Stable Cluster Structure Research Articles

Cluster energy prediction based on multiple strategy fusion whale optimization algorithm and light gradient boosting machine

BackgroundClusters, a novel hierarchical material structure that emerges from atoms or molecules, possess unique reactivity and catalytic properties, crucial in catalysis, biomedicine, and optoelectronics. Predicting cluster energy provides insights into electronic structure, magnetism, and stability. However, the structure of clusters and their potential energy surface is exceptionally intricate. Searching for the global optimal structure (the lowest energy) among these isomers poses a significant challenge. Currently, modelling cluster energy predictions with traditional machine learning methods has several issues, including reliance on manual expertise, slow computation, heavy computational resource demands, and less efficient parameter tuning.ResultsThis paper introduces a predictive model for the energy of a gold cluster comprising twenty atoms (referred to as Au20 cluster). The model integrates the Multiple Strategy Fusion Whale Optimization Algorithm (MSFWOA) with the Light Gradient Boosting Machine (LightGBM), resulting in the MSFWOA-LightGBM model. This model employs the Coulomb matrix representation and eigenvalue solution methods for feature extraction. Additionally, it incorporates the Tent chaotic mapping, cosine convergence factor, and inertia weight updating strategy to optimize the Whale Optimization Algorithm (WOA), leading to the development of MSFWOA. Subsequently, MSFWOA is employed to optimize the parameters of LightGBM for supporting the energy prediction of Au20 cluster.ConclusionsThe experimental results show that the most stable Au20 cluster structure is a regular tetrahedron with the lowest energy, displaying tight and uniform atom distribution, high geometric symmetry. Compared to other models, the MSFWOA-LightGBM model excels in accuracy and correlation, with MSE, RMSE, and R2 values of 0.897, 0.947, and 0.879, respectively. Additionally, the MSFWOA-LightGBM model possesses outstanding scalability, offering valuable insights for material design, energy storage, sensing technology, and biomedical imaging, with the potential to drive research and development in these areas.Graphical

Regulating Polysulfide Transformation and Stabilizing Lithium Anode Using [PMo12O40]3− Cluster@Carbon Nanotube‐Modified Separator for Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li−S) batteries emerge as compelling contenders for next‐generation energy‐storage devices, boasting a noteworthy mass‐specific energy of 2600 Wh kg−1. However, the cycle stability and commercialization of Li−S batteries encounter challenges because of polysulfide shuttle and uncontrolled lithium dendrite growth. In this study, we present a polyoxometalates‐based dual‐function [PMo12O40]3− cluster@carbon nanotube modified polypropylene (PP) separator (PMo12@CNT/PP) to regulate polysulfide transformation and safeguard the lithium anode in Li−S batteries. Leveraging its multi‐electron redox properties and stable cluster structure, the PMo12 cluster acts as a polysulfide mediator, effectively capturing and promoting electrochemical polysulfide transformation. The incorporation of CNT fosters consistent Li‐ion nucleation, stabilizes the lithium anode, and impedes dendrite formation throughout cycling. Hence, Li−S cells equipped with the PMo12@CNT/PP separator display higher capacity and better stability (675 mAh g−1 at 3.0 C and 0.02 % capacity decay per cycle over 700 cycles). The pouch cells with a sulfur loading 4.5 mg cm−2 exhibit an initial discharge specific capacity of 925 mAh g−1 at 0.1 C, and remain 849 mAh g−1 after 40 cycles, underscoring the significant potential for practical applications of Li−S batteries.

Cluster structure of doped atoms and elastic properties in γ-Ni by first-principles calculations

The cluster structure with two doped atoms (M: W, Mo, Cr, Ti, Ta, Nb, Ru, Re, Al, Co) in γ-Ni was constructed and investigated by first-principles calculations. The doped systems had the most stable cluster structure along 〈100〉 directions except for the 〈111〉 direction of Ru. The W, Mo, Cr, Ti, Re, Al, Co and Ru tended to form the “-M-M-” linear cluster structure, while the Ta and Nb formed the “-M-Ni-M-” linear cluster structure. The doped systems were ductile and enhanced with the addition of M atoms except for Ru atom, while only Ru atom improved the Young's modulus and shear modulus. Cr and Co atoms increased the anisotropy factor, while Ti, Ta, Nb and Ru atoms decreased the anisotropy factor. From the electronic basis, the charge redistribution and the orbital hybridization between the M atoms and Ni atoms contributed to the stability of cluster structure. The modulus anisotropy caused by the linear cluster structure was due to the change in differential charge density along different directions.

Noncanonical vortex states and dynamics in Bose-Einstein condensates

Vortex excitations triggered by nonlinear interactions in Bose-Einstein condensates have attracted interest in the study of ultracold atoms. However, most studies focus on canonical vortex states with integer topological charges. In this paper, we study the dynamic properties of noncanonical vortex condensates with three phase distributions: power-exponent, new type power-exponent and oscillation type. The results show that the noncanonical vortices are dynamic unstable and their density distributions obviously depend on the phase parameters of the initial optical phase masks. Different noncanonical vortices decay into canonical clusters with diverse configurations showing rich topological excitation patterns. In particular, a new power exponential noncanonical vortex state decays into a stable canonical polygonal vortex cluster structure. Because the phase structures of the noncanonical optical vortices destroy the rotational symmetry of the condensate, the angular momentum of the condensate is no longer quantized, and its value changes with the power of the azimuthal angle of the optical field or the oscillation frequency, which is obviously different from the evolution of the corresponding noncanonical vortex optical field itself. In the dynamical process, the center-of-mass trajectory of noncanonical vortex condensates with the new type of power exponent phase is always a point, while for the noncanonical vortex condensates with power exponent and oscillating phase, the center-of-mass trajectories are ellipses centering at the origin of coordinates.

Methods of Sustainable Clustering of Russian Regions by Employment

The problem of the imbalance in the labor market of the Russian Federation cannot be solved without leveling the heterogeneity of its regions by socio-economic and demographic characteristics, since the labor market is a dynamic complex system that is influenced by a variety of factors, such as the economic, demographic situation, quality of education, interests of market participants, technological progress and digitalization, psychological aspects, etc. The article discusses the application of cluster and discriminant analysis methods on socio-economic data, highlights the regional features of the labor market in Russia. Cluster analysis was carried out using traditional hierarchical and iterative methods: the “Nearest Neighbor” method, the “Far Neighbor” method, the “Ward” method and the k-means method, as well as the fanny fuzzy clustering method. The results obtained by these five methods were evaluated for consistency. The conducted discriminant analysis allowed us to obtain a stable cluster structure in terms of the number of employed people by type of economic activity, dividing the regions of Russia into four main groups characterized by positive, average, neutral and negative behavior. Thanks to the construction of profiles of the obtained clusters, poorly informative types of economic activity were identified, employment in which has little effect on the division of regions into groups. The article evaluates the errors of cluster analysis methods for the final stable clustering. The regions with high and low levels of employment are analyzed, atypical subjects of the Russian Federation are identified and their industry specialization is considered. A comparative analysis of the formed groups and atypical regions was carried out, regions that can be conditionally assigned to any cluster were identified. The final typologization of the regions of Russia by the number of employed by type of economic activity has been developed taking into account territorial, social, sectoral and climatic features.

Evaluation of the experimental and computed properties of choline chloride-water formulated deep eutectic solvents

In this study, experimental and computed IR and Raman spectroscopic techniques helped to prove how water as a sole hydrogen bond donor (HBD) participates to form a deep eutectic solvent. Interactions among the components and contributions of the water and chloride have been successfully illustrated by quantum chemical (QC) and radial distribution function (RDF) calculations. These studies suggested that the spontaneous intercalation of water molecules with choline chloride (ChCl) helps to attain the stable cluster structure, where Cl- works as a bridge among the Ch+ and water molecules. Hydrogen bonds played major roles to form the water-based DESs. Solubilities of the studied drug molecules were found to be 1.3 to 6.7 times higher in the solvents than their solubilities in water. Cell viability assay of the WDES1 (1:3 ChCl:H2O) compared to dimethyl sulfoxide (DMSO) against HEK293 cell line proved that the solvent is applicable to the biological system. The RDF analysis from MD simulation suggest the spontaneous intercalation of water molecule in Choline Chloride structure disrupted the ordered structure as well as the Cl-, working as bridge in between Ch+ and water.

EEMDS: An Effective Emergency Message Dissemination Scheme for Urban VANETs.

In Vehicular Adhoc Networks (VANETs), disseminating Emergency Messages (EMs) to a maximum number of vehicles with low latency and low packet loss is critical for road safety. However, avoiding the broadcast storm and dealing with large-scale dissemination of EMs in urban VANETs, particularly at intersections, are the challenging tasks. The problems become even more challenging in a dense network. We propose an Effective Emergency Message Dissemination Scheme (EEMDS) for urban VANETs. The scheme is based on our mobility metrics to avoid communication overhead and to maintain a stable cluster structure. Every vehicle takes into account its direction angle and path loss factor for selecting a suitable cluster head. Moreover, we introduce estimated link stability to choose a suitable relay vehicle that reduces the number of rebroadcasts and communication congestion in the network. Simulation results show that EEMDS provides an acceptable end-to-end delay, information coverage, and packet delivery ratio compared to the eminent EM dissemination schemes.

Mobility prediction-based efficient clustering scheme for connected and automated vehicles in VANETs

Forming a stable cluster structure with minimum cost is essential to develop an efficient and reliable communication infrastructure for connected and automated vehicles (CAVs). In this paper, a novel mobility prediction-based efficient clustering scheme (MPECS) is proposed. The basic idea of MPECS is to divide the whole region into distinct areas using Voronoi diagram; so that each vehicle can predict its own longevity and cost of being the cluster head in its current area. MPECS introduces a novel combined metric called the vehicle lifetime value to characterize the vehicle impact on both clustering stability and cost. An analytical analysis is discussed to explore the parameters set that improves the overall performance of MPECS. Also, performance evaluation via simulation is presented to evaluate MPECS compared to four existing clustering schemes for VANETs. The conducted evaluations show a close agreement between simulation and analytical results and demonstrate that MPECS can significantly improve the stability of the clustering architecture with minimal overhead.

Structural Characterization of Molybdenum Oxide Nanoclusters Using Ion Mobility Spectrometry–Mass Spectrometry and Infrared Action Spectroscopy

Polyoxometalate clusters possess unique catalytic and electromagnetic properties. The structure and function of polyoxometalates is dictated by complex oligomerization processes, which in turn depend on the solution conditions. In this work, small gas-phase polyoxomolybdate nanoclusters (HMonO3n+11–, n = 1–8, and MonO3n+12–, n = 2–8) were investigated after nanoelectrospray of an acidified solution of ammonium heptamolybdate heptahydrate by ion mobility spectrometry–mass spectrometry (IMS–MS), infrared multiple photon dissociation (IRMPD) spectroscopy, and infrared action spectroscopy in helium nanodroplets. The spectra and collision cross sections obtained were matched to predictions from density-functional theory (DFT) to unravel the structural progression of nanoclusters with increasing size. For doubly charged clusters, transitions among chain (n = 2–3), ring (n = 4–5), and compact (n ≥ 6) structures are observed in IMS–MS and IR spectroscopy experiments, in agreement with low-energy structures from DFT calculations. For singly charged clusters, reduced Coulombic repulsion and hydrogen bonding interactions are found to strongly influence the most stable cluster structure. Notably, a noncovalent ring structure is observed for HMo3O101–, stabilized by a strong intramolecular hydrogen bond, and a compact structure is observed for HMo5O161–, in contrast to the ring structure favored for Mo5O162–.

CuS/MnS composite hexagonal nanosheet clusters: Synthesis and enhanced pseudocapacitive properties

The CuS/MnS composite hexagonal nanosheet clusters were fabricated through a one-step facile hydrothermal method without any surfactant. The adding of CuS plays a role of template for the growth of CuS/MnS composite, as CuS can induce the growth of MnS, forming a stable three-dimensional cluster structure composed by hexagonal nanosheets, which provides easy access of electrolyte, effective electronic transmission and stable circulation structure. The as synthesized CuS/MnS composite electrode (3 h) shows a high specific capacitance (1144 F g-1 at 1 A g−1), which is five times higher than that of either CuS or MnS electrode under the same conditions, excellent rate property (567 F g-1 at 50 A g−1 and 40.8% rate retention even at 100 A g−1), and good cycling stability (85.9% of the initial capacity after 10000 cycles). So, the CuS/MnS nano-composite should be a promising candidate electrode material for supercapacitors.

An Efficient Clustering in MANETs with Minimum Communication and Reclustering Overhead

A flat structure in MANETs based on proactive or reactive routing schemes face scalability problems with increase in both mobility and network size. Clustering offers hierarchical organization of mobile nodes by forming disjoint groups (clusters). So clustering techniques solve the scalability issue in large MANETs but, requires extra message exchange among mobile nodes for maintenance of cluster structure. Due to mobility in MANETs stability of cluster structure is greatly affected as such it often leads to Ripple effect of reclustering. In this paper, the authors present clustering algorithm that eliminates the requirement of frozen period and minimizes reclustering of entire network by locally repairing cluster structure that gets affected due to moment of head node. They have reduced the number of messages exchanged in their proposed work by including different range of transmission for each node and overall stability of entire structure is enhanced.

Trust Factor Based Secure Congestion Control For Vanet

Weight-based clustering algorithm in ad hoc network is an on demand clustering algorithm for multi-hop packet radio network. These types of networks are ad hoc networks and dynamic in nature due to mobility of nodes. Clustering in mobile ad hoc network can be defined as various partitions into various groups. It is an important concept of VANNET, because clustering makes it possible to guarantee of system performance, such as throughput delay and also security issues. So in the algorithm they select the cluster head whose performance is well and formation of cluster in ad hoc network. The cluster head is elected based on weight factor, so it is called weighted clustering algorithm. Weighted clustering algorithm is basically appropriate cluster selection in wireless adhoc network where it is necessary to provide robustness in face of topological changes caused by node motion, node failure and node insertion or node removal. The WCA select the cluster head which has lowest weight among the nodes and some other factor also consider the election for cluster head. The cluster head, form a dominant set in the network, determine the topology and its stability. The weighted clustering algorithm takes into consideration the ideal degree, transmission power, mobility and battery power of nodes. Traffic efficiency applications are becoming increasingly popular over the road networks in the last few years. This type of applications aims mainly at increasing the traffic fluency over the road network, which minimizes the travel time of each vehicle towards its targeted destinations. The Vehicular Ad-Hoc Networks (VANETs) technology has been utilized to design these applications. Communications between vehicles, V2V, and between vehicles and installed Road Side Units (RSUs), V2I, helped designing these applications. Malicious, selfish and intruder drivers can take advantages of other cooperative drivers and use their trust. a Secure Congestion control protocol. This protocol aims to guarantee integrity and authenticity of transmitted data. It is designed to provide the security requirements of traffic efficiency protocols that have been proposed using the technology of VANETs. SCOOL also aims to preserve the privacy of the cooperative vehicles and drivers. The main contribution of work is new strategy for clustering a wireless ad hoc network and improvement in WCA. Author derived a simple stability model and a load balancing clustering scheme. They showed that the algorithm outperform in term of cluster formation and stability. Main idea of approach is to avoid cluster re-election and reduce the computation and communication cost. The improved weighted clustering algorithm, the goals of algorithm are maintaining stable clustering structure, minimizing the overhead for clustering set up, maximize lifetime of nodes in the system and achieving good performance. Keyword - Weight-based clustering, SCOOL, WCA, VANETs.

A Virtual Laboratory to Practice Mobile Wireless Sensor Networks: A Case Study on Energy Efficient and Safe Weighted Clustering Algorithm

In this paper, we present a virtual laboratory platform (VLP) baptized Mercury allowing students to make practical work (PW) on different aspects of mobile wireless sensor networks (WSNs). Our choice of WSNs is motivated mainly by the use of real experiments needed in most courses about WSNs. These experiments require an expensive investment and a lot of nodes in the classroom. To illustrate our study, we propose a course related to energy efficient and safe weighted clustering algorithm. This algorithm which is coupled with suitable routing protocols, aims to maintain stable clustering structure, to prevent most routing attacks on sensor networks, to guaranty energy saving in order to extend the lifespan of the network. It also offers a better performance in terms of the number of re-affiliations. The platform presented here aims at showing the feasibility, the flexibility and the reduced cost of such a realization. We demonstrate the performance of the proposed algorithms that contribute to the familiarization of the learners in the field of WSNs.

A Stable Clustering Scheme Based on Adaptive Multiple Metric in Vehicular Ad-hoc Networks

Vehicular Ad-hoc Networks (VANETs) are the special class of Mobile Ad-hoc Networks (MANETs) with high mobility and frequent changes of topology. Clustering is applied in VANETs to divide the network into smaller groups of mobile vehicles and improve routing, information dissemination and data gathering. In this paper, we propose a 2-layer stable clustering scheme based on adaptive multiple metric combining both the features of static and dynamic clustering methods. The cluster head is selected among the cluster members based on a new multiple metric called suitability value. It is derived from both mobility metrics such as relative speed, position and time to leave the road segment and Quality of Service metrics including available bandwidth, neighborhood degree and RSU link quality. Due to the proposed adaptive metric, the higher cluster stability as well as QoS is achieved. The simulation results clarify effectiveness of our proposed method in a highway scenario and show that our technique has better results and provides more stable cluster structure compared with the other related methods.

Two New Clustering Algorithms for Vehicular Ad-Hoc Network Based on Ant Colony System

In vehicular ad-hoc network (VANET), vehicles are dynamic nodes communicating with each other by wireless technology in their own transmission range. Consequently, with regard to larger communication due to the greater number of vehicles and high mobility of nodes, communication management and creation of a stable network in VANET are most challenging subjects. Hence, clustering as a possible solution to address this challenge, should take into consideration to produce stable clustering structure. Clustering technique is for organizing nodes into groups, making the network more robust and scalable. This paper introduces two new Improved Ant System-based Clustering algorithm (IASC1 and IASC2) suitable for dynamic environment of the VANET. Simulation is run to evaluate the introduced methods and compare them with the most commonly VANET clustering algorithms as found in the literature review. Results reveal the proposed algorithms have improved the stability and the runtime of VANET clustering algorithm and have a relatively good performance compared with other algorithms.

A Mobility Prediction-Based Weighted Clustering Algorithm for Vehicular Ad-Hoc Network

For dynamical changed network topology and unstable links, this paper proposes a mobility prediction-based weighted clustering algorithm for vehicular ad-hoc network with high mobility nodes. In the CH election stage, it computes vehicle’s priority through the similarity, intimacy and centrality, the vehicles with the highest priority in their neighborhoods are selected as the CHs, this scheme suitable for large scale network. NS2 simulation results show that the proposed clustering scheme improves the stability of cluster structure, prolongs the CH duration time, improves the delivery ratio.

Density functional theory study of structure characteristics and stabilities of Al2Sn(n=2-10) clusters

The geometric configurations and electronic structures of the Al2Sn (n=2-10) clusters are calculated by the B3LYP (density functional theory) method at 6-311G** level. The variations of the ground state structure, charge transfer and bonding characteristic of the aluminum-sulfur doped clusters are discussed in detail. The results show that the structures of pure Sn clusters are fundamentally changed due to the doping of the Al atoms. Our work exhibits that the all the ground states of Al2Sn clusters share the same four-member Al2S2 ring, and from single ring to three rings plane and three-dimensional structure structures are formed by inserting one S atom or S clusters. The stability of cluster structure is influenced by both the chemical bond structure and number. The stability information of Al2Sn clusters is obtained by analyzing the dissociation energies and the second-order difference energies of the ground state structures.

The Application of Ant Colony Optimization in Wireless Sensor Network Routing

The paper proposes wireless sensor clustering routing protocol based on ant colony algorithm(ACO). The method firstly uses the network self-topology to get a stable cluster structure based on modularity clustering algorithm; secondly make a new cluster-head selection function according to each cluster node residual energy and the distribution of cluster node; then we propose inter-cluster multi-hop routing algorithm based on ant colony optimization, which in order to balance the energy between consumption on the transmission path and residual one of cluster-head node, developing new ant transmission probability and pheromone updating strategy, we verify the validity of algorithm through simulation.

Thermal stability of cluster structure in Bi x Sn1− x molten alloys in vicinity of eutectic point

Structure of liquid Bi x Sn1− x molten alloys has been studies in the vicinity of eutectic point at temperatures of complete melting and above by 100 K. It is shown that the structure parameter concentration dependences reveal the deviation from linear function with extremum points at eutectic composition. Such features exist also at higher temperatures. The reason of untypical behaviour of structure parameters is supposed to be attributed to the existence of two kinds of clusters with Sn‐ and Bi‐like structures.

PassCAR: A passive clustering aided routing protocol for vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) are a promising architecture for vehicle-to-vehicle communications in the transportation field. However, the frequent topology changes in VANETs create many challenges to data delivery because the vehicle velocity varies with time. Thus, designing an efficient routing protocol for stable and reliable communication is essential. Existing studies show that clustering is an elegant approach to efficient routing in a mobile environment. In particular, the passive clustering (PC) mechanism has been validated as a more efficient approach compared to traditional clustering mechanisms. However, the PC mechanism was primarily designed for mobile ad hoc networks (MANETs), and may be unsuitable for constructing a cluster structure in VANETs because it does not account for vehicle behavior and link quality. In this paper, we propose a passive clustering aided routing protocol, named PassCAR, to enhance routing performance in the one-way multi-lane highway scenario. The main goal of PassCAR is to determine suitable participants for constructing a stable and reliable cluster structure during the route discovery phase. Each candidate node self-determines its own priority to compete for a participant using the proposed multi-metric election strategy based on metrics such as node degree, expected transmission count, and link lifetime. Simulation results show that, compared with the original PC mechanism, PassCAR not only increases the successful probability of route discovery, but also selects more suitable nodes to participate in the created cluster structure. This well-constructed cluster structure significantly improves the packet delivery ratio and achieves a higher network throughput due to its preference for reliable, stable, and durable routing paths.