Methyl 3-(4-chloro­phen­yl)-2-(1,3-dimethyl-2,5-dioxo-4-phenyl­imidazolidin-4-yl)-3-oxopropano­ate

The title compound, C21H19ClN2O5, is a tetra­substituted hydantoin derivative which contains an imidazolidine-2,4-dione core. The dihedral angle between the aromatic rings is 64.53 (14)°. In the crystal, weak inter­molecular C—H⋯O hydrogen bonding is found. An intra­molecular C—H⋯O inter­action also occurs

Interactive Effects of Water and Fertilizer on Yield, Soil Water and Nitrate Dynamics of Young Apple Tree in Semiarid Region of Northwest China

Exploring the interactive effect of water and fertilizer on yield, soil water and nitrate dynamics of young apple tree is of great importance to improve the management of irrigation and fertilization in the apple-growing region of semiarid northwest China. A two-year pot experiment was conducted in a mobile rainproof shelter of the water-saving irrigation experimental station in Northwest A&F University, and the investigation evaluated the response of soil water and fertilizer migration, crop water productivity (CWP), irrigation water use efficiency (IWUE), partial factor productivity (PFP) of young apple tree to different water and fertilizer regimes (four levels of soil water: 75%–85%, 65%–75%, 55%–65% and 45%–55% of field capacity, designated W1, W2, W3 and W4, respectively; three levels of N-P2O5-K2O fertilizer, 30-30-10, 20-20-10 and 10-10-10 g plant−1, designated F1, F2 and F3, respectively). Results showed that F1W1, F2W1 and F3W1 had the highest average soil water content at 0~90 cm compared with the other treatments. When fertilizer level was fixed, the average soil water content was gradually increased with increasing irrigation amount. For W1, W2, W3 and W4, high levels of water content were mainly distributed at 50~80 cm, 40~70 cm, 30~50 cm and 10~30 cm, respectively. There was no significant difference in soil water content at all fertilizer treatments. However, F1 and F2 significantly increased soil nitrate-N content by 146.3%~246.4% and 75.3%~151.5% compared with F3. The highest yield appeared at F1W1 treatment, but there was little difference between F1W1 and F2W2 treatment. F2W2treatment decreased yield by 7.5%, but increased IWUE by 11.2% compared with F1W1 treatment. Meanwhile, the highest CWP appeared at F2W2 treatment in the two years. Thus, F2W2 treatment (soil moisture was controlled in 65–75% of field capacity, N-P2O5-K2O were controlled at 20-20-10 g·tree−1) reached the best water and fertilizer coupling mode and it was the optimum combinations of water and fertilizer saving

Research on multi-physical field analysis and assessment technique of virtual connection defects in cluster cable joints based on digital twin technology

As the “blood vessels” and “nerves” of the power grid, cables are important carriers for transmitting electric energy, and their failures will affect the safe and stable operation of the power grid. In this paper, a digital twin model of thermal characteristics is constructed for 10 kV YJV×400 cluster cable and its joint model. Based on the multi-physical field coupling analysis method, the fluid field, temperature field and current-carrying capacity of the cluster cable are analyzed. The temperature rise and airflow distribution characteristics of the joint and its external insulation when the defect of joint false connection occurs are analyzed. Based on the fuzzy analytic hierarchy process (FAHP), weights are assigned to the locations of multiple measurement points of the cable external insulation, and the temperature distribution of each measurement point is combined with the digital twin technology to calculate the hot spot temperature of the cable, so as to assess the defects of the joints of the cables. The digital twin platform is used for real-time monitoring of cable status and assessment of defects. The temperature rise experiments of cables under different carrying capacity and joint defects show that this method can accurately and efficiently calculate hot spot temperatures and assess defects of joints in cluster cables

A prioritization metric and modelling framework for fragmented saltmarsh patches restoration

Saltmarsh is a coastal ecosystem providing crucial ecosystem services, and its continued degradation and fragmentation has drawn increasing attention. However, how to effectively restore the connectivity between fragmented saltmarsh patches remains an open challenge. In this study, we developed a metric and modelling framework that prioritised saltmarsh patches for restoration. To demonstrate our approach, we simulated spatially explicit restoration schedules for Suaeda salsa patches at the Yellow River Delta National Nature Reserve, China, using three strategies: increasing-patch-area, increasing-number-of-patches and a benchmark unrestrictive prioritization strategy. We prioritised patches for restoration based on a number of widely used graph-theoretic landscape connectivity and metapopulation capacity metrics. Our simulation results suggested the rank connectivity-importance of extant patches was correlated within the group of graph-theoretic connectivity metrics or metapopulation capacity metrics, but unrelated across group. The unrestrictive prioritization strategy clearly outperformed the strategies of increasing-patch-area and increasing-number-of-patches which returned comparable connectivity restoration outcomes. For the more effective unrestrictive prioritization strategy, there were substantial differences in the simulated priority patches between metrics that considered stepping stone effects and those did not. While the former resulted in corridor-building priority patches that led to a more connected landscape throughout the region, the latter led to local clustering. We recommend use of the total probability of connectivity (PC) among the metrics we tested due to similarity of results to other metrics and its simulation efficiency. The proposed framework is readily applicable to prioritise areas for connectivity conservation and restoration in any monospecific ecosystem at the regional scale

Risk Factors of Subclinical Atherosclerosis and Plaque Burden in High Risk Individuals: Results From a Community-Based Study

China is going through major change and the incidence of first-ever stroke has increased dramatically. In this study, we aim to determine the ultrasound characteristics of carotid intima-media thickness (CIMT) and carotid plaques (CP) in the Chinese community-based population with high risk of stroke. 1009 stroke-free participants from Datun community were classified at high risk of stroke and included in this cross-sectional study. We performed B-mode carotid ultrasound imaging in all of the study subjects to measure the CIMT in the common carotid artery (CCA) far wall and CP in the CCA, bifurcation and internal carotid artery. Stepwise logistic regression analyses were used to determine factors associated with elevated CIMT and subclinical atherosclerosis, as well as plaque burden (≥2 plaques). Our results showed that traditional risk factors including aging, hypertension, current smoking and the level of high density lipoprotein cholesterol are associated with subclinical atherosclerosis and plaque burden in high-risk community residents. To improve primary prevention in this population, we may consider intense blood pressure and lipid management, and smoking cessation

Valley-polarized Exitonic Mott Insulator in WS2/WSe2 Moir\'e Superlattice

Strongly enhanced electron-electron interaction in semiconducting moir\'e superlattices formed by transition metal dichalcogenides (TMDCs) heterobilayers has led to a plethora of intriguing fermionic correlated states. Meanwhile, interlayer excitons in a type-II aligned TMDC heterobilayer moir\'e superlattice, with electrons and holes separated in different layers, inherit this enhanced interaction and strongly interact with each other, promising for realizing tunable correlated bosonic quasiparticles with valley degree of freedom. We employ photoluminescence spectroscopy to investigate the strong repulsion between interlayer excitons and correlated electrons in a WS2/WSe2 moir\'e superlattice and combine with theoretical calculations to reveal the spatial extent of interlayer excitons and the band hierarchy of correlated states. We further find that an excitonic Mott insulator state emerges when one interlayer exciton occupies one moir\'e cell, evidenced by emerging photoluminescence peaks under increased optical excitation power. Double occupancy of excitons in one unit cell requires overcoming the energy cost of exciton-exciton repulsion of about 30-40 meV, depending on the stacking configuration of the WS2/WSe2 heterobilayer. Further, the valley polarization of the excitonic Mott insulator state is enhanced by nearly one order of magnitude. Our study demonstrates the WS2/WSe2 moir\'e superlattice as a promising platform for engineering and exploring new correlated states of fermion, bosons, and a mixture of both

Hopf bifurcation for an SIR model with age structure

This paper deals with an SIR model with age structure of infected individuals. We formulate the model as an abstract non-densely defined Cauchy problem and derive the conditions for the existence of all the feasible equilibrium points of the system. The criteria for both stability and instability involving system parameters are obtained. Bifurcation analysis indicates that the system with age structure exhibits Hopf bifurcation which is the main result of this paper. Finally, some numerical examples are provided to illustrate our obtained results

Self-adaptable reactive power-voltage controller for virtual synchronous generators

With a higher and higher penetration of renewable energy in the grid, the principle of the virtual synchronous generator (VSG) is proposed as an attractive solution to controlling the grid-connected inverters. In common, active power-frequency and reactive power-voltage controllers play major roles in VSG control system. However, the line impedance and local loads are the critical case effecting on the control result of the two controllers. Compared with reactive power-voltage controller, active power-frequency controller is more easier to product the load sharing among the VSGs accurately. This paper presents a self-adaptable reactive power-voltage controller to deal with the sharing problem of reactive power in the parallel VSGs system, using the reactive power difference to adjust reactive power-voltage control coefficient. Then, a linearised small-signal model is established for stability analysis of the reactive power-voltage control coefficient to the parallel VSGs system. Finally, an experiment of two parallel VSGs system based on the self-adaptable reactive power-voltage controllers is performed, with different line impedance. Results obtained from the experiment verify the effectiveness of the proposed self-adaptable reactive power-voltage controllers in the parallel VSGs system

Parallel operation of virtual synchronous generators and synchronous generators in a microgrid

Aiming for integration of a large-scale of distributed generators (DGs) such as photovoltaic into the microgrids, the virtual synchronous generator (VSG) control concept has been developed. By this concept, DGs based on inverters can exhibit the characteristics of synchronous generators (SGs) such as the inertial, damping, and droop functions and can participate in the microgrid control and stability. Here, a detailed VSG model is presented and analysed in order to investigate that, VSGs have really the similar structure of SGs. Then, the paper studies the microgrid with both VSG and ordinary SG. Then, parallel arrangements of VSG-VSG are set up in order to compare the dynamic behaviour of the VSG with the standard SG in an isolated microgrid. The dynamic responses are compared under equal sharing and proportional sharing of the load demand. Simulation results are presented using matlab/simulink