Real Distributions Research Articles

An Iterative and Truthful MultiUnit Auction Scheme for Coordinated Sharing of Spectrum White Spaces

We consider the use of dynamic auctions for coordinating spectrum sharing among secondary users, and propose an online multi-unit, iterative auction mechanism called VERUM that is truthful and efficient (the item is always won by the bidder who values it the most). VERUM is an adaptation of the well known Ausubel's clinching auction [1] to suit the dynamic spectrum sharing context. As a use case for VERUM, we consider TV white space (TVWS) spectrum sharing among home networks, and compare VERUM with two existing efficient and truthful multi-unit spectrum auction schemes, VERITAS and SATYA. Our evaluations, using real distributions of homes in a dense urban neighborhood in London and realistic TVWS spectrum availability maps for the UK, show that VERUM outperforms the other two schemes in terms of revenue, spectrum utilization and percentage of winning bidders.

Network coding is the 5G Key Enabling Technology: effects and strategies to manage heterogeneous packet lengths

ABSTRACTThe exponential growth of the mobile devices market, not only smartphones but also tablets, laptops or wearables, poses a serious challenge for 5G communications. Random linear network coding is a promising solution for present and future networks as it has been shown to provide increased throughput, security and robustness for the transmission of data through the network. Most of the analysis and the demonstrators have focused on the study of data packets with the same size (number of bytes). This constitutes a best‐case scenario as coded packets will incur little overhead to handle such packets. However, packet lengths are quite heterogeneous in real networks, which can cause a high overhead or, alternatively, a high delay in the transmission of data packets. As we show, this can have a severe effect on a variety of applications. This paper proposes a series of mechanisms to manage heterogeneous packet lengths and analyses the induced overhead of those mechanisms using real packet length distributions provided by the Center for Applied Internet Data Analysis (CAIDA) and own measurements using video content. Our results show that an appropriate packetisation of the data packets can reduce the overhead from over 100 per cent (zero‐padding packets) to below 5 per cent for CAIDA packet distributions and that the right choice of parameters can reduce the overhead to less than 10 per cent in the case of video data. Copyright © 2014 John Wiley & Sons, Ltd.

Slow drift mirror kinetic instability at a finite electron temperature in a nonmaxwellian space plasma

A slow drift mirror (SDM) instability has been analyzed in the scope of kinetic approximation, with accounting for the electron pressure for different particle distribution functions. The dependence of the SDM instability increment growth rate on the parameters of the anisotropic κ distribution with the loss cone, which is used to model real space plasma particle distributions, has been studied. An analysis indicated that the appearance of the loss cone in the ion distribution function results in a decrease in the SDM mode frequency, and an enhancement of the suprathermal tail (a decrease in κ) increases the SDM mode frequency as compared to the Maxwellian distribution. In other words, particle redistribution from the region of low velocities into that of high velocities results in an increase in the SDM mode frequency.

Phylogeny, paleontology, and primates: do incomplete fossils bias the tree of life?

Paleontological systematics relies heavily on morphological data that have undergone decay and fossilization. Here, we apply a heuristic means to assess how a fossil's incompleteness detracts from inferring its phylogenetic relationships. We compiled a phylogenetic matrix for primates and simulated the extinction of living species by deleting an extant taxon's molecular data and keeping only those morphological characters present in actual fossils. The choice of characters present in a given living taxon (the subject) was defined by those present in a given fossil (the template). By measuring congruence between a well-corroborated phylogeny to those incorporating artificial fossils, and by comparing real vs. random character distributions and states, we tested the information content of paleontological datasets and determined if extinction of a living species leads to bias in phylogeny reconstruction. We found a positive correlation between fossil completeness and topological congruence. Real fossil templates sampled for 36 or more of the 360 available morphological characters (including dental) performed significantly better than similarly complete templates with random states. Templates dominated by only one partition performed worse than templates with randomly sampled characters across partitions. The template based on the Eocene primate Darwinius masillae performs better than most other templates with a similar number of sampled characters, likely due to preservation of data across multiple partitions. Our results support the interpretation that Darwinius is strepsirhine, not haplorhine, and suggest that paleontological datasets are reliable in primate phylogeny reconstruction.

Random Polynomials and Pluripotential-Theoretic Extremal Functions

There is a natural pluripotential-theoretic extremal function V K,Q associated to a closed subset K of $\mathbb {C}^{m}$ and a real-valued, continuous function Q on K. We define random polynomials H n whose coefficients with respect to a related orthonormal basis are independent, identically distributed complex-valued random variables having a very general distribution (which includes both normalized complex and real Gaussian distributions) and we prove results on a.s. convergence of a sequence $\{\frac {1}{n}\log |H_{n}|\}$ pointwise and in $L^{1}_{loc}(\mathbb {C}^{m})$ to V K,Q . In addition we obtain results on a.s. convergence of a sequence of normalized zero currents $\{dd^{c}\left (\frac {1}{n}\log |H_{n}|\right )\}$ to d d c V K,Q as well as asymptotics of expectations of these currents. All these results extend to random polynomial mappings and to a more general setting of positive holomorphic line bundles over a compact Kähler manifold.

A Swedish case study on the prediction of detailed product recovery from individual stem profiles based on airborne laser scanning

Improved and cost-efficient predictions of detailed product recovery from logging operations may increase efficiency and improve value chains based on modern cut-to-length harvesting (CTL). The objective of this study was to investigate and evaluate the use of individual tree data estimates from two inventory techniques: (a) established airborne laser scanner inventory (ALS case) and (b) traditional field inventory (BAU case) for predicting product recovery in a Swedish case study. Statistics from previous harvester production files within the region were used to generate realistic levels of simulated stem defects. Bucking simulations were performed to optimise log products according to stem profiles, stem defects, and an operational price list expressing the demand of the industry customer. All simulation results at the stand level were compared to operational harvester production data that were used to provide an accurate measure of the ‘true’ product recovery. The total harvested area was 139 ha including 16 forest stands. Seven groups of log products were included in the analysis. The predicted versus real top diameter distributions of sawlogs were evaluated using an error index to express deviations. At the stand level, the average error index values were 0.15 and 0.18 for the ALS and BAU approaches, respectively. As a consequence of an overall bias of the ALS tree lists the opposite was found at the total wood flow level, with the field-based data yielding a lower error index. The volume predictions for different log product groups were slightly more accurate in the ALS case than in the BAU case.

Supervised variational model with statistical inference and its application in medical image segmentation.

Automated and general medical image segmentation can be challenging because the foreground and the background may have complicated and overlapping density distributions in medical imaging. Conventional region-based level set algorithms often assume piecewise constant or piecewise smooth for segments, which are implausible for general medical image segmentation. Furthermore, low contrast and noise make identification of the boundaries between foreground and background difficult for edge-based level set algorithms. Thus, to address these problems, we suggest a supervised variational level set segmentation model to harness the statistical region energy functional with a weighted probability approximation. Our approach models the region density distributions by using the mixture-of-mixtures Gaussian model to better approximate real intensity distributions and distinguish statistical intensity differences between foreground and background. The region-based statistical model in our algorithm can intuitively provide better performance on noisy images. We constructed a weighted probability map on graphs to incorporate spatial indications from user input with a contextual constraint based on the minimization of contextual graphs energy functional. We measured the performance of our approach on ten noisy synthetic images and 58 medical datasets with heterogeneous intensities and ill-defined boundaries and compared our technique to the Chan-Vese region-based level set model, the geodesic active contour model with distance regularization, and the random walker model. Our method consistently achieved the highest Dice similarity coefficient when compared to the other methods.

GMOBench: Benchmarking generic moving objects

In real world scenarios, people's movement include several environments rather than one, for example, road network, pavement areas and indoor. This imposes a new challenge for moving objects database that the complete trip needs to be managed by a database system. In the meantime, novel queries regarding different transportation modes should also be supported. Since existing methods are limited to trips in a single environment and do not support queries on moving objects with different transportation modes, new technologies are essentially needed in a database system. In this paper, we introduce a benchmark called GMOBench that aims to evaluate the performance of a database system managing moving objects in different environments. GMOBench is settled in a realistic scenario and is comprised of three components: (1) a data generator with the capability of creating a scalable set of trips representing the complete movement of humans (both indoor and outdoor); (2) a set of carefully designed and benchmark queries; (3) Mode-RTree, an index structure for managing generic moving objects. The generator defines some parameters so that users can control the characteristics of results. We create the benchmark data in such a way that the dataset can mirror important characteristics and real world distributions of human mobility. Efficient access methods and optimization techniques are developed for query processing. In particular, we propose an index structure called Mode-RTree to manage moving objects in different environments. By employing the proposed index, the cost of benchmark queries is greatly reduced. GMOBench is implemented in a real database system to have a practical result. We perform an extensive experimental study on comprehensive datasets to evaluate the performance. The results show that by using the Mode-RTree we achieve significant performance improvement over the baseline method, demonstrating the effectiveness and efficiency of our approaches.

Micro-mechanical analysis of the in situ effect in polymer composite laminates

A micro-mechanical finite element model of a composite sublaminate is proposed to study the mechanical response of ultra-thin plies, consisting of a representative volume element of a 90° thin lamina in-between two homogenised ±θ° plies. Random fibre distributions, materially and statistically equivalent to real distributions, are analysed. A three-dimensional computational micro-mechanics framework, with a special focus on the elastic–plastic and damage constitutive behaviours of the matrix and on the response of the fibre–matrix interface, is used in the present analysis. Varying the 90° ply thickness, it is possible to assess its effect on the mechanical response of laminated composites — the in situ effect. The proposed framework is able to accurately represent the micro-mechanical response of ultra-low grades, including (i) the mechanics of transverse cracking onset and propagation, (ii) the constraining effect observed in the laminae embedded in multidirectional laminates, (iii) the gradual, slow stress relaxation and progressive transverse cracking observed in very thin plies, and consequent increase of the crack density, (iv) the reduction in crack-opening displacement of the transverse cracks with ply thinness, (v) the formation of thin necks of matrix material around the regions where interfacial damage is more pronounced, and (vi) the in situ strengths.

A Computational Fluid Dynamic Study on Transient Thermal Characteristics of Two-Phase Gas Metal Arc Welding Process

Gas Metal Arc Welding (GMAW) is a welding process where an electrode wire is continuously fed from an automatic wire feeder through a conduit and welding gun to the base metal, where a weld pool is created. The formation of droplet and transfer of droplet are governed by the conservation equations. This study on GMAW aims to simulate transient behavior of welding arc and shielding gas flow. Computational Fluid Dynamics (CFD) is used as a tool to understand multifaceted physics involved in GMAW process. A two dimensional axisymmetric model is prepared to reduce computational time. The heat transfer and fluid flow in the arc column were studied based on the transient distributions of velocity, turbulence, voltage, current density, and temperature. An interactive coupling between welding arc, plasma, current and temperature were considered. The assumed steady state and laminar gas flow in traditional models studied so for does not reflect the real distributions in the welding process. Hence influence of the welding arc on the shielding gas flow and vice versa was taken up for study. From the study it is found that as the arc is struck, the shielding gas is accelerated towards axis. When the plasma reaches towards workpiece, axial momentum of gases is changed to radial momentum and flows away from the workpiece. The shielding gas also carries current from electrode to workpiece which helps in reducing spatter of the arc and hence concentrated arc is obtained

SU‐E‐T‐517: Analytic Formalism to Compute in Real Time Dose Distributions Delivered by HDR Units

Purpose:Develop an analytical algorithm to compute the dose delivered by Ir‐192 dwell positions with high accuracy using the 3‐dimensional (3D) dose distribution of an HDR source. Using our analytical function, the dose delivered by an HDR unit as treatment progresses can be determined using the actual delivered temporal and positional data of each individual dwell. Consequently, true delivered dose can be computed when each catheter becomes active. We hypothesize that the knowledge of such analytical formulation will allow developing HDR systems with a real time treatment evaluation tool to avoid mistreatments.Methods:In our analytic formulation, the dose is computed by using the full anisotropic function data of the TG 43 formalism with 3D ellipsoidal function. The discrepancy between the planned dose and the delivered dose is computed using an analytic perturbation method over the initial dose distribution. This methodology speeds up the computation because only changes in dose discrepancies originated by spatial and temporal deviations are computed. A dose difference map at the point of interest is obtained from these functions and this difference can be shown during treatment in real time to examine the treatment accuracy.Results:We determine the analytical solution and a perturbation function for the 3 translational 3 rotational, and 1D temporal errors in source distributions. The analytic formulation is a sequence of simple equations that can be processed in any modern computer in few seconds. Because computations are based in an analytical solution, small deviations of the dose when sub‐millimeter positional changes occur can be detected.Conclusions:We formulated an analytical method to compute 4D dose distributions and dose differences based on an analytical solution and perturbations to the original dose. This method is highly accurate and can be

Double Constrained NMF for Hyperspectral Unmixing

Given only the collected hyperspectral data, unmixing aims at obtaining the latent constituent materials and their corresponding fractional abundances. Recently, many <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nonnegative matrix factorization</i> (NMF)-based algorithms have been developed to deal with this issue. Considering that the abundances of most materials may be sparse, the sparseness constraint is intuitively introduced into NMF. Although sparse NMF algorithms have achieved advanced performance in unmixing, the result is still susceptible to unstable decomposition and noise corruption. To reduce the aforementioned drawbacks, the structural information of the data is exploited to guide the unmixing. Since similar pixel spectra often imply similar substance constructions, clustering can explicitly characterize this similarity. Through maintaining the structural information during the unmixing, the resulting fractional abundances by the proposed algorithm can well coincide with the real distributions of constituent materials. Moreover, the additional clustering-based regularization term also lessens the interference of noise to some extent. The experimental results on synthetic and real hyperspectral data both illustrate the superiority of the proposed method compared with other state-of-the-art algorithms.

Identification of spatial distributions and uncertainties of multiple heavy metal concentrations by using spatial conditioned Latin Hypercube sampling

This work develops spatial conditioned Latin hypercube sampling (scLHS), a novel advance on conditioned Latin hypercube sampling (cLHS) [Minasny and McBratney, Computers & Geosciences (2006) 1378–1388]. The difference between cLHS and scLHS is that the latter introduces variograms of ancillary variables into the objective function of the optimization procedure that selects sampling locations. The improvement of scLHS was evaluated by applying both scLHS and cLHS to simulated samples of multiple heavy metals (Cr, Cu, Ni, and Zn) in the soil of Changhua County in Taiwan. Simulation was done by using sequential indicator simulation (SIS), which generated 1000 realizations of spatial distributions of the heavy metals, based on existing sample data, to represent the real distributions of heavy metals. The results of the Ripley K analysis show that the locations of samples obtained by both approaches were not significantly spatially segregated. The sampling results show that the declustering of sample locations may dominate the optimization process in cLHS and scLHS. Statistical analysis indicated that compared with cLHS, the means, standard deviations and contamination proportions of scLHS samples captured more efficiently the variability of the SIS realizations. Moreover, the experimental variograms of scLHS samples, especially for small sample sizes, captured the experimental variograms of the SIS realizations more efficiently. Therefore, the use of the scLHS approach is recommended as a novel alternative sampling approach without the need for a reconnaissance survey to increase the efficiency of capturing the spatial structures of soil heavy metals and delineating contaminated sites.

Determination of solid solubility level of Ho nanoparticles in Y-123 superconducting matrix and strong Cu1 site preference of nanoparticles

This comprehensive study reports the effect of the Ho inclusions on the microstructural, electrical, mechanical and superconducting characteristics of YBa2Cu3O7−δ ceramic superconductors with the aid of standard characterization methods including the bulk density, dc resistivity (ρ–T), transport critical current density (Jc), X-ray diffraction (XRD), electron dispersive X-ray (EDX), scanning electron microscopy (SEM) and Vickers microhardness (HV) investigations. The experimental results such as the degree of granularity, hole (filling) localization effect, room temperature resistivity, onset–offset critical transition temperature, degree of the broadening, thermodynamic fluctuations (spin-gap opening temperature), crystallinity, crystal plane alignments (texturing), crystal structure, grain size, phase purity and lattice parameters, appearance of flux pinning centers, grain boundary weak-links (interaction between the superconducting grains), surface morphologies (grain size distribution), real (load independent) microhardness values, elemental compositions and distributions belonging to the pure and Y-site Ho substituted Y-123 superconducting samples are discussed in detail for the first time. Moreover, mechanical characterization enables us to theoretically determine the elastic (Young’s) modulus and yield strength being in charge of the potential mechanical applications. Additionally, the load dependent microhardness values of the Y-site Ho substituted Y-123 materials have not been modeled by the available theoretical methods (Hays–Kendall and indentation-induced cracking approach) up to the present. All the experimental findings show that the microstructural, electrical, mechanical and superconducting properties improve regularly with the increment in the Ho concentration level at the Y-site in the superconducting matrix until a certain value of x=0.100 (optimum) beyond which the characteristics tend to retrograde rapidly. This is attributed to the fact that excess (0.100<x) penetration of the homovalent Ho-sites on the Y-sites damages the crucial properties given above. In other words, from the Ho content level of x=0.100 onwards in the Y-123 matrix, the oxygen content in the Cu–O chains begins to increase considerably and new induced oxygen atoms reorder the unit cell structure (rapid increment of the a axis length), so the structural phase transits from the orthorhombic to pseudotetragonal, being one of the most striking points deduced from this paper. Another vital discussion relies on the fact that the degradation of the mobile hole concentration (hole localization effect) in the Cu-sites leads to transition from optimally doped to the underdoped position in the crystal structure. Besides, the rapid degradation in the mechanical properties due to the increase of the specimen cracking/porosity, grain boundary weak-links and irregular grain orientation distribution confirms the relationships between the microstructure and mechanical properties of the Y-123 superconducting materials. Furthermore, all the samples exhibit the typical Reverse Indentation Size Effect (RISE) behavior under the applied indentation test load. As for the theoretical modeling of the hardness evidences, the calculations performed by IIC model are quite closer to the values of the plateau region as compared to those of HK approach. Based on the results, the IIC model is found to be superior to HK approach for the description of the real microhardness values belonging to all the superconducting samples.

Inland Wind Resource Assessment in Southeast Finland

Rapid development of wind power technologies is enabling many nations to increase the share of wind energy in total electricity production. Finland, in common with many other countries, has a target of raising the contribution of wind resources to national energy production. The majority of existing and planned turbines in Finland are located in coastal areas, where the wind resources can provide favorable conditions for wind farms. However, considerable wind potential may exist in inland areas of the country. This paper presents a wind resource analysis of the southeast of Finland. The wind data, consisting of meteorological mast and LIDAR measurements at several heights, were collected in 2009 – 2011. The analysis includes monthly average wind speed, diurnal wind behavior and wind shear assessment. The energy output is estimated for a 3 MW wind turbine based on real wind speed distributions. Capacity factors are calculated to assess 3 MW wind turbine feasibility at the site. The obtained results demonstrate that inland wind conditions have sufficient potential to allow wind energy to thrive.

METHODOLOGY OF CALCULATION THE TERMINAL SETTLING VELOCITY DISTRIBUTION OF SPHERICAL PARTICLES FOR HIGH VALUES OF THE REYNOLD’S NUMBER

Abstract The particle settling velocity is the feature of separation in such processes as flowing classification and jigging. It characterizes material forwarded to the separation process and belongs to the so-called complex features because it is the function of particle density and size. i.e. the function of two simple features. The affiliation to a given subset is determined by the values of two properties and the distribution of such feature in a sample is the function of distributions of particle density and size. The knowledge about distribution of particle settling velocity in jigging process is as much important factor as knowledge about particle size distribution in screening or particle density distribution in dense media beneficiation. The paper will present a method of determining the distribution of settling velocity in the sample of spherical particles for the turbulent particle motion in which the settling velocity is expressed by the Newton formula. Because it depends on density and size of particle which are random variable of certain distributions, the settling velocity is a random variable. Applying theorems of probability, concerning distributions function of random variables, the authors present general formula of probability density function of settling velocity for the turbulent motion and particularly calculate probability density function for Weibull’s forms of frequency functions of particle size and density. Distribution of settling velocity will calculate numerically and perform in graphical form. The paper presents the simulation of calculation of settling velocity distribution on the basis of real distributions of density and projective diameter of particles assuming that particles are spherical.

Ensuring portability of Linux applications through standardization and knowledge base driven analysis

Problems with portability of applications across various Linux distributions is one of the major sore spots of independent software vendors (ISVs) wishing to support the Linux platform in their products. The source of the problem is that different distributions have different sets of system libraries that vary in the interfaces (APIs) provided. And the critical questions arise for ISVs such as “which distributions my application would run on?” or “what can I specifically do to make my application run on a greater number of distributions?”. This article refers to an industry-wide approach to mitigate the problem of Linux platform fragmentation through standardization of common interfaces—the Linux Standard Base (LSB) standard, the leading effort for the “single Linux specification”. The article shows how extending this approach with a knowledge base about the composition of real world Linux distributions can enable automatic portability analysis for Linux applications even if they use interfaces outside the scope of the standard. The knowledge base powered Linux Application Checker tool is described that can help answer the above questions by automatically analyzing the target application and confronting collected data about its external dependencies with what various distributions provide. Additionally, Linux Application Checker is an official tool approved by the Linux Foundation for certifying applications for compliance with the LSB standard.

Gamma-GQM Time Headway Model: Endogenous Effects in Rural Two-lane Two-way Roads

Study of vehicle time headway distributions is essential in many traffic engineering applications, such as capacity and level of service analysis and, in recent years, in the fields of vehicle generation in traffic micro-simulation models and driving simulation applications. This paper presents results from an experimental analysis of vehicle time headway distributions on two-lane two-way rural roads. Analysis focused on estimating a well-known model, the gamma-generalized queuing model (gamma-GQM). A trendless analysis of observed time headways was also carried out. The endogenous traffic parameters considered as affecting time headway distributions were flow rate and flow composition (percentage of heavy vehicles). Exogenous conditions, such as weather and geometric futures, were common to all time periods and cross-sections analysed. Gamma-GQM pdf appears to be very suitable for representing real headway distributions in all the analysed situations; it fits real-time headway distributions well, despite flow rate range and traffic composition (range of percentage of heavy vehicles).

Automatic Realistic Real Time Stimulation/Recording in Weakly Electric Fish: Long Time Behavior Characterization in Freely Swimming Fish and Stimuli Discrimination

Weakly electric fish are unique model systems in neuroethology, that allow experimentalists to non-invasively, access, central nervous system generated spatio-temporal electric patterns of pulses with roles in at least 2 complex and incompletely understood abilities: electrocommunication and electrolocation. Pulse-type electric fish alter their inter pulse intervals (IPIs) according to different behavioral contexts as aggression, hiding and mating. Nevertheless, only a few behavioral studies comparing the influence of different stimuli IPIs in the fish electric response have been conducted. We developed an apparatus that allows real time automatic realistic stimulation and simultaneous recording of electric pulses in freely moving Gymnotus carapo for several days. We detected and recorded pulse timestamps independently of the fish’s position for days. A stimulus fish was mimicked by a dipole electrode that reproduced the voltage time series of real conspecific according to previously recorded timestamp sequences. We characterized fish behavior and the eletrocommunication in 2 conditions: stimulated by IPIs pre-recorded from other fish and random IPI ones. All stimuli pulses had the exact Gymontus carapo waveform. All fish presented a surprisingly long transient exploratory behavior (more than 8 h) when exposed to a new environment in the absence of electrical stimuli. Further, we also show that fish are able to discriminate between real and random stimuli distributions by changing several characteristics of their IPI distribution.

Theoretical and experimental study of the role of cell-cell dipole interaction in dielectrophoretic devices: application to polynomial electrodes.

BackgroundWe aimed to investigate the effect of cell-cell dipole interactions in the equilibrium distributions in dielectrophoretic devices.MethodsWe used a three dimensional coupled Monte Carlo-Poisson method to theoretically study the final distribution of a system of uncharged polarizable particles suspended in a static liquid medium under the action of an oscillating non-uniform electric field generated by polynomial electrodes. The simulated distributions have been compared with experimental ones observed in the case of MDA-MB-231 cells in the same operating conditions.ResultsThe real and simulated distributions are consistent. In both cases the cells distribution near the electrodes is dominated by cell-cell dipole interactions which generate long chains.ConclusionsThe agreement between real and simulated cells’ distributions demonstrate the method’s reliability. The distribution are dominated by cell-cell dipole interactions even at low density regimes (105 cell/ml). An improved estimate for the density threshold governing the interaction free regime is suggested.