Ceria- and yttria-doped tetragonal polycrystalline zirconia ceramics were ground at temperatures as high as 1100°C. X-ray diffraction revealed that the intensity ratio I (002)/ I (200) increased (to as high as ∼4.5) compared with that from the as-sintered surfaces (∼0.55). The enhancement in I (002)/ I (200) at temperatures well above the m → t transition temperature shows that it is not related to transformation, reversible or otherwise, but can be explained by ferroelastic domain switching. 相似文献
In this work, we aim to update the understanding of how impurity or promoter metals segregate on metal surfaces, particularly in the application of single-atom alloys (SAA) for catalysis. Using density functional theory, we calculated the relative stability of the idealized SAA relative to subsurface, dimer, and adatom configurations to determine the tendency of the promoter atom to diffuse into the bulk, form surface clusters, or avoid alloying with the host, respectively. We selected 26 d-block metals augmented with Al and Pb to create a 28?×?28 database that indicates a total of 250 combinations for which the SAA configuration is most stable, and an additional 358 systems for which the SAA geometry is within 0.5 eV of the most stable configuration. We classified the data using decision tree, support vector machine, and neural network machine learning algorithms with tabulated atomic properties as the input vector. These black box approaches are unable to extrapolate to other possible geometries, which was circumvented by redefining the stability problem as a regression. We propose a physical bond counting model to formulate intuitive criteria for the formation of stable SAAs. The accuracy is then improved by using the bonding configuration and tabulated atomic properties with a kernel ridge regression (KRR) algorithm. The hybrid KRR model correctly identifies 190 SAAs with 85 false positives. Importantly, its physical basis allows the hybrid model to extend to similar geometries not included in the training data, thereby expanding the domain where the model is useful.
The inflection point of spectral reflectance of crop in the red edge region (680–780 nm) is termed as the red edge position (REP), which is sensitive to crop biochemical and biophysical parameters. We propose a technique for automatic detection of four dynamic wavebands, i.e. two in the far-red and two in the near-infrared (NIR) region from hyperspectral data, for REP estimation using the linear extrapolation method. A field experiment was conducted at the SHIATS Farm, Allahabad, India, with four levels of nitrogen and irrigation treatments to assess the sensitivity of REP towards crop stress. A correlation analysis was carried out between REPs and different biophysical parameters, such as leaf area index (LAI) and chlorophyll content index (CCI), recorded in each plot at 50, 70, and 90 days after sowing of wheat crop under the field experiment. The inter-comparison among different REP extraction techniques revealed that the proposed technique, i.e. the modified linear extrapolation (MLE) method, has a better ability to distinguish different crop stress conditions. REPs extracted using the MLE technique showed high correlations with a wide range of LAI, CCI, and LAI × CCI, being comparable with results obtained using the traditional linear extrapolation and polynomial fitting techniques. The behaviour of the new techniques was found to be stable at both narrower and broader bandwidth, i.e. 2 and 10 nm. A new red-edge-based index, i.e. area under REP (AREP), was used to detect the cumulative stress over wheat crop by utilizing the REP and its rate of change information at different crop growth stages. A high coefficient of determination (R2 = 0.89) was found between AREP and dry grain yield (Q ha?1) up to 50 Q ha?1 of wheat crop, whereas, beyond this range the relationship was found to be diminishing. 相似文献
This paper presents a new contact heat transfer model for estimation of wallto- bed heat transfer rates based exclusively on information on particle flow and mixing within a stirred granular bed. The effects of solids flow ability, bed height, blade rotational speed, size of the annular wall-to-blade clearance, vessel diameter and aeration of the bed on the overall solids mixing patterns, particle renewal rates and contact heat transfer in vessels agitated with flat paddles are presented and discussed. The model is shown to yield satisfactory agreement With expenrnental data. 相似文献
This paper uses an agent-based simulation model to estimate the costs associated with Mycobacterium avium ssp. paratuberculosis (MAP), or Johne's disease, in a milking herd, and to determine the net benefits of implementing various control strategies. The net present value (NPV) of a 1,000-cow milking herd is calculated over 20 yr, parametrized to a representative US commercial herd. The revenues of the herd are generated from sales of milk and culled animals. The costs include all variable and fixed costs necessary to operate a representative 1,000-cow milking herd. We estimate the NPV of the herd with no MAP infection, under an expected endemic infection distribution with no controls, and under an expected endemic infection distribution with various controls. The initial number of cows in a herd with an endemic MAP infection is distributed as 75% susceptible, 13% latent, 9% low MAP shedding, and 3% high MAP shedding. Control strategies include testing using ELISA and fecal culture tests and culling of cows that test positive, and culling based on observable milk production decrease. Results show that culling cows based on test results does not increase the herd's NPV and in most cases decreases NPV due to test costs as well as false positives and negatives with their associated costs (e.g., culling healthy cows and keeping infected cows). Culling consistently low producing cows when MAP is believed to be present in the herd produces higher NPV over the strategy of testing and culling MAP infected animals, and over the case of no MAP control. 相似文献