Active distribution power system with multi-terminal DC links

A fast power restoration operational scheme and relevant stabilizing control is proposed for active distribution power systems with multi-terminal DC network in replacement of the conventional normal open switches. A 9-feeder benchmark distribution power system is established with a 4-terminal medium power DC system injected. The proposed power restoration scheme is based on the coordination among distributed control among relays, load switches, voltage source converters and autonomous operation of multi-terminal DC system. A DC stabilizer is proposed with virtual impedance method to damp out potential oscillation caused by constant power load terminals. The proposed system and controls are validated by frequency domain state space model and time domain case study with Matlab/Simulink

Active distribution power system with multi-terminal MVDC links

An active distribution power system with multi-terminal MVDC links is investigated in this paper. A sample system is established with 3 terminal MVDC links, which connect charging station and feeders. This active distribution power system benefits from a more flexible power flow control with high penetration of distributed generation and limited fault current. Simulation results using Matlab/Simulink are provided to validate the system performance during fault

Trait Depression and Subjective Well-Being: The Chain Mediating Role of Community Feeling and Self-Compassion

Although subjective well-being has been widely discussed as being one of the important indicators of clinical depression, few studies have explored how it relates to trait depression. In particular, increasing the number of positive experiences has long been a potential goal for depression-related clinical interventions, but the mechanisms by which such interventions work in countering depression have been poorly studied. Grounded in the cognitive theory of depression, the current study aimed to address this specific gap by testing the mediating effects of community feeling and self-compassion between trait depression and subjective well-being. A survey of 783 college students found that trait depression was not only able to directly and negatively predict individual subjective well-being but also indirectly predict individual subjective well-being through the mediating role of community feeling and self-compassion alone and through the chain mediating role of self-compassion from community feeling. These findings reveal the internal mechanisms of trait depression that, to some extent, impede subjective well-being and offer certain guiding significance for the self-regulation of interventions for clinical and non-clinical individuals with trait depression

Effect of current density on Ni-W coatings of SS316L current collectors for Na-S batteries

In this study, we investigated the effects of current density on the behavior of an amorphous Ni-W coating on a stainless steel 316 L (SS316L) surface. The performances of the Ni-W coatings and SS316L were studied though SEM, XRD and four-probe resistance tester. The corrosion resistance of the coatings was determined through static corrosion tests in a sulfur environment at 350 °C. The amorphous Ni-W coating at different current densities slowed the corrosion rate and improved the conductivity of the SS316L current collector. At a current density of 15 A·dm ^−2 , the crystal structure of the Ni -W coating was densest. The corrosion rate of the coating was 0.0856 mm·y ^−1 , which was lower than that of SS316L (0.5123 mm·y ^−1 ) after 72 h in a 350 °C molten sulfur environment, and the block resistance was 0.3312 mΩ, which was also lower than that of SS316L (0.3825 mΩ)

Distribution Characteristics of Phosphorus in the Yarlung Zangbo River Basin

Phosphorus is an important limiting biogenic material. The special topography and climate of the Yarlung Zangbo River Basin generate unique distribution and transport characteristics of total phosphorus (TP). A survey of TP concentration, precipitation, runoff, sediment content, suspended load discharge, and relevant data was carried out for the Yarlung Zangbo River Basin in the last ten years. In combination with the regional geography and social economies, the basic spatial-temporal characteristics of P-water-sediment were analyzed by using the correlation and time series analysis methods. Furthermore, the transport characteristics of P and the main control factors were also studied. The results show that the TP concentration in this basin displays the characteristics of interannual cyclical variation and annual phasic variation, and the peak value appears in the wet season. Among the Yarlung Zangbo River, Nyangqu River, Lhasa River, and Nyang River, the TP concentration is the highest in the Nyangqu River, exceeding 0.4 mg/L several times in the wet season. In this basin, the distribution patterns of the TP concentration are similar to those of the rainfall, runoff, suspended load discharge, and sediment concentration. The coupling property of the TP concentration is the strongest with the suspended load discharge among the meteorological and hydrological parameters. The spatial variation of dissolved P in the wet and dry seasons in 2016 responded to the distribution patterns of the population density, environmental factors, farming, and animal husbandry. This indicates that the TP in the water is mainly from non-point sources and is affected by agricultural, geographical, and ecological factors. The transport of TP is mainly controlled by the suspended load discharge due to precipitation

Design strategy of TiC reinforced heterogeneous Ti-composites with an induced slip system for achieving high strength-ductility

Achieving high strength and ductility for Ti alloys and their composites has been a key objective and also a great challenge for their engineering applications. Herein, we designed TiC/(TC18 + TC4) composites with bionic and heterogeneously lamella structures, achieving an exceptional combination of high strength and ductility. This is attributed to the formation of alternative layers of TC18-coarse grains and TC4-fine grains with TiC precipitated at their interfaces. Plastic incompatibility of these three-phases produces significant hetero-deformation-induced hardening, induced by mutual interactions of heterogeneous grains and TiC precipitates, as well as activation of extensive slip groups. An optimal yield strength of ∼ 1168 MPa and a uniform elongation of ∼ 6% have been achieved, which are much higher than those of the TC4 matrix (i.e. ∼919 MPa and ∼2%). This study provides a new strategy for composite designs to overcome the trade-off dilemma for strength-ductility.</p