Separate Edge Research Articles

Local Stability and Hopf Bifurcation Analysis for Compound TCP

We conduct a local stability and Hopf bifurcation analysis for Compound transmission control protocol (TCP), with small Drop-Tail buffers, in three topologies. The first topology consists of two sets of TCP flows having different round-trip times and feeding into a core router. The second topology consists of two distinct sets of TCP flows, regulated by a single-edge router and feeding into a core router. The third topology comprises two distinct sets of TCP flows, regulated by two separate edge routers and feeding into a core router. In each case, we conduct a local stability analysis and obtain conditions on the network and protocol parameters to ensure stability. If these conditions get marginally violated, we show that the underlying systems lose local stability via a Hopf bifurcation. After exhibiting a Hopf, a key concern is to determine the asymptotic orbital stability of the bifurcating limit cycles. We then present a detailed analytical framework to address the stability of the limit cycles and the type of the Hopf bifurcation by invoking Poincare normal forms and the center manifold theory. We finally conduct packet-level simulations to corroborate our analytical insights.

Investigation of end and edge effects on results of numerical simulation of single lap adhesive joint with non-linear materials

This paper presents systematic numerical study of stresses in the adhesive of a single-lap joint with the objective to improve understanding of the main material and geometrical parameters determining performance of adhesive joints. For this purpose a 3D model as well as 2D model, optimized with respect to the computational efficiency by use of novel displacement coupling conditions able to correctly represent monoclinic materials (off-axis layers of composite laminates), are employed. The model accounts for non-linearity of materials (adherend and adhesive) as well as geometrical non-linearity. The parameters of geometry of the joint are normalized with respect to the dimensions of adhesive (e.g. thickness) thus making analysis of results more general and applicable to wide range of different joints. Optimal geometry of the single-lap joint allowing to separate edge effect from end effects is selected based on results of the parametric analysis by using peel and shear stress distributions in the adhesive layer as a criterion. Three different types of single lap joint with similar and dissimilar (hybrid) materials are considered in this study: a) metal-metal; b) composite-composite; c) composite-metal. In case of composite laminates, four lay-ups are evaluated: uni-directional ([08]T and [908]T) and quasi-isotropic laminates ([0/45/90/-45]S and [90/45/0/-45]S). The influence of the abovementioned parameters on peel and shear stress distributions in the adhesive layer is examined carefully and mechanical parameters governing the stress concentrations in the joint have been identified, this dependence can be described by simple but accurate fitting function. The effect of the used material model (linear vs non-linear) on results is also demonstrated.

Multi‐directional colour edge detector using LQS convolution

A new linear colour image filter based on linear quaternion systems (LQSs) is introduced. It detects horizontal, vertical, left- and right-diagonal edges with a single LQS convolution mask. The proposed filter is a canonic minimal filter of four LQS filters, each with different angles of rotation combined parallel wise. Different angles of rotation are a key features of the new filter such that horizontal, vertical, left, and right-diagonal LQS filter masks rotate pixels through angles , , , and , respectively. Although, the four LQS masks are combined parallel to make a single LQS mask but derived using four quaternion convolutions, one for each direction of edges, the LQS filter produces a result without the combination of results from four separate edge detectors. This methodology could be generalised to design more elaborate LQS filters to perform other geometric operations on colour image pixels. The proposed filter translates smoothly changing colours to different shades of grey and produces coloured edges in multiple directions, where there is a sudden change of colour in the original image. Another key idea of the proposed filter is that it is linear because it operates in homogeneous coordinates.

Control-Data Separation With Decentralized Edge Control in Fog-Assisted Uplink Communications

Fog-aided network architectures for 5G systems encompass wireless edge nodes, referred to as remote radio systems (RRSs), as well as remote cloud center (RCC) processors, which are connected to the RRSs via a fronthaul access network. RRSs and RCC are operated via network functions virtualization, enabling a flexible split of network functionalities that adapts to network parameters such as fronthaul latency and capacity. This paper focuses on uplink communications and investigates the cloud-edge allocation of two important network functions, namely, the control functionality of rate selection and the data-plane function of decoding. Three functional splits are considered: 1) distributed radio access network, in which both functions are implemented in a decentralized way at the RRSs; 2) cloud RAN, in which instead both functions are carried out centrally at the RCC; and 3) a new functional split, referred to as fog RAN (F-RAN), with separate decentralized edge control and centralized cloud data processing. The model under study consists of a time-varying uplink channel with fixed scheduling and cell association in which the RCC has global but delayed channel state information due to fronthaul latency, while the RRSs have local but more timely CSI. Using the adaptive sum-rate as the performance criterion, it is concluded that the F-RAN architecture can provide significant gains in the presence of user mobility.

Quantum Anomalous Hall Effect and Spin-filter Design Under the Control of Light and Exchange Field

We advance the theory that achieving quantum Hall effect in silicone can be possible. We investigate that a bulk band gap can be reopened by regulating optical and exchange field. Through tuning these external fields, perfectly nearly 100% spin-filter can be achieved with interesting spin separated edge state and be verified by calculating the spin polarizability. This finding provides a platform for designing high efficiency spin-filter.

Doping and tilting on optics in noncentrosymmetric multi-Weyl semimetals

Weyl semimetal (WSM) feature tilted Dirac cones and can be type I or II depending on the magnitude of the tilt parameter ($C$). The boundary between the two types is at $C=1$ where the cones are tipped and there is a Lifshitz transition. The topological charge of a WSM is one. In multi-Weyl it can be two or more depending on the value of the winding number $J$. We calculate the absorptive part of the AC optical conductivity both along the tilt direction ($\sigma_{zz}$) and perpendicular to it ($\sigma_{xx}$) as a function of the tilt ($C$) and chemical potential ($\mu$). For zero tilt there is a discontinuous rise in both $\sigma_{xx}$ and $\sigma_{zz}$ at photon energy $\Omega=2\mu$ followed by the usual linear in $\Omega$ law for $\sigma_{xx}$ at $J=1,2$ and $\sigma_{zz}$ at $J=1$. For $J=2$ and $\sigma_{zz}$ the interband background is constant rather than linear in $\Omega$. For type I there is a readjustment of optical spectral weight as the tilt is increased. The absorption starts from zero at $2\mu/(1+C)$ and then rises in a quasilinear fashion till it merge with the usual undoped untilted interband background at $2\mu/(1-C)$. The discontinuous rise at twice the chemical potential of the untilted case is lost. For type II the interband background of the undoped untilted case is never recovered. For noncentrosymmetric materials the energies of a pair of opposite chirality Weyl nodes become shifted by $\pm Q_{0}$ and this leads to two separate absorption edges corresponding to the effective chemical potential of each of the two nodes at $2(\mu+\chi Q_{0})$ depending on chirality $\chi=\pm$. We provide analytic expressions for the conductivity in this case which depend only on the ratio $Q_{0}/\mu$ and tilt when plotted against $\Omega/\mu$. The signature of finite energy shift $Q_{0}$ is more pronounced for $\sigma_{zz}$ and $J=2$ than for the other cases.

Control of rollover of sheared edge in punching of high strength steel sheets

The rollover along the contour line on the separated edge of a punched product is not homogeneous especially when the counter shape of the punched product is locally concave or convex. This variety of rollover is adverse for the following processes such as hole expanding or deep drawing. Therefore, it is necessary to develop a punching technology to assure the magnitude of the rollover homogeneous along the counter line. An improvement of the punch profile in its axial direction as a method to control rollover was adopted and the performance of the punch was tested by the experimental approach with high strength steels.

THE INFLUENCE OF SURFACTANTS ON THE RHEOLOGICAL PROPERTIES OF CRUDE OIL OF NORTH-KOMSOMOLSKOYE FIELD

The present work analyses the effects of stearic acid, 2-bis(2-hydroxyethyl) amino ethyl stearate, 2-bis (2-hydroxyethyl) amino ethyl oleate, N-(2-hydroxyethyl) stearamide, N-(2-hydroxyethyl) oleamide, triglyceride of oleic acid with purity of 98 % and neonols AF 9-6, AF 9-10 on crude oil rheology of North-Komsomolskoye field aimed at develop-ment of oil viscosity regulatory methods, consistency setting of spatial structures of coagulator - crystallization type formation within different temperatures. The study of the effective viscosity dependence on shearing rate showed that in the investigated tempera-ture range -10 - +50 °C crude oil floods according to the law of Newton, i.e. the emul-sion is in the range behaves as a Newtonian liquid. At temperatures above 16 °C in a water-oil emulsion appears the destruction of low-energy paraffin- asphaltenes structures at the border of phase separation (the average energy stability 14.4 kJ/mol), in which paraffin hydrocarbons, resin- asphaltenes compounds and mineralized water probably take part. It has been established that surfactants based on stearic and oleic acids which contain fragments of monoethanolamine and triethanolamine increase the effective vis-cosity of the water-oil emulsion, and the triglyceride of oleic acid and neonols AF 9 - 6 and AF 9-10 reduce it. The results showed that neonol AF 9-10 reduces the viscosity of crude heavy oil in the North-Komsomolskoye deposit by 25 times. The use of the Turbiscan technology which allows us to analyze the stability of dispersed systems helps us to determine that the decreasing of the crude oil effective viscosity in the presence of neonol AF 9 - 10 is the result of the loss of stability of oil-water emulsion, which is evi-denced by the increase in the Turbiscan stability index in ~15 times. The laser scanning method shows that at a 5 % neonol concentration of AF 9 - 10 within 20-30 h, more than 20 stable emulsion forms of different density are evolving as a result of adsorption of neonol AF 9 - 10 at the edge of phase separation and its interaction with asphaltenes and oil resins in the formation of solvate layers of the dispersed phase.

Traffic noise impacts on urban forest soundscapes in south‐eastern Australia

AbstractWhile the negative impacts of road infrastructure on faunal diversity and abundance have been extensively studied, many traffic noise studies have been conducted in the presence of confounding factors. Therefore, the extent to which traffic noise alone is responsible for impacts is not well known and a better understanding is required to inform urban planning and management decisions. We examined the impact of traffic noise on soundscape patterns at road edges in urban forests. Acoustic sensors were deployed at road and powerline edges, as well as within interior habitat, at three sites in south‐east Queensland, Australia. Powerline edges were included to separate edge effects from traffic noise impacts. We used soundscape power (normalized watts per kHz) of technophony (traffic noise in the 1–2 kHz range) and biophony (animal sounds in the 3–11 kHz range) to investigate soundscape patterns. The results showed that biophony was consistently lower at road edges and was negatively correlated with traffic noise and positively correlated with distance to road edge. Technophony was higher at road edges and was found to correlate negatively with distance to road edge and positively with traffic noise. Technophony and biophony at powerline edges generally exhibited values comparable to interior habitat. These results indicate that traffic noise affects urban forest soundscape patterns at road edges in south‐eastern Australia.

Control-Data Separation With Decentralized Edge Control in Fog-Assisted Uplink Communications

Fog-aided network architectures for 5G systems encompass wireless edge nodes, referred to as remote radio systems (RRSs), as well as remote cloud center (RCC) processors, which are connected to the RRSs via a fronthaul access network. RRSs and RCC are operated via Network Functions Virtualization (NFV), enabling a flexible split of network functionalities that adapts to network parameters such as fronthaul latency and capacity. This work focuses on uplink communications and investigates the cloud-edge allocation of two important network functions, namely the control functionality of rate selection and the data-plane function of decoding. Three functional splits are considered: (i) Distributed Radio Access Network (D-RAN), in which both functions are implemented in a decentralized way at the RRSs, (ii) Cloud RAN (C-RAN), in which instead both functions are carried out centrally at the RCC, and (iii) a new functional split, referred to as Fog RAN (F-RAN), with separate decentralized edge control and centralized cloud data processing. The model under study consists of a time-varying uplink channel in which the RCC has global but delayed channel state information (CSI) due to fronthaul latency, while the RRSs have local but more timely CSI. Using the adaptive sum-rate as the performance criterion, it is concluded that the F-RAN architecture can provide significant gains in the presence of user mobility.

Boundary conditions and formation of pure spin currents in magnetic field

Schrödinger equation for an electron confined to a two-dimensional strip is considered in the presence of homogeneous orthogonal magnetic field. Since the system has edges, the eigenvalue problem is supplied by the boundary conditions (BC) aimed in preventing the leakage of matter away across the edges. In the case of spinless electrons the Dirichlet and Neumann BC are considered. The Dirichlet BC result in the existence of charge carrying edge states. For the Neumann BC each separate edge comprises two counterflow sub-currents which precisely cancel out each other provided the system is populated by electrons up to certain Fermi level. Cancelation of electric current is a good starting point for developing the spin-effects. In this scope we reconsider the problem for a spinning electron with Rashba coupling. The Neumann BC are replaced by Robin BC. Again, the two counterflow electric sub-currents cancel out each other for a separate edge, while the spin current survives thus modeling what is known as pure spin current – spin flow without charge flow.

Excitation Condition for Self-Sustained Oscillation in Flow Past a Louvered Cavity

AbstractLouvered cavities are extensively employed in engineering applications. In the configurations of flow past these cavities, self-sustained oscillations will be excited. This can give rise to structure vibrations or noise. Numerical models are established to analyze excitation condition for of these oscillations. Computational results reveal that the excitation condition can be quantitatively described by the ratio of gap width G to the boundary layer thickness δ at the separation edge. When G/δ exceeds a certain critical value G/δc, self-sustained oscillations are excited. Otherwise, disturbances will dissipate and the flow configuration along the louver will be like a parallel plate flow. The critical value G/δc decreases with the ratio of G to the thickness of the louver plate H. This suggests that the excitation condition is more easily satisfied for a louver with sparse fins. The bottom boundary of the cavity restricts the feedback flow and then suppresses the excitation of self-sustained oscillations. With an increasing cavity height Hc, which reflects the distance between the louver and the bottom boundary, the critical value G/δc decreases and the decreasing rate reduces gradually. In contrast, because G/δc is relatively insensitive to the cavity length Lc, the side boundaries have no obvious influence on the excitation condition.

DEM–FEM analysis of soil failure process via the separate edge coupling method

SummaryThe concurrent multiscale method, which couples the discrete element method (DEM) for predicting the local micro‐scale evolution of the soil particle skeleton with the finite element method (FEM) for estimating the remaining macro‐scale continuum deformation, is a versatile tool for modeling the failure process of soil masses. This paper presents the separate edge coupling method, which is degenerated from the generalized bridging domain method and is good at eliminating spurious reflections that are induced by coupling models of different scales, to capture the granular behavior in the domain of interest and to coarsen the mesh to save computational cost in the remaining domain. Cundall non‐viscous damping was used as numerical damping to dissipate the kinetic energy for simulating static failure problems. The proposed coupled DEM–FEM scheme was adopted to model the wave propagation in a 1D steel bar, a soil slope because of the effect of a shallow foundation and a plane‐strain cone penetration test (CPT). The numerical results show that the separate edge coupling method is effective when it is adopted for a problem with Cundall non‐viscous damping; it qualitatively reproduces the failure process of the soil masses and is consistent with the full micro‐scale discrete element model. Stress discontinuity is found in the coupling domain. Copyright © 2017 John Wiley & Sons, Ltd.

Edge reconstruction in fractional quantum Hall states

Questions on the nature of edge reconstruction and "where does the current flow" in the quantum Hall effect (QHE) have been debated for years. Moreover, the recent observation of proliferation of "upstream" neutral modes in the fractional QHE raised doubts about the present models of edge channels. In this article we focus on hole-conjugate states, nu=2/3 and nu=3/5, and present a new picture of their edge reconstruction. For example, while the present model for nu=2/3 consists of a single downstream charge channel with conductance 2/3 e^2/h and an upstream neutral mode, we show that the current is carried by two separate downstream edge channels, each with conductance 1/3 e^2/h, accompanied by upstream neutral mode(s). We find that if the two downstream channels are not equilibrated, inter-mode equilibration (via particle exchange) takes place over a distance of microns, with the two channels effectively behaving as a single channel. Moreover, the inter-channel equilibration is accompanied by an excitation of upstream neutral modes. In turn, the counter-propagating neutral modes, moving in close proximity to the charge modes, fragment into propagating charges, inducing thus downstream current fluctuations with zero net current - a novel mechanism for non-equilibrium noise. This unexpected edge reconstruction underlines the need for better understanding of edge reconstruction and energy transport in all fractional QHE states.

Plasmon-Enhanced Photoelectrical Hydrogen Evolution on Monolayer MoS2 Decorated Cu1.75 S-Au Nanocrystals.

Hydrogen production from water splitting through an efficient photoelectrochemical route requires photoinduced electron transfer from light harvesters to efficient electrocatalysts. Here, the plasmon-enhanced photoelectrical nanocatalysts (NCs) have been successfully developed by coating a monolayer MoS2 on the Cu1.75 S-Au hetero-nanoparticle for hydrogen evolution reaction (HER). The plasmonic NCs dramatically improve the HER, leading to 29.5-fold increase of current under 650 nm excitation (1.0 W cm-2 ). These NCs generate an exceptionally high current density of 200 mA cm-2 at overpotential of 182.8 mV with a Tafel slope of 39 mV per decade and excellent stability, which is better than or comparable to the Pt-free catalysts with carbon rod as counter electrode. The enhanced HER performance can be attributed to the significantly improved broad light absorption (400-3000 nm), more efficient charge separation and abundant active edge sites of monolayer MoS2 . The studies may provide a facile strategy for the fabrication of efficient plasmon-enhanced photoelectrical NCs for HER.

Adiabatic Edge Channel Transport in a Nanowire Quantum Point Contact Register.

We report on a prototype device geometry where a number of quantum point contacts are connected in series in a single quasi-ballistic InAs nanowire. At finite magnetic field the backscattering length is increased up to the micron-scale and the quantum point contacts are connected adiabatically. Hence, several input gates can control the outcome of a ballistic logic operation. The absence of backscattering is explained in terms of selective population of spatially separated edge channels. Evidence is provided by regular Aharonov-Bohm-type conductance oscillations in transverse magnetic fields, in agreement with magnetoconductance calculations. The observation of the Shubnikov-de Haas effect at large magnetic fields corroborates the existence of spatially separated edge channels and provides a new means for nanowire characterization.

Tunable and direction-dependent group velocities in topologically protected edge states

Topological effects continue to fascinate physicists since more than three decades. One of their main applications are high-precision measurements of the resistivity. We propose to make also use of the spatially separated edge states. It is possible to realize strongly direction-dependent group velocities. They can also be tuned over orders of magnitude so that robust delay lines and interference devices are within reach.

An Improved Method for Edge Detection and Image Segmentation Using Fuzzy Cellular Automata

ABSTRACTImage segmentation is one of the most important and challenging problems in image processing. The main purpose of image segmentation is to partition an image into a set of disjoint regions with uniform attributes. In this study, we propose an improved method for edge detection and image segmentation using fuzzy cellular automata. In the first stage, we introduce a new edge detection method based on fuzzy cellular automata, called the texture histogram, and empirically demonstrate the efficiency of the proposed method and its robustness in denoising images. In the second stage, we propose an edge detection algorithm by considering the mean values of the edges matrix. In this algorithm, we use four fuzzy rules instead of 32 fuzzy rules reported earlier in the literature. In the third and final stage, we use the local edge in the edge detection stage to more accurately accomplish image segmentation. We demonstrate that the proposed method produces better output images in comparison with the separate segmentation and edge detection methods studied in the literature. In addition, we show that the method proposed in this study is more flexible and efficient when noise is added to an image.

Forest cover dynamics of shifting cultivation in the Democratic Republic of Congo: a remote sensing-based assessment for 2000–2010

Shifting cultivation has traditionally been practiced in the Democratic Republic of Congo by carving agricultural fields out of primary and secondary forest, resulting in the rural complex: a characteristic land cover mosaic of roads, villages, active and fallow fields and secondary forest. Forest clearing has varying impacts depending on where it occurs relative to this area: whether inside it, along its primary forest interface, or in more isolated primary forest areas. The spatial contextualization of forest cover loss is therefore necessary to understand its impacts and plan its management. We characterized forest clearing using spatial models in a Geographical Information System, applying morphological image processing to the Forets d’Afrique Central Evaluee par Teledetection product. This process allowed us to create forest fragmentation maps for 2000, 2005 and 2010, classifying previously homogenous primary forest into separate patch, edge, perforated, fragmented and core forest subtypes. Subsequently we used spatial rules to map the established rural complex separately from isolated forest perforations, tracking the growth of these areas in time. Results confirm that the expansion of the rural complex and forest perforations has high variance throughout the country, with consequent differences in local impacts on forest ecology and habitat fragmentation. Between 2000 and 2010 the rural complex grew by 10.2% (46 182 ha), increasing from 11.9% to 13.1% of the total land area (1.2% change) while perforated forest grew by 74.4% (23 856 ha), from 0.8% to 1.5%. Core forest decreased by 3.8% (54 852 ha), from 38% to 36.6% of the 2010 land area. Of particular concern is the nearly doubling of perforated forest, a land dynamic that represents greater spatial intrusion of forest clearing within core forest areas and a move away from the established rural complex.

Band Gap Engineering of Boron Nitride by Graphene and Its Application as Positive Electrode Material in Asymmetric Supercapacitor Device.

Nanostructured hexagonal boron nitride (h-BN)/reduced graphene oxide (RGO) composite is prepared by insertion of h-BN into the graphene oxide through hydrothermal reaction. Formation of the super lattice is confirmed by the existence of two separate UV-visible absorption edges corresponding to two different band gaps. The composite materials show enhanced electrical conductivity as compared to the bulk h-BN. A high specific capacitance of ∼824 F g(-1) is achieved at a current density of 4 A g(-1) for the composite in three-electrode electrochemical measurement. The potential window of the composite electrode lies in the range from -0.1 to 0.5 V in 6 M aqueous KOH electrolyte. The operating voltage is increased to 1.4 V in asymmetric supercapacitor (ASC) device where the thermally reduced graphene oxide is used as the negative electrode and the h-BN/RGO composite as the positive electrode. The ASC exhibits a specific capacitance of 145.7 F g(-1) at a current density of 6 A g(-1) and high energy density of 39.6 W h kg(-1) corresponding to a large power density of ∼4200 W kg(-1). Therefore, a facile hydrothermal route is demonstrated for the first time to utilize h-BN-based composite materials as energy storage electrode materials for supercapacitor applications.