Template effect in TiN/AlN multilayered coatings from first principles

Multilayered TiN/AlN coatings find many technological applications where superhardness is suspected to be affected by AlN structures and template effect. Here, we demonstrate, by first-principles calculations on alternative adsorptions of Al and N atoms on Ti- and N-terminated TiN surfaces, that the preferred stacking sequences (i.e., having the largest adsorption energy) transform from fcc- to hcp- mode in first a few AlN layers. Using several analytic methods, we identify that for the T-terminated surface, the third added N layer is critical to inducing the structural transition of AlN, weakening the interaction between the second added Al and first added N atoms. The findings provide insight to the complicated template effects in TiN/AlN multilayered coatings, which are practically relevant for further improving property of multilayered coatings at the atomic scale

Analysis of blood hydrodynamic characteristics

Advances in modern medical imaging technology and three-dimensional modeling technology provide basic support for the establishment of individual cardiovascular models, which can promote the close integration of cardiovascular hemodynamics research. In this paper, the fluid-solid coupling technology is used to obtain the numerical simulation results of blood on rigid and elastic vessel walls. The results show that the elastic deformation of the wall has an important influence on the hemodynamic characteristics. The peak velocity in elastic blood vessel is about 3.7 % higher than that in rigid blood vessel. The extremum of fluid pressure in elastic blood vessel is about 9.1 % higher than that in rigid blood vessel

A Modified Normalized Difference Impervious Surface Index (MNDISI) for Automatic Urban Mapping from Landsat Imagery

Impervious surface area (ISA) is a key factor for monitoring urban environment and land development. Automatic mapping of impervious surfaces has attracted growing attention in recent years. Spectral built-up indices are considered promising to map ISA distributions due to their easy, parameter-free implementations. This study explores the potentials of impervious surface indices for ISA mapping from Landsat imagery using a case study area in Boston, USA. A modified normalized difference impervious surface index (MNDISI) is proposed, and a Gaussian-based automatic threshold selection method is used to identify the optimal MNDISI threshold for delineating impervious surfaces from background features. To evaluate its effectiveness, comparison analysis is conducted between MNDISI and the original NDISI using Landsat images from three sensors (TM/ETM+/OLI-TIRS) acquired in four seasons. Our results suggest that built-up indices are sensitive to image seasonality, and summer is the best time phase for ISA mapping. With reduced uncertainties from automatic threshold selection, the MNDISI extracts impervious surfaces from all Landsat images in summer with an overall accuracy higher than 87% and an overall Kappa coefficient higher than 0.74. The proposed method is superior to previous index-based ISA mapping from the enhanced thermal integration and automatic threshold selection. The ISA maps from the TM, ETM+ and OLI-TIRS images are not significantly different. With enlarged data pool when all Landsat sensors are considered and automation of threshold selection proposed in this study, the MNDISI could be an effective built-up index for rapid and automatic ISA mapping at regional and global scales

Investigation on acoustic reception pathways in finless porpoise (Neophocaena asiaorientalis sunameri) with insight into an alternative pathway

Author Posting. © The Author(s), 2018. This is the author's version of the work. It is posted here under a nonexclusive, irrevocable, paid-up, worldwide license granted to WHOI. It is made available for personal use, not for redistribution. The definitive version was published in Bioinspiration & Biomimetics 14 (2019): 016004, doi:10.1088/1748-3190/aaeb01.Sound transmission and reception are both vital components to odontocete echolocation and daily life. Here, we combine computed tomography (CT) scanning and Finite Element Modeling to investigate the acoustic propagation of finless porpoise (Neophocaena asiaorientalis sunameri) echolocation pulses. The CT scanning and FEM wave propagation model results support the well-accepted jaw-hearing pathway hypothesis and suggest an additional alternative auditory pathway composed of structures, mandible (lower jaw) and internal mandibular fat, with different acoustic impedances, which may also conduct sounds to the ear complexes. The internal mandibular fat is attached to the ear complex and encased by the mandibles laterally and anteriorly. The simulations show signals in this pathway initially propagate along the solid mandibles and are transmitted to the acoustically coupled soft tissue of the internal mandibular fat which conducts the stimuli posteriorly as it eventually arrives at ear complexes. While supporting traditional theories, this new bone-tissue-conduction pathway might be meaningful to understand the hearing and sound reception processes in a wide variety of odontocetes species.This work is financially supported in part by the National Natural Science Foundation of China (Grants No. 41276040, No. 11174240, and No. 41676023) and the Natural Science Foundation of Fujian Province of China (Grant No. 2012J06010)

Dynamic Crack Propagating Mechanism of Rock Materials Based on Different Weighted Functions

The singularity at the crack tip can be smoothed by the non-local theory based on different types of weighted functions. In the paper, the characteristics of different types of the weighted functions and their effects on non-local model are analyzed. The effects of the stress intensity factor KI and KII on the all components of stress-strain field in the neighborhood of the crack tip are analyzed by different types of the weighted functions. It is shown that the larger intrinsic characteristic length scale is, the more significant the reduction of non-local strain with respect to the local strain predicted conventionally will be. The size of non-local strain field with the bell-shaped weighted functions is larger than that obtained by either Green's or Gaussian weighted functions. The non-local normal stress-strain components depends on the stress intensity factor KI and KII, the circumferential stress is related to the stress intensity factor KI. The effect of stress intensity factor KI on non-local radial stress is positive while the effect of KII is negative. The non-local circumferential stress is related only to the stress intensity factor KII while the non-local shear stress is related only to the stress intensity factor KI. The larger the intrinsic characteristic scale is, the more significant the reduction of non-local strain with respect to the local strain predicted conventionally will be

Atomic-scale structure and nonlinear optical absorption of two-dimensional GeS

info:eu-repo/semantics/publishedVersio

OsHAC1;1 and OsHAC1;2 function as arsenate reductases and regulate arsenic accumulation

Rice is a major dietary source of the toxic metalloid arsenic (As). Reducing its accumulation in rice (Oryza sativa) grain is of critical importance to food safety. Rice roots take up arsenate and arsenite depending on the prevailing soil conditions. The first step of arsenate detoxification is its reduction to arsenite, but the enzyme(s) catalyzing this reaction in rice remains unknown. Here, we identify OsHAC1;1 and OsHAC1;2 as arsenate reductases in rice. OsHAC1;1 and OsHAC1;2 are able to complement an Escherichia coli mutant lacking the endogenous arsenate reductase and to reduce arsenate to arsenite. OsHAC1:1 and OsHAC1;2 are predominantly expressed in roots, with OsHAC1;1 being abundant in the epidermis, root hairs, and pericycle cells while OsHAC1;2 is abundant in the epidermis, outer layers of cortex, and endodermis cells. Expression of the two genes was induced by arsenate exposure. Knocking out OsHAC1;1 or OsHAC1;2 decreased the reduction of arsenate to arsenite in roots, reducing arsenite efflux to the external medium. Loss of arsenite efflux was also associated with increased As accumulation in shoots. Greater effects were observed in a double mutant of the two genes. In contrast, overexpression of either OsHAC1;1 or OsHAC1;2 increased arsenite efflux, reduced As accumulation, and enhanced arsenate tolerance. When grown under aerobic soil conditions, overexpression of either OsHAC1;1 or OsHAC1;2 also decreased As accumulation in rice grain, whereas grain As increased in the knockout mutants. We conclude that OsHAC1;1 and OsHAC1;2 are arsenate reductases that play an important role in restricting As accumulation in rice shoots and grain

Nitrogen fertilisation management in precision agriculture: a preliminary application example on maize

The adoption of precision agriculture techniques for N management has the potential for improving agronomic, economic and environmental efficiency in the use of such input. The present work was aimed at testing a simplified N balance method for the prescription of N fertilisation in uniform management zones defined from information on measured soil properties on grain maize in central Italy. The results of this preliminary experience show that the application of the N balance prescription map did not bring to significant differences, from a uniform N fertilisation, in terms of grain yield, economic return above N cost and nitrate content in the soil profile at the end of the growing season. However, the adoption of the prescribed N fertilisation strategy for the whole field would have caused a limited saving in the amount of fertiliser employed, quantified at about 10 kg N ha–1