Edge Modification Research Articles

Innovative Calibration Strategies for Weirs with Half-Round Crest Edge Modifications

Innovative Calibration Strategies for Weirs with Half-Round Crest Edge Modifications

Size and chemistry of 1–2 layer graphene nanosheets at the transition into photoluminescence and assembly with large shifts from blue to red emission

Synthetic refinement of graphene photoluminescence remains challenging because underlying characteristics have not been well understood from polydisperse mixtures of different sizes and surface chemistries. Here, we isolate and characterise different populations of 1–2 layer graphene (1-2LG) each with narrow size range. Small 1-2LG nanosheets down to 25 nm size remained black and non-luminescent with N. and O. additions at their edges, whereas 15 nm nanosheets transitioned into photoluminescence, while retaining substantial sp2 carbon of graphene. Positively-charged amine modifications overcame the repulsion between nanosheets from the negative zeta potential of sp2 graphene faces in water and allowed assembly of similarly-sized nanosheets with large red shifts (>150 nm) taking blue emission into the red. However, more extensive edge modification into carboxyl groups and neutral amides built negative charge at the edges. Together with smaller nanosheet size and reduced sp2 carbon, red shifts were weakened by half in these isolates, which were most modified and more like graphene oxide and carbon quantum dots. N addition to form amines at nanosheet edges, while avoiding O atom addition and carboxyl groups, presents as a simple refinement for synthesis of self-assembling graphene quantum dots with multi-colour emission, which also retain sp2 carbon properties of graphene.

A Review of Agrivoltaic Systems: Addressing Challenges and Enhancing Sustainability

Agrivoltaics is a relatively new term used originally for integrating photovoltaic (PV) systems into the agricultural landscape and expanded to applications such as animal farms, greenhouses, and recreational parks. The dual use of land offers multiple solutions for the renewable energy sector worldwide, provided it can be implemented without negatively impacting agricultural production. However, agrivoltaics represent a relatively new technology, facing challenges including economic viability, vulnerability to wind loads, and interference with growing crops. This paper reviews the recent research on integrating agrivoltaics with farming applications, focusing on challenges, wind impact on agrivoltaics, and economic solutions. The effect of agrivoltaics on temperature control of the lands is a critical factor in managing (1) water and the soil of the land, (2) animal comfort, and (3) greenhouse productivity, positively or negatively. In this review, a contradiction between the different versions of the American Society of Civil Engineers (ASCE) standards and the wind tunnel results is shown. Important factors affecting the wind load, such as damping and mass increase, optimum stow position, and aerodynamic edge modification, are highlighted with emphasis on the significant knowledge gap in the wind load mitigation methods.

Controlling sonic rectangular jet with nozzle trailing edge modification

Sonic rectangular jet emanating from a convergent nozzle of aspect ratio 2 with modified trailing edge in the form of triangular extension on its widest side is investigated experimentally at different nozzle pressure ratios corresponding to underexpanded states of sonic jet. To assess the impact of trailing edge modification on jet mixing, the sonic rectangular jet from aspect ratio two plain convergent nozzle (without trailing edge modification) is also studied. The centerline pressure decay results at nozzle pressure ratios 2, 3, 4 and 5 confirm the superiority of modified jet (jet from trailing edge modified nozzle) over plain jet from the mixing point of view. At all the pressure ratios, the modified jet possessed shorter core and weaker shock and expansion waves compared to plain jet, which is an outcome of faster mixing of modified jet with ambient fluid. The enhanced mixing caused the modified jet to decay faster than the plain jet. An appreciable core length reduction of about 32% is noticed at pressure ratio of 5. The modified jet experienced increased spread along major axis than along minor axis owing to the restriction offered by the triangular extension on jet spread along minor axis. Thus, the axis switching was absent in modified jet compared to plain jet switching axes at all pressure ratios. The shadowgraph images confirmed the presence of weaker waves in the modified jet. Also, the images confirmed the absence of Mach disk in the modified jet at pressure ratio of 5 compared to plain jet.

Spin-filtering properties of topological structures based on stanene and bismuthene nanoribbons with one edge magnetism

The transport properties of spin filters based on two-dimensional magnetic topological insulators (TI) with magnetism at one edge are theoretically studied. The non-equilibrium-Green’s-function (NEGF) formalism based on density functional theory (DFT) derived Hamiltonian is used to study the one-way helical edge states in these structures. We investigated the electronic and magnetic properties of stanene and bismuthene nanoribbons with various metal edge modifications. Our DFT simulations predict the formation of one-way helical edge states in stanene nanoribbons with asymmetric edge passivation. Our results suggest that the spin filtering properties of such structures outperform a comparable spin filter based on spin-polarized quantum-anomalous-Hall effect, as it bypasses a need for a strict interplay of magnetism, topology, and a large electric field (around 2 V gate voltage difference).

On the dynamics and wear properties of dry friction bearings in motor rotor system considering rough surface contact damping

Maintaining rotor stability and reducing bearing wear hold practical significance for the rotor system. However, the dynamic properties of rotor system supported by dry friction bearings are unknown, hindering effective bearing optimization. To tackle this issue, a 5-degree-of-freedom dynamics model is established for the motor rotor system of the outdoor unit supported by porous bearings. The rough surface damping contact model is employed to calculate the contact performance of the dry friction bearings. The effects of bearing edge modification on system dynamics and bearing wear properties are investigated and compared with well-lubricated bearings. The results demonstrate that an appropriate amount of edge modification can decelerate the impact between the rotor and the bearings and reduce wear under dry friction conditions.

Real-time adaptive scheduling optimization for inter-satellite contact window resources in dynamic satellite networks

Real-time scheduling of contact window resources is a fundamental technology for the future construction of Space–Terrestrial Integrated Networks (STIN). The spatio-temporal dynamics of satellite networks result in continuous variations in satellite relative positions and inter-satellite visibility window resource status. Furthermore, frequent changes in task priority make real-time resource scheduling extremely challenging. Centralized online scheduling methods often lead to a significant amount of waiting time, while distributed online scheduling methods struggle to adapt to the high dynamics of satellite networks. Therefore, the real-time scheduling technology for contact window resources in satellite networks is still in the exploration phase. We propose an inter-satellite online resource allocation method to solve the latency issue caused by the seizure of contact window resources. First, we determine the shortest and maximum flow paths set in the satellite network according to task requirements and construct them as the core network. Then, we comprehensively analyze the supply and demand situation of the task and the core network at a specific moment and verify the reliability of our minimum cost flow-solving method based on the core network. Moreover, we consider factors such as changes in task priority and edge modifications and validate the correctness of our method to update the minimum cost flow at the next moment based on local network changes. Finally, through extensive comparative simulations, we evaluate the absolute advantage of our inter-satellite online scheduling method and validate a significant improvement in task scheduling timeliness.

Existence of long-range magnetic order in Heisenberg spin nanoribbons with edge modification

Long-range magnetic order appears on a side decorated Heisenberg spin nanoribbon at nonzero temperature, although no spontaneous magnetization exists in a one- or two-dimensional isotropic Heisenberg model at any nonzero temperature according to the Mermin–Wagner theorem. By use of the spin Green’s function method, we calculated the magnetizations of Heisenberg nanoribbons decorated by side spins with single-ion anisotropy and found that the system exhibits a nonzero transition temperature, whether the decorated edge spins of the system link together or separate from each other. When the width of the nanoribbon achieves infinite limit, the transition temperatures of the system tend to the same finite constant eventually whether one edge or both edges are decorated by side spins in the nanoribbon. The results reveal that the magnetism of a low-dimensional spin system is different from that of a three-dimensional spin system. When the single-ion anisotropy of edge spins in a Heisenberg spin nanoribbon can be modulated by an electric field experimentally, various useful long-range magnetic orders of the system can be obtained. This work can provide a detailed theoretical basis for designing and fabricating next-generation low-dimensional magnetic random-access memory.

Modification-fair cluster editing

The classic Cluster Editing problem (also known as Correlation Clustering) asks to transform a given graph into a disjoint union of cliques (clusters) by a small number of edge modifications. When applied to vertex-colored graphs (the colors representing subgroups), standard algorithms for the NP-hard Cluster Editing problem may yield solutions that are biased towards subgroups of data (e.g., demographic groups), measured in the number of modifications incident to the members of the subgroups. We propose a modification fairness constraint which ensures that the number of edits incident to each subgroup is proportional to its size. To start with, we study Modification-Fair Cluster Editing for graphs with two vertex colors. We show that the problem is NP-hard even if one may only insert edges within a subgroup; note that in the classic “non-fair” setting, this case is trivially polynomial-time solvable. However, in the more general editing form, the modification-fair variant remains fixed-parameter tractable with respect to the number of edge edits. We complement these and further theoretical results with an empirical analysis of our model on real-world social networks where we find that the price of modification-fairness is surprisingly low, that is, the cost of optimal modification-fair solutions differs from the cost of optimal “non-fair” solutions only by a small percentage.

Investigations of specific modifications in pump as turbine towards performance improvement

ABSTRACT Centrifugal pumps as turbines offer a proven green energy solution for sustainable development, potentially replacing costly custom turbines in micro-hydro power plants and providing cost savings. But the efficiency of the pump as a turbine is lower than that of the dedicatedly designed pump. In this study, new simple modifications are proposed and evaluated on a developed state-of-the-art PAT test rig with impeller of specific speed 43.7 (m-m3/s). Being simple modifications, cost benefits will remain intact without requiring specially designed turbines and trained manpower. New simple modifications in PAT, like balance holes filling, packing seal optimization with appropriate size, leading edge of impeller blade tips modification making it single curve, and inner shroud widening for increasing the width at the inlet of the impeller, were proposed and performed to investigate the influence of the modifications on PAT performance. The experimental study finds that optimal packing seal size and impeller leading edge modifications notably boost PAT efficiency by 3–3.5%, making it worthwhile to implement for resource conservation and performance enhancement. On the other side, inner shroud widening noticed a 1.2% reduction in efficiency, adversely affecting the performance of PAT. Additionally, balance hole filling is neutral and does not have any effect.

Modulation of dual-spin filtering by edge-hybridized pairing of β-SiC7 nanoribbons

Atomic capping is a common approach in edge modification to tune band engineering and can be achieved experimentally through hydrogen plasma etching. Based on first-principles calculations, nine symmetric and asymmetric structures are constructed with different numbers of hydrogen atoms passivated at the edge of β-SiC7 nanoribbons. An in-depth study reveals that different edge hydrogenations realize the transition from semiconductors to half-metals to metals, firstly, because different numbers of hydrogen atoms lead to different edge atomic orbital hybridizations, and, more importantly and specifically, because the bands around the Fermi level of β-SiC7 nanoribbons are all derived from the spatially separated edge states, so that arbitrary pairings of upper and lower edge hybridizations are able to diversify the bands near the Fermi level and bring about a richer electronic properties. We also design the metallic H-zSiC7NR-H and semiconducting 2H-zSiC7NR-H into a heterojunction, which possesses good dual spin filtering properties at low bias, can achieve a spin polarization transition from -100 % to 100 %, and exhibits the NDR phenomenon. These findings suggest that β-SiC7 nanoribbons have promising applications in the field of spintronics.

Influence of surface and edge profile of a spinning disc on its atomization characteristics in direct drop mode

A spinning disc in direct drop regime is useful for contacting applications using one stream as drops. Here, we presenta systematic probe into the effect ofseveral edge and surface modification strategies on droplet characteristics. The characteristics of interest in this study are mean sizes of primary and secondary drops and their spread around respective mean values, and the evenness of circumferential distribution of drops. Exposure controlled static imaging is used to obtain blur free images in high resolution. Concentric grooving on surface offered stable film under limited flow condition, improves circumferential distribution, and significantly eliminates secondary drop formation. Serration at the disc edge controls the pitch of the drop detachment points, a feature naturally unique to only ligament mode. A new scale named maldistribution index (MI) is proposed to quantify circumferential distribution of released droplets.

Electronic properties and modulation effects on edge-modified GeS<sub>2</sub> nanoribbons

GeS<sub>2</sub> monolayers have been successfully prepared in this work. To further expand their applications and discover new physical properties, we construct armchair-type GeS<sub>2</sub> nanoribbons (AGeS<sub>2</sub>NR) and use different concentrations of H and O atoms for the edge modificationand their structural stabilities, electronic properties, carrier mobilities, and physical field modulation effects are studied in depth. The results show that the edge-modified nanoribbon has a higher energy and thermal stability. The bare edge nanoribbon is a nonmagnetic semiconductor, while the edge modification can change the bandgap of AGeS<sub>2</sub>NR and make it a wide or narrowed bandgap semiconductor, or a metal, which is closely related to the elimination or partial elimination of the edge states or the creation of hybridization bands. Thus edge modification extends the application range of nanoribbons in the fields of electronic devices and optical devices. In addition, the carrier mobility is found to be very sensitive to the edge modification: the carriers’ (electrons’ and holes’) mobilities of nanoribbons can be adjusted to a difference of up to one order of magnitude, and the difference in carrier mobility polarization can be tuned to one order of magnitude. Strain effect studies reveal that the semiconducting nanoribbons are robust in keeping the electronic phase unchanged over a wide strain range, which is useful for maintaining the stability of the electron transport in the related device. Most of the semiconducting nanoribbons have the stability to keep the semiconducting properties unchanged under high external electric field, but the bandgap can be reduced significantly with the increase of the electric field. In short, this study provides a theoretical analysis and reference for understanding the property of GeS<sub>2</sub> nanoribbons and developing related devices.

Inducing abundant magnetic phases and enhancing magnetic stability by edge modifications and physical regulations for NiI2 nanoribbons.

Recently, a magnetic semiconducting NiI2 monolayer was successfully fabricated. To obtain richer magneto-electronic properties and find new physics for NiI2, we studied the zigzag-type NiI2 nanoribbon (ZNiI2NR) with edges modified by different concentrations of H and/or O atoms. Results show that these ribbons hold a higher energy stability, thermal stability, and magnetic stability, and the Curie temperature can be increased to 143 from 15 K for the bare-edged ribbons. They feature a half-semiconductor, bipolar magnetic semiconductor, or half-metal, depending on the edge-terminated atomic species and concentrations, and are closely related to the ribbon edge states, impurity bands or hybridized bands. By applying strain or an electric field, ribbons can achieve a reversible multi-magnetic phase transition among a bipolar magnetic semiconductor, half-semiconductor, half-metal, and magnetic metal. This is because strain changes the Ni-I bond length, resulting in a variation of bond configurations (weight of ionic and covalent bonds) and the number of unpaired electrons. The compressive strain can increase the Curie temperature because it makes the edged Ni-I-Ni bond angle closer to 90°, leading to the FM d-p-d superexchange interaction being increased. The electric field varies the magnetic phase because it alters the electrostatic potential of the ribbon edges, and the Curie temperature is enhanced under the electric field because the ribbon is changed to a metallic state (half-metal or magnetic metal), in which the magnetic Ni atoms satisfy the Stoner criterion and hold a large magnetic exchange coefficient and electron state density at the Fermi surface.

EM-IFCM: Fuzzy c-means clustering algorithm based on edge modification for imbalanced data

The improved fuzzy c-means (IFCM) algorithm is an effective technique for handling the “uniform effect” in imbalanced data clustering; it adjusts the weight of each class based on the fuzzy size between clusters. However, the IFCM algorithm produces a “siphon effect” as the imbalance rate increases. It misclassifies the samples in small classes into large ones. Our analysis shows that this effect occurs because all samples have the same weight value of the same classes, the membership values are polarized, resulting in the model failing to converge to the correct interval. Thus, we propose an imbalanced fuzzy c-means clustering based on edge modification (EM-IFCM) algorithm to alleviate the “siphon effect” of the IFCM algorithm. It exhibits stronger inter-class separability by dynamically adjusting the weight of the samples to enhance the influence of edge samples on the model. In addition, we analyze the effectiveness and complexity of the algorithm and proved its convergence. Finally, we conduct extensive experiments on synthesis, machine-learning, and image-segmentation datasets and compare the results with those of six algorithms. The experimental results show that EM-IFCM has higher accuracy and exhibits an imbalance rate that is at least 1.94 times higher than that of the other algorithms.

Band alignment and crystal stability of Y3Al5−xGaxO12 garnets using density functional theory with hybrid functional

In this study, the dependence of band gap, band alignment, and structural stability of Y3Al5−xGaxO12 garnet (YAGG) solid solutions on Ga content (x) have been investigated using density functional theory (DFT) with PBE0 hybrid functional. The most stable model of YAGG for each x is identified using evolutionary algorithm-based USPEX method. The band alignment was determined by connecting valence band maximum (VBM) and conduction band minimum (CBM) to vacuum level via macroscopic average electrostatic potential of the slab model. Solid solution formation energy as a function of x indicates that YAGG with x = 3.0 (Y3Al2Ga3O12) exhibits remarkable structural stability. At x = 3.0, the analysis of the formation energy contribution shows a dominant contribution from electronic charge redistribution energy while there is no contribution from distortion energy. Bader charge, electron localization function, as well as the projected density of state analysis reveal a strong covalent character of Ga under oxygen tetragonal environment. The calculated PBE0 band gap as a function of x agrees well with the experimental results. Ga admixing significantly lowers the CBM, which exhibits a potential to envelop the shallow electron traps from the forbidden gap. The YAGG band alignment calculated using the proposed vacuum-connecting method is consistent with VRBE results from experiment. The proposed methods used to model site-preferred solid solution and calculate the vacuum-connected band alignment are viable in predicting structural stability and band edge modification via compositional engineering of garnet solid solutions. We expect that this work provides a promising strategy for material design through compositional engineering in obtaining high stability and enhanced performance in garnet compounds.

A Node Differential Privacy-Based Method to Preserve Directed Graphs in Wireless Mobile Networks

With the widespread popularity of Wireless Mobile Networks (WMNs) in our daily life, the huge risk to disclose personal privacy of massive graph structure data in WMNs receives more and more attention. Particularly, as a special type of graph data in WMNs, the directed graph contains an amount of sensitive personal information. To provide secure and reliable privacy preservation for directed graphs in WMNs, we develop a node differential privacy-based method, which combines differential privacy with graph modification. In the method, the original directed graph is first divided into several sub-graphs after it is transformed into a weighted graph. Then, in each sub-graph, the node degree sequences are obtained by using an exponential mechanism and micro-aggregation is adopted to get the noised node degree sequences, which is used to generate a synthetic directed sub-graph through edge modification. Finally, all synthetic sub-graphs are merged into a synthetic directed graph that can preserve the original directed graph. The theoretical analysis proves that the proposed method satisfies differential privacy. The results of the experiments demonstrate the effectiveness of the presented method in privacy preservation and data utility.

Photonic Realization of a Generic Type of Graphene Edge States Exhibiting Topological Flat Band.

Cutting a honeycomb lattice (HCL) ends up with three types of edges (zigzag, bearded, and armchair), as is well known in the study of graphene edge states. Here, we propose and demonstrate a distinctive twig-shaped edge, thereby observing new edge states using a photonic platform. Our main findings are (i)the twig edge is a generic type of HCL edge complementary to the armchair edge, formed by choosing the right primitive cell rather than simple lattice cutting or Klein edge modification; (ii)the twig edge states form a complete flat band across the Brillouin zone with zero-energy degeneracy, characterized by nontrivial topological winding of the lattice Hamiltonian; (iii)the twig edge states can be elongated or compactly localized at the boundary, manifesting both flat band and topological features. Although realized here in a photonic graphene, such twig edge states should exist in other synthetic HCL structures. Moreover, our results may broaden the understanding of graphene edge states, as well as new avenues for realization of robust edge localization and nontrivial topological phases based on Dirac-like materials.

Graph Anomaly Detection via Multi-Scale Contrastive Learning Networks with Augmented View

Graph anomaly detection (GAD) is a vital task in graph-based machine learning and has been widely applied in many real-world applications. The primary goal of GAD is to capture anomalous nodes from graph datasets, which evidently deviate from the majority of nodes. Recent methods have paid attention to various scales of contrastive strategies for GAD, i.e., node-subgraph and node-node contrasts. However, they neglect the subgraph-subgraph comparison information which the normal and abnormal subgraph pairs behave differently in terms of embeddings and structures in GAD, resulting in sub-optimal task performance. In this paper, we fulfill the above idea in the proposed multi-view multi-scale contrastive learning framework with subgraph-subgraph contrast for the first practice. To be specific, we regard the original input graph as the first view and generate the second view by graph augmentation with edge modifications. With the guidance of maximizing the similarity of the subgraph pairs, the proposed subgraph-subgraph contrast contributes to more robust subgraph embeddings despite of the structure variation. Moreover, the introduced subgraph-subgraph contrast cooperates well with the widely-adopted node-subgraph and node-node contrastive counterparts for mutual GAD performance promotions. Besides, we also conduct sufficient experiments to investigate the impact of different graph augmentation approaches on detection performance. The comprehensive experimental results well demonstrate the superiority of our method compared with the state-of-the-art approaches and the effectiveness of the multi-view subgraph pair contrastive strategy for the GAD task. The source code is released at https://github.com/FelixDJC/GRADATE.

Edge Modification and Site-Selective Functionalization of Graphene Quantum Dots: A Versatile Technique for Designing Tunable Optoelectronic and Sensing Devices.

This work successfully traces the imprints of zigzag/armchair-edge modification and site-selective functionalization by different chemical species in dictating the structural, electronic, and optical properties of low-symmetry structural isomers of graphene quantum dots (GQDs). Our time-dependent density functional theory-based computations reveal that the electronic band gap reduction is greater for zigzag-edge functionalization than for armchair-edge modification by chlorine atoms. The computed optical absorption profile of functionalized GQDs exhibits an overall red shift with respect to their pristine counterpart, with the shift being more pronounced at higher energies. Markedly, the optical gap energy is regulated more substantially by zigzag-edge chlorine passivation while the armchair-edge chlorine functionalization is more effective in altering the position of the most intense (MI) absorption peak. The MI peak energy is exclusively decided by the significant perturbation in the electron-hole distribution produced by the structural warping of the planar carbon backbone realized by edge-functionalization while the interplay between frontier orbital hybridization and structural distortion governs the energies of the optical gap. In particular, the enhanced tunability range of the MI peak in comparison to the optical gap variation signals that the structural warping plays a more decisive role in modulating the MI peak characteristics. The energy of the optical gap and the MI peak along with the charge-transfer character of the excited states is critically dependent on the electron-withdrawing capability and the site of the functional group. This comprehensive study is extremely crucial for promoting the application of functionalized GQDs in designing highly efficient tunable optoelectronic devices.