4,134 research outputs found
Analytical Study of the Effect of Material Properties on the Formability of Sheet Metals based on the M-K Model
No full textThis paper investigates the effect of material properties on the formability of sheet metals based on the Marciniak-Kuczynski model (M-K model). The hardening behavior of the material is modeled as the Hollomon model with the strain rate effect. The yield surfaces are constructed with Hosford79 yield function. The material properties considered in this study include the R-value, the strain hardening exponent, the strain rate hardening exponent, and the crystal structure of the material. The effect of the crystal structure on formability is roughly expressed as the change of the yield surface by varying the value of the exponent in Hosford79 yield function. Results show that the R-value affects neither the magnitude nor the shape of right hand side forming limit diagrams (FLDs). Higher strain hardening exponent and higher strain rate hardening exponent improve the formability of sheet metals because they stabilize the forming processes. However, increasing the strain hardening exponent and the strain rate hardening exponent reduces the slope of the RHS FLDs
Opportunistic detection of Fusobacterium nucleatum as a marker for the early gut microbial dysbiosis
No full textBackgroundThe essential roles of gut microbiome have been emphasized in modulating human health and disease. Fusobacterium nucleatum (F. nucleatum), an obligate Gram-negative microorganism residing in oral cavity, gastrointestinal tract and elsewhere, has been recently considered as a potential oncobacterium associated with human cancers. However, the consequence of its enrichment was not extensively explored in terms of microbial homeostasis and stability at the early stage of disease development.ResultOur analysis on longitudinal metagenomic data generated by the Integrative Human Microbiome Project (iHMP) showed that F. nucleatum was frequently found in inflammatory bowel diseases (IBD) subjects with reduced microbial diversity. Using non-parametric logarithmic linear discriminant analysis (LDA) effect size (LEfSe) algorithm, 12 IBD- and 14 non-IBD-specific bacterial species were identified in the fecal metagenome and the IBD-specific ones were over-represented in the F. nucleatum-experienced subjects during long-term surveillance. In addition, F. nucleatum experience severely abrogated intra-personal stability of microbiome in IBD patients and induced highly variable gut microbiome between subjects. From the longitudinal comparison between microbial distributions prior and posterior to F. nucleatum detection, 41 species could be proposed as indicative "classifiers" for dysbiotic gut state. By multiple logistic regression models established on these classifiers, the high probability of experiencing F. nucleatum was significantly correlated with decreased alpha-diversity and increased number of biomarker species for IBD and colorectal cancer (CRC). Finally, microbial clustering confirmed that biomarker species for IBD and non-IBD conditions as well as CRC signature markers were well distinguishable and could be utilized for explaining gut symbiosis and dysbiosis.ConclusionF. nucleatum opportunistically appeared under early dysbiotic condition in gut, and discriminative classifier species associated with F. nucleatum were successfully applied to predict microbial alterations in both IBD and non-IBD conditions. Our prediction model and microbial classifier biomarkers for estimating gut dysbiosis should provide a novel aspect of microbial homeostasis/dynamics and useful information on non-invasive biomarker screening.11Ysciescopu
theta-curve polynomials and finite-type invariants
No full textThe normalized Yamada polynomial, (R) over tilde (A), is a polynomial invariant in variable A for theta-curves. In this work, we show that the coefficients of (R) over tilde (x)(e) which is obtained by replacing A with e(x) = Sigma x(n)/n! are finite-type invariants for theta-curves although the coefficients of original (R) over tilde (A) are not finite-type. A similar result can be obtained in the case of Yokota polynomial for theta-curves
Conditional moment closure modeling of turbulent nonpremixed combustion in diluted hot coflow
No full textThe conditional moment closure (CMC) model is applied to predict flame structures and NO formation in the moderate and intense low oxygen dilution combustion mode. The effects of oxygen concentration in a hot diluted oxidant stream are investigated in the experimental condition of Dally et al. [Proc. Combust. Inst. 29 (2002) 1147–1154]. The GRI 2.11 Mech is used for description of chemical reaction including NOx chemistry. The conditional scalar dissipation rate, which describes the effect of turbulent mixing on finite chemistry, is calculated by integrating the transport equation for probability density function (PDF). A new PDF is proposed to describe three stream mixing in terms of a single mixture fraction. The conditional mean predictions of temperature, and CO, OH, and NO mass fractions are in good agreement with measurements. The unconditional Favre mean predictions of CO and NO mass fractions are also in reasonable agreement. Upstream underprediction of OH and NO in the low oxygen concentration case may be attributed to uncertainty in low temperature reaction mechanism and mixing prediction. Differential diffusion effects are shown to be nonnegligible in the present flames. The CMC model is an attractive choice for simulation of MILD combustion in which conditional fluctuations of reactive scalars are small enough for first-order closure of conditional mean reaction rates to remain valid.Seung Hyun Kim, Kang Y. Huh, and Bassam Dallyhttp://www.elsevier.com/wps/find/journaldescription.cws_home/703522/description#descriptio
Evaluation of the turbulence models for gas flow and particle transport in URANS and LES of a cyclone separator
No full textGas-solid separators have played an important role for process or emission control of many facilities including fluidized bed reactors. The flow field and collection efficiency were investigated for a Stairmand-type cyclone separator by Reynolds stress transport model (RSTM) and large eddy simulation (LES) in this work. RSTM and LES both showed good agreement with measured mean tangential velocity, whereas LES reproduced unsteady flow in the core with better agreement of the mean axial velocity profile. The particle dispersion model is required to obtain an accurate overall collection efficiency in both RSTM and LES. Anisotropy in velocity fluctuation should be taken into account, whereas its effect is more significant in RSTM than in LES. The continuous random walk (CRW) model gave more accurate results than the discrete random walk (DRW) model in RSTM, whereas there was no significant difference in LES resolving most large scale eddies. LES made better prediction of the overall particle collection efficiency than RSTM, although further investigation may be required for deviation in the maximum inlet flow case of the cyclone separator. (C) 2018 Elsevier Ltd. All rights reserved.11Nsciescopu
Fluvial geochemistry of the eastern slope of the northeastern Andes and its foredeep in the drainage of the Orinoco in Columbia and Venezuela
No full textThe fluvial geochemistry of the tributaries of the Orinoco draining the eastern branch of the northern Andes in Colombia and Venezuela is determined by lithology and ranges from rivers dominated by aluminosilicate weathering, mainly of shales and mafic rocks, to those bearing the signatures of dissolution of marine limestones and evaporites and of continental playa deposits. These left bank tributaries of the Orinoco provide the overwhelming proportion of the suspended and dissolved loads transported by the main stem although feeding only half the discharge. However, due to the extreme severity of weathering on the Guayana Shield, the right bank tributaries supply about half the silica and 40% of the K carried by the Orinoco. There is a similar partitioning between the Andes and the lowlands in the Amazon drainage. In contrast the Mackenzie, which drains the northern extremity of the continental are of the Western Americas, is completely dominated by the weathering of limestones and evaporites and transports very Little silica. This, again, appears to be a reflection of lithology since the Yukon? in similar latitudes and terrain, has silica concentrations comparable to the Tropical systems. In addition, a conservative deconvolution of the data gives estimates of the net consumption of atmospheric CO2 by aluminosilicate weathering that follows the same pattern. Thus, the available evidence from the Western Americas indicates that exposure and lithology, rather than the climatic variables, temperature, and runoff, dominate the weathering yields in active orogenic belts. These observations contradict the conventional, view of weathering processes and their controls and are at complete variance with the assumptions parameterised in most models of the geochemical cycle.N
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