The presence of water greatly influences time-dependent rock deformation. An understanding of how water can affect the time-dependent mechanical behavior of rock is important when assessing the ...long-term stability of geotechnical projects. While the previous studies have performed brittle creep experiments on oven-dry or fully-saturated rocks, we report here on a study designed to better understand brittle creep at different levels of saturation. We performed brittle creep experiments on oven-dry samples of red sandstone (Hunan province, China) and samples of the sandstone pre-immersed in water for different durations (from 2 to 8 days). These samples were deformed at a constant stress in one of either two conditions: dry or submerged in water. Before performing creep experiments, we first performed a series of water absorption and constant stress rate experiments to guide the stresses required for our creep tests and to assist with their interpretation. Our creep experiments show that immersion in water greatly increased the minimum creep strain rate and greatly shortened the time-to-failure when compared to the dry state. In detail, the minimum creep strain rate and time-to-failure increased and decreased, respectively, as pre-immersion duration increased from 4 to 6 days, but did not change as the duration was further increased to 8 days. We attribute this to the saturation of microcracks between 4 and 6 days (i.e., water imbibition was complete, or close to completion, following 6 days). We also show that oven-dry samples deformed at a constant stress underwater fail at stresses much lower than oven-dry samples deformed under dry conditions, due to the imbibition of water during deformation. Samples pre-immersed in water, but deformed in the dry condition were characterized by lower strain rates and longer time-to-failure than those pre-immersed in water and deformed underwater. Our explanation for this is that, due to the availability of water, crack tips can remain hydrated when the sample is deformed underwater, thus increasing the efficacy of stress corrosion cracking. The relationships and data provided herein inform on the long-term stability of engineering structures.
The moiré-pattern with slightly interlayer-twisted bilayer two-dimensional (2D) materials has recently been receiving substantial attention. One of the major characters for these intriguing ...structures is the appearance of low-energy ultra-flat bands and thus a package of new physics associated with strong electron correlation emerges. However, such new physics may become vague unless the twist-angle θ is sufficiently small such as θ ∼ 1°, making practical applications and control-flexibility hard to handle. In this work, we explore the possible flat-band moiré physics in recently concerned 2D bilayer α-In2Se3 which is antiferroelectric with sublayer out-of-plane (OP) polarizations, addressing the potential role of polarization-bound charges in modulation of electron–electron correlation and interlayer hybridization, based on the extensive first-principles calculations. On one hand, it is found that the low energy band becomes extremely flat in the bilayer α-In2Se3 moiré-pattern with relatively large twist-angle, e.g. θ = 13.17°, which is more easily accessible experimentally. On the other hand, the impact of the sublayer OP polarizations on the band structure is asymmetric, and the flattening effect is much more remarkable for the end-to-end polarization alignment but weaker for the head-to-head alignment. This work thus opens a broad roadmap for technological access to artificial fabrication of novel moiré-patterned 2D materials by means of low-dimensional ferroelectricity.
The bifacial p-type silicon (p-Si) passivated emitter and rear cells (PERCs) are predicted to dominate the industrial bifacial solar cells. In this work, we have investigated the impact of different ...rear surface morphologies on the electrical performance of bifacial PERCs with both five-busbar (5BB) and nine-busbar (9BB) grid design. The passivation and optical properties with differing rear surfaces are evaluated on semi-device structures. The depth of local aluminum back surface field is hardly affected by the rear surface morphology. The calculated efficiency loss analysis indicates that the negative electrical impact with enlarged rear surface area is more serious for rear side than that of front side. The batch conversion efficiency of 9BB bifacial PERCs increases by 0.2%–0.3% comparing to 5BB ones depending on the rear surface roughness. Consequently, a highest front-side average efficiency of 22.57%, with a champion efficiency of 22.75%, has been achieved for 9BB bifacial p-Si PERCs with a nearly planar rear surface. A highest bifaciality of 78.7% is realized for both 5BB and 9BB bifacial PERCs with the roughest rear surface. We have further simulated the relative enhancement of electric generation to compare the performance of bifacial PERCs in practical application.
•The impact of rear surface roughness on the performance of bifacial PERC solar cells with both 5BB and 9BB grid design.•The passivation and optical properties with different rear surface morphologies were evaluated.•The depth of Al-BSF was hardly influenced by rear surface morphology.•The negative electrical impact with enlarged surface area was more serious for rear side than front side.•A highest front-side average efficiency of 22.57% and a bifaciality of 78.7% were obtained.
The bifacial p-type silicon (p-Si) passivated emitter and rear cells (PERCs) have dominated the industrial bifacial solar cells. In this paper, we have investigated the impact of hydrogenated ...amorphous silicon oxynitride (SiOxNy) films on the optical and electrical performance of bifacial p-Si PERCs. Simulation and characterization are carried out to show the improvement of bifacial p-Si PERCs, yielding an absolute front-side efficiency improvement of 0.14% and 016% with SiOxNy films introduced to the front-side and rear-side, respectively. When SiOxNy films are employed to both sides of bifacial p-Si PERCs, the front-side and rear-side efficiency separately increase by 0.27% and 0.26% compared to the baseline without SiOxNy films. We have achieved on the bifacial p-Si PERCs production line an averaged front-side efficiency of 23.23% (champion efficiency of 23.42%), together with a 17.31% averaged rear-side efficiency. Furthermore, the introduction of SiOxNy films has been demonstrated to reduce the rear-side potential induced degradation (PID) effect through both single-cell modules and commercial glass-glass modules, due to the SiOxNy films protecting AlOx from corrosion and maximizing the field-effect passivation of AlOx layers.
•An absolute front-side efficiency improvement of 0.14% and 016% is achieved with SiOxNy films introduced to the front-side and rear-side of bifacial p-Si PERCs, respectively. When SiOxNy films are employed to both sides, the front-side and rear-side efficiency separately increase by 0.27% and 0.26% compared to the baseline without SiOxNy films. Finally an averaged front-side efficiency of 23.23% (champion efficiency of 23.42%) is achieved.•The introduction of SiOxNy films has been demonstrated to reduce the rear-side PID effect through both single-cell modules and commercial glass-glass modules, due to the SiOxNy films protecting AlOx from corrosion and maximizing the field-effect passivation of AlOx layers.
We study the process e^{+}e^{-}→Λ_{c}^{+}Λover ¯_{c}^{-} at twelve center-of-mass energies from 4.6119 to 4.9509 GeV using data samples collected by the BESIII detector at the BEPCII collider. The ...Born cross sections and effective form factors (|G_{eff}|) are determined with unprecedented precision after combining the single and double-tag methods based on the decay process Λ_{c}^{+}→pK^{-}π^{+}. Flat cross sections around 4.63 GeV are obtained and no indication of the resonant structure Y(4630), as reported by Belle, is found. In addition, no oscillatory behavior is discerned in the |G_{eff}| energy dependence of Λ_{c}^{+}, in contrast to what is seen for the proton and neutron cases. Analyzing the cross section together with the polar-angle distribution of the Λ_{c}^{+} baryon at each energy point, the moduli of electric and magnetic form factors (|G_{E}| and |G_{M}|) are extracted and separated. For the first time, the energy dependence of the form factor ratio |G_{E}/G_{M}| is observed, which can be well described by an oscillatory function.
The objective of this study was to investigate the effects of partial substitution of corn silage (CS) with sweet sorghum silage (SS) in the diets of lactating dairy cows on dry matter (DM) intake, ...milk yield and composition, blood biochemistry, and ruminal fermentation and microbial community. Thirty mid-lactation Holstein dairy cows mean ± standard deviation; 639 ± 42.0 kg of body weight; 112 ± 24.0 d in milk (DIM) were assigned to 3 groups (n = 10/treatment) by considering parity, milk yield, and DIM. The cows were fed ad libitum total mixed rations containing 55% forage and 45% concentrate, with only the proportion of CS and SS varying in 3 treatments (DM basis): SS0 (0% substitution of CS), 40% CS and 0% SS; SS25 (25% substitution of CS), 30% CS and 10% SS; and SS50 (50% substitution of CS), 20% CS and 20% SS. Dry matter intake and milk protein concentration tended to linearly decrease with increasing proportion of SS in the diet. Yields of milk (mean ± standard deviation, 30.9 ± 1.12 kg/d), 4% fat-corrected milk (30.0 ± 0.81 kg/d), energy-corrected milk, milk protein, lactose, and total solids, concentrations of milk fat, lactose, somatic cell counts, and milk efficiency did not differ among diets. The concentrations in blood of urea nitrogen, phosphorus, aspartate aminotransferase, and malondialdehyde linearly increased with increasing SS proportion. Blood IgA decreased with increasing SS substitution rate, but blood IgG and IgM were not different among diets. Ruminal pH did not differ among diets, whereas ruminal NH3-N concentration quadratically changed such that it was greater for SS50 than for SS0 and SS25. Molar proportions of propionate and acetate to propionate ratio were less for SS25 than for SS0. Although the diversity and general ruminal microbial community structure were not altered by partially replacing CS with SS, the relative abundances of predominant bacteria were affected by diets at the phylum and genus levels. Firmicutes and Bacteroidetes were dominant phyla in the ruminal bacterial community for all diets, and their relative abundance linearly decreased and increased, respectively, with increasing SS substitution rate. Prevotella_1 and Ruminococcaceae_NK4A214_group were detected as the most and the second most abundant genera, with their relative abundance linearly increased and decreased, respectively, with increasing SS substitution rate. The relative abundance of Fibrobacter linearly increased with increasing dietary SS proportion, with greater abundance observed for SS25 and SS50 than for SS0. These results suggest that substitution of CS with SS altered the relative abundances of some predominant bacteria; however, these changes had little effect on ruminal fermentation and milk yield. Under the current experimental conditions, substituting up to 50% of CS with SS had no negative effects on milk yield, indicating that SS can partially replace CS in the diets of high-producing lactating dairy cows without adding extra grain, when diets are fed for a short time. As the effects of substituting CS with SS depend upon the chemical composition and digestibility of these silages and the nutrient requirements of the cows, additional grain may be required in some cases to compensate for the lower starch content of SS.
Abstract Background and aims Prospective cohort studies are inconsistent regarding the association between magnesium intake and the risk of stroke. The objective was to perform a meta-analysis to ...summarise the relationship between magnesium intake and risk of stroke in observational studies. Methods and results We searched the PubMed and EMBASE databases for studies conducted from 1966 through August 2011. Prospective studies that provided relative risk (RR) estimates with 95% confidence intervals (CIs) for the association between magnesium intake and the risk of total stroke incidence or mortality were included. Data were independently abstracted by two investigators using a standardised protocol. Study-specific risk estimates were combined by using a random effects model. A total of eight studies, with 8367 stroke cases among 304,551 participants, were included in the meta-analysis. The summary RR indicated a significant association between the highest magnesium intake and reduced risk of total stroke (summary RR: 0.89; 95% CI: 0.82, 0.97); our dose–response analysis showed a borderline inverse association between magnesium intake and total stroke risk (an increment of 100 mg day−1 ; summary RR: 0.98; 95% CI: 0.95, 1.00). Subgroup analyses suggested a significant inverse association between highest magnesium intake and the risk of ischaemic stroke (summary RR: 0.88; 95% CI: 0.80, 0.98). Conclusion The present meta-analysis of prospective cohorts suggests that higher magnesium intake is associated with reduced risk of total and ischaemic stroke. However, well-designed randomised controlled trials are needed to draw a definitive conclusion.
With multiple elements mixed at equal or near-equal molar ratios, the emerging, high-entropy alloys (HEAs), also named multi-principal elements alloys (MEAs), have posed tremendous challenges to ...materials scientists and physicists, e.g., how to predict high-entropy phase formation and design alloys. In this paper, we propose some guidelines in predicting phase formation, using thermodynamic and topological parameters of the constituent elements. This guideline together with the existing ones will pave the way toward the composition design of MEAs and HEAs, as well as property optimization based on the composition–structure–property relationship.
► Disclose microstructure evolution of ASB with cutting speed. ► Microhardness distribution across ASB under different cutting speeds. ► Analyze the forming process of ASB during saw-tooth chip ...forming. ► Discuss mechanism of saw-tooth chip formation based on adiabatic shear sensitivity.
The formation of saw-tooth chip is one of the primary characteristics in high-speed cutting and in the machining of difficult-to-cut materials, such as titanium and its alloys, hardened steels. The saw-tooth chips obtained from Ti6Al4V turning were examined geometrically and metallurgically. The segment spacing, adiabatic shear band (ASB) width and the degree of segmentation were determined by micrographic observations. The microstructure evolution of ASB in terms of cutting speed was analyzed. The mechanism of saw-tooth chip formation was discussed depending on the adiabatic shear sensitivity of workpiece materials when processed at high strain and strain rates. Experimental results show that the evolution of microstructure inside the ASBs is: deformed band
→
deformed band
+
transformed band
→
transformed band with cutting speed increasing. As for those workpiece materials possessed high adiabatic shear sensitivity, the catastrophic instability resulting in the formation of saw-tooth chip is thermoplastic instability; as for those workpiece materials that is insensitive to shear localization, the instability in primary shear zone is periodic cracks originated at free surface ahead of tool; as for those workpiece materials in which adiabatic shear sensitivity is situated between the above two kind of materials, the interaction of thermoplastic instability and periodic cracks results in saw-tooth chip formation.
Corundum-structured α-Ga2O3 thin films have been employed to deposit on m-plane (300) α-Al2O3 substrates under different temperature, oxygen pressure, pulse laser energy and frequency by laser ...molecular beam epitaxy method. (300)-oriented α-Ga2O3 epitaxial thin film can be obtained under the appropriate growth parameters. The prepared α-Ga2O3 thin film shows a band gap of 5.15eV which is larger than that of β-Ga2O3, exhibiting an excellent solar-blind ultraviolet (UV) characteristic. The α-Ga2O3 thin film exhibits obvious photoresponse under 254nm UV light irradiation, and it increases in photocurrent with both the increase of optical input power and applied bias. However, it is not sensitive to 365nm light. The results suggest that α-Ga2O3 thin film is a promising candidate for use in solar-blind photodetectors.
•High-quality (300)-oriented corundum-structured α-Ga2O3 epitaxial thin films have been fabricated by LMBE on m-plane α-Al2O3 substrates .•The α-Ga2O3 epitaxial thin film with a band gap of 5.15eV exhibits a promising use in solar-blind photodetectors.
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