Contribution Of Different Layers Research Articles

Understanding the helicoidal damage behavior of bio-inspired laminates by conducting multiscale concurrent simulation and experimental analysis

Bio-inspired helicoidal structures exhibit excellent fracture toughness. A multiscale concurrent simulation of the damage propagation process is critical for understanding the fracture behavior of such structures with pre-existing cracks. However, such an analysis is extremely challenging owing to computational complexity. In this study, the in-plane critical stress intensity factor and energy release rate of six different helicoidal carbon-fiber-reinforced plastic structures are measured experimentally by conducting a single-edge-notch bending test. The damage distribution of the different structures is examined by performing computed tomography scanning. Several multiscale concurrent analyses are conducted by using the self-consistent clustering analysis method to study the specific damage propagation process and evaluate the fracture toughness contribution of different layers. The results indicate that the pitch angle significantly impacts the fracture toughness, whereas the stacking mode changes the crack propagation orientation. When the pitch angle is appropriately adjusted, the fiber damage length is enhanced, resulting in a significant increase in the fracture toughness. The interaction between fiber damage, matrix damage, and hybrid damage during the failure process is interpreted using the dissipated energy ratios of the fiber damage layer, transition layer, and matrix damage layer.

Multicriteria Accuracy Assessment of Digital Elevation Models (DEMs) Produced by Airborne P-Band Polarimetric SAR Tomography in Tropical Rainforests

The penetration capability of P-band radar waves through dense vegetation, along with the ability of tomography to separate the contributions of different layers in a vertical reflectivity profile, make P-band radar tomography a promising tool for digital terrain modeling in forested areas, specifically in dense tropical forests under which terrain topography remains poorly known. This paper aims to assess the overall quality of a digital terrain model (DTM) produced using tomographic processing of airborne P-band SAR imagery acquired during the TropiSAR campaign in French Guiana. Many quality descriptors are used to evaluate the quality of this DTM. Position and slope accuracies are computed based on a lidar DTM considered as the reference, and the impact of several parameters on these accuracies is studied, namely, slope, slope orientation, off-nadir angle and local incidence angle. The realism of the landforms is also studied according to geomorphological criteria. The results of this multicriteria accuracy assessment show the high potential of P-band SAR tomography in depicting the topography under forests, despite the intrinsic limitations related to the slant range geometry: the absolute elevation error is around 2 m; the slope is overestimated with an error of about 16°, mainly due to a processing artifact for which easy and direct solutions exist. Indeed, this error is equal to about 3° in flat artifact-free areas. These errors vary depending on the acquisition parameters and the local topography. The shapes are globally well preserved. These results are also discussed in the frame of the upcoming BIOMASS mission developed by the European Space Agency (ESA) and expected to be launched in 2024.

Understanding near-surface polymer dynamics by a combination of grazing-incidence neutron scattering and virtual experiments.

Neutron spin-echo spectroscopy is a unique experimental method for the investigation of polymer dynamics. The combination of neutron spin-echo spectroscopy with grazing-incidence geometry (GINSES) opens the possibility to probe the dynamics of soft-matter materials in the vicinity of the solid substrate in the time range up to 100 ns. However, the usage of the GINSES technique has some peculiarities and, due to the novelty of the method and complexity of the scattering geometry, difficulties in further data analysis occur. The current work discusses how virtual experiments within the distorted-wave Born approximation using the BornAgain software can improve GINSES data treatment and aid the understanding of polymer dynamics in the vicinity of the solid surface. With two examples, poly(N-isopropyl acrylamide) brushes and poly(ethylene glycol) microgels on Si surfaces, the simulation as well as the application of the simulation to the GINSES data analysis are presented. The approach allowed a deeper insight to be gained of the background effect and scattering contribution of different layers.

Mean temperature profile and thermal displacement thickness in turbulent Rayleigh–Bénard convection

The shape of the mean temperature profile in turbulent Rayleigh–Bénard Convection (RBC) plays an important role in the understanding and prediction of heat transfer. Based on the characteristics of the mean temperature profile, we propose a four-layer structure for each half of a turbulent RBC cell. Layer I, a thin layer adjacent to the bottom or top plate, is the traditional thermal diffusional sub-layer, in which the mean temperature is dominated by linear growth. It is found, empirically, that there exists a layer in which the mean temperature deficit can be approximated by a power-law decay, and this layer is called Layer III. Between Layer I and Layer III there exists a transitional or buffer layer, which is designated Layer II. Outside Layer III is a well-mixed outer layer, Layer IV. In a fully turbulent RBC, Layers I, II, and III occupy a small fraction of the RBC cell, but these layers contain nearly all the temperature increment. Layer IV occupies a large fraction of the RBC cell, but with negligible temperature increment. One parameter that quantifies the shape of the mean temperature is the thermal displacement thickness δθd. The four-layer model is used to clarify the contribution of different layers to the thermal displacement thickness in a turbulent RBC. It is found that the integral in the calculation of the thermal displacement thickness mainly comes from Layer III.

Breaking down the human motor cortex: the layer-specific measurement of corticospinal neuronal activity.

Breaking down the human motor cortex: the layer-specific measurement of corticospinal neuronal activity.

Differences in bacterial community structure between three types of biological soil crusts and soil below crusts from the Gurbantunggut Desert, China

The scarcity of knowledge on differences in the microbial assemblage between biological soil crusts (BSCs) and soil below crusts (SBCs) limits our understanding of the contribution of different layers of topsoil to desert ecosystems. This study used Illumina MiSeq sequencing to determine whether differences in bacterial communities among different types of BSCs (algae, lichen and moss dominated) are greater than those between BSCs and their corresponding underlying soils (0–5 cm) in the Gurbantunggut Desert, China. Alpha and beta diversity of bacterial communities showed that richness and diversity were greater in SBCs than in BSCs, but the absolute bacterial abundance was larger in BSCs than in soils. Differences were mainly in the phyla Cyanobacteria, Actinobacteria, Chloroflexi and Acidobacteria. Cyanobacteria were concentrated in BSCs, especially in algae‐dominated BSCs. The relative abundances of Actinobacteria, Chloroflexi and Acidobacteria in SBCs were more than twice those in BSCs, and they were also abundant in the lichen‐ and moss‐dominant crusts. The number of sample‐specific genera was larger in BSCs, but there were more shared genera among SBCs. These results, combined with the principal coordinate analysis and the predicted function profiles, showed that differences in microbial community structure and function in desert ecosystems were greatest between BSCs and the underlying soils, followed by differences among the three types of BSCs, and differences were smallest between the soils below different crusts. These differences might be closely related to the soil chemical properties, especially to pH and fertility. Our study indicated that microbial communities tended to converge in SBCs of different microhabitats.Highlights We studied bacterial community composition in different types of BSCs and SBCs. Differences in bacterial community were greatest between BSCs and SBCs. BSC components contributed to small‐scale microbial heterogeneity in SBCs. Surface soil bacterial communities were strongly stratified even at the centimetre scale from BSCs.

Multiple markers of cortical morphology reveal evidence of supragranular thinning in schizophrenia.

In vivo structural neuroimaging can reliably identify changes to cortical morphology and its regional variation but cannot yet relate these changes to specific cortical layers. We propose, however, that by synthesizing principles of cortical organization, including relative contributions of different layers to sulcal and gyral thickness, regional patterns of variation in thickness of different layers across the cortical sheet and profiles of layer variation across functional hierarchies, it is possible to develop indirect morphological measures as markers of more specific cytoarchitectural changes. We developed four indirect measures sensitive to changes specifically occurring in supragranular cortical layers, and applied these to test the hypothesis that supragranular layers are disproportionately affected in schizophrenia. Our findings from the four different measures converge to indicate a predominance of supragranular thinning in schizophrenia, independent of medication and illness duration. We propose that these indirect measures offer novel ways of identifying layer-specific cortical changes, offering complementary in vivo observations to existing post-mortem studies.

High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

Crystallization of an isotactic polypropylene (iPP) homopolymer and two propylene/ethylene random copolymers (RACO), induced by high-stress shear, was studied using in situ synchrotron wide-angle X-ray diffraction (WAXD) at 137 °C. The “depth sectioning” method (Fernandez-Ballester Journal of Rheology 2009, 53 (5), 1229−1254) was applied in order to isolate the contributions of different layers in the stress gradient direction and to relate specific structural evolution to the corresponding local stress. This approach gives quantitative results in terms of the specific length of fibrillar nuclei as a function of the applied stress. As expected, crystallization becomes faster with increasing stress—from the inner to the outer layer—for all three materials. Stress-induced crystallization in a RACO with 7.3 mol % ethylene content was triggered at only 1 °C below its nominal melting temperature. The comparison of iPP and RACO’s with 3.4 and 7.3 mol % ethylene monomer reveals the effect of ethylene defects on high-stress shear induced crystallization at 137 °C. It is found that, for a given applied stress, the specific nuclei length formed by flow increases with ethylene content—which is attributed to a greater high molecular weight tail. However, the linear growth rate is significantly reduced by the presence of ethylene comonomers and it is found that this effect dominates the overall crystallization kinetics. Finally, a time lag is found between development of parent lamellae and the emergence of daughter lamellae, consistent with the concept of daughter lamellae nucleated by homoepitaxy on the lateral faces of existing parent lamellae.

Vertical Distribution of Nitrogen in Different Layers of Leaf and Stem and Their Relationship with Grain Quality of Winter Wheat

ABSTRACT With the widespread application of remote sensing (RS) in agriculture, monitoring and prediction of crop quality attracts the attention of many scientists. Because different vertical layers of crop canopy make different contributions to the spectral reflectance, it is important to define the contributions of different layers to spectral reflectance in order to improve the accuracy of canopy information retrieval using RS data. In this study, vertical distribution of nitrogen in the canopy of winter wheat (Triticum aestivum L.) of two cultivars treated with four nitrogen (N) rates (0, 150, 300, and 450 kg N·hm−2) and its contribution to grain quality were investigated. The two cultivars, Jingdong8 (low grain-protein content) and Zhongyou9507 (high grain-protein content), were contrastive in grain quality. Wheat canopy was cut into 3 (at elongation) or 4 (at anthesis and grain filling) layers of equal vertical thickness from top to bottom (layer 1 represented the top, layer 3 or 4 the bottom) in a 1 m2 investigated area of each plot. The objectives of this study were (1) to clarify the N condition of different layers at different growth stages and at various N treatments; (2) to analyze the relationship between N in different layers and grain quality, as well as investigate the contribution of different canopy layers to grain quality; and (3) to provide new data on wheat quality factors in combination with N of different canopy layers potentially to aid retrieval of wheat quality by RS data. The results showed that leaf N concentration decreased from top to bottom. A greater vertical N gradient was observed in leaf than in stem. Leaf N in layer 1 and layer 2 contributed significantly to the grain protein content (GPC) and wet gluten content (WGC) in Jingdong8. Grain quality parameters were significantly related to leaf N in layer 1 of Zhongyou9507. Stem N in Zhongyou9507 made a greater contribution to grain quality than that of Jingdong8. N translocation form the lower layers to the upper layers was associated with grain quality, especially in Zhongyou9507. Greater leaf N gradient 2 (G2) of Zhongyou9507 at anthesis and grain filling was associated with better grain quality.

Interpretation of Transverse Profiles to Determine the Source of Rutting within an Asphalt Pavement System

The transverse profilograph has been recognized as one of the most accurate devices for the measurement of rut depth. However, interpretation of surface transverse profile measurements poses a major challenge in determining the contributions of the different layers to rutting. A literature review has shown that the actual rutting mechanism can be estimated from a surface transverse profile for determination of the relative contribution of the layers to rutting. Unfortunately, much of the research yielded no verification or data. In addition, some techniques presented cannot be used if the rut depth is not well pronounced. Other techniques may be costly and time-consuming. The present research developed an approach that integrates ( a) falling weight deflectometer and core data along with 3.6-m transverse profile measurements to assess the contributions of different pavement layers to rutting and ( b) identifies the presence (or absence) of instability within the asphalt surface layer. This approach can be used regardless of the magnitude of the rut depth. On the basis of the analysis conducted, absolute rut depth should not be used to interpret the performance of the asphalt mixture. In addition, continued instability may not result in an increase in rut depth because the rutted basin broadens as traffic wander compacts or moves the dilated portion of the mixture. The approach developed appears to provide a reasonable way to distinguish between different sources of rutting. The conclusions drawn from analysis of the approach agreed well with observations from the trench cuts taken from four sections.

Influence of field-effect charges on the optical properties of α-sexithiophene thin films

We report on the influence of field-effect charge injection on optical absorption and fluorescence properties of α-sexithiophene ( α-6T) thin films. We have performed electromodulated absorption (EMA) and electromodulated fluorescence (EMF) measurements on metal—semiconductor (MS) devices based on the molecular semiconductor α-6T. Analyzing the influence of the incidence angle on EMA spectra enables a discrimination of the contribution of different layers of the metal—insulator—semiconductor (MIS) device. An EMA peak at 1.5 eV can thus be attributed to an optical absorption modulation located in the channel, induced by charges stored as radical cations α-6T ·+. We have also compared the EMA properties with either gold or aluminum as contact electrodes. An excitation light must assist the injection of charges into α-6T from the aluminum electrode, which is unnecessary when gold is used. A large relative change of the fluorescence efficiency of α-6T shows that each field-effect positive charge quenches the fluorescence of approximately 200 α-6T molecules.

Apparatus Weighting Functions in measuring the line-of-sight velocities by the ?center of gravity? method

The conception of the Apparatus Weighting Function (AWF), numerically characterizing the contributions of different layers of the solar atmosphere to indications of the apparatus used is introduced. For the detection of line-of-sight velocities, measuring the shifts of the ‘center of gravity’ of a spectral line profile, AWFs have been calculated for several single lines used by the authors in their observations of the photospheric velocity field. A comparison of AWFs is given for instruments, based on the principles of measuring both the ‘center of gravity’ shifts and intensity differences in the line wings.

MILITARY MISFORTUNES: PITFALLS IN UNDERSTANDING

Abstract : Military Misfortunes: The Anatomy of Failure in War, by Eliot A. Cohen and John Gooch is an intriguing analysis of military misfortunes that have occurred during 20th-century wars. The authors offer some provocative theories about military misfortune while also providing brief analyses of five cases of well-known military failures: the British expedition to Gallipoli in 1915, the fall of France in 1940, the American anti-submarine campaign of 1942, the defeat of the U.S. Eighth Army in Korea by the Chinese in 1950, and the Israeli defense of the Suez and Golan fronts in 1973. To analyze military misfortune, the authors offer a method involving five steps: (1) identify the failure, (2) identify the critical tasks that went incomplete or unfulfilled and thus are at the root of the overall failure, (3) analyze the contributions of different layers of organization to the failure, (4) construct an analytical matrix that graphically presents the key failures leading to military misfortune, and (5) mark a pathway of misfortune through the analytical matrix. The most important step within this method is the first step, the identification of the precise failure which led to the misfortune. Having identified their methodology, the authors state that there are three basic kinds of failure: failure to learn, failure to anticipate, and failure to adapt. They add that when two types of failure occur together, an aggregate failure will result, and when three types of failure occur together, a catastrophic failure will result. Despite the best efforts of the authors, the model they use for analyzing military misfortunes leads to an oversimplification of some very complex developments, and the analyses of the five cases offer little that is new. More cogent explanations for several of the misfortunes studied by Cohen and Gooch are to be found in specific studies on those subjects.

A model of processes determining the intensity of DAPS and AEAPS signals

A simple model including different processes important for the creation of APS signals formed by electrons is proposed. Mean probabilities of elastic and inelastic interactions of electrons with individual atom layers in the solid are introduced. The contribution of different layers to the DAPS and AEPS signals and the dependence of these signals on the interaction parameters are calculated.

On the mean depth of line formation in a magnetic field

Probability interpretation of radiative transfer is used to calculate the contribution of different layers of the solar atmosphere to the emergent intensity. Generally the mean depths of line formation increase with increasing intensity; this is valid also for arbitrarily polarized constituents of a line formed in a magnetic field.