Single Edge Research Articles

A matching-minor monotone parameter for bipartite graphs

Given a bipartite graph G with bipartition (U,W), we denote by Q(G) the set of all real U×W matrices B=[bu,w] with bu,w=0 if u and w are non-adjacent, bu,w≠0 if u and w are connected by a single edge, and bu,w∈R if u and w are connected by multiple edges. We denote by N(G) the set of all U×W matrices X=[xu,w] with xu,w=0 if u and w are adjacent. We say that a matrix B∈Q(G) has the Asymmetric Strong Arnold Property (ASAP) if for all X∈N(G), if XTB=0 and BXT=0, then X=0.If G is a bipartite graph for which there exists a matrix B∈Q(G) that has the Asymmetric Strong Arnold Property, we define the stable minimum bipartite rank mbrS(G) as the smallest rank of any matrix B∈Q(G) having the ASAP. We show that if H is a matching minor of G, then mbrS(G)≤mbrS(H)+1/2(|V(G)|−|V(H)|). If G has a bipartition with parts of the same size, we define the stable maximum bipartite nullity MbS(G) as the largest nullity of any matrix B∈Q(G) having the ASAP. Then MbS(H)≤MbS(G). We give a characterization in terms of forbidden matching minors of the classes of graphs G with MbS(G)=0 and with MbS(G)≤1.

Effect of in vitro ribosylation on the dynamic fracture behavior of mature bovine cortical bone

In this study, the fracture behavior of ribosylated bovine cortical bone is investigated under loading conditions simulating a fall event. Single edge notched specimens, separated into a control group (n = 11) and a ribosylated group (n = 8), were extracted from the mid-diaphysis of a single bovine femur harvested from a mature cow. A seven-day ribosylation process results in the accumulation of Advanced-Glycation End Products (AGEs) cross-links and AGE adducts. Specimens were subjected to symmetric three point bending (opening mode) and an impact velocity of 1.6 m/s using a drop tower. Near-crack displacement fields up to fracture initiation are determined from high-speed images post-processed using digital image correlation. A constrained over-deterministic least squares regression and orthotropic material linear elastic fracture mechanics theory are used to extract the in-plane critical stress intensity factors at fracture initiation (i.e., fracture initiation toughness values). Statistically significant differences were not observed when comparing the in-plane fracture initiation toughness values (p≥0.96) or energy release rate (p=0.90) between the control and seven-day ribosylated groups. The intrinsic variability of bone may require high sample numbers in order to achieve an adequately powered experiment when assessing dynamic fracture behavior. While there are no detectable differences due to the ribosylation treatment investigated, this is likely due to the limited sample sizes utilized.

Seasonal potential fishing zone model in the regional fisheries management of Indonesia (WPP-RI) 716 based on remote sensing satellite data

The variability of atmosphere-ocean interactions highly influences the distribution of fishing zones in the surrounding Indonesia Through Flow (ITF) channel, such as the WPP-716 region. Therefore, the seasonal determination of the fishing zone is crucial in this zone as one of the regional fisheries managements in Indonesia. This study aims to create a potential fishing zone (PFZ) model in the Regional Fisheries Management of Indonesia (WPP-RI) 716 based on the remote sensing satellite data. This study used the daily SST data extracted from the Suomi-National Polar-Orbiting Partnership-Visible Infrared Imaging Radiometer Suite (SNPP-VIIRS) image Level 2 from 2018 to 2019. A Single Image Edge Detection (SIED) method is applied to determine the PFZ points. Supporting data, such as sea current patterns, chlorophyll-a, fish-catching zones and Catch per Unit of Effort (CpUE), are also considered to bolster this study's findings. The models were validated and compared with the results established by central authority fish catch data. Of particular concern, the highest detection of PFZ is observed during the second transitional season, reaching 1835 points scattered all over the study area. The frequently detected PFZ is identified in northern Sulawesi and Sangihe Islands, where the circular eddy current observed during the second transitional season, ranging from 0.6 to 0.8 m/s, indicating upwelling (high productivity) events proven by the variability of surface temperature and chlorophyll-a and aligned with the high value of CpUE (ranging from 20 to 28 ​kg/GT/day). The developed model is expected to be a basis for further decision-making regarding fishery resources management in the study area.

Delayed fracture caused by time-dependent damage in PDMS

An experimental and theoretical study of delayed fracture of polydimethlsiloxane (PDMS) is presented. Previous works have demonstrated that delayed fracture in single edge notch specimens is caused by time dependent damage due to chain scission. Here we study the interactions between damage and the elastic field using different specimens and crack geometries with blunt and sharp cracks. Our experiments show that initial toughness is not well defined, as stable slow crack growth can occur over a range of applied loads. Our experiments demonstrate that there is a universal relation between crack growth rate and applied energy release rate. A model coupling the nonlinear elastic deformation and rate dependent bond scission is proposed and is in good agreement with experimental data.

Nudged Elastic Bands and Lightly Bound Skyrmions

It has become clear in recent years that the configuration space of the nuclear Skyrme model has, in each topological class, many almost degenerate local energy minima and that the number of such minima grows with the degree (or baryon number) $B$. Rigid body quantization, in which one quantizes motion on the spin-isospin orbit of just one minimum, is thus an ill-justified approximation. Instead, one should identify a (finite-dimensional) moduli space of configurations containing all local minima (for a given $B$) as well as fields interpolating smoothly between them. This paper proposes a systematic computational scheme for generating such a moduli space: one constructs an energy minimizing path between each pair of local minima, then defines the moduli space to be the union of spin-isospin orbits of points on the union of these curves, a principal bundle over a graph. The energy minimizing curves may be constructed in practice using the nudged elastic band method, a standard tool in mathematical chemistry for analyzing reaction paths and computing activation energies. To illustrate, we apply this scheme to the lightly bound Skyrme model in the point particle approximation, constructing the graphs for $5\leq B\leq 10$. We go on to complete the quantization for $B=7$, in which the graph has two vertices and a single edge. The low-lying quantum states with isospin $1/2$ do not strongly localize around either of the local energy minima (the vertices). Their energies rise monotonically with spin, conflicting with experimental data for Lithium-7.

Hiding From Centrality Measures: A Stackelberg Game Perspective

Centrality measures can rank nodes in a social network according to their importance. However, in many cases, a node may want to avoid being highly ranked by such measures, e.g., as is the case with terrorist networks. In this work, we study a confrontation between the seeker—the party analyzing a social network using centrality measures—and the evader—a node attempting to decrease its ranking according to such measures. We analyze the possible outcomes of modifying, i.e., adding or removing, a single edge by the evader, showing that even without complete knowledge about the network, the effects of the modification on the evader's ranking can often be predicted. We study the computational complexity of finding a set of modifications that reduce the evader's centrality ranking in an optimal way, proving that these decision problems are NP-complete. Moreover, we provide a 2-approximation for the degree centrality, and logarithmic approximation boundaries for the closeness and betweenness centralities. Finally, we define and investigate a Stackelberg game between the seeker and the evader, providing a Mixed Integer Linear Programming formulation of finding an equilibrium. Altogether, we provide a thorough analysis of the strategic aspects of hiding from centrality measures in social networks.

Multi-Agent Collaborative Inference via DNN Decoupling: Intermediate Feature Compression and Edge Learning

Recently, deploying deep neural network (DNN) models via collaborative inference, which splits a pre-trained model into two parts and executes them on user equipment (UE) and edge server respectively, becomes attractive. However, the large intermediate feature of DNN impedes flexible decoupling, and existing approaches either focus on the single UE scenario or simply define tasks considering the required CPU cycles, but ignore the indivisibility of a single DNN layer. In this paper, we study the multi-agent collaborative inference scenario, where a single edge server coordinates the inference of multiple UEs. Our goal is to achieve fast and energy-efficient inference for all UEs. To achieve this goal, we design a lightweight autoencoder-based method to compress the large intermediate feature at first. Then we define tasks according to the inference overhead of DNNs and formulate the problem as a Markov decision process (MDP). Finally, we propose a multi-agent hybrid proximal policy optimization (MAHPPO) algorithm to solve the optimization problem with a hybrid action space. We conduct extensive experiments with different types of networks, and the results show that our method can reduce up to 56% of inference latency and save up to 72% of energy consumption.

Privacy-preserving offloading scheme in multi-access mobile edge computing based on MADRL

With the development of industrialization and intelligence, the Industrial Internet of Things (IIoT) has gradually become the direction for traditional industries to transform into modern ones. In order to adapt to the emergence of a large number of edge access devices such as sensors, as well as the demand for high-consumption and low-latency computing tasks, Mobile Edge Computing (MEC) has been proposed as an effective paradigm by the academic community. Users can offload tasks to MEC servers, greatly reducing the computing latency and energy consumption when using services. However, traditional single access point edge computing networks cannot meet the usage requirements of a large number of users. In addition, the privacy leakage issues arising from the offloading process are also easily overlooked. In this paper, we propose a privacy-preserving offloading scheme based on stochastic game theory considering multiple access points. We first construct a multi-access point offloading framework and quality of service (QoS) model. In terms of privacy, the privacy risks caused by the offloading preferences of different edge nodes are studied, and the privacy entropy is used to evaluate the privacy protection level. We comprehensively consider the energy consumption, latency requirements, user experience, and privacy protection of the system and formulate the problem as a Markov Decision Process (MDP). Finally, a joint optimal DRL algorithm with privacy preservation (JODRL-PP) is proposed to achieve the optimal offloading scheme of the system. Simulation results verify the effectiveness of our model and algorithm.

Creep crack tip opening displacement (CCTOD) of X80 pipeline steel at room temperature

The room temperature creep behavior of X80 pipeline steel has attracted increasing attention because it is considered to be the main cause of time-delayed failure in pipeline steel. The crack tip opening displacement (CTOD) is a general criterion to characterize the time-delayed failure and assessment safety of pipeline steel. However, there are few methods to demonstrate crack behavior of the pipeline steel caused by room temperature creep. Based on the traditional CTOD theoretical model, a modified creep crack tip opening displacement (CCTOD) theoretical model is presented to calculate the CCTOD from the crack mouth opening displacement (CMOD). The room temperature creep experiment with a single edge notched beam subjected to three-point bending creep load for 36 h at room temperature is performed to know more about the CCTOD of X80 pipeline steel. Based on a power-law time delayed relationship among creep strain, stress and time fitted from experiment results of tensile creep tests, the finite element model is also established to evaluation the CCTOD of pipeline steel at room temperature. It is found that there is about 10% CTOD increment caused by room temperature creep added to that of the traditional elastic and plastic CTOD which indicates that room temperature creep is also further blunted the crack tip of X80 pipeline steel. Meanwhile, The results will provide an approach for failure evaluation and an integrity guideline for X80 pipeline steel.

Composition optimization of PMMA base denture reinforced with different percentages of Nano Hydroxyapatite and alumina particles to obtain highest KIc and KIIc values using hybrid IWO/PSO algorithm

Composition of three-phase dental denture (Polymethyl methacrylate or PMMA + Nano Hydroxyapatite + Nano Alumina) was optimized using hybrid IWO/PSO algorithm to obtain the highest KIc and KIIc. First, initial fracture toughness tests were performed on nine groups of PMMA base dentures with different percentages of ingredients. Symmetric single edge notch beam and asymmetric three-point bend beam with inclined crack were used for KIc and KIIc testing, respectively. The initial design parameters were considered as: {75–100% PMMA, 0–10% Nano Hydroxyapatite and, 0–15% Nano Alumina}. As the initial guess values for starting the hybrid optimization algorithm, B-spline curves (as the cost function) were fitted to the experimental results of both modes I and II. Then the IWO/PSO algorithm was run to find the optimum composition and maximum fracture toughness value of each mode. The best KIc was found for the composition of {78.5% PMMA + 9% Nano Hydroxyapatide + 12.5% Nano Alumina}. Similarly, using the hybrid IWO/PSO algorithm the optimum composition of {83.4% PMMA + 8.7% Nano Hydroxyapatide + 7.9 % Nano Alumina} was obtained to gain the highest KIIc. The experimental fracture toughness values obtained from the proposed compositions via employing the hybrid algorithm were approximately 40% higher than the all tested nine groups of PMMA base dentures under both modes I and II. The fracture toughness ratio KIIc/KIc of the optimum mix-designs predicted by the hybrid algorithm was equal to 0.78 and showed good agreement with the experimental KIIc/KIc ratio. The fracture toughness for any desired mixed mode condition can also be predicted in-terms of the KIc and stress intensity factors and T-stress of the desired mode mixity.

Fracture Behavior of Concrete under Chlorine Salt Attack Exposed to Freeze-Thaw Cycles Environment.

Fracture behavior is one of the key properties to study concrete cracking under sodium chloride attack exposed to the freeze-thaw cycles environment, which is frequently neglected. In this paper, 24 single edge notch beam specimens and 24 cubes were poured. The corresponding freeze-thaw cycles test in sodium chloride solution, standard cube compressive strength of concrete test, and three-point-bending tests were carried out. The research revealed that the fracture toughness, fracture energy, relative dynamic modulus of elasticity, and standard cube compressive strength were decreased by increasing freeze-thaw cycles under sodium chloride attack, and the damage degree of concrete caused by sodium chloride solution was deeper than that of pure water. In particular, there existed good linear correlation between the fracture behavior and imposed freeze-thaw damage for various solution. Accordingly, a more reliable damage model using fracture control parameters as damage factors was proposed.

Selective laser sintered Pipe Ring Notched Tension specimens for examination of fracture properties of pipeline materials

In order to develop a non-standard method for determining the resistance to fracture and damage of pipeline materials, a new geometry of ring-shaped specimens with sharp notches or cracks has been defined. The need to develop a new method for testing of the specimens cut from the pipes arises due to the difficulties in determination of fracture mechanics parameters on thin-walled pressure pipelines, especially those with a smaller cross-section, by application of the standard procedures/specimens. Previous studies dealing with the topic of pipeline testing by non-standard methods are presented in the introductory part of the paper. In the experimental part of the research, tests on PRNT (Pipe Ring Notched Tension) and SENT (Single Edge Notched Tension) specimens are performed. Samples of these specimens were produced by SLS (Selective Laser Sintering) technique of additive production from PA12 (polyamide PA 2200) material. For the purpose of this study, a tool that is protected at the national level (in Serbia) as intellectual property is used for testing of the ring-shaped PRNT specimens. Tensile testing of both types of specimens is monitored by Aramis GOM 2M system; its operation is based on the method of digital image correlation, DIC. Additionally, finite element analyses are conducted on the PRNT and SENT geometries, enabling the calculation of the fracture mechanics parameter – Stress intensity factor K. It is concluded that the presented procedure based on the PRNT specimen has a good potential for use as a non-standard method for fracture resistance examination of pipeline materials. It can be performed on the specimens cut directly from the pipes (new or from exploitation). The dependence of the fracture resistance on the stress concentrator size is not pronounced, which means that the results depend dominantly on the material properties, rather than on geometry.

Reducible 3-critical graphs

In this paper, we provide further insights into the reducibility of 3-critical graphs. A graph is 3-critical if it is class two, that is, has chromatic index 4, and the removal of any one edge renders a graph with chromatic index 3. We consider two types of reductions: the suppression of a 2-connected subgraph into a single edge; and the suppression of a 3-connected subgraph into a single vertex. That is, in cases where the 2- or 3-connected subgraph is cubic or strictly subcubic. We show that every cyclically 2-connected 3-critical graph can be reduced to a smaller 3-critical graph using this method. We also prove that every 3-critical graph which is cyclically k-connected with k = 2 or k = 3, contains a 3-critical minor which is cyclically k-connected with k ≥ 4.

Infernal and exceptional edge modes: non-Hermitian topology beyond the skin effect

The classification of point gap topology in all local non-Hermitian (NH) symmetry classes has been recently established. However, many entries in the resulting periodic table have only been discussed in a formal setting and still lack a physical interpretation in terms of their bulk-boundary correspondence. Here, we derive the edge signatures of all two-dimensional phases with intrinsic point gap topology. While in one dimension point gap topology invariably leads to the NH skin effect, NH boundary physics is significantly richer in two dimensions. We find two broad classes of non-Hermitian edge states: (1) infernal points, where a skin effect occurs only at a single edge momentum, while all other edge momenta are devoid of edge states. Under semi-infinite boundary conditions, the point gap thereby closes completely, but only at a single edge momentum. (2) NH exceptional point dispersions, where edge states persist at all edge momenta and furnish an anomalous number of symmetry-protected exceptional points. Surprisingly, the latter class of systems allows for a finite, non-extensive number of edge states with a well defined dispersion along all generic edge terminations. Concomitantly, the point gap only closes along the real and imaginary eigenvalue axes, realizing a novel form of NH spectral flow.

Pemetaan Zona Potensial Penangkapan Ikan (ZPPI) Di Perairan Selat Bali Menggunakan Citra Satelit Aqua MODIS


 
 
 
 The abundance and distribution of fish are influenced by environmental productivity, such as chlorophyll-a distribution and variations in sea surface temperature (SST). The lack of technology fishermen use in the waters of the Bali Strait has resulted in the high potential of fish resources not being optimally utilized. This study aimed to determine potential fishing zones by utilizing Aqua MODIS satellite data which can detect SST and chlorophyll-a. The image data observed was from October to December 2018 to 2020. The method used is the Single Image Edge Detection Algorithm, where this algorithm is used to determine potential fishing areas designed to detect fronts in SST images. The results showed that in December 2018, 7 potential fishing points were produced, marked with a chlorophyll-a value of 0.25 mg/m3 and an SST of 29.25°C. In December 2020, 82 potential fishing points were produced, with a chlorophyll-a value of 0.31 mg/m3 and an SPL of 29.79°C. Validation was carried out by analyzing the result of image processing with fish catch data obtained from Pengambengan PPN, Muncar PPP, and Kedonganan TPI. SST, with a value of 27°C, is the ideal temperature for fish where when the temperature increases, the number of potential fish catch points decreases and vice versa. The distribution of chlorophyll-a content with a value of > 0.2 mg/m3 affects the number of potential fishing points, where the higher the chlorophyll-a content, the more fishing ground points and vice versa.
 
 
 

The Immense Impact of Reverse Edges on Large Hierarchical Networks

Hierarchical networks are frequently encountered in animal groups, gene networks, and artificial engineering systems such as multiple robots, unmanned vehicle systems, smart grids, wind farm networks, and so forth. The structure of a large directed hierarchical network is often strongly influenced by reverse edges from lower- to higher-level nodes, such as lagging birds’ howl in a flock or the opinions of lower-level individuals feeding back to higher-level ones in a social group. This study reveals that, for most large-scale real hierarchical networks, the majority of the reverse edges do not affect the synchronization process of the entire network; the synchronization process is influenced only by a small part of these reverse edges along specific paths. More surprisingly, a single effective reverse edge can slow down the synchronization of a huge hierarchical network by over 60%. The effect of such edges depends not on the network size but only on the average in-degree of the involved subnetwork. The overwhelming majority of active reverse edges turn out to have some kind of “bunching” effect on the information flows of hierarchical networks, which slows down synchronization processes. This finding refines the current understanding of the role of reverse edges in many natural, social, and engineering hierarchical networks, which might be beneficial for precisely tuning the synchronization rhythms of these networks. Our study also proposes an effective way to attack a hierarchical network by adding a malicious reverse edge to it and provides some guidance for protecting a network by screening out the specific small proportion of vulnerable nodes.

Energy absorption, free and forced vibrations of flexoelectric nanocomposite magnetostrictive sandwich nanoplates with single sinusoidal edge on the frictional torsional viscoelastic medium

Energy absorption, free and forced vibrations of flexoelectric nanocomposite magnetostrictive sandwich nanoplates with single sinusoidal edge on the frictional torsional viscoelastic medium

Fracture toughness determination for the surface-modified layers of carburized 18CrNiMo7-6 alloy steel via the compact tension method

Anti-fatigue manufacturing technology is the latest manufacturing technology to control surface integrity and modification. Surface modification techniques have been used to construct surface-modified layer (SMLs) on the workpiece surface. In this study, to accurately characterize and measure the fracture toughness of SMLs, a characterization method was proposed for evaluating the J-integral of fracture toughness of SMLs. The elastic–plastic parameters of the SMLs, such as the strain hardening index and yield strength, were obtained via peeling-layer tensile testing. The effect of n was considered when deriving the plasticity factor (ηp). The J-integral of the SML of 18CrNiMo7-6 alloy steel was obtained from single edge notched tension tests and finite element simulations. The results show that the fracture toughness of the SMLs can be accurately characterized using the proposed method.

Experimental Evaluation of KIEAC of a Carbon Steel Using the Pin-Loaded SENT Geometry

Abstract The experimental determination of the threshold stress intensity factor for environment-assisted cracking (KIEAC) is described by several standards, which allow the use of different specimen geometries and methodologies for crack length estimation. In some cases, the combination of structure, specimen size, or both, main loading direction, and crack orientations of the component that need to be characterized limit the use of standardized geometries. Consequently, alternative geometries must be used. In this study, fatigue pre-cracked pin-loaded single edge notched tension specimens as defined by BS 8571:2018, Method of Test for Determination of Fracture Toughness in Metallic Materials Using Single Edge Notched Tension (SENT) Specimens, were applied for the experimental evaluation of the KIEAC of a carbon steel. The specimens were tested in deaerated substitute ocean water solution saturated with carbon dioxide at 40°C and at 1 and 10 bar (100 and 1,000 kPa) under constant load conditions with incremental (step) loading. The crack length during the tests was monitored by direct current potential drop, which was helpful for defining the applied K corresponding to the onset of subcritical crack growth (KIEAC). Additionally, fractographic analysis of KEAC specimens and results from the fracture toughness evaluation of this material in air at room temperature have also been reported.

A Comparison of the Damage Tolerance of AA7075-T6, AA2024-T3, and Boeing Space, Intelligence, and Weapons Systems AM-Built LPBF Scalmalloy

This paper first presents the results of an experimental study into the damage tolerance of AA7075-T6, which is widely used in both fixed- and rotary-wing aircraft, space structures, and laser bed powder fusion (LBPF) Scalmalloy specimens built by Boeing Space, Intelligence, and Weapons Systems. To this end, four single edge notch AA7075-T6 specimens and four identical single edge notch LBPF Scalmalloy specimens were tested. The resultant crack growth curves reveal that Boeing Space, Intelligence, and Weapons Systems AM-built Scalmalloy is more damage tolerant than conventionally built AA7075-T6. This finding leads to the observation that the da/dN versus ΔK curves associated with Scalmalloy and conventionally manufactured AA2024-T3 are similar. These findings highlight the potential for Boeing Space, Intelligence, and Weapons Systems AM-built Scalmalloy to be used to extend the operational lives of military aircraft by the on-demand printing of limited-life Scalmalloy replacement parts.