Water level management of lakes connected to regulated rivers: An integrated modeling and analytical methodology

Reservoir operations significantly alter the hydrological regime of the downstream river and river-connected lake, which has far-reaching impacts on the lake ecosystem. To facilitate the management of lakes connected to regulated rivers, the following information must be provided: (1) the response of lake water levels to reservoir operation schedules in the near future and (2) the importance of different rivers in terms of affecting the water levels in different lake regions of interest. We develop an integrated modeling and analytical methodology for the water level management of such lakes. The data-driven method is used to model the lake level as it has the potential of producing quick and accurate predictions. A new genetic algorithm-based synchronized search is proposed to optimize input variable time lags and data-driven model parameters simultaneously. The methodology also involves the orthogonal design and range analysis for extracting the influence of an individual river from that of all the rivers. The integrated methodology is applied to the second largest freshwater lake in China, the Dongting Lake. The results show that: (1) the antecedent lake levels are of crucial importance for the current lake level prediction; (2) the selected river discharge time lags reflect the spatial heterogeneity of the rivers’ impacts on lake level changes; (3) the predicted lake levels are in very good agreement with the observed data (RMSE ≤ 0.091 m; R2 ≥ 0.9986). This study demonstrates the practical potential of the integrated methodology, which can provide both the lake level responses to future dam releases and the relative contributions of different rivers to lake level changes

Ultrahard carbon film from epitaxial two-layer graphene

Atomically thin graphene exhibits fascinating mechanical properties, although its hardness and transverse stiffness are inferior to those of diamond. To date, there hasn't been any practical demonstration of the transformation of multi-layer graphene into diamond-like ultra-hard structures. Here we show that at room temperature and after nano-indentation, two-layer graphene on SiC(0001) exhibits a transverse stiffness and hardness comparable to diamond, resisting to perforation with a diamond indenter, and showing a reversible drop in electrical conductivity upon indentation. Density functional theory calculations suggest that upon compression, the two-layer graphene film transforms into a diamond-like film, producing both elastic deformations and sp2-to-sp3 chemical changes. Experiments and calculations show that this reversible phase change is not observed for a single buffer layer on SiC or graphene films thicker than 3 to 5 layers. Indeed, calculations show that whereas in two-layer graphene layer-stacking configuration controls the conformation of the diamond-like film, in a multilayer film it hinders the phase transformation.Comment: Published online on Nature Nanotechnology on December 18, 201

Two-dimensional nanostructures for sodium-ion battery anodes

Sodium-ion batteries (SIBs) have attracted great attention recently due to the abundance of sodium resources, particularly for large-scale electric energy storage applications for renewable energy and smart grids. More and more nanostructured anode materials have been developed with the aims of high energy density, high cycling stability, and excellent rate capability, in which two-dimensional (2D) nanostructures are showing promise due to their shortened paths for sodium ion transportation and larger surface areas for sodium ion absorption. Moreover, 2D materials (e.g. graphene) have been proved to be excellent supporting and conducting agents in SIB anodes due to their high electrical conductivity and structural stability, in which synergetic effects between the graphene and the active materials are generally observed. This review is devoted to the recent progress in the use of 2D active materials and in composites consisting of both 2D supports and active materials as anodes for SIBs. Based on the manner of sodium storage, their electrochemical performance for sodium storage is discussed in terms of four classifications, including carbonaceous materials (graphene and carbon nanosheets), alloy based materials (Sn, Sb, and P), conversion materials (phosphides/oxides/sulfides/selenides), and intercalation materials (Ti-based compounds). Finally, the main challenges for and perspectives on 2D nanostructures for sodium storage are discussed

Dynamics Analysis and Synchronous Control of Fractional-Order Entanglement Symmetrical Chaotic Systems

In this paper, the Adomian decomposition method (ADM) semi-analytical solution algorithm is applied to solve a fractional-order entanglement symmetrical chaotic system. The dynamics of the system are analyzed by the Lyapunov exponent spectrum, bifurcation diagrams, poincaré diagrams, and chaos diagrams. The results show that the systems have rich dynamics. Meanwhile, sliding mode synchronizations of fractional-order chaotic systems are investigated theoretically and numerically. The results show the effectiveness of the proposed method and potential application value of fractional-order systems

An Adaptive Backstepping Sliding Mode Cascade-Control Method for a DC Microgrid Based on Nonlinear Virtual Inertia

In order to improve the bus voltage robustness of distributed multi-source DC microgrid, a new cascade control method based on nonlinear virtual inertia and adaptive backstepping sliding mode is proposed. Firstly, the mathematical model of distributed multi-source DC microgrid with a buck–boost interface converter is analyzed and established. A nonlinear virtual inertia control method based on a variable droop coefficient is given by introducing the converter output voltage variation rate feedback term and a saturation function equation. Secondly, the voltage and current double closed-loop cascade controller is designed by using backstepping sliding mode control and adaptive algorithms. Finally, the system and cascade control models are built in MATLAB/Simulink for multi-case simulation. The feasibility and effectiveness of the proposed method is verified by comparing the results with traditional control methods

Biotin and Leucine Alone or in Combination Promoted the Synthesis of Odd- and Branched-Chain Fatty Acids in the Rumen In Vitro

The odd- and branched-chain fatty acids (OBCFA) accumulated in ruminant products are a class of beneficial fatty acids for human health. Since biotin and leucine are involved in OBCFA synthesis, this study aimed to evaluate their effect on OBCFA synthesis in vitro. There were four treatments: the control group that only provided the basal diet, or the basal diet supplemented with biotin (4 mg/kg dry matter, DM), leucine (4 g/kg DM), or a combination of biotin (4 mg/kg DM) and leucine (4 g/kg DM). The results showed that biotin promoted the degradation of DM (p p iso, total anteiso, total branched-chain fatty acids, total OBCFA, and total fatty acids were significantly increased by the supplementation of biotin or leucine (p p < 0.05). In conclusion, the results of this study suggested that biotin and leucine can be used as effective nutrition strategies to promote OBCFA synthesis

An Adaptive Backstepping Sliding Mode Cascade-Control Method for a DC Microgrid Based on Nonlinear Virtual Inertia

In order to improve the bus voltage robustness of distributed multi-source DC microgrid, a new cascade control method based on nonlinear virtual inertia and adaptive backstepping sliding mode is proposed. Firstly, the mathematical model of distributed multi-source DC microgrid with a buck–boost interface converter is analyzed and established. A nonlinear virtual inertia control method based on a variable droop coefficient is given by introducing the converter output voltage variation rate feedback term and a saturation function equation. Secondly, the voltage and current double closed-loop cascade controller is designed by using backstepping sliding mode control and adaptive algorithms. Finally, the system and cascade control models are built in MATLAB/Simulink for multi-case simulation. The feasibility and effectiveness of the proposed method is verified by comparing the results with traditional control methods

Cultural Landscape Reproduction of Typical Religious Architecture in Qingjiangpu Based on Scene Theory

Scenes are important carriers of cultural expression. Cultural landscapes reveal specific cultural connotations through various scenes, and people understand and give things cultural connotations through scenes. In recent years, new techniques for visualizing cultural landscape heritage have been made possible by the advent of mapping and geographic information technology. The Beijing-Hangzhou Grand Canal’s culture is a “living” cultural legacy. As one of the key links in the canal’s cultural chain, Qingjiangpu is crucial to reproducing its cultural landscape. This paper first discusses the relationship between scene theory and the cultural landscape. Starting from the five elements of scene theory, through the collection of online text data and the corresponding data obtained from questionnaire research, the paper analyzed the scene constructed by the cultural landscape and the urban spirituality embodied by the scene. Through the deep excavation of cultural landscape and its historical context, the theoretical framework of “node-neighbor-city” cultural landscape reproduction is proposed. Taking the ancient city of Qingjiangpu as an example, the cultural landscape has been reproduced at different scales and in different dimensions through various technical means. This study can provide a theoretical basis and practical reference for the research of cultural landscape reproduction

Environmentally driven risk assessment for algal bloom occurrence in shallow lakes

An algal bloom is a complex hydro-biological phenomenon driven by multi-attribute environmental processes and thus is still difficult to predict. In this paper, a comprehensive modelling framework for forecasting algal bloom risks in shallow lakes is presented, which is based on long-term field observation and modelling of eutrophic shallow lakes. In the procedure, the major factors and their suitable ranges are investigated, and the individual influence of various driving factors is evaluated quantitatively, using an integrated approach of orthogonal design and regression analysis. By analysing the possible combined effects of the major driving factors and the relationship between algal bloom risk and major bloom-driving factors, a cost-effective environmentally driven risk assessment model is developed to forecast the likelihood of algal bloom occurrence, through a parameter optimization and prediction comparison routine. The risk model has been calibrated and validated against long-term field observations of algal blooms in Taihu Lake, with the prediction accuracy higher than 70%, which only requires readily available meteorological and water quality data. It is noted that for the closed shallow lake, the influence of hydrodynamics can be indirectly reflected by the variation of wind speed; and, total phosphorus, water temperature, photosynthetically active radiation, and average wind speed could be used as major bloom-driving factors in Taihu Lake generally. This study provides a practical framework for the development of algal bloom early warning schemes for shallow lakes and helps to understand the combined function of complex bloom-driving factors

Boosted charge transfer in SnS/SnO2 heterostructures: toward high rate capability for sodium-ion batteries

Constructing heterostructures can endow materials with fascinating performance in high-speed electronics, optoelectronics, and other applications owing to the built-in charge-transfer driving force, which is of benefit to the specific charge-transfer kinetics. Rational design and controllable synthesis of nano-heterostructure anode materials with high-rate performance, however, still remains a great challenge. Herein, ultrafine SnS/SnO2 heterostructures were successfully fabricated and showed enhanced charge-transfer capability. The mobility enhancement is attributed to the interface effect of heterostructures, which induces an electric field within the nanocrystals, giving them much lower ion-diffusion resistance and facilitating interfacial electron transport