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The low-temperature fatigue crack propagation rate of 925A steel, as a rudder steel for polar special ships, has a crucial impact on the evaluation of the fatigue strength of polar ships. The purpose of this article is to study the fatigue crack propagation rate of 925A steel under different low-temperature conditions from room temperature (RT) to −60 °C. The material was subjected to fatigue crack propagation tests and stress intensity factor tests. The experimental tests were conducted according to the Chinese Standard of GB/T6398-2017. The results show that as the temperature decreases, the lifespan of 925A increases. Within a certain stress intensity factor, as the temperature decreases, the fatigue crack propagation rate decreases. At −60 °C, it exhibits ductile fracture; within normal polar temperatures, it can be determined that 925A meets the requirements for low-temperature fatigue crack propagation rates in polar regions. However, in some extreme polar temperatures below −60 °C, preventing brittle failure becomes a key focus of fatigue design. Finally, the fatigue crack propagation behavior at the microscale of 925A steel at low temperatures was described using fracture morphology. The experimental data can provide reference for the design of polar ships to further resist low-temperature fatigue and cold brittle fracture. [ABSTRACT FROM AUTHOR]

Renewable energy sources (RESs) are generally connected to the grid through power electronic interfaces, which generate electrical power instantaneously with little inertia. With the increasing penetration of RESs, the grid will gradually develop into a low inertia and underdamped power system, which results in serious grid frequency stabilization problems. The virtual synchronous generator (VSG) is an emerging technology that mimics the operation characteristics of traditional synchronous generators (SGs). Virtual inertia and damping are therefore introduced, which help to stabilize grid frequency. This paper gives a comprehensive overview of the VSG. The basic operation principle of VSG is introduced and analyzed in depth. The key issues related to VSG are summarized and discussed, including hardware configuration, software control strategies, energy supporting methods, and typical applications. [ABSTRACT FROM AUTHOR]

Power conditioning system (PCS) is the crucial component of superconducting magnetic storage system (SMES), which determines its power control performance and ability. This paper investigates the feasibility of applying Z source converter (ZSC) as the PCS for SMES. A ZSC-based PCS (ZSC-PCS) for SMES is presented, parameter design methods are analyzed, and a novel minimum power losses control scheme is proposed. By dynamically regulating open zero vector duty ratio to its minimum required level, the ZSC-PCS can enlarge both active and reactive power capability of SMES with lowest power losses. The feasibility of the proposed approach is verified by the experimental results on a kVA scale prototype. [ABSTRACT FROM AUTHOR]

When multiple coherent sound sources are distributed on the same side of the holographic surface, the conventional method must use known information such as sound source distribution and geometry. In view of this situation, a method of coherent sound field separation combined with compressive sensing is proposed. The method is based on the plane equivalent source near-field acoustic holography method and the orthogonal matching pursuit algorithm of compressive sensing technology. Get the distribution of the virtual sound source on the plane, and then the virtual sound sources are grouped and selected. Finally, the distribution of sound pressure in the near-field plane after separation of the sound field is calculated using the conduction matrix. The method does not require other prior knowledge. The simulation results show that this method can be used as an effective complementary method for coherent sound field separation based on single-sided measurement. [ABSTRACT FROM AUTHOR]

Weak low voltage ride‐through (LVRT) ability and unstable output power are two major problems faced by the doubly‐fed induction generator (DFIG). To solve these two problems simultaneously, a commercially available fault current limiter‐battery energy storage system (FCL–BESS), which is suitable to be applied in a microgrid, is proposed in this study. During normal operation, the FCL–BESS stabilises the output power of DFIG by compensating the fluctuating component of DFIG output power with energy buffering capability provided by the battery energy storage system (BESS). On occurrence of a grid fault, the FCL–BESS enhances the LVRT ability of DFIG by inserting the fault current limiting inductor into the stator, which weakens the rotor back electromagnetic force voltage and limits the rotor overcurrent. The FCL–BESS also stabilises the DC‐link voltage by the BESS, which further strengthens the controllability of grid‐side converter and rotor‐side converter. Moreover, the FCL–BESS is able to help grid voltage recover fast and smoothly by providing power support to the grid. Experiments under different conditions have been carried out with a 2 kW prototype to evaluate the performance of the proposed FCL–BESS. Experimental results show that the FCL–BESS have much better performance than using single fault current limiter or BESS and can solve the two problems faced by the DFIG simultaneously and effectively. [ABSTRACT FROM AUTHOR]

The Sanjiang Plain (SJP) wetland is the largest freshwater marshland in China. Peatlands were initiated early and are widely distributed across the SJP and form a large carbon (C) pool. Consequently, there is a growing interest in understanding past, present, and future peatland dynamics. Most studies on peatland dynamics have been carried out on boreal and subarctic region; however, there are limited data about peatland dynamics on temperate region, such as SJP wetland, which is sensitive to climate change and human disturbance. Here, we presented a data synthesis of basal peat ages, peatland area, and peat C accumulation rate in the SJP to examine Holocene peatland dynamics and climate sensitivity, along with total C storage and their future fate. We show that peatland initiation in the SJP started in the early Holocene, but the most intense period of peatland initiation occurred during the late Holocene, when the climate was colder and drier than the early and mid-Holocene. And the C accumulation rate also continued to increase during the late Holocene. Our results suggest that insolation and monsoon intensity as well as the local topographic characteristics and hydrology during the late Holocene in the SJP might have played an important role in causing the highest rates of peatland initiation and C accumulation. Based on the Second National Wetland Resources Survey data, we estimated that the total peatland covered an area of about 10,520 km2 on the SJP and currently stores ~0.26 Pg C. However, human activities, together with the widespread warming on the SJP over the past 60 years, not only reduce the area of wetlands but also have switched it from being a net C sink to a significant C source. [ABSTRACT FROM AUTHOR]

To investigate the problem of the lag stability of the capacitance value during the level drop of the dirty U-shaped liquid level sensor, the equivalent circuit of the dirty U-shaped liquid level sensor was analyzed, and the transformer bridge's principle circuit that uses RF admittance technology was designed accordingly. Using the method of controlling a single variable, the measurement accuracy of the circuit was simulated when the dividing capacitance and the regulating capacitance had different values. Then, the right parameter values for the dividing capacitance and the regulating capacitance were found. On this basis, the change of the sensor output capacitance and the change of the length of the attached seawater mixture were controlled separately under the condition of removing the seawater mixture. The simulation outcomes showed that the measurement accuracy was excellent under various situations, validating the transformer principle bridge circuit's efficacy in minimizing the influence of the output capacitance value's lag stability. [ABSTRACT FROM AUTHOR]

A low-voltage ride-through (LVRT) strategy for a doubly fed induction generator (DFIG) with a switch-type fault current limiter (STFCL) is presented in this paper. The STFCL is composed of fault-current-limiting inductors, isolation transformers, a diode bridge, a semiconductor switch, a snubber capacitor, and a fault energy absorption bypass. The presented STFCL can insert fault-current-limiting inductors in series with the stator branches on occurrence of a grid fault, which can limit the rotor overcurrent and weaken the rotor back electromagnetic force voltage simultaneously. The safety and controllability of the rotor side converter can thus be guaranteed. The STFCL can also absorb the excessive energy stored in the stator during LVRT with the fault energy absorption bypass so as to prevent the semiconductor devices from overvoltage. The feasibility of the proposed approach is validated by simulation studies on a typical 1.5-MW wind-turbine-driven DFIG system. The validity of the proposed approach is further verified by the experimental results on a 2-kW DFIG prototype. [ABSTRACT FROM PUBLISHER]

A multicell fault current limiter (MCFCL) is proposed in this paper. The MCFCL is composed of multiple fault current limiting cells. Each fault current limiting cell consists of a fault current limiting inductor and a power electronic module. The proposed MCFCL has the flexibility in expanding the operation voltage by increasing the number of fault current limiting cells. The MCFCL has excellent static and dynamic voltage equalizing capability between different cells, which makes it highly reliable. The MCFCL utilizes the fault energy absorption bypasses instead of varistors to prevent overvoltages across the semiconductor devices, which makes it able to repeat fault current limitation multiple times in a short time interval. Moreover, the MCFCL has rather high efficiency, which is expected to be no less than 99.9% with appropriate semiconductor devices. The operational principles and parameter design methods of the MCFCL are presented. A medium-voltage prototype is developed and tested. The simulation and experimental results are presented to clarify the theory and feasibility of the proposed approaches. [ABSTRACT FROM PUBLISHER]

Two major problems that are faced by doubly fed induction generators are: weak low-voltage ride-through capability and fluctuating output power. To solve these problems, a superconducting fault-current limiter-magnetic energy storage system is presented. The superconducting coil (SC) is utilized as the energy storage device for output power smoothing control during normal operation and as a fault-current limiting inductor to limit the surge current in the stator or rotor during the grid fault. The SC can also weaken the rotor back electromotive force voltage, and thus enhance the controllability of the rotor-side converter (RSC), which helps to protect both the RSC and the gearbox. Simulation results verify the efficacy of the proposed approaches. [ABSTRACT FROM PUBLISHER]

A 0.5 MVA/1 MJ superconducting magnetic energy storage system (SMES) has been installed in a superconducting power substation. The SMES is designed to compensate active power fluctuations, current harmonics and reactive power of the downstream load. The system configurations and control strategies are described. Experimental and field test results show that the proposed SMES can effectively improve the power quality of the power system. [ABSTRACT FROM PUBLISHER]

Isomorphous complexes Zn(dmid)(phen)2 (1) and Cd(dmid)(phen)2 (2) have been synthesized through a ligand substitute reaction. Their structures and properties have been characterized by elemental analysis, IR, UV–Vis, fluorescence and single-crystal X-ray analysis. The octahedral N4S2 coordination geometry, bonding, electronic structure and IR spectra of the Zn(dmid)(phen)2 molecule were studied in detail using DFT and INDO/S methods. In the crystal packing, there exists a strong π–π interaction between two parallel 1,10-phenanthrolines of adjacent molecules. Complex 1 (or 2) in the solid state exhibits an intensive fluorescence band at 539.5 nm (or 536 nm) when the excitation wavelength is 371 nm (or 370.5 nm) at room temperature. [Copyright &y& Elsevier]

• A novel criterion: available Smoothing Energy Capability is proposed for power smoothing. • A novel multi-input and multi-output fuzzy logic (FLC) is proposed for power smoothing. • An offline training and online implementation method is presented to optimize the FLC parameters. Optimal energy management is a major challenge for most energy storage systems (ESSs), which is especially a big concern for the superconducting fault current limiter-magnetic ESS (SFCL-MES). To prevent malfunction, the superconducting coil (SC) current of the SFCL-MES needs to be controlled strictly within a well-defined operational range. To optimally utilize the energy capability of the ESS while keeping the state of charge (SOC) within a safe range, a novel multi-input multi-output fuzzy logic controller (FLC), which adjusts both the filter time constant and the SOC regulator gains, is proposed for optimal energy utilization. The parameters of the FLC were further optimized offline by particle swarm optimization with real collected operational data. The optimized FLC has been successfully implemented on a 1MVA/1MJ prototype installed in a wind farm. The operational results of the prototype demonstrate the good performance of the proposed approaches. [ABSTRACT FROM AUTHOR]

Throughout northeast China, the widely distributed peatlands have formed a large carbon (C) pool. However, the relationship between peatland initiation and climate controls is still poorly documented and understood. Understanding the responses of these C-rich ecosystems to past climate change will provide useful insights into projecting the fate of peatland C in the future. In this study, we present a detailed historical reconstruction of peatland development in northeast China based on 312 basal peat dates, and examine the relationship between Holocene peatland dynamics and climate sensitivity. Our results indicate that peatland initiation started in the early Holocene, and that the majority of peatlands were initiated by and developed during the late Holocene. After the most intensive initiation period of 4.2-0.8 ka, the rate of peatland development slowed, which was concomitant with decreasing insolation and monsoon intensity. The widespread peatland initiation in the late Holocene might have been caused by the cool and moist climate patterns. The optimum timing of the peatland development was not uniform across northeast China, and these spatio-temporal differences indicate the influences of regional climate and terrain on peatland initiation. Peat-core data show variations in the long-term apparent rate of C accumulation ( LORCA) during the Holocene, with an average rate of 37.2 g C m−2 a−1. The peak LORCA occurred during 10.5-9.0 ka, probably in response to higher temperatures and stronger East Asia summer monsoon intensities. Both temperature and humidity are important factors influencing the peatland initiation and C dynamics in this region. [ABSTRACT FROM AUTHOR]

Abstract: We compared reproductive characteristics of Scirpus mariqueter and Spartina alterniflora in monocultures and mixed communities to assess the importance of clonality in the population distribution and colonization of the two species. In the core S. alterniflora zone, individuals were taller and there were fewer underground tillers than in the Spartina–Scirpus zone. Every sexual S. alterniflora individual produced about two underground tillers in the S. alterniflora zone, which was two thirds as many as in the Spartina–Scirpus zone. In contrast, the height of sexual S. mariqueter was the highest in the mixed zone, whereas the numbers of flowering individuals and vegetative individuals were the highest in the core and the Scirpus–tidal flat zones, respectively. In the Scirpus–tidal flat zone each sexual individual produced 14 vegetative individuals, which was 23 times that produced in the mixed zone, and 45 times that in the core zone. Aboveground biomass and density of sexual individuals decreased from the core to the Scirpus–tidal flat zone. The ratio of aboveground to belowground biomass was lower in core zones of the two species than in their mixed zones. From the S. alterniflora to the tidal flat zone there was a decrease in salinity and redox potential and an increase in soil moisture. [Copyright &y& Elsevier]

Combination of a cationic complex [Ni(phen)3]2+ and an anionic complex [Ni(mnt)2]- has resulted in a novel mixed-valence complex [Ni(phen)3]2[Ni(mnt)2]3·2DMF (phen=1,10′-phenathroline, mnt=1,2-dicyanovinylene-1,2-dithiolato, DMF=N,N-dimethylformamide). Its crystal structure consists of two different types of [Ni(mnt)2] units: [Ni(mnt)2]- and [Ni(mnt)2]2-, the arrangement of the [Ni(mnt)2] anion is found to be quite different from segregated stack layers often found for [Ni(mnt)2]-based compounds. Infrared and electronic spectra also confirmed the existence of both [Ni(mnt)2]- and [Ni(mnt)2]2- units. [Copyright &y& Elsevier]

The resistivetype superconducting fault current limiter (R-SFCL) is simple in structure, near zero impedance at normal state and can be quickly triggered by the fault current. Thus, it is a possible solution to limit the fault current in the power grid. In this paper, we report the fabrication and test for an R-SFCL module The R-SFCL module consists of seven bifilar coils connected in parallel, which were wound with two parallel 2G tapes. A 5mm spacer was co-wound between adjacent turns to act as the highvoltage insulation. In the tests, we test the current distribution among the bifilar coils, and then simulated short-circuit tests were conducted on the module to obtain its performance under fault current surge. [ABSTRACT FROM AUTHOR]

Abstract: LiNi0.9Co0.1O2 cathode material was prepared by a rheological phase reaction method with LiOH·H2O and Ni0.9Co0.1(OH)2 as starting materials. The mixture of reactants and a proper amount of water reacted to form a rheological precursor, and then the dried precursor was sintered in flowing oxygen based on the results of thermogravimetric. The sintering temperature has a remarkable effect on the electrochemical performance of the samples. The sample LiNi0.9Co0.1O2 material sintered at 730°C for 6h has the largest initial discharge capacity 195.7mAhg−1 (50mAg−1, 3.0–4.3V) and shows the better electrochemical performance, capacity retention after 20 cycles is 91.4%. This method is simple and effective for preparing cathode materials for lithium batteries. [Copyright &y& Elsevier]

A superconducting magnetic energy storage system (SMES), with stored energy of 1 MJ and compensation power of 0.5 MVA, has been developed successfully, and now is operating at the world's first superconducting power substation at Baiyin National High-Tech Industrial Development Zone, Gansu Province, China. The SMES employs a high Tc superconducting magnet, which consists of 44 pancakes, operates at 4.2 K in liquid helium, and is cooled down by 4 G-M cryo-coolers. The SMES connects to a 10.5 kV power grid by the use of a power conversion system. Since 16 February, 2011, the SMES has been operating reliably, and providing good-quality power for three companies. [ABSTRACT FROM PUBLISHER]

With the increasing depletion of fossil fuels and growing environmental pressure, the mankind has got known the need to vigorously develop the renewable energy and the energy-saving technology. The high Tc superconducting (HTS) power technology will be very helpful to enhance the stability, reliability, and efficiency and transmission capacity of the power grid which would be dominated by the renewable energy. In this paper, we will report the installation and operation of a 10 kV HTS power substation which includes a 75 m/1.5 kA HTS power cable, a 10 kV/1.5 kA HTS fault current limiter, a 1 MJ/0.5 MVA high Tc SMES and a 630 kVA/10 kV/0.4 kV HTS power transformer. [ABSTRACT FROM PUBLISHER]

To identify impact factors on the distribution and characters of natural plants community in reclamation area, with survey data from 67 plant quadrats in July 2009, soil properties data from 216 sampling points in April 2009, and TM (30 m) data in 2006, the composition and characteristics of natural plants community in different time of the Fengxian area in the Changjiang (Yangtze) River estuary were analyzed with two-way indicator species analysis (TWINSPAN), multivariate analysis of variance (MANOVA), detrended canonical correspondence analysis (DCCA) and canonical correspondence analysis (CCA). The results show that: 1) The plant communities in the reclaimed area are mainly mesophytes and helophytic-mesophytic transitional communities, showing a gradient distribution trend with the change in reclamation years. Species richness ( MA), species diversity ( H) and above-ground biomass also increase with the increase of reclamation years. Nevertheless, they appear to decline slightly in the middle and late reclamation period (> 30 years). 2) With the rise in land use levels, the changes in species richness and species diversity tend to increase at first and then decrease; species dominance ( D), however, tends to decline; and above-ground biomass increases slightly. 3) The distribution of the plant community is mainly influenced by the following factors: land use levels ( R = 0.55, p < 0.05), soil moisture ( R = 0.53, p < 0.05), soil salinity ( R = 0.43, p < 0.05) and reclamation time ( R = 0.40, p < 0.05). [ABSTRACT FROM AUTHOR]

The objective of this study is to analyze soil physical and chemical properties, soil comprehensive functions and impact factors after different years of reclamation. Based on the survey data taken from 216 soil sampling points in the Fengxian Reclamation Area of the Changjiang (Yangtze) River Estuary, China in April 2009 and remotely sensed TM data in 2006, while by virtue of multivariate analysis of variance (MANOVA), geo-statistical analysis (GA), principal component analysis (PCA) and canonical correspondence analysis (CCA), it was concluded that: 1) With the increase in reclamation time, soil moisture, soil salinity, soil electric conductivity and soil particle size tended to decline, yet soil organic matter tended to increase. Soil available phosphorous tended to increase in the early reclamation period, yet it tended to decline after about 49 years of reclamation. Soil nitrate nitrogen, soil ammonia nitrogen and pH changed slightly in different reclamation years. Soil physical and chemical properties reached a steady state after about 30 years of reclamation. 2) According to the results of PCA analysis, the weighted value (0.97 in total) that represents soil nutrient factors (soil nitrate nitrogen, soil organic matter, soil available phosphorous, soil ammonia nitrogen, pH and soil particle size) were higher than the weighted value (0.48 in total) of soil limiting factors (soil salinity, soil electric conductivity and soil moisture). The higher the F value is, the better the soil quality is. 3) Different land use types play different roles in the soil function maturity process, with farmlands providing the best contribution. 4) Soil physical and chemical properties in the reclamation area were mainly influenced by reclamation time, and then by land use types. The correlation (0.1905) of the composite index of soil function ( F) with reclamation time was greater than that with land use types (−0.1161). [ABSTRACT FROM AUTHOR]

It is expected that superconducting technologies will play an important role in the future smart grid, because the application of superconductor technologies in the power grid can decrease power losses, relieve overload, avoid higher levels of transmission voltage, increase power transmission capacity, and improve power quality and grid stability. In recent years, high temperature (high-Tc) superconducting power technologies have achieved remarkable progress. High temperature superconducting (HTS) power equipment, such as HTS power cables, HTS transformers, high-Tc superconducting fault current limiters (SFCL), and high-Tc superconducting magnetic energy storage devices (SMES) have been demonstrated in the power grids of many countries. With the development of HTS power equipment, the construction of a HTS power substation is ready. In China, a 10.5 kV HTS power substation is under construction in Baiyin city, Gansu province. The substation integrates a HTS power cable, a HTS transformer, a HTS fault current limiter, and a high-Tc SMES. All these HTS power devices, which were previously developed by the Institute of Electrical Engineering (IEE), Chinese Academy of Sciences (CAS), have been demonstrated to operate for a long time in the commercial power grid. In this paper, the design and constructing progress of the HTS substation are introduced in detail. [ABSTRACT FROM AUTHOR]

Abstract: LiNi1−x Co x O2 cathode material was prepared by a rheological phase reaction method with LiOH·H2O and Ni1−x Co x (OH)2 as starting materials. The mixture of reactants and a proper amount of water reacted to form a rheological precursor, and the dried precursor was calcined in flowing oxygen based on the results of thermogravimetric. The calcination temperature has a remarkable effect on the electrochemical performance of the samples. The sample calcined at 730°C for 6h has the best electrochemical properties. The cobalt content has significant effect on the electrochemical performance for LiNi1−x Co x O2 material. When x-value is less than 0.08, the first discharge capacities and capacity retentions decrease rapidly. The LiNi0.9Co0.1O2 material has the largest initial discharge capacity and the better electrochemical performance. This method is simple and effective for preparing cathode materials for lithium batteries. [Copyright &y& Elsevier]