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Multi-componentization can further improve the heating resistance of Cu–Ni–Al alloys, enabling them to withstand more demanding situations. Unfortunately, the limited researches have been done on the wear and corrosion resistance of the heat-resistant Cu–Ni–Al alloys, resulting in the lack of relevant evidence in the practical application. In this work, a comparative study of differential types of trace element, Si (the stronger enthalpy interaction element), Sn (the weaker enthalpy interaction element) Cr or Zr (grain boundary strengthening element), effects on microstructure, wear and corrosion resistance will be done, Furthermore, the effect of different trace elements on the surface electron work function and electrochemical behavior of Cu–Ni–Al alloys is reflected by SPM surface potential model. The results indicate that the precipitation of dual nano-phase and accelerated precipitation of γ′ phase can be realized through the addition of Si, Sn, Cr and Zr, in which the value of δγ-γ′ increase sharply after adding Si and it is not conducive to the preservation of cuboidal γ′ phase. The addition of Si, Cr and Zr can improve electron work function distribution and mechanical property, wear, and corrosion resistance of the alloys, in which Si is more conducive to the improvement of wear resistance and mechanical properties of the alloy, while the alloy with Cr and Zr shows the excellent corrosion resistance. The addition of Sn will weaken the enthalpy interaction of the alloy system, reduce the electron work function of the alloy, and have adverse effects on the wear and corrosion resistance of the alloy.

The Chlorophyll-a (Chla) concentration is an important parameter characterizing the water quality of rivers and lakes. Satellite remote sensing provides new opportunities for the quantitative monitoring of Chla concentration in large-scale water bodies. In this study, Sentinel-2 satellite remote sensing data integrated on the Google Earth Engine (GEE) remote sensing big data platform are employed, along with hourly measured water quality site data, to establish a quantitative inversion model for Chla concentration water quality parameters in Jiujiang City within Jiangxi Province, China. The Chla concentration is estimated for each quarter from 2020 to 2022, and the spatial distribution is analyzed, revealing the changing trend of Chla concentration over the past three years. The key findings are as follows: (1) The quantitative inversion model for Chla concentration has been validated with measured data, achieving a model accuracy of 0.53; (2) The spatial inversion results of Chla concentration exhibit an increasing trend that is consistent with actual measurement site results; (3) Owing to the influence of human activities and the peak-low water level of rivers and lakes, Chla concentration shows a discernible seasonal variation pattern. This methodology offers a new perspective for analyzing the seasonal variation characteristics of Chla concentration in rivers and lakes, providing valuable insights for the sustainable management of river and lake water quality.

Urban lakes serve an indispensable role in maintaining the ecological balance of cities, ensuring flood safety, and providing recreational spaces for tourism. With the development of human activities and economic, the extent of urban lakes are inevitably influenced. Currently, the ability to detect detailed temporal changes in urban lake areas using high resolution data still has limitations. This study proposed a novel method by combining time series Gaofen-1 (GF-1) remote sensing data and random forest machine learning algorithm to explore the urban lakes change Zhushan Lake located in Wuhan. The research conducted the extraction of surface water for Zhushan Lake and its surrounding pit-ponds from 2013 to 2020. And then, a quantitative analysis of the characteristics and driving factors of lake changes is conducted. We find that (1) the accuracy of surface water extraction using the random forest classification method consistently exceeded 96%. The Kappa coefficient ranges from a minimum of 0.86 to a maximum of 0.99. (2) A noticeable decline was observed in the water areas of Zhushan Lake and its surrounding pit-ponds, predominantly along the northwestern shoreline and in the eastern pond regions. This decline is primarily attributed to pressures from building construction. The methodology proposed in this study is suitable for the area management of lakes in urban areas.

Feature matching plays a crucial role in 3D reconstruction to provide correspondences between overlapped images. The accuracy and efficiency of feature matching significantly impact the performance of 3D reconstruction. The widely used framework with the exhaustive nearest neighbor searching (NNS) between descriptors and RANSAC-based geometric estimation is, however, low-efficient and unreliable for large-scale UAV images. Inspired by indexing-based NNS, this paper implements an efficient feature matching method for large-scale images based on Cascade Hashing and local geometric constraints. Our proposed method improves upon traditional feature matching approaches by introducing a combination of image retrieval, data scheduling, and GPU-accelerated Cascade Hashing. Besides, it utilizes a local geometric constraint to filter matching results within a matching framework. On the one hand, the GPU-accelerated Cascade Hashing technique generates compact and discriminative hash codes based on image features, facilitating the rapid completion of the initial matching process, and significantly reducing the search space and time complexity. On the other hand, after the initial matching is completed, the method employs a local geometric constraint to filter the initial matching results, enhancing the accuracy of the matching results. This forms a three-tier framework based on data scheduling, GPU-accelerated Cascade Hashing, and local geometric constraints. We conducted experiments using two sets of large-scale UAV image data, comparing our method with SIFTGPU to evaluate its performance in initial matching, outlier rejection, and 3D reconstruction. The results demonstrate that our method achieves a feature matching speed 2.0 times that of SIFTGPU while maintaining matching accuracy and producing comparable reconstruction results. This suggests that our method holds promise for efficiently addressing large-scale image matching.

The presence of exceptionally old ice and relative ease of access make Antarctic blue-ice areas (BIAs) attractive paleoclimate archives. However, only a handful of BIAs, mostly situated in West Antarctica and along the Transantarctic Mountains, have been investigated for this purpose. Here, we present the age of surface ice from the Grove Mountains BIA in Princess Elizabeth Land, East Antarctica, determined by measuring 81Kr in the trapped air. Two samples yield an average age of 143-29+33 kyr. Together with the reported terrestrial age of a chondrite, we conclude that the Grove Mountains BIA holds considerable potential for paleoclimate studies.

Fog/cloud drops and aerosol liquid water are important sites for the transformations of atmospheric species, largely through reactions with photoformed oxidants such as the hydroxyl radical (⚫OH), singlet molecular oxygen (1O2∗), and oxidizing triplet excited states of organic matter (3C∗). Despite their importance, few studies have measured these oxidants or their seasonal variations. To address this gap, we collected ambient PM2.5 from Davis, California, over the course of a year and measured photooxidant concentrations and light absorption in dilute aqueous extracts. Mass absorption coefficients (MACs) normalized by dissolved organic carbon range from 0.4–3.8 m2 per gram C at 300 nm. Concentrations of ⚫OH, 1O2∗, and 3C∗ in the extracts range from (0.2–4.7) × 10−15 M, (0.7–45) × 10−13 M, and (0.03–7.9) × 10−13 M, respectively, with biomass burning brown carbon playing a major role in light absorption and the formation of 1O2∗ and 3C∗. Extrapolating photooxidant kinetics from our dilute particle extracts to concentrated aerosol liquid water (ALW) conditions gives an estimated ⚫OH concentration of 7 × 10−15 M and ranges for 1O2∗ and 3C∗ of (0.6–7) × 10−12 M and (0.2–1) × 10−12 M, respectively. Compared to the results in Kaur et al. (2019), our ALW predictions show roughly 10 times higher ⚫OH, up to 5 times higher 3C, and 1O2∗ concentrations that are lower by factors of 20–100. These concentrations suggest that 3C∗ and 1O2∗ in ALW dominate the processing of organic compounds that react quickly with these oxidants (e.g., phenols and furans, respectively), while ⚫OH is more important for less reactive organics.

Structure from Motion (SfM) is a 3D reconstruction framework that has achieved great success on large-scale Unmanned Aerial Vehicle (UAV) images. Due to the high time consumption of feature matching, a matching candidate subset is obtained by image retrieval to improve efficiency. Bag of Word (BoW) based image retrieval has been widely used in SfM systems, but the large number of local features and the high dimension of the BoW vector cause the retrieval method time-consuming. Vector of Locally Aggregated Descriptors (VLAD) and learning-based NetVLAD perform well in image retrieval, and these vector representation methods are evaluated in this study. After images are transformed into vectors, Nearest Neighbour (NN) searching methods like Brute-force and KD-Tree are used to find similar images. But as the number of images and the vector dimension increase, Approximate Nearest Neighbour (ANN) searching methods like Hierarchical Navigable Small World (HNSW) and Locality-Sensitive Hashing (LSH) are considered to replace NN searching to avoid efficiency degradation. These vector searching methods are also evaluated in this study. The test results demonstrate that the optimal method VLAD with HNSW can speed up about 100 times in finding matching candidate subset. A view graph that guides scene partition and sub-scene reconstruction in parallel SfM can be created by the optimal method. With this view graph construction method, the efficiency of SfM is significantly improved.

Dense matching plays an important role in 3D modeling from satellite images. Its purpose is to establish pixel-by-pixel correspondences between two stereo images. The most well-known algorithm is the semi-global matching (SGM), which can generate high-quality 3D models with high computational efficiency. Due to the complex coverage and imaging condition, SGM cannot cope with these situation well. In recent years, deep learning-based stereo matching has attracted wide attention and shown overwhelming benefits over traditional algorithms in terms of precision and completeness. However, existing models are usually evaluated by using close-ranging datasets. Thus, this study investigates the recent deep learning models and evaluate their performance on both close-ranging and satellite image datasets. The results demonstrate that deep learning network can better adapt to the satellite dataset than the typical SGM. Meanwhile, the generalization ability of deep learning-based models is still low for the real application at recent time.

The EPICA (European Project for Ice Coring in Antarctica) Dome C (EDC) ice core drilling in East Antarctica reaches a depth of 3260 m. The reference EDC chronology, the AICC2012 (Antarctic Ice Core Chronology 2012), provides an age vs. depth relationship covering the last 800 kyr (thousands of years), with an absolute uncertainty rising up to 8000 years at the bottom of the ice core. The origins of this relatively large uncertainty are twofold: (1) the δ18Oatm, δO2/N2 and total air content (TAC) records are poorly resolved and show large gaps over the last 800 kyr, and (2) large uncertainties are associated with their orbital targets. Here, we present new highly resolved δ18Oatm, δO2/N2 and δ15N measurements for the EDC ice core covering the last five glacial–interglacial transitions; a new low-resolution TAC record over the period 440–800 ka BP (ka: 1000 years before 1950); and novel absolute 81Kr ages. We have compiled chronological and glaciological information including novel orbital age markers from new data on the EDC ice core as well as accurate firn modeling estimates in a Bayesian dating tool to construct the new AICC2023 chronology. For the first time, three orbital tools are used simultaneously. Hence, it is possible to observe that they are consistent with each other and with the other age markers over most of the last 800 kyr (70 %). This, in turn, gives us confidence in the new AICC2023 chronology. The average uncertainty in the ice chronology is reduced from 1700 to 900 years in AICC2023 over the last 800 kyr (1σ). The new timescale diverges from AICC2012 and suggests age shifts reaching 3800 years towards older ages over marine isotope stages (MISs) 5, 11 and 19. But the coherency between the new AICC2023 timescale and independent chronologies of other archives (Italian Lacustrine succession from Sulmona Basin, Dome Fuji ice core and northern Alpine speleothems) is improved by 1000 to 2000 years over these time intervals.

In this paper, a valve piezoelectric pump structure is proposed, which provides a method for the cooling of metallurgical equipment and avoids the hidden danger of damage to key components due to long-term exposure to high temperatures. In this paper, the research results of simulated flow rate and test flow rate of valved piezoelectric pump are introduced. The results show that the flow rate of the pump is sensitive to the influence of driving voltage, and it has certain feasibility for the cooling of metallurgical equipment.

Aerosol liquid water (ALW) is a unique reaction medium, but its chemistry is poorly understood. For example, little is known of photooxidant concentrations – including hydroxyl radicals (⚫OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states of organic matter (3C*) – even though they likely drive much of ALW chemistry. Due to the very limited water content of particles, it is difficult to quantify oxidant concentrations in ALW directly. To predict these values, we measured photooxidant concentrations in illuminated aqueous particle extracts as a function of dilution and used the resulting oxidant kinetics to extrapolate to ALW conditions. We prepared dilution series from two sets of particles collected in Davis, California: one from winter (WIN) and one from summer (SUM). Both periods are influenced by biomass burning, with dissolved organic carbon (DOC) in the extracts ranging from 10 to 495 mg C L−1. In the winter sample, the ⚫OH concentration is independent of particle mass concentration, with an average value of 5.0 (± 2.2) × 10−15 M, while in summer ⚫OH increases with DOC in the range (0.4–7.7) × 10−15 M. In both winter and summer samples, 3C* concentrations increase rapidly with particle mass concentrations in the extracts and then plateau under more concentrated conditions, with a range of (0.2–7) × 10−13 M. WIN and SUM have the same range of 1O2* concentrations, (0.2–8.5) × 10−12 M, but in WIN the 1O2* concentration increases linearly with DOC, while in SUM 1O2* approaches a plateau. We next extrapolated the relationships of oxidant formation rates and sinks as a function of particle mass concentration from our dilute extracts to the much more concentrated condition of aerosol liquid water. Predicted ⚫OH concentrations in ALW (including mass transport of ⚫OH from the gas phase) are (5–8) × 10−15 M, similar to those in fog/cloud waters. In contrast, predicted concentrations of 3C* and 1O2* in ALW are approximately 10 to 100 times higher than in cloud/fogs, with values of (4–9) × 10−13 M and (1–5) × 10−12 M, respectively. Although ⚫OH is often considered the main sink for organic compounds in the atmospheric aqueous phase, the much higher concentrations of 3C* and 1O2* in aerosol liquid water suggest these photooxidants will be more important sinks for many organics in particle water.

While gas-phase reactions are well established to have significant impacts on the mass concentration, chemical composition, and optical properties of secondary organic aerosol (SOA), the aqueous-phase aging of SOA remains poorly understood. In this study, we performed a series of long-duration photochemical aging experiments to investigate the evolution of the composition and light absorption of the aqueous SOA (aqSOA) from guaiacyl acetone (GA), a semivolatile phenolic carbonyl that is common in biomass burning smoke. The aqSOA was produced from reactions of GA with hydroxyl radical (•OH-aqSOA) or a triplet excited state of organic carbon (3C∗-aqSOA) and was then photoaged in water under conditions that simulate sunlight exposure in northern California for up to 48 h. The effects of increasing aqueous-phase •OH or 3C∗ concentration on the photoaging of the aqSOA were also studied. High-resolution aerosol mass spectrometry (HR-AMS) and UV–Vis spectroscopy were utilized to characterize the composition and the light absorptivity of the aqSOA and to track their changes during aging. Compared to •OH-aqSOA, the 3C∗-aqSOA is produced more rapidly and shows less oxidation, a greater abundance of oligomers, and higher light absorption. Prolonged photoaging promotes fragmentation and the formation of more volatile and less light-absorbing products. More than half of the initial aqSOA mass is lost, and substantial photobleaching occurs after 10.5 h of prolonged aging under simulated sunlight illumination for 3C∗-aqSOA and 48 h for •OH-aqSOA. By performing positive matrix factorization (PMF) analysis of the combined HR-AMS and UV–Vis spectral data, we resolved three generations of aqSOA with distinctly different chemical and optical properties. The first-generation aqSOA shows significant oligomer formation and enhanced light absorption at 340–400 nm. The second-generation aqSOA is enriched in functionalized GA species and has the highest mass absorption coefficients in 300–500 nm, while the third-generation aqSOA contains more fragmented products and is the least light absorbing. These results suggest that intermediately aged phenolic aqSOA is more light absorbing than other generations, and that the light absorptivity of phenolic aqSOA results from a competition between brown carbon (BrC) formation and photobleaching, which is dependent on aging time. Although photoaging generally increases the oxidation of aqSOA, a slightly decreased O/C of the •OH-aqSOA is observed after 48 h of prolonged photoaging with additional •OH exposure. This is likely due to greater fragmentation and evaporation of highly oxidized compounds. Increased oxidant concentration accelerates the transformation of aqSOA and promotes the decay of BrC chromophores, leading to faster mass reduction and photobleaching. In addition, compared with •OH, photoaging by 3C∗ produces more low-volatility functionalized products, which counterbalances part of the aqSOA mass loss due to fragmentation and evaporation.

The ground-based Global Positioning System (GPS) has been used extensively to retrieve integrated water vapour (IWV) and has been adopted as a unique tool for the assessments of atmospheric reanalyses. In this study, we investigated the multi-temporal-scale variabilities and trends of IWV over Europe by using IWV time series from 108 GPS stations for more than 2 decades (1994–2018). We then adopted the GPS IWV as a reference to assess six commonly used atmospheric reanalyses, namely the Climate Forecast System Reanalysis (CFSR); ERA5; ERA-Interim; the Japanese 55-year Reanalysis (JRA-55); the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2); and NCEP-DOE AMIP-II Reanalysis (NCEP-2). The GPS results show that the peaks of the diurnal harmonics are within 15:00–21:00 in local solar time at 90 % of the stations. The diurnal amplitudes are 0–1.2 kg m−2 (0 %–8 % of the daily mean IWV), and they are found to be related to seasons and locations with different mechanisms, such as solar heating, land–sea breeze, and orographic circulation. However, mismatches in the diurnal cycle of ERA5 IWV between 09:00 and 10:00 UTC as well as between 21:00 and 22:00 UTC were found and evaluated for the first time, and they can be attributed to the edge effect in each ERA5 assimilation cycle. The average ERA5 IWV shifts are −0.08 and 0.19 kg m−2 at the two epochs, and they were found to be more significant in summer and in the Alps and in Eastern and central Europe in some cases. Nevertheless, ERA5 outperforms the other reanalyses in reproducing diurnal IWV anomalies at all the 1-, 3-, and 6-hourly temporal resolutions. ERA5 is also superior to the others in modelling the annual cycle and linear trend of IWV. For instance, the IWV trend differences between ERA5 and GPS are quite small, with a mean value and a standard deviation of 0.01 % per decade and 0.97 % per decade, respectively. However, due to significant discrepancies with respect to GPS, CFSR and NCEP-2 are not recommended for the analysis of IWV trends over southern Europe and the whole of Europe, respectively.

We developed a high-quality global integrated water vapour (IWV) dataset from 12 552 ground-based global positioning system (GPS) stations in 2020. It consists of 5 min GPS IWV estimates with a total number of 1 093 591 492 data points. The completeness rates of the IWV estimates are higher than 95 % at 7253 (58 %) stations. The dataset is an enhanced version of the existing operational GPS IWV dataset provided by the Nevada Geodetic Laboratory (NGL). The enhancement is reached by employing accurate meteorological information from the fifth generation of European ReAnalysis (ERA5) for the GPS IWV retrieval with a significantly higher spatiotemporal resolution. A dedicated data screening algorithm is also implemented. The GPS IWV dataset has a good agreement with in situ radiosonde observations at 182 collocated stations worldwide. The IWV biases are within ±3.0 kg m−2 with a mean absolute bias (MAB) value of 0.69 kg m−2. The standard deviations (SD) of IWV differences are no larger than 3.4 kg m−2. In addition, the enhanced IWV product shows substantial improvements compared to NGL's operational version, and it is thus recommended for high-accuracy applications, such as research of extreme weather events and diurnal variations of IWV and intercomparisons with other IWV retrieval techniques. Taking the radiosonde-derived IWV as reference, the MAB and SD of IWV differences are reduced by 19.5 % and 6.2 % on average, respectively. The number of unrealistic negative GPS IWV estimates is also substantially reduced by 92.4 % owing to the accurate zenith hydrostatic delay (ZHD) derived by ERA5. The dataset is available at https://doi.org/10.5281/zenodo.6973528 (Yuan et al., 2022).

The quasi-biennial oscillation (QBO), as the dominant mode in the equatorial stratosphere, modulates the dynamical circulation and the distribution of trace gases in the stratosphere. While the zonal mean QBO signals in stratospheric ozone have been relatively well documented, the zonal (longitudinal) differences in the QBO ozone signals have been less studied. Using satellite-based total column ozone (TCO) data from 1979 to 2020, zonal mean ozone data from 1984 to 2020, three-dimensional (3-D) ozone data from 2002 to 2020, and ERA5 reanalysis and model simulations from 1979 to 2020, we demonstrate that the influences of the QBO (using a QBO index at 20 hPa) on stratospheric ozone are zonally asymmetric. The global distribution of stratospheric ozone varies significantly during different QBO phases. During QBO westerly (QBOW) phases, the TCO and stratospheric ozone are anomalously high in the tropics, while in the subtropics they are anomalously low over most of the areas, especially during the winter–spring of the respective hemisphere. This confirms the results from previous studies. In the polar region, the TCO and stratospheric ozone (50–10 hPa) anomalies are seasonally dependent and zonally asymmetric. During boreal winter (December–February, DJF), positive anomalies of the TCO and stratospheric ozone are evident during QBOW over the regions from North America to the North Atlantic (120∘ W–30∘ E), while significant negative anomalies exist over other longitudes in the Arctic. In boreal autumn (September–November, SON), the TCO and stratospheric ozone are anomalously high from Greenland to Eurasia (60∘ W–120∘ E) but anomalously low in other regions over the Arctic. Weak positive TCO and stratospheric ozone anomalies exist over the South America sector (90∘ W–30∘ E) of the Antarctic, while negative anomalies of the TCO and stratospheric ozone are seen in other longitudes. The consistent features of TCO and stratospheric ozone anomalies indicate that the QBO signals in TCO are mainly determined by the stratospheric ozone variations. Analysis of meteorological conditions indicates that the QBO ozone perturbations are mainly caused by dynamical transport and also influenced by chemical reactions associated with the corresponding temperature changes. QBO affects the geopotential height and the polar vortex and subsequently the transport of ozone-rich air from lower latitudes to the polar region, which therefore influences the ozone concentrations over the polar region. The geopotential height anomalies associated with QBO (QBOW–QBOE) are zonally asymmetric with clear wave number 1 features, which indicates that QBO influences the polar vortex and stratospheric ozone mainly by modifying the wave number 1 activities.

In blue-ice areas (BIAs), deep ice is directly exposed at the surface, allowing for the cost-effective collection of large-sized old-ice samples. However, chronostratigraphic studies on blue-ice areas are challenging owing to fold and fault structures. Here, we report on a surface transect of ice with an undisturbed horizontal stratigraphy from the Larsen BIA, northern Victoria Land, East Antarctica. Ice layers defined by dust bands and ground-penetrating radar (GPR) surveys indicate a monotonic increase in age along the ice flow direction on the downstream side, while the upstream ice exhibits a potential repetition of ages on scales of tens of meters, which result from a complicated fold structure. Stable water isotopes (δ18Oice and δ2Hice) and components of the occluded air (i.e., CO2, N2O, CH4, δ15N–N2, δ18Oatm (=δ18O-O2), δO2/N2, δAr/N2​​​​​​​, 81Kr, and 85Kr) are analyzed for surface ice and shallow ice core samples. Correlating δ18Oice, δ18Oatm, and CH4 records from the Larsen BIA with ice from previously drilled ice cores indicates that the gas age at various shallow vertical coring sites ranges between 9.2–23.4 kyr BP, while the ice age sampled from the surface ranges from 5.6 to 24.7 kyr BP. Absolute radiometric 81Kr dating for the two vertical cores confirms ages within acceptable levels of analytical uncertainty. A tentative climate reconstruction suggests a large deglacial warming of 15 ± 5 ∘C (1σ) and an increase in snow accumulation by a factor of 1.7–4.6 (from 24.3 to 10.6 kyr BP). Our study demonstrates that BIAs in northern Victoria Land may help to obtain high-quality records for paleoclimate and atmospheric greenhouse gas compositions through the last deglaciation, although in general climatic interpretation is complicated by the need for upstream flow corrections, evidence for strong surface sublimation during the last glacial period, and potential errors in the estimated gas age–ice age difference.

Equipped with a high-precision atomic clock can significantly improve the ranging accuracy of the underwater acoustic ranging system. However, the adverse characteristic of underwater acoustic channel (UAC) seriously deteriorates the ranging accuracy. In addition, as a timing device typically commercial cesium atomic clock is only designed to output second-level time reference, which cannot be applied to underwater ranging systems directly. To overcome this limitation, a new underwater acoustic modem with high precision ranging capability based on second-level cesium atomic clock is developed in this paper. The spread spectrum technology is chosen for highly reliable communication and the second-level commercial cesium atomic clock is used to ensure accurate clock synchronization. The proposed modem executes a predetermined ranging scheme based on spread spectrum technology. Specifically, at a certain specified second-level, the transmitter modem sends the ranging signal, and the receiver modem starts timing. Until the receiving modem detects the ranging signal, the propagation time is obtained and the single-item ranging capability is realized. The pool experiment shows the effectiveness of the modem, its ranging accuracy can reach cm level, and the average absolute error of ranging is 8 cm.

Ab initio has been used as a label in nuclear theory for over two decades. Its meaning has evolved and broadened over the years. We present our interpretation, briefly review its historical use, and discuss its present-day relation to theoretical uncertainty quantification.

Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.

Cardiac endothelial cells (ECs) are important targets for cardiovascular gene therapy. However, the approach of stably transducing ECs in vivo using different vectors, including adeno-associated virus (AAV), remains unexamined. Regarding this unmet need, two AAV libraries from DNA shuffling and random peptide display were simultaneously screened in a transgenic mouse model. Cardiac ECs were isolated by cell sorting for salvage of EC-targeting AAV. Two AAV variants, i.e., EC71 and EC73, enriched in cardiac EC, were further characterized for their tissue tropism. Both of them demonstrated remarkably enhanced transduction of cardiac ECs and reduced infection of liver ECs in comparison to natural AAVs after intravenous injection. Significantly, persistent transgene expression was maintained in mouse cardiac ECs in vivo for at least 4 months. The EC71 vector was selected for delivery of the endothelial nitric oxide synthase (eNOS) gene into cardiac ECs in a mouse model of myocardial infarction. Enhanced eNOS activity was observed in the mouse heart and lung, which was correlated with partially improved cardiac function. Taken together, two AAV capsids were evolved with more efficient transduction in cardiovascular endothelium in vivo, but their endothelial tropism might need to be further optimized for practical application to cardiac gene therapy.

Water body plays an irreplaceable role in the global ecosystem and climate system. Sentinel-2 is a new satellite data with higher spatial and spectral resolution. Through analysing spectral characteristics of Sentinel-2 satellite imagery, the brightness of water body in vegetation red edge band and shortwave infrared band showe sharply different than that of the not water body. Therefore, a new type of water index SWI (Sentinel-2 Water Index) was proposed by combing those two bands. Four representative water types, which included Taihu Lake, the Yangtze River Estuary, the ChaKa Salt Lake and the Chain Lake, were selected as experimental areas. Normalized difference water index (NDWI) and Sentinel-2 Water Index (SWI) with Otsu method were employed to extract water body. The results showed that overall accuracy and Kappa coefficient of SWI were higher than that of NDWI and SWI was efficient index to rapidly and accurately extract water for Sentinel-2 data. Therefore, SWI had application potential for larger scale water mapping in the future.

Land use change is an important theme of the research on the impact of human interaction on global change. In this paper, two phases of land use data were interpretated from remote sensing images of 1978 and 2018, and the spatial-temporal characteristics of land use change in China's Inner Mongolia Region from 1978 to 2018 were analyzed. The results indicated that grasslands and arable land are mainly distributed in the central and eastern region of Inner Mongolia, forest land are mainly distributed in the eastern region, and unused land is mainly distributed in the western region. From 1978 to 2018, the area of arable land in Inner Mongolia decreased by 9,000 km2, forest land increased by 900 km2, and the area of grassland decreased by 1,400 km2. Urban and rural, industrial mines, and residential land continued to increase with an area of 7,800 km2; and unused land increased by an area of 11,500 km2. It was indicated that after 40 years of development, land use in urban and rural areas, industrial mines, and residential areas caused by human activities in the Inner Mongolia Region has increased significantly. At the same time, the policy of returning farmland to forests to protect the environment has achieved significant results.

Remote sensing system fitted on UAV (Unmanned Aerial Vehicle) can obtain clear images and high-resolution aerial photographs. It has advantages of flexibility, convenience and ability to work full-time. However, there are some problems of UAV image such as small coverage area, large number, irregular overlap, etc. How to obtain a large regional map quickly becomes a major obstacle to UAV remote sensing application. In this paper, a new method of fast registration of UAV remote sensing images was proposed to meet the needs of practical application. This paper used Progressive Sample Consensus (PROSAC) algorithm to improve the matching accuracy by removed a large number of mismatching point pairs of remote sensing image registration based-on SURF (Speed Up Robust Feature) algorithm, and GPU (Graphic Processing Unit) was also used to accelerate the speed of improved SURF algorithm. Finally, geometric verification was used to achieve mosaic accuracy in survey area. The number of feature points obtained by using improved SURF based-on PROSAC algorithm was only 9.5% than that of SURF algorithm. Moreover, the accuracy rate of improved method was about 99.7%, while the accuracy rate of improved SURF algorithm was increased by 8% than SURF algorithm. Moreover, the improved running time of SURFGPU algorithm for UAV remote sensing image registration was a speed of around 16 times than SURF algorithm, and the image matching time had reached millisecond level. Thus, improved SURF algorithm had better matching accuracy and executing speed to meet the requirements of real-time and robustness in UAV remote sensing image registration.

Quantification of vegetation change and its coupling relationship with climate change has become the central topic in current global change researches. The Normalized Difference Vegetation Index (NDVI) time series data and meteorological data from 1998 to 2016 were collected to investigate the temporal and spatial variations of NDVI in growing season in the Yellow River source region and its response to climate change, based on the trend analysis, Mann-Kendall test and correlation analysis．The results indicated that: (1) In the past 19 years, the average NDVI in the region showed a slow increase, with a growth rate of 0.002/a and a catastrophe point in 2005, and the area with an upward trend accounted for 71.4% of the total area. (2) The climate of the area had been becoming warm and moist since the recent 19 years, both precipitation and temperature in growing season showed an upward trend. The partial correlation analysis showed that NDVI was positively correlated with precipitation and temperature, significantly relevant area accounting for 31.01% and 56.40% of the total area individually. The sensitivity of NDVI to temperature was higher than that of precipitation. According to residual analysis over the 19 years, human activities had negative effects on NDVI accounting 53.58% of the study area, and the implementation of a series of ecological protection engineering measures was the main cause leading to an increasing trend of NDVI after 2005.

Soil moisture is an important physical parameter to investigate water circulation, while it is difficult to be measured with spatiotemporal consistency. During the past several decades, a larger number of soil moisture verification methods were proposed, however, the review of soil moisture verification method from multi-scale perspective is still lacking. This paper investigates the verification method of soil moisture from three scale, such as point-scale, regional scale and remote sensing data verification. The prospect of soil moisture verification is proposed to serve retrieval algorithm validation.

Complex aerosol and photochemical pollution (ozone and peroxyacetyl nitrate, PAN) frequently occur in eastern China, and mitigation strategies to effectively alleviate both kinds of pollution are urgently needed. Although the effectiveness of powerful control measures implemented by the Chinese State Council has been comprehensively evaluated in terms of reducing atmospheric primary pollutants, the effectiveness in mitigating photochemical pollution is less assessed and therefore the underlying mechanisms are still poorly understood. The stringent emission controls implemented from 24 August to 6 September 2016 during the summit for the Group of Twenty (G20) provide us a unique opportunity to address this issue. Surface concentrations of atmospheric O3, PAN, and their precursors including volatile organic compounds (VOCs) and nitrogen dioxides (NOx), in addition to the other trace gases and particulate matter, were measured at the National Reference Climatological Station (NRCS) (30.22∘ N, 120.17∘ E, 41.7 m a.s.l) in urban Hangzhou. We found significant decreases in atmospheric PAN, NOx, total VOCs, PM2.5, and sulfur dioxide (SO2) under the unfavorable meteorological conditions during G20 (DG20) relative to the adjacent period before and after G20 (BG20 and AG20), indicating that the powerful control measures were effective in reducing the pollutant emissions in Hangzhou. Unlike with the other pollutants, daily maximum 8 h average (DMA8) O3 exhibited a slight increase and then decrease from BG20 to AG20, which was mainly attributed to the variation in the solar irradiation intensity and regional transport in addition to the contribution from the implementation of stringent control measures. Results from an observation-based chemical model (OBM) indicated that acetaldehyde and methylglyoxal (MGLY) were the most important second-generation precursors of PAN, accounting for 37.3 %–51.6 % and 22.8 %–29.5 % of the total production rates including the reactions of OVOCs, propagation of other radicals, and other minor sources. Moreover, we confirmed the production of PAN and O3 was sensitive to VOCs throughout the whole period, specifically dominated by aromatics in BG20 and DG20 but by alkenes in AG20. These findings suggested that reducing emissions of aromatics, alkenes, and alkanes would mitigate photochemical pollution including PAN and O3. Source appointment results attributed the reductions of VOC source and ozone formation potentials (OFPs) during G20 to the effective emission controls on traffic (vehicle exhaust) and industrial processes (solvent utilization and industrial manufacturing). However, fuel combustion and biogenic emissions both weakened such an effect with a sizable contribution to the VOC mixing ratios (18.8 % and 20.9 %) and OFPs (25.6 % and 17.8 %), especially during the latter part of G20 (G20 II) when anthropogenic VOCs were substantially reduced. This study highlights the effectiveness of stringent emission controls in relation to traffic and industrial sources, but a coordinated program related to controlling fuel combustion and biogenic emissions is also required to address secondary pollution.

Brown carbon (BrC) contributes significantly to aerosol light absorption and thus can affect the Earth's radiation balance and atmospheric photochemical processes. In this study, we examined the light absorption properties and molecular compositions of water-soluble (WS-BrC) and water-insoluble (WI-BrC) BrC in PM2.5 collected from a rural site in the Guanzhong Basin – a highly polluted region in northwest China. Both WS-BrC and WI-BrC showed elevated light absorption coefficients (Abs) in winter (4–7 times those in summer) mainly attributed to enhanced emissions from residential biomass burning (BB) for heating of homes. While the average mass absorption coefficients (MACs) at 365 nm (MAC365) of WS-BrC were similar between daytime and nighttime in summer (0.99±0.17 and 1.01±0.18 m2 g−1, respectively), the average MAC365 of WI-BrC was more than a factor of 2 higher during daytime (2.45±1.14 m2 g−1) than at night (1.18±0.36 m2 g−1). This difference was partly attributed to enhanced photochemical formation of WI-BrC species, such as oxygenated polycyclic aromatic hydrocarbons (OPAHs). In contrast, the MACs of WS-BrC and WI-BrC were generally similar in winter and both showed few diel differences. The Abs of wintertime WS-BrC correlated strongly with relative humidity, sulfate and NO2, suggesting that aqueous-phase reaction is an important pathway for secondary BrC formation during the winter season in northwest China. Nitrophenols on average contributed 2.44±1.78 % of the Abs of WS-BrC in winter but only 0.12±0.03 % in summer due to faster photodegradation reactions. WS-BrC and WI-BrC were estimated to account for 0.83±0.23 % and 0.53±0.33 %, respectively, of the total down-welling solar radiation in the ultraviolet (UV) range in summer, and 1.67±0.72 % and 2.07±1.24 %, respectively, in winter. The total absorption by BrC in the UV region was about 55 %–79 % relative to the elemental carbon (EC) absorption.

Surface water system is an important part of global ecosystem, and the changes in surface water may lead to disasters, such as drought, waterlog, and water-borne diseases. The rapid development of remote sensing technology has supplied better strategies for water bodies extraction and further monitoring. In this study, AdaBoost and Random Forest (RF), two typical algorithms in integrated learning, were applied to extract water bodies in Chaozhou area (mainly located in Guangzhou Province, China) based on GF-1 data, and the Decision Tree (DT) was used for comparative tests to comprehensively evaluate the performance of classification algorithms listed above for surface water body extraction. The results showed that: (1) Compared with visual interpretation, AdaBoost performed better than RF in the extraction of several typical water bodies, such as rivers, lakes and ponds Moreover, the water extraction results of the strong classifiers using AdaBoost or RF were better than the weak basic classifiers. (2) For the quantitative accuracy statistics, the overall accuracy (96.5%) and kappa coefficient (93%) using AdaBoost exceeded those using RF (5.3% and 10.6%), respectively. The classification time of AdaBoost increased by 403 seconds and 918 seconds relative to RF and DT methods. However, in terms of visual interpretation, quantitative statistical accuracy and classification time, AdaBoost algorithm was more suitable for the water body extraction. (3) For the sample proportion comparison experiment of AdaBoost, four sampling proportions (0.1%, 0.2%, 1% and 2%) were chosen and 0.1% sampling proportion reached the optimum classification accuracy (93.9%) and kappa coefficient (87.8%).

Objective This study was conducted to evaluate the effects of tannins and cellulase on growth performance, nutrient digestibility, blood profiles, intestinal morphology, and carcass characteristics in Hu sheep. Methods A total of 48 three-month-old meat Hu sheep (25.05±0.9 kg) were blocked based on body weight, and randomly allotted to 4 treatments with 3 replicates of 4 sheep each. The experiment lasted for 80 d, and dietary treatments were as follows: i) CON, control diet; ii) TAN, CON+0.1% tannins; iii) CEL, CON+0.1% cellulase; iv) TAN+CEL, CON+0.1% tannins and 0.1% cellulase. Results Compared with CON, CEL, and TAN+CEL had greater (p

Field burning of crop residue in early summer releases a large amount of pollutants into the atmosphere with significant impacts on the air quality and aerosol properties in the North China Plain (NCP). In order to investigate the influence of this regional anthropogenic activity on molecular characteristics of organic aerosols, PM2.5 filter samples were collected with a 3 h interval at a rural site of NCP from 10 to 25 June 2013 and analyzed for more than 100 organic tracer compounds, including both primary (n-alkanes, fatty acids/alcohols, sugar compounds, polycyclic aromatic hydrocarbons, hopanes, and phthalate esters) and secondary organic aerosol (SOA) tracers (phthalic acids, isoprene-, α-/β-pinene, β-caryophyllene, and toluene-derived products), as well as organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC). Total concentrations of the measured organics ranged from 177 to 6248 ng m−3 (mean 1806±1308 ng m−3) during the study period, most of which were contributed by sugar compounds, followed by fatty acids and fatty alcohols. Levoglucosan (240±288 ng m−3) was the most abundant single compound and strongly correlated with OC and WSOC, suggesting that biomass burning (BB) is an important source of summertime organic aerosols in this rural region. Based on the analysis of fire spots and backward trajectories of air masses, two representative periods were classified, which are (1) Period 1 (P1), 13 June 21:00–16 June at 15:00 CST (China Standard Time), when air masses were uniformly distributed from the southeast part of NCP, where intensive open-field biomass burning occurred; and (2) Period 2 (P2), 22 June at 12:00 to 24 June at 06:00 CST, which is representative of local emission. Nearly all the measured PM components showed much higher concentrations in P1 than in P2. Although n-alkanes, fatty acids, and fatty alcohols presented similar temporal–diurnal variations as those of levoglucosan throughout the entire period, their molecular distributions were more dominated by high molecular weight (HMW) compounds in P1, demonstrating an enhanced contribution from BB emissions. In contrast, intensive BB emission in P1 seems to have limited influence on the concentrations of polycyclic aromatic hydrocarbons (PAHs), hopanes, and phthalate esters. Both 3-hydroxyglutaric acid and β-caryophyllinic acid showed strong linearly correlations with levoglucosan (R2=0.72 and 0.80, respectively), indicating that BB is also an important source for terpene-derived SOA formation. A tracer-based method was used to estimate the distributions of biomass-burning OC, fungal-spore OC, and secondary organic carbon (SOC) derived from isoprene, α-/β-pinene, β-caryophyllene, and toluene in the different periods. The results showed that the contribution of biomass-burning OC to total OC in P1 (27.6 %) was 1.7 times that in P2 (17.1 %). However, the contribution of SOC from oxidation of the four kinds of volatile organic compounds (VOCs) increased slightly from 16.3 % in P1 to 21.1 % in P2.

Water-soluble brown carbon in the aqueous core of aerosol may play a role in the photochemical aging of organic film on the aerosol surface. To better understand the reactivity and photochemical aging processes of organic coating on the aqueous aerosol surface, we have simulated the photosensitized reaction of organic films made of several long-chain fatty acids in a Langmuir trough in the presence or absence of irradiation. Several chemicals (imidazole-2-carboxaldehyde and humic acid), PM2.5 samples collected from the field, and secondary organic aerosol samples generated from a simulation chamber were used as photosensitizers to be involved in the photochemistry of the organic films. Stearic acid, elaidic acid, oleic acid, and two different phospholipids with the same carbon chain length and different degrees of saturation, i.e. 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dioleoylsn-glycero-3-phosphocholine (DOPC), were chosen as the common organic film-forming species in this analysis. The double bond (trans and cis) in unsaturated organic compounds has an effect on the surface area of the organic monolayer. The oleic acid (OA) monolayer possessing a cis double bond in an alkyl chain is more expanded than elaidic acid (EA) monolayers on artificial seawater that contain a photosensitizer. Monitoring the change in the relative area of DOPC monolayers has shown that DOPC does not react with photosensitizers under dark conditions. Instead, the photochemical reaction initiated by the excited photosensitizer and molecular oxygen can generate new unsaturated products in the DOPC monolayers, accompanied by an increase in the molecular area. The DSPC monolayers did not yield any photochemical oxidized products under the same conditions. The spectra measured with polarization modulation-infrared reflection–absorption spectroscopy (PM-IRRAS) were also consistent with the results of a surface pressure–area isotherm. Here, a reaction mechanism explaining these observations is presented and discussed. The results of PM2.5 and SOA samples will contribute to our understanding of the processing of organic aerosol aging that alters the aerosol composition.

The objectives of the present study were to compare the dynamic of the growth and photosynthetic characteristics of cotton varieties contrasting in waterlogging (WL) tolerance when subjected to hypoxia stress. The growth of the WL-sensitive genotypes was notably inhibited by WL, mainly as a result of a significant reduction in the net photosynthesis (PN) after two days of hypoxia treatment; in the tolerant varieties, no significant changes in PN were observed until 8 d after hypoxia onset. The intercellular CO2 concentration and maximal photochemical efficiency of PSII significantly declined, and the nonphotochemical quenching increased in the sensitive varieties. Infrared thermography showed that a low stomatal conductance resulted in an increased leaf temperature under hypoxia stress. Spectral image analysis suggested that the pigment content and water content rapidly decreased in the leaves of the sensitive varieties. It is concluded that maintaining stomatal opening through the interaction of ethylene and abscisic acid may be an important strategy to improve waterlogging tolerance in cotton.

Surfactant layers with viscoelastic properties floating on the water surface dampen short gravity-capillary waves. Taking advantage of the known virtue of fish oil to still angry seas, a laboratory study has been made to analyse wind-wave generation and the interaction between wind waves, paddle waves, and airflow. This was done in a tank containing a thin fish-oil film uniformly spread on the water surface. The research was aimed, on the one hand, at quantifying for the first time the effectiveness of this surfactant at impeding the generation of wind waves and, on the other, at using the derived conditions to disentangle relevant mechanisms involved in the air–sea interaction. In particular, our main interest concerned the processes acting on the wind stress and on the wave growth. With oil on the water surface, we have found that in the wind-only condition (no paddle waves) the wave field does not grow from the rest condition. This equilibrium is altered by irregular paddle (long) waves, the generation and evolution of short waves (in clean water and with oil) being modified by their interaction with the orbital velocity of the long waves and their effect on the airflow. Paddle waves do grow under the action of wind, the amount being similar in clean and oily water conditions, a fact we ascribe to the similar distortion of the wind vertical profile in the two cases. We have also verified that the wind-supported stress on the oily water surface was able to generate a surface current, whose magnitude turns out to be comparable to the one in clean water. We stress the benefits of experiments with surfactants to explore in detail the physics at, and the exchanges across, the wavy and non-wavy air–water interface.

Regular inspection of transmission line is an essential work to ensure reliable supply and distribution of electric power. Considering that the conventional time consuming and economic inefficient methods can not satisfy new coming demands, an inspection strategy is proposed in this study, which aims to achieve off-site visual inspection instead of in-site inspection. The most challenging task is 3D model reconstruction of transmission line. Therefore, based on oblique imaging technique and the flexibility of UAV platforms, an UAV-Based oblique photogrammetric system is designed and manufactured for data acquisition of transmission line. The system integrates a dual-camera imaging system, an onboard GNSS (Global Navigation Satellite System) receiver and a ground fixed GNSS station. Beside, using open-source and commercial software packages, a data processing pipeline is also proposed for 3D model reconstruction. The experimental results demonstrate that the UAV-based oblique imaging system could obtain images of power pylons in four different directions and provides enough information for the successful model reconstruction. Without GCPs, the dual-strip flight mode is recommended for flight configuration to achieve high geo-referencing accuracy. Compared with the traditional methods, the proposed solution can achieve off-site inspection of transmission line.

On space remote sensing stereo mapping field, the angle variation between the star sensor’s optical axis and the earth observation camera’s optical axis on-orbit affects the positioning accuracy, when optical mapping is without ground control points (GCPs). This work analyses the formation factors and elimination methods for both the star sensor’s error and the angles error between the star sensor’s optical axis and the earth observation camera’s optical axis. Based on that, to improve the low attitude stability and long calibration time necessary of current satellite cameras, a method is then proposed for real-time on-orbit calibration of the angles between star sensor’s optical axis and the earth observation camera’s optical axis based on the principle of auto-collimation. This method is experimentally verified to realize real-time on-orbit autonomous calibration of the angles between the star sensor’s optical axis and the earth observation camera’s optical axis.

While photooxidants are important in atmospheric condensed phases, there are very few measurements in particulate matter (PM). Here we measure light absorption and the concentrations of three photooxidants – hydroxyl radical (⚫OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states of organic matter (3C*) – in illuminated aqueous extracts of wintertime particles from Davis, California. 1O2* and 3C*, which are formed from photoexcitation of brown carbon (BrC), have not been previously measured in PM. In the extracts, mass absorption coefficients for dissolved organic compounds (MACDOC) at 300 nm range between 13 000 and 30 000 cm2 (g C)−1 are approximately twice as high as previous values in Davis fogs. The average (±1σ)⚫OH steady-state concentration in particle extracts is 4.4(±2.3)×10-16 M, which is very similar to previous values in fog, cloud, and rain: although our particle extracts are more concentrated, the resulting enhancement in the rate of ⚫OH photoproduction is essentially canceled out by a corresponding enhancement in concentrations of natural sinks for ⚫OH. In contrast, concentrations of the two oxidants formed primarily from brown carbon (i.e., 1O2* and 3C*) are both enhanced in the particle extracts compared to Davis fogs, a result of higher concentrations of dissolved organic carbon and faster rates of light absorption in the extracts. The average 1O2* concentration in the PM extracts is 1.6(±0.5)×10-12 M, 7 times higher than past fog measurements, while the average concentration of oxidizing triplets is 1.0(±0.4)×10-13 M, nearly double the average Davis fog value. Additionally, the rates of 1O2* and 3C* photoproduction are both well correlated with the rate of sunlight absorption. Since we cannot experimentally measure photooxidants under ambient particle water conditions, we measured the effect of PM dilution on oxidant concentrations and then extrapolated to ambient particle conditions. As the particle mass concentration in the extracts increases, measured concentrations of ⚫OH remain relatively unchanged, 1O2* increases linearly, and 3C* concentrations increase less than linearly, likely due to quenching by dissolved organics. Based on our measurements, and accounting for additional sources and sinks that should be important under PM conditions, we estimate that [⚫OH] in particles is somewhat lower than in dilute cloud/fog drops, while [3C*] is 30 to 2000 times higher in PM than in drops, and [1O2*] is enhanced by a factor of roughly 2400 in PM compared to drops. Because of these enhancements in 1O2* and 3C* concentrations, the lifetimes of some highly soluble organics appear to be much shorter in particle liquid water than under foggy/cloudy conditions. Based on extrapolating our measured rates of formation in PM extracts, BrC-derived singlet molecular oxygen and triplet excited states are overall the dominant sinks for organic compounds in particle liquid water, with an aggregate rate of reaction for each oxidant that is approximately 200–300 times higher than the aggregate rate of reactions for organics with ⚫OH. For individual, highly soluble reactive organic compounds it appears that 1O2* is often the major sink in particle water, which is a new finding. Triplet excited states are likely also important in the fate of individual particulate organics, but assessing this requires additional measurements of triplet interactions with dissolved organic carbon in natural samples.

The reliability of a computer program simulating rockfall trajectory depends on the ascertainment of reasonable values for the coefficients of restitution, which typically vary with the kinematic parameters and terrain conditions. The effects of the impact angle with respect to the slope on the coefficients of restitution have been identified and studied using small-scale laboratory tests. To investigate whether the existing conclusion based on small-scale laboratory tests is valid when the test scale changes as well as the role of rotation in the effect of the impact angle on the coefficients of restitution, this study performed a medium-scale laboratory test using spherical limestone polyhedrons to impact concrete slabs. Free-fall tests are conducted, and the velocities before and after the impact are obtained by a 3-D motion capture system. The comparison of results between our test and the existing small-scale tests verified that several general laws occur when accounting for the effect of the impact angle, regardless of the test scales and conditions. Increasing the impact angle will induce reductions in the normal coefficient of restitution Rn, the kinematic coefficient of restitution Rv and the kinetic energy coefficient of restitution RE, whereas it will lead to increases in the tangential coefficient of restitution Rt. The rotation plays an important role in the effect of the impact angle. A higher percentage of kinetic energy converted to rotational energy always induces a higher normal coefficient of restitution Rn and a lower tangential coefficient of restitution Rt. As the impact angle decreases, the ratio between the rebound angle β and the impact angle α increases, and the percentage of kinetic energy dissipated in rotation as the collision became higher. Considering that the effect of block shape and the detailed impact orientations are not involved in the present study, the test results are valid for trajectory simulation codes based on a lumped-mass model and can be referenced in the trajectory predication of spherical rocks impacting hard surfaces using a rigid body model.

We present the design of an agile slow wave structure for a “crab-like” A12 relativistic magnetron with diffraction output using single-stepped cavities. By regrouping the interaction region as three sets of four cavities, the TE31 operating mode is generated at 2.60 GHz with 1.0 GW output power for an applied voltage of U = 350 kV and a magnetic field of B = 0.34 T. By regrouping the interaction region as four sets of three cavities, the TE41 operating mode is generated at 2.82 GHz with 1.0 GW output power for an applied voltage of U = 355 kV and a magnetic field of B = 0.36 T. Furthermore, by regrouping the interaction region as six sets of two cavities, the TE31 mode and the TE21 mode are generated. When an applied voltage of U = 350 kV and a magnetic field of B = 0.33 T are used, its output power can be as high as 1.0 GW for the TE31 mode operating at 2.5 GHz. In addition, when an applied voltage of U = 350 kV and a magnetic field of B = 0.42 T are used, its output power can be as high as 1.0 GW with operating mode TE21 at 2.62 GHz. It was found that the rearrangement of the slow wave structure can control the operating mode and, at the same time, lower the operating condition of the beam/wave interaction compared to the traditional 12-cavity relativistic magnetron. The result suggests that this configuration is favorable for mode switching through mechanical rearrangement of the slow wave structure. This work seeks to design a compact high power microwave source for a narrowband directed microwave beam that is suitable for mode switching investigations.

ABSTRACT: Solanum nigrum L. (black nightshade), an annual to short-lived perennial weed, has become a problem weed in farming systems in central China. Laboratory and greenhouse experiments were conducted to examine the influence of various abiotic factors on seed germination of black nightshade to develop effective weed control programs. Seeds germinated at a range of constant temperatures from 15 to 30 oC, but no germination occurred at temperatures below 10 oC or above 35 oC. Seeds also germinated at alternating temperature regimes from 15/5 to 40/30 oC, with maximum germination (> 93.5%) at the alternating temperatures of 25/15 and 30/20 oC. Germination decreased as osmotic potential became more negative, and no germination was observed at ≤ -0.8 MPa. Moreover, germination was reduced by saline and alkaline stresses and no germination occurred at ≥ 200 mM NaCl or ≥ 150 mM NaHCO3 concentrations. Seed germination was not significantly affected by pH values from 5 to 10. Seedling emergence was significantly affected by burial depth with maximum emergence (93.1%) at 1 cm depth.

We present the design of an oscillator that is an evolution of our previously proposed “clamp klystron.” In this new embodiment, we utilize sloping cavities and increase the operating frequency to 94 GHz and 100 GHz (W-band). In this study, we utilized the UNIPIC particle-in-cell code. Simulations confirmed that this new oscillator with one sloping “buncher” cavity and one sloping “catcher” cavity with an inclination angle of 5° and shaped like a “clamp” produces 700 kW output power with an efficiency of 7.1% at 94 GHz when powered using an applied voltage U = 90 kV and beam current 110 A. When one sloping “buncher” cavity and one sloping “catcher” cavity are utilized with an inclination angle of 15°, the oscillator produces 270 kW output power with 3.0% efficiency at 100 GHz when powered using the same electron beam parameters. If two oscillators with sloping cavities along the z-axis are combined serially, then the output power can be as high as 800 kW with 8.0% efficiency at 100 GHz. This new oscillator design can be a promising approach to high power millimeter wave source designs at W-band and higher frequencies.

Geocoding is a fundamental task of Geographic Information System (GIS) processing and analysis. It allows the transformation between a location reference (i.e., an address or an alphanumeric code) and coordinates, which is often an essential step when performing spatial analysis, mapping, and other geolocation related processes. Providing software functionality through RESTful APIs is a common practice in geospatial applications. Client programs are able to access or process geospatial data easily through a lightweight and scalable RESTful web service. Existing geocoding RESTful API providers include Google Maps Geocoding API, ArcGIS Geocoding REST API, MapQuest Open Geocoding API and what3words (w3w) Geocoding API. Extensions of what3words geocoding system have recently been proposed to overcome its limitation of fixed resolution and lack of consideration of the third dimension. This paper considers one of the extensions, the Quadtree Extension Model (QTEM) and introduces a RESTful API that provides operations for forward geocoding, reverse geocoding, single line and polygon encoding, and centre points encoding for a given area. The resources published by the web service could be implemented by software programs performing indoor and outdoor location referencing, location marking and path finding. This API could facilitate various geographic applications such as facility management, emergency evacuation, navigation and student survey data management in a university campus environment.

A new 11Be(d,p)12Be transfer reaction experiment was carried out in inverse kinematics at 26.9A MeV, with special efforts devoted to the determination of the deuteron target thickness and of the required optical potentials from the present elastic scattering data. In addition a direct measurement of the cross section for the 02+ state was realized by applying an isomer-tagging technique. The s-wave spectroscopic factors of 0.20−0.04+0.03 and 0.41−0.11+0.11 were extracted for the 01+ and 02+ states, respectively, in 12Be. Using the ratio of these spectroscopic factors, together with the previously reported results for the p-wave components, the single-particle component intensities in the bound 0+ states of 12Be were deduced, allowing a direct comparison with the theoretical predictions. It is evidenced that the ground-state configuration of 12Be is dominated by the d-wave intruder, exhibiting a dramatic evolution of the intruding mechanism from 11Be to 12Be, with a persistence of the N=8 magic number broken. Keywords: Transfer reaction, 12Be, Intruder configuration

This paper presents a new standardized data format named Fire Markup Language (FireML), extended by the Geography Markup Language (GML) of OGC, to elaborate upon the fire hazard model. The proposed FireML is able to standardize the input and output documents of a fire model for effectively communicating with different disaster management systems to ensure a good interoperability. To demonstrate the usage of FireML and testify its feasibility, an adopted forest fire spread model being compatible with FireML is described. And a 3DGIS disaster management system is developed to simulate the dynamic procedure of forest fire spread with the defined FireML documents. The proposed approach will enlighten ones who work on other disaster models' standardization work.

Water body identifying is critical to climate change, water resources, ecosystem service and hydrological cycle. Multi-layer perceptron(MLP) is the popular and classic method under deep learning framework to detect target and classify image. Therefore, this study adopts this method to identify the water body of Landsat8. To compare the performance of classification, the maximum likelihood and water index are employed for each study area. The classification results are evaluated from accuracy indices and local comparison. Evaluation result shows that multi-layer perceptron(MLP) can achieve better performance than the other two methods. Moreover, the thin water also can be clearly identified by the multi-layer perceptron. The proposed method has the application potential in mapping global scale surface water with multi-source medium-high resolution satellite data.

This paper briefly describes the post-processing influence assessment experiment, the experiment includes three steps: the physical simulation, image processing, and image quality assessment. The physical simulation models sampled imaging system in laboratory, the imaging system parameters are tested, the digital image serving as image processing input are produced by this imaging system with the same imaging system parameters. The gathered optical sampled images with the tested imaging parameters are processed by 3 digital image processes, including calibration pre-processing, lossy compression with different compression ratio and image post-processing with different core. Image quality assessment method used is just noticeable difference (JND) subject assessment based on ISO20462, through subject assessment of the gathered and processing images, the influence of different imaging parameters and post-processing to image quality can be found. The six JND subject assessment experimental data can be validated each other. Main conclusions include: image post-processing can improve image quality; image post-processing can improve image quality even with lossy compression, image quality with higher compression ratio improves less than lower ratio; with our image post-processing method, image quality is better, when camera MTF being within a small range.

The Yangtze River Delta (YRD) is one of the most densely populated regions in China with severe air quality issues that have not been fully understood. Thus, in this study, based on 1-year (2013) continuous measurement at a National Reference Climatological Station (NRCS, 30.22° N, 120.17° E; 41.7 m a.s.l.) in the center of Hangzhou in the YRD, we investigated the seasonal characteristics, interspecies relationships, and the local emissions and the regional potential source contributions of trace gases (including O3, NOx, NOy, SO2, and CO) and particulate matter (PM2.5 and PM10). Results revealed that severe two-tier air pollution (photochemical and haze pollution) occurred in this region, with frequent exceedances in O3 (38 days) and PM2.5 (62 days). O3 and PM2.5 both exhibited distinct seasonal variations with reversed patterns: O3 reaching a maximum in warm seasons (May and July) but PM2.5 reaching a maximum in cold seasons (November to January). The overall results from interspecies correlation indicated a strong local photochemistry favoring the O3 production under a volatile organic compound (VOC)-limited regime, whereas it moved towards an optimum O3 production zone during warm seasons, accompanied by the formation of secondary fine particulates under high O3. The emission maps of PM2.5, CO, NOx, and SO2 demonstrated that local emissions were significant for these species on a seasonal scale. The contributions from the regional transport among inland cities (Zhejiang, Jiangsu, Anhui, and Jiangxi Province) on a seasonal scale were further confirmed to be crucial to air pollution at the NRCS site by using backward trajectory simulations. Air masses transported from the offshore areas of the Yellow Sea, East Sea, and South Sea were also found to be highly relevant to the elevated O3 at the NRCS site through the analysis of potential source contribution function (PSCF). Case studies of photochemical pollution (O3) and haze (PM2.5) episodes both suggested the combined importance of local atmospheric photochemistry and synoptic conditions during the accumulation (related with anticyclones) and dilution process (related with cyclones). Apart from supplementing a general picture of the air pollution state in the city of Hangzhou in the YRD region, this study specifically elucidates the role of local emission and regional transport, and it interprets the physical and photochemical processes during haze and photochemical pollution episodes. Moreover, this work suggests that cross-regional control measures are crucial to improve air quality in the YRD region, and it further emphasizes the importance of local thermally induced circulation for air quality.

β-decay studies of neutron-rich nuclei in and around the “island of inversion” have been performed. With a systematic investigation of half-lives for the isotonic chains from N=19 to 22, conspicuous kinks observed at Z=13 provide a clear signature of a boundary on the northern (high-Z) side of the island. Based on the comparison with shell model calculations using Gogny D1S and SDPF-M interactions, a newly determined 22+ state in 34Si at 4519 keV presents an experimental evidence of triaxiality in this region and sheds more light on the structure of the transition across the northern boundary of the island.

Cloud and Shadow removal is a significant step in remote sensing image process. As we all know, the ground object coverage type of the same area of the remote sensing image has little change in the short term. But for cloud and shadow coverage areas, the ground object coverage type has large change. Therefore, according to the difference between the two Landsat / OLI images caused by changes in the cover, this paper presents a method of extracting clouds and shadows based on differences in luminance values. This method selects two thresholds for the difference of brightness values, and extracts the clouds and shadows respectively, and validates them with random point method, which can obtain high precision of extracting cloud and shadow and satisfy the actual application needs.