Science.gov

Sample records for dynamic permeability characteristics

  1. Dynamical instability in surface permeability characteristics of building sandstones in response to salt accumulation over time

    NASA Astrophysics Data System (ADS)

    McCabe, S.; McKinley, J. M.; Gomez-Heras, M.; Smith, B. J.

    2011-07-01

    This paper explores how the surface permeability of sandstone blocks changes over time in response to repeated salt weathering cycles. Surface permeability controls the amount of moisture and dissolved salt that can penetrate in and facilitate decay. Connected pores permit the movement of moisture (and hence soluble salts) into the stone interior, and where areas are more or less permeable soluble salts may migrate along preferred pathways at differential rates. Previous research has shown that salts can accumulate in the near-surface zone and lead to partial pore blocking which influences subsequent moisture ingress and causes rapid salt accumulation in the near-surface zone. Two parallel salt weathering simulations were carried out on blocks of Peakmoor Sandstone of different volumes. Blocks were removed from simulations after 2, 5, 10, 20 and 60 cycles. Permeability measurements were taken for these blocks at a resolution of 20 mm, providing a grid of 100 permeability values for each surface. The geostatistical technique of ordinary kriging was applied to the data to produce a smoothed interpolation of permeability for these surfaces, and hence improve understanding of the evolution of permeability over time in response to repeated salt weathering cycles. Results illustrate the different responses of the sandstone blocks of different volumes to repeated salt weathering cycles. In both cases, after an initial subtle decline in the permeability (reflecting pore blocking), the permeability starts to increase — reflected in a rise in mean, maximum and minimum values. However, between 10 and 20 cycles, there is a jump in the mean and range permeability of the group A block surfaces coinciding with the onset of meaningful debris release. After 60 cycles, the range of permeability in the group A block surface had increased markedly, suggesting the development of a secondary permeability. The concept of dynamic instability and divergent behaviour is applied at the

  2. Study of permeability characteristics of membranes

    NASA Technical Reports Server (NTRS)

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

    1971-01-01

    Pressure-permeation experiments were performed with the concentration-clamp cell. Streaming potentials and hydraulic permeabilities were measured for an AMF C-103 cation-exchange membrane bounded by 0.1 N NaCl solutions. The streaming potential calculated from the slope of the recorded potential differences versus the applied pressure, yields a value of 1.895 millivolt/dekabar. When comparison with other membranes of similar characteristics could be made, good agreement was found. The values of the hydraulic permeability varied somewhat with the applied pressure difference and are between 1.3 x 10 to the minus 8th power and 3.9 x 10 to the minus 8th power sq cm/dekabar-sec. The specific hydraulic permeabilities were also calculated and compared with data from the literature. Fair agreement was found. The diffusion coefficient of the chloride ion in the AMF C-103 membrane was calculated, using Fick's first law of diffusion based on ion concentrations calculated from the Donnan equilibrium concentration of Cl(-).

  3. 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.

  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. Physical and Permeability Characteristic of Recycle Glass-Kaolin Ceramic

    SciTech Connect

    Sahar, M. R.; Safwan, A. P; Noorhidayah, C. M.

    2010-07-07

    A series of Recycle Glass-Kaolin ceramic has successful been made by solid state reaction and their physical and permeability characteristic has been studied. Infrared spectroscopy has been used to characterize the effect of OH group in the sample. It is found that the bulk density is in the range of 1.785gcm{sup -3} to 2.2817gcm{sup -3} while the impact energy is 1.785gcm{sup -3} to 2.2817gcm{sup -3} depending on the cullet content. Meanwhile, the permeability coefficient is found to be 5.208x10{sup -4}cms{sup -1} to 1.812x10{sup -4}cms{sup -1} which is in the reducing trend. The IR Spectroscopy shows that the OH group decrease, the permeability decreases.

  6. Insulin permeability across an in vitro dynamic model of endothelium.

    PubMed

    Salvetti, Francesca; Cecchetti, Paolo; Janigro, Damir; Lucacchini, Antonio; Benzi, Luca; Martini, Claudia

    2002-04-01

    Endothelium insulin permeability was investigated using in vitro, dynamic culture of endothelial cells. Endothelial cells were cultured in a hollow fiber apparatus and continuously exposed to a flow. Transendothelial electrical resistance and permeability to [14C]sucrose and [14C]inulin were used to monitor the integrity of the endothelial monolayer. Under these experimental conditions, measurements of insulin permeability, investigated at increasing hormone concentrations, suggested that the predominant transendothelial insulin fluxes were attributable to bidirectional convective transport rather than to a saturable transport mechanism, in agreement with in vivo experiment results published earlier. Analytical determinations of insulin catabolism demonstrated a low percent of insulin degradation by the endothelium, leading to production of insulin metabolites qualitatively identical to those produced by human monocytes. The findings of this paper indicated that (a) insulin crosses the endothelial monolayer by paracellular "leak" and endothelial insulin receptors have a minor (if any) role in insulin transport; (b) degradation of the hormone by BAEC is minimal; (c) the in vitro, dynamic culture of endothelial cells presented here should represent a valuable transport model system to study permeability mechanisms of insulin and many other drugs.

  7. Dynamic characterization of permeabilities and flows in microchannels.

    PubMed

    Castro, M; Bravo-Gutiérrez, M E; Hernández-Machado, A; Poiré, E Corvera

    2008-11-28

    We make an analytical study of the nonsteady flow of Newtonian fluids in microchannels. We consider the slip boundary condition at the solid walls with Navier hypothesis and calculate the dynamic permeability, which gives the system's response to dynamic pressure gradients. We find a scaling relation in the absence of slip that is broken in its presence. We discuss how this might be useful to experimentally determine--by means of microparticle image velocimetry technology--whether slip exists or not in a system, the value of the slip length, and the validity of Navier hypothesis in dynamic situations.

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

    NASA Astrophysics Data System (ADS)

    Adler, P.; Pazdniakou, A.

    2012-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Pazdniakou, A.; Adler, P. M.

    2011-12-01

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

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

    PubMed

    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. Published by Elsevier Inc.

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. 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...

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

    NASA Astrophysics Data System (ADS)

    Lee, M.; Keehm, Y.

    2013-12-01

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

  18. Role of crystal orientation on electrical tuning of dynamic permeability in strain-mediated multiferroic structures

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Ong, C. K.

    2017-06-01

    Multiferroic structures of FeCo/NiFe/[Pb(Mg1/3Nb2/3)O3]0.68-[PbTiO3]0.32 (PMN-PT) with three different crystal orientations of PMN-PT(0 1 1), PMN-PT(0 0 1) and PMN-PT(1 1 1) were fabricated by a sputtering deposition system. Their dynamic magnetic properties were characterized under various applied electrical fields. The sample with PMN-PT(0 1 1) orientation shows a large tuning of the permeability spectra while the ones with PMN-PT(0 0 1) and PMN-PT(1 1 1) orientations exhibit a moderate and little change in the permeability spectra, respectively. The result can be explained via the magnetoelectric effect by considering the role of the piezoelectric coefficients being highly dependent on the crystal orientation along which the PMN-PT is poled. This explanation is consistent with the static magnetic characteristics of the samples before and after poling.

  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. Quantifying Intracranial Plaque Permeability with Dynamic Contrast-Enhanced MRI: A Pilot Study

    PubMed Central

    Vakil, P.; Elmokadem, A.H.; Syed, F.H.; Cantrell, C.G.; Dehkordi, F.H.; Carroll, T.J.; Ansari, S.A.

    2016-01-01

    BACKGROUND AND PURPOSE Intracranial atherosclerotic disease plaque hyperintensity and/or gadolinium contrast enhancement have been studied as imaging biomarkers of acutely symptomatic ischemic presentations using single static MR imaging measurements. However, the value in modeling the dynamics of intracranial plaque permeability has yet to be evaluated. The purpose of this study was to use dynamic contrast-enhanced MR imaging to quantify the contrast permeability of intracranial atherosclerotic disease plaques in symptomatic patients and to compare these parameters against existing markers of plaque volatility using black-blood MR imaging pulse sequences. MATERIALS AND METHODS We performed a prospective study of contrast uptake dynamics in the major intracranial vessels proximal and immediately distal to the circle of Willis using dynamic contrast-enhanced MR imaging, specifically in patients with symptomatic intracranial atherosclerotic disease. Using the Modified Tofts model, we extracted the volume transfer constant (Ktrans) and fractional plasma volume (Vp) parameters from plaque-enhancement curves. Using regression analyses, we compared these parameters against time from symptom onset as well as intraplaque hyperintensity and postcontrast enhancement derived from T1 SPACE, a black-blood MR vessel wall imaging sequence. RESULTS We completed analysis in 10 patients presenting with symptomatic intracranial atherosclerotic disease. Ktrans and Vp measurements were higher in plaques versus healthy white matter and similar or less than values in the choroid plexus. Only Ktrans correlated significantly with time from symptom onset (P = .02). Dynamic contrast-enhanced MR imaging parameters were not found to correlate significantly with intraplaque enhancement or intraplaque hyperintensity (P = .4 and P = .17, respectively). CONCLUSIONS Elevated Ktrans and Vp values found in intracranial atherosclerotic disease plaques versus healthy white matter suggest that dynamic

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

    PubMed

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

    2011-08-01

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

  2. The effect of solids concentration and formation characteristics on formation damage and permeability recovery

    SciTech Connect

    Ismail, A.R.; Arshad, A.M.; Peden, J.M.

    1994-12-31

    An experimental study has been made to investigate the effect of solids concentration and filter media on fluid loss and permeability recovery of cores. KCl-polymer muds of different barite concentrations and different types of core were used to perform the tests. Filtration tests showed that fluid loss increased as solids concentration in the mud increased. Increasing the solids concentration in the mud appears to improve permeability recovery when the cores were backflushed. However, high spurt loss and poor permeability recovery were observed if muds containing polymer materials were used without the addition of solid particles. Filtration and permeability restoration are not only affected by the size, shape and solids concentration in the mud but also to the pore size distribution and core characteristics. Detailed observation using scanning electron microscope was used to identify the solids impairment at the core face. Therefore, to reduce formation damage and improve recovery, suitable size, shape and concentration of solids in the mud must be properly selected.

  3. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Particulate Organic Matter in Permeable Marine Sands—Dynamics in Time and Depth

    NASA Astrophysics Data System (ADS)

    Rusch, A.; Huettel, M.; Forster, S.

    2000-10-01

    In a North Sea intertidal sandflat sediment, depth profiles of dissolved and particulate compounds were measured and evaluated with respect to transport and degradation of particulate organic matter (POM). Bimonthly from July 1997 to July 1998, the amount was measured of fine-grained (<70 μm) material in the permeable sand matrix, its N, C organd chlorophyll content as well as porewater DIC, NO-x and NH+4 concentrations. Depth profiles of fine particle concentrations indicated hydrodynamic influence down to 4-8 cm below the sediment surface. Worst-case calculations on the macrofaunal contribution to particle transport resulted in a biodiffusion coefficient of D B≤1·85×10 -6cm 2 s -1, corresponding to less than 50% of total transport. Chl and POC contents and DIN concentrations exhibited summer/autumn and winter/spring characteristics in their profiles, revealing the seasonal importance of early diagenesis and advective transport, respectively. Areal inventories of POC, PN and Chl indicated the dominance of degradation and hydrodynamic removal of organic material during autumn/winter and fresh POM input throughout spring and summer. In the upper 5 cm, seasonal variation in the particle, POC, PN and Chl concentrations of the sediment was 1·4-5·3 times as large as below. Calculations based on POC loss or short-term DIC accumulation yielded estimates of annual carbon turnover rates ranging between 55 and 123 g C m -2 yr -1. Possible implications of POM dynamics on the role of permeable sands in the marine carbon cycle are discussed.

  5. 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...

  6. 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...

  7. Transient Permeability Enhancement via Dynamic Stressing: The Role of Shear Displacement

    NASA Astrophysics Data System (ADS)

    Madara, B.; Riviere, J.; Marone, C.; Elsworth, D.

    2016-12-01

    Reservoir productivity is reliant on the presence and quality of flow pathways. The creation or stimulation of fracture networks has the potential to improve the efficiency of energy production and recovery. Changes in stress conditions by dynamic perturbations have been shown to increase permeability of aquifer systems at both field and lab scales1,2. The primary mechanism for this increase has been identified by previous studies as a mobilization of fine particles2. Here, we describe results of a laboratory study focused on the role of dynamic stressing and flow perturbations. We used both intact and fractured Berea sandstone samples to investigate the mobilization of fines and the relation between shear displacement and fracture permeability. Intact L-shaped samples were subjected to true triaxial stress conditions on the order of 10MPa. The initially intact samples were fractured in situ and permeability evolution was recorded throughout the experiments. Flow was forced across the sample and the resulting fracture plane, by maintaining a differential fluid pressure along a line source at the fracture inlet and outlet. After fracture, we measured permeability at multiple shear displacement steps. At each stage of the experiment (intact, then fractured, and after each discrete shear displacement step), the sample was dynamically stressed through pore pressure or normal stress oscillations at 1Hz. The resulting transient permeability enhancements are compared at each stage and for multiple samples. The results of these experiments will lead to a better understanding of the relationship between dynamic stressing, shear displacement, and permeability evolution. References: 1 Elkhoury, Jean E., et al., Nature 441.7097 (2006): 1135-1138. 2 Candela, Thibault, et al., J. Geophys. Res., 120.4 (2015): 2037-2055.

  8. Experimental study on the response characteristics of coal permeability to pore pressure under loading and unloading conditions

    NASA Astrophysics Data System (ADS)

    Ye, Zhiwei; Zhang, Lei; Hao, Dingyi; Zhang, Cun; Wang, Chen

    2017-10-01

    In order to study the response characteristics of coal permeability to pore pressure, seepage experiments under different simulated in situ stresses on loading and unloading paths are carried out using the self-developed Gas Flow and Displacement Testing Apparatus (GFDTA) system. Based on the analysis of the experimental data, the relationship between average pore pressure and permeability is found to basically obey the function distribution of a two degree polynomial. In this paper, two aspects of the relationship between permeability and pore pressure are explained: the Klinbenberg effect and expansion, and the penetration of the initial fracture. Under low pore pressure, the decrease in the Klinbenberg effect is the main reason for the decrease in permeability with increased pore pressure. Under relatively high pore pressure, the increase in pore pressure leads to the initial fracture expansion and penetration of the coal sample, which causes an increase in permeability. In order to evaluate the sensitivity of the permeability response to pore pressure changes, the permeability dispersion and pore pressure sensitivity coefficients are defined. After the sensitivity analysis, it was concluded that the loading history changed the fracture structure of the original coal sample and reduced its permeability sensitivity to pore pressure. Under low pore pressure, the Klinbenberg effect is the reason for the decrease in pore pressure sensitivity. Lastly, the permeability-pore pressure relationship is divided into three stages to describe the different response characteristics individually.

  9. Permeability characteristics and osmotic sensitivity of rhesus monkey (Macaca mulatta) oocytes.

    PubMed

    Songsasen, N; Ratterree, M S; VandeVoort, C A; Pegg, D E; Leibo, S P

    2002-07-01

    Permeability characteristics and sensitivity to osmotic shock are principal parameters that are important to derive procedures for the successful cryopreservation of mammalian oocytes. The osmotically inactive volume of rhesus monkey oocytes was determined by measuring their volumes in the presence of hypertonic solutions of sucrose from 0.2 to 1.5 mol/l, compared with their volume in isotonic TALP-HEPES solution. Boyle-van't Hoff plots at infinite osmolality indicated that the non-osmotic volumes of immature and mature oocytes were 20 and 17% respectively. Osmotic responses of oocytes exposed to 1.0 mol/l solutions of glycerol, dimethylsulphoxide (DMSO) and ethylene glycol (EG) were determined. Rhesus monkey oocytes appeared to be less permeable to glycerol than to DMSO or to EG. Sensitivity of oocytes to osmotic shock was determined by exposing them to various solutions of EG (0.1 to 5.0 mol/l) and then abruptly diluting them into isotonic medium. Morphological survival, as measured by membrane integrity, of oocytes diluted out of EG depended significantly on the concentration of EG (P < 0.01). Determination of permeability characteristics and sensitivity to osmotic shock of rhesus oocytes will aid in the derivation of procedures for their cryopreservation.

  10. Molecular Dynamics as a tool for in silico screening of skin permeability.

    PubMed

    Rocco, Paolo; Cilurzo, Francesco; Minghetti, Paola; Vistoli, Giulio; Pedretti, Alessandro

    2017-08-30

    Prediction of skin permeability can have manifold applications ranging from drug delivery to toxicity prediction. Along with the semi-empirical or mechanistic models proposed in the last decades, Molecular Dynamics simulations have recently become a fruitful tool for investigating membrane permeability, in particular as they allow the involved mechanisms to be modelled at a molecular level. Despite their significant structural complexity, Molecular Dynamics simulations can also be utilized to study permeation through the lipid matrix that characterizes the stratum corneum. In this work, Steered Molecular Dynamics simulations are performed on a suitably developed stratum corneum lipid matrix model. Regardless of their actual tortuous path within the stratum corneum, the permeants, taken from a Fully Validated dataset of 80 compounds of known permeability coefficient, are moved through the bilayer along its normal. This allows the exploration of all the possible conformational and physicochemical constraints the molecule experiences when moving through the bilayer. The so performed Steered Molecular Dynamics simulations are then utilized to extract the corresponding lipophilicity and diffusion parameters as computed by subdividing the entire path in 18 regions of different polarity and composition. Correlative analyses showed that the water-lipids interface is the best performing region and that significant enhancements can be gained by including parameters accounting for the temperature effect. Taken together, the developed models possess an enhanced predictive power compared to the existing equations and statistics are approaching the best possible results, given the uncertainty in the utilized permeability data. Copyright © 2017. Published by Elsevier B.V.

  11. Flow characteristics of surfactant solutions in porous media and their role in permeability modification

    SciTech Connect

    Kalpakci, B.; Klaus, E.E.; Duda, J.L.; Nagarajan, R.

    1981-12-01

    This work presents a study on flow properties of surfactant solutions in porous media, using the Penn State porous media viscometer. The effects of permeability, shear rate, and surface characteristics of porous media on the flow of oil- and water-external microemulsions, as well as surfactant solutions with lamellar structures, are examined. Untreated Bradford and Berea sand-stones, oil- and water-wet treated sandstones, and filter papers are used as porous media. The study shows that the effective viscosity of the surfactant solution (as measured in porous media), on the basis of initial permeabilities, is greater than the bulk viscosity (as measured by conventional viscometers). This increase is small for Newtonian surfactant solutions but is quite substantial for non-Newtonian surfactant solutions. 31 refs.

  12. Water Transport in Aquaporins: Osmotic Permeability Matrix Analysis of Molecular Dynamics Simulations

    PubMed Central

    Hashido, Masanori; Kidera, Akinori; Ikeguchi, Mitsunori

    2007-01-01

    Single-channel osmotic water permeability (pf) is a key quantity for investigating the transport capability of the water channel protein, aquaporin. However, the direct connection between the single scalar quantity pf and the channel structure remains unclear. In this study, based on molecular dynamics simulations, we propose a pf-matrix method, in which pf is decomposed into contributions from each local region of the channel. Diagonal elements of the pf matrix are equivalent to the local permeability at each region of the channel, and off-diagonal elements represent correlated motions of water molecules in different regions. Averaging both diagonal and off-diagonal elements of the pf matrix recovers pf for the entire channel; this implies that correlated motions between distantly-separated water molecules, as well as adjacent water molecules, influence the osmotic permeability. The pf matrices from molecular dynamics simulations of five aquaporins (AQP0, AQP1, AQP4, AqpZ, and GlpF) indicated that the reduction in the water correlation across the Asn-Pro-Ala region, and the small local permeability around the ar/R region, characterize the transport efficiency of water. These structural determinants in water permeation were confirmed in molecular dynamics simulations of three mutants of AqpZ, which mimic AQP1. PMID:17449664

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  15. 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.

  16. 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

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

    PubMed

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

    2014-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  19. Permeability characteristics of human oocytes in the presence of the cryoprotectant dimethylsulphoxide.

    PubMed

    Paynter, S J; Cooper, A; Gregory, L; Fuller, B J; Shaw, R W

    1999-09-01

    Equilibration of oocytes with cryoprotectants is a prerequisite of low temperature storage. However, cryoprotectant exposure may induce damage via osmotic stress. Knowledge of cell membrane permeability characteristics and their temperature dependence would facilitate the design of cryopreservation protocols in which osmotic stress is minimized and the incidence of intracellular freezing is reduced. To obtain such data, the volume change of donated human oocytes following exposure to cryoprotectant was measured at a variety of temperatures. After removal of cumulus cells, each oocyte was placed in a 5 microl droplet of phosphate-buffered medium. The oocyte was held in position by suction generated using a fine pipette and perfused with 1 ml 1.5 mol/l dimethylsulphoxide (DMSO) at 30, 24 or 10 degrees C. The volume of the oocyte before, during and after perfusion was recorded by videomicroscopy. Oocyte volume was calculated from radius measurements and the Kedem-Katchalsky (K-K) passive coupled transport coefficients, namely L(p) (hydraulic permeability), P(DMSO) (permeability to DMSO) and sigma (reflection coefficient) were derived. The resulting coefficients were L(p) = 1. 65 +/- 0.15, 0.70 +/- 0.06 and 0.28 +/- 0.04 microm/min.atm; P(DMSO) = 0.79 +/- 0.10, 0.25 +/- 0.04 and 0.06 +/- 0.01 microm/s and sigma = 0.97 +/- 0.01, 0.94 +/- 0.03 and 0.96 +/- 0.01 at 30, 24 and 10 degrees C respectively. The activation energy for L(p) was 14.70 and for P(DMSO) was 20.82 kcal/mol. The permeability parameters of human oocytes are higher than those of murine oocytes, suggesting that they require a shorter period of exposure to DMSO with concomitantly reduced toxic effects.

  20. Crustal permeability

    USGS Publications Warehouse

    Gleeson, Tom; Ingebritsen, Steven E.

    2016-01-01

    Permeability is the primary control on fluid flow in the Earth’s crust and is key to a surprisingly wide range of geological processes, because it controls the advection of heat and solutes and the generation of anomalous pore pressures.  The practical importance of permeability – and the potential for large, dynamic changes in permeability – is highlighted by ongoing issues associated with hydraulic fracturing for hydrocarbon production (“fracking”), enhanced geothermal systems, and geologic carbon sequestration.  Although there are thousands of research papers on crustal permeability, this is the first book-length treatment.  This book bridges the historical dichotomy between the hydrogeologic perspective of permeability as a static material property and the perspective of other Earth scientists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. 

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

    NASA Astrophysics Data System (ADS)

    Ou, Miao-Jung Yvonne

    2014-09-01

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

  2. Impact of Spatial Permeability Distribution Characteristics on Hyporheic Flow Using a Physical System and Simulations

    NASA Astrophysics Data System (ADS)

    Stonedahl, S. H.; Gibson, C.; Reiter, C.; Stonedahl, F.; Sawyer, A. H.

    2015-12-01

    Permeability heterogeneity has been found to significantly affect the volume and speed with which water flows through the hyporheic zone. In this study we investigated how characteristics of spatial permeability distributions within a simple Tóthian system affected hyporheic flow both in physical and simulated domains. Our setup consisted of a 13x7x1 grid of two sediments with a divide bisecting the surface water and top middle cell creating two regions of constant head, which induced flow through the grid. Cells were filled with sand and sandy-gravel in a 2:1 ratio and positioned according to TProGS outputs. We ran a blue dye and salt solution through the system, recorded dye location using time-lapse photography, and measured the electrolytic conductivity as the water exited the system. We also calculated a grid of head values using MODFLOW and simulated flow through the system, yielding simulated dye-fronts, residence times, and exiting salt concentrations for the modeled system. We found strong agreement between the simulation and experimental procedure. We generated an additional 100 grids with the 2:1 sediment ratio for each of the transition probabilities 0.25, 0.50, and 1.0. We simulated these with 1, 2, and 3 order of magnitude differences in permeability values and used moving averages with varying window sizes to investigate the effect of the abruptness of transitions between sediment types. For these cases we compared cumulative residence time distributions, volumetric flux, and deviation from the normalized velocity field for homogenous sediment. We found that smoothing the transition between grid cells increased the volumetric flux, decreased the median residence times, and increased the deviation from a normalized homogenous velocity field. These effects were generally greater on grids created with larger transition probabilities and greater differences in K values.

  3. 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.

  4. 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

  5. Permeability and resonance characteristics of metamaterial constructed by a wire coil wound on a ferrite core

    NASA Astrophysics Data System (ADS)

    Li, Z. W.; Huang, R. F.; Kong, L. B.

    2009-11-01

    Metamaterial constructed by a Cu-wire coil wound on a ferrite core exhibits greatly enhanced imaginary permeability μmax″, large negative real permeability μ'-, and resonance frequency fR controlled through varying the number of coil turns, N. Based on an equivalent lumped parameter model, the special permeability spectrum shape and the dependence of permeability parameters on N are deduced for the metamaterial. The theoretical prediction is well consistent with the experimental results.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  7. The Permeability Enhancing Mechanism of DMSO in Ceramide Bilayers Simulated by Molecular Dynamics

    PubMed Central

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

    2007-01-01

    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 (≥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. PMID:17513383

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  10. Functional and pharmacological characteristics of permeability transition in isolated human heart mitochondria.

    PubMed

    Morota, Saori; Manolopoulos, Theodor; Eyjolfsson, Atli; Kimblad, Per-Ola; Wierup, Per; Metzsch, Carsten; Blomquist, Sten; Hansson, Magnus J

    2013-01-01

    The objective of the present study was to validate the presence and explore the characteristics of mitochondrial permeability transition (mPT) in isolated mitochondria from human heart tissue in order to investigate if previous findings in animal models of cardiac disorders are translatable to human disease. Mitochondria were rapidly isolated from fresh atrial tissue samples obtained from 14 patients undergoing Maze surgery due to atrial fibrillation. Human heart mitochondria exhibited typical mPT characteristics upon calcium overload such as swelling, evaluated by changes in light scattering, inhibition of respiration and loss of respiratory coupling. Swelling was a morphologically reversible event following transient calcium challenge. Calcium retention capacity (CRC), a quantitative measure of mPT sensitivity assayed by following extramitochondrial [Ca(2+)] and changes in respiration during a continuous calcium infusion, was significantly increased by cyclophilin D (CypD) inhibitors. The thiol-reactive oxidant phenylarsine oxide sensitized mitochondria to calcium-induced mPT. Release of the pro-apoptotic intermembrane protein cytochrome c was increased after, but not before, calcium discharge and respiratory inhibition in the CRC assay. From the present study, we conclude that adult viable heart mitochondria have a CypD- and oxidant-regulated mPT. The findings support that inhibition of mPT may be a relevant pharmacological target in human cardiac disease and may underlie the beneficial effect of cyclosporin A in reperfusion injury.

  11. Reservoir characteristics of low-permeability sandstones in the Rocky Mountains

    SciTech Connect

    Byrnes, A.P.

    1997-01-01

    Understanding gas production from low-permeability sandstones requires an understanding of the in situ porosity, brine saturation, and effective gas permeability at reservoir brine saturation. Diagenesis in these sandstones commonly resulted in the destruction of much of the original intergranular porosity and left dissolved grains, clay-filled pores, and sheet-like connecting intergranular pore throats. Pore throats or channels that connect larger pores typically range in size from 1 to 0.1 micron and represent only a small portion of the total porosity. In most low-permeability sandstones, porosity is not significantly changed by confining stress changes, but in situ effective gas permeabilities range from 10 to 1,000 times less than routine air permeability. The influence of confining stress on permeability can be attributed primarily to the decrease in size of the thin, tabular pore throats that connect the larger pores. Under stress, pore throats decrease in diameter by up to 50% to 70% resulting in permeability decreases of 10 to 40 times. Gas effective permeabilities also decrease rapidly to less than 1% of absolute values at water saturations above approximately 40% to 50%. {open_quotes}Irreducible{close_quotes} water saturations increase with decreasing porosity and permeability, and, in sandstones with less than 0.01 md permeability, {open_quotes}irreducible{close_quotes} water saturations increase dramatically. Cumulative flow and storage capacity plots indicate that very thin higher permeability intervals typically yield a large percentage of the cumulative flow capacity. Increased water saturations due to drilling or stimulation result in lower effective gas permeabilities and can unknowingly be stabilized by capillary pressure forces if pore pressures are decreased. This type of formation damage can be remedied by increasing the gas pore pressure to displace mobile water.

  12. 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

  13. The permeability enhancing mechanism of menthol on skin lipids: a molecular dynamics simulation study.

    PubMed

    Wang, Huanjie; Meng, Fancui

    2017-09-15

    The stratum corneum (SC), the outermost layer of skin, represents the primary barrier to molecules penetrating the skin. Menthol is widely used in clinical medicine as a penetration enhancer due to its high efficiency and relative safety. In this study, molecular dynamics simulations have been performed to investigate the effect of menthol molecules on the structural and permeability of both single component and ternary mixed bilayers. The lipid matrix is modeled as pure ceramide (CER2) or as a 2:2:1 mixture of CER2, cholesterol (CHOL), and free fatty acid (FFA). The effect of menthol on the SC bilayer was investigated at various concentrations of menthol. For both models, the area per lipid decreases and the membrane thickness increases with increased menthol concentration, which may be due to the fact that menthol molecules penetrate into the bilayer and aggregate at the bilayer center. As for ternary mixed bilayer at high concentration, the lipids rearranged, and one more layer formed inside the former two leaflets. Our simulation results are consistent with the experimental evidence that high concentrations of menthol fluidize the SC lipids and enhance permeability. The penetration enhancement of menthol may take place through direct interactions with lipids rather than by forming water pores. Graphical abstract The effect of menthol on the structural and permeability of skin lipids was investigated using a molecular dynamics simulation method. Increased menthol concentration makes the area per lipid decrease and the membrane thickness increase. Our results show that the penetration enhancement of menthol may take place through direct interactions with lipids.

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  16. Roughness and intermittent dynamics of imbibition fronts due to capillary and permeability disorder.

    PubMed

    Planet, Ramon; Santucci, Stéphane; Ortín, Jordi

    2011-03-01

    We follow the propagation of an air-liquid interface during forced-flow imbibition of a viscous wetting liquid by a random medium, using a high resolution fast camera. Our model disordered medium mimics an open fracture by a Hele-Shaw cell with a two-valued gap spacing randomly distributed in the fracture (or Hele-Shaw) plane. By systematically varying the imposed flow rate we achieve average imbibition front velocities in the range 0.057permeability of the medium (mixed capillary and permeability regime). We analyze the scaling properties of the front morphology in these two regimes, and find that the local roughness exponent changes from α(loc)≃0.8 in the capillary regime to 0.5 in the mixed capillary-permeability regime. In contrast, the statistics of the spatially-averaged (global) velocity of the front V(l)(t) does not seem to be influenced by the randomness in the permeability. The fluctuations of V(l)(t) follow a non-Gaussian distribution, whose skewness γ~1/v in both regimes. Similarly, sizes and durations of the avalanches of the global velocity present the same statistical distributions in both regimes. In the mixed capillary-permeability regime, the power-law exponents that characterize these distributions take the values α=0.97±0.05 for the sizes, τ=1.16±0.10 for the durations, and x=1.3±0.1 for the joint distribution of sizes vs. durations. These values are in excellent agreement with the ones measured previously in the capillary regime (Planet et al., 2009). The dynamics therefore appear to be equivalent in both regimes, a result that we relate to the fact that the correlation length of the local velocities along the front is observed to follow the same dependence l(c)~1/v in both regimes. Copyright © 2010

  17. 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).

  18. Imaging alpha-hemolysin with molecular dynamics: ionic conductance, osmotic permeability, and the electrostatic potential map.

    PubMed

    Aksimentiev, Aleksij; Schulten, Klaus

    2005-06-01

    alpha-Hemolysin of Staphylococcus aureus is a self-assembling toxin that forms a water-filled transmembrane channel upon oligomerization in a lipid membrane. Apart from being one of the best-studied toxins of bacterial origin, alpha-hemolysin is the principal component in several biotechnological applications, including systems for controlled delivery of small solutes across lipid membranes, stochastic sensors for small solutes, and an alternative to conventional technology for DNA sequencing. Through large-scale molecular dynamics simulations, we studied the permeability of the alpha-hemolysin/lipid bilayer complex for water and ions. The studied system, composed of approximately 300,000 atoms, included one copy of the protein, a patch of a DPPC lipid bilayer, and a 1 M water solution of KCl. Monitoring the fluctuations of the pore structure revealed an asymmetric, on average, cross section of the alpha-hemolysin stem. Applying external electrostatic fields produced a transmembrane ionic current; repeating simulations at several voltage biases yielded a current/voltage curve of alpha-hemolysin and a set of electrostatic potential maps. The selectivity of alpha-hemolysin to Cl(-) was found to depend on the direction and the magnitude of the applied voltage bias. The results of our simulations are in excellent quantitative agreement with available experimental data. Analyzing trajectories of all water molecule, we computed the alpha-hemolysin's osmotic permeability for water as well as its electroosmotic effect, and characterized the permeability of its seven side channels. The side channels were found to connect seven His-144 residues surrounding the stem of the protein to the bulk solution; the protonation of these residues was observed to affect the ion conductance, suggesting the seven His-144 to comprise the pH sensor that gates conductance of the alpha-hemolysin channel.

  19. Connexin channels provide a target to manipulate brain endothelial calcium dynamics and blood–brain barrier permeability

    PubMed Central

    De Bock, Marijke; Culot, Maxime; Wang, Nan; Bol, Mélissa; Decrock, Elke; De Vuyst, Elke; da Costa, Anaelle; Dauwe, Ine; Vinken, Mathieu; Simon, Alexander M; Rogiers, Vera; De Ley, Gaspard; Evans, William Howard; Bultynck, Geert; Dupont, Geneviève; Cecchelli, Romeo; Leybaert, Luc

    2011-01-01

    The cytoplasmic Ca2+ concentration ([Ca2+]i) is an important factor determining the functional state of blood–brain barrier (BBB) endothelial cells but little is known on the effect of dynamic [Ca2+]i changes on BBB function. We applied different agonists that trigger [Ca2+]i oscillations and determined the involvement of connexin channels and subsequent effects on endothelial permeability in immortalized and primary brain endothelial cells. The inflammatory peptide bradykinin (BK) triggered [Ca2+]i oscillations and increased endothelial permeability. The latter was prevented by buffering [Ca2+]i with BAPTA, indicating that [Ca2+]i oscillations are crucial in the permeability changes. Bradykinin-triggered [Ca2+]i oscillations were inhibited by interfering with connexin channels, making use of carbenoxolone, Gap27, a peptide blocker of connexin channels, and Cx37/43 knockdown. Gap27 inhibition of the oscillations was rapid (within minutes) and work with connexin hemichannel-permeable dyes indicated hemichannel opening and purinergic signaling in response to stimulation with BK. Moreover, Gap27 inhibited the BK-triggered endothelial permeability increase in in vitro and in vivo experiments. By contrast, [Ca2+]i oscillations provoked by exposure to adenosine 5′ triphosphate (ATP) were not affected by carbenoxolone or Gap27 and ATP did not disturb endothelial permeability. We conclude that interfering with endothelial connexin hemichannels is a novel approach to limiting BBB-permeability alterations. PMID:21654699

  20. Cholesterol effect on water permeability through DPPC and PSM lipid bilayers: a molecular dynamics study.

    PubMed

    Saito, Hiroaki; Shinoda, Wataru

    2011-12-29

    Water permeability of two different lipid bilayers of dipalmitoylphosphatidylcholine (DPPC) and palmitoylsphingomyelin (PSM) in the absence and presence of cholesterol (0-50 mol %) have been studied by molecular dynamics simulations to elucidate the molecular mechanism of the reduction in water leakage across the membranes by the addition of cholesterol. An enhanced free energy barrier was observed in these membranes with increased cholesterol concentration, and this was explained by the reduced cavity density around the cholesterol in the hydrophobic membrane core. There was an increase of trans conformers in the hydrophobic lipid chains adjacent to the cholesterol, which reduced the cavity density. The enhanced free energy barrier was found to be the main reason to reduce the water permeability with increased cholesterol concentration. At low cholesterol concentrations the PSM bilayer exhibited a higher free energy barrier than the DPPC bilayer for water permeation, while at greater than 30 mol % of cholesterol the difference became minor. This tendency for the PSM and DPPC bilayers to resemble each other at higher cholesterol concentrations was similar to commonly observed trends in several structural properties, such as order parameters, cross-sectional area per molecule, and cavity density profiles in the hydrophobic regions of bilayer membranes. These results demonstrate that DPPC and PSM bilayers with high cholesterol contents possess similar physical properties, which suggests that the solubility of cholesterol in these lipid bilayers has importance for an understanding of multicomponent lipid membranes with cholesterol.

  1. Dynamical modeling of liver Aquaporin-9 expression and glycerol permeability in hepatic glucose metabolism.

    PubMed

    Gena, Patrizia; Buono, Nicoletta Del; D'Abbicco, Marcello; Mastrodonato, Maria; Berardi, Marco; Svelto, Maria; Lopez, Luciano; Calamita, Giuseppe

    2017-01-01

    Liver is crucial in the homeostasis of glycerol, an important metabolic intermediate. Plasma glycerol is imported by hepatocytes mainly through Aquaporin-9 (AQP9), an aquaglyceroporin channel negatively regulated by insulin in rodents. AQP9 is of critical importance in glycerol metabolism since hepatic glycerol utilization is rate-limited at the hepatocyte membrane permeation step. Glycerol kinase catalyzes the initial step for the conversion of the imported glycerol into glycerol-3-phosphate, a major substrate for de novo synthesis of glucose (gluconeogenesis) and/or triacyglycerols (lipogenesis). A model addressing the glucose-insulin system to describe the hepatic glycerol import and metabolism and the correlation with the glucose homeostasis is lacking so far. Here we consider a system of first-order ordinary differential equations delineating the relevance of hepatocyte AQP9 in liver glycerol permeability. Assuming the hepatic glycerol permeability as depending on the protein levels of AQP9, a mathematical function is designed describing the time course of the involvement of AQP9 in mouse hepatic glycerol metabolism in different nutritional states. The resulting theoretical relationship is derived fitting experimental data obtained with murine models at the fed, fasted or re-fed condition. While providing useful insights into the dynamics of liver AQP9 involvement in male rodent glycerol homeostasis our model may be adapted to the human liver serving as an important module of a whole body-model of the glucose metabolism both in health and metabolic diseases.

  2. 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.

  3. Multiscale Bayesian inversion of binary permeability fields from static and dynamic observations

    NASA Astrophysics Data System (ADS)

    Ray, J.; McKenna, S. A.; Marzouk, Y. M.; van Bloemenwaanders, B.

    2009-12-01

    Binary fields are a useful fine-scale representation of heterogeneous porous media. Averaged properties of these fields can characterize flow through porous media at the macroscale. These averaged properties are not easily measured, however, and direct upscaling poses a challenge. Upscaled properties can instead be inferred from indirect measurements at the coarse scale, using appropriate link functions or subgrid models to connect the disparate scales and to generate realizations of fine scale fields conditioned on all available data. Truncated Gaussian random fields provide a flexible geometrical model for binary media of inclusions embedded in a matrix. We utilize a recently developed subgrid model based on excursion sets of Gaussian random fields for upscaling binary permeability fields to a coarse (block) scale effective permeability. This subgrid model requires an estimate of the proportion of high permeability inclusions and associated parameters at the block scale. Computations of the upscaled properties are inexpensive and provide a robust link between fine and block scales. We employ the subgrid model in a multiscale Bayesian inversion process, thus conditioning the proportion and geometry of the latent binary field on coarse-scale observations of permeability and on tracer recovery data. In this inversion process, the variogram of the proportion field is assumed known. The proportion field is efficiently represented via its Karhunen-Loève expansion. From limited and noisy observations of static and dynamic data, we infer the posterior distribution of the coefficients of the Karhunen-Loève modes and associated geometrical parameters of the binary field. We then generate posterior realizations of the fine scale binary media and simulate tracer recovery with these fields; the resulting predictive distributions are compared to a predetermined “ground truth” response. Additionally, we evaluate the sensitivity of the posterior distribution to different

  4. Geologic characteristics of permeable groundwater intervals defined by electromagnetic borehole flowmeter surveys on the Oak Ridge Reservation

    SciTech Connect

    Neuhoff, P.S.; Lemiszki, P.J.; Dreier, R.B. )

    1993-03-01

    The groundwater system in the Oak Ridge Reservation (ORR) area is stratigraphically controlled and divisible into aquitards, where flow is through fractures only, and aquifers, where flow is in karst conduits. An electromagnetic borehole flowmeter was used to survey 60 piezometer wells and 12 coreholes on the ORR. Piezometer well depths ranges from 5--80 ft with screen lengths of approximately 10 ft at various depths, and open corehole surveys reached depths of 350 ft. Previously, the results were used to develop a model for groundwater flow paths by assuming that permeable intervals consist of a single fracture intersecting the borehole. The purpose was to test this assumption by direct examination of core within permeable intervals. In addition, the geologic characteristics of the permeable intervals in non-cored piezometer wells have been interpreted based on correlations with nearby coreholes and geophysical logs. Occasionally, pinpointing the exact feature responsible for flow within a permeable interval was hampered by a relatively large sampling interval (>1 ft) of the flowmeter surveys. Regardless, potential transmissive features were identified by the presence of iron staining, euhedral calcite and gypsum crystallization, partial infilling of fractures, and dissolution features. Within carbonate units permeable intervals are associated with a number of different features: (1) open fractures normal and oblique to bedding that are parallel, oblique, and perpendicular to bedrock strike; (2) [<=]2 cm vugs that form within fracture mineral fillings; (3) [>=]3 cm solution cavities that are not fracture related; (4) open bed-parallel clay seams; and (5) open bed-parallel shear fractures. Within non-carbonate units permeable intervals consist of highly fractured zones, associated with changes in bedding dip and the development of shear fractures that are related to the development of faults and folds.

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

    PubMed Central

    2015-01-01

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

  6. 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

  7. The dynamic characteristics of hydrostatic bearings

    NASA Astrophysics Data System (ADS)

    Pang, Zhicheng; Sun, Jingwu; Zhai, Wenjie; Liu, Qingming; Chi, Wei

    1993-07-01

    Results of a theoretical study of the characteristics of hydrostatic bearings performed in terms of the compressibility of the air-contained oil are presented. A formula for the stability criterion of a hydrostatic bearing system and a dynamic stiffness formula is derived. It is found that, under the sinusoidal load, each of the pressure compensation systems has its own load frequency-film characteristics. The greater that compressible volume, V(oa), of oil, the smaller the dynamic stiffness. V(oa) must be reduced in the design of high-precision hydrostatic bearings. If the load frequency is in the low-stiffness area, the dynamic stiffness is small. Methods to enhance the dynamic stiffness are discussed.

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

    PubMed Central

    Moshelion, Menachem; Moran, Nava; Chaumont, François

    2004-01-01

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

  9. Quantifying Intracranial Aneurysm Wall Permeability for Risk Assessment Using Dynamic Contrast-Enhanced MRI: A Pilot Study.

    PubMed

    Vakil, P; Ansari, S A; Cantrell, C G; Eddleman, C S; Dehkordi, F H; Vranic, J; Hurley, M C; Batjer, H H; Bendok, B R; Carroll, T J

    2015-05-01

    Pathological changes in the intracranial aneurysm wall may lead to increases in its permeability; however the clinical significance of such changes has not been explored. The purpose of this pilot study was to quantify intracranial aneurysm wall permeability (K(trans), VL) to contrast agent as a measure of aneurysm rupture risk and compare these parameters against other established measures of rupture risk. We hypothesized K(trans) would be associated with intracranial aneurysm rupture risk as defined by various anatomic, imaging, and clinical risk factors. Twenty-seven unruptured intracranial aneurysms in 23 patients were imaged with dynamic contrast-enhanced MR imaging, and wall permeability parameters (K(trans), VL) were measured in regions adjacent to the aneurysm wall and along the paired control MCA by 2 blinded observers. K(trans) and VL were evaluated as markers of rupture risk by comparing them against established clinical (symptomatic lesions) and anatomic (size, location, morphology, multiplicity) risk metrics. Interobserver agreement was strong as shown in regression analysis (R(2) > 0.84) and intraclass correlation (intraclass correlation coefficient >0.92), indicating that the K(trans) can be reliably assessed clinically. All intracranial aneurysms had a pronounced increase in wall permeability compared with the paired healthy MCA (P < .001). Regression analysis demonstrated a significant trend toward an increased K(trans) with increasing aneurysm size (P < .001). Logistic regression showed that K(trans) also predicted risk in anatomic (P = .02) and combined anatomic/clinical (P = .03) groups independent of size. We report the first evidence of dynamic contrast-enhanced MR imaging-modeled contrast permeability in intracranial aneurysms. We found that contrast agent permeability across the aneurysm wall correlated significantly with both aneurysm size and size-independent anatomic risk factors. In addition, K(trans) was a significant and size

  10. 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.

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

    SciTech Connect

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

    1987-01-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

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

    PubMed Central

    Burke, Jeffrey M.; Ivory, Cornelius F.

    2010-01-01

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

  15. Permeability characteristics of novel mydriatic agents using an in vitro cell culture model that utilizes SIRC rabbit corneal cells.

    PubMed

    Goskonda, V R; Khan, M A; Hutak, C M; Reddy, I K

    1999-02-01

    The purpose of this study was to evaluate the permeability characteristics of a previously reported in vitro corneal model that utilizes SIRC rabbbit corneal cells and to investigate the permeability of three novel esters of phenylephrone chemical delivery systems (CDS) under different pH conditions using this in vitro model. The SIRC rabbit corneal cell line was grown on transwell polycarbonate membranes, and the barrier properties were assessed by measuring transepithelial electrical resistance (TEER) using a voltohmmeter. The permeabilities of esters of phenylephrone CDS across the SIRC cell layers were measured over a pH range 4.0-7. 4. The esters tested include phenylacetyl (1), isovaleryl (2), and pivalyl (3). The SIRC rabbit corneal cell line, when grown on permeable filters, formed tight monolayers of high electrical resistance with TEER values increasing from 71.6 +/- 20.8 Omega.cm2 at day 3 in culture to 2233.42 +/- 15.2 Omega.cm2 at day 8 in culture and remained constant through day 14 in culture. The transepithelial permeability coefficients (Papp) at pH 7.4 ranged from 0.58 x 10(-6) cm/s for the hydrophilic marker, mannitol, to 43. 5 x 10(-6) cm/s for the most lipophilic molecule, testosterone. The Papp at pH 7.4 for phenylephrine was 4.21 x 10(-6) cm/s. The Papp values and the lag times of the three esters of phenylephrone were pH dependent. The Papp for 1, 2, and 3 at pH 7.4 were 14.76 x 10(-6), 13.19 x 10(-6), and 12.86 x 10(-6) cm/s, respectively and the permeabilities decreased at conditions below pH 7.4. The lag times at pH 7.4 were 0.10, 0.17, and 0.12 h for 1, 2, and 3, respectively, and the values increased at lower pH conditions. The TEER values of SIRC cell line observed at day 8 to day 14 in the present investigation are similar to the resistance value reported for rabbit cornea (2 kOmega.cm2). All the esters showed significantly (p < 0.05) higher permeabilities than phenylephrine at pH 7.4. The rate and extent of transport of the drugs

  16. Estimation of anisotropic permeability in trabecular bone based on microCT imaging and pore-scale fluid dynamics simulations.

    PubMed

    Daish, C; Blanchard, R; Gulati, K; Losic, D; Findlay, D; Harvie, D J E; Pivonka, P

    2017-06-01

    In this paper, a comprehensive framework is proposed to estimate the anisotropic permeability matrix in trabecular bone specimens based on micro-computed tomography (microCT) imaging combined with pore-scale fluid dynamics simulations. Two essential steps in the proposed methodology are the selection of (i) a representative volume element (RVE) for calculation of trabecular bone permeability and (ii) a converged mesh for accurate calculation of pore fluid flow properties. Accurate estimates of trabecular bone porosities are obtained using a microCT image resolution of approximately 10 μm. We show that a trabecular bone RVE in the order of 2 × 2 × 2 mm(3) is most suitable. Mesh convergence studies show that accurate fluid flow properties are obtained for a mesh size above 125,000 elements. Volume averaging of the pore-scale fluid flow properties allows calculation of the apparent permeability matrix of trabecular bone specimens. For the four specimens chosen, our numerical results show that the so obtained permeability coefficients are in excellent agreement with previously reported experimental data for both human and bovine trabecular bone samples. We also identified that bone samples taken from long bones generally exhibit a larger permeability in the longitudinal direction. The fact that all coefficients of the permeability matrix were different from zero indicates that bone samples are generally not harvested in the principal flow directions. The full permeability matrix was diagonalized by calculating the eigenvalues, while the eigenvectors showed how strongly the bone sample's orientations deviated from the principal flow directions. Porosity values of the four bone specimens range from 0.83 to 0.86, with a low standard deviation of ± 0.016, principal permeability values range from 0.22 to 1.45 ⋅ 10( -8) m(2), with a high standard deviation of ± 0.33. Also, the anisotropic ratio ranged from 0.27 to 0.83, with high standard deviation. These

  17. Spatial and Temporal Dynamics of Mitochondrial Membrane Permeability Waves during Apoptosis

    PubMed Central

    Bhola, Patrick D.; Mattheyses, Alexa L.; Simon, Sanford M.

    2009-01-01

    Abstract Change in the permeability of the mitochondrial membrane to proteins (cytochrome c and Smac) and protons is a critical step in apoptosis. Although the time from the induction of apoptosis to the change of mitochondrial permeability is variable over a period of hours, the release of proteins is an “all or none” phenomenon that is completed in an individual cell within minutes. Here, using single-cell fluorescence microscopy, we show that the release of cytochrome c from a single mitochondrion occurs in a single step. However, this increased permeability of the outer membrane to cytochrome c propagates throughout the cell as a slower, spatially coordinated wave. The permeability of the outer membrane to Smac propagates with the same spatial pattern but lagging in time. This is followed by a wave of increased permeability of the inner membrane to protons. Only afterward do the mitochondria fission. The spatial dependence of the permeability wave was inhibited by thapsigargin, an inhibitor of the endoplasmic reticulum calcium pumps, but buffering cytosolic calcium had no effect. These results show that the trigger for apoptosis is spatially localized, initiating at one or only a few mitochondria preceding the loss of mitochondrial energetics, and the subsequent temporal propagation of mitochondrial membrane permeability is calcium-dependent. PMID:19843454

  18. Permeability Characteristics and Amino Acid Incorporation during Senescence (Ripening) of Banana Tissue 1

    PubMed Central

    Sacher, J. A.

    1966-01-01

    Changes in free space of banana tissue during ripening were measured using radioisotopes. Free space increased significantly about 44 hours before the onset of, and rose exponentially during the respiratory climacteric. The increase in free space indicates a progressive increase in the proportion of cells which becomes completely permeable to solutes in the ambient solution by simple diffusion. At the respiratory peak the tissue was essentially 100% free space to mannitol, sucrose, fructose and chloride. The capacity for active uptake of solutes declined about one day before the onset of the respiratory rise and fell to a very low level by the respiratory peak. There was no change in the level of protein or amino acids during ripening. Assays of tissue sections before and after washing indicated an increased rate of leakage of amino acids during ripening. Studies of incorporation of 3 concentrations of 14C-labeled leucine and phenylalanine indicated marked changes in the size and specific activity of the amino acid pool at the site of protein synthesis just prior to and during the climacteric rise, due to a diffusive mixing of the labeled substrate with the previously sequestered endogenous, unlabeled pool of substrate. The use of a high concentration of exogenous substrate (above saturation for uptake) resulted in an apparent constant specific activity of the metabolic pool through the ripening period. Data from these studies indicated a decline in amino acid incorporation during the climacteric. It was concluded that the initiation of permeability changes marks the onset of senescence in banana. The causative relations between alterations in permeability, the respiratory rise and other chemical changes attending fruit ripening are discussed. PMID:16656308

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

    PubMed

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

    2015-03-01

    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. 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.

  20. 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

  1. 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

  2. On the Dynamic Measurements of Hydraulic Characteristics

    NASA Astrophysics Data System (ADS)

    Hasmatuchi, Vlad; Bosioc, Alin; Münch-Alligné, Cécile

    2016-11-01

    The present work introduces the implementation and validation of a faster method to measure experimentally the efficiency characteristics of hydraulic turbomachines at a model scale on a test rig. The case study is represented by a laboratory prototype of an in-line axial microturbine for water supply networks. The 2.65 kW one-stage variable speed turbine, composed by one upstream 5-blade runner followed by one counter-rotating downstream 7-blade runner, has been installed on the HES-SO Valais/Wallis universal test rig dedicated to assess performances of small hydraulic machinery following the IEC standard recommendations. In addition to the existing acquisition/control system of the test rig used to measure the 3D hill-chart of a turbine by classical static point-by-point method, a second digitizer has been added to acquire synchronized dynamic signals of the employed sensors. The optimal acceleration/deceleration ramps of the electrical drives have been previously identified in order to cope with the purpose of a reduced measurement time while avoiding errors and hysteresis on the acquired hydraulic characteristics. Finally, the comparison between the turbine efficiency hill-charts obtained by dynamic and static point-by-point methods shows a very good agreement in terms of precision and repeatability. Moreover, the applied dynamic method reduces significantly (by a factor of up to ten) the time necessary to measure the efficiency characteristics on model testing.

  3. Dynamic Characteristics of Excited Atomic Systems

    NASA Astrophysics Data System (ADS)

    Bezuglov, N. N.; Dimitrijevic, M. S.; Klyucharev, A. N.; Mihajlov, A. A.

    2014-12-01

    The dynamics of excited atom interactions with other atoms, which often lead to associative ionization, is largely governed by stochastic diffusion of the valence electron through Rydberg states prior to the ionization. Such processes are associated with random changes of the energy state of the highly excited electron, and they are likely to influence the nuclear dynamics, especially at subthermal collision energies. Possibilities of manipulation of the chaotic dynamics of Rydberg states require a detailed exploration. For an electron in a given Rydberg state moving in a microwave field, which can be generated via interaction with another atom or molecule, there exists critical field strength, above which motion of the electron in the energy space is chaotic. Recently a way to block the dynamic chaos regime was shown, if a given Rydberg state is located somewhat above the middle between the two other states with the orbital quantum number differing by one, whereby level shifts can be controlled by employing Stark/Zeeman shifts in external DC electric/magnetic fields. The stochastic effects in collisions involving Rydberg particles, in which the initial and final reaction channels are connected via intermediate highly excited collision complexes with multiple crossings of energy levels, can be treated using the dynamic chaos approach (Chirikov criterion, Standard and Keppler mapping of time evolution of the Rydberg electron, solution of the Fokker-Plank- and Langevin-type of equations, etc.). Such approach to obtaining dynamics characteristics is a natural choice, since the treatment of Rydberg electron dynamics as a kind of diffusion process allowing one to bypass the multi-level-crossing problem, which can hardly be solved by conventional quantum chemistry methods.

  4. Dynamic model of intermediate melting zones formation within the permeable lithosphere

    NASA Astrophysics Data System (ADS)

    Sorokin, Konstantin; Perepechko, Yury; Sharapov, Viktor; Chudnenko, Konstantin; Perepechko, Ludmila

    2017-04-01

    The paper discusses a model of mantle-crustal magmatic fluid systems in the collision domains in the southern and eastern margins of the Siberian Platform and as well within the mantle wedges beneath the epicontinental volcanic arcs of the Pacific Ocean. The study of the fluid-magmatic systems evolution is based on the nonstationary nonlinear dynamic model of heat and mass transfer of the multicomponent heterogeneous media, which takes into account the deformation of the rock. The interfacial interaction corresponding to the local parameters of the hydrodynamic flow is described within the model of flow-type multi-vessel reactor based on the minimization of the Gibbs potential. Numerical simulation of the wehrlitization of rocks of the deeper parts of the mantle wedge under the frontal area of the volcanic arcs of the Northwest Pacific Ocean demonstrates the following features of the hydrodynamic and metasomatic processes. A permeable region of the mantle wedge above the magmatic source quickly reaches a quasi-stationary distribution of pressure, which is somewhat less than lithostatic pressure in the rock massif. The variation of the interphase interaction parameters during fluid flow in a permeable zone and an increase in the interfacial viscous friction can lead to a significant change in the temperature distribution in the subsurface of the fluid system. At weak interfacial friction, the increase in temperature by a few degrees is recorded at the bottom flow. This leads to a significant change in the structure of a front metasomatic zoning that results in doubling of the carbonatization region developing in the zone of fluid penetration into the system. At that, the basification zone beyond the second area of carbonatization is more significant. A strong temperature increase appears due to a strong interfacial viscous friction, which leads to a qualitative change in the nature of the zoning evolution in the metasomatic columns which is observed along the fluid

  5. Dynamic measurement of temperature dependent permittivity and permeability by microwave irradiation

    NASA Astrophysics Data System (ADS)

    Nikawa, Yoshio

    2016-11-01

    To measure the temperature dependent complex permittivity and permeability of materials, measuring systems using cavity resonator in the frequency band of 2.45 GHz have been developed. To measure low loss material with wide temperature range, TE103 mode cavity resonator system excited by magnetron as power source has been applied. To measure higher loss material with high accuracy, TM010 mode cavity resonator system excited by solid state power source with vector network analyzer has been applied. By measuring transmission or reflection coefficient of the cavity with measuring the temperature using infrared thermograph, the temperature depending complex permittivity and permeability can be obtained. By using the developed systems, temperature dependent permittivity and permeability for metallic powders and ceramics have been measured and the results are shown in this paper.

  6. A Method to Predict Blood-Brain Barrier Permeability of Drug-Like Compounds Using Molecular Dynamics Simulations

    PubMed Central

    Carpenter, Timothy S.; Kirshner, Daniel A.; Lau, Edmond Y.; Wong, Sergio E.; Nilmeier, Jerome P.; Lightstone, Felice C.

    2014-01-01

    The blood-brain barrier (BBB) is formed by specialized tight junctions between endothelial cells that line brain capillaries to create a highly selective barrier between the brain and the rest of the body. A major problem to overcome in drug design is the ability of the compound in question to cross the BBB. Neuroactive drugs are required to cross the BBB to function. Conversely, drugs that target other parts of the body ideally should not cross the BBB to avoid possible psychotropic side effects. Thus, the task of predicting the BBB permeability of new compounds is of great importance. Two gold-standard experimental measures of BBB permeability are logBB (the concentration of drug in the brain divided by concentration in the blood) and logPS (permeability surface-area product). Both methods are time-consuming and expensive, and although logPS is considered the more informative measure, it is lower throughput and more resource intensive. With continual increases in computer power and improvements in molecular simulations, in silico methods may provide viable alternatives. Computational predictions of these two parameters for a sample of 12 small molecule compounds were performed. The potential of mean force for each compound through a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer is determined by molecular dynamics simulations. This system setup is often used as a simple BBB mimetic. Additionally, one-dimensional position-dependent diffusion coefficients are calculated from the molecular dynamics trajectories. The diffusion coefficient is combined with the free energy landscape to calculate the effective permeability (Peff) for each sample compound. The relative values of these permeabilities are compared to experimentally determined logBB and logPS values. Our computational predictions correlate remarkably well with both logBB (R2 = 0.94) and logPS (R2 = 0.90). Thus, we have demonstrated that this approach may have the potential to provide reliable

  7. 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

  8. Normal versus sickle red blood cells: hemodynamic and permeability characteristics in reperfusion lung injury.

    PubMed

    Haynes, J; Seibert, A; Shah, A; Taylor, A

    1990-01-01

    Decreased deformability and increased internal viscosity of the sickle red blood cell (SRBC) contribute to abnormal flow in the microcirculation. Since the lungs are commonly affected in sickle cell disease, we compared the hemodynamics of the normal human red blood cell (NRBC) with the SRBC in the pulmonary circulation. The SRBC has decreased antioxidant enzyme activities compared with the NRBC. Thus, using the capillary filtration coefficient (Kfc), we determined the ability of the NRBC and the SRBC to attenuate the increased permeability and resulting edema seen in the oxidant stress of reperfusion lung injury (RLI). We found that lungs perfused with a 5% SRBC perfusate had higher pulmonary arterial pressures (Ppa) and resistances than lungs perfused with a 5% NRBC perfusate. Lungs made ischemic and reperfused with a physiologic cell-free perfusate resulted in a significant increase (P less than .05) in Kfc compared with the preischemic Kfc (.45 +/- .06 to 1.4 +/- 22 mL.min-1.cm H2O.100 g-1). In lungs reperfused with 5% RBC-containing perfusates, the Kfc did not change from preischemic Kfc with NRBCs and decreased from the preischemic Kfc with SRBCs. These findings suggest that the SRBC causes physiologically significant increases in Ppa and resistances and the SRBC, like the NRBC, offers apparent protection in RLI.

  9. 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

  10. Triatoma virus recombinant VP4 protein induces membrane permeability through dynamic pores.

    PubMed

    Sánchez-Eugenia, Rubén; Goikolea, Julen; Gil-Cartón, David; Sánchez-Magraner, Lissete; Guérin, Diego M A

    2015-04-01

    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. 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 permeabilization in

  11. 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.

  12. 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

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

    PubMed

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

    2015-03-10

    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.

  14. 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.

  15. Cyclic activity at silicic volcanoes: A response to dynamic permeability variations

    NASA Astrophysics Data System (ADS)

    Lamur, Anthony; Lavallée, Yan; Kendrick, Jackie; Eggertsson, Gudjon; Ashworth, James; Wall, Richard

    2017-04-01

    Silicic volcanoes exhibit cyclic eruptive activity characterised by effusive (dome growth) to quiescent periods punctuated by short explosive episodes. The latter, characterised by fast emissions of gas and ash into the atmosphere, results from stress release through fracturing and causes significant hazards to the surrounding environment. Understanding the formation, development and closure of fractures as well as their impact on the volcanic system is hence vital for better constraining current models. Here, we present the results of two sets of experiments designed to understand first, the development of permeability through fracturing and second, the timescale over which these fractures can persist in magmas. To characterise the influence of a macro-fracture, the permeability of intact volcanic rocks with a wide porosity range (1-41%) was measured at varying effective pressures (-0.001-30 MPa). We then fractured each sample using the Brazilian disc method to induce a tensile macro-fracture, before measuring the permeability under the same conditions. While our results for intact samples are consistent with previous studies, the results for fractured samples display a distinct permeability-porosity relationship. We show that low porosity samples (<18%) suffer a net increase in permeability of up to 4 orders of magnitude upon fracturing, compared to high porosity samples (>18%) that show a less than 1 order of magnitude increase. This suggests that a macro-fracture has the ability to efficiently localise the flow in low porosity rocks by becoming the prevailing structure in a previously micro-fracture-dominated porous network, whereas at higher porosities fluid flow remains controlled by pore connectivity, irrespective of the presence of a fracture. To assess the longevity of fractures in magmas we developed a novel experimental set-up, in which two glass rods were placed in contact for different timescales at high temperatures before being pulled apart to test

  16. 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.

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

    PubMed

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

    2013-12-04

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

  18. 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

  19. The dynamic placenta: II. Hypothetical model of a fetus driven transplacental water balance mechanism producing low apparent permeability in a highly permeable placenta.

    PubMed

    Sebire, N J; Talbert, D

    2004-01-01

    In vitro and isotopic studies in vivo have reported the paradox that the human placenta is highly permeable, water exchanging at 3.6 litres per hour at 35 weeks of gestation, but clinical measurements in vivo show net transfer is minimal, around 2 ml/day. Current theories are based on osmotic pressure balances, but changes in maternofetal hydrostatic pressure change much faster than osmotic factors could respond. An alternative explanation might be that net transfer is not in fact the result of passive mechanisms, but is actively controlled by the fetus itself. The fetus is well equipped to monitor changes in blood volume, such as via sensors in venous and atrial stretch receptors to control ANF and hence urine production. Transplacental water regulation requires modification of transvillus pressures. Placental sub-chorial arteries and veins (of extra-embryonic origin) have different sensitivities from fetal body tissues to some vasoactive substances, and stem villous veins have unusually well developed vascular smooth muscle. It is thus theoretically possible for the fetus to modify subchorial venous resistances, and hence villous capillary pressure with a suitable circulating placental venous constrictive agent. A computer modelling study was undertaken using a fictitious placental venous constricting agent "fictensin", considered to be released by the fetus in proportion to disturbance of vascular volume. The effective placental permeability fell in proportion to the tightness of this fetal control mechanism, suggesting that the apparent placental permeability measured in vivo is a measure of fetal control, not true permeability. However, the range of compensatory pressures that the fetus can produce by this means is limited and failure of such a mechanism could allow flooding or dehydration of the feto-placental unit. This may shed new light on disorders such as polyhydramnios and fetal hydrops.

  20. Nonlinear Dynamic Characteristics of the Railway Vehicle

    NASA Astrophysics Data System (ADS)

    Uyulan, Çağlar; Gokasan, Metin

    2017-06-01

    The nonlinear dynamic characteristics of a railway vehicle are checked into thoroughly by applying two different wheel-rail contact model: a heuristic nonlinear friction creepage model derived by using Kalker 's theory and Polach model including dead-zone clearance. This two models are matched with the quasi-static form of the LuGre model to obtain more realistic wheel-rail contact model. LuGre model parameters are determined using nonlinear optimization method, which it's objective is to minimize the error between the output of the Polach and Kalker model and quasi-static LuGre model for specific operating conditions. The symmetric/asymmetric bifurcation attitude and stable/unstable motion of the railway vehicle in the presence of nonlinearities which are yaw damping forces in the longitudinal suspension system are analyzed in great detail by changing the vehicle speed. Phase portraits of the lateral displacement of the leading wheelset of the railway vehicle are drawn below and on the critical speeds, where sub-critical Hopf bifurcation take place, for two wheel-rail contact model. Asymmetric periodic motions have been observed during the simulation in the lateral displacement of the wheelset under different vehicle speed range. The coexistence of multiple steady states cause bounces in the amplitude of vibrations, resulting instability problems of the railway vehicle. By using Lyapunov's indirect method, the critical hunting speeds are calculated with respect to the radius of the curved track parameter changes. Hunting, which is defined as the oscillation of the lateral displacement of wheelset with a large domain, is described by a limit cycle-type oscillation nature. The evaluated accuracy of the LuGre model adopted from Kalker's model results for prediction of critical speed is higher than the results of the LuGre model adopted from Polach's model. From the results of the analysis, the critical hunting speed must be resolved by investigating the track tests

  1. 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

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

    PubMed

    Jelvehgari, M; Maghsoodi, M; Nemati, H

    2010-01-01

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

  3. Development and permeability of a dynamic membrane for anaerobic wastewater treatment.

    PubMed

    Alibardi, Luca; Cossu, Raffaello; Saleem, Mubashir; Spagni, Alessandro

    2014-06-01

    Dynamic membranes (DMs) have recently been proposed as an alternative to microfiltration and ultrafiltration in membrane bioreactors (MBRs) in order to contain capital and management costs. This study aims to develop an anaerobic dynamic MBR for wastewater treatment by using a large pore-sized mesh. The study demonstrated that a DM can be developed by using a mesh of 200μm pore-size and applying low cross flow velocity. The bench-scale reactor achieved COD removal efficiency between 65% and 92% and proved to be able to remove approximately 99% of the mixed liquor suspended solids, maintaining a solids retention time well above 200d. A significant quantity of biogas was produced by the external dynamic membrane module and was released with the effluent stream. The flux-step experiment, designed to estimate the critical flux in ultrafiltration MBR, can also be used for monitoring the development and stability of DMs.

  4. 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

  5. Dynamics of snap-off and pore-filling events during two-phase fluid flow in permeable media.

    PubMed

    Singh, Kamaljit; Menke, Hannah; Andrew, Matthew; Lin, Qingyang; Rau, Christoph; Blunt, Martin J; Bijeljic, Branko

    2017-07-12

    Understanding the pore-scale dynamics of two-phase fluid flow in permeable media is important in many processes such as water infiltration in soils, oil recovery, and geo-sequestration of CO2. The two most important processes that compete during the displacement of a non-wetting fluid by a wetting fluid are pore-filling or piston-like displacement and snap-off; this latter process can lead to trapping of the non-wetting phase. We present a three-dimensional dynamic visualization study using fast synchrotron X-ray micro-tomography to provide new insights into these processes by conducting a time-resolved pore-by-pore analysis of the local curvature and capillary pressure. We show that the time-scales of interface movement and brine layer swelling leading to snap-off are several minutes, orders of magnitude slower than observed for Haines jumps in drainage. The local capillary pressure increases rapidly after snap-off as the trapped phase finds a position that is a new local energy minimum. However, the pressure change is less dramatic than that observed during drainage. We also show that the brine-oil interface jumps from pore-to-pore during imbibition at an approximately constant local capillary pressure, with an event size of the order of an average pore size, again much smaller than the large bursts seen during drainage.

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

    PubMed Central

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

    2012-01-01

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

  7. Effect of the ripening time under vacuum and packaging film permeability on processing and quality characteristics of low-fat fermented sausages.

    PubMed

    Liaros, N G; Katsanidis, E; Bloukas, J G

    2009-12-01

    The effect of vacuum ripening of low-fat fermented sausages packaged in films with different permeabilities on their microbiological, physicochemical and sensorial characteristics was studied. High-fat control sausages were produced with 30% initial fat and low-fat sausages with 10% initial fat. The low-fat sausages were separated into: (a) non-packaged (control) and (b) packaged under vacuum on 7th, 12th and 17th day of processing, remaining under vacuum during the ripening period for 21, 16 and 11days, respectively, in three different oxygen (100, 38 and⩽5cm(3)/m(2)/24h/1atm) and water vapour (4.5, <2.5 and 1g/m(2)24h) permeability plastic bags. Vacuum packaging reduced (p<0.05) the weight loss, the hardness and extent of lipid oxidation in the sausages, increased (p<0.05) their lightness, but had no effect (p>0.05) on the redness, compared to the control sausages. Packaging low-fat fermented sausages under vacuum for the last 11days of ripening in packaging film with high permeability increased (p<0.05) the lactic acid bacteria count. The same product packaged in film with medium permeability had a higher (p<0.05) Micrococcaceae count and the same (p>0.05) hardness and overall acceptability as the high-fat control sausages. A ripening time of 11days and the medium packaging film permeability were the most appropriate conditions for the vacuum packaging of low-fat fermented sausages.

  8. 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.

  9. Permeability Parameters Measured with Dynamic Contrast-Enhanced MRI: Correlation with the Extravasation of Evans Blue in a Rat Model of Transient Cerebral Ischemia.

    PubMed

    Choi, Hyun Seok; Ahn, Sung Soo; Shin, Na-Young; Kim, Jinna; Kim, Jae Hyung; Lee, Jong Eun; Lee, Hye Yeon; Heo, Ji Hoe; Lee, Seung-Koo

    2015-01-01

    The purpose of this study was to correlate permeability parameters measured with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) using a clinical 3-tesla scanner with extravasation of Evans blue in a rat model with transient cerebral ischemia. Sprague-Dawley rats (n = 13) with transient middle cerebral artery occlusion were imaged using a 3-tesla MRI with an 8-channel wrist coil. DCE-MRI was performed 12 hours, 18 hours, and 36 hours after reperfusion. Permeability parameters (K(trans), ve, and vp) from DCE-MRI were calculated. Evans blue was injected after DCE-MRI and extravasation of Evans blue was correlated as a reference with the integrity of the blood-brain barrier. Correlation analysis was performed between permeability parameters and the extravasation of Evans blue. All permeability parameters (K(trans), ve, and vp) showed a linear correlation with extravasation of Evans blue. Among them, K(trans) showed highest values of both the correlation coefficient and the coefficient of determination (0.687 and 0.473 respectively, p < 0.001). Permeability parameters obtained by DCE-MRI at 3-T are well-correlated with Evans blue extravasation, and K(trans) shows the strongest correlation among the tested parameters.

  10. Measurement of blood-brain barrier permeability with t1-weighted dynamic contrast-enhanced MRI in brain tumors: a comparative study with two different algorithms.

    PubMed

    Bergamino, Maurizio; Saitta, Laura; Barletta, Laura; Bonzano, Laura; Mancardi, Giovanni Luigi; Castellan, Lucio; Ravetti, Jean Louis; Roccatagliata, Luca

    2013-01-01

    The purpose of this study was to assess the feasibility of measuring different permeability parameters with T1-weighted dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) in order to investigate the blood brain-barrier permeability associated with different brain tumors. The Patlak algorithm and the extended Tofts-Kety model were used to this aim. Twenty-five adult patients with tumors of different histological grades were enrolled in this study. MRI examinations were performed at 1.5 T. Multiflip angle, fast low-angle shot, and axial 3D T1-weighted images were acquired to calculate T1 maps, followed by a DCE acquisition. A region of interest was placed within the tumor of each patient to calculate the mean value of different permeability parameters. Differences in permeability measurements were found between different tumor grades, with higher histological grades characterized by higher permeability values. A significant difference in transfer constant (K (trans)) values was found between the two methods on high-grade tumors; however, both techniques revealed a significant correlation between the histological grade of tumors and their K (trans) values. Our results suggest that DCE acquisition is feasible in patients with brain tumors and that K (trans) maps can be easily obtained by these two algorithms, even if the theoretical model adopted could affect the final results.

  11. The dynamic characteristics of a valve-less micropump

    NASA Astrophysics Data System (ADS)

    Jiang, Dan; Li, Song-Jing

    2012-07-01

    The aim of this paper is to investigate the dynamic characteristics of a valve-less micropump. A dynamic mathematical model of the micropump based on a hydraulic analogue system and a simulation method using AMESim software are developed. By using the finite-element analysis method, the static analysis of the diaphragm is carried out to obtain the maximum deflection and volumetric displacement. Dynamic characteristics of the valve-less micropump under different excitation voltages and frequencies are simulated and tested. Because of the discrepancy between simulation results and experimental data at frequencies other than the natural frequency, the revised model for the diaphragm maximum volumetric displacement is presented. Comparison between the simulation results based on the revised model and experimental data shows that the dynamic mathematical model based on the hydraulic analogue system is capable of predicting dynamic characteristics of the valve-less micropump at any excitation voltage and frequency.

  12. A simulation of mud invasion and characteristics of array laterolog responses in a low-permeability gas reservoir: a case study

    NASA Astrophysics Data System (ADS)

    Jiang, Yanjiao; Sun, Jianmeng; Gao, Jianshen; Zhang, Pengyun; Cui, Jiangman

    2017-06-01

    Mud invasion is a complex problem in reservoir evaluation. The original distribution of formation fluid and resistivity near the wellbore changes when mud filtrate invades the permeability formations, and the electric logging response always shows distortion. In this study, the influencing factors in mud invasion analysis are investigated for a low-permeability gas reservoir based on a numerical simulation method. These factors include overbalance pressure, formation permeability, initial water saturation, and relative permeability, and we acquire the law of mud invasion and the main controlling factors of the invasion. Based on the simulation results, the array laterolog responses of different invasion situations are calculated by a three-dimensional finite element method, and we hold the opinion that the characteristics of these responses and the separation differences of the curves at different investigation depths are affected by the depth of the mud invasion. Furthermore, combined with the logging data and invasion simulation results, the calculation relation of the invasion depth is established using physical property parameters and array laterolog responses. This method effectively hides the influencing factors of invasion time and has good applications regarding the logging data of different invasion moments. In a low-invasion well case, the calculated result is in accordance with the actual situation and verifies the reliability of the method. The research shows that the combination of mud invasion characteristics and array laterolog responses can be applied to the prediction and evaluation of mud invasion depth in the study area. Furthermore, it can provide a service for fluid property evaluation and resistivity correction, as well as improve the reliability of reservoir evaluation by electrical logging.

  13. Predicting Dynamic Separation Characteristics of General Configurations.

    DTIC Science & Technology

    1987-07-01

    Cebeci et al. (15) and Le Balleur (16), among others. In addition, the method provides a foundation for ap- plying improved modeling techniques ...AD-A196 669 PREDICTING DYNAMIC SEPRATION CHRACTERISTICS OF / GENERAL CONFIGURRTIONS(U) ANALYTICAL METHODS INC REDMOND MA B "ASKEW ET AL. JUL 87 AMI...a NAME Of MONI1TORING ORGANIZATION Analytical Methods , Inc. ItgpabIAir Force Office of Scientific Research 6c. A DD0R ESS (City. S tote and ZIP Code

  14. 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.

  15. Effect of Size and Surface Charge of Gold Nanoparticles on their Skin Permeability: A Molecular Dynamics Study.

    PubMed

    Gupta, Rakesh; Rai, Beena

    2017-03-28

    Molecular level understanding of permeation of nanoparticles through human skin establishes the basis for development of novel transdermal drug delivery systems and design and formulation of cosmetics. Recent experiments suggest that surface coated nano-sized gold nanoparticles (AuNPs) can penetrate the rat and human skin. However, the mechanisms by which these AuNPs penetrate are not well understood. In this study, we have carried out coarse grained molecular dynamics simulations to explore the permeation of dodecanethiol coated neutral hydrophobic AuNPs of different sizes (2-5 nm) and surface charges (cationic and anionic) through the model skin lipid membrane. The results indicate that the neutral hydrophobic AuNPs disrupted the bilayer and entered in it with in ~200 ns, while charged AuNPs were adsorbed on the bilayer headgroup. The permeation free energy calculation revealed that at the head group of the bilayer, a very small barrier existed for neutral hydrophobic AuNP while a free energy minimum was observed for charged AuNPs. The permeability was maximum for neutral 2 nm gold nanoparticle (AuNP) and minimum for 3 nm cationic AuNP. The obtained results are aligned with recent experimental findings. This study would be helpful in designing customized nanoparticles for cosmetic and transdermal drug delivery application.

  16. Effect of Size and Surface Charge of Gold Nanoparticles on their Skin Permeability: A Molecular Dynamics Study

    PubMed Central

    Gupta, Rakesh; Rai, Beena

    2017-01-01

    Molecular level understanding of permeation of nanoparticles through human skin establishes the basis for development of novel transdermal drug delivery systems and design and formulation of cosmetics. Recent experiments suggest that surface coated nano-sized gold nanoparticles (AuNPs) can penetrate the rat and human skin. However, the mechanisms by which these AuNPs penetrate are not well understood. In this study, we have carried out coarse grained molecular dynamics simulations to explore the permeation of dodecanethiol coated neutral hydrophobic AuNPs of different sizes (2–5 nm) and surface charges (cationic and anionic) through the model skin lipid membrane. The results indicate that the neutral hydrophobic AuNPs disrupted the bilayer and entered in it with in ~200 ns, while charged AuNPs were adsorbed on the bilayer headgroup. The permeation free energy calculation revealed that at the head group of the bilayer, a very small barrier existed for neutral hydrophobic AuNP while a free energy minimum was observed for charged AuNPs. The permeability was maximum for neutral 2 nm gold nanoparticle (AuNP) and minimum for 3 nm cationic AuNP. The obtained results are aligned with recent experimental findings. This study would be helpful in designing customized nanoparticles for cosmetic and transdermal drug delivery application. PMID:28349970

  17. Hierarchical transport networks optimizing dynamic response of permeable energy-storage materials.

    PubMed

    Nilson, Robert H; Griffiths, Stewart K

    2009-07-01

    Channel widths and spacing in latticelike hierarchical transport networks are optimized to achieve maximum extraction of gas or electrical charge from nanoporous energy-storage materials during charge and discharge cycles of specified duration. To address a range of physics, the effective transport diffusivity is taken to vary as a power, m , of channel width. Optimal channel widths and spacing in all levels of the hierarchy are found to increase in a power-law manner with normalized system size, facilitating the derivation of closed-form approximations for the optimal dimensions. Characteristic response times and ratios of channel width to spacing are both shown to vary by the factor 2/m between successive levels of any optimal hierarchy. This leads to fractal-like self-similar geometry, but only for m=2 . For this case of quadratic dependence of diffusivity on channel width, the introduction of transport channels permits increases in system size on the order of 10;{4} , 10;{8} , and 10;{10} , without any reduction in extraction efficiency, for hierarchies having 1, 2 and, 8 levels, respectively. However, we also find that for a given system size there is an optimum number of hierarchical levels that maximizes extraction efficiency.

  18. 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.

  19. Permeability of porour rhyolite

    NASA Astrophysics Data System (ADS)

    Cashman, K.; Rust, A.; Wright, H.; Roberge, J.

    2003-04-01

    connecting individual vesicles. This interpretation is supported by the observation that clasts with high porosities but unusually low k1 and k2 also have high percentages of isolated pores (>10%), indicating extensive vesiculation but limited bubble coalescence; such clasts seem to be characteristic of ignimbrite deposits. 1Innocentini MDM, Salvini VR, Pandolfelli VC, Coury JC (1999) The permeability of ceramic foams. Amer Ceram Soc Bull 79:78-94. 2Klug C, Cashman KV (1996) Permeability development in vesiculating magmas - implications for fragmentation. Bull. Volcanol.58:87-100; Klug C, Cashman KV, Bacon C (2002) Structure and physical characteristics of pumice from the climactic eruption of Mt. Mazama (Crater Lake), Oregon. Bull Volcanol 64:486-501

  20. Criticality Characteristics of Current Oil Price Dynamics

    NASA Astrophysics Data System (ADS)

    Drożdż, S.; Kwapień, J.; Oświęcimka, P.

    2008-10-01

    Methodology that recently leads us to predict to an amazing accuracy the date (July 11, 2008) of reverse of the oil price up trend is briefly summarized and some further aspects of the related oil price dynamics elaborated. This methodology is based on the concept of discrete scale invariance whose finance-prediction-oriented variant involves such elements as log-periodic self-similarity, the universal preferred scaling factor λ≈2, and allows a phenomenon of the "super-bubble". From this perspective the present (as of August 22, 2008) violent - but still log-periodically decelerating - decrease of the oil prices is associated with the decay of such a "super-bubble" that has started developing about one year ago on top of the longer-term oil price increasing phase (normal bubble) whose ultimate termination is evaluated to occur in around mid 2010.

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

    NASA Astrophysics Data System (ADS)

    Gensterblum, Y.; Krooss, B. M.

    2013-12-01

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

  3. Changes in electroencephalographic characteristics and blood-brain barrier permeability in WAG/Rij rats with cortical dysplasia.

    PubMed

    Sahin, Deniz; Yilmaz, Canan Ugur; Orhan, Nurcan; Arican, Nadir; Kaya, Mehmet; Gürses, Candan; Ates, Nurbay; Ahishali, Bulent

    2017-02-01

    This study investigated the effects of cortical dysplasia (CD) on electrophysiology and blood-brain barrier (BBB) permeability in WAG/Rij rats with genetic absence epilepsy. Pregnant WAG/Rij rats were exposed to 145cGy of gamma-irradiation on embryonic day 17 to induce CD. An electroencephalogram was recorded from cortices subdurally in the offspring of the pregnant animals. Horseradish peroxidase (HRP) was used as determinant of BBB permeability. A massive tissue loss in the cerebral cortex was seen in WAG/Rij rats with CD (p<0.05). There was a significant decrease in the number and duration of spike-and-wave discharges (SWDs) and an increase in the frequency of SWDs in the WAG/Rij rats with CD when compared with the properties of SWDs in intact WAG/Rij rats (p<0.01). Ultrastructurally, the accumulation of HRP reaction products in the cerebral cortex and thalamus of WAG/Rij rats was significantly higher than that of control values (p<0.01). The accumulation of HRP reaction products in the cerebral cortex and thalamus regions of WAG/Rij rats with CD increased and was higher than that of the control and WAG/Rij animals (p<0.01). In our study, we showed that number and duration of SWDs decreased and SWD frequency increased in WAG/Rij rats with CD, suggesting a shift in seizure pattern. The association of these alterations with significant loss of cortical thickness and increased BBB permeability to HRP tracer may represent a causal relation of the EEG abnormalities with cerebral structural changes in these animals. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Characteristics, dynamics and significance of marine snow

    NASA Astrophysics Data System (ADS)

    Alldredge, Alice L.; Silver, Mary W.

    Macroscopic aggregates of detritus, living organisms and inorganic matter known as marine snow, have significance in the ocean both as unique, partially isolated microenvironments and as transport agents: much of surface-derived matter in the ocean fluxes to the ocean interior and the sea floor as marine snow. As microhabitats, marine snow aggregates contain enriched microbial communities and chemical gradients within which processes of photosynthesis, decomposition, and nutrient regeneration occur at highly elevated levels. Microbial communities associated with marine snow undergo complex successional changes on time scales of hours to days which significantly alter the chemical and biological properties of the particles. Marine snow can be produced either de novo by living plants and animals especially as mucus feeding webs of zooplankton, or by the biologically-enhanced physical aggregation of smaller particles. By the latter pathway, microaggregates, phytoplankton, fecal pellets, organic debris and clay-mineral particles collide by differential settlement or physical shear and adhere by the action of various, biologically-generated, organic compounds. Diatom flocculation is a poorly understood source of marine snow of potential global significance. Rates of snow production and breakdown are not known but are critical to predicting flux and to understanding biological community structure and transformations of matter and energy in the water column. The greatest challenge to the study of marine snow at present is the development of appropriate technology to measure abundances and characteristics of aggregates in situ.

  5. Dual-temporal resolution dynamic contrast-enhanced MRI protocol for blood-brain barrier permeability measurement in enhancing multiple sclerosis lesions.

    PubMed

    Jelescu, I O; Leppert, I R; Narayanan, S; Araújo, D; Arnold, D L; Pike, G B

    2011-06-01

    To design a more accurate and reproducible technique for the measurement of blood-brain barrier (BBB) permeability in gadolinium-enhancing multiple sclerosis (MS) lesions. Four MS patients were scanned using a new dynamic contrast-enhanced (DCE)-magnetic resonance imaging (MRI) protocol based on an uninterrupted two-part acquisition consisting of an initial part at high temporal and low spatial resolutions and a second part at low temporal and high spatial resolutions. The method preserves both the high spatial resolution needed for the often small size of lesions and the high temporal resolution required during the first minute after injection to sufficiently sample the first-pass bolus. Simulations compared the performance of this new protocol with the conventional one at low temporal and high spatial resolutions throughout. The BBB permeability estimates changed by up to 33% between the two protocols. The new protocol led to simulated error on K(trans) of 7%-10%, versus 7%-30% with the conventional protocol, and was more robust with respect to offsets between acquisition and injection start times, differences in shape of the first-pass peak, and permeability values. The dual-temporal resolution protocol produces improved BBB permeability estimates and provides a more complete view of active inflammatory MS lesion pathology. Copyright © 2011 Wiley-Liss, Inc.

  6. Characteristics of hydrogenotrophic denitrification in a combined system of gas-permeable membrane and a biofilm reactor.

    PubMed

    Lu, Caixia; Gu, Ping; He, Pan; Zhang, Guanghui; Song, Chao

    2009-09-15

    A double Monod form was employed to describe two-step hydrogenotrophic denitrification, and the saturation constants of nitrate, nitrite and hydrogen were determined by batch tests. A combined system of gas-permeable membrane and a biofilm reactor (GPM-BR) was employed to remove nitrate from drinking water. The gas-permeable membrane was tested to exclusively deliver hydrogen to an independent attached growth system. The denitrification performance of the GPM-BR was investigated with different nitrate loadings of 96.78, 163.16 and 342.58 mg N/(Ld). The nitrate removal rate (NRR) of the reactor could achieve 471.36 mg N/(Ld) with sufficient dissolved hydrogen (DH) in the batch tests. While in the continuous experiments, NRR ranged from 96.72 to 301.44 mg N/(Ld) under different nitrate loadings. Although low nitrate loading of 96.78 mg N/(Ld) led to better nitrate removal, the denitrification capacity of GPM-BR would be limited and sulfate reduction occurred.

  7. Estimating skin permeability from physicochemical characteristics of drugs: a comparison between conventional models and an in vivo-based approach.

    PubMed

    Farahmand, Sara; Maibach, Howard I

    2009-06-22

    This study evaluates the correlation of some widely used skin permeability predictive models with a recently proposed empirical model based on human in vivo dermatopharmacokinetic data. Drug fluxes through the skin have been calculated using in vitro- and in vivo-based models, and observed in vivo data, and the values compared. Most in vitro-based models underestimate the in vivo data by 1-100-fold. The discrepancy between observed data and prediction reaches the maximum (1000-10,000-fold underestimation) for nicotine (with the smallest molecular weight and logK(oct)), nitroglycerin (with the largest number of hydrogen bond acceptor groups), and for oxybutynin (with the largest molecular weight and logK(oct)) where there was a 1000-fold flux overestimation. However, most models correlated well with the in vivo data and the in vivo-based model (p<0.05). The vehicle effect and using non-steady state in vivo data in the flux calculations partly account for the observed discrepancies between predicted and observed values. Nevertheless, these results reveal the need for further refinement of skin permeability predictive equations, using the steady state in vivo data, and consideration of formulation effect.

  8. 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.

  9. Dynamic changes in the main regulatory genes of mitochondrial permeability transition pore in Eimeria tenella host cells.

    PubMed

    Xu, Zhi-Yong; Zheng, Ming-Xue; Zhang, Yan; Cui, Xiao-Zhen; Yang, Sha-Sha; Liu, Rui-Li; Li, Shan; Xi, Rou; Gong, Xin; Bai, Rui

    2016-12-01

    The purpose of the present study was to investigate the dynamic changes in the main regulatory genes of the mitochondrial permeability transition pore in E. tenella host cells. Primary chick embryo cecum epithelial cell culture techniques, spectrophotometer technology, Hoechst-Annexin V-PI apoptosis staining and ELISA were used to detect the apoptosis rate and dynamic changes of Bcl-2, Bcl-xl, Bax, Bak, Bid, Bad, HK-II, and ATP content in E. tenella host cells at 4, 24, 48, 72, 96, and 120 h. The rates of early apoptosis, late apoptosis, and necrosis of group T0 were significantly lower (P < 0.05) or highly significantly lower (P < 0.01) than those of group C at 4 h, but higher (P < 0.05 or P < 0.01) at varying degrees than those of the same group at 24-120 h. Compared to group C, the amount of Bcl-2, ATP, Bax and Bad in group T0 were visibly lower (P < 0.05 or P < 0.01) at 4 h, whereas Bcl-xl/Bax was highly significantly higher (P < 0.01) at 4 h. In addition, group T0 had less ATP at 24-120 h than group C, whereas the amount of Bcl-2, Bcl-xl, Bax, Bak, Bid, Bad and HK-II in group T0 inversely increased in varying degrees at 24-120 h compared with group C. Moreover, Bcl-2/Bax was lower (P < 0.01) at 24, 48, and 96 h, and Bcl-xl/Bax was lower (P < 0.05) at 48 h in group T0 than in group C, respectively. Taken together, these observations indicate that in the early developmental stages of E. tenella, the host-cell apoptosis rate decreased; although the amount of anti- and pro-apoptotic genes in host cells decreased, the ratios of anti-apoptotic to pro-apoptotic bcl-2 gene-family members increased. In the middle and later developmental stages of E. tenella, the host-cell apoptosis rate increased; the amount of anti- and pro-apoptotic genes increased, while the ratios of anti-apoptotic to pro-apoptotic bcl-2 gene-family members decreased. In addition, ATP decreased at all developmental stages of E. tenella.

  10. 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.

  11. Analyzing dynamic characteristics of NC table with SVD

    NASA Astrophysics Data System (ADS)

    Wang, Linhong; Wu, Bo

    2008-12-01

    This article employs SVD (singular value decomposition) method to study dynamic characteristics of NC (numerical control) table. Acceleration signals of the NC table at three directions were tested; the singular spectrum of the signals was acquired with SVD; principal components of the signals were found out; the dynamic characteristics of the signals and its contributing factors were studied through extracting dynamic characteristics of principal components; and quantitative analysis was made on signals and principal components through calculating signal energy. The results indicated that signal characteristics of the previous two principal components are apparent, based on which dynamic characteristics of chaotic signal can be extracted; signal at perpendicular direction of table is greatly correlated with that at the horizontal moving direction, indicating that they are excited from the same vibration source. But signals perpendicular to each other in terms of moving direction at the horizontal level is rarely correlated; total signal energy is maximum at moving direction, minimum at horizontal non-moving direction and in the middle at perpendicular non-moving direction; bending vibration of lead screw at perpendicular direction is far more violent than that at horizontal direction.

  12. 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.

  13. 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.

  14. Linear contact interface parameter identification using dynamic characteristic equation

    NASA Astrophysics Data System (ADS)

    Jalali, Hassan

    2016-01-01

    The stiffness characteristics of the contact interfaces in joints or boundary conditions have a great effect on dynamic response of assembled structures. Predictive analytical/numerical modeling of mechanical structures is not possible without representing the contact interfaces accurately. Because of the complex mechanisms involved, contact interfaces introduce difficulties both in modeling the inherent dynamics and identification of the model parameters. In this paper an identification approach employing the dynamic characteristic equation is proposed for linear interface parameters. The proposed method is applicable to both analytical and numerical problems. The accuracy of the proposed method is investigated by simulation results of a beam with elastic boundary support and experimental results of a bolted lap-joint.

  15. 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.

  16. Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content

    PubMed Central

    Han, Jae-Woong; Jeon, Ji-Hong; Park, Chan-Gi

    2015-01-01

    We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ≥21 MPa and a flexural strength of ≥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement). The ratio of latex polymer to rapid-set binder material was varied through 0.40, 0.33, 0.29, and 0.25. Mechanical characterization revealed that the mechanical performance, permeability, and impact resistance increased as the ratio of latex polymer to rapid-set binder decreased. The mixture exhibited a compressive strength of ≥21 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ≤0.29. The mixture exhibited a flexural strength of ≥3.5 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ≤0.33. The permeability resistance to chloride ions satisfied 2000 C after 7 days of curing for all ratios. The ratio of latex polymer to rapid-set binder material that satisfied all conditions for emergency pavement repair was ≤0.29. PMID:28793596

  17. Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content.

    PubMed

    Han, Jae-Woong; Jeon, Ji-Hong; Park, Chan-Gi

    2015-10-01

    We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ¥21 MPa and a flexural strength of ¥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement). The ratio of latex polymer to rapid-set binder material was varied through 0.40, 0.33, 0.29, and 0.25. Mechanical characterization revealed that the mechanical performance, permeability, and impact resistance increased as the ratio of latex polymer to rapid-set binder decreased. The mixture exhibited a compressive strength of ¥21 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.29. The mixture exhibited a flexural strength of ¥3.5 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.33. The permeability resistance to chloride ions satisfied 2000 C after 7 days of curing for all ratios. The ratio of latex polymer to rapid-set binder material that satisfied all conditions for emergency pavement repair was ¤0.29.

  18. Estimation of three-phase relative permeability by simulating fluid dynamics directly on rock-microstructure images

    NASA Astrophysics Data System (ADS)

    Jiang, F.; Tsuji, T.

    2017-01-01

    Given the world's growing demand for energy, a combination of geological CO2 sequestration and enhanced oil recovery (EOR) technologies is currently regarded as a promising solution, as it would provide a means of reducing carbon emissions into the atmosphere while also leading to the economic benefit of simultaneously recovering oil. The optimization of injection strategies to maximize CO2 storage and increase the oil recovery factors requires complicated pore-scale flow information within a reservoir system consisting of coexisting oil, water, and CO2 phases. In this study, an immiscible three-phase lattice-Boltzmann (LB) model was developed to investigate the complicated flow state with interaction between water, oil, and CO2 systems in porous media. The two main mechanisms of oil remobilization, namely, double-drainage and film flow, can be captured by our model. The estimation of three-phase relative permeability is proposed using the digital rock physics (DRP) simulations. The results indicate that the relative permeability of CO2 as calculated using our steady state method is not sensitive to the initial oil fraction if the oil distribution is originally uniform. Baker's (1988) empirical model was tested and found to be able to provide a good prediction of the three-phase relative permeability data. Our numerical method provides a new tool for accurately predicting three-phase relative permeability data directly based on micro-CT rock images.

  19. 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.

  20. 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.

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

    PubMed

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

    2016-07-30

    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.

  2. 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

  3. Analysis of the Dynamic Characteristics of Elliptical Gears

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Nagamura, Kazuteru; Ikejo, Kiyotaka

    To date, elliptical gear has been commonly used in automobile, automatic machinery, pumps, flow meters and printing presses for its particular non-uniform rotation. However, the dynamic characteristics of elliptical gears have not been clarified yet. In this study, The calculation as well as the experiment of two elliptical gears, which are a single elliptical gear and a double elliptical gear, is carried out to analyze the dynamic characteristics of elliptical gears. General factors including the torque, the rotation speed and the tooth root stress of the test gears are investigated. According to the analysis conducted in this study, the dynamic input torque variation of elliptical gear becomes larger along with the increase of operating gear rotation speed and the experimental one increases much faster than the calculated one over the Critical Rotation Speed of Tooth Separation (CRSTS) of elliptical gear. The experimental input rotation speed varies according to the variation of input torque, leading to the difference between the experimental output rotation speed and the desired one. The calculation results of the CRSTS of elliptical gears are almost equal to the experimental ones. The dynamic load variation ratios of elliptical gear at different angular position as well as their changing trends with operating gear rotation speed are quite different from each other. And the experimental dynamic load variation ratios of elliptical gear show difference from the calculated ones because of tooth separation and tooth impact. The agreement of the calculation and experimental results proves the validity of this study.

  4. 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.

  5. 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.

  6. Static and dynamic characteristics of large deployable space reflectors

    NASA Technical Reports Server (NTRS)

    El-Raheb, M.; Wagner, P.

    1981-01-01

    A linear numerical model of the structural characteristics of deployable reflectors was developed. Due to cyclic symmetry of the reflector structure about its axis, only one of many segments is modeled using finite elements. The succeeding segments satisfy continuity of displacement and slope at the interface between consecutive segments. This process leads to (N/2+1) static or dynamic problems of smaller order and bandwidth where N is the number of segments. The solution of each reduced problem leads to motions having a distinct circumferential wave number. The dynamic coupling to the feed support structure is studied adopting modal synthesis.

  7. Study on Dynamic Characteristics of Ammonia Refrigerator System

    NASA Astrophysics Data System (ADS)

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

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

  8. Unified power flow controller: modeling and dynamic characteristic

    NASA Astrophysics Data System (ADS)

    Bach, D. H.; Loc, H. D.

    2005-12-01

    Unified power flow controller (UPFC) consists two converters. There are three purposes of this paper, firstly to illustrate the UPFC device based VSC designs, then to describe a decoupling method the UPFC's controller into two separate control systems of the shunt and the series converters respectively in realizing an appropriate coordination between them. Finally, using the Matlab tool to build a discrete simulator for the UPFC with 12 pulse converters. The simulation results show that the developed UPFC model is reflected the static and dynamic characteristics of the UPFC. The harmonics of the output of the model were analyzed. Using the simple power system with UPFC as an example, the dynamics characteristics were studied. The fault status of the system with UPFC was analyzed too.

  9. 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.

  10. Structural and dynamic characteristics in monolayer square ice

    NASA Astrophysics Data System (ADS)

    Zhu, YinBo; Wang, FengChao; Wu, HengAn

    2017-07-01

    When water is constrained between two sheets of graphene, it becomes an intriguing monolayer solid with a square pattern due to the ultrahigh van der Waals pressure. However, the square ice phase has become a matter of debate due to the insufficient experimental interpretation and the slightly rhomboidal feature in simulated monolayer square-like structures. Here, we performed classical molecular dynamics simulations to reveal monolayer square ice in graphene nanocapillaries from the perspective of structure and dynamic characteristics. Monolayer square-like ice (instantaneous snapshot), assembled square-rhombic units with stacking faults, is a long-range ordered structure, in which the square and rhombic units are assembled in an order of alternative distribution, and the other rhombic unit forms stacking faults (polarized water chains). Spontaneous flipping of water molecules in monolayer square-like ice is intrinsic and induces transformations among different elementary units, resulting in the structural evolution of monolayer square ice in dynamics. The existence of stacking faults should be attributed to the spontaneous flipping behavior of water molecules under ambient temperature. Statistical averaging results (thermal average positions) demonstrate the inherent square characteristic of monolayer square ice. The simulated data and insight obtained here might be significant for understanding the topological structure and dynamic behavior of monolayer square ice.

  11. Structural and dynamic characteristics in monolayer square ice.

    PubMed

    Zhu, YinBo; Wang, FengChao; Wu, HengAn

    2017-07-28

    When water is constrained between two sheets of graphene, it becomes an intriguing monolayer solid with a square pattern due to the ultrahigh van der Waals pressure. However, the square ice phase has become a matter of debate due to the insufficient experimental interpretation and the slightly rhomboidal feature in simulated monolayer square-like structures. Here, we performed classical molecular dynamics simulations to reveal monolayer square ice in graphene nanocapillaries from the perspective of structure and dynamic characteristics. Monolayer square-like ice (instantaneous snapshot), assembled square-rhombic units with stacking faults, is a long-range ordered structure, in which the square and rhombic units are assembled in an order of alternative distribution, and the other rhombic unit forms stacking faults (polarized water chains). Spontaneous flipping of water molecules in monolayer square-like ice is intrinsic and induces transformations among different elementary units, resulting in the structural evolution of monolayer square ice in dynamics. The existence of stacking faults should be attributed to the spontaneous flipping behavior of water molecules under ambient temperature. Statistical averaging results (thermal average positions) demonstrate the inherent square characteristic of monolayer square ice. The simulated data and insight obtained here might be significant for understanding the topological structure and dynamic behavior of monolayer square ice.

  12. Dynamic Characteristics of Retinal Ganglion Cell Responses in Goldfish

    PubMed Central

    Schellart, Nico A. M.; Spekreijse, Henk

    1972-01-01

    A cross-correlation technique has been applied to quantify the dependence of the dynamic characteristics of retinal ganglion cell responses in goldfish on intensity, wavelength, spatial configuration, and spot size. Both theoretical and experimental evidence justify the use of the cross-correlation procedure which allows the completion of rather extensive measurements in a relatively short time. The findings indicate the following. (a) The shape of the amplitude characteristics depends on the energy per unit of time (power) falling within the center of a receptive field rather than on the intensity of the stimulus spot. For spot diameters of up to 1 mm, identical amplitude characteristics can be obtained by interchanging area and intensity. Therefore the receptor processes do not contribute to the change in the amplitude characteristics as a function of the power of the stimulus light. (b) For high frequencies the amplitude characteristics obtained as a function of power join together in a common envelope if plotted on an absolute sensitivity scale. For spontaneous ganglion cells this envelope holds over a range of three log units and the shape is identical for central and peripheral processes. (c) The amplitude characteristics of the central and peripheral processes converging to a ganglion cell are identical, irrespective of the sign (on or off) and the spectral coding of the response. Therefore we have no evidence for interneurons in the goldfish retina unique to the periphery of the receptive field. PMID:5007262

  13. Relaxation and dynamical characteristics of nematic liquid crystals

    NASA Astrophysics Data System (ADS)

    Nevskaya, G. E.; Shadrin, V. S.

    1988-04-01

    We study the volt-ampere, volt-farad, and magnetofarad characteristics of homeo-tropically oriented MBBA samples of different thicknesses. The characteristics are obtained for different rates of change of the displacement voltage. It is shown that the volt-farad and magnetofarad curves have an obvious threshold. Increase in the scan rate leads to a shift of the threshold in the volt-farad curves to the higher voltage region. The dynamical volt-ampere curves have regions where the variation of the current is nonmonotonic at small scan rates and have a sharp maximum for large rates. Comparison of the volt-ampere and volt-farad characteristics shows that the physical processes causing the threshold in the volt-farad curves and the features of the volt-ampere curves are related to one another. A discussion of the results is given.

  14. Measurement of choroid plexus perfusion using dynamic susceptibility MR imaging: capillary permeability and age-related changes.

    PubMed

    Bouzerar, Roger; Chaarani, Bader; Gondry-Jouet, Catherine; Zmudka, Jadwiga; Balédent, Olivier

    2013-12-01

    The cerebrospinal fluid (CSF) plays a major role in the physiology of the central nervous system. The continuous turnover of CSF is mainly attributed to the highly vascularized choroid plexus (CP) located in the cerebral ventricles which represent a complex interface between blood and CSF. We propose a method for evaluating CP functionality in vivo using perfusion MR imaging and establish the age-related changes of associated parameters. Fifteen patients with small intracranial tumors were retrospectively studied. MR Imaging was performed on a 3T MR Scanner. Gradient-echo echo planar images were acquired after bolus injection of gadolinium-based contrast agent (CA). The software developed used the combined T1- and T2-effects. The decomposition of the relaxivity signals enables the calculation of the CP capillary permeability (K2). The relative cerebral blood volume (rCBV), mean transit time (MTT), and signal slope decrease (SSD) were also calculated. The mean permeability K2 of the extracted CP was 0.033+/-0.18 s(-1). K2 and SSD significantly decreased with subject's age whereas MTT significantly increased with subject's age. No significant correlation was found for age-related changes in rCBV and rCBF. The decrease in CP permeability is in line with the age-related changes in CSF secretion observed in animals. The MTT increase indicates significant structural changes corroborated by microscopy studies in animals or humans. Overall, DSC MR-perfusion enables an in vivo evaluation of the hemodynamic state of CP. Clinical applications such as neurodegenerative diseases could be considered thanks to specific functional studies of CP.

  15. Drug permeability prediction using PMF method.

    PubMed

    Meng, Fancui; Xu, Weiren

    2013-03-01

    Drug permeability determines the oral availability of drugs via cellular membranes. Poor permeability makes a drug unsuitable for further development. The permeability may be estimated as the free energy change that the drug should overcome through crossing membrane. In this paper the drug permeability was simulated using molecular dynamics method and the potential energy profile was calculated with potential of mean force (PMF) method. The membrane was simulated using DPPC bilayer and three drugs with different permeability were tested. PMF studies on these three drugs show that doxorubicin (low permeability) should pass higher free energy barrier from water to DPPC bilayer center while ibuprofen (high permeability) has a lower energy barrier. Our calculation indicates that the simulation model we built is suitable to predict drug permeability.

  16. An efficient calculation method for pharmacokinetic parameters in brain permeability study using dynamic contrast-enhanced MRI.

    PubMed

    Wang, Chunhao; Yin, Fang-Fang; Chang, Zheng

    2016-02-01

    To develop an efficient method for calculating pharmacokinetic (PK) parameters in brain DCE-MRI permeability studies. A linear least-squares fitting algorithm based on a derivative expression of the two-compartment PK model was proposed to analytically solve for the PK parameters. Noise in the expression was minimized through low-pass filtering. Simulation studies were conducted in which the proposed method was compared with two existing methods in terms of accuracy and efficiency. Five in vivo brain studies were demonstrated for potential clinical application. In the simulation studies using chosen parameter values, the calculated percent difference of K(trans) by the proposed method was <5.0% with a temporal resolution (Δt) < 5 s, and the accuracies of all parameter results were better or comparable to existing methods. When analyzed within certain parameter intensity ranges, the proposed method was more accurate than the existing methods and improved the efficiency by a factor of up to 458 for a Δt = 1 s and up to 38 for a Δt = 5 s. In the in vivo study, the calculated parameters using the proposed method were comparable to those using the existing methods with improved efficiencies. An efficient method was developed for the accurate and efficient calculation of parameters in brain DCE-MRI permeability studies. © 2015 Wiley Periodicals, Inc.

  17. Bubbly flow model for the dynamic characteristics of cavitating pumps

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1978-01-01

    The recent experimental transfer matrices obtained by Ng and Brennen (1978) for some axial flow pumps revealed some dynamic characteristics which were unaccounted for by any existing theoretical analysis; their visual observations suggested that the bubbly cavitating flow in the blade passages could be responsible for these effects. A theoretical model of the dynamic response of this bubbly blade-passage flow is described in the present paper. Void-fraction fluctuations in this flow result not only from pressure fluctuations but also because the fluctuating angle of attack causes fluctuations in the rate of production of bubbles near the leading edge. The latter causes kinematic waves which interact through the boundary conditions with the dynamic waves caused by pressure fluctuation. The resulting theoretical transfer functions which results are in good qualitative agreement with the experiments; with appropriate choices of two parameters good quantitative agreement is also obtained. The theoretical model also provides one possible explanation of the observation that the pump changes from an essentially passive dynamic element in the absence of cavitation to a progressively more active element as the extent of cavitation increases.

  18. Bubbly flow model for the dynamic characteristics of cavitating pumps

    NASA Technical Reports Server (NTRS)

    Brennen, C.

    1978-01-01

    The recent experimental transfer matrices obtained by Ng and Brennen (1978) for some axial flow pumps revealed some dynamic characteristics which were unaccounted for by any existing theoretical analysis; their visual observations suggested that the bubbly cavitating flow in the blade passages could be responsible for these effects. A theoretical model of the dynamic response of this bubbly blade-passage flow is described in the present paper. Void-fraction fluctuations in this flow result not only from pressure fluctuations but also because the fluctuating angle of attack causes fluctuations in the rate of production of bubbles near the leading edge. The latter causes kinematic waves which interact through the boundary conditions with the dynamic waves caused by pressure fluctuation. The resulting theoretical transfer functions which results are in good qualitative agreement with the experiments; with appropriate choices of two parameters good quantitative agreement is also obtained. The theoretical model also provides one possible explanation of the observation that the pump changes from an essentially passive dynamic element in the absence of cavitation to a progressively more active element as the extent of cavitation increases.

  19. 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.

  20. Dynamic characteristics of a molten carbonate fuel cell stack

    NASA Astrophysics Data System (ADS)

    Sasaki, Akira; Matsumoto, Shuichi; Tanaka, Toshihide; Ohtsuki, Jitsuji

    Dynamic characteristics have been investigated for a molten carbonate fuel cell (MCFC) prototype stack, which is, an eletrochemical energy conversion device for electric power generation. The authors identify the MCFC stack and construct a control strategy for MCFC plants in operation. Both an experimental approach and a theoretical approach are described. Basic data are first obtained with respect to indicial responses of an MCFC stack including a cathode gas recycle loop for cooling use. These data are assumed to be sets of dead time and first-order lag, and a matrix transfer function is derived. A physically based model is then developed to describe the dynamics of the MCFC stack. This model consists of a semiempirical MCFC performance model and a thermodynamical gas flow model. The potential of this model for examining control problems for MCFC plant operations is discussed.

  1. Dynamic characteristics of the LLNL Precision Engineering Research Lathe

    SciTech Connect

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

    1988-08-31

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

  2. 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.

  3. Charge dynamic characteristics in corona-charged polytetrafluoroethylene film electrets.

    PubMed

    Chen, Gang-Jin; Xiao, Hui-Ming; Zhu, Chun-Feng

    2004-08-01

    In this work, the charge dynamics characteristics of injection, transport and decay in porous and non-porous polytetrafluoroethylene (PTFE) film electrets were investigated by means of corona charging, isothermal and thermal stimulating surface-potential decay measurements. The results showed that the initial surface potential, whether positively or negatively charging, is much higher in non-porous PTFE than in porous PTFE. For porous film the value of initial surface potentials increases with increase of film thickness. Higher charging temperature can remarkably improve charge stability. The charge dynamics are correlated to materials microstructure according to their scanning electron micrographs. For non-porous PTFE films, polarizability change of C-F bonds is the main origin of electret charges; but for porous PTFE film a large number of bulk and interface type traps are expected because of the greater area of interface and higher crystallinity.

  4. Human dynamics scaling characteristics for aerial inbound logistics operation

    NASA Astrophysics Data System (ADS)

    Wang, Qing; Guo, Jin-Li

    2010-05-01

    In recent years, the study of power-law scaling characteristics of real-life networks has attracted much interest from scholars; it deviates from the Poisson process. In this paper, we take the whole process of aerial inbound operation in a logistics company as the empirical object. The main aim of this work is to study the statistical scaling characteristics of the task-restricted work patterns. We found that the statistical variables have the scaling characteristics of unimodal distribution with a power-law tail in five statistical distributions - that is to say, there obviously exists a peak in each distribution, the shape of the left part closes to a Poisson distribution, and the right part has a heavy-tailed scaling statistics. Furthermore, to our surprise, there is only one distribution where the right parts can be approximated by the power-law form with exponent α=1.50. Others are bigger than 1.50 (three of four are about 2.50, one of four is about 3.00). We then obtain two inferences based on these empirical results: first, the human behaviors probably both close to the Poisson statistics and power-law distributions on certain levels, and the human-computer interaction behaviors may be the most common in the logistics operational areas, even in the whole task-restricted work pattern areas. Second, the hypothesis in Vázquez et al. (2006) [A. Vázquez, J. G. Oliveira, Z. Dezsö, K.-I. Goh, I. Kondor, A.-L. Barabási. Modeling burst and heavy tails in human dynamics, Phys. Rev. E 73 (2006) 036127] is probably not sufficient; it claimed that human dynamics can be classified as two discrete university classes. There may be a new human dynamics mechanism that is different from the classical Barabási models.

  5. Permeability testing of biomaterial membranes.

    PubMed

    Dreesmann, L; Hajosch, R; Ahlers, M; Nuernberger, J Vaz; Schlosshauer, B

    2008-09-01

    The permeability characteristics of biomaterials are critical parameters for a variety of implants. To analyse the permeability of membranes made from crosslinked ultrathin gelatin membranes and the transmigration of cells across the membranes, we combined three technical approaches: (1) a two-chamber-based permeability assay, (2) cell culturing with cytochemical analysis and (3) biochemical enzyme electrophoresis (zymography). Based on the diffusion of a coloured marker molecule in conjunction with photometric quantification, permeability data for a gelatin membrane were determined in the presence or absence of gelatin degrading fibroblasts. Cytochemical evaluation after cryosectioning of the membranes was used to ascertain whether fibroblasts had infiltrated the membrane inside. Zymography was used to investigate the potential release of proteases from fibroblasts, which are known to degrade collagen derivatives such as gelatin. Our data show that the diffusion equilibrium of a low molecular weight dye across the selected gelatin membrane is approached after about 6-8 h. Fibroblasts increase the permeability due to cavity formation in the membrane inside without penetrating the membrane for an extended time period (>21 days in vitro). Zymography indicates that cavity formation is most likely due to the secretion of matrix metalloproteinases. In summary, the combination of the depicted methods promises to facilitate a more rational development of biomaterials, because it provides a rapid means of determining permeability characteristics and bridges the gap between descriptive methodology and the mechanistic understanding of permeability alterations due to biological degradation.

  6. 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.

  7. Dynamic characteristics of photonic crystal quantum dot lasers.

    PubMed

    Banihashemi, Mehdi; Ahmadi, Vahid

    2014-04-20

    In this paper, we analyze the dynamic characteristics of quantum dot (QD) photonic crystal lasers by solving Maxwell equations coupled to rate equations through linear susceptibility of QDs. Here, we study the effects of the quality factor of the microcavity and temperature on the delay, relaxation oscillation frequency, and output intensity of the lasers. Moreover, we investigate the dependence of the Purcell factor on temperature. We show that when the quality factor of the microcavity is so high that we can consider its linewidth as a delta function in comparison with QDs, the Purcell factor significantly drops with increasing temperature.

  8. 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.

  9. Evaluation of water binding, seed coat permeability and germination characteristics of wheat seeds equilibrated at different relative humidities.

    PubMed

    Chatterjee, Nabamita; Nagarajan, Shantha

    2006-08-01

    The relative binding of seed water and seed coat membrane stability were measured in two contrasting wheat (Triticum aestivum L) varieties, HDR 77 (drought-tolerant) and HD 2009 (susceptible) using seed water sorption isotherms, electrical conductivity (EC) of leachates and desorption-absorption isotherms. Analysis of sorption isotherm at 25 degrees C showed that the seeds of HDR 77 had significantly higher number of strong binding sites, with correspondingly greater amount of seed water as strongly bound water, as compared to HD 2009. Total number of binding sites was also higher in HDR 77 than HD 2009, which explained the better desiccation tolerance and higher capacity to bind water in seeds of HDR 77. EC of seed leachate in both varieties did not change with respect to change in equilibrium relative humidity (RII), indicating the general seed coat membrane stability of wheat seeds. However, absolute conductivity values were higher for HD 2009. showing its relatively porous seed coat membrane. Significantly lower area enclosed by the desorption-absorption isotherm loop in HDR 77, as compared to HD 2009 also indicated the greater membrane integrity of HDR 77. Germination and seedling vigour of HD 2009 were reduced when equilibrated over very low and very high RH. In contrast, germination and vigour in HDR 77 were maintained high, except at very high RH, indicating again its desiccation tolerance. Thus, the study demonstrated the relative drought tolerance of HDR 77, on the basis of seed water-binding characteristics and seed membrane stability. Seed membrane stability as measured by seed leachate conductivity or as area under dehydration-rehydration loop may be used as a preliminary screening test for drought tolerance in wheat.

  10. Interfacial characteristics of resin-modified glass-ionomer materials: a study on fluid permeability using confocal fluorescence microscopy.

    PubMed

    Sidhu, S K; Watson, T F

    1998-09-01

    The tooth interface with resin-modified glass-ionomer cements (RM GICs) is poorly understood. This study examined the interface, especially with dentin. Cervical cavities in extracted teeth were restored with Fuji II LC, Vitremer, Photac-Fil, or a conventional GIC, Fuji Cap II. Fluorescent dye was placed in the pulp chambers for 3 hrs before the specimens were sectioned. Examination of the tooth/material interface with a confocal microscope showed that dye uptake by the restoration varied among materials. A "structureless", non-particulate, highly-stained layer of GIC was observed next to dentin in Fuji II LC. This layer varied in width, was prominent where the dentin tubules were cut "end-on" and in areas closer to the pulp, and was not seen adjacent to enamel. Vitremer showed minimal dye uptake, and the "structureless" layer was barely discernible. Photac-Fil showed more uniform uptake and absence of this layer. Cracking of enamel was also noted with these materials. The conventional GIC did not show any dye uptake, presence of a "structureless" layer, or enamel cracking. We elucidated the potential mechanisms involved in the formation of a "structureless" interfacial layer in Fuji II LC by studying the variables of cavity design, surface pre-treatment, water content of the tooth, time for it to develop, early finishing, and coating of the restoration. This layer, the "absorption layer", is probably related to water flux within the maturing cement, depending on environmental moisture changes and communication with the pulp in a wet tooth. The "micropermeability model" was useful in this study of the interfacial characteristics of RM GICs.

  11. Radiation characteristics and implosion dynamics of Z-pinch dynamic hohlraums performed on PTS facility

    NASA Astrophysics Data System (ADS)

    Huang, Xian Bin; Ren, Xiao Dong; Dan, Jia Kun; Wang, Kun Lun; Xu, Qiang; Zhou, Shao Tong; Zhang, Si Qun; Cai, Hong Chun; Li, Jing; Wei, Bing; Ji, Ce; Feng, Shu Ping; Wang, Meng; Xie, Wei Ping; Deng, Jian Jun

    2017-09-01

    The preliminary experimental results of Z-pinch dynamic hohlraums conducted on the Primary Test Stand (PTS) facility are presented herein. Six different types of dynamic hohlraums were used in order to study the influence of load parameters on radiation characteristics and implosion dynamics, including dynamic hohlraums driven by single and nested arrays with different array parameters and different foams. The PTS facility can deliver a current of 6-8 MA in the peak current and 60-70 ns in the 10%-90% rising time to dynamic hohlraum loads. A set of diagnostics monitor the implosion dynamics of plasmas, the evolution of shock waves in the foam and the axial/radial X-ray radiation, giving the key parameters characterizing the features of dynamic hohlraums, such as the trajectory and related velocity of shock waves, radiation temperature, and so on. The experimental results presented here put our future study on Z-pinch dynamic hohlraums on the PTS facility on a firm basis.

  12. Effects of chlorpromazine on plasma membrane permeability and fluidity in the rat brain: a dynamic positron autoradiography and fluorescence polarization study.

    PubMed

    Maruoka, Nobuyuki; Murata, Tetsuhito; Omata, Naoto; Takashima, Yasuhiro; Tanii, Hideji; Yonekura, Yoshiharu; Fujibayashi, Yasuhisa; Wada, Yuji

    2007-01-30

    Antipsychotic drugs have been widely used in psychiatry for the treatment of various mental disorders, but the underlying biochemical mechanisms of their actions still remain unclear. Although phenothiazine antipsychotic drugs have been reported to directly interact with the peripheral plasma membrane, it is not known whether these drugs actually affect plasma membrane integrity in the central nervous system. To clarify these issues, we investigated the effect of chlorpromazine (CPZ), a typical phenothiazine antipsychotic drug, on plasma membrane permeability in fresh rat brain slices using a dynamic positron autoradiography technique and [(18)F]2-fluoro-2-deoxy-D-glucose ([(18)F]FDG) as a tracer. Treatment with CPZ (> or =100 microM) resulted in the leakage of [(18)F]FDG-6-phosphate, but not [(18)F]FDG, suggesting that the [(18)F]FDG-6-phosphate efflux was not mediated by glucose transporters, but rather by plasma membrane permeabilization. The leakage of [(18)F]FDG-6-phosphate was followed by slower leakage of cytoplasmic lactate dehydrogenase, suggesting that CPZ could initially induce small membrane holes that enlarged with time. Furthermore, the addition of CPZ (> or =100 microM) caused a decrease in 1,6-diphenyl-1,3,5-hexatriene fluorescence anisotropy, which implies an increase in membrane fluidity. CPZ loading dose-dependently increased both membrane permeability and membrane fluidity, which suggested the involvement of a perturbation of membrane order in the mechanisms of membrane destabilization induced by antipsychotic drugs.

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

    SciTech Connect

    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 assessed as a function of key system parameters including kink density, step attachment barriers, and the step edge diffusion rate.

  14. 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

  15. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

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

    PubMed

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

    2015-06-09

    Steering magnetism by electric fields upon interfacing ferromagnetic (FM) and ferroelectric (FE) materials to achieve an emergent multiferroic response bears a great potential for nano-scale devices with novel functionalities. FM/FE heterostructures allow, for instance, the electrical manipulation of magnetic anisotropy via interfacial magnetoelectric (ME) couplings. A charge-mediated ME effect is believed to be generally weak and active in only a few angstroms. Here we present an experimental evidence uncovering a new magnon-driven, strong ME effect acting on the nanometer range. For Co92Zr8 (20 nm) film deposited on ferroelectric PMN-PT we show via ferromagnetic resonance (FMR) that this type of linear ME allows for electrical control of simultaneously the magnetization precession and its damping, both of which are key elements for magnetic switching and spintronics. The experiments unravel further an electric-field-induced negative magnetic permeability effect.

  18. 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.

  19. Dynamic characteristics and mechatronics model for maglev blood pump

    NASA Astrophysics Data System (ADS)

    Sun, Kun; Chen, Chen

    2017-01-01

    Magnetic bearing system(MBs) has been developed in the new-generation blood pump due to its low power consumption, low blood trauma and high durability. However, MBs for a blood pump were almost influenced by a series of factors such as hemodynamics, rotation speeds and actuator response in working fluids, compared with those applied in other industrial fields. In this study, the dynamic characteristics of MBs in fluid environments, including the influence of the pumping fluid and rotation of the impeller on the radial dynamic model were investigated by measuring the frequency response to sinusoidal excitation upon coils, and the response of radial displacement during a raise in the speed. The excitation tests were conducted under conditions in which the blood pump was levitated in air and water and with or without rotation. The experimental and simulated results indicate that rotations of the impeller affected the characteristics of MBs in water apparently, and the vibration in water was decreased, compared with that in air due to the hydraulic force. During the start-up and rotation, the actuator failed to operate fully and timely, and the voltage supplied can be chosen under the consideration of the rotor displacement and consumption.

  20. 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.

  1. [Adsorption dynamics and breakthrough characteristics based on the fluidization condition].

    PubMed

    Wang, Jun; Wang, Yao; Huang, Xing; Yuan, Yi-Long; Chen, Rui-Hui; Zhou, Hang; Zhou, Dan-Dan

    2014-02-01

    Few studies on the adsorption dynamics and breakthrough characteristics based on the fluidization condition have been reported. In a fluidized bed adsorption reactor with phenol as the adsorbate and granular activated carbon as the adsorbent, the adsorption efficiency, adsorption dynamic characteristics, adsorption breakthrough curves and adsorption capacities were studied and compared with those of a fixed bed operated under the same conditions. The results showed that the adsorption efficiencies exceeded 93% in 5 min in both the fluidized conditions and fixed conditions at the superficial velocities of 8 mm x s(-1) and 13 mm x s(-1). Meanwhile, the above adsorption reactions fitted to Pseudo-second-order with linear correlation coefficients greater than 0.999. The adsorption capacity of fluidized conditions was 8.77 mg x g(-1) and 24.70 mg x g(-1) at the superficial velocities of 6 mm x s(-1) and 8 mm x s(-1). Generally, the fluidized bed reactor showed a higher adsorption efficiency and greater adsorption capacity than the fixed bed reactor.

  2. 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.

  3. 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.

  4. Dynamic characteristics of a simple bursting neuron model

    NASA Astrophysics Data System (ADS)

    Nakajima, Koji; Sato, Shigeo; Hayakawa, Yoshihiro

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

  5. 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).

  6. Ca2+ imaging of mouse neocortical interneurone dendrites: Contribution of Ca2+-permeable AMPA and NMDA receptors to subthreshold Ca2+dynamics

    PubMed Central

    Goldberg, Jesse H; Yuste, Rafael; Tamas, Gabor

    2003-01-01

    In this second study, we have combined two-photon calcium imaging with whole-cell recording and anatomic reconstructions to directly characterize synaptically evoked calcium signals in three types of mouse V1 supragranular interneurones: parvalbumin-positive fast spikers (FS), calretinin-positive irregular spikers (IS), and adapting cells (AD). We observed that subthreshold synaptic activation evoked calcium signals locally restricted to individual dendritic compartments. These signals were mediated by NMDA receptors (NMDARs) in AD and IS cells, whereas in FS cells, calcium-permeable AMPA receptors (CP-AMPARs) provided an additional and kinetically distinct influx. Furthermore, even a single, subthreshold synaptic activation evoked a larger dendritic calcium influx than backpropagating action potentials. Our results demonstrate that NMDARs dominate subthreshold calcium dynamics in interneurones and reveal the functional contribution of CP-AMPARs to a specific subclass of cortical interneurone. These data highlight different strategies in dendritic signal processing by distinct classes of interneurones. PMID:12844507

  7. The percolation threshold and permeability evolution of ascending magmas

    NASA Astrophysics Data System (ADS)

    Burgisser, Alain; Chevalier, Laure; Gardner, James E.; Castro, Jonathan M.

    2017-07-01

    The development of gas permeability in magmas is a complex phenomenon that directly influences the style of a volcanic eruption. The emergence of permeability is linked to the concept of percolation threshold, which is the point beyond which gas bubbles are connected in a continuous network that allows gas escape. Measurements of the percolation threshold, however, range from ∼30 to 78 vol%. No known combination of parameters can explain such a wide range of threshold values, which affects our understanding of the relationship between percolation and permeability. We present permeability calculations on bubble-bearing rhyolitic melts that underwent experimental decompression. Samples were analyzed by X-ray microtomography to image the bubble networks in 3D. We develop a percolation threshold for magmas that depends on the bubble network characteristics of this sample set. This relationship recovers the behavior of a wide range of volcanic samples by separating permeable samples from impermeable ones with a success rate of 88%. We use this percolation threshold to propose simplified permeability relationships that rely on parameters widely used in numerical modeling of magma flow. These relationships are valid within one order of magnitude for the viscous permeability coefficient and within two orders of magnitude for the inertial coefficient. They recover the ranges of values previously covered by isolated relationships, reassembling them within a single framework. We test the implications of such unification on eruptive dynamics with a 1D, two-phase conduit flow model. This test shows that varying the percolation threshold has little influence on vertical gas loss and ascent dynamics.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  10. Drivers of bacterial diversity dynamics in permeable carbonate and silicate coral reef sands from the Red Sea.

    PubMed

    Schöttner, Sandra; Pfitzner, Barbara; Grünke, Stefanie; Rasheed, Mohammed; Wild, Christian; Ramette, Alban

    2011-07-01

    Permeable sediments and associated microbial communities play a fundamental role in nutrient recycling within coral reef ecosystems by ensuring high levels of primary production in oligotrophic environments. A previous study on organic matter degradation within biogenic carbonate and terrigenous silicate reef sands in the Red Sea suggested that observed sand-specific differences in microbial activity could be caused by variations in microbial biomass and diversity. Here, we tested this hypothesis by comparing bacterial abundance and community structure in both sand types, and by further exploring the structuring effects of time (season) and space (sediment depth, in/out-reef). Changes in bacterial community structure, as determined via automated ribosomal intergenic spacer analysis (ARISA), were primarily driven by sand mineralogy at specific seasons, sediment depths and reef locations. By coupling ARISA with 16S-ITS rRNA sequencing, we detected significant community shifts already at the bacterial class level, with Proteobacteria (Gamma-, Delta-, Alpha-) and Actinobacteria being prominent members of the highly diverse communities. Overall, our findings suggest that reef sand-associated bacterial communities vary substantially with sand type. Especially in synergy with environmental variation over time and space, mineralogical differences seem to play a central role in maintaining high levels of bacterial community heterogeneity. The local co-occurrence of carbonate and silicate sands may thus significantly increase the availability of microbial niches within a single coral reef ecosystem. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

  11. Design of helicopter rotor blades for optimum dynamic characteristics

    NASA Technical Reports Server (NTRS)

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

    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.

  12. Characteristics of SBS dynamics in single-mode optical fibres

    SciTech Connect

    Gordeev, A A; Efimkov, V F; Zubarev, I G; Mikhailov, S I; Sobolev, V B

    2016-03-31

    The characteristics of the gain of Stokes pulses in single-mode optical fibres by stimulated Brillouin scattering (SBS) of monochromatic and nonmonochromatic pump signals have been investigated by numerical simulation using a spectral approach. Conditions under which 'slow light' (caused by a group delay) can be implemented are found (it is reasonable to apply this term to a process in which a pulse is delayed with conservation of its shape). The plane-wave interaction model is shown to describe adequately the dynamics of this process in single-mode fibres. A number of gain modes are investigated for Stokes pulses with different time structures upon monochromatic and nonmonochromatic excitation. A new data transfer technique is proposed, which is based on the conversion of stepwise phase modulation of the input Stokes signal into amplitude modulation of the output signal. (nonlinear optical phenomena)

  13. 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.

  14. Design of helicopter rotor blades for optimum dynamic characteristics

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  15. Dynamics of Stride Interval Characteristics during Continuous Stairmill Climbing.

    PubMed

    Raffalt, Peter C; Vallabhajosula, Srikant; Renz, Jessica J; Mukherjee, Mukul; Stergiou, Nicholas

    2017-01-01

    It has been shown that statistical persistence in stride intervals characteristics exist during walking, running and cycling and were speed-dependent among healthy young adults. The purpose of this study was to determine if such statistical persistence in stride time interval, stride length and stride speed also exists during self-paced continuous stairmill climbing and if the strength is dependent on stepping rate. Stride time, stride length, and stride speed were collected from nine healthy participants during 3 min of stairmill climbing at 100, 110, and 120% of their preferred stepping rate (PSR) and 5 min of treadmill walking at preferred walking speed (PWS). The amount of variability (assessed by standard deviation and coefficient of variation) and dynamics (assessed by detrended fluctuation analysis and sample entropy) of the stride time, stride length, and stride speed time series were investigated. The amounts of variability were significantly higher during stairmill climbing for the stride time, stride length, and stride speed and did only change with increased stepping rate for stride speed. In addition to a more irregular pattern during stairmill climbing, the detrended fluctuation analysis (DFA) revealed that the stride length fluctuations were statistical anti-persistent for all subjects. On a group level both stride time and stride speed fluctuations were characterized by an uncorrelated pattern which was more irregular compared to that during treadmill walking. However, large inter-participant differences were observed for these two variables. In addition, the dynamics did not change with increase in stepping rate.

  16. Physical characteristics of cometary dust from dynamical studies - A review

    NASA Technical Reports Server (NTRS)

    Sekanina, Z.

    1980-01-01

    Progress made in the determination of the physical characteristics of cometary dust particles from studies of dust tail dynamics is reviewed. Applications of the combined dynamical photometric approach of Finson and Probstein (1968) to studies of cometary tails exhibiting continuous light intensity variations are discussed, with attention given to determinations of the particle-size-related distribution function of the solar radiation pressure exerted on the particles, the contribution of comets to the interplanetary dust, calculations of dust ejection rates and a Monte Carlo approach to the analysis of dust tails. Investigations of dust streamers and striae, which are believed to be related to comet outbursts entailing brief but sharp enhancements of dust production, are then reviewed, with particular attention given to observations of Comet West 1976 VI. Finally, the question of cometary particle type is addressed, and it is pointed out that the presence of submicron absorbing particles in the striae of Comet West is not incompatible with the presence of micron-size dielectric particles in the inner coma.

  17. Dynamics of Stride Interval Characteristics during Continuous Stairmill Climbing

    PubMed Central

    Raffalt, Peter C.; Vallabhajosula, Srikant; Renz, Jessica J.; Mukherjee, Mukul; Stergiou, Nicholas

    2017-01-01

    It has been shown that statistical persistence in stride intervals characteristics exist during walking, running and cycling and were speed-dependent among healthy young adults. The purpose of this study was to determine if such statistical persistence in stride time interval, stride length and stride speed also exists during self-paced continuous stairmill climbing and if the strength is dependent on stepping rate. Stride time, stride length, and stride speed were collected from nine healthy participants during 3 min of stairmill climbing at 100, 110, and 120% of their preferred stepping rate (PSR) and 5 min of treadmill walking at preferred walking speed (PWS). The amount of variability (assessed by standard deviation and coefficient of variation) and dynamics (assessed by detrended fluctuation analysis and sample entropy) of the stride time, stride length, and stride speed time series were investigated. The amounts of variability were significantly higher during stairmill climbing for the stride time, stride length, and stride speed and did only change with increased stepping rate for stride speed. In addition to a more irregular pattern during stairmill climbing, the detrended fluctuation analysis (DFA) revealed that the stride length fluctuations were statistical anti-persistent for all subjects. On a group level both stride time and stride speed fluctuations were characterized by an uncorrelated pattern which was more irregular compared to that during treadmill walking. However, large inter-participant differences were observed for these two variables. In addition, the dynamics did not change with increase in stepping rate. PMID:28878688

  18. 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.

  19. 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.

  20. Towards an improved understanding of the nitrate dynamics in lowland, permeable river-systems: Applications of INCA-N

    NASA Astrophysics Data System (ADS)

    Wade, Andrew J.; Butterfield, D.; Whitehead, P. G.

    2006-10-01

    SummaryThe Integrated Catchment Model of Nitrogen (INCA-N) was applied to the Lambourn and Pang river-systems to integrate current process-knowledge and available-data to test two hypotheses and thereby determine the key factors and processes controlling the movement of nitrate at the catchment-scale in lowland, permeable river-systems: (i) that the in-stream nitrate concentrations were controlled by two end-members only: groundwater and soil-water, and (ii) that the groundwater was the key store of nitrate in these river-systems. Neither hypothesis was proved true or false. Due to equifinality in the model structure and parameters at least two alternative models provided viable explanations for the observed in-stream nitrate concentrations. One model demonstrated that the seasonal-pattern in the stream-water nitrate concentrations was controlled mainly by the mixing of ground- and soil-water inputs. An alternative model demonstrated that in-stream processes were important. It is hoped further measurements of nitrate concentrations made in the catchment soil- and ground-water and in-stream may constrain the model and help determine the correct structure, though other recent studies suggest that these data may serve only to highlight the heterogeneity of the system. Thus when making model-based assessments and forecasts it is recommend that all possible models are used, and the range of forecasts compared. In this study both models suggest that cereal production contributed approximately 50% the simulated in-stream nitrate load in the two catchments, and the point-source contribution to the in-stream load was minimal.

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

    SciTech Connect

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

    1998-10-01

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

  2. 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.

  3. 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

  4. 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

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

    2016-01-01

    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. 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. 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 K(trans); 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). 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.

  5. 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.

  6. Permeability evolution of shale during spontaneous imbibition

    DOE PAGES

    Chakraborty, N.; Karpyn, Z. T.; Liu, S.; ...

    2017-01-05

    Shales have small pore and throat sizes ranging from nano to micron scales, low porosity and limited permeability. The poor permeability and complex pore connectivity of shales pose technical challenges to (a) understanding flow and transport mechanisms in such systems and, (b) in predicting permeability changes under dynamic saturation conditions. This paper presents quantitative experimental evidence of the migration of water through a generic shale core plug using micro CT imaging. In addition, in-situ measurements of gas permeability were performed during counter-current spontaneous imbibition of water in nano-darcy permeability Marcellus and Haynesville core plugs. It was seen that water blocksmore » severely reduced the effective permeability of the core plugs, leading to losses of up to 99.5% of the initial permeability in experiments lasting 30 days. There was also evidence of clay swelling which further hindered gas flow. When results from this study were compared with similar counter-current gas permeability experiments reported in the literature, the initial (base) permeability of the rock was found to be a key factor in determining the time evolution of effective gas permeability during spontaneous imbibition. With time, a recovery of effective permeability was seen in the higher permeability rocks, while becoming progressively detrimental and irreversible in tighter rocks. Finally, these results suggest that matrix permeability of ultra-tight rocks is susceptible to water damage following hydraulic fracturing stimulation and, while shut-in/soaking time helps clearing-up fractures from resident fluid, its effect on the adjacent matrix permeability could be detrimental.« less

  7. Measurement of perfusion and permeability from dynamic contrast-enhanced MRI in normal and pathological vertebral bone marrow.

    PubMed

    Biffar, Andreas; Sourbron, Steven; Schmidt, Gerwin; Ingrisch, Michael; Dietrich, Olaf; Reiser, Maximilian F; Baur-Melnyk, Andrea

    2010-07-01

    Dynamic contrast-enhanced MRI data in vertebral bone marrow (vBM) are currently analyzed with descriptive indices. The purpose of this study was to develop and evaluate a quantitative approach, considering the tissue composition of vBM. Therefore, a measurement of the water fraction, f(wat), and the precontrast relaxation times, T(10 wat), T(10 fat), was added to the routine protocol. Signal analysis was generalized by allowing for an arbitrary fraction of fat. Plasma flow, plasma volume, extraction flow, and interstitial volume were determined from dynamic contrast-enhanced-MRI data. Simulations were used to determine the sensitivity to the precontrast values and to retrospectively verify the choice of the sequence parameters. Measurements were performed in healthy vertebral bodies (n = 30) and lesions of 15 patients with vertebral fractures. Extraction flow (milliliters per 100 mL/min) provided the strongest normal/abnormal separation: mean (standard deviation) was 0.3 (0.8) in healthy vBM and 6(4) in the fractures. Neglecting the fat component and the approximated signal analysis using relative signal enhancement produced significant differences. We conclude that correcting for the fat component in the signal and parametrization by tracer-kinetic analysis is necessary to avoid misinterpretation and/or systematic errors. The quantitative analysis is equally well suited as a descriptive parameter for the differentiation between normal and abnormal vertebral bone marrow. (c) 2010 Wiley-Liss, Inc.

  8. Dynamic characteristics of a WPC—comparison of transfer matrix method and FE method

    NASA Astrophysics Data System (ADS)

    Chen, Guo-Long; Nie, Wu

    2003-12-01

    To find the difference in dynamic characteristics between conventional monohull ship and wave penetrating catamaran (WPC), a WPC was taken as an object; its dynamic characteristics were computed by transfer matrix method and finite element method respectively. According to the comparison of the nature frequency results and mode shape results, the fact that FEM method is more suitable to dynamic characteristics analysis of a WPC was pointed out, special features on dynamic characteristics of WPC were given, and some beneficial suggestions are proposed to optimize the strength of a WPC in design period.

  9. Dynamic characteristics of controlled MR-STMDs of Wolgograd Bridge

    NASA Astrophysics Data System (ADS)

    Weber, F.

    2013-09-01

    This paper describes the dynamic characteristics of an adaptive tuned mass damper concept that is based on a real-time semi-actively controlled MR damper (MR-STMD) and is installed in the Wolgograd Bridge. The measurements and simulations of the prototype MR-STMD on the 15.6 m Empa bridge at different disturbing force levels demonstrate that the MR-STMD can cope with the nonlinear effect by which the resonance frequency and damping ratio of the Empa bridge depend on the amplitude and thereby on the excitation level. Whereas the efficiency of the MR-STMD is hardly affected by the aforementioned nonlinear effects, the passive TMD shows strong de-tuning. The tests for fast changes in frequency and amplitude of the disturbing force show that the response of the Empa bridge with the MR-STMD is smaller both during steady state and transient conditions than with a passive TMD, and the relative motion amplitudes in the MR-STMD are smaller or equal to those in the passive TMD. The force tracking accuracies of the prototype MR-STMD and of the Wolgograd MR-STMD are shown to be accurate, which generates precise frequency tuning of the MR-STMD in real-time and thereby explains the achievements described above. The test results indicate that the real-time controlled MR-STMD is an efficient and robust tool for the mitigation of structural vibrations.

  10. Cryoemission of Nitrous Oxide and Ethanol: Dynamic and Energy Characteristics

    NASA Astrophysics Data System (ADS)

    Drobyshev, A.; Strzhemechny, Yu.; Aldiyarov, A.; Korshikov, E.; Kurnosov, V.; Sokolov, D.

    2017-04-01

    We studied dynamic and spectral characteristics of light emission produced during cryodeposition of nitrous oxide and ethanol onto metal substrates at a temperature of 10 K and a pressure of a gas phase of 10^{-2} Torr. It was established that this radiation is comprised of a large number of individual flashes of varying amplitude, wavelength and duration. Our measurements indicated that for nitrous oxide the rise time required to reach the maximum intensity of a single flash is 0.015 × 10^{-3} s, whereas for ethanol such time is 0.3× 10^{-3} s (i.e., 20 times greater). We attribute such discrepancy to the significant difference between the intrinsic molecular dipole moments of nitrous oxide (μ = 0.097 D) and ethanol (μ = 1.68 D). Emission spectra of both nitrous oxide and ethanol were measured in the wavelength range of 350-1050 nm. They consist of discrete peaks located at 517, 562, 690, 726, 805 and 866 nm for nitrous oxide and 387, 392, 822, 995 and 1019 nm for ethanol. To explain the obtained results, we consider two models based on the assumptions of existence of isomeric states of the nitrous oxide molecules, as well as of processes of molecular dipole ordering/disordering during cryodeposition from the gas phase.

  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. 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.

  13. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  15. Permeability of the rocks from the Kola superdeep borehole at high temperature and pressure: implication to fluid dynamics in the continental crust

    NASA Astrophysics Data System (ADS)

    Zharikov, A. V.; Vitovtova, V. M.; Shmonov, V. M.; Grafchikov, A. A.

    2003-07-01

    Permeability of the samples collected from the surface and from the depths of 8-11 km in the Kola SG-3 and from the depth of 3.8 in the KTB boreholes was studied at temperatures up to 600 °C and pressures up to 150 MPa. These PT correspond to in situ conditions of the deep parts of the superdeep boreholes and to the conditions of progressive and regressive metamorphism of the Kola series rocks. The experiments were carried out with fluid filtration parallel and normal to rock foliation and parallel to core axis. The temperature-permeability trend behavior depends on effective pressure and depth of sample collection. At low effective pressure, a temperature increase leads first to a permeability decrease and then to its increase. At higher effective pressure, inversions appear on all the temperature trends of the samples collected from great depths. In contrast, permeability of the samples selected at shallow depth (3.8 km) and on the surface decreases within the entire temperature range. As a rule, with flow parallel to foliation, the values of permeability are higher than with flow normal to foliation. The results of microstructure studies allow to conclude that microcrack initiation and closure, due to a competitive influence of temperature and pressure cause such permeability behavior. In the samples, there are two families of microcracks: with low aspect ratio and those with high aspect ratio. Their effect on rock permeability changes with temperature. On sample heating, the low aspect ratio microcracks close and, on the contrary, high aspect ratio ones open. The total effect is expressed by minima in the temperature-permeability trends. Permeability anisotropy increases with temperature, reaches a maximum at 200 °C and then decreases. Sample permeability decreases with different gradients at simultaneous increase of temperature and pressure, simulating in situ depth increase. Hence, the deep seat rocks can vary greatly in permeability and against the common

  16. On modelling the flow controls on macrophyte and epiphyte dynamics in a lowland permeable catchment: the River Kennet, southern England.

    PubMed

    Wade, A J; Whitehead, P G; Hornberger, G M; Snook, D L

    2002-01-23

    A new in-stream model of phosphorus (P) and macrophyte dynamics, the Kennet Model, was applied to a reach of the River Kennet to investigate the impacts of changing flow conditions on macrophyte growth. The investigation was based on the assessment of two flow change scenarios, which both included the simulation of decreasing total phosphorus concentrations from a sewage treatment works due to improved effluent treatment. In the first scenario, the precipitation and potential evaporation outputs from a climate change model (HadCM2 GGx) where input into the catchment model INCA to predict the mean daily flows in the reach. In the second scenario, the mean daily flows observed in a historically dry year were repeated as input to the in-stream model to simulate an extended low flow period over 2 years. The simulation results suggest that changes in the seasonal distribution of flow were not detrimental to macrophyte growth. However, the simulation of extended periods of low flow suggests that a proliferation of epiphytic algae occurs, even when the in-stream phosphorus concentrations are reduced due to effluent treatment. This epiphytic growth was predicted to reduce the macrophyte peak biomass within the reach by approximately 80%. Thus, the model simulations suggest that flow was more important in controlling the macrophyte biomass in the River Kennet, than the in-stream phosphorus concentrations, which are elevated due to agricultural diffuse sources.

  17. Clogging in permeable concrete: A review.

    PubMed

    Kia, Alalea; Wong, Hong S; Cheeseman, Christopher R

    2017-05-15

    Permeable concrete (or "pervious concrete" in North America) is used to reduce local flooding in urban areas and is an important sustainable urban drainage system. However, permeable concrete exhibits reduction in permeability due to clogging by particulates, which severely limits service life. This paper reviews the clogging mechanism and current mitigating strategies in order to inform future research needs. The pore structure of permeable concrete and characteristics of flowing particulates influence clogging, which occurs when particles build-up and block connected porosity. Permeable concrete requires regular maintenance by vacuum sweeping and pressure washing, but the effectiveness and viability of these methods is questionable. The potential for clogging is related to the tortuosity of the connected porosity, with greater tortuosity resulting in increased potential for clogging. Research is required to develop permeable concrete that can be poured on-site, which produces a pore structure with significantly reduced tortuosity.

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

    PubMed Central

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

    2011-01-01

    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 O2 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 (PN) and radial O2 loss to sediments is highlighted. O2 microelectrodes were used in situ to monitor pO2 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 PN, loss of tissue water, radial O2 loss, and light microscopy. Tissue and sediment pO2 showed large diurnal amplitudes and internal O2 was more similar to sediment pO2 than water pO2. In early afternoon, sediment pO2 was often higher than tissue pO2 and although sediment O2 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 PN by the green portions, presumably by increasing the surface area for CO2 entry. In addition, these leaf bases would contribute to loss of O2 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 CO2, or exit for O2, with the surrounding sediment. PMID:21841181

  19. 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.

  20. Pyrotechnic deflagration velocity and permeability

    SciTech Connect

    Begeal, D R; Stanton, P L

    1982-01-01

    Particle size, porosity, and permeability of the reactive material have long been considered to be important factors in propellant burning rates and the deflagration-to-detonation transition in explosives. It is reasonable to assume that these same parameters will also affect the deflagration velocity of pyrotechnics. This report describes an experimental program that addresses the permeability of porous solids (particulate beds), in terms of particle size and porosity, and the relationship between permeability and the behavior of pyrotechnics and explosives. The experimental techniques used to acquire permeability data and to characterize the pyrotechnic burning are discussed. Preliminary data have been obtained on the burning characteristics of titanium hydride/potassium perchlorate (THKP) and boron/calcium chromate (BCCR). With THKP, the velocity of a pressure wave (from hot product gases) in the unburned region shows unsteady behavior which is related to the initial porosity or permeability. Simultaneous measurements with pressure gauges and ion gauges reveal that the pressure wave precedes the burn front. Steady burning of BCCR was observed with pressure gauge diagnostics and with a microwave interferometry technique.

  1. Dynamic characteristics of laser-Doppler flux data.

    PubMed

    Popivanov, D; Mineva, A; Dushanova, J

    1999-01-01

    Methods for tracking the dynamics of the blood flow microcirculation obtained by laser-Doppler flowmetry (LDF) technique are described. It was shown that LDF signals have complex dynamics. It was mainly characterized by fractal structures and chaos, though multiperiodic, trend-like and stochastic components were also established. Procedures for (i) describing the dynamic structure and (ii) tracking the dynamic changes in time of LDF data are proposed. Examples illustrating the efficiency of these procedures are given using both simulated and LDF data collected in experiments with reactive hyperemia. Irrespective of the universality of the methods, the procedures should be specified according to the problem-oriented clinical and experimental studies.

  2. 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...

  3. 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...

  4. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

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

  5. Application of histogram analysis for the evaluation of vascular permeability in glioma by the K2 parameter obtained with the dynamic susceptibility contrast method: Comparisons with Ktrans obtained with the dynamic contrast enhance method and cerebral blood volume.

    PubMed

    Taoka, Toshiaki; Kawai, Hisashi; Nakane, Toshiki; Hori, Saeka; Ochi, Tomoko; Miyasaka, Toshiteru; Sakamoto, Masahiko; Kichikawa, Kimihiko; Naganawa, Shinji

    2016-09-01

    The "K2" value is a factor that represents the vascular permeability of tumors and can be calculated from datasets obtained with the dynamic susceptibility contrast (DSC) method. The purpose of the current study was to correlate K2 with Ktrans, which is a well-established permeability parameter obtained with the dynamic contrast enhance (DCE) method, and determine the usefulness of K2 for glioma grading with histogram analysis. The subjects were 22 glioma patients (Grade II: 5, III: 6, IV: 11) who underwent DSC studies, including eight patients in which both DSC and DCE studies were performed on separate days within 10days. We performed histogram analysis of regions of interest of the tumors and acquired 20th percentile values for leakage-corrected cerebral blood volume (rCBV20%ile), K2 (K220%ile), and for patients who underwent a DCE study, Ktrans (Ktrans20%ile). We evaluated the correlation between K220%ile and Ktrans20%ile and the statistical difference between rCBV20%ile and K220%ile. We found a statistically significant correlation between K220%ile and Ktrans20%ile (r=0.717, p<0.05). rCBV20%ile showed a significant difference between Grades II and III and between Grades II and IV, whereas K220%ile showed a statistically significant (p<0.05) difference between Grades II and IV and between Grades III and IV. The K2 value calculated from the DSC dataset, which can be obtained with a short acquisition time, showed a correlation with Ktrans obtained with the DCE method and may be useful for glioma grading when analyzed with histogram analysis. Copyright © 2016 Elsevier Inc. All rights reserved.

  6. The effect of pectin on swelling and permeability characteristics of free films containing Eudragit RL and/or RS as a coating formulation aimed for colonic drug delivery

    PubMed Central

    Akhgari, A.; Farahmand, F.; Afrasiabi Garekani, H.; Sadeghi, F.; Vandamme, T.

    2010-01-01

    Background and the purpose of the study The potential of pectin as a bacterially degradable polysaccharide for colon drug delivery has been demonstrated. Due to the high solubility and swelling properties of pectin in aqueous media, it is frequently used in combination with water insoluble polymers for targeting drugs to the colon. The aim of this study was to evaluate free films containing pectin as a bacterially-degradable polysaccharide in combination with Eudragit RL (ERL) and/or RS (ERS) as a coating formulation for colonic drug delivery. Methods Isolated free films comprising 20% pectin and 80% ERL or ERS and their combination in 1:1 ratio were prepared by casting method. Then, free films were evaluated by water vapor transmission (WVT), swelling and permeability experiments for theophylline and indomethacin in different media. Results Formulations containing ERL exhibited higher WVT, swelling and permeability compared with formulations containing ERS. The permeability of theophylline through free films composed of pectin and eudragit polymers in simulated colonic media was not significantly different from those obtained in other media. However indomethacin free films containing pectin and ERL showed higher permeation in simulated colonic fluid (SCF) compared to the other media. Major conclusion Formulation containing pectin and ERL may be suitable as a coating formulation for colon targeted delivery of drugs of low solubility such as indomethacin. PMID:22615600

  7. 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

  8. Vascular permeability in cerebral cavernous malformations

    PubMed Central

    Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik BW; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A

    2015-01-01

    Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy. PMID:25966944

  9. Vascular permeability in cerebral cavernous malformations.

    PubMed

    Mikati, Abdul G; Khanna, Omaditya; Zhang, Lingjiao; Girard, Romuald; Shenkar, Robert; Guo, Xiaodong; Shah, Akash; Larsson, Henrik B W; Tan, Huan; Li, Luying; Wishnoff, Matthew S; Shi, Changbin; Christoforidis, Gregory A; Awad, Issam A

    2015-10-01

    Patients with the familial form of cerebral cavernous malformations (CCMs) are haploinsufficient for the CCM1, CCM2, or CCM3 gene. Loss of corresponding CCM proteins increases RhoA kinase-mediated endothelial permeability in vitro, and in mouse brains in vivo. A prospective case-controlled observational study investigated whether the brains of human subjects with familial CCM show vascular hyperpermeability by dynamic contrast-enhanced quantitative perfusion magnetic resonance imaging, in comparison with CCM cases without familial disease, and whether lesional or brain vascular permeability correlates with CCM disease activity. Permeability in white matter far (WMF) from lesions was significantly greater in familial than in sporadic cases, but was similar in CCM lesions. Permeability in WMF increased with age in sporadic patients, but not in familial cases. Patients with more aggressive familial CCM disease had greater WMF permeability compared to those with milder disease phenotype, but similar lesion permeability. Subjects receiving statin medications for routine cardiovascular indications had a trend of lower WMF, but not lesion, permeability. This is the first demonstration of brain vascular hyperpermeability in humans with an autosomal dominant disease, as predicted mechanistically. Brain permeability, more than lesion permeability, may serve as a biomarker of CCM disease activity, and help calibrate potential drug therapy.

  10. Crustal permeability: Introduction to the special issue

    USGS Publications Warehouse

    Ingebritsen, Steven E.; Gleeson, Tom

    2015-01-01

    The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

  11. The effect of aspirin and smoking on urinary excretion profiles of lactulose and mannitol in young women: toward a dynamic, aspirin augmented, test of gut mucosal permeability.

    PubMed

    Sequeira, I R; Lentle, R G; Kruger, M C; Hurst, R D

    2012-09-01

    We explored the temporal dynamics of the lactulose mannitol test and the influence of a single dose of aspirin. Twenty healthy female volunteers each received 600 mg aspirin or placebo in random sequence and were subsequently dosed with 10 g lactulose and 5 g mannitol, their urine collected every half hour for 6h. The lactulose:mannitol ratios (LMR) of urine samples collected over the entire 6-h period were significantly higher than those collected in the first 3 h. Greater quantities of mannitol were excreted over the first than the subsequent 3 h. A similar pattern of temporal variation in mannitol excretion was found in smokers and non-smokers and was maintained following administration of a single 600 mg dose of aspirin. The rates at which lactulose was excreted were relatively constant over the entire 6 h period of collection, but mean levels were increased over the entire 6 h following the administration of aspirin. The effect of aspirin did not differ significantly between smokers and non-smokers.   While the LMR test is sufficiently sensitive to reproducibly detect the increase in intestinal permeability resulting from a single 600 mg oral dose of aspirin, the temporal patterns of excretion of mannitol and lactulose differ both in the presence and absence of aspirin. Hence, variation in sampling period and in method of dosage are likely to influence the result and it is preferable to examine the patterns of absorption of component sugars separately with due regard to the method of dosage. © 2012 Blackwell Publishing Ltd.

  12. Movement Characteristics Analysis and Dynamic Simulation of Collaborative Measuring Robot

    NASA Astrophysics Data System (ADS)

    guoqing, MA; li, LIU; zhenglin, YU; guohua, CAO; yanbin, ZHENG

    2017-03-01

    Human-machine collaboration is becoming increasingly more necessary, and so collaborative robot applications are also in high demand. We selected a UR10 robot as our research subject for this study. First, we applied D-H coordinate transformation of the robot to establish a link system, and we then used inverse transformation to solve the robot’s inverse kinematics and find all the joints. Use Lagrange method to analysis UR robot dynamics; use ADAMS multibody dynamics simulation software to dynamic simulation; verifying the correctness of the derived kinetic models.

  13. Nonlinear dynamic characteristic analysis of jointed beam with clearance

    NASA Astrophysics Data System (ADS)

    Zhang, Jing; Guo, Hong-Wei; Liu, Rong-Qiang; Wu, Juan; Kou, Zi-Ming; Deng, Zong-Quan

    2016-12-01

    The impact and elasticity of discontinuous beams with clearance frequently affect the dynamic response of structures used in space missions. This study investigates the dynamic response of jointed beams which are the periodic units of deployable structures. The vibration process of jointed beams includes free-play and impact stages. A method for the dynamic analysis of jointed beams with clearance is proposed based on mode superposition and instantaneous static deformation. Transfer matrix, which expresses the relationship of the responses before and after the impact of jointed beams, is derived to calculate the response of the jointed beams after a critical position. The dynamic responses of jointed beams are then simulated. The effects of various parameters on the displacement and velocity of beams are investigated.

  14. Evaluation of Airfoil Dynamic Stall Characteristics for Maneuverability

    NASA Technical Reports Server (NTRS)

    Bousman, William G.; Aiken, Edwin W. (Technical Monitor)

    2000-01-01

    In severe maneuvers, out of necessity for a military aircraft or inadvertently for a civil aircraft, a helicopter airfoil will stall in a dynamic manner and provide lift beyond what would be calculated based on static airfoil tests. The augmented lift that occurs in dynamic stall is related to a vortex that is shed near the leading edge of the airfoil. However, directly related to the augmented lift that results from the dynamic stall vortex are significant penalties in pitching moment and drag. An understanding of the relationship between the augmented lift in dynamic stall and the associated moment and drag penalties is the purpose of this paper. This relationship is characterized using data obtained in two-dimensional wind tunnel tests and related to the problem of helicopter maneuverability.

  15. 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.

  16. Prediction of Dynamic Stall Characteristics Using Advanced Nonlinear Panel Methods,

    DTIC Science & Technology

    This paper presents preliminary results of work in which a surface singularity panel method is being extended for modelling the dynamic interaction...between a separated wake and a surface undergoing an unsteady motion. The method combines the capabilities of an unsteady time-stepping code and a... technique for modelling extensive separation using free vortex sheets. Routines are developed for treating the dynamic interaction between the separated

  17. Film Permeability Determination Using Static Permeability Cells

    EPA Pesticide Factsheets

    The permeability of tarps to soil fumigant pesticides varies depending on the active ingredient chemical: dimethyl disulfide (DMDS), methyl bromide, chloropicrin, or other. The diffusion rate can be represented by the mass transfer coefficient (MTC).

  18. An experimental study on the static and dynamic characteristics of pump annular seals

    NASA Technical Reports Server (NTRS)

    Iwatsubo, T.; Sheng, B. C.; Matsumoto, T.

    1989-01-01

    A test apparatus was constructed and was applied to investigate static and dynamic characteristics of annular seals for turbopumps. The fluid forces acting on the seals were measured for various parameters such as 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 was investigated from the experimental results. As a result, preswirl affects the dynamic characteristics strongly. Especially, the preswirl opposing the rotating direction has a stabilizing role on the rotor system.

  19. 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.

  20. Dynamic Characteristics Analysis of Analogue Networks Design Process

    NASA Astrophysics Data System (ADS)

    Zemliak, Alexander M.

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

  1. Fracture and Faulting Induced Permeability Change in Porous Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Zhu, W.-L.

    2012-04-01

    Flow of interstitial fluids exerts important control over seismogenic, sedimentary, and metamorphic processes. Since the seminal work of Hubbert and Rubey [1959] on the motion of thrust sheet, elevated pore fluid pressure has been used to reconcile the heat flow paradox during seismogenic faulting, and more recently, as a possible mechanism for slow slip events observed at subduction zones. Many working hypotheses for generating and maintaining high pore fluid pressure have been proposed. However, one important ingredient still missing in these models is quantitative knowledge of permeability as a dynamics physical property that varies significantly in different tectonic settings. In this study, we conducted systematic laboratory characterization of how permeability and its anisotropy evolve as porous sandstones and limestones undergo the transition from brittle faulting to cataclastic flow. Our data show that highly porous silicate rocks experience permeability reduction during dilatant brittle fracture whereas their low porosity counterparts exhibit permeability enhancement. With increasing confinement, brittle fracture is inhibited and the porous rocks exhibit shear enhanced compaction, resulting in significant porosity reduction accompanied by strain hardening and drastic loss of permeability. Hertzian fracture and pore collapse are the primary micomechanisms responsible for the brittle faulting or pervasive fracturing in porous silicate rocks. In contrast, the stress-induced permeability evolution in porous limestones is markedly different. Because crystal plasticity as well as solution transfer can be activated at relatively low temperatures in calcite compared to quartz, the inelastic behavior and failure mode of carbonate rocks are not only a function of pressure, but also sensitive to temperature. Laboratory measurements show that the presence of water enhances compaction and considerably lower the yield strength of carbonate rocks. The yield cap is

  2. 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.

  3. Stochastic modeling of uncertain mass characteristics in rigid body dynamics

    NASA Astrophysics Data System (ADS)

    Richter, Lanae A.; Mignolet, Marc P.

    2017-03-01

    This paper focuses on the formulation, assessment, and application of a modeling strategy of uncertainty on the mass characteristics of rigid bodies, i.e. mass, position of center of mass, and inertia tensor. These characteristics are regrouped into a 4×4 matrix the elements of which are represented as random variables with joint probability density function derived following the maximum entropy framework. This stochastic model is first shown to satisfy all properties expected of the mass and tensor of inertia of rigid bodies. Its usefulness and computational efficiency are next demonstrated on the behavior of a rigid body in pure rotation exhibiting significant uncertainty in mass distribution.

  4. Effects of water activity and low molecular weight humectants on skin permeability and hydration dynamics - a double-blind, randomized and controlled study.

    PubMed

    Albèr, C; Buraczewska-Norin, I; Kocherbitov, V; Saleem, S; Lodén, M; Engblom, J

    2014-10-01

    The mammalian skin is a barrier that effectively separates the water-rich interior of the body from the normally dryer exterior. Changes in the external conditions, for example ambient humidity, have been shown to affect the skin barrier properties. The prime objective of this study was to evaluate the effect of water activity of a topical formulation on skin hydration and permeability. A second objective was to gain more understanding on how two commonly used humectants, urea and glycerol, affect skin barrier function in vivo. Simple aqueous formulations were applied under occlusion to the volar forearm of healthy volunteers. Following 4-h exposure, skin water loss (by transepidermal water loss measurements), skin hydration (by Corneometry) and skin permeability (by time to vasodilation due to benzyl nicotinate exposure) were monitored. The results demonstrate that a relatively small change in the water activity of a topical formulation is sufficient to induce considerable effects on stratum corneum hydration and permeability to exogenous substances. Exposing the skin to high water activity leads to increased skin hydration and also increased permeability. Furthermore, urea and glycerol promote skin hydration and permeability even at reduced water activity of the applied formulation. These results highlight the importance of considering the water activity in topically applied formulations and the potential benefit of using humectants. The results may impact formulation optimization in how to facilitate skin hydration and to modify skin permeability by temporarily open and close the skin barrier. © 2014 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  5. Novel permeability characteristics of red blood cells from sickle cell patients heterozygous for HbS and HbC (HbSC genotype).

    PubMed

    Dalibalta, S; Ellory, J C; Browning, J A; Wilkins, R J; Rees, D C; Gibson, J S

    2010-06-15

    Individuals heterozygous for HbS and HbC (HbSC) represent about 1/3(rd) of sickle cell disease (SCD) patients. Whilst HbSC disease is generally milder, there is considerable overlap in symptoms with HbSS disease. HbSC patients, as well as HbSS ones, present with the chronic anaemia and panoply of acute vaso-occlusive complications that characterize SCD. However, there are important clinical and haematological differences. Certain complications occur with greater frequency in HbSC patients (like proliferative retinopathy and osteonecrosis) whilst intravascular haemolysis is reduced. Patients with HbSC disease can be considered as a discrete subset of SCD cases. Although much work has been carried out on understanding the pathogenesis of SCD in HbSS homozygotes, including the contribution of altered red blood cell permeability, relatively little pertains directly to HbSC individuals. Results reported in the literature suggest that HbSC cells, and particularly certain subpopulations, present with similar permeability to HbSS cells but there are also important differences - these have not been well characterized. We hypothesise that their unique cell transport properties accounts for the different pattern of disease in HbSC patients and represents a potential chemotherapeutic target not shared in red blood cells from HbSS patients. The distinct pattern of clinical haematology in HbSC disease is emphasised here. We analyse some of the electrophysiological properties of single red blood cells from HbSC patients, comparing them with those from HbSS patients and normal HbAA individuals. We also use the isosmotic haemolysis technique to investigate the behaviour of total red blood cell populations. Whilst both HbSS and HbSC cells show increased monovalent and divalent (Ca(2+)) cation conductance further elevated upon deoxygenation, the distribution of current magnitudes differs, and outward rectification is greatest for HbSC cells. In addition, although Gd(3+) largely

  6. Approximating the head characteristics and characteristic surfaces of dynamic pumps by means of an exponential function

    NASA Astrophysics Data System (ADS)

    Shekun, G. D.

    2009-08-01

    Results obtained from statistical and experimental studies of the head characteristics of commercially available centrifugal and free-vortex pumps are presented. A regression equation in the form of an exponential function written in a reduced-relative system of coordinates for approximating the head characteristics of blade pumps is obtained.

  7. Nonlinear dynamic analysis and characteristics diagnosis of seasonally perturbed predator-prey systems

    NASA Astrophysics Data System (ADS)

    Zhang, Huayong; Huang, Tousheng; Dai, Liming

    2015-05-01

    Predator-prey interaction widely exists in nature and the research on predator-prey systems is an important field in ecology. The nonlinear dynamic characteristics of a seasonally perturbed predator-prey system are studied in this research. To study the nonlinear characteristics affected by a wide variety of system parameters, the PR approach is employed and periodic, quasiperiodic, chaotic behaviors and the behaviors between period and quasiperiod are found in the system. Periodic-quasiperiodic-chaotic region diagrams are generated for analyzing the global characteristics of the predator-prey system with desired ranges of system parameters. The ecological significances of the dynamical characteristics are discussed and compared with the theoretical research results existing in the literature. The approach of this research demonstrates effectiveness and efficiency of PR method in analyzing the complex dynamical characteristics of nonlinear ecological systems.

  8. MDCK cell permeability characteristics of a sulfenamide prodrug: strategic implications in considering sulfenamide prodrugs for oral delivery of NH-acids.

    PubMed

    Guarino, Victor R; Nti-Addae, Kwame; Stella, Valentino J

    2011-01-01

    The objective of this Letter is both to report the permeability results of a linezolid-based sulfenamide prodrug in an MDCK cell model (enterocyte surrogate system) and to discuss the strategic implications of these results for considering sulfenamide prodrugs to enhance the oral delivery of weakly acidic NH-acids (e.g., amides, ureas, etc.). The two main findings from this study are that the sulfenamide prodrug does not appear to survive intracellular transport due to conversion to linezolid and that there appears to be an apically-oriented surface conversion pathway that can additionally serve to convert the sulfenamide prodrug to linezolid upon approach of the apical membrane. It is hoped that these findings, along with the discussion of the strategic implications, will facilitate a greater awareness of the potential strengths and weaknesses inherent in the sulfenamide prodrug approach for enhancing the oral delivery of weakly acidic NH-acid drugs.

  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 corona characteristics of water droplets on charged conductor surface

    NASA Astrophysics Data System (ADS)

    Xu, Pengfei; Zhang, Bo; Wang, Zezhong; Chen, Shuiming; He, Jinliang

    2017-03-01

    The formation of the Taylor cone of a water droplet on the surface of the conductor in a line-ground electrode system is captured using a high-speed camera, while the corona current is synchronously measured using a current measurement system. Repeated Taylor cone deformation is observed, yielding regular groupings of corona current pulses. The underlying mechanism of this deformation is studied and the correlation between corona discharge characteristics and cone deformation is investigated. Depending on the applied voltage and rate of water supply, the Taylor cone may be stable or unstable and has a significant influence on the characteristics of the corona currents. If the rate of water supply is large enough, the Taylor cone tends to be unstable and generates corona-current pulses of numerous induced current pulses with low amplitudes. In consequence, this difference suggests that large rainfall results in simultaneously lower radio interference and higher corona loss.

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

    ERIC Educational Resources Information Center

    Bedley, Gene

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

  13. 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.

  14. Characteristic dynamics near two coalescing eigenvalues incorporating continuum threshold effects

    NASA Astrophysics Data System (ADS)

    Garmon, Savannah; Ordonez, Gonzalo

    2017-06-01

    It has been reported in the literature that the survival probability P(t) near an exceptional point where two eigenstates coalesce should generally exhibit an evolution P (t ) ˜t2e-Γ t, in which Γ is the decay rate of the coalesced eigenstate; this has been verified in a microwave billiard experiment [B. Dietz et al., Phys. Rev. E 75, 027201 (2007)]. However, the heuristic effective Hamiltonian that is usually employed to obtain this result ignores the possible influence of the continuum threshold on the dynamics. By contrast, in this work we employ an analytical approach starting from the microscopic Hamiltonian representing two simple models in order to show that the continuum threshold has a strong influence on the dynamics near exceptional points in a variety of circumstances. To report our results, we divide the exceptional points in Hermitian open quantum systems into two cases: at an EP2A two virtual bound states coalesce before forming a resonance, anti-resonance pair with complex conjugate eigenvalues, while at an EP2B two resonances coalesce before forming two different resonances. For the EP2B, which is the case studied in the microwave billiard experiment, we verify that the survival probability exhibits the previously reported modified exponential decay on intermediate time scales, but this is replaced with an inverse power law on very long time scales. Meanwhile, for the EP2A the influence from the continuum threshold is so strong that the evolution is non-exponential on all time scales and the heuristic approach fails completely. When the EP2A appears very near the threshold, we obtain the novel evolution P (t ) ˜1 -C1√{t } on intermediate time scales, while further away the parabolic decay (Zeno dynamics) on short time scales is enhanced.

  15. Characteristics of wavelike fluctuations in Dynamics Explorer neutral composition data

    NASA Technical Reports Server (NTRS)

    Hedin, A. E.; Mayr, H. G.

    1987-01-01

    Wavelike fluctuations in neutral composition data obtained with the neutral atmospheric composition system quadrupole mass spectrometer carried aboard the Dynamics Explorer (DE 2) satellite are at a maximum in the vicinity of the magnetic poles. Typical rms amplitudes near the poles for N2, O, He, and Ar fluctuations in the 400- to 4000-km-wavelength band are found to be 11, 6, 6, and 20 percent, respectively. Amplitudes near the equator are roughly a third of the polar amplitudes, and activity in the 50- to 400-km-wavlength band is roughly 20 percent of the longer-wavelength activity.

  16. 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

  17. Theoretical and experimental study of the dynamic transient characteristics of a hydrostatic bearing

    NASA Astrophysics Data System (ADS)

    Pang, Zhicheng; Wang, Shuguo; Liu, Qingming; Chi, Wei

    1993-01-01

    The transient characteristics of a hydrostatic bearing under a step load have been studied by considering the compressibility of oil (containing air bubbles). The characteristic equations of the beating during the transient stage have been set up, the duration of the transient stage has been obtained and the effects of the main parameters of the bearing system on the transient characteristics have been analyzed. This study provides a new theoretical basis for improving the dynamic support precision of high quality bearings.

  18. Dynamic Energy Loss Characteristics in the Native Aortic Valve

    NASA Astrophysics Data System (ADS)

    Hwai Yap, Choon; Dasi, Laksmi P.; Yoganathan, Ajit P.

    2009-11-01

    Aortic Valve (AV) stenosis if untreated leads to heart failure. From a mechanics standpoint, heart failure implies failure to generate sufficient mechanical power to overcome energy losses in the circulation. Thus energy efficiency-based measures are direct measures of AV disease severity, which unfortunately is not used in current clinical measures of stenosis severity. We present an analysis of the dynamic rate of energy dissipation through the AV from direct high temporal resolution measurements of flow and pressure drop across the AV in a pulsatile left heart setup. Porcine AV was used and measurements at various conditions were acquired: varying stroke volumes; heart rates; and stenosis levels. Energy dissipation waveform has a distinctive pattern of being skewed towards late systole, attributed to the explosive growth of flow instabilities from adverse pressure gradient. Increasing heart rate and stroke volume increases energy dissipation, but does not alter the normalized shape of the dissipation temporal profile. Stenosis increases energy dissipation and also alters the normalized shape of dissipation waveform with significantly more losses during late acceleration phase. Since stenosis produces a departure from the signature dissipation waveform shape, dynamic energy dissipation analysis can be extended into a clinical tool for AV evaluation.

  19. 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.

  20. 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.

  1. On the formulation of the aerodynamic characteristics in aircraft dynamics

    NASA Technical Reports Server (NTRS)

    Tobak, M.; Schiff, L. B.

    1976-01-01

    The theory of functionals is used to reformulate the notions of aerodynamic indicial functions and superposition. Integral forms for the aerodynamic response to arbitrary motions are derived that are free of dependence on a linearity assumption. Simplifications of the integral forms lead to practicable nonlinear generalizations of the linear superpositions and stability derivative formulations. Applied to arbitrary nonplanar motions, the generalization yields a form for the aerodynamic response that can be compounded of the contributions from a limited number of well-defined characteristic motions, in principle reproducible in the wind tunnel. Further generalizations that would enable the consideration of random fluctuations and multivalued aerodynamic responses are indicated.

  2. Numerical Modeling of Sea Ice Dynamics and Ice Thickness Characteristics.

    DTIC Science & Technology

    1985-03-01

    taken off the North Slope of Alaska. Figure 3 shows the salient characteristics of the data set that are rele- vant to the redistribution theory . The...must obey the equation f y(h’,h)hdh =h’. (17) 0 Strengths can be estimated from this kind of theory , if it is insisted that the rate of defor- mation...feature of the Thorndike et al. (1975) theory is that it presents an "Eulerian" description in thickness space. In particular, growth takes place by

  3. 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.

  4. A study of regenerator characteristics in dynamic converters

    NASA Astrophysics Data System (ADS)

    Umarov, A. G.

    The thermal and hydraulic characteristics of various types of regenerator packing were studied using a test bench consisting of a Stirling engine and a system for measuring instantaneous thermodynamic parameters. The types of packing investigated include brass and stainless steel wire mesh, matted-wire packing, and tubular packing. It is shown that the same maximum indicated efficiency can be achieved with any of these packing materials by varying the volume and geometry of the packing. For an indicated efficiency of 48-50 percent, the highest maximum power is achieved with the packing having the largest specific surface.

  5. Dynamic characteristic of a 30-cm mercury ion thruster

    NASA Technical Reports Server (NTRS)

    Serafini, J. S.; Mantenieks, M. A.; Rawlin, V. K.

    1975-01-01

    Measurements of the fluctuations of the discharge and beam plasmas of a 30 centimeter ion thruster were performed using 60 Hertz laboratory type power supplies. The time-varying properties of the discharge voltage and current, the ion beam current, and neutralizer keeper current were measured. The intensities of the fluctuations were found to depend on the beam and magnetic baffle currents. The shape of the frequency spectra of the discharge plasma fluctuations was found to be related to the beam and magnetic baffle currents. The measurements indicated that the discharge current fluctuations directly contribute to the beam current fluctuations and that the power supply characteristics modify these fluctuations.

  6. 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.

  7. 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.

  8. Dynamic characteristics of Non Newtonian fluid Squeeze film damper

    NASA Astrophysics Data System (ADS)

    Palaksha, C. P.; Shivaprakash, S.; Jagadish, H. P.

    2016-09-01

    The fluids which do not follow linear relationship between rate of strain and shear stress are termed as non-Newtonian fluid. The non-Newtonian fluids are usually categorized as those in which shear stress depends on the rates of shear only, fluids for which relation between shear stress and rate of shear depends on time and the visco inelastic fluids which possess both elastic and viscous properties. It is quite difficult to provide a single constitutive relation that can be used to define a non-Newtonian fluid due to a great diversity found in its physical structure. Non-Newtonian fluids can present a complex rheological behaviour involving shear-thinning, viscoelastic or thixotropic effects. The rheological characterization of complex fluids is an important issue in many areas. The paper analyses the damping and stiffness characteristics of non-Newtonian fluids (waxy crude oil) used in squeeze film dampers using the available literature for viscosity characterization. Damping and stiffness characteristic will be evaluated as a function of shear strain rate, temperature and percentage wax concentration etc.

  9. Permeability of Dentine

    PubMed Central

    Ghazali, Farid Bin Che

    2003-01-01

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

  10. Permeability of dentine.

    PubMed

    Ghazali, Farid Bin Che

    2003-01-01

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

  11. Static and dynamic characteristics of a piezoceramic strut

    NASA Technical Reports Server (NTRS)

    Pokines, Brett J.; Belvin, W. Keith; Inman, Daniel J.

    1993-01-01

    The experimental study of a piezoceramic active truss is presented. This active strut is unique in that the piezoceramic configurations allow the stroke length of the strut not to be dependent on the piezoceramic material's expansion range but on the deflection range of the piezoceramic bender segment. A finite element model of a piezoceramic strut segment was constructed. Piezoceramic actuation was simulated using thermally induced strains. This model yielded information on the stiffness and force range of a bender element. The static and dynamic properties of the strut were identified experimentally. Feedback control was used to vary the stiffness of the strut. The experimentally verified model was used to explore implementation possibilities of the strut.

  12. Statistical characteristics of topographic surfaces and dynamic smoothing of landscapes

    NASA Astrophysics Data System (ADS)

    Bartlett, M. S.; Laio, F.; Ridolfi, L.; Vico, G.; Porporato, A. M.

    2011-12-01

    We analyze the local statistics of topographic surfaces, including slope and aspect, as a function of scale, and explore their relations with landscape features, such as age, vegetation, and geology. These results build upon the previous work of Vico and Porporato (JGR 114, F01011, 2009), which characterized slope using generalized t-Student distributions. We find that the number of degrees of freedom of such distributions, which determines the heaviness of their tails, is linked to the age of the topographic relief of the considered regions, tending to normal distributions for very old mountain ranges. Based on these findings, and inspired by models of critical phenomena, we develop physically-based, space-time stochastic differential equations that reproduce this dynamic smoothing of rough landscapes.

  13. 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.

  14. 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.

  15. Bioenergetics dysfunction, mitochondrial permeability transition pore opening and lipid peroxidation induced by hydrogen sulfide as relevant pathomechanisms underlying the neurological dysfunction characteristic of ethylmalonic encephalopathy.

    PubMed

    Cardoso, Gabriela Miranda Fernandez; Pletsch, Julia Tauana; Parmeggiani, Belisa; Grings, Mateus; Glanzel, Nícolas Manzke; Bobermin, Larissa Daniele; Amaral, Alexandre Umpierrez; Wajner, Moacir; Leipnitz, Guilhian

    2017-09-01

    Hydrogen sulfide (sulfide) accumulates at high levels in brain of patients with ethylmalonic encephalopathy (EE). In the present study, we evaluated whether sulfide could disturb energy and redox homeostasis, and induce mitochondrial permeability transition (mPT) pore opening in rat brain aiming to better clarify the neuropathophysiology of EE. Sulfide decreased the activities of citrate synthase and aconitase in rat cerebral cortex mitochondria, and of creatine kinase (CK) in rat cerebral cortex, striatum and hippocampus supernatants. Glutathione prevented sulfide-induced CK activity decrease in the cerebral cortex. Sulfide also diminished mitochondrial respiration in cerebral cortex homogenates, and dissipated mitochondrial membrane potential (ΔΨm) and induced swelling in the presence of calcium in brain mitochondria. Alterations in ΔΨm and swelling caused by sulfide were prevented by the combination of ADP and cyclosporine A, and by ruthenium red, indicating the involvement of mPT in these effects. Furthermore, sulfide increased the levels of malondialdehyde in cerebral cortex supernatants, which was prevented by resveratrol and attenuated by glutathione, and of thiol groups in a medium devoid of brain samples. Finally, we verified that sulfide did not alter cell viability and DCFH oxidation in cerebral cortex slices, primary cortical astrocyte cultures and SH-SY5Y cells. Our data provide evidence that bioenergetics disturbance and lipid peroxidation along with mPT pore opening are involved in the pathophysiology of brain damage observed in EE. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Numerical method for gas dynamics combining characteristic and conservation concepts

    NASA Technical Reports Server (NTRS)

    Coakley, T. J.

    1981-01-01

    An efficient implicit numerical method that solves the compressible Navier-Stokes equations in arbitrary curvilinear coordinates by the finite-volume technique is presented. An intrinsically dissipative difference scheme and a fully implicit treatment of boundary conditions, based on characteristic and conservation concepts, are used to improve stability and accuracy. Efficiency is achieved by using a diagonal form of the implicit algorithm and spatially varying time-steps. Comparisons of various schemes and methods are presented for one- and two-dimensional flows, including transonic separated flow past a thick circular-arc airfoil in a channel. The new method is equal to or better than a version of MacCormack's hybrid method in accuracy and it converges to a steady state up to an order of magnitude faster.

  17. Numerical method for gas dynamics combining characteristic and conservation concepts

    NASA Technical Reports Server (NTRS)

    Coakley, T. J.

    1981-01-01

    An efficient implicit numerical method that solves the compressible Navier-Stokes equations in arbitrary curvilinear coordinates by the finite-volume technique is presented. An intrinsically dissipative difference scheme and a fully implicit treatment of boundary conditions, based on characteristic and conservation concepts, are used to improve stability and accuracy. Efficiency is achieved by using a diagonal form of the implicit algorithm and spatially varying time-steps. Comparisons of various schemes and methods are presented for one- and two-dimensional flows, including transonic separated flow past a thick circular-arc airfoil in a channel. The new method is equal to or better than a version of MacCormack's hybrid method in accuracy and it converges to a steady state up to an order of magnitude faster.

  18. Permeable Gas Flow Influences Magma Fragmentation Speed.

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  19. 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.

  20. 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.

  1. Dynamic characteristics of silver nanoparticles in physiological fluids: toxicological implications.

    PubMed

    Braydich-Stolle, Laura K; Breitner, Emily K; Comfort, Kristen K; Schlager, John J; Hussain, Saber M

    2014-12-23

    The field of nanotoxicology has made tremendous progress identifying novel and potentially adverse biological effects following nanomaterial (NM) exposure. However, one facet yet to be satisfactorily explored is how a physiological environment modifies NM physicochemical properties, thus introducing novel complexities associated with solid phase material exposures. In this study, artificial alveolar, lysosomal, and interstitial fluids were used to identify environmental-specific modulations to the properties and behavior of hydrocarbon-coated (Ag-HC) and polysaccharide-coated (Ag-PS) silver NMs. As inhalation is a common route of exposure, an alveolar macrophage cell model with deposition dosages representing approximately 2.5 months and 10 years of occupational exposure (0.5 and 25 ng/mL, respectively) were employed. Following dispersion in the artificial fluids, the Ag-HC and Ag-PS NMs demonstrated significant alterations to morphology, aggregation patterns, and particle reactivity. However, the Ag-PS also demonstrated a loss of particle coating, which elicited increased cytotoxicity, phagocytosis, and inflammation not associated with the original Ag-PS. This study demonstrated that in a physiological system NMs undergo considerable modulation, introducing a scenario where the toxicity of NMs may increase over time due to internal bioconditions. These findings highlight the critical influence that the dynamic and insoluble nature of NMs have on bioeffects and the importance of characterizing this behavior.

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

    PubMed Central

    Karmali, Faisal; Shelhamer, Mark

    2008-01-01

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

  3. Simulation, fabrication, and dynamics characteristics of electrostatically actuated switches

    NASA Astrophysics Data System (ADS)

    Postnikov, A. V.; Amirov, Ildar I.; Naumov, V. V.; Kalnov, V. A.

    2008-03-01

    A MEMS capacitive-type sensor is basically an electrostatic transducer that depends on electrical energy in terms of constant voltage (voltage drive) or constant charge storage (current drive) to facilitate monitoring of capacitance change due to an external mechanical excitation, such as force, acoustical pressure or acceleration. Microfabricated cantilever beams are widely used in MEMS capacitive-type sensors as the sensing element1. One such representative of movable microdevices are the surface micromachined mechanical resonators that come in many geometrical configurations, such as laterally movable comb resonators, laterally and vertically movable beam resonators, and torsional resonators. The successful design and fabrication of these devices requires computer-aided design _CAD_ simulation tools capable of accurately simulating the electromechanical performance of MEMS devices. Accurate simulations are critical for the expeditious development of commercial products at reasonable cost. All CAD simulation tools require accurate measurements to verify models and to provide the values of the constants used in the models. In particular, in the case of micromechanical resonators, it is challenging to determine the mechanical properties of both static and dynamic behaviors of such micromechanical resonators2,3. The testing of these movable structures is usually performed using electrostatic excitation and detection by capacitive, piezoresistive, and optical methods4. This paper presents the design, fabrication and testing of capacitive aluminum resonator with various movable membrane geometries, fabricated with surface micromachining.

  4. [Grain filling dynamics and germination characteristics of Bupleurum chinense seeds].

    PubMed

    Jin, Xin; Ren, Bing; Cao, Ai-Nong; Jin, Xiao-Jun

    2014-10-01

    Bupleurum chinense used in the study were cultivated in the experimental fields of Gansu agricultural University for three years. The seeds of B. chinense were collected every 3 days 10 d after the blossom. The result showed that the 1 000-grain fresh weight reached the maximum 43 d after the blossom and then decreased rapidly, at the mature period the fresh weight of seeds were falling to the same level of the dry weight. The dynamic change of the grain dry matter accumulation showed as an S-shape curve, the rapid increase stage was 25-34 d following the flower, and the grain filling was ended 46 d after blossom. Grain filling rate was under the law "fast-slow-fast-slow". And there were two peaks of grain filling rate appeared, after reached the second peak 28 d after the flower the filling rate decreased rapidly and stayed steadily 43 d after flowering. The dehydration rate was also measured at its maximum 43 d following flower. The indexes of seeds all reached the top 52 days following the blossom, when the germination rate reached the peak (34.33%) and water content of seeds was near 10%. The rate of germination and the 1 000-graid weight of seed showed significant positive correlation, while the water content of seeds was found significant negatively correlation with germination percentage. So the best time for harvest should be 52 d after flowering (9 month), the seeds collected at that time showed both high quality and germination rate.

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

    Peng, Yueping; Wang, Jue; Zheng, Chongxun

    2016-01-01

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

  7. State-space analysis of the dynamic characteristics of a variable thrust liquid propellant rocket engine

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Lin

    This paper states the application of state-space method to the analysis of the dynamic characteristics of a variable thrust liquid propellant rocket engine and presents a set of state equations for describing the dynamic process of the engine. An efficient numerical method for solving these system equations is developed. The theoretical solutions agree well with the experimental data. The analysis leads to the following conclusion: the set coefficient of the pulse width, the working frequency of the solenoid valves and the deviation of the critical working points of these valves are important parameters for determining the dynamic response time and the control precision of this engine. The methods developed in this paper may be used effectively in the analysis of dynamic characteristics of variable thrust liquid propellant rocket engines.

  8. Experimental Volcanology: Fragmentation and Permeability

    NASA Astrophysics Data System (ADS)

    Spieler, O.

    2005-12-01

    An increasing number of scientists design new experiments to analyse processes that control the dynamics of explosive eruptions. There research is mostly coupled to numerical models and aims toward its controlling parameters. The fragmentation process, its threshold and the speed of the fragmentation wave as well as the energy consumed by the fragmentation are some hot spots of the experimental volcanology. Analysing the fragmentation behaviour of volcaniclastics as close to the natural system as possible, we found a number of physical constrains. Identifying the porosity as determining factor of the threshold, we realised that neither threshold nor the speed of the fragmentation process are solely controlled by the rock density. The later results of the shock tube type apparatus lead to the analysis of the specific surface area and permeability as direct links to textural features. Permeability analysis performed in a modified shock tube type apparatus, show two clear, distinct trends for dome rock and pyroclastic samples. The specific surface determined by Argon sorbtion (BET) as well as textural features of pumices from Campi Flegrei, Montserrat and Krakatoa (1883) give in contrary evidence of a more complex story. Large spherical, or ellipsoidal bubbles around fractured crystals prove that the high permeability of the pumice has partially developed after the fixing of the bubble size distribution. This puts up the question, if permeability measurements on pyroclastic samples reveal relevant numbers! The surface tension controlled 'self sealing' behaviour of surfaces from foaming obsidian hinders in situ measurements. Close textural investigations will have to clarify how the 'post process' samples deviate from the syneruptive conduit filling.

  9. Study on the dynamic characteristics, refrigerant and lubricating oil in the high-pressure hermetic compressor.

    NASA Astrophysics Data System (ADS)

    Okada, Tetsuji

    The dynamics characteristics and refrigerant and lubricating oil in the high-pressure hermeti compressor has been studied. The compressor is 1 HP for the air conditioner of home use. The experiment and the analytic simulation have been researched. As a result, the theoretic compressor model was proposed. This model has three processes inside of compressor. They are the suction process, the compression process, and the discharge process. In each process, mass equations and energy equations are considered. Also, the inlet refrigerant conditions (2-phase refrigerant) were simulated and the dynamic characteristics of refrigerant and refrigerant and lubricating oil at starting was obtaied.

  10. Measurement of dynamic characteristics of latex foams by the antiresonance method

    NASA Astrophysics Data System (ADS)

    Tsarevskii, W.; Apinis, R.; Jirgens, L.

    2000-03-01

    Measuring and calculation methods for the dynamic characteristics of tubular specimens of low-modulus latex foams and composites based on them, under longitudinal vibrations in a low-frequency region (up to 200 Hz), are developed. The method is based on the effect of antiresonance. Data on the influence of the basic formulation-processing factors on the dynamic characteristics (gelatination time and content of the plasticizer and chopped fibers) are presented. The results obtained can be used to choose the composition of latex foams for lining acoustic channels, injectors, ejectors, and phase inverters, as well as to control products quality. This method can be applied directly to full-size articles.

  11. On the tribological characteristics of dynamically loaded journal bearing with micropolar fluids

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Wang, Kongying; Zhu, Keqin

    2004-01-01

    The addition of the additives to the lubricant oil to enhance the characteristics of the lubricant will influence the performance of the bearings. Based on the theory of micropolar fluids, the tribological characteristics of a dynamically-loaded journal bearing are numerically studied. Comparisons are made between the Newtonian fluids and the micropolar fluids. It is shown that for a dynamically-loaded journal bearing, the micropolar fluids yield an increase not only in the friction force, but also in the friction coefficient. In addition, the oil film pressure and the oil film thickness are obviously higher than that of Newtonian fluids.

  12. 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.

  13. 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).

  14. Permeability of displaced fractures

    NASA Astrophysics Data System (ADS)

    Kluge, Christian; Milsch, Harald; Blöcher, Guido

    2017-04-01

    Flow along fractures or in fissured systems becomes increasingly important in the context of Enhanced Geothermal Systems (EGS), shale gas recovery or nuclear waste deposit. Commonly, the permeability of fractures is approximated using the Hagen-Poiseuille solution of Navier Stokes equation. Furthermore, the flow in fractures is assumed to be laminar flow between two parallel plates and the cubic law for calculating the velocity field is applied. It is a well-known fact, that fracture flow is strongly influenced by the fracture surface roughness and the shear displacement along the fracture plane. Therefore, a numerical approach was developed which calculates the flow pattern within a fracture-matrix system. The flow in the fracture is described by a free fluid flow and the flow in the matrix is assumed to be laminar and therefore validates Darcy's law. The presented approach can be applied for artificially generated fractures or real fractures measured by surface scanning. Artificial fracture surfaces are generated using the power spectral density of the surface height random process with a spectral exponent to define roughness. For calculating the permeability of such fracture-matrix systems the mean fracture aperture, the shear displacement and the surface roughness are considered by use of a 3D numerical simulator. By use of this approach correlation between shear displacement and mean aperture, shear displacement and permeability, as well as surface roughness and permeability can be obtained. Furthermore, the intrinsic measured permeability presents a combination of matrix and fracture permeability. The presented approach allows the separation and quantification of the absolute magnitudes of the matrix and the fracture permeability and the permeability of displaced fractures can be calculated. The numerical approach which is a 3D numerical simulation of the fracture-matrix system can be applied for artificial as well as real systems.

  15. 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

    2017-06-01

    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.

  16. 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.

  17. Dynamic characteristics of laser-induced vapor bubble formation in water based on high speed camera

    NASA Astrophysics Data System (ADS)

    Zhang, Xian-zeng; Guo, Wenqing; Zhan, Zhenlin; Xie, Shusen

    2013-08-01

    In clinical practice, laser ablation usually works under liquid environment such as water, blood or their mixture. Laser-induced vapor bubble or bubble formation and its consequent dynamics were believed to have important influence on tissue ablation. In the paper, the dynamic process of vapor bubble formation and consequently collapse induced by pulsed Ho:YAG laser in static water was investigated by using high-speed camera. The results showed that vapor channel / bubble can be produced with pulsed Ho:YAG laser, and the whole dynamic process of vapor bubble formation, pulsation and consequently collapse can be monitored by using high-speed camera. The dynamic characteristics of vapor bubble, such as pulsation period, the maximum depth and width were determined. The dependence of above dynamic parameters on incident radiant exposure was also presented. Based on which, the influence of vapor bubble on hard tissue ablation was discussed.

  18. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general rules-of-thumb'' for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  19. Characteristics of identifying linear dynamic models from impulse response data using Prony analysis

    SciTech Connect

    Trudnowski, D.J.

    1992-12-01

    The purpose of the study was to investigate the characteristics of fitting linear dynamic models to the impulse response of oscillatory dynamic systems using Prony analysis. Many dynamic systems exhibit oscillatory responses with multiple modes of oscillations. Although the underlying dynamics of such systems are often nonlinear, it is frequently possible and very useful to represent the system operating about some set point with a linear model. Derivation of such linear models can be done using two basic approaches: model the system using theoretical derivations and some linearization method such as a Taylor series expansion; or use a curve-fitting technique to optimally fit a linear model to specified system response data. Prony analysis belongs to the second class of system modeling because it is a method of fitting a linear model to the impulse response of a dynamic system. Its parallel formulation inherently makes it well suited for fitting models to oscillatory system data. Such oscillatory dynamic effects occur in large synchronous-generator-based power systems in the form of electromechanical oscillations. To study and characterize these oscillatory dynamics, BPA has developed computer codes to analyze system data using Prony analysis. The objective of this study was to develop a highly detailed understanding of the properties of using Prony analysis to fit models to systems with characteristics often encountered in power systems. This understanding was then extended to develop general ``rules-of-thumb`` for using Prony analysis. The general characteristics were investigated by performing fits to data from known linear models under controlled conditions. The conditions studied include various mathematical solution techniques; different parent system configurations; and a large variety of underlying noise characteristics.

  20. Dynamic Characteristics of PEM-FC/Woody Biomass Engine Hybrid Micro Grid

    NASA Astrophysics Data System (ADS)

    Obara, Shin'ya; Kito, Shunsuke; Hoshi, Akira; Sasaki, Seizi

    The combustion exhaust heat of woody biomass engine using Stirling cycle is high temperature. This exhaust heat is used for the city gas reforming reaction of a proton exchange membrane fuel cell (PEM-FC) system. The woody biomass engine generator has the characteristic that the greenhouse gas amount of emission with power generation is greatly reducible. In this paper, the micro grid system that introduces PEM-FC/woody biomass engine hybrid cogeneration (PWHC) is proposed. It depends on the dynamic characteristics of the grid for the power quality at the time of load fluctuation being added to the micro grid. Especially, the dynamic characteristics of the independent micro grid are important on security of power quality. So, in this paper, the response characteristic of PEM-FC and woody biomass engine was investigated by the experiment and the numerical analysis. Furthermore, the response characteristic of the PWHC independent micro grid including auxiliary machinery was investigated by the numerical simulation. Moreover, an improvement of dynamic characteristics is proposed using the method of adding proportional-plus-integral control to PWHC. If woody biomass engine is introduced into a house, 10.2s will be required to stabilize power quality at the maximum. On the other hand, when woody biomass engine corresponds to a base load and PEM-FC corresponds to the load exceeding the base load, settling time is less than 1.6 s. In this study, relation between the system configuration of the PWHC micro grid and the dynamic characteristics of the power was clarified.

  1. 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.

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

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

  5. 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.

  6. Nonlinear dynamic characteristics of SMA intravascular stent under radial stochastic loads.

    PubMed

    Zhu, Zhiwen; Zhang, Qingxin; Xu, Jia

    2014-01-01

    Nonlinear dynamic characteristics of shape memory alloy (SMA) intravascular stent under radial stochastic loads were studied in this paper. Von de Pol item was improved to interpret the hysteretic phenomena of SMA, and the nonlinear dynamic model of SMA intravascular stent under radial stochastic loads was developed. The conditions of stochastic stability of the system were obtained in singular boundary theory. The steady-state probability density function of the dynamic response of the system was given, and the stochastic Hopf bifurcation characteristics of the system were analyzed. Theoretical analysis and numerical simulation show that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process, which can cause stent fracture or loss. The results of this paper are helpful to application of SMA intravascular stent in biomedical engineering fields.

  7. Damped harmonic oscillator model for analyzing the dynamic characteristics of STM system

    NASA Astrophysics Data System (ADS)

    Liu, A. P.; Yao, X. X.; Wang, X.; Yang, D. X.; Zhang, X. M.

    2015-09-01

    Recognizing and distinguishing the dynamic characteristics of scanning tunneling microscopy (STM) system is fatal for studying STM image. In this paper, a method for analyzing system’s characteristics by using a damped harmonic oscillator model is presented. The model is driven by random force and all of its properties are described by damping and periodic. For the general solution of such harmonic oscillator’s Langevin equation is deduced and the auto-correlation function (ACF) is obtained for fitting curve. It is shown that damping and periodic property of the two curves have a good agreement by comparing the fitting curve with the auto-correlation curve of time series dates which are acquired by STM. It could be concluded that the damped harmonic oscillator model and auto-correlation method are feasible for analyzing the dynamic characteristics of STM system.

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

    PubMed

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

    2013-10-01

    This paper studies the temporal variation of soil gas radon activity concentration in a highly permeable (k = 2.0E-11 m(2)) sandy-gravelly soil in order to understand if temporal variation of soil gas radon activity concentration can affect geogenic radon potential determination. Geogenic radon potential provides information about the potential risk from radon. Its calculation takes into account the equilibrium, saturated at infinite depth, soil gas radon activity concentration (c∞). This concentration may vary at annual time scale due to the environmental conditions. A long-term (yearly) and high temporal resolution (15 min) observation, applied in this study, reveal various temporal features such as long-term trend, seasonality, daily periodicity and sudden events in soil gas radon time series. Results show seasonal and daily periodical variation of the measured soil gas radon activity concentration (csoilRn) in a highly permeable sandy-gravelly soil with definite seasons without obvious long transitional periods. The winter (from October 2010 to April 2011) is characterized by 2.5 times higher average soil gas radon activity concentration (median is 7.0 kBq m(-3)) than the summer (August, September 2010 and May, June, July 2011) (median is 2.8 kBq m(-3)). Daily periodicity, which is much less than the seasonal one, controls the soil gas radon activity concentration mainly in the summer season. Average (AM) value of csoilRn is higher at night than in the daytime with about 18% and 3.8% in summer and in winter, respectively. As a conclusion, in case of single csoilRn measurement on a highly permeable (k ≥ 2.0E-11 m(2)) soil, similar to our test site, csoilRn should be corrected according to the seasons for calculating the equilibrium activity concentration c∞ value. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Permeable pavement study (Edison)

    EPA Pesticide Factsheets

    While permeable pavement is increasingly being used to control stormwater runoff, field-based, side-by-side investigations on the effects different pavement types have on nutrient concentrations present in stormwater runoff are limited. In 2009, the U.S. EPA constructed a 0.4-ha parking lot in Edison, New Jersey, that incorporated permeable interlocking concrete pavement (PICP), pervious concrete (PC), and porous asphalt (PA). Each permeable pavement type has four, 54.9-m2, lined sections that direct all infiltrate into 5.7-m3 tanks enabling complete volume collection and sampling. This paper highlights the results from a 12-month period when samples were collected from 13 rainfall/runoff events and analyzed for nitrogen species, orthophosphate, and organic carbon. Differences in infiltrate concentrations among the three permeable pavement types were assessed and compared with concentrations in rainwater samples and impervious asphalt runoff samples, which were collected as controls. Contrary to expectations based on the literature, the PA infiltrate had significantly larger total nitrogen (TN) concentrations than runoff and infiltrate from the other two permeable pavement types, indicating that nitrogen leached from materials in the PA strata. There was no significant difference in TN concentration between runoff and infiltrate from either PICP or PC, but TN in runoff was significantly larger than in the rainwater, suggesting meaningful inter-event dry de

  10. 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

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

    PubMed Central

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

    2015-01-01

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

  12. New literal approximations for the longitudinal dynamic characteristics of flexible flight vehicles

    NASA Technical Reports Server (NTRS)

    Livneh, Rafael; Schmidt, David K.

    1992-01-01

    The goal of the literal approximation method is to obtain simple literal (analytical) approximations for key dynamic characteristics of flexible flight vehicles. A basic question regarding the method is its usefulness as an additional design tool for existing design and simulation procedures. Two aspects of this question are: (1) ease of derivation and use of the literal approximations, and (2) the suitability of one set of literal approximations to describe the dynamics of a large set of significantly different vehicles. These issues are addressed by incorporating symbolic manipulation software into the literal approximation method for the analysis of a fifth order model of the longitudinal dynamics of a flexible flight vehicle. The automated literal approximation generated in this fashion reduces the manual derivation time by an approximate factor of four. A single set of literal approximations is shown to provide adequate approximations for the dynamics of significantly different flight vehicles configurations, such as an aircraft, a missile, and a hypersonic vehicle.

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

    PubMed

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

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

  15. 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

  16. Permeability evolution governed by shear: An example during spine extrusion at Unzen volcano, Japan

    NASA Astrophysics Data System (ADS)

    Ashworth, James; Lavallée, Yan; Wallace, Paul; Kendrick, Jackie; Coats, Rebecca; Miwa, Takahiro; Hess, Kai-Uwe

    2017-04-01

    . The sheared rocks are strongly micro-fractured, resulting in a porosity decrease of up to 4% and permeability decrease of over one order of magnitude with increasing effective pressure (effective pressure = confining pressure - pore pressure) between 5 - 100 MPa, representative of increasing lithostatic pressure from 200 m to 4 km depth in the crust. In contrast, our field study of the second spine section, which features a 2 cm wide by 3 metre-long tensile fracture flanked by a 40-cm wide shear damage zone, reveals that dilational shear can result in an increase in permeability of approximately three orders of magnitude. The contrasting shear zone characteristics can be attributed to different shear regimes, which likely occur at different depths in the conduit. At greater depth in the system, where lithostatic pressures largely exceed pore pressure, compactional shear appears to dominate, reducing the permeable porous network as magma strains along the conduit margin, whereas at shallower levels, where the effective pressure is low, dilational shear becomes dominant, resulting in the creation of permeable pathways. We conclude that contrasting shearing regimes may simultaneously affect magma ascent dynamics in volcanic conduits, causing a range of dynamic permeability variations (positive and negative), which dictate eruptive behaviour.

  17. 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.

  18. Robotic guidance benefits the learning of dynamic, but not of spatial movement characteristics.

    PubMed

    Lüttgen, Jenna; Heuer, Herbert

    2012-10-01

    Robotic guidance is an engineered form of haptic-guidance training and intended to enhance motor learning in rehabilitation, surgery, and sports. However, its benefits (and pitfalls) are still debated. Here, we investigate the effects of different presentation modes on the reproduction of a spatiotemporal movement pattern. In three different groups of participants, the movement was demonstrated in three different modalities, namely visual, haptic, and visuo-haptic. After demonstration, participants had to reproduce the movement in two alternating recall conditions: haptic and visuo-haptic. Performance of the three groups during recall was compared with regard to spatial and dynamic movement characteristics. After haptic presentation, participants showed superior dynamic accuracy, whereas after visual presentation, participants performed better with regard to spatial accuracy. Added visual feedback during recall always led to enhanced performance, independent of the movement characteristic and the presentation modality. These findings substantiate the different benefits of different presentation modes for different movement characteristics. In particular, robotic guidance is beneficial for the learning of dynamic, but not of spatial movement characteristics.

  19. 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.

  20. 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.

  1. 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.

  2. IR image quality assessment and real-time optimum seeking method based on dynamic visual characteristics

    NASA Astrophysics Data System (ADS)

    Li, Bin; Liu, Gang; Gao, Yongmin; Lei, Hao; Wu, Haiying; Wang, Yu; Rong, Xiaolong

    2016-10-01

    Image quality is an important factor that influences the dynamic target information perception; it is the key factor of real-time target state analysis and judgment. In order to solve the multi-observation station comparison and video optimum seeking problem in the process of target information perception and recognition, an image quality assessment method based on visual characteristics is proposed for infrared target tracking. First, it analyses the basic infrared target image characteristics and application requirements, analyses the status and problems of the multi station optimum seeking technology. According to the expected research results, the processing flow of image processing is established. Then, the image quality objective assessment index is established, which reflects the basic characteristics of the target image, and the assessment index is integrated into the normalized assessment function. According to the quality assessment function, the infrared image quality assessment based on infrared target recognition and image analysis processing is realized, which is mainly characterized by the region of interest and dynamic visual characteristics. And on the basis of this technology, the real-time optimum seeking of multi station infrared target tracking image is completed. In order to verify the effectiveness of the method and the practical application effect, it designs the quality assessment and comparison of different station infrared images. Example shows that the method proposed in this paper can realize multi-observation station infrared image assessment comparison, image quality sorting, the optimum seeking of the infrared image based on the quality assessment. The results accord with the characteristics of infrared target image and dynamic visual characteristics.

  3. Super-resolution infrared time measurement method based on target dynamic characteristics

    NASA Astrophysics Data System (ADS)

    Li, Bin; Hu, Qiuping; Tang, Zili; Zhang, Sanxi; Zhang, Hua; Yue, Peng; Liu, Biao

    2016-10-01

    High precision time control in the use of weapons and equipment is an important part of product design and development. In order to satisfy the data acquisition requirement of high accuracy and reliability in the rapid flight process, the super-resolution time measurement method based on target dynamic characteristics was put forward and proved by the cabin opening time measurement experiment. First, the changes of explosion pressure wave and image in the cabin opening process were analyzed in detail. The change regulation of explosion flame shape was analyzed by the characteristics of typical pressure wave, and then the high frequency images of the explosion process were shot by high speed camera. The change regulation of the infrared image was obtained through the comparison of visible and infrared image mechanism. Then, combined with the target motion features, and the observed station parameters, the observation model of movement process was built. On the basis of the above research, the infrared characteristic and the movement characteristic were transformed, and the super resolution model was established. For test method, combined with the actual class time measuring process in experimental design, to obtain the special radar for measuring high precision open class time as the true value of the precision appraisal. Experimental results show that the infrared feature and motion feature can realize open class time super resolution measurement, can effectively improve the accuracy and reliability of the data, to achieve specific action of high accuracy measurement that plays an important role by making use of the target dynamic characteristics.

  4. 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.

  5. 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.

  6. Dynamic Analysis of Resonance: Bifurcation Characteristics of Non-linear Parametric Systems

    NASA Astrophysics Data System (ADS)

    Hortel, M.; Škuderová, A.; Kratochvíl, C.; Houfek, M.

    The dynamic analysis is an important part of basic research of complex planetary transmission systems with split power flow. The bifurcation characteristics of the resonance courses especially for high-speed weakly and strongly non-linear parametric and in the damping time-heteronymous systems are highly sensitive to their parameters, i.e. to the quality and quantity of their bifurcation features and ambiguities. In the case of mass discretization, their analytical—numerical solution leads to complex integro-differential equations with solving kernels in the form of Green's resolventes and complex simulation models in MATLAB/Simulink. The case of one branch of the planetary transmission system with six degrees of freedom is analysed in terms of internal dynamics in this paper, i.e. the causes of the quantity and quality of resonance bifurcation curves and formation of ambiguity characteristics of relative motion in gear meshes.

  7. Dynamic characteristics of two-phase thermal control system for spacecraft

    NASA Astrophysics Data System (ADS)

    Malozemov, Vladimir V.; Kudryavtseva, Natal'ya S.; Antonov, Viktor A.; Zagar, Oleg V.; Chernobaev, Nikolaj N.

    1992-07-01

    This paper deals with review of the issues associated with modelling the dynamic processes in the spacecraft two-phase thermal control systems. The work presents the results of modelling the nonstationary conditions of the evaporative and condensation heat exchangers functioning, investigates their response to the characteristic external influences. Disclosed are the results of the computer-aided modelling the two-phase thermal control system with a pump. The dynamic characteristics of the change in the inputs of pressures, temperatures and vapor content of a coolant in various branches of the system, as well as the lengths of the heat transfer zones in the evaporator and condenser under effect of the typical disturbing actions are obtained. The attained transients are analyzed.

  8. Dynamic characteristics of the herringbone planetary gear set during the variable speed process

    NASA Astrophysics Data System (ADS)

    Liu, Changzhao; Qin, Datong; Lim, Teik C.; Liao, Yinghua

    2014-12-01

    In this study, a dynamic model for herringbone planetary gears is proposed which can be applied in the dynamic analysis of variable speed processes (including acceleration, deceleration, and large speed fluctuation process, etc.). The dynamic responses of the acceleration process of an example of a herringbone planetary gear set are simulated in cases where the profile error excitations are ignored and included. The phenomenon of tooth separations can be observed as the rotating speed increases in the simulation, and the effect of the profile error excitations on the phenomenon is also investigated. Furthermore, the effects of the profile error excitations on the vibrations and dynamic meshing forces are investigated before and after the appearance of tooth separations. Moreover, the dynamic characteristics of the herringbone planetary gear set are also compared with that of the spur/helical herringbone planetary gear set briefly. Finally, some advice for the design of planetary gear sets is given to avoid the phenomena of tooth separation and tooth back contacts and suppress the vibrations and dynamic meshing forces.

  9. Permeability of Hollow Microspherical Membranes to Helium

    NASA Astrophysics Data System (ADS)

    Zinoviev, V. N.; Kazanin, I. V.; Pak, A. Yu.; Vereshchagin, A. S.; Lebiga, V. A.; Fomin, V. M.

    2016-01-01

    This work is devoted to the study of the sorption characteristics of various hollow microspherical membranes to reveal particles most suitable for application in the membrane-sorption technologies of helium extraction from a natural gas. The permeability of the investigated sorbents to helium and their impermeability to air and methane are shown experimentally. The sorption-desorption dependences of the studied sorbents have been obtained, from which the parameters of their specific permeability to helium are calculated. It has been established that the physicochemical modification of the original particles exerts a great influence on the coefficient of the permeability of a sorbent to helium. Specially treated cenospheres have displayed high efficiency as membranes for selective extraction of helium.

  10. 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.

  11. 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.

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

    NASA Technical Reports Server (NTRS)

    Townsend, John S.

    1987-01-01

    A detailed dynamic analysis is performed of a vibrating beam with bending stiffness periodic in the spatial coordinate. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

    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.

  14. 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.

  15. Molecular dynamics simulation aiming at interfacial characteristics of polymer chains on nanotubes with different layers

    NASA Astrophysics Data System (ADS)

    Li, Kun; Gu, Boqin; Zhu, Wanfu

    2017-03-01

    A molecular dynamics (MD) simulations study is performed on multiwalled carbon nanotubes (MWNTs)/acrylonitrile-butadiene rubber (NBR) composites. The physisorption and interfacial characteristics between the various MWNTs and polymer macromolecular chains are identified. The effects of nanotube layers on the nanotubes/polymer interactions are examined. Each of the situation result and surface features is characterized by binding energy (Eb). It is shown that the binding energy (Eb) increase with the number of layers.

  16. Dynamic characteristics of a jacket type offshore structure considering non-linear behavior of pile foundations

    SciTech Connect

    Aaghaakouchak, A.A.; Asgarian, B.

    1996-12-31

    Dynamic characteristics of a typical six legged jacket type platform in Persian Gulf have been studied. An equivalent linearized pile stub has been used to model the pile-soil system. The properties of pile stub have been calculated for different levels of the pile-head deformations resulting from the action of different waves. Natural frequencies and mode shapes of resulting linear models have been determined and compared to each other.

  17. Low-Dimensional Dynamical Characteristics of Shock Wave /Turbulent Boundary Layer Interaction in Conical Flows

    DTIC Science & Technology

    2014-12-16

    Shock Wave /Turbulent Boundary Layer Interaction in Conical Flows FA9550-11-1-0203 Dr. Charles E. Tinney, Aerospace Engineering and Engineering...Low-Dimensional Dynamical Characteristics of Shock Wave /Turbulent Boundary Layer Interaction in Conical Flows Contract/Grant Number: FA9550-11-1-0203...driven by transonic resonance (Zaman et al, 2002). What is common about many of these planar nozzle studies is that there is just one single

  18. Synthesis of mechanisms with flexible centrifugal-inertial connections according to fixed dynamic characteristics

    NASA Technical Reports Server (NTRS)

    Ragulskis, K. M.; Yaroslavskiy, I. K.

    1973-01-01

    The criteria for the selection of dynamic characteristics of flexible centrifugal-inertial couplings are discussed. The basic properties considered are: (1) vibration isolation, (2) vibration quenching, and (3) transmission properties. It is stated that the most promising couplings are those with a nonlinear relation between the magnitude of the torque transmitted and the magnitude of deformation of the coupling. The efforts of various investigators are briefly analyzed. Mathematical models are developed to show the relationships of the parameters involved.

  19. Relationship between force-time and velocity-time characteristics of dynamic and isometric muscle actions.

    PubMed

    Khamoui, Andy V; Brown, Lee E; Nguyen, Diamond; Uribe, Brandon P; Coburn, Jared W; Noffal, Guillermo J; Tran, Tai

    2011-01-01

    Previous research has investigated the force-time curve characteristics of isometric and dynamic muscle actions; however, few studies have addressed their relationship to dynamic exercise velocity-time variables. The purpose of this study was to investigate relationships between velocity-time characteristics (high pull and vertical jump peak velocity and rate of velocity development [HPPV, HPRVD, VJPV, VJRVD]), force-time characteristics (isometric peak force [IsoPF], body mass adjusted isometric peak force [IsoPF/BM], isometric rate of force development at different millisecond windows [IsoRFD50-250], dynamic peak force [HPPF], body mass adjusted dynamic peak force [HPPF/BM]), and vertical jump height (VJHeight). Nineteen recreationally trained men (age 23.89 ± 2.92 yr; height 176.32 ± 7.06 cm; mass 78.76 ± 16.50 kg) completed 2 testing sessions. The first session consisted of 3 isometric mid-thigh pulls on a force plate with each repetition held for 3 seconds. On the second testing session, subjects completed 3 dynamic mid-thigh high pulls with 30% IsoPF followed by 3 vertical jumps on a force plate. The HPRVD correlated with IsoRFD50 (r = 0.52) and IsoRFD100 (r = 0.49). The HPPV correlated with IsoPF/BM (r = -0.60), IsoRFD50 (r = 0.56), and IsoRFD100 (r = 0.56). The VJHeight correlated with IsoPF/BM (r = 0.61), whereas VJPV correlated with IsoPF/BM (r = 0.62). These correlations suggest that explosive isometric force production within 50 to 100 milliseconds may influence the ability to accelerate an implement or body and attain high velocity, albeit in a moderate fashion. In addition, body mass adjusted strength may positively influence vertical jump parameters.

  20. 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.

  1. Neuronal uptake affects dynamic characteristics of heart rate response to sympathetic stimulation.

    PubMed

    Nakahara, T; Kawada, T; Sugimachi, M; Miyano, H; Sato, T; Shishido, T; Yoshimura, R; Miyashita, H; Inagaki, M; Alexander, J; Sunagawa, K

    1999-07-01

    Recently, studies in our laboratory involving the use of a Gaussian white noise technique demonstrated that the transfer function from sympathetic stimulation frequency to heart rate (HR) response showed dynamic characteristics of a second-order low-pass filter. However, determinants for the characteristics remain to be established. We examined the effect of an increase in mean sympathetic stimulation frequency and that of a blockade of the neuronal uptake mechanism on the transfer function in anesthetized rabbits. We found that increasing mean sympathetic stimulation frequency from 1 to 4 Hz significantly (P < 0.01) decreased the dynamic gain of the transfer function without affecting other parameters, such as the natural frequency, lag time, or damping coefficient. In contrast, the administration of desipramine (0.3 mg/kg iv), a neuronal uptake blocking agent, significantly (P < 0.01) decreased both the dynamic gain and the natural frequency and prolonged the lag time. These results suggest that the removal rate of norepinephrine at the neuroeffector junction, rather than the amount of available norepinephrine, plays an important role in determining the low-pass filter characteristics of the HR response to sympathetic stimulation.

  2. 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).

  3. Comments on ''Rigorous link between fluid permeability, electrical conductivity, and relaxation times for transport in porous media''

    NASA Astrophysics Data System (ADS)

    Lafarge, Denis

    1993-02-01

    Recently, Avellaneda and Torquato [Phys. Fluids A 3, 2529 (1991)] derived several expressions for both the static and dynamic permeability for flow through porous media, in terms of the characteristic viscous relaxation times. In this Brief Communication the focus is on the physical interpretation, Darcy's law is explicitly obtained, and a slightly misleading statement (which has no effect on the mathematics but may induce erroneous interpretations) is corrected.

  4. 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.

  5. 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...

  6. 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...

  7. Manufacturing Error Effects on Mechanical Properties and Dynamic Characteristics of Rotor Parts under High Acceleration

    NASA Astrophysics Data System (ADS)

    Jia, Mei-Hui; Wang, Cheng-Lin; Ren, Bin

    2017-07-01

    Stress, strain and vibration characteristics of rotor parts should be changed significantly under high acceleration, manufacturing error is one of the most important reason. However, current research on this problem has not been carried out. A rotor with an acceleration of 150,000 g is considered as the objective, the effects of manufacturing errors on rotor mechanical properties and dynamic characteristics are executed by the selection of the key affecting factors. Through the force balance equation of the rotor infinitesimal unit establishment, a theoretical model of stress calculation based on slice method is proposed and established, a formula for the rotor stress at any point derives. A finite element model (FEM) of rotor with holes is established with manufacturing errors. The changes of the stresses and strains of a rotor in parallelism and symmetry errors are analyzed, which verify the validity of the theoretical model. The pre-stressing modal analysis is performed based on the aforementioned static analysis. The key dynamic characteristics are analyzed. The results demonstrated that, as the parallelism and symmetry errors increase, the equivalent stresses and strains of the rotor slowly increase linearly, the highest growth rate does not exceed 4%, the maximum change rate of natural frequency is 0.1%. The rotor vibration mode is not significantly affected. The FEM construction method of the rotor with manufacturing errors can be utilized for the quantitative research on rotor characteristics, which will assist in the active control of rotor component reliability under high acceleration.

  8. Static and Dynamic Characteristics of DC-DC Converter Using a Digital Filter

    NASA Astrophysics Data System (ADS)

    Kurokawa, Fujio; Okamatsu, Masashi

    This paper presents the regulation and dynamic characteristics of the dc-dc converter with digital PID control, the minimum phase FIR filter or the IIR filter, and then the design criterion to improve the dynamic characteristics is discussed. As a result, it is clarified that the DC-DC converter using the IIR filter method has superior performance characteristics. The regulation range is within 1.3%, the undershoot against the step change of the load is less than 2% and the transient time is less than 0.4ms with the IIR filter method. In this case, the switching frequency is 100kHz and the step change of the load R is from 50 Ω to 10 Ω. Further, the superior characteristics are obtained when the first gain, the second gain and the second cut-off frequency are relatively large, and the first cut-off frequency and the passing frequency are relatively low. Moreover, it is important that the gain strongly decreases at the second cut-off frequency because the upper band pass frequency range must be always less than half of the sampling frequency based on the sampling theory.

  9. A benchmark test of accuracy and precision in estimating dynamical systems characteristics from a time series.

    PubMed

    Rispens, S M; Pijnappels, M; van Dieën, J H; van Schooten, K S; Beek, P J; Daffertshofer, A

    2014-01-22

    Characteristics of dynamical systems are often estimated to describe physiological processes. For instance, Lyapunov exponents have been determined to assess the stability of the cardio-vascular system, respiration, and, more recently, human gait and posture. However, the systematic evaluation of the accuracy and precision of these estimates is problematic because the proper values of the characteristics are typically unknown. We fill this void with a set of standardized time series with well-defined dynamical characteristics that serve as a benchmark. Estimates ought to match these characteristics, at least to good approximation. We outline a procedure to employ this generic benchmark test and illustrate its capacity by examining methods for estimating the maximum Lyapunov exponent. In particular, we discuss algorithms by Wolf and co-workers and by Rosenstein and co-workers and evaluate their performances as a function of signal length and signal-to-noise ratio. In all scenarios, the precision of Rosenstein's algorithm was found to be equal to or greater than Wolf's algorithm. The latter, however, appeared more accurate if reasonably large signal lengths are available and noise levels are sufficiently low. Due to its modularity, the presented benchmark test can be used to evaluate and tune any estimation method to perform optimally for arbitrary experimental data.

  10. Dynamics of photosensitized singlet oxygen generation and photophysical characteristics of chlorin e 6 in photolon ointment

    NASA Astrophysics Data System (ADS)

    Parkhats, M. V.; Galievskii, V. A.; Zharnikova, E. S.; Knyukshto, V. N.; Lepeshkevich, S. V.; Stashevskii, A. S.; Trukhacheva, T. V.; Dzhagarov, B. M.

    2011-05-01

    We have used luminescence and absorption spectroscopy to study the dynamics of photosensitized singlet oxygen generation and the photophysical characteristics of chlorin e 6 in Photolon ointment. We have shown that dimethylsulfoxide and polyethylene glycol 400, in concentrations comparable with their content in the ointment form of the drug Photolon, do not lead to appreciable changes in the spectral characteristics of chlorin e 6. Substantial changes in the photophysical characteristics of the photosensitizer are observed at significantly higher concentrations of the excipients in the ointment. We have shown that in buffer solution, chlorin e 6 forms a complex with polyethylene glycol 1500. For the first time, we have detected luminescence of singlet oxygen from the surface of biological tissue treated with Photolon ointment.

  11. 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

  12. 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.

  13. 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.

  14. Permeability, storage and hydraulic diffusivity controlled by earthquakes

    NASA Astrophysics Data System (ADS)

    Brodsky, E. E.; Fulton, P. M.; Xue, L.

    2016-12-01

    Earthquakes can increase permeability in fractured rocks. In the farfield, such permeability increases are attributed to seismic waves and can last for months after the initial earthquake. Laboratory studies suggest that unclogging of fractures by the transient flow driven by seismic waves is a viable mechanism. These dynamic permeability increases may contribute to permeability enhancement in the seismic clouds accompanying hydraulic fracking. Permeability enhancement by seismic waves could potentially be engineered and the experiments suggest the process will be most effective at a preferred frequency. We have recently observed similar processes inside active fault zones after major earthquakes. A borehole observatory in the fault that generated the M9.0 2011 Tohoku earthquake reveals a sequence of temperature pulses during the secondary aftershock sequence of an M7.3 aftershock. The pulses are attributed to fluid advection by a flow through a zone of transiently increased permeability. Directly after the M7.3 earthquake, the newly damaged fault zone is highly susceptible to further permeability enhancement, but ultimately heals within a month and becomes no longer as sensitive. The observation suggests that the newly damaged fault zone is more prone to fluid pulsing than would be expected based on the long-term permeability structure. Even longer term healing is seen inside the fault zone of the 2008 M7.9 Wenchuan earthquake. The competition between damage and healing (or clogging and unclogging) results in dynamically controlled permeability, storage and hydraulic diffusivity. Recent measurements of in situ fault zone architecture at the 1-10 meter scale suggest that active fault zones often have hydraulic diffusivities near 10-2 m2/s. This uniformity is true even within the damage zone of the San Andreas fault where permeability and storage increases balance each other to achieve this value of diffusivity over a 400 m wide region. We speculate that fault zones

  15. 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.

  16. A new quasi-steady method to measure gas permeability of weakly permeable porous media

    NASA Astrophysics Data System (ADS)

    Jannot, Yves; Lasseux, Didier

    2012-01-01

    A new quasi-steady method for the determination of the apparent gas permeability of porous materials is presented in this paper along with the corresponding interpretative physical model derived from the unsteady flow equations. This method is mainly dedicated to the measurement of very low permeability of thin porous media, although thicker but more permeable samples may also be analyzed. The method relies on quasi-steady flow resulting from a (quasi) constant pressure maintained at the inlet face of the sample. Gas flow-rate, as low as 3 × 10-10 m3/s, is determined from the record of pressure increase in a reservoir connected to the outlet face of the sample. An estimate of the characteristic time, tc, to reach quasi-steady flow after imposing a constant pressure at the inlet is derived. It is validated by direct numerical simulations of the complete unsteady flow, clearly defining the required experimental duration for the method to apply. Experimental results obtained on rather permeable and thick rock samples are reported showing an excellent agreement of the measured permeability with that determined independently on the same sample whereas the experimental value of tc is also in very good agreement with the predicted one. The method is further employed on a composite material sheet allowing the identification of an apparent gas permeability of about 10-23 m2.

  17. 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.

  18. 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

  19. Computational fluid dynamics simulations of respiratory airflow in human nasal cavity and its characteristic dimension study

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Liu, Yingxi; Sun, Xiuzhen; Yu, Shen; Yu, Chi

    2008-04-01

    To study the airflow distribution in human nasal cavity during respiration and the characteristic parameters of nasal structure, three-dimensional, anatomically accurate representations of 30 adult nasal cavity models were reconstructed based on processed tomography images collected from normal people. The airflow fields in nasal cavities were simulated by fluid dynamics with finite element software ANSYS. The results showed that the difference of human nasal cavity structure led to different airflow distribution in the nasal cavities and variation of the main airstream passing through the common nasal meatus. The nasal resistance in the regions of nasal valve and nasal vestibule accounted for more than half of the overall resistance. The characteristic model of nasal cavity was extracted on the basis of characteristic points and dimensions deduced from the original models. It showed that either the geometric structure or the airflow field of the two kinds of models was similar. The characteristic dimensions were the characteristic parameters of nasal cavity that could properly represent the original model in model studies on nasal cavity.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  2. Molecular dynamics investigation of the physisorption and interfacial characteristics of NBR chains on carbon nanotubes with different characteristics

    NASA Astrophysics Data System (ADS)

    Li, Kun; Gu, Boqin

    2017-07-01

    The present study investigates the physisorption and interfacial interactions between multiwalled carbon nanotubes (MWNTs) with different characteristics, including different numbers of walls and different functional groups, and acrylonitrile-butadiene rubber (NBR) polymer chains based on molecular dynamics simulations performed using modeled MWNT/NBR compound systems. The effects of the initial orientation of NBR chains and their relative distances to nanotubes, number of nanotube layers, and the surface functional groups of nanotubes on nanotube/polymer interactions are examined. Analysis is conducted according to the final configuration obtained in conjunction with the binding energy (Eb), radius of gyration (Rg) and end-to-end distance (h). The results show that the final conformations of NBR chains adsorbed on MWNT surfaces is associated with the initial relative angle of the NBR chains and their distance from the nanotubes. For non-functionalized MWNTs, Eb is almost directly proportional to Rg under equivalent parameters. Moreover, it is observed that functional groups hinder the wrapping of NBR chains on the MWNT surfaces. This indicates that functional groups do not always benefit the macro-mechanical properties of the composites. Moreover, the type of the major interaction force has been dramatically changed into electrostatic force from vdW force because of functionalization.

  3. Connexin Channel Permeability to Cytoplasmic Molecules

    PubMed Central

    Harris, Andrew L.

    2007-01-01

    Connexin channels are known to be permeable to a variety of cytoplasmic molecules. The first observation of second messenger junctional permeability, made ∼30 years ago, sparked broad interest in gap junction channels as mediators of intercellular molecular signaling. Since then, much has been learned about the diversity of connexin channels with regard to isoform diversity, tissue and developmental distribution, modes of channel regulation, assembly and expression, biochemical modification and permeability, all of which appear to be dynamically regulated. This information has expanded the potential roles of connexin channels in development, physiology and disease, and made their elucidation much more complex - 30 years ago such an orchestra of junctional dynamics was unanticipated. Only recently, however, have investigators been able to directly address, in this more complex framework, the key issue: What specific biological molecules, second messengers and others, are able to permeate the various types of connexin channels, and how well? An important related issue, given the ever-growing list of connexin-related pathologies, is how these permeabilities are altered by disease-causing connexin mutations. Together, many studies show that a variety of cytoplasmic molecules can permeate the different types of connexin channels. A few studies reveal differences in permeation by different molecules through a particular type of connexin channel, and differences in permeation by a particular molecule through different types of connexin channels. This article describes and evaluates the various methods used to obtain these data, presents an annotated compilation of the results, and discusses the findings in the context of what can be inferred about mechanism of selectivity and potential relevance to signaling. The data strongly suggest that highly specific interactions take place between connexin pores and specific biological molecular permeants, and that those

  4. 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.

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

    PubMed

    Aria, Adrianus I; Gharib, Morteza

    2014-06-17

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

  6. Effects of Gas Rarefaction on Dynamic Characteristics of Micro Spiral-Grooved Thrust Bearing.

    PubMed

    Liu, Ren; Wang, Xiao-Li; Zhang, Xiao-Qing

    2012-04-01

    The effects of gas-rarefaction on dynamic characteristics of micro spiral-grooved-thrust-bearing are studied. The Reynolds equation is modified by the first order slip model, and the corresponding perturbation equations are then obtained on the basis of the linear small perturbation method. In the converted spiral-curve-coordinates system, the finite-volume-method (FVM) is employed to discrete the surface domain of micro bearing. The results show, compared with the continuum-flow model, that under the slip-flow regime, the decrease in the pressure and stiffness become obvious with the increasing of the compressibility number. Moreover, with the decrease of the relative gas-film-thickness, the deviations of dynamic coefficients between slip-flow-model and continuum-flow-model are increasing.

  7. Force-time curve characteristics of dynamic and isometric muscle actions of elite women olympic weightlifters.

    PubMed

    Haff, G Gregory; Carlock, Jon M; Hartman, Michael J; Kilgore, J Lon; Kawamori, Naoki; Jackson, Janna R; Morris, Robert T; Sands, William A; Stone, Michael H

    2005-11-01

    Six elite women weightlifters were tested to evaluate force-time curve characteristics and intercorrelations of isometric and dynamic muscle actions. Subjects performed isometric and dynamic mid-thigh clean pulls at 30% of maximal isometric peak force and 100 kg from a standardized position on a 61.0 x 121.9 cm AMTI forceplate. Isometric peak force showed strong correlations to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.93, 0.64, and 0.80 respectively). Isometric rate of force development showed moderate to strong relationships to the athletes' competitive snatch, clean and jerk, and combined total (r = 0.79, 0.69, and 0.80 respectively). The results of this study suggest that the ability to perform maximal snatch and clean and jerks shows some structural and functional foundation with the ability to generate high forces rapidly in elite women weightlifters.

  8. 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.

  9. Dynamic characteristics of nitrogen and phosphorus in the representative input tributaries of Miyun Reservoir

    NASA Astrophysics Data System (ADS)

    Du, L. F.; Liu, J.; Li, S. J.; Li, X. R.; Yang, J. F.; Zhao, T. K.; Ma, M. T.

    2017-08-01

    The study analyzed dynamic characteristic of nitrogen and phosphorus and influencing variables in three representative input tributaries of Miyun Reservoir from 2012 to 2016. The results showed that Chaohe River in the study period had relatively high TN, NO3 --N and NH4 +-N concentrations. While high phosphorus content was found in Qinghe River. Basing on environmental quality standard for surface water, NO3 --N, NH+-N and TP met the drinking water criterion in most samples. However, TN content met the drinking water criterion only in less than 15% samples. In Qingshuihe River, pH and TSS were significantly variable due to nitrogen variations and TOC was significantly variable for phosphorus variations. However, water parameters (BOD, COD, TSS, TOC, EC and pH) had no significant effects on nitrogen and phosphorus dynamics in Chaohe River and Baihe River.

  10. 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.

  11. Dynamic characteristics of two 300 kW class dual keel space station concepts

    NASA Technical Reports Server (NTRS)

    Dorsey, J. T.; Sutter, T. R.; Lake, M. S.; Cooper, P. A.

    1986-01-01

    Results from an investigation of the dynamic behavior of a 300 kW class solar dynamic powered, dual kell space station are presented. The purpose of the investigation was to determine and assess the influence of space station truss bay size on station controllability during rigid body attitude adjustment and orbit reboost maneuvers. The dual keel space station concept is defined and two finite element models (one which has a truss bay size of 5m and another with a truss bay size of 9 feet) are described. Rigid and flexible body characteristics of the two space station models are also presented. Finally, results from a transient response analysis, where the stations are subjected to an orbit reboost maneuver, are summarized.

  12. Paradoxical response to an emotional task: trait characteristics and heart-rate dynamics.

    PubMed

    Balocchi, Rita; Varanini, Maurizio; Paoletti, Giulia; Mecacci, Giulio; Santarcangelo, Enrica L

    2015-01-01

    The present study evaluated the heart-rate dynamics of subjects reporting decreased (responders) or paradoxically increased relaxation (nonresponders) at the end of a threatening movie. Heart-rate dynamics were characterized by indices extracted through recurrence quantification analysis (RQA) and detrended fluctuation analysis (DFA). These indices were studied as a function of a few individual characteristics: hypnotizability, gender, absorption, anxiety, and the activity of the behavioral inhibition and activation systems (BIS/BAS). Results showed that (a) the subjective experience of responsiveness is associated with the activity of the behavioral inhibition system and (b) a few RQA and DFA indices are able to capture the influence of cognitive-emotional traits, including hypnotizability, on the responsiveness to the threatening task.

  13. Dynamic characteristics and performance evaluation for the part strut failure of the vibration isolation platform on satellites

    NASA Astrophysics Data System (ADS)

    Zhang, Yao; Sheng, Chao; Guo, Zixi; Wang, Youyi; Li, Wenbo

    2017-04-01

    The dynamic characteristics and performance evaluation for the part strut failure of the vibration isolation platform are presented in this paper. The first step provides and mathematically describes two types of strut failure: fractured and stuck. Secondly, the dynamic model of the vibration isolation platform, which considers the part strut failure, is established using the Newton-Euler method and a constraint equation to evaluate its dynamic characteristics and performance. Then, with reasonable assumptions, the dynamic model of the satellite, which has a vibration isolation platform and vibration sources (such as control moment gyros) of three working situations (without and with two types of strut failure), is simplified to analyse the frequency domain characteristic and coupling characteristic with the attitude control system. Finally, a numerical simulation is used to study the effect of the vibration isolation platform with part strut failure on the attitude control and stabilization, and the attitude control performance is evaluated.

  14. Dynamic Characteristics Analysis of Two-DOF Oscillatory Actuator and Experimental Verification of Prototype

    NASA Astrophysics Data System (ADS)

    Takamichi, Yoshimoto; Hirata, Katsuhiro; Asai, Yasuyoshi; Ueyama, Kenji; Hashimoto, Eiichiro; Takagi, Takahiro

    Recently, linear oscillatory actuators have been used in a wide range of applications. In particular, small linear oscillatory actuators are expected to be applied to haptic devices by extension to multi-degree-of-freedom motion with an arbitrary acceleration. In this paper, we propose a compact two-DOF oscillatory actuator that can move in various directions on the plane. The static and dynamic characteristics of the actuator are determined by the 3-D finite element method. The effectiveness of this method is shown through a comparison of the obtained results with the experimental results of a prototype.

  15. 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.

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

    NASA Technical Reports Server (NTRS)

    Stiffler, A. K.

    1975-01-01

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

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

    DOE PAGES

    Diesen, Elias; Saalmann, Ulf; Richter, Martin; ...

    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.

  18. Dynamic response characteristics of steel portal frames having semi-rigid joints under sinusoidal wave excitation

    NASA Astrophysics Data System (ADS)

    Bhatti, Abdul Qadir

    2017-08-01

    To demonstrate the characteristics of the nonlinear response of steel frames, an elastic dynamic response analysis of the semi-rigid frame is performed under the harmonic wave. The semi-rigid contact is represented by the alternating spring which is given stiffness by a three-parameter energy model which approaches the hysterical curve by hardening model. The properties of spectra and hysteric curves are presented. This study shows that (1) the greater the acceleration input capacitance the smaller the instant connection capability and the smaller is the response. (2) However, by allowing an extreme increase in capacitance input acceleration, response spectra can be increased as the contact stiffness results near zero.

  19. 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.

  20. An algorithmic approach for static and dynamic gesture recognition utilising mechanical and biomechanical characteristics.

    PubMed

    Parvini, Farid; Shahabi, Cyrus

    2007-01-01

    We propose a novel approach for recognising static and dynamic hand gestures by analysing the raw data streams generated by the sensors attached to the human hands. We utilise the concept of 'range of motion' in the movement of fingers and exploit this characteristic to analyse the acquired data for recognising hand signs. Our approach for hand gesture recognition addresses two major problems: user-dependency and device-dependency. Furthermore, we show that our approach neither requires calibration nor involves training. We apply our approach for recognising American Sign Language (ASL) signs and show that more than 75% accuracy in sign recognition can be achieved.

  1. Prediction of Dynamic Stall Characteristics Using Advanced Non-Linear Panel Methods.

    DTIC Science & Technology

    1984-04-04

    three- dimensional method , incorporating the techniques that are being examined in the two-dimensional pilot code. r.• - t... . .. -..-. .°.- S °"°"° I...RD-Ai48 453 PREDICTION OF DYNAMIC STRLL CHARACTERISTICS USING 1/1 RDVRNCED NON-LINERR PAN..(U) ANALYTICAL METHODS INC REDMOND WA B MRSKEW ET AL. 84...1 2.0 micROCOPY RESOLUTION TEST CHART hAyl0#dM. @UAU M STAUIOAPOI A VOSR-TR 84.0 97 5 Analytical methods Report 8406 FINAL REPORT Tw. ’ PREDICITON OF

  2. 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.

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

    SciTech Connect

    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.

  4. 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.

  5. 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.

  6. Research on influence factor about the dynamic characteristic of armored vehicle hydraulic-driven fan system

    NASA Astrophysics Data System (ADS)

    Chao, Zhiqiang; Mao, Feiyue; Liu, Xiangbo; Li, Huaying; Han, Shousong

    2017-01-01

    In view of the large power of armored vehicle cooling system, the demand for high fan speed control and energy saving, this paper expounds the basic composition and principle of hydraulic-driven fan system and establishes the mathematical model of the system. Through the simulation analysis of different parameters, such as displacement of motor and working volume of fan system, the influences of performance parameters on the dynamic characteristic of hydraulic-driven fan system are obtained, which can provide theoretical guidance for system optimization design.

  7. On the improvement design of dynamic characteristics for the roller follower of a variable-speed plate cam mechanism

    NASA Astrophysics Data System (ADS)

    Fan, Hui Ching; Yan, Hong Sen

    2012-03-01

    Without modifying the cam contour, a cam mechanism with a variable input speed trajectory offers an alternative solution to flexibly achieve kinematic and dynamic characteristics, and then decrease the follower's residual vibration. Firstly, the speed trajectory of cam is derived by employing Bezier curve, and motion continuity conditions are investigated. Then the motion characteristics between the plate cam and its roller follower are derived. To analyze the residual vibration, a single degree of freedom dynamic model of the elastic cam-follower system is introduced. Based on the motion equation derived from the dynamic model, the residual vibration of the follower is yielded. The design procedure to improve the kinematic and dynamic motion characteristics is presented and two design examples with discussions are provided. Finally, the simulations of the kinematic and dynamic models by ADAMS are carried out and verified that the design models as well as the performances of the mechanism are feasible.

  8. Molecular dynamics models and thermodynamic characteristics of hydrogen bonds in 1,2-ethanediol

    NASA Astrophysics Data System (ADS)

    Usacheva, T. M.; Zhuravlev, V. I.; Lifanova, N. V.; Matveev, V. K.

    2017-06-01

    A correlation between the lifetimes of hydrogen bonds and the thermodynamic characteristics of their formation and breaking, and the experimental relaxation times of dielectric spectra and the energy characteristics of relaxation processes, is observed via molecular dynamics (MD) simulation of the rearranging of the network structure of 1,2-ethanediol. The MD torsional frequency of the transition of gauche conformer tGg' at 224.1 cm-1 and the experimental frequency of the band maximum of torsional vibrations at 230 cm-1 in the infrared spectrum correlate with the oscillation frequency of molecules at 240 cm-1 inside clusters in the Dissado-Hill (DH) model. The MD and DH models indicate a predominantly parallel alignment of the electric dipole moments of conformers tGg' in the three-dimensional network of hydrogen bonds of the liquid 1,2-ethanediol phase.

  9. 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.

  10. Analysing periodicity, nonlinearity and transitional characteristics of nonlinear dynamic systems with Periodicity Ratio (PR)

    NASA Astrophysics Data System (ADS)

    Dai, L.; Han, L.

    2011-12-01

    The multiple-periodicity, nonlinearity and transitional characteristics of nonlinear dynamic systems subjected to external excitations are studied in this research. Diagnoses of the number and changing multiple-periodicities of Duffing's systems are performed with implementation of the Periodicity Ratio (PR). The multiple-periodicity diagram is generated such that the periodicities and nonlinearity of the systems with respect to the system parameters can be graphically studied. The stability and convergence of the systems are investigated. The results of the research show that the number of period of periodicity of the systems increases continuously when certain system parameters increase. Transitional characteristics of the systems are also investigated. Both Lyapunov Exponents and Periodicity Ratio are implemented to diagnose the transitional routes of the systems. New symmetrical transition characters from periodicity to quasi-periodicity and chaos are displayed in terms of PR values. Comparing to Lyapunov Exponents, the Periodicity Ratio discloses more detailed and accurate transition information.

  11. 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.

  12. 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.

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

    PubMed

    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.

  14. 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

  15. Differential permeability of the proximal and distal rabbit small bowel

    PubMed Central

    Ross, Allan; Rubin, Allen W.; Deren, Julius J.

    1972-01-01

    The permeability of the proximal and distal rabbit intestine for two to six carbon polyhydric alcohols was compared. Intestinal segments were mounted in chambers that permitted the measurement of the unidirectional flux across the brush border membrane. For both proximal and distal intestine, the permeability for a series of polyhydric alcohols decreased with increasing size. The proximal intestine was more permeable for four, five, and six carbon polyhydric alcohols than distal intestine. This regional permeability difference can be attributed to variations in the permeability characteristics of the brush border specifically. The uptake of alcohols was nonsaturable and was not inhibited by phlorizine or n-ethylmaleimide. The results are compatible with the concept that the brush border membrane has properties similar to artificial porous membranes and that the equivalent radius of the pores of the proximal intestine exceeds that of the distal gut. PMID:4639025

  16. Controlled release with coating layer of permeable particles.

    PubMed

    Ito, Ryusei; Golman, Boris; Shinohara, Kunio

    2003-10-30

    An enhanced method was proposed for controlled release of core material using a coating layer of fine permeable particles dispersed in an impermeable wax prepared by dry-based process. A mathematical model was constructed to describe in detail the core material release by diffusion through the connected permeable particles inside the coating layer. The effective diffusivity was simulated by a random walk method taking into account the structure of the coating layer. The released characteristics were measured for the urea core particle coated with the layer of the starch permeable particles dispersed in the paraffin wax. The calculated results were in a good quantitative agreement with experimental data in all range of coating conditions. As a result, the low release rate was proven to be obtained with thicker coating layer of lower volume fraction of permeable particles. Moreover, the application of permeable particles instead of soluble ones [J. Chem. Eng. Jpn. 35 (2002) 40] resulted in significant decrease in release rate.

  17. 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.

  18. Static, dynamic, and noise characteristics of vertical- cavity surface-emitting lasers

    NASA Astrophysics Data System (ADS)

    Law, Joanne Y.

    1998-07-01

    An important aspect of vertical-cavity surface-emitting lasers (VCSELs) that needs to be improved is its stable operation in a single transverse mode. Due to relatively large dimensions of VCSELs (~10 μm radius), spatial hole-burning and carrier diffusion affect device performance significantly, especially because VCSELs often operate in several transverse modes at high injection currents. In this thesis, a comprehensive numerical study of such spatial effects on the static, dynamic, and noise characteristics of VCSELs is presented. The computer model includes the spatial dependences of both the optical field and the carrier density. Device characteristics are analyzed under different operating conditions, including continuous-wave (CW) operation, gain-switched operation, optical feedback, and optical injection. Both single-mode and two-mode operations are analyzed. Under CW operation, transverse-mode competition induced by spatial hole-burning is found to affect the static and noise characteristics significantly. In particular, transverse-mode competition affects the mode-partition noise. Under single-mode gain-switched operation, it is shown that by using an appropriate electrical contact, spatial hole-burning can be avoided and shorter pulses can be obtained. Under two-mode gain-switched operation, transverse-mode competition gives rise to rich nonlinear dynamics. The effect of external influence has also been studied. It is found that optical feedback or optical injection can force a two-mode VCSEL to operate in a single transverse mode under appropriate conditions. However, distant feedback or injection outside the locking region can destabilize the CW operation and lead to interesting nonlinear dynamics. The feedback strength and the injection power at which oscillations occur depend critically on the strength of intermodal coupling. In general, results indicate that strong intermodal coupling reduces the sensitivity of the VCSEL towards external influence

  19. Dynamic susceptibility contrast and dynamic contrast-enhanced MRI characteristics to distinguish microcystic meningiomas from traditional Grade I meningiomas and high-grade gliomas.

    PubMed

    Hussain, Namath S; Moisi, Marc D; Keogh, Bart; McCullough, Brendan J; Rostad, Steven; Newell, David; Gwinn, Ryder; Foltz, Gregory; Mayberg, Marc; Aguedan, Brian; Good, Valerie; Fouke, Sarah J

    2016-06-10

    OBJECTIVE Microcystic meningioma (MM) is a meningioma variant with a multicystic appearance that may mimic intrinsic primary brain tumors and other nonmeningiomatous tumor types. Dynamic susceptibility contrast (DSC) and dynamic contrast-enhanced (DCE) MRI techniques provide imaging parameters that can differentiate these tumors according to hemodynamic and permeability characteristics with the potential to aid in preoperative identification of tumor type. METHODS The medical data of 18 patients with a histopathological diagnosis of MM were identified through a retrospective review of procedures performed between 2008 and 2012; DSC imaging data were available for 12 patients and DCE imaging data for 6. A subcohort of 12 patients with Grade I meningiomas (i.e., of meningoepithelial subtype) and 54 patients with Grade IV primary gliomas (i.e., astrocytomas) was also included, and all preoperative imaging sequences were analyzed. Clinical variables including patient sex, age, and surgical blood loss were also included in the analysis. Images were acquired at both 1.5 and 3.0 T. The DSC images were acquired at a temporal resolution of either 1500 msec (3.0 T) or 2000 msec (1.5 T). In all cases, parameters including normalized cerebral blood volume (CBV) and transfer coefficient (kTrans) were calculated with region-of-interest analysis of enhancing tumor volume. The normalized CBV and kTrans data from the patient groups were analyzed with 1-way ANOVA, and post hoc statistical comparisons among groups were conducted with the Bonferroni adjustment. RESULTS Preoperative DSC imaging indicated mean (± SD) normalized CBVs of 5.7 ± 2.2 ml for WHO Grade I meningiomas of the meningoepithelial subtype (n = 12), 4.8 ± 1.8 ml for Grade IV astrocytomas (n = 54), and 12.3 ± 3.8 ml for Grade I meningiomas of the MM subtype (n = 12). The normalized CBV measured within the enhancing portion of the tumor was significantly higher in the MM subtype than in typical meningiomas and Grade

  20. Osmo-sensitive and stretch-activated calcium-permeable channels in Vicia faba guard cells are regulated by actin dynamics.

    PubMed

    Zhang, Wei; Fan, Liu-Min; Wu, Wei-Hua

    2007-03-01

    In responses to a number of environmental stimuli, changes of cytoplasmic [Ca(2+)](cyt) in stomatal guard cells play important roles in regulation of stomatal movements. In this study, the osmo-sensitive and stretch-activated (SA) Ca(2+) channels in the plasma membrane of Vicia faba guard cells are identified, and their regulation by osmotic changes and actin dynamics are characterized. The identified Ca(2+) channels were activated under hypotonic conditions at both whole-cell and single-channel levels. The channels were also activated by a stretch force directly applied to the membrane patches. The channel-mediated inward currents observed under hypotonic conditions or in the presence of a stretch force were blocked by the Ca(2+) channel inhibitor Gd(3+). Disruption of actin filaments activated SA Ca(2+) channels, whereas stabilization of actin filaments blocked the channel activation induced by stretch or hypotonic treatment, indicating that actin dynamics may mediate the stretch activation of these channels. In addition, [Ca(2+)](cyt) imaging demonstrated that both the hypotonic treatment and disruption of actin filaments induced significant Ca(2+) elevation in guard cell protoplasts, which is consistent with our electrophysiological results. It is concluded that stomatal guard cells may utilize SA Ca(2+) channels as osmo sensors, by which swelling of guard cells causes elevation of [Ca(2+)](cyt) and consequently inhibits overswelling of guard cells. This SA Ca(2+) channel-mediated negative feedback mechanism may coordinate with previously hypothesized positive feedback mechanisms and regulate stomatal movement in response to environmental changes.

  1. Osmo-Sensitive and Stretch-Activated Calcium-Permeable Channels in Vicia faba Guard Cells Are Regulated by Actin Dynamics1[OA

    PubMed Central

    Zhang, Wei; Fan, Liu-Min; Wu, Wei-Hua

    2007-01-01

    In responses to a number of environmental stimuli, changes of cytoplasmic [Ca2+]cyt in stomatal guard cells play important roles in regulation of stomatal movements. In this study, the osmo-sensitive and stretch-activated (SA) Ca2+ channels in the plasma membrane of Vicia faba guard cells are identified, and their regulation by osmotic changes and actin dynamics are characterized. The identified Ca2+ channels were activated under hypotonic conditions at both whole-cell and single-channel levels. The channels were also activated by a stretch force directly applied to the membrane patches. The channel-mediated inward currents observed under hypotonic conditions or in the presence of a stretch force were blocked by the Ca2+ channel inhibitor Gd3+. Disruption of actin filaments activated SA Ca2+ channels, whereas stabilization of actin filaments blocked the channel activation induced by stretch or hypotonic treatment, indicating that actin dynamics may mediate the stretch activation of these channels. In addition, [Ca2+]cyt imaging demonstrated that both the hypotonic treatment and disruption of actin filaments induced significant Ca2+ elevation in guard cell protoplasts, which is consistent with our electrophysiological results. It is concluded that stomatal guard cells may utilize SA Ca2+ channels as osmo sensors, by which swelling of guard cells causes elevation of [Ca2+]cyt and consequently inhibits overswelling of guard cells. This SA Ca2+ channel-mediated negative feedback mechanism may coordinate with previously hypothesized positive feedback mechanisms and regulate stomatal movement in response to environmental changes. PMID:17259289

  2. Reaction-induced fracturing of low permeability solids

    NASA Astrophysics Data System (ADS)

    Kobchenko, Maya; Dysthe, Dag Kristian; Renard, Francois; Jamtveit, Bjørn; Malthe-Sørenssen, Anders

    2015-04-01

    Escape of internally generated fluids from low permeability elastic solids plays an important role in several natural environments. Primary migration of hydrocarbons, dehydration of sediments and hydrated mantle rocks in subduction zones are examples where the existing permeability cannot accommodate transport of generated fluids in low permeability rocks and fluid pressure build-up may alter the permeability by fracturing. Fractures form and propagate in the rock due to internal pressure build-up. We have performed experiments on organic-rich shales and analogue gels using time-resolved X-ray microtomography, 2D imaging and pressure burst recordings. Fracture nucleation, propagation and coalescence as well as network evolution dynamics during internal fluid genertion was described. The spatial organization of the fracture networks appeared as intermediate between tree networks and hierarchical fractures. The dynamics of intermittent fluid release via fracture pathways show both periodic, 1/f and 1/fˆ2 behaviour of fluid release spectrum.

  3. Dynamic and thermodynamic characteristics associated with the glass transition of amorphous trehalose-water mixtures.

    PubMed

    Weng, Lindong; Elliott, Gloria D

    2014-06-21

    The glass transition temperature Tg of biopreservative formulations is important for predicting the long-term storage of biological specimens. As a complementary tool to thermal analysis techniques, which are the mainstay for determining Tg, molecular dynamics simulations have been successfully applied to predict the Tg of several protectants and their mixtures with water. These molecular analyses, however, rarely focused on the glass transition behavior of aqueous trehalose solutions, a subject that has attracted wide scientific attention via experimental approaches. Important behavior, such as hydrogen-bonding dynamics and self-aggregation has yet to be explored in detail, particularly below, or in the vicinity of, Tg. Using molecular dynamics simulations of several dynamic and thermodynamic properties, this study reproduced the supplemented phase diagram of trehalose-water mixtures (i.e., Tg as a function of the solution composition) based on experimental data. The structure and dynamics of the hydrogen-bonding network in the trehalose-water systems were also analyzed. The hydrogen-bonding lifetime was determined to be an order of magnitude higher in the glassy state than in the liquid state, while the constitution of the hydrogen-bonding network exhibited no noticeable change through the glass transition. It was also found that trehalose molecules preferred to form small, scattered clusters above Tg, but self-aggregation was substantially increased below Tg. The average cluster size in the glassy state was observed to be dependent on the trehalose concentration. Our findings provided insights into the glass transition characteristics of aqueous trehalose solutions as they relate to biopreservation.

  4. 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.

  5. 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

  6. Investigation of dynamic characteristics of a rotor system with surface coatings

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Cao, Dengqing; Wang, Deyou

    2017-02-01

    A Jeffcott rotor system with surface coatings capable of describing the mechanical vibration resulting from unbalance and rub-impact is formulated in this article. A contact force model proposed recently to describe the impact force between the disc and casing with coatings is employed to do the dynamic analysis for the rotor system with rubbing fault. Due to the variation of penetration, the contact force model is correspondingly modified. Meanwhile, the Coulomb friction model is applied to simulate the friction characteristics. Then, the case study of rub-impact with surface coatings is simulated by the Runge-Kutta method, in which a linear interpolation method is adopted to predict the rubbing instant. Moreover, the dynamic characteristics of the rotor system with surface coatings are analyzed in terms of bifurcation plot, waveform, whirl orbit, Poincaré map and spectrum plot. And the effects of the hardness of surface coatings on the response are investigated as well. Finally, compared with the classical models, the modified contact force model is shown to be more suitable to solve the rub-impact of aero-engine with surface coatings.

  7. 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.

  8. Numerical study on air-structure coupling dynamic characteristics of the axial fan blade

    NASA Astrophysics Data System (ADS)

    Chen, Q. G.; Xie, B.; Li, F.; Gu, W. G.

    2013-12-01

    In order to understand the dynamic characteristics of the axial-flow fan blade due to the effect of rotating stress and the action of unsteady aerodynamic forces caused by the airflow, a numerical simulation method for air-structure coupling in an axial-flow fan with fixed rear guide blades was performed. The dynamic characteristics of an axial-flow fan rotating blade were studied by using the two-way air-structure coupling method. Based on the standard k-ε turbulence model, and using weak coupling method, the preceding six orders modal parameters of the rotating blade were obtained, and the distributions of stress and strain on the rotating blade were presented. The results show that the modal frequency from the first to the sixth order is 3Hz higher than the modal frequency without considering air-structure coupling interaction; the maximum stress and the maximum strain are all occurred in the vicinity of root area of the blade no matter the air-structure coupling is considered or not, thus, the blade root is the dangerous location subjected to fatigue break; the position of maximum deformation is at the blade tip, so the vibration of the blade tip is significant. This study can provide theoretical references for the further study on the strength analysis and mechanical optimal design.

  9. Molecular-dynamics study on characteristics of energy and tangential momentum accommodation coefficients

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hiroki; Matsuda, Yu; Niimi, Tomohide

    2017-07-01

    Gas-surface interaction is studied by the molecular dynamics method to investigate qualitatively characteristics of accommodation coefficients. A large number of trajectories of gas molecules colliding to and scattering from a surface are statistically analyzed to calculate the energy (thermal) accommodation coefficient (EAC) and the tangential momentum accommodation coefficient (TMAC). Considering experimental measurements of the accommodation coefficients, the incident velocities are stochastically sampled to represent a bulk condition. The accommodation coefficients for noble gases show qualitative coincidence with experimental values. To investigate characteristics of these accommodation coefficients in detail, the gas-surface interaction is parametrically studied by varying the molecular mass of gas, the gas-surface interaction strength, and the molecular size of gas, one by one. EAC increases with increasing every parameter, while TMAC increases with increasing the interaction strength, but decreases with increasing the molecular mass and the molecular size. Thus, contradictory results in experimentally measured TMAC for noble gases could result from the difference between the surface conditions employed in the measurements in the balance among the effective parameters of molecular mass, interaction strength, and molecular size, due to surface roughness and/or adsorbed molecules. The accommodation coefficients for a thermo-fluid dynamics field with a temperature difference between gas and surface and a bulk flow at the same time are also investigated.

  10. Numerical investigation of refrigeration machine compressor operation considering single-phase electric motor dynamic characteristics

    NASA Astrophysics Data System (ADS)

    Baidak, Y.; Smyk, V.

    2017-08-01

    Using as the base the differential equations system which was presented in relative units for generalized electric motor of hermetic refrigeration compressor, mathematical model of the software for dynamic performance calculation of refrigeration machine compressors drive low-power asynchronous motors was developed. Performed on its ground calculations of the basic model of two-phase electric motor drive of hermetic compressor and the proposed newly developed model of the motor with single-phase stator winding, which is an alternative to the industrial motor winding, have confirmed the benefits of the motor with innovative stator winding over the base engine. Given calculations of the dynamic characteristics of compressor drive motor have permitted to determine the value of electromagnetic torque swinging for coordinating compressor and motor mechanical characteristics, and for taking them into consideration in choosing compressor elements construction materials. Developed and used in the process of investigation of refrigeration compressor drive asynchronous single-phase motor mathematical and software can be considered as an element of computer-aided design system for design of the aggregate of refrigeration compression unit refrigerating machine.

  11. Dynamic Model Investigation of the Rough-Water Landing Characteristics of a Spacecraft

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Dynamic Model Investigation of the Rough-Water Landing Characteristics of a Spacecraft. The investigation was made to study the rough-water landing characteristics of a Gemini type of spacecraft. The investigations were made with a 1/6-scale dynamic model in a simulated sea state 4 rough water. Parachute letdown landings were simulated with the model at various yaw angles and horizontal velocities. The vertical velocity and landing attitude remained constant. The range of maximum lateral and longitudinal acceleration was from about 3-1/2g to 16g while that for the maximum normal acceleration was from lg to 15g. The range of maximum angular acceleration was from about 0 to 190 radians per second(exp 2). The smoothest behavior and the lowest angular acceleration occurred at the 90 degree yaw angle. The normal acceleration was near minimum at this condition. [Entire movie available on DVD from CASI as Doc ID 20070031004. Contact help@sti.nasa.gov

  12. 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.

  13. 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.

  14. Dynamic characteristics of Bridgestone low shear modulus-high damping seismic isolation bearings

    SciTech Connect

    Chang, Y.W.; Seidensticker, R.W.

    1993-06-01

    Bridgestone Company of Japan is one of the leading seismic bearing manufacturers in the world. Their bearings have very good performance records. It appears that Bridgestone`s high damping bearings are made of a blend of filled natural and synthetic rubbers with fillers and plastizers whereas in the United States, the high damping compound is a carbon filled natural rubber. To compare the properties of the two different kinds of high damping compounds, Argonne National Laboratory (ANL) purchased eight bearings from Bridgestone: four of which were made of high shear modulus-high damping rubber compound KL401; the other four were made of low shear modulus-high damping rubber compounds: two with KL301 elastomer and two with KL302 elastomer. Tests of the Bridgestone bearings were performed at the Earthquake Engineering Research Center. The dynamic characteristics of the high shear modulus Bridgestone bearings, KL401, are described in ANL/Shimizu Report ANL-003. This report describes the dynamic and failure characteristics of the low shear modulus Bridgestone bearings, KL301 and KL302.

  15. [Anti-fouling characteristics of the novel precoating reagent in dynamic membrane bioreactor].

    PubMed

    Ye, Mao-Sheng; Zhang, Han-Min; Yang, Feng-Lin; Cui, Xia

    2007-11-01

    Further research was made on precoating reagents in dynamic membrane process, in which novel precoating reagent-polyvinyl alcohol microsphere (PVA-MS) was prepared through emulsive polymerization of PVA and glutaraldehyde (GA). Furthermore, polymerization mechanism and anti-fouling characteristics through adsorption of membrane major fouling substances EPS upon PVA-MS were studied. The results showed that hemiacetals reaction played a major role in emulsive polymerization process, as the quantity of hydroxyl on PVA was decreased a little, PVA-MS surface behaved good hydrophilic, and the adsorption of protein and amylose upon PVA microsphere was stable and low, which was 0.543 mg x g(-1) and 0.694 mg x g(-1) respectively. In addition, PVA-MS surface behaved electronic negativity, which acted electrostatic repulsion to active sludge floc. Upon this characteristics and data, it was concluded that membrane fouling was delayed in microscopy structure. Diameter of PVA-MS in precoating liquid was about 1.14 microm, and Zeta-potential of precoating liquid with different precoating reagent concentration was less than - 39 mV, which made PVA microsphere diffused and stable from each other, then sedimentate rapidly on porous support membrane surface and internal wall of hole path. Besides, the morphology of PVA-MS and dynamic membrane formed from PVA-MS on support membrane were observed through SEM.

  16. Dynamic characteristics of signatures: effects of writer style on genuine and simulated signatures.

    PubMed

    Mohammed, Linton; Found, Bryan; Caligiuri, Michael; Rogers, Doug

    2015-01-01

    The aims of this study were to determine if computer-measured dynamic features (duration, size, velocity, jerk, and pen pressure) differ between genuine and simulated signatures. Sixty subjects (3 equal groups of 3 signature styles) each provided 10 naturally written (genuine) signatures. Each of these subjects then provided 15 simulations of each of three model signatures. The genuine (N = 600) and simulated (N = 2700) signatures were collected using a digitizing tablet. MovAlyzeR(®) software was used to estimate kinematic parameters for each pen stroke. Stroke duration, velocity, and pen pressure were found to discriminate between genuine and simulated signatures regardless of the simulator's own style of signature or the style of signature being simulated. However, there was a significant interaction between style and condition for size and jerk (a measure of smoothness). The results of this study, based on quantitative analysis and dynamic handwriting features, indicate that the style of the simulator's own signature and the style of signature being simulated can impact the characteristics of handwriting movements for simulations. Writer style characteristics might therefore need to be taken into consideration as potentially significant when evaluating signature features with a view to forming opinions regarding authenticity. © 2014 American Academy of Forensic Sciences.

  17. 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

  18. Permeability and permeability anisotropy in Crab Orchard sandstone: Experimental insights into spatio-temporal effects

    NASA Astrophysics Data System (ADS)

    Gehne, Stephan; Benson, Philip M.

    2017-08-01

    Permeability in tight crustal rocks is primarily controlled by the connected porosity, shape and orientation of microcracks, the preferred orientation of cross-bedding, and sedimentary features such as layering. This leads to a significant permeability anisotropy. Less well studied, however, are the effects of time and stress recovery on the evolution of the permeability hysteresis which is becoming increasingly important in areas ranging from fluid migration in ore-forming processes to enhanced resource extraction. Here, we report new data simulating spatio-temporal permeability changes induced using effective pressure, simulating burial depth, on a tight sandstone (Crab Orchard). We find an initially (measured at 5 MPa) anisotropy of 2.5% in P-wave velocity and 180% in permeability anisotropy is significantly affected by the direction of the effective pressure change and cyclicity; anisotropy values decrease to 1% and 10% respectively after 3 cycles to 90 MPa and back. Furthermore, we measure a steadily increasing recovery time (10-20 min) for flow parallel to cross-bedding, and a far slower recovery time (20-50 min) for flow normal to cross-bedding. These data are interpreted via strain anisotropy and accommodation models, similar to the ;seasoning; process often used in dynamic reservoir extraction.

  19. Dynamic characteristics of a magnetically levitated impeller in a centrifugal blood pump.

    PubMed

    Asama, Junichi; Shinshi, Tadahiko; Hoshi, Hideo; Takatani, Setsuo; Shimokohbe, Akira

    2007-04-01

    Centrifugal blood pumps that employ hybrid active/passive magnetic bearings to support noncontact impellers have been developed in order to reduce bearing wear, pump size, the power consumption of the active magnetic bearing, and blood trauma. However, estimates made at the design stage of the vibration of the impeller in the direction of passive suspension during pump operation were inaccurate, because the influence of both the pumping fluid and the rotation of the impeller on the dynamic characteristics was not fully recognized. The purpose of this study is to investigate the dynamic characteristics in a fluid of a magnetically levitated rotating impeller by measuring both the frequency response to sinusoidal excitation of the housing over a wide frequency range and the displacement due to input of a pulsatile flow during left ventricular (LV) assist. The excitation tests were conducted under conditions in which the impeller was levitated in either air or water, and with or without rotation. The experimental and analytical results indicate that vibration of the impeller due to the external force in water was decreased, compared with that in air due to the hydraulic force of water. The axial resonant frequency rose quadratically with rotational speed, and the tilt mode had two resonant frequencies while rotating due to the gyroscopic effect. With the pump inserted into a mock systemic circulatory loop, the dynamic stability of the impeller when pulsatile pressure was applied during LV assist was verified experimentally. The amplitudes of vibration in response to the pulsatile flow in the passively constrained directions were considerably smaller in size than the dimensions of initial gaps between the impeller and the pump housing.

  20. The Epidemiological Characteristics and Dynamic Transmission of Dengue in China, 2013

    PubMed Central

    lu, Liang; Bi, Peng; Lv, Ming; Liu, Qiyong

    2016-01-01

    Background There was a dengue epidemic in several regions of China in 2013. No study has explored the dynamics of dengue transmission between different geographical locations with dengue outbreaks in China. The purpose of the study is to analyze the epidemiological characteristics and to explore the dynamic transmission of dengue in China, 2013. Methodology and Principal Findings Records of dengue cases of 2013 were obtained from the China Notifiable Disease Surveillance System. Full E-gene sequences of dengue virus detected from the outbreak regions of China were download from GenBank. Geographical Information System and heatmaps were used to describe the epidemiological characteristics. Maximum Likelihood phylogenetic and Bayesian phylogeographic analyses were conducted to explore the dengue dynamic transmission. Yunnan Province and Guangdong Province had the highest imported cases in the 2013 epidemic. In the locations with local dengue transmission, most of imported cases occurred from June to November 2013 while local dengue cases developed from July to December, 2013. There were significant variations for the incidences of dengue, in terms of age distributions, among different geographic locations. However, gender differences were identified in Guangzhou, Foshan and Xishuangbanna. DENV 1–3 were detected in all locations with the disease outbreaks. Some genotypes were detected in more than one locations and more than one genotypes have been detected in several locations. The dengue viruses introduced to outbreak areas were predominantly from Southeast Asia. In Guangdong Province, the phylogeographical results indicated that dengue viruses of DENV 1 were transmitted to neighboring cities Foshan and Zhongshan from Guangzhou city, and then transmitted to Jiangmen city. The virus in DENV 3 was introduced to Guangzhou city, Guangdong Province from Xishuangbanna prefecture, Yunnan Province. Conclusions Repeated dengue virus introductions from Southeast Asia and

  1. Methodology to determine failure characteristics of planar soft tissues using a dynamic tensile test.

    PubMed

    Jacquemoud, C; Bruyere-Garnier, K; Coret, M

    2007-01-01

    Predicting the injury risk in automotive collisions requires accurate knowledge of human tissues, more particularly their mechanical properties under dynamic loadings. The present methodology aims to determine the failure characteristics of planar soft tissues such as skin, hollow organs and large vessel walls. This consists of a dynamic tensile test, which implies high-testing velocities close to those in automotive collisions. To proceed, I-shaped tissue samples are subjected to dynamic tensile tests using a customized tensile device based on the drop test principle. Data acquisition has especially been adapted to heterogeneous and soft biological tissues given that standard measurement systems (considered to be global) have been completed with a non-contact and full-field strain measurement (considered to be local). This local measurement technique, called the Image Correlation Method (ICM) provides an accurate strain analysis by revealing strain concentrations and avoids damaging the tissue. The methodology has first been applied to human forehead skin and can be further expanded to other planar soft tissues. The failure characteristics for the skin in terms of ultimate stress are 3 MPa +/- 1.5 MPa. The ultimate global longitudinal strains are equal to 9.5%+/-1.9% (Green-Lagrange strain), which contrasts with the ultimate local longitudinal strain values of 24.0%+/-5.3% (Green-Lagrange strain). This difference is a consequence of the tissue heterogeneity, clearly illustrated by the heterogeneous distribution of the local strain field. All data will assist in developing the tissue constitutive law that will be implemented in finite element models.

  2. 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

  3. 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.

  4. Segmented Aluminum Honeycomb Characteristics in T-Direction, Dynamic Crush Environments

    SciTech Connect

    BATEMAN,VESTA I.; BROWN,FREDERICK A.; NUSSER,MICHAEL A.; SWANSON,LLOYD H.

    2000-08-23

    Thirteen segmented aluminum honeycomb samples (5 in. diameter and 1.5 in. height) have been crushed in an experimental configuration that uses a drop table impact machine. The 38.0 pcf bulk density samples are a unique segmented geometry that allows the samples to be crushed while maintaining a constant cross-sectional area. A crush weight of 175 lb was used to determine the rate sensitivity of the honeycomb's highest strength orientation, T-direction, in a dynamic environment of {approx}50 fps impact velocity. Experiments were conducted for two honeycomb manufacturers and at two temperatures, ambient and +165 F. Independent measurements of the crush force were made with a custom load cell and a force derived from acceleration measurements on the drop table using the Sum of Weighted Accelerations Technique with a Calibrated Force (SWAT-CAL). Normalized stress-strain curves for all thirteen experiments are included and have excellent repeatability. These data are strictly valid for material characteristics in the T orientation because the cross-sectional area of the honeycomb did not change during the crush. The dynamic crush data have a consistent increase in crush strength of {approximately}7--19% as compared to quasi-static data and suggest that dynamic performance may be inferred from static tests. An uncertainty analysis estimates the error in these data is {+-} 11%.

  5. Dynamic Characteristics of Micro-Beams Considering the Effect of Flexible Supports

    PubMed Central

    Zhong, Zuo-Yang; Zhang, Wen-Ming; Meng, Guang

    2013-01-01

    Normally, the boundaries are assumed to allow small deflections and moments for MEMS beams with flexible supports. The non-ideal boundary conditions have a significant effect on the qualitative dynamical behavior. In this paper, by employing the principle of energy equivalence, rigorous theoretical solutions of the tangential and rotational equivalent stiffness are derived based on the Boussinesq's and Cerruti's displacement equations. The non-dimensional differential partial equation of the motion, as well as coupled boundary conditions, are solved analytically using the method of multiple time scales. The closed-form solution provides a direct insight into the relationship between the boundary conditions and vibration characteristics of the dynamic system, in which resonance frequencies increase with the nonlinear mechanical spring effect but decrease with the effect of flexible supports. The obtained results of frequencies and mode shapes are compared with the cases of ideal boundary conditions, and the differences between them are contrasted on frequency response curves. The influences of the support material property on the equivalent stiffness and resonance frequency shift are also discussed. It is demonstrated that the proposed model with the flexible supports boundary conditions has significant effect on the rigorous quantitative dynamical analysis of the MEMS beams. Moreover, the proposed analytical solutions are in good agreement with those obtained from finite element analyses.

  6. Effects of carbon nanofiller characteristics on PTT chain conformation and dynamics: A computational study

    NASA Astrophysics Data System (ADS)

    Asadinezhad, Ahmad; Kelich, Payam

    2017-01-01

    The effects of nanofiller chemistry and geometry on static and dynamic properties of an aromatic polyester, poly (trimethylene terephthalate), were addressed thanks to long-run classical molecular dynamics simulation. Two carbon nanofillers, graphene and carbon nanotube, were employed, where graphene was used in pristine and functionalized forms and carbon nanotube was used in two different diameters. The nanofiller geometry and chemistry were found to exert significant effects on conformation and dynamic behavior of PTT chain at the interface within the time scale the simulation was performed. It was found that PTT chain underwent interaction of van der Waals type with nanofiller via two subsequent phases, adsorption and orientation. The former stage, with definite characteristic time, involved translation of polymer chain toward interface while the latter was controlled by vibrational motions of chain atoms. The consequence of interaction was an increase in conformational order of polymer chain by transition to folded shape being favorable for any subsequent structural ordering (crystallization). The interaction of polymer with nanofiller gave rise to a reduction in overall mobility of polymer chain characterized by crossover from normal diffusive motion to subdiffusive mode.

  7. Determination of tailless aircraft tumbling and stability characteristics through computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Saephan, Syta

    Tailless aircraft configurations such as flying wings are susceptible to tumbling. Tumbling involves an autorotative pitching motion primarily about an axis parallel to the aircraft's lateral axis combined with planar translation. Tumbling is the suspected cause of a tailless aircraft (Northrop YB-49) crash in the late 1940s and is a potential problem for future flying wing and blended wing body aircraft. It may be difficult if not impossible for a tailless aircraft to escape the tumbling motion once it begins. It is therefore important for aircraft designers to know the causes of tumbling in order to prevent its onset. Tumbling has been demonstrated in qualitative free-flight wind tunnel experiments, but few have attempted to quantify the motion using computational fluid dynamics. The purpose of this research is to use computational fluid dynamics to study the tumbling characteristics of a tailless aircraft and then determine dynamic stability information from the simulations. Specifically, the effects of initial conditions, degrees-of-freedom, Reynolds number, and aircraft static margin will be investigated. Lumped pitch damping derivatives will be determined from the simulations.

  8. 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.

  9. 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.

  10. The isolation characteristics of an archetypal dynamical model with stable-quasi-zero-stiffness

    NASA Astrophysics Data System (ADS)

    Hao, Zhifeng; Cao, Qingjie

    2015-03-01

    In this paper, a single-degree-of-freedom geometrically nonlinear oscillator with stable-quasi-zero-stiffness (SQZS) is presented, which can be extensively applied in vibration isolation due to its high static load bearing capacity and low dynamic stiffness. This model comprises a lumped mass denoeing the isolated object and a pair of horizontal springs providing negative stiffness paralleled with a vertical linear spring to bear the load. The equation of motion of the system is formulated with an originally irrational nonlinearity based upon SD oscillator instead of the conventionally approximate Duffing system of polynomial type, which will produce results with a high precision unquestionably, especially for the prediction of a large displacement behaviour. The frequency response characteristics particularly for transmissibility of the model, subjected to harmonic forcing and vibrating base, are obtained by using an extended averaging approach to achieve the parameter optimization for maximum frequency band of isolation. Furthermore, numerical simulations are carried out to detect the complex dynamical phenomena of periodic, chaotic motions and coexistence of multiple solutions, and so on, in addition to verifying the analytical results. Finally, an interesting strategy is proposed to extend the frequency band of isolation by controlling the initial value within the attraction basin of a small amplitude attractor, which can be utilized for an effective isolation. The results presented herein provide an insight of dynamics into the SQZS mechanism for its application in vibration engineering.

  11. 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.

  12. Numerical study on dynamic characteristics for sharp opening procedure of boundary-layer suction slot

    NASA Astrophysics Data System (ADS)

    He, Yubao; Yin, Hang; Huang, Hongyan; Yu, Daren

    2017-08-01

    Based on the sharp forward of shock train and taking the forthcoming unstart for a background, the dynamic characteristics for sharp opening procedure of boundary-layer suction slot are investigated numerically using the dynamic mesh technique. Results indicate that the climbing path of shock train with the complex background waves exhibits a sharp and slow forward state at different time. The compression waves in the primary shock sweep the trailing edge of the separation bubble, and the recirculation within the shock train is communicated with the separation bubble, which reveals that the flow is in a critical state and is about to be unstart at the subsequent time. Furthermore, the dynamic pattern for sharp opening procedure of boundary-layer suction slot can be classified into four distinct stages, namely, the formation of the jet plume without suction mass loss, the formation of the barrier shock with suction mass loss characterized by gradient increase and subsequent two oscillations, the evolution of the barrier shock and jet plume with suction mass loss that ramps up via a series of discrete step increases, and the formation of the stable structure accompanied by the linear suction mass loss.

  13. Dynamic characteristics of a continuous optimization method based on fictitious play theory

    NASA Astrophysics Data System (ADS)

    Lee, Chang-Yong

    2017-05-01

    In this paper, we propose a continuous optimization algorithm based on fictitious play theory and investigate the dynamic characteristics of the proposed algorithm. Fictitious play is a model for a learning rule in evolutionary game theory, and it can be used as an optimization method when all players have an identical utility function. In order to apply fictitious play to a continuous optimization algorithm, we consider two methods, equal width and equal frequency, of discretizing continuous values into a finite set of a player's strategies. The equal-frequency method turns out to outperform the equal-width method in terms of minimizing inseparable functions. To understand the mechanism of the equal-frequency method, we investigate two important quantities, the mixed strategy and the best response, in the algorithm from the statistical physics viewpoint. We find that the dynamics of the mixed strategies can be described as a 1/ f noise. In addition, we adopt the set of best responses as the probability measure and find that the probability distribution of the set can be best characterized by a multifractal; moreover, the support of the measure has a fractal dimension. The dynamics of the proposed algorithm with equal-frequency discretization contains a complex and rich structure that can be related to the optimization mechanism.

  14. 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

  15. 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.

  16. Trench dynamics: Effects of dynamically migrating trench on subducting slab morphology and characteristics of subduction zones systems

    NASA Astrophysics Data System (ADS)

    Yoshida, Masaki

    2017-07-01

    Understanding the mechanisms of trench migration (retreat or advance) is crucial to characterizing the driving forces of Earth's tectonics plates, the origins of subducting slab morphologies in the deep mantle, and identifying the characteristics of subduction zones systems, which are among the fundamental issues of solid Earth science. A series of numerical simulations of mantle convection, focusing on plate subduction in a three-dimensional (3-D) regional spherical shell coordinate system, was performed to examine subduction zone characteristics, including geodynamic relationships among trench migration, back-arc stress, and slab morphology. The results show that a subducting slab tends to deflect around the base of the mantle transition zone and form a sub-horizontal slab because its front edge (its 'toe') is subject to resistance from the highly viscous lower mantle. As the sub-horizontal slab starts to penetrate into the lower mantle from its 'heel,' the toe of the slab is drawn into the lower mantle. The results for models with dynamically migrating trenches suggest that trench retreat is the dynamically self-consistent phenomenon in trench migration. The reason for this is that the strong lateral mantle flow that is generated as a sequence of events leading from corner flow at the subduction initiation to return flow of the formation of a sub-horizontal slab in the shallower part of mantle wedge produces the retreat of the subducting slab. In fact, a 'mantle suction force,' which is generated in the mantle wedge to fill space left by the retreating subducting plate, is enhanced by the subsequent trench retreat. Even when upwelling flow with significant positive buoyancy originates just above a mantle phase boundary at a depth of 410 km (as inferred from independent seismic tomographic, geodynamic, geochemical, and mineral physics), reaches the base of the overriding plate, and the overriding plate is slightly thinned, lithospheric stress tends to be

  17. Gas permeability and flow characterization of simulated lunar regolith

    NASA Astrophysics Data System (ADS)

    Toutanji, Houssam; Goff, Christopher M.; Ethridge, Edwin; Stokes, Eric

    2012-04-01

    Recent discoveries of water ice trapped within lunar topsoil (regolith) have placed a new emphasis on the recovery and utilization of water for future space exploration. Upon heating the lunar ice to sublimation, the resulting water vapor could theoretically transmit through the lunar regolith, to be captured on the surface. As the permeability of lunar regolith is essential to this process, this paper seeks to experimentally determine the permeability and flow characteristics of various gas species through simulated lunar regolith (SLR). Two different types of SLR were compacted and placed into the permeability setup to measure the flow-rate of transmitted gas through the sample. Darcy's permeability constant was calculated for each sample and gas combination, and flow characteristics were determined from the results. The results show that Darcy's permeability constant varies with SLR compaction density, and identified no major difference in permeable flow between the several tested gas species. Between the two tested SLR types, JSC-1A was shown to be more permeable than NU-LHT under similar conditions. In addition, a transition zone was identified in the flow when the gas pressure differential across the sample was less than ˜40 kPa.

  18. 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.

  19. [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.

  20. Dynamic characteristics of the SMH actuator using hydrogen-absorbing alloys

    NASA Astrophysics Data System (ADS)

    Kim, Kyong; Pang, D. Y.; Choi, K. H.; Lee, S. C.; Kim, Y. Y.; Kwon, T. K.; Hong, C. U.; Kim, N. G.

    2005-12-01

    The dynamic characteristics of the special metal hydride(SMH) actuator using hydrogen absorbing alloys has been studied through the experiments on the characteristics of the temperature-pressure relation using a Peltier module. The SMH actuator uses the reversible reactions between thermal energy and mechanical energy inside hydrogen-absorbing alloys. It is well known that hydrogen-absorbing alloys can reversely absorb and desorb a large volume of hydrogen gas, more than about 1000 times of their own volume. By using Peltier element, we can actively control the energy conversion through hydrogen-absorbing alloys through hydriding and dehydriding reactions. Heating hydrogen-absorbing alloys using Peltier element will increase the equilibrium pressure of hydrogen gas resulting in the desorption of hydrogen gas by the alloys. Whereas, by cooling the alloys, the equilibrium pressure of hydrogen gas will decrease and hydrogen gas will be absorbed. In the present study, a simple special metal hydride (SMH) actuator, consisting of plated hydrogen-absorbing alloys as a power source, Peltier elements as a heat source, and a cylinder with metal bellows as a mechanical functioning part, has been developed. An electro-less copper plating has been used to improve the thermal conductivity of the hydrogen-absorbing alloys. To study the effects of the electro-less copper plating and the dynamic characteristics of the newly developed SMH actuator, a series of experiments has been performed and analyzed. The experiment demonstrated that the SMH actuator, which contains only 14.5 g of hydrogen-absorbing alloys, was able to easily lift 40 kg of weight with the displacement of 35 mm. The displacement of the cylinder was controlled in the periodic movement. The developed SMH actuator has merits in its small size, light weight, noiseless operation, and compliances similar to those of human bodies. Therefore, the SMH actuator is suitable for uses in medical and rehabilitation applications.

  1. Identification of the dynamic characteristics of a viscoelastic, nonlinear adhesive joint

    NASA Astrophysics Data System (ADS)

    Naraghi, T.; Nobari, A. S.

    2015-09-01

    In this paper, the nonlinear mechanical characteristics of an adhesive (Sikaflex-252) are identified over frequency range, using eigenvalues of nonlinear system and inverse eigen-sensitivity method and experimental data. Sikaflex-252 is selected as an adhesive which is mainly used as a joining medium (joint) in structural applications. In order to simulate the viscoelastic behaviour of the adhesive, the frequency dependent Young's modulus and damping coefficient are assumed in identification process leading to the updating process being repeated for different ranges of frequencies to identify stiffness and damping properties of the adhesive. Using the optimum equivalent linear frequency response function (OELF) concept, in order to realize the nonlinear nature of the adhesive, modal tests are performed under two different random excitation levels which illustrate the stiffness softening characteristic of adhesive which can have serious implications regarding dynamic stability of structures. Furthermore, based on the identified characteristics, the paper examines the possibility of tuning of the Standard Linear Solid model (SLS), in representing the adhesive viscoelastic behaviour. Results of this attempt proved that the S.L.S. model with tuned parameters significantly improves the fidelity of finite element (FE) model to experimental results.

  2. Golgi apparatus self-organizes into the characteristic shape via postmitotic reassembly dynamics.

    PubMed

    Tachikawa, Masashi; Mochizuki, Atsushi

    2017-05-16

    The Golgi apparatus is a membrane-bounded organelle with the characteristic shape of a series of stacked flat cisternae. During mitosis in mammalian cells, the Golgi apparatus is once fragmented into small vesicles and then reassembled to form the characteristic shape again in each daughter cell. The mechanism and details of the reassembly process remain elusive. Here, by the physical simulation of a coarse-grained membrane model, we reconstructed the three-dimensional morphological dynamics of the Golgi reassembly process. Considering the stability of the interphase Golgi shape, we introduce two hypothetical mechanisms-the Golgi rim stabilizer protein and curvature-dependent restriction on membrane fusion-into the general biomembrane model. We show that the characteristic Golgi shape is spontaneously organized from the assembly of vesicles by proper tuning of the two additional mechanisms, i.e., the Golgi reassembly process is modeled as self-organization. We also demonstrate that the fine Golgi shape forms via a balance of three reaction speeds: vesicle aggregation, membrane fusion, and shape relaxation. Moreover, the membrane fusion activity decreases thickness and the number of stacked cisternae of the emerging shapes.

  3. Targeted Control of Permeability Using Carbonate Dissolution/Precipitation Reactions

    NASA Astrophysics Data System (ADS)

    Clarens, A. F.; Tao, Z.; Plattenberger, D.

    2016-12-01

    Targeted mineral precipitation reactions are a promising approach for controlling fluid flow in the deep subsurface. Here we studied the potential to use calcium and magnesium bearing silicates as cation donors that would react with aqueous phase CO2 under reservoir conditions to form solid carbonate precipitates. Preliminary experiments in high pressure and temperature columns suggest that these reactions can effectively lower the permeability of a porous media. Wollastonite (CaSiO3) was used as the model silicate, injected as solid particles into the pore space of a packed column, which was then subsequently flooded with CO2(aq). The reactions occur spontaneously, leveraging the favorable kinetics that occur at the high temperature and pressure conditions characteristic of the deep subsurface, to form solid phase calcium carbonate (CaCO3) and amorphous silica (SiO2) within the pore space. Both x-ray tomography imaging of reacted columns and electron microscopy imaging of thin sections were used to characterize where dissolution/precipitation occurred within the porous media. The spatial distribution of the products was closely tied to the flow rate and the duration of the experiment. The SiO2 product precipitated in close spatial proximity to the CaSiO3 reactant. The CaCO3 product, which is sensitive to the low pH and high pCO2 brine, precipitated out of solution further down the column as Ca2+ ions moved with the brine. The permeability of the columns decreased by several orders of magnitude after injecting the CaSiO3 particles. Following carbonation, the permeability decreased even further as precipitates filled flow paths within the pore network. A pore network model was developed to help understand the interplay between precipitation kinetics and flow in altering the permeability of the porous media. The effect of particle concentration and size, pore size, reaction time, and pCO2, are explored on pore/fracture aperture and reaction extent. To provide better

  4. Permeability of the Body Wall of Romanomermis culicivorax to Lanthanum

    PubMed Central

    Platzer, Ann; Platzer, Edward G.

    1985-01-01

    Ultrastructural study of the body wall of preparasitic, parasitic, and postparasitic stages of Romanomermis culicivorax showed that the cuticle of all three stages was permeable to lanthanum. The cuticle of the parasitic stage was the thinnest and showed the greatest permeability. Lanthanum accumulated on the apical surfaces of the hypodermal cells but was not found intracellularly. The negative staining characteristics of lanthanum enhanced the detection of numerous smooth septate junctions in the hypodermis of the parasitic stage. PMID:19294092

  5. Rocks of low permeability

    NASA Astrophysics Data System (ADS)

    The 17th International Congress of the IAH (International Association of Hydrogeologists) will meet in Tucson, Ariz., January 7-10, 1985. The deadline for abstracts is March 1, 1984, and final papers are due October 15, 1984.The topic of the congress will be “Hydrogeology of Rocks of Low Permeability,” and speakers will include W. Back, J. F. Bredehoeft, G. de Marsily, J. E. Gale, P. Fritz, L. W. Gelhar, G. E. Grisak, C. W. Kreitler, M. R. Llamas, T. N. Narasimhan, I. Neretnieks, and E. P. Weeks. The congress will conclude with a panel discussion moderated by S. P. Neuman. Panelists include S. N. Davis, G. de Marsily, R. A. Freeze, P. A. Witherspoon, and I. Neretnieks.

  6. Placental Permeability of Lead

    PubMed Central

    Carpenter, Stanley J.

    1974-01-01

    The detection of lead in fetal tissues by chemical analysis has long been accepted as prima facie evidence for the permeability of the placenta to this nonessential trace metal. However, only a few investigations, all on lower mammalian species, have contributed any direct experimental data bearing on this physiological process. Recent radioactive tracer and radioautographic studies on rodents have shown that lead crosses the placental membranes rapidly and in significant amounts even at relatively low maternal blood levels. While it is not possible to extrapolate directly the results of these experiments to humans because of differences in placental structure and other factors, the results do serve as a warning of the possible hazard to the human embryo and fetus of even low levels of lead in the maternal system. PMID:4857497

  7. Dynamic characteristics of atmospheric planetary waves during stratospheric warmings in winter 2008

    NASA Astrophysics Data System (ADS)

    Chernigovskaya, Marina; Medvedev, Andrey; Tolstikov, Maxim; Medvedeva, Irina; Ratovsky, Konstantin

    2010-05-01

    The wave mechanism of energy transfer is quite significant in transferring energy in the Earth's atmosphere. Atmospheric internal waves of different spatial and temporal scales (including 1-30-day planetary waves) transfer a great deal of kinetic energy from the troposphere and stratosphere to higher atmospheric layers. As deduced from experimental data, systems of strong zonal stratospheric winds prevent penetration of planetary waves from the troposphere to the upper atmosphere (mesosphere and thermosphere), but the part of their energy reaches the upper atmosphere. Planetary waves are in many respects associated with such interesting phenomena in the Earth's stratosphere as sudden winter stratospheric warmings (SSW), observed almost every winter and characterized by geographical nonuniformity. High concentration of stratospheric warming centers is typical of the Asian region of Russia. We examined dynamic characteristics of atmospheric planetary waves observed in the Asian region of Russia in the longitudinal sector of ~80-125°E during stratospheric warmings in winter 2008. Satellite data on vertical temperature distribution obtained by the Microwave Limb Sounder (MLS) aboard the spacecraft EOS Aura and Irkutsk digisonde DPS-4 data were used. It has been established that pronounced wave-like temperature disturbances with characteristic periods of 10-14 days were observed in the Asian region of Russia in the sector of ~80-125°E and 40-64°N over a height range of 20-90 km during development of the SSW in January-February 2008. Revealed here is a high correlation between temperature disturbances and the minimum frequency of reflection in the Irkutsk digisonde DPS-4 ionograms. This paper offers a method for investigating characteristics of propagation of long-term temperature disturbances by a cross-correlation analysis. This method consists in determining delays between disturbances observed at different points and in deriving a system of linear equations for

  8. Permeable Boundaries in Organizational Learning

    NASA Astrophysics Data System (ADS)

    Hazy, James K.; Tivnan, Brian F.; Schwandt, David R.

    The nature of the organizational boundary is investigated in the context of organizational learning. Boundary permeability is defined and hypotheses relating it to performance are tested computationally using data from 5,500 artificial organizations. We find that matching boundary permeability to the environment predicts both agent and organization survival.

  9. Application of dynamic priorities for controlling the characteristics of a queuing system

    NASA Astrophysics Data System (ADS)

    Polyanskiy, S. V.; Katsman, Yu Ya

    2017-01-01

    This paper considers the development and modification of an imitation model of a queuing system. The initial model uses the laws of control (discipline of expectation and service) with mixed priorities. The work investigates the model with three types of entities (absolute priority, relative priority and priority-free ones) in the regime of overload, i.e. a system with losses. Verification and validation of the created imitation model confirmed its adequateness and accuracy of received results. The application of dynamic priorities for changing the laws of model control substantially alters certain system characteristics. The creation of the model in MatLab Simulink environment with the use of SimEvents and Stateflow library modules allowed creating a fairly complex queuing system and obtain new interesting results.

  10. 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.

  11. Numerical analysis of supersonic gas-dynamic characteristic in laser cutting

    NASA Astrophysics Data System (ADS)

    Guo, Shaogang; Jun, Hu; Lei, Luo; Yao, Zhenqiang

    2009-01-01

    The influence of the processing parameters on the dynamic characteristic of supersonic impinging jet in laser cutting is studied numerically. The numerical modeling of a supersonic jet impinging on a plate with a hole is presented to analyze the gas jet-workpiece interaction. The model is able to make quantitative predictions of the effect of the standoff distance and exit Mach number on the mass flow rate and the axial thrust. The numerical results show that the suitable cutting range is slightly different for different exit Mach number, but the optimal cutting parameter for certain exit total pressure is nearly changeless. So the better cut quality and capacity can be obtained mainly by setting the suitable standoff distance for a certain nozzle pressure.

  12. Dynamic behavior of water droplets and flashover characteristics on a superhydrophobic silicone rubber surface

    NASA Astrophysics Data System (ADS)

    Li, Yufeng; Jin, Haiyun; Nie, Shichao; Zhang, Peng; Gao, Naikui

    2017-05-01

    In this paper, a superhydrophobic surface is used to increase the flashover voltage when water droplets are present on a silicone rubber surface. The dynamic behavior of a water droplet and the associated flashover characteristics are studied on common and superhydrophobic silicone rubber surfaces under a high DC voltage. On common silicone rubber, the droplet elongates and the flashover voltage decreases with increasing droplet volume and conductivity. In contrast, the droplet slides off the superhydrophobic surface, leading to an increased flashover voltage. This droplet sliding is due to the low adhesion of the superhydrophobic surface and a sufficiently high electrostatic force provided by the DC voltage. Experimental results show that a superhydrophobic surface is effective at inhibiting flashover.

  13. Effect of anisotropy of electron velocity distribution function on dynamic characteristics of sheath in Hall thrusters

    SciTech Connect

    Zhang Fengkui; Wu Xiande; Ding Yongjie; Li Hong; Yu Daren

    2011-10-15

    In Hall thrusters, the electron velocity distribution function is not only depleted at high energies, but also strongly anisotropic. With these electrons interacting with the channel wall, the sheath will be changed in its dynamic characteristics. In the present letter, a two dimensional particle-in-cell code is used to simulate these effects in a collisionless plasma slab. The simulated results indicate that the sheath changes from steady regime to temporal oscillation regime when the electron velocity distribution function alters from isotropy to anisotropy. Moreover, the temporal oscillation sheath formed by the anisotropic electrons has a much greater oscillating amplitude and a much smaller average potential drop than that formed by the isotropic electrons has. The anisotropic electrons are also found to lower the critical value of electron temperature needed for the appearance of the spatial oscillation sheath.

  14. 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.

  15. 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.

  16. Normal dynamic deformation characteristics of non-consecutive jointed rock masses under impact loads

    NASA Astrophysics Data System (ADS)

    Zeng, Sheng; Jiang, Bowei; Sun, Bing

    2017-08-01

    In order to study deformation characteristics of non-consecutive single jointed rock masses under impact loads, we used the cement mortar materials to make simulative jointed rock mass samples, and tested the samples under impact loads by the drop hammer. Through analyzing the time-history signal of the force and the displacement, first we find that the dynamic compression displacement of the jointed rock mass is significantly larger than that of the intact jointless rock mass, the compression displacement is positively correlated with the joint length and the impact height. Secondly, the vertical compressive displacement of the jointed rock mass is mainly due to the closure of opening joints under small impact loads. Finally, the peak intensity of the intact rock mass is larger than that of the non-consecutive jointed rock mass and negatively correlated with the joint length under the same impact energy.

  17. Compressive characteristics of single walled carbon nanotube with water interactions investigated by using molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Wong, C. H.; Vijayaraghavan, V.

    2014-01-01

    The elastic properties of single walled carbon nanotube (SWCNT) with surrounding water interactions are studied using molecular dynamics simulation technique. The compressive loading characteristic of carbon nanotubes (CNTs) in a fluidic medium such as water is critical for its role in determining the lifetime and stability of CNT based nano-fluidic devices. In this paper, we conducted a comprehensive analysis on the effect of geometry, chirality and density of encapsulated water on the elastic properties of SWCNT. Our studies show that defect density and distribution can strongly impact the compressive resistance of SWCNTs in water. Further studies were conducted on capped SWCNTs with varying densities of encapsulated water, which is necessary to understand the strength of CNT as a potential drug carrier. The results obtained from this paper will help determining the potential applications of CNTs in the field of nano-electromechanical systems (NEMS) such as nano-biological and nano-fluidic devices.

  18. Dynamic and spectroscopic characteristics of atmospheric gliding arc in gas-liquid two-phase flow

    NASA Astrophysics Data System (ADS)

    Tu, X.; Yu, L.; Yan, J. H.; Cen, K. F.; Chéron, B. G.

    2009-11-01

    In this study, an atmospheric alternating-current gliding arc device in gas-liquid two-phase flow has been developed for the purpose of waste water degradation. The dynamic behavior of the gas-liquid gliding arc is investigated through the oscillations of electrical signals, while the spatial evolution of the arc column is analyzed by high speed photography. Different arc breakdown regimes are reported, and the restrike mode is identified as the typical fluctuation characteristic of the hybrid gliding arc in air-water mixture. Optical emission spectroscopy is employed to investigate the active species generated in the gas-liquid plasma. The axial evolution of the OH (309 nm) intensity is determined, while the rotational and vibrational temperatures of the OH are obtained by a comparison between the experimental and simulated spectra. The significant discrepancy between the rotational and translational temperatures has also been discussed.

  19. Calculation of Dynamic Characteristics of Coupled Herringbone Journal and Thrust Hydrodynamic Bearings

    NASA Astrophysics Data System (ADS)

    Zang, Yan; Hatch, Michael R.

    We describe a numerical method for the analysis of dynamic characteristics of coupled herringbone-type journal and thrust hydrodynamic bearings. The non-dimensional generalized Reynolds equation is discretized on a non-orthogonal grid which is mapped into a square. The computational domain conforms to the herringbone grooves to improve the accuracy of the solution. The journal and thrust regions are mapped separately and connected through internal flux boundary conditions. The discretized pressure field is solved iteratively using the rapidly convergent ADI method. The stiffness and damping coefficients are obtained by perturbing the equilibrium solution of the Reynolds equation and solving the perturbation equations. The accuracy of the present calculation is confirmed by comparing with previously existing data. Analyses are performed for self-contained coupled hydrodynamic bearing systems which can be used to support the spindle motor of a magnetic hard-disk drive.

  20. Virtual instrument based measurement system for analysis of static and dynamic characteristics of temperature transducers

    NASA Astrophysics Data System (ADS)

    Walendziuk, Wojciech; Baczewski, Michał

    2014-11-01

    The present work shows the structure of a measurement system dedicated to examine static and dynamic characteristics of sensors used to measure temperature. The measurement system was built on the basis of a set of signal conditioners connected with a data acquisition card built in a PC. The data acquisition was completed with the use of a virtual measurement device developed in the LabVIEW environment. A was used as the source of reference temperature. During the experiments, the sensors were submersed in water of given temperature with the use of a computer controlled arm. The article also presents the results of the calibration procedure which was carried out, as well as selected application schemes.

  1. 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

  2. Study of Dynamic Characteristics for Hydraulic System on 300MN Die-forging Press

    NASA Astrophysics Data System (ADS)

    Chen, Guoqiang; Tan, Jianping

    2017-06-01

    The faults such as seal breakdown and pressure sensor damage occur in 300MN Die-forging press frequently. First, the fault phenomenon and harm of the hydraulic system was compiled statistics, the theoretical analysis of the hydraulic impact of hydraulic system are carried out based on the momentum theorem; Then, the co-simulation model of hydraulic system was established by AMESim and Simulink software and the correctness was verified. Finally, the dynamic characteristics of hydraulic system for the key working condition “forging stroke changing to mold collision” was analyzed, the influences rules of system parameters such as the leak gap of valve, diameter of water way pipeline, emulsion temperature and air contain act on hydraulic system are obtained. This conclusions have a theoretical guiding significance to the improvement and maintains of high pressure and large flow hydraulic system.

  3. 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.

  4. 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)

  5. Characteristics of strong ground motion generation areas by fully dynamic earthquake cycles

    NASA Astrophysics Data System (ADS)

    Galvez, P.; Somerville, P.; Ampuero, J. P.; Petukhin, A.; Yindi, L.

    2016-12-01

    During recent subduction zone earthquakes (2010 Mw 8.8 Maule and 2011 Mw 9.0 Tohoku), high frequency ground motion radiation has been detected in deep regions of seismogenic zones. By semblance analysis of wave packets, Kurahashi & Irikura (2013) found strong ground motion generation areas (SMGAs) located in the down dip region of the 2011 Tohoku rupture. To reproduce the rupture sequence of SMGA's and replicate their rupture time and ground motions, we extended previous work on dynamic rupture simulations with slip reactivation (Galvez et al, 2016). We adjusted stresses on the most southern SMGAs of Kurahashi & Irikura (2013) model to reproduce the observed peak ground velocity recorded at seismic stations along Japan for periods up to 5 seconds. To generate higher frequency ground motions we input the rupture time, final slip and slip velocity of the dynamic model into the stochastic ground motion generator of Graves & Pitarka (2010). Our results are in agreement with the ground motions recorded at the KiK-net and K-NET stations.While we reproduced the recorded ground motions of the 2011 Tohoku event, it is unknown whether the characteristics and location of SMGA's will persist in future large earthquakes in this region. Although the SMGA's have large peak slip velocities, the areas of largest final slip are located elsewhere. To elucidate whether this anti-correlation persists in time, we conducted earthquake cycle simulations and analysed the spatial correlation of peak slip velocities, stress drops and final slip of main events. We also investigated whether or not the SMGA's migrate to other regions of the seismic zone.To perform this study, we coupled the quasi-dynamic boundary element solver QDYN (Luo & Ampuero, 2015) and the dynamic spectral element solver SPECFEM3D (Galvez et al., 2014; 2016). The workflow alternates between inter-seismic periods solved with QDYN and coseismic periods solved with SPECFEM3D, with automated switch based on slip rate

  6. A study of the influence of the rolling of moving part on the dynamic characteristics of OPU actuator

    NASA Astrophysics Data System (ADS)

    Ru, Jigang; Pan, Longfa; Ma, Jianshe; Shi, Hongwei

    2005-09-01

    As the executive part, the actuator of optical pick-up (OPU) accomplishes the servo action actually. The dynamic characteristics of the OPU actuator determine the precision of focusing and tracking servo system, so it will influence the reading performance of optical pick-up. As the density of optical storage increases, the OPU actuator has a high servo bandwidth for its focusing and tracking control to follow dynamic disturbances by high density and high rotational speed of disk. The dynamic response curve should be as smooth as possible in its linear area. In this paper, the influence of the rolling of moving part on the actuator's dynamic characteristics is studied. Because of some design reasons, the moving part of the actuator may roll in three dimensions during the working status. It's one of the most important factors to influence the dynamic characteristics of actuator. Firstly, the reason of rolling and the influence on dynamic characteristics are studied. In the design of actuator we should pay attention to three important points, which are the gravitational point, the equivalent driving force point and the equivalent sustained point. When the three points are not accordant during the moving action, the rolling occurs. The dynamic response curve will have some unexpected resonances at certain frequency area. This phenomenon is analyzed by kinetic method. Secondly, a model of the actuator is founded referring to an actual type of actuator. By finite element analysis software (ANSYS), the mechanical and magnetic simulation is performed. The special distributing of electromagnetic field is described and the driving force is analyzed. Thirdly, the dynamic characteristics of some actuators with rolling are tested. The experimental result is consistent with the simulation result. So the validity of this study is verified. At last, the possible methods to avoid rolling of moving part are introduced.

  7. Supersonic dynamic stability characteristics of the test technique demonstrator NASP configuration

    NASA Technical Reports Server (NTRS)

    Dress, David A.; Boyden, Richmond P.; Cruz, Christopher I.

    1992-01-01

    Wind tunnel tests of a National Aero-Space Plane (NASP) configuration were conducted in both test sections of the Langley Unitary Plan Wind Tunnel. The model used is a Langley designed blended body NASP configuration. Dynamic stability characteristics were measured on this configuration at Mach numbers of 2.0, 2.5, 3.5, and 4.5. In addition to tests of the baseline configuration, component buildup tests were conducted. The test results show that the baseline configuration generally has positive damping about all three axes with only isolated exceptions. In addition, there was generally good agreement between the in-pulse dynamic parameters and the corresponding static data which were measured during another series of tests in the Unitary Plan Wind Tunnel. Also included are comparisons of the experimental damping parameters with results from the engineering predictive code APAS (Aerodynamic Preliminary Analysis System). These comparisons show good agreement at low angles of attack; however, the comparisons are generally not as good at the higher angles of attack.

  8. Dynamic wetting and spreading characteristics of a liquid droplet impinging on hydrophobic textured surfaces.

    PubMed

    Lee, Jae Bong; Lee, Seong Hyuk

    2011-06-07

    We report on the wetting dynamics of a 4.3 μL deionized (DI) water droplet impinging on microtextured aluminum (Al 6061) surfaces, including microhole arrays (hole diameter 125 μm and hole depth 125 μm) fabricated using a conventional microcomputer numerically controlled (μ-CNC) milling machine. This study examines the influence of the texture area fraction ϕ(s) and drop impact velocity on the spreading characteristics from the measurement of the apparent equilibrium contact angle, dynamic contact angle, and maximum spreading diameter. We found that for textured surfaces the measured apparent contact angle (CA) takes on values of up to 125.83°, compared to a CA of approximately 80.59° for a nontextured bare surface, and that the spreading factor decreases with the increased texture area fraction because of increased hydrophobicity, partial penetration of the liquid, and viscous dissipation. In particular, on the basis of the model of Ukiwe and Kwok (Ukiwe, C.; Kwok, D. Y. Langmuir 2005, 21, 666), we suggest a modified equation for predicting the maximum spreading factor by considering various texturing effects and wetting states. Compared with predictions by using earlier published models, the present model shows better agreement with experimental measurements of the maximum spreading factor.

  9. 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.

  10. Supersonic dynamic stability characteristics of the test technique demonstrator NASP configuration

    NASA Technical Reports Server (NTRS)

    Dress, David A.; Boyden, Richmond P.; Cruz, Christopher I.

    1992-01-01

    Wind tunnel tests of a National Aero-Space Plane (NASP) configuration were conducted in both test sections of the Langley Unitary Plan Wind Tunnel. The model used is a Langley designed blended body NASP configuration. Dynamic stability characteristics were measured on this configuration at Mach numbers of 2.0, 2.5, 3.5, and 4.5. In addition to tests of the baseline configuration, component buildup tests were conducted. The test results show that the baseline configuration generally has positive damping about all three axes with only isolated exceptions. In addition, there was generally good agreement between the in-pulse dynamic parameters and the corresponding static data which were measured during another series of tests in the Unitary Plan Wind Tunnel. Also included are comparisons of the experimental damping parameters with results from the engineering predictive code APAS (Aerodynamic Preliminary Analysis System). These comparisons show good agreement at low angles of attack; however, the comparisons are generally not as good at the higher angles of attack.

  11. Dynamic characteristic analysis of HIV mother to child transmission in China.

    PubMed

    Wang, Jun-Jie; Reilly, Kathleen Heather; Han, Hua; Peng, Zhi-Hang; Wang, Ning

    2010-10-01

    To explore dynamic characteristics of the HIV mother to child transmission (MTCT) epidemic in China. A deterministic dynamic transmission model was used to determine the effect of key parameters on the likely long-term trends of the HIV MTCT epidemic in China. Matlab 7.0 was used to develop the model. The number of the susceptibles (S), the transmission rate (β), and the screening proportion (α) of HIV positive pregnant women have the greatest impact on the HIV MTCT epidemic in China. The growth of the MTCT epidemic in China could not be controlled only by decreasing the MTCT transmission rate. The prevalence of HIV positive women should be reduced and more pregnant women should be tested for HIV. Prevention of MTCT (PMTCT) should focus not only on the reduction of HIV transmission rates and incidences of HIV among women but also on the increase of HIV testing for pregnant women. The most cost-effective PMTCT means for China should be investigated in future studies. Copyright © 2010 The Editorial Board of Biomedical and Environmental Sciences. Published by Elsevier B.V. All rights reserved.

  12. Intermanual transfer characteristics of dynamic learning: direction, coordinate frame, and consolidation of interlimb generalization

    PubMed Central

    Thürer, Benjamin; Focke, Anne; Stein, Thorsten

    2015-01-01

    Intermanual transfer, i.e., generalization of motor learning across hands, is a well-accepted phenomenon of motor learning. Yet, there are open questions regarding the characteristics of this transfer, particularly the intermanual transfer of dynamic learning. In this study, we investigated intermanual transfer in a force field adaptation task concerning the direction and the coordinate frame of transfer as well as the influence of a 24-h consolidation period on the transfer. We tested 48 healthy human subjects for transfer from dominant to nondominant hand, and vice versa. We considered two features of transfer. First, we examined transfer to the untrained hand using force channel trials that suppress error feedback and learning mechanisms to assess intermanual transfer in the form of a practice-dependent bias. Second, we considered transfer by exposing the subjects to the force field with the untrained hand to check for faster learning of the dynamics (interlimb savings). Half of the subjects were tested for transfer immediately after adaptation, whereas the other half were tested after a 24-h consolidation period. Our results showed intermanual transfer both from dominant to nondominant hand and vice versa in extrinsic coordinates. After the consolidation period, transfer effects were weakened. Moreover, the transfer effects were negligible compared with the subjects' ability to rapidly adapt to the force field condition. We conclude that intermanual transfer is a bidirectional phenomenon that vanishes with time. However, the ability to transfer motor learning seems to play a minor role compared with the rapid adaptation processes. PMID:26424581

  13. Temporal-spatial characteristic evaluation in a dynamic flat-panel detector system

    NASA Astrophysics Data System (ADS)

    Kawashima, H.; Tanaka, R.; Matsubara, K.; Ichikawa, K.; Sakuta, K.; Minami, S.; Hayashi, N.; Sanada, S.; Kawamura, M.; Yamamoto, T.

    2010-04-01

    This report presents the fundamental temporospatial characteristics of a dynamic flat-panel detector (FPD) system. We investigated the relationship between pixel value and X-ray pulse output, and examined reproducibility, dependence on pulse width, tube voltage, and pulse rate. Sequential images were obtained using a direct conversion-type dynamic FPD. The exposure conditions were: 110 kV, 80 mA, 6.3 ms, 7.5 fps, source-to-image distance (SID) 1.5 m. X-ray pulse output was measured using a dosimetry system with a sampling interval of 70 μs, to determine temporal changes in each X-ray pulse output. Temporal changes in pixel value were measured in the obtained images, and the relationship between pixel value and X-ray pulse output was examined. Reproducibility was assessed by comparing the results in two sequential images obtained under the same exposure conditions. Moreover, the relationships and properties were evaluated by changing the pulse width (12 ms and 25 ms), tube voltage (80 kV, 90 kV, and 100 kV), and pulse rate (3.75 fps and 15 fps). The results showed a good correlation between the X-ray pulse output and pixel values. Fluctuation of the pixel value measured in sequential images is thought to be mainly due to changes in X-ray pulse output, and is not caused by FPD.

  14. Prolonged persistence of measles virus RNA is characteristic of primary infection dynamics

    PubMed Central

    Lin, Wen-Hsuan W.; Kouyos, Roger D.; Adams, Robert J.; Grenfell, Bryan T.; Griffin, Diane E.

    2012-01-01

    Measles virus (MeV) is the poster child for acute infection followed by lifelong immunity. However, recent work shows the presence of MeV RNA in multiple sites for up to 3 mo after infection in a proportion of infected children. Here, we use experimental infection of rhesus macaques to show that prolonged RNA presence is characteristic of primary infection. We found that viral RNA persisted in the blood, respiratory tract, or lymph nodes four to five times longer than the infectious virus and that the clearance of MeV RNA from blood happened in three phases: rapid decline coincident with clearance of infectious virus, a rebound phase with increases up to 10-fold, and a phase of slow decrease to undetectable levels. To examine the effect of individual host immune factors on MeV load dynamics further, we developed a mathematical model that expressed viral replication and elimination in terms of the strength of MeV-specific T-cell responses, antibody responses, target cell limitations, and immunosuppressive activity of regulatory T cells. Based on the model, we demonstrate that viral dynamics, although initially regulated by T cells, require antibody to eliminate viral RNA. These results have profound consequences for our view of acute viral infections, the development of prolonged immunity, and, potentially, viral evolution. PMID:22872860

  15. 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.

  16. Optimum Dynamic Characteristics of Stockbridge Dampers for Dead-End Spans

    NASA Astrophysics Data System (ADS)

    Markiewicz, M.

    1995-11-01

    Stockbridge dampers are commonly used to protect conductors of overhead transmission lines from aeolian vibrations. Standard Stockbridge dampers are designed so that their mechanical impedance matches as closely as possible the optimum damper impedance determined for the cable to be protected. Since the optimum impedance is evaluated assuming that the cable is clamped at its extremity, the optimally tuned standard dampers will work efficiently only when they are mounted near suspension clamps. In some spans, however, conductors are connected to the tower by means of special tension equipment which may influence the efficiency of the mounted standard damper. The present analysis shows that the optimum damper impedance required for such spans (called dead-end spans) differs significantly from the optimum impedance of the standard damper. The reason for this is the dynamic interaction between the tension insulator assembly and the damper itself. This interaction cannot be neglected for vibration frequencies which are close to the resonance frequencies of the tension insulator assembly. This paper presents a method and computational model for the evaluation of the optimum dynamic characteristics of Stockbridge dampers to be mounted near tension insulator assemblies. It also shows how the efficiency of a standard damper used in such spans may be improved by its proper location on a cable.

  17. An evaluation of dynamic lip-tooth characteristics during speech and smile in adolescents.

    PubMed

    Ackerman, Marc B; Brensinger, Colleen; Landis, J Richard

    2004-02-01

    This retrospective study was conducted to measure lip-tooth characteristics of adolescents. Pretreatment video clips of 1242 consecutive patients were screened for Class-I skeletal and dental patterns. After all inclusion criteria were applied, the final sample consisted of 50 patients (27 boys, 23 girls) with a mean age of 12.5 years. The raw digital video stream of each patient was edited to select a single image frame representing the patient saying the syllable "chee" and a second single image representing the patient's posed social smile and saved as part of a 12-frame image sequence. Each animation image was analyzed using a SmileMesh computer application to measure the smile index (the ratio of the intercommissure width divided by the interlabial gap), intercommissure width (mm), interlabial gap (mm), percent incisor below the intercommissure line, and maximum incisor exposure (mm). The data were analyzed using SAS (version 8.1). All recorded differences in linear measures had to be > or = 2 mm. The results suggest that anterior tooth display at speech and smile should be recorded independently but evaluated as part of a dynamic range. Asking patients to say "cheese" and then smile is no longer a valid method to elicit the parameters of anterior tooth display. When planning the vertical positions of incisors during orthodontic treatment, the orthodontist should view the dynamics of anterior tooth display as a continuum delineated by the time points of rest, speech, posed social smile, and a Duchenne smile.

  18. Meso-mechanical analysis of deformation characteristics for dynamically triggered slip in a granular medium

    NASA Astrophysics Data System (ADS)

    Griffa, M.; Ferdowsi, B.; Daub, E. G.; Guyer, R. A.; Johnson, P. A.; Marone, C.; Carmeliet, J.

    2012-10-01

    The deformation characteristics of a sheared granular layer during stick-slip are studied from a meso-mechanical viewpoint, both in the absence and in the presence of externally applied vibration. The ultimate goal is to characterize the physics of dynamic earthquake triggering, where one earthquake, i.e., slip on one fault, is triggered via the seismic waves radiated by another spatially and temporally distant seismic event. Toward this goal, we performed Discrete Element Method simulations of a two-dimensional packing of disks, mimicking a mature geologic fault. These simulations were used to investigate the affine and non-affine deformations inside the granular layer and their spatial-temporal evolution across the stick-slip cycle. The simulation results show that slip in general is accompanied by the appearance of localized regions with high values of both affine and non-affine deformations. These regions are temporally correlated and are mainly concentrated in a shear zone at the interface between the granular layer and the driving block. Dynamic triggering is found to initiate slip when vibration is applied late in the stick-slip cycle, when the system is close to a critical state. It is also found that vibration itself introduces a large amount of affine and non-affine strains, which leads to the initiation of slip at lower shear stress than an equivalent slip event without vibration.

  19. 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

  20. Dynamic characteristics of osteoporotic lumbar spine under vertical vibration after cement augmentation.

    PubMed

    Su, Xinlin; Shen, Hao; Shi, Weidong; Yang, Huilin; Lv, Feng; Lin, Jun

    2017-01-01

    Being beneficial in restoring stability and stiffness of osteoporotic vertebraes, cement augmentation techniques including vertebroplasty (VP) and kyphoplasty (KP) have been demonstrated to be effective for the treatment of patients with osteoporotic vertebral compressive fractures (OVCFs). However, it is unclear the influence of cement augmentation on the dynamics of pathologic and adjacent vertebraes under vibration condition. In this study, we developed a three-dimensional (3D) finite-element (FE) model of the spinal T12-Pelvis segment by using CT scan data of lumbar spine of an adult woman with no physical abnormalities. By modulating model parameters we further simulated osteoporotic conditions of the T12-Pelvis FE model with or without polymethyl methacrylate (PMMA) augmentation. Dynamic characteristics of the osteoporotic T12-Pelvis model were detected at the first order of vertical resonant frequencies (FOVRFs) under vertical vibration, which included vertical axial displacements, anteroposterior (AP) displacements and rotational angles of each vertebrae and intervertebral disc (IVD). The results showed that axial and AP displacements of both vertebraes and IVDs decreased in some point after PMMA augmentation. Axial displacements of the L4-L5 motion segment decreased most significantly and the changing ratios ranged from 20% to 30%. AP displacements of L5, D1-2 (the IVD between vertebraes L1 and L2) and D3-4 reduced most obviously after 1, 2 or 3 levels PMMA augmentation. No significant difference of axial or AP displacements of each vertebrae and IVD was observed between one-level and multilevel PMMA augmentation. Thus, we demonstrated that PMMA augmentation could reduce vertical axial and AP deformations of the osteoporotic lumbar motion segments under vertical vibration, especially for the inferior adjacent motion segments. However, the influence of the number of vertebraes with PMMA augmentation on the dynamics of osteoporotic lumbar spine was

  1. Evaluation of space shuttle main engine fluid dynamic frequency response characteristics

    NASA Technical Reports Server (NTRS)

    Gardner, T. G.

    1980-01-01

    In order to determine the POGO stability characteristics of the space shuttle main engine liquid oxygen (LOX) system, the fluid dynamic frequency response functions between elements in the SSME LOX system was evaluated, both analytically and experimentally. For the experimental data evaluation, a software package was written for the Hewlett-Packard 5451C Fourier analyzer. The POGO analysis software is documented and consists of five separate segments. Each segment is stored on the 5451C disc as an individual program and performs its own unique function. Two separate data reduction methods, a signal calibration, coherence or pulser signal based frequency response function blanking, and automatic plotting features are included in the program. The 5451C allows variable parameter transfer from program to program. This feature is used to advantage and requires only minimal user interface during the data reduction process. Experimental results are included and compared with the analytical predictions in order to adjust the general model and arrive at a realistic simulation of the POGO characteristics.

  2. 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.

  3. Dynamic characteristic investigation on the fuel pressure of diesel engines electronic in-line pump system

    NASA Astrophysics Data System (ADS)

    Liu, You; Yuan, Zhi-Guo; Fan, Li-Yun; Tian, Bin-Qi

    2010-12-01

    The electronic in-line pump (EIP) is a complex system consisting of mechanical, hydraulic, and electromagnetic parts. Experimental study showed that the fuel pressure of the plunger and the fuel drainage of the pressure system after fuel injection could result in fuel pressure fluctuation in the low pressure system. Such fluctuation exhibited pulsating cycle fluctuation as the amplitude rose with the increase of the injection pulse width. The time domain analysis found that the pressure time history curve and injection cylinders corresponded with a one-to-one relationship. By frequency domain analysis, the result was that with the increase of the working cylinder number, the high frequency amplitude gradually increased and the basic frequency amplitude gradually decreased. The conclusion was that through wavelet transformation, the low pressure signal simultaneously moved towards low frequency as the high frequency of the wavelet transformation signal with the working cylinder number increased. Lastly, by using the numerical model, the study investigated the simulation research concerning the relationship of the fluctuation dynamic characteristic in the low pressure system and the fuel injection characteristic of the high pressure system, completing the conclusions obtained by the experimental study.

  4. Static and Dynamic Characteristics of a Long-Span Cable-Stayed Bridge with CFRP Cables.

    PubMed

    Xie, Xu; Li, Xiaozhang; Shen, Yonggang

    2014-06-23

    In this study, the scope of CFRP cables in cable-stayed bridges is studied by establishing a numerical model of a 1400-m span of the same. The mechanical properties and characteristics of CFRP stay cables and of a cable-stayed bridge with CFRP cables are here subjected to comprehensive analysis. The anomalies in the damping properties of free vibration, nonlinear parametric vibration and wind fluctuating vibration between steel cables and CFRP cables are determined. The structural stiffness, wind resistance and traffic vibration of the cable-stayed bridge with CFRP cables are also analyzed. It was found that the static performances of a cable-stayed bridge with CFRP cables and steel cables are basically the same. The natural frequencies of CFRP cables do not coincide with the major natural frequencies of the cable-stayed bridge, so the likelihood of CFRP cable-bridge coupling vibration is minuscule. For CFRP cables, the response amplitudes of both parametric vibration and wind fluctuating vibration are smaller than those of steel cables. It can be concluded from the research that the use of CFRP cables does not change the dynamic characteristics of the vehicle-bridge coupling vibration. Therefore, they can be used in long-span cable-stayed bridges with an excellent mechanical performance.

  5. 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 he