In this paper, a two-stage onboard battery charger is analyzed for plug-in electric vehicles (PEVs). An interleaved boost topology is employed in the first stage for power factor correction (PFC) and ...to reduce total harmonic distortion (THD). In the second stage, a full-bridge LLC-based multiresonant converter is adopted for galvanic isolation and dc/dc conversion. Design considerations are discussed, focusing on reducing the charger volume and optimizing the conversion efficiency over the wide battery-pack voltage range. A detailed design procedure is provided for a 1-kW prototype, charging the battery with an output voltage range of 320-420 V from 110-V 60-Hz single-phase grid. Experimental results show that the first-stage PFC converter achieves THD of less than 4% and a power factor higher than 0.99, and the second-stage LLC converter operates with 95.4% peak efficiency and good overall efficiency over wide output voltage ranges.
In this paper, a variable dc link technique is proposed to track the maximum efficiency point of the LLC converter for plug-in electric vehicle battery-charging applications over a wide battery ...state-of-charge (SOC) range. With the proposed variable dc link control approach, the dc link voltage follows the battery pack voltage. The operating point of the LLC converter is always constrained to the proximity of the primary resonant frequency so that the circulating current in the magnetizing inductor and the turning-off currents of MOSFETs are minimized. In comparison with conventional approaches, the proposed variable dc link voltage methodology demonstrates efficiency improvement across the wide SOC range. Efficiency improvements of 2.1% at the heaviest load condition and 9.1% at the lightest load condition are demonstrated.
AgBr nanoparticles supported on graphitic‐C3N4‐decorated nitrogen‐doped graphene intercorrelated ternary superhybrid composites (ACNNG‐x) acting as a novel visible‐light driven photocatalyst are ...reported. Because of the fast interfacial charge separation and photoelectrochemical performance, the representative of ACNNG‐50 superhybrid structure achieves high efficiency and stable photocatalytic capability for organic contaminant degradation and CO2 reduction.
Rocks in engineering works and as building materials are always suffering freeze-thaw (F-T) and thermal shock (TS) weathering, and engineering rocks usually involve responses to impact loads from ...blasting operation, mechanized construction and seismic oscillation. Sedimentary rock distributes extensively and is important for engineering geological and hydrogeological works. For a deeper understanding of the F-T and TS effects on the rock behaviors, physical tests, static compressions and dynamic impacts were carried out on red-sandstone free from and after artificial F-T or TS cycles in this work. Laboratory tests show the significant physic-mechanical deterioration of red-sandstone after F-T or TS weathering. Compared to fresh specimens, red-sandstone after 10F-T or TS cycles performs poorly in both the static compression and SHPB impact tests, and F-T/TS induced decreases of UCS and modulus are more remarkable under dynamic impacts than under static loads. Dynamic mechanical behaviors of both fresh and F-T/TS weathered red-sandstone have distinguishable strain rate effects, and water content significantly affects the strain rate effects on mechanical behaviors. Water and temperature variation play important roles in the rock weathering process. In this work, water effects during the rock weathering process were summarized as solvent effect and medium effect, while temperature variation damaged red-sandstone meanly in two ways, non-uniform thermal deformation of mineral grains and phase-transition of water.
•Impact tests are applied on rock before and after freeze-thaw/thermal shock cycles.•Strain rate effects on mechanical behaviors of weathering-damaged rock are studied.•Mechanisms of hydro-thermal effects during rock weathering process are analyzed.•Water effects during weathering are summarized as solvent effect and medium effect.•For rock weathering, temperature works by thermal deformation and phase-transition.
A conventional phase-shift full-bridge (PSFB) converter suffers from easy failure of zero-voltage switching (ZVS) in the lagging leg under light load conditions. This poses a significant challenge to ...the optimal design of PSFB-based plug-in electric vehicle (PEV) onboard chargers. In this paper, a self-reconfigured integrated onboard charger architecture is proposed for PEVs to cope with this design challenge. In this architecture, the PSFB converter is adopted as the main topology to charge the high-voltage battery pack, while the half-bridge LLC resonant converter is employed to charge the low-voltage auxiliary battery. Under light-charging mode, the half-bridge LLC converter is reconfigured to be paralleled with the PSFB topology to guarantee the ZVS of the lagging leg MOSFETs. Moreover, a capacitor-diode-diode snubber is added to resolve the duty cycle loss issue of the PSFB converter and to reduce the circulating current. Practical design considerations are presented for both the PSFB and the half-bridge LLC converters. Frequency modulation and the phase-shift modulation provide two degrees of freedom to regulate the output voltage/current of both converters. The proposed charger architecture maintains low cost and high efficiency in this specific application. A 390 V input, 420 V/2.4 A, 14 V/21 A outputs, 1.3 kW rated converter prototype is designed, analyzed, and tested to verify the proof of concept.
In LLC-based onboard battery charging architectures used in plug-in electric vehicles (PEV), the dc link voltage can be actively regulated to follow the battery pack voltage so that the LLC converter ...can operate in proximity of resonant frequency and achieve high efficiencies over the wide range of battery pack voltage. However, conventional boost-type power factor correction (PFC) converters are unable to provide ultrawide dc link voltages since their output voltages should always be larger than their input voltages. This paper proposes a Silicon Carbide (SiC)-based onboard PEV charger using single-ended primary-inductor converter (SEPIC) PFC converter followed by an isolated LLC resonant converter. With the proposed charger architecture, the SEPIC PFC converter is able to provide an ultrawide range for dc link voltage, and consequently enhance the efficiency of the LLC stage by ensuring operation in proximity of resonant frequency. A 1-kW SiC-based prototype is designed to validate the proposed idea. The experimental result shows that the SEPIC PFC converter achieves unity power factor, 2.72% total harmonic distortion, and 95.3% peak conversion efficiency. The LLC converter achieves 97.1% peak efficiency and always demonstrates a very high efficiency across the ultrawide dc-link voltage range. The overall efficiency of the charger is 88.5% to 93.5% from 20% of the rated load to full load.
Implanted scaffolds with inductive niches can facilitate the recruitment and differentiation of host cells, thereby enhancing endogenous tissue regeneration. Extracellular matrix (ECM) scaffolds ...derived from cultured cells or natural tissues exhibit superior biocompatibility and trigger favourable immune responses. However, the lack of hierarchical porous structure fails to provide cells with guidance cues for directional migration and spatial organization, and consequently limit the morpho-functional integration for oriented tissues. Here, we engineer ECM scaffolds with parallel microchannels (ECM-C) by subcutaneous implantation of sacrificial templates, followed by template removal and decellularization. The advantages of such ECM-C scaffolds are evidenced by close regulation of in vitro cell activities, and enhanced cell infiltration and vascularization upon in vivo implantation. We demonstrate the versatility and flexibility of these scaffolds by regenerating vascularized and innervated neo-muscle, vascularized neo-nerve and pulsatile neo-artery with functional integration. This strategy has potential to yield inducible biomaterials with applications across tissue engineering and regenerative medicine.
•• The green economic efficiency (GEE) is measured through a super-efficient SBM model.•• The digital economy development level is calculated by principal component analysis.•• The digital economy ...has a positive effect on urban GEE.•• Mechanisms base on marketization, industry, innovation and energy are detected.•• The effects vary between different urban location, scale and environmental regulation intensity.
The development of the digital economy has changed human lifestyles and production and provided a new approach to achieving the United Nations Sustainable Development Goals (SDGs). As an important indicator reflecting both economic growth and ecological protection, the green economic efficiency (GEE) indicator is employed to express the level of sustainable development. By building an indicator system, introducing carbon dioxide emissions as an unexpected output and using a super-efficient slack-based measure (SBM) model, the the GEE of 273 cities in China are calculated. The development level of digital economy is calculated through principal component analysis (PCA). Unlike previous provincial-level studies, this study focuses on analyzing at the urban level. This study then uses a fixed effect model to analyze the effect of the digital economy on urban GEE. Based on various aspects, the transmission mechanisms of the digital economy on GEE have also been deeply analyzed. The results indicate that the digital economy has a positive effect on GEE. This conclusion is validated by endogeneity analysis and other robustness tests. The digital economy has a positive influence on urban GEE in Eastern, Central and Northeastern China. In large cities, medium-sized cities and cities with stricter governmental environmental regulations, the effect of the digital economy on GEE is more prominent. The mechanism analysis indicates that the digital economy mainly promotes urban GEE through the technological innovation effect, industrial structure optimization, energy structure transformation and market-oriented development. This study clarifies the role of the digital economy in advancing GEE and provides a reference to promote ecological development in developing countries.
Rock engineering and stone constructions are always suffering recurrent thermal shock (TS) generated by sudden changes in temperature, and rock mechanical behaviors in projects usually involve ...responses to stress pulses or impact loads due to the widely existed blasting operation, mechanized construction and seismic oscillation. In this work, physical tests as well as static and dynamic mechanical experiments were carried out on red-sandstone free from and after 10, 20, 30, and 40 artificial TS cycles. TS-induced changes of physico-mechanical properties, including micromorphology, density, porosity, P-wave velocity, uniaxial compressive strength (UCS) and deformation modulus (Ed), illustrated the deterioration of sandstone after different TS cycles. Strengthening effects of strain rate on the dynamic mechanical properties of TS-weathered red-sandstone were analyzed. Considering the strain rate effect, deterioration models of dynamic UCS and Ed were built to predict the dynamic mechanical degradation of porous rock after repeated TS weathering. The model parameters, decay constant (λ) which indicated the mean relative integrity loss by the action of any single TS cycle, and half-life (N1/2) which measured the number of cycles necessary to reduce the integrity to half its value, were both expressed as functions of strain rate.
•Impact tests are applied on sandstone free from or after thermal shock (TS) cycles.•Physico-mechanical properties before or after different TS cycles are studied.•Strain rate effects on mechanical behaviors of TS-damaged rock are analyzed.•Decay models considering strain-rate effects are built to predict the degradation.•Functions of decay-model-parameters versus strain rate are built through regression.
This study presented an intuitive approach to derive large‐scale tidal flat's Digital Elevation Model (DEM). We first developed an automated method for accurately extracting the waterline from ...Synthetic Aperture Radar images acquired in Subei Sandbanks along the Yellow Sea coast of China between 2015 and 2020 based on deep convolutional neural networks. The statistical results show this method has appreciable accuracy for efficient waterline extraction even under complex imaging conditions with a mean recall and precision of 0.90 and 0.80, respectively. Then the pixel‐level extracted waterlines are calibrated with a global tide model to construct the large‐scale tidal flat's DEM in the study region. The comparison against in situ topographic data shows an error of 29 cm, demonstrating the usefulness of monitoring the morpho‐sedimentary evolution in intertidal areas. Furthermore, the Subei Sandbanks remained stable from 2015 to 2020, while the coastal region changed drastically due to human activities.
Plain Language Summary
Monitoring the geomorphological evolution of tidal flats is critical for coastal development and wetland conservation. Compared to traditional surveying approaches, the waterline method can provide topographic maps more frequently with a lower cost and higher coverage. However, both the signal returned from the sea surface and the exposed tidal flats on radar images change drastically under different sea conditions. Benefiting from the development of deep learning, especially the deep convolutional neural networks, waterlines of tidal flats on complex Synthetic Aperture Radar images can now be automatically and accurately extracted. Furthermore, with a calibrated ocean tide model that can make the tidal evaluation instantly, we develop an automatic approach to topographic map the large‐scale tidal flats, which may provide timely information for stakeholders related to coastal management and ecosystem protection.
Key Points
A deep‐learning‐based technique was developed to extract waterline from synthetic aperture radar images
A combination of the deep‐learning model and tidal analysis is used for automatic topographic mapping of large‐scale tidal flats
Multi‐year digital elevation model series in the study region are obtained with morpho‐sedimentary evolution analysis
PDF
