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Identifying Emerging Reservoirs along Regulated Rivers Using Multi-Source Remote Sensing Observations
摘要： The number of reservoirs is rapidly increasing owing to the growth of the world’s economy and related energy and water needs. Yet, for the vast majority of reservoirs around the world, their locations and related information, especially for newly dammed reservoirs, are not readily available due to financial, political, or legal considerations. This study proposes an automated method of identifying newly dammed reservoirs from time series of MODIS-derived NDWI (normalized difference water index) images. Its main idea lies in the detection of abrupt changes in the NDWI time series that are associated with land-to-water conversion due to the reservoir impoundment. The proposed method is tested in the upper reach of the Yellow River that is severely regulated by constructed reservoirs. Our results show that five newly dammed reservoirs were identified in the test area during 2000–2018. Validated against high-resolution Google Earth imagery, our method is effective to determine both locations of the emerging medium-size reservoirs and the timing of their initial water impoundments. Such information then allows for a refined calculation of the reservoir inundation extents and storage capacities through the combination of higher-resolution Landsat imagery and SRTM DEM. The comparison of our estimated reservoir areas and capacities against documented information further indicates that the integration of multi-mission remote sensing data may provide useful information for understanding reservoir operations and impacts on river discharges. Our method also demonstrates a potential for regional or global inventory of emerging reservoirs, which is crucial to assessing human impacts on river systems and the global water cycle.
关键词： reservoir,time series,NDWI,remote sensing,BFAST,Yellow River
更新于2025-09-23 15:23:52
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Automatic fracture–vug identification and extraction from electric imaging logging data based on path morphology
摘要： We present a path morphology method to separate total rock pore space into matrix, fractures and vugs and derive their pore structure spectrum. Thus, we can achieve fine pore evaluation in fracture–vug reservoirs based on electric imaging logging data. We automatically identify and extract fracture–vug information from the electric imaging images by adopting a path morphological operator that remains flexible enough to fit rectilinear and slightly curved structures because they are independent of the structuring element shape. The Otsu method was used to extract fracture–vug information from the background noise caused by the matrix. To accommodate the differences in scale and form of the different target regions, including fracture and vug path, operators with different lengths were selected for their recognition and extraction at the corresponding scale. Polynomial and elliptic functions are used to fit the extracted fractures and vugs, respectively, and the fracture–vug parameters are deduced from the fitted edge. Finally, test examples of numerical simulation data and several measured well data have been provided for the verification of the effectiveness and adaptability of the path morphology method in the application of electric imaging logging data processing. This also provides algorithm support for the fine evaluation of fracture–vug reservoirs.
关键词： Path morphology,Electric imaging logging,Fracture–vug reservoir,Image automatic identification
更新于2025-09-23 15:23:52
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Fiber Bragg grating-based experimental and numerical investigations of CO <sub/>2</sub> migration front in saturated sandstone under subcritical and supercritical conditions
摘要： Carbon dioxide (CO2) can be at risk of leakage during its storage in deep saline aquifers due to stress field changes in the reservoir. The aim of this study was to investigate the effects of CO2 injection pressure on dynamic strain response of the reservoir and the CO2 migration process. A series of core flooding experiments was performed with the-state-of-art fiber Bragg grating sensors. The results show that the surface strain response was linearly correlated with CO2 injection pressure. Carbon dioxide migration velocity can be estimated from the strain response time differences among three gratings. The migration velocity of supercritical CO2 is higher than that of liquid CO2 but lower than gaseous CO2. Finally, numerical simulation was applied to model the CO2 migration process and the simulated values were compatible with those of experiments.
关键词： reservoir sandstone,core flooding,CO2 geological storage,CO2 migration front,fiber Bragg grating,strain response
更新于2025-09-23 15:23:52
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Effects of spectral diffusion on the nonlinear optical properties in two- and three-state quantum systems in a four-wave mixing signal
摘要： Effects of spectral diffusion on the third-order nonlinear susceptibility for two- and three-level quantum systems, immersed in a thermal reservoir, are evaluated with a four-wave mixing (FWM) signal through the density matrix formalism. For this, inhomogeneously broadened two- and three-level quantum systems are used. In these models, the distribution of natural frequencies follows a Lorentzian function. The absorptive and dispersive nonlinear optical responses are determined for the considered quantum models. The results presented in this work show potential applications in the development of optical switches and provide a potential method to measure spectral diffusion relaxation times in three-level quantum systems.
关键词： reservoir state,three-level quantum system,Spectral diffusion,cross-relaxation,four-wave mixing
更新于2025-09-23 15:22:29
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Proximal VIS-NIR spectrometry to retrieve substance concentrations in surface waters using partial least squares modelling
摘要： Many water quality parameters such as concentrations of suspended matter, nutrients and algae directly or indirectly change the electromagnetic reflectance and transmission properties of surface water bodies. Optical measurement approaches have shown great potential to partially substitute water sampling and laboratory analyses, but are obstructed by limited flexibility or high maintenance demands. In order to overcome these problems and to bridge the gap between in situ and remote sensing measurements, the use of close-range, above-surface reflectance measurements in the VIS-NIR domain to measure water quality parameters in surface water bodies was investigated. Remote sensing reflectance in a 1 m3 water tank with increasing, known concentrations of suspended solids was measured. A partial least squares model was trained to predict concentrations from reflectance curves, which performed well, considering the wide range of concentrations and illumination conditions (R2cal ? 0.96, R2val ? 0.97). The approach was then transferred to the field and further parameters were tested. Using a semi-autonomous spectrometer mounted to a boom stand on a motor boat, we traced substance concentrations in close intervals along a longitudinal gradient from inflow to dam in a drinking water reservoir in Brazil. The method is suitable for parameters directly influencing the reflection properties of the water body (e.g. suspended solids (R2cal ? 0.93), chlorophyll-a (R2cal ? 0.74)), or for parameters closely related to those (e.g. total phosphorus (R2cal ? 0.97)). For chemical oxygen demand, the method is not well suited (R2cal ? 0.14, R2val ? 0.45). Once calibrated to the local conditions, the spectrometer can be used stationary or on moving platforms to map and monitor surface waters. The integration of the procedure into acoustic and imaging techniques is further investigated.
关键词： water quality,suspended solids,hyperspectral,reservoir,partial least squares,proximal sensing
更新于2025-09-23 15:22:29
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Buchwald-Hartwig Coupling at the Naphthalenediimide Core: Access to Dendritic, Panchromatic NIR Absorbers with Exceptionally Low Band Gap
摘要： The ?rst successful Buchwald?Hartwig reaction at the naphthalenediimide core is reported, leading to the coupling of diverse secondary aromatic amines including dendritic donors. The G1-dendrimer-based donor exhibit blackish color, providing access to black absorbing systems. λ onset values up to 1070 nm was achieved, which is the maximum from a single NDI sca?old. These dyes also manifest multielectron reservoir properties. A total of eight-redox states with a band gap of ～0.95 eV was accomplished.
关键词： dendritic donors,low band gap,black absorbing systems,Buchwald?Hartwig reaction,naphthalenediimide,multielectron reservoir properties,NIR absorbers
更新于2025-09-23 15:21:21
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Hybrid of quantum dots for interfacial tension reduction and reservoir alteration wettability for enhanced oil recovery (EOR)
摘要： Nanoparticle stabilized emulsions in enhanced oil recovery are more attractive and practical than conventional emulsions which stabilized by colloidal particles and different surfactants due to their advantages and special characteristics such as high stability in harsh condition, move long distance in reservoirs without high retention due to small size of nanoparticles. Only one third of original oil in place (OIP) is usually produced and two third of oil in place will be trapped to reservoir rockthus suitable chemical enhanced oil recovery (C-EOR) methods should be used. In this research, we have suggested a novel, economical and commercial method for synthesis N-doped graphene quantum dots (N-GQDs)/MoS2 quantum dots (MQDs) nanohybrids for preparing different percentage of Nanoemulsions which can reduce alterfacial tension significantly so it can used for Enhanced Oil Recovery (EOR) application. MoO3 material was used as a base of MQDs. MQDs was synthesized via exfoliation of MoS2 nanoparticles by Butyl lithium under N2 atmosphere condition. N-GQDs were synthesized by citric acid and urea materials via hydrothermal method. GQDs/MQDs were prepared via a simple sol-gel method for 5 h string. Synthetic materials were characterized with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV–visible absorption, Scanning Microscopic Electron (SEM), EDX profile and mapping, Transmission electron microscopy (TEM), High Resolution Transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). Then, emulsions were prepared with two different cationic and anionic surfactants and the stability and morphology of emulsion droplets were investigated in condition close to reservoir environment. Our results show that 10% GQDs/MQDs in cationic surfactant and 50% GQDs/MQDs in anionic surfactant have good stability and very small and fine emulsion droplets in simulated reservoir conditions in laboratory. The Interfacial Tension (IFT) measurement shows N70% improvement which indicates the high ability of these nanohybrids in reducing the surface tension than previous nanohybrids. Contact angle values show that these nanohybrids can alter the wettability of reservoir rock from oil-wet to water-wet so the trapped oil in the porous region of rock can be easily extracted in the presence of a layer of these nanohybrids. Furthermore, according to the results of altering the density and viscosity of nanohybrids, these are not as limiting parameters and only about 1% increasing observed for density and viscosity, respectively. Coreflooding test revealed the high oil recovery efficiency (22%) at very low nanofluid concentration (0.01 wt%).
关键词： Molybdenum disulfide quantum dots,Graphene quantum dots,Nanohybrids emulsion,Enhanced oil recovery (EOR),Quantum dot hybrids,Rock reservoir alteration wettability
更新于2025-09-23 15:21:01
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High-Speed Neuromorphic Reservoir Computing Based on a Semiconductor Nanolaser with Optical Feedback Under Electrical Modulation
摘要： A high-speed neuromorphic reservoir computing system based on a semiconductor nanolaser with optical feedback (SNL-based RC) under electrical modulation is proposed for the first time and demonstrated numerically. A Santa-Fe chaotic time series prediction task is employed to quantify the prediction performance of the SNL-based RC system. The effects of the Purcell cavity-enhanced spontaneous emission factor F and the spontaneous emission coupling factor β on the proposed RC system are analyzed extensively. It is found that, in general, increased F and β extend the range of good prediction performance of the SNL-based RC system. Moreover, the influences of bias current and feedback phase are also considered. Due to the ultra-short photon lifetime in SNL, the information processing rate of the SNL-based RC system reaches 10Gpbs. The proposed high-speed SNL-based RC system in this paper provides theoretical guidelines for the design of RC-based integrated neuromorphic photonic systems.
关键词： spontaneous emission coupling factor,Purcell factor,reservoir computing,Semiconductor nanolaser,delay systems
更新于2025-09-23 15:21:01
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Estimating the Optical Properties of Inorganic Matter-Dominated Oligo-to-Mesotrophic Inland Waters
摘要： Many studies over the years have focused on bio-optical modeling of inland waters to monitor water quality. However, those studies have been conducted mainly in eutrophic and hyper-eutrophic environments dominated by phytoplankton. With the launch of the Ocean and Land Colour Instrument (OLCI)/Sentinel-3A in 2016, a range of bands became available including the 709 nm band recommended for scaling up these bio-optical models for productive inland waters. It was found that one category of existing bio-optical models, the quasi-analytical algorithms (QAAs), when applied to colored dissolved organic matter (CDOM) and detritus-dominated waters, produce large errors. Even after shifting the reference wavelength to 709 nm, the recently re-parameterized QAA versions could not accurately retrieve the inherent optical properties (IOPs) in waterbodies dominated by inorganic matter. In this study, three existing versions of QAA were implemented and proved inefficient for the study site. Therefore, several changes were incorporated into the QAA, starting with the re-parameterization of the empirical steps related to the total absorption coefficient retrieval. The re-parameterized QAA, QAAOMW showed a significant improvement in the mean absolute percentage error (MAPE). MAPE decreased from 58.05% for existing open ocean QAA (QAALv5) to 16.35% for QAAOMW. Considerable improvement was also observed in the estimation of the absorption coefficient of CDOM and detritus from a MAPE of 91.05% for QAALv5 to 18.87% for QAAOMW. The retrieval of the absorption coefficient of phytoplankton (aφ) using the native form of QAA proved to be inaccurate for the oligo-to-mesotrophic waterbody due to the low aφ returning negative predictions. Therefore, a novel approach based on the normalized aφ was adopted to maintain the spectral shape and retrieve positive values, resulting in an improvement of 119% in QAAOMW. Further tuning and scale-up of QAAOMW to OLCI bands will aid in monitoring water resources and associated watershed processes.
关键词： water quality,bio-optics,quasi-analytical algorithm,Brazilian reservoir,inland waters,inherent optical properties
更新于2025-09-19 17:15:36
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Potential of floating photovoltaic plant in a tropical reservoir in Brazil
摘要： The increasing global demand for electricity has led to a significant increase in the search for low-impact alternative sources, with solar photovoltaic being identified as one of the most feasible options. However, photovoltaic power plants require large ground areas, which represent a major constraint. If the panels are installed on water bodies, this restriction may be avoided. In this work, a simulation was performed to assess the potential of floating photovoltaic power generation in the tropical Gavi~ao reservoir, located in the Northeast of Brazil. A payback analysis indicated that the investment in construction of the system is fully recovered in eight years, and that water losses due to evaporation can be reduced by approximately 2.6 (cid:3) 106 m3/year, sufficient to supply roughly 50,000 people.
关键词： surface reservoir,floating photovoltaic plant,renewable energy
更新于2025-09-19 17:13:59