ALBERT

Beschreibung: The electronic and magnetic properties of the newly synthesized single-layer (1 L) transition-metal dichalcogenide (TMD) PtSe 2 are studied by first-principles calculations. We find the strain or selenium vacancy (V Se ) alone cannot induce the magnetism. However, an interplay between strain and V Se leads to the magnetism due to the breaking of Pt-Pt metallic bonds. Different from the case of 1 L-MoS 2 with V S , the defective 1 L-PtSe 2 has the spatially extended spin density, which is responsible for the obtained long range ferromagnetic coupling. Moreover, the 1 L-PtSe 2 with V Se undergoes a spin reorientation transition from out-of-plane to in-plane magnetization, accompanying a maximum magnetocrystalline anisotropy energy of ∼9–10.6 meV/V Se . These results indicate the strain not only can effectively tune the magnetism but also can manipulate the magnetization direction of 1 L-TMDs.

Beschreibung: Rural revitalization is an important strategy to promote sustainable development of rural areas in China. Rural revitalization listed companies play an important role in implementing the rural revitalization strategy and developing the agricultural industry. However, the financing problem has always been a bottleneck problem with Chinese listed companies. This study used a two-stage DEA (data envelopment analysis) method to evaluate the funds raising efficiency, funds using efficiency, and overall financing efficiency of 34 rural revitalization listed companies in 2018. The results show that the financing efficiencies of 34 sample companies were low, only six companies have overall efficient financing, and there was much room for improvement. Financing efficiency varied greatly depending on the nature of the company, the industry, and the listing board. The efficiency of funds using of state-owned enterprises was much lower than that of private companies. The average efficiency value of agricultural company funds raising was lower than that of manufacturing. The efficiency of small and middle-size enterprises (SMEs) was lower than that of main board companies, but the growth enterprise market (GEM) companies achieved higher efficiency in the funds using. Further, by using the grey relational analysis (GRA) method, we found that the key factors affecting the financing efficiency of sample companies included capital structure, debt-paying ability, governance structure, company age, and operating ability. To improve financing efficiency, the companies should not only optimize their capital structure and governance structure but also improve their management and innovation capabilities. At the same time, the state also needs to give different policies support according to the characteristics of the companies.

Beschreibung: Fe-Co-Cr-Mo-W-V-C alloy is one of the most important materials for manufacturing drills, dies, and other cutting tools owing to its excellent hardness. However, it is prone to cracking due to its poor hot ductility during continuous hot working processes. In this investigation, the microstructure characteristics and carbide transformations of the alloy in as-cast and wrought states are studied, respectively. Microstructural observation and first-principles calculation were conducted on the research of types and mechanical properties of carbides. The results reveal that carbides in as-cast Fe-Co-Cr-Mo-W-V-C alloy are mainly Mo2C, VC, and Cr-rich carbides (Cr7C3 and Cr23C6). The carbides in wrought Fe-Co-Cr-Mo-W-V-C alloy consist of Fe2Mo4C, VC, Cr7C3, and a small amount of retained Mo2C. For these carbides, Cr7C3 presents the maximum bulk modulus and B/G values of 316.6 GPa and 2.48, indicating Cr7C3 has the strongest ability to resist the external force and crack initiation. VC presents the maximum shear modulus and Yong’s modulus values of 187.3 GPa and 465.3 GPa, which means VC can be considered as a potential hard material. Hot isothermal compression tests were performed using a Gleeble-3500 device to simulate the flow behavior of the alloy during hot deformation. As-cast specimens were uniaxially compressed to a 70% height reduction over the temperature range of 1323–1423 K and strain rates of 0.05–1 s−1. A constitutive equation was established to characterize the relationship of peak true stress, strain rate, and deformation temperature of the alloy. The calculated results were in a good agreement with the experimental data. In order to study the texture evolution, the microstructures of the deformed specimens were observed, and an optimal deformation temperature was selected. Using the laboratorial optimal temperature (1373 K) in forging of an industrial billet resulted in uniform grains, with the largest size of 17 µm, surrounded by homogenous spherical carbides.

Beschreibung: Drought is one of the most common natural disasters on a global scale and has a wide range of socioeconomic impacts. In this study, we analyzed the spatiotemporal variations of meteorological drought in a typical agricultural province of China (i.e., Shaanxi Province) based on the Standard Precipitation Evapotranspiration Index (SPEI). We also investigated the response of winter wheat and summer maize yields to drought by a correlation analysis between the detrended SPEI and the time series of yield anomaly during the crop growing season. Moreover, agricultural drought risks were assessed across the province using a conceptual risk assessment model that emphasizes the combined role of drought hazard and vulnerability. The results indicated that droughts have become more severe and frequent in the study area after 1995. The four typical timescales of SPEI showed a consistent decreasing trend during the period 1960–2016; the central plains of the province showed the most significant decreasing trend, where is the main producing area of the province’s grain. Furthermore, the frequency and intensity of drought increased significantly after 1995; the most severe drought episodes occurred in 2015–2016. Our results also showed that the sensitivity of crop yield to drought varies with the timescales of droughts. Droughts at six-month timescales that occurred in March can explain the yield losses for winter wheat to the greatest extent, while the yield losses of summer maize are more sensitive to droughts at three-month timescales that occurred in August. The assessment agricultural drought risk showed that some areas in the north of the province are exposed to a higher risk of drought and other regions are dominated by low risk.

Beschreibung: In this paper, the dual-frequency (DF) glow discharges in atmospheric helium were experimented by electrical and optical measurements in terms of current voltage characteristics and optical emission intensity. It is shown that the waveforms of applied voltages or discharge currents are the results of low frequency (LF) waveforms added to high frequency (HF) waveforms. The HF mainly influences discharge currents, and the LF mainly influences applied voltages. The gas temperatures of DF discharges are mainly affected by HF power rather than LF power.

Beschreibung: In recent years, China has launched YaoGan-13 and GaoFen-3, high-resolution synthetic aperture radar (SAR) satellites that can acquire global high-resolution images. The absolute positioning accuracy of such satellites is important for mapping areas without ground reference points and for automated processing. However, satellites without geometric calibration have poor absolute positioning accuracy, greatly restricting their application (e.g., land resource surveys). Therefore, they cannot meet national demands for high-resolution SAR images with good geometric accuracy. Here, we propose a series of methods to improve the absolute positioning accuracy of YaoGan-13 and GaoFen-3, such as the multiple-image combined calibration strategy and geometric calibration model for a real continuously moving configuration, including consideration of atmospheric propagation delay. Using high-accuracy ground control data collected from different areas, the 2-D and 3-D absolute positioning accuracies of YaoGan-13 and GaoFen-3 were assessed after implementation of the improvement measures. Experimental results showed that, after calibration, the 2-D absolute positioning accuracy of YaoGan-13 and GaoFen-3 are improved from 43.86 m to 2.57 m and from 30.34 m to 4.29 m, respectively. In addition, the 3-D absolute positioning accuracies of YaoGan-13 in plane and elevation are 3.21 m and 2.22 m, respectively. Improving the absolute positioning accuracy of these satellites could broaden the scope of their potential applications in the future.

Beschreibung: Ginkgo (Ginkgo biloba L.) is not only considered a ‘living fossil’, but also has important ecological, economic, and medicinal values. However, the impact of climate change on the performance and distribution of this plant is an increasing concern. In this study, we developed a bioclimatic model based on data about the occurrence of ginkgo from 277 locations, and validated model predictions using a wide-ranging field test (12 test sites, located at the areas from 22.49° N to 39.32° N, and 81.11° E to 123.53° E). We found that the degree-days below zero were the most important climate variable determining ginkgo distribution. Based on the model predictions, we classified the habitat suitability for ginkgo into four categories (high, medium, low, and unsuitable), accounting for 9.29%, 6.09%, 8.46%, and 76.16% of China’s land area, respectively. The ANOVA results of the validation test showed significant differences in observed leaf-traits among the four habitat types (p 〈 0.05), and importantly the rankings of the leaf traits were consistent with our classification of the habitat suitability, suggesting the effectiveness of our classification in terms of biological and economic significance. In addition, we projected that suitable (high and medium) habitats for ginkgo would shrink and shift northward under both the RCP4.5 and RCP8.5 climate change scenarios for three future periods (the 2020s, 2050s, and 2080s). However, the area of low-suitable habitat would increase, resulting in a slight decrease in unsuitable habitats. Our findings contribute to a better understanding of climate change impact on this plant and provide a scientific basis for developing adaptive strategies for future climate.

Beschreibung: The change in river flows at the basin scale reflects the combined influences of changes in various environmental factors associated with climatic and underlying surface properties. Distinguishing the relative contribution of each of these factors to runoff change is critical for sustainable water resource management, but it is also challenging. The headstream region of the Yangtze River, known as “China’s Water Tower”, has undergone a significant runoff change over the past decades. However, the relative contribution of environmental factors to runoff change is still unclear. Here, we designed a series of detrending experiments based on a grid-based hydrological model to quantify the combined influences of multiple environmental factors on runoff change and the relative contribution of an individual factor to runoff change. The results indicate that changes in climate and vegetation significantly increased water yield in the study basin over the past three decades, and the increase in water yield primarily came from the contribution from the upstream of the basin. On the basin scale, the change in precipitation dominated the runoff change that contributed up to 113.2% of the runoff change, followed by the wind speed change with a contribution rate of −15.1%. Other factors, including changes in temperature, relative humidity, sunshine duration (as a surrogate for net radiation), and albedo (as a surrogate for vegetation) had limited effects on runoff change, and the contribution rate of these factors to runoff change ranged from −5% to 5%. On spatial patterns, the influences of changes in some environmental factors on runoff changes were affected by elevation, particularly for temperature. The rising temperature had mixed effects on runoff change, which generally increased water yield at high altitudes of the basin but decreased water yield at low altitudes of the basin.

Beschreibung: Security is a main concern for the Internet of Things (IoT) infrastructure as large volumes of data are collected and processed in the systems. Due to the limited resources of interconnected sensors and devices in the IoT systems, efficiency is one of the key considerations when deploying security solutions (e.g., symmetric/asymmetric encryption, authentication, etc.) in IoT. In this paper, we present an efficient Hierarchical Identity-Based Encryption (HIBE) system with short parameters for protecting data confidentiality in distributed IoT infrastructure. Our proposed HIBE system has the public parameters, private key, and ciphertext, each consisting of a constant number of group elements. We prove the full security of the HIBE system in the standard model using the dual system encryption technique. We also implement the proposed scheme and compare the performance with the original Lewko–Waters HIBE. To the best of our knowledge, our construction is the first HIBE system that achieves both full security in the standard model and short parameters in terms of the public parameters, private key, and ciphertext.

Beschreibung: The traditional modeling methods of aircraft fuel center of gravity (CG) based on sensor data have some disadvantages, such as large data storage requirements and low computational efficiency. In this article, a novel hybrid heuristic search-simulated annealing (HS-SA) algorithm is used to reduce the data storage requirements and improve the efficiency of the established models based on sensor data. First, a fuel CG model is established based on the multidimensional interpolation of flight sensors and fuel tank data, which can accurately reflect the nonlinear characteristics of the problem and reduce the data storage needs. Then, the calculation nodes are reasonably selected and optimized based on the proposed HS-SA algorithm to improve the precision of the model of the aircraft fuel CG. The established model of the fuel CG has obvious advantages over traditional methods in improving the temporal efficiency and meeting the storage requirements for sensor data in actual flights. Finally, detailed simulations are conducted based on more than 16,000 sets of sensor data, and the results demonstrate the effectiveness of the proposed HS-SA algorithm.