Feasible Coefficient Region Analysis and Dual-Loop Adaptive Feedback Control for Transient Stability of VSG Under Severe Grid Voltage Sag

Aiming at the transient instability and overcurrent issues of the virtual synchronous generator (VSG) under severe grid voltage sag, the accurate and simultaneous control for the phase angle and current of VSG is hard to be achieved without using the fault information. And the requirement of the grid code for the reactive current should be also considered. To address the issues, this paper proposes a non-fault information based dual-loop adaptive feedback control to take transient angle stability, current limitation and the demand of the reactive current of VSG into account. First the large-signal model of VSG with a dual-loop control is built. To design the feedback coefficients, the feasible coefficient region under different fault degrees and cases is analyzed subsequently. It provides reference for the curve fitting, which is further applied in the self-adaptive regulation of the feedback coefficients. Thereby, a dual-loop adaptive feedback control is realized based on an additional reactive power feedback loop. With the proposed control scheme, all of the three control objectives can be achieved without the fault information, since the feedback coefficients are within the feasible coefficient region by the self-adaptive regulation. Finally, the effectiveness and robustness of the proposed control scheme for both VSG and a paralleled system of VSG and grid-following (GFL) converter are validated by the simulation results and the experimental results

Fuzzy Assessment of Steel Deck Pavement for Long Suspension Bridge of the Fourth Nanjing Yangtze River Bridge

The Fourth Nanjing Yangtze River Bridge (the Fourth Bridge) with the main span of 1418 m is the largest three-span suspension bridge in China and the third largest in the world. The service circumstance of steel deck pavement on the Fourth Bridge is complex and severe, so that the scheme evaluation for steel deck pavement is a huge program. To rapidly and comprehensively evaluate the schemes for pavement, a fuzzy evaluation method was introduced in this paper. A three-level logical assessment structure including 21 basic impact factors was built according to analytic hierarchy process (AHP), and the weight for each judgment matrix was determined by the Delphi method. Consequently, a fuzzy evaluation theory was used to value each scheme to propose the optimal one. Based on this method, four pavement schemes were evaluated to choose the optimal one, and the performance of the optimal scheme was highly corresponding to the practical engineering practice. The fuzzy evaluation method can supply a theoretical support to fast determine the scheme for long-span steel deck pavement

Modeling Chloride Diffusion Coefficient of Steel Fiber Reinforced Concrete under Bending Load

The chloride diffusion coefficient is the most important parameter when predicting chloride ingress in concrete. This paper proposed a model for calculating the chloride diffusion coefficient of steel fiber reinforced concrete (SFRC). Considering the concrete structures in service are usually subjected to external loads, the effect of bending load was discussed and expressed with a stress factor ks in the model. The chloride diffusion coefficient of cement paste was calculated with capillary porosity and then used to predict the chloride diffusion coefficient of SFRC. Some factors in the model were determined with experimental results. Chloride bulk diffusion tests were performed on SFRC and plain concrete (without fiber) specimens under bending load. SFRC showed slightly better chloride resistance for unstressed specimens. The compressive stress decreased the chloride diffusion coefficient of SFRC, while it caused no change in plain concrete. For the tensile zone, the chloride resistance of concrete was improved significantly by adding steel fibers. Overall, SFRC performed better chloride resistance, especially under bending load. The proposed model provides a simple approach for calculating the chloride diffusion coefficient of SFRC under bending load

PREDICTION OF CHLORIDE INGRESS IN STEEL FIBRE REINFORCED CONCRETE UNDER BENDING LOAD

Chloride induced corrosion is an important reason for the deterioration of reinforced concrete structures. The chloride transport properties of steel fibre reinforced concrete (SFRC) coupled with and without bending load (stress level of 0.5) were investigated through bulk diffusion test. A prediction model for chloride ingress in SFRC under bending load was established based on the Fick's second law. The time-dependent chloride diffusion coefficient was discussed and calculated. Apparent chloride diffusion coefficient was used to predict the corrosion initiation of SFRC structures. The experimental results showed that SFRC had better chloride resistance than plain concrete, especially when specimens were under bending load. The chloride diffusion coefficient of SFRC under tension was 30∼38% lower than that of plain concrete. For unstressed concrete, the calculated corrosion initiation of SFRC was 6∼40% longer compared with plain concrete. For concrete under bending load, the corrosion initiation of SFRC was 2.2∼3.6 times of that for plain concrete, varying with fibres dosage and cover thickness

Strength Design of Ultra-High-Performance Fiber-Reinforced Cementitious Composites Using Local Ecological Admixture

The ultra-high-performance fiber-reinforced cementitious composite (UHPFRC) is a new generation of building material with extremely high mechanical strength and durability, which can be used for ultra-high, thin-wall or long-span construction, that prolongs the service life of construction in severe environments. In this study, UHPFRC was prepared with a high range of local ecological admixture to decrease the material’s cost and the environmental impact. Raw materials’ proportions, water/binder ratio, fiber-volume contents, and hybrid-fiber ratio were studied on the property improvement of UHPFRC, and an F-test analysis was induced to reveal the important significance on compressive strength. The results demonstrated that the compressive strength of 237.8 MPa was achieved with mineral admixture substitution over 40%. The particle-packing density and the binder reactivity both succeeded on the compressive strength. Water/binder ratio determined the hydration degree and the flowability of UHPFRC, which affected compressive strength through hydration products and microstructure. Also, compressive strength was more sensitive with hybrid-fiber than fiber-volume content. The order of importance for compressive strength was powder proportion > hybrid-fiber ratio > fiber-volume content > water/binder ratio

Strength Design of Ultra-High-Performance Fiber-Reinforced Cementitious Composites Using Local Ecological Admixture

The ultra-high-performance fiber-reinforced cementitious composite (UHPFRC) is a new generation of building material with extremely high mechanical strength and durability, which can be used for ultra-high, thin-wall or long-span construction, that prolongs the service life of construction in severe environments. In this study, UHPFRC was prepared with a high range of local ecological admixture to decrease the material’s cost and the environmental impact. Raw materials’ proportions, water/binder ratio, fiber-volume contents, and hybrid-fiber ratio were studied on the property improvement of UHPFRC, and an F-test analysis was induced to reveal the important significance on compressive strength. The results demonstrated that the compressive strength of 237.8 MPa was achieved with mineral admixture substitution over 40%. The particle-packing density and the binder reactivity both succeeded on the compressive strength. Water/binder ratio determined the hydration degree and the flowability of UHPFRC, which affected compressive strength through hydration products and microstructure. Also, compressive strength was more sensitive with hybrid-fiber than fiber-volume content. The order of importance for compressive strength was powder proportion > hybrid-fiber ratio > fiber-volume content > water/binder ratio

Comparative analysis of the complete chloroplast genomes of seven Populus species: Insights into alternative female parents of Populus tomentosa.

Populus tomentosa, of section Populus, is distributed mainly in northern China. This species has high resistance to many diseases and insects, and it plays key roles in shelterbelts and urban afforestation in northern China. It has long been suspected to be a hybrid, but its parents remain unknown. In the present study, we report four newly sequenced complete cp genomes from section Populus and comparative genomic analyses of these new sequences and three published cp genome sequences. The seven cp genomes ranged from 155,853 bp (P. tremula var. davidiana) to 156,746 bp (P. adenopoda) in length, and their gene orders, gene numbers and GC contents were similar. We analyzed SNPs, indels, SSRs and repeats among the seven cp genomes, and eight small inversions were detected in the ndhC-trnV, rbcL-accD, petA-psbJ, trnW-trnP, rpl16-rps3, trnL-ycf15, ycf15-trnL, and ndhF-trnL intergenic regions. Furthermore, seven divergent regions (trnH-psbA, matK, psbM-psbD, ndhC-trnV, ycf1, ndhF-ccsA and ccsA-ndhD) were found in more highly variable regions. The phylogenetic tree reveals that P. tomentosa is closely related to P. alba and P. alba var. pyramidalis. Hence, P. alba was involved in the formation of P. tomentosa

Preparation and Color Performance of White Ultra-High-Performance Concrete with Large Fraction of Quaternary Binders

White ultra-high-performance concrete (WUHPC) performed outstanding mechanical, durability, and aesthetical properties, which was preferred in infrastructure to avoid the secondary painting, decrease the maintenance, and prolong the service life. Supplementary cementitious materials (SCMs) were often used in WUHPC to reduce the environment impacts and material costs. In this study, limestone powder (LP), metakaolin (MK), and silica fume (SF) were used as SCMs to largely substitute white Portland cement (WPC) to prepare WUHPC, the effects of substituted ratio on flowability, strength, and whiteness were studied, and the hydration products were also analyzed by quantitative-XRD method and SEM. The whiteness was calculated in chromatic space CIELAB by measuring tristimulus values of L, a*, and b*, and the controlled factor on whiteness was also investigated. As the results, the WUHPC with compressive strength exceeded 150 MPa and whiteness over 90 was prepared with WPC substitution of 35~65%. The SF improved the flowability and strength about 10% due to its filling and ball effect, while the irregular particle sharp and non-uniform size distribution of MK caused the reversed development. The increased dosage of raw materials with higher L value, such as LP and MK, made the WUHPC whiter. The hydration products with varied SCMs ratio were in the same category by different content. It was supposed that CaCO3 and C-S-H gel in hydration products caused higher whiteness, while C3S, CaMg(CO3)2, and SiO2 were against the whiteness. The results proved that with a large fraction of SCMs, the WUHPC with high strength and good appearance were prepared, and the whiteness of WUHPC were both controlled by the raw materials and the content of hydration products

Long-Chain Fluorescent Probe for Straightforward and Nondestructive Staining Mitochondria in Fixed Cells and Tissues

Normally, small-molecule fluorescent probes dependent on the mitochondrial membrane potential (MMP) are invalid for fixed cells and tissues, which limits their clinical applications when the fixation of pathological specimens is imperative. Given that mitochondrial morphology is closely associated with disease, we developed a long-chain mitochondrial probe for fixed cells and tissues, DMPQ-12, by installing a C12-alkyl chain into the quinoline moiety. In fixed cells stained with DMPQ-12, filament mitochondria and folded cristae were observed with confocal and structural illumination microscopy, respectively. In titration test with three major phospholipids, DMPQ-12 exhibited a stronger binding force to mitochondria-exclusive cardiolipin, revealing its targeting mechanism. Moreover, mitochondrial morphological changes in the three lesion models were clearly visualized in fixed cells. Finally, by DMPQ-12, three kinds of mitochondria with different morphologies were observed in situ in fixed muscle tissues. This work breaks the conventional concept that organic fluorescent probes only stain mitochondria with normal membrane potentials and opens new avenues for comprehensive mitochondrial investigations in research and clinical settings

Cross-ethnic meta-analysis identifies association of the GPX3-TNIP1 locus with amyotrophic lateral sclerosis

Cross-ethnic genetic studies can leverage power from differences in disease epidemiology and population-specific genetic architecture. In particular, the differences in linkage disequilibrium and allele frequency patterns across ethnic groups may increase gene-mapping resolution. Here we use cross-ethnic genetic data in sporadic amyotrophic lateral sclerosis (ALS), an adult-onset, rapidly progressing neurodegenerative disease. We report analyses of novel genome-wide association study data of 1,234 ALS cases and 2,850 controls. We find a significant association of rs10463311 spanning GPX3-TNIP1 with ALS (p = 1.3 × 10−⁸), with replication support from two independent Australian samples (combined 576 cases and 683 controls, p = 1.7 × 10−³). Both GPX3 and TNIP1 interact with other known ALS genes (SOD1 and OPTN, respectively). In addition, GGNBP2 was identified using gene-based analysis and summary statistics-based Mendelian randomization analysis, although further replication is needed to confirm this result. Our results increase our understanding of genetic aetiology of ALS