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New Insights for Detecting and Deriving Thermal Properties of Lava Flow Using Infrared Satellite during 2014–2015 Effusive Eruption at Holuhraun, Iceland
摘要： A new lava ?eld was formed at Holuhraun in the Icelandic Highlands, north of Vatnaj?kull glacier, in 2014–2015. It was the largest effusive eruption in Iceland for 230 years, with an estimated lava bulk volume of ~1.44 km3 covering an area of ~84 km2. Satellite-based remote sensing is commonly used as preliminary assessment of large scale eruptions since it is relatively ef?cient for collecting and processing the data. Landsat-8 infrared datasets were used in this study, and we used dual-band technique to determine the subpixel temperature (Th) of the lava. We developed a new spectral index called the thermal eruption index (TEI) based on the shortwave infrared (SWIR) and thermal infrared (TIR) bands allowing us to differentiate thermal domain within the lava ?ow ?eld. Lava surface roughness effects are accounted by using the Hurst coef?cient (H) for deriving the radiant ?ux (Φ rad) and the crust thickness (?h). Here, we compare the results derived from satellite images with ?eld measurements. The result from 2 December 2014 shows that a temperature estimate (1096 ?C; occupying area of 3.05 m2) from a lava breakout has a close correspondence with a thermal camera measurement (1047 ?C; occupying area of 4.52 m2). We also found that the crust thickness estimate in the lava channel during 6 September 2014 (~3.4–7.7 m) compares closely with the lava height measurement from the ?eld (~2.6–6.6 m); meanwhile, the total radiant ?ux peak is underestimated (~8 GW) compared to other studies (~25 GW), although the trend shows good agreement with both ?eld observation and other studies. This study provides new insights for monitoring future effusive eruption using infrared satellite images.
关键词： TEI,radiant ?ux,SWIR,crust thickness,TIR,dual-band,Landsat-8,effusive eruption,Hurst coef?cient
更新于2025-09-04 15:30:14
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Angle-resolved photoelectron spectroscopy and scanning tunnelling spectroscopy studies of the endohedral fullerene Li@C <sub/>60</sub>
摘要： Gas phase photoelectron spectroscopy (Rydberg Fingerprint Spectroscopy), TDDFT calculations and low temperature STM studies are combined to provide detailed information on the properties of the di?use, low-lying Rydberg-like SAMO states of isolated Li@C60 endohedral fullerenes. The presence of the encapsulated Li is shown by the calculations to produce a signi?cant distortion of the lowest-lying S- and P-SAMOs that is dependent on the position of the Li inside the fullerene cage. Under the high temperature conditions of the gas phase experiments, the Li is mobile and able to access di?erent positions within the cage. This is accounted for in the comparison with theory that shows a very good agreement of the photoelectron angular distributions, allowing the symmetry of the observed SAMO states to be identi?ed. When adsorbed on a metal substrate at low temperature, a strong interaction between the low-lying SAMOs and the metal substrate moves these states to energies much closer to the Fermi energy compared to the situation for empty C60 while the Li remains frozen in an o?-centre position.
关键词： Rydberg Fingerprint Spectroscopy,SAMO states,TDDFT calculations,Li@C60,STM studies
更新于2025-09-04 15:30:14
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SAR Automatic Target Recognition Using a Roto-Translational Invariant Wavelet-Scattering Convolution Network
摘要： The algorithm of synthetic aperture radar (SAR) for automatic target recognition consists of two stages: feature extraction and classification. The quality of extracted features has significant impacts on the final classification performance. This paper presents a SAR automatic target classification method based on the wavelet-scattering convolution network. By introducing a deep scattering convolution network with complex wavelet filters over spatial and angular variables, robust feature representations can be extracted across various scales and angles without training data. Conventional dimension reduction and a support vector machine classifier are followed to complete the classification task. The proposed method is then tested on the moving and stationary target acquisition and recognition (MSTAR) benchmark data set and achieves an average accuracy of 97.63% on the classification of ten-class targets without data augmentation.
关键词： automatic target classification (ATR),wavelet transform,scattering convolution network,roto-translation invariance,synthetic aperture radar
更新于2025-09-04 15:30:14
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Efficient bifunctional vanadium doped Ni3S2 nanorod array for overall water splitting
摘要： Electrochemical water splitting, allowing energy conversion from renewable resources into non-polluting chemical fuels, is vital in the future sustainable energy system, and great efforts have been paid on developing efficient and cheap bifunctional electrocatalysts. Herein we report a bifunctional vanadium doped Ni3S2 nanorod array electrode for overall water splitting in alkaline media. To afford a catalytic current of 10 mA cm-2, the designed V-Ni3S2 electrode only requires the overpotentials of 133 mV for hydrogen evolution and 148 mV for oxygen generation, meanwhile showing high long-term stability. The excellent catalytic properties are assigned to the V dopants and geometric advantages of nanorod array. The V-Ni3S2 electrodes are simultaneously utilized as cathode and anode in one two-electrode cell to function overall water splitting, exhibiting a cell voltage of 1.421 V at 10 mA cm-2. The water splitting in this cell can also be feasibly driven by a single-cell AA battery (1.5 V). Our report shows substantial advancement in the exploration of efficient bifunctional electrocatalysts for water splitting.
关键词： bifunctional electrocatalysts,water splitting,nanorod array,alkaline media,vanadium doped Ni3S2
更新于2025-09-04 15:30:14
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Ag nanoparticle decorated MnO <sub/>2</sub> flakes as flexible SERS substrates for rhodamine 6G detection
摘要： Smart design of advanced substrates for surface-enhanced Raman scattering (SERS) activity is challenging but vital. Herein, we synthesized a new kind of AgNPs/MnO2@Al flexible substrate as a SERS substrate for the detection of the analyte rhodamine 6G (R6G). The fabrication of porous MnO2 nanoflakes on Al foil was conducted via a facile hydrothermal strategy. Owing to the large active surface area of the MnO2 nanoflakes, the Ag nanoparticles were immobilized and displayed superior SERS performance with a low detection concentration of 1 × 10?6 M for R6G. In addition, the SERS performance was found to be strongly related to the morphology of the MnO2@Al substrate material. Our smart design may provide a new method of construction for other advanced SERS substrates for the detection of R6G.
关键词： Ag nanoparticles,rhodamine 6G detection,MnO2 flakes,flexible SERS substrates
更新于2025-09-04 15:30:14
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Monitoring Crop Evapotranspiration and Crop Coefficients over an Almond and Pistachio Orchard Throughout Remote Sensing
摘要： In California, water is a perennial concern. As competition for water resources increases due to growth in population, California’s tree nut farmers are committed to improving the efficiency of water used for food production. There is an imminent need to have reliable methods that provide information about the temporal and spatial variability of crop water requirements, which allow farmers to make irrigation decisions at field scale. This study focuses on estimating the actual evapotranspiration and crop coefficients of an almond and pistachio orchard located in Central Valley (California) during an entire growing season by combining a simple crop evapotranspiration model with remote sensing data. A dataset of the vegetation index NDVI derived from Landsat-8 was used to facilitate the estimation of the basal crop coefficient (Kcb), or potential crop water use. The soil water evaporation coefficient (Ke) was measured from microlysimeters. The water stress coefficient (Ks) was derived from airborne remotely sensed canopy thermal-based methods, using seasonal regressions between the crop water stress index (CWSI) and stem water potential (Ψstem). These regressions were statistically-significant for both crops, indicating clear seasonal differences in pistachios, but not in almonds. In almonds, the estimated maximum Kcb values ranged between 1.05 to 0.90, while for pistachios, it ranged between 0.89 to 0.80. The model indicated a difference of 97 mm in transpiration over the season between both crops. Soil evaporation accounted for an average of 16% and 13% of the total actual evapotranspiration for almonds and pistachios, respectively. Verification of the model-based daily crop evapotranspiration estimates was done using eddy-covariance and surface renewal data collected in the same orchards, yielding an R2 ≥ 0.7 and average root mean square errors (RMSE) of 0.74 and 0.91 mm·day?1 for almond and pistachio, respectively. It is concluded that the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions.
关键词： thermal images,pistachio,almond,evapotranspiration,CWSI,remote sensing
更新于2025-09-04 15:30:14
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Phase behavior of main-chain liquid crystalline polymer networks synthesized by alkyne–azide cycloaddition chemistry
摘要： Liquid crystalline polymer networks (LCNs) couple polymer chain organization to molecular ordering, the switching of which has been shown to impart stimuli-responsive properties, including actuation and one-way shape memory, to the networks. While LCNs have long been proposed as artificial muscles, recent reports have also suggested potential as dynamic biomaterial substrates. In contrast to many existing LCNs synthesized using hydrophobic spacers, this work investigates networks synthesized using more hydrophilic spacers to promote interaction with water. A challenge with such materials is liquid crystalline phases could be disrupted in hydrated networks. This work thus investigates the impact of polyether spacers and mesogen composition on the phase behavior of LCNs. Main-chain LCNs were synthesized using alkyne–azide cycloaddition ("click" chemistry), where two different mesogens (5yH and 5yMe) and a non-LC monomer (5yTe) were coupled with one of two different polyether spacers, poly(ethylene glycol) and poly(propylene glycol), and a crosslinker. The chemistry led to high gel fraction materials, the workup of which resulted in networks that displayed no difference in cellular toxicity due to leachable components compared to tissue culture plastic control. Calorimetric analysis, dynamic mechanical analysis, and X-ray scattering revealed the LC microstructure and temperature-responsive properties of the networks. The use of low molecular weight polyether spacers was found to prevent their crystallization within the LC network, and adjusting mesogen composition to enhance its LC phase stability allowed the use of spacers with larger molecular weights and pendant groups. Hydrated networks were found to rearrange their structure compared to dry networks, while maintaining their LC phases. Like other crosslinked LC materials, the networks display shape changes (actuation) that are tied to changes in LC ordering. The result is a new synthetic approach for polydomain networks that form stable LC phases that are tailorable using polyether spacers and may enable future application as hydrated, stimuli-responsive materials.
关键词： Liquid crystalline polymer networks,Phase behavior,Alkyne–azide cycloaddition,Stimuli-responsive materials,Polyether spacers
更新于2025-09-04 15:30:14
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Sea Ice Albedo from MISR and MODIS: Production, Validation, and Trend Analysis
摘要： The Multi-angle Imaging SpectroRadiometer (MISR) sensor onboard the Terra satellite provides high accuracy albedo products. MISR deploys nine cameras each at different view angles, which allow a near-simultaneous angular sampling of the surface anisotropy. This is particularly important to measure the near-instantaneous albedo of dynamic surface features such as clouds or sea ice. However, MISR’s cloud mask over snow or sea ice is not yet sufficiently robust because MISR’s spectral bands are only located in the visible and the near infrared. To overcome this obstacle, we performed data fusion using a specially processed MISR sea ice albedo product (that was generated at Langley Research Center using Rayleigh correction) combining this with a cloud mask of a sea ice mask product, MOD29, which is derived from the MODerate Resolution Imaging Spectroradiometer (MODIS), which is also, like MISR, onboard the Terra satellite. The accuracy of the MOD29 cloud mask has been assessed as >90% due to the fact that MODIS has a much larger number of spectral bands and covers a much wider range of the solar spectrum. Four daily sea ice products have been created, each with a different averaging time window (24 h, 7 days, 15 days, 31 days). For each time window, the number of samples, mean and standard deviation of MISR cloud-free sea ice albedo is calculated. These products are publicly available on a predefined polar stereographic grid at three spatial resolutions (1 km, 5 km, 25 km). The time span of the generated sea ice albedo covers the months between March and September of each year from 2000 to 2016 inclusive. In addition to data production, an evaluation of the accuracy of sea ice albedo was performed through a comparison with a dataset generated from a tower based albedometer from NOAA/ESRL/GMD/GRAD. This comparison confirms the high accuracy and stability of MISR’s sea ice albedo since its launch in February 2000. We also performed an evaluation of the day-of-year trend of sea ice albedo between 2000 and 2016, which confirm the reduction of sea ice shortwave albedo with an order of 0.4–1%, depending on the day of year and the length of observed time window.
关键词： calibration,MODIS,Sea ice,albedo,climate change,MISR
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Metallic Metasurface Antennas for Space
摘要： In metasurface (MTS) antennas, a surface-wave (SW) is gradually radiated by modulating an equivalent reactance tensor in the aperture plane. Such modulation results in the (-1) indexed Floquet mode entering the visible region, thus becoming a leaky-wave (LW) mode with curvilinear phase-contour. This paper explores the use of a class of metallic MTS in the synthesis of the reactance tensor required to obtain the objective radiation patterns. The absence of dielectric is useful to survive harsh environments in space exploration. The proposed element consists of a metallic cylinder with elliptical cross-section, placed on a ground plane and arranged in a square lattice with sub-wavelength unit-cell side. We have applied this structure in the design of a right-handed circularly polarized antenna, with a broadside pencil beam in the Ka band. The obtained performance has been veri?ed by full-wave simulations. A prototype has been manufactured and measurements will be available at the time of the conference.
关键词： surface waves,leaky waves,metasurfaces,circular polarization,millimeter waves,Ka band
更新于2025-09-04 15:30:14
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[Institution of Engineering and Technology 12th European Conference on Antennas and Propagation (EuCAP 2018) - London, UK (9-13 April 2018)] 12th European Conference on Antennas and Propagation (EuCAP 2018) - Antennas for Space Instruments from GHz to THz
摘要： In this paper we present an overview of different antenna technologies for space-based instruments. We show that some of the designs that work well at gigahertz frequencies are difficult to implement at terahertz frequencies due to tight tolerance and rms surface finish requirements. We also show that antenna designs are dictated not only by the frequency of operations but also by the space platform of choice. In this paper, we also present ideas for low-profile terahertz antennas for implementation on SmallSat and CubeSat platforms.
关键词： silicon,micromachining,antenna,terahertz,low-profile,micro-lens
更新于2025-09-04 15:30:14