Given that the heat treatment states of the base metal have a great influence on the surfacing repair layer, this paper carried out a feasibility study for the remanufacturing of the failed cutter ...rings of TBM disc cutters with uniform wear (hereinafter referred to as normally-worn ring) using the gas metal arc welding technology (GMAW). Firstly, this paper developed a heat treatment process route for H13 steel cutter rings. Secondly, the heat treatment process is numerically analyzed based on the developed route, and the rationality of the route is verified from the distribution characteristics of temperature, phase, and stress fields. Subsequently, heat treatment tests were carried out, and the physical and mechanical properties of the base metal samples prepared under laboratory conditions were evaluated respectively and systematically. Based on the comprehensive performance evaluation value calculated by the weighted comparative analysis method, it was clear that the comprehensive performance of the quenched base metal samples was 7.6% higher than that of the engineering cutter ring interior. Therefore, it is reasonable to replace the failed engineering cutter rings repaired under laboratory conditions with the prepared samples as economical alternatives. Finally, the remanufacturing of the base metal samples using GMAW was carried out, and then the remanufacturing performance of the base metal samples was analyzed. The study concluded that the comprehensive performance of the surfacing repair layer was slightly lower than that of the engineering cutter ring edge (4.1%), thus proving that the idea of surfacing remanufacturing of the normally-worn ring proposed in this paper was basically feasible.
In the context of the double carbon target, this study aims to reduce the metal resource consumption caused by the replacement of the failed disc cutter rings of tunnel boring machine (hereafter ...referred to as cutter rings). For this purpose, for the first time, a cutter-ring remanufacturing method is introduced considering key heat-treatment processes of preheating and post-weld tempering through metal active gas arc welding. First, a finite element model was developed to simulate this remanufacturing process route, establishing the optimal parameter ranges for the preheating and tempering temperatures. Subsequently, a self-developed integrated experimental platform was designed combining heat treatment and surfacing remanufacturing. A three-factor and three-level orthogonal experiment was conducted within the optimized parameter ranges. Further, a weighted comparative and range analysis method is proposed, and the impacts of the critical heat-treatment processes on the remanufacturing performance of the cutter rings exhibiting a uniform wear are investigated, resulting in the identification of the optimal heat-treatment combination. Results revealed that these pivotal heat treatments are instrumental in curbing defects (e.g., cracks) and substantially decreasing the residual stress in remanufactured cutter rings. Furthermore, the post-weld tempering temperature is the primary factor influencing the comprehensive performance and an array of physical and mechanical properties, including indent depth, hardness, shear strength, and impact toughness. The comprehensive performance of the best-produced sample impressively surged by 10.5 % compared to a standard engineering cutter ring.
Abstract Utilizing variable-sweep wing technology can further enhance the flight performance of hypersonic aircraft in a wide range of high-altitude, high-speed environments. Existing research on ...hypersonic variable-sweep flying wings has mainly focused on aerodynamic shape design, with limited research on the internal thermal protection of the aircraft. This study firstly investigates the performance improvement of a hypersonic flying wing using variable-sweep technology through CFD simulations. Secondly, to address the high-temperature issues induced by variable-sweep wings, an insulated wing storage box with a corrugated structure is designed, incorporating a thermal insulation layer made of corrugated webs and insulating materials. Heat transfer simulations are conducted by applying thermal loads to the wing storage box to study the temperature distribution during the variable-sweep process. Finally, a comparison between the corrugated structure design and the non-corrugated structure design of the wing storage box is performed to analyze the thermal insulation performance of the insulation layer. The results show that the heated area of the wing storage box is primarily influenced by the wing’s sweep angle, and the corrugated thermal insulation layer can effectively reduce heat transfer efficiency, resulting in a 30% reduction in the external temperature of the wing storage box.
Chlordecone (CLD), also named Kepone, is a synthetic organochlorine pesticide. As one of the common persistent organic pollutants (POPs) in nature, CLD has a profound impact on the environment and ...human health. The study aims to investigate the reproductive toxicity effects of CLD on male
Caenorhabditis elegans
and on progeny. L1-stage male nematodes were exposed to the control group (M9 solution) and four dose groups (0.02, 0.2, 2, and 20 μg/L). After exposure for 48 h, the male nematodes were picked to mating experiment and progeny experiment that the number of progeny and the time of observation in male parent and in F1 generation were counted; the number of germ cells and the number of sperm in the meiotic division of male nematodes were counted by staining with dimercaptophenyl hydrazine (DAPI), and the nematode gland area was observed under the bright field of the microscope. In male nematodes, the results showed that a number of progeny were 351.20 ± 31.40, 321.60 ± 24.70, 307.30 ± 19.30, 240.10 ± 27.60, and 227.90 ± 22.70 (
P
< 0.05); the generation times were 55.80 ± 1.95 h, 56.40 ± 1.60 h, 56.70 ± 0.92 h, 60.80 ± 0.95 h, and 69.60 ± 1.97 h (
P
< 0.05); relative areas of gonad were (99.80 ± 6.27)%, (93.00 ± 1.70)%, (85.00 ± 1.70)%, (70.70 ± 9.81)%, and (60.00 ± 5.23)% (
P
< 0.05); DAPI staining results showed the number of germ cells in meiosis area were 191.00 ± 10.97, 181.10 ± 15.56, 177.00 ± 9.20, 147.50 ± 10.56, and 139.30 ± 23.79 (
P
< 0.05); the sperm numbers were 335.60 ± 21.31, 308.60 ± 19.60, 306.00 ± 11.23, 260.10 ± 27.41, and 255.00 ± 3.72 (
P
< 0.05). In the F1 generation, the progeny numbers were 328.10 ± 22.28, 167.50 ± 15.30, 150.00 ± 13.65, 131.30 ± 18.40, and 130.20 ± 16.17 (
P
< 0.05); the generation times were 55.50 ± 2.36, 71.10 ± 0.97, 70.90 ± 0.52, 74.10 ± 2.07, and 73.90 ± 1.35 h (
P
< 0.05). The groups are grouped in order as M9 solution, 0.02, 0.2, 2, and 20 μg/L. The results revealed that CLD caused decrease in progeny number, relative area of gonad, number of germ cells, and sperm number and prolonged the generation time in the male nematode. In offspring grown up without CLD, the effect of CLD on generation time and sperm number can still be observed on offspring. In conclusion, CLD induces male nematode reproductive toxicity and causes defects in offspring.
Single-atom catalysts (SACs) have attracted considerable attention in the catalysis community. However, fabricating intrinsically stable SACs on traditional supports (N-doped carbon, metal oxides, ...etc.) remains a formidable challenge, especially under high-temperature conditions. Here, we report a novel entropy-driven strategy to stabilize Pd single-atom on the high-entropy fluorite oxides (CeZrHfTiLa)O
(HEFO) as the support by a combination of mechanical milling with calcination at 900 °C. Characterization results reveal that single Pd atoms are incorporated into HEFO (Pd
@HEFO) sublattice by forming stable Pd-O-M bonds (M = Ce/Zr/La). Compared to the traditional support stabilized catalysts such as Pd@CeO
, Pd
@HEFO affords the improved reducibility of lattice oxygen and the existence of stable Pd-O-M species, thus exhibiting not only higher low-temperature CO oxidation activity but also outstanding resistance to thermal and hydrothermal degradation. This work therefore exemplifies the superiority of high-entropy materials for the preparation of SACs.
This article proposes a robust self-triggered model predictive control (MPC) algorithm for a class of constrained linear systems subject to bounded additive disturbances, in which the intersampling ...time is determined by a fast convergence self-triggered mechanism. The main idea of the self-triggered mechanism is to select a sampling interval so that a rapid decrease in the predicted costs associated with optimal predicted control inputs is guaranteed. This allows for a reduction in the required computation without compromising performance. By using a constraint tightening technique and exploring the nature of the open-loop control between sampling instants, a set of minimally conservative constraints is imposed on nominal states to ensure robust constraint satisfaction. A multistep open-loop MPC optimization problem is formulated, which ensures recursive feasibility for all possible realizations of the disturbance. The closed-loop system is guaranteed to satisfy a mean-square stability condition. To further reduce the computational load, when states reach a predetermined neighborhood of the origin, the control law of the robust self-triggered MPC algorithm switches to a self-triggered local controller. A compact set in the state space is shown to be robustly asymptotically stabilized. Numerical comparisons are provided to demonstrate the effectiveness of the proposed strategies.
Covalent organic frameworks (COFs) are distinguished from other organic polymers by their crystallinity
, but it remains challenging to obtain robust, highly crystalline COFs because the ...framework-forming reactions are poorly reversible
. More reversible chemistry can improve crystallinity
, but this typically yields COFs with poor physicochemical stability and limited application scope
. Here we report a general and scalable protocol to prepare robust, highly crystalline imine COFs, based on an unexpected framework reconstruction. In contrast to standard approaches in which monomers are initially randomly aligned, our method involves the pre-organization of monomers using a reversible and removable covalent tether, followed by confined polymerization. This reconstruction route produces reconstructed COFs with greatly enhanced crystallinity and much higher porosity by means of a simple vacuum-free synthetic procedure. The increased crystallinity in the reconstructed COFs improves charge carrier transport, leading to sacrificial photocatalytic hydrogen evolution rates of up to 27.98 mmol h
g
. This nanoconfinement-assisted reconstruction strategy is a step towards programming function in organic materials through atomistic structural control.
•Potato responses to various RFM were assessed based on 2 years field experiments.•Completely film mulching (CF, CR) produced the highest tuber yield and WUE.•CF and CR resulted in higher dry matter ...(DM), RGR and net revenue.•CR produced tubers with acceptable commercial, nutritional and processing qualities.•CR is the best planting pattern for potato in semi-arid areas.
Field experiments were conducted to study the effects of different ridge–furrow plastic-mulching planting patterns (RFM) on potato (Solanum tuberosum L.) growth, tuber yield and quality, and water use efficiency (WUE) in an arid area of Northwestern China in 2010 and 2011.
Six treatments were used: (1) a flat plot without mulch (CK); (2) alternating mulched with plastic film and bare plots with no ridges (MNR); (3) completely mulched alternating wide and narrow ridges with furrow planting (CF); (4) completely mulched alternating wide and narrow ridges with ridge planting (CR); (5) alternating mulched ridges and bare plots with no ridges and with furrow planting (HF); (6) alternating mulched ridges and bare plots with no ridges and with ridge planting (HR).
RFM systems greatly improved tuber yield and WUE of potato in comparsion to CK. Compared to CK, the magnitude of yield in RFM increase were 50.1–86.8% in 2010 and 36.3–60.5% in 2011, respectively. Two completely mulched treatments (CF, CR) produced the highest tuber yield. Compared to CK, the highest increase in WUE was 83.9% (CR) and 65.8% (CF) in 2010 and 2011, respectively. Evapotranspiration in RFM was significantly decreased compared to CK during the early and end growing stages. But ET in CF, CR, HF and HR became higher at vigorous growth stages (from 6 July to 27 August) due to higher transpiration, which may imply a higher ratio of transpiration/evaporation. CF and CR treatments resulted in higher dry matter and relative growth rate than other treatments, and had higher output efficiency of dry matter from aboveground to tuber. Potato in CR showed the highest tuber yield, output value, net revenue and WUE, produced tubers with good size, low percentages of green and blemished tubers, and high protein content. In conclusion, CR is the best planting pattern for rain-fed potato.
Grassland degradation has become a global environmental concern. Livestock grazing under inappropriate grassland management and climate change contribute to this. Mitigating grassland degradation ...through revising the management pattern is needed to improve livestock production sustainability. The current study explores if a multi-household management pattern (M-pattern) is a better approach than single-household pattern (S-pattern) from the perspective of ecological efficiency (EE). EE reflects the ability of a household to gain economic output with less inputs and undesirable environmental conditions. We divided the sample households into multi-group (M group), single-renting group (S-R group) and single-no-renting group (S-NR group). The M group households graze livestock on their merged contracted grasslands; the S-R group households graze on contracted grasslands individually; and the S-NR group households graze on contracted and rented grasslands individually. A slack-based model was used to estimate the EE of 413 herders surveyed from three grassland types of two major areas in Inner Mongolia. The EE of the M group was 0.38, significantly higher than that of the S-R group (0.31) and the S-NR group (0.24). The higher EE of the M group was due to better environmental, economic, and input performances when compared with the S-R group and due to better environmental performance and input performances when compared with the S-NR group. The findings indicate that the M-pattern is a better fit for grassland management from the perspective of EE. This suggests that under the private grassland tenure arrangement, the M-pattern should be promoted to reduce grassland degradation and improve economic sustainability.
Display omitted
•The inactivation effects of pulsed magnetic field on L. monocytogenes was studied.•The transcriptomic responses of L. monocytogenes after PMF treatment was demonstrated.•It could ...provide a reference for the studied of the inactivation mechanism of PMF sterilization.
Pulsed magnetic field (PMF) is an emerging non-thermal decontamination technology. The lack of research on microbial inactivation mechanisms restricts the wide application of PMF. In this study the effect of PMF on the gene expression level of Listeria monocytogenes (L. monocytogenes) was evaluated to explore the inactivation mechanism of PMF. Transcriptomics was applied to study the gene expression level of Listeria monocytogenes and 588 differentially expressed genes (DEGs) including 307 up-regulated and 281 down-regulated genes were identified after PMF treatment (8 T, 20 pulses). Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis have demonstrated significant changes in mobility, carbohydrate metabolism, energy metabolism, amino acid metabolism, phosphorylation and dephosphorylation, membrane, quorum sensing, two-component regulatory system and ATP-binding cassette (ABC) transporters. The expression level of 5 relevant genes was subsequently confirmed by quantitative real-time PCR assay.
PDF
