Patchy reconnection in the solar corona

NASA Astrophysics Data System (ADS)

Guidoni, Silvina Esther

2011-05-01

Magnetic reconnection in plasmas, a process characterized by a change in connectivity of field lines that are broken and connected to other ones with different topology, owes its usefulness to its ability to unify a wide range of phenomena within a single universal principle. There are newly observed phenomena in the solar corona that cannot be reconciled with two-dimensional or steady-state standard models of magnetic reconnection. Supra-arcade downflows (SADs) and supra-arcade downflowing loops (SADLs) descending from reconnection regions toward solar post-flare arcades seem to be two different observational signatures of retracting, isolated reconnected flux tubes with irreducible three-dimensional geometries. This dissertation describes work in refining and improving a novel model of patchy reconnection, where only a small bundle of field lines is reconnected across a current sheet (magnetic discontinuity) and forms a reconnected thin flux tube. Traditional models have not been able to explain why some of the observed SADs appear to be hot and relatively devoid of plasma. The present work shows that plasma depletion naturally occurs in flux tubes that are reconnected across nonuniform current sheets and slide trough regions of decreasing magnetic field magnitude. Moreover, through a detailed theoretical analysis of generalized thin flux tube equations, we show that the addition to the model of pressure-driven parallel dynamics, as well as temperature-dependent, anisotropic viscosity and thermal conductivity is essential for self-consistently producing gas-dynamic shocks inside reconnected tubes that heat and compress plasma to observed temperatures and densities. The shock thickness can be as long as the entire tube and heat can be conducted along tube's legs, possibly driving chromospheric evaporation. We developed a computer program that solves numerically the thin flux tube equations that govern the retraction of reconnected tubes. Simulations carried out with this program corroborate our theoretical predictions. A comparison of these simulations with fully three-dimensional magnetohydrodynamic simulations is presented to assess the validity of the thin flux tube model. We also present an observational method based on total emission measure and mean temperature to determine where in the current sheet a tube was reconnected.

Method of calculating gas dynamics and heat transfer in single stage refrigeration units

NASA Technical Reports Server (NTRS)

Zhitomirskiy, I. S.; Popolskiy, A. B.

1974-01-01

A generalized mathematical model of gas-dynamic and heat transfer processes in single-stage regenerative installations operating in Stirling, MacMahon, Gifford-MacMahon, and pulsating tube cycles is proposed. A numerical method os solving initial equations on a digital computer is given. This makes it possible to calculate the change in the thermodynamic parameters in the working cycle in different machine components, as well as the dependence of cold productivity on the temperature level in the steady regime.

Free energetics of carbon nanotube association in aqueous inorganic NaI salt solutions: Temperature effects using all-atom molecular dynamics simulations.

PubMed

Ou, Shu-Ching; Cui, Di; Wezowicz, Matthew; Taufer, Michela; Patel, Sandeep

2015-06-15

In this study, we examine the temperature dependence of free energetics of nanotube association using graphical processing unit-enabled all-atom molecular dynamics simulations (FEN ZI) with two (10,10) single-walled carbon nanotubes in 3 m NaI aqueous salt solution. Results suggest that the free energy, enthalpy and entropy changes for the association process are all reduced at the high temperature, in agreement with previous investigations using other hydrophobes. Via the decomposition of free energy into individual components, we found that solvent contribution (including water, anion, and cation contributions) is correlated with the spatial distribution of the corresponding species and is influenced distinctly by the temperature. We studied the spatial distribution and the structure of the solvent in different regions: intertube, intratube and the bulk solvent. By calculating the fluctuation of coarse-grained tube-solvent surfaces, we found that tube-water interfacial fluctuation exhibits the strongest temperature dependence. By taking ions to be a solvent-like medium in the absence of water, tube-anion interfacial fluctuation shows similar but weaker dependence on temperature, while tube-cation interfacial fluctuation shows no dependence in general. These characteristics are discussed via the malleability of their corresponding solvation shells relative to the nanotube surface. Hydrogen bonding profiles and tetrahedrality of water arrangement are also computed to compare the structure of solvent in the solvent bulk and intertube region. The hydrophobic confinement induces a relatively lower concentration environment in the intertube region, therefore causing different intertube solvent structures which depend on the tube separation. This study is relevant in the continuing discourse on hydrophobic interactions (as they impact generally a broad class of phenomena in biology, biochemistry, and materials science and soft condensed matter research), and interpretations of hydrophobicity in terms of alternative but parallel signatures such as interfacial fluctuations, dewetting transitions, and enhanced fluctuation probabilities at interfaces. © 2015 Wiley Periodicals, Inc.

Comparative Tests of Pitot-static Tubes

NASA Technical Reports Server (NTRS)

Merriam, Kenneth G; Spaulding, Ellis R

1935-01-01

Comparative tests were made on seven conventional Pitot-static tubes to determine their static, dynamic, and resultant errors. The effect of varying the dynamic opening, static opening, wall thickness, and inner-tube diameter was investigated. Pressure-distribution measurements showing stem and tip effects were also made. A tentative design for a standard Pitot-static tube for use in measuring air velocity is submitted.

System and method for reducing combustion dynamics and NO.sub.x in a combustor

DOEpatents

Uhm, Jong H.; Johnson, Thomas Edward

2015-11-20

A system for reducing combustion dynamics and NO.sub.x in a combustor includes a tube bundle that extends radially across at least a portion of the combustor, wherein the tube bundle comprises an upstream surface axially separated from a downstream surface. A shroud circumferentially surrounds the upstream and downstream surfaces. A plurality of tubes extends through the tube bundle from the upstream surface through the downstream surface, wherein the downstream surface is stepped to produce tubes having different lengths through the tube bundle. A method for reducing combustion dynamics and NO.sub.x in a combustor includes flowing a working fluid through a plurality of tubes radially arranged between an upstream surface and a downstream surface of an end cap that extends radially across at least a portion of the combustor, wherein the downstream surface is stepped.

Concept of a Pitot tube able to detect blockage by ice, volcanic ash, sand and insects, and to clear the tube

NASA Astrophysics Data System (ADS)

Jackson, David A.

2015-12-01

A conceptual coaxial Pitot tube (PT) has been developed using fiber optic sensors combined with actuators to monitor and maintain its correct operation under different environmental conditions. Experiments were performed showing that the dynamic and static tubes can be cleared of ice. It was also demonstrated that the dynamic tube could be cleared of dust and sand which was not the case for the static tube in the coaxial configuration. An approach was proposed to overcome this problem involving a conventional configuration where the static tube was operated independently orthogonal to the dynamic tube, and a second set of sensors and actuators was used. Sensors and associated actuators were developed for temperature and intensity for a linear PT. The aim of this work is to propose a solution for a problem that has caused the loss of the lives of many passengers and crew of aircraft. Resources were not available to test a full implementation of a PT incorporating the proposed modifications.

High spatial resolution measurements of ram accelerator gas dynamic phenomena

NASA Technical Reports Server (NTRS)

Hinkey, J. B.; Burnham, E. A.; Bruckner, A. P.

1992-01-01

High spatial resolution experimental tube wall pressure measurements of ram accelerator gas dynamic phenomena are presented. The projectile resembles the centerbody of a ramjet and travels supersonically through a tube filled with a combustible gaseous mixture, with the tube acting as the outer cowling. Pressure data are recorded as the projectile passes by sensors mounted in the tube wall at various locations along the tube. Data obtained by using a special highly instrumented section of tube has allowed the recording of gas dynamic phenomena with a spatial resolution on the order of one tenth the projectile length. High spatial resolution tube wall pressure data from the three regimes of propulsion studied to date (subdetonative, transdetonative, and superdetonative) are presented and reveal the 3D character of the flowfield induced by projectile fins and the canting of the projectile body relative to the tube wall. Also presented for comparison to the experimental data are calculations made with an inviscid, 3D CFD code.

System and method for reducing combustion dynamics in a combustor

DOEpatents

Uhm, Jong Ho; Johnson, Thomas Edward; Zuo, Baifang; York, William David

2015-09-01

A system for reducing combustion dynamics in a combustor includes an end cap having an upstream surface axially separated from a downstream surface, and tube bundles extend from the upstream surface through the downstream surface. A divider inside a tube bundle defines a diluent passage that extends axially through the downstream surface, and a diluent supply in fluid communication with the divider provides diluent flow to the diluent passage. A method for reducing combustion dynamics in a combustor includes flowing a fuel through tube bundles, flowing a diluent through a diluent passage inside a tube bundle, wherein the diluent passage extends axially through at least a portion of the end cap into a combustion chamber, and forming a diluent barrier in the combustion chamber between the tube bundle and at least one other adjacent tube bundle.

Mapping the Protein Fold Universe Using the CamTube Force Field in Molecular Dynamics Simulations.

PubMed

Kukic, Predrag; Kannan, Arvind; Dijkstra, Maurits J J; Abeln, Sanne; Camilloni, Carlo; Vendruscolo, Michele

2015-10-01

It has been recently shown that the coarse-graining of the structures of polypeptide chains as self-avoiding tubes can provide an effective representation of the conformational space of proteins. In order to fully exploit the opportunities offered by such a 'tube model' approach, we present here a strategy to combine it with molecular dynamics simulations. This strategy is based on the incorporation of the 'CamTube' force field into the Gromacs molecular dynamics package. By considering the case of a 60-residue polyvaline chain, we show that CamTube molecular dynamics simulations can comprehensively explore the conformational space of proteins. We obtain this result by a 20 μs metadynamics simulation of the polyvaline chain that recapitulates the currently known protein fold universe. We further show that, if residue-specific interaction potentials are added to the CamTube force field, it is possible to fold a protein into a topology close to that of its native state. These results illustrate how the CamTube force field can be used to explore efficiently the universe of protein folds with good accuracy and very limited computational cost.

System and method for reducing combustion dynamics in a combustor

DOEpatents

Uhm, Jong Ho; Ziminsky, Willy Steve; Johnson, Thomas Edward; Srinivasan, Shiva; York, William David

2016-11-29

A system for reducing combustion dynamics in a combustor includes an end cap that extends radially across the combustor and includes an upstream surface axially separated from a downstream surface. A combustion chamber is downstream of the end cap, and tubes extend from the upstream surface through the downstream surface. Each tube provides fluid communication through the end cap to the combustion chamber. The system further includes means for reducing combustion dynamics in the combustor. A method for reducing combustion dynamics in a combustor includes flowing a working fluid through tubes that extend axially through an end cap that extends radially across the combustor and obstructing at least a portion of the working fluid flowing through a first set of the tubes.

Dynamic tube movement after reimplantation of Ahmed glaucoma valve in a child with glaucoma in aphakia

PubMed Central

Senthil, Sirisha; Badakare, Akshay

2014-01-01

A 10-year-old girl underwent an Ahmed glaucoma valve (AGV) implantation as a primary procedure for glaucoma in aphakia due to congenital cataract surgery. Following an unintended accidental excision of AGV tube during bleb revision for hypertensive phase, AGV was explanted and a second AGV was implanted in the same quadrant after 2 weeks. This resulted in a rare complication of dynamic tube movement in the anterior chamber with tube corneal touch and localised corneal oedema. Excision of the offending unstable tube and placement of a paediatric AGV in a different quadrant led to resolution of this complication, stable vision and well-controlled intraocular pressure. This case highlights the possible causes of dynamic tube, related complications and its management. This case also highlights the importance of understanding the various physiological phases after glaucoma drainage device implantation and their appropriate management. PMID:24695662

Smoothed Particle Hydrodynamics Simulations of Ultrarelativistic Shocks with Artificial Viscosity

NASA Astrophysics Data System (ADS)

Siegler, S.; Riffert, H.

2000-03-01

We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables of rest-mass density, 3-velocity, and thermodynamic pressure have to be determined. We present the corresponding equations for an ideal gas and show the existence and uniqueness of the solution. On the basis of the Lagrangian formulation we have developed a three-dimensional general relativistic smoothed particle hydrodynamics (SPH) code using the standard SPH formalism as known from nonrelativistic fluid dynamics. One-dimensional simulations of a shock tube and a wall shock are presented together with a two-dimensional test calculation of an inclined shock tube. With our method we can model ultrarelativistic fluid flows including shocks with Lorentz factors of even 1000.

F-16B Pacer Aircraft Trailing Cone Length Extension Tube Investigative Study (HAVE CLETIS)

DTIC Science & Technology

2007-06-01

the axial load experienced during high incompressible dynamic pressures and prevent the coupling from locking up as was observed for the 35-foot... axial loads due to incompressible dynamic pressure. (R4) “Guitar stringing” was used to describe the high frequency vibration of the pressure tube...Modify the design of the pressure tube and drag cone coupling to allow independent pressure tube and drag cone rotation under axial loads due to

Quantifying chain reptation in entangled polymer melts: Topological and dynamical mapping of atomistic simulation results onto the tube model

NASA Astrophysics Data System (ADS)

Stephanou, Pavlos S.; Baig, Chunggi; Tsolou, Georgia; Mavrantzas, Vlasis G.; Kröger, Martin

2010-03-01

The topological state of entangled polymers has been analyzed recently in terms of primitive paths which allowed obtaining reliable predictions of the static (statistical) properties of the underlying entanglement network for a number of polymer melts. Through a systematic methodology that first maps atomistic molecular dynamics (MD) trajectories onto time trajectories of primitive chains and then documents primitive chain motion in terms of a curvilinear diffusion in a tubelike region around the coarse-grained chain contour, we are extending these static approaches here even further by computing the most fundamental function of the reptation theory, namely, the probability ψ(s,t) that a segment s of the primitive chain remains inside the initial tube after time t, accounting directly for contour length fluctuations and constraint release. The effective diameter of the tube is independently evaluated by observing tube constraints either on atomistic displacements or on the displacement of primitive chain segments orthogonal to the initial primitive path. Having computed the tube diameter, the tube itself around each primitive path is constructed by visiting each entanglement strand along the primitive path one after the other and approximating it by the space of a small cylinder having the same axis as the entanglement strand itself and a diameter equal to the estimated effective tube diameter. Reptation of the primitive chain longitudinally inside the effective constraining tube as well as local transverse fluctuations of the chain driven mainly from constraint release and regeneration mechanisms are evident in the simulation results; the latter causes parts of the chains to venture outside their average tube surface for certain periods of time. The computed ψ(s,t) curves account directly for both of these phenomena, as well as for contour length fluctuations, since all of them are automatically captured in the atomistic simulations. Linear viscoelastic properties such as the zero shear rate viscosity and the spectra of storage and loss moduli obtained on the basis of the obtained ψ(s,t) curves for three different polymer melts (polyethylene, cis-1,4-polybutadiene, and trans-1,4-polybutadiene) are consistent with experimental rheological data and in qualitative agreement with the double reptation and dual constraint models. The new methodology is general and can be routinely applied to analyze primitive path dynamics and chain reptation in atomistic trajectories (accumulated through long MD simulations) of other model polymers or polymeric systems (e.g., bidisperse, branched, grafted, etc.); it is thus believed to be particularly useful in the future in evaluating proposed tube models and developing more accurate theories for entangled systems.

Dynamic pressure sensitivity determination with Mach number method

NASA Astrophysics Data System (ADS)

Sarraf, Christophe; Damion, Jean-Pierre

2018-05-01

Measurements of pressure in fast transient conditions are often performed even if the dynamic characteristic of the transducer are not traceable to international standards. Moreover, the question of a primary standard in dynamic pressure is still open, especially for gaseous applications. The question is to improve dynamic standards in order to respond to expressed industrial needs. In this paper, the method proposed in the EMRP IND09 ‘Dynamic’ project, which can be called the ‘ideal shock tube method’, is compared with the ‘collective standard method’ currently used in the Laboratoire de Métrologie Dynamique (LNE/ENSAM). The input is a step of pressure generated by a shock tube. The transducer is a piezoelectric pressure sensor. With the ‘ideal shock tube method’ the sensitivity of a pressure sensor is first determined dynamically. This method requires a shock tube implemented with piezoelectric shock wave detectors. The measurement of the Mach number in the tube allows an evaluation of the incident pressure amplitude of a step using a theoretical 1D model of the shock tube. Heat transfer, other actual effects and effects of the shock tube imperfections are not taken into account. The amplitude of the pressure step is then used to determine the sensitivity in dynamic conditions. The second method uses a frequency bandwidth comparison to determine pressure at frequencies from quasi-static conditions, traceable to static pressure standards, to higher frequencies (up to 10 kHz). The measurand is also a step of pressure generated by a supposed ideal shock tube or a fast-opening device. The results are provided as a transfer function with an uncertainty budget assigned to a frequency range, also deliverable frequency by frequency. The largest uncertainty in the bandwidth of comparison is used to trace the final pressure step level measured in dynamic conditions, owing that this pressure is not measurable in a steady state on a shock tube. A reference sensor thereby calibrated can be used in a comparison measurement process. At high frequencies the most important component of the uncertainty in this method is due to actual shock tube complex effects not already functionalized nowadays or thought not to be functionalized in this kind of direct method. After a brief review of both methods and a brief review of the determination of the transfer function of pressure transducers, and the budget of associated uncertainty for the dynamic calibration of a pressure transducer in gas, this paper presents a comparison of the results obtained with the ‘ideal shock tube’ and the ‘collective standard’ methods.

Bubble Motion through a Generalized Power-Law Fluid Flowing in a Vertical Tube

PubMed Central

Mukundakrishnan, Karthik; Eckmann, David M.; Ayyaswamy, P. S.

2009-01-01

Intravascular gas embolism may occur with decompression in space flight, as well as during cardiac and vascular surgery. Intravascular bubbles may be deposited into any end organ, such as the heart or the brain. Surface interactions between the bubble and the endothelial cells lining the vasculature result in serious impairment of blood flow and can lead to heart attack, stroke, or even death. To develop effective therapeutic strategies, there is a need for understanding the dynamics of bubble motion through blood and its interaction with the vessel wall through which it moves. Toward this goal, we numerically investigate the axisymmetric motion of a bubble moving through a vertical circular tube in a shear-thinning generalized power-law fluid, using a front-tracking method. The formulation is characterized by the inlet Reynolds number, capillary number, Weber number, and Froude number. The flow dynamics and the associated wall shear stresses are documented for a combination of two different inlet flow conditions (inlet Reynolds numbers) and three different effective bubble radii (ratio of the undeformed bubble radii to the tube radii). The results of the non-Newtonian model are then compared with that of the model assuming a Newtonian blood viscosity. Specifically, for an almost occluding bubble (effective bubble radius = 0.9), the wall shear stress and the bubble residence time are compared for both Newtonian and non-Newtonian cases. Results show that at low shear rates, for a given pressure gradient the residence time for a non-Newtonian flow is higher than that for a Newtonian flow. PMID:19426324

Mapping the Protein Fold Universe Using the CamTube Force Field in Molecular Dynamics Simulations

PubMed Central

Dijkstra, Maurits J. J.; Abeln, Sanne; Camilloni, Carlo; Vendruscolo, Michele

2015-01-01

It has been recently shown that the coarse-graining of the structures of polypeptide chains as self-avoiding tubes can provide an effective representation of the conformational space of proteins. In order to fully exploit the opportunities offered by such a ‘tube model’ approach, we present here a strategy to combine it with molecular dynamics simulations. This strategy is based on the incorporation of the ‘CamTube’ force field into the Gromacs molecular dynamics package. By considering the case of a 60-residue polyvaline chain, we show that CamTube molecular dynamics simulations can comprehensively explore the conformational space of proteins. We obtain this result by a 20 μs metadynamics simulation of the polyvaline chain that recapitulates the currently known protein fold universe. We further show that, if residue-specific interaction potentials are added to the CamTube force field, it is possible to fold a protein into a topology close to that of its native state. These results illustrate how the CamTube force field can be used to explore efficiently the universe of protein folds with good accuracy and very limited computational cost. PMID:26505754

Behavior of plywood and fiberglass steel composite tube structures subjected to impact loading

NASA Astrophysics Data System (ADS)

Armaghani, Seyamend Bilind

Paratransit buses are custom built as the major vehicle manufacturer produces the custom built passenger cage installed on the chassis for the Paratransit bus. In order for these Paratransit bus members to be sufficient, they have to be evaluated for crashworthiness and energy absorption. This has prompted Florida Department of Transportation (FDOT) to fund research for the safety evaluation of Paratransit busses consisting of crash and safety analysis. There has been a large body of research done on steel subjected to static loads, but more research is needed for steel applied under dynamic loading and high speeds in order to improve crashworthiness in events such as rollovers and side impacts. Bare steel Hollow Structural Section (HSS) tubing are used a lot as structural members of Paratransit buses because of their lightness and progressive buckling under loading. The research will be conducted on quantifying the tubing's behavior under bending by conducting static three point bending and impact loading tests. In addition to the bare tubing, plywood and fiberglass composites are investigated because they are both strong and lightweight and their behavior under dynamic loading hasn't been quantified. As a result, the main purpose of this research is to quantify the differences between the dynamic and static behavior of plywood steel composite and fiberglass steel composite tubing and compare these findings with those of bare steel tubing. The differences will be quantified using detailed and thorough experiments that will examine the composites behavior under both static and dynamic loading. These tests will determine if there are any advantages of using the composite materials and thus allow for recommendations to be made to the FDOT with the goal of improving the safety of Paratransit busses. Tensile tests were conducted to determine the material properties of the tested specimens. Before the static and dynamic experiments are run to investigate the differences between static and dynamic behavior, Preliminary three point bending testing was conducted to determine the parameters for the final experiments. Static bending testing was conducted on the bare, plywood composite, and fiberglass composite steel tubing. The point of these experiments was to produce a Moment vs. Rotation plot to determine the specimens' maximum moments and their associated rotation, as that is when the steel buckles and fails. The dynamic three point bending experiments were conducted using the impact loading apparatus and had the same purpose as the static experiments. For both static and dynamic experiments, the performances of the different types of specimens were compared based upon their Moment vs. Rotation plots. This will determine the effect that the composite has on the rotation and maximum moment at which the tubing fails. After conducting these experiments, amplification factors were established for each specimen by comparing the maximum moment and their associated rotation between static and dynamic testing. lambda was calculated to quantify the ratio between the static and dynamic maximum moments. beta was used to quantify the ratio between the rotation needed to produce the maximum moment between static and dynamic events. A small amplification factor denotes that material performs well under impact loading and the material doesn't experience dramatic change in behavior during dynamic events. Amplification factors were compared between the bare, plywood, and fiberglass composite steel tubing in order to evaluate the performance of the composites. After comparing the amplification factors of the different types of tubing, recommendations can be made. Fiberglass and plywood composite were shown to be valuable because it decreased the effect of dynamic forces as beta was reduced by a factor of 2 in comparison to bare tubing. Based upon the amplification factors, it was recommended to use 14 gauge fiberglass composite tubing as Paratransit bus structural members because it was affected the least by dynamic loading.

CFD study of a simple orifice pulse tube cooler

NASA Astrophysics Data System (ADS)

Zhang, X. B.; Qiu, L. M.; Gan, Z. H.; He, Y. L.

2007-05-01

Pulse tube cooler (PTC) has the advantages of long-life and low vibration over the conventional cryocoolers, such as G-M and Stirling coolers because of the absence of moving parts in low temperature. This paper performs a two-dimensional axis-symmetric computational fluid dynamic (CFD) simulation of a GM-type simple orifice PTC (OPTC). The detailed modeling process and the general results such as the phase difference between velocity and pressure at cold end, the temperature profiles along the wall as well as the temperature oscillations at cold end with different heat loads are presented. Emphases are put on analyzing the complicated phenomena of multi-dimensional flow and heat transfer in the pulse tube under conditions of oscillating pressure. Swirling flow pattern in the pulse tube is observed and the mechanism of formation is analyzed in details, which is further validated by modeling a basic PTC. The swirl causes undesirable mixing in the thermally stratified fluid and is partially responsible for the poor overall performance of the cooler, such as unsteady cold-end temperature.

CFD simulation and experimental validation of a GM type double inlet pulse tube refrigerator

NASA Astrophysics Data System (ADS)

Banjare, Y. P.; Sahoo, R. K.; Sarangi, S. K.

2010-04-01

Pulse tube refrigerator has the advantages of long life and low vibration over the conventional cryocoolers, such as GM and stirling coolers because of the absence of moving parts in low temperature. This paper performs a three-dimensional computational fluid dynamic (CFD) simulation of a GM type double inlet pulse tube refrigerator (DIPTR) vertically aligned, operating under a variety of thermal boundary conditions. A commercial computational fluid dynamics (CFD) software package, Fluent 6.1 is used to model the oscillating flow inside a pulse tube refrigerator. The simulation represents fully coupled systems operating in steady-periodic mode. The externally imposed boundary conditions are sinusoidal pressure inlet by user defined function at one end of the tube and constant temperature or heat flux boundaries at the external walls of the cold-end heat exchangers. The experimental method to evaluate the optimum parameters of DIPTR is difficult. On the other hand, developing a computer code for CFD analysis is equally complex. The objectives of the present investigations are to ascertain the suitability of CFD based commercial package, Fluent for study of energy and fluid flow in DIPTR and to validate the CFD simulation results with available experimental data. The general results, such as the cool down behaviours of the system, phase relation between mass flow rate and pressure at cold end, the temperature profile along the wall of the cooler and refrigeration load are presented for different boundary conditions of the system. The results confirm that CFD based Fluent simulations are capable of elucidating complex periodic processes in DIPTR. The results also show that there is an excellent agreement between CFD simulation results and experimental results.

SEORious business: structural proteins in sieve tubes and their involvement in sieve element occlusion.

PubMed

Knoblauch, Michael; Froelich, Daniel R; Pickard, William F; Peters, Winfried S

2014-04-01

The phloem provides a network of sieve tubes for long-distance translocation of photosynthates. For over a century, structural proteins in sieve tubes have presented a conundrum since they presumably increase the hydraulic resistance of the tubes while no potential function other than sieve tube or wound sealing in the case of injury has been suggested. Here we summarize and critically evaluate current speculations regarding the roles of these proteins. Our understanding suffers from the suggestive power of images; what looks like a sieve tube plug on micrographs may not actually impede translocation very much. Recent reports of an involvement of SEOR (sieve element occlusion-related) proteins, a class of P-proteins, in the sealing of injured sieve tubes are inconclusive; various lines of evidence suggest that, in neither intact nor injured plants, are SEORs determinative of translocation stoppage. Similarly, the popular notion that P-proteins serve in the defence against phloem sap-feeding insects is unsupported by empirical facts; it is conceivable that in functional sieve tubes, aphids actually could benefit from inducing a plug. The idea that rising cytosolic Ca(2+) generally triggers sieve tube blockage by P-proteins appears widely accepted, despite lacking experimental support. Even in forisomes, P-protein assemblages restricted to one single plant family and the only Ca(2+)-responsive P-proteins known, the available evidence does not unequivocally suggest that plug formation is the cause rather than a consequence of translocation stoppage. We conclude that the physiological roles of structural P-proteins remain elusive, and that in vivo studies of their dynamics in continuous sieve tube networks combined with flow velocity measurements will be required to (hopefully) resolve this scientific roadblock.

System and method for reducing combustion dynamics in a combustor

DOEpatents

Uhm, Jong Ho; Johnson, Thomas Edward; Zuo, Baifang; York, William David

2013-08-20

A system for reducing combustion dynamics in a combustor includes an end cap having an upstream surface axially separated from a downstream surface, and tube bundles extend through the end cap. A diluent supply in fluid communication with the end cap provides diluent flow to the end cap. Diluent distributors circumferentially arranged inside at least one tube bundle extend downstream from the downstream surface and provide fluid communication for the diluent flow through the end cap. A method for reducing combustion dynamics in a combustor includes flowing fuel through tube bundles that extend axially through an end cap, flowing a diluent through diluent distributors into a combustion chamber, wherein the diluent distributors are circumferentially arranged inside at least one tube bundle and each diluent distributor extends downstream from the end cap, and forming a diluent barrier in the combustion chamber between at least one pair of adjacent tube bundles.

F*** Yeah Fluid Dynamics: Inside the science communication process

NASA Astrophysics Data System (ADS)

Sharp, Nicole

2016-11-01

Communicating scientific research to general audiences may seem daunting, but it does not have to be. For six years, fluid dynamics outreach blog FYFD has been sharing the community's scientific output with an audience of nearly a quarter of a million readers and viewers of all ages and backgrounds. This talk will focus on the process behind science communication and some of the steps and exercises that can help scientists communicate to broad audiences more effectively. Using examples from the FYFD blog and YouTube channel, the talk will illustrate this communication process in action.

Dynamic axial crushing of bitubular tubes with curvy polygonal inner-tube sections

NASA Astrophysics Data System (ADS)

Ahmed, Naveed; Xue, Pu; Zafar, Naeem

Bitubular structural configurations, where the outer tube is circular, square and curvy square in shape while the inner-tube section is curvy triangular, square and hexagonal in different proposed configurations, are numerically crushed under dynamic axial loading. The crashworthiness effectiveness for changing inner-tube polygonal cross-section for each of the outer tube sections is studied and compared with changing outer tube shape. The deformation plots and energy absorption (EA) parameters such as peak crushing force (PCF) mean crushing force (MCF), energy absorption and crush force efficiency for each case are evaluated. Most of the configurations showed ovalization with low PCF and MCF and moderate crush force efficiency. Afterwards, effects of L/D and t/R on deformation modes and EA are demonstrated by selecting one of the configurations from each group using published experimental results.

Analysis of Eustachian Tube Dysfunction by Dynamic Slow Motion Video Endoscopy and Eustachian Tube Dysfunction Questionnaire in Chronic Otitis Media

PubMed Central

Han, Won Gue; Yoo, Jun; Rah, Yoon Chan; Chang, Jiwon; Im, Gi Jung; Song, Jae-Jun; Chae, Sung Won; Jung, Hak Hyun; Choi, June

2017-01-01

Objectives Eustachian tube dysfunction has been associated with most cases of middle-ear disease. We aimed to assess the effectiveness of dynamic slow motion video endoscopy (DSVE) as a test of eustachian tube dysfunction. Furthermore, we assessed the correlation of the test with the Valsalva maneuver, the seven-item Eustachian Tube Dysfunction Questionnaire (ETDQ-7), and intraoperative findings of the eustachian tube. Methods We retrospectively reviewed medical records from April to September 2014 to identify patients who were diagnosed with chronic otitis media (COM) at Korea University Ansan Hospital. They all underwent surgery because of COM without cholesteatoma and were assessed via the DSVE and ETDQ-7 to determine eustachian tube function. Results We reviewed 46 COM patients and examined 46 ears with COM and 46 ears on the contralateral side to COM that were thought to be normal. The mean DSVE grade in COM ears was 1.57±0.96, while the mean DSVE grade in contralateral ears was 1.15±0.94. The difference in DSVE between COM ears and normal ears was statistically significant (P=0.006). In the ETDQ-7, a higher score was related to intraoperative obstruction of the eustachian tube (P=0.012). Conclusion DSVE and ETDQ-7 can provide information regarding preoperative status of eustachian tube dysfunction by measuring dynamic structural changes of the eustachian tube in combination with other diagnostic tests. PMID:28602066

Analysis of Actin-Based Intracellular Trafficking in Pollen Tubes.

PubMed

Jiang, Yuxiang; Zhang, Meng; Huang, Shanjin

2017-01-01

Underlying rapid and directional pollen tube growth is the active intracellular trafficking system that carries materials necessary for cell wall synthesis and membrane expansion to the expanding point of the pollen tube. The actin cytoskeleton has been shown to control various intracellular trafficking events in the pollen tube, but the underlying cellular and molecular mechanisms remain poorly understood. To better understand how the actin cytoskeleton is involved in the regulation of intracellular trafficking events, we need to establish assays to visualize and quantify the distribution and dynamics of organelles, vesicles, or secreted proteins. In this chapter, we introduce methods regarding the visualization and quantification of the distribution and dynamics of organelles or vesicles in pollen tubes.

Dynamics of explosively imploded pressurized tubes

NASA Astrophysics Data System (ADS)

Szirti, Daniel; Loiseau, Jason; Higgins, Andrew; Tanguay, Vincent

2011-04-01

The detonation of an explosive layer surrounding a pressurized thin-walled tube causes the formation of a virtual piston that drives a precursor shock wave ahead of the detonation, generating very high temperatures and pressures in the gas contained within the tube. Such a device can be used as the driver for a high energy density shock tube or hypervelocity gas gun. The dynamics of the precursor shock wave were investigated for different tube sizes and initial fill pressures. Shock velocity and standoff distance were found to decrease with increasing fill pressure, mainly due to radial expansion of the tube. Adding a tamper can reduce this effect, but may increase jetting. A simple analytical model based on acoustic wave interactions was developed to calculate pump tube expansion and the resulting effect on the shock velocity and standoff distance. Results from this model agree quite well with experimental data.

Strain and dynamic measurements using fiber optic sensors embedded into graphite/epoxy tubes

NASA Technical Reports Server (NTRS)

Dehart, D. W.; Doederlein, T.; Koury, J.; Rogowski, R. S.; Heyman, J. S.; Holben, M. S., Jr.

1989-01-01

Graphite/epoxy tubes were fabricated with embedded optical fibers to evaluate the feasibility of monitoring strains with a fiber optic technique. Resistance strain gauges were attached to the tubes to measure strain at four locations along the tube for comparison with the fiber optic sensors. Both static and dynamic strain measurements were made with excellent agreement between the embedded fiber optic strain sensor and the strain gauges. Strain measurements of 10(exp -7) can be detected with the optical phase locked loop (OPLL) system using optical fiber. Because of their light weight, compatibility with composites, immunity to electromagnetic interference, and based on the static and dynamic results obtained, fiber optic sensors embedded in composites may be useful as the sensing component of smart structures.

Enhancements for a Dynamic Data Warehousing and Mining System for Large-scale HSCB Data

DTIC Science & Technology

2016-06-20

YouTube Data Collection ................................................................................. 2 1.1.1 Scraawl YouTube Data Collection API...Development ............................... 2 1.1.2 Scraawl UI Development for YouTube Searches ....................................... 3 2 Current...following tasks.  Developed automated YouTube data collection capabilities. We have developed automated YouTube video metadata collection capabilities and

Evolutionary Design and Simulation of a Tube Crawling Inspection Robot

NASA Technical Reports Server (NTRS)

Craft, Michael; Howsman, Tom; ONeil, Daniel; Howell, Joe T. (Technical Monitor)

2002-01-01

The Space Robotics Assembly Team Simulation (SpaceRATS) is an expansive concept that will hopefully lead to a space flight demonstration of a robotic team cooperatively assembling a system from its constitutive parts. A primary objective of the SpaceRATS project is to develop a generalized evolutionary design approach for multiple classes of robots. The portion of the overall SpaceRats program associated with the evolutionary design and simulation of an inspection robot's morphology is the subject of this paper. The vast majority of this effort has concentrated on the use and modification of Darwin2K, a robotic design and simulation software package, to analyze the design of a tube crawling robot. This robot is designed for carrying out inspection duties in relatively inaccessible locations within a liquid rocket engine similar to the SSME. A preliminary design of the tube crawler robot was completed, and the mechanical dynamics of the system were simulated. An evolutionary approach to optimizing a few parameters of the system was utilized, resulting in a more optimum design.

An isentropic compression-heated Ludweig tube transient wind tunnel

NASA Technical Reports Server (NTRS)

Magari, Patrick J.; Lagraff, John E.

1991-01-01

Theoretical development and experimental results show that the Ludweig tube with isentropic heating (LICH) transient wind tunnel described is a viable means of producing flow conditions that are suitable for a variety of experimental investigations. A complete analysis of the wave dynamics of the pump tube compression process is presented. The LICH tube operating conditions are very steady and run times are greater than those of other types of transient facilities such as shock tubes and gas tunnels. This facility is well suited for producing flow conditions that are dynamically similar to those found in a gas turbine, i.e., transonic Mach number, gas-to-wall temperature ratios of about 1.5, and Reynolds numbers greater than 10 to the 6th.

Identification of black hole horizons using scalar curvature invariants

NASA Astrophysics Data System (ADS)

Coley, Alan; McNutt, David

2018-01-01

We introduce the concept of a geometric horizon, which is a surface distinguished by the vanishing of certain curvature invariants which characterize its special algebraic character. We motivate its use for the detection of the event horizon of a stationary black hole by providing a set of appropriate scalar polynomial curvature invariants that vanish on this surface. We extend this result by proving that a non-expanding horizon, which generalizes a Killing horizon, coincides with the geometric horizon. Finally, we consider the imploding spherically symmetric metrics and show that the geometric horizon identifies a unique quasi-local surface corresponding to the unique spherically symmetric marginally trapped tube, implying that the spherically symmetric dynamical black holes admit a geometric horizon. Based on these results, we propose a suite of conjectures concerning the application of geometric horizons to more general dynamical black hole scenarios.

Drop tube technical tasks

NASA Technical Reports Server (NTRS)

Workman, G. L.

1986-01-01

Criteria, using fundamental thermochemical dynamics, were developed to assist a scientist using the Drop Tube Facility in designing a good experiment. The types of parameters involved in designing the experiments include the type of furnace, the type of atmosphere, and in general which materials are better behaved than others as determined by past experience in the facility. One of the major advantages of the facility lies in its ability to provide large undercoolings in the cooling curve during the drops. A beginning was to consider the effect of oxygen and other gases upon the amount of undercooling observed. The starting point of the thermochemistry was given by Ellingham and later transformed into what is known as the Richardson Chart. The effect of surface oxidations upon the nucleation phenomena can be observed in each specimen.

Design optimization of hydraulic turbine draft tube based on CFD and DOE method

NASA Astrophysics Data System (ADS)

Nam, Mun chol; Dechun, Ba; Xiangji, Yue; Mingri, Jin

2018-03-01

In order to improve performance of the hydraulic turbine draft tube in its design process, the optimization for draft tube is performed based on multi-disciplinary collaborative design optimization platform by combining the computation fluid dynamic (CFD) and the design of experiment (DOE) in this paper. The geometrical design variables are considered as the median section in the draft tube and the cross section in its exit diffuser and objective function is to maximize the pressure recovery factor (Cp). Sample matrixes required for the shape optimization of the draft tube are generated by optimal Latin hypercube (OLH) method of the DOE technique and their performances are evaluated through computational fluid dynamic (CFD) numerical simulation. Subsequently the main effect analysis and the sensitivity analysis of the geometrical parameters of the draft tube are accomplished. Then, the design optimization of the geometrical design variables is determined using the response surface method. The optimization result of the draft tube shows a marked performance improvement over the original.

YoTube: Searching Action Proposal Via Recurrent and Static Regression Networks

NASA Astrophysics Data System (ADS)

Zhu, Hongyuan; Vial, Romain; Lu, Shijian; Peng, Xi; Fu, Huazhu; Tian, Yonghong; Cao, Xianbin

2018-06-01

In this paper, we present YoTube-a novel network fusion framework for searching action proposals in untrimmed videos, where each action proposal corresponds to a spatialtemporal video tube that potentially locates one human action. Our method consists of a recurrent YoTube detector and a static YoTube detector, where the recurrent YoTube explores the regression capability of RNN for candidate bounding boxes predictions using learnt temporal dynamics and the static YoTube produces the bounding boxes using rich appearance cues in a single frame. Both networks are trained using rgb and optical flow in order to fully exploit the rich appearance, motion and temporal context, and their outputs are fused to produce accurate and robust proposal boxes. Action proposals are finally constructed by linking these boxes using dynamic programming with a novel trimming method to handle the untrimmed video effectively and efficiently. Extensive experiments on the challenging UCF-101 and UCF-Sports datasets show that our proposed technique obtains superior performance compared with the state-of-the-art.

A Molecular Dynamics Study of Single-Walled Carbon Nanotubes (SWCNTs) Dispersed in Bile Salt Surfactants

NASA Astrophysics Data System (ADS)

Phelan, Frederick, Jr.; Sun, Huai

2014-03-01

Single-walled carbon nanotubes (SWNCTs) are materials with structural, electronic and optical properties that make them attractive for a myriad of advanced technology applications. A practical barrier to their use is that SWCNT synthesis techniques produce heterogeneous mixtures of varying lengths and chirality, whereas applications generally require tubes with narrow size distributions and individual type. Most separation techniques currently in use to obtain monodisperse tube fractions rely on dispersion of these materials in aqueous solution using surfactants. The dispersion process results in a mixture of colloidal structures in which individual tubes are dispersed and contained in a surfactant shell. Understanding the structure and properties of the SWCNT-surfactant complex at the molecular level, and how this is affected by chirality, is key to understanding and improving separations processes. In this study, we use molecular dynamics (MD) simulations to study the structure and properties of SWCNT-surfactant colloidal complexes. We tested a number of methods and protocols in order to build an accurate model for simulating SWCNT systems for a variety of bile salt surfactants as well as anionic co-surfactants, components that are widely used and important in experimental separation studies at NIST. The custom force field parameters used here will be stored in WebFF, a Web-hosted smart force-field repository for polymeric and organic materials being developed at NIST for the Materials Genome Initiative.

Fullerene Derived Molecular Electronic Devices

NASA Technical Reports Server (NTRS)

Menon, Madhu; Srivastava, Deepak; Saini, Subbash

1998-01-01

The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale electronic devices. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal grapheme sheet, more complex joints require other mechanisms. In this work we explore structural and electronic properties of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme.

Path probability of stochastic motion: A functional approach

NASA Astrophysics Data System (ADS)

Hattori, Masayuki; Abe, Sumiyoshi

2016-06-01

The path probability of a particle undergoing stochastic motion is studied by the use of functional technique, and the general formula is derived for the path probability distribution functional. The probability of finding paths inside a tube/band, the center of which is stipulated by a given path, is analytically evaluated in a way analogous to continuous measurements in quantum mechanics. Then, the formalism developed here is applied to the stochastic dynamics of stock price in finance.

Modeling meniscus rise in capillary tubes using fluid in rigid-body motion approach

NASA Astrophysics Data System (ADS)

Hamdan, Mohammad O.; Abu-Nabah, Bassam A.

2018-04-01

In this study, a new term representing net flux rate of linear momentum is introduced to Lucas-Washburn equation. Following a fluid in rigid-body motion in modeling the meniscus rise in vertical capillary tubes transforms the nonlinear Lucas-Washburn equation to a linear mass-spring-damper system. The linear nature of mass-spring-damper system with constant coefficients offers a nondimensional analytical solution where meniscus dynamics are dictated by two parameters, namely the system damping ratio and its natural frequency. This connects the numerous fluid-surface interaction physical and geometrical properties to rather two nondimensional parameters, which capture the underlying physics of meniscus dynamics in three distinct cases, namely overdamped, critically damped, and underdamped systems. Based on experimental data available in the literature and the understanding meniscus dynamics, the proposed model brings a new approach of understanding the system initial conditions. Accordingly, a closed form relation is produced for the imbibition velocity, which equals half of the Bosanquet velocity divided by the damping ratio. The proposed general analytical model is ideal for overdamped and critically damped systems. While for underdamped systems, the solution shows fair agreement with experimental measurements once the effective viscosity is determined. Moreover, the presented model shows meniscus oscillations around equilibrium height occur if the damping ratio is less than one.

Capillary-tube-based extension of thermoacoustic theory for a random medium

NASA Astrophysics Data System (ADS)

Roh, Heui-Seol; Raspet, Richard; Bass, Henry E.

2005-09-01

Thermoacoustic theory for a single capillary tube is extended to random bulk medium on the basis of capillary tubes. The characteristics of the porous stack inside the resonator such as the tortuosity, dynamic shape factor, and porosity are introduced for the extension of wave equation by following Attenborough's approach. Separation of the dynamic shape factor for the viscous and thermal effect is adopted and scaling using the dynamic shape factor and tortuosity factor is demonstrated. The theoretical and experimental comparison of thermoviscous functions in reticulated vitreous carbon (RVC) and aluminum foam shows reasonable agreement. The extension is useful for investigations of the properties of a stack with arbitrary shapes of non-parallel pores.

Development and characterization of a dynamic lesion phantom for the quantitative evaluation of dynamic contrast-enhanced MRI.

PubMed

Freed, Melanie; de Zwart, Jacco A; Hariharan, Prasanna; Myers, Matthew R; Badano, Aldo

2011-10-01

To develop a dynamic lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human dynamic contrast-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI. The dynamic lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a contrast agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml/s) to evaluate the resultant kinetic curve shape and homogeneity of the contrast agent distribution in the dynamic lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the dynamic lesion for benign and malignant example curves. DCE-MRI example data were acquired of the dynamic phantom using a clinical protocol. The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml/s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves. The authors have constructed a dynamic lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to improved discrimination of breast cancer lesions.

Confirming nasogastric tube placement: Is the colorimeter as sensitive and specific as X-ray? A diagnostic accuracy study.

PubMed

Mordiffi, Siti Zubaidah; Goh, Mien Li; Phua, Jason; Chan, Yiong-Huak

2016-09-01

The effect of delivering enteral nutrition or medications via a nasogastric tube that is inadvertently located in the tracheobronchial tract can cause respiratory complications. Although radiographic examination is accepted as the gold standard for confirming the position of patients' enteral tubes, it is costly, involves risks of radiation, and is not failsafe. Studies using carbon dioxide sensors to detect inadvertent nasogastric tube placements have been conducted in intensive care settings. However, none involved patients in general wards. The objective of this study was to ascertain the diagnostic measure of colorimeter, with radiographic examination as the reference standard, to confirm the location of nasogastric tubes in patients. A prospective observational study of a diagnostic test. This study was conducted in the general wards of an approximately 1100-bed acute care tertiary hospital of an Academic Medical Center in Singapore. Adult patients with nasogastric tubes admitted to the general wards were recruited into the study. The colorimeter was attached to the nasogastric tube to detect for the presence of carbon dioxide, suggestive of a tracheobronchial placement. The exact location of the nasogastric tube was subsequently confirmed by a radiographic examination. A total of 192 tests were undertaken. The colorimeter detected carbon dioxide in 29 tested nasogastric tubes, of which radiographic examination confirmed that four tubes were located in the tracheobronchial tract. The colorimeter failed to detect carbon dioxide in one nasogastric tube that was located in the tracheobronchial tract, thus, demonstrating a sensitivity of 0.80 [95% CI (0.376, 0.964)]. The colorimeter detected absence of carbon dioxide in 163 tested nasogastric tubes in which radiographic examination confirmed 160 gastrointestinal and one tracheobronchial placements, demonstrating a specificity of 0.865 [95% CI (0.808, 0.907)]. The colorimeter detected one tracheobronchial nasogastric tube placement that the radiographic examination was misinterpreted. The study found that the use of the colorimeter in the general ward setting was not 100% sensitive or specific in ascertaining the location of a nasogastric tube as previously reported by many studies undertaken in intensive care settings. This is the first study on the use of a colorimeter to confirm the placement of a nasogastric tube in adult patients in the general ward setting. More research on the use of a colorimeter in the general ward setting and its potential use in certain processes for confirming the placement of a nasogastric tube is warranted. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dynamics of magnetic flux tubes in an advective flow around a black hole

NASA Astrophysics Data System (ADS)

Deb, Arnab; Giri, Kinsuk; Chakrabarti, Sandip K.

2017-12-01

Entangled magnetic fields entering into an accretion flow would very soon be stretched into a dominant toroidal component due to strong differentially rotating motion inside the accretion disc. This is particularly true for weakly viscous, low angular momentum transonic or advective discs. We study the trajectories of toroidal flux tubes inside a geometrically thick flow that undergoes a centrifugal force supported shock. We also study effects of these flux tubes on the dynamics of the inflow and the outflow. We use a finite difference method (total variation diminishing) for this purpose and specifically focused on whether these flux tubes significantly affect the properties of the outflows such as its collimation and the rate. It is seen that depending upon the cross-sectional radius of the flux tubes that control the drag force, these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surfaces) along the vertical direction. A comparison of results obtained with and without flux tubes show these flux tubes could play a pivotal role in collimation and acceleration of jets and outflows.

The Hyperloop as a Source of Interesting Estimation Questions

NASA Astrophysics Data System (ADS)

Allain, Rhett

2014-03-01

The Hyperloop is a conceptual high speed transportation system proposed by Elon Musk. The basic idea uses passenger capsules inside a reduced pressure tube. Even though the actual physics of dynamic air flow in a confined space can be complicated, there are a multitude estimation problems that can be addressed. These back-of-the-envelope questions can be approximated by physicists of all levels as well as the general public and serve as a great example of the fundamental aspects of physics.

Design Analysis of Corridors-in-the-Sky

NASA Technical Reports Server (NTRS)

Xue, Min

2008-01-01

Corridors-in-the-sky or tubes is one of new concepts in dynamic airspace configuration. It accommodates high density traffic, which has similar trajectories. Less air traffic controllers workload is expected than classic airspaces, thus, corridors-in-the-sky may increase national airspace capacity and reduce flight delays. To design corridors-in-the-sky, besides identifying their locations, their utilization, altitudes, and impacts on remaining system need to be analyzed. This paper chooses one tube candidate and presents analyses of spatial and temporal utilization of the tube, the impact on the remaining traffic, and the potential benefit caused by off-loading the traffic from underlying sectors. Fundamental issues regarding to the benefits have been also clarified. Methods developed to assist the analysis are described. Analysis results suggest dynamic tubes in terms of varied utilizations during different time periods. And it is found that combined lane options would be a good choice to lower the impact on non-tube users. Finally, it shows significant reduction of peak aircraft count in underlying sectors with only one tube enabled.

Copper Tube Compression in Z-Current Geometry, Numerical Simulations and Comparison with Cyclope Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lefrancois, A.; L'Eplattenier, P.; Burger, M.

2006-02-13

Metallic tubes compressions in Z-current geometry were performed at the Cyclope facility from Gramat Research Center in order to study the behavior of metals under large strain at high strain rate. 3D configurations of cylinder compressions have been calculated here to benchmark the new beta version of the electromagnetism package coupled with the dynamics in Ls-Dyna and compared with the Cyclope experiments. The electromagnetism module is being developed in the general-purpose explicit and implicit finite element program LS-DYNA{reg_sign} in order to perform coupled mechanical/thermal/electromagnetism simulations. The Maxwell equations are solved using a Finite Element Method (FEM) for the solid conductorsmore » coupled with a Boundary Element Method (BEM) for the surrounding air (or vacuum). More details can be read in the references.« less

Application of Tube Dynamics to Non-Statistical Reaction Processes

NASA Astrophysics Data System (ADS)

Gabern, F.; Koon, W. S.; Marsden, J. E.; Ross, S. D.; Yanao, T.

2006-06-01

A technique based on dynamical systems theory is introduced for the computation of lifetime distributions and rates of chemical reactions and scattering phenomena, even in systems that exhibit non-statistical behavior. In particular, we merge invariant manifold tube dynamics with Monte Carlo volume determination for accurate rate calculations. This methodology is applied to a three-degree-of-freedom model problem and some ideas on how it might be extended to higher-degree-of-freedom systems are presented.

Computational Fluid Dynamics (CFD) simulations of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, Carl; Sitaraman, Hariswaran; Leachman, Jake

2017-11-01

A 3D Computational Fluid Dynamics (CFD) simulation of a Heisenberg Vortex Tube (HVT) is performed to estimate cooling potential with cryogenic hydrogen. The main mechanism driving operation of the vortex tube is the use of fluid power for enthalpy streaming in a highly turbulent swirl in a dual-outlet tube. This enthalpy streaming creates a temperature separation between the outer and inner regions of the flow. Use of a catalyst on the peripheral wall of the centrifuge enables endothermic conversion of para-ortho hydrogen to aid primary cooling. A κ- ɛ turbulence model is used with a cryogenic, non-ideal equation of state, and para-orthohydrogen species evolution. The simulations are validated with experiments and strategies for parametric optimization of this device are presented.

Aridopsis COBRA-LIKE 10, a GPI-anchored protien, mediates directional growth of pollen tubes

USDA-ARS?s Scientific Manuscript database

Successful reproduction of flowering plants requires constant communication between female tissues and growing pollen tubes. Female cells secrete molecules and peptides as nutrients or guidance cues for fast and directional tube growth, which is executed by dynamic changes of intracellular activitie...

Dynamic calibration of fast-response probes in low-pressure shock tubes

NASA Astrophysics Data System (ADS)

Persico, G.; Gaetani, P.; Guardone, A.

2005-09-01

Shock tube flows resulting from the incomplete burst of the diaphragm are investigated in connection with the dynamic calibration of fast-response pressure probes. As a result of the partial opening of the diaphragm, pressure disturbances are observed past the shock wave and the measured total pressure profile deviates from the envisaged step signal required by the calibration process. Pressure oscillations are generated as the initially normal shock wave diffracts from the diaphragm's orifice and reflects on the shock tube walls, with the lowest local frequency roughly equal to the ratio of the sound speed in the perturbed region to the shock tube diameter. The energy integral of the perturbations decreases with increasing distance from the diaphragm, as the diffracted leading shock and downwind reflections coalesce into a single normal shock. A procedure is proposed to calibrate fast-response pressure probes downwind of a partially opened shock tube diaphragm.

A dynamic pressure source for the calibration of pressure transducers

NASA Technical Reports Server (NTRS)

Vezzetti, C. F.; Hilten, J. S.; Mayo-Wells, J. F.; Lederer, P. S.

1976-01-01

A dynamic pressure source is described for producing sinusoidally varying pressures of up to 34 kPa zero to peak, over the frequency range of approximately 50 Hz to 2 kHz. The source is intended for the dynamic calibration of pressure transducers. The transducer to be calibrated is mounted near the base of the thick walled aluminum tube forming the vessel so that the pressure sensitive element is in contact with the liquid in the tube. A section of the tube is filled with small steel balls to damp the motion of the 10-St dimethyl siloxane working fluid in order to extend the useful frquency range to higher frequencies than would be provided by an undamped system. The dynamic response of six transducers provided by the sponsor was evaluated using the pressure sources; the results of these calibrations are given.

Investigations on KONUS beam dynamics using the pre-stripper drift tube linac at GSI

NASA Astrophysics Data System (ADS)

Xiao, C.; Du, X. N.; Groening, L.

2018-04-01

Interdigital H-mode (IH) drift tube linacs (DTLs) based on KONUS beam dynamics are very sensitive to the rf-phases and voltages at the gaps between tubes. In order to design these DTLs, a deep understanding of the underlying longitudinal beam dynamics is mandatory. The report presents tracking simulations along an IH-DTL using the PARTRAN and BEAMPATH codes together with MATHCAD and CST. Simulation results illustrate that the beam dynamics design of the pre-stripper IH-DTL at GSI is sensitive to slight deviations of rf-phase and gap voltages with impact to the mean beam energy at the DTL exit. Applying the existing geometrical design, rf-voltages, and rf-phases of the DTL were re-adjusted. In simulations this re-optimized design can provide for more than 90% of transmission of an intense 15 emA beam keeping the reduction of beam brilliance below 25%.

Dynamic loads on human and animal surrogates at different test locations in compressed-gas-driven shock tubes

NASA Astrophysics Data System (ADS)

Alay, E.; Skotak, M.; Misistia, A.; Chandra, N.

2018-01-01

Dynamic loads on specimens in live-fire conditions as well as at different locations within and outside compressed-gas-driven shock tubes are determined by both static and total blast overpressure-time pressure pulses. The biomechanical loading on the specimen is determined by surface pressures that combine the effects of static, dynamic, and reflected pressures and specimen geometry. Surface pressure is both space and time dependent; it varies as a function of size, shape, and external contour of the specimens. In this work, we used two sets of specimens: (1) anthropometric dummy head and (2) a surrogate rodent headform instrumented with pressure sensors and subjected them to blast waves in the interior and at the exit of the shock tube. We demonstrate in this work that while inside the shock tube the biomechanical loading as determined by various pressure measures closely aligns with live-fire data and shock wave theory, significant deviations are found when tests are performed outside.

Aircraft Hydraulic Systems Dynamic Analysis Component Data Handbook

DTIC Science & Technology

1980-04-01

82 13. QUINCKE TUBE ...................................... 85 14. 11EAT EXCHANGER ............. ................... 90...Input Parameters ....... ........... .7 61 )uincke Tube Input Parameters with Hole Locat ions 87 62 "rototype Quincke Tube Data ........... 89 6 3 Fo-,:ed...Elasticity (Line 3) PSI 1.6E7 FIGURE 58 HSFR INPUT DATA FOR PULSCO TYPE ACOUSTIC FILTER 84 13. QUINCKE TUBE A means to dampen acoustic noise at resonance

Handling apparatus

DOEpatents

Cody, John P.; Kane, James J.

1976-01-01

1. A device of the character described comprising the combination of a guide tube having a normally open end, a support frame having a port therethrough, linkage means pivotally connected with the tube and with the frame and rotatably supporting the tube for movement between a position in longitudinal alignment with said port and with its open end in registry with the port and an additional position in which the tube lies adjacent the port with a side portion of the tube extending generally transversely across said port, an elongated track carried by said frame disposed generally parallel to and adjacent the tube in its said additional position, means connected with and projecting laterally from said tube adjacent its open end engaging and movable along said elongated track for cooperating with the track to direct the tube during movement between said positions, and means carried by the tube for moving an article therethrough toward and away from said port.

Boiling and condensation in microfin tubes

NASA Astrophysics Data System (ADS)

Schlager, Lynn M.

A general overview of microfin tubes and their applications is presented. Manufacturing processes, commercial availability, experimental heat transfer, and pressure drop data for various refrigerants (including alternative refrigerants and refrigerant-oil mixtures), physical mechanisms of enhancement, and the incorporation of microfin tubes in common heat exchanger configurations are discussed. Microfin tubes, also known by various trade names, are characterized by numerous small fins which typically spiral down the inside wall of tubes at angles ranging from 10 to 30 degrees. The number of fins ranges from 48 to 70 with typical fin heights of 0.12 to 0.30 mm (fin height generally less than 3 percent of the inside diameter of the tube). Fin shapes may vary and the inside surface area of microfin tubes is 10 to 70 percent greater than the area of equivalent smooth tubes. Heat transfer can be enhanced by up to a factor of three with microfin tubes.

Calcium dynamics in tomato pollen tubes using the Yellow Cameleon 3.6 sensor.

PubMed

Barberini, María Laura; Sigaut, Lorena; Huang, Weijie; Mangano, Silvina; Juarez, Silvina Paola Denita; Marzol, Eliana; Estevez, José; Obertello, Mariana; Pietrasanta, Lía; Tang, Weihua; Muschietti, Jorge

2018-06-01

In vitro tomato pollen tubes show a cytoplasmic calcium gradient that oscillates with the same period as growth. Pollen tube growth requires coordination between the tip-focused cytoplasmic calcium concentration ([Ca 2+ ] cyt ) gradient and the actin cytoskeleton. This [Ca 2+ ] cyt gradient is necessary for exocytosis of small vesicles, which contributes to the delivery of new membrane and cell wall at the pollen tube tip. The mechanisms that generate and maintain this [Ca 2+ ] cyt gradient are not completely understood. Here, we studied calcium dynamics in tomato (Solanum lycopersicum) pollen tubes using transgenic tomato plants expressing the Yellow Cameleon 3.6 gene under the pollen-specific promoter LAT52. We use tomato as an experimental model because tomato is a Solanaceous plant that is easy to transform, and has an excellent genomic database and genetic stock center, and unlike Arabidopsis, tomato pollen is a good system to do biochemistry. We found that tomato pollen tubes showed an oscillating tip-focused [Ca 2+ ] cyt gradient with the same period as growth. Then, we used a pharmacological approach to disturb the intracellular Ca 2+ homeostasis, evaluating how the [Ca 2+ ] cyt gradient, pollen germination and in vitro pollen tube growth were affected. We found that cyclopiazonic acid (CPA), a drug that inhibits plant P IIA -type Ca 2+ -ATPases, increased [Ca 2+ ] cyt in the subapical zone, leading to the disappearance of the Ca 2+ oscillations and inhibition of pollen tube growth. In contrast, 2-aminoethoxydiphenyl borate (2-APB), an inhibitor of Ca 2+ released from the endoplasmic reticulum to the cytoplasm in animals cells, completely reduced [Ca 2+ ] cyt at the tip of the tube, blocked the gradient and arrested pollen tube growth. Although both drugs have antagonistic effects on [Ca 2+ ] cyt , both inhibited pollen tube growth triggering the disappearance of the [Ca 2+ ] cyt gradient. When CPA and 2-APB were combined, their individual inhibitory effects on pollen tube growth were partially compensated. Finally, we found that GsMTx-4, a peptide from spider venom that blocks stretch-activated Ca 2+ channels, inhibited tomato pollen germination and had a heterogeneous effect on pollen tube growth, suggesting that these channels are also involved in the maintenance of the [Ca 2+ ] cyt gradient. All these results indicate that tomato pollen tube is an excellent model to study calcium dynamics.

Dynamic wetting of a liquid film in a vertical hydrophobic tube

NASA Astrophysics Data System (ADS)

Pigeonneau, Franck; Hayoun, Pascaline; Barthel, Etienne; Lequeux, Francois; Verneuil, Emilie; Letailleur, Alban; Teisseire, Jeremie; Saint-Gobain Recherche Collaboration; Espci-Physico-Chimie Des Polymeres Et Milieux Disperses Collaboration; Surface Du Verre Et Interfaces Collaboration

2016-11-01

The drop of a liquid plug through a tube occurs for instance in vending machine. In such a system, the fouling is linked to the creation of the liquid film at the rear of the liquid plug. Consequently, the conditions leading to the film creation are important to know. We study numerically the dynamic wetting transition of a liquid plug undergoing gravity on hydrophobic surface in a vertical tube. Using a lubrication theory, the liquid film thickness obeys the mass conservation equation with a volume flow rate depending on the relative motion of the tube, capillary and gravity forces. An ad hoc friction at the triple line is used to take into account the wetting dynamics. The lubrication equation is solved using a finite difference technique in space and a time integrator for stiff system with an adaptive time step. The numerical results are compared to experimental data. The complex film morphology due to the transients and the critical slowing down at the dynamic transition are reproduced. However, several experimental features are not predicted numerically especially the width of the transition. Our preliminary calculations suggest that the dispersion relation of the liquid film mode can explain the discrepancy.

Coordination of Receptor Tyrosine Kinase Signaling and Interfacial Tension Dynamics Drives Radial Intercalation and Tube Elongation. | Office of Cancer Genomics

Cancer.gov

We sought to understand how cells collectively elongate epithelial tubes. We first used 3D culture and biosensor imaging to demonstrate that epithelial cells enrich Ras activity, phosphatidylinositol (3,4,5)-trisphosphate (PIP3), and F-actin to their leading edges during migration within tissues. PIP3 enrichment coincided with, and could enrich despite inhibition of, F-actin dynamics, revealing a conserved migratory logic compared with single cells. We discovered that migratory cells can intercalate into the basal tissue surface and contribute to tube elongation.

Siphon flows in isolated magnetic flux tubes. III - The equilibrium path of the flux-tube arch

NASA Technical Reports Server (NTRS)

Thomas, John H.; Montesinos, Benjamin

1990-01-01

It is shown how to calculate the equilibrium path of a thin magnetic flux tube in a stratified, nonmagnetic atmosphere when the flux tube contains a steady siphon flow. The equilbrium path of a static thin flux tube in an infinite stratified atmosphere generally takes the form of a symmetric arch of finite width, with the flux tube becoming vertical at either end of the arch. A siphon flow within the flux tube increases the curvature of the arched equilibrium path in order that the net magnetic tension force can balance the inertial force of the flow, which tries to straighten the flux tube. Thus, a siphon flow reduces the width of the arched equilibrium path, with faster flows producing narrower arches. The effect of the siphon flow on the equilibrium path is generally greater for flux tubes of weaker magnetic field strength. Examples of the equilibrium are shown for both isothemal and adiabatic siphon flows in thin flux tubes in an isothermal external atmosphere.

Development and characterization of a dynamic lesion phantom for the quantitative evaluation of dynamic contrast-enhanced MRI

PubMed Central

Freed, Melanie; de Zwart, Jacco A.; Hariharan, Prasanna; R. Myers, Matthew; Badano, Aldo

2011-01-01

Purpose: To develop a dynamic lesion phantom that is capable of producing physiological kinetic curves representative of those seen in human dynamic contrast-enhanced MRI (DCE-MRI) data. The objective of this phantom is to provide a platform for the quantitative comparison of DCE-MRI protocols to aid in the standardization and optimization of breast DCE-MRI. Methods: The dynamic lesion consists of a hollow, plastic mold with inlet and outlet tubes to allow flow of a contrast agent solution through the lesion over time. Border shape of the lesion can be controlled using the lesion mold production method. The configuration of the inlet and outlet tubes was determined using fluid transfer simulations. The total fluid flow rate was determined using x-ray images of the lesion for four different flow rates (0.25, 0.5, 1.0, and 1.5 ml∕s) to evaluate the resultant kinetic curve shape and homogeneity of the contrast agent distribution in the dynamic lesion. High spatial and temporal resolution x-ray measurements were used to estimate the true kinetic curve behavior in the dynamic lesion for benign and malignant example curves. DCE-MRI example data were acquired of the dynamic phantom using a clinical protocol. Results: The optimal inlet and outlet tube configuration for the lesion molds was two inlet molds separated by 30° and a single outlet tube directly between the two inlet tubes. X-ray measurements indicated that 1.0 ml∕s was an appropriate total fluid flow rate and provided truth for comparison with MRI data of kinetic curves representative of benign and malignant lesions. DCE-MRI data demonstrated the ability of the phantom to produce realistic kinetic curves. Conclusions: The authors have constructed a dynamic lesion phantom, demonstrated its ability to produce physiological kinetic curves, and provided estimations of its true kinetic curve behavior. This lesion phantom provides a tool for the quantitative evaluation of DCE-MRI protocols, which may lead to improved discrimination of breast cancer lesions. PMID:21992378

Full-field Deformation Measurement Techniques for a Rotating Composite Shaft

NASA Technical Reports Server (NTRS)

Kohlman, Lee W.; Ruggeri, Charles R.; Martin, Richard E.; Roberts, Gary D.; Handschuh, Robert F.; Roth, Don J.

2012-01-01

Test methods were developed to view global and local deformation in a composite tube during a test in which the tube is rotating at speeds and torques relevant to rotorcraft shafts. Digital image correlation (DIC) was used to provide quantitative displacement measurements during the tests. High speed cameras were used for the DIC measurements in order to capture images at sufficient frame rates and with sufficient resolution while the tube was rotating at speeds up to 5,000 rpm. Surface displacement data was resolved into cylindrical coordinates in order to measure rigid body rotation and global deformation of the tube. Tests were performed on both undamaged and impact damaged tubes in order to evaluate the capability to detect local deformation near an impact damaged site. Measurement of radial displacement clearly indicated a local buckling deformation near the impacted site in both dynamic and static tests. X-ray computed tomography (CT) was used to investigate variations in fiber architecture within the composite tube and to detect impact damage. No growth in the impact damage area was observed by DIC during dynamic testing or by x-ray CT in post test inspection of the composite tube.

Action-derived molecular dynamics simulations for the migration and coalescence of vacancies in graphene and carbon nanotubes.

PubMed

Lee, Alex Taekyung; Ryu, Byungki; Lee, In-Ho; Chang, K J

2014-03-19

We report the results of action-derived molecular dynamics simulations for the migration and coalescence processes of monovacancies in graphene and carbon nanotubes with different chiralities. In carbon nanotubes, the migration pathways and barriers of a monovacancy depend on the tube chirality, while there is no preferential pathway in graphene due to the lattice symmetry and the absence of the curvature effect. The probable pathway changes from the axial to circumferential direction as the chirality varies from armchair to zigzag. The chirality dependence is attributed to the preferential orientation of the reconstructed bond formed around each vacancy site. It is energetically more favourable for two monovacancies to coalesce into a divacancy via alternative movements rather than simultaneous movements. The energy barriers for coalescence are generally determined by the migration barrier for the monovacancy, although there are some variations due to interactions between two diffusing vacancies. In graphene and armchair nanotubes, two monovacancies prefer to migrate along different zigzag atomic chains rather than a single atomic chain connecting these vacancies. On the other hand, in zigzag tubes, the energy barrier for coalescence increases significantly unless monovacancies lie on the same circumference.

High spatial resolution measurements in a single stage ram accelerator

NASA Technical Reports Server (NTRS)

Hinkey, J. B.; Burnham, E. A.; Bruckner, A. P.

1992-01-01

High spatial resolution experimental tube wall pressure measurements of ram accelerator gas dynamic phenomena are presented in this paper. The ram accelerator is a ramjet-in-tube device which operates in a manner similar to that of a conventional ramjet. The projectile resembles the centerbody of a ramjet and travels supersonically through a tube filled with a combustible gaseous mixture, with the tube acting as the outer cowling. Pressure data are recorded as the projectile passes by sensors mounted in the tube wall at various locations along the tube. Utilization of special highly instrumented sections of tube has allowed the recording of gas dynamic phenomena with high resolution. High spatial resolution tube wall pressure data from the three regimes of propulsion studied to date (subdetonative, transdetonative, and superdetonative) in a single stage gas mixture are presented and reveal the three-dimensional character of the flow field induced by projectile fins and the canting of the fins and the canting of the projectile body relative to the tube wall. Also presented for comparison to the experimental data are calculations made with an inviscid, three-dimensional CFD code. The knowledge gained from these experiments and simulations is useful in understanding the underlying nature of ram accelerator propulsive regimes, as well as assisting in the validation of three-dimensional CFD coded which model unsteady, chemically reactive flows.

Characterisation of detergent-insoluble membranes in pollen tubes of Nicotiana tabacum (L.)

PubMed Central

Moscatelli, Alessandra; Gagliardi, Assunta; Maneta-Peyret, Lilly; Bini, Luca; Stroppa, Nadia; Onelli, Elisabetta; Landi, Claudia; Scali, Monica; Idilli, Aurora Irene; Moreau, Patrick

2015-01-01

ABSTRACT Pollen tubes are the vehicle for sperm cell delivery to the embryo sac during fertilisation of Angiosperms. They provide an intriguing model for unravelling mechanisms of growing to extremes. The asymmetric distribution of lipids and proteins in the pollen tube plasma membrane modulates ion fluxes and actin dynamics and is maintained by a delicate equilibrium between exocytosis and endocytosis. The structural constraints regulating polarised secretion and asymmetric protein distribution on the plasma membrane are mostly unknown. To address this problem, we investigated whether ordered membrane microdomains, namely membrane rafts, might contribute to sperm cell delivery. Detergent insoluble membranes, rich in sterols and sphingolipids, were isolated from tobacco pollen tubes. MALDI TOF/MS analysis revealed that actin, prohibitins and proteins involved in methylation reactions and in phosphoinositide pattern regulation are specifically present in pollen tube detergent insoluble membranes. Tubulins, voltage-dependent anion channels and proteins involved in membrane trafficking and signalling were also present. This paper reports the first evidence of membrane rafts in Angiosperm pollen tubes, opening new perspectives on the coordination of signal transduction, cytoskeleton dynamics and polarised secretion. PMID:25701665

Nuclear magnetic resonance magnet actively cooled by pulse tube refrigerator

NASA Astrophysics Data System (ADS)

Kirichek, Oleg; Carr, Philip; Johnson, Chris; Atrey, Milind

2005-05-01

High field NMR spectrometers have been an essential tool for biomolecular scientists for many years. They have been instrumental in the pursuit of understanding of the structure, function and dynamics of proteins and other biological molecules. In addition, NMR is increasingly used for small molecule applications such as metabonomics, providing capabilities that aid drug discovery, as well as general organic and inorganic chemistry [M. Pellecchia et al., Nature Reviews Drug Discovery 1, 211 (2002)]. However, access to these systems is restricted due to the requirement to periodically refill them with liquid cryogens. This is both logistically demanding and expensive. A new system combining NMR spectrometry and Pulse Tube Refrigeration (PTR) has been developed and successfully tested. This approach eliminates the dependence on liquid cryogens, reduces spectrometer downtime, and also significantly reduces the size of the system. In the near future this new type of analytical tool may become ubiquitous in biomedical and chemical laboratories.

The nonlinear modified equation approach to analyzing finite difference schemes

NASA Technical Reports Server (NTRS)

Klopfer, G. H.; Mcrae, D. S.

1981-01-01

The nonlinear modified equation approach is taken in this paper to analyze the generalized Lax-Wendroff explicit scheme approximation to the unsteady one- and two-dimensional equations of gas dynamics. Three important applications of the method are demonstrated. The nonlinear modified equation analysis is used to (1) generate higher order accurate schemes, (2) obtain more accurate estimates of the discretization error for nonlinear systems of partial differential equations, and (3) generate an adaptive mesh procedure for the unsteady gas dynamic equations. Results are obtained for all three areas. For the adaptive mesh procedure, mesh point requirements for equal resolution of discontinuities were reduced by a factor of five for a 1-D shock tube problem solved by the explicit MacCormack scheme.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oughton, S.; Matthaeus, W. H.; Dmitruk, P.

Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examinedmore » here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.« less

Dynamic Testing of a Pre-stretched Flexible Tube for Identifying the Factors Affecting Modal Parameter Estimation

NASA Astrophysics Data System (ADS)

Unnikrishnan, Madhusudanan; Rajan, Akash; Basanthvihar Raghunathan, Binulal; Kochupillai, Jayaraj

2017-08-01

Experimental modal analysis is the primary tool for obtaining the fundamental dynamic characteristics like natural frequency, mode shape and modal damping ratio that determine the behaviour of any structure under dynamic loading conditions. This paper discusses about a carefully designed experimental method for calculating the dynamic characteristics of a pre-stretched horizontal flexible tube made of polyurethane material. The factors that affect the modal parameter estimation like the application time of shaker excitation, pause time between successive excitation cycles, averaging and windowing of measured signal, as well as the precautions to be taken during the experiment are explained in detail. The modal parameter estimation is done using MEscopeVESTM software. A finite element based pre-stressed modal analysis of the flexible tube is also done using ANSYS ver.14.0 software. The experimental and analytical results agreed well. The proposed experimental methodology may be extended for carrying out the modal analysis of many flexible structures like inflatables, tires and membranes.

Many Body Effects on Particle Diffusion in Polymer Nanocomposites

NASA Astrophysics Data System (ADS)

Dell, Zachary E.; Schweizer, Kenneth S.

2014-03-01

Recent statistical mechanical theories of nanoparticle motion in polymer melts and networks have focused on the dilute particle limit. By combining PRISM theory predictions for microscopic structural correlations, and a new formulation of self-consistent dynamical mode coupling theory, we extend dilute theories to finite filler loading. As a minimalist model, the polymer dynamics are first assumed to be unperturbed by the presence of the nanoparticles. The long time particle diffusivity in unentangled and entangled melts is determined as a function of polymer tube diameter and radius of gyration, nanoparticle diameter, and polymer-filler attraction strength under both constant volume and constant pressure situations. The influence of nanocomposite statistical structure (depletion, steric stabilization, bridging) on dynamics is also investigated. Using recent theoretical developments for predicting tube diameters in nanocomposites, the consequences of filler-induced tube dilation on nanoparticle motion is established. In entangled melts, increasing filler loading first modestly speeds up diffusion, and then dramatically when the inter-filler separation becomes smaller than the tube diameter. At very high loadings, a filler glass transition is generically predicted.

Places to Go: YouTube

ERIC Educational Resources Information Center

Downes, Stephen

2008-01-01

Founded in 2005 by three former PayPal employees, YouTube has revolutionized the Internet, marking a change from the static Internet to the dynamic Internet. In this edition of Places to Go, Stephen Downes discusses how the rise of a ubiquitous media format--Flash video--has made YouTube's success possible and argues that Flash video has important…

A novel method for calculating the dynamic capillary force and correcting the pressure error in micro-tube experiment.

PubMed

Wang, Shuoliang; Liu, Pengcheng; Zhao, Hui; Zhang, Yuan

2017-11-29

Micro-tube experiment has been implemented to understand the mechanisms of governing microcosmic fluid percolation and is extensively used in both fields of micro electromechanical engineering and petroleum engineering. The measured pressure difference across the microtube is not equal to the actual pressure difference across the microtube. Taking into account the additional pressure losses between the outlet of the micro tube and the outlet of the entire setup, we propose a new method for predicting the dynamic capillary pressure using the Level-set method. We first demonstrate it is a reliable method for describing microscopic flow by comparing the micro-model flow-test results against the predicted results using the Level-set method. In the proposed approach, Level-set method is applied to predict the pressure distribution along the microtube when the fluids flow along the microtube at a given flow rate; the microtube used in the calculation has the same size as the one used in the experiment. From the simulation results, the pressure difference across a curved interface (i.e., dynamic capillary pressure) can be directly obtained. We also show that dynamic capillary force should be properly evaluated in the micro-tube experiment in order to obtain the actual pressure difference across the microtube.

Equilibrium structure of solar magnetic flux tubes: Energy transport with multistream radiative transfer

NASA Technical Reports Server (NTRS)

Hasan, S. S.; Kalkofen, W.

1994-01-01

We examine the equilibrium structure of vertical intense magnetic flux tubes on the Sun. Assuming cylindrical geometry, we solve the magnetohydrostatic equations in the thin flux-tube approximation, allowing for energy transport by radiation and convection. The radiative transfer equation is solved in the six-stream approximation, assuming gray opacity and local thermodynamic equilibrium. This constitutes a significant improvement over a previous study, in which the transfer was solved using the multidimensional generalization of the Eddington approximation. Convection in the flux tube is treated using mixing-length theory, with an additional parameter alpha, characterizing the suppression of convective energy transport in the tube by the strong magnetic field. The equations are solved using the method of partial linearization. We present results for tubes with different values of the magnetic field strength and radius at a fixed depth in the atmosphere. In general, we find that, at equal geometric heights, the temperature on the tube axis, compared to the ambient medium, is higher in the photosphere and lower in the convection zone, with the difference becoming larger for thicker tubes. At equal optical depths the tubes are generally hotter than their surroundings. The results are comparatively insensitive to alpha but depend upon whether radiative and convective energy transport operate simultaneously or in separate layers. A comparison of our results with semiempirical models shows that the temperature and intensity contrast are in broad agreement. However, the field strengths of the flux-tube models are somewhat lower than the values inferred from observations.

Density Enhancements and Voids Following Patchy Reconnection

NASA Astrophysics Data System (ADS)

Guidoni, S. E.; Longcope, D. W.

2011-04-01

We show, through a simple patchy reconnection model, that retracting reconnected flux tubes may present elongated regions relatively devoid of plasma, as well as long lasting, dense central hot regions. Reconnection is assumed to happen in a small patch across a Syrovatskiiˇ (non-uniform) current sheet (CS) with skewed magnetic fields. The background magnetic pressure has its maximum at the center of the CS plane and decreases toward its edges. The reconnection patch creates two V-shaped reconnected tubes that shorten as they retract in opposite directions, due to magnetic tension. One of them moves upward toward the top edge of the CS, and the other one moves downward toward the top of the underlying arcade. Rotational discontinuities (RDs) propagate along the legs of the tubes and generate parallel supersonic flows that collide at the center of the tube. There, gas-dynamic shocks that compress and heat the plasma are launched outwardly. The descending tube moves through the bottom part of the CS where it expands laterally in response to the decreasing background magnetic pressure. This effect may decrease plasma density by 30%-50% of background levels. This tube will arrive at the top of the arcade that will slow it to a stop. Here, the perpendicular dynamics is halted, but the parallel dynamics continues along its legs; the RDs are shut down, and the gas is rarified to even lower densities. The hot post-shock regions continue evolving, determining a long lasting hot region on top of the arcade. We provide an observational method based on total emission measure and mean temperature that indicates where in the CS the tube has been reconnected.

Live-cell imaging of phosphatidic acid dynamics in pollen tubes visualized by Spo20p-derived biosensor.

PubMed

Potocký, Martin; Pleskot, Roman; Pejchar, Přemysl; Vitale, Nicolas; Kost, Benedikt; Zárský, Viktor

2014-07-01

Although phosphatidic acid (PA) is structurally the simplest membrane phospholipid, it has been implicated in the regulation of many cellular events, including cytoskeletal dynamics, membrane trafficking and stress responses. Plant PA shows rapid turnover but the information about its spatio-temporal distribution in plant cells is missing. Here we demonstrate the use of a lipid biosensor that enables us to monitor PA dynamics in plant cells. The biosensor consists of a PA-binding domain of yeast SNARE Spo20p fused to fluorescent proteins. Live-cell imaging of PA dynamics in transiently transformed tobacco (Nicotiana tabacum) pollen tubes was performed using confocal laser scanning microscopy. In growing pollen tubes, PA shows distinct annulus-like fluorescence pattern in the plasma membrane behind the extreme tip. Coexpression studies with markers for other plasmalemma signaling lipids phosphatidylinositol 4,5-bisphosphate and diacylglycerol revealed limited colocalization at the shoulders of the apex. PA distribution and concentrations show distinct responses to various lipid signaling inhibitors. Fluorescence recovery after photobleaching (FRAP) analysis suggests high PA turnover in the plasma membrane. Our data show that a biosensor based on the Spo20p-PA binding domain is suitable for live-cell imaging of PA also in plant cells. In tobacco pollen tubes, distinct subapical PA maximum corroborates its involvement in the regulation of endocytosis and actin dynamics. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

Event-by-Event Study of Space-Time Dynamics in Flux-Tube Fragmentation

DOE PAGES

Wong, Cheuk-Yin

2017-05-25

In the semi-classical description of the flux-tube fragmentation process for hadron production and hadronization in high-energymore » $e^+e^-$ annihilations and $pp$ collisions, the rapidity-space-time ordering and the local conservation laws of charge, flavor, and momentum provide a set of powerful tools that may allow the reconstruction of the space-time dynamics of quarks and mesons in exclusive measurements of produced hadrons, on an event-by-event basis. We propose procedures to reconstruct the space-time dynamics from event-by-event exclusive hadron data to exhibit explicitly the ordered chain of hadrons produced in a flux tube fragmentation. As a supplementary tool, we infer the average space-time coordinates of the $q$-$$\\bar q$$ pair production vertices from the $$\\pi^-$$ rapidity distribution data obtained by the NA61/SHINE Collaboration in $pp$ collisions at $$\\sqrt{s}$$ = 6.3 to 17.3 GeV.« less

Event-by-Event Study of Space-Time Dynamics in Flux-Tube Fragmentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wong, Cheuk-Yin

In the semi-classical description of the flux-tube fragmentation process for hadron production and hadronization in high-energymore » $e^+e^-$ annihilations and $pp$ collisions, the rapidity-space-time ordering and the local conservation laws of charge, flavor, and momentum provide a set of powerful tools that may allow the reconstruction of the space-time dynamics of quarks and mesons in exclusive measurements of produced hadrons, on an event-by-event basis. We propose procedures to reconstruct the space-time dynamics from event-by-event exclusive hadron data to exhibit explicitly the ordered chain of hadrons produced in a flux tube fragmentation. As a supplementary tool, we infer the average space-time coordinates of the $q$-$$\\bar q$$ pair production vertices from the $$\\pi^-$$ rapidity distribution data obtained by the NA61/SHINE Collaboration in $pp$ collisions at $$\\sqrt{s}$$ = 6.3 to 17.3 GeV.« less

21 CFR 872.6570 - Impression tube.

Code of Federal Regulations, 2010 CFR

2010-04-01

... DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6570 Impression tube. (a) Identification. An impression tube is a device consisting of a hollow copper tube intended to take an impression of a single tooth...) Classification. Class I (general controls). The device is exempt from the premarket notification procedures in...

The Fuge Tube Diode Array Spectrophotometer

ERIC Educational Resources Information Center

Arneson, B. T.; Long, S. R.; Stewart, K. K.; Lagowski, J. J.

2008-01-01

We present the details for adapting a diode array UV-vis spectrophotometer to incorporate the use of polypropylene microcentrifuge tubes--fuge tubes--as cuvettes. Optical data are presented validating that the polyethylene fuge tubes are equivalent to the standard square cross section polystyrene or glass cuvettes generally used in…

General Information About Ovarian, Fallopian Tube, and Primary Peritoneal Cancer

MedlinePlus

... condition or to keep cancer from starting. General Information About Ovarian, Fallopian Tube, and Primary Peritoneal Cancer ... PDQ Screening and Prevention Editorial Board . Clinical Trial Information A clinical trial is a study to answer ...

A Kolsky tension bar technique using a hollow incident tube

NASA Astrophysics Data System (ADS)

Guzman, O.; Frew, D. J.; Chen, W.

2011-04-01

Load control of the incident pulse profiles in compression Kolsky bar experiments has been widely used to subject the specimen to optimal testing conditions. Tension Kolsky bars have been used to determine dynamic material behavior since the 1960s with limited capability to shape the loading pulses due to the pulse-generating mechanisms. We developed a modified Kolsky tension bar where a hollow incident tube is used to carry the incident stress waves. The incident tube also acts as a gas gun barrel that houses the striker for impact. The main advantage of this new design is that the striker impacts on an impact cap of the incident tube. Compression pulse shapers can be attached to the impact cap, thus fully utilizing the predictive compression pulse-shaping capability in tension experiments. Using this new testing technique, the dynamic tensile material behavior for Al 6061-T6511 and TRIP 800 (transformation-induced plasticity) steel has been obtained.

Linearized traveling wave amplifier with hard limiter characteristics

NASA Technical Reports Server (NTRS)

Kosmahl, H. G. (Inventor)

1986-01-01

A dynamic velocity taper is provided for a traveling wave tube with increased linearity to avoid intermodulation of signals being amplified. In a traveling wave tube, the slow wave structure is a helix including a sever. A dynamic velocity taper is provided by gradually reducing the spacing between the repeating elements of the slow wave structure which are the windings of the helix. The reduction which takes place coincides with the ouput point of helix. The spacing between the repeating elements of the slow wave structure is ideally at an exponential rate because the curve increases the point of maximum efficiency and power, at an exponential rate. A coupled cavity traveling wave tube having cavities is shown. The space between apertured discs is gradually reduced from 0.1% to 5% at an exponential rate. Output power (or efficiency) versus input power for a commercial tube is shown.

Customized Videos on a YouTube Channel: A beyond the Classroom Teaching and Learning Platform for General Chemistry Courses

ERIC Educational Resources Information Center

Ranga, Jayashree S.

2017-01-01

Videos are an integral part of online courses. In this study, customized YouTube videos were explored as teaching and learning materials in place of face-to-face discussion sessions in General Chemistry courses. The videos were created using a budget-friendly and interactive app on an iPad. The customized YouTube videos were available to students…

21 CFR 868.5780 - Tube introduction forceps.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) Identification. Tube introduction forceps (e.g., Magill forceps) are a right-angled device used to grasp a tracheal tube and place it in a patient's trachea. (b) Classification. Class I (general controls). The...

21 CFR 868.5780 - Tube introduction forceps.

Code of Federal Regulations, 2011 CFR

2011-04-01

...) Identification. Tube introduction forceps (e.g., Magill forceps) are a right-angled device used to grasp a tracheal tube and place it in a patient's trachea. (b) Classification. Class I (general controls). The...

21 CFR 868.5780 - Tube introduction forceps.

Code of Federal Regulations, 2014 CFR

2014-04-01

...) Identification. Tube introduction forceps (e.g., Magill forceps) are a right-angled device used to grasp a tracheal tube and place it in a patient's trachea. (b) Classification. Class I (general controls). The...

21 CFR 868.5780 - Tube introduction forceps.

Code of Federal Regulations, 2012 CFR

2012-04-01

...) Identification. Tube introduction forceps (e.g., Magill forceps) are a right-angled device used to grasp a tracheal tube and place it in a patient's trachea. (b) Classification. Class I (general controls). The...

21 CFR 868.5780 - Tube introduction forceps.

Code of Federal Regulations, 2013 CFR

2013-04-01

...) Identification. Tube introduction forceps (e.g., Magill forceps) are a right-angled device used to grasp a tracheal tube and place it in a patient's trachea. (b) Classification. Class I (general controls). The...

Microscopic theory of topologically entangled fluids of rigid macromolecules

NASA Astrophysics Data System (ADS)

Sussman, Daniel M.; Schweizer, Kenneth S.

2011-06-01

We present a first-principles theory for the slow dynamics of a fluid of entangling rigid crosses of zero excluded volume based on a generalization of the dynamic mean-field approach of Szamel for infinitely thin nonrotating rods. The latter theory exactly includes topological constraints at the two-body collision level and self-consistently renormalizes an effective diffusion tensor to account for many-body effects. Remarkably, it predicts scaling laws consistent with the phenomenological reptation-tube predictions of Doi and Edwards for the long-time diffusion and the localization length in the heavily entangled limit. We generalize this approach to a different macromolecular architecture, infinitely thin three-dimensional crosses, and also extend the range of densities over which a dynamic localization length can be calculated for rods. Ideal gases of nonrotating crosses have recently received attention in computer simulations and are relevant as a simple model of both a strong-glass former and entangling star-branched polymers. Comparisons of our theory with these simulations reveal reasonable agreement for the magnitude and reduced density dependence of the localization length and also the self-diffusion constant if the consequences of local density fluctuations are taken into account.

Morphogenesis of the mouse neural plate depends on distinct roles of cofilin 1 in apical and basal epithelial domains

PubMed Central

Grego-Bessa, Joaquim; Hildebrand, Jeffrey; Anderson, Kathryn V.

2015-01-01

The genetic control of mammalian epithelial polarity and dynamics can be studied in vivo at cellular resolution during morphogenesis of the mouse neural tube. The mouse neural plate is a simple epithelium that is transformed into a columnar pseudostratified tube over the course of ∼24 h. Apical F-actin is known to be important for neural tube closure, but the precise roles of actin dynamics in the neural epithelium are not known. To determine how the organization of the neural epithelium and neural tube closure are affected when actin dynamics are blocked, we examined the cellular basis of the neural tube closure defect in mouse mutants that lack the actin-severing protein cofilin 1 (CFL1). Although apical localization of the adherens junctions, the Par complex, the Crumbs complex and SHROOM3 is normal in the mutants, CFL1 has at least two distinct functions in the apical and basal domains of the neural plate. Apically, in the absence of CFL1 myosin light chain does not become phosphorylated, indicating that CFL1 is required for the activation of apical actomyosin required for neural tube closure. On the basal side of the neural plate, loss of CFL1 has the opposite effect on myosin: excess F-actin and myosin accumulate and the ectopic myosin light chain is phosphorylated. The basal accumulation of F-actin is associated with the assembly of ectopic basal tight junctions and focal disruptions of the basement membrane, which eventually lead to a breakdown of epithelial organization. PMID:25742799

Method and system for small scale pumping

DOEpatents

Insepov, Zeke [Darien, IL; Hassanein, Ahmed [Bolingbrook, IL

2010-01-26

The present invention relates generally to the field of small scale pumping and, more specifically, to a method and system for very small scale pumping media through microtubes. One preferred embodiment of the invention generally comprises: method for small scale pumping, comprising the following steps: providing one or more media; providing one or more microtubes, the one or more tubes having a first end and a second end, wherein said first end of one or more tubes is in contact with the media; and creating surface waves on the tubes, wherein at least a portion of the media is pumped through the tube.

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.

The Prediction of Microstructure Evolution of 6005A Aluminum Alloy in a P-ECAP Extrusion Study

NASA Astrophysics Data System (ADS)

Lei, Shi; Jiu-Ba, Wen; Chang, Ren

2018-05-01

Finite element modeling (FEM) was applied for predicting the recrystallized structure in extruded 6005 aluminum alloy, and simulated results were experimentally validated. First, microstructure evolution of 6005 aluminum alloy during deformation was studied by means of isothermal compression test, where the processing parameters were chosen to reproduce the typical industrial conditions. Second, microstructure evolution was analyzed, and the obtained information was used to fit a dynamic recrystallization model implementing inside the DEFORM-3D FEM code environment. FEM of deformation of 6005 aluminum has been established and validated by microstructure comparison. Finally, the obtained dynamic recrystallization model was applied to tube extrusion by using a portholes-equal channel angular pressing die. The finite element analysis results showed that coarse DRX grains occur in the extruded tube at higher temperature and in the extruded tube at the faster speed of the stem. The test results showed material from the front end of the extruded tube has coarse grains (60 μm) and other extruded tube has finer grains (20 μm).

The Prediction of Microstructure Evolution of 6005A Aluminum Alloy in a P-ECAP Extrusion Study

NASA Astrophysics Data System (ADS)

Lei, Shi; Jiu-Ba, Wen; Chang, Ren

2018-04-01

Finite element modeling (FEM) was applied for predicting the recrystallized structure in extruded 6005 aluminum alloy, and simulated results were experimentally validated. First, microstructure evolution of 6005 aluminum alloy during deformation was studied by means of isothermal compression test, where the processing parameters were chosen to reproduce the typical industrial conditions. Second, microstructure evolution was analyzed, and the obtained information was used to fit a dynamic recrystallization model implementing inside the DEFORM-3D FEM code environment. FEM of deformation of 6005 aluminum has been established and validated by microstructure comparison. Finally, the obtained dynamic recrystallization model was applied to tube extrusion by using a portholes-equal channel angular pressing die. The finite element analysis results showed that coarse DRX grains occur in the extruded tube at higher temperature and in the extruded tube at the faster speed of the stem. The test results showed material from the front end of the extruded tube has coarse grains (60 μm) and other extruded tube has finer grains (20 μm).

The heart tube forms and elongates through dynamic cell rearrangement coordinated with foregut extension.

PubMed

Kidokoro, Hinako; Yonei-Tamura, Sayuri; Tamura, Koji; Schoenwolf, Gary C; Saijoh, Yukio

2018-03-29

In the initiation of cardiogenesis, the heart primordia transform from bilateral flat sheets of mesoderm into an elongated midline tube. Here, we discover that this rapid architectural change is driven by actomyosin-based oriented cell rearrangement and resulting dynamic tissue reshaping (convergent extension, CE). By labeling clusters of cells spanning the entire heart primordia, we show that the heart primordia converge toward the midline to form a narrow tube, while extending perpendicularly to rapidly lengthen it. Our data for the first time visualize the process of early heart tube formation from both the medial (second) and lateral (first) heart fields, revealing that both fields form the early heart tube by essentially the same mechanism. Additionally, the adjacent endoderm coordinately forms the foregut through previously unrecognized movements that parallel those of the heart mesoderm and elongates by CE. In conclusion, our data illustrate how initially two-dimensional flat primordia rapidly change their shapes and construct the three-dimensional morphology of emerging organs in coordination with neighboring morphogenesis. © 2018. Published by The Company of Biologists Ltd.

In-Situ Imaging of Particles during Rapid Thermite Deflagrations

NASA Astrophysics Data System (ADS)

Grapes, Michael; Sullivan, Kyle; Reeves, Robert; Densmore, John; Willey, Trevor; van Buuren, Tony; Fezaa, Kamel

The dynamic behavior of rapidly deflagrating thermites is a highly complex process involving rapid decomposition, melting, and outgassing of intermediate and/or product gases. Few experimental techniques are capable of probing these phenomena in situ due to the small length and time scales associated with the reaction. Here we use a recently developed extended burn tube test, where we initiate a small pile of thermite on the closed end of a clear acrylic tube. The length of the tube is sufficient to fully contain the reaction as it proceeds and flows entrained particles down the tube. This experiment was brought to the Advanced Photon Source, and the particle formation was X-ray imaged at various positions down the tube. Several formulations, as well as formulation parameters were varied to investigate the size and morphology of the particles, as well as to look for dynamic behavior attributed to the reaction. In all cases, we see evidence of particle coalescence and condensed-phase interfacial reactions. The results improve our understanding of the procession of reactants to products in these systems. Funding provided by the LLNL LDRD program (PLS-16FS-028).

Clinical use and material wear of polymeric tracheostomy tubes.

PubMed

Björling, Gunilla; Axelsson, Sara; Johansson, Unn-Britt; Lysdahl, Michael; Markström, Agneta; Schedin, Ulla; Aune, Ragnhild E; Frostell, Claes; Karlsson, Sigbritt

2007-09-01

The objectives were to compare the duration of use of polymeric tracheostomy tubes, i.e., silicone (Si), polyvinyl chloride (PVC), and polyurethane (PU), and to determine whether surface changes in the materials could be observed after 30 days of patient use. Data were collected from patient and technical records for all tracheostomized patients attending the National Respiratory Center in Sweden. In the surface study, 19 patients with long-term tracheostomy were included: six with Bivona TTS Si tubes, eight with Shiley PVC tubes, and five with Trachoe Twist PU tubes. All tubes were exposed in the trachea for 30 days before being analyzed by scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). New tubes and tubes exposed in phosphate-buffered saline were used as reference. Si tubes are used for longer periods of time than those made of PVC (P<.0001) and PU (P=.021). In general, all polymeric tubes were used longer than the recommended 30-day period. Eighteen of the 19 tubes exposed in patients demonstrated, in one or more areas of the tube, evident surface changes. The morphologic changes identified by SEM correlate well with the results obtained by ATR-FTIR. Si tracheostomy tubes are in general used longer than those made of PVC and PU. Most of the tubes exposed in the trachea for 30 days suffered evident surface changes, with degradation of the polymeric chains as a result.

Dynamics of Voluntary Cough Maneuvers

NASA Astrophysics Data System (ADS)

Naire, Shailesh

2008-11-01

Voluntary cough maneuvers are characterized by transient peak expiratory flows (PEF) exceeding the maximum expiratory flow-volume (MEFV) curve. In some cases, these flows can be well in excess of the MEFV, generally referred to as supramaximal flows. Understanding the flow-structure interaction involved in these maneuvers is the main goal of this work. We present a simple theoretical model for investigating the dynamics of voluntary cough and forced expiratory maneuvers. The core modeling idea is based on a 1-D model of high Reynolds number flow through flexible-walled tubes. The model incorporates key ingredients involved in these maneuvers: the expiratory effort generated by the abdominal and expiratory muscles, the glottis and the flexibility and compliance of the lung airways. Variations in these allow investigation of the expiratory flows generated by a variety of single cough maneuvers. The model successfully reproduces PEF which is shown to depend on the cough generation protocol, the glottis reopening time and the compliance of the airways. The particular highlight is in simulating supramaximal PEF for very compliant tubes. The flow-structure interaction mechanisms behind these are discussed. The wave speed theory of flow limitation is used to characterize the PEF. Existing hypotheses of the origin of PEF, from cough and forced expiration experiments, are also tested using this model.

An MHD 3-D solution to the evolution of a CME observed by the STEREO mission on May 2007

NASA Astrophysics Data System (ADS)

Berdichevsky, D. B.; Stenborg, G. A.

2009-12-01

Nature offers a variety of examples on the dynamics of matter trapped electromagnetic fields. In particular, sudden ejections of large amounts of solar mass embedded in magnetic field structures develop in the heliosphere, their evolution being affected by the background solar wind. Their plasma and magnetic field values can be obtained by in-situ instruments onboard existing space missions. A particular example of such process is the passage of a magnetic field flux tube-like structure (~ 0.1 AU in cross section) exhibiting a flux-rope topology observed on May 2007 with their in-situ instruments by the Venus Express and Messenger missions. STEREO remote observations obtained with the SECCHI instruments allowed the tracking of this quite weak event from its origins in the Sun to approximately the orbit of Mercury. In this work, we i) discuss on the dynamic evolution of the event as described by the magnetic force-free magneto-hydrodynamic solution proposed in [1], and ii) generalize it to add curvature to the MHD solution. The magneto-hydrodynamic analytical solution obtained allows us to make quantitative estimates on the size of the flux tube just after the ejection, magnetic field intensity, and mass density. [1] Berdichevsky, DB, RP Lepping, and CJ Farrugia, Phys Rev E, 67(3), 036405, 2003.

Ceramic vacuum tubes for geothermal well logging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, R.D.

1977-01-01

Useful design data acquired in the evaluation of ceramic vacuum tubes for the development of a 500/sup 0/C instrumentation amplifier are presented. The general requirements for ceramic vacuum tubes are discussed for application to the development of high temperature well logs. Commercially available tubes are described and future contract activities that specifically relate to ceramic vacuum tubes are detailed. Supplemental data are presented in the appendix.

26 CFR 48.4221-7 - Tax-free sales of tires and tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 26 Internal Revenue 16 2010-04-01 2010-04-01 true Tax-free sales of tires and tubes. 48.4221-7... Tax-free sales of tires and tubes. (a) In general. A manufacturer of tires or inner tubes that are... articles taxable under section 4071 may be sold tax free: (1) The tire or tube is sold for use by the...

27 CFR 40.384 - Disposal of forfeited, condemned, and abandoned cigarette papers and tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

..., condemned, and abandoned cigarette papers and tubes. 40.384 Section 40.384 Alcohol, Tobacco Products and... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes General § 40.384 Disposal of forfeited, condemned, and abandoned cigarette papers and...

27 CFR 40.384 - Disposal of forfeited, condemned, and abandoned cigarette papers and tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

..., condemned, and abandoned cigarette papers and tubes. 40.384 Section 40.384 Alcohol, Tobacco Products and... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes General § 40.384 Disposal of forfeited, condemned, and abandoned cigarette papers and...

49 CFR 393.45 - Brake tubing and hoses; hose assemblies and end fittings.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 49 Transportation 5 2013-10-01 2013-10-01 false Brake tubing and hoses; hose assemblies and end... assemblies and end fittings. (a) General construction requirements for tubing and hoses, assemblies, and end fittings. All brake tubing and hoses, brake hose assemblies, and brake hose end fittings must meet the...

49 CFR 393.45 - Brake tubing and hoses; hose assemblies and end fittings.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 49 Transportation 5 2011-10-01 2011-10-01 false Brake tubing and hoses; hose assemblies and end... assemblies and end fittings. (a) General construction requirements for tubing and hoses, assemblies, and end fittings. All brake tubing and hoses, brake hose assemblies, and brake hose end fittings must meet the...

49 CFR 393.45 - Brake tubing and hoses; hose assemblies and end fittings.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 49 Transportation 5 2014-10-01 2014-10-01 false Brake tubing and hoses; hose assemblies and end... assemblies and end fittings. (a) General construction requirements for tubing and hoses, assemblies, and end fittings. All brake tubing and hoses, brake hose assemblies, and brake hose end fittings must meet the...

27 CFR 40.384 - Disposal of forfeited, condemned, and abandoned cigarette papers and tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

..., condemned, and abandoned cigarette papers and tubes. 40.384 Section 40.384 Alcohol, Tobacco Products and... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes General § 40.384 Disposal of forfeited, condemned, and abandoned cigarette papers and...

27 CFR 40.384 - Disposal of forfeited, condemned, and abandoned cigarette papers and tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

..., condemned, and abandoned cigarette papers and tubes. 40.384 Section 40.384 Alcohol, Tobacco Products and... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes General § 40.384 Disposal of forfeited, condemned, and abandoned cigarette papers and...

27 CFR 40.384 - Disposal of forfeited, condemned, and abandoned cigarette papers and tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

..., condemned, and abandoned cigarette papers and tubes. 40.384 Section 40.384 Alcohol, Tobacco Products and... MANUFACTURE OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO Manufacture of Cigarette Papers and Tubes General § 40.384 Disposal of forfeited, condemned, and abandoned cigarette papers and...

Screening for Generalized Anxiety Disorder (GAD)

MedlinePlus

... Print this form Follow Us Facebook Twitter RSS YouTube Advertisement Find A Therapist Search our directory of ... direct service organization. Follow Us Facebook Twitter RSS YouTube Follow Us Facebook Twitter YouTube LinkedIn ADAA is ...

Magnetic merging in colliding flux tubes

NASA Technical Reports Server (NTRS)

Zweibel, Ellen G.; Rhoads, James E.

1995-01-01

We develop an analytical theory of reconnection between colliding, twisted magnetic flux tubes. Our analysis is restricted to direct collisions between parallel tubes and is based on the collision dynamics worked out by Bogdan (1984). We show that there is a range of collision velocities for which neutral point reconnection of the Parker-Sweet type can occur, and a smaller range for which reconnection leads to coalescence. Mean velocities within the solar convection zone are probably significantly greater than the upper limit for coalescence. This suggests that the majority of flux tube collisions do not result in merging, unless the frictional coupling of the tubes to the background flow is extremely strong.

High-fidelity gravity modeling applied to spacecraft trajectories and lunar interior analysis

NASA Astrophysics Data System (ADS)

Chappaz, Loic P. R.

As the complexity and boldness of emerging mission proposals increase, and with the rapid evolution of the available computational capabilities, high-accuracy and high-resolution gravity models and the tools to exploit such models are increasingly attractive within the context of spaceflight mechanics, mission design and analysis, and planetary science in general. First, in trajectory design applications, a gravity representation for the bodies of interest is, in general, assumed and exploited to determine the motion of a spacecraft in any given system. The focus is the exploration of trajectories in the vicinity of a system comprised of two small irregular bodies. Within this context, the primary bodies are initially modeled as massive ellipsoids and tools to construct third-body trajectories are developed. However, these dynamical models are idealized representations of the actual dynamical regime and do not account for any perturbing effects. Thus, a robust strategy to maintain a spacecraft near reference third-body trajectories is constructed. Further, it is important to assess the perturbing effect that dominates the dynamics of the spacecraft in such a region as a function of the baseline orbit. Alternatively, the motion of the spacecraft around a given body may be known to extreme precision enabling the derivation of a very high-accuracy gravity field for that body. Such knowledge can subsequently be exploited to gain insight into specific properties of the body. The success of the NASA's GRAIL mission ensures that the highest resolution and most accurate gravity data for the Moon is now available. In the GRAIL investigation, the focus is on the specific task of detecting the presence and extent of subsurface features, such as empty lava tubes beneath the mare surface. In addition to their importance for understanding the emplacement of the mare flood basalts, open lava tubes are of interest as possible habitation sites safe from cosmic radiation and micrometeorite impacts. Tools are developed to best exploit the rich gravity data toward the numerical detection of such small features.

Liquid oscillations in a U-tube

NASA Astrophysics Data System (ADS)

Munguía Aguilar, Horacio; Maldonado, Rigoberto Franco; Barba Navarro, Luis

2018-01-01

In hydrostatics, pressure measurement with U-gauges and their relationship to density is a well-known experiment. Very little is studied or experimented with the dynamics of the movement of a liquid in a U-tube probably due to its theoretical complexity but, after all, it is a simple damped oscillating system. In this paper we present a relatively simple experiment that allows studying in some detail the dynamics of the movement of a liquid in a U-tube when an initial pressure gradient is applied. In order to record the information of the column displacement as a function of time we have developed a position sensor system based on a solar cell that allows the recording of the experiment using a simple data acquisition system.

Kinematics and dynamics of vortex rings in a tube

NASA Technical Reports Server (NTRS)

Brasseur, J. G.

1979-01-01

Kinematic theory and flow visualization experiments were combined to examine the dynamic processes which control the evolution of vortex rings from very low to very high Reynolds numbers, and to assess the effects of the wall as a vortex ring travels up a tube. The kinematic relationships among the size, shape, speed, and strength of vortex rings in a tube were computed from the theory. Relatively simple flow visualization measurements were used to calculate the total circulation of a vortex rings at a given time. Using this method, the strength was computated and plotted as a function of time for experimentally produced vortex rings. Reynolds number relationships are established and quantitative differences among the three Reynolds number groups are discussed.

Modeling and Simulation of U-tube Steam Generator

NASA Astrophysics Data System (ADS)

Zhang, Mingming; Fu, Zhongguang; Li, Jinyao; Wang, Mingfei

2018-03-01

The U-tube natural circulation steam generator was mainly researched with modeling and simulation in this article. The research is based on simuworks system simulation software platform. By analyzing the structural characteristics and the operating principle of U-tube steam generator, there are 14 control volumes in the model, including primary side, secondary side, down channel and steam plenum, etc. The model depends completely on conservation laws, and it is applied to make some simulation tests. The results show that the model is capable of simulating properly the dynamic response of U-tube steam generator.

Flux-split algorithms for flows with non-equilibrium chemistry and vibrational relaxation

NASA Technical Reports Server (NTRS)

Grossman, B.; Cinnella, P.

1990-01-01

The present consideration of numerical computation methods for gas flows with nonequilibrium chemistry thermodynamics gives attention to an equilibrium model, a general nonequilibrium model, and a simplified model based on vibrational relaxation. Flux-splitting procedures are developed for the fully-coupled inviscid equations encompassing fluid dynamics and both chemical and internal energy-relaxation processes. A fully coupled and implicit large-block structure is presented which embodies novel forms of flux-vector split and flux-difference split algorithms valid for nonequilibrium flow; illustrative high-temperature shock tube and nozzle flow examples are given.

Anisotropic Nanomechanics of Boron Nitride Nanotubes: Nanostructured "Skin" Effect

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Menon, Madhu; Cho, KyeongJae

2000-01-01

The stiffness and plasticity of boron nitride nanotubes are investigated using generalized tight-binding molecular dynamics and ab-initio total energy methods. Due to boron-nitride BN bond buckling effects, compressed zigzag BN nanotubes are found to undergo novel anisotropic strain release followed by anisotropic plastic buckling. The strain is preferentially released towards N atoms in the rotated BN bonds. The tubes buckle anisotropically towards only one end when uniaxially compressed from both. A "skin-effect" model of smart nanocomposite materials is proposed which will localize the structural damage towards the 'skin' or surface side of the material.

Heat transfer simulation of unsteady swirling flow in a vortex tube

NASA Astrophysics Data System (ADS)

Veretennikov, S. V.; Piralishvili, Sh A.; Evdokimov, O. A.; Guryanov, A. I.

2018-03-01

Effectiveness of not-adiabatic vortex tube application in the cooling systems of gas turbine blades depends on characteristics of swirling flows formed in the energy separation chamber. An analysis of the flow structure in the vortex tube channels has shown a presence of a complex three-dimensional spiral vortex, formed under relatively high turbulence intensity and vortex core precession. This indicates the presence of a significant unsteady flow in the energy separation chamber of the vortex tube that has a great influence on convective heat transfer of the swirling flow to the inner surface of tube. The paper contains the results of investigation of gas dynamics and heat transfer in the vortex tube taking into account the flow unsteadiness.

O+ trough zones in the polar cap ionosphere-magnetosphere coupling region

NASA Astrophysics Data System (ADS)

Horwitz, James; Zeng, Wen; Jaafari, Fajer

Regions of low-density troughs in O+ have been observed at 1 RE altitude in the polar cap ionosphere-magnetosphere region by the Thermal Ion Dynamics Experiment(TIDE) on the POLAR spacecraft. In this presentation, the UT Arlington Dynamic Fluid-Kinetic (DyFK) code is employed to investigate the formation of such O+ density troughs. We utilize convection paths of flux tubes in the high-latitude region as prescribed by an empirical convection model with solar wind inputs to track the evolution of ionospheric plasma transport and in particular O+ densities along these tubes with time/space. The flux tubes are subjected to auroral processes of precipitation and wave-driven ion heating when they pass through the auroral oval, which tends to elevate the plasma densities in these tubes. When the F-regions of such tubes traverse locations where the F-region is in darkness, recombination there causes the higher-altitude regions to drain and the densities to decline throughout. Owing to the varying effects of these processes, significant and low trough-like densities at higher altitudes developed along these flux tubes. The modeled densities near 6000 km altitudes will be compared with multiple POLAR passes featuring POLAR/TIDE-measured O+ densities for inside and outside of such trough regions.

[The dynamics of calcium distribution in stigma and style of lettuce (Lactuca sativa L.) before and after pollination].

PubMed

Qiu, Yi Lan; Liu, Ru Shi; Xie, Chao Tian; Yang, Yan Hong; Gu, Li; Tian, Hui Qiao

2005-08-01

Potassium antimonite was used to deposit calcium in the stigma and style of lettuce (Lactuca sativa L.) before and after pollination. The stigma of lettuce is two splits. Abundant calcium granules are displayed in the wall of papillae on the receptive surface of stigma before and after pollination, which may facilitate pollen germination. However, a few calcium granules in the wall of epidermis cell on no-receptive surface. Calcium distribution in style presents a gradient in transmitting tissue and parenchyma cells from the top to the base of the style before pollination. After pollination, calcium in transmitting tissue distinctly increased and its gradient distribution became more evident. Pollen tubes grow in the intercellular gaps of transmitting tissue. When pollen tubes grew into transmitting tissue, calcium granules in parenchyma around transmitting tissue decreased, suggesting a calcium movement was controlled by pollen tubes. The calcium gradient distribution also appeared in the trachea of vascular bundle of style. In general, calcium in style displays a feature of time-special distribution: transmitting tissue doesn't need much more calcium that is only stored in the parenchyma before pollination. However, calcium in parenchyma cells may be transported to transmitting tissue and make the latter contain more calcium to form an evident calcium gradient and meet the requirement of pollen tubes directionally growing after pollination. This is the second sample of calcium gradient existing in style, which was found by using potassium antimonite method.

27 CFR 44.65 - Liability for tax on tobacco products, and cigarette papers and tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... tobacco products, and cigarette papers and tubes. 44.65 Section 44.65 Alcohol, Tobacco Products and... EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.65 Liability for tax on tobacco products, and cigarette papers and tubes. The...

27 CFR 44.65 - Liability for tax on tobacco products, and cigarette papers and tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... tobacco products, and cigarette papers and tubes. 44.65 Section 44.65 Alcohol, Tobacco Products and... EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.65 Liability for tax on tobacco products, and cigarette papers and tubes. The...

27 CFR 44.65 - Liability for tax on tobacco products, and cigarette papers and tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... tobacco products, and cigarette papers and tubes. 44.65 Section 44.65 Alcohol, Tobacco Products and... EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.65 Liability for tax on tobacco products, and cigarette papers and tubes. The...

27 CFR 44.65 - Liability for tax on tobacco products, and cigarette papers and tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... tobacco products, and cigarette papers and tubes. 44.65 Section 44.65 Alcohol, Tobacco Products and... EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.65 Liability for tax on tobacco products, and cigarette papers and tubes. The...

27 CFR 44.65 - Liability for tax on tobacco products, and cigarette papers and tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... tobacco products, and cigarette papers and tubes. 44.65 Section 44.65 Alcohol, Tobacco Products and... EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.65 Liability for tax on tobacco products, and cigarette papers and tubes. The...

Using Additive Manufacturing to Optimize FLiBe Coolant Blanket in Fusion Reactors

NASA Astrophysics Data System (ADS)

Fry, Vincent Michael

Fusion reactors have often been hailed as the holy grail of clean energy generation, though a power-generating reactor has never been built due to a multitude of limiting factors. One such factor is the immense 12-15 MW/m2 heat fluxes experienced by the inner wall of the reactor. Multiple groups have proposed the use of tungsten swirl tubes to withstand the heat generated within the reactor core. The primary focus of this investigation is to parameterize this 'first wall' interior structure to determine the highest achievable heat transfer coefficient given the many tungsten configurations enabled via additive manufacturing. Two general tube structures were considered: an orthogonal three-dimensional mesh of various diameters and spacings, as well as a swirl tube geometry with varying 'tape' thicknesses. The coolant liquid proposed is FLiBe (2LiF-BeF2) due to its high specific heat capacity as well as its ability to breed tritium, the fuel for the reactor. This was accomplished using theoretical calculations; computational fluid dynamics and conjugate heat transfer simulations in ANSYS Workbench; as well as an experimental setup to confirm tube pressure drop along the pipe. It was determined that heat transfer coefficients between upwards of 60,000 W/m 2K were readily achievable, keeping the first wall temperature around 1300 K. A multitude of designs proved to be feasible given the pumping power restrictions, though the suggested design going forward is a swirl tube with 2 mm 'tape' thickness and 3 m/s inlet velocity. Simulated pressure drop with water was accurate to within 30% of experimentally measured values, giving confidence in the credibility of the results.

Deployment Simulation Methods for Ultra-Lightweight Inflatable Structures

NASA Technical Reports Server (NTRS)

Wang, John T.; Johnson, Arthur R.

2003-01-01

Two dynamic inflation simulation methods are employed for modeling the deployment of folded thin-membrane tubes. The simulations are necessary because ground tests include gravity effects and may poorly represent deployment in space. The two simulation methods are referred to as the Control Volume (CV) method and the Arbitrary Lagrangian Eulerian (ALE) method. They are available in the LS-DYNA nonlinear dynamic finite element code. Both methods are suitable for modeling the interactions between the inflation gas and the thin-membrane tube structures. The CV method only considers the pressure induced by the inflation gas in the simulation, while the ALE method models the actual flow of the inflation gas. Thus, the transient fluid properties at any location within the tube can be predicted by the ALE method. Deployment simulations of three packaged tube models; namely coiled, Z-folded, and telescopically-folded configurations, are performed. Results predicted by both methods for the telescopically-folded configuration are correlated and computational efficiency issues are discussed.

27 CFR 40.431 - General.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TOBACCO Manufacture of Cigarette Papers and Tubes Operations by Manufacturers § 40.431 General. Every manufacturer of cigarette papers and tubes must provide a true and accurate inventory on TTB Form 5230.2 in accordance with instructions for the form. Such inventory is subject to verification by the appropriate TTB...

Unsteady numerical simulation of the flow in the U9 Kaplan turbine model

NASA Astrophysics Data System (ADS)

Javadi, Ardalan; Nilsson, Håkan

2014-03-01

The Reynolds-averaged Navier-Stokes equations with the RNG k-ε turbulence model closure are utilized to simulate the unsteady turbulent flow throughout the whole flow passage of the U9 Kaplan turbine model. The U9 Kaplan turbine model comprises 20 stationary guide vanes and 6 rotating blades (696.3 RPM), working at best efficiency load (0.71 m3/s). The computations are conducted using a general finite volume method, using the OpenFOAM CFD code. A dynamic mesh is used together with a sliding GGI interface to include the effect of the rotating runner. The clearance is included in the guide vane. The hub and tip clearances are also included in the runner. An analysis is conducted of the unsteady behavior of the flow field, the pressure fluctuation in the draft tube, and the coherent structures of the flow. The tangential and axial velocity distributions at three sections in the draft tube are compared against LDV measurements. The numerical result is in reasonable agreement with the experimental data, and the important flow physics close to the hub in the draft tube is captured. The hub and tip vortices and an on-axis forced vortex are captured. The numerical results show that the frequency of the forced vortex in 1/5 of the runner rotation.

Filmwise Condensation on Low Integral-Fin Tubes of Different Diameter

DTIC Science & Technology

1988-12-01

the prime mover of condensate . Therefore, the Nusselt analysis was not valid for finned tubes. They therefore divided the finned tube into two regions...the objectives of this thesis. Prior to these modifications, cooling water to the secondary condenser was con- tained in two helically wound coils made...temperature difference across condensate film (K), il = dynamic viscosity of condensate (N. s/m 2). By substituting the Nusselt - and the Sieder-Tate

Numerical and Experimental Case Study of Blasting Works Effect

NASA Astrophysics Data System (ADS)

Papán, Daniel; Valašková, Veronika; Drusa, Marian

2016-10-01

This article introduces the theoretical and experimental case study of dynamic monitoring of the geological environment above constructed highway tunnel. The monitored structure is in this case a very important water supply pipeline, which crosses the tunnel and was made from steel tubes with a diameter of 800 mm. The basic dynamic parameters had been monitored during blasting works, and were compared with the FEM (Finite Element Method) calculations and checked by the Slovak standard limits. A calibrated FEM model based on the experimental measurement data results was created and used in order to receive more realistic results in further predictions, time and space extrapolations. This case study was required and demanded by the general contractor company and also by the owner of water pipeline, and it was an answer of public safety evaluation of risks during tunnel construction.

Probing Phonon Dynamics in Individual Single-Walled Carbon Nanotubes.

PubMed

Jiang, Tao; Hong, Hao; Liu, Can; Liu, Wei-Tao; Liu, Kaihui; Wu, Shiwei

2018-04-11

Interactions between elementary excitations, such as carriers, phonons, and plasmons, are critical for understanding the optical and electronic properties of materials. The significance of these interactions is more prominent in low-dimensional materials and can dominate their physical properties due to the enhanced interactions between these excitations. One-dimensional single-walled carbon nanotubes provide an ideal system for studying such interactions due to their perfect physical structures and rich electronic properties. Here we investigated G-mode phonon dynamics in individual suspended chirality-resolved single-walled carbon nanotubes by time-resolved anti-Stokes Raman spectroscopy. The improved technique allowed us to probe the intrinsic phonon information on a single-tube level and exclude the influences of tube-tube and tube-substrate interactions. We found that the G-mode phonon lifetime ranges from 0.75-2.25 ps and critically depends on whether the tube is metallic or semiconducting. In comparison with the phonon lifetimes in graphene and graphite, we revealed structure-dependent carrier-phonon and phonon-phonon interactions in nanotubes. Our results provide new information for optimizing the design of nanotube electronic/optoelectronic devices by better understanding and utilizing their phonon decay channels.

Dislocation Onset and Glide in Carbon Nanotubes under Torsion

NASA Astrophysics Data System (ADS)

Dumitrica, Traian; Zhang, Dong-Bo; James, Richard

2009-03-01

The torsional plastic response of carbon nanotubes is comprehensively described in the objective molecular dynamics framework [1-3]. It is shown that an (n,m) tube is prone to slip along a nearly-axial helical path, which introduces a distinct (+1,-1) change in the wrapping index. The low energy realization occurs without loss of mass, via nucleation of a 5-7-7-5 dislocation dipole, followed by a nearly-axial glide of the 5-7 dislocation. The onset of plasticity depends not only on chirality but also on handedness. For a given handedness of the applied twist, chiral tubes of opposed handedness are most susceptible to yield. A right-handed applied twist on an armchair (zig-zag) tube leads to a right- (left-) handed tube. [4pt] [1] T. Dumitrica and R.D. James, Objective Molecular Dynamics, Journal of the Mechanics and Physics of Solids 55, 2206 (2007). [0pt] [2] D.-B. Zhang, M. Hua, and T. Dumitrica, Stability of Polycrystalline and Wurtzite Si Nanowires via Symmetry-Adapted Tight-Binding Objective Molecular Dynamics, Journal of Chemical Physics 128, 084104 (2008). [0pt] [3] D.-B. Zhang and T. Dumitrica, Elasticity of Ideal Single-Walled Carbon Nanotubes via Symmetry-Adapted Tight-Binding Objective Modeling, Applied Physics Letters 93, 031919 (2008).

Dynamic Runner Forces and Pressure Fluctuations on the Draft Tube Wall of a Model Pump-Turbine

NASA Astrophysics Data System (ADS)

Kirschner, O.; Ruprecht, A.; Göde, E.; Riedelbauch, S.

2016-11-01

When Francis-turbines and pump-turbines operate at off-design conditions, typically a vortex rope develops. The vortex rope causes pressure oscillations leading to fluctuations of the forces affecting the runner. The presence of dynamic runner forces over a long period of time might damage the bearings and possibly the runner. In this experimental investigation, the fluctuating part of the runner forces and the pressure oscillations on the draft tube wall were measured on a model pump-turbine with a simplified straight cone draft tube in different operating conditions. The investigation focuses on the correlation of the pressure fluctuations frequency measured at the draft tube wall with the frequency of the fluctuating forces on the runner. The comparison between pressure fluctuations and dynamic forces shows a significant correlation in all operating points. For the comparison of different components in the spatial directions of the forces, the pressure fluctuations were separated in a synchronous part and a rotating part for operating points with higher amplitudes. The rotating pressure fluctuations correlate with the radial forces especially in the operating points with a rotating vortex rope. At frequencies with higher amplitudes in the pressure fluctuations caused by the vortex rope movement, there are also higher amplitudes in the radial forces at the same frequencies.

A dynamic response model for pressure sensors in continuum and high Knudsen number flows with large temperature gradients

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A.; Petersen, Brian J.; Scott, David D.

1996-01-01

This paper develops a dynamic model for pressure sensors in continuum and rarefied flows with longitudinal temperature gradients. The model was developed from the unsteady Navier-Stokes momentum, energy, and continuity equations and was linearized using small perturbations. The energy equation was decoupled from momentum and continuity assuming a polytropic flow process. Rarefied flow conditions were accounted for using a slip flow boundary condition at the tubing wall. The equations were radially averaged and solved assuming gas properties remain constant along a small tubing element. This fundamental solution was used as a building block for arbitrary geometries where fluid properties may also vary longitudinally in the tube. The problem was solved recursively starting at the transducer and working upstream in the tube. Dynamic frequency response tests were performed for continuum flow conditions in the presence of temperature gradients. These tests validated the recursive formulation of the model. Model steady-state behavior was analyzed using the final value theorem. Tests were performed for rarefied flow conditions and compared to the model steady-state response to evaluate the regime of applicability. Model comparisons were excellent for Knudsen numbers up to 0.6. Beyond this point, molecular affects caused model analyses to become inaccurate.

Study of crash energy absorption characteristics of inversion tube on passenger vehicle

NASA Astrophysics Data System (ADS)

Liu, Jiandong; Liu, Tao; Yao, Shengjie; Zhao, Rutao

2017-09-01

This article studied the energy absorption characteristics of the inversion tube and acquired the inversion tube design key dimensions under theoretical conditions by performing formula derivation in the quasi-static and dynamic state based on the working principle of the inversion tube: free inversion. The article further adopted HyperMesh and LS-Dyna to perform simulation and compared the simulation result with the theoretical calculating value for comparison. The design was applied in the full-vehicle model to perform 50km/h front fullwidth crash simulation. The findings showed that the deformation mode of the inversion tube in the full-vehicle crash was consistent with the design mode, and the inversion tube absorbed 33.0% of total energy, thereby conforming to the vehicle safety design requirements.

Phloem ultrastructure and pressure flow: Sieve-Element-Occlusion-Related agglomerations do not affect translocation.

PubMed

Froelich, Daniel R; Mullendore, Daniel L; Jensen, Kåre H; Ross-Elliott, Tim J; Anstead, James A; Thompson, Gary A; Pélissier, Hélène C; Knoblauch, Michael

2011-12-01

Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Münch's classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing Arabidopsis thaliana Sieve-Element-Occlusion-Related1 (SEOR1)-yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed.

Phloem Ultrastructure and Pressure Flow: Sieve-Element-Occlusion-Related Agglomerations Do Not Affect Translocation[W

PubMed Central

Froelich, Daniel R.; Mullendore, Daniel L.; Jensen, Kåre H.; Ross-Elliott, Tim J.; Anstead, James A.; Thompson, Gary A.; Pélissier, Hélène C.; Knoblauch, Michael

2011-01-01

Since the first ultrastructural investigations of sieve tubes in the early 1960s, their structure has been a matter of debate. Because sieve tube structure defines frictional interactions in the tube system, the presence of P protein obstructions shown in many transmission electron micrographs led to a discussion about the mode of phloem transport. At present, it is generally agreed that P protein agglomerations are preparation artifacts due to injury, the lumen of sieve tubes is free of obstructions, and phloem flow is driven by an osmotically generated pressure differential according to Münch’s classical hypothesis. Here, we show that the phloem contains a distinctive network of protein filaments. Stable transgenic lines expressing Arabidopsis thaliana Sieve-Element-Occlusion-Related1 (SEOR1)–yellow fluorescent protein fusions show that At SEOR1 meshworks at the margins and clots in the lumen are a general feature of living sieve tubes. Live imaging of phloem flow and flow velocity measurements in individual tubes indicate that At SEOR1 agglomerations do not markedly affect or alter flow. A transmission electron microscopy preparation protocol has been generated showing sieve tube ultrastructure of unprecedented quality. A reconstruction of sieve tube ultrastructure served as basis for tube resistance calculations. The impact of agglomerations on phloem flow is discussed. PMID:22198148

Ceramic vacuum tubes for geothermal well logging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, R.D.

1977-01-12

The results of investigations carried out into the availability and suitability of ceramic vacuum tubes for the development of logging tools for geothermal wells are summarized. Design data acquired in the evaluation of ceramic vacuum tubes for the development of a 500/sup 0/C instrumentation amplifier are presented. The general requirements for ceramic vacuum tubes for application to the development of high temperature well logs are discussed. Commercially available tubes are described and future contract activities that specifically relate to ceramic vacuum tubes are detailed. Supplemental data is presented in the appendix. (MHR)

Normal stress effects on Knudsen flow

NASA Astrophysics Data System (ADS)

Eu, Byung Chan

2018-01-01

Normal stress effects are investigated on tube flow of a single-component non-Newtonian fluid under a constant pressure gradient in a constant temperature field. The generalized hydrodynamic equations are employed, which are consistent with the laws of thermodynamics. In the cylindrical tube flow configuration, the solutions of generalized hydrodynamic equations are exactly solvable and the flow velocity is obtained in a simple one-dimensional integral quadrature. Unlike the case of flow in the absence of normal stresses, the flow develops an anomaly in that the flow in the boundary layer becomes stagnant and the thickness of such a stagnant velocity boundary layer depends on the pressure gradient, the aspect ratio of the radius to the length of the tube, and the pressure (or density and temperature) at the entrance of the tube. The volume flow rate formula through the tube is derived for the flow. It generalizes the Knudsen flow rate formula to the case of a non-Newtonian stress tensor in the presence of normal stress differences. It also reduces to the Navier-Stokes theory formula in the low shear rate limit near equilibrium.

Interdependence of endomembrane trafficking and actin dynamics during polarized growth of Arabidopsis pollen tubes

USDA-ARS?s Scientific Manuscript database

During polarized growth of pollen tubes, endomembrane trafficking and actin polymerization are two critical processes that establish membrane/wall homeostasis and maintain growth polarity. Fine-tuned interactions between these two processes are therefore necessary but poorly understood. To better un...

Eustachian Tube Function.

PubMed

Ars, Bernard; Dirckx, Joris

2016-10-01

The fibrocartilaginous eustachian tube is part of a system of contiguous organs including the nose, palate, rhinopharynx, and middle ear cleft. The middle ear cleft consists of the tympanic cavity, which includes the bony eustachian tube (protympanum) and the mastoid gas cells system. The tympanic cavity and mastoid gas cells are interconnected and allow gaseous exchange and pressure regulation. The fibrocartilaginous eustachian tube is a complex organ consisting of a dynamic conduit with its mucosa, cartilage, surrounding soft tissue, peritubal muscles (ie, tensor and levator veli palatine, salpingopharyngeus and tensor tympani), and superior bony support (the sphenoid sulcus). Copyright © 2016 Elsevier Inc. All rights reserved.

Aerodynamic Characteristics of Tube-Launched Tandem Wing Unmanned Aerial Vehicle

NASA Astrophysics Data System (ADS)

Rosid, Nurhayyan H.; Irsyad Lukman, E.; Fadlillah, M. Ahmad; Agoes Moelyadi, M.

2018-04-01

Tube Launched UAV with expandable tandem-wing configuration becomes one of the most interesting topic to be investigated. Folding wing mechanism is used due to the requirements that the UAV should be folded into tubular launcher. This paper focuses on investigating the aerodynamics characteristics because of the effects of folding wing mechanism, tandem wing configuration, and rapid deploying process from tube launcher. The aerodynamic characteristics investigation is conducted using computational fluid dynamics (CFD) at low Reynolds numbers (Re < 200000). The results of the simulation are used for the development of ITB Tube-launched UAV prototype and for future studies.

Theory and computation of non-RRKM lifetime distributions and rates in chemical systems with three or more degrees of freedom

NASA Astrophysics Data System (ADS)

Gabern, Frederic; Koon, Wang S.; Marsden, Jerrold E.; Ross, Shane D.

2005-11-01

The computation, starting from basic principles, of chemical reaction rates in realistic systems (with three or more degrees of freedom) has been a longstanding goal of the chemistry community. Our current work, which merges tube dynamics with Monte Carlo methods provides some key theoretical and computational tools for achieving this goal. We use basic tools of dynamical systems theory, merging the ideas of Koon et al. [W.S. Koon, M.W. Lo, J.E. Marsden, S.D. Ross, Heteroclinic connections between periodic orbits and resonance transitions in celestial mechanics, Chaos 10 (2000) 427-469.] and De Leon et al. [N. De Leon, M.A. Mehta, R.Q. Topper, Cylindrical manifolds in phase space as mediators of chemical reaction dynamics and kinetics. I. Theory, J. Chem. Phys. 94 (1991) 8310-8328.], particularly the use of invariant manifold tubes that mediate the reaction, into a tool for the computation of lifetime distributions and rates of chemical reactions and scattering phenomena, even in systems that exhibit non-statistical behavior. Previously, the main problem with the application of tube dynamics has been with the computation of volumes in phase spaces of high dimension. The present work provides a starting point for overcoming this hurdle with some new ideas and implements them numerically. Specifically, an algorithm that uses tube dynamics to provide the initial bounding box for a Monte Carlo volume determination is used. The combination of a fine scale method for determining the phase space structure (invariant manifold theory) with statistical methods for volume computations (Monte Carlo) is the main contribution of this paper. The methodology is applied here to a three degree of freedom model problem and may be useful for higher degree of freedom systems as well.

Age as a Determinant to Select an Anesthesia Method for Tympanostomy Tube Insertion in a Pediatric Population

PubMed Central

Jung, Kihwan; Kim, Hojong

2015-01-01

Background and Objectives To evaluate the relationship between age and anesthesia method used for tympanostomy tube insertion (TTI) and to provide evidence to guide the selection of an appropriate anesthesia method in children. Subjects and Methods We performed a retrospective review of children under 15 years of age who underwent tympanostomy tube insertion (n=159) or myringotomy alone (n=175) under local or general anesthesia by a single surgeon at a university-based, secondary care referral hospital. Epidermiologic data between local and general anesthesia groups as well as between TTI and myringotomy were analyzed. Medical costs were compared between local and general anesthesia groups. Results Children who received local anesthesia were significantly older than those who received general anesthesia. Unilateral tympanostomy tube insertion was performed more frequently under local anesthesia than bilateral. Logistic regression modeling showed that local anesthesia was more frequently applied in older children (odds ratio=1.041) and for unilateral tympanostomy tube insertion (odds ratio=8.990). The cut-off value of age for local anesthesia was roughly 5 years. Conclusions In a pediatric population at a single medical center, age and whether unilateral or bilateral procedures were required were important factors in selecting an anesthesia method for tympanostomy tube insertion. Our findings suggest that local anesthesia can be preferentially considered for children 5 years of age or older, especially in those with unilateral otitis media with effusion. PMID:26185791

Dynamics of Magnetic Flux Tubes in an Advective Flow around a Black Hole

NASA Astrophysics Data System (ADS)

Deb, Arnab; Chakrabarti, Sandip Kumar; Giri, Kinsuk

2016-07-01

Magnetic fields cannibalized by an accretion flow would very soon have a dominant toroidal component. Without changing the topology, we study the movements of these flux tubes inside a geometrically thick advective disk which undergo centrifugal pressure supported shocks. We also consider the effects of the flux tubes on the flow. We use a finite element method (Total Variation Diminishing) for this purpose and specifically focussed whether the flux tubes contribute to changes in outflow properties in terms of its collimation and outflow rates. It is seen that depending upon the cross sectional radius of the flux tubes (which control the drag force), these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surface). These interesting results obtained with and without flux tubes point to the role the flux tubes play in collimation of jets and outflows.

Shock tubes and waves; Proceedings of the Thirteenth International Symposium, Niagara Falls, NY, July 6-9, 1981

NASA Astrophysics Data System (ADS)

Treanor, C. E.; Hall, J. G.

1982-10-01

The present conference on shock tubes and waves considers shock tube drivers, luminous shock tubes, shock tube temperature and pressure measurement, shock front distortion in real gases, nonlinear standing waves, transonic flow shock wave turbulent boundary interactions, wall roughness effects on reflected shock bifurcation, argon thermal conductivity, pattern generation in gaseous detonations, cylindrical resonators, shock tunnel-produced high gain lasers, fluid dynamic aspects of laser-metal interaction, and the ionization of argon gas behind reflected shock waves. Also discussed are the ionization relaxation of shock-heated plasmas and gases, discharge flow/shock tube studies of singlet oxygen, rotational and vibrational relaxation, chemiluminescence thermal and shock wave decomposition of hydrogen cyanide and hydrogen azide, shock wave structure in gas-particle mixtures at low Mach numbers, binary nucleation in a Ludwieg tube, shock liquefaction experiments, pipeline explosions, the shock wave ignition of pulverized coal, and shock-initiated methane combustion.

Effects of Fuel Distribution on Detonation Tube Performance

NASA Technical Reports Server (NTRS)

Perkins, H. Douglas; Sung, Chih-Jen

2003-01-01

A pulse detonation engine uses a series of high frequency intermittent detonation tubes to generate thrust. The process of filling the detonation tube with fuel and air for each cycle may yield non-uniform mixtures. Uniform mixing is commonly assumed when calculating detonation tube thrust performance. In this study, detonation cycles featuring idealized non-uniform Hz/air mixtures were analyzed using a two-dimensional Navier-Stokes computational fluid dynamics code with detailed chemistry. Mixture non-uniformities examined included axial equivalence ratio gradients, transverse equivalence ratio gradients, and partially fueled tubes. Three different average test section equivalence ratios were studied; one stoichiometric, one fuel lean, and one fuel rich. All mixtures were detonable throughout the detonation tube. Various mixtures representing the same average test section equivalence ratio were shown to have specific impulses within 1% of each other, indicating that good fuel/air mixing is not a prerequisite for optimal detonation tube performance under conditions investigated.

Drained Lava Tubes and Lobes From Eocretaceous Paraná-Etendeka Province, Brazil

NASA Astrophysics Data System (ADS)

Waichel, B. L.; Lima, E. F. D.; Mouro, L. D.; Briske, D. R.; Tratz, E. B.

2017-12-01

The identification of lava tubes in continental flood basalt provinces (CFBP) is difficult and reports of preserved drained tubes and lobes are rare. The large extension of CFBP must be related to an efficient transport of lava and tubes are the most efficient mechanism to transport lava in insulated pathways, like observed in modern volcanic fields. Looking for caves in the central portion of Paraná-Etendeka Province, we discovered drained lava tubes (4) and lobes (6) in a volcanic sequence constituted by pahoehoe flows. Lava tubes are: Casa de Pedra, Perau Branco, Dal Pae and Pinhão. The Casa de Pedra tube system is composed of two principal chambers with similar dimensions, reaching up to 10 m long and 4.0 m high connected by a narrow passage. The general form of the chamber is hemispherical, with re-entrances of ellipsoidal shape probably formed by small lava lobes and collapse structures in the roof. The second chamber is connected with three secondary lava tubes. Columns in the cave are formed when the flowing lava separates in two lava channels that join again further down the system, forming and anastomosing tube network. Lateral lava benches and lava drainings at the walls are observed in secondary tubes. The general lava flow is to SW. The Perau Branco system is composed of five tubes with ellipsoidal openings. The main features are the long tubes that emerge from the small flattened chambers. One tube is more than 20 m long, with alternating circular and flattened ellipsoidal sections. The general lava flow is to NE. Pinhão tube is spherical with 3 meters diameter and 15 m long, with lava flow orientation to NW. This tube has a bottleneck shape with linings (up to 3 cm thick), which are observed in the roof and walls. Dal Pae Tube is 10 m long with an ellipsoidal opening, bottleneck shape and orientation to NE. The lava flow directions measured in the tubes is to SW (Casa de Pedra, Pinhão) and NE (Perau Branco, Dal Pae) and this pattern is related to orientation of the Ponta Grossa swarm feeder dikes (NW). The drained lava lobes show variable dimensions, typical lobate morphology and form sub-crustal caves. The smaller are up to 1.5 m high, 10 m wide and 15 long; the majors are up to 6m high, 20 m wide and 25 m long. Collapsed roofs are observed in big caves and collapses of overlying thin pahoehoe lobes are common in smaller lobes.

Literature search for ceramic vacuum tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cannon, W.

1977-01-12

The NTIS and Engineering Index files were searched for citations relating to Ceramic and/or Metal Electron Tubes and High Temperature Electronics. A total of 24 citations were found relating directly to ceramic tubes and 24 to high temperature electronics. A search for electron tubes in general was examined for high temperature applications and 39 were obtained. Computer printouts of the abstracts are included in appendices. (MHR)

Study on Influence of Tube Arrays on Fluid Elastic Instability

NASA Astrophysics Data System (ADS)

Ishihara, Kunihiko; Kitayama, Gen

The tube bank is used in boilers, heat exchangers in power plants and steam generators in nuclear plants. These tubes sometimes vibrate violently and come to the fatigue failure due to the flow induced vibration which is caused by the cross flow. This phenomenon is that the large vibrations arise at the critical flow velocity and it is called fluid elastic instability. However the relation between the onset velocity of fluid elastic instability and the tube array's geometry has not been clarified sufficiently. There is a few reference related to the relation between the pitch to diameter ratio and the onset velocity even in the lattice arrays. In this paper, the influence of tube arrays on fluid elastic instability is examined by experiments. As a result, it is clarified that the tube vibrations become large as T/D increases and L/D decreases, and the tube vibrations strongly depend on the dynamic characteristics of tubes such as the natural frequency and the damping ability.

Gas sampling system for a mass spectrometer

DOEpatents

Taylor, Charles E; Ladner, Edward P

2003-12-30

The present invention relates generally to a gas sampling system, and specifically to a gas sampling system for transporting a hazardous process gas to a remotely located mass spectrometer. The gas sampling system includes a capillary tube having a predetermined capillary length and capillary diameter in communication with the supply of process gas and the mass spectrometer, a flexible tube surrounding and coaxial with the capillary tube intermediate the supply of process gas and the mass spectrometer, a heat transfer tube surrounding and coaxial with the capillary tube, and a heating device in communication the heat transfer tube for substantially preventing condensation of the process gas within the capillary tube.

Flow dynamics in pediatric rigid bronchoscopes using computer-aided design modeling software.

PubMed

Barneck, Mitchell D; Webb, J Taylor; Robinson, Ryan E; Grimmer, J Fredrik

2016-08-01

Observed complications during rigid bronchoscopy, including hypercarbia and hypoxemia, prompted us to assess how well rigid bronchoscopes serve as an airway device. We performed computer-aided design flow analysis of pediatric rigid bronchoscopes to gain insight into flow dynamics. We made accurate three-dimensional computer models of pediatric rigid bronchoscopes and endotracheal tubes. SOLIDWORKS (Dassault Systemes, Vélizy-Villacoublay, France) flow analysis software was used to analyze fluid dynamics during pressure-controlled and volume-controlled ventilation. Flow analysis was performed on rigid bronchoscopes and similar outer diameter endotracheal tubes comparing resistance, flow, and turbulence during two ventilation modalities and in common surgical scenarios. Increased turbulent flow was observed in bronchoscopes compared to more laminar flow in endotracheal tubes of similar outer diameter. Flow analysis displayed higher resistances in all pediatric bronchoscope sizes except one (3.0 bronchoscope) compared to similar-sized endotracheal tubes. Loss of adequate ventilation was observed if the bronchoscope was not assembled correctly or if increased peak inspiratory pressures were needed. Anesthesia flow to the patient was reduced by 63% during telescope insertion. Flow analysis illustrates increased turbulent flow and increased airflow resistance in all but one size of pediatric bronchoscopes compared to endotracheal tubes. This increased turbulence and resistance, along with the unanticipated gas distal exit pattern, may contribute to the documented hypercarbia and hypoxemia during procedures. These findings may explain why hypoxemia and hypercarbia are commonly observed during rigid bronchoscopy, especially when positive pressure ventilation is needed. NA Laryngoscope, 126:1940-1945, 2016. © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

A comparison of neural tube defects identified by two independent routine recording systems for congenital malformations in Northern Ireland.

PubMed

Nevin, N C; McDonald, J R; Walby, A L

1978-12-01

The efficiency of two systems for recording congenital malformations has been compared; one system, the Registrar General's Congenital Malformation Notification, is based on registering all malformed infants, and the other, the Child Health System, records all births. In Northern Ireland for three years [1974--1976], using multiple sources of ascertainment, a total of 686 infants with neural tube defects was identified among 79 783 live and stillbirths. The incidence for all neural tube defects in 8 60 per 1 000 births. The Registrar General's Congenital Malformation Notification System identified 83.6% whereas the Child Health System identified only 63.3% of all neural tube defects. Both systems together identified 86.2% of all neural tube defects. The two systems are suitable for monitoring of malformations and the addition of information from the Genetic Counselling Clinics would enhance the data for epidemiological studies.

Tube-Forming Assays.

PubMed

Brown, Ryan M; Meah, Christopher J; Heath, Victoria L; Styles, Iain B; Bicknell, Roy

2016-01-01

Angiogenesis involves the generation of new blood vessels from the existing vasculature and is dependent on many growth factors and signaling events. In vivo angiogenesis is dynamic and complex, meaning assays are commonly utilized to explore specific targets for research into this area. Tube-forming assays offer an excellent overview of the molecular processes in angiogenesis. The Matrigel tube forming assay is a simple-to-implement but powerful tool for identifying biomolecules involved in angiogenesis. A detailed experimental protocol on the implementation of the assay is described in conjunction with an in-depth review of methods that can be applied to the analysis of the tube formation. In addition, an ImageJ plug-in is presented which allows automatic quantification of tube images reducing analysis times while removing user bias and subjectivity.

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 19 Customs Duties 2 2013-04-01 2013-04-01 false Cigars, cigarettes, and cigarette papers and tubes...; DEPARTMENT OF THE TREASURY (CONTINUED) LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and...

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 19 Customs Duties 2 2014-04-01 2014-04-01 false Cigars, cigarettes, and cigarette papers and tubes...; DEPARTMENT OF THE TREASURY (CONTINUED) LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and...

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 19 Customs Duties 2 2011-04-01 2011-04-01 false Cigars, cigarettes, and cigarette papers and tubes...; DEPARTMENT OF THE TREASURY (CONTINUED) LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and...

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 19 Customs Duties 2 2012-04-01 2012-04-01 false Cigars, cigarettes, and cigarette papers and tubes...; DEPARTMENT OF THE TREASURY (CONTINUED) LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and...

19 CFR 159.5 - Cigars, cigarettes, and cigarette papers and tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 19 Customs Duties 2 2010-04-01 2010-04-01 false Cigars, cigarettes, and cigarette papers and tubes...; DEPARTMENT OF THE TREASURY (CONTINUED) LIQUIDATION OF DUTIES General Provisions § 159.5 Cigars, cigarettes, and cigarette papers and tubes. The internal revenue taxes imposed on cigars, cigarettes, and...

Motion of a rigid sphere through an elastic tube with a lubrication film

NASA Astrophysics Data System (ADS)

Tani, Marie; Cambau, Thomas; Bico, Jose; Reyssat, Etienne

2017-11-01

The motion of large objects through narrow tubes is a common problem in physiology and more generally in the biological world. We built a model experiment where a rigid sphere is moved inside a narrower elastic tube coated with a lubricating fluid. The friction force is generally lower than in a non-lubricated situation. Interestingly, the force increases with the pulling velocity to the power 1/3, and also depends on the viscosity of the lubricant, the geometry and the mechanical properties of the tube. All our experimental data are well described by a scaling law combining lubrication and elasticity equations. We furthermore measured the thickness of the lubricant film. We present all these results.

Investigation of the effect of a bend in a transfer line that separates a pulse tube cold head and a pressure wave generator

NASA Astrophysics Data System (ADS)

Dev, A. A.; Atrey, M. D.; Vanapalli, S.

2017-02-01

A transfer line between a pulse tube cold head and a pressure wave generator is usually required to isolate the cold head from the vibrations of the compressor. Although it is a common practice to use a thin and narrow straight tube, a bent tube would allow design flexibility and easy mounting of the cold head, such as in a split Stirling type pulse tube cryocooler. In this paper, we report a preliminary investigation on the effect of the bending of the tube on the flow transfer characteristics. A numerical study using commercial computational fluid dynamics model is performed to gain insight into the flow characteristics in the bent tube. Oscillating flow experiments are performed with a straight and a bent tube at a filling pressure of 15 bar and an operating frequency of 40, 50 and 60 Hz. The data and the corresponding numerical simulations point to the hypothesis that the secondary flow in the bent tube causes a decrease in flow at a fixed pressure amplitude.

Research in structures, structural dynamics and materials, 1989

NASA Technical Reports Server (NTRS)

Hunter, William F. (Compiler); Noor, Ahmed K. (Compiler)

1989-01-01

Topics addressed include: composite plates; buckling predictions; missile launch tube modeling; structural/control systems design; optimization of nonlinear R/C frames; error analysis for semi-analytic displacement; crack acoustic emission; and structural dynamics.

Carbon Nanotubes: Molecular Electronic Components

NASA Technical Reports Server (NTRS)

Srivastava, Deepak; Saini, Subhash; Menon, Madhu

1997-01-01

The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

A study on the gas-solid particle flows in a needle-free drug delivery device

NASA Astrophysics Data System (ADS)

Rasel, Md. Alim Iftekhar; Taher, Md. Abu; Kim, H. D.

2013-08-01

Different systems have been used over the years to deliver drug particles to the human skin for pharmaceutical effect. Research has been done to improve the performance and flexibility of these systems. In recent years a unique system called the transdermal drug delivery has been developed. Transdermal drug delivery opened a new door in the field of drug delivery as it is more flexible and offers better performance than the conventional systems. The principle of this system is to accelerate drug particles with a high speed gas flow. Among different transdermal drug delivery systems we will concentrate on the contour shock tube system in this paper. A contoured shock tube is consists of a rupture chamber, a shock tube and a supersonic nozzle section. The drug particles are retained between a set of bursting diaphragm. When the diaphragm is ruptured at a certain pressure, a high speed unsteady flow is initiated through the shock tube which accelerates the particles. Computational fluid dynamics is used to simulate and analyze the flow field. The DPM (discrete phase method) is used to model the particle flow. As an unsteady flow is initiated though the shock tube the drag correlation proposed by Igra et al is used other than the standard drag correlation. The particle velocities at different sections including the nozzle exit are investigated under different operating conditions. Static pressure histories in different sections in the shock tube are investigated to analyze the flow field. The important aspects of the gas and particle dynamics in the shock tube are discussed and analyzed in details.

High accuracy differential pressure measurements using fluid-filled catheters - A feasibility study in compliant tubes.

PubMed

Rotman, Oren Moshe; Weiss, Dar; Zaretsky, Uri; Shitzer, Avraham; Einav, Shmuel

2015-09-18

High accuracy differential pressure measurements are required in various biomedical and medical applications, such as in fluid-dynamic test systems, or in the cath-lab. Differential pressure measurements using fluid-filled catheters are relatively inexpensive, yet may be subjected to common mode pressure errors (CMP), which can significantly reduce the measurement accuracy. Recently, a novel correction method for high accuracy differential pressure measurements was presented, and was shown to effectively remove CMP distortions from measurements acquired in rigid tubes. The purpose of the present study was to test the feasibility of this correction method inside compliant tubes, which effectively simulate arteries. Two tubes with varying compliance were tested under dynamic flow and pressure conditions to cover the physiological range of radial distensibility in coronary arteries. A third, compliant model, with a 70% stenosis severity was additionally tested. Differential pressure measurements were acquired over a 3 cm tube length using a fluid-filled double-lumen catheter, and were corrected using the proposed CMP correction method. Validation of the corrected differential pressure signals was performed by comparison to differential pressure recordings taken via a direct connection to the compliant tubes, and by comparison to predicted differential pressure readings of matching fluid-structure interaction (FSI) computational simulations. The results show excellent agreement between the experimentally acquired and computationally determined differential pressure signals. This validates the application of the CMP correction method in compliant tubes of the physiological range for up to intermediate size stenosis severity of 70%. Copyright © 2015 Elsevier Ltd. All rights reserved.

Aircraft Hydraulic Systems Dynamic Analysis

DTIC Science & Technology

1977-10-01

WHEQUT) for a Quincke tube resonator was revised. A similar subroutine was developed to simulate a hydraulic syscem acoustic filter available commer...input datt’l. Tlhe’ .il l t ’p. ol ý", nel-, r , ’li l t io (11 WAý: alq I SO ij•jI Ld t 0 t l• 11 ’ W11 I’ ( Quincke tube) subroutine. With these...studying pump hanger torque, precompression, decompression WHEQUT Subroutine 1) Revised, made corrections to, and ran Quincke tube subroutine (WHEQUT) b

Dynamic Fluid in a Porous Transducer-Based Angular Accelerometer

PubMed Central

Cheng, Siyuan; Fu, Mengyin; Wang, Meiling; Ming, Li; Fu, Huijin; Wang, Tonglei

2017-01-01

This paper presents a theoretical model of the dynamics of liquid flow in an angular accelerometer comprising a porous transducer in a circular tube of liquid. Wave speed and dynamic permeability of the transducer are considered to describe the relation between angular acceleration and the differential pressure on the transducer. The permeability and streaming potential coupling coefficient of the transducer are determined in the experiments, and special prototypes are utilized to validate the theoretical model in both the frequency and time domains. The model is applied to analyze the influence of structural parameters on the frequency response and the transient response of the fluidic system. It is shown that the radius of the circular tube and the wave speed affect the low frequency gain, as well as the bandwidth of the sensor. The hydrodynamic resistance of the transducer and the cross-section radius of the circular tube can be used to control the transient performance. The proposed model provides the basic techniques to achieve the optimization of the angular accelerometer together with the methodology to control the wave speed and the hydrodynamic resistance of the transducer. PMID:28230793

Characterizing the Peano fluidic muscle and the effects of its geometry properties on its behavior

NASA Astrophysics Data System (ADS)

Veale, Allan Joshua; Xie, Sheng Quan; Anderson, Iain Alexander

2016-06-01

In this work, we explore the basic static and dynamic behavior of a hydraulically actuated Peano muscle and how its geometry affects key static and dynamic performance metrics. The Peano muscle, or pouch motor is a fluid powered artificial muscle. Similar to McKibben pneumatic artificial muscles (PAMs), it has the ability to generate the high forces of biological muscles with the low threshold pressure of pleated PAMs, but in a slim, easily distributed form. We found that Peano muscles have similar characteristics to other PAMs, but produce lower free-strains. A test rig capable of measuring high-speed flow rates with a Venturi tube revealed that their efficiency peaks at about 40% during highly dynamic movements. Peano muscles with more tubes and of a greater size do not move faster. Also, their muscle tubes should have an aspect ratio of at least 1:3 and channel width greater than 20% to maximize performance. These findings suggest that finite element modeling be used to optimize more complex Peano muscle geometries.

Experimental investigation of door dynamic opening caused by impinging shock wave

NASA Astrophysics Data System (ADS)

Biamino, L.; Jourdan, G.; Mariani, C.; Igra, O.; Massol, A.; Houas, L.

2011-02-01

To prevent damage caused by accidental overpressure inside a closed duct (e.g. jet engine) safety valves are introduced. The present study experimentally investigates the dynamic opening of such valves by employing a door at the end of a shock tube driven section. The door is hung on an axis and is free to rotate, thereby opening the tube. The evolved flow and wave pattern due to a collision of an incident shock wave with the door, causing the door opening, is studied by employing a high speed schlieren system and recording pressures at different places inside the tube as well as on the rotating door. Analyzing this data sheds light on the air flow evolution and the behavior of the opening door. In the present work, emphasis is given to understanding the complex, unsteady flow developed behind the transmitted shock wave as it diffracts over the opening door. It is shown that both the door inertia and the shock wave strength influence the opening dynamic evolution, but not in the proportions that might be expected.

Chest Tube Drainage of the Pleural Space: A Concise Review for Pulmonologists.

PubMed

Porcel, José M

2018-04-01

Chest tube insertion is a common procedure usually done for the purpose of draining accumulated air or fluid in the pleural cavity. Small-bore chest tubes (≤14F) are generally recommended as the first-line therapy for spontaneous pneumothorax in non-ventilated patients and pleural effusions in general, with the possible exception of hemothoraces and malignant effusions (for which an immediate pleurodesis is planned). Large-bore chest drains may be useful for very large air leaks, as well as post-ineffective trial with small-bore drains. Chest tube insertion should be guided by imaging, either bedside ultrasonography or, less commonly, computed tomography. The so-called trocar technique must be avoided. Instead, blunt dissection (for tubes >24F) or the Seldinger technique should be used. All chest tubes are connected to a drainage system device: flutter valve, underwater seal, electronic systems or, for indwelling pleural catheters (IPC), vacuum bottles. The classic, three-bottle drainage system requires either (external) wall suction or gravity ("water seal") drainage (the former not being routinely recommended unless the latter is not effective). The optimal timing for tube removal is still a matter of controversy; however, the use of digital drainage systems facilitates informed and prudent decision-making in that area. A drain-clamping test before tube withdrawal is generally not advocated. Pain, drain blockage and accidental dislodgment are common complications of small-bore drains; the most dreaded complications include organ injury, hemothorax, infections, and re-expansion pulmonary edema. IPC represent a first-line palliative therapy of malignant pleural effusions in many centers. The optimal frequency of drainage, for IPC, has not been formally agreed upon or otherwise officially established. Copyright©2018. The Korean Academy of Tuberculosis and Respiratory Diseases.

Chest Tube Drainage of the Pleural Space: A Concise Review for Pulmonologists

PubMed Central

2018-01-01

Chest tube insertion is a common procedure usually done for the purpose of draining accumulated air or fluid in the pleural cavity. Small-bore chest tubes (≤14F) are generally recommended as the first-line therapy for spontaneous pneumothorax in non-ventilated patients and pleural effusions in general, with the possible exception of hemothoraces and malignant effusions (for which an immediate pleurodesis is planned). Large-bore chest drains may be useful for very large air leaks, as well as post-ineffective trial with small-bore drains. Chest tube insertion should be guided by imaging, either bedside ultrasonography or, less commonly, computed tomography. The so-called trocar technique must be avoided. Instead, blunt dissection (for tubes >24F) or the Seldinger technique should be used. All chest tubes are connected to a drainage system device: flutter valve, underwater seal, electronic systems or, for indwelling pleural catheters (IPC), vacuum bottles. The classic, three-bottle drainage system requires either (external) wall suction or gravity (“water seal”) drainage (the former not being routinely recommended unless the latter is not effective). The optimal timing for tube removal is still a matter of controversy; however, the use of digital drainage systems facilitates informed and prudent decision-making in that area. A drain-clamping test before tube withdrawal is generally not advocated. Pain, drain blockage and accidental dislodgment are common complications of small-bore drains; the most dreaded complications include organ injury, hemothorax, infections, and re-expansion pulmonary edema. IPC represent a first-line palliative therapy of malignant pleural effusions in many centers. The optimal frequency of drainage, for IPC, has not been formally agreed upon or otherwise officially established. PMID:29372629

Molecular Dynamics Simulations of an Idealized Shock Tube: N2 in Ar Bath Driven by He

NASA Astrophysics Data System (ADS)

Piskulich, Ezekiel Ashe; Sewell, Thomas D.; Thompson, Donald L.

2015-06-01

The dynamics of 10% N2 in Ar initially at 298 K in an idealized shock tube driven by He was studied using molecular dynamics. The simulations were performed using the Large-Scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code. Nitrogen was modeled as a Morse oscillator and non-covalent interactions were approximated by the Buckingham exponential-6 pair potential. The initial pressures in the He driver gas and the driven N2/Ar gas were 1000 atm and 20 atm, respectively. Microcanonical trajectories were followed for 2 ns following release of the driver gas. Results for excitation and subsequent relaxation of the N2, as well as properties of the gas during the simulations, will be reported.

Unsteady, one-dimensional gas dynamics computations using a TVD type sequential solver

NASA Technical Reports Server (NTRS)

Thakur, Siddharth; Shyy, Wei

1992-01-01

The efficacy of high resolution convection schemes to resolve sharp gradient in unsteady, 1D flows is examined using the TVD concept based on a sequential solution algorithm. Two unsteady flow problems are considered which include the problem involving the interaction of the various waves in a shock tube with closed reflecting ends and the problem involving the unsteady gas dynamics in a tube with closed ends subject to an initial pressure perturbation. It is concluded that high accuracy convection schemes in a sequential solution framework are capable of resolving discontinuities in unsteady flows involving complex gas dynamics. However, a sufficient amount of dissipation is required to suppress oscillations near discontinuities in the sequential approach, which leads to smearing of the solution profiles.

Deployment Simulation of Ultra-Lightweight Inflatable Structures

NASA Technical Reports Server (NTRS)

Wang, John T.; Johnson, Arthur R.

2002-01-01

Dynamic deployment analyses of folded inflatable tubes are conducted to investigate modeling issues related to the deployment of solar sail booms. The analyses are necessary because ground tests include gravity effects and may poorly represent deployment in space. A control volume approach, available in the LS-DYNA nonlinear dynamic finite element code, and the ideal gas law are used to simulate the dynamic inflation deployment process. Three deployment issues are investigated for a tube packaged in a Z-fold configuration. The issues are the effect of the rate of inflation, the effect of residual air, and the effect of gravity. The results of the deployment analyses reveal that the time and amount of inflation gas required to achieve a full deployment are related to these issues.

iMAST FY2007 Annual Report

DTIC Science & Technology

2007-01-01

laser cladding techniques. Customer: COMSUBPAC NAVSEASYSCOM Pearl Harbor Naval Shipyard...motion device to laser clad and re-dimension the affected tube to original specifications. Benefits: ° Reduce life cycle costs of tube...coatings via cold gas dynamic spraying and EB–PVD ° Spray-formed HT aluminum alloys ° Localized laser HT and cladding for wear

A QUANTITATIVE STUDY OF THE EVOLUTION OF GASES FROM ELECTRON TUBES AND MATERIALS.

DTIC Science & Technology

spectrometer, ion pumps, ionization gauges and precision orifices to measure the flow rate of individual gases. It has been used to examine several...amounts comprise about 95% of the gas evolved during cathode conversion and activation. Additional experiments in the dynamic analysis of tube processes are suggested. (Author)

Molecular Dynamics Simulations of Carbon Nanotubes in Water

NASA Technical Reports Server (NTRS)

Walther, J. H.; Jaffe, R.; Halicioglu, T.; Koumoutsakos, P.

2000-01-01

We study the hydrophobic/hydrophilic behavior of carbon nanotubes using molecular dynamics simulations. The energetics of the carbon-water interface are mainly dispersive but in the present study augmented with a carbon quadrupole term acting on the charge sites of the water. The simulations indicate that this contribution is negligible in terms of modifying the structural properties of water at the interface. Simulations of two carbon nanotubes in water display a wetting and drying of the interface between the nanotubes depending on their initial spacing. Thus, initial tube spacings of 7 and 8 A resulted in a drying of the interface whereas spacing of > 9 A remain wet during the course of the simulation. Finally, we present a novel particle-particle-particle-mesh algorithm for long range potentials which allows for general (curvilinear) meshes and "black-box" fast solvers by adopting an influence matrix technique.

Extension of HCDstruct for Transonic Aeroservoelastic Analysis of Unconventional Aircraft Concepts

NASA Technical Reports Server (NTRS)

Quinlan, Jesse R.; Gern, Frank H.

2017-01-01

A substantial effort has been made to implement an enhanced aerodynamic modeling capability in the Higher-fidelity Conceptual Design and structural optimization tool. This additional capability is needed for a rapid, physics-based method of modeling advanced aircraft concepts at risk of structural failure due to dynamic aeroelastic instabilities. To adequately predict these instabilities, in particular for transonic applications, a generalized aerodynamic matching algorithm was implemented to correct the doublet-lattice model available in Nastran using solution data from a priori computational fluid dynamics anal- ysis. This new capability is demonstrated for two tube-and-wing aircraft configurations, including a Boeing 737-200 for implementation validation and the NASA D8 as a first use case. Results validate the current implementation of the aerodynamic matching utility and demonstrate the importance of using such a method for aircraft configurations featuring fuselage-wing aerodynamic interaction.

State and Spectral Properties of Chloride Oscillations in Pollen

PubMed Central

Zonia, Laura; Feijó, José A.

2003-01-01

Pollen tube growth is a dynamic system expressing a number of oscillating circuits. Our recent work identified a new circuit, oscillatory efflux of Cl− anion from the pollen tube apex. Cl− efflux is the first ion signal found to be coupled in phase with growth oscillations. Functional analyses indicate an active role for Cl− flux in pollen tube growth. In this report the dynamical properties of Cl− efflux are examined. Phase space analysis demonstrates that the system trajectory converges on a limit cycle. Fourier analysis reveals that two harmonic frequencies characterize normal growth. Cl− efflux is inhibited by the channel blocker DIDS, is stimulated by hypoosmotic treatment, and is antagonized by the signal encoded in inositol 3,4,5,6-tetrakisphosphate. These perturbations induce transitions of the limit cycle to new metastable states or cause system collapse to a static attractor centered near the origin. These perturbations also transform the spectral profile, inducing subharmonic frequencies, transitions to period doubling and tripling, superharmonic resonance, and chaos. These results indicate that Cl− signals in pollen tubes display features that are characteristic of active oscillators that carry frequency-encoded information. A reaction network of the Cl− oscillator coupled to two nonlinear feedback circuits that may drive pollen tube growth oscillations is considered. PMID:12547818

Experimental investigation of multi-scale non-equilibrium plasma dynamics

NASA Astrophysics Data System (ADS)

Bellan, Paul

2013-10-01

Lab experiments at Caltech resolve complex, detailed MHD dynamics spatially and temporally. Unbalanced forces drive fast plasma flows which tend to self-collimate via self-pinching. Collimation results from flow stagnation compressing embedded magnetic flux and so amplifying the magnetic field responsible for pinching. Measurements show that the collimated flow is essentially a dense plasma jet with embedded axial and azimuthal magnetic fields, i.e., a magnetic flux tube (flux rope). The measured jet velocity is in good agreement with an MHD acceleration model. Depending on how flux tube radius varies with axial position, jets flow into a flux tube from both ends or from just one end. Jets kink when the flux tube in which they are embedded breaches the Kruskal-Shafranov stability limit. The lateral acceleration of a sufficiently strong kink can produce an enormous effective gravity which provides the environment for an observed fine-scale, extremely fast Rayleigh-Taylor (RT) instability. The RT can erode the jet current channel to be smaller than the ion skin depth so there is a cascade from the ideal MHD scale of the kink to the non-MHD ion skin depth scale. This process can result in a magnetic reconnection whereby the jet and its embedded flux tube break. Supported by USDOE.

In-Situ Imaging of Particles during Rapid Thermite Deflagrations

NASA Astrophysics Data System (ADS)

Grapes, Michael; Reeves, Robert; Densmore, John; Fezzaa, Kamel; van Buuren, Tony; Willey, Trevor; Sullivan, Kyle

2017-06-01

The dynamic behavior of rapidly deflagrating thermites is a highly complex process involving rapid decomposition, melting, and outgassing of intermediate and/or product gases. Few experimental techniques are capable of probing these phenomena in situ due to the small length and time scales associated with the reaction. Here we use a recently developed extended burn tube test, where we initiate a small pile of thermite on the closed end of a clear acrylic tube. The length of the tube is sufficient to fully contain the reaction as it proceeds and flows entrained particles down the tube. This experiment was brought to the Advanced Photon Source, and the particle formation was X-ray imaged at various positions down the tube. Several formulations, as well as formulation parameters were varied to investigate the size and morphology of the particles, as well as to look for dynamic behavior attributed to the reaction. In all cases, we see evidence of particle coalescence and condensed-phase interfacial reactions. The results improve our understanding of the procession of reactants to products in these systems. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-691140.

Geology of selected lava tubes in the Bend Area, Oregon

NASA Technical Reports Server (NTRS)

Greely, R.

1971-01-01

Longitudinal profiles representing 5872.5 m of mapped lava tubes and a photogeologic map relating lava tubes to surface geology, regional structure and topography are presented. Three sets of lava tubes were examined: (1) Arnold Lava Tube System (7km long) composed of collapsed and uncollapsed tube segments and lava ponds, (2) Horse Lava Tube System (11 km long) composed of parallel and anastomosing lava tube segments, and (3) miscellaneous lava tubes. Results of this study tend to confirm the layered lava hypothesis of Ollier and Brown (1965) for lava tube formation; however, there are probably several modes of formation for lava tubes in general. Arnold System is a single series of tubes apparently formed in a single basalt flow on a relatively steep gradient. The advancing flow in which the tubes formed was apparently temporarily halted, resulting in the formation of lava ponds which were inflated and later drained by the lava tube system. Horse System probably formed in multiple, interconnected flows. Pre-flow gradient appears to have been less than for Arnold System, and resulted in meandrous, multiple tube networks.

27 CFR 41.25 - Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

..., condemned, and abandoned tobacco products and cigarette papers and tubes. 41.25 Section 41.25 Alcohol... (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO General § 41.25 Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and...

27 CFR 46.192 - Definitions used in this subpart.

Code of Federal Regulations, 2010 CFR

2010-04-01

... PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.192 Definitions used in this subpart. As used in..., Miscellaneous Regulations Relating to Tobacco Products and Cigarette Papers and Tubes. (b) Articles subject to...

27 CFR 46.192 - Definitions used in this subpart.

Code of Federal Regulations, 2013 CFR

2013-04-01

... PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.192 Definitions used in this subpart. As used in..., Miscellaneous Regulations Relating to Tobacco Products and Cigarette Papers and Tubes. (b) Articles subject to...

27 CFR 46.192 - Definitions used in this subpart.

Code of Federal Regulations, 2012 CFR

2012-04-01

... PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.192 Definitions used in this subpart. As used in..., Miscellaneous Regulations Relating to Tobacco Products and Cigarette Papers and Tubes. (b) Articles subject to...

27 CFR 46.192 - Definitions used in this subpart.

Code of Federal Regulations, 2011 CFR

2011-04-01

... PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.192 Definitions used in this subpart. As used in..., Miscellaneous Regulations Relating to Tobacco Products and Cigarette Papers and Tubes. (b) Articles subject to...

27 CFR 41.25 - Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

..., condemned, and abandoned tobacco products and cigarette papers and tubes. 41.25 Section 41.25 Alcohol... (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO General § 41.25 Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and...

27 CFR 41.25 - Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

..., condemned, and abandoned tobacco products and cigarette papers and tubes. 41.25 Section 41.25 Alcohol... (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO General § 41.25 Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and...

27 CFR 41.25 - Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

..., condemned, and abandoned tobacco products and cigarette papers and tubes. 41.25 Section 41.25 Alcohol... (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO General § 41.25 Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and...

27 CFR 41.25 - Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and tubes.

Code of Federal Regulations, 2010 CFR

2010-04-01

..., condemned, and abandoned tobacco products and cigarette papers and tubes. 41.25 Section 41.25 Alcohol... (CONTINUED) TOBACCO IMPORTATION OF TOBACCO PRODUCTS, CIGARETTE PAPERS AND TUBES, AND PROCESSED TOBACCO General § 41.25 Disposal of forfeited, condemned, and abandoned tobacco products and cigarette papers and...

27 CFR 46.192 - Definitions used in this subpart.

Code of Federal Regulations, 2014 CFR

2014-04-01

... PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.192 Definitions used in this subpart. As used in..., Miscellaneous Regulations Relating to Tobacco Products and Cigarette Papers and Tubes. (b) Articles subject to...

Temperature control of thermal-gas-dynamical installation in cleaning oil-well tubes

NASA Astrophysics Data System (ADS)

Penner, V. A.; Martemyanov, D. B.; Pshenichnikova, V. V.

2017-08-01

The article provides the study results of cleaning oil-well tubes, the oil-well tube failure reasons for service by their types have been considered. The chemical method of cleaning oil-well tubes as the least expensive has been reviewed when acid solution moves to the interptube space mixing up with oil and liquidates paraffin and pitches deposits on the internal pipe surface. Except the chemical method of pipes cleaning the mechanical one was considered as well. Also the disadvantages -such as the low productivity of cleaning and design complexity- of this deposits removal method on the internal oil-well tube surface have been considered. An effective method for cleaning oil-well tubing from paraffin and pitches by the thermodynamic plant based on the aircraft engine has been introduced for the first time. The temperature distribution graph in the gas stream at the engine output has been given.

Tube Visualization and Properties from Isoconfigurational Averaging

NASA Astrophysics Data System (ADS)

Qin, Jian; Bisbee, Windsor; Milner, Scott

2012-02-01

We introduce a simulation method to visualize the confining tube in polymer melts and measure its properties. We studied bead-spring ring polymers, which conveniently suppresses constraint release and contour length fluctuations. We allow molecules to cross and reach topologically equilibrated states by invoking various molecular rebridging moves in Monte Carlo simulations. To reveal the confining tube, we start with a well equilibrated configuration, turn off rebridging moves, and run molecular dynamics simulation multiple times, each with different initial velocities. The resulting set of ``movies'' of molecular trajectories defines an isoconfigurational ensemble, with the bead positions at different times and in different ``movies'' giving rise to a cloud. The cloud shows the shape, range and strength of the tube confinement, which enables us to study the statistical properties of tube. Using this approach, we studied the effects of free surface, and found that the tube diameter near the surface is greater than the bulk value by about 25%.

Moisture separator reheater with round tube bundle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Byerley, W. M.

1984-11-27

A moisture separator reheater having a central chamber with cylindrical wall protions and a generally round tube bundle, the tube bundle having arcuate plates disposed on each side of the bundle which form a wrapper on each side of the bundle and having a tongue and groove juncture between the wrapper and cylindrical wall portions to provide a seal therebetween and a track for installing and removing the tube bundle from the central chamber.

MAGNETOHYDRODYNAMIC SIMULATION OF THE X2.2 SOLAR FLARE ON 2011 FEBRUARY 15. II. DYNAMICS CONNECTING THE SOLAR FLARE AND THE CORONAL MASS EJECTION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inoue, S.; Magara, T.; Choe, G. S.

2015-04-20

We clarify a relationship between the dynamics of a solar flare and a growing coronal mass ejection (CME) by investigating the dynamics of magnetic fields during the X2.2-class flare taking place in the solar active region 11158 on 2011 February 15, based on simulation results obtained from Inoue et al. We found that the strongly twisted lines formed through tether-cutting reconnection in the twisted lines of a nonlinear force-free field can break the force balance within the magnetic field, resulting in their launch from the solar surface. We further discover that a large-scale flux tube is formed during the eruptionmore » as a result of the tether-cutting reconnection between the eruptive strongly twisted lines and these ambient weakly twisted lines. The newly formed large flux tube exceeds the critical height of the torus instability. Tether-cutting reconnection thus plays an important role in the triggering of a CME. Furthermore, we found that the tangential fields at the solar surface illustrate different phases in the formation of the flux tube and its ascending phase over the threshold of the torus instability. We will discuss these dynamics in detail.« less

Sound and vision: visualization of music with a soap film

NASA Astrophysics Data System (ADS)

Gaulon, C.; Derec, C.; Combriat, T.; Marmottant, P.; Elias, F.

2017-07-01

A vertical soap film, freely suspended at the end of a tube, is vibrated by a sound wave that propagates in the tube. If the sound wave is a piece of music, the soap film ‘comes alive’: colours, due to iridescences in the soap film, swirl, split and merge in time with the music (see the snapshots in figure 1 below). In this article, we analyse the rich physics behind these fascinating dynamical patterns: it combines the acoustic propagation in a tube, the light interferences, and the static and dynamic properties of soap films. The interaction between the acoustic wave and the liquid membrane results in capillary waves on the soap film, as well as non-linear effects leading to a non-oscillatory flow of liquid in the plane of the film, which induces several spectacular effects: generation of vortices, diphasic dynamical patterns inside the film, and swelling of the soap film under certain conditions. Each of these effects is associated with a characteristic time scale, which interacts with the characteristic time of the music play. This article shows the richness of those characteristic times that lead to dynamical patterns. Through its artistic interest, the experiments presented in this article provide a tool for popularizing and demonstrating science in the classroom or to a broader audience.

Numerical simulation analysis of four-stage mutation of solid-liquid two-phase grinding

NASA Astrophysics Data System (ADS)

Li, Junye; Liu, Yang; Hou, Jikun; Hu, Jinglei; Zhang, Hengfu; Wu, Guiling

2018-03-01

In order to explore the numerical simulation of solid-liquid two-phase abrasive grain polishing and abrupt change tube, in this paper, the fourth order abrupt change tube was selected as the research object, using the fluid mechanics software to simulate,based on the theory of solid-liquid two-phase flow dynamics, study on the mechanism of AFM micromachining a workpiece during polishing.Analysis at different inlet pressures, the dynamic pressure distribution pipe mutant fourth order abrasive flow field, turbulence intensity, discuss the influence of the inlet pressure of different abrasive flow polishing effect.

Development of a dynamic pressure calibration technique

NASA Technical Reports Server (NTRS)

Vezzetti, C. F.; Hilten, J. S.; Lederer, P. S.

1975-01-01

The report deals with work continuing on the development of a method of producing sinusoidally varying pressures of at least 34 kPa zero-to-peak with amplitude variations within plus or minus 5% up to 2 kHz for the dynamic calibration of pressure transducers. Sinusoidally varying pressures of 34 kPa zero-to-peak were produced between 40 Hz and 750 Hz by vibrating a 10-cm column of a dimethyl siloxane liquid at 36gn zero-to-peak. Damping of the liquid column was accomplished by packing the fixture tube with a number of smaller diameter tubes.

Capillary descent.

PubMed

Delannoy, Joachim; de Maleprade, Hélène; Clanet, Christophe; Quéré, David

2018-05-31

A superhydrophobic capillary tube immersed in water and brought in contact with the bath surface will be invaded by air, owing to its aerophilicity. We discuss this phenomenon where the ingredients of classical capillary rise are inverted, which leads to noticeable dynamical features. (1) The main regime of air invasion is linear in time, due to the viscous resistance of water. (2) Menisci in tubes with millimetre-size radii strongly oscillate before reaching their equilibrium depth, a consequence of inertia. On the whole, capillary descent provides a broad variety of dynamics where capillary effects, viscous friction and liquid inertia all play a role.

Designing high speed diagnostics

NASA Astrophysics Data System (ADS)

Veliz Carrillo, Gerardo; Martinez, Adam; Mula, Swathi; Prestridge, Kathy; Extreme Fluids Team Team

2017-11-01

Timing and firing for shock-driven flows is complex because of jitter in the shock tube mechanical drivers. Consequently, experiments require dynamic triggering of diagnostics from pressure transducers. We explain the design process and criteria for setting up re-shock experiments at the Los Alamos Vertical Shock Tube facility, and the requirements for particle image velocimetry and planar laser induced fluorescence measurements necessary for calculating Richtmeyer-Meshkov variable density turbulent statistics. Dynamic triggering of diagnostics allows for further investigation of the development of the Richtemeyer-Meshkov instability at both initial shock and re-shock. Thanks to the Los Alamos National Laboratory for funding our project.

Experiments in a Combustion-Driven Shock Tube with an Area Change

NASA Astrophysics Data System (ADS)

Schmidt, B. E.; Bobbitt, B.; Parziale, N. J.; Shepherd, J. E.

Shock tubes are versatile and useful tools for studying high temperature gas dynamics and the production of hypervelocity flows. High shock speeds are desirable for creating higher enthalpy, pressure, and temperature in the test gas which makes the study of thermo-chemical effects on fluid dynamics possible. Independent of construction and operational cost, free-piston drivers, such as the one used in the T5 facility at Caltech, give the best performance [3]. The high operational cost and long turnaround time of such a facility make a more economical option desirable for smaller-scale testing.

Measurement of unsteady airflow velocity at nozzle outlet

NASA Astrophysics Data System (ADS)

Pyszko, René; Machů, Mário

2017-09-01

The paper deals with a method of measuring and evaluating the cooling air flow velocity at the outlet of the flat nozzle for cooling a rolled steel product. The selected properties of the Prandtl and Pitot sensing tubes were measured and compared. A Pitot tube was used for operational measurements of unsteady dynamic pressure of the air flowing from nozzles to abtain the flow velocity. The article also discusses the effects of air temperature, pressure and relative air humidity on air density, as well as the influence of dynamic pressure filtering on the error of averaged velocity.

ANSYS Fluent Modelling of an Underexpanded Supersonic Sootblower Jet Impinging into Recovery Boiler Tube Geometries

NASA Astrophysics Data System (ADS)

Doroudi, Shahed

Sootblowers generate high pressure supersonic steam jets to control fireside deposition on heat transfer tubes of a kraft recovery boiler. Sootblowing is energy expensive, using 3-12% of the mill's total steam production. This motivates research on the dynamics of sootblower jet interaction with tubes and deposits, to optimize their use. A CFD investigation was performed using ANSYS Fluent 15.0 to model three-dimensional steady-state impingement of a Mach 2.5 mildly underexpanded (PR 1.2) air jet onto arrays of cylindrical tubes with and without fins, at various nozzle-to-tube centerline offsets. A free jet and four impingement cases for each of the economizer and generating bank geometries are compared to experimental visualizations. Pressure distributions on impinging surfaces suggest that the fins in the economizer produce a reduced but uniform sootblowing force. Pressure contours along the tubes (in the vertical direction) show a sharp decline one tube diameter away from the jet mid-plane.

The hummingbird tongue is a fluid trap, not a capillary tube

PubMed Central

Rico-Guevara, Alejandro; Rubega, Margaret A.

2011-01-01

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue–fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics). PMID:21536916

The hummingbird tongue is a fluid trap, not a capillary tube.

PubMed

Rico-Guevara, Alejandro; Rubega, Margaret A

2011-06-07

Hummingbird tongues pick up a liquid, calorie-dense food that cannot be grasped, a physical challenge that has long inspired the study of nectar-transport mechanics. Existing biophysical models predict optimal hummingbird foraging on the basis of equations that assume that fluid rises through the tongue in the same way as through capillary tubes. We demonstrate that the hummingbird tongue does not function like a pair of tiny, static tubes drawing up floral nectar via capillary action. Instead, we show that the tongue tip is a dynamic liquid-trapping device that changes configuration and shape dramatically as it moves in and out of fluids. We also show that the tongue-fluid interactions are identical in both living and dead birds, demonstrating that this mechanism is a function of the tongue structure itself, and therefore highly efficient because no energy expenditure by the bird is required to drive the opening and closing of the trap. Our results rule out previous conclusions from capillarity-based models of nectar feeding and highlight the necessity of developing a new biophysical model for nectar intake in hummingbirds. Our findings have ramifications for the study of feeding mechanics in other nectarivorous birds, and for the understanding of the evolution of nectarivory in general. We propose a conceptual mechanical explanation for this unique fluid-trapping capacity, with far-reaching practical applications (e.g., biomimetics).

Grid-converged solution and analysis of the unsteady viscous flow in a two-dimensional shock tube

NASA Astrophysics Data System (ADS)

Zhou, Guangzhao; Xu, Kun; Liu, Feng

2018-01-01

The flow in a shock tube is extremely complex with dynamic multi-scale structures of sharp fronts, flow separation, and vortices due to the interaction of the shock wave, the contact surface, and the boundary layer over the side wall of the tube. Prediction and understanding of the complex fluid dynamics are of theoretical and practical importance. It is also an extremely challenging problem for numerical simulation, especially at relatively high Reynolds numbers. Daru and Tenaud ["Evaluation of TVD high resolution schemes for unsteady viscous shocked flows," Comput. Fluids 30, 89-113 (2001)] proposed a two-dimensional model problem as a numerical test case for high-resolution schemes to simulate the flow field in a square closed shock tube. Though many researchers attempted this problem using a variety of computational methods, there is not yet an agreed-upon grid-converged solution of the problem at the Reynolds number of 1000. This paper presents a rigorous grid-convergence study and the resulting grid-converged solutions for this problem by using a newly developed, efficient, and high-order gas-kinetic scheme. Critical data extracted from the converged solutions are documented as benchmark data. The complex fluid dynamics of the flow at Re = 1000 are discussed and analyzed in detail. Major phenomena revealed by the numerical computations include the downward concentration of the fluid through the curved shock, the formation of the vortices, the mechanism of the shock wave bifurcation, the structure of the jet along the bottom wall, and the Kelvin-Helmholtz instability near the contact surface. Presentation and analysis of those flow processes provide important physical insight into the complex flow physics occurring in a shock tube.

Spent nuclear fuel system dynamic stability under normal conditions of transportation

DOE PAGES

Jiang, Hao; Wang, Jy-An John

2016-10-14

In a horizontal layout of a spent nuclear fuel (SNF) assembly under normal conditions of transportation (NCT), the fuel assembly’s skeleton formed by guide tubes and spacer grids is the primary load bearing structure for carrying and transferring the vibration loads within an SNF assembly. Therefore, the integrity of guide tubes and spacer grids will dictate the vibration amplitude/intensity of the fuel assembly during transport, and must be considered when designing multipurpose purpose canister (MPC) for safe SNF transport. This paper investigates the SNF assembly deformation dynamics during normal vibration mode, as well as the transient shock mode inside themore » cask during NCT. In conclusion, dynamic analyses were performed in the frequency domain to study frequency characteristic of the fuel assembly system and in the time domain to simulate the transient dynamic response of the fuel assembly.« less

Spent nuclear fuel system dynamic stability under normal conditions of transportation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Hao; Wang, Jy-An John

In a horizontal layout of a spent nuclear fuel (SNF) assembly under normal conditions of transportation (NCT), the fuel assembly’s skeleton formed by guide tubes and spacer grids is the primary load bearing structure for carrying and transferring the vibration loads within an SNF assembly. Therefore, the integrity of guide tubes and spacer grids will dictate the vibration amplitude/intensity of the fuel assembly during transport, and must be considered when designing multipurpose purpose canister (MPC) for safe SNF transport. This paper investigates the SNF assembly deformation dynamics during normal vibration mode, as well as the transient shock mode inside themore » cask during NCT. In conclusion, dynamic analyses were performed in the frequency domain to study frequency characteristic of the fuel assembly system and in the time domain to simulate the transient dynamic response of the fuel assembly.« less

Cooling arrangement for a superconducting coil

DOEpatents

Herd, K.G.; Laskaris, E.T.

1998-06-30

A superconducting device is disclosed, such as a superconducting rotor for a generator or motor. A vacuum enclosure has an interior wall surrounding a cavity containing a vacuum. A superconductive coil is placed in the cavity. A generally-annularly-arranged, thermally-conductive sheet has an inward-facing surface contacting generally the entire outward-facing surface of the superconductive coil. A generally-annularly-arranged coolant tube contains a cryogenic fluid and contacts a generally-circumferential portion of the outward-facing surface of the sheet. A generally-annularly-arranged, thermally-insulative coil overwrap generally circumferentially surrounds the sheet. The coolant tube and the inward-facing surface of the coil overwrap together contact generally the entire outward-facing surface of the sheet. 3 figs.

Method and apparatus for assembling solid oxide fuel cells

DOEpatents

Szreders, Bernard E.; Campanella, Nicholas

1989-01-01

A plurality of jet air tubes are supported and maintained in a spaced matrix array by a positioning/insertion assembly for insertion in respective tubes of a solid oxide fuel cell (SOFC) in the assembly of an SOFC module. The positioning/insertion assembly includes a plurality of generally planar, elongated, linear vanes which are pivotally mounted at each end thereof to a support frame. The vanes, which each include a plurality of spaced slots along the facing edges thereof, may be pivotally displaced from a generally vertical orientation, wherein each jet air tube is positioned within and engaged by the aligned slots of a plurality of paired upper and lower vanes to facilitate their insertion in respective aligned SOFC tubes arranged in a matrix array, to an inclined orientation, wherein the jet air tubes may be removed from the positioning/insertion assembly after being inserted in the SOFC tubes. A rectangular compression assembly of adjustable size is adapted to receive and squeeze a matrix of SOFC tubes so as to compress the inter-tube nickel felt conductive pads which provide series/parallel electrical connection between adjacent SOFCs, with a series of increasingly larger retainer frames used to maintain larger matrices of SOFC tubes in position. Expansion of the SOFC module housing at the high operating temperatures of the SOFC is accommodated by conductive, flexible, resilient expansion, connector bars which provide support and electrical coupling at the top and bottom of the SOFC module housing.

Liquid Oscillations in a U-Tube

ERIC Educational Resources Information Center

Aguilar, Horacio Munguía; Maldonado, Rigoberto Franco; Navarro, Luis Barba

2018-01-01

In hydrostatics, pressure measurement with U-gauges and their relationship to density is a well-known experiment. Very little is studied or experimented with the dynamics of the movement of a liquid in a U-tube probably due to its theoretical complexity but, after all, it is a simple damped oscillating system. In this paper we present a relatively…

Overexpression of Arabidopsis thaliana PTEN caused accumulation of autophagic bodies in pollen tubes by disrupting phosphatidylinositol 3-phosphate dynamics

USDA-ARS?s Scientific Manuscript database

Autophagy is a pathway in eukaryotes by which nutrient remobilization occurs through bulk protein and organelle turnover. Autophagy not only aides cells in coping with harsh environments but also plays a key role in many physiological processes that include pollen germination and tube growth. Most a...

Pulsating flow past a tube bundle

NASA Astrophysics Data System (ADS)

Molochnikov, V. M.; Mikheev, N. I.; Vazeev, T. A.; Paereliy, A. A.

2017-11-01

Visualization of the pulsating cross-flow past the in-line and staggered tube bundles has been performed. The frequency and amplitude of forced flow pulsations and the tube pitch in the bundle varied in the experiments. The main attention was focused on the flow pattern in the near wake of the third-row tube. The most indicative regimes of flow past a tube in a bundle have been revealed depending on forced flow unsteadiness parameters. The obtained data have been generalized in the flow maps in the space of dimensionless frequency (Strouhal number, St) and relative pulsation amplitude, β, individually for the in-line and staggered tube arrangement. Three most indicative regimes of pulsating flow past the tubes in a bundle have been singled out in each flow map.

The magnetic non-equilibrium of buoyant flux tubes in the solar corona

NASA Technical Reports Server (NTRS)

Browning, P. K.; Priest, E. R.

1984-01-01

The magnetic field in the convection zone and photosphere of the sun exists mostly as concentrated tubes of magnetic flux. It is, therefore, necessary to study the basic properties of magnetic flux tubes to obtain a basis for understanding the behavior of the sun's magnetic field. The present investigation is concerned with the global equilibrium shape of a flux tube in the stratified solar atmosphere. A fundamental property of isolated flux tubes is magnetic buoyancy. Attention is given to flux tubes with external field, and twisted flux tubes. It is shown that the analysis of Parker (1975, 1979) and Spruit (1981) for calculating the equilibrium of a slender flux tube in a stratified atmosphere may be extended to more general situations. The slender tube approximation provides a method of solving the problem of modeling the overall curvature of flux tubes. It is found that for a twisted flux tube, there can be two possible equilibrium values of the height.

Probable causes of damage of heat-exchange tubes of low-pressure-exchanges of PND-3 type and repair methods

NASA Astrophysics Data System (ADS)

Trifonov, N. N.; Esin, S. B.; Nikolaenkova, E. K.; Sukhorukov, Yu. G.; Svyatkin, F. A.; Sintsova, T. G.; Modestov, V. S.

2017-08-01

The structures of low-pressure heaters (LPH), which are installed at nuclear power plants with the K-1000-60/1500 type turbine plants are considered. It was revealed that only the PND-3 type low-pressure heaters have the damages of the heat exchange tubes. For a short operation life, the number of the damaged heat-exchange tubes of PND-3 is approximately 50 pcs for Kalinin NPP and 100-150 pcs for Balakovo NPP. The low-pressure heaters were manufactured at AO Ural Plant of Chemical Machine-Building "Uralkhimmash," OAO Taganrog Boiler-Making Works "Krasny Kotelshchik," and Vitkovice Machinery Group, but the damage nature of the heat-exchange tubes is identical for all PND-3. The damages occur in the place of passage of the heat exchange tubes through the first, the second, and the third partitions over the lower tube plate (the first path of the turbine condensate). Hydraulic shocks can be one of the possible causes of the damage of the heat-exchange tubes of PND-3. The analysis of the average thermal and dynamic loads of the tube systems of PND-1-PND-4 revealed that PND-3 by the thermal power are loaded 1.4-1.6 times and by the dynamic effects are loaded 1.8-2.0 times more than the remaining LPHs. Another possible cause of damage can be the cascaded drain of the separate into PND-4 and then through the drainage heat exchange into PND-3. An additional factor can be the structure of the condensate drainage unit. The advanced system of the heating steam flow and pumping scheme of the separate drain using the existing drainage pumps of PND-3 for K-1000-60/1500 turbine plants for Balakovo and Kalinin NPPs were proposed. The considered decisions make it possible to reduce the flow rate of the heating steam condensate from PND-3 into PND-4 and the speed of the heating steam in the tube space of PND-3 and eliminate the occurrence of hydraulic shocks and damages of the heat exchanger tubes.

27 CFR 44.63 - Restrictions on disposal of tobacco products, and cigarette papers and tubes on vessels and...

Code of Federal Regulations, 2012 CFR

2012-04-01

... tobacco products, and cigarette papers and tubes on vessels and aircraft. 44.63 Section 44.63 Alcohol... (CONTINUED) TOBACCO EXPORTATION OF TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES, WITHOUT PAYMENT OF TAX, OR WITH DRAWBACK OF TAX General § 44.63 Restrictions on disposal of tobacco products, and cigarette...

Chemical Dosimeter Tube With Coaxial Sensing Rod

NASA Technical Reports Server (NTRS)

Lueck, Dale E.

1993-01-01

Improved length-of-stain (LOS) chemical dosimeter indicates total dose of chemical vapor in air. Made with rods and tubes of various diameters to obtain various sensitivities and dynamic ranges. Sensitivity larger and dose range smaller when more room for diffusion in gap between tube and rod. Offers greater resistance to changing of color of exposed dye back to color of unexposed condition, greater sensitivity, and higher degree of repeatability. Developed to measure doses of gaseous HCI, dosimeter modified by use of other dyes to indicate doses of other chemical vapors.

Explosive instability and erupting flux tubes in a magnetized plasma

PubMed Central

Cowley, S. C.; Cowley, B.; Henneberg, S. A.; Wilson, H. R.

2015-01-01

The eruption of multiple flux tubes in a magnetized plasma is proposed as a mechanism for explosive release of energy in plasmas. A significant fraction of the linearly stable isolated flux tubes are shown to be metastable in a box model magnetized atmosphere in which ends of the field lines are embedded in conducting walls. The energy released by destabilizing such field lines can be a large proportion of the gravitational energy stored in the system. This energy can be released in a fast dynamical time. PMID:26339193

Torus Breakdown and Homoclinic Chaos in a Glow Discharge Tube

NASA Astrophysics Data System (ADS)

Ginoux, Jean-Marc; Meucci, Riccardo; Euzzor, Stefano

2017-12-01

Starting from historical researches, we used, like Van der Pol and Le Corbeiller, a cubic function for modeling the current-voltage characteristic of a direct current low-pressure plasma discharge tube, i.e. a neon tube. This led us to propose a new four-dimensional autonomous dynamical system allowing to describe the experimentally observed phenomenon. Then, mathematical analysis and detailed numerical investigations of such a fourth-order torus circuit enabled to highlight bifurcation routes from torus breakdown to homoclinic chaos following the Newhouse-Ruelle-Takens scenario.

Modeling and dynamic properties of dual-chamber solid and liquid mixture vibration isolator

NASA Astrophysics Data System (ADS)

Li, F. S.; Chen, Q.; Zhou, J. H.

2016-07-01

The dual-chamber solid and liquid mixture (SALiM) vibration isolator, mainly proposed for vibration isolation of heavy machines with low frequency, consists of four principle parts: SALiM working media including elastic elements and incompressible oil, multi-layers bellows container, rigid reservoir and the oil tube connecting the two vessels. The isolation system under study is governed by a two-degrees-of-freedom (2-DOF) nonlinear equation including quadratic damping. Simplifying the nonlinear damping into viscous damping, the equivalent stiffness and damping model is derived from the equation for the response amplitude. Theoretical analysis and numerical simulation reveal that the isolator's stiffness and damping have multiple properties with different parameters, among which the effects of exciting frequency, vibrating amplitude, quadratic damping coefficient and equivalent stiffness of the two chambers on the isolator's dynamics are discussed in depth. Based on the boundary characteristics of stiffness and damping and the main causes for stiffness hardening effect, improvement strategies are proposed to obtain better dynamic properties. At last, experiments were implemented and the test results were generally consistent with the theoretical ones, which verified the reliability of the nonlinear dynamic model.

27 CFR 41.29 - Delegations of the Administrator.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 41, Importation of Tobacco Products and Cigarette Papers and Tubes. You may obtain a copy of this... AND TUBES, AND PROCESSED TOBACCO General § 41.29 Delegations of the Administrator. The regulatory...

Gastrostomy Tube (G-Tube)

MedlinePlus

... developmental delay, or some neuromuscular conditions, like severe cerebral palsy failure to thrive , which is a general diagnosis ... Surgery A Primer on Preemies Failure to Thrive Cerebral Palsy (CP) Dietary Needs for Kids With Cerebral Palsy ...

Half-value-layer increase owing to tungsten buildup in the x-ray tube: fact or fiction.

PubMed

Stears, J G; Felmlee, J P; Gray, J E

1986-09-01

The half-value layer (HVL) of an x-ray beam is generally believed to increase with x-ray tube use. This increase in HVL has previously been attributed to the hardening of the x-ray beam as a result of a buildup of tungsten on the x-ray tube glass window. Radiographs and HVL measurements were obtained to determine the effect of tungsten deposited on the x-ray tube windows. This work, along with the HVL data from approximately 200 functioning x-ray tubes used for all applications that were monitored for more than 8 years, indicated there is no significant increase in HVL with diagnostic x-ray tube use.

Steady Capillary Driven Flow

NASA Technical Reports Server (NTRS)

Weislogel, Mark M.

1996-01-01

A steady capillary driven flow is developed for a liquid index in a circular tube which is partially coated with a surface modifier to produce a discontinuous wetting condition from one side of the tube to the other. The bulk flow is novel in that it is truly steady, and controlled solely by the physics associated with dynamic wetting. The influence of gravity on the flow is minimized through the use of small diameter tubes approximately O(1 mm) tested horizontally in a laboratory and larger tubes approximately O(10 mm) tested in the low gravity environment of a drop tower. Average steady velocities are predicted and compared against a large experimental data set which includes the effects of tube dimensions and fluid properties. The sensitivity of the velocity to surface cleanliness is dramatic and the advantages of experimentation in a microgravity environment are discussed.

Burning invariant manifolds for reaction fronts in three-dimensional fluid flows

NASA Astrophysics Data System (ADS)

Mitchell, Kevin; Solomon, Tom

2017-11-01

The geometry of reaction fronts that propagate in fully three-dimensional (3D) fluid flows is studied using the tools of dynamical systems theory. The evolution of an infinitesimal front element is modeled as a six-dimensional ODE-three dimensions for the position of the front element and three for the orientation of its unit normal. This generalizes an earlier approach to understanding front propagation in two-dimensional (2D) fluid flows. As in 2D, the 3D system exhibits prominent burning invariant manifolds (BIMs). In 3D, BIMs are two-dimensional dynamically defined surfaces that form one-way barriers to the propagation of reaction fronts within the fluid. Due to the third dimension, BIMs in 3D exhibit a richer topology than their cousins in 2D. In particular, whereas BIMs in both 2D and 3D can originate from fixed points of the dynamics, BIMs in 3D can also originate from limit cycles. Such BIMs form robust tube-like channels that guide and constrain the evolution of the front within the bulk of the fluid. Supported by NSF Grant CMMI-1201236.

Simulated nuclear reactor fuel assembly

DOEpatents

Berta, V.T.

1993-04-06

An apparatus for electrically simulating a nuclear reactor fuel assembly. It includes a heater assembly having a top end and a bottom end and a plurality of concentric heater tubes having electrical circuitry connected to a power source, and radially spaced from each other. An outer target tube and an inner target tube is concentric with the heater tubes and with each other, and the outer target tube surrounds and is radially spaced from the heater tubes. The inner target tube is surrounded by and radially spaced from the heater tubes and outer target tube. The top of the assembly is generally open to allow for the electrical power connection to the heater tubes, and the bottom of the assembly includes means for completing the electrical circuitry in the heater tubes to provide electrical resistance heating to simulate the power profile in a nuclear reactor. The embedded conductor elements in each heater tube is split into two halves for a substantial portion of its length and provided with electrical isolation such that each half of the conductor is joined at one end and is not joined at the other end.

Method for preventing jamming conditions in a compression device

DOEpatents

Williams, Paul M.; Faller, Kenneth M.; Bauer, Edward J.

2002-06-18

A compression device for feeding a waste material to a reactor includes a waste material feed assembly having a hopper, a supply tube and a compression tube. Each of the supply and compression tubes includes feed-inlet and feed-outlet ends. A feed-discharge valve assembly is located between the feed-outlet end of the compression tube and the reactor. A feed auger-screw extends axially in the supply tube between the feed-inlet and feed-outlet ends thereof. A compression auger-screw extends axially in the compression tube between the feed-inlet and feed-outlet ends thereof. The compression tube is sloped downwardly towards the reactor to drain fluid from the waste material to the reactor and is oriented at generally right angle to the supply tube such that the feed-outlet end of the supply tube is adjacent to the feed-inlet end of the compression tube. A programmable logic controller is provided for controlling the rotational speed of the feed and compression auger-screws for selectively varying the compression of the waste material and for overcoming jamming conditions within either the supply tube or the compression tube.

Simulated nuclear reactor fuel assembly

DOEpatents

Berta, Victor T.

1993-01-01

An apparatus for electrically simulating a nuclear reactor fuel assembly. It includes a heater assembly having a top end and a bottom end and a plurality of concentric heater tubes having electrical circuitry connected to a power source, and radially spaced from each other. An outer target tube and an inner target tube is concentric with the heater tubes and with each other, and the outer target tube surrounds and is radially spaced from the heater tubes. The inner target tube is surrounded by and radially spaced from the heater tubes and outer target tube. The top of the assembly is generally open to allow for the electrical power connection to the heater tubes, and the bottom of the assembly includes means for completing the electrical circuitry in the heater tubes to provide electrical resistance heating to simulate the power profile in a nuclear reactor. The embedded conductor elements in each heater tube is split into two halves for a substantial portion of its length and provided with electrical isolation such that each half of the conductor is joined at one end and is not joined at the other end.

Dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes.

PubMed

Li, Rui; Fan, Jianfen; Li, Hui; Yan, Xiliang; Yu, Yi

2015-07-07

Classical molecular dynamics simulations have been performed to investigate the dynamic behaviors and transport properties of ethanol molecules in transmembrane cyclic peptide nanotubes (CPNTs) with various radii, i.e., 8×(WL¯)n=3,4,5/POPE. The results show that ethanol molecules spontaneously fill the octa- and deca-CPNTs, but not the hexa-CPNT. In the octa-CPNT, ethanol molecules are trapped at individual gaps with their carbon skeletons perpendicular to the tube axis and hydroxyl groups towards the tube wall, forming a broken single-file chain. As the channel radius increases, ethanol molecules inside the deca-CPNT tend to form a tubular layer and the hydroxyl groups mainly stretch towards the tube axis. Computations of diffusion coefficients indicate that ethanol molecules in the octa-CPNT nearly lost their diffusion abilities, while those in the deca-CPNT diffuse as 4.5 times as in a (8, 8) carbon nanotube with a similar tube diameter. The osmotic and diffusion permeabilities (pf and pd, respectively) of the octa- and deca-CPNTs transporting ethanol were deduced for the first time. The distributions of the gauche and trans conformers of ethanol molecules in two CPNTs are quite similar, both with approximately 57% gauche conformers. The non-bonded interactions of channel ethanol with a CPNT wall and surrounding ethanol were explored. The potential of mean force elucidates the mechanism underlying the transporting characteristics of channel ethanol in a transmembrane CPNT.

Intuitive reasoning about abstract and familiar physics problems

NASA Technical Reports Server (NTRS)

Kaiser, Mary Kister; Jonides, John; Alexander, Joanne

1986-01-01

Previous research has demonstrated that many people have misconceptions about basic properties of motion. Two experiments examined whether people are more likely to produce dynamically correct predictions about basic motion problems involving situations with which they are familiar, and whether solving such problems enhances performance on a subsequent abstract problem. In experiment 1, college students were asked to predict the trajectories of objects exiting a curved tube. Subjects were more accurate on the familiar version of the problem, and there was no evidence of transfer to the abstract problem. In experiment 2, two familiar problems were provided in an attempt to enhance subjects' tendency to extract the general structure of the problems. Once again, they gave more correct responses to the familiar problems but failed to generalize to the abstract problem. Formal physics training was associated with correct predictions for the abstract problem but was unrelated to performance on the familiar problems.

Modeling of microjoule and millijoule energy LIDARs with PMT/SiPM/APD detectors: a sensitivity analysis.

PubMed

Agishev, Ravil

2018-05-10

This paper demonstrates a renewed concept and applications of the generalized methodology for atmospheric light detection and ranging (LIDAR) capability prediction as a continuation of a series of our previous works, where the dimensionless parameterization appeared as a tool for comparing systems of a different scale, design, and applications. The modernized concept applied to microscale and milliscale LIDARs with relatively new silicon photomultiplier detectors and traditional photomultiplier tube and avalanche photodiode detectors allowed prediction of the remote sensing instruments' performance and limitations. Such a generalized, uniform, and objective concept is applied for evaluation of the increasingly popular class of limited-energy LIDARs using the best optical detectors, operating on different targets (back-scatter or topographic, static or dynamic) and under intense sky background conditions. It can be used in the LIDAR community to compare different instruments and select the most suitable and effective ones for specific applications.

Dissipative particle dynamics simulations of deformation and aggregation of healthy and diseased red blood cells in a tube flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Ting; Phan-Thien, Nhan, E-mail: Nhan@nus.edu.sg; Khoo, Boo Cheong

In this paper, we report simulation results assessing the deformation and aggregation of mixed healthy and malaria-infected red blood cells (RBCs) in a tube flow. A three dimensional particle model based on Dissipative Particle Dynamics (DPD) is developed to predict the tube flow containing interacting cells. The cells are also modelled by DPD, with a Morse potential to characterize the cell-cell interaction. As validation tests, a single RBC in a tube flow and two RBCs in a static flow are simulated to examine the cell deformation and intercellular interaction, respectively. The study of two cells, one healthy and the othermore » malaria-infected RBCs in a tube flow demonstrates that the malaria-infected RBC (in the leading position along flow direction) has different effects on the healthy RBC (in the trailing position) at the different stage of parasite development or at the different capillary number. With parasitic development, the malaria-infected RBC gradually loses its deformability, and in turn the corresponding trailing healthy RBC also deforms less due to the intercellular interaction. With increasing capillary number, both the healthy and malaria-infected RBCs are likely to undergo an axisymmetric motion. The minimum intercellular distance becomes small enough so that rouleaux is easily formed, i.e., the healthy and malaria-infected RBCs are difficultly disaggregated.« less

Role of size on the relative importance of fluid dynamic losses in linear cryocoolers

NASA Astrophysics Data System (ADS)

Kirkconnell, Carl; Ghavami, Ali; Ghiaasiaan, S. Mostafa; Perrella, Matthew

2017-12-01

Thermodynamic modeling results for a novel small satellite (SmallSat) Stirling Cryocooler, capable of delivering over 200 mW net cooling power at 80 K for less than 6 W DC input power, are used in this paper as the basis for related pulse tube computational fluid dynamics (CFD) analysis. Industry and government requirements for SmallSat infrared sensors are driving the development of ever-more miniaturized cryocooler systems. Such cryocoolers must be extremely compact and lightweight, a challenge met by this research team through operating a Stirling cryocooler at a frequency of approximately 300 Hz. The primary advantage of operating at such a high frequency is that the required compression and expansion swept volumes are reduced relative to linear coolers operating at lower frequencies, which evidently reduces the size of the motor mechanisms and the thermodynamic components. In the case of a pulse tube cryocooler, this includes a reduction in diameter of the pulse tube itself. This unfortunately leads to high boundary layer losses, as the presented results demonstrate. Using a Stirling approach with a mechanical moving expander piston eliminates this small pulse tube loss mechanism, but other challenges are introduced, such as maintaining very tight clearance gaps between moving and stationary elements. This paper focuses on CFD modelling results for a highly miniaturized pulse tube cooler.

Vibrational energy transfer between carbon nanotubes and liquid water: a molecular dynamics study.

PubMed

Nelson, Tammie R; Chaban, Vitaly V; Kalugin, Oleg N; Prezhdo, Oleg V

2010-04-08

The rates and magnitudes of vibrational energy transfer between single-wall carbon nanotubes (CNTs) and water are investigated by classical molecular dynamics. The interactions between the CNT and solvent confined inside of the tube, the CNT and solvent surrounding the tube, as well as the solvent inside and outside of the tube are considered for the (11,11), (15,15), and (19,19) armchair CNTs. The vibrational energy transfer exhibits two time scales, subpicosecond and picosecond, of roughly equal importance. Solvent molecules confined within CNTs are more strongly coupled to the tubes than the outside molecules. The energy exchange is facilitated by slow collective motions, including CNT radial breathing modes (RBM). The transfer rate between CNTs and the inside solvent shows strong dependence on the CNT diameter. In smaller tubes, the transfer is faster and the solvent coupling to RBMs is stronger. The magnitude of the CNT-outside solvent interaction scales with the CNT surface area, while that of the CNT-inside solvent exhibits scaling that is intermediate between the CNT volume and surface. The Coulomb interaction between the solvent molecules inside and outside of the CNTs is much weaker than the CNT-solvent interactions. The results indicate that the excitation energy supplied to CNTs in chemical and biological applications is rapidly deposited to the active molecular agents and should remain localized sufficiently long in order to perform the desired function.

76 FR 70706 - Frontseating Service Valves From the People's Republic of China: Final Results of the 2008-2010...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-15

... more of the following components: A valve body, field connection tube, factory connection tube or valve charge port. The valve body is a rectangular block, or brass forging, machined to be hollow in the interior, with a generally square shaped seat (bottom of body). The field connection tube and factory...

A molecular dynamics and ab initio analysis of the electronic structure of single-walled carbon nanotubes adhered to a substrate

NASA Astrophysics Data System (ADS)

Van Der Geest, A. G.; Lu, Z.; Lusk, M. T.; Dunn, M. L.

2011-04-01

Single-wall nanotubes can adhere to planar surfaces via van der Waals forces, and this causes the tubes to deform. We use classical molecular dynamics to estimate this deformation and density functional theory to quantify its impact on electronic band structure. For (n,0) tubes, adhesion causes the maximum bandgap to rise more rapidly with diameter, but the value of the maximum is not affected. The influence of adhesion forces on bandgap was found to correlate with that associated with lateral, uniaxial compression for moderate values of adhesion energy and compressive distortion.

Volume of interest CBCT and tube current modulation for image guidance using dynamic kV collimation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, David, E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca; Robar, James L., E-mail: david.parsons@dal.ca, E-mail: james.robar@nshealth.ca

2016-04-15

Purpose: The focus of this work is the development of a novel blade collimation system enabling volume of interest (VOI) CBCT with tube current modulation using the kV image guidance source on a linear accelerator. Advantages of the system are assessed, particularly with regard to reduction and localization of dose and improvement of image quality. Methods: A four blade dynamic kV collimator was developed to track a VOI during a CBCT acquisition. The current prototype is capable of tracking an arbitrary volume defined by the treatment planner for subsequent CBCT guidance. During gantry rotation, the collimator tracks the VOI withmore » adjustment of position and dimension. CBCT image quality was investigated as a function of collimator dimension, while maintaining the same dose to the VOI, for a 22.2 cm diameter cylindrical water phantom with a 9 mm diameter bone insert centered on isocenter. Dose distributions were modeled using a dynamic BEAMnrc library and DOSXYZnrc. The resulting VOI dose distributions were compared to full-field CBCT distributions to quantify dose reduction and localization to the target volume. A novel method of optimizing x-ray tube current during CBCT acquisition was developed and assessed with regard to contrast-to-noise ratio (CNR) and imaging dose. Results: Measurements show that the VOI CBCT method using the dynamic blade system yields an increase in contrast-to-noise ratio by a factor of approximately 2.2. Depending upon the anatomical site, dose was reduced to 15%–80% of the full-field CBCT value along the central axis plane and down to less than 1% out of plane. The use of tube current modulation allowed for specification of a desired SNR within projection data. For approximately the same dose to the VOI, CNR was further increased by a factor of 1.2 for modulated VOI CBCT, giving a combined improvement of 2.6 compared to full-field CBCT. Conclusions: The present dynamic blade system provides significant improvements in CNR for the same imaging dose and localization of imaging dose to a predefined volume of interest. The approach is compatible with tube current modulation, allowing optimization of the imaging protocol.« less

Analysis and test of a breadboard cryogenic hydrogen/Freon heat exchanger

NASA Technical Reports Server (NTRS)

Desjardins, L. F.; Hooper, J.

1973-01-01

System studies required to verify a tube-in-tube cryogenic heat exchanger as optimum for the space shuttle mission are described. Design of the optimum configuration, which could be fabricated from commercially available hardware, is discussed. Finally, testing of the proposed configuration with supercritical hydrogen and Freon 21 is discussed and results are compared with thermal and dynamic analysis.

Creating a YouTube-Like Collaborative Environment in Mathematics: Integrating Animated Geogebra Constructions and Student-Generated Screencast Videos

ERIC Educational Resources Information Center

Lazarus, Jill; Roulet, Geoffrey

2013-01-01

This article discusses the integration of student-generated GeoGebra applets and Jing screencast videos to create a YouTube-like medium for sharing in mathematics. The value of combining dynamic mathematics software and screencast videos for facilitating communication and representations in a digital era is demonstrated herein. We share our…

Transient Expression of Chimeric Fluorescent Reporter Proteins in Pollen Tubes to Study Protein Polar Secretion and Dynamics.

PubMed

Zhong, Guitao; Liu, Ronghe; Zhuang, Menglong; Wang, Hao

2017-01-01

Transient expression of chimeric fluorescent reporter proteins by biolistic bombardment is a quick and useful procedure for studying subcellular protein localization and dynamics in plants. It is especially beneficial in specific plant cells which are not suitable for protoplast-based and Agrobacterium-mediated protein transient expression. Polar protein secretion and vesicular trafficking play essential functions for cell polarization and tip growth. The growing pollen tube is regarded as an ideal model plant cell system to study the machinery and regulation of polar protein trafficking and targeting. A large amount of newly synthesized proteins are packed and polarly transported to the apical region to support the rapid and highly polarized tip growth. Here, we described a detailed step-by-step protocol for the transient expression of chimeric fluorescent reporter proteins in growing Arabidopsis and tobacco pollen tubes to study polar transportation logistics and mechanisms. In addition, we have optimized the Arabidopsis and tobacco in vitro pollen germination medium and the conditions to maximize the efficiency of protein expression. As a proof of concept, we have used this protocol to express actin microfilament and late endosomal fluorescent markers in Arabidopsis and tobacco pollen tubes.

Dyonic Flux Tube Structure of Nonperturbative QCD Vacuum

NASA Astrophysics Data System (ADS)

Chandola, H. C.; Pandey, H. C.

We study the flux tube structure of the nonperturbative QCD vacuum in terms of its dyonic excitations by using an infrared effective Lagrangian and show that the dyonic condensation of QCD vacuum has a close connection with the process of color confinement. Using the fiber bundle formulation of QCD, the magnetic symmetry condition is presented in a gauge covariant form and the gauge potential has been constructed in terms of the magnetic vectors on global sections. The dynamical breaking of the magnetic symmetry has been shown to lead the dyonic condensation of QCD vacuum in the infrared energy sector. Deriving the asymptotic solutions of the field equations in the dynamically broken phase, the dyonic flux tube structure of QCD vacuum is explored which has been shown to lead the confinement parameters in terms of the vector and scalar mass modes of the condensed vacuum. Evaluating the charge quantum numbers and energy associated with the dyonic flux tube solutions, the effect of electric excitation of monopole is analyzed using the Regge slope parameter (as an input parameter) and an enhancement in the dyonic pair correlations and the confining properties of QCD vacuum in its dyonically condensed mode has been demonstrated.

Experimentation and Modeling of Jet A Thermal Stability in a Heated Tube

NASA Technical Reports Server (NTRS)

Khodabandeh, Julia W.

2005-01-01

High performance aircraft typically use hydrocarbon fuel to regeneratively cool the airframe and engine components. As the coolant temperatures increase, the fuel may react with dissolved oxygen forming deposits that limit the regenerative cooling system performance. This study investigates the deposition of Jet A using a thermal stability experiment and computational fluid dynamics (CFD) modeling. The experimental portion of this study is performed with a high Reynolds number thermal stability (HiRets) tester in which fuel passes though an electrically heated tube and the fuel outlet temperature is held constant. If the thermal stability temperature of the fuel is exceeded, deposits form and adhere to the inside of the tube creating an insulating layer between the tube and the fuel. The HiRets tester measures the tube outer wall temperatures near the fuel outlet to report the effect of deposition occurring inside the tube. Final deposits are also estimated with a carbon burn off analysis. The CFD model was developed and used to simulate the fluid dynamics, heat transfer, chemistry, and transport of the deposit precursors. The model is calibrated to the experiment temperature results and carbon burn-off deposition results. The model results show that the dominant factor in deposition is the heated wall temperature and that most of the deposits are formed in the laminar sublayer. The models predicted a 7.0E-6 kilograms per square meter-sec deposition rate, which compared well to the carbon burn-off analysis deposition rate of 1.0E-6 kilograms per square meter-sec.

Academy of General Dentistry

MedlinePlus

... Patient Resources Contact Us Facebook Twitter LinkedIn YouTube Instagram close Enter Keyword Search close Main Site Search ... 6600 888.AGD.DENT Facebook Twitter LinkedIn YouTube Instagram Join AGD Member Center My Profile Career Stages ...

The mathematical model that describes the periodic spouting of a geyser induced by boiling

NASA Astrophysics Data System (ADS)

Kagami, Hiroyuki

2017-04-01

We have derived and modified the dynamical model of a geyser induced by gas inflow and regular or irregular spouting dynamics of geysers induced by gas inflow has been reproduced by the model. On the other hand, though we have derived the dynamical model of a geyser induced by boiling, periodic change between the spouting state and the pause state has not been adequately modeled by the model. In this connection, concerning a geyser induced by gas inflow we have proposed the model as described below. Because pressure in the spouting tube decreases obeying to the Bernoulli's theorem when the spouting state begins and water in the spouting tube begins to flow, inflow of groundwater into the spouting tube occurs. When the amount of this inflow reaches a certain amount, the spouting state transforms to the pause state. In this study, by applying this idea to the dynamical model of a geyser induced by boiling, the periodic change between the spouting state and the pause state could be reappeared. As a result, the whole picture of the spouting mechanism of a geyser induced by boiling became clear. This research results would give hints on engineering repair in order to prevent the weakening or the depletion of the geyser. And this study would be also useful for protection of geysers as tourism and environmental resources.

Parsimonious evaluation of concentric-tube continuum robot equilibrium conformation.

PubMed

Rucker, Daniel Caleb; Webster Iii, Robert J

2009-09-01

Dexterous at small diameters, continuum robots consisting of precurved concentric tubes are well-suited for minimally invasive surgery. These active cannulas are actuated by relative translations and rotations applied at the tube bases, which create bending via elastic tube interaction. An accurate kinematic model of cannula shape is required for applications in surgical and other settings. Previous models are limited to circular tube precurvatures, and neglect torsional deformation in curved sections. Recent generalizations account for arbitrary tube preshaping and bending and torsion throughout the cannula, providing differential equations that define cannula shape. In this paper, we show how to simplify these equations using Frenet-Serret frames. An advantage of this approach is the interpretation of torsional components of the preset tube shapes as "forcing functions" on the cannula's differential equations. We also elucidate a process for numerically solving the differential equations, and use it to produce simulations illustrating the implications of torsional deformation and helical tube shapes.

Conformable apparatus in a drill string

DOEpatents

Hall, David R [Provo, UT; Hall, Jr., H. Tracy; Pixton, David S [Lehi, UT; Fox, Joe [Spanish Fork, UT

2007-08-28

An apparatus in a drill string comprises an internally upset drill pipe. The drill pipe comprises a first end, a second end, and an elongate tube intermediate the first and second ends. The elongate tube and the ends comprising a continuous an inside surface with a plurality of diameters. A conformable metal tube is disposed within the drill pipe intermediate the ends thereof and terminating adjacent to the ends of the drill pipe. The conformable metal tube substantially conforms to the continuous inside surface of the metal tube. The metal tube may comprise a non-uniform section which is expanded to conform to the inside surface of the drill pipe. The non-uniform section may comprise protrusions selected from the group consisting of convolutions, corrugations, flutes, and dimples. The non-uniform section extends generally longitudinally along the length of the tube. The metal tube may be adapted to stretch as the drill pipes stretch.

Tube radial distribution phenomenon with a two-phase separation solution of a fluorocarbon and hydrocarbon organic solvent mixture in a capillary tube and metal compounds separation.

PubMed

Kitaguchi, Koichi; Hanamura, Naoya; Murata, Masaharu; Hashimoto, Masahiko; Tsukagoshi, Kazuhiko

2014-01-01

A fluorocarbon and hydrocarbon organic solvent mixture is known as a temperature-induced phase-separation solution. When a mixed solution of tetradecafluorohexane as a fluorocarbon organic solvent and hexane as a hydrocarbon organic solvent (e.g., 71:29 volume ratio) was delivered in a capillary tube that was controlled at 10°C, the tube radial distribution phenomenon (TRDP) of the solvents was clearly observed through fluorescence images of the dye, perylene, dissolved in the mixed solution. The homogeneous mixed solution (single phase) changed to a heterogeneous solution (two phases) with inner tetradecafluorohexane and outer hexane phases in the tube under laminar flow conditions, generating the dynamic liquid-liquid interface. We also tried to apply TRDP to a separation technique for metal compounds. A model analyte mixture, copper(II) and hematin, was separated through the capillary tube, and detected with a chemiluminescence detector in this order within 4 min.

Analytical and numerical performance models of a Heisenberg Vortex Tube

NASA Astrophysics Data System (ADS)

Bunge, C. D.; Cavender, K. A.; Matveev, K. I.; Leachman, J. W.

2017-12-01

Analytical and numerical investigations of a Heisenberg Vortex Tube (HVT) are performed to estimate the cooling potential with cryogenic hydrogen. The Ranque-Hilsch Vortex Tube (RHVT) is a device that tangentially injects a compressed fluid stream into a cylindrical geometry to promote enthalpy streaming and temperature separation between inner and outer flows. The HVT is the result of lining the inside of a RHVT with a hydrogen catalyst. This is the first concept to utilize the endothermic heat of para-orthohydrogen conversion to aid primary cooling. A review of 1st order vortex tube models available in the literature is presented and adapted to accommodate cryogenic hydrogen properties. These first order model predictions are compared with 2-D axisymmetric Computational Fluid Dynamics (CFD) simulations.

Dynamic Load Measurement of Ballistic Gelatin Impact Using an Instrumented Tube

NASA Technical Reports Server (NTRS)

Seidt, J. D.; Periira, J. M.; Hammer, J. T.; Gilat, A.; Ruggeri, C. R.

2012-01-01

Bird strikes are a common problem for the aerospace industry and can cause serious damage to an aircraft. Ballistic gelatin is frequently used as a surrogate for actual bird carcasses in bird strike tests. Numerical simulations of these tests are used to supplement experimental data, therefore it is necessary to use numerical modeling techniques that can accurately capture the dynamic response of ballistic gelatin. An experimental technique is introduced to validate these modeling techniques. A ballistic gelatin projectile is fired into a strike plate attached to a 36 in. long sensor tube. Dynamic load is measured at two locations relative to the strike plate using strain gages configured in a full Wheatstone bridge. Data from these experiments are used to validate a gelatin constitutive model. Simulations of the apparatus are analyzed to investigate its performance.

27 CFR 46.193 - Persons liable for floor stocks tax.

Code of Federal Regulations, 2013 CFR

2013-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.193 Persons liable for floor...

27 CFR 46.193 - Persons liable for floor stocks tax.

Code of Federal Regulations, 2011 CFR

2011-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.193 Persons liable for floor...

27 CFR 46.193 - Persons liable for floor stocks tax.

Code of Federal Regulations, 2012 CFR

2012-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.193 Persons liable for floor...

27 CFR 46.193 - Persons liable for floor stocks tax.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.193 Persons liable for floor...

27 CFR 46.193 - Persons liable for floor stocks tax.

Code of Federal Regulations, 2014 CFR

2014-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.193 Persons liable for floor...

Sampling trace-level organic solutes with polymeric tubing. Part 2: Dynamic studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parker, L.V.; Ranney, T.A.

1998-12-31

This is the second part of a study conducted to determine whether polymeric sampling tubing can affect organic analyte concentrations during a sampling event. In this part of the study, the authors looked for sorption and desorption of trichloroethylene (TCE) and leaching of organic constituents in water pumped through five types of polymeric tubing. The materials tested were a rigid fluoropolymer, a flexible fluoropolymer, low-density polyethylene (LDPE), and two plasticized polypropylene tubings. The effects of tubing length and flow rate were examined. The least sorptive tubings, both initially and at equilibrium, were the fluoropolymers. However, in some instances the LDPEmore » tubing had little effect on TCE concentrations. This was when a slow flow rate was used to sample relatively shallow wells (50 feet [15 m] or less) or when a faster flow rate (1 L/min) was used to sample wells that are less than 500 feet (152 m). Further testing is recommended using more sorptive analytes. Using high performance liquid chromatography (HPLC), the authors were unable to detect any constituents leaching from any of the tubings used in these studies, even when a slow flow rate was used. However, desorption of sorbed analytes is a concern for all the tubings tested, including the rigid fluoropolymer.« less

Propagation of atmospheric-pressure ionization waves along the tapered tube

NASA Astrophysics Data System (ADS)

Xia, Yang; Wang, Wenchun; Liu, Dongping; Yan, Wen; Bi, Zhenhua; Ji, Longfei; Niu, Jinhai; Zhao, Yao

2018-02-01

Gas discharge in a small radius dielectric tube may result in atmospheric pressure plasma jets with high energy and density of electrons. In this study, the atmospheric pressure ionization waves (IWs) were generated inside a tapered tube. The propagation behaviors of IWs inside the tube were studied by using a spatially and temporally resolved optical detection system. Our measurements show that both the intensity and velocity of the IWs decrease dramatically when they propagate to the tapered region. After the taper, the velocity, intensity, and electron density of the IWs are improved with the tube inner diameter decreasing from 4.0 to 0.5 mm. Our analysis indicates that the local gas conductivity and surface charges may play a role in the propagation of the IWs under such a geometrical constraint, and the difference in the dynamics of the IWs after the taper can be related to the restriction in the size of IWs.

Impact Deformation of Thin-Walled Circular Tube Filled with Aluminum Foam in Lateral Compression

NASA Astrophysics Data System (ADS)

Kobayashi, Hidetoshi; Horikawa, Keitaro; Ogawa, Kinya; Hori, Masahiro

In this study, the impact deformation of thin-walled circular tubes filled with aluminum foam in lateral compression was investigated using a special load cell for long time measurement and a high-speed video camera to check the displacement of specimens. It was found that the absorbed energy up to the deformation of 60% of the specimen diameter obtained from impact tests is greater than that obtained in static tests, because of strain rate dependency of aluminum foam. The loaddisplacement curve of circular tubes with aluminum foam just inserted was consistent with the sum of the curves individually obtained. In both dynamic and static tests, however, the load of the tube with the foam inserted and glued by adhesive resin became larger than the sum of the individual loads, because of the interaction between circular tubes and aluminum foam cores.

High gradient lens for charged particle beam

DOEpatents

Chen, Yu-Jiuan

2014-04-29

Methods and devices enable shaping of a charged particle beam. A dynamically adjustable electric lens includes a series of alternating a series of alternating layers of insulators and conductors with a hollow center. The series of alternating layers when stacked together form a high gradient insulator (HGI) tube to allow propagation of the charged particle beam through the hollow center of the HGI tube. A plurality of transmission lines are connected to a plurality of sections of the HGI tube, and one or more voltage sources are provided to supply an adjustable voltage value to each transmission line of the plurality of transmission lines. By changing the voltage values supplied to each section of the HGI tube, any desired electric field can be established across the HGI tube. This way various functionalities including focusing, defocusing, acceleration, deceleration, intensity modulation and others can be effectuated on a time varying basis.

The effect of external visible light on the breakdown voltage of a long discharge tube

NASA Astrophysics Data System (ADS)

Shishpanov, A. I.; Ionikh, Yu. Z.; Meshchanov, A. V.

2016-06-01

The breakdown characteristics of a discharge tube with a configuration typical of gas-discharge light sources and electric-discharge lasers (a so-called "long discharge tube") filled with argon or helium at a pressure of 1 Torr have been investigated. A breakdown has been implemented using positive and negative voltage pulses with a linear leading edge having a slope dU/ dt ~ 10-107 V/s. Visible light from an external source (halogen incandescent lamp) is found to affect the breakdown characteristics. The dependences of the dynamic breakdown voltage of the tube on dU/ dt and on the incident light intensity are measured. The breakdown voltage is found to decrease under irradiation of the high-voltage anode of the tube in a wide range of dU/ dt. A dependence of the effect magnitude on the light intensity and spectrum is obtained. Possible physical mechanisms of this phenomenon are discussed.

Robust rotation of rotor in a thermally driven nanomotor

PubMed Central

Cai, Kun; Yu, Jingzhou; Shi, Jiao; Qin, Qing-Hua

2017-01-01

In the fabrication of a thermally driven rotary nanomotor with the dimension of a few nanometers, fabrication and control precision may have great influence on rotor’s stability of rotational frequency (SRF). To investigate effects of uncertainty of some major factors including temperature, tube length, axial distance between tubes, diameter of tubes and the inward radial deviation (IRD) of atoms in stators on the frequency’s stability, theoretical analysis integrating with numerical experiments are carried out. From the results obtained via molecular dynamics simulation, some key points are illustrated for future fabrication of the thermal driven rotary nanomotor. PMID:28393898

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keiser, J.R.; Taljat, B.; Wang, X.L.

Cracking of co-extruded (generally identified as composite) floor tubes in kraft black liquor recovery boilers was first observed in Scandinavia, but this problem has now been found in many North American boilers. In most cases, cracking in the outer 304L stainless steel has not progressed into the carbon steel, but the potential for such crack propagation is a cause of concern. A multidimensional study has been initiated to characterize the cracking seen in composite floor tubes, to measure the residual stresses resulting from composite tube fabrication, and to predict the stresses in tubes under operating conditions. The characterization studies includemore » review of available reports and documents on composite tube cracking, metallographic examination of a substantial number of cracked tubes, and evaluation of the dislocation structure in cracked tubes. Neutron and X-ray diffraction are being used to determine the residual stresses in composite tubes from two major manufacturers, and finite element analysis is being used to predict the stresses in the tubes during normal operation and under conditions where thermal fluctuations occur.« less

Performance of a GM tube based environmental dose rate monitor operating in the Time-To-Count mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zickefoose, J.; Kulkarni, T.; Martinson, T.

The events at the Fukushima Daiichi power plant in the aftermath of a natural disaster underline the importance of a large array of networked environmental monitors to cover areas around nuclear power plants. These monitors should meet a few basic criteria: have a uniform response over a wide range of gamma energies, have a uniform response over a wide range of incident angles, and have a large dynamic range. Many of these criteria are met if the probe is qualified to the international standard IEC 60532 (Radiation protection instrumentation - Installed dose rate meters, warning assemblies and monitors - Xmore » and gamma radiation of energy between 50 keV and 7 MeV), which specifically deals with energy response, angle of incidence, dynamic range, response time, and a number of environmental characteristics. EcoGamma is a dual GM tube environmental gamma radiation monitor designed specifically to meet the requirements of IEC 60532 and operate in the most extreme conditions. EcoGamma utilizes two energy compensated GM tubes operating with a Time-To-Count (TTC) collection algorithm. The TTC algorithm extends the lifetime and range of a GM tube significantly and allows the dual GM tube probe to achieve linearity over approximately 10 decades of gamma dose rate (from the Sv/hr range to 100 Sv/hr). In the TTC mode of operation, the GM tube is not maintained in a biased condition continuously. This is different from a traditional counting system where the GM tube is held at a constant bias continuously and the total number of strikes that the tube registers are counted. The traditional approach allows for good sensitivity, but does not lend itself to a long lifetime of the tube and is susceptible to linearity issues at high count rates. TTC on the other hand only biases the tube for short periods of time and in effect measures the time between events, which is statistically representative of the total strike rate. Since the tube is not continually biased, the life of the tube is extended and the linearity is greatly improved. Testing has been performed at Pacific Northwest National Laboratory (PNNL) in the USA and confirms compliance to IEC 60532 as well as linearity (± 10%) up to 100 Sv/hr. Furthermore, a network of EcoGamma probes may be linked through available supervisory software to provide a dose rate map of an area. This allows for real time monitoring of dose rates from one (or multiple) remote locations. (authors)« less

Method and apparatus for assembling solid oxide fuel cells

DOEpatents

Szreders, B.E.; Campanella, N.

1988-05-11

This invention relates generally to solid oxide fuel power generators and is particularly directed to improvements in the assembly and coupling of solid oxide fuel cell modules. A plurality of jet air tubes are supported and maintained in a spaced matrix array by a positioning/insertion assembly for insertion in respective tubes of a solid oxide fuel cell (SOFC) in the assembly of an SOFC module. The positioning/insertion assembly includes a plurality of generally planar, elongated, linear vanes which are pivotally mounted at each end thereof to a support frame. A rectangular compression assembly of adjustable size is adapted to receive and squeeze a matrix of SOFC tubes so as to compress the inter-tube nickel felt conductive pads which provide series/parallel electrical connection between adjacent SOFCs, with a series of increasingly larger retainer frames used to maintain larger matrices of SOFC tubes in position. Expansion of the SOFC module housing at the high operating temperatures of the SOFC is accommodated by conductive, flexible, resilient expansion, connector bars which provide support and electrical coupling at the top and bottom of the SOFC module housing. 17 figs.

Shock Tube and Ballistic Range Facilities at NASA Ames Research Center

NASA Technical Reports Server (NTRS)

Grinstead, Jay H.; Wilder, Michael C.; Reda, Daniel C.; Cornelison, Charles J.; Cruden, Brett A.; Bogdanoff, David W.

2010-01-01

The Electric Arc Shock Tube (EAST) facility and the Hypervelocity Free Flight Aerodynamic Facility (HFFAF) at NASA Ames Research Center are described. These facilities have been in operation since the 1960s and have supported many NASA missions and technology development initiatives. The facilities have world-unique capabilities that enable experimental studies of real-gas aerothermal, gas dynamic, and kinetic phenomena of atmospheric entry.

Dynamics of miscible displacements in round tubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meiburg, E.; Maxworthy, T.; Chen, C.Y.

A combined experimental and numerical investigation of miscible two-phase flow in a capillary tube is reported. The fraction of fluid left behind on the wall is obtained as a function of the Peclet, Atwood, and Froude numbers. Scaling arguments are presented for two distinct flow regimes, dominated by diffusion and convection, respectively. In the latter one, an effective surface tension value can be estimated.

Crimpable double tubes for segmental retraction.

PubMed

Martins, Renato Parsekian; Gandini, Luiz Gonzaga; Martins, Isabela Parsekian; Martins, Lidia Parsekian

2011-01-01

When a T-loop is used in segmental mechanics, it is generally attached posteriorly to an auxiliary tube in the first molars and anteriorly to a crimpable cross tube or a Burstone canine bracket. This article illustrates the use of a crimpable tube with a 90-degree bend on the base wire to secure a T-loop in segmental retraction. Both of these approaches allow a T-loop to be reactivated in a simple manner without undesirable changes in the system of forces, which could happen if the T-loop is skewed posteriorly.

Compression device for feeding a waste material to a reactor

DOEpatents

Williams, Paul M.; Faller, Kenneth M.; Bauer, Edward J.

2001-08-21

A compression device for feeding a waste material to a reactor includes a waste material feed assembly having a hopper, a supply tube and a compression tube. Each of the supply and compression tubes includes feed-inlet and feed-outlet ends. A feed-discharge valve assembly is located between the feed-outlet end of the compression tube and the reactor. A feed auger-screw extends axially in the supply tube between the feed-inlet and feed-outlet ends thereof. A compression auger-screw extends axially in the compression tube between the feed-inlet and feed-outlet ends thereof. The compression tube is sloped downwardly towards the reactor to drain fluid from the waste material to the reactor and is oriented at generally right angle to the supply tube such that the feed-outlet end of the supply tube is adjacent to the feed-inlet end of the compression tube. A programmable logic controller is provided for controlling the rotational speed of the feed and compression auger-screws for selectively varying the compression of the waste material and for overcoming jamming conditions within either the supply tube or the compression tube.

Dynamic cross-correlations between entangled biofilaments as they diffuse

PubMed Central

Tsang, Boyce; Dell, Zachary E.; Jiang, Lingxiang; Schweizer, Kenneth S.; Granick, Steve

2017-01-01

Entanglement in polymer and biological physics involves a state in which linear interthreaded macromolecules in isotropic liquids diffuse in a spatially anisotropic manner beyond a characteristic mesoscopic time and length scale (tube diameter). The physical reason is that linear macromolecules become transiently localized in directions transverse to their backbone but diffuse with relative ease parallel to it. Within the resulting broad spectrum of relaxation times there is an extended period before the longest relaxation time when filaments occupy a time-averaged cylindrical space of near-constant density. Here we show its implication with experiments based on fluorescence tracking of dilutely labeled macromolecules. The entangled pairs of aqueous F-actin biofilaments diffuse with separation-dependent dynamic cross-correlations that exceed those expected from continuum hydrodynamics up to strikingly large spatial distances of ≈15 µm, which is more than 104 times the size of the solvent water molecules in which they are dissolved, and is more than 50 times the dynamic tube diameter, but is almost equal to the filament length. Modeling this entangled system as a collection of rigid rods, we present a statistical mechanical theory that predicts these long-range dynamic correlations as an emergent consequence of an effective long-range interpolymer repulsion due to the de Gennes correlation hole, which is a combined consequence of chain connectivity and uncrossability. The key physical assumption needed to make theory and experiment agree is that solutions of entangled biofilaments localized in tubes that are effectively dynamically incompressible over the relevant intermediate time and length scales. PMID:28283664

Shock tubes and waves; Proceedings of the Sixteenth International Symposium, Rheinisch-Westfaelische Technische Hochschule, Aachen, Federal Republic of Germany, July 26-31, 1987

NASA Astrophysics Data System (ADS)

Groenig, Hans

Topics discussed in this volume include shock wave structure, propagation, and interaction; shocks in condensed matter, dusty gases, and multiphase media; chemical processes and related combustion and detonation phenomena; shock wave reflection, diffraction, and focusing; computational fluid dynamic code development and shock wave application; blast and detonation waves; advanced shock tube technology and measuring technique; and shock wave applications. Papers are presented on dust explosions, the dynamics of shock waves in certain dense gases, studies of condensation kinetics behind incident shock waves, the autoignition mechanism of n-butane behind a reflected shock wave, and a numerical simulation of the focusing process of reflected shock waves. Attention is also given to the equilibrium shock tube flow of real gases, blast waves generated by planar detonations, modern diagnostic methods for high-speed flows, and interaction between induced waves and electric discharge in a very high repetition rate excimer laser.

Lifeact-mEGFP Reveals a Dynamic Apical F-Actin Network in Tip Growing Plant Cells

PubMed Central

Hepler, Peter K.; Bezanilla, Magdalena

2009-01-01

Background Actin is essential for tip growth in plants. However, imaging actin in live plant cells has heretofore presented challenges. In previous studies, fluorescent probes derived from actin-binding proteins often alter growth, cause actin bundling and fail to resolve actin microfilaments. Methodology/Principal Findings In this report we use Lifeact-mEGFP, an actin probe that does not affect the dynamics of actin, to visualize actin in the moss Physcomitrella patens and pollen tubes from Lilium formosanum and Nicotiana tobaccum. Lifeact-mEGFP robustly labels actin microfilaments, particularly in the apex, in both moss protonemata and pollen tubes. Lifeact-mEGFP also labels filamentous actin structures in other moss cell types, including cells of the gametophore. Conclusions/Significance Lifeact-mEGFP, when expressed at optimal levels does not alter moss protonemal or pollen tube growth. We suggest that Lifeact-mEGFP represents an exciting new versatile probe for further studies of actin's role in tip growing plant cells. PMID:19478943

Controlled Growth of Gigantic Swirls in a Laboratory Magnetosphere

NASA Astrophysics Data System (ADS)

Worstell, M. W.; Mauel, M. E.; Roberts, T. M.

2012-10-01

Space and laboratory plasma confined by a strong magnetic field have remarkable properties. Low frequency mixing of the plasma occurs through the interchange of long plasma-filled tubes aligned with the magnetic field. The plasma dynamics becomes two-dimensional because these tubes can only move radially or circulate around the poles of the magnetic dipole. Studies of turbulent interchange dynamics made using the Collisionless Terella Experiment (CTX) show that turbulence appears as chaotic time-varying modes with broad global mode structures that interact nonlinearly and form an inverse cascade.footnotetextB.A. Grierson, M.W. Worstell, M.E. Mauel, Phys. Plasmas 16 055902 (2009) When we drive vortex mixing through the application of electrostatic bias to multiple probes, we break the rotational symmetry of the plasma and small vortex tubes are seen to drive larger ``gigantic'' swirls. Statistical analysis of the time-evolving spectra and measurement of the bicoherence of the turbulence show an increase of three wave coupling during non-axisymmetric electrostatic drive of the probe array.

Low-current traveling wave tube for use in the microwave power module

NASA Technical Reports Server (NTRS)

Palmer, Raymond W.; Ramins, Peter; Force, Dale A.; Dayton, James A.; Ebihara, Ben T.; Gruber, Robert P.

1993-01-01

The results of a traveling-wave-tube/multistage depressed-collector (TWT-MDC) design study in support of the Advanced Research Projects Agency/Department of Defense (ARPA/DOD) Microwave Power Module (MPM) Program are described. The study stressed the possible application of dynamic and other tapers to the RF output circuit of the MPM traveling wave tube as a means of increasing the RF and overall efficiencies and reducing the required beam current (perveance). The results indicate that a highly efficient, modified dynamic velocity taper (DVT) circuit can be designed for the broadband MPM application. The combination of reduced cathode current (lower perveance) and increased RF efficiency leads to (1) a substantially higher overall efficiency and reduction in the prime power to the MPM, and (2) substantially reduced levels of MDC and MPM heat dissipation, which simplify the cooling problems. However, the selected TWT circuit parameters need to be validated by cold test measurements on actual circuits.

Regulation of the Pollen-Specific Actin-Depolymerizing Factor LlADF1

PubMed Central

Allwood, Ellen G.; Anthony, Richard G.; Smertenko, Andrei P.; Reichelt, Stefanie; Drobak, Bjorn K.; Doonan, John H.; Weeds, Alan G.; Hussey, Patrick J.

2002-01-01

Pollen tube growth is dependent on a dynamic actin cytoskeleton, suggesting that actin-regulating proteins are involved. We have examined the regulation of the lily pollen-specific actin-depolymerizing factor (ADF) LlADF1. Its actin binding and depolymerizing activity is pH sensitive, inhibited by certain phosphoinositides, but not controlled by phosphorylation. Compared with its F-actin binding properties, its low activity in depolymerization assays has been used to explain why pollen ADF decorates F-actin in pollen grains. This low activity is incompatible with a role in increasing actin dynamics necessary to promote pollen tube growth. We have identified a plant homolog of actin-interacting protein, AIP1, which enhances the depolymerization of F-actin in the presence of LlADF1 by ∼60%. Both pollen ADF and pollen AIP1 bind F-actin in pollen grains but are mainly cytoplasmic in pollen tubes. Our results suggest that together these proteins remodel actin filaments as pollen grains enter and exit dormancy. PMID:12417710

27 CFR 46.194 - Persons not liable for floor stocks tax.

Code of Federal Regulations, 2014 CFR

2014-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.194 Persons not liable for floor...

27 CFR 46.194 - Persons not liable for floor stocks tax.

Code of Federal Regulations, 2013 CFR

2013-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.194 Persons not liable for floor...

On the interpretation of combined torsion and tension tests of thin-wall tubes

NASA Technical Reports Server (NTRS)

Prager, W

1948-01-01

General ways of testing thin-wall tubes under combined tension and torsion as a means of checking the various theories of plasticity are discussed. Suggestions also are given for the interpretation of the tests.

27 CFR 46.194 - Persons not liable for floor stocks tax.

Code of Federal Regulations, 2012 CFR

2012-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.194 Persons not liable for floor...

27 CFR 46.194 - Persons not liable for floor stocks tax.

Code of Federal Regulations, 2011 CFR

2011-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.194 Persons not liable for floor...

27 CFR 46.194 - Persons not liable for floor stocks tax.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for Sale on April 1, 2009 General § 46.194 Persons not liable for floor...

The influence of focal spot blooming on high-contrast spatial resolution in CT imaging.

PubMed

Grimes, Joshua; Duan, Xinhui; Yu, Lifeng; Halaweish, Ahmed F; Haag, Nicole; Leng, Shuai; McCollough, Cynthia

2015-10-01

The objective of this work was to investigate focal spot blooming effects on the spatial resolution of CT images and to evaluate an x-ray tube that uses dynamic focal spot control for minimizing focal spot blooming. The influence of increasing tube current at a fixed tube potential of 80 kV on high-contrast spatial resolution of seven different CT scanner models (scanners A-G), including one scanner that uses dynamic focal spot control to reduce focal spot blooming (scanner A), was evaluated. Spatial resolution was assessed using a wire phantom for the modulation transfer function (MTF) calculation and a copper disc phantom for measuring the slice sensitivity profile (SSP). The impact of varying the tube potential was investigated on two scanner models (scanners A and B) by measuring the MTF and SSP and also by using the resolution bar pattern module of the ACR CT phantom. The phantoms were scanned at 70-150 kV on scanner A and 80-140 kV on scanner B, with tube currents from 100 mA up to the maximum tube current available on each scanner. The images were reconstructed using a slice thickness of 0.6 mm with both smooth and sharp kernels. Additionally, focal spot size at varying tube potentials and currents was directly measured using pinhole and slit camera techniques. Evaluation of the MTF and SSP data from the 7 CT scanner models evaluated demonstrated decreased focal spot blooming for newer scanners, as evidenced by decreasing deviations in MTF and SSP as tube current varied. For scanners A and B, where focal spot blooming effects as a function of tube potential were assessed, the spatial resolution variation in the axial plane was much smaller on scanner A compared to scanner B as tube potential and current changed. On scanner A, the 50% MTF never decreased by more than 2% from the 50% MTF measured at 100 mA. On scanner B, the 50% MTF decreased by as much as 19% from the 50% MTF measured at 100 mA. Assessments of the SSP, the bar patterns in the ACR phantom and the pinhole and slit camera measurements were consistent with the MTF calculations. Focal spot blooming has a noticeable effect on spatial resolution in CT imaging. The focal spot shaping technology of scanner A greatly reduced blooming effects.

Fluid mechanics and heat transfer spirally fluted tubing

NASA Astrophysics Data System (ADS)

Larue, J. C.; Libby, P. A.; Yampolsky, J. S.

1981-08-01

The objective of this program is to develop both a qualitative and a quantitative understanding of the fluid mechanics and heat transfer mechanisms that underlie the measured performance of the spirally fluted tubes under development at General Atomic. The reason for the interest in the spirally fluted tubes is that results to date have indicated three advantages to this tubing concept: The fabrication technique of rolling flutes on strip and subsequently spiralling and simultaneously welding the strip to form tubing results in low fabrication costs, approximately equal to those of commercially welded tubing. The heat transfer coefficient is increased without a concomitant increase of the friction coefficient on the inside of the tube. In single-phase axial flow of water, the helical flutes continuously induce rotation of the flow both within and without the tube as a result of the effect of curvature. An increase in condensation heat transfer on the outside of the tube is achieved. In a vertical orientation with fluid condensing on the outside of the helically fluted tube, the flutes provide a channel for draining the condensed fluid.

Dynamic characteristics of hydrocarbon fuel within the channel at supercritical and pyrolysis condition

NASA Astrophysics Data System (ADS)

Yu, Bin; Zhou, Weixing; Qin, Jiang; Bao, Wen

2017-12-01

Regenerative cooling with fuel as the coolant is used in the scramjet engine. In order to grasp the dynamic characteristics of engine fuel supply processes, this article studies the dynamic characteristics of hydrocarbon fuel within the channel. A one-dimensional dynamic model was proved, the thermal energy storage effect, fuel volume effect and chemical dynamic effect have been considered in the model, the ordinary differential equations were solved using a 4th order Runge-Kutta method. The precision of the model was validated by three groups of experimental data. The effects of input signal, working condition, tube size on the dynamic characteristics of pressure, flow rate, temperature have been simulated. It is found that cracking reaction increased the compressibility of the fuel pyrolysis mixture and lead to longer responding time of outlet flow. The responding time of outlet flow can reach 3s when tube is 5m long which will greatly influence the control performance of the engine thrust system. Meanwhile, when the inlet flow rate appears the step change, the inlet pressure leads to overshoot, the overshoot can reach as much as 100%, such highly transient impulse will result in detrimental effect on fuel pump.

Fluid dynamics in flexible tubes: An application to the study of the pulmonary circulation

NASA Technical Reports Server (NTRS)

Kuchar, N. R.

1971-01-01

Based on an analysis of unsteady, viscous flow through distensible tubes, a lumped-parameter model for the dynamics of blood flow through the pulmonary vascular bed was developed. The model is nonlinear, incorporating the variation of flow resistance with transmural pressure. Solved using a hybrid computer, the model yields information concerning the time-dependent behavior of blood pressures, flow rates, and volumes in each important class of vessels in each lobe of each lung in terms of the important physical and environmental parameters. Simulations of twenty abnormal or pathological situations of interest in environmental physiology and clinical medicine were performed. The model predictions agree well with physiological data.

Resonance tube hazards in oxygen systems. Ph.D. Thesis - Toledo Univ., 1975

NASA Technical Reports Server (NTRS)

Phillips, B. R.

1982-01-01

An experimental and analytical program was carried out to determine whether fluid dynamic oscillations could create a hazard in gaseous oxygen flow systems. The particular fluid dynamic oscillation studied was the resonance tube phenomena as it was excited in a tee-shaped configuration characteristic of configurations found in many industrial high pressure gas flow systems. The types of hazards that could be caused by the oscillations were direct heating and ignition of the piping system by the gas, the greatly augmented heating that could occur if inert contaminants were present, and the ignition of metallic contaminants. Asbestos was used as the inert contaminant; titanium, aluminum, magnesium and steel were chosen as ignitable metallic contaminants. The oscillations in the tee-shaped configuration were compared to oscillations driven by choked convergent nozzles and were found to differ markedly. Temperature generated at the end or base of the resonance tube exceeded 1089 K for both gaseous oxygen and nitrogen and reached 1645 K when asbestos was added. Aluminum in both powder and fiber form was readily ignited within the resonance tube when the supply pressures were less than 8270 kPa whereas at higher supply pressures the mixture exploded with enough violence to destory the apparatus in less than 10 sec. In addition to aluminum, magnesium, and titanium, samples of 400 series stainless steels were also ignited within the resonance tube. The ignition occurred within a few seconds after the oxygen flow began.

Design and Control of Concentric-Tube Robots

PubMed Central

Dupont, Pierre E.; Lock, Jesse; Itkowitz, Brandon; Butler, Evan

2010-01-01

A novel approach toward construction of robots is based on a concentric combination of precurved elastic tubes. By rotation and extension of the tubes with respect to each other, their curvatures interact elastically to position and orient the robot’s tip, as well as to control the robot’s shape along its length. In this approach, the flexible tubes comprise both the links and the joints of the robot. Since the actuators attach to the tubes at their proximal ends, the robot itself forms a slender curve that is well suited for minimally invasive medical procedures. This paper demonstrates the potential of this technology. Design principles are presented and a general kinematic model incorporating tube bending and torsion is derived. Experimental demonstration of real-time position control using this model is also described. PMID:21258648

27 CFR 46.201 - General.

Code of Federal Regulations, 2012 CFR

2012-04-01

... TREASURY (CONTINUED) TOBACCO MISCELLANEOUS REGULATIONS RELATING TO TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for... the method to use for each to determine quantities: Article Inventory method Small cigarettes Count...

77 FR 12845 - Announcement of Requirements and Registration for Surgeon General's (SG) Youth Video Contest

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-02

... YouTube playlist throughout the contest. CDC also reserves the right to make all submitted videos... based on the contest rules prior to being transferred to CDC's YouTube channel for public voting...

27 CFR 46.201 - General.

Code of Federal Regulations, 2014 CFR

2014-04-01

... TREASURY (CONTINUED) TOBACCO MISCELLANEOUS REGULATIONS RELATING TO TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for... the method to use for each to determine quantities: Article Inventory method Small cigarettes Count...

27 CFR 46.201 - General.

Code of Federal Regulations, 2010 CFR

2010-04-01

... TREASURY (CONTINUED) TOBACCO MISCELLANEOUS REGULATIONS RELATING TO TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for... the method to use for each to determine quantities: Article Inventory method Small cigarettes Count...

27 CFR 46.201 - General.

Code of Federal Regulations, 2011 CFR

2011-04-01

... TREASURY (CONTINUED) TOBACCO MISCELLANEOUS REGULATIONS RELATING TO TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for... the method to use for each to determine quantities: Article Inventory method Small cigarettes Count...

27 CFR 46.201 - General.

Code of Federal Regulations, 2013 CFR

2013-04-01

... TREASURY (CONTINUED) TOBACCO MISCELLANEOUS REGULATIONS RELATING TO TOBACCO PRODUCTS AND CIGARETTE PAPERS AND TUBES Floor Stocks Tax on Certain Tobacco Products, Cigarette Papers, and Cigarette Tubes Held for... the method to use for each to determine quantities: Article Inventory method Small cigarettes Count...

Endurance of Damping Properties of Foam-Filled Tubes

PubMed Central

Strano, Matteo; Marra, Alessandro; Mussi, Valerio; Goletti, Massimo; Bocher, Philippe

2015-01-01

The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools. PMID:28793425

Endurance of Damping Properties of Foam-Filled Tubes.

PubMed

Strano, Matteo; Marra, Alessandro; Mussi, Valerio; Goletti, Massimo; Bocher, Philippe

2015-07-07

The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1) square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2) round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve) with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools.

On the Relativistic Correction of Particles Trajectory in Tandem Type Electrostatic Accelerator

NASA Astrophysics Data System (ADS)

Minárik, Stanislav

2015-08-01

A constant potential is applied to the acceleration of the ion-beam in the tandem type electrostatic accelerator. However, not just one voltage is applied, but instead a number of applications can be made in succession by means of the tandem arrangement of high voltage tubes. This number of voltage applications, which is the number of so-called "stages" of a tandem accelerator, may be two, three, or four, depending on the chosen design. Electrostatic field with approximately constant intensity acts on ions in any stage. In general, non-relativistic dynamics is used for the description of the ion transport in tandem accelerator. Energies of accelerated ions are too low and relativistic effects cannot be commonly observed by standard experimental technique. Estimation of possible relativistic correction of ion trajectories is therefore only a matter of calculation. In this note, we briefly present such calculation. Our aim is to show how using the relativistic dynamics modifies the particles trajectory in tandem type accelerator and what parameters determine this modification.

Deterministic and stochastic algorithms for resolving the flow fields in ducts and networks using energy minimization

NASA Astrophysics Data System (ADS)

Sochi, Taha

2016-09-01

Several deterministic and stochastic multi-variable global optimization algorithms (Conjugate Gradient, Nelder-Mead, Quasi-Newton and global) are investigated in conjunction with energy minimization principle to resolve the pressure and volumetric flow rate fields in single ducts and networks of interconnected ducts. The algorithms are tested with seven types of fluid: Newtonian, power law, Bingham, Herschel-Bulkley, Ellis, Ree-Eyring and Casson. The results obtained from all those algorithms for all these types of fluid agree very well with the analytically derived solutions as obtained from the traditional methods which are based on the conservation principles and fluid constitutive relations. The results confirm and generalize the findings of our previous investigations that the energy minimization principle is at the heart of the flow dynamics systems. The investigation also enriches the methods of computational fluid dynamics for solving the flow fields in tubes and networks for various types of Newtonian and non-Newtonian fluids.

A tip-localized RhoGAP controls cell polarity by globally inhibiting Rho GTPase at the cell apex.

PubMed

Hwang, Jae-Ung; Vernoud, Vanessa; Szumlanski, Amy; Nielsen, Erik; Yang, Zhenbiao

2008-12-23

Highly elongated eukaryotic cells (e.g., neuronal axons, fungal hyphae, and pollen tubes) are generated through continuous apically restricted growth (tip growth), which universally requires tip-localized Rho GTPases. We used the oscillating pollen tube as a model system to determine the function and regulation of Rho GTPases in tip growth. Our previous work showed that the spatiotemporal dynamics of the apical cap of the activated Rho-like GTPase from Plant 1 (ROP1) are critical for tip growth in pollen tubes. However, the underlying mechanism for the generation and maintenance of this dynamic apical cap is poorly understood. A screen for mutations that enhance ROP1-overexpression-induced depolarization of pollen-tube growth identified REN1 (ROP1 enhancer 1) in Arabidopsis, whose null mutations turn elongated pollen tubes into bulbous cells. REN1 encodes a novel Rho GTPase-activating protein (RhoGAP) required for restricting the ROP1 activity to the pollen-tube tip. REN1 was localized to exocytic vesicles accumulated in the pollen-tube apex, as well as to the apical plasma membrane at the site of ROP1 activation. The apical localization of REN1 and its function in controlling growth polarity was compromised by disruption of ROP1-dependent F-actin and vesicular trafficking, which indicates that REN1 targeting and function is regulated by ROP1 downstream signaling. Our findings suggest that the REN1 RhoGAP controls a negative-feedback-based global inhibition of ROP1. This function provides a critical self-organizing mechanism, by which ROP signaling is spatially limited to the growth site and temporally oscillates during continuous tip growth. Similar spatiotemporal control of Rho GTPase signaling may also play an important role in cell-polarity control in other systems, including tip growth in fungi and cell movement in animals.

Exocyst SEC3 and Phosphoinositides Define Sites of Exocytosis in Pollen Tube Initiation and Growth1[OPEN

PubMed Central

Bloch, Daria; Pleskot, Roman; Vukašinović, Nemanja

2016-01-01

Polarized exocytosis is critical for pollen tube growth, but its localization and function are still under debate. The exocyst vesicle-tethering complex functions in polarized exocytosis. Here, we show that a sec3a exocyst subunit null mutant cannot be transmitted through the male gametophyte due to a defect in pollen tube growth. The green fluorescent protein (GFP)-SEC3a fusion protein is functional and accumulates at or proximal to the pollen tube tip plasma membrane. Partial complementation of sec3a resulted in the development of pollen with multiple tips, indicating that SEC3 is required to determine the site of pollen germination pore formation. Time-lapse imaging demonstrated that SEC3a and SEC8 were highly dynamic and that SEC3a localization on the apical plasma membrane predicts the direction of growth. At the tip, polar SEC3a domains coincided with cell wall deposition. Labeling of GFP-SEC3a-expressing pollen with the endocytic marker FM4-64 revealed the presence of subdomains on the apical membrane characterized by extensive exocytosis. In steady-state growing tobacco (Nicotiana tabacum) pollen tubes, SEC3a displayed amino-terminal Pleckstrin homology-like domain (SEC3a-N)-dependent subapical membrane localization. In agreement, SEC3a-N interacted with phosphoinositides in vitro and colocalized with a phosphatidylinositol 4,5-bisphosphate (PIP2) marker in pollen tubes. Correspondingly, molecular dynamics simulations indicated that SEC3a-N associates with the membrane by interacting with PIP2. However, the interaction with PIP2 is not required for polar localization and the function of SEC3a in Arabidopsis (Arabidopsis thaliana). Taken together, our findings indicate that SEC3a is a critical determinant of polar exocytosis during tip growth and suggest differential regulation of the exocytotic machinery depending on pollen tube growth modes. PMID:27516531

Confined polar mixtures within cylindrical nanocavities.

PubMed

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

2010-06-17

Using molecular dynamics experiments, we have extended our previous analysis of equimolar mixtures of water and acetonitrile confined between silica walls [J. Phys. Chem. B 2009, 113, 12744] to examine similar solutions trapped within carbon nanotubes and cylindrical silica pores. Two different carbon tube sizes were investigated, (8,8) tubes, with radius R(cnt) = 0.55 nm, and (16,16) ones, with R(cnt) = 1.1 nm. In the narrowest tubes, we found that the cylindrical cavity is filled exclusively by acetonitrile; as the radius of the tube reaches approximately 1 nm, water begins to get incorporated within the inner cavities. In (16,16) tubes, the analysis of global and local concentration fluctuations shows a net increment of the global acetonitrile concentration; in addition, the aprotic solvent is also the prevailing species at the vicinity of the tube walls. Mixtures confined within silica nanopores of radius approximately 1.5 nm were also investigated. Three pores, differing in the effective wall/solvent interactions, were analyzed, (i) a first class, in which dispersive forces prevail (hydrophobic cavities), (ii) a second type, where oxygen sites at the pore walls are transformed into polar silanol groups (hydrophilic cavities), and (iii) finally, an intermediate scenario, in which 60% of the OH groups are replaced by mobile trimethylsilyl groups. Within the different pores, we found clear distinctions between the solvent layers that lie in close contact with the silica substrate and those with more central locations. Dynamical modes of the confined liquid phases were investigated in terms of diffusive and rotational time correlation functions. Compared to bulk results, the characteristic time scales describing different solvent motions exhibit significant increments. In carbon nanotubes, the most prominent modifications operate in the narrower tubes, where translations and rotations become severely hindered. In silica nanopores, the manifestations of the overall retardations are more dramatic for solvent species lying at the vicinity of trimethylsilyl groups.

Exocyst SEC3 and Phosphoinositides Define Sites of Exocytosis in Pollen Tube Initiation and Growth.

PubMed

Bloch, Daria; Pleskot, Roman; Pejchar, Přemysl; Potocký, Martin; Trpkošová, Pavlína; Cwiklik, Lukasz; Vukašinović, Nemanja; Sternberg, Hasana; Yalovsky, Shaul; Žárský, Viktor

2016-10-01

Polarized exocytosis is critical for pollen tube growth, but its localization and function are still under debate. The exocyst vesicle-tethering complex functions in polarized exocytosis. Here, we show that a sec3a exocyst subunit null mutant cannot be transmitted through the male gametophyte due to a defect in pollen tube growth. The green fluorescent protein (GFP)-SEC3a fusion protein is functional and accumulates at or proximal to the pollen tube tip plasma membrane. Partial complementation of sec3a resulted in the development of pollen with multiple tips, indicating that SEC3 is required to determine the site of pollen germination pore formation. Time-lapse imaging demonstrated that SEC3a and SEC8 were highly dynamic and that SEC3a localization on the apical plasma membrane predicts the direction of growth. At the tip, polar SEC3a domains coincided with cell wall deposition. Labeling of GFP-SEC3a-expressing pollen with the endocytic marker FM4-64 revealed the presence of subdomains on the apical membrane characterized by extensive exocytosis. In steady-state growing tobacco (Nicotiana tabacum) pollen tubes, SEC3a displayed amino-terminal Pleckstrin homology-like domain (SEC3a-N)-dependent subapical membrane localization. In agreement, SEC3a-N interacted with phosphoinositides in vitro and colocalized with a phosphatidylinositol 4,5-bisphosphate (PIP 2 ) marker in pollen tubes. Correspondingly, molecular dynamics simulations indicated that SEC3a-N associates with the membrane by interacting with PIP 2 However, the interaction with PIP 2 is not required for polar localization and the function of SEC3a in Arabidopsis (Arabidopsis thaliana). Taken together, our findings indicate that SEC3a is a critical determinant of polar exocytosis during tip growth and suggest differential regulation of the exocytotic machinery depending on pollen tube growth modes. © 2016 American Society of Plant Biologists. All Rights Reserved.

Development of dynamic calibration methods for POGO pressure transducers. [for space shuttle

NASA Technical Reports Server (NTRS)

Hilten, J. S.; Lederer, P. S.; Vezzetti, C. F.; Mayo-Wells, J. F.

1976-01-01

Two dynamic pressure sources are described for the calibration of pogo pressure transducers used to measure oscillatory pressures generated in the propulsion system of the space shuttle. Rotation of a mercury-filled tube in a vertical plane at frequencies below 5 Hz generates sinusoidal pressures up to 48 kPa, peak-to-peak; vibrating the same mercury-filled tube sinusoidally in the vertical plane extends the frequency response from 5 Hz to 100 Hz at pressures up to 140 kPa, peak-to-peak. The sinusoidal pressure fluctuations can be generated by both methods in the presence of high pressures (bias) up to 55 MPa. Calibration procedures are given in detail for the use of both sources. The dynamic performance of selected transducers was evaluated using these procedures; the results of these calibrations are presented. Calibrations made with the two sources near 5 Hz agree to within 3% of each other.

Gaseous Detonation-Driven Fracture of Tubes

DTIC Science & Technology

2004-03-01

understanding, in addition to leading to safer piping system design in nuclear power plants, can also assist accident investigators in learning what type...load, there are derived expressions in the literature from which one can learn about some essential features of mode I dynamic fracture. For a...along a 0.2-mm deep longitudinal groove. Pressure histories were measured by pressure transducers mounted inside the tube, axial and circumferen- tial

The Subgenus Persicargas (Ixodoidea, Argasidae, Argas). Part 2. Ecology and Seasonal Dynamics of A. (P). Arboreus, Kaiser, Hoogstraal and Kohls in Egypt

DTIC Science & Technology

1971-10-30

tube closed at 1 end by a plaster and Aulad Nigmr Bahgura. Nag Hammadi (Iboth of Paris plug and covered by muslin at the other Qena Governorate), and El...Ilindaw, Dakhla 4,11d. The tubes were put in paper cups in outdoor Oasis (El Wadi el Gedid Governorate) (Hoogstraal shade beside the NAMRU-3 Medical

[AGGLUTINATION OF MESOPHYLL PLASTIDS AND OBLITERATION OF PHLOEM SIEVE TUBES ARE THE TOTAL RESULT OF SEASONAL PAUSES IN PHOTOSYNTHATE EXPORT].

PubMed

Gamalei, Yu V

2015-01-01

Chloroplast agglutination and sieve tube obliteration are related to the different plant tissues: the agglutination--to the leaf mesophyll, and the obliteration--to the axis phloem. Being equally produced by photosynthate export dynamics, both phenomena are synchronous and can be used for diagnostics of seasonal flashes and pauses of photosynthetic activity with equal success. The nature of the mobility of chloroplast and their shuttle displacements from the nuclear envelope to the cell periphery connected with export dynamics have been established. It is assumed that nuclear envelope is the base structure of the endoplasmic reticulum (ER) inside which the chloroplasts are localized. Activation of photosynthesis and sugar accumulation inside the ER induces its expansion followed by centrifugal diffusion of chloroplasts. Come back effect--ER collapse, its return to the source--can be induced by the blockade of photosynthesis. Centripetal collapse is accompanied by plastid concentration around the nuclear envelope. Displacements of ER and the chloroplasts dislocating inside it are reversible. It depends on seasonal fluctuations of photosynthesis and export intensities. Changes in the volume of sieve tubes, which are due to the same reason, are irreversible. Each seasonal wave of photosynthesis and sugar export forms new series of sieve tubes, replacing obliterated ones.

Magnetic swirls and associated fast magnetoacoustic kink waves in a solar chromospheric flux tube

NASA Astrophysics Data System (ADS)

Murawski, K.; Kayshap, P.; Srivastava, A. K.; Pascoe, D. J.; Jelínek, P.; Kuźma, B.; Fedun, V.

2018-02-01

We perform numerical simulations of impulsively generated magnetic swirls in an isolated flux tube that is rooted in the solar photosphere. These swirls are triggered by an initial pulse in a horizontal component of the velocity. The initial pulse is launched either (a) centrally, within the localized magnetic flux tube or (b) off-central, in the ambient medium. The evolution and dynamics of the flux tube are described by three-dimensional, ideal magnetohydrodynamic equations. These equations are numerically solved to reveal that in case (a) dipole-like swirls associated with the fast magnetoacoustic kink and m = 1 Alfvén waves are generated. In case (b), the fast magnetoacoustic kink and m = 0 Alfvén modes are excited. In both these cases, the excited fast magnetoacoustic kink and Alfvén waves consist of a similar flow pattern and magnetic shells are also generated with clockwise and counter-clockwise rotating plasma within them, which can be the proxy of dipole-shaped chromospheric swirls. The complex dynamics of vortices and wave perturbations reveals the channelling of sufficient amount of energy to fulfil energy losses in the chromosphere (˜104 W m-1) and in the corona (˜102 W m-1). Some of these numerical findings are reminiscent of signatures in recent observational data.

Role of surfactants in carbon nanotubes density gradient separation.

PubMed

Carvalho, Elton J F; dos Santos, Maria Cristina

2010-02-23

Several strategies aimed at sorting single-walled carbon nanotubes (SWNT) by diameter and/or electronic structure have been developed in recent years. A nondestructive sorting method was recently proposed in which nanotube bundles are dispersed in water-surfactant solutions and submitted to ultracentrifugation in a density gradient. By this method, SWNTs of different diameters are distributed according to their densities along the centrifuge tube. A mixture of two anionic amphiphiles, namely sodium dodecylsulfate (SDS) and sodium cholate (SC), presented the best performance in discriminating nanotubes by diameter. We present molecular dynamics studies of the water-surfactant-SWNT system. The simulations revealed one aspect of the discriminating power of surfactants: they can actually be attracted toward the interior of the nanotube cage. The binding energies of SDS and SC on the outer nanotube surface are very similar and depend weakly on diameter. The binding inside the tubes, on the contrary, is strongly diameter dependent: SDS fits best inside tubes with diameters ranging from 8 to 9 A, while SC is best accommodated in larger tubes, with diameters in the range 10.5-12 A. The dynamics at room temperature showed that, as the amphiphile moves to the hollow cage, water molecules are dragged together, thereby promoting the nanotube filling. The resulting densities of filled SWNT are in agreement with measured densities.

Sampling Artifacts from Conductive Silicone Tubing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timko, Michael T.; Yu, Zhenhong; Kroll, Jesse

2009-05-15

We report evidence that carbon impregnated conductive silicone tubing used in aerosol sampling systems can introduce two types of experimental artifacts: 1) silicon tubing dynamically absorbs carbon dioxide gas, requiring greater than 5 minutes to reach equilibrium and 2) silicone tubing emits organic contaminants containing siloxane that adsorb onto particles traveling through it and onto downstream quartz fiber filters. The consequence can be substantial for engine exhaust measurements as both artifacts directly impact calculations of particulate mass-based emission indices. The emission of contaminants from the silicone tubing can result in overestimation of organic particle mass concentrations based on real-time aerosolmore » mass spectrometry and the off-line thermal analysis of quartz filters. The adsorption of siloxane contaminants can affect the surface properties of aerosol particles; we observed a marked reduction in the water-affinity of soot particles passed through conductive silicone tubing. These combined observations suggest that the silicone tubing artifacts may have wide consequence for the aerosol community and should, therefore, be used with caution. Gentle heating, physical and chemical properties of the particle carriers, exposure to solvents, and tubing age may influence siloxane uptake. The amount of contamination is expected to increase as the tubing surface area increases and as the particle surface area increases. The effect is observed at ambient temperature and enhanced by mild heating (<100 oC). Further evaluation is warranted.« less

Nonlinear truncation error analysis of finite difference schemes for the Euler equations

NASA Technical Reports Server (NTRS)

Klopfer, G. H.; Mcrae, D. S.

1983-01-01

It is pointed out that, in general, dissipative finite difference integration schemes have been found to be quite robust when applied to the Euler equations of gas dynamics. The present investigation considers a modified equation analysis of both implicit and explicit finite difference techniques as applied to the Euler equations. The analysis is used to identify those error terms which contribute most to the observed solution errors. A technique for analytically removing the dominant error terms is demonstrated, resulting in a greatly improved solution for the explicit Lax-Wendroff schemes. It is shown that the nonlinear truncation errors are quite large and distributed quite differently for each of the three conservation equations as applied to a one-dimensional shock tube problem.

A tale of two neglected systems-structure and function of the thin- and thick-walled sieve tubes in monocotyledonous leaves.

PubMed

Botha, C E J

2013-01-01

There is a large body of information relating to the ontogeny, development and the vasculature of eudicotyledonous leaves. However, there is less information available concerning the vascular anatomy of monocotyledonous leaves. This is surprising, given that there are two uniquely different phloem systems present in large groups such as grasses and sedges. Monocotyledonous leaves contain marginal, large, intermediate, and small longitudinal veins that are interconnected by numerous transverse veins. The longitudinal veins contain two metaphloem sieve tube types, which, based upon their ontogeny and position within the phloem, are termed early (thin-walled) and late (thick-walled) sieve tubes. Early metaphloem comprises sieve tubes, companion cells and vascular parenchyma (VP) cells, whilst the late metaphloem, contains thick-walled sieve tubes (TSTs) that lack companion cells. TSTs are generally adjacent to, or no more than one cell removed from the metaxylem. Unlike thin-walled sieve tube (ST) -companion cell complexes, TSTs are connected to parenchyma by pore-plasmodesma units and are generally symplasmically isolated from the STs. This paper addresses key structural and functional differences between thin- and thick-walled sieve tubes and explores the unique advantages of alternate transport strategies that this 5-7 million years old dual system may offer. It would seem that these two systems may enhance, add to, or play a significant role in increasing the efficiency of solute retrieval as well as of assimilate transfer.

A tale of two neglected systems—structure and function of the thin- and thick-walled sieve tubes in monocotyledonous leaves

PubMed Central

Botha, C. E. J.

2013-01-01

There is a large body of information relating to the ontogeny, development and the vasculature of eudicotyledonous leaves. However, there is less information available concerning the vascular anatomy of monocotyledonous leaves. This is surprising, given that there are two uniquely different phloem systems present in large groups such as grasses and sedges. Monocotyledonous leaves contain marginal, large, intermediate, and small longitudinal veins that are interconnected by numerous transverse veins. The longitudinal veins contain two metaphloem sieve tube types, which, based upon their ontogeny and position within the phloem, are termed early (thin-walled) and late (thick-walled) sieve tubes. Early metaphloem comprises sieve tubes, companion cells and vascular parenchyma (VP) cells, whilst the late metaphloem, contains thick-walled sieve tubes (TSTs) that lack companion cells. TSTs are generally adjacent to, or no more than one cell removed from the metaxylem. Unlike thin-walled sieve tube (ST) -companion cell complexes, TSTs are connected to parenchyma by pore-plasmodesma units and are generally symplasmically isolated from the STs. This paper addresses key structural and functional differences between thin- and thick-walled sieve tubes and explores the unique advantages of alternate transport strategies that this 5–7 million years old dual system may offer. It would seem that these two systems may enhance, add to, or play a significant role in increasing the efficiency of solute retrieval as well as of assimilate transfer. PMID:23964280

Sensing Shallow Seafloor and Sediment Properties, Recent History

DTIC Science & Technology

2008-09-01

instances, larger samplers, i.e. box corers, can be further subsampled with small push-in tubes , yielding relatively undisturbed specimens. Corers...sediment within the sampling tube 3 during retrieval. Generally, common gravity corers can retrieve up to 5m (in softer sediments) of soil, whereas... tube that can be generated. Vibro-corers are similar to the gravity corers but have a motorized unit added to the top of the assembly, generating an

The Vibration Analysis of Tube Bundles Induced by Fluid Elastic Excitation in Shell Side of Heat Exchanger

NASA Astrophysics Data System (ADS)

Bao, Minle; Wang, Lu; Li, Wenyao; Gao, Tianze

2017-09-01

Fluid elastic excitation in shell side of heat exchanger was deduced theoretically in this paper. Model foundation was completed by using Pro / Engineer software. The finite element model was constructed and imported into the FLUENT module. The flow field simulation adopted the dynamic mesh model, RNG k-ε model and no-slip boundary conditions. Analysing different positions vibration of tube bundles by selecting three regions in shell side of heat exchanger. The results show that heat exchanger tube bundles at the inlet of the shell side are more likely to be failure due to fluid induced vibration.

System for reducing combustion dynamics and NO.sub.x in a combustor

DOEpatents

Uhm, Jong Ho; Ziminsky, Willy Steve; Johnson, Thomas Edward; Hughes, Michael John; York, William David

2016-05-31

A combustor includes an end cap that extends radially across at least a portion of the combustor. The end cap includes an upstream surface axially separated from a downstream surface. A plurality of tubes extend from the upstream surface through the downstream surface of the end cap to provide fluid communication through the end cap. Each tube in a first set of the plurality of tubes has an inlet proximate to the upstream surface and an outlet downstream from the downstream surface. Each outlet has a first portion that extends a different axial distance from the inlet than a second portion.

Transition to chaos of a vertical collapsible tube conveying air flow

NASA Astrophysics Data System (ADS)

Castillo Flores, F.; Cros, A.

2009-05-01

"Sky dancers", the large collapsible tubes used as advertising, are studied in this work through a simple experimental device. Our study is devoted to the nonlinear dynamics of this system and to its transition to chaos. Firstly, we have shown that after a collapse occurs, the air fills the tube at a different speed rate from the flow velocity. Secondly, the temporal intermittency is studied as the flow rate is increased. A statistical analysis shows that the chaotic times maintain roughly the same value by increasing air speed. On the other hand, laminar times become shorter, until the system reaches a completely chaotic state.

The Caenorhabditis elegans Excretory System: A Model for Tubulogenesis, Cell Fate Specification, and Plasticity

PubMed Central

Sundaram, Meera V.; Buechner, Matthew

2016-01-01

The excretory system of the nematode Caenorhabditis elegans is a superb model of tubular organogenesis involving a minimum of cells. The system consists of just three unicellular tubes (canal, duct, and pore), a secretory gland, and two associated neurons. Just as in more complex organs, cells of the excretory system must first adopt specific identities and then coordinate diverse processes to form tubes of appropriate topology, shape, connectivity, and physiological function. The unicellular topology of excretory tubes, their varied and sometimes complex shapes, and the dynamic reprogramming of cell identity and remodeling of tube connectivity that occur during larval development are particularly fascinating features of this organ. The physiological roles of the excretory system in osmoregulation and other aspects of the animal’s life cycle are only beginning to be explored. The cellular mechanisms and molecular pathways used to build and shape excretory tubes appear similar to those used in both unicellular and multicellular tubes in more complex organs, such as the vertebrate vascular system and kidney, making this simple organ system a useful model for understanding disease processes. PMID:27183565

CUA Annual Meeting Abstracts addition.

PubMed

2012-08-01

: Foley catheters are assumed to drain the bladder to completion. We have previously shown that dependent loops along the drainage tubing create air-locks, which obstruct antegrade urine flow and result in un-drained residual bladder urine. We hypothesized that drainage characteristics of Foley catheters remain poorly understood by urologists and general surgeons. We conducted a nationwide survey of general surgery and urology training program faculty and residents, to assess perceptions of Foley catheter drainage. We designed a novel catheter drainage tube/bag that eliminates air-locks. : An anonymous illustrated questionnaire assessing Foley catheter use patterns and perception was sent to general surgery and urology residency programs (N=108) nationwide. A modified catheter drainage tube/bag unit was designed and tested. An ex vivo catheterized bladder model was designed to measure and compare urine drainage rates with the standard drainage system, versus with our novel design. : A total of 307 responses were collected from residents (55%) and faculty (45%); responses were similar among both groups (p<0.05). The majority reported that at their centers Foley catheter drainage tubes are generally positioned with a dependent loop (94.1%), and, that positioning with a dependent loop, versus without (78.1%) promoted optimal drainage. Antegrade drainage does not occur with a traditional drainage system when a >5.5 inch dependent loop in place. With our proposed design, which eliminates dependent loops, the bladder model emptied to completion consistently. : Traditional Foley catheter drainage systems, as commonly used, evacuate the bladder sub- optimally. More reliable and complete bladder drainage may decrease the incidence of catheter related UTI. The novel modified Foley catheter drainage tube/bag design presented here eliminates dependent loops, to optimize antegrade drainage.

Deaths associated with insertion of nasogastric tubes for enteral nutrition in the medical intensive care unit: Clinical and autopsy findings

PubMed Central

Smith, Avery L.; Santa Ana, Carol A.; Fordtran, John S.; Guileyardo, Joseph M.

2018-01-01

ABSTRACT It is generally assumed that blind insertion of nasogastric tubes for enteral nutrition in patients admitted to medical intensive care units is safe; that is, does not result in life-threatening injury. If death occurs in temporal association with insertion of a nasogastric tube, caregivers typically attribute it to underlying diseases, with little or no consideration of iatrogenic death due to tube insertion. The clinical and autopsy results in three recent cases at Baylor University Medical Center challenge the validity of these notions. PMID:29904295

Enhancements for a Dynamic Data Warehousing and Mining System for Large-scale HSCB Data

DTIC Science & Technology

2016-07-20

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Monthly Report No. 4 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale HSCB...including Top Videos, Top Users, Top Words, and Top Languages, and also applied NER to the text associated with YouTube posts. We have also developed UI for

Enhancements for a Dynamic Data Warehousing and Mining System for Large-Scale HSCB Data

DTIC Science & Technology

2016-07-20

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Page | 2 Intelligent Automation Incorporated Monthly Report No. 4 Enhancements for a Dynamic Data Warehousing and Mining System Large-Scale HSCB...including Top Videos, Top Users, Top Words, and Top Languages, and also applied NER to the text associated with YouTube posts. We have also developed UI for

Effects of Acoustic and Fluid Dynamic Interactions in Resonators: Applications in Thermoacoustic Refrigeration

NASA Astrophysics Data System (ADS)

Antao, Dion Savio

Thermoacoustic refrigeration systems have gained increased importance in cryogenic cooling technologies and improvements are needed to increase the efficiency and effectiveness of the current cryogenic refrigeration devices. These improvements in performance require a re-examination of the fundamental acoustic and fluid dynamic interactions in the acoustic resonators that comprise a thermoacoustic refrigerator. A comprehensive research program of the pulse tube thermoacoustic refrigerator (PTR) and arbitrarily shaped, circular cross-section acoustic resonators was undertaken to develop robust computational models to design and predict the transport processes in these systems. This effort was divided into three main focus areas: (a) studying the acoustic and fluid dynamic interactions in consonant and dissonant acoustic resonators, (b) experimentally investigating thermoacoustic refrigeration systems attaining cryogenic levels and (c) computationally studying the transport processes and energy conversion through fluid-solid interactions in thermoacoustic pulse tube refrigeration devices. To investigate acoustic-fluid dynamic interactions in resonators, a high fidelity computational fluid dynamic model was developed and used to simulate the flow, pressure and temperature fields generated in consonant cylindrical and dissonant conical resonators. Excitation of the acoustic resonators produced high-amplitude standing waves in the conical resonator. The generated peak acoustic overpressures exceeded the initial undisturbed pressure by two to three times. The harmonic response in the conical resonator system was observed to be dependent on the piston amplitude. The resultant strong acoustic streaming structures in the cone resonator highlighted its potential over a cylindrical resonator as an efficient mixer. Two pulse tube cryogenic refrigeration (PTR) devices driven by a linear motor (a pressure wave generator) were designed, fabricated and tested. The characterization of the systems over a wide range of operating conditions helped to better understand the factors that govern and affect the performance of the PTR. The operating frequency of the linear motor driving the PTR affected the systems' performance the most. Other parameters that resulted in performance variations were the mean operating pressure, the pressure amplitude output from the linear motor, and the geometry of the inertance tube. The effect of the inertance tube's geometry was controlled by a single parameter labeled the "inertance". External/ambient conditions affected the performance of the cryocoolers too. To prevent the influence of the ambient conditions on the performance, a vacuum chamber was fabricated to isolate the low temperature regions of the PTR from the variable ambient atmosphere. The experiments provided important information and guidelines for the simulation studies of the PTR that were carried out concurrently. A time-dependent high fidelity computational fluid dynamic model of the entire PTR system was developed to gain a better understanding of internal interactions between the refrigerant fluid and the porous heat-exchangers in its various components and to facilitate better design of PTR systems based on the knowledge gained. The compressible forms of the conservation of mass, momentum and energy equations are solved in the gas and porous media (appropriate estimation of fluid dynamics in heat-exchangers) regions. The heat transfer in the porous regions is governed by a thermal non-equilibrium heat transfer model that calculates a separate gas and solid temperature and accounts for heat transfer between the two. The numerical model was validated using both temporal and quasi-steady state results obtained from the experimental studies. The validated model was applied to study the effects of different operating parameters (frequency, pressure and geometry of the components) on the PTR's performance. The simulations revealed interesting steady-periodic flow patterns that develop in the pulse tube due to the fluctuations caused by the piston and the presence of the inertance tube. Similar to the experiments, the simulations provided important information that help guide the design of efficient PTR systems.

Micro-blast waves using detonation transmission tubing

NASA Astrophysics Data System (ADS)

Samuelraj, I. Obed; Jagadeesh, G.; Kontis, K.

2013-07-01

Micro-blast waves emerging from the open end of a detonation transmission tube were experimentally visualized in this study. A commercially available detonation transmission tube was used (Nonel tube, M/s Dyno Nobel, Sweden), which is a small diameter tube coated with a thin layer of explosive mixture (HMX + traces of Al) on its inner side. The typical explosive loading for this tube is of the order of 18 mg/m of tube length. The blast wave was visualized using a high speed digital camera (frame rate 1 MHz) to acquire time-resolved schlieren images of the resulting flow field. The visualization studies were complemented by computational fluid dynamic simulations. An analysis of the schlieren images showed that although the blast wave appears to be spherical, it propagates faster along the tube axis than along a direction perpendicular to the tube axis. Additionally, CFD analysis revealed the presence of a barrel shock and Mach disc, showing structures that are typical of an underexpanded jet. A theory in use for centered large-scale explosions of intermediate strength (10 < Δ {p}/{p}_0 ≲ 0.02) gave good agreement with the blast trajectory along the tube axis. The energy of these micro-blast waves was found to be 1.25 ± 0.94 J and the average TNT equivalent was found to be 0.3. The repeatability in generating these micro-blast waves using the Nonel tube was very good (± 2 %) and this opens up the possibility of using this device for studying some of the phenomena associated with muzzle blasts in the near future.

Program and charts for determining shock tube, and expansion tunnel flow quantities for real air

NASA Technical Reports Server (NTRS)

Miller, C. G., III; Wilder, S. E.

1975-01-01

A computer program in FORTRAN 4 language was written to determine shock tube, expansion tube, and expansion tunnel flow quantities for real-air test gas. This program permits, as input data, a number of possible combinations of flow quantities generally measured during a test. The versatility of the program is enhanced by the inclusion of such effects as a standing or totally reflected shock at the secondary diaphragm, thermochemical-equilibrium flow expansion and frozen flow expansion for the expansion tube and expansion tunnel, attenuation of the flow in traversing the acceleration section of the expansion tube, real air as the acceleration gas, and the effect of wall boundary layer on the acceleration section air flow. Charts which provide a rapid estimation of expansion tube performance prior to a test are included.

Photomultiplier tube reliability study for the HEAO program

NASA Technical Reports Server (NTRS)

Richardson, C.

1974-01-01

Results concerning the research on photomultiplier tubes required for the HEAO program are reported. The general specifications are discussed for providing a series of tests for helping the operational reliability of its application, and for permitting comparison of performance of similar types, from various manufacturers.

Large-scale thermal energy storage using sodium hydroxide /NaOH/

NASA Technical Reports Server (NTRS)

Turner, R. H.; Truscello, V. C.

1977-01-01

A technique employing NaOH phase change material for large-scale thermal energy storage to 900 F (482 C) is described; the concept consists of 12-foot diameter by 60-foot long cylindrical steel shell with closely spaced internal tubes similar to a shell and tube heat exchanger. The NaOH heat storage medium fills the space between the tubes and outer shell. To charge the system, superheated steam flowing through the tubes melts and raises the temperature of NaOH; for discharge, pressurized water flows through the same tube bundle. A technique for system design and cost estimation is shown. General technical and economic properties of the storage unit integrated into a solar power plant are discussed.

A research program to reduce interior noise in general aviation airplanes: Investigation of the characteristics of an acoustic panel test facility

NASA Technical Reports Server (NTRS)

Grosveld, F.; Vanaken, J.

1978-01-01

Sound pressure levels in the test facility were studied that are caused by varying: (1) microphone positions; (2) equalizer setting; and (3) panel clamping forces. Measurements were done by using a Beranek tube or this Beranek tube in combinations with an extension tube and a special test section. In all configurations tests were executed with and without a test panel installed. The influence of the speaker back panel and the back panel of the Beranek tube on the sound pressure levels inside the test tube were also investigated. It is shown that the definition of noise reduction is more useful in relation to this test facility than transmission loss.

Control system for a small fission reactor

DOEpatents

Burelbach, J.P.; Kann, W.J.; Saiveau, J.G.

1985-02-08

A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired.

Nondestructive testing of moisture separator reheater tubing system using Hall sensor array

NASA Astrophysics Data System (ADS)

Le, Minhhuy; Kim, Jungmin; Kim, Jisoo; Do, Hwa Sik; Lee, Jinyi

2018-01-01

This paper presents a nondestructive testing system for inspecting the moisture separator reheater (MSR) tubing system in a nuclear power plant. The technique is based on partial saturation eddy current testing in which a Hall sensor array is used to measure the radial component of the electromagnetic field distributed in the tubes. A finned MRS tube of ferritic stainless steel (SS439) with artificial, flat-bottom hole-type defects was used in the experiments. The results show that the proposed system has potential applications in the MSR system or ferromagnetic material tubes in general, which could detect the artificial defects of about 20% of the wall thickness (0.24 mm). Furthermore, the defect volume could be quantitatively evaluated.

PULSE AMPLIFIER

DOEpatents

Johnstone, C.W.

1958-06-17

The improvement of pulse amplifiers used with scintillation detectors is described. The pulse amplifier circuit has the advantage of reducing the harmful effects of overloading cause by large signal inputs. In general the pulse amplifier circuit comprises two amplifier tubes with the input pulses applied to one amplifier grid and coupled to the second amplifier tube through a common cathode load. The output of the second amplifier is coupled from the plate circuit to a cathode follower tube grid and a diode tube in connected from grid to cathode of the cathode follower tube. Degenerative feedback is provided in the second amplifier by coupling a signal from the cathode follower cathode to the second amplifier grid. The circuit proqides moderate gain stability, and overload protection for subsequent pulse circuits.

Flow instabilities of magnetic flux tubes. IV. Flux storage in the solar overshoot region

NASA Astrophysics Data System (ADS)

Işık, E.; Holzwarth, V.

2009-12-01

Context: Flow-induced instabilities of magnetic flux tubes are relevant to the storage of magnetic flux in the interiors of stars with outer convection zones. The stability of magnetic fields in stellar interiors is of importance to the generation and transport of solar and stellar magnetic fields. Aims: We consider the effects of material flows on the dynamics of toroidal magnetic flux tubes located close to the base of the solar convection zone, initially within the overshoot region. The problem is to find the physical conditions in which magnetic flux can be stored for periods comparable to the dynamo amplification time, which is of the order of a few years. Methods: We carry out nonlinear numerical simulations to investigate the stability and dynamics of thin flux tubes subject to perpendicular and longitudinal flows. We compare the simulations with the results of simplified analytical approximations. Results: The longitudinal flow instability induced by the aerodynamic drag force is nonlinear in the sense that the growth rate depends on the perturbation amplitude. This result is consistent with the predictions of linear theory. Numerical simulations without friction show that nonlinear Parker instability can be triggered below the linear threshold of the field strength, when the difference in superadiabaticity along the tube is sufficiently large. A localised downflow acting on a toroidal tube in the overshoot region leads to instability depending on the parameters describing the flow, as well as the magnetic field strength. We determined ranges of the flow parameters for which a linearly Parker-stable magnetic flux tube is stored in the middle of the overshoot region for a period comparable to the dynamo amplification time. Conclusions: The longitudinal flow instability driven by frictional interaction of a flux tube with its surroundings is relevant to determining the storage time of magnetic flux in the solar overshoot region. The residence time for magnetic flux tubes with 2 × 1021 Mx in the convective overshoot layer can be comparable to the dynamo amplification time, provided that the average speed and the duration of an external downflow do not exceed about 50 m s -1 and 100 days, respectively, and that the lateral extension of the flow is smaller than about 10°. Appendix C and movies are only available in electronic form at http://www.aanda.org

Dynamo generation of magnetic fields in three-dimensional space - Solar cycle main flux tube formation and reversals

NASA Astrophysics Data System (ADS)

Yoshimura, H.

1983-08-01

The case of the solar magnetic cycle is investigated as a prototype of the dynamo processes involved in the generation of magnetic fields in astrophysics. Magnetohydrodynamic (MHD) equations are solved using a numerical method with a prescribed velocity field in order follow the movement and deformation. It is shown that a simple combination of differential rotation and global convection, given by a linear analysis of fluid dynamics in a rotating sphere, can perpetually create and reverse great magnetic flux tubes encircling the sun. These main flux tubes of the solar cycle are the progenitors of small-scale flux ropes of the solar activity. These findings indicate that magnetic fields can be generated by fluid motions and that MHD equations have a new type of oscillatory solution. It is shown that the solar cycle can be identified with one of these oscillatory solutions. It is proposed that the formation of magnetic flux tubes by streaming plasma flows is a universal mechanism of flux tube formation in astrophysics.

RECORDING DEVICE FOR 128 CHANNEL IONIZATION CHAMBERS (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goryunov, N.N.

1959-05-01

Descriptions are given of a 128-channel amplitude recording device desiged for operation with ionization chambers. Each channl has a large puse recording dynamic amplitude range (amplitudes can vary from each other up to 8000 fold). The recording of amplitudes is accomplished by photographing pulses on a cathode ray tube. With the aid of a commutation device it is possible to record 64 pulses simultaneously on one tube screen. (tr-auth)

An Elastic Tube Gage for Measuring Static and Dynamic Pressures

DTIC Science & Technology

1948-05-01

AUXILIARY HEAT RADIATORS - .-. • • /•’ • • • AUXILIARY ELECTRICAL AND RECORDING EQUIPMENT . . . . .. RESULTS OF FIELD TESTS...time and resources and to permit a greater flexibility in use where measurements are required of a large number or variety of quantities.. Since...gages are first prercürved to fit the tube., and then cemented with Duco. After air-drying for H8 hours, the gages, are heated with infrared lamps to

DOE Office of Scientific and Technical Information (OSTI.GOV)

Means, Gregory Scott; Boardman, Gregory Allen; Berry, Jonathan Dwight

A combustor for a gas turbine generally includes a radial flow fuel nozzle having a fuel distribution manifold, and a fuel injection manifold axially separated from the fuel distribution manifold. The fuel injection manifold generally includes an inner side portion, an outer side portion, and a plurality of circumferentially spaced fuel ports that extend through the outer side portion. A plurality of tubes provides axial separation between the fuel distribution manifold and the fuel injection manifold. Each tube defines a fluid communication path between the fuel distribution manifold and the fuel injection manifold.

Small Particle Driven Chain Disentanglements in Polymer Nanocomposites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Senses, Erkan; Ansar, Siyam M.; Kitchens, Christopher L.

2017-04-01

Using neutron spin-echo spectroscopy, X-ray photon correlation spectroscopy and bulk rheology, we studied the effect of particle size on the single chain dynamics, particle mobility, and bulk viscosity in athermal polyethylene oxide-gold nanoparticle composites. The results reveal an ≈ 25 % increase in the reptation tube diameter with addition of nanoparticles smaller than the entanglement mesh size (≈ 5 nm), at a volume fraction of 20 %. The tube diameter remains unchanged in the composite with larger (20 nm) nanoparticles at the same loading. In both cases, the Rouse dynamics is insensitive to particle size. These results provide a directmore » experimental observation of particle size driven disentanglements that can cause non-Einstein-like viscosity trends often observed in polymer nanocomposites.« less

Optical Spectroscopy and Photophysics of Single Wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Brus, Louis

2006-03-01

We explore the fundamental nature and dynamics of excited electronic states in SWNT. Psec luminescence and photobleaching dynamics of SWNTs in micellar solution show that non-radiative Auger recombination is extremely fast. At low pH, nanotube surface endoperoxides protonate and introduce holes that quench the luminescence. At higher concentration these holes also bleach the band gap optical absorption. Near infrared two photon luminescence excitation spectra quantitatively reveal the importance of excitons. In order to characterize excited states in both metallic and semiconducting SWNTs at the single-tube level, we detect white-light Rayleigh scattering from individual tubes suspended over an open slit in a substrate. Diagnostic spectra with high signal to noise are obtained in just a few minutes.

Localization and elasticity in entangled polymer liquids as a mesoscopic glass transition

NASA Astrophysics Data System (ADS)

Schweizer, Kenneth

2010-03-01

The reptation-tube model is widely viewed as the correct zeroth order model for entangled linear polymer dynamics under quiescent conditions. Its key ansatz is the existence of a mesoscopic dynamical length scale that prohibits transverse chain motion beyond a tube diameter of order 3-10 nm. However, the theory is phenomenological and lacks a microscopic foundation, and many fundamental questions remain unanswered. These include: (i) where does the confining tube field come from and can it be derived from statistical mechanics? (ii) what is the microscopic origin of the magnitude, and power law scaling with concentration and packing length, of the plateau shear modulus? (iii) is the tube diameter time-dependent? (iv) does the confinement field contribute to elasticity ? (v) do entanglement constraints have a finite strength? Building on our new force-level theories for the dynamical crossover and activated barrier hopping in glassy colloidal suspensions and polymer melts, a first principles self-consistent theory has been developed for entangled polymers. Its basic physical elements, and initial results that address the questions posed above, will be presented. The key idea is that beyond a critical degree of polymerization, the chain connectivity and excluded volume induced intermolecular correlation hole drives temporary localization on an intermediate length scale resulting in a mesoscopic ``ideal kinetic glass transition.'' Large scale isotropic motion is effectively quenched due to the emergence of chain length dependent entropic barriers. However, the barrier height is not infinite, resulting in softening of harmonic localization at large displacements, temporal increase of the confining length scale, and a finite strength of entanglement constraints which can be destroyed by applied stress.

Slip-spring model of entangled rod-coil block copolymers

NASA Astrophysics Data System (ADS)

Wang, Muzhou; Likhtman, Alexei E.; Olsen, Bradley D.

2015-03-01

Understanding the dynamics of rod-coil block copolymers is important for optimal design of functional nanostructured materials for organic electronics and biomaterials. Recently, we proposed a reptation theory of entangled rod-coil block copolymers, predicting the relaxation mechanisms of activated reptation and arm retraction that slow rod-coil dynamics relative to coil and rod homopolymers, respectively. In this work, we introduce a coarse-grained slip-spring model of rod-coil block copolymers to further explore these mechanisms. First, parameters of the coarse-grained model are tuned to match previous molecular dynamics simulation results for coils, rods, and block copolymers. For activated reptation, rod-coil copolymers are shown to disfavor configurations where the rod occupies curved portions of the entanglement tube of randomly varying curvature created by the coil ends. The effect of these barriers on diffusion is quantitatively captured by considering one-dimensional motion along an entanglement tube with a rough free energy potential. Finally, we analyze the crossover between the two mechanisms. The resulting dynamics from both mechanisms acting in combination is faster than from each one individually.

The Caltech experimental investigation of fast 3D non-equilbrium dynamics: an overview

NASA Astrophysics Data System (ADS)

Bellan, Paul; Shikama, Taiichi; Chai, Kilbyoung; Ha, Bao; Chaplin, Vernon; Kendall, Mark; Moser, Auna; Stenson, Eve; Tobin, Zachary; Zhai, Xiang

2012-10-01

The formation and dynamics of writhing, plasma-filled, twisted open magnetic flux tubes is being investigated using pulsed-power laboratory experiments. This work is relevant to solar corona loops, astrophysical jets, spheromak formation, and open field lines in tokamaks and RFP's. MHD forces have been observed to drive fast axial plasma flows into the flux tube from the boundary it intercepts. These flows fill the flux tube with plasma while simultaneously injecting linked frozen-in azimuthal flux; helicity injection is thus associated with mass injection. Recent results include observation of a secondary instability (Rayleigh-Taylor driven by the effective gravity of an exponentially growing kink mode), color-coded plasmas manifesting bidirectional axial flows in a geometry similar to a solar corona loop, and spectroscopic measurements of the internal vector magnetic field. Experiments underway include investigating how an external magnetic field straps down a solar loop, investigation of the details of the Rayleigh-Taylor instability, development of a fast EUV movie camera, increasing the jet velocity, excitation of Alfven waves, and investigating 3D magnetic reconnection.

Validation of the generalized model of two-phase thermosyphon loop based on experimental measurements of volumetric flow rate

NASA Astrophysics Data System (ADS)

Bieliński, Henryk

2016-09-01

The current paper presents the experimental validation of the generalized model of the two-phase thermosyphon loop. The generalized model is based on mass, momentum, and energy balances in the evaporators, rising tube, condensers and the falling tube. The theoretical analysis and the experimental data have been obtained for a new designed variant. The variant refers to a thermosyphon loop with both minichannels and conventional tubes. The thermosyphon loop consists of an evaporator on the lower vertical section and a condenser on the upper vertical section. The one-dimensional homogeneous and separated two-phase flow models were used in calculations. The latest minichannel heat transfer correlations available in literature were applied. A numerical analysis of the volumetric flow rate in the steady-state has been done. The experiment was conducted on a specially designed test apparatus. Ultrapure water was used as a working fluid. The results show that the theoretical predictions are in good agreement with the measured volumetric flow rate at steady-state.

COTS MEMS Flow-Measurement Probes

NASA Technical Reports Server (NTRS)

Redding, Chip; Smith, Floyd A.; Blank, Greg; Cruzan, Charles

2004-01-01

As an alternative to conventional tubing instrumentation for measuring airflow, designers and technicians at Glenn Research Center have been fabricating packaging components and assembling a set of unique probes that contain commercial off-the-shelf (COTS) microelectromechanical systems (MEMS) sensor chips. MEMS sensor chips offer some compelling advantages over standard macroscopic measurement devices. MEMS sensor technology has matured through mass production and use in the automotive and aircraft industries. At present, MEMS are the devices of choice for sensors in such applications as tire-pressure monitors, altimeters, pneumatic controls, cable leak detectors, and consumer appliances. Compactness, minimality of power demand, rugged construction, and moderate cost all contribute to making MEMS sensors attractive for instrumentation for future research. Conventional macroscopic flow-measurement instrumentation includes tubes buried beneath the aerodynamic surfaces of wind-tunnel models or in wind-tunnel walls. Pressure is introduced at the opening of each such tube. The pressure must then travel along the tube before reaching a transducer that generates an electronic signal. The lengths of such tubes typically range from 20 ft (approx.= 6 m) to hundreds of feet (of the order of 100 m). The propagation of pressure signals in the tubes damps the signals considerably and makes it necessary to delay measurements until after test rigs have reached steady-state operation. In contrast, a MEMS pressure sensor that generates electronic output can take readings continuously under dynamic conditions in nearly real time. In order to use stainless-steel tubing for pressure measurements, it is necessary to clean many tubes, cut them to length, carefully install them, delicately deburr them, and splice them. A cluster of a few hundred 1/16-in.- (approx.=1.6-mm-) diameter tubes (such clusters are common in research testing facilities) can be several inches (of the order of 10 cm) in diameter and could weigh enough that two technicians are needed to handle it. Replacing hard tubing with electronic chips can eliminate much of the bulk. Each sensor would fit on the tip of a 1/16-in. tube with room to spare. The Lucas NovaSensor P592 piezoresistive silicon pressure sensor was chosen for this project because of its cost, availability, and tolerance to extreme ambient conditions. The sensor chip is 1 mm square by 0.6 mm thick (about 0.039 by 0.039 by 0.024 in.) and includes 0.12-mm (approx.=0.005-in.) wire connection tabs. The figure shows a flow-angularity probe that was built by use of three such MEMS chips. It is planned to demonstrate this MEMS probe as an alternative to a standard tube-type "Cobra" probe now used routinely in wind tunnels and aeronautical hardware. This MEMS probe could be translated across a flow field by use of a suitable actuator, so that its accuracy and the shortness of its response time could be exploited to obtain precise dynamic measurements of a sort that cannot be made by use of conventional tubing-based instrumentation.

A small, single stage orifice pulse tube cryocooler demonstration

NASA Technical Reports Server (NTRS)

Hendricks, John B.

1990-01-01

This final report summarizes and presents the analytical and experimental progress in the present effort. The principal objective of this effort was the demonstration of a 0.25 Watt, 80 Kelvin orifice pulse tube refrigerator. The experimental apparatus is described. The design of a partially optimized pulse tube refrigerator is included. The refrigerator demonstrates an ultimate temperature of 77 K, has a projected cooling power of 0.18 Watts at 80 K, and has a measured cooling power of 1 Watt at 97 K, with an electrical efficiency of 250 Watts/Watt, much better than previous pulse tube refrigerators. A model of the pulse tube refrigerator that provides estimates of pressure ratio and mass flow within the pulse tube refrigerator, based on component physical characteristics is included. A model of a pulse tube operation based on generalized analysis which is adequate to support local optimization of existing designs is included. A model of regenerator performance based on an analogy to counterflow heat exchangers is included.

Fluid mechanics and heat transfer spirally fluted tubing

NASA Astrophysics Data System (ADS)

Yampolsky, J. S.; Libby, P. A.; Launder, B. E.; Larue, J. C.

1984-12-01

The objective of this program is to develop an understanding of the fluid mechanics and heat transfer mechanisms that result in the demonstrated performance of the spiral fluted tubing under development at GA Technologies Inc. Particularly emphasized are the processes that result in the augmentation of the heat transfer coefficient without an increase in friction coefficient in the single-phase flow. Quantitative delineation of these processes would allow for their application to the optimal solution of heat transfer problems in general was well as to tubular heat exchanges using spiral fluted tubes. The experimental phase of the program consisted of the following: (1) Flow visualization studies using high-speed photography of dye injected into water flowing in a cast acrylic spiral fluted tube. (2) Time-resolved axial velocity measurements as a function of radius at the exit plane of a spiral fluted tube with water flowing through the tube. (3) Simultaneous time-resolved measurements of the axial and radial velocity components and temperature with heated air flowing through the tube cooled by a water jacket.

A novel vortex tube-based N2-expander liquefaction process for enhancing the energy efficiency of natural gas liquefaction

NASA Astrophysics Data System (ADS)

Qyyum, Muhammad Abdul; Wei, Feng; Hussain, Arif; Ali, Wahid; Sehee, Oh; Lee, Moonyong

2017-11-01

This research work unfolds a simple, safe, and environment-friendly energy efficient novel vortex tube-based natural gas liquefaction process (LNG). A vortex tube was introduced to the popular N2-expander liquefaction process to enhance the liquefaction efficiency. The process structure and condition were modified and optimized to take a potential advantage of the vortex tube on the natural gas liquefaction cycle. Two commercial simulators ANSYS® and Aspen HYSYS® were used to investigate the application of vortex tube in the refrigeration cycle of LNG process. The Computational fluid dynamics (CFD) model was used to simulate the vortex tube with nitrogen (N2) as a working fluid. Subsequently, the results of the CFD model were embedded in the Aspen HYSYS® to validate the proposed LNG liquefaction process. The proposed natural gas liquefaction process was optimized using the knowledge-based optimization (KBO) approach. The overall energy consumption was chosen as an objective function for optimization. The performance of the proposed liquefaction process was compared with the conventional N2-expander liquefaction process. The vortex tube-based LNG process showed a significant improvement of energy efficiency by 20% in comparison with the conventional N2-expander liquefaction process. This high energy efficiency was mainly due to the isentropic expansion of the vortex tube. It turned out that the high energy efficiency of vortex tube-based process is totally dependent on the refrigerant cold fraction, operating conditions as well as refrigerant cycle configurations.

J-resistance curves for Inconel 690 and Incoloy 800 nuclear steam generators tubes at room temperature and at 300 °C

NASA Astrophysics Data System (ADS)

Bergant, Marcos A.; Yawny, Alejandro A.; Perez Ipiña, Juan E.

2017-04-01

The structural integrity of steam generator tubes is a relevant issue concerning nuclear plant safety. In the present work, J-resistance curves of Inconel 690 and Incoloy 800 nuclear steam generator tubes with circumferential and longitudinal through wall cracks were obtained at room temperature and 300 °C using recently developed non-standard specimens' geometries. It was found that Incoloy 800 tubes exhibited higher J-resistance curves than Inconel 690 for both crack orientations. For both materials, circumferential cracks resulted into higher fracture resistance than longitudinal cracks, indicating a certain degree of texture anisotropy introduced by the tube fabrication process. From a practical point of view, temperature effects have found to be negligible in all cases. The results obtained in the present work provide a general framework for further application to structural integrity assessments of cracked tubes in a variety of nuclear steam generator designs.

Measurements of the canonical helicity evolution of a gyrating kinked plasma column

NASA Astrophysics Data System (ADS)

von der Linden, Jens; Sears, Jason; Intrator, Thomas; You, Setthivoine

2017-10-01

Conversions between kinetic and magnetic energy occur over a wide range of plasma scales as exhibited in astrophysical and solar dynamos, and reconnection in the solar corona and laboratory experiments. Canonical flux tubes present the distinct advantage of reconciling all plasma regimes - e.g. kinetic, two-fluid, and MHD - with the topological concept of helicity: twists, writhes, and linkages. This poster presents the first visualization and analysis of the 3D dynamics of canonical flux tubes and their relative helicity evolution from experimental measurements. Ion and electron canonical flux tubes are visualized from Mach, triple, and Ḃ probe measurements at over 10,000 spatial locations of a gyrating kinked plasma column. The flux tubes co-gyrate with the peak density and electron temperature in and out of a measurement volume. The electron and ion canonical flux tubes twist with opposite handedness and the ion flux tube writhes around the electron flux tube. The relative cross helicity between the magnetic and ion flow vorticity flux tubes dominates the relative ion canonical helicity and is anticorrelated with the relative magnetic helicity. The 3D nature of the kink and a reverse eddy current affect the helicity evolution. This work is supported by DOE Grant DE-SC0010340 and the DOE Office of Science Graduate Student Research Program and prepared in part by LLNL under Contract DE-AC52-07NA27344. LLNL-ABS-734669.

Thermal expansion method for lining tantalum alloy tubing with tungsten

NASA Technical Reports Server (NTRS)

Watson, G. K.; Whittenberger, J. D.; Mattson, W. F.

1973-01-01

A differential-thermal expansion method was developed to line T-111 (tantalum - 8 percent tungsten - 2 percent hafnium) tubing with a tungsten diffusion barrier as part of a fuel element fabrication study for a space power nuclear reactor concept. This method uses a steel mandrel, which has a larger thermal expansion than T-111, to force the tungsten against the inside of the T-111 tube. Variables investigated include lining temperature, initial assembly gas size, and tube length. Linear integrity increased with increasing lining temperature and decreasing gap size. The method should have more general applicability where cylinders must be lined with a thin layer of a second material.

Investigation of heat transfer of tube line of staggered tube bank in two-phase flow

NASA Astrophysics Data System (ADS)

Jakubcionis, Mindaugas

2015-06-01

This article presents the results of experimental investigation of heat transfer process, carried out using the model of heat exchanger. Two-phase statically stable foam flow was used as a heat transfer fluid. Heat exchanger model consisted of staggered tube bank. Experimental results are presented with the focus on influence of tube position in the line of the bank, volumetric void component and velocity of gas component of the foam. The phenomena of liquid draining in cellular foam flow and its influence on heat transfer rate has also been discussed. The experimental results have been generalized by relationship between Nusselt, Reynolds and Prandtl numbers.

Tube Thoracostomy: Complications and Its Management

PubMed Central

Kesieme, Emeka B.; Dongo, Andrew; Ezemba, Ndubueze; Irekpita, Eshiobo; Jebbin, Nze; Kesieme, Chinenye

2012-01-01

Background. Tube thoracostomy is widely used throughout the medical, surgical, and critical care specialities. It is generally used to drain pleural collections either as elective or emergency. Complications resulting from tube thoracostomy can occasionally be life threatening. Aim. To present an update on the complications and management of complications of tube thoracostomy. Methods. A review of the publications obtained from Medline search, medical libraries, and Google on tube thoracostomy and its complications was done. Results. Tube thoracostomy is a common surgical procedure which can be performed by either the blunt dissection technique or the trocar technique. Complication rates are increased by the trocar technique. These complications have been broadly classified as either technical or infective. Technical causes include tube malposition, blocked drain, chest drain dislodgement, reexpansion pulmonary edema, subcutaneous emphysema, nerve injuries, cardiac and vascular injuries, oesophageal injuries, residual/postextubation pneumothorax, fistulae, tumor recurrence at insertion site, herniation through the site of thoracostomy, chylothorax, and cardiac dysrhythmias. Infective complications include empyema and surgical site infection. Conclusion. Tube thoracostomy, though commonly performed is not without risk. Blunt dissection technique has lower risk of complications and is hence recommended. PMID:22028963

Thermal inactivation of Listeria innocua in salmon (Oncorhynchus keta) caviar using conventional glass and novel aluminum thermal-death-time tubes.

PubMed

Al-Holy, M; Quinde, Z; Guan, D; Tang, J; Rasco, B

2004-02-01

Differences in the come-up times and thermal inactivation parameters of Listeria innocua in salmon (Oncorhynchus keta) caviar containing 2.5% salt using conventional thermal-death-time (TDT) glass tubes and a novel aluminum tube were tested and compared. Generally, the come-up times and decimal reduction times (D-values) were shorter and the change in temperature required to change the D-value (z-value) was longer in the aluminum than in the glass tubes. The D-values at 60, 63, and 65 degrees C for the aluminum TDT tubes were 2.97, 0.77, and 0.40 min, respectively, and for the glass TDT tubes, these values were 3.55, 0.84, and 0.41 min. The z-values were 5.7 degrees C in the aluminum and 5.3 degrees C in the glass. Because of the shorter come-up time, the aluminum TDT tubes may provide a more precise measurement of microbial thermal inactivation than the glass TDT tubes, particularly for viscous materials, solid foods, and foods containing particulate matter.

Incipient singularities in the Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Siggia, E. D.; Pumir, A.

1985-01-01

Infinite pointwise stretching in a finite time for general initial conditions is found in a simulation of the Biot-Savart equation for a slender vortex tube in three dimensions. Viscosity is ineffective in limiting the divergence in the vorticity as long as it remains concentrated in tubes. Stability has not been shown.

78 FR 17285 - Airworthiness Directives; The Boeing Company Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2013-03-21

... inspections for dirt, loose particles, or blockage of the flanged tube and drain hole for the pressure seals... aft pressure seals; doing repetitive inspections for dirt, loose particles, or blockage of the flanged... AD, do a general visual inspection for dirt, loose particles, and blockage of the flanged tube and...

Dynamics of membrane nanotubes coated with I-BAR

NASA Astrophysics Data System (ADS)

Barooji, Younes F.; Rørvig-Lund, Andreas; Semsey, Szabolcs; Reihani, S. Nader S.; Bendix, Poul M.

2016-07-01

Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of ~50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes.

Phase velocity enhancement of linear explosive shock tubes

NASA Astrophysics Data System (ADS)

Loiseau, Jason; Serge, Matthew; Szirti, Daniel; Higgins, Andrew; Tanguay, Vincent

2011-06-01

Strong, high density shocks can be generated by sequentially detonating a hollow cylinder of explosives surrounding a thin-walled, pressurized tube. Implosion of the tube results in a pinch that travels at the detonation velocity of the explosive and acts like a piston to drive a shock into the gas ahead of it. In order to increase the maximum shock velocities that can be obtained, a phase velocity generator can be used to drag an oblique detonation wave along the gas tube at a velocity much higher than the base detonation velocity of the explosive. Since yielding and failure of the gas tube is the primary limitation of these devices, it is desirable to retain the dynamic confinement effects of a heavy-walled tamper without interfering with operation of the phase velocity generator. This was accomplished by cutting a slit into the tamper and introducing a phased detonation wave such that it asymmetrically wraps around the gas tube. This type of configuration has been previously experimentally verified to produce very strong shocks but the post-shock pressure and shock velocity limits have not been investigated. This study measured the shock trajectory for various fill pressures and phase velocities to ascertain the limiting effects of tube yield, detonation obliquity and pinch aspect ratio.

Salt-induced square prism Pd microtubes and their ethanol electrocatalysis properties

NASA Astrophysics Data System (ADS)

Jiang, Kunpeng; Ma, Shenghua; Wang, Yinan; Zhang, Ying; Han, Xiaojun

2017-05-01

The synthesis of square prism tubes are always challenging due to their thermo and dynamical instability. We demonstrated a simple method using Pd2+ doped PoPD oligomers as building blocks to assemble into 1D square prism metal-organic microtubes, which consists of cataphracted nanosheets on the surfaces. After high temperature treatment, the microtubes became square prism Pd tubes with a cross section size of 3 μm. The pure Pd microtubes showed excellent catalyzing activity towards the electro oxidation of ethanol. Their electrochemically active surface area is 48.2 m2 g-1, which indicates the square prism Pd tubes have great potential in the field of fuel cell.

Electrical system for measurement of breakdown voltage of vacuum and gas-filled tubes using a dynamic method

NASA Astrophysics Data System (ADS)

Pejović, Milić M.; Milosavljević, Čedomir S.; Pejović, Momčilo M.

2003-06-01

This article describes an electrical system aimed at measuring and data acquisition of breakdown voltages of vacuum and gas-filled tubes. The measurements were performed using a nitrogen-filled tube at 4 mbar pressure. Based on the measured breakdown voltage data as a function of the applied voltage increase rate, a static breakdown voltage is estimated for the applied voltage gradient ranging from 0.1 to 1 V s-1 and from 1 to 10 V s-1. The histograms of breakdown voltages versus applied voltage increase rates from 0.1 and 0.5 V s-1 are approximated by the probability density functions using a fitting procedure.

Intubation simulation with a cross-sectional visual guidance.

PubMed

Rhee, Chi-Hyoung; Kang, Chul Won; Lee, Chang Ha

2013-01-01

We present an intubation simulation with deformable objects and a cross-sectional visual guidance using a general haptic device. Our method deforms the tube model when it collides with the human model. Mass-Spring model with the Euler integration is used for the tube deformation. For the trainee's more effective understanding of the intubation process, we provide a cross-sectional view of the oral cavity and the tube. Our system also applies a stereoscopic rendering to improve the depth perception and the reality of the simulation.

NMDA Receptor Signaling Is Important for Neural Tube Formation and for Preventing Antiepileptic Drug-Induced Neural Tube Defects.

PubMed

Sequerra, Eduardo B; Goyal, Raman; Castro, Patricio A; Levin, Jacqueline B; Borodinsky, Laura N

2018-05-16

Failure of neural tube closure leads to neural tube defects (NTDs), which can have serious neurological consequences or be lethal. Use of antiepileptic drugs (AEDs) during pregnancy increases the incidence of NTDs in offspring by unknown mechanisms. Here we show that during Xenopus laevis neural tube formation, neural plate cells exhibit spontaneous calcium dynamics that are partially mediated by glutamate signaling. We demonstrate that NMDA receptors are important for the formation of the neural tube and that the loss of their function induces an increase in neural plate cell proliferation and impairs neural cell migration, which result in NTDs. We present evidence that the AED valproic acid perturbs glutamate signaling, leading to NTDs that are rescued with varied efficacy by preventing DNA synthesis, activating NMDA receptors, or recruiting the NMDA receptor target ERK1/2. These findings may prompt mechanistic identification of AEDs that do not interfere with neural tube formation. SIGNIFICANCE STATEMENT Neural tube defects are one of the most common birth defects. Clinical investigations have determined that the use of antiepileptic drugs during pregnancy increases the incidence of these defects in the offspring by unknown mechanisms. This study discovers that glutamate signaling regulates neural plate cell proliferation and oriented migration and is necessary for neural tube formation. We demonstrate that the widely used antiepileptic drug valproic acid interferes with glutamate signaling and consequently induces neural tube defects, challenging the current hypotheses arguing that they are side effects of this antiepileptic drug that cause the increased incidence of these defects. Understanding the mechanisms of neurotransmitter signaling during neural tube formation may contribute to the identification and development of antiepileptic drugs that are safer during pregnancy. Copyright © 2018 the authors 0270-6474/18/384762-12$15.00/0.

Numerical investigation on nonlinear effect and vortex formation of oscillatory flow throughout a short tube in a thermoacoustic Stirling engine

NASA Astrophysics Data System (ADS)

Yang, Peng; Chen, Hui; Liu, Yingwen

2017-06-01

In this paper, a two-dimensional axisymmetric model of a thermoacoustic Stirling engine with a short tube where the cross section narrows has been developed. The transient streamlines and vortex formation through short tubes with different diameters in oscillatory flow have been investigated visually by computational fluid dynamics. Three dimensionless parameters, Reynolds number (Re), Keulegan-Carpenter number (KC), and Womersley number (Wo), are used to describe the flow regime and vortex characteristic throughout the short tube. High Re and Wo numbers indicate that the oscillatory flow develops into the turbulent flow through the short tube. The KC number has a direct effect on the transition of streamlines and the development of the vortex. For a small cross section where KC ≈ 1, streamlines rotate and the vortex forms at both sides of the short tube. The vortex stays in the main flow region, and intensity varies as streamlines are convected downstream. The velocity along the radius presents a Poiseuille profile within the influence of the vortex. For a large cross section where KC < 1, streamlines pass the short tube with little rotation and the vortex disappears in the main flow region and confines near the short tube. The velocity profile tends to be flat. The nonlinear effects including instantaneous pressure drop and power dissipation throughout the short tube are also discussed. It shows that the time averaged pressure drop is generated at the cost of power dissipation. Finally, the "effectiveness" is applied to evaluate the performance of the short tube. The results suggest that increasing the diameter of the short tube is in favor of reducing power dissipation, which is beneficial to improve "effectiveness."

Experimental study of the processes accompanying argon breakdown in a long discharge tube at a reduced pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meshchanov, A. V.; Ionikh, Yu. Z., E-mail: y.ionikh@spbu.ru; Shishpanov, A. I.

Results are presented from experimental studies of the breakdown stage of a low-pressure discharge (1 and 5 Torr) in a glass tube the length of which (75 cm) is much larger than its diameter (2.8 cm). Breakdowns occurred under the action of positive voltage pulses with an amplitude of up to 9.4 kV and a characteristic rise time of 2–50 μs. The discharge current in the steady-state mode was 10–120 mA. The electrode voltage, discharge current, and radiation from the discharge gap were detected simultaneously. The dynamic breakdown voltage was measured, the prebreakdown ionization wave was recorded, and its velocitymore » was determined. The dependence of the discharge parameters on the time interval between voltage pulses (the socalled “memory effect”) was analyzed. The memory effect manifests itself in a decrease or an increase in the breakdown voltage and a substantial decrease in its statistical scatter. The time interval between pulses in this case can reach 0.5 s. The effect of illumination of the discharge tube with a light source on the breakdown was studied. It is found that the irradiation of the anode region of the tube by radiation with wavelengths of ≤500 nm substantially reduces the dynamic breakdown voltage. Qualitative explanations of the obtained results are offered.« less

Segmentation of Pollen Tube Growth Videos Using Dynamic Bi-Modal Fusion and Seam Carving.

PubMed

Tambo, Asongu L; Bhanu, Bir

2016-05-01

The growth of pollen tubes is of significant interest in plant cell biology, as it provides an understanding of internal cell dynamics that affect observable structural characteristics such as cell diameter, length, and growth rate. However, these parameters can only be measured in experimental videos if the complete shape of the cell is known. The challenge is to accurately obtain the cell boundary in noisy video images. Usually, these measurements are performed by a scientist who manually draws regions-of-interest on the images displayed on a computer screen. In this paper, a new automated technique is presented for boundary detection by fusing fluorescence and brightfield images, and a new efficient method of obtaining the final cell boundary through the process of Seam Carving is proposed. This approach takes advantage of the nature of the fusion process and also the shape of the pollen tube to efficiently search for the optimal cell boundary. In video segmentation, the first two frames are used to initialize the segmentation process by creating a search space based on a parametric model of the cell shape. Updates to the search space are performed based on the location of past segmentations and a prediction of the next segmentation.Experimental results show comparable accuracy to a previous method, but significant decrease in processing time. This has the potential for real time applications in pollen tube microscopy.

Thin liquid film in polymer tubing : dynamics and dewetting in partial wetting condition

NASA Astrophysics Data System (ADS)

Hayoun, Pascaline; Letailleur, Alban; Teisseire, Jérémie; Verneuil, Emilie; Lequeux, François; Barthel, Etienne

2015-11-01

Polymers such as PVC and Silicone are low cost materials widely used in industry to produce tubing for fluid transport. Most of these applications involve repeated, intermittent flow of liquids which can lead to unwanted contamination. This study aims at better understanding contamination mechanisms during intermittent flow in polymer tubing, and at elucidating the relation between flow, wetting and contamination. We experimentally and theoretically investigate, flow regimes as well as dewetting process at the triple line induced by gravity flow of a vertical liquid slug in a cylindrical geometry. Our results for Newtonian fluids evidence a succession of thick film formation, hydraulic jump creation in the thickness profile, oscillatory regime and destabilization leading to substrate contamination. In order to understand theoretically the flow, one crucial quantity to assess is the film thickness in the inside of the tube. Based on an absorption measurement method, we provide explanations for behaviors and flow regimes observed experimentally.

Oxytropism: a new twist in pollen tube orientation

NASA Technical Reports Server (NTRS)

Blasiak, J.; Mulcahy, D. L.; Musgrave, M.

2001-01-01

Chemical gradients and structural features within the pistil have been previously proposed as factors determining the directionality of pollen tube growth. In this study, we examine the behavior of pollen of eight species germinated in a dynamic oxygen gradient. While the germination rates of some species decreased directly with decreasing oxygen tension, other species showed no decrease in germination at oxygen tensions as low as 2 kPa. In one species, germination was consistently greater at decreased oxygen tensions than at ambient atmospheric levels. In three of the eight species tested, the developing pollen tube showed clear directional growth away from the more-oxygenated regions of the growth medium, while in one species growth was towards the more-oxygenated region. The remaining four species showed random tube growth. The pattern of oxytropic responses among the taxa suggests that this tropic behavior is both widespread and phylogenetically unpredictable.

The effect of working gas impurities on plasma jets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X. Y.; He, M. B., E-mail: pulhmb@mail.hust.edu.cn; IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240

Air intrusion reduced the purity of working gas inside the tube for plasma jet, and thereby, affected the discharge dynamics. In this paper, the effect of using working gas with different purity level (helium purity 99.99999%, 99.99%, 99.9%, and 99%) on photoionization and the chemical reactivity of plasma jet were studied using a 2 dimensional plasma jet model. Photoionization of air species acted as a source of pre-ionization in front of the ionization region, which facilitated the transition from localized discharge to streamers inside the tube. The density of reactive species inside the tube was found to increase with themore » concentration of working gas impurities. For the highest purity helium (99.99999%), despite a low photoionization rate and the distance between the photoionization region and ionization region inside the tube, by increasing the applied voltage and decreasing the distance between the electrode and nozzle, plasma jets were formed.« less

NASA Lewis Stirling SPRE testing and analysis with reduced number of cooler tubes

NASA Technical Reports Server (NTRS)

Wong, Wayne A.; Cairelli, James E.; Swec, Diane M.; Doeberling, Thomas J.; Lakatos, Thomas F.; Madi, Frank J.

1992-01-01

Free-piston Stirling power converters are candidates for high capacity space power applications. The Space Power Research Engine (SPRE), a free-piston Stirling engine coupled with a linear alternator, is being tested at the NASA Lewis Research Center in support of the Civil Space Technology Initiative. The SPRE is used as a test bed for evaluating converter modifications which have the potential to improve the converter performance and for validating computer code predictions. Reducing the number of cooler tubes on the SPRE has been identified as a modification with the potential to significantly improve power and efficiency. Experimental tests designed to investigate the effects of reducing the number of cooler tubes on converter power, efficiency and dynamics are described. Presented are test results from the converter operating with a reduced number of cooler tubes and comparisons between this data and both baseline test data and computer code predictions.

Implementation of a state-to-state analytical framework for the calculation of expansion tube flow properties

NASA Astrophysics Data System (ADS)

James, C. M.; Gildfind, D. E.; Lewis, S. W.; Morgan, R. G.; Zander, F.

2018-03-01

Expansion tubes are an important type of test facility for the study of planetary entry flow-fields, being the only type of impulse facility capable of simulating the aerothermodynamics of superorbital planetary entry conditions from 10 to 20 km/s. However, the complex flow processes involved in expansion tube operation make it difficult to fully characterise flow conditions, with two-dimensional full facility computational fluid dynamics simulations often requiring tens or hundreds of thousands of computational hours to complete. In an attempt to simplify this problem and provide a rapid flow condition prediction tool, this paper presents a validated and comprehensive analytical framework for the simulation of an expansion tube facility. It identifies central flow processes and models them from state to state through the facility using established compressible and isentropic flow relations, and equilibrium and frozen chemistry. How the model simulates each section of an expansion tube is discussed, as well as how the model can be used to simulate situations where flow conditions diverge from ideal theory. The model is then validated against experimental data from the X2 expansion tube at the University of Queensland.

Computations of Axisymmetric Flows in Hypersonic Shock Tubes

NASA Technical Reports Server (NTRS)

Sharma, Surendra P.; Wilson, Gregory J.

1995-01-01

A time-accurate two-dimensional fluid code is used to compute test times in shock tubes operated at supersonic speeds. Unlike previous studies, this investigation resolves the finer temporal details of the shock-tube flow by making use of modern supercomputers and state-of-the-art computational fluid dynamic solution techniques. The code, besides solving the time-dependent fluid equations, also accounts for the finite rate chemistry in the hypersonic environment. The flowfield solutions are used to estimate relevant shock-tube parameters for laminar flow, such as test times, and to predict density and velocity profiles. Boundary-layer parameters such as bar-delta(sub u), bar-delta(sup *), and bar-tau(sub w), and test time parameters such as bar-tau and particle time of flight t(sub f), are computed and compared with those evaluated by using Mirels' correlations. This article then discusses in detail the effects of flow nonuniformities on particle time-of-flight behind the normal shock and, consequently, on the interpretation of shock-tube data. This article concludes that for accurate interpretation of shock-tube data, a detailed analysis of flowfield parameters, using a computer code such as used in this study, must be performed.

Folate receptor 1 is necessary for neural plate cell apical constriction during Xenopus neural tube formation

PubMed Central

Balashova, Olga A.; Visina, Olesya

2017-01-01

Folate supplementation prevents up to 70% of neural tube defects (NTDs), which result from a failure of neural tube closure during embryogenesis. The elucidation of the mechanisms underlying folate action has been challenging. This study introduces Xenopus laevis as a model to determine the cellular and molecular mechanisms involved in folate action during neural tube formation. We show that knockdown of folate receptor 1 (Folr1; also known as FRα) impairs neural tube formation and leads to NTDs. Folr1 knockdown in neural plate cells only is necessary and sufficient to induce NTDs. Folr1-deficient neural plate cells fail to constrict, resulting in widening of the neural plate midline and defective neural tube closure. Pharmacological inhibition of folate action by methotrexate during neurulation induces NTDs by inhibiting folate interaction with its uptake systems. Our findings support a model in which the folate receptor interacts with cell adhesion molecules, thus regulating the apical cell membrane remodeling and cytoskeletal dynamics necessary for neural plate folding. Further studies in this organism could unveil novel cellular and molecular events mediated by folate and lead to new ways of preventing NTDs. PMID:28255006

Shatter Complex Formation in the Twin Craters Lava Flow, Zuni-Bandera Field, New Mexico

NASA Astrophysics Data System (ADS)

von Meerscheidt, H. C.; Bleacher, J. E.; Brand, B. D.; deWet, A.; Samuels, R.; Hamilton, C.; Garry, W. B.; Bandfield, J. L.

2013-12-01

Lava channels, tubes and sheets are transport structures that deliver flowing lava to a flow front. The type of structure can vary within a flow field and evolve throughout an eruption. The 18.0 × 1.0 ka Twin Craters lava flow in the Zuni-Bandera lava field provides a unique opportunity to study morphological changes of a lava flow partly attributable to interaction with a topographic obstacle. Facies mapping and airborne image analysis were performed on an area of the Twin Craters flow that includes a network of channels, lava tubes, shatter features, and disrupted pahoehoe flows surrounding a 45 m tall limestone bluff. The bluff is 1000 m long (oriented perpendicular to flow.) The general flow characteristics upstream from the bluff include smooth, lobate pahoehoe flows and a >2.5 km long lava tube (see Samuels et al., this meeting.) Emplacement characteristics change abruptly where the flow encountered the bluff, to include many localized areas of disrupted pahoehoe and several pahoehoe-floored depressions. Each depression is fully or partly surrounded by a raised rim of blocky material up to 4 m higher than the surrounding terrain. The rim is composed of 0.05 - 4 m diameter blocks, some of which form a breccia that is welded by lava, and some of which exhibit original flow textures. The rim-depression features are interpreted as shatter rings based on morphological similarity to those described by Orr (2011.Bul Volcanol.73.335-346) in Hawai';i. Orr suggests that shatter rings develop when fluctuations in the lava supply rate over-pressurize the tube, causing the tube roof to repeatedly uplift and subside. A rim of shattered blocks and breccias remains surrounding the sunken tube roof after the final lava withdraws from the system. One of these depressions in the Twin Craters flow is 240 m wide and includes six mounds of shattered material equal in height to the surrounding undisturbed terrain. Several mounds have depressed centers floored with rubbly pahoehoe. Prominent ';a';a channels travel around the bluff, leaving a 'wake' of uncovered ground on the downstream side. We interpret this shatter area to have been a branching tube network within an active sheet. The limestone bluff acted as an obstacle that caused a backup of lava within the tubes, driving episodes of shattering. The mounds likely represent earlier solidified sections between active, possibly braided, tube branches, which remained as mounds within the shatter area after the adjacent crust subsided. When lava broke out from the pressurized sheet-like lobe, it formed the ';a';a channels. This section of the flow field is interpreted using inferences from shatter ring formation, but is perhaps better termed a shatter sheet or shatter complex. This study has implications for understanding lava flow dynamics at constriction points, as well as the evolution and morphology of shatter rings.

Enhancements for a Dynamic Data Warehousing and Mining System for Large-Scale Human Social Cultural Behavioral (HSBC) Data

DTIC Science & Technology

2016-09-26

Intelligent Automation Incorporated Enhancements for a Dynamic Data Warehousing and Mining ...Enhancements for a Dynamic Data Warehousing and Mining System for N00014-16-P-3014 Large-Scale Human Social Cultural Behavioral (HSBC) Data 5b. GRANT NUMBER...Representative Media Gallery View. We perform Scraawl’s NER algorithm to the text associated with YouTube post, which classifies the named entities into

Working session 1: Tubing degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kharshafdjian, G.; Turluer, G.

1997-02-01

A general introductory overview of the purpose of the group and the general subject area of SG tubing degradation was given by the facilitator. The purpose of the session was described as to {open_quotes}develop conclusions and proposals on regulatory and technical needs required to deal with the issues of SG tubing degradation.{close_quotes} Types, locations and characteristics of tubing degradation in steam generators were briefly reviewed. The well-known synergistic effects of materials, environment, and stress and strain/strain rate, subsequently referred to by the acronym {open_quotes}MESS{close_quotes} by some of the group members, were noted. The element of time (i.e., evolution of thesemore » variables with time) was emphasized. It was also suggested that the group might want to consider the related topics of inspection capabilities, operational variables, degradation remedies, and validity of test data, and some background information in these areas was provided. The presentation given by Peter Millet during the Plenary Session was reviewed; Specifically, the chemical aspects and the degradation from the secondary side of the steam generator were noted. The main issues discussed during the October 1995 EPRI meeting on secondary side corrosion were reported, and a listing of the potential SG tube degradations was provided and discussed.« less

Combined Steady-State and Dynamic Heat Exchanger Experiment

ERIC Educational Resources Information Center

Luyben, William L.; Tuzla, Kemal; Bader, Paul N.

2009-01-01

This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…

General view looking down the approximate centerline of the expansion ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

General view looking down the approximate centerline of the expansion nozzle of a Space Shuttle Main Engine (SSME) mounted on a SSME Engine Handler in the SSME Processing Facility at Kennedy Space Center. This view shows the 1080 cooling tubes used to regeneratively cool the Nozzle and Combustion Chamber by circulating relatively low temperature fuel through the tubes and manifolds before being ignited in the Main Combustion Chamber. - Space Transportation System, Space Shuttle Main Engine, Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX

CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers.

PubMed

Li, Jun-De

2013-02-01

This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected.

CFD simulation of water vapour condensation in the presence of non-condensable gas in vertical cylindrical condensers

PubMed Central

Li, Jun-De

2013-01-01

This paper presents the simulation of the condensation of water vapour in the presence of non-condensable gas using computational fluid dynamics (CFD) for turbulent flows in a vertical cylindrical condenser tube. The simulation accounts for the turbulent flow of the gas mixture, the condenser wall and the turbulent flow of the coolant in the annular channel with no assumptions of constant wall temperature or heat flux. The condensate film is assumed to occupy a negligible volume and its effect on the condensation of the water vapour has been taken into account by imposing a set of boundary conditions. A new strategy is used to overcome the limitation of the currently available commercial CFD package to solve the simultaneous simulation of flows involving multispecies and fluids of gas and liquid in separate channels. The results from the CFD simulations are compared with the experimental results from the literature for the condensation of water vapour with air as the non-condensable gas and for inlet mass fraction of the water vapour from 0.66 to 0.98. The CFD simulation results in general agree well with the directly measured quantities and it is found that the variation of heat flux in the condenser tube is more complex than a simple polynomial curve fit. The CFD results also show that, at least for flows involving high water vapour content, the axial velocity of the gas mixture at the interface between the gas mixture and the condensate film is in general not small and cannot be neglected. PMID:24850953

Probing the Interaction of Ionic Liquids with CO2: A Raman Spectroscopy and Ab Initio Study

DTIC Science & Technology

2008-05-05

called physisorption. Regardless of the sorption mechanism, a few quantitative parameters can be used to describe a gas-liquid interaction at a...Controllers (I and II) I II 22 and tube fittings, 0.062 inch perfluoroalkoxy ( PFA ) tubing, Tylan General Model FC-128 Flow Controllers

Quantitative Modeling of Entangled Polymer Rheology: Experiments, Tube Models and Slip-Link Simulations

NASA Astrophysics Data System (ADS)

Desai, Priyanka Subhash

Rheology properties are sensitive indicators of molecular structure and dynamics. The relationship between rheology and polymer dynamics is captured in the constitutive model, which, if accurate and robust, would greatly aid molecular design and polymer processing. This dissertation is thus focused on building accurate and quantitative constitutive models that can help predict linear and non-linear viscoelasticity. In this work, we have used a multi-pronged approach based on the tube theory, coarse-grained slip-link simulations, and advanced polymeric synthetic and characterization techniques, to confront some of the outstanding problems in entangled polymer rheology. First, we modified simple tube based constitutive equations in extensional rheology and developed functional forms to test the effect of Kuhn segment alignment on a) tube diameter enlargement and b) monomeric friction reduction between subchains. We, then, used these functional forms to model extensional viscosity data for polystyrene (PS) melts and solutions. We demonstrated that the idea of reduction in segmental friction due to Kuhn alignment is successful in explaining the qualitative difference between melts and solutions in extension as revealed by recent experiments on PS. Second, we compiled literature data and used it to develop a universal tube model parameter set and prescribed their values and uncertainties for 1,4-PBd by comparing linear viscoelastic G' and G" mastercurves for 1,4-PBds of various branching architectures. The high frequency transition region of the mastercurves superposed very well for all the 1,4-PBds irrespective of their molecular weight and architecture, indicating universality in high frequency behavior. Therefore, all three parameters of the tube model were extracted from this high frequency transition region alone. Third, we compared predictions of two versions of the tube model, Hierarchical model and BoB model against linear viscoelastic data of blends of 1,4-PBd star and linear melts. The star was carefully synthesized and characterized. We found massive failures of tube models to predict the terminal relaxation behavior of the star/linear blends. In addition, these blends were also tested against a coarse-grained slip-link model, the "Cluster Fixed Slip-link Model (CFSM)" of Schieber and coworkers. The CFSM with only two parameters gave excellent agreement with all experimental data for the blends.

Modeling Platform Dynamics and Physiological Response to Short Arm Centrifugation

DTIC Science & Technology

1994-03-01

the "venous pump." There is no provision for such a muscular pumping action in the current version of the model, thus this effect is not apparent in...VCt; Dick, DE. Difference-Differential Equations for Fluid Flow in Distensible Tubes. IEEE Trans. Bio-Med. Engr. 14(4): 171-177; 1967. 29. Snyder, MF...Flow in Distensible Tube. IEEE Transactions on efo-Nedical C... Engineering. Vol WNE-14, NO. 3, pp 1M1-177. Jut 1967. C... C... Re - 1*SmCPtl(Sepi

An Analysis of the Loads on and Dynamic Response of a Floating Flexible Tube in Waves and Currents

DTIC Science & Technology

2014-05-09

the tube about 4.57 meters. The CFD code associated with the SolidWorks Flow Simulation tool was applied for this application. Flow Simulation uses...Liquid-Filled Membrane Structure in Waves," Journal of Fluids and Structures, no. 9, pp. 937-956, 1995. [16] SolidWorks , " Flow Simulation 2012...influence of Reynolds number on the drag coefficient. Simulations were performed with the 100% full (solid) model with flow velocities that yielded

In situ silicone tube microextraction: a new method for undisturbed sampling of root-exuded thiophenes from marigold (Tagetes erecta L.) in soil.

PubMed

Mohney, Brian K; Matz, Tricia; Lamoreaux, Jessica; Wilcox, David S; Gimsing, Anne Louise; Mayer, Philipp; Weidenhamer, Jeffrey D

2009-11-01

The difficulties of monitoring allelochemical concentrations in soil and their dynamics over time have been a major barrier to testing hypotheses of allelopathic effects. Here, we evaluate three diffusive sampling strategies that employ polydimethylsiloxane (PDMS) sorbents to map the spatial distribution and temporal dynamics of root-exuded thiophenes from the African marigold, Tagetes erecta. Solid phase root zone extraction (SPRE) probes constructed by inserting stainless steel wire into PDMS tubing were used to monitor thiophene concentrations at various depths beneath marigolds growing in PVC pipes. PDMS sheets were used to map the distribution of thiophenes beneath marigolds grown in thin glass boxes. Concentrations of the two major marigold thiophenes measured by these two methods were extremely variable in both space and time. Dissection and analysis of roots indicated that distribution of thiophenes in marigold roots also was quite variable. A third approach used 1 m lengths of PDMS microtubing placed in marigold soil for repeated sampling of soil without disturbance of the roots. The two ends of the tubing remained out of the soil so that solvent could be washed through the tubing to collect samples for HPLC analysis. Unlike the other two methods, initial experiments with this approach show more uniformity of response, and suggest that soil concentrations of marigold thiophenes are affected greatly even by minimal disturbance of the soil. Silicone tube microextraction gave a linear response for alpha-terthienyl when maintained in soils spiked with 0-10 ppm of this thiophene. This method, which is experimentally simple and uses inexpensive materials, should be broadly applicable to the measurement of non-polar root exudates, and thus provides a means to test hypotheses about the role of root exudates in plant-plant and other interactions.

Distribution of Callose Synthase, Cellulose Synthase, and Sucrose Synthase in Tobacco Pollen Tube Is Controlled in Dissimilar Ways by Actin Filaments and Microtubules1[W

PubMed Central

Cai, Giampiero; Faleri, Claudia; Del Casino, Cecilia; Emons, Anne Mie C.; Cresti, Mauro

2011-01-01

Callose and cellulose are fundamental components of the cell wall of pollen tubes and are probably synthesized by distinct enzymes, callose synthase and cellulose synthase, respectively. We examined the distribution of callose synthase and cellulose synthase in tobacco (Nicotiana tabacum) pollen tubes in relation to the dynamics of actin filaments, microtubules, and the endomembrane system using specific antibodies to highly conserved peptide sequences. The role of the cytoskeleton and membrane flow was investigated using specific inhibitors (latrunculin B, 2,3-butanedione monoxime, taxol, oryzalin, and brefeldin A). Both enzymes are associated with the plasma membrane, but cellulose synthase is present along the entire length of pollen tubes (with a higher concentration at the apex) while callose synthase is located in the apex and in distal regions. In longer pollen tubes, callose synthase accumulates consistently around callose plugs, indicating its involvement in plug synthesis. Actin filaments and endomembrane dynamics are critical for the distribution of callose synthase and cellulose synthase, showing that enzymes are transported through Golgi bodies and/or vesicles moving along actin filaments. Conversely, microtubules appear to be critical in the positioning of callose synthase in distal regions and around callose plugs. In contrast, cellulose synthases are only partially coaligned with cortical microtubules and unrelated to callose plugs. Callose synthase also comigrates with tubulin by Blue Native-polyacrylamide gel electrophoresis. Membrane sucrose synthase, which expectedly provides UDP-glucose to callose synthase and cellulose synthase, binds to actin filaments depending on sucrose concentration; its distribution is dependent on the actin cytoskeleton and the endomembrane system but not on microtubules. PMID:21205616

Compact particle accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elizondo-Decanini, Juan M.

2017-08-29

A compact particle accelerator having an input portion configured to receive power to produce particles for acceleration, where the input portion includes a switch, is provided. In a general embodiment, a vacuum tube receives particles produced from the input portion at a first end, and a plurality of wafer stacks are positioned serially along the vacuum tube. Each of the plurality of wafer stacks include a dielectric and metal-oxide pair, wherein each of the plurality of wafer stacks further accelerate the particles in the vacuum tube. A beam shaper coupled to a second end of the vacuum tube shapes themore » particles accelerated by the plurality of wafer stacks into a beam and an output portion outputs the beam.« less

Stability of phenytoin in blood collected in vacuum blood collection tubes.

PubMed

Parish, R C; Alexander, T

1990-01-01

The stability of phenytoin in blood collected in plain and serum separator tubes (SSTs) was investigated under simulated storage and transport conditions. The drug was generally more stable in plain collection tubes than in SSTs. No degradation occurred in plain red-top tubes or in refrigerated SSTs, but clinically significant degradation was present in SSTs stored at room temperature (25 degrees C) and at elevated temperature (32 degrees C) 24 h after collection. The mean loss was 17.9% at 25 degrees C and 25.9% at 32 degrees C. It is recommended that if blood is to be transported or stored in SSTs, the samples be refrigerated unless assay can be performed within 8 h.

Dynamics of the axisymmetric core-annular flow. II. The less viscous fluid in the core, saw tooth waves

NASA Astrophysics Data System (ADS)

Kouris, Charalampos; Tsamopoulos, John

2002-03-01

The nonlinear dynamics of the concentric, two-phase flow of two immiscible fluids in a circular tube is studied when the viscosity ratio of the fluid in the annulus to that in the core of the tube, μ, is larger than or equal to unity. For these values of the viscosity ratio the perfect core-annular flow (CAF) is linearly unstable and it is necessary to keep the ratio of the thickness of the annulus to the radius of the tube small so that the solutions remain uniformly bounded. The simulations are based on a pseudospectral numerical method while special care has been taken in order to minimize as far as possible the effect of the boundary conditions imposed in the axial direction allowing for multiple waves of different lengths to develop and interact. The time integration originates with the analytical solution for the pressure driven, perfect CAF or the perfect CAF seeded with either the most unstable mode or random disturbances. Quite regular wave patterns are predicted in the first two cases, whereas multiple unstable modes grow and remain even after saturation of the instability in the last case. The resulting waves generally travel in the same direction and faster than the undisturbed interface, except for the case with μ=1 for which they are stationary with respect to it. Depending on parameter values, waves move with the same velocity or interact with each other exchanging their amplitudes or merge and split giving rise to either chaotic or organized solutions. For fluids of equal viscosities and densities (μ=ρ=1) and for a Reynolds number, Re(≡Λρ̂1R̂2Ŵ0/μ̂1)=0.0275 and an inverse Weber number, W(≡T̂/(ρ̂1Ŵ02R̂2))=145.4, both based on the properties of the inner fluid, the tube radius, R̂2, and the average flow velocity, Ŵ0, small amplitude waves are predicted. The increase of μ by almost two orders of magnitude does not affect their amplitudes, but increases their temporal period linearly. Varying W by more than three orders of magnitude increases their amplitudes proportionately, while their period increases with the logarithm of W. Similar to that is the effect of increasing Re. The present analysis confirms and extends results based on long wave expansions, which lead to the Kuramoto-Sivashinsky equation and modifications of it.

Biochemical and Immunocytological Characterizations of Arabidopsis Pollen Tube Cell Wall1[C][W][OA

PubMed Central

Dardelle, Flavien; Lehner, Arnaud; Ramdani, Yasmina; Bardor, Muriel; Lerouge, Patrice; Driouich, Azeddine; Mollet, Jean-Claude

2010-01-01

During plant sexual reproduction, pollen germination and tube growth require development under tight spatial and temporal control for the proper delivery of the sperm cells to the ovules. Pollen tubes are fast growing tip-polarized cells able to perceive multiple guiding signals emitted by the female organ. Adhesion of pollen tubes via cell wall molecules may be part of the battery of signals. In order to study these processes, we investigated the cell wall characteristics of in vitro-grown Arabidopsis (Arabidopsis thaliana) pollen tubes using a combination of immunocytochemical and biochemical techniques. Results showed a well-defined localization of cell wall epitopes. Low esterified homogalacturonan epitopes were found mostly in the pollen tube wall back from the tip. Xyloglucan and arabinan from rhamnogalacturonan I epitopes were detected along the entire tube within the two wall layers and the outer wall layer, respectively. In contrast, highly esterified homogalacturonan and arabinogalactan protein epitopes were found associated predominantly with the tip region. Chemical analysis of the pollen tube cell wall revealed an important content of arabinosyl residues (43%) originating mostly from (1→5)-α-l-arabinan, the side chains of rhamnogalacturonan I. Finally, matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of endo-glucanase-sensitive xyloglucan showed mass spectra with two dominant oligosaccharides (XLXG/XXLG and XXFG), both being mono O-acetylated, and accounting for over 68% of the total ion signals. These findings demonstrate that the Arabidopsis pollen tube wall has its own characteristics compared with other cell types in the Arabidopsis sporophyte. These structural features are discussed in terms of pollen tube cell wall biosynthesis and growth dynamics. PMID:20547702

Biochemical and immunocytological characterizations of Arabidopsis pollen tube cell wall.

PubMed

Dardelle, Flavien; Lehner, Arnaud; Ramdani, Yasmina; Bardor, Muriel; Lerouge, Patrice; Driouich, Azeddine; Mollet, Jean-Claude

2010-08-01

During plant sexual reproduction, pollen germination and tube growth require development under tight spatial and temporal control for the proper delivery of the sperm cells to the ovules. Pollen tubes are fast growing tip-polarized cells able to perceive multiple guiding signals emitted by the female organ. Adhesion of pollen tubes via cell wall molecules may be part of the battery of signals. In order to study these processes, we investigated the cell wall characteristics of in vitro-grown Arabidopsis (Arabidopsis thaliana) pollen tubes using a combination of immunocytochemical and biochemical techniques. Results showed a well-defined localization of cell wall epitopes. Low esterified homogalacturonan epitopes were found mostly in the pollen tube wall back from the tip. Xyloglucan and arabinan from rhamnogalacturonan I epitopes were detected along the entire tube within the two wall layers and the outer wall layer, respectively. In contrast, highly esterified homogalacturonan and arabinogalactan protein epitopes were found associated predominantly with the tip region. Chemical analysis of the pollen tube cell wall revealed an important content of arabinosyl residues (43%) originating mostly from (1-->5)-alpha-L-arabinan, the side chains of rhamnogalacturonan I. Finally, matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of endo-glucanase-sensitive xyloglucan showed mass spectra with two dominant oligosaccharides (XLXG/XXLG and XXFG), both being mono O-acetylated, and accounting for over 68% of the total ion signals. These findings demonstrate that the Arabidopsis pollen tube wall has its own characteristics compared with other cell types in the Arabidopsis sporophyte. These structural features are discussed in terms of pollen tube cell wall biosynthesis and growth dynamics.

Study on the flow nonuniformity in a high capacity Stirling pulse tube cryocooler

NASA Astrophysics Data System (ADS)

You, X.; Zhi, X.; Duan, C.; Jiang, X.; Qiu, L.; Li, J.

2017-12-01

High capacity Stirling-type pulse tube cryocoolers (SPTC) have promising applications in high temperature superconductive motor and gas liquefaction. However, with the increase of cooling capacity, its performance deviates from well-accepted one-dimensional model simulation, such as Sage and Regen, mainly due to the strong field nonuniformity. In this study, several flow straighteners placed at both ends of the pulse tube are investigated to improve the flow distribution. A two-dimensional model of the pulse tube based on the computational fluid dynamics (CFD) method has been built to study the flow distribution of the pulse tube with different flow straighteners including copper screens, copper slots, taper transition and taper stainless slot. A SPTC set-up which has more than one hundred Watts cooling power at 80 K has been built and tested. The flow straighteners mentioned above have been applied and tested. The results show that with the best flow straightener the cooling performance of the SPTC can be significantly improved. Both CFD simulation and experiment show that the straighteners have impacts on the flow distribution and the performance of the high capacity SPTC.

Alloy 690 qualification: Corrosion under prototypic heat flux and temperature conditions. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baum, A.J.

1995-05-01

The objective of this program was to perform qualification tests of industrial heats of thermally treated alloy 690 steam generator tubing under heat transfer conditions. Primary emphasis was focused on testing of alternate tube to tubesheet expansion processes. In addition, a background report was written to document the evolution of the alloy 690 process specification and the supporting qualification testing. While the testing was able to produce some localized corrosion of alloy 690 in the tube to tubesheet joint transition regions under highly alkaline conditions, the corrosion rates were between two and three orders of magnitude lower than the comparablemore » rates in mill annealed alloy 600 tubing. The corrosion morphology was a combination of intergranular and general corrosion, rather than the stress corrosion cracking typically found in mill annealed alloy 600 tubing.« less

A novel procedure employing laser ultrasound technique and simplex algorism for the characterization of mechanical and geometrical properties in Zircaloy tubes with different levels of hydrogen charging

NASA Astrophysics Data System (ADS)

Liu, I.-Hung; Yang, Che-Hua

2011-01-01

In this research, a procedure employing a laser ultrasound technique (LUT) and an inversion algorism is reported for nondestructive characterization of mechanical and geometrical properties in Zircaloy tubes with different levels of hydrogen charging. With the LUT, guided acoustic waves are generated to propagate in the Zircaloy tubes and are detected remotely by optical means. By measuring the dispersive wavespeeds followed by the inversion algorism, mechanical properties such as elastic moduli and geometrical property such as wall-thickness of Zircaloy tubes are characterized for different levels of hydrogen charging. Having the advantages of remote, non-contact and point-wise generation/detection, the reported procedure serves as a competitive candidate for the characterization of Zircaloy tubes generally operated in irradiative and temperature-elevated environments.

Quantitative, depth-resolved determination of particle motion using multi-exposure, spatial frequency domain laser speckle imaging.

PubMed

Rice, Tyler B; Kwan, Elliott; Hayakawa, Carole K; Durkin, Anthony J; Choi, Bernard; Tromberg, Bruce J

2013-01-01

Laser Speckle Imaging (LSI) is a simple, noninvasive technique for rapid imaging of particle motion in scattering media such as biological tissue. LSI is generally used to derive a qualitative index of relative blood flow due to unknown impact from several variables that affect speckle contrast. These variables may include optical absorption and scattering coefficients, multi-layer dynamics including static, non-ergodic regions, and systematic effects such as laser coherence length. In order to account for these effects and move toward quantitative, depth-resolved LSI, we have developed a method that combines Monte Carlo modeling, multi-exposure speckle imaging (MESI), spatial frequency domain imaging (SFDI), and careful instrument calibration. Monte Carlo models were used to generate total and layer-specific fractional momentum transfer distributions. This information was used to predict speckle contrast as a function of exposure time, spatial frequency, layer thickness, and layer dynamics. To verify with experimental data, controlled phantom experiments with characteristic tissue optical properties were performed using a structured light speckle imaging system. Three main geometries were explored: 1) diffusive dynamic layer beneath a static layer, 2) static layer beneath a diffuse dynamic layer, and 3) directed flow (tube) submerged in a dynamic scattering layer. Data fits were performed using the Monte Carlo model, which accurately reconstructed the type of particle flow (diffusive or directed) in each layer, the layer thickness, and absolute flow speeds to within 15% or better.

Precise digit use increases the expression of handedness in Colombian spider monkeys (Ateles fusciceps rufiventris).

PubMed

Nelson, Eliza L; Boeving, Emily R

2015-12-01

Decades of research on the hand use patterns of nonhuman primates can be aptly summarized by the following phrase: measurement matters. There is a general consensus that simple reaching is a poor indicator of handedness in most species, while tasks that constrain how the hands are used elicit individual, and in some cases, population-level biases. The TUBE task has become a popular measure of handedness, although there is variability in its administration across studies. The goal of this study was to investigate whether TUBE performance is affected by tube diameter, with the hypothesis that decreasing tube diameter would increase task complexity, and therefore the expression of handedness. We predicted that hand preference strength, but not direction, would be affected by tube diameter. We administered the TUBE task using a 1.3 cm tube to Colombian spider monkeys, and compared their performance to a previous study using a larger 2.5 cm diameter tube. Hand preference strength increased significantly on the smaller diameter tube. Hand preference direction was not affected. Notably, spider monkeys performed the TUBE task using a single digit, despite the longstanding view that this species has poor dexterity. We encourage investigators who use the TUBE task to carefully consider the diameter of the tube used in testing, and to report digit use consistently across studies. In addition, we recommend that researchers who cannot use the TUBE task try to incorporate the key features from this task into their own species appropriate measures: bimanual coordination and precise digit use. © 2015 Wiley Periodicals, Inc.

THE TOPOLOGY OF CANONICAL FLUX TUBES IN FLARED JET GEOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavine, Eric Sander; You, Setthivoine, E-mail: Slavine2@uw.edu, E-mail: syou@aa.washington.edu

2017-01-20

Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). We outline here a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of the species’ canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. A flared, current-carrying magnetic flux tube in an ion-electron plasma with finite ion momentum is thus equivalent to either a pair of electron andmore » ion flow flux tubes, a pair of electron and ion canonical momentum flux tubes, or a pair of electron and ion canonical vorticity flux tubes. We examine the morphology of all these flux tubes for increasing electrical currents, different radial current profiles, different electron Mach numbers, and a fixed, flared, axisymmetric magnetic geometry. Calculations of gauge-invariant relative canonical helicities track the evolution of magnetic, cross, and kinetic helicities in the system, and show that ion flow fields can unwind to compensate for an increasing magnetic twist. The results demonstrate that including a species’ finite momentum can result in a very long collimated canonical vorticity flux tube even if the magnetic flux tube is flared. With finite momentum, particle density gradients must be normal to canonical vorticities, not to magnetic fields, so observations of collimated astrophysical jets could be images of canonical vorticity flux tubes instead of magnetic flux tubes.« less

The microtubule cytoskeleton and pollen tube Golgi vesicle system are required for in vitro S-RNase internalization and gametic self-incompatibility in apple.

PubMed

Meng, Dong; Gu, Zhaoyu; Yuan, Hui; Wang, Aide; Li, Wei; Yang, Qing; Zhu, Yuandi; Li, Tianzhong

2014-05-01

S-RNase is the female determinant of gametophytic self-incompatibility in apple and is usually considered to be the reason for rejection of pollen. In this study, we investigated the role of microtubules (MTs) in internalization of S-RNases by pollen tubes cultured in vitro. The results showed that S-RNase was imported into the pollen tube where it inhibits pollen tube growth, and that S-RNase is co-localized with the Golgi vesicle during the internalization process. Moreover, MT depolymerization is observed following accumulation of S-RNases in the pollen cytosol. On the other hand, S-RNase was prevented from entering the pollen tube when the pollen was treated with the actin filament (AF) inhibitor latrunculin A (LatA), the MT inhibitor oryzalin, or the MT stabilizer taxol at subtoxic concentrations. These hindered the construction of the MT, with pollen tubes capable of growth under these conditions. Pollen tubes showed improved growth in self-pollinated styles that were pre-treated with taxol. This suggests that cytoskeleton antagonists can prevent S-RNase-mediated inhibition of pollen tubes in vivo by blocking S-RNase internalization. These results suggest that an intact and dynamic cytoskeleton is required for the in vitro internalization of S-RNase, as shown by the effects of various cytoskeleton inhibitors. S-RNase internalization takes place via a membrane/cytoskeleton-based Golgi vesicle system, which can also affect self-incompatibility in apple.

Dynamic Deformation and Collapse of Granular Columns

NASA Astrophysics Data System (ADS)

Uenishi, K.; Tsuji, K.; Doi, S.

2009-12-01

Large dynamic deformation of granular materials may be found in nature not only in the failure of slopes and cliffs — due to earthquakes, rock avalanches, debris flows and landslides — but also in earthquake faulting itself. Granular surface flows often consist of solid grains and intergranular fluid, but the effect of the fluid may be usually negligible because the volumetric concentration of grains is in many cases high enough for interparticle forces to dominate momentum transport. Therefore, the investigation of dry granular flow of a mass might assist in further understanding of the above mentioned geophysical events. Here, utilizing a high-speed digital video camera system, we perform a simple yet fully-controlled series of laboratory experiments related to the collapse of granular columns. We record, at an interval of some microseconds, the dynamic transient granular mass flow initiated by abrupt release of a tube that contains dry granular materials. The acrylic tube is partially filled with glass beads and has a cross-section of either a fully- or semi-cylindrical shape. Upon sudden removal of the tube, the granular solid may fragment under the action of its own weight and the particles spread on a rigid horizontal plane. This study is essentially the extension of the previous ones by Lajeunesse et al. (Phys. Fluids 2004) and Uenishi and Tsuji (JPGU 2008), but the striped layers of particles in a semi-cylindrical tube, newly introduced in this contribution, allow us to observe the precise particle movement inside the granular column: The development of slip lines inside the column and the movement of particles against each other can be clearly identified. The major controlling parameters of the spreading dynamics are the initial aspect ratio of the granular (semi-)cylindrical column, the frictional properties of the horizontal plane (substrate) and the size of beads. We show the influence of each parameter on the average flow velocity and final radius and height of the deposit, i.e., the fraction of granular mass mobilized by the flow, and the final shape of the deposit.

Design Optimization and Development of Tubular Isogrid Composites Tubes for Lower Limb Prosthesis

NASA Astrophysics Data System (ADS)

Junqueira, Diego Morais; Gomes, Guilherme Ferreira; Silveira, Márcio Eduardo; Ancelotti, Antonio Carlos

2018-04-01

From the beginnings of humanity, natural or unnatural misfortunes such as illnesses, wars, automobile accidents cause loss of body limbs like teeth, arms, legs, etc. The solution found for the replacement of these missing limbs is in the use of prostheses. Lower limbs tubes or pylons are prosthetics components that are claimed to support loads during walking and other daily tasks activities. Commonly, prosthetic tubes are manufactured using metal materials such as stainless steel, aluminum and titanium. The mass of these tubes is generally high compared to tubes made of carbon fiber reinforced polymer matrix (CFRP) composite. Therefore, this work has the objective of design, manufacturing and analyzing the feasibility of a new tube concept, made of composite material, which makes use of lattice structure and inner layer. Until the present moment, lower limb prosthesis tubes using lattice structure and ineer layer have never been studied and/or tested to date. It can be stated that the tube of rigid ribs with inner layer and angle of 40° is more efficient than those of 26° and 30°. The proposed design allows a structural weight reduction in high performance prostheses from 120 g to 40 g.

Computational Fluid Dynamic Investigation of Loss Mechanisms in a Pulse-Tube Refrigerator

NASA Astrophysics Data System (ADS)

Martin, K.; Esguerra, J.; Dodson, C.; Razani, A.

2015-12-01

In predicting Pulse-Tube Cryocooler (PTC) performance, One-Dimensional (1-D) PTR design and analysis tools such as Gedeon Associates SAGE® typically include models for performance degradation due to thermodynamically irreversible processes. SAGE®, in particular, accounts for convective loss, turbulent conductive loss and numerical diffusion “loss” via correlation functions based on analysis and empirical testing. In this study, we compare CFD and SAGE® estimates of PTR refrigeration performance for four distinct pulse-tube lengths. Performance predictions from PTR CFD models are compared to SAGE® predictions for all four cases. Then, to further demonstrate the benefits of higher-fidelity and multidimensional CFD simulation, the PTR loss mechanisms are characterized in terms of their spatial and temporal locations.

Hydrodynamic conditions in designed spiral photobioreactors.

PubMed

Wu, L B; Li, Z; Song, Y Z

2010-01-01

In this work, a series of spiral tube PBRs were introduced. Flow dynamics of microalgae fluid, light intensity histories of tracked cells and swirl numbers within the spiral PBRs were numerically simulated. Results show that strong swirl motions are formed in the cross-sections along axial coordinate of spiral PBRs, but no such vortice is observed for tubular PBR. The light intensity histories identify that the microalgae cells experience the so-called light/dark cycle, which is necessary to their growth. With high swirl numbers ranging from 0.15 to 0.35, the mixing performances of the spiral tube PBRs are much better than that of tubular PBR, indicating such innovative geometries of spiral tube PBRs may be applicable for large scale commercial cultivation of microalgae in the future.

Experimental Investigation on the Resonance of a Liquid Column in a Capillary Tube.

PubMed

Hilpert; Miller

1999-11-01

Using a visualization technique, we observed the resonance of a water column trapped in a vertically oriented capillary tube due to acoustic excitation. The analysis of the quasi-static response suggests that the upper nonvisible meniscus followed the imposed flow by means of a sliding contact line without changing its shape. We compared the experiments with a previously developed theoretical model that addresses dissipation by assuming an axially symmetric and incompressible flow field that is spatially constant along the tube axis. Whereas the model agrees well with the measured quasi-static response, the deviations in the dynamic response reveal shortcomings of the model due to the simplified treatment of the viscous dissipation. Copyright 1999 Academic Press.

Memory functions reveal structural properties of gene regulatory networks

PubMed Central

Perez-Carrasco, Ruben

2018-01-01

Gene regulatory networks (GRNs) control cellular function and decision making during tissue development and homeostasis. Mathematical tools based on dynamical systems theory are often used to model these networks, but the size and complexity of these models mean that their behaviour is not always intuitive and the underlying mechanisms can be difficult to decipher. For this reason, methods that simplify and aid exploration of complex networks are necessary. To this end we develop a broadly applicable form of the Zwanzig-Mori projection. By first converting a thermodynamic state ensemble model of gene regulation into mass action reactions we derive a general method that produces a set of time evolution equations for a subset of components of a network. The influence of the rest of the network, the bulk, is captured by memory functions that describe how the subnetwork reacts to its own past state via components in the bulk. These memory functions provide probes of near-steady state dynamics, revealing information not easily accessible otherwise. We illustrate the method on a simple cross-repressive transcriptional motif to show that memory functions not only simplify the analysis of the subnetwork but also have a natural interpretation. We then apply the approach to a GRN from the vertebrate neural tube, a well characterised developmental transcriptional network composed of four interacting transcription factors. The memory functions reveal the function of specific links within the neural tube network and identify features of the regulatory structure that specifically increase the robustness of the network to initial conditions. Taken together, the study provides evidence that Zwanzig-Mori projections offer powerful and effective tools for simplifying and exploring the behaviour of GRNs. PMID:29470492

Comparison between the angle of Eustachian tube in patients with chronic suppurative otitis media and normal ears based on computed tomography scan of temporal bones in Haji Adam Malik general hospital Medan

NASA Astrophysics Data System (ADS)

Masita, S.; Zahara, D.; Aboet, A.

2018-03-01

The function of the Eustachian tube plays a significant role in increased risk chronic suppurative otitis media (CSOM). The angle of the Eustachian tube is a predisposing factor for Eustachian tube dysfunction and clearance disorder of the middle ear. The aim of this study was to compare the mean angle of a Eustachian tube of CSOM ears and normal ears. This research was a cross-sectional study consisting of 19 patients of CSOM without cholesteatoma, 19 patients of CSOM with cholesteatoma and 19 patients with normal ears. All patients were examined using CT Temporal, and the angle of the eustachian tube was measured using multiplanar reconstruction technique. The mean angle of Eustachian tube in CSOM patients without cholesteatoma was 32.82° (SD=3.82), in CSOM with cholesteatoma was 27.74° (SD=4.44) and in normal ears was 33.61° (SD=3.83). Based on Kruskal-Wallis test, there was a significant difference in the angle of a Eustachian tube of these three groups (p<0.001). There was a significant difference between the mean angle of the Eustachian tube in CSOM ears and normal ears.

Easy come, easy go: a simple and effective orthodontic enamel anchor for endotracheal tube stabilization in a child with extensive facial burns.

PubMed

Sakata, Shinichiro; Hallett, Kerrod B; Brandon, Matthew S; McBride, Craig A

2009-11-01

Endotracheal tube stabilization in patients with facial burns is crucial and often challenging. We present a simple method of securing an endotracheal tube using two orthodontic brackets bonded to the maxillary central incisor teeth and a 0.08'' stainless steel ligature wire. Our technique is less traumatic, and is easier to maintain oral hygiene than with previously described methods. This anchorage system takes 5 min to apply and can be removed on the ward without the need for a general anaesthetic.

Examples of grid generation with implicitly specified surfaces using GridPro (TM)/az3000. 1: Filleted multi-tube configurations

NASA Technical Reports Server (NTRS)

Cheng, Zheming; Eiseman, Peter R.

1995-01-01

With examples, we illustrate how implicitly specified surfaces can be used for grid generation with GridPro/az3000. The particular examples address two questions: (1) How do you model intersecting tubes with fillets? and (2) How do you generate grids inside the intersected tubes? The implication is much more general. With the results in a forthcoming paper which develops an easy-to-follow procedure for implicit surface modeling, we provide a powerful means for rapid prototyping in grid generation.

Elastic Stability of Concentric Tube Robots: A Stability Measure and Design Test

PubMed Central

Gilbert, Hunter B.; Hendrick, Richard J.; Webster, Robert J.

2016-01-01

Concentric tube robots are needle-sized manipulators which have been investigated for use in minimally invasive surgeries. It was noted early in the development of these devices that elastic energy storage can lead to rapid snapping motion for designs with moderate to high tube curvatures. Substantial progress has recently been made in the concentric tube robot community in designing snap-free robots, planning stable paths, and characterizing conditions that result in snapping for specific classes of concentric tube robots. However, a general measure for how stable a given robot configuration is has yet to be proposed. In this paper, we use bifurcation and elastic stability theory to provide such a measure, as well as to produce a test for determining whether a given design is snap-free (i.e. whether snapping can occur anywhere in the unloaded robot’s workspace). These results are useful in designing, planning motions for, and controlling concentric tube robots with high curvatures. PMID:27042170

Elastic Stability of Concentric Tube Robots: A Stability Measure and Design Test.

PubMed

Gilbert, Hunter B; Hendrick, Richard J; Webster, Robert J

2016-02-01

Concentric tube robots are needle-sized manipulators which have been investigated for use in minimally invasive surgeries. It was noted early in the development of these devices that elastic energy storage can lead to rapid snapping motion for designs with moderate to high tube curvatures. Substantial progress has recently been made in the concentric tube robot community in designing snap-free robots, planning stable paths, and characterizing conditions that result in snapping for specific classes of concentric tube robots. However, a general measure for how stable a given robot configuration is has yet to be proposed. In this paper, we use bifurcation and elastic stability theory to provide such a measure, as well as to produce a test for determining whether a given design is snap-free (i.e. whether snapping can occur anywhere in the unloaded robot's workspace). These results are useful in designing, planning motions for, and controlling concentric tube robots with high curvatures.

Vibration analysis of the tympanic membrane with a ventilation tube and a perforation by holography

NASA Astrophysics Data System (ADS)

Maeta, Manabu; Kawakami, Shinichiro; Ogawara, Toshiaki; Masuda, Yu

1991-08-01

For severe otitis media with effusion, insertion of a ventilation tube is performed for the purpose of ventilation of the middle ear cavity and normalization of the eustachian tubular function and middle ear mucosa. The ventilation tube is left in place for as long as several months or even a few years. However, the influence of the indwelling tube on vibration of the tympanic membrane is unknown. Therefore, the authors observed the influence by means of time-averaged holography using human tympanic membranes. The following results were obtained. After insertion of a ventilation tube, vibration pattern of the tympanic membrane was not obviously changed, but the vibration amplitude of the tympanic membrane was decreased, especially at 500 Hz. Generally speaking, the change caused by insertion of a ventilation tube was very small. Also, the vibration pattern of perforated tympanic membrane was not changed, but the vibration amplitude of perforated tympanic membrane was decreased at the low frequency area.

High-Throughput Top-Down and Bottom-Up Processes for Forming Single-Nanotube Based Architectures for 3D Electronics

NASA Technical Reports Server (NTRS)

Kaul, Anupama B.; Megerian, Krikor G.; von Allmen, Paul; Kowalczyk, Robert; Baron, Richard

2009-01-01

We have developed manufacturable approaches to form single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 micron deep trenches. These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled Cryo-etchers for forming the 3D nanoscale architectures. The tube growth was performed using dc plasma-enhanced chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. Tube characteristics were also engineered to some extent, by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth. Such scalable, high throughput top-down fabrication techniques, combined with bottom-up tube synthesis, should accelerate the development of PECVD tubes for applications such as interconnects, nano-electromechanical (NEMS), sensors or 3D electronics in general.

Dynamics of deformation and pinch-off of a migrating compound droplet in a tube

NASA Astrophysics Data System (ADS)

Borthakur, Manash Pratim; Biswas, Gautam; Bandyopadhyay, Dipankar

2018-04-01

A computational fluid dynamic investigation has been carried out to study the dynamics of a moving compound droplet inside a tube. The motions associated with such a droplet is uncovered by solving the axisymmetric Navier-Stokes equations in which the spatiotemporal evolution of a pair of twin-deformable interfaces has been tracked employing the volume-of-fluid approach. The deformations at the interfaces and their subsequent dynamics are found to be stimulated by the subtle interplay between the capillary and viscous forces. The simulations uncover that when a compound drop composed of concentric inner and outer interfaces migrates inside a tube, initially in the unsteady domain of evolution, the inner drop shifts away from the concentric position to reach a morphology of constant eccentricity at the steady state. The coupled motions of the droplets in the unsteady regime causes a continuous deformation of the inner and outer interfaces to obtain a configuration with a (an) prolate (oblate) shaped outer (inner) interface. The magnitudes of capillary number and viscosity ratio are found to have significant influence on the temporal evolution of the interfacial deformations as well as the eccentricity of the droplets. Further, the simulations uncover that, following the asymmetric deformation of the interfaces, the migrating compound droplet can undergo an uncommon breakup stimulated by a rather irregular pinch-off of the outer shell. The breakup is found to initiate with the thinning of the outer shell followed by the pinch-off. Interestingly, the kinetics of the thinning of outer shell is found to follow two distinct power-law regimes—a swiftly thinning stage at the onset followed by a rate limiting stage before pinch-off, which eventually leads to the uncommon breakup of the migrating compound droplets.

Computer-Aided Thermohydraulic Design of TEMA Type E Shell and Tube Heat Exchangers for Use in Low Pressure, Liquid-to-Liquid, Single Phase Applications.

DTIC Science & Technology

1985-04-01

and Standards .. ... ....... ....... 9 A. General . ... .. .. ... ..... .. .. ... 9 B. ASME Boiler and Pressure Vessel Code .. .. ......9 C. Foreign...several different sources. B. American Society of Mechanial Engineers (ASME) Boiler and Pressure Vessel Code A shell and tube heat exchanger is indeed a

POD- Mapping and analysis of hydroturbine exit flow dynamics

NASA Astrophysics Data System (ADS)

Kjeldsen, Morten; Finstad, Pal Henrik

2012-11-01

Pairwise radial dynamic measurements of the swirling draft tube flow have been made at the 25 MW Svorka power plant in Surnadal operating at 48% load at 6 radial and 7 angular positions. The data is analyzed with traditional methods as well as with POD. The measurements were made in the turbine draft tube/exit flow in an axial measurement plane about 1200mm downstream the turbine runner. The draft tube diameter in the measurement plane is about 1300mm. The flow rate during measurements was close to 5.8m3/s. Two probes were used; both of length Le=700 mm and made of stainless steel with an outer diameter of Do=20 mm and inner diameter Di=4mm. At the end of each probe a full bridge cylindrical KULITE xcl152, 0-3.5, was mounted. 90 seconds samples at 10 kS/s were taken. The POD analysis largely follows that of Tutkun et al. (see e.g. AIAA J., 45,5,2008). The analysis shows that 26% of the pressure pulsation energy can be addressed to azimuthal mode 1. The work has been supported by Energy Norway.

32. GENERAL VIEW LOOKING NORTHEAST, SHOWING DRAFT CONES AND INTAKE ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

32. GENERAL VIEW LOOKING NORTHEAST, SHOWING DRAFT CONES AND INTAKE TUBES. - Wilson Dam & Hydroelectric Plant, Spanning Tennessee River at Wilson Dam Road (Route 133), Muscle Shoals, Colbert County, AL

21 CFR 880.5475 - Jet lavage.

Code of Federal Regulations, 2013 CFR

2013-04-01

... GENERAL HOSPITAL AND PERSONAL USE DEVICES General Hospital and Personal Use Therapeutic Devices § 880.5475..., and a means of propelling the fluid through the tubing, such as an electric roller pump. (b...

F-Actin Dynamics in Neurospora crassa ▿ †

PubMed Central

Berepiki, Adokiye; Lichius, Alexander; Shoji, Jun-Ya; Tilsner, Jens; Read, Nick D.

2010-01-01

This study demonstrates the utility of Lifeact for the investigation of actin dynamics in Neurospora crassa and also represents the first report of simultaneous live-cell imaging of the actin and microtubule cytoskeletons in filamentous fungi. Lifeact is a 17-amino-acid peptide derived from the nonessential Saccharomyces cerevisiae actin-binding protein Abp140p. Fused to green fluorescent protein (GFP) or red fluorescent protein (TagRFP), Lifeact allowed live-cell imaging of actin patches, cables, and rings in N. crassa without interfering with cellular functions. Actin cables and patches localized to sites of active growth during the establishment and maintenance of cell polarity in germ tubes and conidial anastomosis tubes (CATs). Recurrent phases of formation and retrograde movement of complex arrays of actin cables were observed at growing tips of germ tubes and CATs. Two populations of actin patches exhibiting slow and fast movement were distinguished, and rapid (1.2 μm/s) saltatory transport of patches along cables was observed. Actin cables accumulated and subsequently condensed into actin rings associated with septum formation. F-actin organization was markedly different in the tip regions of mature hyphae and in germ tubes. Only mature hyphae displayed a subapical collar of actin patches and a concentration of F-actin within the core of the Spitzenkörper. Coexpression of Lifeact-TagRFP and β-tubulin–GFP revealed distinct but interrelated localization patterns of F-actin and microtubules during the initiation and maintenance of tip growth. PMID:20139238

The Dynamics of Miscible Interfaces: Simulations

NASA Technical Reports Server (NTRS)

Meiburg, Eckart

2002-01-01

The goal of this experimental/computational investigation (joint with Prof Maxworthy at USC) has been to study the dynamics of miscible interfaces, both from a scientific and a practical point of view, and to prepare a related experiment to be flown on the International Space Station. In order to address these effects, we have focused experimental and computational investigations on miscible displacements in cylindrical capillary tubes, as well as in Hele-Shaw cells. Regarding the flow in a capillary tube, the question was addressed as to whether Korteweg stresses and/or divergence effects can potentially account for discrepancies observed between conventional Stokes flow simulations and experiments for miscible flows in capillary tubes. An estimate of the vorticity and streamfunction fields induced by the Kortewegs stresses was derived, which shows these stresses to result in the formation of a vortex ring structure near the tip of the concentration front. Through this mechanism the propagation velocity of the concentration front is reduced, in agreement with the experimental observations. Divergence effects, on the other hand, were seen to be very small, and they have a negligible influence on the tip velocity. As a result, it can be concluded that they are not responsible for the discrepancies between experiments and conventional Stokes simulations. A further part of our investigation focussed on the development of high-accuracy three-dimensional spectral element simulation techniques for miscible flows in capillary tubes, including the effects of variable density and viscosity. Towards this end, the conservation equations are treated in cylindrical coordinates.

Controlling microtube permeability via grafted polymers and solvent quality.

PubMed

Suo, Tongchuan; Whitmore, Mark D

2014-03-21

We examine pressure-driven flow through a microtube with grafted polymers using a "doubly self-consistent field" steady-state theory. Our focus is on the structure of the polymer layer, the tube permeability, and the effects of solvent quality, for different regimes of open and closed tubes. We find that, within experimentally attainable pressure gradients, the flow has very little effect on the grafted layer. However, the polymers, and in particular variations in the solvent quality and cylinder radii, can have large effects on the flow. We find that the permeability can either increase or decrease with either the radius or solvent quality, and we identify the regimes for different behaviors in terms of general parameters that can be used to generalize to other systems. This allows us to identify regimes where the systems are most sensitive to these "tuning" parameters, and we find that they correspond to the boundaries between open and closed tubes identified earlier.

Polymer dynamics: Floored by the rings

NASA Astrophysics Data System (ADS)

McLeish, Tom

2008-12-01

The tube model can explain how mutually entangled polymer chains move and interact, but it relies on the loose ends of chains to generate relaxation. Ring polymers have no ends - so how do they relax?

Polar Expansion Dynamics in the Plant Kingdom: A Diverse and Multifunctional Journey on the Path to Pollen Tubes

PubMed Central

Domozych, David S.; Fujimoto, Chelsea; LaRue, Therese

2013-01-01

Polar expansion is a widespread phenomenon in plants spanning all taxonomic groups from the Charophycean Green Algae to pollen tubes in Angiosperms and Gymnosperms. Current data strongly suggests that many common features are shared amongst cells displaying polar growth mechanics including changes to the structural features of localized regions of the cell wall, mobilization of targeted secretion mechanisms, employment of the actin cytoskeleton for directing secretion and in many cases, endocytosis and coordinated interaction of multiple signal transduction mechanisms prompted by external biotic and abiotic cues. The products of polar expansion perform diverse functions including delivery of male gametes to the egg, absorption, anchorage, adhesion and photo-absorption efficacy. A comparative analysis of polar expansion dynamics is provided with special emphasis on those found in early divergent plants. PMID:27137370

Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.

PubMed

Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin

2015-07-07

Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.

Kinetics of gravity-driven slug flow in partially wettable capillaries of varying cross section

NASA Astrophysics Data System (ADS)

Nissan, Alon; Wang, Qiuling; Wallach, Rony

2016-11-01

A mathematical model for slug (finite liquid volume) motion in not-fully-wettable capillary tubes with sinusoidally varying cross-sectional areas was developed. The model, based on the Navier-Stokes equation, accounts for the full viscous terms due to nonuniform geometry, the inertial term, the slug's front and rear meniscus hysteresis effect, and dependence of contact angle on flow velocity (dynamic contact angle). The model includes a velocity-dependent film that is left behind the advancing slug, reducing its mass. The model was successfully verified experimentally by recording slug movement in uniform and sinusoidal capillary tubes with a gray-scale high-speed camera. Simulation showed that tube nonuniformity has a substantial effect on slug flow pattern: in a uniform tube it is monotonic and depends mainly on the slug's momentary mass/length; an undulating tube radius results in nonmonotonic flow characteristics. The static nonzero contact angle varies locally in nonuniform tubes owing to the additional effect of wall slope. Moreover, the nonuniform cross-sectional area induces slug acceleration, deceleration, blockage, and metastable-equilibrium locations. Increasing contact angle further amplifies the geometry effect on slug propagation. The developed model provides a modified means of emulating slug flow in differently wettable porous media for intermittent inlet water supply (e.g., raindrops on the soil surface).

Molecular basis for endothelial lumen formation and tubulogenesis during vasculogenesis and angiogenic sprouting

PubMed Central

Davis, George E.; Stratman, Amber N.; Sacharidou, Anastasia; Koh, Wonshill

2013-01-01

Many studies reveal a fundamental role for extracellular matrix-mediated signaling through integrins and Rho GTPases as well as matrix metalloproteinases (MMPs) in the molecular control of vascular tube morphogenesis in three-dimensional (3D) tissue environments. Recent work has defined an EC lumen signaling complex of proteins that controls these vascular morphogenic events. These findings reveal a signaling interdependence between Cdc42 and MT1-MMP to control the 3D matrix-specific process of EC tubulogenesis. The EC tube formation process results in the creation of a network of proteolytically-generated vascular guidance tunnels in 3D matrices that are utilized to remodel EC-lined tubes through EC motility and could facilitate processes such as flow-induced remodeling and arteriovenous EC sorting and differentiation. Within vascular guidance tunnels, key dynamic interactions occur between endothelial cells (ECs) and pericytes to affect vessel remodeling, diameter, and vascular basement membrane matrix assembly, a fundamental process necessary for endothelial tube maturation and stabilization. Thus, the EC lumen and tube formation mechanism coordinates the concomitant establishment of a network of vascular tubes within tunnel spaces to allow for flow responsiveness, EC-mural cell interactions, and vascular extracellular matrix assembly to control the development of the functional microcirculation. PMID:21482411

Alternative Bio-Derived JP-8 Class Fuel and JP-8 Fuel: Flame Tube Combustor Test Results Compared using a GE TAPS Injector Configuration

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Anderson, Robert; Tedder, Sarah

2016-01-01

This paper presents results from tests in a NASA Glenn Research Center (GRC) flame tube facility, where a bio-derived alternate fuel was compared with JP-8 for emissions and general combustion performance. A research version of General Electric Aviation (GE) TAPS injector was used for the tests. Results include 2D, planar laser-based imaging as well as basic flow visualization of the flame. Four conditions were selected that simulate various engine power conditions relevant to NASA Fundamental Aeronautics Supersonics and Environmentally Responsible Aviation Projects were tested.

In-Situ Contained And Of Volatile Soil Contaminants

DOEpatents

Varvel, Mark Darrell

2005-12-27

The invention relates to a novel approach to containing and removing toxic waste from a subsurface environment. More specifically the present invention relates to a system for containing and removing volatile toxic chemicals from a subsurface environment using differences in surface and subsurface pressures. The present embodiment generally comprises a deep well, a horizontal tube, at least one injection well, at least one extraction well and a means for containing the waste within the waste zone (in-situ barrier). During operation the deep well air at the bottom of well (which is at a high pressure relative to the land surface as well as relative to the air in the contaminated soil) flows upward through the deep well (or deep well tube). This stream of deep well air is directed into the horizontal tube, down through the injection tube(s) (injection well(s)) and into the contaminate plume where it enhances volatization and/or removal of the contaminants.

In-Situ Containment and Extraction of Volatile Soil Contaminants

DOEpatents

Varvel, Mark Darrell

2005-12-27

The invention relates to a novel approach to containing and removing toxic waste from a subsurface environment. More specifically the present invention relates to a system for containing and removing volatile toxic chemicals from a subsurface environment using differences in surface and subsurface pressures. The present embodiment generally comprises a deep well, a horizontal tube, at least one injection well, at least one extraction well and a means for containing the waste within the waste zone (in-situ barrier). During operation the deep well air at the bottom of well (which is at a high pressure relative to the land surface as well as relative to the air in the contaminated soil) flows upward through the deep well (or deep well tube). This stream of deep well air is directed into the horizontal tube, down through the injection tube(s) (injection well(s)) and into the contaminate plume where it enhances volatization and/or removal of the contaminants.

Equilibrium Conformations of Concentric-tube Continuum Robots

PubMed Central

Rucker, D. Caleb; Webster, Robert J.; Chirikjian, Gregory S.; Cowan, Noah J.

2013-01-01

Robots consisting of several concentric, preshaped, elastic tubes can work dexterously in narrow, constrained, and/or winding spaces, as are commonly found in minimally invasive surgery. Previous models of these “active cannulas” assume piecewise constant precurvature of component tubes and neglect torsion in curved sections of the device. In this paper we develop a new coordinate-free energy formulation that accounts for general preshaping of an arbitrary number of component tubes, and which explicitly includes both bending and torsion throughout the device. We show that previously reported models are special cases of our formulation, and then explore in detail the implications of torsional flexibility for the special case of two tubes. Experiments demonstrate that this framework is more descriptive of physical prototype behavior than previous models; it reduces model prediction error by 82% over the calibrated bending-only model, and 17% over the calibrated transmissional torsion model in a set of experiments. PMID:25125773

Generalized three-dimensional simulation of ferruled coupled-cavity traveling-wave-tube dispersion and impedance characteristics

NASA Technical Reports Server (NTRS)

Maruschek, Joseph W.; Kory, Carol L.; Wilson, Jeffrey D.

1993-01-01

The frequency-phase dispersion and Pierce on-axis interaction impedance of a ferruled, coupled-cavity, traveling-wave tube (TWT), slow-wave circuit were calculated using the three-dimensional simulation code Micro-SOS. The utilization of the code to reduce costly and time-consuming experimental cold tests is demonstrated by the accuracy achieved in calculating these parameters. A generalized input file was developed so that ferruled coupled-cavity TWT slow-wave circuits of arbitrary dimensions could be easily modeled. The practicality of the generalized input file was tested by applying it to the ferruled coupled-cavity slow-wave circuit of the Hughes Aircraft Company model 961HA TWT and by comparing the results with experimental results.

Experimental and clinical trial of measuring urinary velocity with the pitot tube and a transrectal ultrasound guided video urodynamic system.

PubMed

Tsujimoto, Yukio; Nose, Yorihito; Ohba, Kenkichi

2003-01-01

The pitot tube is a common device to measure flow velocity. If the pitot tube is used as an urodynamic catheter, urinary velocity and urethral pressure may be measured simultaneously. However, to our knowledge, urodynamic studies with the pitot tube have not been reported. We experimentally and clinically evaluated the feasibility of the pitot tube to measure urinary velocity with a transrectal ultrasound guided video urodynamic system. We carried out a basal experiment measuring flow velocity in model urethras of 4.5-8.0 mm in inner diameter with a 12-Fr pitot tube. In a clinical trial, 79 patients underwent transrectal ultrasound guided video urodynamic studies with the 12-Fr pitot tube. Urinary velocity was calculated from dynamic pressure (Pd) with the pitot tube formula and the correcting equation according to the results of the basal experiment. Velocity measured by the pitot tube was proportional to the average velocity in model urethras and the coefficients were determined by diameters of model urethras. We obtained a formula to calculate urinary velocity from the basal experiment. The urinary velocity could be obtained in 32 of 79 patients. Qmax was 8.1 +/- 4.3 mL/s (mean +/- SD; range, 18.4-1.3 mL/s), urethral diameter was 7.3 +/- 3.0 mm (mean +/- SD; range, 18.7-4.3 mm) and urinary velocity was 69.4 +/- 43.6 (mean +/- SD; range, 181.3-0 cm/s) at maximum flow rate. The correlation coefficient of Qmax measured by a flowmeter versus Qdv flow rate calculated with urethral diameter and velocity was 0.41 without significant difference. The use of the pitot tube as an urodynamic catheter to a transrectal ultrasound-guided video urodynamic system can measure urethral pressure, diameter and urinary velocity simultaneously. However, a thinner pitot tube and further clinical trials are needed to obtain more accurate results.

Optimized manufacture of nuclear fuel cladding tubes by FEA of hot extrusion and cold pilgering processes

NASA Astrophysics Data System (ADS)

Gaillac, Alexis; Ly, Céline

2018-05-01

Within the forming route of Zirconium alloy cladding tubes, hot extrusion is used to deform the forged billets into tube hollows, which are then cold rolled to produce the final tubes with the suitable properties for in-reactor use. The hot extrusion goals are to give the appropriate geometry for cold pilgering, without creating surface defects and microstructural heterogeneities which are detrimental for subsequent rolling. In order to ensure a good quality of the tube hollows, hot extrusion parameters have to be carefully chosen. For this purpose, finite element models are used in addition to experimental tests. These models can take into account the thermo-mechanical coupling conditions obtained in the tube and the tools during extrusion, and provide a good prediction of the extrusion load and the thermo-mechanical history of the extruded product. This last result can be used to calculate the fragmentation of the microstructure in the die and the meta-dynamic recrystallization after extrusion. To further optimize the manufacturing route, a numerical model of the cold pilgering process is also applied, taking into account the complex geometry of the tools and the pseudo-steady state rolling sequence of this incremental forming process. The strain and stress history of the tube during rolling can then be used to assess the damage risk thanks to the use of ductile damage models. Once validated vs. experimental data, both numerical models were used to optimize the manufacturing route and the quality of zirconium cladding tubes. This goal was achieved by selecting hot extrusion parameters giving better recrystallized microstructure that improves the subsequent formability. Cold pilgering parameters were also optimized in order to reduce the potential ductile damage in the cold rolled tubes.

Pollen tube energetics: respiration, fermentation and the race to the ovule

PubMed Central

Rounds, Caleb M.; Winship, Lawrence J.; Hepler, Peter K.

2011-01-01

Background Pollen tubes grow by transferring chemical energy from stored cellular starch and newly assimilated sugars into ATP. This drives myriad processes essential for cell elongation, directly or through the creation of ion gradients. Respiration plays a central role in generating and regulating this energy flow and thus in the success of plant reproduction. Pollen tubes are easily grown in vitro and have become an excellent model for investigating the contributions of respiration to plant cellular growth and morphogenesis at the molecular, biochemical and physiological levels. Scope In recent decades, pollen tube research has become increasingly focused on the molecular mechanisms involved in cellular processes. Yet, effective growth and development requires an intact, integrated set of cellular processes, all supplied with a constant flow of energy. Here we bring together information from the current and historical literature concerning respiration, fermentation and mitochondrial physiology in pollen tubes, and assess the significance of more recent molecular and genetic investigations in a physiological context. Conclusions The rapid growth of the pollen tube down the style has led to the evolution of high rates of pollen tube respiration. Respiration rates in lily predict a total energy turnover of 40–50 fmol ATP s−1 per pollen grain. Within this context we examine the energetic requirements of cell wall synthesis, osmoregulation, actin dynamics and cyclosis. At present, we can only estimate the amount of energy required, because data from growing pollen tubes are not available. In addition to respiration, we discuss fermentation and mitochondrial localization. We argue that the molecular pathways need to be examined within the physiological context to understand better the mechanisms that control tip growth in pollen tubes. PMID:22476489

Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

NASA Technical Reports Server (NTRS)

Bershader, D. (Editor); Hanson, R. (Editor)

1986-01-01

A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

Shock waves and shock tubes; Proceedings of the Fifteenth International Symposium, Berkeley, CA, July 28-August 2, 1985

NASA Astrophysics Data System (ADS)

Bershader, D.; Hanson, R.

A detailed survey is presented of shock tube experiments, theoretical developments, and applications being carried out worldwide. The discussions explore shock tube physics and the related chemical, physical and biological science and technology. Extensive attention is devoted to shock wave phenomena in dusty gases and other multiphase and heterogeneous systems, including chemically reactive mixtures. Consideration is given to techniques for measuring, visualizing and theoretically modeling flowfield, shock wave and rarefaction wave characteristics. Numerical modeling is explored in terms of the application of computational fluid dynamics techniques to describing flowfields in shock tubes. Shock interactions and propagation, in both solids, fluids, gases and mixed media are investigated, along with the behavior of shocks in condensed matter. Finally, chemical reactions that are initiated as the result of passage of a shock wave are discussed, together with methods of controlling the evolution of laminar separated flows at concave corners on advanced reentry vehicles.

Enhancement of the water flow velocity through carbon nanotubes resulting from the radius dependence of the friction due to electron excitations

NASA Astrophysics Data System (ADS)

Sokoloff, J. B.

2018-03-01

Secchi et al. [Nature (London) 537, 210 (2016), 10.1038/nature19315] observed a large enhancement of the permeability and slip length in carbon nanotubes when the tube radius is of the order of 15 nm, but not in boron nitride nanotubes. It will be pointed out that none of the parameters that appear in the usual molecular dynamics treatments of water flow in carbon nanotubes have a length scale comparable to 15 nm, which could account for the observed flow velocity enhancement. It will be demonstrated here, however, that if the friction force between the water and the tube walls in carbon nanotubes is dominated by friction due to electron excitations in the tube walls, the enhanced flow can be accounted for by a reduction in the contribution to the friction due to electron excitations in the wall, resulting from the dependence of the electron energy band gap on the tube radius.

Numerical evaluation of laminar heat transfer enhancement in nanofluid flow in coiled square tubes

PubMed Central

2011-01-01

Convective heat transfer can be enhanced by changing flow geometry and/or by enhancing thermal conductivity of the fluid. This study proposes simultaneous passive heat transfer enhancement by combining the geometry effect utilizing nanofluids inflow in coils. The two nanofluid suspensions examined in this study are: water-Al2O3 and water-CuO. The flow behavior and heat transfer performance of these nanofluid suspensions in various configurations of coiled square tubes, e.g., conical spiral, in-plane spiral, and helical spiral, are investigated and compared with those for water flowing in a straight tube. Laminar flow of a Newtonian nanofluid in coils made of square cross section tubes is simulated using computational fluid dynamics (CFD)approach, where the nanofluid properties are treated as functions of particle volumetric concentration and temperature. The results indicate that addition of small amounts of nanoparticles up to 1% improves significantly the heat transfer performance; however, further addition tends to deteriorate heat transfer performance. PMID:21711901

Surface characterization and free thyroid hormones response of chemically modified poly(ethylene terephthalate) blood collection tubes

NASA Astrophysics Data System (ADS)

Jalali Dil, Ebrahim; Kim, Samuel C.; Saffar, Amir; Ajji, Abdellah; Zare, Richard N.; Sattayapiwat, Annie; Esguerra, Vanessa; Bowen, Raffick A. R.

2018-06-01

The surface chemistry and surface energy of chemically modified polyethylene terephthalate (PET) blood collection tubes (BCTs) were studied and the results showed a significant increase in hydrophilicity and polarity of modified PET surface. The surface modification created nanometer-sized, needle-like asperities through molecular segregation at the surface. The surface dynamics of the modified PET was examined by tracking its surface properties over a 280-day period. The results showed surface rearrangement toward a surface with lower surface energy and fewer nanometer-sized asperities. Thromboelastography (TEG) was used to evaluate and compare the thrombogenicity of the inner walls of various types of BCTs. The TEG tracings and data from various types of BCTs demonstrated differences in the reactionand coagulation times but not in clot strength. The performance of the modified tubes in free triiodothyronine (FT3) and free thyroxine (FT4) hormone tests was examined, and it was found that the interference of modified PET tubes was negligible compared to that of commercially available PET BCTs.

An Evaluation of High Temperature Airframe Seals for Advanced Hypersonic Vehicles

NASA Technical Reports Server (NTRS)

DeMange, Jeffrey J.; Dunlap, Patrick H.; Steinetz, Bruce M.; Drlik, Gary J.

2007-01-01

High temperature seals are required for advanced hypersonic airframe applications. In this study, both spring tube thermal barriers and innovative wafer seal systems were evaluated under relevant hypersonic test conditions (temperatures, pressures, etc.) via high temperature compression testing and room temperature flow assessments. Thermal barriers composed of a Rene 41 spring tube filled with Saffil insulation and overbraided with a Nextel 312 sheath showed acceptable performance at 1500 F in both short term and longer term compression testing. Nextel 440 thermal barriers with Rene 41 spring tubes and Saffil insulation demonstrated good compression performance up to 1750 F. A silicon nitride wafer seal/compression spring system displayed excellent load performance at temperatures as high as 2200 F and exhibited room temperature leakage values that were only 1/3 those for the spring tube rope seals. For all seal candidates evaluated, no significant degradation in leakage resistance was noted after high temperature compression testing. In addition to these tests, a superalloy seal suitable for dynamic seal applications was optimized through finite element techniques.

Experimental analysis of refrigerants flow boiling inside small sized microfin tubes

NASA Astrophysics Data System (ADS)

Diani, Andrea; Rossetto, Luisa

2017-07-01

The refrigerant charge reduction is one of the most challenging issues that the scientific community has to cope to reduce the anthropic global warming. Recently, mini microfin tubes have been matter of research, since they can reach better thermal performance in small domains, leading to a further refrigerant charge reduction. This paper presents experimental results about R134a flow boiling inside a microfin tube having an internal diameter at the fin tip of 2.4 mm. The mass flux was varied between 375 and 940 kg m-2 s-1, heat flux from 10 to 50 kW m-2, vapor quality from 0.10 to 0.99. The saturation temperature at the inlet of the test section was kept constant and equal to 30 °C. R134a thermal and fluid dynamic performances are presented and compared against those obtained with R1234ze(E) and R1234yf and against values obtained during R134a flow boiling inside a 3.4 mm ID microfin tube.

Science Notes.

ERIC Educational Resources Information Center

School Science Review, 1984

1984-01-01

Presents 26 activities, experiments, demonstrations, games, and computer programs for biology, chemistry, and physics. Background information, laboratory procedures, equipment lists, and instructional strategies are given. Topics include eye measurements, nutrition, soil test tube rack, population dynamics, angular momentum, transition metals,…

Gas dynamics of a supersonic radial jet. Part II

NASA Astrophysics Data System (ADS)

Kosarev, V. F.; Klinkov, S. V.; Zaikovskii, V. N.

2016-05-01

The paper presents the radial distributions of the pressure measured with a Pitot tube for the case of a radial jet with/without swirling of the input flow in the pre-chamber; the length of the supersonic part of the jet, dependency of the jet thickness as a function of the distance from the nozzle outlet, and approximating analytical formula for the jet thickness that generalizes the experimental data. Experimental data demonstrated that at the deposition distances lower than 4-6 gauges from the nozzle outlet, the solid particle velocity and temperature are almost uniform over the jet cross section. This means that the target surface can be allocated here without loss in coating quality and deposition coefficient. The maximal recommended distance where the deposition is still possible is the length of l s0 ~ 16 gauges.

ARPA-E: Advancing the Electric Grid

ScienceCinema

Lemmon, John; Ruiz, Pablo; Sommerer, Tim; Aziz, Michael

2018-06-07

The electric grid was designed with the assumption that all energy generation sources would be relatively controllable, and grid operators would always be able to predict when and where those sources would be located. With the addition of renewable energy sources like wind and solar, which can be installed faster than traditional generation technologies, this is no longer the case. Furthermore, the fact that renewable energy sources are imperfectly predictable means that the grid has to adapt in real-time to changing patterns of power flow. We need a dynamic grid that is far more flexible. This video highlights three ARPA-E-funded approaches to improving the grid's flexibility: topology control software from Boston University that optimizes power flow, gas tube switches from General Electric that provide efficient power conversion, and flow batteries from Harvard University that offer grid-scale energy storage.

Numerical studies on heat transfer and pressure drop characteristics of flat finned tube bundles with various fin materials

NASA Astrophysics Data System (ADS)

Peng, Y.; Zhang, S. J.; Shen, F.; Wang, X. B.; Yang, X. R.; Yang, L. J.

2017-11-01

The air-cooled heat exchanger plays an important role in the field of industry like for example in thermal power plants. On the other hand, it can be used to remove core decay heat out of containment passively in case of a severe accident circumstance. Thus, research on the performance of fins in air-cooled heat exchangers can benefit the optimal design and operation of cooling systems in nuclear power plants. In this study, a CFD (Computational Fluid Dynamic) method is implemented to investigate the effects of inlet velocity, fin spacing and tube pitch on the flow and the heat transfer characteristics of flat fins constructed of various materials (316L stainless steel, copper-nickel alloy and aluminium). A three dimensional geometric model of flat finned tube bundles with fixed longitudinal tube pitch and transverse tube pitch is established. Results for the variation of the average convective heat transfer coefficient with respect to cooling air inlet velocity, fin spacing, tube pitch and fin material are obtained, as well as for the pressure drop of the cooling air passing through finned tube. It is shown that the increase of cooling air inlet velocity results in enhanced average convective heat transfer coefficient and decreasing pressure drop. Both fin spacing and tube pitch engender positive effects on pressure drop and have negative effects on heat transfer characteristics. Concerning the fin material, the heat transfer performance of copper-nickel alloy is superior to 316L stainless steel and inferior to aluminium.

Mapping Self-Guided Learners' Searches for Video Tutorials on YouTube

ERIC Educational Resources Information Center

Garrett, Nathan

2016-01-01

While YouTube has a wealth of educational videos, how self-guided learners use these resources has not been fully described. An analysis of search engine queries for help with the use of Microsoft Excel shows that few users search for specific features or functions but instead use very general terms. Because the same videos are returned in…

Counter tube window and X-ray fluorescence analyzer study

NASA Technical Reports Server (NTRS)

Hertel, R.; Holm, M.

1973-01-01

A study was performed to determine the best design tube window and X-ray fluorescence analyzer for quantitative analysis of Venusian dust and condensates. The principal objective of the project was to develop the best counter tube window geometry for the sensing element of the instrument. This included formulation of a mathematical model of the window and optimization of its parameters. The proposed detector and instrument has several important features. The instrument will perform a near real-time analysis of dust in the Venusian atmosphere, and is capable of measuring dust layers less than 1 micron thick. In addition, wide dynamic measurement range will be provided to compensate for extreme variations in count rates. An integral pulse-height analyzer and memory accumulate data and read out spectra for detail computer analysis on the ground.

Dynamic morphologies of pollen plastids visualised by vegetative-specific FtsZ1-GFP in Arabidopsis thaliana.

PubMed

Fujiwara, Makoto T; Hashimoto, Haruki; Kazama, Yusuke; Hirano, Tomonari; Yoshioka, Yasushi; Aoki, Seishiro; Sato, Naoki; Itoh, Ryuuichi D; Abe, Tomoko

2010-06-01

The behaviour and multiplication of pollen plastids have remained elusive despite their crucial involvement in cytoplasmic inheritance. Here, we present live images of plastids in pollen grains and growing tubes from transgenic Arabidopsis thaliana lines expressing stroma-localised FtsZ1-green-fluorescent protein fusion in a vegetative cell-specific manner. Vegetative cells in mature pollen contained a morphologically heterogeneous population of round to ellipsoidal plastids, whilst those in late-developing (maturing) pollen included plastids that could have one or two constriction sites. Furthermore, plastids in pollen tubes exhibited remarkable tubulation, stromule (stroma-filled tubule) extension, and back-and-forth movement along the direction of tube growth. Plastid division, which involves the FtsZ1 ring, was rarely observed in mature pollen grains.

Design, development and testing twin pulse tube cryocooler

NASA Astrophysics Data System (ADS)

Gour, Abhay Singh; Sagar, Pankaj; Karunanithi, R.

2017-09-01

The design and development of Twin Pulse Tube Cryocooler (TPTC) is presented. Both the coolers are driven by a single Linear Moving Magnet Synchronous Motor (LMMSM) with piston heads at both ends of the mover shaft. Magnetostatic analysis for flux line distribution was carried-out during design and development of LMMSM based pressure wave generator. Based on the performance of PWG, design of TPTC was carried out using Sage and Computational Fluid Dynamics (CFD) analysis. Detailed design, fabrication and testing of LMMSM, TPTC and their integration tests are presented in this paper.

COLD CATHODE DECADE TUBES AS ADDRESS ELEMENTS & CHANNEL STORES IN MULTICHANNEL ANALYZER SYSTEMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parwardhan, P.K.; Phadnis, M.G.

1963-07-01

ABS>The application of dekatron tubes in address logic and channel stores in multichannel analyzer systems is considered, and circuits for dekatron drive developed for this purpose are discussed. The glow dynamics in such circuits is explained on the basis of the new concept of alpha and beta transfers. A brief account of the design and performance (bringing out the effect of certain parameters on overall performance) of an integrated 100-channel analyzer system, which incorporates the new circuits, is also included. (auth)

New Way of Characterizing the State of the Ring Current

NASA Astrophysics Data System (ADS)

Wolf, R.; Bao, S.; Gkioulidou, M.; Yang, J.; Toffoletto, F.

2017-12-01

The flux tube entropy S is invariant in ideal MHD and is a good way to characterize the degree to which a closed flux tube is loaded with particle energy. Flux tube entropy generally increases with increasing geocentric distance. A flux tube that is injected from the plasma sheet into the ring current tends to be a bubble that has a lower S value than typical plasma sheet flux tubes, and it tends to penetrate to a position where the surroundings matches its S. From this point of view, a good way to characterize the state of the ring current is through the function dF/dS, which specifies how much magnetic flux is occupied by tubes with different degrees of loading. By displaying dF/dS curves before and during storm main phases simulated with the RCM-E code, we determine that, in the model, the injection of the stormtime ring current consists of replacing pre-storm low-S flux tubes with tubes from the plasma sheet that have a certain limited range of S, which is well below typical plasma-sheet values. We also display dF/dS curves for passes by the Van Allen Probes before and during storm main phases, and compare with the RCM-E-derived curves, to gain insight into the nature of the flux tubes that are injected to form the real storm-time ring current.

On the dynamic response of pressure transmission lines in the research of helium-charged free piston Stirling engines

NASA Technical Reports Server (NTRS)

Miller, Eric L.; Dudenhoefer, James E.

1989-01-01

In free piston Stirling engine research the integrity of both amplitude and phase of the dynamic pressure measurements is critical to the characterization of cycle dynamics and thermodynamics. It is therefore necessary to appreciate all possible sources of signal distortion when designing pressure measurement systems for this type of research. The signal distortion inherent to pressure transmission lines is discussed. Based on results from classical analysis, guidelines are formulated to describe the dynamic response properties of a volume-terminated transmission tube for applications involving helium-charged free piston Stirling engines. The scope and limitations of the dynamic response analysis are considered.

Gastric fistula secondary to drainage tube penetration: A report of a rare case.

PubMed

Shao, Hui-Jiang; Lu, Bao-Chun; Xu, Huan-Jian; Ruan, Xin-Xian; Yin, Jing-Song; Shen, Zhi-Hong

2016-03-01

Cases of gastric fistula secondary to drainage tube penetration have rarely been reported. The current study presents a case of gastric penetration caused by misplacement of a drainage tube after a splenectomy. The patient was admitted to the Department of Hepatobiliary Surgery, (Shaoxing People's Hospital, Shaoxing Hospital of Zhejiang University, Shaoxing, Zhejiang, China) for blunt abdominal trauma due to injuries sustained in an automobile accident. A ruptured spleen was found and successfully removed surgically. On post-operative day 7, the patient complained of slight discomfort and tenderness in the left upper quadrant of the abdomen. In addition, 500 ml of bile-colored fluid with small food particles was noted in the drainage tube. Barium X-ray revealed a gastric fistula in the upper gastrointestinal tract. Gastroscopy indicated infiltration of the drainage tube into the gastric cavity. No significant peritoneal effusion was observed, as revealed by abdominal ultrasound examination. These results confirmed the diagnosis of a gastric fistula secondary to perforation by the drainage tube. Following conservative treatment with antibiotics and total parenteral nutrition, the general condition of the patient improved significantly. The drainage tube was withdrawn progressively, as the amount of fluid being discharged was decreasing. Gastroenterography confirmed perforation closure and the tube was finally removed on post-operative day 44.

Implications of depleted flux tubes in the Jovian magnetosphere

NASA Astrophysics Data System (ADS)

Russell, C. T.; Kivelson, M. G.; Kurth, W. S.; Gurnett, D. A.

2000-10-01

A rare but persistent phenomenon in the jovian magnetosphere is the occurrence of apparently depleted flux tubes, whose magnetic pressures are significantly above ambient levels. These flux tubes occur about 0.25% of the observing time in the region of the Io torus in the Galileo high resolution data. The importance of these tubes is that they can return to the inner magnetosphere the magnetic flux that has been convected radially outward with the iogenic plasma to the tail. The paucity of these tubes is consistent with the expected flux return rates if the tubes are moving inward at an average rate of about 5-10 km/s in the torus. Depleted flux tubes have yet to be observed inside of the Io orbit where the plasma beta is lower than in the hot torus. Estimates of the plasma density outside the tube from plasma wave measurements enable the average perpendicular temperature to be obtained from the magnetic field change. Extrapolating this temperature back to Io, we obtain an average ion temperature of approximately 60 eV. These values are generally consistent with earlier Voyager observations but on the low side of their range of uncertainty, and agree quite well with contemporaneous Galileo measurements where these are available.

Implications of Depleted flux Tubes in the Jovian Magnetosphere

NASA Technical Reports Server (NTRS)

Russell, C. T.; Kivelson, M. G.; Kurth, W. S.; Gurnett, D. A.

2000-01-01

A rare but persistent phenomenon in the jovian magnetosphere is the occurrence of apparently depleted flux tubes, whose magnetic pressures are significantly above ambient levels. These flux tubes occur about 0.25% of the observing time in the region of the Io torus in the Galileo high resolution data. The importance of these tubes is that they can return to the inner magnetosphere the magnetic flux that has been convected radially outward with the iogenic plasma to the tail. The paucity of these tubes is consistent with the expected flux return rates if the tubes are moving inward at an average rate of about 5-10 km/s in the torus. Depleted flux tubes have yet to be observed inside of the lo orbit where the plasma beta is lower than in the hot torus. Estimates of the plasma density outside the tube from plasma wave measurements enable the average perpendicular temperature to be obtained from the magnetic field change. Extrapolating this temperature back to lo, we obtain an average ion temperature of approximately 60 eV. These values are generally consistent with earlier Voyager observations but on the low side of their range of uncertainty, and agree quite well with contemporaneous Galileo measurements where these are available.

Programming chemical kinetics: engineering dynamic reaction networks with DNA strand displacement

NASA Astrophysics Data System (ADS)

Srinivas, Niranjan

Over the last century, the silicon revolution has enabled us to build faster, smaller and more sophisticated computers. Today, these computers control phones, cars, satellites, assembly lines, and other electromechanical devices. Just as electrical wiring controls electromechanical devices, living organisms employ "chemical wiring" to make decisions about their environment and control physical processes. Currently, the big difference between these two substrates is that while we have the abstractions, design principles, verification and fabrication techniques in place for programming with silicon, we have no comparable understanding or expertise for programming chemistry. In this thesis we take a small step towards the goal of learning how to systematically engineer prescribed non-equilibrium dynamical behaviors in chemical systems. We use the formalism of chemical reaction networks (CRNs), combined with mass-action kinetics, as our programming language for specifying dynamical behaviors. Leveraging the tools of nucleic acid nanotechnology (introduced in Chapter 1), we employ synthetic DNA molecules as our molecular architecture and toehold-mediated DNA strand displacement as our reaction primitive. Abstraction, modular design and systematic fabrication can work only with well-understood and quantitatively characterized tools. Therefore, we embark on a detailed study of the "device physics" of DNA strand displacement (Chapter 2). We present a unified view of strand displacement biophysics and kinetics by studying the process at multiple levels of detail, using an intuitive model of a random walk on a 1-dimensional energy landscape, a secondary structure kinetics model with single base-pair steps, and a coarse-grained molecular model that incorporates three-dimensional geometric and steric effects. Further, we experimentally investigate the thermodynamics of three-way branch migration. Our findings are consistent with previously measured or inferred rates for hybridization, fraying, and branch migration, and provide a biophysical explanation of strand displacement kinetics. Our work paves the way for accurate modeling of strand displacement cascades, which would facilitate the simulation and construction of more complex molecular systems. In Chapters 3 and 4, we identify and overcome the crucial experimental challenges involved in using our general DNA-based technology for engineering dynamical behaviors in the test tube. In this process, we identify important design rules that inform our choice of molecular motifs and our algorithms for designing and verifying DNA sequences for our molecular implementation. We also develop flexible molecular strategies for "tuning" our reaction rates and stoichiometries in order to compensate for unavoidable non-idealities in the molecular implementation, such as imperfectly synthesized molecules and spurious "leak" pathways that compete with desired pathways. We successfully implement three distinct autocatalytic reactions, which we then combine into a de novo chemical oscillator. Unlike biological networks, which use sophisticated evolved molecules (like proteins) to realize such behavior, our test tube realization is the first to demonstrate that Watson-Crick base pairing interactions alone suffice for oscillatory dynamics. Since our design pipeline is general and applicable to any CRN, our experimental demonstration of a de novo chemical oscillator could enable the systematic construction of CRNs with other dynamic behaviors.

Detonation re-initiation in a concentric tube arrangement for C_2H_2/O_2/Ar mixtures

NASA Astrophysics Data System (ADS)

Wu, Y.; Lee, J. H. S.; Weng, C.

2017-05-01

Re-initiation of detonation in a concentric tube arrangement where a detonation exiting from a small diameter inner tube to a large diameter outer tube has been investigated. The outer tube diameter D is 50.8 mm and inner tube diameters d are 38, 25.4, and 12.7 mm giving diameter ratios D/d=1.34, 2, and 4. Stoichiometric C_2H_2-O_2 mixtures with argon dilution of 0, 25, 50, and 70% are used in the present study. Velocity measurements are made using photodiodes, and smoked foils downstream of the exit of the inner tube are also used to record the re-initiation process. Upon exit from the inner tube, the detonation suffers an abrupt decrease in velocity and at critical conditions, the velocity downstream of the exit is of the order of 50% of the Chapman-Jouguet velocity. It is found that re-initiation generally occurs within 10 tube diameters downstream of the exit. If re-initiation is not successful, the detonation continues to propagate at a low velocity for distances of the order of 30 tube diameters without any indication of flame acceleration of deflagration-to-detonation transition (DDT). Thus, the re-initiation process is clearly defined and distinct from the usual DDT in a smooth tube. The critical d/λ value ratio in the concentric tube is significantly lower than the usual unconfined case of d/λ =13 where λ is the detonation cell size. Thus, it is a result of re-initiation at the Mach stem of the reflected shock from the wall of the outer concentric tube. If re-initiation is not successful upon the first reflection, then subsequent multiple reflections at the tube axis and wall of the outer tube can also result in re-initiation. However, this is only observed for undiluted mixtures. For high-argon-diluted mixtures, re-initiation only occurs at the Mach stem of the first reflection.

27 CFR 44.188 - General.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 27 Alcohol, Tobacco Products and Firearms 2 2011-04-01 2011-04-01 false General. 44.188 Section 44.188 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE... Tubes by Manufacturers and Export Warehouse Proprietors Consignment of Shipment § 44.188 General...

27 CFR 44.188 - General.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 27 Alcohol, Tobacco Products and Firearms 2 2010-04-01 2010-04-01 false General. 44.188 Section 44.188 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE... Tubes by Manufacturers and Export Warehouse Proprietors Consignment of Shipment § 44.188 General...

27 CFR 44.188 - General.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 27 Alcohol, Tobacco Products and Firearms 2 2012-04-01 2011-04-01 true General. 44.188 Section 44.188 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE... Tubes by Manufacturers and Export Warehouse Proprietors Consignment of Shipment § 44.188 General...

27 CFR 44.188 - General.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 27 Alcohol, Tobacco Products and Firearms 2 2014-04-01 2014-04-01 false General. 44.188 Section 44.188 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE... Tubes by Manufacturers and Export Warehouse Proprietors Consignment of Shipment § 44.188 General...

27 CFR 44.188 - General.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 27 Alcohol, Tobacco Products and Firearms 2 2013-04-01 2013-04-01 false General. 44.188 Section 44.188 Alcohol, Tobacco Products and Firearms ALCOHOL AND TOBACCO TAX AND TRADE BUREAU, DEPARTMENT OF THE... Tubes by Manufacturers and Export Warehouse Proprietors Consignment of Shipment § 44.188 General...

The Relationship of Aluminium and Silver to Neural Tube Defects; a Case Control

PubMed Central

Ramírez-Altamirano, María de Jesús; Fenton-Navarro, Patricia; Sivet-Chiñas, Elvira; Harp-Iturribarria, Flor de María; Martínez-Cruz, Ruth; Cruz, Pedro Hernández; Cruz, Margarito Martínez; Pérez-Campos, Eduardo

2012-01-01

Objective The purpose of this study was to identify the relationship of neurotoxic inorganic elements in the hair of patients with the diagnosis of Neural Tube Defects. Our initial hypothesis was that neurotoxic inorganic elements were associated with Neural Tube Defects. Methods Twenty-three samples of hair from newborns were obtained from the General Hospital, “Aurelio Valdivieso” in the city of Oaxaca, Mexico. The study group included 8 newborn infants with neural tube pathology. The control group was composed of 15 newborns without this pathology. The presence of inorganic elements in the hair samples was determined by inductively-coupled plasma spectroscopy (spectroscopic emission of the plasma). Findings The population of newborns with Neural Tube Defects showed significantly higher values of the following elements than the control group: Aluminium, Neural Tube Defects 152.77±51.06 µg/g, control group 76.24±27.89 µg/g; Silver, Neural Tube Defects 1.45±0.76, control group 0.25±0.53 µg/g; Potassium, Neural Tube Defects 553.87±77.91 µg/g, control group 341.13±205.90 µg/g. Association was found at 75 percentile between aluminium plus silver, aluminium plus potassium, silver plus potassium, and potassium plus sodium. Conclusion In the hair of newborns with Neural Tube Defects, the following metals were increased: aluminium, silver. Given the neurotoxicity of the same, and association of Neural Tube Defects with aluminum and silver, one may infer that they may be participating as factors in the development of Neural Tube Defects. PMID:23400307

Dermatology on YouTube.

PubMed

Boyers, Lindsay N; Quest, Tyler; Karimkhani, Chante; Connett, Jessica; Dellavalle, Robert P

2014-06-15

YouTube, reaches upwards of six billion users on a monthly basis and is a unique source of information distribution and communication. Although the influence of YouTube on personal health decision-making is well established, this study assessed the type of content and viewership on a broad scope of dermatology related content on YouTube. Select terms (i.e. dermatology, sun protection, skin cancer, skin cancer awareness, and skin conditions) were searched on YouTube. Overall, the results included 100 videos with over 47 million viewers. Advocacy was the most prevalent content type at 24% of the total search results. These 100 videos were "shared" a total of 101,173 times and have driven 6,325 subscriptions to distinct YouTube user pages. Of the total videos, 35% were uploaded by or featured an MD/DO/PhD in dermatology or other specialty/field, 2% FNP/PA, 1% RN, and 62% other. As one of the most trafficked global sites on the Internet, YouTube is a valuable resource for dermatologists, physicians in other specialties, and the general public to share their dermatology-related content and gain subscribers. However, challenges of accessing and determining evidence-based data remain an issue.

How useful is YouTube in learning heart anatomy?

PubMed

Raikos, Athanasios; Waidyasekara, Pasan

2014-01-01

Nowadays more and more modern medical degree programs focus on self-directed and problem-based learning. That requires students to search for high quality and easy to retrieve online resources. YouTube is an emerging platform for learning human anatomy due to easy access and being a free service. The purpose of this study is to make a quantitative and qualitative analysis of the available human heart anatomy videos on YouTube. Using the search engine of the platform we searched for relevant videos using various keywords. Videos with irrelevant content, animal tissue, non-English language, no sound, duplicates, and physiology focused were excluded from further elaboration. The initial search retrieved 55,525 videos, whereas only 294 qualified for further analysis. A unique scoring system was used to assess the anatomical quality and details, general quality, and the general data for each video. Our results indicate that the human heart anatomy videos available on YouTube conveyed our anatomical criteria poorly, whereas the general quality scoring found borderline. Students should be selective when looking up on public video databases as it can prove challenging, time consuming, and the anatomical information may be misleading due to absence of content review. Anatomists and institutions are encouraged to prepare and endorse good quality material and make them available online for the students. The scoring rubric used in the study comprises a valuable tool to faculty members for quality evaluation of heart anatomy videos available on social media platforms. Copyright © 2013 American Association of Anatomists.

An overview of the dynamic calibration of piezoelectric pressure transducers

NASA Astrophysics Data System (ADS)

Theodoro, F. R. F.; Reis, M. L. C. C.; d’ Souto, C.

2018-03-01

Dynamic calibration is a research area that is still under development and is of great interest to aerospace and automotive industries. This study discusses some concepts regarding dynamic measurements of pressure quantities and presents an overview of dynamic calibration of pressure transducers. Studies conducted by the Institute of Aeronautics and Space focusing on research regarding piezoelectric pressure transducer calibration in shock tube are presented. We employed the Guide to the Expression of Uncertainty and a Monte Carlo Method in the methodology. The results show that both device and methodology employed are adequate to calibrate the piezoelectric sensor.

Online in-tube microextractor coupled with UV-Vis spectrophotometer for bisphenol A detection.

PubMed

Poorahong, Sujittra; Thammakhet, Chongdee; Thavarungkul, Panote; Kanatharana, Proespichaya

2013-01-01

A simple and high extraction efficiency online in-tube microextractor (ITME) was developed for bisphenol A (BPA) detection in water samples. The ITME was fabricated by a stepwise electrodeposition of polyaniline, polyethylene glycol and polydimethylsiloxane composite (CPANI) inside a silico-steel tube. The obtained ITME coupled with UV-Vis detection at 278 nm was investigated. By this method, the extraction and pre-concentration of BPA in water were carried out in a single step. Under optimum conditions, the system provided a linear dynamic range of 0.1 to 100 μM with a limit of detection of 20 nM (S/N ≥3). A single in-tube microextractor had a good stability of more than 60 consecutive injections for 10.0 μM BPA with a relative standard deviation of less than 4%. Moreover, a good tube-to-tube reproducibility and precision were obtained. The system was applied to detect BPA in water samples from six brands of baby bottles and the results showed good agreement with those obtained from the conventional GC-MS method. Acceptable percentage recoveries from the spiked water samples were obtained, ranging from 83-102% for this new method compared with 73-107% for the GC-MS standard method. This new in-tube CPANI microextractor provided an excellent extraction efficiency and a good reproducibility. In addition, it can also be easily applied for the analysis of other polar organic compounds contaminated in water sample.

A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles

NASA Astrophysics Data System (ADS)

Whitty, Kevin J.; Siddoway, Michael

2010-07-01

Gas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization.

Innovative coupling of cogeneration units with fire tube boilers: thermo-fluid dynamics of the fire tubes

NASA Astrophysics Data System (ADS)

Cioccolanti, L.; Arteconi, A.; Bartolini, C. M.; Polonara, F.

2017-11-01

Nowadays the thermal energy demand in the industrial sector is usually satisfied by means of fire tube boilers while electricity is supplied from the grid. Alternatively cogeneration units could be adopted for thermal and electrical energy self-production, whilst installing boilers only as back-up units. However, even when cogeneration is profitable, it is not widespread because industries are usually unwilling to accept cogeneration plants for reliability and high investment costs issues. In this work a system aimed at overcoming the above mentioned market difficulties is proposed. It consists of an innovative coupling of a combined heat and power unit with a modified fire tube boiler. In particular, a CFD analysis was carried out by the authors in order to address the most critical aspects related with the coupling of the two systems. More precisely, the following aspects were evaluated in detail: (i) pressure losses of the exhausts going from the prime mover to the boiler due to the sudden cross-section area variations; (ii) thermal power recoverable from the exhausts in the tubes of the boiler; (iii) dependence of the system on the final users’ specification.

A system for measuring bubble voidage and frequency around tubes immersed in a fluidized bed of particles.

PubMed

Whitty, Kevin J; Siddoway, Michael

2010-07-01

Gas-solid fluidized beds are common in chemical processing and energy production industries. These types of reactors frequently have banks of tubes immersed within the bed to provide heating or cooling, and it is important that the fluid dynamics within these bundles is efficient and uniform. This paper presents a simple, low-cost method for quantitatively analyzing the behavior of gas bubbles within banks of tubes in a fluidized bed cold flow model. Two probes, one containing an infrared emitter and one containing an infrared (IR) detector, are placed into adjacent glass tubes such that the emitter and detector face each other. As bubbles pass through the IR beam, the detector signal increases due to less solid material blocking the path between the emitter and detector. By calibrating the signal response to known voidage of the material, one can measure the bubble voidage at various locations within the tube bundle. The rate and size of bubbles passing through the beam can also be determined by high frequency data collection and subsequent analysis. This technique allows one to develop a map of bubble voidage within a fluidized bed, which can be useful for model validation and system optimization.

Class XI Myosins Move Specific Organelles in Pollen Tubes and Are Required for Normal Fertility and Pollen Tube Growth in Arabidopsis1[OPEN

PubMed Central

Madison, Stephanie L.; Buchanan, Matthew L.; Glass, Jeremiah D.; McClain, Tarah F.; Park, Eunsook; Nebenführ, Andreas

2015-01-01

Pollen tube growth is an essential aspect of plant reproduction because it is the mechanism through which nonmotile sperm cells are delivered to ovules, thus allowing fertilization to occur. A pollen tube is a single cell that only grows at the tip, and this tip growth has been shown to depend on actin filaments. It is generally assumed that myosin-driven movements along these actin filaments are required to sustain the high growth rates of pollen tubes. We tested this conjecture by examining seed set, pollen fitness, and pollen tube growth for knockout mutants of five of the six myosin XI genes expressed in pollen of Arabidopsis (Arabidopsis thaliana). Single mutants had little or no reduction in overall fertility, whereas double mutants of highly similar pollen myosins had greater defects in pollen tube growth. In particular, myo11c1 myo11c2 pollen tubes grew more slowly than wild-type pollen tubes, which resulted in reduced fitness compared with the wild type and a drastic reduction in seed set. Golgi stack and peroxisome movements were also significantly reduced, and actin filaments were less organized in myo11c1 myo11c2 pollen tubes. Interestingly, the movement of yellow fluorescent protein-RabA4d-labeled vesicles and their accumulation at pollen tube tips were not affected in the myo11c1 myo11c2 double mutant, demonstrating functional specialization among myosin isoforms. We conclude that class XI myosins are required for organelle motility, actin organization, and optimal growth of pollen tubes. PMID:26358416

Chemically differentiating ascorbate-mediated dissolution of quantum dots in cell culture media

NASA Astrophysics Data System (ADS)

Su, Cheng-Kuan; Sun, Yuh-Chang

2013-02-01

To investigate the dynamic dissolution of quantum dots (QDs) in cell culture media, in this study we constructed an online automatic analytical system comprising a sequential in-tube solid phase extraction (SPE) device and an inductively coupled plasma (ICP) mass spectrometer. By means of selectively extracting QDs and cadmium ions (Cd2+) onto the interior surface of the polytetrafluoroethylene (PTFE) tube, this novel SPE device could be used to determine the degree of QD dissolution through a simple adjustment of sample acidity. To the best of our knowledge, this study is the first to exploit PTFE tubing as a selective SPE adsorbent for the online chemical differentiation of QDs and Cd2+ ions with the goal of monitoring the phenomenon of QD dissolution in complicated biological matrices. We confirmed the analytical reliability of this system through comparison of the measured Cd-to-QD ratios to the expected values. When analyzing QDs and Cd2+ ions at picomolar levels, a temporal resolution of 8 min was required to load sufficient amounts of the analytes to meet the sensitivity requirements of the ICP mass spectrometer. To demonstrate the practicability of this developed method, we measured the dynamic variations in the Cd-to-QD705 ratio in the presence of ascorbate as a physiological stimulant to generate reactive oxygen species in cell culture media and trigger the dissolution of QDs; our results suggest that the ascorbate-induced QD dissolution was dependent on the time, treatment concentration, and nature of the biomolecule.To investigate the dynamic dissolution of quantum dots (QDs) in cell culture media, in this study we constructed an online automatic analytical system comprising a sequential in-tube solid phase extraction (SPE) device and an inductively coupled plasma (ICP) mass spectrometer. By means of selectively extracting QDs and cadmium ions (Cd2+) onto the interior surface of the polytetrafluoroethylene (PTFE) tube, this novel SPE device could be used to determine the degree of QD dissolution through a simple adjustment of sample acidity. To the best of our knowledge, this study is the first to exploit PTFE tubing as a selective SPE adsorbent for the online chemical differentiation of QDs and Cd2+ ions with the goal of monitoring the phenomenon of QD dissolution in complicated biological matrices. We confirmed the analytical reliability of this system through comparison of the measured Cd-to-QD ratios to the expected values. When analyzing QDs and Cd2+ ions at picomolar levels, a temporal resolution of 8 min was required to load sufficient amounts of the analytes to meet the sensitivity requirements of the ICP mass spectrometer. To demonstrate the practicability of this developed method, we measured the dynamic variations in the Cd-to-QD705 ratio in the presence of ascorbate as a physiological stimulant to generate reactive oxygen species in cell culture media and trigger the dissolution of QDs; our results suggest that the ascorbate-induced QD dissolution was dependent on the time, treatment concentration, and nature of the biomolecule. Electronic supplementary information (ESI) available: The operation sequence, optimized parameters, instrumental operation conditions, and schematic representations for the proposed sequential in-tube PTFE SPE-ICP-MS hyphenated system are provided. See DOI: 10.1039/c2nr33365a

52. GENERAL INTERIOR VIEW LOOKING DOWN LENGTH OF POWERHOUSE #1 ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

52. GENERAL INTERIOR VIEW LOOKING DOWN LENGTH OF POWERHOUSE #1 AT LEVEL -23; PASSAGEWAY IS KNOWN AS DRAFT TUBE GALLERY. - Bonneville Project, Powerhouse No.1, Spanning Bradford Slough, from Bradford Island, Bonneville, Multnomah County, OR

Molecular Dynamics Simulations of the Thermal Conductivity of Single-Wall Carbon Nanotubes

NASA Technical Reports Server (NTRS)

Osman, M.; Srivastava, Deepak; Govindan,T. R. (Technical Monitor)

2000-01-01

Carbon nanotubes (CNT) have very attractive electronic, mechanical. and thermal properties. Recently, measurements of thermal conductivity in single wall CNT mats showed estimated thermal conductivity magnitudes ranging from 17.5 to 58 W/cm-K at room temperature. which are better than bulk graphite. The cylinderical symmetry of CNT leads to large thermal conductivity along the tube axis, additionally, unlike graphite. CNTs can be made into ropes that can be used as heat conducting pipes for nanoscale applications. The thermal conductivity of several single wall carbon nanotubes has been calculated over temperature range from l00 K to 600 K using non-equilibrium molecular dynamics using Tersoff-Brenner potential for C-C interactions. Thermal conductivity of single wall CNTs shows a peaking behavior as a function of temperature. Dependence of the peak position on the chirality and radius of the tube will be discussed and explained in this presentation.

High-efficiency helical traveling-wave tube with dynamic velocity taper and advanced multistage depressed collector

NASA Technical Reports Server (NTRS)

Curren, Arthur N.; Palmer, Raymond W.; Force, Dale A.; Dombro, Louis; Long, James A.

1987-01-01

A NASA-sponsored research and development contract has been established with the Watkins-Johnson Company to fabricate high-efficiency 20-watt helical traveling wave tubes (TWTs) operating at 8.4 to 8.43 GHz. The TWTs employ dynamic velocity tapers (DVTs) and advanced multistage depressed collectors (MDCs) having electrodes with low secondary electron emission characteristics. The TWT designs include two different DVTs; one for maximum efficiency and the other for minimum distortion and phase shift. The MDC designs include electrodes of untreated and ion-textured graphite as well as copper which has been treated for secondary electron emission suppression. Objectives of the program include achieving at least 55 percent overall efficiency. Tests with the first TWTs (with undepressed collectors) indicate good agreement between predicted and measured RF efficiencies with as high as 30 percent improvement in RF efficiency over conventional helix designs.

Analysis of ionization wave dynamics in low-temperature plasma jets from fluid modeling supported by experimental investigations

NASA Astrophysics Data System (ADS)

Yousfi, M.; Eichwald, O.; Merbahi, N.; Jomaa, N.

2012-08-01

This work is devoted to fluid modeling based on experimental investigations of a classical setup of a low-temperature plasma jet. The latter is generated at atmospheric pressure using a quartz tube of small diameter crossed by helium gas flow and surrounded by an electrode system powered by a mono-polar high-voltage pulse. The streamer-like behavior of the fast plasma bullets or ionization waves launched in ambient air for every high-voltage pulse, already emphasized in the literature from experimental or analytical considerations or recent preliminary fluid models, is confirmed by a numerical one-moment fluid model for the simulation of the ionization wave dynamics. The dominant interactions between electron and the main ions present in He-air mixtures with their associated basic data are taken into account. The gradual dilution of helium in air outside the tube along the axis is also considered using a gas hydrodynamics model based on the Navier-Stokes equation assuming a laminar flow. Due to the low magnitude of the reduced electric field E/N (not exceeding 15 Td), it is first shown that consideration of the stepwise ionization of helium metastables is required to reach the critical size of the electron avalanches in order to initiate the formation of ionization waves. It is also shown that a gas pre-ionization ahead of the wave front of about 109 cm-3 (coming from Penning ionization without considering the gas photo-ionization) is required for the propagation. Furthermore, the second ionization wave experimentally observed during the falling time of the voltage pulse, between the powered electrode and the tube exit, is correlated with the electric field increase inside the ionized channel in the whole region between the electrode and the tube exit. The propagation velocity and the distance traveled by the front of the ionization wave outside the tube in the downstream side are consistent with the present experimental measurements. In comparison with the streamer dynamics in a classical corona discharge, it is shown that under the same gas composition the plasma jet ionization waves propagate with a lower velocity (about 5 times), and have a higher diameter (at least 10 times) and a lower plasma density (at least 100 times).

Comprehensive analysis of tobacco pollen transcriptome unveils common pathways in polar cell expansion and underlying heterochronic shift during spermatogenesis

PubMed Central

2012-01-01

Background Many flowering plants produce bicellular pollen. The two cells of the pollen grain are destined for separate fates in the male gametophyte, which provides a unique opportunity to study genetic interactions that govern guided single-cell polar expansion of the growing pollen tube and the coordinated control of germ cell division and sperm cell fate specification. We applied the Agilent 44 K tobacco gene chip to conduct the first transcriptomic analysis of the tobacco male gametophyte. In addition, we performed a comparative study of the Arabidopsis root-hair trichoblast transcriptome to evaluate genetic factors and common pathways involved in polarized cell-tip expansion. Results Progression of pollen grains from freshly dehisced anthers to pollen tubes 4 h after germination is accompanied with > 5,161 (14.9%) gametophyte-specific expressed probes active in at least one of the developmental stages. In contrast, > 18,821 (54.4%) probes were preferentially expressed in the sporophyte. Our comparative approach identified a subset of 104 pollen tube-expressed genes that overlap with root-hair trichoblasts. Reverse genetic analysis of selected candidates demonstrated that Cu/Zn superoxide dismutase 1 (CSD1), a WD-40 containing protein (BP130384), and Replication factor C1 (NtRFC1) are among the central regulators of pollen-tube tip growth. Extension of our analysis beyond the second haploid mitosis enabled identification of an opposing-dynamic accumulation of core regulators of cell proliferation and cell fate determinants in accordance with the progression of the germ cell cycle. Conclusions The current study provides a foundation to isolate conserved regulators of cell tip expansion and those that are unique for pollen tube growth to the female gametophyte. A transcriptomic data set is presented as a benchmark for future functional studies using developing pollen as a model. Our results demonstrated previously unknown functions of certain genes in pollen-tube tip growth. In addition, we highlighted the molecular dynamics of core cell-cycle regulators in the male gametophyte and postulated the first genetic model to account for the differential timing of spermatogenesis among angiosperms and its coordination with female gametogenesis. PMID:22340370

Large-Flow-Area Flow-Selective Liquid/Gas Separator

NASA Technical Reports Server (NTRS)

Vasquez, Arturo; Bradley, Karla F.

2010-01-01

This liquid/gas separator provides the basis for a first stage of a fuel cell product water/oxygen gas phase separator. It can separate liquid and gas in bulk in multiple gravity environments. The system separates fuel cell product water entrained with circulating oxygen gas from the outlet of a fuel cell stack before allowing the gas to return to the fuel cell stack inlet. Additional makeup oxygen gas is added either before or after the separator to account for the gas consumed in the fuel cell power plant. A large volume is provided upstream of porous material in the separator to allow for the collection of water that does not exit the separator with the outgoing oxygen gas. The water then can be removed as it continues to collect, so that the accumulation of water does not impede the separating action of the device. The system is designed with a series of tubes of the porous material configured into a shell-and-tube heat exchanger configuration. The two-phase fluid stream to be separated enters the shell-side portion of the device. Gas flows to the center passages of the tubes through the porous material and is then routed to a common volume at the end of the tubes by simple pressure difference from a pumping device. Gas flows through the porous material of the tubes with greater ease as a function of the ratio of the dynamic viscosity of the water and gas. By careful selection of the dimensions of the tubes (wall thickness, porosity, diameter, length of the tubes, number of the tubes, and tube-to-tube spacing in the shell volume) a suitable design can be made to match the magnitude of water and gas flow, developed pressures from the oxygen reactant pumping device, and required residual water inventory for the shellside volume.

Commercial-Off-The-Shelf Microelectromechanical Systems (MEMS) Flow-Measurement Probes Fabricated And Assembled

NASA Technical Reports Server (NTRS)

Redding, Chip

2002-01-01

As an alternative to conventional tubing instrumentation for measuring airflow, designers and technicians at the NASA Glenn Research Center have been fabricating packaging components and assembling a set of unique probes using commercial-off-the-shelf microelectromechanical systems (MEMS) integrated circuits (computer chips). Using MEMS as an alternative has some compelling advantages over standard measurement devices. Sensor technologies have matured through high-production usage in industries such as automotive and aircraft manufacturers. Currently, MEMS are the choice in applications such as tire pressure monitors, altimeters, pneumatic controls, cable leak detectors, and consumer appliances. Conventional instrumentation uses tubing buried in the model aerodynamic surfaces or wind tunnel walls. The measurements are made when pressure is introduced at the tube opening. The pressure then must travel the tubing for lengths ranging from 20 to hundreds of feet before reaching an electronic signal conditioner. This condition causes a considerable amount of damping and requires measurements to be made only after the test rig has reached steady-state operation. The electronic MEMS pressure sensor is able to take readings continuously under dynamic states in nearly real time. The use of stainless steel tubing for pressure measurements requires many tubes to be cleaned, cut to length, carefully installed, and delicately deburred and spliced for use. A cluster of a few hundred 1/16-in.- (0.0625-in.-) diameter tubes (not uncommon in research testing facilities) can be several inches in diameter and may weigh enough to require two men to handle. Replacing hard tubing with electronic chips can eliminate much of the bulk. Each sensor would fit on the tip of the 1/16-in. tubing with room to spare. The P592 piezoresistive silicon pressure sensor (Lucas NovaSensor, Fremont, CA) was chosen for this project because of its cost, availability, and tolerance to extreme ambient conditions. The chip is 1 mm square by 0.6 mm thick (0.039 by 0.023 in.) with 0.12-mm (0.005-in.) wire connection tabs. Three MEMS chips were used to build the first type of flow-angularity probe. This MEMS probe will be demonstrated as an alternative to a standard tube type "Cobra Probe" now used routinely in wind tunnel and aeronautical hardware applications. The response time and accuracy would allow the probe to be translated on an actuator across a flow field, yielding precision dynamic measurements not possible with conventional instrumentation. The low profile, the minimal power requirement, the rugged construction, and the moderate cost all contribute to making MEMS sensors the enticing choice instrument in future research measurement needs. The MEMS probe efforts are a continuation of work initiated by Brian Willis, without whose foresight and efforts this project would never have been realized. This task was funded through cooperation with the NASA Electronic Parts and Packaging (NEPP) program at the Jet Propulsion Laboratory.

Use of Family History Information for Neural Tube Defect Prevention: Integration into State-Based Recurrence Prevention Programs

ERIC Educational Resources Information Center

Green, Ridgely Fisk; Ehrhardt, Joan; Ruttenber, Margaret F.; Olney, Richard S.

2011-01-01

A family history of neural tube defects (NTDs) can increase the risk of a pregnancy affected by an NTD. Periconceptional folic acid use decreases this risk. Purpose: Our objective was to determine whether second-degree relatives of NTD-affected children showed differences in folic acid use compared with the general population and to provide them…

Two-phase simulations of the full load surge in Francis turbines

NASA Astrophysics Data System (ADS)

Wack, J.; Riedelbauch, S.

2016-11-01

At off-design conditions, Francis turbines experience cavitation which may reduce the power output and can cause severe damage in the machine. Certain conditions can cause self-excited oscillations of the vortex rope in the draft tube at full load operating point. For the presented work, two-phase simulations are carried out at model scale on a domain ranging from the inlet of the spiral case to the outlet of the draft tube. At different locations, wall pressure measurements are available and compared to the simulation results. Furthermore, the dynamics of the cavity volume in the draft tube cone and at the trailing edge of the runner blades are investigated by comparing with high speed visualization. To account for the selfexcited behaviour, proper boundary conditions need to be set. In this work, the focus lies on the treatment of the boundary condition at the inlet. In the first step, the dynamic behaviour of the cavity regions is investigated using a constant mass flow. Thereafter, oscillations of the total pressure and mass flow rate are prescribed using various frequencies and amplitudes. This methodology enables to examine the response of the cavity dynamics due to different excitations. It can be observed that setting a constant mass flow boundary condition is not suitable to account for the self-excited behaviour. Prescribing the total pressure has the result that the frequency of the vapour volume oscillation is the same as the frequency of the excitation signal. Contrary to that, for an excitation with a mass flow boundary condition, the response of the system is not equal to the excitation.

Prediction of forced convective heat transfer and critical heat flux for subcooled water flowing in miniature tubes

NASA Astrophysics Data System (ADS)

Shibahara, Makoto; Fukuda, Katsuya; Liu, Qiusheng; Hata, Koichi

2018-02-01

The heat transfer characteristics of forced convection for subcooled water in small tubes were clarified using the commercial computational fluid dynamic (CFD) code, PHENICS ver. 2013. The analytical model consists of a platinum tube (the heated section) and a stainless tube (the non-heated section). Since the platinum tube was heated by direct current in the authors' previous experiments, a uniform heat flux with the exponential function was given as a boundary condition in the numerical simulation. Two inner diameters of the tubes were considered: 1.0 and 2.0 mm. The upward flow velocities ranged from 2 to 16 m/s and the inlet temperature ranged from 298 to 343 K. The numerical results showed that the difference between the surface temperature and the bulk temperature was in good agreement with the experimental data at each heat flux. The numerical model was extended to the liquid sublayer analysis for the CHF prediction and was evaluated by comparing its results with the experimental data. It was postulated that the CHF occurs when the fluid temperature near the heated wall exceeds the saturated temperature, based on Celata et al.'s superheated layer vapor replenishment (SLVR) model. The suggested prediction method was in good agreement with the experimental data and with other CHF data in literature within ±25%.

The influence of chemical composition of LNG on the supercritical heat transfer in an intermediate fluid vaporizer

NASA Astrophysics Data System (ADS)

Xu, Shuangqing; Chen, Xuedong; Fan, Zhichao; Chen, Yongdong; Nie, Defu; Wu, Qiaoguo

2018-04-01

A three-dimensional transient computational fluid dynamics (CFD) model has been established for the simulations of supercritical heat transfer of real liquefied natural gas (LNG) mixture in a single tube and a tube bundle of an intermediate fluid vaporizer (IFV). The influence of chemical composition of LNG on the thermal performance has been analyzed. The results have also been compared with those obtained from the one-dimensional steady-state calculations using the distributed parameter model (DPM). It is found that the current DPM approach can give reasonable prediction accuracy for the thermal performance in the tube bundle but unsatisfactory prediction accuracy for that in a single tube as compared with the corresponding CFD data. As benchmarked against pure methane, the vaporization of an LNG containing about 90% (mole fraction) of methane would lead to an absolute deviation of 5.5 K in the outlet NG temperature and a maximum relative deviation of 11.4% in the tube side HTC in a bundle of about 816 U tubes at the inlet pressure of 12 MPa and mass flux of 200 kg·m-2·s-1. It is concluded that the influence of LNG composition on the thermal performance should be taken into consideration in order to obtain an economic and reliable design of an IFV.

Molecular Dynamics Study of Surfactant Self-Assembly on Single-Walled Carbon Nanotubes (SWCNTs)

NASA Astrophysics Data System (ADS)

Phelan, Frederick, Jr.

2015-03-01

Single-walled carbon nanotubes (SWNCTs) are materials with structural, electronic and optical properties that make them attractive for a myriad of advanced technology applications. Increased adaptation of these materials requires advancement in separation techniques which enables them to be sorted with increased reliability into monodisperse fractions with respect to length and chirality. Most separation techniques currently in use rely on dispersion of tubes in aqueous solution using surfactants. This results in a colloidal mixture in which tubes are packed and individually dispersed in a surfactant shell. Understanding the structure and properties of the SWCNT-surfactant complex at the molecular level, and how this is affected by chirality, will help to improve separations processes. In this work, we study the structure and properties of SWCNT-surfactant colloidal complexes using all-atom molecular dynamics. Self-assembled structures are computed for a number of combinations SWCNT/surfactant, and also, co-surfactant mixtures for the bile salt surfactant sodium deoxycholate (DOC) and the anionic surfactant sodium dodecyl sulfate (SDS). From the radial distribution function we estimate the size of the SWCNT hydration layer, and use that information to compute the buoyant densities of unfilled tubes for a number of concentrations. Estimates of the change in hydrodynamic radius with increased surfactant packing and the binding energies of the individual surfactants are also obtained.

Sloshing motion dynamics of a free surface in the draft tube cone of a Francis turbine operating in synchronous condenser mode

NASA Astrophysics Data System (ADS)

Vagnoni, Elena; Andolfatto, Loïc; Favrel, Arthur; Avellan, François

2016-11-01

The penetration of the electrical grid by intermittent renewable energy sources induces grid fluctuations which must be compensated in order to guarantee the stability of the grid. Hydropower plants can supply reactive power to ensure the grid stabilization by operating in condenser mode. In this operating mode, the turbine operates with the tail water depressed to let the runner spin in air to reduce the power consumption. Pressurized air is injected in the draft tube cone to maintain the water level below the runner and this induces air-water interaction phenomena which cause important power losses. Flow visualization and pressure fluctuation measurements are performed in a reduced scale physical model of a Francis turbine operating in condenser mode to investigate the dynamics of the air-water interaction in the draft tube cone which causes the sloshing motion of the free surface. An image post-processing method is developed, enabling a quantitative description of the sloshing motion. The latter depends on the Froude number. By increasing the value of the Froude number, the amplitude of the sloshing motion decreases, as well as the amplitude of the pressure fluctuations. The frequency of the sloshing motion corresponds to the first natural frequency of the water volume.

The Dynamics of Miscible Fluids: A Space Flight Experiment (MIDAS)

NASA Technical Reports Server (NTRS)

Maxworthy, T.; Meiburg, E.; Balasubramaniam, R.; Rashidnia, N.; Lauver, R.

2001-01-01

We propose a space flight experiment to study the dynamics of miscible interfaces. A less viscous fluid displaces one of higher viscosity within a tube. The two fluids are miscible in all proportions. An intruding "finger" forms that occupies a fraction of the tube. As time progresses diffusion at the interface combined with flow induced straining between the two fluids modifies the concentration and velocity distributions within the whole tube. Also, under such circumstances it has been proposed that the interfacial stresses could depend on the local concentration gradients (Korteweg stresses) and that the divergence of the velocity need not be zero, even though the flow is incompressible. We have obtained reasonable agreement for the tip velocity between numerical simulations (that ignored the Korteweg stress and divergence effects) and physical experiments only at high Peelet Numbers. However at moderate to low Pe agreement was poor. As one possibility we attributed this lack of agreement to the disregard of these effects. We propose a space experiment to measure the finger shape, tip velocity, and the velocity and concentration fields. From intercomparisons between the experiment and the calculations we can then extract values for the coefficients of the Korteweg stress terms and confirm or deny the importance of these stresses.

The Dynamics of Miscible Fluids: A Space Flight Experiment (MIDAS)

NASA Technical Reports Server (NTRS)

Maxworthy, T.; Meiburg, E.; Balasubramaniam, R.; Rashidnia, N.; Lauver, R.

2001-01-01

We propose a space flight experiment to study the dynamics of miscible interfaces. A less viscous fluid displaces one of higher viscosity within a tube. The two fluids are miscible in all proportions. An intruding "finger" forms that occupies a fraction of the tube. As time progresses diffusion at the interface combined with flow induced straining between the two fluids modifies the concentration and velocity distributions within the whole tube. Also, under such circumstances it has been proposed that the interfacial stresses could depend on the local concentration gradients (Korteweg stresses) and that the divergence of the velocity need not be zero, even though the flow is incompressible. We have obtained reasonable agreement for the tip velocity between numerical simulations (that ignored the Korteweg stress and divergence effects) and physical experiments only at high Peclet Numbers. However at moderate to low Pe agreement was poor. As one possibility we attributed this lack of agreement to the disregard of these effects. We propose a space experiment to measure the finger shape, tip velocity, and the velocity and concentration fields. From intercomparisons between the experiment and the calculations we can then extract values for the coefficients of the Korteweg stress terms and confirm or deny the importance of these stresses.