Linear Edge Research Articles

Dental functional morphology predicts the scaling of chewing rate in mammals

How food intake and mastication scale to satisfy the metabolic needs of mammals has been the subject of considerable scientific debate. Existing theory suggests that the negative allometric scaling of metabolic rate with body mass is compensated by a matching allometric scaling of the chewing rate. Why empirical studies have found that the scaling coefficients of the chewing rate seem to be systematically smaller than expected from theory remains unknown. Here we explain this imparity by decoupling the functional surface area of teeth from overall surface area. The functional surface area is relatively reduced in forms emphasizing linear edges (e.g., lophodont) compared with forms lacking linear structures (e.g., bunodont). In forms with reduced relative functional surface, the deficit in food processed per chew appears to be compensated for by increased chewing rate, such that the metabolic requirements are met. This compensation accounts for the apparent difference between theoretically predicted and observed scaling of chewing rates. We suggest that this reflects adaptive functional evolution to plant foods with different fracture properties and extend the theory to incorporate differences in functional morphology.

Tight-binding methods for general longitudinally driven photonic lattices: Edge states and solitons

A systematic approach for deriving tight-binding approximations in general longitudinally driven lattices is presented. As prototypes, honeycomb and staggered square lattices are considered. Time-reversal symmetry is broken by varying/rotating the waveguides, longitudinally, along the direction of propagation. Different sublattice rotation and structure are allowed. Linear Floquet bands are constructed for intricate sublattice rotation patterns such as counter rotation, phase offset rotation, as well as different lattice sizes and frequencies. An asymptotic analysis of the edge modes, valid in a rapid-spiraling regime, reveals linear and nonlinear envelopes which are governed by linear and nonlinear Schrodinger equations, respectively. Nonlinear states, referred to as topologically protected edge solitons are unidirectional edge modes. Direct numerical simulations for both the linear and nonlinear edge states agree with the asymptotic theory. Topologically protected modes are found; they possess unidirectionality and do not scatter at lattice defect boundaries.

AETC: Segmentation and classification of the oil spills from SAR imagery

ABSTRACTIdentification of oil spills from synthetic aperture radar (SAR) images is a complex task that has recently come into use. Existing oil spill detection methods have been found to be expensive and complex and require high processing power and time. Also, noise removal and extracting the features of oil-spill images are major issues. To overcome these drawbacks, a novel segmentation technique, adaptive edge and texture clustering (AETC), is proposed in this article to detect and classify the oil-spill area in a given image. The proposed technique contains four main stages: preprocessing, segmentation, feature extraction, and classification. Initially, the input image is preprocessed to eliminate speckle noise and to enhance the quality of the image by using the Gaussian distribution function. After that, the preprocessed image is segmented with the help of the linear edge weighted (LEW) clustering technique. In this stage, the boundary region is identified and the contour is segmented. The features of the segmented image are extracted using the convoluted horizontal vertical (CHV) pattern extraction technique. Finally, the relevance vector machine (RVM) classification technique is applied to classify the oil spill portions from the given image. The experimental results evaluate the performance of the proposed system in terms of accuracy, sensitivity, specificity, Jaccard, Dice, and Hausdorff distance. Here, the existing back scatter-gradient-artificial neural network technique is compared with the proposed CHV-RVM technique. From this analysis, it is proved that the proposed techniques provide the best results.

Advanced mechanical characterization of asphalt mastics containing tourmaline modifier

Tourmaline modified bitumen as an environmentally friendly pavement material has got an increasing attention in recent years in China. In this regard, previous studies mainly focused on the linear viscoelastic properties of asphalt or asphalt mastic. In this paper, multiple stress creep and recovery (MSCR) test, linear amplitude sweep (LAS) test and double edge notched tension (DENT) test were adopted as fundamental performance evaluation methods for high-temperature rutting, fatigue, and low-temperature thermal cracking of asphalt binder, respectively. Moreover, straight run asphalt and polymer modified asphalt containing various percentages of two kinds of tourmaline as asphalt modifier were also prepared to gain the knowledge of the interaction between asphalt and tourmaline. To study the feasibility of applying tourmaline as an alternative modifier and compare its performance with conventional fillers, asphalt mastic containing limestone was also prepared. The results show that small amount of modifier can enhance the mechanical properties of asphalt binder, but different modifiers do not have similar effect. In addition, market available tourmaline additive has different chemical composition and physical properties; asphalt mastic containing tourmaline ions powder showed the best performance among modifiers utilized here.

Linearity of the edge states energy spectrum in the 2D topological insulator

Linearity of the topological insulator edge state spectrum plays a crucial role for various transport phenomena. Previous studies found that this linearity exists near the spectrum crossing point, but did not determine how perfect the linearity is. The purpose of the present study is to answer this question in various edge states models. We examine Volkov and Pankratov (VP) model for the Dirac Hamiltonian and the model BHZ for the Bernevig, Hughes and Zhang (BHZ) Hamiltonian with zero boundary conditions. It is found that both models yield ideally linear edge states. In the BHZ1 model the linearity is conserved up to the spectrum ending points corresponding to the tangency of the edge spectrum with the boundary of 2D states. In contrast, the model BHZ2 with mixed boundary conditions for BHZ Hamiltonian and the 2D tight-binding (TB) model yield weak nonlinearity.

Engineering the magnetic anisotropy of an ultrathin Co layer sandwiched between films of Mo or Au

Magnetic properties of an ultrathin Co layer deposited on the Mo(1 1 0) or Au(1 1 1) buffers crucially depend on magnetic layer thickness and a cap layer type (Au or Mo, studied in this work). Depending on the sandwich configuration, magnetization is oriented in a perpendicular direction to the plane in the range of smaller Co layer thickness (below 2 nm) or in the sample plane for a thicker layer (3 nm). Moreover, a well-developed two-fold in-plane magnetic anisotropy occurs in the Co layer deposited on the Mo buffer. These features are correlated with crystalline structure studied with the use of numerous complementary methods: reflection high-energy electron diffraction, x-ray diffraction, x-ray reflectivity, nuclear magnetic resonance, and element-sensitive synchrotron techniques, i.e. x-ray linear dichroism and x-ray absorption near edge spectroscopy. Magnetic behaviour, exhibiting volume and surface contributions, is thoroughly discussed in terms of the buffer and cap layer type, thickness-dependent crystalline structure of the Co layer, and the interface quality.

Antipodal Vivaldi Antenna to Detect UHF Signals That Leaked Out of the Joint of a Transformer

In recent years, extensive research has been conducted on the ultrahigh-frequency (UHF) method. Considering that acquiring a partial discharge UHF signal is the first step in a series of tasks, such as fault diagnosis and defect location, the UHF sensor plays an important role in the UHF method. An antipodal Vivaldi antenna installed at a transformer’s joint is designed in this study according to the structural features of 750 kV transformers in China. Several effective structures, such as linear gradient microstrip and slot edge, are employed to improve the return loss and radiation characteristics. A metal box is designed after analyzing the influence of the metal around the antenna. The metal box can effectively shield against electromagnetic interference and does not deteriorate the performance of the antenna significantly. Experimental data show that this antenna is much more sensitive than the rectangular plane spiral antenna. The proposed antipodal Vivaldi antenna is suitable for detecting partial discharge in large transformers.

Object shape dependency of in-plane resolution for iterative reconstruction of computed tomography

The present study aimed to investigate whether the in-plane resolution property of iterative reconstruction (IR) of computed tomography (CT) data is object shape-dependent by testing columnar shapes with diameters of 3, 7, and 10cm (circular edge method) and a cubic shape with 5-cm side lengths (linear edge method). For each shape, objects were constructed of acrylic (contrast in Hounsfield units [ΔHU]=120) as well as a soft tissue equivalent material (ΔHU=50). For each shape, we measured the modulation transfer functions (MTFs) of IR and filtered back projection (FBP) using two multi-slice CT scanners at scan doses of 5 and 10mGy. In addition, we evaluated a thin metal wire using the conventional method at 10mGy. For FBP images, the MTF results of the tested objects and the wire method showed substantial agreement, thus demonstrating the validity of our analysis technique. For IR images, the MTF results of different shapes were nearly identical for each object contrast and dose combination, and we did not observe shape-dependent effects of the resolution properties of either tested IR. We conclude that both the circular edge method and linear edge method are equally useful for evaluating the resolution properties of IRs.

Structural Phase Transition and Material Properties of Few-Layer Monochalcogenides.

GeSe and SnSe monochalcogenide monolayers and bilayers undergo a two-dimensional phase transition from a rectangular unit cell to a square unit cell at a critical temperature T_{c} well below the melting point. Its consequences on material properties are studied within the framework of Car-Parrinello molecular dynamics and density-functional theory. No in-gap states develop as the structural transition takes place, so that these phase-change materials remain semiconducting below and above T_{c}. As the in-plane lattice transforms from a rectangle into a square at T_{c}, the electronic, spin, optical, and piezoelectric properties dramatically depart from earlier predictions. Indeed, the Y and X points in the Brillouin zone become effectively equivalent at T_{c}, leading to a symmetric electronic structure. The spin polarization at the conduction valley edge vanishes, and the hole conductivity must display an anomalous thermal increase at T_{c}. The linear optical absorption band edge must change its polarization as well, making this structural and electronic evolution verifiable by optical means. Much excitement is drawn by theoretical predictions of giant piezoelectricity and ferroelectricity in these materials, and we estimate a pyroelectric response of about 3×10^{-12} C/K m here. These results uncover the fundamental role of temperature as a control knob for the physical properties of few-layer group-IV monochalcogenides.

Modulational instability and solitary waves in polariton topological insulators

Optical microcavities supporting exciton–polariton quasi-particles offer one of the most powerful platforms for the investigation of the rapidly developing area of topological photonics in general, and of photonic topological insulators in particular. Energy bands of the microcavity polariton graphene are readily controlled by a magnetic field and influenced by the spin-orbit (SO) coupling effects, a combination leading to the formation of linear unidirectional edge states in polariton topological insulators as very recently predicted. In this work we depart from the linear limit of non-interacting polaritons and predict instabilities of the nonlinear topological edge states resulting in the formation of the localized topological quasi-solitons, which are exceptionally robust and immune to backscattering wave packets propagating along the graphene lattice edge. Our results provide a background for experimental studies of nonlinear polariton topological insulators and can influence other subareas of photonics and condensed matter physics, where nonlinearities and SO effects are often important and utilized for applications.

Linear edge effects on liana and tree communities in two tropical forest ecosystems in Ghana

AbstractThe study determined linear edge effects on liana and tree community assemblages in moist semi‐deciduous (Afram Headwaters Forest Reserve) and upland evergreen (Tano Offin Forest Reserve) forests in Ghana. Fifteen plots (20 × 20 m2) were randomly set up at each habitat in the forests: edge habitat (0–40 m) and interior habitat (≥500 m). Lianas (diameter at 1.30 m from rooting base ≥1 cm) and trees (diameter at breast height, dbh ≥5 cm) were identified and enumerated in the plots. In the forest ecosystems, liana and tree species composition differed significantly between the two habitats. Liana and tree diversity did not differ significantly between edge and interior habitats. Nevertheless, edge habitat in moist semi‐deciduous forest supported significantly higher liana abundance and basal area than its interior habitat, whereas edge habitat in upland evergreen forest harboured significantly lower liana basal area than its corresponding interior habitat. Edge habitat in moist semi‐deciduous and upland evergreen forests had significantly lower tree abundance and basal area, respectively, than interior habitat. The results suggest that overall, linear edge effects on liana and tree assemblages were more pronounced in moist semi‐deciduous forest than upland evergreen forest. Lianas exhibited dominance over trees in edge habitat within moist semi‐deciduous forest, implying that they can have serious implications on tree diversity and ecosystem functioning in the forest. As our study is the first of its kind in the tropics with respect to edge type and forest ecosystems studied, our findings can contribute towards edge theory development.

Spatial analysis of ambient gamma dose equivalent rate data by means of digital image processing techniques

A detailed ambient gamma dose equivalent rate mapping based on field measurements at ground level and at 1 m height was carried out at 142 sites in 80 × 90 km area in Pest County, Hungary. Detailed digital image processing analysis was carried out to identify and characterise spatial features such as outlying points, anomalous zones and linear edges in a smoothed TIN interpolated surface. The applied method proceeds from the simple shaded relief model and digital cross-sections to the more complex gradient magnitude and gradient direction maps, 2nd derivative profile curvature map, relief map and lineament density map. Each map is analysed for statistical characteristics and histogram-based image segmentation is used to delineate areas homogeneous with respect to the parameter values in these maps. Assessment of spatial anisotropy is implemented by 2D autocorrelogram and directional variogram analyses. The identified spatial features are related to underlying geological and tectonic conditions using GIS technology. Results show that detailed digital image processing is efficient in revealing the pattern present in field-measured ambient gamma dose equivalent rates and they are related to regional scale tectonic zones and surface sedimentary lithological conditions in the study area.

Analysis of shading periods caused by moving clouds

Fast variability of solar radiation is the main cause of fluctuating photovoltaic power production. Shadows caused by moving clouds are the main reason of such variability. Irradiance transitions caused by edges of cloud shadows can be very steep and large and might lead to failures in maximum power point tracking causing extra losses. Further, fast fluctuations of the power fed to the electric grid can cause power balance and quality problems for the grid.This paper presents a method to identify shading periods caused by moving clouds in measured irradiance data. A total of around 12,000 shading periods were identified in a measured data of 15months around midsummer in 2011–2014 and their shading strength, duration, time of occurrence etc. were analysed. It was found that the duration of shading periods varies a lot from about four seconds up to almost 1.5h with an average duration of around 60s. Furthermore, the Linear Cloud Edge method was used to determine the velocity of shadows and their speed, direction of movement, length etc. were analysed. The determination of velocity was conducted by two different ways based directly on measured irradiance values and on the curve fits of a mathematical model of irradiance transitions. The use of curve fits mitigates the effects of irregularities present on shadow edges. The speed of shadows varies greatly with an average value of around 13m/s.

Edge absorption and circular photogalvanic effect in 2D topological insulator edges

The electron absorption on the edge states and the edge photocurrent of a 2D topological insulator (TI) are studied. We consider the optical transitions within linear edge branches of the energy spectrum. The interaction with impurities is taken into account. The circular polarization is found to produce the edge photocurrent, the direction of which is determined by light polarization and edge orientation.

Effect of temperature and pH on structural, optical and electrical properties of Ni doped ZnSe nanoparticles

Ni doped ZnSe precipitated particles were prepared using three different pH precursor solutions (8, 9 and 10) and two different solution temperatures (303K and 363K) by wet chemical precipitation technique. The SEM analysis reveals that the size of the particles is in the order of 5nm at 303K and it becomes 20nm at 363K. The XRD studies show that the prepared nanoparticles of Ni:ZnSe switch from cubic zinc blende to hexagonal wuzurite structure as the temperature increase from 303K to 363K. The UV–vis spectra of Ni:ZnSe nanoparticles show that there is no change in optical band gap with increase in pH value at 303K but the gap increases slightly at 363K. Linear incremental and non linear decremental natured band edge absorptions were identified for the nanoparticles prepared at different conditions of pH and temperature. The weak interaction between Se2- and Zn2+/Ni2+ and the property of superficially adhered functional groups were confirmed from the analysis of FT-IR absorption spectra. The conductivity and dielectric studies confirm that the material can be used in high frequency applications.

A Parallel Tool for Numerical Approximation of 3D Electromagnetic Surveys in Geophysics

This paper presents an edge-based parallel code for the data computation that arises when applying one of the most popular electromagnetic methods in geophysics, namely, the controlled-source electromagnetic method (CSEM). The computational implementation is based on the linear Edge Finite Element Method in 3D isotropic domains because it has the ability to eliminate spurious solutions and is claimed to yield accurate results. The framework structure is able to exploit the embarrassingly-parallel tasks and the advantages of the geometric flexibility as well as to work with three different orientations for the dipole, or excitation source, on unstructured tetrahedral meshes in order to represent complex geological bodies through a local refinement technique. We demonstrate the performance and accuracy of our tool on the Marenostrum supercomputer (Barcelona Supercomputing Center) through scaling tests and canonical tests, respectively.

Quasi-three-level model applied to measured spectra of nonlinear absorption and refraction in organic molecules

Materials with a large nonlinear refractive index (n2) and relatively small linear and nonlinear absorption losses, namely, two-photon absorption (2PA, of coefficient α2), have long been sought after for applications such as all-optical switching (AOS). Here we experimentally determine the linear and 2PA properties of several organic molecules, which we approximate as centrosymmetric, and use a simplified essential-state model (quasi-three-level model) to predict the dispersion of n2. We then compare these predictions with experimental measurements of n2 and find good agreement. Here “quasi”-three-level means using a single one-photon allowed intermediate state and multiple (here two) two-photon allowed states. This also allows predictions of the figure-of-merit (FOM), defined as the ratio of nonlinear refractive phase shift to the 2PA fractional loss, that determines the viability for such molecules to be used in device applications. The model predicts that the optimized wavelength range for a large FOM lies near the short wavelength linear absorption edge for cyanine-like dyes where the magnitude of n2 is quite large. However, 2PA bands lying close to the linear absorption edge in certain classes of molecules can greatly reduce this FOM. We identify two molecules having a large FOM for AOS. We note that the FOM is often defined as the ratio of real to imaginary parts of the third-order susceptibility (χ(3)) with multiple processes leading to both components. As explained later in this paper, such definitions require care to only include the 2PA contribution to the imaginary part of χ(3) in regions of transparency.

Observation of dispersive shock waves developing from initial depressions in shallow water

We investigate surface gravity waves in a shallow water tank, in the limit of long wavelengths. We report the observation of non-stationary dispersive shock waves rapidly expanding over a 90 m flume. They are excited by means of a wave maker that allows us to launch a controlled smooth (single well) depression with respect to the unperturbed surface of the still water, a case that contains no solitons. The dynamics of the shock waves are observed at different levels of nonlinearity equivalent to a different relative smallness of the dispersive effect. The observed undulatory behavior is found to be in good agreement with the dynamics described in terms of a Korteweg–de Vries equation with evolution in space, though in the most nonlinear cases the description turns out to be improved over the quasi linear trailing edge of the shock by modeling the evolution in terms of the integro-differential (nonlocal) Whitham equation.

Reconstruction of binary geological images using analytical edge and object models

Reconstruction of fields using partial measurements is of vital importance in different applications in geosciences. Solving such an ill-posed problem requires a well-chosen model. In recent years, training images (TI) are widely employed as strong prior models for solving these problems. However, in the absence of enough evidence it is difficult to find an adequate TI which is capable of describing the field behavior properly. In this paper a very simple and general model is introduced which is applicable to a fairly wide range of binary images without any modifications. The model is motivated by the fact that nearly all binary images are composed of simple linear edges in micro-scale. The analytic essence of this model allows us to formulate the template matching problem as a convex optimization problem having efficient and fast solutions. The model has the potential to incorporate the qualitative and quantitative information provided by geologists. The image reconstruction problem is also formulated as an optimization problem and solved using an iterative greedy approach. The proposed method is capable of recovering the image unknown values with accuracies about 90% given samples representing as few as 2% of the original image.

Giant spin-orbit coupling topological insulator h-Ga2Bi2 with exotic O-bridge states.

The two-dimensional (2D) topological insulator (TI) is a promising material for designing dissipationless spintronic devices. Although many candidates have been found, few of them have a massive spin-orbit coupling (SOC) strength with high stability. In the present work, we demonstrate that h-Ga2Bi2 is a highly stable 2D TI with a massive Eg(Γ) at the Γ point of 1.477 eV, while the global band gap is 0.20 eV, which is sufficiently large for room temperature (∼26 meV). The edge states are greatly affected by the geometrical configuration of ribbon edges. The linear dispersive edge states still hold when the nanoribbon is limited to 1.7 nm, which actually realizes the ideal nanowire as theoretically derived in the field of TI. Most excitingly, an exotic 'O-atom bridge' is proposed here, and resides in the inner part of the nanoribbon, and so is thus highly protected from damage. The corresponding 'O-bridge states' display the interaction of electrons in a clear pattern, which leads to a better understanding of the 2D TI.