104 research outputs found
INTRUSION DETECTION FOR MANETS
No full text<p>Mobile Ad hoc networks are playing very important role in the present world. They are applied to several popular wireless technologies including cellular phone services, disaster relief, emergency services, battlefield scenarios, and other applications. MANETs are decentralized networks, and the network topology is unpredictably dynamic because of node mobility. As a result, mobile nodes in MANETs act as both hosts and routers since MANETs are decentralized; all mobile nodes need to discover the dynamic topology and deliver messages by themselves. MANETs rely on the cooperation of all mobile nodes in the network to ensure reliable routing services in the presence of dynamic topology caused by their mobility. The dynamic and cooperative nature of MANETs presents substantial challenges for network security. Therefore, sufficient protection should be provided to secure MANETs to guarantee the integrity of routing messages and availability of routing services. In other words, the goal of this dissertation is to examine how to secure the routing services of MANETs in order to provide reliable communication among nodes. </p>
RELATIVE STUDY OF OUTLIER DETECTION PROCEDURES
No full textData Mining just alludes to the extraction of exceptionally intriguing patterns of the data from the monstrous data sets. Outlier detection is one of the imperative parts of data mining which Rexall discovers the perceptions that are going amiss from the normal expected conduct. Outlier detection and investigation is once in a while known as Outlier mining. In this paper, we have attempted to give the expansive and a far reaching literature survey of Outliers and Outlier detection procedures under one rooftop, to clarify the lavishness and multifaceted nature connected with each Outlier detection technique. Besides, we have likewise given a wide correlation of the different strategies for the diverse Outlier techniques. Outliers are the focuses which are unique in relation to or conflicting with whatever is left of the information. They can be novel, new, irregular, strange or uproarious data. Outliers are in some cases more fascinating than most of the information. The principle difficulties of Outlier detection with the expanding many-sided quality, size and assortment of datasets, are the manner by which to get comparable Outliers as a gathering, and how to assess the Outliers data set
A Study of Reduced Order 4D-VAR with a Finite Element Shallow Water Model
No full textForecast models often depend on unknown parameters, such as model initial and boundary conditions, or other tunable parameters not necessarily having any physical meaning. Calibration of these parameters to minimize errors between forecasted and observed states is called data assimilation. A common approach in this context are variational methods, of which four dimensional data variation (4D-VAR) is studied in this thesis. In 4D-VAR, a cost function is defined that penalizes misfits between observations and the corresponding numerical model results, obtained by running the model with the chosen configuration. Performing optimization with regard to this cost function yields an improved initial parameter set. Associated with this type of methods, however, are difficulties in connection with programming the adjoint model, which is needed to compute the exact gradient of the cost function. Additionally, having to integrate the adjoint model backwards in time adds significantly to the computational cost of the data assimilation process. To avoid manual implementation of adjoint code and to reduce computational complexity, approximation of the gradient calculation is considered through the use of proper orthogonal decomposition (POD), a flexible data-driven order reduction method. To facilitate this, a finite element model of the shallow water equations is tested with both the full adjoint 4D-VAR method and two different POD-reduced approaches. Twin experiments are performed and comparisons are made in terms of accuracy, computational complexity and sensitivity to perturbation and number of observation points.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Model reduced variational data assimilation for shallow water flow models
No full textIdentifying uncertain parameters in large-scale numerical flow models can be done using the variational method. However, for implementing the variational method the adjoint model have to be available, which requires highly complex computer code and maintenance and thus hampers its applications. To ease this problem, this thesis has explored several methods for efficiently identifying uncertain parameters in a large-scale tidal model of the entire European continental shelf which does not require the implementation of these complex adjoint code. In this study, as a first step an estimation method based on model reduction is developed and investigated for the estimation of diffusion coefficient in a simple 2D-advection diffusion model. Two projection based model reduction methods were considered, namely proper orthogonal decomposition (POD) and Balanced proper orthogonal decomposition (BPOD). In the POD based estimation method an ensemble of forward model simulations is used to determine an approximation of the covariance matrix of the model variability and a small number of the leading eigenvectors of this matrix is used to define a model subspace. By projecting the original model onto this subspace an approximate linear reduced model is obtained. Once the reduced model is available its adjoint can be implemented easily and the minimization problem is solved completely in reduced space with very low computational cost. BPOD is also a model reduction method which considers both inputs and outputs of the system while determining the reduce subspace. The estimation method has been extended by including BPOD procedure into the estimation procedure. Numerical results from a simple pollution model demonstrate that the POD based estimation approach successfully estimate the diffusion coefficient for both advection dominated problems as for diffusion dominated problems. Another important message in this study, although lots of effort had been made in constructing a reduced order model by the BPOD method, the minimization results demonstrated that both the POD and the BPOD methods performed similarly. Preliminary results showed the validity of the POD based model reduction methods for parameter estimation. As a next step, the POD based estimation method is used to calibrate numerical tidal models. Results from (twin) numerical experiments showed that the POD based calibration method performed very efficiently to estimate depth values in the selected regions of the model domain. The computational costs of the POD based calibration method are dominated by the generation of an ensemble of forward model simulations where the simulation period of the ensemble is equivalent to the timescale of the original model. It has also been found in the study that it is not needed to use a full simulations of the original model for the generation of the ensemble. The POD based calibration method has also been implemented for the estimation of the water depth and space varying bottom friction coefficient values in a very large-scale DCSM model. The recently designed large-scale spherical grid based water level model for the northwest European continental shelf (around 1000000 computational grid points) has been used for this purpose. This has been the first application of the POD based calibration method to a very large-scale model and with real data. Results from numerical experiments showed that the calibration method performs very efficiently. An overall improvement of more than 50\% was observed after the calibration in comparison with the initial model. The results also demonstrated that the POD based calibration method offered a very efficient minimization technique compared to the classical adjoint method without the burden of implementation of the adjoint. As a concluding step, to estimate depth values in the model DCSM, a Simultaneous perturbation stochastic approximation (SPSA) method has been used. The method uses stochastic simultaneous perturbation of all model parameters to generate a search at each iteration. SPSA is based on a highly efficient and easily implemented simultaneous perturbation approximation to the gradient. This gradient approximation for the central difference method uses only two objective function evaluations independent of the number of parameters being optimized. The results from experiments showed that SPSA has a lower convergence rate than POD based calibration method, however the computational cost in each iteration of the SPSA method is usually far less then the POD based calibration method. The results also demonstrated that the SPSA algorithm proved to be a promising optimization algorithm for model calibration for cases where adjoint code is not available for computing the gradient of the objective function.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Harpactus Shuckard 1837
No full textGenus Harpactus Shuckard, 1837 Arpactus Jurine, 1807: 192, junior homonym of Arpactus Panzer, 1805, and of Arpactus Panzer, 1806 (both junior synonyms of Gorytes Latreille, 1804). Type species: Arpactus formosus Jurine, 1807, designated by Shuckard 1837: 220. Harpactus Shuckard 1837: 221. Emendation of Arpactus Jurine, 107 on linguistic grounds, thus an available new name, with its own date and author (Articles 19 and 33.2). Since Harpactus is an emendation, it has the same type-species as Arpactus Jurine (Article 67.8). Harpactes Dahlbom 1843: 147, junior homonym of Harpactes Swainson, 1837 (Aves), and of Harpactes Templeton, 1834 (Arachnida). Emendation of Harpactus Shuckard. Dienoplus W.J. Fox 1894: 548. Type species: Dienoplus pictifrons Fox, 1894, by monotypy. Key to Harpactus species of India and adjacent territories 1. Head and mesosoma without distinct punctures............................................................. 2 - Head, mesosoma, [and T2] distinctly foveolate-punctate, with scattered foveae. [Kashmir].......... H. pulawskii sp. nov. 2. Propodeum with oblique and irregular striae................................................................ 3 - Propodeum with distinct coarse, longitudinal striae [Pakistan].................................. H. vividus (Turner) 3. Fore wing with fuscous patch in radial and cubital cells; propodeal enclosure red. [Northern India; Myanmar]................................................................................................. H. ornatus (Smith) - Fore wing usually without fuscous patch in radial and cubital cells; propodeal enclosure black. [Oriental India].............................................................................................. H. impudens (Nurse)Published as part of Binoy, C., Kumar, P. Girish, Monks, Joseph & Sheikh, Altaf Hussain, 2022, A review of digger wasp genus Harpactus Shuckard, 1837 (Hymenoptera Crabronidae) of the Indian subcontinent, with description of a new species and rediscovery of Harpactus impudens (Nurse, 1903), pp. 531-542 in Zootaxa 5190 (4) on page 532, DOI: 10.11646/zootaxa.5190.4.3, http://zenodo.org/record/713847
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