles (NPs) are regarded as good candidates for many technological applications, where their functional environment is often an aqueous solution. The correct description of metal oxide electronic structure is still a challenge for local and semilocal density functionals, whereas hybrid functional methods provide an improved description, and local atomic function-based codes such as CRYSTAL17 outperform plane wave codes when it comes to hybrid functional calculations. However, the computational cost of hybrids are still prohibitive for systems of real sizes, in a real environment. Therefore, we here present and critically assess the accuracy of our electrostatic embedding quantum mechanical/molecular mechanical (QM/MM) coupling between CRYSTAL17 and AMBER16, and demonstrate some of its capabilities via the case study of TiO2 NPs in water. First, we produced new Lennard–Jones (LJ) parameters that improve the accuracy of water–water interactions in the B3LYP/TIP3P coupling. We found that optimizing LJ parameters based on water tri- to deca-mer clusters provides a less overstructured QM/MM liquid water description than when fitting LJ parameters only based on the water dimer. Then, we applied our QM/MM coupling methodology to describe the interaction of a 1 nm wide multilayer of water surrounding a spherical TiO2 nanoparticle (NP). Optimizing the QM/MM water–water parameters was found to have little to no effect on the local NP properties, which provide insights into the range of influence that can be attributed to the LJ term in the QM/MM coupling. The effect of adding additional water in an MM fashion on the geometry optimized nanoparticle structure is small, but more evident effects are seen in its electronic properties. We also show that there is good transferability of existing QM/MM LJ parameters for organic molecules–water interactions to our QM/MM implementation, even though these parameters were obtained with a different QM code and QM/MM implementation, but with the same functional.
关键词： water,geometry optimization,nanoparticles,QM/MM,molecular dynamics,force field parameters,titanium dioxide,multiscale
更新于2025-09-04 15:30:14
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Investigation on Perceptron Learning for Water Region Estimation Using Large-Scale Multispectral Images
摘要： Land cover classification and investigation of temporal changes are considered to be common applications of remote sensing. Water/non-water region estimation is one of the most fundamental classification tasks, analyzing the occurrence of water on the Earth’s surface. However, common remote sensing practices such as thresholding, spectral analysis, and statistical approaches are not sufficient to produce a globally adaptable water classification. The aim of this study is to develop a formula with automatically derived tuning parameters using perceptron neural networks for water/non-water region estimation, which we call the Perceptron-Derived Water Formula (PDWF), using Landsat-8 images. Water/non-water region estimates derived from PDWF were compared with three different approaches—Modified Normalized Difference Water Index (MNDWI), Automatic Water Extraction Index (AWEI), and Deep Convolutional Neural Network—using various case studies. Our proposed method outperforms all three approaches, showing a significant improvement in water/non-water region estimation. PDWF performance is consistently better even in cases of challenging conditions such as low reflectance due to hill shadows, building-shadows, and dark soils. Moreover, our study implemented a sunglint correction to adapt water/non-water region estimation over sunglint-affected pixels.
关键词： surface water bodies,Landsat-8,MNDWI,deep neural network,perceptron neural network,AWEI,PDWF
更新于2025-09-04 15:30:14
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Genetic Algorithm–Genetic Programming Approach to Identify Hierarchical Models for Ultraviolet Disinfection Reactors
摘要： The performance of ultraviolet (UV) disinfection reactors using experimental data poses major challenges to the water treatment industry, and a regression model has been developed in the water treatment industry to predict UV reactor performance. Genetic programming (GP) can be applied using a process of symbolic regression to create empirical models of data describing a process or system. While classical regression analysis specifies the model structure a priori, GP automatically evolves both the structure and numeric coefficients of the model. GP-derived equations are often computationally complex, however, and do not generalize well for new data sets. This research develops a new model identification procedure that simultaneously identifies an equation to describe a system and hierarchical parameters that are fit for separate data sets. A coupled genetic algorithm (GA) and genetic programming approach (GA-GP) is developed to search for the best-fitting model structure and hierarchical parameter values. Modifications were made to the GA-GP approach to reduce model error while limiting the growth of complex tree structures. The GA-GP method is applied here to identify models for multiple UV reactors by training a model for three data sets. The GA-GP method identified a model with lower error across multiple data sets compared to GP alone, linear regression, and the industry regression model. Including hierarchical terms allowed the search to identify a model that generalizes across multiple data sets.
关键词： System identification,Drinking water treatment,Evolutionary computation,Bloat,Symbolic regression
更新于2025-09-04 15:30:14
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Note: Plasma optical emission spectroscopy for water vapor quantification and detection during vacuum drying process
摘要： A methodology involving plasma optical emission spectroscopy driven by a direct current (dc) plasma source is developed to quantify water vapor concentration in a gaseous stream. The experimental setup consists of a dc driven low-pressure plasma cell in which the emission from the plasma discharge is measured by using an optical emission spectrometer. The emission from Hα at 656.2 nm—the first transition in the Balmer series, was found to be the most sensitive to the water vapor concentration in the gas stream. Consistent linear trends of the emission signals with respect to variation in concentration of water are observed for multiple combinations of operating parameters. This method has been applied to a vacuum drying process of a mock nuclear fuel assembly to quantify the concentration of water vapor during the drying process.
关键词： Hα emission,direct current plasma source,plasma optical emission spectroscopy,vacuum drying process,water vapor quantification
更新于2025-09-04 15:30:14
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A Study on Retrieval Algorithm of Black Water Aggregation in Taihu Lake Based on HJ-1 Satellite Images
摘要： The phenomenon of black water aggregation (BWA) occurs in inland water when massive algal bodies aggregate, die, and react with the toxic sludge in certain climate conditions to deprive the water of oxygen. This process results in the deterioration of water quality and damage to the ecosystem. Because charge coupled device (CCD) camera data from the Chinese HJ environmental satellite shows high potential in monitoring BWA, we acquired four HJ-CCD images of Taihu Lake captured during 2009 to 2011 to study this phenomenon. The first study site was selected near the Shore of Taihu Lake. We pre-processed the HJ-CCD images and analyzed the digital number (DN) gray values in the research area and in typical BWA areas. The results show that the DN values of visible bands in BWA areas are obviously lower than those in the research areas. Moreover, we developed an empirical retrieving algorithm of BWA based on the DN mean values and variances of research areas. Finally, we tested the accuracy of this empirical algorithm. The retrieving accuracies were89.9%, 58.1%, 73.4%, and 85.5%, respectively, which demonstrates the efficiency of empirical algorithm in retrieving the approximate distributions of BWA.
关键词： Taihu Lake,Retrieval Algorithm,Black Water Aggregation,HJ-1 Satellite Images
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI, USA (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Testing of an Anti-Soiling Coating for PV Module Cover Glass
摘要： Soiling of solar module cover glass can significantly reduce the module power output. Coatings can be applied to the cover glass surface to reduce adhesion and make the surfaces easier to clean. These coatings should be resilient and resistant to environmental damage. A hydrophobic anti-soiling coating was exposed to a variety of environmental and abrasion stress tests. The hydrophobic performance of the coating was measured by monitoring the water contact angle and the water roll off angle after exposure to a range of environmental and mechanical stress tests. The coating was shown to be highly resistant to damp heat and thermal cycling. However, it was degraded by UV exposure and damaged during abrasion tests. The coating was also exposed to outdoor testing to compare the laboratory results with real performance degradation.
关键词： coating degradation,water contact angle,anti-soiling coating,hydrophobic coating
更新于2025-09-04 15:30:14
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Mixed-Phase (2H and 1T) MoS2 Catalyst for a Highly Efficient and Stable Si Photocathode
摘要： We describe the direct formation of mixed-phase (1T and 2H) MoS2 layers on Si as a photocathode via atomic layer deposition (ALD) for application in the photoelectrochemical (PEC) reduction of water to hydrogen. Without typical series-metal interfaces between Si and MoS2, our p-Si/SiOx/MoS2 photocathode showed efficient and stable operation in hydrogen evolution reactions (HERs). The resulting performance could be explained by spatially genuine device architectures in three dimensions (i.e., laterally homo and vertically heterojunction structures). The ALD-grown MoS2 overlayer with the mixed-phase 1T and 2H homojunction passivates light absorber and surface states and functions as a monolithic structure for effective charge transport within MoS2. It is also beneficial in the operation of p-i-n heterojunctions with inhomogeneous barrier heights due to the presence of mixed-phase cocatalysts. The effective barrier heights reached up to 0.8 eV with optimized MoS2 thicknesses, leading to a 670 mV photovoltage enhancement without employing buried Si p-n junctions. The fast-transient behaviors via light illumination show that the mixed-phase layered chalcogenides can serve as efficient cocatalysts by depinning the Fermi levels at the interfaces. A long-term operation of ~70 h was also demonstrated in a 0.5 M H2SO4 solution.
关键词： pinch-off effect,molybdenum disulfide,photoelectrochemical water splitting (PEC),p-i-n heterojunction,atomic layer deposition (ALD)
更新于2025-09-04 15:30:14
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Reduced Current Sensor Based Solar PV Fed Motion Sensorless Induction Motor Drive for Water Pumping
摘要： This paper proposes a solar photovoltaic (PV) array fed induction motor (IM) drive operated water pumping system with an speed adaptive estimator. It focuses on the implementation of a space vector modulation (SVM) of voltage source inverter (VSI) without current sensors. The motor phase currents are estimated from the DC link current. The VSI is used for maximum power tracking and to drive an IM. A generalized integrator based flux adaptation approach is used to improve the drive performance. Moreover, a modified model reference adaptive system (MRAS) based speed estimation with rotor fluxes and stationary frame currents enhances its stability throughout the operating range. A modified algorithm based on incremental-conductance (InC) is proposed for maximum power point (MPP), which is used for peak power tracking at each insolation with a technique to control flow-rate. The overall system incorporating a single-stage PV powered space vector modulation (SVM) based VSI fed IM driven water pump is modeled and its performance is simulated in MATLAB/Simulink environment. The appropriateness of proposed system is verified experimentally on a prototype developed in the laboratory under various operating conditions.
关键词： Incremental-conductance (InC) algorithm,Speed adaptation,PV array,Induction motor drive (IMD),Water pump,Current sensor reduction,Field-oriented control (FOC)
更新于2025-09-04 15:30:14
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Strategic Selection of the Oxygen Source for Low Temperature-Atomic Layer Deposition of Al <sub/>2</sub> O <sub/>3</sub> Thin Film
摘要： The influence of two oxygen source types, H2O and O3, on residual C-related impurities in atomic-layer-deposited (ALD) Al2O3 film is systematically examined. ALD Al2O3 film grown using H2O contains negligible C-related impurities irrespective of growth temperature. However, the C-related impurity in film grown using O3 exhibits strong dependence on growth temperature; only Al carbonate (Al-CO3) is present in film grown at 300 °C, but C-related impurities with lower oxidation states, such as Al-COOH and Al-CHO, appear as the temperature decreases to 150 °C. This suggests that the reactivity of O3 and H2O in the ALD process has a different temperature dependence; from a residual impurity perspective, compared to O3, H2O is a beneficial oxygen source for low temperature processes. Electrical properties, such as charge trapping and gate leakage current, are also examined. For a growth temperature of 300 °C, the film grown using O3 is slightly superior to the film grown using H2O due to its high film density. However, the film grown using H2O demonstrates better electrical characteristics at low growth temperature, 150 °C.
关键词： oxygen source,atomic layer deposition,low temperature process,ozone,water
更新于2025-09-04 15:30:14
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ALD of Space-Efficient SnO2 Underlayers for BiVO4 Host-Guest Architectures for Photoassisted Water Splitting
摘要： Bismuth vanadate (BiVO4) is promising for solar-assisted water splitting. The performance of BiVO4 is limited by charge separation for >70 nm films or by light harvesting for <700 nm films. To resolve this mismatch, host-guest architectures use thin film coatings on 3D scaffolds. Recombination, however, is exacerbated at the extended host-guest interface. Underlayers are used to limit this recombination with a host-underlayer-guest series. Such underlayers consume precious pore volume where typical SnO2 underlayers are optimized with 65-80 nm. Here we examine conformal and ultrathin SnO2 underlayers with low defect density produced by atomic layer deposition (ALD). This shifts the optimized thickness to just 8 nm with significantly improved space-efficiency. The materials chemistry thus determines the dimension optimization. Lastly, we demonstrate host-guest architectures with an applied bias photon-to-charge efficiency of 0.71%, a new record for a photoanode absorber prepared by ALD.
关键词： host-guest architectures,solar-assisted water splitting,atomic layer deposition,SnO2 underlayers,Bismuth vanadate
更新于2025-09-04 15:30:14