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Sample records for dynamic permeability characteristics

  1. Accurate determination of characteristic relative permeability curves

    NASA Astrophysics Data System (ADS)

    Krause, Michael H.; Benson, Sally M.

    2015-09-01

    A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.

  2. Ni 80Fe 20 permalloy nanoparticles: Wet chemical preparation, size control and their dynamic permeability characteristics when composited with Fe micron particles

    NASA Astrophysics Data System (ADS)

    Qin, G. W.; Pei, W. L.; Ren, Y. P.; Shimada, Y.; Endo, Y.; Yamaguchi, M.; Okamoto, S.; Kitakami, O.

    2009-12-01

    Ni 80Fe 20 permalloy nanoparticles (NPs) have been prepared by the polyol processing at 180 °C for 2 h and their particle sizes can be precisely controlled in the size range of 20-440 nm by proper addition of K 2PtCl 4 agent. X-ray diffraction results show that the Ni-Fe NPs are of FCC structure, and a homogeneous composition and a narrow size distribution of these NPs have been confirmed by scanning electron microscopy assisted with energy dispersion spectroscopy of X-ray (SEM-EDX). The saturation magnetization of ~440nm NPs is 80.8 emu/g that is comparable to that of bulk Ni 80Fe 20 alloys, but it decreases to 28.7 emu/g for ~20 nm NPs. The coercive force decreases from 90 to 3 Oe with decreasing NP size. The wide range of particle size is exploited to seek for high permeability composite particles. The planar type samples composed of the NiFe NPs exhibit low initial permeability due to the deteriorated magnetic softness and low packing density. However, when they are mixed with Fe micron particles, the initial permeability significantly increases depending on the mixing ratio and the NiFe NP size. A maximum initial permeability is achieved to be ~9.1 at 1 GHz for the Fe-10 vol%NiFe (~20 nmΦ), which is about three times that of pure Fe micron particles. The effects of Ni-Fe particle size, volume percentage and solvent on the static and dynamic permeability are discussed.

  3. Polymer nanocomposites: permeability, chain dynamics, mechanical properties

    NASA Astrophysics Data System (ADS)

    Sahu, Laxmi

    2005-03-01

    Polymer nanocomposites based on dispersion of surfactant treated expandable smectite clays such as montmorillonite layered silicates (MLS) have shown promise as organic-inorganic hybrids with the potential to improve barrier properties. Separately, flexible displays based on plastic substrates have reduced lifetimes tied to the low barrier properties. While there has been a general attribution of improved barrier properties to the tortuous path, this does not consider the influence the introduction of a secondary filler has on the morphology of the host polymer. Here we examine the influence of MLS nanoplatelets on the barrier properties and chain dynamics of polymers. We investigate the potential for host polymer modification by comparing two crystallizable polymers nylon and PET and resulting well dispersed nanocomposites. We study mechanical, cyclic fatigue and permeability of films. Permeability of the biaxially stretched film and when the film undergoes fatigue of 50 and 10000 cycles are also measured. Chain dynamics were modeled based on the Burger model fit to creep-recovery data. A systematic approach to predict the permeability considering amorphous, crystalline and MLS content and comparison with experimental values were done. We also conducted water absorption measurements to highlight the water absorption differences in the two polymers. Dimensional stability of PET was studied by measuring coefficient of thermal expansion of thin film on Si substrate by ellipsometry method.

  4. Simulating bioclogging effects on dynamic riverbed permeability and infiltration

    NASA Astrophysics Data System (ADS)

    Newcomer, Michelle E.; Hubbard, Susan S.; Fleckenstein, Jan H.; Maier, Ulrich; Schmidt, Christian; Thullner, Martin; Ulrich, Craig; Flipo, Nicolas; Rubin, Yoram

    2016-04-01

    Bioclogging in rivers can detrimentally impact aquifer recharge. This is particularly so in dry regions, where losing rivers are common, and where disconnection between surface water and groundwater (leading to the development of an unsaturated zone) can occur. Reduction in riverbed permeability due to biomass growth is a time-variable parameter that is often neglected, yet permeability reduction from bioclogging can introduce order of magnitude changes in seepage fluxes from rivers over short (i.e., monthly) timescales. To address the combined effects of bioclogging and disconnection on infiltration, we developed numerical representations of bioclogging processes within a one-dimensional, variably saturated flow model representing losing-connected and losing-disconnected rivers. We tested these formulations using a synthetic case study informed with biological data obtained from the Russian River, California, USA. Our findings show that modeled biomass growth reduced seepage for losing-connected and losing-disconnected rivers. However, for rivers undergoing disconnection, infiltration declines occurred only after the system was fully disconnected. Before full disconnection, biologically induced permeability declines were not significant enough to offset the infiltration gains introduced by disconnection. The two effects combine to lead to a characteristic infiltration curve where peak infiltration magnitude and timing is controlled by permeability declines relative to hydraulic gradient gains. Biomass growth was found to hasten the onset of full disconnection; a condition we term `effective disconnection'. Our results show that river infiltration can respond dynamically to bioclogging and subsequent permeability declines that are highly dependent on river connection status.

  5. Experimental Observations of Permeability Enhancements by Dynamic Stresses

    NASA Astrophysics Data System (ADS)

    Elkhoury, J. E.; Niemeijer, A.; Brodsky, E. E.; Marone, C.

    2008-12-01

    Shaking produced by seismic faulting often triggers distant and nearby earthquakes. Seismic waves are also known to increase stream flow and spring discharge and enhance oil production; in some cases tripling the effective permeability of the natural system. These observations have been attributed to shaking-induced increases in permeability. However, the underlying mechanism is poorly understood. Here we present experimental evidence of permeability enhancement in fractured rock samples subject to dynamic stresses. We use Berea sandstone samples under triaxial stresses with confining pressure of 9 MPa and 20 MPa of normal stress. We flow deionized water through a fracture produced in-situ and find that oscillations in pore pressure, of 20 second period and 120 second duration, induce transient increases in permeability. Permeability increases scale with the amplitude of pore pressure oscillations. The maximum value of the permeability enhancement is 5x10-16 m2 over a background permeability of 1x10-15 m2. After the oscillations, permeability recovers as the inverse square root of time. The recovery indicates a reversible mechanism, such as clogging/unclogging of fractures, as opposed to an irreversible one, like micro-fracturing. Our result has clear consequences for earthquake triggering mediated by permeability enhancement. Moreover, our data point at the feasibility of dynamically controlling permeability of fractured systems with applications to hydrology and oil reservoir engineering.

  6. Dynamic permeability of porous media by the lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Pazdniakou, A.; Adler, P. M.

    2013-12-01

    The lattice Boltzmann method (LBM) is applied to calculate the dynamic permeability K(ω) of porous media; an oscillating macroscopic pressure gradient is imposed in order to generate oscillating flows. The LBM simulation yields the time dependent seepage velocity of amplitude A and phase shift B which are used to calculate K(ω). The procedure is validated for plane Poiseuille flows where excellent agreement with the analytical solution is obtained. The limitations of the method are discussed. When the ratio between the kinematic viscosity and the characteristic size of the pores is high, the corresponding Knudsen number Kn is high and the numerical values of K(ω) are incorrect with a positive imaginary part; it is only when Kn is small enough that correct values are obtained. The influence of the time discretization of the oscillating body force is studied; simulation results are influenced by an insufficient discretization, i.e., it is necessary to avoid using too high frequencies. The influence of absolute errors in the seepage velocity amplitude δA and the phase shift δB on K(ω) shows that for high ω even small errors in B can cause drastic errors in ReK(ω). The dynamic permeability of reconstructed and real (sandstone) porous media is calculated for a large range of frequencies and the universal scaling behavior is verified. Very good correspondences with the theoretical predictions are observed.

  7. Nanochannel flow past permeable walls via molecular dynamics

    NASA Astrophysics Data System (ADS)

    Xie, Jian-Fei; Cao, Bing-Yang

    2016-07-01

    The nanochannel flow past permeable walls with nanopores is investigated by molecular dynamics (MD) simulations, including the density distribution, velocity field, molecular penetration mechanism and surface friction coefficient. A low density distribution has been found at the gas-wall interface demonstrating the low pressure region. In addition, there exists a jump of the gas density on the permeable surface, which indicates the discontinuity of the density distribution across the permeable surface. On the other hand, the nanoscale vortices are observed in nanopores of the permeable wall, and the reduced mass flux of the flow in nanopores results in a shifted hydrodynamic boundary above the permeable surface. Particularly the slip length of the gas flow on the permeable surface is pronounced a non-linear function of the molecular mean free path, which produces a large value of the tangential momentum accommodation coefficient (TMAC) and a big portion of the diffusive refection. Moreover, the gas-gas interaction and multi-collision among gas molecules may take place in nanopores, which contribute to large values of TMAC. Consequently the boundary friction coefficient on the permeable surface is increased because of the energy dissipation consumed by the nanoscale vortices in nanopores. The molecular boundary condition provides us with a new picture of the nanochannel flow past the permeable wall with nanopores.

  8. Dynamic permeability of porous media by the lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Adler, P.; Pazdniakou, A.

    2012-04-01

    The main objective of our work is to determine the dynamic permeability of three dimensional porous media by means of the Lattice Boltzmann method (LBM). The Navier-Stokes equation can be numerically solved by LBM which is widely used to address various fluid dynamics problems. Space is discretized by a three-dimensional cubic lattice and time is discretized as well. The generally accepted notation for lattice Boltzmann models is DdQq where D stands for space dimension and Q for the number of discrete velocities. The present model is denoted by D3Q19. Moreover, the Two Relaxation Times variant of the Multi Relaxation Times model is implemented. Bounce back boundary conditions are used on the solid-fluid interfaces. The porous medium is spatially periodic. Reconstructed media were used; they are obtained by imposing a porosity and a correlation function characterized by a correlation length. Real samples can be obtained by MicroCT. In contrast with other previous contributions, the dynamic permeability K(omega) which is a complex number, is derived by imposing an oscillating body force of pulsation omega on the unit cell and by deriving the amplitude and the phase shift of the resulting time dependent seepage velocity. The influence of two limiting parameters, namely the Knudsen number Kn and the discretization for high frequencies, on K(omega) is carefully studied for the first time. Kn is proportional to nu/(cs H) where nu is the kinematic viscosity, cs the speed of sound in the fluid and H a characteristic length scale of the porous medium. Several porous media such as the classical plane Poiseuille flow and the reconstructed media are used to show that it is only for small enough values of Kn that reliable results are obtained. Otherwise, the data depend on Kn and may even be totally unphysical. However, it should be noticed that the limiting value of Kn could not be derived in general since it depends very much on the structure of the medium. Problems occur at

  9. Dynamic permeability of porous media by the lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Pazdniakou, A.; Adler, P. M.

    2011-12-01

    The main objective of our work is to determine the dynamic permeability of three dimensional porous media by means of the Lattice Boltzmann method (LBM). The Navier-Stokes equation can be numerically solved by LBM which is widely used to address various fluid dynamics problems. Space is discretized by a three-dimensional cubic lattice and time is discretized as well. The generally accepted notation for lattice Boltzmann models is DdQq where D stands for space dimension and Q for the number of discrete velocities. The present model is denoted by D3Q19. Moreover, the Two Relaxation Times variant of the Multi Relaxation Times model is implemented. Bounce back boundary conditions are used on the solid-fluid interfaces. The porous medium is spatially periodic. Reconstructed media were used; they are obtained by imposing a porosity and a correlation function characterized by a correlation length. Real samples can be obtained by MicroCT. In contrast with other previous contributions, the dynamic permeability K(omega) which is a complex number, is derived by imposing an oscillating body force of pulsation omega on the unit cell and by deriving the amplitude and the phase shift of the resulting time dependent seepage velocity. The influence of two limiting parameters, namely the Knudsen number Kn and the discretization for high frequencies, on K(omega) is carefully studied for the first time. Kn is proportional to nu/(c_s H) where nu is the kinematic viscosity, c_s the speed of sound in the fluid and H a characteristic length scale of the porous medium. Several porous media such as the classical plane Poiseuille flow and the reconstructed media are used to show that it is only for small enough values of Kn that reliable results are obtained. Otherwise, the data depend on Kn and may even be totally unphysical. However, it should be noticed that the limiting value of Kn could not be derived in general since it depends very much on the structure of the medium. Problems occur

  10. A study of the osmotic characteristics, water permeability, and cryoprotectant permeability of human vaginal immune cells

    PubMed Central

    Shu, Zhiquan; Hughes, Sean M.; Fang, Cifeng; Huang, Jinghua; Fu, Baiwen; Zhao, Gang; Fialkow, Michael; Lentz, Gretchen; Hladik, Florian; Gao, Dayong

    2016-01-01

    Cryopreservation of specimens taken from the genital tract of women is important for studying mucosal immunity during HIV prevention trials. However, it is unclear whether the current, empirically developed cryopreservation procedures for peripheral blood cells are also ideal for genital specimens. The optimal cryopreservation protocol depends on the cryobiological features of the cells. Thus, we obtained tissue specimens from vaginal repair surgeries, isolated and flow cytometry-purified immune cells, and determined fundamental cryobiological characteristics of vaginal CD3+ T cells and CD14+ macrophages using a microfluidic device. The osmotically inactive volumes of the two cell types (Vb) were determined relative to the initial cell volume (V0) by exposing the cells to hypotonic and hypertonic saline solutions, evaluating the equilibrium volume, and applying the Boyle van't Hoff relationship. The cell membrane permeability to water (Lp) and to four different cryoprotective agent (CPA) solutions (Ps) at room temperature were also measured. Results indicated Vb values of 0.516 V0 and 0.457 V0 for mucosal T cells and macrophages, respectively. Lp values at room temperature were 0.196 and 0.295 μm/min/atm for T cells and macrophages, respectively. Both cell types had high Ps values for the three CPAs, dimethyl sulfoxide (DMSO), propylene glycol (PG) and ethylene glycol (EG) (minimum of 0.418 × 10−3 cm/min), but transport of the fourth CPA, glycerol, occurred 50–150 times more slowly. Thus, DMSO, PG, and EG are better options than glycerol in avoiding severe cell volume excursion and osmotic injury during CPA addition and removal for cryopreservation of human vaginal immune cells. PMID:26976225

  11. A study of the osmotic characteristics, water permeability, and cryoprotectant permeability of human vaginal immune cells.

    PubMed

    Shu, Zhiquan; Hughes, Sean M; Fang, Cifeng; Huang, Jinghua; Fu, Baiwen; Zhao, Gang; Fialkow, Michael; Lentz, Gretchen; Hladik, Florian; Gao, Dayong

    2016-04-01

    Cryopreservation of specimens taken from the genital tract of women is important for studying mucosal immunity during HIV prevention trials. However, it is unclear whether the current, empirically developed cryopreservation procedures for peripheral blood cells are also ideal for genital specimens. The optimal cryopreservation protocol depends on the cryobiological features of the cells. Thus, we obtained tissue specimens from vaginal repair surgeries, isolated and flow cytometry-purified immune cells, and determined fundamental cryobiological characteristics of vaginal CD3(+) T cells and CD14(+) macrophages using a microfluidic device. The osmotically inactive volumes of the two cell types (Vb) were determined relative to the initial cell volume (V0) by exposing the cells to hypotonic and hypertonic saline solutions, evaluating the equilibrium volume, and applying the Boyle van't Hoff relationship. The cell membrane permeability to water (Lp) and to four different cryoprotective agent (CPA) solutions (Ps) at room temperature were also measured. Results indicated Vb values of 0.516 V0 and 0.457 V0 for mucosal T cells and macrophages, respectively. Lp values at room temperature were 0.196 and 0.295 μm/min/atm for T cells and macrophages, respectively. Both cell types had high Ps values for the three CPAs, dimethyl sulfoxide (DMSO), propylene glycol (PG) and ethylene glycol (EG) (minimum of 0.418 × 10(-3) cm/min), but transport of the fourth CPA, glycerol, occurred 50-150 times more slowly. Thus, DMSO, PG, and EG are better options than glycerol in avoiding severe cell volume excursion and osmotic injury during CPA addition and removal for cryopreservation of human vaginal immune cells. PMID:26976225

  12. [Progress with research on the permeability characteristics of reproductive cell membranes].

    PubMed

    Zhou, Zheng; Chen, Guangming; Zhang, Shaozhi

    2012-04-01

    The successful cryopreservation of reproductive cells has important practical significance in many fields. In order to improve the recovery rate and viability of cryopreserved cells, it is necessary to study the permeability characteristics of cell membrane to both water and cryoprotectant. In this paper we review the studies on membrane permeability of animal reproductive cell for the recent years. We firstly list the typical permeability data of spermatozoa and oocyte membrane for water and cryoprotectant. We then analyze the effects of these characteristics on the design of cryopreservation protocol. We also introduce the latest experimental methods to measure the cell membrane permeability. PMID:22616195

  13. Laboratory evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Brodsky, Emily E.; Marone, Chris; Elsworth, Derek

    2014-04-01

    It is well-established that seismic waves can increase the permeability in natural systems, yet the mechanism remains poorly understood. We investigate the underlying mechanics by generating well-controlled, repeatable permeability enhancement in laboratory experiments. Pore pressure oscillations, simulating dynamic stresses, were applied to intact and fractured Berea sandstone samples under confining stresses of tens of MPa. Dynamic stressing produces an immediate permeability enhancement ranging from 1 to 60%, which scales with the amplitude of the dynamic strain (7×10-7 to 7×10-6) followed by a gradual permeability recovery. We investigated the mechanism by: (1) recording deformation of samples both before and after fracturing during the experiment, (2) varying the chemistry of the water and therefore particle mobility, (3) evaluating the dependence of permeability enhancement and recovery on dynamic stress amplitude, and (4) examining micro-scale pore textures of the rock samples before and after experiments. We find that dynamic stressing does not produce permanent deformation in our samples. Water chemistry has a pronounced effect on the sensitivity to dynamic stressing, with the magnitude of permeability enhancement and the rate of permeability recovery varying with ionic strength of the pore fluid. Permeability recovery rates generally correlate with the permeability enhancement sensitivity. Microstructural observations of our samples show clearing of clay particulates from fracture surfaces during the experiment. From these four lines of evidence, we conclude that a flow-dependent mechanism associated with mobilization of fines controls both the magnitude of the permeability enhancement and the recovery rate in our experiments. We also find that permeability sensitivity to dynamic stressing increases after fracturing, which is a process that generates abundant particulate matter in situ. Our results suggest that fluid permeability in many areas of the

  14. Natural Hydrofracturing, Dynamic Permeability, and Gas recovery (Invited)

    NASA Astrophysics Data System (ADS)

    Cathles, L. M.

    2013-12-01

    Hydrofracturing has suddenly transformed the hydrocarbon industry, turning even quite recent supply projections upside down. The miracle is that it can work so well. It will take time to understand the processes which allow oil and gas to be so effectively recovered from extremely impermeable carbonate and shale formations. Two factors seem particularly important: First, nature has already gas-fractured the shales during hydrocarbon generation. In the case of the Marcellus, the maturation process left the residual organic matter a froth of very small (2-5 nm) connected gas pockets, which drained into larger (perhaps now closed) fractures, and then into the surrounding formations where they produced joints. Second, the organic surfaces tend to be gas-wet and hydrophobic, whereas the silicate surfaces in the shale tend to be the reverse (hydrophilic and gas-phobic). The fluid phase interactions are thus complicated. The talk will briefly review these aspects of the complex hydrofracturing environment, and then explore whether the dynamic permeability produced when the hydrocarbons were expelled could be retained or recovered during a second, human, hydrofracturing.

  15. Three-phase permeabilities and other characteristics of 260-mD fired Berea

    SciTech Connect

    Maloney, D.; Brinkmeyer, A.

    1992-04-01

    A laboratory investigation was conducted to determine relative permeabilities and other characteristics of a 260-mD fired Berea sandstone. The mineralogical and physical characteristics of the sample were characterized by XRD tests, thin section analyses, mercury injection tests, and centrifuge capillary pressure and wettability tests. Two-phase oil/water relative permeabilities were measured under several stress conditions. Resistivity characteristics of the sample were also evaluated during several of the oil/water tests. Oil/gas and gas/water relative permeabilities were measured during steady-state tests. Three-phase steady-state oil/gas/water tests were performed for six DDI saturation trajectories (decreasing brine and oil saturations, increasing gas saturation) in which the sample was not cleaned between saturation trajectories.

  16. Dynamics of hydrofracturing and permeability evolution in layered reservoirs

    NASA Astrophysics Data System (ADS)

    Ghani, Irfan; Koehn, Daniel; Toussaint, Renaud; Passchier, Cees

    2015-09-01

    A coupled hydro-mechanical model is presented to model fluid driven fracturing in layered porous rocks. In the model the solid elastic continuum is described by a discrete element approach coupled with a fluid continuum grid that is used to solve Darcy based pressure diffusion. The model assumes poro-elasto-plastic effects and yields real time dynamic aspects of the fracturing and effective stress evolution under the influence of excess fluid pressure gradients. We show that the formation and propagation of hydrofractures are sensitive to mechanical and tectonic conditions of the system. In cases where elevated fluid pressure is the sole driving agent in a stable tectonic system, sealing layers induce permutations between the principal directions of the local stress tensor, which regulate the growth of vertical fractures and may result in irregular pattern formation or sub-horizontal failure below the seal. Stiffer layers tend to concentrate differential stresses and lead to vertical fracture growth, whereas the layer-contact tends to fracture if the strength of the neighboring rock is comparably high. If the system has remained under extension for a longer time period, the developed hydrofractures propagate by linking up confined tensile fractures in competent layers. This leads to the growth of large-scale normal faults in the layered systems, so that subsequently the effective permeability is highly variable over time and the faults drain the system. The simulation results are shown to be consistent with some of the field observations carried out in the Oman Mountains, where abnormal fluid pressure is reported to be a significant factor in the development of several generations of local and regional fracture and fault sets.

  17. Modeling of permeability and compaction characteristics of soils using evolutionary polynomial regression

    NASA Astrophysics Data System (ADS)

    Ahangar-Asr, A.; Faramarzi, A.; Mottaghifard, N.; Javadi, A. A.

    2011-11-01

    This paper presents a new approach, based on evolutionary polynomial regression (EPR), for prediction of permeability ( K), maximum dry density (MDD), and optimum moisture content (OMC) as functions of some physical properties of soil. EPR is a data-driven method based on evolutionary computing aimed to search for polynomial structures representing a system. In this technique, a combination of the genetic algorithm (GA) and the least-squares method is used to find feasible structures and the appropriate parameters of those structures. EPR models are developed based on results from a series of classification, compaction, and permeability tests from the literature. The tests included standard Proctor tests, constant head permeability tests, and falling head permeability tests conducted on soils made of four components, bentonite, limestone dust, sand, and gravel, mixed in different proportions. The results of the EPR model predictions are compared with those of a neural network model, a correlation equation from the literature, and the experimental data. Comparison of the results shows that the proposed models are highly accurate and robust in predicting permeability and compaction characteristics of soils. Results from sensitivity analysis indicate that the models trained from experimental data have been able to capture many physical relationships between soil parameters. The proposed models are also able to represent the degree to which individual contributing parameters affect the maximum dry density, optimum moisture content, and permeability.

  18. Assessment of Clogging Dynamics in Permeable Pavement Systems with Time Domain Reflectometers

    EPA Science Inventory

    Infiltration is a primary functional mechanism in green infrastructure stormwater controls. This study used time domain reflectometers (TDRs) to measure spatial infiltration and assess clogging dynamics of permeable pavement systems in Edison, NJ, and Louisville, KY. In 2009, t...

  19. Preliminary results on estimating permeability characteristics of carbonate rocks using pore microstructures

    NASA Astrophysics Data System (ADS)

    Lee, M.; Keehm, Y.

    2013-12-01

    Direct numerical simulation on pore microstructures from X-ray microtomography is regarded as a good tool to determine and characterize the physical properties of rocks, especially for sandstone. When the same approach is considered for carbonate rocks, we face many difficulties mostly from the heterogeneous nature of carbonates. In this study, we report preliminary results on permeability estimation of carbonate rocks from X-ray tomographic pore microstructures. Since carbonate rocks have quite different types of pore geometry depending on depositional and diagenetic environments, we choose three rock samples with different porosity types: interparticle; vuggy/moldic; and fracture, and obtain high-resolution 3D pore microstructures using X-ray microtomography technique. From the original 3D pore geometry (typically 2,000^3 voxels), we choose various digital sub-blocks to determine local variation and length dependency, and calculate permeability using the Lattice-Boltzmann method. For the interparticle case, the calculated permeability values show very similar trends to clastic sediments, and we can determine a porosity-permeability relation for a given formation as we do with the Koneny-Carman relation. On the other hand, for vuggy or fracture cases, we cannot observe any significant dependence of permeability on porosity. Thus we focus more on the local variation and scale variation of permeability. We perform analyses on percolation probability; local porosity distribution; and direction/length/width of fractures. And we present preliminary conceptual models to determine permeability characteristics. Although the results are from a few limited samples and more detailed researches will be required, our approach will be helpful to estimate and characterize permeability of carbonate rocks, and to investigate scaling and representativeness issues. Acknowledgements: This research was supported by the Basic Research Project of the Korea Institute of Geoscience and

  20. Dynamics of cell membrane permeability changes at supraphysiological temperatures.

    PubMed Central

    Bischof, J C; Padanilam, J; Holmes, W H; Ezzell, R M; Lee, R C; Tompkins, R G; Yarmush, M L; Toner, M

    1995-01-01

    A quantitative fluorescent microscopy system was developed to characterize, in real time, the effects of supraphysiological temperatures between 37 degrees and 70 degrees C on the plasma membrane of mouse 3T3 fibroblasts and isolated rat skeletal muscle cells. Membrane permeability was assessed by monitoring the leakage as a function of time of the fluorescent membrane integrity probe calcein. The kinetics of dye leakage increased with increasing temperature in both the 3T3 fibroblasts and the skeletal muscle cells. Analytical solutions derived from a two-compartment transport model showed that, for both cell types, a time-dependent permeability assumption provided a statistically better fit of the model predictions to the data than a constant permeability assumption. This finding suggests that the plasma membrane integrity is continuously being compromised while cells are subjected to supraphysiological temperatures. Images FIGURE 1 FIGURE 2 FIGURE 3 PMID:7647264

  1. Encapsulation and Permeability Characteristics of Plasma Polymerized Hollow Particles

    PubMed Central

    Shahravan, Anaram; Matsoukas, Themis

    2012-01-01

    In this protocol, core-shell nanostructures are synthesized by plasma enhanced chemical vapor deposition. We produce an amorphous barrier by plasma polymerization of isopropanol on various solid substrates, including silica and potassium chloride. This versatile technique is used to treat nanoparticles and nanopowders with sizes ranging from 37 nm to 1 micron, by depositing films whose thickness can be anywhere from 1 nm to upwards of 100 nm. Dissolution of the core allows us to study the rate of permeation through the film. In these experiments, we determine the diffusion coefficient of KCl through the barrier film by coating KCL nanocrystals and subsequently monitoring the ionic conductivity of the coated particles suspended in water. The primary interest in this process is the encapsulation and delayed release of solutes. The thickness of the shell is one of the independent variables by which we control the rate of release. It has a strong effect on the rate of release, which increases from a six-hour release (shell thickness is 20 nm) to a long-term release over 30 days (shell thickness is 95 nm). The release profile shows a characteristic behavior: a fast release (35% of the final materials) during the first five minutes after the beginning of the dissolution, and a slower release till all of the core materials come out. PMID:22929119

  2. Portable device and method for determining permeability characteristics of earth formations

    DOEpatents

    Shuck, Lowell Z.

    1977-01-01

    The invention is directed to a device which is used for determining permeability characteristics of earth formations at the surface thereof. The determination of the maximum permeability direction and the magnitude of permeability are achieved by employing a device comprising a housing having a central fluid-injection port surrounded by a plurality of spaced-apart fluid flow and pressure monitoring ports radially extending from the central injection port. With the housing resting on the earth formation in a relatively fluid-tight manner as provided by an elastomeric pad disposed therebetween, fluid is injected through the central port into the earth formation and into registry with the fluid-monitoring ports disposed about the injection port. The fluid-monitoring ports are selectively opened and the flow of the fluid through the various fluid ports is measured so as to provide a measurement of flow rates and pressure distribution about the center hole which is indicative on the earth formation permeability direction and magnitude. For example, the azimuthal direction of the fluid-monitoring ports in the direction through which the greatest amount of injected fluid flows as determined by the lowest pressure distribution corresponds to the direction of maximum permeability in the earth formation.

  3. Dynamic permeability of electrically conducting fluids under magnetic fields in annular ducts.

    PubMed

    Cuevas, S; del Río, J A

    2001-07-01

    The dynamic response of an electrically conducting fluid (either Newtonian or Maxwellian) flowing between straight concentric circular cylinders under a constant radial magnetic field, is analyzed. The isothermal flow is studied using the time Fourier transform, so that the dynamic generalization of Darcy's law in the frequency domain is obtained and analytical expressions for the dynamic permeability are derived. For the Newtonian case, the range of frequencies where the dynamic permeability approaches the static value is enlarged the smaller the gap between the cylinders and the higher the magnetic-field strength. For the Maxwell fluid, the presence of the inner cylinder shifts the frequencies that lead to the enhancement of the real part of the dynamic permeability to larger values and increases its maximum values relative to the case where the inner cylinder is absent. In addition, the Ohmic dissipation causes the damping of the amplitude of the response. PMID:11461397

  4. Membrane permeability characteristics and osmotic tolerance limits of sea urchin (Evechinus chloroticus) eggs.

    PubMed

    Adams, Serean L; Kleinhans, F W; Mladenov, Philip V; Hessian, Paul A

    2003-08-01

    Development of effective cryopreservation protocols relies on knowledge of the fundamental cryobiological characteristics for a particular cell type. These characteristics include osmotic behaviour, membrane permeability characteristics, and osmotic tolerance limits. Here, we report on measures of these characteristics for unfertilized and fertilised eggs of the sea urchin (Evechinus chloroticus). In NaCl solutions of varying osmolalities, sea urchin eggs behaved as ideal linear osmometers. The osmotically inactive volume (vb) was similar for unfertilized and fertilised eggs, 0.367+/-0.008 (mean+/-SE) and 0.303+/-0.007, respectively. Estimates of water solubility (Lp) and solute permeability (Ps) and their respective activation energies (Ea) for unfertilized and fertilised eggs were determined following exposure to cryoprotectant (CPA) solutions at different temperatures. Irrespective of treatment, fertilised eggs had higher values of Lp and Ps. The presence of a CPA decreased Lp. Among CPAs, solute permeability was highest for propylene glycol followed by dimethyl sulphoxide and then ethylene glycol. Measures of osmotic tolerance limits of the eggs revealed unfertilized eggs were able to tolerate volumetric changes of -20% and +30% of their equilibrium volume; fertilised eggs were able to tolerate changes +/-30%. Using membrane permeability data and osmotic tolerance limits, we established effective methods for loading and unloading CPAs from the eggs. The results of this study establish cryobiological characteristics for E. chloroticus eggs of use for developing an effective cryopreservation protocol. The approach we outline can be readily adapted for determining cryobiological characteristics of other species and cell types, as an aid to successful cryopreservation. PMID:12963407

  5. Dynamic fluid loss in hydraulic fracturing under realistic shear conditions in high-permeability rocks

    SciTech Connect

    Navarrete, R.C.; Cawiezel, K.E.; Constien, V.G.

    1996-08-01

    A study of the dynamic fluid loss of hydraulic fracturing fluids under realistic shear conditions is presented. During a hydraulic fracturing treatment, a polymeric solution is pumped under pressure down the well to create and propagate a fracture. Part of the fluid leaks into the rock formation, leaving a skin layer of polymer or polymer filter cake, at the rock surface or in the pore space. This study focuses on the effects of shear rate and permeability on dynamic fluid-loss behavior of crosslinked and linear fracturing gels. Previous studies of dynamic fluid loss have mainly been with low-permeability cores and constant shear rates. Here, the effect of shear history and fluid-loss additive on the dynamic leakoff of high-permeability cores is examined.

  6. Evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, T.; Brodsky, E. E.; Marone, C.; Elsworth, D.

    2013-12-01

    Dynamic permeability change by seismic waves is a well-established natural phenomenon yet the mechanism remains poorly understood. We investigate the mechanism by generating well-controlled repeatable permeability enhancement in a laboratory experiment. Each experiment proceeded as: (1) pore pressure oscillations, simulating dynamic stresses, were applied at one end of intact Berea sandstone samples under triaxial stresses of tens of megapascals, (2) samples were fractured within the apparatus, and (3) pore pressure oscillations resumed post-fracturing. In this way, both the fracture and porous media response to the dynamic stresses were investigated. In addition, we controled the mobility of fine particles by adjusting the pore fluid chemistry (deionized water, and brines of: NaCl 5%, NaCl 35%, CaCl2 5%). Our results are consistent with natural observations. Dynamic stressing produces an immediate permeability enhancement ranging from 1-60%, which scales with the amplitude of the dynamic strain, 7*10^-7 to 7*10^-6, followed by a progressive permeability recovery. In our experiments a flow-dependent mechanism associated with mobilization of fines appears to control both the magnitude of the permeability enhancement and the recovery rate. Both processes operate at two time scales, i.e., fast flushing/unclogging of the fines during the pore pressure oscillations and progressive clogging of the pore throats by particle migration, and were influenced by the fluid chemistry. The dynamic permeability changes were not associated with permanent deformation. We show that: 1) injection of unequilibrated fluids favors particle mobilization, and 2) transient permeability change results from the migration of fines which in turn results from dynamic stressing. Our results suggest that areas where pore fluids are in disequilibrium should be more sensitive to dynamic stressing. Interestingly, early observations of dynamic earthquake-triggering revealed preferential triggering in

  7. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES - PHASE I - METHODS DEVELOPMENT AND TESTING

    EPA Science Inventory

    The report gives results of Phase I of a laboratory assessment of the permeability and diffusion characteristics of Florida concretes. (NOTE: The ability of concrete to permit air flow under pressure (permeability) and the passage of radon gas without any pressure difference (dif...

  8. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES - PHASE I. METHODS DEVELOPMENT AND TESTING

    EPA Science Inventory

    The report gives results of Phase I of a laboratory assessment of the permeability and diffusion characteristics of Florida concretes. (NOTE: The ability of concrete to permit air flow under pressure (permeability) and the passage of radon gas without any pressure difference (dif...

  9. Temperature dependence dynamical permeability characterization of magnetic thin film using near-field microwave microscopy.

    PubMed

    Hung, Le Thanh; Phuoc, Nguyen N; Wang, Xuan-Cong; Ong, C K

    2011-08-01

    A temperature dependence characterization system of microwave permeability of magnetic thin film up to 5 GHz in the temperature range from room temperature up to 423 K is designed and fabricated as a prototype measurement fixture. It is based on the near field microwave microscopy technique (NFMM). The scaling coefficient of the fixture can be determined by (i) calibrating the NFMM with a standard sample whose permeability is known; (ii) by calibrating the NFMM with an established dynamic permeability measurement technique such as shorted microstrip transmission line perturbation method; (iii) adjusting the real part of the complex permeability at low frequency to fit the value of initial permeability. The algorithms for calculating the complex permeability of magnetic thin films are analyzed. A 100 nm thick FeTaN thin film deposited on Si substrate by sputtering method is characterized using the fixture. The room temperature permeability results of the FeTaN film agree well with results obtained from the established short-circuited microstrip perturbation method. Temperature dependence permeability results fit well with the Landau-Lifshitz-Gilbert equation. The temperature dependence of the static magnetic anisotropy H(K)(sta), the dynamic magnetic anisotropy H(K)(dyn), the rotational anisotropy H(rot), together with the effective damping coefficient α(eff), ferromagnetic resonance f(FMR), and frequency linewidth Δf of the thin film are investigated. These temperature dependent magnetic properties of the magnetic thin film are important to the high frequency applications of magnetic devices at high temperatures. PMID:21895260

  10. Predicting permeability from the characteristic relaxation time and intrinsic formation factor of complex conductivity spectra

    NASA Astrophysics Data System (ADS)

    Revil, A.; Binley, A.; Mejus, L.; Kessouri, P.

    2015-08-01

    Low-frequency quadrature conductivity spectra of siliclastic materials exhibit typically a characteristic relaxation time, which either corresponds to the peak frequency of the phase or the quadrature conductivity or a typical corner frequency, at which the quadrature conductivity starts to decrease rapidly toward lower frequencies. This characteristic relaxation time can be combined with the (intrinsic) formation factor and a diffusion coefficient to predict the permeability to flow of porous materials at saturation. The intrinsic formation factor can either be determined at several salinities using an electrical conductivity model or at a single salinity using a relationship between the surface and quadrature conductivities. The diffusion coefficient entering into the relationship between the permeability, the characteristic relaxation time, and the formation factor takes only two distinct values for isothermal conditions. For pure silica, the diffusion coefficient of cations, like sodium or potassium, in the Stern layer is equal to the diffusion coefficient of these ions in the bulk pore water, indicating weak sorption of these couterions. For clayey materials and clean sands and sandstones whose surface have been exposed to alumina (possibly iron), the diffusion coefficient of the cations in the Stern layer appears to be 350 times smaller than the diffusion coefficient of the same cations in the pore water. These values are consistent with the values of the ionic mobilities used to determine the amplitude of the low and high-frequency quadrature conductivities and surface conductivity. The database used to test the model comprises a total of 202 samples. Our analysis reveals that permeability prediction with the proposed model is usually within an order of magnitude from the measured value above 0.1 mD. We also discuss the relationship between the different time constants that have been considered in previous works as characteristic relaxation time, including

  11. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete.

    PubMed

    Singh, M P; Singh, S P; Singh, A P

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together. PMID:27379298

  12. Experimental Study on the Strength Characteristics and Water Permeability of Hybrid Steel Fibre Reinforced Concrete

    PubMed Central

    Singh, M. P.; Singh, S. P.; Singh, A. P.

    2014-01-01

    Results of an investigation conducted to study the effect of fibre hybridization on the strength characteristics such as compressive strength, split tensile strength, and water permeability of steel fibre reinforced concrete (SFRC) are presented. Steel fibres of different lengths, that is, 12.5 mm, 25 mm, and 50 mm, having constant diameter of 0.6 mm, were systematically combined in different mix proportions to obtain mono, binary, and ternary combinations at each of 0.5%, 1.0%, and 1.5% fibre volume fraction. A concrete mix containing no fibres was also cast for reference purpose. A total number of 1440 cube specimens of size 100∗100∗100 mm were tested, 480 each for compressive strength, split tensile strength, and water permeability at 7, 28, 90, and 120 days of curing. It has been observed from the results of this investigation that a fibre combination of 33% 12.5 mm + 33% 25 mm + 33% 50 mm long fibres can be adjudged as the most appropriate combination to be employed in hybrid steel fibre reinforced concrete (HySFRC) for optimum performance in terms of compressive strength, split tensile strength and water permeability requirements taken together. PMID:27379298

  13. Dispersion characteristics of blood during nanoparticle assisted drug delivery process through a permeable microvessel.

    PubMed

    Shaw, Sachin; Ganguly, Suvankar; Sibanda, Precious; Chakraborty, Suman

    2014-03-01

    Nanoparticle assisted drug delivery holds considerable promise as a means of next generation of medicine that allows for the intravascular delivery of drugs and contrast agents. We analyze the dispersion characteristics of blood during a nanoparticle-assisted drug delivery process through a permeable microvessel. The contribution of molecular and convective diffusion is based on Taylor's theory of shear dispersion. The aggregation of red blood cells in blood flowing through small tubes (less than 40 μm) leads to the two-phase flow with a core of rouleaux surrounded by a cell-depleted peripheral layer. The core region models as a non-Newtonian Casson fluid and the peripheral region acts as a Newtonian fluid. We investigate the influence of the nanoparticle volume fraction, the permeability of the blood vessel, pressure distribution, yield stress and the radius of the nanoparticle on the effective dispersion. We show that the effective diffusion of the nanoparticles reduces with an increase in nanoparticle volume fraction. The permeability of the blood vessels increases the effective dispersion at the inlet. The present study contributes to the fundamental understanding on how the particulate nature of blood influences nanoparticle delivery, and is of particular significance in nanomedicine design for targeted drug delivery applications. PMID:24406843

  14. Characterizing permeability and stability of microcapsules for controlled drug delivery by dynamic NMR microscopy

    NASA Astrophysics Data System (ADS)

    Henning, Stefan; Edelhoff, Daniel; Ernst, Benedikt; Leick, Sabine; Rehage, Heinz; Suter, Dieter

    2012-08-01

    Microscopic capsules made from polysaccharides are used as carriers for drugs and food additives. Here, we use NMR microscopy to assess the permeability of capsule membranes and their stability under different environmental conditions. The results allow us to determine the suitability of different capsules for controlled drug delivery. As a measure of the membrane permeability, we monitor the diffusion of paramagnetic molecules into the microcapsules by dynamic NMR microimaging. We obtained the diffusion coefficients of the probe molecules in the membranes and in the capsule core by comparing the measured time dependent concentration maps with numerical solutions of the diffusion equation. The results reveal that external coatings strongly decrease the permeability of the capsules. In addition, we also visualized that the capsules are stable under gastric conditions but dissolve under simulated colonic conditions, as required for targeted drug delivery. Depending on the capsule, the timescales for these processes range from 1 to 28 h.

  15. Stationary and Dynamic Permeability and Coupling Coefficient Measurements in Sintered Glass Bead Systems

    NASA Astrophysics Data System (ADS)

    Gueven, I.; Steeb, H.; Luding, S.

    2014-12-01

    Electrokinetic waves describe the coupling between seismic and electromagnetic waves that exist in porous media. The coupling between them arise from an electrochemical boundary layer between grain and fluid interface of saturated porous media. Acoustical waves cause a disturbance of the electrical fluid charge within the double layer, which therefore creates an electric streaming current (seismoelectric effect). Inversely, electromagnetic waves can generate mechanical signals (electroseismic effect). Electrokinetic conversion potentially combines high seismic resolution with good electromagnetic hydrocarbon sensitivity. The (stationary and frequency-dependent) streaming potential coefficient is a key property, which gives rise to the coupling between electromagnetic and acoustical waves. It depends strongly on the fluid conductivity, porosity, tortuosity, permeability, pore throat and zeta potential of porous media. We examine experimentally both, the stationary and dynamic permeabilities and coupling coefficients of sintered glass bead systems. For this purpose a multi-purpose measuring cell was developed which allows us to carry out - besides common ultrasound experiments - also to perform stationary and frequency-dependent permeability and coupling coefficient measurements. For the experiments sintered mono- and slightly polydisperse glass bead samples with different glass bead diameters between 0.4 and 8mm and porosities ranging between 21 and 39% were used. The stationary and dynamic permeability and streaming potential measurements are supported by μCT scans which enable us a deeper insight into the porous medium. Based on the μCT scans of the produced sintered glass bead samples essential influence parameters, like tortuosity, porosity, effective particle diameters and pore throats in different regions of the entire scanned region have been analyzed in detail to understand the laboratory experiments, cf. Illustration 1. In addition lattice Boltzmann

  16. On reconstruction of dynamic permeability and tortuosity from data at distinct frequencies

    NASA Astrophysics Data System (ADS)

    Ou, Miao-Jung Yvonne

    2014-09-01

    This article focuses on the mathematical problem of reconstructing the dynamic permeability K(\\omega ) and dynamic tortuosity of poroelastic composites from permeability data at different frequencies, utilizing the analytic structure of the Stieltjes function representation of K(\\omega ) derived by Avellaneda and Tortquato (1991 Phys. Fluids A 3 2529), which is valid for all pore space geometry. The integral representation formula (IRF) for dynamic tortuosity is derived and its analytic structure exploited for reconstructing the function from a finite data set. All information of pore-space microstructure is contained in the measure of the IRF. The theory of multipoint Padé approximates for Stieltjes functions guarantees the existence of relaxation kernels that can approximate the dynamic permeability function and the dynamic tortuosity function with high accuracy. In this paper, a numerical algorithm is proposed for computing the relaxation time and the corresponding strength for each element in the relaxation kernels. In the frequency domain, this approximation can be regarded as approximating the Stieltjes function by rational functions with simple poles and positive residues. The main difference between this approach and the curve fitting approach is that the relaxation times and the strengths are computed from the partial fraction decomposition of the multipoint Padé approximates, which is the main subject of the proposed approximation scheme. With the idea from dehomogenization, we also established the exact relations between the moments of the positive measures in the IRFs of permeability and tortuosity with two important parameters in the theory of poroelasticity: the infinite-frequency tortuosity {{\\alpha }_{\\infty }} for the general case and the weighted volume-to-surface ratio Λ for the JKD model, which is regarded as a special case of the general model. From these relations, we suggest a new way for evaluating these two microstructure

  17. Zinc-Permeable Ion Channels: Effects on Intracellular Zinc Dynamics and Potential Physiological/Pathophysiological Significance

    PubMed Central

    Inoue, Koichi; O'Bryant, Zaven; Xiong, Zhi-Gang

    2015-01-01

    Zinc (Zn2+) is one of the most important trace metals in the body. It is necessary for the normal function of a large number of proteins including enzymes and transcription factors. While extracellular fluid may contain up to micromolar Zn2+, intracellular Zn2+ concentration is generally maintained at a subnanomolar level; this steep gradient across the cell membrane is primarily attributable to Zn2+ extrusion by Zn2+ transporting systems. Interestingly, systematic investigation has revealed that activities, previously believed to be dependent on calcium (Ca2+), may be partially mediated by Zn2+. This is also supported by new findings that some Ca2+-permeable channels such as voltage-dependent calcium channels (VDCCs), N-methyl-D-aspartate receptors (NMDA), and amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptors (AMPA-Rs) are also permeable to Zn2+. Thus, the importance of Zn2+ in physiological and pathophysiological processes is now more widely appreciated. In this review, we describe Zn2+-permeable membrane molecules, especially Zn2+-permeable ion channels, in intracellular Zn2+dynamics and Zn2+ mediated physiology/pathophysiology. PMID:25666796

  18. Molecular Dynamics Simulations of Hydration Effects on Solvation, Diffusivity, and Permeability in Chitosan/Chitin Films.

    PubMed

    McDonnell, Marshall T; Greeley, Duncan A; Kit, Kevin M; Keffer, David J

    2016-09-01

    The effects of hydration on the solvation, diffusivity, solubility, and permeability of oxygen molecules in sustainable, biodegradable chitosan/chitin food packaging films were studied via molecular dynamics and confined random walk simulations. With increasing hydration, the membrane has a more homogeneous water distribution with the polymer chains being fully solvated. The diffusivity increased by a factor of 4 for oxygen molecules and by an order of magnitude for water with increasing the humidity. To calculate the Henry's constant and solubility of oxygen in the membranes with changing hydration, the excess chemical potential was calculated via free energy perturbation, thermodynamic integration and direct particle deletion methods. The simulations predicted a higher solubility and permeability for the lower humidity, in contradiction to experimental results. All three methods for calculating the solubility were in good agreement. It was found that the Coulombic interactions in the potential caused the oxygen to bind too strongly to the protonated amine group. Insight from this work will help guide molecular modeling of chitosan/chitin membranes, specifically permeability measurements for small solute molecules. Efforts to chemically tailor chitosan/chitin membranes to favor discrete as opposed to continuous aqueous domains could reduce oxygen permeability. PMID:27487964

  19. Characterization of fracture reservoirs using static and dynamic data: From sonic and 3D seismic to permeability distribution. Annual report, March 1, 1996--February 28, 1997

    SciTech Connect

    Parra, J.O.; Collier, H.A.; Owen, T.E.

    1997-06-01

    In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. They also may connect the borehole to remote zones of better reservoir characteristics. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based on the effects of such conditions on the propagation of acoustic and seismic waves in the rock. The project is a study directed toward the evaluation of acoustic logging and 3D-seismic measurement techniques as well as fluid flow and transport methods for mapping permeability anisotropy and other petrophysical parameters for the understanding of the reservoir fracture systems and associated fluid dynamics. The principal application of these measurement techniques and methods is to identify and investigate the propagation characteristics of acoustic and seismic waves in the Twin Creek hydrocarbon reservoir owned by Union Pacific Resources (UPR) and to characterize the fracture permeability distribution using production data. This site is located in the overthrust area of Utah and Wyoming. UPR drilled six horizontal wells, and presently UPR has two rigs running with many established drill hole locations. In addition, there are numerous vertical wells that exist in the area as well as 3D seismic surveys. Each horizontal well contains full FMS logs and MWD logs, gamma logs, etc.

  20. Colloid Mobilization and Porous Media Permeability Changes by Dynamic Stress Stimulations

    SciTech Connect

    Abdel-Fattah, Amr I.; Roberts, Peter M; Tarimala, Sowmitri; Ibrahim, Reem; Beckham, Richard

    2010-12-10

    Laboratory experiments on porous rock cores have shown that seismic-band (100 Hz or less) mechanical stress/strain cycling of the rock matrix can mobilize sub-pore-size particles (colloids) trapped in the pore space and allow them to be expelled during steady-state water flow. This coupling of dynamic stress to colloid mobility is a potential key mechanism whereby seismic waves may alter formation permeability and porous mass transport in Earth's crust. Experiments where colloid suspensions were injected into Fontainebleau sandstone cores demonstrated that colloid size and the ionic strength of the suspending fluid are major parameters that will control the ability of the colloids to attach to pore walls or to form particle bridges at pore throats. Both effects can lead to significant changes in permeability. A unique core-holder apparatus that applies low-frequency mechanical stress/strain to 2.54-cm-diameter porous rock samples during constant-rate fluid flow was used for those experiments. Microsphere injection caused the core's permeability to decline due to colloid bridging at pore throats. It was found that dynamic stress at 25 to 50 Hz mobilized these trapped colloids mainly when the ionic strength is low, and thereby partially restored the permeability of the sample. These earlier experiments on natural rocks were difficult to interpret in terms of how the colloids distributed themselves throughout the heterogeneous pore space and what interactions were occurring between the colloids and the solid matrix. Observed permeability changes appeared to be confined to the first 5-10 cm of the rock where the colloids were injected, yet significant transport of colloids was observed along the entire length of the sample. The 'natural rock' system is too complex geometrically at the pore scale to allow quantification of mass transport properties along its entire length. To remedy this problem, new colloid transport experiments were performed with a synthetic glass

  1. Grain-Size Dynamics Beneath Mid-Ocean Ridges: Implications for Permeability and Melt Extraction

    NASA Astrophysics Data System (ADS)

    Turner, A. J.; Katz, R. F.; Behn, M. D.

    2014-12-01

    The permeability structure of the sub-ridge mantle plays an important role in how melt is focused and extracted at mid-ocean ridges. Permeability is controlled by porosity and the grain size of the solid mantle matrix, which is in turn controlled by the deformation conditions. To date, models of grain size evolution and mantle deformation have not been coupled to determine the influence of spatial variations in grain-size on the permeability structure at mid-ocean ridges. Rather, current models typically assume a constant grain size for the whole domain [1]. Here, we use 2-D numerical models to evaluate the influence of grain-size variability on the permeability structure beneath a mid-ocean ridge and use these results to speculate on the consequences for melt focusing and extraction. We construct a two-dimensional, single phase model for the steady-state grain size beneath a mid-ocean ridge. The model employs a composite rheology of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a brittle stress limiter. Grain size is calculated using the "wattmeter" model of Austin and Evans [2]. We investigate the sensitivity of the model to global variations in grain growth exponent, potential temperature, spreading-rate, and grain boundary sliding parameters [3,4]. Our model predicts that permeability varies by two orders of magnitude due to the spatial variability of grain size within the expected melt region of a mid-ocean ridge. The predicted permeability structure suggests grain size may promote focusing of melt towards the ridge axis. Furthermore, the calculated grain size structure should focus melt from a greater depth than models that exclude grain-size variability. Future work will involve evaluating this hypothesis by implementing grain-size dynamics within a two-phase mid-ocean ridge model. The developments of such a model will be discussed. References: [1] R. F. Katz, Journal of Petrology, volume 49, issue 12, page 2099

  2. Probing the permeability of porous media by NMR measurement of stochastic dispersion dynamics

    NASA Astrophysics Data System (ADS)

    Brosten, Tyler; Maier, Robert; Codd, Sarah; Vogt, Sarah; Seymour, Joseph

    2011-11-01

    A generalized short-time expansion of hydrodynamic dispersion is derived using non-linear response theory. The result is in accordance with the well-known reduced cases of shear flow in ducts and pipes. In terms of viscous dominated (low Reynolds number) flow in porous media the generalized expansion facilitates the measurement of permeability by PGSE-NMR measurement of time dependent molecular displacement dynamics. To be more precise, for porous media characterized by a homogeneous permeability coefficient along the direction of flow K, and fluid volume fraction ɛ, the effective dispersion coefficient D (t) = < | R- |2 > /6 t of molecular displacements R due to flow and diffusion for a saturating fluid of molecular diffusivity κ in viscous dominated flow is shown to be partially governed by the coefficient of permeability at short times. The short-time expansion is shown to be in agreement with pulsed field gradient spin echo NMR measurement of D (t) in a random sphere pack media and analogous pore-scale random-walk particle tracking transport simulation.

  3. CO2/H2 separation using a highly permeable polyurethane membrane: Molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Azizi, Morteza; Mousavi, Seyyed Abbas

    2015-11-01

    In this study, Molecular Dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulations were conducted to investigate the diffusivity, solubility, and permeability of CO2, CO, H2, and H2O in a polyurethane membrane at three different temperatures. The characterization of the simulated structures was carried out using XRD, FFV, Tg and density calculation, and cavity size distribution. The obtained results were within the expectations reported data in the literature based on the experimental approach, indicating the authenticity of approached in this work. The results showed that the highest diffusivity and permeability coefficients were observed for H2; while the highest values of solubility coefficient were found for H2O and CO2 gases. The increase of operating temperature from 298 K to 318 K has a positive effect on the permeation of all gases and a corresponding negative effect on the selectivity of the gas pair CO2/H2. Also, the results vividly showed that CO2 and H2O gases have a profound affinity with hard phase of polyurethane, while H2 and CO were conversely adsorbed by soft one. Moreover, the enhancement of permeability and permselectivity of CO2/H2 pair confirmed using Robeson Upper-Bond graph showed its good capacity for CO2/H2 separation application.

  4. The dynamics of coherent flow structures within a submerged permeable bed

    NASA Astrophysics Data System (ADS)

    Blois, G.; Best, J.; Sambrook Smith, G.; Hardy, R. J.; Lead, J.

    2009-12-01

    The existence of complex 3D coherent vortical structures in turbulent boundary layers has been widely reported from experimental observations (Adrian et al., 2007, Christensen and Adrian, 2001) and investigations of natural open channel flows (e.g. Kostaschuk and Church, 1993; Best, 2005). The interaction between these flow structures and the solid boundary that is responsible for their generation is also receiving increasing attention due to the central role played by turbulence in governing erosion-deposition processes. Yet, for the majority of studies, the bed roughness has been represented using rough impermeable surfaces. While not inherently acknowledged, most research in this area is thus only strictly applicable to those natural river beds composed either of bedrock or clay, or that have armoured, impermeable, surfaces. Recently, many researchers have noted the need to account for the role of bed permeability in order to accurately reproduce the true nature of flow over permeable gravel-bed rivers. For these cases, the near-bed flow is inherently and mutually linked to the interstitial-flow occurring in the porous solid matrix. This interaction is established through turbulence mechanisms occurring across the interface that may be important for influencing the incipient motion of cohesionless sediment. However, the nature of this turbulence and the formation of coherent structures within such permeable beds remain substantially unresolved due to the technical challenges of collecting direct data in this region. In this paper, we detail the existence and dynamic nature of coherent vortical structures within the individual pore spaces of a permeable bed submerged by a free stream flow. Laboratory experiments are reported in which a permeable flume bed was constructed using spheres packed in an offset cubic arrangement. We applied a high resolution E-PIV (Endoscopic Particle Image Velocimetry) approach in order to fully resolve the instantaneous structure of

  5. Uses And Characteristics Of Dynamic Tradeoff Evaluation

    NASA Technical Reports Server (NTRS)

    Schwuttke, Ursula M.

    1995-01-01

    Report discusses basic concepts, some applications, and performance characteristics of dynamic tradeoff evaluation (DTE). Basic concepts of DTE also described in "Dynamic Restructuring of Problems in Artificial Intelligence" (NPO-18488). DTE is method of enhancing real-time performance of artificial-intelligence system such as might be used to monitor data from multiple sensors in factory, aircraft, spacecraft, or other complex system of equipment. Report presents evaluation of DTE as applied to spacecraft-monitoring problems.

  6. Fault zone characteristics, fracture systems and permeability implications of Middle Triassic Muschelkalk in Southwest Germany

    NASA Astrophysics Data System (ADS)

    Meier, Silke; Bauer, Johanna F.; Philipp, Sonja L.

    2015-01-01

    Fault zone structure and lithology affect permeability of Triassic Muschelkalk limestone-marl-alternations in Southwest Germany, a region characterized by a complex tectonic history. Field studies of eight fault zones provide insights into fracture system parameters (orientation, density, aperture, connectivity, vertical extension) within fault zone units (fault core, damage zone). Results show decreasing fracture lengths with distances to the fault cores in well-developed damage zones. Fracture connectivity at fracture tips is enhanced in proximity to the slip surfaces, particularly caused by shorter fractures. Different mechanical properties of limestone and marl layers obviously affect fracture propagation and thus fracture system connectivity and permeability. Fracture apertures are largest parallel and subparallel to fault zones and prominent regional structures (e.g., Upper Rhine Graben) leading to enhanced fracture-induced permeabilities. Mineralized fractures and mineralizations in fault cores indicate past fluid flow. Permeability is increased by the development of hydraulically active pathways across several beds (non-stratabound fractures) to a higher degree than by the formation of fractures interconnected at fracture tips. We conclude that there is an increase of interconnected fractures and fracture densities in proximity to the fault cores. This is particularly clear in more homogenous rocks. The results help to better understand permeability in Muschelkalk rocks.

  7. Effects of microstructure on permeability and power loss characteristics of the NiZn ferrites

    NASA Astrophysics Data System (ADS)

    Su, Hua; Zhang, Huaiwu; Tang, Xiaoli; Shi, Yu

    Polycrystalline Ni 0.35Zn 0.55Cu 0.1Fe 2O 4 ferrites with different microstructures were investigated. It was found that although the two samples had greatly different microstructures, their initial permeability values were almost the same. This fact was attributed to the advantage of big grain size on permeability could be counteracted by the disadvantage of closed pores on permeability. The sample with large grain size had worse frequency stability due to the low-frequency resonance induced by big grain size. When samples excited under large flux density, the sample with large grain size and closed pores could obtain lower power loss (Pcv). However, for the low induction condition, the sample with small grain size had better performance on Pcv in our testing frequency range. These results were explained in terms of the influences of grain boundaries and closed pores to the domain wall movement.

  8. Crustal Permeability

    NASA Astrophysics Data System (ADS)

    Ingebritsen, S.; Gleeson, T.

    2014-12-01

    Existing data and models support a distinction between the hydrodynamics of the brittle upper crust, where topography, permeability contrasts, and magmatic heat sources dominate patterns of flow and externally derived (meteoric) fluids are common, and the ductile lower crust, dominated by devolatilization reactions and internally derived fluids. The permeability structure of the uppermost (~<1 km) crust is highly heterogeneous, and controls include primary lithology, porosity, rheology, geochemistry, and tectonic and time-temperature histories of the rocks. Systematic permeability differences among original lithologies persist to contact-metamorphic depths of 3-10 km, but are not evident at regional-metamorphic depths of 10-30+ km - presumably because, at such depths, metamorphic textures become largely independent of the original lithology. Permeability can vary in time as well as space, and its temporal evolution may be gradual or abrupt: streamflow responses to moderate to large earthquakes demonstrate that dynamic stresses can instantaneously change permeability by factors of up to 20 on a regional scale, whereas a 10-fold decrease in the permeability of a package of shale in a compacting basin may require 107years. Temporal variation is enhanced by strong chemical and thermal disequilibrium; thus lab experiments involving hydrothermal flow in crystalline rocks under pressure, temperature, and chemistry gradients often result in 10-fold permeability decreases over daily to sub-annual time scales. Recent research on enhanced geothermal reservoirs, ore-forming systems, and the hydrologic effects of earthquakes consistently shows that shear dislocation caused by tectonic forcing or fluid injection can increase near-to intermediate-field permeability by factors of 100 to 1000. Nonetheless, considering permeability as static parameter is often a reasonable assumption for low-temperature hydrogeologic investigations with time scales of days to decades.

  9. On Permeability Dynamics in Carbonaceous Aquifers used in Energy Storage Applications

    NASA Astrophysics Data System (ADS)

    Brady, Ds; Tilley, Bs; Ueckert, M.; Baumann, T.

    2015-11-01

    Geothermal energy harvesting applications use deep groundwater aquifers to store harvested energy. The impact of this additional energy to the aquifer chemistry is crucial for long-term operation. Gaseous CO2 is added to the injected water to compensate potential precipitates of carbonates and to prevent structural changes to the aquifer. Both of these effects affect the local chemical equilibrium of the aquifer, and we consider an effective model through homogenization which captures the hydrochemistry, heat transfer, fluid flow and permeability dynamics of the aquifer as heated fluid is added to the aquifer (injection), and as it is later removed (production). The impact of these different physical mechanisms of the heat storage performance of the aquifer is discussed. Support from the Bavarian State Ministry for the Economy is gratefully acknowledged.

  10. Dynamic and Performance Characteristics of Baseball Bats

    ERIC Educational Resources Information Center

    Bryant, Fred O.; And Others

    1977-01-01

    The dynamic and performance characteristics of wooden and aluminum baseball bats were investigated in two phases; the first dealing with the velocity of the batted balls, and the second with a study of centers of percussion and impulse response at the handle. (MJB)

  11. Dynamics of mantle rock metasomatic transformation in permeable lithospheric zones beneath Siberian craton

    NASA Astrophysics Data System (ADS)

    Sharapov, Victor; Sorokin, Konstantin; Perepechko, Yury

    2015-04-01

    The numerical descriptions of hydrodynamic model of two - velocity heat and mass transfer in permeable zones above the asthenospheric lenses was formulated and solved basing on the study the composition of inclusions in minerals of low crust ultra metamorphic rocks and lithospheric mantle metasomatites and estimation of thermodynamic conditions of the processes. Experimental study of influence of the simulated hot reduced gas flows on the minerals of low crust and mantle xenolith of the Siberian craton platform (SP) give the basic information for this processes. In detail: 1. Thermobarometric study of composition of inclusions in granulite and lithospheric mantle rocks beneath the diamondiferous cratons allowed to estimate the gas phase compositions during the metamorphism and metasomatism as well as products of their re equilibration during decompression. 2. Results of the pilot study of the influence of hot gas impact flows on minerals of mantle xenoliths are taken into account. This allowed to reproduce the elements and heterophase kinetics of interactions within a temperature range of about 300 to 1300o on relative to the interactions between the solid, liquid and gas phases. 3. Correct mathematical two-velocities model of fluid dynamics for compressible multiphase fluid -rock systems. 4. Numerical schemes are simulated and solved for the problems of quantitative description of 2D dynamics behavior of P and T within the permeable zone above the asthenospheric lens. 5. Quantitative description of heterophase non isothermal fluid-rock interaction within the framework of the approximation was obtained on the basis of the parallel solutions of the exchange between the ideal gas flow and solid phase according to the model of multi-reservoir reactors based on minimization of the Gibbs potential. Qualitatively the results of numerical simulation are as follows: 1) appearance in permeable zones of the any composition fluid flows from the upper mantle magma chambers

  12. Structure, Permeability and Production Characteristics of the Heber, California Geothermal Field

    SciTech Connect

    James, E.D.; Hoang, V.T.; Epperson, I.J.

    1987-01-20

    The three key permeability elements of the Heber reservoir are “capping” clays above 1800', a sedimentary “matrix permeability” reservoir from 1800'-5500', and fracture permeability in indurated sediments below 5500'. The fractures are related to NW trending strike-slip faults and NE trending normal faults. Maps and cross sections with dipmeter, lost circulation, temperature and Kh data illustrate the structures and their control on the movement of thermal waters. Production creates a strong initial pressure decline in the field that rapidly stabilizes. The long-term pressure decline is predicted to be low (less than 5%). Temperature data show that current development is north of the source of the thermal plume. Reservoir modeling indicates that reservoir pressures will support further development. 14 figs., 2 refs.

  13. Dynamic, Nonsink Method for the Simultaneous Determination of Drug Permeability and Binding Coefficients in Liposomes

    PubMed Central

    2015-01-01

    Drug release from liposomal formulations is governed by a complex interplay of kinetic (i.e., drug permeability) and thermodynamic factors (i.e., drug partitioning to the bilayer surface). Release studies under sink conditions that attempt to mimic physiological conditions are insufficient to decipher these separate contributions. The present study explores release studies performed under nonsink conditions coupled with appropriate mathematical models to describe both the release kinetics and the conditions in which equilibrium is established. Liposomal release profiles for a model anticancer agent, topotecan, under nonsink conditions provided values for both the first-order rate constant for drug release and the bilayer/water partition coefficient. These findings were validated by conducting release studies under sink conditions via dynamic dialysis at the same temperature and buffer pH. A nearly identical rate constant for drug release could be obtained from dynamic dialysis data when appropriate volume corrections were applied and a mechanism-based mathematical model was employed to account for lipid bilayer binding and dialysis membrane transport. The usefulness of the nonsink method combined with mathematical modeling was further explored by demonstrating the effects of topotecan dimerization and bilayer surface charge potential on the bilayer/water partition coefficient at varying suspension concentrations of lipid and drug. PMID:24628304

  14. Analysis of air permeability and WVTR characteristics of highly impermeable novel rubber nanocomposite

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Chattopadhyay, S.; Sreejesh, A.; Nair, Sujith; Unnikrishnan, G.; Nando, G. B.

    2015-02-01

    This work focuses on analyzing the barrier properties of novel Bromobutyl (BIIR)- Polyepichlorohydrin (CO) rubber nanocomposites and developing a unique model to ease the understanding of the water vapor transmission rate (WVTR) properties. Air permeability, WVTR and morphology of BIIR-CO nanocomposites were investigated and compared with the standard BIIR vulcanizate. From the morphological studies using AFM imaging technique and HR-TEM measurements, the developed BIIR-CO nanocomposites were considered to have a mostly intercalated structure. However, the dispersion of the nanoclay in the composites was very good. Air permeability of BIIR-CO nanocomposites decreased dramatically by 64% as compared to that of the standard BIIR vulcanizate. Considerable reduction in WVTR up to 25% was also achieved for BIIR-CO nanocomposites. Attempts were made to fit the experimental data of the relative gas permeability of nanocomposites with various models predicted earlier. It was observed that the nanoclay orientation ranged from perfect to random, which was decisive in improving the gas barrier properties. A basic model has been developed to predict the water vapor ingress by considering the polarity factor along with tortuosity factor which has been presented schematically. It reiterates the dependency of water vapor ingress on the polarity of the BIIR-CO rubber nanocomposites.

  15. Role of the Outer Pore Domain in Transient Receptor Potential Vanilloid 1 Dynamic Permeability to Large Cations*

    PubMed Central

    Munns, Clare H.; Chung, Man-Kyo; Sanchez, Yuly E.; Amzel, L. Mario; Caterina, Michael J.

    2015-01-01

    Transient receptor potential vanilloid 1 (TRPV1) has been shown to alter its ionic selectivity profile in a time- and agonist-dependent manner. One hallmark of this dynamic process is an increased permeability to large cations such as N-methyl-d-glucamine (NMDG). In this study, we mutated residues throughout the TRPV1 pore domain to identify loci that contribute to dynamic large cation permeability. Using resiniferatoxin (RTX) as the agonist, we identified multiple gain-of-function substitutions within the TRPV1 pore turret (N628P and S629A), pore helix (F638A), and selectivity filter (M644A) domains. In all of these mutants, maximum NMDG permeability was substantially greater than that recorded in wild type TRPV1, despite similar or even reduced sodium current density. Two additional mutants, located in the pore turret (G618W) and selectivity filter (M644I), resulted in significantly reduced maximum NMDG permeability. M644A and M644I also showed increased and decreased minimum NMDG permeability, respectively. The phenotypes of this panel of mutants were confirmed by imaging the RTX-evoked uptake of the large cationic fluorescent dye YO-PRO1. Whereas none of the mutations selectively altered capsaicin-induced changes in NMDG permeability, the loss-of-function phenotypes seen with RTX stimulation of G618W and M644I were recapitulated in the capsaicin-evoked YO-PRO1 uptake assay. Curiously, the M644A substitution resulted in a loss, rather than a gain, in capsaicin-evoked YO-PRO1 uptake. Modeling of our mutations onto the recently determined TRPV1 structure revealed several plausible mechanisms for the phenotypes observed. We conclude that side chain interactions at a few specific loci within the TRPV1 pore contribute to the dynamic process of ionic selectivity. PMID:25568328

  16. Dynamic Changes in the Osmotic Water Permeability of Protoplast Plasma Membrane1[w

    PubMed Central

    Moshelion, Menachem; Moran, Nava; Chaumont, François

    2004-01-01

    The osmotic water permeability coefficient (Pf) of plasma membrane of maize (Zea mays) Black Mexican Sweet protoplasts changed dynamically during a hypoosmotic challenge, as revealed using a model-based computational approach. The best-fitting model had three free parameters: initial Pf, Pf rate-of-change (slopePf), and a delay, which were hypothesized to reflect changes in the number and/or activity of aquaporins in the plasma membrane. Remarkably, the swelling response was delayed 2 to 11 s after start of the noninstantaneous (but accounted for) bath flush. The Pf during the delay was ≤1 μm s−1. During the swelling period following the delay, Pf changed dynamically: within the first 15 s Pf either (1) increased gradually to approximately 8 μm s−1 (in the majority population of low-initial-Pf cells) or (2) increased abruptly to 10 to 20 μm s−1 and then decreased gradually to 3 to 6 μm s−1 (in the minority population of high-initial-Pf cells). We affirmed the validity of our computational approach by the ability to reproduce previously reported initial Pf values (including the absence of delay) in control experiments on Xenopus oocytes expressing the maize aquaporin ZmPIP2;5. Although mercury did not affect the Pf in swelling Black Mexican Sweet cells, phloretin, another aquaporin inhibitor, inhibited swelling in a predicted manner, prolonging the delay and slowing Pf increase, thereby confirming the hypothesis that Pf dynamics, delay included, reflected the varying activity of aquaporins. PMID:15310831

  17. Alginate-magnesium aluminum silicate composite films: effect of film thickness on physical characteristics and permeability.

    PubMed

    Pongjanyakul, Thaned; Puttipipatkhachorn, Satit

    2008-01-01

    The different film thicknesses of the sodium alginate-magnesium aluminum silicate (SA-MAS) microcomposite films were prepared by varying volumes of the composite dispersion for casting. Effect of film thickness on thermal behavior, solid-state crystallinity, mechanical properties, water uptake and erosion, and water vapor and drug permeability of the microcomposite films were investigated. The film thickness caused a small change in thermal behavior of the films when tested using DSC and TGA. The crystallinity of the thin films seemed to increase when compared with the thick films. The thin films gave higher tensile strength than the thick films, whereas % elongation of the films was on the contrary resulted in the lower Young's modulus of the films when the film thickness was increased. This was due to the weaker of the film bulk, suggesting that the microscopic matrix structure of the thick films was looser than that of the thin films. Consequently, water uptake and erosion, water vapor permeation and drug diffusion coefficient of the thick films were higher than those of the thin films. The different types of drug on permeability of the films also showed that a positive charge and large molecule of drug, propranolol HCl, had higher lag time and lower diffusion coefficient that acetaminophen, a non-electrolyte and small molecule. This was because of a higher affinity of positive charge drug on MAS in the films. The findings suggest that the evaporation rate of solvent in different volumes of the composite dispersion used in the preparation method could affect crystallinity and strength of the film surface and film bulk of the microcomposite films. This led to a change in water vapor and drug permeability of the films. PMID:17611056

  18. Influence of the semi-permeable membrane on the performance of dynamic field gradient focusing

    PubMed Central

    Burke, Jeffrey M.; Ivory, Cornelius F.

    2010-01-01

    This paper is part of our continued effort to understand the underlying principles of dynamic field gradient focusing. In this investigation, we examined three problems associated with the use of a semi-permeable membrane. First, the influence of steric and ionic exclusion of current carrying ions through the membrane was examined. It was found that resistance to the transport of ions across the membrane resulted in a shallowing of the electric field profile and an increase in the size of the defocusing zone, which is where the slope of the electric field is reversed so that it disperses rather than concentrates solutes. These problems could be reduced by using a membrane with large pores relative to the size of the buffering ions and completely void of fixed charges. Next, a numerical simulation was used to investigate concentration polarization of protein onto the surface of the membrane. Due to the presence of a transverse electric field, species were pulled toward the membrane. If the membrane is restrictive to those species, a concentrated, polarized layer will form on the surface. The simulation showed that by decreasing the channel to a depth of 20 μm, the concentrated region next to the membrane could be reduced. Finally, it was found that changes in column volume due to loss of membrane structural integrity could be mitigated by including a porous ceramic support. The variation in peak elution times was decreased from greater than 20% to less than 3%. PMID:20191552

  19. Application of fluid dynamics principles in tilted permeable media to terrestrial hydrothermal systems

    SciTech Connect

    Criss, R.E.; Hofmeister, A.M.

    1991-02-01

    Fluid dynamics principles require that circulation of aqueous fluid will be practically ubiquitous in tectonically active parts of the Earth's crust and upper mantle. Both experiment and theory demonstrate that flow, generally in the form of unicells (Hadley circulation), always occurs for isothermal tilts above a very small critical angle ({approximately}5{degree}), for any non-zero permeability or Rayleigh number, and even for hot over cold geometries. Interestingly, heat transport rates in the unicellular regime are essentially conductive, so such flow, unlike more vigorous flow at higher Rayleigh number, is not properly termed convective. These principles have numerous geological ramifications, including: (1) many of the hydrothermal systems developed around epizonal intrusions should be dominantly unicellular in nature, which explains their aspect ratios and the smooth and very regular {delta}{sup 18}O variations that are produced in the rocks; (2) large, long-lived unicells are predicted to occur deep in the Earth's crust wherever Rayleigh numbers are finite and isotherms are substantially inclined, as in zones of batholith intrusion, regional metamorphism, and collision; (3) unicells with lateral dimensions of several hundred kilometers are predicted to be associated with subduction zones dipping more than 6-12{degree}, with fluid advection into the hot mantle wedge being instrumental in mantle metasomatism and in the generation of andesitic magmas.

  20. Borehole Geophysics, Hydraulic Characteristics and Chemistry of Groundwater Flow in Fractured Granite With Very Low Permeability

    NASA Astrophysics Data System (ADS)

    Lukes, J.; Rukavickova, L.; Paces, T.

    2005-12-01

    Three test boreholes 10.9 and 10.5 meters apart were drilled in a compact granite at locality Podles' in the Bohemian Massif of central Europe. The depths of the drill boreholes were 349, 300 and 296 m. The location of the boreholes form a triangle. The main goal of this study was to determine the degree to which the very compact granite is fractured and what is the hydraulic conductivity of the fracture system. A combination of neutron log, electrical resistivity logs, gama gama log, fluid-resistivity log, and acoustic log was used to test the function of the fracture system. The hydraulic connection among the boreholes was determined from the fluid-resistivity log using injected salt as a tracer. The pressure communication through fractures among boreholes was investigated by a set of water pressure tests (WPT) in one borehole with simultaneous monitoring of responses in the other two holes equipped by a multipacker system. The connection of selected permeable fracture systems was verified by a combination of hydraulic stress tests in one borehole and simultaneous fluid-resistivity logging in other two boreholes. Indication of salt in water in adjoining boreholes was registered as anomalies on curves of the fluid-resistivity record. Several communications between boreholes were along a horizontal level, however, some connections were through combination of both horizontal and vertical fractures. The hydraulic connection between two of the boreholes was fast and straightforward. The connection with the third borehole was inexpressive. This difference was due to the position of the boreholes with regard to the direction of main fractures and the direction of natural groundwater flow. All fractures were identified using acoustic tele-viewer and inspection of core. The density of the fractures varied with depth. The density was 3 fractures per meter near surface, the density dropped to 0.9 fractures per meter at the depth of 80 m. Between 80 and 300 m, the density

  1. Grain-size dynamics beneath mid-ocean ridges: Implications for permeability and melt extraction

    PubMed Central

    Turner, Andrew J; Katz, Richard F; Behn, Mark D

    2015-01-01

    Grain size is an important control on mantle viscosity and permeability, but is difficult or impossible to measure in situ. We construct a two-dimensional, single phase model for the steady state mean grain size beneath a mid-ocean ridge. The mantle rheology is modeled as a composite of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a plastic stress limiter. The mean grain size is calculated by the paleowattmeter relationship of Austin and Evans (2007). We investigate the sensitivity of our model to global variations in grain growth exponent, potential temperature, spreading-rate, and mantle hydration. We interpret the mean grain-size field in terms of its permeability to melt transport. The permeability structure due to mean grain size may be approximated as a high permeability region beneath a low permeability region. The transition between high and low permeability regions occurs across a boundary that is steeply inclined toward the ridge axis. We hypothesize that such a permeability structure generated from the variability of the mean grain size may focus melt toward the ridge axis, analogous to Sparks and Parmentier (1991)-type focusing. This focusing may, in turn, constrain the region where significant melt fractions are observed by seismic or magnetotelluric surveys. This interpretation of melt focusing via the grain-size permeability structure is consistent with MT observation of the asthenosphere beneath the East Pacific Rise. Key Points: The grain-size field beneath MORs can vary over orders of magnitude The grain-size field affects the rheology and permeability of the asthenosphere The grain-size field may focus melt toward the ridge axis PMID:26693211

  2. Assessment of vessel permeability by combining dynamic contrast-enhanced and arterial spin labeling MRI.

    PubMed

    Liu, Ho-Ling; Chang, Ting-Ting; Yan, Feng-Xian; Li, Cheng-He; Lin, Yu-Shi; Wong, Alex M

    2015-06-01

    The forward volumetric transfer constant (K(trans)), a physiological parameter extracted from dynamic contrast-enhanced (DCE) MRI, is weighted by vessel permeability and tissue blood flow. The permeability × surface area product per unit mass of tissue (PS) in brain tumors was estimated in this study by combining the blood flow obtained through pseudo-continuous arterial spin labeling (PCASL) and K(trans) obtained through DCE MRI. An analytical analysis and a numerical simulation were conducted to understand how errors in the flow and K(trans) estimates would propagate to the resulting PS. Fourteen pediatric patients with brain tumors were scanned on a clinical 3-T MRI scanner. PCASL perfusion imaging was performed using a three-dimensional (3D) fast-spin-echo readout module to determine blood flow. DCE imaging was performed using a 3D spoiled gradient-echo sequence, and the K(trans) map was obtained with the extended Tofts model. The numerical analysis demonstrated that the uncertainty of PS was predominantly dependent on that of K(trans) and was relatively insensitive to the flow. The average PS values of the whole tumors ranged from 0.006 to 0.217 min(-1), with a mean of 0.050 min(-1) among the patients. The mean K(trans) value was 18% lower than the PS value, with a maximum discrepancy of 25%. When the parametric maps were compared on a voxel-by-voxel basis, the discrepancies between PS and K(trans) appeared to be heterogeneous within the tumors. The PS values could be more than two-fold higher than the K(trans) values for voxels with high K(trans) levels. This study proposes a method that is easy to implement in clinical practice and has the potential to improve the quantification of the microvascular properties of brain tumors. PMID:25880892

  3. Three-dimensional dynamic contrast-enhanced MRI for the accurate, extensive quantification of microvascular permeability in atherosclerotic plaques.

    PubMed

    Calcagno, Claudia; Lobatto, Mark E; Dyvorne, Hadrien; Robson, Philip M; Millon, Antoine; Senders, Max L; Lairez, Olivier; Ramachandran, Sarayu; Coolen, Bram F; Black, Alexandra; Mulder, Willem J M; Fayad, Zahi A

    2015-10-01

    Atherosclerotic plaques that cause stroke and myocardial infarction are characterized by increased microvascular permeability and inflammation. Dynamic contrast-enhanced MRI (DCE-MRI) has been proposed as a method to quantify vessel wall microvascular permeability in vivo. Until now, most DCE-MRI studies of atherosclerosis have been limited to two-dimensional (2D) multi-slice imaging. Although providing the high spatial resolution required to image the arterial vessel wall, these approaches do not allow the quantification of plaque permeability with extensive anatomical coverage, an essential feature when imaging heterogeneous diseases, such as atherosclerosis. To our knowledge, we present the first systematic evaluation of three-dimensional (3D), high-resolution, DCE-MRI for the extensive quantification of plaque permeability along an entire vascular bed, with validation in atherosclerotic rabbits. We compare two acquisitions: 3D turbo field echo (TFE) with motion-sensitized-driven equilibrium (MSDE) preparation and 3D turbo spin echo (TSE). We find 3D TFE DCE-MRI to be superior to 3D TSE DCE-MRI in terms of temporal stability metrics. Both sequences show good intra- and inter-observer reliability, and significant correlation with ex vivo permeability measurements by Evans Blue near-infrared fluorescence (NIRF). In addition, we explore the feasibility of using compressed sensing to accelerate 3D DCE-MRI of atherosclerosis, to improve its temporal resolution and therefore the accuracy of permeability quantification. Using retrospective under-sampling and reconstructions, we show that compressed sensing alone may allow the acceleration of 3D DCE-MRI by up to four-fold. We anticipate that the development of high-spatial-resolution 3D DCE-MRI with prospective compressed sensing acceleration may allow for the more accurate and extensive quantification of atherosclerotic plaque permeability along an entire vascular bed. We foresee that this approach may allow for

  4. Influences of Bi 2O 3 additive on the microstructure, permeability, and power loss characteristics of Ni-Zn ferrites

    NASA Astrophysics Data System (ADS)

    Su, Hua; Tang, Xiaoli; Zhang, Huaiwu; Jia, Lijun; Zhong, Zhiyong

    2009-10-01

    Nickel-zinc ferrite materials containing different Bi 2O 3 concentrations have been prepared by the conventional ceramic technique. Micrographs have clearly revealed that the Bi 2O 3 additive promoted grain growth. When the Bi 2O 3 content reached 0.15 wt%, a dual microstructure with both small grains (<5 μm) and some extremely large grains (>50 μm) appeared. With higher Bi 2O 3 content, the samples exhibited a very large average grain size of more than 30 μm. The initial permeability gradually decreased with increasing Bi 2O 3 content. When the Bi 2O 3 content exceeded 0.15 wt%, the permeability gradually decreased with frequency due to the low-frequency resonance induced by the large grain size. Neither the sintering density nor the saturation magnetization was obviously influenced by the Bi 2O 3 content or microstructure of the samples. However, power loss (Pcv) characteristics were evidently influenced. At low flux density, the sample with 0.10 wt% Bi 2O 3, which was characterized by an average grain size of 3-4 μm and few closed pores, displayed the lowest Pcv, irrespective of frequency. When the flux density was equal to or greater than the critical value of 40 mT, the sample with 0.20 wt% Bi 2O 3, which had the largest average grain size, displayed the lowest Pcv.

  5. Quantification of pore clogging characteristics in potential permeable reactive barrier (PRB) substrates using image analysis

    NASA Astrophysics Data System (ADS)

    Wantanaphong, J.; Mooney, S. J.; Bailey, E. H.

    2006-08-01

    Permeable reactive barriers (PRBs) are now an established approach for groundwater remediation. However, one concern is the deterioration of barrier material performance due to pore clogging. This study sought to quantify the effect of pore clogging on the alteration of the physical porous architecture of two novel potential PRB materials (clinoptilolite and calcified seaweed) using image analysis of SEM-derived images. Results after a water treatment contaminated with heavy metals over periods of up to 10 months identified a decrease in porosity from c. 22% to c. 15% for calcified seaweed and from c. 22% to c. 18% for clinoptilolite. Porosity was reduced by as much as 37% in a calcified seaweed column that clogged. The mean pore size (2D) of both materials slightly decreased after water treatment with c. 11% reduction in calcified seaweed and c. 7% reduction in clinoptilolite. An increase in the proportion of crack-shaped pores was observed in both materials after the contaminated water treatment, most noticeably in the bottom of columns where contaminated water first reacted with the material. The distribution of pores (within a given image) derived from the distance transform indicated the largest morphological differences in materials was recorded in calcified seaweed columns, which is likely to impact significantly on their performance as barrier materials. The magnitude of porosity reduction over a short time period in relation to predicted barrier longevity suggest these and similar materials may be unsuited for barrier installation in their present form.

  6. Dynamic permeability of the lacunar–canalicular system in human cortical bone

    PubMed Central

    Benalla, M.; Palacio-Mancheno, P. E.; Fritton, S. P.; Cardoso, L.

    2013-01-01

    A new method for the experimental determination of the permeability of a small sample of a fluid-saturated hierarchically structured porous material is described and applied to the determination of the lacunar–canalicular permeability (KLC) in bone. The interest in the permeability of the lacunar–canalicular pore system (LCS) is due to the fact that the LCS is considered to be the site of bone mechanotransduction due to the loading-driven fluid flow over cellular structures. The permeability of this space has been estimated to be anywhere from 10−17 to 10−25 m2. However, the vascular pore system and LCS are intertwined, rendering the permeability of the much smaller-dimensioned LCS challenging to measure. In this study, we report a combined experimental and analytical approach that allowed the accurate determination of the KLC to be on the order of 10−22 m2 for human osteonal bone. It was found that the KLC has a linear dependence on loading frequency, decreasing at a rate of 2 × 10−24 m2/Hz from 1 to 100 Hz, and using the proposed model, the porosity alone was able to explain 86 % of the KLC variability. PMID:24146291

  7. REDUCING RISK IN LOW-PERMEABILITY GAS FORMATIONS: UNDERSTANDING THE ROCK/FLUID CHARACTERISTICS OF ROCKY MOUNTAIN LARAMIDE BASINS

    SciTech Connect

    Ronald C. Surdam

    2003-12-29

    An anomalous velocity model was constructed for the Wind River Basin (WRB) based on {approx}2000 mi of 2-D seismic data and 175 sonic logs, for a total of 132,000 velocity/depth profiles. Ten cross sections were constructed through the model coincident with known gas fields. In each cross section, an intense, anomalously slow velocity domain coincided with the gas-productive rock/fluid interval. The anomalous velocity model: (1) Easily isolates gas-charged rock/fluid systems characterized by anomalously slow velocities and water-rich rock/fluid systems characterized by normal velocities; and (2) Delineates the regional velocity inversion surface, which is characterized by steepening of the Ro/depth gradient, a significant increase in capillary displacement pressure, a significant change in formation water composition, and acceleration of the reaction rate of smectite-to-illite diagenesis in mixed-layer clays. Gas chimneys are observed as topographic highs on the regional velocity inversion surface. Beneath the surface are significant fluid-flow compartments, which have a gas-charge in the fluid phase and are isolated from meteoric water recharge. Water-rich domains may occur within regional gas-charged compartments, but are not being recharged from the meteoric water system (i.e., trapped water). The WRB is divided into at least two regionally prominent fluid-flow compartments separated by the velocity inversion surface: a water-dominated upper compartment likely under strong meteoric water drive and a gas-charged, anomalously pressured lower compartment. Judging from cross sections, numerous gas-charged subcompartments occur within the regional compartment. Their geometries and boundaries are controlled by faults and low-permeability rocks. Commercial gas production results when a reservoir interval characterized by enhanced porosity/permeability intersects one of these gas-charged subcompartments. The rock/fluid characteristics of the Rocky Mountain Laramide

  8. Triatoma Virus Recombinant VP4 Protein Induces Membrane Permeability through Dynamic Pores

    PubMed Central

    Sánchez-Eugenia, Rubén; Goikolea, Julen; Gil-Cartón, David; Sánchez-Magraner, Lissete

    2015-01-01

    ABSTRACT In naked viruses, membrane breaching is a key step that must be performed for genome transfer into the target cells. Despite its importance, the mechanisms behind this process remain poorly understood. The small protein VP4, encoded by the genomes of most viruses of the order Picornavirales, has been shown to be involved in membrane alterations. Here we analyzed the permeabilization activity of the natively nonmyristoylated VP4 protein from triatoma virus (TrV), a virus belonging to the Dicistroviridae family within the Picornavirales order. The VP4 protein was produced as a C-terminal maltose binding protein (MBP) fusion to achieve its successful expression. This recombinant VP4 protein is able to produce membrane permeabilization in model membranes in a membrane composition-dependent manner. The induced permeability was also influenced by the pH, being greater at higher pH values. We demonstrate that the permeabilization activity elicited by the protein occurs through discrete pores that are inserted on the membrane. Sizing experiments using fluorescent dextrans, cryo-electron microscopy imaging, and other, additional techniques showed that recombinant VP4 forms heterogeneous proteolipidic pores rather than common proteinaceous channels. These results suggest that the VP4 protein may be involved in the membrane alterations required for genome transfer or cell entry steps during dicistrovirus infection. IMPORTANCE During viral infection, viruses need to overcome the membrane barrier in order to enter the cell and replicate their genome. In nonenveloped viruses membrane fusion is not possible, and hence, other mechanisms are implemented. Among other proteins, like the capsid-forming proteins and the proteins required for viral replication, several viruses of the order Picornaviridae contain a small protein called VP4 that has been shown to be involved in membrane alterations. Here we show that the triatoma virus VP4 protein is able to produce membrane

  9. Dual permeability modeling of tile drain management influences on hydrologic and nutrient transport characteristics in macroporous soil

    NASA Astrophysics Data System (ADS)

    Frey, Steven K.; Hwang, Hyoun-Tae; Park, Young-Jin; Hussain, Syed I.; Gottschall, Natalie; Edwards, Mark; Lapen, David R.

    2016-04-01

    Tile drainage management is considered a beneficial management practice (BMP) for reducing nutrient loads in surface water. In this study, 2-dimensional dual permeability models were developed to simulate flow and transport following liquid swine manure and rhodamine WT (strongly sorbing) tracer application on macroporous clay loam soils under controlled (CD) and free drainage (FD) tile management. Dominant flow and transport characteristics were successfully replicated, including higher and more continuous tile discharge and lower peak rhodamine WT concentrations in FD tile effluent; in relation to CD, where discharge was intermittent, peak rhodamine concentrations higher, and mass exchange from macropores into the soil matrix greater. Explicit representation of preferential flow was essential, as macropores transmitted >98% of surface infiltration, tile flow, and tile solute loads for both FD and CD. Incorporating an active 3rd type lower boundary condition that facilitated groundwater interaction was imperative for simulating CD, as the higher (relative to FD) water table enhanced water and soluble nutrient movement from the soil profile into deeper groundwater. Scenario analysis revealed that in conditions where slight upwards hydraulic gradients exist beneath tiles, groundwater upwelling can influence the concentration of surface derived solutes in tile effluent under FD conditions; whereas the higher and flatter CD water table can restrict groundwater upwelling. Results show that while CD can reduce tile discharge, it can also lead to an increase in surface-application derived nutrient concentrations in tile effluent and hence surface water receptors, and it can promote NO3 loading into groundwater. This study demonstrates dual permeability modeling as a tool for increasing the conceptual understanding of tile drainage BMPs.

  10. Quantitative Measurement of Blood-Brain Barrier Permeability in Human Using Dynamic Contrast-Enhanced MRI with Fast T1 Mapping

    PubMed Central

    Taheri, Saeid; Gasparovic, Charles; Shah, Nadim Jon; Rosenberg, Gary A.

    2016-01-01

    Breakdown of the blood-brain barrier (BBB), occurring in many neurological diseases, has been difficult to measure noninvasively in humans. Dynamic contrast-enhanced magnetic resonance imaging measures BBB permeability. However, important technical challenges remain and normative data from healthy humans is lacking. We report the implementation of a method for measuring BBB permeability, originally developed in animals, to estimate BBB permeability in both healthy subjects and patients with white matter pathology. Fast T1 mapping was used to measure the leakage of contrast agent Gadolinium diethylene triamine pentaacetic acid (Gd-DTPA) from plasma into brain. A quarter of the standard Gd-DTPA dose for dynamic contrast-enhanced magnetic resonance imaging was found to give both sufficient contrast-to-noise and high T1 sensitivity. The Patlak graphical approach was used to calculate the permeability from changes in 1/T1. Permeability constants were compared with cerebrospinal fluid albumin index. The upper limit of the 95% confidence interval for white matter BBB permeability for normal subjects was 3 × 10−4 L/g min. MRI measurements correlated strongly with levels of cerebrospinal fluid albumin in those subjects undergoing lumbar puncture. Dynamic contrast-enhanced magnetic resonance imaging with low dose Gd-DTPA and fast T1 imaging is a sensitive method to measure subtle differences in BBB permeability in humans and may have advantages over techniques based purely on the measurement of pixel contrast changes. PMID:21413067

  11. The 3D pore structure and fluid dynamics simulation of macroporous monoliths: High permeability due to alternating channel width.

    PubMed

    Jungreuthmayer, Christian; Steppert, Petra; Sekot, Gerhard; Zankel, Armin; Reingruber, Herbert; Zanghellini, Jürgen; Jungbauer, Alois

    2015-12-18

    Polymethacrylate-based monoliths have excellent flow properties. Flow in the wide channel interconnected with narrow channels is theoretically assumed to account for favorable permeability. Monoliths were cut into 898 slices in 50nm distances and visualized by serial block face scanning electron microscopy (SBEM). A 3D structure was reconstructed and used for the calculation of flow profiles within the monolith and for calculation of pressure drop and permeability by computational fluid dynamics (CFD). The calculated and measured permeabilities showed good agreement. Small channels clearly flowed into wide and wide into small channels in a repetitive manner which supported the hypothesis describing the favorable flow properties of these materials. This alternating property is also reflected in the streamline velocity which fluctuated. These findings were corroborated by artificial monoliths which were composed of regular (interconnected) cells where narrow cells followed wide cells. In the real monolith and the artificial monoliths with interconnected flow channels similar velocity fluctuations could be observed. A two phase flow simulation showed a lateral velocity component, which may contribute to the transport of molecules to the monolith wall. Our study showed that the interconnection of small and wide pores is responsible for the excellent pressure flow properties. This study is also a guide for further design of continuous porous materials to achieve good flow properties. PMID:26615711

  12. No Dynamic Changes in Blood-brain Barrier Permeability Occur in Developing Rats During Local Cortex Exposure to Microwaves.

    PubMed

    Masuda, Hiroshi; Hirota, Shogo; Ushiyama, Akira; Hirata, Akimasa; Arima, Takuji; Kawai, Hiroki; Wake, Kanako; Watanabe, Soichi; Taki, Masao; Nagai, Akiko; Ohkubo, Chiyoji

    2015-01-01

    Little information is available about the effects of exposure to radiofrequency electromagnetic fields (RF) on cerebral microcirculation during rat developmental stages. We investigated whether the permeability of the blood-brain barrier (BBB) in juvenile and young adult rats was modified during local cortex exposure to RF under non-thermal conditions. The cortex tissue targeted was locally exposed to 1457 MHz RF at an average specific absorption rate of 2.0 W/kg in the target area for 50 min and permeability changes in the BBB of the pia mater were measured directly, using intravital fluorescence microscopy. There was no significant difference in extravasation of intravenously-injected dye between exposed and sham-exposed groups of either category of rats. No histological evidence of albumin leakage was found in any of the brains just after exposure, indicating that no traces of BBB disruption remained. These findings suggest that no dynamic changes occurred in BBB permeability of the rats at either of these developmental stages, even during local RF exposure at non-thermal levels. PMID:25977380

  13. Dynamic characteristics of multisensory facilitation and inhibition.

    PubMed

    Wang, W Y; Hu, L; Valentini, E; Xie, X B; Cui, H Y; Hu, Y

    2012-10-01

    Multimodal integration, which mainly refers to multisensory facilitation and multisensory inhibition, is the process of merging multisensory information in the human brain. However, the neural mechanisms underlying the dynamic characteristics of multimodal integration are not fully understood. The objective of this study is to investigate the basic mechanisms of multimodal integration by assessing the intermodal influences of vision, audition, and somatosensory sensations (the influence of multisensory background events to the target event). We used a timed target detection task, and measured both behavioral and electroencephalographic responses to visual target events (green solid circle), auditory target events (2 kHz pure tone) and somatosensory target events (1.5 ± 0.1 mA square wave pulse) from 20 normal participants. There were significant differences in both behavior performance and ERP components when comparing the unimodal target stimuli with multimodal (bimodal and trimodal) target stimuli for all target groups. Significant correlation among reaction time and P3 latency was observed across all target conditions. The perceptual processing of auditory target events (A) was inhibited by the background events, while the perceptual processing of somatosensory target events (S) was facilitated by the background events. In contrast, the perceptual processing of visual target events (V) remained impervious to multisensory background events. PMID:24082962

  14. In Silico Determination of Gas Permeabilities by Non-Equilibrium Molecular Dynamics: CO2 and He through PIM-1

    PubMed Central

    Frentrup, Hendrik; Hart, Kyle E.; Colina, Coray M.; Müller, Erich A.

    2015-01-01

    We study the permeation dynamics of helium and carbon dioxide through an atomistically detailed model of a polymer of intrinsic microporosity, PIM-1, via non-equilibrium molecular dynamics (NEMD) simulations. This work presents the first explicit molecular modeling of gas permeation through a high free-volume polymer sample, and it demonstrates how permeability and solubility can be obtained coherently from a single simulation. Solubilities in particular can be obtained to a very high degree of confidence and within experimental inaccuracies. Furthermore, the simulations make it possible to obtain very specific information on the diffusion dynamics of penetrant molecules and yield detailed maps of gas occupancy, which are akin to a digital tomographic scan of the polymer network. In addition to determining permeability and solubility directly from NEMD simulations, the results shed light on the permeation mechanism of the penetrant gases, suggesting that the relative openness of the microporous topology promotes the anomalous diffusion of penetrant gases, which entails a deviation from the pore hopping mechanism usually observed in gas diffusion in polymers. PMID:25764366

  15. Absorbance characteristics of a liquid-phase gas sensor based on gas-permeable liquid core waveguides.

    PubMed

    Peng, Pei; Wang, Wei; Zhang, Li; Su, Shiguang; Wang, Jiahui

    2013-12-01

    The absorbance characteristics and influential factors on these characteristics for a liquid-phase gas sensor, which is based on gas-permeable liquid core waveguides (LCWs), are studied from theoretical and experimental viewpoints in this paper. According to theory, it is predicted that absorbance is proportional to the analyte concentration, sampling time, analyte diffusion coefficient, and geometric factor of this device when the depletion layer of the analyte is ignored. The experimental results are in agreement with the theoretical hypothesis. According to the experimental results, absorbance is time-dependent and increasing linearly over time after the requisite response time with a linear correlation coefficient r(2)>0.999. In the linear region, the rate of absorbance change (RAC) indicates improved linearity with sample concentration and a relative higher sensitivity than instantaneous absorbance does. By using a core liquid that is more affinitive to the analyte, reducing wall thickness and the inner diameter of the tubing, or increasing sample flow rate limitedly, the response time can be decreased and the sensitivity can be increased. However, increasing the LCW length can only enhance sensitivity and has no effect on response time. For liquid phase detection, there is a maximum flow rate, and the absorbance will decrease beyond the stated limit. Under experimental conditions, hexane as the LCW core solvent, a tubing wall thickness of 0.1 mm, a length of 10 cm, and a flow rate of 12 mL min(-1), the detection results for the aqueous benzene sample demonstrate a response time of 4 min. Additionally, the standard curve for the RAC versus concentration is RAC=0.0267c+0.0351 (AU min(-1)), with r(2)=0.9922 within concentrations of 0.5-3.0 mg L(-1). The relative error for 0.5 mg L(-1) benzene (n=6) is 7.4±3.7%, and the LOD is 0.04 mg L(-1). This research can provide theoretical and practical guides for liquid-phase gas sensor design and development based on a

  16. Nonlinear Flow Numerical Simulation of an Ultra-Low Permeability Reservoir

    NASA Astrophysics Data System (ADS)

    Yu, Rong-Ze; Lei, Qun; Yang, Zheng-Ming; Bian, Ya-Nan

    2010-07-01

    A nonlinear flow mathematical model is established and the grid equation is deduced. A nonlinear flow reservoir numerical simulation program is compiled. The permeability loss coefficient is used to describe the permeability loss. A pilot calculation is made on the basis of actual field data, which reflects the reservoir development characteristics. The numerical simulation program based on nonlinear flow can anticipate the dynamic characteristics of the ultra-low permeability reservoir exploitation more exactly.

  17. Heat transfer characteristics for the Maxwell fluid flow past an unsteady stretching permeable surface embedded in a porous medium with thermal radiation

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, S.; Ranjan De, P.; Layek, G. C.

    2013-05-01

    An unsteady boundary layer flow of a non-Newtonian fluid over a continuously stretching permeable surface in the presence of thermal radiation is investigated. The Maxwell fluid model is used to characterize the non-Newtonian fluid behavior. Similarity solutions for the transformed governing equations are obtained. The transformed boundary layer equations are then solved numerically by the shooting method. The flow features and heat transfer characteristics for different values of the governing parameters (unsteadiness parameter, Maxwell parameter, permeability parameter, suction/blowing parameter, thermal radiation parameter, and Prandtl number) are analyzed and discussed in detail.

  18. Dynamic magnetic characteristics of Fe78Si13B9 amorphous alloy subjected to operating temperature

    NASA Astrophysics Data System (ADS)

    He, Aina; Wang, Anding; Yue, Shiqiang; Zhao, Chengliang; Chang, Chuntao; Men, He; Wang, Xinmin; Li, Run-Wei

    2016-06-01

    The operating temperature dependence of dynamic magnetic characteristics of the annealed Fe78Si13B9 amorphous alloy core was systematically investigated. The core loss, magnetic induction intensity and complex permeability of the amorphous core were analyzed by means of AC B-H loop tracer and impedance analyzer. It is found that the operating temperature below 403 K has little impact on core loss when the induction (B) is less than 1.25 T. As B becomes higher, core loss measured at high temperature becomes higher. For the cores measured at power frequency, the B at 80 A/m and the coercivity (Hc) at 1 T decline slightly as the temperature goes up. Furthermore, the real part of permeability (μ‧) increases with the rise of temperature. The imaginary part of permeability (μ″) maxima shifts to lower frequency side with increasing temperature, indicating the magnetic relaxation behavior in the sample. In addition, with the rise in the operating temperature of the annealed amorphous core, the relaxation time tends to increase.

  19. Simulation and Experimental Investigation of Structural Dynamic Frequency Characteristics Control

    PubMed Central

    Zhang, Xingwu; Chen, Xuefeng; You, Shangqin; He, Zhengjia; Li, Bing

    2012-01-01

    In general, mechanical equipment such as cars, airplanes, and machine tools all operate with constant frequency characteristics. These constant working characteristics should be controlled if the dynamic performance of the equipment demands improvement or the dynamic characteristics is intended to change with different working conditions. Active control is a stable and beneficial method for this, but current active control methods mainly focus on vibration control for reducing the vibration amplitudes in the time domain or frequency domain. In this paper, a new method of dynamic frequency characteristics active control (DFCAC) is presented for a flat plate, which can not only accomplish vibration control but also arbitrarily change the dynamic characteristics of the equipment. The proposed DFCAC algorithm is based on a neural network including two parts of the identification implement and the controller. The effectiveness of the DFCAC method is verified by several simulation and experiments, which provide desirable results. PMID:22666072

  20. Development of theophylline floating microballoons using cellulose acetate butyrate and/or Eudragit RL 100 polymers with different permeability characteristics

    PubMed Central

    Jelvehgari, M.; Maghsoodi, M.; Nemati, H.

    2010-01-01

    The objective of the present investigation was to design a sustained release floating microcapsules of theophylline using two polymers of different permeability characteristics; Eudragit RL 100 (Eu RL) and cellulose acetate butyrate (CAB) using the oil-in-oil emulsion solvent evaporation method. Polymers were used separately and in combination to prepare different microcapsules. The effect of drug-polymer interaction was studied for each of the polymers and for their combination. Encapsulation efficiency, the yield, particle size, floating capability, morphology of microspheres, powder X-ray diffraction analysis (XRD), and differential scanning calorimetry (DSC) were evaluated. The in vitro release studies were performed in PH 1.2 and 7.4. The optimized drug to polymer ratios was found to be 4:1 (F2) and 0.75:1 (F'2) with Eu RL and CAB, respectively. The best drug to polymer ratio in mix formulation was 4:1:1 (theophylline: Eu RL: CAB ratio). Production yield, loading efficiencies, and particle size of F2 and F’2 were found to be 59.14% and 45.39%, 73.93% and 95.87%, 372 and 273 micron, respectively. Microsphere prepared with CAB showed the best floating ability (80.3 ± 4.02% buoyancy) in 0.1 M HCl for over 12 h. The XRD and DSC showed that theophylline in the drug loaded microspheres was stable and in crystaline form. Microparticles prepared using blend of Eu RL and CAB polymers indicated more sustained pattern than the commercial tablet (P<0.05). Drug loaded floating microballoons prepared of combination of Eu RL and CAB with 1:1 ratio were found to be a suitable delivery system for sustained release delivery of theophylline which contained lower amount of polymer contents in the microspheres. PMID:21589766

  1. Biogeochemical dynamics in zero-valent iron columns: Implications for permeable reactive barriers

    SciTech Connect

    Gu, B.; Phelps, T.J.; Liang, L.; Palumbo, A.V.; Jacobs, G.K.; Dickey, M.J.; Roh, Y.; Kinsall, B.L.

    1999-07-01

    The impact of microbiological and geochemical processes has been a major concern for the long-term performance of permeable reactive barriers containing zero-valent iron (Fe{sup 0}). To evaluate potential biogeochemical impacts, laboratory studies were performed over a 5-month period using columns containing a diverse microbial community. The conditions chosen for these experiments were designed to simulate high concentrations of bicarbonate and sulfate containing groundwater regimes. Groundwater chemistry was found to significantly affect corrosion rates of Fe{sup 0} filings and resulted in the formation of a suite of mineral precipitates. HCO{sub 3}{sup {minus}} ions in SO{sub 4}{sup 2{minus}}-containing water were particularly corrosive to Fe{sup 0}, resulting in the formation of ferrous carbonate and enhanced H{sub 2} gas generation that stimulated the growth of microbial populations and increased SO{sub 4}{sup 2{minus}} reduction. Major mineral precipitates identified included lepidocrocite, akaganeite, mackinawite, magnetite/maghemite, goethite, siderite, and amorphous ferrous sulfide. Sulfide was formed as a result of microbial reduction of SO{sub 4}{sup 2{minus}} that became significant after about 2 months of column operations. This study demonstrates that biogeochemical influences on the performance and reaction of Fe{sup 0} may be minimal in the short term, necessitating longer-term operations to observe the effects of biogeochemical reactions on the performance of Fe{sup 0} barriers. Although major failures of in-ground treatment barriers have not been problematic to date, the accumulation of iron oxyhydroxides, carbonates, and sulfides from biogeochemical processes could reduce the reactivity and permeability of Fe{sup 0} beds, thereby decreasing treatment efficiency.

  2. A correlative study of clinical-pathologic characteristics of human brain tumors and blood brain barrier (BBB) permeability evaluated with Ga-68 EDTA and positron emission tomography

    SciTech Connect

    Wapenski, J.A.; Hawkins, R.A.; Mazziotta, J.C.; Phelps, M.E.; Huang, S.C.

    1985-05-01

    The authors investigated the relationship between quantitative estimates of BBB permeability and the clinical and pathologic characteristics of human brain tumors. BBB permeability in 12 patients with either primary (4) or metastatic (8) brain tumors were studied with Ga-68 EDTA and PET with a two compartment model. The clinical and pathologic characteristics of the tumors were reviewed retrospectively. PET estimates of the transfer constant K/sub 1/ (ml/min/gm) paralleled the X-ray CT evidence of BBB disruption. Biopsies of four patients provided histologic support for the presumed pathophysiologic mechanism of BBB disruption, in the degree of alteration of brain vascularity and cellular architecture. For example, a patient with a hemorrhagic melanoma and a K/sub 1/ = 0.0049 ml/min/gm had gross hemorrhage, little recognizeable brain tissue and evidence of neovascularization on biopsy.

  3. Numerical investigation of bubble nonlinear dynamics characteristics

    SciTech Connect

    Shi, Jie Yang, Desen; Shi, Shengguo; Hu, Bo; Zhang, Haoyang; Jiang, Wei

    2015-10-28

    The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

  4. Dynamic characteristics of two-phase media

    SciTech Connect

    Fedotovskiy, V.S.; Sinyavskiy, V.F.; Terenik, L.V.; Spirov, V.S.

    1990-01-01

    This paper presents the results of investigations into the effective dynamic properties of heterogeneous media formed by a liquid and rigid spherical or cylindrical inclusions contained in it. Oscillations of a pipeline with a two-phase mixture in the general case having a non-uniform distribution of phases over the cross section are considered. Relations are obtained for the effective mass and hydrodynamic damping that determine the frequencies and dynamic-response factors. Oscillations of the bundles of elastic rods in a liquid are considered as in a two-phase mixture formed by a liquid and cylindrical inclusions and which has equivalent inertia and viscous properties.

  5. Numerical investigation of bubble nonlinear dynamics characteristics

    NASA Astrophysics Data System (ADS)

    Shi, Jie; Yang, Desen; Zhang, Haoyang; Shi, Shengguo; Jiang, Wei; Hu, Bo

    2015-10-01

    The complicated dynamical behaviors of bubble oscillation driven by acoustic wave can provide favorable conditions for many engineering applications. On the basis of Keller-Miksis model, the influences of control parameters, including acoustic frequency, acoustic pressure and radius of gas bubble, are discussed by utilizing various numerical analysis methods, Furthermore, the law of power spectral variation is studied. It is shown that the complicated dynamic behaviors of bubble oscillation driven by acoustic wave, such as bifurcation and chaos, further the stimulated scattering processes are revealed.

  6. Characteristic of In Situ Stress and Its Control on the Coalbed Methane Reservoir Permeability in the Eastern Margin of the Ordos Basin, China

    NASA Astrophysics Data System (ADS)

    Zhao, Junlong; Tang, Dazhen; Xu, Hao; Li, Yong; Li, Song; Tao, Shu; Lin, Wenji; Liu, Zhenxing

    2016-08-01

    Coalbed methane (CBM) development faces many challenges, among which in situ stress and permeability are two of the most important and fundamental factors. Knowledge of the characteristics of these factors is crucial to CBM exploration and development. Based on measured injection/falloff and in situ stress well test data of 55 CBM wells in the eastern margin of the Ordos Basin, correlations between parameters including initial reservoir pressure, in situ stress, lateral stress coefficient, well test permeability, and burial depth were determined. The distribution of in situ stress was analyzed systematically and its influence on permeability was also addressed. The results indicate that the maximum horizontal principal stress ( σ H 10.13-37.84 MPa, average 22.50 MPa), minimum horizontal principal stress ( σ h 6.98-26.88 MPa, average 15.04 MPa) and vertical stress ( σ v 12.30-35.72 MPa, average 22.48 MPa) all have positive correlations with coal burial depth. Stress ratios ( σ H/ σ h, σ H/ σ v, and σ h/ σ v) and lateral stress coefficient slowly attenuated with depth. With increase of horizontal principal stresses, coal reservoir permeability (0.01-3.33 mD, average 0.65 mD) decreases. The permeability variation is basically consistent with change of stress state at a certain burial depth, the essence of which is the deformation and destruction of coal pore structures under the action of stresses. Three types of stress fields exist in the area: in the shallow coal seam at burial depths <700 m, the horizontal principal stress is dominant, revealing a strike slip regime ( σ H > σ v > σ h), with average permeability 0.89 mD; from 700 to 1000 m depths, there is a stress transition zone ( σ H ≈ σ v > σ h) with average permeability 0.73 mD; in the deep coal seam with burial depths >1000 m, the vertical principal stress is dominant, demonstrating a normal stress regime ( σ v > σ H > σ h) with average permeability 0.11 mD.

  7. Hydrothermal Fluid Permeability, Temperature, and Nutrient Fluxes: Three Controls on the Structure and the Dynamics of Subsurface Extremophilic Microbe Communities

    NASA Astrophysics Data System (ADS)

    Ryan, M. P.; Yang, J.

    2002-05-01

    We continue to develop a set of models whose aim is to provide broad constraints on the range of possible community structures for subsurface thermally-tolerant microbes. We combine studies of the three-dimensional internal structure of the dike and sill complexes of active volcanoes, studies of the scale- and direction-dependent 3-D in-situ permeability of intrusive and extrusive rocks from in-situ and laboratory data, numerical modelling of hydrothermal convection in volcanic interiors, data on the optimal metabolic and life-limiting thermal requirements of extremophilic microbes, with the set of nutrients and nutrient pathways required for the survival of given species of thermophiles and hyperthermophiles. With this mix of data bases and analysis tools, we can begin to divine a set of broad theoretical guidelines for constraining the structure and dynamics of extremophilic communities in the subsurface environments of volcanoes. We are searching for the first-order controls on transport. The effects of mineral attachment, detachment, and microbial reproduction may be incorporated in refinements of this basic model. Critical thermal intervals and/or isotherms that correlate with (1) optimal metabolic and (2) life-limiting temperatures for thermophilic microbes are, e.g., in degrees Celcius: Thermus thermophilius [70, 85]; Thermomicrobium roseum [70-75, 85]; Thermus aquaticus [70, 79]; and Sulfolobus acidocaldarius [70-75, 90]. Numerical models of the convective migration of thermophilic (50-80 C), and hyperthermophilic (80-113 C) microbes and their macromolecular amino acid building blocks (113- ~200 C) have been developed that explicitly incorporate the roles of fractures and fluid properties. Fluid transport properties are evaluated through the optimal metabolic and life-limiting temperate ranges and beyond. These models quantify our intuition with respect to controls on community structure and dynamics. Important relationships appear to be: (1) Great

  8. Dynamic Characteristics of a Simple Brayton Cryocycle

    NASA Astrophysics Data System (ADS)

    Kutzschbach, A.; Kauschke, M.; Haberstroh, Ch.; Quack, H.

    2006-04-01

    The goal of the overall program is to develop a dynamic numerical model of helium refrigerators and the associated cooling systems based on commercial simulation software. The aim is to give system designers a tool to search for optimum control strategies during the construction phase of the refrigerator with the help of a plant "simulator". In a first step, a simple Brayton refrigerator has been investigated, which consists of a compressor, an after-cooler, a counter-current heat exchanger, a turboexpander and a heat source. Operating modes are "refrigeration" and "liquefaction". Whereas for the steady state design only component efficiencies are needed and mass and energy balances have to be calculated, for the dynamic calculation one needs also the thermal masses and the helium inventory. Transient mass and energy balances have to be formulated for many small elements and then solved simultaneously for all elements. Starting point of the simulation of the Brayton cycle is the steady state operation at design conditions. The response of the system to step and cyclic changes of the refrigeration or liquefaction rate are calculated and characterized.

  9. LABORATORY ASSESSMENT OF THE PERMEABILITY AND DIFFUSION CHARACTERISTICS OF FLORIDA CONCRETES: PHASE II. FIELD SAMPLES AND ANALYSES

    EPA Science Inventory

    The report gives results of a study to: (1) establish the capability of measuring concrete's permeability and diffusivity, (2) measure these parameters in a small sampling of the typical types of Florida concrete, and (3) if possible, correlate the physical parameters of the conc...

  10. Quantifying the role of immobile water on pollutant fluxes in double-permeable media under dynamic flow conditions

    NASA Astrophysics Data System (ADS)

    Knorr, Bastian; Krämer, Florian; Stumpp, Christine; Maloszewski, Piotr

    2014-05-01

    Sustainable use of water resources and their protection against pollution requires fundamental understanding of filter, buffer and storage functions of groundwater systems. Of particular importance are heterogeneous porous aquifers including zones with mobile and immobile water. Pollutants diffuse from high permeable areas into immobile zones with low permeability. Consequently, pollutants can be stored in such immobile water regions and their residence time in double-permeable aquifers is much longer compared to water residence times. However, it still remains unknown how the heterogeneity of an aquifer and time-dependent variability of the water flow influences the pollutant fate in such systems. The objective of this study was to develop experimental and mathematical methods to understand the role of immobile water zones on the pollutant retention, kinetic ad-/desorption and degradation. In saturated column experiments at three different flow rates multitracer experiments were conducted and 4-Chloronitrobenzene (intermediate in the production of explosives) was used as pollutant. The columns were packed with an outer cylinder of clay containing mainly immobile water whereas the centre was filled with coarse quartz sand containing mobile water. In the resulting breakthrough curves of the conservative tracers characterized by different diffusion properties, differences were observed in peak concentration and tailing. These differences indicated a mass exchange with immobile water zones driven by diffusion and were depended on the tracers' molecular diffusion coefficient. The mass exchange increased with decreasing flow rates and was quantified for conservative tracers applying a Single-Fissure Dispersion Model (SFDM) to porous media for the first time. The observed concentrations of the reactive solute 4-Chloronitronbenzen indicated that sorption onto clay minerals enhanced the mass exchange into the immobile water zone. On the other hand sorption and degradation

  11. Nonlinear Dynamic Characteristics of Oil-in-Water Emulsions

    NASA Astrophysics Data System (ADS)

    Yin, Zhaoqi; Han, Yunfeng; Ren, Yingyu; Yang, Qiuyi; Jin, Ningde

    2016-08-01

    In this article, the nonlinear dynamic characteristics of oil-in-water emulsions under the addition of surfactant were experimentally investigated. Firstly, based on the vertical upward oil-water two-phase flow experiment in 20 mm inner diameter (ID) testing pipe, dynamic response signals of oil-in-water emulsions were recorded using vertical multiple electrode array (VMEA) sensor. Afterwards, the recurrence plot (RP) algorithm and multi-scale weighted complexity entropy causality plane (MS-WCECP) were employed to analyse the nonlinear characteristics of the signals. The results show that the certainty is decreasing and the randomness is increasing with the increment of surfactant concentration. This article provides a novel method for revealing the nonlinear dynamic characteristics, complexity, and randomness of oil-in-water emulsions with experimental measurement signals.

  12. Relations between structural and dynamic thermal characteristics of building walls

    SciTech Connect

    Kossecka, E.; Kosny, J.

    1996-10-01

    The effect of internal thermal structure on dynamic characteristics of walls is analyzed. The concept of structure factors is introduced and the conditions they impose on response factors are given. Simple examples of multilayer walls, representing different types of thermal resistance and capacity distribution, are analyzed to illustrate general relations between structure factors and response factors. The idea of the ``thermally equivalent wall``, a plane multilayer structure, with dynamic characteristics similar to those of a complex structure, in which three-dimensional heat flow occurs, is presented.

  13. Examples of Department of Energy Successes for Remediation of Contaminated Groundwater: Permeable Reactive Barrier and Dynamic Underground Stripping ASTD Projects

    SciTech Connect

    Purdy, C.; Gerdes, K.; Aljayoushi, J.; Kaback, D.; Ivory, T.

    2002-02-27

    Since 1998, the Department of Energy's (DOE) Office of Environmental Management has funded the Accelerated Site Technology Deployment (ASTD) Program to expedite deployment of alternative technologies that can save time and money for the environmental cleanup at DOE sites across the nation. The ASTD program has accelerated more than one hundred deployments of new technologies under 76 projects that focus on a broad spectrum of EM problems. More than 25 environmental restoration projects have been initiated to solve the following types of problems: characterization of the subsurface using chemical, radiological, geophysical, and statistical methods; treatment of groundwater contaminated with DNAPLs, metals, or radionuclides; and other projects such as landfill covers, purge water management systems, and treatment of explosives-contaminated soils. One of the major goals of the ASTD Program is to deploy a new technology or process at multiple DOE sites. ASTD projects are encouraged to identify subsequent deployments at other sites. Some of the projects that have successfully deployed technologies at multiple sites focusing on cleanup of contaminated groundwater include: Permeable Reactive Barriers (Monticello, Rocky Flats, and Kansas City), treating uranium and organics in groundwater; and Dynamic Underground Stripping (Portsmouth, and Savannah River), thermally treating DNAPL source zones. Each year more and more new technologies and approaches are being used at DOE sites due to the ASTD program. DOE sites are sharing their successes and communicating lessons learned so that the new technologies can replace the baseline or standard approaches at DOE sites, thus expediting cleanup and saving money.

  14. Phosphorylation of Ser-180 of rat aquaporin-4 shows marginal affect on regulation of water permeability: molecular dynamics study.

    PubMed

    Sachdeva, Ruchi; Singh, Balvinder

    2014-04-01

    Water permeation through rat aquaporin-4 (rAQP4), predominantly found in mammalian brain is regulated by phosphorylation of Ser-180. The present study has been carried out to understand the structural mechanism of regulation of water permeability across the channel. Molecular dynamics (MD) simulations have been carried out to investigate the structural changes caused due to phosphorylation of Ser-180 in the tetrameric assembly of rAQP4 along with predicted C-terminal region (255-323). The interactions involving opposite charges are observed between cytoplasmic loops and the C-terminal region during MD simulations. This results in movement of C-terminal region of rAQP4 towards the cytoplasmic mouth of water channel. Despite this movement, there was a gap between C-terminal region and cytoplasmic mouth of the channel through which water molecules were able to gain entry into the channel. The interactions between C-terminus and loop D of neighboring monomers in a tetrameric assembly appear to prevent the complete closure of cytoplasmic mouth of the water channel. Further, the rates of water permeation through phosphorylated and unphosphorylated rAQP4 have also been compared. The simulation studies showed a continuous movement of water in a single file across pore of unphosphorylated as well as phosphorylated rAQP4. PMID:23651078

  15. Molecular dynamics simulations reveal highly permeable oxygen exit channels shared with water uptake channels in photosystem II.

    PubMed

    Vassiliev, Serguei; Zaraiskaya, Tatiana; Bruce, Doug

    2013-10-01

    Photosystem II (PSII) catalyzes the oxidation of water in the conversion of light energy into chemical energy in photosynthesis. Water delivery and oxygen removal from the oxygen evolving complex (OEC), buried deep within PSII, are critical requirements to facilitate the reaction and minimize reactive oxygen damage. It has often been assumed that water and oxygen travel through separate channels within PSII, as demonstrated in cytochrome c oxidase. This study describes all-atom molecular dynamics simulations of PSII designed to investigate channels by fully characterizing the distribution and permeation of both water and oxygen. Interestingly, most channels found in PSII were permeable to both oxygen and water, however individual channels exhibited different energetic barriers for the two solutes. Several routes for oxygen diffusion within PSII with low energy permeation barriers were found, ensuring its fast removal from the OEC. In contrast, all routes for water showed significant energy barriers, corresponding to a much slower permeation rate for water through PSII. Two major factors were responsible for this selectivity: (1) hydrogen bonds between water and channel amino acids, and (2) steric restraints. Our results reveal the presence of a shared network of channels in PSII optimized to both facilitate the quick removal of oxygen and effectively restrict the water supply to the OEC to help stabilize and protect it from small water soluble inhibitors. PMID:23816955

  16. Modeling the Permeability Anisotropy due to Reservoir-Scale Fault Damage Zones Using Dynamic Rupture Propagation: Applications to a Faulted Hydrocarbon Reservoir and the Nojiima Fault

    NASA Astrophysics Data System (ADS)

    Paul, P. K.; Zoback, M. D.; Hennings, P. H.

    2007-12-01

    Secondary fractures and faults associated with reservoir scale faults affect both permeability and permeability anisotropy and hence may play an important role in controlling production from a faulted reservoir. It is well known from geologic studies that there is a concentration of secondary fractures and faults in a damage zone adjacent to larger-scale faults. Because there is usually inadequate data to incorporate permeability anisotropy due to these damage zone fractures and faults into reservoir flow models, in this study we utilize the principles of dynamic rupture propagation from earthquake seismology to predict the nature of fractured/damage zones associated with reservoir scale faults. We discuss the concepts of dynamic rupture propagation and propose a workflow to model damage zones on the real field scale faults. The model we propose calculates the extent of the damage zone along the fault plane by estimating the stress perturbation associated with dynamic rupture propagation. To verify this technique we compare the modeling results of damage zone width for a reservoir scale fault with field observations. Also, we model the damage zone width associated with the Nojima Fault for the rupture that occurred in the 1996 Kobe earthquake and compare the results with the measurements on core samples from a scientific borehole drilled through the fault after the earthquake. In both the cases this technique gives a reasonable first order approximation of the damage zone width. Using fine scale simulations we show that the fractures associated with the damage zone effects the permeability distribution in both horizontal and vertical directions and defines the permeability anisotropy of the reservoir.

  17. Relative permeability hysteresis and capillary trapping characteristics of supercritical CO2/brine systems: An experimental study at reservoir conditions

    NASA Astrophysics Data System (ADS)

    Akbarabadi, Morteza; Piri, Mohammad

    2013-02-01

    We present the results of an experimental study on the effects of hysteresis on capillary trapping and relative permeability of CO2/brine systems at reservoir conditions. We performed thirty unsteady- and steady-state drainage and imbibition full-recirculation flow experiments in three different sandstone rock samples, low- and high-permeability Berea and Nugget sandstones. The experiments were carried out at various flow rates with both supercritical CO2 (scCO2)/brine and gaseous CO2 (gCO2)/brine fluid systems. The unsteady-state experiments were carried out with a wide range of flow rates to establish a broad range of initial brine saturations (Swi). This allowed investigation of the sensitivity of residual trapped CO2 saturation (S) to changes in Swi. The values were successfully compared with those available in the literature. For a given Swi, the trapped scCO2 saturation was less than that of gCO2 in the same sample. This was attributed to brine being less wetting in the presence of scCO2 than in the presence of gCO2. Post-imbibition dissolution of trapped CO2 and formation of dissolution front was also investigated. During the steady-state experiments, scCO2 and brine were co-injected with monotonically increasing or decreasing fractional flows to perform drainage and imbibition processes. We carried out seven sets of steady-state flow tests with various trajectories generating a comprehensive group of relative permeability hysteresis curves. The scanning curves revealed distinct features with potentially important implications for storage of scCO2 in geological formations. For both series of experiments, the ratio of S to initial CO2 saturation (1- Swi) was found to be much higher for low initial CO2 saturations. The results indicate that very promising fractions (about 49 to 83%) of the initial CO2 saturation can be stored through capillary trapping.

  18. Solar dynamic heat receiver thermal characteristics in low earth orbit

    NASA Technical Reports Server (NTRS)

    Wu, Y. C.; Roschke, E. J.; Birur, G. C.

    1988-01-01

    A simplified system model is under development for evaluating the thermal characteristics and thermal performance of a solar dynamic spacecraft energy system's heat receiver. Results based on baseline orbit, power system configuration, and operational conditions, are generated for three basic receiver concepts and three concentrator surface slope errors. Receiver thermal characteristics and thermal behavior in LEO conditions are presented. The configuration in which heat is directly transferred to the working fluid is noted to generate the best system and thermal characteristics. as well as the lowest performance degradation with increasing slope error.

  19. In situ intestinal permeability and in vivo absorption characteristics of olmesartan medoxomil in self-microemulsifying drug delivery system.

    PubMed

    Kang, Myung J; Kim, Hyung S; Jeon, Ho S; Park, Jong H; Lee, Bong S; Ahn, Byeong K; Moon, Ki Y; Choi, Young W

    2012-05-01

    To characterize the intestinal absorption behavior of olmesartan medoxomil (OLM) and to evaluate the absorption-improving potential of a self-microemulsifying drug delivery system (SMEDDS), we performed in situ single-pass intestinal perfusion (SPIP) and in vivo pharmacokinetic studies in rats. The SPIP study revealed that OLM is absorbed throughout whole intestinal regions, favoring proximal segments, at drug levels of 10-90 μM. The greatest value for effective permeability coefficient (P(eff)) was 11.4 × 10(-6) cm/s in the duodenum (90 μM); the lowest value was 2.9 × 10(-6) cm/s in the ileum (10 μM). A SMEDDS formulation consisting of Capryol 90, Labrasol, and Transcutol, which has a droplet size of 200 nm and self-dispersion time of 21 s, doubled upper intestinal permeability of OLM. The SMEDDS also improved oral bioavailability of OLM in vivo: a 2.7-fold increase in the area under the curve (AUC) with elevated maximum plasma concentration (C(max)) and shortened peak time (T(max)) compared to an OLM suspension. A strong correlation (r(2) = 0.955) was also found between the in situ jejunal P(eff) and the in vivo AUC values. Our study illustrates that the SMEDDS formulation holds great potential as an alternative to increased oral absorption of OLM. PMID:21988221

  20. A study on the dynamic characteristics of rocket structure

    NASA Astrophysics Data System (ADS)

    Kim, K. O.; Lee, J. M.; Kim, J. H.; Kim, S. J.

    The dynamic characteristics of a rocket structure are studied in various aspects. Modeling of the structure used by the finite element method is performed, and analysis of stress under various loading condition is carried out. In particular, stresses and deflections are investigated for the structure subjected to internal pressure, thermal load, and aerodynamic forces during flight. Natural frequencies and mode shapes are also calculated.

  1. Flow characteristics of the dynamic "EPA flux chamber"

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A dynamic flux chamber, commonly referred as the “EPA chamber”, is one method that has been adapted to investigate spatial gas emission on feedlot surfaces. However, the flow characteristics within the chamber have not been evaluated to determine if it can be effectively used outside of its origina...

  2. Dynamic characteristics of peripheral jet ACV. II - Pitching motion

    NASA Astrophysics Data System (ADS)

    Mori, T.; Maeda, H.

    The dynamic pitching characteristics of peripheral jet ACV (Air Cushion Vehicle) which have a stability curtain are investigated analytically and experimentally. The measured values of moment, lift and cushion pressure are compared with numerical results noting applicability to the pitching motion. The response of ACV to the sinusoidal pitching oscillation of the ground is also studied.

  3. Design of helicopter rotor blades for optimum dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Peters, D. A.; Ko, T.; Korn, A.; Rossow, M. P.

    1985-01-01

    The mass and stiffness distributions for helicopter rotor blades are tailored in such a way to give a predetermined placement of blade natural frequencies. The optimal design is pursued with respect of minimum weight, sufficient inertia, and reasonable dynamic characteristics. Finite element techniques are used as a tool. Rotor types include hingeless, articulated, and teetering.

  4. Fluid-dynamical and poro-elastic coupling of gas permeability of inert and sorbing gases on an Australian sub-bituminous coal

    NASA Astrophysics Data System (ADS)

    Gensterblum, Y.; Krooss, B. M.

    2013-12-01

    The interaction and the coupling of slip-flow, a fluid dynamic phenomenon, and the cleat volume compressibility which is a poroelastic phenomenon has been investigated on two samples from the Taroom coal measure, Surat Basin, Queensland Australia. Measurements were performed using inert (helium and argon) and sorbing gases (nitrogen, methane and carbon dioxide) at controlled effective stress. We observed the following regular sequence of permeability coefficients for the different gases: Helium >> argon => nitrogen > methane >> CO2 Even after slip-flow correction, different intrinsic permeability coefficients are obtained for the same sample if different gases are used in the tests. The permeability values determined with helium are largest while those measured with CO2 are lowest. Inert gases like helium and argon show higher apparent- and even slip flow-corrected permeability coefficients than sorbing gases like methane or carbon dioxide. This observation is contrary to the prediction that the slip-flow corrected permeability have to be the same for all gases. The cleat volume compressibility cf was evaluated using the 'matchstick approach' [1, 2]. The cleat volume compressibility coefficients cf are almost identical for the two samples taken from the same well. However, for one sample a strong dependence of the cf with the mean pore pressure was observed. This is attributed to a strong slip-flow effect caused by a narrow cleat system as compared to the sister sample. The cleat volume compressibility coefficient cf is almost the same for inert and sorbing gases. We conclude that the occurrence of slip-flow in coals is able to compensate the permeability reduction resulting from increasing effective stress. This should lead to a much higher productivity of coal bed methane reservoirs in the third production phase (pseudo-steady state phase; [3]). This conclusion appears to be also valid for shale gas and tight gas reservoirs, where the gas transport takes place in

  5. Dynamic characteristics of magnetically-levitated vehicle systems.

    SciTech Connect

    Cai, Y.; Chen, S. S.; Energy Technology

    1997-11-01

    The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, while vehicle stability is an important safety related element. To design a guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade off between guideway smoothness and levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. This report, which reviews various aspects of the dynamic characteristics, experiments and analysis, and design guidelines for maglev systems, discusses vehicle stability, motion dependent magnetic force components, guideway characteristics, vehicle/ guideway interaction, ride quality, suspension control laws, aerodynamic loads and other excitations, and research needs.

  6. A review of dynamic characteristics of magnetically levitated vehicle systems

    SciTech Connect

    Cai, Y.; Chen, S.S.

    1995-11-01

    The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, while vehicle stability is an important safety-related element. To design a guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade-off between guideway smoothness and levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. This report, which reviews various aspects of the dynamic characteristics, experiments and analysis, and design guidelines for maglev systems, discusses vehicle stability, motion dependent magnetic force components, guideway characteristics, vehicle/ guideway interaction, ride quality, suspension control laws, aerodynamic loads and other excitations, and research needs.

  7. Numerical and Experimental Dynamic Characteristics of Thin-Film Membranes

    NASA Technical Reports Server (NTRS)

    Young, Leyland G.; Ramanathan, Suresh; Hu, Jia-Zhu; Pai, P. Frank

    2004-01-01

    Presented is a total-Lagrangian displacement-based non-linear finite-element model of thin-film membranes for static and dynamic large-displacement analyses. The membrane theory fully accounts for geometric non-linearities. Fully non-linear static analysis followed by linear modal analysis is performed for an inflated circular cylindrical Kapton membrane tube under different pressures, and for a rectangular membrane under different tension loads at four comers. Finite element results show that shell modes dominate the dynamics of the inflated tube when the inflation pressure is low, and that vibration modes localized along four edges dominate the dynamics of the rectangular membrane. Numerical dynamic characteristics of the two membrane structures were experimentally verified using a Polytec PI PSV-200 scanning laser vibrometer and an EAGLE-500 8-camera motion analysis system.

  8. Dynamic energy absorption characteristics of hollow microlattice structures

    SciTech Connect

    Liu, YL; Schaedler, TA; Chen, X

    2014-10-01

    Hollow microlattice structures are promising candidates for advanced energy absorption and their characteristics under dynamic crushing are explored. The energy absorption can be significantly enhanced by inertial stabilization, shock wave effect and strain rate hardening effect. In this paper we combine theoretical analysis and comprehensive finite element method simulation to decouple the three effects, and then obtain a simple model to predict the overall dynamic effects of hollow microlattice structures. Inertial stabilization originates from the suppression of sudden crushing of the microlattice and its contribution scales with the crushing speed, v. Shock wave effect comes from the discontinuity across the plastic shock wave front during dynamic loading and its contribution scales with e. The strain rate effect increases the effective yield strength upon dynamic deformation and increases the energy absorption density. A mechanism map is established that illustrates the dominance of these three dynamic effects at a range of crushing speeds. Compared with quasi-static loading, the energy absorption capacity a dynamic loading of 250 m/s can be enhanced by an order of magnitude. The study may shed useful insight on designing and optimizing the energy absorption performance of hollow microlattice structures under various dynamic loads. (C) 2014 Elsevier Ltd. All rights reserved.

  9. Dynamic and attitude control characteristics of an International Space Station

    NASA Technical Reports Server (NTRS)

    Sutter, Thomas R.; Cooper, Paul A.; Young, John W.; Mccutchen, Don K.

    1987-01-01

    The structural dynamic characteristics of the International Space Station (ISS), the interim reference configuration established for NASA's Space Station developmental program, are discussed, and a finite element model is described. Modes and frequencies of the station below 2.0 Hz are derived, and the dynamic response of the station is simulated for an external impulse load corresponding to a failed shuttle-docking maneuver. A three-axis attitude control system regulates the ISS orientation, with control moment gyros responding to attitude and attitude rate signals. No instabilities were found in the attitude control system.

  10. Permeability characteristics of complement-damaged membranes: evaluation of the membrane leak generated by the complement proteins C5b-9.

    PubMed

    Sims, P J

    1981-03-01

    Permeability characteristics of the membrane lesion generated by the terminal complement proteins are considered in light of recent observations that the measured diffusion of solute across complement-damaged membranes does not conform to the "doughnut hole" model of a discrete transmembrane pore formed by the inserted C5b-9 complex. By using the measured kinetics of steady-state tracer isotope diffusion of nonelectrolytes across resealed erythrocyte ghost membranes treated with C5b-9, a new transport model is developed. This model considers the apparent membrane lesion strictly in terms of the operational criteria of a functional conducting pathway for the observed diffusing solute, independent of a priori assumptions about the geometry or molecular properties of the membrane lesion. With this definition of the unit membrane lesion and the assumption that the exclusion size of the conducting pathway varies directly with the multiplicity of bound C5b-9 (as suggested by previous measurements under conditions of varying input of C5b-9), numerical estimates of te apparent permeability of the complement-damaged membrane to four diffusing nonelectrolytes are derived. These results suggest that the pathway for a particle diffusing across the complement lesion cannot be a pore and is functionally equivalent to an aqueous leak pathway, free of pore constraints. Implications of these results are discussed in terms of current molecular models for the mechanism of membrane damage by the complement proteins. PMID:6940192

  11. Study on Dynamic Characteristics of Ammonia Refrigerator System

    NASA Astrophysics Data System (ADS)

    Nakashima, Minoru; Ikegami, Yasuyuki; Hirao, Yasuhiro; Sudoh, Gaku; Shingoh, Masashi; Uehara, Haruo

    The dynamic characteristics of ammonia refrigerator system are observed when the expansion valve's opening is slightly changed. The refrigerator system is constructed with the reciprocal compressor, the plate type heat exchanger for the condenser and the evaporator, and the expansion valve. A simple simulation model for this refrigerator system is proposed to develop the computer-simulator of this ammonia refrigerator system and those simulation results are compared to above experimental results. For the development of the computer-simulator, simple but useful models, which can represent the dynamic characteristics of the refrigerator, are adopted for each components of the refrigerator system. The simulation shows the overall good agreement with experiment, without the time constant in the variation of the temperature at the evaporator outlet.

  12. The permeability characteristics and interaction of the main components from Zhizi Bopi decoction in the MDCK cell model.

    PubMed

    Qian, Zhengyue; Huang, Cheng; Shen, Chenlin; Meng, Xiaoming; Chen, Zhaolin; Hu, Tingting; Li, Yangyang; Li, Jun

    2016-08-01

    1. Although emerging evidence indicates the therapeutic effects of Zhizi Bopi Decoction, the extent to which essential ingredients are absorbed and the possible synergistic actions are poorly understood. 2. In this study, MDCK cell model was used to determine the bi-directional permeability and interaction between the main components (geniposide, berberine and glycyrrhizic acid) of Zhizi Bopi Decoction. 3. The transport of the active ingredients was concentration-dependent in both directions. Moreover, the Papp (AP-BL) values of berberine and glycyrrhizic acid were significantly reduced when co-incubation with an ATP inhibitor. Additionally, uptake of berberine, glycyrrhizic acid were clearly inhibited by the inhibitors of P-glycoprotein and MRP2, indicating that P-gp and MRP2 may be involved in the transport of berberine and glycyrrhizic acid, respectively. However, it was found that geniposide may be purely passive diffusion. Furthermore, the combined incubation of geniposide with berberine and glycyrrhizic acid had a powerful sorbefacient effect than use of a single drug alone which may be regulated by tight junctions. 4. In summary, our study provides useful information for pharmacological applications of Zhizi Bopi Decoction and offers new insights into this ancient decoction for further researches, especially in drug synergism. PMID:26634613

  13. Comparisons of the dynamic characteristics of magnetorheological and hydraulic dampers

    NASA Astrophysics Data System (ADS)

    Zhang, Yi; Oyadiji, S. O.

    2015-04-01

    A magnetorheological (MR) damper can adapt its dynamic performance to the vibration environment by controlling the current applied. Compared to other types of dampers, the MR damper has a wider range of dynamic characteristics. Two different dampers: hydraulic, and MR dampers were tested under forced sinusoidal excitations of low to high frequencies. Also, different currents were applied on the MR damper to investigate its performance under varying electromagnetic fields. The results reveal that the two dampers have nonlinear dynamic characteristics and that characteristics of the hydraulic damper are different from those of the MR damper. The hydraulic damper provides slight nonlinear damping force whereas the MR damper shows a strong nonlinear property. In addition, the hydraulic damper is designed to provide an asymmetric damping force of rebound and compression whereas the MR damper provides a symmetric damping force. In the experiments conducted, the excitation frequency was varied from 3 Hz to 11 Hz and the amplitude from 2.5 mm to 12 mm. For the hydraulic damper, the lowest compression damping force only increases by about 0.54 kN while the rebound force increases by about 1.9 kN. In contrast, the variations of compression and rebound forces of the MR damper are 1.9 and 2.0 kN, respectively. Furthermore, the damping force of the MR damper increases as the current increases from 0 to 0.75 A.

  14. Evaluating the Dynamic Characteristics of Retrofitted RC Beams

    NASA Astrophysics Data System (ADS)

    Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang

    2008-07-01

    The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.

  15. Evaluating the Dynamic Characteristics of Retrofitted RC Beams

    SciTech Connect

    Ghods, Amir S.; Esfahani, Mohamad R.; Moghaddasie, Behrang

    2008-07-08

    The aim of this experimental study was to investigate the relationship between the damage and changes in dynamic characteristics of reinforced concrete members strengthened with Carbon Fiber Reinforced Polymer (CFRP). Modal analysis is a popular non-destructive method for evaluating health of structural systems. A total of 8 reinforced concrete beams with similar dimensions were made using concrete with two different compressive strengths and reinforcement ratios. Monotonic loading was applied with four-point-bending setup in order to generate different damage levels in the specimens while dynamic testing was conducted to monitor the changes in dynamic characteristics of the specimens. In order to investigate the effect of CFRP on static and dynamic properties of specimens, some of the beams were loaded to half of their ultimate load carrying capacity and then were retrofitted using composite laminates with different configuration. Retrofitted specimens demonstrated elevated load carrying capacity, higher flexural stiffness and lower displacement ductility. By increasing the damage level in specimens, frequencies of the beams were decreased and after strengthening these values were improved significantly. The intensity of the damage level in each specimen affects the shape of its mode as well. Fixed points and curvatures of mode shapes of beams tend to move toward the location of the damage in each case.

  16. Scales of rock permeability

    NASA Astrophysics Data System (ADS)

    Guéguen, Y.; Gavrilenko, P.; Le Ravalec, M.

    1996-05-01

    Permeability is a transport property which is currently measured in Darcy units. Although this unit is very convenient for most purposes, its use prevents from recognizing that permeability has units of length squared. Physically, the square root of permeability can thus be seen as a characteristic length or a characteristic pore size. At the laboratory scale, the identification of this characteristic length is a good example of how experimental measurements and theoretical modelling can be integrated. Three distinct identifications are of current use, relying on three different techniques: image analysis of thin sections, mercury porosimetry and nitrogen adsorption. In each case, one or several theoretical models allow us to derive permeability from the experimental data (equivalent channel models, statistical models, effective media models, percolation and network models). Permeability varies with pressure and temperature and this is a decisive point for any extrapolation to crustal conditions. As far as pressure is concerned, most of the effect is due to cracks and a model which does not incorporate this fact will miss its goal. Temperature induced modifications can be the result of several processes: thermal cracking (due to thermal expansion mismatch and anisotropy, or to fluid pressure build up), and pressure solution are the two main ones. Experimental data on pressure and temperature effects are difficult to obtain but they are urgently needed. Finally, an important issue is: up to which point are these small scale data and models relevant when considering formations at the oil reservoir scale, or at the crust scale? At larger scales the identification of the characteristic scale is also a major goal which is examined.

  17. Dynamic contrast-enhanced MRI and CT provide comparable measurement of blood-brain barrier permeability in a rodent stroke model.

    PubMed

    Merali, Zamir; Wong, Teser; Leung, Jackie; Gao, Meah MingYang; Mikulis, David; Kassner, Andrea

    2015-10-01

    In the current management of acute ischemic stroke (AIS), clinical criteria are used to estimate the risk of hemorrhagic transformation (HT), which is a devastating early complication. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and computed tomography (DCE-CT) may serve as physiologically-based decision making tools to more reliably assess the risk of HT. Before these tools can be properly validated, the comparability of the blood-brain barrier (BBB) permeability measurements they generate should be assessed. Sixteen rats were subjected to a transient middle cerebral artery occlusion before successively undergoing DCE-CT and DCE-MRI at 24-hours. BBB permeability (K(trans)) values were generated from both modalities. A correlation of R=0.677 was found (p<0.01) and the resulting relationship was [DCE-CT=(0.610*DCE-MRI)+4.140]. A variance components analysis found the intra-rat coefficient of variation to be 0.384 and 0.258 for K(trans) values from DCE-MRI and DCE-CT respectively. Permeability measures from DCE-CT were 22% higher than those from DCE-MRI. The results of this study demonstrate for the first time comparability between DCE-CT and DCE-MRI in the assessment of AIS. These results may provide a foundation for future clinical trials making combined use of these modalities. PMID:26117703

  18. Static and dynamic characteristics of parallel-grooved seals

    NASA Technical Reports Server (NTRS)

    Iwatsubo, Takuzo; Yang, Bo-Suk; Ibaraki, Ryuji

    1987-01-01

    Presented is an analytical method to determine static and dynamic characteristics of annular parallel-grooved seals. The governing equations were derived by using the turbulent lubrication theory based on the law of fluid friction. Linear zero- and first-order perturbation equations of the governing equations were developed, and these equations were analytically investigated to obtain the reaction force of the seals. An analysis is presented that calculates the leakage flow rate, the torque loss, and the rotordynamic coefficients for parallel-grooved seals. To demonstrate this analysis, we show the effect of changing number of stages, land and groove width, and inlet swirl on stability of the boiler feed water pump seals. Generally, as the number of stages increased or the grooves became wider, the leakage flow rate and rotor-dynamic coefficients decreased and the torque loss increased.

  19. Dynamic characteristics of the LLNL Precision Engineering Research Lathe

    SciTech Connect

    Franse, J.; Roblee, J.W.; Modemann, K.

    1988-08-31

    The dynamic characteristics of the Precision Engineering Research Lathe (PERL) have been investigated experimentally, up to a frequency of 1000 Hz. In successive tests, the exciting force was applied to either the X slide or the (non-rotating) spindle, and in the X or Z direction. These are the critical directions for turning operations on this T base type lathe. Each of these tests was furthermore done with the servo system active and with the servo system off (slides clamped, control loops open). The applied force fluctuations and the resulting relative displacement, between a capacitive probe mounted on the X slide and the spindle, were measured during the experiments. From these data, the relative dynamic compliances between the tool and the workpiece, in the Z and X directions, have been determined. The most important resonant frequencies, modes, and compliances are reported. Their consequences with regard to the surface quality of diamond turned parts are also discussed. 3 refs., 11 figs.

  20. The physico-chemical characteristics of the phosphocholine-containing glycoglycerolipid MfGL-II govern the permeability properties of Mycoplasma fermentans.

    PubMed

    Ben-Menachem, G; Byström, T; Rechnitzer, H; Rottem, S; Rilfors, L; Lindblom, G

    2001-07-01

    Mycoplasma fermentans seems to be involved in several pathogenic conditions in humans, and is among other things capable of fusing with T-cells and lymphocytes. The choline-containing phosphoglycolipid 6'-O-(3"-phosphocholine-2"-amino-1"-phospho-1",3"-propanediol)-alpha-D-glucopyranosyl-(1'-->3)-1,2-diacylglycerol (MfGL-II) in the membrane of M. fermentans has been suggested to enhance the fusion process, and the characteristics of MfGL-II were therefore investigated. When a cell culture ages the fraction of MfGL-II increases, and the fraction of the other major membrane lipid, phosphatidylglycerol (PtdGro), decreases concomitantly. Swelling experiments showed that the permeability and osmotic fragility are markedly reduced in aged cells. MfGL-II is selectively released into the surrounding medium when aged M. fermentans cells are incubated in buffer containing EDTA. The physico-chemical properties of MfGL-II were studied by NMR spectroscopy and differential scanning calorimetry, and they can explain the biochemical results. The temperature for the transition between gel and lamellar liquid crystalline (Lalpha) phases is 35-45 degrees C higher for MfGL-II than for PtdGro, which most probably gives rise to the reduced permeability in aged cells. At high water contents MfGL-II forms an Lalpha phase and isotropic aggregates which were interpreted to be vesicles with a radius of approximately 450 A. It is proposed that MfGL-II forms vesicles in the surrounding medium when it is released from the cell membrane. Neither EDTA nor Ca2+ ions have a significant influence on the aggregate structures formed by MfGL-II. Our results indicate that MfGL-II has no fusogenic properties. It is more probable that a recently identified lysolipid in the M. fermentans membrane acts as a fusogen. PMID:11432735

  1. The Dynamic Characteristic and Hysteresis Effect of an Air Spring

    NASA Astrophysics Data System (ADS)

    Löcken, F.; Welsch, M.

    2015-02-01

    In many applications of vibration technology, especially in chassis, air springs present a common alternative to steel spring concepts. A design-independent and therefore universal approach is presented to describe the dynamic characteristic of such springs. Differential and constitutive equations based on energy balances of the enclosed volume and the mountings are given to describe the nonlinear and dynamic characteristics. Therefore all parameters can be estimated directly from physical and geometrical properties, without parameter fitting. The numerically solved equations fit very well to measurements of a passenger car air spring. In a second step a simplification of this model leads to a pure mechanical equation. While in principle the same parameters are used, just an empirical correction of the effective heat transfer coefficient is needed to handle some simplification on this topic. Finally, a linearization of this equation leads to an analogous mechanical model that can be assembled from two common spring- and one dashpot elements in a specific arrangement. This transfer into "mechanical language" enables a system description with a simple force-displacement law and a consideration of the nonobvious hysteresis and stiffness increase of an air spring from a mechanical point of view.

  2. Characteristic ion distributions in the dynamic auroral transition region

    NASA Astrophysics Data System (ADS)

    Zeng, W.; Horwitz, J. L.; Tu, J.-N.

    2006-04-01

    A Dynamic Fluid Kinetic (DyFK) simulation is conducted to study the H+/O+ flows and distribution functions in the high-latitude dynamic transition region, specifically from 1000 km to about 4000 km altitude. Here, the collisional-to-collisionless transition region is that region where Coulomb collisions have significant but not dominant effects on the ion distributions. In this study, a simulation flux tube, which extends from 120 km to 3 RE altitude, is assumed to experience a pulse of auroral effects for approximately 20 minutes, including both soft electron precipitation and transverse wave heating, and then according to different geophysical circumstances, either to relax following the cessation of such auroral effects or to be heated further continuously by waves with power at higher frequencies. Our principal purpose in this investigation is to elicit the characteristic ion distribution functions in the auroral transition region, where both collisions and kinetic processes play significant roles. The characteristics of the simulated O+ and H+ velocity distributions, such as kidney bean shaped H+ distributions, and O+ distributions having cold cores with upward folded conic wings, resemble those observed by satellites at similar altitudes and geographic conditions. From the simulated distribution function results under different geophysical conditions, we find that O+-O+ and O+-H+ collisions, in conjunction with the kinetic and auroral processes, are key factors in the velocity distributions up to 4000 km altitude, especially for the low speed portions, for both O+ and H+ ions.

  3. Strength and dynamic characteristics analyses of wound composite axial impeller

    NASA Astrophysics Data System (ADS)

    Wang, Jifeng; Olortegui-Yume, Jorge; Müller, Norbert

    2012-03-01

    A low cost, light weight, high performance composite material turbomachinery impeller with a uniquely designed blade patterns is analyzed. Such impellers can economically enable refrigeration plants to use water as a refrigerant (R718). A strength and dynamic characteristics analyses procedure is developed to assess the maximum stresses and natural frequencies of these wound composite axial impellers under operating loading conditions. Numerical simulation using FEM for two-dimensional and three-dimensional impellers was investigated. A commercially available software ANSYS is used for the finite element calculations. Analysis is done for different blade geometries and then suggestions are made for optimum design parameters. In order to avoid operating at resonance, which can make impellers suffer a significant reduction in the design life, the designer must calculate the natural frequency and modal shape of the impeller to analyze the dynamic characteristics. The results show that using composite Kevlar fiber/epoxy matrix enables the impeller to run at high tip speed and withstand the stresses, no critical speed will be matched during start-up and shut-down, and that mass imbalances of the impeller shall not pose a critical problem.

  4. Rapid, dynamic changes in glomerular permeability to macromolecules during systemic angiotensin II (ANG II) infusion in rats.

    PubMed

    Axelsson, Josefin; Rippe, Anna; Oberg, Carl M; Rippe, Bengt

    2012-09-15

    The actions of systemic angiotensin II (ANG II) infusions on glomerular permeability were investigated in vivo. In anesthetized Wistar rats (250-280 g), the left ureter was cannulated for urine collection, while simultaneously blood access was achieved. Rats were continuously infused intravenously with either of four doses of ANG II ranging from 16 ng·kg(-1)·min(-1) (Lo-ANG II) to 1.82 μg·kg(-1)·min(-1) (Hi-ANG II), and in separate experiments with aldosterone (Aldo; 0.22 mg·kg(-1)·min(-1)), or with the calcium channel blocker nimodipine, or with the Aldo antagonist spironolactone together with a high ANG II dose (910 ng·kg(-1)·min(-1); Hi-Int-ANG II), respectively, and with polydisperse FITC-Ficoll-70/400 (molecular radius 10-80 Å) and (51)Cr-EDTA. Plasma and urine samples were taken at 5, 15, 30, 60, and 120 min and analyzed by high performance size-exclusion chromatography for determination of glomerular sieving coefficients (θ) to Ficoll. Mean arterial pressure (MAP) and glomerular filtration rate (GFR) were also assessed. For ANG II, there was a rapid, marked, partly reversible increase in glomerular permeability (θ) for Ficoll molecules >34 Å in radius, peaking at 5-15 min, which was completely abrogated by the ANG II blocker candesartan but not affected by spironolactone at 15 and 30 min. For Aldo, the response was similar to that found for the lowest dose of ANG II infused. For the two highest ANG II doses given (Hi-Int-ANG II and Hi-ANG II), GFR decreased transiently, concomitant with marked, sustained increases in MAP. Nimodipine completely blocked all hemodynamic ANG II actions, whereas the glomerular permeability response remained unchanged. Thus ANG II directly increased glomerular permeability independently of its hemodynamic actions and largely independently of the concomitant Aldo response. The ANG II-induced increases in glomerular permeability were, according to a two-pore and a log-normal distributed pore model, compatible with an

  5. Dynamic characteristics of a simple bursting neuron model

    NASA Astrophysics Data System (ADS)

    Nakajima, Koji; Sato, Shigeo; Hayakawa, Yoshihiro

    We present a simple neuron model that shows a rich property in spite of the simple structure derived from the simplification of the Hindmarsh-Rose, the Morris-Lecar, and the Hodgkin-Huxley models. The model is a typical example whose characteristics can be discussed through the concept of potential with active areas. A potential function is able to provide a global landscape for dynamics of a model, and the dynamics is explained in connection with the disposition of the active areas on the potential, and hence we are able to discuss the global dynamic behaviors and the common properties among these realistic models. The obtained outputs are broadly classified as simple oscillations, spiking, bursting, and chaotic oscillations. The bursting outputs are classified as with spike undershoot and without spike undershoot, and the bursts without spike undershoot are classified as with tapered and without tapered. We show the parameter dependence of these outputs and discuss the connection between these outputs and the potential with active areas.

  6. Morphological characteristics of motile plants for dynamic motion

    NASA Astrophysics Data System (ADS)

    Song, Kahye; Yeom, Eunseop; Kim, Kiwoong; Lee, Sang Joon

    2014-11-01

    Most plants have been considered as non-motile organisms. However, plants move in response to environmental changes for survival. In addition, some species drive dynamic motions in a short period of time. Mimosa pudica is a plant that rapidly shrinks its body in response to external stimuli. It has specialized organs that are omnidirectionally activated due to morphological features. In addition, scales of pinecone open or close up depending on humidity for efficient seed release. A number of previous studies on the dynamic motion of plants have been investigated in a biochemical point of view. In this study, the morphological characteristics of those motile organs were investigated by using X-ray CT and micro-imaging techniques. The results show that the dynamic motions of motile plants are supported by structural features related with water transport. These studies would provide new insight for better understanding the moving mechanism of motile plant in morphological point of view. This research was financially supported by the Creative Research Initiative of the Ministry of Science, ICT and Future Planning (MSIP) and the National Research Foundation (NRF) of Korea (Grant Number: 2008-0061991).

  7. Dynamic characteristics of piezoelectric shear deformable composite plates

    NASA Astrophysics Data System (ADS)

    Kolar, Ramesh

    2004-07-01

    Layered composites have attracted attention for their high specific stiffness, high specific strength, and application specific tailoring of their properties. It is also recognized that layered composites are prone to delamination failure in addition to other failure modes. Consideration of transverse shear on the deformation behavior of the composites is an important aspect in the study of delamination mode failure of such plates. In this paper, we consider the effects of including the transverse shear deformation on the vibration characteristics of layered piezoelectric composites. The formulation is based on the Raleigh-Ritz method using the beam characteristic functions. MATLAB based symbollic math tool box is used in evaluating th eintegrals resulting from the Raleigh Ritz approach. Various commonly occuring boundary conditions are discussed. Results are provided showing the effects of the shear deformation on the dynamics of layered laminated composites. The effects of laminate thickness, fiber orientation, and the plate aspect ratios on the free vibration characteristics of the composite laminates are given to demonstrate the methodology described.

  8. Control of the Aquaporin-4 Channel Water Permeability by Structural Dynamics of Aromatic/Arginine Selectivity Filter Residues.

    PubMed

    Kitchen, Philip; Conner, Alex C

    2015-11-17

    The aquaporins (AQPs) make up a family of integral membrane proteins that control cellular water flow. Gating of the water channel by conformational changes induced by phosphorylation or protein-protein interactions is an established regulatory mechanism for AQPs. Recent in silico and crystallographic analyses of the structural biology of AQPs suggest that the rate of water flow can also be controlled by small movements of single-amino acid side chains lining the water pore. Here we use measurements of the membrane water permeability of mammalian cells expressing AQP4 mutants to provide the first in vitro evidence in support of this hypothesis. PMID:26512424

  9. Fluid mechanics of dynamic stall. II - Prediction of full scale characteristics

    NASA Technical Reports Server (NTRS)

    Ericsson, L. E.; Reding, J. P.

    1988-01-01

    Analytical extrapolations are made from experimental subscale dynamics to predict full scale characteristics of dynamic stall. The method proceeds by establishing analytic relationships between dynamic and static aerodynamic characteristics induced by viscous flow effects. The method is then validated by predicting dynamic test results on the basis of corresponding static test data obtained at the same subscale flow conditions, and the effect of Reynolds number on the static aerodynamic characteristics are determined from subscale to full scale flow conditions.

  10. Design of helicopter rotor blades for optimum dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.

    1983-01-01

    The possibilities and limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are discussed. The extent that changes in mass of stiffness distribution can be used to place rotor frequencies at desired locations is determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass, moment of inertia, size, strength, and stability are formulated. The extent that the hub loads can be minimized by proper choice of E1 distribution, and the minimum hub loads which can be approximated by a design for a given set of natural frequencies are determined. Aerodynamic couplings that might affect the optimum blade design, and the relative effectiveness of mass and stiffness distribution on the optimization procedure are investigated.

  11. Design of helicopter rotor blades for optimum dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Peters, D. A.; Ko, T.; Korn, A. E.; Rossow, M. P.

    1982-01-01

    The possibilities and the limitations of tailoring blade mass and stiffness distributions to give an optimum blade design in terms of weight, inertia, and dynamic characteristics are investigated. Changes in mass or stiffness distribution used to place rotor frequencies at desired locations are determined. Theoretical limits to the amount of frequency shift are established. Realistic constraints on blade properties based on weight, mass moment of inertia size, strength, and stability are formulated. The extent hub loads can be minimized by proper choice of EL distribution is determined. Configurations that are simple enough to yield clear, fundamental insights into the structural mechanisms but which are sufficiently complex to result in a realistic result for an optimum rotor blade are emphasized.

  12. Dynamic characteristics and seismic stability of expanded polystyrene geofoam embankments

    NASA Astrophysics Data System (ADS)

    Amini, Zahra A.

    Expanded Polystyrene (EPS) geofoam has become a preferred material in various construction applications due to its light weight. Application of EPS accelerates the projects particularly on soft soils. The focus of this research is on the application of the EPS in embankments and its behavior mainly under harmonic vibration. The goal of this study was to investigate dynamic characteristics of freestanding vertical EPS geofoam embankment and address potential seismic issues that result from the distinguished dynamic behavior of such systems due to the layered and discrete block structure. A series of experimental studies on EPS 19 and a commercially available adhesive was conducted. Two-dimensional numerical analyses were performed to replicate the response of EPS geofoam embankment to horizontal and vertical harmonic motions. The results of the analyses have shown that for some acceleration amplitude levels interlayer sliding is expected to occur in EPS geofoam embankments almost immediately after the start of the base excitation; however, as a highly efficient energy dissipation mechanism sliding ceases rapidly. Shear keys and adhesive may be used to prevent interlayer sliding if they cover the proper extent of area of the embankment. EPS blocks placed in the corners of the embankment and at the edges of the segment prohibited from sliding may experience high stress concentrations. The embankment may show horizontal sway and rocking once sliding is prevented.

  13. Effects of pressure on pore characteristics and permeability of porous rocks as estimated from seismic wave velocities in cores from TCDP Hole-A

    NASA Astrophysics Data System (ADS)

    Kitamura, Keigo; Takahashi, Miki; Mizoguchi, Kazuo; Masuda, Koji; Ito, Hisao; Song, Sheng-Rong

    2010-09-01

    Changes in Vp/Vs (Poisson's ratio) around a fault are related to changes in the fluid transport properties of rocks, which play a significant role in seismogenic processes. Here we report a notable relationship between Vp/Vs and the permeability of porous fault-related rocks (Chelungpu fault, Taiwan) by direct and simultaneous measurement of elastic wave velocities (Vp and Vs) and permeability under increasing effective confining pressure (Peff) up to 25 MPa. Vp and Vs for all samples increased with Peff in the range up to 20 MPa, then were nearly constant as Peff increased to 25 MPa. Most silty sandstones with large proportions of fine-grained material showed positive correlations between Vp/Vs and permeability with rising pressure. On the other hand, well-sorted sandstones showed only slight changes in permeability with respect to Vp/Vs with rising pressure. We infer that grain size distributions, in particular the amount of silt- and clay-size grains, are responsible for the change in permeability with pressure as small particles clog pore networks with increasing Peff, causing the decrease in permeability. These findings may be useful to explain changes in permeability and pore pressure in the deep crust.

  14. Dislocation loop dynamics in freestanding smectic films: the role of the disjoining pressure and of the finite permeability of the meniscus.

    PubMed

    Oswald, P; Picano, F; Caillier, F

    2003-12-01

    When a dislocation loop nucleates in a freestanding film, it collapses or grows depending on whether its radius r is smaller or larger than a critical radius r(c). In this paper, we analyze the growth dynamics of a dislocation loop in the limit of r>r(c). Experiments with pure octylcyanobiphenyl show that the dislocation velocity is constant in thick films (more than 100 layers) regardless of their thicknesses, and only depends on the pressure in the meniscus. At intermediate thickness (between 100 and 15 layers), the velocity is no longer constant and tends to decrease in time on account of the finite permeability of the meniscus. In very thin films (less than 15 layers), the dislocations move faster than in thick films, although their velocities continue to decrease in time. The thinner the film, the larger the global acceleration is. This effect is linked to a supplementary force acting on the dislocations caused by the attraction between the free surfaces (where the smectic order parameter is enhanced). The progressive deceleration is due to the finite permeability of the meniscus. PMID:14754219

  15. Permeability and kinetic coefficients for mesoscale BCF surface step dynamics: Discrete two-dimensional deposition-diffusion equation analysis

    DOE PAGESBeta

    Zhao, Renjie; Evans, James W.; Oliveira, Tiago J.

    2016-04-08

    Here, a discrete version of deposition-diffusion equations appropriate for description of step flow on a vicinal surface is analyzed for a two-dimensional grid of adsorption sites representing the stepped surface and explicitly incorporating kinks along the step edges. Model energetics and kinetics appropriately account for binding of adatoms at steps and kinks, distinct terrace and edge diffusion rates, and possible additional barriers for attachment to steps. Analysis of adatom attachment fluxes as well as limiting values of adatom densities at step edges for nonuniform deposition scenarios allows determination of both permeability and kinetic coefficients. Behavior of these quantities is assessedmore » as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.« less

  16. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    NASA Astrophysics Data System (ADS)

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-06-01

    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.

  17. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics.

    PubMed

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    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. PMID:26058060

  18. Electric tuning of magnetization dynamics and electric field-induced negative magnetic permeability in nanoscale composite multiferroics

    PubMed Central

    Jia, Chenglong; Wang, Fenglong; Jiang, Changjun; Berakdar, Jamal; Xue, Desheng

    2015-01-01

    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. PMID:26058060

  19. Dynamics and control characteristics of a reference Space Station configuration

    NASA Technical Reports Server (NTRS)

    Sutter, Thomas R.; Cooper, Paul A.; Young, John W.

    1988-01-01

    This paper describes the structural dynamic characteristics of a NASA reference space station configuration as defined in the November 1987 Space Station Program - Systems Engineering and Integration Engineering Data Book. The modes and frequencies of the station below 2.0 Hz were obtained and selected results along with rigid body properties are presented. A three-axis attitude control system using control moment gyros responding to attitude and attitude rate signals is used to regulate the orientation of the station. The stability of the control system with non-collocated sensors is investigated for both compensated and uncompensated control signals. Results from a closed-loop simulation of a commanded attitude change about three axes, and from a closed-loop simulation of the response of the station to an externally applied unit force impulse at the docking port are presented. These simulation results are used to evaluate the possible degree of control/structures interaction which could occur during normal operation of the station.

  20. The dynamical characteristics and wave structure of typhoon Rananim (2004)

    NASA Astrophysics Data System (ADS)

    Ming, Jie; Ni, Yunqi; Shen, Xinyong

    2009-05-01

    Typhoon Rananim (2004) was one of the severest typhoons landfalling the Chinese mainland from 1996 to 2004. It brought serious damage and induced prodigious economical loss. Using a new generation of mesoscale model, named the Weather Research and Forecasting (WRF) modeling system, with 1.667 km grid horizontal spacing on the finest nested mesh, Rananim was successfully simulated in terms of track, intensity, eye, eyewall, and spiral rainbands. We compared the structures of Rananim to those of hurricanes in previous studies and observations to assess the validity of simulation. The three-dimensional (3D) dynamic and thermal structures of eye and eyewall were studied based on the simulated results. The focus was investigation of the characteristics of the vortex Rossby waves in the inner-core region. We found that the Rossby vortex waves propagate azimuthally upwind against the azimuthal mean tangential flow around the eyewall, and their period was longer than that of an air parcel moving within the azimuthal mean tangential flow. They also propagated outward against the boundary layer inflow of the azimuthal mean vortex. Futhermore, we studied the connection between the spiral potential vorticity (PV) bands and spiral rainbands, and found that the vortex Rossby waves played an important role in the formation process of spiral rainbands.

  1. Measurement of human pilot dynamic characteristics in flight simulation

    NASA Technical Reports Server (NTRS)

    Reedy, James T.

    1987-01-01

    Fast Fourier Transform (FFT) and Least Square Error (LSE) estimation techniques were applied to the problem of identifying pilot-vehicle dynamic characteristics in flight simulation. A brief investigation of the effects of noise, input bandwidth and system delay upon the FFT and LSE techniques was undertaken using synthetic data. Data from a piloted simulation conducted at NASA Ames Research Center was then analyzed. The simulation was performed in the NASA Ames Research Center Variable Stability CH-47B helicopter operating in fixed-basis simulator mode. The piloting task consisted of maintaining the simulated vehicle over a moving hover pad whose motion was described by a random-appearing sum of sinusoids. The two test subjects used a head-down, color cathode ray tube (CRT) display for guidance and control information. Test configurations differed in the number of axes being controlled by the pilot (longitudinal only versus longitudinal and lateral), and in the presence or absence of an important display indicator called an 'acceleration ball'. A number of different pilot-vehicle transfer functions were measured, and where appropriate, qualitatively compared with theoretical pilot- vehicle models. Some indirect evidence suggesting pursuit behavior on the part of the test subjects is discussed.

  2. Characterization of fracture reservoirs using static and dynamic data: From sonic and 3D seismic to permeability distribution

    SciTech Connect

    Parra, J.O.; Hackett, C.L.; Brown, R.L.; Collier, H.A.; Datta-Gupta, A.

    1998-10-01

    To characterize the Buena Vista Hills field, the authors have implemented methods of modeling, processing and interpretation. The modeling methods are based on deterministic and stochastic solutions. Deterministic solutions were developed in Phase 1 and applied in Phase 2 to simulate acoustic responses of laminated reservoirs. Specifically, the simulations were aimed at implementing processing techniques to correct P-wave and S-wave velocity logs for scattering effects caused by thin layering. The authors are also including a summary of the theory and the processing steps of this new method for predicting intrinsic dispersion and attenuation in Section 2. Since the objective for correcting velocity scattering effects is to predict intrinsic dispersion from velocity data, they are presenting an application to illustrate how to relate permeability anisotropy with intrinsic dispersion. Also, the theoretical solution for calculating full waveform dipole sonic that was developed in Phase 1 was applied to simulate dipole responses at different azimuthal source orientations. The results will be used to interpret the effects of anisotropy associated with the presence of vertical fractures at Buena Vista Hills. The results of the integration of core, well logs, and geology of Buena Vista Hills is also given in Section 2. The results of this integration will be considered as the input model for the inversion technique for processing production data. Section 3 summarizes accomplishments. In Section 4 the authors present a summary of the technology transfer and promotion efforts associated with this project. In the last section, they address the work to be done in the next six months and future work by applying the processing, modeling and inversion techniques developed in Phases 1 and 2 of this project.

  3. Identification of dynamic characteristics of flexible rotors as dynamic inverse problem

    NASA Technical Reports Server (NTRS)

    Roisman, W. P.; Vajingortin, L. D.

    1991-01-01

    The problem of dynamic and balancing of flexible rotors were considered, which were set and solved as the problem of the identification of flexible rotor systems, which is the same as the inverse problem of the oscillation theory dealing with the task of the identifying the outside influences and system parameters on the basis of the known laws of motion. This approach to the problem allows the disclosure the picture of disbalances throughout the rotor-under-test (which traditional methods of flexible rotor balancing, based on natural oscillations, could not provide), and identify dynamic characteristics of the system, which correspond to a selected mathematical model. Eventually, various methods of balancing were developed depending on the special features of the machines as to their design, technology, and operation specifications. Also, theoretical and practical methods are given for the flexible rotor balancing at far from critical rotation frequencies, which does not necessarily require the knowledge forms of oscillation, dissipation, and elasticity and inertia characteristics, and to use testing masses.

  4. Effect of random structure on permeability and heat transfer characteristics for flow in 2D porous medium based on MRT lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    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.

  5. Assessment of Blood-Brain Barrier Permeability by Dynamic Contrast-Enhanced MRI in Transient Middle Cerebral Artery Occlusion Model after Localized Brain Cooling in Rats

    PubMed Central

    Kim, Eun Soo; Kwon, Mi Jung; Lee, Phil Hye; Ju, Young-Su; Yoon, Dae Young; Kim, Hye Jeong; Lee, Kwan Seop

    2016-01-01

    Objective The purpose of this study was to evaluate the effects of localized brain cooling on blood-brain barrier (BBB) permeability following transient middle cerebral artery occlusion (tMCAO) in rats, by using dynamic contrast-enhanced (DCE)-MRI. Materials and Methods Thirty rats were divided into 3 groups of 10 rats each: control group, localized cold-saline (20℃) infusion group, and localized warm-saline (37℃) infusion group. The left middle cerebral artery (MCA) was occluded for 1 hour in anesthetized rats, followed by 3 hours of reperfusion. In the localized saline infusion group, 6 mL of cold or warm saline was infused through the hollow filament for 10 minutes after MCA occlusion. DCE-MRI investigations were performed after 3 hours and 24 hours of reperfusion. Pharmacokinetic parameters of the extended Tofts-Kety model were calculated for each DCE-MRI. In addition, rotarod testing was performed before tMCAO, and on days 1-9 after tMCAO. Myeloperoxidase (MPO) immunohisto-chemistry was performed to identify infiltrating neutrophils associated with the inflammatory response in the rat brain. Results Permeability parameters showed no statistical significance between cold and warm saline infusion groups after 3-hour reperfusion 0.09 ± 0.01 min-1 vs. 0.07 ± 0.02 min-1, p = 0.661 for Ktrans; 0.30 ± 0.05 min-1 vs. 0.37 ± 0.11 min-1, p = 0.394 for kep, respectively. Behavioral testing revealed no significant difference among the three groups. However, the percentage of MPO-positive cells in the cold-saline group was significantly lower than those in the control and warm-saline groups (p < 0.05). Conclusion Localized brain cooling (20℃) does not confer a benefit to inhibit the increase in BBB permeability that follows transient cerebral ischemia and reperfusion in an animal model, as compared with localized warm-saline (37℃) infusion group. PMID:27587960

  6. Impact of heterogeneous permeability distribution on the groundwater flow systems of a small sedimentary basin

    NASA Astrophysics Data System (ADS)

    Zech, Alraune; Zehner, Björn; Kolditz, Olaf; Attinger, Sabine

    2016-01-01

    Ground water flow systems of shallow sedimentary basins are studied in general by analyzing the fluid dynamics at the real world example of the Thuringian Basin. The impact of the permeability distribution and density differences on the flow velocity pattern, the salt concentration, and the temperature distribution is quantified by means of transient coupled simulations of fluid flow, heat, and mass transport processes. Simulations are performed with different permeabilities in the sedimentary layering and heterogeneous permeability distributions as well as with a non-constant fluid density. Three characteristic numbers are useful to describe the effects of permeability on the development of flow systems and subsurface transport: the relation of permeability between aquiclude and aquifer, the variance, and the correlation length of the log-normal permeability distribution. Density dependent flow due to temperature or concentration gradients is of minor importance for the distribution of the flow systems, but can lead to increased mixing dissolution of salt. Thermal convection is in general not present. The dominant driver of groundwater flow is the topography in combination with the permeability distribution. The results obtained for the Thuringian Basin give general insights into the dynamics of a small sedimentary basin due to the representative character of the basin structure as well as the transferability of the settings to other small sedimentary basins.

  7. Joint modeling of thermal creep and radiation damage interaction with gas permeability and release dynamics: The role of percolation

    NASA Astrophysics Data System (ADS)

    Ovaska, M.; Alava, M. J.

    2015-10-01

    Nuclear fuel material is an example of a sintered, porous ceramic material. We formulate a two-dimensional model which couples three physical mechanisms in the material: (scalar) damage accumulation by thermal creep and radiation effects, porosity changes due to the damage, and the time-dependent diffusion of (radiation-induced) gases in the pore system thus created. The most important effect in the dynamics arises from the process where the pore system is swept through the percolation transition. The main conclusions that can be drawn concern the fractional gas release and its dependence on the three effects present in the damage dynamics: creep, radiation-induced bubble formation, and recovery due to bubble closure. In the main, the model reproduces the experimentally observed quick gas release phenomenon qualitatively.

  8. Sediment characteristics and transportation dynamics of the Ganga River

    NASA Astrophysics Data System (ADS)

    Singh, Munendra; Singh, Indra Bir; Müller, German

    2007-04-01

    Understanding of river systems that have experienced various forcing mechanisms such as climate, tectonics, sea level fluctuations and their linkages is a major concern for fluvial scientists. The 2525-km-long Ganga River derives its fluvial flux from northern part of the Indian subcontinent and drops in the Ganga-Brahmaputra delta and the Bengal fan regions. This paper presents a study of the Ganga River sediments for their textural properties, grainsize characteristics, and transportation dynamics. A suite of recently deposited sediments (189 bedload samples and 27 suspended load samples) of the river and its tributaries was collected from 63 locations. Dry and wet sieve methods of grainsize analysis were performed and Folk and Ward's parameters were calculated. Transportation dynamics of the sediment load was assessed by means of channel hydrology, flow/sediment rating curves, bedform mechanics, grainsize images, and cumulative curves. Textural properties of the bedload sediments of the Ganga River tributaries originating from the Himalaya orogenic belt, the northern Indian craton and the Ganga alluvial plain regions are characterised by the predominance of fine to very fine sand, medium to fine sand, and very fine sand to clay, respectively. Downstream textural variations in the bedload and suspended load sediments of the Ganga River are, therefore, complex and are strongly influenced by lateral sediment inputs by the tributaries and channel slope. At the base of the Himalaya, a very sharp gravel-sand transition is present in which median grainsize of bedload sediments decreases from over - 0.16 Φ to 2.46 Φ within a distance of 35 km. Downstream decline in mean grainsize of bedload sediments in the upper Ganga River within the alluvial plain can be expressed by an exponential formula as: mean grainsize (in Φ) = 0.0024 × Distance (in kilometres from the Himalayan front) + 1.29. It is a result of selective transport phenomena rather than of abrasion, the

  9. Permeability of soils in Mississippi

    USGS Publications Warehouse

    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.

  10. An Analysis on Ice Storing CharacterIstics in Dynamic-type Ice Storage System using Supercooled Water

    NASA Astrophysics Data System (ADS)

    Aizawa, Naoki; Tanino, Masayuki; Kozawa, Yoshiyuki

    For an application of the Dynamic-type Ice Storage System to the District Cooling and Heating System, the effects of ice content (IPF) and mass flow rate of supplying ice-slurry on the ice storing characteristics in a tank were investigated by experiments and analyses. In the analytical model, we considered that the ice-rich layer would be ununiform by raising of IPF and the water permeability in the ice-rich layer increases. By raising of IPF and reducing of mass flow rate of supplying ice-slurry, ice-rich layer could not spread in a tank. The porosity of ice-rich layer was contracting to the value of 0.8-0.9 in the ice storing process. The stored ice quantity depends on distribution and porosity of ice-rich layer in a tank decreased to 10% by raising IPF from 2.5wt% to 10wt% and reducing mass flow rate as constant ice flow rate. The analytical results could express the experimental results about stored ice quantity. Our analytical model is considered to be applicable to prediction of the ice storing characteristics and to design of an ice storage tank.

  11. A set of measurement system for the dynamic laser scatter characteristics of target

    NASA Astrophysics Data System (ADS)

    Wei, Xiangquan; Huang, Jianming; Xiao, Yuzhi; Fan, Xiaoli

    2015-12-01

    It is an important measure to observe target by using laser sensor in the field of target detection. Exact and reliable dynamic laser scatter characteristics of observing target, can not only be used for the design and development of laser sensor as well as the research of algorithm for target capture, recognition and tracking, but also can offer reference bases for the test flow programming. A set of simulation, measurement system for the dynamic laser scatter characteristics of observing target is introduced in this paper. The simulation problem of dynamic laser scatter characteristics of observing target is solved, under the circumstance of laboratory with different azimuth angle and pitch angle of observation. The dynamic laser scatter characteristics of observing target can be obtained directly by such system, the test data can be used for the verification of the analyzing model for the laser scatter characteristics of observing target, and can also offer basis for the development of laser detecting sensor.

  12. Dynamic Characteristics of Penor Peat Using MASW Method

    NASA Astrophysics Data System (ADS)

    Zainorabidin, A.; Said, M. J. M.

    2016-07-01

    The dynamic behaviour of soil affected the mechanical properties of soil such as shear wave velocity, shear modulus, damping ratio and poisson's ratio [1] which is becoming important aspect need to be considered for structures influences by dynamic movement. This study is to determine the dynamic behaviour of Penor peat such as shear wave velocity using MASW and estimation its shear modulus. Peat soils are very problematic soils since it's have high compressibility, low shear strength, high moisture content and low bearing capacity which is very not suitable materials to construct any foundation structures. Shear wave velocity ranges between 32.94 - 95.89 m/s and shear modulus are ranging between 0.93 - 8.01 MPa. The differences of both dynamic properties are due to the changes of peat density and affected by the fibre content, organic content, degree of degradation and moisture content.

  13. Polar cusp: optical and particle characteristics-dynamics

    SciTech Connect

    Sandholt, P.E.; Egeland, A.; Asheim, S.; Lybekk, B.; Hardy, D.A.

    1985-01-01

    Photometric observations from two stations on Svalbard, Norway, were used to map the location and dynamics of polar-cusp auroras. Coordinated observations of low-energy electron precipitation from satellite HILAT and optical observations from the ground are discussed. Cases are presented showing the dynamical behavior of cusp auroras and the local magnetic field related to changes in the interplanetary magnetic field (IMF) and irregularities in the solar wind plasma. Dynamical phenomena with different time scales are studied. South and northward expansions of the midday sector of the auroral oval are discussed in relation to IMF variations and geomagnetic substorm activity. Intensifications and rapid poleward motions of discrete auroral structures in the cusp region are shown to be associated with local Pi type magnetic pulsations, each event lasting a few minutes. These small scale dynamical phenomena are discussed in relation to different models of plasma penetration across the dayside magnetopause, from the magnetosheath to the polar cusp region of the magnetosphere.

  14. Membrane permeability during pressure ulcer formation: A computational model of dynamic competition between cytoskeletal damage and repair.

    PubMed

    Jagannathan, N Suhas; Tucker-Kellogg, Lisa

    2016-05-24

    Pressure ulcers are debilitating wounds that arise frequently in people who have lost mobility. Mechanical stress, oxidative stress and ischemia-reperfusion injury are potential sources of damage during pressure ulcer formation, but cross-talk between these sources has rarely been investigated. In vitro experiments with mechanically-induced cell damage previously demonstrated that non-lethal amounts of static cell deformation could induce myoblast membrane permeabilization. Permeabilization, in turn, has the potential to induce oxidative stress via leakage of calcium, myoglobin or alarmins. In this work, we constructed a hypothetical causal network of cellular-scale effects resulting from deformation and permeabilization, and we investigated the theoretical sensitivity of cell death toward various parameters and pathways of the model. Simulations showed that the survival/death outcome was particularly sensitive to the speed of membrane repair. The outcome was also sensitive to whether oxidative stress could decrease the speed of membrane repair. Finally, using the assumption that apoptosis and necrosis would have opposite effects on membrane leakage in dying cells, we showed that promoting apoptosis might under certain conditions have the paradoxical effect of decreasing, rather than increasing, total cell death. Our work illustrates that apoptosis may have hidden benefits at preventing spatial spread of death. More broadly, our work shows the importance of membrane repair dynamics and highlights the need for experiments to measure the effects of ischemia, apoptosis induction, and other co-occurring sources of cell stress toward the speed of membrane repair. PMID:26772800

  15. Determination of the effect of lipophilicity on the in vitro permeability and tissue reservoir characteristics of topically applied solutes in human skin layers.

    PubMed

    Cross, Sheree E; Magnusson, Beatrice M; Winckle, Gareth; Anissimov, Yuri; Roberts, Michael S

    2003-05-01

    In order to establish the relationship between solute lipophilicity and skin penetration (including flux and concentration behavior), we examined the in vitro penetration and membrane concentration of a series of homologous alcohols (C2-C10) applied topically in aqueous solutions to human epidermal, full-thickness, and dermal membranes. The partitioning/distribution of each alcohol between the donor solution, stratum corneum, viable epidermis, dermis, and receptor phase compartments was determined during the penetration process and separately to isolated samples of each tissue type. Maximum flux and permeability coefficients are compared for each membrane and estimates of alcohol diffusivity are made based on flux/concentration data and also the related tissue resistance (the reciprocal of permeability coefficient) for each membrane type. The permeability coefficient increased with increasing lipophilicity to alcohol C8 (octanol) with no further increase for C10 (decanol). Log vehicle:stratum corneum partition coefficients were related to logP, and the concentration of alcohols in each of the tissue layers appeared to increase with lipophilicity. No difference was measured in the diffusivity of smaller more polar alcohols in the three membranes; however, the larger more lipophilic solutes showed slower diffusivity values. The study showed that the dermis may be a much more lipophilic environment than originally believed and that distribution of smaller nonionized solutes into local tissues below a site of topical application may be estimated based on knowledge of their lipophilicity alone. PMID:12713577

  16. Dynamic Stall Characteristics of Drooped Leading Edge Airfoils

    NASA Technical Reports Server (NTRS)

    Sankar, Lakshmi N.; Sahin, Mehmet; Gopal, Naveen

    2000-01-01

    Helicopters in high-speed forward flight usually experience large regions of dynamic stall over the retreating side of the rotor disk. The rapid variations in the lift and pitching moments associated with the stall process can result in vibratory loads, and can cause fatigue and failure of pitch links. In some instances, the large time lag between the aerodynamic forces and the blade motion can trigger stall flutter. A number of techniques for the alleviation of dynamic stall have been proposed and studied by researchers. Passive and active control techniques have both been explored. Passive techniques include the use of high solidity rotors that reduce the lift coefficients of individual blades, leading edge slots and leading edge slats. Active control techniques include steady and unsteady blowing, and dynamically deformable leading edge (DDLE) airfoils. Considerable amount of experimental and numerical data has been collected on the effectiveness of these concepts. One concept that has not received as much attention is the drooped-leading edge airfoil idea. It has been observed in wind tunnel studies and flight tests that drooped leading edge airfoils can have a milder dynamic stall, with a significantly milder load hysteresis. Drooped leading edge airfoils may not, however, be suitable at other conditions, e.g. in hover, or in transonic flow. Work needs to be done on the analysis and design of drooped leading edge airfoils for efficient operation in a variety of flight regimes (hover, dynamic stall, and transonic flow). One concept that is worthy of investigation is the dynamically drooping airfoil, where the leading edge shape is changed roughly once-per-rev to mitigate the dynamic stall.

  17. Dynamic Characteristics Analysis of Analogue Networks Design Process

    NASA Astrophysics Data System (ADS)

    Zemliak, Alexander M.

    The process of designing analogue circuits is formulated as a controlled dynamic system. For analysis of such system's properties it is suggested to use the concept of Lyapunov's function for a dynamic system. Various forms of Lyapunov's function are suggested. Analyzing the behavior of Lyapunov's function and its first derivative allowed us to determine significant correlation between this function's properties and processor time used to design the circuit. Numerical results prove the possibility of forecasting the behavior of various designing strategies and processor time based on the properties of Lyapunov's function for the process of designing the circuit.

  18. Auditory virtual environment with dynamic room characteristics for music performances

    NASA Astrophysics Data System (ADS)

    Choi, Daniel Dhaham

    A room-adaptive system was designed to simulate an electro-acoustic space that changes room characteristics in real-time according to the content of sound. In this specific case, the focus of the sound components is on the different styles and genres of music. This system is composed of real-time music recognition algorithms that analyze the different elements of music, determine the desired room characteristics, and output the acoustical parameters via multi-channel room simulation mechanisms. The system modifies the acoustic properties of a space and enables it to "improvise" its acoustical parameters based on the sounds of the music performances.

  19. The dynamic adsorption characteristics of phenol by granular activated carbon.

    PubMed

    Namane, A; Hellal, A

    2006-09-01

    The objective of the present work is to determine the operating conditions of an activated carbon filter, based on the characteristics of breakthrough curves. For this we apply the technical developed by Mickaels for the ionic exchange and applied by Luchkis for the adsorption, and which is the mass transfer zone. To reach our goal, an evaluation of the operating conditions (height of the bed, flow and concentration of effluent) on the characteristics of the mass transfer zone was made and an explanation of the mechanism of adsorption was given. Thereafter a modeling of the experimental results was done. PMID:16621251

  20. EPA Permeable Surface Research

    EPA Science Inventory

    EPA recognizes permeable surfaces as an effective post-construction infiltration-based Best Management Practice to mitigate the adverse effects of stormwater runoff. The professional user community conceptually embraces permeable surfaces as a tool for making runoff more closely...

  1. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

    This paper presents an investigation on the effect of clay addition on water permeability and air permeability of concretes. Clay concrete mixes consisted of 0 to 40% clay content incorporated as cement replacement. Flow methods using triaxial cells and air permeameters were used for measuring the injected water and air flows under pressure. It was found that the higher the clay content in the mixture, the greater the permeability. At higher water-cement ratios (w/c), the paste matrix is less dense and easily allows water to ingress into concrete. But at high clay contents of 30 to 40% clay, the variation in permeability was significantly diminished among different concrete mixtures. It was confirmed that air permeability results were higher than the corresponding water permeability values when all permeability coefficients were converted to intrinsic permeability values.

  2. Dynamic characteristics of mixtures of plutonium, Nevada tuff, and water

    SciTech Connect

    Myers, W.; Rojas, S.; Kimpland, R.H.; Jaegers, P.J.; Sanchez, R.G.; Hayes, D.; Paternoster, R.; Anderson, R.; Stratton, W.

    1996-02-01

    One of the technical options being considered for long term disposition of weapons grade plutonium is geologic storage at Yucca Mountain. Multikilogram quantities of plutonium are to be vitrified, placed within a heavy steel container, and buried in the material know as Nevada tuff. It has been postulated that after ten thousand years, geologic and chemical processes would have disintegrated the steel container and created the possibility for plutonium to form mixtures with Nevada tuff and water that could lead to a nuclear explosion in the range of kilotons. A survey and description of critical homogeneous mixtures of plutonium, silicon dioxide, Nevada tuff, and water which also identified the mixture regimes where autocatalytic dynamic behavior is possible was completed. This study is a follow up of this survey and the major objective is to examine the dynamic behavior of the worst case critical and supercritical configurations of plutonium, water and Nevada tuff.

  3. Nike Black Brant V high altitude dynamic instability characteristics

    NASA Technical Reports Server (NTRS)

    Montag, W. H.; Walker, L. L., Jr.

    1979-01-01

    Flight experience on the Nike Black Brant V has demonstrated the existence of plume induced flow separation over the fins and aft body of the Black Brant V motor. Modelling of the forces associated with this phenomenon as well as analysis of the resultant vehicle coning motion and its effect on the velocity vector heading are presented. A summary of Nike Black Brant V flight experience with high altitude dynamic instability is included.

  4. Some Recent Laboratory Measurements of Fault Zone Permeability

    NASA Astrophysics Data System (ADS)

    Morrow, C. A.; Lockner, D. A.

    2005-12-01

    The permeability of fault zone material is key to understanding fluid circulation and the role of pore fluids in earthquake generation and rupture dynamics. Permeability results of core samples from several scientific drillholes are presented, including new results from the SAFOD drillsite in California and the Chelungpu Fault in Taiwan. Permeability values at simulated in situ pressures range from 10-18 to 10-23 m2, a broad range reflecting differences in rock type, proximity to the fault (i.e., fault core, damage zone or country rock), and degree of interseismic healing and sealing. In addition to these natural characteristics, stress-relief and thermal cracking damage resulting from core retrieval will tend to increase the permeability of some of the deepest crystalline rock samples, although testing under in situ conditions can reduce these errors. Recently active fault rocks, with an interconnected network of fractures, tend toward the higher end of the permeability range, whereas fault rocks that have had time to heal through hydrothermal processes tend to have lower permeabilities. In addition, the permeability of borehole-derived core samples was found to be more sensitive to applied pressure than equivalent rocks obtained from surface outcrops because of weathering and other processes. Thus, permeability values of surface samples can not be adequately extrapolated to depth, highlighting the importance of deep drilling studies in determining in situ transport properties. Permeability studies also reveal the storage capacity of the fault rocks, an important parameter in the determination of excess fluid pressure potential. Storage capacity was found to be 10-10 to 10-11/Pa in the Chelungpu Fault cores. Typical down-hole permeability measurements are generally 1-2 orders of magnitude higher than laboratory-derived values because they sample joints and fractures in the damage zone that are larger in scale than the core samples. Consequently, most fluid flow at

  5. Dynamic Monitoring Reveals Motor Task Characteristics in Prehistoric Technical Gestures

    PubMed Central

    Pfleging, Johannes; Stücheli, Marius; Iovita, Radu; Buchli, Jonas

    2015-01-01

    Reconstructing ancient technical gestures associated with simple tool actions is crucial for understanding the co-evolution of the human forelimb and its associated control-related cognitive functions on the one hand, and of the human technological arsenal on the other hand. Although the topic of gesture is an old one in Paleolithic archaeology and in anthropology in general, very few studies have taken advantage of the new technologies from the science of kinematics in order to improve replicative experimental protocols. Recent work in paleoanthropology has shown the potential of monitored replicative experiments to reconstruct tool-use-related motions through the study of fossil bones, but so far comparatively little has been done to examine the dynamics of the tool itself. In this paper, we demonstrate that we can statistically differentiate gestures used in a simple scraping task through dynamic monitoring. Dynamics combines kinematics (position, orientation, and speed) with contact mechanical parameters (force and torque). Taken together, these parameters are important because they play a role in the formation of a visible archaeological signature, use-wear. We present our new affordable, yet precise methodology for measuring the dynamics of a simple hide-scraping task, carried out using a pull-to (PT) and a push-away (PA) gesture. A strain gage force sensor combined with a visual tag tracking system records force, torque, as well as position and orientation of hafted flint stone tools. The set-up allows switching between two tool configurations, one with distal and the other one with perpendicular hafting of the scrapers, to allow for ethnographically plausible reconstructions. The data show statistically significant differences between the two gestures: scraping away from the body (PA) generates higher shearing forces, but requires greater hand torque. Moreover, most benchmarks associated with the PA gesture are more highly variable than in the PT gesture

  6. Dynamic Monitoring Reveals Motor Task Characteristics in Prehistoric Technical Gestures.

    PubMed

    Pfleging, Johannes; Stücheli, Marius; Iovita, Radu; Buchli, Jonas

    2015-01-01

    Reconstructing ancient technical gestures associated with simple tool actions is crucial for understanding the co-evolution of the human forelimb and its associated control-related cognitive functions on the one hand, and of the human technological arsenal on the other hand. Although the topic of gesture is an old one in Paleolithic archaeology and in anthropology in general, very few studies have taken advantage of the new technologies from the science of kinematics in order to improve replicative experimental protocols. Recent work in paleoanthropology has shown the potential of monitored replicative experiments to reconstruct tool-use-related motions through the study of fossil bones, but so far comparatively little has been done to examine the dynamics of the tool itself. In this paper, we demonstrate that we can statistically differentiate gestures used in a simple scraping task through dynamic monitoring. Dynamics combines kinematics (position, orientation, and speed) with contact mechanical parameters (force and torque). Taken together, these parameters are important because they play a role in the formation of a visible archaeological signature, use-wear. We present our new affordable, yet precise methodology for measuring the dynamics of a simple hide-scraping task, carried out using a pull-to (PT) and a push-away (PA) gesture. A strain gage force sensor combined with a visual tag tracking system records force, torque, as well as position and orientation of hafted flint stone tools. The set-up allows switching between two tool configurations, one with distal and the other one with perpendicular hafting of the scrapers, to allow for ethnographically plausible reconstructions. The data show statistically significant differences between the two gestures: scraping away from the body (PA) generates higher shearing forces, but requires greater hand torque. Moreover, most benchmarks associated with the PA gesture are more highly variable than in the PT gesture

  7. Climate Creators. Dynamic Characteristics of People Who Create Positive Organizational Climate.

    ERIC Educational Resources Information Center

    Bedley, Gene

    This book contains practical information on creating a positive work climate within an organization. Twenty separate characteristics of successful "climate creators" are discussed. Information is also included on: (1) climate; (2) climate creators; (3) dynamic characteristics of climate creators; (4) the challenge of creating a positive climate;…

  8. Dynamic characteristics of peripheral jet ACV. III - Coupling motion of heaving and pitching

    NASA Astrophysics Data System (ADS)

    Mori, T.; Maeda, H.

    The paper presents the dynamic characteristics of peripheral jet ACV (Air Cushion Vehicle) which has two degrees of freedom, i.e., heaving and pitching motion. The experiments are carried out for an ACV model, noting that the experimental results agree considerably with the analytical values. Furthermore, the response characteristics of ACV induced by the ground board oscillations of various modes are also investigated.

  9. Prediction and measurement of human pilot dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Hess, Ronald A.; Reedy, James T.

    1988-01-01

    An analytical and experimental study of human pilot control strategies in a manned rotorcraft simulation is described. The task simulated involves a low-speed, constant-altitude maneuvering task in which a head-down display is utilized to allow the pilot to track a moving hover point. The efficacy of the display law driving an 'acceleration symbol' is determined and the manner in which the prediction and measurement of pilot/vehicle dynamics can be made part of man/machine system evaluations is demonstrated.

  10. Dynamic characteristics of an assembly of prop-fan blades

    NASA Technical Reports Server (NTRS)

    Srinivasan, A. V.; Kielb, R. E.; Lawrence, C.

    1986-01-01

    In contrast to conventional propellers, propfan blades are thin and highly swept-back, thereby giving rise to large bending and twisting deformations and complex vibratory characteristics. Aerodynamic performance depends on the extent of steady state deformation, and the aeroelastic response depends on the vibratory frequency and mode shape. Attention is presently given to the principal results of structural analyses for a five-bladed propfan assembly; these results are compared with test data. The results encompass both steady deformations and vibratory frequencies and mode shapes in a vacuum centrifugal environment.

  11. Chemistry in interstellar space. [environment characteristics influencing reaction dynamics

    NASA Technical Reports Server (NTRS)

    Donn, B.

    1973-01-01

    The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.

  12. Dynamic tuning of lattice plasmon lasers with long coherence characteristics

    NASA Astrophysics Data System (ADS)

    Hoang, Thang; Yang, Ankun; Schatz, George; Odom, Teri; Mikkelsen, Maiken

    Here, we experimentally demonstrate dynamic tuning of an optically-pumped lattice plasmon laser based on arrays of gold nanoparticles and liquid gain materials [A. Yang, T.B. Hoang et al., Nature Communications 6, 6939 (2015)]. The structure consists of an array of 120 nm diameter gold disks with a height of 50 nm and 600 nm spacing. A liquid gain material composed of IR-140 dye molecules dissolved in a variety of organic solvents is placed on top of the disks and held in place by a thin glass coverslip. At a lasing wavelength of 860 nm, time-resolved measurements show a dramatic reduction of the decay time from 1 ns to less than 20 ps when the optical excitation power density increases from below to above the lasing threshold, indicating the transition from spontaneous to stimulated emission. By changing the dielectric environment surrounding the gold disks in real time, the lasing wavelength can be dynamically tuned over a 55 nm range. Finally, we will discuss recent experiments where we probe both the temporal and spatial coherence properties of the lattice plasmon laser. This advance of tunable plasmon lasers offer prospects to enhance and detect weak physical and chemical processes on the nanoscale in real time.

  13. Dynamic characteristics of a magnetorheological pin joint for civil structures

    NASA Astrophysics Data System (ADS)

    Li, Yancheng; Li, Jianchun

    2014-03-01

    Magnetorheological (MR) pin joint is a novel device in which its joint moment resistance can be controlled in real-time by altering the applied magnetic field. The smart pin joint is intended to be used as a controllable connector between the columns and beams of a civil structure to instantaneously shift the structural natural frequencies in order to avoid resonance and therefore to reduce unwanted vibrations and hence prevent structural damage. As an intrinsically nonlinear device, modelling of this MR fluid based device is a challenging task and makes the design of a suitable control algorithm a cumbersome situation. Aimed at its application in civil structure, the main purpose of this paper is to test and characterise the hysteretic behaviour of MR pin joint. A test scheme is designed to obtain the dynamic performance of MR pin joint in the dominant earthquake frequency range. Some unique phenomena different from those of MR damper are observed through the experimental testing. A computationally-efficient model is proposed by introducing a hyperbolic element to accurately reproduce its dynamic behaviour and to further facilitate the design of a suitable control algorithm. Comprehensive investigations on the model accuracy and dependences of the proposed model on loading condition (frequency and amplitude) and input current level are reported in the last section of this paper.

  14. Dynamic characteristics of vibration isolation platforms considering the joints of the struts

    NASA Astrophysics Data System (ADS)

    Zhang, Jingrui; Guo, Zixi; Zhang, Yao

    2016-09-01

    This paper discusses the dynamic characteristics of the impacts and corresponding frictions generated by the clearances of joints of vibration isolation platforms for control moment gyroscopes (CMGs) on spacecraft. A contact force model is applied using a nonlinear contact force model, and the frictions in the joints are considered in the dynamic analysis. First, the dynamic characteristics of a single isolation strut with spherical joints were studied, and joints with different initial clearance sizes were separately analyzed. Then, dynamic models of the vibration isolation platform for a CMG cluster with both perfect joints and joints with clearances were established. During the numeral simulation, joints with different elastic moduli were used to study the nonlinear characteristics. Finally, the distributions of the collision points, which can serve as a reference for the reliability and lifetime of a platform, were given.

  15. Impact of heterogeneous permeability distribution and salt transport on the groundwater flow of the Thuringian sedimentary basin

    NASA Astrophysics Data System (ADS)

    Zech, Alraune; Zehner, Björn; Kolditz, Olaf; Attinger, Sabine

    2016-04-01

    Ground water flow systems of the Thuringian Basin are studied by analyzing the fluid dynamics at this real world example of a shallow sedimentary basin. The impact of the permeability distribution and density differences on the flow velocity pattern, the salt concentration, and the temperature distribution is quantified by means of transient coupled simulations of fluid flow, heat, and mass transport processes. Simulations are performed with different permeabilities in the sedimentary layering and heterogeneous permeability distributions as well as with a non-constant fluid density. Three characteristic numbers are useful to describe the effects of permeability on the development of flow systems and subsurface transport: the relation of permeability between aquiclude and aquifer, the variance, and the correlation length of the log-normal permeability distribution. Density dependent flow due to concentration gradients is of minor importance for the distribution of the flow systems, but can lead to increased mixing dissolution of salt. Thermal convection is in general not present. The dominant driver of groundwater flow is the topography in combination with the permeability distribution. The results obtained for the Thuringian Basin give general insights into the dynamics of a small sedimentary basin due to the representative character of the basin structure as well as the transferability of the settings to other small sedimentary basins.

  16. Effect of drive mechanisms on dynamic characteristics of spacecraft tracking-drive flexible systems

    NASA Astrophysics Data System (ADS)

    Zhu, Shi-yao; Lei, Yong-jun; Wu, Xin-feng; Zhang, Da-peng

    2015-05-01

    Spacecraft tracking-drive flexible systems (STFS) consist of drive mechanisms and flexible structures, including solar array and a variety of large-scale antennas. The electromechanical interaction inside drive mechanisms makes it quite complicated to directly analyze the dynamic characteristics of an STFS. In this paper, an indirect dynamic characteristic analysis method for operating-state STFS is presented. The proposed method utilizes the structure dynamics approximation of drive mechanisms that converts the electromechanical model of an STFS into a structure dynamic model with elastic boundary conditions. The structure dynamics approximation and the dynamic characteristic analysis method are validated by experimental and analytical results, respectively. The analysis results indicate that the gear transmission ratio and viscous friction coefficient are the primary factors in approximating boundary stiffness and damping. Dynamic characteristics of an STFS with a large gear transmission ratio are close to that of a flexible structure with a cantilever boundary. Otherwise, torsion-mode natural frequencies of the STFS become smaller and corresponding modal damping ratios become larger, as a result of the local stiffness and damping features of drive mechanisms.

  17. Dynamic characteristics of peripheral jet ACV. I - Heaving motion

    NASA Astrophysics Data System (ADS)

    Mori, T.; Maeda, H.

    The theory of the dynamics of peripheral jet ACV is presented. The flow patterns under the bottom of the ACV are classified into two types, i.e. underfed and overfed regimes. The mathematical models associated with such regimes are presented and the equations of those models are derived. The forced heaving oscillation of a two-dimensional ACV model is investigated experimentally and variations of cushion pressure and lift force are measured and compared with the results obtained by the numerical calculation. The coincidence of these two results seems to be reasonable. The heaving motion of ACV which is induced by the simple harmonic oscillation of the ground board is also analyzed numerically.

  18. Subsonic and Transonic Dynamic Stability Characteristics of the X-33

    NASA Technical Reports Server (NTRS)

    Tomek, D.; Boyden, R.

    2000-01-01

    Dynamic stability testing was conducted on a 2.5% scale model of the X-33 technology demonstrator sub-orbital flight-test vehicle. This testing was conducted at the NASA Langley Research Center (LaRC) l6-Foot Transonic Wind Tunnel with the LaRC High-speed Dynamic Stability system. Forced oscillation data were acquired for various configurations over a Mach number range of 0.3 to 1.15 measuring pitch, roll and yaw damping, as well as the normal force due to pitch rate and the cross derivatives. The test angle of attack range was from -2 to 24 degrees, except for those cases where load constraints limited the higher angles of attack at the higher Mach numbers. A variety of model configurations with and without control surfaces were employed, including a body alone configuration. Stable pitch damping is exhibited for the baseline configuration throughout the angle of attack range for Mach numbers 0.3, 0.8, and 1.15. Stable pitch damping is present for Mach numbers 0.9 and 0.6 with the exception of angles 2 and 16 degrees, respectively. Constant and stable roll damping were present for the baseline configuration over the range of Mach numbers up to an angle of attack of 16 degrees. The yaw damping for the baseline is somewhat stable and constant for the angle of attack range from -2 to 8 degrees, with the exception of Mach numbers 0.6 and 0.8. Yaw damping becomes highly unstable for all Mach numbers at angles of attack greater than 8 degrees.

  19. Kinematic/Dynamic Characteristics for Visual and Kinesthetic Virtual Environments

    NASA Technical Reports Server (NTRS)

    Bortolussi, Michael R. (Compiler); Adelstein, B. D.; Gold, Miriam

    1996-01-01

    Work was carried out on two topics of principal importance to current progress in virtual environment research at NASA Ames and elsewhere. The first topic was directed at maximizing the temporal dynamic response of visually presented Virtual Environments (VEs) through reorganization and optimization of system hardware and software. The final results of this portion of the work was a VE system in the Advanced Display and Spatial Perception Laboratory at NASA Ames capable of updating at 60 Hz (the maximum hardware refresh rate) with latencies approaching 30 msec. In the course of achieving this system performance, specialized hardware and software tools for measurement of VE latency and analytic models correlating update rate and latency for different system configurations were developed. The second area of activity was the preliminary development and analysis of a novel kinematic architecture for three Degree Of Freedom (DOF) haptic interfaces--devices that provide force feedback for manipulative interaction with virtual and remote environments. An invention disclosure was filed on this work and a patent application is being pursued by NASA Ames. Activities in these two areas are expanded upon below.

  20. The dynamics of parabolic flight: flight characteristics and passenger percepts.

    PubMed

    Karmali, Faisal; Shelhamer, Mark

    2008-09-01

    Flying a parabolic trajectory in an aircraft is one of the few ways to create freefall on Earth, which is important for astronaut training and scientific research. Here we review the physics underlying parabolic flight, explain the resulting flight dynamics, and describe several counterintuitive findings, which we corroborate using experimental data. Typically, the aircraft flies parabolic arcs that produce approximately 25 seconds of freefall (0 g) followed by 40 seconds of enhanced force (1.8 g), repeated 30-60 times. Although passengers perceive gravity to be zero, in actuality acceleration, and not gravity, has changed, and thus we caution against the terms "microgravity" and "zero gravity. " Despite the aircraft trajectory including large (45°) pitch-up and pitch-down attitudes, the occupants experience a net force perpendicular to the floor of the aircraft. This is because the aircraft generates appropriate lift and thrust to produce the desired vertical and longitudinal accelerations, respectively, although we measured moderate (0.2 g) aft-ward accelerations during certain parts of these trajectories. Aircraft pitch rotation (average 3°/s) is barely detectable by the vestibular system, but could influence some physics experiments. Investigators should consider such details in the planning, analysis, and interpretation of parabolic-flight experiments. PMID:19727328

  1. The dynamics of parabolic flight: Flight characteristics and passenger percepts

    NASA Astrophysics Data System (ADS)

    Karmali, Faisal; Shelhamer, Mark

    2008-09-01

    Flying a parabolic trajectory in an aircraft is one of the few ways to create freefall on Earth, which is important for astronaut training and scientific research. Here we review the physics underlying parabolic flight, explain the resulting flight dynamics, and describe several counterintuitive findings, which we corroborate using experimental data. Typically, the aircraft flies parabolic arcs that produce approximately 25 s of freefall (0 g) followed by 40 s of enhanced force (1.8 g), repeated 30-60 times. Although passengers perceive gravity to be zero, in actuality acceleration, and not gravity, has changed, and thus we caution against the terms "microgravity" and "zero gravity." Despite the aircraft trajectory including large (45°) pitch-up and pitch-down attitudes, the occupants experience a net force perpendicular to the floor of the aircraft. This is because the aircraft generates appropriate lift and thrust to produce the desired vertical and longitudinal accelerations, respectively, although we measured moderate (0.2 g) aft-ward accelerations during certain parts of these trajectories. Aircraft pitch rotation (average 3°/s) is barely detectable by the vestibular system, but could influence some physics experiments. Investigators should consider such details in the planning, analysis, and interpretation of parabolic-flight experiments.

  2. The dynamics of parabolic flight: flight characteristics and passenger percepts

    PubMed Central

    Karmali, Faisal; Shelhamer, Mark

    2008-01-01

    Flying a parabolic trajectory in an aircraft is one of the few ways to create freefall on Earth, which is important for astronaut training and scientific research. Here we review the physics underlying parabolic flight, explain the resulting flight dynamics, and describe several counterintuitive findings, which we corroborate using experimental data. Typically, the aircraft flies parabolic arcs that produce approximately 25 seconds of freefall (0 g) followed by 40 seconds of enhanced force (1.8 g), repeated 30–60 times. Although passengers perceive gravity to be zero, in actuality acceleration, and not gravity, has changed, and thus we caution against the terms "microgravity" and "zero gravity. " Despite the aircraft trajectory including large (45°) pitch-up and pitch-down attitudes, the occupants experience a net force perpendicular to the floor of the aircraft. This is because the aircraft generates appropriate lift and thrust to produce the desired vertical and longitudinal accelerations, respectively, although we measured moderate (0.2 g) aft-ward accelerations during certain parts of these trajectories. Aircraft pitch rotation (average 3°/s) is barely detectable by the vestibular system, but could influence some physics experiments. Investigators should consider such details in the planning, analysis, and interpretation of parabolic-flight experiments. PMID:19727328

  3. An experimental study of relative permeability hysteresis, capillary trapping characteristics, and capillary pressure of CO2/brine systems at reservoir conditions

    NASA Astrophysics Data System (ADS)

    Austin Suthanthiraraj, Pearlson Prashanth

    We present the results of an extensive experimental study on the effects of hysteresis on permanent capillary trapping and relative permeability of CO2/brine and supercritical (sc)CO2+SO2/brine systems. We performed numerous unsteady- and steady-state drainage and imbibition full-recirculation flow experiments in three different sandstone rock samples, i.e., low and high-permeability Berea, Nugget sandstones, and Madison limestone carbonate rock sample. A state-of-the-art reservoir conditions core-flooding system was used to perform the tests. The core-flooding apparatus included a medical CT scanner to measure in-situ saturations. The scanner was rotated to the horizontal orientation allowing flow tests through vertically-placed core samples with about 3.8 cm diameter and 15 cm length. Both scCO2 /brine and gaseous CO2 (gCO2)/brine fluid systems were studied. The gaseous and supercritical CO2/brine experiments were carried out at 3.46 and 11 MPa back pressures and 20 and 55°C temperatures, respectively. Under the above-mentioned conditions, the gCO2 and scCO2 have 0.081 and 0.393 gr/cm3 densities, respectively. During unsteady-state tests, the samples were first saturated with brine and then flooded with CO2 (drainage) at different maximum flow rates. The drainage process was then followed by a low flow rate (0.375 cm 3/min) imbibition until residual CO2 saturation was achieved. Wide flow rate ranges of 0.25 to 20 cm3/min for scCO2 and 0.125 to 120 cm3min for gCO2 were used to investigate the variation of initial brine saturation (Swi) with maximum CO2 flow rate and variation of trapped CO2 saturation (SCO2r) with Swi. For a given Swi, the trapped scCO2 saturation was less than that of gCO2 in the same sample. This was attributed to brine being less wetting in the presence of scCO2 than in the presence of gCO 2. During the steady-state experiments, after providing of fully-brine saturated core, scCO2 was injected along with brine to find the drainage curve and as

  4. Phosphorus sorbing materials: sorption dynamics and physicochemical characteristics.

    PubMed

    Leader, J W; Dunne, E J; Reddy, K R

    2008-01-01

    The effectiveness of various management practices to reduce phosphorus (P) loss from soil to water can potentially be improved by using by-product materials that have the capacity to sorb phosphorus. This study evaluated the P sorption and desorption potential, and the physicochemical characteristics of various phosphorus sorbing materials. Twelve materials were selected and P sorption potentials ranged between 66 and 990 mg kg(-1). Iron, and calcium drinking water treatment residuals (DWTRs), a magnesium fertilizer by-product, aluminum, and humate materials all removed substantial amounts of P from solution and desorbed little. Humate had the highest maximum P sorption capacity (S(max)). Materials which had a low equilibrium P concentration (EPC(0)) and a high S(max) included aluminum and humate by-products. In a kinetic study, the Fe-DWTR, Ca-DWTR, aluminum, and magnesium by-product materials all removed P (to relatively low levels) from solution within 4 h. Phosphorus fractionation suggests that most materials contained little or no P that was readily available to water. Sand materials contained the greatest P fraction associated with fulvic and humic acids. In general, materials (not Ca-DWTR) and magnesium by-product were composed of sand-sized particles. There were no relationships between particle size distributions and P sorption in materials other than sands. The Ca- and Fe-DWTR, and magnesium by-product also contained plant nutrients and thus, may be desirable as soil amendments after being used to sorb P. Further, using Ca-DWTRs and Fe-DWTRs as soil amendments may also increase soil cation exchange and water holding capacity. PMID:18178890

  5. Dismissing Attachment Characteristics Dynamically Modulate Brain Networks Subserving Social Aversion

    PubMed Central

    Krause, Anna Linda; Borchardt, Viola; Li, Meng; van Tol, Marie-José; Demenescu, Liliana Ramona; Strauss, Bernhard; Kirchmann, Helmut; Buchheim, Anna; Metzger, Coraline D.; Nolte, Tobias; Walter, Martin

    2016-01-01

    our observation of direct prediction of neuronal responses by individual attachment and trauma characteristics and reversely prediction of subjective experience by intrinsic functional connections. We consider these findings of activation of within-network and between-network connectivity modulated by inter-individual differences as substantial for the understanding of interpersonal processes, particularly in clinical settings. PMID:27014016

  6. Study on dynamic characteristics' change of hippocampal neuron reduced models caused by the Alzheimer's disease.

    PubMed

    Peng, Yueping; Wang, Jue; Zheng, Chongxun

    2016-01-01

    In the paper, based on the electrophysiological experimental data, the Hippocampal neuron reduced model under the pathology condition of Alzheimer's disease (AD) has been built by modifying parameters' values. The reduced neuron model's dynamic characteristics under effect of AD are comparatively studied. Under direct current stimulation, compared with the normal neuron model, the AD neuron model's dynamic characteristics have obviously been changed. The neuron model under the AD condition undergoes supercritical Andronov-Hopf bifurcation from the rest state to the continuous discharge state. It is different from the neuron model under the normal condition, which undergoes saddle-node bifurcation. So, the neuron model changes into a resonator with monostable state from an integrator with bistable state under AD's action. The research reveals the neuron model's dynamic characteristics' changing under effect of AD, and provides some theoretic basis for AD research by neurodynamics theory. PMID:26998957

  7. Proceedings of Workshop XVI; The dynamic characteristics of faulting inferred from recordings of strong ground motion

    USGS Publications Warehouse

    1982-01-01

    The strong ground motions radiated by earthquake faulting are controlled by the dynamic characteristics of the faulting process. Although this assertion seems self-evident, seismologists have only recently begun to derive and test quantitative relations between common measures of strong ground motion and the dynamic characteristics of faulting. Interest in this problem has increased dramatically in past several years, however, resulting in a number of important advances. The research presented in this workshop is a significant part of this scientific development. Watching this development occur through the work of many scientists is exciting; to be able to gather a number of these scientists together in one workshop is a remarkable opportunity.

  8. Permeability and relative permeability in rocks

    SciTech Connect

    Blair, S.C.; Berryman, J.G.

    1990-10-01

    Important features of the topology of the pore space of rocks can be usefully quantified by analyzing digitized images of rock cross sections. One approach computes statistical correlation functions using modern image processing techniques. These correlation functions contain information about porosity, specific surface area, tortuosity, formation factor, and elastic constants, as well as the fluid permeability and relative permeability. The physical basis of this approach is discussed and examples of the results for various sandstones are presented. The analysis shows that Kozeny-Carman relations and Archie's empirical laws must be modified to account for finite percolation thresholds in order to avoid unphysical behavior in the calculated relative permeabilities. 33 refs., 4 figs., 1 tab.

  9. Numerical simulation of dynamic processes in biomechanics using the grid-characteristic method

    NASA Astrophysics Data System (ADS)

    Beklemysheva, K. A.; Vasyukov, A. V.; Petrov, I. B.

    2015-08-01

    Results of the numerical simulation of mechanical processes occurring in biological tissues under dynamic actions are presented. The grid-characteristic method on unstructured grids is used to solve the system of equations of mechanics of deformable solids; this method takes into account the characteristic properties of the constitutive system of partial differential equations and produces adequate algorithms on interfaces between media and on the boundaries of integration domains.

  10. A Dynamic Photovoltaic Model Incorporating Capacitive and Reverse-Bias Characteristics

    SciTech Connect

    Kim, KA; Xu, CY; Jin, L; Krein, PT

    2013-10-01

    Photovoltaics (PVs) are typically modeled only for their forward-biased dc characteristics, as in the commonly used single-diode model. While this approach accurately models the I-V curve under steady forward bias, it lacks dynamic and reverse-bias characteristics. The dynamic characteristics, primarily parallel capacitance and series inductance, affect operation when a PV cell or string interacts with switching converters or experiences sudden transients. Reverse-bias characteristics are often ignored because PV devices are not intended to operate in the reverse-biased region. However, when partial shading occurs on a string of PVs, the shaded cell can become reverse biased and develop into a hot spot that permanently degrades the cell. To fully examine PV behavior under hot spots and various other faults, reverse-bias characteristics must also be modeled. This study develops a comprehensive mathematical PV model based on circuit components that accounts for forward bias, reverse bias, and dynamic characteristics. Using a series of three experimental tests on an unilluminated PV cell, all required model parameters are determined. The model is implemented in MATLAB Simulink and accurately models the measured data.

  11. Permeability of Dentine

    PubMed Central

    Ghazali, Farid Bin Che

    2003-01-01

    This is an update on the present integrated knowledge regarding dentine permeability that assumed a role in dentine sensitivity and contribute clinically to the effective bonding properties of restorative dental materials. This paper will attempt to refer to in vivo and in vitro studies of dentine permeability and the various interrelated factors governing it. PMID:23365497

  12. Abnormal blood–brain barrier permeability in normal appearing white matter in multiple sclerosis investigated by MRI☆☆☆

    PubMed Central

    Cramer, S.P.; Simonsen, H.; Frederiksen, J.L.; Rostrup, E.; Larsson, H.B.W.

    2013-01-01

    Objectives To investigate whether blood–brain barrier (BBB) permeability is disrupted in normal appearing white matter in MS patients, when compared to healthy controls and whether it is correlated with MS clinical characteristics. Methods Dynamic contrast-enhanced MRI was used to measure BBB permeability in 27 patients with MS and compared to 24 matched healthy controls. Results Permeability measured as Ktrans was significantly higher in periventricular normal appearing white matter (NAWM) and thalamic gray matter in MS patients when compared to healthy controls, with periventricular NAWM showing the most pronounced difference. Recent relapse coincided with significantly higher permeability in periventricular NAWM, thalamic gray matter, and MS lesions. Immunomodulatory treatment and recent relapse were significant predictors of permeability in MS lesions and periventricular NAWM. Our results suggest that after an MS relapse permeability gradually decreases, possibly an effect of immunomodulatory treatment. Conclusions Our results emphasize the importance of BBB pathology in MS, which we find to be most prominent in the periventricular NAWM, an area prone to development of MS lesions. Both the facts that recent relapse appears to cause widespread BBB disruption and that immunomodulatory treatment seems to attenuate this effect indicate that BBB permeability is intricately linked to the presence of MS relapse activity. This may reveal further insights into the pathophysiology of MS. PMID:24371801

  13. Permeable membrane experiment

    NASA Technical Reports Server (NTRS)

    Slavin, Thomas J.; Cao, Tuan Q.; Kliss, Mark H.

    1993-01-01

    The purpose of the Permeable Membrane Experiment is to gather flight data on three areas of membrane performance that are influenced by the presence of gravity. These areas are: (1) Liquid/gas phase separation, (2) gas bubble interference with diffusion through porous membranes and (3) wetting characteristics of hydrophilic membrane surfaces. These data are important in understaning the behavior of membrane/liquid/gas interfaces where surface tension forces predominate. The data will be compared with 1-g data already obtained and with predicted micrograviity behavior. The data will be used to develop designs for phase separation and plant nutrient delivery systems and will be available to the life support community for use in developing technologies which employ membranes. A conceptual design has been developed to conduct three membrane experiments, in sequence, aboard a single Complex Autonomous Payload (CAP) carrier to be carried in the Shuttle Orbiter payload bay. One experiment is conducted for each of the three membrane performance areas under study. These experiments are discussed in this paper.

  14. Ditching Investigations of Dynamic Models and Effects of Design Parameters on Ditching Characteristics

    NASA Technical Reports Server (NTRS)

    Fisher, Lloyd J; Hoffman, Edward L

    1958-01-01

    Data from ditching investigations conducted at the Langley Aeronautical Laboratory with dynamic scale models of various airplanes are presented in the form of tables. The effects of design parameters on the ditching characteristics of airplanes, based on scale-model investigations and on reports of full-scale ditchings, are discussed. Various ditching aids are also discussed as a means of improving ditching behavior.

  15. Dynamic Characteristics of High Intensity Shock Effect for Medium Weight Shock Testing Machine

    NASA Astrophysics Data System (ADS)

    Song, Feng; Sai, Jiangang; Yun, He; Bo, Gao

    This paper analyses the dynamic characteristics of MWMS by optimizing the design of the anvil table to ensure the waveform in allowing limit, simulating the impact of MWMS, and demonstrating the influence of the low-pass filter and the height of hammer drop to test results.

  16. Dynamic Characteristics of Prosthetic Feet: A Comparison Between Modal Parameters of Walking, Running and Sprinting Foot

    NASA Astrophysics Data System (ADS)

    Noroozi, S.; Rahman, A. G. A.; Dupac, M.; Vinney, J. E.

    Current methods of evaluating the performance of Energy Storing and Returning (ESR) prosthesis are subjective and rely on VO2 consumption. Current prosthetic feet are designed for specific applications and the majority are designed for walking and moderate running. These mechanical feet have fixed mechanical and dynamic characteristics. They have to be selected to meet the requirement of the task and any use outside the domain of the task can result in extreme/severe lack of gait symmetry and loss of energy. Poor gait symmetry results is excess consumption of energy, back pain or fatigue. To investigate if a multipurpose foot can be designed to passively adapt to the walking or running condition one must first understand the different dynamics that are involved and are required from the task specific foot. Static tests have shown these feet to have non-linear stiffness, making the prediction of their dynamic response difficult. The most reliable method to test for dynamic characteristics is drop and modal testing. A method approach has been developed as part of this research to test and compare the dynamic characteristics of three different types of foot (natural frequency, mode shapes and damping). This is needed to explore the differences in the responses of these feet that allow one to be used for walking, one to be used for running and one to be used for sprinting with ease.

  17. Permeable Gas Flow Influences Magma Fragmentation Speed.

    NASA Astrophysics Data System (ADS)

    Richard, D.; Scheu, B.; Spieler, O.; Dingwell, D.

    2008-12-01

    Highly viscous magmas undergo fragmentation in order to produce the pyroclastic deposits that we observe, but the mechanisms involved remain unclear. The overpressure required to initiate fragmentation depends on a number of physical parameters, such as the magma's vesicularity, permeability, tensile strength and textural properties. It is clear that these same parameters control also the speed at which a fragmentation front travels through magma when fragmentation occurs. Recent mathematical models of fragmentation processes consider most of these factors, but permeable gas flow has not yet been included in these models. However, it has been shown that permeable gas flow through a porous rock during a sudden decompression event increases the fragmentation threshold. Fragmentation experiments on natural samples from Bezymianny (Russia), Colima (Mexico), Krakatau (Indonesia) and Augustine (USA) volcanoes confirm these results and suggest in addition that high permeable flow rates may increase the speed of fragmentation. Permeability from the investigated samples ranges from as low as 5 x 10-14 to higher than 9 x 10- 12 m2 and open porosity ranges from 16 % to 48 %. Experiments were performed for each sample series at applied pressures up to 35 MPa. Our results indicate that the rate of increase of fragmentation speed is higher when the permeability is above 10-12 m2. We confirm that it is necessary to include the influence of permeable flow on fragmentation dynamics.

  18. Pressure dynamic characteristics of pressure controlled ventilation system of a lung simulator.

    PubMed

    Shi, Yan; Ren, Shuai; Cai, Maolin; Xu, Weiqing; Deng, Qiyou

    2014-01-01

    Mechanical ventilation is an important life support treatment of critically ill patients, and air pressure dynamics of human lung affect ventilation treatment effects. In this paper, in order to obtain the influences of seven key parameters of mechanical ventilation system on the pressure dynamics of human lung, firstly, mechanical ventilation system was considered as a pure pneumatic system, and then its mathematical model was set up. Furthermore, to verify the mathematical model, a prototype mechanical ventilation system of a lung simulator was proposed for experimental study. Last, simulation and experimental studies on the air flow dynamic of the mechanical ventilation system were done, and then the pressure dynamic characteristics of the mechanical system were obtained. The study can be referred to in the pulmonary diagnostics, treatment, and design of various medical devices or diagnostic systems. PMID:25197318

  19. Measurement, simulation on dynamic characteristics of a wire gauze fluid damping shock absorber

    NASA Astrophysics Data System (ADS)

    Ping, Yang; Yonghong, Tan; Jianmin, Yang; Nin, Sun

    2006-04-01

    A new kind of shock absorber with Coulomb-fluid damping through coupling oil, wire gauze, rubber and spring by ingenious tactics is designed for reinforcement of electronic-information equipment in atrocious vibration and impact. The physical mechanism of the shock absorber is systematically investigated. The key-model machine shows complex non-linear dynamic characteristics in multi-parameter coupling dynamic test; otherwise, it has a good dynamic performance for attenuating vibration and resisting violent impact. Based on this, the non-linear dynamic model for attenuating vibration mode of the shock absorber is presented by analysing coupling physical mechanism of fluid and Coulomb friction and other factors for designing the shock absorber with high validity. The analytical results obtained in experimental data have been compared with the numerical ones obtained by performing the Runge-Kutta method with the mathematical model. As the model results agree well with the test data, it can be used for engineering design.

  20. Pressure Dynamic Characteristics of Pressure Controlled Ventilation System of a Lung Simulator

    PubMed Central

    Shi, Yan; Ren, Shuai; Cai, Maolin; Xu, Weiqing; Deng, Qiyou

    2014-01-01

    Mechanical ventilation is an important life support treatment of critically ill patients, and air pressure dynamics of human lung affect ventilation treatment effects. In this paper, in order to obtain the influences of seven key parameters of mechanical ventilation system on the pressure dynamics of human lung, firstly, mechanical ventilation system was considered as a pure pneumatic system, and then its mathematical model was set up. Furthermore, to verify the mathematical model, a prototype mechanical ventilation system of a lung simulator was proposed for experimental study. Last, simulation and experimental studies on the air flow dynamic of the mechanical ventilation system were done, and then the pressure dynamic characteristics of the mechanical system were obtained. The study can be referred to in the pulmonary diagnostics, treatment, and design of various medical devices or diagnostic systems. PMID:25197318

  1. Experimental and analytical determination of characteristics affecting light aircraft landing-gear dynamics

    NASA Technical Reports Server (NTRS)

    Fasanella, E. L.; Mcgehee, J. R.; Pappas, M. S.

    1977-01-01

    An experimental and analytical investigation was conducted to determine which characteristics of a light aircraft landing gear influence gear dynamic behavior significantly. The investigation focused particularly on possible modification for load control. Pseudostatic tests were conducted to determine the gear fore-and-aft spring constant, axial friction as a function of drag load, brake pressure-torque characteristics, and tire force-deflection characteristics. To study dynamic tire response, vertical drops were conducted at impact velocities of 1.2, 1.5, and 1.8 m/s onto a level surface; to determine axial-friction effects, a second series of vertical drops were made at 1.5 m/s onto surfaces inclined 5 deg and 10 deg to the horizontal. An average dynamic axial-friction coefficient of 0.15 was obtained by comparing analytical data with inclined surface drop test data. Dynamic strut bending and associated axial friction were found to be severe for the drop tests on the 10 deg surface.

  2. Dynamics of soil gas radon concentration in a highly permeable soil based on a long-term high temporal resolution observation series.

    PubMed

    Szabó, Katalin Zsuzsanna; Jordan, Gyozo; Horváth, Ákos; Szabó, Csaba

    2013-10-01

    This paper studies the temporal variation of soil gas radon activity concentration in a highly permeable (k = 2.0E-11 m(2)) sandy-gravelly soil in order to understand if temporal variation of soil gas radon activity concentration can affect geogenic radon potential determination. Geogenic radon potential provides information about the potential risk from radon. Its calculation takes into account the equilibrium, saturated at infinite depth, soil gas radon activity concentration (c∞). This concentration may vary at annual time scale due to the environmental conditions. A long-term (yearly) and high temporal resolution (15 min) observation, applied in this study, reveal various temporal features such as long-term trend, seasonality, daily periodicity and sudden events in soil gas radon time series. Results show seasonal and daily periodical variation of the measured soil gas radon activity concentration (csoilRn) in a highly permeable sandy-gravelly soil with definite seasons without obvious long transitional periods. The winter (from October 2010 to April 2011) is characterized by 2.5 times higher average soil gas radon activity concentration (median is 7.0 kBq m(-3)) than the summer (August, September 2010 and May, June, July 2011) (median is 2.8 kBq m(-3)). Daily periodicity, which is much less than the seasonal one, controls the soil gas radon activity concentration mainly in the summer season. Average (AM) value of csoilRn is higher at night than in the daytime with about 18% and 3.8% in summer and in winter, respectively. As a conclusion, in case of single csoilRn measurement on a highly permeable (k ≥ 2.0E-11 m(2)) soil, similar to our test site, csoilRn should be corrected according to the seasons for calculating the equilibrium activity concentration c∞ value. PMID:23669415

  3. Influence of external perturbations on dynamical characteristics of dust clusters (simulation)

    SciTech Connect

    Lisin, E. A. Vaulina, O. S.

    2012-11-15

    The results of a numerical study of the dynamics of interacting particles in cluster systems under the action of an external perturbing field on them are presented. The relaxation rates and characteristic relaxation times of a cluster to its equilibrium state are analyzed. The conditions for the formation of dynamical structures of charged particles in the field of external nonpotential forces are investigated. The peculiarities of diagnosing the pair potential of particles in nonequilibrium systems are considered. The numerical simulation conditions for the problem were close to the conditions of experiments in a dusty plasma.

  4. Dynamic switching characteristic dependence on sidewall angle for phase change memory

    NASA Astrophysics Data System (ADS)

    Long, X. M.; Miao, X. S.; Sun, J. J.; Cheng, X. M.; Tong, H.; Li, Y.; Yang, D. H.; Huang, J. D.; Liu, C.

    2012-01-01

    In this paper, the volume-minimized model of phase change memory (PCM) cell with Ge 2Sb 2Te 5 (GST) material has been established to study the dynamic switching (set-to-reset) characteristic dependence on the sidewall angle. Joule heating volume, threshold current, dynamic resistance and phase transition rate of PCM cells by current pulse are all calculated. The results show that the threshold current increases with decreasing the sidewall angle and is significantly impacted by the feature size and aspect ratio. The PCM cell of 90° sidewall angle exhibits the smallest Joule heating volume, the highest RESET resistance and the fastest phase transition property.

  5. User's Manual for Computer Program ROTOR. [to calculate tilt-rotor aircraft dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Yasue, M.

    1974-01-01

    A detailed description of a computer program to calculate tilt-rotor aircraft dynamic characteristics is presented. This program consists of two parts: (1) the natural frequencies and corresponding mode shapes of the rotor blade and wing are developed from structural data (mass distribution and stiffness distribution); and (2) the frequency response (to gust and blade pitch control inputs) and eigenvalues of the tilt-rotor dynamic system, based on the natural frequencies and mode shapes, are derived. Sample problems are included to assist the user.

  6. Molecular dynamics insights into human aquaporin 2 water channel.

    PubMed

    Binesh, A R; Kamali, R

    2015-12-01

    In this study, the first molecular dynamics simulation of the human aquaporin 2 is performed and for a better understanding of the aquaporin 2 permeability performance, the characteristics of water transport in this protein channel and key biophysical parameters of AQP2 tetramer including osmotic and diffusive permeability constants and the pore radius are investigated. For this purpose, recently recovered high resolution X-ray crystal structure of` the human aquaporin 2 is used to perform twenty nanosecond molecular dynamics simulation of fully hydrated tetramer of this protein embedded in a lipid bilayer. The resulting water permeability characteristics of this protein channel showed that the water permeability of the human AQP2 is in a mean range in comparison with other human aquaporins family. Finally, the results reported in this research demonstrate that molecular dynamics simulation of human AQP2 provided useful insights into the mechanisms of water permeation and urine concentration in the human kidney. PMID:26489820

  7. Dynamic characteristics of 4H-SiC drift step recovery diodes

    SciTech Connect

    Ivanov, P. A. Kon’kov, O. I.; Samsonova, T. P.; Potapov, A. S.; Grekhov, I. V.

    2015-11-15

    The dynamic characteristics of 4H-SiC p{sup +}–p–n{sub 0}–n{sup +} diodes are experimentally studied in the pulsed modes characteristic of the operation of drift step recovery diodes (DSRD-mode). The effect of the subnanosecond termination of the reverse current maintained by electron-hole plasma preliminarily pumped by a forward current pulse is analyzed in detail. The influence exerted on the DSRD effect by the amplitude of reverse-voltage pulses, the amplitude and duration of forward-current pulses, and the time delay between the forward and reverse pulses is demonstrated and accounted for.

  8. [Study on nonlinear dynamic characteristic indexes of epileptic electroencephalography and electroencephalography subbands].

    PubMed

    Huang, Ruimei; Du, Shouhong; Chen, Ziyi; Zhang, Zhen; Zhou, Yi

    2014-02-01

    Electroencephalogram (EEG) is the primary tool in investigation of the brain science. It is necessary to carry out a deepgoing study into the characteristics and information hidden in EEGs to meet the needs of the clinical research. In this paper, we present a wavelet-nonlinear dynamic methodology for analysis of nonlinear characteristic of EEGs and delta, theta, alpha, and beta sub-bands. We therefore studied the effectiveness of correlation dimension (CD), largest Lyapunov exponen, and approximate entropy (ApEn) in differentiation between the interictal EEG and ictal EEG based on statistical significance of the differences. The results showed that the nonlinear dynamic char acteristic of EEG and EEG subbands could be used as effective identification statistics in detecting seizures. PMID:24804477

  9. Dynamic Characteristic Analysis of Spinal Motor Control Between 11- and 15-Year-Old Children.

    PubMed

    Chow, Daniel H; Lau, Newman M

    2016-07-01

    Spinal motor control can provide substantial insight for the causes of spinal musculoskeletal disorders. Its dynamic characteristics however, have not been fully investigated. The objective of this study is to explore the dynamic characteristics of spinal motor control via the fractional Brownian motion mathematical technique. Spinal curvatures and repositioning errors of different spinal regions in 64 children age 11- or 15-years old during upright stance were measured and compared for the effects of age and gender. With the application of the fractional Brownian motion analytical technique to the changes of spinal curvatures, distinct persistent movement behaviors could be determined, which could be interpreted physiologically as open-loop behaviors. Moreover, it was found that the spinal motor control of 15-year-old children was better than that of 11-year-old children with smaller repositioning error and less curvature variability as well as shorter response time and smaller curvature deformation. PMID:26314089

  10. Effects of automobile steering characteristics on driver vehicle system dynamics in regulation tasks

    NASA Technical Reports Server (NTRS)

    Mcruer, D. T.; Klein, R.

    1975-01-01

    A regulation task which subjected the automobile to a random gust disturbance which is countered by driver control action is used to study the effects of various automobile steering characteristics on the driver/vehicle system. The experiments used a variable stability automobile specially configured to permit insertion of the simulated gust disturbance and the measurement of the driver/vehicle system characteristics. Driver/vehicle system dynamics were measured and interpreted as an effective open loop system describing function. Objective measures of system bandwidth, stability, and time delays were deduced and compared. These objective measures were supplemented by driver ratings. A tentative optimum range of vehicle dynamics for the directional regulation task was established.

  11. Dynamic characteristics of noncontacting seal and evaluation of its effect on stability of rotor system

    NASA Astrophysics Data System (ADS)

    Iwatsubo, Takuzo

    Recent investigations on dynamic characteristics of the labyrinth seal and the pump seal are reviewed, and contributions of each element to stability of the rotor are illustrated for both seals. A method to evaluate the contribution of each element to the stability of a machine is presented. It is shown how to synthesize the rotor system by using the contribution of each element to stability.

  12. Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness

    NASA Technical Reports Server (NTRS)

    Townsend, John S.

    1987-01-01

    A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. Using a perturbation expansion technique the free vibration solution is obtained in a closed-form, and the effects of system parameters on beam response are explored. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.

  13. Dynamic characteristics of a vibrating beam with periodic variation in bending stiffness

    NASA Technical Reports Server (NTRS)

    Townsend, John S.

    1987-01-01

    A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. The effects of system parameters on beam response are explored with a perturbation expansion technique. It is found that periodic stiffness acts to modulate the modal displacements from the characteristic shape of a simple sine wave. The results are verified by a finite element solution and through experimental testing.

  14. Characteristics of a self-forming dynamic membrane coupled with a bioreactor for municipal wastewater treatment.

    PubMed

    Fan, Bin; Huang, Xia

    2002-12-01

    A self-forming dynamic membrane (SFDM) method that used the biomass layer formed on a coarse mesh to effect solid-liquid separation was proposed. A 100-microm Dacron mesh material was used to make the SFDM modules. A SFDM coupled bioreactor (SFDMBR) was tested to treat actual municipal wastewater, and the performance and mechanisms of the SFDM were investigated. The SFDMBR worked by gravity filtration, and the water head drop was generally <5 cm. The effluent suspended solid concentrations were undetectable in most cases, and the COD and NH3 N removal efficiencies averaged 84.2% and 98.03%, respectively. An aeration in situ was adequate for cleaning the clogged modules, and the SFDM was readily and quickly re-formed. The biomass layer of the SFDM consisted of a cake layer and a gel layer. The gel layer had structures like conventional membranes and acted the key role in the SFDM. The permeability of the used mesh attached to the gel layer could be improved because the gel layer made the filtration surface more hydrophilic. PMID:12523444

  15. Dynamic neural-based buffer management for Queuing systems with self-similar characteristics.

    PubMed

    Yousefi'zadeh, Homayoun; Jonckheere, Edmond A

    2005-09-01

    Buffer management in queuing systems plays an important role in addressing the tradeoff between efficiency measured in terms of overall packet loss and fairness measured in terms of individual source packet loss. Complete partitioning (CP) of a buffer with the best fairness characteristic and complete sharing (CS) of a buffer with the best efficiency characteristic are at the opposite ends of the spectrum of buffer management techniques. Dynamic partitioning buffer management techniques aim at addressing the tradeoff between efficiency and fairness. Ease of implementation is the key issue when determining the practicality of a dynamic buffer management technique. In this paper, two novel dynamic buffer management techniques for queuing systems accommodating self-similar traffic patterns are introduced. The techniques take advantage of the adaptive learning power of perceptron neural networks when applied to arriving traffic patterns of queuing systems. Relying on the water-filling approach, our proposed techniques are capable of coping with the tradeoff between packet loss and fairness issues. Computer simulations reveal that both of the proposed techniques enjoy great efficiency and fairness characteristics as well as ease of implementation. PMID:16252824

  16. Modelling and Analysis on Biomechanical Dynamic Characteristics of Knee Flexion Movement under Squatting

    PubMed Central

    Wang, Jianping; Tao, Kun; Li, Huanyi; Wang, Chengtao

    2014-01-01

    The model of three-dimensional (3D) geometric knee was built, which included femoral-tibial, patellofemoral articulations and the bone and soft tissues. Dynamic finite element (FE) model of knee was developed to simulate both the kinematics and the internal stresses during knee flexion. The biomechanical experimental system of knee was built to simulate knee squatting using cadaver knees. The flexion motion and dynamic contact characteristics of knee were analyzed, and verified by comparing with the data from in vitro experiment. The results showed that the established dynamic FE models of knee are capable of predicting kinematics and the contact stresses during flexion, and could be an efficient tool for the analysis of total knee replacement (TKR) and knee prosthesis design. PMID:25013852

  17. A study of the effect of forcing function characteristics on human operator dynamics in manual control

    NASA Technical Reports Server (NTRS)

    Washizu, K.; Tanaka, K.; Osawa, T.

    1978-01-01

    The effect of the spectrum of the forcing function on the human pilot dynamics in manual control was investigated. A simple compensatory tracking experiment was conducted, where the controlled element was of a second-order dynamics and the forcing function was a random noise having a dominant frequency. The dominant frequency and the power of the forcing function were two variable parameters during the experiment. The results show that the human pilot describing functions are dependent not only on the dynamics of the controlled element, but also on the characteristics of the forcing function. This suggests that the human pilot behavior should be expressed by the transfer function taking into consideration his ability to sense and predict the forcing function.

  18. Dynamic response characteristics of two transport models tested in the National Transonic Facility

    NASA Technical Reports Server (NTRS)

    Young, Clarence P., Jr.

    1993-01-01

    This paper documents recent experiences with measuring the dynamic response characteristics of a commercial transport and a military transport model during full scale Reynolds number tests in the National Transonic Facility. Both models were limited in angle of attack while testing at full scale Reynolds number and cruise Mach number due to pitch or stall buffet response. Roll buffet (wing buzz) was observed for both models at certain Mach numbers while testing at high Reynolds number. Roll buffet was more severe and more repeatable for the military transport model at cruise Mach number. Miniature strain-gage type accelerometers were used for the first time for obtaining dynamic data as a part of the continuing development of miniature dynamic measurements instrumentation for cryogenic applications. This paper presents the results of vibration measurements obtained for both the commercial and military transport models and documents the experience gained in the use of miniature strain gage type accelerometers.

  19. Experimental investigation on dynamic characteristics and strengthening mechanism of laser-induced cavitation bubbles.

    PubMed

    Ren, X D; He, H; Tong, Y Q; Ren, Y P; Yuan, S Q; Liu, R; Zuo, C Y; Wu, K; Sui, S; Wang, D S

    2016-09-01

    The dynamic features of nanosecond laser-induced cavitation bubbles near the light alloy boundary were investigated with the high-speed photography. The shock-waves and the dynamic characteristics of the cavitation bubbles generated by the laser were detected using the hydrophone. The dynamic features and strengthening mechanism of cavitation bubbles were studied. The strengthening mechanisms of cavitation bubble were discussed when the relative distance parameter γ was within the range of 0.5-2.5. It showed that the strengthening mechanisms caused by liquid jet or shock-waves depended on γ much. The research results provided a new strengthening method based on laser-induced cavitation shotless peening (CSP). PMID:27150764

  20. Performance limitations of bilateral force reflection imposed by operator dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Chapel, Jim D.

    1989-01-01

    A linearized, single-axis model is presented for bilateral force reflection which facilitates investigation into the effects of manipulator, operator, and task dynamics, as well as time delay and gain scaling. Structural similarities are noted between this model and impedance control. Stability results based upon this model impose requirements upon operator dynamic characteristics as functions of system time delay and environmental stiffness. An experimental characterization reveals the limited capabilities of the human operator to meet these requirements. A procedure is presented for determining the force reflection gain scaling required to provide stability and acceptable operator workload. This procedure is applied to a system with dynamics typical of a space manipulator, and the required gain scaling is presented as a function of environmental stiffness.

  1. Dynamic characteristics of very-high-rate GPS observations for seismology

    NASA Astrophysics Data System (ADS)

    Ebinuma, Takuji; Kato, Teruyuki

    2012-05-01

    GPS observations with higher than once-per-second sampling are becoming increasingly important for seismology. A number of reports have shown that very-high-rate GPS receivers are capable of capturing dynamic ground displacements from significant earthquakes. The higher output rate, however, does not necessarily mean higher frequency content of the corresponding observations. In order to examine dynamic effects on very-high-rate GPS observations, the frequency response characteristics of several geodetic GPS receivers were evaluated using a GPS signal simulator in controlled laboratory conditions. The tested receivers include Trimble Net-R8, NovAtel OEMV, and TOPCON Net-G3A. The experiment results suggest that the dynamic characteristics of the signal tracking loops put a limit on the frequency of the received signals, and all the tested receivers except for Trimble show good signal tracking performance at up to 5 Hz under dynamic stress of 2 G acceleration. The power spectral densities of the kinematic solutions obtained from the simulated seismic motion of the 2008 Iwate-Miyagi Inland earthquake ( M w 6.8) are also evaluated. The power spectral densities of both the NovAtel and TOPCON receivers agree with the simulated ground displacement at up to 5 Hz. By contrast, the Trimble receiver provides a pronounced increase in spectral energy above 2 Hz.

  2. Seismic waves increase permeability.

    PubMed

    Elkhoury, Jean E; Brodsky, Emily E; Agnew, Duncan C

    2006-06-29

    Earthquakes have been observed to affect hydrological systems in a variety of ways--water well levels can change dramatically, streams can become fuller and spring discharges can increase at the time of earthquakes. Distant earthquakes may even increase the permeability in faults. Most of these hydrological observations can be explained by some form of permeability increase. Here we use the response of water well levels to solid Earth tides to measure permeability over a 20-year period. At the time of each of seven earthquakes in Southern California, we observe transient changes of up to 24 degrees in the phase of the water level response to the dilatational volumetric strain of the semidiurnal tidal components of wells at the Piñon Flat Observatory in Southern California. After the earthquakes, the phase gradually returns to the background value at a rate of less than 0.1 degrees per day. We use a model of axisymmetric flow driven by an imposed head oscillation through a single, laterally extensive, confined, homogeneous and isotropic aquifer to relate the phase response to aquifer properties. We interpret the changes in phase response as due to changes in permeability. At the time of the earthquakes, the permeability at the site increases by a factor as high as three. The permeability increase depends roughly linearly on the amplitude of seismic-wave peak ground velocity in the range of 0.21-2.1 cm s(-1). Such permeability increases are of interest to hydrologists and oil reservoir engineers as they affect fluid flow and might determine long-term evolution of hydrological and oil-bearing systems. They may also be interesting to seismologists, as the resulting pore pressure changes can affect earthquakes by changing normal stresses on faults. PMID:16810253

  3. Flight-determined derivatives and dynamic characteristics of the CV-990 airplane

    NASA Technical Reports Server (NTRS)

    Gilyard, G. B.

    1972-01-01

    Flight-determined longitudinal and lateral-directional stability and control derivatives are presented for the CV-990 airplane for various combinations of Mach number, altitude, and flap setting throughout the flight envelope up to a Mach number of 0.87. Also presented are the dynamic characteristics of the aircraft calculated from the flight-obtained derivatives and the measured phugoid characteristics. The derivative characteristics were obtained from flight records of longitudinal and lateral-directional transient oscillation maneuvers by using a modified Newton-Raphson digital derivative determination technique. Generally the derivatives exhibited consistent variation with lift coefficient in the low-speed data and with Mach number and altitude in the high-speed data. Many also varied with flap deflection, notably spoiler effectiveness and directional stability.

  4. Honeycomb Core Permeability Under Mechanical Loads

    NASA Technical Reports Server (NTRS)

    Glass, David E.; Raman, V. V.; Venkat, Venki S.; Sankaran, Sankara N.

    1997-01-01

    A method for characterizing the air permeability of sandwich core materials as a function of applied shear stress was developed. The core material for the test specimens was either Hexcel HRP-3/16-8.0 and or DuPont Korex-1/8-4.5 and was nominally one-half inch thick and six inches square. The facesheets where made of Hercules' AS4/8552 graphite/epoxy (Gr/Ep) composites and were nominally 0.059-in. thick. Cytec's Metalbond 1515-3M epoxy film adhesive was used for co-curing the facesheets to the core. The permeability of the specimens during both static (tension) and dynamic (reversed and non-reversed) shear loads were measured. The permeability was measured as the rate of air flow through the core from a circular 1-in2 area of the core exposed to an air pressure of 10.0 psig. In both the static and dynamic testing, the Korex core experienced sudden increases in core permeability corresponding to a core catastrophic failure, while the URP core experienced a gradual increase in the permeability prior to core failure. The Korex core failed at lower loads than the HRP core both in the transverse and ribbon directions.

  5. Permeability of the blood–brain barrier predicts conversion from optic neuritis to multiple sclerosis

    PubMed Central

    Modvig, Signe; Simonsen, Helle J.; Frederiksen, Jette L.; Larsson, Henrik B. W.

    2015-01-01

    Optic neuritis is an acute inflammatory condition that is highly associated with multiple sclerosis. Currently, the best predictor of future development of multiple sclerosis is the number of T2 lesions visualized by magnetic resonance imaging. Previous research has found abnormalities in the permeability of the blood–brain barrier in normal-appearing white matter of patients with multiple sclerosis and here, for the first time, we present a study on the capability of blood–brain barrier permeability in predicting conversion from optic neuritis to multiple sclerosis and a direct comparison with cerebrospinal fluid markers of inflammation, cellular trafficking and blood–brain barrier breakdown. To this end, we applied dynamic contrast-enhanced magnetic resonance imaging at 3 T to measure blood–brain barrier permeability in 39 patients with monosymptomatic optic neuritis, all referred for imaging as part of the diagnostic work-up at time of diagnosis. Eighteen healthy controls were included for comparison. Patients had magnetic resonance imaging and lumbar puncture performed within 4 weeks of onset of optic neuritis. Information on multiple sclerosis conversion was acquired from hospital records 2 years after optic neuritis onset. Logistic regression analysis showed that baseline permeability in normal-appearing white matter significantly improved prediction of multiple sclerosis conversion (according to the 2010 revised McDonald diagnostic criteria) within 2 years compared to T2 lesion count alone. There was no correlation between permeability and T2 lesion count. An increase in permeability in normal-appearing white matter of 0.1 ml/100 g/min increased the risk of multiple sclerosis 8.5 times whereas having more than nine T2 lesions increased the risk 52.6 times. Receiver operating characteristic curve analysis of permeability in normal-appearing white matter gave a cut-off of 0.13 ml/100 g/min, which predicted conversion to multiple sclerosis with a

  6. LVP modeling and dynamic characteristics prediction of a hydraulic power unit in deep-sea

    NASA Astrophysics Data System (ADS)

    Cao, Xue-peng; Ye, Min; Deng, Bin; Zhang, Cui-hong; Yu, Zu-ying

    2013-03-01

    A hydraulic power unit (HPU) is the driving "heart" of deep-sea working equipment. It is critical to predict its dynamic performances in deep-water before being immerged in the seawater, while the experimental tests by simulating deep-sea environment have many disadvantages, such as expensive cost, long test cycles, and difficult to achieve low-temperature simulation, which is only used as a supplementary means for confirmatory experiment. This paper proposes a novel theoretical approach based on the linear varying parameters (LVP) modeling to foresee the dynamic performances of the driving unit. Firstly, based on the varying environment features, dynamic expressions of the compressibility and viscosity of hydraulic oil are derived to reveal the fluid performances changing. Secondly, models of hydraulic system and electrical system are accomplished respectively through studying the control process and energy transfer, and then LVP models of the pressure and flow rate control is obtained through the electro-hydraulic models integration. Thirdly, dynamic characteristics of HPU are obtained by the model simulating within bounded closed sets of varying parameters. Finally, the developed HPU is tested in a deep-sea imitating hull, and the experimental results are well consistent with the theoretical analysis outcomes, which clearly declare that the LVP modeling is a rational way to foresee dynamic performances of HPU. The research approach and model analysis results can be applied to the predictions of working properties and product designs for other deep-sea hydraulic pump.

  7. Study about the influence of cavitation on the dynamic characteristics for the sliding bearing

    NASA Astrophysics Data System (ADS)

    Zhai, L. M.; Luo, Y. Y.; Wang, Z. W.

    2015-01-01

    Sliding bearings are employed to support the rotor system and limit the vibration amplitude. In high speed rotor system, cavitation often occurs in the oil film and affects the dynamic characteristics of the sliding bearing greatly. In this paper, numerical method is adopted to simulate the cavitation in the oil film with homogeneous two-phase mixture flow using Singhal-et-al cavitation model in the commercial code FLUENT-solver. Cases without cavitation model were also calculated at the same time. Many computations with different frequency ratios were conducted. Then the rotor dynamic characteristics of the sliding bearing were retrieved. The results show that the cavitation has great influences on the pressure distribution in the oil film. As the rotational speed or whirling speed of the journal increases, the cavitation will become prominent. The dynamic coefficients of the bearing such as stiffness and damping with cavitation model considered are quite different from that without cavitation. So it is worth to pay attention to and do further study about the cavitation in the sliding bearing in the high speed rotor system.

  8. Equilibrium and Dynamical Characteristics of Imidazole Langmuir Monolayers on Graphite Sheets.

    PubMed

    Rodriguez, Javier; Elola, M Dolores; Laria, D

    2015-07-23

    Using molecular dynamics techniques, we examine structural and dynamical characteristics of liquid-like imidazole (Im) monolayers physisorbed onto a planar graphite sheet, at T = 384 K. Our simulations reveal that molecular orientations in the saturated monolayer exhibit a bistable distribution, characterized by an inner parallel arrangement of the molecules in close contact with the substrate and a slanted alignment, in those lying in adjacent, outer locations. Compared to the results found in three-dimensional, bulk phases, the analysis of the spatial correlations between sites participating in hydrogen bonding shows a clear enhancement of the intermolecular interactions, which also leads to stronger dipolar correlations. As a result, the gross structural features of the monolayer can be cast in terms of mesoscopic domains, comprising units articulated via winding hydrogen bonds, that persist along typical time intervals of a few tens of picoseconds. On the dynamical side, a similar comparison of the characteristic decorrelation time for orientational motions shows a 4-fold increment. Contrasting, the reduction of the system dimensionality leads to a larger diffusion constant. Possible substrate-induced anisotropies in the diffusive motions are also investigated. PMID:25423289

  9. A novel approach to detecting breathing-fatigue cracks based on dynamic characteristics

    NASA Astrophysics Data System (ADS)

    Yan, Guirong; De Stefano, Alessandro; Matta, Emiliano; Feng, Ruoqiang

    2013-01-01

    During the service life of structures, breathing-fatigue cracks may occur in structural members due to dynamic loadings acting on them. These fatigue cracks, if undetected, might lead to a catastrophic failure of the whole structural system. Although a number of approaches have been proposed to detect breathing-fatigue cracks, some of them appear rather sophisticated or expensive (requiring complicated equipment), and others suffer from a lack of sensitivity. In this study, a simple and efficient approach to detecting breathing-fatigue cracks is developed based on dynamic characteristics of breathing cracks. First, considering that breathing cracks introduce bilinearity into structures, a simple system identification method for bilinear systems is proposed by taking best advantage of dynamic characteristics of bilinear systems. This method transfers nonlinear system identification into linear system identification by dividing impulse or free-vibration responses into different parts corresponding to each stiffness region according to the stiffness interface. In this way, the natural frequency of each region can be identified using any modal identification approach applicable to linear systems. Second, the procedure for identifying the existence of breathing fatigue cracks and quantifying the cracks qualitatively is proposed by looking for the difference in the identified natural frequency between regions. Third, through introducing Hilbert transform, the proposed procedure is extended to identify fatigue cracks in piecewise-nonlinear systems. The proposed system identification method and crack detection procedure have been successfully validated by numerical simulations and experimental tests.

  10. Dynamical characteristics of surface EMG signals of hand grasps via recurrence plot.

    PubMed

    Ouyang, Gaoxiang; Zhu, Xiangyang; Ju, Zhaojie; Liu, Honghai

    2014-01-01

    Recognizing human hand grasp movements through surface electromyogram (sEMG) is a challenging task. In this paper, we investigated nonlinear measures based on recurrence plot, as a tool to evaluate the hidden dynamical characteristics of sEMG during four different hand movements. A series of experimental tests in this study show that the dynamical characteristics of sEMG data with recurrence quantification analysis (RQA) can distinguish different hand grasp movements. Meanwhile, adaptive neuro-fuzzy inference system (ANFIS) is applied to evaluate the performance of the aforementioned measures to identify the grasp movements. The experimental results show that the recognition rate (99.1%) based on the combination of linear and nonlinear measures is much higher than those with only linear measures (93.4%) or nonlinear measures (88.1%). These results suggest that the RQA measures might be a potential tool to reveal the sEMG hidden characteristics of hand grasp movements and an effective supplement for the traditional linear grasp recognition methods. PMID:24403424

  11. Direct numerical simulation of turbulent channel flow with permeable walls

    NASA Astrophysics Data System (ADS)

    Hahn, Seonghyeon; Je, Jongdoo; Choi, Haecheon

    2002-01-01

    The main objectives of this study are to suggest a proper boundary condition at the interface between a permeable block and turbulent channel flow and to investigate the characteristics of turbulent channel flow with permeable walls. The boundary condition suggested is an extended version of that applied to laminar channel flow by Beavers & Joseph (1967) and describes the behaviour of slip velocities in the streamwise and spanwise directions at the interface between the permeable block and turbulent channel flow. With the proposed boundary condition, direct numerical simulations of turbulent channel flow that is bounded by the permeable wall are performed and significant skin-friction reductions at the permeable wall are obtained with modification of overall flow structures. The viscous sublayer thickness is decreased and the near-wall vortical structures are significantly weakened by the permeable wall. The permeable wall also reduces the turbulence intensities, Reynolds shear stress, and pressure and vorticity fluctuations throughout the channel except very near the wall. The increase of some turbulence quantities there is due to the slip-velocity fluctuations at the wall. The boundary condition proposed for the permeable wall is validated by comparing solutions with those obtained from a separate direct numerical simulation using both the Brinkman equation for the interior of a permeable block and the Navier Stokes equation for the main channel bounded by a permeable block.

  12. In-situ permeability determining method

    SciTech Connect

    Dowling, D.J.; Arnold, D.M.; Richter, A.P. Jr.; Warren, W.F.

    1985-01-29

    A method of determining the permeability of a particular stratum in an earth formation traversed by a borehole includes injecting a liquid into the borehole at a first pressure thereby causing liquid flow into the stratum. A first flow rate of the liquid is determined at the first pressure. The pressure of the liquid being injected into the borehole is then changed to a second pressure level and a second flow rate of the liquid flowing into the stratum is determined at the second pressure. An indication of the permeability of the stratum is then derived in accordance with the two pressures, the two flow rates and known characteristics of the stratum.

  13. Study of permeability characteristics of membranes

    NASA Technical Reports Server (NTRS)

    Spiegler, K. S.; Moore, R. J.; Leibovitz, J.; Messalem, R. M.

    1972-01-01

    A method is reported for evaluating transport experiments with membranes which is based on conservative fluxes, i.e. fluxes of quantities which do not vary across the membrane in the steady state. Conductance coefficients were calculated for the system: 0.05 N NaCl - C-103 cation-exchange membrane- 0.1 N NaCl. It is concluded that this method can be used to characterize any system of the type - solution-membrane-solution.

  14. Chemical dissolution-front instability associated with water-rock reactions in groundwater hydrology: Analyses of porosity-permeability relationship effects

    NASA Astrophysics Data System (ADS)

    Zhao, Chongbin; Hobbs, B. E.; Ord, A.

    2016-09-01

    Because dissolution of rocks may create and enhance groundwater flow channels, the chemical dissolution-front instability (CDFI) can control the quality of groundwater. This paper presents the theoretical analyses of porosity-permeability relationship effects on the CDFI in water-saturated porous rocks. Since the CDFI in a water-rock reaction system can be assessed by comparing the comprehensive dimensionless dynamic characteristic (CDDC) number with the corresponding critical CDDC number of the geochemical dissolution system, it is necessary to investigate theoretically how different porosity-permeability relationships can affect the CDDC number and critical CDDC number of a water-rock reaction system. With the commonly-used Kozeny-Carman (KC) formula taken as a reference porosity-permeability formula, the permeability variation indicator (PVI), which is defined as the ratio of the permeability obtained from any porosity-permeability formula to that obtained from the KC formula, is proposed to reflect the effect of the porosity-permeability formula on the CDFI in a water-rock reaction system. The theoretical results demonstrated that: (1) since the porosity-permeability formula with a higher PVI can result in a stronger Darcy flow velocity, it may have a significant influence on the CDFI in the water-rock reaction system. (2) With an increase in the PVI of a porosity-permeability formula, there is a decrease in the critical CDDC number of the water-rock reaction system. This means that the porous rock with a higher PVI can enable the CDFI to take place much easier in the water-rock reaction system. (3) The use of the porosity-permeability formula with a higher PVI can also cause an increase in both the dimensionless growth rate of a perturbation and the propagation speed of the chemical dissolution front in the water-rock reaction system.

  15. The Permeable Classroom.

    ERIC Educational Resources Information Center

    Sandy, Leo R.

    1998-01-01

    Discusses the concept of permeability as knowledge flow into and out of the classroom and applies it to three college courses taught by the author at Plymouth State College (New Hampshire). Experiential knowledge comes into the classroom through interviews, guest speakers, and panel presentations, and flows out through service-learning students…

  16. Dynamic characteristics of an axially polarized multilayer piezoelectric/elastic composite cylindrical transducer.

    PubMed

    Wang, Jianjun; Shi, Zhifei

    2013-10-01

    An analytical model of the dynamic characteristics of an axially polarized multilayer piezoelectric/elastic composite cylindrical transducer is proposed in this paper. Based on the plane stress assumption, the dynamic analytical solution of the transducer under an external harmonic voltage load is obtained, and the electric admittance is also derived analytically. Inherent properties of the transducer, such as resonance and anti-resonance frequencies, are presented and discussed. In addition, comparisons with other related investigations are also given, and good agreement is found. The present investigation is very helpful for the design of axially polarized multilayer piezoelectric/elastic composite cylindrical transducers, which can be used in applications related to ultrasonic and underwater sound waves. PMID:24081268

  17. Physicochemical characteristics and droplet impact dynamics of superhydrophobic carbon nanotube arrays.

    PubMed

    Aria, Adrianus I; Gharib, Morteza

    2014-06-17

    The physicochemical and droplet impact dynamics of superhydrophobic carbon nanotube arrays are investigated. These superhydrophobic arrays are fabricated simply by exposing the as-grown carbon nanotube arrays to a vacuum annealing treatment at a moderate temperature. This treatment, which allows a significant removal of oxygen adsorbates, leads to a dramatic change in wettability of the arrays, from mildly hydrophobic to superhydrophobic. Such change in wettability is also accompanied by a substantial change in surface charge and electrochemical properties. Here, the droplet impact dynamics are characterized in terms of critical Weber number, coefficient of restitution, spreading factor, and contact time. Based on these characteristics, it is found that superhydrophobic carbon nanotube arrays are among the best water-repellent surfaces ever reported. The results presented herein may pave a way for the utilization of superhydrophobic carbon nanotube arrays in numerous industrial and practical applications, including inkjet printing, direct injection engines, steam turbines, and microelectronic fabrication. PMID:24866696

  18. Dynamic Characteristics of Vertically Coupled Structures and the Design of a Decoupled Micro Gyroscope

    PubMed Central

    Choi, Bumkyoo; Lee, Seung-Yop; Kim, Taekhyun; Baek, Seog Soon

    2008-01-01

    In a vertical type, vibratory gyroscope, the coupled motion between reference (driving) and sensing vibrations causes the zero-point output, which is the unwanted sensing vibration without angular velocity. This structural coupling leads to an inherent discrepancy between the natural frequencies of the reference and the sensing oscillations, causing curve veering in frequency loci. The coupled motion deteriorates sensing performance and dynamic stability. In this paper, the dynamic characteristics associated with the coupling phenomenon are theoretically analyzed. The effects of reference frequency and coupling factor on the rotational direction and amplitude of elliptic oscillation are determined. Based on the analytical studies on the coupling effects, we propose and fabricate a vertically decoupled vibratory gyroscope with the frequency matching.

  19. Stability and Load Sharing Characteristics of a Posterior Dynamic Stabilization Device

    PubMed Central

    Cook, Daniel J.; Yeager, Matthew S.; Thampi, Shankar S.; Whiting, Donald M.

    2015-01-01

    Background Lumbar interbody fusion is a common treatment for a variety of spinal pathologies. It has been hypothesized that insufficient mechanical loading of the interbody graft can prevent proper fusion of the joint. The purpose of this study was to evaluate the mechanical stability and anterior column loading sharing characteristics of a posterior dynamic system compared to titanium rods in an anterior lumbar interbody fusion (ALIF) model. Methods Range of motion, interpedicular kinematics and interbody graft loading were measured in human cadaveric lumbar segments tested under a pure moment flexibility testing protocol. Results Both systems provided significant fixation compared to the intact condition and to an interbody spacer alone in flexion extension and lateral bending. No significant differences in fixation were detected between the devices. A significant decrease in graft loading was detected in flexion for the titanium rod treatment compared to spacer alone. No significant differences in graft loading were detected between the spacer alone and posterior dynamic system or between the posterior dynamic system and the titanium rod. Conclusions The results of this study indicate that the posterior dynamic system provides similar fixation compared to that of a titanium rod, however, studies designed to evaluate the efficacy of fixation in a cadaver model may not be sufficiently powered to establish differences in load sharing using the techniques described here. PMID:26131403

  20. Dynamic spectral characteristics measurement of DFB interband cascade laser under injection current tuning

    NASA Astrophysics Data System (ADS)

    Du, Zhenhui; Luo, Gang; An, Ying; Li, Jinyi

    2016-07-01

    The dynamic spectral properties of semiconductor lasers during its tuning are very important for frequency modulation-based applications. The spectral properties of a distributed feedback (DFB) interband cascade laser (ICL) under injection current tuning (i.e., slope efficiency, dynamic tuning rate, and instantaneous linewidth) were measured by using short delayed self-heterodyne interferometry combined with time-frequency analysis of the interferometric signal. The relations of these spectral characteristics with the injection current, tuning frequency, and operating temperature of the laser were investigated as well. The dynamic tuning rate of the laser varies from 0.07 nm/mA to 0.16 nm/mA depending on the injection current and tuning frequency, which is considerably below the static tuning rate 0.20 nm/mA. The laser instantaneous linewidth increases within 360 kHz to 760 kHz as the injection current increases or the tuning frequency increases. Unexpectedly, both the dynamic tuning rate and linewidth seem not to be related to the operating temperature of the laser. These results will be very useful for understanding the spectral properties and optimizing the frequency modulation of DFB-ICLs.

  1. Frequency-response method for determination of dynamic stability characteristics of airplanes with automatic controls

    NASA Technical Reports Server (NTRS)

    Greenberg, Harry

    1947-01-01

    A frequency-response method for determining the critical control-gearing and hunting oscillations of airplanes with automatic pilots is presented. The method is graphical and has several advantages over the standard numerical procedure based on Routh's discriminant. The chief advantage of the method is that direct use can be made of the measured response characteristics of the automatic pilot. This feature is especially useful in determining the existence, amplitude, and frequency of the hunting oscillations that may be present when the automatic pilot has nonlinear dynamic characteristics. Several examples are worked out to illustrate the application of the frequency-response method in determining the effect of automatic-pilot lag or lead on critical control gearing and in determining the amplitude and frequency hunting. It is shown that the method may be applied to the case of a control geared to airplane motions about two axes.

  2. Air Dispersion Characteristics and Thermal Comparison of Traditional and Fabric Ductwork using Computational Fluid Dynamics

    NASA Astrophysics Data System (ADS)

    Andreopoulou, Areti

    This thesis research compares the air dispersion and thermal comfort characteristics of conventional diffuser and fabric-based ductwork systems. Heating, ventilation, and air-conditioning (HVAC) systems in buildings produce and regulate airflow traveling through ductwork. The performance characteristics of conventional ductwork are compared with recent advancements in fabric-based ductwork. Using computational fluid dynamics (CFD) analysis, thermal and air distribution flow patterns are compared between the two types of ductwork and preliminary thermal comfort and efficiency conclusions are drawn. Results of the Air Distribution Performance Index (ADPI) for both ducting systems reflect that, under the given test conditions, the fabric duct system is approximately 23% more comfortable than the traditional diffuser system in terms of air speed flow uniformity into the space, while staying within the Effective Draft Temperature comfort zone of -3 to +2°F.

  3. Finite element analysis of dynamic characteristics of diamond circular saw blades

    SciTech Connect

    Wang, W.; Pang, S.S.; Yang, C.; Jerro, H.D.; Mirshams, R.A.

    1997-07-01

    The diamond circular saw is an extensively used tool in stone, construction and road maintenance industries for sawing stone and concrete. However, its vibration and noise have been nuisances to users, and little literature is available concerning this subject. The major aspects of this investigation include: the first thirty five natural frequencies and resonant modes of circular saw blades of two different diameters are computed using the finite element method; based on these thirty five natural frequencies and resonant modes, the harmonic analysis is carried out to obtain their response spectrum; and through analyzing the computational results, some conclusions on the dynamic characteristics of diamond circular saw blades are reached.

  4. Structural dynamic characteristics of a Space Station Freedom first assembly flight concept

    NASA Technical Reports Server (NTRS)

    Kaszubowski, Martin J.; Martinovic, Zoran N.; Cooper, Paul A.

    1990-01-01

    A study has been conducted of the dynamic characteristics of the first flight of NASA's Space Station Freedom and its response to a typical preboost excitation; the FEM model of the structure used encompasses 88 flexible modes below 5 Hz. The low frequency modes of the system are noted to have been dominated by the relatively low stiffness of such components as the photovoltaic arrays, thermal radiators, and alpha joint. The spacecraft backbone-forming truss was stiffer, exhibiting no deformation below 3 Hz. Reboost forcing-function response was moderate.

  5. Studies on the dynamic characteristics of gas film bearings and dampers

    NASA Technical Reports Server (NTRS)

    Stiffler, A. K.

    1975-01-01

    The dynamic characteristics of inherently compensated gas film bearings have been investigated for small excursion ratios. Both circular and rectangular cases have been solved for the stiffness and damping as a function of supply pressure, restrictor coefficient, and squeeze number. The effect of disturbance amplitude has been studied for the inherently compensated strip. Analytical solutions for the simple gas film damper problem have established the effect of disturbance amplitude at low squeeze numbers. These results are applicable to pressurized bearings as limiting case of the restrictor coefficient.

  6. Dynamical Characteristics of Rydberg Electrons Released by a Weak Electric Field.

    PubMed

    Diesen, Elias; Saalmann, Ulf; Richter, Martin; Kunitski, Maksim; Dörner, Reinhard; Rost, Jan M

    2016-04-01

    The dynamics of ultraslow electrons in the combined potential of an ionic core and a static electric field is discussed. With state-of-the-art detection it is possible to create such electrons through strong intense-field photoabsorption and to detect them via high-resolution time-of-flight spectroscopy despite their very low kinetic energy. The characteristic feature of their momentum spectrum, which emerges at the same position for different laser orientations, is derived and could be revealed experimentally with an energy resolution of the order of 1 meV. PMID:27104706

  7. Dynamical Characteristics of Rydberg Electrons Released by a Weak Electric Field

    NASA Astrophysics Data System (ADS)

    Diesen, Elias; Saalmann, Ulf; Richter, Martin; Kunitski, Maksim; Dörner, Reinhard; Rost, Jan M.

    2016-04-01

    The dynamics of ultraslow electrons in the combined potential of an ionic core and a static electric field is discussed. With state-of-the-art detection it is possible to create such electrons through strong intense-field photoabsorption and to detect them via high-resolution time-of-flight spectroscopy despite their very low kinetic energy. The characteristic feature of their momentum spectrum, which emerges at the same position for different laser orientations, is derived and could be revealed experimentally with an energy resolution of the order of 1 meV.

  8. Dynamic Characteristics and Stability Analysis of Space Shuttle Main Engine Oxygen Pump

    NASA Technical Reports Server (NTRS)

    Gunter, Edgar J.; Branagan, Lyle

    1991-01-01

    The dynamic characteristics of the Space Shuttle high pressure oxygen pump are presented. Experimental data is presented to show the vibration spectrum and response under actual engine operation and also in spin pit testing for balancing. The oxygen pump appears to be operating near a second critical speed and is sensitive to self excited aerodynamic cross coupling forces in the turbine and pump. An analysis is presented to show the improvement in pump stability by the application of turbulent flow seals, preburner seals, and pump shaft cross sectional modifications.

  9. Dynamic Characteristics of a Model and Prototype for 3D-RC Structure

    NASA Astrophysics Data System (ADS)

    Moniuddin, Md. Khaja; Vasanthalakshmi, G.; Chethan, K.; Babu, R. Ramesh

    2016-06-01

    Infill walls provide durable and economical partitions that have relatively excellent thermal and sound insulation with high fire resistance. Monolithic infilled walls are provided within RC structures without being analyzed as a combination of concrete and brick elements, although in reality they act as a single unit during earthquakes. The performance of such structures during earthquakes has proved to be superior in comparison to bare frames in terms of stiffness, strength and energy dissipation. To know the dynamic characteristics of monolithic infill wall panels and masonry infill, modal, response spectrum and time history analyses have been carried out on a model and prototype of a 3D RC structure for a comparative study.

  10. Dynamic characteristics of power-tower space stations with 15-foot truss bays

    NASA Technical Reports Server (NTRS)

    Dorsey, J. T.

    1986-01-01

    A power tower space station concept which generates power with photovoltaic arrays and where the truss structure has a bay size of 15 ft is described. Rigid body and flexible body dynamic characteristics are presented for a 75-kW Initial Operating Capability (IOC) and 150-kW and 300-kW growth stations. The transient response of the IOC and 300-kW growth stations to shuttle dock, orbit reboost, and mobile remote manipulator system translation loads are studied. Displacements, accelerations, and bending moments at various locations on the IOC and 300-kW growth stations are presented.