Edge Modification Research Articles

Flow separation control using the cetacean species nose design

Most of the flow separation control devices used in the aircraft wing are effective at high angles of attack, and adversely affect the performance of the wing at low angles of attack. In flight mission, the cruise phase takes major portion than the take-off and landing. Therefore, the flow separation control devices installed on wing may reduce the performance of the aircraft in total flight mission. A bio-inspired passive flow control method is used by introducing leading edge modification. The leading edge modification inspired by the cetacean species (Porpoise) has been analyzed on NACA2412 and NACA66215 airfoils at different subsonic speed using 2D analysis. The effect of the spanwise location and extent of these leading edge modifications is analyzed using a three-dimensional numerical investigation. The porpoise nose design (shorter length and medium depth i.e. depth — 2.25 % of chord, nose length — 0.75 % chord, and nose diameter — 2 % chord) delay the flow separation and improves the aerodynamic efficiency up to the critical Mach number. After critical Mach number, the shock wave formation affects the porpoise nose performance and shows similar flow behavior as base airfoil. A finite wing with a porpoise nose design of full spanwise length showed the better aerodynamic efficiency than base wing model. This rigid design improves aerodynamic performance of a wing without major structural modification.

Editing to Prime Graphs

Given a graph G, a subset M of V(G) is a module of G if for each $$v\in V(G)\setminus M$$ and $$x,y\in M$$ , $$vx \in E(G)$$ if and only if $$vy \in E(G)$$ . The trivial modules of G are $$\varnothing ,\{u\}(u\in V(G))$$ and V(G). Let G be a graph with at least four vertices. The graph G is prime if all its modules are trivial. We are interested in the minimum number $$\delta (G)$$ of edge modifications (edge deletions and/or additions) that are needed to transform G into a prime graph. We prove that $$\delta (G) \le v(G)-1$$ , where $$v(G) = |V(G)|$$ , and that the upper bound is uniquely reached by the complete graphs and their complements. We then characterize the graphs G such that $$\delta (G) = v(G)-2$$ or $$v(G)-3$$ , respectively. Lastly, we look for the $$\delta $$ -critical graphs, i.e. the graphs G for which $$\delta (H) > \delta (G)$$ for every graph H obtained from G by deleting one vertex. We prove that the $$\delta $$ -critical graphs are precisely the half graphs and their complements.

A Proper Shape of the Trailing Edge Modification to Solve a Housing Damage Problem in a Gas Turbine Power Plant

To solve the housing damage problem of a fractured compressor blade (CB) caused by an impact on the inner casing of a gas turbine in the seventh stage (from 15 stages), modifications of the trailing edge (TE) of the CB have been proposed, namely 6.5 mm curved cutting and a combination of 4 mm straight cutting with 6.5 mm curved cutting. The simulation results of the modifications in both aerodynamics variables Cl and Cd and the pressure ratio, including structural dynamics such as a normalized power spectrum, frequency, total deformation, equivalent stress, and the safety factor, found that 6.5 mm curved cutting could deliver the aerodynamics and structural dynamics similar to the original CB. This result also overcomes the previous work that proposed 5.0 mm straight cutting. This work also indicates that the operation of a CB gives uneven pressure and temperature, which get higher in the TE area. The slightly modified CB can present the difference in the properties of both the aerodynamics and the structural dynamics. Therefore, any modifications of the TE should be investigated for both properties simultaneously. Finally, the results from this work can be very useful information for the modification of the CB in the housing damage problem of the other rotating types of machinery in a gas turbine power plant.

First-principles study on the mechanical and electromagnetic properties of porous two-dimensional C7N2 crystals

By uniformly introducing pyrazine defects on monolayer C 3 N, the porous 2D C 7 N 2 (p2D-C 7 N 2 ) crystals were obtained. Based on first-principles calculations, we systematically investigate the mechanical, electronic, and magnetic properties of p2D-C 7 N 2 crystals. The p2D-C 7 N 2 crystals have excellent performance in terms of structural and thermodynamic stability. Furthermore, we systemically study the electronic and magnetic properties of various nanoribbons by cutting from a monolayer p2D-C 7 N 2 crystals along the typical crystallographic orientations. All the nanoribbons are magnetic metals. The C 7 N 2 nanoribbons exhibit sensitive responses to edge modifications using H and O atoms. We find that the edge modifications can induce the spin semiconductor phase, non-magnetic metal phase, half-semiconductor phase, and half-metal phase. These results can open up the two-dimensional material frontier to some extent and can also provide some theoretical support for the potential application and development of nanoelectronic devices based on C 7 N 2 . • The holey 2D C 7 N 2 sheet has excellent performance in terms of structural and thermodynamic stability. • The holey 2D C 7 N 2 has the intrinsic ferromagnetic state magnetic order. • All the original C 7 N 2 nanoribbons are magnetic metals. • The edge modifications by H and O atoms in the C 7 N 2 nanoribbons can induce the different phase.

Effect of outer edge modification on dynamic characteristics of pump turbine runner

It is currently in the period of high-speed construction of pumped storage projects. However, the problems caused by vibration of pump turbine units, especially the runners, are very serious. It is of great significance to study the dynamic characteristics of pump turbine runner for the safety and stability of power station. In this paper, the natural modes of a pump turbine runner in the air and in the flow channels are calculated by numerical method. The influence and mechanism of the outer edge modification on the natural frequencies of the runner are studied. The results show that, for the object studied in this paper, the frequency of most modes will be decreased by thickening the outer edge. The frequency change can be attributed to two aspects, one is the change of the mass and the stiffness of the runner, and the other is the change of added mass of the water. Furthermore, the main mechanism of outer edge modification affecting the added mass coefficient is that the height of the radial clearance is changed.

Realization Methods of Computer-aided Diagnosis System of Medical Images

In this paper, medical images are used to realize the Computer-Aided Diagnosis (CAD) system, which develops targeted solutions to existing problems. Relying on the MiCOM platform, this system has collected and collated cases of all kinds, based on which a unified data model is constructed according to the gold standard derived by deducting each instance. Afterwards, the object segmentation algorithm is employed to segment the diseased tissues. Edge modification and feature extraction are performed for the tissue block segmented. The features extracted are classified by applying support vector machines or the Naive Bayesian classification algorithm. From the simulation results, the CAD system developed in this paper allows the realization of diagnosis and treatment and sharing of data resources.

On 2-Clubs in Graph-Based Data Clustering: Theory and Algorithm Engineering

Editing a graph into a disjoint union of clusters is a standard optimization task in graph-based data clustering. Here, complementing classical work where the clusters shall be cliques, we focus on clusters that shall be 2-clubs, that is, subgraphs of diameter at most two. This naturally leads to the two NP-hard problems $\rm{2-C \small{LUB}}$ $\rm{C{\small LUSTER}}$ $\rm{E{\small DITING}}$ (the editing operations are edge insertions and edge deletions) and $\rm{2-C \small{LUB}}$ $\rm{C{\small LUSTER}}$ $\rm{V{\small ERTEX}}$ $\rm{D{\small ELETION}}$ (the editing operations are vertex deletions). Answering an open question from the literature, we show that $\rm{2-C \small{LUB}}$ $\rm{C{\small LUSTER}}$ $\rm{E{\small DITING}}$ is W[2]-hard with respect to the number of edge modifications, thus contrasting the fixed-parameter tractability result for the classical $\rm{C{\small LUSTER}}$ $\rm{E{\small DITING}}$ problem (considering cliques instead of 2-clubs). Then, focusing on $\rm{2-C \small{LUB}}$ $\rm{C{\small LUSTER}}$ $\rm{V{\small ERTEX}}$ $\rm{D{\small ELETION}}$, which is easily seen to be fixed-parameter tractable, we show that under standard complexity-theoretic assumptions it does not have a polynomial-size problem kernel when parameterized by the number of vertex deletions. Nevertheless, we develop several effective data reduction and pruning rules, resulting in a competitive solver, outperforming a standard ILP formulation in most instances of an established biological test data set.

Effect of edge on nonlinear optical property of graphene quantum dots

Graphene is a two-dimensional material with single-layer honeycomb lattice structure formed by sp<sup>2</sup> hybrid connection of carbon atoms. Graphene has excellent optical, electrical, thermal and mechanical properties, and it is considered to be an ideal material for future flexible optoelectronic devices. In recent years, the nonlinear optical properties and regulation of graphene nanostructures have attracted experimental and theoretical interest. Graphene has good delocalization of π-electrons and its unique plane structure, showing good nonlinear optical properties. Graphene quantum dots can be regarded as small graphene nanoflakes. Their unique electronic structure is closely related to the non-bond orbitals on the boundary/edge. Therefore, it is very important to study the boundary/edge effect on the electronic and optical properties of nanographene. In this paper, effects of the number of edge C=C double bonds and Borazine (B<sub>3</sub>N<sub>3</sub>) doping on the nonlinear optical properties and UV-Vis absorption spectrum of graphene quantum dots are studied by the quantum chemical calculation methods, respectively. It is found that the symmetry of hexagonal graphene quantum dots decreases and the symmetry of charge distribution is broken when C=C double bond is introduced into the armchair edge, which leads the second-order nonlinear optical activity to be enhanced. During the transition from armchair to zigzag edge, the polarizability and the second hyperpolarizability of hexagonal graphene quantum dots and B<sub>3</sub>N<sub>3</sub>-doped graphene quantum dots increase linearly with the number of introduced C=C double bonds incrrasing. In addition, the edge also has an important influence on the absorption spectrum of graphene quantum dots. For graphene quantum dots and B<sub>3</sub>N<sub>3</sub>-doped graphene quantum dots, the introduction of C=C double bond at the armchair edge increases the highest occupied molecular orbital energy level and also reduces the lowest unoccupied molecular orbital energy level, which reduces the energy gap between the frontier molecular orbitals, and thus resulting in the red-shift of the maximum absorption wavelength. The doping of B<sub>3</sub>N<sub>3</sub> ring will increase the energy gap between molecular frontier orbitals of graphene quantum dots, leading the UV-Vis absorption spectrum of graphene quantum dots to be blue-shifted. This study provides theoretical guidance for controlling the nonlinear optical response of graphene quantum dots by edge modification.

Energy-Transfer Edge Centrality and Its Role in Enhancing Network Controllability

The ability to modify the structure of network systems offers great opportunities to enhance their operation, improve their efficiency, and increase their resilience against failures and attacks. This paper focuses on the edge modification problem, i.e., improving network controllability by adding and/or re-weighting interconnections while keeping the actuation structure fixed. We consider a network system following linear dynamics and propose a novel edge centrality measure that captures the extent to which an edge facilitates energy exchange across the network through its defining nodes. We analyze the effectiveness of the proposed measure by characterizing its relationship with the gradient (with respect to edge weights) of trace, log determinant, and inverse of the trace inverse of the Gramian. We show that the optimal solution of the edge modification problem lies on the boundary of the feasible search space when the objective is the trace of the Gramian or the network has a diagonal controllability Gramian and the objective is either log determinant or the inverse of the trace inverse of the Gramian. Finally, using the proposed edge centrality measure we design two network modification algorithms that restrict the search space to a smaller subset of all possible edges and numerically demonstrate their efficacy.

Boron and nitrogen edges modify the thermal conductivity of phagraphene nanoribbons: Molecular dynamics simulations

Phagraphene was recently identified as a low-energy two-dimensional (2D) material with distorted Dirac cones that has received increasing attention. We used molecular dynamics simulations to study the effects of modifying the edges with B and N atoms on the thermal conductivity of phagraphene. Our simulation results showed that compared with bare nanoribbons, those with modified edges have higher thermal conductivity, and the improvement in the thermal conductivity by adding nitride is more obvious. This is due to the addition of fringe atoms that weaken the bond anharmonicity, which reduces edge phonon scattering. Interestingly, under tensile strain, the thermal conductivity of bare phagraphene and edge modified nanoribbons shows different trends. In bare nanoribbons, the thermal conductivity gradually decreases with increasing strain, whereas for edge modified nanoribbons, as the strain increases, the thermal conductivity first increases and then decreases. Our research provides important value for the effects of edge modifications and tensile strain on the thermal transport of this new 2D material.

Thermohydraulic and entropy characteristics of Al2O3‐water nanofluid in a ribbed interrupted microchannel heat exchanger

AbstractIn this study, an interrupted microchannel heat sink with rib turbulators was studied for its thermohydraulic effectiveness and entropy generation in a compact space. The rib edges are modified to enhance the overall functioning of the system by reducing the pressure drop. The working fluid used was Al2O3‐water nanofluid, and increasing the Reynolds number and nanoparticle concentration triggered a reduction in the heat sink's maximum temperature. These also offer a decrease in resistance to heat transfer, and there is an improvement in the evenness of the temperature of the interrupted microchannel heat sink, as regions with the likelihood of hot spot reduced drastically. At Re = 100, increasing the nanoparticle concentration from 0% to 4% enhanced the heat transfer coefficient by 38.41% for the interrupted microchannel heat sink‐base (IMCH‐B) configuration. Under similar conditions, the convective heat transfer coefficient for the interrupted microchannel heat sink‐fillet (IMCH‐F) increased by 43.69%. Furthermore, at 0.5% concentration, changing the Reynolds number from 100 to 700 augmented the heat transfer coefficient by 70.65%. Thus, the maximum temperature of the substrate's bottom surface was reduced by 53.83°C when the system was operated at Re = 700 and nanoparticle concentration of 4%. The IMCH‐C also showed relatively close results at all observed volume fractions. For the IMCH‐C, the maximum temperature of the bottom surface was reduced by 41.98°C at Re = 700 when compared with Re = 100% and 4% concentration. Although at high Reynolds numbers and concentrations, the pressure drops are higher, the performance enhancement criteria prove that the nanofluid is superior to water and the edge modifications show significant performance improvement. More importantly, the IMCH‐F heat sink showed the optimum performance based on the performance evaluation criteria at Re = 300 and (ie, at this point, the heat transfer coefficient is maximum and the pressure drop is minimum). On the other hand, the optimal thermodynamic performance was observed at Re = 700 and . The numerical results demonstrated a potential way to exploit nano‐suspensions for thermal applications, especially for high‐energy flux systems with compact space constraints.

Super antimagic total labeling under duplication operations

For a graph G the duplication operation of a vertex v by a new edge e = uw results in a new graph G’ such that N (u) = {v, w} and N (w) = {v, u}. The duplication operation of an edge e = uv by a new vertex w results in a new graph G’’ such that N (w) = {u, v}. In this article we have discussed that the properties of a graph, with minimum degree 2 of any vertex, to be super vertex-antimagic total and to be super edge-antimagic total are invariant under the above duplication operations. Also, we have discussed on the existence of the so-called k super vertex-antimagic total vertex modifications and k super edge-antimagic total edge modifications for graphs.

A graph modification approach for k-anonymity in social networks using the genetic algorithm

Social networks, which have become so popular today, allow their users to share information. The main challenge the users are facing is the security preservation of their information and privacy. Therefore, structural anonymity techniques were introduced that would hide the identity of users. One of the drawbacks of these techniques, which are based on graph modification, is the lack of attention about the structural semantics of graphs. This paper focuses on the popular notion of a privacy protection method called k-degree anonymization and tries to reduce utility loss on the graph. The new k-degree anonymization method, genetic k-degree edge modification, has two steps. The first step includes partitioning of vertices and community detection in the graph. The result of these two determines the needed increase in edges for every vertex in each society to achieve k-degree anonymization. The second step is graph modification using the genetic algorithm by adding some edges between vertices in each community. Average Path Length (APL), Average Clustering Coefficient, and Transitivity (T) are employed to evaluate the method. The proposed algorithm has been tested on four datasets, and the results have shown the average relative performance demonstrates more stability than the other four well-known algorithms. Also, APL criterion in our algorithm is better preserved than all other algorithms; furthermore, Transitivity parameters are the best result in most cases.

COFs Meet Graphene Nanoribbons

2D covalent organic frameworks (COFs) have received considerable attention because of their crystallinity, permanent porosity, and tunability, yet they exhibit low in-plane conductivity. In this issue of Chem, Fischer and co-workers report an approach for growing 2D COF thin films featuring high in-plane conductivity for potential use in organic electronics.

Effects of circular trailing edge with the dimple on flow separation of NACA S1210 hydrofoil

Flow separation over a hydrofoil affects its hydrodynamic performance and ultimately reduces the power production of a turbine. Therefore, the different flow control methods have been proposed by the researchers to overcome these challenges. In this study, the combined effects of circular trailing edge with dimple have been investigated numerically on NACA S1210 hydrofoil to control the flow separation of the hydrofoil. The results showed that the coupled effects of the dimple and circular trailing edge modification appeared effective compared to baseline hydrofoil at a wide range of angles of attack. Maximum lift coefficient increments are 9 and 12% at an angle of attack of 10° and 12°, respectively, for circular trailing edge hydrofoil. The maximum increase of glide ratio for the coupled effect (circular trailing edge with outward dimple) is approximately 114% at an angle of attack of 12°. The outcome will be advantageous to design a proper blade profile for horizontal axis current turbines.

First-principles prediction of the electronic property, carrier mobility and optical absorption in edge-modified pristine sawtooth penta-graphene nanoribbons (SSPGNRs)

Based on the first-principle calculations, we systematically study the electronic property, carrier mobility and optical absorption spectra in the monohydrogen(H), dihydrogen(2H) and Al edge-modified pristine sawtooth penta-graphene nanoribbons (SSPGNRs), respectively. Our results show that the SSPGNRs have suitable band gap, high carrier mobility and good optical absorption. The charge carrier mobility of SSPGNRs can be as high as 104 cm2 V−1 s−1, behave like n-type semiconductor, the different edge modifications enable SSPGNRs to convert from n-type to p-type semiconductor, and specifically, spin-splitting occurs in the band structure of the 2H-SSPGNR. Furthermore, the edge modifications can change the optical absorption that the absorption spectrum of Al-SSPGNR increases in visible and ultraviolet light regions obviously. The spin and optoelectronic properties of SSPGNRs with different edge modifications suggest its potential applications in spin electronics, optoelectronic devices and solar cells, which also provide some theoretical guidance for regulating the properties of SSPGNRs by edge modifications.

Anisotropic active ligandations in siRNA-Loaded hybrid nanodiscs lead to distinct carcinostatic outcomes by regulating nano-bio interactions

Active targeting modification is one of the foremost nanomedicine strategies for the efficacy improvement. Compared to the homogeneous ligandation on spherical nanocarriers, non-spherical nanomedicines usually make the ligand modification more complicated. The modified ligands always exhibit anisotropy and heterogeneity. However, there is very little systematic study on these diversified anisotropic modifications. The efficacy difference and underlying mechanism were still unclear. Here, we separately fabricated hybrid nanodiscs (NDs) conjugated with cRGD on the edge and plane surfaces to engineer two anisotropic targeting nanocarriers (E-cRGD-NDs and P-cRGD-NDs, respectively) for gene delivery. The ligand anisotropy endowed NDs with diversified cellular interactions, and caused different efficacies between E-cRGD-NDs and P-cRGD-NDs. Of note, E-cRGD-NDs showed significant superiority in siRNA loading, cellular uptake, silence efficiency, protein expression and even in vivo efficacy. The mechanism investigation revealed the functional anisotropy specifically for E-cRGD-NDs. The edge modification of cRGD efficiently separated the targeting and siRNA loading domains, maximizing their respective functions. These findings reflected the unique effect of ligand anisotropy, also provided a new strategy for the targeting screening of extensive nanomedicines.

Effect of cavity flow control on high-speed train pantograph and roof aerodynamic noise

The pantograph and its recess on the train roof are major aerodynamic noise sources on high-speed trains. Reducing this noise is particularly important because conventional noise barriers usually do not shield the pantograph. However, less attention has been paid to the pantograph recess compared with the pantograph. In this paper, the flow features and noise contribution of two types of noise reduction treatments rounded and chamfered edges are studied for a simplified high-speed train pantograph recess, which is represented as a rectangular cavity and numerically investigated at 1/10 scale. Improved delayed detached-eddy simulations are performed for the near-field turbulent flow simulation, and the Ffowcs Williams and Hawkings aeroacoustic analogy is used for far-field noise prediction. The highly unsteady flow over the cavity is significantly reduced by the cavity edge modifications, and consequently, the noise radiated from the cavity is reduced. Furthermore, effects of the rounded cavity edges on the flow and noise of the pantographs (one raised and one folded) are investigated by comparing the flow features and noise contributions from the cases with and without rounding of the cavity edges. Different train running directions are also considered. Flow analysis shows that the highly unsteady flow within the cavity is reduced by rounding the cavity edges and a slightly lower flow speed occurs around the upper parts of the raised pantograph, whereas the flow velocity in the cavity is slightly increased by the rounding. Higher pressure fluctuations occur on the folded pantograph and the lower parts of the raised pantograph, whereas weaker fluctuations are found on the panhead of the raised pantograph. This study shows that by rounding the cavity edges, a reduction in radiated noise at the side and the top receiver positions can be achieved. Noise reductions in the other directions can also be found.

Parameterized algorithms for Module Map problems

Motivated by applications in the analysis of genetic networks, we introduce and study the NP-hard Module Map problem which has as input a graph G=(V,E) with red and blue edges and an integer k and asks to transform G by at most k edge modifications into a graph G′ which has the following properties: the vertex set of G′ can be partitioned into so-called clusters such that inside a cluster every pair of vertices is connected by a blue edge and for two distinct clusters A and B either all vertices u∈A and v∈B are connected by a red edge or there is no edge between A and B. We show that Module Map can be solved in O(3k⋅(|V|+|E|)) time and O(2k⋅|V|3) time, respectively. Furthermore, we show that Module Map admits a kernel with O(k2) vertices.

On the impact of edge modifications for networked control systems

Abstract This paper investigates the impact of addition/removal of edges in complex networks. Growing a network by the addition of edges has for instance been suggested as a way to improve network robustness to external disturbances. Moreover, when network controllability is considered, designing edge additions is a promising alternative to add more actuation capabilities in order to improve different performance metrics. We quantify the impact of an edge modification with the H∞ and H2 norms. For networks with positive edge weights we show how the H∞ norm can be computed exactly for each possible single edge modification, while for the H2 norm we instead obtain a lower bound. This bound is linked to the trace of the controllability Gramian, hence it can be used for instance to reduce the energy needed for control.