Hopping Algorithm Research Articles

Interference robust channel hopping strategies for wireless sensor networks

Due to the shared nature of the wireless medium, the performance of wireless sensor network is often limited by both internal interference and external interference. The internal interference is that simultaneous traffic activity by neighboring nodes in the same network, while the external interference is from wireless transmissions by other types of devices, such as Wi-Fi and Bluetooth nodes. In this paper, we present two channel hopping algorithms for multichannel, single-radio wireless sensor networks. The first algorithm achieves collision-free transmission environment while do not introduce extra control overhead. The second algorithm, in addition to reducing internal interference effects, reduces the external interference effects from Wi-Fi devices. Simulation results show that both of them significantly improve performance in wireless sensor network.

Research on the Positioning in WSN Based on an Improved DV-HOP Algorithm

In order to reduce the positioning error of the sensor nodes, this paper first analyzes the reasons for the low accuracy of DV - HOP algorithm currently, and then proposes an improved DV - HOP algorithm. The algorithm can be divided into four stages, including data information overlapping stage, average skip distance calculation stage, optimum choice of anchor nodes and redundant node positioning. In the data information overlapping stage, the joint probability density is used for improvement; in the average skip distance calculation, the zero deviation estimation value is introduced; in the optimal selection of anchor nodes, optimal strategy is used; and the nodes are positioned in the redundant node positioning with the method of gradually increasing the skip distance. Simulation results show that the algorithm of this paper can effectively reduce the position error in calculation and improve the positioning accuracy.

Molcas 8: New capabilities for multiconfigurational quantum chemical calculations across the periodic table.

In this report, we summarize and describe the recent unique updates and additions to the Molcas quantum chemistry program suite as contained in release version 8. These updates include natural and spin orbitals for studies of magnetic properties, local and linear scaling methods for the Douglas-Kroll-Hess transformation, the generalized active space concept in MCSCF methods, a combination of multiconfigurational wave functions with density functional theory in the MC-PDFT method, additional methods for computation of magnetic properties, methods for diabatization, analytical gradients of state average complete active space SCF in association with density fitting, methods for constrained fragment optimization, large-scale parallel multireference configuration interaction including analytic gradients via the interface to the Columbus package, and approximations of the CASPT2 method to be used for computations of large systems. In addition, the report includes the description of a computational machinery for nonlinear optical spectroscopy through an interface to the QM/MM package Cobramm. Further, a module to run molecular dynamics simulations is added, two surface hopping algorithms are included to enable nonadiabatic calculations, and the DQ method for diabatization is added. Finally, we report on the subject of improvements with respects to alternative file options and parallelization.

Communication: Fully coherent quantum state hopping.

In this paper, we describe a new and fully coherent stochastic surface hopping method for simulating mixed quantum-classical systems. We illustrate the approach on the simple but unforgiving problem of quantum evolution of a two-state quantum system in the limit of unperturbed pure state dynamics and for dissipative evolution in the presence of both stationary and nonstationary random environments. We formulate our approach in the Liouville representation and describe the density matrix elements by ensembles of trajectories. Population dynamics are represented by stochastic surface hops for trajectories representing diagonal density matrix elements. These are combined with an unconventional coherent stochastic hopping algorithm for trajectories representing off-diagonal quantum coherences. The latter generalizes the binary (0,1) "probability" of a trajectory to be associated with a given state to allow integers that can be negative or greater than unity in magnitude. Unlike existing surface hopping methods, the dynamics of the ensembles are fully entangled, correctly capturing the coherent and nonlocal structure of quantum mechanics.

Surface hopping, transition state theory and decoherence. I. Scattering theory and time-reversibility.

We provide an in-depth investigation of transmission coefficients as computed using the augmented-fewest switches surface hopping algorithm in the low energy regime. Empirically, microscopic reversibility is shown to hold approximately. Furthermore, we show that, in some circumstances, including decoherence on top of surface hopping calculations can help recover (as opposed to destroy) oscillations in the transmission coefficient as a function of energy; these oscillations can be studied analytically with semiclassical scattering theory. Finally, in the spirit of transition state theory, we also show that transmission coefficients can be calculated rather accurately starting from the curve crossing point and running trajectories forwards and backwards.

Interatomic Coulombic decay in polyatomic rare-gas clusters

SynopsisA new method for a complete theoretical description of Interatomic Coulombic decay (ICD) in large polyatomic rare-gas clusters will be presented. This original method combines the projection-operator formalism of resonant scattering theory, the diatomics-in-molecules technique and a surface hopping algorithm. Such combined approach has fairly low computational costs and constitutes an efficient tool for studying ICD in polyatomic clusters. Benchmark examples will be given to illustrate the method. Results on ICD in large rare-gas clusters will finally be reported.

A Clustering Algorithm Based on Mobility Properties in Mobile Ad Hoc Networks

We propose a context-awareness routing algorithm—the DDV- (Dynamic Direction Vector-) hop algorithm—in mobile ad hoc networks. The existing algorithm in MANET has the limitations of the dynamic network topology and the absence of network expandability of the mobility of nodes. The proposed algorithm performs cluster formation for the base station using the range of direction and threshold of velocity. We calculate the exchange of the cluster head node probability using the direction and velocity for maintaining cluster formation. The DDV-hop algorithm, a probabilistic routing protocol for such networks, is proposed and then compared to the earlier presented algorithms through simulations. The simulations are conducted on a number of clusters, network areas, transmission ranges, and velocity of nodes in mobile networks. Our results suggest that the DDV-hop algorithm demonstrates efficiency of eventual delivery and maintains the proper number of clusters and cluster members regardless of topology changes with a lower communication overhead in several interesting environments.

Matrix-Based Channel Hopping Algorithms for Cognitive Radio Networks

Cognitive radio networks (CRNs) have emerged as a critical technique for solving spectrum shortage problems and enhancing the utilization of licensed channels. To prevent interference with the co-locate incumbent networks, before data transmission, nodes in CRNs should rendezvous on an available channel (i.e., idle licensed channel) for establishing a link or exchanging control information. However, implementing rendezvous is challenging because the availability of channels is time-varying and position-varying. For reducing rendezvous failure and increasing throughput, a node pair in CRN should be able to rendezvous on every licensed channels (i.e., maximizing rendezvous diversity) and rendezvous on an available channel as soon as possible (i.e., minimizing maximum conditional time to rendezvous (MCTTR)). Besides, to take full advantage of the frequency diversity of multi-channel medium access, rendezvous should be spread out in time and channel (i.e., minimizing channel loading). In this paper, we propose two rendezvous channel hopping algorithms, T-CH and D-CH, which can be used without time synchronization and role pre-assignment (each node has a pre-assigned role as either a sender or a receiver). D-CH requires that SUs in CRNs should have a unique ID (identifier), while T-CH does not. Both our T-CH and D-CH have maximum rendezvous diversity and minimum channel loading, and outperform in terms of MCTTR.

Stability of Hydrated Methylamine: Structural Characteristics and H2N···H-O Hydrogen Bonds.

Methylamine is the simplest aliphatic amine found in human urine, blood, and tissues. It is thought to play a significant part in central nervous system disturbances observed during renal and hepatic disease. In this work we have investigated the methylamine hydration clusters using a basin hopping (BH) algorithm with the density functional theory (DFT). The results presented herein yield a detailed understanding of the structure and stability for a system consisting of one methylamine molecule and up to seven waters: the most stable geometries arise from a fusion of tetramer or pentamer rings; by the geometrical parameters and topological parameters analysis, the strengths of the H2N···H-O hydrogen bonds of the global minima increase as the sizes of clusters increase, except for n = 5 where there is a slight fluctuation. This work may shed light on the form mechanism of methylamine existing in organisms and the hydration structures of larger molecules containing amino functional groups and their interaction with the water molecules nearby.

Application communication reliability of wireless sensor networks

This paper considers application communication reliability (ACR) of wireless sensor networks (WSNs) supporting K-coverage in the presence of shadowing for a specific monitored area. Application communication relates to the acquisition of sensed data from a specific area and network connectivity that concerns the reliable delivery of the observed data from sensor nodes to the sink node. The analytical evaluation of ACR involves two steps: first identifying all the K-coverage sets, and then evaluating the communication reliability of delivering the observed data from sensor nodes within the identified K-coverage sets to the sink node. Two single-path routing algorithms, shortest-path distance algorithm and shortest-path hop algorithm, are considered for evaluating the communication reliability during the second step. Their performances in terms of ACR and energy consumptions are compared through an empirical analysis of several examples. Results show that WSNs using the shortest-path distance algorithm are more reliable than those using the shortest-path hop algorithm in most cases, but consume more energy for delivering the sensed data to the sink node. Different scenarios are also considered to evaluate the impact of node density, channel condition and different monitored areas on ACR of WSNs.

에드 혹 네트워크에서 노드의 동적 속성 기반 클러스터링 알고리즘 연구

In this paper, we propose a context-awareness routing algorithm DDV (Dynamic Direction Vector)-hop algorithm in Mobile Ad Hoc Networks. The existing algorithm in MANET, it has a vulnerability that the dynamic network topology and the absence of network expandability of mobility of nodes. The proposed algorithm performs cluster formation using a range of direction and threshold of velocity for the base-station, we calculate the exchange of the cluster head node probability using the direction and velocity for maintaining cluster formation. The DDV algorithm forms a cluster based on the cluster head node. As a result of simulation, our scheme could maintain the proper number of cluster and cluster members regardless of topology changes.

Surface hopping outperforms secular Redfield theory when reorganization energies range from small to moderate (and nuclei are classical)

We evaluate the accuracy of Tully's surface hopping algorithm for the spin-boson model in the limit of small to moderate reorganization energy. We calculate transition rates between diabatic surfaces in the exciton basis and compare against exact results from the hierarchical equations of motion; we also compare against approximate rates from the secular Redfield equation and Ehrenfest dynamics. We show that decoherence-corrected surface hopping performs very well in this regime, agreeing with secular Redfield theory for very weak system-bath coupling and outperforming secular Redfield theory for moderate system-bath coupling. Surface hopping can also be extended beyond the Markovian limits of standard Redfield theory. Given previous work [B. R. Landry and J. E. Subotnik, J. Chem. Phys. 137, 22A513 (2012)] that establishes the accuracy of decoherence-corrected surface-hopping in the Marcus regime, this work suggests that surface hopping may well have a very wide range of applicability.

Surface hopping with a manifold of electronic states. I. Incorporating surface-leaking to capture lifetimes.

We investigate the incorporation of the surface-leaking (SL) algorithm into Tully's fewest-switches surface hopping (FSSH) algorithm to simulate some electronic relaxation induced by an electronic bath in conjunction with some electronic transitions between discrete states. The resulting SL-FSSH algorithm is benchmarked against exact quantum scattering calculations for three one-dimensional model problems. The results show excellent agreement between SL-FSSH and exact quantum dynamics in the wide band limit, suggesting the potential for a SL-FSSH algorithm. Discrepancies and failures are investigated in detail to understand the factors that will limit the reliability of SL-FSSH, especially the wide band approximation. Considering the easiness of implementation and the low computational cost, we expect this method to be useful in studying processes involving both a continuum of electronic states (where electronic dynamics are probabilistic) and processes involving only a few electronic states (where non-adiabatic processes cannot ignore short-time coherence).

A Simple Algorithm for Automatic Hopping among Pools in the Bitcoin Mining Network

A Simple Algorithm for Automatic Hopping among Pools in the Bitcoin Mining Network

STRUCTURE IN THE 3D GALAXY DISTRIBUTION. II. VOIDS AND WATERSHEDS OF LOCAL MAXIMA AND MINIMA

The major uncertainties in studies of the multi-scale structure of the Universe arise not from observational errors but from the variety of legitimate definitions and detection methods for individual structures. To facilitate the study of these methodological dependencies we have carried out 12 different analyses defining structures in various ways. This has been done in a purely geometrical way by utilizing the HOP algorithm as a unique parameter-free method of assigning groups of galaxies to local density maxima or minima. From three density estimation techniques (smoothing kernels, Bayesian Blocks and self organizing maps) applied to three data sets (the Sloan Digital Sky Survey Data Release 7, the Millennium Simulation and randomly distributed points) we tabulate information that can be used to construct catalogs of structures connected to local density maxima and minima. The resulting sizes follow continuous multi-scale distributions with no indication of the presence of a discrete hierarchy. We also introduce a novel void finder that utilizes a method to assemble Delaunay tetrahedra into connected structures and characterizes regions very nearly empty of galaxies in the source catalog.

A surface hopping algorithm for nonadiabatic minimum energy path calculations.

The article introduces a robust algorithm for the computation of minimum energy paths transiting along regions of near-to or degeneracy of adiabatic states. The method facilitates studies of excited state reactivity involving weakly avoided crossings and conical intersections. Based on the analysis of the change in the multiconfigurational wave function the algorithm takes the decision whether the optimization should continue following the same electronic state or switch to a different state. This algorithm helps to overcome convergence difficulties near degeneracies. The implementation in the MOLCAS quantum chemistry package is discussed. To demonstrate the utility of the proposed procedure four examples of application are provided: thymine, asulam, 1,2-dioxetane, and a three-double-bond model of the 11-cis-retinal protonated Schiff base.

Design of SCS Protocol and Analysis of Quality of Service Parameters for Wireless Sensor Networks

For wireless applications, significant research has been devoted to support real-time transmission with better quality of service requirements. For next generation, a wireless hybrid network that integrates a MANET (Mobile Adhoc Wireless Network) network has been proven to be a better alternative. Guaranteeing of QoS in hybrid networks remains an open problem. In this paper, we propose a new SCS protocol to enhance the QoS Support capability of hybrid networks. This SCS protocol incorporates four algorithms: 1) Path Selection Algorithm to identify the neighbouring node at shortest distance to reduce the delay 2) Routing Algorithm for hopping of data packets via different nodes.3) Mobility Algorithm to decrease the transmission time.4) Multipath Selection Algorithm in order to improve the QoS. Analytical and simulation results of SCS can provide high QoS performance in terms of delay, average delay, throughput, packet delivery ratio. The main objective of our project is to implement the routing protocols in NS2 and to compare simulation parameters like delivery ratio, end to end delay, packet drop, packet sent using SCS, AODV and DSR protocol to provide quality of service in wireless ad hoc network.

The Research of DV-HOP Positioning Algorithm Based on RSSI Calibration

Because of the DV-HOP algorithm in wireless sensor network (WSN), the first jump range error, which affect the positioning error of the whole node network problems. This paper puts forward an improved algorithm is proposed. The algorithm is mainly using the RSSI ranging technology, in the process of DV-HOP first jump range through correction of RSSI ranging technology, to reduce the distance measuring error, in order to improve positioning accuracy. The simulation results show that compared with traditional DV - HOP algorithm. The improved algorithm can without additional hardware and computation under the premise of improving positioning accuracy.

Optimization of the Wireless Sensor Nodes Localization Algorithm Based on Genetic Algorithm

The node localization technology is a foundation for practical application in wireless sensor networks. According to DV-HOP positioning algorithm in wireless sensor network low precision, the defect of inaccurate positioning, this paper presents an optimization algorithm of improved DV-HOP based on genetic algorithm. The algorithm is to redefine the scope of initial population, the reference weight, redesigned the fitness function and selection of anchor nodes. The simulation results show that compared with the traditional DV - HOP algorithm, the algorithm without any increase in the node hardware overhead on the basis of significantly higher positioning accuracy.

The Research of DV-HOP Positioning Algorithm Based on RSSI Calibration

Because of the DV-HOP algorithm in wireless sensor network (WSN), the first jump range error, which affect the positioning error of the whole node network problems. This paper puts forward an improved algorithm is proposed. The algorithm is mainly using the RSSI ranging technology, in the process of DV-HOP first jump range through correction of RSSI ranging technology, to reduce the distance measuring error, in order to improve positioning accuracy. The simulation results show that compared with traditional DV - HOP algorithm. The improved algorithm can without additional hardware and computation under the premise of improving positioning accuracy.