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The first source catalog of the Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a very high energy gamma-ray source, 1LHAASO J1219+2915. This Letter presents a further detailed study of the spectral and temporal behavior of this pointlike source. The best-fit position of the TeV source (R.A. = 185.°05 ± 0.°04, decl. = 29.°25 ± 0.°03) is compatible with NGC 4278 within ∼0.°03. Variation analysis shows an indication of variability on a timescale of a few months in the TeV band, which is consistent with low-frequency observations. Based on these observations, we report the detection of TeV γ -ray emissions from this low-luminosity active galactic nucleus. The observation by LHAASO's Water Cherenkov Detector Array during the active period has a significance level of 8.8 σ with a best-fit photon spectral index Γ = 2.56 ± 0.14 and a flux f _1–10 TeV = (7.0 ± 1.1 _sta ± 0.35 _syst ) × 10 ^−13 photons cm ^−2 s ^−1 , or approximately 5% of the Crab Nebula. The discovery of VHE gamma-ray emission from NGC 4278 indicates that compact, weak radio jets can efficiently accelerate particles and emit TeV photons.

Abstract Tropical cyclones (TCs) are known to bring heavy rainfall, strong winds and severe storm surges simultaneously, resulting in tremendous damage beyond the effects of a single hazard. However, the compound impacts of TC multi‐hazards remain unexplored in macroeconomic assessments. Here, we provide empirical evidence on the multi‐hazard economic losses of TC for the first time. We used a national panel of provincial economic output in China over 2000–2020. Our results show that the total macroeconomic impact of the severest TC multi‐hazards can represent up to 14 times the value of merely TC winds. Specifically, the vast majority (over 80%) of the combined TC impacts is caused by precipitation, with wider and greater economic impacts than TC winds and storm surges. Furthermore, high‐latitude and interior regions of China are more vulnerable to TCs due to the interactions with temperature variability and TC wind intensity variability. High‐income areas and secondary industries respond markedly to all TC hazards, and the economic impact of TC precipitation is significant over all sectors. Our findings provide new implications for the socio‐economic impact mechanisms of multiple hazards of TCs and valuable insights into the design of climate policy for compound hazard risks.

We present the first catalog of very-high-energy and ultra-high-energy gamma-ray sources detected by the Large High Altitude Air Shower Observatory. The catalog was compiled using 508 days of data collected by the Water Cherenkov Detector Array from 2021 March to 2022 September and 933 days of data recorded by the Kilometer Squared Array from 2020 January to 2022 September. This catalog represents the main result from the most sensitive large coverage gamma-ray survey of the sky above 1 TeV, covering decl. from −20° to 80°. In total, the catalog contains 90 sources with an extended size smaller than 2° and a significance of detection at >5 σ . Based on our source association criteria, 32 new TeV sources are proposed in this study. Among the 90 sources, 43 sources are detected with ultra-high energy ( E > 100 TeV) emission at >4 σ significance level. We provide the position, extension, and spectral characteristics of all the sources in this catalog.

Abstract The focal plane camera is the core component of the Wide Field-of-view Cherenkov/fluorescence Telescope Array (WFCTA) of the Large High-Altitude Air Shower Observatory (LHAASO). Because of the capability of working under moonlight without aging, silicon photomultipliers (SiPM) have been proven to be not only an alternative but also an improvement to conventional photomultiplier tubes (PMT) in this application. Eighteen SiPM-based cameras with square light funnels have been built for WFCTA. The telescopes have collected more than 100 million cosmic ray events and preliminary results indicate that these cameras are capable of working under moonlight. The characteristics of the light funnels and SiPMs pose challenges (e.g. dynamic range, dark count rate, assembly techniques). In this paper, we present the design features, manufacturing techniques and performances of these cameras. Finally, the test facilities, the test methods and results of SiPMs in the cameras are reported here.

Endmember mixing analysis (EMMA) is often used by hydrogeochemists to interpret the sources of stream solutes, but variations in stream concentrations and discharges remain difficult to explain. We discovered that machine learning can be used to highlight patterns in stream chemistry that reveal information about sources of solutes and subsurface groundwater flowpaths. The investigation has implications, in turn, for the balance of CO2 in the atmosphere. For example, CO2-driven weathering of silicate minerals removes carbon from the atmosphere over ∼106-year timescales. Weathering of another common mineral, pyrite, releases sulfuric acid that in turn causes dissolution of carbonates. In that process, however, CO2 is released instead of sequestered from the atmosphere. Thus, understanding long-term global CO2 sequestration by weathering requires quantification of CO2- versus H2SO4-driven reactions. Most researchers estimate such weathering fluxes from stream chemistry, but interpreting the reactant minerals and acids dissolved in streams has been fraught with difficulty. We apply a machine-learning technique to EMMA in three watersheds to determine the extent of mineral dissolution by each acid, without pre-defining the endmembers. The results show that the watersheds continuously or intermittently sequester CO2, but the extent of CO2 drawdown is diminished in areas heavily affected by acid rain. Prior to applying the new algorithm, CO2 drawdown was overestimated. The new technique, which elucidates the importance of different subsurface flowpaths and long-timescale changes in the watersheds, should have utility as a new EMMA for investigating water resources worldwide.

To investigate the impacts of multiscale circulations on the planetary boundary layer (PBL), we have carried out the PBL thermodynamic structure field experiment with a Doppler wind profile lidar, a microwave radiometer, and a ceilometer from January 2018 to December 2019 in Beijing. We found that the direct regulatory effect of synoptic circulation worked through transporting and accumulating pollutants in front of mountains in the daytime, while the indirect effect of multiscale circulations worked through coupling mechanisms in the nighttime. The horizontal coupling of different-direction winds produced a severe pollution convergent zone. The vertical coupling of upper environmental winds and lower regional breezes regulated the mixing and diffusion of pollutants by generating dynamic wind shear and advective temperature inversion. We also found that the dominating synoptic circulations led to great differences in PBL thermodynamic structure and pollution. The cyclonic circulation resulted in a typical multilayer PBL characterized by high vertical shear (600 m), temperature inversion (900 m), and an inhomogeneous stratification. Meanwhile, strong regional breezes pushed the pollution convergent zone to the south of Beijing. The southwesterly circulation resulted in a mono-layer PBL characterized by low vertical shear (400 m) and inversion (200 m). The westerly circulation led to a hybrid-structure PBL, and the advective inversion was generated by the vertical shear of zonal winds. Strong environmental winds of southwesterly and westerly circulations pushed the severe-pollution zone to the front of mountains. There was no distinct PBL structure under the anticyclone circulation. The study systematically revealed the appreciable effects of synoptic and regional circulations on PBL structure and air quality, which enriched the prediction theory of atmospheric pollution in the complex terrain.

Predicting landslide displacement is challenging, but accurate predictions can prevent casualties and economic losses. Many factors can affect the deformation of a landslide, including the geological conditions, rainfall and reservoir water level. Time series analysis was used to decompose the cumulative displacement of landslide into a trend component and a periodic component. Then the least-squares support vector machine (LSSVM) model and genetic algorithm (GA) were used to predict landslide displacement, and we selected a representative landslide with episodic movement deformation as a case study. The trend component displacement, which is associated with the geological conditions, was predicted using a polynomial function, and the periodic component displacement which is associated with external environmental factors, was predicted using the GA-LSSVM model. Furthermore, based on a comparison of the results of the GA-LSSVM model and those of other models, the GA-LSSVM model was superior to other models in predicting landslide displacement, with the smallest root mean square error (RMSE) of 62.4146 mm, mean absolute error (MAE) of 53.0048 mm and mean absolute percentage error (MAPE) of 1.492 % at monitoring station ZG85, while these three values are 87.7215 mm, 74.0601 mm and 1.703 % at ZG86 and 49.0485 mm, 48.5392 mm and 3.131 % at ZG87. The results of the case study suggest that the model can provide good consistency between measured displacement and predicted displacement, and periodic displacement exhibited good agreement with trends in the major influencing factors.

The simultaneous observation and analysis of atmospheric fine particles (PM2.5) on a regional scale is an important approach to develop control strategies for haze pollution. In this study, samples of filtered PM2.5 were collected simultaneously at three urban sites (Beijing, Tianjin, and Shijiazhuang) and at a regional background site (Xinglong) in the Beijing–Tianjin–Hebei (BTH) region from June 2014 to April 2015. The PM2.5 at the four sites was mainly comprised of organic matter, secondary inorganic ions, and mineral dust. Positive matrix factorization (PMF) demonstrated that, on an annual basis, secondary inorganic aerosol was the largest PM2.5 source in this region, accounting for 29.2–40.5 % of the PM2.5 mass at the urban sites; the second-largest PM2.5 source was motor vehicle exhaust, particularly in Beijing (24.9 %), whereas coal combustion was also a large source in Tianjin (12.4 %) and Shijiazhuang (15.5 %), with particular dominance in winter. Secondary inorganic aerosol plays a vital role in the haze process, with the exception of the spring haze in Shijiazhuang and Tianjin, for which the dust source was crucial. In addition to secondary transformations, local direct emissions (coal combustion and motor vehicle exhaust) significantly contribute to the winter haze at the urban sites. Moreover, with the aggravation of haze pollution, the OC ∕ EC mass ratio of PM2.5 decreased considerably and the nitrate-rich secondary aerosol increased during all four seasons in Beijing, both of which indicate that local motor vehicle emissions significantly contribute to the severe haze episodes in Beijing. To assess the impacts of regional transport on haze pollution, the PMF results were further processed with backward-trajectory cluster analysis, revealing that haze pollution usually occurred when air masses originating from polluted industrial regions in the south prevailed and is characterized by high PM2.5 loadings with considerable contributions from secondary aerosols. This study suggests that control strategies to mitigate haze pollution in the BTH region should focus on the reduction of gaseous precursor emissions from fossil fuel combustion (motor vehicle emissions in Beijing and coal combustion in Tianjin, Hebei, and nearby provinces).

Owing to unique size- and shape- dependent localized surface plasmon resonance (LSPR) of noble metal nanoparticles (NPs), the optical extinction spectroscopy method (OES) has received much attention to characterize the geometry of metal NPs by fitting experimental UV-vis-NIR spectra. In this work, we aimed to develop a more convenient and accurate OES method to characterize the structural parameters and concentration of the gold nanorods (GNRs) ensemble. The main difference between our approach and previous OES methods is that we solve this inverse spectra problem by establishing the LSPR relation equations of GNRs ensemble so that there is no need of UV-vis-NIR spectra fitting process. The aspect ratio (AR) and AR distribution can be directly retrieved from two of UV-vis-NIR spectral parameters (peak position and full width at half maximum) using the obtained relation equations. Furthermore, the relation equations are modified for applying to the more general GNRs samples by considering the plasmon shift due to the near distance dielectric sensitivity. Finally, instead of inductively coupled plasma mass spectrometry (ICP-MS) measurement, we provide a more facile measure of the mass-volume concentration which can be determined from the extinction value at 400 nm. By comparing with the experimental results, it shows that the retrieved results by the relation equations are reliable.

The healthy status of product reflects its ability to perform a specified task at a reliable and maintainable level in a certain period of time. It is significant for long-term storage and disposable products to estimate storage reliability, determine maintenance intervals, optimize storage cost and accomplish product tasks by means of establishing product health management center (PHMC) aiming at monitoring and managing product’s healthy state synthetically. This paper, regarding PHMC as a system of systems (SoS), builds a framework of PHMC based on the U.S. Department of Defense Architecture Framework (DoDAF), on the basis of comprehensive analysis of the characteristics of usage and maintenance for long-term storage and disposable product in maritime industry. The framework involves personnel, organization, and a variety of maintenance and support activities in relation to product health management. This framework describes the top-level design of the system with the help of high-level conceptual diagram. This paper also makes a specific design of the system in detail based on activity-based modelling (ABM) method. It shows that the framework is a useful practice in terms of adopting systems of system engineering (SOSE) ideas and DoDAF architecture to build PHMC system. Outcomes of the system implementation indicate that, for long-term storage and disposable product, PHMC can improve the efficiency of maintenance and support, at the same time it can reduce maintenance and support cost.