Upscaling of permeability field of fractured rock system: Numerical examples
Bao, K.
2012-01-01
When the permeability field of a given porous medium domain is heterogeneous by the existence of randomly distributed fractures such that numerical investigation becomes cumbersome, another level of upscaling may be required. That is such complex permeability field could be relaxed (i.e., smoothed) by constructing an effective permeability field. The effective permeability field is an approximation to the real permeability field that preserves certain quantities and provides an overall acceptable description of the flow field. In this work, the effective permeability for a fractured rock system is obtained for different coarsening scenarios starting from very coarse mesh all the way towards the fine mesh simulation. In all these scenarios, the effective permeability as well as the pressure at each cell is obtained. The total flux at the exit boundary is calculated in all these cases, and very good agreement is obtained.
Energy Technology Data Exchange (ETDEWEB)
Lenormand, R.; Thiele, M.R. [Institut Francais du Petrole, Rueil Malmaison (France)
1997-08-01
The paper describes the method and presents preliminary results for the calculation of homogenized relative permeabilities
Li, Hui; Kayhanian, Masoud; Harvey, John T
2013-03-30
Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability. Copyright © 2013 Elsevier Ltd. All rights reserved.
Akhmetsafina, A.; Willmann, M.; Kinzelbach, W.
2012-04-01
In contemporary groundwater engineering heterogeneous aquifers with complex-structured permeability fields are of high interest. Heterogeneous fields create difficulties in up-scaling, increase the computation time, and may influence on selection of hydrodynamic model. A major problem us to relate permeability fields, flow and concentration behavior. Our overall goal is to investigate the correlation between permeability field and modifications of concentration. We consider binary fields, comprised of high-permeable and low permeable zones with a varying high permeability ratio. Low-permeable zones represent a matrix and high-permeable zones represent randomly distributed inclusions in the shape of discs. In this case percolation theory is applicable and connectivity can be defined accordingly. If the intensity of inclusions is high enough, permeable areas construct cluster, that provide main fluid flow and percolation exists. Such a critical intensity is unique and percolation occurs suddenly with intensity increasing through this threshold. We are interested in cases nearby the percolation threshold. Darcy velocity field becomes heterogeneous. Fast "channels" and almost immobile zones appear that allows us talking about dual media: dual-porosity, dual-permeability models for Darcy equation and multi-rate model for advection-dispersion equation. We assume a stationary flow in a rectangular 2D domain with first type boundary condition. Using the resulting velocity fields we solve the advection-diffusion equation with a unit pulse of concentration at the left border. Two singularities can be observed: fast channels lead to early first-arrival times of the concentration. Secondly, almost immobile zones collect concentration at first and then give it back into clear water flow causing anormal tailing of the BTC. This is the reason why separate transport up-scaling is needed. We calibrate multi-rate model's parameters responsible for early arrivals (ratio between
Lunar magnetic permeability, magnetic fields, and electrical conductivity temperature
Parkin, C. W.
1978-01-01
In the time period 1969-1972 a total of five magnetometers were deployed on the lunar surface during four Apollo missions. Data from these instruments, along with simultaneous measurements from other experiments on the moon and in lunar orbit, were used to study properties of the lunar interior and the lunar environment. The principal scientific results from analyses of the magnetic field data are discussed. The results are presented in the following main categories: (1) lunar electrical conductivity, temperature, and structure; (2) lunar magnetic permeability, iron abundance, and core size limits; (3) the local remnant magnetic fields, their interaction with the solar wind, and a thermoelectric generator model for their origin. Relevant publications and presented papers are listed.
Random walks, random fields, and disordered systems
Černý, Jiří; Kotecký, Roman
2015-01-01
Focusing on the mathematics that lies at the intersection of probability theory, statistical physics, combinatorics and computer science, this volume collects together lecture notes on recent developments in the area. The common ground of these subjects is perhaps best described by the three terms in the title: Random Walks, Random Fields and Disordered Systems. The specific topics covered include a study of Branching Brownian Motion from the perspective of disordered (spin-glass) systems, a detailed analysis of weakly self-avoiding random walks in four spatial dimensions via methods of field theory and the renormalization group, a study of phase transitions in disordered discrete structures using a rigorous version of the cavity method, a survey of recent work on interacting polymers in the ballisticity regime and, finally, a treatise on two-dimensional loop-soup models and their connection to conformally invariant systems and the Gaussian Free Field. The notes are aimed at early graduate students with a mod...
Random scalar fields and hyperuniformity
Ma, Zheng; Torquato, Salvatore
2017-06-01
Disordered many-particle hyperuniform systems are exotic amorphous states of matter that lie between crystals and liquids. Hyperuniform systems have attracted recent attention because they are endowed with novel transport and optical properties. Recently, the hyperuniformity concept has been generalized to characterize two-phase media, scalar fields, and random vector fields. In this paper, we devise methods to explicitly construct hyperuniform scalar fields. Specifically, we analyze spatial patterns generated from Gaussian random fields, which have been used to model the microwave background radiation and heterogeneous materials, the Cahn-Hilliard equation for spinodal decomposition, and Swift-Hohenberg equations that have been used to model emergent pattern formation, including Rayleigh-Bénard convection. We show that the Gaussian random scalar fields can be constructed to be hyperuniform. We also numerically study the time evolution of spinodal decomposition patterns and demonstrate that they are hyperuniform in the scaling regime. Moreover, we find that labyrinth-like patterns generated by the Swift-Hohenberg equation are effectively hyperuniform. We show that thresholding (level-cutting) a hyperuniform Gaussian random field to produce a two-phase random medium tends to destroy the hyperuniformity of the progenitor scalar field. We then propose guidelines to achieve effectively hyperuniform two-phase media derived from thresholded non-Gaussian fields. Our investigation paves the way for new research directions to characterize the large-structure spatial patterns that arise in physics, chemistry, biology, and ecology. Moreover, our theoretical results are expected to guide experimentalists to synthesize new classes of hyperuniform materials with novel physical properties via coarsening processes and using state-of-the-art techniques, such as stereolithography and 3D printing.
Field Evidence for a Low Permeability, High Storage Fault Core at the Santa Susana Field Laboratory
Allègre, V.; Brodsky, E. E.; Parker, B. L.; Cherry, J. A.
2015-12-01
In situ measurements of hydrogeologic properties within fault zones are few, in part because of the challenges of measuring the scale-dependent quantities in fractured rock reservoirs. This work aims to fill the gap by utilizing a combination of tidal, barometric and seismic response analyses on pressure head time-series from the Santa Susana Field Laboratory in Southern California. The techniques sample different effective volumes and so allow us to investigate the scale-dependent structure near fault zones. Permeability and specific storage were inverted from tidal response at 14 locations, and specific storage was also computed from barometric efficiencies at 10 locations. In addition, we computed hydro-seismic transfer functions after nine local earthquakes and teleseismic events. We found that permeability computed from tidal response are quite homogeneous within about one and a half orders of magnitude over the site regardless of the presence of moderate to large faults. This result is consistent with the earlier aquifer tests using standard methods. The tidal responses also showed higher variability of specific storage inside the fault zones suggesting that fault damage zone generates a storage architecture. The storage from the tidal responses can be consistently interpreted for the tidal, barometric and seismic responses. However, the observations require that the permeability inside the fault zones at the spatial scale of the seismic response (~meters) is much lower than at the spatial scale of the tidal response (~10's of meters). The result suggests possible sensitivity to the low permeability fault core, which has been historically difficult to measure at the field scale.
Energy Technology Data Exchange (ETDEWEB)
Lucia, F.J. (Bureau of Economic Geology, Austin, TX (USA))
1987-02-01
Dune field contains little vuggy porosity so total porosity and particle size become the determining factors. Three pore-geometry families are distiguished: intergranular porosity between 300-{mu}m grains in grainstones, intercrystalline porosity between 50-{mu}m dolomite crystals in dolomitized wackestones/packestones, and rocks with an intimate mixture of these two end members. Unique porosity-permeability transform functions for these three pore-type families are determined. The presence of up to 55% gypsum in Dune field complicates calculations of total porosity. Particle size was determined by relating particle size to irreducible water saturation. In the oil column, irreducible water saturation is a function of interparticle porosity and particle size. Assuming similar porosity values, rocks with finer pores will have higher water saturations than those with larger pores. In Dune field, intergranular pores are larger than the intercrystalline pores, and saturation values calculated from wireline logs show lower water saturations for the intergranular pore-type families than for the intercrystalline pore-type families. The mixed family is intermediate. Permeabilities are calculated from sonic and resistivity logs by determining the pore-type family from the saturation values and the permeability from the porosity-permeability relationship for that family. The resulting permeability profiles compare favorably with core analysis profiles. Permeability logs are correlated assuming parallel beds, and permeability cross sections and permeability-thickness maps are prepared. The results show that the reservoir can be divided into upper and lower members separated by a 25-ft permeability barrier. The permeability in either member varies on scales from 600 ft to 1 mi and can be related to depositional and diagenetic facies.
Effects of Collar Permeability on the Field Quality of the Large Aperture Quadrupoles for the LHC
Catalan-Lasheras, N; Kirby, G; Mess, K H; Ostojic, R; Russenschuck, Stephan
2008-01-01
The LHC contains a number of large aperture quadrupoles (MQY) in the insertions. The acceptance of these magnets was based on warm magnetic measurements performed before delivery to CERN. During the series production of the MQY quadrupoles, the permeability of the collars drifted from the nominal value, and effects on the transfer function and multipole components became evident. To study the effects on the magnetic field, variable permeability of the stainless-steel collars as a function of local field and temperature was introduced into a numerical model. Comparing the results with measured data, we could isolate the contribution of permeability deviation on the magnetic field quality. The extrapolation of transfer function and field multipoles to operating temperature and current gives the necessary offsets, which are compared with measurements on a reduced set of magnets.
Optical investigation of effective permeability of dilute magnetic dielectrics with magnetic field
Energy Technology Data Exchange (ETDEWEB)
Banerjee, Ananya, E-mail: banerjee.ananya2008@gmail.com; Sarkar, A. [Dept. of Physics, Bijoy Krishna Girls’ College, 5/3 M.G. Road, Howrah 711101, W.B. (India)
2016-05-06
The prime objective of this paper is to investigate the magnetic nature of dilute magnetic dielectrics (DMD) under variation of external magnetic field. The said variation is studied over developed nano-sized Gadolinium Oxide as a DMD system. The observed experimental field variation of the effective magnetic permeability is analyzed results of optical experiment. The experiment records the variation of Brewster angle of incident polarized LASER beam from the surface of developed DMD specimen with applied out of plane external magnetic field. The effective refractive index and hence relative magnetic permeability were estimated following electro-magnetic theory. The overall results obtained and agreement between theory and experiment are good.
Variational Infinite Hidden Conditional Random Fields
Bousmalis, Konstantinos; Zafeiriou, Stefanos; Morency, Louis-Philippe; Pantic, Maja; Ghahramani, Zoubin
2015-01-01
Hidden conditional random fields (HCRFs) are discriminative latent variable models which have been shown to successfully learn the hidden structure of a given classification problem. An Infinite hidden conditional random field is a hidden conditional random field with a countably infinite number of
Xu, Ganggang
2016-07-15
We propose a new class of trans-Gaussian random fields named Tukey g-and-h (TGH) random fields to model non-Gaussian spatial data. The proposed TGH random fields have extremely flexible marginal distributions, possibly skewed and/or heavy-tailed, and, therefore, have a wide range of applications. The special formulation of the TGH random field enables an automatic search for the most suitable transformation for the dataset of interest while estimating model parameters. Asymptotic properties of the maximum likelihood estimator and the probabilistic properties of the TGH random fields are investigated. An efficient estimation procedure, based on maximum approximated likelihood, is proposed and an extreme spatial outlier detection algorithm is formulated. Kriging and probabilistic prediction with TGH random fields are developed along with prediction confidence intervals. The predictive performance of TGH random fields is demonstrated through extensive simulation studies and an application to a dataset of total precipitation in the south east of the United States.
Synergistic effect of electric field and lipid oxidation on the permeability of cell membranes.
Yusupov, M; Van der Paal, J; Neyts, E C; Bogaerts, A
2017-04-01
Strong electric fields are known to affect cell membrane permeability, which can be applied for therapeutic purposes, e.g., in cancer therapy. A synergistic enhancement of this effect may be accomplished by the presence of reactive oxygen species (ROS), as generated in cold atmospheric plasmas. Little is known about the synergy between lipid oxidation by ROS and the electric field, nor on how this affects the cell membrane permeability. We here conduct molecular dynamics simulations to elucidate the dynamics of the permeation process under the influence of combined lipid oxidation and electroporation. A phospholipid bilayer (PLB), consisting of di-oleoyl-phosphatidylcholine molecules covered with water layers, is used as a model system for the plasma membrane. We show how oxidation of the lipids in the PLB leads to an increase of the permeability of the bilayer to ROS, although the permeation free energy barriers still remain relatively high. More importantly, oxidation of the lipids results in a drop of the electric field threshold needed for pore formation (i.e., electroporation) in the PLB. The created pores in the membrane facilitate the penetration of reactive plasma species deep into the cell interior, eventually causing oxidative damage. This study is of particular interest for plasma medicine, as plasma generates both ROS and electric fields, but it is also of more general interest for applications where strong electric fields and ROS both come into play. Copyright © 2017 Elsevier B.V. All rights reserved.
Sun, F
2013-01-01
In this paper a novel compressor for static magnetic fields is proposed based on finite embedded transformation optics. When the DC magnetic field passes through the designed device, the magnetic field can be compressed inside the device. After it passes through the device, one can obtain an enhanced static magnetic field behind the output surface of the device (in a free space region). We can also combine our compressor with some other structures to get a higher static magnetic field enhancement in a free space region. In contrast with other devices based on transformation optics for enhancing static magnetic fields, our device is not a closed structure and thus has some special applications (e.g., for controlling magnetic nano-particles for gene and drag delivery). The designed compressor can be constructed by using currently available materials or DC meta-materials with positive permeability. Numerical simulation verifies good performance of our device.
Field Induced Memory Effects in Random Nematics
Directory of Open Access Journals (Sweden)
Amid Ranjkesh
2014-01-01
Full Text Available We studied numerically external field induced memory effects in randomly perturbed nematic liquid crystals. Random anisotropy nematic-type lattice model was used. The impurities imposing orientational disorder were randomly spatially distributed with the concentration p below the percolation threshold. Simulations were carried for finite temperatures, where we varied p, interaction strength between LC molecules, and impurities and external field B. In the {B,T} plane we determined lines separating short range—quasi long range and quasi long range—long range order. Furthermore, crossover regime separating external field and random field dominated regime was estimated. We calculated remanent nematic ordering in samples at B=0 as a function of the previously experienced external field strength B.
Characterization of Permeability Fields and Fluid Flow through Rock Core during CO2 Sequestration
Kong, X.; Tutolo, B. M.; Luhmann, A. J.; Saar, M. O.; Seyfried, W. E.
2012-12-01
Dissolution of carbon dioxide (CO2) in subsurface formation fluids produces a weakly acidic fluid, which can undergo a sequence of chemical reactions with reservoir minerals. These processes may induce mineral dissolution and precipitation which can modify pore space geometries (pore connectivity, pore volume, pore surface area, and specific surface area of connected flow paths) thereby affecting permeability tensor fields in the reservoir. In this study, we quantify these effects on a dolomite core which underwent a 3-day single-pass experiment at 100 °C, 15 MPa, and a flow rate of 0.1 ml/min. The working fluid is 1 mol NaCl/kg H2O with a CO2 concentration of 0.6 mol/kg H2O. A novel and efficient approach was implemented in Matlab to extract the connected pore network and the network surface area of the 3D pore structure, which was reconstructed from XRCT images. Using this approach, the changes in pore space geometry are quantified by comparing the pore connectivity, pore volume, pore surface area, and specific surface area of connected flow paths before and after the experiment. The specific surface area can later be used as accessible reactive specific surface area to scale the dissolution rate constants for dolomite. The permeability tensor fields are determined by conducting pore-scale lattice-Boltzmann fluid flow simulations. The logarithms of the permeability values along the flow paths were found to linearly decrease with specific surface area of connected flow paths. This relationship would be helpful in developing empirical parameterized equations for permeability as a function of minerals, temperature, pressure, and time.
Markov Random Field Surface Reconstruction
DEFF Research Database (Denmark)
Paulsen, Rasmus Reinhold; Bærentzen, Jakob Andreas; Larsen, Rasmus
2010-01-01
) and knowledge about data (the observation model) in an orthogonal fashion. Local models that account for both scene-specific knowledge and physical properties of the scanning device are described. Furthermore, how the optimal distance field can be computed is demonstrated using conjugate gradients, sparse...
Concentration inequalities for random fields via coupling
Chazottes, J. R.; Collet, P.; Kuelske, C.; Redig, F.
We present a new and simple approach to concentration inequalities in the context of dependent random processes and random fields. Our method is based on coupling and does not use information inequalities. In case one has a uniform control on the coupling, one obtains exponential concentration
Field-scale forward and back diffusion through low-permeability zones
Yang, Minjune; Annable, Michael D.; Jawitz, James W.
2017-07-01
Understanding the effects of back diffusion of groundwater contaminants from low-permeability zones to aquifers is critical to making site management decisions related to remedial actions. Here, we combine aquifer and aquitard data to develop recommended site characterization strategies using a three-stage classification of plume life cycle based on the solute origins: aquifer source zone dissolution, source zone dissolution combined with back diffusion from an aquitard, and only back diffusion. We use measured aquitard concentration profile data from three field sites to identify signature shapes that are characteristic of these three stages. We find good fits to the measured data with analytical solutions that include the effects of advection and forward and back diffusion through low-permeability zones, and linearly and exponentially decreasing flux resulting from source dissolution in the aquifer. Aquifer contaminant time series data at monitoring wells from a mature site were well described using analytical solutions representing the combined case of source zone and back diffusion, while data from a site where the source had been isolated were well described solely by back diffusion. The modeling approach presented in this study is designed to enable site managers to implement appropriate remediation technologies at a proper timing for high- and low-permeability zones, considering estimated plume life cycle.
Hristopulos, Dionissios
2001-03-01
Quenched random disorder models represent the heterogeneity of the saturated fluid permeability of porous media in steady-state flow conditions. The effective permeability is based on the stochastic average of local fluctuations and measures large-scale effects of the disorder. Explicit calculations of effective permeability require various restrictive assumptions on the disorder distribution, and numerical methods are computationally intensive. We propose a semianalytical approach based on the coherent potential approximation (CPA), used for electronic band structure calculations in disordered semiconductors. The PCPA does not require the restrictions of explicit methods and admits efficient numerical solutions. The PCPA equations yield the exact effective permeability (the harmonic mean), in one spatial dimension. The leading order solution in higher dimensions agrees with the standard perturbation expansion. It is known that the effective permeability of a two-dimensional medium with lognormal disorder is given exactly by the geometric mean. We show that the numerical solutions of the PCPA are in good agreement with the exact expression.
Entropy estimates for simple random fields
DEFF Research Database (Denmark)
Forchhammer, Søren; Justesen, Jørn
1995-01-01
We consider the problem of determining the maximum entropy of a discrete random field on a lattice subject to certain local constraints on symbol configurations. The results are expected to be of interest in the analysis of digitized images and two dimensional codes. We shall present some examples...... of binary and ternary fields with simple constraints. Exact results on the entropies are known only in a few cases, but we shall present close bounds and estimates that are computationally efficient...
Random field estimation approach to robot dynamics
Rodriguez, Guillermo
1990-01-01
The difference equations of Kalman filtering and smoothing recursively factor and invert the covariance of the output of a linear state-space system driven by a white-noise process. Here it is shown that similar recursive techniques factor and invert the inertia matrix of a multibody robot system. The random field models are based on the assumption that all of the inertial (D'Alembert) forces in the system are represented by a spatially distributed white-noise model. They are easier to describe than the models based on classical mechanics, which typically require extensive derivation and manipulation of equations of motion for complex mechanical systems. With the spatially random models, more primitive locally specified computations result in a global collective system behavior equivalent to that obtained with deterministic models. The primary goal of applying random field estimation is to provide a concise analytical foundation for solving robot control and motion planning problems.
Markov random fields on triangle meshes
DEFF Research Database (Denmark)
Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jakob Andreas
2010-01-01
In this paper we propose a novel anisotropic smoothing scheme based on Markov Random Fields (MRF). Our scheme is formulated as two coupled processes. A vertex process is used to smooth the mesh by displacing the vertices according to a MRF smoothness prior, while an independent edge process label...
Markov Random Fields on Triangle Meshes
DEFF Research Database (Denmark)
Andersen, Vedrana; Aanæs, Henrik; Bærentzen, Jakob Andreas
2010-01-01
In this paper we propose a novel anisotropic smoothing scheme based on Markov Random Fields (MRF). Our scheme is formulated as two coupled processes. A vertex process is used to smooth the mesh by displacing the vertices according to a MRF smoothness prior, while an independent edge process label...
Chen, X.; Johnson, T. C.; Hammond, G. E.; Zachara, J. M.
2014-12-01
The hydrological and biogeochemical processes at the groundwater and river water interface are largely controlled by the exchange dynamics between the two water bodies. Accurate characterization of the heterogeneous permeability field at such interface is critical for modeling the bulk flow as well as the biogeochemical processes that are coupled with the flow. Taking advantage of the distinct conductivities in groundwater and rive water, time lapse electrical resistivity tomography (ERT) can provide rich spatial and temporal data for characterizing the permeability field, by imaging the change in subsurface electric conductivity driven by river water intrusion and retreat. We installed a large-scale (300 m by 300 m) 3-dimensional ERT array to monitor river water intrusion and retreat through time at a major river corridor, and the 4-dimensional electrical geophysical data is assimilated to invert for the underlying permeability field using ensemble-based algorithms (e.g., ensemble Kalman filter and ensemble smoother). We developed a new high-performance hydrogeophysical code by coupling an ERT imaging code E4D (Johnson et al., 2010) with a site-scale flow and transport code, PFLOTRAN (Hammond et al., 2012). The coupled code provides the key modeling capability of multi-physics processes, parallel efficiency, and multi-realization simulation capability for hydrogeophysical inversion. We assimilated both well-based point measurements of water table and specific conductance and spatially continuous ERT images in a sequential Bayesian way. Our study demonstrates the effectiveness of joint hydrogeophysical inversion for large-scale characterization of subsurface properties in the groundwater and river water interaction zone. Our investigation of spatial versus temporal data assimilation strategies have inspired systematic data worth analyses to identify the most valuable data sets for hydrogeophysical inversion. The high performance computing is performed on the Hopper
Gaussian Markov random fields theory and applications
Rue, Havard
2005-01-01
Gaussian Markov Random Field (GMRF) models are most widely used in spatial statistics - a very active area of research in which few up-to-date reference works are available. This is the first book on the subject that provides a unified framework of GMRFs with particular emphasis on the computational aspects. This book includes extensive case-studies and, online, a c-library for fast and exact simulation. With chapters contributed by leading researchers in the field, this volume is essential reading for statisticians working in spatial theory and its applications, as well as quantitative researchers in a wide range of science fields where spatial data analysis is important.
Manga, Michael; Beresnev, Igor; Brodsky, Emily E.; Elkhoury, Jean E.; Elsworth, Derek; Ingebritsen, Steve E.; Mays, David C.; Wang, Chi-Yuen
2012-01-01
Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10–6 can increase discharge in streams and springs, change the water level in wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to prestimulated values over a period of months to years. Mechanisms that can change permeability at such small stresses include unblocking pores, either by breaking up permeability-limiting colloidal deposits or by mobilizing droplets and bubbles trapped in pores by capillary forces. The recovery time over which permeability returns to the prestimulated value is governed by the time to reblock pores, or for geochemical processes to seal pores. Monitoring permeability in geothermal systems where there is abundant seismicity, and the response of flow to local and regional earthquakes, would help test some of the proposed mechanisms and identify controls on permeability and its evolution.
Permeability of displaced fractures
Kluge, Christian; Milsch, Harald; Blöcher, Guido
2017-04-01
Flow along fractures or in fissured systems becomes increasingly important in the context of Enhanced Geothermal Systems (EGS), shale gas recovery or nuclear waste deposit. Commonly, the permeability of fractures is approximated using the Hagen-Poiseuille solution of Navier Stokes equation. Furthermore, the flow in fractures is assumed to be laminar flow between two parallel plates and the cubic law for calculating the velocity field is applied. It is a well-known fact, that fracture flow is strongly influenced by the fracture surface roughness and the shear displacement along the fracture plane. Therefore, a numerical approach was developed which calculates the flow pattern within a fracture-matrix system. The flow in the fracture is described by a free fluid flow and the flow in the matrix is assumed to be laminar and therefore validates Darcy's law. The presented approach can be applied for artificially generated fractures or real fractures measured by surface scanning. Artificial fracture surfaces are generated using the power spectral density of the surface height random process with a spectral exponent to define roughness. For calculating the permeability of such fracture-matrix systems the mean fracture aperture, the shear displacement and the surface roughness are considered by use of a 3D numerical simulator. By use of this approach correlation between shear displacement and mean aperture, shear displacement and permeability, as well as surface roughness and permeability can be obtained. Furthermore, the intrinsic measured permeability presents a combination of matrix and fracture permeability. The presented approach allows the separation and quantification of the absolute magnitudes of the matrix and the fracture permeability and the permeability of displaced fractures can be calculated. The numerical approach which is a 3D numerical simulation of the fracture-matrix system can be applied for artificial as well as real systems.
Prajapati, N.; Ankit, K.; Selzer, M.; Nestler, B.; Schmidt, C.; Hilgers, C.
2016-12-01
Prediction of cement volumes is an integral part of reservoir modeling. Quantitative determination of petrophysical charateristics such as permeability and water saturation are essential in order to assess the sufficiency of hydrocarbons in pore space. Conventional techniques such as well-logging provide only a qualitative understanding of the cementation history and future pore evolution. Diffused modeling approach such as the phase-field method is a viable alternative that can be used to numerically simulate pore cementation under different boundary conditions in a thermodynamically-consistent manner. Here, we use a multiphase-field model to investigate the dynamics of polycrystalline quartz precipitation from supersaturated solution in porous rock. To begin with, we validate the faceted-type anisotropy formulations of the interfacial energy function that corresponds to monocrystalline quartz using the volume-preservation technique. Next, we numerically simulate the unitaxial evolution of quartz in a 2D open space and investigate the role of misorientations and c/a ratios in the formation of quartz cement that is extensively observed in nature. Based on this sensitivity analysis, we choose a realistic c/a ratio to computationally mimic the anisotropic sealing of pore space in sandstone. We observe a large deviation of 3D sealing kinetics as compared to 2D. The decrease in 3D pore space volume during cementation is found to be inversely dependent (non-linear) on the inter-nuclei distance. Using CFD analysis, we then derive the temporal evolution of permeability in partially sealed microstructures. Finally, we highlight the capabilities of the present numerical approaches in numerically simulating 3D reactive flow during progressive sealing in porous rocks based on innovative post-processing analyses and visualization techniques.
Random Circles and Fields on Circles.
1986-05-01
p is on the true circle C ; X is the corresponding radius of the random circle -5- Examples and comments Let W be a Wiener process on 3+, let a > 0 be...properties on C when M = W, it is expected that X be the analog of the Ornstein-Uhlenbeck process on the circle C . Indeed, the representation (2.12) shows this...evolution in time of a random field on the circle C . -35- The message of the following theorem is that the sections of X are all stationary and Markov
Random wave fields and scintillated beams
CSIR Research Space (South Africa)
Roux, FS
2009-01-01
Full Text Available fields . Artificial vortex fields CSIR National Laser Centre – p.2/29 Scintillated optical beams When an optical beam propagates through a turbulent atmosphere, the index variations cause random phase modulations that lead to distortions of the optical... beam. CSIR National Laser Centre – p.3/29 Weak scintillation If the scintillation is weak the resulting phase function of the optical beam is still continuous. Such a weakly scintillated beam can be corrected by an adaptive optical system. CSIR National...
Gradient Boosting for Conditional Random Fields
2014-09-23
evidence boosting. In Proceedings of the 20th International Joint Conference on Artifical Intelligence , IJCAI’07, 2007. [13] O. Meshi, D. Sontag, T...Conference on Artificial Intelligence and Statistics (AISTATS’10), 2010. [3] J. Domke. Structured learning via logistic regression. In Advances in Neural...Artificial Intelligence (UAI’10), pages 302–311, 2010. [12] L. Liao, T. Choudhury, D. Fox, and H. Kautz. Training conditional random fields using virtual
Variational Infinite Hidden Conditional Random Fields.
Bousmalis, Konstantinos; Zafeiriou, Stefanos; Morency, Louis-Philippe; Pantic, Maja; Ghahramani, Zoubin
2015-09-01
Hidden conditional random fields (HCRFs) are discriminative latent variable models which have been shown to successfully learn the hidden structure of a given classification problem. An Infinite hidden conditional random field is a hidden conditional random field with a countably infinite number of hidden states, which rids us not only of the necessity to specify a priori a fixed number of hidden states available but also of the problem of overfitting. Markov chain Monte Carlo (MCMC) sampling algorithms are often employed for inference in such models. However, convergence of such algorithms is rather difficult to verify, and as the complexity of the task at hand increases the computational cost of such algorithms often becomes prohibitive. These limitations can be overcome by variational techniques. In this paper, we present a generalized framework for infinite HCRF models, and a novel variational inference approach on a model based on coupled Dirichlet Process Mixtures, the HCRF-DPM. We show that the variational HCRF-DPM is able to converge to a correct number of represented hidden states, and performs as well as the best parametric HCRFs-chosen via cross-validation-for the difficult tasks of recognizing instances of agreement, disagreement, and pain in audiovisual sequences.
Schwarz, Lothar; Hermanowski, Mona-Lena
2008-01-01
With a simple experimental set-up, common packaging materials were tested for their ninhydrin permeability. The packaging material was loaded with a ninhydrin treated paper on the inside and covered with an amino acid treated paper on the outside. If ninhydrin penetrates through the packaging film, "Ruhemann's purple" will form on the amino acid treated paper. In all, 28 packaging materials were tested over a period of 24 weeks. It turned out that all the films made of polyethylene (PE) showed ninhydrin permeability. With one exception, this permeability occurred after three days already. All packages made of other film material were not permeable to ninhydrin.
The Permeability of Boolean Sets of Cylinders
Directory of Open Access Journals (Sweden)
Willot F.
2016-07-01
Full Text Available Numerical and analytical results on the permeability of Boolean models of randomly-oriented cylinders with circular cross-section are reported. The present work investigates cylinders of prolate (highly-elongated and oblate (nearly flat types. The fluid flows either inside or outside of the cylinders. The Stokes flow is solved using full-fields Fourier-based computations on 3D binarized microstructures. The permeability is given for varying volume fractions of pores. A new upper-bound is derived for the permeability of the Boolean model of oblate cylinders. The behavior of the permeability in the dilute limit is discussed.
Positive random fields for modeling material stiffness and compliance
DEFF Research Database (Denmark)
Hasofer, Abraham Michael; Ditlevsen, Ove Dalager; Tarp-Johansen, Niels Jacob
1998-01-01
with material properties modeled in terms of the considered random fields.The paper addsthe gamma field, the Fisher field, the beta field, and their reciprocal fields to the catalogue. These fields are all defined on the basis of sums of squares of independent standard Gaussian random variables.All the existing......Positive random fields with known marginal properties and known correlation function are not numerous in the literature. The most prominent example is the log\\-normal field for which the complete distribution is known and for which the reciprocal field is also lognormal. It is of interest...... to supplement the catalogue of positive fields beyond the class of those obtained by simple marginal transformation of a Gaussian field, this class containing the lognormal field.As a minimum for a random field to be included in the catalogue itis required that an algorithm for simulation of realizations can...
Yang, PeiPei; Wen, Zhi; Dou, RuiFeng; Liu, Xunliang
2016-08-01
Flow and heat transfer through a 2D random porous medium are studied by using the lattice Boltzmann method (LBM). For the random porous medium, the influence of disordered cylinder arrangement on permeability and Nusselt number are investigated. Results indicate that the permeability and Nusselt number for different cylinder locations are unequal even with the same number and size of cylinders. New correlations for the permeability and coefficient b‧Den of the Forchheimer equation are proposed for random porous medium composed of Gaussian distributed circular cylinders. Furthermore, a general set of heat transfer correlations is proposed and compared with existing experimental data and empirical correlations. Our results show that the Nu number increases with the increase of the porosity, hence heat transfer is found to be accurate considering the effect of porosity.
Field test to study the pressure equilization on air permeable facade elements
Bentum, C.A. van; Kalkman, I.M.; Geurts, C.P.W.
2014-01-01
The net wind load on the outer layer of a façade consisting of multiple layers is determined by the external pressure and the cavity pressure. For an air-permeable outer layer, the cavity pressure is dependent on the extent to which the external pressure equalizes over the openings. Minimizing the
Directory of Open Access Journals (Sweden)
Karpushkin Sergey
2017-01-01
Full Text Available The paper presents a method of calculating a constant value of magnetic permeability of ferromagnetic materials, equivalent to the basic magnetization curve by the criterion of real power. The proposed method makes it possible to use linear differential equations of the electromagnetic field in the analysis of three-dimensional fields of eddy currents in ferromagnetic materials, thus significantly reducing the calculation time. We propose a method of calculating the power of inductors using two-dimensional axisymmetric models. The scope of the proposed methods is limited to the case of placement of the inductor inside the ferromagnetic body.
Conrad: gene prediction using conditional random fields.
DeCaprio, David; Vinson, Jade P; Pearson, Matthew D; Montgomery, Philip; Doherty, Matthew; Galagan, James E
2007-09-01
We present Conrad, the first comparative gene predictor based on semi-Markov conditional random fields (SMCRFs). Unlike the best standalone gene predictors, which are based on generalized hidden Markov models (GHMMs) and trained by maximum likelihood, Conrad is discriminatively trained to maximize annotation accuracy. In addition, unlike the best annotation pipelines, which rely on heuristic and ad hoc decision rules to combine standalone gene predictors with additional information such as ESTs and protein homology, Conrad encodes all sources of information as features and treats all features equally in the training and inference algorithms. Conrad outperforms the best standalone gene predictors in cross-validation and whole chromosome testing on two fungi with vastly different gene structures. The performance improvement arises from the SMCRF's discriminative training methods and their ability to easily incorporate diverse types of information by encoding them as feature functions. On Cryptococcus neoformans, configuring Conrad to reproduce the predictions of a two-species phylo-GHMM closely matches the performance of Twinscan. Enabling discriminative training increases performance, and adding new feature functions further increases performance, achieving a level of accuracy that is unprecedented for this organism. Similar results are obtained on Aspergillus nidulans comparing Conrad versus Fgenesh. SMCRFs are a promising framework for gene prediction because of their highly modular nature, simplifying the process of designing and testing potential indicators of gene structure. Conrad's implementation of SMCRFs advances the state of the art in gene prediction in fungi and provides a robust platform for both current application and future research.
Estimation of soil permeability
Directory of Open Access Journals (Sweden)
Amr F. Elhakim
2016-09-01
Full Text Available Soils are permeable materials because of the existence of interconnected voids that allow the flow of fluids when a difference in energy head exists. A good knowledge of soil permeability is needed for estimating the quantity of seepage under dams and dewatering to facilitate underground construction. Soil permeability, also termed hydraulic conductivity, is measured using several methods that include constant and falling head laboratory tests on intact or reconstituted specimens. Alternatively, permeability may be measured in the field using insitu borehole permeability testing (e.g. [2], and field pumping tests. A less attractive method is to empirically deduce the coefficient of permeability from the results of simple laboratory tests such as the grain size distribution. Otherwise, soil permeability has been assessed from the cone/piezocone penetration tests (e.g. [13,14]. In this paper, the coefficient of permeability was measured using field falling head at different depths. Furthermore, the field coefficient of permeability was measured using pumping tests at the same site. The measured permeability values are compared to the values empirically deduced from the cone penetration test for the same location. Likewise, the coefficients of permeability are empirically obtained using correlations based on the index soil properties of the tested sand for comparison with the measured values.
Random Network Coding over Composite Fields
DEFF Research Database (Denmark)
Geil, Olav; Lucani Rötter, Daniel Enrique
2017-01-01
Random network coding is a method that achieves multicast capacity asymptotically for general networks [1, 7]. In this approach, vertices in the network randomly and linearly combine incoming information in a distributed manner before forwarding it through their outgoing edges. To ensure success...
Fuzzy conditional random fields for temporal data mining
Nurma Yulita, Intan; Setiawan Abdullah, Atje
2017-10-01
Temporal data mining is one of the interesting problems in computer science and its application has been performed in a wide variety of fields. The difference between the temporal data mining and data mining is the use of variable time. Therefore, the method used must be capable of processing variables of time. Compared with other methods, conditional random field has advantages in the processing variables of time. The method is a directed graph models that has been widely applied for segmenting and labelling sequence data that appears in various domains. In this study, we proposed use of Fuzzy Logic to be applied in Conditional Random Fields to overcome the problems of uncertainty. The experiment is compared Fuzzy Conditional Random Fields, Conditional Random Fields, and Hidden Markov Models. The result showed that accuracy of Fuzzy Conditional Random Fields is the best.
Permeability prediction in chalks
DEFF Research Database (Denmark)
Alam, Mohammad Monzurul; Fabricius, Ida Lykke; Prasad, Manika
2011-01-01
prediction, so we have investigated the use of velocity data to predict permeability. The compressional velocity fromwireline logs and core plugs of the chalk reservoir in the South Arne field, North Sea, has been used for this study. We compared various methods of permeability prediction from velocities......-permeability relationships were replaced by relationships between velocity of elastic waves and permeability using laboratory data, and the relationships were then applied to well-log data. We found that the permeability prediction in chalk and possibly other sediments with large surface areas could be improved...
Singh, M.
2015-12-01
The instability of plane interface between two superposed Rivlin-Ericksen elastico-viscous fluids saturated through a porous medium has been studied to include the suspended (dust) particles effect. Following the linearized stability theory and normal mode analysis the dispersion relation is obtained. For stationary convection, the Rivlin-Ericksen elastico-viscous fluid behaves like Newtonian fluids. It found that for a potentially stable arrangement the Rivlin-Ericksen elastico-viscous fluid of different permeabilities in the presence of suspended particles in a porous medium is stable, whereas in a potentially unstable case instability of the system occurs. In the presence of a magnetic field for a potentially stable arrangement the system is always stable and for the potentially unstable arrangement, the magnetic field succeeds in stabilizing certain wave-number band which was unstable in the absence of the magnetic field.
Ordering and phase transitions in random-field Ising systems
Maritan, Amos; Swift, Michael R.; Cieplak, Marek; Chan, Moses H. W.; Cole, Milton W.; Banavar, Jayanth R.
1991-01-01
An exact analysis of the Ising model with infinite-range interactions in a random field and a local mean-field theory in three dimensions is carried out leading to a phase diagram with several coexistence surfaces and lines of critical points. The results show that the phase diagram depends crucially on whether the distribution of random fields is symmetric or not. Thus, Ising-like phase transitions in a porous medium (the asymmetric case) are in a different universality class from the conventional random-field model (symmetric case).
Level sets and extrema of random processes and fields
Azais, Jean-Marc
2009-01-01
A timely and comprehensive treatment of random field theory with applications across diverse areas of study Level Sets and Extrema of Random Processes and Fields discusses how to understand the properties of the level sets of paths as well as how to compute the probability distribution of its extremal values, which are two general classes of problems that arise in the study of random processes and fields and in related applications. This book provides a unified and accessible approach to these two topics and their relationship to classical theory and Gaussian processes and fields, and the most modern research findings are also discussed. The authors begin with an introduction to the basic concepts of stochastic processes, including a modern review of Gaussian fields and their classical inequalities. Subsequent chapters are devoted to Rice formulas, regularity properties, and recent results on the tails of the distribution of the maximum. Finally, applications of random fields to various areas of mathematics a...
Effects of random fields in an antiferromagnetic Ising bilayer film
Kaneyoshi, T.
2017-10-01
The magnetic properties (phase diagrams and magnetizations) of an antiferromagnetic Ising bilayer film with random fields are investigated by the use of the effective field theory with correlations. It is examined how an uncompensated magnetization can be realized in the system, due to the effects of random fields in the two layers. They show the tricritical, compensation point and reentrant phenomena, depending on these parameters.
Energy Technology Data Exchange (ETDEWEB)
Minissale, Angelo; Montegrossi, Giordano; Orlando, Andrea [Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR), Via G. La Pira 4, 50121 Florence (Italy); Borrini, Daniele; Tassi, Franco [Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence (Italy); Vaselli, Orlando [Institute of Geosciences and Earth Resources, National Research Council of Italy (CNR), Via G. La Pira 4, 50121 Florence (Italy); Department of Earth Sciences, University of Florence, Via G. La Pira 4, 50121 Florence (Italy); Huertas, Antonio Delgado [Estacion Experimental de Zaidin (CSIC), Prof. Albareda 1, 18008 Granada (Spain); Yang, Jincheng; Cheng, Wanquing [Aode Renewable Energy Research Institute, 90 Weijin South Road, Nankai District, 300381 Tianjin (China); Tedesco, Dario [Department of Environmental Sciences, Second University of Naples, Via Vivaldi 43, Caserta 81100 (Italy); Institute of Environmental Geology and Geo Engineering (CNR), Piazzale A. Moro 5, Roma 00100 (Italy); Poreda, Robert [Department of Earth and Environmental Sciences, University of Rochester, 227 Hutchison Hall, Rochester, NY 14627 (United States)
2008-08-15
Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at the end of the 1990s. Well injectivities declined after 3-4 years because of self-sealing processes that reduced reservoir permeability. The study focuses on the factors that may have caused the observed decrease in permeability, using chemical and isotopic data on fluids (water and gas) and mineral phases collected from production and injection wells. The results of data processing and interpretation indicate that (1) it is very unlikely that calcite and silica precipitation is taking place in the reservoir; (2) the Fe- and Zn-rich mineral phases (e.g. sulfides, hydroxides and silicates) show positive saturation indexes; (3) SEM and XRD analyses of filtered material reveal that the latter mineral phases are common; (4) visual observation of casings and surface installations, and of corrosion products, suggests that a poor quality steel was used in their manufacture; (5) significant quantities of solids (e.g. quartz and feldspar crystals) are carried by the geothermal fluid; (6) seasonal changes in fluid composition lead to a reduction in casing corrosion during the summer. It was concluded that the decrease in injectivity in the Tianjin wells is caused only in part by the oxidation of casings, downhole pumps, and surface installations, triggered by free oxygen in the injected fluids; the utilization of better quality steels should drastically reduce this type of corrosion. Self-sealing of pores and fractures by reservoir formation solids and by the Fe-corrosion products suspended in the injected fluids seems to be a more important phenomenon, whose effect could be greatly reduced by installing filtering devices at all sites. (author)
Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng
2015-06-09
Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.
Wijck, van K.; Verlinden, T.J.M.; Eijk, van H.M.H.; Dekker, J.; Buurman, W.A.; Dejong, C.H.C.; Lenaerts, K.
2013-01-01
Background & aims: Increased gastrointestinal (GI) permeability is an important hallmark of many conditions, potentially leading to antigen exposure and sepsis. Current permeability tests are hampered by analytical limitations. This study aims to compare the accuracy of our multi-sugar (MS) and
Supplementary Material for: Tukey g-and-h Random Fields
Xu, Ganggang
2016-01-01
We propose a new class of transGaussian random fields named Tukey g-and-h (TGH) random fields to model non-Gaussian spatial data. The proposed TGH random fields have extremely flexible marginal distributions, possibly skewed and/or heavy-tailed, and, therefore, have a wide range of applications. The special formulation of the TGH random field enables an automatic search for the most suitable transformation for the dataset of interest while estimating model parameters. Asymptotic properties of the maximum likelihood estimator and the probabilistic properties of the TGH random fields are investigated. An efficient estimation procedure, based on maximum approximated likelihood, is proposed and an extreme spatial outlier detection algorithm is formulated. Kriging and probabilistic prediction with TGH random fields are developed along with prediction confidence intervals. The predictive performance of TGH random fields is demonstrated through extensive simulation studies and an application to a dataset of total precipitation in the south east of the United States. Supplementary materials for this article are available online.
Stochastic analysis for gaussian random processes and fields with applications
Mandrekar, Vidyadhar S
2015-01-01
Stochastic Analysis for Gaussian Random Processes and Fields: With Applications presents Hilbert space methods to study deep analytic properties connecting probabilistic notions. In particular, it studies Gaussian random fields using reproducing kernel Hilbert spaces (RKHSs).The book begins with preliminary results on covariance and associated RKHS before introducing the Gaussian process and Gaussian random fields. The authors use chaos expansion to define the Skorokhod integral, which generalizes the Itô integral. They show how the Skorokhod integral is a dual operator of Skorokhod differenti
Dual permeability soil water dynamics and water uptake by roots in irrigated potato fields
DEFF Research Database (Denmark)
Dolezal, F; Zumir, D; Vacek, J
2007-01-01
Water movement and uptake by roots in a drip-irrigated potato field was studied by combining field experiments, outputs of numerical simulations and summary results of an EU project (www.fertorganic.org). Detailed measurements of soil suction and weather conditions in the Bohemo-Moravian highland...
Directory of Open Access Journals (Sweden)
Roberio Dias LEITE
2013-03-01
Full Text Available Context Glutamine is the main source of energy of the enterocyte and diarrhea and weight loss are frequent in HIV infected patients. Objective To determine the effect of alanyl-glutamine supplementation on intestinal permeability and absorption in these patients. Methods Randomized double-blinded, placebo-controlled study using isonitrogenous doses of alanyl-glutamine (24 g/day and placebo (glycine, 25 g/day during 10 days. Before and after this nutritional supplementation lactulose and mannitol urinary excretion were determined by high performance liquid chromatography. Results Forty six patients with HIV/AIDS, 36 of whom were male, with 37.28 ± 3 (mean ± standard error years were enrolled. Twenty two and 24 subjects were treated with alanyl-glutamine and with glycine respectively. In nine patients among all in the study protocol that reported diarrhea in the 14 days preceding the beginning of the study, mannitol urinary excretion was significantly lower than patients who did not report this symptom [median (range: 10.51 (3.01–19.75 vs. 15.37 (3.93–46.73; P = 0.0281] and lactulose/mannitol ratio was significantly higher [median (range: 0.04 (0.00–2.89 vs. 0.02 (0.00–0.19; P = 0.0317]. There was also a significant increase in mannitol urinary excretion in the group treated with alanyl-glutamine [median (range: 14.38 (8.25–23.98 before vs 21.24 (6.27–32.99 after treatment; n = 14, P = 0.0382]. Conclusion Our results suggest that the integrity and intestinal absorption are more intensely affected in patients with HIV/AIDS who recently have had diarrhea. Additionally, nutritional supplementation with alanyl-glutamine was associated with an improvement in intestinal absorption.
The space transformation in the simulation of multidimensional random fields
Christakos, G.
1987-01-01
Space transformations are proposed as a mathematically meaningful and practically comprehensive approach to simulate multidimensional random fields. Within this context the turning bands method of simulation is reconsidered and improved in both the space and frequency domains. ?? 1987.
Random-Field Model of a Cooper Pair Insulator
Proctor, Thomas; Chudnovsky, Eugene; Garanin, Dmitry
2013-03-01
The model of a disordered superconducting film with quantum phase fluctuations is mapped on a random-field XY spin model in 2+1 dimensions. Analytical studies within continuum field theory, supported by our recent numerical calculations on discrete lattices, show the onset of the low-temperature Cooper pair insulator phase. The constant external field in the random-field spin model maps on the Josephson coupling between the disordered film and a bulk superconductor. Such a coupling, if sufficiently strong, restores superconductivity in the film. This provides an experimental test for the quantum fluctuation model of a superinsulator.
Chen, Meng-Huo
2016-06-01
Nanoparticles are particles that are between 1 and 100 nanometers in size. They present possible dangers to the environment due to the high surface to volume ratio, which can make the particles very reactive or catalytic. Furthermore, rapid increase in the implementation of nanotechnologies has released large amount of the nanowaste into the environment. In the last two decades, transport of nanoparticles in the subsurface and the potential hazard they impose to the environment have attracted the attention of researchers. In this work, we use numerical simulation to investigate the problem regarding the transport phenomena of nanoparticles in anisotropic porous media. We consider the case in which the permeability in the principal direction components will vary with respect to time. The interesting thing in this case is the fact that the anisotropy could disappear with time. We investigate the effect of the degenerating anisotropy on various fields such as pressure, porosity, concentration and velocities.
Study of heat transfer and flow of nanofluid in permeable channel in the presence of magnetic field
Directory of Open Access Journals (Sweden)
M. Fakour
2015-03-01
Full Text Available In this paper, laminar fluid flow and heat transfer in channel with permeable walls in the presence of a transverse magnetic field is investigated. Least square method (LSM for computing approximate solutions of nonlinear differential equations governing the problem. We have tried to show reliability and performance of the present method compared with the numerical method (Runge-Kutta fourth-rate to solve this problem. The influence of the four dimensionless numbers: the Hartmann number, Reynolds number, Prandtl number and Eckert number on non-dimensional velocity and temperature profiles are considered. The results show analytical present method is very close to numerically method. In general, increasing the Reynolds and Hartman number is reduces the nanofluid flow velocity in the channel and the maximum amount of temperature increase and increasing the Prandtl and Eckert number will increase the maximum amount of theta.
Properties and simulation of α-permanental random fields
DEFF Research Database (Denmark)
Møller, Jesper; Rubak, Ege Holger
An α-permanental random field is briefly speaking a model for a collection of random variables with positive associations, where α is a positive number and the probability generating function is given in terms of a covariance or more general function so that density and moment expressions are giv......, and second to study stochastic constructions and simulation techniques, which should provide a useful basis for discussing the statistical aspects in future work. The paper also discusses some examples of α-permanental random fields....
de Roos, N M; van Hemert, S; Rovers, J M P; Smits, M G; Witteman, B J M
2017-12-01
Migraine, associated with several gastrointestinal disorders, may result from increased intestinal permeability, allowing endotoxins to enter the bloodstream. We tested whether probiotics could reduce migraine through an effect on intestinal permeability and inflammation. In total, 63 patients were randomly allocated to the probiotic (n=31) or the placebo group (n=32). Participants ingested a multispecies probiotic (5x109 colony-forming units) or placebo daily for 12 weeks. Migraine was assessed with the Migraine Disability Assessment Scale (MIDAS), the Headache Disability Inventory (HDI) and headache diaries. At baseline and 12 weeks, intestinal permeability was measured with the urinary lactulose/mannitol test and fecal and serum zonulin; inflammation was measured from interleukin (IL) -6, IL-10, tumor necrosis factor-α and C-reactive protein in serum. The MIDAS migraine intensity score significantly decreased in both groups (Pmigraine days in the first month, 4 in the second month (P=0.002) and 5 in the last month, which was not significantly different from the 5, 4, and 4 days in the placebo group. A ⩾2day reduction in migraine days was seen in 12/31 patients in the probiotics group versus 7/29 in the placebo group (ns). Probiotic use did not significantly affect medication use, intestinal permeability or inflammation compared to placebo. In this study, we could not confirm significant benefit from a multispecies probiotic compared to a placebo on the outcome parameters of migraine and intestinal integrity.
Effective diffusion equation in a random velocity field
Vinals, Jorge; Sekerka, Robert F.
1992-01-01
The effects are studied of assumed random velocity fields on diffusion in a binary fluid. Random velocity fields can result, for example, from the high-frequency components of residual accelerations onboard spacecraft (often called g-jitter). An effective diffusion equation is derived for an average concentration which includes spatial and temporal correlations induced by the fluctuating velocity fields assumed to be Gaussianly distributed. The resulting equation becomes nonlocal, and if correlations between different components of the velocity field exist, it is also anisotropic. The simple limiting case of short correlation times is discussed and an effective diffusivity is obtained which reflects the enhanced mixing caused by the velocity fields. The results obtained in the limit of short correlation times are valid even if the probability distribution of the velocity field is not Gaussian.
Measurement of the Oxygen Permeability of a Composite Test Structure for the ALICE TPC Field Cage
Mast, M; CERN. Geneva; Bächler, J
2000-01-01
Abstract This note reports on measurements of oxygen permeation through a sample of a low-mass composite structure proposed for the manufacture of the TPC field cage vessels. The investigated test structure was commercially fabricated of three separate pieces glued together via two solid splices. The specimen was produced by Fischer Advanced Composite Components G.m.b.H. in Ried/Austria in cooperation with CERN.
Permeable pavement study (Edison)
U.S. Environmental Protection Agency — While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types...
Efficient Incorporation of Markov Random Fields in Change Detection
DEFF Research Database (Denmark)
Aanæs, Henrik; Nielsen, Allan Aasbjerg; Carstensen, Jens Michael
2009-01-01
Many change detection algorithms work by calculating the probability of change on a pixel-wise basis. This is a disadvantage since one is usually looking for regions of change, and such information is not used in pixel-wise classification - per definition. This issue becomes apparent in the face...... of noise, implying that the pixel-wise classifier is also noisy. There is thus a need for incorporating local homogeneity constraints into such a change detection framework. For this modelling task Markov Random Fields are suitable. Markov Random Fields have, however, previously been plagued by lack...... of efficient optimization methods or numerical solvers. We here address the issue of efficient incorporation of local homogeneity constraints into change detection algorithms. We do this by exploiting recent advances in graph based algorithms for Markov Random Fields. This is combined with an IR-MAD change...
Acharyya, Muktish
2013-05-01
The dynamical steady state behaviour of the random field Ising ferromagnet swept by a propagating magnetic field wave is studied at zero temperature by Monte Carlo simulation in two dimensions. The distribution of the random field is bimodal type. For a fixed set of values of the frequency, wavelength and amplitude of propagating magnetic field wave and the strength of the random field, four distinct dynamical steady states or nonequilibrium phases were identified. These four nonequilibrium phases are characterised by different values of structure factors. State or phase of first kind, where all spins are parallel (up). This phase is a frozen or pinned where the propagating field has no effect. The second one is the propagating type, where the sharp strips formed by parallel spins are found to move coherently. The third one is also propagating type, where the boundary of the strips of spins is not very sharp. The fourth kind shows no propagation of strips of magnetic spins, forming a homogeneous distribution of up and down spins. This is disordered phase. The existence of these four dynamical phases or modes depends on the value of the amplitude of propagating magnetic field wave and the strength of random (static) field. A phase diagram has also been drawn, in the plane formed by the amplitude of propagating field and the strength of random field. It is also checked that the existence of these dynamical phases is neither a finite size effect nor a transient phenomenon.
Stochastic geometry, spatial statistics and random fields models and algorithms
2015-01-01
Providing a graduate level introduction to various aspects of stochastic geometry, spatial statistics and random fields, this volume places a special emphasis on fundamental classes of models and algorithms as well as on their applications, for example in materials science, biology and genetics. This book has a strong focus on simulations and includes extensive codes in Matlab and R, which are widely used in the mathematical community. It can be regarded as a continuation of the recent volume 2068 of Lecture Notes in Mathematics, where other issues of stochastic geometry, spatial statistics and random fields were considered, with a focus on asymptotic methods.
Gleeson, Tom; Ingebritsen, Steven E.
2016-01-01
Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures. The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration. Although there are thousands of research papers on crustal permeability, this is the first book-length treatment. This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions.
Energy Technology Data Exchange (ETDEWEB)
Siegrist, R.L.; Smuin, D.R.; Korte, N.E.; Greene, D.W.; Pickering, D.A.; Lowe, K.S.; Strong-Gunderson, J.
2000-08-01
Chlorocarbons like trichloroethylene (TCE) are common contaminants of concern at US Department of Energy (DOE) facilities and industrial sites across the US and abroad. These contaminants of concern are present in source areas and in soil and ground water plumes as dissolved or sorbed phase constituents as well as dense nonaqueous-phase liquids (DNAPLs). These DNAPL compounds can be released to the environment through a variety of means including leaks in storage tanks and transfer lines, spills during transportation, and land treatment of wastes. When DNAPL compounds are present in low permeability media (LPM) like silt and clay layers or deposits, there are major challenges with assessment of their behavior and implementation of effective in situ remediation technologies. This report describes a field demonstration that was conducted at the Portsmouth Gaseous Diffusion Plant (PORTS) Clean Test Site (CTS) to evaluate the feasibility of permeation and dispersal of reagents into LPM. Various reagents and tracers were injected at seven test cells primarily to evaluate the feasibility of delivery, but also to evaluate the effects of the injected reagents on LPM. The various reagents and tracers were injected at the PORTS CTS using a multi-port injection system (MPIS) developed and provided by Hayward Baker Environmental, Inc.
Variational Hidden Conditional Random Fields with Coupled Dirichlet Process Mixtures
Bousmalis, K.; Zafeiriou, S.; Morency, L.P.; Pantic, Maja; Ghahramani, Z.
Hidden Conditional Random Fields (HCRFs) are discriminative latent variable models which have been shown to successfully learn the hidden structure of a given classification problem. An infinite HCRF is an HCRF with a countably infinite number of hidden states, which rids us not only of the
Development of a Layered Conditional Random Field Based ...
African Journals Online (AJOL)
PROF. OLIVER OSUAGWA
2014-12-01
Dec 1, 2014 ... Conditional Estimation in NLP Models,” Proc. ACL Conf. Empirical. Methods in Natural Language Processing (EMNLP '02), Association for. Computational Linguistics, 10, (9-16). [39] Sutton, C. and McCallum, A (2006). “An Introduction to Conditional Random Fields for. Relational Learning,” Introduction to ...
Modeling fiber type grouping by a binary Markov random field
Venema, H. W.
1992-01-01
A new approach to the quantification of fiber type grouping is presented, in which the distribution of histochemical type in a muscle cross section is regarded as a realization of a binary Markov random field (BMRF). Methods for the estimation of the parameters of this model are discussed. The first
Infinite conditional random fields for human behavior analysis
Bousmalis, Konstantinos; Zafeiriou, Stefanos; Morency, Louis-Philippe; Pantic, Maja
Hidden conditional random fields (HCRFs) are discriminative latent variable models that have been shown to successfully learn the hidden structure of a given classification problem (provided an appropriate validation of the number of hidden states). In this brief, we present the infinite HCRF
Fuzzy Field Theory as a Random Matrix Model
Tekel, Juraj
This dissertation considers the theory of scalar fields on fuzzy spaces from the point of view of random matrices. First we define random matrix ensembles, which are natural description of such theory. These ensembles are new and the novel feature is a presence of kinetic term in the probability measure, which couples the random matrix to a set of external matrices and thus breaks the original symmetry. Considering the case of a free field ensemble, which is generalization of a Gaussian matrix ensemble, we develop a technique to compute expectation values of the observables of the theory based on explicit Wick contractions and we write down recursion rules for these. We show that the eigenvalue distribution of the random matrix follows the Wigner semicircle distribution with a rescaled radius. We also compute distributions of the matrix Laplacian of the random matrix given by the new term and demonstrate that the eigenvalues of these two matrices are correlated. We demonstrate the robustness of the method by computing expectation values and distributions for more complicated observables. We then consider the ensemble corresponding to an interacting field theory, with a quartic interaction. We use the same method to compute the distribution of the eigenvalues and show that the presence of the kinetic terms rescales the distribution given by the original theory, which is a polynomially deformed Wigner semicircle. We compute the eigenvalue distribution of the matrix Laplacian and the joint distribution up to second order in the correlation and we show that the correlation between the two changes from the free field case. Finally, as an application of these results, we compute the phase diagram of the fuzzy scalar field theory, we find multiscaling which stabilizes this diagram in the limit of large matrices and compare it with the results obtained numerically and by considering the kinetic part as a perturbation.
Random vectorial fields representing the local structure of turbulence
Energy Technology Data Exchange (ETDEWEB)
Chevillard, Laurent [Laboratoire de Physique de l' ENS Lyon, CNRS, Universite de Lyon, 46 allee d' Italie, 69007 Lyon (France); Robert, Raoul [Institut Fourier, CNRS, Universite Grenoble 1, 100 rue des Mathematiques, BP 74, 38402 Saint-Martin d' Heres cedex (France); Vargas, Vincent, E-mail: laurent.chevillard@ens-lyon.fr [Ceremade, CNRS, Universite Paris-Dauphine, F-75016 Paris (France)
2011-12-22
We propose a method to build up a random homogeneous, isotropic and incompressible turbulent velocity field that mimics turbulence in the inertial range. The underlying Gaussian field is given by a modified Biot-Savart law. The long range correlated nature of turbulence is then incorporated heuristically using a non linear transformation inspired by the recent fluid deformation imposed by the Euler equations. The resulting velocity field shows a non vanishing mean energy transfer towards the small scales and realistic alignment properties of vorticity with the eigenframe of the deformation rate.
Driving a Superconductor to Insulator Transition with Random Gauge Fields.
Nguyen, H Q; Hollen, S M; Shainline, J; Xu, J M; Valles, J M
2016-11-30
Typically the disorder that alters the interference of particle waves to produce Anderson localization is potential scattering from randomly placed impurities. Here we show that disorder in the form of random gauge fields that act directly on particle phases can also drive localization. We present evidence of a superfluid bose glass to insulator transition at a critical level of this gauge field disorder in a nano-patterned array of amorphous Bi islands. This transition shows signs of metallic transport near the critical point characterized by a resistance , indicative of a quantum phase transition. The critical disorder depends on interisland coupling in agreement with recent Quantum Monte Carlo simulations. We discuss how this disorder tuned SIT differs from the common frustration tuned SIT that also occurs in magnetic fields. Its discovery enables new high fidelity comparisons between theoretical and experimental studies of disorder effects on quantum critical systems.
Kik, R.; Van den Bos, J.P.; Maertens, J.; Verhagen, H.J.; Van der Meer, J.W.
2012-01-01
Different layer design of a rock slope and under layers has a large effect on the strengths on the rock slope itself. In the stability formula developed of VAN DER MEER [1988] this effect is represented by the term Notional Permeability with symbol P. A more open, or permeable, structure underneath
Energy Technology Data Exchange (ETDEWEB)
Kretz, V.
2002-11-01
The prediction of oil recovery or pollutant dispersion requires an accurate knowledge of the permeability field distribution. Available data are usually measurements in well bores, and, since a few years, 4D-seismic data (seismic mappings repeated in time). Such measurements allow to evaluate fluids displacements fronts evolution. The purpose of the thesis is to evaluate the possibility to determinate permeability fields from fluid displacement measurements in heterogeneous porous media. At the laboratory scale, experimental studies are made on a model and on numerical simulations. The system uses blocks of granular materials whose individual geometries and permeabilities are controlled. The fluids displacements are detected with an acoustical. The key parameters of the study are the size and spatial correlation of the permeability heterogeneity distribution, and the influence of viscosity and gravity contrasts between the injected ant displaced fluid. Then the inverse problem - evaluating the permeability field from concentration fronts evolution - is approached. At the reservoir scale, the work will mainly be focused on the integration of 4D-seismic data into inversion programs on a 3D synthetic case. A particular importance will be given to the calculation of gradients, in order to obtain a complementary information about the sensitivity of data. The information provided by 4D-seismic data consists in maps showing the vertical average of oil saturation or the presence of gas. The purpose is to integrate this qualitative information in the inversion process and to evaluate the impact on the reservoir characterization. Comparative studies - with or without 4D-seismic data - will be realized on a synthetic case. (author)
Quantifying Evaporation in a Permeable Pavement System
Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. Th...
Shape modelling using Markov random field restoration of point correspondences.
Paulsen, Rasmus R; Hilger, Klaus B
2003-07-01
A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized shapes and improves the capability of reconstruction of the training data. Furthermore, the method leads to an overall reduction in the total variance of the point distribution model. Thus, it finds correspondence between semi-landmarks that are highly correlated in the shape tangent space. The method is demonstrated on a set of human ear canals extracted from 3D-laser scans.
Shape Modelling Using Markov Random Field Restoration of Point Correspondences
DEFF Research Database (Denmark)
Paulsen, Rasmus Reinhold; Hilger, Klaus Baggesen
2003-01-01
A method for building statistical point distribution models is proposed. The novelty in this paper is the adaption of Markov random field regularization of the correspondence field over the set of shapes. The new approach leads to a generative model that produces highly homogeneous polygonized...... shapes and improves the capability of reconstruction of the training data. Furthermore, the method leads to an overall reduction in the total variance of the point distribution model. Thus, it finds correspondence between semilandmarks that are highly correlated in the shape tangent space. The method...
Efficient approximation of random fields for numerical applications
Harbrecht, Helmut
2015-01-07
We consider the rapid computation of separable expansions for the approximation of random fields. We compare approaches based on techniques from the approximation of non-local operators on the one hand and based on the pivoted Cholesky decomposition on the other hand. We provide an a-posteriori error estimate for the pivoted Cholesky decomposition in terms of the trace. Numerical examples validate and quantify the considered methods.
Joint Conditional Random Field Filter for Multi-Object Tracking
Directory of Open Access Journals (Sweden)
Luo Ronghua
2011-03-01
Full Text Available Object tracking can improve the performance of mobile robot especially in populated dynamic environments. A novel joint conditional random field Filter (JCRFF based on conditional random field with hierarchical structure is proposed for multi-object tracking by abstracting the data associations between objects and measurements to be a sequence of labels. Since the conditional random field makes no assumptions about the dependency structure between the observations and it allows non-local dependencies between the state and the observations, the proposed method can not only fuse multiple cues including shape information and motion information to improve the stability of tracking, but also integrate moving object detection and object tracking quite well. At the same time, implementation of multi-object tracking based on JCRFF with measurements from the laser range finder on a mobile robot is studied. Experimental results with the mobile robot developed in our lab show that the proposed method has higher precision and better stability than joint probabilities data association filter (JPDAF.
Directory of Open Access Journals (Sweden)
K. А. Kuznetsov
2016-11-01
Full Text Available Modulation of the biological effects produced by ionizing radiation (IR using microwave and magnetic fields has important theoretical and practical applications. Response of human buccal epithelium cells to different physical agents (single and combined exposure to 0.5–5 Gy γ-radiation (60Co; microwaves with the frequency of 36.64 GHz and power densities of 0.1 and 1 W/m2, and static magnetic field with the intensity of 25 mT has been investigated. The stress response of the cells was evaluated by counting heterochromatin granules quantity (HGQ in the cell nuclei stained with orcein. Membrane permeability was assessed by the percentage of cells stained with indigocarmine (cells with damaged membrane. The increase of heterochromatin granules quantity (HGQ, i.e. chromatin condensation was detected at the doses of 2 Gy and higher. Changes in the cell membrane permeability to indigocarmine expressed the threshold effect. Membrane permeability reached the threshold at the doses of 2–3 Gy for the cells of different donors and did not change with the increase of the dose of γ-radiation. Cells obtained from different donors revealed some individual peculiarities in their reaction to γ-radiation. The static magnetic field and microwaves applied before or after γ-radiation decreased its impact, as revealed by means of HGQ assessment.
Statistical Downscaling Based on Spartan Spatial Random Fields
Hristopulos, Dionissios
2010-05-01
Stochastic methods of space-time interpolation and conditional simulation have been used in statistical downscaling approaches to increase the resolution of measured fields. One of the popular interpolation methods in geostatistics is kriging, also known as optimal interpolation in data assimilation. Kriging is a stochastic, linear interpolator which incorporates time/space variability by means of the variogram function. However, estimation of the variogram from data involves various assumptions and simplifications. At the same time, the high numerical complexity of kriging makes it difficult to use for very large data sets. We present a different approach based on the so-called Spartan Spatial Random Fields (SSRFs). SSRFs were motivated from classical field theories of statistical physics [1]. The SSRFs provide a different approach of parametrizing spatial dependence based on 'effective interactions,' which can be formulated based on general statistical principles or even incorporate physical constraints. This framework leads to a broad family of covariance functions [2], and it provides new perspectives in covariance parameter estimation and interpolation [3]. A significant advantage offered by SSRFs is reduced numerical complexity, which can lead to much faster codes for spatial interpolation and conditional simulation. In addition, on grids composed of rectangular cells, the SSRF representation leads to an explicit expression for the precision matrix (the inverse covariance). Therefore SSRFs could provide useful models of error covariance for data assimilation methods. We use simulated and real data to demonstrate SSRF properties and downscaled fields. keywords: interpolation, conditional simulation, precision matrix References [1] Hristopulos, D.T., 2003. Spartan Gibbs random field models for geostatistical applications, SIAM Journal in Scientific Computation, 24, 2125-2162. [2] Hristopulos, D.T., Elogne, S. N. 2007. Analytic properties and covariance
Visibility graphs of random scalar fields and spatial data
Lacasa, Lucas; Iacovacci, Jacopo
2017-07-01
We extend the family of visibility algorithms to map scalar fields of arbitrary dimension into graphs, enabling the analysis of spatially extended data structures as networks. We introduce several possible extensions and provide analytical results on the topological properties of the graphs associated to different types of real-valued matrices, which can be understood as the high and low disorder limits of real-valued scalar fields. In particular, we find a closed expression for the degree distribution of these graphs associated to uncorrelated random fields of generic dimension. This result holds independently of the field's marginal distribution and it directly yields a statistical randomness test, applicable in any dimension. We showcase its usefulness by discriminating spatial snapshots of two-dimensional white noise from snapshots of a two-dimensional lattice of diffusively coupled chaotic maps, a system that generates high dimensional spatiotemporal chaos. The range of potential applications of this combinatorial framework includes image processing in engineering, the description of surface growth in material science, soft matter or medicine, and the characterization of potential energy surfaces in chemistry, disordered systems, and high energy physics. An illustration on the applicability of this method for the classification of the different stages involved in carcinogenesis is briefly discussed.
DEFF Research Database (Denmark)
Jeanette, Mortensen; Engstrøm, Finn; Lind, Ida
1998-01-01
X. On 24 of the core plugs the specific surface was determined by BET and on 14 of these samples image analysis was made. The data was rationalized by the use of the Kozeny equation and it was found that each geologic unit had a characteristic relationship between porosity, permeability and specific...
Qin, Ruijun; Gao, Suduan; Thomas, John E; Wang, Dong; Hanson, Bradley D
2017-12-15
Carbonated fumigants have been shown to distribute quickly and uniformly in sandy soils and improve pest control efficacy for annual crops. Low permeability films, such as VaporSafe® (TIF), could further improve fumigant dispersion by effectively retaining the fumigant in soil; however, there is a concern that the TIF can lead to higher off-tarp edge emissions. An orchard field trial was conducted to determine the off-tarp emissions, distribution, efficacy, and fate of carbonated Telone® C35 [63.4% 1,3-dichloropropene (1,3-D), 34.7% chloropicrin (CP)] that was shank-injected at 46cm soil depth. Treatments included carbonated fumigants at full- or 2/3 rates and a full rate of regular (nitrogen-pressurized) fumigants covered with standard polyethylene (PE) film, TIF, or no surface seal. Fumigant emissions at the regular tarp edge (25cm from the shank line) peaked at 3.98μgm(-2)s(-1) for 1,3-D and 0.05μgm(-2)s(-1) for CP. The addition of a TIF tarp extension (to 85cm from the shank line) reduce peak off-tarp emissions to <1 and <0.03μgm(-2)s(-1) for 1,3-D and CP, respectively. Fumigant concentration under TIF was usually at least twice that under PE regardless of carbonation. Carbonation at 345KPa with 1.5% of dissolved CO2 did not significantly improve fumigant dispersion in soil profile compared to the conventional nitrogen pressurization. In a citrus nematode bioassay, only the 2/3 rate of carbonated fumigation treatment sealed with PE failed to control nematodes at 25cm away from shank line. This research indicates that a 60-cm TIF extension can effectively reduce off-tarp edge emissions in strip fumigation treatments. While the adaptability of carbonation of fumigants is still questionable, further research efforts are needed in finding effective solutions to control plant parasitic nematodes, which remain a challenge in orchard fumigation. Copyright © 2017 Elsevier B.V. All rights reserved.
Extremes in random fields a theory and its applications
Yakir, Benjamin
2013-01-01
Presents a useful new technique for analyzing the extreme-value behaviour of random fields Modern science typically involves the analysis of increasingly complex data. The extreme values that emerge in the statistical analysis of complex data are often of particular interest. This book focuses on the analytical approximations of the statistical significance of extreme values. Several relatively complex applications of the technique to problems that emerge in practical situations are presented. All the examples are difficult to analyze using classical methods, and as a result, the author pr
Markov random fields for static foreground classification in surveillance systems
Fitzsimons, Jack K.; Lu, Thomas T.
2014-09-01
We present a novel technique for classifying static foreground in automated airport surveillance systems between abandoned and removed objects by representing the image as a Markov Random Field. The proposed algorithm computes and compares the net probability of the region of interest before and after the event occurs, hence finding which fits more naturally with their respective backgrounds. Having tested on a dataset from the PETS 2006, PETS 2007, AVSS20074, CVSG, VISOR, CANDELA and WCAM datasets, the algorithm has shown capable of matching the results of the state-of-the-art, is highly parallel and has a degree of robustness to noise and illumination changes.
A note on moving average models for Gaussian random fields
DEFF Research Database (Denmark)
Hansen, Linda Vadgård; Thorarinsdottir, Thordis L.
The class of moving average models offers a flexible modeling framework for Gaussian random fields with many well known models such as the Matérn covariance family and the Gaussian covariance falling under this framework. Moving average models may also be viewed as a kernel smoothing of a Lévy...... basis, a general modeling framework which includes several types of non-Gaussian models. We propose a new one-parameter spatial correlation model which arises from a power kernel and show that the associated Hausdorff dimension of the sample paths can take any value between 2 and 3. As a result...
Deep recurrent conditional random field network for protein secondary prediction
DEFF Research Database (Denmark)
Johansen, Alexander Rosenberg; Sønderby, Søren Kaae; Sønderby, Casper Kaae
2017-01-01
Deep learning has become the state-of-the-art method for predicting protein secondary structure from only its amino acid residues and sequence profile. Building upon these results, we propose to combine a bi-directional recurrent neural network (biRNN) with a conditional random field (CRF), which...... of the labels for all time-steps. We condition the CRF on the output of biRNN, which learns a distributed representation based on the entire sequence. The biRNN-CRF is therefore close to ideally suited for the secondary structure task because a high degree of cross-talk between neighboring elements can...
Random field Ising model and community structure in complex networks
Son, S.-W.; Jeong, H.; Noh, J. D.
2006-04-01
We propose a method to determine the community structure of a complex network. In this method the ground state problem of a ferromagnetic random field Ising model is considered on the network with the magnetic field Bs = +∞, Bt = -∞, and Bi≠s,t=0 for a node pair s and t. The ground state problem is equivalent to the so-called maximum flow problem, which can be solved exactly numerically with the help of a combinatorial optimization algorithm. The community structure is then identified from the ground state Ising spin domains for all pairs of s and t. Our method provides a criterion for the existence of the community structure, and is applicable equally well to unweighted and weighted networks. We demonstrate the performance of the method by applying it to the Barabási-Albert network, Zachary karate club network, the scientific collaboration network, and the stock price correlation network. (Ising, Potts, etc.)
Parsing citations in biomedical articles using conditional random fields.
Zhang, Qing; Cao, Yong-Gang; Yu, Hong
2011-04-01
Citations are used ubiquitously in biomedical full-text articles and play an important role for representing both the rhetorical structure and the semantic content of the articles. As a result, text mining systems will significantly benefit from a tool that automatically extracts the content of a citation. In this study, we applied the supervised machine-learning algorithms Conditional Random Fields (CRFs) to automatically parse a citation into its fields (e.g., Author, Title, Journal, and Year). With a subset of html format open-access PubMed Central articles, we report an overall 97.95% F1-score. The citation parser can be accessed at: http://www.cs.uwm.edu/∼qing/projects/cithit/index.html. Copyright © 2011 Elsevier Ltd. All rights reserved.
Relations between Lagrangian models and synthetic random velocity fields.
Olla, Piero; Paradisi, Paolo
2004-10-01
The authors propose an alternative interpretation of Markovian transport models based on the well-mixed condition, in terms of the properties of a random velocity field with second order structure functions scaling linearly in the space-time increments. This interpretation allows direct association of the drift and noise terms entering the model, with the geometry of the turbulent fluctuations. In particular, the well-known nonuniqueness problem in the well-mixed approach is solved in terms of the antisymmetric part of the velocity correlations; its relation with the presence of nonzero mean helicity and other geometrical properties of the flow is elucidated. The well-mixed condition appears to be a special case of the relation between conditional velocity increments of the random field and the one-point Eulerian velocity distribution, allowing generalization of the approach to the transport of nontracer quantities. Application to solid particle transport leads to a model satisfying, in the homogeneous isotropic turbulence case, all the conditions on the behavior of the correlation times for the fluid velocity sampled by the particles. In particular, correlation times in the gravity and in the inertia dominated case, respectively, longer and shorter than in the passive tracer case; in the gravity dominated case, correlation times longer for velocity components along gravity, than for the perpendicular ones. The model produces, in channel flow geometry, particle deposition rates in agreement with experiments.
Böttger, B.; Haberstroh, C.; Giesselmann, N.
2016-01-01
Based on the results of microstructure simulations, fluid flow through the semisolid region during directional solidification of the technical Ni-base alloy 718 has been studied. Three-dimensional microstructures at different positions in the semisolid region were obtained by using a multicomponent multiphase-field model that was online coupled to a commercial thermodynamic database. For the range of five different primary dendrite distances λ 1 between 50 µm and 250 µm, the flow velocity and the permeability perpendicular to the dendrite growth direction was evaluated by using a proprietary Lattice-Boltzmann model. The commercial CFD software ANSYS FLUENT was alternatively applied for reference. Consistent values of the average flow velocity along the dendrites were obtained for both methods. From the results of the fluid flow simulations, the cross-permeability was evaluated as a function of temperature and fraction liquid for each of the five different primary dendrite distances λ 1. The obtained permeability values can be approximated by a single analytical function of the fraction liquid and λ 1 and are discussed and compared with known relations from the literature.
Quantum Coherence and Random Fields at Mesoscopic Scales
Energy Technology Data Exchange (ETDEWEB)
Rosenbaum, Thomas F. [Univ. of Chicago, IL (United States)
2016-03-01
We seek to explore and exploit model, disordered and geometrically frustrated magnets where coherent spin clusters stably detach themselves from their surroundings, leading to extreme sensitivity to finite frequency excitations and the ability to encode information. Global changes in either the spin concentration or the quantum tunneling probability via the application of an external magnetic field can tune the relative weights of quantum entanglement and random field effects on the mesoscopic scale. These same parameters can be harnessed to manipulate domain wall dynamics in the ferromagnetic state, with technological possibilities for magnetic information storage. Finally, extensions from quantum ferromagnets to antiferromagnets promise new insights into the physics of quantum fluctuations and effective dimensional reduction. A combination of ac susceptometry, dc magnetometry, noise measurements, hole burning, non-linear Fano experiments, and neutron diffraction as functions of temperature, magnetic field, frequency, excitation amplitude, dipole concentration, and disorder address issues of stability, overlap, coherence, and control. We have been especially interested in probing the evolution of the local order in the progression from spin liquid to spin glass to long-range-ordered magnet.
Kumar, Manoj; Banerjee, Varsha; Puri, Sanjay
2017-11-08
In this paper, we study the random field Ising model (RFIM) in an external magnetic field h . A computationally efficient graph-cut method is used to study ground state (GS) morphologies in this system for three different disorder types: Gaussian, uniform and bimodal. We obtain the critical properties of this system and find that they are independent of the disorder type. We also study GS morphologies via pinned-cluster distributions, which are scale-free at criticality. The spin-spin correlation functions (and structure factors) are characterized by a roughness exponent [Formula: see text]. The corresponding scaling function is universal for all disorder types and independent of h.
Chen, Si; Liu, Xiang; Wang, Li; Wan, Chunli
2017-05-15
In order to prevent vertical migration of pollutant in soil matrix, this study firstly proposed to construct an in situ low permeable barrier (LPB) through synchronously transporting calcium and carbonate. After LPB construction, the soil permeability was declined tenfold. Exchangeable calcium (37.3%) and calcium bonding to carbonate (41.7%) respectively alleviated flocculation of microaggregates and cementation of marcoaggregates. Accordingly, smaller particles (2 mm) after electrokinetic remediation. The other soil characters like pH, moisture, and bacterial communities were well preserved after remediation. In addition, the pollutant prevention was divided into two phases as unsaturated phase and saturated phase. In unsaturated phase, phenol, F(-), Cd(2+), and Ni(2+) in filtrate were all lower than 0.1 mg, and Cr2O4(2-)-Cr discharged from LPB was 1/5.1 than that from initial soil. In saturated phase, LPB prevented 4.3-12.1 fold pollutant than initial soil. Taken together, proposed method could effectively prevent vertical migration of pollutants, indicating significant values for saving soil remediation cost or avoiding contamination of underground water. Copyright © 2017 Elsevier Ltd. All rights reserved.
Randomly evolving idiotypic networks: modular mean field theory.
Schmidtchen, Holger; Behn, Ulrich
2012-07-01
We develop a modular mean field theory for a minimalistic model of the idiotypic network. The model comprises the random influx of new idiotypes and a deterministic selection. It describes the evolution of the idiotypic network towards complex modular architectures, the building principles of which are known. The nodes of the network can be classified into groups of nodes, the modules, which share statistical properties. Each node experiences only the mean influence of the groups to which it is linked. Given the size of the groups and linking between them the statistical properties such as mean occupation, mean lifetime, and mean number of occupied neighbors are calculated for a variety of patterns and compared with simulations. For a pattern which consists of pairs of occupied nodes correlations are taken into account.
Random Field Ising Models: Fractal Interfaces and their Implications
Bupathy, A.; Kumar, M.; Banerjee, V.; Puri, S.
2017-10-01
We use a computationally efficient graph-cut (GC) method to obtain exact ground-states of the d = 3 random field Ising model (RFIM) on simple cubic (SC), bodycentered cubic (BCC) and face-centered cubic (FCC) lattices with Gaussian, Uniform and Bimodal distributions for the disorder Δ. At small-r, the correlation function C(r; Δ) shows a cusp singularity characterised by a non-integer roughness exponent α signifying rough fractal interfaces with dimension d f = d – α. In the paramagnetic phase (Δ > Δ c ), α ≃ 0:5 for all lattice and disorder types. In the ferromagnetic phase (Δ Fractal interfaces have important implications on growth and relaxation.
Classification of hyperspectral images based on conditional random fields
Hu, Yang; Saber, Eli; Monteiro, Sildomar T.; Cahill, Nathan D.; Messinger, David W.
2015-02-01
A significant increase in the availability of high resolution hyperspectral images has led to the need for developing pertinent techniques in image analysis, such as classification. Hyperspectral images that are correlated spatially and spectrally provide ample information across the bands to benefit this purpose. Conditional Random Fields (CRFs) are discriminative models that carry several advantages over conventional techniques: no requirement of the independence assumption for observations, flexibility in defining local and pairwise potentials, and an independence between the modules of feature selection and parameter leaning. In this paper we present a framework for classifying remotely sensed imagery based on CRFs. We apply a Support Vector Machine (SVM) classifier to raw remotely sensed imagery data in order to generate more meaningful feature potentials to the CRFs model. This approach produces promising results when tested with publicly available AVIRIS Indian Pine imagery.
Permeable pavement study (Edison)
While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types have on nutrient concentrations present in stormwater runoff are limited. In 2009, the U.S. EPA constructed a 0.4-ha parking lot in Edison, New Jersey, that incorporated permeable interlocking concrete pavement (PICP), pervious concrete (PC), and porous asphalt (PA). Each permeable pavement type has four, 54.9-m2, lined sections that direct all infiltrate into 5.7-m3 tanks enabling complete volume collection and sampling. This paper highlights the results from a 12-month period when samples were collected from 13 rainfall/runoff events and analyzed for nitrogen species, orthophosphate, and organic carbon. Differences in infiltrate concentrations among the three permeable pavement types were assessed and compared with concentrations in rainwater samples and impervious asphalt runoff samples, which were collected as controls. Contrary to expectations based on the literature, the PA infiltrate had significantly larger total nitrogen (TN) concentrations than runoff and infiltrate from the other two permeable pavement types, indicating that nitrogen leached from materials in the PA strata. There was no significant difference in TN concentration between runoff and infiltrate from either PICP or PC, but TN in runoff was significantly larger than in the rainwater, suggesting meaningful inter-event dry de
5th Seminar on Stochastic Processes, Random Fields and Applications
Russo, Francesco; Dozzi, Marco
2008-01-01
This volume contains twenty-eight refereed research or review papers presented at the 5th Seminar on Stochastic Processes, Random Fields and Applications, which took place at the Centro Stefano Franscini (Monte Verità) in Ascona, Switzerland, from May 30 to June 3, 2005. The seminar focused mainly on stochastic partial differential equations, random dynamical systems, infinite-dimensional analysis, approximation problems, and financial engineering. The book will be a valuable resource for researchers in stochastic analysis and professionals interested in stochastic methods in finance. Contributors: Y. Asai, J.-P. Aubin, C. Becker, M. Benaïm, H. Bessaih, S. Biagini, S. Bonaccorsi, N. Bouleau, N. Champagnat, G. Da Prato, R. Ferrière, F. Flandoli, P. Guasoni, V.B. Hallulli, D. Khoshnevisan, T. Komorowski, R. Léandre, P. Lescot, H. Lisei, J.A. López-Mimbela, V. Mandrekar, S. Méléard, A. Millet, H. Nagai, A.D. Neate, V. Orlovius, M. Pratelli, N. Privault, O. Raimond, M. Röckner, B. Rüdiger, W.J. Runggaldi...
Gerke, Kirill
2015-04-01
In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy\\'s equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes\\' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software\\'s applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.
Clustering, randomness, and regularity in cloud fields. 4: Stratocumulus cloud fields
Lee, J.; Chou, J.; Weger, R. C.; Welch, R. M.
1994-01-01
To complete the analysis of the spatial distribution of boundary layer cloudiness, the present study focuses on nine stratocumulus Landsat scenes. The results indicate many similarities between stratocumulus and cumulus spatial distributions. Most notably, at full spatial resolution all scenes exhibit a decidedly clustered distribution. The strength of the clustering signal decreases with increasing cloud size; the clusters themselves consist of a few clouds (less than 10), occupy a small percentage of the cloud field area (less than 5%), contain between 20% and 60% of the cloud field population, and are randomly located within the scene. In contrast, stratocumulus in almost every respect are more strongly clustered than are cumulus cloud fields. For instance, stratocumulus clusters contain more clouds per cluster, occupy a larger percentage of the total area, and have a larger percentage of clouds participating in clusters than the corresponding cumulus examples. To investigate clustering at intermediate spatial scales, the local dimensionality statistic is introduced. Results obtained from this statistic provide the first direct evidence for regularity among large (more than 900 m in diameter) clouds in stratocumulus and cumulus cloud fields, in support of the inhibition hypothesis of Ramirez and Bras (1990). Also, the size compensated point-to-cloud cumulative distribution function statistic is found to be necessary to obtain a consistent description of stratocumulus cloud distributions. A hypothesis regarding the underlying physical mechanisms responsible for cloud clustering is presented. It is suggested that cloud clusters often arise from 4 to 10 triggering events localized within regions less than 2 km in diameter and randomly distributed within the cloud field. As the size of the cloud surpasses the scale of the triggering region, the clustering signal weakens and the larger cloud locations become more random.
A dissipative random velocity field for fully developed fluid turbulence
Chevillard, Laurent; Pereira, Rodrigo; Garban, Christophe
2016-11-01
We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectory. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model depending on a single free parameter that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments, including the intermittent corrections, and the existence of energy transfers across scales. We quantify the dependence of these basic properties of turbulent flows on the free parameter and derive analytically the spectrum of exponents of the structure functions in a simplified non dissipative case. A perturbative expansion shows that energy transfers indeed take place, justifying the dissipative nature of this random field.
Directory of Open Access Journals (Sweden)
Sima Kalantari
2015-02-01
Full Text Available Background: Electromagnetic fields (EMF have teratogenic effects during the embryonic development. In current study, histopathological and physiological effects of sinusoidal EMF on the brain were investigated. We sought to determine the apoptosis level and changes in blood brain barrier permeability in brain tissue of pre-incubated white leghorn hen eggs in the field of EMF. Materials and Methods: In this experimental study, 300 healthy, fresh, and fertilized eggs (55-65 g were divided into experimental (3 groups, N=50, control (N=75 and sham (N=75 groups. Experimental eggs (inside the coil were exposed to 3 different intensities of 1.33, 2.66 and 7.32 mT and sham groups were also located inside the same coil but with no exposure, for 24 hrs before incubation. Control, sham and experimental groups were incubated in an incubator (38±0.5ºC, 60% humidity. Brains of 14 day old chicken embryos of all groups were removed, fixed in formalin (10%, stained with H & E and TUNEL, apoptotic cells were studied under light microscope. Brains of other embryos were prepared for scanning electron microscope. By injections of Evans blue, any possible changes in brain vessels were also investigated. Results: Our results showed electromagnetic fields have toxic effects on cell organelles and cell membranes. EMF would increase the level of cellular apoptosis in the brain. They also would tear up the blood vessels. Thereafter, they would affect the permeability of blood brain barrier of exposed chicken embryos. Conclusion: These findings suggest that electromagnetic fields induce different degrees of brain damages in chicken embryos brain tissue.
Elperin, T; Kleeorin, N; Rogachevskii, I; Sokoloff, D
2001-08-01
Mean-field theory for turbulent transport of a passive scalar (e.g., particles and gases) is discussed. Equations for the mean number density of particles advected by a random velocity field, with a finite correlation time, are derived. Mean-field equations for a passive scalar comprise spatial derivatives of high orders due to the nonlocal nature of passive scalar transport in a random velocity field with a finite correlation time. A turbulent velocity field with a random renewal time is considered. This model is more realistic than that with a constant renewal time used by Elperin et al. [Phys. Rev. E 61, 2617 (2000)], and employs two characteristic times: the correlation time of a random velocity field tau(c), and a mean renewal time tau. It is demonstrated that the turbulent diffusion coefficient is determined by the minimum of the times tau(c) and tau. The mean-field equation for a passive scalar was derived for different ratios of tau/tau(c). The important role of the statistics of the field of Lagrangian trajectories in turbulent transport of a passive scalar, in a random velocity field with a finite correlation time, is demonstrated. It is shown that in the case tau(c)
In search of random uncorrelated particle motion (RUM) in a simple random flow field
Reeks, Michael W; Soldati, Alfredo
2012-01-01
DNS studies of dispersed particle motion in isotropic homogeneous turbulence [1] have revealed the existence of a component of random uncorrelated motion (RUM)dependent on the particle inertia {\\tau}p(normalised particle response time or Stoke number). This paper reports the presence of RUM in a simple linear random smoothly varying flow field of counter rotating vortices where the two-particle velocity correlation was measured as a function of spatial separation. Values of the correlation less than one for zero separation indicated the presence of RUM. In terms of Stokes number, the motion of the particles in one direction corresponds to either a heavily damped ({\\tau}p 0.25)harmonic oscillator. In the lightly damped case the particles overshoot the stagnation lines of the flow and are projected from one vortex to another (the so-called sling-shot effect). It is shown that RUM occurs only when {\\tau}p > 0.25, increasing monotonically with increasing Stokes number. Calculations of the particle pair separatio...
Kouritzin, Michael A; Newton, Fraser; Wu, Biao
2013-04-01
Herein, we propose generating CAPTCHAs through random field simulation and give a novel, effective and efficient algorithm to do so. Indeed, we demonstrate that sufficient information about word tests for easy human recognition is contained in the site marginal probabilities and the site-to-nearby-site covariances and that these quantities can be embedded directly into certain conditional probabilities, designed for effective simulation. The CAPTCHAs are then partial random realizations of the random CAPTCHA word. We start with an initial random field (e.g., randomly scattered letter pieces) and use Gibbs resampling to re-simulate portions of the field repeatedly using these conditional probabilities until the word becomes human-readable. The residual randomness from the initial random field together with the random implementation of the CAPTCHA word provide significant resistance to attack. This results in a CAPTCHA, which is unrecognizable to modern optical character recognition but is recognized about 95% of the time in a human readability study.
Conditional random field modelling of interactions between findings in mammography
Kooi, Thijs; Mordang, Jan-Jurre; Karssemeijer, Nico
2017-03-01
Recent breakthroughs in training deep neural network architectures, in particular deep Convolutional Neural Networks (CNNs), made a big impact on vision research and are increasingly responsible for advances in Computer Aided Diagnosis (CAD). Since many natural scenes and medical images vary in size and are too large to feed to the networks as a whole, two stage systems are typically employed, where in the first stage, small regions of interest in the image are located and presented to the network as training and test data. These systems allow us to harness accurate region based annotations, making the problem easier to learn. However, information is processed purely locally and context is not taken into account. In this paper, we present preliminary work on the employment of a Conditional Random Field (CRF) that is trained on top the CNN to model contextual interactions such as the presence of other suspicious regions, for mammography CAD. The model can easily be extended to incorporate other sources of information, such as symmetry, temporal change and various patient covariates and is general in the sense that it can have application in other CAD problems.
A Markov Random Field Groupwise Registration Framework for Face Recognition.
Liao, Shu; Shen, Dinggang; Chung, Albert C S
2014-04-01
In this paper, we propose a new framework for tackling face recognition problem. The face recognition problem is formulated as groupwise deformable image registration and feature matching problem. The main contributions of the proposed method lie in the following aspects: (1) Each pixel in a facial image is represented by an anatomical signature obtained from its corresponding most salient scale local region determined by the survival exponential entropy (SEE) information theoretic measure. (2) Based on the anatomical signature calculated from each pixel, a novel Markov random field based groupwise registration framework is proposed to formulate the face recognition problem as a feature guided deformable image registration problem. The similarity between different facial images are measured on the nonlinear Riemannian manifold based on the deformable transformations. (3) The proposed method does not suffer from the generalizability problem which exists commonly in learning based algorithms. The proposed method has been extensively evaluated on four publicly available databases: FERET, CAS-PEAL-R1, FRGC ver 2.0, and the LFW. It is also compared with several state-of-the-art face recognition approaches, and experimental results demonstrate that the proposed method consistently achieves the highest recognition rates among all the methods under comparison.
Conditional Random Fields for Pattern Recognition Applied to Structured Data
Directory of Open Access Journals (Sweden)
Tom Burr
2015-07-01
Full Text Available Pattern recognition uses measurements from an input domain, X, to predict their labels from an output domain, Y. Image analysis is one setting where one might want to infer whether a pixel patch contains an object that is “manmade” (such as a building or “natural” (such as a tree. Suppose the label for a pixel patch is “manmade”; if the label for a nearby pixel patch is then more likely to be “manmade” there is structure in the output domain that can be exploited to improve pattern recognition performance. Modeling P(X is difficult because features between parts of the model are often correlated. Therefore, conditional random fields (CRFs model structured data using the conditional distribution P(Y|X = x, without specifying a model for P(X, and are well suited for applications with dependent features. This paper has two parts. First, we overview CRFs and their application to pattern recognition in structured problems. Our primary examples are image analysis applications in which there is dependence among samples (pixel patches in the output domain. Second, we identify research topics and present numerical examples.
Rigorously testing multialternative decision field theory against random utility models.
Berkowitsch, Nicolas A J; Scheibehenne, Benjamin; Rieskamp, Jörg
2014-06-01
Cognitive models of decision making aim to explain the process underlying observed choices. Here, we test a sequential sampling model of decision making, multialternative decision field theory (MDFT; Roe, Busemeyer, & Townsend, 2001), on empirical grounds and compare it against 2 established random utility models of choice: the probit and the logit model. Using a within-subject experimental design, participants in 2 studies repeatedly choose among sets of options (consumer products) described on several attributes. The results of Study 1 showed that all models predicted participants' choices equally well. In Study 2, in which the choice sets were explicitly designed to distinguish the models, MDFT had an advantage in predicting the observed choices. Study 2 further revealed the occurrence of multiple context effects within single participants, indicating an interdependent evaluation of choice options and correlations between different context effects. In sum, the results indicate that sequential sampling models can provide relevant insights into the cognitive process underlying preferential choices and thus can lead to better choice predictions. PsycINFO Database Record (c) 2014 APA, all rights reserved.
Segmentation and labeling of documents using conditional random fields
Shetty, Shravya; Srinivasan, Harish; Beal, Matthew; Srihari, Sargur
2007-01-01
The paper describes the use of Conditional Random Fields(CRF) utilizing contextual information in automatically labeling extracted segments of scanned documents as Machine-print, Handwriting and Noise. The result of such a labeling can serve as an indexing step for a context-based image retrieval system or a bio-metric signature verification system. A simple region growing algorithm is first used to segment the document into a number of patches. A label for each such segmented patch is inferred using a CRF model. The model is flexible enough to include signatures as a type of handwriting and isolate it from machine-print and noise. The robustness of the model is due to the inherent nature of modeling neighboring spatial dependencies in the labels as well as the observed data using CRF. Maximum pseudo-likelihood estimates for the parameters of the CRF model are learnt using conjugate gradient descent. Inference of labels is done by computing the probability of the labels under the model with Gibbs sampling. Experimental results show that this approach provides for 95.75% of the data being assigned correct labels. The CRF based model is shown to be superior to Neural Networks and Naive Bayes.
Germán Rubino, J; Monachesi, Leonardo B; Müller, Tobias M; Guarracino, Luis; Holliger, Klaus
2013-12-01
Oscillatory fluid movements in heterogeneous porous rocks induced by seismic waves cause dissipation of wave field energy. The resulting seismic signature depends not only on the rock compressibility distribution, but also on a statistically averaged permeability. This so-called equivalent seismic permeability does not, however, coincide with the respective equivalent flow permeability. While this issue has been analyzed for one-dimensional (1D) media, the corresponding two-dimensional (2D) and three-dimensional (3D) cases remain unexplored. In this work, this topic is analyzed for 2D random medium realizations having strong permeability fluctuations. With this objective, oscillatory compressibility simulations based on the quasi-static poroelasticity equations are performed. Numerical analysis shows that strong permeability fluctuations diminish the magnitude of attenuation and velocity dispersion due to fluid flow, while the frequency range where these effects are significant gets broader. By comparing the acoustic responses obtained using different permeability averages, it is also shown that at very low frequencies the equivalent seismic permeability is similar to the equivalent flow permeability, while for very high frequencies this parameter approaches the arithmetic average of the permeability field. These seemingly generic findings have potentially important implications with regard to the estimation of equivalent flow permeability from seismic data.
Heterogeneous Web Data Extraction Algorithm Based On Modified Hidden Conditional Random Fields
Cui Cheng
2014-01-01
As it is of great importance to extract useful information from heterogeneous Web data, in this paper, we propose a novel heterogeneous Web data extraction algorithm using a modified hidden conditional random fields model. Considering the traditional linear chain based conditional random fields can not effectively solve the problem of complex and heterogeneous Web data extraction, we modify the standard hidden conditional random fields in three aspects, which are 1) Using the hidden Markov mo...
Error Bounds Due to Random Noise in Cylindrical Near-Field Measurements
Romeu Robert, Jordi; Jofre Roca, Lluís
1991-01-01
The far field errors due to near field random noise are statistically bounded when performing cylindrical near to far field transform. In this communication, the far field noise variance it is expressed as a function of the measurement parameters and the near field noise variance. Peer Reviewed
Bearing Fault Classification Based on Conditional Random Field
Directory of Open Access Journals (Sweden)
Guofeng Wang
2013-01-01
Full Text Available Condition monitoring of rolling element bearing is paramount for predicting the lifetime and performing effective maintenance of the mechanical equipment. To overcome the drawbacks of the hidden Markov model (HMM and improve the diagnosis accuracy, conditional random field (CRF model based classifier is proposed. In this model, the feature vectors sequences and the fault categories are linked by an undirected graphical model in which their relationship is represented by a global conditional probability distribution. In comparison with the HMM, the main advantage of the CRF model is that it can depict the temporal dynamic information between the observation sequences and state sequences without assuming the independence of the input feature vectors. Therefore, the interrelationship between the adjacent observation vectors can also be depicted and integrated into the model, which makes the classifier more robust and accurate than the HMM. To evaluate the effectiveness of the proposed method, four kinds of bearing vibration signals which correspond to normal, inner race pit, outer race pit and roller pit respectively are collected from the test rig. And the CRF and HMM models are built respectively to perform fault classification by taking the sub band energy features of wavelet packet decomposition (WPD as the observation sequences. Moreover, K-fold cross validation method is adopted to improve the evaluation accuracy of the classifier. The analysis and comparison under different fold times show that the accuracy rate of classification using the CRF model is higher than the HMM. This method brings some new lights on the accurate classification of the bearing faults.
Geothermal Permeability Enhancement - Final Report
Energy Technology Data Exchange (ETDEWEB)
Joe Beall; Mark Walters
2009-06-30
The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.
Exact simulation of Brown-Resnick random fields at a finite number of locations
DEFF Research Database (Denmark)
Dieker, Ton; Mikosch, Thomas Valentin
2015-01-01
We propose an exact simulation method for Brown-Resnick random fields, building on new representations for these stationary max-stable fields. The main idea is to apply suitable changes of measure....
Gesture Recognition using Latent-Dynamic based Conditional Random Fields and Scalar Features
Yulita, I. N.; Fanany, M. I.; Arymurthy, A. M.
2017-02-01
The need for segmentation and labeling of sequence data appears in several fields. The use of the conditional models such as Conditional Random Fields is widely used to solve this problem. In the pattern recognition, Conditional Random Fields specify the possibilities of a sequence label. This method constructs its full label sequence to be a probabilistic graphical model based on its observation. However, Conditional Random Fields can not capture the internal structure so that Latent-based Dynamic Conditional Random Fields is developed without leaving external dynamics of inter-label. This study proposes the use of Latent-Dynamic Conditional Random Fields for Gesture Recognition and comparison between both methods. Besides, this study also proposes the use of a scalar features to gesture recognition. The results show that performance of Latent-dynamic based Conditional Random Fields is not better than the Conditional Random Fields, and scalar features are effective for both methods are in gesture recognition. Therefore, it recommends implementing Conditional Random Fields and scalar features in gesture recognition for better performance
Pastoriza, Loraine; Holdsworth, Robert; McCaffrey, Kenneth; Dempsey, Eddie; Walker, Richard; Gluyas, Jon; Reyes, Jonathan
2017-04-01
Fluid flow pathway characterisation is critical to geothermal exploration and exploitation. It requires a good understanding of the structural evolution, fault distribution and fluid flow properties. A dominantly fieldwork-based approach has been used to evaluate the potential fracture permeability characteristics of a typical high-temperature geothermal reservoir in the Southern Negros Geothermal Field, Philippines. This is a liquid-dominated geothermal resource hosted in the andesitic to dacitic Quaternary Cuernos de Negros Volcano in Negros Island. Fieldwork reveals two main fracture groups based on fault rock characteristics, alteration type, relative age of deformation, and associated thermal manifestation, with the younger fractures mainly related to the development of the modern geothermal system. Palaeostress analyses of cross-cutting fault and fracture arrays reveal a progressive counterclockwise rotation of stress axes from the (?)Pliocene up to the present-day, which is consistent with the regional tectonic models. A combined slip and dilation tendency analysis of the mapped faults indicates that NW-SE structures should be particularly promising drilling targets. Frequency versus length and aperture plots of fractures across six to eight orders of magnitude show power-law relationships with a change in scaling exponent in the region of 100 to 500m length-scales. Finally, evaluation of the topology of the fracture branches shows the dominance of Y-nodes that are mostly doubly connected suggesting good connectivity and permeability within the fracture networks. The results obtained in this study illustrate the value of methods that can be globally applied during exploration to better characterize fracture systems in geothermal reservoirs using multiscale datasets.
Reduction of the Random Variables of the Turbulent Wind Field
DEFF Research Database (Denmark)
Sichani, Mahdi Teimouri; Nielsen, Søren R.K.
2012-01-01
Applicability of the Probability Density Evolution Method (PDEM) for realizing evolution of the probability density for the wind turbines has rather strict bounds on the basic number of the random variables involved in the model. The efficiency of most of the Advanced Monte Carlo (AMC) methods, i.......e. Importance Sampling (IS) or Subset Simulation (SS), will be deteriorated on problems with many random variables. The problem with PDEM is that a multidimensional integral has to be carried out over the space defined by the random variables of the system. The numerical procedure requires discretization...... of the integral domain; this becomes increasingly difficult as the dimensions of the integral domain increase. On the other hand efficiency of the AMC methods is closely dependent on the design points of the problem. Presence of many random variables may increase the number of the design points, hence affects...
Optimal Exact Simulation of Max-Stable and Related Random Fields
Liu, Zhipeng; Blanchet, Jose H.; Dieker, A. B.; Mikosch, Thomas
2016-01-01
We consider the random field M(t)=\\sup_{n\\geq 1}\\big\\{-\\log A_{n}+X_{n}(t)\\big\\}\\,,\\qquad t\\in T\\, for a set $T\\subset \\mathbb{R}^{m}$, where $(X_{n})$ is an iid sequence of centered Gaussian random fields on $T$ and $0
Energy Technology Data Exchange (ETDEWEB)
BOWLES NA
2010-10-06
The objective of this field test instruction is to provide technical guidance for aqueous injection emplacement of an extension apatite permeable reactive barrier (PRE) for the sequestration of strontium-90 (Sr-90) using a high concentration amendment formulation. These field activities will be conducted according to the guidelines established in DOE/RL-2010-29, 100-NR-2 Design Optimization Study, hereafter referred to as the DOS. The DOS supports the Federal Facility Agreement Consent Order (EPA et al., 1989), Milestone M-16-06-01, and 'Complete Construction of a Permeable Reactive Barrier at 100-N.' Injections of apatite precursor chemicals will occur at an equal distance intervals on each end of the existing PRE to extend the PRB from the existing 91 m (300 ft) to at least 274 m (900 ft). Field testing at the 100-N Area Apatite Treatability Test Site, as depicted on Figure 1, shows that the barrier is categorized by two general hydrologic conceptual models based on overall well capacity and contrast between the Hanford and Ringold hydraulic conductivities. The upstream portion of the original barrier, shown on Figure 1, is characterized by relatively low overall well specific capacity. This is estimated from well development data and a lower contrast in hydraulic conductivity between the Hanford formation and Ringold Formations. Comparison of test results from these two locations indicate that permeability contrast between the Hanford formation and Ringold Formation is significantly less over the upstream one-third of the barrier. The estimated hydraulic conductivity for the Hanford formation and Ringold Formation over the upstream portion of the barrier based on observations during emplacement of the existing 91 m (300 ft) PRB is approximately 12 and 10 m/day (39 and 32 ft/day), respectively (PNNL-17429). However, these estimates should be used as a rough guideline only, as significant variability in hydraulic conductivity is likely to be observed in
Zlotnik, V.A.; McGuire, V.L.
1998-01-01
Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial aquifer (MSEA site, Shelton, Nebraska). During well installation, disturbed core samples were collected every 0.6 m using a split-spoon sampler. Vertical profiles of hydraulic conductivity were produced on the basis of grain-size analysis of the disturbed core samples. These results closely correlate with the vertical profile of horizontal hydraulic conductivity obtained by interpreting multi-level slug test responses using the modified SG model. The identification method was applied to interpret the response from 474 slug tests in 156 locations at the MSEA site. More than 60% of responses were oscillatory. The method produced a good match to experimental data for both oscillatory and monotonic responses using an automated curve matching procedure. The proposed method allowed us to drastically increase the efficiency of each well used for aquifer characterization and to process massive arrays of field data. Recommendations generalizing this experience to massive application of the proposed method are developed.Using the developed theory and modified Springer-Gelhar (SG) model, an identification method is proposed for estimating hydraulic conductivity from multi-level slug tests. The computerized algorithm calculates hydraulic conductivity from both monotonic and oscillatory well responses obtained using a double-packer system. Field verification of the method was performed at a specially designed fully penetrating well of 0.1-m diameter with a 10-m screen in a sand and gravel alluvial
Directory of Open Access Journals (Sweden)
Ge Xianxi
2006-04-01
Full Text Available Abstract Background Sensorineural hearing loss, a subset of all clinical hearing loss, may be correctable through the use of gene therapy. We are testing a delivery system of therapeutics through a 3 cell-layer round window membrane model (RWM model that may provide an entry of drugs or genes to the inner ear. We designed an in vitro RWM model similar to the RWM (will be referred to throughout the paper as RWM model to determine the feasibility of using superparamagnetic iron oxide (Fe3O4 nanoparticles (SPION for targeted delivery of therapeutics to the inner ear. The RWM model is a 3 cell-layer model with epithelial cells cultured on both sides of a small intestinal submucosal (SIS matrix and fibroblasts seeded in between. Dextran encapsulated nanoparticle clusters 130 nm in diameter were pulled through the RWM model using permanent magnets with flux density 0.410 Tesla at the pole face. The SIS membranes were harvested at day 7 and then fixed in 4% paraformaldehyde. Transmission electron microscopy and fluorescence spectrophotometry were used to verify transepithelial transport of the SPION across the cell-culture model. Histological sections were examined for evidence of SPION toxicity, as well to generate a timeline of the position of the SPION at different times. SPION also were added to cells in culture to assess in vitro toxicity. Results Transepithelial electrical resistance measurements confirmed epithelial confluence, as SPION crossed a membrane consisting of three co-cultured layers of cells, under the influence of a magnetic field. Micrographs showed SPION distributed throughout the membrane model, in between cell layers, and sometimes on the surface of cells. TEM verified that the SPION were pulled through the membrane into the culture well below. Fluorescence spectrophotometry quantified the number of SPION that went through the SIS membrane. SPION showed no toxicity to cells in culture. Conclusion A three-cell layer model of the
Transport properties of a two-dimensional electron gas due to a spatially random magnetic field
Rushforth, A. W.; Gallagher, B. L.; Main, P. C.; Neumann, A. C.; Marrows, C. H.; Zoller, I.; Howson, M. A.; Hickey, B. J.; Henini, M.
2000-02-01
We have studied the magnetoresistance of a near-surface two-dimensional electron gas (2DEG) in the presence of a random magnetic field produced by CoPd multilayers deposited onto the surface of the heterostructure. This novel method allows us to switch the random field on and off by applying an external magnetic field and also to control the amplitude and correlation length of the random field by varying the growth parameters of the multilayers. The presence of the random field is confirmed by quenching of the Shubnikov-de Haas oscillations and we see an enhanced magnetoresistance which can be interpreted semi-classically. We also observe other unusual features which may be quantum in origin.
Modulation of electromagnetic fields by a depolarizer of random polarizer array
DEFF Research Database (Denmark)
Ma, Ning; Hanson, Steen Grüner; Wang, Wei
2016-01-01
with randomly distributed polarization angles, where the incident fields experience a random polarization modulation after passing through the depolarizer. The propagation of the modulated electric fields through any quadratic optical system is examined within the framework of the complex ABCD matrix to show......The statistical properties of the electric fields with random changes of the polarization state in space generated by a depolarizer are investigated on the basis of the coherence matrix. The depolarizer is a polarizer array composed of a multitude of contiguous square cells of polarizers...
Gibert, Oriol; Cortina, José Luis; de Pablo, Joan; Ayora, Carlos
2013-11-01
A permeable reactive barrier (PRB) was installed in Aznalcóllar (Spain) in order to rehabilitate the Agrio aquifer groundwater severely contaminated with acid mine drainage after a serious mining accident. The filling material of the PRB consisted of a mixture of calcite, vegetal compost and, locally, Fe(0) and sewage sludge. Among the successes of the PRB are the continuous neutralisation of pH and the removal of metals from groundwater within the PRB (removals of >95%). Among the shortcomings are the improper PRB design due to the complexity of the internal structure of the Agrio alluvial deposits (which resulted in an inefficient capture of the contaminated plume), the poor degradability of the compost used and the short residence time within the PRB (which hindered a complete sulphate reduction), the clogging of a section of the PRB and the heterogeneities of the filling material (which resulted in preferential flows within the PRB). Undoubtedly, it is only through accumulated experience at field-scale systems that the potentials and limits of the PRB technology can be determined.
Külske, C
2003-01-01
We derive useful general concentration inequalities for functions of Gibbs fields in the uniqueness regime. We also consider expectations of random Gibbs measures that depend on an additional disorder field, and prove concentration w.r.t the disorder field. Both fields are assumed to be in the uniqueness regime, allowing in particular for non-independent disorder field. The modification of the bounds compared to the case of an independent field can be expressed in terms of constants that resemble the Dobrushin contraction coefficient, and are explicitly computable. On the basis of these inequalities, we obtain bounds on the deviation of a diffraction pattern created by random scatterers located on a general discrete point set in the Euclidean space, restricted to a finite volume. Here we also allow for thermal dislocations of the scatterers around their equilibrium positions. Extending recent results for independent scatterers, we give a universal upper bound on the probability of a deviation of the random sc...
On Closely Coupled Dipoles in a Random Field
DEFF Research Database (Denmark)
Andersen, Jørgen Bach; Vincent, L.
2006-01-01
Reception of partially correlated fields by two closely coupled electrical dipoles is discussed as a function of load impedances and open-circuit correlations. Two local maxima of the power may be achieved for two different load impedances, but in those cases the output correlations are high...
The Continuous Spin Random Field Model : Ferromagnetic Ordering in d ≥ 3
Külske, Christof
1999-01-01
We investigate the Gibbs-measures of ferromagnetically coupled continuous spins in double-well potentials subjected to a random field (our specific example being the φ4 theory), showing ferromagnetic ordering in d ≥ 3 dimensions for weak disorder and large energy barriers. We map the random
Random fields of initial out of straightness leading to column buckling
DEFF Research Database (Denmark)
Kala, Zdeněk; Valeš, Jan; Jönsson, Jeppe
2017-01-01
to compression, bending and torsion from the onset of loading. Numerical simulations are performed using the geometrically non-linear model created using the ANSYS software package. Each simulation run has input random realizations of yield strength and the random field generated using the Latin Hypercube...
On the Inference of Spatial Continuity using Spartan Random Field Models
Elogne, Samuel; Hristopulos, Dionisis
2006-01-01
This paper addresses the inference of spatial dependence in the context of a recently proposed framework. More specifically, the paper focuses on the estimation of model parameters for a class of generalized Gibbs random fields, i.e., Spartan Spatial Random Fields (SSRFs). The problem of parameter inference is based on the minimization of a distance metric. The latter involves a specifically designed distance between sample constraints (variance, generalized ``gradient'' and ``curvature'') an...
DEFF Research Database (Denmark)
Wang, W.; Hanson, Steen Grüner; Miyamoto, Y.
2005-01-01
We present the first direct experimental evidence of the local properties of optical vortices in a random laser speckle field. We have observed the Berry anisotropy ellipse describing the anisotropic squeezing of phase lines close to vortex cores and quantitatively verified the Dennis angular mom...... momentum rule for its phase. Some statistics associated with vortices, such as density, anisotropy ellipse eccentricity, and its relation to zero crossings of real and imaginary parts of the random field, are also investigated by experiments....
Restoration of dimensional reduction in the random-field Ising model at five dimensions.
Fytas, Nikolaos G; Martín-Mayor, Víctor; Picco, Marco; Sourlas, Nicolas
2017-04-01
The random-field Ising model is one of the few disordered systems where the perturbative renormalization group can be carried out to all orders of perturbation theory. This analysis predicts dimensional reduction, i.e., that the critical properties of the random-field Ising model in D dimensions are identical to those of the pure Ising ferromagnet in D-2 dimensions. It is well known that dimensional reduction is not true in three dimensions, thus invalidating the perturbative renormalization group prediction. Here, we report high-precision numerical simulations of the 5D random-field Ising model at zero temperature. We illustrate universality by comparing different probability distributions for the random fields. We compute all the relevant critical exponents (including the critical slowing down exponent for the ground-state finding algorithm), as well as several other renormalization-group invariants. The estimated values of the critical exponents of the 5D random-field Ising model are statistically compatible to those of the pure 3D Ising ferromagnet. These results support the restoration of dimensional reduction at D=5. We thus conclude that the failure of the perturbative renormalization group is a low-dimensional phenomenon. We close our contribution by comparing universal quantities for the random-field problem at dimensions 3≤DIsing model at D-2 dimensions, and we provide a clear verification of the Rushbrooke equality at all studied dimensions.
Random walk study of electron motion in helium in crossed electromagnetic fields
Englert, G. W.
1972-01-01
Random walk theory, previously adapted to electron motion in the presence of an electric field, is extended to include a transverse magnetic field. In principle, the random walk approach avoids mathematical complexity and concomitant simplifying assumptions and permits determination of energy distributions and transport coefficients within the accuracy of available collisional cross section data. Application is made to a weakly ionized helium gas. Time of relaxation of electron energy distribution, determined by the random walk, is described by simple expressions based on energy exchange between the electron and an effective electric field. The restrictive effect of the magnetic field on electron motion, which increases the required number of collisions per walk to reach a terminal steady state condition, as well as the effect of the magnetic field on electron transport coefficients and mean energy can be quite adequately described by expressions involving only the Hall parameter.
Revisiting Boltzmann learning: parameter estimation in Markov random fields
DEFF Research Database (Denmark)
Hansen, Lars Kai; Andersen, Lars Nonboe; Kjems, Ulrik
1996-01-01
This article presents a generalization of the Boltzmann machine that allows us to use the learning rule for a much wider class of maximum likelihood and maximum a posteriori problems, including both supervised and unsupervised learning. Furthermore, the approach allows us to discuss regularization...... and generalization in the context of Boltzmann machines. We provide an illustrative example concerning parameter estimation in an inhomogeneous Markov field. The regularized adaptation produces a parameter set that closely resembles the “teacher” parameters, hence, will produce segmentations that closely reproduce...
Extremes of random fields over arbitrary domains with application to concrete rupture stresses
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
2004-01-01
To find the exact probability distribution of the global maximum or minimum of a random field within a bounded domain is a pending problem even for Gaussian fields. Except for very special examples of fields, recourse must be taken to approximate reasoning or asymptotic considerations to be judged...... functions of a smooth approximately Gaussian field, herein called a broken line Hino field. For completeness this particular field type is defined in Appendices A and B. The paper concludes with a statistical application on data for plain concrete tensile strength. (C) 2004 Elsevier Ltd. All rights reserved....
A dissipative random velocity field for fully developed fluid turbulence
Pereira, Rodrigo M; Chevillard, Laurent
2015-01-01
We investigate the statistical properties, based on numerical simulations and analytical calculations, of a recently proposed stochastic model for the velocity field of an incompressible, homogeneous, isotropic and fully developed turbulent flow. A key step in the construction of this model is the introduction of some aspects of the vorticity stretching mechanism that governs the dynamics of fluid particles along their trajectory. An additional further phenomenological step aimed at including the long range correlated nature of turbulence makes this model depending on a single free parameter $\\gamma$ that can be estimated from experimental measurements. We confirm the realism of the model regarding the geometry of the velocity gradient tensor, the power-law behaviour of the moments of velocity increments (i.e. the structure functions), including the intermittent corrections, and the existence of energy transfers across scales. We quantify the dependence of these basic properties of turbulent flows on the free...
Effect of a dilute random field on a continuous-symmetry order parameter
Proctor, T. C.; Chudnovsky, E. M.
2015-04-01
X Y and Heisenberg spins, subjected to strong random fields acting at a few points in space with a concentration cr≪1 , are studied numerically on three-dimensional lattices containing over 4 ×106 sites. Glassy behavior with a strong dependence on initial conditions is found. Beginning with a random initial orientation of spins, the system evolves into ferromagnetic domains inversely proportional to cr in size. The area of the hysteresis loop m (H ) scales as cr2. These findings are explained by mapping the effect of a strong dilute random field onto the effect of a weak continuous random field. Our theory applies directly to ferromagnets with magnetic impurities, and is conceptually relevant to strongly pinned vortex lattices in superconductors and pinned charge-density waves.
Gartin, Patrick R.
1995-01-01
Asserts that several analytical issues in randomized field experiments conducted by criminal justice scholars must be addressed more systematically. Notes that issues related to statistical power and desired sample size remain unresolved. Reviews related literature from the field of medicine to provide insights regarding the dilemmas created by…
Kato, Takayuki; Honda, Yasushi; Kurita, Yusuke; Iwasaki, Akito; Sato, Takamitsu; Kessoku, Takaomi; Uchiyama, Shiori; Ogawa, Yuji; Ohkubo, Hidenori; Higurashi, Takuma; Yamanaka, Takeharu; Usuda, Haruki; Wada, Koichiro; Nakajima, Atsushi
2017-01-01
The barrier function of the small intestinal mucosa prevents the introduction of undesired pathogens into the body. Breakdown of this barrier function increases intestinal permeability. This has been proposed to induce not only gastrointestinal diseases, including inflammatory bowel disease and irritable bowel syndrome, but also various other diseases, including allergies, diabetes mellitus, liver diseases, and collagen diseases, which are associated with this so called "leaky gut syndrome." As such, a method to prevent leaky gut syndrome would have substantial clinical value. However, no drugs have been demonstrated to improve disturbed intestinal permeability in humans to date. Therefore, we investigated whether a drug used to treat chronic constipation, lubiprostone, was effective for this purpose. Healthy male volunteers were treated with lubiprostone (24 μg/day) for 28 days. Intestinal permeability was evaluated by measuring the lactulose-mannitol ratio (LMR) after administration of diclofenac and compared with an untreated group. The examination was conducted three times in total, i.e., at baseline before diclofenac administration and after 14 and 28 days of lubiprostone treatment. Blood endotoxin activity was also evaluated at the same time points. The final analysis was conducted on 28 subjects (14 in the lubiprostone group and 14 in the untreated group). The LMR after 28 days of treatment was significantly lower in the lubiprostone group than that in the untreated group (0.017 vs. 0.028, respectively; 95% confidence interval, -0.022--0.0001; p = 0.049). Blood endotoxin activity exhibited almost no change over time in the lubiprostone and untreated groups and displayed no significant differences at any time point of examination. This study is the first to report an improvement in leaky gut using an available drug in humans. The result suggests that lubiprostone may prevent and ameliorate "leaky gut syndrome". However, a pivotal trial is needed to confirm
Directory of Open Access Journals (Sweden)
Takayuki Kato
Full Text Available The barrier function of the small intestinal mucosa prevents the introduction of undesired pathogens into the body. Breakdown of this barrier function increases intestinal permeability. This has been proposed to induce not only gastrointestinal diseases, including inflammatory bowel disease and irritable bowel syndrome, but also various other diseases, including allergies, diabetes mellitus, liver diseases, and collagen diseases, which are associated with this so called "leaky gut syndrome." As such, a method to prevent leaky gut syndrome would have substantial clinical value. However, no drugs have been demonstrated to improve disturbed intestinal permeability in humans to date. Therefore, we investigated whether a drug used to treat chronic constipation, lubiprostone, was effective for this purpose.Healthy male volunteers were treated with lubiprostone (24 μg/day for 28 days. Intestinal permeability was evaluated by measuring the lactulose-mannitol ratio (LMR after administration of diclofenac and compared with an untreated group. The examination was conducted three times in total, i.e., at baseline before diclofenac administration and after 14 and 28 days of lubiprostone treatment. Blood endotoxin activity was also evaluated at the same time points.The final analysis was conducted on 28 subjects (14 in the lubiprostone group and 14 in the untreated group. The LMR after 28 days of treatment was significantly lower in the lubiprostone group than that in the untreated group (0.017 vs. 0.028, respectively; 95% confidence interval, -0.022--0.0001; p = 0.049. Blood endotoxin activity exhibited almost no change over time in the lubiprostone and untreated groups and displayed no significant differences at any time point of examination.This study is the first to report an improvement in leaky gut using an available drug in humans. The result suggests that lubiprostone may prevent and ameliorate "leaky gut syndrome". However, a pivotal trial is needed
Segmentation of RGB-D indoor scenes by stacking random forests and conditional random fields
DEFF Research Database (Denmark)
Thøgersen, Mikkel; Guerrero, Sergio Escalera; Gonzàlez, Jordi
2016-01-01
on stacked classifiers; the benefits are two fold: on one hand, the system scales well to consider different types of complex features and, on the other hand, the use of stacked classifiers makes the performance of the proposed technique more accurate. The proposed method consists of a random forest using...... better performance than state of the art methods on the same dataset. The results show an improvement of 2.3% over the base model by using MMSSL and displays that the method is effective in this problem domain....
Metal-insulator transition of 2d electron gas in a random magnetic field
Wang, X R; Liu, D Z
1999-01-01
We study the metal-insulator transition of a two-dimensional electron gas in the presence of a random magnetic field from the localization property. The localization length is directly calculated using a transfer matrix technique and finite size scaling analysis. We argue that there is a metal-insulator transition in such a system and show strong numerical evidence that the system undergoes a disorder driven Kosterlitz-Thouless type metal-insulator transition. We will also discuss a mean field theory which maps the random field system into a two-dimensional XY-model. The vortex and antivortex excitations in the XY-model correspond to two different kinds of magnetic domains in the random field system.
Film Permeability Determination Using Static Permeability Cells
The permeability of tarps to soil fumigant pesticides varies depending on the active ingredient chemical: dimethyl disulfide (DMDS), methyl bromide, chloropicrin, or other. The diffusion rate can be represented by the mass transfer coefficient (MTC).
rft1d: Smooth One-Dimensional Random Field Upcrossing Probabilities in Python
Directory of Open Access Journals (Sweden)
Todd C. Pataky
2016-07-01
Full Text Available Through topological expectations regarding smooth, thresholded n-dimensional Gaussian continua, random field theory (RFT describes probabilities associated with both the field-wide maximum and threshold-surviving upcrossing geometry. A key application of RFT is a correction for multiple comparisons which affords field-level hypothesis testing for both univariate and multivariate fields. For unbroken isotropic fields just one parameter in addition to the mean and variance is required: the ratio of a field's size to its smoothness. Ironically the simplest manifestation of RFT (1D unbroken fields has rarely surfaced in the literature, even during its foundational development in the late 1970s. This Python package implements 1D RFT primarily for exploring and validating RFT expectations, but also describes how it can be applied to yield statistical inferences regarding sets of experimental 1D fields.
Submicron structure random field on granular soil material with retinex algorithm optimization
Liang Yu; Tao Chenyuan; Zhou Bingcheng; Huang Shuai; Huang Linchong
2017-01-01
In this paper, a Retinex scale optimized image enhancement algorithm is proposed, which can enhance the micro vision image and eliminate the influence of the uneven illumination. Based on that, a random geometric model of the microstructure of granular materials is established with Monte-Carlo method, the numerical simulation including consolidation process of granular materials is compared with the experimental data. The results have proved that the random field method with Retinex image enh...
A test for stationarity of spatio-temporal random fields on planar and spherical domains
Jun, Mikyoung
2012-01-01
A formal test for weak stationarity of spatial and spatio-temporal random fields is proposed. We consider the cases where the spatial domain is planar or spherical, and we do not require distributional assumptions for the random fields. The method can be applied to univariate or to multivariate random fields. Our test is based on the asymptotic normality of certain statistics that are functions of estimators of covariances at certain spatial and temporal lags under weak stationarity. Simulation results for spatial as well as spatio-temporal cases on the two types of spatial domains are reported. We describe the results of testing the stationarity of Pacific wind data, and of testing the axial symmetry of climate model errors for surface temperature using the NOAA GFDL model outputs and the observations from the Climate Research Unit in East Anglia and the Hadley Centre.
Phase-space representation and polarization domains of random electromagnetic fields.
Castaneda, Roman; Betancur, Rafael; Herrera, Jorge; Carrasquilla, Juan
2008-08-01
The phase-space representation of stationary random electromagnetic fields is developed by using electromagnetic spatial coherence wavelets. The propagation of the field's power and states of spatial coherence and polarization results from correlations between the components of the field vectors at pairs of points in space. Polarization domains are theoretically predicted as the structure of the field polarization at the observation plane. In addition, the phase-space representation provides a generalization of the Poynting theorem. Theoretical predictions are examined by numerically simulating the Young experiment with electromagnetic waves. The experimental implementation of these results is a current subject of research.
Excursion sets of infinitely divisible random fields with convolution equivalent Lévy measure
DEFF Research Database (Denmark)
Rønn-Nielsen, Anders; Jensen, Eva B. Vedel
2017-01-01
We consider a continuous, infinitely divisible random field in ℝ d , d = 1, 2, 3, given as an integral of a kernel function with respect to a Lévy basis with convolution equivalent Lévy measure. For a large class of such random fields, we compute the asymptotic probability that the excursion set ...... at level x contains some rotation of an object with fixed radius as x → ∞. Our main result is that the asymptotic probability is equivalent to the right tail of the underlying Lévy measure....
Excursion sets of infinitely divisible random fields with convolution equivalent Lévy measure
DEFF Research Database (Denmark)
Rønn-Nielsen, Anders; Jensen, Eva B. Vedel
We consider a continuous, infinitely divisible random field in R d , d = 1, 2, 3, given as an integral of a kernel function with respect to a Lévy basis with convolution equivalent Lévy measure. For a large class of such random fields we compute the asymptotic probability that the excursion set a...... at level x contains some rotation of an object with fixed radius as x → ∞. Our main result is that the asymptotic probability is equivalent to the right tail of the underlying Lévy measure...
Random magnetic field and quasiparticle transport in the mixed state of high- Tc cuprates.
Ye, J
2001-01-08
By a singular gauge transformation, the quasiparticle transport in the mixed state of high- Tc cuprates is mapped into a charge-neutral Dirac moving in short-range correlated random scalar and long-range correlated vector potential. A fully quantum mechanical approach to longitudinal and transverse thermal conductivities is presented. The semiclassical Volovik effect is presented in a quantum mechanical way. The quasiparticle scattering from the random magnetic field which was completely missed in all the previous semiclassical approaches is the dominant scattering mechanism at sufficient high magnetic field. The implications for experiments are discussed.
The limiting behavior of the estimated parameters in a misspecified random field regression model
DEFF Research Database (Denmark)
Dahl, Christian Møller; Qin, Yu
This paper examines the limiting properties of the estimated parameters in the random field regression model recently proposed by Hamilton (Econometrica, 2001). Though the model is parametric, it enjoys the flexibility of the nonparametric approach since it can approximate a large collection......, as a consequence the random field model specification introduces non-stationarity and non-ergodicity in the misspecified model and it becomes non-trivial, relative to the existing literature, to establish the limiting behavior of the estimated parameters. The asymptotic results are obtained by applying some...
Carbon nanotube field emitters on KOVAR substrate modified by random pattern
Energy Technology Data Exchange (ETDEWEB)
Park, Seol Ah; Song, Eun-Ho; Kang, Byung Hyun; Ju, Byeong-Kwon, E-mail: bkju@korea.ac.kr [Korea University, Display and Nanosystem Laboratory, College of Engineering (Korea, Republic of)
2015-07-15
We investigated the field emission characteristics of patterned carbon nanotubes (CNTs) on KOVAR substrates with different surface morphologies. The substrate with a micro-sized random pattern was fabricated through chemical wet etching, whereas the substrate with a nano-sized random pattern was formed by surface roughening process of polymer and chemical wet etching. The field emission characteristics of these substrates were the compared with those of non-treated substrates. It was clearly revealed that the field emission characteristics of CNTs were influenced by the surface morphology of the cathode substrate. When the surface of cathode was modified by random pattern, the modified substrate provided a large surface area and a wider print area. Also, the modified surface morphology of the cathode provided strong adhesion between the CNT paste and the cathode. Particularly, the substrate with the nano-sized random pattern showed that the turn-on field value decreases and the field enhancement factor value improves as compared with non-treated substrate.
Permeability measurement and control for epoxy composites
Chang, Tsun-Hsu; Tsai, Cheng-Hung; Wong, Wei-Syuan; Chen, Yen-Ren; Chao, Hsien-Wen
2017-08-01
The coupling of the electric and magnetic fields leads to a strong interplay in materials' permittivity and permeability. Here, we proposed a specially designed cavity, called the mu cavity. The mu cavity, consisting of a mushroom structure inside a cylindrical resonator, is exclusively sensitive to permeability, but not to permittivity. It decouples materials' electromagnetic properties and allows an accurate measurement of the permeability. With the help of an epsilon cavity, these two cavities jointly determine the complex permeability and permittivity of the materials at microwave frequencies. Homemade epoxy-based composite materials were prepared and tested. Measurement and manipulation of the permeability and permittivity of the epoxy composites will be shown. The results will be compared with the effective medium theories.
Kraft, Matthew A.; Dougherty, Shaun M.
2013-01-01
In this study, we evaluate the efficacy of teacher communication with parents and students as a means of increasing student engagement. We estimate the causal effect of teacher communication by conducting a randomized field experiment in which sixth- and ninth-grade students were assigned to receive a daily phone call home and a text/written…
The Role of Treatment Fidelity on Outcomes during a Randomized Field Trial of an Autism Intervention
Mandell, David S; Stahmer, Aubyn C; Shin, Sujie; Xie, Ming; Reisinger, Erica; Marcus, Steven C
2013-01-01
This randomized field trial comparing Strategies for Teaching based on Autism Research and Structured Teaching enrolled educators in 33 kindergarten-through-second-grade autism support classrooms and 119 students, aged 5-8 years in the School District of Philadelphia. Students were assessed at the beginning and end of the academic year using the…
High Performance Ambipolar Field-Effect Transistor of Random Network Carbon Nanotubes
Bisri, Satria Zulkarnaen; Gao, Jia; Derenskyi, Vladimir; Gomulya, Widianta; Iezhokin, Igor; Gordiichuk, Pavlo; Herrmann, Andreas; Loi, Maria Antonietta
2012-01-01
Ambipolar field-effect transistors of random network carbon nanotubes are fabricated from an enriched dispersion utilizing a conjugated polymer as the selective purifying medium. The devices exhibit high mobility values for both holes and electrons (3 cm(2)/V.s) with a high on/off ratio (10(6)). The
Magnetoresistance of a two-dimensional electron gas in a random magnetic field
DEFF Research Database (Denmark)
Smith, Anders; Taboryski, Rafael Jozef; Hansen, Luise Theil
1994-01-01
We report magnetoresistance measurements on a two-dimensional electron gas made from a high-mobility GaAs/AlxGa1-xAs heterostructure, where the externally applied magnetic field was expelled from regions of the semiconductor by means of superconducting lead grains randomly distributed...
The effect of early entrepreneurship education: evidence from a randomized field experiment
Rosendahl Huber, L.; Sloof, R.; van Praag, M.
2012-01-01
The aim of this study is to analyze the effectiveness of early entrepreneurship education. To this end, we conduct a randomized field experiment to evaluate a leading entrepreneurship education program that is taught worldwide in the final grade of primary school. We focus on pupils' development of
Is Bonferroni correction more sensitive than Random Field Theory for most fMRI studies?
Tierney, Tim M; Carmichael, David W
2016-01-01
Random Field Theory has been used in the fMRI literature to address the multiple comparisons problem. The method provides an analytical solution for the computation of precise p-values when its assumptions are met. When its assumptions are not met the thresholds generated by Random Field Theory can be more conservative than Bonferroni corrections, which are arguably too stringent for use in fMRI. As this has been well documented theoretically it is surprising that a majority of current studies (~80%) would not meet the assumptions of Random Field Theory and therefore would have reduced sensitivity. Specifically most data is not smooth enough to meet the good lattice assumption. Current studies smooth data on average by twice the voxel size which is rarely sufficient to meet the good lattice assumption. The amount of smoothing required for Random Field Theory to produce accurate p-values increases with image resolution and decreases with degrees of freedom. There is no rule of thumb that is valid for all study...
Joint modeling of ChIP-seq data via a Markov random field model
Bao, Yanchun; Vinciotti, Veronica; Wit, Ernst; 't Hoen, Peter A C
Chromatin ImmunoPrecipitation-sequencing (ChIP-seq) experiments have now become routine in biology for the detection of protein-binding sites. In this paper, we present a Markov random field model for the joint analysis of multiple ChIP-seq experiments. The proposed model naturally accounts for
Application of operator-scaling anisotropic random fields to binary mixtures
Anders, Denis; Hoffmann, Alexander; Scheffler, Hans-Peter; Weinberg, Kerstin
2011-10-01
In modern technical applications various multiphase mixtures are used to meet demanding mechanical, chemical and electrical requirements. To understand their structural properties as continuous macroscopic materials, it is important to capture the microstructure of these mixtures. Due to their vast range of applications multicomponent systems are subjected to microstructural changes such as phase separation and coarsening. Therefore the ultimate microstructural arrangement depends on the system's configuration and on exterior driving forces. In addition to this, random physical imperfections within the material and random noise in the exterior thermodynamic fields influence in essence the microstructural evolution. Since all physical processes are subjected to a certain degree of random inhomogeneity under realistic conditions, the influence of random phenomena cannot be neglected in modern physical models. An advanced mathematical description and an implementation of these stochastic processes are required to adapt simulation results based on deterministic mathematical models to experimental observations. In our contribution we will present an operator-scaling anisotropic random field embedded in the Cahn-Hilliard phase-field model to describe the phase evolution in a binary mixture. The arising nonlinear diffusion equation will be solved numerically in the innovative framework of the isogeometric finite element method. To illustrate the flexibility and versatility of our approach, numerical and experimental results for a eutectic Sn-Pb alloy are contraposed. This is the first time that the microstructural evolution in a multicomponent system has been associated with operator-scaling anisotropic random fields. Due to its enormous potential as an essential ingredient in stochastic mathematical and physical modeling it is only a matter of time until these processes will become prevalent in engineering applications.
Exact Partition Function for the Random Walk of an Electrostatic Field
Directory of Open Access Journals (Sweden)
Gabriel González
2017-01-01
Full Text Available The partition function for the random walk of an electrostatic field produced by several static parallel infinite charged planes in which the charge distribution could be either ±σ is obtained. We find the electrostatic energy of the system and show that it can be analyzed through generalized Dyck paths. The relation between the electrostatic field and generalized Dyck paths allows us to sum overall possible electrostatic field configurations and is used for obtaining the partition function of the system. We illustrate our results with one example.
Maximizing Entropy of Pickard Random Fields for 2x2 Binary Constraints
DEFF Research Database (Denmark)
Søgaard, Jacob; Forchhammer, Søren
2014-01-01
This paper considers the problem of maximizing the entropy of two-dimensional (2D) Pickard Random Fields (PRF) subject to constraints. We consider binary Pickard Random Fields, which provides a 2D causal finite context model and use it to define stationary probabilities for 2x2 squares, thus...... allowing us to calculate the entropy of the field. All possible binary 2x2 constraints are considered and all constraints are categorized into groups according to their properties. For constraints which can be modeled by a PRF approach and with positive entropy, we characterize and provide statistics...... of the maximum PRF entropy. As examples, we consider the well known hard square constraint along with a few other constraints....
The van Hemmen model and effect of random crystalline anisotropy field
Energy Technology Data Exchange (ETDEWEB)
Morais, Denes M. de [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá, Mato Grosso (Brazil); Godoy, Mauricio, E-mail: mgodoy@fisica.ufmt.br [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá, Mato Grosso (Brazil); Arruda, Alberto S. de, E-mail: aarruda@fisica.ufmt.br [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá, Mato Grosso (Brazil); Silva, Jonathas N. da [Universidade Estadual Paulista, 14800-901, Araraquara, São Paulo (Brazil); Ricardo de Sousa, J. [Instituto Nacional de Sistemas Complexos, Departamento de Fisica, Universidade Federal do Amazona, 69077-000, Manaus, Amazonas (Brazil)
2016-01-15
In this work, we have presented the generalized phase diagrams of the van Hemmen model for spin S=1 in the presence of an anisotropic term of random crystalline field. In order to study the critical behavior of the phase transitions, we employed a mean-field Curie–Weiss approach, which allows calculation of the free energy and the equations of state of the model. The phase diagrams obtained here displayed tricritical behavior, with second-order phase transition lines separated from the first-order phase transition lines by a tricritical point. - Highlights: • Several phase diagrams are obtained for the model. • The influence of the random crystalline anisotropy field on the model is investigated. • Three ordered (spin-glass, ferromagnetic and mixed) phases are found. • The tricritical behavior is examined.
One-dimensional classical diffusion in a random force field with weakly concentrated absorbers
Texier, C.; Hagendorf, C.
2009-05-01
A one-dimensional model of classical diffusion in a random force field with a weak concentration ρ of absorbers is studied. The force field is taken as a Gaussian white noise with langphi(x)rang=0 and langphi(x)phi(x')rang=g δ(x- x'). Our analysis relies on the relation between the Fokker-Planck operator and a quantum Hamiltonian in which absorption leads to breaking of supersymmetry. Using a Lifshits argument, it is shown that the average return probability is a power law \\langle {P(x,t\\vert x,0)} \\rangle \\sim t^{-\\sqrt{2\\rho/g}} (to be compared with the usual Lifshits exponential decay exp-(ρ2t)1/3 in the absence of the random force field). The localisation properties of the underlying quantum Hamiltonian are discussed as well.
Yang, Yongchao; Sun, Peng; Nagarajaiah, Satish; Bachilo, Sergei M.; Weisman, R. Bruce
2017-07-01
Structural damage is typically a local phenomenon that initiates and propagates within a limited area. As such high spatial resolution measurement and monitoring is often needed for accurate damage detection. This requires either significantly increased costs from denser sensor deployment in the case of global simultaneous/parallel measurements, or increased measurement time and labor in the case of global sequential measurements. This study explores the feasibility of an alternative approach to this problem: a computational solution in which a limited set of randomly positioned, low-resolution global strain measurements are used to reconstruct the full-field, high-spatial-resolution, two-dimensional (2D) strain field and rapidly detect local damage. The proposed approach exploits the implicit low-rank and sparse data structure of the 2D strain field: it is highly correlated without many edges and hence has a low-rank structure, unless damage-manifesting itself as sparse local irregularity-is present and alters such a low-rank structure slightly. Therefore, reconstruction of the full-field, high-spatial-resolution strain field from a limited set of randomly positioned low-resolution global measurements is modeled as a low-rank matrix completion framework and damage detection as a sparse decomposition formulation, enabled by emerging convex optimization techniques. Numerical simulations on a plate structure are conducted for validation. The results are discussed and a practical iterative global/local procedure is recommended. This new computational approach should enable the efficient detection of local damage using limited sets of strain measurements.
Ruffolo, D. J.; Snodin, A. P.; Oughton, S.; Servidio, S.; Matthaeus, W. H.
2013-12-01
The random walk of magnetic field lines is examined analytically and numerically in the context of reduced magnetohydrodynamic (RMHD) turbulence, which provides a useful description of plasmas dominated by a strong mean field, such as in the solar corona. A nonperturbative theory of magnetic field line diffusion [1] is compared with the diffusion coefficients obtained by accurate numerical tracing of magnetic field lines for both synthetic models and direct numerical simulations of RMHD. Statistical analysis of an ensemble of trajectories confirms the applicability of the theory, which very closely matches the numerical field line diffusion coefficient as a function of distance z along the mean magnetic field for a wide range of the Kubo number R. The theory employs Corrsin's independence hypothesis, sometimes thought to be valid only at low R. However, the results demonstrate that it works well up to R=10, both for a synthetic RMHD model and an RMHD simulation. The numerical results from RMHD simulation are compared with and without phase randomization, demonstrating an effect of coherent structures on the field line random walk for low Kubo number. Partially supported by a postdoctoral fellowship from Mahidol University, the Thailand Research Fund, POR Calabria FSE-2007/2013, the US NSF (AGS-1063439 and SHINE AGS-1156094), NASA (Heliophysics Theory NNX08AI47G & NNX11AJ44G), by the Solar Probe Plus Project through the ISIS Theory team, by the MMS Theory and Modeling team, and by EU Marie Curie Project FP7 PIRSES-2010-269297 'Turboplasmas' at Università della Calabria. [1] D. Ruffolo and W. H. Matthaeus, Phys. Plasmas, 20, 012308 (2013).
Random fields generation on the GPU with the spectral turning bands method
Hunger, L.; Cosenza, B.; Kimeswenger, S.; Fahringer, T.
2014-08-01
Random field (RF) generation algorithms are of paramount importance for many scientific domains, such as astrophysics, geostatistics, computer graphics and many others. Some examples are the generation of initial conditions for cosmological simulations or hydrodynamical turbulence driving. In the latter a new random field is needed every time-step. Current approaches commonly make use of 3D FFT (Fast Fourier Transform) and require the whole generated field to be stored in memory. Moreover, they are limited to regular rectilinear meshes and need an extra processing step to support non-regular meshes. In this paper, we introduce TBARF (Turning BAnd Random Fields), a RF generation algorithm based on the turning band method that is optimized for massively parallel hardware such as GPUs. Our algorithm replaces the 3D FFT with a lower order, one-dimensional FFT followed by a projection step, and is further optimized with loop unrolling and blocking. We show that TBARF can easily generate RF on non-regular (non uniform) meshes and can afford mesh sizes bigger than the available GPU memory by using a streaming, out-of-core approach. TBARF is 2 to 5 times faster than the traditional methods when generating RFs with more than 16M cells. It can also generate RF on non-regular meshes, and has been successfully applied to two real case scenarios: planetary nebulae and cosmological simulations.
Negative permeability in magnetostatics and its experimental demonstration
Mach-Batlle, Rosa; Parra, Albert; Prat-Camps, Jordi; Laut, Sergi; Navau, Carles; Sanchez, Alvaro
2017-09-01
The control of magnetic fields, essential for our science and technology, is currently achieved by magnetic materials with positive permeability, including ferromagnetic, paramagnetic, and diamagnetic types. Here we introduce materials with negative static permeability as a new paradigm for manipulating magnetic fields. As a first step, we extend the solutions of Maxwell magnetostatic equations to include negative-permeability values. The understanding of these new solutions allow us to devise a negative-permeability material as a suitably tailored set of currents arranged in space, overcoming the fact that passive materials with negative permeability do no exist in magnetostatics. We confirm the theory by experimentally creating a spherical shell that emulates a negative-permeability material in a uniform magnetic field. Our results open new possibilities for creating and manipulating magnetic fields, which can be useful for practical applications.
DEFF Research Database (Denmark)
Barrera Figueroa, Salvador; Henriquez, Vicente Cutanda; Jacobsen, Finn
2006-01-01
to the definition of the latter, a number of plane waves coming from random directions and having random phases impinge simultaneously upon the microphone. The random-incidence sensitivity can be estimated using measurements made in an anechoic chamber, while the diffuse-field sensitivity requires a reverberation...
Joint random field model for all-weather moving vehicle detection.
Wang, Yang
2010-09-01
This paper proposes a joint random field (JRF) model for moving vehicle detection in video sequences. The JRF model extends the conditional random field (CRF) by introducing auxiliary latent variables to characterize the structure and evolution of visual scene. Hence, detection labels (e.g., vehicle/roadway) and hidden variables (e.g., pixel intensity under shadow) are jointly estimated to enhance vehicle segmentation in video sequences. Data-dependent contextual constraints among both detection labels and latent variables are integrated during the detection process. The proposed method handles both moving cast shadows/lights and various weather conditions. Computationally efficient algorithm has been developed for real-time vehicle detection in video streams. Experimental results show that the approach effectively deals with various illumination conditions and robustly detects moving vehicles even in grayscale video.
Analysis of family-wise error rates in statistical parametric mapping using random field theory.
Flandin, Guillaume; Friston, Karl J
2017-11-01
This technical report revisits the analysis of family-wise error rates in statistical parametric mapping-using random field theory-reported in (Eklund et al. []: arXiv 1511.01863). Contrary to the understandable spin that these sorts of analyses attract, a review of their results suggests that they endorse the use of parametric assumptions-and random field theory-in the analysis of functional neuroimaging data. We briefly rehearse the advantages parametric analyses offer over nonparametric alternatives and then unpack the implications of (Eklund et al. []: arXiv 1511.01863) for parametric procedures. Hum Brain Mapp, 2017. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc. © 2017 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
Statistics of highly heterogeneous flow fields confined to three-dimensional random porous media
Jin, C.; Langston, P. A.; Pavlovskaya, G. E.; Hall, M. R.; Rigby, S. P.
2016-01-01
We present a strong relationship between the microstructural characteristics of, and the fluid velocity fields confined to, three-dimensional random porous materials. The relationship is revealed through simultaneously extracting correlation functions Ru u(r ) of the spatial (Eulerian) velocity fields and microstructural two-point correlation functions S2(r ) of the random porous heterogeneous materials. This demonstrates that the effective physical transport properties depend on the characteristics of complex pore structure owing to the relationship between Ru u(r ) and S2(r ) revealed in this study. Further, the mean excess plot was used to investigate the right tail of the streamwise velocity component that was found to obey light-tail distributions. Based on the mean excess plot, a generalized Pareto distribution can be used to approximate the positive streamwise velocity distribution.
A Modified FCM Classifier Constrained by Conditional Random Field Model for Remote Sensing Imagery
Directory of Open Access Journals (Sweden)
WANG Shaoyu
2016-12-01
Full Text Available Remote sensing imagery has abundant spatial correlation information, but traditional pixel-based clustering algorithms don't take the spatial information into account, therefore the results are often not good. To this issue, a modified FCM classifier constrained by conditional random field model is proposed. Adjacent pixels' priori classified information will have a constraint on the classification of the center pixel, thus extracting spatial correlation information. Spectral information and spatial correlation information are considered at the same time when clustering based on second order conditional random field. What's more, the global optimal inference of pixel's classified posterior probability can be get using loopy belief propagation. The experiment shows that the proposed algorithm can effectively maintain the shape feature of the object, and the classification accuracy is higher than traditional algorithms.
Simulation of the pressure field near a jet by randomly distributed vortex rings
Fung, Y. T.; Liu, C. H.; Gunzburger, M. D.
1979-01-01
Fluctuations of the pressure field in the vicinity of a jet are simulated numerically by a flow model consisting of axially symmetric vortex rings with viscous cores submerged in a uniform stream. The time interval between the shedding of successive vortices is taken to be a random variable with a probability distribution chosen to match that from experiments. It is found that up to 5 diameters downstream of the jet exit, statistics of the computed pressure field are in good agreement with experimental results. Statistical comparisons are provided for the overall sound pressure level, the peak amplitude, and the Strouhal number based on the peak frequency of the pressure signals.
Phase transitions of Ising mixed spin 1 and 3/2 with random crystal field distribution
Sabri, S.; EL Falaki, M.; EL Yadari, M.; Benyoussef, A.; EL Kenz, A.
2016-10-01
The thermal and magnetic properties of the mixed spin-1 and spin-3/2 in the presence of the random crystal field are studied within the mean field approach based on the Bogoliubov inequality for the Gibbs free energy. The model exhibits first, second order transitions, a tricritical point, triple point and an isolated critical end point. It is found that the system displays simple and double compensation temperatures, five topologies of the phase diagrams. A re-entrant phenomenon is also discussed and the thermal dependences of total magnetization according to extended Neel classification have been also given.
Spatial Random Field Models Inspired from Statistical Physics with Applications in the Geosciences
Hristopulos, D. T.
2005-01-01
The spatial structure of fluctuations in spatially inhomogeneous processes can be modeled in terms of Gibbs random fields. A local low energy estimator (LLEE) is proposed for the interpolation (prediction) of such processes at points where observations are not available. The LLEE approximates the spatial dependence of the data and the unknown values at the estimation points by low-lying excitations of a suitable energy functional. It is shown that the LLEE is a linear, unbiased, non-exact est...
Prediction of the spatial occurrence of fire induced spalling in concrete slabs using random fields
Directory of Open Access Journals (Sweden)
Van Coile R.
2013-09-01
Full Text Available As the loss of concrete cover can significantly influence the reliability of concrete elements during fire, spalling should be taken into account when performing reliability calculations. However, the occurrence and spatial variation of spalling are highly uncertain. A first step towards a probabilistic analysis of spalling is made by combining existing deterministic models with a stochastic representation of the concrete tensile strength and by using random fields to model the tensile strength spatial variation.
Spectral turning bands for efficient Gaussian random fields generation on GPUs and accelerators
Hunger, L.; Cosenza, B.; Kimeswenger, S.; Fahringer, T.
2015-11-01
A random field (RF) is a set of correlated random variables associated with different spatial locations. RF generation algorithms are of crucial importance for many scientific areas, such as astrophysics, geostatistics, computer graphics, and many others. Current approaches commonly make use of 3D fast Fourier transform (FFT), which does not scale well for RF bigger than the available memory; they are also limited to regular rectilinear meshes. We introduce random field generation with the turning band method (RAFT), an RF generation algorithm based on the turning band method that is optimized for massively parallel hardware such as GPUs and accelerators. Our algorithm replaces the 3D FFT with a lower-order, one-dimensional FFT followed by a projection step and is further optimized with loop unrolling and blocking. RAFT can easily generate RF on non-regular (non-uniform) meshes and efficiently produce fields with mesh sizes bigger than the available device memory by using a streaming, out-of-core approach. Our algorithm generates RF with the correct statistical behavior and is tested on a variety of modern hardware, such as NVIDIA Tesla, AMD FirePro and Intel Phi. RAFT is faster than the traditional methods on regular meshes and has been successfully applied to two real case scenarios: planetary nebulae and cosmological simulations.
Fluorescence microscopy image noise reduction using a stochastically-connected random field model.
Haider, S A; Cameron, A; Siva, P; Lui, D; Shafiee, M J; Boroomand, A; Haider, N; Wong, A
2016-02-17
Fluorescence microscopy is an essential part of a biologist's toolkit, allowing assaying of many parameters like subcellular localization of proteins, changes in cytoskeletal dynamics, protein-protein interactions, and the concentration of specific cellular ions. A fundamental challenge with using fluorescence microscopy is the presence of noise. This study introduces a novel approach to reducing noise in fluorescence microscopy images. The noise reduction problem is posed as a Maximum A Posteriori estimation problem, and solved using a novel random field model called stochastically-connected random field (SRF), which combines random graph and field theory. Experimental results using synthetic and real fluorescence microscopy data show the proposed approach achieving strong noise reduction performance when compared to several other noise reduction algorithms, using quantitative metrics. The proposed SRF approach was able to achieve strong performance in terms of signal-to-noise ratio in the synthetic results, high signal to noise ratio and contrast to noise ratio in the real fluorescence microscopy data results, and was able to maintain cell structure and subtle details while reducing background and intra-cellular noise.
Validity of the mean-field approximation for diffusion on a random comb
Revathi, S.; Balakrishnan, V.; Lakshmibala, S.; Murthy, K. P. N.
1996-09-01
We consider unbiased diffusion on a random comb structure (an infinitely long backbone with loopless branches of arbitrary length emanating from it). If w=T0 is the mean time (averaged over all random walks) for first passage from an arbitrary origin 0 on the backbone to either of the sites +j or -j on it in a given realization of the structure, the exact diffusion constant for the problem is defined as K=limj-->∞j2c, where c stands for the configuration average over the realizations of the random comb. The diffusion constant in the mean-field approximation is given by KMF=limj-->∞j2/c. We compute T0 exactly for an arbitrary realization of the comb and then show rigorously that, owing to the suppression of the relative fluctuations in T0 in the ``thermodynamic limit'' j-->∞, we have KMF=K whenever the moments of certain random variables Γ(L,α,β) are finite; here the site-dependent random variables L, α, and β are, respectively, the branch length, stay probability at the tip of a branch, and the backbone-to-branch jump probability. Finally, we discuss different situations in which K will not be equal to KMF, although the transport remains diffusive, as opposed to those in which anomalous diffusion occurs.
Reddy Reddisekhar Reddy, Seethi; Bala Anki Reddy, P.; Sandeep, N.
2017-11-01
This work concentrates on the study of the unsteady hydromagnetic heat and mass transfer of a Newtonian fluid in a permeable stretching surface with viscous dissipation and chemical reaction. Thermal radiation, velocity slip, concentrate slip are also considered. The unsteady in the flow, velocity, temperature and concentration distribution is past by the time dependence of stretching velocity surface temperature and surface concentration. Appropriate similarity transformations are used to convert the governing partial differential equations into a system of coupled non-linear differential equations. The resulting coupled non-linear differential equations are solved numerically by using the fourth order Runge-Kutta method along with shooting technique. The impact of various pertinent parameters on velocity, temperature, concentration, skin friction coefficient, Nusselt number and the Sherwood number are presented graphically and in tabular form. Our computations disclose that fluid temperature has inverse relationship with the radiation parameter.
Hudier, E. J.
2013-12-01
Sea ice presents two roughness scales: one in the millimetre range and the other up to several meters due to ridging. The larger roughness elements are the result of compression and sheer, causing ice blocks to pile up and down at the line of contact between converging ice floes. In terms of boundary limit dynamic, they create obstacles that induce, in their wake, a pressure gradient at the ice water interface. Sea ice is a porous medium and as such, is permeable when subject to pressure gradients. Models have shown that, at spring, when ice permeability increases, sea water can be forced through the ice water interface into the bottom ice layer while brine is pumped out of it under obstacle induced pressure gradients. These results suggest that ice ocean heat budgets have to include a porous flow component and its associated latent heat import/export caused by through volume melting/thawing inside the bottom ice layer subject to sea water infiltration. With the initiation of a melt/thaw dynamic within the porous bottom ice layer, the porous network restructures. Our research show an enlargement of the larger brine channels while smaller ones close due ice growth. Similarly, ice volume of smaller cross size tend to disappear while larger ones evolve slowly. As heat fluxes due to latent heat exchanges become several orders of magnitude larger than any other exterior forcing, such as radiation, heat budgets within ice individual volumes balance fluxes in and out caused by melting/thaw on channel walls. Our simulations were run from an early spring C shape temperature profile to an isothermal state showing that structural change becomes significant only after the temperature profile becomes positive upward.
Markov Random Field Restoration of Point Correspondences for Active Shape Modelling
DEFF Research Database (Denmark)
Hilger, Klaus Baggesen; Paulsen, Rasmus Reinhold; Larsen, Rasmus
2004-01-01
In this paper it is described how to build a statistical shape model using a training set with a sparse of landmarks. A well defined model mesh is selected and fitted to all shapes in the training set using thin plate spline warping. This is followed by a projection of the points of the warped...... model mesh to the target shapes. When this is done by a nearest neighbour projection it can result in folds and inhomogeneities in the correspondence vector field. The novelty in this paper is the use and extension of a Markov random field regularisation of the correspondence field. The correspondence...... model that produces highly homogeneous polygonised shapes with improved reconstruction capabilities of the training data. Furthermore, the method leads to an overall reduction in the total variance of the resulting point distribution model. The method is demonstrated on a set of human ear canals...
Analytical description of field-line random walk in Goldreich-Sridhar turbulence
Shalchi, A.; Kolly, A.
2013-05-01
We describe analytically the random walk of magnetic field lines for two correlation tensors based on the Goldreich-Sridhar model. We show that for this type of tensor, field-line wandering is normal diffusive in contrast to subdiffusive and superdiffusive transport obtained for other turbulence models. Furthermore, we demonstrate that there are two transport regimes. The first one corresponds to quasi-linear theory, whereas the second one is non-linear. We show that for one of the tensors the quasi-linear regime is obtained in the limit of strong turbulence, whereas the non-linear regime is found for weak turbulence. For the other tensor, we obtain a field-line diffusion coefficient which behaves more like diffusion parameters derived previously.
Qin, Z.
2016-12-01
Permeability of fracture-matrix system is an important but difficult to estimate parameter in evaluation and production in fractured tight sandstone reservoirs. Because nuclear magnetic resonance (NMR) logs cannot indicate fracture permeability, NMR can be used to obtain accurate matrix permeability in fractured tight sandstones. Considering lateral logs can be used to identify and evaluate fracture, thus the fracture permeability can be estimated using lateral logs. In the interval without fracture, the permeability of fracture-matrix system is equal to the matrix permeability; while in the only fracture permeable interval, it is equal to the fracture permeability. Considering the obtained matrix permeability from NMR logs may include the contribution of fracture porosity in fractured tight sandstones, the estimated matrix permeability and estimated fracture permeability have overlap. Thus the permeability of fracture-matrix system is not a simple summation of the estimated fracture permeability and the estimated matrix permeability. A new method is proposed to obtain consecutive permeability in fractured tight sandstones. In the method, we believe that the obtained fracture permeability from lateral logs contains the actual fracture permeability and the fracture porosity permeability, which is contributed from the fracture porosity in rock. After calculating fracture width by using the Faivre-Sibbit (F-S) model, the fracture porosity can be estimated. Based on the hydraulic flow unit (HFU) approach, the fracture porosity permeability can be calculated, and then the actual fracture permeability can be obtained. Thus the Permeability of fracture-matrix system is the summation of actual fracture permeability and the estimated matrix permeability. Compared with the simple summation in the field example, the method can be used to obtain more reliable permeability of fracture-matrix system.
Fundametal Study On Permeability Pavement
川口, 基広; 建部, 英博
1997-01-01
This study aimed at the thing which develops a water permeability pavement which improved a drainage pavement. Then it examined possibility of the permeability pavement which can secure water permeability and strength, which it uses water granulated iron-blast-furnace slag in subgrade roadbed and it makes an asphalt mixture mix a stainless steel fiber, to solve a problem of permeability pavement
Yao, Xi; Yang, Yang; Zhou, Jian-Ping; Chen, Xiao-Ming; Liang, Peng-Fei; You, Caiyin
2018-02-01
(1 – x)Ni0.4Zn0.6Fe2O4+x Pb(Zr0.53Ti0.47)O3 (x = 0–1) multiferroic composite materials were prepared by a conventional sintering process. The magnetic permeability and permittivity were researched at high frequency in detail. The permittivity ε‧ decreases slightly with the frequency and the permittivity ε″ shows a peak in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The magnetic resonances of the domain wall and spin rotation were excited by the external dc magnetic field in the microwave frequency. The resonance peaks in the imaginary permeability move to high frequency with the magnetic field, but shift to low frequency in the composite samples. The permittivity spectra exhibit two resonance peaks after polarization. The changes of the permittivity and permeability under magnetic field or/and after polarization confirm the interaction between ferromagnetism and ferroelectricity in the microwave frequency. The observed phenomena were understood by employing a resonance equation for the domain wall motion and a Landau–Gilbert equation for the spin rotation. The results indicate that permittivity and permeability can be adjusted by the magnetic field or electric field.
Submicron structure random field on granular soil material with retinex algorithm optimization
Liang, Yu; Tao, Chenyuan; Zhou, Bingcheng; Huang, Shuai; Huang, Linchong
2017-06-01
In this paper, a Retinex scale optimized image enhancement algorithm is proposed, which can enhance the micro vision image and eliminate the influence of the uneven illumination. Based on that, a random geometric model of the microstructure of granular materials is established with Monte-Carlo method, the numerical simulation including consolidation process of granular materials is compared with the experimental data. The results have proved that the random field method with Retinex image enhancement algorithm is effective, the image of microstructure of granular materials becomes clear and the contrast ratio is improved, after using Retinex image enhancement algorithm to enhance the CT image. The fidelity of enhanced image is higher than that dealing with other method, which have explained that the algorithm can preserve the microstructure information of the image well. The result of numerical simulation is similar with the one obtained from conventional three axis consolidation test, which proves that the simulation result is reliable.
Submicron structure random field on granular soil material with retinex algorithm optimization
Directory of Open Access Journals (Sweden)
Liang Yu
2017-01-01
Full Text Available In this paper, a Retinex scale optimized image enhancement algorithm is proposed, which can enhance the micro vision image and eliminate the influence of the uneven illumination. Based on that, a random geometric model of the microstructure of granular materials is established with Monte-Carlo method, the numerical simulation including consolidation process of granular materials is compared with the experimental data. The results have proved that the random field method with Retinex image enhancement algorithm is effective, the image of microstructure of granular materials becomes clear and the contrast ratio is improved, after using Retinex image enhancement algorithm to enhance the CT image. The fidelity of enhanced image is higher than that dealing with other method, which have explained that the algorithm can preserve the microstructure information of the image well. The result of numerical simulation is similar with the one obtained from conventional three axis consolidation test, which proves that the simulation result is reliable.
Larrasa, J; Garcia, A; Ambrose, N C; Alonso, J M; Parra, A; de Mendoza, M Hermoso; Salazar, J; Rey, J; de Mendoza, J Hermoso
2002-04-01
Dermatophilus congolensis is the pathogenic actinomycete that causes dermatophilosis in cattle, lumpy wool in sheep and rain scald in horses. Phenotypic variation between isolates has previously been described, but its genetic basis, extent and importance have not been investigated. Standard DNA extraction methods are not always successful for D. congolensis due to its complex life cycle, one stage of which is encapsulated. Here we describe the development of rapid and reliable DNA extraction and random amplified polymorphic DNA (RAPD) methods that can be used for genotyping D. congolensis field isolates. Our results suggest that genotypic variation between isolates correlates with host species. Several DNA extraction methods and RAPD protocols were compared. An extraction method based on incubation of the bacterium in lysozyme, sodium dodecyl sulphate (SDS) and proteinase K treatments and phenolic extraction yielded high-quality DNA, which was used to optimize RAPD-polymerase chain reaction (PCR) protocols for two random primers. An alternative rapid, non-phenolic extraction method based on proteinase K treatment and thermal shock was selected for routine RAPD typing of isolates. DNA extracted from reference strains from cattle, sheep and horse using either method gave reproducible banding patterns with different DNA batches and different thermal cyclers. The rapid DNA extraction method and RAPD-PCR were applied to 38 D. congolensis field isolates. The band patterns of the field and type isolates correlated with host species but not with geographical location.
Directory of Open Access Journals (Sweden)
Géraud Thierry
2004-01-01
Full Text Available We present a fast method for road network extraction in satellite images. It can be seen as a transposition of the segmentation scheme "watershed transform region adjacency graph Markov random fields" to the extraction of curvilinear objects. Many road extractors which are composed of two stages can be found in the literature. The first one acts like a filter that can decide from a local analysis, at every image point, if there is a road or not. The second stage aims at obtaining the road network structure. In the method we propose to rely on a "potential" image, that is, unstructured image data that can be derived from any road extractor filter. In such a potential image, the value assigned to a point is a measure of its likelihood to be located in the middle of a road. A filtering step applied on the potential image relies on the area closing operator followed by the watershed transform to obtain a connected line which encloses the road network. Then a graph describing adjacency relationships between watershed lines is built. Defining Markov random fields upon this graph, associated with an energetic model of road networks, leads to the expression of road network extraction as a global energy minimization problem. This method can easily be adapted to other image processing fields, where the recognition of curvilinear structures is involved.
Random-field Ising model: Insight from zero-temperature simulations
Directory of Open Access Journals (Sweden)
P.E. Theodorakis
2014-12-01
Full Text Available We enlighten some critical aspects of the three-dimensional (d=3 random-field Ising model (RFIM from simulations performed at zero temperature. We consider two different, in terms of the field distribution, versions of model, namely a Gaussian RFIM and an equal-weight trimodal RFIM. By implementing a computational approach that maps the ground-state of the system to the maximum-flow optimization problem of a network, we employ the most up-to-date version of the push-relabel algorithm and simulate large ensembles of disorder realizations of both models for a broad range of random-field values and systems sizes V=LxLxL, where L denotes linear lattice size and Lmax=156. Using as finite-size measures the sample-to-sample fluctuations of various quantities of physical and technical origin, and the primitive operations of the push-relabel algorithm, we propose, for both types of distributions, estimates of the critical field hmax and the critical exponent ν of the correlation length, the latter clearly suggesting that both models share the same universality class. Additional simulations of the Gaussian RFIM at the best-known value of the critical field provide the magnetic exponent ratio β/ν with high accuracy and clear out the controversial issue of the critical exponent α of the specific heat. Finally, we discuss the infinite-limit size extrapolation of energy- and order-parameter-based noise to signal ratios related to the self-averaging properties of the model, as well as the critical slowing down aspects of the algorithm.
Chen, Mingsheng; Yan, Qingguang; Qin, Mingxin
2017-12-01
Image segmentation is a preliminary and fundamental step in computer aided magnetic resonance imaging (MRI) images analysis. But the performance of most current image segmentation methods is easily depreciated by noise in MRI images. A precise and anti-noise segmentation of MRI images is desired in modern medical image diagnosis. This paper presents a segmentation of MRI images which combines fuzzy clustering and Markov random field (MRF). In order to utilize gray level information sufficiently and alleviate noise disturbance, fuzzy clustering is carried out on the original image and the coarse scale image of multi-scale decomposition. The spatial constraints between neighboring pixels are modeled by a defined potential function in the MRF to reduce the effect of noise and increase the integrity of segmented regions. Spatial constraints and the gray level information refined by Fuzzy C-Means (FCM) algorithm are integrated by maximum a posteriori Markov random field (MAP-MRF). In the proposed method, the fuzzy clustering membership obtained from the original image and the coarse scale image is integrated into the single-site clique potential functions by MAP-MRF. The defined potential functions and the distance weight are introduced to model the neighborhood constraint with MRF. The experiments are carried out on noised synthetic images, simulated brain MR images and real MR images. The experimental results show that the proposed method has strong robustness and satisfying performance. Meanwhile the method is compared with FCM, FGFCM and FLICM algorithms visually and statistically in the experiments. In the comparison, the proposed method has achieved the best results. In the statistical comparison, the proposed method has an average similarity index of 36.8%, 33.7%, 2.75% increase against FCM, FGFCM and FLICM. This paper proposes a MRI segmentation method combining fuzzy clustering and Markov random field. The method is tested in the noised image databases and
Traffic Video Image Segmentation Model Based on Bayesian and Spatio-Temporal Markov Random Field
Zhou, Jun; Bao, Xu; Li, Dawei; Yin, Yongwen
2017-10-01
Traffic video image is a kind of dynamic image and its background and foreground is changed at any time, which results in the occlusion. In this case, using the general method is more difficult to get accurate image segmentation. A segmentation algorithm based on Bayesian and Spatio-Temporal Markov Random Field is put forward, which respectively build the energy function model of observation field and label field to motion sequence image with Markov property, then according to Bayesian' rule, use the interaction of label field and observation field, that is the relationship of label field’s prior probability and observation field’s likelihood probability, get the maximum posterior probability of label field’s estimation parameter, use the ICM model to extract the motion object, consequently the process of segmentation is finished. Finally, the segmentation methods of ST - MRF and the Bayesian combined with ST - MRF were analyzed. Experimental results: the segmentation time in Bayesian combined with ST-MRF algorithm is shorter than in ST-MRF, and the computing workload is small, especially in the heavy traffic dynamic scenes the method also can achieve better segmentation effect.
Reduced Wiener Chaos representation of random fields via basis adaptation and projection
Energy Technology Data Exchange (ETDEWEB)
Tsilifis, Panagiotis, E-mail: tsilifis@usc.edu [Department of Mathematics, University of Southern California, Los Angeles, CA 90089 (United States); Department of Civil Engineering, University of Southern California, Los Angeles, CA 90089 (United States); Ghanem, Roger G., E-mail: ghanem@usc.edu [Department of Civil Engineering, University of Southern California, Los Angeles, CA 90089 (United States)
2017-07-15
A new characterization of random fields appearing in physical models is presented that is based on their well-known Homogeneous Chaos expansions. We take advantage of the adaptation capabilities of these expansions where the core idea is to rotate the basis of the underlying Gaussian Hilbert space, in order to achieve reduced functional representations that concentrate the induced probability measure in a lower dimensional subspace. For a smooth family of rotations along the domain of interest, the uncorrelated Gaussian inputs are transformed into a Gaussian process, thus introducing a mesoscale that captures intermediate characteristics of the quantity of interest.
Spatial random field models inspired from statistical physics with applications in the geosciences
Hristopulos, Dionissios T.
2006-06-01
The spatial structure of fluctuations in spatially inhomogeneous processes can be modeled in terms of Gibbs random fields. A local low energy estimator (LLEE) is proposed for the interpolation (prediction) of such processes at points where observations are not available. The LLEE approximates the spatial dependence of the data and the unknown values at the estimation points by low-lying excitations of a suitable energy functional. It is shown that the LLEE is a linear, unbiased, non-exact estimator. In addition, an expression for the uncertainty (standard deviation) of the estimate is derived.
Markov random field and Gaussian mixture for segmented MRI-based partial volume correction in PET
Bousse, Alexandre; Pedemonte, Stefano; Thomas, Benjamin A.; Erlandsson, Kjell; Ourselin, Sébastien; Arridge, Simon; Hutton, Brian F.
2012-10-01
In this paper we propose a segmented magnetic resonance imaging (MRI) prior-based maximum penalized likelihood deconvolution technique for positron emission tomography (PET) images. The model assumes the existence of activity classes that behave like a hidden Markov random field (MRF) driven by the segmented MRI. We utilize a mean field approximation to compute the likelihood of the MRF. We tested our method on both simulated and clinical data (brain PET) and compared our results with PET images corrected with the re-blurred Van Cittert (VC) algorithm, the simplified Guven (SG) algorithm and the region-based voxel-wise (RBV) technique. We demonstrated our algorithm outperforms the VC algorithm and outperforms SG and RBV corrections when the segmented MRI is inconsistent (e.g. mis-segmentation, lesions, etc) with the PET image.
Statistical Shape Modelling and Markov Random Field Restoration (invited tutorial and exercise)
DEFF Research Database (Denmark)
Hilger, Klaus Baggesen
This tutorial focuses on statistical shape analysis using point distribution models (PDM) which is widely used in modelling biological shape variability over a set of annotated training data. Furthermore, Active Shape Models (ASM) and Active Appearance Models (AAM) are based on PDMs and have proven...... themselves a generic holistic tool in various segmentation and simulation studies. Finding a basis of homologous points is a fundamental issue in PDMs which effects both alignment and decomposition of the training data, and may be aided by Markov Random Field Restoration (MRF) of the correspondence...... deformation field between shapes. The tutorial demonstrates both generative active shape and appearance models, and MRF restoration on 3D polygonized surfaces. ''Exercise: Spectral-Spatial classification of multivariate images'' From annotated training data this exercise applies spatial image restoration...
Biostable glucose permeable polymer
DEFF Research Database (Denmark)
2017-01-01
A new biostable glucose permeable polymer has been developed which is useful, for example, in implantable glucose sensors. This biostable glucose permeable polymer has a number of advantageous characteristics and, for example, does not undergo hydrolytic cleavage and degradation, thereby providing...... a composition that facilitates long term sensor stability in vivo. The versatile characteristics of this polymer allow it to be used in a variety of contexts, for example to form the body of an implantable glucose sensor. The invention includes the polymer composition, sensor systems formed from this polymer...
Morshedi Pour, Amin; Lotfpour, Masoud; Enayati, Aliasghar
2010-05-01
Porosity value is one of the most important factors which determine the oil volume and also basis of economical or uneconomical calculation of a distinct oil field. By combining the logs, nowadays, very detailed and precise issues could be recognized, for instance we could point examining of porosity types and trends in permeability by using the velocity deviation log (VDL). Velocity devotion log which is calculated by combination sonic log with the Norton porosity or density log provides tool to obtain down hole information on the predominate pore type in carbonates the log can be use to trace the down hole distribution of digenetic processes and to estimate trends in permeability. Generally speaking, porosity and velocity have inverted relationship; nevertheless the type of porosity changes this relationship. In order to establish the velocity deviation log at first; by using the Wyllie equation, porosity log was exchanged to synthetic velocity log, acquired real velocity difference from sonic log and the acquired synthetic velocity from the porosity log is expressed as velocity deviation log. With log being deviated to left and right, the type of porosity would be identified .this method is applied for the Asmari and Jahrum reservoirs units of the Khesht oil field in Kazeroon (Fars),And in one of the wells. This log approves the boundary of Formations which is along with unconformities and even zoning whether is based on porosity value or change of lithology, and also the results which are gotten from the log have close similarities with the results of thin section studies in terms of porosity. Drawing of log and calculation of petrophysic parameters are done by Geolog software.
Lamb's problem on random mass density fields with fractal and Hurst effects.
Nishawala, V V; Ostoja-Starzewski, M; Leamy, M J; Porcu, E
2016-12-01
This paper reports on a generalization of Lamb's problem to a linear elastic, infinite half-space with random fields (RFs) of mass density, subject to a normal line load. Both, uncorrelated and correlated (with fractal and Hurst characteristics) RFs without any weak noise restrictions, are proposed. Cellular automata (CA) is used to simulate the wave propagation. CA is a local computational method which, for rectangular discretization of spatial domain, is equivalent to applying the finite difference method to the governing equations of classical elasticity. We first evaluate the response of CA to an uncorrelated mass density field, more commonly known as white-noise, of varying coarseness as compared to CA's node density. We then evaluate the response of CA to multiscale mass density RFs of Cauchy and Dagum type; these fields are unique in that they are able to model and decouple the field's fractal dimension and Hurst parameter. We focus on stochastic imperfection sensitivity; we determine to what extent the fractal or the Hurst parameter is a significant factor in altering the solution to the planar stochastic Lamb's problem by evaluating the coefficient of variation of the response when compared with the coefficient of variation of the RF.
Adaptive Multi-GPU Exchange Monte Carlo for the 3D Random Field Ising Model
Navarro, C A; Deng, Youjin
2015-01-01
The study of disordered spin systems through Monte Carlo simulations has proven to be a hard task due to the adverse energy landscape present at the low temperature regime, making it difficult for the simulation to escape from a local minimum. Replica based algorithms such as the Exchange Monte Carlo (also known as parallel tempering) are effective at overcoming this problem, reaching equilibrium on disordered spin systems such as the Spin Glass or Random Field models, by exchanging information between replicas of neighbor temperatures. In this work we present a multi-GPU Exchange Monte Carlo method designed for the simulation of the 3D Random Field Model. The implementation is based on a two-level parallelization scheme that allows the method to scale its performance in the presence of faster and GPUs as well as multiple GPUs. In addition, we modified the original algorithm by adapting the set of temperatures according to the exchange rate observed from short trial runs, leading to an increased exchange rate...
Seeking mathematics success for college students: a randomized field trial of an adapted approach
Gula, Taras; Hoessler, Carolyn; Maciejewski, Wes
2015-11-01
Many students enter the Canadian college system with insufficient mathematical ability and leave the system with little improvement. Those students who enter with poor mathematics ability typically take a developmental mathematics course as their first and possibly only mathematics course. The educational experiences that comprise a developmental mathematics course vary widely and are, too often, ineffective at improving students' ability. This trend is concerning, since low mathematics ability is known to be related to lower rates of success in subsequent courses. To date, little attention has been paid to the selection of an instructional approach to consistently apply across developmental mathematics courses. Prior research suggests that an appropriate instructional method would involve explicit instruction and practising mathematical procedures linked to a mathematical concept. This study reports on a randomized field trial of a developmental mathematics approach at a college in Ontario, Canada. The new approach is an adaptation of the JUMP Math program, an explicit instruction method designed for primary and secondary school curriculae, to the college learning environment. In this study, a subset of courses was assigned to JUMP Math and the remainder was taught in the same style as in the previous years. We found consistent, modest improvement in the JUMP Math sections compared to the non-JUMP sections, after accounting for potential covariates. The findings from this randomized field trial, along with prior research on effective education for developmental mathematics students, suggest that JUMP Math is a promising way to improve college student outcomes.
Karimaghaloo, Zahra; Shah, Mohak; Francis, Simon J; Arnold, Douglas L; Collins, D Louis; Arbel, Tal
2012-06-01
Gadolinium-enhancing lesions in brain magnetic resonance imaging of multiple sclerosis (MS) patients are of great interest since they are markers of disease activity. Identification of gadolinium-enhancing lesions is particularly challenging because the vast majority of enhancing voxels are associated with normal structures, particularly blood vessels. Furthermore, these lesions are typically small and in close proximity to vessels. In this paper, we present an automatic, probabilistic framework for segmentation of gadolinium-enhancing lesions in MS using conditional random fields. Our approach, through the integration of different components, encodes different information such as correspondence between the intensities and tissue labels, patterns in the labels, or patterns in the intensities. The proposed algorithm is evaluated on 80 multimodal clinical datasets acquired from relapsing-remitting MS patients in the context of multicenter clinical trials. The experimental results exhibit a sensitivity of 98% with a low false positive lesion count. The performance of the proposed algorithm is also compared to a logistic regression classifier, a support vector machine and a Markov random field approach. The results demonstrate superior performance of the proposed algorithm at successfully detecting all of the gadolinium-enhancing lesions while maintaining a low false positive lesion count.
Extreme of random field over rectangle with application to concrete rupture stresses
DEFF Research Database (Denmark)
Ditlevsen, Ove Dalager
2000-01-01
Probabilities of excursions of random processes and fields into critical domains are of fundamental interestin many civil engineering decision problems. Examples are reliability evaluations of structures subject torandom load processes, the influence of the size of a structural element on the car......Probabilities of excursions of random processes and fields into critical domains are of fundamental interestin many civil engineering decision problems. Examples are reliability evaluations of structures subject torandom load processes, the influence of the size of a structural element...... results for such probabilities. However, dueto the engineering importance of the problem, several approximate assessment methods have been suggestedin the past. The suitability and accuracy of each of these methods depends on the type of process or fieldunder consideration. Often recourse must be taken...... to the area of the rectangle and the side lengths of therectangle. Published rupture stress data for plain concrete beams illustrate the applicability of the derivedclosed form extreme value distributions as models for distributions of rupture stresses related to weakest linkmechanisms....
Quantifying Evaporation in a Permeable Pavement System ...
Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. The U.S. Environmental Protection Agency (USEPA) constructed a 0.4-ha parking lot in Edison, NJ, that incorporated three different permeable pavement types in the parking lanes – permeable interlocking concrete pavers (PICP), pervious concrete (PC), and porous asphalt (PA). An impermeable liner installed 0.4 m below the driving surface in four 11.6-m by 4.74-m sections per each pavement type captures all infiltrating water and routes it to collection tanks that can contain events up to 38 mm. Each section has a design impervious area to permeable pavement area ratio of 0.66:1. Pressure transducers installed in the underdrain collection tanks measured water level for 24 months. Level was converted to volume using depth-to-volume ratios for individual collection tanks. Using a water balance approach, the measured infiltrate volume was compared to rainfall volume on an event-basis to determine the rainfall retained in the pavement strata and underlying aggregate. Evaporation since the previous event created additional storage in the pavement and aggregate layers. Events were divided into three groups based on antecedent dry period (ADP) and three, four-month categories of potential e
Bolourinejad, Panteha; Herber, Rien
The most suitable candidates for subsurface storage of CO2 are depleted gas fields. Their ability to retain CO2 can however be influenced by the effect which impurities in the CO2 stream (e.g. H2S and SO2) have on the mineralogy of reservoir and seal. In order to investigate the effects of SO2 we
Energy Technology Data Exchange (ETDEWEB)
ChiBin, Zhang; XiaoHui, Lin, E-mail: lxh60@seu.edu.cn; ZhaoMin, Wang; ChangBao, Wang
2017-03-15
In experiments and theoretical analyses, this study examines the capture efficiency (CE) of magnetic drug carrier particles (MDCPs) for implant-assisted magnetic drug targeting (IA-MDT) in microvessels. It also proposes a three-dimensional statistical transport model of MDCPs for IA-MDT in permeable microvessels, which describes blood flow by the two-fluid (Casson and Newtonian) model. The model accounts for the permeable effect of the microvessel wall and the coupling effect between the blood flow and tissue fluid flow. The MDCPs move randomly through the microvessel, and their transport state is described by the Boltzmann equation. The regulated changes and factors affecting the CE of the MDCPs in the assisted magnetic targeting were obtained by solving the theoretical model and by experimental testing. The CE was negatively correlated with the blood flow velocity, and positively correlated with the external magnetic field intensity and microvessel permeability. The predicted CEs of the MDCPs were consistent with the experimental results. Additionally, under the same external magnetic field, the predicted CE was 5–8% higher in the IA-MDT model than in the model ignoring the permeability effect of the microvessel wall. - Highlights: • A model of MDCPs for IA-MDT in permeable microvessels was established. • An experimental device was established, the CE of MDCPs was measured. • The predicted CE of MDCPs was 5–8% higher in the IA-MDT model.
Turbulence generation by a shock wave interacting with a random density inhomogeneity field
Huete Ruiz de Lira, C.
2010-12-01
When a planar shock wave interacts with a random pattern of pre-shock density non-uniformities, it generates an anisotropic turbulent velocity/vorticity field. This turbulence plays an important role in the early stages of the mixing process in a compressed fluid. This situation emerges naturally in a shock interaction with weakly inhomogeneous deuterium-wicked foam targets in inertial confinement fusion and with density clumps/clouds in astrophysics. We present an exact small-amplitude linear theory describing such an interaction. It is based on the exact theory of time and space evolution of the perturbed quantities behind a corrugated shock front for a single-mode pre-shock non-uniformity. Appropriate mode averaging in two dimensions results in closed analytical expressions for the turbulent kinetic energy, degree of anisotropy of velocity and vorticity fields in the shocked fluid, shock amplification of the density non-uniformity and sonic energy flux radiated downstream. These explicit formulae are further simplified in the important asymptotic limits of weak/strong shocks and highly compressible fluids. A comparison with the related problem of a shock interacting with a pre-shock isotropic vorticity field is also presented.
Gushchin, A. A.
1982-12-01
CONTENTSIntroduction § 1. Basic notation and definitions § 2. The Doléans measure and increasing fields § 3. Theorems on predictable projections. Decomposition of weak submartingales § 4. Weakly predictable random fields § 5. Theorems on weakly predictable projections § 6. Decomposition of strong martingales References
A Coupled Hidden Markov Random Field Model for Simultaneous Face Clustering and Tracking in Videos
Wu, Baoyuan
2016-10-25
Face clustering and face tracking are two areas of active research in automatic facial video processing. They, however, have long been studied separately, despite the inherent link between them. In this paper, we propose to perform simultaneous face clustering and face tracking from real world videos. The motivation for the proposed research is that face clustering and face tracking can provide useful information and constraints to each other, thus can bootstrap and improve the performances of each other. To this end, we introduce a Coupled Hidden Markov Random Field (CHMRF) to simultaneously model face clustering, face tracking, and their interactions. We provide an effective algorithm based on constrained clustering and optimal tracking for the joint optimization of cluster labels and face tracking. We demonstrate significant improvements over state-of-the-art results in face clustering and tracking on several videos.
High energy X-ray phase and dark-field imaging using a random absorption mask.
Wang, Hongchang; Kashyap, Yogesh; Cai, Biao; Sawhney, Kawal
2016-07-28
High energy X-ray imaging has unique advantage over conventional X-ray imaging, since it enables higher penetration into materials with significantly reduced radiation damage. However, the absorption contrast in high energy region is considerably low due to the reduced X-ray absorption cross section for most materials. Even though the X-ray phase and dark-field imaging techniques can provide substantially increased contrast and complementary information, fabricating dedicated optics for high energies still remain a challenge. To address this issue, we present an alternative X-ray imaging approach to produce transmission, phase and scattering signals at high X-ray energies by using a random absorption mask. Importantly, in addition to the synchrotron radiation source, this approach has been demonstrated for practical imaging application with a laboratory-based microfocus X-ray source. This new imaging method could be potentially useful for studying thick samples or heavy materials for advanced research in materials science.
Sign language recognition with the Kinect sensor based on conditional random fields.
Yang, Hee-Deok
2014-12-24
Sign language is a visual language used by deaf people. One difficulty of sign language recognition is that sign instances of vary in both motion and shape in three-dimensional (3D) space. In this research, we use 3D depth information from hand motions, generated from Microsoft's Kinect sensor and apply a hierarchical conditional random field (CRF) that recognizes hand signs from the hand motions. The proposed method uses a hierarchical CRF to detect candidate segments of signs using hand motions, and then a BoostMap embedding method to verify the hand shapes of the segmented signs. Experiments demonstrated that the proposed method could recognize signs from signed sentence data at a rate of 90.4%.
Adaptive Markov Random Fields for Example-Based Super-resolution of Faces
Directory of Open Access Journals (Sweden)
Stephenson Todd A
2006-01-01
Full Text Available Image enhancement of low-resolution images can be done through methods such as interpolation, super-resolution using multiple video frames, and example-based super-resolution. Example-based super-resolution, in particular, is suited to images that have a strong prior (for those frameworks that work on only a single image, it is more like image restoration than traditional, multiframe super-resolution. For example, hallucination and Markov random field (MRF methods use examples drawn from the same domain as the image being enhanced to determine what the missing high-frequency information is likely to be. We propose to use even stronger prior information by extending MRF-based super-resolution to use adaptive observation and transition functions, that is, to make these functions region-dependent. We show with face images how we can adapt the modeling for each image patch so as to improve the resolution.
Sign Language Recognition with the Kinect Sensor Based on Conditional Random Fields
Directory of Open Access Journals (Sweden)
Hee-Deok Yang
2014-12-01
Full Text Available Sign language is a visual language used by deaf people. One difficulty of sign language recognition is that sign instances of vary in both motion and shape in three-dimensional (3D space. In this research, we use 3D depth information from hand motions, generated from Microsoft’s Kinect sensor and apply a hierarchical conditional random field (CRF that recognizes hand signs from the hand motions. The proposed method uses a hierarchical CRF to detect candidate segments of signs using hand motions, and then a BoostMap embedding method to verify the hand shapes of the segmented signs. Experiments demonstrated that the proposed method could recognize signs from signed sentence data at a rate of 90.4%.
Bayesian Clustering Using Hidden Markov Random Fields in Spatial Population Genetics
François, Olivier; Ancelet, Sophie; Guillot, Gilles
2006-01-01
We introduce a new Bayesian clustering algorithm for studying population structure using individually geo-referenced multilocus data sets. The algorithm is based on the concept of hidden Markov random field, which models the spatial dependencies at the cluster membership level. We argue that (i) a Markov chain Monte Carlo procedure can implement the algorithm efficiently, (ii) it can detect significant geographical discontinuities in allele frequencies and regulate the number of clusters, (iii) it can check whether the clusters obtained without the use of spatial priors are robust to the hypothesis of discontinuous geographical variation in allele frequencies, and (iv) it can reduce the number of loci required to obtain accurate assignments. We illustrate and discuss the implementation issues with the Scandinavian brown bear and the human CEPH diversity panel data set. PMID:16888334
Durner, Maximilian; Márton, Zoltán.; Hillenbrand, Ulrich; Ali, Haider; Kleinsteuber, Martin
2017-03-01
In this work, a new ensemble method for the task of category recognition in different environments is presented. The focus is on service robotic perception in an open environment, where the robot's task is to recognize previously unseen objects of predefined categories, based on training on a public dataset. We propose an ensemble learning approach to be able to flexibly combine complementary sources of information (different state-of-the-art descriptors computed on color and depth images), based on a Markov Random Field (MRF). By exploiting its specific characteristics, the MRF ensemble method can also be executed as a Dynamic Classifier Selection (DCS) system. In the experiments, the committee- and topology-dependent performance boost of our ensemble is shown. Despite reduced computational costs and using less information, our strategy performs on the same level as common ensemble approaches. Finally, the impact of large differences between datasets is analyzed.
Broadcast News Story Segmentation Using Conditional Random Fields and Multimodal Features
Wang, Xiaoxuan; Xie, Lei; Lu, Mimi; Ma, Bin; Chng, Eng Siong; Li, Haizhou
In this paper, we propose integration of multimodal features using conditional random fields (CRFs) for the segmentation of broadcast news stories. We study story boundary cues from lexical, audio and video modalities, where lexical features consist of lexical similarity, chain strength and overall cohesiveness; acoustic features involve pause duration, pitch, speaker change and audio event type; and visual features contain shot boundaries, anchor faces and news title captions. These features are extracted in a sequence of boundary candidate positions in the broadcast news. A linear-chain CRF is used to detect each candidate as boundary/non-boundary tags based on the multimodal features. Important interlabel relations and contextual feature information are effectively captured by the sequential learning framework of CRFs. Story segmentation experiments show that the CRF approach outperforms other popular classifiers, including decision trees (DTs), Bayesian networks (BNs), naive Bayesian classifiers (NBs), multilayer perception (MLP), support vector machines (SVMs) and maximum entropy (ME) classifiers.
Superresolution with compound Markov random fields via the variational EM algorithm.
Kanemura, Atsunori; Maeda, Shin-ichi; Ishii, Shin
2009-09-01
This study deals with a reconstruction-type superresolution problem and the accompanying image registration problem simultaneously. We propose a Bayesian approach in which the prior is modeled as a compound Gaussian Markov random field (MRF) and marginalization is performed over unknown variables to avoid overfitting. Our algorithm not only avoids overfitting, but also preserves discontinuity in the estimated image, unlike existing single-layer Gaussian MRF models for Bayesian superresolution. Maximum-marginal-likelihood estimation of the registration parameters is carried out using a variational EM algorithm where hidden variables are marginalized out, and the posterior distribution is variationally approximated by a factorized trial distribution. High-resolution image estimates are obtained through the process of posterior computation in the EM algorithm. Experiments show that our Bayesian approach with the two-layer compound model exhibits better performance both in quantitative measures and visual quality than the single-layer model.
Hidden State Conditional Random Field for Abnormal Activity Recognition in Smart Homes
Directory of Open Access Journals (Sweden)
Yu Tong
2015-03-01
Full Text Available As the number of elderly people has increased worldwide, there has been a surge of research into assistive technologies to provide them with better care by recognizing their normal and abnormal activities. However, existing abnormal activity recognition (AAR algorithms rarely consider sub-activity relations when recognizing abnormal activities. This paper presents an application of the Hidden State Conditional Random Field (HCRF method to detect and assess abnormal activities that often occur in elderly persons’ homes. Based on HCRF, this paper designs two AAR algorithms, and validates them by comparing them with a feature vector distance based algorithm in two experiments. The results demonstrate that the proposed algorithms favorably outperform the competitor, especially when abnormal activities have same sensor type and sensor number as normal activities.
Nakagami Markov random field as texture model for ultrasound RF envelope image.
Bouhlel, N; Sevestre-Ghalila, S
2009-06-01
The aim of this paper is to propose a new Markov random field (MRF) model for the backscattered ultrasonic echo in order to get information about backscatter characteristics, such as the scatterer density, amplitude and spacing. The model combines the Nakagami distribution that describes the envelope of backscattered echo with spatial interaction using MRF. In this paper, the parameters of the model and the estimation parameter method are introduced. Computer simulation using ultrasound radio-frequency (RF) simulator and experiments on choroidal malignant melanoma have been undertaken to test the validity of the model. The relationship between the parameters of MRF model and the backscatter characteristics has been established. Furthermore, the ability of the model to distinguish between normal and abnormal tissue has been proved. All the results can show the success of the model.
PReFerSim: fast simulation of demography and selection under the Poisson Random Field model.
Ortega-Del Vecchyo, Diego; Marsden, Clare D; Lohmueller, Kirk E
2016-11-15
The Poisson Random Field (PRF) model has become an important tool in population genetics to study weakly deleterious genetic variation under complicated demographic scenarios. Currently, there are no freely available software applications that allow simulation of genetic variation data under this model. Here we present PReFerSim, an ANSI C program that performs forward simulations under the PRF model. PReFerSim models changes in population size, arbitrary amounts of inbreeding, dominance and distributions of selective effects. Users can track summaries of genetic variation over time and output trajectories of selected alleles. PReFerSim is freely available at: https://github.com/LohmuellerLab/PReFerSim CONTACT: klohmueller@ucla.eduSupplementary information: Supplementary data are available at Bioinformatics online. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
Cross-covariance functions for multivariate random fields based on latent dimensions
Apanasovich, T. V.
2010-02-16
The problem of constructing valid parametric cross-covariance functions is challenging. We propose a simple methodology, based on latent dimensions and existing covariance models for univariate random fields, to develop flexible, interpretable and computationally feasible classes of cross-covariance functions in closed form. We focus on spatio-temporal cross-covariance functions that can be nonseparable, asymmetric and can have different covariance structures, for instance different smoothness parameters, in each component. We discuss estimation of these models and perform a small simulation study to demonstrate our approach. We illustrate our methodology on a trivariate spatio-temporal pollution dataset from California and demonstrate that our cross-covariance performs better than other competing models. © 2010 Biometrika Trust.
A multiscale Markov random field model in wavelet domain for image segmentation
Dai, Peng; Cheng, Yu; Wang, Shengchun; Du, Xinyu; Wu, Dan
2017-07-01
The human vision system has abilities for feature detection, learning and selective attention with some properties of hierarchy and bidirectional connection in the form of neural population. In this paper, a multiscale Markov random field model in the wavelet domain is proposed by mimicking some image processing functions of vision system. For an input scene, our model provides its sparse representations using wavelet transforms and extracts its topological organization using MRF. In addition, the hierarchy property of vision system is simulated using a pyramid framework in our model. There are two information flows in our model, i.e., a bottom-up procedure to extract input features and a top-down procedure to provide feedback controls. The two procedures are controlled simply by two pyramidal parameters, and some Gestalt laws are also integrated implicitly. Equipped with such biological inspired properties, our model can be used to accomplish different image segmentation tasks, such as edge detection and region segmentation.
Incorporating conditional random fields and active learning to improve sentiment identification.
Zhang, Kunpeng; Xie, Yusheng; Yang, Yi; Sun, Aaron; Liu, Hengchang; Choudhary, Alok
2014-10-01
Many machine learning, statistical, and computational linguistic methods have been developed to identify sentiment of sentences in documents, yielding promising results. However, most of state-of-the-art methods focus on individual sentences and ignore the impact of context on the meaning of a sentence. In this paper, we propose a method based on conditional random fields to incorporate sentence structure and context information in addition to syntactic information for improving sentiment identification. We also investigate how human interaction affects the accuracy of sentiment labeling using limited training data. We propose and evaluate two different active learning strategies for labeling sentiment data. Our experiments with the proposed approach demonstrate a 5%-15% improvement in accuracy on Amazon customer reviews compared to existing supervised learning and rule-based methods. Copyright © 2014 Elsevier Ltd. All rights reserved.
Laifa, Oumeima; Le Guillou-Buffello, Delphine; Racoceanu, Daniel
2017-11-01
The fundamental role of vascular supply in tumor growth makes the evaluation of the angiogenesis crucial in assessing effect of anti-angiogenic therapies. Since many years, such therapies are designed to inhibit the vascular endothelial growth factor (VEGF). To contribute to the assessment of anti-angiogenic agent (Pazopanib) effect on vascular and cellular structures, we acquired data from tumors extracted from a murine tumor model using Multi- Fluorescence Scanning. In this paper, we implemented an unsupervised algorithm combining the Watershed segmentation and Markov Random Field model (MRF). This algorithm allowed us to quantify the proportion of apoptotic endothelial cells and to generate maps according to cell density. Stronger association between apoptosis and endothelial cells was revealed in the tumors receiving anti-angiogenic therapy (n = 4) as compared to those receiving placebo (n = 4). A high percentage of apoptotic cells in the tumor area are endothelial. Lower density cells were detected in tumor slices presenting higher apoptotic endothelial areas.
A novel approach to assess the treatment response using Gaussian random field in PET
Energy Technology Data Exchange (ETDEWEB)
Wang, Mengdie [Department of Biomedical Engineering, Tsinghua University, Beijing 100084, China and Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Guo, Ning [Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Hu, Guangshu; Zhang, Hui, E-mail: hzhang@mail.tsinghua.edu.cn, E-mail: li.quanzheng@mgh.harvard.edu [Department of Biomedical Engineering, Tsinghua University, Beijing 100084 (China); El Fakhri, Georges; Li, Quanzheng, E-mail: hzhang@mail.tsinghua.edu.cn, E-mail: li.quanzheng@mgh.harvard.edu [Center for Advanced Medical Imaging Science, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, Boston, Massachusetts 02115 (United States)
2016-02-15
Purpose: The assessment of early therapeutic response to anticancer therapy is vital for treatment planning and patient management in clinic. With the development of personal treatment plan, the early treatment response, especially before any anatomically apparent changes after treatment, becomes urgent need in clinic. Positron emission tomography (PET) imaging serves an important role in clinical oncology for tumor detection, staging, and therapy response assessment. Many studies on therapy response involve interpretation of differences between two PET images, usually in terms of standardized uptake values (SUVs). However, the quantitative accuracy of this measurement is limited. This work proposes a statistically robust approach for therapy response assessment based on Gaussian random field (GRF) to provide a statistically more meaningful scale to evaluate therapy effects. Methods: The authors propose a new criterion for therapeutic assessment by incorporating image noise into traditional SUV method. An analytical method based on the approximate expressions of the Fisher information matrix was applied to model the variance of individual pixels in reconstructed images. A zero mean unit variance GRF under the null hypothesis (no response to therapy) was obtained by normalizing each pixel of the post-therapy image with the mean and standard deviation of the pretherapy image. The performance of the proposed method was evaluated by Monte Carlo simulation, where XCAT phantoms (128{sup 2} pixels) with lesions of various diameters (2–6 mm), multiple tumor-to-background contrasts (3–10), and different changes in intensity (6.25%–30%) were used. The receiver operating characteristic curves and the corresponding areas under the curve were computed for both the proposed method and the traditional methods whose figure of merit is the percentage change of SUVs. The formula for the false positive rate (FPR) estimation was developed for the proposed therapy response
Adaptation of the projection-slice theorem for stock valuation estimation using random Markov fields
Riasati, Vahid R.
2009-04-01
The Projection-Slice Synthetic Discriminant function filter is utilized with Random Markov Fields, RMF to estimate trends that may be used as prediction for stock valuation through the representation of the market behavior as a hidden Markov Model, HMM. In this work, we utilize a set of progressive and contiguous time segments of a given stock, and treat the set as a two dimensional object that has been represented by its one-d projections. The abstract two-D object is thus an incarnation of N-temporal projections. The HMM is then utilized to generate N+1 projections that maximizes the two-dimensional correlation peak between the data and the HMM-generated stochastic processes. This application of the PSDF provides a method of stock valuation prediction via the market stochastic behavior utilized in the filter.
Roy, Pallab Kanti; Bhuiyan, Alauddin; Janke, Andrew; Desmond, Patricia M; Wong, Tien Yin; Abhayaratna, Walter P; Storey, Elsdon; Ramamohanarao, Kotagiri
2015-10-01
White matter lesions (WMLs) are small groups of dead cells that clump together in the white matter of brain. In this paper, we propose a reliable method to automatically segment WMLs. Our method uses a novel filter to enhance the intensity of WMLs. Then a feature set containing enhanced intensity, anatomical and spatial information is used to train a random forest classifier for the initial segmentation of WMLs. Following that a reliable and robust edge potential function based Markov Random Field (MRF) is proposed to obtain the final segmentation by removing false positive WMLs. Quantitative evaluation of the proposed method is performed on 24 subjects of ENVISion study. The segmentation results are validated against the manual segmentation, performed under the supervision of an expert neuroradiologist. The results show a dice similarity index of 0.76 for severe lesion load, 0.73 for moderate lesion load and 0.61 for mild lesion load. In addition to that we have compared our method with three state of the art methods on 20 subjects of Medical Image Computing and Computer Aided Intervention Society's (MICCAI's) MS lesion challenge dataset, where our method shows better segmentation accuracy compare to the state of the art methods. These results indicate that the proposed method can assist the neuroradiologists in assessing the WMLs in clinical practice. Copyright © 2015 Elsevier Ltd. All rights reserved.
Distribution of the Height of Local Maxima of Gaussian Random Fields*
Cheng, Dan; Schwartzman, Armin
2015-01-01
Let {f(t) : t ∈ T} be a smooth Gaussian random field over a parameter space T, where T may be a subset of Euclidean space or, more generally, a Riemannian manifold. We provide a general formula for the distribution of the height of a local maximum P{f(t0)>u∣t0 is a local maximum of f(t)} when f is non-stationary. Moreover, we establish asymptotic approximations for the overshoot distribution of a local maximum P{f(t0)>u+v∣t0 is a local maximum of f(t) and f(t0) > v} as v → ∞. Assuming further that f is isotropic, we apply techniques from random matrix theory related to the Gaussian orthogonal ensemble to compute such conditional probabilities explicitly when T is Euclidean or a sphere of arbitrary dimension. Such calculations are motivated by the statistical problem of detecting peaks in the presence of smooth Gaussian noise. PMID:26478714
A Tutorial of the Poisson Random Field Model in Population Genetics
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Praveen Sethupathy
2008-01-01
Full Text Available Population genetics is the study of allele frequency changes driven by various evolutionary forces such as mutation, natural selection, and random genetic drift. Although natural selection is widely recognized as a bona-fide phenomenon, the extent to which it drives evolution continues to remain unclear and controversial. Various qualitative techniques, or so-called “tests of neutrality”, have been introduced to detect signatures of natural selection. A decade and a half ago, Stanley Sawyer and Daniel Hartl provided a mathematical framework, referred to as the Poisson random field (PRF, with which to determine quantitatively the intensity of selection on a particular gene or genomic region. The recent availability of large-scale genetic polymorphism data has sparked widespread interest in genome-wide investigations of natural selection. To that end, the original PRF model is of particular interest for geneticists and evolutionary genomicists. In this article, we will provide a tutorial of the mathematical derivation of the original Sawyer and Hartl PRF model.
Ensemble of Neural Network Conditional Random Fields for Self-Paced Brain Computer Interfaces
Directory of Open Access Journals (Sweden)
Hossein Bashashati
2017-07-01
Full Text Available Classification of EEG signals in self-paced Brain Computer Interfaces (BCI is an extremely challenging task. The main diﬃculty stems from the fact that start time of a control task is not defined. Therefore it is imperative to exploit the characteristics of the EEG data to the extent possible. In sensory motor self-paced BCIs, while performing the mental task, the user’s brain goes through several well-defined internal state changes. Applying appropriate classifiers that can capture these state changes and exploit the temporal correlation in EEG data can enhance the performance of the BCI. In this paper, we propose an ensemble learning approach for self-paced BCIs. We use Bayesian optimization to train several different classifiers on different parts of the BCI hyper- parameter space. We call each of these classifiers Neural Network Conditional Random Field (NNCRF. NNCRF is a combination of a neural network and conditional random field (CRF. As in the standard CRF, NNCRF is able to model the correlation between adjacent EEG samples. However, NNCRF can also model the nonlinear dependencies between the input and the output, which makes it more powerful than the standard CRF. We compare the performance of our algorithm to those of three popular sequence labeling algorithms (Hidden Markov Models, Hidden Markov Support Vector Machines and CRF, and to two classical classifiers (Logistic Regression and Support Vector Machines. The classifiers are compared for the two cases: when the ensemble learning approach is not used and when it is. The data used in our studies are those from the BCI competition IV and the SM2 dataset. We show that our algorithm is considerably superior to the other approaches in terms of the Area Under the Curve (AUC of the BCI system.
Boulware, David R
2006-01-01
Jellyfish stings are a common occurrence among ocean goers worldwide with an estimated 150 million envenomations annually. Fatalities and hospitalizations occur annually, particularly in the Indo-Pacific regions. A new topical jellyfish sting inhibitor based on the mucous coating of the clown fish prevents 85% of jellyfish stings in laboratory settings. The field effectiveness is unknown. The objective is to evaluate the field efficacy of the jellyfish sting inhibitor, Safe Sea. A double-blind, randomized, placebo-controlled trial occurred at the Dry Tortugas National Park, FL, USA and Sapodilla Cayes, Belize. Participants were healthy volunteers planning to snorkel for 30 to 45 minutes. Ten minutes prior to swimming, each participant was directly observed applying a blinded sample of Safe Sea (Nidaria Technology Ltd, Jordan Valley, Israel) to one side of their body and a blinded sample of Coppertone (Schering-Plough, Kenilworth, NJ, USA) to the contralateral side as placebo control. Masked 26 g samples of both Safe Sea SPF15 and Coppertone SPF15 were provided in identical containers to achieve 2 mg/cm(2) coverage. Sides were randomly chosen by participants. The incidence of jellyfish stings was the main outcome measure. This was assessed by participant interview and examination as subjects exited the water. A total of 82 observed water exposures occurred. Thirteen jellyfish stings occurred during the study period for a 16% incidence. Eleven jellyfish stings occurred with placebo, two with the sting inhibitor, resulting in a relative risk reduction of 82% (95% confidence interval: 21%-96%; p= 0.02). No seabather's eruption or side effects occurred. Safe Sea is a topical barrier cream effective at preventing >80% jellyfish stings under real-world conditions.
Bayesian Markov Random Field analysis for protein function prediction based on network data.
Kourmpetis, Yiannis A I; van Dijk, Aalt D J; Bink, Marco C A M; van Ham, Roeland C H J; ter Braak, Cajo J F
2010-02-24
Inference of protein functions is one of the most important aims of modern biology. To fully exploit the large volumes of genomic data typically produced in modern-day genomic experiments, automated computational methods for protein function prediction are urgently needed. Established methods use sequence or structure similarity to infer functions but those types of data do not suffice to determine the biological context in which proteins act. Current high-throughput biological experiments produce large amounts of data on the interactions between proteins. Such data can be used to infer interaction networks and to predict the biological process that the protein is involved in. Here, we develop a probabilistic approach for protein function prediction using network data, such as protein-protein interaction measurements. We take a Bayesian approach to an existing Markov Random Field method by performing simultaneous estimation of the model parameters and prediction of protein functions. We use an adaptive Markov Chain Monte Carlo algorithm that leads to more accurate parameter estimates and consequently to improved prediction performance compared to the standard Markov Random Fields method. We tested our method using a high quality S. cereviciae validation network with 1622 proteins against 90 Gene Ontology terms of different levels of abstraction. Compared to three other protein function prediction methods, our approach shows very good prediction performance. Our method can be directly applied to protein-protein interaction or coexpression networks, but also can be extended to use multiple data sources. We apply our method to physical protein interaction data from S. cerevisiae and provide novel predictions, using 340 Gene Ontology terms, for 1170 unannotated proteins and we evaluate the predictions using the available literature.
IMPLEMENTATION OF THE MARKOV RANDOM FIELD FOR URBAN LAND COVER CLASSIFICATION OF UAV VHIR DATA
Directory of Open Access Journals (Sweden)
Jati Pratomo
2016-10-01
Full Text Available The usage of Unmanned Aerial Vehicle (UAV has grown rapidly in various fields, such as urban planning, search and rescue, and surveillance. Capturing images from UAV has many advantages compared with satellite imagery. For instance, higher spatial resolution and less impact from atmospheric variations can be obtained. However, there are difficulties in classifying urban features, due to the complexity of the urban land covers. The usage of Maximum Likelihood Classification (MLC has limitations since it is based on the assumption of the normal distribution of pixel values, where, in fact, urban features are not normally distributed. There are advantages in using the Markov Random Field (MRF for urban land cover classification as it assumes that neighboring pixels have a higher probability to be classified in the same class rather than a different class. This research aimed to determine the impact of the smoothness (λ and the updating temperature (Tupd on the accuracy result (κ in MRF. We used a UAV VHIR sized 587 square meters, with six-centimetre resolution, taken in Bogor Regency, Indonesia. The result showed that the kappa value (κ increases proportionally with the smoothness (λ until it reaches the maximum (κ, then the value drops. The usage of higher (Tupd has resulted in better (κ although it also led to a higher Standard Deviations (SD. Using the most optimal parameter, MRF resulted in slightly higher (κ compared with MLC.
Directory of Open Access Journals (Sweden)
Ibrahim Ben Daya
Full Text Available 3-D ultrasound imaging offers unique opportunities in the field of non destructive testing that cannot be easily found in A-mode and B-mode images. To acquire a 3-D ultrasound image without a mechanically moving transducer, a 2-D array can be used. The row column technique is preferred over a fully addressed 2-D array as it requires a significantly lower number of interconnections. Recent advances in 3-D row-column ultrasound imaging systems were largely focused on sensor design. However, these imaging systems face three intrinsic challenges that cannot be addressed by improving sensor design alone: speckle noise, sparsity of data in the imaged volume, and the spatially dependent point spread function of the imaging system. In this paper, we propose a compensated row-column ultrasound image reconstruction system using Fisher-Tippett multilayered conditional random field model. Tests carried out on both simulated and real row-column ultrasound images show the effectiveness of our proposed system as opposed to other published systems. Visual assessment of the results show our proposed system's potential at preserving detail and reducing speckle. Quantitative analysis shows that our proposed system outperforms previously published systems when evaluated with metrics such as Peak Signal to Noise Ratio, Coefficient of Correlation, and Effective Number of Looks. These results show the potential of our proposed system as an effective tool for enhancing 3-D row-column imaging.
Multi-fidelity Gaussian process regression for prediction of random fields
Energy Technology Data Exchange (ETDEWEB)
Parussini, L. [Department of Engineering and Architecture, University of Trieste (Italy); Venturi, D., E-mail: venturi@ucsc.edu [Department of Applied Mathematics and Statistics, University of California Santa Cruz (United States); Perdikaris, P. [Department of Mechanical Engineering, Massachusetts Institute of Technology (United States); Karniadakis, G.E. [Division of Applied Mathematics, Brown University (United States)
2017-05-01
We propose a new multi-fidelity Gaussian process regression (GPR) approach for prediction of random fields based on observations of surrogate models or hierarchies of surrogate models. Our method builds upon recent work on recursive Bayesian techniques, in particular recursive co-kriging, and extends it to vector-valued fields and various types of covariances, including separable and non-separable ones. The framework we propose is general and can be used to perform uncertainty propagation and quantification in model-based simulations, multi-fidelity data fusion, and surrogate-based optimization. We demonstrate the effectiveness of the proposed recursive GPR techniques through various examples. Specifically, we study the stochastic Burgers equation and the stochastic Oberbeck–Boussinesq equations describing natural convection within a square enclosure. In both cases we find that the standard deviation of the Gaussian predictors as well as the absolute errors relative to benchmark stochastic solutions are very small, suggesting that the proposed multi-fidelity GPR approaches can yield highly accurate results.
A Poisson random field model of pathogen transport in surface water
Yeghiazarian, L.; Samorodnitsky, G.; Montemagno, C. D.
2009-11-01
To address the uncertainty associated with microbial transport and surface water contamination events, we developed a new comprehensive stochastic framework that combines processes on the microscopic (single microorganism) and macroscopic (ensembles of microorganisms) scales. The spatial and temporal population behavior is modeled as a nonhomogeneous Poisson random field with Markovian field dynamics. The model parameters are based on the actual physical and biological characteristics of the Cryptosporidium parvum transport process and can be extended to cover a variety of other pathogens. Since soil particles have been shown to be a major vehicle in microbial transport, a U.S. Department of Agriculture approved erosion model (Water Erosion Prediction Project) is incorporated into the model. Risk assessment is an integral part of the stochastic model and is conducted using a set of simple calculations. Poisson intensity functions and correlations are computed. The results consistently indicate that surface water contamination events are transient, with traveling high peaks of microorganism concentrations. Correlations between microorganism populations at different points in time and space reach relatively significant levels even at large distances from one another. This information is aimed to assist water resources management teams in the decision-making process to identify the likely timing and locations of high-risk areas and thus to avoid collection of contaminated water.
Random-field Potts model for the polar domains of lead magnesium niobate and lead scandium tantalate
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Qian, H.; Bursill, L.A
1997-06-01
A random filed Potts model is used to establish the spatial relationship between the nanoscale distribution of charges chemical defects and nanoscale polar domains for the perovskite-based relaxor materials lead magnesium niobate (PMN) and lead scandium tantalate (PST). The random fields are not set stochastically but are determined initially by the distribution of B-site cations (Mg, Nb) or (Sc, Ta) generated by Monte Carlo NNNI-model simulations for the chemical defects. An appropriate random field Potts model is derived and algorithms developed for a 2D lattice. It is shown that the local fields are strongly correlated with the chemical domain walls and that polar domains as a function of decreasing temperature is simulated for the two cases of PMN and PST. The dynamics of the polar clusters is also discussed. 33 refs., 9 figs.
Energy Technology Data Exchange (ETDEWEB)
Zentner, I. [IMSIA, UMR EDF-ENSTA-CNRS-CEA 9219, Université Paris-Saclay, 828 Boulevard des Maréchaux, 91762 Palaiseau Cedex (France); Ferré, G., E-mail: gregoire.ferre@ponts.org [CERMICS – Ecole des Ponts ParisTech, 6 et 8 avenue Blaise Pascal, Cité Descartes, Champs sur Marne, 77455 Marne la Vallée Cedex 2 (France); Poirion, F. [Department of Structural Dynamics and Aeroelasticity, ONERA, BP 72, 29 avenue de la Division Leclerc, 92322 Chatillon Cedex (France); Benoit, M. [Institut de Recherche sur les Phénomènes Hors Equilibre (IRPHE), UMR 7342 (CNRS, Aix-Marseille Université, Ecole Centrale Marseille), 49 rue Frédéric Joliot-Curie, BP 146, 13384 Marseille Cedex 13 (France)
2016-06-01
In this paper, a new method for the identification and simulation of non-Gaussian and non-stationary stochastic fields given a database is proposed. It is based on two successive biorthogonal decompositions aiming at representing spatio–temporal stochastic fields. The proposed double expansion allows to build the model even in the case of large-size problems by separating the time, space and random parts of the field. A Gaussian kernel estimator is used to simulate the high dimensional set of random variables appearing in the decomposition. The capability of the method to reproduce the non-stationary and non-Gaussian features of random phenomena is illustrated by applications to earthquakes (seismic ground motion) and sea states (wave heights).
ANALYSIS AND VALIDATION OF GRID DEM GENERATION BASED ON GAUSSIAN MARKOV RANDOM FIELD
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F. J. Aguilar
2016-06-01
Full Text Available Digital Elevation Models (DEMs are considered as one of the most relevant geospatial data to carry out land-cover and land-use classification. This work deals with the application of a mathematical framework based on a Gaussian Markov Random Field (GMRF to interpolate grid DEMs from scattered elevation data. The performance of the GMRF interpolation model was tested on a set of LiDAR data (0.87 points/m2 provided by the Spanish Government (PNOA Programme over a complex working area mainly covered by greenhouses in Almería, Spain. The original LiDAR data was decimated by randomly removing different fractions of the original points (from 10% to up to 99% of points removed. In every case, the remaining points (scattered observed points were used to obtain a 1 m grid spacing GMRF-interpolated Digital Surface Model (DSM whose accuracy was assessed by means of the set of previously extracted checkpoints. The GMRF accuracy results were compared with those provided by the widely known Triangulation with Linear Interpolation (TLI. Finally, the GMRF method was applied to a real-world case consisting of filling the LiDAR-derived DSM gaps after manually filtering out non-ground points to obtain a Digital Terrain Model (DTM. Regarding accuracy, both GMRF and TLI produced visually pleasing and similar results in terms of vertical accuracy. As an added bonus, the GMRF mathematical framework makes possible to both retrieve the estimated uncertainty for every interpolated elevation point (the DEM uncertainty and include break lines or terrain discontinuities between adjacent cells to produce higher quality DTMs.
Transverse eV Ion Heating by Random Electric Field Fluctuations in the Plasmasphere
Artemyev, A. V.; Mourenas, D.; Agapitov, O. V.; Blum, L.
2017-01-01
Charged particle acceleration in the Earth inner magnetosphere is believed to be mainly due to the local resonant wave-particle interaction or particle transport processes. However, the Van Allen Probes have recently provided interesting evidence of a relatively slow transverse heating of eV ions at distances about 2-3 Earth radii during quiet times. Waves that are able to resonantly interact with such very cold ions are generally rare in this region of space, called the plasmasphere. Thus, non-resonant wave-particle interactions are expected to play an important role in the observed ion heating. We demonstrate that stochastic heating by random transverse electric field fluctuations of whistler (and possibly electromagnetic ion cyclotron) waves could explain this weak and slow transverse heating of H+ and O+ ions in the inner magnetosphere. The essential element of the proposed model of ion heating is the presence of trains of random whistler (hiss) wave packets, with significant amplitude modulations produced by strong wave damping, rapid wave growth, or a superposition of wave packets of different frequencies, phases, and amplitudes. Such characteristics correspond to measured characteristics of hiss waves in this region. Using test particle simulations with typical wave and plasma parameters, we demonstrate that the corresponding stochastic transverse ion heating reaches 0.07-0.2 eV/h for protons and 0.007-0.015 eV/h for O+ ions. This global temperature increase of the Maxwellian ion population from an initial Ti approx. 0.3 eV could potentially explain the observations.
Transverse eV ion heating by random electric field fluctuations in the plasmasphere
Artemyev, A. V.; Mourenas, D.; Agapitov, O. V.; Blum, L.
2017-02-01
Charged particle acceleration in the Earth inner magnetosphere is believed to be mainly due to the local resonant wave-particle interaction or particle transport processes. However, the Van Allen Probes have recently provided interesting evidence of a relatively slow transverse heating of eV ions at distances about 2-3 Earth radii during quiet times. Waves that are able to resonantly interact with such very cold ions are generally rare in this region of space, called the plasmasphere. Thus, non-resonant wave-particle interactions are expected to play an important role in the observed ion heating. We demonstrate that stochastic heating by random transverse electric field fluctuations of whistler (and possibly electromagnetic ion cyclotron) waves could explain this weak and slow transverse heating of H+ and O+ ions in the inner magnetosphere. The essential element of the proposed model of ion heating is the presence of trains of random whistler (hiss) wave packets, with significant amplitude modulations produced by strong wave damping, rapid wave growth, or a superposition of wave packets of different frequencies, phases, and amplitudes. Such characteristics correspond to measured characteristics of hiss waves in this region. Using test particle simulations with typical wave and plasma parameters, we demonstrate that the corresponding stochastic transverse ion heating reaches 0.07-0.2 eV/h for protons and 0.007-0.015 eV/h for O+ ions. This global temperature increase of the Maxwellian ion population from an initial Ti˜0.3 eV could potentially explain the observations.
Mahdian, M.; Motagh, M.; Akbari, V.
2013-09-01
In recent years, the use of Polarimetric Synthetic Aperture Radar (PolSAR) data in different applications dramatically has been increased. In SAR imagery an interference phenomenon with random behavior exists which is called speckle noise. The interpretation of data encounters some troubles due to the presence of speckle which can be considered as a multiplicative noise affecting all coherent imaging systems. Indeed, speckle degrade radiometric resolution of PolSAR images, therefore it is needful to perform speckle filtering on the SAR data type. Markov Random Field (MRF) has proven to be a powerful method for drawing out eliciting contextual information from remotely sensed images. In the present paper, a probability density function (PDF), which is fitted well with the PolSAR data based on the goodness-of-fit test, is first obtained for the pixel-wise analysis. Then the contextual smoothing is achieved with the MRF method. This novel speckle reduction method combines an advanced statistical distribution with spatial contextual information for PolSAR data. These two parts of information are combined based on weighted summation of pixel-wise and contextual models. This approach not only preserves edge information in the images, but also improves signal-to-noise ratio of the results. The method maintains the mean value of original signal in the homogenous areas and preserves the edges of features in the heterogeneous regions. Experiments on real medium resolution ALOS data from Tehran, and also high resolution full polarimetric SAR data over the Oberpfaffenhofen test-site in Germany, demonstrate the effectiveness of the algorithm compared with well-known despeckling methods.
Heinemann, Colleen
Research in material science is increasingly reliant on image-based data from experiments, demanding construction of new analysis tools that help scientists discover information from digital images. Because there is such a wide variety of materials and image modalities, detecting different compounds from imaged materials continues to be a challenging task. A vast collection of algorithms for filtering, image segmentation, and texture description have facilitated and improved accuracy for sample measurements (see Chapter 1 Introduction and Literature Review). Despite this, the community still lacks scalable, general purpose, easily configurable image analysis frameworks that allow pattern detection on different imaging modalities across multiple scales. The need for such a framework was the motivation behind the development of a distributed-memory parallel Markov Random Field based framework. Markov Random Field (MRF) algorithms provide the ability to explore contextual information about a given dataset. Given the complexity of such algorithms, however, they are limited by performance when running serial. Thus, running in some sort of parallel fashion is necessary. The effects are twofold. Not only does running the MRF algorithm in parallel provide the ability to run current datasets faster and more efficiently, it also provides the ability for datasets to continue to grow in size and still be able to be run with such frameworks. The variation of the Markov Random Field algorithm utilized in this study first oversegments the given input image and constructs a graph model based on photometric and geometric distances. Next, the resulting graph model is refactored specifically into the MRF model to target image segmentation. Finally, a distributed approach is used for the optimization process to obtain the best labeling for the graph, which is essentially the goal of using a MRF algorithm. Given the concept of using a distributed memory parallel framework, specifically
Relative permeability through fractures
Energy Technology Data Exchange (ETDEWEB)
Diomampo, Gracel, P.
2001-08-01
The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.
Permeability measuremens of brazilian Eucalyptus
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Marcio Rogério da Silva
2010-09-01
Full Text Available The permeability of Brazilian Eucalyptus grandis and Eucalyptus citriodora wood was measured in a custom build gas analysis chamber in order to determine which species could be successfully treated with preservatives. Liquid permeability was tested using an emulsion of Neen oil and a control of distillated water. Air was used to test the gas phase permeability. For both Eucalyptus grandis and Eucalyptus citriodora, the longitudinal permeability of gas was shown to be about twice as great as the liquid phase permeability. No radial permeability was observed for either wood. The permeability of air and water through the sapwood of Eucalyptus grandis was greater than that through the sapwood of Eucalyptus citriodora. The permeability of neen oil preservative through the sapwood of Eucalyptus grandis was also greater than through the sapwood of E. Citradora, but the difference was not statistically significant. Scanning Electron Microscopy images showed that the distribution and obstruction in the vessels could be correlated with observed permeability properties. Irrespective of the causes of differences in permeability between the species, the fluid phase flux through the sapwood of both species was significant, indicating that both Eucalyptus grandis and Eucalyptus citriodora could be successfully treated with wood preservative.
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Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.
2005-11-01
The DECOVALEX project is an international cooperativeproject initiated by SKI, the Swedish Nuclear Power Inspectorate, withparticipation of about 10 international organizations. The name DECOVALEXstands for DEvelopment of COupled models and their VALidation againstExperiments. The general goal of this project is to encouragemultidisciplinary interactive and cooperative research on modelingcoupled processes in geologic formations in support of the performanceassessment for underground storage of radioactive waste. Three multi-yearproject stages of DECOVALEX have been completed in the past decade,mainly focusing on coupled thermal-hydrological-mechanicalprocesses.Currently, a fourth three-year project stage of DECOVALEX isunder way, referred to as DECOVALEX-THMC. THMC stands for Thermal,Hydrological, Mechanical, and Chemical processes. The new project stageaims at expanding the traditional geomechanical scope of the previousDECOVALEX project stages by incorporating geochemical processes importantfor repository performance. The U.S. Department of Energy (DOE) leadsTask D of the new DECOVALEX phase, entitled "Long-termPermeability/Porosity Changes in the EDZ and Near Field due to THC andTHM Processes for Volcanic and Crystalline-Bentonite Systems." In itsleadership role for Task D, DOE coordinates and sets the direction forthe cooperative research activities of the international research teamsengaged in Task D.
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Ferfera, F.
1997-09-15
The permeability evolution of a reservoir rock may be attributed to three successive phenomena: closure of the existing fissures, elastic deformation of the pore space and finally, non-reversible damage to the pore walls. Simultaneous measurements of strains and single-phase permeability were performed in a Vosges sandstone. Several loadings paths have been investigated together with several pore pressure and confining pressure levels. Results are analyzed in order to show the influence of the effective means stress (p`) and the deviatoric stress (q). It is shown that a criterion can be defined in the (p`-q) plot for the permeability evolution. Inside the domain defined by the criterion, the permeability change is nil or small whatever the loading path. Outside the domain, the permeability steadily decreases and may vary strongly. It is also shown that the permeability reduction rate is controlled by stress path independently of the stress level. The most deviatoric stress path induced the lowest reduction rate; it is thus possible to derive the permeability changes if the stress path and the deviatoric stress value are known
Using artificial intelligence to predict permeability from petrographic data
Ali, Maqsood; Chawathé, Adwait
2000-10-01
Petrographic data collected during thin section analysis can be invaluable for understanding the factors that control permeability distribution. Reliable prediction of permeability is important for reservoir characterization. The petrographic elements (mineralogy, porosity types, cements and clays, and pore morphology) interact with each other uniquely to generate a specific permeability distribution. It is difficult to quantify accurately this interaction and its consequent effect on permeability, emphasizing the non-linear nature of the process. To capture these non-linear interactions, neural networks were used to predict permeability from petrographic data. The neural net was used as a multivariate correlative tool because of its ability to learn the non-linear relationships between multiple input and output variables. The study was conducted on the upper Queen formation called the Shattuck Member (Permian age). The Shattuck Member is composed of very fine-grained arkosic sandstone. The core samples were available from the Sulimar Queen and South Lucky Lake fields located in Chaves County, New Mexico. Nineteen petrographic elements were collected for each permeability value using a combined minipermeameter-petrographic technique. In order to reduce noise and overfitting the permeability model, these petrographic elements were screened, and their control (ranking) with respect to permeability was determined using fuzzy logic. Since the fuzzy logic algorithm provides unbiased ranking, it was used to reduce the dimensionality of the input variables. Based on the fuzzy logic ranking, only the most influential petrographic elements were selected as inputs for permeability prediction. The neural net was trained and tested using data from Well 1-16 in the Sulimar Queen field. Relying on the ranking obtained from the fuzzy logic analysis, the net was trained using the most influential three, five, and ten petrographic elements. A fast algorithm (the scaled conjugate
Segmentation of cone-beam CT using a hidden Markov random field with informative priors
Moores, M.; Hargrave, C.; Harden, F.; Mengersen, K.
2014-03-01
Cone-beam computed tomography (CBCT) has enormous potential to improve the accuracy of treatment delivery in image-guided radiotherapy (IGRT). To assist radiotherapists in interpreting these images, we use a Bayesian statistical model to label each voxel according to its tissue type. The rich sources of prior information in IGRT are incorporated into a hidden Markov random field model of the 3D image lattice. Tissue densities in the reference CT scan are estimated using inverse regression and then rescaled to approximate the corresponding CBCT intensity values. The treatment planning contours are combined with published studies of physiological variability to produce a spatial prior distribution for changes in the size, shape and position of the tumour volume and organs at risk. The voxel labels are estimated using iterated conditional modes. The accuracy of the method has been evaluated using 27 CBCT scans of an electron density phantom. The mean voxel-wise misclassification rate was 6.2%, with Dice similarity coefficient of 0.73 for liver, muscle, breast and adipose tissue. By incorporating prior information, we are able to successfully segment CBCT images. This could be a viable approach for automated, online image analysis in radiotherapy.
Directory of Open Access Journals (Sweden)
Min Chen
2011-04-01
Full Text Available Genome-wide association studies (GWAS examine a large number of markers across the genome to identify associations between genetic variants and disease. Most published studies examine only single markers, which may be less informative than considering multiple markers and multiple genes jointly because genes may interact with each other to affect disease risk. Much knowledge has been accumulated in the literature on biological pathways and interactions. It is conceivable that appropriate incorporation of such prior knowledge may improve the likelihood of making genuine discoveries. Although a number of methods have been developed recently to prioritize genes using prior biological knowledge, such as pathways, most methods treat genes in a specific pathway as an exchangeable set without considering the topological structure of a pathway. However, how genes are related with each other in a pathway may be very informative to identify association signals. To make use of the connectivity information among genes in a pathway in GWAS analysis, we propose a Markov Random Field (MRF model to incorporate pathway topology for association analysis. We show that the conditional distribution of our MRF model takes on a simple logistic regression form, and we propose an iterated conditional modes algorithm as well as a decision theoretic approach for statistical inference of each gene's association with disease. Simulation studies show that our proposed framework is more effective to identify genes associated with disease than a single gene-based method. We also illustrate the usefulness of our approach through its applications to a real data example.
A Joint Land Cover Mapping and Image Registration Algorithm Based on a Markov Random Field Model
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Apisit Eiumnoh
2013-10-01
Full Text Available Traditionally, image registration of multi-modal and multi-temporal images is performed satisfactorily before land cover mapping. However, since multi-modal and multi-temporal images are likely to be obtained from different satellite platforms and/or acquired at different times, perfect alignment is very difficult to achieve. As a result, a proper land cover mapping algorithm must be able to correct registration errors as well as perform an accurate classification. In this paper, we propose a joint classification and registration technique based on a Markov random field (MRF model to simultaneously align two or more images and obtain a land cover map (LCM of the scene. The expectation maximization (EM algorithm is employed to solve the joint image classification and registration problem by iteratively estimating the map parameters and approximate posterior probabilities. Then, the maximum a posteriori (MAP criterion is used to produce an optimum land cover map. We conducted experiments on a set of four simulated images and one pair of remotely sensed images to investigate the effectiveness and robustness of the proposed algorithm. Our results show that, with proper selection of a critical MRF parameter, the resulting LCMs derived from an unregistered image pair can achieve an accuracy that is as high as when images are perfectly aligned. Furthermore, the registration error can be greatly reduced.
Language Recognition Using Latent Dynamic Conditional Random Field Model with Phonological Features
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Sirinoot Boonsuk
2014-01-01
Full Text Available Spoken language recognition (SLR has been of increasing interest in multilingual speech recognition for identifying the languages of speech utterances. Most existing SLR approaches apply statistical modeling techniques with acoustic and phonotactic features. Among the popular approaches, the acoustic approach has become of greater interest than others because it does not require any prior language-specific knowledge. Previous research on the acoustic approach has shown less interest in applying linguistic knowledge; it was only used as supplementary features, while the current state-of-the-art system assumes independency among features. This paper proposes an SLR system based on the latent-dynamic conditional random field (LDCRF model using phonological features (PFs. We use PFs to represent acoustic characteristics and linguistic knowledge. The LDCRF model was employed to capture the dynamics of the PFs sequences for language classification. Baseline systems were conducted to evaluate the features and methods including Gaussian mixture model (GMM based systems using PFs, GMM using cepstral features, and the CRF model using PFs. Evaluated on the NIST LRE 2007 corpus, the proposed method showed an improvement over the baseline systems. Additionally, it showed comparable result with the acoustic system based on i-vector. This research demonstrates that utilizing PFs can enhance the performance.
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M. Bassier
2017-11-01
Full Text Available Point cloud segmentation is a crucial step in scene understanding and interpretation. The goal is to decompose the initial data into sets of workable clusters with similar properties. Additionally, it is a key aspect in the automated procedure from point cloud data to BIM. Current approaches typically only segment a single type of primitive such as planes or cylinders. Also, current algorithms suffer from oversegmenting the data and are often sensor or scene dependent. In this work, a method is presented to automatically segment large unstructured point clouds of buildings. More specifically, the segmentation is formulated as a graph optimisation problem. First, the data is oversegmented with a greedy octree-based region growing method. The growing is conditioned on the segmentation of planes as well as smooth surfaces. Next, the candidate clusters are represented by a Conditional Random Field after which the most likely configuration of candidate clusters is computed given a set of local and contextual features. The experiments prove that the used method is a fast and reliable framework for unstructured point cloud segmentation. Processing speeds up to 40,000 points per second are recorded for the region growing. Additionally, the recall and precision of the graph clustering is approximately 80%. Overall, nearly 22% of oversegmentation is reduced by clustering the data. These clusters will be classified and used as a basis for the reconstruction of BIM models.
Scene Segmentation with Low-Dimensional Semantic Representations and Conditional Random Fields
Yang, Wen; Triggs, Bill; Dai, Dengxin; Xia, Gui-Song
2010-12-01
This paper presents a fast, precise, and highly scalable semantic segmentation algorithm that incorporates several kinds of local appearance features, example-based spatial layout priors, and neighborhood-level and global contextual information. The method works at the level of image patches. In the first stage, codebook-based local appearance features are regularized and reduced in dimension using latent topic models, combined with spatial pyramid matching based spatial layout features, and fed into logistic regression classifiers to produce an initial patch level labeling. In the second stage, these labels are combined with patch-neighborhood and global aggregate features using either a second layer of Logistic Regression or a Conditional Random Field. Finally, the patch-level results are refined to pixel level using MRF or over-segmentation based methods. The CRF is trained using a fast Maximum Margin approach. Comparative experiments on four multi-class segmentation datasets show that each of the above elements improves the results, leading to a scalable algorithm that is both faster and more accurate than existing patch-level approaches.
A Deep-Structured Conditional Random Field Model for Object Silhouette Tracking.
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Mohammad Javad Shafiee
Full Text Available In this work, we introduce a deep-structured conditional random field (DS-CRF model for the purpose of state-based object silhouette tracking. The proposed DS-CRF model consists of a series of state layers, where each state layer spatially characterizes the object silhouette at a particular point in time. The interactions between adjacent state layers are established by inter-layer connectivity dynamically determined based on inter-frame optical flow. By incorporate both spatial and temporal context in a dynamic fashion within such a deep-structured probabilistic graphical model, the proposed DS-CRF model allows us to develop a framework that can accurately and efficiently track object silhouettes that can change greatly over time, as well as under different situations such as occlusion and multiple targets within the scene. Experiment results using video surveillance datasets containing different scenarios such as occlusion and multiple targets showed that the proposed DS-CRF approach provides strong object silhouette tracking performance when compared to baseline methods such as mean-shift tracking, as well as state-of-the-art methods such as context tracking and boosted particle filtering.
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P. M. A. Diaz
2016-06-01
Full Text Available This paper presents a method to estimate the temporal interaction in a Conditional Random Field (CRF based approach for crop recognition from multitemporal remote sensing image sequences. This approach models the phenology of different crop types as a CRF. Interaction potentials are assumed to depend only on the class labels of an image site at two consecutive epochs. In the proposed method, the estimation of temporal interaction parameters is considered as an optimization problem, whose goal is to find the transition matrix that maximizes the CRF performance, upon a set of labelled data. The objective functions underlying the optimization procedure can be formulated in terms of different accuracy metrics, such as overall and average class accuracy per crop or phenological stages. To validate the proposed approach, experiments were carried out upon a dataset consisting of 12 co-registered LANDSAT images of a region in southeast of Brazil. Pattern Search was used as the optimization algorithm. The experimental results demonstrated that the proposed method was able to substantially outperform estimates related to joint or conditional class transition probabilities, which rely on training samples.
Tao, R.; Tang, H.
Chocolate is one of the most popular food types and flavors in the world. Unfortunately, at present, chocolate products contain too much fat, leading to obesity. For example, a typical molding chocolate has various fat up to 40% in total and chocolate for covering ice cream has fat 50 -60%. Especially, as children are the leading chocolate consumers, reducing the fat level in chocolate products to make them healthier is important and urgent. While this issue was called into attention and elaborated in articles and books decades ago and led to some patent applications, no actual solution was found unfortunately. Why is reducing fat in chocolate so difficult? What is the underlying physical mechanism? We have found that this issue is deeply related to the basic science of soft matters, especially to their viscosity and maximally random jammed (MRJ) density φx. All chocolate productions are handling liquid chocolate, a suspension with cocoa solid particles in melted fat, mainly cocoa butter. The fat level cannot be lower than 1-φxin order to have liquid chocolate to flow. Here we show that that with application of an electric field to liquid chocolate, we can aggregate the suspended particles into prolate spheroids. This microstructure change reduces liquid chocolate's viscosity along the flow direction and increases its MRJ density significantly. Hence the fat level in chocolate can be effectively reduced. We are looking forward to a new class of healthier and tasteful chocolate coming to the market soon. Dept. of Physics, Temple Univ, Philadelphia, PA 19122.
Zhang, Yifan
2016-08-18
For face naming in TV series or movies, a typical way is using subtitles/script alignment to get the time stamps of the names, and tagging them to the faces. We study the problem of face naming in videos when subtitles are not available. To this end, we divide the problem into two tasks: face clustering which groups the faces depicting a certain person into a cluster, and name assignment which associates a name to each face. Each task is formulated as a structured prediction problem and modeled by a hidden conditional random field (HCRF) model. We argue that the two tasks are correlated problems whose outputs can provide prior knowledge of the target prediction for each other. The two HCRFs are coupled in a unified graphical model called coupled HCRF where the joint dependence of the cluster labels and face name association is naturally embedded in the correlation between the two HCRFs. We provide an effective algorithm to optimize the two HCRFs iteratively and the performance of the two tasks on real-world data set can be both improved.
Financial versus health motivation to quit smoking: a randomized field study.
Sindelar, Jody L; O'Malley, Stephanie S
2014-02-01
Smoking is the most preventable cause of death, thus justifying efforts to effectively motivate quitting. We compared the effectiveness of financial versus health messages to motivate smoking cessation. Low-income individuals disproportionately smoke and, given their greater income constraints, we hypothesized that making financial costs of smoking more salient would encourage more smokers to try quitting. Further, we predicted that financial messages would be stronger in financial settings where pecuniary constraints are most salient. We conducted a field study in low-income areas of New Haven, Connecticut using brochures with separate health vs. financial messages to motivate smoking cessation. Displays were rotated among community settings-check-cashing, health clinics, and grocery stores. We randomized brochure displays with gain-framed cessation messages across locations. Our predictions were confirmed. Financial messages attracted significantly more attention than health messages, especially in financial settings. These findings suggest that greater emphasis on the financial gains to quitting and use of financial settings to provide cessation messages may be more effective in motivating quitting. Importantly, use of financial settings could open new, non-medical venues for encouraging cessation. Encouraging quitting could improve health, enhance spending power of low-income smokers, and reduce health disparities in both health and purchasing power. © 2013.
Detection of microcalcification with top-hat transform and the Gibbs random fields.
Bharadwaj, Akshay S; Celenk, Mehmet
2015-01-01
Breast cancer is one of the most common causes of death in women aged 40 and above. Early detection of breast cancer has been one of the prime topics of research in biomedical engineering area. Micro-calcifications (MCs) are the indicators of early stages of breast cancer, and the detection of these MCs will, in turn, lead to diagnosis and treatment of breast cancer at its earliest stages. This paper proposes a new method to detect MCs in a digital mammogram. The approach starts with the segmentation of the digital mammogram to isolate the breast region, using fuzzy C means clustering algorithm. The segmented image is then further segmented using top-hat transform to localize the region of interest. A watershed transform is used to isolate the region of interest from rest of the image. The Gibbs random fields are employed to analyze the pixels in conjunction with the devised clique patterns and detect MCs in the image. A thresholding is performed on the processed image where the MCs are detected. The proposed algorithm is highly effective in reducing the region of interest to the region which has a high probability of finding a calcification or MC. It has an overall detection rate of 94.4% and accuracy of 88.2% with a false negative detection rate of 5.6%, respectively.
Statistical inference of selection and divergence from a time-dependent Poisson random field model.
Directory of Open Access Journals (Sweden)
Amei Amei
Full Text Available We apply a recently developed time-dependent Poisson random field model to aligned DNA sequences from two related biological species to estimate selection coefficients and divergence time. We use Markov chain Monte Carlo methods to estimate species divergence time and selection coefficients for each locus. The model assumes that the selective effects of non-synonymous mutations are normally distributed across genetic loci but constant within loci, and synonymous mutations are selectively neutral. In contrast with previous models, we do not assume that the individual species are at population equilibrium after divergence. Using a data set of 91 genes in two Drosophila species, D. melanogaster and D. simulans, we estimate the species divergence time t(div = 2.16 N(e (or 1.68 million years, assuming the haploid effective population size N(e = 6.45 x 10(5 years and a mean selection coefficient per generation μ(γ = 1.98/N(e. Although the average selection coefficient is positive, the magnitude of the selection is quite small. Results from numerical simulations are also presented as an accuracy check for the time-dependent model.
Zeng, Jia; Liu, Zhi-Qiang
2008-05-01
This paper proposes a statistical-structural character modeling method based on Markov random fields (MRFs) for handwritten Chinese character recognition (HCCR). The stroke relationships of a Chinese character reflect its structure, which can be statistically represented by the neighborhood system and clique potentials within the MRF framework. Based on the prior knowledge of character structures, we design the neighborhood system that accounts for the most important stroke relationships. We penalize the structurally mismatched stroke relationships with MRFs using the prior clique potentials, and derive the likelihood clique potentials from Gaussian mixture models, which encode the large variations of stroke relationships statistically. In the proposed HCCR system, we use the single-site likelihood clique potentials to extract many candidate strokes from character images, and use the pairsite clique potentials to determine the best structural match between the input candidate strokes and the MRF-based character models by relaxation labeling. The experiments on the KAIST character database demonstrate that MRFs can statistically model character structures, and work well in the HCCR system.
Kazemzadeh, Farnoud; Shafiee, Mohammad J.; Wong, Alexander; Clausi, David A.
2014-09-01
The prevalence of compressive sensing is continually growing in all facets of imaging science. Com- pressive sensing allows for the capture and reconstruction of an entire signal from a sparse (under- sampled), yet sufficient, set of measurements that is representative of the target being observed. This compressive sensing strategy reduces the duration of the data capture, the size of the acquired data, and the cost of the imaging hardware as well as complexity while preserving the necessary underlying information. Compressive sensing systems require the accompaniment of advanced re- construction algorithms to reconstruct complete signals from the sparse measurements made. Here, a new reconstruction algorithm is introduced specifically for the reconstruction of compressive multispectral (MS) sensing data that allows for high-quality reconstruction from acquisitions at sub-Nyquist rates. We propose a multilayered conditional random field (MCRF) model, which extends upon the CRF model by incorporating two joint layers of certainty and estimated states. The proposed algorithm treats the reconstruction of each spectral channel as a MCRF given the sparse MS measurements. Since the observations are incomplete, the MCRF incorporates an extra layer determining the certainty of the measurements. The proposed MCRF approach was evaluated using simulated compressive MS data acquisitions, and is shown to enable fast acquisition of MS sensing data with reduced imaging hardware cost and complexity.
Analysis of tree stand horizontal structure using random point field methods
Directory of Open Access Journals (Sweden)
O. P. Sekretenko
2015-06-01
Full Text Available This paper uses the model approach to analyze the horizontal structure of forest stands. The main types of models of random point fields and statistical procedures that can be used to analyze spatial patterns of trees of uneven and even-aged stands are described. We show how modern methods of spatial statistics can be used to address one of the objectives of forestry – to clarify the laws of natural thinning of forest stand and the corresponding changes in its spatial structure over time. Studying natural forest thinning, we describe the consecutive stages of modeling: selection of the appropriate parametric model, parameter estimation and generation of point patterns in accordance with the selected model, the selection of statistical functions to describe the horizontal structure of forest stands and testing of statistical hypotheses. We show the possibilities of a specialized software package, spatstat, which is designed to meet the challenges of spatial statistics and provides software support for modern methods of analysis of spatial data. We show that a model of stand thinning that does not consider inter-tree interaction can project the size distribution of the trees properly, but the spatial pattern of the modeled stand is not quite consistent with observed data. Using data of three even-aged pine forest stands of 25, 55, and 90-years old, we demonstrate that the spatial point process models are useful for combining measurements in the forest stands of different ages to study the forest stand natural thinning.
Automatic Lung Tumor Segmentation on PET/CT Images Using Fuzzy Markov Random Field Model
Directory of Open Access Journals (Sweden)
Yu Guo
2014-01-01
Full Text Available The combination of positron emission tomography (PET and CT images provides complementary functional and anatomical information of human tissues and it has been used for better tumor volume definition of lung cancer. This paper proposed a robust method for automatic lung tumor segmentation on PET/CT images. The new method is based on fuzzy Markov random field (MRF model. The combination of PET and CT image information is achieved by using a proper joint posterior probability distribution of observed features in the fuzzy MRF model which performs better than the commonly used Gaussian joint distribution. In this study, the PET and CT simulation images of 7 non-small cell lung cancer (NSCLC patients were used to evaluate the proposed method. Tumor segmentations with the proposed method and manual method by an experienced radiation oncologist on the fused images were performed, respectively. Segmentation results obtained with the two methods were similar and Dice’s similarity coefficient (DSC was 0.85 ± 0.013. It has been shown that effective and automatic segmentations can be achieved with this method for lung tumors which locate near other organs with similar intensities in PET and CT images, such as when the tumors extend into chest wall or mediastinum.
spam: A Sparse Matrix R Package with Emphasis on MCMC Methods for Gaussian Markov Random Fields
Directory of Open Access Journals (Sweden)
Reinhard Furrer
2010-10-01
Full Text Available spam is an R package for sparse matrix algebra with emphasis on a Cholesky factorization of sparse positive definite matrices. The implemantation of spam is based on the competing philosophical maxims to be competitively fast compared to existing tools and to be easy to use, modify and extend. The first is addressed by using fast Fortran routines and the second by assuring S3 and S4 compatibility. One of the features of spam is to exploit the algorithmic steps of the Cholesky factorization and hence to perform only a fraction of the workload when factorizing matrices with the same sparsity structure. Simulations show that exploiting this break-down of the factorization results in a speed-up of about a factor 5 and memory savings of about a factor 10 for large matrices and slightly smaller factors for huge matrices. The article is motivated with Markov chain Monte Carlo methods for Gaussian Markov random fields, but many other statistical applications are mentioned that profit from an efficient Cholesky factorization as well.
Wei, Qikang; Chen, Tao; Xu, Ruifeng; He, Yulan; Gui, Lin
2016-01-01
The recognition of disease and chemical named entities in scientific articles is a very important subtask in information extraction in the biomedical domain. Due to the diversity and complexity of disease names, the recognition of named entities of diseases is rather tougher than those of chemical names. Although there are some remarkable chemical named entity recognition systems available online such as ChemSpot and tmChem, the publicly available recognition systems of disease named entities are rare. This article presents a system for disease named entity recognition (DNER) and normalization. First, two separate DNER models are developed. One is based on conditional random fields model with a rule-based post-processing module. The other one is based on the bidirectional recurrent neural networks. Then the named entities recognized by each of the DNER model are fed into a support vector machine classifier for combining results. Finally, each recognized disease named entity is normalized to a medical subject heading disease name by using a vector space model based method. Experimental results show that using 1000 PubMed abstracts for training, our proposed system achieves an F1-measure of 0.8428 at the mention level and 0.7804 at the concept level, respectively, on the testing data of the chemical-disease relation task in BioCreative V. Database URL: http://219.223.252.210:8080/SS/cdr.html PMID:27777244
The effects of random field at surface on the magnetic properties in the Ising nanotube and nanowire
Kaneyoshi, T.
2016-12-01
The phase diagrams and temperature dependences of total magnetization mT in two nanosystems (nanotube and nanowire) with a random magnetic field at the surface shell are studied by the uses of the effective-field theory with correlations. Some characteristic phenomena (reentrant phenomena and unconventional thermal variation of total magnetization) are found in the two systems. They are rather different between the two systems, which mainly come from the structural differences of the cores
Yan, Yuan
2017-07-13
Gaussian likelihood inference has been studied and used extensively in both statistical theory and applications due to its simplicity. However, in practice, the assumption of Gaussianity is rarely met in the analysis of spatial data. In this paper, we study the effect of non-Gaussianity on Gaussian likelihood inference for the parameters of the Matérn covariance model. By using Monte Carlo simulations, we generate spatial data from a Tukey g-and-h random field, a flexible trans-Gaussian random field, with the Matérn covariance function, where g controls skewness and h controls tail heaviness. We use maximum likelihood based on the multivariate Gaussian distribution to estimate the parameters of the Matérn covariance function. We illustrate the effects of non-Gaussianity of the data on the estimated covariance function by means of functional boxplots. Thanks to our tailored simulation design, a comparison of the maximum likelihood estimator under both the increasing and fixed domain asymptotics for spatial data is performed. We find that the maximum likelihood estimator based on Gaussian likelihood is overall satisfying and preferable than the non-distribution-based weighted least squares estimator for data from the Tukey g-and-h random field. We also present the result for Gaussian kriging based on Matérn covariance estimates with data from the Tukey g-and-h random field and observe an overall satisfactory performance.
Roeser, Robert W.; Schonert-Reichl, Kimberly A.; Jha, Amishi; Cullen, Margaret; Wallace, Linda; Wilensky, Rona; Oberle, Eva; Thomson, Kimberly; Taylor, Cynthia; Harrison, Jessica
2013-01-01
The effects of randomization to mindfulness training (MT) or to a waitlist-control condition on psychological and physiological indicators of teachers' occupational stress and burnout were examined in 2 field trials. The sample included 113 elementary and secondary school teachers (89% female) from Canada and the United States. Measures were…
Low Permeability Polyimide Insulation Project
National Aeronautics and Space Administration — Resodyn Technologies proposes a new technology that enables the application of polyimide based cryogenic insulation with low hydrogen permeability. This effort...
A Lagrangian description of nearshore hydrodynamics and rip currents forced by a random wave field
Leandro, S.; Cienfuegos, R.; Escauriaza, C. R.
2011-12-01
Nonlinear processes become important for waves propagating in the shoaling and surf zones. Wave shape changes when approaching the coast under the influence of bathymetry, becoming increasingly asymmetric until reaching the breaking limit. In the shoaling zone, non-linearities induce a net velocity in the direction of wave propagation, a phenomenon called Stokes drift, while in the surf zone, currents are mainly driven by spatio-temporal variations in energy dissipation gradients. In this work we aim at investigating and characterizing the nearshore circulation forced by a random wave field propagating over a variable bathymetry. We carry out numerical simulations over a laboratory experiment conducted in a wave basin over a realistic bathymetry [Michallet et al. 2010]. For the hydrodynamics, we use a 2D shock-capturing finite-volume model that solves the non-linear shallow water equations, taking into account energy dissipation by breaking, friction, bed-slope variations, and an accurate description for the moving shoreline in the swash zone [Marche et al. 2007;Guerra et al. 2010]. Model predictions are compared and validated against experimental data giving confidence for its use in the description of wave propagation in the surf/swash zone, together with mean eulerian velocities. The resulting wave propagation and circulation provided by the 2D model will then be used to describe drifter's patterns in the surf zone and construct Lagrangian particle tracking. The chosen experimental configuration is of great interest due to the random wave forcing (slowly modulated), the beach non-uniformities, and the existence of several bar-rip channels that enhance quasi-periodic rip instabilities. During the experiment, balloons filled with water, with a diameter between 5 and 10 cm, were placed in the surf zone in order to characterize circulation in a Lagrangian framework [Castelle et al. 2010]. The time-location of the balloons was continuously tracked by a shore
SAR-based change detection using hypothesis testing and Markov random field modelling
Cao, W.; Martinis, S.
2015-04-01
The objective of this study is to automatically detect changed areas caused by natural disasters from bi-temporal co-registered and calibrated TerraSAR-X data. The technique in this paper consists of two steps: Firstly, an automatic coarse detection step is applied based on a statistical hypothesis test for initializing the classification. The original analytical formula as proposed in the constant false alarm rate (CFAR) edge detector is reviewed and rewritten in a compact form of the incomplete beta function, which is a builtin routine in commercial scientific software such as MATLAB and IDL. Secondly, a post-classification step is introduced to optimize the noisy classification result in the previous step. Generally, an optimization problem can be formulated as a Markov random field (MRF) on which the quality of a classification is measured by an energy function. The optimal classification based on the MRF is related to the lowest energy value. Previous studies provide methods for the optimization problem using MRFs, such as the iterated conditional modes (ICM) algorithm. Recently, a novel algorithm was presented based on graph-cut theory. This method transforms a MRF to an equivalent graph and solves the optimization problem by a max-flow/min-cut algorithm on the graph. In this study this graph-cut algorithm is applied iteratively to improve the coarse classification. At each iteration the parameters of the energy function for the current classification are set by the logarithmic probability density function (PDF). The relevant parameters are estimated by the method of logarithmic cumulants (MoLC). Experiments are performed using two flood events in Germany and Australia in 2011 and a forest fire on La Palma in 2009 using pre- and post-event TerraSAR-X data. The results show convincing coarse classifications and considerable improvement by the graph-cut post-classification step.
Randomized Soil Survey of the Distribution of Burkholderia pseudomallei in Rice Fields in Laos ▿ †
Rattanavong, Sayaphet; Wuthiekanun, Vanaporn; Langla, Sayan; Amornchai, Premjit; Sirisouk, Joy; Phetsouvanh, Rattanaphone; Moore, Catrin E.; Peacock, Sharon J.; Buisson, Yves; Newton, Paul N.
2011-01-01
Melioidosis is a major cause of morbidity and mortality in Southeast Asia, where the causative organism (Burkholderia pseudomallei) is present in the soil. In the Lao People's Democratic Republic (Laos), B. pseudomallei is a significant cause of sepsis around the capital, Vientiane, and has been isolated in soil near the city, adjacent to the Mekong River. We explored whether B. pseudomallei occurs in Lao soil distant from the Mekong River, drawing three axes across northwest, northeast, and southern Laos to create nine sampling areas in six provinces. Within each sampling area, a random rice field site containing a grid of 100 sampling points each 5 m apart was selected. Soil was obtained from a depth of 30 cm and cultured for B. pseudomallei. Four of nine sites (44%) were positive for B. pseudomallei, including all three sites in Saravane Province, southern Laos. The highest isolation frequency was in east Saravane, where 94% of soil samples were B. pseudomallei positive with a geometric mean concentration of 464 CFU/g soil (95% confidence interval, 372 to 579 CFU/g soil; range, 25 to 10,850 CFU/g soil). At one site in northwest Laos (Luangnamtha), only one sample (1%) was positive for B. pseudomallei, at a concentration of 80 CFU/g soil. Therefore, B. pseudomallei occurs in Lao soils beyond the immediate vicinity of the Mekong River, alerting physicians to the likelihood of melioidosis in these areas. Further studies are needed to investigate potential climatic, soil, and biological determinants of this heterogeneity. PMID:21075883
Jin, Ick Hoon; Yuan, Ying; Bandyopadhyay, Dipankar
2016-01-01
Research in dental caries generates data with two levels of hierarchy: that of a tooth overall and that of the different surfaces of the tooth. The outcomes often exhibit spatial referencing among neighboring teeth and surfaces, i.e., the disease status of a tooth or surface might be influenced by the status of a set of proximal teeth/surfaces. Assessments of dental caries (tooth decay) at the tooth level yield binary outcomes indicating the presence/absence of teeth, and trinary outcomes at the surface level indicating healthy, decayed, or filled surfaces. The presence of these mixed discrete responses complicates the data analysis under a unified framework. To mitigate complications, we develop a Bayesian two-level hierarchical model under suitable (spatial) Markov random field assumptions that accommodates the natural hierarchy within the mixed responses. At the first level, we utilize an autologistic model to accommodate the spatial dependence for the tooth-level binary outcomes. For the second level and conditioned on a tooth being non-missing, we utilize a Potts model to accommodate the spatial referencing for the surface-level trinary outcomes. The regression models at both levels were controlled for plausible covariates (risk factors) of caries, and remain connected through shared parameters. To tackle the computational challenges in our Bayesian estimation scheme caused due to the doubly-intractable normalizing constant, we employ a double Metropolis-Hastings sampler. We compare and contrast our model performances to the standard non-spatial (naive) model using a small simulation study, and illustrate via an application to a clinical dataset on dental caries.
Transverse permeability of woven fabrics
Grouve, Wouter Johannes Bernardus; Akkerman, Remko; Loendersloot, Richard; van den Berg, S.
2008-01-01
The transverse permeability is an essential input in describing the consolidation process of CETEX® laminates. A two-dimensional, finite difference based, Stokes flow solver has been developed to determine the mesoscopic permeability of arbitrary fabric structures. The use of a multigrid solver
Energy Technology Data Exchange (ETDEWEB)
Seemann, K. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Material-forschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)]. E-mail: klaus.seemann@imf.fzk.de; Leiste, H. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Material-forschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Bekker, V. [Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft, Institut fuer Material-forschung I, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)
2004-12-01
In order to investigate the anisotropy and high-frequency behaviour, soft magnetic FeCoTaN and FeCoAlN films were fabricated by reactive RF-magnetron sputtering. Six-inch targets consisting of Fe47Co36Ta17 and Fe49Co36Al15 were used to grow the films on oxidized (100)-silicon substrates with a TiN seed layer for better film adhesion. The concentration of nitrogen was adjusted by a flow control system. For applications in, e.g., aluminium CMOS processed components the films were annealed at temperatures of about 400-bar C in a static magnetic field of 50mT to induce a uniaxial anisotropy in the film plane by activating an atomic ordering process. Controlling the anisotropy by annealing demands a specified elaboration and results in an in-plane uniaxial anisotropy between 3 and 4mT. Nitrogen in both materials caused the formation of TaN or AlN which mainly supported the suppression of polycrystalline film growth. After deposition the films showed an amorphous structure and turned to be nanocrystalline after the annealing procedure. A saturation polarization in both materials amounted to between 1.1 and 1.2T. Ferromagnetic resonance frequencies of about 1.9GHz for FeCoTaN and 1.8GHz for FeCoAlN, determined by measuring the frequency-dependent permeability by means of a strip line permeameter up to 5GHz, were observed. The experimental results where compared with a spin dynamic model based on the Landau-Lifschitz and Maxwell's eddy current equation in the total frequency range.
Pradhan, M.; Suryadarma, D.; Beatty, A.; Wong, M.; Alishjabana, A.; Gaduh, A.
2011-01-01
This study evaluates the effect of four randomized interventions aimed at strengthening school committees, and subsequently improving learning outcomes, in public primary schools in Indonesia. All study schools were randomly allocated to either a control group receiving no intervention, or to
Khrennikov, Andrei
2017-02-01
The scientific methodology based on two descriptive levels, ontic (reality as it is) and epistemic (observational), is briefly presented. Following Schrödinger, we point to the possible gap between these two descriptions. Our main aim is to show that, although ontic entities may be unaccessible for observations, they can be useful for clarification of the physical nature of operational epistemic entities. We illustrate this thesis by the concrete example: starting with the concrete ontic model preceding quantum mechanics (the latter is treated as an epistemic model), namely, prequantum classical statistical field theory (PCSFT), we propose the natural physical interpretation for the basic quantum mechanical entity-the quantum state ("wave function"). The correspondence PCSFT ↦ QM is not straightforward, it couples the covariance operators of classical (prequantum) random fields with the quantum density operators. We use this correspondence to clarify the physical meaning of the pure quantum state and the superposition principle-by using the formalism of classical field correlations. In classical mechanics the phase space description can be considered as the ontic description, here states are given by points λ =(x , p) of phase space. The dynamics of the ontic state is given by the system of Hamiltonian equations.We can also consider probability distributions on the phase space (or equivalently random variables valued in it). We call them probabilistic ontic states. Dynamics of probabilistic ontic states is given by the Liouville equation.In classical physics we can (at least in principle) measure both the coordinate and momentum and hence ontic states can be treated as epistemic states as well (or it is better to say that here epistemic states can be treated as ontic states). Probabilistic ontic states represent probabilities for outcomes of joint measurement of position and momentum.However, this was a very special, although very important, example of
Albert, Lena; Rottensteiner, Franz; Heipke, Christian
2017-08-01
We propose a new approach for the simultaneous classification of land cover and land use considering spatial as well as semantic context. We apply a Conditional Random Fields (CRF) consisting of a land cover and a land use layer. In the land cover layer of the CRF, the nodes represent super-pixels; in the land use layer, the nodes correspond to objects from a geospatial database. Intra-layer edges of the CRF model spatial dependencies between neighbouring image sites. All spatially overlapping sites in both layers are connected by inter-layer edges, which leads to higher order cliques modelling the semantic relation between all land cover and land use sites in the clique. A generic formulation of the higher order potential is proposed. In order to enable efficient inference in the two-layer higher order CRF, we propose an iterative inference procedure in which the two classification tasks mutually influence each other. We integrate contextual relations between land cover and land use in the classification process by using contextual features describing the complex dependencies of all nodes in a higher order clique. These features are incorporated in a discriminative classifier, which approximates the higher order potentials during the inference procedure. The approach is designed for input data based on aerial images. Experiments are carried out on two test sites to evaluate the performance of the proposed method. The experiments show that the classification results are improved compared to the results of a non-contextual classifier. For land cover classification, the result is much more homogeneous and the delineation of land cover segments is improved. For the land use classification, an improvement is mainly achieved for land use objects showing non-typical characteristics or similarities to other land use classes. Furthermore, we have shown that the size of the super-pixels has an influence on the level of detail of the classification result, but also on the
Energy Technology Data Exchange (ETDEWEB)
Pereira, Nelson [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil). Exploracao e Producao; Altman, Raphael; Rasmus, John; Oliveira, Jansen [Schlumberger Servicos de Petroleo Ltda., Rio de Janeiro, RJ (Brazil)
2008-07-01
This paper describes how permeability and permeability anisotropy is estimated in horizontal wells using LWD (logging-while-drilling) laterolog resistivity data. Laterolog-while-drilling resistivity passes of while-drilling and timelapse (while reaming) were used to capture the invasion process. Radial positions of water based mud invasion fronts were calculated from while-drilling and reaming resistivity data. The invasion process was then recreated by constructing forward models with a fully implicit, near-wellbore numerical simulation such that the invasion front at a given time was consistent with the position of the front predicted by resistivity inversions. The radial position of the invasion front was shown to be sensitive to formation permeability. The while-drilling environment provides a fertile scenario to investigate reservoir dynamic properties because mud cake integrity and growth is not fully developed which means that the position of the invasion front at a particular point in time is more sensitive to formation permeability. The estimation of dynamic formation properties in horizontal wells is of particular value in marginal fields and deep-water offshore developments where running wireline and obtaining core is not always feasible, and where the accuracy of reservoir models can reduce the risk in field development decisions. (author)
CSIR Research Space (South Africa)
Salmon, BP
2015-07-01
Full Text Available In this paper the authors present a 2-tier higher order Conditional Random Field which is used for land cover classification. The Conditional Random Field is based on probabilistic messages being passed along a graph to compute efficiently...
Permeability testing of biomaterial membranes
Energy Technology Data Exchange (ETDEWEB)
Dreesmann, L; Hajosch, R; Nuernberger, J Vaz; Schlosshauer, B [NMI Natural and Medical Sciences Institute at University Tuebingen, Markwiesenstr. 55, D-72770 Reutlingen (Germany); Ahlers, M [GELITA AG, Gammelsbacher Str. 2, D-69412 Eberbach (Germany)], E-mail: schlosshauer@nmi.de
2008-09-01
The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts. Cytochemical evaluation after cryosectioning of the membranes was used to ascertain whether fibroblasts had infiltrated the membrane inside. Zymography was used to investigate the potential release of proteases from fibroblasts, which are known to degrade collagen derivatives such as gelatin. Our data show that the diffusion equilibrium of a low molecular weight dye across the selected gelatin membrane is approached after about 6-8 h. Fibroblasts increase the permeability due to cavity formation in the membrane inside without penetrating the membrane for an extended time period (>21 days in vitro). Zymography indicates that cavity formation is most likely due to the secretion of matrix metalloproteinases. In summary, the combination of the depicted methods promises to facilitate a more rational development of biomaterials, because it provides a rapid means of determining permeability characteristics and bridges the gap between descriptive methodology and the mechanistic understanding of permeability alterations due to biological degradation.
Arnaut, Luk R
2010-04-01
We derive an integral expression for the plane-wave expansion of the time-varying (nonstationary) random field inside a mode-stirred reverberation chamber. It is shown that this expansion is a so-called oscillatory process, whose kernel can be expressed explicitly in closed form. The effect of nonstationarity is a modulation of the spectral density of the field on a time scale that is a function of the cavity relaxation time. It is also shown how the contribution by a nonzero initial value of the field can be incorporated into the expansion. The results are extended to a special class of second-order processes, relevant to the reception of a mode-stirred reverberation field by a device under test with a first-order (relaxation-type) frequency response.
Directory of Open Access Journals (Sweden)
XU Miaozhong
2015-02-01
Full Text Available In consideration of the visual system's tremendous ability to perceive and identify the information, a new image segmentation method is presented which simulates the mechanism of visual system for the high resolution remote sensing image segmentation with Markov random field model. Firstly, the characteristics of the visual system have been summarized as: hierarchy, learning ability, feature detection capability and sparse coding property. Secondly, the working mechanism of visual system is simulated by wavelet transform, unsupervised clustering algorithm, feature analysis and Laplace distribution. Then, the segmentation is achieved by the visual mechanism and the Markov random field. Different satellites remote sensing images are adopted as the experimental data, and the segmentation results demonstrate the proposed method have good performance in high resolution remote sensing images.
Directory of Open Access Journals (Sweden)
Phil Diamond
2003-01-01
Full Text Available Sensitivity of output of a linear operator to its input can be quantified in various ways. In Control Theory, the input is usually interpreted as disturbance and the output is to be minimized in some sense. In stochastic worst-case design settings, the disturbance is considered random with imprecisely known probability distribution. The prior set of probability measures can be chosen so as to quantify how far the disturbance deviates from the white-noise hypothesis of Linear Quadratic Gaussian control. Such deviation can be measured by the minimal Kullback-Leibler informational divergence from the Gaussian distributions with zero mean and scalar covariance matrices. The resulting anisotropy functional is defined for finite power random vectors. Originally, anisotropy was introduced for directionally generic random vectors as the relative entropy of the normalized vector with respect to the uniform distribution on the unit sphere. The associated a-anisotropic norm of a matrix is then its maximum root mean square or average energy gain with respect to finite power or directionally generic inputs whose anisotropy is bounded above by a≥0. We give a systematic comparison of the anisotropy functionals and the associated norms. These are considered for unboundedly growing fragments of homogeneous Gaussian random fields on multidimensional integer lattice to yield mean anisotropy. Correspondingly, the anisotropic norms of finite matrices are extended to bounded linear translation invariant operators over such fields.
Study of self-compensation of random field errors in low-/β insertion triplets of hadron colliders
Shi, Jicong
1999-06-01
The presence of unavoidable field errors in superconducting low-β insertion triplets is one of the major causes for limiting the dynamic aperture of colliders during collisions. Sorting of quadrupoles of the triplets, in which the quadrupoles are installed in the ring according to a certain sequence based on the measured multipole errors, is a way to reduce the adverse effects of random field errors without an increase in the cost. Because of a very small phase advance within each triplet, significant self-compensation of random field errors of the triplet can be achieved even with sorting of a small number of quadrupoles. A study on low-β insertion triplets of the LHC interaction regions show that sorting of the quadrupoles with the vector sorting scheme is quite effective in enlargement of the dynamic aperture and improvement of the linearity of the phase-space region occupied by beams. Since the sorting scheme is based entirely on the local compensation of random errors, the effectiveness of the sorting is independent of the operational condition of the collider.
Characterization and estimation of permeability correlation structure from performance data
Energy Technology Data Exchange (ETDEWEB)
Ershaghi, I.; Al-Qahtani, M. [Univ. of Southern California, Los Angeles, CA (United States)
1997-08-01
In this study, the influence of permeability structure and correlation length on the system effective permeability and recovery factors of 2-D cross-sectional reservoir models, under waterflood, is investigated. Reservoirs with identical statistical representation of permeability attributes are shown to exhibit different system effective permeability and production characteristics which can be expressed by a mean and variance. The mean and variance are shown to be significantly influenced by the correlation length. Detailed quantification of the influence of horizontal and vertical correlation lengths for different permeability distributions is presented. The effect of capillary pressure, P{sub c1} on the production characteristics and saturation profiles at different correlation lengths is also investigated. It is observed that neglecting P{sub c} causes considerable error at large horizontal and short vertical correlation lengths. The effect of using constant as opposed to variable relative permeability attributes is also investigated at different correlation lengths. Next we studied the influence of correlation anisotropy in 2-D reservoir models. For a reservoir under five-spot waterflood pattern, it is shown that the ratios of breakthrough times and recovery factors of the wells in each direction of correlation are greatly influenced by the degree of anisotropy. In fully developed fields, performance data can aid in the recognition of reservoir anisotropy. Finally, a procedure for estimating the spatial correlation length from performance data is presented. Both the production performance data and the system`s effective permeability are required in estimating the correlation length.
The rate of separation of magnetic lines of force in a random magnetic field.
Jokipii, J. R.
1973-01-01
The mixing of magnetic lines of force, as represented by their rate of separation, as a function of distance along the magnetic field, is considered with emphasis on neighboring lines of force. This effect is particularly important in understanding the transport of charged particles perpendicular to the average magnetic field. The calculation is carried out in the approximation that the separation changes by an amount small compared with the correlation scale normal to the field, in a distance along the field of a few correlation scales. It is found that the rate of separation is very sensitive to the precise form of the power spectrum. Application to the interplanetary and interstellar magnetic fields is discussed, and it is shown that in some cases field lines, much closer together than the correlation scale, separate at a rate which is effectively as rapid as if they were many correlation lengths apart.
Adiabatic hydrodynamic modes in dielectric environment in a random electric field
Stupka, Anton
2016-01-01
Dielectric is considered in the electric field that has equal to zero the first moment and different from zero the second moment of strength in an equilibrium. The equations of ideal hydrodynamics are obtained in such a field for the case of the neglect of dissipative effects. A new variable - the second moment of electric field strength is included in the Euler equation. A temporal equation for this variable is obtained on the basis of Maxwell equations in the hydrodynamic approximation. Adi...
Permeability of soils in Mississippi
O'Hara, Charles G.
1994-01-01
The permeability of soils in Mississippi was determined and mapped using a geographic information system (GIS). Soil permeabilities in Mississippi were determined to range in value from nearly 0.0 to values exceeding 5.0 inches per hour. The U.S. Soil Conservation Service's State Soil Geographic Data Base (STATSGO) was used as the primary source of data for the determination of area-weighted soil permeability. STATSGO provides soil layer properties that are spatially referenced to mapped areas. These mapped areas are referred to as polygons in the GIS. The polygons arc boundaries of soils mapped as a group and are given unique Map Unit Identifiers (MUIDs). The data describing the physical characteristics of the soils within each polygon are stored in a tabular data base format and are referred to as attributes. The U.S. Soil Conservation Service developed STATSGO to be primarily used as a guide for regional resource planning, management, and monitoring. STATSGO was designed so that soil information could be extracted from properties tables at the layer level, combined by component, and statistically expanded to cover the entire map unit. The results of this study provide a mapped value for permeability which is representative of the vertical permeability of soils in that area. The resultant permeability map provides a representative vertical soil permeability for a given area sufficient for county, multi- county, and area planning, and will be used as the soil permeability data component in the evaluation of the susceptibility of major aquifers to contami- nation in Mississippi.
Schießl, Stefan P.; Rother, Marcel; Lüttgens, Jan; Zaumseil, Jana
2017-11-01
The field-effect mobility is an important figure of merit for semiconductors such as random networks of single-walled carbon nanotubes (SWNTs). However, owing to their network properties and quantum capacitance, the standard models for field-effect transistors cannot be applied without modifications. Several different methods are used to determine the mobility with often very different results. We fabricated and characterized field-effect transistors with different polymer-sorted, semiconducting SWNT network densities ranging from low (≈6 μm-1) to densely packed quasi-monolayers (≈26 μm-1) with a maximum on-conductance of 0.24 μS μm-1 and compared four different techniques to evaluate the field-effect mobility. We demonstrate the limits and requirements for each method with regard to device layout and carrier accumulation. We find that techniques that take into account the measured capacitance on the active device give the most reliable mobility values. Finally, we compare our experimental results to a random-resistor-network model.
Directory of Open Access Journals (Sweden)
Malihe Asadollahi
2016-09-01
Full Text Available Introduction: Hospitalization in neonatal intensive care unit may leads to many stresses for premature infants. Since premature infants cannot properly process stressors, identifying interventions that reduce the stress level for them is seems necessary. The aim of present study was to compare the effects of Field massage and Gentle Human Touch (GHT techniques on the urine level of cortisol, as an indicator of stress in preterm infants. Methods: This randomized, controlled clinical trial was carried out in Al-Zahra hospital, Tabriz. A total of 84 premature infants were randomly assigned into three groups. First groups were touched by their mothers three times a day (15 minutes in each session for 5 days by GHT technique. The second group was received 15 minutes Field massage with sunflower oil three times a day by their mothers for 5 days. The third group received routine care. In all groups, 24-hours urine samples were collected in the first and sixth day after the intervention and analyzed for cortisol level. Data were analyzed by SPSS software. Results: There were significant differences between mean of changes in cortisol level between GHT and control groups and Field massage and control groups (0.026. Conclusion: Although the massage with Field technique resulted in a significant reduction in blood cortisol level, but the GHT technique have also a similar effect. So, both methods are recommended for decreasing of stress in preterm infants.
Waldorp, Lourens J
2016-01-01
It was recently shown how graphs can be used to provide descriptions of psychopathologies, where symptoms of, say, depression, affect each other and certain configurations determine whether someone could fall into a sudden depression. To analyse changes over time and characterise possible future behaviour is rather difficult for large graphs. We describe the dynamics of networks using one-dimensional discrete time dynamical systems theory obtained from a mean field approach to (elementary) probabilistic cellular automata (PCA). Often the mean field approach is used on a regular graph (a grid or torus) where each node has the same number of edges and the same probability of becoming active. We show that we can use variations of the mean field of the grid to describe the dynamics of the PCA on a random and small-world graph. Bifurcation diagrams for the mean field of the grid, random, and small-world graphs indicate possible phase transitions for certain parameter settings. Extensive simulations indicate for di...
Permeability theory and Palace Athena.
Stamps, Arthur E
2013-06-01
Permeability theory suggests that safety in environments depends on how far and how easily one can perceive or move through environments. Parts of environments that limit perception or retard locomotion elicit impressions of being enclosed, so properties of environments that influence perceived enclosure are important in permeability theory. One prediction of permeability theory is that the more permeable the boundary, the less enclosed the region within that boundary will seem to be. Another prediction is that boundary depth will have little influence on perceived enclosure. These predictions were tested in the venue of Greek temples. 30 participants were tested (14 men, 16 women; M age = 40 yr.), who rated perceived enclosure for 18 stimuli. The stimuli were constructed using a virtual scene from the Tholos in Delphi with the positions of the columns forming the boundaries. The boundaries were designed to have different levels of permeability and depth. Data were analyzed in terms of effect sizes and focused comparisons. Results indicated that perceived enclosure was most strongly influenced by the visual permeability of the boundary, while depth of boundary had a much smaller effect on perceived enclosure.
Patterns of effective permeability of leaf cuticles to acids
Energy Technology Data Exchange (ETDEWEB)
Hauser, H.D.; Walters, K.D.; Berg, V.S. (Univ. of Northern Iowa, Cedar Falls (United States))
1993-01-01
Plants in the field are frequently exposed to anthropogenic acid precipitation with pH values of 4 and below. For the acid to directly affect leaf tissues, it must pass through the leaf cuticle, but little is known about the permeability of cuticles to protons, of about the effect of different anions on this permeability. We investigated the movement of protons through isolated astomatous leaf cuticles of grapefruit (Citrus x paradisi Macfady.), rough lemon (Citrus limon [L.] Burm. fils cv Ponderosa), and pear (Pyrus communis L.) using hydrochloric, sulfuric, and nitric acids. Cuticles were enzymically isolated from leaves and placed in a diffusion apparatus with pH 4 acid on the morphological outer surface of the cuticle and degassed distilled water on the inner surface. Changes in pH of the solution on the inner surface were used to determine rates of effective permeability of the cuticles to the protons of these acids. Most cuticles exhibited an initial low permeability, lasting hours to days, then after a short transition displayed a significant higher permeability, which persisted until equilibrium was approached. The change in effective permeability appears to be reversible. Effective permeabilities were higher for sulfuric acid than for the others. A model of the movement of protons through the cuticle is presented, proposing that dissociated acid groups in channels within the cutin are first protonated by the acid, accounting for the low initial effective permeability; then protons pass freely through the channels, resulting in a higher effective permeability. 26 refs., 6 figs., 2 tabs.
Explaining Feast or Famine in Randomized Field Trials: Medical Science and Criminology Compared.
Shepherd, Jonathan P.
2003-01-01
Discusses the contrast between the frequency of randomized clinical trials in the health sciences and the relative famine of such studies in criminology. Attributes this difference to the contexts in which research is done and the difference in the status of situational research in the two disciplines. (SLD)
Beardslee, Joseph A; Sadtler, Bryce; Lewis, Nathan S
2012-11-27
External magnetic fields have been used to vertically align ensembles of silicon microwires coated with ferromagnetic nickel films. X-ray diffraction and image analysis techniques were used to quantify the degree of vertical orientation of the microwires. The degree of vertical alignment and the minimum field strength required for alignment were evaluated as a function of the wire length, coating thickness, magnetic history, and substrate surface properties. Nearly 100% of 100 μm long, 2 μm diameter, Si microwires that had been coated with 300 nm of Ni could be vertically aligned by a 300 G magnetic field. For wires ranging from 40 to 60 μm in length, as the length of the wire increased, a higher degree of alignment was observed at lower field strengths, consistent with an increase in the available magnetic torque. Microwires that had been exposed to a magnetic sweep up to 300 G remained magnetized and, therefore, aligned more readily during subsequent magnetic field alignment sweeps. Alignment of the Ni-coated Si microwires occurred at lower field strengths on hydrophilic Si substrates than on hydrophobic Si substrates. The magnetic field alignment approach provides a pathway for the directed assembly of solution-grown semiconductor wires into vertical arrays, with potential applications in solar cells as well as in other electronic devices that utilize nano- and microscale components as active elements.
Mixed spin Ising model with four-spin interaction and random crystal field
Energy Technology Data Exchange (ETDEWEB)
Benayad, N., E-mail: n.benayad@fsac.ac.ma [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Ghliyem, M. [Groupe de Mecanique Statistique, Laboratoire de physique theorique et appliquee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco); Laboratoire de physique des hautes energies et de la matiere condensee, Faculte des sciences-Aien Chock, Universite Hassan II-Casablanca, B.P 5366 Maarif, Casablanca 20100 (Morocco)
2012-01-01
The effects of fluctuations of the crystal field on the phase diagram of the mixed spin-1/2 and spin-1 Ising model with four-spin interactions are investigated within the finite cluster approximation based on a single-site cluster theory. The state equations are derived for the two-dimensional square lattice. It has been found that the system exhibits a variety of interesting features resulting from the fluctuation of the crystal field interactions. In particular, for low mean value D of the crystal field, the critical temperature is not very sensitive to fluctuations and all transitions are of second order for any value of the four-spin interactions. But for relatively high D, the transition temperature depends on the fluctuation of the crystal field, and the system undergoes tricritical behaviour for any strength of the four-spin interactions. We have also found that the model may exhibit reentrance for appropriate values of the system parameters.
Adiabatic hydrodynamic modes in dielectric environment in a random electric field
Stupka, Anton
2016-01-01
Dielectric is considered in the electric field that has equal to zero the first moment and different from zero the second moment of strength in an equilibrium. The equations of ideal hydrodynamics are obtained in such a field for the case of the neglect of dissipative effects. A new variable - the second moment of electric field strength is included in the Euler equation. A temporal equation for this variable is obtained on the basis of Maxwell equations in the hydrodynamic approximation. Adiabatic one-dimensional waves of small amplitude are studied in this system. Proceeding from the theoretical estimation of the intracrystalline field in an ionic crystal the good consent of the obtained numerical values of transversal velocity of this wave with transversal velocity of sound for isotropic crystals of alkali halides is found.
Support Vector Driven Markov Random Fields towards DTI Segmentation of the Human Skeletal Muscle
Neji, Radhouène; Fleury, Gilles; Deux, J.-F.; Rahmouni, A.; Bassez, G.; Vignaud, A.; Paragios, Nikolaos
2008-01-01
International audience; In this paper we propose a classification-based method towards the segmentation of diffusion tensor images. We use Support Vector Machines to classify diffusion tensors and we extend linear classification to the non linear case. To this end, we discuss and evaluate three different classes of kernels on the space of symmetric definite positive matrices that are well suited for the classification of tensor data. We impose spatial constraints by means of a Markov random f...
The permeability of heterogeneous rocks
Selvadurai, Patrick
2017-04-01
Darcy's original concept of permeability is largely associated with estimation of the hydraulic conductivity characteristics of isotropic and homogeneous porous media where the fluid flow characteristics can be estimated by appeal to a single scalar measure. Naturally occurring geomaterials are heterogeneous and the estimation of the effective permeability characteristics of such geomaterials presents a challenge not only in terms of the experimental procedures that should be used to ensure flow through the porous medium but also in the correct use of the theoretical concepts needed to accurately interpret the data. Relatively widely referred to rocks such as Indiana Limestone can exhibit spatial heterogeneity in the permeability characteristics even though the visual appearance can suggest the absence of such spatial and directional attributes (Selvadurai and Selvadurai, 2010). Argillaceous rocks such as the Cobourg Limestone found in southern Ontario, Canada can display hydraulic heterogeneity that is attributed to the presence of dolomitic and calcite nodular regions separated by calcite rock partings that contain an argillaceous component (Figure 1). Also, these rocks have extremely low permeability that requires the use of transient hydraulic pulse tests for the estimation of permeability. The performance of such pulse tests will be influenced by the bulk compressibility and bulk porosity of the porous skeleton consisting of the identifiable phases and their spatial distributions. The concepts of effective compressibilities and porosities therefore needs to be introduced if convenient procedures are to be developed for the accurate interpretation of even bench scale experiments (Selvadurai and Gɫowacki, 2017). The paper will describe both experimental and theoretical approaches for interpreting the effective Darcy permeability of the heterogeneous rocks using both experimental and computational approaches. In particular, the applicability of the "Geometric
Falagas, Matthew E; Grigori, Tatiana; Ioannidou, Eleni
2009-03-01
We sought to evaluate the trends in the methodological quality of randomized controlled trials in various medical fields. Relevant studies were retrieved by the PubMed and the ISI Web of science databases. Thirty-five out of 457 retrieved studies met the inclusion criteria. Twenty-one out of 35 selected studies reported significant improvement in at least one methodological quality factor. Overall quality scores were increased in 13 out of 26 studies providing relevant data. The most commonly separately examined key quality factors were allocation concealment and blinding in 13 out of 21 studies that reported relevant data. Allocation concealment was the quality characteristic most commonly reported as significantly improving during the reviewed period (in five out of eight studies reporting relevant comparative data). Certain aspects of methodological quality have improved significantly over time, but others remain stagnant. Further efforts to improve study design, conduct, and reporting of randomized controlled trials are warranted.
Brémaud, Pierre
2017-01-01
The emphasis in this book is placed on general models (Markov chains, random fields, random graphs), universal methods (the probabilistic method, the coupling method, the Stein-Chen method, martingale methods, the method of types) and versatile tools (Chernoff's bound, Hoeffding's inequality, Holley's inequality) whose domain of application extends far beyond the present text. Although the examples treated in the book relate to the possible applications, in the communication and computing sciences, in operations research and in physics, this book is in the first instance concerned with theory. The level of the book is that of a beginning graduate course. It is self-contained, the prerequisites consisting merely of basic calculus (series) and basic linear algebra (matrices). The reader is not assumed to be trained in probability since the first chapters give in considerable detail the background necessary to understand the rest of the book. .
Li, Ningzhi; Li, Shizhe; Shen, Jun
2017-06-01
In vivo 13C magnetic resonance spectroscopy (MRS) is a unique and effective tool for studying dynamic human brain metabolism and the cycling of neurotransmitters. One of the major technical challenges for in vivo 13C-MRS is the high radio frequency (RF) power necessary for heteronuclear decoupling. In the common practice of in vivo 13C-MRS, alkanyl carbons are detected in the spectra range of 10-65ppm. The amplitude of decoupling pulses has to be significantly greater than the large one-bond 1H-13C scalar coupling (1JCH=125-145 Hz). Two main proton decoupling methods have been developed: broadband stochastic decoupling and coherent composite or adiabatic pulse decoupling (e.g., WALTZ); the latter is widely used because of its efficiency and superb performance under inhomogeneous B1 field. Because the RF power required for proton decoupling increases quadratically with field strength, in vivo 13C-MRS using coherent decoupling is often limited to low magnetic fields (Drug Administration (FDA). Alternately, carboxylic/amide carbons are coupled to protons via weak long-range 1H-13C scalar couplings, which can be decoupled using low RF power broadband stochastic decoupling. Recently, the carboxylic/amide 13C-MRS technique using low power random RF heteronuclear decoupling was safely applied to human brain studies at 7T. Here, we review the two major decoupling methods and the carboxylic/amide 13C-MRS with low power decoupling strategy. Further decreases in RF power deposition by frequency-domain windowing and time-domain random under-sampling are also discussed. Low RF power decoupling opens the possibility of performing in vivo 13C experiments of human brain at very high magnetic fields (such as 11.7T), where signal-to-noise ratio as well as spatial and temporal spectral resolution are more favorable than lower fields.
Bentonite Permeability at Elevated Temperature
Directory of Open Access Journals (Sweden)
Katherine A. Daniels
2017-01-01
Full Text Available Repository designs frequently favour geological disposal of radioactive waste with a backfill material occupying void space around the waste. The backfill material must tolerate the high temperatures produced by decaying radioactive waste to prevent its failure or degradation, leading to increased hydraulic conductivity and reduced sealing performance. The results of four experiments investigating the effect of temperature on the permeability of a bentonite backfill are presented. Bentonite is a clay commonly proposed as the backfill in repository designs because of its high swelling capacity and very low permeability. The experiments were conducted in two sets of purpose-built, temperature controlled apparatus, designed to simulate isotropic pressure and constant volume conditions within the testing range of 4–6 MPa average effective stress. The response of bentonite during thermal loading at temperatures up to 200 °C was investigated, extending the previously considered temperature range. The results provide details of bentonite’s intrinsic permeability, total stress, swelling pressure and porewater pressure during thermal cycles. We find that bentonite’s hydraulic properties are sensitive to thermal loading and the type of imposed boundary condition. However, the permeability change is not large and can mostly be accounted for by water viscosity changes. Thus, under 150 °C, temperature has a minimal impact on bentonite’s hydraulic permeability.
Near field heat transfer between random composite materials. Applications and limitations
Energy Technology Data Exchange (ETDEWEB)
Santiago, Eva Yazmin; Esquivel-Sirvent, Raul [Univ. Nacional Autonoma de Mexico (Mexico). Inst. de Fisica
2017-05-01
We present a theoretical study of the limits and bounds of using effective medium approximations in the calculation of the near field radiative heat transfer between a composite system made of Au nanoparticles in a SiC host and an homogeneous SiC slab. The effective dielectric function of the composite slab is calculated using three different approximations: Maxwell-Garnett, Bruggeman, and Looyenga's. In addition, we considered an empirical fit to the effective dielectric function by Grundquist and Hunderi. We show that the calculated value of the heat flux in the near field is dependent on the model, and the difference in the effective dielectric function is larger around the plasmonic response of the Au nanoparticles. This, in turn, accounts for the difference in the near field radiative heat flux. For all values of filling fractions, the Looyenga approximation gives a lower bound for the heat flux.
Energy Technology Data Exchange (ETDEWEB)
Yigit, Ali, E-mail: ayigit80@karatekin.edu.tr [Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I Karatekin University, Department of Physics, 18100 Cank Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I (Turkey); Albayrak, Erhan [Erciyes University, Department of Physics, 38039 Kayseri (Turkey)
2013-03-15
The effects of bimodal random crystal field on the phase diagrams and magnetization curves of ferrimagnetic mixed spin-1/2 and spin-3/2 Blume-Capel model are examined by using the effective field theory with correlations for honeycomb lattice. The phase diagrams are obtained on the ({Delta},kT/|J|), ({Delta},T{sub comp}) and (p,kT/|J|) planes for given values of p and {Delta}, respectively. The model exhibits only the second-order phase transitions as in the Blume-Capel model with constant crystal fields. In addition, it was found that the model presents one or two compensation temperatures for appropriate values of random crystal field for given probability in contrast to constant crystal field case. Therefore, it is shown that the random crystal field considerably affects the thermal variations of net and sublattice magnetizations. - Highlights: Black-Right-Pointing-Pointer Mixed spin-1/2 and spin-3/2 BC model with random crystal field was investigated. Black-Right-Pointing-Pointer Effective-field theory with correlations was used in obtaining the critical temperatures. Black-Right-Pointing-Pointer The phase diagrams of the model were shown for various planes. Black-Right-Pointing-Pointer Randomness of the crystal field leads to emergence the compensation temperatures. Black-Right-Pointing-Pointer It was found that the model exhibits only second-order phase transitions.
Energy Technology Data Exchange (ETDEWEB)
Lee, C.G.; Chen, C.H. [Univ. of Massachusetts, North Dartmouth, MA (United States)
1996-12-31
In this paper a novel multiresolution wavelet analysis (MWA) and non-stationary Gaussian Markov random field (GMRF) technique is introduced for the identification of microcalcifications with high accuracy. The hierarchical multiresolution wavelet information in conjunction with the contextual information of the images extracted from GMRF provides a highly efficient technique for microcalcification detection. A Bayesian teaming paradigm realized via the expectation maximization (EM) algorithm was also introduced for edge detection or segmentation of larger lesions recorded on the mammograms. The effectiveness of the approach has been extensively tested with a number of mammographic images provided by a local hospital.
Directory of Open Access Journals (Sweden)
S Zein
2016-09-01
Full Text Available In this paper, we are interested in simulating a stochastic permeability distribution constrained by some pressure measures coming from a steady flow (Poisson problem over a two-dimensional domain. The permeability is discretized over a regular rectangular gird and considered to be constant by cell but it can take randomly a finite number of values. When such permeability is modeled using a multidimensional Markov chain, it can be constrained by some permeability measures. The purpose of this work is to propose an algorithm that simulates stochastic permeability constrained not only by some permeability measures but also by pressure measures at some points of the domain. The simulation algorithm couples the MCMC sampling technique with the multidimensional Markov chain model in a Bayesian framework.
Estimating adhesive seed-dispersal distances : field experiments and correlated random walks
Mouissie, AM; Lengkeek, W; van Diggelen, R
1. In this study we aimed to estimate distance distributions of adhesively dispersed seeds and the factors that determine them. 2. Seed attachment and detachment were studied using field experiments with a real sheep, a sheep dummy and a cattle dummy. Seed-retention data were used in correlated
Near-field short correlation in optical waves transmitted through random media
Emiliani, V.; Intonti, F.; caza, M.; Wiersma, D.S.; Colocci, M.; Aliev, F.; Lagendijk, Aart
2003-01-01
Two-dimensional near-field images of light transmitted through a disordered dielectric structure have been measured for two probe wavelengths. From these data, the 2D spatial dependence of the intensity correlation function, C(¿R¿), has been extracted. We observe that the spatial dependence of C is
On the Gibbsian Nature of the Random Field Kac Model under Block-Averaging
Külske, Christof
2001-01-01
We consider the Kac–Ising model in an arbitrary configuration of local magnetic fields η=(ηi)i ∈ Zd, in any dimension d, at any inverse temperature. We investigate the Gibbs properties of the ‘renormalized’ infinite volume measures obtained by block averaging any of the Gibbs-measures corresponding
Flux theory for Poisson distributed pores with Gaussian permeability.
Salinas, Dino G
2016-01-01
The mean of the solute flux through membrane pores depends on the random distribution and permeability of the pores. Mathematical models including such randomness factors make it possible to obtain statistical parameters for pore characterization. Here, assuming that pores follow a Poisson distribution in the lipid phase and that their permeabilities follow a Gaussian distribution, a mathematical model for solute dynamics is obtained by applying a general result from a previous work regarding any number of different kinds of randomly distributed pores. The new proposed theory is studied using experimental parameters obtained elsewhere, and a method for finding the mean single pore flux rate from liposome flux assays is suggested. This method is useful for pores without requiring studies by patch-clamp in single cells or single-channel recordings. However, it does not apply in the case of ion-selective channels, in which a more complex flux law combining the concentration and electrical gradient is required.
N. Renders (Nicole); Y. Romling; A.F. van Belkum (Alex); H.A. Verbrugh (Henri)
1996-01-01
textabstractEighty-seven strains of Pseudomonas aeruginosa were typed by random amplification of polymorphic DNA (RAPD) and pulsed-field gel electrophoresis (PFGE) of macrorestriction fragments. Stains were clustered on the basis of interpretative criteria as presented
PERMEABILITY OF BACTERIAL SPORES I.
Black, S. H.; Gerhardt, Philipp
1961-01-01
Black, S. H. (The University of Michigan, Ann Arbor) and Philipp Gerhardt. Permeability of bacterial spores. I. Characterization of glucose uptake. J. Bacteriol. 82:743–749. 1961.—The total uptake of glucose by masses of clean, dormant spores was measured to assess their permeability. After correction for intercellular space, packed spores of Bacillus cereus strain terminalis were found in 87 determinations to be permeated by glucose to 40% of their weight. The glucose uptake was relatively independent of environmental variables, and thus was concluded to occur principally through a process of passive diffusion. PMID:13869665
DEFF Research Database (Denmark)
Jensen, J.L.
1993-01-01
Previous results on Edgeworth expansions for sums over a random field are extended to the case where the strong mixing coefficient depends not only on the distance between two sets of random variables, but also on the size of the two sets. The results are applied to the Poisson and the Strauss...
The random field model of the spatial distribution of heavy vehicle loads on long-span bridges
Chen, Zhicheng; Bao, Yuequan; Li, Hui
2016-04-01
A stochastic model based on Markov random field is proposed to model the spatial distribution of vehicle loads on longspan bridges. The bridge deck is divided into a finite set of discrete grid cells, each cell has two states according to whether the cell is occupied by the heavy vehicle load or not, then a four-neighbor lattice-structured undirected graphical model with each node corresponding to a cell state variable is proposed to model the location distribution of heavy vehicle loads on the bridge deck. The node potential is defined to quantitatively describe the randomness of node state, and the edge potential is defined to quantitatively describe the correlation of the connected node pair. The junction tree algorithm is employed to obtain the systematic solutions of inference problems of the graphical model. A marked random variable is assigned to each node to represent the amplitude of the total weight of vehicle applied on the corresponding cell of the bridge deck. The rationality of the model is validated by a Monte Carlo simulation of a learned model based on monitored data of a cable-stayed bridge.
Wang, Yonggang; Hui, Cong; Liu, Chong; Xu, Chao
2016-04-01
The contribution of this paper is proposing a new entropy extraction mechanism based on sampling phase jitter in ring oscillators to make a high throughput true random number generator in a field programmable gate array (FPGA) practical. Starting from experimental observation and analysis of the entropy source in FPGA, a multi-phase sampling method is exploited to harvest the clock jitter with a maximum entropy and fast sampling speed. This parametrized design is implemented in a Xilinx Artix-7 FPGA, where the carry chains in the FPGA are explored to realize the precise phase shifting. The generator circuit is simple and resource-saving, so that multiple generation channels can run in parallel to scale the output throughput for specific applications. The prototype integrates 64 circuit units in the FPGA to provide a total output throughput of 7.68 Gbps, which meets the requirement of current high-speed quantum key distribution systems. The randomness evaluation, as well as its robustness to ambient temperature, confirms that the new method in a purely digital fashion can provide high-speed high-quality random bit sequences for a variety of embedded applications.
Asymmetry of the Hall Conductance Fluctuations in a Random Magnetic Field
1998-06-01
and CNRS-LCMI, F-38042, Grenoble, France § Paul Scherrer Institute, CH-5232 Villigen-PSI, Switzerland ¶ Instituto de Fisica de Sao Carlos, 13560-970...samples (2 × 2 /•m×/zm) with a dimpled 2 DEG. This type of structures provides an experimental alternative for studying a spatially varying magnetic field...height of the dimples 0.1 Itm, which agrees well the experimental observations. The Hall resistance together with B-linear background reveals
Space-time models based on random fields with local interactions
Hristopulos, Dionissios T.; Tsantili, Ivi C.
2016-08-01
The analysis of space-time data from complex, real-life phenomena requires the use of flexible and physically motivated covariance functions. In most cases, it is not possible to explicitly solve the equations of motion for the fields or the respective covariance functions. In the statistical literature, covariance functions are often based on mathematical constructions. In this paper, we propose deriving space-time covariance functions by solving “effective equations of motion”, which can be used as statistical representations of systems with diffusive behavior. In particular, we propose to formulate space-time covariance functions based on an equilibrium effective Hamiltonian using the linear response theory. The effective space-time dynamics is then generated by a stochastic perturbation around the equilibrium point of the classical field Hamiltonian leading to an associated Langevin equation. We employ a Hamiltonian which extends the classical Gaussian field theory by including a curvature term and leads to a diffusive Langevin equation. Finally, we derive new forms of space-time covariance functions.
Energy Technology Data Exchange (ETDEWEB)
Birkholzer, J.; Rutqvist, J.; Sonnenthal, E. [Lawrence Berkeley National Laboratory, CA (United States); Barr, D. [Office of Repository Development, DOE (United States)
2007-02-15
The general goal of this project is to encourage multidisciplinary interactive and cooperative research on modeling coupled processes in geologic formations in support of the performance assessment for underground storage of radioactive waste. Three multi-year project stages of DECOVALEX have been completed in the past decade, mainly focusing on coupled thermal-hydrological-mechanical processes. Currently, a fourth three-year project stage of DECOVALEX is under way, referred to as DECOVALEX-THMC. THMC stands for Thermal, Hydrological, Mechanical, and Chemical processes. The new project stage aims at expanding the traditional geomechanical scope of the previous DECOVALEX project stages by incorporating geochemical processes important for repository performance. The U.S. Department of Energy (DOE) leads Task D of the new DECOVALEX phase, entitled 'Long-term Permeability/Porosity Changes in the EDZ and Near Field due to THC and THM Processes for Volcanic and Crystalline-Bentonite Systems.' In its leadership role for Task D, DOE coordinates and sets the direction for the cooperative research activities of the international research teams engaged in Task D. The research program developed for Task D of DECOVALEX-THMC involves geomechanical and geochemical research areas. THM and THC processes may lead to changes in hydrological properties that are important for performance because the flow processes in the vicinity of emplacement tunnels will be altered from their initial state. Some of these changes can be permanent (irreversible), in which case they persist after the thermal conditions have returned to ambient; i.e., they will affect the entire regulatory compliance period. Geochemical processes also affect the water and gas chemistry close to the waste packages, which are relevant for waste package corrosion, buffer stability, and radionuclide transport. Research teams participating in Task D evaluate long-term THM and THC processes in two generic geologic
Dyrba, Martin; Grothe, Michel J; Mohammadi, Abdolreza; Binder, Harald; Kirste, Thomas; Teipel, Stefan J
2017-07-01
Alzheimer's disease (AD) is characterized by a cascade of pathological processes that can be assessed in vivo using different neuroimaging methods. Recent research suggests a systematic sequence of pathogenic events on a global biomarker level, but little is known about the associations and dependencies of distinct lesion patterns on a regional level. Markov random fields are a probabilistic graphical modeling approach that represent the interaction between individual random variables by an undirected graph. We propose the novel application of this approach to study the interregional associations and dependencies between multimodal imaging markers of AD pathology and to compare different hypotheses regarding the spread of the disease. We retrieved multimodal imaging data from 577 subjects enrolled in the Alzheimer's Disease Neuroimaging Initiative. Mean amyloid load (AV45-PET), glucose metabolism (FDG-PET), and gray matter volume (MRI) were calculated for the six principle nodes of the default mode network- a functional network of brain regions that appears to be preferentially targeted by AD. Multimodal Markov random field models were developed for three different hypotheses regarding the spread of the disease: the "intraregional evolution model", the "trans-neuronal spread" hypothesis, and the "wear-and-tear" hypothesis. The model likelihood to reflect the given data was evaluated using tenfold cross-validation with 1,000 repetitions. The most likely graph structure contained the posterior cingulate cortex as main hub region with edges to various other regions, in accordance with the "wear-and-tear" hypothesis of disease vulnerability. Probabilistic graphical models facilitate the analysis of interactions between several variables in a network model and therefore afford great potential to complement traditional multiple regression analyses in multimodal neuroimaging research.
Extension of the Multipole Approach to Random Metamaterials
Directory of Open Access Journals (Sweden)
A. Chipouline
2012-01-01
Full Text Available Influence of the short-range lateral disorder in the meta-atoms positioning on the effective parameters of the metamaterials is investigated theoretically using the multipole approach. Random variation of the near field quasi-static interaction between metaatoms in form of double wires is shown to be the reason for the effective permittivity and permeability changes. The obtained analytical results are compared with the known experimental ones.
Evaluating Permeability Enchancement Using Electrical Techniques
Energy Technology Data Exchange (ETDEWEB)
John W. Pritchett
2008-09-01
Enhanced Geothermal Systems (EGS) development projects involve the artificial stimulation of relatively impermeable high-temperature underground regions (at depths of 2-4 kilometers or more) to create sufficient permeability to permit underground fluid circulation, so that hot water can be withdrawn from production wells and used to generate electric power. Several major research projects of this general type have been undertaken in the past in New Mexico (Fenton Hill), Europe, Japan and Australia. Recent U.S. activities along these lines focus mainly on stimulating peripheral areas of existing operating hydrothermal fields rather than on fresh 'greenfield' sites, but the long-term objective of the Department of Energy's EGS program is the development of large-scale power projects based on EGS technology (MIT, 2006; NREL, 2008). Usually, stimulation is accomplished by injecting water into a well at high pressure, enhancing permeability by the creation and propagation of fractures in the surrounding rock (a process known as 'hydrofracturing'). Beyond just a motivation, low initial system permeability is also an essential prerequisite to hydrofracturing. If the formation permeability is too high, excessive fluid losses will preclude the buildup of sufficient pressure to fracture rock. In practical situations, the actual result of injection is frequently to re-open pre-existing hydrothermally-mineralized fractures, rather than to create completely new fractures by rupturing intact rock. Pre-existing fractures can often be opened using injection pressures in the range 5-20 MPa. Creation of completely new fractures will usually require pressures that are several times higher. It is preferable to undertake development projects of this type in regions where tectonic conditions are conducive to shear failure, so that when pre-existing fractures are pressurized they will fail by shearing laterally. If this happens, the fracture will often stay open
The permeability of oral leukoplakia.
Bánóczy, Jolán; Squier, Christopher A; Kremer, Mary; Wertz, Philip W; Kövesi, György; Szende, Béla; Dombi, Csaba
2003-08-01
The significant increase in oral cancer mortality necessitates further research on the mechanisms of tumorigenesis. It was the aim of this study to compare the permeability, lipid composition and histopathological characteristics of oral leukoplakia with non-lesional specimens of the same region in 30 cases as well as 11 specimens originating from healthy control buccal mucosa. The permeability (Kp) of tissue biopsies to tritiated nitrosonornicotine was determined in a continuous through-flow perfusion system, lipids were extracted and identified by thin-layer chromatography, and thickness of epithelium and keratin layer assessed by histopathological methods. Results of the measurements showed that the permeability to the tobacco carcinogen, nitrosonornicotine for leukoplakic tissue was higher than for normal control buccal specimens. Non-lesional areas of buccal mucosa, adjacent to leukoplakias, showed hyperplasia and significantly higher permeability values than both leukoplakic and normal buccal control mucosa. The lipid content of the non-lesional sites was intermediate between the increased values of the leukoplakic lesion and of normal control mucosa. The data strongly suggest that the presence of tobacco in the oral cavity may bring about generalized changes even in regions that do not show leukoplakia.
Explaining feast or famine in randomized field trials. Medical science and criminology compared.
Shepherd, Jonathan P
2003-06-01
A feast of randomized controlled trials (RCTs) in medical science and comparative famine in criminology can be explained in terms of cultural and structural factors. Of central importance is the context in which the evaluation of interventions is done and the difference in status of situational research in the two disciplines. Evaluation of medical interventions has traditionally been led by practitioner (clinical) academics. This is not the case in criminal justice, where theory has had higher status than intervention research. Medical science has advanced in, or closely associated with, university teaching hospitals, but links between criminology and criminal justice services are far more tenuous. The late development of situational crime prevention seems extraordinary from a medical perspective, as does the absence of university police schools in the United Kingdom and elsewhere. These structural and cultural factors explain concentration of expectation, resource, and RCT productivity in medical science. The Campbell Collaboration and the Academy of Experimental Criminology are forces which are reducing this polarization of feast and famine in RCTs. But unless scientific criminology is embedded in university schools which are responsible for the education and training of law, probation, and police practitioners, convergence in terms of RCTs and implementation of findings in practice seems unlikely.
Energy Technology Data Exchange (ETDEWEB)
Rodriguez, L. [PDVSA (Venezuela)
2011-07-01
In oil production, characterization of the reservoir has to be undertaken in order to optimize the hydrocarbon production rate. Permeability is one of the most important parameters of a reservoir but estimation is difficult in heavy oil reservoirs and requires the use of multiple techniques. The objective of this paper was to evaluate the results of implementing a multi-scale permeability estimation method. Scale support effect and the physics of the measurements were looked into through a study which was conducted in Venezuela on two of PDVSA's fields, the Cerro Negro Field and the Morichal Field. Results showed that the proposed methodology captured efficiently the influence of parameters on permeability production and was successful in removing the local bias from the permeability data. The multi scale permeability estimation methodology was shown to address the issues encountered with a unique approach and to provide excellent results.
Nutrient Infiltrate Concentrations from Three Permeable Pavement Types
While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types have on nutrient concentrations present in stormwater runoff are limited. In 2009, the U.S. EPA constructed a 0.4-ha...
Advanced Organic Permeable-Base Transistor with Superior Performance.
Klinger, Markus P; Fischer, Axel; Kaschura, Felix; Scholz, Reinhard; Lüssem, Björn; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Kasemann, Daniel; Leo, Karl
2015-12-16
An optimized vertical organic permeable-base transistor (OPBT) competing with the best organic field-effect transistors in performance, while employing low-cost fabrication techniques, is presented. The OPBT stands out by its excellent power efficiency at the highest frequencies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effect of age of permeable pavements on their infiltration function
Terry Lucke; ir. Floris Boogaard; Simon Beecham
2013-01-01
This study describes field investigations designed to compare the infiltration capacities of 55 permeable pavement systems installed in the Netherlands and in Australia. The ages of the pavements varied from 1 to 12 years. Using infiltrometer testing, the performance of the pavements has been
Directory of Open Access Journals (Sweden)
Ningzhi Li
2017-06-01
Full Text Available In vivo13C magnetic resonance spectroscopy (MRS is a unique and effective tool for studying dynamic human brain metabolism and the cycling of neurotransmitters. One of the major technical challenges for in vivo13C-MRS is the high radio frequency (RF power necessary for heteronuclear decoupling. In the common practice of in vivo13C-MRS, alkanyl carbons are detected in the spectra range of 10–65 ppm. The amplitude of decoupling pulses has to be significantly greater than the large one-bond 1H-13C scalar coupling (1JCH = 125–145 Hz. Two main proton decoupling methods have been developed: broadband stochastic decoupling and coherent composite or adiabatic pulse decoupling (e.g., WALTZ; the latter is widely used because of its efficiency and superb performance under inhomogeneous B1 field. Because the RF power required for proton decoupling increases quadratically with field strength, in vivo13C-MRS using coherent decoupling is often limited to low magnetic fields [<=4 Tesla (T] to keep the local and averaged specific absorption rate (SAR under the safety guidelines established by the International Electrotechnical Commission (IEC and the US Food and Drug Administration (FDA. Alternately, carboxylic/amide carbons are coupled to protons via weak long-range 1H-13C scalar couplings, which can be decoupled using low RF power broadband stochastic decoupling. Recently, the carboxylic/amide 13C-MRS technique using low power random RF heteronuclear decoupling was safely applied to human brain studies at 7T. Here, we review the two major decoupling methods and the carboxylic/amide 13C-MRS with low power decoupling strategy. Further decreases in RF power deposition by frequency-domain windowing and time-domain random under-sampling are also discussed. Low RF power decoupling opens the possibility of performing in vivo13C experiments of human brain at very high magnetic fields (such as 11.7T, where signal-to-noise ratio as well as spatial and temporal
Critical behavior of mean-field spin glasses on a dilute random graph
DeSanctis, Luca; Barra, Adriano; Folli, Viola
2008-05-01
We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.
Critical behavior of mean-field spin glasses on a dilute random graph
Energy Technology Data Exchange (ETDEWEB)
De Sanctis, Luca [Dipartimento di Matematica e di Psicologia, Universita di Bologna, P.zza di Porta San Donato 5, 40126 Bologna (Italy); Barra, Adriano; Folli, Viola [Dipartimento di Fisica, Universita La Sapienza, P.le Aldo Moro 5, 00185 Roma (Italy)], E-mail: desanctis@dm.unibo.it, E-mail: adriano.barra@roma1.infn.it, E-mail: viola.folli@roma1.infn.it
2008-05-30
We provide a rigorous strategy to find the critical exponents of the overlaps for dilute spin glasses, in the absence of an external field. Such a strategy is based on the expansion of a suitably perturbed average of the overlaps, which is used in the formulation of the free energy as the difference between a cavity part and the derivative of the free energy itself, considered as a function of the connectivity of the model. We assume the validity of certain reasonable approximations, equivalent to assuming a second-order transition, e.g. that higher powers of overlap monomials are of smaller magnitude near the critical point, of which we do not provide a rigorous proof.
Random-field induced memory effects in inhomogeneously diluted antiferromagnets K2NixZn1−xF4
DEFF Research Database (Denmark)
Dikken, B. J.; Arts, A. F. M.; de Wijn, H. W.
1986-01-01
Using neutron diffraction a random-field generated memory is observed in K2NixZn1−xF4 with x = 0.96, 0.85, and 0.75. The intensities and profiles of magnetic Bragg reflections are found to follow unique trajectories determined by switching the external magnetic field on and off while cooling...
Irrational use of antimalarial drugs in rural areas of eastern Pakistan: a random field study
Directory of Open Access Journals (Sweden)
Khan Shafaat Yar
2012-11-01
Full Text Available Abstract Background Prescription of antimalarial drugs in the absence of malarial disease is a common practice in countries where malaria is endemic. However, unwarranted use of such drugs can cause side effects in some people and is a financial drain on local economies. In this study, we surveyed the prevalence of malaria parasites in humans, and the prevalence of the malaria transmitting mosquito vectors in the study area. We also investigated the use of antimalarial drugs in the local people. We focused on randomly selected rural areas of eastern Pakistan where no malaria cases had been reported since May 2004. Methods Mass blood surveys, active case detection, passive case detection, and vector density surveys were carried out in selected areas of Sargodha district from September 2008 to August 2009. Data pertaining to the quantities and types of antimalarial drugs used in these areas were collected from health centers, pharmacies, and the district CDC program of the Health Department of the Government of the Punjab. Results Seven hundred and forty four blood samples were examined, resulting in a Blood Examination Rate (BER of 3.18; microscopic analysis of blood smears showed that none of the samples were positive for malaria parasites. Investigation of the mosquito vector density in 43 living rooms (bedrooms or rooms used for sleeping, 23 stores, and 32 animal sheds, revealed no vectors capable of transmitting malaria in these locations. In contrast, the density of Culex mosquitoes was high. Substantial consumption of a variety of antimalarial tablets, syrups, capsules and injections costing around 1000 US$, was documented for the region. Conclusion Use of antimalarial drugs in the absence of malarial infection or the vectors that transmit the disease was common in the study area. Continuous use of such drugs, not only in Pakistan, but in other parts of the world, may lead to drug-induced side effects amongst users. Better training of
Dynamic up-scaling of relative permeability in chalk
Energy Technology Data Exchange (ETDEWEB)
Frykman, P.; Lindgaard, H.F.
1997-12-31
This paper describes how fine-scale geo-statistic reservoir models can be utilised for the up-scaling of two-phase flow properties, including both relative permeability and capillary pressure function. The procedure is applied to a North Sea chalk carbonate reservoir example, which is a high-porosity/low-permeability reservoir type. The study focuses on waterflooding as the main recovery scheme and for the given flow regime in the reservoir. The main purpose of the paper is to demonstrate the use of dynamic multi-step up-scaling methods in the preparation of detailed geological information for full field reservoir simulation studies. (au) EFP-96. 39 refs.
The kinetics of denitrification in permeable sediments
DEFF Research Database (Denmark)
Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.
2013-01-01
Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to st...
Permeable Pavement Research - Edison, New Jersey
This presentation provides the background and summary of results collected at the permeable pavement parking lot monitored at the EPA facility in Edison, NJ. This parking lot is surfaced with permeable interlocking concrete pavers (PICP), pervious concrete, and porous asphalt. ...
One-Step Recurrences for Stationary Random Fields on the Sphere
Beatson, R. K.; zu Castell, W.
2016-04-01
Recurrences for positive definite functions in terms of the space dimension have been used in several fields of applications. Such recurrences typically relate to properties of the system of special functions characterizing the geometry of the underlying space. In the case of the sphere S^{d-1} subset R^d the (strict) positive definiteness of the zonal function f(cos θ) is determined by the signs of the coefficients in the expansion of f in terms of the Gegenbauer polynomials {C^λ_n}, with λ=(d-2)/2. Recent results show that classical differentiation and integration applied to f have positive definiteness preserving properties in this context. However, in these results the space dimension changes in steps of two. This paper develops operators for zonal functions on the sphere which preserve (strict) positive definiteness while moving up and down in the ladder of dimensions by steps of one. These fractional operators are constructed to act appropriately on the Gegenbauer polynomials {C^λ_n}.
Liao, Liang; Lin, Tusheng; Li, Bi; Zhang, Weidong
2008-12-01
A modified algorithm using fuzzy Gibbs random field model and fuzzy c-means (FCM) clustering is proposed for segmentation of Magnetic resonance(MR) brain images. Spatial constraints using the definitions of homogeneity of cliques and fuzzy Gibbs clique potential are introduced in this algorithm. A new modified objective function , which is established by introducing the spatial constraints into the traditional intensity based FCM algorithm, leads to the establishment of new iterative formulas for membership matrix and centroids. This algorithm can improve the performance of corresponding traditional one by modifying the original intensity based segmentation model. Experiments on synthetic images and MR phantoms show the validation of the proposed algorithm, which is usually a better alternative for segmenting medical MR images corrupted by noise.
Complete Many-Body Localization in the t-J Model Caused by a Random Magnetic Field.
Lemut, Gal; Mierzejewski, Marcin; Bonča, Janez
2017-12-15
The many body localization (MBL) of spin-1/2 fermions poses a challenging problem. It is known that the disorder in the charge sector may be insufficient to cause full MBL. Here, we study dynamics of a single hole in one dimensional t-J model subject to a random magnetic field. We show that strong disorder that couples only to the spin sector localizes both spin and charge degrees of freedom. Charge localization is confirmed also for a finite concentration of holes. While we cannot precisely pinpoint the threshold disorder, we conjecture that there are two distinct transitions. Weaker disorder first causes localization in the spin sector. Carriers become localized for somewhat stronger disorder, when the spin localization length is of the order of a single lattice spacing.
Directory of Open Access Journals (Sweden)
H. E. Schulz
2009-09-01
Full Text Available Mass transfer across a gas-liquid interface was studied theoretically and experimentally, using transfer of oxygen into water as the gas-liquid system. The experimental results support the conclusions of a theoretical description of the concentration field that uses random square waves approximations. The effect of diffusion over the concentration records was quantified. It is shown that the peak of the normalized rms concentration fluctuation profiles must be lower than 0.5, and that the position of the peak of the rms value is an adequate measure of the thickness of the diffusive layer. The position of the peak is the boundary between the regions more subject to molecular diffusion or to turbulent transport of dissolved mass.
Dong, Zhen; Wang, Jianjun; Zhou, Xin
2017-05-01
Antifreeze proteins (AFPs) are the key biomolecules that protect many species from suffering the extreme conditions. Their unique properties of antifreezing provide the potential of a wide range of applications. Inspired by the present experimental approaches of creating an antifreeze surface by coating AFPs, here we present a two-dimensional random-field lattice Ising model to study the effect of AFPs on heterogeneous ice nucleation. The model shows that both the size and the free-energy effect of individual AFPs and their surface coverage dominate the antifreeze capacity of an AFP-coated surface. The simulation results are consistent with the recent experiments qualitatively, revealing the origin of the surprisingly low antifreeze capacity of an AFP-coated surface when the coverage is not particularly high as shown in experiment. These results will hopefully deepen our understanding of the antifreeze effects and thus be potentially useful for designing novel antifreeze coating materials based on biomolecules.
Directory of Open Access Journals (Sweden)
Z. Zhang
2013-05-01
Full Text Available Feature fusion of remote sensing images and LiDAR points cloud data, which have strong complementarity, can effectively play the advantages of multi-class features to provide more reliable information support for the remote sensing applications, such as object classification and recognition. In this paper, we introduce a novel multi-source hierarchical conditional random field (MSHCRF model to fuse features extracted from remote sensing images and LiDAR data for image classification. Firstly, typical features are selected to obtain the interest regions from multi-source data, then MSHCRF model is constructed to exploit up the features, category compatibility of images and the category consistency of multi-source data based on the regions, and the outputs of the model represents the optimal results of the image classification. Competitive results demonstrate the precision and robustness of the proposed method.
Dong, Zhen; Wang, Jianjun; Zhou, Xin
2017-05-01
Antifreeze proteins (AFPs) are the key biomolecules that protect many species from suffering the extreme conditions. Their unique properties of antifreezing provide the potential of a wide range of applications. Inspired by the present experimental approaches of creating an antifreeze surface by coating AFPs, here we present a two-dimensional random-field lattice Ising model to study the effect of AFPs on heterogeneous ice nucleation. The model shows that both the size and the free-energy effect of individual AFPs and their surface coverage dominate the antifreeze capacity of an AFP-coated surface. The simulation results are consistent with the recent experiments qualitatively, revealing the origin of the surprisingly low antifreeze capacity of an AFP-coated surface when the coverage is not particularly high as shown in experiment. These results will hopefully deepen our understanding of the antifreeze effects and thus be potentially useful for designing novel antifreeze coating materials based on biomolecules.
Shenje, Justin; Millard, Peter S
2016-01-01
The World Health Organization has solicited rapid and minimally invasive techniques to facilitate scale-up of voluntary medical male circumcision (VMMC). Non-blinded randomized controlled field trial with 2:1 allocation ratio. 75 adult male volunteers. Outpatient primary care clinic. Open surgical circumcision under local anesthetic with suturing vs. Unicirc disposable instrument under topical anesthetic and wound sealing with cyanoacrylate tissue adhesive. Intraoperative duration. Intraoperative and postoperative pain; adverse events; time to healing; patient satisfaction; cosmetic result. The intraoperative time was less with the Unicirc technique (median 12 vs. 25 min, p Wound healing and cosmetic results were superior in the Unicirc group. Adverse events were similar in both groups. VMMC with Unicirc under topical anesthetic and wound sealing with cyanoacrylate tissue adhesive is rapid, heals by primary intention with superior cosmetic results, and is potentially safer and more cost-effective than open surgical VMMC. Clinicaltrials.gov NCT02443792.
DEFF Research Database (Denmark)
Thamsborg, G; Florescu, A; Oturai, P
2005-01-01
OBJECTIVE: The investigation aimed at determining the effectiveness of pulsed electromagnetic fields (PEMF) in the treatment of osteoarthritis (OA) of the knee by conducting a randomized, double-blind, placebo-controlled clinical trial. DESIGN: The trial consisted of 2h daily treatment 5 days per...... (WOMAC) questionnaire. RESULTS: Within group analysis revealed a significant improvement in ADL, stiffness and pain in the PEMF-treated group at all evaluations. In the control group there was no effect on ADL after 2 weeks and a weak significance was seen after 6 and 12 weeks. Significant effects were...... years using between group analysis revealed a significant improvement for stiffness on treated knee after 2 weeks, but this effect was not observed for ADL and pain. CONCLUSIONS: Applying between group analysis we were unable to demonstrate a beneficial symptomatic effect of PEMF in the treatment...
Directory of Open Access Journals (Sweden)
Elena Tutubalina
2017-01-01
Full Text Available Adverse drug reactions (ADRs are an essential part of the analysis of drug use, measuring drug use benefits, and making policy decisions. Traditional channels for identifying ADRs are reliable but very slow and only produce a small amount of data. Text reviews, either on specialized web sites or in general-purpose social networks, may lead to a data source of unprecedented size, but identifying ADRs in free-form text is a challenging natural language processing problem. In this work, we propose a novel model for this problem, uniting recurrent neural architectures and conditional random fields. We evaluate our model with a comprehensive experimental study, showing improvements over state-of-the-art methods of ADR extraction.
Variability of permeability with diameter of conduit
Indian Academy of Sciences (India)
... creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus ...
Transport zonation limits coupled nitrification-denitrification in permeable sediments
DEFF Research Database (Denmark)
Kessler, Adam John; Glud, R.N.; Cardenas, M.B.
2013-01-01
Measurement of biogeochemical processes in permeable sediments (including the hyporheic zone) is difficult because of complex multidimensional advective transport. This is especially the case for nitrogen cycling, which involves several coupled redox-sensitive reactions. To provide detailed insig......- and N-15-N-2 gas. The measured two-dimensional profiles correlate with computational model simulations, showing a deep pool of N-2 gas forming, and being advected to the surface below ripple peaks. Further isotope pairing calculations on these data indicate that coupled nitrification......-denitrification is severely limited in permeable sediments because the flow and transport field limits interaction between oxic and anoxic pore water. The approach allowed for new detailed insight into subsurface denitrification zones in complex permeable sediments....
Directory of Open Access Journals (Sweden)
Poeze Martijn
2011-05-01
Full Text Available Abstract Background The scaphoid bone is the most commonly fractured of the carpal bones. In the Netherlands 90% of all carpal fractures is a fracture of the scaphoid bone. The scaphoid has an essential role in functionality of the wrist, acting as a pivot. Complications in healing can result in poor functional outcome. The scaphoid fracture is a troublesome fracture and failure of treatment can result in avascular necrosis (up to 40%, non-union (5-21% and early osteo-arthritis (up to 32% which may seriously impair wrist function. Impaired consolidation of scaphoid fractures results in longer immobilization and more days lost at work with significant psychosocial and financial consequences. Initially Pulsed Electromagnetic Fields was used in the treatment of tibial pseudoarthrosis and non-union. More recently there is evidence that physical forces can also be used in the treatment of fresh fractures, showing accelerated healing by 30% and 71% reduction in nonunion within 12 weeks after initiation of therapy. Until now no double blind randomized, placebo controlled trial has been conducted to investigate the effect of this treatment on the healing of fresh fractures of the scaphoid. Methods/Design This is a multi center, prospective, double blind, placebo controlled, randomized trial. Study population consists of all patients with unilateral acute scaphoid fracture. Pregnant women, patients having a life supporting implanted electronic device, patients with additional fractures of wrist, carpal or metacarpal bones and pre-existing impairment in wrist function are excluded. The scaphoid fracture is diagnosed by a combination of physical and radiographic examination (CT-scanning. Proven scaphoid fractures are treated with cast immobilization and a small Pulsed Electromagnetic Fields bone growth stimulating device placed on the cast. Half of the devices will be disabled at random in the factory. Study parameters are clinical consolidation
Tile-Level Annotation of Satellite Images Using Multi-Level Max-Margin Discriminative Random Field
Directory of Open Access Journals (Sweden)
Hong Sun
2013-05-01
Full Text Available This paper proposes a multi-level max-margin discriminative analysis (M3DA framework, which takes both coarse and fine semantics into consideration, for the annotation of high-resolution satellite images. In order to generate more discriminative topic-level features, the M3DA uses the maximum entropy discrimination latent Dirichlet Allocation (MedLDA model. Moreover, for improving the spatial coherence of visual words neglected by M3DA, conditional random field (CRF is employed to optimize the soft label field composed of multiple label posteriors. The framework of M3DA enables one to combine word-level features (generated by support vector machines and topic-level features (generated by MedLDA via the bag-of-words representation. The experimental results on high-resolution satellite images have demonstrated that, using the proposed method can not only obtain suitable semantic interpretation, but also improve the annotation performance by taking into account the multi-level semantics and the contextual information.
Le Maitre, Olivier
2015-01-07
We address model dimensionality reduction in the Bayesian inference of Gaussian fields, considering prior covariance function with unknown hyper-parameters. The Karhunen-Loeve (KL) expansion of a prior Gaussian process is traditionally derived assuming fixed covariance function with pre-assigned hyperparameter values. Thus, the modes strengths of the Karhunen-Loeve expansion inferred using available observations, as well as the resulting inferred process, dependent on the pre-assigned values for the covariance hyper-parameters. Here, we seek to infer the process and its the covariance hyper-parameters in a single Bayesian inference. To this end, the uncertainty in the hyper-parameters is treated by means of a coordinate transformation, leading to a KL-type expansion on a fixed reference basis of spatial modes, but with random coordinates conditioned on the hyper-parameters. A Polynomial Chaos (PC) expansion of the model prediction is also introduced to accelerate the Bayesian inference and the sampling of the posterior distribution with MCMC method. The PC expansion of the model prediction also rely on a coordinates transformation, enabling us to avoid expanding the dependence of the prediction with respect to the covariance hyper-parameters. We demonstrate the efficiency of the proposed method on a transient diffusion equation by inferring spatially-varying log-diffusivity fields from noisy data.
Effect of aggregate grain size distribution on properties of permeable ...
African Journals Online (AJOL)
) ratio on the mechanical properties of permeable concrete is investigated. The aim of this study is to prepare permeable concrete mixture with optimum properties in terms of strength and permeability. For this purpose, five different permeable ...
On the permeability of fractal tube bundles
Zinovik, I
2011-01-01
The permeability of a porous medium is strongly affected by its local geometry and connectivity, the size distribution of the solid inclusions and the pores available for flow. Since direct measurements of the permeability are time consuming and require experiments that are not always possible, the reliable theoretical assessment of the permeability based on the medium structural characteristics alone is of importance. When the porosity approaches unity, the permeability-porosity relationships represented by the Kozeny-Carman equations and Archie's law predict that permeability tends to infinity and thus they yield unrealistic results if specific area of the porous media does not tend to zero. The goal of this paper is an evaluation of the relationships between porosity and permeability for a set of fractal models with porosity approaching unity and a finite permeability. It is shown that the two-dimensional foams generated by finite iterations of the corresponding geometric fractals can be used to model poro...
Al-Amri, Meshal; Mahmoud, Mohamed; Elkatatny, Salaheldin; Al-Yousef, Hasan; Al-Ghamdi, Tariq
2017-07-01
Accurate estimation of permeability is essential in reservoir characterization and in determining fluid flow in porous media which greatly assists optimize the production of a field. Some of the permeability prediction techniques such as Porosity-Permeability transforms and recently artificial intelligence and neural networks are encouraging but still show moderate to good match to core data. This could be due to limitation to homogenous media while the knowledge about geology and heterogeneity is indirectly related or absent. The use of geological information from core description as in Lithofacies which includes digenetic information show a link to permeability when categorized into rock types exposed to similar depositional environment. The objective of this paper is to develop a robust combined workflow integrating geology and petrophysics and wireline logs in an extremely heterogeneous carbonate reservoir to accurately predict permeability. Permeability prediction is carried out using pattern recognition algorithm called multi-resolution graph-based clustering (MRGC). We will bench mark the prediction results with hard data from core and well test analysis. As a result, we showed how much better improvements are achieved in the permeability prediction when geology is integrated within the analysis. Finally, we use the predicted permeability as an input parameter in J-function and correct for uncertainties in saturation calculation produced by wireline logs using the classical Archie equation. Eventually, high level of confidence in hydrocarbon volumes estimation is reached when robust permeability and saturation height functions are estimated in presence of important geological details that are petrophysically meaningful.
Aboud, Frances E; Moore, Anna C; Akhter, Sadika
2008-10-01
Responsive complementary feeding, whereby the mother feeds her child in response to child cues of hunger state and psychomotor abilities, is a problem in some countries, and likely contributes to malnutrition. Interventions are needed to evaluate whether promoting responsive feeding would add any benefit. Using a cluster randomized field trial, we evaluated a six-session educational programme that emphasized practice of two key behaviours, namely child self-feeding and maternal responsiveness. One hundred mothers and their 12- to 24-month-olds attended the sessions as part of village clusters randomly assigned to the intervention group. A similar number of controls received sessions on foods to feed and nutritional disorders. Outcomes assessed at pre-test, 2-week post-intervention and again 5-months post-intervention included weight, mouthfuls of food taken, self-feeding and maternal responsiveness. Research assistants, blind to group assignment, observed and coded mother and child behaviours during the midday meal. Secondary measures included foods fed and feeding messages recalled. Analysis was based on intention to treat and accounted for clustering. Only 10% of each group was lost to follow-up. Weight (d = 0.28), weight gain (d = 0.48) and child self-feeding (d = 0.30) were significantly higher in the responsive feeding group. Mouthfuls of food eaten and maternal responsiveness were not significantly increased by the intervention. Mothers in the intervention gave their children more vegetables, and spontaneously recalled more feeding messages at the 5-month follow-up. These results provide evidence that self-feeding and weight gain can improve by targeting specific behaviours, while maternal responsiveness may require more intensive strategies.
Jin, Y. Q.; Kong, J. A.
1984-01-01
The strong fluctuation theory is applied to the study of electromagnetic wave scattering from a layer of random discrete scatterers. The singularity of the dyadic Green's function is taken into account in the calculation of the effective permittivity functions. The correlation functions for the random medium with different scatterer constituents and size distributions are derived. Applying the dyadic Green's function for a two-layer medium and using the bilocal and distorted Born approximations, the first and the second moments of the fields are then calculated. Both the backscattering and bistatic scattering coefficients are obtained, and the former is shown to match favorably with experimental data obtained from snow fields.
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Aysel Yavuz
2012-04-01
Full Text Available This research in which components of permeability concept is tried to be set forth, presents the results of a field study conducted on a pedestrian-shopping street in Trabzon, a coastal city in the eastern Black Sea Region. The criteria affecting permeability are dealt with in physical, functional and perceptual properties. Accordingly, three hypotheses are proposed in this article. The study was a two-stage survey. The first survey is prepared to determine user preferences. With the second survey prepared in the light of the data obtained from the first one, characteristics defining the permeability concept were sought for. As a result, permeability level of a street is found to be closely related with the physical, functional and perceptual properties providing such permeability and, permeability is determined to be best provided by considering all the three properties together, and new perspective to the concept of permeability is brought with this model.
Fracture network topology and characterization of structural permeability
Hansberry, Rowan; King, Rosalind; Holford, Simon
2017-04-01
There are two fundamental requirements for successful geothermal development: elevated temperatures at accessible depths, and a reservoir from which fluids can be extracted. The Australian geothermal sector has successfully targeted shallow heat, however, due in part to the inherent complexity of targeting permeability, obtaining adequate flow rates for commercial production has been problematic. Deep sedimentary aquifers are unlikely to be viable geothermal resources due to the effects of diagenetic mineral growth on rock permeability. Therefore, it is likely structural permeability targets, exploiting natural or induced fracture networks will provide the primary means for fluid flow in geothermal, as well as unconventional gas, reservoirs. Recent research has focused on the pattern and generation of crustal stresses across Australia, while less is known about the resultant networks of faults, joints, and veins that can constitute interconnected sub-surface permeability pathways. The ability of a fracture to transmit fluid is controlled by the orientation and magnitude of the in-situ stress field that acts on the fracture walls, rock strength, and pore pressure, as well as fracture properties such as aperture, orientation, and roughness. Understanding the distribution, orientation and character of fractures is key to predicting structural permeability. This project focuses on extensive mapping of fractures over various scales in four key Australian basins (Cooper, Otway, Surat and Perth) with the potential to host geothermal resources. Seismic attribute analysis is used in concert with image logs from petroleum wells, and field mapping to identify fracture networks that are usually not resolved in traditional seismic interpretation. We use fracture network topology to provide scale-invariant characterisation of fracture networks from multiple data sources to assess similarity between data sources, and fracture network connectivity. These results are compared with
Zulkifley, Mohd Asyraf; Moran, Bill; Rawlinson, David
2012-01-01
Foreground detection has been used extensively in many applications such as people counting, traffic monitoring and face recognition. However, most of the existing detectors can only work under limited conditions. This happens because of the inability of the detector to distinguish foreground and background pixels, especially in complex situations. Our aim is to improve the robustness of foreground detection under sudden and gradual illumination change, colour similarity issue, moving background and shadow noise. Since it is hard to achieve robustness using a single model, we have combined several methods into an integrated system. The masked grey world algorithm is introduced to handle sudden illumination change. Colour co-occurrence modelling is then fused with the probabilistic edge-based background modelling. Colour co-occurrence modelling is good in filtering moving background and robust to gradual illumination change, while an edge-based modelling is used for solving a colour similarity problem. Finally, an extended conditional random field approach is used to filter out shadow and afterimage noise. Simulation results show that our algorithm performs better compared to the existing methods, which makes it suitable for higher-level applications.
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David Rawlinson
2012-05-01
Full Text Available Foreground detection has been used extensively in many applications such as people counting, traffic monitoring and face recognition. However, most of the existing detectors can only work under limited conditions. This happens because of the inability of the detector to distinguish foreground and background pixels, especially in complex situations. Our aim is to improve the robustness of foreground detection under sudden and gradual illumination change, colour similarity issue, moving background and shadow noise. Since it is hard to achieve robustness using a single model, we have combined several methods into an integrated system. The masked grey world algorithm is introduced to handle sudden illumination change. Colour co-occurrence modelling is then fused with the probabilistic edge-based background modelling. Colour co-occurrence modelling is good infiltering moving background and robust to gradual illumination change, while an edge-based modelling is used for solving a colour similarity problem. Finally, an extended conditional random field approach is used to filter out shadow and afterimage noise. Simulation results show that our algorithm performs better compared to the existing methods, which makes it suitable for higher-level applications.
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Maihemuti Maimaiti
2017-11-01
Full Text Available Uyghur is an agglutinative and a morphologically rich language; natural language processing tasks in Uyghur can be a challenge. Word morphology is important in Uyghur part-of-speech (POS tagging. However, POS tagging performance suffers from error propagation of morphological analyzers. To address this problem, we propose a few models for POS tagging: conditional random fields (CRF, long short-term memory (LSTM, bidirectional LSTM networks (BI-LSTM, LSTM networks with a CRF layer, and BI-LSTM networks with a CRF layer. These models do not depend on stemming and word disambiguation for Uyghur and combine hand-crafted features with neural network models. State-of-the-art performance on Uyghur POS tagging is achieved on test data sets using the proposed approach: 98.41% accuracy on 15 labels and 95.74% accuracy on 64 labels, which are 2.71% and 4% improvements, respectively, over the CRF model results. Using engineered features, our model achieves further improvements of 0.2% (15 labels and 0.48% (64 labels. The results indicate that the proposed method could be an effective approach for POS tagging in other morphologically rich languages.
Larrasa, José; García-Sánchez, Alfredo; Ambrose, Nicholas C; Parra, Alberto; Alonso, Juan M; Rey, Joaquín M; Hermoso-de-Mendoza, Miguel; Hermoso-de-Mendoza, Javier
2004-11-01
This study aimed to evaluate molecular typing methods useful for standardization of strains in experimental work on dermatophilosis. Fifty Dermatophilus congolensis isolates, collected from sheep, cattle, horse and a deer, were analyzed by randomly amplified polymorphic DNA (RAPD) method using twenty-one different primers, and the results were compared with those obtained by typing with a pulsed field gel electrophoresis (PFGE) method using the restriction digest enzyme Sse8387I. The typeability, reproducibility and discriminatory power of RAPD and Sse8387I-PFGE typing were calculated. Both typing methods were highly reproducible. Of the two techniques, Sse8387I-PFGE was the least discriminating (Dice Index (DI), 0.663) and could not distinguish between epidemiologically related isolates, whereas RAPD showed an excellent discriminatory power (DI, 0.7694-0.9722). Overall, the degree of correlation between RAPD and PFGE typing was significantly high (r, 0.8822). We conclude that the DNA profiles generated by either RAPD or PFGE can be used to differentiate epidemiologically unrelated isolates. The results of this study strongly suggest that at least two independent primers are used for RAPD typing in order to improve its discriminatory power, and that PFGE is used for confirmation of RAPD results.
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Yisu Lu
2014-01-01
Full Text Available Brain-tumor segmentation is an important clinical requirement for brain-tumor diagnosis and radiotherapy planning. It is well-known that the number of clusters is one of the most important parameters for automatic segmentation. However, it is difficult to define owing to the high diversity in appearance of tumor tissue among different patients and the ambiguous boundaries of lesions. In this study, a nonparametric mixture of Dirichlet process (MDP model is applied to segment the tumor images, and the MDP segmentation can be performed without the initialization of the number of clusters. Because the classical MDP segmentation cannot be applied for real-time diagnosis, a new nonparametric segmentation algorithm combined with anisotropic diffusion and a Markov random field (MRF smooth constraint is proposed in this study. Besides the segmentation of single modal brain-tumor images, we developed the algorithm to segment multimodal brain-tumor images by the magnetic resonance (MR multimodal features and obtain the active tumor and edema in the same time. The proposed algorithm is evaluated using 32 multimodal MR glioma image sequences, and the segmentation results are compared with other approaches. The accuracy and computation time of our algorithm demonstrates very impressive performance and has a great potential for practical real-time clinical use.
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Fermín Segovia
2017-10-01
Full Text Available 18F-DMFP-PET is an emerging neuroimaging modality used to diagnose Parkinson's disease (PD that allows us to examine postsynaptic dopamine D2/3 receptors. Like other neuroimaging modalities used for PD diagnosis, most of the total intensity of 18F-DMFP-PET images is concentrated in the striatum. However, other regions can also be useful for diagnostic purposes. An appropriate delimitation of the regions of interest contained in 18F-DMFP-PET data is crucial to improve the automatic diagnosis of PD. In this manuscript we propose a novel methodology to preprocess 18F-DMFP-PET data that improves the accuracy of computer aided diagnosis systems for PD. First, the data were segmented using an algorithm based on Hidden Markov Random Field. As a result, each neuroimage was divided into 4 maps according to the intensity and the neighborhood of the voxels. The maps were then individually normalized so that the shape of their histograms could be modeled by a Gaussian distribution with equal parameters for all the neuroimages. This approach was evaluated using a dataset with neuroimaging data from 87 parkinsonian patients. After these preprocessing steps, a Support Vector Machine classifier was used to separate idiopathic and non-idiopathic PD. Data preprocessed by the proposed method provided higher accuracy results than the ones preprocessed with previous approaches.
Lu, Yisu; Jiang, Jun; Chen, Wufan
2014-01-01
Brain-tumor segmentation is an important clinical requirement for brain-tumor diagnosis and radiotherapy planning. It is well-known that the number of clusters is one of the most important parameters for automatic segmentation. However, it is difficult to define owing to the high diversity in appearance of tumor tissue among different patients and the ambiguous boundaries of lesions. In this study, a nonparametric mixture of Dirichlet process (MDP) model is applied to segment the tumor images, and the MDP segmentation can be performed without the initialization of the number of clusters. Because the classical MDP segmentation cannot be applied for real-time diagnosis, a new nonparametric segmentation algorithm combined with anisotropic diffusion and a Markov random field (MRF) smooth constraint is proposed in this study. Besides the segmentation of single modal brain-tumor images, we developed the algorithm to segment multimodal brain-tumor images by the magnetic resonance (MR) multimodal features and obtain the active tumor and edema in the same time. The proposed algorithm is evaluated using 32 multimodal MR glioma image sequences, and the segmentation results are compared with other approaches. The accuracy and computation time of our algorithm demonstrates very impressive performance and has a great potential for practical real-time clinical use. PMID:25254064
Crystalline Electric-Field Randomness in the Triangular Lattice Spin-Liquid YbMgGaO_{4}.
Li, Yuesheng; Adroja, Devashibhai; Bewley, Robert I; Voneshen, David; Tsirlin, Alexander A; Gegenwart, Philipp; Zhang, Qingming
2017-03-10
We apply moderate-high-energy inelastic neutron scattering (INS) measurements to investigate Yb^{3+} crystalline electric field (CEF) levels in the triangular spin-liquid candidate YbMgGaO_{4}. Three CEF excitations from the ground-state Kramers doublet are centered at the energies ℏω=39, 61, and 97 meV in agreement with the effective spin-1/2 g factors and experimental heat capacity, but reveal sizable broadening. We argue that this broadening originates from the site mixing between Mg^{2+} and Ga^{3+} giving rise to a distribution of Yb-O distances and orientations and, thus, of CEF parameters that account for the peculiar energy profile of the CEF excitations. The CEF randomness gives rise to a distribution of the effective spin-1/2 g factors and explains the unprecedented broadening of low-energy magnetic excitations in the fully polarized ferromagnetic phase of YbMgGaO_{4}, although a distribution of magnetic couplings due to the Mg/Ga disorder may be important as well.
Large deviations of the finite-time magnetization of the Curie-Weiss random-field Ising model.
Paga, Pierre; Kühn, Reimer
2017-08-01
We study the large deviations of the magnetization at some finite time in the Curie-Weiss random field Ising model with parallel updating. While relaxation dynamics in an infinite-time horizon gives rise to unique dynamical trajectories [specified by initial conditions and governed by first-order dynamics of the form m_{t+1}=f(m_{t})], we observe that the introduction of a finite-time horizon and the specification of terminal conditions can generate a host of metastable solutions obeying second-order dynamics. We show that these solutions are governed by a Newtonian-like dynamics in discrete time which permits solutions in terms of both the first-order relaxation ("forward") dynamics and the backward dynamics m_{t+1}=f^{-1}(m_{t}). Our approach allows us to classify trajectories for a given final magnetization as stable or metastable according to the value of the rate function associated with them. We find that in analogy to the Freidlin-Wentzell description of the stochastic dynamics of escape from metastable states, the dominant trajectories may switch between the two types (forward and backward) of first-order dynamics. Additionally, we show how to compute rate functions when uncertainty in the quenched disorder is introduced.
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Ehwa Yang
2017-03-01
Full Text Available Due to the reasonably acceptable performance of state-of-the-art object detectors, tracking-by-detection is a standard strategy for visual multi-object tracking (MOT. In particular, online MOT is more demanding due to its diverse applications in time-critical situations. A main issue of realizing online MOT is how to associate noisy object detection results on a new frame with previously being tracked objects. In this work, we propose a multi-object tracker method called CRF-boosting which utilizes a hybrid data association method based on online hybrid boosting facilitated by a conditional random field (CRF for establishing online MOT. For data association, learned CRF is used to generate reliable low-level tracklets and then these are used as the input of the hybrid boosting. To do so, while existing data association methods based on boosting algorithms have the necessity of training data having ground truth information to improve robustness, CRF-boosting ensures sufficient robustness without such information due to the synergetic cascaded learning procedure. Further, a hierarchical feature association framework is adopted to further improve MOT accuracy. From experimental results on public datasets, we could conclude that the benefit of proposed hybrid approach compared to the other competitive MOT systems is noticeable.
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Teerapong Panboonyuen
2017-07-01
Full Text Available Object segmentation of remotely-sensed aerial (or very-high resolution, VHS images and satellite (or high-resolution, HR images, has been applied to many application domains, especially in road extraction in which the segmented objects are served as a mandatory layer in geospatial databases. Several attempts at applying the deep convolutional neural network (DCNN to extract roads from remote sensing images have been made; however, the accuracy is still limited. In this paper, we present an enhanced DCNN framework specifically tailored for road extraction of remote sensing images by applying landscape metrics (LMs and conditional random fields (CRFs. To improve the DCNN, a modern activation function called the exponential linear unit (ELU, is employed in our network, resulting in a higher number of, and yet more accurate, extracted roads. To further reduce falsely classified road objects, a solution based on an adoption of LMs is proposed. Finally, to sharpen the extracted roads, a CRF method is added to our framework. The experiments were conducted on Massachusetts road aerial imagery as well as the Thailand Earth Observation System (THEOS satellite imagery data sets. The results showed that our proposed framework outperformed Segnet, a state-of-the-art object segmentation technique, on any kinds of remote sensing imagery, in most of the cases in terms of precision, recall, and F 1 .
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Hong-Jie Dai
2015-01-01
Full Text Available Electronic health record (EHR is a digital data format that collects electronic health information about an individual patient or population. To enhance the meaningful use of EHRs, information extraction techniques have been developed to recognize clinical concepts mentioned in EHRs. Nevertheless, the clinical judgment of an EHR cannot be known solely based on the recognized concepts without considering its contextual information. In order to improve the readability and accessibility of EHRs, this work developed a section heading recognition system for clinical documents. In contrast to formulating the section heading recognition task as a sentence classification problem, this work proposed a token-based formulation with the conditional random field (CRF model. A standard section heading recognition corpus was compiled by annotators with clinical experience to evaluate the performance and compare it with sentence classification and dictionary-based approaches. The results of the experiments showed that the proposed method achieved a satisfactory F-score of 0.942, which outperformed the sentence-based approach and the best dictionary-based system by 0.087 and 0.096, respectively. One important advantage of our formulation over the sentence-based approach is that it presented an integrated solution without the need to develop additional heuristics rules for isolating the headings from the surrounding section contents.
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Justin Shenje
Full Text Available The World Health Organization has solicited rapid and minimally invasive techniques to facilitate scale-up of voluntary medical male circumcision (VMMC.Non-blinded randomized controlled field trial with 2:1 allocation ratio.75 adult male volunteers.Outpatient primary care clinic.Open surgical circumcision under local anesthetic with suturing vs. Unicirc disposable instrument under topical anesthetic and wound sealing with cyanoacrylate tissue adhesive.Intraoperative duration.Intraoperative and postoperative pain; adverse events; time to healing; patient satisfaction; cosmetic result.The intraoperative time was less with the Unicirc technique (median 12 vs. 25 min, p < 0.001. Wound healing and cosmetic results were superior in the Unicirc group. Adverse events were similar in both groups.VMMC with Unicirc under topical anesthetic and wound sealing with cyanoacrylate tissue adhesive is rapid, heals by primary intention with superior cosmetic results, and is potentially safer and more cost-effective than open surgical VMMC.Clinicaltrials.gov NCT02443792.
An effective way to increase the high-frequency permeability of Fe3O4 nanorods
Ren, Xiao; Yang, Haitao; Tang, Jin; Li, Zi-An; Su, Yi Kun; Geng, Sai; Zhou, Jun; Zhang, Xiangqun; Cheng, Zhaohua
2016-06-01
Uniform Fe3O4 magnetic nanorods (NRs) were successfully synthesized and oriented in epoxy resin under a rotating magnetic field. Magnetic induction fields within and around a single Fe3O4 nanorod in the remanence state were obtained by off-axis electron holography. The induction fields indicated a single domain state of the highly anisotropic Fe3O4 nanorod due to its strong magnetic shape anisotropy. Quantitative magnetic moment analysis of the obtained phase image yielded an average magnetization of 0.53 T of a single Fe3O4 nanorod. Moreover, the real part of the permeability (μ') of magnetic-oriented Fe3O4 NRs is obviously higher than that of random Fe3O4 NRs in the GHz range. The oriented Fe3O4 NRs exhibit a higher resonance peak at 4.75 GHz compared to the bulk counterpart (1.2 GHz) in the frequency dependence of μ in the range of 1-10 GHz. Moreover, the calculated μ value of the oriented Fe3O4 NRs could be improved to 4.22 with the increased dipolar interaction strength using the OOMMF software. These results could play a guiding significance in the development of an effective method to improve the permeability of magnetic nanomaterials at GHz working frequency.Uniform Fe3O4 magnetic nanorods (NRs) were successfully synthesized and oriented in epoxy resin under a rotating magnetic field. Magnetic induction fields within and around a single Fe3O4 nanorod in the remanence state were obtained by off-axis electron holography. The induction fields indicated a single domain state of the highly anisotropic Fe3O4 nanorod due to its strong magnetic shape anisotropy. Quantitative magnetic moment analysis of the obtained phase image yielded an average magnetization of 0.53 T of a single Fe3O4 nanorod. Moreover, the real part of the permeability (μ') of magnetic-oriented Fe3O4 NRs is obviously higher than that of random Fe3O4 NRs in the GHz range. The oriented Fe3O4 NRs exhibit a higher resonance peak at 4.75 GHz compared to the bulk counterpart (1.2 GHz) in the
Steam-water relative permeability
Energy Technology Data Exchange (ETDEWEB)
Ambusso, W.; Satik, C.; Home, R.N. [Stanford Univ., CA (United States)
1997-12-31
A set of relative permeability relations for simultaneous flow of steam and water in porous media have been measured in steady state experiments conducted under the conditions that eliminate most errors associated with saturation and pressure measurements. These relations show that the relative permeabilities for steam-water flow in porous media vary approximately linearly with saturation. This departure from the nitrogen/water behavior indicates that there are fundamental differences between steam/water and nitrogen/water flows. The saturations in these experiments were measured by using a high resolution X-ray computer tomography (CT) scanner. In addition the pressure gradients were obtained from the measurements of liquid phase pressure over the portions with flat saturation profiles. These two aspects constitute a major improvement in the experimental method compared to those used in the past. Comparison of the saturation profiles measured by the X-ray CT scanner during the experiments shows a good agreement with those predicted by numerical simulations. To obtain results that are applicable to general flow of steam and water in porous media similar experiments will be conducted at higher temperature and with porous rocks of different wetting characteristics and porosity distribution.
Experimental Study on Permeability of Concrete
Yang, Honglu; Liu, Rentai; Zheng, Zhuo; Liu, Haojie; Gao, Yan; Liu, Yankai
2018-01-01
To study the influencing factors on permeability of pervious concrete, by adding inorganic organic composite materials obtained experimental results show that different aggregate size, aggregate cement ratio of different, different water cement ratio on the permeability performance. The permeability of the concrete was tested by using the self - made permeable device. The experimental results showed that the permeation coefficient of the experiment was obtained and the factors influencing the permeability of the concrete were compared and analyzed. At the same time, the porosity of pervious concrete was measured, the influence of various variables on porosity was studied, and the influence of various factors on the permeability of voids was found. Finally, through comprehensive analysis of a variety of factors, the optimal water cement ratio is 0.28. At this time, the pervious performance of concrete is optimal.
Clogging in permeable concrete: A review.
Kia, Alalea; Wong, Hong S; Cheeseman, Christopher R
2017-05-15
Permeable concrete (or "pervious concrete" in North America) is used to reduce local flooding in urban areas and is an important sustainable urban drainage system. However, permeable concrete exhibits reduction in permeability due to clogging by particulates, which severely limits service life. This paper reviews the clogging mechanism and current mitigating strategies in order to inform future research needs. The pore structure of permeable concrete and characteristics of flowing particulates influence clogging, which occurs when particles build-up and block connected porosity. Permeable concrete requires regular maintenance by vacuum sweeping and pressure washing, but the effectiveness and viability of these methods is questionable. The potential for clogging is related to the tortuosity of the connected porosity, with greater tortuosity resulting in increased potential for clogging. Research is required to develop permeable concrete that can be poured on-site, which produces a pore structure with significantly reduced tortuosity. Copyright © 2017 Elsevier Ltd. All rights reserved.
Air permeability of polyester nonwoven fabrics
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Zhu Guocheng
2015-03-01
Full Text Available Air permeability is one of the most important properties of non-woven fabrics in many applications. This paper aims to investigate the effects of thickness, porosity and density on the air permeability of needle-punched non-woven fabrics and compare the experimental values with two models which are based on hydraulic radius theory and drag theory, respectively. The air permeability of the samples was measured by an air permeability tester FX3300. The results showed that the air permeability of non-woven fabrics decreased with the increase in thickness and density of samples, increased with the increase of porosity, and the air permeability was not directly proportional to the pressure gradient. Meanwhile, the prediction model based on hydraulic radius theory had a better agreement with experimental values than the model based on drag theory, but the values were much higher than the experimental results, especially for higher porosity and higher pressure gradient.
Random functions and turbulence
Panchev, S
1971-01-01
International Series of Monographs in Natural Philosophy, Volume 32: Random Functions and Turbulence focuses on the use of random functions as mathematical methods. The manuscript first offers information on the elements of the theory of random functions. Topics include determination of statistical moments by characteristic functions; functional transformations of random variables; multidimensional random variables with spherical symmetry; and random variables and distribution functions. The book then discusses random processes and random fields, including stationarity and ergodicity of random
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Márcia Regina Vitolo
2014-12-01
Full Text Available OBJECTIVE: To assess the impact of a child feeding training program for primary care health professionals about breastfeeding and complementary feeding practices. METHODS: Cluster-randomized field trial conducted in the city of Porto Alegre, (RS, Brazil. Twenty primary health care centers (HCC were randomized into intervention (n = 9 and control (n = 11 groups. The health professionals (n = 200 at the intervention group centers received training about healthy feeding practices. Pregnant women were enrolled at the study. Up to six months of child's age, home visits were made to obtain variables related to breastfeeding and introduction of foods. RESULTS: 619 children were evaluated: 318 from the intervention group and 301 from the control group. Exclusive breastfeeding prevalence in the first (72.3 versus 59.4%; RR = 1.21; 95%CI 1.08 - 1.38, second (62.6 versus 48.2%; RR = 1.29; 95%CI 1.10 - 1.53, and third months of life (44.0% versus 34.6%; RR = 1.27; 95%CI 1.04 - 1.56 was higher in the intervention group compared to the control group. The prevalence of children who consumed meat four or five times per week was higher in the intervention group than in the control group (36.8 versus 22.6%; RR = 1.62; 95%CI 1.32 - 2.03. The prevalence of children who had consumed soft drinks (34.9 versus 52.5%; RR = 0.66; 95%CI 0.54 - 0.80, chocolate (24.5 versus 36.7% RR = 0.66 95%CI 0.53 - 0.83, petit suisse (68.9 versus 79.7; 95%CI 0.75 - 0.98 and coffee (10.4 versus 20.1%; RR = 0.51; 95%CI 0.31 - 0.85 in their six first months of life was lower in the intervention group. CONCLUSION: The training of health professionals had a positive impact on infant feeding practices, contributing to the promotion of child health.
Vitolo, Márcia Regina; Louzada, Maria Laura da Costa; Rauber, Fernanda
2014-12-01
To assess the impact of a child feeding training program for primary care health professionals about breastfeeding and complementary feeding practices. Cluster-randomized field trial conducted in the city of Porto Alegre, (RS), Brazil. Twenty primary health care centers (HCC) were randomized into intervention (n = 9) and control (n = 11) groups. The health professionals (n = 200) at the intervention group centers received training about healthy feeding practices. Pregnant women were enrolled at the study. Up to six months of child's age, home visits were made to obtain variables related to breastfeeding and introduction of foods. 619 children were evaluated: 318 from the intervention group and 301 from the control group. Exclusive breastfeeding prevalence in the first (72.3 versus 59.4%; RR = 1.21; 95%CI 1.08 - 1.38), second (62.6 versus 48.2%; RR = 1.29; 95%CI 1.10 - 1.53), and third months of life (44.0% versus 34.6%; RR = 1.27; 95%CI 1.04 - 1.56) was higher in the intervention group compared to the control group. The prevalence of children who consumed meat four or five times per week was higher in the intervention group than in the control group (36.8 versus 22.6%; RR = 1.62; 95%CI 1.32 - 2.03). The prevalence of children who had consumed soft drinks (34.9 versus 52.5%; RR = 0.66; 95%CI 0.54 - 0.80), chocolate (24.5 versus 36.7% RR = 0.66 95%CI 0.53 - 0.83), petit suisse (68.9 versus 79.7; 95%CI 0.75 - 0.98) and coffee (10.4 versus 20.1%; RR = 0.51; 95%CI 0.31 - 0.85) in their six first months of life was lower in the intervention group. The training of health professionals had a positive impact on infant feeding practices, contributing to the promotion of child health.
Karimaghaloo, Zahra; Arnold, Douglas L; Arbel, Tal
2016-01-01
Detection and segmentation of large structures in an image or within a region of interest have received great attention in the medical image processing domains. However, the problem of small pathology detection and segmentation still remains an unresolved challenge due to the small size of these pathologies, their low contrast and variable position, shape and texture. In many contexts, early detection of these pathologies is critical in diagnosis and assessing the outcome of treatment. In this paper, we propose a probabilistic Adaptive Multi-level Conditional Random Fields (AMCRF) with the incorporation of higher order cliques for detecting and segmenting such pathologies. In the first level of our graphical model, a voxel-based CRF is used to identify candidate lesions. In the second level, in order to further remove falsely detected regions, a new CRF is developed that incorporates higher order textural features, which are invariant to rotation and local intensity distortions. At this level, higher order textures are considered together with the voxel-wise cliques to refine boundaries and is therefore adaptive. The proposed algorithm is tested in the context of detecting enhancing Multiple Sclerosis (MS) lesions in brain MRI, where the problem is further complicated as many of the enhancing voxels are associated with normal structures (i.e. blood vessels) or noise in the MRI. The algorithm is trained and tested on large multi-center clinical trials from Relapsing-Remitting MS patients. The effect of several different parameter learning and inference techniques is further investigated. When tested on 120 cases, the proposed method reaches a lesion detection rate of 90%, with very few false positive lesion counts on average, ranging from 0.17 for very small (3-5 voxels) to 0 for very large (50+ voxels) regions. The proposed model is further tested on a very large clinical trial containing 2770 scans where a high sensitivity of 91% with an average false positive
Vascular permeability in cerebral cavernous malformations.
Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik B W; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A
2015-10-01
Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy.
Vascular permeability in cerebral cavernous malformations
Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik BW; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A
2015-01-01
Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy. PMID:25966944
Directory of Open Access Journals (Sweden)
Dalia M. Kamel
2017-01-01
Full Text Available The aim of this study was to compare the effects of pulsed electromagnetic field versus pulsed ultrasound in treating patients with postnatal carpal tunnel syndrome. The study was a randomized, double-blinded trial. Forty postnatal female patients with idiopathic carpal tunnel syndrome were divided randomly into two equal groups. One group received pulsed electromagnetic field, with nerve and tendon gliding exercises for the wrist, three times per week for four weeks. The other group received pulsed ultrasound and the same wrist exercises. Pain level, sensory and motor distal latencies and conduction velocities of the median nerve, functional status scale and hand grip strength were assessed pre- and post-treatment. There was a significant decrease (P 0.05. In conclusion, while the symptoms were alleviated in both groups, pulsed electromagnetic field was more effective than pulsed ultrasound in treating postnatal carpal tunnel syndrome.
Indio, Valentina; Martelli, Pier Luigi; Savojardo, Castrense; Fariselli, Piero; Casadio, Rita
2013-04-15
Targeting peptides are the most important signal controlling the import of nuclear encoded proteins into mitochondria and plastids. In the lack of experimental information, their prediction is an essential step when proteomes are annotated for inferring both the localization and the sequence of mature proteins. We developed TPpred a new predictor of organelle-targeting peptides based on Grammatical-Restrained Hidden Conditional Random Fields. TPpred is trained on a non-redundant dataset of proteins where the presence of a target peptide was experimentally validated, comprising 297 sequences. When tested on the 297 positive and some other 8010 negative examples, TPpred outperformed available methods in both accuracy and Matthews correlation index (96% and 0.58, respectively). Given its very low-false-positive rate (3.0%), TPpred is, therefore, well suited for large-scale analyses at the proteome level. We predicted that from ∼4 to 9% of the sequences of human, Arabidopsis thaliana and yeast proteomes contain targeting peptides and are, therefore, likely to be localized in mitochondria and plastids. TPpred predictions correlate to a good extent with the experimental annotation of the subcellular localization, when available. TPpred was also trained and tested to predict the cleavage site of the organelle-targeting peptide: on this task, the average error of TPpred on mitochondrial and plastidic proteins is 7 and 15 residues, respectively. This value is lower than the error reported by other methods currently available. The TPpred datasets are available at http://biocomp.unibo.it/valentina/TPpred/. TPpred is available on request from the authors. Supplementary data are available at Bioinformatics online.
Ozgüçlü, Erkan; Cetin, Alp; Cetin, Meral; Calp, Emel
2010-08-01
The aim of this study was to evaluate if pulsed electromagnetic field therapy (PEMF) has additional effect on the classical physical treatment of knee osteoarthritis (OA) composed of hot pack, therapeutic ultrasound, and terminal isometric exercises. Forty patients (29 women and 11 men), ages 44 to 78 (mean age was 61.3 +/- 7.8 years) were included in our study. Patients with knee osteoarthritis [Kellgren-Lawrence criteria grade 2 and above and an average pain intensity of 40 or more on a 100-mm visual analog scale (VAS)] recruited from outpatient physical medicine and rehabilitation clinic were randomly assigned to receive PEMF or sham PEMF treatment in addition to their physical therapy. Both the PEMF and sham PEMF treatments being evaluated were 55 min/session, five sessions per week for 2 weeks. Each session comprise 20-min hot pack, 5-min therapeutic ultrasound, and 30-min PEMF or sham PEMF treatment applied to the knee of the patients. Patients were evaluated by the Western Ontario and McMasters Universities Osteoarthritis (WOMAC) Index and VAS at the baseline and at the end of treatment. Both PEMF and sham PEMF treatment groups showed statistically significant improvement in WOMAC pain and functional scores at the end of treatment (p < 0.001 in both groups). There were no statistically significant differences between groups in WOMAC pain, stiffness, and physical function scores after treatment (p = 0.906, p = 0.855, p = 0.809, respectively). There was neither difference in concomitant used acetaminophen dose in both groups (p = 0.289). The results of this study show that PEMF does not have additional effect on the classical physical treatment in reducing symptoms of knee OA.
Energy Technology Data Exchange (ETDEWEB)
Lamotte, T.; Dinten, J.M. [CEA Grenoble (DTBS/STD), Lab. d' Electronique et de Technologie de l' Informatique, LETI, 38 (France); Peyrin, F. [Institut National des Sciences Appliquees (INSA), CREATIS, UMR CNRS 5515, inserm U630, 69 - Villeurbanne (France)
2004-07-01
Imaging trabecular bone micro-architecture in vivo non-invasively is still a challenging issue due to the complexity and small size of the structure. Thus, having a realistic 3D model of bone micro-architecture could be useful in image segmentation or image reconstruction. The goal of this work was to develop a 3D model of trabecular bone micro-architecture which can be seen as a problem of texture synthesis. We investigated a statistical model based on 3D Markov Random Fields (MRF's). Due to the Hammersley-Clifford theorem MRF's may equivalently be defined by an energy function on some set of cliques. In order to model 3D binary bone texture images (bone / background), we first used a particular well-known subclass of MRFs: the Ising model. The local energy function at some voxel depends on the closest neighbors of the voxels and on some parameters which control the shape and the proportion of bone. However, simulations yielded textures organized as connected clusters which even when varying the parameters did not approach the complexity of bone micro-architecture. Then, we introduced a second level of cliques taking into account neighbors located at some distance d from the site s and a new set of cliques allowing to control the plate thickness and spacing. The 3D bone texture images generated using the proposed model were analyzed using the usual bone-architecture quantification tools in order to relate the parameters of the MRF model to the characteristic parameters of bone micro-architecture (trabecular spacing, trabecular thickness, number of trabeculae...). (authors)
Al Otaiba, Stephanie; Connor, Carol M; Folsom, Jessica Sidler; Greulich, Luana; Meadows, Jane; Li, Zhi
2011-06-01
The purpose of this cluster-randomized control field trial was to was to examine the extent to which kindergarten teachers could learn a promising instructional strategy, wherein kindergarten reading instruction was differentiated based upon students' ongoing assessments of language and literacy skills and documented child characteristic by instruction (CXI) interactions; and to test the efficacy of this differentiated reading instruction on the reading outcomes of students from culturally diverse backgrounds. The study involved 14 schools and included 23 treatment ( n = 305 students) and 21 contrast teacher ( n = 251 students). Teachers in the contrast condition received only a baseline professional development that included a researcher-delivered summer day-long workshop on individualized instruction. Data sources included parent surveys, individually administered child assessments of language, cognitive, and reading skills and videotapes of classroom instruction. Using Hierarchical Multivariate Linear Modeling (HMLM), we found students in treatment classrooms outperformed students in the contrast classrooms on a latent measure of reading skills, comprised of letter-word reading, decoding, alphabetic knowledge, and phonological awareness (ES = .52). Teachers in both conditions provided small group instruction, but teachers in the treatment condition provided significantly more individualized instruction. Our findings extend research on the efficacy of teachers using Individualized Student Instruction to individualize instruction based upon students' language and literacy skills in first through third grade. Findings are discussed regarding the value of professional development related to differentiating core reading instruction and the challenges of using Response to Intervention approaches to address students' needs in the areas of reading in general education contexts.
Al Otaiba, Stephanie; Connor, Carol M; Folsom, Jessica Sidler; Greulich, Luana; Meadows, Jane; Li, Zhi
2010-01-01
The purpose of this cluster-randomized control field trial was to was to examine the extent to which kindergarten teachers could learn a promising instructional strategy, wherein kindergarten reading instruction was differentiated based upon students’ ongoing assessments of language and literacy skills and documented child characteristic by instruction (CXI) interactions; and to test the efficacy of this differentiated reading instruction on the reading outcomes of students from culturally diverse backgrounds. The study involved 14 schools and included 23 treatment (n = 305 students) and 21 contrast teacher (n = 251 students). Teachers in the contrast condition received only a baseline professional development that included a researcher-delivered summer day-long workshop on individualized instruction. Data sources included parent surveys, individually administered child assessments of language, cognitive, and reading skills and videotapes of classroom instruction. Using Hierarchical Multivariate Linear Modeling (HMLM), we found students in treatment classrooms outperformed students in the contrast classrooms on a latent measure of reading skills, comprised of letter-word reading, decoding, alphabetic knowledge, and phonological awareness (ES = .52). Teachers in both conditions provided small group instruction, but teachers in the treatment condition provided significantly more individualized instruction. Our findings extend research on the efficacy of teachers using Individualized Student Instruction to individualize instruction based upon students’ language and literacy skills in first through third grade. Findings are discussed regarding the value of professional development related to differentiating core reading instruction and the challenges of using Response to Intervention approaches to address students’ needs in the areas of reading in general education contexts. PMID:21818158
Shaw, S.; Sutradhar, A.; Murthy, PVSN
2017-05-01
In the present paper, we investigated the influence of permeability of the carrier particle and stress jump condition on the porous spherical surface in magnetic drug targeting through a permeable microvessel. The nature of blood is defined by non-Newtonian Casson fluid in the core region of the microvessel and Newtonian fluid in the peripheral region which is located near the surface of the wall of the microvessel. The magnetic particles are considered as spherical and in nanosize, embedded in the carrier particle along with drug particles. A magnet is placed near the tumor position to generate a magnetic field. The relative motion of the carrier particle is the resultant of the fluidic force, magnetic force and Saffman drag force which are calculated for the spherical carrier particle. Trajectories of the carrier particle along the radial and axial direction are calculated. Effect of different parameters such as stress-jump constant, permeability of the carrier particle, pressure gradient, yield stress, Saffman force, volume fraction of the embedded magnetic nanoparticles, permeability of the microvessel wall, and the radius of the carrier particle on the trajectory of the carrier particle are discussed and displayed graphically.
Gyroid Nanoporous Membranes with Tunable Permeability
DEFF Research Database (Denmark)
Li, Li; Schulte, Lars; Clausen, Lydia D.
2011-01-01
Understanding the relevant permeability properties of ultrafiltration membranes is facilitated by using materials and procedures that allow a high degree of control on morphology and chemical composition. Here we present the first study on diffusion permeability through gyroid nanoporous cross-linked...
Alterations in Intestinal Permeability After Thermal Injury,
1992-01-01
Permeability After Burns-LeVoyer et al R wthe Arrihtv.of Su~gy8 4• u’y 1992, Voue 127 Copright 1992. Akn • Med/kaf Awoctahbn Patlenbs Controls 4. (n-=1...may have a role in the tinal tract is enteral nutrition . I was wondering if by any chance development of increased permeability, then we can evaluate
Pressure sensitivity of low permeability sandstones
Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.
1987-01-01
Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.
Intercomparison on measurement of water vapour permeability
DEFF Research Database (Denmark)
Hansen, Kurt Kielsgaard
Three different materials are tested - hard woodfibre board - damp proof course - underlay for roofing The water vapour permeability has been measured according to EN ISO 12572 (2001).......Three different materials are tested - hard woodfibre board - damp proof course - underlay for roofing The water vapour permeability has been measured according to EN ISO 12572 (2001)....
A Negative Permeability Material at Red Light
DEFF Research Database (Denmark)
Yuan, Hsiao-Kuan; Chettiar, Uday K.; Cai, Wenshan
2007-01-01
A negative permeability in a periodic array of pairs of thin silver strips is demonstrated experimentally for two distinct samples. The effect of the strip surface roughness on negative permeability is evaluated. The first sample, Sample A, is fabricated of thinner strips with a root mean square ...
Crustal permeability: Introduction to the special issue
Ingebritsen, Steven E.; Gleeson, Tom
2015-01-01
The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.
Lopez-Dominguez, V.; Garcia, M. A.; Marin, P.; Hernando, A.
2017-12-01
We present here a new free space method to measure the magnetic permeability of a single amorphous magnetic microwire (AMM) at microwave frequencies. The technique consists in inducing a high frequency electric current along the AMM axis by illumination with an electromagnetic wave at antenna resonance conditions. Fitting the induced electric current to the Hallen-Pocklington equation allows computing the relative magnetic permeability of the microwire as a function of the wave frequency. The method results particularly useful for the study of the giant magnetoimpedance effect of AMM by measuring the magnetic permeability upon the application of DC magnetic fields.
Microorganism Removal in Permeable Pavement Parking Lots ...
Three types of permeable pavements (pervious concrete, permeable interlocking concrete pavers, and porous asphalt) were monitored at the Edison Environmental Center in Edison, New Jersey for indicator organisms such as fecal coliform, enterococci, and E. coli. Results showed that porous asphalt had much lower concentration in monitored infiltrate compared to pervious concrete and permeable interlocking concrete pavers. Concentrations of monitored organisms in infiltrate from porous asphalt were consistently below the bathing water quality standard. Fecal coliform and enterococci exceeded bathing water quality standards more than 72% and 34% of the time for permeable interlocking concrete pavers and pervious concrete, respectively. Purpose is to evaluate the performance of permeable pavement in removing indicator organisms from infiltrating stormwater runoff.
Modelling of water permeability in cementitious materials
DEFF Research Database (Denmark)
Guang, Ye; Lura, Pietro; van Breugel, K.
2006-01-01
This paper presents a network model to predict the permeability of cement paste from a numerical simulation of its microstructure. Based on a linked list pore network structure, the effective hydraulic conductivity is estimated and the fluid flow is calculated according to the Hagen-Poiseuille law....... The pressure gradient at all nodes is calculated with the Gauss elimination method and the absolute permeability of the pore network is calculated directly from Darcy's law. Finally, the permeability model is validated by comparison with direct water permeability measurements. According to this model...... and by the connectivity of the pore structure, regardless of w/c ratio and curing age. The permeability of cement pastes could be predicted reasonably well when a minimum particle size 1 mu m was chosen for the cement....
Vascular permeability in cerebral cavernous malformations
DEFF Research Database (Denmark)
Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao
2015-01-01
-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability...... vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy....... correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive...
Directory of Open Access Journals (Sweden)
Hao-Jiang Yang
2013-07-01
Full Text Available AIM: To evaluate the outcome of high oxygen permeable contact lens used after photorefractive keratectomy(PRKsurgery.METHODS: Totally 95 patients(190 eyesafter PRK were included. Patients were randomly assigned to wear high oxygen permeable contact lens in one eye and normal lens in the fellow eye after surgery. The subjective symptoms and corneal epithelial status after PRK were evaluated. Uncorrected visual acuity(UCVAand haze were assessed at 6 months after PRK.RESULTS: Complaints of blurred vision, pain and photophobia were statistically more among the normal lens group than high oxygen permeable contact lens group(PPP=0.35. There was no difference in UCVA and haze 6 months after surgery(P=0.55. CONCLUSION: High oxygen permeable contact lens can significantly produce less the corneal irritated symptoms, reduce the discomfort feeling and promote healing of corneal epithelium after PRK.
Gas and Water Permeability of Concrete
Energy Technology Data Exchange (ETDEWEB)
Villar, M. V.; Martin, P. L.; Romero, F. J.; Gutierrez-Rodirgo, V.; Barcala, J. M.
2012-11-01
The gas pressure of concrete samples was measured in an unsteady-state equipment working under low injection pressures and in a newly fine tuned steady-state setup working under different pressures. These measurements allowed the estimation of the intrinsic and relative gas permeability of the concrete and of the effect of boundary conditions on them. Permeability decreased with water content, but it was also greatly affected by the hydraulic history of concrete, i.e. if it had been previously dried or wetted. In particular, and for a given degree of saturation, the gas permeability of concrete previously saturated was lower than if the concrete had been just air dried or saturated after air drying. In any case, the gas permeability was about two orders of magnitude higher than the liquid water permeability (10-16 vs. 10-18 m2), probably due to the chemical reactions taking place during saturation (carbonation). The relative gas permeability of concrete increased sharply for water degrees of saturation smaller than 50%. The boundary conditions also affected the gas permeability, which seemed to be mostly conditioned by the back pressure and the confining pressure, increasing as the former increased and decreasing as the latter increased, i.e. decreasing as the effective pressure increased. Overall the increase of pressure head or injection pressure implied a decrease in gas permeability. External,microcracking during air-drying could not be ruled out as responsible for the decrease of permeability with confining pressure. The apparent permeability obtained applying the Klinkenberg method for a given effective pressure was only slightly smaller than the average of all the values measured for the same confining pressure range. For this reason it is considered that the Klinkenberg effect was not relevant in the range of pressures applied. (Author) 37 refs.
Connectivity, formation factor and permeability of 2D fracture network
Tang, Y. B.; Li, M.; Li, X. F.
2017-10-01
The purpose of this paper is to investigate the effects of fracture connectivity and length distributions on the electrical formation factor, F, of random fracture network using percolation theory. We assumed that the matrix was homogeneous and low-permeable, but the connectivity and length distributions of fracture system were randomly variable. F of fracture network is analyzed via finite element method. The main result is that: different from the classical percolation ;universal; power law for porous-type rocks, F of fracture network obeys a normalized ;universal; scaling relation using the length-scale / L ( is fracture mean length, and L is the domain size). Our proposed formation factor model, derived from the normalized ;universal; scaling relationship, is valid in fracture network with constant fracture length and length distributions, showing that the normalized ;universal; scaling law is independent of fracture patterns. The normalized scaling relation is also successfully used to derive the permeability model of 2D random fracture network using the previously published dataset, which obtained better fitting results than before.
Flow of a Newtonian fluid in a non-uniform wavy and permeable tube
Directory of Open Access Journals (Sweden)
Tesfahun Berhane
2017-10-01
equations of motion are linearized by perturbation method by assuming ? (ratio of inlet width to wavelength as a small parameter and the resulting equations are solved by numerical methods. The effects of permeability parameter (?, slope parameter (k, slip coefficient (? and Reynolds number (Re on the velocity profiles, pressure and ?ow rate are presented graphically. Results concerning the velocity, pressure and flow rate, indicate that the slip and permeability parameters influence the flow field significantly. Discussions are made from physiological point of view.
Directory of Open Access Journals (Sweden)
Jaewook Jung
2016-12-01
Full Text Available Railways have been used as one of the most crucial means of transportation in public mobility and economic development. For safe railway operation, the electrification system in the railway infrastructure, which supplies electric power to trains, is an essential facility for stable train operation. Due to its important role, the electrification system needs to be rigorously and regularly inspected and managed. This paper presents a supervised learning method to classify Mobile Laser Scanning (MLS data into ten target classes representing overhead wires, movable brackets and poles, which are key objects in the electrification system. In general, the layout of the railway electrification system shows strong spatial regularity relations among object classes. The proposed classifier is developed based on Conditional Random Field (CRF, which characterizes not only labeling homogeneity at short range, but also the layout compatibility between different object classes at long range in the probabilistic graphical model. This multi-range CRF model consists of a unary term and three pairwise contextual terms. In order to gain computational efficiency, MLS point clouds are converted into a set of line segments to which the labeling process is applied. Support Vector Machine (SVM is used as a local classifier considering only node features for producing the unary potentials of the CRF model. As the short-range pairwise contextual term, the Potts model is applied to enforce a local smoothness in the short-range graph; while long-range pairwise potentials are designed to enhance the spatial regularities of both horizontal and vertical layouts among railway objects. We formulate two long-range pairwise potentials as the log posterior probability obtained by the naive Bayes classifier. The directional layout compatibilities are characterized in probability look-up tables, which represent the co-occurrence rate of spatial relations in the horizontal and vertical
Wang, Hui; Wellmann, Florian; Verweij, Elizabeth; von Hebel, Christian; van der Kruk, Jan
2017-04-01
Lateral and vertical spatial heterogeneity of subsurface properties such as soil texture and structure influences the available water and resource supply for crop growth. High-resolution mapping of subsurface structures using non-invasive geo-referenced geophysical measurements, like electromagnetic induction (EMI), enables a characterization of 3D soil structures, which have shown correlations to remote sensing information of the crop states. The benefit of EMI is that it can return 3D subsurface information, however the spatial dimensions are limited due to the labor intensive measurement procedure. Although active and passive sensors mounted on air- or space-borne platforms return 2D images, they have much larger spatial dimensions. Combining both approaches provides us with a potential pathway to extend the detailed 3D geophysical information to a larger area by using remote sensing information. In this study, we aim at extracting and providing insights into the spatial and statistical correlation of the geophysical and remote sensing observations of the soil/vegetation continuum system. To this end, two key points need to be addressed: 1) how to detect and recognize the geometric patterns (i.e., spatial heterogeneity) from multiple data sets, and 2) how to quantitatively describe the statistical correlation between remote sensing information and geophysical measurements. In the current study, the spatial domain is restricted to shallow depths up to 3 meters, and the geostatistical database contains normalized difference vegetation index (NDVI) derived from RapidEye satellite images and apparent electrical conductivities (ECa) measured from multi-receiver EMI sensors for nine depths of exploration ranging from 0-2.7 m. The integrated data sets are mapped into both the physical space (i.e. the spatial domain) and feature space (i.e. a two-dimensional space framed by the NDVI and the ECa data). Hidden Markov Random Fields (HMRF) are employed to model the
Energy Technology Data Exchange (ETDEWEB)
Shaw, S., E-mail: sachinshaw@gmail.com [Department of Mathematics and Statistical Sciences, Botswana International University of Science and Technology, Private Bag 16, Palapye (Botswana); Sutradhar, A.; Murthy, PVSN [Department of Mathematics, Indian Institute of Technology Kharagpur, Kharagpur 721302, West Bengal (India)
2017-05-01
In the present paper, we investigated the influence of permeability of the carrier particle and stress jump condition on the porous spherical surface in magnetic drug targeting through a permeable microvessel. The nature of blood is defined by non-Newtonian Casson fluid in the core region of the microvessel and Newtonian fluid in the peripheral region which is located near the surface of the wall of the microvessel. The magnetic particles are considered as spherical and in nanosize, embedded in the carrier particle along with drug particles. A magnet is placed near the tumor position to generate a magnetic field. The relative motion of the carrier particle is the resultant of the fluidic force, magnetic force and Saffman drag force which are calculated for the spherical carrier particle. Trajectories of the carrier particle along the radial and axial direction are calculated. Effect of different parameters such as stress-jump constant, permeability of the carrier particle, pressure gradient, yield stress, Saffman force, volume fraction of the embedded magnetic nanoparticles, permeability of the microvessel wall, and the radius of the carrier particle on the trajectory of the carrier particle are discussed and displayed graphically. - Highlights: • In the present manuscript, we considered the porous carrier particle which provide a larger surface area contact with the fluid than the solid spherical carrier particle. It shows that the porous carrier particle are captured easily than the solid carrier particle. • Introduce Suffman force on the carrier particle which commences an additional resistance which acts opposite to the surface wall and helps the particles to go away from the tumor position. • Considered stress jump condition at the surface of the porous carrier particle which enhanced the tendency of the carrier particle to be capture near the tumor. • Used Darcy model to define the permeability of the wall of the microvessel.
Permeability estimation from inflow data during underbalanced drilling
Energy Technology Data Exchange (ETDEWEB)
Farshidi, S.; Mattar, L. [Fekete Associates Inc., Calgary, AB (Canada); Yu, F. [Calgary Univ., AB (Canada); Slade, J. [EnCana Corp., Calgary, AB (Canada); Pooladi-Darvish, M. [Fekete Associates Inc., Calgary, AB (Canada)]|[Calgary Univ., AB (Canada)
2007-07-01
Underbalanced drilling is often used to prevent fluid invasion during drilling operations. Inflow from the reservoir into the wellbore is continuously measured at the wellhead during underbalanced drilling operations. This paper provided details of a mathematical model designed to estimate reservoir permeability along the wellbore using inflow measurements at the wellhead. The model accounted for the fact that producing intervals continuously increase with time. The reservoir was horizontal, isotropic and heterogeneous, with a constant thickness and porosity, and an infinite lateral extension. Radial flow in the vertical plane was neglected. Flow was 1-D and perpendicular to the wellbore. Bottomhole pressure was constant, and a mechanical skin of zero was assumed. A 1-D diffusivity equation was used to describe the instantaneous single phase flow of gas. The model was validated using data obtained from previous simulations and applied to a number of field cases. Estimated permeability values from field studies were used along with reported downhole pressure to calculate gas inflow. Gas inflow was then compared with total measured inflow. Results of the evaluation showed that good agreement was obtained between the measured and predicted inflow values. Sensitivity analyses conducted to investigate sensitivity errors in reported information showed that the estimated permeability profile remained comparatively unchanged. 10 refs., 1 tab., 9 figs.
Fluid flow and permeabilities in basement fault zones
Hollinsworth, Allan; Koehn, Daniel
2017-04-01
Fault zones are important sites for crustal fluid flow, specifically where they cross-cut low permeability host rocks such as granites and gneisses. Fluids migrating through fault zones can cause rheology changes, mineral precipitation and pore space closure, and may alter the physical and chemical properties of the host rock and deformation products. It is therefore essential to consider the evolution of permeability in fault zones at a range of pressure-temperature conditions to understand fluid migration throughout a fault's history, and how fluid-rock interaction modifies permeability and rheological characteristics. Field localities in the Rwenzori Mountains, western Uganda and the Outer Hebrides, north-west Scotland, have been selected for field work and sample collection. Here Archaean-age TTG gneisses have been faulted within the upper 15km of the crust and have experienced fluid ingress. The Rwenzori Mountains are an anomalously uplifted horst-block located in a transfer zone in the western rift of the East African Rift System. The north-western ridge is characterised by a tectonically simple western flank, where the partially mineralised Bwamba Fault has detached from the Congo craton. Mineralisation is associated with hydrothermal fluids heated by a thermal body beneath the Semliki rift, and has resulted in substantial iron oxide precipitation within porous cataclasites. Non-mineralised faults further north contain foliated gouges and show evidence of leaking fluids. These faults serve as an analogue for faults associated with the Lake Albert oil and gas prospects. The Outer Hebrides Fault Zone (OHFZ) was largely active during the Caledonian Orogeny (ca. 430-400 Ma) at a deeper crustal level than the Ugandan rift faults. Initial dry conditions were followed by fluid ingress during deformation that controlled its rheological behaviour. The transition also altered the existing permeability. The OHFZ is a natural laboratory in which to study brittle fault
Upscaling of permeability in Shale with Heterogeneous Kerogen Distribution
Cao, G.; Lin, M.
2016-12-01
Apparent permeability is a vital parameter for accurate estimation of exploitable gas reserve in shale. In this paper, we introduce a new model to investigate multi-scale gas-transport phenomena in organic-rich-shale with heterogeneous kerogen distribution. The formulation is decomposed into two subdomains: kerogen and inorganic matrix. On the one hand, considering the molecular phenomena (slip and diffusive transport) is significant in kerogen for its enrichment of nanopores, we use pore-scale network model (PNM) to represent it and apply Javadpour's apparent permeability formula(2009) to calculate flow in the nanoscale throats. On the other hand, inorganic matrix, with relatively large pores, micro natural fractures and manual hydraulic fracturing cracks, its flow is approximate to Darcy, so we model it as continuum-scale models FVM. The two subdomains are coupled using mortars. Mortars are finite-element spaces employed to couple independent subdomains by ensuring interfacial pressures and fluxes are matched. Considering the local heterogeneities, kerogen is treated as several nanoporous organic material blocks randomly dispersed within the inorganic matrix. We study on four factors: the distribution of kerogen, the permeability of inorganic matrix (Ki), the magnitude of pressure, and the TOC of coupling model. The results are shown intuitively by APF (apparent permeability function) graph. We conclude that: (1) when Ki is greater than the Darcy permeability of kerogen, the APF graphs with different TOC and distribution have an intersection point, and this point is only decided by permeability of Ki and the pore size distribution of kerogen; (2) when pressure is close to or higher than the pressure of intersection point, the influence of heterogeneous distribution can be ignored, and the complex coupling model can instead by a simple equivalent model. This work is supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB
Thermal treatment of low permeability soils using electrical resistance heating
Energy Technology Data Exchange (ETDEWEB)
Udell, K.S. [Univ. of California, Berkeley, CA (United States)
1996-08-01
The acceleration of recovery rates of second phase liquid contaminants from the subsurface during gas or water pumping operations is realized by increasing the soil and ground water temperature. Electrical heating with AC current is one method of increasing the soil and groundwater temperature and has particular applicability to low permeability soils. Several mechanisms have been identified that account for the enhanced removal of the contaminants during electrical heating. These are vaporization of liquid contaminants with low boiling points, temperature-enhanced evaporation rates of semi-volatile components, and removal of residual contaminants by the boiling of residual water. Field scale studies of electrical heating and fluid extraction show the effectiveness of this technique and its applicability to contaminants found both above and below the water table and within low permeability soils. 10 refs., 8 figs.
Directory of Open Access Journals (Sweden)
Mitsuru Itoh, Toshirou Yagi, Yoshiaki Uesu, Wolfgang Kleemann and Robert Blinc
2004-01-01
Full Text Available The oxygen isotope exchange of 16O by 18O in SrTiO3 causes a drastic change from paraelectric to ferroelectric, due to the suppression of quantum fluctuation. The phase transition and origin of the huge domain wall response were evaluated by dielectric, magnetic (NMR, and optical measurements (SHG, light scattering. The results obtained corroborate (1 smeared ferroelectric transition at Tc due to quenched random field, (2 a quite large dielectric contribution from domain walls, (3 incomplete softening of the transverse optic mode, and (4 a large contribution from the relaxational mode to the phase transition. Quantitative explanations, given to individual results, may give hints to grasp the mechanism for the evolution of ferroelectricity, in which quantum fluctuation and random fields are dominant perturbations. Finally, some of the news studies on the SrTiO3 were also introduced.
Energy Technology Data Exchange (ETDEWEB)
Boor, S.; Huebner, S. [KBB Underground Technologies GmbH, Hannover (Germany); Schweinsberg, H.J. [IVG Logistik GmbH, Bonn (Germany); Tryller, H. von [SOCON, Giessen (Germany)
2007-09-13
In the course of restructuring and extension measures in the Etzel cavern field, IVG Logistik GmbH has been retrofitting oil storage caverns into gas storage caverns since November 2005. Before completion can be started, gastightness of all wells had to be checked. This was done, for the first time, using the SoMIT (Sonar Mechanical Integrity Testing) process in which the level is gauged continuously by an ultrasonic probe. This method is more accurate by about a power of ten than the conventional gamma-gamma probe. Further, continuous measurement enables in-time evaluation of trends. As IVG had good results with the conventional test method in Etzel cavern field, the higher accuracy of the SoMIT method was used for shortening the test time and achieving a cost reduction. SoMIT also has operative advantages. For example, there are no repeated measurements which would require resetting of the probe to the reference depth and might also cause measuring errors. Further, the measurements are not influenced by oil residues in the cavern as the ultrasonic probe is used above the fluid level. (orig.)
Changes in Permeability Produced By Distant Earthquakes
Manga, M.; Wang, C. Y.; Shi, Z.
2014-12-01
Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10-6 can increase discharge in streams and springs, change the water level of wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to pre-stimulated values over a period of months to years. This presentation will review some of the observations that indicate that dynamic stresses produced by seismic waves change permeability. We use the response of a set of wells distributed throughout China to multiple large earthquakes to probe the relationship between earthquake-generated stresses and water-level changes in wells. We find that dynamic stresses dominate the responses at distances more than 1 fault length from the earthquake and that permeability changes may explain the water level changes. Regions with high deformation rates are most sensitive to seismic waves. We also consider the response of a large alluvial fan in Taiwan to the 1999 M7.5 Chi-Chi earthquake where there were sustained changes in groundwater temperature after the earthquake. Using groundwater flow models, we infer that permeability increased by an order of magnitude over horizontal scales of tens of km, and vertical scales of several km. Permeability returned to the pre-earthquake value over many months. As much as half the total transport in the fan occurs during the short time periods with enhanced permeability.
Osorio-Murillo, C. A.; Over, M. W.; Frystacky, H.; Ames, D. P.; Rubin, Y.
2013-12-01
A new software application called MAD# has been coupled with the HTCondor high throughput computing system to aid scientists and educators with the characterization of spatial random fields and enable understanding the spatial distribution of parameters used in hydrogeologic and related modeling. MAD# is an open source desktop software application used to characterize spatial random fields using direct and indirect information through Bayesian inverse modeling technique called the Method of Anchored Distributions (MAD). MAD relates indirect information with a target spatial random field via a forward simulation model. MAD# executes inverse process running the forward model multiple times to transfer information from indirect information to the target variable. MAD# uses two parallelization profiles according to computational resources available: one computer with multiple cores and multiple computers - multiple cores through HTCondor. HTCondor is a system that manages a cluster of desktop computers for submits serial or parallel jobs using scheduling policies, resources monitoring, job queuing mechanism. This poster will show how MAD# reduces the time execution of the characterization of random fields using these two parallel approaches in different case studies. A test of the approach was conducted using 1D problem with 400 cells to characterize saturated conductivity, residual water content, and shape parameters of the Mualem-van Genuchten model in four materials via the HYDRUS model. The number of simulations evaluated in the inversion was 10 million. Using the one computer approach (eight cores) were evaluated 100,000 simulations in 12 hours (10 million - 1200 hours approximately). In the evaluation on HTCondor, 32 desktop computers (132 cores) were used, with a processing time of 60 hours non-continuous in five days. HTCondor reduced the processing time for uncertainty characterization by a factor of 20 (1200 hours reduced to 60 hours.)
DEFF Research Database (Denmark)
Skibsted, U.; Baggesen, Dorte Lau; Dessau, R.
1998-01-01
Isolates of Salmonella Enteritidis from 81 patients from Herlev Hospital or from Copenhagen County were analysed by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE) and phage-typing. Fourteen polymorphic markers from five decamer primers unambiguously placed...... that RAPD is useful as a tool in investigations of microbial outbreaks in its own right, or to supplement phage-typing and PFGE of Salmonella Enteritidis....
Effect of temperature on sandstone permeability
DEFF Research Database (Denmark)
Rosenbrand, Esther; Kjøller, Claus
with the Kozeny equation and the Klinkenberg procedure. Both methods overestimated the measured brine permeability; this suggests that additional factors, possibly related to clay morphology, contributed to a lower brine permeability. Thermal expansion would have a negligible effect on permeability as estimated...... interaction forces. Quantitative analysis of images, in which mineralogy was mapped based on backscatter electron intensity in combination with energy dispersive X-ray analysis by using the QEMSCAN® system, was used to compare a tested sample to an untested Berea sandstone sample. During the experiment...
Ammonia and urea permeability of mammalian aquaporins
DEFF Research Database (Denmark)
Litman, Thomas; Søgaard, Rikke; Zeuthen, Thomas
2009-01-01
The human aquaporins,AQP3,AQP7, AQP8,AQP9, and possibly AQP10, are permeable to ammonia, and AQP7, AQP9, and possibly AQP3, are permeable to urea. In humans, these aquaporins supplement the ammonia transport of the Rhesus (Rh) proteins and the urea transporters (UTs). The mechanism by which...... and 9 are found together with Rh proteins in cells exposed to portal blood coming from the intestine. In the kidney, AQP3 might participate in the excretion of NH(4) (+) in the collecting duct. The interplay between the ammonia-permeable aquaporins and the other types of ammonia- and urea...
Meadows, Cheyney; Guerino, Frank; Sun, Fangshi
2017-01-01
Background Fleas are a common ectoparasite of domestic cats and there is a need for novel treatments that improve feline flea control. Methods This investigator-blinded, multi-center randomized, positive-controlled study evaluated the flea control in cats provided by a single owner-applied treatment with a fluralaner topical formulation compared with a positive control. Households with up to five healthy cats, all at least 12?weeks of age and weighing at least 1.2?kg (2.6?lb), were randomized...
Energy Technology Data Exchange (ETDEWEB)
Watanabe, K.; Aizawa, T.; Yanagisawa, K.; Sakuma, H.; Pushc, R. (Saitama Univ., Saitama, (Japan) Power Reactor and Nuclear Fuel Development Corp., Tokyo Lund Univ.,, (Sweden) Yamamoto, H., Univ. of Tokyo, Tokyo, (Japan). Faculty of Engineering Kanda, N., Tokyo Keisoku Co. Ltd., Tokyo, (Japan))
1990-03-25
A technique of evaporation measurement was put to practical test at the drifts of two mines, namely, the Stripa mine in Sweden and the Tono mine in Japan. Details of the technique are given in the authors {prime} preceding papaer (1989). At the test site the measurement was confirmed to be significant in its accuracy in the manner that evaporation rate was measured by means of the present technique on a mass of wet soil placed within a cup and was compared with that determined by measuring changes in the weight of the mass. Remarkable results obtained by this field test are as follows: first, evaporation rate can be well determined even if the humidity of the air is 95% or higher; second, the spatial variation of evaporation rate along a fracture can be distinctly observed; third, a considerable amount of groundwater is shown to evaporate from a dried fracture. Moreover, a discussion is given of the assumption that evaporation rate is identical with the rate of groundwater discharge at the surface of rock mass and evaporation measurement is not affected by winds in drifts when they are limited in their velocity. 7 refs., 23 figs.
Different Methods of Predicting Permeability in Shale
DEFF Research Database (Denmark)
Mbia, Ernest Ncha; Fabricius, Ida Lykke; Krogsbøll, Anette
Permeability is often very difficult to measure or predict in shale lithology. In this work we are determining shale permeability from consolidation tests data using Wissa et al., (1971) approach and comparing the results with predicted permeability from Kozeny’s model. Core and cuttings materials...... in shale useful in assessing their integrity for CO2 storage, gas shale exploitation and other engineering applications....... were obtained from Fjerritslev shale Formation in Juassic interval of Stenlille and Vedsted on-shore wells of Danish basin. The calculated permeability from specific surface and porosity vary from 0.09 to 48.53 μD while that calculated from consolidation tests data vary from 1000 μD at a low vertical...
Permeability Tests on Silkeborg Sand No. 0000
DEFF Research Database (Denmark)
Lund, Willy; Jakobsen, Kim Parsberg
The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends on the charact......The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends...... on the characteristics of the soil matrix, the permeability is determined for different void ratios. All tests are performed on reconstituted specimens of Silkeborg Sand No. 0000. The permeability is determined by use of a falling head apparatus. The apparatus, test procedures and the analysis method are described...
Permeability Tests on Eastern Scheldt Sand
DEFF Research Database (Denmark)
Jakobsen, Kim Parsberg
The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends on the charact......The flow through porous media plays an important role in various engineering disciplines, as for example in ground water hydrology and soil mechanics. In the present study the permeability is determined for a fine, saturated sand. As the flow through a porous media strongly depends...... on the characteristics of the soil matrix, the permeability is determined for different void ratios. All tests are performed on reconstituted specimens of Eastern Scheldt Sand. The permeability is determined by use of a falling head apparatus. Finally the test results are briefly summarised and a relationship between...
Biopartitioning micellar chromatography to predict skin permeability.
Martínez-Pla, J J; Martín-Biosca, Y; Sagrado, S; Villanueva-Camañas, R M; Medina-Hernández, M J
2003-12-01
Dermal absorption of chemicals is an area of increasing interest to the pharmaceutical and cosmetic industries, as well as in dermal exposure and risk assessment processes. In this paper the capability of biopartitioning micellar chromatography (BMC) as an in vitro technique to describe compound percutaneous absorption is evaluated. A multivariate study (principal component analysis, partial least squares) is performed in order to evaluate the importance of some physicochemical variables on the skin permeability constant values. From these results, a quantitative retention-activity relationship model for predicting the skin permeability constants that uses the BMC retention data and melting point as descriptor variables was obtained from a heterogeneous set of 43 compounds. The main advantage of the proposed methodology is that it allows the obtention of permeability constants of ionic compound and it can be very useful to predict the effect of pH of vehicle on the skin permeability of xenobiotics. Copyright 2003 John Wiley & Sons, Ltd.
DEFF Research Database (Denmark)
Berisso, Feto Esimo; Schjønning, Per; Lamandé, Mathieu
The impact of wheel traffic on soil physical properties is usually quantified by randomly collecting soil cores at specific depths below the wheeled surface. However, modeling studies as well as few measurements indicated a non-uniform stress distribution in a catena across the wheel rut, which...... might induce different effects on soil physical properties. The objective of this study was to investigate the impact of vehicle traffic on soil physical properties and air permeability by systematic collection of samples in a transect running from the center to the outside of the wheel rut. A field...... experiment was conducted on a clay loam soil at Suberg, Switzerland, in 2010. Four repeated wheeling were performed by driving a forage harvester (wheel load of 6100 kg and a tyre width of 0.8 m) forward and rearward in the same track. We sampled 100 cm3 intact cores at 10, 30 and 50 cm depth in a soil...
Pneumatic fracturing of low permeability media
Energy Technology Data Exchange (ETDEWEB)
Schuring, J.R. [New Jersey Institute of Technology, Newark, NJ (United States)
1996-08-01
Pneumatic fracturing of soils to enhance the removal and treatment of dense nonaqueous phase liquids is described. The process involves gas injection at a pressure exceeding the natural stresses and at a flow rate exceeding the permeability of the formation. The paper outlines geologic considerations, advantages and disadvantages, general technology considerations, low permeability media considerations, commercial availability, efficiency, and costs. Five case histories of remediation using pneumatic fracturing are briefly summarized. 11 refs., 2 figs., 1 tab.
Surface sedimentation at permeable pavement systems
DEFF Research Database (Denmark)
Støvring, Jan; Dam, Torben; Jensen, Marina Bergen
2018-01-01
Newly installed permeable pavement (PP) systems provide high surface infiltration capacity, but the accumulation of sediments causes a decrease in capacity over time, eventually leading to surface clogging. With the aim of investigating local sedimentation processes and the importance of restorat......Newly installed permeable pavement (PP) systems provide high surface infiltration capacity, but the accumulation of sediments causes a decrease in capacity over time, eventually leading to surface clogging. With the aim of investigating local sedimentation processes and the importance...
Meadows, Cheyney; Guerino, Frank; Sun, Fangshi
2017-01-19
Fleas are a common ectoparasite of domestic cats and there is a need for novel treatments that improve feline flea control. This investigator-blinded, multi-center randomized, positive-controlled study evaluated the flea control in cats provided by a single owner-applied treatment with a fluralaner topical formulation compared with a positive control. Households with up to five healthy cats, all at least 12 weeks of age and weighing at least 1.2 kg (2.6 lb), were randomized in an approximate 3:1 ratio of fluralaner to positive control. All cats in households randomized to the positive control group were dispensed three treatments, at 4-week intervals, of a commercial formulation of fipronil/(S)-methoprene. All cats in households randomized to the fluralaner group were dispensed an initial treatment at enrollment and a second treatment at week 12 for an additional 3-week observation of treatment safety. One primary cat with at least five live fleas at enrollment was randomly selected within each household. Flea counts were performed on all primary cats at 4-week intervals through week 12. Efficacy measurement was based on reduction in flea counts from baseline. Treatment was considered effective at weeks 4, 8 and 12 if mean live flea count reductions were 90% or greater and statistically significantly different (P ≤ 0.05) from counts at enrollment. In 18 investigational veterinary clinics across 11 USA states, 116 households (224 cats) were randomized to receive topical fluralaner and 45 households (87 cats) were randomized to the fipronil-methoprene combination. Fluralaner was demonstrated to be effective at 4 weeks (99.1% flea count reduction), 8 weeks (99.5%), and 12 weeks (99.0%), and all reductions were significantly different from the enrollment count (all P fluralaner topical treatment was safe in cats and was highly effective in killing fleas over the subsequent 12 weeks.
Intestinal permeability in patients with atopic eczema.
Bjarnason, I; Goolamali, S K; Levi, A J; Peters, T J
1985-03-01
Intestinal permeability was investigated in adult patients with atopic eczema by in vivo and in vitro techniques. Patients with symptoms of 'immediate' food allergy were specifically excluded. A 51Cr-labelled ethylenediaminetetraacetate absorption test was carried out in eighteen patients. Their mean (+/- s.d.) 24-hour urine excretion following oral administration of the test substance (2.1 +/- 0.9%) did not differ significantly from that of thirty-four normal controls (1.9 +/- 0.5%). Small bowel permeability was estimated directly in jejunal mucosal samples in ten patients with three permeability probes of differing molecular weight. Mucosal permeability did not differ significantly from that of fifteen control patients for any of the test substances. Two patients had abnormal results by both tests and in one this was due to coeliac disease. These results suggest that altered intestinal permeability is not important in the pathogenesis of eczema. Patients demonstrating increased intestinal permeability should undergo jejunal biopsy to exclude significant small bowel disease.
Charge Inversion in semi-permeable membranes
Das, Siddhartha; Sinha, Shayandev; Jing, Haoyuan
Role of semi-permeable membranes like lipid bilayer is ubiquitous in a myriad of physiological and pathological phenomena. Typically, lipid membranes are impermeable to ions and solutes; however, protein channels embedded in the membrane allow the passage of selective, small ions across the membrane enabling the membrane to adopt a semi-permeable nature. This semi-permeability, in turn, leads to electrostatic potential jump across the membrane, leading to effects such as regulation of intracellular calcium, extracellular-vesicle-membrane interactions, etc. In this study, we theoretically demonstrate that this semi-permeable nature may trigger the most remarkable charge inversion (CI) phenomenon in the cytosol-side of the negatively-charged lipid bilayer membrane that are selectively permeable to only positive ions of a given salt. This CI is manifested as the changing of the sign of the electrostatic potential from negative to positive from the membrane-cytosol interface to deep within the cytosol. We study the impact of the parameters such as the concentration of this salt with selectively permeable ions as well as the concentration of an external salt in the development of this CI phenomenon. We anticipate such CI will profoundly influence the interaction of membrane and intra-cellular moieties (e.g., exosome or multi-cellular vesicles) having implications for a host of biophysical processes.
Modeling the Hydrologic Processes of a Permeable Pavement ...
A permeable pavement system can capture stormwater to reduce runoff volume and flow rate, improve onsite groundwater recharge, and enhance pollutant controls within the site. A new unit process model for evaluating the hydrologic performance of a permeable pavement system has been developed in this study. The developed model can continuously simulate infiltration through the permeable pavement surface, exfiltration from the storage to the surrounding in situ soils, and clogging impacts on infiltration/exfiltration capacity at the pavement surface and the bottom of the subsurface storage unit. The exfiltration modeling component simulates vertical and horizontal exfiltration independently based on Darcy’s formula with the Green-Ampt approximation. The developed model can be arranged with physically-based modeling parameters, such as hydraulic conductivity, Manning’s friction flow parameters, saturated and field capacity volumetric water contents, porosity, density, etc. The developed model was calibrated using high-frequency observed data. The modeled water depths are well matched with the observed values (R2 = 0.90). The modeling results show that horizontal exfiltration through the side walls of the subsurface storage unit is a prevailing factor in determining the hydrologic performance of the system, especially where the storage unit is developed in a long, narrow shape; or with a high risk of bottom compaction and clogging. This paper presents unit
A complex permittivity and permeability measurement system for elevated temperatures
Friederich, Paul
1990-01-01
The three goals of this research include: (1) to fully develop a method to measure the permittivity and permeability of special materials as a function of frequency in the range of 2.6 to 18 GHz, and of temperatures in the range of 25 to 1100 C; (2) to assist LeRC in setting up an in-house system for the measurement of high-temperature permittivity and permeability; and (3) to measure the complex permittivity and permeability of special materials as a function of frequency and temperature to demonstrate the capability of the method. The method chosen for characterizing the materials relies on perturbation of a resonant cavity with a small volume of sample material. Different field configurations in the cavity can be used to separate electric and magnetic effects. The cavity consists of a section of rectangular waveguide terminated at each end of a vertical slot iris. The center of one wall is a small hole through which the sample is introduced.
Energy Technology Data Exchange (ETDEWEB)
Fang, Yi [Department of Energy and Mineral Engineering, EMS Energy Institute, and G3 Center, Pennsylvania State University, University Park Pennsylvania USA; Elsworth, Derek [Department of Energy and Mineral Engineering, EMS Energy Institute, and G3 Center, Pennsylvania State University, University Park Pennsylvania USA; Department of Geosciences, EMS Energy Institute, and G3 Center, Pennsylvania State University, University Park Pennsylvania USA; Wang, Chaoyi [Department of Energy and Mineral Engineering, EMS Energy Institute, and G3 Center, Pennsylvania State University, University Park Pennsylvania USA; Ishibashi, Takuya [Department of Energy and Mineral Engineering, EMS Energy Institute, and G3 Center, Pennsylvania State University, University Park Pennsylvania USA; Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, Koriyama Japan; Fitts, Jeffrey P. [Department of Civil and Environmental Engineering, Princeton University, Princeton New Jersey USA
2017-01-01
There is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO_{2} sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction-stability-permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate-rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate-rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction-stability-permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.
2013-05-01
University of New Hampshire Stormwater Center (UNHSC) completed a two year field verification study of a permeable interlocking concrete pavement (PICP) stormwater management system. The purpose of this study was to evaluate the cold climate function...
Guo, Xinxing; Kong, Xiangbin; Huang, Rui; Jin, Ling; Ding, Xiaohu; He, Mingguang; Liu, Xing; Patel, Mehul Chimanlal; Congdon, Nathan G
2014-01-07
We evaluated the effect of ginkgo biloba extract on visual field defect and contrast sensitivity in a Chinese cohort with normal tension glaucoma. In this prospective, randomized, placebo-controlled crossover study, patients newly diagnosed with normal tension glaucoma, either in a tertiary glaucoma clinic (n = 5) or in a cohort undergoing routine general physical examinations in a primary care clinic (n = 30), underwent two 4-week phases of treatment, separated by a washout period of 8 weeks. Randomization determined whether ginkgo biloba extract (40 mg, 3 times per day) or placebo (identical-appearing tablets) was received first. Primary outcomes were change in contrast sensitivity and mean deviation on 24-2 SITA standard visual field testing, while secondary outcomes included IOP and self-reported adverse events. A total of 35 patients with mean age 63.7 (6.5) years were randomized to the ginkgo biloba extract-placebo (n = 18) or the placebo-ginkgo biloba extract (n = 17) sequence. A total of 28 patients (80.0%, 14 in each group) who completed testing did not differ at baseline in age, sex, visual field mean deviation, contrast sensitivity, IOP, or blood pressure. Changes in visual field and contrast sensitivity did not differ by treatment received or sequence (P > 0.2 for all). Power to have detected a difference in mean defect as large as previously reported was 80%. In contrast to some previous reports, ginkgo biloba extract treatment had no effect on mean defect or contrast sensitivity in this group of normal tension glaucoma patients. (http://www.chictr.org number, ChiCTR-TRC-08000724).
Artificial neural network models for prediction of intestinal permeability of oligopeptides
Directory of Open Access Journals (Sweden)
Kim Min-Kook
2007-07-01
Full Text Available Abstract Background Oral delivery is a highly desirable property for candidate drugs under development. Computational modeling could provide a quick and inexpensive way to assess the intestinal permeability of a molecule. Although there have been several studies aimed at predicting the intestinal absorption of chemical compounds, there have been no attempts to predict intestinal permeability on the basis of peptide sequence information. To develop models for predicting the intestinal permeability of peptides, we adopted an artificial neural network as a machine-learning algorithm. The positive control data consisted of intestinal barrier-permeable peptides obtained by the peroral phage display technique, and the negative control data were prepared from random sequences. Results The capacity of our models to make appropriate predictions was validated by statistical indicators including sensitivity, specificity, enrichment curve, and the area under the receiver operating characteristic (ROC curve (the ROC score. The training and test set statistics indicated that our models were of strikingly good quality and could discriminate between permeable and random sequences with a high level of confidence. Conclusion We developed artificial neural network models to predict the intestinal permeabilities of oligopeptides on the basis of peptide sequence information. Both binary and VHSE (principal components score Vectors of Hydrophobic, Steric and Electronic properties descriptors produced statistically significant training models; the models with simple neural network architectures showed slightly greater predictive power than those with complex ones. We anticipate that our models will be applicable to the selection of intestinal barrier-permeable peptides for generating peptide drugs or peptidomimetics.
STAVREV, A.
2013-03-01
The uncertainty of geometric imperfections in a series of nominally equal I-beams leads to a variability of corresponding buckling loads. Its analysis requires a stochastic imperfection model, which can be derived either by the simple variation of the critical eigenmode with a scalar random variable, or with the help of the more advanced theory of random fields. The present paper first provides a concise review of the two different modeling approaches, covering theoretical background, assumptions and calibration, and illustrates their integration into commercial finite element software to conduct stochastic buckling analyses with the Monte-Carlo method. The stochastic buckling behavior of an example beam is then simulated with both stochastic models, calibrated from corresponding imperfection measurements. The simulation results show that for different load cases, the response statistics of the buckling load obtained with the eigenmode-based and the random field-based models agree very well. A comparison of our simulation results with corresponding Eurocode 3 limit loads indicates that the design standard is very conservative for compression dominated load cases. © 2013 World Scientific Publishing Company.
Bandiera, R.; Petruk, O.
2016-06-01
The maps of intensity and polarization of the radio synchrotron emission from shell-type supernova remnants (SNRs) contain a considerable amount of information, although of not easy interpretation. With the aim of deriving constraints on the 3D spatial distribution of the emissivity, as well as on the structure of both ordered and random magnetic fields (MFs), we present here a scheme to model maps of the emission and polarization in SNRs. We first generalize the classical treatment of the synchrotron emission to the case in which the MF is composed of an ordered MF plus an isotropic random component, with arbitrary relative strengths. For a power-law particle energy distribution, we derive analytic formulae that formally resemble those for the classical case. We also treat the shock compression of a fully random upstream field and we predict that the polarization fraction in this case should be higher than typically measured in SNRs. We implement the above treatment into a code, which simulates the observed polarized emission of an emitting shell, taking into account also the effect of the internal Faraday rotation. Finally, we show simulated maps for different orientations with respect to the observer, levels of the turbulent MF component, Faraday rotation levels, distributions of the emissivity (either barrel-shaped or limited to polar caps) and geometries for the ordered MF component (either tangential to the shell or radial). Their analysis allows us to outline properties useful for the interpretation of radio intensity and polarization maps.
Bouchet, Audrey; Potez, Marine; Coquery, Nicolas; Rome, Claire; Lemasson, Benjamin; Bräuer-Krisch, Elke; Rémy, Chantal; Laissue, Jean; Barbier, Emmanuel L; Djonov, Valentin; Serduc, Raphael
2017-08-01
To compare the blood-brain barrier permeability changes induced by synchrotron microbeam radiation therapy (MRT, which relies on spatial fractionation of the incident x-ray beam into parallel micron-wide beams) with changes induced by a spatially uniform synchrotron x-ray radiation therapy. Male rats bearing malignant intracranial F98 gliomas were randomized into 3 groups: untreated, exposed to MRT (peak and valley dose: 241 and 10.5 Gy, respectively), or exposed to broad beam irradiation (BB) delivered at comparable doses (ie, equivalent to MRT valley dose); both applied by 2 arrays, intersecting orthogonally the tumor region. Vessel permeability was monitored in vivo by magnetic resonance imaging 1 day before (T-1) and 1, 2, 7, and 14 days after treatment start. To determine whether physiologic parameters influence vascular permeability, we evaluated vessel integrity in the tumor area with different values for cerebral blood flow, blood volume, edema, and tissue oxygenation. Microbeam radiation therapy does not modify the vascular permeability of normal brain tissue. Microbeam radiation therapy-induced increase of tumor vascular permeability was detectable from T2 with a maximum at T7 after exposure, whereas BB enhanced vessel permeability only at T7. At this stage MRT was more efficient at increasing tumor vessel permeability (BB vs untreated: +19.1%; P=.0467; MRT vs untreated: +44.8%; Ptumor than BB. Microbeam radiation therapy-induced increased tumor vascular permeability is: (1) significantly greater; (2) earlier and more prolonged than that induced by BB irradiation, especially in highly proliferative tumor areas; and (3) targets all tumor areas discriminated by physiologic characteristics, including those not damaged by homogeneous irradiation. Copyright © 2017 Elsevier Inc. All rights reserved.
DEFF Research Database (Denmark)
Yura, Harold; Hanson, Steen Grüner
2012-01-01
Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set with the......Methods for simulation of two-dimensional signals with arbitrary power spectral densities and signal amplitude probability density functions are disclosed. The method relies on initially transforming a white noise sample set of random Gaussian distributed numbers into a corresponding set...... with the desired spectral distribution, after which this colored Gaussian probability distribution is transformed via an inverse transform into the desired probability distribution. In most cases the method provides satisfactory results and can thus be considered an engineering approach. Several illustrative...
Directory of Open Access Journals (Sweden)
Thomas Koenig
2011-01-01
Full Text Available We present a program (Ragu; Randomization Graphical User interface for statistical analyses of multichannel event-related EEG and MEG experiments. Based on measures of scalp field differences including all sensors, and using powerful, assumption-free randomization statistics, the program yields robust, physiologically meaningful conclusions based on the entire, untransformed, and unbiased set of measurements. Ragu accommodates up to two within-subject factors and one between-subject factor with multiple levels each. Significance is computed as function of time and can be controlled for type II errors with overall analyses. Results are displayed in an intuitive visual interface that allows further exploration of the findings. A sample analysis of an ERP experiment illustrates the different possibilities offered by Ragu. The aim of Ragu is to maximize statistical power while minimizing the need for a-priori choices of models and parameters (like inverse models or sensors of interest that interact with and bias statistics.
Koenig, Thomas; Kottlow, Mara; Stein, Maria; Melie-García, Lester
2011-01-01
We present a program (Ragu; Randomization Graphical User interface) for statistical analyses of multichannel event-related EEG and MEG experiments. Based on measures of scalp field differences including all sensors, and using powerful, assumption-free randomization statistics, the program yields robust, physiologically meaningful conclusions based on the entire, untransformed, and unbiased set of measurements. Ragu accommodates up to two within-subject factors and one between-subject factor with multiple levels each. Significance is computed as function of time and can be controlled for type II errors with overall analyses. Results are displayed in an intuitive visual interface that allows further exploration of the findings. A sample analysis of an ERP experiment illustrates the different possibilities offered by Ragu. The aim of Ragu is to maximize statistical power while minimizing the need for a-priori choices of models and parameters (like inverse models or sensors of interest) that interact with and bias statistics.
Del Valle-Pinero, Arseima Y.; Van Deventer, Hendrick E.; Fourie, Nicolaas H.; Martino, Angela C.; Patel, Nayan S.; Remaley, Alan T.; Henderson, Wendy A.
2013-01-01
Background Abnormal gastrointestinal permeability has been linked to irritable bowel syndrome (IBS). The lactulose-to-mannitol ratio is traditionally used to assess small intestine permeability while sucralose and sucrose are used to assess colonic and gastric permeability respectively. We used a single 4-probe test solution to assess permeability throughout the gastrointestinal tract in IBS patients and healthy controls by measuring the recovery of the probes in urine after ingestion using a modified liquid chromatography mass spectrometry protocol. Methods Fasting participants (N = 59) drank a permeability test solution (100 ml: sucralose, sucrose, mannitol, and lactulose). Urine was collected over a 5-h period and kept frozen until analysis. Urinary sugar concentrations were measured using an liquid chromatography/triple quadruple mass spectrometer. Results Colonic permeability was significantly lower in IBS patients when compared to healthy controls (p = 0.011). Gastric and small intestinal permeability did not significantly differ between the groups. Conclusions The study demonstrates the clinical potential of this non-invasive method for assessing alterations in gastrointestinal permeability in patients with IBS. PMID:23328210
Meadows, Cheyney; Guerino, Frank; Sun, Fangshi
2017-01-19
Orally administered fluralaner effectively controls fleas and ticks on dogs for 12 weeks. This study evaluates the flea control efficacy achieved with topically applied fluralaner in dogs. This investigator-blinded, multi-center randomized, positive controlled study evaluated flea control efficacy in dogs following a single owner-applied treatment of topical fluralaner. A positive control group received three treatments, at 4-week intervals, of a commercial formulation of fipronil/(S)-methoprene. All dogs in households randomized to the fluralaner group were dispensed an initial treatment at enrollment and a second treatment at week 12 for an additional 3-week observation of treatment safety. Households with up to five healthy dogs, all at least 12 weeks of age and weighing at least 2 kg (4.4 lb), were randomized in a ratio of 3:1 of fluralaner to positive control. Within households, one primary dog with at least 10 live fleas at enrollment was randomly selected. Flea counts were performed on all primary dogs every 4 weeks through week 12. Efficacy measurement was based on reduction from baseline flea counts. Treatment was considered effective if geometric mean live flea count reductions at weeks 4, 8, and 12 were 90% or greater and significantly different from counts at enrollment. In addition, for each time point the arithmetic mean live flea counts, the efficacy based on arithmetic means, the number and percentage of dogs with at least a 90% reduction in flea count, and the number and percentage of flea free dogs were calculated. Statistical comparisons were also made between treatment groups. At 12 sites, across 10 states, 121 households (221 dogs) were randomized to receive fluralaner and 44 households (100 dogs) were randomized to receive the positive control. Fluralaner was demonstrated to be significantly effective (all P ≤ 0.0001) at 4 weeks (99.8% reduction), 8 weeks (99.9%), and 12 weeks (99.9%). The positive control was significantly
Chen, Ming; Bao, Yong; Ma, Hong-Lian; Wang, Jin; Wang, Yan; Peng, Fang; Zhou, Qi-Chao; Xie, Cong-Hua
2013-01-01
This prospective randomized study is to evaluate the locoregional failure and its impact on survival by comparing involved field radiotherapy (IFRT) with elective nodal irradiation (ENI) in combination with concurrent chemotherapy for locally advanced non-small cell lung cancer. It appears that higher dose could be delivered in IFRT arm than that in ENI arm, and IFRT did not increase the risk of initially uninvolved or isolated nodal failures. Both a tendency of improved locoregional progression-free survival and a significant increased overall survival rate are in favor of IFRT arm in this study. PMID:23762840
Vascular permeability alterations induced by arsenic.
Chen, Shih-Chieh; Tsai, Ming-Hsien; Wang, Hsiu-Jen; Yu, Hsin-Su; Chang, Louis W
2004-01-01
The impact of arsenic on the integrity of blood vessels in vivo via in situ exposure (local injection) of arsenic was investigated. Vascular permeability changes were evaluated by means of the Evans blue assay and the India ink tracer techniques. Rats were intravenously injected with Evans blue followed by intradermal injections of various doses of sodium arsenite on the back skins of the animals. Evans blue at different time points was extracted and assayed as indices of vascular leakage. Skin at various time point injection sites was sampled for arsenic measurement via graphite furnace atomic absorption spectroscopy. Our time course study with Evans blue technique demonstrated a biphasic pattern of vascular permeability change: an early phase of permeability reduction and a later phase of permeability promotion at all dose levels tested. The India ink tracer technique also demonstrated a time-correlated increase in vascular labelling in the tissues examined, signifying an increase in vascular leakage with time. Moreover, we found that despite an early increase in tissue arsenic content at time of injection, tissue arsenic declined rapidly and returned to near control levels after 30-60 min. Thus, an inverse correlation between tissue arsenic content and the extent of vascular permeability was apparent. This study provides the first demonstration that in situ exposure to arsenic will produce vascular dysfunction (vascular leakage) in vivo.
Changes in permeability caused by earthquakes
Manga, Michael; Wang, Chi-Yuen; Shi, Zheming
2016-04-01
Earthquakes induce a range of hydrological responses, including changes in streamflow and changes in the water level in wells. Here we show that many of these responses are caused the changes in permeability produced by the passage of seismic waves. First we analyze streams that were dry or nearly dry before the 2014 M6 Napa, California, earthquake butstarted to flow after the earthquake. We show that the new flows were meteoric in origin and originate in the nearby mountains. Responses are not correlated with the sign of static strains implying seismic waves liberated this water, presumably by changing permeability. We also analyze a large network of wells in China that responded to 4 large earthquakes. We monitor permeability changes through their effect on the water level response to solid Earth tides. We find that when earthquakes produce sustained changes in water level, permeability also changes. Wells with water level changes that last for only days show no evidence for changes in aquifer permeability.
Water permeability and characterization of aquaporin-11.
Yakata, Kaya; Tani, Kazutoshi; Fujiyoshi, Yoshinori
2011-05-01
The water permeability of aquaporin-11 (AQP11), which has a cysteine substituted for an alanine at a highly conserved asparagine-proline-alanine (NPA) motif in the water channel family, is controversial. Our previous study, however, showed that AQP11 is water permeable in proteoliposomes in which AQP11 molecules were reconstituted after purification with Fos-choline 10, which is the most suitable detergent available for stable solubilization of AQP11. In our previous study, we were unable to exclude the effect of the detergent on the water conductance. Therefore, in the present study, we measured the water permeability of AQP11 without detergent using vesicles that directly formed from Sf9 cell membranes expressing AQP11 molecules. The water permeability of AQP11 was 8-fold lower than that of AQP1 and 3-fold higher than that of mock-infected cell membrane, and was reversibly inhibited by mercury ions. Considering the slow but constant water permeable functions of AQP11, we performed homology modeling to search for a common structural feature. When comparing our model with those of other AQP structures, we found that Tyr83 facing the channel pore might be a key amino acid residue that decreases the water permeation of AQP11. Our findings indicate that AQP11 could be involved in slow but constant water movement across the membrane. Copyright © 2011 Elsevier Inc. All rights reserved.
Durability Evaluation in Concrete Using Cracked Permeability and Chloride Permeability Tests
Directory of Open Access Journals (Sweden)
V. M. Sounthararajan
2013-01-01
Full Text Available The objective of this study is to identify the possibilities of utilizing the quarry dust in concrete to obtain an improved strength and durability properties of concrete. In the present study, the addition of quarry dust as alternative for natural sand has been investigated, and the durability properties of concrete were evaluated systematically by means of cracked water permeability and rapid chloride permeability tests. The permeability of concrete was assessed with initial stress applied to the concrete specimen and later checked for water permeability. Concrete mixes were casted using ordinary river sand and compared with 100% quarry dust substituted concrete. The addition of quarry dust significantly improved the concrete matrix properties in terms of strength and permeability resistance. The addition of fine quarry dust in concrete resulted in improved matrix densification compared to conventional concrete. Matrix densification has been studied qualitatively through petrographical examination using digital optical microscopy.
Random fixed points and random differential inclusions
Directory of Open Access Journals (Sweden)
Nikolaos S. Papageorgiou
1988-01-01
Full Text Available In this paper, first, we study random best approximations to random sets, using fixed point techniques, obtaining this way stochastic analogues of earlier deterministic results by Browder-Petryshyn, KyFan and Reich. Then we prove two fixed point theorems for random multifunctions with stochastic domain that satisfy certain tangential conditions. Finally we consider a random differential inclusion with upper semicontinuous orientor field and establish the existence of random solutions.
Xiao, Liang; Liu, Xiao-Peng; Zou, Chang-Chun; Hu, Xiao-Xin; Mao, Zhi-Qiang; Shi, Yu-Jiang; Guo, Hao-Peng; Li, Gao-Ren
2014-02-01
Based on the analysis of mercury injection capillary pressure (MICP) and nuclear magnetic resonance (NMR) experimental data for core plugs, which were drilled from two Chinese tight sandstone reservoirs, permeability prediction models, such as the classical SDR, Timur-Coates, the Swanson parameter, the Capillary Parachor, the R10 and R35 models, are calibrated to estimating permeabilities from field NMR logs, and the applicabilities of these permeability prediction models are compared. The processing results of several field examples show that the SDR model is unavailable in tight sandstone reservoirs. The Timur-Coates model is effective once the optimal T 2cutoff can be acquired to accurately calculate FFI and BVI from field NMR logs. The Swanson parameter model and the Capillary Parachor model are not always available in tight sandstone reservoirs. The R35 based model cannot effectively work in tight sandstone reservoirs, while the R10 based model is optimal in permeability prediction.
de Haan, Gera; Melis-Dankers, Bart; Brouwer, Wiebo; Tucha, Oliver; Heutink, Joost
2015-01-01
Background: Homonymous visual field defects (HVFD) are a common consequence of postchiasmatic acquired brain injury and often lead to mobility-related difficulties. Different types of compensatory scanning training have been developed, aimed at decreasing consequences of the HVFD by changing the use
Chaffin, Mark; Funderburk, Beverly; Bard, David; Valle, Linda Anne; Gurwitch, Robin
2011-01-01
Objective: A package of parent-child interaction therapy (PCIT) combined with a self-motivational (SM) orientation previously was found in a laboratory trial to reduce child abuse recidivism compared with services as usual (SAU). Objectives of the present study were to test effectiveness in a field agency rather than in a laboratory setting and to…
Nikken, J.J.; Oei, E.H.; Ginai, A.Z.; Krestin, G.P.; Verhaar, J.A.N.; Vugt, A.B. van; Hunink, M.G.M.
2005-01-01
PURPOSE: To assess prospectively if a short imaging examination performed with low-field-strength dedicated magnetic resonance (MR) imaging in addition to radiography is effective and cost saving compared with the current diagnostic imaging strategy (radiography alone) in patients with recent acute
Directory of Open Access Journals (Sweden)
Danilo Maciel Carneiro
2014-01-01
Full Text Available In this double-blind, randomized clinical trial, 36 healthy male volunteers were randomly distributed into three groups (n=12 that underwent a three-step treatment. For four consecutive days, we alternately administered a standardized dried extract of Equisetum arvense (EADE, 900 mg/day, placebo (corn starch, 900 mg/day, or hydrochlorothiazide (25 mg/day, separated by a 10-day washout period. Each volunteer served as his own control, and the groups’ results were compared. We repeated the same evaluation after each stage of treatment to evaluate the safety of the drug. The diuretic effect of EADE was assessed by monitoring the volunteers’ water balance over a 24 h period. The E. arvense extract produced a diuretic effect that was stronger than that of the negative control and was equivalent to that of hydrochlorothiazide without causing significant changes in the elimination of electrolytes. There was no significant increase in the urinary elimination of catabolites. Rare minor adverse events were reported. The clinical examinations and laboratory tests showed no changes before or after the experiment, suggesting that the drug is safe for acute use. Further research is needed to better clarify the mechanism of diuretic action and the other possible pharmacological actions of this phytomedicine.
Low-field magnetization process and complex permeability of ...
Indian Academy of Sciences (India)
Biphase wires consisting of a soft magnetic amorphous nucleus surrounded by a hard magnetic CoNi layer of variable thickness were obtained by means of rotating water-quenching method and subsequent electroplating technique. Magnetization processes for all the biphase wires were resolved in terms of reversible ...
Low-field magnetization process and complex permeability of ...
Indian Academy of Sciences (India)
I BETANCOURT, M E HERNÁNDEZ-ROJAS†,. G A BADINI-CONFALONIERI#, A JACAS# and M VÁZQUEZ#. Departamento de Materiales Metálicos y Cerámicos, Instituto de Investigaciones en Materiales, Universidad Nacional. Autónoma de México, México D.F. 04510, México. †Departamento de Recursos de la Tierra, ...
Water absorption tests for measuring permeability of field concrete.
2013-09-01
The research results from CFIRE Project 04-06 were communicated to engineers and researchers in this project. : Specifically, the water absorption of concrete samples (i.e., 2-in. thick, 4-in. diameter discs cut from concrete : cylinders) was found s...
Study of the effects of stress sensitivity on the permeability and porosity of fractal porous media
Energy Technology Data Exchange (ETDEWEB)
Tan, Xiao-Hua, E-mail: xiaohua-tan@163.com; Li, Xiao-Ping; Liu, Jian-Yi; Zhang, Lie-Hui; Fan, Zhou
2015-10-16
Flow in porous media under stress is very important in various scientific and engineering fields. It has been shown that stress plays an important role in effect of permeability and porosity of porous media. In this work, novel predictive models for permeability and porosity of porous media considering stress sensitivity are developed based on the fractal theory and mechanics of materials. Every parameter in the proposed models has clear physical meaning. The proposed models are evaluated using previously published data for permeability and porosity measured in various natural materials. The predictions of permeability and porosity show good agreement with those obtained by the available experimental data and illustrate that the proposed models can be used to characterize the flow in porous media under stress accurately. - Highlights: • Predictive models for permeability and porosity of porous media considering stress sensitivity are developed. • The fractal theory and mechanics of materials are used in these models. • The predictions of permeability and porosity show good agreement with those obtained by the available experimental data. • The proposed models can be used to characterize the flow in porous media under stress accurately.
New well pattern optimization methodology in mature low-permeability anisotropic reservoirs
Qin, Jiazheng; Liu, Yuetian; Feng, Yueli; Ding, Yao; Liu, Liu; He, Youwei
2018-02-01
In China, lots of well patterns were designed before people knew the principal permeability direction in low-permeability anisotropic reservoirs. After several years’ production, it turns out that well line direction is unparallel with principal permeability direction. However, traditional well location optimization methods (in terms of the objective function such as net present value and/or ultimate recovery) are inapplicable, since wells are not free to move around in a mature oilfield. Thus, the well pattern optimization (WPO) of mature low-permeability anisotropic reservoirs is a significant but challenging task, since the original well pattern (WP) will be distorted and reconstructed due to permeability anisotropy. In this paper, we investigate the destruction and reconstruction of WP when the principal permeability direction and well line direction are unparallel. A new methodology was developed to quantitatively optimize the well locations of mature large-scale WP through a WPO algorithm on the basis of coordinate transformation (i.e. rotating and stretching). For a mature oilfield, large-scale WP has settled, so it is not economically viable to carry out further infill drilling. This paper circumvents this difficulty by combining the WPO algorithm with the well status (open or shut-in) and schedule adjustment. Finally, this methodology is applied to an example. Cumulative oil production rates of the optimized WP are higher, and water-cut is lower, which highlights the potential of the WPO methodology application in mature large-scale field development projects.
Small-bowel permeability in collagenous colitis
DEFF Research Database (Denmark)
Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J
2006-01-01
OBJECTIVE: Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small...... permeability. MATERIAL AND METHODS: Ten patients with CC and chronic diarrhoea participated in the study. Coeliac disease was excluded by small-bowel biopsy and/or serology. Intestinal permeability was assessed as urinary excretion (ratios) 2, 4 and 6 h after ingestion of 14C-labelled mannitol (14C......-intestinal biopsies, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal...
Magnetic levitation from negative permeability materials
Energy Technology Data Exchange (ETDEWEB)
Coffey, Mark W., E-mail: mcoffey@mines.edu [Department of Physics, Colorado School of Mines, Golden, CO 80401 (United States)
2012-09-03
As left-handed materials and metamaterials are becoming more prevalent, we examine the effect of negative permeability upon levitation force. We first consider two half spaces of differing permeability and a point magnetic source, so that the method of images may be employed. We determine that the resulting force may be larger than for conventional magnetic materials. We then illustrate the inclusion of a finite sample thickness. -- Highlights: ► The effect of negative permeability upon levitation force is considered. ► Such an effect could be realized with metamaterials. ► The resulting force may be larger than with conventional materials. ► The analysis is extended to allow for a finite sample thickness. ► Representative numerical values are given.
Permeability of Hollow Microspherical Membranes to Helium
Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.
2016-01-01
This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.
Beach protection by a system of permeable groins
Boczar-Karakiewicz, B.; Romanczyk, W.; Roy, N.
2002-12-01
A new type of permeable groin (called System of Groins Maltec-Savard - SGMS) has been installed at three eroded sites located in the coastal area on the north shore of the St. Lawrence, Quebec, Canada. In this area, the narrow sandy beaches with sandy or sand-silty cliff of variable height (10-15~m) are exposed to obliquely incident waves arriving from both west (summer) and east (autumn), and to tidal currents (maximum tidal rate is 4.3~m). The periods of summer waves equal 3-5~s, with wave heights of about 0.4-0.7~m. In the autumn, major storm waves reach periods of up to 7-10~s, with wave heights of 1.0-1.2~m. The new groins are sediment traps formed by a central double and permeable groin with several smaller lateral, groins installed on one or both sides of the central groin (Boczar-Karakiewicz et al., 2001). The permeable central and lateral groins are structured by inserting double ranges of wooden piles (diameter of about 10 cm). The space between the ranges of piles (some 0.8~m wide) is filled with tree branches (e.g., the top parts of pine trees, a waste product of the local forest industry). A permeable grid covering the top of the groins forms a cage that holds the branches in place. The lateral groins, are identical but much shorter than the central groin. The whole system dissipates the incident energy of wave- and tidally-generated currents and causes accretion of sand transported by these currents. The GSMS also allows the by-pass of some sediment to adjacent zones without groins. Observations and results of measurements from three experiments field show that: (1) a sandy beach in front of a coastal cliff secures its stability and attenuates the erosion caused by waves and tidal currents; (2) permeability and flexibility of the SGMS causes the accretion of sediment in the protected area without erosion in the neighboring zones; (3) the SGMS does not generate wave reflection and any secondary current; (4) the materials of the groins are easily
RADIOMETRIC PROPERTIES OFAGRICULTURAL PERMEABLE COVERINGS
Directory of Open Access Journals (Sweden)
Sergio Castellano
2010-06-01
Full Text Available Nets are commonly used for agricultural applications. However, only little is known about the radiometric properties of net types and how to influence them. In order to investigate the influence of net construction parameters on their radiometric properties, a set of radiometric tests were performed on 45 types of agricultural nets. Laboratory tests on large size net samples was performed using a large and a small integrating sphere. Open field radiometric test were carried out by means of an experimental set up (120x120x50 cm and a full scale shade house. Small differences (less than 5% occurred between laboratory and open field tests. Results highlighted that the porosity and the mesh size, combined with the colour and secondarily, with the fabric and the kind of threads of the net influenced the shading performance of the net. The colour influenced the spectral distribution of the radiation passing through the net absorbing its complementary colours. Since nets are three-dimensional structures the transmissivity of direct light under different angles of incident of solar radiation changes when installed in the warp or weft direction. Transmissivity could be considered one of the main parameters involved in the agronomic performances of the netting system.
Irgens, Audun C.; Hoffart, Asle; Nysæter, Tor E.; Haaland, Vegard Ø.; Borge, Finn-Magnus; Pripp, Are H.; Martinsen, Egil W.; Dammen, Toril
2017-01-01
Background: Thought field therapy (TFT) is used for many psychiatric conditions, but its efficacy has not been sufficiently documented. Hence, there is a need for studies comparing TFT to well-established treatments. This study compares the efficacy of TFT and cognitive behavioral therapy (CBT) for patients with agoraphobia. Methods: Seventy-two patients were randomized to CBT (N = 24), TFT (N = 24) or a wait-list condition (WLC) (N = 24) after a diagnostic procedure including the MINI PLUS that was performed before treatment or WLC. Following a 3 months waiting period, the WL patients were randomized to CBT (n = 12) or TFT (n = 12), and all patients were reassessed after treatment or waiting period and at 12 months follow-up. At first we compared the three groups CBT, TFT, and WL. After the post WL randomization, we compared CBT (N = 12 + 24 = 36) to TFT (N = 12 + 24 = 36), applying the pre-treatment scores as baseline for all patients. The primary outcome measure was a symptom score from the Anxiety Disorders Interview Scale that was performed by an interviewer blinded to the treatment condition. For statistical comparisons, we used the independent sample’s t-test, the Fisher’s exact test and the ANOVA and ANCOVA tests. Results: Both CBT and TFT showed better results than the WLC (p agoraphobia. Trial Registration: https://clinicaltrials.gov/, identifier NCT00932919. PMID:28676782
Small-bowel permeability in collagenous colitis
DEFF Research Database (Denmark)
Wildt, Signe; Madsen, Jan L; Rumessen, Jüri J
2006-01-01
Collagenous colitis (CC) is a chronic inflammatory bowel disease that affects the colon. However, some patients with CC present with accompanying pathologic small-bowel manifestations such as coeliac disease, defects in bile acid absorption and histopathologic changes in small-intestinal biopsies......, indicating that CC is a pan-intestinal disease. In small-intestinal disease, the intestinal barrier function may be impaired, and the permeability of the small intestine altered. The purpose of this research was to study small-bowel function in patients with CC as expressed by intestinal permeability....
Rough and partially-cemented fracture permeability
Landry, C. J.; Eichhubl, P.; Prodanovic, M.
2016-12-01
Numerical studies of mass transport in fractured rock, such as discrete fracture network models, use models to assign estimates of permeability to individual fractures. These fracture permeability models typically employ statistical moments of the fracture aperture distribution to estimate permeability. Although it is known that these fracture permeability models are in error, the quantification of this error is limited. We use a digital rock physics workflow to quantify this error in four fracture samples, a barren artificially-induced fracture in sandstone, a calcite-lined fracture sampled from outcrop, and two quartz-bridged fractures sampled from reservoir core. Each of the fracture samples is imaged using three-dimensional x-ray computed microtomography. The images are then processed, segmented and used in a lattice-Boltzmann-method-based flow simulation. We also vary the kinematic apertures of the barren and calcite-lined fractures through digital dilatation and closure in order to investigate sensitivity to the relative fracture roughness. We define the scalar error, F, between the actual permeability determined from simulation, kLB, and that predicted using the fracture permeability model of Zimmerman and Bodvarsson (1996), kZB, as, F±1=kZB/kLB. Although the pore space shape of the fractures appears quite different, the scalar error as a function of relative roughness is found to be similar for all fracture samples investigated, with a maximum of approximately 2. Considering two-dimensional cross-sections of fractures are more readily available than three-dimensional images we then plot the scalar error as a function of relative roughness and the number of observations measured from two-dimensional images (width of fracture analyzed). In general, the rougher the fracture, the greater the number of observations that are required to define the statistical moment inputs for the fracture permeability model. We use these results to approximate the width of the
Directory of Open Access Journals (Sweden)
Noella Angele Piquette
2014-12-01
Full Text Available The present paper reports a cluster randomized control trial evaluation of teaching using ABRACADABRA (ABRA, an evidence-based and web-based literacy intervention (http://abralite.concordia.ca with 107 kindergarten and 96 grade 1 children in 24 classes (12 intervention 12 control classes from all 12 elementary schools in one school district in Canada. Children in the intervention condition received 10-12 hours of whole class instruction using ABRA between pre- and post-test. Hierarchical linear modeling of post-test results showed significant gains in letter-sound knowledge for intervention classrooms over control classrooms. In addition, medium effect sizes were evident for three of five outcome measures favoring the intervention: letter-sound knowledge (d = +.66, phonological blending (d = +.52, and word reading (d = +.52, over effect sizes for regular teaching. It is concluded that regular teaching with ABRA technology adds significantly to literacy in the early elementary years.
DEFF Research Database (Denmark)
Miskowiak, K. W.; Ott, C. V.; Petersen, Jeff Zarp
2016-01-01
Cognitive impairment is a core feature of Major Depressive Disorder (MDD) but treatments targeting cognition are lacking. Numerous pre-clinical and clinical studies have investigated potential cognition treatments, but overall the evidence is conflicting. We conducted a systematic search following...... the PRISMA guidelines on PubMed and PsychInfo to evaluate the extant evidence and methodological challenges in randomized controlled trials (RCTs) of biological, psychological and behavioural candidate treatments targeting cognition in MDD. Inclusion criteria were RCTs with a placebo control assessing...... potential pro-cognitive effects of candidate treatments in MDD. Two independent authors reviewed the studies and assessed their risk of bias with the Cochrane Collaboration׳s Risk of Bias tool. Twenty-eight eligible studies (24 biological and four psychological or behavioural studies) were identified...
DEFF Research Database (Denmark)
Tran, Marie Thi Dao; Skovbjerg, Sine; Arendt-Nielsen, Lars
2013-01-01
a promising new treatment for refractory depression and can be targeted at the brain, thereby activating biochemical cell processes.Methods/Design: In a parallel, randomized, double-blind, placebo-controlled trial conducted at the Danish Research Centre for Chemical Sensitivities, the effects of PEMF in MCS...... follow-up according to a predefined timetable. The primary outcome will be a measurement of the impact of MCS on everyday life. The secondary outcomes will be measurements of MCS symptoms, psychological distress (stress, anxiety or depressive symptoms), capsaicin-induced secondary punctate hyperalgesia......, immunological markers in serum, and quality of life.Discussion: This trial will assess the effects of PEMF therapy for MCS. Currently, there is no treatment with a documented effect on MCS, and in terms of healthcare there is very little to offer these patients. There is thus a great need for well...
Tandon, Vivek; Raheja, Amol; Suri, Ashish; Chandra, P Sarat; Kale, Shashank S; Kumar, Rajinder; Garg, Ajay; Kalaivani, Mani; Pandey, Ravindra M; Sharma, Bhawani S
2017-03-01
Till date there are no randomized trials to suggest the superiority of intra-operative magnetic resonance imaging (IOMRI) guided trans-sphenoidal pituitary resection over two dimensional fluoroscopic (2D-F) guided resections. We conducted this trial to establish the superiority of IOMRI in pituitary surgery. Primary objective was to compare extent of tumor resection between the two study arms. It was a prospective, randomized, outcome assessor and statistician blinded, two arm (A: IOMRI, n=25 and B: 2D-F, n=25), parallel group clinical trial. 4 patients from IOMRI group cross-over to 2D-F group and were consequently analyzed in latter group, based on modified intent to treat method. A total of 50 patients were enrolled till completion of trial (n=25 in each study arm). Demographic profile and baseline parameters were comparable among the two arms (p>0.05) except for higher number of endoscopic procedures and experienced neurosurgeons (>10years) in arm B (p=0.02, 0.002 respectively). Extent of resection was similar in both study arms (A, 94.9% vs B, 93.6%; p=0.78), despite adjusting for experience of operating surgeon and use of microscope/endoscope for surgical resection. We observed that use of IOMRI helped optimize the extent of resection in 5/20 patients (25%) for pituitary tumor resection in-group A. Present study failed to observe superiorty of IOMRI over conventional 2D-F guided resection in pituitary macroadenoma surgery. By use of this technology, younger surgeons could validate their results intra-operatively and hence could increase EOR without causing any increase in complications. Copyright © 2016 Elsevier Ltd. All rights reserved.
Lattice Boltzmann heat transfer model for permeable voxels
Pereira, Gerald G.; Wu, Bisheng; Ahmed, Shakil
2017-12-01
We develop a gray-scale lattice Boltzmann (LB) model to study fluid flow combined with heat transfer for flow through porous media where voxels may be partially solid (or void). Heat transfer in rocks may lead to deformation, which in turn can modulate the fluid flow and so has significant contribution to rock permeability. The LB temperature field is compared to a finite difference solution of the continuum partial differential equations for fluid flow in a channel. Excellent quantitative agreement is found for both Poiseuille channel flow and Brinkman flow. The LB model is then applied to sample porous media such as packed beds and also more realistic sandstone rock sample, and both the convective and diffusive regimes are recovered when varying the thermal diffusivity. It is found that while the rock permeability can be comparatively small (order milli-Darcy), the temperature field can show significant variation depending on the thermal convection of the fluid. This LB method has significant advantages over other numerical methods such as finite and boundary element methods in dealing with coupled fluid flow and heat transfer in rocks which have irregular and nonsmooth pore spaces.
Meadows, Cheyney; Guerino, Frank; Sun, Fangshi
2014-08-16
The novel isoxazoline molecule fluralaner provides 12 weeks activity against fleas and 8 to 12 weeks against tick infestations according to label claims. This blinded, multi-center study in client-owned dogs evaluated the flea control provided by a single oral fluralaner treatment (25-56 mg/kg; Bravecto™, Merck Animal Health) compared to a control group administered three oral spinosad (30 - 60 mg/kg; Comfortis®, Elanco) treatments at 4-week intervals together with an amitraz collar (9%, Preventic®, Virbac). Households were randomized (3:1 ratio) to either fluralaner (224 dogs, 118 households) or control (70 dogs, 39 households). Within households, one primary dog with at least 10 live fleas at enrollment was randomly selected for whole body flea counts every 4 weeks through Week 12; all dogs were followed for safety until Week 12. Fluralaner dogs received two additional doses at Weeks 12 and 24 for further safety and palatability observations through Week 26. Geometric mean flea count reductions from baseline for the fluralaner group at Weeks 4, 8, and 12 were 99.7%, 99.8%, and 99.8%, respectively; and 96.1%, 99.5%, and 99.6% for the spinosad controls. Percentages of flea-free primary dogs at Weeks 4, 8, and 12 were 91.1%, 95.4%, and 95.3% for the fluralaner group; and 44.7%, 88.2%, and 84.4% for the controls; the differences were significant at Weeks 4 (P Fluralaner tablets were accepted free choice in over 90% of doses. The most common adverse event was vomiting, occurring in 7.1% of the fluralaner group and 14.3% of the controls. No treatment related serious adverse events were reported. A single treatment of dogs with the palatable fluralaner flavored chewable tablet provides a safe and effective option for 12 weeks of flea control at least equivalent to that of 3 sequential treatments with spinosad tablets. Linked to the high level of flea control was a substantial alleviation of associated signs of FAD.
Permeability and selectivity of reverse osmosis membranes: correlation to swelling revisited.
Dražević, Emil; Košutić, Krešimir; Freger, Viatcheslav
2014-02-01
Membrane swelling governs both rejection of solutes and permeability of polymeric membranes, however very few data have been available on swelling in water of salt-rejecting reverse osmosis (RO) membranes. This study assesses swelling, thickness and their relation to water permeability for four commercial polyamide (PA) RO membranes (SWC4+, ESPA1, XLE and BW30) using atomic force microscopy (AFM) and attenuated total reflection Fourier transform IR spectroscopy (ATR-FTIR). ATR-FTIR offered a significantly improved estimate of the actual barrier thickness of PA, given AFM is biased by porosity ("fluffy parts") or wiggling of the active layer or presence of a coating layer. Thus obtained intrinsic permeability (permeability times thickness) and selectivity of aromatic polyamides plotted versus swelling falls well on a general trend, along with previously reported data on several common materials showing RO and NF selectivity. The observed general trend may be rationalized by viewing the polymers as a random composite medium containing molecularly small pores. The results suggest that the combination of a rigid low dielectric matrix, limiting the pore size, with multiple hydrophilic H-bonding sites may be a common feature of RO/NF membranes, allowing both high permeability and selectivity. Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.
Endothelial monolayer permeability under controlled oxygen tension.
Funamoto, Kenichi; Yoshino, Daisuke; Matsubara, Kento; Zervantonakis, Ioannis K; Funamoto, Kiyoe; Nakayama, Masafumi; Masamune, Jun; Kimura, Yoshitaka; Kamm, Roger D
2017-06-19
Endothelial permeability has been extensively investigated in the context of pathologies such as cancer and also in studies of drug delivery from the circulation. Hypoxia is a critical regulator of endothelial cell (EC) behavior and affects the barrier function of endothelial linings, yet its role has been little studied. This paper reveals the effect of hypoxia on the permeability of an EC monolayer by cellular experiments using a microfluidic device and a conventional cell culture dish. Human umbilical vein endothelial cells (HUVECs) were seeded into one microfluidic channel, creating an EC monolayer on each vertical surface of a collagen gel confined to a central chamber. Oxygen tension was regulated to produce normoxic (21% O2) or hypoxic (3% O2) conditions by the supply of gas mixtures of oxygen, carbon dioxide, and nitrogen at predefined ratios into channels fabricated into the device. Permeability of the EC monolayer quantified by analyzing diffusion of fluorescence-labelled dextrans into the collagen gel increases with barrier function loss by 6 hour hypoxic exposure, showing 11-fold and 4-fold increases for 70 kDa and 10 kDa dextrans, respectively, on average. Consistent with this, subsequent immunofluorescent staining and separate western blot analysis of HUVECs on a culture dish demonstrate loose cell-cell adhesion resulting from internalization of VE-cadherin under hypoxia. Thus, hypoxic stress increases endothelial permeability by altering cell-cell junction integrity.
Pump and treat in low permeability media
Energy Technology Data Exchange (ETDEWEB)
Mackay, D.M. [Univ. of Waterloo, Ontario (Canada)
1996-08-01
Pump and Treat (P&T) is a commonly applied technology whose primary promise for the low permeability environments of interest to these technology reviews is almost certainly containment of the problem. Conventional P&T would be expected to offer little promise of complete restoration in such environments, unless very long time frames (decades or centuries) are considered. A variety of approaches have been proposed to enhance the efficiency of P&T; some appear to offer little promise in low or mixed permeability environments, while others may offer more promise (e.g. hydro- or pneumatic-fracturing, which are described elsewhere in this document, and application of vacuum to the extraction well(s), which is a proprietary technology whose promise is currently difficult to assess objectively). Understanding the potential advantages and means of optimizing these enhancement approaches requires more understanding of the basic processes limiting P&T performance in low or mixed permeability media. These efforts are probably also necessary to understand the advantages and means of optimizing many of the very different remedial technologies that may be applicable to low or mixed permeability environments. Finally, since a reasonably certain capability of P&T is containment (i.e. prevention of further migration of contaminants), P&T may generally be required as a sort of safety net around sites at which the alternative technologies are being tested or applied. 23 refs.
Variability of permeability with diameter of conduit
Indian Academy of Sciences (India)
If the velocity changes followed a parabolic profile across a unit cross-sectional area, it is reasonable to think that the permeability k, of the porous medium should follow the same parabolic profile, i.e. the value should not be linear across the cross- section. If a porous system is conceived to be a bundle of capillary tubes of ...
Magnetic levitation induced by negative permeability
Rangelov, A. A.
2011-01-01
In this paper we study the interaction between a point magnetic dipole and a semi-infinite metamaterial using the method of images. We obtain analytical expressions for the levitation force for an arbitrarily oriented dipole. Surprisingly the maximal levitation force for negative permeability is found to be stronger compared to the case when the dipole is above a superconductor.
Cadmium substituted high permeability lithium ferrite
Indian Academy of Sciences (India)
Unknown
action becomes weaker than the B–B interaction. This disturbs the parallel arrangement of spin magnetic moments on B-site paving way for canted spins. Zn2+ and Cd2+ substituted ferrites have showed similar type of canting behaviour above a certain limit of their contents. The compositional variation of initial permeability.
Radionuclide assessment of pulmonary microvascular permeability
Energy Technology Data Exchange (ETDEWEB)
Groeneveld, A.B.J. [Medical Intensive Care Unit, Department of Internal Medicine, Free University Hospital, De Boelelaan 1117, 1081 HV Amsterdam (Netherlands)
1997-04-01
The literature has been reviewed to evaluate the technique and clinical value of radionuclide measurements of microvascular permeability and oedema formation in the lungs. Methodology, modelling and interpretation vary widely among studies. Nevertheless, most studies agree on the fact that the measurement of permeability via pulmonary radioactivity measurements of intravenously injected radiolabelled proteins versus that in the blood pool, the so-called pulmonary protein transport rate (PTR), can assist the clinician in discriminating between permeability oedema of the lungs associated with the adult respiratory distress syndrome (ARDS) and oedema caused by an increased filtration pressure, for instance in the course of cardiac disease, i.e. pressure-induced pulmonary oedema. Some of the techniques used to measure PTR are also able to detect subclinical forms of lung microvascular injury not yet complicated by permeability oedema. This may occur after cardiopulmonary bypass and major vascular surgery, for instance. By paralleling the clinical severity and course of the ARDS, the PTR method may also serve as a tool to evaluate new therapies for the syndrome. Taken together, the currently available radionuclide methods, which are applicable at the bedside in the intensive care unit, may provide a gold standard for detecting minor and major forms of acute microvascular lung injury, and for evaluating the severity, course and response to treatment. (orig.). With 2 tabs.
Permeable pavement research – Edison, New Jersey
These are the slides for the New York City Concrete Promotional Council Pervious Concrete Seminar presentation. The basis for the project, the monitoring design and some preliminary monitoring data from the permeable pavement parking lot at the Edison Environmental Center are pre...
Altered membrane permeability in multidrug resistant Escherichia ...
African Journals Online (AJOL)
PRECIOUS
2009-11-02
Nov 2, 2009 ... Key words: Outer membrane proteins, porins, Escherichia coli, multidrug resistance, extra-intestinal, extended spectrum β-Lactamase (ESBL). INTRODUCTION. Membrane permeability is the first step involved in resis- tance of bacteria to an antibiotic. The outer membrane proteins that constitute porins play ...
Fan, Desheng; Meng, Xiangfeng; Wang, Yurong; Yang, Xiulun; Pan, Xuemei; Peng, Xiang; He, Wenqi; Dong, Guoyan; Chen, Hongyi
2015-04-10
A multiple-image authentication method with a cascaded multilevel architecture in the Fresnel domain is proposed, in which a synthetic encoded complex amplitude is first fabricated, and its real amplitude component is generated by iterative amplitude encoding, random sampling, and space multiplexing for the low-level certification images, while the phase component of the synthetic encoded complex amplitude is constructed by iterative phase information encoding and multiplexing for the high-level certification images. Then the synthetic encoded complex amplitude is iteratively encoded into two phase-type ciphertexts located in two different transform planes. During high-level authentication, when the two phase-type ciphertexts and the high-level decryption key are presented to the system and then the Fresnel transform is carried out, a meaningful image with good quality and a high correlation coefficient with the original certification image can be recovered in the output plane. Similar to the procedure of high-level authentication, in the case of low-level authentication with the aid of a low-level decryption key, no significant or meaningful information is retrieved, but it can result in a remarkable peak output in the nonlinear correlation coefficient of the output image and the corresponding original certification image. Therefore, the method realizes different levels of accessibility to the original certification image for different authority levels with the same cascaded multilevel architecture.
Moussaoui, L S; Naef, D; Tissot, J-D; Desrichard, O
2016-05-01
Many communication campaigns to encourage people to give blood rely on "save lives" messages, even though there is no experimental evidence as to the effectiveness of this kind of argument with respect to blood donation. The objective of this study is to test experimentally if it is indeed an effective way to prompt people to give blood, in order for communication campaigns to be evidenced-based. One thousand and twenty-two lapsed blood donors were sent, at random, either a standard letter or the same letter containing an additional "save lives" message. The blood donation center measured intention to donate and actual donor return rate (3%) after 10months. Although fewer people in the "save lives" condition said they had no intention to give blood again, the "save lives" letter did not lead to more donor returns than the standard letter. Our results suggest that contrary to intuition, campaigns to promote blood donation should not rely blindly on "save lives" arguments. Copyright © 2016 Elsevier Masson SAS. All rights reserved.
GHz permeability of sprayed NiZn ferrite films
Energy Technology Data Exchange (ETDEWEB)
Acher, O. [CEA Le Ripault, BP 16 F-37260 Monts (France)]. E-mail: olivier.acher@cea.fr; Ledieu, M. [CEA Le Ripault, BP 16 F-37260 Monts (France); Abe, M. [Department of Physical Electronics, Tokyo Institute of Technology, Tokyo 152-8552 (Japan); Tada, M. [Department of Physical Electronics, Tokyo Institute of Technology, Tokyo 152-8552 (Japan); Matsushita, N. [Department of Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Yoshimura, M. [Department of Materials and Structures Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama 226-8503 (Japan); Kondo, K. [NEC-Tokin Corporation, 6-7-1 Koriyama, Taihaku-ku, Sendai 982-8510 (Japan)
2007-03-15
The high-frequency permeability of NiZn ferrite films prepared by roll spray ferrite plating is investigated. Significant magnetoelastic effects are observed. The permeability is nearly isotropic in film plane, and Bouchaud-Zerah effective medium model for the permeability seems to give a fair account of the permeability spectra. According to this model, the isotropic in-plane complex permeability is the square root of the hard axis gyromagnetic permeability of a thin film with uniform magnetization, which is easily expressed through Landau-Gilbert formulation.
A Microring Resonator Based Negative Permeability Metamaterial Sensor
Directory of Open Access Journals (Sweden)
Yao-Zhong Lan
2011-08-01
Full Text Available Metamaterials are artificial multifunctional materials that acquire their material properties from their structure, rather than inheriting them directly from the materials they are composed of, and they may provide novel tools to significantly enhance the sensitivity and resolution of sensors. In this paper, we derive the dispersion relation of a cylindrical dielectric waveguide loaded on a negative permeability metamaterial (NPM layer, and compute the resonant frequencies and electric field distribution of the corresponding Whispering-Gallery-Modes (WGMs. The theoretical resonant frequency and electric field distribution results are in good agreement with the full wave simulation results. We show that the NPM sensor based on a microring resonator possesses higher sensitivity than the traditional microring sensor since with the evanescent wave amplification and the increase of NPM layer thickness, the sensitivity will be greatly increased. This may open a door for designing sensors with specified sensitivity.