Comparison of the simulation and experimental fatigue crack behaviors in the aluminum alloy HS6061-T6

AbstractThis work deals with rotating bending fatigue tests on aluminum alloy HS6061-T6. Results have been obtained for two sizes of narrow section diameter for specimens with one hole. Results show that fatigue endurance is reduced in the case of the hole. In order to explain this behavior, numerical analysis by FEM were carried out to determine the stress concentrations for the two types of specimens. It is found that the important factor affects fatigue life is the narrow section diameter of the specimens, and the maximum damage occurs in the outer part of the specimen at the first stages of loading, however, it moves toward the center of the bar under uniaxial loading. The number of cycles to failure predicted numerically is higher than the experimental one. This difference is attributed mainly to an upper stage of fatigue crack growth, particularly, the interaction between fatigue crack growth and growth that can not be accounted for in the numerical model

Magnetic phase diagram in Eu1−x_{1-x}Lax_xFe2_2As2_2 single crystals

We have systematically measured resistivity, susceptibility and specific heat under different magnetic fields (H) in Eu$_{1-x}$La$_x$Fe$_2$As$_2$ single crystals. It is found that a metamagnetic transition from A-type antiferromagnetism to ferromagnetism occurs at a critical field for magnetic sublattice of $Eu^{2+}$. The jump of specific heat is suppressed and shifts to low temperature with increasing H up to the critical value, then shifts to high temperature with further increasing H. Such behavior supports the metamagnetic transition. Detailed H-T phase diagrams for x=0 and 0.15 crystals are given, and possible magnetic structure is proposed. Magnetoresistance measurements indicate that there exists a strong coupling between local moment of $Eu^{2+}$ and charge in Fe-As layer. These results are very significant to understand the underlying physics of FeAs superconductors.Comment: 5 pages, 4 figure

Re-evaluation of Sympoventuriaceae

Sympoventuriaceae (Venturiales, Dothideomycetes) comprises genera including saprophytes, endo-phytes, plant pathogens, as well as important animal or human opportunistic pathogens with diverse ecologies and wide geographical distributions. Although the taxonomy of Sympoventuriaceae has been well studied, generic boundaries within the family remain poorly resolved due to the lack of type materials and molecular data. To address this issue and establish a more stable and reliable classification system in Sympoventuriaceae, we performed multi-locus phylogenetic analyses using sequence data of seven genes (SSU, ITS, LSU, act1, tub2, tef1 and rpb2) with increased taxon sampling and morphological analysis. The molecular data combined with detailed morphological studies of 143 taxa resolved 22 genera within the family, including one new genus, eight new species, five new combinations and one new name. Finally, we further investigated the evolutionary history of Sympoventuriaceae by reconstructing patterns of lifestyle diversification, indicating the ancestral state to be saprophytic, with transitions to endophytic, animal or human opportunistic and plant pathogens

The association between distal findings and proximal colorectal neoplasia: a systematic review and meta-analysis

Objectives: Whether screening participants with distal hyperplastic polyps (HPs) detected by flexible sigmoidoscopy (FS) should be followed by subsequent colonoscopy is controversial. We evaluated the association between distal HPs and proximal neoplasia (PN)/advanced proximal neoplasia (APN) in asymptomatic, average-risk patients. Methods: We searched Ovid Medline, EMBASE, and the Cochrane Library from inception to 30 June 2016 and included all screening studies that examined the relationship between different distal findings and PN/APN. Data were independently extracted by two reviewers with disagreements resolved by a third reviewer. We pooled absolute risks and odds ratios (ORs) with a random effects meta-analysis. Seven subgroup analyses were performed according to study characteristics. Heterogeneity was characterized with theI2 statistics. Results: We analyzed 28 studies (104,961 subjects). When compared with normal distal findings, distal HP was not associated with PN (OR=1.16, 95% confidence interval (CI)=0.89–1.51,P=0.14,I2=40%) or APN (OR=1.09, 95% CI=0.87–1.36,P=0.39,I2=5%), while subjects with distal non-advanced or advanced adenoma had higher odds of PN/APN. Higher odds of PN/APN were observed for more severe distal lesions. Weaker association between distal and proximal findings was noticed in studies with higher quality, larger sample size, population-based design, and more stringent endoscopy quality-control measures. The Egger’s regression tests showed allP>0.05. Conclusions: Distal HP is not associated with PN/APN in asymptomatic screening population when compared with normal distal findings. Hence, the presence of distal HP alone detected by FS does not automatically indicate colonoscopy referral for all screening participants, as other risk factors of PN/APN should be considered

Water stress in maize production in the drylands of the Loess Plateau

Water stress during two maize (Zea mays L.) growing seasons (2013 and 2014) was investigated in a semiarid region of northwest China. The HYDRUS-1D model gave good simulation of the soil water content in different layers throughout a 0- to 200-cm depth during the maize growing season, with R-2 values of 70.6 and 77.0% for the calibration and validation periods, respectively. Water stress for maize production was observed in June of 2013 and in July of 2014. The soil water storage (SWS) decreased significantly during the early stage of the maize growing season, especially in 2014. The root depth and crop height were 20 cm deeper and 100 cm higher, respectively, in 2014 than in 2013 at the early stage. These results suggest that in the early stage of the maize growing season, pre-seeding SWS can alleviate crop water stress effectively via deep roots. Model simulation showed that the plow pan layer (at a depth of 20-40 cm), with high soil bulk density and a lower soil water retention curve, significantly reduced infiltration. High evapotranspiration and low precipitation result in a temporary dry layer during the early stage, highlighting the plow pan as the sensitive layer for water stress during the drought period. Effective management practices such as deep plowing, plastic film mulching, or water conservation treatments in the fallow period are needed to avoid the formation of this temporary dry layer during the drought period at the early stage and thus improve maize production in rainfed agriculture on the Loess Plateau of China

Dissociative chemisorption of methane on Ni(111) using a chemically accurate fifteen dimensional potential energy surface

Theoretical Chemistr

Absence of First-order Transition and Tri-critical Point in the Dynamic Phase Diagram of a Spatially Extended Bistable System in an Oscillating Field

It has been well established that spatially extended, bistable systems that are driven by an oscillating field exhibit a nonequilibrium dynamic phase transition (DPT). The DPT occurs when the field frequency is on the order of the inverse of an intrinsic lifetime associated with the transitions between the two stable states in a static field of the same magnitude as the amplitude of the oscillating field. The DPT is continuous and belongs to the same universality class as the equilibrium phase transition of the Ising model in zero field [G. Korniss et al., Phys. Rev. E 63, 016120 (2001); H. Fujisaka et al., Phys. Rev. E 63, 036109 (2001)]. However, it has previously been claimed that the DPT becomes discontinuous at temperatures below a tricritical point [M. Acharyya, Phys. Rev. E 59, 218 (1999)]. This claim was based on observations in dynamic Monte Carlo simulations of a multipeaked probability density for the dynamic order parameter and negative values of the fourth-order cumulant ratio. Both phenomena can be characteristic of discontinuous phase transitions. Here we use classical nucleation theory for the decay of metastable phases, together with data from large-scale dynamic Monte Carlo simulations of a two-dimensional kinetic Ising ferromagnet, to show that these observations in this case are merely finite-size effects. For sufficiently small systems and low temperatures, the continuous DPT is replaced, not by a discontinuous phase transition, but by a crossover to stochastic resonance. In the infinite-system limit the stochastic-resonance regime vanishes, and the continuous DPT should persist for all nonzero temperatures

Characterization of starch synthetic genes and starch granule during seeds development between synthetic hexaploid wheat and its parents

To study the development of starch granules in polyploid wheats, we investigated the expression of starch synthetic genes between the synthetic hexaploid wheat SHW-L1, its parents T. turgidum AS2255 and diploid Ae. tauschii AS60. The synthetic hexaploid wheat SHW-L1 showed significantly higher starch content and grain weight than its parents. Scanning electron microscopy (SEM) showed that SHW-L1 rapidly developed starch granules than AS2255 and AS60. The amount of B-type granule in AS60 was less than that in SHW-L1 and AS2255. RT-qPCR result showed that the starch synthetic genes AGPLSU1, AGPLSU2, AGPSSU1, AGPSSU2, GBSSI, SSIII, PHO1 and PHO2 expressed at earlier stages with larger quantity in SHW-L1 than in its parents during wheat grain development. The expression of the above mentioned genes in AS60 was slower than in SHW-L1 and AS2255. The expression pattern of starch synthase genes was also associated with the grain weight and starch content in all three genotypes. The results suggested that the synthetic hexaploid wheat inherited the pattern of starch granule development and starch synthase gene expression from tetraploid parent. The results suggest that tetraploid wheat could plays more important role for starch quality improvement in hexaploid wheat

An integrated climate and water resource climate service prototype for long term water allocation in the Upper Yellow River Region of China

Water Resourcing in China has historically been a complex issue requiring the ability to deal with regular floods, droughts and diverse water needs. Climate change represents another challenge to this sector, albeit one that is not traditionally considered by water managers. In this sector in China water management is predominantly based on historic, seasonal and annual forecast data while multi-annual and (multi-)decadal data are seldom used. In this paper, we present the co-development of a climate service prototype designed to provide water managers with insights into the impacts of climate change on the Upper Yellow River region for the next century. The paper is an outcome from our project that encouraged water resource planners and water resource managers to utilise long-term climate information to understand the uncertainties and the challenges our changing climate is likely to have in the region. Using an interdisciplinary team and adopting a user-centred, co-production approach, a prototype web-based data visualisation tool was developed. The development of the prototype was based on a design specification constructed from the findings of detailed interviews that allowed it to be developed and tested under SARS-CoV-2 pandemic restrictions that prevented the typical development process to be undertaken. The developed prototype presents climate information and communicates uncertainties regarding climate change in the remainder of the century through data sets that are typically used by the water sector in China in a simple, easy to understand style. Models that estimate river levels under different extraction scenarios and results about estimated river level and flow, and flood risk are also presented. The prototype was shown to be successful, as key messages relating to the impact of climate change and the challenges for water resource management could be effectively communicated through the tool interface. Practical implications Understanding the impacts of climate change on water resourcing is complicated and multifaceted. There is a need for better data about what water there is and how it is moving around between and within catchments. Estimates of past, present and future climate variables along with historical measurements of river flow can be used to help visualise some of the uncertainties and changes that may happen in the next 50 years. In addition, there is a need to understand changing water demands and water resource management practices. Current water resource management practices are based on historical conditions and assumptions that are less likely to hold true in a more variable and warmer climate. Communicating how future changes will impact future water resourcing is critical to water resources in a changing climate (Belcher et al. 2018). This research outlines the construction of a tool to visualise the impacts of climate change on water availability in part of China that is typically water scarce, using models developed using the Soil Water Assessment Toolkit (SWAT). A model of the Upper Yellow River (UYR) was developed to demonstrate the impact of climate change on river levels in the catchment based on climate variables. The rainfall-runoff model was based on climate predictions from the CMIP5 assessment HadGEM3-GC3.05 climate model and incorporated information about water resource allocations for different administrative regions of the catchment The general climate trend for the region is that it is expected to become significantly warmer. The total amount of precipitation is likely to be about the same, and yet it is expected that overall, the catchment will become significantly drier over time as winter shortens and summer lengthens. The outputs from the model reflect the changes in climate variables. The uncertainties were communicated via a Web based tool. Water resource managers in China helped to coproduce the tool by participating in workshops and providing feedback on prototypes. The workshops helped scientists and water resource managers to communicate about climate change impacts on water resources and water resource management