Science.gov

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. 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.

  3. On the dynamic viscous permeability tensor symmetry.

    PubMed

    Perrot, Camille; Chevillotte, Fabien; Panneton, Raymond; Allard, Jean-François; Lafarge, Denis

    2008-10-01

    Based on a direct generalization of a proof given by Torquato for symmetry property in static regime, this express letter clarifies the reasons why the dynamic permeability tensor is symmetric for spatially periodic structures having symmetrical axes which do not coincide with orthogonal pairs being perpendicular to the axis of three-, four-, and sixfold symmetry. This somewhat nonintuitive property is illustrated by providing detailed numerical examples for a hexagonal lattice of solid cylinders in the asymptotic and frequency dependent regimes. It may be practically useful for numerical implementation validation and/or convergence assessment.

  4. Glassy Dynamics, Cell Mechanics and Endothelial Permeability

    PubMed Central

    Hardin, Corey; Rajendran, Kavitha; Manomohan, Greeshma; Tambe, Dhananjay T.; Butler, James P.; Fredberg, Jeffrey J.; Martinelli, Roberta; Carman, Christopher V.; Krishnan, Ramaswamy

    2013-01-01

    A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H202, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition. PMID:23638866

  5. 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.

  6. Flow Characteristics in Permeable Reactive Barrier Affected by Biological Clogging

    NASA Astrophysics Data System (ADS)

    Seki, K.; Hanada, J.; Miyazaki, T.

    2004-12-01

    Permeable reactive barriers (PRB) are becoming popular for the in situ remediation of contaminated groundwater. The efficiency of the PRB is affected by permeability of the reactive zone, because when permeability decreases contaminants can bypass the reactive zone without degraded. One of the factors affecting permeability of the permeable reactive zone is biological clogging of soil pore, i.e., biomass buildup and resultant decrease in hydraulic conductivity. So far biological clogging in laboratory was mostly observed in one-dimensional flow field, but the actual flow field in PRB is better simulated in two-dimensional flow field. The objective of this study is to observe the flow characteristics in PRB by using simulated flow cells in laboratory, by comparing one-dimensional and two-dimensional flow field. One-dimensional flow field was simulated by 20 cm length and 1 cm width flow cell, and two-dimensional flow field was simulated by 20 cm length and 10 cm width flow cell. Each flow cell was operated under water-saturated conditions, in horizontal position, and at a constant temperature of 20 degree centigrade. Glass beads of 0.1 mm mean diameter was packed uniformly in the flow cells and inoculum was injected into the nutrient injection ports at the middle of the flow cells. After 24 h incubation time continuous flow was started. Background flow of de-ionized water was supplied to the inlet ports, and the mineral medium was supplied from the nutrient injection ports. The flux was measured every day and local hydraulic head distribution was measured by water manometer, and hydraulic conductivity was calculated. The flow cell experiments were continued for 9 days. In one-dimensional flow cell, hydraulic conductivity of the nutrient supplied part decreased to about half of the initial value in 9 days flow period, where the hydraulic conductivity of the part where nutrient was not supplied remained constant. Bacterial and fungal number in the moderately clogged

  7. Characteristics of permeability in carbonate areas of Korea

    NASA Astrophysics Data System (ADS)

    Park, Y.; Lee, J.; Lim, H.; Keehm, Y.

    2010-12-01

    Permeability (hydraulic conductivity) in carbonate areas is affected by various factors such as fracture, pore and degree of weathering and diagenesis. Also, caves developed in carbonate area are main factors. This study was performed to understand factors controlling the permeability in carbonate areas in Korea. In order to conduct this study, the permeability and well logging data (n=30) were collected from many literatures and rock samples were collected around wells. Vertical profile of the carbonate areas can be classified into soil, weathered carbonate and fresh carbonate zone. They show a different range at each region. Most of the rock samples were hardly weathered. The permeability showed wide ranges (0.009 to 1.1 m/day). The average value of the permeability was 0.159 m/day. However, 80% (n=24) of total data had the permeability valves lower than 0.1 m/day. The permeability values were distinguished according to degree of development of fractures. The permeability showed low values (approximately <0.04 m/day) in hardly fractured carbonate area, intermediate values (approximately 0.04 to 0.5 m/day) in fractured carbonate area and high values (approximately >0.5 m/day) in highly fractured carbonate. These results mean that fractures are dominant factors controlling the permeability in carbonate areas of Korea than others. This work was supported by Energy Resource R&D program (2009T100200058) under the Ministry of Knowledge Economy, Republic of Korea.

  8. 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

  9. 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

  10. The Interplay Between Saline Fluid Flow and Dynamic Permeability in Magmatic-Hydrothermal Systems

    NASA Astrophysics Data System (ADS)

    Weis, P.

    2014-12-01

    Magmatic-hydrothermal ore deposits document the interplay between saline fluid flow and rock permeability. Numerical simulations of multi-phase flow of variably miscible, compressible H20-NaCl fluids in concert with a dynamic permeability model can reproduce characteristics of porphyry copper and epithermal gold systems. This dynamic permeability model incorporates depth-dependent permeability profiles characteristic for tectonically active crust as well as pressure- and temperature-dependent relationships describing hydraulic fracturing and the transition from brittle to ductile rock behavior. In response to focused expulsion of magmatic fluids from a crystallizing upper crustal magma chamber, the hydrothermal system self-organizes into a hydrological divide, separating an inner part dominated by ascending magmatic fluids under near-lithostatic pressures from a surrounding outer part dominated by convection of colder meteoric fluids under near-hydrostatic pressures. This hydrological divide also provides a mechanism to transport magmatic salt through the crust, and prevents the hydrothermal system to become "clogged" by precipitation of solid halite due to depressurization of saline, high-temperature magmatic fluids. The same physical processes at similar permeability ranges, crustal depths and flow rates are relevant for a number of active systems, including geothermal resources and excess degassing at volcanos. The simulations further suggest that the described mechanism can separate the base of free convection in high-enthalpy geothermal systems from the magma chamber as a driving heat source by several kilometers in the vertical direction in tectonic settings with hydrous magmatism. This hydrology would be in contrast to settings with anhydrous magmatism, where the base of the geothermal systems may be closer to the magma chamber.

  11. 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

  12. 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.

  13. 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.

  14. 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...

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    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 Hrot, together with the effective damping coefficient αeff, ferromagnetic resonance fFMR, 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.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. Moisture diffusion and permeability characteristics of hydroxypropylmethylcellulose and hard gelatin capsules.

    PubMed

    Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

    2015-01-30

    The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration. PMID:25526672

  2. Moisture diffusion and permeability characteristics of hydroxypropylmethylcellulose and hard gelatin capsules.

    PubMed

    Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

    2015-01-30

    The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration.

  3. 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...

  4. 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

  5. Dynamic interpretation of slug tests in highly permeable aquifers

    USGS Publications Warehouse

    Zurbuchen, B.R.; Zlotnik, V.A.; Butler, J.J.

    2002-01-01

    Considerable progress has been made in developing a theoretical framework for modeling slug test responses in formations with high hydraulic conductivity K. However, several questions of practical significance remain unresolved. Given the rapid and often oscillatory nature of test responses, the traditional hydrostatic relationship between the water level and the transducer-measured head in the water column may not be appropriate. A general dynamic interpretation is proposed that describes the relationship between water level response and transducer-measured head. This theory is utilized to develop a procedure for transforming model-generated water level responses to transducer readings. The magnitude of the difference between the actual water level position and the apparent position based on the transducer measurement is a function of the acceleration and velocity of the water column, test geometry, and depth of the transducer. The dynamic approach explains the entire slug test response, including the often-noted discrepancy between the actual initial water level displacement and that measured by a transducer in the water column. Failure to use this approach can lead to a significant underestimation of K when the transducer is a considerable distance below the static water level. Previous investigators have noted a dependence of test responses on the magnitude of the initial water level displacement and have developed various approximate methods for analyzing such data. These methods are re-examined and their limitations clarified. Practical field guidelines are proposed on the basis of findings of this work. The soundness of the dynamic approach is demonstrated through a comparison of K profiles from a series of multilevel slug tests with those from dipole-flow tests performed in the same wells.

  6. Permeability analysis of neuroactive drugs through a dynamic microfluidic in vitro blood-brain barrier model.

    PubMed

    Booth, R; Kim, H

    2014-12-01

    This paper presents the permeability analysis of neuroactive drugs and correlation with in vivo brain/plasma ratios in a dynamic microfluidic blood-brain barrier (BBB) model. Permeability of seven neuroactive drugs (Ethosuximide, Gabapentin, Sertraline, Sunitinib, Traxoprodil, Varenicline, PF-304014) and trans-endothelial electrical resistance (TEER) were quantified in both dynamic (microfluidic) and static (transwell) BBB models, either with brain endothelial cells (bEnd.3) in monoculture, or in co-culture with glial cells (C6). Dynamic cultures were exposed to 15 dyn/cm(2) shear stress to mimic the in vivo environment. Dynamic models resulted in significantly higher average TEER (respective 5.9-fold and 8.9-fold increase for co-culture and monoculture models) and lower drug permeabilities (average respective decrease of 0.050 and 0.052 log(cm/s) for co-culture and monoculture) than static models; and co-culture models demonstrated higher average TEER (respective 90 and 25% increase for static and dynamic models) and lower drug permeability (average respective decrease of 0.063 and 0.061 log(cm/s) for static and dynamic models) than monoculture models. Correlation of the resultant logP e values [ranging from -4.06 to -3.63 log(cm/s)] with in vivo brain/plasma ratios (ranging from 0.42 to 26.8) showed highly linear correlation (R (2) > 0.85) for all model conditions, indicating the feasibility of the dynamic microfluidic BBB model for prediction of BBB clearance of pharmaceuticals.

  7. 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

  8. 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.

  9. 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.

  10. Permeability characteristics of erythrocyte ghosts prepared under isoionic conditions by a glycol-induced osmotic lysis.

    PubMed

    Billah, M M; Finean, J B; Coleman, R; Michell, R H

    1977-03-17

    A detailed study has been made of the permeability characteristics of human erythrocyte ghosts prepared under isoionic conditions by a glycol-induced lysis (Billah, M.M., Finean, J.B., Coleman, R. and Michell, R.H. (1976) Biochim. Biophys. Acta 433, 45-54). Impermeability to large molecules such as dextran (average molecular weight 70 000) was restored immediately and spontaneously after each of the 5-7 lyses that were required to remove all of the haemoglobin. Permeabilities to smaller molecules such as MgATP2-, [3H]inositol and [14C]choline were initially high but could be greatly reduced by incubation at 37 degrees C for an hour. The extent of such resealing decreased as the number of lyses to which the ghosts had been subjected increased. Both removal of haemoglobin and permeabilities to small molecules were affected significantly by pH, CA3+ concentrations and divalent cation chelators. Maximum resealing was achieved in ghosts prepared in the basic ionic medium (130 mM KCl, 10 nM NaCl, 2 mM MgCl2, 10 mM N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES)) at pH 7.0 (0 degrees C) and with a calcium level around 10(-5) M. Acidic pH facilitated the removal of haemoglobin whilst the presence of divalent cation chelators showed down its release. Retention of K+ by ghosts leaded with K+ during the first lysis and subsequently incubated at 37 degrees C was substantial but lation chelators slowed down its released. Retention of K+ by ghosts loaded with K+ during the first lysis and subsequently incubated at 37 degrees C was substantial but little K+ could be retained within the haemoglobin-free ghosts. Permeability of the ghosts to K+ after one lysis was affected by temperature, pH, Ca2+ concentrations and by the presence of divalent cation chelators.

  11. Dynamic modulation of ANO1/TMEM16A HCO3(-) permeability by Ca2+/calmodulin.

    PubMed

    Jung, Jinsei; Nam, Joo Hyun; Park, Hyun Woo; Oh, Uhtaek; Yoon, Joo-Heon; Lee, Min Goo

    2013-01-01

    Anoctamin 1 (ANO1)/transmembrane protein 16A (TMEM16A) is a calcium-activated anion channel that may play a role in HCO(3)(-) secretion in epithelial cells. Here, we report that the anion selectivity of ANO1 is dynamically regulated by the Ca(2+)/calmodulin complex. Whole-cell current measurements in HEK 293T cells indicated that ANO1 becomes highly permeable to HCO(3)(-) at high [Ca(2+)](i). Interestingly, this result was not observed in excised patches, indicating the involvement of cytosolic factors in this process. Further studies revealed that the direct association between ANO1 and calmodulin at high [Ca(2+)](i) is responsible for changes in anion permeability. Calmodulin physically interacted with ANO1 in a [Ca(2+)](i)-dependent manner, and addition of recombinant calmodulin to the cytosolic side of excised patches reversibly increased P(HCO3)/P(Cl). In addition, the high [Ca(2+)](i)-induced increase in HCO(3)(-) permeability was reproduced in mouse submandibular gland acinar cells, in which ANO1 plays a critical role in fluid secretion. These results indicate that the HCO(3)(-) permeability of ANO1 can be dynamically modulated and that ANO1 may play an important role in cellular HCO(3)(-) transport, especially in transepithelial HCO(3)(-) secretion.

  12. 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

  13. 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

  14. Including swell-shrink dynamics in dual-permeability numerical modeling of preferential water flow and solute transport in soils

    NASA Astrophysics Data System (ADS)

    Coppola, Antonio; Comegna, Alessandro; Gerke, Horst; Basile, Angelo

    2015-04-01

    The classical dual-permeability approach introduced by Gerke and van Genuchten for modeling water flow and solute transport in porous media with preferential flow pathways, was extended to account for shrinking effects on macropore and matrix domain hydraulic properties. Conceptually, the soil is treated as a dual-permeability bulk porous medium consisting of two dynamic interacting pore domains (1) the fracture (from shrinkage) pore domain and (2) the aggregate (interparticles plus structural) or matrix pore domain, respectively. The model assumes that the swell-shrink dynamics is represented by the inversely proportional volume changes of the fracture and matrix domains, while the overall porosity of the total soil, and hence the layer thickness, remains constant. Swell-shrink dynamics was incorporated in the model by either changing the coupled domain-specific hydraulic properties according to the shrinkage characteristics of the matrix, or partly by allowing the fractional contribution of the two domains to change with the pressure head. As a first step, the hysteresis in the swell-shrink dynamics was not included. We also assumed that the aggregate behavior and its hydraulic properties depend only on the average aggregate water content and not on its internal real distribution. Compared to the rigid approach, the combined effect of the changing weight and that of the void ratio on the hydraulic properties in the shrinking approach induce much larger and deeper water and solute transfer from the fractures to the matrix during wetting processes. The analysis shows a systematic underestimation of the wetting front propagation times, as well as of the solute travel times and concentrations when the volume of the aggregate domain is assumed to remain constant. The combined and interacting effects of the dynamic weight and the evolution of matrix pressure head in the shrinking approach is responsible for a bimodal behavior of the water exchange term, which in turn

  15. 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.

  16. 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

  17. 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.

  18. The permeability enhancing mechanism of DMSO in ceramide bilayers simulated by molecular dynamics.

    PubMed

    Notman, Rebecca; den Otter, Wouter K; Noro, Massimo G; Briels, W J; Anwar, Jamshed

    2007-09-15

    The lipids of the topmost layer of the skin, the stratum corneum, represent the primary barrier to molecules penetrating the skin. One approach to overcoming this barrier for the purpose of delivery of active molecules into or via the skin is to employ chemical permeability enhancers, such as dimethylsulfoxide (DMSO). How these molecules exert their effect at the molecular level is not understood. We have investigated the interaction of DMSO with gel-phase bilayers of ceramide 2, the predominant lipid in the stratum corneum, by means of molecular dynamics simulations. The simulations satisfactorily reproduce the phase behavior and the known structural parameters of ceramide 2 bilayers in water. The effect of DMSO on the gel-phase bilayers was investigated at various concentrations over the range 0.0-0.6 mol fraction DMSO. The DMSO molecules accumulate in the headgroup region and weaken the lateral forces between the ceramides. At high concentrations of DMSO (> or =0.4 mol fraction), the ceramide bilayers undergo a phase transition from the gel phase to the liquid crystalline phase. The liquid-crystalline phase of ceramides is expected to be markedly more permeable to solutes than the gel phase. The results are consistent with the experimental evidence that high concentrations of DMSO fluidize the stratum corneum lipids and enhance permeability.

  19. Low-grade and anaplastic oligodendrogliomas: differences in tumour microvascular permeability evaluated with dynamic contrast-enhanced magnetic resonance imaging.

    PubMed

    Jia, Zhongzheng; Geng, Daoying; Liu, Ying; Chen, Xingrong; Zhang, Jun

    2013-08-01

    This study was designed to quantitatively assess the microvascular permeability of oligodendroglioma using the volume transfer constant (K(trans)) and the volume of the extravascular extracellular space per unit volume of tissue (V(e)) with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). We aimed to evaluate the effectiveness of K(trans) and V(e) in distinguishing between low-grade and anaplastic oligodendroglioma. The maximal values of K(trans) and V(e) for 65 patients with oligodendroglioma (27 grade II, 38 grade III) were obtained. Differences in K(trans) and V(e) between the two groups were analysed using the Mann-Whitney rank-sum test. Receiver operating characteristic (ROC) curve analyses were performed to determine the cut-off values for the K(trans) and Ve that could differentiate between low-grade and anaplastic oligodendrogliomas. Values for K(trans) and Ve in low-grade oligodendrogliomas were significantly lower than those in anaplastic oligodendrogliomas (p < 0.001 and p < 0.001, respectively). ROC curve analysis showed that cut-off values of the K(trans) (0.037 min(-1)) and Ve (0.079) could be used to distinguish between low-grade and anaplastic oligodendrogliomas in a statistically significant manner. Our results suggest that DCE-MRI can distinguish the differences in microvascular permeability between low-grade and anaplastic oligodendrogliomas.

  20. The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles

    PubMed Central

    Vitali, Victoria; Sutka, Moira; Amodeo, Gabriela; Chara, Osvaldo; Ozu, Marcelo

    2016-01-01

    Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf. We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf/Ps), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements

  1. The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles

    PubMed Central

    Vitali, Victoria; Sutka, Moira; Amodeo, Gabriela; Chara, Osvaldo; Ozu, Marcelo

    2016-01-01

    Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf. We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf/Ps), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements

  2. Investigation of aerodynamic characteristics of a hypersonic flow around bodies of revolution with a permeable tip

    NASA Astrophysics Data System (ADS)

    Sidnyaev, N. I.

    2007-03-01

    Results of experimental investigations of aerodynamic characteristics of models of high-velocity flying vehicles consisting of a combination of a blunt cone, a cylinder, and a conical tail fin are presented. The model forebody is cooled by porous blowing. The choice of such a configuration is determined by the necessity of optimizing the arrangement of high-velocity flying vehicles on the launcher and their aerodynamic characteristics under conditions of intense surface mass transfer (decrease in drag and heat transfer and increase in static and dynamic stability).

  3. Laboratory Characterization of Mechanical and Permeability Properties of Dynamically Compacted Crushed Salt

    SciTech Connect

    Hansen, F.D.; Mellegard, K.D.; Pfeifle, T.W.

    1999-02-01

    The U. S. Department of Energy plans to dispose of transuranic wastes at the Waste Isolation Pilot Plant (WIPP), a geologic repository located at a depth of about 655 meters. The WIPP underground facility is located in the bedded salt of the Salado Formation. Access to the facility is provided through vertical shafts, which will be sealed after decommissioning to limit the release of hazardous waste from the repository and to limit flow into the facility. Because limited data are available to characterize the properties of dynamically compacted crushed salt, Sandia National Laboratories authorized RE/SPEC to perform additional tests on specimens of dynamically compacted crushed salt. These included shear consolidation creep, permeability, and constant strain-rate triaxial compression tests. A limited number of samples obtained from the large compacted mass were available for use in the testing program. Thus, additional tests were performed on samples that were prepared on a smaller scale device in the RE/SPEC laboratory using a dynamic-compaction procedure based on the full-scale construction technique. The laboratory results were expected to (1) illuminate the phenomenology of crushed-salt deformation behavior and (2) add test results to a small preexisting database for purposes of estimating parameters in a crushed-salt constitutive model. The candidate constitutive model for dynamically compacted crushed salt was refined in parallel with this laboratory testing.

  4. Permeability characteristics of human endothelial monolayers seeded on different extracellular matrix proteins.

    PubMed Central

    Nooteboom, A; Hendriks, T; Ottehöller, I; van der Linden, C J

    2000-01-01

    OBJECTIVE: To investigate whether endothelial monolayer permeability changes induced by inflammatory mediators are affected by the extracellular matrix protein used for cell seeding. METHODS: Human umbilical venular endothelial cells (HUVEC) were grown to confluent monolayers on membranes coated with either collagen, fibronectin or gelatin. The permeability to albumin and dextran was then assessed, both under normal conditions and after treatment with tumor necrosis factor-alpha (TNF-alpha) and bacterial lipopolysaccharide (LPS). RESULTS: With any of the three protein coatings, tight junctions were formed all over the monolayers. The permeability of the coated membranes to albumin and dextran was reduced strongly by confluent monolayers; the relative reduction was similar for the three matrix proteins used. Pre-incubation of the monolayers with either TNF-alpha or LPS increased permeability dose dependently. However, the relative increase due to either treatment was independent of the protein used for membrane coating. CONCLUSION: The extracellular matrix protein used for initial seeding of endothelial cultures plays a minor role in determining the permeability changes induced in HUVEC monolayers by inflammatory mediators. PMID:11200364

  5. 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.

  6. 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

  7. Role of the outer pore domain in transient receptor potential vanilloid 1 dynamic permeability to large cations.

    PubMed

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

    2015-02-27

    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.

  8. 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

  9. 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)

  10. Effects of heterogeneous structure and diffusion permeability of body tissues on decompression gas bubble dynamics.

    PubMed

    Nikolaev, V P

    2000-07-01

    To gain insight into the special nature of gas bubbles that may form in astronauts, aviators and divers, we developed a mathematical model which describes the following: 1) the dynamics of extravascular bubbles formed in intercellular cavities of a hypothetical tissue undergoing decompression; and 2) the dynamics of nitrogen tension in a thin layer of intercellular fluid and in a thick layer of cells surrounding the bubbles. This model is based on the assumption that, due to limited cellular membrane permeability for gas, a value of effective nitrogen diffusivity in the massive layer of cells in the radial direction is essentially lower compared to conventionally accepted values of nitrogen diffusivity in water and body tissues. Due to rather high nitrogen diffusivity in intercellular fluid, a bubble formed just at completion of fast one-stage reduction of ambient pressure almost instantly grows to the size determined by the initial volume of the intercellular cavity, surface tension of the fluid, the initial nitrogen tension in the tissue, and the level of final pressure. The rate of further bubble growth and maximum bubble size depend on comparatively low effective nitrogen diffusivity in the cell layer, the tissue perfusion rate, the initial nitrogen tension in the tissue, and the final ambient pressure. The tissue deformation pressure performs its conservative action on bubble dynamics only in a limited volume of tissue (at a high density of formed bubbles). Our model is completely consistent with the available data concerning the random latency times to the onset of decompression sickness (DCS) symptoms associated with hypobaric decompressions simulating extravehicular activity. We believe that this model could be used as a theoretical basis for development of more adequate methods for the DCS risk prediction.

  11. 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.

  12. Permeability assessment of the focused ultrasound-induced blood-brain barrier opening using dynamic contrast-enhanced MRI

    NASA Astrophysics Data System (ADS)

    Vlachos, F.; Tung, Y.-S.; Konofagou, E. E.

    2010-09-01

    Focused ultrasound (FUS) in conjunction with microbubbles has been shown to successfully open the blood-brain barrier (BBB) in the mouse brain. In this study, we compute the BBB permeability after opening in vivo. The spatial permeability of the BBB-opened region was assessed using dynamic contrast-enhanced MRI (DCE-MRI). The DCE-MR images were post-processed using the general kinetic model (GKM) and the reference region model (RRM). Permeability maps were generated and the Ktrans values were calculated for a predefined volume of interest in the sonicated and the control area for each mouse. The results demonstrated that Ktrans in the BBB-opened region (0.02 ± 0.0123 for GKM and 0.03 ± 0.0167 min-1 for RRM) was at least two orders of magnitude higher when compared to the contra-lateral (control) side (0 and 8.5 × 10-4 ± 12 × 10-4 min-1, respectively). The permeability values obtained with the two models showed statistically significant agreement and excellent correlation (R2 = 0.97). At histological examination, it was concluded that no macroscopic damage was induced. This study thus constitutes the first permeability assessment of FUS-induced BBB opening using DCE-MRI, supporting the fact that the aforementioned technique may constitute a safe, non-invasive and efficacious drug delivery method.

  13. 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.

  14. 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

  15. Simultaneous acquisition of perfusion and permeability from corrected relaxation rates with dynamic susceptibility contrast dual gradient echo.

    PubMed

    Kim, Eun-Ju; Kim, Dae-Hong; Lee, Sang Hoon; Huh, Yong-Min; Song, Ho-Taek; Suh, Jin-Suck

    2004-04-01

    This study compared two methods, corrected (separation of T(1) and T(2)* effects) and uncorrected, in order to determine the suitability of the perfusion and permeability measures through Delta R(2)* and Delta R(1) analyses. A dynamic susceptibility contrast dual gradient echo (DSC-DGE) was used to image the fixed phantoms and flow phantoms (Sephadex perfusion phantoms and dialyzer phantom for the permeability measurements). The results confirmed that the corrected relaxation rate was linearly proportional to gadolinium-diethyltriamine pentaacetic acid (Gd-DTPA) concentration, whereas the uncorrected relaxation rate did not in the fixed phantom and simulation experiments. For the perfusion measurements, it was found that the correction process was necessary not only for the Delta R(1) time curve but also for the Delta R(2)* time curve analyses. Perfusion could not be measured without correcting the Delta R(2)* time curve. The water volume, which was expressed as the perfusion amount, was found to be closer to the theoretical value when using the corrected Delta R(1) curve in the calculations. However, this may occur in the low concentration of Gd-DTPA in tissue used in this study. For the permeability measurements based on the two-compartment model, the permeability factor (k(ev); e = extravascular, v = vascular) from the outside to the inside of the hollow fibers was greater in the corrected Delta R(1) method than in the uncorrected Delta R(1) method. The differences between the corrected and the uncorrected Delta R(1) values were confirmed by the simulation experiments. In conclusion, this study proposes that the correction for the relaxation rates, Delta R(2)* and Delta R(1), is indispensable in making accurate perfusion and permeability measurements, and that DSC-DGE is a useful method for obtaining information on perfusion and permeability, simultaneously. PMID:15062926

  16. 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

  17. 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

  18. 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.

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

    PubMed

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

    2006-08-10

    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.

  20. The role of python eggshell permeability dynamics in a respiration-hydration trade-off.

    PubMed

    Stahlschmidt, Zachary R; Heulin, Benoit; DeNardo, Dale F

    2010-01-01

    Parental care is taxonomically widespread because it improves developmental conditions and thus fitness of offspring. Although relatively simplistic compared with parental behaviors of other taxa, python egg-brooding behavior exemplifies parental care because it mediates a trade-off between embryonic respiration and hydration. However, because egg brooding increases gas-exchange resistance between embryonic and nest environments and because female pythons do not adjust their brooding behavior in response to the increasing metabolic requirements of developing offspring, python egg brooding imposes hypoxic costs on embryos during the late stages of incubation. We conducted a series of experiments to determine whether eggshells coadapted with brooding behavior to minimize the negative effects of developmental hypoxia. We tested the hypotheses that python eggshells (1) increase permeability over time to accommodate increasing embryonic respiration and (2) exhibit permeability plasticity in response to chronic hypoxia. Over incubation, we serially measured the atomic and structural components of Children's python (Antaresia childreni) eggshells as well as in vivo and in vitro gas exchange across eggshells. In support of our first hypothesis, A. childreni eggshells exhibited a reduced fibrous layer, became more permeable, and facilitated greater gas exchange as incubation progressed. Our second hypothesis was not supported, as incubation O(2) concentration did not affect the shells' permeabilities to O(2) and H(2)O vapor. Our results suggest that python eggshell permeability changes during incubation but that the alterations over time are fixed and independent of environmental conditions. These findings are of broad evolutionary interest because they demonstrate that, even in relatively simple parental-care models, successful parent-offspring relationships depend on adjustments made by both the parent (i.e., egg-brooding behavioral shifts) and the offspring (i

  1. 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

  2. Dynamic characteristics of pulsed supersonic fuel sprays

    NASA Astrophysics Data System (ADS)

    Pianthong, K.; Matthujak, A.; Takayama, K.; Milton, B. E.; Behnia, M.

    2008-06-01

    This paper describes the dynamic characteristics of pulsed, supersonic liquid fuel sprays or jets injected into ambient air. Simple, single hole nozzles were employed with the nozzle sac geometries being varied. Different fuel types, diesel fuel, bio-diesel, kerosene, and gasoline were used to determine the effects of fuel properties on the spray characteristics. A vertical two-stage light gas gun was employed as a projectile launcher to provide a high velocity impact to produce the liquid jet. The injection pressure was around 0.88-1.24 GPa in all cases. The pulsed, supersonic fuel sprays were visualized by using a high-speed video camera and shadowgraph method. The spray tip penetration and velocity attenuation and other characteristics were examined and are described here. An instantaneous spray tip velocity of 1,542 m/s (Mach number 4.52) was obtained. However, this spray tip velocity can be sustained for only a very short period (a few microseconds). It then attenuates very quickly. The phenomenon of multiple high frequency spray pulses generated by a single shot impact and the changed in the angle of the shock structure during the spray flight, which had already been observed in previous studies, is again noted. Multiple shock waves from the conical nozzle spray were also clearly captured.

  3. 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.

  4. 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

  5. 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.

  6. 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

  7. Aluminum Honeycomb Characteristics in Dynamic Crush Environments

    SciTech Connect

    Bateman, Vesta I.; Swanson, Lloyd H.

    1999-07-01

    Fifteen aluminum honeycomb cubes (3 in.) have been crushed in the Mechanical Shock Laboratory's drop table testing machines. This report summarizes shock experiments with honeycomb densities of 22.1 pcf and 38.0 pcf and with crush weights of 45 lb, 168 lb, and 268 lb. The honeycomb samples were crushed in all three orientations, W, L, and T. Most of the experiments were conducted at an impact velocity of {approx}40 fps, but higher velocities of up to 90 fps were used for selected experiments. Where possible, multiple experiments were conducted for a specific orientation and density of the honeycomb samples. All results are for Hexcel honeycomb except for one experiment with Alcore honeycomb and have been evaluated for validity. This report contains the raw acceleration data measured on the top of the drop table carriage, pictures of the crushed samples, and normalized force-displacement curves for all fifteen experiments. These data are not strictly valid for material characteristics in L and T orientations because the cross-sectional area of the honeycomb changed (split) during the crush. However, these are the best data available at this time. These dynamic crush data do suggest a significant increase in crush strength to 8000 psi ({approximately} 25-30% increase) over quasi-static values of {approximately}6000 psi for the 38.0 pcf Hexcel Honeycomb in the T-orientation. An uncertainty analysis is included and estimates the error in these data.

  8. 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

  9. 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.

  10. Dynamics and Interactions of OmpF and LPS: Influence on Pore Accessibility and Ion Permeability.

    PubMed

    Patel, Dhilon S; Re, Suyong; Wu, Emilia L; Qi, Yifei; Klebba, Phillip E; Widmalm, Göran; Yeom, Min Sun; Sugita, Yuji; Im, Wonpil

    2016-02-23

    The asymmetric outer membrane of Gram-negative bacteria is formed of the inner leaflet with phospholipids and the outer leaflet with lipopolysaccharides (LPS). Outer membrane protein F (OmpF) is a trimeric porin responsible for the passive transport of small molecules across the outer membrane of Escherichia coli. Here, we report the impact of different levels of heterogeneity in LPS environments on the structure and dynamics of OmpF using all-atom molecular dynamics simulations. The simulations provide insight into the flexibility and dynamics of LPS components that are highly dependent on local environments, with lipid A being the most rigid and O-antigen being the most flexible. Increased flexibility of O-antigen polysaccharides is observed in heterogeneous LPS systems, where the adjacent O-antigen repeating units are weakly interacting and thus more dynamic, compared to homogeneous LPS systems in which LPS interacts strongly with each other with limited overall flexibility due to dense packing. The model systems were validated by comparing molecular-level details of interactions between OmpF surface residues and LPS core sugars with experimental data, establishing the importance of LPS core oligosaccharides in shielding OmpF surface epitopes recognized by monoclonal antibodies. There are LPS environmental influences on the movement of bulk ions (K(+) and Cl(-)), but the ion selectivity of OmpF is mainly affected by bulk ion concentration. PMID:26910429

  11. 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

  12. Enhanced Neuroplasticity by the Metabolic Enhancer Piracetam Associated with Improved Mitochondrial Dynamics and Altered Permeability Transition Pore Function

    PubMed Central

    Stockburger, Carola; Miano, Davide; Pallas, Thea; Müller, Walter E.

    2016-01-01

    The mitochondrial cascade hypothesis of dementia assumes mitochondrial dysfunction leading to reduced energy supply, impaired neuroplasticity, and finally cell death as one major pathomechanism underlying the continuum from brain aging over mild cognitive impairment to initial and advanced late onset Alzheimer's disease. Accordingly, improving mitochondrial function has become an important strategy to treat the early stages of this continuum. The metabolic enhancer piracetam has been proposed as possible prototype for those compounds by increasing impaired mitochondrial function and related aspects like mechanisms of neuroplasticity. We here report that piracetam at therapeutically relevant concentrations improves neuritogenesis in the human cell line SH-SY5Y over conditions mirroring the whole spectrum of age-associated cognitive decline. These effects go parallel with improvement of impaired mitochondrial dynamics shifting back fission and fusion balance to the energetically more favorable fusion site. Impaired fission and fusion balance can also be induced by a reduction of the mitochondrial permeability transition pore (mPTP) function as atractyloside which indicates the mPTP has similar effects on mitochondrial dynamics. These changes are also reduced by piracetam. These findings suggest the mPTP as an important target for the beneficial effects of piracetam on mitochondrial function. PMID:27747106

  13. 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.

  14. Modeling the dynamic characteristics of pneumatic muscle.

    PubMed

    Reynolds, D B; Repperger, D W; Phillips, C A; Bandry, G

    2003-03-01

    A pneumatic muscle (PM) system was studied to determine whether a three-element model could describe its dynamics. As far as the authors are aware, this model has not been used to describe the dynamics of PM. A new phenomenological model consists of a contractile (force-generating) element, spring element, and damping element in parallel. The PM system was investigated using an apparatus that allowed precise and accurate actuation pressure (P) control by a linear servo-valve. Length change of the PM was measured by a linear potentiometer. Spring and damping element functions of P were determined by a static perturbation method at several constant P values. These results indicate that at constant P, PM behaves as a spring and damper in parallel. The contractile element function of P was determined by the response to a step input in P, using values of spring and damping elements from the perturbation study. The study showed that the resulting coefficient functions of the three-element model describe the dynamic response to the step input of P accurately, indicating that the static perturbation results can be applied to the dynamic case. This model is further validated by accurately predicting the contraction response to a triangular P waveform. All three elements have pressure-dependent coefficients for pressure P in the range 207 < or = P < or = 621 kPa (30 < or = P < or = 90 psi). Studies with a step decrease in P (relaxation of the PM) indicate that the damping element coefficient is smaller during relaxation than contraction.

  15. Dynamic characteristics of observed sudden warmings

    NASA Technical Reports Server (NTRS)

    Dartt, D. G.; Venne, D. E.

    1986-01-01

    The planetary wave dynamics of stratospheric sudden warmings in the Northern Hemisphere for a large number of observed events that occurred during winters from 1970 to 1975 and 1978 to 1981 are investigated. The analysis describes wave propagation and zonal flow interaction from the troposphere upwards to near 50 km, and in some years to near 80 km. Three primary topics are covered here: (1) the interaction of zonally propagating and quasi-stationary planetary waves during warming events; (2) planetary wave influence on zonal flow near the stratopause; and (3) planetary wave propagation to near 80 km as seen from Stratospheric and Mesospheric Sounder (SAMS) data.

  16. Precision in measurements of perfusion and microvascular permeability with T1-weighted dynamic contrast-enhanced MRI.

    PubMed

    Kershaw, Lucy E; Buckley, David L

    2006-11-01

    Dynamic contrast-enhanced MRI is used to estimate microvascular parameters by tracer kinetics analysis. The time for the contrast agent to travel from the artery to the tissue of interest (bolus arrival time (BAT)) is an important parameter that must be measured in such studies because inaccurate estimates or neglect of BAT contribute to inaccuracy in model fitting. Furthermore, although the precision with which these parameters are estimated is very important, it is rarely reported. To address these issues, two investigations were undertaken. First, simulated data were used to validate an independent method for estimation of BAT. Second, the adiabatic approximation to the tissue homogeneity model was fitted to experimental data acquired in prostate and muscle tissue of 22 patients with prostate cancer. A bootstrap error analysis was performed to estimate the precision of parameter estimates. The independent method of estimating BAT was found to be more accurate and precise than a model-fitting approach. Estimated precisions for parameters measured in the prostate gland were 14% for extraction fraction (median coefficient of variation), 19% for blood flow, 28% for permeability-surface area product, 35% for volume of the extravascular-extracellular space, and 36% for blood volume. Techniques to further reduce uncertainty are discussed.

  17. 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.

  18. 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

  19. Permeability Asymmetry in Composite Porous Ceramic Membranes

    NASA Astrophysics Data System (ADS)

    Kurcharov, I. M.; Laguntsov, N. I.; Uvarov, V. I.; Kurchatova, O. V.

    The results from the investigation of transport characteristics and gas transport asymmetry in bilayer composite membranes are submitted. These membranes are produced by SHS method. Asymmetric effect and hysteresis of permeability in nanoporous membranes are detected. It's shown, that permeability ratio (asymmetry value of permeability) increases up to several times. The asymmetry of permeability usually decreases monotonically with the pressure decrease.

  20. Dynamical characteristics of Phobos and Deimos.

    NASA Technical Reports Server (NTRS)

    Burns, J. A.

    1972-01-01

    The orbital properties of the two small Martian satellites, Phobos and Deimos, are discussed, as well as those dynamical constants of Mars that can be determined from the satellite orbits. The secular acceleration of the mean motion of Phobos is shown to be very small. Of mechanisms that could cause any such acceleration, only tidal friction appears to be important. From the orbital evolution of the Martian satellites under tidal forces, Phobos and Deimos seem to have originated in nearly circular orbits of low inclination fairly close to the distance at which a satellite's orbital period is the planet's rotation period. It is proposed that the Martian satellites were born at the same time as Mars from equatorial dust clouds. The satellites are predicted to be locked in synchronous rotation, with their axes of minimum moment of inertia pointing on the average toward Mars, whereas their maximum axes are approximately normal to their orbit planes.

  1. Dynamic characteristics of tweeting and tweet topics

    NASA Astrophysics Data System (ADS)

    Kwon, Hyun Woong; Choi, M. Y.; Kim, Ho Sung; Lee, Keumsook

    2012-02-01

    Twitter, having more than 200 million world users and more than 4 million Korean users, is still growing fast. Because Twitter users can `tweet' about any topic within the 140-character limit, and other users who follow the users and see the tweets can `retweet' them, Twitter is regarded as a new medium of transferring and sharing information. Nevertheless, the propensities of Twitter users to tweet or to retweet still remain unclear. In order to investigate these propensities, we propose a simple model for the dynamics of the total number of tweets about specific topics. We then observe that the topics can be categorized into three kinds according to predictability and sustainability: predictable events, unpredictable events, and sustainable events. Comparing model results with real data, we infer the tweet propensities motivated by external causes as well as retweet propensities.

  2. The contract murderer: patterns, characteristics, and dynamics.

    PubMed

    Schlesinger, L B

    2001-09-01

    A case of an independent professional contract murderer, who killed over 100 people, is reported. After eluding law enforcement for 30 years, the subject killed several associates who he believed could implicate him in various crimes. These homicides eventually led to his arrest, since the victims were individuals who could be linked to him. This hit man had a background of poverty and childhood abuse but, as an adult, had pursued a middle-class lifestyle and kept his family totally separate from his criminal career. In addition, he had a number of characteristics that helped him carry out his crimes in a highly planned, methodical, and organized manner: he had adept social judgment; personality traits of orderliness, control, and paranoid vigilance; useful defense mechanisms of rationalization and reframing; and an exceptional ability to encapsulate emotions. This case is discussed within the context of contract murder, a crime that occurs relatively frequently and is probably increasing; yet it often goes undetected, the arrest rate is low, and the offender is rarely studied.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Dynamic Permeability Increase During Flow of CO2 Saturated Water Through a Siliciclastic Caprock: an Experimental and Analytical Approach into the Geochemical Impact of CO2 Injection

    NASA Astrophysics Data System (ADS)

    Worden, R. H.; Armitage, P. J.; Faulkner, D. R.

    2011-12-01

    Field trials into CO2 sequestration are currently being undertaken at the In Salah gas field, Algeria. As a part of a wider project, we are experimentally investigating the geochemical and geomechanical effects of CO2 sequestration on the lower caprock. These are poorly sorted siltstones, cemented with quartz, illite, siderite and chlorite. CO2 injection into saline aquifers and depleted petroleum reservoirs alters in situ geochemical conditions. CO2-rich aqueous fluids are acidic and have the potential to geochemically interact with caprocks. These changes will affect caprock properties such as strength and fluid flow properties, which in turn may facilitate CO2 migration and escape from the intended storage structure. Evaluation of these effects on samples of well characterised caprocks will be crucial in helping to evaluate the long term integrity of CO2 storage. We present results from direct experimental and analytical evaluation of dynamic permeability evolution for the flow of CO2 saturated water through a sample of the lower caprock from the In Salah CO2 storage site. Permeability of this sample was approximately 10-20 m2. Permeability was found to increase by approximately 1 order of magnitude over 72 hours of continuous flow. Porosity was also found to increase, whilst surface area, and sample weight decreased. SEM, XRD, and FTIR analyses revealed dissolution of chlorite and siderite to be the cause of the increase in permeability. This change in permeability, and dissolution of minerals, may locally lead to decreased strength of the caprock and decreased sealing capacity. However, local re-precipitation processes may serve to reverse these processes.

  9. 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.

  10. 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.

  11. 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.

  12. Edible arabinoxylan-based films. 1. Effects of lipid type on water vapor permeability, film structure, and other physical characteristics.

    PubMed

    Péroval, Claudine; Debeaufort, Frédéric; Despré, Denis; Voilley, Andrée

    2002-07-01

    Arabinoxylans (AX) are natural fibers extracted from maize bran, an industrial byproduct. To promote this polymer as a food ingredient, development of edible coatings and films had been proposed. Indeed, composite arabinoxylan-based films were prepared by emulsifying a fat: palmitic acid, oleic acid, triolein, or a hydrogenated palm oil (OK35). Lipid effects on water vapor permeability (WVP), surface hydrophobicity (contact angles), lipid particle size, and mechanical properties were investigated. Results showed that OK35-AX emulsion films had the lowest WVP. Emulsified films presented a bimodal particle size distribution; however, the smallest particle mean diameter (0.54 microm) was observed in OK35-AX emulsion films. Contact angles of water comparable to those observed for LDPE films (>90 degrees ) are measured on the OK35-AX film surface. Finally, only triolein-AX emulsion films had elongation higher than films without lipid. These results suggest that OK35 enhances functional properties of AX-based films and should be retained for further research.

  13. Dynamic Calibration and Verification Device of Measurement System for Dynamic Characteristic Coefficients of Sliding Bearing.

    PubMed

    Chen, Runlin; Wei, Yangyang; Shi, Zhaoyang; Yuan, Xiaoyang

    2016-01-01

    The identification accuracy of dynamic characteristics coefficients is difficult to guarantee because of the errors of the measurement system itself. A novel dynamic calibration method of measurement system for dynamic characteristics coefficients is proposed in this paper to eliminate the errors of the measurement system itself. Compared with the calibration method of suspension quality, this novel calibration method is different because the verification device is a spring-mass system, which can simulate the dynamic characteristics of sliding bearing. The verification device is built, and the calibration experiment is implemented in a wide frequency range, in which the bearing stiffness is simulated by the disc springs. The experimental results show that the amplitude errors of this measurement system are small in the frequency range of 10 Hz-100 Hz, and the phase errors increase along with the increasing of frequency. It is preliminarily verified by the simulated experiment of dynamic characteristics coefficients identification in the frequency range of 10 Hz-30 Hz that the calibration data in this frequency range can support the dynamic characteristics test of sliding bearing in this frequency range well. The bearing experiments in greater frequency ranges need higher manufacturing and installation precision of calibration device. Besides, the processes of calibration experiments should be improved. PMID:27483283

  14. Dynamic Calibration and Verification Device of Measurement System for Dynamic Characteristic Coefficients of Sliding Bearing

    PubMed Central

    Chen, Runlin; Wei, Yangyang; Shi, Zhaoyang; Yuan, Xiaoyang

    2016-01-01

    The identification accuracy of dynamic characteristics coefficients is difficult to guarantee because of the errors of the measurement system itself. A novel dynamic calibration method of measurement system for dynamic characteristics coefficients is proposed in this paper to eliminate the errors of the measurement system itself. Compared with the calibration method of suspension quality, this novel calibration method is different because the verification device is a spring-mass system, which can simulate the dynamic characteristics of sliding bearing. The verification device is built, and the calibration experiment is implemented in a wide frequency range, in which the bearing stiffness is simulated by the disc springs. The experimental results show that the amplitude errors of this measurement system are small in the frequency range of 10 Hz–100 Hz, and the phase errors increase along with the increasing of frequency. It is preliminarily verified by the simulated experiment of dynamic characteristics coefficients identification in the frequency range of 10 Hz–30 Hz that the calibration data in this frequency range can support the dynamic characteristics test of sliding bearing in this frequency range well. The bearing experiments in greater frequency ranges need higher manufacturing and installation precision of calibration device. Besides, the processes of calibration experiments should be improved. PMID:27483283

  15. 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.

  16. 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.

  17. 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.

  18. Dynamic characteristics of double tunneling-injection quantum dot lasers

    NASA Astrophysics Data System (ADS)

    Asryan, Levon V.

    2015-03-01

    Dynamic characteristics of double tunneling-injection (DTI) quantum dot (QD) lasers are studied. To reveal the potential of such lasers for high-speed direct modulation of their optical output by pump current, fast carrier injection into QDs and no carrier leakage from QDs are assumed. The small-signal analysis of rate equations is applied. The modulation bandwidth is calculated as a function of the dc component of the injection current density and parameters of the laser structure.

  19. 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.

  20. 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.

  1. 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.

  2. Dynamic fluid-loss characteristics of CO/sub 2/ foam fracturing fluids

    SciTech Connect

    Harris, P.C.

    1984-09-01

    High quality carbon dioxide foam fracturing has become a very popular new stimulation tool in the past two years. Dynamic fluid loss measurements were performed on a broad range of core samples to measure the effect of several parameters on CO/sub 2/ foam fluid loss coefficients. The parameters tested were core permeability, foam quality, gelling agent concentration in the aqueous phase, and core temperature. Measurements were performed in a recirculating fluid flow test loop. A variation of one order of magnitude in Cw for two orders of magnitude change in permeability was observed from 0.02 to 10 md. For permeability below 1 md, there was no effect due to quality. Fluid loss control improved as gelling agent concentration in the liquid phase increased. Cw increased with increasing temperature due to temperature thinning of the aqueous phase. Passage of CO/sub 2/ foams through porous media caused a significant modification in quality from the input to the effluent fluid. The ratio of liquid to gas passing through the core was measured as a function of core permeability, quality and gelling agent concentration. In low permeability cores flow proceeded as separate phases; whereas, in higher permeability cores, the foam structure remained more nearly intact. CO/sub 2/ foams were found to be very similar to N/sub 2/ foams with respect to the above parameters.

  3. Hydroelastic dynamic characteristics of a slender axis-symmetric body

    NASA Astrophysics Data System (ADS)

    Chen, Weimin; Li, Min; Zheng, Zhongqin; Zhang, Liwu

    2010-07-01

    The slender axis-symmetric submarine body moving in the vertical plane is the object of our investigation. A coupling model is developed where displacements of a solid body as a Euler beam (consisting of rigid motions and elastic deformations) and fluid pressures are employed as basic independent variables, including the interaction between hydrodynamic forces and structure dynamic forces. Firstly the hydrodynamic forces, depending on and conversely influencing body motions, are taken into account as the governing equations. The expressions of fluid pressure are derived based on the potential theory. The characteristics of fluid pressure, including its components, distribution and effect on structure dynamics, are analyzed. Then the coupling model is solved numerically by means of a finite element method (FEM). This avoids the complicacy, combining CFD (fluid) and FEM (structure), of direct numerical simulation, and allows the body with a non-strict ideal shape so as to be more suitable for practical engineering. An illustrative example is given in which the hydroelastic dynamic characteristics, natural frequencies and modes of a submarine body are analyzed and compared with experimental results. Satisfactory agreement is observed and the model presented in this paper is shown to be valid.

  4. The effect of cavitation on the hydrofoil dynamic characteristics

    NASA Astrophysics Data System (ADS)

    Yang, J.; Zhou, L. J.; Wang, Z. W.; Zhi, F. L.

    2013-12-01

    Cavitation in hydraulic machinery usually causes a change of fluid dynamic characteristics. In order to predict the effect of cavitation on hydrofoil characteristics, the cavitation around a hydrofoil was studied numerically. The full cavitation model and a modified RNG k ε-turbulence model were used. The finite volume method with the SIMPLEC scheme was used to discretize the time-dependent equations. The second-order upwind scheme was used for the convection terms with the central difference scheme used for the diffusion terms. Fluid dynamic characteristics including cavity's length, shedding frequency, pressure coefficient and lift and drag force coefficients features in a range of cavitation number were analyzed. Computations were made on the three-dimensional flow field around a NACA66 hydrofoil at 8° angle of attack. The recording force signals exhibit periodic behaviours with the time. And the cavity shedding frequency increases with the cavitation number, however the length of cavity decreases with the cavitation number, which result in changing of lift-drag ratio. Especially for larger cavitation numbers, the lift drag ratio of cavitation field is getting closer and closer to that of non-cavitation field.

  5. 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

  6. 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.

  7. Effects of rail dynamics and friction characteristics on curve squeal

    NASA Astrophysics Data System (ADS)

    Ding, B.; Squicciarini, G.; Thompson, D. J.

    2016-09-01

    Curve squeal in railway vehicles is an instability mechanism that arises in tight curves under certain running and environmental conditions. In developing a model the most important elements are the characterisation of friction coupled with an accurate representation of the structural dynamics of the wheel. However, the role played by the dynamics of the rail is not fully understood and it is unclear whether this should be included in a model or whether it can be safely neglected. This paper makes use of previously developed time domain and frequency domain curve squeal models to assess whether the presence of the rail and the falling characteristics of the friction force can modify the instability mechanisms and the final response. For this purpose, the time-domain model has been updated to include the rail dynamics in terms of its state space representation in various directions. Frequency domain and time domain analyses results show that falling friction is not the only reason for squeal and rail dynamics can play an important role, especially under constant friction conditions.

  8. Quantifying dynamic characteristics of human walking for comprehensive gait cycle.

    PubMed

    Mummolo, Carlotta; Mangialardi, Luigi; Kim, Joo H

    2013-09-01

    Normal human walking typically consists of phases during which the body is statically unbalanced while maintaining dynamic stability. Quantifying the dynamic characteristics of human walking can provide better understanding of gait principles. We introduce a novel quantitative index, the dynamic gait measure (DGM), for comprehensive gait cycle. The DGM quantifies the effects of inertia and the static balance instability in terms of zero-moment point and ground projection of center of mass and incorporates the time-varying foot support region (FSR) and the threshold between static and dynamic walking. Also, a framework of determining the DGM from experimental data is introduced, in which the gait cycle segmentation is further refined. A multisegmental foot model is integrated into a biped system to reconstruct the walking motion from experiments, which demonstrates the time-varying FSR for different subphases. The proof-of-concept results of the DGM from a gait experiment are demonstrated. The DGM results are analyzed along with other established features and indices of normal human walking. The DGM provides a measure of static balance instability of biped walking during each (sub)phase as well as the entire gait cycle. The DGM of normal human walking has the potential to provide some scientific insights in understanding biped walking principles, which can also be useful for their engineering and clinical applications.

  9. [Dynamic characteristics of alternate strides in cross-country skiing].

    PubMed

    Gagnon, M

    1980-03-01

    Seven instructors in cross-country skiing were filmed during the performance of the alternate stride at three different velocities: maximal, medium and slow. The dynamic characteristics of the movement were analyzed. On the basis of spatio-temporal analyses, it was found that the alternate stride is a motion essentially propulsive with the predominance of the superior limbs to propulsion. The skier maintains or increases his velocity at the beginning of the glide which is possibly attributed to the transfer of momentum of the recovery leg. A decrease in horizontal velocity is observed at the end of the glide. At maximal speed, the asynchronous character of the actions by the superior and inferior limbs is more important; there is a reduced emphasis in the actions by the superior limbs. At medium speed, the following characteristics are observed: a reduced importance in the asynchronous actions, a larger preponderance to the gliding phase and a smaller elevation of the skier's center of gravity.

  10. Study of Dynamic Characteristics of Aeroelastic Systems Utilizing Randomdec Signatures

    NASA Technical Reports Server (NTRS)

    Chang, C. S.

    1975-01-01

    The feasibility of utilizing the random decrement method in conjunction with a signature analysis procedure to determine the dynamic characteristics of an aeroelastic system for the purpose of on-line prediction of potential on-set of flutter was examined. Digital computer programs were developed to simulate sampled response signals of a two-mode aeroelastic system. Simulated response data were used to test the random decrement method. A special curve-fit approach was developed for analyzing the resulting signatures. A number of numerical 'experiments' were conducted on the combined processes. The method is capable of determining frequency and damping values accurately from randomdec signatures of carefully selected lengths.

  11. The Evolution of Deformation-Induced Grain-Boundary Porosity and Dynamic Permeability in Crustal Fault Zones: Insights From the Alpine Fault, New Zealand

    NASA Astrophysics Data System (ADS)

    Sauer, K. M.; Toy, V.

    2015-12-01

    Fluids and minor phases have an important influence on the bulk rheology of a deforming rock mass, but they are not uniformly distributed at any scale within fault zones. Additionally, exhumed ductile shear zones show little interconnected porosity or static permeability, requiring a dynamic process at depth to allow fluids to access the deforming rock mass. It was recently recognized that reactive fluids interact with high-strain sites to generate cavities on quartz grain boundaries, increasing the grain-scale porosity and dynamic permeability of the rock and allowing for additional fluids to infiltrate the shear zone along interlinking cavities, stimulating further reaction and cavitation. Grain-boundary cavities and fine-grained secondary phases impede grain-boundary mobility and cause a transition in deformation mechanisms from grain-size insensitive dislocation creep to grain-size sensitive creep, which is recognized as a weakening mechanism that promotes strain localisation. At present, it is unclear how the distribution of grain-boundary pores within fault rocks reflects the bulk mineralogy and phase arrangement, which is a function of shear strain. We have used micro-computed x-ray tomography (μ-CT), SEM imaging, and EDS analyses to examine how the distribution of grain-boundary pores varies in relation to the arrangement of secondary phases in exhumed protomylonites, mylonites, and ultramylonites within the actively-deforming Alpine Fault zone, and in samples acquired from the Deep Fault Drilling Project (DFDP). Additionally, EBSD is coupled with µ-CT and EDS analyses to characterise the evolution of microstructures in three dimensions across a finite strain gradient. Here we examine the relationship and competition between grain-boundary cavitation and microstructural processes during deformation in a high-strain shear zone, and discuss the implications of these grain-scale deformation processes on strain localisation and continental fault zone dynamics.

  12. Permeability equipment for porous friction surfaces

    NASA Astrophysics Data System (ADS)

    Standiford, D. L.; Graul, R. A.; Lenke, L. R.

    1985-04-01

    Hydroplaning is the loss of traction between tires and pavement due to the presence of a layer of water. This loss of traction can result in loss of vehicle control. A porous friction surface (PFS) applied over an existing pavement permits the water to drain laterally and vertically away from the tire path, effectively lowering hydroplaning potential. Equipment used to measure pavement drainage (permeability) is discussed with respect to usage on porous friction surface. Background information on hydroplaning, flow theory, and PFS field performance as they are affected by permeability are also presented. Two dynamic test devices and four static devices are considered for measuring PFS permeability. Permeability tests are recommended to measure PFS permeability for maintenance purposes and construction control. Dynamic devices cited could possibly estimate hydroplaning potential; further research must be done to determine this. Permeability devices cannot be used to accurately estimate friction of a pavement surface, however, decreased permeability of a pavement infers a decrease in friction.

  13. 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.

  14. 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.

  15. Experiment of static and dynamic characteristics of spiral grooved seals

    NASA Technical Reports Server (NTRS)

    Iwatsubo, T.; Sheng, B. C.; Ono, M.

    1991-01-01

    The leakages and the dynamic characteristics of six types of spiral grooved seals are experimentally investigated. The effect of the helix angle of the seal is investigated mainly under the condition of the same nominal clearances, land and groove lengths, and groove depths. The dynamic characteristics are measured for various parameters such as preswirl velocity, pressure difference between inlet and outlet of the seal, whirling amplitude, whirling speed, and rotating speed of the rotor. The results are also compared with leakage increases with the increase of the helix angle, but as the rotating speed increases, the leakages of the larger helix angle seals quickly drop. The leakage of the smooth-stator (SS)/smooth-grooved rotor (SGR) seal drops faster than that of the spiral-grooved stator (SGS)/smooth-rotor (SR) seal. It is found that a circumferential flow can be produced by the flow along the helix angle direction, and this circumferential flow acts as a negative swirl. For the present helix angle range, there is an optimum helix angle with which the seal has a comparatively positive effect on the rotor stability. Compared with the SGS/SR seals, the SS/SGR seal has a worse effect on the rotor stability.

  16. 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.

  17. 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

  18. 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.

  19. 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

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

    DOE PAGES

    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

  1. Metal hydrides reactors with improved dynamic characteristics for a fast cycling hydrogen compressor

    NASA Astrophysics Data System (ADS)

    Popeneciu, G.; Coldea, I.; Lupu, D.; Misan, I.; Ardelean, O.

    2009-08-01

    This paper presents an investigation of coupled heat and mass transfer process in metal hydrides hydrogen storage reactors. Hydrogen storage and compression performance of our designed and developed reactors are studied by varying the operating parameters and analyzing the effects of metal hydride bed parameters. The metal alloy selected to characterize the cycling behaviour of reactors is LaNi5, material synthesized and characterized by us in the range 20-80°C. Four types of metal hydride reactors were tested with the aim to provide a fast hydrogen absorption-desorption cycle, able to be thermally cycled at rapid rates. Some new technical solutions have been studied to make a step forward in reducing the duration of the reactors cycle, which combines the effective increase of the thermal conductivity and good permeability to hydrogen gas. Dynamic characteristic of developed fast metal hydride reactors is improved using our novel mixture metal hydride-CA conductive additive due to the increased effective thermal conductivity of the alloy bed. The advanced hydride bed design with high heat transfer capabilities can be thermally cycled at a rapid rate, under 120 seconds, in order to process high hydrogen flow rates.

  2. 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).

  3. 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.

  4. Dynamics and Stability and Control Characteristics of the X-37

    NASA Technical Reports Server (NTRS)

    Chaudhary, Ashwani; Nguyen, Viet; Tran, Hoi; Poladian, David; Falangas, Eric; Turner, Susan G. (Technical Monitor)

    2001-01-01

    This paper presents the stability and control analysis and the control design results for the Boeing/NASA/AFRL X-37. The X-37 is a flight demonstrator vehicle that will go into space and after its mission, autonomously reenter and land on a conventional runway. This paper studies the dynamics and control of the X-37 from atmospheric reentry through landing. A nominal trajectory that lands on the Edwards Air Force Base Lakebed is considered for all the analysis and design. The X-37's longitudinal and lateral/directional bare-airframe characteristics are presented. The level of maneuvering control power is assessed. Vehicle trim with multiple surfaces is discussed. Special challenges where the wings loose roll effectiveness are discussed and solutions are presented. Aerodynamic uncertainties and flexibility modeling issues are presented. Control design results and robustness analysis methods are presented. Results are provided for the Entry, Terminal Area Energy Management (TAEM), and Approach and Land phases.

  5. 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.

  6. The dynamic impact characteristics of tennis balls with tennis rackets.

    PubMed

    Haake, S J; Carré, M J; Goodwill, S R

    2003-10-01

    The dynamic properties of six types of tennis balls were measured using a force platform and high-speed digital video images of ball impacts on rigidly clamped tennis rackets. It was found that the coefficient of restitution reduced with velocity for impacts on a rigid surface or with a rigidly clamped tennis racket. Pressurized balls had the highest coefficient of restitution, which decreased by 20% when punctured. Pressureless balls had a coefficient of restitution approaching that of a punctured ball at high speeds. The dynamic stiffness of the ball or the ball-racket system increased with velocity and pressurized balls had the highest stiffness, which decreased by 35% when punctured. The characteristics of pressureless balls were shown to be similar to those of punctured balls at high velocity and it was found that lowering the string tension produced a smaller range of stiffness or coefficient of restitution. It was hypothesized that players might consider high ball stiffness to imply a high coefficient of restitution. Plots of coefficient of restitution versus stiffness confirmed the relationship and it was found that, generally, pressurized balls had a higher coefficient of restitution and stiffness than pressureless balls. The players might perceive these parameters through a combination of sound, vibration and perception of ball speed off the racket. PMID:14620027

  7. 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.

  8. Dynamical characteristics of atmospheric aerosols over IG region

    NASA Astrophysics Data System (ADS)

    Sharma, Manish; Singh, Ramesh P.; Kumar, Rajesh

    2016-05-01

    The dynamical characteristics of atmospheric aerosols over the Indo-Gangetic (IG) region are primarily dependent on the geographical settings and meteorological conditions. Detailed analysis of multi satellite data and ground observations have been carried out over three different cities i.e. Kanpur, Greater Noida and Amritsar during 2010-2013. Level-3 Moderate Resolution Imaging Spectroradiometer (MODIS) terra daily global grid product with spatial resolution of 1° × 1° shows the mean AOD at 500 nm wavelength value of 0.73, 0.70 and 0.67 with the standard deviation of 0.43, 0.39 and 0.36 respectively over Amritsar, Greater Noida and Kanpur. Our detailed analysis shows characteristic behavior of aerosols from west to east in the IG region depending upon the proximity of desert regions of Arabia. We have observed large influx of dusts from the Thar desert and Arabia peninsula during pre-monsoon season (April-June), highly affecting Amritsar which is close to the desert region.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Analysis of Cancer-Targeting Alkylphosphocholine Analogue Permeability Characteristics Using a Human Induced Pluripotent Stem Cell Blood-Brain Barrier Model.

    PubMed

    Clark, Paul A; Al-Ahmad, Abraham J; Qian, Tongcheng; Zhang, Ray R; Wilson, Hannah K; Weichert, Jamey P; Palecek, Sean P; Kuo, John S; Shusta, Eric V

    2016-09-01

    Cancer-targeting alkylphosphocholine (APC) analogues are being clinically developed for diagnostic imaging, intraoperative visualization, and therapeutic applications. These APC analogues derived from chemically synthesized phospholipid ethers were identified and optimized for cancer-targeting specificity using extensive structure-activity studies. While they strongly label human brain cancers associated with disrupted blood-brain barriers (BBB), APC permeability across intact BBB remains unknown. Three of our APC analogues, CLR1404 (PET radiotracer), CLR1501 (green fluorescence), and CLR1502 (near-infrared fluorescence), were tested for permeability across a BBB model composed of human induced pluripotent stem cell-derived brain microvascular endothelial cells (iPSC-derived BMECs). This in vitro BBB system has reproducibly consistent high barrier integrity marked by high transendothelial electrical resistance (TEER > 1500 Ω-cm(2)) and functional expression of drug efflux transporters. The radioiodinated and fluorescent APC analogues demonstrated fairly low permeability across the iPSC-BMEC (35 ± 5.7 (CLR1404), 54 ± 3.2 (CLR1501), and 26 ± 4.9 (CLR1502) × 10(-5) cm/min) compared with BBB-impermeable sucrose (13 ± 2.5) and BBB-permeable diazepam (170 ± 29). Only the fluorescent APC analogues (CLR1501, CLR1502) underwent BCRP and MRP polarized drug efflux transport in the brain-to-blood direction of the BBB model, and this efflux can be specifically blocked with pharmacological inhibition. None of the tested APC analogues appeared to undergo substantial P-gp transport. Limited permeability of the APC analogues across an intact BBB into normal brain likely contributes to the high tumor to background ratios observed in initial human trials. Moreover, addition of fluorescent moieties to APCs resulted in greater BMEC efflux via MRP and BCRP, and may affect fluorescence-guided applications. Overall, the characterization of APC analogue permeability across human BBB

  15. Analysis of Cancer-Targeting Alkylphosphocholine Analogue Permeability Characteristics Using a Human Induced Pluripotent Stem Cell Blood-Brain Barrier Model.

    PubMed

    Clark, Paul A; Al-Ahmad, Abraham J; Qian, Tongcheng; Zhang, Ray R; Wilson, Hannah K; Weichert, Jamey P; Palecek, Sean P; Kuo, John S; Shusta, Eric V

    2016-09-01

    Cancer-targeting alkylphosphocholine (APC) analogues are being clinically developed for diagnostic imaging, intraoperative visualization, and therapeutic applications. These APC analogues derived from chemically synthesized phospholipid ethers were identified and optimized for cancer-targeting specificity using extensive structure-activity studies. While they strongly label human brain cancers associated with disrupted blood-brain barriers (BBB), APC permeability across intact BBB remains unknown. Three of our APC analogues, CLR1404 (PET radiotracer), CLR1501 (green fluorescence), and CLR1502 (near-infrared fluorescence), were tested for permeability across a BBB model composed of human induced pluripotent stem cell-derived brain microvascular endothelial cells (iPSC-derived BMECs). This in vitro BBB system has reproducibly consistent high barrier integrity marked by high transendothelial electrical resistance (TEER > 1500 Ω-cm(2)) and functional expression of drug efflux transporters. The radioiodinated and fluorescent APC analogues demonstrated fairly low permeability across the iPSC-BMEC (35 ± 5.7 (CLR1404), 54 ± 3.2 (CLR1501), and 26 ± 4.9 (CLR1502) × 10(-5) cm/min) compared with BBB-impermeable sucrose (13 ± 2.5) and BBB-permeable diazepam (170 ± 29). Only the fluorescent APC analogues (CLR1501, CLR1502) underwent BCRP and MRP polarized drug efflux transport in the brain-to-blood direction of the BBB model, and this efflux can be specifically blocked with pharmacological inhibition. None of the tested APC analogues appeared to undergo substantial P-gp transport. Limited permeability of the APC analogues across an intact BBB into normal brain likely contributes to the high tumor to background ratios observed in initial human trials. Moreover, addition of fluorescent moieties to APCs resulted in greater BMEC efflux via MRP and BCRP, and may affect fluorescence-guided applications. Overall, the characterization of APC analogue permeability across human BBB

  16. 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.

  17. In situ O2 dynamics in submerged Isoetes australis: varied leaf gas permeability influences underwater photosynthesis and internal O2.

    PubMed

    Pedersen, Ole; Pulido, Cristina; Rich, Sarah Meghan; Colmer, Timothy David

    2011-08-01

    A unique type of vernal pool are those formed on granite outcrops, as the substrate prevents percolation so that water accumulates in depressions when precipitation exceeds evaporation. The O(2) dynamics of small, shallow vernal pools with dense populations of Isoetes australis were studied in situ, and the potential importance of the achlorophyllous leaf bases to underwater net photosynthesis (P(N)) and radial O(2) loss to sediments is highlighted. O(2) microelectrodes were used in situ to monitor pO(2) in leaves, shallow sediments, and water in four vernal pools. The role of the achlorophyllous leaf bases in gas exchange was evaluated in laboratory studies of underwater P(N), loss of tissue water, radial O(2) loss, and light microscopy. Tissue and sediment pO(2) showed large diurnal amplitudes and internal O(2) was more similar to sediment pO(2) than water pO(2). In early afternoon, sediment pO(2) was often higher than tissue pO(2) and although sediment O(2) declined substantially during the night, it did not become anoxic. The achlorophyllous leaf bases were 34% of the surface area of the shoots, and enhanced by 2.5-fold rates of underwater P(N) by the green portions, presumably by increasing the surface area for CO(2) entry. In addition, these leaf bases would contribute to loss of O(2) to the surrounding sediments. Numerous species of isoetids, seagrasses, and rosette-forming wetland plants have a large proportion of the leaf buried in sediments and this study indicates that the white achlorophyllous leaf bases may act as an important area of entry for CO(2), or exit for O(2), with the surrounding sediment.

  18. 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

  19. Characteristics of dynamic triaxial testing of asphalt mixtures

    NASA Astrophysics Data System (ADS)

    Ulloa Calderon, Alvaro

    Due to the increasing traffic loads and tire pressures, a serious detrimental impact has occurred on flexible pavements in the form of excessive permanent deformation once the critical combination of loading and environmental conditions are reached. This distress, also known as rutting, leads to an increase in road roughness and ultimately jeopardizes the road users' safety. The flow number (FN) simple performance test for asphalt mixtures was one of the final three tests selected for further evaluation from the twenty-four test/material properties initially examined under the NCHRP 9-19 project. Currently, no standard triaxial testing conditions in terms of the magnitude of the deviator and confining stresses have been specified. In addition, a repeated haversine axial compressive load pulse of 0.1 second and a rest period of 0.9 second are commonly used as part of the triaxial testing conditions. The overall objective of this research was to define the loading conditions that created by a moving truck load in the hot mixed asphalt (HMA) layer. The loading conditions were defined in terms of the triaxial stress levels and the corresponding loading time. Dynamic mechanistic analysis with circular stress distribution was used to closely simulate field loading conditions. Extensive mechanistic analyses of three different asphalt pavement structures subjected to moving traffic loads at various speeds and under braking and non-braking conditions were conducted using the 3D-Move model. Prediction equations for estimating the anticipated deviator and confining stresses along with the equivalent deviator stress pulse duration as a function of pavement temperature, vehicle speed, and asphalt mixture's stiffness have been developed. The magnitude of deviator stress, sigmad and confining stress, sigmac, were determined by converting the stress tensor computed in the HMA layer at 2" below pavement surface under a moving 18-wheel truck using the octahedral normal and shear

  20. Biomass properties and permeability in an immersed hollow fibre membrane bioreactor at high sludge concentrations.

    PubMed

    Wang, Z Z; Zsirai, T; Connery, K; Fabiyi, M; Larrea, A; Li, J; Judd, S J

    2014-01-01

    This study aimed to investigate the influence of biomass properties and high mixed liquor suspended solids (MLSS) concentrations on membrane permeability in a pilot-scale hollow fibre membrane bioreactor treating domestic wastewater. Auxiliary molasses solution was added to maintain system operation at constant food-to-microorganisms ratio (F/M = 0.13). Various physicochemical and biological biomass parameters were measured throughout the trial, comprising pre-thickening, thickening and post-thickening periods with reference to the sludge concentration and with aerobic biotreatment continuing throughout. Correlations between dynamic changes in biomass characteristics and membrane permeability decline as well as permeability recovery were further assessed by statistical analyses. Results showed the MLSS concentration to exert the greatest influence on sustainable membrane permeability, with a weaker correlation with particle size distribution. The strong dependence of absolute recovered permeability on wet accumulated solids (WACS) concentration, or clogging propensity, revealed clogging to deleteriously affect membrane permeability decline and recovery (from mechanical declogging and chemical cleaning), with WACS levels increasing with increasing MLSS. Evidence from the study indicated clogging may permanently reduce membrane permeability post declogging and chemical cleaning, corroborating previously reported findings.

  1. 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...

  2. 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.

  3. 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.

  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 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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.

  13. Changes in Permeability Produced By Distant Earthquakes

    NASA Astrophysics Data System (ADS)

    Manga, M.; Wang, C. Y.; Shi, Z.

    2014-12-01

    Oscillations in stress, such as those created by earthquakes, can increase permeability and fluid mobility in geologic media. In natural systems, strain amplitudes as small as 10-6 can increase discharge in streams and springs, change the water level of wells, and enhance production from petroleum reservoirs. Enhanced permeability typically recovers to pre-stimulated values over a period of months to years. This presentation will review some of the observations that indicate that dynamic stresses produced by seismic waves change permeability. We use the response of a set of wells distributed throughout China to multiple large earthquakes to probe the relationship between earthquake-generated stresses and water-level changes in wells. We find that dynamic stresses dominate the responses at distances more than 1 fault length from the earthquake and that permeability changes may explain the water level changes. Regions with high deformation rates are most sensitive to seismic waves. We also consider the response of a large alluvial fan in Taiwan to the 1999 M7.5 Chi-Chi earthquake where there were sustained changes in groundwater temperature after the earthquake. Using groundwater flow models, we infer that permeability increased by an order of magnitude over horizontal scales of tens of km, and vertical scales of several km. Permeability returned to the pre-earthquake value over many months. As much as half the total transport in the fan occurs during the short time periods with enhanced permeability.

  14. Thermo-dynamic characteristics of NITINOL-reinforced composite beams

    NASA Astrophysics Data System (ADS)

    Baz, A.; Ro, J.

    The fundamental principles governing the operation of NITINOL-reinforced composite beams are investigated by determining the individual contributions of the composite matrix, the NITINOL fibers, and the shape memory effect to the overall dynamic performance of the beams. The effect of the temperature distribution inside the composite, which results from the activation of a small subset of the NITINOL fibers, on the overall performance of the entire beam was investigated theoretically and experimentally. Particular attention was given to the effects of intentional electrical heating of a selected subset of NITINOL fibers, and the associated thermal energy propagating through the composite, on the unintentional thermal activation of additional subsets of the fibers.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. FE analysis of dynamic characteristics for mill's liners

    NASA Astrophysics Data System (ADS)

    Feng, Xianzhang; Cui, Yanmei; Jiang, Zhiqiang; Hou, Tao

    2009-07-01

    Slab side pressing is an online regulation width technology for continuous casting slab, the liner at the bottom of the framework under the larger impact force, it often can occurrence accident of liner Board broken during working of sizing press rolling mill. In order to analyze force distribution and its peak in the liner of rolling mill during side pressing, liner dynamics model is established using nonlinear function of finite element software, and the contact mode is established for liner and wheel by Hertz law theory. It yields the relations between maximal stress and tap hole in the liner, the design scheme is extracted for improving condition of linerboard's stress, and the calculated results were much inosculated with the measured values. The studied results indicated that the liner's life gets improve obviously in field.

  2. Dynamic characteristics of gas-water interfacial plasma under water

    SciTech Connect

    Zheng, S. J.; Zhang, Y. C.; Ke, B.; Ding, F.; Tang, Z. L.; Yang, K.; Zhu, X. D.

    2012-06-15

    Gas-water interfacial plasmas under water were generated in a compact space in a tube with a sandglass-like structure, where two metal wires were employed as electrodes with an applied 35 kHz ac power source. The dynamic behaviors of voltage/current were investigated for the powered electrode with/without water cover to understand the effect of the gas-water interface. It is found that the discharge exhibits periodic pulsed currents after breakdown as the powered electrode is covered with water, whereas the electrical current reveals a damped oscillation with time with a frequency about 10{sup 6} Hz as the powered electrode is in a vapor bubble. By increasing water conductivity, a discharge current waveform transition from pulse to oscillation presents in the water covering case. These suggest that the gas-water interface has a significant influence on the discharge property.

  3. 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.

  4. Health Insurance Coverage at Midlife: Characteristics, Costs, and Dynamics

    PubMed Central

    Johnson, Richard W.; Crystal, Stephen

    1997-01-01

    Recent data from the first two waves of the Health and Retirement Study are analyzed to evaluate prevalence of different types of health insurance, characteristics of different plan types, and changes in coverage as individuals approach retirement age. Although overall rates of coverage are quite high among the middle-aged, the risk of non-coverage is high within many disadvantaged groups, including Hispanics, low-wage earners, and the recently disabled. Sixty percent of individuals with health benefits are enrolled in health maintenance organizations (HMOs) or preferred provider organizations (PPOs). In addition, one-fourth of enrollees in fee-for-service (FFS) plans report restrictions in their access to specialists. PMID:10170345

  5. 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.

  6. 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.

  7. Fluid dynamic characteristics of monopivot magnetic suspension blood pumps.

    PubMed

    Yamane, T; Nishida, M; Asztalos, B; Tsutsui, T; Jikuya, T

    1997-01-01

    A monopivot magnetic suspension blood pump is a centrifugal pump under development with a magnetic suspension and a ceramic pivot to support the impeller with minimum contact. The pump size has been reduced by implementing a direct impeller drive mechanism in place of a magnetic coupling and motor. Flow visualization studies revealed that high shear, which seems to be closely related to hemolysis, concentrates in boundary layers near the walls. This implies that fluid dynamic shear can be reduced not by widening the gap, but by reducing the impeller velocity. Therefore, compared with the results of the previous semi-open curved vane impeller model, impeller velocity was reduced by 30% with a closed impeller having radial straight vanes, and smaller impeller/housing gaps. The volute shape around the impeller tip was also changed such that the outflow from the impeller enters along the center plane of the volute. To examine the effect of the improvements, hemolysis testing was conducted and found that the newly developed closed impeller model generated a lower level of hemolysis than the previous semi-open impeller model. PMID:9360122

  8. 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.

  9. 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

  10. Dynamic characteristics of Prochlorococcus and Synechococcus consumption by bacterivorous nanoflagellates.

    PubMed

    Christaki, U; Courties, C; Karayanni, H; Giannakourou, A; Maravelias, C; Kormas, K Ar; Lebaron, P

    2002-04-01

    We compared the characteristics of ingestion of Prochlorococcus and Synechococcus by the marine heterotrophic nanoflagellate Pseudobodo sp. and by a mixed nanoflagellate culture (around 3 microm in size) obtained from an open sea oligotrophic area. Maximum ingestion rate on Synechococcus (2.7 Syn flagellate(-1) h(-1)) was reached at concentrations of 5 x 10(5) Syn mL(-1) and decreased between 6 x 10(5) and 1.5 x 10(6) Syn mL(-1). In order to validate laboratory data, one set of data on Synechococcus grazing was obtained during a field study in the oligotrophic northeastern Mediterranean Sea. Ingestion rates by heterotrophic nanoflagellates were related to Synechococcus abundance in the water, and the feeding rate showed a clear diel rhythm with consumption being highest during the night, declining during the day hours, and being lowest at dusk. Ingestion rates on Prochlorococcus increased linearly for the whole range of prey density used (i.e., from 1 x 10(3) to 3 x 10(6) Proc mL(-1)), with maximum ingestion of 6.7 Proc flagellate(-1) h(-1). However, for prey concentrations in the range of 10(3)-10(5), which are usually encountered in aquatic systems, ingestion rates were significantly less than on Synechococcus. In our experiments, both Prochlorococcus and Synechococcus proved to be poor food items for support of nanoflagellate growth.

  11. 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.

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

    PubMed

    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

    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.

  13. 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

  14. 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.

  15. Compressibility effects on the dynamic characteristics of gas lubricated mechanical components

    NASA Astrophysics Data System (ADS)

    Arghir, Mihai; Matta, Pierre

    2009-11-01

    The present Note deals with the effects of compressibility on the linearized dynamic characteristics of gas lubricated mechanical components (journal and thrust bearings). Although the effect of compressibility on the static characteristics is well known, its influence on the dynamic characteristics is still not clearly understood. The present Note uses Lubrication's simplest model problems (the 1D slider) to qualitatively describe this effect. An analytic solution obtained for the parallel 1D slider depicts the variation of stiffness and damping with the excitation frequency and shows that this nonlinearity must be taken into account for squeeze number larger than 1. A convenient way of handling this nonlinearity in a dynamic system is described for an aerodynamic thrust bearing. To cite this article: M. Arghir, P. Matta, C. R. Mecanique 337 (2009).

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

    USGS Publications Warehouse

    Boatwright, John; Jacobson, Muriel L.

    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.

  17. 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.

  18. Novel lipid-based formulations enhancing the in vitro dissolution and permeability characteristics of a poorly water-soluble model drug, piroxicam.

    PubMed

    Prabhu, Sunil; Ortega, Maru; Ma, Chan

    2005-09-14

    PXCM from all formulations, with formulation (C) showing the maximum increase followed by formulations (B) and (A), when compared to control. The apparent permeability coefficients (Papp) were calculated to be 7.92x10(-6), 9.48x10(-6), 9.2x10(-6) and 5.6x10(-6)cm/s for formulations (A)-(C) and control, respectively. Overall, permeation appeared to improve for all formulations over the control. Stability studies at various temperatures showed all formulations to have good stability for the first 6 months; then a decline in dissolution rates was observed, especially for PEG-based lipid carrier systems, attributed to the increase in crystalline content of the solid dispersions upon storage.

  19. 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.

  20. Permeability of edible coatings.

    PubMed

    Mishra, B; Khatkar, B S; Garg, M K; Wilson, L A

    2010-01-01

    The permeabilities of water vapour, O2 and CO2 were determined for 18 coating formulations. Water vapour transmission rate ranged from 98.8 g/m(2).day (6% beeswax) to 758.0 g/m(2).day (1.5% carboxymethyl cellulose with glycerol). O2 permeability at 14 ± 1°C and 55 ± 5% RH ranged from 1.50 to 7.95 cm(3)cm cm(-2)s(-1)Pa(-1), with CO2 permeability 2 to 6 times as high. Permeability to noncondensable gases (O2 and CO2) was higher for hydrophobic (peanut oil followed by beeswax) coatings as compared to hydrophilic (whey protein concentrate and carboxymethyl cellulose).

  1. Static and dynamic characteristics of angular velocity and acceleration transducers based on optical tunneling effect

    NASA Astrophysics Data System (ADS)

    Busurin, V. I.; Korobkov, V. V.; Htoo Lwin, Naing; Tuan, Phan Anh

    2016-08-01

    Theoretical and experimental analysis of quasi-linear conversion function of angular velocity and acceleration microoptoelectromechnical (MOEM) transducers based on optical tunneling effect (OTE) are conducted. Equivalent oscillating circuit is developed and dynamic characteristics of angular velocity and acceleration MOEM-transducers are investigated.

  2. 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.

  3. Novel method for estimating the dynamic characteristics of pressure sensor in shock tube calibration test.

    PubMed

    Li, Qiang; Wang, Zhongyu; Wang, Zhuoran; Yan, Hu

    2015-06-01

    A shock tube is usually used to excite the dynamic characteristics of the pressure sensor used in an aircraft. This paper proposes a novel estimation method for determining the dynamic characteristic parameters of the pressure sensor. A preprocessing operation based on Grey Model [GM(1,1)] and bootstrap method (BM) is employed to analyze the output of a calibrated pressure sensor under step excitation. Three sequences, which include the estimated value sequence, upper boundary, and lower boundary, are obtained. The processing methods on filtering and modeling are used to explore the three sequences independently. The optimal estimated, upper boundary, and lower boundary models are then established. The three models are solved, and a group of dynamic characteristic parameters corresponding to the estimated intervals are obtained. A shock tube calibration test consisting of two experiments is performed to validate the performance of the proposed method. The results show that the relative errors of the dynamic characteristic parameters of time and frequency domains do not exceed 9% and 10%, respectively. Moreover, the nominal and estimated values of the parameters fall into the estimated intervals limited by the upper and lower values. PMID:26133863

  4. Effect of Nesting on the Permeability of Multilayer Unidirectional Fabrics

    NASA Astrophysics Data System (ADS)

    Jiang, Jianjun; Su, Yang; Zhou, Linchao; Guo, Qiang; Xu, Chumeng; Deng, Guoli; Chen, Xing; Yao, Xuming; Fang, Liangchao

    2016-10-01

    Nesting of layers is the main source of the variations in permeability values in liquid composite molding (LCM) processes. In this paper, the permeability of unidirectional fabrics was modeled as a function of layer shift and geometrical yarn parameters to study the effect of nesting. Firstly, three different unit cells of two layers were modeled based on the range of layer shift and decomposed into zones of characteristic yarn arrangement, respectively. The overall permeability of each unit cell was then modeled as a mixture of local permeabilities of different zones with the electrical resistance analogy. Secondly, every two adjacent layers were regarded as porous media with different permeabilities. The permeability of multilayer unidirectional fabrics was then modeled with electrical resistance analogy. As the unpredictability of layer shifting in actual process, the statistical characteristics were analyzed theoretically and validated with experimental measurements. Excellent agreement was found between predictions and experiment data.

  5. 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

  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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. Floating clamping mechanism of PT fuel injector and its dynamic characteristics analysis

    NASA Astrophysics Data System (ADS)

    Wang, Xinqing; Liang, Sheng; Xia, Tian; Wang, Dong; Qian, Shuhua

    2012-05-01

    PT fuel injector is one of the most important parts of modern diesel engine. To satisfy the requirements of the rapid and accurate test of PT fuel injector, the self-adaptive floating clamping mechanism was developed and used in the relevant bench. Its dynamic characteristics directly influence the test efficiency and accuracy. However, due to its special structure and complex oil pressure signal, related documents for evaluating dynamic characteristics of this mechanism are lack and some dynamic characteristics of this mechanism can't be extracted and recognized effectively by traditional methods. Aiming at the problem above-mentioned, a new method based on Hilbert-Huang transform (HHT) is presented. Firstly, combining with the actual working process, the dynamic liquid pressure signal of the mechanism is acquired. By analyzing the pressure fluctuation during the whole working process in time domain, oil leakage and hydraulic shock in the clamping chamber are discovered. Secondly, owing to the nonlinearity and nonstationarity of pressure signal, empirical mode decomposition is used, and the signal is decomposed and reconstructed into forced vibration, free vibration and noise. By analyzing forced vibration in the time domain, machining error and installation error of cam are revealed. Finally, free vibration component is analyzed in time-frequency domain with HHT, the traits of free vibration in the time-frequency domain are revealed. Compared with traditional methods, Hilbert spectrum has higher time-frequency resolutions and higher credibility. The improved mechanism based on the above analyses can guarantee the test accuracy of injector injection. This new method based on the analyses of the pressure signal and combined with HHT can provide scientific basis for evaluation, design improvement of the mechanism, and give references for dynamic characteristics analysis of the hydraulic system in the interrelated fields.

  12. Measurement of Soil-Ionization Characteristics of Groundingand its Analysis using Dynamic Grounding Model

    NASA Astrophysics Data System (ADS)

    Yasuda, Yoh; Kondo, Shuhei; Hara, Takehisa; Ikeda, Keiichi; Sonoi, Yasuo; Furuoka, Yoshihiro

    It is well known that grounding resistance has a current-dependent characteristic, whose phenomena and models have been reported and proposed by many investigators as well as Liew and Darveniza. As far as lightning analysis, especially in Japan, the grounding resistance has been simulated as a simple constant lump resistance. The goal of the authors’ investigation is to utilize those characteristics to lightning protection and make a certain methodology to save construction cost for UHV transmission tower on very high resistivity soil. We, therefore, focus on the characteristic of grounding resistance of tower footing for 500 kV transmission line. In this paper, we discuss measurement on high-current injected experiment using an actual tower footing base and its analysis, where we employ dynamic characteristic of the grounding resistance proposed by Liew and Darveniza. Comparison between the observed result and the calculated one is also discussed.

  13. Dynamic characteristics of helium adsorbents. Influence of the heat removal conditions

    NASA Astrophysics Data System (ADS)

    Shcherbachenko, R. I.; Grigor'ev, V. N.

    2008-06-01

    The static and dynamic characteristics of the adsorbent SKN-1K at 4.2K are investigated under conditions corresponding to the working conditions of adsorption pumps in dilution refrigerators. It is shown that gluing this adsorbent to the cooled surface leads to a substantial lowering of the pressure in the pump in the dynamic regime. On the basis of experimental data for the glued and free adsorbent an estimate is made of the hydrodynamic contribution to the pressure due to the resistance of the pores of the adsorbent. This estimate falls within the error of measurement.

  14. 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.

  15. Permeability of the blood-brain barrier predicts conversion from optic neuritis to multiple sclerosis.

    PubMed

    Cramer, Stig P; Modvig, Signe; Simonsen, Helle J; Frederiksen, Jette L; Larsson, Henrik B W

    2015-09-01

    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 sensitivity of

  16. Dual-permeability model for water flow and solute transport in shrinking soils

    NASA Astrophysics Data System (ADS)

    Coppola, Antonio; Gerke, Horst; Comegna, Alessandro; Basile, Angelo

    2014-05-01

    A dual-permeability approach was extended to describe preferential water flow and solute transport in shrinking soils. In the approach, the soil is treated as a dual-permeability bulk porous medium consisting of dynamic interacting matrix and fractures pore domains. Water flow and solute transport in both the domains are described by the Richards' equation and advection-dispersion equation, respectively. In the model the contributions of the two regions to water flow and solute transport is changed dynamically according to the shrinkage characteristic exhibited under soil drying. Aggregate deformation during wetting/drying cycles is assumed to change only the relative proportions of voids in the fractures and in the aggregates, while the total volume of pores (and thus the layer thickness) remains unchanged. Thus, the partial contributions of the fracture and aggregate domains, are now a function of the water content (or the pressure head h), while their sum, the bulk porosity, is assumed to be constant. Any change in the aggregate contribution to total porosity is directly converted into a proportional change in the fracture porosity. This means that bulk volume change during shrinkage is mainly determined by change in crack volume rather than by change in layer thickness. This simplified approach allows dealing with an expansive soil as with a macroscopically rigid soil. The model was already tested by investigating whether and how well hydraulic characteristics obtained under the assumption of "dynamic" dual-permeability hydraulic parameterizations, or, alternatively, assuming the rigidity of the porous medium, reproduced measured soil water contents in a shrinking soil. Here we will discuss theoretical implications of the model in terms of relative importance of the parameters involved. The relative importance will be evaluated for different flow and transport processes and for different initial and top boundary conditions. Key words: Preferential flow and

  17. Effect Of Dynamic Characteristics of Power Supplies on Aerosol Composition While Welding With Coated Electrodes

    NASA Astrophysics Data System (ADS)

    Il'yaschenko, D. P.; Chinakhov, D. A.; Sadikov, I. D.

    2016-08-01

    In the context of a significant increase in production output and use of welding technologies in the manufacturing of engineering products the problem of hygienic characteristics of working conditions in arc fusion welding is becoming increasingly important. The work represents how the dynamic characteristics of a power supply affect the transfer of alloying elements from a coated electrode into a base metal, a slag phase and a solid component of welding fumes. Short-circuit current limiting in inverters reduces overheating of electrode metal drops by 15%; welding fumes quantitative component - to 38%; manganese - to 30%; thermal radiation intensity - by 37%.

  18. 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.

  19. Dynamic voltage-current characteristics for a water jet plasma arc

    SciTech Connect

    Yang Jiaxiang; Lan Sheng; Xu Zuoming

    2008-05-05

    A virtual instrument technology is used to measure arc current, arc voltage, dynamic V-I characteristics, and nonlinear conductance for a cone-shaped water jet plasma arc under ac voltage. Experimental results show that ac arc discharge mainly happens in water vapor evaporated from water when heated. However, due to water's cooling effect and its conductance, arc conductance, reignition voltage, extinguish voltage, and current zero time are very different from those for ac arc discharge in gas work fluid. These can be valuable to further studies on mechanism and characteristics of plasma ac discharge in water, and even in gas work fluid.

  20. 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.

  1. 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.

  2. Aerodynamic characteristics of the standard dynamics model in coning motion at Mach 0.6

    NASA Technical Reports Server (NTRS)

    Jermey, C.; Schiff, L. B.

    1985-01-01

    A wind tunnel test was conducted on the Standard Dynamics Model (a simplified generic fighter aircraft shape) undergoing coning motion at Mach 0.6. Six component force and moment data are presented for a range of angle of attack, sideslip, and coning rates. At the relatively low non-dimensional coning rate employed (omega b/2V less than or equal to 0.04), the lateral aerodynamic characteristics generally show a linear variation with coning rate.

  3. Stress-induced variation in magnetization and the dynamic magnetostrictive characteristic of soft magnetic materials

    NASA Astrophysics Data System (ADS)

    Gonda, P.

    1980-04-01

    The low-field magnetostrictive properties of amorphous ribbons are examined. From the measured hysteresis loops of as-prepared samples of Fe 35Co 32B 20Si 10Al 3, (FeNi) 80B 17.5Al 2Si 0.5 the stress-induced variation of the magnetization is used for the calculation of the dynamic magnetostrictive characteristic Δλ( H) and λ( H). The resulting hysteresis loops may be attributed to the curling magnetization mode.

  4. 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.

  5. 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.

  6. Loading Dynamics and Characteristics of a Far Off-Resonance Optical Dipole Trap

    NASA Astrophysics Data System (ADS)

    Mickelson, P. G.; Martinez, Y. N.; Nagel, S. B.; Traverso, A. J.; Killian, T. C.

    2007-10-01

    We implement an optical dipole trap in a crossed beam configuration for experiments with ultracold strontium. Strontium atoms cooled to nearly 1 μK are loaded into the optical dipole trap from a magneto-optical trap operating on the 689 nm intercombination line. Loading dynamics and characteristics of the far off-resonance dipole trap are explored as part of our group's study of ultracold collisions in strontium.

  7. 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.

  8. 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…

  9. 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).

  10. 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

  11. Modelling and analysis on biomechanical dynamic characteristics of knee flexion movement under squatting.

    PubMed

    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.

  12. 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

  13. Ten minutes of dynamic stretching is sufficient to potentiate vertical jump performance characteristics.

    PubMed

    Turki, Olfa; Chaouachi, Anis; Drinkwater, Eric J; Chtara, Moktar; Chamari, Karim; Amri, Mohamed; Behm, David G

    2011-09-01

    The current literature recommends dynamic rather than static stretching for the athletic warm-up. Dynamic stretching and various conditioning stimuli are used to induce potentiation in subsequent athletic performance. However, it is unknown as to which type of activity in conjunction with dynamic stretching within a warm-up provides the optimal potentiation of vertical jump performance. It was the objective of the study to examine the possible potentiating effect of various types of conditioning stimuli with dynamic stretching. Twenty athletes participated in 6 protocols. All the experimental protocols included 10 minutes of dynamic stretching. After the dynamic stretching, the subjects performed a (a) concentric (DS/CON): 3 sets of 3 repetition maximum deadlift exercise; (b) isometric (DS/ISOM): 3 sets of 3-second maximum voluntary contraction back squats; (c) plyometric (DS/PLYO): 3 sets of 3 tuck jumps; (d) eccentric (DS/ECC): 3 modified drop jumps; (e) dynamic stretching only (DS), and (f) control protocol (CON). Before the intervention and at recovery periods of 15 seconds, 4, 8, 12, 16, and 20 minutes, the participants performed 1-2 maximal countermovement jumps. The DS and DS/CON protocols generally had a 95-99% likelihood of exceeding the smallest worthwhile change for vertical jump height, peak power, velocity and force. However, the addition of the deadlift to the DS did not augment the potentiating effect. Time-to-peak potentiation was variable between individuals but was most consistent between 3 and 5 minutes. Thus, the volume and the intensity associated with 10 minutes of dynamic stretching were sufficient to provide the potentiation of vertical jump characteristics. Additional conditioning activities may promote fatigue processes, which do not permit further potentiation. PMID:21792071

  14. 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.

  15. 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.

  16. GROUNDWATER FLOW IN LOW-PERMEABILITY ENVIRONMENTS.

    USGS Publications Warehouse

    Neuzil, C.E.

    1986-01-01

    Certain geologic media are known to have small permeability; subsurface environments composed of these media and lacking well developed secondary permeability have groundwater flow systems with many distinctive characteristics. Moreover, groundwater flow in these environments appears to influence the evolution of certain hydrologic, geologic, and geochemical systems, may affect the accumulation of petroleum and ores, and probably has a role in the structural evolution of parts of the crust. Such environments are also important in the context of waste disposal. This review attempts to synthesize the diverse contributions of various disciplines to the problem of flow in low-permeability environments. Problems hindering analysis are enumerated together with suggested approaches to overcoming them. A common thread running through the discussion is the significance of size- and time-scale limitations of the ability to directly observe flow behavior and make significance of size- and time-scale limitations of the ability to directly observe flow behavior and make measurements of parameters.

  17. Blood flow and permeability in microvessels

    NASA Astrophysics Data System (ADS)

    Sugihara-Seki, Masako; Fu, Bingmei M.

    2005-07-01

    The mechanics of blood flow in microvessels and microvessel permeability are reviewed. In the first part, characteristics of blood flow in vivo and in vitro are described from a fluid-mechanical point of view, and mathematical models for blood flow in microvessels are presented. Possible causes of the increased flow resistance obtained in vivo compared to in vitro are examined, including the effects of irregularities of vessel lumen, the presence of endothelial surface glycocalyx and white blood cells. In the second part, the ultrastructural pathways and mechanisms whereby endothelial cells and the clefts between the cells modulate microvessel permeability to water and solutes are introduced. Previous and current models for microvessel permeability to water and solutes are reviewed. These models examine the role of structural components of interendothelial cleft, such as junction strands and surface glycocalyx, in the determination of water and solute transport across the microvessel walls. Transport models in the tissue space surrounding the microvessel are also described.

  18. Steam-water relative permeability

    SciTech Connect

    Ambusso, W.; Satik, C.; Home, R.N.

    1997-12-31

    A set of relative permeability relations for simultaneous flow of steam and water in porous media have been measured in steady state experiments conducted under the conditions that eliminate most errors associated with saturation and pressure measurements. These relations show that the relative permeabilities for steam-water flow in porous media vary approximately linearly with saturation. This departure from the nitrogen/water behavior indicates that there are fundamental differences between steam/water and nitrogen/water flows. The saturations in these experiments were measured by using a high resolution X-ray computer tomography (CT) scanner. In addition the pressure gradients were obtained from the measurements of liquid phase pressure over the portions with flat saturation profiles. These two aspects constitute a major improvement in the experimental method compared to those used in the past. Comparison of the saturation profiles measured by the X-ray CT scanner during the experiments shows a good agreement with those predicted by numerical simulations. To obtain results that are applicable to general flow of steam and water in porous media similar experiments will be conducted at higher temperature and with porous rocks of different wetting characteristics and porosity distribution.

  19. Preasymptotic hydrodynamic dispersion as a quantitative probe of permeability.

    PubMed

    Brosten, Tyler R; Vogt, Sarah J; Seymour, Joseph D; Codd, Sarah L; Maier, Robert S

    2012-04-01

    We interpret a generalized short-time expansion of stochastic hydrodynamic dispersion dynamics in the case of small Reynolds number flow through macroscopically homogenous permeable porous media to directly determine hydrodynamic permeability. The approach allows determination of hydrodynamic permeability from pulsed field gradient spin-echo nuclear magnetic resonance measurement of the short-time effective hydrodynamic dispersion coefficient. The analytical expansion of asymptotic dynamics agrees with experimental NMR data and lattice Boltzmann simulation of hydrodynamic dispersion in consolidated random sphere pack media. PMID:22680531

  20. In situ permeability testing of rock salt

    SciTech Connect

    Peterson, E.W.; Lagus, P.L.; Broce, R.D.; Lie, K.

    1981-04-01

    Storage of transuranic (TRU) wastes in bedded salt formations requires a knowledge of the in situ permeability of SENM rock salt. Since assumptions for safety assessments have been made in which these wastes could generate gas pressures on the order of the lithostatic pressure over geologic time scales, the permeability of the surrounding formation becomes an important parameter for determining the manner in which the gases will be contained or dispersed. This report describes the series of tests conducted in the AEC-7 borehole, located near the WIPP site, to determine the in situ gas flow characteristics of the bedded salt. In these tests, compressed air was injected into the borehole and flow into the surrounding formation measured. These measured flow rates were interpreted in terms of formation permeabilities and porosities which were, in turn, used as modeling parameters for the repository response analysis. Two series of field tests were performed. The first series consisted of a number of whole-hole flow tests conducted to provide preliminary design information required for future operation of a guarded straddle packer system capable of measuring permeabilities > or = 0.1 ..mu..darcy. The second series of tests were conducted using the Systems, Science and Software (S-Cubed) designed guarded straddle packer system. In these interval permeability tests, 100-foot lengths of borehole were isolated and the flow characteristics of the surrounding formation examined. In this report, a complete description of the test procedures, instrumentation, and measurement techniques is first given. The analytical/numerical methods used for data interpretation are then presented, followed by results of the interval and permeability tests. (The whole-hole tests are summarized in Appendix A.) Conclusions are presented in the final section.

  1. 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.

  2. EPA Permeable Surface Research - Poster

    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...

  3. 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.

  4. Experimental determination of dynamic characteristics of the VentrAssist implantable rotary blood pump.

    PubMed

    Chung, Michael K H; Zhang, Nong; Tansley, Geoff D; Qian, Yi

    2004-12-01

    The VentrAssist implantable rotary blood pump, intended for long-term ventricular assist, is under development and is currently being tested for its rotor-dynamic stability. The pump consists of a shaftless impeller, which also acts as the rotor of the brushless DC motor. The impeller remains passively suspended in the pump cavity by hydrodynamic forces, which result from the small clearances between the outside surfaces of the impeller and the pump cavity. These small clearances range from approximately 50 microm to 230 microm in size in the version of pump reported here. This article presents experimental investigation into the dynamic characteristics of the impeller-bearing-pump housing system of the rotary blood pump for increasing pump speeds at different flow rates. The pump was mounted on a suspension system consisting of a platform and springs, where the natural frequency and damping ratio for the suspension system were determined. Real-time measurements of the impeller's displacement were performed using Hall effect sensors. A vertical disturbance force was exerted onto the pump housing, causing the impeller to be displaced in vertical direction from its dynamic equilibrium position within the pump cavity. The impeller displacement was represented by a decaying sine wave, which indicated the impeller restoring to its equilibrium position. From the decaying sine wave the natural frequency and stiffness coefficient of the system were determined. Furthermore, the logarithmic decrement method was used to determine the damping ratio and eventually the damping coefficient of the system. Results indicate that stiffness and damping coefficients increased as flow rate and pump speed increased, representing an increase in stability with these changing conditions. However, pump speed had a greater influence on the stiffness and damping coefficients than flow rate did, which was evident through dynamic analysis. Overall the experimental method presented in this

  5. Liquid-permeable electrode

    DOEpatents

    Folser, George R.

    1980-01-01

    Electrodes for use in an electrolytic cell, which are liquid-permeable and have low electrical resistance and high internal surface area are provided of a rigid, porous, carbonaceous matrix having activated carbon uniformly embedded throughout. The activated carbon may be catalyzed with platinum for improved electron transfer between electrode and electrolyte. Activated carbon is mixed with a powdered thermosetting phenolic resin and compacted to the desired shape in a heated mold to melt the resin and form the green electrode. The compact is then heated to a pyrolyzing temperature to carbonize and volatilize the resin, forming a rigid, porous structure. The permeable structure and high internal surface area are useful in electrolytic cells where it is necessary to continuously remove the products of the electrochemical reaction.

  6. [Venoruton and capillary permeability].

    PubMed

    Cesarone, M R; Laurora, G; Gabini, M; Errichi, B M; Candiani, C; Belcaro, G

    1989-05-01

    A new system to evaluate capillary permeability, the vacuum suction chamber (VSC) device, was used to assess the effects of Venoruton in patients with venous hypertension. A temporary, superficial skin lesion (wheal) was produced with the VSC device by negative pressure (30 mmHg) applied for 10 minutes on the internal, perimalleolar region. Wheals disappear in less than 60 minutes in normals while in patients with venous hypertension the wheal is more persistent, requiring a significantly longer time to disappear. This new technique was used in association with laser-Doppler flowmetry to evaluate the efficacy of Venoruton (1000 mgs t.i.d.) administered for 2 weeks on venous hypertension. Results indicate a positive effect of Venoruton in reducing the abnormally increased capillary permeability in venous hypertension and are proportional to the changes observed in signs and symptoms after treatment.

  7. Effect of plate permeability on nonlinear stability of the asymptotic suction boundary layer

    NASA Astrophysics Data System (ADS)

    Wedin, Hâkan; Cherubini, Stefania; Bottaro, Alessandro

    2015-07-01

    The nonlinear stability of the asymptotic suction boundary layer is studied numerically, searching for finite-amplitude solutions that bifurcate from the laminar flow state. By changing the boundary conditions for disturbances at the plate from the classical no-slip condition to more physically sound ones, the stability characteristics of the flow may change radically, both for the linearized as well as the nonlinear problem. The wall boundary condition takes into account the permeability K ̂ of the plate; for very low permeability, it is acceptable to impose the classical boundary condition (K ̂=0 ). This leads to a Reynolds number of approximately Rec=54 400 for the onset of linearly unstable waves, and close to Reg=3200 for the emergence of nonlinear solutions [F. A. Milinazzo and P. G. Saffman, J. Fluid Mech. 160, 281 (1985), 10.1017/S0022112085003482; J. H. M. Fransson, Ph.D. thesis, Royal Institute of Technology, KTH, Sweden, 2003]. However, for larger values of the plate's permeability, the lower limit for the existence of linear and nonlinear solutions shifts to significantly lower Reynolds numbers. For the largest permeability studied here, the limit values of the Reynolds numbers reduce down to Rec=796 and Reg=294 . For all cases studied, the solutions bifurcate subcritically toward lower Re, and this leads to the conjecture that they may be involved in the very first stages of a transition scenario similar to the classical route of the Blasius boundary layer initiated by Tollmien-Schlichting (TS) waves. The stability of these nonlinear solutions is also investigated, showing a low-frequency main unstable mode whose growth rate decreases with increasing permeability and with the Reynolds number, following a power law Re-ρ, where the value of ρ depends on the permeability coefficient K ̂. The nonlinear dynamics of the flow in the vicinity of the computed finite-amplitude solutions is finally investigated by direct numerical simulations, providing a

  8. 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.

  9. 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.

  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. Stainless Steel Permeability

    SciTech Connect

    Buchenauer, Dean A.; Karnesky, Richard A.

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  12. The articulatory characteristics of the tongue in anterior openbite: observation by use of dynamic palatography.

    PubMed

    Suzuki, N; Sakuma, T; Michi, K; Ueno, T

    1981-01-01

    The tongue movements during the production of Japanese speech sounds in five patients with anterior openbite associated with 1-5 mm of overjet were investigated using dynamic palatography and cinematography. The dynamic palatograph is an electric device capable of recording constantly changing palatolingual contact as a function of time by use of a thin plastic artificial palate equipped with 63 electrodes. As a result, the following articulatory characteristics were observed during the utterance of the Japanese sounds /s/,/f/,/t/,/d/,/n/,/r/,/ts/,/tf/,/dz/,/d3/. (1) The area of maximal palatolingual contacts was smaller than the normal. (2) Forward positioning of the tongue was confirmed in all cases. (3) The interruption of the breath stream was made with the dorsal surface of the tongue and the maxillary anterior teeth. (4) The sounds /s/,/f/,/dz/,/d3/, were recognized as distorted sound as /theta/, in English.

  13. Dynamic response characteristics analysis of the doubly-fed wind power system under grid voltage drop

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Wang, J.; Wang, H. H.; Yang, L.; Chen, W.; Xu, Y. T.

    2016-08-01

    Double-fed induction generator (DFIG) is sensitive to the disturbances of grid, so the security and stability of the grid and the DFIG itself are under threat with the rapid increase of DFIG. Therefore, it is important to study dynamic response of the DFIG when voltage drop failure is happened in power system. In this paper, firstly, mathematical models and the control strategy about mechanical and electrical response processes is respectively introduced. Then through the analysis of response process, it is concluded that the dynamic response characteristics are related to voltage drop level, operating status of DFIG and control strategy adapted to rotor side. Last, the correctness of conclusion is validated by the simulation about mechanical and electrical response processes in different voltage levels drop and different DFIG output levels under DIgSILENT/PowerFactory software platform.

  14. Subsonic static and dynamic stability characteristics of the test technique demonstrator NASP configuration

    NASA Technical Reports Server (NTRS)

    Boyden, Richmond P.; Dress, David A.; Fox, Charles H., Jr.; Huffman, Jarrett K.; Cruz, Christopher I.

    1993-01-01

    The paper describes the procedure used for and the results obtained of wind-tunnel tests of the National Aerospace Plane (NASP) configuration, which were conducted in the NASA Langley Research Center High Speed Tunnel using a blended body NASP configuration designed by the research center. Static and dynamic stability characteristics were measured at Mach numbers 0.3, 0.6, and 0.8. In addition to tests of the baseline configuration, component buildup tests with a canard surface and with a body flap were carried out. Results demonstrated a positive static stability of the baseline configuration, except at the higher angles of attack at Mach 0.8. A good agreement was found between the inphase dynamic parameters and the corresponding static data.

  15. 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.

  16. 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

  17. Study on dynamic characteristics of coupled model for deep-water lifting system

    NASA Astrophysics Data System (ADS)

    Wu, Yunxia; Lu, Jianhui; Zhang, Chunlei

    2016-10-01

    The underwater installation of marine equipment in deep-water development requires safe lifting and accurate positioning. The heave compensation system is an important technology to ensure normal operation and improve work accuracy. To provide a theoretical basis for the heave compensation system, in this paper, the continuous modeling method is employed to build up a coupled model of deep-water lifting systems in vertical direction. The response characteristics of dynamic movement are investigated. The simulation results show that the resonance problem appears in the process of the whole releasing load, the lifting system generates resonance and the displacement response of the lifting load is maximal when the sinking depth is about 2000 m. This paper also analyzes the main influencing factors on the dynamic response of load including cable stiffness, damping coefficient of the lifting system, mass and added mass of lifting load, among which cable stiffness and damping coefficient of the lifting system have the greatest influence on dynamic response of lifting load when installation load is determined. So the vertical dynamic movement response of the load is reduced by installing a damper on the lifting cable and selecting the appropriate cable stiffness.

  18. Damage identification method based on structural dynamic characteristics and strain measurements

    NASA Astrophysics Data System (ADS)

    Teng, Jun; Lu, Wei

    2009-03-01

    More and more large span structures have been built or are being built and their health is concerned about by civil engineers and investors, which arises to the problem of studying on several damage identification methods to give estimation on the health of the structure and the identification on damage location and damage degree. The damage identification methods in civil engineering are mostly based on dynamic characteristics, which have difficulties when applied to practical structures. Meanwhile, the strains of the structural important elements can give more exactly and more directly information for damage identification on damage location and damage degree. The information fusion for acceleration sensors and strain sensors is used for making a strategic decision on damage identification and the Dempster-Shafer evidence theory is used as the information fusion strategic decision, in which the strategic decision information fusion is a method to give the final decision based on the decision made by each kind of sensors according to some principle and some synthesized evaluation, that is, the final damage identification results are given based on the damage identification results using the structural dynamic characteristics and strain measurements. In addition, a finite element model of large span space shell structure is built and several damage cases of it are simulated, in the example, the structural dynamic characteristics damage index and strain measurements damage index are used to give the damage identification results, combining which the final damage identification result by strategic decision fusion is given too, while the method presented in the paper is proofed to be reliable and effective according to comparing the three kinds of damage identification results mentioned above.

  19. A planar shock isolation system with high-static-low-dynamic-stiffness characteristic based on cables

    NASA Astrophysics Data System (ADS)

    Ma, Yanhui; He, Minghua; Shen, Wenhou; Ren, Gexue

    2015-12-01

    In this paper, a simple and designable shock isolation system with ideal high-static-low-dynamic-stiffness (HSLDS) is proposed, which is intended for the horizontal plane shock isolation application. In this system, the isolated object is suspended by several bearing cables and constrained by a number of uniformly distributed pretensioned cables in the horizontal plane, where the low dynamic stiffness of the system is main controlled by the pretension of the planar cables, whilst the high static stiffness is determined by the axial stiffness of the planar cables and their geometric settings. To obtain the HSLDS characteristic of the system, a brief theoretical description of the relationship between the restoring force and displacement is derived. By obtaining the three-order Taylor expansion with sufficient accuracy of the restoring force, influence of planar cable parameters on the low dynamic and high static stiffness is thus given, therefore, the required HSLDS isolator can be easily designed by adjusting the planar cable length, pretension and tensile stiffness. Finally, the isotropy characteristic of the restoring force of the system with different numbers of planar cables is investigated. To evaluate the performance of the system, a rigid isolated object and flexible cables coupling simulation model considering the contacts of the system is established by using multibody dynamics approach. In this model, flexible cables are simulated by 3-node cable element based on the absolute nodal coordinate formulation; the contact between cable and isolated object is simulated based on Hertz contact theory. Finally, the time-domain shock excitation is converted from the design shock spectrum on the basis of BV043/85 criterion. The design procedure of this isolator and some useful guidelines for choosing cable parameters are presented. In addition, a summary about the performance of the isolators with different numbers of cables shocking in an arbitrary direction is

  20. Spin-Entry Characteristics of a Large Supersonic Bomber as Determined by Dynamic Model Tests

    NASA Technical Reports Server (NTRS)

    Bowman, James S.

    1965-01-01

    An investigation has been conducted in the Langley spin tunnel and at a catapult launch facility of a 1/60-scale dynamic model to determine the spin-entry characteristics of a large supersonic bomber. Catapult tests indicated that spin-entry motions were obtainable for a center-of-gravity location of 0.21 mean aerodynamic chord but were not obtainable at a center-of-gravity location of 0.25 mean aerodynamic chord. Deflected ailerons were effective in promoting or preventing the spin- entry motion and this effect was qualitatively the same as it was for the fully developed spin. Varying the configuration had little significant effect on the spin-entry characteristics. Brief tests conducted with the model in the Langley spin tunnel indicated that fully developed spins were obtainable at the forward center-of-gravity location and that spins were highly unlikely at the rearward center-of-location.

  1. 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.

  2. Kinematic, Dynamic, and Energy Characteristics of Diastolic Flow in the Left Ventricle

    PubMed Central

    Khalafvand, Seyed Saeid; Hung, Tin-Kan; Ng, Eddie Yin-Kwee; Zhong, Liang

    2015-01-01

    Blood flow characteristics in the normal left ventricle are studied by using the magnetic resonance imaging, the Navier-Stokes equations, and the work-energy equation. Vortices produced during the mitral valve opening and closing are modeled in a two-dimensional analysis and correlated with temporal variations of the Reynolds number and pressure drop. Low shear stress and net pressures on the mitral valve are obtained for flow acceleration and deceleration. Bernoulli energy flux delivered to blood from ventricular dilation is practically balanced by the energy influx and the rate change of kinetic energy in the ventricle. The rates of work done by shear and energy dissipation are small. The dynamic and energy characteristics of the 2D results are comparable to those of a 3D model. PMID:26417381

  3. 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.

  4. Lightning Surge Analysis for 500-kV Transmission Lines using Grounding Model with Dynamic Characteristics

    NASA Astrophysics Data System (ADS)

    Yasuda, Yoh; Kondo, Shuhei; Hara, Takehisa; Ikeda, Keiichi; Sonoi, Yasuo; Furuoka, Yoshihiro

    It is well known that grounding resistance under huge lightning current injection has current-dependent characteristics, whose mathematical model was already proposed by Liew and Darveniza in 1974. In this paper, where our final goal is reasonable design for lightning protection of 500-kV transmission tower, we adopt the dynamic grounding-resistance model to MODELS-ATP simulation. The effect of the model for the lightning surge analysis on 500-kV transmission line systems is discussed in detail.

  5. 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.

  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. 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.

  8. Nonlinear characteristics of joints as elements of multi-body dynamic systems

    NASA Technical Reports Server (NTRS)

    Crawley, Edward F.

    1989-01-01

    As the connecting elements in multi-body structures, joints play a pivotal role in the overall dynamic response of these systems. Obviously, the linear stiffness of the joint strongly influences the system frequencies, but the joints are also likely to be the dominant sources of damping and nonlinearities, especially in aircraft and space structures. The general characteristics of such joints will be discussed. Then the state of the art in nonlinear joint characterization techniques will be surveyed. Finally, the impact that joints have on the overall response of structures will be evaluated.

  9. Dynamical characteristics of Rydberg electrons released by a weak electric field

    DOE PAGES

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

    2016-04-08

    This paper discuss the dynamics of ultraslow electrons in the combined potential of an ionic core and a static electric field. 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.

  10. 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.

  11. 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.

  12. Relative permeability through fractures

    SciTech Connect

    Diomampo, Gracel, P.

    2001-08-01

    The mechanism of two-phase flow through fractures is of importance in understanding many geologic processes. Currently, two-phase flow through fractures is still poorly understood. In this study, nitrogen-water experiments were done on both smooth and rough parallel plates to determine the governing flow mechanism for fractures and the appropriate methodology for data analysis. The experiments were done using a glass plate to allow visualization of flow. Digital video recording allowed instantaneous measurement of pressure, flow rate and saturation. Saturation was computed using image analysis techniques. The experiments showed that gas and liquid phases flow through fractures in nonuniform separate channels. The localized channels change with time as each phase path undergoes continues breaking and reforming due to invasion of the other phase. The stability of the phase paths is dependent on liquid and gas flow rate ratio. This mechanism holds true for over a range of saturation for both smooth and rough fractures. In imbibition for rough-walled fractures, another mechanism similar to wave-like flow in pipes was also observed. The data from the experiments were analyzed using Darcy's law and using the concept of friction factor and equivalent Reynold's number for two-phase flow. For both smooth- and rough-walled fractures a clear relationship between relative permeability and saturation was seen. The calculated relative permeability curves follow Corey-type behavior and can be modeled using Honarpour expressions. The sum of the relative permeabilities is not equal one, indicating phase interference. The equivalent homogeneous single-phase approach did not give satisfactory representation of flow through fractures. The graphs of experimentally derived friction factor with the modified Reynolds number do not reveal a distinctive linear relationship.

  13. Determination of thermal/dynamic characteristics of lava flow from surface thermal measurements

    NASA Astrophysics Data System (ADS)

    Ismail-Zadeh, Alik; Melnik, Oleg; Korotkii, Alexander; Tsepelev, Igor; Kovtunov, Dmitry

    2016-04-01

    Rapid development of ground based thermal cameras, drones and satellite data allows getting repeated thermal images of the surface of the lava flow. Available instrumentation allows getting a large amount of data during a single lava flow eruption. These data require development of appropriate quantitative techniques to link subsurface dynamics with observations. We present a new approach to assimilation of thermal measurements at lava's surface to the bottom of the lava flow to determine lava's thermal and dynamic characteristics. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. Using an adjoint method we develop a numerical approach to the mathematical problem based on the determination of the missing boundary condition and lava flow characteristics. Numerical results show that in the case of smooth input data lava temperature and velocity can be determined with a high accuracy. A noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. The proposed approach to assimilate measured data brings an opportunity to estimate thermal budget of the lava flow.

  14. Effect of temperature on the dynamic characteristics of the glass-carbon fiber hybrid composites

    NASA Astrophysics Data System (ADS)

    Hidayat, Yon Afif; Susilo, Didik Djoko; Raharjo, Wijang W.

    2016-03-01

    This study aimed to investigate the effect of temperature on the dynamic characteristics of hybrid composites. Hybrid composites consisting of unsaturated polyester resin and glass fiber reinforced with carbon fiber. The volume fraction used in this study was 0.4. The hybrid composite was made using hand lay-up technique. The dynamic characteristics were obtained through vibration testing. The testing was conducted according to ASTM E756. The variables studied were composite without heating, heating at 100 °C, 200 °C and 280 °C. The experiments were done in three mounting configurations, i.e. upright, downward and horizontal configurations. The natural frequency and damping ratio was determined using half-power bandwidth method. The results showed that heating of composite structure affects the natural frequency and damping ratio of the hybrid composite. Heating until 100 °C will increase the natural frequency of the hybrid composite and decrease the damping ratio, but heating at the temperature above 100 °C will decrease the natural frequency and will damage the hybrid composite structure. The composite mounting configurations do not give significant effect to natural frequency and damping ratio of the hybrid composites.

  15. Dynamic modeling and characteristics analysis of a modal-independent linear ultrasonic motor.

    PubMed

    Li, Xiang; Yao, Zhiyuan; Zhou, Shengli; Lv, Qibao; Liu, Zhen

    2016-12-01

    In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor.

  16. Dynamic modeling and characteristics analysis of a modal-independent linear ultrasonic motor.

    PubMed

    Li, Xiang; Yao, Zhiyuan; Zhou, Shengli; Lv, Qibao; Liu, Zhen

    2016-12-01

    In this paper, an integrated model is developed to analyze the fundamental characteristics of a modal-independent linear ultrasonic motor with double piezoelectric vibrators. The energy method is used to model the dynamics of the two piezoelectric vibrators. The interface forces are coupled into the dynamic equations of the two vibrators and the moving platform, forming a whole machine model of the motor. The behavior of the force transmission of the motor is analyzed via the resulting model to understand the drive mechanism. In particular, the relative contact length is proposed to describe the intermittent contact characteristic between the stator and the mover, and its role in evaluating motor performance is discussed. The relations between the output speed and various inputs to the motor and the start-stop transients of the motor are analyzed by numerical simulations, which are validated by experiments. Furthermore, the dead-zone behavior is predicted and clarified analytically using the proposed model, which is also observed in experiments. These results are useful for designing servo control scheme for the motor. PMID:27518427

  17. Vascular Permeability and Drug Delivery in Cancers

    PubMed Central

    Azzi, Sandy; Hebda, Jagoda K.; Gavard, Julie

    2013-01-01

    The endothelial barrier strictly maintains vascular and tissue homeostasis, and therefore modulates many physiological processes such as angiogenesis, immune responses, and dynamic exchanges throughout organs. Consequently, alteration of this finely tuned function may have devastating consequences for the organism. This is particularly obvious in cancers, where a disorganized and leaky blood vessel network irrigates solid tumors. In this context, vascular permeability drives tumor-induced angiogenesis, blood flow disturbances, inflammatory cell infiltration, and tumor cell extravasation. This can directly restrain the efficacy of conventional therapies by limiting intravenous drug delivery. Indeed, for more effective anti-angiogenic therapies, it is now accepted that not only should excessive angiogenesis be alleviated, but also that the tumor vasculature needs to be normalized. Recovery of normal state vasculature requires diminishing hyperpermeability, increasing pericyte coverage, and restoring the basement membrane, to subsequently reduce hypoxia, and interstitial fluid pressure. In this review, we will introduce how vascular permeability accompanies tumor progression and, as a collateral damage, impacts on efficient drug delivery. The molecular mechanisms involved in tumor-driven vascular permeability will next be detailed, with a particular focus on the main factors produced by tumor cells, especially the emblematic vascular endothelial growth factor. Finally, new perspectives in cancer therapy will be presented, centered on the use of anti-permeability factors and normalization agents. PMID:23967403

  18. Internal Dynamics and Boundary Forcing Characteristics Associated with Interannual Variability of the Asian Summer Monsoon

    NASA Technical Reports Server (NTRS)

    Lau, K.- M.; Kim, K.-M.; Yang, S.

    1998-01-01

    In this paper, we present a description of the internal dynamics and boundary forcing characteristics of two major components of the Asian summer monsoon (ASM), i.e., the South Asian (SAM) and the Southeast-East Asian monsoon (SEAM). The description is based on a new monsoon-climate paradigm in which the variability of ASM is considered as the outcome of the interplay of a "fast" and an "intermediate" monsoon subsystem, under the influenced of the "slow" varying external forcings. Two sets of regional monsoon indices derived from dynamically consistent rainfall and wind data are used in this study. For SAM, the internal dynamics is represented by that of a "classical" monsoon system where the anomalous circulation is governed by Rossby-wave dynamics, i.e., generation of anomalous vorticity induced by an off-equatorial heat source is balanced by planetary vorticity advection. On the other hand, the internal dynamics of SEAM is characterized by a "hybrid" monsoon system featuring multi-cellular meridional circulation over the East Asian section, extending from the deep tropics to midlatitudes. These meridional-cells link tropical heating to extratropical circulation system via the East Asian jetstream, and are responsible for the characteristic occurrences of zonally oriented anomalous rainfall patterns over East Asian and the subtropical western Pacific. In the extratropical regions, the major upper level vorticity balance is by anomalous vorticity advection and generation by the anomalous divergent circulation. A consequence of this is that compared to SAM, the SEAM is associated with stronger teleconnection patterns to regions outside the ASM. A strong SAM is linked to basin-scale sea surface temperature (SST) fluctuation with significant signal in the equatorial eastern Pacific. During the boreal spring SST warming in the Arabian Sea and the subtropical western Pacific may lead to a strong SAM. For SEAM, interannual variability is tied to SSTA over the Sea of

  19. Dynamic response characteristics of the high-temperature superconducting maglev system under lateral eccentric distance

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Zheng, Jun; Si, Shuaishuai; Qian, Nan; Li, Haitao; Li, Jipeng; Deng, Zigang

    2016-07-01

    Off-centre operation of high-temperature superconducting (HTS) maglev systems caused by inevitable conditions such as the misregistration of vehicle, crosswind and curve negotiation, may change the distribution of the trapped flux in the HTS bulks and the magnetic interaction between HTS bulks and the PMG. It impacts on the performance of HTS maglev, and more seriously makes the maglev vehicle overturned. Therefore, understanding the performance of the HTS maglev in off-center operation is very important. In this paper, the dynamic response characteristics of a cryostat with twenty-four onboard YBaCuO superconductor bulks were experimentally investigated at different eccentric distances under loads before the initial FC process. Parameters such as vibration accelerations, displacement, natural frequency and dynamic stiffness were acquired and analyzed via the B&K vibration analyzer and laser displacement sensors. Results suggest that the natural frequency and dynamic stiffness of the maglev vehicle would be obviously reduced with the eccentric distance, posing negative effects on the stability of HTS maglev.

  20. Dynamic thermal characteristics of heat pipe via segmented thermal resistance model for electric vehicle battery cooling

    NASA Astrophysics Data System (ADS)

    Liu, Feifei; Lan, Fengchong; Chen, Jiqing

    2016-07-01

    Heat pipe cooling for battery thermal management systems (BTMSs) in electric vehicles (EVs) is growing due to its advantages of high cooling efficiency, compact structure and flexible geometry. Considering the transient conduction, phase change and uncertain thermal conditions in a heat pipe, it is challenging to obtain the dynamic thermal characteristics accurately in such complex heat and mass transfer process. In this paper, a "segmented" thermal resistance model of a heat pipe is proposed based on thermal circuit method. The equivalent conductivities of different segments, viz. the evaporator and condenser of pipe, are used to determine their own thermal parameters and conditions integrated into the thermal model of battery for a complete three-dimensional (3D) computational fluid dynamics (CFD) simulation. The proposed "segmented" model shows more precise than the "non-segmented" model by the comparison of simulated and experimental temperature distribution and variation of an ultra-thin micro heat pipe (UMHP) battery pack, and has less calculation error to obtain dynamic thermal behavior for exact thermal design, management and control of heat pipe BTMSs. Using the "segmented" model, the cooling effect of the UMHP pack with different natural/forced convection and arrangements is predicted, and the results correspond well to the tests.

  1. Improving the dynamic characteristics of body-in-white structure using structural optimization.

    PubMed

    Yahaya Rashid, Aizzat S; Ramli, Rahizar; Mohamed Haris, Sallehuddin; Alias, Anuar

    2014-01-01

    The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process. PMID:25101312

  2. Vulcanization characteristics and dynamic mechanical behavior of natural rubber reinforced with silane modified silica.

    PubMed

    Chonkaew, Wunpen; Minghvanish, Withawat; Kungliean, Ulchulee; Rochanawipart, Nutthaya; Brostow, Witold

    2011-03-01

    Two silane coupling agents were used for hydrolysis-condensation reaction modification of nanosilica surfaces. The surface characteristics were analyzed using Fourier transform infrared spectroscopy (FTIR). The vulcanization kinetics of natural rubber (NR) + silica composites was studied and compared to behavior of the neat NR using differential scanning calorimetry (DSC) in the dynamic scan mode. Dynamic mechanical analysis (DMA) was performed to evaluate the effects of the surface modification. Activation energy E(a) values for the reaction are obtained. The presence of silica, modified or otherwise, inhibits the vulcanization reaction of NR. The neat silica containing system has the lowest cure rate index and the highest activation energy for the vulcanization reaction. The coupling agent with longer chains causes more swelling and moves the glass transition temperature T(g) downwards. Below the glass transition region, silica causes a lowering of the dynamic storage modulus G', a result of hindering the cure reaction. Above the glass transition, silica-again modified or otherwise-provides the expected reinforcement effect. PMID:21449342

  3. Evaporation characteristics of thin film liquid argon in nano-scale confinement: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Hasan, Mohammad Nasim; Shavik, Sheikh Mohammad; Rabbi, Kazi Fazle; Haque, Mominul

    2016-07-01

    Molecular dynamics simulation has been carried out to explore the evaporation characteristics of thin liquid argon film in nano-scale confinement. The present study has been conducted to realize the nano-scale physics of simultaneous evaporation and condensation inside a confined space for a three phase system with particular emphasis on the effect of surface wetting conditions. The simulation domain consisted of two parallel platinum plates; one at the top and another at the bottom. The fluid comprised of liquid argon film at the bottom plate and vapor argon in between liquid argon and upper plate of the domain. Considering hydrophilic and hydrophobic nature of top and bottom surfaces, two different cases have been investigated: (i) Case A: Both top and bottom surfaces are hydrophilic, (ii) Case B: both top and bottom surfaces are hydrophobic. For all cases, equilibrium molecular dynamics (EMD) was performed to reach equilibrium state at 90 K. Then the lower wall was set to four different temperatures such as 110 K, 120 K, 130 K and 140 K to perform non-equilibrium molecular dynamics (NEMD). The variation of temperature and density as well as the variation of system pressure with respect to time were closely monitored for each case. The heat fluxes normal to top and bottom walls were estimated and discussed to illuminate the effectiveness of heat transfer in both hydrophilic and hydrophobic confinement at various boundary temperatures of the bottom plate.

  4. Vulcanization characteristics and dynamic mechanical behavior of natural rubber reinforced with silane modified silica.

    PubMed

    Chonkaew, Wunpen; Minghvanish, Withawat; Kungliean, Ulchulee; Rochanawipart, Nutthaya; Brostow, Witold

    2011-03-01

    Two silane coupling agents were used for hydrolysis-condensation reaction modification of nanosilica surfaces. The surface characteristics were analyzed using Fourier transform infrared spectroscopy (FTIR). The vulcanization kinetics of natural rubber (NR) + silica composites was studied and compared to behavior of the neat NR using differential scanning calorimetry (DSC) in the dynamic scan mode. Dynamic mechanical analysis (DMA) was performed to evaluate the effects of the surface modification. Activation energy E(a) values for the reaction are obtained. The presence of silica, modified or otherwise, inhibits the vulcanization reaction of NR. The neat silica containing system has the lowest cure rate index and the highest activation energy for the vulcanization reaction. The coupling agent with longer chains causes more swelling and moves the glass transition temperature T(g) downwards. Below the glass transition region, silica causes a lowering of the dynamic storage modulus G', a result of hindering the cure reaction. Above the glass transition, silica-again modified or otherwise-provides the expected reinforcement effect.

  5. Effects of cockpit lateral stick characteristics on handling qualities and pilot dynamics

    NASA Technical Reports Server (NTRS)

    Mitchell, David G.; Aponso, Bimal L.; Klyde, David H.

    1992-01-01

    This report presents the results of analysis of cockpit lateral control feel-system studies. Variations in feel-system natural frequency, damping, and command sensing reference (force and position) were investigated, in combination with variations in the aircraft response characteristics. The primary data for the report were obtained from a flight investigation conducted with a variable-stability airplane, with additional information taken from other flight experiments and ground-based simulations for both airplanes and helicopters . The study consisted of analysis of handling qualities ratings and extraction of open-loop, pilot-vehicle describing functions from sum-of-sines tracking data, including, for a limited subset of these data, the development of pilot models. The study confirms the findings of other investigators that the effects on pilot opinion of cockpit feel-system dynamics are not equivalent to a comparable level of added time delay, and until a more comprehensive set of criteria are developed, it is recommended that feel-system dynamics be considered a delay-inducing element in the aircraft response. The best correlation with time-delay requirements was found when the feel-system dynamics were included in the delay measurements, regardless of the command reference. This is a radical departure from past approaches.

  6. Improving the Dynamic Characteristics of Body-in-White Structure Using Structural Optimization

    PubMed Central

    Yahaya Rashid, Aizzat S.; Mohamed Haris, Sallehuddin; Alias, Anuar

    2014-01-01

    The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process. PMID:25101312

  7. Improving the dynamic characteristics of body-in-white structure using structural optimization.

    PubMed

    Yahaya Rashid, Aizzat S; Ramli, Rahizar; Mohamed Haris, Sallehuddin; Alias, Anuar

    2014-01-01

    The dynamic behavior of a body-in-white (BIW) structure has significant influence on the noise, vibration, and harshness (NVH) and crashworthiness of a car. Therefore, by improving the dynamic characteristics of BIW, problems and failures associated with resonance and fatigue can be prevented. The design objectives attempt to improve the existing torsion and bending modes by using structural optimization subjected to dynamic load without compromising other factors such as mass and stiffness of the structure. The natural frequency of the design was modified by identifying and reinforcing the structure at critical locations. These crucial points are first identified by topology optimization using mass and natural frequencies as the design variables. The individual components obtained from the analysis go through a size optimization step to find their target thickness of the structure. The thickness of affected regions of the components will be modified according to the analysis. The results of both optimization steps suggest several design modifications to achieve the target vibration specifications without compromising the stiffness of the structure. A method of combining both optimization approaches is proposed to improve the design modification process.

  8. Navier-Stokes Simulation of the Canard-Wing-Body Longitudinal Dynamic Stability Characteristics

    NASA Technical Reports Server (NTRS)

    Tu, Eugene L.; VanDalsem, William R. (Technical Monitor)

    1996-01-01

    Many modern aircraft are canard-configured for aircraft control and improved aerodynamic performance. Canards can often enhance aircraft cruise performance, maneuverability and agility. For close-coupled canard configurations, the aerodynamic interaction between the canard and wing significantly changes the flow characteristics of the wing. In unsteady flow, such changes in the flow structure and performance of wings can be quite pronounced. Accurate modeling of the unsteady aerodynamics is essential for potential CFD design and analysis of such configurations. A time-accurate numerical simulation is performed to study the unsteady aerodynamic interaction between a canard and wing with emphasis on the effects of the canard on the configuration's dynamic response characteristics. The thin-layer Reynolds-averaged Navier-Stokes Equations with various turbulence models are used in this study. Computations are made on a generic, analytically-defined, close-coupled canard-wing-body configuration which has been the subject of numerous previously published experimental studies during the 1970's to mid-80's. More recently, a series of steady-flow simulations has been performed and published by the author. In the current study, the configuration is given prescribed ramp and oscillatory motions in order to predict characteristics such as the damping-in-pitch and oscillatory longitudinal stability parameters. The current computations are made at high-subsonic and transonic Mach numbers, moderate angles-of- attack from -4 to 20 degrees, and at various pitch rates and reduced frequencies. Comparisons of pressures and integrated force quantities (e.g. lift, drag, pitching moment and selected dynamic parameters) are made with other published computational results and available experimental data. Results showing the unsteady effects of the canard on surface pressures, integrated forces, canard-wing vortex interaction and vortex breakdown will be presented.

  9. Extreme Rainfall Impacts in Fractured Permeable Catchments

    NASA Astrophysics Data System (ADS)

    Ireson, A. M.; Butler, A. P.

    2009-12-01

    Serious groundwater flooding events have occurred on Chalk catchments in both the UK and north west Europe in the last decade, causing substantial amounts of disruption and economic damage. These fractured, permeable catchments are characterized by low surface runoff, high baseflow indices and strongly attenuated streamflow hydrographs. They have a general resilience to drought and pluvial/fluvial flooding. The small pore size of the Chalk matrix (~ 1 µm) exerts a high suction, such that dynamic storage is primarily due to the fractures, and amounts to ~ 1% of the total volume. As a result, under sustained rainfall the water table can rise up to exceptional levels leading to surface water emergence from springs and valleys. Floodwater may slowly drain with the topography, or, in localized depressions, it may simply pond until the groundwater levels decline. In winter 2000/1, a sequence of individually unexceptional rainfall events over several months led to large scale flooding in the Pang catchment, Berkshire, UK. By contrast, an extreme rainfall event on 20th July 2007 in the same catchment caused a very rapid response at the water table, but due to the antecedent conditions did not lead to flooding. The objective of this study is to quantify how the water table in a fractured permeable catchment responds to different types of rainfall, and the implications of this for groundwater flooding. We make use of measurements from the Pang catchment, including: rainfall (tipping bucket gauges); actual evaporation (eddy flux correlation); soil water content (profile probes and neutron probes); near surface matric potential (tensiometers and equitensiometers); deep (>10m) matric potential (deep jacking tensiometers); and water table elevation (piezometers). Conventional treatment of recharge in Chalk aquifers considers a fixed bypass component of rainfall, normally 15%, to account for the role of the fractures. However, interpretation of the field data suggest three modes

  10. Instrumentation for Measurement of Gas Permeability of Polymeric Membranes

    NASA Technical Reports Server (NTRS)

    Upchurch, Billy T.; Wood, George M.; Brown, Kenneth G.; Burns, Karen S.

    1993-01-01

    A mass spectrometric 'Dynamic Delta' method for the measurement of gas permeability of polymeric membranes has been developed. The method is universally applicable for measurement of the permeability of any gas through polymeric membrane materials. The usual large sample size of more than 100 square centimeters required for other methods is not necessary for this new method which requires a size less than one square centimeter. The new method should fulfill requirements and find applicability for industrial materials such as food packaging, contact lenses and other commercial materials where gas permeability or permselectivity properties are important.

  11. Permeability of alkaline magmas: a study from Campi Flegrei, Italy

    NASA Astrophysics Data System (ADS)

    Polacci, M.; Bouvet de Maissoneuve, C.; Giordano, D.; Piochi, M.; Degruyter, W.; Bachmann, O.; Mancini, L.

    2012-04-01

    Knowledge of permeability is of paramount importance for understanding the evolution of magma degassing during pre-, syn- and post-eruptive volcanic processes. Most permeability estimates existing to date refer to magmas of calc-alkaline compositions. We report here the preliminary results of permeability measurements performed on alkali-trachyte products erupted from the Campanian Ignimbrite (CI) and Monte Nuovo (MTN), two explosive eruptions from Campi Flegrei (CF), an active, hazardous caldera west of Naples, Southern Italy. Darcian (viscous) permeability spans a wide range between 10^-11 and 10^-14 m^2. We observe that the most permeable samples are the scoria clasts from the upper units of MTN; pumice samples from the Breccia Museo facies of CI are instead the least permeable. Non-Darcian (inertial) permeability follows the same trend as Darcian permeability. The first implication of this study is that porosity in alkaline as well as calc-alkaline magmas does not exert a first order control on permeability (e.g. the MTN samples are the most permeable but not the most porous). Second, sample geometry exhibits permeability anisotropy (higher permeability in the direction of vesicle elongation), suggesting stronger degassing in the vertical direction in the conduit. In addition, inertial effects are higher across the sample. As inertial effects are potentially generated by tortuosity (or tortuous vesicle paths), tortuosity is likely higher horizontally than vertically in the conduit. Finally, the measured CF permeability values overlap with those of rhyolitic pumice clasts from the Kos Plateau Tuff (Bouvet de Maisonneuve et al., 2009), together with CI one of the major Quaternary explosive eruptions of the Mediterranean region. This indicates that gas flow is strongly controlled by the geometry of the porous media, which is generated by the bubble dynamics during magma ascent. Therefore, permeability will depend on composition through the rheological properties

  12. [Research on permeability of landfill's body in primary compression].

    PubMed

    Liu, Hui; Huang, Tao; Zhang, Chi

    2009-12-01

    Refuse degradation and landfill leachate treatment are the main research directions of landfill technology at present, but permeability characteristics of landfill body are paid little attention on. According to this actuality, the study selected four kinds of landfill's bodies under different pressures as study objects and tested the permeability characteristics in the stage of main compression settlement. Through the laboratory physical simulation experiments, the results show that the data of determination and analysis on landfill's bodies under four difference pressures conform to Darcy's law. Because the change of COD is in the phase of acid producing, its impact on permeability can not be considered. Based on these conditions, the calculation results of permeability coefficient indicate that during the course of the main compression settlement, the change law of landfill permeability coefficient index is approximately agreed with nature exponential law, expect for the condition of landfill body without pressure. Meanwhile, the landfill permeability coefficient values under four difference pressures are in the range of 10(-4.5)-10(-5.3) m x s(-1), which are consistent with the typical representative values of garbage permeability coefficient.

  13. Characterization and estimation of permeability correlation structure from performance data

    SciTech Connect

    Ershaghi, I.; Al-Qahtani, M.

    1997-08-01

    In this study, the influence of permeability structure and correlation length on the system effective permeability and recovery factors of 2-D cross-sectional reservoir models, under waterflood, is investigated. Reservoirs with identical statistical representation of permeability attributes are shown to exhibit different system effective permeability and production characteristics which can be expressed by a mean and variance. The mean and variance are shown to be significantly influenced by the correlation length. Detailed quantification of the influence of horizontal and vertical correlation lengths for different permeability distributions is presented. The effect of capillary pressure, P{sub c1} on the production characteristics and saturation profiles at different correlation lengths is also investigated. It is observed that neglecting P{sub c} causes considerable error at large horizontal and short vertical correlation lengths. The effect of using constant as opposed to variable relative permeability attributes is also investigated at different correlation lengths. Next we studied the influence of correlation anisotropy in 2-D reservoir models. For a reservoir under five-spot waterflood pattern, it is shown that the ratios of breakthrough times and recovery factors of the wells in each direction of correlation are greatly influenced by the degree of anisotropy. In fully developed fields, performance data can aid in the recognition of reservoir anisotropy. Finally, a procedure for estimating the spatial correlation length from performance data is presented. Both the production performance data and the system`s effective permeability are required in estimating the correlation length.

  14. Fractal Analysis of Stress Sensitivity of Permeability in Porous Media

    NASA Astrophysics Data System (ADS)

    Tan, Xiao-Hua; Li, Xiao-Ping; Liu, Jian-Yi; Zhang, Lie-Hui; Cai, Jianchao

    2015-12-01

    A permeability model for porous media considering the stress sensitivity is derived based on mechanics of materials and the fractal characteristics of solid cluster size distribution. The permeability of porous media considering the stress sensitivity is related to solid cluster fractal dimension, solid cluster fractal tortuosity dimension, solid cluster minimum diameter and solid cluster maximum diameter, Young's modulus, Poisson's ratio, as well as power index. Every parameter has clear physical meaning without the use of empirical constants. The model predictions of permeability show good agreement with those obtained by the available experimental expression. The proposed model may be conducible to a better understanding of the mechanism for flow in elastic porous media.

  15. Wind tunnel tests of the dynamic characteristics of the fluidic rudder

    NASA Technical Reports Server (NTRS)

    Belsterling, C. A.

    1976-01-01

    The fourth phase is given of a continuing program to develop the means to stabilize and control aircraft without moving parts or a separate source of power. Previous phases have demonstrated the feasibility of (1) generating adequate control forces on a standard airfoil, (2) controlling those forces with a fluidic amplifier and (3) cascading non-vented fluidic amplifiers operating on ram air supply pressure. The foremost objectives of the fourth phase covered under Part I of this report were to demonstrate a complete force-control system in a wind tunnel environment and to measure its static and dynamic control characteristics. Secondary objectives, covered under Part II, were to evaluate alternate configurations for lift control. The results demonstrate an overall response time of 150 msec, confirming this technology as a viable means for implementing low-cost reliable flight control systems.

  16. Dynamic characteristics of dual-frequency nematic liquid crystal with quasi-homeotropic twist structure

    NASA Astrophysics Data System (ADS)

    Konshina, E. A.; Fedorov, M. A.; Amosova, L. P.

    2010-07-01

    Dynamic characteristics of a liquid crystal (LC) cell with a quasi-homeotropic twist structure formed in a dual-frequency nematic liquid crystal (DFNLC) layer with the director pretilt angle increased to 60° have been experimentally studied. The cell was switched from the off to on state using a 30-kHz electric field, while the reverse (off/on) switching was effected by a 1-kHz field. An increase in the director pretilt angle allowed the switch-on time of a 6.4-μm-thick DFNLC cell to be reduced to 1 ms and the relaxation (switch-off) time, to 0.5 ms.

  17. Dynamic response characteristics of a circulation control rotor model pneumatic system

    NASA Technical Reports Server (NTRS)

    Watkins, C. B.; Reader, K. R.; Dutta, S. K.

    1985-01-01

    Numerical and experimental simulation of unsteady airflow through the control valve and slotted air duct of a circulation control rotor is described. The numerical analysis involves the solution of the quasi-one-dimensional compressible fluid-dynamic equations in the blade air duct together with the coupled isentropic flow equations for flow into the blade through the valve and out of the blade through the Coanda slot. Numerical solutions are compared with basic experimental results obtained for a mockup of a circulation control rotor and its pneumatic valving system. The pneumodynamic phenomena that were observed are discussed with particular emphasis on the characteristic system time lags associated with the response of the flow variables to transient and periodic control valve inputs.

  18. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

    PubMed Central

    Zhou, Li-li; Liu, Rang-su; Tian, Ze-an; Liu, Hai-rong; Hou, Zhao-yang; Peng, Ping

    2016-01-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule. PMID:27526660

  19. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study.

    PubMed

    Zhou, Li-Li; Liu, Rang-Su; Tian, Ze-An; Liu, Hai-Rong; Hou, Zhao-Yang; Peng, Ping

    2016-01-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90-150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule. PMID:27526660

  20. An opportunity for directly estimating the characteristics of zero-point dynamics in polyethylene crystals

    NASA Astrophysics Data System (ADS)

    Vettegren, V. I.; Slutsker, A. I.; Titenkov, L. S.; Kulik, V. B.; Gilyarov, V. L.

    2007-02-01

    For large polyethylene crystallites (100 × 60 × 60 nm), the width of the Raman band at 1129 cm-1 and the angular position of the x-ray equatorial 110 reflection were measured as a function of temperature over the range 5-300 K. It is found that the Raman bandwidth has an athermic (zero-point) component at low temperatures. This component is used to estimate the zero-point energies of torsional and bending vibrations of polyethylene molecules. These energies are close to those obtained from analyzing the x-ray diffraction data. It is concluded that the characteristics of zero-point dynamics can be determined directly from measuring the zero-point width of a Raman band.

  1. Crystallization characteristics in supercooled liquid zinc during isothermal relaxation: A molecular dynamics simulation study

    NASA Astrophysics Data System (ADS)

    Zhou, Li-Li; Liu, Rang-Su; Tian, Ze-An; Liu, Hai-Rong; Hou, Zhao-Yang; Peng, Ping

    2016-08-01

    The crystallization characteristics in supercooled liquid Zn during isothermal relaxation were investigated using molecular dynamics simulations by adopting the cluster-type index method (CTIM) and the tracing method. Results showed that the crystallization process undergo three different stages. The size of the critical nucleus was found to be approximately 90–150 atoms in this system; the growth of nuclei proceeded via the successive formation of hcp and fcc structures with a layered distribution; and finally, the system evolved into a much larger crystal with a distinct layered distribution of hcp and fcc structures with an 8R stacking sequence of ABCBACAB by adjusting all of the atoms in the larger clusters according to a certain rule.

  2. Dynamic response characteristics of the potentiometric carbon dioxide sensor for the determination of aspartame.

    PubMed

    Nikolelis, D P; Krull, U J

    1990-07-01

    The dynamic response characteristics of a carbon dioxide gas sensor were studied to determine the potential for application of the device to the kinetic assay of substrate(s) under pseudo first-order kinetics. The dependence of the time constant on the concentration of carbon dioxide was determined by using convolution mathematics to analyse potentiometric changes caused by abrupt alterations of gas concentration. The operational conditions of the CO2 sensor were optimised for the development of enzyme electrodes, so that the mass-transport phenomena occurring during the course of the enzymic reactions were enhanced. As a result, the kinetic analysis of substrate(s) was performed more rapidly (2-6 min), with greater sensitivity and with an improved detection limit (10-5 M). A kinetic reaction-rate method for the determination of aspartame in dietary foodstuffs is proposed as a rapid and inexpensive alternative to a classical high-performance liquid chromatographic method.

  3. Dual-permeability model for flow in shrinking soil with dominant horizontal deformation

    NASA Astrophysics Data System (ADS)

    Coppola, Antonio; Gerke, Horst H.; Comegna, Alessandro; Basile, Angelo; Comegna, Vincenzo

    2012-08-01

    In this study, a dual-permeability approach is discussed for modeling preferential flow in shrinking soils by accounting for shrinking effects on macropore and matrix domain hydraulic properties. Conceptually, the soil is treated as a dual-permeability bulk porous medium consisting of two dynamic interacting pore domains: (1) the fracture (from shrinkage) pore domain and (2) the aggregate (interparticles plus structural) or matrix pore domain. The model assumes that the swell-shrink dynamics is represented by the inversely proportional volume changes of the fracture and matrix domains, while the overall porosity of the total soil, and hence the layer thickness, remains constant. This assumption can be justified for soils with dominant horizontal soil deformation in the swelling-shrinkage process (shrinkage geometry factor,rs> 3). The swell-shrink dynamics was included in a one-dimensional dual-permeability model in which water flow in both domains was described with the Richards' equation. Swell-shrink dynamics was incorporated in the model partly by changing the coupled domain-specific hydraulic properties according to the shrinkage characteristics of the matrix and partly by allowing the fractional contribution of the two domains to change with the pressure head. As a first step, the hysteresis in the swell-shrink dynamics was not included. We also assumed that the aggregate behavior and its hydraulic properties depend only on the average aggregate water content and not on its internal real distribution. The model proved, describing successfully effects of shrinkage on the spatial and temporal evolution of water contents measured in a silty loam soil in the field.

  4. Simulation and experimental validation of vehicle dynamic characteristics for displacement-sensitive shock absorber using fluid-flow modelling

    NASA Astrophysics Data System (ADS)

    Lee, Choon-Tae; Moon, Byung-Young

    2006-02-01

    In this study, a new mathematical dynamic model of shock absorber is proposed to predict the dynamic characteristics of an automotive system. The performance of shock absorber is directly related to the car behaviours and performance, both for handling and ride comfort. Damping characteristics of automotive can be analysed by considering the performance of displacement-sensitive shock absorber (DSSA) for the ride comfort. The proposed model of the DSSA is considered as two modes of damping force (i.e. soft and hard) according to the position of piston. For the simulation validation of vehicle-dynamic characteristics, the DSSA is mathematically modelled by considering the fluid flow in chamber and valve in accordance with the hard, transient and soft zone. And the vehicle dynamic characteristic of the DSSA is analysed using quarter car model. To show the effectiveness of the proposed damper, the analysed results of damping characteristics were compared with the experimental results, which showed similar behaviour with the corresponding experimental one. The simulation results of frequency response are compared with the ones of passive shock absorber. From the simulation results of the DSSA, it can be concluded that the ride comfort of the DSSA increased at the low-amplitude road condition and the driving safety was increased partially at the high-amplitude road condition. The results reported herein will provide a better understanding of the shock absorber. Moreover, it is believed that those properties of the results can be utilised in the dynamic design of the automotive system.

  5. Dynamic characteristics of an active coastal spreading area using ambient noise measurements—Anchor Bay, Malta

    NASA Astrophysics Data System (ADS)

    Galea, Pauline; D'Amico, Sebastiano; Farrugia, Daniela

    2014-11-01

    Anchor Bay and surrounding regions are located on the northwest coast of the island of Malta, Central Mediterranean. The area is characterized by a coastal cliff environment having an outcropping layer of hard coralline limestone (UCL) resting on a thick (up to 50 m) layer of clays and marls (Blue Clay, BC). This configuration gives rise to coastal instability effects, in particular lateral spreading phenomena and rock falls. Previous and ongoing studies have identified both lateral spreading rates and vertical motions of several millimetres per year. The area is an interesting natural laboratory as coastal detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of this study area by recording ambient noise time-series at more than 30 points, over an area of 0.07 km2, using a portable three-component seismograph. The time-series are processed to give both horizontal-to-vertical spectral ratio graphs (H/V) as well as frequency-dependent polarisation analysis. The H/V graphs illustrate and quantify aspects of site resonance effects due both to underlying geology as well as to mechanical resonance of partly or wholly detached blocks. The polarization diagrams indicate the degree of linearity and predominant directions of vibrational effects. H/V curves closer to the cliff edge show complex responses at higher frequencies, characteristic of the dynamic behaviour of individual detached blocks. Particle motion associated with the higher frequencies shows strongly directional polarization and a high degree of linearity at well-defined frequencies, indicative of normal-mode vibration. The stable plateau areas, on the other hand, show simple, single-peak H/V curves representative of the underlying stratification and no predominant polarization direction. These results, which will be compared with those from other experiments in the area, have important implications for the

  6. Zonal Wind Speeds, Vortex Characteristics, and Wave Dynamics in Saturn's Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Blalock, John J.; Draham, R. L.; Holmes, J. A.; Sayanagi, K. M.

    2013-10-01

    We examine images returned from Cassini spacecraft's ISS camera between 2007 and 2012 to analyze zonal wind speeds, vortex characteristics, and wave dynamics in Saturn's northern hemisphere. Our analysis focused on datasets that provided near-simultaneous coverage in the near-infrared continuum band at 752 nm (CB2 filter) and the methane bands at 727 and 890 nm (MT2 and MT3 filters). We measure the zonal wind speeds by analyzing cloud motions using one-dimensional correlation method similar to Limaye (1986). Our goal is to determine the vertical wind shear on Saturn in a manner similar to that done for Jupiter by Li et al (2006). Because the images captured in the methane bands are sensitive to higher altitudes than those in the continuum band, we are able to measure wind speeds at different altitudes. Next, we study the characteristics of multiple northern hemisphere vortices using methods similar to the analysis of a long-lived cyclonic spot in the southern hemisphere of Saturn (del Rio-Gatztelurrutia et al, 2010). We analyze the interactions and evolutions of the vortices, and compare them with the Voyager-era northern hemisphere study (Sromovsky et al, 1983). Finally, we analyze the dynamics of the wave propagating at 45 degree N planetocentric latitude in the northern flank of an eastward zonal jet that peaks at 42 degree N. This new wave is located to the north of the Ribbon wave at 42 degree N originally found during Voyager (Sromovsky et al, 1983; Godfrey and Moore, 1986); the Ribbon wave was not present in our 2007-2012 images. We calculate the Fourier components of the new wave, and compare our findings with previous analyses and prediction of the Ribbon wave (Sromovsky et al, 1983; Godfrey and Moore, 1986; Sanchez-Lavega, 2002; Sayanagi et al, 2010).

  7. Optimal rheological characteristics in dynamic stability of polymer flow through porous media: Topical report

    SciTech Connect

    Gao, H.W.; French, T.R.

    1988-04-01

    To identify the optimal rheological characteristics for maintaining the dynamic stability of polymer solutions flowing through porous media, displacement tests with a Newtonian fluid and a non-Newtonian fluid were performed in a 4-ft Berea sandstone core. A solution of 63 wt pct gylcerin in 53 meg/1 NaCL and a solution of 1500 ppM Pusher 500 in 53 meq/1 NaCl were used as the Newtonian fluid and non-Newtonian fluid, respectively. Two flow rates one in the purely viscous regime and one in the viscoelastic flow regime of Pusher 500 in Berea sandstone, were used in the displacement tests. The effluents collected were analyzed to determine polymer and tracer concentrations. The viscosities of the effluents were also measured with a Contraves viscometer. By comparing the concentration profiles obtained in tests with Pusher 500 and in those with gylcerin, the effects of flow rate, mobility ratio, and rheological characteristics on the dynamic stability of polymer flow in porous media were determined. At both leading and trailing edges of the polymer slug, stability increases with decreasing mobility ratio. At both high and low flow rates, a Newtonian fluid gives a more stable displacement at the fluid front than does a non-Newtonian fluid. Measurements on the mixing lengths at the back edge show that the size of the mobility buffer bank required for a flow rate at reservior conditions (viscous flow regime) would be less for a Newtonian fluid than for a non-Newtonian fluid. At a flow rate in the viscoelastic flow regime, the required size of the mobility buffer bank is less for a non-Newtonian fluid than for a Newtonian fluid. 39 refs., 13 figs., 1 tab.

  8. Neutron Transport Characteristics of a Nuclear Reactor Based Dynamic Neutron Imaging System

    SciTech Connect

    Khaial, Anas M.; Harvel, Glenn D.; Chang, Jen-Shih

    2006-07-01

    An advanced dynamic neutron imaging system has been constructed in the McMaster Nuclear Reactor (MNR) for nondestructive testing and multi-phase flow studies in energy and environmental applications. A high quality neutron beam is required with a thermal neutron flux greater than 5.0 x 10{sup 6} n/cm{sup 2}-s and a collimation ratio of 120 at image plane to promote high-speed neutron imaging up to 2000 frames per second. Neutron source strength and neutron transport have been experimentally and numerically investigated. Neutron source strength at the beam tube entrance was evaluated experimentally by measuring the thermal and fast neutron fluxes, and simple analytical neutron transport calculations were performed based upon these measured neutron fluxes to predict facility components in accordance with high-speed dynamic neutron imaging and operation safety requirements. Monte-Carlo simulations (using MCNP-4B code) with multiple neutron energy groups have also been used to validate neutron beam parameters and to ensure shielding capabilities of facility shutter and cave walls. Neutron flux distributions at the image plane and the neutron beam characteristics were experimentally measured by irradiating a two-dimensional array of Copper foils and using a real-time neutron radiography system. The neutron image characteristics -- such as neutron flux, image size, beam quality -- measured experimentally and predicted numerically for beam tube, beam shutter and radiography cave are compared and discussed in detail in this paper. The experimental results show that thermal neutron flux at image plane is nearly uniform over an imaging area of 20.0-cm diameter and its magnitude ranges from 8.0 x 10{sup 6} - 1.0 x 10{sup 7} n/cm{sup 2}-sec while the neutron-to-gamma ratio is 6.0 x 10{sup 5} n/cm{sup 2}-{mu}Sv. (authors)

  9. The effect of nonsymmetric pressure stiffness on the dynamic characteristics of Solid Rocket Motors

    NASA Technical Reports Server (NTRS)

    Christensen, Eric R.

    1993-01-01

    This paper discusses the effect of pressure on the dynamics of pre-stiffened structures such as the Advanced Solid Rocket Motor (ASRM). Previous work in which the stiffness terms resulting from constant pressure were derived has been extended to enable modeling of nonconstant pressure applied over nonenclosed volumes. These conditions will result in nonsymmetric terms in the global stiffness matrix which will not cancel out. Three new pressure stiffness elements incorporating these nonsymmetric terms have been implemented as dummy elements in COSMIC NASTRAN and have been tested on various simple examples as well as an existing ASRM NASTRAN finite element model. The results indicate that for all load cases of practical interest to the ASRM program, the nonsymmetric terms have very little effect on the dynamic characteristics. In addition, the pressure stiffness elements developed in the previous work which assumed constant pressure gave virtually the same results as the new elements even for problems in which the pressures are not constant. The original elements appear to work well as long as the pressure gradient across any individual element is no larger than about 0.75 psi/inch. The new elements are therefore most useful for determining the conditions under which the original pressure stiffness elements can be used.

  10. Theoretical approach to obtaining dynamic characteristics of noncontacting spiral-grooved seals

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    The dynamic characteristics of spiral-grooved seals are theoretically obtained by using the Navier-Stokes equation. First, with the inertia term of the fluid considered, the flow and pressure in the steady state are obtained for the directions parallel to and perpendicular to the groove. Next, the dynamic character is obtained by analyzing the steady state and by analyzing the labyrinth seal. As a result, the following conclusions were drawn: (1) As the land width becomes shorter or the helix angle decreases, the cross-coupling stiffness, direct and cross-coupling damping, and add mass coefficients decrease; (2) As the axial Reynolds number increases, the stiffness and damping coefficients increase. But the add mass coefficient is not influenced by the axial Reynolds number; (3) The rotational Reynolds number influences greatly the direct and cross-coupling stiffness and direct damping coefficients; and (4) As the journal rotating frequency increases, the leakage flow decreases. Therefore zero net leakage flow is possible at a particular rotating frequency.

  11. Dynamic secondary electron emission characteristics of polymers in negative charging process

    NASA Astrophysics Data System (ADS)

    Weng, Ming; Hu, Tian-Cun; Zhang, Na; Cao, Meng

    2016-04-01

    We studied the dynamic secondary electron emission (SEE) characteristics of a polyimide sample in negative charging process under electron bombardment. The time evolution of secondary electron yield (SEY) has been measured with a pulsed electron gun. The dynamic SEY, as well as the surface potential have been analyzed using a capacitance model. The shift in surface potential caused by the negative charge accumulation on the sample reduces the landing energy of the primary electrons (PEs), which in turn alters the SEY. The charging process tends to be stable when the landing energy of PEs reaches the secondary crossover energy where the corresponding SEY is 1. The surface potential has an approximately negative exponential relationship with the irradiation time. The total accumulated charge at the stable state is found to be proportional to the product of the sample capacitance and the difference between initial incident energy and the secondary crossover energy. The time constant of the exponential function is proportional to the ratio of final accumulated charge to the incident current.

  12. Quantitative reconstruction of thermal and dynamic characteristics of lava flow from surface thermal measurements

    NASA Astrophysics Data System (ADS)

    Korotkii, Alexander; Kovtunov, Dmitry; Ismail-Zadeh, Alik; Tsepelev, Igor; Melnik, Oleg

    2016-06-01

    We study a model of lava flow to determine its thermal and dynamic characteristics from thermal measurements of the lava at its surface. Mathematically this problem is reduced to solving an inverse boundary problem. Namely, using known conditions at one part of the model boundary we determine the missing condition at the remaining part of the boundary. We develop a numerical approach to the mathematical problem in the case of steady-state flow. Assuming that the temperature and the heat flow are prescribed at the upper surface of the model domain, we determine the flow characteristics in the entire model domain using a variational (adjoint) method. We have performed computations of model examples and showed that in the case of smooth input data the lava temperature and the flow velocity can be reconstructed with a high accuracy. As expected, a noise imposed on the smooth input data results in a less accurate solution, but still acceptable below some noise level. Also we analyse the influence of optimization methods on the solution convergence rate. The proposed method for reconstruction of physical parameters of lava flows can also be applied to other problems in geophysical fluid flows.

  13. A Theoretical Investigation of the Dynamic Lateral Stability Characteristics of the MX-838 (XB-51) Airplane

    NASA Technical Reports Server (NTRS)

    Paulson, Jon W.

    1948-01-01

    At the request of the Air Material Command, U. S. Air Force, a theoretical study has been made of the dynamic lateral stability characteristics of the MX-838 (XB-51) airplane. The calculations included the determination of the neutral-oscillatory-stability boundary (R = 0), the period and time to damp to one-half amplitude of the lateral oscillation, end the time to damp to one-half amplitude for the spiral mode. Factors varied in the investigation were lift coefficient, wing incidence, wing loading, and altitude. The results of the investigation showed that the lateral oscillation of the airplane is unstable below a lift coefficient of 1.2 with flaps . deflected 40deg but is stable over the entire speed range with flaps deflected 20deg or 0deg. The results showed that satisfactory oscillatory stability can probably be obtained for all lift coefficients with the proper variation of flap deflection and wing incidence with airspeed. Reducing the positive wing incidence improved the oscillatory stability characteristics. The airplane is spirally unstable for most conditions but the instability is mild and the Air Force requirements are easily met.

  14. Statistical characteristics of dynamics for population migration driven by the economic interests

    NASA Astrophysics Data System (ADS)

    Huo, Jie; Wang, Xu-Ming; Zhao, Ning; Hao, Rui

    2016-06-01

    Population migration typically occurs under some constraints, which can deeply affect the structure of a society and some other related aspects. Therefore, it is critical to investigate the characteristics of population migration. Data from the China Statistical Yearbook indicate that the regional gross domestic product per capita relates to the population size via a linear or power-law relation. In addition, the distribution of population migration sizes or relative migration strength introduced here is dominated by a shifted power-law relation. To reveal the mechanism that creates the aforementioned distributions, a dynamic model is proposed based on the population migration rule that migration is facilitated by higher financial gains and abated by fewer employment opportunities at the destination, considering the migration cost as a function of the migration distance. The calculated results indicate that the distribution of the relative migration strength is governed by a shifted power-law relation, and that the distribution of migration distances is dominated by a truncated power-law relation. These results suggest the use of a power-law to fit a distribution may be not always suitable. Additionally, from the modeling framework, one can infer that it is the randomness and determinacy that jointly create the scaling characteristics of the distributions. The calculation also demonstrates that the network formed by active nodes, representing the immigration and emigration regions, usually evolves from an ordered state with a non-uniform structure to a disordered state with a uniform structure, which is evidenced by the increasing structural entropy.

  15. Study on the Characteristics of Gas Molecular Mean Free Path in Nanopores by Molecular Dynamics Simulations

    PubMed Central

    Liu, Qixin; Cai, Zhiyong

    2014-01-01

    This paper presents studies on the characteristics of gas molecular mean free path in nanopores by molecular dynamics simulation. Our study results indicate that the mean free path of all molecules in nanopores depend on both the radius of the nanopore and the gas-solid interaction strength. Besides mean free path of all molecules in the nanopore, this paper highlights the gas molecular mean free path at different positions of the nanopore and the anisotropy of the gas molecular mean free path at nanopores. The molecular mean free path varies with the molecule’s distance from the center of the nanopore. The least value of the mean free path occurs at the wall surface of the nanopore. The present paper found that the gas molecular mean free path is anisotropic when gas is confined in nanopores. The radial gas molecular mean free path is much smaller than the mean free path including all molecular collisions occuring in three directions. Our study results also indicate that when gas is confined in nanopores the gas molecule number density does not affect the gas molecular mean free path in the same way as it does for the gas in unbounded space. These study results may bring new insights into understanding the gas flow’s characteristic at nanoscale. PMID:25046745

  16. Hemodynamic Characteristics Regarding Recanalization of Completely Coiled Aneurysms: Computational Fluid Dynamic Analysis Using Virtual Models Comparison

    PubMed Central

    Park, Wonhyoung; Song, Yunsun; Park, Kye Jin; Koo, Hae-Won; Yang, Kuhyun

    2016-01-01

    Purpose Hemodynamic factors are considered to play an important role in initiation and progression of the recurrence after endosaccular coiling of the intracranial aneurysms. We made paired virtual models of completely coiled aneurysms which were subsequently recanalized and compared to identify hemodynamic characteristics related to the recurred aneurysmal sac. Materials and Methods We created paired virtual models of computational fluid dynamics (CFD) in five aneurysms which were initially regarded as having achieved complete occlusion and then recurred during follow-up. Paired virtual models consisted of the CFD model of 3D rotational angiography obtained in the recurred aneurysm and the control model of the initial, parent artery after artificial removal of the coiled and recanalized aneurysm. Using the CFD analysis of the virtual model, we analyzed the hemodynamic characteristics on the neck of each aneurysm before and after its recurrence. Results High wall shear stress (WSS) was identified at the cross-sectionally identified aneurysm neck at which recurrence developed in all cases. A small vortex formation with relatively low velocity in front of the neck was also identified in four cases. The aneurysm recurrence locations corresponded to the location of high WSS and/or small vortex formation. Conclusion Recanalized aneurysms revealed increased WSS and small vortex formation at the cross-sectional neck of the aneurysm. This observation may partially explain the hemodynamic causes of future recanalization after coil embolization. PMID:26958410

  17. Hydrogeologic modeling for permeable reactive barriers.

    PubMed

    Gupta, N; Fox, T C

    1999-08-12

    The permeable reactive barrier technology for in situ treatment of chlorinated solvents and other groundwater contaminants is becoming increasingly popular. Field scale implementation of this and other in situ technologies requires careful design based on the site-specific hydrogeology and contaminant plume characteristics. Groundwater flow modeling is an important tool in understanding the hydraulic behavior of the site and optimizing the reactive barrier design. A combination of groundwater flow modeling and particle tracking techniques was used to illustrate the effect of hydraulic conductivity of the aquifer and reactive media on key permeable barrier design parameters, such as the capture zone width, residence time, flow velocity, and discharge. Similar techniques were used to illustrate the modeling approach for design of different configurations of reactive barriers in homogeneous and heterogeneous settings.

  18. Influence of atomic vacancies on the dynamic characteristics of nanoresonators based on double walled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Patel, Ajay M.; Joshi, Anand Y.

    2015-06-01

    The dynamic analysis of double walled carbon nanotubes (DWCNTs) with different boundary conditions has been performed using atomistic finite element method. The double walled carbon nanotube is modeled considering it as a space frame structure similar to a three dimensional beam. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. It has been reported that atomic vacancies are formed during the manufacturing process in DWCNT which tend to migrate leading to a change in the mechanical characteristics of the same. Simulations have been carried out to visualize the behavior of such defective DWCNTs subjected to different boundary conditions and when used as mass sensing devices. The variation of such atomic vacancies in outer wall of Zigzag and Armchair DWCNT is performed along the length and the change in response is noted. Moreover, as CNTs have been used as mass sensors extensively, the present approach is focused to explore the use of zigzag and armchair DWCNT as sensing device with a mono-atomic vacancy in it. The results clearly state that the dynamic characteristics are greatly influenced by defects like vacancies in it. A higher frequency shift is observed when the vacancy is located away from the fixed end for both Armchair as well as zigzag type of CNTs. A higher frequency shift is reported for armchair CNT for a mass of 10-22 g which remains constant for 10-21 g and then decreases gradually. Comparison with the other experimental and theoretical studies exhibits good association which suggests that defective DWCNTs can further be explored for mass sensing. This investigation is helpful

  19. An experimental study on the static and dynamic characteristics of pump annular seals with two phase flow

    NASA Technical Reports Server (NTRS)

    Iwatsubo, T.; Nishino, T.

    1994-01-01

    A new test apparatus is reconstructed and is applied to investigate static and dynamic characteristics of annular seals leaked by two phase flow (gas and liquid) for turbopumps. The fluid forces acting on the seals are measured for various parameters such as void ratio, the preswirl velocity, the pressure difference between the inlet and outlet of the seal, the whirling amplitude, and the ratio of whirling speed to spinning speed of the rotor. Influence of these parameters on the static and dynamic characteristics is investigated from the experimental results. As a result, with regard to the two phase flow, as the void ratio increases, the flow induced force decreases. Another dynamic characteristic of two phase flow is as almost similar as that of the monophase flow.

  20. Electrokinetic effects and fluid permeability

    NASA Astrophysics Data System (ADS)

    G. Berryman, James

    2003-10-01

    Fluid permeability of porous media depends mainly on connectivity of the pore space and two physical parameters: porosity and a pertinent length-scale parameter. Electrical imaging methods typically establish connectivity and directly measure electrical conductivity, which can then often be related to porosity by Archie's law. When electrical phase measurements are made in addition to the amplitude measurements, information about the pertinent length scale can then be obtained. Since fluid permeability controls the ability to flush unwanted fluid contaminants from the subsurface, inexpensive maps of permeability could improve planning strategies for remediation efforts. Detailed knowledge of fluid permeability is also important for oil field exploitation, where knowledge of permeability distribution in three dimensions is a common requirement for petroleum reservoir simulation and analysis, as well as for estimates on the economics of recovery.

  1. Influence of catchment characteristics on the spatio-temporal dynamics of streamwater temperatures in montane headwaters

    NASA Astrophysics Data System (ADS)

    Dick, Jonathan; Tetzlaff, Doerthe; Soulsby, Chris

    2014-05-01

    Streamwater temperature is an important physical parameter in riverine ecosystems. It governs many processes; from water quality to biogeochemical dynamics, and is thus essential to consider when producing river basin management plans. The thermal regimes of streams are determined by a complex series of inter-linkages which can be categorised in one of the three groups: atmospheric conditions, terrestrial controls and stream geomorphology. The climatic conditions are the most important factors as they are the drivers of the processes of heat fluxes at the air-surface interface, however terrestrial and aquatic factors such as elevation, aspect and vegetation are the main modulators of the atmospheric processes. Here we will couple spatially distributed streamwater, groundwater and riparian wetland surface water temperatures to provide insight into dynamics and controls of thermal dynamics at different spatial and temporal scales. The study is located in a 3.2 km2 upland watershed in the North East Scottish Highlands, and covers an 18 month period of measurements. The objectives are to characterise the streamwater thermal fingerprints of the three different headwaters with contrasting landscape description units (fen dominated, steep valley and a wetland dominated corrie), and infer the controls on the spatial and temporal patterns of water temperature throughout the catchment stream network. Results indicate that the temperature of the stream represents the energy balance of the source areas when the riparian zone is connected with the stream network and not just the energy balance of the stream network alone. There are significant differences between the characteristically different headwaters with a significant reduction in the diurnal temperature variability in the largest headwater catchment. The headwater catchment also contains the greatest percentage of wetland soils suggesting groundwater contributions act in the dampening of streamwater temperatures

  2. Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of the linear compressor for the pulse tube cryocooler

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Dang, H. Z.; Tan, J.; Bao, D.; Zhao, Y. B.; Qian, G. Z.

    2015-12-01

    Theoretical and experimental investigations on the dynamic and thermodynamic characteristics of a linear compressor incorporating the thermodynamic characteristics of the inertance tube pulse tube cold finger have been made. Both the compressor and cold finger are assumed as a one-dimensional thermodynamic model. The governing equations of the thermodynamic characteristics of the working gas are summarized, and the effects of the cooling performance on the working gas in the compression space are discussed. Based on the analysis of the working gas, the governing equations of the dynamic and thermodynamic characteristics of the compressor are deduced, and then the principles of achieving the optimal performance of the compressor are discussed in detail. Systematic experimental investigations are conducted on a developed moving-coil linear compressor which drives a pulse tube cold finger, which indicate the general agreement with the simulated results, and thus verify the rationality of the theoretical model and analyses.

  3. Predicting the extent of metabolism using in vitro permeability rate measurements and in silico permeability rate predictions

    PubMed Central

    Hosey, Chelsea M; Benet, Leslie Z

    2015-01-01

    The Biopharmaceutics Drug Disposition Classification System (BDDCS) can be utilized to predict drug disposition, including interactions with other drugs and transporter or metabolizing enzyme effects based on the extent of metabolism and solubility of a drug. However, defining the extent of metabolism relies upon clinical data. Drugs exhibiting high passive intestinal permeability rates are extensively metabolized. Therefore, we aimed to determine if in vitro measures of permeability rate or in silico permeability rate predictions could predict the extent of metabolism, to determine a reference compound representing the permeability rate above which compounds would be expected to be extensively metabolized, and to predict the major route of elimination of compounds in a two-tier approach utilizing permeability rate and a previously published model predicting the major route of elimination of parent drug. Twenty-two in vitro permeability rate measurement data sets in Caco-2 and MDCK cell lines and PAMPA were collected from the literature, while in silico permeability rate predictions were calculated using ADMET Predictor™ or VolSurf+. The potential for permeability rate to differentiate between extensively and poorly metabolized compounds was analyzed with receiver operating characteristic curves. Compounds that yielded the highest sensitivity-specificity average were selected as permeability rate reference standards. The major route of elimination of poorly permeable drugs was predicted by our previously published model and the accuracies and predictive values were calculated. The areas under the receiver operating curves were >0.90 for in vitro measures of permeability rate and >0.80 for the VolSurf+ model of permeability rate, indicating they were able to predict the extent of metabolism of compounds. Labetalol and zidovudine predicted greater than 80% of extensively metabolized drugs correctly and greater than 80% of poorly metabolized drugs correctly in Caco

  4. Relative Permeability of Fractured Rock

    SciTech Connect

    Mark D. Habana

    2002-06-30

    Contemporary understanding of multiphase flow through fractures is limited. Different studies using synthetic fractures and various fluids have yielded different relative permeability-saturation relations. This study aimed to extend the understanding of multiphase flow by conducting nitrogen-water relative permeability experiments on a naturally-fractured rock from The Geysers geothermal field. The steady-state approach was used. However, steady state was achieved only at the endpoint saturations. Several difficulties were encountered that are attributed to phase interference and changes in fracture aperture and surface roughness, along with fracture propagation/initiation. Absolute permeabilities were determined using nitrogen and water. The permeability values obtained change with the number of load cycles. Determining the absolute permeability of a core is especially important in a fractured rock. The rock may change as asperities are destroyed and fractures propagate or st rain harden as the net stresses vary. Pressure spikes occurred in water a solute permeability experiments. Conceptual models of an elastic fracture network can explain the pressure spike behavior. At the endpoint saturations the water relative permeabilities obtained are much less than the nitrogen gas relative permeabilities. Saturations were determined by weighing and by resistivity calculations. The resistivity-saturation relationship developed for the core gave saturation values that differ by 5% from the value determined by weighing. Further work is required to complete the relative permeability curve. The steady-state experimental approach encountered difficulties due to phase interference and fracture change. Steady state may not be reached until an impractical length of time. Thus, unsteady-state methods should be pursued. In unsteady-state experiments the challenge will be in quantifying rock fracture change in addition to fluid flow changes.

  5. Nonlinear structural joint model updating based on instantaneous characteristics of dynamic responses

    NASA Astrophysics Data System (ADS)

    Wang, Zuo-Cai; Xin, Yu; Ren, Wei-Xin

    2016-08-01

    This paper proposes a new nonlinear joint model updating method for shear type structures based on the instantaneous characteristics of the decomposed structural dynamic responses. To obtain an accurate representation of a nonlinear system's dynamics, the nonlinear joint model is described as the nonlinear spring element with bilinear stiffness. The instantaneous frequencies and amplitudes of the decomposed mono-component are first extracted by the analytical mode decomposition (AMD) method. Then, an objective function based on the residuals of the instantaneous frequencies and amplitudes between the experimental structure and the nonlinear model is created for the nonlinear joint model updating. The optimal values of the nonlinear joint model parameters are obtained by minimizing the objective function using the simulated annealing global optimization method. To validate the effectiveness of the proposed method, a single-story shear type structure subjected to earthquake and harmonic excitations is simulated as a numerical example. Then, a beam structure with multiple local nonlinear elements subjected to earthquake excitation is also simulated. The nonlinear beam structure is updated based on the global and local model using the proposed method. The results show that the proposed local nonlinear model updating method is more effective for structures with multiple local nonlinear elements. Finally, the proposed method is verified by the shake table test of a real high voltage switch structure. The accuracy of the proposed method is quantified both in numerical and experimental applications using the defined error indices. Both the numerical and experimental results have shown that the proposed method can effectively update the nonlinear joint model.

  6. Dynamic Characteristics of Positive Pulsed Dielectric Barrier Discharge for Ozone Generation in Air

    NASA Astrophysics Data System (ADS)

    Wei, Linsheng; Peng, Bangfa; Li, Ming; Zhang, Yafang; Hu, Zhaoji

    2016-02-01

    A comprehensive dynamic model consisting of 66 reactions and 24 species is developed to investigate the dynamic characteristics of ozone generation by positive pulsed dielectric barrier discharge (DBD) using parallel-plate reactor in air. The electron energy conservation equation is coupled to the electron continuity equation, the heavy species continuity equation, and Poisson's equation for a better description. The reliability of the model is experimentally confirmed. The model can be used to predict the temporal and spatial evolution of species, as well as streamer propagation. The simulation results show that electron density increases nearly exponentially in the direction to the anode at the electron avalanche. Streamer propagation velocity is about 5.26 × 104 m/s from anode to cathode in the simulated condition. The primary positive ion, negative ion, and excited species are O2+, O3- and O2(1Δg) in pulsed DBD in air, respectively. N2O has the largest density among nitrogen oxides. e and N2+ densities in the streamer head increase gradually to maximum values with the development of the streamer. Meanwhile, the O2+, O, O3, N2(A3Σ) and N2O densities reach maximum values in the vicinity of the anode. supported by National Natural Science Foundation of China (Nos. 51366012 and 11105067), Jiangxi Province Young Scientists (Jinggang Star) Cultivation Plan of China (No. 20133BCB23008), Natural Science Foundation of Jiangxi, China (No. 20151BAB206047) and Jiangxi Province Higher School Science and Technology Landing Plan of China (No. KJLD-14015)

  7. Analysis of the dynamic characteristics of a slant-cracked cantilever beam

    NASA Astrophysics Data System (ADS)

    Ma, Hui; Zeng, Jin; Lang, Ziqiang; Zhang, Long; Guo, Yuzhu; Wen, Bangchun

    2016-06-01

    In this study, the dynamic characteristics of a slant-cracked cantilever beam are studied based on a new finite element (FE) model where both plane and beam elements are used to reduce the computational costs. Simulation studies show that the proposed model has the same system natural frequencies and vibration responses as those in the pure plane element model but is computationally more efficient. Based on the new model, the effects of loads such as gravity Fg, excitation force amplitude F0 and direction angles of excitation force φ, and crack parameters including slant crack angle θ, dimensionless crack depth s and dimensionless crack location p, on system dynamics have been analyzed. The results indicate that (1) the gravity has a more significant effect on the sub-harmonic resonance responses than on the super-harmonic resonance and resonance responses; (2) The amplitudes of the system responses at both excitation force frequencies fe and its harmonics such as 2fe and 3fe increase almost linearly with the increase of the excitation force amplitude F0; (3) Under the constant excitation force in the flexural direction, the tensile and compressive forces along the longitudinal direction can lead to opposite breathing behaviors of the crack within the super-harmonic and sub-harmonic resonance frequency regions; (4) Vibration is most severe under the straight crack angle (θ=90°) and near the straight crack angle such as θ=100° and 110°, and the vibration responses under smaller or larger crack angles such as θ=30° and θ=150° become weaker; (5) The resonance at 2fe is sensitive to the faint crack signals when s is small and p is large. In addition, the significant vibration responses at the multiple frequency of 3fe and the fractional frequency of 0.5fe can be regarded as a distinguishable feature of the serious crack with large s and small p.

  8. Characteristics, and carbon and nitrogen dynamics in soil irrigated with wastewater for different lengths of time.

    PubMed

    Ramirez-Fuentes, E; Lucho-constantino, C; Escamilla-Silva, E; Dendooven, L

    2002-11-01

    Irrigation of agricultural land with wastewater will increase crop production, but also heavy metal concentrations and the rate of infection of farmers with pathogens. The risks associated with the use of wastewater are reduced by treating the wastewater, but treatment also reduces organic material, phosphorus and inorganic N for crops. We investigated characteristics, e.g. heavy metal concentrations, of soils of the valley of the Mezquital (Mexico) irrigated with waste from Mexico City water since 1912, 1925, 1965, 1976, 1996 or 1997, or not irrigated at all, and dynamics of C and N when soil was amended with wastewater or drainage water. Concentrations of total Mg, Hg, Mo, Ca, Cu and Cr, available concentrations of Pb, Cd and Cu increased significantly with length of irrigation (P < 0.05), but were not at hazardous concentrations. Although organic C, total N, microbial biomass C and N, and microbial activity, as witnessed by CO2 production, increased with length of irrigation, N mineralization did not. Oxidation of NO2- was inhibited and could be due to increases in salinity, toxic compounds or heavy metals. We found that N mineralization was low or absent so it will not compensate for the loss of N when the wastewater is treated and application of N fertilizer will be required to maintain the same level of crop production. The characteristics of the soils appear not to have deteriorated after years of application of wastewater, but further irrigation even with treated wastewater might increase sodicity and salinity and pose a threat to future crop production.

  9. Dynamic moisture sorption characteristics of xerogels from water-swellable oligo(oxyethylene) lignin derivatives.

    PubMed

    Passauer, Lars; Struch, Marlene; Schuldt, Stefan; Appelt, Joern; Schneider, Yvonne; Jaros, Doris; Rohm, Harald

    2012-11-01

    Highly swellable lignin derivatives were prepared by cross-linking of oxidatively preactivated spruce organosolv lignin (OSL) with poly(ethylene) glycol diglycidyl ether (PEGDGE). The lignin gels obtained are considered to be an environmentally friendly alternative to synthetic hydrogels and superabsorbents and represent a novel type of lignin based functional materials. For their application, it is not only the absorption of water in terms of hydrogel swelling that plays an important role, but also the adsorption and retention of moisture by the corresponding xerogels. To reveal the mechanisms involved in moistening and reswelling of the lignin gels, the interaction of water vapor with lyophilized xerogels was investigated and compared with sorption characteristics of parent lignin. The chemical structure of PEGDGE-modified lignin was investigated using attenuated total reflectance Fourier-transformed infrared spectroscopy and selective aminolysis and was related to its sorption and swelling characteristics. Bound and free water in hydrogels was determined by differential scanning calorimetry and by measuring the free swelling capacity of the gels. Moisture sorption of OSL and PEGDGE-modified lignin xerogels was determined using dynamic vapor sorption analysis. In order to determine monolayer and multilayer sorption parameters, sorption data were fitted to the Brunauer-Emmett-Teller and the Guggenheim-Anderson-de Boer model. Swelling properties of the hydrogels and moisture sorption of the corresponding xerogels were found to be strongly dependent on the degree of chemical modification with PEGDGE: Total and free water content of hydrogels decrease with increasing cross-linking density; on the other hand, water bound in hydrogels and moisture sorption of xerogels at high levels of water activity strongly increase, presumably because of the hydration of hydrophilic oligo(oxyethylene) and oligo(oxyethylene) glycol substituents, which lead to moisture diffusion into

  10. Porosity and Permeability of Chondritic Materials

    NASA Technical Reports Server (NTRS)

    Zolensky, Michael E.; Corrigan, Catherine M.; Dahl, Jason; Long, Michael

    1996-01-01

    We have investigated the porosity of a large number of chondritic interplanetary dust particles and meteorites by three techniques: standard liquid/gas flow techniques, a new, non-invasive ultrasonic technique, and image processing of backscattered images . The latter technique is obviously best suited to sub-kg sized samples. We have also measured the gas and liquid permeabilities of some chondrites by two techniques: standard liquid/gas flow techniques, and a new, non-destructive pressure release technique. We find that chondritic IDP's have a somewhat bimodal porosity distribution. Peaks are present at 0 and 4% porosity; a tail then extends to 53%. These values suggest IDP bulk densities of 1.1 to 3.3 g/cc. Type 1-3 chondrite matrix porosities range up to 30%, with a peak at 2%. The bulk porosities for type 1-3 chondrites have the same approximate range as exhibited by matrix, indicating that other components of the bulk meteorites (including chondrules and aggregates) have the same average porosity as matrix. These results reveal that the porosity of primitive materials at scales ranging from nanogram to kilogram are similar, implying similar accretion dynamics operated through 12 orders of size magnitude. Permeabilities of the investigated chondrites vary by several orders of magnitude, and there appears to be no simple dependence of permeability with degree of aqueous alteration, or chondrite type.

  11. Hydrologic characteristics and suspended sediment dynamics in the Gradašica river basin

    NASA Astrophysics Data System (ADS)

    Kogoj, Mojca; Rusjan, Simon; Vidmar, Andrej; Mikoš, Matjaž

    2013-04-01

    Sediment transport in catchments is an important aspect of environmental research because of its role in the transport of sediment-associated nutrients, pesticides and other contaminants. High turbidity levels in water bodies affect stream morphology, aquatic organisms and their habitats, cause siltation of water reservoirs and have other side effects. For maintaining adequate water quality, reducing excessive soil erosion and proper estimation of the amount of transported material it is necessary to define and understand main factors that control sediment production and transport in rivers. Understanding the hydrological response of catchments on hydrometeorological phenomena and their influences on changes in suspended sediment concentrations require measurements of the processes at time scales that correspond to hydrological dynamics of a catchment. Our research aims to investigate hydrological and seasonal controls over suspended sediment production and obtain an insight into a suspended sediment concentration dynamics and total loads in a forested catchment. For this purpose, we study several factors actively controlling suspended sediment mobilization and transport in a small experimental catchment in Polhov Gradec mountainous area in the central part of Slovenia, drained by the Gradaščica river. Steep slopes, relatively high altitudes and abundance of precipitation (average yearly sums between 1600 to 1700 mm) result in a quick rise in the water level and consequently, in torrential response of the Gradaščica river. The studied headwaters lay on dolomite and limestone with a mainly natural land cover. The area is a subject to erosion with debris sources in the dolomite and additional catchment characteristics that contribute to high sediment transport rates. The main categories of factors that actively control sediment mobilization and transport from catchments, studied in our research, are hydrological and meteorological controls, physiographic factors

  12. Relative Permeabilities: a pore-level model study of the capillary number dependence

    SciTech Connect

    Ferer, M.V.; Mason, G.; Bromhal, G.S.; Smith, D.H.

    2008-03-01

    Relative permeabilities are widely used by the petroleum industry in reservoir simulations of recovery strategies. In recent years, pore level modeling has been used to determine relative permeabilities at zero capillary number for a variety of more and more realistic model porous media. Unfortunately, these studies cannot address the issue of the observed capillary number dependence of the relative permeabilities. Several years ago, we presented a method for determining the relative permeabilities from pore-level modeling at general capillary number. We have used this method to determine the relative permeabilities at several capillary numbers and stable viscosity ratios. In addition, we have determined these relative permeabilities using one of the standard dynamic methods for determining relative permeabilities from core flood experiments. Our results from the two methods are compared with each other and with experimental results.

  13. Permeability-porosity relationships in sedimentary rocks

    USGS Publications Warehouse

    Nelson, Philip H.

    1994-01-01

    In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (??). The slope, intercept, and degree of scatter of these log(k)-?? trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing ??. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as ?? decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings from a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-?? plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-?? data trends cut the curves of constant pore size from the pore-dimension models

  14. Endothelial cell permeability to water and antipyrine

    SciTech Connect

    Garrick, R.A.

    1986-03-05

    The endothelium provides a structural barrier between plasma constituents and the tissues. The permeability characteristics of the the endothelial cells regulate the transcellular movement of materials across this barrier while other movement is paracellular. In this study the permeability of the endothelial cells to tritiated water (/sup 3/HHO) and /sup 14/C-labeled antipyrine (AP) was investigated. The cells were isolated non-enzymatically from calf pulmonary artery and were maintained in culture and used between the seventh and fifteenth passage. The cells were removed from the T-flasks with a rubber policeman, titurated with a 22g needle and centrifuged. The cells were mixed with an extracellular marker, drawn into polyethylene tubing and packed by centrifugation for use in the linear diffusion technique. All measurements were made at 37 C. The diffusion coefficients for /sup 3/HHO through the packed cells (D), the intracellular material (D/sub 2/), and the extracellular material (D/sub 1/) were 0.682, 0.932 and 2.45 x 10/sup -5/ cm/sup 2/ s/sup -1/ and for AP were 0.273, 0.355 and 1.13 x 10/sup -5/ cm/sup 2/ s/sup -1/ respectively. The permeability coefficient calculated by the series-parallel pathway model for /sup 3/HHO was higher than that for AP and for both /sup 3/HHO and AP were lower than those calculated for isolated lung cells and erythrocytes.

  15. Influence of induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches

    SciTech Connect

    Kantsyrev, V. L.; Esaulov, A. A.; Safronova, A. S.; Osborne, G. C.; Shrestha, I.; Weller, M. E.; Stafford, A.; Shlyaptseva, V. V.; Velikovich, A. L.; Rudakov, L. I.; Williamson, K. M.

    2011-10-15

    The influence of an induced axial magnetic field on plasma dynamics and radiative characteristics of Z pinches is investigated. An axial magnetic field was induced in a novel Z-pinch load: a double planar wire array with skewed wires (DPWAsk), which represents a planar wire array in an open magnetic configuration. The induced axial magnetic field suppressed magneto-Rayleigh-Taylor (MRT) instabilities (with m = 0 and m = 1 instability modes) in the Z-pinch plasma. The influence of the initial axial magnetic field on the structure of the plasma column at stagnation was manifested through the formation of a more uniform plasma column compared to a standard double planar wire array (DPWA) load [V. L. Kantsyrev et al., Phys. Plasmas 15, 030704 (2008)]. The DPWAsk load is characterized by suppression of MRT instabilities and by the formation of the sub-keV radiation pulse that occurs before the main x-ray peak. Gradients in plasma parameters along the cathode-anode gap were observed and analyzed for DPWAsk loads made from low atomic number Z (Al) and mid-Z (brass) wires.

  16. Bifurcation characteristics and flame dynamics of a ducted non-premixed flame with finite rate chemistry

    NASA Astrophysics Data System (ADS)

    Rana, Subhas Chandra; Sujith, Raman

    2015-09-01

    The influence of system parameters such as the flame location, Peclet number and Damköhler number on the bifurcation characteristics and flame dynamics of a ducted non-premixed flame with finite rate chemistry is presented in this paper. In the bifurcation plot with flame location as the bifurcation parameter, subcritical Hopf bifurcation is found for lower values of flame location and supercritical Hopf bifurcation for higher values of flame location, for all the Damköhler numbers used in this study. The flame shapes are captured at eight different phases of a cycle of time series data of acoustic velocity at both the fold and Hopf points for bifurcation with flame location as the parameter. We find that the range of flame height variations at the Hopf point is more than the range of flame height variations obtained at the fold point. We also find that the flame oscillates in the same phase as pressure fluctuation but in a phase different from both velocity and heat release rate fluctuations in the region of hysteresis for bifurcation with flame location. The non-dimensional hysteresis width is plotted as a function of Damköhler number for variation of flame location in the subcritical region. An inverse power law relation is found between the non-dimensional hysteresis width and the Damköhler number. The bifurcation plot with Peclet number as parameter shows a subcritical Hopf bifurcation.

  17. Probability characteristics of nonlinear dynamical systems driven by δ-pulse noise.

    PubMed

    Dubkov, Alexander A; Rudenko, Oleg V; Gurbatov, Sergey N

    2016-06-01

    For a nonlinear dynamical system described by the first-order differential equation with Poisson white noise having exponentially distributed amplitudes of δ pulses, some exact results for the stationary probability density function are derived from the Kolmogorov-Feller equation using the inverse differential operator. Specifically, we examine the "effect of normalization" of non-Gaussian noise by a linear system and the steady-state probability density function of particle velocity in the medium with Coulomb friction. Next, the general formulas for the probability distribution of the system perturbed by a non-Poisson δ-pulse train are derived using an analysis of system trajectories between stimuli. As an example, overdamped particle motion in the bistable quadratic-cubic potential under the action of the periodic δ-pulse train is analyzed in detail. The probability density function and the mean value of the particle position together with average characteristics of the first switching time from one stable state to another are found in the framework of the fast relaxation approximation. PMID:27415226

  18. Experimental and analytical investigation of dynamic characteristics of extension-twist-coupled composite tubular spars

    NASA Technical Reports Server (NTRS)

    Lake, Renee C.; Izadpanah, Amir P.; Baucom, Robert M.

    1993-01-01

    The results from a study aimed at improving the dynamic and aerodynamic characteristics of composite rotor blades through the use of extension-twist coupling are presented. A set of extension-twist-coupled composite spars was manufactured with four plies of graphite-epoxy cloth prepreg. These spars were noncircular in cross-section design and were therefore subject to warping deformations. Three different cross-sectional geometries were developed: D-shape, square, and flattened ellipse. Three spars of each type were fabricated to assess the degree of repeatability in the manufacturing process of extension-twist-coupled structures. Results from free-free vibration tests of the spars were compared with results from normal modes and frequency analyses of companion shell-finite-element models. Five global modes were identified within the frequency range from 0 to 2000 Hz for each spar. The experimental results for only one D-shape spar could be determined, however, and agreed within 13.8 percent of the analytical results. Frequencies corresponding to the five global modes for the three square spars agreed within 9.5, 11.6, and 8.5 percent of the respective analytical results and for the three elliptical spars agreed within 4.9, 7.7, and 9.6 percent of the respective analytical results.

  19. Characteristics of dynamic cerebral autoregulation in cerebral small vessel disease: Diffuse and sustained.

    PubMed

    Guo, Zhen-Ni; Xing, Yingqi; Wang, Shuang; Ma, Hongyin; Liu, Jia; Yang, Yi

    2015-01-01

    Cerebral small vessel disease is a major cause of stroke and vascular dementia; however, the pathogenesis is largely unclear. In this study, we investigated the characteristics of the impairment of dynamic cerebral autoregulation (dCA) in lacunar infarction patients. Seventy-one lacunar infarction patients were enrolled in the study, including 46 unilateral middle cerebral artery (MCA) territory stroke patients and 25 unilateral posterior cerebral artery (PCA) territory stroke patients. Each group of patients was randomly divided into two subgroups. Group 1 underwent dCA assessments in the bilateral MCAs, and Group 2 underwent dCA assessments in the bilateral PCAs. All patients were followed up for 6 months. Transfer function analysis was applied to derive the autoregulatory parameters of gain and phase difference. In the unilateral MCA territory stroke patients, impairments of dCA were observed in both the MCAs and PCAs, and the same results were observed in the unilateral PCA territory stroke patients. These impairments remained unchanged during the 6-month follow-up. In lacunar infarction, which is most prevalent type of cerebral small vessel disease, though patients with unilateral MCA territory/PCA territory stroke, the impairments of dCA were global and sustained. This finding suggests that the physiological changes associated with lacunar infarction were diffuse.

  20. [Dynamic Characteristics of Base Cations During Wet Deposition in Evergreen Broad-leaf Forest Ecosystem].

    PubMed

    An, Si-wei; Sun, Tao; Ma, Ming; Wang, Ding-yong

    2015-12-01

    Based on field tests and laboratory experiments, effects of precipitation, throughfall, litterfall, and groundwater runoff of the ever-green broad-leaf forest on the dynamic characteristics of base cations in Simian Mountain were investigated from September 2012 to August 2013. The results showed that the rainfall of Simian Mountain was apparently acidic, with average pH of 4.90 and maximum pH of 5.14. The soil and canopies could increase pH of precipitation, with soils having the maximum increment, followed by the forest canopy. Forest canopy only had the function of interception on Na⁺. And precipitation could leach out Ca2⁺, Mg2⁺ and K⁺ of the canopies. Moreover, the degradation of litter was probably the main reason for the increase of base cations concentrations in the surface litter water. The litter water leached Ca2⁺, Mg2⁺ and Na⁺ of the forest soil through downward infiltration. The total retention rates of Ca²⁺, Mg²⁺, Na⁺ and K⁺ were 33.82%, -7.06%, 74.36% and 42.87%, respectively. Ca²⁺, Na⁺, K⁺ were found to be reserved in the forest ecosystem, and the highest interception rate was found for Na⁺. PMID:27011975

  1. [Dynamic Characteristics of Base Cations During Wet Deposition in Evergreen Broad-leaf Forest Ecosystem].

    PubMed

    An, Si-wei; Sun, Tao; Ma, Ming; Wang, Ding-yong

    2015-12-01

    Based on field tests and laboratory experiments, effects of precipitation, throughfall, litterfall, and groundwater runoff of the ever-green broad-leaf forest on the dynamic characteristics of base cations in Simian Mountain were investigated from September 2012 to August 2013. The results showed that the rainfall of Simian Mountain was apparently acidic, with average pH of 4.90 and maximum pH of 5.14. The soil and canopies could increase pH of precipitation, with soils having the maximum increment, followed by the forest canopy. Forest canopy only had the function of interception on Na⁺. And precipitation could leach out Ca2⁺, Mg2⁺ and K⁺ of the canopies. Moreover, the degradation of litter was probably the main reason for the increase of base cations concentrations in the surface litter water. The litter water leached Ca2⁺, Mg2⁺ and Na⁺ of the forest soil through downward infiltration. The total retention rates of Ca²⁺, Mg²⁺, Na⁺ and K⁺ were 33.82%, -7.06%, 74.36% and 42.87%, respectively. Ca²⁺, Na⁺, K⁺ were found to be reserved in the forest ecosystem, and the highest interception rate was found for Na⁺.

  2. Characteristics and relaxation dynamics of van der Waals complexes between p-difluorobenzene and Ne.

    PubMed

    Jayasekharan, Thankan; Parmenter, Charles S

    2004-06-22

    Characteristics of the single and double Ne van der Waals complexes of p-difluorobenzene (pDFB) have been explored with ultraviolet fluorescence excitation and dispersed fluorescence spectroscopy. Eight S(1)-S(0) fluorescence excitation bands involving six ring modes of pDFB-Ne and two bands of pDFB-Ne(2) have been identified. Band assignments are confirmed by dispersed fluorescence from the pumped band. Shifts of the complex bands from the analogous monomer bands are generally 4 cm(-1) to the red for pDFB-Ne and 8 cm(-1) for pDFB-Ne(2). None of the observed ring modes is significantly perturbed by complexation in either the S(1) or S(0) states. The pDFB-Ne S(1) van der Waals binding energy D(0')dynamics of the S(1) complexes pDFB-Ar and pDFB-N(2).

  3. [Diurnal dynamics of photosynthetic characteristics of alfalfa on Kerqin sandy land].

    PubMed

    Xu, Li-Jun; Wang, Bo; Sun, Qi-Zhong

    2008-10-01

    By using a Li-6400 portable photosynthesis system, the diurnal dynamics of the photosynthetic characteristics of three alfalfa varieties Medicago sativa L. cv. Aohan, M. sativa L. cv. Rangelander, and M. sativa L. cv. Algonquin were studied. The results showed that for the test alfalfa varieties, the diurnal variation curves of their P(n), T(r), and WUE were not all presented double-peak. For Aohan and Algonquin, the maximum P(n) and T(r) occurred at 9:00-11:00; while for Rangelander, they appeared at 11:00. The minimum P(n) and T(r) of the three varieties all appeared at 7:00 and 19:00. The maximum WUE of Rangelander and Algonquin appeared at 7:00 and that of Aohan was at 9:00, and the minimum WUE of the three varieties all appeared at 15:00-17:00. Comprehensive analysis on the photosynthetic performance indices P(n), T(r), and WUE indicated that 2 years old alfalfa was in the best state, followed by 1 year old, and 4 years old. Correlation analysis showed that air temperature (T(a)) was the main environmental factor affecting P(n) and T(r), followed by water vapor pressure deficit (VPD) and relative humidity (RH).

  4. Characteristics of dynamic cerebral autoregulation in cerebral small vessel disease: Diffuse and sustained

    PubMed Central

    Guo, Zhen-Ni; Xing, Yingqi; Wang, Shuang; Ma, Hongyin; Liu, Jia; Yang, Yi

    2015-01-01

    Cerebral small vessel disease is a major cause of stroke and vascular dementia; however, the pathogenesis is largely unclear. In this study, we investigated the characteristics of the impairment of dynamic cerebral autoregulation (dCA) in lacunar infarction patients. Seventy-one lacunar infarction patients were enrolled in the study, including 46 unilateral middle cerebral artery (MCA) territory stroke patients and 25 unilateral posterior cerebral artery (PCA) territory stroke patients. Each group of patients was randomly divided into two subgroups. Group 1 underwent dCA assessments in the bilateral MCAs, and Group 2 underwent dCA assessments in the bilateral PCAs. All patients were followed up for 6 months. Transfer function analysis was applied to derive the autoregulatory parameters of gain and phase difference. In the unilateral MCA territory stroke patients, impairments of dCA were observed in both the MCAs and PCAs, and the same results were observed in the unilateral PCA territory stroke patients. These impairments remained unchanged during the 6-month follow-up. In lacunar infarction, which is most prevalent type of cerebral small vessel disease, though patients with unilateral MCA territory/PCA territory stroke, the impairments of dCA were global and sustained. This finding suggests that the physiological changes associated with lacunar infarction were diffuse. PMID:26469343

  5. Operational Characteristics of a 14-W 140-GHz Gyrotron for Dynamic Nuclear Polarization

    PubMed Central

    Joye, Colin D.; Griffin, Robert G.; Hornstein, Melissa K.; Hu, Kan-Nian; Kreischer, Kenneth E.; Rosay, Melanie; Shapiro, Michael A.; Sirigiri, Jagadishwar R.; Temkin, Richard J.; Woskov, Paul P.

    2006-01-01

    The operating characteristics of a 140-GHz 14-W long pulse gyrotron are presented. The device is being used in dynamic nuclear polarization enhanced nuclear magnetic resonance (DNP/NMR) spectroscopy experiments. The gyrotron yields 14 W peak power at 139.65 GHz from the TE(0,3) operating mode using a 12.3-kV 25-mA electron beam. Additionally, up to 12 W peak has been observed in the TE(2,3) mode at 136.90 GHz. A series of mode converters transform the TE(0,3) operating mode to the TE(1,1) mode. Experimental results are compared with nonlinear simulations and show reasonable agreement. The millimeter-wave output beam was imaged in a single shot using a pyroelectric camera. The mode patterns matched reasonably well to theory for both the TE(0,1) mode and the TE(1,1) mode. Repeatable mode patterns were obtained at intervals ranging from 0.8 s apart to 11 min apart at the output of the final mode converter. PMID:17431442

  6. Probability characteristics of nonlinear dynamical systems driven by δ -pulse noise

    NASA Astrophysics Data System (ADS)

    Dubkov, Alexander A.; Rudenko, Oleg V.; Gurbatov, Sergey N.

    2016-06-01

    For a nonlinear dynamical system described by the first-order differential equation with Poisson white noise having exponentially distributed amplitudes of δ pulses, some exact results for the stationary probability density function are derived from the Kolmogorov-Feller equation using the inverse differential operator. Specifically, we examine the "effect of normalization" of non-Gaussian noise by a linear system and the steady-state probability density function of particle velocity in the medium with Coulomb friction. Next, the general formulas for the probability distribution of the system perturbed by a non-Poisson δ -pulse train are derived using an analysis of system trajectories between stimuli. As an example, overdamped particle motion in the bistable quadratic-cubic potential under the action of the periodic δ -pulse train is analyzed in detail. The probability density function and the mean value of the particle position together with average characteristics of the first switching time from one stable state to another are found in the framework of the fast relaxation approximation.

  7. Dynamic characteristics of a cable-stayed bridge measured from traffic-induced vibrations

    NASA Astrophysics Data System (ADS)

    Wang, Yun-Che; Chen, Chern-Hwa

    2012-09-01

    This paper studies the dynamic characteristics of the Kao-Ping-Hsi cable-stayed bridge under daily traffic conditions. Experimental data were measured from a structural monitoring system, and system-identification techniques, such as the random decrement (RD) technique and Ibrahim time-domain (ITD) method, were adopted. The first five modes of the bridge were identified for their natural frequencies and damping ratios under different traffic loading conditions, in terms of root-mean-square (RMS) deck velocities. The magnitude of the torsion mode of the Kao-Ping-Hsi cable-stayed bridge is found to be one order-of-magnitude less than the transfer mode, and two orders-of-magnitude less than the vertical modes. Out results indicated that vibrations induced by traffic flow can be used as an indicator to monitor the health of the bridge due to their insensitivity to the natural frequencies of the cable-stayed bridge. Furthermore, the damping ratios may be used as a more sensitive indicator to describe the condition of the bridge.

  8. Geothermal Permeability Enhancement - Final Report

    SciTech Connect

    Joe Beall; Mark Walters

    2009-06-30

    The overall objective is to apply known permeability enhancement techniques to reduce the number of wells needed and demonstrate the applicability of the techniques to other undeveloped or under-developed fields. The Enhanced Geothermal System (EGS) concept presented in this project enhances energy extraction from reduced permeability zones in the super-heated, vapor-dominated Aidlin Field of the The Geysers geothermal reservoir. Numerous geothermal reservoirs worldwide, over a wide temperature range, contain zones of low permeability which limit the development potential and the efficient recovery of heat from these reservoirs. Low permeability results from poorly connected fractures or the lack of fractures. The Enhanced Geothermal System concept presented here expands these technologies by applying and evaluating them in a systematic, integrated program.

  9. Dynamic Characteristics of Mechanical Ventilation System of Double Lungs with Bi-Level Positive Airway Pressure Model

    PubMed Central

    Shen, Dongkai; Zhang, Qian

    2016-01-01

    In recent studies on the dynamic characteristics of ventilation system, it was considered that human had only one lung, and the coupling effect of double lungs on the air flow can not be illustrated, which has been in regard to be vital to life support of patients. In this article, to illustrate coupling effect of double lungs on flow dynamics of mechanical ventilation system, a mathematical model of a mechanical ventilation system, which consists of double lungs and a bi-level positive airway pressure (BIPAP) controlled ventilator, was proposed. To verify the mathematical model, a prototype of BIPAP system with a double-lung simulators and a BIPAP ventilator was set up for experimental study. Lastly, the study on the influences of key parameters of BIPAP system on dynamic characteristics was carried out. The study can be referred to in the development of research on BIPAP ventilation treatment and real respiratory diagnostics.

  10. Dynamic Characteristics of Mechanical Ventilation System of Double Lungs with Bi-Level Positive Airway Pressure Model

    PubMed Central

    Shen, Dongkai; Zhang, Qian

    2016-01-01

    In recent studies on the dynamic characteristics of ventilation system, it was considered that human had only one lung, and the coupling effect of double lungs on the air flow can not be illustrated, which has been in regard to be vital to life support of patients. In this article, to illustrate coupling effect of double lungs on flow dynamics of mechanical ventilation system, a mathematical model of a mechanical ventilation system, which consists of double lungs and a bi-level positive airway pressure (BIPAP) controlled ventilator, was proposed. To verify the mathematical model, a prototype of BIPAP system with a double-lung simulators and a BIPAP ventilator was set up for experimental study. Lastly, the study on the influences of key parameters of BIPAP system on dynamic characteristics was carried out. The study can be referred to in the development of research on BIPAP ventilation treatment and real respiratory diagnostics. PMID:27660646

  11. Experimental Measurement of Vertical and Horizontal Permeability of Caprocks from the Krechba Field, Algeria and the Controls on their Permeability

    NASA Astrophysics Data System (ADS)

    Armitage, P. J.; Faulkner, D. R.; Worden, R. H.; Illife, J.

    2008-12-01

    Caprock properties play a crucial role in determining the seal capacity of a structure and so are important during exploration, appraisal and field development. Less attention has been paid to caprocks than reservoirs since if petroleum is present, then the seal must be working. However, injection of CO2 to underlying reservoirs will alter the reservoir conditions from those against which the caprock was previously effective. Increased knowledge of the petrological and petrophysical characteristics of caprocks is required in order to lay a foundation to predict the effect of the altered conditions caused by CO2 injection. Vertical (kv) and horizontal (kh) permeability were measured experimentally across a range of effective pressures for an unusually coarse grained, heterogeneous caprock (siltstone) to a natural gas reservoir and current CO2 storage reservoir, from the Krechba Field, Algeria. Permeabilities as low as 10-23m2 were recorded and were in the range of, or lower than typical fine grained siliciclastic caprock lithologies. The permeability was analysed in conjunction with mercury injection porosimetry data, and textural and mineralogical data from traditional light microscopy, backscatter secondary electron microscopy (BSEM) and cathode luminescence (CL) techniques as well as new QEMSCAN techniques to elucidate the controls on permeability. As predicted and measured by previous experimental work on fine grained siliciclastic lithologies, permeability is effectively controlled by porosity, pore size distribution and clay fraction. Permeability generally decreases with decreasing porosity and poresize distribution and increasing clay content. However, scatter in the trends was caused by heterogeneity of the sample leading to large kv and kh ratios. Primary depositional features led to layers of relatively low and high permeability in the samples, with kv controlled by the lowest permeability layer, and kh controlled by highest permeability layer. Thus kh

  12. Flow rate dictates permeability enhancement during fluid pressure oscillations in laboratory experiments

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Seismic waves have been observed to increase the permeability in fractured aquifers. A detailed, predictive understanding of the process has been hampered by a lack of constraint on the primary physical controls. What aspect of the oscillatory forcing is most important in determining the magnitude of the permeability enhancement? Here we present laboratory results showing that flow rate is the primary control on permeability increases in the laboratory. We fractured Berea sandstone samples under triaxial stresses of tens of megapascals and applied dynamic fluid stresses via pore pressure oscillations. In each experiment, we varied either the amplitude or the frequency of the pressure changes. Amplitude and frequency each separately correlated with the resultant permeability increase. More importantly, the permeability changes correlate with the flow rate in each configuration, regardless of whether flow rate variations were driven by varying amplitude or frequency. We also track the permeability evolution during a single set of oscillations by measuring the phase lags (time delays) of successive oscillations. Interpreting the responses with a poroelastic model shows that 80% of the permeability enhancement is reached during the first oscillation and the final permeability enhancement scales exponentially with the imposed change in flow rate integrated over the rock volume. The establishment of flow rate as the primary control on permeability enhancement from seismic waves opens the door to quantitative studies of earthquake-hydrogeological coupling. The result also suggests that reservoir permeability could be engineered by imposing dynamic stresses and changes in flow rate.

  13. Flow rate dictates permeability enhancement during fluid pressure oscillations in laboratory experiments

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    Seismic waves have been observed to increase the permeability in fractured aquifers. A detailed, predictive understanding of the process has been hampered by a lack of constraint on the primary physical controls. What aspect of the oscillatory forcing is most important in determining the magnitude of the permeability enhancement? Here we present laboratory results showing that flow rate is the primary control on permeability increases in the laboratory. We fractured Berea sandstone samples under triaxial stresses of tens of megapascals, and applied dynamic fluid-stresses via pore pressure oscillations. In each experiment, we varied either the amplitude or the frequency of the pressure changes. Amplitude and frequency each separately correlated with the resultant permeability increase. More importantly, the permeability changes correlate with the flow rate in each configuration, regardless of whether flow rate variations were driven by varying amplitude or frequency. We also track the permeability evolution during a single set of oscillations by measuring the phase lags (time delays) of successive oscillations. Interpreting the responses with a poroelastic model shows that 80% of the permeability enhancement is reached during the first oscillation and the final permeability enhancement scales exponentially with the imposed change in flow rate integrated over the rock volume. The establishment of flow rate as the primary control on permeability enhancement from seismic waves opens the door to quantitative studies of earthquake-hydrogeological coupling. The result also suggests that reservoir permeability could be engineered by imposing dynamic stresses and changes in flow rate.

  14. The kinetics of denitrification in permeable sediments

    NASA Astrophysics Data System (ADS)

    Evrard, Victor; Glud, Ronnie N.; Cook, Perran L. M.

    2013-04-01

    Permeable sediments comprise the majority of shelf sediments, yet the rates of denitrification remain highly uncertain in these environments. Computational models are increasingly being used to understand the dynamics of denitrification in permeable sediments, which are complex environments to study experimentally. The realistic implementation of such models requires reliable experimentally derived data on the kinetics of denitrification. Here we undertook measurements of denitrification kinetics as a function of nitrate concentration and in the presence and absence of oxygen, in carefully controlled flow through reactor experiments on sediments taken from six shallow coastal sites in Port Phillip Bay, Victoria, Australia. The results showed that denitrification commenced rapidly (within 30 min) after the onset of anoxia and the kinetics could be well described by Michaelis-Menten kinetics with half saturation constants (apparent Km) ranging between 1.5 and 19.8 μM, and maximum denitrification rate (Vmax) were in the range of 0.9-7.5 nmol mL-1 h-1. The production of N2 through anaerobic ammonium oxidation (anammox) was generally found to be less than 10% that of denitrification. Vmax were in the same range as previously reported in cohesive sediments despite organic carbon contents one order of magnitude lower for the sediments studied here. The ratio of sediment O2 consumption to Vmax was in the range of 0.02-0.09, and was on average much lower than the theoretical ratio of 0.8. The most likely explanation for this is that the microbial community is not able to instantaneously shift or optimally use a particular electron acceptor in the highly dynamic redox environment experienced in permeable sediments. Consistent with this explanation, subsequent longer-term experiments over 5 days showed that denitrification rates increased by a factor of 10 within 3 days of the permanent onset of anoxia. In contrast to previous studies, we did not observe any significant

  15. Numerical simulation study of polar lows in Russian Arctic: dynamical characteristics

    NASA Astrophysics Data System (ADS)

    Verezemskaya, Polina; Baranyuk, Anastasia; Stepanenko, Victor

    2015-04-01

    Polar Lows (hereafter PL) are intensive mesoscale cyclones, appearing above the sea surface, usually behind the arctic front and characterized by severe weather conditions [1]. All in consequence of the global warming PLs started to emerge in the arctic water area as well - in summer and autumn. The research goal is to examine PLs by considering multisensory data and the resulting numerical mesoscale model. The main purpose was to realize which conditions induce PL development in such thermodynamically unusual season and region as Kara sea. In order to conduct the analysis we used visible and infrared images from MODIS (Aqua). Atmospheric water vapor V, cloud liquid water Q content and surface wind fields W were resampled by examining AMSR-E microwave radiometer data (Aqua)[2], the last one was additionally extracted from QuickSCAT scatterometer. We have selected some PL cases in Kara sea, appeared in autumn of 2007-2008. Life span of the PL was between 24 to 36 hours. Vortexes' characteristics were: W from 15m/s, Q and V values: 0.08-0.11 kg/m2 and 8-15 kg/m2 relatively. Numerical experiments were carried out with Weather Research and Forecasting model (WRF), which was installed on supercomputer "Lomonosov" of Research Computing Center of Moscow State University [3]. As initial conditions was used reanalysis data ERA-Interim from European Centre for Medium-Range Weather Forecasts. Numerical experiments were made with 5 km spatial resolution, with Goddard center microphysical parameterization and explicit convection simulation. Modeling fields were compared with satellite observations and shown good accordance. Than dynamic characteristics were analyzed: evolution of potential and absolute vorticity [4], surface heat and momentum fluxes, and CAPE and WISHE mechanisms realization. 1. Polar lows, J. Turner, E.A. Rasmussen, 612, Cambridge University press, Cambridge, 2003. 2. Zabolotskikh, E. V., Mitnik, L. M., & Chapron, B. (2013). New approach for severe marine

  16. The dynamics and spectral characteristics of the GPS TEC wave packets excited by the solar terminator

    NASA Astrophysics Data System (ADS)

    Afraimovich, E. L.; Edemsky, I. K.; Voeykov, S. V.; Yasukevich, Y. V.; Zhivetiev, I. V.

    2009-04-01

    The great variety of solar terminator (ST) -linked phenomena in the atmosphere gave rise to a num¬ber of studies on the analysis of ionosphere parameter variations obtained by different ionosphere sounding methods. Main part of experimental data was obtained using methods for analyzing the spectrum of ionosphere parameter variations in separate local points. To identify ST-generated wave disturbances it is necessary to measure the dynamic and spectral characteristics of the wave disturbances and to compare it with spatial-temporal characteristics of ST. Using TEC measurements from the dense network of GPS sites GEONET (Japan), we have obtained the first GPS-TEC image of the space structure of medium-scale traveling wave packets (MS TWP) excited by the solar terminator. We use two known forms of the 2D GPS-TEC image for our presentation of the space structure of ST-generated MS TWP: 1) - the diagram "distance-time"; 2) - the 2D-space distribution of the values of filtered TEC series dI (λ, φ, t) on the latitude φ and longitude λ for each 30-sec TEC counts. We found that the time period and wave-length of ST-generated wave packets are about 10-20 min and 200-300 km, respectively. Dynamic images analysis of dI (λ, φ, t) gives precise estimation of velocity and azimuth of TWP wave front propagation. We use the method of determining velocity of traveling ionosphere disturbances (SADM-GPS), which take into account the relative moving of subionosphere points. We found that the velocity of the TWP phase front, traveling along GEONET sites, varies in accordance with the velocity of the ST line displacement. The space image of MS TWP manifests itself in pronounced anisotropy and high coherence over a long distance of about 2000 km. The TWP wave front extends along the ST line with the angular shift of about 20°. The hypothesis on the connection between the TWP generation and the solar terminator can be tested in the terminator local time (TLT) system: d

  17. Characteristics-Based Methods for Efficient Parallel Integration of the Atmospheric Dynamical Equations

    NASA Astrophysics Data System (ADS)

    Norman, Matthew Ross

    The social need for realistic atmospheric simulation in weather prediction, climate change attribution, seasonal forecasting, and climate projection is great. To obtain realistic simulations, we need more physical processes included in the model with greater fidelity and finer spatial resolution. Spatial resolution primarily drives the need for computational resources because reducing the model grid spacing by a factor f requires f 4 times more computation (assuming 3-D refinement). This compute power comes from large parallel machines with 10,000s of separate nodes and accelerators such as graphics processing units (GPUs) making efficiency a complicated problem. Efficiency parallel integration algorithms need low internode communication, minimal synchronization, large time steps, and clustered computation. To this end, we propose new characteristics-based methods for the atmospheric dynamical equations with these properties in mind. These schemes are capable of simulating at a large CFL time step in only one stage of computations, needing only one copy of the state variables. They are implemented in a 2-D non-hydrostatic compressible equation set in an x-z (horizontal-vertical) Cartesian plane to simulate buoyancy-driven flows such as rising thermals and internal gravity waves. The schemes are implemented to run on CPU and multi-GPU architectures using Nvidia's CUDA (Compute Unified Device Architecture) language to test relative efficiency. Even with- out memory tuning, the GPU code showed roughly 2.5x (5x) better performance per Watt. With optimization, this could increase by an order of magnitude. The methods can use any spatial interpolant, so two major formulations are proposed and tested. One uses WENO interpolants which are pre-computed, and the other uses standard polynomials and computes them on-the-fly. The advantage of on-the-fly calculations is a significant reduction in the volume of data communicated to and from the GPU's slow global memory. In some

  18. Analysis of Adhesive Characteristics of Asphalt Based on Atomic Force Microscopy and Molecular Dynamics Simulation.

    PubMed

    Xu, Meng; Yi, Junyan; Feng, Decheng; Huang, Yudong; Wang, Dongsheng

    2016-05-18

    Asphalt binder is a very important building material in infrastructure construction; it is commonly mixed with mineral aggregate and used to produce asphalt concrete. Owing to the large differences in physical and chemical properties between asphalt and aggregate, adhesive bonds play an important role in determining the performance of asphalt concrete. Although many types of adhesive bonding mechanisms have been proposed to explain the interaction forces between asphalt binder and mineral aggregate, few have been confirmed and characterized. In comparison with chemical interactions, physical adsorption has been considered to play a more important role in adhesive bonding between asphalt and mineral aggregate. In this study, the silicon tip of an atomic force microscope was used to represent silicate minerals in aggregate, and a nanoscale analysis of the characteristics of adhesive bonding between asphalt binder and the silicon tip was conducted via an atomic force microscopy (AFM) test and molecular dynamics (MD) simulations. The results of the measurements and simulations could help in better understanding of the bonding and debonding procedures in asphalt-aggregate mixtures during hot mixing and under traffic loading. MD simulations on a single molecule of a component of asphalt and monocrystalline silicon demonstrate that molecules with a higher atomic density and planar structure, such as three types of asphaltene molecules, can provide greater adhesive strength. However, regarding the real components of asphalt binder, both the MD simulations and AFM test indicate that the colloidal structural behavior of asphalt also has a large influence on the adhesion behavior between asphalt and silicon. A schematic model of the interaction between asphalt and silicon is presented, which can explain the effect of aging on the adhesion behavior of asphalt. PMID:27115043

  19. Characteristics of quantitative perfusion parameters on dynamic contrast-enhanced MRI in mammographically occult breast cancer.

    PubMed

    Ryu, Jung Kyu; Rhee, Sun Jung; Song, Jeong Yoon; Cho, Soo Hyun; Jahng, Geon-Ho

    2016-01-01

    The purpose of this study was to compare the characteristics of quantitative per-fusion parameters obtained from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) in patients with mammographically occult (MO) breast cancers and those with mammographically visible (MV) breast cancers. Quantitative parameters (AUC, Ktrans, kep, ve, vp, and wi) from 13 MO breast cancers and 16 MV breast cancers were mapped after the DCE-MRI data were acquired. Various prog-nostic factors, including axillary nodal status, estrogen receptor (ER), progesterone receptor (PR), Ki-67, p53, E-cadherin, and human epidermal growth factor receptor 2 (HER2) were obtained in each group. Fisher's exact test was used to compare any differences of the various prognostic factors between the two groups. The Mann- Whitney U test was applied to compare the quantitative parameters between these two groups. Finally, Spearman's correlation was used to investigate the relation-ships between perfusion indices and four factors - age, tumor size, Ki-67, and p53 - for each group. Although age, tumor size, and the prognostic factors were not statistically different between the two groups, the mean values of the quantitative parameters, except wi in the MV group, were higher than those in the MO group without statistical significance (p = 0.219). The kep value was significantly differ-ent between the two groups (p = 0.048), but the other parameters were not. In the MO group, vp with size, ve with p53, and Ktrans and vp with Ki-67 had significant correlations (p < 0.05). However, in the MV group, only kep showed significant correlation with age. The kep value was only the perfusion parameter of statistical significance between MO and MV breast cancers. PMID:27685105

  20. [Dynamic characteristics of nitrogen and phosphorus in the representative input tributaries of Danjiangkou Reservoir].

    PubMed

    Lei, Pei; Zhang, Hong; Shan, Bao-Qing

    2012-09-01

    Three representative input tributaries of Danjiangkou Reservoir in the upper reach of Hanjiang River, the largest tributary of Yangtze River, were selected for annual water quality monitoring from April 2010 to April 2011, to analyze dynamic characteristics of nitrogen (N) and phosphorus (P) in the river mouth areas, and then to assess the states of nutrition by comprehensive trophic level index. The results showed that the annual average concentrations of total nitrogen (TN) and total phosphorus (TP) in Shendinghe River, receiving both industrial and domestic wastewater from Shiyan City, were 11.63 mg x L(-1) and 0.93 mg x L(-1), which were 3 times and 12 times higher respectively comparing to that of Wulongchi stream that received little agricultural non-point source pollution. While for Dabaihe River, polluted by moderate agricultural non-point source pollution combining with waster water from a small town, had slightly higher TN and TP concentrations than that of Wulongchi stream. In temporal scale, TN concentrations during the flooding season were higher than those during the dry season, while the situation was opposite for TP. The mean mass fraction of NH4(+) -N/TN was 69% in Shendinghe River, while 20% less than others. As for nitrate nitrogen (NO3(-) -N), it ranged from 1.3 to 2.7 mg x L(-1) and the mass fractions of SRP/TP varied from 30% to 45%. All of these three tributaries were in the state of eutrophication, and nutrition stoichiometry analysis revealed that Shendinghe River was in the state of nitrogen limitation, while the river mouth area stayed in phosphorus limitation.

  1. Analysis of Adhesive Characteristics of Asphalt Based on Atomic Force Microscopy and Molecular Dynamics Simulation.

    PubMed

    Xu, Meng; Yi, Junyan; Feng, Decheng; Huang, Yudong; Wang, Dongsheng

    2016-05-18

    Asphalt binder is a very important building material in infrastructure construction; it is commonly mixed with mineral aggregate and used to produce asphalt concrete. Owing to the large differences in physical and chemical properties between asphalt and aggregate, adhesive bonds play an important role in determining the performance of asphalt concrete. Although many types of adhesive bonding mechanisms have been proposed to explain the interaction forces between asphalt binder and mineral aggregate, few have been confirmed and characterized. In comparison with chemical interactions, physical adsorption has been considered to play a more important role in adhesive bonding between asphalt and mineral aggregate. In this study, the silicon tip of an atomic force microscope was used to represent silicate minerals in aggregate, and a nanoscale analysis of the characteristics of adhesive bonding between asphalt binder and the silicon tip was conducted via an atomic force microscopy (AFM) test and molecular dynamics (MD) simulations. The results of the measurements and simulations could help in better understanding of the bonding and debonding procedures in asphalt-aggregate mixtures during hot mixing and under traffic loading. MD simulations on a single molecule of a component of asphalt and monocrystalline silicon demonstrate that molecules with a higher atomic density and planar structure, such as three types of asphaltene molecules, can provide greater adhesive strength. However, regarding the real components of asphalt binder, both the MD simulations and AFM test indicate that the colloidal structural behavior of asphalt also has a large influence on the adhesion behavior between asphalt and silicon. A schematic model of the interaction between asphalt and silicon is presented, which can explain the effect of aging on the adhesion behavior of asphalt.

  2. The Dynamic Characteristics on the Wall Traveling of the HTS Bulk Superconducting Actuator

    NASA Astrophysics Data System (ADS)

    Sawae, M.; Kim, S. B.; Ozasa, S.; Nakano, H.; Kobayashi, H.

    The electric device applications of a high temperature superconducting (HTS) bulk having stable levitation and suspension properties due to their strong flux pinning force have been proposed and developed. We have been investigating the three-dimensional (3-D) superconducting actuator using HTS bulk to develop the transportation device with non-contact and moves in free space. It is expected that our proposed 3-D superconducting actuator to be useful as a transporter used in clean room which manufactures the silicon wafer where dislikes mechanical contact and dust. Proposed the actuator consists of a field-cooled HTS bulk for mover and two-dimensional arranged multiple electromagnets as a stator. In our previous study, the dynamic characteristics on the floor traveling of the HTS bulk mover had been studied. Therefore in this study, a system for the wall traveling was proposed to use the limited space effectively. It is expected that the wall traveling system is very useful to apply the transporter used in the tunnels which flammable gas may be produced. In this paper, the optimal angle between electromagnets located at floor and wall for moving to the wall traveling from the floor traveling was investigated experimentally. The position displacement on the rotating of the HTS bulk during the wall traveling was measured. As a result, the bulk with initial gap of 2 mm could move to the wall traveling from the floor traveling. Also, the position displacement on the height direction during the rotating of the HTS bulk was 18 mm from the initial position because of its gravity,but it was possible to rotate by changing the pattern NSNS of the trapped magnetic field in near the initial position.

  3. Experimental and analytical dynamic flow characteristics of an axial-flow fan from an air cushion landing system model

    NASA Technical Reports Server (NTRS)

    Thompson, W. C.; Boghani, A. B.; Leland, T. J. W.

    1977-01-01

    An investigation was conducted to compare the steady-state and dynamic flow characteristics of an axial-flow fan which had been used previously as the air supply fan for some model air cushion landing system studies. Steady-state flow characteristics were determined in the standard manner by using differential orifice pressures for the flow regime from free flow to zero flow. In this same regime, a correlative technique was established so that fan inlet and outlet pressures could be used to measure dynamic flow as created by a rotating damper. Dynamic tests at damper frequencies up to 5 Hz showed very different flow characteristics when compared with steady-state flow, particularly with respect to peak pressures and the pressure-flow relationship at fan stall and unstall. A generalized, rational mathematical fan model was developed based on physical fan parameters and a steady-state flow characteristic. The model showed good correlation with experimental tests at damper frequencies up to 5 Hz.

  4. Effects of structural and dynamic family characteristics on the development of depressive and aggressive problems during adolescence. The TRAILS study.

    PubMed

    Sijtsema, J J; Oldehinkel, A J; Veenstra, R; Verhulst, F C; Ormel, J

    2014-06-01

    Both structural (i.e., SES, familial psychopathology, family composition) and dynamic (i.e., parental warmth and rejection) family characteristics have been associated with aggressive and depressive problem development. However, it is unclear to what extent (changes in) dynamic family characteristics have an independent effect on problem development while accounting for stable family characteristics and comorbid problem development. This issue was addressed by studying problem development in a large community sample (N = 2,230; age 10-20) of adolescents using Linear Mixed models. Paternal and maternal warmth and rejection were assessed via the Egna Minnen Beträffande Uppfostran for Children (EMBU-C). Aggressive and depressive problems were assessed via subscales of the Youth/Adult Self-Report. Results showed that dynamic family characteristics independently affected the development of aggressive problems. Moreover, maternal rejection in preadolescence and increases in paternal rejection were associated with aggressive problems, whereas decreases in maternal rejection were associated with decreases in depressive problems over time. Paternal and maternal warmth in preadolescence was associated with fewer depressive problems during adolescence. Moreover, increases in paternal warmth were associated with fewer depressive problems over time. Aggressive problems were a stable predictor of depressive problems over time. Finally, those who increased in depressive problems became more aggressive during adolescence, whereas those who decreased in depressive problems became also less aggressive. Besides the effect of comorbid problems, problem development is to a large extent due to dynamic family characteristics, and in particular to changes in parental rejection, which leaves much room for parenting-based interventions. PMID:24043499

  5. Hybrid green permeable pave with hexagonal modular pavement systems

    NASA Astrophysics Data System (ADS)

    Rashid, M. A.; Abustan, I.; Hamzah, M. O.

    2013-06-01

    Modular permeable pavements are alternatives to the traditional impervious asphalt and concrete pavements. Pervious pore spaces in the surface allow for water to infiltrate into the pavement during rainfall events. As of their ability to allow water to quickly infiltrate through the surface, modular permeable pavements allow for reductions in runoff quantity and peak runoff rates. Even in areas where the underlying soil is not ideal for modular permeable pavements, the installation of under drains has still been shown to reflect these reductions. Modular permeable pavements have been regarded as an effective tool in helping with stormwater control. It also affects the water quality of stormwater runoff. Places using modular permeable pavement has been shown to cause a significant decrease in several heavy metal concentrations as well as suspended solids. Removal rates are dependent upon the material used for the pavers and sub-base material, as well as the surface void space. Most heavy metals are captured in the top layers of the void space fill media. Permeable pavements are now considered an effective BMP for reducing stormwater runoff volume and peak flow. This study examines the extent to which such combined pavement systems are capable of handling load from the vehicles. Experimental investigation were undertaken to quantify the compressive characteristics of the modular. Results shows impressive results of achieving high safety factor for daily life vehicles.

  6. Permeability extraction: A sonic log inversion

    SciTech Connect

    Akbar, N.; Kim, J.J.

    1994-12-31

    In this paper the authors provide the missing important link between permeability and acoustic velocities by generating a permeability-dependent synthetic sonic log in a carbonate reservoir. The computations are based on Akbar`s theory that relates wave velocity to frequency, rock properties (e.g., lithology, permeability, and porosity), and fluid saturation and properties (viscosity, density, and compressibility). An inverted analytical expression of the theory is used to extract permeability from sonic velocity. The synthetic sonic and the computed permeability are compared with the observed sonic log and with plug permeability, respectively. The results demonstrate, as predicted by theory, that permeability can be related directly to acoustic velocities.

  7. Permeability of stylolite-bearing chalk

    SciTech Connect

    Lind, I.; Nykjaer, O.; Priisholm, S. ); Springer, N.

    1994-11-01

    Permeabilities were measured on core plugs from stylolite-bearing chalk of the Gorm field in the Danish North Sea. Air and liquid permeabilities were measured in directions parallel to and perpendicular to the stylolite surface. Permeability was measured with sleeve pressure equal to in-situ reservoir stress. Permeabilities of plugs with stylolites but without stylolite-associated fractures were equal in the two directions. The permeability is equal to the matrix permeability of non-stylolite-bearing chalk. In contrast, when fractures were associated with the stylolites, permeability was enhanced. The enhancement was most significant in the horizontal direction parallel to the stylolites.

  8. The effects of fracture permeability on acoustic wave propagation in the porous media: A microscopic perspective.

    PubMed

    Wang, Ding; Wang, Liji; Ding, Pinbo

    2016-08-01

    An illustrative theory is developed to analyze the acoustic wave propagation characteristics in the porous media with anisotropic permeability. We focus here on the role of fracture permeability in the unconsolidated porous media, looking in particular at the compressional P-wave phase velocity and attenuation. Two fluid pressure equilibration characteristic time factors are defined, which are corresponding to crack-pore system and crack-crack system, respectively. The theoretical results show that the dispersion and attenuation characteristics of acoustic wave are affected by porous matrix and fracture permeability simultaneously. Due to the fluid exchange that takes place between fractures and pores dominantly, the influence of the fracture connectivity on the wave propagation is very weak when the permeability of background medium is relatively high. However, correlation between wave propagation and fracture permeability is significant when the matrix permeability at a low level. A second attenuation peak occurs for the fluid flow within fractures in high-frequency region for more and more higher fracture permeability. The exact analytical solutions that are compared to numerical forward modeling of wave propagation in fractured media allow us to verify the correctness of the new model. If there exists another approach for obtaining the connectivity information of background media, we can use this model to analyze qualitatively the permeability of fractures or afford an indicator of in-situ permeability changes in a oil reservoir, for example, fracturing operations.

  9. The effects of fracture permeability on acoustic wave propagation in the porous media: A microscopic perspective.

    PubMed

    Wang, Ding; Wang, Liji; Ding, Pinbo

    2016-08-01

    An illustrative theory is developed to analyze the acoustic wave propagation characteristics in the porous media with anisotropic permeability. We focus here on the role of fracture permeability in the unconsolidated porous media, looking in particular at the compressional P-wave phase velocity and attenuation. Two fluid pressure equilibration characteristic time factors are defined, which are corresponding to crack-pore system and crack-crack system, respectively. The theoretical results show that the dispersion and attenuation characteristics of acoustic wave are affected by porous matrix and fracture permeability simultaneously. Due to the fluid exchange that takes place between fractures and pores dominantly, the influence of the fracture connectivity on the wave propagation is very weak when the permeability of background medium is relatively high. However, correlation between wave propagation and fracture permeability is significant when the matrix permeability at a low level. A second attenuation peak occurs for the fluid flow within fractures in high-frequency region for more and more higher fracture permeability. The exact analytical solutions that are compared to numerical forward modeling of wave propagation in fractured media allow us to verify the correctness of the new model. If there exists another approach for obtaining the connectivity information of background media, we can use this model to analyze qualitatively the permeability of fractures or afford an indicator of in-situ permeability changes in a oil reservoir, for example, fracturing operations. PMID:27259119

  10. Transport characteristics of a finite-difference dynamics model combined with a spectral transport model of the middle atmosphere

    NASA Technical Reports Server (NTRS)

    Duncan, T.; Fairlie, A.; Turner, Richard E.; Siskind, David E.

    1994-01-01

    A three-dimensional off-line spectral transport model has been combined with a global, mechanistic, finite-difference dynamics model of the middle atmosphere in order to study transport and photochemistry in the middle atmosphere for specific, observed episodes. In this paper, the basic transport characteristics of the combined models are examined, first using steady, idealized flow fields and second using time-dependent flow fields closely related to observed atmospheric behavior. Transport conducted with the combined models is found to compare favorably with transport conducted on-line in the dynamics model, given appropriate time averaging of the flow fields and suitable choice of artificial diffusion.

  11. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  12. Influence of gas bubbles on nonlinear dynamic characteristics of the oil film of a tilting pad bearing

    NASA Astrophysics Data System (ADS)

    Khlopenko, N. Ya.

    1996-01-01

    The influence of a comparatively low volume concentration of gas microbubbles contained in oil on nonlinear characteristics describing the behavior of an oil film in the guide gap of a hydrodynamic tilting pad bearing under action of a low-frequency harmonic force is analyzed using a numerical dynamic model of a collar-oil film-pad system. It is shown that bubbles in the oil greatly affect the efficiency of the tilting pad bearing. Results of oil-film-dynamics investigations reported previously (including those of the present author) are generalized.

  13. Paranodal permeability in `myelin mutants'

    PubMed Central

    Shroff, S.; Mierzwa, A.; Scherer, S.S.; Peles, E.; Arevalo, J.C.; Chao, M.V.; Rosenbluth, J.

    2011-01-01

    Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three `myelin mutant' mice, Caspr-null, cst-null and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3kDa, 10kDa), which penetrate most fibers, and to larger tracers (40kDa, 70kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of transverse bands in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of transverse bands. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of transverse bands but does depend on the length of the paranode and, in turn, on the length of `pathway 3', the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613

  14. Paranodal permeability in "myelin mutants".

    PubMed

    Shroff, Seema; Mierzwa, Amanda; Scherer, Steven S; Peles, Elior; Arevalo, Juan C; Chao, Moses V; Rosenbluth, Jack

    2011-10-01

    Fluorescent dextran tracers of varying sizes have been used to assess paranodal permeability in myelinated sciatic nerve fibers from control and three "myelin mutant" mice, Caspr-null, cst-null, and shaking. We demonstrate that in all of these the paranode is permeable to small tracers (3 kDa and 10 kDa), which penetrate most fibers, and to larger tracers (40 kDa and 70 kDa), which penetrate far fewer fibers and move shorter distances over longer periods of time. Despite gross diminution in transverse bands (TBs) in the Caspr-null and cst-null mice, the permeability of their paranodal junctions is equivalent to that in controls. Thus, deficiency of TBs in these mutants does not increase the permeability of their paranodal junctions to the dextrans we used, moving from the perinodal space through the paranode to the internodal periaxonal space. In addition, we show that the shaking mice, which have thinner myelin and shorter paranodes, show increased permeability to the same tracers despite the presence of TBs. We conclude that the extent of penetration of these tracers does not depend on the presence or absence of TBs but does depend on the length of the paranode and, in turn, on the length of "pathway 3," the helical extracellular pathway that passes through the paranode parallel to the lateral edge of the myelin sheath. PMID:21618613

  15. Measuring Vascular Permeability In Vivo.

    PubMed

    Meijer, Eelco F J; Baish, James W; Padera, Timothy P; Fukumura, Dai

    2016-01-01

    Over the past decades, in vivo vascular permeability measurements have provided significant insight into vascular functions in physiological and pathophysiological conditions such as the response to pro- and anti-angiogenic signaling, abnormality of tumor vasculature and its normalization, and delivery and efficacy of therapeutic agents. Different approaches for vascular permeability measurements have been established. Here, we describe and discuss a conventional 2D imaging method to measure vascular permeability, which was originally documented by Gerlowski and Jain in 1986 (Microvasc Res 31:288-305, 1986) and further developed by Yuan et al. in the early 1990s (Microvasc Res 45:269-289, 1993; Cancer Res 54:352-3356, 1994), and our recently developed 3D imaging method, which advances the approach originally described by Brown et al. in 2001 (Nat Med 7:864-868, 2001). PMID:27581015

  16. Micromechanics-Based Permeability Evolution in Brittle Materials at High Strain Rates

    NASA Astrophysics Data System (ADS)

    Perol, Thibaut; Bhat, Harsha S.

    2016-08-01

    We develop a micromechanics-based permeability evolution model for brittle materials at high strain rates (≥ 100 s^{-1}). Extending for undrained deformation the mechanical constitutive description of brittle solids, whose constitutive response is governed by micro-cracks, we now relate the damage-induced strains to micro-crack aperture. We then use an existing permeability model to evaluate the permeability evolution. This model predicts both the percolative and connected regime of permeability evolution of Westerly Granite during triaxial loading at high strain rate. This model can simulate pore pressure history during earthquake coseismic dynamic ruptures under undrained conditions.

  17. Permeability enhancement by shock cooling

    NASA Astrophysics Data System (ADS)

    Griffiths, Luke; Heap, Michael; Reuschlé, Thierry; Baud, Patrick; Schmittbuhl, Jean

    2015-04-01

    The permeability of an efficient reservoir, e.g. a geothermal reservoir, should be sufficient to permit the circulation of fluids. Generally speaking, permeability decreases over the life cycle of the geothermal system. As a result, is usually necessary to artificially maintain and enhance the natural permeability of these systems. One of the methods of enhancement -- studied here -- is thermal stimulation (injecting cold water at low pressure). This goal of this method is to encourage new thermal cracks within the reservoir host rocks, thereby increasing reservoir permeability. To investigate the development of thermal microcracking in the laboratory we selected two granites: a fine-grained (Garibaldi Grey granite, grain size = 0.5 mm) and a course-grained granite (Lanhelin granite, grain size = 2 mm). Both granites have an initial porosity of about 1%. Our samples were heated to a range of temperatures (100-1000 °C) and were either cooled slowly (1 °C/min) or shock cooled (100 °C/s). A systematic microstructural (2D crack area density, using standard stereological techniques, and 3D BET specific surface area measurements) and rock physical property (porosity, P-wave velocity, uniaxial compressive strength, and permeability) analysis was undertaken to understand the influence of slow and shock cooling on our reservoir granites. Microstructurally, we observe that the 2D crack surface area per unit volume and the specific surface area increase as a result of thermal stressing, and, for the same maximum temperature, crack surface area is higher in the shock cooled samples. This observation is echoed by our rock physical property measurements: we see greater changes for the shock cooled samples. We can conclude that shock cooling is an extremely efficient method of generating thermal microcracks and modifying rock physical properties. Our study highlights that thermal treatments are likely to be an efficient method for the "matrix" permeability enhancement of

  18. Effects of incoming surface wind conditions on the wake characteristics and dynamic wind loads acting on a wind turbine model

    NASA Astrophysics Data System (ADS)

    Tian, Wei; Ozbay, Ahmet; Hu, Hui

    2014-12-01

    An experimental investigation was conducted to examine the effects of incoming surface wind conditions on the wake characteristics and dynamic wind loads acting on a wind turbine model. The experimental study was performed in a large-scale wind tunnel with a scaled three-blade Horizontal Axial Wind Turbine model placed in two different types of Atmospheric Boundary Layer (ABL) winds with distinct mean and turbulence characteristics. In addition to measuring dynamic wind loads acting on the model turbine by using a force-moment sensor, a high-resolution Particle Image Velocimetry system was used to achieve detailed flow field measurements to characterize the turbulent wake flows behind the model turbine. The measurement results reveal clearly that the discrepancies in the incoming surface winds would affect the wake characteristics and dynamic wind loads acting on the model turbine dramatically. The dynamic wind loads acting on the model turbine were found to fluctuate much more significantly, thereby, much larger fatigue loads, for the case with the wind turbine model sited in the incoming ABL wind with higher turbulence intensity levels. The turbulent kinetic energy and Reynolds stress levels in the wake behind the model turbine were also found to be significantly higher for the high turbulence inflow case, in comparison to those of the low turbulence inflow case. The flow characteristics in the turbine wake were found to be dominated by the formation, shedding, and breakdown of various unsteady wake vortices. In comparison with the case with relatively low turbulence intensities in the incoming ABL wind, much more turbulent and randomly shedding, faster dissipation, and earlier breakdown of the wake vortices were observed for the high turbulence inflow case, which would promote the vertical transport of kinetic energy by entraining more high-speed airflow from above to re-charge the wake flow and result in a much faster recovery of the velocity deficits in the

  19. Urban land use: Remote sensing of ground-basin permeability

    NASA Technical Reports Server (NTRS)

    Tinney, L. R.; Jensen, J. R.; Estes, J. E.

    1975-01-01

    A remote sensing analysis of the amount and type of permeable and impermeable surfaces overlying an urban recharge basin is discussed. An effective methodology for accurately generating this data as input to a safe yield study is detailed and compared to more conventional alternative approaches. The amount of area inventoried, approximately 10 sq. miles, should provide a reliable base against which automatic pattern recognition algorithms, currently under investigation for this task, can be evaluated. If successful, such approaches can significantly reduce the time and effort involved in obtaining permeability data, an important aspect of urban hydrology dynamics.

  20. Dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during deep penetration fiber laser welding

    NASA Astrophysics Data System (ADS)

    Pang, Shengyong; Shao, Xinyu; Li, Wen; Chen, Xin; Gong, Shuili

    2016-07-01

    The compressible metallic vapor plume or plasma plume behaviors in the keyhole during deep penetration laser welding have significant effects on the joint quality. However, these behaviors and their responses to process parameter variations have not been well understood. In this paper, we first systematically study the dynamic characteristics and mechanisms of compressible metallic vapor plume behaviors in transient keyhole during fiber laser welding of 304 stainless steels based on a multiple timescale multiphase model. The time-dependent temperature, pressure, velocity and Mach number distributions of vapor plume under different process parameters are theoretically predicted. It is found that the distributions of the main physical characteristics of vapor plume such as pressure, velocity as well as Mach number in keyhole are usually highly uneven and highly time dependent. The peak difference of the velocity, pressure, temperature and Mach number of the vapor plume in a keyhole could be greater than 200 m/s, 20 kPa, 1000 K and 0.6 Mach, respectively. The vapor plume characteristics in a transient keyhole can experience significant changes within several hundreds of nanoseconds. The formation mechanisms of these dynamic characteristics are mainly due to the mesoscale keyhole hump (sized in several tens of microns) dynamics. It is also demonstrated that it is possible to suppress the oscillations of compressible vapor plume in the keyhole by improving the keyhole stability through decreasing the heat input. However, stabilizing the keyhole could only weaken, but not eliminate, the observed highly uneven and transient characteristics. This finding may pose new challenges for accurate experimental measurements of vapor plume induced by laser welding.

  1. Investigation of dynamic characteristics of an elastic wing model by using corrections of mass and stiffness matrices

    NASA Astrophysics Data System (ADS)

    Hashemi-Kia, M.; Cutchins, M. A.; Tinker, M. L.

    1988-02-01

    The effects of theoretical changes in mass and stiffness matrices on the dynamic characteristics of a model wing are considered. The NASTRAN computer code is utilized to find theoretical mass and stiffness matrices with their corresponding natural frequencies and mode shapes. The dynamic response is then calculated by using theoretical mass and stiffness matrices and theoretical modal data. Experimentally measured mode shapes and natural frequencies are used to improve the stiffness and mass matrices. The resulting improved stiffness and mass matrices are further used to calculate again the dynamic response for the model. Analysis of the computational results and experimental data show that the improved theoretical model represents the experimental model better than the original theoretical model. Other means of improving the theoretical model are summarized.

  2. Mapping permeability in low-resolution micro-CT images: A multiscale statistical approach

    NASA Astrophysics Data System (ADS)

    Botha, Pieter W. S. K.; Sheppard, Adrian P.

    2016-06-01

    We investigate the possibility of predicting permeability in low-resolution X-ray microcomputed tomography (µCT). Lower-resolution whole core images give greater sample coverage and are therefore more representative of heterogeneous systems; however, the lower resolution causes connecting pore throats to be represented by intermediate gray scale values and limits information on pore system geometry, rendering such images inadequate for direct permeability simulation. We present an imaging and computation workflow aimed at predicting absolute permeability for sample volumes that are too large to allow direct computation. The workflow involves computing permeability from high-resolution µCT images, along with a series of rock characteristics (notably open pore fraction, pore size, and formation factor) from spatially registered low-resolution images. Multiple linear regression models correlating permeability to rock characteristics provide a means of predicting and mapping permeability variations in larger scale low-resolution images. Results show excellent agreement between permeability predictions made from 16 and 64 µm/voxel images of 25 mm diameter 80 mm tall core samples of heterogeneous sandstone for which 5 µm/voxel resolution is required to compute permeability directly. The statistical model used at the lowest resolution of 64 µm/voxel (similar to typical whole core image resolutions) includes open pore fraction and formation factor as predictor characteristics. Although binarized images at this resolution do not completely capture the pore system, we infer that these characteristics implicitly contain information about the critical fluid flow pathways. Three-dimensional permeability mapping in larger-scale lower resolution images by means of statistical predictions provides input data for subsequent permeability upscaling and the computation of effective permeability at the core scale.

  3. Scale Dependence of Soil Permeability to Air: Measurement Method and Field Investigation

    SciTech Connect

    Garbesi, K.; Sextro, R.G.; Robinson, Arthur L.; Wooley, J.D.; Owens, J.A.; Nazaroff, W.W.

    1995-11-01

    This work investigates the dependence soil air-permeability on sampling scale in near-surface unsaturated soils. A new dual-probe dynamic pressure technique was developed to measure permeability in situ over different length scales and different spatial orientations in the soil. Soils at three sites were studied using the new technique. Each soil was found to have higher horizontal than vertical permeability. Significant scale dependence of permeability was also observed at each site. Permeability increased by a factor of 20 as sampling scale increased from 0.1 to 2 m in a sand soil vegetated with dry grass, and by a factor of 15 as sampling scale increased from 0.1 to 3.5 m in a sandy loam with mature Coast Live Oak trees (Quercus agrifolia). The results indicate that standard methods of permeability assessment can grossly underestimate advective transport of gas-phase contaminants through soils.

  4. Investigation of Dynamic Force/Vibration Transmission Characteristics of Four-Square Type Gear Durability Test Machines

    NASA Technical Reports Server (NTRS)

    Kahraman, Ahmet

    2002-01-01

    In this study, design requirements for a dynamically viable, four-square type gear test machine are investigated. Variations of four-square type gear test machines have been in use for durability and dynamics testing of both parallel- and cross-axis gear set. The basic layout of these machines is illustrated. The test rig is formed by two gear pairs, of the same reduction ratio, a test gear pair and a reaction gear pair, connected to each other through shafts of certain torsional flexibility to form an efficient, closed-loop system. A desired level of constant torque is input to the circuit through mechanical (a split coupling with a torque arm) or hydraulic (a hydraulic actuator) means. The system is then driven at any desired speed by a small DC motor. The main task in hand is the isolation of the test gear pair from the reaction gear pair under dynamic conditions. Any disturbances originated at the reaction gear mesh might potentially travel to the test gearbox, altering the dynamic loading conditions of the test gear mesh, and hence, influencing the outcome of the durability or dynamics test. Therefore, a proper design of connecting structures becomes a major priority. Also, equally important is the issue of how close the operating speed of the machine is to the resonant frequencies of the gear meshes. This study focuses on a detailed analysis of the current NASA Glenn Research Center gear pitting test machine for evaluation of its resonance and vibration isolation characteristics. A number of these machines as the one illustrated has been used over last 30 years to establish an extensive database regarding the influence of the gear materials, processes surface treatments and lubricants on gear durability. This study is intended to guide an optimum design of next generation test machines for the most desirable dynamic characteristics.

  5. Diagnostic study of coupled solar wind-magnetosphere-ionosphere dynamics in D-region ionosphere via VLF signal propagation characteristic

    NASA Astrophysics Data System (ADS)

    Nwankwo, Victor U. J.; Chakrabarti, Sandip Kumar

    2016-07-01

    Geomagnetic disturbances and storms are known to produce significant global disturbances in the ionosphere, including the middle atmosphere and troposphere. There is little understanding about the mechanism and dynamics that drive these processes in lower ionosphere. The ionosphere is also thought to be sensitive to seismic events, and it is believed that it exhibits precursory characteristics as reported in studies via characteristic anomalies in VLF signal. However, distinguishing or separating seismically induced ionospheric fluctuations from those of other origins (e.g., Solar activity, planetary and tidal waves, stratospheric warming etc.) remain vital to robust conclusion, and challenging too. The unique propagation characteristic of VLF radio signal makes it an ideal tool for the study and diagnosis of variability of D-region ionosphere. In this work, we present the analysis of solar wind-magnetosphere-ionosphere coupling dynamics in D-region ionosphere using VLF signal characteristics, and performed an investigation of previously reported 'ionospheric precursors' to understand the true origins of measured anomalies.

  6. The geometric mean concept for interpreting the permeability of heterogeneous geomaterials

    NASA Astrophysics Data System (ADS)

    Selvadurai, Patrick; Selvadurai, Paul

    2015-04-01

    Naturally occurring geomaterials are heterogeneous and the estimation of the effective permeability characteristics of such geomaterials presents a challenge not only in terms of the experimental procedures that should be used to ensure flow through the porous medium but also in the correct use of the theoretical concepts needed to accurately interpret the data. The general consensus is that the flow path in a test needs to be drastically reduced if steady state tests are considered as a suitable experimental technique. The disadvantage of flow path reduction is that the tested volume may not be altogether representative of the rock, particularly if it displays heterogeneity in the scale of the sample being tested. Also, if the sample is not correctly restrained, the differential pressures needed to initiate steady flow can introduce damage in the sample leading to erroneous estimates of permeability. The alternative approach is to use large enough samples that can capture the spatial heterogeneity but develop testing procedures that can test examine the steady state flow process as a problem in three-dimensional fluid flow that can capture the spatial distribution of permeability. The paper discusses theoretical and computational approaches that have been developed for the estimation of the spatial distribution of permeability in a cuboidal Indiana Limestone sample measuring 450 mm. The "Patch Permeability Test" developed in connection with the research allows the measurements of the surface permeability of the block and through kriging techniques estimate the permeability within the block sample. The research promotes the use of the "Geometric Mean" concept for the description of the effective permeability of the heterogeneous porous medium where the spatial distribution conforms to a lognormal pattern. The effectiveness of the approach is that the techniques can be applied to examine the effective permeability of heterogeneous low permeability materials such as

  7. Electrohydraulic shock wave generation as a means to increase intrinsic permeability of mortar

    SciTech Connect

    Maurel, O.; Reess, T.; Matallah, M.; De Ferron, A.; Chen, W.; La Borderie, C.; Pijaudier-Cabot, G.; Jacques, A.; Rey-Bethbeder, F.

    2010-12-15

    This article discusses the influence of compressive shock waves on the permeability of cementitious materials. Shock waves are generated in water by Pulsed Arc Electrohydraulic Discharges (PAED). The practical aim is to increase the intrinsic permeability of the specimens. The maximum pressure amplitude of the shock wave is 250 MPa. It generates damage in the specimens and the evolution of damage is correlated with the intrinsic permeability of the mortar. A threshold of pressure is observed. From this threshold, the increase of permeability is linear in a semi-log plot. The influence of repeated shocks on permeability is also discussed. Qualitative X Ray Tomography illustrates the evolution of the microstructure of the material leading to the increase of permeability. Comparative results from mercury intrusion porosimetry (MIP) show that the micro-structural damage process starts at the sub-micrometric level and that the characteristic size of pores of growing volume increases.

  8. Flow and permeability structure of the Beowawe, Nevada hydrothermal system

    SciTech Connect

    Faulder, D.D.; Johnson, S.D.; Benoit, W.R.

    1997-05-01

    A review of past geologic, geochemical, hydrological, pressure transient, and reservoir engineering studies of Beowawe suggests a different picture of the reservoir than previously presented. The Beowawe hydrothermal contains buoyant thermal fluid dynamically balanced with overlying cold water, as shown by repeated temperature surveys and well test results. Thermal fluid upwells from the west of the currently developed reservoir at the intersection of the Malpais Fault and an older structural feature associated with mid-Miocene rifting. A tongue of thermal fluid rises to the east up the high permeability Malpais Fault, discharges at the Geysers area, and is in intimate contact with overlying cooler water. The permeability structure is closely related to the structural setting, with the permeability of the shallow hydrothermal system ranging from 500 to 1,000 D-ft, while the deeper system ranges from 200 to 400 D-ft.

  9. Benthic exchange and biogeochemical cycling in permeable sediments.

    PubMed

    Huettel, Markus; Berg, Peter; Kostka, Joel E

    2014-01-01

    The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

  10. High membrane permeability for melatonin.

    PubMed

    Yu, Haijie; Dickson, Eamonn J; Jung, Seung-Ryoung; Koh, Duk-Su; Hille, Bertil

    2016-01-01

    The pineal gland, an endocrine organ in the brain, synthesizes and secretes the circulating night hormone melatonin throughout the night. The literature states that this hormone is secreted by simple diffusion across the pinealocyte plasma membrane, but a direct quantitative measurement of membrane permeability has not been made. Experiments were designed to compare the cell membrane permeability to three indoleamines: melatonin and its precursors N-acetylserotonin (NAS) and serotonin (5-HT). The three experimental approaches were (1) to measure the concentration of effluxing indoleamines amperometrically in the bath while cells were being dialyzed internally by a patch pipette, (2) to measure the rise of intracellular indoleamine fluorescence as the compound was perfused in the bath, and (3) to measure the rate of quenching of intracellular fura-2 dye fluorescence as indoleamines were perfused in the bath. These measures showed that permeabilities of melatonin and NAS are high (both are uncharged molecules), whereas that for 5-HT (mostly charged) is much lower. Comparisons were made with predictions of solubility-diffusion theory and compounds of known permeability, and a diffusion model was made to simulate all of the measurements. In short, extracellular melatonin equilibrates with the cytoplasm in 3.5 s, has a membrane permeability of ∼1.7 µm/s, and could not be retained in secretory vesicles. Thus, it and NAS will be "secreted" from pineal cells by membrane diffusion. Circumstances are suggested when 5-HT and possibly catecholamines may also appear in the extracellular space passively by membrane diffusion. PMID:26712850

  11. High membrane permeability for melatonin

    PubMed Central

    Yu, Haijie; Dickson, Eamonn J.; Jung, Seung-Ryoung; Koh, Duk-Su

    2016-01-01

    The pineal gland, an endocrine organ in the brain, synthesizes and secretes the circulating night hormone melatonin throughout the night. The literature states that this hormone is secreted by simple diffusion across the pinealocyte plasma membrane, but a direct quantitative measurement of membrane permeability has not been made. Experiments were designed to compare the cell membrane permeability to three indoleamines: melatonin and its precursors N-acetylserotonin (NAS) and serotonin (5-HT). The three experimental approaches were (1) to measure the concentration of effluxing indoleamines amperometrically in the bath while cells were being dialyzed internally by a patch pipette, (2) to measure the rise of intracellular indoleamine fluorescence as the compound was perfused in the bath, and (3) to measure the rate of quenching of intracellular fura-2 dye fluorescence as indoleamines were perfused in the bath. These measures showed that permeabilities of melatonin and NAS are high (both are uncharged molecules), whereas that for 5-HT (mostly charged) is much lower. Comparisons were made with predictions of solubility-diffusion theory and compounds of known permeability, and a diffusion model was made to simulate all of the measurements. In short, extracellular melatonin equilibrates with the cytoplasm in 3.5 s, has a membrane permeability of ∼1.7 µm/s, and could not be retained in secretory vesicles. Thus, it and NAS will be “secreted” from pineal cells by membrane diffusion. Circumstances are suggested when 5-HT and possibly catecholamines may also appear in the extracellular space passively by membrane diffusion. PMID:26712850

  12. Controlling ferrofluid permeability across the blood-brain barrier model

    NASA Astrophysics Data System (ADS)

    Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J.

    2014-02-01

    In the present study, an in vitro blood-brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood-brain barrier model was completed by examining the permeability of FITC-Dextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood-brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood-brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood-brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood-brain barrier (e.g. CPB).

  13. Controlling ferrofluid permeability across the blood–brain barrier model.

    PubMed

    Shi, Di; Sun, Linlin; Mi, Gujie; Sheikh, Lubna; Bhattacharya, Soumya; Nayar, Suprabha; Webster, Thomas J

    2014-02-21

    In the present study, an in vitro blood–brain barrier model was developed using murine brain endothelioma cells (b.End3 cells). Confirmation of the blood–brain barrier model was completed by examining the permeability of FITCDextran at increasing exposure times up to 96 h in serum-free medium and comparing such values with values from the literature. After such confirmation, the permeability of five novel ferrofluid (FF) nanoparticle samples, GGB (ferrofluids synthesized using glycine, glutamic acid and BSA), GGC (glycine, glutamic acid and collagen), GGP (glycine, glutamic acid and PVA), BPC (BSA, PEG and collagen) and CPB (collagen, PVA and BSA), was determined using this blood–brain barrier model. All of the five FF samples were characterized by zeta potential to determine their charge as well as TEM and dynamic light scattering for determining their hydrodynamic diameter. Results showed that FF coated with collagen passed more easily through the blood–brain barrier than FF coated with glycine and glutamic acid based on an increase of 4.5% in permeability. Through such experiments, diverse magnetic nanomaterials (such as FF) were identified for: (1) MRI use since they were less permeable to penetrate the blood–brain barrier to avoid neural tissue toxicity (e.g. GGB) or (2) brain drug delivery since they were more permeable to the blood–brain barrier (e.g. CPB). PMID:24457539

  14. Time-Structured and Net Intraindividual Variability: Tools for Examining the Development of Dynamic Characteristics and Processes

    PubMed Central

    Ram, Nilam; Gerstorf, Denis

    2009-01-01

    The study of intraindividual variability is the study of fluctuations, oscillations, adaptations, and “noise” in behavioral outcomes that manifest on micro-time scales. This paper provides a descriptive frame for the combined study of intraindividual variability and aging/development. At the conceptual level, we highlight that the study of intraindividual variability provides access to dynamic characteristics – construct-level descriptions of individuals' capacities for change (e.g., lability), and dynamic processes – the systematic changes individuals' exhibit in response to endogenous and exogenous influences (e.g., regulation). At the methodological level, we review how quantifications of net intraindividual variability (e.g., iSD) and models of time-structured intraindividual variability (e.g., time-series) are being used to measure and describe dynamic characteristics and processes. At the research design level, we point to the benefits of measurement burst study designs, wherein data are obtained across multiple time scales, for the study of development. PMID:20025395

  15. Permeability of the San Andreas Fault Zone at Depth

    NASA Astrophysics Data System (ADS)

    Rathbun, A. P.; Song, I.; Saffer, D.

    2010-12-01

    Quantifying fault rock permeability is important toward understanding both the regional hydrologic behavior of fault zones, and poro-elastic processes that affect fault mechanics by mediating effective stress. These include long-term fault strength as well as dynamic processes that may occur during earthquake slip, including thermal pressurization and dilatancy hardening. Despite its importance, measurements of fault zone permeability for relevant natural materials are scarce, owing to the difficulty of coring through active fault zones seismogenic depths. Most existing measurements of fault zone permeability are from altered surface samples or from thinner, lower displacement faults than the SAF. Here, we report on permeability measurements conducted on gouge from the actively creeping Central Deformation Zone (CDZ) of the San Andreas Fault, sampled in the SAFOD borehole at a depth of ~2.7 km (Hole G, Run 4, sections 4,5). The matrix of the gouge in this interval is predominantly composed of particles <10 µm, with ~5 vol% clasts of serpentinite, very fine-grained sandstone, and siltstone. The 2.6 m-thick CDZ represents the main fault trace and hosts ~90% of the active slip on the SAF at this location, as documented by repeated casing deformation surveys. We measured permeability in two different configurations: (1) in a uniaxial pressure cell, in which a sample is placed into a rigid steel ring which imposes a zero lateral strain condition and subjected to axial load, and (2) in a standard triaxial system under isostatic stress conditions. In the uniaxial configuration, we obtained permeabilities at axial effective stresses up to 90 MPa, and in the triaxial system up to 10 MPa. All experiments were conducted on cylindrical subsamples of the SAFOD core 25 mm in diameter, with lengths ranging from 18mm to 40mm, oriented for flow approximately perpendicular to the fault. In uniaxial tests, permeability is determined by running constant rate of strain (CRS) tests up

  16. Osmotic Flow through Fully Permeable Nanochannels

    NASA Astrophysics Data System (ADS)

    Lee, C.; Cottin-Bizonne, C.; Biance, A.-L.; Joseph, P.; Bocquet, L.; Ybert, C.

    2014-06-01

    Osmosis across membranes is intrinsically associated with the concept of semipermeability. Here, however, we demonstrate that osmotic flow can be generated by solute gradients across nonselective, fully permeable nanochannels. Using a fluorescence imaging technique, we are able to measure the water flow rate inside single nanochannels to an unprecedented sensitivity of femtoliters per minute flow rates. Our results indicate the onset of a convective liquid motion under salinity gradients, from the higher to lower electrolyte concentration, which is attributed to diffusio-osmotic transport. To our knowledge, this is the first experimental evidence and quantitative investigation of this subtle interfacially driven transport, which need to be accounted for in nanoscale dynamics. Finally, diffusio-osmotic transport under a neutral polymer gradient is also demonstrated. The experiments highlight the entropic depletion of polymers that occurs at the nanochannel surface, resulting in convective flow in the opposite direction to that seen for electrolytes.

  17. Osmotic flow through fully permeable nanochannels.

    PubMed

    Lee, C; Cottin-Bizonne, C; Biance, A-L; Joseph, P; Bocquet, L; Ybert, C

    2014-06-20

    Osmosis across membranes is intrinsically associated with the concept of semipermeability. Here, however, we demonstrate that osmotic flow can be generated by solute gradients across nonselective, fully permeable nanochannels. Using a fluorescence imaging technique, we are able to measure the water flow rate inside single nanochannels to an unprecedented sensitivity of femtoliters per minute flow rates. Our results indicate the onset of a convective liquid motion under salinity gradients, from the higher to lower electrolyte concentration, which is attributed to diffusio-osmotic transport. To our knowledge, this is the first experimental evidence and quantitative investigation of this subtle interfacially driven transport, which need to be accounted for in nanoscale dynamics. Finally, diffusio-osmotic transport under a neutral polymer gradient is also demonstrated. The experiments highlight the entropic depletion of polymers that occurs at the nanochannel surface, resulting in convective flow in the opposite direction to that seen for electrolytes. PMID:24996091

  18. Permeable Pavement Research - Edison, New Jersey

    EPA Science Inventory

    This presentation provides the background and summary of results collected at the permeable pavement parking lot monitored at the EPA facility in Edison, NJ. This parking lot is surfaced with permeable interlocking concrete pavers (PICP), pervious concrete, and porous asphalt. ...

  19. Quantifying Evaporation in a Permeable Pavement System

    EPA Science Inventory

    Studies quantifying evaporation from permeable pavement systems are limited to a few laboratory studies and one field application. This research quantifies evaporation for a larger-scale field application by measuring the water balance from lined permeable pavement sections. Th...

  20. Dynamic modelling and response characteristics of a magnetic bearing rotor system including auxiliary bearings

    NASA Technical Reports Server (NTRS)

    Free, April M.; Flowers, George T.; Trent, Victor S.

    1993-01-01

    Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotor-dynamic model and assess the dynamic behavior of a magnetic bearing rotor system which includes the effects of auxiliary bearings. Of particular interest is the effects of introducing sideloading into such a system during failure of the magnetic bearing. A model is developed from an experimental test facility and a number of simulation studies are performed. These results are presented and discussed.

  1. Dynamic characteristics of a hydraulic amplification mechanism for large displacement actuators systems.

    PubMed

    Arouette, Xavier; Matsumoto, Yasuaki; Ninomiya, Takeshi; Okayama, Yoshiyuki; Miki, Norihisa

    2010-01-01

    We have developed a hydraulic displacement amplification mechanism (HDAM) and studied its dynamic response when combined with a piezoelectric actuator. The HDAM consists of an incompressible fluid sealed in a microcavity by two largely deformable polydimethylsiloxane (PDMS) membranes. The geometry with input and output surfaces having different cross-sectional areas creates amplification. By combining the HDAM with micro-actuators, we can amplify the input displacement generated by the actuators, which is useful for applications requiring large deformation, such as tactile displays. We achieved a mechanism offering up to 18-fold displacement amplification for static actuation and 12-fold for 55 Hz dynamic actuation. PMID:22319281

  2. Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport

    NASA Technical Reports Server (NTRS)

    Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.

    2010-01-01

    A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.

  3. Two Relations to Estimate Membrane Permeability Using Milestoning.

    PubMed

    Votapka, Lane W; Lee, Christopher T; Amaro, Rommie E

    2016-08-25

    Prediction of passive permeation rates of solutes across lipid bilayers is important to drug design, toxicology, and other biological processes such as signaling. The inhomogeneous solubility-diffusion (ISD) equation is traditionally used to relate the position-dependent potential of mean force and diffusivity to the permeability coefficient. The ISD equation is derived via the Smoluchowski equation and assumes overdamped system dynamics. It has been suggested that the complex membrane environment may exhibit more complicated damping conditions. Here we derive a variant of the inhomogeneous solubility diffusion equation as a function of the mean first passage time (MFPT) and show how milestoning, a method that can estimate kinetic quantities of interest, can be used to estimate the MFPT of membrane crossing and, by extension, the permeability coefficient. We further describe a second scheme, agnostic to the damping condition, to estimate the permeability coefficient from milestoning results or other methods that compute a probability of membrane crossing. The derived relationships are tested using a one-dimensional Langevin dynamics toy system confirming that the presented theoretical methods can be used to estimate permeabilities given simulation and milestoning results. PMID:27154639

  4. Two Relations to Estimate Membrane Permeability Using Milestoning

    PubMed Central

    2016-01-01

    Prediction of passive permeation rates of solutes across lipid bilayers is important to drug design, toxicology, and other biological processes such as signaling. The inhomogeneous solubility-diffusion (ISD) equation is traditionally used to relate the position-dependent potential of mean force and diffusivity to the permeability coefficient. The ISD equation is derived via the Smoluchowski equation and assumes overdamped system dynamics. It has been suggested that the complex membrane environment may exhibit more complicated damping conditions. Here we derive a variant of the inhomogeneous solubility diffusion equation as a function of the mean first passage time (MFPT) and show how milestoning, a method that can estimate kinetic quantities of interest, can be used to estimate the MFPT of membrane crossing and, by extension, the permeability coefficient. We further describe a second scheme, agnostic to the damping condition, to estimate the permeability coefficient from milestoning results or other methods that compute a probability of membrane crossing. The derived relationships are tested using a one-dimensional Langevin dynamics toy system confirming that the presented theoretical methods can be used to estimate permeabilities given simulation and milestoning results. PMID:27154639

  5. Dynamic Characteristics of X-pinch Experiments Conducted in a Small Capacitive Generator:Refractive Optical Observations.

    NASA Astrophysics Data System (ADS)

    Sepúlveda, Adolfo; Pavez, Cristian; Pedreros, José; Avaria, Gonzalo; San Martín, Patricio; Soto, Leopoldo

    2016-05-01

    Among the dense plasmas configurations of interest for applications as a portable intense source of X-rays, the X-pinches are the most attractive by their brightness, source size, short duration and space localization, being particularly reproducible when they are conducted with fast pulsed power generators. In recent time, several characteristics of the dynamics and emission have been reproduced in compact generators (typically capacitive generators) of low current rise-rate (less than 0.5 kA/ns). In this work, a preliminary characterization of the dynamic of X-pinch plasma conducted in a small capacitive generator is reported. In order to obtain the plasma dynamics and quantitative information of the plasma density, the dark field Schlieren technique and interferometry were implemented. The experiments were carried out on the multipurpose generator (1.2 μF, 345 J, 47.5 nH, T/4=375 ns and Z = 0.2 Ω in short circuit) capable to produce currents up to 122 kA with 500 ns quarter period, when a charging voltage of 24 kV and metallic X-pinches are used as load. The electrical behavior of the discharge and the X-ray emission are monitored with a Rogowski coil and filtered PIN diodes respectively. For the refractive optical diagnostics a 532 nm frequency- doubled Nd-YAG laser was used. As from a single Schlieren record per shot, a sequence with the time evolution of the plasma is constructed. From the images, a similar dynamic of X- pinches conducted in fast generators of high current is observed, where structures such as coronal plasma, plasma flares and plasma jets are identified. The plasma dynamics observed from a VUV gated pinhole image system is compared with registered dynamic with refractive optical techniques.

  6. Vapor-liquid phase separator permeability results

    NASA Technical Reports Server (NTRS)

    Yuan, S. W. K.; Frederking, T. H. K.

    1981-01-01

    Continued studies are described in the area of vapor-liquid phase separator work with emphasis on permeabilities of porous sintered plugs (stainless steel, nominal pore size 2 micrometer). The temperature dependence of the permeability has been evaluated in classical fluid using He-4 gas at atmospheric pressure and in He-2 on the basis of a modified, thermosmotic permeability of the normal fluid.

  7. Structure/Permeability Relationships Of Polyimide Membranes

    NASA Technical Reports Server (NTRS)

    St. Clair, A. K.; Yamamoto, H.; Mi, Y.; Stern, S. A.

    1995-01-01

    Report describes experimental study of permeabilities, by each of five gases, of membranes made of four different polyimides. Conducted to gain understanding of effects of molecular structures of membranes on permeabilities and to assess potential for exploitation of selective permeability in gas-separation processes. Gases used: H2, O2, N2, CO2, and CH4.

  8. Novel additives to retard permeable flow

    SciTech Connect

    Golombok, Michael; Crane, Carel; Ineke, Erik; Welling, Marco; Harris, Jon

    2008-09-15

    Low concentrations of surfactant and cosolute in water, can selectively retard permeable flow in high permeability rocks compared to low permeability ones. This represents a way forward for more efficient areal sweep efficiency when water flooding a reservoir during improved oil recovery. (author)

  9. Heredity characteristics of schizophrenia shown by dynamic functional connectivity analysis of resting-state functional MRI scans of unaffected siblings.

    PubMed

    Su, Jianpo; Shen, Hui; Zeng, Ling-Li; Qin, Jian; Liu, Zhening; Hu, Dewen

    2016-08-01

    Previous static resting-state functional connectivity (FC) MRI (rs-fcMRI) studies have suggested certain heredity characteristics of schizophrenia. Recently, dynamic rs-fcMRI analysis, which can better characterize the time-varying nature of intrinsic activity and connectivity and may therefore unveil the special connectivity patterns that are always lost in static FC analysis, has shown a potential neuroendophenotype of schizophrenia. In this study, we have extended previous static rs-fcMRI studies to a dynamic study by exploring whether healthy siblings share aberrant dynamic FC patterns with schizophrenic patients, which may imply a potential risk for siblings to develop schizophrenia. We utilized the dynamic rs-fcMRI method using a sliding window approach to evaluate FC discrepancies within transient states across schizophrenic patients, unaffected siblings, and matched healthy controls. Statistical analysis showed five trait-related connections that are related to cingulo-opercular, occipital, and default mode networks, reflecting the shared connectivity alterations between schizophrenic patients and their unaffected siblings. The findings suggested that schizophrenic patients and their unaffected siblings shared common transient functional disconnectivity, implying a potential risk for the healthy siblings of developing schizophrenia.

  10. Differences in the dynamic baroreflex characteristics of unmyelinated and myelinated central pathways are less evident in spontaneously hypertensive rats.

    PubMed

    Turner, Michael J; Kawada, Toru; Shimizu, Shuji; Fukumitsu, Masafumi; Sugimachi, Masaru

    2015-12-01

    The aim of the study was to identify the contribution of myelinated (A-fiber) and unmyelinated (C-fiber) baroreceptor central pathways to the baroreflex control of sympathetic nerve activity (SNA) and arterial pressure (AP) in anesthetized Wistar-Kyoto (WKY; n = 8) and spontaneously hypertensive rats (SHR; n = 8). The left aortic depressor nerve (ADN) was electrically stimulated with two types of binary white noise signals designed to preferentially activate A-fibers (A-BRx protocol) or C-fibers (C-BRx protocol). In WKY, the central arc transfer function from ADN stimulation to SNA estimated by A-BRx showed strong derivative characteristics with the slope of dynamic gain between 0.1 and 1 Hz (Gslope) of 14.63 ± 0.89 dB/decade. In contrast, the central arc transfer function estimated by C-BRx exhibited nonderivative characteristics with Gslope of 0.64 ± 1.13 dB/decade. This indicates that A-fibers are important for rapid baroreflex regulation, whereas C-fibers are likely important for more sustained regulation of SNA and AP. In SHR, the central arc transfer function estimated by A-BRx showed higher Gslope (18.46 ± 0.75 dB/decade, P < 0.01) and that estimated by C-BRx showed higher Gslope (8.62 ± 0.64 dB/decade, P < 0.001) with significantly lower dynamic gain at 0.01 Hz (6.29 ± 0.48 vs. 2.80 ± 0.36%/Hz, P < 0.001) compared with WKY. In conclusion, the dynamic characteristics of the A-fiber central pathway are enhanced in the high-modulation frequency range (0.1-1 Hz) and those of the C-fiber central pathway are attenuated in the low-modulation frequency range (0.01-0.1 Hz) in SHR.

  11. Differences in the dynamic baroreflex characteristics of unmyelinated and myelinated central pathways are less evident in spontaneously hypertensive rats.

    PubMed

    Turner, Michael J; Kawada, Toru; Shimizu, Shuji; Fukumitsu, Masafumi; Sugimachi, Masaru

    2015-12-01

    The aim of the study was to identify the contribution of myelinated (A-fiber) and unmyelinated (C-fiber) baroreceptor central pathways to the baroreflex control of sympathetic nerve activity (SNA) and arterial pressure (AP) in anesthetized Wistar-Kyoto (WKY; n = 8) and spontaneously hypertensive rats (SHR; n = 8). The left aortic depressor nerve (ADN) was electrically stimulated with two types of binary white noise signals designed to preferentially activate A-fibers (A-BRx protocol) or C-fibers (C-BRx protocol). In WKY, the central arc transfer function from ADN stimulation to SNA estimated by A-BRx showed strong derivative characteristics with the slope of dynamic gain between 0.1 and 1 Hz (Gslope) of 14.63 ± 0.89 dB/decade. In contrast, the central arc transfer function estimated by C-BRx exhibited nonderivative characteristics with Gslope of 0.64 ± 1.13 dB/decade. This indicates that A-fibers are important for rapid baroreflex regulation, whereas C-fibers are likely important for more sustained regulation of SNA and AP. In SHR, the central arc transfer function estimated by A-BRx showed higher Gslope (18.46 ± 0.75 dB/decade, P < 0.01) and that estimated by C-BRx showed higher Gslope (8.62 ± 0.64 dB/decade, P < 0.001) with significantly lower dynamic gain at 0.01 Hz (6.29 ± 0.48 vs. 2.80 ± 0.36%/Hz, P < 0.001) compared with WKY. In conclusion, the dynamic characteristics of the A-fiber central pathway are enhanced in the high-modulation frequency range (0.1-1 Hz) and those of the C-fiber central pathway are attenuated in the low-modulation frequency range (0.01-0.1 Hz) in SHR. PMID:26377561

  12. Prediction of dynamic and mixing characteristics of drop-laden mixing layers using DNS and LES

    NASA Technical Reports Server (NTRS)

    Okong'o, N.; Leboissetier, A.; Bellan, J.

    2004-01-01

    Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) have been conducted of a temporal mixing layer laden with evaporating drops, in order to assess the ability of LES to reproduce dynamic and mixing aspects of the DNS which affect combustion, independently of combustion models.

  13. Sensitivity analysis of permeability parameters for flows on Barcelona networks

    NASA Astrophysics Data System (ADS)

    Rarità, Luigi; D'Apice, Ciro; Piccoli, Benedetto; Helbing, Dirk

    We consider the problem of optimizing vehicular traffic flows on an urban network of Barcelona type, i.e. square network with streets of not equal length. In particular, we describe the effects of variation of permeability parameters, that indicate the amount of flow allowed to enter a junction from incoming roads. On each road, a model suggested by Helbing et al. (2007) [11] is considered: free and congested regimes are distinguished, characterized by an arrival flow and a departure flow, the latter depending on a permeability parameter. Moreover we provide a rigorous derivation of the model from fluid dynamic ones, using recent results of Bretti et al. (2006) [3]. For solving the dynamics at nodes of the network, a Riemann solver maximizing the through flux is used, see Coclite et al. (2005) [4] and Helbing et al. (2007) [11]. The network dynamics gives rise to complicate equations, where the evolution of fluxes at a single node may involve time-delayed terms from all other nodes. Thus we propose an alternative hybrid approach, introducing additional logic variables. Finally we compute the effects of variations on permeability parameters over the hybrid dynamics and test the obtained results via simulations.

  14. Permeability relation for periodic structures.

    PubMed

    Dunn, K J; LaTorraca, G A; Bergman, D J

    1998-01-01

    The permeability relation for periodic porous media is studied with respect to other petrophysical parameters such as formation factor, porosity, surface-to-volume ratio, and nuclear magnetic resonance (NMR) relaxation time. All these quantities were computed for periodic structures of simple, body-centered, and face-centered cubic arrays of touching and overlapping spheres. The formation factors were calculated by using a method which is based on a Fourier-space representation of an integral equation for the electric potential in a two-component composite. The nuclear magnetic resonance relaxation time for the case where surface-enchanced relaxation plays a dominant role is known to be V P/rho S (VP is the pore volume, S is the pore surface, is the surface relaxation strength) when rho is not too large. Previously calculated permeabilities for these structures from the literature were used for correlation studies with other petrophysical parameters. Various correlation schemes among these quantities, such as k = aTbFc, and k = aTb phi c, were investigated, where k is permeability, T is the NMR relaxation time, phi is the porosity, and F is the formation factor. PMID:9803908

  15. Quasi-Static and Dynamic Response Characteristics of F-4 Bias-Ply and Radial-Belted Main Gear Tires

    NASA Technical Reports Server (NTRS)

    Davis, Pamela A.

    1997-01-01

    An investigation was conducted at Langley Research Center to determine the quasi-static and dynamic response characteristics of F-4 military fighter 30x11.5-14.5/26PR bias-ply and radial-belted main gear tires. Tire properties were measured by the application of vertical, lateral, and fore-and-aft loads. Mass moment-of-inertia data were also obtained. The results of the study include quasi-static load-deflection curves, free-vibration time-history plots, energy loss associated with hysteresis, stiffness and damping characteristics, footprint geometry, and inertia properties of each type of tire. The difference between bias-ply and radial-belted tire construction is given, as well as the advantages and disadvantages of each tire design. Three simple damping models representing viscous, structural, and Coulomb friction are presented and compared with the experimental data. The conclusions discussed contain a summary of test observations.

  16. The effects of the pedestal/floor interface on the dynamic characteristics of the storage ring girder support assemblies

    SciTech Connect

    Jendrzejczyk, J.A.; Chen, S.S.; Zhu, S.; Mangra, D.; Smith, R.K.

    1993-05-01

    To avoid unacceptable vibration of the storage ring quadrupoles, and to ensure that the established vibration criteria are satisfied, the philosophy from inception of the APS has been (1) to locate and design the machine to minimize motion of the storage ring basemat and, (2) following construction, to monitor machine operation and user experiments to ensure that vibration sources are not introduced. This report addresses the design of the storage ring girder support assemblies, and, specifically, the effect of the pedestal/floor interface on the dynamic characteristics (i.e., resonant frequencies, damping, and mode shape).

  17. Asymmetric dual-gate-structured one-transistor dynamic random access memory cells for retention characteristics improvement

    NASA Astrophysics Data System (ADS)

    Kim, Hyungjin; Lee, Jong-Ho; Park, Byung-Gook

    2016-08-01

    One of the major concerns of one-transistor dynamic random access memory (1T-DRAM) is poor retention time. In this letter, a 1T-DRAM cell with two separated asymmetric gates was fabricated and evaluated to improve sensing margin and retention characteristics. It was observed that significantly enhanced sensing margin and retention time over 1 s were obtained using a negatively biased second gate and trapped electrons in the nitride layer because of increased hole capacity in the floating body. These findings indicate that the proposed device could serve as a promising candidate for overcoming retention issues of 1T-DRAM cells.

  18. Engine dynamic analysis with general nonlinear finite element codes. Part 2: Bearing element implementation overall numerical characteristics and benchmaking

    NASA Technical Reports Server (NTRS)

    Padovan, J.; Adams, M.; Fertis, J.; Zeid, I.; Lam, P.

    1982-01-01

    Finite element codes are used in modelling rotor-bearing-stator structure common to the turbine industry. Engine dynamic simulation is used by developing strategies which enable the use of available finite element codes. benchmarking the elements developed are benchmarked by incorporation into a general purpose code (ADINA); the numerical characteristics of finite element type rotor-bearing-stator simulations are evaluated through the use of various types of explicit/implicit numerical integration operators. Improving the overall numerical efficiency of the procedure is improved.

  19. Adolescents with Disabilities in High School Setting: Student Characteristics and Setting Dynamics

    ERIC Educational Resources Information Center

    Deshler, Donald D.; Lenz, B. Keith; Bulgren, Janis; Schumaker, Jean B.; Davis, Betsy; Grossen, Bonnie; Marquis, Janet

    2004-01-01

    The purpose of this investigation was two-fold: (1) to gather descriptive information in the areas of salient student characteristics, level of participation in general education classes, current level of functioning, and student outcomes (e.g., GPAs, performance on state or national exams) for students with disabilities (SWDs) in high school…

  20. A Large Block Experiment for Measurement of the Effective Permeability of Indiana Limestone

    NASA Astrophysics Data System (ADS)

    Selvadurai, P. A.; Selvadurai, A. P.

    2009-12-01

    The measurement of permeability of large specimens of a rock specimen is bound to provide a clearer picture of the distribution of permeability of predominantly sedimentary rocks. Such distributions can be the basis for evaluating the effective permeability of the rock specimen in the presence of permeability inhomogeneity. This paper discusses the development of a patch permeability test that can be used to measure the near surface permeability characteristics of a large cuboidal block of Indiana Limestone measuring 508 mm. The test is used to generate the near surface permeability of six faces of the cuboid and these estimates are used to generate, via a kriging procedure, the interior permeability distributions of permeability. These permeability distributions are used to examine the validity of theoretical estimates that have been developed in the literature to determine the effective permeability of the material. The classical Wiener (1912) bounds, the estimates provided by Matheron (1967) and Journel et al. (1993) are developed using the experimentally derived data. The procedure is also validated by conducting computational experiments involving one-dimensional flow along three orthogonal directions. References: Wiener, O. (1912) Die Theorie des Mischkörpers für das Feld des stationaären Strömung. Erste Abhandlung die Mittelswertesätsze für Kraft, Polarisation und Energie. Abh. Math.-Physischen Klasse Königl. Säcsh Gesell. Wissen, 32: 509-604. Matheron, G. (1967) Eléments pour une Théorie des Milieux Poroeux, Masson, Paris. Journel, A.G, Deutsch, C.V. and Desbrats, A.J. (1986) Power averaging for block effective permeability, SPE 15128, Society of Petroleum Engineers.

  1. Dynamic modelling and response characteristics of a magnetic bearing rotor system with auxiliary bearings

    NASA Technical Reports Server (NTRS)

    Free, April M.; Flowers, George T.; Trent, Victor S.

    1995-01-01

    Auxiliary bearings are a critical feature of any magnetic bearing system. They protect the soft iron core of the magnetic bearing during an overload or failure. An auxiliary bearing typically consists of a rolling element bearing or bushing with a clearance gap between the rotor and the inner race of the support. The dynamics of such systems can be quite complex. It is desired to develop a rotordynamic model which describes the dynamic behavior of a flexible rotor system with magnetic bearings including auxiliary bearings. The model is based upon an experimental test facility. Some simulation studies are presented to illustrate the behavior of the model. In particular, the effects of introducing sideloading from the magnetic bearing when one coil fails is studied.

  2. On the characteristics of aerosol indirect effect based on dynamic regimes in global climate models

    DOE PAGES

    Zhang, Shipeng; Wang, Minghuai; Ghan, Steven J.; Ding, Aijun; Wang, Hailong; Zhang, Kai; Neubauer, David; Lohmann, Ulrike; Ferrachat, Sylvaine; Takeamura, Toshihiko; et al

    2016-03-04

    Aerosol–cloud interactions continue to constitute a major source of uncertainty for the estimate of climate radiative forcing. The variation of aerosol indirect effects (AIE) in climate models is investigated across different dynamical regimes, determined by monthly mean 500 hPa vertical pressure velocity (ω500), lower-tropospheric stability (LTS) and large-scale surface precipitation rate derived from several global climate models (GCMs), with a focus on liquid water path (LWP) response to cloud condensation nuclei (CCN) concentrations. The LWP sensitivity to aerosol perturbation within dynamic regimes is found to exhibit a large spread among these GCMs. It is in regimes of strong large-scale ascentmore » (ω500  <  −25 hPa day−1) and low clouds (stratocumulus and trade wind cumulus) where the models differ most. Shortwave aerosol indirect forcing is also found to differ significantly among different regimes. Shortwave aerosol indirect forcing in ascending regimes is close to that in subsidence regimes, which indicates that regimes with strong large-scale ascent are as important as stratocumulus regimes in studying AIE. It is further shown that shortwave aerosol indirect forcing over regions with high monthly large-scale surface precipitation rate (> 0.1 mm day−1) contributes the most to the total aerosol indirect forcing (from 64 to nearly 100 %). Results show that the uncertainty in AIE is even larger within specific dynamical regimes compared to the uncertainty in its global mean values, pointing to the need to reduce the uncertainty in AIE in different dynamical regimes.« less

  3. Efficient assembly of finite-element subsystems with large relative rotations. [for rotorcraft dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Fuh, Jon-Shen; Panda, Brahmananda; Peters, David A.

    1988-01-01

    A finite element approach is presented for the modeling of rotorcraft undergoing elastic deformation in addition to large rigid body motion with respect to inertial space, with particular attention given to the coupling of the rotor and fuselage subsystems subject to large relative rotations. The component synthesis technique used here allows the coupling of rotors to the fuselage for different rotorcraft configurations. The formulation is general and applicable to any rotorcraft vibration, aeroelasticity, and dynamics problem.

  4. Risk and experience: effects of experiential learning and patient characteristics in interpretation of dynamic risk graphics.

    PubMed

    Ancker, Jessica S; Senathirajah, Yalini; Weber, Elke U; Kukafka, Rita

    2006-01-01

    Risks can be explained to patients in narratives, numbers, or graphs. All these methods depend upon description. However, decisions from description differ systematically from decisions about risks that are experienced through activities such as drawing cards from a deck. We have developed a dynamic graphic interface that provides a virtual experience of event probabilities, with potential applications in patient education and decision support. PMID:17238464

  5. Influence on disease spread dynamics of herd characteristics in a structured livestock industry.

    PubMed

    Lindström, Tom; Lewerin, Susanna Sternberg; Wennergren, Uno

    2012-06-01

    Studies of between-herd contacts may provide important insight to disease transmission dynamics. By comparing the result from models with different levels of detail in the description of animal movement, we studied how factors influence the final epidemic size as well as the dynamic behaviour of an outbreak. We investigated the effect of contact heterogeneity of pig herds in Sweden due to herd size, between-herd distance and production type. Our comparative study suggests that the production-type structure is the most influential factor. Hence, our results imply that production type is the most important factor to obtain valid data for and include when modelling and analysing this system. The study also revealed that all included factors reduce the final epidemic size and also have yet more diverse effects on initial rate of disease spread. This implies that a large set of factors ought to be included to assess relevant predictions when modelling disease spread between herds. Furthermore, our results show that a more detailed model changes predictions regarding the variability in the outbreak dynamics and conclude that this is an important factor to consider in risk assessment.

  6. Effects of kerosene heating on dynamic characteristics of GOx/kerosene combustor

    NASA Astrophysics Data System (ADS)

    Song, Wooseok; Kim, Dohun; Lee, Keonwoong; Shin, Bongchul; Ko, Sangho; Koo, Jaye

    2016-09-01

    The objective of this study was to observe low-frequency instabilities caused by heating of kerosene under supercritical operating conditions. Gaseous oxygen and liquid kerosene were injected using a shear-coaxial injector. Under specific heating conditions, the fuel heating system induced an extremely low frequency pressure fluctuation ranging from 9.9 to 11.4 Hz. When pressure oscillation occurred in the heating system, low-frequency combustion instability was subsequently induced in the range of 30-200 Hz. To understand the effects of the fuel heating temperature on the combustion instability, the dynamic pressure and OH* chemiluminescence intensity were measured in a combustion chamber at high speed. Further, the reacting spray of the combustion was visualized by a shadowgraph technique. In this experiment, an approximate fuel pressure of 3.0 MPa was employed in order to attain a supercritical condition of kerosene. The measured dynamic pressure and chemiluminescence intensity in the time domain were converted to frequency-domain spectra by fast Fourier transform. Analysis of the dynamic pressure and chemiluminescence intensity measurements confirmed that the low-frequency pressure oscillation in the heating system had an influence on the combustion instability. From the visualization data, it was also revealed that there existed varying amplitude levels of flow rate fluctuation. This fluctuation in turn caused a periodic injection of kerosene at a frequency similar to both the combustion instability frequency and the OH* chemiluminescence intensity frequency.

  7. Experimental study on the dynamic characteristics of kW-scale molten carbonate fuel cell systems

    NASA Astrophysics Data System (ADS)

    Kang, Byoung Sam; Koh, Joon-Ho; Lim, Hee Chun

    The aim of this work is to develop dynamic models for two types of kW-scale molten carbonate fuel cell (MCFC) systems on the basis of experimental data. The dynamic models are represented as a 3×3 transfer function matrix for a multi-input and multi-output (MIMO) system with three inputs and three outputs. The three controlled variables which severely affect the stack performance and lifetime are the temperature difference in the stack and the pressure drop at the anode and the cathode. Three manipulated variables, namely, current load, fuel and oxidant utilization, are selected to keep the three controlled variables within their safety limits for the reliable operation and protection of the system in case of emergency. Each element in the transfer function matrix is in the form of a first-order model using a simple, unit step, response test during operation. The non-zero off-diagonal elements in the transfer function matrix show that some interactions exist among the operating variables, and two zeros show no interaction between fuel and oxidant flow without gas cross-over. The stability of both dynamic models is analyzed using the relative gain array (RGA) method. Large diagonal elements in the RGA matrix show that the pairing between the manipulated and controlled variables is appropriate. Proper pairing is also proven by the singular value analysis (SVA) method with a smaller singular value in each system.

  8. Comparison of Dynamic Characteristics for an Inflatable Solar Concentrator in Atmospheric and Thermal Vacuum Conditions

    NASA Technical Reports Server (NTRS)

    Slade, Kara N.; Tinker, Michael L.; Lassiter, John O.; Engberg, Robert

    2000-01-01

    Dynamic testing of an inflatable solar concentrator structure in a thermal vacuum chamber as well as in ambient laboratory conditions is described in detail. Unique aspects of modal testing for the extremely lightweight inflatable are identified, including the use of a noncontacting laser vibrometer measurement system. For the thermal vacuum environment, mode shapes and frequency response functions are compared for three different test article inflation pressures at room temperature. Modes that persist through all the inflation pressure regimes are identified, as well as modes that are unique for each pressure. In atmospheric pressure and room temperature conditions, dynamic measurements were obtained for the expected operational inflation pressure of 0.5 psig. Experimental mode shapes and frequency response functions for ambient conditions are described and compared to the 0.5 psig results from the thermal vacuum tests. Only a few mode shapes were identified that occurred in both vacuum and atmospheric environments. This somewhat surprising result is discussed in detail, and attributed at least partly to 1.) large differences in modal damping, and 2.) significant differences in the mass of air contained by the structure, in the two environments. Results of this investigation point out the necessity of testing inflatable space structures in vacuum conditions before they can be launched. Ground testing in atmospheric pressure is not sufficient for predicting on-orbit dynamics of non-rigidized inflatable systems.

  9. Reservoir condition special core analyses and relative permeability measurements on Almond formation and Fontainebleu sandstone rocks

    SciTech Connect

    Maloney, D.

    1993-11-01

    This report describes the results from special core analyses and relative permeability measurements conducted on Almond formation and Fontainebleu sandstone plugs. Almond formation plug tests were performed to evaluate multiphase, steady-state,reservoir-condition relative permeability measurement techniques and to examine the effect of temperature on relative permeability characteristics. Some conclusions from this project are as follows: An increase in temperature appeared to cause an increase in brine relative permeability results for an Almond formation plug compared to room temperature results. The plug was tested using steady-state oil/brine methods. The oil was a low-viscosity, isoparaffinic refined oil. Fontainebleu sandstone rock and fluid flow characteristics were measured and are reported. Most of the relative permeability versus saturation results could be represented by one of two trends -- either a k{sub rx} versus S{sub x} or k{sub rx} versus Sy trend where x and y are fluid phases (gas, oil, or brine). An oil/surfactant-brine steady-state relative permeability test was performed to examine changes in oil/brine relative permeability characteristics from changes in fluid IFTS. It appeared that, while low interfacial tension increased the aqueous phase relative permeability, it had no effect on the oil relative permeability. The BOAST simulator was modified for coreflood simulation. The simulator was useful for examining effects of variations in relative permeability and capillary pressure functions. Coreflood production monitoring and separator interface level measurement techniques were developed using X-ray absorption, weight methods, and RF admittance technologies. The three types of separators should be useful for routine and specialized core analysis applications.

  10. Ocular Albumin Fluorophotometric Quantitation of Endotoxin-Induced Vascular Permeability

    PubMed Central

    Cousins, Scott W.; Rosenbaum, James T.; Guss, Robert B.; Egbert, Peter R.

    1982-01-01

    Bacterial endotoxin (lipopolysaccharide; LPS) is known to alter systemic vascular permeability, but this effect is difficult to monitor and quantitate in vivo. The ocular vessels of the rabbit are particularly sensitive to LPS. Using a slit lamp equipped with a fluorophotometer, we have adapted a method to quantitate endotoxin-induced ocular vascular permeability by measuring the accumulation of fluorescein isothiocyanate-conjugated albumin into the anterior chamber of the eye. After intravenous administration of Salmonella typhimurim LPS, the anterior chamber fluorescence and blood fluorescence were measured at intervals of 15 min and 1 h, respectively, over 4 h. In controls, maximal fluorescence in the anterior chamber was 3.1 ± 0.8% of blood fluorescence. Doses of LPS as low as 0.25 μg/kg produced an ocular/serum fluorescence ratio of 17.6 ± 4.9. A dose of 2.5 μg of LPS per kg tended to produce a higher ratio (68.0 ± 7.1) than a larger dose of 50 μg/kg (30.5 ± 16.6). Permeability changes began within 30 min after LPS, and the rate of dye accumulation varied over time, with maximal leakage usually occurring 90 min after LPS, but occasionally occurring much later. Repeated doses produced tolerance. By conjugating albumin to rhodamine and utilizing a second filter with the slit lamp to measure accumulation of this dye, we demonstrated the persistence of marked permeability during a period when intraocular fluorescein isothiocyanate and albumin levels were relatively constant. This methodology indicates that extremely low doses of LPS induce ocular permeability changes and that neither the time course nor the dose response of this effect is linear. Ocular fluorophotometry is a sensitive, noninvasive technique to study the dynamics and pharmacology of LPS-induced permeability changes. PMID:6806194

  11. [Investigation of dynamic spectral characteristics of water in blood plasma hydrosols from breast cancer patients].

    PubMed

    Anichkov, N M; Manikhas, A G; Rozin, I T; Khaloimov, A I

    2006-01-01

    Our data on spectral characteristics of water in blood plasma hydrosols from breast cancer patients and healthy subjects are presented. A substantial difference between the two groups was found. As it was shown by us earlier, in breast cancer patients, as well as in other cancer patients, changes in spectral characteristics of water influence tissue hydrosols of the whole body. They persist even after tumor is radically removed. Such differences were probably linked to those in water molecular resonance frequencies. Using infrared spectroscopy, we confirmed the evidence available on carcinogenic (promoting) effect of both native and synthetic estrogens. It is suggested that healthy adult women have a certain "frequency immunity" which protects from the monthly autogenous promoting influences of estrogens. Our findings may contribute to devising further therapeutic frequency-assisted means of impacting on malignant tissue hydrosols.

  12. Effect of non-Newtonian viscosity on the fluid-dynamic characteristics in stenotic vessels

    NASA Astrophysics Data System (ADS)

    Huh, Hyung Kyu; Ha, Hojin; Lee, Sang Joon

    2015-08-01

    Although blood is known to have shear-thinning and viscoelastic properties, the effects of such properties on the hemodynamic characteristics in various vascular environments are not fully understood yet. For a quantitative hemodynamic analysis, the refractive index of a transparent blood analogue needs to be matched with that of the flowing conduit in order to minimize the errors according to the distortion of the light. In this study, three refractive index-matched blood analogue fluids with different viscosities are prepared—one Newtonian and two non-Newtonian analogues—which correspond to healthy blood with 45 % hematocrit (i.e., normal non-Newtonian) and obese blood with higher viscosity (i.e., abnormal non-Newtonian). The effects of the non-Newtonian rheological properties of the blood analogues on the hemodynamic characteristics in the post-stenosis region of an axisymmetric stenosis model are experimentally investigated using particle image velocimetry velocity field measurement technique and pathline flow visualization. As a result, the centerline jet flow from the stenosis apex is suppressed by the shear-thinning feature of the blood analogues when the Reynolds number is smaller than 500. The lengths of the recirculation zone for abnormal and normal non-Newtonian blood analogues are 3.67 and 1.72 times shorter than that for the Newtonian analogue at Reynolds numbers smaller than 200. The Reynolds number of the transition from laminar to turbulent flow for all blood analogues increases as the shear-thinning feature increases, and the maximum wall shear stresses in non-Newtonian fluids are five times greater than those in Newtonian fluids. However, the shear-thinning effect on the hemodynamic characteristics is not significant at Reynolds numbers higher than 1000. The findings of this study on refractive index-matched non-Newtonian blood analogues can be utilized in other in vitro experiments, where non-Newtonian features dominantly affect the flow

  13. Characteristics of Sucrose Transport through the Sucrose-Specific Porin ScrY Studied by Molecular Dynamics Simulations

    PubMed Central

    Sun, Liping; Bertelshofer, Franziska; Greiner, Günther; Böckmann, Rainer A.

    2016-01-01

    Sucrose-specific porin (ScrY) is a transmembrane protein that allows for the uptake of sucrose under growth-limiting conditions. The crystal structure of ScrY was resolved before by X-ray crystallography, both in its uncomplexed form and with bound sucrose. However, little is known about the molecular characteristics of the transport mechanism of ScrY. To date, there has not yet been any clear demonstration for sucrose transport through the ScrY. Here, the dynamics of the ScrY trimer embedded in a phospholipid bilayer as well as the characteristics of sucrose translocation were investigated by means of atomistic molecular dynamics (MD) simulations. The potential of mean force (PMF) for sucrose translocation through the pore showed two main energy barriers within the constriction region of ScrY. Energy decomposition allowed to pinpoint three aspartic acids as key residues opposing the passage of sucrose, all located within the L3 loop. Mutation of two aspartic acids to uncharged residues resulted in an accordingly modified electrostatics and decreased PMF barrier. The chosen methodology and results will aid in the design of porins with modified transport specificities. PMID:26913282

  14. Optimized balance rehabilitation training strategy for the elderly through an evaluation of balance characteristics in response to dynamic motions

    PubMed Central

    Jung, HoHyun; Chun, Keyoung Jin; Hong, Jaesoo; Lim, Dohyung

    2015-01-01

    Balance is important in daily activities and essential for maintaining an independent lifestyle in the elderly. Recent studies have shown that balance rehabilitation training can improve the balance ability of the elderly, and diverse balance rehabilitation training equipment has been developed. However, there has been little research into optimized strategies for balance rehabilitation training. To provide an optimized strategy, we analyzed the balance characteristics of participants in response to the rotation of a base plate on multiple axes. Seven male adults with no musculoskeletal or nervous system-related diseases (age: 25.5±1.7 years; height: 173.9±6.4 cm; body mass: 71.3±6.5 kg; body mass index: 23.6±2.4 kg/m2) were selected to investigate the balance rehabilitation training using customized rehabilitation equipment. Rotation of the base plate of the equipment was controlled to induce dynamic rotation of participants in the anterior–posterior, right-diagonal, medial–lateral, and left-diagonal directions. We used a three-dimensional motion capture system employing infrared cameras and the Pedar Flexible Insoles System to characterize the major lower-extremity joint angles, center of body mass, and center of pressure. We found statistically significant differences between the changes in joint angles in the lower extremities in response to dynamic rotation of the participants (P<0.05). The maximum was greater with anterior–posterior and medial–lateral dynamic rotation than with that in other directions (P<0.05). However, there were no statistically significant differences in the frequency of center of body mass deviations from the base of support (P>0.05). These results indicate that optimizing rotation control of the base plate of balance rehabilitation training equipment to induce anterior–posterior and medial–lateral dynamic rotation preferentially can lead to effective balance training. Additional tests with varied speeds and ranges of

  15. Non-linear characteristics in the dynamic responses of seated subjects exposed to vertical whole-body vibration.

    PubMed

    Matsumoto, Yasunao; Griffin, Michael J

    2002-10-01

    The effect of the magnitude of vertical vibration on the dynamic response of the seated human body has been investigated. Eight male subjects were exposed to random vibration in the 0.5 to 20 Hz frequency range at five magnitudes: 0.125, 0.25, 0.5, 1.0 and 2.0 ms(-2) r.m.s. The dynamic responses of the body were measured at eight locations: at the first, fifth, and tenth thoracic vertebrae (T1, T5, T10), at the first, third, and fifth lumbar vertebrae (L1, L3, L5) and at the pelvis (the posterior-superior iliac spine). At each location, the motions on the body surface were measured in the three orthogonal axes within the sagittal plane (i.e., the vertical, fore-and-aft, and pitch axes). The force at the seat surface was also measured. Frequency response functions (i.e., transmissibilities and apparent mass) were used to represent the responses of the body. Non-linear characteristics were observed in the apparent mass and in the transmissibilities to most measurement locations. Resonance frequencies in the frequency response functions decreased with increases in the vibration magnitude (e.g. for the vertical transmissibility to L3, a reduction from 6.25 to 4.75 Hz when the vibration magnitude increased from 0.125 to 2.0 ms(-2) r.m.s.). The transmission of vibration within the spine also showed some evidence of a non-linear characteristic. It can be concluded from this study that the dynamic responses of seated subjects are clearly non-linear with respect to vibration magnitude, whereas previous studies have reported inconsistent conclusions. More understanding of the dependence on vibration magnitude of both the dynamic responses of the soft tissues of the body and the muscle activity (voluntary and involuntary) is required to identify the causes of the non-linear characteristics observed in this study.

  16. Optimized balance rehabilitation training strategy for the elderly through an evaluation of balance characteristics in response to dynamic motions.

    PubMed

    Jung, HoHyun; Chun, Keyoung Jin; Hong, Jaesoo; Lim, Dohyung

    2015-01-01

    Balance is important in daily activities and essential for maintaining an independent lifestyle in the elderly. Recent studies have shown that balance rehabilitation training can improve the balance ability of the elderly, and diverse balance rehabilitation training equipment has been developed. However, there has been little research into optimized strategies for balance rehabilitation training. To provide an optimized strategy, we analyzed the balance characteristics of participants in response to the rotation of a base plate on multiple axes. Seven male adults with no musculoskeletal or nervous system-related diseases (age: 25.5±1.7 years; height: 173.9±6.4 cm; body mass: 71.3±6.5 kg; body mass index: 23.6±2.4 kg/m(2)) were selected to investigate the balance rehabilitation training using customized rehabilitation equipment. Rotation of the base plate of the equipment was controlled to induce dynamic rotation of participants in the anterior-posterior, right-diagonal, medial-lateral, and left-diagonal directions. We used a three-dimensional motion capture system employing infrared cameras and the Pedar Flexible Insoles System to characterize the major lower-extremity joint angles, center of body mass, and center of pressure. We found statistically significant differences between the changes in joint angles in the lower extremities in response to dynamic rotation of the participants (P<0.05). The maximum was greater with anterior-posterior and medial-lateral dynamic rotation than with that in other directions (P<0.05). However, there were no statistically significant differences in the frequency of center of body mass deviations from the base of support (P>0.05). These results indicate that optimizing rotation control of the base plate of balance rehabilitation training equipment to induce anterior-posterior and medial-lateral dynamic rotation preferentially can lead to effective balance training. Additional tests with varied speeds and ranges of angles of

  17. Channel Characteristics and Planform Dynamics in the Indian Terai, Sharda River

    NASA Astrophysics Data System (ADS)

    Midha, Neha; Mathur, Pradeep K.

    2014-01-01

    The Sharda River creates and maintains the ecologically diverse remnant patches of rare Terai ecosystem in northern India. This study used repeat satellite imagery and geographic information system analysis to assess the planform dynamics along a 60 km length of the Sharda River between 1977 and 2001 to understand the altered dynamics and its plausible causes in this data-poor region. Analyses revealed that the Sharda River has undergone significant change corresponding to enhanced instability in terms of increased number of neck cut-offs and consistent occurrence of avulsions in subsequent shorter assessment periods. An increased channel area (8 %), decreased sinuosity (15 %), increased braiding intensity, and abrupt migrations were also documented. The river has migrated toward the east with its west bankline being more unstable. The maximum shifts were 2.85 km in 13 years (1977-1990), 2.33 km in next 9 years (1990-1999), and a substantial shift of 2.39 km in just 2 years (1999-2001). The altered dynamics is making the future of critical wildlife habitats in Kishanpur Wildlife Sanctuary and North Kheri Forest Division precarious and causing significant economic damage. Extensive deforestation and expansion of agriculture since the 1950s in the catchment area are presumed to have severely impacted the equilibrium of the river, which urgently needs a management plan including wildlife habitat conservation, control, and risk reduction. The present study provides a strong foundation for understanding channel changes in the Sharda River and the finding can serve as a valuable information base for effective management planning and ecological restoration.

  18. Permeability mapping in porous media by magnetization prepared centric-scan SPRITE

    NASA Astrophysics Data System (ADS)

    Romanenko, Konstantin V.; Balcom, Bruce J.

    2011-02-01

    The ability of porous media to transmit fluids is commonly referred to as permeability. The concept of permeability is central for hydrocarbon recovery from petroleum reservoirs and for studies of groundwater flow in aquifers. Spatially resolved measurements of permeability are of great significance for fluid dynamics studies. A convenient concept of local Darcy's law is suggested for parallel flow systems. The product of porosity and mean velocity images in the plane across the average flow direction is directly proportional to permeability. Single Point Ramped Imaging with T 1 Enhancement (SPRITE) permits reliable quantification of local fluid content and flow in porous media. It is particularly advantageous for reservoir rocks characterized by fast magnetic relaxation of a saturating fluid. Velocity encoding using the Cotts pulsed field gradient scheme improves the accuracy of measured flow parameters. The method is illustrated through measurements of 2D permeability maps in a capillary bundle, glass bead packs and composite sandstone samples.

  19. Permeability Evolution of Shale and Coal Under Differential Sorption of He, CH4 And CO2

    NASA Astrophysics Data System (ADS)

    Kumar, H.; Elsworth, D.; Marone, C. J.; Mathews, J.

    2010-12-01

    Carbon dioxide injection in coal seams or in shales may be an option for geological sequestration of CO2 each with concurrent methane production. Permeability of the fractured porous medium is a crucial parameter influencing injectivity of CO2. The evolution of permeability is further complicated by dynamic changes in the coal/shale shrinkage/swelling with the reduction/increase in gas content. Complex geomechanical processes (transport of gas, adsorption, desorption, adjusting horizontal stresses and vertical strains) and chemical interaction between CO2, water and mineral matter content are some factors responsible for the various responses in permeability evolution. Adsorption of CO2 in micropores may result in matrix swelling therefore closing the existing natural fractures and lowering the ability of fluid flow. On the other hand presence of water may react with CO2 forming carbonic acid and removing carbonaceous mineral matter - either increasing or decreasing permeability. To address these issues we report experimental measurements of permeability evolution in shales infiltrated by helium, methane and carbon dioxide under varying pore pressure and deviatoric stresses. The role of gas (CO2 and CH4) adsorption and desorption under variable moisture contents and pore pressures have also been examined for sub-bituminous coals. Adsorption of CO2 in Coal and shale reduces the reservoir permeability even when the fractured media are mechanically unconstrained. However we found that permeability loss is temporary. In the specific case of Marcellus shale, adsorption of CO2 in the sample reduces the permeability to half the original value. Permeability values returns to its original value if sample is allowed to interact for sufficient time. Variation of permeability with deviotoric stress suggests the compaction band formation above a threshold value of stress. These deformations are permanent and shale loses its permeability. Several observations on permeability

  20. Dynamic switching characteristics of InGaAsP/InP multimode interference optical waveguide switch.

    PubMed

    Tomofuji, Shinji; Matsuo, Shinji; Kakitsuka, Takaaki; Kitayama, Ken-ichi

    2009-12-21

    Multimode interference (MMI) waveguide switches show promise for switch in optical packet switching (OPS). In this work, we fabricated 1 x 4 InGaAsP/InP MMI waveguide switch device which consists of a 1 x 4 MMI splitter, 4 equally spaced single-mode waveguides with phase shifters, and a 4 x 4 MMI combiner. Good crosstalk and extinction ratio of -14.47 dB and 23.39 dB, respectively, are obtained. In addition, we experimentally demonstrate dynamic switching, and the rise and fall time of 1.4 ns and 1.2 ns, respectively, are obtained.

  1. Characteristics of a dynamic holographic sensor for shape control of a large reflector

    NASA Technical Reports Server (NTRS)

    Welch, Sharon S.; Cox, David E.

    1991-01-01

    Design of a distributed holographic interferometric sensor for measuring the surface displacement of a large segmented reflector is proposed. The reflector's surface is illuminated by laser light of two wavelengths and volume holographic gratings are formed in photorefractive crystals of the wavefront returned from the surface. The sensor is based on holographic contouring with a multiple frequency source. It is shown that the most stringent requirement of temporal stability affects both the temporal resolution and the dynamic range. Principal factor which limit the sensor performance include the response time of photorefractive crystal, laser power required to write a hologram, and the size of photorefractive crystal.

  2. Effect of dynamic and thermal prehistory on aerodynamic characteristics and heat transfer behind a sudden expansion in a round tube

    NASA Astrophysics Data System (ADS)

    Terekhov, V. I.; Bogatko, T. V.

    2016-06-01

    The results of a numerical study of the influence of the thicknesses of dynamic and thermal boundary layers on turbulent separation and heat transfer in a tube with sudden expansion are presented. The first part of this work studies the influence of the thickness of the dynamic boundary layer, which was varied by changing the length of the stabilization area within the maximal extent possible: from zero to half of the tube diameter. In the second part of the study, the flow before separation was hydrodynamically stabilized and the thermal layer before the expansion could simultaneously change its thickness from 0 to D1/2. The Reynolds number was varied in the range of {Re}_{{{{D}}1 }} = 6.7 \\cdot 103 {{to}} 1.33 \\cdot 105 , and the degree of tube expansion remained constant at ER = (D 2/D 1)2 = 1.78. A significant effect of the thickness of the separated boundary layer on both dynamic and thermal characteristics of the flow is shown. In particular, it was found out that with an increase in the thickness of the boundary layer the recirculation zone increases and the maximal Nusselt number decreases. It was determined that the growth of the heat layer thickness does not affect the hydrodynamic characteristics of the flow after separation but does lead to a reduction of heat transfer intensity in the separation area and removal of the coordinates of maximal heat transfer from the point of tube expansion. The generalizing dependence for the maximal Nusselt number at various thermal layer thicknesses is given. Comparison with experimental data confirmed the main trends in the behavior of heat and mass transfer processes in separated flows behind a step with different thermal prehistories.

  3. Non-linear dynamic characteristics and optimal control of giant magnetostrictive film subjected to in-plane stochastic excitation

    SciTech Connect

    Zhu, Z. W.; Zhang, W. D. Xu, J.

    2014-03-15

    The non-linear dynamic characteristics and optimal control of a giant magnetostrictive film (GMF) subjected to in-plane stochastic excitation were studied. Non-linear differential items were introduced to interpret the hysteretic phenomena of the GMF, and the non-linear dynamic model of the GMF subjected to in-plane stochastic excitation was developed. The stochastic stability was analysed, and the probability density function was obtained. The condition of stochastic Hopf bifurcation and noise-induced chaotic response were determined, and the fractal boundary of the system's safe basin was provided. The reliability function was solved from the backward Kolmogorov equation, and an optimal control strategy was proposed in the stochastic dynamic programming method. Numerical simulation shows that the system stability varies with the parameters, and stochastic Hopf bifurcation and chaos appear in the process; the area of the safe basin decreases when the noise intensifies, and the boundary of the safe basin becomes fractal; the system reliability improved through stochastic optimal control. Finally, the theoretical and numerical results were proved by experiments. The results are helpful in the engineering applications of GMF.

  4. [Influence of Medication on the Oscillatory and Dynamic Characteristics of Subthalamic Local Field Potentials in Patients with Parkinson's Disease].

    PubMed

    Wang, Yanan; Geng, Xinyi; Huang, Yongzhi; Wang, Shouyan

    2016-02-01

    The dysfunction of subthalamic nucleus is the main cause of Parkinson's disease. Local field potentials in human subthalamic nucleus contain rich physiological information. The present study aimed to quantify the oscillatory and dynamic characteristics of local field potentials of subthalamic nucleus, and their modulation by the medication therapy for Parkinson's disease. The subthalamic nucleus local field potentials were recorded from patients with Parkinson's disease at the states of on and off medication. The oscillatory features were characterised with the power spectral analysis. Furthermore, the dynamic features were characterised with time-frequency analysis and the coefficient of variation measure of the time-variant power at each frequency. There was a dominant peak at low beta-band with medication off. The medication significantly suppressed the low beta component and increased the theta component. The amplitude fluctuation of neural oscillations was measured by the coefficient of variation. The coefficient of variation in 4-7 Hz and 60-66 Hz was increased by medication. These effects proved that medication had significant modulation to subthalamic nucleus neural oscillatory synchronization and dynamic features. The subthalamic nucleus neural activities tend towards stable state under medication. The findings would provide quantitative biomarkers for studying the mechanisms of Parkinson's disease and clinical treatments of medication or deep brain stimulation. PMID:27382739

  5. Permittivity and permeability of semi-infinite metamaterial

    NASA Astrophysics Data System (ADS)

    Porvatkina, O. V.; Tishchenko, A. A.; Strikhanov, M. N.

    2016-08-01

    In our work we investigate dielectric and magnetic properties of semi-infinite metamaterial consisting of particles of different possible nature: atoms, molecules, nanoparticles, etc. It is important that these particles would have magnetic properties. Polarization of a near-surface layer is known to differ from its bulk value for non-magnetic materials; for magnetic materials, including metamaterials, the situation should be similar, which is the subject of our research. We obtain analogues of the Clausius-Mossotti relation both for permittivity and permeability taking into account the local field effects in the longwave approximation for semi-infinite metamaterial. These relations describe the connection between macroscopic characteristics of the semi-infinite metamaterial (permittivity and permeability) and characteristics of constituent particles (dielectric polarizability and magnetic polarizability), which is a bright example of multi-scale approach - method very popular today in physical and computer simulating.

  6. Hormonal regulation of hepatocyte tight junctional permeability

    SciTech Connect

    Lowe, P.J.; Miyai, K.; Steinbach, J.H.; Hardison, W.G.M. Univ. of California, San Diego )

    1988-10-01

    The authors have investigated the effects of hormones on the permeability of the hepatocyte tight junction to two probes, ({sup 14}C)sucrose and horseradish peroxidase, using one-pass perfused rat livers. Using a single injection of horseradish peroxidase the authors have demonstrated that this probe can enter bile by two pathways that are kinetically distinct, a fast pathway, which corresponds to the passage of the probe through the hepatocyte tight junctions, and a slow pathway, which corresponds to the transcytotic entry into bile. The passage of horseradish peroxidase through the hepatocyte tight junctions was confirmed by electron microscopic histochemistry. Vasopressin, epinephrine, and angiotensin II, hormones that act in the hepatocyte through the intracellular mediators calcium, the inositol polyphosphates, and diacylglycerol, increased the bile-to-perfusion fluid ratio of ({sup 14}C)sucrose and the rapid entry of horseradish peroxidase into bile, indicating that the permeability of the tight junctions to these probes was increased. The effect of these hormones was dose dependent and in the cases of angiotensin II and epinephrine was inhibited by the specific inhibitors (Sar{sup 1},Thr{sup 8})angiotensin II and prazosin, respectively. Dibutyryl adenosine 3{prime},5{prime}-cyclic monophosphate did not affect the ({sup 14}C)sucrose bile-to-perfusion fluid ratio or the fast entry of horseradish peroxidase into bile. These results suggest that the hepatocyte tight junction can no longer be considered a static system of pores separating blood from bile. It is rather a dynamic barrier potentially capable of influencing the composition of the bile.

  7. Turbulent Hyporheic Exchange in Permeable Sediments

    NASA Astrophysics Data System (ADS)

    Roche, K. R.; Aubeneau, A. F.; Li, A.; Packman, A. I.

    2015-12-01

    Solute delivery from the water column into a streambed strongly influences metabolism in rivers. Current hydrological models simplify surface-subsurface (hyporheic) exchange by treating each domain separately, constraining turbulent flows to the water column. Studies have shown, however, that turbulence penetrates into permeable sediments. Evidence is lacking for how this highly coupled flow regime influences hyporheic exchange. We characterized the dynamics of turbulent exchange between surface and porewaters in a 2.5 m recirculating flume. The channel was packed with 3.8 cm PVC spheres to form a coarse gravel bed, with a total depth of 21 cm. We implanted microsensors onto an array of spheres to measure in situsalt concentrations within the streambed. Water was recirculated in the channel, and concentrated salt solution was continuously injected upstream of the sensor array. We observed solute exchange increased with free-stream Reynolds number and decreased with depth in the sediment bed. Mass of injected solute remaining in the bed decreased rapidly in all cases, with only 10-30% of mass recovered 50 cm downstream of the injection point at Re = 25,000. We observed high-frequency (1-10 Hz) concentration fluctuations at bed depths of at least 4.75 cm, and sporadic low-frequency fluctuations at depths of 12.5 cm. Spectral analysis revealed increased filtering of high frequencies with depth. We used particle-tracking simulations to fit depth-dependent turbulent diffusion profiles to experimental results. These results demonstrate that free-stream turbulence impacts hyporheic mixing deep into permeable streambeds, and mixing is strongly influenced by the coupled surface-subsurface flow field.

  8. Characteristics and control response of the TOPAZ II Reactor System Real-time Dynamic Simulator

    SciTech Connect

    Kwok, K.S.

    1993-11-12

    A dynamic simulator of the TOPAZ II reactor system has been developed for the Nuclear Electric Propulsion Space Test Program. The simulator combines first-principle modeling and empirical correlations in its algorithm to attain the modeling accuracy and computational through-put that are required for real-time execution. The overall execution time of the simulator for each time step is 15 ms when no data is written to the disk, and 18 ms when nine double precision data points are written to the disk once in every time step. The simulation program has been tested and it is able to handle a step decrease of $8 worth of reactivity. It also provides simulations of fuel, emitter, collector, stainless steel, and ZrH moderator failures. Presented in this paper are the models used in the calculations, a sample simulation session, and a discussion of the performance and limitations of the simulator. The simulator has been found to provide realistic real-time dynamic response of the TOPAZ II reactor system under both normal and casualty conditions.

  9. Effects of characteristic length scales on the exciton dynamics in rubrene single crystals

    NASA Astrophysics Data System (ADS)

    Gieseking, Björn; Schmeiler, Teresa; Müller, Benjamin; Deibel, Carsten; Engels, Bernd; Dyakonov, Vladimir; Pflaum, Jens

    2014-11-01

    We present temperature dependent time-resolved photoluminescence (PL) investigations on well-defined morphologies of the prototypical organic semiconductor rubrene. By their respective degree of spatial constraint these morphologies directly influence the temperature dependent excitonic processes and their dynamics. While in bulk single crystals singlet exciton decay is governed by thermally activated fission at a time constant of 20 ps, this mechanism appears to be absent in rubrene microcrystals. Here the dynamics are characterized by a pronounced increase of the average exciton lifetime as confirmed by the dominating PL decay channel with an effective time constant of 100 ps. The enhanced surface-to-volume ratio indicates that the participating states might originate from microcrystal boundaries which could be reached by the substantial amount of migrating excitons prior to the onset of other decay processes. The suppression of singlet fission in these crystalline microstructures is promoted by the significantly lower activation energy of 25 meV for the 100 ps channel compared to the singlet fission barrier of 44 meV and imposes severe consequences for its utilization in, e.g., thin film photovoltaics. For the crystalline samples, an additional relaxation channel with a time constant of around 500 ps becomes relevant at very low temperatures. As this process is the only one observed for amorphous rubrene thin films it points at the local nature of the underlying decay mechanism.

  10. Research on the structure and dynamic characteristics of a fast-steering mirror

    NASA Astrophysics Data System (ADS)

    Zhou, Jianmin; Yin, Hongyan; Wang, Yonghui

    2009-05-01

    Based on the analysis of mechanical structures and characteristics of several shafting reflecting mirror at home and abroad, the composition principle of FSM is introduced in detail, and a concrete designing scheme of shaftless FSM is proposed. Using resonant frequency as a starting point, according to elastic mechanics, a vibration system of FSM is established. The structure of elastic system of FSM, material, manufacturing and heat treatment are also introduced. The computer simulation of the structure is completed by using COSMOS software. At last, the corresponding experimental result of property of open-loop of FSM is also given.

  11. Detecting the dynamic linkage between landscape characteristics and water quality in a subtropical coastal watershed, Southeast China.

    PubMed

    Huang, Jinliang; Li, Qingsheng; Pontius, Robert Gilmore; Klemas, Victor; Hong, Huasheng

    2013-01-01

    Geospatial analysis and statistical analysis are coupled in this study to determine the dynamic linkage between landscape characteristics and water quality for the years 1996, 2002, and 2007 in a subtropical coastal watershed of Southeast China. The landscape characteristics include Percent of Built (%BL), Percent of Agriculture, Percent of Natural, Patch Density and Shannon's Diversity Index (SHDI), with water quality expressed in terms of COD(Mn) and NH(4)(+)-N. The %BL was consistently positively correlated with NH(4)(+)-N and COD(Mn) at time three points. SHDI is significantly positively correlated with COD(Mn) in 2002. The relationship between NH(4)(+)-N, COD(Mn) and landscape variables in the wet precipitation year 2007 is stronger, with R(2) = 0.892, than that in the dry precipitation years 1996 and 2002, which had R(2) values of 0.712 and 0.455, respectively. Two empirical regression models constructed in this study proved more suitable for predicting COD(Mn) than for predicting NH(4)(+)-N concentration in the unmonitored watersheds that do not have wastewater treatment plants. The calibrated regression equations have a better predictive ability over space within the wet precipitation year of 2007 than over time during the dry precipitation years from 1996 to 2002. Results show clearly that climatic variability influences the linkage of water quality-landscape characteristics and the fit of empirical regression models.

  12. Detecting the Dynamic Linkage between Landscape Characteristics and Water Quality in a Subtropical Coastal Watershed, Southeast China

    NASA Astrophysics Data System (ADS)

    Huang, Jinliang; Li, Qingsheng; Pontius, Robert Gilmore; Klemas, Victor; Hong, Huasheng

    2013-01-01

    Geospatial analysis and statistical analysis are coupled in this study to determine the dynamic linkage between landscape characteristics and water quality for the years 1996, 2002, and 2007 in a subtropical coastal watershed of Southeast China. The landscape characteristics include Percent of Built (%BL), Percent of Agriculture, Percent of Natural, Patch Density and Shannon's Diversity Index (SHDI), with water quality expressed in terms of CODMn and NH4 +-N. The %BL was consistently positively correlated with NH4 +-N and CODMn at time three points. SHDI is significantly positively correlated with CODMn in 2002. The relationship between NH4 +-N, CODMn and landscape variables in the wet precipitation year 2007 is stronger, with R2 = 0.892, than that in the dry precipitation years 1996 and 2002, which had R2 values of 0.712 and 0.455, respectively. Two empirical regression models constructed in this study proved more suitable for predicting CODMn than for predicting NH4 +-N concentration in the unmonitored watersheds that do not have wastewater treatment plants. The calibrated regression equations have a better predictive ability over space within the wet precipitation year of 2007 than over time during the dry precipitation years from 1996 to 2002. Results show clearly that climatic variability influences the linkage of water quality-landscape characteristics and the fit of empirical regression models.

  13. The biopharmaceutics of successful controlled release drug product: Segmental-dependent permeability of glipizide vs. metoprolol throughout the intestinal tract.

    PubMed

    Zur, Moran; Cohen, Noa; Agbaria, Riad; Dahan, Arik

    2015-07-15

    The purpose of this work was to study the challenges and prospects of regional-dependent absorption in a controlled-release scenario, through the oral biopharmaceutics of the sulfonylurea antidiabetic drug glipizide. The BCS solubility class of glipizide was determined, and its physicochemical properties and intestinal permeability were thoroughly investigated, both in-vitro (PAMPA and Caco-2) and in-vivo in rats. Metoprolol was used as the low/high permeability class boundary marker. Glipizide was found to be a low-solubility compound. All intestinal permeability experimental methods revealed similar trend; a mirror image small intestinal permeability with opposite regional/pH-dependency was obtained, a downward trend for glipizide, and an upward trend for metoprolol. Yet the lowest permeability of glipizide (terminal Ileum) was comparable to the lowest permeability of metoprolol (proximal jejunum). At the colon, similar permeability was evident for glipizide and metoprolol, that was higher than metoprolol's jejunal permeability. We present an analysis that identifies metoprolol's jejunal permeability as the low/high permeability class benchmark anywhere throughout the intestinal tract; we show that the permeability of both glipizide and metoprolol matches/exceeds this threshold throughout the entire intestinal tract, accounting for their success as controlled-release dosage form. This represents a key biopharmaceutical characteristic for a successful controlled-release dosage form.

  14. The bridge permeameter; An alternative method for single-phase, steady-state permeability measurements

    SciTech Connect

    Graf, D.C.; Warpinski, N.R.

    1994-03-01

    Laboratory measurements of single-phase, steady-state permeability of porous rock are important for a number of different applications. The oil and gas industry uses permeability data as a key indicator of the producability of a hydrocarbon reservoir; effective containment of large volumes of oil in underground salt caverns is directly dependent upon the permeability of the adjacent cavern walls; and safe, long term underground isolation of radioactive and hazardous waste is contingent upon the flow and transport characteristics of the surrounding geologic formations. An alternative method for measuring single-phase, steady-state permeability of porous rock is presented. The use of troublesome and expensive mass flow meters is eliminated and replaced with a bridge configuration of flow resistors. Permeability values can be determined directly from differential pressures across the bridge network, resulting in potentially significant cost savings and simplification for conducting these types of measurements. Results from the bridge permeameter are compared with results obtained using conventional methods.

  15. Depth-weighted, mean soil permeability in Kansas

    USGS Publications Warehouse

    Juracek, Kyle E.

    2000-01-01

    This digital spatial data set provides information on the magnitude and spatial pattern of depth-weighted, mean soil permeability throughout the State of Kansas. The data set was assembled using 1:24,000-scale cartographic and attribute information on the spatial distribution and characteristics of Kansas soils. The data set is in grid (raster) format with a grid-cell size of 10,000 square meters.

  16. Review of the dynamic characteristics of AlGaInAs/InP microlasers subject to optical injection

    NASA Astrophysics Data System (ADS)

    Huang, Yong-Zhen; Ma, Xiu-Wen; Yang, Yue-De; Xiao, Jin-Long

    2016-11-01

    Semiconductor lasers subject to optical injection exhibit many nonlinear dynamic behaviors that can be applied to enhance the modulation speed and generate a microwave signal. In this paper, the dynamic characteristics of AlGaInAs/InP microdisk lasers subject to optical injection are investigated numerically and experimentally. The different dynamic states and bifurcation and stability diagrams are simulated using rate equations, and a greatly enhanced modulation bandwidth is expected based on small-signal analysis of microlasers in the injection locking state. Four-wave mixing, period-one and period-two oscillations, and injection locking states are demonstrated experimentally from the lasing spectra and photonic generation microwaves for a microdisk laser subject to optical injection at different detuning frequencies, and enhancement of the modulation bandwidth is realized for the optical injection locking state. Furthermore, low-noise photonically generated microwaves are obtained for microdisk lasers subject to optical injection and optoelectronic feedback, with the beating signal obtained from a high-speed photodetector being applied to the microdisk laser as sideband injection locking is realized in the period-one state. In addition to external optical injection, dynamic optical injection behaviors are realized for integrated twin-microdisk lasers with mutually internal optical injection, similar to semiconductor microdisk lasers subject to external optical injection. As well as obtaining microwaves by light beating at a high-speed photodetector, microwave signals are obtained from the electrode of a square microlaser subject to optical injection related to carrier density oscillation, with the microwave power versus frequency being in good agreement with the small-signal modulation response curve. It is expected that low-noise tunable microwave signals and enhanced modulation speed microlasers will be obtained from photonic integrated circuits, with the

  17. Data mining methods for predicting event runoff coefficients in ungauged basins using static and dynamic catchment characteristics

    NASA Astrophysics Data System (ADS)

    Loritz, Ralf; Weiler, Markus; Seibert, Simon

    2015-04-01

    Transferring hydrological information into ungauged basin by regionalisation approaches is an ongoing field of research. Usually regionalisation techniques use physical landscape descriptors to transfer either model parameters or hydrological characteristics from a catchment to another. A common problem of these approaches is the high degree of uncertainty associated to their results. One reason is that often solely static (structural) catchment characteristics such as catchment area, physiographic properties or land use data are used for regionalisation. However, it is well known that the hydrological response of a 'natural' system is a complex and a non-linear interaction of its structure, state and forcing. Here it is important to note, that only structure is a static property. State and forcing are highly dynamic when considering the temporal and spatial scale of a rainfall-runoff event. To overcome the limitations associated with 'static' regionalisation techniques we propose a regionalisation technique for event runoff coefficients combining static and dynamic catchment properties. The approach is based on the two data mining algorithms 'random forests' and 'quantile regression forests'. The static catchment characteristics include standard variables such as physiographic properties, land cover and soil data. The dynamic variables include event based properties of the forcing (i.e. rainfall amount, intensity,...) and proxies for the initial state of the catchment (i.e. initial soil moisture). Together with the runoff coefficient these quantities were extracted form hydro-meteorological time series (precipitation, discharge and soil moisture) using an automated rainfall-runoff event detection technique. We tested our method using a set of 60 meso-scale catchments (3.1 to 205,6 km2, covering a range of different geologies and land uses) from Southwest Germany. We randomly separated the catchments in two groups. The first group (30 donor catchments) was used to

  18. Dynamic characteristics of a Space Station Freedom Mars evolution reference configuration

    NASA Technical Reports Server (NTRS)

    Ayers, J. Kirk; Lim, Tae W.; Cooper, Paul A.

    1990-01-01

    One concept for a manned mission to Mars uses as a transportation mode an evolutionary version of Space Station Freedom (SSF), termed the Mars Evolution Reference Configuration (MERC). The MERC is configured by adding to SSF dual keels, an upper and lower boom, additional laboratory and habitation modules, increased power, and an assembly platform. A finite-element model of the MERC was formulated to investigate the expected low frequency modes, and its variations with the addition of large payload. A basic reboost procedure using near-continuous firing of reaction control system jets is described with the closed-loop attitude control system. The elastic dynamic behavior at critical points during a reboost of the MERC, both with and without the Mars piloted vehicle installed, is examined.

  19. Comprehensive comparisons of geodesic acoustic mode characteristics and dynamics between Tore Supra experiments and gyrokinetic simulations

    NASA Astrophysics Data System (ADS)

    Storelli, A.; Vermare, L.; Hennequin, P.; Gürcan, Ö. D.; Dif-Pradalier, G.; Sarazin, Y.; Garbet, X.; Görler, T.; Singh, Rameswar; Morel, P.; Grandgirard, V.; Ghendrih, P.

    2015-06-01

    In a dedicated collisionality scan in Tore Supra, the geodesic acoustic mode (GAM) is detected and identified with the Doppler backscattering technique. Observations are compared to the results of a simulation with the gyrokinetic code GYSELA. We found that the GAM frequency in experiments is lower than predicted by simulation and theory. Moreover, the disagreement is higher in the low collisionality scenario. Bursts of non harmonic GAM oscillations have been characterized with filtering techniques, such as the Hilbert-Huang transform. When comparing this dynamical behaviour between experiments and simulation, the probability density function of GAM amplitude and the burst autocorrelation time are found to be remarkably similar. In the simulation, where the radial profile of GAM frequency is continuous, we observed a phenomenon of radial phase mixing of the GAM oscillations, which could influence the burst autocorrelation time.

  20. Comprehensive comparisons of geodesic acoustic mode characteristics and dynamics between Tore Supra experiments and gyrokinetic simulations

    SciTech Connect

    Storelli, A. Vermare, L.; Hennequin, P.; Gürcan, Ö. D.; Singh, Rameswar; Morel, P.; Dif-Pradalier, G.; Sarazin, Y.; Garbet, X.; Grandgirard, V.; Ghendrih, P.; Görler, T.

    2015-06-15

    In a dedicated collisionality scan in Tore Supra, the geodesic acoustic mode (GAM) is detected and identified with the Doppler backscattering technique. Observations are compared to the results of a simulation with the gyrokinetic code GYSELA. We found that the GAM frequency in experiments is lower than predicted by simulation and theory. Moreover, the disagreement is higher in the low collisionality scenario. Bursts of non harmonic GAM oscillations have been characterized with filtering techniques, such as the Hilbert-Huang transform. When comparing this dynamical behaviour between experiments and simulation, the probability density function of GAM amplitude and the burst autocorrelation time are found to be remarkably similar. In the simulation, where the radial profile of GAM frequency is continuous, we observed a phenomenon of radial phase mixing of the GAM oscillations, which could influence the burst autocorrelation time.

  1. Acoustic characteristics and dynamic structural loading of an ASTOVL aircraft in hover

    NASA Astrophysics Data System (ADS)

    Mitchell, L. K.; Norum, Thomas D.; Johns, Albert L.

    1992-01-01

    Measurements of surface dynamic loading and freestream acoustics were made for an ASTOVL model in hover, to quantify the effects of elevated temperature on the acoustic field and surface loading. Data were acquired for a many combinations of operating parameters: model height above the ground plane, nozzle pressure ratio, and jet exit stagnation temperature. For many conditions, strong tones were observed, with amplitudes up to 150 dB. The frequencies of the strongest tones were well predicted by a model assuming feedback between the nozzle exit and the ground plane. The model also accounts for many of the variations in frequency observed with changes in model height, nozzle pressure ratio, and jet temperature. Broadband sound pressure levels up to 170 dB were also recorded. The maximum levels occurred at approximately 3 equivalent jet diameters above the ground plane. For the majority of the cases, the increase in noise due to temperature was less than expected based on free jet correlations.

  2. Dynamic characteristic prediction of inverted pendulum under the reduced-gravity space environments

    NASA Astrophysics Data System (ADS)

    Li, Guohui; Liu, Xue

    2010-09-01

    A new multi-local linear model based on the Tkakgi-Sugeno approach is presented to carry out controlling of a nonlinear unsteady system and to make a design of inverted pendulum fuzzy controller. Nonlinear multi-variance behaviors are transformed to a multi-local linear model using a fuzzy approximation method, which is used to implement control steadily and rapidly for the global system. Detailed investigations on dynamic behaviors of inverted pendulum under reduced-gravity space environments are performed using Simulink simulations. Results showed that stabilization of an inverted pendulum is greatly affected by reduced-gravity conditions and effects of θ angle variation are the largest. When θ is greater than 1.571 rad threshold value, balances will be lost under earth, lunar and microgravity conditions. Furthermore, microgravity is favorable for keeping balance status. An appropriate compensation controlling provided by the presented fuzzy controller can keep a better balance for inverted pendulum.

  3. Dosimetric and mechanical characteristics of a commercial dynamic {mu}MLC used in SRS

    SciTech Connect

    Galal, Mohamed M.; Keogh, Sinead; Khalil, Sultan

    2011-07-15

    Purpose: The aim of this work is to carry out mechanical and dosimetric assessments on a commercial dynamic micromulti leaf collimator system to be used for stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). Mechanical parameters such as leaf position accuracy with different gantry angles and leaf position reproducibility were measured. Also dosimetric measurements of the interleaf leakage, intraleaf transmission, penumbra width, and light field alignment were carried out. Furthermore, measurements of output factors (S{sub cp}) and in-air factors (S{sub c}) for the {mu}MLC system will be reported. Methods: EBT2 films were used to assess the leaf position error with gantry angle and after stress test, penumbra width and light field alignment. Leaf leakage was quantified using both EBT2 film and a pinpoint ion chamber. With regard to output factors, the pinpoint chamber was placed in a water phantom at 10 cm depth and 100 cm SSD. For in-air output factor measurements, 0.2 cm of brass was placed above the photon diode as build-up. Results: Measurements of mechanical parameters gave values of 0.05 cm (SD 0.035) for the average leaf position accuracy for different gantry angles and after stress test. Dosimetric measurements, yielded values of 0.22 {+-} 0.01 and 0.24 {+-} 0.01 cm, respectively, for side and head leaf penumbras. Also, average leaf abutting, leakage and transmission were found to be 0.65, 0.91, and 0.20%, respectively. Conclusions: (a) The add-on {mu}MLC system in combination with our LINAC has been commissioned to be used for clinical purposes and showed good agreement with published results for different {mu}MLC types. (b) This work has lead to the recommendation that leaves should be recalibrated after ten static beams or after each dynamic arc.

  4. Dynamic, six-axis stiffness matrix characteristics of the intact intervertebral disc and a disc replacement.

    PubMed

    Holsgrove, Timothy P; Gill, Harinderjit S; Miles, Anthony W; Gheduzzi, Sabina

    2015-11-01

    Thorough pre-testing is critical in assessing the likely in vivo performance of spinal devices prior to clinical use. However, there is a lack of data available concerning the dynamic testing of lumbar (porcine model) total disc replacements in all six axes under preload conditions. The aim of this study was to provide new data comparing porcine lumbar spinal specimen stiffness between the intact state and after the implantation of an unconstrained total disc replacement, in 6 degrees of freedom. The dynamic, stiffness matrix testing of six porcine lumbar isolated disc specimens was completed using triangle waves at a test frequency of 0.1 Hz. An axial preload of 500 N was applied during all testing. Specimens were tested both in the intact condition and after the implantation of the total disc replacement. Sixteen key stiffness terms were identified for the comparison of the intact and total disc replacement specimens, comprising the 6 principal stiffness terms and 10 key off-axis stiffness terms. The total disc replacement specimens were significantly different to the intact specimens in 12 of these key terms including all six principal stiffness terms. The implantation of the total disc replacement resulted in a mean reduction in the principal stiffness terms of 100%, 91%, and 98% in lateral bending, flexion-extension, and axial rotation, respectively. The novel findings of this study have demonstrated that the unconstrained, low-friction total disc replacement does not replicate the stiffness of the intact specimens. It is likely that other low-friction total disc replacements would produce similar results due to stiffness being actively minimised as part of the design of low-friction devices, without the introduction of stiffening elements or mechanisms to more accurately replicate the mechanical properties of the natural intervertebral disc. This study has demonstrated, for the first time, a method for the quantitative comparative mechanical function

  5. Particle Motion Analysis Reveals Nanoscale Bond Characteristics and Enhances Dynamic Range for Biosensing.

    PubMed

    Visser, Emiel W A; van IJzendoorn, Leo J; Prins, Menno W J

    2016-03-22

    Biofunctionalized colloidal particles are widely used as labels in bioanalytical assays, lab-on-chip devices, biophysical research, and in studies on live biological systems. With detection resolution going down to the level of single particles and single molecules, understanding the nature of the interaction of the particles with surfaces and substrates becomes of paramount importance. Here, we present a comprehensive study of motion patterns of colloidal particles maintained in close proximity to a substrate by short molecular tethers (40 nm). The motion of the particles (500-1000 nm) was optically tracked with a very high localization accuracy (below 3 nm). A surprisingly large variation in motion patterns was observed, which can be attributed to properties of the particle-molecule-substrate system, namely the bond number, the nature of the bond, particle protrusions, and substrate nonuniformities. Experimentally observed motion patterns were compared to numerical Monte Carlo simulations, revealing a close correspondence between the observed motion patterns and properties of the molecular system. Particles bound via single tethers show distinct disc-, ring-, and bell-shaped motion patterns, where the ring- and bell-shaped patterns are caused by protrusions on the particle in the direct vicinity of the molecular attachment point. Double and triple tethered particles exhibit stripe-shaped and triangular-shaped motion patterns, respectively. The developed motion pattern analysis allows for discrimination between particles bound by different bond types, which opens the possibility to improve the limit of detection and the dynamic range of bioanalytical assays, with a projected increase of dynamic range by nearly 2 orders of magnitude.

  6. Spectral-induced polarization measurements on sieved sands and the relationship to permeability

    NASA Astrophysics Data System (ADS)

    Joseph, Sheen; Ingham, Malcolm; Gouws, Gideon

    2016-06-01

    Laboratory measurements of the permeability and spectral-induced polarization (SIP) response of samples consisting of unconsolidated sands typical of those found in New Zealand aquifers have been made. After correction of measured formation factors to allow for the fact that some were measured at only one fluid conductivity, predictions of permeability from the grain size (d) of the samples are found to agree well with measured values of permeability. The Cole-Cole time constant (derived from the SIP measurements) is found, as expected, to depend upon d2, but can be affected by the inclusion of smaller grains in the sample. Measurements made on samples comprising of mixtures of grain sizes show that inclusion in a sample of even 10% of smaller grains can significantly reduce both the Cole-Cole time constant (τCC) and the permeability, and support theoretical derivation of how the permeability of a mixture of grain sizes varies with the content of the mixture. Proposed relationships for using τCC as a predictor for permeability are tested and found to be crucially dependent on the assumed relationship between the dynamic pore radius and grain size. The inclusion of a multiplicative constant to take account of numerical approximations results in good predictions for the permeability of the samples in this study. It seems unlikely, however, that there is a single global expression for predicting permeability from SIP data for all samples.

  7. The investigation of parachute fabric permeability under an unsteady pressure differential

    NASA Astrophysics Data System (ADS)

    Rondeau, Nichole C.

    An apparatus for assessing permeability of textiles subjected to time-varying pressure differentials is presented. A Computer Numerically Controlled Piston Permeability Apparatus (CNC-PPA) that can control the volume flow rate through a fabric has been designed and built. This test device has been developed in an effort to improve the understanding and design choices for aerodynamic decelerators. Preliminary results for a low permeability fabric (PIA-C-44378, Type IV) under both steady and unsteady loads are presented. The results from this investigation do indicate a small effect of unsteady pressure differential on the fabric permeability. The fabric permeability is slightly higher than the static permeability when the pressure differential is increasing with respect to time and the opposite is true when the pressure differential is decreasing. This change in permeability is more pronounced as the pressure is higher and the pressure changes more rapidly with respect to time, suggesting dynamic permeability likely affects highly unsteady phenomena such as parachute opening.

  8. Dynamic Stiffness and Damping Characteristics of a High-Temperature Air Foil Journal Bearing

    NASA Technical Reports Server (NTRS)

    Howard, Samuel A.; DellaCorte, Christopher; Valco, Mark J.; Prahl, Joseph M.; Heshmat, Hooshang

    2001-01-01

    Using a high-temperature optically based displacement measurement system, a foil air bearing's stiffness and damping characteristics were experimentally determined. Results were obtained over a range of modified Sommerfeld Number from 1.5E6 to 1.5E7, and at temperatures from 25 to 538 C. An Experimental procedure was developed comparing the error in two curve fitting functions to reveal different modes of physical behavior throughout the operating domain. The maximum change in dimensionless stiffness was 3.0E-2 to 6.5E-2 over the Sommerfeld Number range tested. Stiffness decreased with temperature by as much as a factor of two from 25 to 538 C. Dimensionless damping was a stronger function of Sommerfeld Number ranging from 20 to 300. The temperature effect on damping being more qualitative, showed the damping mechanism shifted from viscous type damping to frictional type as temperature increased.

  9. Structural stiffness, strength and dynamic characteristics of large tetrahedral space truss structures

    NASA Technical Reports Server (NTRS)

    Mikulas, M. M., Jr.; Bush, H. G.; Card, M. F.

    1977-01-01

    Physical characteristics of large skeletal frameworks for space applications are investigated by analyzing one concept: the tetrahedral truss, which is idealized as a sandwich plate with isotropic faces. Appropriate analytical relations are presented in terms of the truss column element properties which for calculations were taken as slender graphite/epoxy tubes. Column loads, resulting from gravity gradient control and orbital transfer, are found to be small for the class structure investigated. Fundamental frequencies of large truss structures are shown to be an order of magnitude lower than large earth based structures. Permissible loads are shown to result in small lateral deflections of the truss due to low-strain at Euler buckling of the slender graphite/epoxy truss column elements. Lateral thermal deflections are found to be a fraction of the truss depth using graphite/epoxy columns.

  10. Dynamic characteristics of two-state lasing quantum dot lasers under large signal modulation

    SciTech Connect

    Lv, Zun-Ren; Ji, Hai-Ming Luo, Shuai; Gao, Feng; Xu, Feng; Yang, Tao; Xiao, De-Hang

    2015-10-15

    Large signal modulation characteristics of the simultaneous ground-state (GS) and excited-state (ES) lasing quantum dot lasers are theoretically investigated. Relaxation oscillations of ‘0 → 1’ and ‘1 → 0’ in the GS lasing region (Region I), the transition region from GS lasing to two-state lasing (Region II) and the two-state lasing region (Region III) are compared and analyzed. It is found that the overshooting power and settling time in both Regions I and III decrease as the bias current increases. However, there exist abnormal behaviors of the overshooting power and settling time in Region II owing to the occurrence of ES lasing, which lead to fuzzy eye diagrams of the GS and ES lasing. Moreover, the ES lasing in Region III possesses much better eye diagrams because of its shorter settling time and smaller overshooting power over the GS lasing in Region I.

  11. A modelling investigation of solute transport in permeable porous media containing a discrete preferential flow feature

    NASA Astrophysics Data System (ADS)

    Sebben, Megan L.; Werner, Adrian D.

    2016-08-01

    Preferential flow features (PFFs, e.g. fractures and faults) are common features in rocks that otherwise have significant matrix permeability. Despite this, few studies have explored the influence of a PFF on the distribution of solute plumes in permeable rock formations, and the current understanding of PFF effects on solute plumes is based almost entirely on low-permeability rock matrices. This research uses numerical modelling to examine solute plumes that pass through a PFF in permeable rock, to explore the PFF's influence on plume migration. The study adopts intentionally simplified arrangements involving steady-state solute plumes in idealised, moderate-to-high-permeability rock aquifers containing a single PFF. A range of matrix-PFF permeability ratios (4.9 × 10-6-2.5 × 10-2), typical of fractured sedimentary aquifers, is considered. The results indicate that for conditions representative of high-to-moderate-permeability sedimentary rock matrices containing a medium-sized fracture, the effect of the PFF on solute plume displacement and spreading can be considerable. For example, plumes are between 1.3 and 19 times wider than in associated porous media only scenarios, and medium-sized PFFs in moderately permeable matrices can reduce the maximum solute concentration by up to 104 times. Plume displacement and spreading is lower in aquifers of higher matrix-PFF permeability ratios, and where solute plumes are more dispersed at the point of intersection with the PFF. Asymmetry in the plume caused by the passage through the PFF is more pronounced for more dispersive plumes. The current study demonstrates that PFFs most likely govern solute plume characteristics in typical permeable matrices, given that a single PFF of aperture representing a medium-sized fracture (i.e. 5.0 × 10-4m) produces the equivalent spreading effects of 0.22-7.88 m of plume movement through the permeable matrix.

  12. Food flavor and nutritional characteristics alter dynamics of food preference in lambs.

    PubMed

    Early, D M; Provenza, F D

    1998-03-01

    We addressed two questions involving food preference. First, we determined how a food's flavor and nutritional characteristics affected preference. In three trials, we offered lambs isonitrogenous foods differing in energy (trial 1, 90% TDN; trial 2, 100% TDN; trial 3, 110% TDN); each food was offered in apple and maple flavors. We hypothesized that preference for apple- or maple-flavored food would decrease with increasing duration of exposure (1, 2, or 4 d), and we speculated that the change in preference would intensify when food contained inadequate or excessive levels of energy. After eating food in one flavor, lambs preferred the alternative flavor, even after only a 1-d exposure, and preference for the alternative flavor was greater when the food had inadequate or excessive energy (P < .05). The second experiment determined whether eating a food with rapidly or slowly digestible sources of energy in the morning affected lambs' food preferences in the evening. We speculated that lambs fed rapidly digestible food in the morning may prefer a slowly digestible food in the afternoon because slowly digestible food better maintains nutrient status throughout the night or because preference for the rapidly digestible food decreases after exposure in the morning. We offered lambs isonitrogenous and isocaloric foods, that differed in rates of digestion, in apple and maple flavors. Lambs fed rapidly digestible food in the morning preferred slowly digestible food in the alternative flavor in the evening. However, lambs fed slowly digestible food in either flavor in the morning preferred slowly digestible food in both flavors in the evening (P < .05). These results show that lambs' preferences change as a result of food ingestion, and the degree of change in preference depends on the nutritional characteristics of the food. These findings further suggest food intake might be increased by providing a variety of foods to livestock on rangelands, pastures, or in confinement.

  13. Distinctions between dynamic characteristics of the single EG5 motor protein along neural vs. cancerous microtubules.

    PubMed

    Feizabadi, Mitra Shojania; Jun, Yonggun; Reddy, J N Babu

    2016-09-30

    The kinesin 5 motor contributes critically to mitosis, and is often upregulated in cancer. In vitro motility studies of kinesin 5 moving along bovine brain microtubules indicate that the motors have limited processivity. Cancer cells have abnormal mitotic behavior, so one might wonder whether the functional properties of kinesin 5 change in such a background. Because there could be multiple unknown changes in cancerous vs normal cells, we chose to address this question in a controlled in vitro environment. Specifically, through a series of parallel experiments along bovine brain vs. breast cancer microtubules, we quantified the in vitro motility characteristics of single Eg5 molecular motors along these two types of microtubules, combining the utilization of an optical trapping technique with a study of motion in the unloaded regime. The obtained values indicate that Eg5 processivity is 40% less along MCF7 microtubules, compared to that measured on bovine brain MTs. Interestingly, not all single-molecule properties are altered, as the velocity of the single motor doesn't show any significant changes on either track, though the binding time along MCF7 microtubules is almost 25% shorter. The current results, in conjunction with our previously reported outcomes of the evaluation of the Eg5's characteristics under external load, show that in transition from no-load to high-load regime, the Eg5 binding time has less sensitivity on MCF7 as compared to bovine brain MTs. This finding is intriguing, as it suggests that, potentially, groups of Eg5 motors function more effectively in the cancer background of a large ensemble, possibly contributing to faster mitosis in cancer cells.

  14. Distinctions between dynamic characteristics of the single EG5 motor protein along neural vs. cancerous microtubules.

    PubMed

    Feizabadi, Mitra Shojania; Jun, Yonggun; Reddy, J N Babu

    2016-09-30

    The kinesin 5 motor contributes critically to mitosis, and is often upregulated in cancer. In vitro motility studies of kinesin 5 moving along bovine brain microtubules indicate that the motors have limited processivity. Cancer cells have abnormal mitotic behavior, so one might wonder whether the functional properties of kinesin 5 change in such a background. Because there could be multiple unknown changes in cancerous vs normal cells, we chose to address this question in a controlled in vitro environment. Specifically, through a series of parallel experiments along bovine brain vs. breast cancer microtubules, we quantified the in vitro motility characteristics of single Eg5 molecular motors along these two types of microtubules, combining the utilization of an optical trapping technique with a study of motion in the unloaded regime. The obtained values indicate that Eg5 processivity is 40% less along MCF7 microtubules, compared to that measured on bovine brain MTs. Interestingly, not all single-molecule properties are altered, as the velocity of the single motor doesn't show any significant changes on either track, though the binding time along MCF7 microtubules is almost 25% shorter. The current results, in conjunction with our previously reported outcomes of the evaluation of the Eg5's characteristics under external load, show that in transition from no-load to high-load regime, the Eg5 binding time has less sensitivity on MCF7 as compared to bovine brain MTs. This finding is intriguing, as it suggests that, potentially, groups of Eg5 motors function more effectively in the cancer background of a large ensemble, possibly contributing to faster mitosis in cancer cells. PMID:27590585

  15. Investigation of the feasibility of developing low permeability polymeric films

    NASA Technical Reports Server (NTRS)

    Hoggatt, J. T.

    1971-01-01

    The feasibility of reducing the gas permeability rate of Mylar and Kapton films without drastically effecting their flexibility characteristics at cryogenic temperatures was considered. This feasibility was established using a concept of diffusion bonding two layers of metallized films together forming a film-metal-film sandwich laminate. The permeability of kapton film to gaseous helium was reduced from a nominal ten = to the minus 9 power cc-mm/sq cm sec. cm Hg to ten to the minus 13 power cc-mm/ sq cm - sec. cm Hg with some values as low as ten to the minus 15 power cc - mm/sq cm m-sec - cm Hg being obtained. Similar reductions occurred in the liquid hydrogen permeability at -252 C. In the course of the program the permeability, flexibility and bond strength of plain, metalized and diffusion bond film were determined at +25 C, -195 C and -252 C. The cryogenic flexibility of Kapton film was reduced slightly due to the metallization process but no additional loss in flexibility resulted from the diffusion bonding process.

  16. Hydrological and Dynamical Characteristics of Summertime Droughts over U.S. Great Plains.

    NASA Astrophysics Data System (ADS)

    Chang, Fong-Chiau; Smith, Eric A.

    2001-05-01

    A drought pattern and its time evolution over the U.S. Great Plains are investigated from time series of climate divisional monthly mean surface air temperature and total precipitation anomalies. The spatial pattern consists of correlated occurrences of high (low) surface air temperature and deficit (excess) rainfall. The center of maximum amplitude in rain fluctuation is around Kansas City; that of temperature is over South Dakota. Internal consistency between temperature and precipitation variability is the salient feature of the drought pattern. A drought index is used to quantify drought severity for the period 1895-1996. The 12 severest drought months (in order) during this period are June 1933, June 1988, July 1936, August 1983, July 1934, July 1901, June 1931, August 1947, July 1930, June 1936, July 1954, and August 1936. Hydrological conditions are examined using National Centers for Environmental Prediction (NCEP) reanalysis precipitable water (PW) and monthly surface observations from Kansas City, Missouri, and Bismarck, North Dakota, near the drought centers. This analysis explains why droughts exhibit negative surface relative humidity anomalies accompanied by larger than normal monthly mean daily temperature ranges and why maximum PWs are confined to a strip of about 10° longitude from New Mexico and Arizona into the Dakotas and Minnesota.Dynamical conditions are examined using NCEP reanalysis sea level pressures and 500- and 200-mb geopotential heights. The analysis indicates a midtroposphere wave train with positive centers situated over the North Pacific, North America, and the North Atlantic, with negative centers in the southeastern Gulf of Alaska and Davis Strait. Above-normal sea level pressures over New Mexico, the North Atlantic, and the subtropical Pacific along with below-normal sea level pressures over the Gulf of Alaska eastward to Canada, Davis Strait, and Greenland are present during drought periods. The most prominent feature is the

  17. Forest feeder root dynamics are controlled by spatiotemporal position, inherent characteristics and resource availability

    NASA Astrophysics Data System (ADS)

    Coleman, M.

    2012-12-01

    Fine roots are the conduit for carbon allocation from forest trees to soil. Information on species-specific allocation patterns is crucial for predicting responses to changing environmental conditions. Yet models for belowground allocation are based on generalizations with few supporting observations. It is rare to have long-term observations of fine root dynamics compared among species and levels of resource availability. Here I present the results for fine root dynamics monitored over six years following establishment of a replicated trial comparing cottonwood (CW) and loblobloly pine (LP) grown without amendment (C), with fertilization (F), irrigation (I) or their combination (IF). The trial is located at the Savannah River Site near New Ellenton, SC, USA. Species and time since establishment had larger effects on feeder root production and mortality with relatively minor effects from irrigation and fertilization treatments. Both cumulative production and mortality followed sigmoid growth curves during six years of establishment. Cumulative production for LP was consistently 30% lower than CW throughout observations, while species differences in cumulative mortality reached the same magnitude and direction, but only after four growing seasons. Fertilization, but not irrigation, had a significant positive effect on cottonwood feeder root production. Fertilized cottonwood cumulative feeder root production was 57% greater than non-fertilizer, while fertilized pine cumulative production was 16% lower than non-fertilizer. There were no irrigation and fertilizer treatment differences in cumulative feeder root mortality identified with the repeated measures analysis approach. Survival analysis was used to evaluate factors controlling the risk of root mortality, account for covariates and to achieve greater sensitivity. Predominate factors affecting the risk of root mortality were in order: depth in soil, year of observation, root diameter at appearance, and season of

  18. The manual control of vehicles undergoing slow transitions in dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Moriarty, T. E.

    1974-01-01

    The manual control was studied of a vehicle with slowly time-varying dynamics to develop analytic and computer techniques necessary for the study of time-varying systems. The human operator is considered as he controls a time-varying plant in which the changes are neither abrupt nor so slow that the time variations are unimportant. An experiment in which pilots controlled the longitudinal mode of a simulated time-varying aircraft is described. The vehicle changed from a pure double integrator to a damped second order system, either instantaneously or smoothly over time intervals of 30, 75, or 120 seconds. The regulator task consisted of trying to null the error term resulting from injected random disturbances with bandwidths of 0.8, 1.4, and 2.0 radians per second. Each of the twelve experimental conditons was replicated ten times. It is shown that the pilot's performance in the time-varying task is essentially equivalent to his performance in stationary tasks which correspond to various points in the transition. A rudimentary model for the pilot-vehicle-regulator is presented.

  19. Study on the dynamic characteristics of a high frequency brake based on giant magnetostrictive material

    NASA Astrophysics Data System (ADS)

    Xu, Ai Qun

    2016-06-01

    In order to meet the requirements of rapid and smooth braking, high-frequency braking using a giant magnetostrictive actuator is proposed, which can solve the problems in hydraulic braking, such as, it leaks easily, catches fire easily, is difficult to find failures, high cost on maintenance and repairing, etc. The main factors affecting the force of a high-frequency braking actuator are emphatically analyzed, the brakes dynamic model is established and a performance testing device for high frequency braking is constructed based on LabVIEW. The output force of the actuator increases with the excitation current of the driving coil increasing, and the increased multiple of the output force is greater than that of the excitation current; the range of the actuator force amplitude is 121.63 N ∼ 158.14 N, which changes little, while excitation frequency changes between 200 Hz ∼ 1000 Hz. In a minor range of pre-stress, the output force decreases with an increase in the axial pre-stress of the giant magnetostrictive rod, but is not obvious. It is known by finite element simulation analysis that high-frequency braking shortens the braking displacement and time effectively, which proves the feasibility and effectiveness of high frequency braking. Theoretical analysis and experimental results indicate that the output force of the actuator changes at the same frequency with excitation current; it is controllable and its mechanical properties meet the requirements of high frequency braking.

  20. Characteristics of scar margin dynamic with time based on multiphoton microscopy.

    PubMed

    Zhu, Xiaoqin; Zhuo, Shuangmu; Zheng, Liqin; Jiang, Xingshan; Chen, Jianxin; Lin, Bifang

    2011-03-01

    Scar margins dynamic with time were quantitatively characterized using multiphoton microscopy (MPM). 2D large-area and 3D focused images of elastin and collagen at scar margins were obtained to extract quantitative parameters. An obvious boundary was observed at the scar margin, showing altered morphological patterns of elastin and collagen on both sides. Content alteration of elastin and collagen between the two sides of boundary were defined to characterize scar margins from different individuals. The statistical results from 15 normal scar samples strongly demonstrated that content alteration degree of elastin and collagen had decreasing tendency with the increase of patient age or scar duration, consistent with the fact of normal scars regressing spontaneously over time. It indicated that alteration degree can potentially serve as quantitative indicators to examine wound healing and scar progression over time. With the advent of clinical portable multiphoton endoscopes, the MPM technique can be applied in tracking scar formation and progression in vivo by examination of scar margin.

  1. Frequency domain modeling and dynamic characteristics evaluation of existing wind turbine systems

    NASA Astrophysics Data System (ADS)

    Chiang, Chih-Hung; Yu, Chih-Peng

    2016-04-01

    It is quite well accepted that frequency domain procedures are suitable for the design and dynamic analysis of wind turbine structures, especially for floating offshore wind turbines, since random wind loads and wave induced motions are most likely simulated in the frequency domain. This paper presents specific applications of an effective frequency domain scheme to the linear analysis of wind turbine structures in which a 1-D spectral element was developed based on the axially-loaded member. The solution schemes are summarized for the spectral analyses of the tower, the blades, and the combined system with selected frequency-dependent coupling effect from foundation-structure interactions. Numerical examples demonstrate that the modal frequencies obtained using spectral-element models are in good agreement with those found in the literature. A 5-element mono-pile model results in less than 0.3% deviation from an existing 160-element model. It is preliminarily concluded that the proposed scheme is relatively efficient in performing quick verification for test data obtained from the on-site vibration measurement using the microwave interferometer.

  2. Gas flow characteristics of a time modulated APPJ: the effect of gas heating on flow dynamics

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Sobota, A.; van Veldhuizen, E. M.; Bruggeman, P. J.

    2015-01-01

    This work investigates the flow dynamics of a radio-frequency (RF) non-equilibrium argon atmospheric pressure plasma jet. The RF power is at a frequency of 50 Hz or 20 kHz. Combined flow pattern visualizations (obtained by shadowgraphy) and gas temperature distributions (obtained by Rayleigh scattering) are used to study the formation of transient vortex structures in initial flow field shortly after the plasma is switched on and off in the case of 50 Hz modulation. The transient vortex structures correlate well with observed temperature differences. Experimental results of the fast modulated (20 kHz) plasma jet that does not induce changes of the gas temperature are also presented. The latter result suggests that momentum transfer by ions does not have dominant effect on the flow pattern close to the tube. It is argued that the increased gas temperature and corresponding gas velocity increase at the tube exit due to the plasma heating increases the admixing of surrounding air and reduces the effective potential core length. With increasing plasma power a reduction of the effective potential core length is observed with a minimum length for 5.6 W after which the length extends again. Possible mechanisms related to viscosity effects and ionic momentum transfer are discussed.

  3. Dynamic characteristics of the 40- by 80-/80- by 120-foot wind tunnel drive fan blades

    NASA Technical Reports Server (NTRS)

    Warmbrodt, W.

    1983-01-01

    The existing 40- by 80-Foot Wind Tunnel at Ames Research Center is being modified to upgrade and expand the research capabilty of the facility. The modification project includes an enhancement of the wind-tunnel drive power capability by installing large capacity electric motors and new drive fans to attain higher airspeeds in the existing 40- by 80-ft test section. It also involves the constructin of a new tunnel leg which includes a larger 80-- by 120-ft test section. The 40-by 80-ft test section will have a maximum airspeed approaching 300 knots. It was previously limited to about 200 knots. The maximum airspeed of the 80- by 120-ft test section will be about 100 knots. Becaue of the critical nature of the drive fans in the operation of the facility, an extensive effort was undertaken to verify, for each blade-retention system, its structural integrity and its dynamic characteristics.

  4. Thermokarst dynamics and soil organic matter characteristics controlling initial carbon release from permafrost soils in the Siberian Yedoma region

    NASA Astrophysics Data System (ADS)

    Weiss, Niels; Blok, Daan; Elberling, Bo; Hugelius, Gustaf; Jørgensen, Christian Juncher; Siewert, Matthias Benjamin; Kuhry, Peter

    2016-07-01

    This study relates soil organic matter (SOM) characteristics to initial soil incubation carbon release from upper permafrost samples in Yedoma region soils of northeastern Siberia, Russia. Carbon (C) and nitrogen (N) content, carbon to nitrogen ratios (C:N), δ13C and δ15N values show clear trends that correspond with SOM age and degree of decomposition. Incubation results indicate that older and more decomposed soil material shows higher C respiration rates per unit incubated C than younger and less decomposed samples with higher C content. This is important as undecomposed material is often assumed to be more reactive upon thawing. Large stocks of SOM and their potential decomposability, in combination with complex landscape dynamics that include one or more events of Holocene thaw in most of the landscape, are of consequence for potential greenhouse gas release from permafrost soils in the Yedoma region.

  5. RELATIONSHIP BETWEEN DAMAGE AND CHANGE OF DYNAMIC CHARACTERISTICS IN AN EXISTING BRIDGE FOR VIBRATION-BASED STRUCTURAL HEALTH MONITORING

    NASA Astrophysics Data System (ADS)

    Miyashita, Takeshi; Tamada, Kazuya; Liu, Cuiping; Iwasaki, Hidenori; Nagai, Masatsugu

    The objective of this study is to understand the relationship between damage and the change of dynamic characteristics in an existing bridge for vibration-based structural health monitoring. Focused bridge is a demolished pedestrian bridge, which is a composite steel girder with two main girders. The first damages are slits by gas cutting, which are given to a lower flange in the lateral direction. Then, outstanding plate in the lower flange is removed along the span. Vibration measurement was carried out in each damage case. As a result, it was confirmed that natural frequencies decreased depending on the progress of damage. Its reduction rate was greater in the modes without torsion. For reproducible analysis, spectral element and finite element analyses were carried out. Analytical results also showed the similar reduction of natural frequencies to measurement.

  6. Decision trees to characterise the roles of permeability and solubility on the prediction of oral absorption.

    PubMed

    Newby, Danielle; Freitas, Alex A; Ghafourian, Taravat

    2015-01-27

    Oral absorption of compounds depends on many physiological, physiochemical and formulation factors. Two important properties that govern oral absorption are in vitro permeability and solubility, which are commonly used as indicators of human intestinal absorption. Despite this, the nature and exact characteristics of the relationship between these parameters are not well understood. In this study a large dataset of human intestinal absorption was collated along with in vitro permeability, aqueous solubility, melting point, and maximum dose for the same compounds. The dataset allowed a permeability threshold to be established objectively to predict high or low intestinal absorption. Using this permeability threshold, classification decision trees incorporating a solubility-related parameter such as experimental or predicted solubility, or the melting point based absorption potential (MPbAP), along with structural molecular descriptors were developed and validated to predict oral absorption class. The decision trees were able to determine the individual roles of permeability and solubility in oral absorption process. Poorly permeable compounds with high solubility show low intestinal absorption, whereas poorly water soluble compounds with high or low permeability may have high intestinal absorption provided that they have certain molecular characteristics such as a small polar surface or specific topology.

  7. Characteristics of L-band backscatter coefficients of rubber plantation and their seasonal dynamics

    NASA Astrophysics Data System (ADS)

    Trisasongko, Bambang H.; Panuju, Dyah R.

    2015-09-01

    As one of primary land uses in Indonesia, rubber plantation requires frequent, wide-scale monitoring. Due to the nature of tropical region, optical sensors are often inapplicable and therefore Synthetic Aperture Radar (SAR) plays a role. Dual-polarized SAR data have been a definitive imaging mode since fully polarimetric mode consumes higher energy. In this paper, characteristics of returning SAR signals from young rubber stands are investigated in terms of different polarization and time of acquisition. The research shows that strong ground attenuation is observed in very young plantation, which is similar to amplified Bragg scattering in rice field. Seasonal defoliation is also evident at this age, possibly due to limited root depth which reduces ability to obtain moisture in lower solum. Temporal change of canopy cover is detectable by HV polarization, which has been known sensitive to canopy structure. This research suggests that seasonal variation of HV backscatter coefficients may affect biophysical estimation, and therefore time of acquisition needs to be considered carefully.

  8. Dynamic Characteristics of Pressure Build Up Tank for HTS Power Cable Refrigeration System

    NASA Astrophysics Data System (ADS)

    Kim, Dongmin; Park, Heecheol; Kim, Seokho; Jang, Hyunman; Kim, Yanghun

    HTS power cables are cooled by the forced circulation of sub-cooled liquid nitrogen to remove heat loss and maintain a cryogenic temperature. The refrigeration systems used consist of cryocoolers, a pressure build-up tank, heat exchangers, and circulation pumps. Liquid nitrogen expands or shrinks according to the temperature variation inside the fixed volume of the refrigeration system and the cable cryostat. The system pressure also changes depending on the volume change of the liquid nitrogen. The pressure of the liquid nitrogen should be kept above a certain level to ensure its dielectric strength. In addition, the pressure should be kept below the allowable pressure level considering the mechanical strength of the refrigeration system. To enhance the pressure controllability, external heating and cooling should be possible in the pressure build-up tank. For the precise modeling of the pressure build-up tank, thermal stratification and axial thermal conduction are considered. An analysis of such a refrigeration system is performed using the commercial code 'Sinda/fluint', a comprehensive finite-difference, one-dimensional, lumped parameter tool. This paper presents the transient thermo-hydraulic characteristics and the design directions of an HTS cable refrigeration system according to a variable heat load including pressure build-up tank.

  9. Numerical study on wave dynamics and wave-induced bed erosion characteristics in Potter Cove, Antarctica

    NASA Astrophysics Data System (ADS)

    Lim, Chai Heng; Lettmann, Karsten; Wolff, Jörg-Olaf

    2013-12-01

    Wave generation, propagation, and transformation from deep ocean over complex bathymetric terrains to coastal waters around Potter Cove (King George Island, South Shetland Islands, Antarctica) have been simulated for an austral summer month using the Simulating Waves Nearshore (SWAN) wave model. This study aims to examine and understand the wave patterns, energy fluxes, and dissipations in Potter Cove. Bed shear stress due to waves is also calculated to provide a general insight on the bed sediment erosion characteristics in Potter Cove.A nesting approach has been implemented from an oceanic scale to a high-resolution coastal scale around Potter Cove. The results of the simulations were compared with buoy observations obtained from the National Data Buoy Center, the WAVEWATCH III model results, and GlobWave altimeter data. The quality of the modelling results has been assessed using two statistical parameters, namely the Willmott's index of agreement D and the bias index. Under various wave conditions, the significant wave heights at the inner cove were found to be about 40-50 % smaller than the ones near the mouth of Potter Cove. The wave power in Potter Cove is generally low. The spatial distributions of the wave-induced bed shear stress and active energy dissipation were found to be following the pattern of the bathymetry, and waves were identified as a potential major driving force for bed sediment erosion in Potter Cove, especially in shallow water regions. This study also gives some results on global ocean applications of SWAN.

  10. Fluid Flow Characteristic Simulation of the Original TRIGA 2000 Reactor Design Using Computational Fluid Dynamics Code

    NASA Astrophysics Data System (ADS)

    Fiantini, Rosalina; Umar, Efrizon

    2010-06-01

    Common energy crisis has modified the national energy policy which is in the beginning based on natural resources becoming based on technology, therefore the capability to understanding the basic and applied science is needed to supporting those policies. National energy policy which aims at new energy exploitation, such as nuclear energy is including many efforts to increase the safety reactor core condition and optimize the related aspects and the ability to build new research reactor with properly design. The previous analysis of the modification TRIGA 2000 Reactor design indicates that forced convection of the primary coolant system put on an effect to the flow characteristic in the reactor core, but relatively insignificant effect to the flow velocity in the reactor core. In this analysis, the lid of reactor core is closed. However the forced convection effect is still presented. This analysis shows the fluid flow velocity vector in the model area without exception. Result of this analysis indicates that in the original design of TRIGA 2000 reactor, there is still forced convection effects occur but less than in the modified TRIGA 2000 design.

  11. Detection of biological objects using dynamic characteristics of double-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Patel, Ajay M.; Joshi, Anand Y.

    2015-08-01

    This study explores double-walled carbon nanotubes as the sensing devices for biological objects including viruses and bacteria. The biological objects studied include alanine with amino terminal residue, deoxyadenosine with free residue, Coronaviridae and Bartonella bacilliformis. An expression has been articulated to identify the mass of biological objects from the shift of frequency. Sensitivity of the sensor has been calculated when subjected to such biological objects. Molecular structural mechanics approach has been used for investigating the vibrational responses of zigzag and armchair double-walled carbon nanotube-based nano biosensors. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. Based on the sensitivity and the frequency shift it can be concluded that cantilever zigzag DWCNTs are better candidates for detecting the biological objects.

  12. Influence of bacterial dynamics upon the final characteristics of model Portuguese traditional cheeses.

    PubMed

    Pereira, Cláudia I; Graça, João A; Ogando, Natacha S; Gomes, Ana M P; Malcata, F Xavier

    2010-05-01

    The microbiological profile in raw milk cheeses is typically characterized by a multitude of microbial groups, with interactions among them throughout ripening that are not fully understood to date. Incidence of undesired microorganisms in raw cheesemaking milk, as is the case of either spoilage or even pathogenic ones, is a common trait in Portuguese traditional cheeses. Hence, they will likely contribute to the physicochemical changes occurring therein and, consequently, to the characteristics of the final product. In order to gain insight into their role, model cheese systems, manufactured as far as possible according to artisanal practices (except that the initial microbial load and biodiversity were controlled), were experimentally tested. Single contaminants, or a consortium thereof, were inoculated at two levels in sterilized raw ewe's milk, and duly combined with inocula containing one or two lactic acid bacteria normally found in those traditional cheeses. The physicochemical composition, organic acid profile, and evolution of both protein breakdown and rheology were monitored throughout a 60 d-ripening period. Modifications brought about within the cheese matrix as a result of microbial metabolism, especially those arising from the interaction between lactic acid bacteria and unwanted microorganisms, included the enhanced release of peptides and free amino acids, which in turn led to higher viscoelastic moduli. The final model cheeses could be well discriminated, based on the impact of the various inocula considered upon the levels of organic acids. Conversely, proteolysis and viscoelastic properties appeared to be essentially independent of the initial microflora.

  13. Fluid Flow Characteristic Simulation of the Original TRIGA 2000 Reactor Design Using Computational Fluid Dynamics Code

    SciTech Connect

    Fiantini, Rosalina; Umar, Efrizon

    2010-06-22

    Common energy crisis has modified the national energy policy which is in the beginning based on natural resources becoming based on technology, therefore the capability to understanding the basic and applied science is needed to supporting those policies. National energy policy which aims at new energy exploitation, such as nuclear energy is including many efforts to increase the safety reactor core condition and optimize the related aspects and the ability to build new research reactor with properly design. The previous analysis of the modification TRIGA 2000 Reactor design indicates that forced convection of the primary coolant system put on an effect to the flow characteristic in the reactor core, but relatively insignificant effect to the flow velocity in the reactor core. In this analysis, the lid of reactor core is closed. However the forced convection effect is still presented. This analysis shows the fluid flow velocity vector in the model area without exception. Result of this analysis indicates that in the original design of TRIGA 2000 reactor, there is still forced convection effects occur but less than in the modified TRIGA 2000 design.

  14. H-mode Characteristics and ELM Dynamics at Near-Unity Aspect Ratio

    NASA Astrophysics Data System (ADS)

    Thome, K. E.; Bodner, G. M.; Bongard, M. W.; Burke, M. G.; Fonck, R. J.; Schlossberg, D. J.

    2014-10-01

    Ohmic H-mode is achieved at near-unity aspect ratio in the Pegasus Toroidal Experiment through the use of high-field-side fueling in both limited and diverted geometries. This regime is characterized by: increased edge rotation shear; increased central heating; and measured energy confinement consistent with the ITER98pb(y,2) scaling. In limited plasmas the power threshold is ~ 10 × higher than predicted by the high- A empirical tokamak scaling for nG = 0 . 1- 0 . 6 . No significant reduction in the power threshold has been observed in favorable ∇B SN plasma when compared to limited plasmas. Two classes of ELMs have been identified to date by their proximity to the power threshold and measured n spectra. Small, Type III-like ELMs are present at input power POH ~Pth and have n <= 4 . At POH >>Pth , they transition to large, Type-I-like ELMs with intermediate 5 < n < 15. These general mode numbers are opposite those seen at large A and reflect the increased peeling drive present at low A . The unique operating characteristics available at A ~ 1 in Pegasus allow long-sought measurements of the time evolution of the Jedge (R) pedestal collapse during an ELM event. They show a complex, multimodal pedestal collapse and the subsequent ejection of a current-carrying filament. Work supported by US DOE Grant DE-FG02-96ER54375.

  15. Snag characteristics and dynamics following natural and artificially induced mortality in a managed loblolly pine forest

    SciTech Connect

    Zarnoch, Stanley J.; Vukovich, Mark A.; Kilgo, John C.; Blake, John I.

    2013-09-01

    A 14-year study of snag characteristics was established in 41- to 44-year old loblolly pine (Pinus taeda L.) stands in southeastern USA. During the initial 5.5 years, no stand manipulation or unusually high-mortality events occurred. Afterwards, three treatments were applied consisting of trees thinned and removed, trees felled and not removed, and artificial creation of snags produced by girdling and herbicide injection. The thinned treatments were designed to maintain the same live canopy density as the snag-created treatment, disregarding snags that remained standing.We monitored snag height, diameter, density, volume, and bark percentage; the number of cavities was monitored in natural snags only. During the first 5.5 years, recruitment and loss rates were stable, resulting in a stable snag population. Large snags (≥25 cm diameter) were common, but subcanopy small snags (10 to <25 cm diameter) dominated numerically. Large natural snags survived (90% quantile) significantly longer (6.0–9.4 years) than smaller snags (4.4–6.9 years). Large artificial snags persisted the longest (11.8 years). Cavities in natural snags developed within 3 years following tree death. The mean number of cavities per snag was five times greater in large versus small snags and large snags were more likely to have multiple cavities, emphasizing the importance of mature pine stands for cavity-dependent wildlife species.

  16. Characteristic footprints of an exceptional point in the dynamics of Li dimer under a laser field

    SciTech Connect

    Haritan, Idan; Amitay, Zohar; Gilary, Ido; Moiseyev, Nimrod

    2015-10-21

    Non-hermitian quantum mechanics is a formalism that excels in describing time-dependent states such as resonances. As one, it opens up a window to explore new and undiscovered phenomena. Under this formalism coalescence of two eigenstates and a deficient spectrum are a possible situation. These situations are unique and can occur solely in specific conditions known as Exceptional Points (EPs). An EP holds unique characteristics. One of which is a switch-like behavior: upon adiabatically changing the conditions in a closed loop around the EP, the population of one resonance can be transferred completely to another resonance. The phenomenon was not experimentally observed in an atomic or molecular system so far, although experiments involving nonlinear PT symmetry optics and microwave cavities have already indicated its existence. In this work, we demonstrate and confirm that the switch-like behavior exists in the spectrum of a lithium dimer taking into account both the rotations and the vibrations of the system. Moreover, a footprint of the EP is also shown to exist in the photo-association process of the lithium dimer. In this process, the EP’s resonances serve as the mean to associate two free lithium atoms into a dimer. Based on this, we suggest a corresponding experiment to demonstrate for the first time the EP phenomenon in a molecular system.

  17. Research of dynamical Characteristics of slow deformation Waves as Massif Responses on Explosions

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg; Shipeev, Oleg

    2013-04-01

    The research of massif state with use of approaches of open system theory [1-3] was developed for investigation the criterions of dissipation regimes for real rock massifs, which are under heavy man-caused influence. For realization of that research we used the data of seismic catalogue of Tashtagol mine. As a result of the analyze of that data we defined character morphology of phase trajectories of massif response, which was locally in time in a stable state: on the phase plane with coordinates released by the massif during the dynamic event energy E and lg(dE/dt) there is a local area as a ball of twisted trajectories and some not great bursts from that ball, which are not greater than 105 joules. In some time intervals that burst can be larger, than 105 joules, achieving 106 joules and yet 109 joules. [3]. Evidently there are two reciprocal depend processes: the energy accumulation in the attracted phase trajectories area and resonance fault of the accumulated energy. But after the fault the system returns again to the same attracted phase trajectories area. For analyzing of the thin structure of the chaotic area we decided to add the method of processing of the seismic monitoring data by new parameters. We shall consider each point of explosion as a source of seismic or deformation waves. Using the kinematic approach of seismic information processing we shall each point of the massif response use as a time point of the first arrival of the deformation wave for calculation of the wave velocity, because additionally we know the coordinates of the fixed response and the coordinates of explosion. The use of additional parameter-velocity of slow deformation wave propagation allowed us with use method of phase diagrams identify their hierarchic structure, which allow us to use that information for modeling and interpretation the propagation seismic and deformation waves in hierarchic structures. It is researched with use of that suggested processing method the thin

  18. Dynamic Proteomic Characteristics and Network Integration Revealing Key Proteins for Two Kernel Tissue Developments in Popcorn

    PubMed Central

    Du, Chunguang; Xiong, Wenwei; Chen, Xinjian; Deng, Fei; Ma, Zhiyan; Qiao, Dahe; Hu, Chunhui; Ren, Yangliu; Li, Yuling

    2015-01-01

    The formation and development of maize kernel is a complex dynamic physiological and biochemical process that involves the temporal and spatial expression of many proteins and the regulation of metabolic pathways. In this study, the protein profiles of the endosperm and pericarp at three important developmental stages were analyzed by isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with LC-MS/MS in popcorn inbred N04. Comparative quantitative proteomic analyses among developmental stages and between tissues were performed, and the protein networks were integrated. A total of 6,876 proteins were identified, of which 1,396 were nonredundant. Specific proteins and different expression patterns were observed across developmental stages and tissues. The functional annotation of the identified proteins revealed the importance of metabolic and cellular processes, and binding and catalytic activities for the development of the tissues. The whole, endosperm-specific and pericarp-specific protein networks integrated 125, 9 and 77 proteins, respectively, which were involved in 54 KEGG pathways and reflected their complex metabolic interactions. Confirmation for the iTRAQ endosperm proteins by two-dimensional gel electrophoresis showed that 44.44% proteins were commonly found. However, the concordance between mRNA level and the protein abundance varied across different proteins, stages, tissues and inbred lines, according to the gene cloning and expression analyses of four relevant proteins with important functions and different expression levels. But the result by western blot showed their same expression tendency for the four proteins as by iTRAQ. These results could provide new insights into the developmental mechanisms of endosperm and pericarp, and grain formation in maize. PMID:26587848

  19. Characteristics of Dynamic Magnetic Resonance Image Enhancement in Prolactinomas Resistant to Dopamine Agonist Therapy

    PubMed Central

    Guo, Qinghua; Erickson, Bradley J.; Chang, Alice Y.; Erickson, Dana

    2015-01-01

    Objective To determine whether dynamic magnetic resonance imaging (dMRI) enhancement parameters could predict dopamine agonist (DA) resistance in prolactinomas. Methods We retrospectively identified patients with prolactinomas who were treated with DA and underwent dMRI from 2001 through 2012 at Mayo Clinic (Rochester, Minnesota). Intensities of the adenoma and pituitary gland were measured by drawing regions of interest on the images. Enhancement ratio, enhancement peak, prepeak slope (PPS), and enhancement time were compared between DA-resistant and DA-responsive groups, between DA-treated and DA-naïve groups, and between the first and follow-up dMRIs. Results We identified 49 patients with prolactinomas, with 6 (12.2%) that showed DA resistance. Thirty-seven patients (75.5%) underwent dMRI while receiving treatment, 12 (25.5%) underwent dMRI before starting therapy, and 10 (20.4%) had follow-up dMRI after DA therapy. The PPS of the tumor was higher in the treatment-resistant group vs the responsive group (mean [SD], 4.42 [3.19] vs 2.65 [1.59]; P=.03), whereas no difference was noted in the pituitary gland (5.79 [2.21] vs 4.06 [2.48]; P=.11). Logistic regression analysis indicated that tumor PPS was associated with DA resistance (odds ratio, 1.71; 95% CI, 1.07-3.27; P=.02). Conclusions dMRI with PPS analysis potentially can be used early in the treatment course to evaluate DA resistance in pituitary prolactinomas. PMID:25551412

  20. Extracting source characteristics and dynamics of the August 2010 Mount Meager landslide from broadband seismograms

    NASA Astrophysics Data System (ADS)

    Allstadt, Kate

    2013-09-01

    methods can substantially improve the characterization of the dynamics of large and rapid landslides. Such landslides often generate strong long-period seismic waves due to the large-scale acceleration of the entire landslide mass, which, according to theory, can be approximated as a single-force mechanism at long wavelengths. I apply this theory and invert the long-period seismic waves generated by the 48.5 Mm3 August 2010 Mount Meager rockslide-debris flow in British Columbia. Using data from five broadband seismic stations 70 to 276 km from the source, I obtain a time series of forces the landslide exerted on the Earth, with peak forces of 1.0 × 1011 N. The direction and amplitude of the forces can be used to determine the timing and occurrence of events and subevents. Using this result, in combination with other field and geospatial evidence, I calculate an average horizontal acceleration of the rockslide of 0.39 m/s2 and an average apparent coefficient of basal friction of 0.38 ± 0.02, which suggests elevated basal fluid pressures. The direction and timing of the strongest forces are consistent with the centripetal acceleration of the debris flow around corners in its path. I use this correlation to estimate speeds, which peak at 92 m/s. This study demonstrates that the time series recording of forces exerted by a large and rapid landslide derived remotely from seismic records can be used to tie post-slide evidence to what actually occurred during the event and can serve to validate numerical models and theoretical methods.

  1. Dynamic Proteomic Characteristics and Network Integration Revealing Key Proteins for Two Kernel Tissue Developments in Popcorn.

    PubMed

    Dong, Yongbin; Wang, Qilei; Zhang, Long; Du, Chunguang; Xiong, Wenwei; Chen, Xinjian; Deng, Fei; Ma, Zhiyan; Qiao, Dahe; Hu, Chunhui; Ren, Yangliu; Li, Yuling

    2015-01-01

    The formation and development of maize kernel is a complex dynamic physiological and biochemical process that involves the temporal and spatial expression of many proteins and the regulation of metabolic pathways. In this study, the protein profiles of the endosperm and pericarp at three important developmental stages were analyzed by isobaric tags for relative and absolute quantification (iTRAQ) labeling coupled with LC-MS/MS in popcorn inbred N04. Comparative quantitative proteomic analyses among developmental stages and between tissues were performed, and the protein networks were integrated. A total of 6,876 proteins were identified, of which 1,396 were nonredundant. Specific proteins and different expression patterns were observed across developmental stages and tissues. The functional annotation of the identified proteins revealed the importance of metabolic and cellular processes, and binding and catalytic activities for the development of the tissues. The whole, endosperm-specific and pericarp-specific protein networks integrated 125, 9 and 77 proteins, respectively, which were involved in 54 KEGG pathways and reflected their complex metabolic interactions. Confirmation for the iTRAQ endosperm proteins by two-dimensional gel electrophoresis showed that 44.44% proteins were commonly found. However, the concordance between mRNA level and the protein abundance varied across different proteins, stages, tissues and inbred lines, according to the gene cloning and expression analyses of four relevant proteins with important functions and different expression levels. But the result by western blot showed their same expression tendency for the four proteins as by iTRAQ. These results could provide new insights into the developmental mechanisms of endosperm and pericarp, and grain formation in maize. PMID:26587848

  2. Molecular dynamics investigation of hexagonal boron nitride sputtering and sputtered particle characteristics

    NASA Astrophysics Data System (ADS)

    Smith, Brandon D.; Boyd, Iain D.

    2016-08-01

    The sputtering of hexagonal boron nitride (h-BN) by impacts of energetic xenon ions is investigated using a molecular dynamics (MD) model. The model is implemented within an open-source MD framework that utilizes graphics processing units to accelerate its calculations, allowing the sputtering process to be studied in much greater detail than has been feasible in the past. Integrated sputter yields are computed over a range of ion energies from 20 eV to 300 eV, and incidence angles from 0° to 75°. Sputtering of boron is shown to occur at energies as low as 40 eV at normal incidence, and sputtering of nitrogen at as low as 30 eV at normal incidence, suggesting a threshold energy between 20 eV and 40 eV. The sputter yields at 0° incidence are compared to existing experimental data and are shown to agree well over the range of ion energies investigated. The semi-empirical Bohdansky curve and an empirical exponential function are fit to the data at normal incidence, and the threshold energy for sputtering is calculated from the Bohdansky curve fit as 35 ± 2 eV. These results are shown to compare well with experimental observations that the threshold energy lies between 20 eV and 40 eV. It is demonstrated that h-BN sputters predominantly as atomic boron and diatomic nitrogen, and the velocity distribution function (VDF) of sputtered boron atoms is investigated. The calculated VDFs are found to reproduce the Sigmund-Thompson distribution predicted by Sigmund's linear cascade theory of sputtering. The average surface binding energy computed from Sigmund-Thompson curve fits is found to be 4.5 eV for ion energies of 100 eV and greater. This compares well to the value of 4.8 eV determined from independent experiments.

  3. Dynamic response characteristics of high temperature superconducting maglev systems: Comparison between Halbach-type and normal permanent magnet guideways

    NASA Astrophysics Data System (ADS)

    Wang, B.; Zheng, J.; Che, T.; Zheng, B. T.; Si, S. S.; Deng, Z. G.

    2015-12-01

    The permanent magnet guideway (PMG) is very important for the performance of the high temperature superconducting (HTS) system in terms of electromagnetic force and operational stability. The dynamic response characteristics of a HTS maglev model levitating on two types of PMG, which are the normal PMG with iron flux concentration and Halbach-type PMG, were investigated by experiments. The dynamic signals for different field-cooling heights (FCHs) and loading/unloading processes were acquired and analyzed by a vibration analyzer and laser displacement sensors. The resonant frequency, stiffness and levitation height of the model were discussed. It was found that the maglev model on the Halbach-type PMG has higher resonant frequency and higher vertical stiffness compared with the normal PMG. However, the low lateral stiffness of the model on the Halbach-type PMG indicates poor lateral stability. Besides, the Halbach-type PMG has better loading capacity than the normal PMG. These results are helpful to design a suitable PMG for the HTS system in practical applications.

  4. The dynamics of Hawaiian-style eruptions: a century of study: Chapter 8 in Characteristics of Hawaiian volcanoes

    USGS Publications Warehouse

    Mangan, Margaret T.; Cashman, Katharine V.; Swanson, Donald A.; Poland, Michael P.; Takahashi, T. Jane; Landowski, Claire M.

    2014-01-01

    This chapter, prepared in celebration of the Hawaiian Volcano Observatoryʼs centennial, provides a historical lens through which to view modern paradigms of Hawaiian-style eruption dynamics. The models presented here draw heavily from observations, monitoring, and experiments conducted on Kīlauea Volcano, which, as the site of frequent and accessible eruptions, has attracted scientists from around the globe. Long-lived eruptions in particular—Halema‘uma‘u 1907–24, Kīlauea Iki 1959, Mauna Ulu 1969–74, Pu‘u ‘Ō‘ō-Kupaianaha 1983–present, and Halema‘uma‘u 2008–present—have offered incomparable opportunities to conceptualize and constrain theoretical models with multidisciplinary data and to field-test model results. The central theme in our retrospective is the interplay of magmatic gas and near-liquidus basaltic melt. A century of study has shown that gas exsolution facilitates basaltic dike propagation; volatile solubility and vesiculation kinetics influence magma-rise rates and fragmentation depths; bubble interactions and gas-melt decoupling modulate magma rheology, eruption intensity, and plume dynamics; and pyroclast outgassing controls characteristics of eruption deposits. Looking to the future, we anticipate research leading to a better understanding of how eruptive activity is influenced by volatiles, including the physics of mixed CO2-H2O degassing, gas segregation in nonuniform conduits, and vaporization of external H2O during magma ascent.

  5. Evaluating the impact of built environment characteristics on urban boundary layer dynamics using an advanced stochastic approach

    NASA Astrophysics Data System (ADS)

    Song, Jiyun; Wang, Zhi-Hua

    2016-05-01

    Urban land-atmosphere interactions can be captured by numerical modeling framework with coupled land surface and atmospheric processes, while the model performance depends largely on accurate input parameters. In this study, we use an advanced stochastic approach to quantify parameter uncertainty and model sensitivity of a coupled numerical framework for urban land-atmosphere interactions. It is found that the development of urban boundary layer is highly sensitive to surface characteristics of built terrains. Changes of both urban land use and geometry impose significant impact on the overlying urban boundary layer dynamics through modification on bottom boundary conditions, i.e., by altering surface energy partitioning and surface aerodynamic resistance, respectively. Hydrothermal properties of conventional and green roofs have different impacts on atmospheric dynamics due to different surface energy partitioning mechanisms. Urban geometry (represented by the canyon aspect ratio), however, has a significant nonlinear impact on boundary layer structure and temperature. Besides, managing rooftop roughness provides an alternative option to change the boundary layer thermal state through modification of the vertical turbulent transport. The sensitivity analysis deepens our insight into the fundamental physics of urban land-atmosphere interactions and provides useful guidance for urban planning under challenges of changing climate and continuous global urbanization.

  6. Dynamics of ecological and biological characteristics of soddy-podzolic soils under long-term oil pollution

    NASA Astrophysics Data System (ADS)

    Petrov, A. M.; Versioning, A. A.; Karimullin, L. K.; Akaikin, D. V.; Tarasov, O. Yu.

    2016-07-01

    The dynamics of respiratory and enzyme activities and toxicological properties of loamy-sandy and loamy soddy-podzolic soils (Retisols) under the long-term influence of oil pollution were studied. The concentrations of the pollutant, at which the activity (the ability of self-purification) of the indigenous soil microflora is preserved, were determined. The dynamics of the decrease of oil product content and the time of elimination of the toxic effects on higher plants at the initial pollutant contents were revealed. The parameters of the respiratory and enzyme activities in the course of the 365-day experiment showed that the microbial community of the loamy-sandy soil was more sensitive to oil pollution. The phytotoxic characteristics of the oil-containing loamy-sandy and loamy soils did not correlate with their respiratory and enzyme activities. This fact testifies to some differences in the mechanisms of their influence on living organisms with different organizational levels and to the necessity of taking into account a complex of parameters when assessing the state of the soils under the long-term effects of oil and its products.

  7. Evaluation of the membrane permeability (PAMPA and skin) of benzimidazoles with potential cannabinoid activity and their relation with the Biopharmaceutics Classification System (BCS).

    PubMed

    Alvarez-Figueroa, M Javiera; Pessoa-Mahana, C David; Palavecino-González, M Elisa; Mella-Raipán, Jaime; Espinosa-Bustos, Cristián; Lagos-Muñoz, Manuel E

    2011-06-01

    The permeability of five benzimidazole derivates with potential cannabinoid activity was determined in two models of membranes, parallel artificial membrane permeability assay (PAMPA) and skin, in order to study the relationship of the physicochemical properties of the molecules and characteristics of the membranes with the permeability defined by the Biopharmaceutics Classification System. It was established that the PAMPA intestinal absorption method is a good predictor for classifying these molecules as very permeable, independent of their thermodynamic solubility, if and only if these have a Log P(oct) value <3.0. In contrast, transdermal permeability is conditioned on the solubility of the molecule so that it can only serve as a model for classifying the permeability of molecules that possess high solubility (class I: high solubility, high permeability; class III: high solubility, low permeability).

  8. Development and use of an apparatus to measure the dynamic surface properties of coal-water slurry fuels for applications to atomization characteristics

    SciTech Connect

    Kihm, K.D.

    1993-01-31

    The Texas A M University (TAMU) has been awarded a DOE contract to study dynamic properties and atomization characteristics of coal-water slurry (CWS) fuels. Additives are essential for better mixing and stable suspension of coal powders and these additives change CWS properties. Dynamic properties will have major effects on CWS fuel atomization, which constitutes highly dynamic processes, and will determine the combustion as well as the pollutant formation behaviors. The dynamic surface tension of CWS fuels can be much higher than the corresponding static surface tension. Experimental study of correlating the atomization characteristics and dynamic properties of CWS fuels will be performed during the contract period. The research projects consists of five tasks. Task 1 selects appropriate additives and surfactants for CWS fuels by measuring the stabilizing characteristics and critical micelle concentrations (CMC). Task 2 implements the dynamic surface tensiometer operating based on the formation of maximum bubble pressure. Task 3 measures dynamic properties of CWS fuels as functions of bubble frequency while the fuel parameters are varied. The fuel parameters include coal loading, type of stabilizer and type of surfactant. Task 4 will devise a CWS fuel spray system and Task 5 will measure the spray droplet sizes using a laser diffraction technique.

  9. Spatio-temporal dynamics and synoptic characteristics of wet and drought extremes in Northern Eurasia

    NASA Astrophysics Data System (ADS)

    Utkuzova, Dilyara; Khan, Valentina

    2015-04-01

    Synoptical-statistical analysis has been conducted using SPI index calculated for 478 stations with records from 1966 through 2013. Different parameters of SPI frequency distribution and long-term tendencies were calculated as well as spatial characteristics indicating drought and wetness propagation. Results of analysis demonstrate that during last years there is a tendency of increasing of the intensity of draught and wetness extremes over Russia. There are fewer droughts in the northern regions. The drought propagation for the European territory of Russia is decreasing in June and August, and increasing in July. The situation is opposite for the wetness tendencies. For the Asian territory of Russia, the drought propagation is significantly increasing in July along with decreasing wetness trend. Synoptic conditions favorable for the formation of wet and drought extremes were identified by comparing synoptic charts with the spatial patterns of SPI. For synoptic analysis, episodes of extremely wet (6 episodes for the APR and 7 episodes for the EPR) and drought (6 episodes for the APR and 6 for the EPR) events were classified using A. Katz' typology of weather regimes. For European part of Russia, extreme DROUGHT events are linked to the weather type named "MIXED", for Asian part of Russia - the type "CENTRAL". For European part of Russia, extreme WET events associated with "CENTRAL" type. There is a displacement of the planetary frontal zone into southward direction approximately for 5-25 degrees relatively to normal climatological position during WET extreme events linked to «EASTERN» classification type. Intercomparison of SPI calculated on the base of NOAA NCEP CPC CAMS for the same period and with the resolution 0,5 degree, month precipitation data, Era-Interim Daily fields archive for the period 1979-2014 with the resolution 0,5 degree reanalysis and observational precipitation data was done. The results of comparative analysis has been discussed.

  10. Acid tolerance, proton permeabilities, and membrane ATPases of oral streptococci.

    PubMed Central

    Bender, G R; Sutton, S V; Marquis, R E

    1986-01-01

    Differences in acid tolerance among representative oral streptococci were found to be related more closely to the dynamic permeabilities of the bacteria to protons than to differences in the sensitivities of cell membranes to gross damage caused by environmental acidification. For Streptococcus mutans GS-5, Streptococcus sanguis NCTC 10904, and Streptococcus salivarius ATCC 13419, gross membrane damage, indicated by the release of magnesium from whole cells, occurred at pH values below about 4 and was rapid and extensive at pH values of about 3 or less. A more aciduric, lactic acid bacterium, Lactobacillus casei ATCC 4646, was more resistant to environmental acidification, and gross membrane damage was evident only at pH values below 3. Assessments of the movements of protons into S. mutans cells after an acid pulse at various pH values indicated that permeability to protons was minimal at a pH value of about 5, at which the average half time for pH equilibration across the cell membrane was about 12 min. The corresponding values for the less aciduric organism S. sanguis were pH 7 and 8.2 min, and the values for the intermediate organism S. salivarius were pH 6 and 6.6 min. The ATPase inhibitor dicyclohexylcarbodiimide acted to increase markedly the permeability of each organism to protons, and this action indicated that permeability involved not only the passive inflow of protons but also active outflow through the proton-translocating membrane ATPase. Membranes were isolated from each of the bacteria, and pH profiles for ATPase activities indicated pH optima of about 7.5, 7.0, 6.0, and 5.0 for S. sanguis, S. salivarius, S. mutans, and L. casei, respectively. Thus, the pH profiles for the enzymes reflected the acid tolerances of the bacteria and the permeabilities of whole cells to protons. PMID:3015800

  11. Role of different biodegradable polymers on the permeability of ciprofloxacin

    PubMed Central

    Chakraborti, Chandra Kanti; Sahoo, Subhashree; Behera, Pradipta Kumar

    2014-01-01

    Since permeability across biological membranes is a key factor in the absorption and distribution of drugs, drug permeation characteristics of three oral suspensions of ciprofloxacin were designed and compared. The three suspensions of ciprofloxacin were prepared by taking biodegradable polymers such as carbopol 934, carbopol 940, and hydroxypropyl methylcellulose (HPMC). The permeability study was performed by using a Franz diffusion cell through both synthetic cellulose acetate membrane and excised goat gastrointestinal membranes in acidic as well as alkaline pH. To know the permeability of drug from control/formulations through different membranes in acidic/alkaline pH, cumulative percentage drug permeation, apparent permeability (Papp), flux, and enhancement ratio (ER) were calculated. Considering Papp and flux values of all formulations, it is evident that formulation containing HPMC was the most beneficial for improving permeation and diffusivity of ciprofloxacin even after 16 h. Hence, this preparation may be considered as the most suitable formulation to obtain prolonged release action of the drug. The ER values of all formulations, through excised goat intestinal mucosal membrane in alkaline pH, were higher than those formulations through goat stomach mucosal membrane in acidic pH. Enhancement ratio values of those formulations indicate that the permeability of the drug was more enhanced by the polymers in the intestinal part, leading to more bioavailability and prolonged action in that portion of the gastrointestinal tract. It may also be concluded from our results that HPMC containing formulation was the best suspension, which may show effective controlled release action. Even carbopol containing formulations might also produce controlled release action. PMID:25126536

  12. Influence of fiber packing structure on permeability

    NASA Technical Reports Server (NTRS)

    Cai, Zhong; Berdichevsky, Alexander L.

    1993-01-01

    The study on the permeability of an aligned fiber bundle is the key building block in modeling the permeability of advanced woven and braided preforms. Available results on the permeability of fiber bundles in the literature show that a substantial difference exists between numerical and analytical calculations on idealized fiber packing structures, such as square and hexagonal packing, and experimental measurements on practical fiber bundles. The present study focuses on the variation of the permeability of a fiber bundle under practical process conditions. Fiber bundles are considered as containing openings and fiber clusters within the bundle. Numerical simulations on the influence of various openings on the permeability were conducted. Idealized packing structures are used, but with introduced openings distributed in different patterns. Both longitudinal and transverse flow are considered. The results show that openings within the fiber bundle have substantial effect on the permeability. In the longitudinal flow case, the openings become the dominant flow path. In the transverse flow case, the fiber clusters reduce the gap sizes among fibers. Therefore the permeability is greatly influenced by these openings and clusters, respectively. In addition to the porosity or fiber volume fraction, which is commonly used in the permeability expression, another fiber bundle status parameter, the ultimate fiber volume fraction, is introduced to capture the disturbance within a fiber bundle.

  13. A method of determination of permeability

    SciTech Connect

    Kuznetsov, S.V.; Trofimov, V.A.

    2007-11-15

    A method is proposed for determining permeability of coals under conditions of steady-state deformation and stationary filtration mode by employing a reference core made of gas-non-sorbing material with a known permeability. The approach has been developed to assess the time of transition to the stable filtration.

  14. Pressure sensitivity of low permeability sandstones

    USGS Publications Warehouse

    Kilmer, N.H.; Morrow, N.R.; Pitman, J.K.

    1987-01-01

    Detailed core analysis has been carried out on 32 tight sandstones with permeabilities ranging over four orders of magnitude (0.0002 to 4.8 mD at 5000 psi confining pressure). Relationships between gas permeability and net confining pressure were measured for cycles of loading and unloading. For some samples, permeabilities were measured both along and across bedding planes. Large variations in stress sensitivity of permeability were observed from one sample to another. The ratio of permeability at a nominal confining pressure of 500 psi to that at 5000 psi was used to define a stress sensitivity ratio. For a given sample, confining pressure vs permeability followed a linear log-log relationship, the slope of which provided an index of pressure sensitivity. This index, as obtained for first unloading data, was used in testing relationships between stress sensitivity and other measured rock properties. Pressure sensitivity tended to increase with increase in carbonate content and depth, and with decrease in porosity, permeability and sodium feldspar. However, scatter in these relationships increased as permeability decreased. Tests for correlations between pressure sensitivity and various linear combinations of variables are reported. Details of pore structure related to diagenetic changes appears to be of much greater significance to pressure sensitivity than mineral composition. ?? 1987.

  15. Effect of Dead Algae on Soil Permeability

    SciTech Connect

    Harvey, R.S.

    2003-02-21

    Since existing basins support heavy growths of unicellular green algae which may be killed by temperature variation or by inadvertent pH changes in waste and then deposited on the basin floor, information on the effects of dead algae on soil permeability was needed. This study was designed to show the effects of successive algal kills on the permeability of laboratory soil columns.

  16. Spontaneous Imbibition in Low Permeability Medium, SUPRI TR-114

    SciTech Connect

    Kovscek, Anthony R.; Schembre, Josephina

    1999-08-09

    A systematic experimental investigation of capillary pressure characteristics and fluid flow in diatomite was begun. Using an X-ray CT scanner and a specially constructed imbibition cell, we study spontaneous water imbibition processes in diatomite and, for reference, Berea sandstone and chalk. The mass of water imbibed as a function of time is also measured. Imbibition is restricted to concurrent flow. Despite a marked difference in rock properties such as permeability and porosity, we find similar trends in saturation profiles and weight gain versus time functions. Imbibition in diatomote is relatively rapid when initial water saturation is low due to large capillary forces. Using a non-linear regression analysis together with the experimental data, the capillary pressure and water relative permeability curves are determined for the diatomite in the water-air system. The results given for displacement profiles by numerical simulation match the experimental results.

  17. Drainage hydraulics of permeable friction courses

    NASA Astrophysics Data System (ADS)

    Charbeneau, Randall J.; Barrett, Michael E.

    2008-04-01

    This paper describes solutions to the hydraulic equations that govern flow in permeable friction courses (PFC). PFC is a layer of porous asphalt approximately 50 mm thick that is placed as an overlay on top of an existing conventional concrete or asphalt road surface to help control splash and hydroplaning, reduce noise, and enhance quality of storm water runoff. The primary objective of this manuscript is to present an analytical system of equations that can be used in design and analysis of PFC systems. The primary assumptions used in this analysis are that the flow can be modeled as one-dimensional, steady state Darcy-type flow and that slopes are sufficiently small so that the Dupuit-Forchheimer assumptions apply. Solutions are derived for cases where storm water drainage is confined to the PFC bed and for conditions where the PFC drainage capacity is exceeded and ponded sheet flow occurs across the pavement surface. The mathematical solutions provide the drainage characteristics (depth and residence time) as a function of rainfall intensity, PFC hydraulic conductivity, pavement slope, and maximum drainage path length.

  18. Compact rock material gas permeability properties

    NASA Astrophysics Data System (ADS)

    Wang, Huanling; Xu, Weiya; Zuo, Jing

    2014-09-01

    Natural compact rocks, such as sandstone, granite, and rock salt, are the main materials and geological environment for storing underground oil, gas, CO2, shale gas, and radioactive waste because they have extremely low permeabilities and high mechanical strengths. Using the inert gas argon as the fluid medium, the stress-dependent permeability and porosity of monzonitic granite and granite gneiss from an underground oil storage depot were measured using a permeability and porosity measurement system. Based on the test results, models for describing the relationships among the permeability, porosity, and confining pressure of rock specimens were analyzed and are discussed. A power law is suggested to describe the relationship between the stress-dependent porosity and permeability; for the monzonitic granite and granite gneiss (for monzonitic granite (A-2), the initial porosity is approximately 4.05%, and the permeability is approximately 10-19 m2; for the granite gneiss (B-2), the initial porosity is approximately 7.09%, the permeability is approximately 10-17 m2; and the porosity-sensitivity exponents that link porosity and permeability are 0.98 and 3.11, respectively). Compared with moderate-porosity and high-porosity rocks, for which φ > 15%, low-porosity rock permeability has a relatively lower sensitivity to stress, but the porosity is more sensitive to stress, and different types of rocks show similar trends. From the test results, it can be inferred that the test rock specimens' permeability evolution is related to the relative particle movements and microcrack closure.

  19. Dynamic characteristics of a coastal area of lateral spreading using ambient noise time series - Anchor Bay, Malta

    NASA Astrophysics Data System (ADS)

    Galea, Pauline; D'Amico, Sebastiano; Farrugia, Daniela

    2013-04-01

    Anchor Bay and surrounding regions are located on the northwest coast of the island of Malta, Central Mediterranean. The area is characterized by a coastal cliff environment having an outcropping layer of hard coralline limestone (UCL) resting on a thick (up to 50m) layer of clays and marls (Blue Clay, BC). This configuration gives rise to a number of processes leading to coastal instability, in particular lateral spreading phenomena and rock falls. Previous and ongoing studies have identified both lateral spreading rates and vertical motions of up to 27mm per year (Mantovani et al, 2012). The area is an interesting natural laboratory as coastal detachment processes in a number of different stages can be identified and are easily accessible. We investigate the site dynamic characteristics of this study area by recording ambient noise time series (20 minutes long) at over 20 points, over an area of 0.07 km2, using a portable 3-component seismograph (Tromino ) The time series are processed to give both horizontal-to-vertical spectral ratio graphs (HVSR) as well as frequency-dependent polarisation analysis as proposed by Burjanek (2011, 2012). The HVSR graphs illustrate and quantify aspects of site resonance effects due both to underlying geology as well as to mechanical resonance of partly or wholly detached boulders or blocks. The polarization diagrams i