Real Structural Features Research Articles

A Review of Coastal Protection Using Artificial and Natural Countermeasures—Mangrove Vegetation and Polymers

Any stretch of coastline requires protection when the rate of erosion exceeds a certain threshold and seasonal coastal drift fluctuations fail to restore balance. Coast erosion can be caused by natural, synthetic, or a combination of the two. Severe storm occurrences, onshore interventions liable for sedimentation, wave action on the coastlines, and rising sea levels caused by climate change are instances of natural factors. The protective methods used to counteract or prevent coastal flooding are categorized as hard and soft engineering techniques. This review paper is based on extensive reviews and analyses of scientific publications. In order to establish a foundation for the selection of appropriate adaptation measures for coastal protection, this research compiles literature on a combination of both natural and artificial models using mangrove trees and polymer-based models’ configurations and their efficiency in coastal flooding. Mangrove roots occur naturally and cannot be manipulated unlike artificial model configuration which can be structurally configured with different hydrodynamic properties. Artificial models may lack the real structural features and hydrodynamic resistance of the mangrove root it depicts, and this can reduce its real-life application and accuracy. Further research is required on the integration of hybrid configuration to fully optimize the functionality of mangrove trees for coastal protection.

An ISOMAP Analysis of Sea Surface Temperature for the Classification and Detection of El Niño & La Niña Events

Isometric feature mapping (ISOMAP) is a nonlinear dimensionality reduction method used for extracting features from spatiotemporal data. The traditional principal component analysis (PCA), a linear dimensionality reduction method, measures the distance between two data points based on the Euclidean distance (line segment), which cannot reflect the actual distance between the data points in a nonlinear space. By contrast, the ISOMAP measures the distance between two data points based on the geodesic distance, which more closely reflects the actual distance by the view of tracing along the local linearity in the original nonlinear structure. Thus, ISOMAP-reconstructed data points can reflect the features of real structures and can be classified more accurately than traditional PCA-reconstructed data points. Moreover, these ISOMAP-reconstructed data points can be used for cluster analysis by emphasizing the differences among the points more than those by the traditional PCA. In this study, sea surface temperature (SST) data points reconstructed using the traditional PCA and ISOMAP were compared. The classification based on these reconstructed SST points was tested using the Niño 3.4 index, which labels El Niño, La Niña, or normal events. The mean differences from the ISOMAP data points were larger than those from the traditional PCA data points. The ISOMAP not only helped differentiate the points in two different events but also provided better difference measurement of the points belonging to the same class (e.g., 82/83 and 97/98 El Niño events). On examining the evolution of the leading three temporal eigen components of the SST PCA, or especially the SST ISOMAP, we found that the trajectories were similar to the Lorenz 63 model on a phase space figure. This implies that NWP perturbations can be traced using the ISOMAP to measure growing unstable behaviors. Spatial eigenmodes (empirical orthogonal function) between the traditional PCA and ISOMAP were also determined and compared herein.

Micro-Computed Tomography to Assess the Processing Quality of the Additive Manufacturing of Spiral Microcoils.

Additive manufactured polymers and metallized microstructures are widely used in the production of electronic components. However, such three-dimensional printed metallized electrical components inevitably have processing errors that affect their performance. It is vital to understand defects' effects on the performance of the final product. In this study, we simulated micro-computed tomography (CT) data. A spiral cavity is printed by stereolithography and spiral inductors with different numbers of turns are fabricated by injecting Gallium Indium liquid metal (EGaIn). Through the theoretical simulation of the spiral inductor and the characterization of the electrical performance, we found that the relative error in the simulation of 2.5-turn, 4.5-turn, and 6.5-turn spiral inductors is +30.6%, +13%, and +6%, respectively, compared with the experimental data. The CT data are obtained by a CT scanning microcoil and a reconstruction model with real structural features is established based on the data. The results show that the relative error between the reconstructed model with real defects and the experimental data is +10.4%, -3.7%, and -1.5%, respectively, which is closer to the experimental data. According to the CT data simulation that provides a more accurate theoretical prediction, the actual effect of a defect on the final product can be assessed. The difference between the experimental results and the theoretical simulation can be inferred from the reconstruction model.

Implementation of software for data processing of X-ray optical measurements for the analysis of structural parameters

The development of semiconductor nanoelectronic technology requires the use of new approaches to metrological control of critically important stages of device structure formation. The development and use of complex measurement methods based on various physical principles allowing one to obtain exhaustive information about the features of real structures, including the existence of hidden and unaccounted layers in transition areas, are of special interest. This paper presents the idea of implementing a complex approach to X-ray optical studies for a two-wavelength measurement scheme, including the methods of relative X-ray reflectometry, refractometry and diffuse X-ray scattering, and its application to the analysis of dimensional parameters of thin-film structures. The study was carried out with the help of a software package for analysing TiN diffusion-barrier layers. A comparison of the results obtained with the results of one-wavelength methods shows the high efficiency of the implemented approach for performing various tasks of metrological control of nanoelectronic devices.

Особенности реальной структуры наночастиц металлического серебра, размещенных в каналах мезопористого силиката SBA-15

Проведен анализ особенностей дифракции от наночастиц серебра, размещенных в каналах мезопористого силиката SBA-15. Выполнено компьютерное моделирование дифракционных картин для кристаллитов разных размеров с кубической структурой и планарными дефектами упаковки. Проведено сравнение экспериментальных дифракционных картин с модельными. Определена концентрация дефектов упаковки и средние размеры кристаллитов в кристаллической структуре в направлении плотнейшей упаковки и вдоль слоев.

Simultaneous enzyme mimicking and chemical reduction mechanisms for nanoceria as a bio-antioxidant: a catalytic model bridging computations and experiments for nanozymes.

The bio-antioxidant ability of nanoceria has been mainly ascribed to its ability to mimic superoxide dismutase (SOD) and catalase (CAT), and its mechanisms are thought to be analogous to those of the natural enzymes. Accordingly, nanoceria has been called a nanozyme, a nanomaterial mimicking enzymes. Because they overlook the real structural features of nanoceria, these hypothetical mechanisms cannot explain the important antioxidant experiments of nanoceria and have little predictive power. We hereby study the O2˙- and H2O2 scavenging mechanisms of nanoceria using first principles calculations, taking into account the role of oxygen vacancies that are practically abundant in nanoceria. The results reveal atomistic-level mechanisms responsible for the SOD and CAT mimetic activities of nanoceria. The newly created surface defect states in the electronic band structures of the shortly-lived intermediate species, called transient surface defect states (TSDSs), play critical roles in the enzyme mimetic catalysis and can serve as the bridge between computations and experiments at the atomistic level. The energy levels of TSDSs, which depend on the concentration and distribution of oxygen vacancies, determine whether the nanoceria is eligible for the catalysis. Besides the known enzyme mimicking mechanisms, the non-catalytic chemical reduction mechanisms are also responsible for the scavenging of O2˙- and H2O2, in which nanoceria serves as a reducing agent rather than a catalyst. The chemical reduction pathways poison the active sites of nanoceria which serve to mimic SOD and thus deteriorate its SOD mimetic activity. The results provide guidance for the engineering of nanoceria for bio-antioxidant applications. In particular, the proposed catalytic model can be generalized for the screening and design of high-performance nanozymes based on semiconductor nanomaterials.

Topochemical conversion of an imine- into a thiazole-linked covalent organic framework enabling real\xa0structure analysis

Stabilization of covalent organic frameworks (COFs) by post-synthetic locking strategies is a powerful tool to push the limits of COF utilization, which are imposed by the reversible COF linkage. Here we introduce a sulfur-assisted chemical conversion of a two-dimensional imine-linked COF into a thiazole-linked COF, with full retention of crystallinity and porosity. This post-synthetic modification entails significantly enhanced chemical and electron beam stability, enabling investigation of the real framework structure at a high level of detail. An in-depth study by electron diffraction and transmission electron microscopy reveals a myriad of previously unknown or unverified structural features such as grain boundaries and edge dislocations, which are likely generic to the in-plane structure of 2D COFs. The visualization of such real structural features is key to understand, design and control structure–property relationships in COFs, which can have major implications for adsorption, catalytic, and transport properties of such crystalline porous polymers.

Structural study of growth, orientation and defects characteristics in the functional microelectromechanical system material aluminium nitride

The real structure and morphology of piezoelectric aluminum nitride (AlN) thin films as essential components of magnetoelectric sensors are investigated via advanced transmission electron microscopy methods. State of the art electron diffraction techniques, including precession electron diffraction and automated crystal orientation mapping (ACOM), indicate a columnar growth of the AlN grains optimized for piezoelectric application with a {0 0 0 1} texture. Comparing ACOM with piezoresponse force microscopy measurements, a visual correlation of the structure and the piezoelectric properties is enabled. With a quantitative analysis of the ACOM measurements, a statistical evaluation of grain rotations is performed, indicating the presence of coincidence site lattices with Σ7, Σ13a, Σ13b, Σ25. Using a geometric phase analysis on high resolution micrographs, the occurrence of strain is detected almost exclusively at the grain boundaries. Moreover, high resolution imaging was applied for solving the atomic structure at stacking mismatch boundaries with a displacement vector of 1/2 ⟨1 0 -1 1⟩. All real structural features can be interpreted via simulations based on crystallographic computing in terms of a supercell approach.

Non-damage-related influences on Lamb wave–based structural health monitoring of carbon fiber–reinforced plastic structures

Structural health monitoring with actively excited Lamb waves is a promising technology for health monitoring of aerospace carbon fiber–reinforced plastic structures with reasonable effort, as it has the potential to cover large areas with few sensors and a high sensitivity to damage. The high signal complexity inherent to wave propagation in complex, finite, and anisotropic structures, especially in combination with the sensitivity toward environmental and operational loads, presents the main challenge on the road toward the utilization of this potential. In this study, the effects that real structural features and damage, in combination with environmental conditioning, have on Lamb wave propagation and measurement are investigated. For this, the composite-specific behavior is discussed. Based on the local temporal coherence method, changes of sensor responses containing reflections and interaction with stiffness discontinuities, both unrelated and related to damage, are identified in anisotropic composite materials. The amount of signal changes unrelated to damage, as well as their high dependency on the specific conditions of the measurements, is an indicator for the complex issues faced by compensation. While damage of a sufficient size will be detectable even in the most complex, finite, and anisotropic structures, the establishment of a sufficiently reliable damage detection with an acceptable low detection threshold will require even more careful consideration of the monitored structure and its environmental and operational loads than for metallic structures.

Characterization of single-crystal sapphire substrates by X-ray methods and atomic force microscopy

The possibility of characterizing a number of practically important parameters of sapphire substrates by X-ray methods is substantiated. These parameters include wafer bending, traces of an incompletely removed damaged layer that formed as a result of mechanical treatment (scratches and marks), surface roughness, damaged layer thickness, and the specific features of the substrate real structure. The features of the real structure of single-crystal sapphire substrates were investigated by nondestructive methods of double-crystal X-ray diffraction and plane-wave X-ray topography. The surface relief of the substrates was investigated by atomic force microscopy and X-ray scattering. The use of supplementing analytical methods yields the most complete information about the structural inhomogeneities and state of crystal surface, which is extremely important for optimizing the technology of substrate preparation for epitaxy.

Multi-objective preview control of active vehicle suspensions

This paper develops the LMI-based solution for the design of a discrete-time multi-objective preview controller, and considers it for an active vehicle suspension system. A quarter car model, which captures many features of real structures, is used in this study and hence the look-ahead preview control is considered. To provide ride comfort for a wide range of road irregularities, H∞ norm is used as a comfort measure, while generalized H2 is used to care for the constraints on suspension working space, tire deflection and actuator saturation. Moreover, to ensure desired stability margins for the feedback part of the system, pole location constraints are considered in the design. The effects of inclusion of preview information in control law on ride comfort, ride safety, working space and power requirements, for various road profiles, are examined. The results demonstrate the effectiveness of the preview-included multi-objective design to pure feedback scheme.

Validation of x-ray microfocus computed tomography as an imaging tool for porous structures

X-ray microfocus computed tomography (micro-CT) is recently put forward to qualitatively and quantitatively characterize the internal structure of porous materials. However, it is known that artifacts such as the partial volume effect are inherently present in micro-CT images, thus resulting in a visualization error with respect to reality. This study proposes a validation protocol that in the future can be used to quantify this error for porous structures in general by matching micro-CT tomograms to microscopic sections. One of the innovations of the protocol is the opportunity to reconstruct an interpolated micro-CT image under the same angle as the physical cutting angle of the microscopic sections. Also, a novel thresholding method is developed based on matching micro-CT and microscopic images. In this study, titanium porous structures are assessed as proof of principle. It is concluded for these structures that micro-CT visualizes 89% of the total amount of voxels (solid and pore) correctly. However, 8% represents an overestimation of the real structure and 3% are real structural features not visualized by micro-CT. When exclusively focusing on the solid fraction in both the micro-CT and microscopic images, only an overestimation of about 5% is found.

Negative hyperconjugation of some fluorine containing groups

Energies of some aromatic or conjugated aliphatic compounds fluorine containing were calculated within the framework of the density functional theory at the level B3LYP/6-311+G(d.p)//B3LYP/6-311+G(d.p). Evaluation proceeded in terms of isodesmic reactions, in which the groups CF3, SF5 and SCF3 acted as substituents. All these groups behave as rather strong resonance acceptors. The pertinent canonical structures must be formulated with one C–F bond broken—no-bond resonance or negative hyperconjugation. In agreement with these formulae, the C–F bond lengths are elongated; they increase particularly strongly if a conjugated donor group is present. The principle of negative hyperconjugation is thus able to predict qualitatively several observable facts (energy, geometry), even when the pertinent formulae much exaggerate the real structural features.

A wave equation migration method for receiver function imaging: 2. Application to the Japan subduction zone

The newly developed wave equation poststack depth migration method for receiver function imaging is applied to study the subsurface structures of the Japan subduction zone using the Fundamental Research on Earthquakes and Earth's Interior Anomalies (FREESIA) broadband data. Three profiles are chosen in the subsurface imaging, two in northeast (NE) Japan to study the subducting Pacific plate and one in southwest (SW) Japan to study the Philippine Sea plate. The descending Pacific plate in NE Japan is well imaged within a depth range of 50–150 km. The slab image exhibits a little more steeply dipping angle (∼32°) in the south than in the north (∼27°), although the general characteristics between the two profiles in NE Japan are similar. The imaged Philippine Sea plate in eastern SW Japan, in contrast, exhibits a much shallower subduction angle (∼19°) and is only identifiable at the uppermost depths of no more than 60 km. Synthetic tests indicate that the top 150 km of the migrated images of the Pacific plate is well resolved by our seismic data, but the resolution of deep part of the slab images becomes poor due to the limited data coverage. Synthetic tests also suggest that the breakdown of the Philippine Sea plate at shallow depths reflects the real structural features of the subduction zone, rather than caused by insufficient coverage of data. Comparative studies on both synthetics and real data images show the possibility of retrieval of fine‐scale structures from high‐frequency contributions if high‐frequency noise can be effectively suppressed and a small bin size can be used in future studies. The derived slab geometry and image feature also appear to have relatively weak dependence on overlying velocity structure. The observed seismicity in the region confirms the geometries inferred from the migrated images for both subducting plates. Moreover, the deep extent of the Pacific plate image and the shallow breakdown of the Philippine Sea plate image are observed to correlate well with the depth extent of the seismicity beneath NE and SW Japan. Such a correlation supports the inference that the specific appearance of slabs and intermediate‐depth earthquakes are a consequence of temperature‐dependent dehydration induced metamorphism occurring in the hydrated descending oceanic crust.

Stacking Faults in Kaolin-Group Minerals in the Light of Real Structural Features

AbstractA comparison of the structural characteristics of the kaolin-group minerals, mainly kaolinite and dickite, shows that they differ in both the two-dimensional periodicity in the 1:1 layers and the rotation angles of the polyhedra. Distortions in a real 1:1 layer, compared with an idealized layer, do not allow such stacking faults as ± 120° layer rotations and vacancy displacements, because the second layer is incommensurable with the first. The 1:1 layer structure and the fact that the unit cell is symmetrical with respect to the plane passing through the long diagonal of the unit cell suggest the possibility of defects resulting from the two stacking sequences for the same layers. For a regular alternation of translations, a halloysite-like structure should be the end-member of such a series of defect kaolinite types.The formation of layers having vacant octahedral C-sites is another possible type of fault. Because of the minor dilference between γ and 90°, dickite-like layers should exist. A regular alternation of B and C layers yields dickite as the end-member structure. In materials containing few defects, stacking faults of both types lead to similar X-ray powder diffraction patterns. Thus, the nature of the stacking faults is difficult to determine experimentally. In materials containing many defects, however, the two models lead to different calculated diffraction patterns. Therefore, only a study of defect-rich types of kaolinite can determine which types of defects exist in natural kaolinite samples.

Analysis and Interpretation of Diffraction Data from Amorphous Materials

Amorphous materials give rise to rather diffuse diffraction patterns. In contrast to diffraction patterns from polycrystalline materials which are characterized by a large number of sharp diffraction rings, patterns from amorphous materials are composed of relatively few broadened features. Such a diffuse pattern, however, contains much structural information in the form of an interatomic distance distribution that may be computed directly from the measured diffraction pattern. This radial distribution function (RDF) provides information concerning bonded distances, the types of atomic groupings and the extent of ordering in the sample. Special care, however, must be taken during the analysis to avoid introducing spurious details into the RDF that may be confused with, or mask real structural features. Such false detail may arise both from data collection and data reduction procedures. The availability of modern computers has greatly facilitated the calculation of accurate RDF's by readily permitting the introduction of physical criteria into the data reduction procedure that must be satisfied by the RDF.