Assessing the impact of extreme droughts on dryland vegetation by multi-satellite solar-induced chlorophyll fluorescence

Satellite-estimated solar-induced chlorophyll fluorescence (SIF) is proven to be an effective indicator for dynamic drought monitoring, while the capability of SIF to assess the variability of dryland vegetation under water and heat stress remains challenging. This study presents an analysis of the responses of dryland vegetation to the worst extreme drought over the past two decades in Australia, using multi-source spaceborne SIF derived from the Global Ozone Monitoring Experiment-2 (GOME-2) and TROPOspheric Monitoring Instrument (TROPOMI). Vegetation functioning was substantially constrained by this extreme event, especially in the interior of Australia, in which there was hardly seasonal growth detected by neither satellite-based observations nor tower-based flux measurements. At a 16-day interval, both SIF and enhanced vegetation index (EVI) can timely capture the reduction at the onset of drought over dryland ecosystems. The results demonstrate that satellite-observed SIF has the potential for characterizing and monitoring the spatiotemporal dynamics of drought over water-limited ecosystems, despite coarse spatial resolution coupled with high-retrieval noise as compared with EVI. Furthermore, our study highlights that SIF retrieved from TROPOMI featuring substantially enhanced spatiotemporal resolution has the promising capability for accurately tracking the drought-induced variation of heterogeneous dryland vegetation

Enhancing Thermoelectric Performance in Single-Crystal-Like Semiconducting Films by Tuning the Carrier Scattering Mechanism

College of Engineering-Interdepartmenta

Analyses of canopy photosynthesis derived from three-dimensional model simulations of sun-induced chlorophyll fluorescence

University of Technology Sydney. Faculty of Science.Recently, measurements of sun-induced chlorophyll fluorescence (SIF) has become a new approach to estimate vegetation photosynthetic activity and detect vegetation stress. However, the environmental factors controlling SIF largely remain unknown for different vegetation biome types. In addition, SIF measured at the top of canopy (TOC) is confounded by interactions between solar radiation and vertical canopy structures. Hence, development of three-dimensional (3-D) radiative transfer models, capable of simulating SIF, would be of immense benefit to test and verify various hypothesises. The goal of this thesis is to develop a new 3-D SIF model and apply it to assess the relationship between SIF and plant photosynthetic activity across different spatial and temporal scales. Specifically, I (1) developed a new SIF module for FLiES (Forest Light Environmental Simulator) model (FLiES-SIF) and validated it with SIF observations at the seasonal scale; (2) partitioned SIF signals to overstory and understory layers by using FLiES-SIF, and then analysed the impact of solar radiation and canopy structure on understory SIF; (3) normalized the OCO-2 SIF dataset at nadir, hotspot and darkspot viewing directions by using the FLiES model, and assessed the relationship between SIF and GPP; and (4) identified that SIF observed at the top of canopy was strongly influenced by understory reflectance and canopy structure. Results showed (1) the TOC SIF simulated by FLiES-SIF was closely correlated with SIF observations at a forest test site, and its performance was better than a 1-D model (Soil Canopy Observation, Photochemistry and Energy fluxes, SCOPE) and 3-D model (Discrete anisotropic radiative Transfer, DART); (2) the SIF emitted from understory contributed more than 51% to the total SIF in the wet season of a tropical savanna site, however, it only accounted for less than 10% of total SIF in an evergreen forest site; (3) SIF was most correlated with GPP in the hotspot direction, and the normalised SIF yield could better explain the variations of light use efficiency (LUE); (4) compared to canopy structure and leaf properties, the understory reflectance was the primary factor influencing the observed SIF at the top of the canopy. This thesis highlights the advantage of FLiES-SIF in capturing vegetation photosynthetic activities of ecosystems with complex canopy structures. This will significantly improve our understanding of vegetation responses to climate change, and this model can be implement for numerous related purposes

Estimating Bluetooth mac scanner based pedestrian flow characteristic by taking the through pedestrian flow as a case study

The Bluetooth scanner has been widely used as vehicle traffic detector in recent years. A new solution based on the Bluetooth scanner has been deliver to detect pedestrian traffic by estimating the pedestrian flow characteristic. The equipment is tuned to scan Bluetooth devices more frequently. Consequentially, the unique Bluetooth MAC can be detected multiple times by the scanner. The numeric simulation also suggests median detection is the chosen one to calculate traveling time. In this study, Bluetooth MAC scanning, as a non-intrusive technology, is tested in a pedestrian transfer tunnel, including antenna compatibility working within buildings. The penetration rate also increases slightly. Finally, the proposed solution offers a mature technology for pedestrian study, integrating scanner configuration, antenna selection and the traveling time calculation method

Estimating Bluetooth mac scanner based pedestrian flow characteristic by taking the through pedestrian flow as a case study

The Bluetooth scanner has been widely used as vehicle traffic detector in recent years. A new solution based on the Bluetooth scanner has been deliver to detect pedestrian traffic by estimating the pedestrian flow characteristic. The equipment is tuned to scan Bluetooth devices more frequently. Consequentially, the unique Bluetooth MAC can be detected multiple times by the scanner. The numeric simulation also suggests median detection is the chosen one to calculate traveling time. In this study, Bluetooth MAC scanning, as a non-intrusive technology, is tested in a pedestrian transfer tunnel, including antenna compatibility working within buildings. The penetration rate also increases slightly. Finally, the proposed solution offers a mature technology for pedestrian study, integrating scanner configuration, antenna selection and the traveling time calculation method

Phase evolution of a novel Al–Zn–Mg–Cu–Zr–Sm alloy during homogenization annealing treatment

The effects of pretreatment and homogenization on the microstructure of a new Al-6.7Zn-2.6Mg-2.0Cu-0.1Zr-0.3Sm alloy were investigated. The results show that severe dendritic segregation is visible at the grain boundaries of the as-cast microstructure, which consists of the η (Mg (Zn, Cu, Al) _2 ), Al _10 Cu _7 Sm _2 and Fe-rich phases. Besides, some small η and needle-shaped θ (Al _2 Cu) phases are distributed inside of the grains. After pretreatment at 400 °C for 10 h, the η phase and θ phase in the grains are dissolved, and Al _3 Zr particles are precipitated inside of the grains by homogeneous nucleation. However, dendritic segregation still exists at the grain boundaries. After homogenization annealing, the η phase present at the grain boundaries completely dissolves, and only a small number of Al _10 Cu _7 Sm _2 and Fe-rich phases remain. The alloy microstructure becomes more uniform and the volume fraction of residual eutectic decreases to 0.70% after homogenization annealing. The optimal homogenization processing is determined as 400 °C/10 h + 470 °C/24 h, which is in perfect accordance with the results obtained via homogenizing kinetic analysis

Crack-Insensitive Wearable Electronics Enabled Through High-Strength Kevlar Fabrics

Mechanical robustness is one of the key factors for future commercialization of wearable electronics. Wearable electronics are thin electronics constructed on flexible polymer or rubber substrates. Due to their thin geometry, wearable electronics are typically vulnerable under tearing or stretching, especially when cracks exist. This paper presents the designs and manufacturing of crack-insensitive wearable electronics realized through incorporating high-strength Kevlar fabrics. Manufacturing strategies of transfer printing prefabricated electronics onto Kevlar fabric with adhesion layer and dip coating constructed devices have been illustrated. The device examples include ultrathin single-crystalline Si-based photodiodes, organic photodetectors, and carbon nanotube-based supercapacitors. Systematic studies highlight the fabrication procedures, mechanical characterization, and device performance evaluation, and offer practical routes to realize robust crack-insensitive wearable electronics